JP2000330359A - Charging member and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member exhibiting characteristics opposite to conventional environmental characteristics, and to provide a charging member and an image forming apparatus which reduce environmental dependency by using this member as a charging member. It is to be. A charging member for charging the surface of an image carrier by contacting the surface of the image carrier, wherein the charging member is provided with a single-layer or multi-layer conductive tube outside a conductive elastic layer, Charging member having a conductive particle layer covered with conductive particles, and an image forming apparatus containing the charging member and an image carrier, wherein the image carrier has a photosensitive layer on a conductive support. An image forming apparatus comprising an electrophotographic photoreceptor having a charge injection layer on the outermost layer of the conductive support, wherein the charge injection layer is injected with a charge through a contact portion with the charging member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member and an image forming apparatus in an electrophotographic system used for a copying machine, a printer, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, many electrophotographic methods are known. Generally, a photoreceptor using a photoconductive material is used, the surface of the photoreceptor is uniformly charged to a predetermined polarity and potential by a charging unit, and an electrostatic latent image is formed on the photoreceptor by an exposure unit. Then, the latent image is formed into a visible image with toner, and the visible image is transferred to a transfer material such as paper.Then, the image is fixed on the transfer material by heat, pressure, heat and pressure, and the copy or print is formed. What you get. The toner remaining on the photoconductor without being transferred onto the transfer material is removed from the photoconductor by a cleaning process.

As a charging means in such an electrophotographic method, a means utilizing corona discharge called a so-called corotron or scorotron has been used. However, a large amount of ozone is generated when corona discharge, particularly negative or positive corona is generated. Therefore, it is necessary to provide the electrophotographic apparatus with a filter for capturing ozone, and there have been problems such as an increase in the size of the apparatus and an increase in running costs.

As a technique for solving such a problem, a charging member such as a roller or a blade is brought into contact with the surface of a photoreceptor to form a narrow space in the vicinity of the contacting portion, which is interpreted according to the so-called Paschen's law. A contact charging method has been developed in which generation of ozone is suppressed as much as possible by forming a discharge that can be performed.
JP, JP-A-56-104351, JP-A-58-104351
Japanese Patent No. 40566, Japanese Patent Application Laid-Open No. 58-139156, and Japanese Patent Application Laid-Open No. 58-150975.

[0005] One of the major problems in the contact charging system is the environmental dependence of the charging member. Rollers, blades, fur brushes, magnetic brushes, etc. are used for the contact charging method.Each of these members tends to have a conductive property that depends on the atmosphere of the environment in which it is used. There is a problem that image defects such as fogging due to poor charging occur, the resistance decreases on the high-temperature and high-humidity side, and a leak easily occurs between the charging member and the photosensitive member.

In order to solve the above-mentioned problem, Japanese Patent Laid-Open Publication No.
Japanese Patent Publication No. 3 discloses a conductive roll in which the charging member is composed of a base layer and a conductive layer, and the base layer and the conductive layer have opposite environmental dependence and reduced environmental fluctuation. However, all the materials used for the charging member have a characteristic that the resistance increases on the low-temperature and low-humidity side and decreases on the high-temperature and high-humidity side. Therefore, this technique has not been implemented to date.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a member exhibiting characteristics opposite to those of conventional environmental characteristics,
An object of the present invention is to provide a charging member and an image forming apparatus that reduce environmental dependency by using this member as a charging member.

[0008]

According to the present invention, there is provided a charging member for charging a surface of an image carrier by contacting the surface of the image carrier, wherein the charging member comprises a single layer or a plurality of layers outside a conductive elastic layer. There is provided a charging member which is coated with a conductive tube and has a conductive particle layer covered with conductive particles on the outermost surface.

According to the present invention, there is provided an image forming apparatus including a charging member and an image carrier, wherein the image carrier has a photosensitive layer on a conductive support and charge is injected into an outermost layer of the conductive support. An image forming apparatus is provided which is an electrophotographic photoreceptor having a layer and a charge injection layer into which a charge is injected through a contact portion with the charging member.

[0010]

Embodiments of the present invention will be described below in detail.

A general configuration of a charging roller has a configuration in which a conductive elastic layer and a surface layer composed of a single layer or multiple layers are provided on a conductive support. For the conductive support, a conductive material such as stainless steel, iron, or copper is used.For the conductive elastic layer, elastic rubber or elastomer is used to secure a sufficient nip width between the photoconductor and the conductive elastic layer. Have been. The surface layer is formed by dissolving a conductive pigment dispersed in a resin in an organic solvent, and coating the solution on the surface of the elastic layer by dipping, roll coating, or spray coating. The environmental characteristics of a charging member having a surface layer formed by coating show that the resistance increases under low temperature and low humidity and decreases under high temperature and high humidity.

The charging member of the present invention has a technical feature in that the surface layer of the charging roller is constituted by a conductive tube.
The present invention is based on the finding that there is an environmental dependence that is inconsistent with conventional charging members.

FIG. 3 shows the structure of the charging member of the present invention. The charging member is a conductive support 3a such as a metal (stainless steel),
Conductive elastic layer 3b, surface layer 3 covering conductive tube
c, having a configuration of an outermost surface layer 3d composed of a conductive particle layer covered with conductive particles. In the present invention, the surface layer made of the conductive tube can be formed into a multilayer for the purpose of adjusting the resistance and improving the durability. FIG. 3B shows two surface layers 3c1.
The structure of the charging member having 3c2 and 3c2 is shown. In the case of multiple layers,
In addition to a method of coating a single-layer tube stepwise by a manufacturing method described later, a method of preparing a multi-layer tube at once and coating the conductive elastic layer may be used.

