JPH086355A - Electrophotographic apparatus and image forming method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an electrophotographic apparatus and an image forming method capable of giving a uniform image to a surface of a photoreceptor and obtaining a stable image. In an electrophotographic apparatus having an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and a contact charging member made of magnetic particles for applying a voltage to the photosensitive member, the photosensitive member is supported by the support. It has a charge injection layer farthest from the body, the resistance value between the voltage applying portion of the charging member and the portion in contact with the photosensitive member is 10 ⁴ to 10 ⁷ Ω, and the surface of the magnetic particles is smooth. An electrophotographic apparatus, which is a mixture of magnetic particles A and magnetic particles B having an uneven surface, and an image forming method including a step of charging using the electrophotographic apparatus.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a number of methods are known as electrophotography, but generally, a photoconductive substance is used to form an electric latent image on a photoconductor by various means, and then the electrophotographic image is formed. The latent image is developed with toner to make it a visible image, and if necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat or pressure to obtain a copy. It is a thing. Further, the toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by the 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 in which a charge generation layer and a charge transport layer are laminated has been put into practical use.
It is installed in copiers, printers, and facsimiles. As a charging means in such an electrophotographic method, a means utilizing a corona discharge has been used, but it is necessary to provide a filter because a large amount of ozone is generated, thus making the apparatus large and running cost. There were problems such as ups.

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 the photosensitive member to form a narrow space in the vicinity of the contact portion, which is interpreted by the so-called Paschen's law. A charging method that suppresses ozone generation as much as possible by forming such a discharge has been developed. Among them, the roller charging method using a charging roller as a charging member is preferably used from the viewpoint of charging stability. .

Specifically, since charging is performed by discharging from the charging member to the body to be charged, the charging is started by applying a voltage equal to or higher than a certain threshold voltage. For example, when a 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 begins to rise when a voltage of about 640 V or higher is applied, and thereafter the applied voltage is increased. On the other hand, with a slope of 1, the photosensitive member surface potential increases linearly.
Hereinafter, this threshold voltage is defined as the charging start voltage Vth. That is, in order to obtain the photoreceptor surface potential Vd, the charging roller needs a DC voltage of Vd + Vth, which is higher than the required DC voltage. Further, since the resistance value of the contact charging member fluctuates due to environmental fluctuations, it is difficult to set the potential of the photoconductor to a desired value.

Therefore, as disclosed in Japanese Patent Laid-Open No. 63-149669, a DC voltage corresponding to a desired Vd has a peak-to-peak voltage of 2 × Vth or more in order to further uniformize the charging. An AC charging method is used in which a voltage with an AC component superimposed is applied to the contact charging member. This is A
This is for the purpose of leveling the potential by C, and the potential of the charged body converges on 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, since the essential charging mechanism uses the discharge phenomenon from the charging member to the photosensitive member, the voltage required for charging as described above. Is required to have a value equal to or higher than the surface potential of the photoconductor. In addition, when AC charging is performed for uniform charging, vibration and noise (hereinafter referred to as AC charging sound) of the charging member and the photoconductor due to the electric field of the AC voltage are generated, and also the photoconductor surface of the photoconductor is discharged. Deterioration became noticeable and became a new problem.

On the other hand, as disclosed in Japanese Patent Laid-Open No. 61-57958, there is an image forming method in which a photosensitive member having a conductive protective film is charged with conductive fine particles. According to this, a photoconductor having a semiconductive protective film having a resistance of 10 ⁷ to 10 ¹³ Ωcm is used as the photoconductor, and the photoconductor is charged by using conductive fine particles having a resistance of 10 ¹⁰ Ωcm or less. It is described that, by doing so, it is possible to uniformly charge the photosensitive member by discharge without injecting charges into the photosensitive layer and to perform good image reproduction. According to this method, vibration and noise, which are problems in AC charging, can be prevented, but toner remains on the charging member due to scraping of the transfer residual toner by the conductive fine particles as the charging member, Changes in charging characteristics occur. Further, since the surface of the photoconductor is deteriorated due to the discharge because it is charged by the discharge, a high-voltage power supply is also required.

