JPH09309975A - Semiconductive rubber roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-hardness semiconductive rubber roll which does not exhibit bleed-out and hence does not stain a photoreceptor. SOLUTION: A semiconductive rubber roll is obtd. by mixing and kneading 70 pts. acrylonitrile-butadiene rubber (having a number average mol.wt. of about 100, 000, an acrylonitrile unit content of 33%, and a butadiene unit content of 67%), 30 pts.liq. acrylonitrile-butadiene rubber (having a number average mol.wt. of 3,000, an acrylonitrile unit content of 30%, and a butadiene unit content of 70 %), 0.5 pt. sulfur, 1 pt. tetramethylthiuram disulfide, 1 pt. stearic acid, 5 pts. zinc oxide, 20 pts. calcium carbonate, and 1 pt. antioxidant, molding the resultant compsn. into a tube (for the rubber layer of a roll), inserting a 250mm-length stainless steel rod with its surface coated with an adhesive into the hole of the tube, vulcanizing the tube at 160 deg.C for 30min, grinding the exterior surface of it, and exposing the surface to ultraviolet rays for 3min.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductive rubber roll. More specifically, the present invention relates to a low-hardness semiconductive rubber roll for an electrophotographic apparatus, which suppresses the occurrence of contamination of a photoreceptor due to bleeding or the like.

[0002]

2. Description of the Related Art In an electrophotographic apparatus such as an electrophotographic copying machine or an electrophotographic printing machine, the outer peripheral surface of a photosensitive drum is uniformly charged, and then the outer peripheral surface of the photosensitive drum is exposed to a printing pattern or a copying pattern to make it static. A device having a mechanism for printing or copying by forming an electrostatic latent image, adhering toner to the electrostatic latent image to form (develop) a toner image, and transferring the toner image to a copy sheet or a printing sheet. Is. In an electrophotographic apparatus, a rubber roll serves as a charging roll for uniformly charging the outer peripheral surface of the photoconductor drum, and a developing roll for developing an electrostatic latent image on the outer peripheral surface of the photoconductor drum into a toner image. It is used as a supply roll for supplying the toner or a transfer roll for transferring the toner image. As a rubber roll used in an electrophotographic machine, a rubber roll in which a conductivity-imparting agent such as carbon black is added to reduce electric resistance is known. The hardness of the rubber roll to which the conductivity imparting agent is added increases as the amount of the conductivity imparting agent increases. Therefore, the nip when contacted with other members cannot be sufficiently secured, which may cause a problem as an electrophotographic apparatus. It has been proposed to add a plasticizer or a softening agent in order to reduce the hardness of the rubber roll to which the conductivity-imparting agent is added. However, the plasticizer or the like may bleed out to the peripheral surface of the rubber roll while applying a voltage to the rubber roll, and may contaminate other members, particularly the photoconductor. As a measure to prevent bleed-out, coating the peripheral surface of the roll with a resin is performed, but is not sufficient. On the other hand, attempts have been made to develop a rubber roll having low electric resistance (semi-conductivity) without adding a conductivity-imparting agent. For example, a rubber roll using a rubber composition mainly composed of epichlorohydrin rubber or acrylonitrile butadiene rubber. Is proposed. However, the hardness of this rubber roll is not sufficiently low.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a semi-conductive rubber roll having a low hardness, which prevents contamination of the photoreceptor due to bleed-out.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies to achieve the above object, the present inventors have found that an ethylenically unsaturated nitrile-conjugated diene solid rubber and an ethylenically unsaturated nitrile-conjugated diene are used. It has been found that a rubber roll obtained by molding a composition containing a liquid rubber of a system can have a low hardness without causing contamination of the photoreceptor, and based on this finding, the present invention has been completed.

Thus, according to the present invention, (1) a cored bar made of a conductive rigid body and a rubber layer laminated on the outer peripheral surface of the cored bar, wherein the rubber layer is a unit of ethylenically unsaturated nitrile. 10 to 60% by weight, conjugated diene monomer 40 to 9
0 wt% and other ethylenically unsaturated monomers 0-20
40 to 90 parts by weight of solid rubber (A) obtained by polymerizing 10% by weight and 10 to 60% by weight of ethylenically unsaturated nitrile monomer,
Liquid rubber (B) 10 to 60 parts by weight and other solid rubber (C) 0 obtained by polymerizing 40 to 90% by weight of conjugated diene monomer and 0 to 20% by weight of other ethylenically unsaturated monomer.
~ 50 parts by weight (however, solid rubber (A) and liquid rubber (B)
And the total amount of other solid rubber (C) are 100 parts by weight)
There is provided a semiconductive rubber roll characterized by comprising a vulcanized product of a composition containing.

