JP3159601B2 - Contact charging member and electrophotographic apparatus having the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging member used in an electrophotographic image forming apparatus in contact with a photosensitive member.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus has
As shown in FIG. 4, the image forming process includes the main processes of forming an electrostatic latent image, developing, transferring, cleaning, and fixing. Here, a photoreceptor is frequently used as an image carrier, and the photoreceptor is charged and exposed to an image to form an electrostatic latent image.

In the step of charging a photoreceptor during the image forming process, a contact charging device has been recently proposed in which the photoreceptor is charged by directly contacting the photoreceptor. In a contact type charging device, a charging member is pressed against a surface of an object to be charged, and a voltage (such as a DC voltage or a superimposed voltage of a DC voltage and an AC voltage) is applied to the charging member so that the surface of the object to be charged has a predetermined polarity and potential. Is charged.

Such a contact-type charging device has advantages such as using a lower applied voltage and generating less ozone than a non-contact type corona charging device.

When the voltage applied to the charging member is a voltage obtained by superimposing an alternating current on a direct current, the charging member vibrates due to the frequency of the alternating voltage, thereby generating a “charging sound” and giving an unpleasant feeling. To prevent this charging noise, the charging member is made to have a low hardness and its vibration is absorbed by the charging member.
A method using a foamed member is proposed in, for example, Japanese Patent Application Laid-Open Publication No. HEI 9-64139.

[0006] When a polyurethane resin is used for the foam, a method for imparting conductivity to the polyurethane resin is a method in which a polyurethane raw material contains a conductive compound such as carbon, a metal, or an electrolyte salt and is molded and foamed. It has been proposed in Japanese Unexamined Patent Publication No. Hei 2-18490 and Japanese Unexamined Patent Publication No. Hei 2-40683.

Further, a conductive resin composition exhibiting conductivity using pyrrole, which is a conductive monomer, is disclosed in
No. 49066 and JP-A-2-50172.

[0008]

However, when the polyurethane resin is imparted with conductivity by the above-mentioned conventional method, in the case of carbon, since the viscosity of the polyurethane raw material is high, fluidity is low and handling is difficult. In the case of metal, there is a problem that the metal precipitates in the raw material. If there is such a problem, the resistance unevenness and resistance in the volume direction and the surface direction of the charging member or in a part thereof become non-uniform, and an image defect occurs.

In the case of a foam, the resistance value fluctuates because the state of the conduction path changes depending on the cell diameter of the foam material.

Furthermore, the medium resistance region used particularly for the charging member changes rapidly depending on the dispersion state of the conductive compound, the cell diameter of the foam, and the like, so that it is difficult to stably secure the medium resistance region. There is a problem.

[0011] Further, a method for preparing a conductive resin composition using pyrrole, which is proposed in JP-A-2-49066 and JP-A-2-50172, dissolves a matrix resin in an organic solvent, and At a very low temperature of -40 ° C, pyrrole and a polymerization catalyst are added, and the polymerization solution is poured into water to aggregate and stop the reaction to obtain a polymer, which is washed with water, dissolved in an organic solvent, etc., and molded. To
The molding is complicated, there are many steps, and there is a problem in productivity, and it is difficult to form a foam using the resin.

SUMMARY OF THE INVENTION An object of the present invention is to provide a contact charging member which solves the above-mentioned conventional disadvantages of lacking moldability and productivity.

It is a further object of the present invention to stably secure and provide a charging member having a medium resistance.

Another object of the present invention is to provide a contact charging device which does not generate charging noise.

[0015]

[Means for Solving the Problems] The above object, the contact of performing charging by the voltage obtained by superimposing a DC and an AC voltage by contacting a charging member to the photosensitive member, or only a DC voltage is applied to energize the photoreceptor A charging member , wherein the contact charging member has a resin layer on a conductive support, the resin layer has at least a layer containing a foamed member, and the foamed member is a polyether-based , open cell polyurethane resins der conductive obtained by polymerizing the urethane surface conductive monomer gas phase to the polyurethane resin in the form of it is, on the layer of the foamed member
To be achieved by the contact charging member, characterized in Rukoto to have a least one layer of the coating layer.

