JP2002236407A - Electrifying member, process cartridge and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member which has an elastic layer having sufficient elasticity and adhesiveness with a core metal and which shows extremely uniform electrification property without causing distortion in a coating layer on the elastic layer. SOLUTION: In the electrifying member having a conductive core metal, a semiconductive foamed elastic layer on the outer surface of the core metal, and a functional multilayered film on the semiconductive foamed elastic layer, the semiconductive foamed elastic layer is produced by passing the core metal and a semiconductive rubber composition before vulcanizing and foaming through the cross head die of an extrusion machine to dispose the composition on the outer surface of the core metal and then vulcanizing and foaming the composition. The semiconductive rubber composition has 15 to 30 Mooney viscosity and has <=40% vulcanization percentage when the foaming pressure reaches 50%. The functional multilayered film is a multilayered tube containing thin layers which are difficult to be formed and applied as a single tube. The process cartridge and the electrophotographic device have the above electrifying member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member which is placed in contact with a member to be charged and charges the member by applying a voltage. Further, the present invention is a process cartridge and an electrophotographic apparatus provided with such a charging member.

[0002]

2. Description of the Related Art In recent years, as a charging means used in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a charging means of a contact charging system has been adopted. Contact charging is
By applying a voltage to a charging member that is placed in contact with the object to be charged, the object to be charged is charged to a predetermined polarity and potential, and the voltage of the power supply can be reduced. There are advantages that generation can be reduced, the structure is simple and the cost can be reduced.

In addition to the method of applying only DC (DC application method), the voltage applied to the charging member has a peak-to-peak voltage that is twice or more the charging start voltage of the charged body when a DC voltage is applied to the contact charging member. There is a method of forming an oscillating electric field having a voltage (an electric field whose voltage value changes periodically with time) between a contact charging member and a charged body to charge the surface of the charged body (AC application method). Can be more uniformly charged.

Further, the contact charging device is based on a roller type charging device using a charging member as a roller-shaped member (charging roller) (Japanese Patent Laid-Open Publication No. Sho 63-163).
7380 and JP-A-56-91253), a blade-type charger (such as JP-A-56-194349) as a blade-like member (charging blade) and a brush as a brush-like member (charging brush). Type charger (JP-A-64-24264).

[0005] The charging roller is rotatably supported by a bearing and pressed against the member to be charged at a predetermined pressure, and is rotated by the movement of the member to be charged. Further, the charging roller is usually a multilayer having a core provided at the center as a substrate, a conductive elastic layer provided in a roller shape on the outer periphery of the core, and an intermediate layer and a surface layer further provided on the outer periphery thereof. It is a structure.

[0006] Of the above layers, the metal core (metal layer) is a rigid body for maintaining the shape of the roller, and also has a role as a power supply electrode.

Further, the elastic layer has a size of 1 × 10 ² to 1 ×.
Since it is required to have a volume resistivity of 10 ¹⁰ Ω · cm and to be able to ensure uniform contact with the member to be charged by being elastically deformed, usually, a rubber hardness (JISA) 70 to which conductivity is imparted is used. A vulcanized rubber having a flexibility of not more than a degree is used. Conventional charging rollers include a foam type using a rubber foam (or sponge-like rubber) as an elastic layer and a solid type using no rubber foam. In the AC application method, there is a problem that a force acts between the charging roller and the member to be charged due to the action of the oscillating electric field, and the member to be charged vibrates to generate noise. It is preferred to use the body.

[0008] The intermediate layer is provided on the surface layer by relieving the compression set of the elastic layer and preventing bleeding of a softener such as an oil or a plasticizer used for lowering the hardness of the elastic layer. It has functions such as increasing the degree of freedom of the material used. The surface resistivity of the intermediate layer is usually 1 ×
It is 10 ⁵ to 1 × 10 ¹² Ω / □, and has conventionally been formed by applying a conductive paint or covering a seamless tube.

The surface layer improves the charging uniformity of the member to be charged, prevents the occurrence of leaks due to pinholes or the like on the surface of the member to be charged, and also prevents the adhesion of toner particles and paper powder. It also has functions. The surface layer usually has a surface resistivity of 1 × 10 ⁵ to 1 × 10 ¹³ Ω / □ and, like the intermediate layer, was formed by applying a conductive paint or covering a seamless tube.

As a method for producing the elastic layer, an unvulcanized and unfoamed semiconductive foamable rubber material is extruded into a tube by an extruder, and then heated and vulcanized and foamed in a vulcanizing furnace or the like. A method of bonding a cored bar and a semiconductive foamed rubber tube by forming a conductive foamed rubber tube, further inserting a core coated with a hot melt adhesive into the semiconductive foamed rubber tube, and heating the cored bar. It has been known. However, this method has a problem that the manufacturing cost is increased due to the large number of steps.

On the other hand, Japanese Unexamined Patent Publication No. Hei 10-221930 discloses that a core metal coated with an adhesive is passed through a crosshead die of an extruder, and an unvulcanized and non-foamed half-core After arranging the conductive foamable rubber material, by using a vulcanizer / continuous vulcanizing furnace, etc., the vulcanization and foaming of the rubber material and the bonding between the core metal and the semiconductive foamed rubber are simultaneously performed. A method for reducing the number of steps is described.

However, in this method, when a semiconductive foamed rubber composition having a high foaming ratio is used, the foamed semiconductive foamed rubber makes it easier for the semiconductive foamed rubber to rise from the core metal. Therefore, there was a problem that a foamed rubber having sufficiently low hardness could not be obtained, and charging unevenness was caused by an effect of a raised portion.

As another method for obtaining a foamed rubber having a low hardness, a method of adding a large amount of a softening agent to a rubber composition is also known. If kneading cannot be performed due to slippage during kneading or if a large amount of a softening agent is added little by little so as not to cause a slip, kneading takes a lot of time and leads to an increase in cost. There was a problem that it would.

