JP2002278217A - Device and method for contact electrifying, image forming device, and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying device which is supplied with a sufficient electrifying voltage in a short time through low-voltage operation by projecting CNT to the surface of an electrifying member and can prevent electrifying charging from being uneven as a contact electrifying device which electrify a body to be electrified to a specific surface potential by applying a potential difference between the body to be electrified and the electrifying member. SOLUTION: Fig. 2 is an enlarged figure of the contact type electrifying device as an implementation example. A film 21 having the CNT projected on the surface is manufactured first. The CNT in use is either a multi-layered carbon nano-tube or a single-layer carbon nano-tube. As a method for projecting the CNT on the surface, polishing is used here, but dry etching, ashing, or processing using chemicals is applicable. In this example, the surface of a photosensitive body 1 has an electrifying start voltage of -200 V as shown in Fig. 3 in this example and an electrifying potential with a gradient 1 to an applied voltage can be obtained, so that sufficient electrostatic charge can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact band type charging device for an image forming apparatus such as a copying machine, a printer, a facsimile and the like, and an image forming apparatus equipped with the same.

[0002]

2. Description of the Related Art Conventionally, for example, in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an image carrier (a charged body) such as an electrophotographic photosensitive member or an electrostatic recording dielectric is required to have a predetermined potential of a polarity. As a charging device for uniformly charging (including a static elimination process), corotrons and scorotrons using corona discharge have been the mainstream. However, in these non-contact chargers, corona discharge applies a high electric field in the air, and thus generates a large amount of harmful substances such as ozone and NOx, and consumes much power. Accordingly, a contact charging device having advantages such as low ozone, NOx, and low power consumption has recently been put into practical use from the viewpoint of the environment. The contact charging device contacts a member to be charged, which is an image carrier, with a conductive charging member such as a roller type (charging roller), a film type, a fur brush type, a magnetic brush type, or a blade type. By applying the charging bias, the member to be charged is charged to a charging potential of a predetermined polarity. This charging involves (1)
There are discharge type charging and (2) charge injection charging.

First, in discharge-type charging, the surface of a member to be charged is charged by a discharge phenomenon occurring in a minute space between the contact charging member and the member to be charged. In this case, since it has a constant discharge threshold, it is necessary to apply a voltage higher than the charging potential to the contact charging member. Although the amount of generation is much smaller than that of a corona charger such as a scorotron or a corotron, a discharge phenomenon cannot be avoided in principle, so ozone and NOx are generated, and the harmful effects of these active substances cannot be avoided. Typical examples thereof include a roller charger, a fur brush, and a film. In particular, a roller charger is widely used. A roller charger is a method in which a conductive rubber roller is brought into contact with a photoreceptor, and a discharge is caused in a minute gap between the photoreceptor and the charging roller to charge the photoreceptor surface, and the deterioration of the photoreceptor is equal to or worse than that of a corotron. There is a tendency. In this discharge-type charging, the photoreceptor is greatly deteriorated, and ozone and NOx are generated in a small amount.

[0004] The charge injection charging does not cause a discharge,
In this method, charges are directly injected from the contact charging member into the member to be charged. Ozone is not generated in principle, and the photoreceptor does not deteriorate. In addition, the charged object can be charged to a voltage corresponding to the applied voltage below the discharge threshold value. Examples include special charging rollers, magnetic brushes, and fur brushes. First, JP-A-6-7
Japanese Patent No. 5449 discloses tetracyanoquinodimethane (TCN).
Q) and an electron accepting compound such as tetrathiafulvalene (T
A technique is disclosed in which a charge transfer complex composed of an electron-donating compound such as TF) is replaced with a polymer network, and a charging roller is made of a conductive rubber made of a polymer material having conductivity as a whole.

[0005] However, Japan Hardcop
y'92, pp 287-290 reports 80% RH
It can be seen that a sufficient charging voltage can be obtained for the organic photoreceptor (hereinafter abbreviated as OPC) under high humidity, but when the humidity is 30 to 50% RH, only half of the applied voltage is charged and the injection speed is low. Further, in the invention described in Japanese Patent Application Laid-Open No. Hei 7-140729, electric charges are injected into the photoreceptor using a water-absorbing sponge roller. When a water-absorbing sponge roller is used, the water content of the roller has a large effect on the roller resistance and the charge injection speed, so that the charging potential may fluctuate due to evaporation of water from the roller.