The present inventors have found that the use of a conductive tube in the surface layer of a charging member allows the environmental characteristics of the charging member to be reduced at low temperature and low humidity, and increased at high temperature and high humidity. Was found. When the environment dependence of the elastic layer alone was confirmed, it was found that this characteristic was attributable to the conductive tube itself, since the elastic layer alone exhibited characteristics of reduced resistance on the high temperature and high humidity side.

The conditions for the charging member of the present invention to exhibit a specific environmental dependency include a method of forming a surface layer by inserting an elastic layer while enlarging the outer diameter of the tube. Further, as another example of a method for coating the conductive layer on the elastic layer, there is a method in which the inner diameter of the tube is larger than the outer diameter of the elastic layer, and the tube is coated on the elastic layer by utilizing heat shrinkage. However, it was confirmed that the tube obtained by this heat shrinkage method exhibited the same characteristics as the prior art that the resistance was reduced under high temperature and high humidity. From this fact, although the details are not clear, it is presumed that elongation of the tube may provide an environmental characteristic peculiar to the tube.

As a method for forming the conductive tube, generally, various molding methods such as an extrusion molding method, an inflation molding method, an injection molding method, and a blow molding method can be mentioned. It is necessary to apply a sufficient stretching force to the formed tube, and it is particularly preferable to produce the conductive tube by an extrusion method.

In the method for producing a tube by extrusion molding of the charging member of the present invention, a compound obtained by a pressure kneader is extruded from a die heated to a high temperature by an extruder and cooled to form a tube continuously. How to In particular, in the extrusion molding method, when a tube extruded from a die is cooled by a cooling device, a conductive tube exhibiting a specific environmental dependency is formed by forcibly extracting the tube for controlling the film thickness. It is supposed to be.

The conductive tube used for the charging member of the present invention needs to have sufficient stretchability. The 100% modulus as an index of the stretchability is 1
It is preferably in the range of ^{0kg / cm 2 ~90kg / cm 2} . The 100% modulus is a JIS standard, and is a force per unit cross-sectional area required to further lengthen a sample of length L by 100% (100%), and indicates the ease of stretching or difficulty of stretching of the sample. .

The 100% modulus is 90 kg / cm ²
If it exceeds, not only the stretching force required for the tube cannot be obtained but also it is difficult to increase the outer diameter, so that the above-mentioned coating cannot be performed. Further, if the 100% modulus is less than 10 kg / cm ^2, it is not preferable because the outer diameter (or inner diameter) may be changed at the time of coating the tube and the film thickness may be uneven because the tube is relatively easily deformed by pressurization. The 100% modulus of the conductive tube is measured according to JIS K-6301 vulcanized rubber physical test method.

In the charging member having a surface layer made of a conductive tube according to the present invention, the inner diameter A of the tube is in the range of (5/6) × B ≦ A <B, where B is the outer diameter of the elastic layer. Preferably, there is. Tube inner diameter is (5/6) × B
If it is less than 3, the outer diameter must be excessively enlarged to cover the tube, and in this case, it becomes very difficult to control the charging member to a specified diameter.

Further, the present inventors have determined that the magnitude of the environmental dependence of the conductive tube depends on the Vicat softening point (° C.) of the material used for the tube, that is, the lower the softening point, the greater the environmental dependence. It has been found that the higher the softening point, the lower the environmental dependency tends to be. Thereby, the optimum tube material can be appropriately selected from the environment dependence of the elastic layer and the environment dependence of the conductive particle layer. The range of the Vicat softening point of the tube material that sufficiently exerts the effects of the present invention is 150 ° C.
The following are the preferred ranges. Vicat softening point of the material is 1
If the temperature exceeds 50 ° C., the environment dependency of the conductive tube is small, and the environmental characteristics of the charging member are easily affected by the elastic layer, so that the performance unique to the conductive tube cannot be utilized.

The present invention is an invention utilizing the specific performance of a charging member coated with a conductive tube, and is characterized in that a conductive particle layer is provided by further attaching conductive particles to the surface of the tube. .

The conductive particles applied to the charging member of the present invention are conductive particles whose resistance increases in a low-temperature and low-humidity environment and decreases in a high-temperature and high-humidity environment. That is,
The environment dependency is opposite to that of the charging member covering the tube. Therefore, when the tube-coated charging member exhibits a specific environmental dependency, environmental fluctuation can be minimized in combination with the conductive particles.

The conductive particle layer is formed on the surface of the charging member by a powder coating method such as an electrostatic powder coating method, a fluid immersion coating method, an electrostatic fluid immersion coating method, and a thermal spraying powder coating method. Direct coating of conductive particles is effective. In addition, a method in which conductive particles are sprayed on a charging member surface by spray coating or the like, and a dispersion obtained by mixing and diluting conductive particles in a solvent such as an alcohol-based, ketone-based, or hydrocarbon-based solvent, is equivalent to powder coating. An adhered state is obtained.

There is a concern that the conductive particles on the surface of the charging member may be lost due to repeated use of the image forming apparatus.
For example, there is a method in which a brush roller for applying conductive particles is provided in contact with the charging member. However, if a new means for applying the conductive particles is provided, the size of the image forming apparatus is increased and the cost is increased. In a preferred embodiment of the present invention, the conductive particles of the present invention are mixed with toner particles in a developer for visualizing an electrostatic latent image formed on a photoreceptor. By doing so, the conductive particles are automatically replenished to the charging member surface by repeated use of the image forming apparatus, so that the size and cost of the image forming apparatus are suppressed, and the conductive particles are easily supplied. This is preferable because the method can be realized.

