JP3308706B2 - Charging member for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member for electrophotography, and more particularly to a charging member for electrophotography having a coating layer having a small resistance variation due to environment.

[0002]

2. Description of the Related Art In a charging process in an electrophotographic process using an electrophotographic photosensitive member, charging is performed by a corona generated by applying a high voltage (DC 5 to 8 kV) to a metal wire in most cases. However, the corona products of ozone and NO _X, etc. generated during charging in this way will by alteration of the photosensitive member surface, or causing the image blurring or deterioration, contamination of the wire affects the image quality, image There were problems such as white spots and black streaks. In addition, the electric current flowing toward the photoreceptor is only 5 to 30% of the whole, and most of the electric current flows to the shield plate, so that the charging means is inefficient.

In order to solve such disadvantages, for example, Japanese Patent Application Laid-Open No. 57-104351 and Japanese Patent Application Laid-Open No.
No. 67, JP-A-58-40566 and JP-A-58-139156 disclose a so-called direct charging method in which a photosensitive member is charged by applying a voltage to a charging member arranged in contact with the photosensitive member. Is disclosed. However, in practice, there is a problem that spot-like image defects caused by uneven charging and streak-like or band-like image defects caused by dielectric breakdown of the photoreceptor occur.

Therefore, for example, JP-A-64-66674 and JP-A-64-66676 propose to use a nylon resin as a surface layer of a charging member, as disclosed in JP-A-2-49066 and JP-A-2-49066. Kaihei 2-51
No. 562 proposes to use a pyrrole-based conductive resin for the charging member, but these resin layers have not been sufficiently satisfactory in terms of environmental stability.

Furthermore, it has been found that the composition of the above-mentioned nylon resin gradually changes when a charging member using the same is repeatedly charged and discharged. This is a phenomenon in which a methoxymethyl group in a nylon polymer chain is affected by discharge energy or a discharge product, and a crosslinking reaction in the polymer chain progresses little by little. Initially, the preferred resistance as a charging member can be maintained and a uniform charge can be applied to the photoreceptor.However, after repeated charging and discharging, the initially non-crosslinked nylon resin is crosslinked. It changes to a macromolecule with molecular chains that have no flexibility, and the overall resistance also increases. Therefore, charging failure occurs in the charging member, an appropriate potential cannot be applied to the photoconductor, and an image becomes fogged or has a low density, making the image unusable. On the other hand, JP-A-2-40683 and JP-A-5-88508 propose to use polyurethane as a material used for a charging member. Polyurethane in general is not suitable for the material for the charging member, among them,
It has been found that there is a suitable monomer configuration that satisfies moisture resistance, water absorption, abrasion resistance and resistance controllability.

Further, Japanese Patent Application Laid-Open No. Sho 63-170673,
JP-A-2-198470 and JP-A-4-867
No. 64 discloses a charging member having a resin layer containing a conductive additive. However, these methods disperse the conductive additive uniformly by selecting a resin as a dispersion medium. In some cases, uniform conductivity could not be obtained. In order to obtain a resistance of the coating layer of 10 ² to 10 ¹⁰ Ω / square, besides adding the above-mentioned conductive additive, it is also possible to apply an ionic material such as a surfactant to the surface of the coating layer. However, the coating film generally has a low frictional strength, and immediately causes peeling and dislocation. Also,
It also has poor water resistance, and thus has poor durability, such as a gradual decrease in its antistatic ability under the influence of water vapor in the atmosphere.

Accordingly, an object of the present invention is to provide an electrophotographic charging member in which the above-mentioned disadvantages are improved.

It is another object of the present invention to provide a charging member for electrophotography which has a small resistance variation in an environment from high temperature and high humidity to low temperature and low humidity.

It is another object of the present invention to provide an electrophotographic charging member which does not change its composition even by repeated discharge-charging.

Another object of the present invention is to provide a charging member for electrophotography which has good dispersibility of a conductive additive and can be uniformly charged.

