JP2001117324A - Processing cartridge and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device that the occurrence of unevenness in excessive electrifying potential is prevented, failure in electrification due to soiling of a conductive member does not occur and a good electrifying characteristic is maintained over a long period of time. SOLUTION: Relating to the processing cartridge and the electrophotographic device provided with the processing cartridge, an electrophotographic photoreceptor and the conductive member that is arranged in contact with the electrophotographic photoreceptor and voltage is applied are included, and the electrophotographic photoreceptor and the conductive part are supported integrally and is able to be freely attached to or detached from an electrophotographic device main body, the characteristics are; the electrophotographic photoreceptor is provided with a supporting body, a charge generating layer and a charge transporting layer in this order, the charge transporting layer has thickness of 12 to 49 μm, the conductive member is provided with a coated layer on a conductive supporting body and a time constant of current τ of the conductive member is <=0.1 second.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member and a conductive member used in a process cartridge and an electrophotographic apparatus, and more particularly, to an electrophotographic apparatus such as a printer, a facsimile, and a copying machine, and a removable electrophotographic apparatus. The present invention relates to a conductive member for electrically controlling an object to be contacted such as an electrophotographic photosensitive member, a charging member, a developer carrying member, a transfer member, a cleaning member, and a charge removing member used in a process cartridge.

[0002]

2. Description of the Related Art Conventionally, a charging process in an electrophotographic process is performed by applying a high voltage (DC voltage of 6 to 8 k) to a metal wire.
A corona charger that uniformly charges a surface of a photoreceptor, which is a charged body, to a predetermined polarity and potential by a corona shower generated by applying V) has been widely used. However, there are problems such as requiring a high-voltage power supply and generating a relatively large amount of ozone.

On the other hand, a contact charging system in which a voltage is applied while a charging member is in contact with a photosensitive member to charge the surface of the photosensitive member has been put to practical use. That is, a charging member as a charge supply member such as a roller type, a blade type, a brush type and a magnetic brush type is brought into contact with the photoreceptor, and a predetermined charging bias is applied to the contact charging member to bring the photoreceptor surface into a predetermined state. This is to uniformly charge to polarity and potential.

[0004] This charging system has the advantages of lowering the voltage of the power supply and generating less ozone. Among them, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferably used from the viewpoint of charging stability.

However, the charging uniformity is somewhat disadvantageous as compared with the corona charger.

In order to improve the charging uniformity, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Application Laid-Open No. 149669, an AC voltage component (AC voltage component) having a peak-to-peak voltage equal to or more than twice the charging start voltage (V _TH ) in a DC voltage corresponding to a desired surface potential Vd of a charged body. Is applied to the contact charging member (pulse voltage; voltage whose voltage value periodically changes with time). This is for the purpose of the potential leveling effect of the AC voltage, and the potential of the member to be charged is the potential Vd at the center of the peak of the AC voltage.
This is an excellent method as a contact charging method without being affected by disturbances such as the environment.

[0007]

However, in order to superimpose a high AC voltage that is a peak-to-peak voltage that is twice or more the discharge starting voltage (V _TH ) when a DC voltage is applied, an AC power supply is provided separately from the DC power supply. This necessitates an increase in the cost of the device itself. Furthermore, there is a problem that the durability of the charging roller and the photoreceptor is easily reduced by consuming a large amount of the alternating current.

Further, these problems can be solved by applying only a DC voltage to the charging roller to perform charging. However, applying only a DC voltage to the charging roller causes the following problems.

When only a DC voltage is applied to the conventional charging member, a non-uniform potential is generated on the surface of a member to be charged such as a photoreceptor, which is excessively charged to a desired charging potential or more (hereinafter referred to as excessive charging potential non-uniformity). ). In particular, in an electrophotographic process without pre-exposure, which is a step for erasing the potential on the photoconductor before primary charging, the potential is likely to be generated in a potential portion of a halftone image area. When the surface potential of the photoreceptor in the halftone potential portion is measured using a surface potentiometer, potential unevenness in which the potential difference is excessively charged by several tens of volts is observed at a position corresponding to a position after the second round of the photoreceptor. be able to.

When a halftone image is output by, for example, an electrophotographic apparatus using a reversal developing method using a conventional charging roller having such a problem, the above-described excessive charging potential unevenness is partially caused on the image. There is a problem in that the image appears as a halftone image surface with white spots or roughness and image quality is reduced. The occurrence of the excessive charging potential unevenness tends to appear particularly remarkably in a low-temperature and low-humidity environment.

As a method for obtaining uniform charging by applying only a DC voltage, Japanese Patent Laid-Open Publication No. Hei 5-341626 discloses a method in which light is applied to a small upstream gap formed between a charging member and a member to be charged. There is disclosed a technique of irradiating (nip exposure) to remove charges on the surface of a charged body and performing charging through a minute gap on the downstream side. According to this method, the surface of the member to be charged can be charged relatively uniformly, but it has not been sufficient.

Further, in an electrophotographic apparatus using a contact charging method, unevenness in image density and the like tend to occur due to poor charging due to contamination of the charging member (adhesion of the surface of the developer), causing a problem in durability. There is an urgent need to prevent the influence of poor charging due to dirt on the prints to enable printing of a plurality of sheets. In particular, in the case of a DC charging system in which only a DC voltage is applied to the charging member, the influence of contamination on the charging member is reduced by AC.
As compared with the charging system, the image tends to appear as an image defect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide an image forming apparatus in which excessive charging potential unevenness is obtained even when only a DC voltage is applied to a conductive member to perform charging of a member to be charged. An object of the present invention is to provide a process cartridge and an electrophotographic apparatus which are less likely to occur.

Another object of the present invention is to provide a process cartridge and an electrophotographic apparatus capable of maintaining good charging characteristics for a long period of time without causing poor charging due to contamination of a conductive member. It is in.

[0015]

That is, the present invention comprises an electrophotographic photosensitive member and a conductive member which is disposed in contact with the electrophotographic photosensitive member and to which a voltage is applied, and the electrophotographic photosensitive member and the conductive member are provided. Is a process cartridge that is integrally supported and detachable from an electrophotographic apparatus main body, wherein the electrophotographic photosensitive member has a support, a charge generation layer, and a charge transport layer in this order, and the charge transport layer has a thickness of 12 to 40 μm. A process cartridge having a thickness, wherein the conductive member has a coating layer on a conductive support, and a time constant τ of current of the conductive member is 0.1 second or less.

According to the present invention, there is provided an electrophotographic apparatus having an electrophotographic photosensitive member and a conductive member which is disposed in contact with the electrophotographic photosensitive member and to which a voltage is applied, wherein the electrophotographic photosensitive member includes a support, a charge generation layer And a charge transport layer in this order, the charge transport layer has a thickness of 12 to 40 μm, the conductive member has a coating layer on a conductive support, and a time constant τ of current of the conductive member is Is 0.1 second or less.

[0017]

FIG. 1 shows an electrophotographic apparatus using the conductive member of the present invention as a contact charging member (charging roller). When a voltage is applied to the charging member, a discharge occurs in a minute space between the charging member and the photoconductor, and the surface of the photoconductor is charged.

According to our investigation, it has been found that the current flowing from the charging member has an attenuation curve as shown in FIG.

In order to achieve more uniform charging, it is considered most preferable that the photosensitive member surface is charged by a discharge current in a steady state settled at a constant value as shown in FIG.

Compared to a stable steady state, a larger amount of current is flowing from the charging member (I ₀ ) at the initial stage when a voltage is applied. That is, it is considered that the charging member is in a state of low resistance at the initial stage when the current starts flowing. In other words, the initial stage when the current starts to flow is as if the charging process is performed with a conductor having low resistance such as metal. According to our previous studies, it has been found that a uniform charged surface cannot be obtained even when the photosensitive member is charged using a metal.

That is, when a certain point on the surface of the charging member reaches the discharge region with the photosensitive member, the discharging current of the charging member instantaneously reaches a steady state (I ₁ ). We thought it was ideal. Therefore, we use the time constant τ as a measure of the decay curve of the discharge current of the charging member.
We paid attention to.

