JP3327689B2 - Electrophotographic apparatus and image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus having an electrophotographic photosensitive member and a member for contact-charging the photosensitive member, wherein the electrophotographic device is charged by applying a voltage from the contact charging member to the photosensitive member. It relates to a forming method.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. The latent image is developed into a visible image by developing with toner, and the toner image is transferred to a transfer material such as paper as necessary, and then the toner image is fixed on the transfer material by heat, pressure, etc. to obtain a copy. Things. Further, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

In recent years, various organic photoconductive materials have been developed as photoconductive materials for electrophotographic photoreceptors, and in particular, a function-separated type having a charge generation layer and a charge transport layer laminated thereon has been put into practical use.
It is installed in copiers, printers, and facsimile machines. As a charging means in such an electrophotographic method, a means utilizing corona discharge has been used. However, since a large amount of ozone is generated, it is necessary to provide a filter. There were problems such as up.

As a technique for solving such a problem, a charging member such as a roller or a blade is brought into contact with the surface of a photoreceptor to form a narrow space in the vicinity of the contacting portion, which is interpreted according to the so-called Paschen's law. A charging method has been developed in which the generation of ozone is suppressed as much as possible by forming a discharge as possible, and among them, a roller charging method using a charging roller as a charging member is particularly preferably used in terms of charging stability. .

More specifically, since charging is performed by discharging from the charging member to the member to be charged, the charging is started by applying a voltage equal to or higher than a certain threshold voltage. For example, when the charging roller is brought into contact with an OPC photosensitive member having a photosensitive layer thickness of 25 μm, the surface potential of the photosensitive member starts to increase when a voltage of about 640 V or more is applied, and thereafter, the applied voltage is increased. The photosensitive member surface potential increases linearly at an inclination of 1.
Hereinafter, this threshold voltage is defined as a charging start voltage Vth. That is, in order to obtain the photoconductor surface potential Vd, the charging roller needs a DC voltage higher than Vd + Vth. Further, since the resistance value of the contact charging member fluctuates due to environmental fluctuations or the like, it has been difficult to set the potential of the photoconductor to a desired value.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 63-149669, a DC voltage corresponding to a desired Vd has a peak-to-peak voltage of 2 × Vth or more, as disclosed in JP-A-63-149669. An AC charging method in which a voltage on which an AC component is superimposed is applied to a contact charging member is used. This is A
The purpose of this is to achieve a leveling effect of the potential by C. The potential of the charged body converges to Vd, which is the center of the peak of the AC voltage, and is not affected by disturbance such as the environment.

However, even in such a contact charging device, the essential charging mechanism uses a discharge phenomenon from the charging member to the photosensitive member, and thus the voltage required for charging as described above. Requires a value equal to or higher than the photoconductor surface potential. When AC charging is performed for uniform charging, vibration and noise (hereinafter referred to as AC charging noise) of the charging member and the photoconductor due to the electric field of the AC voltage are generated, and the surface of the photoconductor is discharged. Deterioration and the like became remarkable, and this was a new problem.

On the other hand, as disclosed in JP-A-61-57958, there is an image forming method in which a photosensitive member having a conductive protective film is charged by using conductive fine particles. According to this, a photosensitive member having a semiconductive protective film having a resistance of 10 ⁷ to 10 ¹³ Ωcm is used as the photosensitive member, and the photosensitive member is charged by using conductive fine particles having a resistance of 10 ¹⁰ Ωcm or less. It is described that the photoreceptor can be uniformly charged by the discharge without unevenness without injecting electric charge into the photosensitive layer, thereby achieving good image reproduction. According to this method, vibration, noise, and the like, which are problems in AC charging, can be prevented. However, the toner adheres to the charging member due to scraping of the transfer residual toner by the conductive fine particles serving as the charging member. A change in charging characteristics occurs. Further, since the photosensitive member is charged by the discharge, the surface of the photosensitive member is still deteriorated by the discharge, and a high-voltage power source is required.

For this reason, charging by direct injection of charges into the photosensitive member has been desired. A method of applying a voltage to a contact charging member such as a charging roller, a charging brush, a charging magnetic brush, and injecting a charge into a trap level on the surface of the photoreceptor to perform contact injection charging is described in Japan Hardcopy, 1992, P287. As described in "Contact charging characteristics using conductive rollers", etc., these methods are methods in which injection charging is performed with a low-resistance charging member to which a voltage is applied to a photosensitive member having insulated darkness. There is a condition that the resistance value of the charging member is sufficiently low and that a material (conductive filler or the like) for imparting conductivity to the charging member is sufficiently exposed on the surface. For this reason, the above-mentioned literature also states that the charging member is preferably an aluminum foil or an ion-conductive charging member having a sufficiently reduced resistance value in a high-humidity environment. According to the study by the present applicants, the resistance value of the charging member capable of sufficiently injecting electric charge into the photoreceptor is 1 × 10 ³ Ωcm or less, and above this, a difference occurs between the applied voltage and the charging potential. It is known that a problem arises in the convergence of the charging potential at first.

However, when such a charging member having a low resistance value is actually used, scratches generated on the surface of the photoreceptor,
Excessive leakage current flows from the contact charging member into the pinhole or the like, causing poor charging in the surroundings, enlargement of the pinhole, and destruction of the electrification member.

In order to prevent this, the resistance of the charging member must be about 1 × 10 ⁴ Ω or higher. And the contradiction that charging is not performed occurs.

