JPH07295335A - Electrophotographic electrifying member - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic electrifying member less in change in resistance in various environments from a high temp. and high humidity to a low temp. and low humidity and having no change in the compsn. even when charging and discharging are repeated and good in dispersibility of a conductive additive so that uniform electrification is possible and excellent images can be supplied for a long time by using a specified polymer to form coating layers. CONSTITUTION:This electrophotographic electrifying member has coating layers 2, 3 on a conductive supporting body 1. The coating layers 2, 3 consist of a polymer obtd. by the reaction of polyetherpolyol having at least two kinds of oxyalkylene groups, and aromatic isocyanate and aliphatic isocyanate. When the electrifying member has a multilayer structure, the polymer can be used for any of coating layers 2, 3. The elastic coating layer 2 contains this polymer and other rubber and resin. Namely, when this polymer is used, characteristics of the polymer may be changed into a rubberlike state or given elasticity by producing elastomers, or other rubber and resin may be further added or mixed as far as the characteristics of the material are not degraded.

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 whose resistance fluctuation due to the environment is small.

[0002]

2. Description of the Related Art In a charging process in an electrophotographic process using an electrophotographic photosensitive member, a corona generated by applying a high voltage (DC 5 to 8 kV) to a metal wire has been used for charging. However, with this method, corona products such as ozone and NO _x generated at the time of charging change the surface of the photoconductor, causing blurring or deterioration of the image, or wire stains affecting the image quality, There were problems such as white spots and black streaks. Further, in terms of electric power, the current flowing to the photoconductor is only 5 to 30% of the whole, and most of the current flows to the shield plate, so that the charging means is inefficient.

In order to solve these drawbacks, for example, JP-A-57-104351 and JP-A-57-1782.
67, JP-A-58-40566 and JP-A-58-139156, a so-called direct charging method in which a photoreceptor is charged by applying a voltage to a charging member disposed in contact with the photoreceptor. Is disclosed. However, in practice, there is a problem in that spot-shaped image defects due to uneven charging and streak-shaped or band-shaped image defects due to dielectric breakdown of the photoconductor occur.

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

Further, it has been found that the composition of the above-mentioned nylon resin gradually changes when the 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 the energy of discharge or a discharge product, and a crosslinking reaction in the polymer chain gradually progresses. In the initial stage, it is possible to maintain a preferable resistance as a charging member and to give a uniform charge to the photoconductor, but after repeated charging-discharging, the nylon resin which was not initially crosslinked is crosslinked. It changes into a polymer with a molecular chain without flexibility, and the overall resistance also rises. Therefore, charging failure occurs as a charging member, an appropriate potential cannot be applied to the photoconductor, and an image is fogged or has a low density, which makes it unusable. On the other hand, in JP-A-2-40683 and JP-A-5-88508, it is proposed to use polyurethane as a material for the charging member. However, according to the study by the present inventors, Polyurethane in general is not suitable as a material for charging members, and among them,
It has been found that there is a suitable monomer composition which satisfies moisture resistance, water absorption, abrasion resistance and resistance controllability.

[0006] Further, JP-A-63-170673,
JP-A-2-198470 and JP-A-4-867
No. 64, etc. disclose a charging member having a resin layer containing a conductive additive. In these methods, the conductive additive is uniformly dispersed depending on the selection of the resin as the 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, it is also possible to apply an ionic material such as a surfactant to the surface of the coating layer in addition to the above-mentioned conductive additive. Although the coating film has been applied, the coating film generally has a low frictional strength, and peeling or scratching occurs immediately. Also,
Since it also has a poor water resistance, it is inferior in durability such that the antistatic ability gradually decreases under the influence of water vapor in the atmosphere.

Therefore, an object of the present invention is to provide a charging member for electrophotography, which has improved the above drawbacks.

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

Another object of the present invention is to provide an electrophotographic charging member which does not change in 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 a charging member for electrophotography which can provide an excellent image by achieving the above object.

[0012]

That is, according to the present invention, in a charging member for electrophotography having a coating layer on a conductive support, the coating layer contains at least 2 oxyalkylene groups.
A charging member for electrophotography, which is a polymer obtained by reacting a polyether polyol having at least one species with an aromatic isocyanate and an aliphatic isocyanate.