The relationship between the time constant of the charging member and the time required to pass through the discharge region is disclosed in Japanese Patent Application Laid-Open No. 10-26866, but the invention is to be solved in Japanese Patent Application Laid-Open No. 10-26866. The phenomenon of "local charging unevenness" mentioned as a problem is different from the phenomenon of "excessive charging potential unevenness" to be solved by the present invention. For example, Japanese Patent Application Laid-Open No. H10-26866 describes that a phenomenon called “local charging unevenness” is likely to occur when the surface moving speed of the charging member is increased. However, the problem to be solved by the present invention is “ Excessive charging potential unevenness "
As a result of our repeated studies, JP-A-10-26866
Contrary to the publication, the slower the surface moving speed of the charging member, the more likely it is for the charging member to occur.

In Japanese Patent Application Laid-Open No. Hei 10-26866, the time constant τ is obtained by calculation from the product of the capacitance C and the resistance value R. When the time constant τ is calculated by the method described in Japanese Patent Application Laid-Open No. 10-26866, it is found that the conductive member of the present invention and the other conductive members have the same value of the time constant τ. Was. However, when both conductive members were evaluated and evaluated for “excessive charge potential unevenness”, the conductive member of the present invention did not generate excess charge potential unevenness, but other conductive members having the same time constant In, excessive charging potential unevenness occurred.

As a result of our intensive studies, a device as shown in FIG. 5 is used to apply a DC voltage to the conductive member, read the current value of the conductive member into a recorder, and obtain the waveform data of the obtained current value. In addition, when the time constant τ is calculated by an approximate expression, according to the time constant calculation method described in JP-A-10-26866, even if the conductive members have the same time constant, It was found that the time constant τ was shown, and it was possible to distinguish between the two. In the figure, 2 is a conductive member, 11 is a cylindrical electrode (metal roller), 1
2 denotes a fixed resistor, 13 denotes a recorder, and S3 denotes a power supply.

[0025] Particularly, in the apparatus as shown in FIG. 5, when the DC voltage applied to the conductive member and the V _0, the value of the DC voltage V _0, the discharge start voltage when the conductive member charges the body to be charged It has been found that the difference in the time constant τ between the conductive member of the present invention and the conductive member other than that can be clearly distinguished by setting the voltage higher than V _TH .

Further, since the conductive member is in contact with the member to be charged, the resistance of the conductive member at the time of actual charging includes an electrical contact resistance, and the contact area between the conductive member and the member to be charged, and It also depends on the degree of deformation of the conductive member. Therefore, the current value of the conductive member reflects the actual charging state when the current value measured with the contact state between the conductive member and the electrode being the same as that of the member to be charged. Therefore, in the present invention, the current value of the conductive member close to the actual charging time is determined by the current measuring method as shown in FIG.

Further, since the unevenness of the overcharging potential is remarkable in a low-temperature and low-humidity environment, the current value of the conductive member is measured in a low-temperature and low-humidity environment (for example, at a temperature of 15 ° C. and a humidity of 10%). It is preferable to determine the time constant from the value.

It has been found that a conductive member having a current time constant τ calculated by the measuring method of the present invention of 0.1 or less is very effective in preventing the occurrence of “excessive charging potential unevenness”. Was.

In the present invention, if the coefficient of static friction on the surface of the conductive member is 1.0 or less, dirt hardly adheres to the surface of the conductive member, and poor charging due to dirt on the conductive member hardly occurs. Acting synergistically with the configuration of the conductive member of the present invention, a very excellent image can be obtained. In particular,
As shown in FIG. 1, a so-called developing and cleaning (cleanerless) system is adopted, in which a developing unit collects toner remaining on a photoreceptor after transfer without an independent cleaning unit, and prints a plurality of sheets of an electrophotographic apparatus. It is effective to enable

Further, in the present invention, the surface roughness of the conductive member is defined as a ten-point average surface roughness R according to JIS B0601.
By setting z to 10 μm or less, it is possible to prevent the occurrence of charging unevenness due to irregularities on the surface of the conductive member, act synergistically with the configuration of the conductive member of the present invention, and enable extremely uniform charging. I do.

Next, the schematic structure of the electrophotographic apparatus of the present invention will be described.

(1) Example of Electrophotographic Apparatus FIG. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus provided with the process cartridge of the present invention. The electrophotographic apparatus of this example is
It is a reversal developing system and a developing and cleaning system (cleanerless) using a transfer type electrophotography.

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

Reference numeral 2 denotes a charging roller (conductive member of the present invention) as a charging means for the photoconductor, which is brought into contact with the photoconductor 1 with a predetermined pressing force. And rotate at a constant speed. A predetermined DC voltage (in this case, -1) is supplied from the charging bias applying power source S1 to the charging roller 2.
(At 300 V), the surface of the photoreceptor 1 is uniformly charged to a predetermined polarity potential (dark portion potential -700 V) by a contact charging method or a DC charging method.

Reference numeral 3 denotes an exposure unit, for example, a laser beam scanner. Exposure L corresponding to the target image information is performed on the uniformly charged surface of the rotating photoreceptor 1 by the exposing means 3 so that the potential of the exposed light portion on the charged surface of the photoreceptor (bright portion potential -120 V). Is selectively reduced (decay)
As a result, an electrostatic latent image is formed.

Reference numeral 4 denotes a reversal developing means, which selectively applies toner (negative toner) charged to the exposed portion of the electrostatic latent image on the photoreceptor surface to the same polarity as the photoreceptor (development bias -350 V). To visualize the electrostatic latent image as a toner image. In the figure, 4a is a developing roller, 4b is a toner supply roller, and 4c is a toner layer thickness regulating member.

Reference numeral 5 denotes a transfer roller as transfer means.
The transfer nip portion is formed by contacting the photoconductor 1 with a predetermined pressing force, and rotates at a peripheral speed substantially equal to the rotation peripheral speed of the photoconductor in the forward direction with the rotation of the photoconductor. Further, a transfer voltage having a polarity opposite to the charge polarity of the toner is applied from the transfer bias application power source S2. The transfer material P is fed to the transfer nip from a feed mechanism (not shown) at a predetermined control timing.
The back surface of the sheet transfer material P is charged by the transfer roller 5 to which the transfer voltage is applied to a polarity opposite to the charge polarity of the toner, so that the toner image on the photoconductor 1 surface side in the transfer nip portion is transferred to the transfer material P. It is electrostatically transferred to the front side.

The transfer material on which the toner image has been transferred at the transfer nip is separated from the surface of the rotating photoreceptor, introduced into a toner image fixing means (not shown), subjected to a toner image fixing process, and output as an image-formed product. You. In the case of the double-sided image forming mode or the multiple image forming mode, this image-formed product is introduced into a recirculation transport mechanism (not shown) and is again introduced into the transfer nip portion.

Residues on the photoreceptor such as transfer residual toner are as follows:
The charging roller 2 charges the photosensitive member to the same polarity as that of the photosensitive member.

Then, the transfer residual toner reaches the developing means 4 through the exposure section, is electrically collected in the developing device by the back contrast, and achieves the development and cleaning (cleanerless).

In this embodiment, the electrophotographic photosensitive member 1, the charging roller 2, and the developing means 4 are integrally supported, and the process cartridge 6 is detachable from the main body of the electrophotographic apparatus. On this occasion,
The developing means may be separate.

(2) Electrophotographic Photoreceptor The electrophotographic photoreceptor 1 as an image carrier used in the process cartridge and the electrophotographic apparatus of the present invention is configured as follows (FIG. 6).

The photosensitive layer 1b is provided on a conductive support 1a.

As the support 1a, a cylinder such as metal such as aluminum and stainless steel, paper, and plastic, or a cylindrical cylinder, sheet or film is used. In addition, these cylindrical cylinders, sheets or films may be, if necessary, a conductive polymer layer or tin oxide,
It may have a resin layer containing conductive particles such as titanium oxide and silver particles.