Another object of the present invention is to provide an electrophotographic charging member capable of providing an excellent image by achieving the above object.

[0012]

That is, the present invention relates to an electrophotographic charging member having a coating layer on a conductive support, wherein the coating layer comprises an oxyalkylene which imparts hydrophilicity.
Group-containing polyether diols and
Polyether di-ol with Kishiarukiren group, Ri polymer der obtained by reacting an aromatic isocyanate and an aliphatic isocyanate, with the hydrophilic
Oxyalkylene group to impart and oxy to impart the hydrophobicity
An alkylene group ratio of 2 to 4.5: 8 to 5.5,
Ratio of the aromatic isocyanate and the aliphatic isocyanate
Rate 9.5: 0.5 to 5.5: 4.5 is electrophotographic charging member according to claim der Rukoto.

Hereinafter, the present invention will be described in detail.

Generally, a so-called polyurethane, which is a polymer obtained by reacting a polyol with an isocyanate,
Depending on the selection of the material, a polymer having a significantly different hygroscopic property between a high temperature and high humidity environment and a low temperature and low humidity environment may be obtained. When such a material is used for the charging member, the resistance fluctuation between the above-mentioned environments becomes too large, and it becomes impossible to maintain constant and stable charging characteristics. On the other hand, the choice of material determines the hardness of the polymer. If the hardness is too high, the surface of the photoreceptor with which the charging member contacts may be scraped unevenly, or contaminants such as toner and paper powder adhering to the charging member may be transferred and adhered to the surface of the photoreceptor. This may cause image defects. On the other hand, if it is too soft, the contact area between the charging member and the photoreceptor becomes too large, making it difficult to obtain uniform charging or causing a leak phenomenon when bias is applied.

However, in the present invention, by specifying the polyol and the isocyanate constituting the polyurethane, the resistance is small, the hardness is such that uniform charging can be obtained when contacting the photoreceptor, and the conductive material is A polymer having good dispersibility could be obtained, and the invention was completed.

The oxyalkylene group of the polyether diol used in the present invention is determined by the moisture absorption of the resulting polymer.
It is chosen to balance moisture resistance. Thus, for example oxypropylene groups hydrophobicity compels as increasing its proportion in Porieteruji ol. This tendency becomes stronger as the number of carbon atoms in the alkylene group increases.
Also because there always as hydrophilic oxyethylene groups Conversely, the proportion of the groups in Porieteruji ol is increased, so that the moisture resistance is poor.

Therefore, by appropriately selecting the ratio of the oxyethylene group to the other oxyalkylene group imparting hydrophobicity, the charge-up phenomenon under low temperature and low humidity and the leak phenomenon under high temperature and high humidity can be prevented. Stable uniform charging can be obtained. Oxy ratio of alkylene groups that impart oxyalkylene group and a hydrophobic which imparts hydrophilicity in Porieteruji ol 2 to 4.5: 8 to 5.5, preferably 3 to 4: is 7-6. In the present invention, particularly preferred embodiments of the combination of two oxyalkylene groups include, for example, oxyethylene and oxypropylene, oxypropylene and oxytetramethylene, oxypropylene and oxybutylene, and oxyethylene and oxytetrane. Methylene group, oxypropylene group and oxypentyl group, oxypropylene group and oxyhexylene group, in the case of three types, oxyethylene group, oxypropylene group and oxytetramethylene group, oxyethylene group, oxypropylene group and oxybutylene group , Etc.,
When three or more oxyalkylene groups are used, the ratio must be carefully selected in consideration of moisture absorption and moisture resistance, charge-up characteristics and leak characteristics.

In general, with regard to the reactivity of isocyanates, it is said that aromatic isocyanates are more active and more reactive than aliphatic isocyanates.
Particularly, toluene diisocyanate reacts quickly, and hexamethylene diisocyanate is particularly slow. The present invention focused on the difference in reactivity and the difference in isocyanate structure, and controlled the hardness of the obtained polymer and the deterioration characteristics of the polymer due to charge-discharge.

