JP2000122377A - Image forming device and electrification member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrification member for DC charging capable of minimizing a toner soiling, suitable to simultaneous developing and cleaning system, and an image forming device provided with this electrification member, capable of stably transferring and forming the image with excellent image quality over a long period. SOLUTION: In this image forming device applying the reversal developing system/simultaneous developing and cleaning system, the charge for the image carrier by charging means 2, is performed by the electrification member arranged in contact with or close to the image carrier, on which DC voltage is applied, and the triboelectric charge polarity with regard to the toner on the surface opposite to the image carrier of the electrification member 2 is made opposite to the toner charge polarity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member.
For a transfer-type image forming apparatus that transfers a toner image formed on an image carrier such as an electrostatic recording dielectric to a transfer material and outputs an image-formed product, the residual toner is removed from the image carrier after the transfer process. The present invention relates to a cleanerless transfer type image forming apparatus which does not require an essential cleaning device as a dedicated device for performing the cleaning. Further, the present invention relates to a charging member used in the image forming apparatus.

[0002]

2. Description of the Related Art For convenience, a transfer-type electrophotographic LBP is used.
(Laser beam printer), a copier, a facsimile, and other image forming apparatuses will be described as examples.

A transfer type electrophotographic image forming apparatus generally uses a rotating drum type photoreceptor using a photoconductive material as an image carrier. A) The rotating photoreceptor is charged to a predetermined polarity and potential by charging means. B) Image exposure is performed on the uniformly charged surface of the rotating photoreceptor by image exposure means (laser beam scanning exposure means, projection image exposure means for original image, etc.) to obtain exposure image information. An image exposing step of forming a corresponding electrostatic latent image c) a developing step of developing the formed electrostatic latent image as a toner image by a developing means d) a transfer material such as paper from the photoreceptor side of the toner image by a transfer means E) a fixing step of fixing the toner image of the transfer material separated from the photoreceptor to the transfer material surface by fixing means with heat or pressure, etc. f) a fixing operation of the toner image on the transfer material after transfer of the toner image to the transfer material Transcription By executing the image formed by the cleaning step to remove the toner remaining cleaning the photoreceptor surface without those obtained image forming material (copies, prints). The cleaned photoreceptor is repeatedly used for image formation.

[0004] In the above, various methods and configurations are specifically known as the respective process means a) to f).

In recent years, the size of such an image forming apparatus has been reduced, but there has been a limit to merely reducing the size of the image carrier and each of the process means constituting the apparatus.

The toner remaining on the surface of the photoreceptor after transfer of the toner image to the transfer material is removed by cleaning means (cleaning device) to become waste toner.
From the point of view of ecology, a system that does not mean that the waste toner is effectively used has been desired.

Conventionally, as an essential cleaning device as a dedicated device for removing toner remaining on the photoreceptor after the transfer step, devices such as a blade cleaning system, a fur brush cleaning system, and a roller cleaning system have been used. However, in any case, a cleaning member such as a blade, a fur brush, and a roller is brought into contact with the surface of the photoreceptor to mechanically scrape off or transfer the remaining toner and collect it in a waste toner container. There is also a problem caused by such a cleaning member being pressed against the surface of the photoconductor. For example, it is possible to wear the photoconductor by strongly pressing the cleaning member to shorten the life of the photoconductor.

Therefore, by using the developing means also as a cleaning means for the toner remaining on the photoreceptor surface after the transfer of the toner image to the transfer material, there is no need to provide a cleaning means as a dedicated device. Or "cleaner-less" image forming apparatuses have also appeared (JP-A-59-133573, 62).
-203182, 63-133179,
JP-A-4-20587, JP-A-2-51168, JP-A-2-302772, JP-A-5-2287, JP-A-5-2289, JP-A-5-53482,
No. 5-61383, etc.).

In the simultaneous cleaning with development, the transfer residual toner on the photosensitive member is transferred from the transfer portion to the development portion, and the toner is transferred to the toner carrying member (toner supply member, developing member) of the developing means at the time of development in the next and subsequent steps. Fogging potential difference V, which is the potential difference between the DC voltage applied to the carrier and the photoconductor surface potential
It is collected by back.

According to this, even if there is no cleaning device as a dedicated device, the transfer residual toner is collected by the developing means and used for the development after the next step, so that the waste toner can be eliminated. In addition, since there is no need to provide a cleaning device as a dedicated device, there is a great advantage in terms of space, and the device can be significantly reduced in size.

In an image forming apparatus, a corona charger has been widely used as a means for charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric. In recent years, attention has been paid to contact charging type and proximity charging type means and devices, and their use has been put to practical use.

1) Corona charging This is a method in which a corona charger is disposed on a photoreceptor as an image carrier in a non-contact manner with its discharge opening facing the corona charger, and a corona shower discharged from the discharge opening of the corona charger. The surface of the photoreceptor is uniformly exposed to a predetermined polarity and potential. However, there are problems such as generation of a relatively large amount of ozone that requires a high-voltage power supply.

2) Contact charging This involves contacting a photosensitive member with a charging member as a charge supply member such as a roller type, blade type, brush type, or magnetic brush type, and applying a predetermined charging bias to the contact charging member. Thus, the surface of the photoreceptor is uniformly charged to a predetermined polarity and potential.

In comparison with the charging process using the corona charger, the power supply can be reduced in voltage, the amount of generated ozone is small, and the power is reduced.

Among them, a roller charging system using a conductive roller (charging roller) as a contact charging member is preferably used from the viewpoint of charging stability.

More specifically, since the charging is performed by discharging from the charging member to the member to be charged, the charging is started by applying a voltage higher than a certain threshold voltage. For example, when a charging roller is pressed against an OPC photosensitive member having a 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 photoconductor surface potential linearly increases at a slope of 1 with respect to the applied voltage. Hereinafter, this threshold voltage is defined as a discharge start voltage (charging start voltage) Vth (application to a contact charging member when a DC voltage is applied to the contact charging member to start charging an image carrier as a member to be charged). Voltage value).