Therefore, there has been a demand for charging by directly injecting charges into the photoconductor. A method of applying a voltage to a contact charging member such as a charging roller, a charging brush, or a charging magnetic brush to inject charges into a trap level on the surface of a photosensitive member to perform contact injection charging is described in Japan Hardcopy 1992, P287. Although it is described in "Contact charging characteristics using a conductive roller", these methods are methods of performing injection charging with a low-resistance charging member to which a voltage is applied to a dark-insulating photoconductor. It is a condition that the resistance value of the charging member is sufficiently low and that the material (conducting filler, etc.) that makes the charging member electrically conductive is sufficiently exposed on the surface. For this reason, in the above-mentioned documents, it is said that the charging member is preferably an aluminum foil or an ion-conducting charging member having a sufficiently low 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 charge into the photoconductor is 1 × 10 ³ Ωcm or less, and above this, a difference occurs between the applied voltage and the charging potential. At the beginning, it is known that a problem occurs in the convergence of the charging potential.

However, when such a charging member having a low resistance value is actually used, scratches generated on the surface of the photosensitive member,
Excessive leakage current flows from the contact charging member to the pinhole and the like, resulting in defective charging around the pinhole, enlargement of the pinhole, and electrical breakdown of the charging member.

In order to prevent this, the resistance value of the charging member needs to be about 1 × 10 ⁴ Ω or more. However, as described above, the charging member having the resistance value has the property of injecting charge into the photosensitive member. Will decrease, resulting in a contradiction that charging is not performed.

Therefore, the problems as described above in the contact type charging device or the image forming method using the charging device are solved, that is, the charge injection which is not caused unless the low resistance contact charging member is used is excellent. It has been desired to achieve both the antistatic property and the contradictory property of pinhole leak on the body to be charged, which cannot be prevented by the low-resistance contact charging member.

Further, in the image forming method using contact charging, image defects are likely to occur due to defective charging due to stains (spent) of the charging member, and durability tends to be problematic. Also in this case, it is an urgent task to prevent the influence of charging failure due to dirt on the charging member, in order to enable printing on a large number of sheets.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to have an electrophotographic photosensitive member and a member for injecting and charging the photosensitive member, and charging the photosensitive member by applying a voltage from the injection charging member. An 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 composed of magnetic particles for applying a voltage to the photosensitive member. In the electrophotographic apparatus, the photoconductor has a charge injection layer farthest from the support, and the resistance value between the voltage application part of the charging member and the part in contact with the photoconductor is 1
The electrophotographic apparatus is characterized in that the magnetic particles are 0 ⁴ to 10 ⁷ Ω and the magnetic particles are a mixture of magnetic particles A having a smooth surface and magnetic particles B having an uneven surface.

The present invention also includes an image having a step of charging a charging member made of magnetic particles to 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 farthest from the support, and the resistance value between the voltage applying portion of the charging member and the portion in contact with the photoreceptor is 10 ⁴ to 1 1.
0 is ⁷ Omega, and an image forming method, wherein the magnetic particles have a smooth surface magnetic particles A and the surface is a mixture of uneven magnetic particles B.

The present invention is an image forming method which is excellent in durability and stability while being less affected by toner spent while maintaining the charging characteristics.

The contact charging member charges the charge injection layer of the photoreceptor.
The role of injecting the
The charging current concentrates on the defects, and the charging member and the photoconductor are energized.
It must also have the role of preventing destruction. contact
The resistance value of the charging member is 1 × 10 ^Four Pinhole is less than Ω
1 x 10⁷ Necessary for charging when exceeding Ω
Can not flow a large current. Therefore, the charging member
The resistance value from the pressure applied part to the part in contact with the photoconductor is 1 ×
10^Four Ω ~ 1 x 10⁷ Must be in the Ω range. Well
In order to control the resistance value within the above range, the present invention
The volume resistance value of the magnetic particles concerned is 10^Four Ωcm-10⁷ Ω
It is preferably cm.

Further, the magnetic particles are a mixture of those having a smooth surface shape (magnetic particles A) and those having an uneven surface (magnetic particles B), and the prevention of charge deterioration due to contamination of the particle surface is achieved. That is, it is because the specific surface area of the magnetic particles is increased, the magnetic particles are easily replaced, and stable charging is always obtained even if a part of the surface is contaminated.