As shown in FIG. 6, the photosensitive layer 1b is constituted by sequentially laminating at least a charge generation layer 11b and a charge transport layer 12b on a support 1a. At this time, as shown in FIG. 7, the support 1a and the photosensitive layer 1b (the charge generation layer 11b)
In between, an undercoat layer 1c having a barrier function and an adhesive function
Can be provided.

The undercoat layer is used for improving the adhesiveness of the photosensitive layer, improving the coating property, protecting the support, covering defects on the support, improving the charge injection property from the support, and protecting the photosensitive layer against electrical breakdown. Formed for Its thickness is preferably 0.2 to 2 μm.

As the charge generating substance, pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthantrone pigments, dibenzopyrene quinone pigments, pyratron pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanines, quinocyanines and the like can be used. Can be.

As the charge transport material, hydrazone compounds, pyrazoline compounds, styryl compounds, oxazole compounds, thiazole compounds, triarylmethane compounds, polyarylalkane compounds and the like can be used.

The charge generation layer 11b comprises a homogenizer, an ultrasonic wave, a ball mill, a vibrating ball mill, a sand mill, an attritor, a roll mill, and the like. It is well dispersed by a method such as a high-pressure collision disperser, coated and dried. Its thickness is 5 μm or less, especially 0.01 to 1
The range of μm is preferred.

The charge transport layer 12b is generally formed by dissolving the above-described charge transport material and binder resin in a solvent and applying the resulting solution. The mixing ratio of the charge transport material and the binder resin is preferably from 2: 1 to 1: 2 on a mass basis. Examples of the solvent include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, and chlorinated hydrocarbons such as chlorobenzene, chloroform and carbon tetrachloride. Used. When applying this solution, for example, a coating method such as a dip coating method, a spray coating method and a spin coating method can be used, and drying is preferably performed at 10 ° C to 200 ° C, more preferably at 20 ° C to 150 ° C. The drying can be carried out at a temperature in the range, preferably from 5 minutes to 5 hours, more preferably from 10 minutes to 2 hours under blow drying or still drying.

The thickness of the formed charge transport layer is 12 to 40.
μm, preferably 12 to 23 μm, particularly preferably 12 to 18 μm. In an electrophotographic photoreceptor having a charge transport layer thickness of more than 40 μm, when contact charging is performed by applying only a DC voltage, in a low-temperature and low-humidity environment, a minute minute charge which is considered to be caused by excessive charge potential unevenness on an image. White spots and rough edges are likely to occur. On the other hand, when the thickness is less than 12 μm, there is a tendency that potential fluctuation due to scraping is large. For example, for the same amount of scraping, the photoconductor having a thin charge transport layer has a larger change in capacitance and a larger potential fluctuation than that of a photoconductor having a thick charge transport layer. In particular, in the case of the DC charging method, the discharge starting voltage _VTH changes due to scraping, which is not preferable in terms of charging potential stability and durability.

The thickness of the layer can be measured by observing the cross section of the electrophotographic photosensitive member with a transmission electron microscope.

Examples of the binder resin used to form the charge transport layer include acrylic resins, styrene resins, polyesters, polycarbonate resins, polyarylate resins,
Preferred are resins selected from polysulfone resins, polyphenylene oxide resins, epoxy resins, polyurethane resins, alkyd resins, unsaturated resins, and the like. Particularly preferred resins include polymethyl methacrylate, polystyrene,
Examples thereof include a styrene-acrylonitrile copolymer, a polycarbonate resin, a diallyl phthalate resin, and a polyarylate resin.

The charge generation layer or the charge transport layer may contain various additives such as an antioxidant, an ultraviolet absorber and a lubricant.

As a method for roughening the surface of the electrophotographic photosensitive member according to the present invention, in addition to a polishing method using a polishing agent, a mechanical polishing method such as a sand blast method, or the like, a metal oxide or a metal oxide is contained in the surface layer of the photosensitive member. A method of dispersing electrically inactive particles such as resin powder or the like can be used.

(3) Charging Roller The time constant τ in the present invention is a material constituting the conductive member,
Although it depends on various factors such as the ratio of the materials used and the mixing state of the materials used, in the present invention, it is important that the time constant is 0.1 or less, and the means for realizing the time constant is not particularly limited. There is no.

In the present invention, the time constant is preferably not more than 0.05 seconds, particularly preferably not less than 0.00001 seconds. If the time constant exceeds 0.1 seconds,
The remarkable effect of the present invention cannot be obtained, and 0.000
If the duration is less than 01 second, when a pinhole is present in the electrophotographic photosensitive member, the potential around the pinhole as well as the location of the pinhole also drops, and an image in which the periphery of the pinhole is blurred particularly in a Harton image. easy.

For example, the charging member is in the form of a roller as shown in FIG. 2, and has a conductive support 2a, an elastic layer 2b integrally formed on its outer periphery as a coating layer, and an outer periphery of the elastic layer. The surface layer 2c is formed.

FIG. 3 shows another structure of the charging member of the present invention. As shown in FIG. 3, the charging member may be a three-layer structure including an elastic layer 2b, a resistance layer 2d and a surface layer 2c, or a second resistance layer 2e provided between the resistance layer 2d and the surface layer 2c. Alternatively, a configuration in which four or more layers are formed on the conductive support 2a may be employed.

The conductive support 2a used in the present invention comprises:
Round bars of metal materials such as iron, copper, stainless steel, aluminum and nickel can be used. Further, plating may be applied to these metal surfaces for the purpose of imparting rust prevention and scratch resistance, but it is necessary that the conductivity is not impaired.

In the charging roller 2, the elastic layer 2b has appropriate conductivity and elasticity for supplying power to the photosensitive member 1 as a member to be charged and for ensuring good uniform adhesion of the charging roller 2 to the photosensitive member 1. I have. Also, the charging roller 2
It is also preferable to form the elastic layer 2b into a shape having the largest thickness at the center and becoming thinner toward both ends by polishing, that is, a so-called crown shape, in order to ensure uniform adhesion between the photosensitive member 1 and the photosensitive member 1. The charging roller 2 generally used is a support 2
Since a predetermined pressing force is applied to both ends of the photosensitive member 1 and the photosensitive member 1 is in contact with the photosensitive member 1, the pressing force at the center is small, and the pressing force at both ends is large. If it is not enough, there is no problem, but if it is not enough, density unevenness may occur in the images corresponding to the center and both ends. The crown shape is formed to prevent this.

The conductivity of the elastic layer 2b is such that a conductive agent having an electron conducting mechanism such as carbon black, graphite, or a conductive metal oxide and an ion conducting mechanism such as an alkali metal salt or a quaternary ammonium salt are contained in an elastic material such as rubber. It is preferable to adjust to less than 10 ¹⁰ Ωcm by appropriately adding a conductive agent having As a specific elastic material of the elastic layer 2b, for example, natural rubber or ethylene propylene rubber (EPD)
M), styrene butadiene rubber (SBR), silicone rubber, urethane rubber, epichlorohydrin rubber, isoprene rubber (IR), butadiene rubber (BR), nitrile butadiene rubber (NBR) and chloroprene rubber (C
Synthetic rubbers such as R), polyamide resins, polyurethane resins and silicone resins. In order to achieve the electrical characteristics of the present invention, it is particularly preferable to use a medium resistance polar rubber (e.g., epichlorohydrin rubber, NBR, CR and urethane rubber) or a polyurethane resin as the elastic material. These polar rubbers and polyurethane resins are considered to have a small amount of conductivity due to moisture or impurities in the rubber or resin serving as carriers, and it is considered that their conductive mechanism is ion conduction. However, an elastic layer is formed without adding any conductive agent to these polar rubbers or polyurethane resins, and the obtained charging member may have a resistance value of 10 ¹⁰ Ωcm or more in a low-temperature and low-humidity environment. Therefore, a high voltage must be applied to the charging member.