That is, in order to obtain the photosensitive member surface potential Vd (dark portion potential) required for electrophotography, the charging roller needs a direct current voltage (DC voltage) of Vd + Vth which is higher than the required potential Vd. .

The method of charging by applying only a DC voltage to the contact charging member in this manner is called a "DC charging method".

As disclosed in JP-A-63-149669, an AC voltage component (AC voltage component) having a peak-to-peak voltage of 2 × Vth or more in a DC voltage corresponding to a desired surface potential Vd of a member to be charged. ) (AC charging method) in which a voltage (alternating voltage, pulsating voltage, and oscillating voltage; a voltage whose voltage value changes periodically with time) is applied to the contact charging member.
Is also used. This is for the purpose of the potential leveling effect by the AC voltage, and the potential of the charged body converges to the potential Vd which is the center of the peak of the AC voltage.

A charge injection layer (charge layer) is provided on the surface of the image carrier as a member to be charged, and a charge is directly injected into the charge injection layer by a contact charging member to which a voltage is applied, so that the surface of the image carrier has a predetermined surface. There is also an injection charging method of charging to a polarity and a potential, which is also a category of contact charging.

3) Proximity charging Even if the charging member does not necessarily come into contact with the surface of the member to be charged, a non-dischargeable region determined by the voltage between the gap and the Paschen curve between the charging member and the surface of the member to be charged is surely guaranteed. It is possible to charge the member to be charged even in an arrangement in which the members are close to each other by contact.

Proximity charging is this. The charging member is disposed in a non-contact manner with a small gap of about several tens to several hundreds of micrometers with respect to the surface of the photosensitive member as a member to be charged. By applying a DC voltage or a DC + AC voltage to the member, the surface to be charged is uniformly charged to a predetermined polarity and potential.

As compared with the charging process using a corona charger, the proximity charging can lower the voltage of the power supply, generate a small amount of ozone, and further, because the charging member is not in contact with the charging member, the charging member is not charged. It has the advantage of not damaging.

[0024]

However, when the image forming apparatus is of the reversal developing type (the toner charging polarity and the photosensitive member charging polarity are the same polarity) and the simultaneous development cleaning type (cleanerless), the toner carrier of the developing means is not used. During development or during the blank before and after development, a DC or AC component bias is applied to control the developing member to a potential that allows development and recovery of the remaining toner on the photoreceptor. Is the charge polarity and charge amount of the toner on the photoreceptor in each step of electrophotography.

For example, when a negatively charged photosensitive member and a negatively charged toner are used to transfer a visualized toner image on the photosensitive member to a transfer material by a positive polarity transfer unit in a transfer step, the voltage applied to the transfer unit is changed. Depending on the relationship between the voltage and the type of transfer material (differences in thickness, resistance, dielectric constant, etc.) and the image area, the charge polarity of the toner remaining after transfer varies from plus to minus. However, due to the negative corona shower or discharge when the negatively chargeable photoreceptor is charged by the charging means, not only the surface of the photoreceptor but also the remaining toner of the transfer, even if the transfer process is swinging to the positive polarity, It is uniformly charged to the negative side.
Therefore, a negatively charged transfer residual toner remains in the light portion potential portion of the photoconductor surface to be developed with the toner,
Due to the developing electric field, the toner is attracted toward the toner carrier of the developing means at the dark potential portion of the photoconductor surface that should not be developed with toner, and no toner remains on the photoconductor having the dark potential.

As will be described later, according to the study of the present inventors,
When the charging method of the photoconductor is contact charging or proximity charging, and an AC charging method in which a DC voltage having an AC component is applied to a charging member is used, the polarity cannot be controlled by a charging process. It was found that it was not possible to apply to the simultaneous cleaning method, and it was necessary to adopt a DC charging method capable of changing the toner polarity to the negative polarity.

However, the DC charging method in the simultaneous development cleaning method has the following problems. That is, the toner remaining after transfer easily adheres to the charging member, resulting in a change in charging characteristics. Specifically, a phenomenon occurs in which the potential on the surface of the photoreceptor becomes uneven and a predetermined potential does not rise, and In addition, image defects such as non-uniform density and fog occur. In this connection, the AC charging method is more advantageous,
The influence on the charging characteristics by the fouling of the charging member is very small.

An object of the present invention is to provide a charging member for DC charging, which is suitable for a simultaneous cleaning method with less toner and has less toner contamination.
Another object of the present invention is to provide an image forming apparatus having the charging member and capable of stably transferring and forming a high-quality image for a long period of time.

[0029]

According to the present invention, there is provided an image forming apparatus and a charging member having the following constitution.

(1) Image carrier, charging means for charging the image carrier, information writing means for forming an electrostatic latent image on the charged surface, and development for visualizing the electrostatic latent image as a toner image And a transfer unit for transferring the toner image to a transfer material. After the transfer step, the remaining toner on the image carrier is collected by the developing unit, and the image carrier is repeatedly used for image formation. In the image forming apparatus, the charging of the image carrier by the charging unit is performed by a charging member that is disposed in contact with or close to the image carrier and to which a DC voltage is applied, and the electrostatic latent image by the developing unit is The visualization as a toner image is performed by reversal development in which the toner charging polarity and the image carrier charging polarity are the same, and the friction charging polarity of the charging member with respect to the toner on the image carrier facing surface is the toner charging polarity. Reverse Image forming apparatus which is a sex.

(2) The image forming apparatus according to (1), wherein the surface of the charging member facing the image carrier contains a charge control agent.

(3) The image bearing member according to (1) or (2), wherein the image carrier is a photosensitive member, and the information writing means for forming an electrostatic latent image on the charged surface is an image exposure means. Image forming device.

(4) The image bearing member is characterized in that the surface has a contact angle with water of 85 degrees or more (1) to (3).
The image forming apparatus according to any one of the above.

(5) The image forming apparatus according to any one of (1) to (4), wherein the surface of the image carrier contains a lubricating powder containing fluorine.