Further, in the invention described in Japanese Patent Application Laid-Open No. 9-101649, the contact area between the conductive fiber and the photoreceptor is increased by changing the conductive fiber of the charging brush into an etching fiber or a split fiber, and the charge injection is performed. It has been proposed to increase speed. By these treatments, conductive fibers having a substantially smaller diameter are used, and the contact area with the photoconductor can be increased. However, the tensile strength of the split fiber is smaller than that of the conductive fiber before splitting by the split amount. As a result, when the fiber comes into contact with the photoreceptor, the split fibers are easily cut, and if used for a long period of time, the charging potential varies, which causes a reduction in the life of the contact charger. Conversely, when trying to obtain a long-life contact-type charger, the contact area cannot be expected to increase significantly because the number of conductive fibers cannot be increased.
Significant improvement in charge injection speed cannot be achieved. Further, in the magnetic brush, since powder is used as the contact charging member, there is a large adverse effect due to the drop of the conductive magnetic particles as the powder. In charge injection charging, it is difficult at present to obtain a sufficient charging potential under a normal use environment, or there is a large adverse effect due to powder falling off.

On the other hand, in recent years, carbon nanotubes (CN
T) is expected as an electron emission source, and its application as an image forming device is suggested.
97 abstracts p221). CNT is a very fine substance having a fibrous structure in which one or several to several tens of cylinders each having a rounded graphite-like carbon atom surface are nested, and the diameter of which is on the order of nanometers. This CN
T has a wide range of electrical characteristics from metal to semiconductor depending on its structure, has a unique shape such as small and large surface area, a large aspect ratio (length / diameter ratio), and is hollow. Because of its unique properties, it is expected to be applied to industry as a new carbon material. In particular, the tip of the CNT has a hemispherical shape having a diameter on the order of nanometers, and the concentration of an electric field can be easily obtained by applying a voltage. Field emission is expected from the tip even at a low applied voltage.

In fact, the research group of Smallley et al. Reported for the first time experimentally the field emission from a single multi-walled carbon nanotube (MWNT) (Scie).
269, 1550 (1995)). Thereafter, the technology described in Japanese Patent Application Laid-Open No. 10-12124 and Japanese Patent Application Laid-Open
No. 11158, Appl. Phys. L
ett. , Vol 72, No. 1; 22 (1998) p29
12, etc., CNT is used as an electron emission source for an electron emission element used for a display device. All of them emit electrons in a high vacuum, and are stable electron emission sources at a lower voltage. According to the above literature, current values originating from field emission by CNTs are observed not only in vacuum but also in the atmosphere (Japan Hard Copy '97 Abstract p.
221), application to a new image recording type electron beam source in which a minute area is directly charged by a minute electron beam source to form a latent image or a conventional electrophotographic type non-contact charger is suggested,
Operation at lower voltages is expected.

[0009]

However, such a CN
In the non-contact charging device using the field emission of T, it is necessary that the charging by the field emission is dominant over the charging by the discharge in order to prevent the generation of ozone and NOx and the deterioration of the photoconductor.
For this purpose, it is necessary to apply an electric field to the CNT tip such that electric field emission from a low voltage starts, and it is desirable that the distance between the surface of the charger and the surface of the member to be charged is sufficiently small (several 100 μm). Or less, preferably 100 μm or less).

On the other hand, with respect to such non-contact charging from the surface where many CNTs protrude, there is a problem that the charging start voltage shifts depending on the distance d between the charged body and the charged body.
The field emission was measured by the Fowler-Nordhei shown in FIG.
It is known to obey the equation for m. Here, many CN
On the surface where T protrudes, the local electric field
Not only the shape of the NT tip but also the distance d between the charged body and the charged body
, The local electric field Flo increases as the distance d increases.
cal becomes smaller, and a local electric field for obtaining a charge required for charging requires a larger applied voltage, so that the charging start voltage shifts to a higher voltage side.

In the examination of the CNT as an electron emission source, data on the distance between the CNT and the opposing electrode in a vacuum is shown in Mitsuyuki Saito et al. (Abstracts of the 61st JSAP, p. 652) Have qualitatively obtained similar results. On the other hand, in electrophotography, the photoreceptor to be charged is in the form of a drum or a belt, and in the image forming process, it rotates at a high speed, so that binding and vibration occur, It is difficult to maintain such a small distance d between the charged body and the charged body evenly. In a charger using field emission, the distance is changed as compared with the conventional discharge. Charging unevenness may occur.

Accordingly, an object of the present invention is to provide a contact charging device that contacts a surface of a member to be charged and applies a potential difference between the member to be charged and a charging member to charge the member to be charged to a predetermined surface potential. Yes, in a charging device in which CNTs protrude from the surface of the charging member, a sufficient charging voltage can be given in a short time with a low voltage operation due to the use of the CNTs, and a triode structure using a grid. An object of the present invention is to provide a charging device, a charging method, an image forming apparatus, and a process cartridge that can prevent charging unevenness with a simple configuration without taking a complicated configuration.

