JP2006350074A - Electrifying member for electrophotography and electrophotographic image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrifying member for electrophotography which restrains the adhesion of a toner or the adhesion of an additive to the surface of an electrifying member to solve a problem on the deterioration in an image caused thereby, and to provide an electrophotographic image forming apparatus using the electrifying member for electrophotography. <P>SOLUTION: The electrifying member for electrophotography having an elastic body layer containing fibrous conductive material, and the image forming apparatus for electrophotography using the same are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charging member used in an electrophotographic image forming apparatus such as a copying machine or a printer using an electrophotographic developing system, and an electrophotographic image forming apparatus using the charging member.

  Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, a charging roll (contact charging member) brought into contact with a photosensitive drum (image carrier) is applied with a charging voltage using a power source. A charging device that uniformly charges the surface of a photosensitive drum to a predetermined potential is known.

  Such a charging roll has a conductive solid structure rubber composition or sponge structure foam in which conductive particles such as carbon black and metal powder are added to the outer peripheral surface of a shaft (core metal). The conductive elastic body layer formed using is provided with a predetermined thickness.

  In such a charging device, if a toner such as transfer residual toner or an external additive adhering to the surface of the photosensitive drum is transferred and adheres to the surface of the charging roll and is fixed, a charging failure occurs and the image quality deteriorates. It becomes a problem.

  As a countermeasure for this, for example, a method in which dirt on the surface of the charging roll is transferred to the surface of the photosensitive drum by rubbing between the surface of the charging roll and the surface of the photosensitive drum, based on the fact that the charging roll is driven by rotation of the photosensitive drum, A method of lightly pressing a cleaning member such as a sponge on the surface of the roll to wipe off the dirt has been used, but the former has insufficient removability of toner and external additives, and the latter may damage the charging roll. is there.

  Further, in order to remove the positively charged toner adhering to the charging roll, a negative voltage is applied to the transfer roll to charge the photosensitive drum to a negative polarity, and a positive voltage is applied to the charging roll. A method of transferring a positively charged toner on a charging roll to a photosensitive drum by forming a strong electric field between the negative charging roll and the negative photosensitive drum is disclosed (for example, see Patent Document 1).

Further, a resin composition further comprising a non- (fluorine-modified) acrylate resin having a glass transition temperature higher than that of the binder resin of the toner together with a fluorine-modified acrylate resin and a fluorinated olefin resin as a protective layer of the charging roll. And a method for suppressing or preventing toner adhesion and external additive adhesion to the roll surface (see, for example, Patent Document 2).
JP-A-10-161500 JP 2001-154456 A

  In the above prior art, by adding a predetermined amount of conductive particles such as carbon black and metal powder to the elastic layer, a percolation structure in which the conductive particles are in continuous contact is provided, and this is applied to the elastic layer. It is used as a conductive path.

  As a result of intensive studies, the present inventors have found that the addition of conductive particles such as carbon black and metal powder is a major factor that affects the adhesion of toner and external additives.

  That is, in the conventional technique, the elastic layer to which conductive particles such as carbon black and metal powder are added has a slow connection of the conductive particles in the percolation structure, so that the charge decay in the elastic layer is slow and adheres to the charging member surface. It is presumed that the toner and the external additive are less likely to be detached, so that the toner and the external additive are easily attached to the surface of the charging member.

  Further, the method disclosed in Patent Document 1 has a problem that it involves an increase in power consumption and an increase in the size of the apparatus.

  Moreover, in the method disclosed in the above-mentioned Patent Document 2, since a fluororesin is used, there is a concern about an environmental load.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic device capable of suppressing the adhesion of toner and external additives to the surface of the charging member and thereby solving the problem of image degradation. It is an object to provide a photographic charging member and an electrophotographic image forming apparatus using the same.