[0019] That is, first, an aromatic isocyanate port
Reacts with Rieteruji ol, to form a rigid main backbone of the polymer, sequentially aliphatic isocyanate polyether
It reacted with di-ol, to form a polymer chain with flexibility in the main skeleton. In this case, the hardness and the discharge deterioration resistance of the polymer can be obtained by selecting the ratio of the aromatic isocyanate to the aliphatic isocyanate, the type of the substituent, and the aliphatic chain.

At least, when the aromatic isocyanate alone is used, the hardness of the polymer becomes too high, which promotes scraping of the photoreceptor. However, the discharge deterioration resistance is good. Also, aliphatic isocyanate alone has too low hardness,
Tack is generated on the surface of the polymer, and the contamination of the charging member with toner and paper powder is remarkable.

Examples of the aromatic isocyanate used in the present invention include paraphenylene diisocyanate, meta-xylylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5
-Naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, parachlorophenyl isocyanate, orthochlorophenyl isocyanate, 3,4
-Dichlorophenyl isocyanate, 2,5-dichlorophenyl isocyanate and the like. As the aliphatic isocyanate, for example, hexamethylene diisocyanate,
Examples include methyl isocyanate, ethyl isocyanate, n-butyl isocyanate, n-propyl isocyanate, and octadecyl isocyanate.

Regarding the isocyanate used in the present invention, irrespective of aromatic or aliphatic, there is no problem even if tri-, tetra-, cyanate or dimer or trimer of isocyanate is used in addition to diisocyanate. Does not occur. The ratio of aromatic isocyanate to aliphatic isocyanate is 9.5: 0.5 to 5.5: 4.5, preferably 9.0: 1.0 to 6.0: 4.0, more preferably 9.0: 1.0 to 7.5: 2.5.

Other monomers applicable as the polymer used in the present invention include, for example, monomers having an ethylenically unsaturated group include hydrocarbon monomers, unsaturated nitriles, and vinyl monomers. , Acrylic acid and its derivatives and (meth) acrylates. Specific examples are shown below, but the present invention is not limited to these.

Examples of the hydrocarbon monomers include styrenes [styrene and alkylstyrene (α-methylstyrene, o-, m- or p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p- n-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, etc.)]
And aliphatic hydrocarbon-based vinyls (such as butadiene).

Examples of the unsaturated nitriles include nitrites (eg, acrylonitrile and methacrylonitrile).

Examples of vinyls include vinyl esters (such as vinyl acetate and vinyl propionate), vinyl ethers (such as vinyl methyl ether and vinyl ethyl ether), vinyl ketones (such as vinyl methyl ketone and vinyl hexyl ketone), and N-vinyl. (Such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone) and vinyl halides (such as vinyl chloride).

As acrylic acid and its derivatives,
(Meth) acrylic acid and (meth) acrylic acid ester ｛alkyl (meth) acrylate [methyl (meth) acrylate, butyl (meth) acrylate, trifluoroethyl (meth) acrylate, etc.], heterocyclic (meth) acrylate [tetrahydro Furfuryl (meth) acrylate, etc.], and amino group-containing (meth) acrylate [dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc.]} and the like.

(Meth) acrylates include (meth) acrylates.
Examples thereof include sodium acrylate, calcium (meth) acrylate, and zinc (meth) acrylate.

Particularly preferred among these are hydrocarbon monomers, unsaturated nitriles, acrylic acid and its derivatives, and (meth) acrylates. Also,
When the carbon is basic, the monomer having an ethylenically unsaturated group is preferably acidic.