On the other hand, as a method of coating the tube, first, both ends of the intermediate layer tube are fixed to the inner wall of the cylindrical mold,
There is a method in which the pressure between the tube and the inner wall of the cylindrical mold is reduced to bring the tube into close contact with the inner wall of the mold, and an elastic roller having an elastic layer formed on the outer periphery of the core is inserted while being pressed. Surface layer tubes can be similarly coated.

However, by preparing a plurality of single-layer tubes and externally fitting them one by one to the elastic layer, when using the charging roller for electrophotography with a coating layer formed by overlapping, both ends of the charging roller are required. Load on the part,
When pressed against the member to be charged at a predetermined pressure and rotated by the movement of the charged member, a torsion force acts due to the difference in the pressure contact force between the end and the center, causing a displacement between the superposed tube layers. As a result of kinking of the tube, a difference in image density may occur between the end and the center. This phenomenon is more likely to occur as the elastic layer is softer and as the pressing force at both ends is larger.

As a method for preventing the kinking of the tube, it is possible to increase the difference between the inner diameter of the tube and the outer diameter of the elastic layer to increase the tightening force of the tube on the elastic layer. The hardness became hard and the charging noise was likely to increase.

When the tube is made of a thermoplastic resin or when the elastic layer has a high hardness, the outer diameter of the charging roller becomes larger due to the elongation of the tube. In some cases, the charged body could not be sufficiently charged. This phenomenon also occurs more remarkably as the elastic layer becomes harder.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to provide an elastic layer having sufficient elasticity and adhesiveness to a metal core, and a very uniform charging without any twisting of the coating layer on the elastic layer. An object of the present invention is to provide a charging member exhibiting the property.

Another object of the present invention is to provide a process cartridge and an electrophotographic apparatus having such a charging member.

[0020]

That is, the present invention provides a conductive core, a semiconductive foamed elastic layer on the outer periphery of the cored bar, and a functional multilayer film on the outer periphery of the semiconductive foamed elastic layer. In the charging member having the semiconductive foamed elastic layer, the cored bar and the unvulcanized unfoamed semiconductive rubber composition were passed through a crosshead die of an extruder and arranged on the outer periphery of the cored bar. The semiconductive rubber composition has a Mooney viscosity of 15 to 30 and a foaming pressure of 50%.
The vulcanization% at the time of reaching 40% is not more than 40%, and the functional multi-layer film is a multi-layer tube including a thin layer which is difficult to be formed and coated as a tube by itself. It is a charging member.

Further, the present invention is a process cartridge and an electrophotographic apparatus having the charging member.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

FIG. 1 shows an example of a charging member (hereinafter also referred to as a charging roller) 1 of the present invention, which is used as a charger of an electrophotographic apparatus. This charging roller has a semiconductive foamed elastic layer 3 made of an elastic material on the outer periphery of a cored bar 2 made of a good conductive material such as metal, alloy and conductive plastic. The outer periphery has a tubular functional multilayer film 4. In the case of FIG. 1, the functional multilayer film 4 includes an inner layer 4b and an outer layer 4a.

As the core metal (metal layer) 2 in the present invention, a good conductor such as aluminum, stainless steel, plated iron, brass or an alloy containing these is preferably used. The core metal 2 used in the present invention is 3
Preferably having a diameter of from 10 to 10 mm,
It may be a metal tube having a thickness of about 1.5 mm or a rod shape.

The semiconductive foamed elastic layer 3 is formed by passing a conductive core 2 and an unvulcanized and unfoamed semiconductive rubber composition through a crosshead die of an extruder to form an outer periphery of the core 2. After being placed on top, it can be obtained by vulcanizing and foaming.

In the present invention, the viscosity of the semiconductive rubber composition is 100 in accordance with JIS K-6300.
It is 15-30 in Mooney viscosity (ML1 + 4) of ° C. If the Mooney viscosity is less than 15, the kneading processability deteriorates remarkably, such as sticking to a roll at the time of kneading. If the Mooney viscosity is more than 30, it is difficult to increase the foaming ratio. The adhesion of the product is poor, and the adhesiveness is deteriorated during foam vulcanization.

The viscosity of the semiconductive rubber composition can be affected by the kind and amount of the materials used, such as the rubber component, the conductive material, and the softener, as well as the conditions for kneading them. In, the means for achieving Mooney viscosity is not particularly limited as long as the Mooney viscosity is 15 to 30.

In the semiconductive rubber composition used in the present invention, the relationship between the foaming rate and the vulcanization rate measured at 140 ° C. reaches 50% when the maximum value of the foaming pressure is 100%. Vulcanization% (hereinafter% Cure @ TP5)
0) is 40% or less of the maximum value of the vulcanization percentage. That is, the foaming speed is dominant in relation to the vulcanization speed. % Cure
If the ＠ TP50 is larger than 40%, the adhesion between the cored bar 2 and the foamed rubber deteriorates. Although the cause is not clear, the vulcanization reaction is more than a certain degree (more than 40% of the final vulcanization reaction amount) in the initial stage of the bubbling gas generation reaction (until the end of the 50% reaction amount of the final bubbling gas generation reaction). When a foamed rubber composition that advances is used, a large amount of foaming gas is generated after vulcanization of the roller surface is progressed by heating from the outside of the roller, and excessive foaming gas is released from the surface. This is presumed to be easy to accumulate between the core metal 2 and the rubber. Preferably,% Cure @ TP50 is 20
Set to less than%. By setting the% Cure @ TP50 to 20% or less, the core metal 2 can be used even for a material having a high expansion ratio.
And the foam rubber are sufficiently adhered.