The contact charging member of the present invention, preferably, the contact resistance of the charging member is in the range of ^{10 2 ~10 10 Ω · cm,} 10 -point average surface roughness of the surface in contact with the photosensitive member charging member However, the compression set of the charging member is 40% or less, and the hardness of the charging member is 50 ° or less.

Hereinafter, the configuration of the present invention will be described in detail.

FIG. 1 is a conceptual diagram of the present invention.

In FIG. 1, a contact charging member 2 disposed on the peripheral surface of a photoreceptor 1 has a core metal 2-c as a conductive support.
A urethane foam layer 2-b is provided thereon, and a surface layer 2-a is provided thereon. Charging of the photoreceptor is applied to the metal core via the foam layer. Charging is performed by voltage. According to the present invention, the foam contained in the charging member uses a polyurethane resin obtained by polymerizing a conductive monomer on the surface of a polyether polyurethane resin.

The above-mentioned conductive polyurethane resin exhibits conductivity by polymerizing a conductive monomer after molding the foam, so that it is not necessary to consider the resistance value when molding the foam. The molding can be performed in consideration of only the foaming form such as the cell diameter. Further, even when the cell diameter or the like after molding is different, since the resistance value is adjusted by polymerizing the conductive monomer after foam molding, the resistance can be easily adjusted by changing the amount or the like of the conductive monomer. Therefore, there is little change in the resistance value due to the difference in cell diameter or dispersion state by the conventional method of dispersing the conductive pigment in the resin and then molding, and a stable charging member having a medium resistance value can be provided.

Further, the conductive polyurethane resin used for the charging member has a relatively high resistance of the resin itself.
Since the adjustment of the resistance largely depends on the conductive monomer, it has little hygroscopicity and is excellent in environmental stability.

The polyether polyol as a raw material of the polyol polyurethane resin in the present invention includes a compound having a structure in which an alkylene oxide is added to a compound having at least two or more active hydrogen atoms, and a mixture thereof.

For example, alkylene glycols such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, and polytetramethylene glycol, and mixtures thereof can be mentioned.

Examples of the polyisocyanate include hexamethylene diisocyanate, isophodiisocyanate, metaphenylene diisocyanate, xylene diisocyanate, derivatives of these diisocyanates, and prepolymers of these and polyols at the terminal NCO.

As the conductive monomer, pyrrole, N-
Examples thereof include methylpyrrole, thiophene, indole, aminopyridine, aslen, pyrenefluore, aniline, diaminobenzene, and benzene. The addition of a substance having an oxidizing ability to the urethane surface facilitates polymerization.

For example, after forming a urethane resin foam, it is immersed in a solution in which an oxidation catalyst is dissolved, for example, an aqueous solution of iron chloride, taken out and dried, and a metal salt having an oxidizing ability is applied to the urethane surface to form a conductive monomer. There is a method of exposing a heterocyclic compound such as pyrrole, for example, to pyrrole vapor to form a polymer of a conductive monomer on the urethane surface to impart conductivity.

The form of the urethane resin foam must be open cells. This is because since the conductive monomer resistance adjustment by exhibiting conductivity by polymerizing the urethane surface, conductive paths between the surface of the conductive support and the charging member is formed of a conductive urethane surface This is because that. If it is a closed cell, since the urethane surface is prevented from being connected between the conductive support and the charging member surface, a conductive path is not formed, the resistance becomes high, and the pressure is applied to the conductive support. The voltage is not reflected on the surface of the charging member, and the photosensitive member cannot be charged.