[0013]

According to the present invention, the object to be charged is charged to a predetermined surface potential by contacting the object to be charged and applying a potential difference between the object to be charged and the charging member. In the contact charging device to be provided, a carbon nanotube protruding from the surface of the charging member is provided, and a distance between the surface of the charging member from which the carbon nanotube protrudes and the surface of the member to be charged continuously changes. And

According to a second aspect of the present invention, in the first aspect of the invention, the charging member has a film or sheet shape. In the invention according to claim 3,
The invention according to claim 1, wherein the charging member is a roller. In the invention according to claim 4,
The invention according to claim 1, wherein the charging member is a blade. In the invention according to claim 5,
The invention according to claim 1, wherein the charging member is a brush.

According to a sixth aspect of the present invention, there is provided a contact charging method for charging a charged body to a predetermined surface potential by contacting the charged body and applying a potential difference between the charged body and a charging member. A protruding carbon nanotube is formed on the surface of the charging member, and the distance between the surface of the charging member from which the carbon nanotube protrudes and the surface of the member to be charged is continuously changed.

According to a seventh aspect of the present invention, there is provided an image carrier, a charging unit for charging the image carrier, an image writing unit for forming an electrostatic latent image on a charged surface of the image carrier, and the electrostatic latent image. Claims: In an image forming apparatus having a developing unit for visualizing an image with toner, a transfer unit for transferring the toner to a recording medium, and an image forming apparatus for repeatedly performing image formation, a unit for charging the image carrier. A charging device according to any one of claims 1 to 5 is used. According to an eighth aspect of the present invention, there is provided a process cartridge which is detachable from an image forming apparatus main body for performing image formation by applying an image forming process including a step of charging the image carrier with the image carrier. At least a step of charging the image bearing member and the image bearing member, wherein the charging means uses the charging device according to any one of claims 1 to 5.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to FIGS. First, an outline of the present embodiment will be described. As described in the related art, the local electric field Flocal depends on the distance d between the surface of the charged body and the surface of the object to be charged. Therefore, as the distance d increases, the local electric field Flocal decreases, and Requires a higher applied voltage, the charging start voltage shifts to a higher voltage side. On the other hand, in the same manner as in the method shown in Example 3, CNTs are dispersed in an epoxy resin and polished to project the CNTs, and the surface roughness of the rectangular parallelepiped 10 is suppressed to 15 nm or less.
A device of mm × 10 mm × 3 mm was prepared. The device was opposed to an Al electrode formed on a Si wafer by providing a space gap, and the degree of vacuum was set to 10-5 Pa. C
By applying a negative voltage to the NT side and changing the space gap, the current value flowing into the Al electrode side due to the field emission of the CNT is measured. As shown in FIG. 5 (the legend indicates a gap), as the gap becomes smaller, the current-voltage characteristic shifts to a lower voltage, but converges with a very small gap.

Further, the distance d between the surface of the charged body from which the CNTs protrude and the photoreceptor formed on the polished Al substrate, which is the charged body, is controlled by using a Mylar film of various thicknesses. The characteristics were measured, and the applied voltage for starting charging was measured. The result was as shown in FIG. This is because the voltage at which the current rises due to field emission converges to a certain value even if the distance between the CNT and the Al electrode is reduced according to the characteristics of FIG. , The charging start voltage also converges to a certain value.

Therefore, regarding the charging by CNT field emission, the CNT is brought into contact with the member to be charged, and the distance d between the surface of the member and the surface of the member from which the CNT protrudes is continuously changed, whereby the member to be charged by binding or the like is changed. Even if the rotation blurring occurs, since a small space from contact to 100 μm can always be secured, the surface potential becomes (applied voltage−converging voltage), which is caused by the fluctuation of the distance between the surface of the charged body and the surface of the charged body. Charge unevenness can be prevented. It is possible to prevent charging unevenness by keeping the gap below the saturated distance and performing non-contact charging.However, maintaining such a small gap for a charged object moving at a high speed is not possible. Very difficult and impractical. These converging voltages change because the local electric field applied to the CNT varies depending on the capacity of the object to be charged (physical quantities defining the capacity, for example, the film thickness and dielectric constant of the object to be charged). The smaller the film thickness and the larger the dielectric constant, the smaller the converged voltage.

Further, these converging voltages depend on the CN used.
The smaller the T diameter and the lower the open tube, the lower the voltage. Depending on the CNT diameter, the ease of field emission of the CNT due to differences in the opening, closing, and modification of the CNT, and the CNT protrusion density I have. Further, the distance d between the surface of the charged body and the surface of the body to be charged continuously increases from the contact, and the width of a region having a small distance of several hundred μm (preferably 100 μm) or less which contributes to charging (see FIG. 2; The distance of the charged body surface is
The width in the moving direction of the charged body or the charged body in the region of several hundred μm or less is defined as the width. Hereinafter, this is referred to as the width of the minute space) is defined by the value of the surface potential of the charged body to be charged, the linear velocity of the charged body, and the projected CNT density,
If the CNT density is high, the width may be small. If the linear velocity of the charged body is high, a large width is required, and the width must be set to a required width depending on those conditions.