FIG. 2 is a graph showing an example of the relationship between the foaming pressure and the vulcanization percentage. In the figure, 5 indicates a foaming pressure curve, and 6 indicates a vulcanization curve (the degree of progress of vulcanization is represented by a torque applied to a test piece). 7 is a point where the foaming pressure is 50%, and the vulcanization percentage when the foaming pressure reaches 50%, that is, Cure @ TP5
0) is 8. 9 shows a point where the vulcanization% is 40%.

The adjustment of% Cure @ TP50 is appropriately adjusted by the type of the vulcanization accelerator, the type of the foaming agent, and the foaming aid.

The rubber component of the semiconductive rubber material used in the present invention is not particularly limited, but a rubber which can be sulfur-vulcanized by various vulcanization methods is preferable. Specifically, ethylene-propylene diene copolymer rubber (EPDM), isoprene rubber (IR), butadiene rubber (BR), styrene-
Butadiene copolymer rubber (SBR), natural rubber (NR),
Acrylonitrile-butadiene copolymer rubber (NBR) and the like are preferred, and among them, ethylene-propylene-diene copolymer rubber (EPDM) is more preferred from the viewpoint of excellent ozone resistance and easy adjustment of the vulcanization rate. .

The vulcanization accelerator is not particularly limited, and a general rubber vulcanization accelerator can be used.

As the foaming agent, a foaming agent for sponge rubber can be used. For example, azodicarbonamide (ADC)
A), p, p'-oxybis (benzenesulfonylhydrazide) (OBSH), N, N'-dinitropentamethylenetetramine (DPT), sodium hydrogencarbonate and the like are preferable, and among them, from the viewpoint that the vulcanization rate is hardly increased. Azodicarbonamide (ADCA) is more preferred.

As the foaming auxiliary, a general foaming auxiliary can be used.

Examples of the conductive material to be incorporated into these rubber compositions include conductive powders such as carbon black, graphite, metals and various conductive metal oxides (such as tin oxide and titanium oxide), carbon fibers and metal oxides. Various conductive fibers such as short fibers of the product can be used. The compounding amount thereof is preferably 4 to 1 with respect to 100 parts by mass of all rubber components, including carbon black as a component of the present invention.
00 parts by mass, particularly preferably 5 to 50 parts by mass, whereby the volume resistance of the semiconductive foamed elastic layer 3 is 1 × 10 ⁴
It is preferable to adjust to about 1 × 10 ⁹ Ω · cm.

In the present invention, in particular, the semiconductive rubber composition contains 4 to 15 parts by mass of a conductive carbon black having a DBP oil absorption of 300 (ml / 100 g) or more per 100 parts by mass of the rubber component. It is preferable that the composition is a semiconductive rubber composition containing a softener twice or more the amount of the conductive carbon black. By using carbon black having a very high DBP oil absorption of 300 (ml / 100 g) or more, a softener is sucked in the initial stage of kneading. Is less likely to occur. In addition, the amount of the carbon black added is 4 parts per 100 parts by mass of the rubber component.
If the amount is less than 10 parts by mass, it is difficult to obtain the slip prevention effect.
If it exceeds 5 parts by mass, the hardness tends to increase. In the present invention, the DBP oil absorption is 400 (ml / 100 g).
More preferably, it is the above. The DBP oil absorption in the present invention is the DBP oil absorption per 100 g when DBP is added to carbon black, and can be measured by an absorbometer.

The carbon black having a DBP oil absorption of 300 (ml / 100 g) or more includes porous carbon black, and examples thereof include Ketjen Black EC and Ketjen Black 600JD. In addition, as the softener, a general rubber softener can be used,
Among them, paraffin oil is preferred.

In the present invention, if necessary, the semiconductive rubber composition may further contain another conductive agent, a reinforcing agent, a filler,
Ordinary rubber compounding agents such as an antioxidant and a vulcanization accelerator can be appropriately mixed.

In the present invention, it is preferable that the roller after polishing the elastic layer to 3 mm after vulcanization and foaming of the semiconductive rubber composition has an Asker C hardness of 33 degrees or less under a load of 500 g. If the hardness is higher than this, the charging noise is likely to increase. In addition, since the elastic layer is easily distorted at the time of contact with the member to be charged, there is no contact gap between the charging roller and the member to be charged, so that the contact is uniform, resulting in less noise ripple and less toner contamination. It is possible to obtain a charging roller that is less likely to cause image unevenness due to uniformity.

In the present invention, the thickness of the elastic layer can be appropriately adjusted according to the model on which the charging member is mounted, but is preferably from 1 to 20 mm, particularly preferably 2 to 20 mm.
It is preferably about 20 mm.

Next, the functional multilayer film 4 used in the present invention will be described. The functional multilayer film 4 in the present invention is a polymer previously formed in the form of a seamless tube, and covers the semiconductive foamed elastic layer 3 on the outer periphery of the cored bar 2.

The materials constituting the functional multilayer film 4 include:
Any extrudable rubber or thermoplastic resin may be used. Specifically, ethylene propylene rubber (EPDM), ethylene vinyl acetate, ethylene ethyl acrylate, ethylene methyl acrylate, styrene butadiene rubber, polyester, polyurethane Polyamides such as nylon 6, nylon 66, nylon 11, nylon 12, and other copolymerized nylon, styrene ethylene butyl, ethylene butyl, nitrile butadiene rubber, chlorosulfonated polyethylene, polysulfide rubber, chlorinated polyethylene, chloroprene rubber, butadiene Rubber,
Rubbers such as 1,2-polybutadiene, isoprene rubber and polynorbornene rubber, and styrene-butadiene-
Thermoplastic rubbers such as styrene (SBS) and styrene-butadiene-styrene water additive (SEBS) can be used, but are not particularly limited.