The object of the present invention is achieved by the following configurations.
(Claim 1)
An electrophotographic charging member having an elastic layer containing a fibrous conductive material.
(Claim 2)
2. The electrophotographic charging member according to claim 1, wherein the fibrous conductive material has a length B in a direction perpendicular to the fiber axis of 1 nm or more and less than 100 μm.
(Claim 3)
The fibrous conductive material has a length A in the fiber axis direction of less than 1 cm, and an A / B that is a ratio of the length A in the fiber axis direction and the length B in the direction perpendicular to the fiber axis is The charging member for electrophotography according to claim 1, wherein the charging member is 2 or more.
(Claim 4)
4. The electrophotographic charging member according to claim 1, wherein a volume resistivity of the fibrous conductive material is 10 ³ Ω · cm or more and 10 ⁸ Ω · cm or less. 5.
(Claim 5)
The charging member for electrophotography according to any one of claims 1 to 4, wherein the fibrous conductive material is a fibrous carbon material.
(Claim 6)
The fibrous carbon material is a fibrous carbon material derived from an organic compound having a residual rate of 20% by mass to 95% by mass when the organic compound is heat-treated at a temperature of 800 ° C. in a nitrogen atmosphere. The charging member for electrophotography according to claim 5.
(Claim 7)
The electrophotographic carbon material according to claim 6, wherein the fibrous carbon material is a fibrous carbon material obtained by heat-treating the organic compound at a temperature of 800 ° C or higher in a non-oxidizing atmosphere. Charging member.
(Claim 8)
8. The charging member for electrophotography according to claim 7, wherein the fibrous carbon material is a fibrous carbon material obtained by performing the heat treatment in a state where the organic compound is formed into a fiber shape. .
(Claim 9)
The charging member for electrophotography according to any one of claims 6 to 8, wherein the organic compound is an organic polymer material.
(Claim 10)
The charging member for electrophotography according to claim 9, wherein the organic polymer material is a phenol resin.
(Claim 11)
The fibrous conductive material and a conductive material having a volume resistivity of less than 10 ³ Ω · cm are used in combination so that the mass fraction is fibrous carbon material / conductive material <1. The charging member for electrophotography according to any one of claims 4 to 10.
(Claim 12)
12. The electrophotographic charging member according to claim 1, wherein the electrophotographic charging member is an electrophotographic charging roll.
(Claim 13)
An electrophotographic image forming apparatus using the electrophotographic charging member according to claim 1.
(Claim 14)
The electrophotographic image forming apparatus according to claim 13, wherein the electrophotographic charging member is charged in contact with an object to be charged.

  The present inventors use an electrophotographic charging member characterized by having an elastic layer containing a fibrous conductive material, so that the elastic layer containing the fibrous conductive material has a percolation structure. By increasing the contact area due to the entanglement of the fibrous conductive materials, the connection is strengthened and the charge decay is accelerated. As a result, the charge of the elastic layer is likely to be attenuated, and as a result, it is possible to suppress the adhesion of toner and external additives to the charging member surface, thereby solving the problem of image deterioration due to the above. The present invention has been reached.

  According to the charging member of the present invention, since the charge attenuation of the elastic layer of the charging member is fast, the adhesion of the toner and the external additive is suppressed, the charging member is hardly stained, and a good image can be obtained.

  Although the example of embodiment regarding this invention is shown below, the aspect of this invention is not limited to these.

<Electrophotographic image forming apparatus>
First, an electrophotographic image forming apparatus using the charging member according to the present invention will be described. In this example, a charging roll is used as a charging member, and a photoconductor is used as a member to be charged.

  FIG. 1 is a sectional view showing an example of an electrophotographic image forming apparatus of the present invention. Reference numeral 4 denotes a photosensitive drum as a member to be charged, which is formed by forming an organic photoconductor (OPC) as a photosensitive layer on the outer peripheral surface of an aluminum drum base, and rotates at a predetermined speed in the direction of an arrow. .

