JP2002287462A - Contact type electrifier, and image forming device and process cartridge using the contact type electrifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact type electrifier realizing the reduction of cost and stable electrification as a contact type electrifier using an electrifying member where a carbon nano-tube is projected on a surface coming into contact with a body to be electrified. SOLUTION: This contact type electrifier electrifies the body to be electrified (photoreceptor 1 or the like) to specified surface potential by coming into contact with the surface of the body to be electrified 1 and applying a potential difference between the body to be electrified 1 and an electrifying member 21. The member 21 is a cylinder where the carbon nano-tube is projected on the surface coming into contact with the body to be electrified 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type charger used in an image recording apparatus such as a copying machine, a printer, a facsimile, etc., an image forming apparatus using the contact type charger, and a process cartridge.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, as a non-contact type charger for uniformly charging or discharging an image carrier (charged body) to a required polarity potential. The mainstream was corotron and scorotron using corona discharge.

[0003] However, corona discharge applies a high electric field to the air, generates a large amount of harmful substances such as ozone and NOx, and consumes a large amount of power. Contact type chargers having advantages such as power consumption have been put to practical use.

[0004] The contact-type charger contacts a charged member as 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, and a blade type. By applying a predetermined charging bias to the charging member, the member to be charged is charged to a charging potential of a predetermined polarity. The charging mechanism includes (1) discharge type charging and (2) charge injection type. There are two types of charging mechanisms,
Each characteristic appears depending on which is dominant.

Here, in (1) 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. In addition, the amount of generation is significantly smaller than that of a non-contact type charger using corona discharge, but since a discharge phenomenon cannot be avoided in principle, ozone and NO
x is generated and the harmful effects of these active substances are inevitable.

[0006] As such a contact charging member, for example, a roller, a fur brush, a film and the like are known, and among them, a roller charger using a roller as a charging member is widely used. In this roller charger, a conductive rubber roller is used as a charging roller, and this charging roller is brought into contact with a photoreceptor as a charged object, and discharge is caused in a minute gap between the photoreceptor and the charging roller to charge the photoreceptor surface. Is the way. However, this roller charger has a problem that the deterioration of the photoconductor tends to be equal to or worse than that of the corotron.

According to Japanese Patent Application Laid-Open No. 4-249270, a contact type charger using a film-shaped charging member as a charging electrode is proposed. This film-shaped charging member has a simpler device configuration than other contact-type charging members,
This is advantageous for cost reduction.

[0008] However, in order to perform uniform charging, it is necessary to form a stable minute space by making uniform contact between the charged object and the film. For this reason, there is a problem that the charging potential is likely to be unstable due to charging due to friction or vibration of the charging electrode, and that the charging potential becomes non-uniform due to the adhesion of foreign substances such as toner to the nip region.

In any case, in such a contact-type charger, a minute amount of ozone or NOx is generated, and therefore, the surface of the member to be charged is significantly deteriorated, which is a new problem.

On the other hand, in (2) charge injection type charging, charges are directly injected from a contact charging member into a member to be charged without causing discharge. Therefore, no active substance such as ozone is generated in principle, and therefore, the photoreceptor as a member to be charged does not deteriorate. In addition, there is an advantage that the member to be charged can be charged to a voltage corresponding to the applied voltage below the discharge threshold value.

As such an electrification injection type charging member,
Special charging rollers, magnetic brushes, fur brushes, and the like are known.

For example, according to JP-A-6-75459, a charge transfer type compound comprising an electron accepting compound such as tetracyanoquinodimethane (TCNQ) and an electron donating compound such as tetrathiafulvalene (TTF) is disclosed. There has been proposed a charging roller made of a conductive rubber made of a polymer material in which a complex is replaced with a polymer network and the whole is provided with conductivity.

However, in such a charging roller, an organic photoconductor (hereinafter abbreviated as OPC) can obtain a sufficient charging voltage under a high humidity of 80% relative humidity.
It has been reported that at a relative humidity of 30% to 50%, only half the applied voltage is charged and the injection rate is low (Japan Hardco by Kagawa, Furukawa, Shinkawa et al.).
py'92, p287-p290). Here, it is expected that it is not easy to reduce the resistance of the conductive rubber while maintaining an appropriate rubber hardness from the viewpoint of selecting a polymer material.

According to Japanese Patent Application Laid-Open No. 7-140729, electric charges are injected into the photosensitive member using a water-absorbing sponge roller. When using a water-absorbing sponge roller,
Since the water content of the roller greatly affects the roller resistance and the charge injection speed, the charging potential may fluctuate due to evaporation of water from the roller. In order to suppress the fluctuation of the charging potential, it is necessary to strictly control the evaporation of water from the roller over a long period of time, and the structure of the contact-type charger becomes complicated and cannot be manufactured at low cost.

According to 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 to an etching fiber or a split fiber, and the charge injection speed is reduced. It has been proposed to improve.