In the present invention, an electron conductor and an ionic conductor may be added as necessary. Examples of preferred electron conductors include graphite, metals (such as copper, aluminum, nickel and silver) and conductive polymers (such as polyaniline, polypyrrole, polythiophene, polyacetylene, polypyridine, polyacene, polyazulene, polydiphenylbenzidine, polyvinylcarbazole, and polycarbazole). -3-alkylthiophene). Of these, metals, polyaniline, polypyrrole and polythiophene are particularly preferred. Examples of preferred ionic conductors include metal salts and ammonium salts. Examples of the metal salt include salts of metals of Group I or Group II, and salts of Li, Na and K having a relatively small cation radius are particularly preferable. The anions constituting these metal salts include halogen ions (F, Cl, Br and I).
Etc.), thiocyanate ion, perchlorate ion, trifluoromethanesulfonate ion, fluoroborate ion and the like. Of these, particularly preferred are thiocyanate, perchlorinated, trifluoromethanesulfonate and fluoroborate. Examples of the ammonium salt include ammonium salts such as carboxylic acid (such as adipic acid, phthalic acid, and azelaic acid), phosphoric acid, boric acid, sulfonic acid (such as arylsulfonic acid), and borofluoric acid. Of these ammonium salts, ammonium carboxylate, ammonium phosphate and ammonium borate are particularly preferred. The electron conductor and the ionic conductor may be used as a mixture.

The carbon which can be added to the present invention is not limited to a production method, and carbon produced by a furnace method, a channel method and a thermal method, and a natural product (eg, graphite) can be used. Acetylene black is preferred. The main performance items of carbon used in the present invention include DBP adsorption amount, specific surface area and volatile matter. DBP adsorption amount (DBP
ml / 100 g) is preferably from 40 to 500, and particularly preferably from 80 to 500. Also,
Specific surface area (BETm ² / g) is preferably from 40 to 2,000, and particularly preferably from 45 to 1,500. Further, the volatile component (% by weight) is preferably 0.1 to 2.0, and particularly preferably 0.1 to 1.0.

The charging member of the present invention has at least a coating layer on a conductive support. Examples of the structure are shown in FIGS. In the case of the so-called contact charging in which the charging member and the photoconductor are in contact, a roller shape as shown in FIGS. 1 and 2 and a blade shape as shown in FIG. 3 are exemplified. More preferably, there is. In addition, when the distance between the charging member and the photosensitive member is 1000 μm or less, and preferably about 500 μm or less, the two are close to each other but not in contact with each other.
5 and various shapes such as an arc shape as shown in FIG. 5 and a plate shape as shown in FIG. 6. Among these, the concentric or arc shape is preferable. Particularly preferred. In each figure, 1 is a conductive support, 2 is an elastic coating layer, 3 is a conductive coating layer, and 4 is a resistance coating layer.

When the charging member of the present invention has a multilayer structure, the polymer of the present invention can be used for any coating layer.

As the conductive support, aluminum,
Metals and alloys such as iron, copper and stainless steel, conductive resins and the like dispersed carbon and metal particles and the like can be used,
Examples of the shape include a rod shape and a plate shape as described above.

The elastic coating layer contains the polymer of the present invention or another rubber or resin. When the polymer of the present invention is used, the properties of the polymer may be rubbery within a range that does not impair the features of the present invention, or elasticity may be imparted by elastification or the like, and the other rubber or other resin may be further used. You may add and mix.

Examples of the rubber include styrene-butadiene rubber, high styrene rubber, butadiene rubber, isoprene rubber, ethylene-propylene copolymer, nitrile butadiene rubber, chloroprene rubber, butyl rubber, silicon rubber, fluorine rubber, nitrile rubber, acrylic Rubber,
Epichlorohydrin rubber and norbornene rubber. Examples of the resins include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, and styrene. -Vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-
Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-
Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylate copolymer, etc. Styrene resin (Homopolymer or copolymer containing styrene or substituted styrene), vinyl chloride resin, styrene-vinyl acetate copolymer, rosin-modified maleic resin, phenol resin, epoxy resin, polyester resin, low molecular weight Examples thereof include polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, and polybutyral resin.

The thickness of the elastic coating layer is preferably 1.5 mm or more, more preferably 2 mm or more, and particularly preferably 3 mm to 13 mm.