Hereinafter, embodiments of the present invention will be described. The numerical values shown in the embodiments are not limited to these. <Embodiment 1> FIG. 1 is a schematic view of an image forming section of an image forming apparatus using an electrophotographic process in this embodiment. A photoreceptor 1 as an image carrier, a contact charging device 2 for charging the photoreceptor 1, an exposure device 3 for forming an electrostatic latent image, and a developing device for visualizing the electrostatic latent image 4, a transfer device 5 for transferring the electrostatic latent image to recording paper,
The apparatus is provided with a static eliminator 6 for removing static electricity from the recording paper to separate the recording paper from the photoconductor, a cleaning device 7 for removing toner remaining on the photoconductor, and the like.

The transfer device 5 includes a transfer belt 52 that conveys a recording sheet 8 as a recording medium, and a charge providing material 51 that supplies transfer charges to the transfer belt. The contact charging device 2 has a CN
Film 21 and film holding member 2 with T projecting to the surface
3 and a DC power supply 22 for applying a voltage to the film 21
It is composed of

FIG. 2 is an enlarged view of the contact-type charging device in this embodiment. First, a film 21 in which CNTs protruded from the surface was produced. The CNT used may be a multi-walled carbon nanotube or a single-walled carbon nanotube. In either case, the tube may be closed or open at the tip, but either may be used, and the tube may be mixed with several types of CNTs. In addition, to control the resistance of the film,
The CNTs alone may be used in combination with metal fillers, metal fine particles, carbon black, metal oxide fine particles, and the like.

Here, a film was prepared from a single-walled carbon nanotube having a closed end. Multi-walled carbon nanotube BU201 produced by DC arc discharge method
(Bucky USA), and it was pulverized to 5 μm or less by a ball mill because the clusters were about 300 μm. The length of CNT used was 500 nm to 6 μm, averaged 1 μm, and the diameter was 15 nm. Since multi-walled carbon nanotubes contain various impurities such as nanopolyhedrons, they are dispersed in an aqueous solution containing an organic solvent or a surfactant, and then centrifuged, ultrafiltered, or oxidized. It may be purified by heating or refluxing with an acid.

Next, as the material of the film, polyethylene, polyester such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyvinylidene chloride, polyolefin, polyimide, polyvinyl alcohol ( PV
A), polyamide (PA), polypropylene (PP),
Resins such as polystyrene (PS), polycarbonate (PC), polyurethane, polyvinylidene fluoride, PES, ethylene-vinyl alcohol copolymer, soft vinyl chloride resin, styrene-butadiene-styrene block copolymer elastomer, acrylic elastomer, etc. Various thermoplastic elastomers, silicone resins, acetal resins such as polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer and the like can also be used. As rubber,
Natural rubber, butadiene rubber, styrene rubber, butadiene-styrene rubber, nitrile-butadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, chloroprene rubber, butyl rubber, silicone rubber, urethane rubber, Acrylic rubber or the like is used.

Here, PC is converted to tetrahydrofuran (T
HF), disperse the CNTs, form a film using a blade, and heat to form a PC film in which the CNTs are dispersed. This film was polished using a polishing pad of alumina abrasive (particle diameter 0.3 μm) and urethane foam, so that the multi-walled carbon nanotubes 24 protruded from the surface of the carbon nanotube resin matrix. The multi-walled carbon nanotubes 24 had a length of 0 to 5 μm and protruded almost randomly on the surface.

The film had a thickness of 60 μm and a volume resistivity of 104 Ωcm. This film was fixed to a film holding member 23 made of SUS using a conductive adhesive. As a method for projecting the CNTs to the surface, polishing is used here, but other methods such as dry etching, ashing, and treatment with a chemical solution may be used. Further, here, the film is used with both ends fixed, but only one may be fixed and the other may be free to be brought into contact with the member to be charged. Further, if the photoconductor is processed into a cylindrical shape (or a belt shape) and driven to rotate with the photoconductor, the friction between the photoconductor and the photoconductor can be reduced.
In film, the structure of the charger is simple, and the width of the minute space formed by the charged object and the film can be controlled relatively easily by the device size, the film thickness, the amount of indentation, the elasticity of the film, etc. It is very preferable for the purpose in this embodiment.

The film thickness is usually 10 μm
A thickness of about 1 mm is preferable, and an appropriate thickness in these ranges varies depending on the resin used and the width of the minute space. It is preferable to make soft contact so as not to scratch the photoreceptor 1. However, compared to conventional carbon black and metal filler, CNT protrudes from the surface, so that frictional resistance is small and thinner than conventional. There is no need and durability is better.