(6) Any one of (1) to (5), wherein a toner having an inorganic fine powder present on its surface is used.
An image forming apparatus according to any one of the preceding claims.

(7) At least one of (1) to (6), wherein at least the image carrier and the charging member are provided in a process cartridge which is detachable from the image forming apparatus.
An image forming apparatus according to any one of the preceding claims.

(8) A charging member which is arranged in contact with or close to the image carrier of an image forming apparatus of a reversal developing system / simultaneous cleaning system and charges the image carrier by applying a DC voltage. A charging member, wherein the triboelectric charging polarity of the toner on the body-facing surface is opposite to that of the toner.

(9) The charging member according to (8), wherein the surface of the charging member facing the image carrier contains a charge control agent.

<Operation> FIG. 1 is a schematic view of an apparatus for evaluating toner charging polarity.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member as an image carrier, which is driven to rotate clockwise as indicated by an arrow.
Reference numeral 2 denotes a charging roller (conductive roller) serving as a photoconductor charging member, which is brought into contact with the photoconductor 1 with a predetermined pressing force, and rotates following the rotation of the photoconductor 1. 3 is a photoreceptor 1
Exposure means 4 are toner development means.

The photoreceptor 1 is rotated, the surface of the photoreceptor is exposed by the exposing means 3, and the potential is maintained near 0V. Developing means 4 develops toner on a photoreceptor having a potential near 0 V. When the toner developing section enters a contact section (charging section) between the charging roller 2 serving as a charging member and the photoconductor 1, a voltage is applied to the charging roller 2 by the voltage applying means S to change the photoconductor potential and the toner charging polarity. Measure.

A and B are the same as the measurement point 1 of the photoreceptor potential and the toner charge polarity, and the measurement point 1 is a portion of the photoreceptor surface downstream of the charging unit in the rotation direction of the photoreceptor and upstream of the exposure unit. The position and measurement point 2 were set at a position on the photosensitive member surface downstream of the developing unit in the photosensitive member rotation direction and upstream of the charging unit.

Tables 1 and 2 show the measurement results when the toner polarity, the photoconductor charging polarity, and the voltage application method (DC application method / AC application method) to the charging means were changed.

Table 1 shows that DC is applied only to the charging means 2.
In the case of the charging method, Table 2 shows a case of the AC charging method in which an AC voltage is superimposed.

In the case of the DC charging system, it is clear that the toner polarity follows the DC application polarity.
In the C charging system, the toner polarity when entering the charging unit is maintained under any conditions.

In the present invention, based on this, the polarity of the residual toner on the image carrier is controlled to a desired polarity by a charging member to which a DC voltage is applied, and the surface of the image carrier is charged to a desired potential. The method was adopted.

On the other hand, as described above, when the transfer residual toner adheres to the charging member, the charging characteristic changes, and more specifically, the potential on the surface of the photoreceptor becomes uneven, or the predetermined potential does not rise. Occurs, resulting in uneven density on the image,
Image defects such as fogging occur. As a result of intensive studies on this point, it has been found that if the triboelectric charging polarity of the charging member facing the image carrier (surface layer) with respect to the toner is opposite to that of the toner, the adhesion of the toner is significantly reduced. Have been found to accumulate, leading to the present invention.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Example of Image Forming Apparatus (FIG. 2) FIG. 2 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus of the present embodiment is a reversal developing system, a simultaneous developing cleaning system (cleanerless), and a process cartridge system using a transfer type electrophotography.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member as an image carrier, which is driven to rotate at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow.

Reference numeral 2 denotes a charging roller (conductive roller) serving as a photosensitive member charging means, which is brought into contact with the photosensitive member 1 with a predetermined pressing force. . When a predetermined DC voltage is applied to the charging roller 2 from a charging bias application power supply Sl, the surface of the rotating photoconductor 1 is uniformly charged to a predetermined polarity and potential by a contact charging method and a DC charging method. It is processed.

Reference numeral 3 denotes an image exposure means, for example, a laser beam scanner. By performing image exposure L corresponding to the target image information on the uniformly charged surface of the rotating photoreceptor 1 by the image exposure means 3, the potential of the exposed light portion of the charged surface of the photoreceptor is selectively reduced (attenuated). ) To form an electrostatic latent image.

Reference numeral 4 denotes a reversal developing means (reversal developing device) for selectively applying toner (negative toner) charged to the same polarity as the charged polarity of the photoreceptor in the exposed portion of the electrostatic latent image on the photoreceptor surface. The electrostatic latent image is visualized as a toner image by being attached. 4a is a toner carrier, S2 is this toner carrier 4a
Is a developing bias application power source S2.

Reference numeral 5 denotes a transfer roller as a transfer means, which is in contact with the photoreceptor 1 at a predetermined pressing force to form a transfer nip portion. It rotates at almost the same peripheral speed. Further, a transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the transfer bias applying power source S3.

A transfer material P is fed to the transfer nip from a feed mechanism (not shown) at a predetermined control timing, and the back surface of the transfer material P is transferred to the toner by a transfer roller 5 to which a transfer voltage is applied. The toner image on the photoconductor 1 surface side is electrostatically transferred to the surface side of the transfer material P in the transfer nip portion by being charged to a polarity opposite to the charging polarity of the transfer material P.

The transfer material to which the toner image has been transferred at the transfer nip is separated from the surface of the rotating photoreceptor, introduced into a toner image fixing means (not shown), subjected to a toner image fixing process, and output as an image formed product. Is done.

In the case of the double-sided image forming mode or the multiple image forming mode, this image-formed product is introduced into a recirculating transport mechanism (not shown) and is again introduced into the transfer nip portion.

In the photoreceptor charging step, a DC voltage is applied to the photoreceptor charging member 2 which is in contact with or in proximity to the photoreceptor, so that the polarity of the transfer residual toner on the rotating photoreceptor surface after the separation of the transfer material is changed. At the same time, the photoconductor is charged to a predetermined potential (DC charging method).

Then, the transfer residual toner passes through the charging unit and the exposure unit, reaches the developing unit 4, and is collected by the simultaneous cleaning with development.

