JPH09204089A - Electrifying member and electrifying device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member and an electrifying device using the electrifying member where toner particles and paper powder are restrained from adhering and sticking to the surface of an electrifying roller and the durability of the electrifying roller is improved. SOLUTION: In this device, DC voltage is used as voltage impressed on a conductive supporting body 101. Then, an elastic layer 102 composed of a semiconductive elastic body is formed on the conductive supporting body 101. Furthermore, a surface layer 103 formed on the elastic layer 102 is formed to include water-polyurethane resin containing hydrophobic silica and have the ratio of the solid components of polymer/silica being 95/5 to 80/20.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to PPC, LBP,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used for primary charging in an electrophotographic image forming apparatus such as a FAX and a charging device using the same, and more particularly to a charging member having a semiconductive elastic body formed on a conductive support and the same. Relates to a charging device using.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a corona discharger has been widely used as a charging method for uniformly charging the entire surface of an image carrier (photoconductor).

This corona discharger is effective as a means for uniformly charging the photoconductor to a certain potential, but on the contrary, it has the following disadvantages. That is, the charging process by the corona discharger requires a high-voltage power source, and ozone is generated with the discharge. In addition, the large amount of ozone generated not only adversely affects the environment but also deteriorates the charging member and the photoconductor due to ozone.

On the other hand, a contact roller charging system in which a charging roller is brought into contact with a photosensitive member and a voltage is applied while being driven to rotate to charge the photosensitive member is disclosed in, for example, Japanese Patent Laid-Open No. 63-16.
No. 7380, “AC induction charging device”. The contact roller charging method disclosed in Japanese Patent Laid-Open No. 63-167380 has the advantages of lowering the voltage of the power source and the amount of ozone generated as compared with the corona charging method, but the charging is uniform. Inferior in terms of sex.

In order to improve the charging uniformity, for example, in the "contact charging method" disclosed in Japanese Patent Laid-Open No. 63-149668, the charging start voltage is doubled when the DC voltage is applied. It is disclosed that the uniformity of charging can be improved by superimposing the AC voltage having the above peak voltage. However, in the contact charging method of charging by applying a voltage in which the AC voltage and the DC voltage are superimposed, the AC voltage of the charging device gives an unpleasant environment as a charging sound due to mechanical vibration, and The consumption of a large amount of alternating current causes a problem that the reduction of ozone generation is impaired.

Although these inconveniences are solved by applying only a DC voltage to the charging device to carry out charging, there is a problem that it is difficult to obtain uniform charging. Japanese Patent Laid-Open No. 5-
According to Japanese Patent No. 341627, by using epichlorohydrin rubber, which is semiconductive by itself, in an elastic layer of a charging member (charging roller), charging uniformity and withstand voltage are improved.

[0007]

However, according to the charging member in which the elastic layer mainly composed of epichlorohydrin rubber is formed on the above-mentioned conventional conductive support, the non-adhesive surface is formed on the semiconductive elastic layer. Although a layer is formed, when it is used as a charging roller of a copying machine for a long time, residual toner particles that have slipped through the cleaning unit and remain on the photosensitive member as it is, are entirely or entirely on the surface of the charging roller in contact with the photosensitive member. Since they adhere to each other in the form of streaks, the electric resistance of the charging roller increases, the charging potential lowers, the image density decreases, and streaky image unevenness occurs. In other words, this problem is that the durability of the charging roller is low.

The present invention has been made in view of the above-mentioned conventional problems, and suppresses toner particles, paper powder, and the like from adhering or adhering to the surface of the charging roller, thereby improving the durability of the charging roller. It is an object of the present invention to provide a charging member capable of improving the charging efficiency and a charging device using the charging member.

[0009]

In order to solve the above problems, the charging member according to claim 1 of the present invention is a charging member having a semiconductive elastic body on a conductive support, wherein the semiconductive A surface layer including an aqueous polyurethane resin layer containing hydrophobic silica is provided on the elastic body.