Alternatively, elastomers such as the above-mentioned resins and copolymers and modified elastomers, and polyethylene, polypropylene, polyethylene terephthalate (PET) and polybutylene terephthalate (PB)
T) and other saturated polyesters, polyethers, polyamides, polycarbonates, polyacetals, acrylonitrile butadiene styrene, polystyrene, high impact polystyrene (HIPS), polyurethane, polyphenylene oxide, polyvinyl acetate, polyvinylidene fluoride, polytetrafluoroethylene, acrylonitrile-butadiene -Styrene resin (ABS), acrylonitrile-ethylene propylene rubber-styrene resin (AE
S) and styrene-based resins such as acrylonitrile-acrylic rubber-styrene resin (AAS), and resins such as acrylic resins, vinyl chloride resins and vinylidene chloride resins, and combinations of materials composed of these copolymers are preferred.

Further, a polymer alloy or a polymer blend comprising two or more kinds of polymers selected from the above rubbers, thermoplastic elastomers and thermoplastic resins can also be used. The tube of the functional multilayer film 4 of the present invention is formed by extrusion molding, injection molding and blow molding of the above-mentioned various polymers and a conductive polymer composition comprising the following conductive material and other additives as necessary. It can be obtained by forming a film in the shape of a tube by using the method described above. Among the above various molding methods, the extrusion molding method is particularly preferable. Further, it is preferable to use a vertical tube extruder in order to obtain a uniform thickness of each thin film layer of the tube to be formed and a more uniform dispersibility such as a conductive material.

As the conductive material, known materials can be used, for example, carbon fine particles such as carbon black and graphite; metal fine particles such as nickel, silver, aluminum and copper; tin oxide, zinc oxide, titanium oxide, and the like.
Conductive metal oxide fine particles containing aluminum oxide and silica as main components and doped with impurity ions having different valences; conductive fibers such as carbon fibers; metal fibers such as stainless steel fibers; carbon whiskers and potassium titanate whiskers. A conductive whisker such as a conductive potassium titanate whisker whose surface is made conductive with a metal oxide or carbon; and a conductive polymer fine particle such as polyaniline and polypyrrole.

The tube of the functional multilayer film 4 used in the present invention can be used by simply forming it by the above-mentioned various molding methods. For example, in order to obtain more excellent durability and environmental resistance, the above-mentioned tube is used. The seamless tube obtained by various molding methods can be further crosslinked to obtain a conductive crosslinked polymer. As a method of cross-linking a conductive polymer formed in a tube shape, a cross-linking agent such as sulfur, an organic peroxide and an amine is added in advance depending on the type of the polymer, and the cross-linking is performed at a high temperature. Is effective, and a radiation cross-linking method of cross-linking by irradiating radiation such as an electron beam or γ-ray is effective. Among the above various crosslinking methods, the electron beam crosslinking method is preferred in that there is no risk of contamination of the member to be charged due to transfer of a crosslinking agent or a decomposition product thereof, and further, there is no need for high-temperature treatment and safety.

The functional multilayer film 4 used in the present invention preferably has a surface resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω / □, particularly 1 × 10 ⁶ to 1 × 10 ⁹ Ω / □. □ is preferred.

The functional multilayer film 4 according to the present invention comprises:
Since the thin-layered tubes, which are appropriately separated in function, are a multi-layered film formed integrally and simultaneously, it is not necessary to make each layer unnecessarily thick, so that the flexibility of the semiconductive foamed elastic layer 3 is effective. It is possible to draw it out. The preferred thickness of the functional multilayer film 4 is 150 μm to 800 μm in the multilayer thickness.
μm, and more preferably 200 μm to 600 μm.

Next, the extruder used in the present invention is shown in FIG.
This will be described with reference to FIG. The die 10 used for molding is provided with an inner and outer double annular extrusion flow path around a central through hole 11 for air introduction. The elastomer 13 for the inner layer 4b constituting the layer film 4 and the elastomer 15 for the outer layer 4a constituting the functional multilayer film 4 from the second extruder 14 are injected under pressure into the outer channel, respectively. The tube 17 of the functional multilayer film 4 obtained by laminating and extruding the outer layer 4a with the outer layer 4a is cooled by a water cooling ring 16 provided on the outer periphery thereof, and is cooled by a tube feeder 18
, And sequentially cut to a predetermined length to cover the semiconductive foamed elastic layer 3 having the metal core 2 as a functional multilayer film 4 for a charging roller in the next step.

As described above, in the present invention, even if the thickness of a single layer is 100 μm or less, which is difficult to cover as a single tube, the thickness of a multiple layer is 150 μm.
m, preferably 200 μm or more, so that it can be handled as a single tube. For example, when the thickness of the outer layer portion 4a / the inner layer portion 4b is 75
It is possible to handle as a single tube by layering thin layers, such as μm / 75 μm and 75 μm / 125 μm, which are difficult to cover alone as a tube. Needless to say, the outer layer 4a / inner layer 4b has a thickness of 100 μm / 400 μm or 100 μm / 200 μm.
m, 50 μm / 350 μm, 20 μm / 350 μm, etc., can also be coated with a functional multi-layered film including a thin layer which is difficult to coat alone as a tube.

In order to form a thin layer more thinly,
Means for increasing the take-up during extrusion molding and further reducing the film thickness at the extrusion port is also effective. Also,
By appropriately performing aging after stretching, stress due to stretching for thinning can be reduced.

In the present invention, for example, the outer layer 4a has a surface resistance of 1 × 10 ⁶ to 1 × 10 ¹² Ω / □, preferably 1 × 10 ⁷ to 1 × 10 ⁹ Ω / □ in order to have a pressure resistance. A resin layer is disposed, and 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω /
□, preferably a resin layer of 1 × 10 ⁸ to 1 × 10 ¹⁰ Ω / □, which is an ideal functional multi-layer for a roller such as a charging roller which needs to control the surface potential of the roller. It becomes a film.