The photosensitive member 1 is formed by a known technique.
Actually, a hole injection blocking layer composed of titanium oxide fine particles is formed on the Al substrate 12 by a dip coating method to a thickness of 5 μm.
Then, an organic photosensitive layer 11 having a thickness of 25 μm, in which a charge generation layer and a charge transport layer are laminated, is formed. The contact type charging device 2 is brought into contact with the photoreceptor 1, the film is bent, and contacts the photoreceptor 1 with a predetermined nip width. In this embodiment, the charging device is of a fixed type, the film holding member 23 made of SUS has a width of 15 mm and a nip width of 7 mm, and the distance d between the film surface and the photosensitive member surface can be continuously formed from contact.
A small area width of not more than 00 μm can be formed about 3 mm before and after the nip (the contact portion with the photoconductor 1). The photoconductor 1 was rotated at a photoconductor peripheral speed of 100 mm / s. A voltage is applied from a DC power supply 22 to the film 21 whose CNTs protrude from the surface through the film holding member 23.

In this embodiment, as shown in FIG. 3, the surface of the photoreceptor 1 has a charging start voltage of -200 V, and a charging potential having a slope of 1 with respect to the applied voltage is obtained. Obtainable. In addition, the variation of the charging potential is, as shown in Comparative Example 1, compared to a case where a charging device in which CNTs are projected from the surface is charged with a gap provided.
It is confirmed that the charge is reduced to 1/3 or less, and stable charging can be performed. Further, ozone was detected while being continuously charged. As shown in FIG. 6, when the ozone concentration was plotted against the surface potential of the photoreceptor, the ozone concentration was compared with that of a scorotron conventionally used. It was 1/100 or less, and at a surface potential as low as -400 V, it was below the detection limit. The generation of NOx was similarly suppressed.

In this embodiment, an organic photoreceptor is used.
The charge potential is limited to negative because the field emission from NT is used, but the member to be charged is not limited to the organic photoreceptor. In addition, although the photosensitive member has a drum shape, the photosensitive member may have a sheet or belt shape. In this embodiment,
Due to the thickness of the photoreceptor, the diameter of the CNT used, the protrusion density, and the tip being closed, the charging start voltage is -200.
Although it is V, it is possible to control the diameter, projection density, state of the tip, etc. of the CNT by reducing the diameter of the CNT or opening the tip to lower the voltage.

Next, an image forming apparatus using the contact charging device will be described with reference to FIG. The contact charger 2 uniformly charges the photosensitive member 1 to about -400V. Then, the exposure device 3 performs raster exposure based on the image signal. By this raster exposure, the charge is lost, and the potential of the exposed portion on the photoconductor is changed from -400 V to about -50.
V, and an electrostatic latent image is formed. Here, when the toner having negative charge on the developing roller as the developing device 4 comes into contact, the toner does not adhere to the portion where the charge of the photoconductor remains, and the portion without charge, that is, the exposed portion is exposed. The toner is attracted to the portion, and a toner image similar to the electrostatic latent image is formed on the photoconductor.

This toner image is applied to the recording paper 8 conveyed by the transfer belt 52 driven at a constant speed in contact with the photoreceptor 1 from the blade-shaped charge applying material 51 to the opposite polarity to the toner particles. Is transferred to a fixing device by an electric field formed by supplying the electric charges to the transfer belt 52, and is transferred onto a recording sheet. The blade-shaped charge applying material contacts the transfer belt to supply charges. Here, the toner remaining on the photoreceptor 1 without being transferred is cleaned by the cleaning device 7. The charge remaining on the photoreceptor is removed by an unillustrated static eliminator. An image forming apparatus having a cartridge capable of replacing a series of electrophotographic processes as described above is provided. When an image was output by the present image forming apparatus, a good image without uneven charging was obtained.

<Embodiment 2> A second embodiment will be described with reference to FIG. Production of roller charger with CNT protruding from the surface. First, single-walled carbon nanotubes are prepared by a known technique. Here, a composite rod obtained by mixing Fe—Ni metal catalyst with graphite was used as an anode, and a graphite rod was used as a cathode.
Single-walled carbon nanotubes were produced by arc discharge in an orr He atmosphere. The synthesized single-walled carbon nanotubes were purified using centrifugation and ultrafiltration.
As the average size of the CNT, the outer diameter is 3 nm, and the length is 0.1 mm.
It was about 5 μm.

The base 26 of the roller charger is made of Al, SU
Metals such as S and Fe are used. Here, Al
Was used. EPDM (Ethylene Propyl)
The single-walled carbon nanotubes were dispersed in an “ene diene rubber” foam to form a single-layer roller 25 having a resistance value of 108Ω. By grinding the surface, the multi-walled carbon nanotubes 24 were randomly projected. The image bearing member 1 to be charged formed an organic photoreceptor drum in the same manner as in Example 1. The outer diameter of the roller from which the CNTs are projected is 14 mm, and the outer diameter of the photoconductor is 4 mm.
0 mm, the nip width was 5 mm, and the rollers were driven to rotate. For rollers, the structure of the charger is simple, and the width of the minute space formed by the charged object and the film is controlled by the roller outer diameter, elastic modulus, pushing amount, or the outer diameter of the drum when the photoconductor is drum-shaped. I do. Also, the frictional resistance is small and the mechanical damage to the photoconductor is small.