Reference numeral 6 denotes a process cartridge which is detachable from the image forming apparatus main body. In this example, the photoconductor 1 and
The charging roller 2 and the reversal developing device 4 include three process devices. The process cartridge 6 includes the photoconductor 1 and at least one process device that acts on the photoconductor 1.

(2) Photoreceptor 1 a) In the present invention, a desirable form of the photoreceptor 1 as an image carrier is that the surface of the photoreceptor has releasability.

By having a releasing property on the surface of the photoreceptor,
The amount of toner remaining after transfer can be significantly reduced, and a system that hardly adversely affects the development due to shading by the toner remaining after transfer can be realized.

The present invention is also effective when the surface of the photoreceptor is mainly composed of a polymer binder. For example, when a protective film mainly composed of a resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or as a charge transport layer of a function-separated organic photoreceptor (OPC photoreceptor), a charge transport material and a resin are used. In some cases, a surface layer is provided, and in addition, a protective layer as described above is further provided thereon. Means for imparting releasability to such a surface layer include: 1. A resin having a low surface energy is used for the resin constituting the film. 2. Add additives that impart water repellency and lipophilicity; And dispersing a material having high releasability into a powdery state.

One example is achieved by introducing a fluorine-containing group, a silicon-containing group, etc. into the structure of the resin.

In the method 2, a surfactant or the like may be used as an additive.

Compounds containing fluorine atoms, ie, polytetrafluoroethylene, polyvinylidene fluoride,
Powders such as carbon fluoride are exemplified. Among them, polytetrafluoroethylene is particularly preferable.

In the present invention, dispersion of a releasable powder such as a fluorine-containing resin is preferred. In order to contain these powders on the surface, a layer in which the powders are dispersed in a binder resin is provided on the outermost surface of the photoreceptor, or if the organic photoreceptor is originally composed mainly of resin. Instead of providing a new surface layer, the powder may be dispersed in the uppermost layer.

The amount of the powder added to the surface layer is preferably 1 to 60% by weight, more preferably 2 to 50% by weight, based on the total weight of the surface layer. If the amount is less than 1% by weight, the residual transfer toner does not decrease sufficiently, the cleaning efficiency of the residual transfer toner is not sufficient, and the ghost prevention effect is insufficient. If the amount exceeds 60% by weight, the strength of the film is reduced and the amount of light incident on the photoreceptor is undesirably reduced.

The particle size of the powder is preferably 1 μm or less, more preferably 0.5 μm or less from the viewpoint of image quality. If it is larger than 1 μm, the line will be poorly cut due to scattering of incident light, which is not practical.

B) FIG. 3 is a schematic diagram showing one preferred layer structure of the photoreceptor used in the present invention.

The photoreceptor 1 has a conductive substrate 11
This is an OPC photoconductor in which a conductive coating layer 12, an undercoat layer 13, a charge generation layer 14, and a charge transport layer 15 are sequentially laminated.

1. As the conductive substrate 11, a cylinder such as a metal such as aluminum or stainless steel, a plastic having a coating layer of an aluminum alloy or an indium oxide-tin oxide alloy, a paper or plastic impregnated with conductive particles, or a plastic having a conductive polymer. Cylinders and films are used.

2. The conductive coating layer 12 is provided as needed.

3. The undercoat layer 13 is used for the purpose of improving adhesiveness of the photosensitive layer, improving coating properties, protecting the substrate, covering defects on the substrate, improving charge injection from the substrate, protecting the photosensitive layer against electrical breakdown, and the like. Provided as needed.

The undercoat layer 13 is made of polyvinyl alcohol, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, casein, polyamide, copolymerized nylon and glue.・ Gelatin ・ Polyurethane ・
It is formed of a material such as aluminum oxide.

The film thickness is usually about 0.1 to 10 μm, preferably about 0.1 to 3 μm.

4. The charge generation layer 14 is made of an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment,
Polycyclic quinone pigments, squarylium pigments, pyrylium salts, thiopyrylium salts, triphenylmethane pigments,
It is formed by dispersing a charge generating substance such as an inorganic substance such as selenium or amorphous silicon in a suitable binder and coating or vapor-depositing.

The binder can be selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacryl resin, phenol resin, silicone resin, epoxy resin. A vinyl acetate resin;

The amount of the binder contained in the charge generation layer 14 is selected to be 80% by weight or less, preferably 0 to 40% by weight.
The thickness of the charge generation layer is 5 μm or less, particularly 0.05 μm.
２2 μm is preferred.

5. The charge transport layer 15 has a function of receiving charge carriers from the charge generation layer 14 in the presence of an electric field and transporting them.

The charge transporting layer 15 is formed by dissolving a charge transporting substance in a solvent together with a binder resin, if necessary, and applying the solution. The film thickness is generally 5 to 40 μm.

Examples of the charge transporting substance include polycyclic aromatic compounds having a structure such as biphenylene / anthracene / pyrene / phenanthrene in the main chain or side chain; nitrogen-containing cyclic compounds such as indole / carbazole / oxadiazole / pyrazoline; Examples include hydrazone compounds, still compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

The binder resin for dispersing these charge transporting materials includes polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin, and the like.
Examples include resins such as acrylic resins and polyamide resins, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

The charging polarity of the photosensitive member may be either positive or negative. In the case of a stacked type photoreceptor, in the case of positive charging, the charge generation layer 14 and the charge transport layer 15 are laminated in this order, and an electron transport compound is used for the charge transport layer 15, or the charge transport layer 15 and the charge The charge transport layer 1
5 may be a hole transporting compound. The same applies to the case of negative chargeability.

Further, a protective layer may be provided as a surface layer.
As the resin of the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenolic resin, or a curing agent of these resins or the like is used alone or in combination of two or more.

Further, conductive fine particles may be dispersed in the resin of the protective layer. Examples of the conductive fine particles include metals and metal oxides, and preferably, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coating titanium oxide, tin coating indium oxide. There are ultrafine particles such as antimony-coated tin oxide and zirconium oxide. These may be used alone or as a mixture of two or more.

