JP2614305B2 - Electrophotographic charging member and electrophotographic apparatus using the charging member - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic charging member, and more particularly, to an electrophotographic charging member for charging an electrophotographic photosensitive member and an electrophotographic apparatus using the charging member. .

[Prior art] The charging process in an electrophotographic process using an electrophotographic photoreceptor is generally performed by applying a high voltage (DC) to a metal wire.
(5 to 8 KV) is applied and charging is performed by the corona generated. However, in this method, ozone or NO _X
There is a problem that the surface of the photoreceptor is deteriorated by corona products such as the above, causing image blurring and deterioration, and contamination of the wire affects the image quality, resulting in image white spots and black stripes.

On the other hand, the electric current flowing toward the photoreceptor is 5 to 30
%, Most of which flowed to the shield plate and was inefficient as a charging means.

In order to compensate for such disadvantages, methods of directly charging have been studied and many methods have been proposed (for example, see Japanese Patent Application Laid-Open No.
178567, JP-A-56-104351, JP-A-58-40
566, JP-A-58-139156, JP-A-58-15097
No. 5 gazette). However, in practice, even if the photosensitive member is charged by the above-described contact charging method, uniform charging of each part of the surface of the photosensitive member is not performed, and spot-like charging unevenness occurs. For example,
In the reversal development method, even if a process of light image exposure or less is applied to the photoreceptor in the spot-like uneven charging state, the output image becomes a black spot image on the spot corresponding to the spot-like uneven charging, and the regular image method causes the spot-like unevenness. On the other hand, a spot-like white spot image is obtained, and a high-quality image is not obtained. In addition, although there are many proposals for the direct charging method, there is no market record at all. The reasons for this include the uniformity of charging and the occurrence of discharge breakdown of the photoconductor due to the direct application of voltage. One of the breakdown points of discharge breakdown is, for example, in the case of a cylindrical photosensitive member, there is a drawback that the charge in the entire axial direction flows to the breakdown point and the charge is not charged.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, and to stably supply a high-quality image free of spot-like fogging due to non-uniform charging and image defects due to discharge breakdown of a photoreceptor. An object of the present invention is to provide a member and an electrophotographic apparatus using the charging member.

[Means for solving the problem]

The charging member for electrophotography of the present invention has a base layer and a surface layer on a substrate, and the surface layer contains a phenol resin.

Further, the electrophotographic apparatus of the present invention includes the above-described charging member for electrophotography, a photosensitive member arranged to be in contact with the charging member, and a photosensitive member for exposing the photosensitive member to form a latent image. The image forming apparatus has an exposure unit and a developing unit for developing the latent image.

 Hereinafter, the present invention will be further described.

The charging member for electrophotography of the present invention has a multilayer structure, and the surface layer of the charging member for electrophotography that contacts the electrophotographic photosensitive member contains a phenol resin.

Examples of the phenol resin include phenol formaldehyde resin, ortho-cresol formaldehyde resin, meta-cresol formaldehyde resin, para-cresol formaldehyde resin, bisphenol A-formaldehyde resin, p-phenyl phenol formaldehyde resin, p
-T-butylphenol formaldehyde resin, pt-
Examples thereof include aminophenol formaldehyde resin, pt-octylphenol formaldehyde resin, and p-nonylphenol formaldehyde resin. Further, another resin or a small amount of conductive particles may be mixed into the surface layer as long as the characteristics as the charging member are not deteriorated.

The volume resistivity of the surface layer is preferably larger than the volume resistivity of the base layer in contact with the surface layer described below, and 10 ⁶ Ωcm to 10 ⁶ Ωcm.
¹² Ω · cm, and particularly preferably 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm.

The thickness of the surface layer is 5 μm to 500 μm, particularly 20 μm to 200 μm.
μm is preferred.

The base layer covers the surface of metals such as aluminum, iron, copper, etc., conductive polymers such as polyacetylene, polypyrrole, and polythiophene, and resin and rubber such as rubber and resin, and polycarbonate and polyester, which are treated by dispersing carbon and metal. One or more layers laminated or coated with a metal or another conductive substance can be used.

The volume resistivity of the base ^{layer, 10 0 Ω · cm~10 11 Ω} · cm, particularly preferably ^{10 2 Ω · cm~10 10 Ω ·} cm.

The thickness of the base layer is preferably from 10 μm to 20 mm, particularly preferably from 20 μm to 10 mm.