When it is necessary to form a plurality of tubes and superimpose them on each other to integrate them, even if the material of each layer is the same kind of resin or different kinds of resin, the interface space is reduced. Therefore, the adhesiveness between the layers tends to be insufficient. As a result, if the tightening force of the tube to the elastic layer is not increased, the tube may be misaligned during use as a charging roller, resulting in an image defect. However, as described above, when the tightening force is strong, the apparent hardness of the elastic layer becomes hard, and the adverse effect that the charging noise is deteriorated also appears.

On the other hand, in the present invention, even if different kinds of resins are used, they come into contact with each other in a high-pressure molten state during the simultaneous multilayer extrusion process, are extruded as a multilayer, and are fixed in that state. Since sufficient adhesion is obtained as a charging member, it is possible to reduce the tightening force of the tube on the elastic layer.

The inner diameter of the tube of the functional multilayer film 4 obtained by the present invention is not particularly limited, and is determined by the outer diameter of the roller using the same.
It is common to use small diameter tubes of 10 mm, preferably 10-20 mm.

When a charging roller or a developing roller is manufactured using the tube of the functional multilayer film 4 obtained by the present invention, a roller in which the semiconductive foam elastic layer 3 is coated on the outer periphery of the cored bar 2 in advance is used. The tube of the functional multi-layer film 4 may be fitted around the outer periphery.

In this fitting, it is preferable that the inner diameter of the tube of the functional multilayer film 4 is slightly smaller than the outer diameter of the semiconductive foamed elastic layer 3 so as not to cause wrinkles on the roller. The outer diameter of the roller as a product is 1
When the thickness of the tube of the functional multilayer film 4 is 0.4 mm including the inner and outer layers, the outer diameter of the semiconductive foamed elastic layer 3 having the cored bar 2 is set to 11.3 mm. It is preferable that the inner diameter of the tube of the functional multilayer film 4 is about 11.1 mm.

When the tube of the functional multilayer film 4 is fitted, the inner surface thereof or the outer periphery of the semiconductive foamed elastic layer 3 may be subjected to a primer treatment and adhered if necessary.
It is also possible to fix by pressure bonding without performing this processing.

The electrophotographic photosensitive member, exposure means, developing means, transfer means and cleaning means used in the present invention are not particularly limited.

FIG. 4 shows an example of the configuration of an electrophotographic apparatus provided with a process cartridge having the conductive member of the present invention as primary charging means.

In FIG. 4, reference numeral 19 denotes an electrophotographic photosensitive member which is driven to rotate at a predetermined peripheral speed in the direction of the arrow. In the rotation process, the electrophotographic photosensitive member 19 is uniformly charged at a predetermined positive or negative potential on its peripheral surface by the charging member 1 of the present invention as a primary charging means, and then is subjected to slit exposure, laser beam scanning exposure, or the like. It receives exposure light 20 from exposure means (not shown). Thus, an electrostatic latent image is sequentially formed on the peripheral surface of the electrophotographic photosensitive member 19.

The formed electrostatic latent image is then transferred to developing means 2
1, and the developed toner developed image is
An electrophotographic photosensitive member 19 and a transfer unit 22 are supplied from a paper feeding unit (not shown).
Is sequentially transferred by the transfer means 22 to the transfer material 23 fed in synchronization with the rotation of the electrophotographic photosensitive member 19.

The transfer material 23 having undergone the transfer is separated from the electrophotographic photosensitive member surface, introduced into the fixing means 24 and subjected to fixing to be printed out of the apparatus as a copy.

The surface of the electrophotographic photoreceptor 19 after the transfer is cleaned and cleaned to remove the untransferred toner by the cleaning means 25, and is used for repeated image formation.

In the present invention, a process cartridge 27 which supports the electrophotographic photosensitive member and the charging member integrally and can be detachably attached to the electrophotographic apparatus using means such as a rail 26 can be used. Such a process cartridge may further include a developing unit and / or a cleaning unit.

[0066]

Hereinafter, the present invention will be described in more detail with reference to specific examples. [Example 1]

(Core metal) The core metal 2 was extruded into a rod having a diameter of about 6 mm by extruding an iron material, and was extruded to a length of 260 mm.
After that, this was subjected to nickel plating to a thickness of about 3 μm. Further, a hot melt adhesive was applied to the surface of the cored bar 2.

100 parts by mass of EPDM (trade name: Esplen 505, manufactured by Sumitomo Chemical Co., Ltd.) as a main raw material, and conductive carbon black (trade name: Ketjen Black 60)
0JD, 12 parts by mass of Lion Akzo Co., Ltd., paraffin oil (trade name: Diana Process Oil PW-38)
0, 75 parts by mass of Idemitsu Kosan Co., Ltd., 5 parts by mass of two types of zinc oxide, 1 part by mass of stearic acid, and 5 parts by mass of calcium oxide (trade name Vesta BS, manufactured by Inoue Lime Industry Co., Ltd.) as a dehydrating agent. 2 parts by weight of 2-mercaptobenzothiazole (MBT) as a vulcanization accelerator, 1 part by weight of zinc dibutyldithiocarbamate (ZDBC), 2 parts by weight of dipentamethylenethiuram tetrasulfide (DPTT), tellurium diethyldithiocarbamate (TDEC) 2 Parts by mass,
2 parts by mass of sulfur as a vulcanizing agent and p, p'-oxybis (benzenesulfonyl hydrazide) (OBS) as a foaming agent
H) 6.5 parts by mass and azodicarbonamide (ADC)
A) 5.5 parts by mass were kneaded to obtain a semiconductive foamed rubber composition for the semiconductive foamed elastic layer 3.

Regarding the obtained composition, JIS K-63
Mooney viscosity at 100 ° C according to 00 (ML1 + 4)
Was 21. Further, using a vulcanization tester MDR-200P (manufactured by Alpha Technologies) with a foaming pressure measuring function at 140 ° C.,% Cure @ TP5
When 0 was measured, it was 35%. Next, the semi-conductive foamed rubber composition and the core 2 coated with the adhesive are simultaneously coated with an unvulcanized and unfoamed semi-conductive rubber layer on the outer periphery of the core 2 by a crosshead die extruder. Formed.