The volume resistivity of the conductive particles in the charging member of the present invention is preferably 1 × 10 ¹⁰ Ω · cm or less. When the volume resistivity of the conductive particles exceeds 1 × 10 ¹⁰ Ω · cm, the conductive particle layer on the outermost surface of the charging member becomes high in resistance, and thus charging failure may occur from the beginning. For this reason, the volume resistivity of the conductive particles is 1 × 10 ¹⁰ Ω.
-More preferably, it is not more than cm.

FIG. 4 shows a method of measuring the volume resistivity used for the conductive particles. A cylinder is filled with conductive particles 47, electrodes 41 and 42 are arranged so as to sandwich the conductive particles 47 from above and below, a voltage is applied between the electrodes by a constant voltage device 46, and the current flowing at that time is measured by an ammeter 44 Can be obtained. Measurement conditions are 23 ° C / 65% RH, 15 ° C / 1
0% RH, 30 ° C./80% RH environment, the contact area between the filled particles and the electrode is 2 cm ² , the thickness is 1 mm, and the upper electrode is 10 k.
g, the applied voltage is 100V.

The average particle size of the conductive particles of the present invention is 10 μm.
m or less. If the average particle size exceeds 10 μm, the adhesion of the conductive particles to the surface of the charging member is weakened, and the conductive particles are likely to drop from the charging member during repeated use.

The average particle size of the conductive particles was determined by the following method. The conductive particles used in the present invention are SEM (Scann).
The size of the conductive particles is measured by a magnification of 1000 times using an Electron Microscope (ing Electron Microscope). Next, the average value of the particle diameters of the 50 particles measured using the SEM was determined and defined as the average particle diameter.

When the surface area of the charging member is defined as S (m ² ), the adhesion amount for forming the conductive particle layer of the charging member of the present invention is 0.1 × S (g) <the adhesion amount (g) <50. It is preferably within the range of × S (g). If the amount of the conductive particles deposited on the surface of the charging member is 0.1 × S (g) or less, the absolute amount for stabilizing the environmental fluctuation of the charging member becomes insufficient.
Further, the amount of the conductive particles adhered to the surface of the charging member is 50 × S
(G) In the case described above, the possibility of occurrence of a leak between the charging member and the photoconductor increases due to the reduction in the resistance of the charging member surface, which is not preferable.

In the contact charging method using the charging member of the present invention, a narrow space is formed near a contact portion between the charging member and the surface of the photoreceptor, and a discharge which can be interpreted by the so-called Paschen's law is formed. Generation can be suppressed as much as possible to charge the photosensitive member. As a new attempt,
It is also possible to adopt a method in which a voltage is applied to a contact charging member such as a charging roller, a charging brush, a charging magnetic brush or the like, and charge is injected into a trap level on the surface of the photoconductor to perform contact injection charging.

In the contact injection charging method, there is no discharge starting point due to a discharge phenomenon, and a charging potential can be obtained almost linearly with applied voltage. For this reason, in the contact injection charging method, it is possible to further reduce the voltage applied to the charging member, and even if the resistance of the conductive particles on the outermost layer of the charging member is significantly reduced in a high-temperature, high-humidity environment, the charging is performed. This is more preferable because it has the advantage of preventing the occurrence of leakage between the member and the photoconductor.

By using a photoreceptor having a charge injection layer in the layer farthest from the conductive support as the electrophotographic photoreceptor, a charging potential can be obtained almost linearly with respect to the applied voltage. The effect is obtained. Therefore,
For the charging method interpreted by Paschen's law,
A further ozoneless charging method can be realized. In this case, when the photoreceptor has a charge injection layer in a layer farthest from the support, a potential of 90% or more of the applied voltage can be formed on the photoreceptor by DC charging.

More specifically, in order to satisfy the condition that sufficient chargeability and image deletion do not occur in the layer farthest from the support, the volume resistivity is 1 × 10 ⁸ Ω · cm to 1 × 10 ¹⁵ Ω.・
The use of a photoreceptor provided with a charge injection layer in the range of cm. More preferably, the volume resistivity is 1 × 10 ¹⁰ Ω · cm to 1 × 10 ¹⁵ Ω · cm from the viewpoint of image deletion, and the volume resistivity is 1 × 10 ¹² Ω · cm in consideration of environmental fluctuations.
It is preferable to use one having a resistance of 1 to 10 ¹⁵ Ω · cm. 1
If the volume resistivity is less than × 10 ⁸ Ω · cm, the electrostatic latent image cannot be retained, and an image flow occurs particularly in a high temperature and high humidity environment. If the resistivity exceeds 1 × 10 ¹⁵ Ω · cm, the charging member is Cannot receive enough charge from the battery, and tends to cause poor charging.

The charge injection layer can be made of a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin. Is also an effective means. By providing such a functional layer surface, it plays a role of retaining the charge injected from the charging member, and also plays a role of releasing this charge to the photosensitive member support during exposure, so that the residual potential can be reduced.

Here, the method of measuring the volume resistivity of the charge injection layer is as follows. A charge injection layer is formed on polyethylene terephthalate having a conductive film deposited on the surface, and the charge injection layer is measured using a volume resistance measuring device (4140B pAMA manufactured by Hewlett-Packard Company).
(TER) in a 23 ° C./65% humidity environment with a voltage of 100 V applied.

The particle size of the conductive particles is preferably 0.3 μm or less from the viewpoint of light transmission, and most preferably 0.1 μm or less. The amount is preferably from 2 to 250 parts by mass, more preferably from 2 to 190 parts by mass, based on 100 parts by mass of the binder resin.
If the amount is less than 2 parts by mass, it is difficult to obtain a preferable volume resistivity, and if it exceeds 250 parts by mass, the film strength tends to decrease, and the charge injection layer tends to crack. The thickness of the charge injection layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

Preferably, the charge injection layer contains a lubricant powder. The expected effect is that the friction between the photosensitive member and the charging member during charging is reduced, the nip involved in charging is enlarged, and the charging characteristics are improved. In addition, since the releasability of the photoreceptor surface is improved, the conductive particles are less likely to adhere. In particular, as the lubricant particles, it is preferable to use a fluororesin, a silicone resin, or a polyolefin resin having a low critical surface tension. Particularly preferably, a tetrafluoroethylene resin is used.