When a conventional insulating resin such as polyurethane or other nylon is used for the surface layer, as shown in Japanese Patent Publication No. 50-13661, charging is not performed unless a high voltage of 4 KV or more is applied, resulting in poor charging efficiency. Moreover, such a high-voltage ozone or NO _x or the like product produced during charging and used in many image blur to the photosensitive member, an adverse effect such flow. On the other hand, by including a phenol resin as in the present invention, charging becomes possible and image defects are remarkably improved.

When the surface of the charging member is made of a conductive material, for example, rubber or insulating resin that has been conductively treated with metal, conductive polymer, carbon dispersion, or the like, or the surface of the insulating material is made of a conductive material. In the case of a laminated or coated one, when discharge breakdown of the photoconductor occurs, 1
Excessive current flows from the charging member to two break points (pinholes), and the voltage applied to the charging member drops.
Poor charging occurs over the entire contact area of the photoreceptor, and a white band appears on the image in the normal development and a black band appears in the reversal phenomenon.

However, by including a phenolic resin in the surface layer, the volume resistivity can be adjusted to reduce the occurrence of a voltage drop due to excess current flowing when the electrophotographic photosensitive member has a defect such as dielectric breakdown.

Furthermore, as a charging member, it is necessary that the electrical resistance is not affected by changes in the external environment, particularly changes in the humidity of the atmosphere, but nylon is particularly low-temperature and low-humidity (eg, 15 ° C, 10% RH). There is also a problem that the volume resistance is increased by three digits.

The charging member for electrophotography containing the phenolic resin of the present invention in the surface layer has a small change in volume resistance even under low temperature and low humidity, and can obtain a stable charging ability.

The shape of the charging member may be any shape such as a roller, a brush, a blade, and a belt, and may be selected according to the specifications and form of the electrophotographic apparatus. Among these, the roller shape is preferable from the viewpoint of charging uniformity.

FIG. 1 is a sectional view of a roller-shaped charging member for electrophotography 1 according to the present invention. In this case, the charging member 1 is basically laminated on the conductive substrate 2 in the order of the base layer 3 and the surface layer 4.

The conductive substrate 2 serves as the central axis of the charging member 1 and can be made of a metal such as iron, copper, stainless steel, aluminum, or an aluminum alloy, or a conductive resin. And the like are used. Another layer such as an adhesive layer may be provided between the conductive substrate 2 and the base layer 3 or between the base layer 3 and the surface layer 4 if necessary.

Examples of a method for manufacturing the charging member 1 include a method in which a base layer and a surface layer are sequentially formed or coated on a conductive substrate, or a method in which the conductive substrate is passed through the center after forming the surface layer. And the like.

When charging the electrophotographic photosensitive member using the charging member of the present invention, a voltage is applied from an external power supply 5 connected to the charging member 1 as shown in FIG. The photoconductor 6 placed in contact is charged.

When an image is formed by an electrophotographic apparatus using the charging member 1, a voltage is applied from an external power supply 5 to the charging member 1 which is arranged in contact with the electrophotographic photosensitive member 5, and the surface of the electrophotographic photosensitive member 6 is cleaned. It is charged, and the image on the original is image-exposed to the photoreceptor by the image exposure means 7 to form an electrostatic latent image. Next, the electrostatic latent image on the photoconductor is developed (visualized) by attaching the toner in the developing device 8 to the photoconductor, and the toner image on the photoconductor is further transferred onto the paper 10 by the transfer charger 9. After the transfer, the toner remaining on the photoreceptor without being transferred to the paper at the time of transfer by the cleaning device 11 is collected.

Although an image can be formed by the above-described electrophotographic process, if residual charges remain on the photoreceptor, it is better to remove the residual charges by the pre-exposure means 12 before charging.

The light source of the image exposure means 7 is a halogen light, a fluorescent light,
Laser light, LED, etc. can be used.

 The developing method may be a normal image method or a reversal phenomenon method.

The method of installing the charging member is not limited to a specific method, and any method such as a method of fixing the charging member and a method of moving the photosensitive member by rotating in the same direction or in the opposite direction to the photosensitive member can be used.

The charging member for electrophotography of the present invention can be used not only for primary charging but also in a transfer charging step and a charge removing step which require charging in an electrophotographic process.