According to these processes, the conductive fibers having a substantially smaller diameter are used, and the contact area with the photosensitive member 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 fibers come into contact with the photoreceptor, the split fibers are easily cut, and when used for a long period of time, the charging potential varies, which causes a reduction in the life of the contact type charger. Conversely, when trying to obtain a long-life contact type charger, the number of conductive fibers cannot be increased, so that a remarkable increase in the contact area cannot be expected, and the charge injection speed cannot be remarkably improved.

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.

[0018]

SUMMARY OF THE INVENTION The applicant of the present invention has disclosed a contact type in which a charged object is charged to a predetermined surface potential by contacting the surface of the charged object and applying a potential difference between the charged object and a charging member. A contact charger using carbon nanotubes has already been proposed as a charging member of the charger.

In such a contact-type charger, at a low voltage,
An image forming apparatus capable of reducing generation of ozone and NOx and obtaining a good image can be provided.

Further, the present applicant has proposed a charging member in which CNTs are arranged by dispersing carbon nanotubes (hereinafter, sometimes abbreviated as CNTs) in a resin and subjecting the CNTs to stretching treatment. According to such a charging member, charging that is not discharge in a minute space is realized, and uniform charging without unevenness and wear of the member to be charged are reduced.
Examples of such a charging member include a roller and a brush,
Sheets, films, belts, and the like have been proposed, and such charging members have been applied to image recording apparatuses (for example, see Japanese Patent Application No. 2000-98951).

Here, CNT (carbon nanotube)
Means one cylinder of graphite-like carbon atoms rounded,
Alternatively, it is a very fine substance having a fibrous structure in which several to several tens of nests are arranged, and the diameter of which is on the order of nanometers. Carbon nanotubes have a wide range of electrical characteristics, from metals to semiconductors, depending on their structure, and have unique shapes such as small, large surface area, large aspect ratio (length / diameter ratio), and hollow. For this reason, the gas molecules have a high adsorptivity, and the application of hydrogen storage in fuel cells has been considered, and is considered more promising than activated carbon fibers. In addition, a strong local electric field is easily generated at the tip, and is promising as an electron beam source by field emission.
It is also reported that the friction coefficient of sliding friction is smaller than that of rolling friction. Most of the surface is formed of a six-membered ring of graphite-like carbon, and is chemically very stable and has high environmental resistance. Therefore, application to industry as a new carbon material is expected.

There are two types of carbon nanotubes: single-walled carbon nanotubes and multi-walled carbon nanotubes. A single cylinder with a graphite-like carbon atom surface rounded is called a single-walled carbon nanotube, and a plurality of carbon nanotubes are called a multi-walled carbon nanotube. Therefore, due to the characteristics of these carbon nanotubes, the charge injection efficiency is improved in contact,
It is considered to be a good charge imparting material. Further, since the friction coefficient is small, there is a possibility that the abrasion of the opposing material can be reduced. The present invention has been made in consideration of such characteristics of carbon nanotubes.

The present invention relates to a contact type charger which contacts the surface of a member to be charged as described above 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. It is intended to further improve the charging stability of a contact-type charger using carbon nanotubes as a charging member.

That is, the present invention provides a contact-type charger using a charging member in which carbon nanotubes protrude from a surface in contact with a member to be charged, which can realize low cost and stable charging. An object is to provide a charger.

[0025]

According to the first aspect of the present invention,
In a contact-type charger, which contacts a surface of an object to be charged and charges the object to be charged to a predetermined surface potential by applying a potential difference between the object to be charged and the charging member, the charging member contacts the object to be charged. A contact-type charger characterized by having a cylindrical shape in which carbon nanotubes protrude from a surface to be formed.

According to this structure, since the contact resistance can be reduced by projecting the carbon nanotube on the surface in contact with the member to be charged, a sufficient charging voltage can be given in a short time with low voltage operation, and And NOx generation can be suppressed. Also, since the charging member is cylindrical,
Simple configuration and low cost. In addition, since the charging member has a cylindrical shape, the contact with the member to be charged can be stably performed, so that non-discharged charge injection charging can be uniformly performed.

According to a second aspect of the present invention, the charging member includes:
The charging member is held by at least two positioning holding members that contact the outer circumferential surface or the inner circumferential surface to hold the cylindrical shape and that rotatably position and hold the charging member following the movement of the charged body. The contact-type charger according to claim 1.

According to this structure, the positioning and holding member contacts the outer peripheral surface or the inner peripheral surface of the cylindrical charging member and is positioned and held, whereby the charging member can be rotated, and the charging member can be rotated with a relatively simple structure. The contact with the member to be charged can be stably performed. In addition, even when there is a foreign substance such as toner, it is possible to uniformly perform non-discharged charge injection charging.

Further, since the member to be charged is rotated following the movement thereof, the frictional resistance with the member to be charged is small, and the wear of the photosensitive member is reduced.

According to a third aspect of the present invention, the contact portion between the charging member, the positioning holding member, and the member to be charged is:
3. The contact-type charger according to claim 2, wherein the charger is disposed at substantially equal intervals in a rotation direction of the charging member.