By adopting the above-mentioned structure, it becomes possible to achieve both charging by charge injection and prevention of pinhole leak, 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 value of the charging member is 1 × 10 ⁴ Ω-1. Although it is possible to set it in the range of × 10 ⁷ Ω, if the durability is increased, the toner remaining on the photosensitive member without being cleaned is scraped off by the charging member, so that toner spent on the charging member occurs. The injection chargeability deteriorates. Therefore, if magnetic particles having an uneven surface are used, the influence of the toner spent can be prevented to some extent by increasing the surface area, but since the fluidity of the carrier is deteriorated, replacement of the carrier is unlikely to occur, which is not preferable for long-term use. Therefore, in the present invention, stable charging characteristics were achieved by mixing the one having a smooth surface shape (magnetic particle A) and the one having an uneven surface (magnetic particle B). It is preferable that each of the magnetic particles A and B is contained in an amount of 10% by weight or more.

The magnetic particles A have a substantially smooth surface,
It is generated by a plasma method or the like at a high temperature above the melting point of the composition material. The magnetic particles B are produced by sintering a raw material, and the shape of the raw material is substantially left on the surface. The average pore diameter of the surface of the magnetic particles B is 0.15 to 2.
5 μm is preferable. More preferably, it is 0.5 to 2 μm.

The surface pore diameter is measured by a mercury porosimetry porosimeter (MERCURY PRE manufactured by Carlo Erba Co.).
(SSURE POROSIMTER MOD220)
Was performed. The measurement of pore size by mercury porosimetry is based on the properties of non-wetting liquids in capillaries. Wetting angle 9
A liquid with a temperature of 0 degrees or more cannot enter the pores by itself because of surface tension, so it is necessary to apply pressure from the outside in order to put the liquid into the pores, and the pressure has a certain relationship with the pore diameter. have. The average pore size is calculated from this pressure and the physical properties of mercury.

The average particle size is preferably 5 to 200 μm. If it is less than 5 μm, the magnetic brush is apt to adhere to the photoconductor, and if it is more than 200 μm, the density of the spikes of the magnetic brush on the sleeve cannot be made dense, and the charging property to the photoconductor is deteriorated. There is a tendency. The thickness is more preferably 10 to 100 μm, and particularly preferably 15 to 50 μm. The average particle size was randomly extracted by 100 or more with an optical microscope or a scanning electron microscope, and the maximum chord length in the horizontal direction was taken as the particle size.

Further, it is also one of the preferable modes that the surface of the magnetic particles is coated with a medium resistance coating layer. At this time, it is preferable that the surface shape is preserved even after forming the coat layer.

The coat layer has a volume resistance value of 1 ×.
A vapor deposition film or a conductive fine particle dispersed resin film in the range of 10 ⁴ Ωcm to 1 × 10 ⁹ Ωcm can be considered, but the conductive fine particle dispersed resin film is preferable from the viewpoint of charging characteristics, productivity and cost. Preferably 10 ⁴ Ωcm to 10 ⁷ Ωc
m. Here, the method for measuring the volume resistance value of the coating layer is as follows. A polyethylene terephthalate (PET) film (about 100 μm) having a conductive fine particle dispersed resin film deposited on the surface
m), a coat layer (about 10 μm) is formed on the layer, and a volume resistance measuring device (manufactured by Hewlett Packard 4140B) is used.
pAMASTER) at 23 ° C, 65% environment 10
The measurement was performed by applying a voltage of 0V.

Although coating the surface of the magnetic particles only with the binder resin is effective in preventing toner spent, the resistance of the coating layer containing only the binder resin is generally 1 × 10 ¹⁰ Ω.
Since it is as high as cm or more, charge injection hardly occurs and it is unsuitable for use as a charging member. Therefore, the conductive fine particle dispersed medium resistance resin film is used as the coat layer.

The binder resin used in the coating layer of the magnetic particles includes styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate and butyric acid. Vinyl ester such as vinyl; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, α-methylene such as dodecyl methacrylate. Aliphatic monocarboxylic acid ester; vinyl ether such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl ketone 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 thereof 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 preventing spent, it is more preferable to contain a resin having a small critical surface tension, such as polyolefin, fluororesin, and silicone resin.

The blending amount is preferably 1.0 to 60% by weight, particularly preferably 2.60% by weight, of the fluororesin, the polyolefin resin or the silicone resin with respect to the total amount of the binder resin.
0-40% by weight is preferred. When the content is less than 1.0% by weight, the effect of surface modification is insufficient and the effect on the toner spent is small. On the other hand, if it exceeds 60% by weight, it is difficult to uniformly disperse both of them, so that partial unevenness in the volume resistance value occurs, and the charging characteristics tend to deteriorate.