The conductive coating layer is a layer having high electric conductivity, and has a volume resistivity of 10 ⁷ Ω · cm or less, and furthermore, 10 ⁶ Ω.
Cm or less, particularly preferably 10 ^-2 to 10 ⁶ Ω · cm. Further, the thickness of the conductive coating layer is preferably a thin layer for transmitting the flexibility of the lower elastic coating layer to the upper layer such as the resistance coating layer or the surface of the photoreceptor. 2 mm or less, especially 20 μm to 1 m
m is preferable.

As the material to be used, in addition to the above-mentioned polymer of the present invention, a metal vapor-deposited film, a conductive particle-dispersed resin, a conductive resin and the like can be mentioned. Specifically, examples of the metal deposited film include those obtained by depositing a metal such as aluminum, indium, nickel, copper, and iron.As the conductive particle dispersed resin, carbon, aluminum, nickel,
Urethane, polyester, conductive particles such as titanium oxide
Examples thereof include those dispersed in a resin such as vinyl acetate-vinyl chloride copolymer and polymethyl methacrylate, and examples of the conductive resin include polyvinyl aniline, polyvinyl pyrrole, polydiacetylene, and polyethylene imine. Among these, a conductive particle-dispersed resin is preferred from the viewpoint of conductivity control.

The resistance coating layer is formed so as to have a higher resistance than the lower conductive coating layer, and has a volume resistivity that is one to six orders of magnitude higher than the volume resistivity of the conductive coating layer, and in particular, 2 to 6 digits. It is preferable that the height be higher by one digit to five orders, and the range is 10 ⁶ to
It is preferably 10 ¹² Ω · cm, particularly preferably 10 ⁷ to 10 ¹¹ Ω · cm. The thickness of the resistance coating layer is 1 μm to 500 μm, particularly 50 μm to 200 μm from the viewpoint of chargeability.
Is preferred.

Examples of the material used include, in addition to the polymer of the present invention, a semiconductive resin, a conductive particle-dispersed resin, and the like. Specifically, as the semiconductive resin, ethyl cellulose, nitrocellulose, methoxymethylated nylon,
Resins such as ethoxymethylated nylon, copolymerized nylon, polyvinylpyrrolidone and casein, and mixtures of these resins.Examples of the conductive particle-dispersed resin include carbon, aluminum, conductive particles such as indium oxide and titanium oxide. Examples thereof include those in which the resistance is adjusted by dispersing a small amount in the above-mentioned semiconductive resin, insulating resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer, and polymethacrylic acid.

In the present invention, in order to make the resistance coating layer a two-layer structure or to improve the adhesiveness of each layer described above,
An adhesive layer can be provided between each layer.

Regardless of the configuration, the charging member of the present invention
Volume resistivity is 10^Two -10 ^TenΩ · cm
Is preferable, and in particular, 10^Four -10⁸ Ω · cm
Is preferred. Furthermore, at least the volume resistance of the surface coating layer
The resistivity is preferably within these ranges.

When the charging member of the present invention is used, regardless of whether the charging member and the photosensitive member are in contact or non-contact, if the surface of the charging member is rough, unevenness of the surface of the charging member causes slight charging unevenness, resulting in poor image quality. May occur. Therefore, it is preferable that the surface of the charging member is smoother.
The 10-point average roughness R _Z in the IS B0601 surface roughness standard is 5 μm or less, and the maximum height R _max is 10
μm or less, and particularly preferably, R _Z is 2 μm or less, and R _max is 5 μm or less.

When the charging member is used in contact with the photoreceptor, the charging member is deformed (compression set) due to long-term contact with the photoreceptor, thereby distorting the discharge area where charging is performed. Since a difference occurs between a portion and a portion other than the portion, a difference occurs in charging, and as a result, an image defect may occur. Therefore, in the present invention, it is preferable that the compression set is 40% or less as measured after standing at 70 ° C. for 22 hours in a state of a compressibility of 25% according to JIS K6301 and further standing at room temperature for 30 minutes. In particular, it is preferably at most 30%.