According to this structure, in addition to the function and effect of the second aspect, the contact portions between the charging member and the positioning and holding member and the member to be charged are arranged at substantially equal intervals in the rotation direction of the charging member. Therefore, since the rotation of the charging member can be performed stably without unevenness, it is possible to provide a contact type charger capable of realizing uniform charging.

According to a fourth aspect of the present invention, there is provided the contact-type charger according to the second aspect, wherein at least one of the positioning and holding members has a mechanism for controlling a pressing force applied to the charging member.

According to this structure, since at least one of the positioning and holding members has a mechanism for controlling the pressing force applied to the charging member, the rotation of the charging member becomes smooth, and the vibration caused by the rotational shake of the photosensitive member is obtained. Therefore, more stable contact can be performed, and as a result, uniform charging can be realized.

According to a fifth aspect of the present invention, at least one of the positioning and holding members has conductivity and also functions as an electrode for applying a voltage to the charging member. It is a contact type charger.

According to this structure, at least one of the positioning and holding members also functions as an electrode.
It is possible to provide a compact, low-cost contact-type charger with fewer constituent members.

According to a sixth aspect of the present invention, in the contact-type charger according to the second aspect, at least one of the positioning and holding members also functions as a cleaning means for cleaning the surface of the charging member. is there.

According to this structure, at least one of the positioning and holding members also functions as a cleaning means for cleaning the surface of the charging member. Can be provided.

According to a seventh aspect of the present invention, there is provided 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 an electrostatic latent image. A developing means for visualizing the toner image with toner, and a transfer means for transferring the toner to a recording medium, wherein the image carrier is charged repeatedly by an image forming apparatus. Item 7. An image forming apparatus comprising the contact-type charger according to any one of Items 1 to 6.

According to this structure, by using the contact-type charger according to any one of claims 1 to 6 for an image forming apparatus, it can operate at a low voltage and can reduce contact resistance. It is possible to provide an image forming apparatus which can provide a sufficient charging voltage in a short time, does not cause image deterioration due to charging unevenness, and can suppress generation of NOx from ozone.

According to a ninth aspect of the present invention, there is provided an image forming apparatus main body which executes an image forming process by applying an image forming process including a step of charging the image carrier to the image carrier. A process cartridge comprising at least the image carrier and the contact-type charger according to any one of claims 1 to 6, which charges the image carrier.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a schematic diagram of an image forming section of an image forming apparatus using an electrophotographic process used as an embodiment of the present invention. The image forming apparatus includes a photoconductor 1 as an image carrier, a contact-type charger 2 for charging the photoconductor 1, and an exposure device 3 for forming an electrostatic latent image.
A developing device 4 for visualizing the electrostatic latent image, a transfer device 5 for transferring the electrostatic latent image to recording paper, a static elimination device 6 for static elimination of the recording paper, and a toner remaining on the photoconductor It is roughly constituted by a cleaning device 7 and the like for removing the toner.

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-type charger 2 includes a cylindrical charging member 21 having CNTs protruding from the surface thereof, and a power supply 22 for applying a voltage to the charging member 21.

In the present invention, a cylindrical charging member 21 having carbon nanotubes (CNT) held on a surface in contact with the photoreceptor 1 as a member to be charged is used as the contact type charger 2.

If such a charging member 21 is cylindrical,
The CNT may be used alone or in combination with another material. For example,
It is preferable to use a film in which CNT is projected on the surface.

Such a film can be obtained by known film forming using CNT as a suitable binder or matrix and a resin or the like. For example, resin and C
It is obtained by heating and mixing NT with NT to form a film. Further, a carbon nanotube resin matrix in which CNTs are dispersed can be obtained by performing a stretching treatment during or after film formation.

The CNT used here may be a multi-walled carbon nanotube or a single-walled carbon nanotube.
Also, in either case, the tube tip may be closed or open, but either may be used,
A mixture of these several types of CNTs may be used.

The resin used for forming the film is not particularly limited. For example, polyethylene, polyethylene terephthalate (PET)
Aromatic polyesters such as polybutylene terephthalate (PBT) and other polyesters (PES), polyvinyl chloride
(PVC), polyvinylidene chloride, polyolefin, polyimide, polyvinyl alcohol (PVA), polyamide (P
A), resin such as polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyurethane, polyvinylidene fluoride, ethylene-vinyl alcohol copolymer, soft vinyl chloride resin, styrene-butadiene-styrene block copolymer elastomer And various thermoplastic elastomers such as acrylic elastomers, silicone resins, acetal resins such as polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer and the like. Also, 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, etc. can also be used.

The film thickness of this film is not particularly limited and depends on the resin used and the like.
It is sufficient that the thickness is at least μm, and a thickness within a range of about 1 mm is preferable.

Since such a charging member 21 acts as a member to be charged in contact with the photoreceptor 1, it is preferable to make soft contact so as not to damage the surface of the photoreceptor 1.
Here, according to the charging member 21, since the CNTs are projected from the surface, the frictional resistance is smaller than that of a conventional charging member using carbon black or a metal filler.