Therefore, in a low-temperature and low-humidity environment, the resistance value of the charging member becomes less than 10 ¹⁰ Ωcm, and the time constant τ
It is preferable that the above-mentioned conductive agent having an electronic conductive mechanism or the conductive agent having an ionic conductive mechanism is appropriately added and adjusted so that the time is 0.1 second or less. As a result of our intensive studies, it has been found that the time constant of the current of the charging member tends to be smaller when the resistance is adjusted by adding a conductive agent having an ionic conduction mechanism. However, a conductive agent having an ionic conduction mechanism has a small effect of lowering the resistance value, and particularly has a small effect in a low-temperature and low-humidity environment. Therefore, the resistance may be adjusted by adding a conductive agent having an electronic conductive mechanism in addition to the addition of a conductive agent having an ionic conductive mechanism.

As a conductive agent having an electron conductive mechanism, it has been preferred that an elastic layer to which a deformed layered compound or whisker, for example, graphite, is added is used.

A foam formed by foaming these elastic materials may be used for the elastic layer 2b.

Since the resistance layer 2d shown in FIG. 3 is formed at a position in contact with the elastic layer, it is provided for the purpose of preventing bleeding out of the surface of the charging member such as softening oil or plasticizer contained in the elastic layer. Or to adjust the electric resistance of the entire charging member.

Examples of the material constituting the resistance layer used in the present invention include epichlorohydrin rubber, NBR, polyolefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, polystyrene-based thermoplastic elastomer, fluororubber-based thermoplastic elastomer, and polyester-based thermoplastic elastomer. Examples thereof include thermoplastic elastomers, polyamide thermoplastic elastomers, polybutadiene thermoplastic elastomers, ethylene vinyl acetate thermoplastic elastomers, polyvinyl chloride thermoplastic elastomers, and chlorinated polyethylene thermoplastic elastomers. These materials may be used alone or as a mixture of two or more kinds, and may be a copolymer. The resistance layer 2d used in the present invention needs to have conductivity or semi-conductivity. Conductivity,
In order to develop semiconductivity, a conductive agent having various electron conductive mechanisms (conductive carbon, graphite, conductive metal oxide, copper, aluminum, nickel, iron powder, etc.) or a conductive agent having an ion conductive mechanism ( Alkali metal salts and ammonium salts) can be used as appropriate. In this case, in order to obtain a desired electric resistance, the above-mentioned various conductive agents are added in two.
More than one species may be used in combination. However, in consideration of environmental fluctuations and contamination of the photoreceptor, a conductive agent having an electronic conductive mechanism is preferable.

The resistance value of the resistance layer is 10 ⁴ to 10 ¹² Ωcm
In order to make the time constant τ 0.1 seconds or less, the resistance is preferably 10 ⁻² to 10 ⁵ times the resistance of the elastic layer.

The thickness is preferably 5 to 1000 μm.

As described above, in the present invention,
It is preferable that the static friction coefficient of the surface of the conductive member is 1.0 or less. In order to achieve this characteristic, it is preferable to select a binder resin having a static friction coefficient of 0.50 or less.

Hereinafter, the static friction coefficient of the surface of the conductive member is represented by μs.
And the coefficient of static friction of the binder resin in the surface layer is μs _B.

In the present invention, the measurement of the static friction coefficient μs _B of the binder resin in the selection of the material of the surface layer is carried out by forming the binder resin as a coating film on an aluminum sheet, obtaining a sample sheet, and measuring the static friction coefficient with a HEIDON. It was measured using Tribogear Muse TYPE: 941 (manufactured by Shinto Kagaku Co., Ltd.), and was set as the static friction coefficient μs _B of the binder resin on the conductive member surface layer.

A material having a static friction coefficient μs _B of 0.50 or less obtained by this measuring method is mixed with a conductive agent and other additives to form a surface layer of a conductive member. Further, the material of the conductive member is designed so that the surface has a static friction coefficient μs of 1.0 or less.

FIG. 8 shows an outline of the measurement of the static friction coefficient μs of the surface of the conductive member according to the present invention. This measurement method is a method suitable for the case where the object to be measured is in the form of a roller, and is a method according to the Euler belt system. According to this method, the object comes into contact with the conductive member as the object at a predetermined angle (θ). One end of the belt (thickness: 20 μm, width: 30 mm, length: 180 mm) is connected to the measurement unit (load meter), and the other end is connected to the weight W. When the conductive member is rotated in a predetermined direction and speed in this state, the force measured by the measuring unit is F (g), and the weight of the weight is W (g), the friction coefficient (μ) is as follows. It is calculated by the following equation.

Μ = (1 / θ) ln (F / W) FIG. 9 shows an example of a chart obtained by this measuring method. Here, it is understood that the value immediately after rotating the conductive member is the force required to start rotation, and the value after that is the force required to continue rotation, so that the rotation start point (ie, The force at time t = 0 seconds) can be referred to as static friction force, and the force at any time 0 <t (seconds) ≦ 60 can be referred to as dynamic friction force at any time.

Therefore, the coefficient of static friction: μs = (1 / θ) l
n (F _{<t = 0>} / W).

In this measurement method, the surface of the belt (the surface that comes into contact with the conductive member) is contacted with a predetermined material (for example, the outermost layer of the photoreceptor or a developer coated with an appropriate means, or a standard material such as stainless steel). By doing so, the coefficient of friction for various substances can be determined. That is,
It is more preferable to match the material of the contact surface, the rotation speed, the load, etc. with the process conditions of the actual machine.However, the friction coefficient between the conductive member and the photoconductor and the friction coefficient between the conductive member and stainless steel are measured and compared. As a result, it was found that the friction coefficient for stainless steel may be used. That is, the coefficient of friction between the conductive member and the photosensitive member = K × the coefficient of friction between the conductive member and stainless steel. Here, K is a numerical value determined by the material and state of the photoreceptor surface, and is a substantially constant value if the photoreceptor material and surface state are the same, but changes if they are slightly different.

Therefore, it is desirable that the material types, their compounding ratios, production conditions, surface properties, and the like be matched as much as possible to the actual system. However, this requires a great deal of complexity and, as described above, the conductive member. The coefficient of friction between the conductive member and the stainless steel has a correlation with the coefficient of friction between the conductive member and the stainless steel. Therefore, in the present invention, for the sake of simplicity, the friction coefficient is set to the value of the stainless steel (ten-point average roughness Rz of the surface is 5 μm). Hereinafter, the rotation speed was measured at 100 rpm and the load was measured at 50 g.

As a result of our intensive studies, when the surface of the conductive member has the above physical properties (μs ≦ 1.0),
Since toner hardly adheres to the surface of the conductive member, uniform charging can be performed even when the total number of printed sheets increases, and fogging on an image does not occur. It was also found that even in a low-temperature and low-humidity environment where image fogging easily occurs due to toner adhesion, image fogging does not occur even when the total number of printed sheets increases. If the coefficient of static friction μs exceeds 1.0, the releasability of the surface of the conductive member becomes small, so that the transfer residual toner tends to adhere, which may cause deterioration of image quality. In particular, in a low-temperature and low-humidity environment, it tends to cause deterioration of image quality. Therefore, in addition to the constitution of the present invention, the fact that the coefficient of static friction μs is 1.0 or less is particularly effective in an image forming apparatus employing a developing and cleaning system (cleanerless system).

The surface layer 2c constitutes the surface of the conductive member, and must not be made of a material composition that comes into contact with the photoreceptor to be charged and contaminates the photoreceptor.

Surface layer 2 for exhibiting the characteristics of the present invention
Examples of the binder resin material of c include fluorine resin, polyamide resin, acrylic resin, polyurethane resin, silicone resin, butyral resin, styrene-ethylene / butylene-
An olefin copolymer (SEBC) and an olefin-ethylene-butylene-olefin copolymer (CEBC) are exemplified.

For the purpose of reducing the coefficient of static friction to these binder resins, a solid lubricant such as graphite, mica, molybdenum disulfide and fluororesin powder, or a fluorosurfactant, wax and silicone oil are added. Is also good.