Next, this was put into a continuous hot-air stove at 200 ° C. to perform vulcanization and foaming, and the end of the elastic layer was cut off to make the length in the axial direction 225 mm, and a rubber roller grinder (traverse grinder) , Manufactured by Mizuguchi Manufacturing Co., Ltd.)
After grinding until hardness measurement, a semiconductive foamed elastic layer having an outer diameter of 11.3 mm was obtained. Asker C hardness under a load of 500 g was 28 degrees.

(Tube formation of functional multilayer film 4) As a material of the outer layer 4a of the functional multilayer film 4, a styrene elastomer (styrene-ethylene / butylene-olefin copolymer elastomer (trade name: Dinalon, Nihon Gosei) 100 parts by mass of rubber), 50 parts by mass of low-density polyethylene and carbon black (trade name Ketjen Black EC,
14 parts by mass (manufactured by Lion Akzo) were mixed in a V-type blender for several minutes. This is further reduced using a pressurized kneader to 1
The mixture was melt-kneaded at 90 ° C. for 10 minutes, cooled, pulverized by a pulverizer, and pelletized by a single screw extruder.

As materials for the inner layer 4b, 100 parts by mass of a polyurethane elastomer (trade name: Kuramilon, manufactured by Kuraray Co., Ltd.), 17 parts by mass of carbon black (Ketjen Black EC, manufactured by Lion Akzo Co., Ltd.), magnesium oxide 10
Parts by mass and 1 part by mass of calcium stearate were pelletized in the same process as the material of the outer layer 4a.

Using a vertical extruder (a custom-made product manufactured by Plagiken Co., Ltd., see FIG. 3), these pellets are combined into a double layer with one crosshead, and hot water (4
(0-90 [deg.] C.), cooled and taken off. Thus, a tube of the functional multilayer film 4 having an inner diameter of about 11.1 mm was obtained.

A part of the tube not used for coating the semiconductive foamed elastic layer 3 is sampled and cut out to measure the surface resistivity of the inner layer 4b (back side) and the outer layer 4a (front side) with a high resistivity meter. (Hiresta IP, manufactured by Dia Instruments), the surface resistivity of the inner layer 4b was 2.0 × 10 ⁸ Ω / □, and the surface resistivity of the outer layer 4a was 5.0 × 10 ⁸ Ω. / □. The cross section was observed with a video microscope, and the thickness of the inner layer 4b and the outer layer 4a was observed.
0 μm, and the thickness of the outer layer 4a was 100 μm.

Next, the tube of the functional multilayer film 4 was
What was cut to a length of 30 mm was fitted around the outer periphery of the semiconductive foamed elastic layer 3 by a tube coating device (not shown),
The charging roller was obtained by pressure contact. The outer diameter of the charging roller is
It was 12.15 mm.

This charging roller is used for a primary charger of a laser beam printer (trade name: LBP-1660, manufactured by Canon) (the contact spring pressure at the time when the charging roller contacts both ends of the charging member at both ends is 500 g per side). As a result of performing image formation, no gap is generated between the functional multilayer film 4 and the semiconductive foamed elastic layer 3, and the functional multilayer film 4 is not wrinkled,
A good image was obtained without image irregularities, linear or dot-like abnormal portions.

Further, in order to evaluate the noise during image formation, the A-characteristic was corrected at a distance of 20 cm from the center line of the electrophotographic photosensitive member in the generatrix direction using a noise meter (trade name: NL-05, manufactured by RION). When the sound thickness level was measured, the amount of change in the charging sound during one rotation period of the charging roller was within 1 dB.

When the outer shape of the charging roller was measured after being left for three months, the outer diameter was unchanged at 12.15 mm, and a good image was obtained.

[Comparative Example 1] Outer diameter similar to that of Example 1
3 mm, semiconductive foamed elastic layer 3 with Asker C hardness of 28 degrees
Was prepared.

As materials for the outer layer 4a, 100 parts by mass of a styrene-based elastomer (styrene-ethylene / butylene-olefin copolymer elastomer, trade name: Dinalon, manufactured by Nippon Synthetic Rubber Co., Ltd.), 50 parts by mass of low-density polyethylene, and carbon black ( Brand name Ketchen Black E
C, manufactured by Lion Akzo Co., Ltd.) was mixed for several minutes in a V-type blender. This was further melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader, cooled, pulverized by a pulverizer, and pelletized by a single screw extruder.

Using a vertical extruder (a custom-made product manufactured by Plagiken Co., Ltd.), only the outer layer is extruded into hot water (40 to 90 ° C.) at an appropriate temperature using a crosshead for a single layer, and further cooled. And picked it up. Thus, the inner diameter 11.8
mm, film thickness 200 μm, surface resistivity 8.0 × 10 ⁷ Ω /
The surface layer tube of □ (single-layer tube for outer layer) was obtained.

As materials for the inner layer 4b, 100 parts by mass of a polyurethane elastomer (trade name: Kuramilon, manufactured by Kuraray Co., Ltd.), 17 parts by mass of carbon black (Ketjen Black EC, manufactured by Lion Akzo Co., Ltd.), magnesium oxide 10
Parts by mass and 1 part by mass of calcium stearate were pelletized in the same process as the material of the outer layer 4a.

Using a vertical extruder (a custom-made product manufactured by Plagiken Co., see FIG. 3) as in the case of the surface layer, only the inner layer is heated to a suitable temperature with a single-layer crosshead.
(90 ° C.), further cooled and taken off. In this way, an intermediate layer tube (single-layer tube for the inner layer) having an inner diameter of 11.1 mm, a film thickness of 400 μm, and a surface resistivity of 3.0 × 10 ⁸ Ω / □ was obtained.