In view of the above, the above-described problems in the contact type charging device or the image forming method using the charging device are solved. It has been desired to achieve a balance between excellent charging properties and contradictory characteristics such as pinhole leakage on a member to be charged, which could not be prevented by a low-resistance contact charging member.

Further, in an image forming method using contact charging, image defects tend to occur due to poor charging due to contamination (spent) of the charging member, causing a problem in durability, and charging due to charge injection into a member to be charged. Also, it has been urgently necessary to prevent the influence of poor charging due to contamination of the charging member in order to enable printing of many sheets.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member and a member for charging and charging the photosensitive member, and the photosensitive member is charged by applying a voltage from the charging member. Another object of the present invention is to provide an electrophotographic apparatus and an image forming method capable of maintaining good charging characteristics for a long period of time.

[0015]

That is, the present invention provides an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and a contact charging member comprising magnetic particles and applying a voltage by contacting the photosensitive member. The photoreceptor has a volume resistance of 10 ⁸ Ωcm or more at a position farthest from the support.
And the magnetic particles are 2 × 10 ⁶ to 2 ×.
An electrophotographic apparatus having a volume resistance value of 10 ⁸ Ωcm and a particle size distribution of the magnetic particles having two or more peaks or shoulders in a range of 0.1 to 200 μm.

Further, the present invention provides an image comprising a step of bringing a charging member made of magnetic particles into contact with an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and applying a voltage to charge the photosensitive member. In the forming method, the photoreceptor has a charge injection layer having a volume resistance value of 10 ⁸ Ωcm or more farthest from the support, and the magnetic particles are 2 × 10 ⁶ to 2 × 10 ⁸ Ωc.
m , and a particle size distribution of the magnetic particles has two or more peaks or shoulders in a range of 0.1 to 200 μm.

The present invention is an image forming method which is less susceptible to toner spent while maintaining charging characteristics, and which has excellent durability stability.

The contact charging member serves to inject electric charges into the charge injection layer of the photoreceptor, and the charging current is concentrated on defects such as pinholes formed on the photoreceptor, thereby preventing the charging member and the photoreceptor from being electrically destructed. Must have a role to do. If the resistance value of the contact charging member is less than 1 × 10 ⁴ Ω, pinhole leakage cannot be prevented, and if it exceeds 1 × 10 ¹⁰ Ω, a current required for charging cannot be passed. Accordingly, the resistance value from the voltage application portion of the charging member to the portion in contact with the photoconductor is 1 × 1.
0 ⁴ Ω~1 should be in the range of × ¹⁰ 10 Ω. The resistance to be controlled within the above range, Oite the present invention,
The volume resistance of the magnetic particles is 2 × 10 ⁶ to 2 × 10 ⁸ Ωcm.
I do .

Further, the particle size distribution of the magnetic particles has two or more peaks or shoulders, thereby preventing the deterioration of charging due to contamination of the particle surface. That is, the specific surface area of the magnetic particles is increased, the density of the magnetic brush is increased, the magnetic particles are easily replaced, and stable charging is always obtained even if the surface is partially contaminated.

With the above configuration, it is possible to achieve both charging by charge injection and prevention of pinhole leakage, and it is possible to maintain stable charging characteristics.

Specifically, when a charged magnetic brush made of magnetic particles such as iron powder, ferrite, or iron oxide such as magnetite is used as the contact charging member, the resistance of the charging member is 1 × 10 ⁴ Ω to 1 × 10 ⁴ Ω. Although it is possible to make the range of × 10 ¹⁰ Ω, when the durability is performed, the toner remaining on the photoreceptor without being cleaned is scraped by the charging member, thereby causing toner spent on the charging member. I will. On the other hand, if magnetic particles of fine particles are used, the effect of toner spent can be prevented to some extent by increasing the surface area and increasing the density of the magnetic brush, but the replacement of the carrier occurs because the fluidity of the carrier deteriorates. It is not preferable for long-term use.

Therefore, in the present invention, the particle size is 10 to 1
A small particle size of 0.5 to 30 μm
It is preferable to mix magnetic particles having a fine particle diameter of m in order to maintain stable charging characteristics. Further, from the viewpoint of increasing the density of magnetic particles as a charging member, increasing the contact points with the photoconductor, and uniformly charging the photoconductor, the maximum peak position (P1) of the particle size distribution is 10 to 50 μm and the second Is more preferably in the range of 0.5 to 20 μm. In order to make the magnetic particles dense, it is effective to set the ratio (P2 / P1) between the maximum peak position and the position of the second peak or shoulder to 0.73, preferably 0.41 or less. . This is such that magnetic particles having a particle size at the position P1 can enter the gaps of the cubic lattice (cubic) (0.73 times or less of the particle size of P1), and preferably can enter the gaps of the planar cubic lattice (P1).
The reason is that magnetic particles having a particle size of P2 are present in the particle size distribution as peaks or shoulders because the magnetic particles are densely arranged and a conductive path is secured. Conceivable. In addition, from the viewpoint that a conductive path is easily secured even when toner enters the magnetic particles, the difference between the maximum peak position and the position of the second peak or shoulder (P1-P
2) is preferably 5 μm or more. More preferably, it is 10 μm or more. When (P1−P2) is less than 5 μm, the magnetic particles having a small particle diameter decrease due to durability, and the injection chargeability tends to slightly deteriorate. Further, the average particle size of the whole is preferably from 5 to 200 μm. If it is smaller than 5 μm, the magnetic brush is likely to adhere to the photoreceptor.
If it is larger than 00 μm, the density of the magnetic brush ears on the sleeve cannot be increased, and the chargeability to be injected into the photoconductor tends to deteriorate. More preferably, it is 10 to 100 μm, particularly preferably 10 to 50 μm. The amount of the fine magnetic particles is preferably 0.1 to 60 parts by weight based on 100 parts by weight of the small magnetic particles.