[0028] In the charging member of the present invention, providing the coating layer on the urethane resin layer. Because the urethane resin is a foam, there is uneven resistance on the surface of the charging member where the resin is present and on the surface where the resin is not present (bubble portion), which causes a difference in the surface potential of the photoconductor. This is to prevent the occurrence of image defects and the occurrence of image defects due to the surface roughness of the foam.

The volume resistivity of the charging member of the present invention is:
The resistance value of the charging member must be in a medium resistance region in order to prevent image failure due to dielectric breakdown due to low resistance of the charging member and image failure due to charging failure due to high resistance, and the resistance value range is 10 ² Ωcm to It is 10 ¹⁰ Ωcm, more preferably 10 ⁵ Ωcm to 10 ⁸ Ωcm.

If the resistance value is less than 10 ² Ωcm, if a pinhole-shaped flaw is present on the photoreceptor, the current is concentrated there, so that the entire photoreceptor is charged in the axial direction. If the resistivity is 10 ¹⁰ Ωcm or more, the resistance is too high, and a predetermined potential is not applied on the photoreceptor, resulting in an image defect.

When the charging member of the present invention is used, if the surface of the charging member in contact with the charging member and the photosensitive member is rough,
Due to the irregularities, charging unevenness is delicately generated, and an image defect occurs. Therefore, the smoother the surface, the better.
B0601 10 points average roughness R in surface roughness standard
z 5 μm or less, and the maximum height R _max is 10 μm
Or less, more preferably, Rz is 2 μm or less,
R _max is 5 μm or less.

Further, when the charging member is used in contact with the photoreceptor, deformation occurs due to long-term contact with the photoreceptor (compression set). Since a difference occurs in a portion, a difference occurs in charging, and an image defect occurs.

Therefore, the compression set is JIS K63.
After leaving for 22 hours at 70 ° C. at a compression ratio of 25% by the method of Example 01,
It is 40% or less, more preferably 30% or less, as measured by taking out at room temperature and leaving it for 30 minutes.

When the charging member is used in contact with the photoreceptor, if the charging member has high hardness, contaminants such as toner on the photoreceptor are rubbed with the photoreceptor by the charging member and mechanically crushed or hit. For this reason, toner or the like is melted on the photosensitive member, that is, an image defect due to so-called fusion occurs. In particular, when the applied voltage is an AC superimposed bias, the above-described phenomenon is more likely to occur than when a DC voltage is applied because the charging member vibrates due to the AC voltage. When the hardness of the charging member is low, rubbing and hitting of the photoreceptor are reduced, so that fusion is less likely to occur.

Therefore, the preferable hardness of the charging member is determined by JI
The A hardness specified by SK6301 is 50 ° or less, more preferably 35 °.

Further, when the applied voltage is an AC superimposed bias, "charging noise" is caused by vibration of the charging member due to the AC voltage.
A sound called, which gives people discomfort. This too
By lowering the hardness of the charging member, this vibration is absorbed and charging noise is reduced. A more preferred hardness is 10 ° or less.

The charging member of the present invention can be applied to, for example, an electrophotographic apparatus as shown in FIG. In this apparatus, a primary charging device (charging member of the present invention) 2, an exposure unit 3, a developing device 5, a transfer device 7, a cleaning device 10, and a pre-exposure device 11 are arranged on a peripheral surface of an electrophotographic photosensitive member 1. I have. Reference numeral 6 denotes a sheet feeding device, and 9 denotes a fixing device.

A voltage is externally applied to a primary charging member in contact with the electrophotographic photoreceptor, and the electrophotographic photoreceptor 1
The surface is charged, and an image on a document is exposed to an image on a photoreceptor by exposure means 3 to form an electrostatic latent image.

Next, the developer in the developing device 5 is adhered to the photoreceptor, thereby developing (visualizing) the electrostatic latent image on the photoreceptor. Then, the developer remaining on the photosensitive member without being transferred to the paper at the time of transfer by the cleaning device 10 is collected by the transfer device such as paper.