The present invention will be described in detail below.

Generally, a so-called polyurethane, which is a polymer obtained by reacting a polyol and an isocyanate, is
Depending on the selection of the material, a polymer having a large hygroscopicity may be obtained between the high temperature and high humidity environment and the low temperature and low humidity environment. If such a material is used for the charging member, the resistance fluctuation between the above environments becomes too large, and it becomes impossible to maintain a constant and stable charging characteristic. On the other hand, the choice of material influences the hardness of the polymer. If the hardness is too high, the surface of the photoconductor with which the charging member comes into contact is shaved unevenly, or contaminants such as toner and paper powder that adhere to the charging member are transferred and adhere to the surface of the photoconductor, resulting in poor charging. It becomes a factor that causes image defects. On the other hand, if it is too soft, the contact area between the charging member and the photoconductor becomes too large, and it becomes difficult to obtain uniform charging, or the leakage phenomenon tends to occur when a bias is applied.

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

The oxyalkylene group contained in the polyol used in the present invention, especially in the diol, is selected so as to balance the moisture absorption-moisture resistance of the resulting polymer. That is, for example, oxypropylene groups become more hydrophobic as their proportion in the polyol increases. This tendency becomes stronger as the number of carbon atoms in the alkylene group increases.
On the contrary, since the oxyethylene group always exists as a hydrophilic group, the increase of the ratio of this group in the polyol means that
Moisture resistance will deteriorate.

Therefore, by appropriately selecting the ratio of the oxyethylene group and the oxyalkylene group which imparts other 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 and uniform charging can be obtained. The ratio of the oxyalkylene group imparting hydrophilicity to the oxyalkylene group imparting hydrophobicity in the diol is 2 to 4.5: 8 to 5.5, preferably 3 to
4: 7-6. In the present invention, a particularly preferable embodiment of the combination of two oxyalkylene groups is, for example, an oxyethylene group and an oxypropylene group, an oxypropylene group and an oxytetramethylene group, an oxypropylene group and an oxybutylene group, an oxyethylene group and an oxytetra group. Methylene group, oxypropylene group and oxypentyl group, oxypropylene group and oxyhexylene group, in the case of 3 kinds, oxyethylene group, oxypropylene group and oxytetramethylene group, oxyethylene group, oxypropylene group and oxybutylene group , Etc., and when using three or more kinds of oxyalkylene groups, the ratio must be carefully selected in consideration of hygroscopicity and moisture resistance, charge-up characteristics and leak characteristics.

Regarding the reactivity of the isocyanate, it is generally said that the aromatic isocyanate is more active and more reactive than the aliphatic isocyanate.
In particular, toluene diisocyanate has a fast reaction, and hexamethylene diisocyanate has a particularly slow reaction. In the present invention, focusing on the difference in reactivity and the structure of isocyanate, the hardness of the obtained polymer and the deterioration characteristics of the polymer due to charge-discharge are controlled.

That is, first, the aromatic isocyanate reacts with the polyol to form a rigid main skeleton of the polymer, and the aliphatic isocyanate sequentially reacts with the polyol,
It forms flexible polymer chains in the main skeleton. At this time, the hardness and the discharge deterioration resistance of the polymer can be obtained by selecting the ratio of the amount of the aromatic isocyanate to the aliphatic isocyanate, the type of the substituent and the aliphatic chain.

At least, when the aromatic isocyanate is used alone, the hardness of the polymer becomes too high, which promotes abrasion of the photoreceptor. However, the discharge deterioration resistance is good. Also, the hardness is too low with aliphatic isocyanate alone,
Tack is generated on the surface of the polymer, so that the charging member is greatly contaminated with toner, paper powder, and the like.

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

Irrespective of aromatic or aliphatic, the isocyanate used in the present invention has no trouble even if tri-, tetra-, cyanate or a dimer or trimer of isocyanate is used together with 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, and more preferably It is 9.0: 1.0 to 7.5: 2.5.

Examples of monomers applicable as the other polymer used in the present invention include, for example, monomers having an ethylenically unsaturated group, hydrocarbon monomers, unsaturated nitriles and vinyl. And acrylic acid and its derivatives and (meth) acrylic acid salts. Specific examples are shown below, but the present invention is not limited thereto.