The average particle size and the particle size distribution of the whole were randomly determined by an optical microscope or a scanning electron microscope.
More than 00 pieces are extracted, the volume particle size distribution is calculated based on the maximum chord length in the horizontal direction, and the 50% average particle size is defined as the average particle size. Further, a peak or a shoulder is specified from the particle size distribution.
The average particle diameter of the magnetic particles was measured using a laser diffraction particle size distribution analyzer HEROS (manufactured by JEOL Ltd.).
The range of m to 200 μm may be measured by 32 logarithmic division, and the average particle size may be defined as the 50% average particle size of the volume distribution.

Further, it is preferable that the surface of the magnetic particles is coated with a medium resistance coat layer.

The coating layer has a volume resistance of 1 ×.
A vapor-deposited film or a conductive fine particle-dispersed resin film in the range of 10 ⁴ Ωcm to 1 × 10 ¹⁰ Ωcm is conceivable, but a conductive fine particle-dispersed resin film is preferable from the viewpoint of charging characteristics, productivity, cost, and the like. Preferably 10 ⁴ Ωcm to 10 ⁷ Ωc
m. Here, the method for measuring the volume resistance value of the above-mentioned coat layer is a polyethylene terephthalate (PET) film (about 100 μm) having a conductive fine particle-dispersed resin film deposited on its surface.
m), a coat layer (approximately 10 μm) was formed thereon, and this was coated with a volume resistance measuring device (4140B manufactured by Hewlett-Packard Company).
pAMATOR) at 10% at 23 ° C and 65%
The measurement was performed by applying a voltage of 0V.

When the surface of the magnetic particles is coated only with a binder resin, it is effective to prevent toner spent. However, the resistance of a coat layer made of only the binder resin is generally 1 × 10 ¹⁰ Ω.
cm or more, charge injection is unlikely to occur, and is unsuitable for use as a charging member. Therefore, the resist layer in which the conductive fine particles are dispersed is used as the coating layer.

Examples of the binder resin used in the coating layer of the magnetic particles include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate and butyric acid. Vinyl esters such as vinyl; α-methylenes such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Aliphatic monocarboxylic acid esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone It is like German polymer or copolymer, particularly typical binder resin, film forming property of the dispersibility and coating layer of the conductive fine particles, and the like toner spent prevented, that productivity, polystyrene,
Examples include styrene-alkyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, and polypropylene. Further, polycarbonate, phenol resin, polyester, polyurethane, epoxy resin, polyolefin, fluororesin, silicone resin, polyamide and the like can be mentioned. In particular, from the viewpoint of prevention of spent, it is more preferable to include a resin having a small critical surface tension, for example, a polyolefin, a fluororesin, a silicone resin, or the like.

As for the blending amount, the ratio of the fluorine-based resin, polyolefin-based resin or silicone-based resin to the total amount of the binder resin is preferably 1.0 to 60% by weight, and particularly preferably 2.
0-40% by weight is preferred. If the content is less than 1.0% by weight, the surface modification effect is not sufficient and the effect on toner spent is small. On the other hand, if it exceeds 60% by weight, both are difficult to be uniformly dispersed, so that a partial unevenness occurs in the volume resistance value, and the charging characteristics tend to deteriorate.

Examples of the fluorine resin include solvent-soluble copolymers such as polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, polytetrafluoroethylene, and polyhexafluoropropylene. Coalescence.

Examples of the silicone resin include KR271, KR282, KR311, and KR manufactured by Shin-Etsu Silicone Co., Ltd.
255, KR155 (straight silicone varnish),
KR211, KR212, KR216, KR213, K
R217, KR9218 (modified silicone varnish),
SA-4, KR206, KR5206 (silicone alkyd varnish), ES1001, ES1001N, ES
1002T, ES1004 (silicone epoxy varnish), KR9706 (silicone acrylic varnish), K
R5203, KR5221 (silicone polyester varnish) and SR2100, SR21 manufactured by Toray Silicone Co., Ltd.
01, SR2107, SR2110, SR2108, S
R2109, SR2400, SR2410, SR241
1, SH805, SH806A, SH840, etc. are used.

As the conductive fine particles, copper, nickel,
Metal such as iron, aluminum, gold, silver or iron oxide,
Metal oxides such as ferrite, zinc oxide, tin oxide, antimony oxide, and titanium oxide, and conductive powders such as carbon black may be used. Further, these conductive fine particles preferably have a volume resistance of 1 × 10 ⁷ Ωcm or less,
The particle size is preferably 1 μm or less. In addition, the conductive fine particles used in the present invention may be subjected to a surface treatment for the purpose of hydrophobicity, charge adjustment, and the like, if necessary.

The coating amount of the coating layer on the material to be coated is as follows:
The coating resin solid content is preferably 0.5 to 20% by weight. If the coating amount is less than 0.5% by weight, the effect of covering the material to be coated is not sufficient, and if it is 20% by weight or more, the effect is not substantially changed, but rather an adverse effect such as an increase in cost occurs.