Examples of the fluororesin include solvent-soluble co-polymers such as polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, polytetrafluoroethylene, polyhexafluoropropylene. An example is 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 Toray Silicone SR2100, SR21
01, SR2107, SR2110, SR2108, S
R2109, SR2400, SR2410, SR241
1, SH805, SH806A, SH840 and the like are used.

The conductive fine particles include copper, nickel,
Metals such as iron, aluminum, gold, silver or iron oxide,
Examples thereof include metal oxides such as ferrite, zinc oxide, tin oxide, antimony oxide and titanium oxide, and conductive powder such as carbon black. The conductive fine particles preferably have a volume resistance value of 1 × 10 ⁷ Ωcm or less,
The particle size is preferably 1 μm or less. The conductive fine particles used in the present invention may be subjected to a surface treatment for the purpose of making them hydrophobic, adjusting the charge, etc., if necessary.

The coating amount of the coating layer on the material to be coated is
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 covering effect of the material to be coated is not sufficient, and if it is 20% by weight or more, the effect does not substantially change, and adverse effects such as cost increase occur.

The magnetic particles are magnetically erected.
And then charge this magnetic brush by contacting it with the photoconductor.
For this purpose, for example, iron, cobalt, nickel
Alloys or compounds containing ferromagnetism elements such as
Which is used. If these are used as they are, the volume resistance value
Does not fall within the preferred range, so there is no need for oxidation or reduction.
What has been done to adjust the volume resistance value to a preferable range,
For example, ferrite whose composition is adjusted, Zn which has been subjected to hydrogen reduction treatment
-Used with Cu ferrite, oxidized magnetite, etc.
Can be. In addition, its volume resistance value is
The same charging characteristics as in the initial stage can be maintained even if a coating layer is provided.
1 x 10 for^Four Ωcm ~ 1 x 10 ⁹ Ωcm range
Is preferred. More preferably 1 × 10^Four Ωc
m ~ 1 × 10⁷ Ωcm.

The method for producing the resin-coated magnetic particles containing the conductive fine particles is as follows. After the particles to be coated are dipped in a solution for the coating layer prepared by dissolving the conductive fine particles and the coating resin in an appropriate solvent, A method of forming a coat layer by volatilizing a solvent using a spray dryer, or drying while coating a solution for a coat layer while forming a fluidized bed by putting particles to be coated in a general fluidized bed coating device, Examples thereof include a method of gradually forming a coat layer.

As the electrophotographic photosensitive member according to the present invention,
As described above, in the layer farthest from the support, the volume resistance value is in the range of 1 × 10 ⁸ Ωcm to 1 × 10 ¹⁵ Ωcm in order to satisfy the conditions of not causing sufficient chargeability and image deletion. It is preferable to use a photoreceptor provided with a certain charge injection layer. More preferably, in view of image deletion, the volume resistance value is 1 × 10 ¹⁰ Ωcm to 1 × 10 ¹⁵ Ωcm, and the volume resistance value is 1 × 10 in consideration of environmental fluctuation of the volume resistance value.
^It is preferable to use one having a resistance of ¹² Ωcm to 1 × 10 ¹⁵ Ωcm. Cause smeared images for charge in a high-humidity environment is not held on the surface direction is less than ^{1 × 10 8 Ωcm, 1 ×} 10 15
If it exceeds Ωcm, the charged charge from the charging member will be injected sufficiently.
It cannot be held and tends to cause poor charging. By providing such a functional layer on the surface of the photoconductor, it plays a role of retaining the charged electric charges injected from the charging member, and also plays a role of releasing the electric charges to the support of the photoconductor during photoexposure, thereby reducing the residual potential. Reduce. Further, by using the charging member and the photosensitive member according to the present invention and adopting such a configuration, the charging start voltage Vh is small and the charging potential of the photosensitive member is converged to almost 90% or more of the voltage applied to the charging member. Became possible. Here, the charge injection layer is characterized by being made of a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin.

Here, the method of measuring the volume resistance value of the charge injection layer is the same as the method of measuring the charging member coating layer material described above.
A charge injection layer was formed on a polyethylene terephthalate (PET) film having a conductive film vapor-deposited on its surface, and this was used as a volume resistance measuring device (4140 manufactured by Hewlett Packard).
B pAMASTER) at 23 ° C, 65% environment 1
The measurement was performed by applying a voltage of 00V.