The photosensitive member was rotated at a peripheral speed of 200 mm / s. A voltage is applied to the roller 25 from the DC power supply 22 through the base 26. In this embodiment, the surface of the photoreceptor has a charging start voltage of -120 V, a charging potential having a slope of 1 with respect to the applied voltage is obtained, and sufficient charging can be obtained. Further, the variation of the charging potential is reduced, and stable charging without uneven charging can be performed. Further, ozone and NOx were not detected at a low surface potential at 1/100 or less of the scorotron as in Example 1.

Here, single-walled carbon nanotubes are used, but multi-walled carbon nanotubes may be used. C
Although grinding was used here as a method of projecting NT,
Other methods such as polishing, dry etching, and treatment with a chemical solution do not cause any problem. As for the roller material for dispersing CNTs, polyethylene, polyester such as poly (ethylene terephthalate) (PET) and polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyvinylidene chloride, polyolefin, polyimide, polyvinyl alcohol ( PVA), polyamide (PA), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyurethane, polyvinylidene fluoride,
PES, resins such as ethylene-vinyl alcohol copolymer, soft vinyl chloride resin, styrene-butadiene-styrene block copolymer elastomer, various thermoplastic elastomers such as acrylic elastomer, silicone resin, acetal resin such as polyvinyl butyral, poly Vinyl acetate, ethylene-vinyl acetate copolymer and the like can also be used.

Examples of the rubber include natural rubber, butadiene rubber, styrene rubber, butadiene-styrene rubber, nitrile-butadiene rubber, chloroprene rubber, butyl rubber,
Silicone rubber, urethane rubber, acrylic rubber, etc. may be used. Further, the resistance may be controlled not only by the carbon nanotube alone but also by a metal filler, metal fine particles, carbon black, metal oxide fine particles, or the like.

Example 3 Production of a blade charger in which CNTs protruded from the surface. The blade charger is not shown. Here, as in the first embodiment, D is closed.
A multi-walled carbon nanotube BU201 (manufactured by BUCKY USA) manufactured by a C arc discharge method was used. This CNT was pulverized by a ball mill, mixed with a low molecular weight polyethylene powder, heated and melted, and then cooled to form a polyethylene matrix in which the CNT was dispersed. This matrix is Al
It was adhered to the substrate with a conductive adhesive, polished with a slurry using alumina, and the surface was randomly coated with CN as in Example 1.
T was protruded. The average diameter of the projected CNTs is 15
nm and the average protrusion length was 1 μm.

As an object to be charged, an organic photosensitive drum was formed in the same manner as in Example 1. The blade width from which the CNTs protruded was 10 mm, the outer diameter of the photoconductor was 40 mm, and the nip width was 2 mm. In the blade, the configuration of the charger is very simple. Here, since the blade surface from which the CNTs protrude is a flat surface, the width of the minute space is defined by the outer diameter of the member to be charged, the elastic modulus of the blade, and the amount of pushing. Also,
The width of the minute space formed by the member to be charged and the blade may be controlled by performing a curved surface processing on the blade surface. For example, a concave surface having a radius R larger than the outer diameter of the photosensitive member is used to obtain a larger minute space width, and a convex surface is used to obtain a smaller minute space width. In the case of a belt photoreceptor, similarly, the blade surface from which the CNTs protrude may be subjected to a curved surface processing, or the blade surface polished as described above may be brought into contact with the photoreceptor with an inclination.

The photosensitive member was rotated at a peripheral speed of 100 mm / s. A voltage is applied to the blade from a DC power supply through the Al substrate. In this example, the photoreceptor surface had a charging start voltage of -200 V, and sufficient surface charging could be obtained with respect to the applied voltage. Further, the variation of the charging potential is reduced, and stable charging without uneven charging can be performed. Further, ozone and NOx were not detected at a low surface potential at 1/100 or less of the scorotron as in Example 1.

Although a multi-walled carbon nanotube is used here, a single-walled carbon nanotube may be used. C
Polishing was used here as a method to protrude NT,
Other methods such as dry etching and treatment with a chemical solution do not cause any problem. As for the blade material for dispersing the CNTs, polyesters such as poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT), polyvinyl chloride (PVC), polyvinylidene chloride, polyolefin, polyimide, polyvinyl alcohol (PVC)
A), polyamide (PA), polypropylene (PP),
Resins such as polystyrene (PS), polycarbonate (PC), polyurethane, polyvinylidene fluoride, PES, ethylene-vinyl alcohol copolymer, soft vinyl chloride resin, styrene-butadiene-styrene block copolymer elastomer, acrylic elastomer, etc. Various thermoplastic elastomers, silicone resins, acetal resins such as polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer and the like can also be used.