The charging member 21 of the present invention does not need to be as thin as the conventional charging member and is excellent in durability, but maintains contact sufficiently stably against vibration of the photosensitive member 1 and the like. The thickness is required to be as large as possible, and one of the thicknesses is the Young's modulus which is an index of the elasticity of the resin or the like. When a resin with a large Young's modulus is used, the film thickness is reduced, while when a resin with a small Young's modulus is used, the film thickness is increased to provide appropriate elasticity and maintain durability. can do.

The volume resistivity of the charging member 21 is 10 ¹⁰ Ω.
cm or less. Volume resistivity is an important factor for charge injection charging. When the volume resistivity satisfies this value, a sufficient charging potential can be secured even when the linear speed of the photoconductor 1 is high. Needless to say, this value also depends on the thickness of the film.

Although such volume resistivity can be controlled by CNT alone, it can also be adjusted and controlled by adding various resistance control agents to CNT and blending them. Examples of such a resistance control agent include a metal filler, carbon black, and a charge transfer complex composed of an electron accepting compound such as tetracyanoquinodimethane (TCNQ) and an electron donating compound such as tetrathiafulvalene (TTF). And these may be used in combination.

On the surface of the film obtained as described above, CN
As a method of projecting T, for example, polishing is easy, but dry etching, ashing, or treatment with a chemical solution may be used. The CNT can be made to protrude from the surface by removing the resin or the like serving as a matrix.

Such a film is formed into a cylindrical shape by an appropriate method, and is held by a positioning holding member. Here, the positioning and holding member is a positioning member that is positioned so that contact charging can be performed by bringing a cylindrical charging member into contact with an object to be charged such as a photoconductor, and is usually fixed to a fixed portion such as a housing of a charger. Have been. Since the charging member is formed in a cylindrical shape, the contact with the photoconductor 1 can be performed stably and appropriately. At this time, the charging member can also be maintained in a cylindrical shape by attaching it to the outer surface of the positioning and holding member having a semicircular cross section, for example. This attachment is performed using an adhesive as needed.

Further, the film-shaped charging member 21 formed in a cylindrical shape may be held by a positioning holding member positioned so as to hold the cylindrical shape from the outer periphery or the inner periphery. In this case, the charging member 2 is used as the positioning holding member.
1, a cleaning member also serving as a cleaning member for cleaning the surface of the photosensitive member 1, a pressure member for controlling the pressing force for urging the charging member 21 toward the photoconductor 1, an electrode for applying a voltage to the charging member 21, and the like. It can also be. In any case, since the electricity-resistant member 21 contacts the photoconductor 1 and charges the photoconductor 1 as a member to be charged, it is positioned so as to have an appropriate nip width with the photoconductor 1. It is important that Therefore, in order to position and hold the charging member 21 in contact with the outer periphery or the inner periphery, the photosensitive member 1
It is preferable that the positioning is performed by the positioning and holding member so that an appropriate urging force acts toward.

Here, in order to maintain the shape of the charging member 21 by contacting the outer peripheral surface or the inner peripheral surface of the charging member 21, the charging member 21 must be brought into contact with the charging member 21 from at least two places on the outer peripheral surface or the inner peripheral surface. Is preferred. Such a positioning and holding member may have any shape as long as it holds the charging member 21 in a cylindrical shape. The shape may be a roll shape, a brush shape, a blade shape, or the like, or may be a fiber, a nonwoven fabric, a sponge, a resin or metal block, or the like.

Incidentally, it is preferable that these positioning and holding members have a structure and a material which can reduce abrasion of the charging member 21. For this purpose, these positioning and holding members may rotate or reciprocate. This makes it possible to provide a compact, low-cost contact-type charger with a simple configuration.

When the positioning and holding members also serve as charge applying members (electrodes), these positioning and holding members need to be conductive. By using the conductive positioning and holding member in contact with the charging member, the positioning and holding member functions as an electrode of the charging member.
In this case, the positioning and holding member can also be used as a cleaning member for cleaning the surface of the charging member, or as a pressing member for adjusting and controlling the pressure for urging the charging member against the photoconductor. Thereby, the structure as a charger is further simplified, and it is advantageous for compactness and cost reduction.

These positioning and holding members may be a general insulating resin, rubber, or the like (hereinafter, referred to as resin, etc.).
When the electrode also functions as an electrode (voltage applying member), for example, a metal material such as aluminum or SUS is used. Resin, carbon black, metal powder, metal filler,
Conductive resin or conductive rubber mixed with conductive particles such as carbon nanotubes may be used. Here, as the resin or the like, the same resin, elastomer,
Rubber or the like can be used.

As shown in FIG. 2, for example, as an image forming apparatus, an Al (aluminum) base 1 is used as a photoreceptor 1.
A well-known photosensitive method in which a hole injection blocking layer made of titanium oxide fine particles is formed on the substrate 2 by dip coating to a thickness of 5 μm, and then a 25 μm-thick organic photosensitive layer 11 in which a charge generation layer and a charge transport layer are laminated. The body 1 can be used as it is.