Further, when the charging member is used in contact with the photoreceptor, if the surface of the charging member is too hard, contaminants such as toner on the photoreceptor are rubbed with the photoreceptor by the charging member, and mechanically. In some cases, a toner or the like is melted on the photosensitive member due to a factor, or an image defect due to so-called fusion may occur. In particular, when the applied voltage is the AC superimposed bias, the above-described phenomenon is more likely to occur than when the DC voltage is applied because the charging member vibrates due to the AC voltage.

Therefore, in the present invention, the surface hardness of the charging member is 50 in A hardness specified in JIS K6301.
° or less, and particularly preferably 35 °.

In addition, when the applied voltage is an AC superimposed bias, “charging noise” is generated by vibration of the charging member due to the AC voltage.
In some cases, the sound may be uncomfortable to humans, and in consideration of the fact that the charging member is reduced in hardness to absorb vibration and reduce charging noise, the hardness may be 20 ° or less. preferable.

The charging member of the present invention is manufactured, for example, as follows.

First, iron is used as a conductive support for the charging member.
Prepare a metal rod using a material such as plated iron, aluminum, and stainless steel. An elastic coating layer is provided by molding the polymer of the present invention on a metal rod by melt molding, injection molding, dip coating or spray coating. Next, the conductive coating layer is formed by molding the material of the conductive coating layer on the elastic coating layer by melt molding, injection molding, dip coating, spray coating, or the like.

Finally, the material of the resistance coating layer is applied on the conductive coating layer by dip coating, spray coating, gravure coating, or the like to provide the resistance coating layer.

The charging member of the present invention has the following properties:
It can be used for any of primary charging, transfer charging and static elimination charging. Of course, they may be used simultaneously.

The charging member of the present invention can be applied to, for example, an electrophotographic apparatus as shown in FIG. This device includes a charging member for primary charging (a charging member of the present invention) 5, an image exposure unit 6, a developing unit 7,
A transfer charging corona charger 8, a cleaning means 9, and a pre-exposure means 10 are provided.

An external voltage (for example, 20) is applied to the primary charging charging member 5 which is arranged in contact with the electrophotographic photosensitive member 11.
DC voltage between 0 V and 2000 V and peak-to-peak voltage 40
A pulsating voltage on which an AC voltage of 00 V or less is superimposed,
The surface of the electrophotographic photosensitive member 11 is charged, and an image on a document is image-exposed on the photosensitive member by the image exposure means 6 to form an electrostatic latent image. Next, the electrostatic latent image on the photoconductor is developed (visualized) by attaching the developer in the developing unit 7 to the photoconductor,
Further, the developer on the photoreceptor is transferred to the transfer member 12 such as paper by the transfer charging unit 8, and the developer remaining on the photoreceptor without being transferred to the paper at the time of transfer by the cleaning unit 11 is collected.

An image can be formed by such an electrophotographic process. However, if residual charge remains on the photosensitive member, the photosensitive member is exposed to light by the pre-exposure means 10 before primary charging. It is better to remove the charge.

When the charging member of the present invention is used for transfer charging, it can be applied to, for example, an electrophotographic apparatus as shown in FIG. The apparatus includes a primary charging corona charger 13, an image exposure unit 6, a developing unit 7, a transfer charging member (a charging member of the present invention) 14 on a peripheral surface of an electrophotographic photosensitive member 11,
Cleaning means 9 and pre-exposure means 10 are arranged.

A voltage (for example, a DC voltage of 40) is applied to the charging member 14 for transfer charging, which is disposed in contact with the electrophotographic photosensitive member 11.
0 to 1000 V) to transfer the developer on the electrophotographic photosensitive member to a member to be transferred such as paper. When the charging member of the present invention is used for static elimination charging, it can be applied to, for example, an electrophotographic apparatus as shown in FIG. In this apparatus, a primary charging corona charger 13, an image exposure unit 6, a developing unit 7, a transfer charging corona charger 8, and a cleaning unit 9 are arranged on a peripheral surface of an electrophotographic photosensitive member 11.