  In FIG. 1, exposure light is emitted from a semiconductor laser light source 1 based on information read by a document reading device (not shown). This is distributed in the direction perpendicular to the paper surface of FIG. 1 by the polygon mirror 2 and irradiated onto the surface of the photoreceptor through an fθ lens 3 that corrects image distortion, thereby forming an electrostatic latent image. The photosensitive drum 4 is uniformly charged by the charging roll 5 in advance, and starts rotating clockwise in accordance with the timing of image exposure.

  The electrostatic latent image on the surface of the photosensitive drum is developed by the negatively charged toner in the developing device 6, and the formed developed image is transferred to the transfer body 8 that has been conveyed in time by the action of the transfer device 7. The Further, the photosensitive drum 4 and the transfer body 8 are separated by a separator (separation pole) 9, but the developed image is transferred and supported on the transfer body 8, guided to the fixing device 10, and fixed.

  Untransferred toner or the like remaining on the surface of the photoreceptor is cleaned by a cleaning blade type cleaning device 11, the residual charge is removed by pre-charge exposure (PCL) 12, and again by the charging roll 5 for the next image formation. Uniformly charged.

  A power supply unit 14 applies a voltage to the charging roll 5 and supplies a predetermined voltage to a shaft body (core metal) 51 of the charging roll 5. The applied voltage is preferably a DC voltage superimposed with an AC voltage.

  Further, the mechanical pressure applied between the charging roll and the electrophotographic photoreceptor is such that the contact pressure of the charging roll to the photoreceptor is 5 to 500 Pa, and the electrical load is the DC voltage applied to the charging roll. When an alternating voltage is applied to an absolute value of 200 to 900 V, it is desirable that the peak-to-peak voltage is adjusted to 500 to 5,000 Vp-p and the frequency is 50 to 3,000 Hz. For example, it is preferable that the applied voltage has a peak-to-peak voltage value that is at least twice the charging start voltage value for the photoreceptor.

  The charging roll may be driven or driven non-rotatingly by a surface-driven driven photoconductor, or a predetermined circumference in the forward or reverse direction in the surface movement direction of the photoconductor at the contact portion. You may make it actively rotate at a speed.

  The transfer member is typically plain paper, but is not particularly limited as long as it can transfer an unfixed image after development, and of course includes an OHP PET base.

  The cleaning blade 13 uses a rubber-like elastic body having a thickness of about 1 to 30 mm, and urethane rubber is most often used as the material. Since this is used in pressure contact with the photoconductor, it is easy to transfer heat, and it is desirable to provide a release mechanism and keep it away from the photoconductor when no image forming operation is performed.

<Charging roll>
Next, the charging roll according to the present invention will be described in detail.

  Hereinafter, a charging roll having an elastic layer made of a rubber layer containing a fibrous carbon material as the fibrous conductive material will be described as an example.

  A charging roll 5 according to the present invention includes a shaft body (core metal) 51 made of a stainless steel rod and an elastic body layer 52 made of a rubber layer containing a fibrous carbon material as a fibrous conductive material on the outer periphery thereof. Has been.

  As the fibrous conductive material, in addition to the fibrous carbon material, a fibrous metal material, a fibrous conductive metal oxide material such as fibrous conductive titanium oxide or fibrous conductive tin oxide can be used. From the viewpoint of control of volume resistivity and elastic modulus and ease of production, a fibrous carbon material is particularly preferable.

  In addition to the rubber layer, the elastic layer may be a foam layer such as polyurethane.

  Further, the charging roll may be provided with one elastic body layer of the present invention as long as the object of the present invention can be achieved, and a plurality of other elastic body layers may be combined in addition to this layer.

  In the present invention, there is no particular limitation on the combination of the elastic layers, but it is preferable that the elastic layer of the present invention is installed from the outermost layer or from the outer side to the second layer in terms of enhancing the antifouling effect. . For example, a resistance adjusting layer or a protective layer may be provided on the elastic layer of the present invention.

The volume resistivity of the elastic layer 52 made of a rubber layer containing a fibrous conductive material such as a fibrous carbon material in the charging roll is 10 ⁵ Ω · cm to 10 ¹¹ Ω · from the viewpoint of charging performance and leakage prevention. cm is preferred.