This 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 vapor-deposited, and the conductive fine particle resin dispersion film is a dipping coating method. , A spray coating method, a roll coat coating method, a beam coat coating method, or another suitable coating method to form a charge injection layer. Further, it may be constituted by mixing or copolymerizing an insulating binder resin with a resin having a high light-transmitting ion conductivity, or a resin having a medium resistance and a photoconductivity alone. In the case of the conductive fine particle resin dispersion film, the addition amount of the conductive fine particles is preferably within the range of 2 to 100% by weight with respect to the binder resin. When it is less than 2% by weight, it is difficult to obtain a desired volume resistance value, and 100% by weight.
If it exceeds, the charge injection layer is likely to be scraped off due to the decrease in film strength, and the life of the photoreceptor tends to be shortened.

The binder resin of the charge injection layer may be the same as the binder resin of the lower layer, but in this case, the coating surface of the charge transport layer is disturbed when the charge injection layer is coated. Be careful when selecting the coating method, as it may result in damage.

Also, a lubricant powder is preferably contained in the charge injection layer. The reason is that the friction between the photosensitive member and the injection charging member is reduced during charging, so the charging nip expands,
This is because the charging characteristics are improved. In particular, it is more preferable to use a fluorine-based resin, a silicone-based resin or a polyolefin-based resin having a low critical surface tension as the lubricant powder. Particularly preferably, tetrafluoroethylene resin (PTFE) is used. In this case, the amount of the lubricant powder added is preferably 2 to 50% by weight, more preferably 5 to 4% by weight with respect to the binder resin.
0% by weight. If it 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 0% by weight, the image resolution and the sensitivity of the photoreceptor tend to be greatly reduced.

[0041]

[Example of toner production]

Styrene-butyl acrylate copolymer (copolymerization 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 in an extruder set at ℃. The obtained kneaded product is cooled, and after roughly crushing with a cutter mill,
The mixture was finely pulverized with a jet mill using a jet stream and subjected to air classification 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.

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

The first layer is an undercoat layer, and has a thickness of about 2 provided to smooth defects such as aluminum drums and to prevent moire due to reflection of laser exposure.
It is a conductive layer of 0 μm.

The second layer is a positive charge injection preventing layer, which plays a role of preventing the positive charges injected from the aluminum support from canceling out the negative charges charged on the surface of the photosensitive member, and the amylan resin and methoxymethylation. By nylon 10 ⁶
It is a medium resistance layer having a thickness of about 1 μm whose resistance is 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 positive and negative charge pairs by being exposed to laser.

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

The fifth layer is a charge injection layer, which is a feature of the present invention, and comprises a photo-curable acrylic resin, SnO ₂ ultra-fine particles, and a contact charging member and a photoconductor, the contact time of which is increased to achieve uniform charging. For this purpose, tetrafluoroethylene resin particles having a particle size of about 0.25 μm are dispersed. Specifically, antimony is doped to reduce the resistance, and the particle size is about 0.03.
70% by weight of SnO ₂ particles of μm with respect to the resin, and further 4
Fluorinated ethylene resin particles 30% by weight, dispersant 1.2
It is dispersed by weight%.

As a result, the resistance of the surface of the photoconductor is 5 × 10 ¹⁵ Ωcm, compared with 2 × 10 ¹⁵ Ωcm for the charge transport layer alone.
It decreased to × 10 ¹² Ωcm.

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

[Photoreceptor Production Example 3] Fifth of Photoreceptor Production Example 1
Photoreceptor Production Example 1 except that the layer was added with antimony-doped SnO ₂ particles having a resistance of about 0.03 μm dispersed in a photocurable acrylic resin in an amount of 200% by weight. A photoconductor was prepared in the same manner as in. As a result, the resistance of the surface of the photoconductor was lowered to 4 × 10 ⁷ Ωcm.

[Charging Member Manufacturing Example 1] Volume resistance value 4 × 10
Magnetic particles coated with Zn-Cu ferrite particles (magnetic particles A) having a smooth surface of ⁶ Ωcm with a medium resistance resin layer and uncoated Zn- having a volume resistance value of 5 × 10 ⁶ Ωcm and having unevenness Cu ferrite particles (magnetic particles B, average pore diameter 1.8 μm) were mixed at a ratio of 2: 1 and magnetic particles having an average particle diameter of 35 μm were used as a charging member.