The charging member according to a second aspect of the present invention is the charging member according to the first aspect, wherein the water-based polyurethane resin of the surface layer and the hydrophobic silica have a solid content ratio of 95/5 as a ratio of polymer to silica. -80/20.

The charging member according to claim 3 is the charging member according to claim 1 or 2, wherein the surface layer has a volume resistance in the range of 10 ⁸ to 10 ¹² [Ω · cm]. .

A charging member according to a fourth aspect is the charging member according to the first, second or third aspect, wherein the thickness of the surface layer is in the range of 5 to 20 [μm].

Further, according to a fifth aspect of the present invention, there is provided a charging device, wherein the charging member according to the first, second, third or fourth aspect is used, in a state where the charging member is in contact with an image carrier, the conductive support member is used. A direct current voltage is used as the voltage applied to.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an outline of a charging member of the present invention and a charging device using the same, and examples of a charging member of the present invention and a charging device using the same will be described.
[First Embodiment], [Second Embodiment], [Third Embodiment], and [Fourth Embodiment] will be described in detail with reference to the drawings.

[Outline of Charging Member of the Present Invention and Charging Device Using the Same] A charging member according to the present invention and a charging device using the same use a DC voltage as a voltage applied to a conductive support, and An elastic layer made of a semi-conductive elastic body is formed on a conductive support, and a surface layer formed on the elastic layer contains a water-based polyurethane resin containing hydrophobic silica and is made of a polymer. / Silica solid content ratio is 95
/ 5 to 80/20, whose electric resistance is 10 ⁸ to 10 ¹² [Ω
.Cm], and the thickness thereof is 5 to 20 [μm].

(Shape and Structure of Charging Member of the Present Invention) The charging member of the present invention is, for example, in the shape of a roller as shown in FIG. 1, and includes a conductive support 101 in the form of a core metal and a conductive support. Semi-conductive elastic layer 1 provided around the body 101
02 and the surface layer 1 formed on the outer peripheral surface of the elastic layer 102.
And 03.

In FIG. 1, the conductive support 101,
An adhesive layer that improves the adhesiveness between the elastic layer 102 and the surface layer 103 may be provided. For example, the conductive support 1
01 may be treated with a conductive primer such as synthetic rubber containing a conductive substance such as carbon black.

As the conductive support 101, a metal such as iron, stainless steel or aluminum, a conductive resin such as a carbon black dispersed resin or a metal particle dispersed resin can be used.

The semiconductive elastic layer 102 preferably has an electric resistance in the range of 10 ⁷ to 10 ⁹ [Ω · cm]. As the material, polar rubber such as epichlorohydrin rubber, nitrile rubber, urethane rubber, chloroprene rubber, and acrylic rubber can be used. Among them, the electric resistance of the rubber itself is low and the electric resistance has little environmental dependence. Further, epichlorohydrin rubber is preferable because the increase in electric resistance is extremely low even when a DC voltage is continuously applied to the roller for a long period of time.

The raw material rubber for epichlorohydrin rubber is a homopolymer of epichlorohydrin, a copolymer of epichlorohydrin and ethylene oxide, a copolymer of epichlorohydrin and allyl glycidyl ether, and a ternary compound of epichlorohydrin, ethylene oxide and allyl glycidyl ether. There is a system copolymer (abbreviation: GECO). Among them, GECO has a relatively low electric resistance, little environmental dependence of electric resistance, and an extremely small increase in electric resistance due to energization. Is preferred.

The elastic layer 102 has a layer thickness of 0.5 to 10 [m].
m] is preferable. The reason is that when the thickness of the semi-conductive elastic layer 102 becomes thinner than 0.5 [mm], the photoreceptor is dielectrically broken or the charging potential becomes unstable. Also, if the thickness is more than 10 [mm], the current necessary for charging does not flow sufficiently, resulting in insufficient charging.

