JP2003076113A - Electrostatic charging member for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrostatic charging member of an image forming device which obviates the abnormal electric discharge by a photoreceptor defect and does not give rise to a break out. SOLUTION: This electrostatic charging member is furnished with a conductive base and a resistance regulating layer formed on the conductive base. The resistance regulating layer consists of a thermoplastic resin composition dispersed with polymeric ion conductive materials and its surface is covered by a protective layer consisting of a resin containing a conductive polymeric material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member of an image forming apparatus, and more specifically, to an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, a facsimile, etc. The present invention relates to a charging member suitable as a charging roller that executes a charging process.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus,
A charging roller is generally used as a charging member for charging a photosensitive drum or the like.

As a charging method using a charging roller, a contact charging method in which a charging roller is brought into contact with a photosensitive drum is generally used, but the contact charging method has the following problems. The material that constitutes the charging roller seeps out from the charging roller, and forms an electric roller mark that adheres to and transfers to the surface of the photosensitive drum. When the AC voltage is applied to the charging roller, the charging roller in contact with the photoconductor drum vibrates and a charging sound is generated. If the toner on the photoconductor adheres to the charging roller, the charging performance is deteriorated, and especially when the above-mentioned bleeding occurs, the toner adheres more easily.
The substances that make up the charging roller adhere to the photoconductor drum. Then, if the rotation of the photosensitive drum is stopped for a long time, the charging roller may be permanently deformed.

To solve this, for example, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 3-240076 describes a proximity charging method in which a charging roller is disposed in the vicinity of a photosensitive drum. In the proximity charging method, for example, a gap or a gap of 0.005 to 0.3 mm is formed, the charging roller is arranged to face the photosensitive drum, and the photosensitive drum is charged by applying a voltage to the charging roller. There is.

In this proximity charging device, since the charging device and the photosensitive drum are not in contact with each other, there is a problem in the contact charging device that the substances constituting the charging roller adhere to the photosensitive drum and the photosensitive drum. There is no permanent deformation of the charging roller that occurs when the charging roller is stopped for a long time. Further, since the amount of toner that adheres to the charging roller decreases, it is difficult for the toner and the like on the photosensitive drum to adhere to the charging roller.

The charging roller of the proximity charging device has a structure in which an elastic body such as vulcanized rubber is coated around a conductive support called a core metal. However, the charging roller formed of such an elastic body causes the following problems in the proximity charging method. In order to form a gap between the photosensitive drum and the charging roller, the charging roller is arranged close to the photosensitive drum with a gap holding member such as a spacer interposed in the non-image area at both ends. Therefore, it is difficult to make the voids uniform, and as a result, charging potential fluctuations and image unevenness caused by the fluctuations occur. Furthermore, the vulcanized rubber material that constitutes the elastic body easily causes changes over time such as fatigue and deformation.
The gap between the charging roller and the photosensitive drum changes due to this change with time.

[0007]

[Patent Document 1] Japanese Patent Application Laid-Open No. 10-1613
The charging member described in Japanese Patent Publication 97 can solve these problems. This charging member is used for a charging roller and a transfer belt, and is made of a thermoplastic resin to which an ion conductive material is added. The thermoplastic resin is made of polyurethane elastomer, and the ion conductive material is made of electrolyte salt such as lithium salt.

In this charging member, since the electrolyte salt is dispersed in the matrix resin at the molecular level, the variation in the resistance value is small, and the partial charging failure does not affect the image quality. However, since such an electrolyte salt tends to bleed out on the surface of the matrix resin,
When used as a charging roller, toner adheres due to bleed-out, causing an image defect.

An object of the present invention is to provide a charging member for an image forming apparatus which does not cause bleed out.

[0010]

In order to achieve the above object, the conductive member of the image forming apparatus of the present invention comprises a conductive support and a resistance adjusting layer formed on the conductive support. The resistance adjusting layer is made of a thermoplastic resin composition in which a polymer ion conductive material is dispersed, and the surface thereof is covered with a protective layer made of a resin containing a conductive polymer material.