  The volume resistivity of the elastic layer containing a fibrous conductive material such as a fibrous carbon material can be measured by the following method.

A rubber containing a fibrous conductive material such as a fibrous carbon material is cut into a cube having a side of 5 cm, and a pressure of 10 ⁷ Pa is applied with a flat plate press heated to 140 ° C. for 20 minutes to form a sheet. An intermediate portion of this sheet is cut out with a width of 1 cm to obtain a sample for measuring volume resistivity. Since the thickness of the sample differs depending on the density of the rubber, it is measured with a thickness meter. Four copper wires having a diameter of 0.2 mm and a length of 4 cm are adhered to the surface of a sample cut into a 1 cm × 5 cm strip shape by using dootite and sufficiently dried. Using the electrode thus formed, volume resistivity is measured by a four-terminal method in an environment adjusted to a temperature and humidity of 25 ° C. and 50% RH.

Furthermore, it is preferable that the volume resistivity of the fibrous conductive material such as a fibrous carbon material is 10 ³ Ω · cm or more and 10 ⁸ Ω · cm or less because the volume resistivity of the elastic layer can be easily controlled. .

Further, in this case, a conductive fiber material such as a fibrous carbon material having a volume resistivity of 10 ³ Ω · cm or more and 10 ⁸ Ω · cm or less and a conductivity higher than that of the fiber conductive material, that is, volume-specific. It is a preferred embodiment to use a combination of a conductive material having a resistance of less than 10 ³ Ω · cm, but the latter is not preferred when added more than the fibrous conductive material. That is, assuming that the added mass of the fibrous conductive material is X and the added mass of the conductive material used in combination is Y, when the mass fraction X / Y is 1 or more, the conductivity of the charging roll tends to be too high, which is not preferable. When X / Y is less than 1, it is preferable because the contribution of the fibrous conductive material to the conductivity is high, the effect of preventing the stain on the roll surface is enhanced, and the conductivity of the elastic layer of the charging roll can be easily controlled. . A carbon powder represented by carbon black or the like is suitable as a conductive material having a volume resistivity of less than 10 ³ Ω · cm, and is a material described in the Carbon Black Handbook edited by the Carbon Black Association.

The volume resistivity of the fibrous conductive material such as the fibrous carbon material is measured by a two-terminal method in an environment adjusted to a temperature and humidity of 25 ° C. and 50% RH after being molded into a tablet. About the manufacturing method of a tablet, it shape | molds with a hydrostatic pressure pressurization of 10 < ⁸ > Pa or more after shape | molding with a tablet molding machine. Hydrostatic pressure pressurization of 5 × 10 ⁸ Pa or more may be applied, but if the pressure is too high, it is difficult to release from the rubber mold, and therefore, preferably less than 5 × 10 ⁸ Pa. More preferably, it is 3 × 10 ⁸ Pa or less.

  Charge amount of fibrous conductive material such as fibrous carbon material added to elastic layer (mass of fibrous conductive material × 100 / mass of elastic layer (for example, rubber layer) as base) In view of the mechanical properties, the content is 30% by mass or less, preferably 20% by mass or less. The minimum required amount of the fibrous carbon material is selected from the charging performance of the charging roll. Considering this condition, the fibrous carbon material is preferably 1% by mass or more, more preferably 3% by mass or more.

  Below, the fibrous carbon material of this invention is demonstrated in detail.

  In the fibrous form of the present invention, the length A in the fiber axis direction is less than 1 cm, and the ratio between the length A in the fiber axis direction and the length B in the direction perpendicular to the fiber axis (that is, the fiber thickness) B The shape in which A / B is 2 or more is preferable, and more preferably 3 or more and less than 1000. When this ratio is too small, the effect of the present invention is reduced. On the other hand, if this ratio is too large, it will be difficult to mix with rubber, such being undesirable. Furthermore, if it is less than 100, it can disperse | distribute more stably to rubber | gum, and if it is less than 50, since the load to a mixing apparatus can be made small, it is suitable.