[0033] As magnetic particles,
And contact the magnetic brush with the photoreceptor to charge it
For example, this material may be iron, cobalt, nickel
Alloys or compounds containing ferromagnetic elements such as
Which is used. If these are used as they are, the volume resistance value
Is not within the preferred range, so that oxidation treatment, reduction treatment, etc.
The volume resistance value adjusted to a preferred range by performing
For example, ferrite with adjusted composition, Zn with hydrogen reduction treatment
-For Cu ferrite and oxidized magnetite
Can be. In addition, the volume resistivity value is
Even if a charge layer is provided, the same charging characteristics as the initial
1 × 10^Four Ωcm-1 × 10 ^TenΩcm range
Is preferred. More preferably 1 × 10^Four Ωc
m ~ 1 × 10⁷ Ωcm.

As a method for producing the resin-coated magnetic particles containing the conductive fine particles, the coated material particles are immersed in a coating layer solution prepared by dissolving the conductive fine particles and the coating resin in an appropriate solvent. A method for forming a coat layer by volatilizing a solvent using a spray dryer, or drying while spraying a solution for a coat layer while forming a fluidized bed by putting the material to be coated in a general fluidized bed coating apparatus, A method of gradually forming a coat layer may, for example, be mentioned.

As the electrophotographic photosensitive member according to the present invention,
As described above, the layer farthest from the support has a volume resistivity of 1 × 10 ⁸ Ωcm or more, preferably 1 × 10 ⁸ Ωcm or more, in order to satisfy the conditions for sufficient chargeability and image deletion.
A photoconductor provided with a charge injection layer having a range of ¹⁵ Ωcm or less is used. More preferably, the volume resistivity is 1 × 10 ¹⁰ Ωcm to 1 × 10 ¹⁵ Ωcm from the viewpoint of image deletion and the like.
It is preferable to use one of 10 ¹² Ωcm to 1 × 10 ¹⁵ Ωcm. If the density is less than 1 × 10 ⁸ Ωcm, image charge may not be held in the surface direction in a high humidity environment, causing image deletion.
If it exceeds 0 ¹⁵ Ωcm, the charge from the charging member cannot be sufficiently injected and held, and the charging tends to be poor. By providing such a functional layer on the surface of the photoreceptor, it plays a role of retaining the charged electric charge injected from the charging member, and also plays a role of releasing this electric charge to the support of the photoreceptor at the time of light exposure, thereby reducing the residual potential. Reduce. Further, using the charging member and the photosensitive member according to the present invention, converged by adopting such a configuration, charge starting voltage V t h is small, more than most 90% of the voltage applied to the photosensitive member charge potential to the charging member It is now possible to do that. Here, as the charge injection layer,
It is characterized by a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin. It is also an effective means to form an inorganic layer having a resistance in the above range on the surface as a charge injection layer.

Here, the method of measuring the volume resistance value of the charge injection layer is the same as the method of measuring the material of the charging member coat layer described above.
A charge injection layer was formed on a polyethylene terephthalate (PET) film having a conductive film deposited on the surface, and this was used as a volume resistance measuring device (4140 manufactured by Hewlett-Packard Company).
B pAMATER) at 23 ° C and 65% environment.
The measurement was performed by applying a voltage of 00V.

The charge injection layer is composed of a metal vapor deposition film or a conductive fine particle resin dispersion film in which conductive fine particles are dispersed in a binder resin. The vapor deposition film is deposited, and the conductive fine particle resin dispersion film is dipped. The charge injection layer is formed by applying an appropriate coating method such as a spray coating method, a roll coating method, and a beam coating method. Further, a resin formed by mixing or copolymerizing an insulating binder resin with a resin having high light transmittance and ionic conductivity, or a resin formed of a single resin having a medium resistance and photoconductive properties may be used. In the case of the conductive fine particle resin dispersion film, the amount of the conductive fine particles preferably falls within the range of 2 to 100% by weight based on the binder resin. If it is less than 2% by weight, it is difficult to obtain a desired volume resistance value,
In the case where the value exceeds, the charge injection layer tends to be scraped off due to a decrease in film strength, and the life of the photoconductor tends to be shortened.

The binder resin of the charge injection layer can be the same as the binder resin of the lower layer. In this case, the coating surface of the charge transport layer is disturbed when the charge injection layer is coated. Care should be taken in selecting a coating method, as it may result.

Preferably, a lubricant powder is contained in the charge injection layer. The reason is that the friction between the photoreceptor and the injection charging member during charging is reduced, so the charging nip expands,
This is because the charging characteristics are improved. In addition, since the releasability of the photoreceptor surface is improved, even if magnetic particles having a small particle size are mixed, it is difficult to adhere to the photoreceptor. In particular, it is more preferable to use a fluorine resin, a silicone resin or a polyolefin resin having a low critical surface tension as the lubricant powder. Particularly preferred is tetrafluoroethylene resin (PTFE).
Is used. In this case, the amount of the lubricant powder is preferably 2 to 50% by weight, more preferably 5 to 40% by weight, based on the binder resin. If the amount is less than 2% by weight, the amount of the lubricant powder is not sufficient, so that the charging characteristics are not sufficiently improved.
If it exceeds 50% by weight, the resolution of the image and the sensitivity of the photoreceptor tend to be greatly reduced. When the surface is coated with an inorganic layer, the underlying photoconductive layer is preferably amorphous silicon, and a blocking layer, a photoconductive layer, and a charge injection surface layer are sequentially formed on a cylinder by a glow discharge method or the like. Preferably, it is formed.