Examples of the rubber include natural rubber, butadiene rubber, styrene rubber, butadiene-styrene rubber, nitrile-butadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, chloroprene rubber, and butyl rubber. ,silicone rubber,
Urethane rubber, acrylic rubber, etc. may be used. Furthermore,
The resistance may be controlled not only by the carbon nanotube alone but also by a metal filler, metal fine particles, carbon black, metal oxide fine particles, or the like.

Example 4 Production of a brush charger in which CNTs protruded from the surface. The brush charger is not shown. As in Example 2, Fe-N
Single-walled carbon nanotubes were prepared by an arc discharge method using the metal catalyst of i, and purified by centrifugation and ultrafiltration.

The CNT was fixed to a conductive nylon fiber having a fineness of 6 denier and a volume resistivity of 1E5 Ωcm 2 using a thermoplastic resin. The brush made of the conductive nylon fiber from which the CNTs are projected is a roll-shaped rotating brush having a brush density of 100 k / inch2, an outer diameter of 14 mm,
The fiber length is 3 mm. Charging was performed by contacting the organic photoreceptor produced in the same manner as in Example 1. The pushing amount of the brush is 1 mm, the outer diameter of the photoconductor is 40 mm, the nip width where the photoconductor and the brush are in contact is 5 mm, and the brush is driven to rotate with respect to the photoconductor. For a brush,
For each fiber, the distance from the contact to the member to be charged is continuously increasing at random from the contact, and it is not clear what corresponds to the width of the minute space of the film-shaped charger, but the nip width In addition to the CNT density and linear velocity, the charging efficiency is affected by the brush density, the brush density, the fiber length, and the fiber hardness. Because of the brush structure, friction with the photoreceptor can be reduced, and cleaning of toner and foreign matter can be expected, and structurally, the foreign matter has little effect on the image.

The photosensitive member was rotated at a peripheral speed of 200 mm / s. A voltage is applied to the brush from a DC power supply.
In this embodiment, the surface of the photoreceptor has a charging start voltage of -100 V, a charging potential having a slope of 1 with respect to the applied voltage, and sufficient charging can be obtained. Further, the variation of the charging potential is reduced, and stable charging without uneven charging can be performed. Furthermore, regarding ozone and NOx,
As in Example 1, no detection was made at a low surface potential at 1/100 or less of that of the scorotron.

In this case, a roll-shaped rotary brush is used and the driven rotation is used. However, the OPC may be rotated in a reverse direction or a forward direction at a speed different from the OPC linear speed. Alternatively, a fixed brush may be used. Although nylon fibers are used here for the brush fibers, rayon, polyester, acrylic, etc. may be used. Furthermore, the resistance may be controlled not only by the carbon nanotube alone but also by a metal filler, metal fine particles, carbon black, metal oxide fine particles, or the like.

<Comparative Example> FIG. 8 shows a comparative example in which the gap is maintained without contact. In the same manner as in Example 3, the multi-walled carbon nanotubes and polyethylene were heated and melted, and bonded to a rectangular parallelepiped substrate 26 made of SUS, and then subjected to rough polishing and precision polishing with alumina slurry to obtain a surface of the roller 25 containing CNTs. , The multi-walled carbon nanotubes 24 were randomly projected. Mirror polishing with a surface roughness of 30 nm or less was performed. The average diameter of the projected CNT is 15 nm, and the average projection length is 1
μm. A mylar film having a thickness of 25 μm was bonded to both ends of the blade to form a spacer 27. By the spacer 27, the blade surface from which the CNTs protruded and the organic photosensitive layer 11 as the charged body could be kept in non-contact, and the distance was 30 μm.

As a member to be charged, an organic photosensitive drum was formed in the same manner as in Example 1. The blade width from which the CNTs protruded was 10 mm, and the outer diameter of the photoconductor was 40 mm.
The photoconductor was rotated at a peripheral speed of 100 mm / s.
A voltage is applied to the blade from the DC power supply 22 through the SUS base 26. In this comparative example, the surface of the photoconductor 1 has a charging start voltage of -350 V, and sufficient surface charging can be obtained with respect to the applied voltage. in this case,
When the surface potential was measured, a variation of ± 20 V was observed when the applied voltage was -750 V and the surface potential was -400 V. Further, when an image was displayed in the same manner as in Example 1,
Image quality defects such as image unevenness and fog caused by charging unevenness were observed.