Next, the intermediate layer tube cut into a length of 230 mm was fitted around the outer periphery of the semiconductive foamed elastic layer 3 by a tube coating device (not shown), and was brought into pressure contact with a roller having an outer diameter of 11.95 mm. Further, the surface layer tube cut into a length of 230 mm was overlapped on the intermediate layer by a tube coating device (not shown) and fitted to obtain a charging roller. The outer diameter of the charging roller was 12.35 mm.

As a result of forming 100 images continuously using this charging roller in the same manner as in Example 1, image fog was observed at both ends. When the charging roller was taken out and observed, the both ends of the surface layer were displaced by about 3 mm between the surface layer and the intermediate layer as compared with the center part, and were in a twisted state. However, when the outer shape was measured after leaving the charging roller for 3 months, the outer diameter was 12.35 mm, and no change was observed.

[Comparative Example 2] Outer diameter similar to Comparative Example 1
3 mm, semiconductive foamed elastic layer 3 with Asker C hardness of 28 degrees
Was prepared.

Further, in the same manner as in Comparative Example 1, the inner diameter was set to 11.
3 mm, film thickness 200 μm, surface resistivity 8.0 × 10 ⁷ Ω
/ □ surface layer tube (single layer tube for outer layer), inner diameter 11.1 mm, film thickness 400 μm, surface resistivity 3.0 ×
A 10 ⁸ Ω / □ intermediate layer tube (single layer tube for the inner layer) was obtained.

Next, the intermediate layer tube cut into a length of 230 mm was fitted around the outer periphery of the semiconductive foamed elastic layer 3 by a tube covering device (not shown), and was brought into pressure contact with a roller having an outer diameter of 11.95 mm. Further, the surface layer tube cut into a length of 230 mm was overlapped on the intermediate layer by a tube coating device (not shown) and fitted to obtain a charging roller. The outer diameter of the charging roller was 12.20 mm.

The charging roller was evaluated in the same manner as in Example 1. As a result, there was no displacement between the surface layer and the intermediate layer, and a good image was obtained without image unevenness, linear or dot-like abnormal portions.

However, when the outer shape of the charging roller was measured after leaving it for 3 months, the outer diameter was 12.30 mm and the outer diameter was 0.1 m.
m and the surface resistivity of the surface layer is 7.0 × 10 ¹² Ω.
/ □, and the whole image fogged due to insufficient charging of the member to be charged.

[Example 2] Outer diameter similar to that of Example 1
3 mm, semiconductive foamed elastic layer 3 with Asker C hardness of 28 degrees
It was created.

Further, in the same manner as in the first embodiment, the inner diameter is set to 11.1.
A 1 mm functional multilayer film 4 tube was obtained. The inner layer has a surface resistivity of 5.0 × 10 ⁸ Ω / □ and a thickness of 200 μm.
And the surface resistivity of the outer layer is 1.0 × 10 ¹⁰ Ω / □
And the thickness was 25 μm.

Next, the tube of the functional multilayer film 4 was
What was cut to a length of 30 mm was fitted around the outer periphery of the semiconductive foamed elastic layer 3 by a tube coating device (not shown),
The charging roller having an outer diameter of 11.60 mm was obtained by pressure contact.

The charging roller was evaluated in the same manner as in Example 1. As a result, no wrinkles were formed between the functional multilayer film 4 and the semiconductive foamed elastic layer 3 and the functional multilayer film 4 was wrinkled. A good image was obtained without any unevenness and without any image unevenness, linear or dot-like abnormal portions. The external shape after leaving for 3 months is 11.6
A good image was obtained as it was at 0 mm.

Further, as a result of forming an image on the charged roller (electrophotographic photosensitive member) with a pinhole of 0.5 mm opened with a needle on the charged member (electrophotographic photosensitive member), a half-tone image was formed.
No image defect other than the black dot image of mm was observed.

The same evaluation was performed on the charging rollers of Example 1 and Comparative Example 2. When the charging roller of Example 1 showed no image defect other than the 0.5 mm black dot image in the halftone image, the comparison was made. In the charging roller of Example 2, the black point spread to about 0.6 mm, and a horizontal black streak image was also seen in the generatrix direction.

Comparative Example 3 In the elastic layer composition of Example 1, the amount of Diana Process Oil PW-380 was changed to 4
A semiconductive foamed rubber composition for the semiconductive foamed elastic layer 3 was obtained in the same manner as in Example 1 except that the amount was changed to 5 parts by mass.

The resulting composition had a Mooney viscosity at 100 ° C. (ML1 + 4) of 35 and a% Cure @ TP50 of 36%.

Except that this semiconductive foamable rubber composition was used, an outer diameter of 11.0 was formed on the outer periphery of the cored bar 2 in the same manner as in Example 1.
3 mm, semiconductive foamed elastic layer 3 with Asker C hardness of 39 degrees
It was created.

Further, in the same manner as in the first embodiment, the inner diameter is set to 11.1.
A 1 mm functional multilayer film 4 tube was obtained. The inner layer has a surface resistivity of 2.0 × 10 ⁸ Ω / □ and a thickness of 400 μm.
And the surface resistivity of the outer layer is 5.0 × 10 ⁸ Ω / □.
And the thickness was 100 μm.

Next, the tube of the functional multilayer film 4 was
What was cut to a length of 30 mm was fitted around the outer periphery of the semiconductive foamed elastic layer 3 by a tube coating device (not shown),
It was pressed and contacted to obtain a charging roller having an outer diameter of 12.20 mm.

When this charging roller was evaluated in the same manner as in Example 1, fog was observed in the center of the halftone image from a place where the number of sheets exceeded 3,000. Also, when the contact state between the charged body and the charging roller was measured, it was found to be floating about 30 μm at the center.

When the noise was evaluated in the same manner as in Example 1, the amount of change in the charging noise during one rotation cycle of the charging roller was 4%.
dB.