Actually, the photosensitive member 1 is uniformly charged to about -400 V by the contact-type charger 2 having the above configuration, and the exposure device 3 performs raster exposure based on an image signal. When the charge is eliminated, the potential of the exposed portion on the photoreceptor changes from -400V to about -50V.
And an electrostatic latent image is formed. Here, when the toner having a negative charge on the developing roller, which is the developing device 4, comes into contact with the toner, the toner does not adhere to the portion of the photoconductor 1 where the charge remains, and the portion without the charge, that is, the exposed portion The toner adsorbs to the portion, and a toner image similar to the electrostatic latent image is formed on the photoconductor 1.

This toner image is transferred to the recording paper 8 conveyed by the transfer belt 52. At this time, a transfer charge having a polarity opposite to that of the toner particles is supplied to the transfer belt 52 from the blade-shaped charge applying material 51, and the toner image is transferred to the recording paper 8 by an electric field. The charge is removed by the charge removing device 6 and sent to a fixing device (not shown) to fix the toner image on the recording paper.

The toner remaining on the photoreceptor 1 without being transferred is cleaned by the cleaning blade 7. The charge remaining on the photoreceptor is removed by an unillustrated static eliminator. As a result, a good image without uneven charging can be obtained from the output image.

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the materials, configurations, numerical values, and the like shown in the following examples. <Example 1> In Example 1, a single-walled carbon nanotube having a closed end was used alone. This multi-walled carbon nanotube can be synthesized by, for example, a DC arc discharge method using helium as an atmospheric gas and a pressure of 500 Torr using a graphite bar for both the anode and the cathode by a known technique.
Since such multi-walled carbon nanotubes contain various impurities after synthesis, they are dispersed in an aqueous solution containing an organic solvent or a surfactant, and then purified to a high purity by centrifugation or ultrafiltration. Is good.

In the first embodiment, PET was used as the resin, and the mixture was heated and mixed with the CNTs synthesized as described above and stretched to form a film composed of the carbon nanotube resin matrix in which the CNTs were dispersed. This film was polished using a urethane foam polishing pad containing an alumina abrasive having a particle diameter of 0.3 μm, so that multi-walled carbon nanotubes protruded from the surface of the film.

The film thus obtained has a thickness of 0 μm
Multi-walled carbon nanotubes having a length of ~ several μm were randomly projected on the surface. The thickness of this film is
It was 80 μm and the volume resistivity was 10 ⁶ Ωcm.

As shown in FIG. 2, this film is adhered to a positioning and holding member 23 made of SUS having a semicircular cross section by using a conductive adhesive, and the film is formed into a tubular shape. 23 and the other half (portion 21a) is free.
1 was produced.

The positioning and holding member 23 was connected to the power supply 22 and the positioning and holding member 23 was also used as an electrode (voltage applying member). Next, the positioning holding member 2
The free portion 21a not supported by 3 is brought into contact with the photoreceptor 1 with a predetermined nip width (for example, a nip width of 7 mm) to fix the film as the charging member 21 to the extent that the film is bent. Thereby, the contact type charger 2 functions as a fixed type, and it is expected that the structure of the contact type charger 2 will be simplified, compact, and low in cost.

The photosensitive member 1 is rotated at a peripheral speed of the photosensitive member of 100 mm / s, and a DC voltage is applied from a power source 22 to the charging member 21 through a positioning holding member 23 also serving as an electrode. An almost linear charging potential with respect to the applied voltage is obtained on the surface of the photoreceptor 1. When a DC voltage of -400 V or less from the discharge starting voltage is applied from the power supply 22, a surface potential of -380 V is obtained. The potential is a potential sufficient to charge the photoconductor 1. In addition, thereby, the entire surface of the photoconductor is uniformly charged.

While continuously charging under these conditions,
Ozone and NOx were detected, but these active substances were not detected. <Comparative Example> For comparison, in the same manner as in Example 1, the multi-walled carbon nanotubes were dispersed in PET, a film having the multi-walled carbon nanotubes protruded on the surface was prepared, and the CNTs were protruded by polishing the surface. Later film thickness is 1
A film having a thickness of 50 μm and a volume resistivity of 10 ⁶ Ωcm was produced. This film was cut into a square, and used as a charging member 211 used in the comparative example.

As shown in FIG. 6, the charging member 211 is connected to a support member 231 made of SUS connected to the power source 22.
, And the support member 231 is used as an electrode.
The photosensitive film 1 was pressed against the same photosensitive member 1 with a predetermined nip width (7 mm) to cause bending of the film. Next, the photosensitive member 1 was rotated at the same photosensitive member peripheral speed as in Example 1: 100 mm / s, and the same DC voltage as in Example 1 was applied.