According to the present invention, (2) a cored bar made of a conductive rigid body and a rubber layer laminated on the outer peripheral surface of the cored bar, the rubber layer being solid nitrile rubber (A) 40-90. Parts by weight and liquid nitrile rubber (B) 10 to 60 parts by weight and other solid rubber (C) 0 to 50 parts by weight (however, solid nitrile rubber (A) and liquid nitrile rubber (B) and other solid rubber (C And a total amount of 100 parts by weight) and a vulcanized product of the composition.

The following are provided as preferred embodiments of the semiconductive rubber roll of the present invention. (3) The semiconductive rubber roll according to (1) or (2) above, wherein the Mooney viscosity of the liquid rubber is 1 or less or cannot be measured. (4) The semiconductive rubber roll according to any one of (1), (2) or (3) above, wherein the solid rubber has a Mooney viscosity of 10 to 200.

(5) The semiconductive rubber roll according to any one of (1) to (4), wherein the solid rubber has a volume resistivity of 10 7 to 10 11 Ω · cm. (6) The vulcanized product is vulcanized with sulfur, a sulfur donor, or a peroxide, and the above (1) to
The semiconductive rubber roll according to any one of (5).

Further, according to the present invention, the above (1)-
(6) The semiconductive rubber roll according to any one of (6) and the photoconductor drum whose outer peripheral surface is uniformly charged and exposed to eliminate the charge, and the semiconductive rubber roll and the photoconductor drum rotate respectively. There is provided an electrophotographic apparatus which can be installed and which is installed in contact with it.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The semiconductive rubber roll of the present invention is
It comprises a cored bar made of a conductive rigid body and a rubber layer laminated on the outer peripheral surface of the cored bar.

The rubber layer is composed of a vulcanized product of a composition containing a solid rubber (A) and a liquid rubber (B).

In the present invention, the solid rubber (A) comprises 10 to 60% by weight of an ethylenically unsaturated nitrile monomer, 40 to 90% by weight of a conjugated diene monomer and 0 to 20 other ethylenically unsaturated monomers. It is obtained by polymerizing wt%.

As the ethylenically unsaturated nitrile monomer, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-methylacrylonitrile, α
-Methoxyacrylonitrile, α-ethoxyacrylonitrile, crotonic acid nitrile, cinnamic acid nitrile, itaconic acid dinitrile, maleic acid dinitrile, fumaric acid dinitrile and the like can be mentioned. Of these, acrylonitrile is preferred. The amount of ethylenically unsaturated nitrile monomer is 10 to 60% by weight, preferably 15 to 5%.
0% by weight.

As the conjugated diene monomer, butadiene,
Isoprene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethylbutadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, chloroprene, 2,3-dichloro butadiene,
1,3-cyclopentadiene etc. can be mentioned. Of these, butadiene is preferred. The amount of the conjugated diene monomer is 40 to 90% by weight, preferably 50 to 8
5% by weight.

Other ethylenically unsaturated monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and cinnamic acid; maleic acid, maleic anhydride, fumaric acid, itaconic acid, Ethylenically unsaturated polycarboxylic acids such as itaconic anhydride, citraconic acid, mesaconic acid and anhydrides; methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, ethyl methacrylate, acrylic acid Monoalkyl ester of ethylenically unsaturated monocarboxylic acid such as amyl; Polyvalent alkyl ester of ethylenically unsaturated polyvalent carboxylic acid such as diethyl maleate, dimethyl itaconic acid, dimethyl maleate; Monoethyl maleate, monomethyl itaconate, Ethylenically unsaturated polyvalent such as monomethyl maleate Partial alkyl esters of carboxylic acids; acrylamide, methacrylamide, crotonic acid amide, monoamide ethylenically unsaturated monocarboxylic acids such as cinnamic acid amide; styrene, alpha-methyl styrene, o
-Methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, o-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 1,1-diphenylethylene, N, N-
Aromatic vinyl monomers such as dimethyl-p-aminostyrene and vinylpyridine; vinyl chloride, vinylidene chloride, vinyl acetate, allyl acetate and the like can be mentioned. The amount of the other ethylenically unsaturated monomer is 0 to 20% by weight, preferably 0 to 15% by weight.