Hydrocarbon monomers include styrenes [styrene and alkylstyrenes (α-methylstyrene, o-, m- or p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p- n-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, etc.)]
And aliphatic hydrocarbon vinyls (butadiene etc.).

Examples of unsaturated nitriles include nitriles (acrylonitrile, methacrylonitrile, etc.) and the like.

The vinyls include vinyl esters (vinyl acetate, vinyl propionate, etc.), vinyl ethers (vinyl methyl ether, vinyl ethyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl hexyl ketone, etc.), N-vinyl. Examples thereof include 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 and trifluoroethyl (meth) acrylate, etc.], heterocyclic (meth) acrylate [tetrahydro Furfuryl (meth) acrylate and the like], and amino group-containing (meth) acrylate [dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate and the like]} and the like.

As the (meth) acrylic acid salts, (meth)
Examples thereof include sodium acrylate, calcium (meth) acrylate and zinc (meth) acrylate.

Of these, particularly preferred are hydrocarbon monomers, unsaturated nitriles, acrylic acid and its derivatives, and (meth) acrylic acid salts. 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 if necessary. Examples of preferable electron conductors include graphite, metals (copper, aluminum, nickel and silver, etc.) and conductive polymers (polyaniline, polypyrrole, polythiophene, polyacetylene, polypyridine, polyacene, polyazulene, polydiphenylbenzidine, polyvinylcarbazole and poly (vinylcarbazole)). -3-alkylthiophene etc.). 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 group I or group II metals, and among them, salts of Li, Na and K having a relatively small cation radius are particularly preferable. The anions that compose 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 preferable are thiocyanate ion, perchlorate ion, trifluoromethanesulfonate ion and fluoroborate ion. Examples of the ammonium salt include carboxylic acid (adipic acid, phthalic acid, azelaic acid, etc.), phosphoric acid, boric acid, sulfonic acid (aryl sulfonic acid, etc.), 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 mixed and used.

The carbon that can be added to the present invention is not limited in the production method, and those produced by the furnace method, the channel method and the thermal method, and natural products (graphite etc.) can be used, but among them, the structure is easily formed. 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 40 to 500, particularly preferably 80 to 500. Also,
The specific surface area (BETm ² / g) is preferably 40 to 2000, and particularly preferably 45 to 1500. Further, the volatile content is preferably (weight%) 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, and examples of its structure are shown in FIGS. 1 to 6. In the case of so-called contact charging in which the charging member and the photoconductor are in contact with each other, the roller shape as shown in FIGS. 1 and 2 and the blade shape as shown in FIG. 3 can be mentioned. More preferably. Further, in the case of so-called non-contact-proximity charging, in which the charging member and the photosensitive member are close to each other with a distance of 1000 μm or less, preferably about 500 μm or less but not in contact with each other, FIG.
Various shapes such as a concentric shape with the photoconductor as shown in FIG. 5, an arc shape as shown in FIG. 5 and a plate shape as shown in FIG. 6 can be adopted. Among them, the concentric shape or the 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 multi-layer structure, the polymer of the present invention can be used in any coating layer.

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

The elastic coating layer contains the polymer of the present invention or other rubber or resin. When the polymer of the present invention is used, the properties of the polymer may be rubber-like or may be imparted with elasticity by making it an elastomer, etc. within a range that does not impair the characteristics of the present invention, and the above-mentioned other rubber or other resin may be further added. 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, silicone rubber, fluorine rubber, nitrile rubber, and acrylic. Rubber,
Examples include epichlorohydrin rubber and norbornene rubber. In addition, examples of the resins include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene. -Vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-
Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-
Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, etc. Styrene resin (styrene or styrene-substituted homopolymer or copolymer), vinyl chloride resin, styrene-vinyl acetate copolymer, rosin-modified maleic acid 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 electrical conductivity, and has a volume resistivity of 10 ⁷ Ω · cm or less, and further 10 ⁶ Ω.
-Cm or less, and particularly preferably 10 ^-2 to 10 ⁶ Ω-cm. Further, the film 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 photoconductor, specifically 3 mm or less, and further 2 mm or less, especially 20 μm to 1 m
It is preferably m.