[0040]

[Example of toner production]

Styrene-butyl acrylate copolymer (copolymer weight ratio 80:20) 100 parts by weight Magnetite 60 parts by weight Metal-containing azo pigment 2 parts by weight Low molecular weight polypropylene 3 parts by weight After mixing the above materials with a Henschel mixer, 130
The mixture was kneaded with an extruder set to ° C. After cooling the obtained kneaded material and coarsely pulverizing with a cutter mill,
The powder was finely pulverized by a jet mill using a jet stream and classified by wind power to obtain a black fine powder (magnetic toner particles) having a weight average particle diameter of 12 μm. For 100 parts by weight of this black fine powder,
0.9 parts by weight of silica hydrophobized with silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.

[Photoreceptor Production Example 1] The photoreceptor is a negatively charged organic photoreceptor (hereinafter referred to as an OPC photoreceptor), and five functional layers are provided on an aluminum drum having a diameter of 30 mm.

The first layer is an undercoat layer having a thickness of about 2 which is provided to smooth defects of the aluminum drum and to prevent the occurrence of moire due to the reflection of laser exposure.
It is a conductive layer of 0 μm.

The second layer is a positive charge injection preventing layer, which functions to prevent the positive charge injected from the aluminum support from canceling the negative charge charged on the surface of the photoreceptor. 10 ⁶ by nylon
This is a medium resistance layer having a thickness of about 1 μm and a resistance adjusted to about Ωcm.

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates a positive and negative charge pair by receiving laser exposure.

The fourth layer is a charge transport layer, in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charges charged on the photoreceptor surface cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the photoreceptor surface.

The fifth layer is a charge injection layer which is a feature of the present invention. The fifth layer is made of a photocurable acrylic resin, SnO ₂ ultrafine particles, and further increases the contact time between the contact charging member and the photoreceptor to achieve uniform charging. In order to carry out the above, tetrafluoroethylene resin particles having a particle size of about 0.25 μm are dispersed. Specifically, the particle diameter is reduced to about 0.03 by doping with antimony.
μm SnO ₂ particles of 70% by weight based on the resin,
30% by weight of fluorinated ethylene resin particles and 1.2 of dispersant
% By weight. As a result, the resistance of the photosensitive member surface was reduced to 5 × 10 ¹² Ωcm, compared with 2 × 10 ¹⁵ Ωcm in the case of the charge transport layer alone.

[Photoconductor Production Example 2]
A photoconductor was prepared in the same manner as in Photoconductor Manufacturing Example 1, except that the tetrafluoroethylene resin particles and the dispersant were not dispersed in the layer. As a result, the resistance of the photoconductor surface is 2 × 10 ¹² Ω
cm.

[Photoreceptor Production Example 3]
Photoconductor Production Example 1 except that the layer was doped with antimony to reduce the resistance and added SnO ₂ particles having a particle size of about 0.03 μm and dispersed in a photocurable acrylic resin at 200% by weight. A photoreceptor was prepared in the same manner as described above. Thereby, the resistance of the photoreceptor surface was reduced to 4 × 10 ⁷ Ωcm.

[Photoconductor Production Example 4] A blocking layer, a photoconductive layer and a surface layer were sequentially formed on a mirror-finished aluminum cylinder by a glow discharge method.

First, after setting the reaction chamber to about 7.5 × 10 ⁻³ Pa, while keeping the aluminum cylinder at 250 ° C.,
While H ₄ , B ₂ H ₆ , NO and H ₂ gas were fed into the reaction chamber, the gas was allowed to flow out of the reaction chamber, the internal pressure was set to about 30 Pa, and glow discharge was generated to form a 5 μm blocking layer.

After that, using a method similar to that for forming the blocking layer, using SiH ₄ and H ₂ gas, and setting the internal pressure to 50 Pa, a photoconductive layer of 20 μm is formed.
_A surface layer made of Si and C having a film thickness of 0.5 μm was formed by glow discharge under a pressure of 55 Pa using a gas of ₄ , CH ₄ and H ₂ to produce an amorphous silicon photoreceptor.

[Charging Member Production Example 1] Zn-Cu ferrite particles having an average particle size of 25 μm and Zn-Cu ferrite particles having an average particle size of 10 μm
Cu ferrite particles are mixed at a weight ratio of 1: 0.05, and the average particle diameter 25 having a peak at each average particle position.
Magnetic particles coated with a medium-resistance resin layer of μm ferrite particles were used as a charging member.

In the coating, 1 part by weight of a fluorine-acrylic resin and 1 part by weight of titanium oxide subjected to a conductive treatment as a conductive material are dissolved in 6 parts by weight of a mixed solution of dimethylformamide and methyl ethyl ketone, and this is mixed with glass beads. The mixture was dispersed with a paint shaker for 2 hours to prepare a solution for a coat layer. When the resistance of the coat layer formed from this coat layer solution was measured by the method described above, the volume resistivity was 7 × 10 ⁷ Ωcm. Next, this solution was applied to 300 parts by weight of the magnetic particles using a fluid bed type applicator (Spiracoater, manufactured by Okada Seiko Co., Ltd.). When the surface was observed with a scanning electron microscope S-800 (hereinafter simply referred to as SEM) manufactured by Hitachi, Ltd., the presence of the coat layer was confirmed throughout. The measurement of the volume resistance value of the magnetic particles was performed using the cell shown in FIG. That is, the cell A was filled with magnetic particles, the electrodes 1 and 2 were arranged so as to be in contact with the filled magnetic particles, a voltage was applied between the electrodes, and the current flowing at that time was measured. The measurement conditions are 23
Contact area S of filled magnetic particles with cells in an environment of 65 ° C. and 65%
= 2cm ² , thickness d = 1mm, load of upper electrode 10k
g, the applied voltage is 100V. The volume resistivity of the coated magnetic particles obtained through the drying step was 8 × 10 ⁶ Ωcm.