[0050]

According to the first and sixth aspects of the present invention, the charged body is brought into a predetermined surface potential by contacting the surface of the charged body and applying a potential difference between the charged body and the charging member. In a charging device, which is a contact charging device for charging, in which carbon nanotubes protrude from the surface of a charging member, a sufficient charging voltage can be given in a short time with a low voltage operation by charging by electric field emission from the CNT, and ozone and N
Since the generation of Ox can be suppressed and the distance between the surface of the charging member from which the carbon nanotubes protrude and the surface of the member to be charged are in continuous contact with each other, a charging device and a charging method free from uneven charging are provided. Can be provided.

According to the second aspect of the present invention, since a film or sheet-shaped charger is used as the charger whose CNTs protrude from the surface, there is provided a charger having no charging unevenness as described in the first aspect. The width of the minute space formed by the member to be charged and the film can be controlled relatively easily according to the device size, the film (sheet) film thickness, the amount of indentation, and the like.

According to the third aspect of the present invention, since a roller-shaped charger is used as the charger whose CNTs protrude from the surface, it is possible to provide a charger having no charging unevenness as described in the first aspect. In addition, the configuration of the charger is simple, and the width of the minute space formed by the member to be charged and the film can be controlled by the outer diameter and the amount of pushing of the roller, or the outer diameter of the drum when the photoreceptor is drum-shaped. Also, the frictional resistance is small and the mechanical damage to the photoconductor is small.

According to the fourth aspect of the present invention, since the blade-shaped charger is used as the charger whose CNTs protrude from the surface, it is possible to provide a charger having no charging unevenness as described in the first aspect. In addition, the configuration of the charger is very simple, and the charger can be manufactured at low cost. According to the fifth aspect of the present invention, a brush-shaped charger is used as the charger whose CNTs protrude from the surface, so that a charger free from uneven charging can be provided as described in claim 1, and friction can be improved. It has low resistance and little mechanical damage to the photoreceptor, and can be expected to clean toner and foreign matter. According to the seventh aspect of the present invention, by using the present contact charging device, a sufficient charging voltage can be given in a short time in a low voltage operation, and ozone and NO
It is possible to provide an image forming apparatus in which the generation of x can be suppressed and the image does not deteriorate due to uneven charging.

According to the eighth aspect of the present invention, by using the present contact charging device, a sufficient charging voltage can be given in a short time with a low voltage operation, generation of ozone and NOx can be suppressed, and uneven charging can be achieved. No compact process cartridge can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged view of a contact-type charging device in the present embodiment.

FIG. 3 is a diagram showing charging characteristics.

FIG. 4 is a diagram showing a relationship between a charging start voltage and a distance.

FIG. 5 is a diagram showing current-voltage characteristics.

FIG. 6 is a diagram showing an ozone concentration.

FIG. 7 is a schematic configuration diagram of a contact-type charging device according to a second embodiment.

FIG. 8 is a schematic configuration diagram of a non-contact type charging device of a comparative example.

FIG. 9 is a diagram showing a Fowler-Nordheim equation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photoreceptor) 2 Contact charging device 3 Exposure device 4 Developing device 5 Transfer device 6 Static eliminator 7 Cleaning device 8 Transfer member (recording paper as a recording medium) 11 Organic photosensitive layer 12 Al substrate 21 Film 22 DC power supply Reference Signs List 23 Film holding member 24 Multi-walled carbon nanotube 25 Roller 26 Base 27 Spacer 51 Charge applying material 52 Transfer belt

Claims (8)

[Claims] 1. A contact charging device that contacts a member to be charged and applies a potential difference between the member to be charged and a charging member to charge the member to be charged to a predetermined surface potential. A contact charging device provided with a protruding carbon nanotube, wherein a distance between the surface of the charging member from which the carbon nanotube protrudes and the surface of the member to be charged changes continuously. 2. The contact charging device according to claim 1, wherein the charging member has a film or sheet shape. 3. The contact charging device according to claim 1, wherein the charging member is a roller. 4. The contact charging device according to claim 1, wherein the charging member is a blade. 5. The contact charging device according to claim 1, wherein the charging member is a brush. 6. A contact charging method for charging an object to be charged to a predetermined surface potential by contacting the object to be charged and applying a potential difference between the object to be charged and the charging member. A contact charging method comprising forming carbon nanotubes and continuously changing the distance between the surface of the charging member and the surface of the member to be charged, from which the carbon nanotubes protrude. 7. An image carrier, charging means for charging the image carrier, image writing means for forming an electrostatic latent image on a charged surface of the image carrier, and visualizing the electrostatic latent image with toner. 6. An image forming apparatus comprising a developing unit and a transfer unit for transferring the toner to a recording medium, wherein the image carrier is repeatedly used for forming an image. An image forming apparatus using the charging device according to claim 1. 8. A process cartridge detachably mountable to an image forming apparatus main body for performing image formation by applying an image forming process including a step of charging the image carrier to the image carrier. 6. The method according to claim 1, further comprising the step of charging the body and the image carrier.
13. A process cartridge using the charging device described in the above section.