In consideration of environmental fluctuations and contamination of the photoreceptor, a conductive agent having an electronic conductive mechanism (conductive carbon, graphite, conductive tin oxide, conductive titanium oxide,
It is preferable to appropriately use copper, aluminum, nickel, iron powder and the like). In this case, in order to obtain a desired electric resistance, two or more of the above-mentioned various conductive agents may be used in combination.

The resistance value of the surface layer is 10 ⁴ to 10 ¹⁵ Ωcm.
In order to make the time constant τ 0.1 seconds or less, the resistance is preferably 10 ⁻² to 10 ⁹ times the resistance of the elastic layer.

The thickness is 1 to 500 μm, especially 1 to 500 μm.
It is preferably 50 μm.

As described above, the ten-point average surface roughness Rz of the conductive member of the present invention is preferably 10 μm or less. When the conductive member of the present invention is used, if the surface of the conductive member is rough, uneven charging on the surface may cause slight uneven charging, resulting in image failure.
Alternatively, the photoconductor surface may be eroded (e.g., scraped). Therefore, the surface of the conductive member is preferably smoother, and the ten-point average surface roughness Rz is preferably 10 μm or less, more preferably 4 μm or less.

(4) Developer (Toner) The toner used in the present invention is not particularly limited, and a known toner can be used. In order to reduce the amount of toner attached to the charging roller, it is preferable to use spherical toner particles having good transfer efficiency.

In an electrophotographic apparatus employing a developing and cleaning system, it is particularly preferable to use spherical toner particles having good transfer efficiency. As the spherical toner particles, for example, toner particles produced by a polymerization method are preferably used.

[0089]

EXAMPLES (Example 1) <Preparation of conductive member> A charging roller as a conductive member of the present invention was prepared in the following manner.

Epichlorohydrin rubber (ternary copolymer) 100 parts Quaternary ammonium salt 2 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acids 2 parts
After kneading for 0 minutes, add 100 parts of epichlorohydrin rubber
On the other hand, 15 parts of an ether ester plasticizer was added,
Kneaded for another 20 minutes with a closed mixer cooled to
Adjust the raw material compound. Raw materials for this compound
A vulcanizing agent is used for 100 parts of rubber epichlorohydrin rubber.
1 part of sulfur, Noxeller DM as vulcanization accelerator
Add 1 part, 0.5 part of Noxeller TS and cool to 20 ° C
The mixture is kneaded for 10 minutes using the two-roll mill. The obtained ko
The compound is φ6 (mm, the same applies hereinafter) stainless steel core
Extrusion molding machine to form a roller around gold
Then, after heat vulcanization molding, it is polished to an outer diameter of φ12.
This was processed to form an elastic layer. The resistance of the elastic layer is 4 × 10 ⁶
Ωcm.

A surface layer as shown below was formed on the elastic layer by coating.

As the material of the surface layer 2c, a fluororesin copolymer obtained by copolymerizing fluoroolefin (tetrafluoride type) hydroxyalkyl vinyl ether carboxylate was used, and 100 parts of the solution (solid content: 50% by mass) was used. %) With a coating obtained by adding 5 parts of isocyanate (HDI) and 45 parts of conductive tin oxide by a dip coating method to form a surface layer having a thickness of 10 μm to form a roller-shaped charging member. Obtained. The resistance of the surface layer was 3 × 10 ¹⁴ Ωcm.

<Preparation of Electrophotographic Photoreceptor> An aluminum cylinder having an outer diameter of φ30, an inner diameter of 28.5, and a length of 260 mm was used as a conductive support. A 5% methanol solution of polyamide (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) was applied thereon by a dip coating method, and the thickness was 0.40 μm.
m was formed.

Next, 10 parts of a disazo pigment having the following structural formula

[0095]

Embedded image And polyvinyl butyral (trade name ESLEC BLS,
10 parts of Sekisui Chemical Co., Ltd.) and cyclohexanone 1
00 parts are 2 with a sand mill using 1φ glass beads.
Dispersed for 0 hours. To this dispersion was added methyl ethyl ketone 10
0 parts, and applied on the undercoat layer to obtain a thickness of 0.20 μm.
Was formed.

Next, 10 parts of a triphenylamine compound having the following structural formula

[0097]

Embedded image 10 parts of a bisphenol Z-type polycarbonate (viscosity average molecular weight 23,000) having the following structural formula was dissolved in 100 parts of monochlorobenzene.

[0098]

Embedded image This solution was applied on the charge generation layer and dried with hot air at 100 ° C. for 1 hour to form a charge transport layer having a thickness of 25 μm. Thus, an electrophotographic photosensitive member of Example 1 was prepared.

"Static friction coefficient μ of surface layer material of charging roller"
the s same binder resin as that forming the measurement "surface layer of the _B and paint was coated on an aluminum sheet using the clear coating material, was used as a sample sheet of static friction coefficient (.mu.s _B) for measurement.

The static friction coefficient of this sample sheet was measured using a static friction coefficient measuring device: HEIDON Tribogear Muse TYPE: 941 (manufactured by Shinto Kagaku Co., Ltd.). The coefficient of static friction μs _B was an average of values measured at five arbitrary points on the sample sheet. The coefficient of static friction of the binder resin of the surface layer in this example was 0.12.

[Measurement of Static Friction Coefficient μs on Charging Roller Surface] As described above, the static friction coefficient μs was measured using a measuring device as shown in FIG. 0.27.

"Measurement of Charging Roller Surface Roughness" The ten-point average surface roughness Rz of the charging roller surface was 2.9 μm.

"Measurement of current of charging roller, calculation of time constant"
The current of the charging member (charging roller) was measured in an environment as shown in FIG. 5 at a temperature of 15 ° C. and a humidity of 10%.
This apparatus is similar to the electrophotographic apparatus shown in FIG. 1 except that the pressing force of the charging roller against the cylindrical electrode is the same as that of the electrophotographic apparatus shown in FIG. In the same way as above, the DC voltage (−
1000 V) was applied, the current value flowing at that time was read by a recorder, and the waveform data was represented by the following approximate expression I = I ₀ exp (−t / τ), and the time constant τ of the current of the charging roller was obtained. As a result, the time constant of the charging roller of this embodiment was τ = 0.021 [sec]. Therefore, τ in the first embodiment is τ ≦ 0.1 [se
c].

"Evaluation of Image When Only DC Voltage is Applied to Charging Roller" The charging roller obtained above was attached to the electrophotographic apparatus shown in FIG.
5%), environment 2 (temperature 32.5 ° C., humidity 80%), and environment 3 (temperature 15 ° C., humidity 10%). Image evaluation was performed visually for the occurrence of partial white spots and roughness. Table 1 shows the results. However, the dark potential V _D of the photosensitive member has output an image by changing the applied voltage so that the vicinity of -700V in each environment.

AA in the table indicates that the obtained image is very good.
A indicates that the image is good, B indicates that the density unevenness and roughness are slightly present in the halftone image, and C indicates that the halftone image has many partial white spots.

Incidentally, as the toner, spherical toner particles (particle diameter 8 μm) prepared by a suspension polymerization method were used.

"Evaluation of Image Fogging Due to Adhesion of Toner on Charging Roller" The charging roller obtained above was attached to the electrophotographic apparatus shown in FIG.
%), Environment 2 (temperature 32.5 ° C, humidity 80%), environment 3
In each environment (temperature: 15 ° C., humidity: 10%), an image endurance test was performed on a plurality of sheets. By visually observing the obtained image, the toner was attached to the charging roller, and the occurrence of fog on the printing paper due to the toner was evaluated. Table 2 shows the results.

AA in the table indicates that the obtained image is very good.
A indicates good, B indicates that the halftone image has uneven density in the charging roller cycle, and C indicates that fogging in the charging roller cycle is observed.

As a result, a good image was obtained from the beginning in all environments, and an image which was almost the same as the initial image was obtained even after 10,000 images were output.

