JP3440281B2 - Charging member and charging device - Google Patents

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 a charging device used in an image forming process such as an electrophotographic process or an electrostatic recording process.

[0002]

2. Description of the Related Art Conventionally, in a charging process in an electrophotographic process, a high voltage (DC 5 to 8 kV) is applied between a shield plate and a metal wire partially surrounded by the shield plate, and a corona generated causes a photoreceptor to be exposed. It is charged. However, with this configuration, when corona occurs, ozone and NO
There are problems that the corona product such as x deteriorates the surface of the photoconductor to promote image blurring and deterioration, and that the wire stain affects the image quality, resulting in white spots and black streaks in the image. On the other hand, in terms of electric power, the current flowing toward the photoconductor is 5 to 3
It is only 0%, and most of it flows to the shield plate surrounding the wire, which is inefficient as a charging device.

In order to make up for such drawbacks, JP-A-57-11
As disclosed in JP-A-78267 and JP-A-56-104351, a structure in which a charging member is brought into contact with a charged member such as a photosensitive member to directly charge the member is being studied. Conventionally, as a charging member used for direct charging, (a) NBR in which low resistance particles such as carbon black are dispersed and whose resistance is adjusted,
A conductive rubber roller having a core metal coated with a rubber material such as acrylic rubber or chloroprene rubber, or (b) JP-B-50-13.
A roller coated with nylon or polyurethane as described in Japanese Patent No. 661 is known.

However, in the conductive rubber roller in which low resistance particles are dispersed as in the former case (a), it is necessary to increase the amount of low resistance particles dispersed in order to maintain the low resistance, so that the rubber hardness is increased. In addition, there is a problem that the hardness of the low resistance particles scattered on the surface may scratch the surface of the charged body such as the photoconductor. If such scratches occur, image defects such as streaks will occur. Therefore, in order to solve this problem, add oil etc.,
If the hardness is made low, there is a problem that oil leaks to the surface of the rubber roller and pollutes the surface of the photoreceptor.

Further, in the case of the roller coated with nylon or polyurethane as in the latter case (b), the charging ability of the charged body such as the photoconductor is changed by the change of use environment, especially the humidity of the atmosphere. There is a problem that the charging ability drastically changes, and the charging ability is extremely lowered under low temperature and low humidity, for example. When the charging ability is lowered in this way, the charged body is not uniformly charged, and when an image is formed, the image density is lowered, and in the reversal development method, a spot-like black dot image (black However, a black and white image (white spot) is obtained in the positive development method, and a high-quality image cannot be obtained in any of them, and environmental safety is poor.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charging member and a charging device which are free from adverse effects such as scratches on the surface of a member to be charged and which are excellent in environmental stability.

Another object of the present invention is to provide a charging member and a charging device capable of uniformly charging a member to be charged without uneven charging, thereby obtaining a good image. .

Another object of the present invention is to provide a charging member and a charging device capable of charging an object to be charged with a relatively low voltage.

[0009]

The present invention has a thickness of 20 μm.
A surface layer containing a moisture permeable polyurethane resin having a water vapor permeability of 2000 or more and a water swelling degree of 5 or less and a water-insoluble inorganic salt of 2 to 50 parts by weight relative to 100 parts by weight of the moisture permeable polyurethane resin. It is a charging member characterized by having.

In the present invention, the moisture-permeable polyurethane resin is a resin obtained by reacting a polyol and a polyisocyanate in the presence of a chain extender, if necessary, and the polyol is a random copolymer of ethylene oxide and tetrahydrofuran. A polymer having a molar ratio of ethylene oxide and tetrahydrofuran of 40/60 in the copolymer.
It is characterized in that it is in the range of 80/20.

The present invention is also characterized in that the random copolymer has a molecular weight in the range of 600 to 3000.

[0012]

Further, the present invention is characterized in that the poorly water-soluble inorganic salt is one or more selected from the group consisting of calcium phosphate, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate and magnesium carbonate.