The surface layer 103 formed on the outer peripheral surface of the elastic layer 102 has a thickness of 5 to 20 [μm] and an electric resistance of 10 ⁸ to 10 ¹² [Ω · cm]. Is preferred. The reason is that when the thickness is less than 5 [μm] and the electric resistance is less than 10 ⁸ [Ω · cm], the photoconductor has a defect such as a pinhole due to some cause (for example, a dent or a foreign substance). However, because the current concentrates on that part and a voltage drop occurs, the desired charging potential cannot be obtained in the pinhole part in the longitudinal direction of the charging roller (contacting direction of the charging roller). This is because the reversal phenomenon, which is common in printers and the like, results in a black band, which significantly deteriorates the image quality. Also,
The surface layer 103 has a thickness of 20 [μm] and an electric resistance of 10 ¹²
If they exceed [Ω · cm], uneven charging and insufficient charging are likely to occur, resulting in image unevenness and insufficient image density.

Further, by using an aqueous polyurethane resin containing hydrophobic silica added to the surface layer 103, the surface layer 103 has excellent non-adhesiveness with respect to toner and the like, and the durability of the charging member can be improved. .

Here, the amount of the hydrophobic silica added to the water-based polyurethane resin is 95 in terms of polymer / silica solid content ratio.
The range of / 5 to 80/20 is preferable. The reason is that if the amount of silica added is less than 95/5, the effect of improving the non-adhesiveness to the toner due to the addition of silica is difficult to obtain, and if the amount added is 80/2.
If it exceeds 0, the hardness of the surface layer 103 becomes too high, and the driven rotation with the photoconductor drum becomes unstable, which may cause uneven charging.

The water-based polyurethane resin is a water-soluble type or self-dispersing type by imparting some hydrophilic groups or hydrophilic segments to a urethane elastomer having a crosslinked structure and does not contain a surfactant. . The reason is that if the surface active agent is contained even a little, it will contaminate the surface of the photoconductor and cause a horizontal stripe-shaped abnormal image at the photoconductor drum pitch or the charging roller pitch. .

The resin is classified into a reactive type and a non-reactive type depending on the presence or absence of reactivity. The reactive type is a type that has reactivity such as a blocked isocyanate group in the structure and regenerates free isocyanate by a treatment such as heating to carry out a crosslinking reaction. The non-reactive type has no reactive group in the structure. A strong coating can be formed by either air drying or heat drying. These resins are marketed by Dai-ichi Kogyo Seiyaku Co., Ltd. under the names of "Elastron" series for reactive type and "Superflex" series for non-reactive type.

Conventional aqueous resin emulsions and latexes such as vinyl acetate emulsion, ethylene vinyl acetate emulsion, vinyl chloride emulsion rubber latex,
Since chloroprene rubber latex contains an emulsifier and a dispersant, they are leached on the surface after forming the surface layer, and the leached emulsifier and dispersant contaminate the surface of the photoconductor. Doing so causes a problem of image deterioration.

Although the charging roller of the present invention, which has only the water-based polyurethane resin as the surface layer, has a durability of about 5 to 10 [K sheets], it is not suitable for mounting on a device requiring higher durability. However, due to lack of non-adhesiveness to toner, toner adheres to the roller surface, resulting in insufficient charging.
However, when hydrophobic silica is added to the water-based polyurethane resin, the non-adhesiveness to the toner can maintain the initial characteristics for a long time.

(Structural Example of Charging Device of the Present Invention) Next, the structure of the charging device of the present invention using the charging member will be described with reference to FIG. In the figure, 201 indicates a charging member of the present invention, and here, the roller-shaped charging member shown in FIG. 1 is used. Further, 202 is the charging member 201.
2 shows a DC power supply for applying a DC voltage to the core metal. The charging member 201 and the DC power source 202 constitute the charging device of the present invention.

FIG. 2 shows an example in which the charging device of the present invention is applied to an electrophotographic device. This electrophotographic device has a primary charging member 20 on the peripheral surface of a drum-shaped electrophotographic photosensitive member 203.
1, an image exposure device (not shown), a developing unit 204, a transfer charging device 205, a cleaning device 206, and a pre-exposure device (not shown) are arranged. In the figure, reference numeral 207 is exposure light emitted from the image exposure device, and 208 is exposure light.
Is the pre-exposure light of the pre-exposure device, and 209 is the transferred member such as paper.