For coating, 1 part by weight of a fluorine-acrylic resin and 1 part by weight of titanium oxide which has been 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 glass beads are added thereto. It was dispersed for 2 hours with the put paint shaker to prepare a coating layer solution. When the resistance of the coating layer prepared from this coating layer solution was measured by the above-mentioned method, the volume resistance value was 7 × 10 ⁷ Ωcm. Next, this solution was applied to 300 parts by weight of the magnetic particles A using a fluidized bed type coating machine (Spira coater, 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 a coat layer was confirmed throughout. The measurement of the volume resistance value of magnetic particles is shown in FIG.
It measured using the cell shown in. That is, it was determined by filling the cell A with magnetic particles, arranging the electrodes 1 and 2 so as to contact the filled magnetic particles, applying a voltage between the electrodes, and measuring the current flowing at that time. The measurement conditions are 23
Contact area S of the filled magnetic particles with the cell in the environment of ℃, 65%
= 2 cm ² , thickness d = 1 mm, upper electrode load 10 k
g, applied voltage 100V. The volume resistance value of the coated magnetic particles obtained through the drying step was 8 × 10 ⁶ Ωcm.

[Charging Member Manufacturing Example 2] Volume resistance value 4 × 10
Zn-Cu ferrite particles having a smooth surface of ⁶ Ωcm (magnetic particles A) and Zn-Cu ferrite particles having a volume resistance value of 5 × 10 ⁶ Ωcm and having irregularities (magnetic particles B,
Magnetic particles having an average particle diameter of 30 μm obtained by mixing (average pore diameter 1.8 μm) in a weight ratio of 2: 1 were used as a charging member.

[Charging Member Manufacturing Example 3] Volume resistance value 1 × 10
Zn-Cu ferrite particles having a smooth surface of ⁶ Ωcm and Z having irregularities on the surface having a volume resistance value of 3 × 10 ⁶ Ωcm
Magnetic particles having an average particle size of 50 μm, in which n-Cu ferrite particles (surface pore size 0.75 μm) were mixed at a weight ratio of 2: 1 were used as a charging member.

[Charging Member Manufacturing Example 4] Average particle diameter 60 μm,
Zn—Cu ferrite particles having a volume resistance value of 5 × 10 ⁹ Ωcm were used as a charging member.

[Charging Member Manufacturing Example 5] Average particle diameter 40 μm,
Magnetite particles having a volume resistance value of 4 × 10 ³ Ωcm were used as a charging member.

[Embodiment 1] The principle of charging by using the above-mentioned photoreceptor and the contact charging member will be described. The present invention is a medium-resistance contact charging member for injecting charges into the surface of a photoconductor having a medium resistance surface resistance. In this embodiment, charges are injected into the trap potential of the photoconductor surface material. Instead, it is the principle of charging by charging the conductive particles of the charge injection layer with electric charges.

Specifically, it is based on the theory that a contact charging member charges a minute 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. is there. At this time, the conductive particles are electrically independent of each other and form a kind of minute float electrode. For this reason, the surface of the photoconductor seems to be charged and charged to a uniform electric potential on a macroscopic scale, but in reality, a myriad of minute charged SnO ₂ covers the surface of the photoconductor. ing. Therefore, even if image exposure is performed with a 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 of this embodiment will be described with reference to FIG. The process speed was 24 mm / sec, and as the photosensitive member, the photosensitive member manufacturing example 1 was used, and durability was performed in an environment of 23 ° C. and 65%.

The contact charging member is composed of the coated magnetic particles prepared in Production Example 1 of the charging member, a non-magnetic conductive sleeve for supporting the coated magnetic particles, and a magnet roll contained therein, and the coated magnetic particles are sleeved. It was coated on the surface with a thickness of 1 mm so that a charging nip having a width of about 5 mm was formed between it and the photoconductor. The gap between the magnetic particle holding sleeve and the photoconductor was about 500 μm. Also, the magnet roll is fixed and rotated so that the sleeve surface rubs in the opposite direction at a speed three times as fast as the peripheral speed of the photosensitive member surface.
The photoconductor and the magnetic brush were contacted uniformly. If the peripheral speed difference is not provided between the magnetic brush and the photoconductor, the magnetic brush itself does not have a physical restoring force.
When the magnetic brush is pushed away due to the deflection or eccentricity of the photosensitive member, the nip of the magnetic brush cannot be ensured and charging failure occurs. For this reason, since it is necessary to constantly apply a new magnetic brush surface, in the present embodiment, the brush was rotated in the reverse direction at a speed three times faster.