[0011]

In the resistance adjusting layer, the polymer ion conductive material is a polymer compound, and moreover, it is uniformly dispersed and fixed in the matrix polymer, so that bleed out does not occur. Then, the polymer type ion conductive material of the resistance adjusting layer and the conductive polymer material forming the protective layer are uniformly dispersed in the binder resin, respectively, so that aggregation or the like does not occur,
Even if there are defects such as uneven thickness and pinholes on the photoreceptor,
No voltage concentration or abnormal discharge occurs in that part.

When the resin forming the protective layer is a water-based resin coating material containing a conductive polymer material, it is possible to carry out production without concern about environmental pollution or surrounding pollution due to residual solvent.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a conductive member of an image forming apparatus of the present invention will be described below with reference to the drawings.

The charging member described as an example is a charging roller of an electrophotographic copying machine. FIG. 2 shows the periphery of the photosensitive drum of this copying machine.

Reference numeral 101 is a photoconductor drum having a photoconductor on the surface of which an electrostatic latent image is formed, 102 is a charging roller of the present invention which is disposed in proximity to the photoconductor drum 101 and performs a charging process, and 103 is a laser beam. Alternatively, exposure of reflected light or the like of an original document, 104 is a developing roller that attaches toner to the electrostatic latent image formed on the photoconductor of the photoconductor drum 101, 105 is a power pack for applying voltage to the charging roller 102, and 106. Is a transfer roller for transferring the toner image on the photoconductor onto the recording paper 107, 108 is a cleaning device for cleaning the photoconductor drum 101 after the transfer process,
Reference numeral 109 is a surface electrometer for measuring the surface potential of the photosensitive drum 101.

To form an image, the charging roller 102 charges the surface of the photoconductor drum 101 to a desired potential, the exposure device projects image light onto the photoconductor drum 101, and the electrostatic image corresponding to the desired image is formed. After the latent image is formed on the photoconductor on the photoconductor drum 101, the developing roller 104 develops the electrostatic latent image with toner to form a toner image on the photoconductor, and the transfer roller 106 is placed on the photoconductor drum. The toner image on the recording paper 10
It is made by transferring to 7. The recording paper 107 to which the toner image is transferred is conveyed to a fixing device (not shown), and the fixing device heats and pressurizes the toner to fix the toner on the recording paper. By repeating these, the recording paper 1
A desired image is formed at 07. The toner remaining on the photosensitive drum 101 without being transferred is cleaned by the cleaning device 108 after the transfer.

FIG. 1 shows details of the charging roller 102. The charging roller 102 includes a conductive support 201 and a resistance adjusting layer 202.

The resistance adjusting layer 202 is made of a thermoplastic resin composition in which a polymer type ion conductive material is dispersed.

Photoreceptor drum 10 by charging roller 102
The charging mechanism to 1 is discharge according to Paschen's law in minute discharge between the charging roller 102 and the photosensitive drum 101. In order to obtain the function of holding the photoconductor at a predetermined charging potential, the material used for the resistance adjusting layer 202 preferably has a volume resistivity of 10 ⁶ to 10 ⁹ Ωcm. If it exceeds 10 ⁹ Ωcm, the charge amount will be insufficient,
It becomes impossible to obtain a sufficient charging potential for obtaining a uniform image. When the volume resistivity is lower than 10 ⁶ Ωcm, voltage concentration or leakage or abnormal discharge occurs.

The thermoplastic resin used for the resistance adjusting layer 202 is not particularly limited as long as it is a non-elastic body. A general-purpose resin such as a polyethylene resin, a polypropylene resin, a polymethylmethacrylate resin, a polystyrene resin, or a copolymer thereof such as an AS resin or an ABS resin is preferable because it can be easily molded.

The polymer type ion conductive material dispersed in the thermoplastic resin preferably has a single resistance value of 10 ⁶ to 10 ¹⁰ Ωcm. Because it is easy to reduce the resistance of the thermoplastic resin,
A compound containing a quaternary ammonium salt group, particularly a polyolefin containing a quaternary ammonium salt group is preferable.
Further, a compound containing a polyether ester amide is also a preferable polymer type ion conductive material.