The voltage applied to the charging member is preferably applied in the form of a pulsating voltage obtained by superimposing a DC voltage and an AC voltage. In this case, the applied voltage is a DC voltage of ± 200 V to ± 1500 V and a peak-to-peak voltage of 200 V.
A pulsating voltage on which an AC voltage of 0 V or less is superimposed is preferable. Further, a DC voltage or an AC voltage can be used as the applied voltage.

The method of applying the voltage depends on the specifications of each electrophotographic apparatus, but in addition to the method of applying the desired voltage instantaneously, the method of gradually increasing the applied voltage for the purpose of protecting the photoconductor, the direct current In the case of application in a form in which AC is superimposed on AC, a method of applying a voltage in the order of DC → AC or AC → DC can be adopted.

The electrophotographic photosensitive member charged by the charging member of the present invention is configured as follows.

The photosensitive layer is provided on a conductive support. As the conductive support, those having conductivity itself, for example, aluminum, aluminum alloys, stainless steel, nickel, and other metals can be used.In addition, aluminum, aluminum alloys, indium oxide-tin oxide alloys, and the like can be used. It is possible to use a plastic having a layer formed by vacuum deposition, a support in which conductive particles (for example, carbon black, tin oxide particles, etc.) are coated on a metal or plastic with an appropriate binder, a plastic having a conductive binder, or the like. it can.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6,
(Nylon 66, nylon 610, copolymer nylon, etc.) Polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 5 μm or less, preferably 0.5 μm or less.
μm to 3 μm is appropriate. The undercoat layer preferably has a resistivity of 10 ⁷ Ω · cm or more in order to exhibit its function.

The photosensitive layer can be formed by coating an organic or inorganic photoconductor with a binder resin as necessary, or can be formed by vapor deposition.

The form of the photosensitive layer is preferably a function-separated laminated photosensitive layer of a charge generation layer and a charge transport layer.

The charge generation layer can be formed by depositing a charge generation material such as an azo pigment, a phthalocyanine pigment, a quinone pigment, or a perylene pigment, or by coating with a suitable binder resin (without a binder).

The thickness of the charge generation layer is 0.01 μm to 5 μm, particularly 0.05 μm.
μm to 2 μm are preferred.

The charge transport layer comprises a hydrazone compound, a styryl compound,
It can be formed by dissolving a charge transport material such as an oxazole compound or a triazoleamine compound in a binder resin having a film-forming property.

The thickness of the charge transport layer is 5 μm to 50 μm, particularly 10 μm
-30 μm is preferred.

Note that a protective layer may be provided on the photosensitive layer to prevent deterioration due to ultraviolet light or the like.

The electrophotographic charging member of the present invention is not limited to a copying machine,
It can also be used in electrophotographic applications such as laser beam printers, CRT printers, and electrophotographic prepress systems.

Example 1 First, a charging member was manufactured as follows.

100 parts by weight of chloroprene rubber was melt-kneaded with 5 parts by weight of conductive carbon, and the mixture was molded to a diameter of 20 × 230 mm through a stainless steel shaft having a diameter of 6 × 250 mm to provide a base layer of a roller-shaped charging member. The volume resistance of this substrate is
It was 3 × 10 ⁴ Ω · cm when measured in an environment of 22 ° C. and 60% humidity.

Next, 10 parts by weight of a phenol formaldehyde resin was dissolved in 90 parts by weight of methanol, dip-coated on this base layer, and a charging member surface layer was provided so that the film thickness after heating and drying was 200 μm. In addition, this surface layer was similarly provided on an aluminum sheet, and the volume resistance was measured.

 Next, an electrophotographic photosensitive member was manufactured as follows.

As a conductive support, an aluminum cylinder having a thickness of 0.5 mm and a diameter of 60 mm × 260 mm was prepared.

Copolymerized nylon (trade name: CM8000, manufactured by Toray Industries, Inc.) 4
Parts by weight and type 8 nylon (trade name: Ratskamide
5003, Dainippon Ink Co., Ltd.) 4 parts by weight of methanol 50
And 50 parts by weight of n-butanol, and dip-coated on the conductive support to form a polyamide undercoat layer having a thickness of 0.6 μm.

The following structural formula Was dispersed in a sand mill for 10 hours together with 120 parts by weight of cyclohexanone together with 10 parts by weight of a disazo pigment and 10 parts by weight of a polyvinyl butyral resin (trade name: Esrec BM2 manufactured by Sekisui Chemical Co., Ltd.). 30 parts by weight of methyl ethyl ketone was added to the dispersion and applied onto the undercoat layer to form a 0.15 μm thick charge generation layer.