In this case, the addition amount of the lubricant powder is preferably 2 to 50 parts by mass with respect to 100 parts by mass of the binder resin.
More preferably, it is 5 to 40 parts by mass. If the amount is less than 2 parts by mass, the amount of the lubricant powder is not sufficient, so that the effect of improving the chargeability of the photoreceptor is not sufficient, and from the viewpoint of a cleanerless device, the transfer residual toner tends to increase. Also, 50
When the amount exceeds the mass part, the resolution of the image and the sensitivity of the photoreceptor tend to decrease.

When the surface protective layer is coated with an inorganic layer, the underlying photoconductive layer is preferably made of amorphous silicon, and the blocking layer, photoconductive layer and charge injection layer are formed on the cylinder by glow discharge or the like. Are preferably formed sequentially. As the photosensitive layer, conventionally known ones can be used. For example, if it is an organic material, a phthalocyanine pigment, an azo pigment and the like can be mentioned.

Further, an intermediate layer can be provided between the surface protective layer and the photosensitive layer. The purpose of such an intermediate layer is to enhance the adhesion between the surface protective layer and the photosensitive layer or to function as a charge barrier layer. As the intermediate layer, for example, a commercially available resin material such as an epoxy resin, a polyester resin, a polyamide resin, a polystyrene resin, an acrylic resin, and a silicone resin can be used.

As the conductive support of the photoreceptor, a metal having aluminum, nickel, stainless steel, steel, or the like, plastic having a conductive film, glass, conductive paper, or the like can be used.

The hardness of the charging member of the present invention is preferably not more than 70 degrees in the measurement of Asker C hardness.
When the hardness is 70 degrees or less, the contact nip width between the charging member and the photosensitive member is widened, so that the number of contact injection points is increased and the injection efficiency can be further improved.

In the same effect, it is more preferable to provide a speed difference between the photosensitive member and the charging member. Instead of the method of rotating the charging member following the photosensitive member, a dedicated driving device is provided for the charging member, and the charging member is driven in the opposite direction to the photosensitive member to provide a constant speed difference from the photosensitive member. With this rotation method, higher contact properties can be obtained than with the method of rotating the photosensitive member following rotation, so that providing a speed difference between the photosensitive member and the charging member is more effective in increasing the number of contact injection points. This is a preferred form.

The charging member of the present invention has a structure in which a conductive elastic layer is provided on a conductive support, and a surface layer comprising a single layer or two or more tubes is provided outside the elastic layer.

As the material of the tube used for the surface layer,
Rubber, elastomers or resins are used, but plasticizers,
It is preferable to use a thermoplastic elastomer from the viewpoint that there is no need for an additive and that it is easy to process. In particular,
Polyolefin-based thermoplastic elastomer (TPO), urethane-based thermoplastic elastomer (TPU), polystyrene-based thermoplastic elastomer (TPS), fluororubber-based thermoplastic elastomer, polyester-based thermoplastic elastomer (TPEE), polyamide-based thermoplastic elastomer (TPA) ), Polybutadiene-based thermoplastic elastomer (PB), ethylene-vinyl acetate-based thermoplastic elastomer (EVA), polyvinyl chloride-based thermoplastic elastomer (PVC), chlorinated polyethylene-based thermoplastic elastomer (CM), and the like. These materials are
They may be used alone or as a mixture of two or more kinds, and may be a copolymer.

These materials are processed into a tube by various molding methods. When an extruder is used, the inner diameter and the film thickness are adjusted by using a means for winding a continuously formed tube and a means for reducing the sizing or external pressure. Further, by providing the surface layer, it is possible to prevent image defects due to contamination or deterioration due to leakage of the plasticizer and various additives from the conductive elastic layer to the surface of the photoreceptor.

The surface layer is preferably adjusted to a predetermined resistance value by dispersing a conductive pigment. As the conductive pigment,
For example, carbon black, graphite, carbon fiber, metal powders (such as gold, silver, copper, nickel and aluminum), metal oxides (such as tin oxide, titanium oxide, zinc oxide and magnesium oxide) and the like can be mentioned. May be used. These conductive pigments may be used as a mixture of two or more, but are not particularly limited.

The constituent material of the conductive elastic layer of the present invention is made of a rubber material in order to satisfy the stabilization of the nip width between the conductive elastic layer and the photosensitive member. The material used is, for example, ethylene propylene rubber (EPDM). , Nitrile rubber (NB
R), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylic rubber (ACM), silicone rubber, fluorine rubber, and the like. The conductive pigment may be dispersed in the conductive elastic layer to adjust the resistance to a predetermined value.

As the cylindrical conductive support used in the present invention, metals and alloys such as aluminum, iron, copper and stainless steel, conductive resins in which carbon and metal particles are dispersed, and the like can be used. Examples thereof include a cylindrical shape as described above, a shape in which a shaft passes through the center of the cylinder, and a shape in which the inside of the cylinder is reinforced.

{Charge Member Production Example 1} 30 parts by weight of conductive carbon black, 20 parts by weight of paraffin oil, 100 parts by weight of EPDM (ethylene propylene rubber)
A conductive compound was prepared by kneading 3 parts by weight of a vulcanizing agent, 2 parts by weight of a vulcanization aid, 3 parts by weight of a vulcanization accelerator, and 20 parts by weight of a filler. Further, the conductive compound was heated and vulcanized at 150 ° C. for 15 minutes on a stainless steel core having a diameter of 6 mm to obtain a rubber roller 1 having a 3 mm-thick elastic layer.
The outer diameter of the obtained rubber roller 1 was 12 mm.