The solid rubber (A) may be obtained by polymerizing the above-mentioned monomer and then adding hydrogen to the unsaturated bond portion or adding a compound having a functional group.

The solid rubber (A) is a rubber in a solid state at room temperature and usually has a molecular weight of more than 10,000. The solid rubber (A) is JIS K
The Mooney viscosity measured according to -6300 is usually 10-200.

Solid rubber (A) has a volume resistivity of
Usually, it is 10 7 to 10 11 Ω · cm, preferably 10 7 to 10 10 Ω · cm. The volume resistivity can be appropriately adjusted by changing the amount of the monomer. If the volume resistivity of the solid rubber (A) is small, the surface potential leaks, which causes a problem as an electrophotographic apparatus.

The amount of the solid rubber (A) is 40 to 100 parts by weight of the rubber constituting the rubber layer (the total amount of the solid rubber (A), the liquid rubber (B) and the other solid rubber (C)). 90
Parts by weight, preferably 50 to 80 parts by weight. If it is less than 40 parts by weight, the compression resistance will be poor, and if it exceeds 90 parts by weight, the effect of lowering the hardness will be lost.

In the present invention, the liquid rubber (B) comprises 10 to 60% by weight of ethylenically unsaturated nitrile monomer, 40 to 90% by weight of conjugated diene monomer and 0 to 20% by weight of other ethylenically unsaturated monomer. % Is polymerized.

As the ethylenically unsaturated nitrile monomer, the conjugated diene monomer and the other ethylenically unsaturated monomer constituting the liquid rubber (B), the same ones as those constituting the above solid rubber should be mentioned. The amount of these monomers is in the same range as that of the solid rubber.

The liquid rubber (B) may be obtained by polymerizing the above-mentioned monomer and then adding hydrogen to the unsaturated bond portion or adding a compound having a functional group.

The liquid rubber (B) is a rubber in a liquid state at room temperature, and its molecular weight is usually 1,000 to 1
It is 50,000. The liquid rubber (B) is
The Mooney viscosity measured according to JIS K-6300 is usually 1 or less, or the Mooney viscosity cannot be measured.

The volume resistivity of the liquid rubber (B) is
Usually, it is 10 7 to 10 11 Ω · cm, preferably 10 7 to 10 10 Ω · cm. If the volume resistivity of the liquid rubber (B) is small, the surface potential leaks, and the electrophotographic apparatus becomes defective.
If the volume resistivity is large, it becomes difficult to obtain a sufficient surface potential.

The amount of the liquid rubber (B) is 10 to 60 parts by weight out of 100 parts by weight of the total amount of the solid rubber (A), the liquid rubber (B) and the other solid rubber (C) constituting the rubber layer. , Preferably 20 to 50 parts by weight. If it is less than 10 parts by weight, the effect of lowering the hardness becomes small, and if it exceeds 60 parts by weight, the compression resistance becomes poor.

The rubber layer may contain other solid rubber (C) in addition to the above solid rubber (A) and liquid rubber (B). Other solid rubbers (C) include styrene-butadiene copolymer rubber, acrylic rubber, epihalohydrin rubber, ethylene oxide-propylene oxide rubber, ethylene-propylene-diene copolymer rubber, chloroprene rubber, butadiene rubber, isoprene rubber, Butyl rubber, urethane rubber, fluororubber, etc. can be mentioned. Of these, epihalohydrin rubber, particularly epichlorohydrin rubber is preferable.

Solid rubber (C) has a volume resistivity of
Usually, it is 10 7 to 10 11 Ω · cm, preferably 10 7 to 10 10 Ω · cm. If the volume resistivity of the solid rubber (C) is small, leakage of the surface potential causes a problem in the electrophotographic apparatus. If the volume resistivity is large, it becomes difficult to obtain a sufficient surface potential.

The amount of the solid rubber (C) is 0 to 50 parts by weight out of 100 parts by weight of the total amount of the solid rubber (A), the liquid rubber (B) and the other solid rubber (C) which form the rubber layer. ,
Preferably it is 0 to 40 parts by weight. If it exceeds 50 parts by weight, bleeding of the liquid rubber (B) is likely to occur.