Comparing the variation of the charged potential between Example 1 and the control example, it was confirmed that the charge potential of Example 1 was reduced to half that of the control example. As a result, it was confirmed that the charging member of the present invention, in which the charging member had a circular cross section and a cylindrical shape, was able to perform stable charging, as compared with a square (film-like or planar) charging member.

The contact type charger 2 according to the first embodiment as described above.
Is suitable as a substitute for a charger of an image forming apparatus such as a black-and-white, color copier, or a printer, which is provided with a general photoconductor cleaning device. <Embodiment 2> In order to produce a charging member 21 that rotates with the photoreceptor 1 using a multi-walled carbon nanotube having a closed end and polycarbonate as a resin, the shape holding property is better than that of Embodiment 1 so as to improve the shape retention. A cylindrical charging member 21 having a large film thickness was manufactured according to Example 1. The film thickness of the obtained charging member 21 was 150 μm, the multi-walled carbon nanotube had a length of 0 μm to several μm, randomly protruded on the outer peripheral surface, and had a volume resistivity of 10 ⁶ Ωcm.

As shown in FIG. 3, the cylindrical charging member 21 is incorporated so as to be supported by three positioning and holding members 23, 24 and 25 and the photosensitive member 1 at three points. Here, reference numeral 23 denotes a positioning and holding member formed of a SUS roller, reference numeral 24 denotes a positioning and holding member formed of an insulating nylon brush (cleaning member) that also serves to clean the surface of the charging member 21, and reference numeral 25 denotes a positioning and holding member.
It is a positioning and holding member that also serves as a roller electrode made of a SUS roller. Thus, the positioning and holding member 24 also serves as a cleaning member, thereby providing a compact, low-cost contact-type charger with a simple configuration. Each of the positioning and holding members 23 to 25 may be fixed to a housing (not shown) or the like. However, the positioning and holding members 23 to 25 can be rotated in accordance with the rotation of the electricity-resistant member 21 or can reciprocate toward the electricity-resistant member 21. Configuration may be adopted.

As a result, the cylindrical charging member 21 is lightly nipped between the roller electrode (positioning and holding member 25) that is inscribed and the nylon brush (positioning and holding member 24) that is circumscribed, while the shape holding roller (positioning and holding member 23) is being held. )
As a result, the portion which is urged toward the photoconductor 1 and is in contact with the photoconductor 1 is slightly bent, a predetermined nip is formed, and the nip is positioned and held.

When the photosensitive member 1 is rotated in the direction of the arrow, the cylindrical charging member 21 is rotated in the direction of the arrow following this movement. Here, the charging member 21 is connected to each of the positioning holding members (2
3, 24, 25) and the contact portion that comes into contact with the photoreceptor 1 is approximately 120 ° at substantially equal intervals to the rotation direction of the charging member 21.
Therefore, the driven rotation is a stable rotation without rotation unevenness, and stable charging can be always performed.

Further, since the charging member 21 rotates following the rotation of the photosensitive member 1, the frictional resistance between the photosensitive member 1 and the charging member 21 is reduced, so that not only the wear of the photosensitive member 1 is reduced, but also the charging member is reduced. Damage due to contact with 21 is also reduced.

As a result, streak-like charge unevenness due to foreign matter such as toner is less likely to occur, and streak-like image unevenness does not occur.

Actually, as in Example 1, the thickness was 25 μm
Nip width 6 with respect to the photoreceptor 1 having the organic photosensitive layer 11 of
mm, photoconductor peripheral speed: when rotated at 200 mm / s,
An almost linear charging potential with respect to the applied voltage was obtained on the surface of the photoreceptor 1, and it was confirmed that the entire surface of the photoreceptor 1 had sufficient charging ability. In addition, good results without variation in charging potential were obtained. Furthermore, while being continuously charged,
Ozone and NOx were detected, but these active substances were not detected.

The image forming apparatus in which the contact-type charger according to the second embodiment is incorporated is suitable for a black-and-white, color copying machine, printer, etc. provided with a conventional photosensitive member 1 cleaning. Further, in this embodiment, since there is a positioning holding member which also serves as cleaning, it can be applied to an image forming apparatus without cleaning.

In the second embodiment, the positioning and holding member is formed in a roll shape or a brush shape so as to reduce the wear of the charging member 21 and is made of a material. Any shape can be used, such as blades, fibers, non-woven fabrics, sponges,
Blocks of resin, metal, etc. may be used. Further, they may rotate or reciprocate.

Although the charging member 21 is equally supported at three points, the supporting points are not necessarily required to be three points and need not be equally divided. These angles may be 90 ° or more and 180 ° or less, for example, and the configuration becomes complicated, but each positioning and holding member may be a large number of two or more. Also, these positioning members need not necessarily be located at symmetric positions. Example 3 Single-Walled Carbon Nanotube and Resin
Except for using PET, in order to produce the charging member 21 that is driven and rotated together with the photoreceptor 1 in the same manner as in Example 2, a cylindrical member having a larger film thickness than that of Example 1 so as to improve shape retention. The charging member 21 was manufactured according to the first embodiment. The thickness of the obtained charging member 21 was 150 μm, and the single-walled carbon nanotubes had a length of 0 μm to several μm and randomly protruded on the outer peripheral surface, and had a volume resistivity of 10 ⁷ Ωcm.