Further, according to the present invention, a metal support member, a conductive intervening layer provided on the outer peripheral surface of the support member and having elasticity, and a moisture permeability when formed on the outer peripheral surface of the intervening layer and having a thickness of 20 μm. Of 200 or more and a water swelling degree of 5 or less and 100 parts by weight of a moisture-permeable polyurethane resin and 2 to 50 parts by weight of a poorly water-soluble inorganic salt, and a surface layer in contact with a body to be charged are formed into a roll shape. And a charging member. Further, according to the present invention, a metal supporting member, a conductive intervening layer having a base end portion fixed to the supporting member and having elasticity, and an outer peripheral surface of the intervening layer are formed. As described above, a surface layer containing 100 parts by weight of a moisture-permeable polyurethane resin having a water swelling degree of 5 or less and 2 to 50 parts by weight of a poorly water-soluble inorganic salt, and having a surface layer in contact with the charged body near the free end of the intervening layer is included. However, the charging member is formed into a blade shape. The present invention also provides (a) an object to be charged, (b) a charging member, (b1) a metal supporting member, and (b2) a conductive member having elasticity provided on an outer peripheral surface of the supporting member. (B3) 100 parts by weight of a moisture-permeable polyurethane resin having a moisture permeability of 2000 or more and a water swelling degree of 5 or less formed on the outer peripheral surface of the intervening layer and having a thickness of 20 μm, and a poorly water-soluble inorganic salt 2 A charging member having a surface layer in contact with the member to be charged, the charging member being in the form of a roll, and (c) a power supply for applying a voltage between the member to be charged and the supporting member. It is a charging device characterized by including.

The present invention also provides (a) a body to be charged, (b) a charging member, (b1) a metal support member, and (b2) a base end portion fixed to the support member, which is elastic. And (b3) 100 parts by weight of a moisture-permeable polyurethane resin having a moisture permeability of 2000 or more and a water swelling degree of 5 or less when formed on the outer peripheral surface of the intervening layer (b3) and having a water swelling degree of 5 or less, and hardly water-soluble. A charging member formed in a blade shape and having a surface layer containing 2 to 50 parts by weight of a water-soluble inorganic salt and contacting the charged body near the free end of the intervening layer, and (c) the charged body. A charging device including a power source for applying a voltage between the supporting member and the supporting member.

[0016]

According to the present invention, at least the surface layer of the charging member has a moisture permeable polyurethane resin having a moisture permeability of 2000 or more and a water swelling degree of 5 or less when the thickness is 20 μm,
2 to 50 parts by weight of a poorly water-soluble inorganic salt is included with respect to 100 parts by weight of the moisture-permeable polyurethane resin.

The hardly water-soluble inorganic salt is preferably 10 to 30.
Parts by weight, particularly preferably about 30 parts by weight. When the amount of the poorly water-soluble inorganic salt is less than 2 parts by weight, the effect on the environmental change is small, and when the amount is more than 50 parts by weight, the strength of the surface layer is decreased and it is wasteful.

The poorly water-soluble inorganic salts include calcium phosphate, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate and magnesium carbonate.

The moisture-permeable polyurethane resin is obtained by reacting a polyol and a polyisocyanate in the presence of a chain extender, if necessary, and the polyol is a random copolymer of ethylene oxide and tetrahydrofuran,
The molar ratio of ethylene oxide and tetrahydrofuran in the copolymer is in the range of 40/60 to 80/20. As a result, a surface layer having both water swelling resistance and moisture permeability is realized. The polyol is obtained by randomly copolymerizing ethylene oxide and tetrahydrofuran. In such a random copolymer, the copolymerization molar ratio is ethylene oxide / tetrahydrofuran = 40 / 60-80.
When it is in the range of / 20, a moisture permeable polyurethane resin film having excellent moisture permeability and water swelling resistance can be obtained. If the molar ratio of ethylene oxide is less than the above range, the water swelling resistance is good, but the moisture permeability is insufficient, while if the ethylene oxide exceeds the above range, the water swelling problem is sufficient although the moisture permeability is sufficient. Occur.