Prepare 10 parts by weight of a polycarbonate Z resin (manufactured by Mitsubishi Gas Chemical Co., Ltd.) having a weight average molecular weight of 20,000, and have the following structural formula Benzene with 10 parts by weight of hydrazone compound
Dissolved in 80 parts by weight. This was applied on the above-mentioned charge generating layer to form a charge transporting layer having a thickness of 16 μm, thereby producing Photoconductor No. 1.

The charging member was mounted in place of the corona charger for temporary charging of a normal image copying machine (PC-20: manufactured by Canon) having the same apparatus configuration as that of FIG. 2, and the photosensitive member used was photosensitive member No. 1. . The applied voltage of the temporary charging was a superposition of a DC voltage of -750 V and an AC peak-to-peak voltage of 1500 V. The potential of the dark part potential and the light part potential were measured, and the image when a 1 mm pinhole was opened on the photoreceptor was examined. The results are shown in Table 1.

Further, the volume resistance of the surface of the charging member in a low-temperature and low-humidity state at a temperature of 15 ° C. and a humidity of 10%, and the potential characteristics and images when the charging member is mounted on a normal image copying machine are also examined. Indicated.

Example 2 A charging member was manufactured in the same manner as in Example 1 except that a meta-cresol formaldehyde resin was used instead of the phenol formaldehyde resin in the charging member of Example 1, and evaluation was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 3 A charging member was manufactured in the same manner as in Example 1 except that pt-butyl phenol formaldehyde resin was used in place of the phenol formaldehyde resin in the charging member of Example 1, and evaluated in the same manner as in Example 1. . The results are shown in Tables 1 and 2.

Example 4 A charging member was manufactured in the same manner as in Example 1 except that a p-nonylphenol formaldehyde resin was used instead of the phenol formaldehyde resin in the charging member of Example 1, and evaluation was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 The charging member base layer of Example 1 was directly attached in place of the primary corona charger, and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 2 A charging member base layer was prepared in the same manner as in Example 1. Next, 0.2 parts by weight of conductive carbon to 10 parts by weight of chloroprene rubber,
90 parts by weight of methyl ethyl ketone was added and dispersed by a ball mill. This dispersion is dip-coated on the charging member base layer,
The charging member surface layer was provided so that the film thickness after drying was 200 μm.

The charging member thus manufactured was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 3 A charging member base layer was prepared in the same manner as in Example 1. Next, 10 parts by weight of nylon-66 was dissolved in 90 parts by weight of dimethylformamide, dip-coated on the charging member base layer, and a charging member surface layer was provided so that the film thickness after drying was 200 μm.

The charging member thus manufactured was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 4 A charging member base layer was prepared in the same manner as in Example 1. Next, 5 parts by weight of polyether polyol and 5 parts by weight of toluylene diisocyanate are dissolved in methyl ethyl ketone, dip coated on the charging member base layer, and provided with a charging member surface layer so that the film thickness after drying becomes 200 μm. Was.

The charging member thus manufactured was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 5 A charging member was manufactured as follows.

100 parts by weight of chloroprene rubber was melt-kneaded with 5 parts by weight of conductive carbon, and was molded to a diameter of 20 × 230 mm through a stainless steel shaft of 6 × 250 mm at the center to provide a roller-shaped charging member base layer. The volume resistance of this substrate is
It was 3 × 10 ⁴ Ω · cm when measured in an environment of 22 ° C. and 60% humidity.

Next, 10 parts by weight of a phenol formaldehyde resin was dissolved in 90 parts by weight of methanol, dip-coated on this base layer, and a charging member surface layer was provided so that the film thickness after drying was 80 μm. In addition, this surface layer was similarly provided on an aluminum sheet, and the volume resistance was measured.

 Next, an electrophotographic photosensitive member was manufactured as follows.

A layer up to the undercoat layer was formed in the same manner as in Example 1, and 20 parts by weight of ε-copper phthalocyanine (manufactured by Toyo Ink), 10 parts by weight of polyvinyl butyral (Esrec BL-S, manufactured by Sekisui Chemical), and 70 parts by weight of methyl ethyl ketone were sand-milled. The dispersion is dip-coated on the undercoating layer to obtain a film thickness of 0.
A 2 μm charge generation layer was formed. Next, a charge transport layer was formed on the charge generation layer in the same manner as in Example 1, and photoconductor No. 2 was manufactured.