In general, when particles are dispersed in a protective layer,
It is necessary that the particle size of the particles is smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed particles, and as the particle size of the conductive and insulating particles dispersed in the protective layer in the present invention, It is preferably 0.5 μm or less.

The content in the protective layer is preferably 2 to 90% by weight, and more preferably 5 to 80% by weight based on the total weight of the protective layer.
Is more preferred.

The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

The application of the surface layer can be performed by spray coating, beam coating or penetrating coating of the resin dispersion.

C) Photoreceptor Production Example An Al cylinder having a diameter of 30 mm and a length of 254 mm was used as the substrate 11, and the following layers 12 to 1 as shown in FIG.
5 were sequentially laminated by dip coating to form a photoreceptor 1.

1. The conductive coating layer 12 is mainly composed of a powder of tin oxide and titanium oxide dispersed in a phenol resin. The thickness is 15 μm.

2. Undercoat layer 13: mainly composed of modified nylon and copolymerized nylon.

The thickness is 0.6 μm.

3. Charge generation layer 14: Mainly a substance in which a titanyl phthalocyanine pigment having absorption in a long wavelength region is dispersed in a butyral resin. The film thickness is 0.6 μm.

4. Charge transport layer 14: Mainly a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight 20,000 according to Ostwald viscosity method) at a weight ratio of 8:10, and a polytetrafluoroethylene powder (particle size 0.2 μm) was added at 10% by superposition with respect to the total solid content, and the mixture was uniformly dispersed. 25 μm thick. The contact angle with water was 95 degrees.

The contact angle was measured using pure water, and the apparatus was a contact angle meter CA-DS, Kyowa Interface Science Co., Ltd.

(3) Charging Member 2 The structure, material or manufacturing method of the charging member 2 used in the present invention will be exemplified.

For example, in the case of a roller type or blade type, a metal such as iron, copper, stainless steel, a carbon-dispersed resin, a metal or a metal oxide-dispersed resin, or the like is used as a conductive substrate. A rod shape, a plate shape and the like can be used.

For example, as the configuration of the elastic roller, a structure in which an elastic layer, a resistance layer, and a surface layer are provided on a conductive substrate is used.

A. As the roller elastic layer, rubber or sponge such as chloroprene rubber, isoprene rubber, EPDM rubber, polyurethane rubber, epoxy rubber, butyl rubber, styrene butadiene thermoplastic elastomer, polyurethane thermoplastic elastomer, polyester thermoplastic elastomer,
It can be formed of a thermoplastic elastomer such as ethylene-vinegar visothermoplastic elastomer.

B. The resistance layer has, for example, a volume resistivity of 10
The layer has a thickness of ⁶ to 10 ¹² Ω / cm, and a semiconductive resin, a conductive particle dispersed insulating resin, or the like can be used.

As the semiconductive resin, ethyl cellulose,
Resins such as nitrocellulose, methoxymethylated nylon, ethoxymethylated nylon, copolymerized nylon, polyvinyl hydrin, and casein are used.

As examples of the conductive particle-dispersed resin, conductive particles such as carbon, aluminum, indium oxide, and titanium oxide are mixed with insulating resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer, and polymethyl methacrylate. And a small amount thereof dispersed therein.

C. The surface layer can be selected from various materials including a semiconductive resin, an insulating resin, and the like that form the resistance layer. However, as described above, a material whose frictional charging polarity with respect to the toner is opposite to the toner charging polarity is used. By selecting, it is possible to significantly reduce the adhesion of the toner.

That is, a material having a negative frictional charging polarity with respect to the toner is used if the toner charging polarity is negative, and a negative material is used if the toner charging polarity is positive.

However, the adhesion of the toner to the surface layer has physical factors (release properties and surface properties of the surface layer) in addition to the electrostatic factors, and other characteristics (photosensitivity of the toner) besides the prevention of contamination. The surface layer must have sufficient hardness and durability to prevent body fusion, so if the improvement cannot be made with the binder alone, consider the combination of the binder and the charge control agent. And good.

D. Examples of the charge control agent used by being mixed in the surface layer are shown below.

A) The following substances can be controlled to be negatively charged.

For example, organic metal complexes and chelate compounds are effective, and monoazo metal complexes, acetylacetone metal complexes,
There are aromatic hydroxycarboxylic acid and aromatic dicarboxylic acid-based metal complexes.

Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and metal salts, anhydrides,
Esters. There are phenol derivatives such as bisphenol.

B) The following substances are controlled to be positively charged.

Modified products such as nigrosine and fatty acid metal salts, quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate;
And onium salts such as phosphonium salts, which are analogs thereof, and lake pigments thereof.

Triphenylmethane dyes and their lake pigments (as the lacking agent, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide and the like).

Metal salts of higher fatty acids, metal complexes of acetylacetone.

Diorganotin oxides such as dibutyltin oxide, dioctyltin oxide and dicyclohexyltin oxide.

Diorganotin borates such as dibutyl tin borate, dioctyl tin borate and dicyclohexyl tin borate.

Of these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

The above is just one example. These can be used alone or in combination of two or more.

(4) Developing Means 4 The conditions of the developing step used in the present invention are not particularly limited except that the reversal developing method is used, but it is preferable that the developer and the surface of the photoreceptor are in contact. It is one of the forms.

A) When the two-component magnetic brush developing method is used, ferrite, magnetite, iron powder or those coated with an acrylic resin, a silicone resin, a fluororesin or the like are used as carriers. At this time, a DC or AC component bias is applied between the toner carrying member (developing member) of the developing means and the photoreceptor serving as the image carrying member at the time of development or at the time of blank before and after the development, and the toner is applied to the photosensitive body. The potential is controlled so that the toner is not developed and the transfer residual toner can be collected.

The important factors at this time are the electrode properties and the charge amount of the toner on the photoreceptor in each step of electrophotography.