  As for the length B (that is, the fiber thickness) B in the direction perpendicular to the fiber axis, if it is too thin, it causes thickening during mixing. Therefore, it is preferably 1 nm or more. If the fiber is too thick, uniform dispersion becomes difficult. Less than is preferable. More preferably, it is less than 50 μm. In view of handling, the thickness is preferably 10 nm or more, and more preferably 100 nm or more.

  Further, these lengths A and B can be measured by observation with an electron microscope. B is defined by the maximum length in a plane perpendicular to the fiber axis, and if it is a circle, it has a length corresponding to the diameter.

  In addition, the fibrous carbon material has a residual ratio ((mass of residue after heat treatment × mass of heat-treated residue × temperature) at a temperature of 800 ° C. in a nitrogen atmosphere because of control of volume resistivity, ease of production, and cost. 100) / (mass of organic compound before heat treatment)) is preferably an organic compound-derived fibrous carbon material of 20 mass% or more and 95 mass% or less. It is particularly important that the residual ratio is 20% by mass or more in that the production cost can be reduced. Moreover, being 95 mass% or less is important in the point which carbonizes an organic compound.

  Specifically, this fibrous carbon material is obtained by heat-treating the organic compound at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere. Examples of the non-oxidizing atmosphere include an atmosphere of an inert gas such as nitrogen.

  The mass of the organic compound residue is measured by thermal mass spectrometry (hereinafter referred to as TGA) in a nitrogen atmosphere. Measure at a heating rate of 10 ° C./min up to 800 ° C. and read the mass of the residue at 800 ° C. A sample once heat-treated in air at 100 ° C. for 60 minutes is used.

  When the organic compound used in the present invention is heat-treated at 800 ° C. in a nitrogen atmosphere among the organic materials, (mass of carbon after heat treatment × 100) / (mass of organic compound before heat treatment) is 20% by mass or more of carbon. An organic compound that can generate carbon is preferable, more preferably 30% by mass or more, more preferably 35% by mass or more, and most preferably an organic compound that generates 40% by mass or more of carbon. The greater the amount of carbon produced, the easier it is to control the volume resistivity of the fibrous carbon material.

  As the organic compound that can be used in the present invention, any organic compound can be used as long as the residual rate of 800 ° C. is satisfied. For example, in the liquid phase, pitch, coal tar, or coal can be used. -Mixtures of coke and pitch are used, and in the solid phase, cross-linked materials such as wood raw materials, furan resins, phenol resins, cellulose, polyacrylonitrile, rayon are used. Carbonaceous materials can be broadly divided into petroleum pitch and other starting materials, generally heat treated at a high temperature of 2000 ° C. or higher, so-called graphitizable carbon materials having a developed graphite structure, and phenol resins and furan resins. There is a so-called non-graphitizable carbon material having a turbulent structure by heat treatment at a relatively low temperature of 2000 ° C. or less using a thermosetting polymer as a starting material.

  In the present invention, any carbon material may be used as long as the object of the invention is not impaired. However, a non-graphitizable carbon material is preferably selected from the viewpoint of easy control of electric conductivity, and an organic compound that generates such a carbon material is organic. Polymer materials, particularly phenolic resins are preferred.

  In addition, by using an organic polymer material, especially a phenol resin, a porous fibrous carbon material can be easily obtained, and the surface area of the interface between the material constituting the elastic layer such as rubber and the fibrous carbon material is increased. As a result, the number of crosslinking points increases, and the strength of the elastic layer such as rubber containing the fibrous carbon material can be improved.

  The phenol resin suitably used in the present invention is, for example, alkylphenols, other substituted phenols, polyhydric phenols and aldehydes such as formaldehyde and paraformaldehyde as raw materials, in addition to phenol. Can be obtained by reacting under an acidic catalyst (novolak type) or an alkaline catalyst (resol type).