Next, conductive carbon black 1 was added to 100 parts by weight of a styrene-ethylene butylene-olefin crystal block copolymer (SEBC, Vicat softening point 90 ° C.).
4 parts by weight and 10 parts by weight of titanium oxide were blended and melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. Furthermore,
After cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder. The pellet was used as an extruder to obtain a conductive tube 1 having an inner diameter of 10.5 mm and a thickness of 250 μm. The 100% modulus of the obtained conductive tube 1 was 34 kg / cm ² .

Subsequently, air was blown into the conductive tube 1 to expand the outer diameter, and the rubber roller 1 was inserted to cover the conductive tube 1 to obtain the charging roller 1. The surface area of the elastic portion of the obtained charging roller 1 is 8.7 × 10
^-3 (m ² ), and Asker C hardness was 58 degrees.

{Production Example 2 of Charging Member} 16 parts by weight of conductive carbon black and 10 parts by weight of titanium oxide were mixed with 100 parts by weight of a polyurethane-based thermoplastic elastomer (Vicat softening point 140 ° C.), and 180 parts by weight were applied using a pressure kneader. ° C
For 10 minutes. Further, after cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder. Using an extruder, the pellets are 10.5 mm in inner diameter and 2
A 50 μm conductive tube 2 was obtained.

The 100% modulus of the obtained conductive tube 2 was 78 kg / cm ² . Subsequently, air was blown into the conductive tube 2 to expand the outer diameter, and the rubber roller 1 was inserted to cover the conductive tube 2 to obtain the charging roller 2. The surface area of the elastic portion of the obtained charging roller 2 was 8.7 × 10 ⁻³ (m ² ), and Asker C hardness was 59 degrees.

<< Charging Member Production Example 3 >> N-methoxymethylated nylon (toluene / methanol = 1/5 solution) 10
0 parts by weight of conductive titanium oxide (surface treated with tin oxide, average primary particle diameter: 0.1 μm, powder resistance: 1)
⁰ 0 Ω · cm) addition of 30 parts by weight, and dispersed using a small bead mill, to prepare a coating material for the surface layer.

Subsequently, the above coating material was dipped and applied on the rubber roller 1 obtained in the charging member production example 1 by dipping, and dried by heating at 130 ° C. for 60 minutes to thereby form a charging roller having a surface layer having a thickness of 15 μm. 3 was obtained. The surface area of the elastic portion of the obtained charging roller 3 is 8.7 × 10 ^−3.
(M ² ), and Asker C hardness was 58 degrees.

<< Charging Member Production Example 4 >> The mixing ratio of the filler of the rubber roller 1 used in the charging member production example 1 was set to EPDM1
Rubber roller 2 was produced in the same manner except that the weight was changed from 20 parts by weight to 40 parts by weight with respect to 00 parts by weight. Subsequently, the same material as that of the tube 1 of the charging member manufacturing example 1 was used.
It was injected into a mold having a thickness of 0.5 mm and a thickness of 250 μm, and was molded to produce a tube. The charging roller 4 was obtained by inserting the rubber roller 2 into the conductive tube obtained here. The surface area of the elastic portion of the obtained charging roller 4 is 8.7 × 10
^-3 (m ² ), and Asker C hardness was 67 degrees.

<< Charging Member Production Example 5 >> 20 parts by weight of conductive carbon black, 10 parts by weight of titanium oxide, 4 parts by weight of a vulcanizing agent, 4 parts by weight of a vulcanization aid, 100 parts by weight of NBR (nitrile rubber), vulcanization 3 parts by weight of an accelerator were mixed, kneaded by a pressure kneader, pulverized by a pulverizer, and then pelletized by a single screw extruder. The pellets are vulcanized at 150 ° C. for 60 minutes in a vulcanizing tube using an extruder. The tube was further processed by polishing to obtain a conductive tube having an inner diameter of 10.5 mm and a thickness of 500 μm.

Subsequently, air was blown into the conductive tube to enlarge the outer diameter, and the rubber roller 1 of the charging member manufacturing example 1 was expanded.
Was inserted to cover the conductive tube to obtain a charging roller 5. The surface area of the elastic portion of the obtained charging roller 5 is 8.7.
× 10 ^-3 (m ² ), and Asker C hardness was 55 degrees.

<< Charging Member Production Example 6 >> In the charging member production example 1, the inner diameter of the produced tube 1 was changed from 10.5 mm to 1 mm.
A charging roller 6 was obtained in the same manner except that the diameter was changed to 0 mm. The surface area of the elastic portion of the obtained charging roller 6 is 8.
It was 7 × 10 ⁻³ (m ² ), and Asker C hardness was 61 degrees.

(Photoreceptor Production Example 1) Four functional layers are provided on an aluminum cylinder having a diameter of 30 mm.

The first layer is a subbing layer, which is a conductive layer having a thickness of about 20 μm and provided for equalizing defects and the like of the aluminum drum and for preventing the occurrence of moire due to reflection of laser exposure. is there.

The second layer is a positive charge injection preventing layer, which functions to prevent the positive charge injected from the aluminum support from canceling the negative charge charged on the surface of the photoreceptor. 10 ⁶ by nylon
This is a medium resistance layer having a film thickness of about 1 μm whose resistance is adjusted to about Ω · cm.

The third layer is a charge generation layer having a thickness of about 0.3 μm in which a titanyl phthalocyanine pigment is dispersed in a resin.
m, and generate a positive and negative charge pair when subjected to laser exposure.