[Charging Member Production Example 2] Zn-Cu ferrite particles having an average particle size of 40 μm and Zn-Cu ferrite particles having an average particle size of 15 μm
Cu ferrite particles are mixed at a weight ratio of 1: 0.5, and an average particle diameter of 30 μm having a peak at each average particle diameter position.
m ferrite particles were used as a charging member. The volume resistivity of the mixed magnetic particles was 5 × 10 ⁶ Ωcm.

[Charging Member Production Example 3] Zn—Cu ferrite particles having an average particle diameter of 20 μm and Zn having an average particle diameter of 1.7 μm
-Cu ferrite particles are mixed at a weight ratio of 1: 0.05, and an average particle diameter 2 having a peak at each average particle diameter position
0 μm ferrite particles were used as a charging member. The volume resistivity of the mixed magnetic particles was 2 × 10 ⁶ Ωcm.

[Charging Member Production Example 4] Average particle size 25 μm
Zn-Cu ferrite particles and Z having an average particle size of 0.3 μm
n-Cu ferrite particles were mixed at a weight ratio of 1: 0.03, and ferrite particles having an average particle diameter of 20 μm and having a peak at each average particle diameter position were used as a charging member. The volume resistivity of the mixed magnetic particles was 2 × 10 ⁸ Ωcm.

[Charging Member Production Example 5]
Zn—Cu ferrite particles having a volume resistance of 5 × 10 ¹⁰ Ωcm were used as the charging member.

[Charging member manufacturing example 6]
Magnetite particles having a volume resistance value of 4 × 10 ³ Ωcm were used as a charging member.

[Embodiment 1] The principle of charging using the above-described photosensitive member and the contact charging member will be described. The present invention relates to a medium-resistance contact charging member for injecting charges into the surface of a photoreceptor having a medium-resistance surface resistance. Instead, the charge is charged by charging the conductive particles of the charge injection layer.

More specifically, it is based on the theory of charging a small capacitor having a charge transport layer as a dielectric and an aluminum support and conductive particles in the charge injection layer as both electrode plates with a contact charging member. is there. At this time, the conductive particles are electrically independent of each other and form a kind of minute float electrode. Therefore, macroscopically, the surface of the photoreceptor appears to be charged and charged to a uniform potential, but in reality, there are situations where countless minutely charged SnO ₂ covers the surface of the photoreceptor. ing. For this reason, even if image exposure is performed by laser, each SnO ₂ particle is electrically independent, so that an electrostatic latent image can be held.

Next, the electrophotographic printer used in the experiment in this embodiment will be described with reference to FIG. The process speed was 48 mm / sec, and the photoreceptor was manufactured under the environment of 23 ° C. and 65% using the photoreceptor production example 1.

The contact charging member is composed of the coated magnetic particles prepared in the charging member production example 1, a non-magnetic conductive sleeve for supporting the coated magnetic particles, and a magnet roll contained therein. It was coated with a thickness of 1 mm to form a charging nip having a width of about 5 mm between the photosensitive member and the photosensitive member. The gap between the magnetic particle holding sleeve and the photoconductor was about 500 μm. The magnet roll was fixed and rotated so that the surface of the sleeve rubbed in the opposite direction at twice the peripheral speed of the surface of the photoreceptor so that the photoreceptor and the magnetic brush were in uniform contact. In addition,
If there is no peripheral speed difference between the magnetic brush and the photoconductor,
Since the magnetic brush itself does not have a physical restoring force, if the magnetic brush is pushed away due to deflection or eccentricity of the photoconductor,
The nip of the magnetic brush cannot be secured, causing charging failure. For this reason, since it is necessary to always apply a new magnetic brush surface, in this embodiment, the magnetic brush is rotated in the reverse direction at three times the speed.

First, the contact charging member to which a DC voltage of -800 V has been applied is brought into contact with the photosensitive member and rotated to perform charging. Next, the exposure unit receives image exposure (image exposure). Next, a laser beam 13 from a laser diode, which has been intensity-modulated in accordance with an image signal, is scanned by a polygon mirror and used as an exposure means to form an electrostatic latent image on the photoconductor.

Next, reversal development is performed using the magnetic one-component insulating toner of the production example. 16m in diameter with magnet
The non-magnetic sleeve 14 is coated with the above-described negative toner, and is rotated at a constant speed with the photosensitive drum in a state where the distance from the surface of the photosensitive member is fixed at 300 μm to apply a voltage to the sleeve. The voltage is a DC voltage of -500V and a frequency of 20.
Jumping development is performed between the sleeve and the photoreceptor using a superimposed rectangular AC voltage of 00 Hz and a peak-to-peak voltage of 1200 V.

The image visualized by the toner in this way is then transferred to the transfer material 16. In the transfer section, a transfer roller 15 having a medium resistance is used. In this embodiment, transfer was performed by applying a DC voltage of +2000 V using a roller having a resistance of 5 × 10 ⁸ Ω.