  In the present invention, it is preferable to obtain a fibrous carbon material through a carbonization process by the above-mentioned heat treatment after the organic compound is molded into a fibrous shape in advance. Moreover, carbonization may be promoted while stretching to form a fibrous material.

  However, the heat treatment temperature for carbonization is preferably 800 ° C. or higher, more preferably 1200 ° C. or higher. A temperature of 2000 ° C. or higher is preferable, but a temperature of 3000 ° C. or higher is not economically preferable. The heating rate up to this heat treatment temperature and the holding time of the heat treatment temperature are not particularly limited because they differ depending on the shape and composition of the carbon material to be treated, but the heating rate is 1 ° C./min or more and less than 50 ° C./min. Is preferably 1 minute or more and less than 24 hours. Moreover, you may perform processes, such as a grinding | pulverization and a classification, after heat processing.

  The elastic body layer of the charging roll of the present embodiment is composed of a fibrous conductive material such as a fibrous carbon material and rubber as basic components, but is crosslinked within a range where the object of the present invention can be achieved if necessary. Other components such as an agent, a surfactant, a mat material, a deterioration preventing agent, an antioxidant, and an ultraviolet absorber may be added. The rubber used is not particularly limited in the present invention. Any material may be used as long as it can be used for general rubber products, and the composition may be anything obtained by blending a plurality of rubbers. Moreover, the mixing method of the fibrous carbon material and rubber is not particularly limited.

  As described above, according to the charging member of the present invention, since the charge decay of the elastic layer of the charging member is fast, the adhesion of the toner and the external additive is suppressed, and the charging member is less likely to become dirty and a good image is obtained. Is obtained.

  In the above embodiment, the example of the charging roll is shown as the charging member. However, the present invention can be applied to charging members such as a blade type, a rod type, and a belt type in addition to the roll type.

  Further, in the above-described embodiment, an example in which the charging roll contacts the photosensitive member that is the charged body to charge the photosensitive body is shown, but the charged body for the charging member of the present invention is not limited to the photosensitive body. For example, the present invention can also be applied to a transfer member (for example, a transfer roll) that charges a transfer material that is an object to be charged.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by an Example.

<Method for producing fibrous carbon material>
After charging 1.2 kg of phenol, 0.6 kg of 50% formalin and 3.5 g of oxalic acid into a 3 liter flask and reacting for 4 hours at the reflux temperature, vacuum dehydration concentration was further performed under heating, and an uncured softening point of 110 ° C. 1 kg of novolak resin was obtained. 200 g of uncured novolak resin was heated and melted and stirred to obtain an uncured novolak resin. This uncured novolak resin was melt-spun at a speed of 260 m / min using a spinneret having 20 holes and a hole diameter of 0.2 mmφ to obtain uncured novolak resin fibers.

  This uncured novolak resin fiber is immersed in a cured aqueous solution mainly composed of formaldehyde and hydrochloric acid, heated to 95 ° C. at a rate of 0.5 ° C./min, and held for 8 hours to be cured novolak resin fiber (phenolic resin). Fiber). The obtained fiber was subjected to thermal mass spectrometry under a nitrogen atmosphere, and the amount of residue at 800 ° C. was determined to be 52% by mass.

The phenol resin fiber was cut to around 1 mm and then heat-treated in an electric furnace at 1000 ° C. for 30 minutes in a nitrogen atmosphere to obtain short carbon fibers. This carbon short fiber is pulverized by jet mill, carbon having a fiber length (corresponding to length A in the fiber axis direction) of 0.5 mm and a fiber diameter (corresponding to length B in the direction perpendicular to the fiber axis) of 0.07 mm. Short fibers were obtained. The volume resistivity of this short carbon fiber was 5 × 10 ⁴ Ω · cm.
Example 1
<Preparation of charging roll 1>
The charging roll 1 of the present invention was produced in the following manner.