The fourth layer is a charge transport layer, in which hydrazine is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charge charged on the photoreceptor surface is
This layer cannot be moved, only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor, and the film thickness is 15 μm. The resistance of the photoreceptor surface was 3 × 10 ¹⁵ Ω · cm in the case of the charge transport layer alone.

(Photoreceptor Production Example 2) Five functional layers are provided on an aluminum cylinder of φ30 mm. 1st layer, 2nd layer
The layer, the third layer, and the fourth layer are manufactured in the same manner as in Photoconductor Production Example 1, and a charge injection layer is formed on the fifth layer. The charge injection layer is obtained by dispersing SnO ₂ ultrafine particles in a photocurable acrylic resin. Specifically, antimony-doped SnO ₂ particles having a particle diameter of about 0.03 μm and having a reduced resistance are formed of resin 1
It is obtained by dispersing 170 parts by mass, 20 parts by mass of tetrafluoroethylene resin particles and 1.2 parts by mass of a dispersant with respect to 00 parts by mass. As a result, the resistance of the photoconductor surface becomes 4 ×
It is 10 ¹² Ω · cm.

{Charging Device 1} As a charging device, a laser beam printer (Las by Hewlett-Packard Company) was used.
er Jet 4plus) was prepared. "Laser
FIG. 1 shows a configuration diagram of “Jet 4plus”. In FIG. 1, reference numeral 12 denotes a charging member. Reference numeral 11 denotes an electrophotographic photosensitive member, which is a member to be charged, and is rotationally driven at a predetermined peripheral speed (a process speed of 95 mm / s) in a clockwise direction indicated by an arrow. Both ends of the charging roller 12 are abutted against the photoconductor with a constant load by a pressure spring, and are driven to rotate by the rotation of the photoconductor.

This “Laser Jet 4plus”
Was modified as follows to obtain a charging device 1. Charging device 1
FIG. 2 shows a configuration diagram of an electrophotographic apparatus to which is applied. The cleaning blade 19, the developing device 13, and the transfer roller 14, which is a transfer member, were removed from the process cartridge to eliminate the possibility of potential fluctuation due to frictional charging between these members and the photosensitive member. Subsequently, the voltage applied to the charging roller 22 is used as an external power supply, and it is possible to apply any of a DC voltage and a superimposed voltage of a DC voltage and an AC voltage.

{Charging Apparatus 2} The method of rotating the charging roller 22 in the charging apparatus 1 is changed from the method of rotating the photosensitive roller following the photosensitive member, and an apparatus for rotating and driving the charging roller 22 is attached.
The driving speed was changed to a peripheral speed difference of 120% from the photosensitive member. The voltage applied to the charging roller 22 is an external power supply,
An external power supply capable of applying either a DC voltage or a superimposed voltage of a DC voltage and an AC voltage was used.

[0071]

The present invention will be described below in more detail with reference to specific examples.

Example 1 Zinc oxide (doped with aluminum), which is a conductive particle, was applied to the surface of the charging member production example 1 to form a charging particle layer having a conductive particle layer, which was designated as charging member production example 1A. The average particle size of zinc oxide is 3.6 μm
And the volume resistivity of each environment is as follows.

Normal environment {23 ° C./60% RH, (N
/ N environment): 2.6 × 10 ⁶ Ω · cm Low temperature and low humidity environment {15 ° C./10%RH, (L / L environment)}:
4.8 × 10 ⁷ Ω · cm High temperature and high humidity environment {30 ° C./80% RH, (H / H environment)}:
3.4 × 10 ⁵ Ω · cm

As a coating method, a method of preparing a 10% diluted solution in which zinc oxide was uniformly dispersed in an isopropyl alcohol (IPA) solution using a homogenizer and applying the solution to the surface of the charging member by spray coating was used. . At this time, it is necessary to calculate in advance the coating efficiency of the spray coating machine when the coating material to be attached to the charging member is used, and to determine the coating amount from the calculated coating efficiency. In this case, coating was performed by adjusting the amount of application so that the amount of adhesion to the charging member was 0.09 g.

<Evaluation Method of Charging Member> Charging member volume resistivity evaluation Low temperature and low humidity environment (15 ° C / 10% RH, (L / L environment)), normal environment (23 ° C / 60% RH, (N / N environment)), high temperature and high humidity environment (30 ° C) / 80% RH, (H / H
Environment) In (2), measure the volume resistivity of the charging member. A method for measuring the volume resistivity of the charging member is as follows. A good conductive thin film such as an aluminum foil is formed around the charging member by a width of 1 cm and a length of 10 cm.
cm, and wound tightly, applying a DC voltage (250 V) to both ends of the conductive support and the thin film and applying a tester (HIOKI 3116 DEGIAL MΩ H).
ITESTER) and apply DC voltage 250V, 10
The value after seconds was read.

II. Evaluation of Charging Potential Using the charging device 1, a charging member manufacturing example 1A was used for the charging member.
The photoreceptor production example 2 was incorporated into the photoreceptor, and the charging method was an injection charging method. The charging member is applied with a voltage from an external power supply to the charging member, and a surface electrometer (Model 34, manufactured by Trek).
4A), the charging potential of the photoconductor is measured in each environment. The value of the saturation potential after voltage application was adopted as the charging potential. Environment setting is low temperature and low humidity environment @ 15 ℃ / 10% RH,
(L / L environment)｝, normal environment ｛23 ° C / 60% RH,
(N / N environment)｝, high temperature and high humidity environment ｛30 ℃ / 80% R
H, (H / H environment)}. The applied voltage of the charging member is
The following changes are made depending on the charging method.