Examples of the material to be used include, in addition to the above-mentioned polymer of the present invention, a metal vapor deposition film, a conductive particle dispersed resin, a conductive resin and the like. Specifically, examples of the metal vapor deposition film include those obtained by vapor deposition of metals such as aluminum, indium, nickel, copper and iron, and examples of the conductive particle dispersion resin include carbon, aluminum, nickel,
Conductive particles such as titanium oxide, urethane, polyester,
Examples thereof include those dispersed in a resin such as a vinyl acetate-vinyl chloride copolymer and polymethylmethacrylate, and examples of the conductive resin include polyvinylaniline, polyvinylpyrrole, polydiacetylene and polyethyleneimine. Among these, the conductive particle-dispersed resin is preferable 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 its volume resistivity is 1 to 6 digits, especially 2 digits higher than that of the conductive coating layer. It is preferable that the digit is higher by 5 digits, and the range is 10 ⁶
It is preferably 10 ¹² Ω · cm, particularly 10 ⁷ to 10 ¹¹ Ω · cm. In addition, the film thickness of the resistance coating layer is 1 μm to 500 μm, particularly 50 μm to 200 μm from the viewpoint of charging property.
Is preferred.

As the material to be used, in addition to the polymer of the present invention, a semiconductive resin, a conductive particle dispersed resin and the like can be mentioned. Specifically, as the semiconductive resin, ethyl cellulose, nitrocellulose, methoxymethylated nylon,
Resins such as ethoxymethylated nylon, copolymerized nylon, polyvinylpyrrolidone and casein, a mixture of these resins and the like can be mentioned.As the conductive particle dispersion resin, carbon, aluminum, conductive particles such as indium oxide and titanium oxide can be used. The semi-conductive resin, urethane, polyester, vinyl acetate-vinyl chloride copolymer, polymethacrylic acid, or other insulating resin may be dispersed in a small amount to adjust the resistance.

In the present invention, the resistance coating layer has a two-layer structure, and in order to improve the adhesiveness of the above-mentioned layers,
An adhesive layer can be provided between each layer.

The charging member of the present invention having any structure
Volume resistivity is 10² -10 ^TenΩ · cm
And particularly 10^Four -10⁸ Ω · cm
And are preferred. Furthermore, at least the volume resistance of the surface coating layer
The resistance is preferably within these ranges.

When the charging member of the present invention is used, regardless of whether the relationship between the charging member and the photosensitive member is contact or non-contact, if the surface of the charging member is rough, the unevenness causes a slight uneven charging, resulting in a defective image. May occur. Therefore, it is preferable that the surface of the charging member is smoother.
The IS B0601 surface roughness standard has a 10-point average roughness R _Z of 5 μm or less, and a maximum height R _max of 10
It is preferable that R _z is 2 μm or less, and further, R _max is 5 μm or less.

Further, when the charging member is used in contact with the photoconductor, the charging member is deformed (compression set) by being in contact with the photoconductor for a long period of time, which distorts the discharge area for charging. A difference may occur in the charging due to a difference between the portion and the other portion, 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 according to the method of JIS K6301, measured at a compression rate of 25%, left at 70 ° C. for 22 hours, and further left at room temperature for 30 minutes. It is particularly preferably 30% or less.

Further, when the charging member is used in contact with the photoconductor, if the surface of the charging member is too hard, the charging member rubs contaminants such as toner on the photoconductor with the photoconductor, causing mechanical damage. The toner may be melted on the photoconductor due to a factor, so that an image defect due to so-called fusion may occur. In particular, when the applied voltage is an AC superimposed bias, the above-mentioned phenomenon occurs more easily than when a 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 terms of A hardness defined by JIS K6301.
It is preferably equal to or less than 0 °, particularly preferably equal to 35 °.

In addition, when the applied voltage is an AC superposed bias, "charging noise" is generated by the vibration of the charging member due to the AC voltage.
In addition, the hardness may be 20 ° or less in consideration of the fact that a noise called "is generated" may cause a person to feel uncomfortable, and that the hardness of the charging member is reduced to absorb vibration and reduce the charging noise. preferable.

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

First, iron is used as the conductive support of the charging member,
A metal rod made of plated iron, aluminum, stainless steel, or the like is prepared. 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 or spray coating.