For example, an electrophotographic photosensitive member 203 such as OPC
The primary charging member (charging member 20) disposed in contact therewith
The voltage (for example, −
1400 [V]) is applied to charge the surface of the electrophotographic photosensitive member 203, and the image on the original is exposed to the electrophotographic photosensitive member 203 by an image exposure device to develop an electrostatic latent image.

Next, the developer in the developing unit 204 is made to adhere to the electrophotographic photosensitive member 203 to develop the electrostatic latent image on the electrophotographic photosensitive member 203, and further to develop on the electrophotographic photosensitive member 203. The transfer charging device 205 transfers the agent
The cleaning device 2 transfers the image to a transfer target member 209 such as paper.
At 06, the developer remaining on the electrophotographic photosensitive member 203 without being transferred to the paper at the time of transfer is collected. Further, when residual charge remains on the electrophotographic photosensitive member 203, it is preferable to remove the residual charge on the electrophotographic photosensitive member 203 by a pre-exposure device before performing the primary charging by the charging member 201.

The process leading to the present invention has been described above by explaining the shape and constitutional example of the charging member of the present invention and the constitutional example of the charging device of the present invention. The charging uniformity of the charging member 201 of the present invention, which is to obtain the charging, is different from that of the conventional charging roller (for example, JP-A-64-73364 and JP-A-64-73367) which is left to superimpose an AC voltage. Naturally, the electrical characteristics (R, C) and the layer structure of the roller are greatly different. That is, the AC voltage superposition type is composed of a conductive elastic layer (rubber in which conductive particles such as carbon black are dispersed) and a surface resistance layer. Since the surface resistance layer functions as a capacitor, the electrostatic capacity is large and the AC voltage is large. The effect of equalizing the charging potential by superposition is great.

On the other hand, in the type only applying the DC voltage of the present invention, since the roller layer acts as a resistor (that is, the electrostatic capacity is small), even if the AC voltage is superposed, the charging can be made uniform. Contributed little.

[Embodiment 1] Next, various embodiments of the charging member of the present invention will be described. In the first embodiment, the charging member (charging roller) is manufactured by the following method.

First, as the conductive support 101, φ8
A [mm] stainless steel core is used. Next, the semiconductive elastic layer 102 is made of the following compound. GECO-based epichlorohydrin raw material rubber (Product name: Epichroma CG102, manufactured by Daiso) 100 parts by weight Calcium carbonate (Product name: Tamapearl TR-222H, manufactured by Okutama Industry Co., Ltd.) 30 parts by weight Sub (Product name: GT, manufactured by Tenma Sub Chemical Co., Ltd.) 10 parts by weight Part Stearic acid 0.5 part by weight Vulcanization accelerator (trade name: Noxera TT, manufactured by Ouchi Shinko Kagaku) 1.0 part by weight Vulcanization accelerator (trade name: Noxera DM, manufactured by Ouchi Shinko Kagaku) 1.5 Parts by weight Vulcanization accelerator (Brand name: Barnock R, manufactured by Ouchi Shinko Chemical) 1.0 parts by weight Vulcanization agent (Brand name: Salfax, manufactured by Tsurumi Chemical) 0.25 parts by weight Incidentally, the composition ratio of GECO epichlorohydrin Is epichlorohydrin 40 [mol%], ethylene oxide 53
[Mol%], allyl glycidyl ether 7 [mol
%].

After the above mixture was kneaded to form a compound having a uniform composition, primary vulcanization (150 [° C.] × 15) was performed on a stainless steel core bar (conductive support 101) of φ8 [mm].
[Min]) and secondary vulcanization (155 [° C.] × 7 [hours]) to form an outer diameter φ14 [mm] × 310 [mm], and the roller-shaped semiconductive elastic layer 102. Was set up.