A voltage (for example, an AC peak-to-peak voltage of 500 to 2,000 V) is applied to the charge member 15 for charge removal (the charging member of the present invention) which is arranged in contact with the electrophotographic photosensitive member 11 to charge the charge on the electrophotographic photosensitive member. Can be neutralized.

In the present invention, the charging member to be brought into contact with the photoreceptor is not limited to a specific method. The charging member may be fixed or may be moved in the same direction as the photoreceptor or rotated in the opposite direction. Can be used. Further, it is also possible for the charging member to function as a developer cleaning device on the photoconductor.

The voltage applied to the charging member and the method of application in the direct charging of the present invention depend on the specifications of each electrophotographic apparatus. Apply the voltage in the order of DC → AC or AC → DC, except for the method of gradually increasing the applied voltage for the purpose of Can be adopted.

When the charging member of the present invention is used for primary charging of an electrophotographic apparatus, it is possible to superimpose a DC voltage and an AC voltage on an electrophotographic photosensitive member in an image output area, or to apply only a DC voltage. It is. When used for transfer charging,
The DC voltage alone or the DC voltage and the AC voltage may be superimposed.

[0062]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the following examples.

Hereinafter, a production example of the polymer of the present invention will be described.

(Production Example) An accurately weighed poly ( oxyalkylene group-containing polyoxyalkylene group )
Had Eteruji ol and second oxyalkylene group
The Porieteruji ol uniformly mixed in a reactor equipped with a stirrer. Next, an appropriate amount of a conductive agent, for example, carbon black, conductive titanium oxide, conductive tin oxide, or the like is added to the above mixture, and mixed until the conductive agent is sufficiently wetted with the mixture and uniformly dispersed. Further, the aromatic and aliphatic isocyanates added to the mixture, and stirring and defoaming, then poured into a mold and inserting a pre-conductive support roller-shaped, at or above room temperature, preferably at 50 ° C. or higher, More preferably, the reaction is carried out by heating at 80 ° C. or higher for several hours to obtain a roller-shaped charging member having the polymer of the present invention as a coating layer. When reacting the Porieteruji ol and isocyanates, in consideration of the reaction promoting catalyst,
For example, cobalt naphthenate, triethylenediamine,
Stannic chloride, ethyl morpholine, n-butyltin trichloride and the like may be added.

Example 1 Using a polymer having the composition shown in Table 1, a roller-shaped charging member was obtained.

The obtained volume resistivity of the charging member was measured by applying a DC voltage (250 V) between the support and the aluminum foil by winding an aluminum foil in close contact with the outer periphery of the charging member and applying a tester (HIOKI 3116 DEGIAL MΩ HI).
Table 1 shows the results of the measurement by TESTER.

Further, a charging member obtained as a charging means for primary charging is mounted and a copying machine (FC-2, Canon Inc.) is used.
, A DC voltage of -1500 V is applied to perform image output, and the obtained image is evaluated by visually observing an image defect due to charging unevenness due to uneven resistance of the charging member. did. Table 2 shows the results.
In the table, ◎ indicates that the obtained image was excellent, ○ indicates that it was good, Δ indicates that it was practical, and X indicates that it was not practical. Further, the photosensitive member of the above copying machine was used as a defective photosensitive member in which the aluminum layer was exposed by stripping the photosensitive layer by 1 mm ² , and the applied voltage was −
An image was displayed at 1800 V, and the pressure resistance was evaluated by observing image whitening caused by dielectric breakdown. Table 2 shows the results. In the table, ◎ indicates excellent (white spots are only defective portions of the photoreceptor), ○ indicates good (white spots are within 15 mm from the defective portion of the photoreceptor in the longitudinal direction of the photoreceptor), and Δ indicates practical use (white spots are sensitized). 30m over 15mm in the body longitudinal direction
m), x is not practical (white spots are 3 in the longitudinal direction of the photoconductor
0 mm).