Finally, the resistance coating layer is provided by applying the material of the resistance coating layer on the conductive coating layer by dip coating, spray coating, gravure coating or the like.

The charging member of the present invention, as shown below,
It can be used for any of primary charging, transfer charging and static charging. Of course, you may use simultaneously.

The charging member of the present invention can be applied to, for example, an electrophotographic apparatus as shown in FIG. This apparatus comprises a charging member for primary charging (charging member of the present invention) 5, an image exposing means 6, a developing means 7, on a peripheral surface of an electrophotographic photoreceptor 11.
A transfer charging corona charger 8, a cleaning unit 9 and a pre-exposure unit 10 are arranged.

A voltage (eg, 20) is applied to the charging member 5 for primary charging, which is disposed in contact with the electrophotographic photosensitive member 11, from the outside.
DC voltage between 0V and 2000V and peak-to-peak voltage 40
Apply a pulsating current voltage on which an AC voltage of 00V or less is superimposed,
The surface of the electrophotographic photosensitive member 11 is charged, and the image exposing means 6 exposes the image on the document to the photosensitive member to form an electrostatic latent image. Next, the developer in the developing means 7 is attached to the photoconductor to develop (visualize) the electrostatic latent image on the photoconductor,
Further, the developer on the photosensitive member is transferred to the transfer target member 12 such as paper by the transfer charging unit 8, and the cleaning unit 11 collects the developer remaining on the photosensitive member without being transferred to the paper.

Although an image can be formed by such an electrophotographic process, when residual charges remain on the photoconductor, the pre-exposure means 10 irradiates the photoconductor with light before the primary charging, and the residual charge remains. 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. This apparatus comprises a corona charger 13 for primary charging, an image exposing unit 6, a developing unit 7, a transfer charging member (charging member of the present invention) 14, on the peripheral surface of an electrophotographic photoreceptor 11.
A cleaning unit 9 and a pre-exposure unit 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.
The developer on the electrophotographic photosensitive member can be transferred to a transfer target member such as paper by applying 0 to 1000 V). 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 exposing unit 6, a developing unit 7, a transfer charging corona charger 8, and a cleaning unit 9 are arranged on the peripheral surface of an electrophotographic photosensitive member 11.

A charge (for example, an AC peak-to-peak voltage of 500 to 2000 V) is applied to a charge-eliminating charging member (charging member of the present invention) 15 disposed in contact with the electrophotographic photosensitive member 11 to charge the electrophotographic photosensitive member. Can be discharged.

The charging member to be brought into contact with the photosensitive member according to the present invention is not limited to a specific method, and the charging member may be a fixed type or a moving type such as rotating in the same direction as the photosensitive member or in the opposite direction. Can be used. Further, the charging member can be made to function as a developer cleaning device on the photoconductor.

The voltage applied to the charging member in the direct charging of the present invention and the method of applying it depend on the specifications of each electrophotographic apparatus, but in addition to the method of instantly applying a desired voltage, the protection of the photoreceptor is also provided. Applying voltage in the order of DC → AC or AC → DC except for the method of increasing the applied voltage stepwise for the purpose of You can take the method of doing.

When the charging member of the present invention is used for the primary charging of the electrophotographic apparatus, it is possible to superimpose a DC voltage and an AC voltage on the electrophotographic photosensitive member in the image output area or to apply only the DC voltage. 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 in detail below with reference to examples, but the present invention is not limited to the following examples.

The production examples of the polymer of the present invention will be described below.

(Production Example) The accurately weighed polyol having the first oxyalkylene group and the second polyol having the second oxyalkylene group are uniformly mixed in a mixing reactor equipped with a stirrer. Next, an appropriate amount of a conductive agent such as carbon black, conductive titanium oxide, conductive tin oxide, etc. is added to the above mixture, and mixed until the conductive agent is sufficiently wet with the mixture and uniformly dispersed. Furthermore, aromatic isocyanate and fatty acid isocyanate are added to this mixture, mixed and stirred while defoaming, and then poured into a mold having a roller-shaped conductive support inserted therein at room temperature or higher, preferably 50 ° C. or higher, 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 polyol and the isocyanate, in consideration of the reaction acceleration, a catalyst, for example,
Cobalt naphthenate, triethylenediamine, stannic chloride, ethylmorpholine, n-butyltin trichloride and the like may be added.