First, the contact charging member to which a DC voltage of -800V is applied is brought into contact with and rotated with respect to the photosensitive member to perform charging. Next, the exposure unit receives image exposure. Next, the laser light 13 from the laser diode whose intensity is modulated in accordance with the image signal is scanned by the polygon mirror to serve as an exposing means, and an electrostatic latent image is formed on the photoconductor.

Next, reversal development is performed using the magnetic one-component insulating toner of the manufacturing example. 16m diameter with magnet included
The non-magnetic sleeve 14 of m is coated with the above-mentioned negative toner, and while the distance from the surface of the photoconductor is fixed at 300 μm, the non-magnetic sleeve 14 is rotated at the same speed as the photoconductor drum to apply a voltage to the sleeve. The voltage is a DC voltage of -500V and a frequency of 20.
A rectangular AC voltage having a frequency of 00 Hz and a peak-to-peak voltage of 1200 V is superimposed, and jumping development is performed between the sleeve and the photoconductor.

The image visualized with the toner in this manner is then transferred to the transfer material 16. A transfer roller 15 having a medium resistance is used in the transfer section. In this embodiment, a roller having a resistance value of 5 × 10 ⁸ Ω was used, and a DC voltage of +2000 V was applied for transfer.

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

Image evaluation was carried out by the printer having the above-mentioned structure. When a DC voltage of -800 V was applied to the sleeve of the charging member and the photosensitive member passed through the charging nip once, it was 0 V at the beginning. The surface potential of the photoconductor was charged to −770 V, and good chargeability could be obtained. Further, at this time, even if a pinhole is formed on the photoconductor, no leakage occurs, and the magnetic particles forming the contact charging member are not developed on the photoconductor, and a good solid black color,
A solid white image was obtained. In addition, even after 1000 sheets were durable, the same charging characteristics as the initial stage were exhibited, and good solid black,
A solid white image was obtained.

Further, when the charging failure occurs in the reversal development, the history on the photosensitive member influences the charging.
In four vertical images, one round of the photosensitive member (about 94 m in this embodiment)
Image evaluation (charging ghost evaluation) was also performed by setting m) as a solid black image (low potential) and immediately after that as solid white (high potential).
If a charging failure occurs, the potential does not rise sufficiently immediately after solid black and appears as a fog in reversal development, but no fog was observed in this image throughout the durability test.

[Example 2] Image evaluation was carried out in the same manner as in Example 1 except that the contact charging member in Example 1 was used as the charging member manufacturing example 2 and the photoconductor was used as the photoconductor manufacturing example 2. Due to a slight charging failure due to a decrease in the charging nip, there was some fog on the solid white image in the evaluation of the charging ghost, but there was no practical problem and good solid black and solid white images were obtained from the initial stage up to 1000 sheets.

[Embodiment 3] Image evaluation was carried out in the same manner as in Embodiment 2 except that the contact charging member in Embodiment 2 was used in Charging Member Manufacturing Example 3, but the initial evaluation was good, but 1000 When the sheets were durable, there was no problem in practical use, but some charging defects (solid white and fog images in the charging ghost evaluation) occurred.

[Comparative Example 1] Image evaluation was performed in the same manner as in Example 2 except that the contact charging member in Example 2 was used in Manufacturing Example 4 for charging member. Fog image) was seen in white.

[Comparative Example 2] An image evaluation was carried out in the same manner as in Example 2 except that the contact charging member in Example 2 was used in Manufacturing Example 5 for charging member. Poor charging (black spots on solid white image) occurred.

[Comparative Example 3] Image evaluation was carried out in the same manner as in Example 1 except that the photoconductor manufacturing example 3 was used as the photoconductor in example 1, and partial charging based on pinhole leak was observed from the initial stage. Defects (black dots in solid white image) occurred.

Further, the electric potential flows in the lateral direction, and image deletion occurs.