In the present invention, the rubber layer is usually prepared by kneading the solid rubber (A), the liquid rubber (B) and the solid rubber (C) or mixing the respective rubber latices to obtain a composition, It is obtained by molding and vulcanizing the composition.

The rubber layer can be molded by an ordinary roll molding method. Specifically, it is molded into a tube by an extrusion molding method or a sheet-shaped molded product is obtained, which is used as a core metal. Wrap it around.

The rubber layer in the present invention is obtained by vulcanizing by mixing the above composition with a vulcanizing agent or a peroxide used for vulcanizing an unsaturated rubber. Examples of the vulcanizing agent include thiuram compounds such as morpholine disulfide and tetramethylthiuram disulfide; sulfur and the like. Examples of peroxides include dicumyl peroxide, di (t-butylperoxy) diisopropylbenzene, 2,5-di-t-butylperoxy-2,5-dimethylhexane and benzoyl peroxide.

A vulcanization aid may be blended in order to efficiently vulcanize the rubber layer with a peroxide. A maleimide compound is suitable as the vulcanization aid, and specific examples thereof include maleimide and phenylene bismaleimide.
Other than the maleimide compound, an acrylate-based or methacrylate-based polyfunctional monomer can be used.

The volume resistivity of the rubber layer is usually 6 of 10
It is the power of 10 to the 12th power Ω · cm. The rubber layer may have the above-mentioned volume resistivity even if a conductivity-imparting agent such as carbon black or metal powder is not particularly blended in the rubber layer. A metal oxide may be blended in order to readjust the volume resistivity. By mixing the metal oxide, the fluctuation of the volume resistivity due to the environmental fluctuation becomes small. Here, the primary particle diameter of the metal oxide is usually 0.01
The thickness is from 10 to 10 μm, preferably from 0.05 to 5 μm. If the particle size is small, it becomes difficult to mix and disperse it in the elastomer, and conversely, if the particle size is large, moldability and physical properties tend to deteriorate. Specific examples of the metal oxide include A
1-doped ZnO, SnO ₂ (antimony oxide-doped) compound TiO ₂ , SnO ₂ (antimony oxide-doped) compound Sn
O ₂ , SnO ₂ belonging TiO ₂ , K ₂ O · nTiO ₂ / SnO ₂ S
Examples thereof include b ₂ O ₆ , SnO ₂ (antimony oxide-doped) complex oxide, zinc oxide, titanium oxide, tin oxide, and antimony oxide. The amount of metal oxide is 0 to 200 parts by weight, preferably 0 to 150 parts by weight, based on 100 parts by weight of the rubber forming the rubber layer. As the amount of metal oxide increases, the hardness of the member increases.

Since the semiconductive rubber roll of the present invention is used as a developing roll or a charging roll, the axial centerline average roughness (Ra) of the outer peripheral surface of the rubber layer is usually 0.
The thickness is 3 to 2.5 μm, preferably 0.3 to 2 μm. R
It is preferable that a is smaller, but it is difficult to set Ra to 0. Therefore, the lower limit is 0.3 μm from the viewpoint of production efficiency.
Becomes On the other hand, when Ra increases, the print density increases.
The center line average roughness is the direction (X
(Axis) only the measurement length (L) is extracted, and when expressed as a function of roughness curve y = f (x) in the roughness direction (Y axis), the absolute value of this function is definitely integrated from x = 0 to L Expressed in μm
The unit value.

The semiconductive roll of the present invention has a ten-point average roughness (Rz ₁ ) in the axial direction of the outer peripheral surface of the rubber layer of ₁ to 10 in order to be used as a developing roll or a charging roll.
μm, preferably 2 to 9 μm. Further, the rubber roll of the present invention has a ten-point average roughness (Rz ₂ ) / circumferential direction /
The ratio of the ten-point average roughness (Rz ₁ ) in the axial direction is usually 0.9
To 1.2, preferably 0.95 to 1.15. Rz
_When the ratio of ₂ / Rz ₁ is large, the print density is high, but the dot reproducibility is low. On the contrary, when the ratio of Rz ₂ / Rz ₁ becomes small, the print density and the dot reproducibility decrease. Note that the ten-point average roughness (Rz ₁ and Rz ₂ ) is the average value of the heights of the highest to fifth peaks and the deepest valleys in the portion extracted by the reference length from the sectional curve of the rubber roll surface. It is the value which expressed the difference with the average value of the depth of the valley from the 5th to 5th in the unit of μm.