The container was evaluated at 32 ° C., 85% RH (environment 1) and 10 ° C.
An environment of 5% RH (environment 2) was appropriately selected.

Further, using the above-mentioned copying machine, the weight voltage (AC: peak-to-peak voltage 1.9 kV, 450 Hz, DC: -7
00V) was applied to form an image, and the charging noise generated at that time was evaluated. Table 2 shows the results. In the table, ◎ is excellent (no charging noise is heard at all), ○ is good (the charging noise is hardly heard), △ is practical (the charging noise is hidden by noise of other machines), and × is practical Indicates that it is not possible (a harsh sound is heard).

The cartridge of the above copying machine is
After leaving for 1 month in an environment of 85 ° C. and 85% RH, the apparatus is mounted on a copying machine main body, a DC voltage of −1500 V is applied to perform image output, and an image defect caused by distortion of the charging member is observed. The strain resistance was evaluated. Table 2 shows the results. In the table, ◎ indicates excellent (no image defects), は indicates good (slight streaks occurred in halftone images), Δ indicates practical use (slightly streaks occurred), and x indicates no practical use (streaks occurred). Indicates that

Further, the obtained charging member was mounted as a primary charging means of a laser beam printer (Laser Jet Si, manufactured by Hewlett Packard), and charged at 32 ° C. and 85 ° C.
Under a% RH environment, a 10,000-image endurance test was performed to evaluate the state of fusion after endurance. Table 2 shows the results. In the table, ◎ indicates excellent (no fusion), は indicates good (observed on the photoreceptor but does not appear in the image), 実 用 indicates practical use (slightly generated in the image), and × indicates impractical (image (Occurs on the entire surface).

Further, the surface roughness (R
_Z ), compression set and hardness were measured as described above. Table 1 shows the results.

Example 2, Comparative Example 1 A charging member was prepared and evaluated in the same manner as in Example 1 except that the composition was changed as shown in Table 1. The results are shown in Tables 1 and 2.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

According to the charging member for electrophotography of the present invention,
Low resistance fluctuation over high to high temperature to low temperature and low humidity environment, no change in composition by repeated discharge-charging, and good dispersibility of conductive additive enables uniform charging, and therefore excellent Images can be supplied for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a charging member of the present invention.

FIG. 2 is a schematic configuration diagram of an example of a charging member of the present invention.

FIG. 3 is a schematic configuration diagram of an example of a charging member of the present invention.

FIG. 4 is a schematic configuration diagram of an example of a charging member of the present invention.

FIG. 5 is a schematic configuration diagram of an example of a charging member of the present invention.

FIG. 6 is a schematic configuration diagram of an example of a charging member of the present invention.

FIG. 7 shows an electrophotographic apparatus to which the charging member of the present invention is applied.
It is a schematic structure figure of an example.

FIG. 8 shows an electrophotographic apparatus to which the charging member of the present invention is applied.
It is a schematic structure figure of an example.

FIG. 9 shows an electrophotographic apparatus to which the charging member of the present invention is applied.
It is a schematic structure figure of an example.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103 C08G 18/08

Claims (1)

(57) [Claims] 1. An electrophotographic charging member having a coating layer on a conductive support, wherein the coating layer imparts hydrophilicity.
Polyether diol having oxyalkylene group
Polyether di-ol having an oxyalkylene group which imparts aqueous polymer der obtained by reacting an aromatic isocyanate and an aliphatic isocyanate
The oxyalkylene group imparting hydrophilicity and the hydrophobicity
Is from 2 to 4.5: 8.
To 5.5, wherein the aromatic isocyanate and the aliphatic
When the ratio of the cyanate is 9.5: 0.5 to 5.5: 4.5.
Electrophotographic charging member according to claim der Rukoto.