The print image on which the toner image has been transferred onto the transfer material is thereafter fixed by the heat fixing roller 18,
Emitted outside the machine. The transfer residual toner is scraped off from the photosensitive drum by the cleaning blade 17 and is prepared for the next image formation.

When an image was evaluated using a printer having the above configuration, a DC voltage of -800 V was applied to the sleeve of the charging member, and the voltage was initially 0 V just after the photosensitive member passed through the charging nip once. The surface potential of the photoreceptor was charged to -770 V, and good chargeability was obtained. Also, at this time, no leak occurs even if a pinhole is formed on the photoconductor, and the magnetic particles constituting the contact charging member are not developed on the photoconductor.
A solid white image was obtained. Even after 4,000 sheets of this were durable, the same charging characteristics as those at the initial stage were exhibited, and a good solid black
A solid white image was obtained.

When charging failure occurs in reversal development, the history on the photosensitive member affects the charging.
One round of the photoconductor in four vertical images (about 94 m in this embodiment)
m) was evaluated as a solid black image (low potential), and immediately after that, a solid white image (high potential) was evaluated (charge ghost evaluation).
If charging failure occurs, the potential does not sufficiently rise immediately after solid black, and appears as fog in reversal development. However, no fog was observed in this image throughout the durability test.

Example 2 Image evaluation was performed in the same manner as in Example 1 except that the contact charging member in Example 1 was used for the charging member production example 2 and the photosensitive member was used for the photoconductor production example 2. Due to slight charging failure due to the reduction of the charging nip, there was a slight fog on the solid white image in the evaluation of the charging ghost, but good solid black and solid white images were obtained from the initial stage to 4000 sheets without practical problems.

Example 3 Image evaluation was performed in the same manner as in Example 1 except that the charging member manufacturing example 3 was used as the contact charging member in Example 1. As a result, good charge was obtained from the initial stage to 4000 sheets. Characteristics were obtained, and good solid black and solid white images were obtained without pinhole leakage or charging ghost.

Example 4 An image evaluation was carried out in the same manner as in Example 2 except that the contact charging member in Example 2 was changed to Production Example 4 of the charging member. When the sheet was durable, there was no problem in practical use, but slight charging failure (a solid white fog image in charging ghost evaluation) occurred. Observation of these magnetic particles by SEM showed that 0.3 μm particles were slightly reduced as compared with the initial stage.

[Embodiment 5] Canon copier, NP6
060, and slightly modified the charged part of the photoconductor,
The charging member described below was installed. The photoreceptor used was Photoreceptor Production Example 4, and the toner was a toner production example.

The contact charging member uses the magnetic particles prepared in the charging member manufacturing example 3, and is constituted by a non-magnetic conductive sleeve and a magnet roll included therein to hold the magnetic particles. 1m thick magnetic particles on sleeve
m, and the distance between the sleeve holding the magnetic particles and the photoconductor was set to about 0.5 mm so that the charging nip with the photoconductor was formed at 8 mm. The magnet is fixed, and the surface of the sleeve is 2
Rotation is performed at twice the speed in such a way that the photosensitive member and the magnetic particles are in uniform contact with each other.

First, a DC voltage of +450 V is applied, and the contact charging member is rotated in contact with the photosensitive member to uniformly charge the surface of the photosensitive member. The charged potential of the photoreceptor at the developed portion was +360 V when measured. However, the dark decay from the charged portion to the developing position is 50 V, and the photoconductor potential at the charged portion is 410 V.
It is. Image exposure is performed on the charged surface of the photoreceptor thus obtained to form an electrostatic latent image on the photoreceptor, developed with toner, and further transferred and fixed.

When an image was evaluated with a copying machine having the above-described configuration, the surface potential of the photosensitive member, which was initially 0 V, passed through the contact portion between the charging member and the photosensitive member, and sufficient charging performance was obtained. Good solid black and solid white images could be obtained.

Further, the copying machine used in this embodiment uses the normal development method, and such performances as the charging uniformity of the photosensitive member can be obtained by evaluating a solid black image. For example, poor charging appears as white streaks or white dots on solid black.

Further, when a durability test was performed on 500 sheets and a solid black image was evaluated, no white streak or white spots appeared.
It was no different from the early days.

Comparative Example 1 Image evaluation was performed in the same manner as in Example 2 except that the charging member manufacturing example 5 was used as the contact charging member in Example 2. Fog image).

Comparative Example 2 Image evaluation was performed in the same manner as in Example 2 except that the charging member manufacturing example 6 was used as the contact charging member in Example 2, and partial evaluation based on pinhole leak was performed from the beginning. Poor charging (black spots in solid white images) occurred.

Comparative Example 3 An image evaluation was performed in the same manner as in Example 1 except that the photosensitive member of Example 1 was changed to Photoconductor Production Example 3. From the initial stage, partial charging based on pinhole leak was performed. Poor (black spot in solid white image) occurred.

Further, the electric potential flowed in the horizontal direction, causing image deletion.

[Comparative Example 4] Using the same photoreceptor as in Example 5 and a modified NP6060 machine, and performing image evaluation using Charging Member Production Example 5 as a charging member, poor charging was observed on solid black from the beginning. The resulting white streaks occurred.

[0083]

According to the present invention, there is provided an electrophotographic apparatus having an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and a contact charging member comprising magnetic particles and applying a voltage in contact with the photosensitive member. The photoreceptor is 10 furthest away from the support
Having a charge injection layer having a volume resistance value of ⁸ Ωcm or more ,
The magnetic particles have a volume resistivity of 2 × 10 ⁶ to 2 × 10 ⁸ Ωcm.
Having a particle size distribution of 0.1 to 200 μm.
An electrophotographic apparatus having two or more peaks or shoulders in the range of m, and an image forming method including a step of charging using the electrophotographic apparatus, imparts a uniform charge to the photoreceptor surface, and obtains a stable image. It became possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically showing an electric resistance measuring device.