The toner used was spherical toner particles (particle diameter: 8 μm) prepared by a suspension polymerization method.

(Example 2) A charging roller and an electrophotographic photosensitive member were prepared in the same manner as in Example 1, except that the charging roller as a charging member had the following structure.

NBR 100 parts Lithium salt 1.5 parts Ester plasticizer 25 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acid 2 parts

The above-mentioned materials are kneaded for 10 minutes by a closed mixer adjusted to 60 ° C., and then further kneaded for 20 minutes by a closed mixer cooled to 20 ° C. to prepare a raw material compound. NBR 10 of raw rubber is added to this compound.
One part of sulfur as a vulcanizing agent and 3 parts of Noxeller TS as a vulcanization accelerator are added to 0 parts, and the mixture is kneaded for 10 minutes by a two-roll machine cooled to 20 ° C. The obtained compound was molded by an extruder so as to form a roller around a φ6 stainless steel cored bar, heated and vulcanized, and then polished to an outer diameter of φ12 to form an elastic layer. .
The resistance of the elastic layer was 7 × 10 ⁷ Ωcm.

On the elastic layer, a surface layer as shown below was formed by coating.

A material for forming the surface layer 2c is a polyvinyl butyral resin, and a dip coating method using a paint obtained by adding 40 parts of conductive titanium oxide to 100 parts of an ethanol solution (solid content: 50% by mass). To form a surface layer having a thickness of 5 μm to obtain a roller-shaped charging member. The resistance of the surface layer was 1 × 10 ¹³ Ωcm.

The same binder resin as the paint on which the surface layer was formed was made into a paint, and the clear paint was used to coat it on an aluminum sheet to obtain a surface layer sample sheet for measuring the coefficient of static friction.

The coefficient of static friction μs _B of the binder resin of this example was 0.26.

Further, the static friction coefficient μs of the charging roller surface of this embodiment was measured by a method as shown in FIG.
0.36.

The time constant of the charging roller current was calculated in the same manner as in Example 1. As a result, the time constant τ was τ = 0.19 [sec]. Therefore, τ in Example 2 is τ ≦ 0.1 [se
c].

Further, the ten-point average surface roughness Rz of the charging roller surface was 1.8 μm.

The obtained charging roller was evaluated in the same manner as in Example 1 for image evaluation of excessive charging potential unevenness and image evaluation for fogging due to toner adhesion.

The environment 3 (temperature 15 ° C., humidity 10
%), The results of image evaluation of the unevenness of the overcharge potential by varying the thickness of the charge transport layer are shown in Table 3. As shown in Table 3, the thickness of the charge transport layer of the electrophotographic photosensitive member was 40
When the thickness is less than μm, a good image free from excessive charging potential unevenness or white spots was obtained.

Example 3 Evaluation and the like were performed in the same manner as in Example 1 except that the charging roller as a charging member had the following configuration.

Epichlorohydrin rubber (ternary copolymer) 100 parts Quaternary ammonium salt 1.5 parts Conductive carbon graphite 30 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acid 2 parts

The above-mentioned materials were kneaded for 10 minutes in a closed mixer adjusted to 60 ° C., and 15 parts of an ether ester plasticizer was added to 100 parts of epichlorohydrin rubber, and the mixture was further cooled to 20 ° C. in a closed mixer. Knead for a minute to adjust the raw material compound. To this compound, 1 part of sulfur as a vulcanizing agent, 1 part of Noxeller DM as a vulcanization accelerator, and 0.5 part of Noxeller TS were added to 100 parts of raw material epichlorohydrin rubber, and 20 parts were added.
The mixture is kneaded for 10 minutes by a two-roll mill cooled to ° C. The obtained compound is molded around a φ6 stainless steel core metal by an extruder so as to form a roller, and after being heated and vulcanized, the outer diameter of the rubber part is central φ12.0, and both ends φ
The elastic layer was formed by polishing treatment so as to have a crown shape of 11.9. The resistance of the elastic layer was 5 × 10 ⁶ Ωcm.

A resistance layer as shown below was formed on the above elastic layer by coating.

As a material for the resistance layer 2d, 100 parts of epichlorohydrin rubber (binary copolymer) is dispersed and dissolved in a toluene solvent to prepare a coating for the resistance layer. This paint was applied on the elastic layer 2b by a dip coating method to form a resistance layer 2d having a thickness of 100 μm. The resistance of the resistance layer was 8 × 10 ⁷ Ωcm.

Further, a surface layer 2c shown below was formed on the resistance layer 2d by coating.

As the material of the surface layer 2c, fluoroolefin (tetrafluoride type) hydroxyalkyl vinyl ether carboxylate vinyl ester

[0130] Using a fluororesin copolymer obtained by copolymerizing the above resin, 5 parts of isocyanate (HDI) and 5 parts of conductive tin oxide were added to 100 parts of the solution (solid content: 50% by mass).
Using a coating material to which 0 parts were added, a surface layer having a thickness of 5 μm was formed by coating by a dip coating method to obtain a roller-shaped charging member. The resistance of the surface layer was 9 × 10 ¹⁴ Ωcm.

[0131] The same binder resin as the paint having the surface layer was formed into a paint, and the clear paint was used to coat on an aluminum sheet to obtain a surface layer sample sheet for measuring the coefficient of static friction.

The coefficient of static friction μs _B of the binder resin of this example was 0.12.

The coefficient of static friction μs of the surface of the charging roller of this embodiment was 0.25.

The time constant of the current of the charging roller was calculated in the same manner as in Example 1. As a result, the time constant τ was τ = 0.042 [sec]. Therefore, τ in Example 3 is τ ≦ 0.1 [se
c].

Further, the ten-point average surface roughness Rz of the charging roller surface was 2.5 μm.

Example 4 Evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member had the following structure.

<Preparation of Electrophotographic Photoreceptor> Same as Example 1 except that the binder resin of the charge transport layer was changed to an arylate resin (weight average molecular weight: 83000) having the following structural formula and the thickness was 35 μm. An electrophotographic photoreceptor was prepared by the method described above.

[0138]

Embedded image (Example 5) <Preparation of charging roller> NBR 100 parts Conductive carbon black 15 parts Ester plasticizer 25 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acid 2 parts

The above-mentioned materials are kneaded for 10 minutes by a closed mixer adjusted to 60 ° C., and then further kneaded for 20 minutes by a closed mixer cooled to 20 ° C. to prepare a raw material compound. NBR 10 of raw rubber is added to this compound.
To 0 part, 1 part of sulfur as a vulcanizing agent and 3 parts of Noxeller TS as a vulcanization accelerator are added, and the mixture is kneaded for 10 minutes by a two-roll machine cooled to 20 ° C. The obtained compound was molded by an extruder so as to form a roller around a φ6 stainless steel cored bar, heated and vulcanized, and then polished to an outer diameter of φ12 to form an elastic layer. . The resistance of the elastic layer was 6 × 10 ⁵ Ωcm.

A resistance layer as shown below was formed on the above elastic layer by coating.

As a material for the resistance layer 2d, 100 parts of epichlorohydrin rubber (binary copolymer) is dispersed and dissolved in a toluene solvent to prepare a coating for the resistance layer. This paint was applied onto the elastic layer 2b by a dip coating method to form a 50 μm thick resistive layer 2d. The resistance of the resistance layer was 1 × 10 ⁸ Ωcm.

A surface layer as shown below was formed on the resistance layer by coating.

The material for forming the surface layer 2c is a polyvinyl butyral resin, and a dip coating method using a paint obtained by adding 35 parts of conductive titanium oxide to 100 parts (solid content: 50% by mass) of an ethanol solution thereof. To form a surface layer having a thickness of 15 μm to obtain a roller-shaped charging member. The resistance of the surface layer was 6 × 10 ¹³ Ωcm.

With respect to the obtained charging roller, the roller characteristics were evaluated in the same manner as in Example 1.

The coefficient of static friction μs _B of the binder resin of this example was 0.26.