Example 1 A roller-shaped charging member was obtained by using the polymers having the constitutions shown in Table 1.

The volume resistivity of the obtained charging member was wound around the outer periphery of the charging member with an aluminum foil in close contact with it, and a DC voltage (250 V) was applied between the support and the aluminum foil to obtain a tester (HIOKI 3116 DEGITAL MΩ HI).
The results measured by TESTER are shown in Table 1.

A copying machine (FC-2, manufactured by Canon Inc.) equipped with the charging member obtained as the charging means for the primary charging is installed.
The image is evaluated by applying a DC voltage of -1500V by using a product manufactured by K.K.), and visually observing an image defect of the obtained image due to uneven charging due to uneven resistance of the charging member. did. The results are shown in Table 2.
In the table, ⊚ indicates that the obtained image is excellent, ∘ indicates that it is good, Δ indicates that it is acceptable, and x indicates that it is not acceptable. Further, the photosensitive member of the above copying machine is a defective photosensitive member in which the photosensitive layer is peeled off by 1 mm ² to expose the aluminum drum, and the applied voltage is −
The pressure resistance was evaluated by displaying an image at 1800 V and observing the white voids in the image due to the dielectric breakdown. The results are shown in Table 2. In the table, ◎ is excellent (white blank is only the defective portion of the photoconductor), ○ is good (white blank is within 15 mm from the defective portion of the photoconductor in the longitudinal direction of the photoconductor), and Δ is practical (white blank is the photosensitive portion). 30m in the longitudinal direction beyond 15mm
m), × is not practical (white blank is 3 in the longitudinal direction of the photoconductor)
It exceeds 0 mm).

The volume resistivity, image and pressure resistance of the container were evaluated at 32 ° C., 85% RH (environment 1) and 10 ° C.
The environment of 5% RH (Environment 2) was appropriately selected and performed.

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

In addition, the cartridge of the above copying machine is 32
After leaving it in the environment of 85 ° C and RH of 85% for one month, it is installed in the main body of the copying machine and a DC voltage of -1500V is applied to output an image. By observing the image defect caused by the distortion of the charging member, The strain resistance was evaluated. The results are shown in Table 2. In the table, ◎ is excellent (no image defect), ○ is good (slightly streaked in halftone image), △ is practical (slightly streaked), × is not practical (streaked) Indicates that.

The charging member thus obtained was mounted as a primary charging means of a laser beam printer (laser jet Si, manufactured by Hewlett Packard), at 32 ° C. and 85 ° C.
An image output durability test of 10,000 was performed in a% RH environment, and the fusion state after durability was evaluated. The results are shown in Table 2. In the table, ◎ is excellent (no fusion), ○ is good (observed on the photoconductor but does not appear in the image), Δ is practical (slightly occurs in the image), × is not practical (image It occurs on the entire surface).

Further, the surface roughness (R
_Z ), compression set and hardness were measured by the methods described above. The results are shown in Table 1.

(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,
There is little resistance variation in the environment from high temperature and high humidity to low temperature and low humidity, there is no composition change even by repeated discharge-charging, and the dispersibility of the conductive additive is good, so uniform charging is possible and therefore excellent. Images can be supplied for a long time.

[Brief description of 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 is an electrophotographic apparatus 1 to which the charging member of the present invention is applied.
It is a schematic block diagram of an example.

FIG. 8 is an electrophotographic apparatus 1 to which the charging member of the present invention is applied.
It is a schematic block diagram of an example.

FIG. 9 is an electrophotographic apparatus 1 to which the charging member of the present invention is applied.
It is a schematic block diagram of an example.

Claims (2)

[Claims] 1. A charging member for electrophotography having a coating layer on a conductive support, wherein the coating layer reacts a polyether polyol having at least two oxyalkylene groups with an aromatic isocyanate and an aliphatic isocyanate. A charging member for electrophotography, which is a polymer obtained by the above. 2. The oxyalkylene group is at least 2
The charging member for electrophotography according to claim 1, wherein the polyether polyol having at least one species has an oxyalkylene group that imparts hydrophilicity and an oxyalkylene group that imparts hydrophobicity.