The electric resistance of this semiconductive elastic roller is 2 ×.
10 ⁷ [Ω · cm], roller rubber hardness 38 [degrees] (J
wasA). The volume resistance of the semi-conductive elastic roller was measured at 20 [° C], 60 [%
25.4 after being left in the environment of R, H] for 16 hours
[Mm] width copper foil tape (Product name: Scotch No. 11)
81, 3M) is wound around the circumference of a semi-conductive elastic roller to form an electrode, and a direct current of 1 [KV] is applied between the roller core metal and the electrode.
Was applied, and the current value after 1 [minute] was measured to obtain the resistance value between the roller core metal and the electrode. Further, the rubber hardness of the semiconductive elastic roller was measured by using a hardness meter JisA described in JisK6301 by applying pressure perpendicular to the central axis direction of the semiconductive elastic roller.

Next, the surface layer 103 was formed on the semiconductive elastic roller as follows. First, the coating material for the surface layer was prepared as follows.

First, the hydrophobic silica is treated with ethanol / water = 1.
The liquid dispersed in 1/1 is prepared as follows. That is, 1
Add 1 part of hydrophobic silica (trade name: Aerosil R972, made by Nippon Aerosil) to 100 parts of ethanol / water of 1/1, and disperse the silica sufficiently with an ultrasonic disperser to disperse the hydrophobic silica. It was a liquid.

Next, a non-reactive water-based urethane resin (trade name: Superflex 107, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 10
0 superposition part, non-reactive type water-based urethane resin (trade name: Superflex 300, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 100 superposition part,
In addition, each of the above-mentioned hydrophobic silica dispersion 175 overlapping parts was added to obtain a uniform dispersion to obtain a coating liquid for the surface layer.

This coating liquid is dip-coated on a semiconductive elastic roller and then cured at 80 ° C. for 3 hours,
The surface layer 103 having a thickness of 8 [μm] was formed.

The electric resistance of the surface layer 103 is 3 × 10 ^10.
It was [Ω · cm]. The electric resistance of only the surface layer 102 was measured by applying a sample of aluminum plate (thickness 0.2 [mm]) coated with the surface layer coating material to a thickness of about 20 [μm] at 20 [° C.], After leaving it in 60 [% R, H] for 16 [hours], it was measured with a resistance meter (R8340A, manufactured by Advantest) using a resistance measurement cell (16008A, manufactured by YHP).

The charging roller (charging member) manufactured as described above is attached instead of the primary corona charger of the regular developing type copying machine FT5500 (manufactured by Ricoh), and brought into contact with the upper surface of the photoreceptor (OPC) drum. I was made to rotate driven. DC voltage as primary charging voltage-1.3 [KV]
Is applied and continuously operated in an environment of 24 ± 1 [° C.], 50-55 [%], 1000, 5000, 10000,
The potential measurement of the dark potential of the photoconductor for each of 15,000 and 20000 [sheets] (A3 size), the contamination state of the charging roller surface, and the image quality were measured and evaluated. Table 1 shows the results of measurement and evaluation of the charging roller of this example.

The state of contamination of toner on the surface of the charging roller was evaluated according to the following criteria. ⊚: A small amount of toner or the like is attached, but the attached matter on the roller surface can be easily wiped off with a cloth or the like. ◯: A small amount of toner etc. remains on the roller surface after wiping. Δ: The film cannot be completely wiped off, and a thin film of toner or the like remains on the roller surface. X: Toner or the like is strongly adhered to the roller surface.

[0046]

[Table 1]

[Embodiment 2] Next, a charging member (charging roller) according to Embodiment 2 of the present invention will be described. In this example, the surface layer 103 was formed on the semiconductive elastic roller similar to that of Example 1 as follows.

100 parts of non-reactive water-based urethane resin (trade name: Superflex 107, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 100 superposed parts of non-reactive water-based urethane resin (trade name: Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) , And a hydrophobic silica dispersion 688 superposed part equivalent to those in Example 1 were added to obtain a uniform dispersion to obtain a coating liquid for the surface layer.