The static friction coefficient μs of the surface of the charging roller of this embodiment was 0.35.

The time constant of the charging roller was calculated in the same manner as in Example 1. As a result, the time constant τ was τ = 0.067 [sec]. Therefore, τ in Example 5 is τ ≦ 0.1 [se
c].

The ten-point average surface roughness Rz of the charging roller surface was 2.5 μm.

<Preparation of Electrophotographic Photoreceptor> The charge transport layer of the electrophotographic photoreceptor of Example 1 was changed to 18 μm in thickness.
An electrophotographic photosensitive member was prepared in the same manner as in Example 1.

The same evaluation as in Example 1 was performed using the charging roller and the electrophotographic photosensitive member described above. The results are shown in Tables 1 and 2.

Example 6 A charging roller and an electrophotographic photosensitive member were prepared and evaluated in the same manner as in Example 1, except that the material of the surface layer of the charging roller in Example 1 was changed as follows.

As the material of the surface layer, urethane resin 100 parts, conductive titanium oxide 60 parts

Is dispersed and dissolved in a methyl ethyl ketone (MEK) solvent to prepare a surface layer paint. This paint is applied on the elastic layer 2b by a dip coating method to obtain a thickness of 1
A 0 μm surface layer was formed to form a roller-shaped charging member. The resistance of the surface layer was 4 × 10 ¹² Ωcm.

The static friction coefficient μs _B of the binder resin on the surface layer of the charging roller of this embodiment was 0.45.

The static friction coefficient μs of the surface of the charging roller of this embodiment was 0.82.

Further, the time constant τ of the current of the charging roller of this embodiment was τ = 0.033 [sec]. Therefore, τ in Example 6 is τ ≦ 0.1 [se
c].

The ten-point average surface roughness Rz of the charging roller surface was 6.2 μm.

Comparative Example 1 A charging roller was prepared by the following method.

EPDM 100 parts Conductive carbon black 30 parts Zinc oxide 5 parts Fatty acid 2 parts

After kneading the above-mentioned materials for 10 minutes in a closed mixer adjusted to 60 ° C., 15 parts of paraffin oil was added to 100 parts of EPDM, and kneaded for another 20 minutes in a closed mixer cooled to 20 ° C. Adjust the raw material compound. EPD of raw rubber is used for this compound.
100 parts of M, 0.5 part of sulfur as a vulcanizing agent, 1 part of MBT, 1 part of TMTD, 1 part of TMTD, ZnM
1.5 parts of DC is added, and the mixture is kneaded for 10 minutes by a two-roll machine cooled to 20 ° C. The obtained compound is
6 An elastic layer was formed around a stainless steel core by heat vulcanization using a press molding machine so as to form a roll having an outer diameter of φ12. The resistance of the elastic layer is 7 × 10 ³ Ωcm
Met.

A resistance layer as shown below was formed on the elastic layer by coating.

As the material of the resistance layer 2d, polyurethane resin 100 parts conductive carbon black 15 parts

Is dispersed and dissolved in a methyl ethyl ketone (MEK) solvent to prepare a coating for a resistance layer. This paint is applied on the elastic layer 2b by a dip coating method to obtain a thickness of 1
A 00 μm resistance layer 2d was formed by coating. The resistance of the resistance layer was 5 × 10 ¹⁰ Ωcm.

Further, a surface layer 2c shown below was formed on the resistance layer 2d by coating.

As the material of the surface layer 2c, SEBS (styrene-ethylenebutylene-styrene) 100 parts conductive carbon black 10 parts

Is dispersed and dissolved in a toluene solvent to prepare a surface layer paint. Using this paint, a surface layer having a thickness of 5 μm was formed by coating by dip coating to obtain a roller-shaped charging member. The resistance of the surface layer is 8 × 10 ¹³
Ωcm.

An aluminum sheet was coated with the same paint as the paint on which the surface layer was formed to obtain a surface layer sample sheet for measuring the coefficient of static friction.

The static friction coefficient μs _B of the binder resin of the charging roller surface layer of Comparative Example 1 was 0.62.

The coefficient of static friction μs on the surface of the charging roller was 1.07.

The time constant of the current of the charging roller was calculated in the same manner as in Example 1. As a result, the time constant τ was τ = 0.112 [sec]. Therefore, τ of Comparative Example 1 is τ ≦ 0.1 [se
c] is not satisfied.

The ten-point average surface roughness Rz of the charging roller surface was 10.5 μm.

The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2. An image output by an electrophotographic apparatus using the charging roller had white spots and roughness due to excessive charging potential unevenness. When the surface potential of the photoconductor in the halftone image area was measured, the potential at the position corresponding to the second rotation of the photoconductor was excessively charged by about −60 V. Further, in the durability test for image output on a plurality of sheets, unevenness in image density due to toner adhesion occurred.

Comparative Example 2 A charging roller was prepared by the following method.

NBR 100 parts Lithium perchlorate 5 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acid 2 parts

After kneading the above-mentioned materials for 10 minutes by a closed mixer adjusted to 60 ° C., 20 parts of DOS plasticizer was added to 100 parts of NBR, and the mixture was further kneaded by a closed mixer cooled to 20 ° C. for 20 minutes. , Adjust the raw material compound. NBR 10 of raw rubber is added to this compound.
To 0 part, 1 part of sulfur as a vulcanizing agent and 3 parts of Noxeller TS as a vulcanization accelerator are added, and the mixture is kneaded for 10 minutes by a two-roll machine cooled to 20 ° C. The obtained compound was molded by an extruder so as to form a roller around a φ6 stainless steel core, heated and vulcanized, and then polished to an outer diameter of φ12 to obtain an elastic layer. . The resistance of the elastic layer was 2 × 10 ⁵ Ωcm.

As the material of the surface layer 2c, 100 parts of polyurethane elastomer, 5 parts of conductive carbon black

Is dispersed and dissolved in a methyl ethyl ketone (MEK) solvent to prepare a surface layer paint. Using this paint, applied by dip coating method, thickness 10μm
To form a roller-shaped charging member. The resistance of the surface layer was 5 × 10 ¹³ Ωcm.

An aluminum sheet was coated with the same paint as the paint on which the surface layer was formed to obtain a surface layer sample sheet for measuring the coefficient of static friction.

The coefficient of static friction μs _B of the binder resin of the charging roller of Comparative Example 2 was 0.57.

Also, the static friction coefficient μs of the surface of the charging roller
Was 1.03.

The time constant of the current of the charging roller was calculated in the same manner as in Example 1. As a result, the time constant τ was τ = 0.102 [sec]. Therefore, τ of Comparative Example 2 is τ ≦ 0.1 [se
c] is not satisfied.

The ten-point average surface roughness Rz of the charging roller surface was 12.1 μm.

The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2. An image output by an electrophotographic apparatus using the charging roller had white spots and roughness due to excessive charging potential unevenness. When the surface potential of the photoconductor in the halftone image area was measured, the potential at the position corresponding to the second round of the photoconductor was excessively charged by about -40 V. Further, in the durability test for image output on a plurality of sheets, unevenness in image density due to toner adhesion occurred.

Comparative Example 3 A charging roller and an electrophotographic photosensitive member were prepared in the same manner as in Example 1, except that the charging roller as a charging member was configured as described below.

NBR 100 parts Lithium perchlorate 5 parts Ester plasticizer 15 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acid 2 parts

The above-mentioned materials are kneaded for 10 minutes by a closed mixer adjusted to 60 ° C., and then further kneaded for 20 minutes by a closed mixer cooled to 20 ° C. to prepare a raw material compound. NBR 10 of raw rubber is added to this compound.
One part of sulfur as a vulcanizing agent and 3 parts of Noxeller TS as a vulcanization accelerator are added to 0 parts, and the mixture is kneaded for 10 minutes by a two-roll machine cooled to 20 ° C. The obtained compound was molded by an extruder so as to form a roller around a φ6 stainless steel cored bar, heated and vulcanized, and then polished to an outer diameter of φ12 to form an elastic layer. .
The resistance of the elastic layer was 1 × 10 ⁸ Ωcm.