As shown in FIG. 4, the cylindrical charging member 21 is incorporated so as to be supported by three positioning support members 23 and 24 and the photosensitive member 1 at three points. Here, reference numeral 23 is a positioning and holding member made of a rubber roller, and reference numeral 24 is a positioning and holding member made of a polyethylene brush (conductive brush) made conductive by carbon black. Also serves as an electrode. Thus, compared to the contact type charger 2 of the second embodiment, the number of constituent elements is further reduced, the structure is simplified, and this is advantageous for downsizing the device.

As a result, the cylindrical charging member 21 is urged toward the photoreceptor 1 by the conductive brush (positioning and holding member 24) and the rubber roller (positioning and holding member 23) which are in contact with the charging member 21. The portion in contact with 1 is slightly bent, and a predetermined nip is formed and held.

When the photoreceptor 1 is rotated in the direction of the arrow, the cylindrical charging member 21 is rotated in the direction of the arrow following this movement, and the charging member 21 is moved to the positioning and holding members (23, 24).
In addition, since the contact portion that comes into contact with the photoreceptor 1 is approximately 120 ° at substantially equal intervals with respect to the rotation direction of the charging member 21, this driven rotation is a stable rotation without rotation unevenness, and a stable charge is always provided. It can be carried out.

Further, since the charging member 21 rotates following the rotation of the photosensitive member 1, the frictional resistance between the photosensitive member 1 and the charging member 21 is reduced, so that not only the wear of the photosensitive member 1 is reduced, but also the charging member is reduced. Damage due to contact with 21 is also reduced.

As a result, streak-like charge unevenness due to foreign matter such as toner is less likely to occur, and streak-like image unevenness does not occur.

Actually, as in Example 1, the thickness was 25 μm.
Nip width 7 for photoreceptor 1 having organic photoconductive layer 11
mm, photoconductor peripheral speed: when rotated at 200 mm / s,
The surface of the photoreceptor 1 had a charging characteristic having a surface potential substantially linear with respect to the applied voltage, and it was confirmed that the entire surface of the photoreceptor 1 had sufficient charging ability. In addition, good charging characteristics without variation in charging potential were obtained. Further, while continuously charged, ozone and NOx were detected, but were not detected.

Further, when this contact type charger was incorporated into a cleaningless type image forming apparatus having improved transfer efficiency and an image was output, a good image free of image unevenness due to charging unevenness could be obtained. did it.

The image forming apparatus incorporating the contact-type charger according to the present invention can be applied to a black-and-white, color copier, printer, etc. provided with a conventional photosensitive member cleaning. <Embodiment 4> This embodiment 4 has the same configuration as the embodiment 2 except that a spring 26 such as a coil spring as an elastic member is provided as shown in FIG. By providing a pressing mechanism that fixes one end of each of a pair of springs 26 (only one in the figure) to both ends of the positioning and holding member 23 made of a SUS roller and presses the positioning and holding member 23, The pressure is adjusted elastically. Thereby, rotation of the cylindrical charging member 21 becomes smooth,
In addition, since vibration caused by rotational shake of the photoconductor 1 can be absorbed,
More stable contact can be performed.

Actually, similarly to the first embodiment, a thickness of 25 μm
Nip width 6 with respect to the photoreceptor 1 having the organic photosensitive layer 11
mm, photoconductor peripheral speed: when rotated at 200 mm / s,
It was confirmed that a charging characteristic having a surface potential substantially linear with respect to the applied voltage was obtained, and that the photoconductor had a uniform charging ability uniformly over the entire surface.

The variation in the charging potential is very small, and is considered to be the effect of the pressing mechanism. Further, while continuously charged, ozone and NOx were detected, but were not detected.

Here, as a mechanism for controlling the pressing force,
Although a spring such as a coil spring is used, other leaf springs or disc springs may be used, or an elastic body such as rubber may be used. It is sufficient that the positioning and holding member 23 can be pressed toward the charging member 21, so that vibration can be absorbed.

The image forming apparatus in which the contact type charger according to this embodiment is incorporated is suitable for a black-and-white, color copier, printer or the like provided with conventional photoconductor cleaning. Further, in this embodiment, since the positioning holding member 24 also serves as cleaning, it can be applied to an image forming apparatus without cleaning.

Further, a series of electrophotographic processes according to the above embodiments can be removably incorporated into an image forming apparatus as a replaceable process cartridge. For example,
A process cartridge including these contact-type chargers can be detachably attached to an image forming apparatus main body that performs image formation by applying an image forming process including a step of charging an image carrier.