In the semiconductive roll of the present invention, the volume resistivity of the rubber layer (determined from the electric resistance value measured from the core metal to the outer peripheral surface of the elastic layer) is usually 10 6 to
10 12 Ω · cm, preferably 10 6.5 to 1
It is 0 to the 11.5th power Ω · cm. By setting the volume resistivity within this range, the toner charging becomes sufficiently uniform, a good printing density is obtained, and the dot reproducibility becomes high.

In the semiconductive roll of the present invention, the compression set of the rubber layer is usually 25% or less, preferably 20%.
Or less, more preferably 20% or less. When the compression set becomes large, it becomes difficult to form a good image.

In the semiconductive rubber roll of the present invention, the core metal is formed of a conductive rigid body, specifically, a metal such as copper, iron, stainless steel, aluminum or nickel. The core metal usually has a cylindrical shape with the same outer diameter from end to end, but the end of another roll or semiconductive rubber roll due to the contact of the semiconductive rubber roll with another roll. In order to reduce the wear of the core metal, it is preferable to make the outer diameter of the end portion of the core metal smaller than that of the center portion of the core metal in the axial direction. The outer peripheral surface of the core metal preferably has a large surface roughness in order to enhance the adhesive force with the rubber layer.
A V-shaped knurling groove is provided on the outer surface of the cored bar.

The rubber layer and the core bar are joined by polishing the outer peripheral surface of the core bar, removing adherents such as rust by sand blasting, washing the oil, and applying an adhesive. Next, the rubber layer Is tubular, the core metal is inserted into the tube cavity to bond the core metal and the rubber layer. When the rubber layer is in the form of a sheet, it can be obtained by winding the sheet rubber around the outer peripheral surface of the core metal and vulcanizing it. If the outer diameter of the core metal is larger than the inner diameter of the part where the core metal of the rubber layer is attached, the bonding force between the core metal and the rubber layer will be stronger, so the bonding part will be destroyed and applied from the core metal to the surface of the rubber layer. It is preferable because it can prevent the occurrence of image defects due to the voltage not being transmitted.

On the outer peripheral surface of the rubber layer, in order to prevent the surface potential from leaking or to prevent the adhesion of toner,
It is preferable to reduce the surface roughness or the friction resistance.
In order to reduce the surface roughness or friction resistance, it is necessary to polish with a polishing machine, irradiate the outer peripheral surface of the rubber layer uniformly with ultraviolet rays, or coat the outer peripheral surface with a polymer such as polyurethane or silicone. To do. The polymer coating can further prevent photoreceptor contamination.

The semiconductive rubber roll of the present invention serves as a charging roll for uniformly charging the outer peripheral surface of the photosensitive drum in an electrophotographic apparatus, and develops an electrostatic latent image on the outer peripheral surface of the photosensitive drum into a toner image. Can be used as a developing roll for supplying toner to the developing roll, a transfer roll for transferring a toner image, or the like.

FIG. 1 is a conceptual diagram showing an example of an electrophotographic apparatus according to the present invention. A description will be given below with reference to this figure.

The electrophotographic apparatus of the present invention comprises the above-mentioned semi-conductive rubber roll (hereinafter also referred to as a developing roll) and a photosensitive drum, and the developing roll and the photosensitive drum can rotate and contact each other. It has been installed. Supply rolls are arranged as needed.

The outer peripheral surface of the photosensitive drum is uniformly charged by a charging device and exposed to light so that the charge is removed. As the charging device, a charging roll obtained by coating the outer peripheral surface of the semiconductive rubber roll of the present invention with a resin can be used.