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

When the charging member of the present invention is used for transfer charging, it can be applied to the transfer device 7 shown in FIG.

A voltage can be externally applied to a transfer charging member placed in contact with the electrophotographic photosensitive member, and further transferred to a transfer-receiving member such as developer paper on the photosensitive member.

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[0044]

【Example】

(Example 1) PPG-based polyether polyol (Mw
5000) and toluene diisocyanate (TDI-8)
0), a foam stabilizer was added, and the mixture was stirred and mixed.

The core metal coated with the conductive adhesive is poured into a roller-shaped mold provided at the center, and
The mixture was heated and reacted at 0 ° C. for 3 hours to obtain a polyurethane resin foam roller having a cell diameter of 350 μm. And immersing the roller in aqueous solution of iron chloride to remove the water was taken out dried, grant iron chloride having oxidizing ability urethane surface which was exposed to the vapor of pyrrole, pyrrole in the gas phase in the urethane surface Polymerization was performed to adjust the resistance value as polypyrrole.

On the urethane resin layer, a paint whose resistance was adjusted by dispersing tin oxide in a water-soluble urethane resin was applied by dipping, and a surface layer was provided to obtain a desired charging roller.

The charging roller was evaluated according to the following items. Evaluation 1) The resistance value of this roller was 32 ° C. and 85% RH.
The measurement was performed in two environments of (1) and 10% RH (2).

The measuring method is such that an aluminum foil is brought into close contact with the outer periphery of the roller, and a DC 250 V voltage is applied between the core metal and the aluminum foil, and a tester (HIOKI 3116 DEGITA) is applied.
(LMΩ HI TESTER). Table 1 shows the results. Evaluation 2) This charging roller was mounted at the position of a primary charging device of a copying machine (FC-2 (manufactured by Canon Inc.)), mounted, and applied with a DC voltage of -1500 V to perform image formation. went. The environment is 2 environments similar to evaluation 1. As a photoconductor, a copying machine NP6030 manufactured by Canon Inc. was used. Table 1 shows the results.

◎ Excellent ○ Good △ Practical × Not practical Evaluation 3) Evaluation 2
Approximately ^2, the defective photoreceptor with the exposed aluminum base layer exposed was mounted, images were formed by applying -1800 V, and image white spots due to dielectric breakdown were evaluated in two environments in the same manner as in Evaluation 1 according to the following evaluation items. .

Table 1 shows the results.

○ Excellent (color loss is limited to the defective portion) △ Good (color loss is no defect and about 30 mm) × not practical (white void) Evaluation 4) Superimposed voltage (450 Hz) using 2 devices , 2K
(vpp, -700 V _DC ) was applied, and charging noise was evaluated according to the following evaluation items.

Table 2 shows the results.

◎ Excellent (no charged sound is heard at all) ○ Good (almost no charged sound is heard) △ Practical (hidden by noise of other machines) × Not practical (audible sound is heard) Evaluation 5) The charging roller was adjusted to the position of the temporary charging period of LBP (Laser Jet si (manufactured by HP)) and mounted for durability of 10,000 sheets, and the image after the durability was evaluated according to the following evaluation items. went.

The durability environment is 32 ° C. and 85% RH. Table 2 shows the results
Shown in

◎ Excellent (no fusion) 観 察 Good (observed on the drum but not in the image) △ Practical possible (slightly generated in black image) × Not practical (improper in image) Evaluation 6) Photosensitivity Table 2 shows the surface roughness and hardness of the surface of the charging member facing the body.

(Example 2) The amount of pyrrole to be polymerized in the gas phase was 1/10 of that in Example 1.
The same evaluation as in Example 1 was carried out except for the above.

Example 3 The same evaluation as in Example 1 was performed except that the amount of pyrrole to be polymerized in the gas phase was 10 times that of Example 1. Comparative Example 1 The same evaluation as in Example 1 was performed except that a single layer was not provided on the urethane resin layer.