This coating solution was applied on the semiconductive elastic roller by dip coating in the same manner as in Example 1, and then 80 [° C.], 3
It was cured for [time] to form a surface layer 103 having a thickness of 8 [μm]. Table 1 shows the measurement and evaluation results of the charging roller (charging member) manufactured as described above, as in Example 1.

[Comparative Example 1] Next, the charging roller of Comparative Example 1 will be described. In this comparative example, the surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows.

Non-reactive water-based urethane resin (trade name: Superflex 107, manufactured by Dai-ichi Kogyo Seiyaku) 100 superposed parts, non-reactive water-based urethane resin (trade name: super flex 300, manufactured by Dai-ichi Kogyo Seiyaku) 100 superposed parts , And a hydrophobic silica dispersion 115 superposed part equivalent to that of Example 1 were added to prepare a coating liquid for the surface layer.

Using this coating solution, a surface layer 103 was formed in the same manner as in Example 1. Table 1 shows the measurement and evaluation results of the charging roller manufactured as described above, as in Example 1.

[Comparative Example 2] Next, a charging roller of Comparative Example 2 will be described. In this comparative example, the surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows.

Non-reactive water-based urethane resin (trade name: Superflex 107, manufactured by Dai-ichi Kogyo Seiyaku) 100 superposed parts, non-reactive water-based urethane resin (trade name: Super flex 300, manufactured by Dai-ichi Kogyo Seiyaku) 100 superposed parts , And a hydrophobic silica dispersion 822 superposed part equivalent to that of Example 1 were added to prepare a coating liquid for the surface layer.

A surface layer 103 was formed using this coating liquid in the same manner as in Example 1. Table 1 shows the measurement and evaluation results of the charging roller manufactured as described above, as in Example 1.

[Embodiment 3] Next, a charging member (charging roller) according to Embodiment 3 of the present invention will be described. In this example, the surface layer 103 was formed on the semiconductive elastic roller similar to that of Example 1 as follows.

Non-reactive aqueous urethane resin (trade name: Superflex 107, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 100, and a hydrophobic silica dispersion similar to that of Example 20
Each of the four superposed parts was added to obtain a uniform dispersion liquid, which was used as a coating liquid for the surface layer.

Using this coating liquid, the surface layer 103 was formed in the same manner as in Example 1. Regarding the charging roller (charging member) manufactured as described above, as in Example 1,
The results of measurement and evaluation are shown in Table 1.

[Embodiment 4] Next, a charging member (charging roller) according to Embodiment 4 of the present invention will be described. In this example, the surface layer 103 was formed on the semiconductive elastic roller similar to that of Example 1 as follows.

100 parts of non-reactive water-based urethane resin (trade name: Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and a hydrophobic silica dispersion similar to that of Example 24 24
Each of the four superposed parts was added to obtain a uniform dispersion liquid, which was used as a coating liquid for the surface layer.

Using this coating liquid, a surface layer 103 was formed in the same manner as in Example 1. Regarding the charging roller (charging member) manufactured as described above, as in Example 1,
The results of measurement and evaluation are shown in Table 1.

Comparative Example 3 Next, the charging roller of Comparative Example 3 will be described. In this comparative example, the surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows.

100 parts of non-reactive water-based urethane resin (trade name: Superflex 160, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and a hydrophobic silica dispersion liquid equivalent to that of Example 24 24
Each of the four superposed parts was added to obtain a coating liquid for the surface layer.

Using this coating solution, a surface layer 103 was formed in the same manner as in Example 1. Table 1 shows the measurement and evaluation results of the charging roller manufactured as described above, as in Example 1.

Comparative Example 4 Next, the charging roller of Comparative Example 4 will be described. In this comparative example, the surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows.

Non-reactive water-based urethane resin (trade name: Superflex E-2000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 100
Superimposed part and hydrophobic silica dispersion equivalent to that in Example 1
407 superposed parts were added to obtain a coating liquid for the surface layer.

Using this coating liquid, a surface layer 103 was formed in the same manner as in Example 1. Table 1 shows the measurement and evaluation results of the charging roller manufactured as described above, as in Example 1.