In the above embodiment, an image forming apparatus using a negatively charged organic photoreceptor has been described as an example. However, the present invention is not limited to this, and the contact-type charger of the present invention is positively charged. It can also be used for inorganic photoreceptors such as Se-based, a-Si (amorphous silicon) -based, and ZnO-based, and other charged objects. Similar effects are expected when used for static elimination. .

[0098]

According to the first aspect of the present invention, the contact resistance can be reduced by projecting the carbon nanotube on the surface in contact with the member to be charged. Given voltage, ozone and NOx
Can be suppressed. In addition, since the charging member has a cylindrical shape, the structure is simple and cost reduction can be realized, and the contact with the member to be charged can be stably performed. It is possible to provide a contact-type charger that can be used.

According to the second aspect of the present invention, the charging member can be rotated by being held in contact with the outer peripheral surface or the inner peripheral surface of the cylindrical charging member by the positioning and holding member, so that a relatively simple configuration is provided. Thus, the contact with the member to be charged can be stably performed. In addition, even when there is a foreign substance such as toner, it is possible to uniformly perform non-discharged charge injection charging.

Further, since the member to be charged is rotated following the movement thereof, the frictional resistance with the member to be charged is small, and the wear of the photosensitive member is reduced.

According to the third aspect of the present invention, the charging members are supported at substantially equal intervals in the rotational direction, and stable rotation without rotation unevenness can be obtained, thereby realizing uniform charging. A contact-type charger that can be provided.

According to the fourth aspect of the present invention, at least one of the positioning and holding members has a mechanism for controlling the pressing force applied to the charging member, so that the pressure of the positioning and holding member can be freely adjusted or the photosensitive member can be adjusted. 1 can absorb vibrations caused by rotational shake, and can smoothly rotate the charging member, and can perform stable contact, and as a result, can provide a contact-type charger that can realize uniform charging.

According to the fifth or sixth aspect of the present invention, at least one of the positioning and holding members is also used as an electrode or a cleaning means, so that the number of constituent members is small, and a compact and low-cost contact type member is provided. A charger can be provided.

According to the seventh aspect of the present invention, the contact resistance can be reduced by the low voltage operation, so that a sufficient charging voltage can be given in a short time, and the generation of ozone and NOx can be suppressed.
It is possible to provide an image forming apparatus in which an image does not deteriorate due to uneven charging.

According to the invention of claim 8, the contact resistance can be reduced by the low voltage operation, so that a sufficient charging voltage can be given in a short time, and the generation of ozone and NOx can be suppressed.
A compact process cartridge without charge unevenness can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus of the present invention.

FIG. 2 is an enlarged schematic configuration diagram near a contact-type charger in the image forming apparatus according to the first exemplary embodiment.

FIG. 3 is an enlarged schematic configuration diagram in the vicinity of a contact-type charger in an image forming apparatus according to a second embodiment.

FIG. 4 is an enlarged schematic configuration diagram near a contact-type charger in an image forming apparatus according to a third embodiment.

FIG. 5 is an enlarged schematic configuration diagram near a contact-type charger in an image forming apparatus according to a fourth embodiment.

FIG. 6 is an enlarged schematic configuration diagram in the vicinity of a contact type charger in the image forming apparatus of Comparative Example 1.

[Explanation of symbols]

 1: Image carrier (photoreceptor: charged body) 2: Contact type charger 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: Aluminum substrate 21: Cylindrical charging member 22: Power supply 23, 24, 25: Positioning and holding member 26: Pressing mechanism (spring) 51: Charge applying material 52: Transfer belt

Claims (8)

[Claims] 1. A contact-type charger which 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. A contact-type charger having a cylindrical shape in which carbon nanotubes protrude from a surface in contact with a member to be charged. 2. The method according to claim 1, wherein the charging member is in contact with an outer peripheral surface or an inner peripheral surface to maintain a cylindrical shape and to rotatably position and hold the charging member in accordance with the movement of the charged member. 2. The contact-type charger according to claim 1, wherein the contact-type charger is held by a holding member. 3. A charging device according to claim 2, wherein contact portions of said charging member with said positioning and holding member and said member to be charged are arranged at substantially equal intervals in a rotating direction of said charging member. Contact type charger. 4. A contact-type charger according to claim 2, wherein at least one of said positioning and holding members has a mechanism for controlling a pressure applied to said charging member. 5. The contact-type charger according to claim 2, wherein at least one of said positioning and holding members has conductivity and also functions as an electrode for applying a voltage to said charging member. 6. A contact type charger according to claim 2, wherein at least one of said positioning and holding members also functions as a cleaning means for cleaning a surface of said charging member. 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 development for visualizing the electrostatic latent image with toner. Means for transferring the toner to a recording medium, wherein the means for charging the image carrier is an image forming apparatus in which the image carrier is repeatedly used for image formation.
7. An image forming apparatus, which is the contact-type charger according to any one of 6. 8. An image forming apparatus that performs image formation by applying an image forming process including a step of charging the image carrier to the image carrier, and is detachable from the image forming apparatus main body. A process cartridge comprising the contact-type charger according to any one of claims 1 to 6, which charges the image carrier.