[0073]

INDUSTRIAL APPLICABILITY The present invention provides an electrophotographic apparatus having an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and a contact charging member composed of magnetic particles for contacting the photosensitive member and applying a voltage thereto. The photoconductor has a charge injection layer farthest from the support, and the resistance value between the voltage application part of the charging member and the part in contact with the photoconductor is 10 ⁴ to 10 ⁷ Ω,
Further, the magnetic particles are a mixture of the magnetic particles A having a smooth surface and the magnetic particles B having an uneven surface, and an image forming method having a step of charging using the electrophotographic apparatus provides uniform charging. It became possible to obtain a stable image by applying it to the surface of the photoconductor.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 Main Electrode 2 Upper Electrode 3 Insulator 4 Ammeter 5 Voltmeter 6 Constant Voltage Device 7 Magnetic Particles 8 Guide Ring 11 Photosensitive Drum 12 Contact Charging Member 13 Exposure Means 14 Developer 15 Transfer Roller 16 Transfer Material 17 Cleaning Blade 18 Thermal Fixing roller

Claims (16)

[Claims] 1. An electrophotographic apparatus having an electrophotographic photosensitive member having a photosensitive layer on a conductive support and a contact charging member made of magnetic particles for contacting the photosensitive member and applying a voltage thereto, wherein the photosensitive member is It has a charge injection layer farthest from the support, the resistance value between the voltage applying portion of the charging member and the portion in contact with the photosensitive member is 10 ⁴ to 10 ⁷ Ω, and the magnetic particles are on the surface. Is a mixture of smooth magnetic particles A and magnetic particles B having an uneven surface. 2. The average pore diameter of the surface of the magnetic particles B is
The electrophotographic apparatus according to claim 1, having a thickness of 0.15 to 2.5 μm. 3. The electrophotographic apparatus according to claim 1, wherein each of the magnetic particles A and the magnetic particles B is contained in an amount of 10% by weight or more. 4. The surface of the magnetic particles has a volume resistivity of 10 ⁴
A coating layer having a thickness of about 10 ⁷ Ωcm.
3. The electrophotographic apparatus according to any one of 3 to 3. 5. The electron according to claim 4, wherein the coating layer of the magnetic particles is a conductive fine particle-dispersed resin film containing conductive fine particles and a fluorine resin, a polyolefin resin or a silicone resin as a binder resin. Photographic equipment. 6. The volume resistivity of the charge injection layer is from 10 ⁸ to
The electrophotographic apparatus according to claim 1, wherein the electrophotographic apparatus has a resistance of 10 ¹⁵ Ωcm. 7. The electrophotographic apparatus according to claim 1, wherein the charge injection layer contains conductive fine particles, a binder resin and a lubricant powder. 8. The electrophotographic apparatus according to claim 7, wherein the lubricant powder is a fluorine resin, a polyolefin resin or a silicone resin. 9. An image forming method comprising a step of bringing a charging member composed of magnetic particles into contact with an electrophotographic photoreceptor having a photosensitive layer on a conductive support and applying a voltage to charge the photoreceptor. The photoconductor has a charge injection layer farthest from the support, and the resistance value between the voltage application part of the charging member and the part in contact with the photoconductor is 10 ⁴ to 10 ⁷ Ω,
An image forming method characterized in that the magnetic particles are a mixture of magnetic particles A having a smooth surface and magnetic particles B having an uneven surface. 10. The average pore diameter of the surface of the magnetic particles B is
The image forming method according to claim 9, having a thickness of 0.15 to 2.5 μm. 11. The magnetic particle A and the magnetic particle B are contained in an amount of 10% by weight or more, respectively.
The image forming method described. 12. The surface of the magnetic particles has a volume resistivity of 10
The image forming method according to claim 9, which is coated with a coating layer having a thickness of ⁴ to 10 ⁷ Ωcm. 13. The image according to claim 12, wherein the coating layer of the magnetic particles is a conductive fine particle-dispersed resin film containing conductive fine particles and a fluorine resin, a polyolefin resin or a silicone resin as a binder resin. Forming method. 14. The volume resistivity of the charge injection layer is 10 ⁸
The image forming method according to claim 9, wherein the image forming method is about 10 ¹⁵ Ωcm. 15. The image forming method according to claim 9, wherein the charge injection layer contains conductive fine particles, a binder resin, and a lubricant powder. 16. The lubricant powder is a fluorine resin, a polyolefin resin or a silicone resin.
5. The image forming method described in 5.