In the case of using the photoreceptor production example 1: DC voltage -700 V AC voltage 1.5 kV (peak-to-peak voltage) In the case of using the photoreceptor production example 2: DC voltage -700 V

As a result, it was confirmed that there was almost no change in the environment of the charging member, and that both the volume resistivity and the charging potential of the photosensitive member were very stable.

Table 1 shows a list of means for combining Example 1 with members of Examples 2 to 13 and Comparative Examples 1 to 4 described later. The method of applying the conductive particles to the surface of the charging member was the same as in Example 1. Table 2 shows the results of the volume resistivity and the charging potential of the photosensitive member of the charging members of Examples 1 to 13 and Comparative Examples 1 to 4. The method for measuring the volume resistivity and the method for measuring the charged potential were the same as those in Example 1.

Example 2 The conductive particles applied to the surface of the charging member production example 1 were anatase type titanium oxide. The average particle size of the anatase type titanium oxide is 0.2 μm,
The volume resistivity of each environment is as follows.

N / N environment: 1.4 × 10 ⁷ Ω · cm L / L environment: 1.1 × 10 ⁸ Ω · cm H / H environment: 2.4 × 10 ⁶ Ω · cm

As a result, the environment of the charging member hardly fluctuated, the volume resistivity and the charging potential of the photosensitive member were both very stable, and it was confirmed that the present invention was effective regardless of the type of the conductive particles. .

(Embodiment 3) Using the charging member manufacturing example 2,
The conductive tube material was changed from SEBC to a polyurethane-based thermoplastic elastomer. The type, amount and method of application of the conductive particles were the same as in Example 1. As a result, there was almost no change in the environment of the charging member, and both the volume resistivity and the charging potential of the photoreceptor were very stable. It was confirmed that the present invention was effective regardless of the molding material.

(Example 4) In Example 1, the photosensitive member to be used is the photosensitive member manufacturing example 2, and the charging method is A
The method was changed to a charging method using C discharge. As a result, it was confirmed that there was almost no change in the environment of the charging member, and that both the volume resistivity and the charging potential of the photoconductor were very stable. At the same time, when the charging methods were compared, it was simultaneously confirmed that the injection charging method was more environmentally friendly than the AC charging method.

(Example 5) The volume resistivity was adjusted as follows by adjusting the treatment amount of aluminum oxide doping of zinc oxide used in Example 1. A charging member was produced by the same application amount and application method as in Example 1 of the conductive particles having an average particle diameter of 3.6 μm.

N / N environment: 2.4 × 10 ⁸ Ω · cm L / L environment: 1.4 × 10 ⁹ Ω · cm H / H environment: 6.3 × 10 ⁷ Ω · cm

As a result, although the volume resistivity was slightly higher, it was confirmed that there was almost no change in the environment of the charging member, and that both the volume resistivity and the charging potential of the photosensitive member were very stable.

Example 6 A conductive particle layer was provided on the surface of a tube-type charging member in the same manner as in Example 1, except that the average particle diameter of zinc oxide (aluminum doping) was 12 μm. The volume resistivity of each environment is as follows.

N / N environment: 3.1 × 10 ⁶ Ω · cm L / L environment: 4.2 × 10 ⁷ Ω · cm H / H environment: 7.5 × 10 ⁵ Ω · cm

Although the coating efficiency during the formation of the conductive particle layer was slightly lower, as a result there was almost no fluctuation in the environment of the charging member, and both the volume resistivity and the charging potential of the photosensitive member were very stable. A sufficient effect was obtained as a particle layer.

(Examples 7 and 8) In Example 1, the difference in characteristics was confirmed by varying the amount of zinc oxide applied to the surface of the charging member. In Example 7, some of the conductive particles fell on the photoreceptor, probably because the coating amount was excessive during the measurement of the charging potential. However, there is no practical problem since the amount is very small and charging unevenness does not occur. In Example 8, although the coating amount was slightly insufficient, as a result, there was almost no fluctuation in the environment of the charging member, the volume resistivity and the charging potential of the photoreceptor were both very stable, and sufficient for the conductive particle layer. The effect was obtained.

(Embodiment 9) Using Production Example 4 of the charging member,
The environmental dependency when the tube molding method was injection molding was confirmed. As a result, there was almost no change in the environment of the charging member, the volume resistivity and the charging potential of the photosensitive member were both very stable, and it was confirmed that the present invention was effective regardless of the molding method.

Example 10 In Example 1, the difference in environmental characteristics was confirmed by changing the method of rotating the charging member to the method of following the photosensitive member. As a result, it was confirmed that the charging potential was lowered in each environment and the injection efficiency was deteriorated, but the environment of the charging member was hardly changed, and both the volume resistivity and the photoconductor charging potential were very stable. Confirmed that.

Example 11 In Example 1, the material of the charging member was changed from a thermoplastic elastomer to a rubber material. As a result, it was confirmed that there was almost no change in the environment of the charging member, and that both the volume resistivity and the charging potential of the photoconductor were very stable. However, it was also confirmed that the processability was difficult as compared with the thermoplastic elastomer, and that a contact trace due to the leakage of the vulcanizing agent in the surface layer was observed on the contact surface (end: non-image portion) of the photoreceptor.

Example 12 In Example 1, the difference in environmental characteristics was confirmed by changing the inner diameter of the conductive tube. As a result, it was confirmed that the charging potential was lowered in each environment and the injection efficiency was deteriorated, but the environment of the charging member was hardly changed, and both the volume resistivity and the photoconductor charging potential were very stable. Confirmed that. When the charging member was removed from the charging device and the charging member was observed, it was confirmed that the outer diameter was smaller than in Example 1, and the contact nip width was reduced.