Example 4 The same evaluation as in Example 1 was performed except that the cell diameter of the urethane foam was 150 μm.

[0059] (Comparative Example 2) Example 4, except that without providing a surface layer on the urethane resin layer and the single layer was evaluated in the same manner as in Example 1.

Example 5 The same evaluation as in Example 1 was performed except that the conductive monomer was thiophene.

Comparative Example 3 The same evaluation as in Example 1 was performed except that the urethane resin layer was a solid rubber roller in which carbon was dispersed in urethane rubber.

Comparative Example 4 The same evaluation as in Example 1 was performed except that the urethane resin layer was a solid rubber roller of hydrin rubber.

(Comparative Example 5 ) The same evaluation as in Example 1 was performed except that the amount of carbon in Comparative Example 3 was increased by a factor of 10.

(Comparative Example 6 ) The same evaluation as in Example 1 was performed except that the amount of carbon in Comparative Example 3 was reduced to 1/10.

[0065]

[Table 1]

[0066]

[Table 2] The charging roller as a contact charging member that contacts the photosensitive drum as the member to be charged may be non-rotating or may be driven to rotate. Further, the charging member is not limited to the roller type, and may have an appropriate shape and form such as a blade type or a pad type as shown in FIGS. 1 (b) and 1 (c). The same effect as the example can be obtained.

[0067]

As described above, uniform charging can be achieved by using a urethane foam resin, which exhibits conductivity by polymerizing a conductive monomer on the surface of a polyether-based polyurethane resin, as a contact charging member. In addition, the environmental stability is improved, and furthermore, a charging member that does not generate charging noise can be produced, in which charging failure and stable resistance in a medium resistance region satisfying pressure resistance can be obtained stably.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a charging member of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the charging member of the present invention.

FIG. 3 is a cross-sectional view showing one embodiment of the charging member of the present invention.

FIG. 4 is an explanatory diagram illustrating a configuration of an electrophotographic image forming apparatus to which the charging member of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Exposure device 5 Developing device 6 Paper feeding device 7 Transfer device 9 Fixing device 10 Cleaning device 11 Pre-exposure device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-296229 (JP, A) JP-A-63-10409 (JP, A) JP-A-62-84115 (JP, A) JP-A-1- 191880 (JP, A) JP-A-3-17669 (JP, A) JP-A-5-46020 (JP, A) JP-A-4-25868 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G03G 13/02 G03G 15/02-15/02 101 G03G 15/08 501 G03G 15/16 103 G03G 21/06

Claims (8)

(57) [Claims] 1. A contact charging member for charging by bringing a charging member into contact with a photoreceptor and superimposing a DC and an AC voltage, or applying only a DC voltage to energize the photoreceptor, wherein the charging is performed. The member has a resin layer on a conductive support, has a layer containing at least a foamed member in the resin layer, and the foamed member is a polyether type and has a form of open cells.
That polyurethane resin Ri conductive polyurethane resins der the conductive monomers were polymerized urethane surface in the vapor phase, on a layer of foam members, have at least one or more layers of the coating layer
Contact charging member, wherein to Rukoto. 2. The contact charging member according to claim 1 , wherein the resistance value is in the range of 10 ² to 10 ¹⁰ Ω · cm. 3. A 10-point average surface roughness of the surfaces in contact before Symbol photoreceptor, the contact charging member according to claim 1 or 2 is 5μm or less. 4. The method of claim compression set of 40% or less
The contact charging member according to any one of claims 1 to 3 . 5. The method according to claim 1, wherein the hardness is 50 ° or less .
The contact charging member according to any one of the above. 6. The contact charging member according to any one of the contact charging according to claim 1-5 member is a member for primary charging. 7. A contact charging member according to any of claims 1-5 wherein the contact charging member is a member for transfer charging. 8. A contact zone according to claim 1,
An electrophotographic apparatus comprising an electric member.