[0104]

According to the charging roller of the present invention in which the functional layer is coated on the low hardness elastic layer, the tube is hardly twisted, so that the clamping force of the tube to the elastic layer can be reduced. As a result, the merit of the elastic layer used in the present invention can be very effectively derived without increasing the apparent hardness of the elastic layer. Further, since the tube is hardly stretched, the outer diameter of the charging roller is less likely to increase, and it is possible to obtain a charging roller having less change in resistance value. Thus, in the present invention, the configuration of the elastic layer and the coating layer on the elastic layer act synergistically, and extremely excellent charging uniformity was obtained. Further, a process cartridge and an electrophotographic apparatus having such a charging member have become possible.

[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 diagram showing an example of a vulcanization curve and a foaming pressure curve of a semiconductive rubber composition used in the present invention.

FIG. 3 is a schematic configuration diagram of an example of an extruder used in the present invention.

FIG. 4 is a schematic view of an electrophotographic apparatus provided with a process cartridge having the charging member of the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 13/00 F16C 13/00 Z (72) Inventor Daisuke Yamada 1888-2 Kusazaki, Kisazaki-cho, Inashiki-gun, Ibaraki Pref. (72) Inventor Hiroshi Ikeda 1888-2 Kusazaki, Kusazaki-cho, Inashiki-gun, Ibaraki Prefecture Within Canon Chemical Co., Ltd. (72) Inventor Kenji Ishii 1888-2 Kusazaki, Kusazaki-cho, Inashiki-gun, Ibaraki Prefecture Canon Chemical Co., Ltd. (72) Inventor: Toshimitsu Nakazawa 1888-2, Kusazaki, Kashizaki-cho, Inashiki-gun, Ibaraki Pref. Reference) 2H200 FA13 FA16 FA19 GA23 GA33 GB12 HA02 HB12 HB22 HB43 HB45 HB46 HB47 LA01 LA38 LC03 MA03 MA04 MA08 MA11 MA12 MA13 MA14 MA20 MB02 MB04 MB05 MC01 M C02 3J103 AA02 AA14 AA51 EA08 FA12 FA15 FA18 GA57 GA58 GA60 HA03 HA12 HA18 HA20 HA42 HA52 4F074 AA05 AA25 AB05 AC02 AG02 BA13 BA18 BB05 CA22 CE02 DA47 4J002 AC011 AC031 AC061 AC071 AC081 AE052 BB15100

Claims (8)

[Claims] 1. A charging member having a conductive core metal, a semiconductive foamed elastic layer on an outer periphery of the cored bar, and a functional multilayer film on an outer periphery of the semiconductive foamed elastic layer, wherein the semiconductive foam is An elastic layer is obtained by passing the core metal and the unvulcanized unfoamed semiconductive rubber composition through a crosshead die of an extruder, and vulcanizing and foaming the material arranged on the outer periphery of the core metal. The semiconductive rubber composition has a Mooney viscosity of 15 to 30, and the vulcanization percentage when the foaming pressure reaches 50% is 40% or less, and the functional multilayer film has: A charging member characterized by being a multi-layer tube including a thin layer which is difficult to form and coat as a single tube. 2. The semiconductive rubber composition has a DBP oil absorption of 3
2. The charge according to claim 1, wherein the amount of the conductive carbon black is 4 to 15 parts by mass per 100 parts by mass of the rubber component, and the softening agent is twice or more the amount of the conductive carbon black. Element. 3. The charging member according to claim 1, wherein the semiconductive rubber composition contains an ethylene-propylene-diene copolymer rubber as a rubber component. 4. The functional multilayer film has a multilayer thickness of 150 μm.
The charging member according to claim 1, wherein the thickness of the charging member is from 800 μm to 800 μm. 5. The functional multilayer film has a multilayer thickness of 200 μm.
The charging member according to claim 4, wherein the thickness is from 600 μm to 600 μm. 6. The thin layer having a thickness of 100 μm or less, which is difficult to form and cover as a tube by itself.
6. The charging member according to any one of claims 1 to 5. 7. A process cartridge having an electrophotographic photosensitive member and a charging member arranged in contact with the electrophotographic photosensitive member, wherein the electrophotographic photosensitive member and the charging member are integrally supported and are detachable from an electrophotographic apparatus main body. Wherein the charging member has a conductive core, a semiconductive foamed elastic layer on the outer periphery of the cored bar, and a functional multilayer film on the outer periphery of the semiconductive foamed elastic layer. The foamed elastic layer is obtained by passing the core metal and the unvulcanized unfoamed semiconductive rubber composition through a crosshead die of an extruder, and vulcanizing and foaming the one arranged on the outer periphery of the core metal. The semiconductive rubber composition has a Mooney viscosity of 15 to 30, and the vulcanization% when the foaming pressure reaches 50% is 40% or less, and the functional multilayer film is Multi-layers, including thin layers that are difficult to form and cover alone as a tube A process cartridge characterized by being a tube. 8. An electrophotographic apparatus having an electrophotographic photoreceptor, a charging member in contact with the electrophotographic photoreceptor, a developing unit, and a transfer unit, wherein the charging member is a conductive metal core, and a periphery of the metal core. An upper semiconductive foamed elastic layer and a functional multilayer film on the outer periphery of the semiconductive foamed elastic layer, wherein the semiconductive foamed elastic layer is formed of an unvulcanized unfoamed semiconductive foam with the core metal. The rubber composition is passed through a crosshead die of an extruder, and vulcanized and foamed on the outer periphery of the cored bar. The semiconductive rubber composition has a Mooney viscosity of 15 to 30. And the vulcanization% when the foaming pressure reaches 50% is 40% or less, and the functional multilayer film includes a thin layer which is difficult to form and cover alone as a tube. An electrophotographic apparatus, which is a multi-layer tube.