(Comparative Examples 1 to 3) In the manufacturing process of the charging member manufacturing example 1, the rubber roller 1 (elastic layer) before coating the tube was set as a comparative example 1, and the charging member manufacturing example 3 was set as a comparative example 2. Comparative Example 3 was a charging member in which a conductive film layer was formed on the surface of the charging member manufacturing example 3 by the same type, application amount, and application method as in Example 1. In Comparative Example 1, when the elastic layer alone was used, the volume resistivity and the charging potential of the photosensitive member were both very stable. However, when the elastic layer was incorporated into the charging device and left in the H / H environment for one day, the contact streaks appeared on the photosensitive member. confirmed. This is considered to be due to contamination or deterioration of the photoconductor due to leakage of the additive in the elastic layer. In Comparative Example 2 and Comparative Example 3, environmental fluctuation was large due to formation of a surface layer by coating, and both volume resistivity and charging potential fluctuated significantly.

(Comparative Example 4) In Comparative Example 3, the photosensitive member used was Photosensitive member production example 1, and the charging method was A
The method was changed to a charging method using C discharge. As a result, environmental fluctuations are particularly large compared to the injection charging method, and the volume resistivity,
The charging potential also fluctuates greatly. In the H / H environment, a leak occurred between the charging member and the photosensitive member during the measurement of the charging potential.

[0098]

[Table 1]

[0099]

[Table 2]

[0100]

According to the present invention, the charging member for charging the surface of the image bearing member in contact with the surface of the image bearing member is a single-layer or multi-layer conductive tube provided outside the conductive elastic layer. The present invention provides an image forming apparatus that is less dependent on the environment since the outermost surface has a conductive particle layer covered with conductive particles.

[Brief description of the drawings]

FIG. 1 is a schematic view of a process cartridge and peripheral devices used in the present invention.

FIG. 2 is a schematic view of a charged potential measuring device used in the present invention.

FIG. 3A is a cross-sectional view of a charging roller of the present invention having a single-layer surface layer and an outermost surface layer on an elastic layer. FIG. 3B is a cross-sectional view of the charging roller of the present invention having a plurality of surface layers and an outermost surface layer on an elastic layer.

FIG. 4 is a schematic view of measuring the volume resistivity of the conductive particles used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Photoconductor 12 Charging roller 13 Toner carrier (developing device) 131 Developing roller 132 Coating roller 133 Coat control blade 14 Transfer roller 15 Feed roller 16 Exposure means 17 Fixing device 18 Cleaning device 21 Photoconductor 22 Charging roller 25 Feeding Roller 27 Fixer 29 Photoconductor surface electrometer 3a Conductive support 3b Conductive elastic layer 3c Surface layer 3c1 Surface layer 1 3c2 Surface layer 2 3d Top surface layer A Measurement cell 41, 42 Electrode 43 Guide ring 44 Ammeter 45 Voltage Total 46 Constant voltage device 47 Measurement sample 48 Insulator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Fumihiro Arahira, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shuichi Aida 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Hiroshi Koyama 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H003 AA00 BB11 CC05 2H068 AA05 AA06 AA08 AA21 BB03 BB31 BB33 FC01

Claims (16)

[Claims] 1. A charging member for charging a surface of an image carrier by contacting the surface of the image carrier, wherein the charging member is provided with a single-layer or multiple-layer conductive tube outside a conductive elastic layer, A charging member having a conductive particle layer covered by conductive particles on the outermost surface. 2. The charging member according to claim 1, wherein the conductive particles have a volume resistivity of 1 × 10 ¹⁰ Ω · cm or less. 3. The charging member according to claim 1, wherein the conductive particles have an average particle size of 10 μm or less. 4. The adhesion amount of the conductive particles on the surface of the charging member is 0.1 × S (g) <the adhesion amount (g), where S (m ² ) is the surface area of the elastic portion of the charging member. The charging member according to claim 1, wherein the charging member has a range of 50 × S (g). 5. An image forming apparatus comprising the charging member according to claim 1 and an image carrier, wherein the image carrier comprises:
Having a photosensitive layer on a conductive support and a charge injection layer in a layer farthest from the conductive support, wherein the charge injection layer is injected with charge through a contact portion with the charging member; An image forming apparatus, which is an electrophotographic photosensitive member. 6. The charge injection layer according to claim 1, wherein said charge injection layer is 1 × 10 ⁸ Ω · cm or more.
The image forming apparatus according to claim 5, wherein the image forming apparatus has a volume resistivity of 1 × 10 ¹⁵ Ω · cm. 7. The image forming apparatus according to claim 5, wherein the charge injection layer is made of conductive fine particles and a binder resin. 8. The image forming apparatus according to claim 5, wherein the charge injection layer contains a lubricant powder. 9. The image forming apparatus according to claim 8, wherein the lubricant powder is selected from a fluorine resin, a silicone resin, and a polyolefin resin. 10. The charging member according to claim 1, wherein the conductive tube is formed by an extruder. 11. The charging member according to claim 1, wherein the conductive tube is formed of a thermoplastic elastomer. 12. The conductive tube has a weight of 10 kg / cm.
The charging member according to claim 10, having a 100% modulus in a range of ^{2 to} 90 kg / cm ² . 13. The conductive tube according to claim 10, wherein the inner diameter A of the conductive tube is formed in the range of (5/6) × B ≦ A <B with respect to the outer diameter B of the conductive elastic layer. Charging member. 14. The charging member according to claim 10, wherein the charging member has an Asker C hardness of 70 degrees or less. 15. The material used for the conductive tube is 1
The charging member according to claim 10, having a Vicat softening point of 50 ° C. or less. 16. The image forming apparatus according to claim 5, wherein the charging member moves in a direction opposite to the image carrier with a constant peripheral speed difference.
An image forming apparatus according to claim 1.