{Invention rubber layer formulation A}
Epichlorohydrin rubber terpolymer 100 parts by weight carbon short fiber 7 parts by weight quaternary ammonium salt 2 parts by weight zinc oxide 5 parts by weight fatty acid 2 parts by weight The above materials were kneaded for 10 minutes in a closed mixer adjusted to 60 ° C. Thereafter, 5 parts by mass of a sebacic acid-based polyester plasticizer was added to 100 parts by mass of the epichlorohydrin rubber terpolymer, and the mixture was further kneaded for 20 minutes with a closed mixer cooled to 20 ° C. to prepare a raw material compound.

  To this compound, 100 parts by mass of the raw rubber epichlorohydrin rubber terpolymer is added 1 part by mass of sulfur as a vulcanizing agent, 1 part by mass of Noxeller DM as a vulcanization accelerator, and 0.5 parts by mass of Noxeller TS. The mixture was kneaded for 10 minutes in a two-roll machine cooled to 1 mm. The obtained compound was molded by an extrusion molding machine so as to form a roll around a stainless steel core, subjected to heat vulcanization molding, and then polished.

The resulting rubber layer had a volume resistivity of 10 ⁷ Ω · cm.

  A charge adjusting roll 1 was obtained by attaching a resistance adjusting layer to the roll obtained here.

That is, as a material for the resistance adjustment layer,
Acrylic polyol solution (active ingredient 70% by weight) 100 parts by weight isocyanate A (IPDI, active ingredient 60% by weight) 40 parts by weight isocyanate B (HDI, active ingredient 80% by weight) 30 parts by weight conductive tin oxide (made by Ishihara Sangyo) 90 parts by mass Negatively charged control resin (CCR1) 12 parts by mass Methyl isobutyl ketone (MIBK) solvent 340 parts by mass was stirred using a mixer to prepare a mixed solution. Subsequently, the mixed solution was subjected to a dispersion treatment using a circulation type bead mill disperser to prepare a dipping paint.

  The above IPDI means isophorone diisocyanate, and HDI means hexamethylene diisocyanate.

  The coating material for dipping is applied on the roll by a dipping method so that the film thickness becomes 10 μm, air-dried for 10 minutes, and then dried at 160 ° C. for 1 hour by a heating type dryer to obtain a charging roll 1. It was.

The obtained charging roll is attached to the electrophotographic image forming apparatus of FIG. 1, and the photosensitive member is charged under the following conditions in an environment of 23 ° C./53% RH, and 1000 predetermined images are continuously printed. Printed out.
Charging condition Photoconductor contact pressure; 50 g / cm,
DC voltage applied to the charging roll; -600 V, AC voltage; 2,000 Vp-p, frequency: 150 Hz
Image evaluation and evaluation of the toner and external additives attached on the charging roll after printing were performed.
<Dirt and image evaluation method>
(1. Dirt evaluation method)
The dirt was evaluated based on the adhesion of the toner to the surface of the antistatic roll and the adhesion of the external additive.

Toner adhesion: The toner adhering to the charging roll was removed with a tape (manufactured by 3M, Scotch Mending Tape), and the density of the adhering toner transferred to the tape was visually observed and evaluated.
○: The tape remains transparent and no toner is transferred.
Δ: A portion where the toner is transferred to the tape is partially recognized.
X: The toner is transferred to the entire surface of the tape.

External additive adhesion: The concentration of the external additive adhering to the charging roll was visually observed and evaluated.
○: The roll has a black appearance, or a part where the external additive is slightly visible is only partially recognized.
(Triangle | delta): The state in which the external additive was on the roll whole surface.
X: A state in which an external additive is placed on the entire roll surface.

  In this adhesion evaluation, in both toner adhesion and external additive adhesion, 性 is two, ◯ is a combination of ○ and △, ○ and × is a combination △, and there is no ◯ is × did.