The supply roll, the developing roll, and the photosensitive drum are fixed so as to be rotatable.
The supply roll and the developing roll are fixed in contact with each other. Further, the developing roll and the photosensitive drum are fixed so as to be in contact with each other. A drive device for rotating each of the supply roll, the photosensitive drum, and the developing roll is usually provided. The rotation direction of the photosensitive drum and the rotation direction of the developing roll are usually set in opposite rotation directions (rubbing in the same direction on the contact surface). The rotation direction of the supply roll and the rotation direction of the development roll are usually set to be the same rotation direction (rubbing in opposite directions on the contact surface). The peripheral speed is 1.5 with respect to the peripheral speed of the photoconductor drum so that the toner adheres sufficiently to the photoconductor and the efficiency of cleaning the residual toner not transferred by the transfer device described later by the developing roll is increased. It is preferable to rotate the developing roll at a peripheral speed of 3 times. Further, it is preferable to rotate the supply roll at a peripheral speed of 0.4 to 0.9 times the peripheral speed of the developing roll.

A voltage is usually applied to the supply roll, the photosensitive drum and the developing roll. Regarding the voltage applied to the photosensitive drum and the developing roll, the relationship between the surface potential (Vc) of the photosensitive drum and the surface potential (Vd) of the developing roll is such that the absolute value of (Vc−Vd) is 50 volts or more. To do. By setting the applied voltage to the above conditions,
Development and cleaning can be performed efficiently at the same time.

A developing blade for controlling the layer thickness and charge state of the toner adhered to the surface of the developing roll is usually in contact with the developing roll. A voltage is usually applied to the developing blade and the supply roll. The voltage applied to the developing blade and the supply roll is
The relationship between the surface potential (Vb) of the developing blade, the surface potential (Vs) of the supply roll, and the surface potential (Vd) of the developing roll is represented by the formula 1. The toner is uniformly charged, and the toner can be efficiently supplied.

[0048]

[Equation 1]

The toner attached to the photosensitive drum by the developing roller is transferred to a paper or resin sheet by a transfer device. The transfer device includes a transfer roll,
Examples include a transfer belt and a corona discharge transfer device. The semi-conductive rubber roll of the present invention can be used as the transfer roll.

The toner applicable to the electrophotographic apparatus of the present invention is not particularly limited, but a spherical non-magnetic one-component toner is preferably used. Spherical toner has a volume average particle size (dv) of 3
.About.15 .mu.m, preferably 5 to 10 .mu.m. A preferable spherical toner has the above volume average particle diameter, and further, the ratio of the volume average particle diameter (dv) to the number average particle diameter (dn) (dv /
dn) is 1 to 1.4, and the value (Sc / Sr) obtained by dividing the area (Sc) of the circle whose diameter is the absolute maximum length of the particle by the substantial projected area (Sr) of the particle is 1 to 1.3. Is. A spherical toner that can be more preferably applied has a product (A × dn × D) of specific surface area (A) [m ² / g] of BET method, number average particle diameter (dn) [μm] and true specific gravity (D) of 5 It is in the range of 10 to 10, and the ratio (Q / A) of the charge amount (Q) [μc / g] to the specific surface area (A) is 40 to 150. Spherical toners also include so-called capsule toners consisting of a core containing a soft or low glass transition temperature polymer and a shell containing a hard or high glass transition temperature polymer. The spherical toner can be usually obtained by a polymerization method.

The toner is usually blended with a colorant, and examples of the colorant include those imparting respective colors such as black, magenta, yellow and cyan, and any colorant is blended. Even the above toner can be applied to an image forming apparatus using the semiconductive member (roll) of the present invention.

The ten-point average roughness (Rz ₁ ) of the developing roll used in the electrophotographic apparatus of the present invention is usually _{1 to} 10 μm, preferably 2 to 9 μm. Rz ₁ is preferably smaller, but it is difficult to bring Rz ₁ close to 0, so the lower limit is 0.3 μm.

Further, the developing roll usually has a ratio of 10-point average roughness (Rz ₂ ) in the circumferential direction / 10-point average roughness (Rz ₁ ) in the axial direction of 0.9 to 1.2. It is preferable. R
When the ratio of z ₂ / Rz ₁ is large, the printing density is high, but the halftone (dot reproducibility of printing) is low. Conversely, R
The print density and the dot reproducibility of the print are reduced when the ratio z ₂ / Rz ₁ is reduced. The ten-point average roughness (Rz ₁ and R
z ₂ ) is the average value of the heights of the 5th to the 5th highest peaks and the averages of the 5th to the 5th deepest valleys of the reference length extracted from the section curve of the rubber roll surface. It is a value in which the difference from the value is expressed in μm.