The charging member was used instead of a primary corona charger of a reversal developing type laser printer (LBP-8: manufactured by Canon) having the same apparatus configuration as that of FIG. 2, and the photoreceptor used was photoreceptor No. 2. The applied voltage for primary charging was a superposition of DC voltage -750 V and AC peak-to-peak voltage of 1500 V, dark potential and light potential were measured, and the image when a 1 mm pinhole was opened on the photoreceptor was examined. .

 The results are shown in Table 3.

Furthermore, the volume resistance of the surface layer of the charging member in a low-temperature and low-humidity state at a temperature of 15 ° C. and a humidity of 10%, and the potential characteristic and image when the charging member was mounted on a reversal developing laser beam printer were simultaneously examined. It was shown to.

Example 6 A charging member was manufactured in the same manner as in Example 5 except that a meta-cresol formaldehyde resin was used instead of the phenol formaldehyde resin in the charging member of Example 5, and evaluation was performed in the same manner as in Example 5. The result is the third
The results are shown in Tables and Table 4.

Example 7 A charging member was produced in the same manner as in Example 5 except that pt-butylphenol formaldehyde resin was used in place of the phenol formaldehyde resin in the charging member of Example 5, and evaluated in the same manner as in Example 5. did. The results are shown in Tables 3 and 4.

Example 8 A charging member was manufactured in the same manner as in Example 5 except that the p-nonylphenol formaldehyde resin was used instead of the phenol formaldehyde resin in the charging member of Example 5, and evaluation was performed in the same manner as in Example 5. The results are shown in Tables 3 and 4.

Comparative Example 5 The charging member base layer of Example 5 was directly attached instead of the primary corona charger, and the photoconductor was evaluated in the same manner as in Example 5. The results are shown in Tables 3 and 4.

Comparative Example 6 A charging member base layer was prepared in the same manner as in Example 5. Next, 0.2 parts by weight of conductive carbon to 10 parts by weight of chloroprene rubber,
90 parts by weight of methyl ethyl ketone was added and dispersed by a ball mill. This dispersion is dip-coated on the charging member base layer,
The charging member surface layer was provided so that the film thickness after drying was 80 μm.

The charging member thus manufactured was evaluated in the same manner as in Example 5. The results are shown in Tables 3 and 4.

Comparative Example 7 A charging member base layer was prepared in the same manner as in Example. Next, 10 parts by weight of nylon-66 were dissolved in 90 parts by weight of dimethylformamide, dip-coated on the charging member base layer, and a charging member surface layer was provided so that the film thickness after drying was 80 μm.

The charging member thus manufactured was evaluated in the same manner as in Example 5. The results are shown in Tables 3 and 4.

Comparative Example 8 A charging member base layer was prepared in the same manner as in Example 5. Next, 5 parts by weight of polyether polyol and 5 parts by weight of toluylene diisocyanate are dissolved in methyl ethyl ketone, dip coated on the charging member base layer, and provided with a charging member surface layer so that the film thickness after drying becomes 80 μm. Was.

The charging member thus manufactured was evaluated in the same manner as in Example 5. The results are shown in Tables 1 and 2.

As is clear from the above results, the charging member containing the phenolic resin according to the present invention in the surface layer has excellent charging ability, maintains an appropriate image density, and suppresses the occurrence of image defects. In addition, leakage due to pinholes is prevented, and horizontal streaks (white spots) are prevented. Further, it exhibits excellent charging characteristics even under low temperature and low humidity, has an appropriate image density, and does not cause image defects.

〔The invention's effect〕

By using the charging member for electrophotography of the present invention, stable potential characteristics can be obtained, image defects are reduced, and leakage due to pinholes can be reduced. Further, stable potential characteristics and image characteristics can be obtained even under low temperature and low humidity.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of the electrophotographic charging member of the present invention, and FIG. 2 is a schematic diagram of an electrophotographic apparatus using the electrophotographic charging member. REFERENCE SIGNS LIST 1 charging member 2 conductive substrate 3 base layer 4 surface layer 6 electrophotographic photoreceptor

Claims (2)

(57) [Claims] 1. A charging member for electrophotography, comprising a base layer and a surface layer on a substrate, wherein the surface layer contains a phenol resin. 2. A charging member for electrophotography according to claim 1, a photosensitive member arranged in contact with said charging member, and an exposing means for exposing said photosensitive member to form a latent image. And a developing means for developing the latent image.