The amount of the polymer ion conductive material blended with the thermoplastic resin is required to have a desired resistance value. Therefore, 30 parts of the polymer ion conductive material is added to 100 parts by weight of the thermoplastic resin. It is preferable to blend in the range of 70 parts by weight. Dispersion with respect to the thermoplastic resin is carried out by a biaxial kneader, a kneader or the like, so that the polymer type ion conductive material is uniformly dispersed in the matrix polymer at the molecular level.

Resistance adjusting layer 20 on the conductive support 201
2 is formed by coating the conductive support 201 with the above semiconductive resin composition by extrusion molding, injection molding, or the like. The required surface accuracy of the resistance adjusting layer 202 is obtained at an arbitrary stage, for example, by forming the resistance adjusting layer 202 on a conductive support and then cutting or grinding the surface of the resistance adjusting layer 202. To be

In the obtained resistance adjusting layer 202, the high molecular weight ion-conductive material is uniformly dispersed in the matrix polymer at the molecular level, so that the resistance value does not vary. Since the polymer type ion conductive material is a polymer compound, it is uniformly dispersed and fixed in the matrix polymer, so that bleed out hardly occurs. Bleed out can also be avoided by using a nonionic polymer type conductive material having a polyether group such as polyalkylene oxide. Since this conductive material has a high molecular weight, it is dispersed and fixed in the matrix resin, and bleeding out to the surface hardly occurs. However, since the nonionic polymer-type conductive agent has a resistance value of 10 ⁸ to 10 ¹¹ Ωcm alone, it has a smaller effect of lowering the resistance than the electrolyte salt disclosed in JP-A-10-161397, so that the charging property is low. It is difficult to control the medium resistance region required for the roller to 10 ⁶ to 10 ⁹ Ωcm.

Further, in the charging roller 102 according to the present invention, the protective layer 203 is formed on the surface of the resistance adjusting layer 202.

The protective layer 203 is made of a resin containing a conductive polymer material. The conductive polymer material is preferably a polymer compound containing a polyaniline component, a polypyrrole component, a polythiophene component and the like.

The protective layer 203 is formed by preparing a mixed solution of such a conductive polymer and a binder resin, and by a dipping method, a spray coating method or the like.
It is done by coating on the surface of 2.

The solvent of the mixed solution is not particularly limited as long as the electroconductive polymer and the binder resin are soluble, but it is water-free because it is non-polluting and can be used without fear of contamination of peripheral members due to residual solvent. Is desirable.

The resistance value of the protective layer 203 can be adjusted by the mixing ratio when the resin binder solution is mixed with the conductive polymer solution. Leakage due to irregularities in the thickness of the photoconductor, defects such as pinholes, and the like can be prevented by making the resistance value of the protective layer 203 higher than that of the resistance adjustment layer 202. If the resistance value of the protective layer 203 is too high, the charging efficiency is lowered. Therefore, the difference between the resistance value of the protective layer 203 and the resistance value of the resistance adjusting layer 202 is preferably 10 ³ Ωcm or less.

Such a conductive roller has a resistance adjusting layer 20.
2 is a polymer type ion conductive material uniformly dispersed in the matrix polymer at the molecular level, does not cause bleed-out, has no variation in resistance value, and the protective layer 203 is also a conductive polymer material and a binder resin. Since and are uniformly mixed at the molecular level, there is no variation in the resistance value. For this reason, even if there are defects such as uneven thickness and pinholes on the photoconductor, voltage concentration, abnormal discharge or leakage does not occur at that portion, and abnormal images such as white spots do not occur. In order to prove this, the present inventor created a charging roller based on the present invention and a charging roller in which the composition of the protective layer was changed, and examined the presence or absence of an abnormal image caused by voltage concentration on the defective portion of the photoconductor and abnormal discharge. . explain in detail.

In the charging roller 102 according to the present invention,
The conductive support 201 is made of stainless steel. The diameter is 8 mm. The resistance adjusting layer 202 is made of an ABS resin and an ion conductive polymer compound containing a quaternary ammonium salt group. The ABS resin is GR-1500 (trade name) manufactured by Denki Kagaku Kogyo Co., Ltd., and the ion-conductive polymer compound containing a quaternary ammonium salt group is Reolex AS-1720 (trade name) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. . The adjustment resistance layer 202 is a GR-1500.
To 100 parts by weight, and 30 parts of ROLEX AS-1720
It is formed by coating a conductive support by injection molding with a composition containing parts by weight. The resistance value of the composition is 1 × 10 ⁸ Ωcm.