Comparative Example 5 Next, the charging roller of Comparative Example 5 will be described. In this comparative example, the surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows. That is, the surface layer 103 was formed in the same manner as in Example 1 except that the hydrophobic silica was completely removed from the formulation of the coating liquid of Example 1. Table 1 shows the measurement and evaluation results of the charging roller manufactured as described above, as in Example 1.

As described above, according to the first to fourth embodiments, by using the charging member of the present invention in the charging device applying the DC voltage, the initial characteristics of the non-adhesiveness with respect to toner and the like can be obtained over a long period of time. It becomes possible to maintain almost the same, and stable image quality can be obtained.

[0070]

As described above, according to the first aspect of the present invention,
According to the charging member described above, in a charging member having a semiconductive elastic body on a conductive support, a surface layer including an aqueous polyurethane resin layer containing hydrophobic silica is provided on the semiconductive elastic body. As a result, the non-adhesiveness of the surface of the charging member to the toner is improved, and stable charging characteristics can be obtained for a long period of time. As a result, it is possible to provide a charging member that can maintain good image quality.

According to the charging member of claim 2,
Regarding the water-based polyurethane resin and hydrophobic silica of the surface layer, the solid content ratio, which is the ratio of polymer to silica, is 95/5 to 8
Since it is set to 0/20, the non-adhesiveness of the surface of the charging member to the toner is improved, stable charging characteristics can be obtained for a long period of time, and as a result, a charging member capable of maintaining good image quality can be provided. it can.

According to the charging member of claim 3,
The volume resistance of the surface layer is 10⁸-10 ¹²Range of [Ω · cm]
Since the enclosure is enclosed, the withstand voltage of the charging member is improved.
Even if the drum has defective parts such as pinholes, it will leak.
Prevents the occurrence of abnormal images such as horizontal white lines on the drum pitch
Charging member capable of maintaining good image quality as a result
Can be provided.

According to the charging member of claim 4,
Since the thickness of the surface layer is in the range of 5 to 20 [μm],
The withstand voltage of the charging member is improved, and even if there is a defective portion such as a pinhole in the OPC drum, it is possible to prevent the occurrence of abnormal images such as drum pitch horizontal white streaks due to leaks, and as a result, good image quality can be maintained A charging member can be provided.

Further, according to the charging device of claim 5,
Since the charging member according to claim 1, 2, 3 or 4 is used in the state where the charging member is in contact with the image carrier, a DC voltage is used as the voltage applied to the conductive support,
Uniform charging is possible by applying only DC voltage. Compared with the conventional application of superimposed voltage by AC voltage and DC voltage,
The amount of ozone generated can be reduced and the cost of the power supply can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a shape and a configuration example of a charging member of the present invention.

FIG. 2 is an explanatory diagram showing a configuration example of a charging device using the charging member of the present invention.

[Explanation of symbols]

 Reference Signs List 101 conductive support 102 semi-conductive elastic layer 103 surface layer 201 primary charging member 202 DC power source 203 electrophotographic photoreceptor 204 developing unit 205 transfer charging device 206 cleaning device 207 exposure light of image exposure device 208 before pre-exposure device Exposure light 209 Transferred member

Claims (5)

[Claims] 1. A charging member having a semiconductive elastic body on a conductive support, wherein a surface layer including an aqueous polyurethane resin layer containing hydrophobic silica is provided on the semiconductive elastic body. And a charging member. 2. The charging member according to claim 1, wherein a solid content ratio, which is a ratio of polymer to silica, of the water-based polyurethane resin and the hydrophobic silica of the surface layer is 95/5 to 80/20. . 3. The surface layer has a volume resistance of 10 ⁸ to 10 ^8.
2. The range is ¹² [Ω · cm].
Or the charging member according to 2. 4. The thickness of the surface layer is 5 to 20 [μm].
The charging member according to claim 1, 2 or 3, wherein 5. The charging member according to claim 1, 2, 3 or 4, wherein a DC voltage is used as a voltage applied to the conductive support while the charging member is in contact with an image carrier. Charging device characterized in that