The volume resistivity of the rubber layer of the developing roll is usually 10 7 to 10 11 Ω · cm, preferably 1
It is 0 to the 7th power to 10 to the 10th power Ω · cm. Within this range, the toner is highly charged and uniform, good print density is obtained, and dot reproducibility is improved.

[0055]

The present invention will be described in more detail by way of examples. In the examples, "%" and "parts" are based on weight unless otherwise specified. The evaluation test method performed in this example is as follows.

[Press fog] Volume average particle size is 7 μm, ratio (dv) of volume average particle size (dv) and number average particle size (dn).
/ Dn) is 1.2, the area (Sc) of the circle whose diameter is the absolute maximum length of the particle, divided by the actual projected area (Sr) of the particle (Sc / Sr) is 1.1, the ratio according to the BET method. The product (A × dn × D) of the surface area (A) [m ² / g], the number average particle size (dn) [μm] and the true specific gravity (D) is 8, and the charge amount (Q) [μc / g] Continuous printing is performed using spherical polymerization method encapsulated toner with a specific surface area (A) ratio (Q / A) of 81, and a microscope is used to check whether or not fogging has occurred in the "white solid print areas" on both ends of the paper. It was observed and evaluated by the following indexes. B: No fog occurs even when continuous printing is performed. Δ: Fogging occurs a little when continuous printing is performed, but there is no problem in image quality. X: Fogging occurs when continuous printing is performed, and the image quality deteriorates.

[Contamination of Photoreceptor] A semiconductive rubber roll was brought into contact with the photoconductor drum so that the load was 500 gf, and 45
After left for 3 weeks in the environment of 80 ° C. and 80% RH, the presence or absence of contamination of the photoconductor was visually confirmed. ◯: No contamination is observed even after 3 weeks. B: After 2 weeks and before 3 weeks, streaky contamination was observed. X: Contamination was observed before 2 weeks had passed.

[Compression resistance] The semiconductive rubber roll is brought into contact with the photosensitive drum so that the deformation rate of the semiconductive rubber roll is 20%, and left for 3 weeks in an environment of 45 ° C. and 80% RH to compress the roller. The permanent set was calculated. Good: The compression set is less than 10%. Δ: The compression set is 10% or more and less than 20%. X: The compression set is 20% or more.

[Volume Specific Resistance] A vulcanized product of the composition forming the rubber layer of the semiconductive rubber roll was formed into a rubber sheet having a thickness of 2 mm, which was sandwiched between electrodes with a guide ring, and a voltage of 500 V DC was applied. The electric resistance value was measured at 23 ° C. and 50% RH. Ten rubber sheets were prepared, the resistance value of each was measured, and the variation was evaluated. Table 1 shows the maximum and minimum resistance values. It is preferable that the difference between the maximum value and the minimum value is within one order.

Example 1 Acrylonitrile-butadiene copolymer rubber (number average molecular weight of about 100,000, acrylonitrile 33%, butadiene 6
7%) 70 parts, liquid acrylonitrile-butadiene copolymer rubber (number average molecular weight 3000, acrylonitrile 3
0%, butadiene 70%) 30 parts, sulfur 0.5 part, tetramethylthiuram disulfide 1 part, stearic acid 1
Part, zinc oxide 5 parts, calcium carbonate 20 parts and antioxidant D1 part are kneaded with a roll and molded into a tube to obtain a rubber layer, on which the outer peripheral surface of a stainless rod having an outer diameter of 8 mm and a length of 250 mm is formed. An adhesive was applied, this was inserted into a tube cavity, and vulcanized at 160 ° C. for 30 minutes. Next, the outer peripheral surface of the rubber layer was polished and irradiated with ultraviolet rays for 3 minutes to obtain a semiconductive rubber roll. Table 1 shows the results of evaluation of the volume resistivity and hardness of the rubber layer of this rubber roll, and the pressure fog state, photoreceptor contamination state and compression resistance when this rubber roll was installed as a developing roll in the electrophotographic apparatus shown in FIG. It was shown to.

Examples 2 to 4 and Comparative Examples 1 to 3 Example 1 except that the rubber layers having the formulations shown in Table 1 or Table 2 were used.
A semi-conductive rubber roll was obtained by the same method as described above, and the evaluation results are shown in Table 1 or Table 2.