For example, when a negatively charged photosensitive member and a negatively charged toner are used and an image visualized by a positive polarity transfer current is transferred to a transfer material in the transfer process, the applied voltage and the transfer material Type (thickness, resistance,
The charge polarity of the transfer residual toner varies from plus to minus depending on the relationship between the image area and the like (difference in dielectric constant). However, even if the toner remaining after transfer remains positive in the transfer process due to the discharge by the charging member to which DC is applied, the toner is uniformly charged to the negative side and at the same time, the surface potential of the photoconductor is reduced to the desired negative potential. As a result, the transfer residual toner charged to a negative polarity remains in the photoconductor light portion potential portion to be developed with toner, and the transfer residual toner in the photoconductor dark portion potential portion not to be developed with toner. Is attracted toward the toner carrier due to the developing electric field, and no transfer residual toner remains on the dark portion potential portion of the photoconductor.

B) Further, in the present invention, a magnetic or non-magnetic one-component developer is used and coated on a metal sleeve or a coated sleeve, a surface of an elastic roller, or the like as a toner carrier. A developing method in which the surface of the photoreceptor is brought into non-contact or in contact with the surface of the photoreceptor is used. A DC or AC bias is used as a developing or cleaning bias.

At this time, regardless of whether the toner is magnetic or non-magnetic, it is important to generate a force to separate the toner from the surface of the photoreceptor in the photoreceptor surface area that should not be developed with the toner.

C) As a preferred developing method, a one-component contact developing method can be mentioned. In this case, the developing is carried out by an electric field acting between the photosensitive member and an elastic roller as a toner carrier facing the photosensitive member surface via the toner. At the same time, since the cleaning is performed, the surface of the elastic roller or the vicinity of the surface has a potential, and it is necessary to have an electric field in a narrow gap between the surface of the photoconductor and the surface of the toner carrier.

For this reason, a method is employed in which the elastic rubber of the elastic roller is resistance-controlled in the medium resistance region to keep the electric field while preventing conduction with the photosensitive member surface, or to provide a thin insulating layer on the surface layer of the conductive roller. Also available.

Further, a configuration in which a conductive layer is provided on the conductive roller on a conductive resin sleeve on which the side facing the photoreceptor is coated with an insulating material, or an insulating sleeve on the side not facing the photoreceptor is also possible. It is.

When the one-component contact developing method is used, the roller carrying the toner may rotate in the same direction as the photosensitive member, or may rotate in the opposite direction. If the rotation is in the same direction, the peripheral speed ratio is 100
% Or more is desirable. If it is less than 100%, the image quality is poor. The higher the peripheral speed ratio, the greater the amount of toner supplied to the development site, the more frequently toner is attached to and detached from the latent image, and unnecessary portions are scraped off and applied to necessary portions. By repeating, an image faithful to the latent image is obtained.

From the viewpoint of simultaneous development and cleaning, the effect of mechanically peeling off the transfer residual toner adhered on the photoreceptor from the surface of the photoreceptor to the portion where the toner is adhered by the peripheral speed difference and recovering by the electric field can be expected. The higher the peripheral speed ratio is, the more convenient it is to collect the transfer residual toner.

D) Developer (Toner) The toner used in the present invention desirably has an inorganic fine powder present on the surface.

The following are used as the inorganic fine powder. For example, colloidal silica, titanium oxide, iron oxide, aluminum oxide, magnesium oxide, calcium titanate, barium titanate, strontium titanate, magnesium titanate, cerium oxide, zirconium oxide, and the like can be used. These can be used alone or in combination of two or more.

2. As the binder resin used for the toner, styrene resin, polyester resin, acrylic resin,
A wide variety of resins known as binder resins for toner, such as phenolic resins and epoxy resins, can be used alone or in combination.

[0135] 3. Conventionally known inorganic / organic dyes / pigments can be used as the colorant. For example, carbon black / aniline black / acetylene black / naphthol yellow / hansa yellow / rodamun lake / alizarin lake / bengala / phthalocyanine Blue indanthrene blue and the like.

These are usually used in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder resin.

4. For the purpose of charge control, a nigrosine dye / quaternary ammonium salt, a salicylic acid-based metal complex or a metal salt / acetylacetone, or the like can be used.

[0138] 5. A known method is used for producing the toner. For example, a binder resin, a wax, a metal salt or a metal complex, a pigment as a colorant, a dye, or a magnetic substance,
If necessary, a charge control agent, other additives, etc. are sufficiently mixed by a mixer such as a Henschel mixer, a pole mill, etc. A metal compound, a pigment, a dye, and a magnetic substance are dispersed or dissolved in a mixture of the compounds, and after cooling and solidifying, pulverization and classification are performed to obtain a developer (toner).

Regardless of the polarity, the toner may be used as a magnetic or non-magnetic one-component developer, or may be mixed with carrier particles and used as a two-component developer.

E) Production Example of Developer 89% by weight of styrene acrylic resin 2% by weight of metal-containing azo dye 2% by weight of carbon black 4% by weight of polyolefin 4% by weight After the above materials were dry-mixed, they were kneaded by a twin-screw extruder set at 140 ° C. . The obtained kneaded product was cooled, finely pulverized by an air-flow type pulverizer, and then classified by a multi-segment classifier to obtain a toner composition having an adjusted particle size distribution. Hydrophobic silica fine particles (BET ²⁰⁰ m ² / g) 5 wt% was externally added to obtain a toner having a weight average particle size of 8.1 μm.

(5) Example 1 a) Apparatus configuration (FIG. 2) As an electrophotographic apparatus, a laser beam printer with a process cartridge detachable (manufactured by Canon: LBP-86)
0) was prepared. The process speed is 47 mm / s.

In the process cartridge of the LBP-860, a charging roller is used as the charging member 2 for the photosensitive member.

The cleaning rubber blade of the process cartridge was removed. That is, it was made cleaner-less.

Next, the developing portion of the process cartridge was modified. That is, instead of the stainless steel sleeve as the toner carrier, a medium-resistance rubber roller (18φ) made of urethane foam was attached as the toner carrier 4a in contact with the photoconductor 1. The rotational speed of the toner carrier 4a is in the same direction at the portion in contact with the photoconductor 1, and the toner carrier 4a is driven to be 150% of the rotational speed of the photoconductor.