A surface layer as shown below was formed on the above elastic layer by coating.

The material for forming the surface layer 2c is formed of a polyurethane resin, and is applied by a dip coating method using a methyl ethyl ketone (MEK) solution (solid content: 25% by mass) to form a surface layer having a thickness of 30 μm. A roller-shaped charging member was obtained. The resistance of the surface layer is 1 × 10 ¹⁴ Ωc
m.

An aluminum sheet was coated with the paint having the surface layer formed thereon to obtain a surface layer sample sheet for measuring the coefficient of static friction.

The coefficient of static friction μs _B of the binder resin of this comparative example was 0.40.

The static friction coefficient μs of the surface of the charging roller of this comparative example was 0.81.

The time constant of the charging roller current was calculated in the same manner as in Example 1. As a result, the time constant τ was τ = 0.125 [sec]. Therefore, τ in Comparative Example 3 is τ ≦ 0.1 [se
c] is not satisfied.

The ten-point average surface roughness Rz of the charging roller surface was 8.0 μm.

This charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2. An image output by an electrophotographic apparatus using the charging roller had white spots and roughness due to excessive charging potential unevenness. When the surface potential of the photoconductor in the halftone image area was measured, the potential at the position corresponding to the second round of the photoconductor was excessively charged by about -25 V. Further, in the durability test for image output on a plurality of sheets, unevenness in image density due to toner adhesion occurred.

[0195]

[Table 1]

[0196]

[Table 2]

[0197]

[Table 3]

[0198]

As described above, according to the present invention, a process cartridge which is less likely to have excessively charged potential unevenness even when only a DC voltage is applied to a conductive member to perform charging of a member to be charged. Electrophotographic equipment has become possible. In addition, it is possible to provide a process cartridge and an electrophotographic apparatus capable of maintaining good charging characteristics over a long period of time without causing poor charging due to contamination of the conductive member, and providing the electrophotographic apparatus.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram of a charging roller.

FIG. 3 is a schematic view of another charging roller.

FIG. 4 is a schematic diagram showing a behavior of a current value of a charging member.

FIG. 5 is a schematic diagram of an apparatus for measuring a current value of a charging member.

FIG. 6 is a sectional view of a layer of the electrophotographic photosensitive member.

FIG. 7 is a layer sectional view of another electrophotographic photosensitive member.

FIG. 8 is a schematic view of an apparatus for measuring a friction coefficient of a charging roller surface.

FIG. 9 is an example of a chart obtained by a friction coefficient measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (electrophotographic photoreceptor) 2 Charging member (charging roller) 3 Image exposure means 4 Developing means 5 Transfer means (transfer roller) S1, S2, S3 Bias power supply P Transfer material 11 Cylindrical electrode (metal roller) 12 Fixed resistor 13 Recorder

Claims (36)

[Claims] 1. An electrophotographic apparatus comprising: an electrophotographic photoreceptor; and a conductive member which is disposed in contact with the electrophotographic photoreceptor and to which a voltage is applied, wherein the electrophotographic photoreceptor and the conductive member are integrally supported. The electrophotographic photosensitive member has a support, a charge generation layer and a charge transport layer in this order, the charge transport layer has a thickness of 12 to 40 μm, and the conductive member is A process cartridge having a coating layer on a conductive support, wherein a time constant τ of current of the conductive member is 0.1 second or less. 2. The process cartridge according to claim 1, wherein the applied voltage is a DC voltage only. 3. The process cartridge according to claim 1, wherein the thickness of the charge transport layer is 12 to 23 μm. 4. The process cartridge according to claim 3, wherein the thickness of the charge transport layer is 12 to 18 μm. 5. The process cartridge according to claim 1, wherein the time constant τ is 0.05 seconds or less. 6. The process cartridge according to claim 1, wherein the time constant τ is 0.00001 seconds or more. 7. The process cartridge according to claim 1, wherein the coating layer has an elastic layer and a layer on the elastic layer. 8. The process cartridge according to claim 7, wherein the layer on the elastic layer contains a conductive agent having an electronic conductive mechanism. 9. The process cartridge according to claim 7, wherein the elastic layer has a resistance value of less than 10 ¹⁰ Ωcm. 10. The layer on the elastic layer is a resistance layer.
The process cartridge as described. 11. The process cartridge according to claim 10, wherein the resistance layer has a resistance value of 10 ⁴ to 10 ¹⁰ Ωcm. 12. The layer on the elastic layer is a surface layer.
The process cartridge as described. 13. The process cartridge according to claim 12, wherein the surface layer has a resistance of 10 ⁴ to 10 ¹⁵ Ωcm. 14. The process cartridge according to claim 7, wherein the layers on the elastic layer are a resistance layer and a surface layer. 15. The process cartridge according to claim 14, wherein the resistance layer has a resistance value of 10 ⁴ to 10 ¹⁰ Ωcm, and the surface layer has a resistance value of 10 ⁴ to 10 ¹⁵ Ωcm. 16. The process cartridge according to claim 1, wherein the surface of the conductive member has a static friction coefficient of 1.0 or less. 17. The process cartridge according to claim 1, wherein the conductive member has a surface roughness of 10 μm or less. 18. The process cartridge according to claim 1, wherein the electrophotographic apparatus employs a developing and cleaning system. 19. An electrophotographic apparatus comprising an electrophotographic photoreceptor and a conductive member which is disposed in contact with the electrophotographic photoreceptor and to which a voltage is applied, wherein the electrophotographic photoreceptor includes a support, a charge generation layer and a charge transport layer. In this order, the charge transport layer has a thickness of 12 to 40 μm, the conductive member has a coating layer on a conductive support, and the time constant τ of the current of the conductive member is 0.1 An electrophotographic apparatus, wherein the time is less than seconds. 20. The electrophotographic apparatus according to claim 19, wherein the applied voltage is a DC voltage only. 21. The electrophotographic apparatus according to claim 19, wherein the thickness of the charge transport layer is 12 to 23 μm. 22. The electrophotographic apparatus according to claim 21, wherein the thickness of the charge transport layer is 12 to 18 μm. 23. The electrophotographic apparatus according to claim 19, wherein the time constant τ is 0.05 seconds or less. 24. The electrophotographic apparatus according to claim 19, wherein the time constant τ is 0.00001 seconds or more. 25. The electrophotographic apparatus according to claim 19, wherein the covering layer has an elastic layer and a layer on the elastic layer. 26. The electrophotographic apparatus according to claim 25, wherein the layer on the elastic layer contains a conductive agent having an electron conductive mechanism. 27. The electrophotographic apparatus according to claim 25, wherein the elastic layer has a resistance value of less than 10 ¹⁰ Ωcm. 28. The layer according to claim 2, wherein the layer on the elastic layer is a resistance layer.
5. The electrophotographic apparatus according to 5. 29. The electrophotographic apparatus according to claim 28, wherein the resistance layer has a resistance value of 10 ⁴ to 10 ¹⁰ Ωcm. 30. The layer on the elastic layer is a surface layer.
5. The electrophotographic apparatus according to 5. 31. The electrophotographic apparatus according to claim 30, wherein the surface layer has a resistance of 10 ⁴ to 10 ¹⁵ Ωcm. 32. The electrophotographic apparatus according to claim 25, wherein the layers on the elastic layer are a resistance layer and a surface layer. 33. The electrophotographic apparatus according to claim 32, wherein the resistance layer has a resistance value of 10 ⁴ to 10 ¹⁰ Ωcm, and the surface layer has a resistance value of 10 ⁴ to 10 ¹⁵ Ωcm. 34. The electrophotographic apparatus according to claim 19, wherein the surface of the conductive member has a static friction coefficient of 1.0 or less. 35. The electrophotographic apparatus according to claim 19, wherein the conductive member has a surface roughness of 10 μm or less. 36. The electrophotographic apparatus according to claim 19, wherein the electrophotographic apparatus employs a developing and cleaning system.