The conductive polymer material constituting the protective layer 203 is TX-CP-SA200 (trade name) manufactured by Nippon Shokubai Co., Ltd. The binder resin is a water-based urethane resin paint, made by Asahi Denka Kogyo Co., Ltd.
350 (product name).

The protective layer 203 is made of these TX-CP-S.
It is formed by mixing A200 and ADEKA BONTITER HUX-350 at a solid content ratio of 2: 8, spray-coating the resulting mixed solution on the resistance adjustment layer 202, and then drying. The obtained charging roller 102 has a diameter of 12 mm.

As a charging roller for comparison, the same as the charging roller of the present invention, a conductive support made of stainless steel and having a diameter of 8 mm was used, and 100 parts by weight of GR-1500 manufactured by Denki Kagaku Kogyo Co., Ltd. as ABS resin was used. Reolex AS-1720 from Daiichi Kogyo Seiyaku Co., Ltd. as an ion-conductive polymer compound containing a quaternary ammonium salt group
It is made by coating a conductive support with a composition having a resistance value of 1 × 10 ⁸ Ωcm mixed with 0 part by weight by injection molding.

The protective layer is composed of polyamide resin and carbon black. The polyamide resin is Daiamide T-171 (trade name) manufactured by Daicel Huls Ltd.
The protective layer is formed by mixing Daiamide T-171 with 10% by weight of carbon black based on the total solid content, spray-coating the mixture onto the resistance adjustment layer, and then drying. The diameter of the obtained charging roller is 12 mm which is the same as that of the present invention.

These charging rollers were incorporated in an image forming apparatus as shown in FIG. 2, and the charging potential of the photosensitive drum 101 and the image on the recording paper were evaluated. At this time, a spacer tape is adhered to both ends of each charging roller as a space regulating member so that the space between the charging roller and the photosensitive drum 101 is 50 μm. A DC voltage of -800 V was applied to the charging roller according to the present invention, and an AC voltage of 2400 Vpp and a frequency of 2 kHz was applied to that of the comparative example.

The following are the evaluation results of the charging roller according to the present invention and that of the comparative example. The evaluation is the presence or absence of an abnormal image caused by voltage concentration on the defective portion of the photoconductor and abnormal discharge.

Charging Potential of Photoreceptor Variation Range of Charging Potential Abnormal Image Comprehensive Evaluation Present Invention -800V 8V No ○ Comparative Example -780V 40V Yes × As apparent from the above, the charging roller 10 according to the present invention
No. 2 has one-fifth variation in the charging potential of the photoconductor,
No abnormal image is generated.

[0039]

As described above, since the conductive member of the image forming apparatus of the present invention has no bleed-out and the conductive material does not agglomerate, an image of excellent quality can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a charging roller that is an example of a charging member of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of an image forming apparatus in which the charging roller shown in FIG. 1 is incorporated.

[Explanation of symbols]

201 ... Conductive support 202 ... Resistance adjustment layer 203 ... protective layer

Claims (6)

[Claims] 1. A conductive support and a resistance adjusting layer formed on the conductive support, wherein the resistance adjusting layer is made of a thermoplastic resin composition in which a polymer ion conductive material is dispersed, and A charging member for an image forming apparatus, the surface of which is covered with a protective layer made of a resin containing a conductive polymer material. 2. The charging member for an image forming apparatus according to claim 1, wherein the resin forming the protective layer is an aqueous resin coating material containing a conductive polymer material. 3. The charging member for an image forming apparatus according to claim 2, wherein the water-based resin coating material is a water-based urethane resin coating material. 4. A charging member for an image forming apparatus according to claim 1, which is made of a polymer compound containing a conductive polymer material polyaniline component. 5. A charging member for an image forming apparatus according to claim 1, wherein the charging member is made of a polymer compound containing a conductive polymer material polypyrrole component. 6. A conductive polymer material comprising a polymer compound containing a polythiophene component.
The charging member of the image forming apparatus according to any one of 1.