FIG. 2 is a schematic diagram illustrating a configuration of an electrophotographic printer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main electrode 2 Upper electrode 3 Insulator 4 Ammeter 5 Voltmeter 6 Constant voltage device 7 Magnetic particle 8 Guide ring 11 Photosensitive drum 12 Contact charging member 13 Exposure means 14 Developing device 15 Transfer roller 16 Transfer material 17 Cleaning blade 18 Thermal fixing roller

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Yano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Harumi Ishiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Tadashi Furuya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-6-258918 (JP, A) JP-A-6-274005 (JP) JP-A-6-282148 (JP, A) JP-A-6-301265 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02 101 G03G 5/147

Claims (18)

(57) [Claims] 1. An electrophotographic apparatus comprising: an electrophotographic photosensitive member having a photosensitive layer on a conductive support; and a contact charging member comprising magnetic particles and applying a voltage by contacting the photosensitive member. A charge injection layer having a volume resistance value of 10 ⁸ Ωcm or more farthest from the support, wherein the magnetic particles have a volume resistance value of 2 × 10 ⁶ to 2 × 10 ⁸ Ωcm, and Wherein the particle size distribution has two or more peaks or shoulders in the range of 0.1 to 200 μm. 2. The electrophotographic apparatus according to claim 1, wherein the peak or shoulder of the particle size distribution of the magnetic particles is in the range of 0.5 to 30 μm and 10 to 100 μm. 3. The relationship between the maximum peak (P1) of the magnetic particles and the second peak or shoulder (P2) is 10%.
The electrophotographic apparatus according to claim 1, wherein P1> P2, and the difference P1−P2 is 5 μm or more. 4. 4. The relationship between the maximum peak (P1) of the magnetic particles and the second peak or shoulder (P2) is P1 = 10.
In the range of ~50μm, P1> is P2, and claims 1 to 3 Neu the ratio P2 / P1 is 0.73 or less
An electrophotographic apparatus according to any of the preceding claims. 5. The surface of the magnetic particles has a volume resistivity of 10 ^4.
2. The coating according to claim 1, wherein the coating layer is coated with a coating layer of ¹⁰ to 10 ¹⁰ Ωcm.
5. The electrophotographic apparatus according to any one of claims 1 to 4. 6. The electrophotography according to claim 5, wherein the coating layer of the magnetic particles is a conductive powder-dispersed resin film containing conductive fine particles and a fluorine resin, a polyolefin resin or a silicone resin as a binder resin. apparatus. 7. The charge injection layer has a volume resistance of 10 ¹⁵ Ω.
The electrophotographic apparatus according to any one of claims 1 to 6 , wherein the size is not more than cm. 8. The charge injection layer, conductive fine particles, an electrophotographic apparatus <br/> according to any one of claims 1 to 7 containing a binder resin and a lubricant powder. 9. The electrophotographic apparatus according to claim 8, wherein said lubricant powder is a fluororesin, a polyolefin resin or a silicone resin. 10. A charging member made of magnetic particles is brought into contact with an electrophotographic photosensitive member having a photosensitive layer on a conductive support,
An image forming method including a step of charging the photosensitive member by applying a voltage, wherein the photosensitive member is located at a position furthest away from the support;
0 ⁸ having a charge injection layer having the above volume resistivity [Omega] cm, the magnetic particles have a volume resistivity of ^{2 × 10 6 ~2 × 10 8} Ωcm, and particle size distribution of the magnetic particles is 0.1 ~ 20
An image forming method having two or more peaks or shoulders in a range of 0 μm. 11. The image forming method according to claim 10, wherein the peak or shoulder of the particle size distribution of the magnetic particles is in the range of 0.5 to 30 μm and 10 to 100 μm. 12. The maximum peak (P1) of said magnetic particles and 2
P1 is 1 in relation to the second peak or shoulder (P2)
The range of 0 to 50 m, P1> P2, and the difference P1-P2 is 5 m or more.
2. The image forming method according to 1. 13. The maximum peak (P1) of said magnetic particles and 2
P1 is 1 in relation to the second peak or shoulder (P2)
The thickness is in the range of 0 to 50 μm, P1> P2, and the ratio P2 / P1 is 0.73 or less.
3. The image forming method according to any one of 2. 14. The magnetic particles having a surface with a volume resistance of 10
The image forming method according to claim 10, wherein the image is coated with a coat layer having a thickness of ⁴ to 10 ¹⁰ Ωcm. 15. The image forming method according to claim 14, wherein the coating layer of the magnetic particles is a conductive powder-dispersed resin film containing conductive fine particles and a fluorine resin, a polyolefin resin or a silicone resin as a binder resin. Method. 16. The charge injection layer having a volume resistance of 10 ¹⁵
The image forming method according to any one of claims 10 to 15, wherein the value is Ωcm or less. 17. charge injection layer is, claims 10 to 16 noise containing conductive fine particles, a binder resin and a lubricant powder
An image forming method according to any one of the preceding claims. 18. The method according to claim 1, wherein the lubricant powder is a fluororesin, a polyolefin resin or a silicone resin.
8. The image forming method according to 7.