(2. Image evaluation method)
○: Good image.
Δ: Image distortion caused by toner or external additive adhering to the charging roll was observed in a part of the image.
X: Image disturbance caused by toner or external additive adhering to the charging roll was observed in the entire image.
(Example 2)
In Example 1, a charging roll was produced and evaluated in the same manner as in Example 1 except that 20 parts by mass of the short carbon fiber was used. Further, the volume resistivity of the obtained rubber layer was 10 ⁶ Ω · cm.
(Example 3)
In Example 1, a charging roll was produced and evaluated in the same manner as in Example 1 except that 3 parts by mass of Ketjen Black EC600JD (Ketjen Black International Co., Ltd.) was used as the conductive material for the rubber layer.

Ketjen Black EC600JD had a volume resistivity of 10 ⁻² Ω · cm, and the resulting rubber layer had a volume resistivity of 10 ⁶ Ω · cm.
(Comparative Example 1)
A charging roll was produced and evaluated in the same manner as in Example 1 except that carbon black (trade name: Ketjen Black EC, manufactured by Lion Akzo Co., Ltd.) was used instead of the short carbon fiber in Example 1.

The ketjen black EC had a volume resistivity of 10 ⁻² Ω · cm, and the rubber layer obtained had a volume resistivity of 10 ⁷ Ω · cm.

  The evaluation results of Examples and Comparative Examples are summarized in Table 1.

  From the examples and comparative examples in Table 1, the charging roll of the present invention has good dirt and image evaluation in the durability test, and achieves the object of the present invention.

1 is a perspective view showing a main part of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser light source 2 Polygon mirror 3 f (theta) lens 4 Photosensitive drum 5 Charging roller 51 Shaft body (core metal)
6 Developing Device 7 Transfer Device 8 Transfer Material 9 Separation Electrode 10 Fixing Device 11 Cleaning Device 12 Pre-Charge Exposure (PCL)
13 Cleaning blade 14 Power supply

Claims (14)

An electrophotographic charging member having an elastic layer containing a fibrous conductive material. 2. The electrophotographic charging member according to claim 1, wherein the fibrous conductive material has a length B in a direction perpendicular to the fiber axis of 1 nm or more and less than 100 μm. The fibrous conductive material has a length A in the fiber axis direction of less than 1 cm, and an A / B that is a ratio of the length A in the fiber axis direction and the length B in the direction perpendicular to the fiber axis is The charging member for electrophotography according to claim 1, wherein the charging member is 2 or more. 4. The electrophotographic charging member according to claim 1, wherein a volume resistivity of the fibrous conductive material is 10 ³ Ω · cm or more and 10 ⁸ Ω · cm or less. 5. The charging member for electrophotography according to any one of claims 1 to 4, wherein the fibrous conductive material is a fibrous carbon material. The fibrous carbon material is a fibrous carbon material derived from an organic compound having a residual rate of 20% by mass to 95% by mass when the organic compound is heat-treated at a temperature of 800 ° C. in a nitrogen atmosphere. The charging member for electrophotography according to claim 5. The electrophotographic carbon material according to claim 6, wherein the fibrous carbon material is a fibrous carbon material obtained by heat-treating the organic compound at a temperature of 800 ° C or higher in a non-oxidizing atmosphere. Charging member. 8. The charging member for electrophotography according to claim 7, wherein the fibrous carbon material is a fibrous carbon material obtained by performing the heat treatment in a state where the organic compound is formed into a fiber shape. . The charging member for electrophotography according to any one of claims 6 to 8, wherein the organic compound is an organic polymer material. The charging member for electrophotography according to claim 9, wherein the organic polymer material is a phenol resin. The fibrous conductive material and a conductive material having a volume resistivity of less than 10 ³ Ω · cm are used in combination so that the mass fraction is fibrous carbon material / conductive material <1. The charging member for electrophotography according to any one of claims 4 to 10. 12. The electrophotographic charging member according to claim 1, wherein the electrophotographic charging member is an electrophotographic charging roll. An electrophotographic image forming apparatus using the electrophotographic charging member according to claim 1. The electrophotographic image forming apparatus according to claim 13, wherein the electrophotographic charging member is charged in contact with an object to be charged.

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