An application roller 4b is provided as a means for applying toner to the toner carrier 4a.
Contacted.

Further, a resin-coated stainless steel blade 4c was attached to control the toner coat layer on the toner carrier 4a.

The photoreceptor was modified so that the surface thereof was charged to a predetermined primary charging potential Vd by a DC charging method using a charging roller 2 to which a DC voltage was applied.

The electrophotographic apparatus was remodeled and process conditions were set so as to be compatible with the remodeling of these process cartridges.

In the modified apparatus, the transfer residual toner on the photoreceptor 1 was adjusted to the same polarity as the desired photoreceptor charging polarity by the charging roller 2, and the photoreceptor 1 was uniformly charged and charge-controlled. While maintaining the transfer residual toner on the photoreceptor 1 at the same polarity as the photoreceptor charging polarity, the image portion is exposed to laser light L to form an electrostatic latent image. Has a process of transferring the toner image to the transfer material P by the transfer roller 5 to which the toner image is applied.

The photoreceptor 1 is a photoreceptor manufactured in the photoreceptor manufacturing example of the above item (2) -c).

The developer (toner) is the developer produced in the developer production example of the above item (4) -e).

The charging roller 2 was manufactured based on the following prescription.

[Preparation of Compound for Elastic Layer] EPDM 100 parts by weight Zinc oxide 5 parts by weight Stearic acid 1 part by weight Conductive carbon black 5 parts by weight Paraffin oil 10 parts by weight Sulfur yellow 2 parts by weight Vulcanization accelerator MBT 1 part by weight 1 part by weight of vulcanization accelerator TMTD Vulcanization accelerator ZnMDC l. 5 parts by weight were mixed for 20 minutes while cooling with two rolls to prepare a compound.

[Preparation of paint for resistance layer (intermediate layer)] Hydrin rubber 100 parts by weight Ethylene thiourea 2 parts by weight Lead oxide 5 parts by weight Tin stearate 2.5 parts by weight Titanium oxide 60 parts by weight (average primary particle diameter 0.02 μm) ) Was kneaded for 20 minutes while cooling with an open roll to prepare a compound.

The compound was diluted and dissolved with toluene to prepare a hydrin rubber coating having a solid content of 5%.

[Preparation of Coating for Surface Layer] 100 parts by weight of a fluorinated resin solution, 2 parts by weight of carbon black, and 100 parts by weight of methyl ethyl ketone were kneaded using a small bead mill to prepare a fluorine coating.

[Preparation of Charging Roller 2] The above-mentioned compound for an elastic layer was heated and vulcanized at 150 ° C. for 15 minutes on a stainless steel core having a diameter of 10 mm to obtain a rubber roller having an elastic layer having a thickness of 3 mm.

The resist layer coating (hydrin rubber coating) was immersed and coated on the rubber roller, and dried by heating at 160 ° C. for 1 hour to obtain a charging member having an intermediate layer having a thickness of 105 μm.

Next, the surface coating material (fluorine coating material) was dip-coated on the charging member and dried by heating at 120 ° C. for 1 hour to obtain a charging roller 2 having a coating layer having a thickness of 10 μm. Was.

-1120 V by charging bias power supply S1
Was applied, the photosensitive member charging potential (dark portion potential Vd) was set to -500 V, and the light portion potential by exposure was set to -100 V.

The developing bias was -300 V DC.

The potential of the photosensitive member after the transfer was +400 V at the portion corresponding to the light portion potential, and +10 V at the portion corresponding to the dark portion potential.
It was 0V.

The discharge starting voltage when the photoconductor of the above-mentioned photoconductor production example is charged using the charging roller 2 is 620V.

B) Evaluation of triboelectric charging property As shown in FIG. 6A, a triboelectric charging plate 61 was prepared by forming a layer 61b of a charging member surface layer material on an aluminum plate 61a with a thickness of about 10 μm. Two of these were prepared.

Next, as shown in FIG. 6B, the charging member surface material layer 61b of one friction charging plate 61 is placed on the upper side, and a predetermined weight of the toner t is placed thereon, in this embodiment, 2 g. Then, another triboelectric charging plate 61 is further stacked thereon with the charging member surface layer material layer 61b on the lower side so as to sandwich the toner t.

Next, the upper triboelectric charging plate 6
A weight 63 having a predetermined weight, in this embodiment, 10 g, is placed on 1 and the upper friction charging plate 61 is rocked in the direction of the arrow e for a predetermined number of times or for a predetermined time while applying a constant load.
In this embodiment, the rocking operation was performed ten times.

Next, as shown in FIG. 6C, the upper frictional charging plate 61 is removed, and the toner t adhered to the charging member surface layer material layer 61b of the lower frictional charging plate 61 is removed.
It is taken into the Faraday gauge 64 by suction with air,
The charge amount of the toner t in the gauge 64 is measured by a coulomb meter 65 connected to the gauge 64.

Then, the weight of the toner taken into the gauge 64 is measured, and the specific charge amount Q / M is calculated by dividing the charge amount Q of the toner by the weight M.

The specific charge amount Q / M obtained as described above is
The frictional charging polarity of the surface material of the charging member with respect to the toner is defined as the triboelectric charging property of the toner. If the polarity of the toner is negative, the polarity of the frictional charging of the surface material of the charging member with respect to the toner is positive. Is negative.

D) Image evaluation The image was evaluated in a low-temperature and low-humidity environment (L / L), a normal-temperature and normal-humidity environment (N / N), and a high-temperature and high-humidity environment (H / H).
A sheet durability test was conducted to evaluate fog on a white background and density uniformity of halftone (formed by a horizontal line of one dot and a blank of two dots).

As the transfer material P, plain paper of 75 g / m ² was used.

The fog was measured using a reflection densitometer (TOKYO DENSHOKU).
CO., LTD, LEFLECTOMETER ODELTC-6DS).