[0062]

[Table 1]

Table 1 Footnote 1) NBR: acrylonitrile-butadiene copolymer rubber, acrylonitrile 33% by weight, butadiene 67% by weight, number average molecular weight about 100,000, Mooney viscosity 782 2) H-NBR: hydrogenated acrylonitrile-butadiene copolymer Polymer rubber, acrylonitrile 36% by weight, butadiene 64% by weight, number average molecular weight about 100,000, hydrogenation rate 90
%, Mooney viscosity 80 3) NBR: acrylonitrile-butadiene-isoprene copolymer rubber, acrylonitrile 33% by weight, butadiene 52% by weight, isoprene 15% by weight, number average molecular weight about 100,000, Mooney viscosity 784 4) Liquid NBR: acrylonitrile -Butadiene copolymer rubber, acrylonitrile 30% by weight, butadiene 70
% By weight, number average molecular weight about 3000 5) Liquid c-NBR: carboxyl group-containing acrylonitrile-butadiene copolymer liquid rubber, acrylonitrile 20% by weight, butadiene 70% by weight, carboxyl group-containing monomer 10% by weight, number average molecular weight about 3000 6) ECO: epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, epichlorohydrin 71% by weight, ethylene oxide 23% by weight,
Allyl glycidyl ether 6% by weight, number average molecular weight about 1
50,000, Mooney viscosity 757) UV irradiation: An ultraviolet lamp with a wavelength of about 280 nm is used with a lamp output of 80 W / cm and a rated power of 4 kw.
Place a roll at a distance of 2 cm and irradiate for 3 minutes while rotating the roll. PU coating: Polyurethane resin (manufactured by Dai-ichi Kogyo Seiyaku Co., Superflex 126; glass transition temperature 72 ° C) aqueous dispersion so that the film thickness is 10 μm. Applied evenly to the outer peripheral surface

[0064]

[Table 2]

Table 2 Footnotes 1), 2), 4), 6) and 7) are the same as in Table 1 8) Conductive carbon: "Ketjen Black EC" manufactured by Ketjen Black International

[0066]

The rubber roll of the present invention is made of liquid rubber,
It is possible to reduce the hardness of the rubber layer, and by using liquid nitrile rubber and solid nitrile rubber in combination, it is possible to prevent liquid nitrile rubber from bleeding out to the outer peripheral surface of the roll and reduce the occurrence of photoconductor contamination. It Further, it has excellent compression resistance and can prevent image defects such as pressure fog.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrophotographic apparatus.

[Explanation of symbols]

 4: Photoreceptor drum 5: Charging roll 6: Developing roll 7: Transfer roll 8: Supply roll 9: Developing blade

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 15/16 G03G 15/00

Claims (3)

[Claims] 1. A core metal comprising a conductive rigid body and a rubber layer laminated on the outer peripheral surface of the core metal, wherein the rubber layer comprises 10 to 60% by weight of an ethylenically unsaturated nitrile monomer and a conjugated diene. 40-90 parts by weight of a solid rubber (A) obtained by polymerizing 40-90% by weight of a monomer and 0-20% by weight of another ethylenically unsaturated monomer, and an ethylenically unsaturated nitrile monomer 10-60 % By weight, 40-90% by weight of conjugated diene monomer and 0-20% by weight of other ethylenically unsaturated monomer, and 10-60 parts by weight of liquid rubber (B) and other solid rubber (C). ) 0 to 50 parts by weight (however, the total amount of the solid rubber (A), the liquid rubber (B), and the other solid rubber (C) is 100 parts by weight). A semi-conductive rubber roll characterized by. 2. A core metal comprising a conductive rigid body and a rubber layer laminated on the outer peripheral surface of the core metal, the rubber layer comprising 40 to 90 parts by weight of solid nitrile rubber (A) and liquid nitrile rubber ( B) 10 to 60 parts by weight and other solid rubber (C) 0
To 50 parts by weight (however, the total amount of the solid nitrile rubber (A), the liquid nitrile rubber (B), and the other solid rubber (C) is 100 parts by weight). A semi-conductive rubber roll characterized by. 3. The semiconductive rubber roll according to claim 1 or 2, which comprises a photosensitive drum whose outer peripheral surface is uniformly charged and exposed to remove the charge by exposure, and a semiconductive rubber roll, An electrophotographic apparatus in which the photosensitive drums are rotatable and are in contact with each other.