The worst value of the reflection density on a white background after printing is D
s, and Ds-Dr when the average reflection density value of the paper before printing was Dr, was defined as the fogging amount.

When the fog amount is 2% or less, a good image having substantially no fogging is obtained, and when it exceeds 5%, an unclear image in which fogging is noticeable.

The density uniformity was visually evaluated.

Table 3 shows the evaluation results.

(6) Example 2 Example 1 was carried out in the same manner as in Example 1 except that the surface layer of the charging roller 2 was changed to the following nylon resin paint. Table 3 shows the evaluation results.

[Preparation of Surface Layer Paint] Methylolated Nylon 100 parts by weight Nigrosine 2 parts by weight Methanol 420 parts by weight Toluene 150 parts by weight (7) Comparative Example 1 The surface layer formulation of the charging roller 2 in Example 2 was changed to the following nylon resin The procedure was performed in the same manner as in Example 1 except that the paint was used.

The results of the evaluation are shown in Table 3. As a result, the image was fogged on the entire surface during the durability test, and the image could not be used at all.

[Preparation of Surface Layer Coating] Methylolated nylon 100 parts by weight Methanol 420 parts by weight Toluene 150 parts by weight (8) Example 3 In Example 1, instead of the charging roller 2 as a photosensitive member charging member, As shown in FIG. 4 and FIG. 5, the plate-like member 2a is arranged by a spacer member 2b of polyacetal resin so as to maintain a gap α of 100 μm with respect to the surface of the photosensitive member, and the photosensitive member charging member (proximity charging member) 2A And The prescription of the plate member 2a is as follows.

[Production of the plate-like member 2a] A sheet in which iron oxide and nigrosine are dispersed in nylon is formed into a sheet having a thickness of 500 μm, and the sheet is bonded to a stainless parallel plate 2c (2c) using a conductive primer. It is. For the evaluation of the durable image, the voltage applied from the power source Sl to the plate member 2a of the photosensitive member charging member 2A was set to a DC component of 1450 V, and the developing bias was set to -300 V DC.

The photosensitive member charging potential (dark portion potential Vd) is -50
0 V, and the exposed light portion potential is -100 V.

The potential of the photoreceptor after the transfer was +400 V at the portion corresponding to the light portion potential, and +10 V at the portion corresponding to the dark portion potential.
It was 0V.

This photosensitive member charging member (proximity charging member) 2A
When the photoreceptor of the photoreceptor production example is charged by using, the discharge starting voltage is 950V.

Table 3 shows the evaluation results.

[0186]

[Table 3]

[0187]

As described above, according to the present invention, the use of a low-contamination charging member makes it possible to configure a reversal developing system and a simultaneous development cleaning system (cleanerless) employing a DC charging system. In addition, it is possible to obtain an image forming apparatus capable of stably transferring and forming a high-quality image for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for evaluating toner charging polarity.

FIG. 2 is a schematic diagram of the apparatus of Example 1.

FIG. 3 is a model diagram of a layer configuration example of a photoconductor.

FIG. 4 is a schematic view of an apparatus according to a third embodiment.

FIG. 5 is a structural model diagram of a proximity charging member used in the device of the third embodiment.

FIG. 6 is an explanatory view of a device for evaluating the triboelectrification of toner on the surface layer of a charging member.

[Explanation of Signs] 1. Image carrier (electrophotographic photosensitive member) 2, 2A. Charging member (charging roller / proximity charging member) 3. Image exposure unit 4. Developing unit 5. Transfer unit (transfer) Roller) 61 ・ ・ Aluminum plate t ・ ・ Toner 63 ・ ・ Weight 64 ・ ・ Gauge 65 ・ ・ Coulomb meter Sl ~ S3 ・ ・ Bias power supply P ・ ・ Transfer material

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiji Tsuru 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H003 BB11 CC05 EE12 2H005 AA08 CB13 2H071 BA04 BA13 DA06 DA08 DA15 2H077 AA37 AC16 AD13 AD17 AD31 AD35 AE03 BA09 GA17

Claims (9)

[Claims] 1. An image bearing member, a charging device for charging the image bearing member, an information writing device for forming an electrostatic latent image on a charged surface thereof, and a developing device for visualizing the electrostatic latent image as a toner image And a transfer unit for transferring the toner image to a transfer material. After the transfer step, the remaining toner on the image carrier is collected by the developing unit, and the image carrier is repeatedly used for image formation. In the image forming apparatus, the charging of the image carrier by the charging unit is performed by a charging member that is disposed in contact with or in close proximity to the image carrier and to which a DC voltage is applied. The visualization as a toner image is performed by reversal development in which the toner charging polarity and the image carrier charging polarity are the same, and the triboelectric charging polarity of the charging member with respect to the toner on the image carrier facing surface is opposite to the toner charging polarity. polarity An image forming apparatus, characterized in that: 2. The image forming apparatus according to claim 1, wherein the surface of the charging member facing the image carrier contains a charge control agent. 3. The image forming apparatus according to claim 1, wherein the image bearing member is a photosensitive member, and the information writing means for forming an electrostatic latent image on the charged surface is an image exposing means. . 4. The image bearing member has a surface contact angle of 8 with water.
The image forming apparatus according to claim 1, wherein the angle is 5 degrees or more. 5. The image forming apparatus according to claim 1, wherein the surface of the image carrier contains a lubricating powder containing fluorine. 6. The image forming apparatus according to claim 1, wherein a toner having an inorganic fine powder present on its surface is used. 7. The image forming apparatus according to claim 1, wherein at least the image carrier and the charging member are provided in a process cartridge detachable from the image forming apparatus. 8. A charging member which is disposed in contact with or in close proximity to an image carrier of an image forming apparatus of a reversal developing system / simultaneous developing system and charges the image carrier by applying a DC voltage. A charging member, wherein the opposite surface has a triboelectric charge polarity with respect to the toner that is opposite to the toner charge polarity. 9. The charging member according to claim 8, wherein the surface of the charging member facing the image carrier contains a charge control agent.