The reason why such moisture permeability is required for the surface layer of the charging member is that the moisture-permeable polyurethane resin of the present invention is more suitable than the charging member having a surface layer of only synthetic resin having no moisture permeability. This is because it is possible to stabilize the member by reducing the change in the charging ability with respect to the change in the environment. The reason for this is not clear, but the charging member having a moisture-permeable polyurethane resin in the surface layer has the ability of the moisture-permeable polyurethane resin to constantly keep moisture absorption constant against changes in the environment. It is considered that a charging member having a moderate amount of water in the layer and thus excellent in environmental stability is realized. Especially at low temperature and low humidity, it is generally difficult to perform good discharge,
In the present invention, by using the moisture permeable polyurethane resin as described above, it is possible to always generate good discharge. As a result, it becomes possible to perform uniform discharge with stable charging ability and without uneven charging.

The molecular weight of the above polyol is 600 to 30.
It is preferably in the range of 00, and when the molecular weight is less than the above range, the elastomer performance is deteriorated, particularly the cold resistance is poor, and cracks may occur during use in cold regions, impairing durability in use. On the other hand, when the molecular weight exceeds the above range, the synthesis conditions are narrowed, and it becomes unfavorable in that it becomes opaque when it is made into a layer, that is, when it is made into a film, and particulate foreign matter is easily generated.

As the polyisocyanate to be reacted with the above-mentioned polyol, for example, preferred ones are:
4'-diphenylmethane diisocyanate (MDI),
Hydrogenated MDI, isophorone diisocyanate, 1,3-
Xylylene diisocyanate, 1,4-xylene diisocyanate, 2,4-tolylene diisocyanate,
There are 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, etc., or these organic polyisocyanates are reacted with a low molecular weight polyol or polyamine to form a terminal isocyanate. Naturally, the urethane prepolymer and the like obtained can be used.

Preferred chain extenders include, for example, ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol,
1,6-hexanediol, ethylenediamine, 1,2
-Propylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, decamethylenediamine, isophoronediamine, m-xylylenediamine, hydrazine, water and the like.

In producing the moisture-permeable polyurethane resin, for example, a catalyst is used in a suitable organic solvent, if necessary, and the equivalent ratio of each raw material is NCO / OH = 0.9-.
It may be adjusted to about 1.1 for the reaction, or may be melt-reacted without a solvent. Further, all the raw materials may be reacted at the same time, or a so-called prepolymer method may be adopted.

The molecular weight of the polyurethane resin is not particularly limited, but in consideration of the strength and film-forming processability when it is layered, that is, when it is used as the surface layer of the charging member, the melt viscosity at 200 ° C. is in the range of 4000-10000 poise. Is preferred.

As a method of forming the surface layer on the surface layer of the charging member, the polyurethane resin is dissolved in a solvent such as DMF, and a sparingly water-soluble inorganic salt is dispersed in the solvent by a ball mill or the like to prepare the charging member. It can be formed on the substrate by a known coating method such as a spray coating method or a dipping coating method.

The thickness of the obtained surface layer is arbitrary, but in view of practical strength and moisture permeability, it is 5 to 100 μm.
A thickness of about m is preferable.

The surface layer containing the moisture-permeable polyurethane resin is
It has a thickness of 20 μm, a water vapor permeability of 2000 or more according to Japanese Industrial Standard JIS Z-0208, and a water swelling degree of 5 or less defined by Equation 1 described later. The degree of water swelling was obtained by cutting a moisture-permeable polyurethane resin film into a size of 5 × 5 cm, drawing a line with a length of 5 cm in the center of the film in the direction of the opposite corners of the film, and applying hot water at 40 ° C. Soak in a petri dish and measure the elongation of the wire after 5 minutes.
It was calculated by

[0029]

[Equation 1]

The hardly water-soluble inorganic salt mixed with the moisture permeable polyurethane resin constituting the surface layer is 2 to 50 parts by weight, preferably 10 to 30 parts by weight, relative to 100 parts by weight of the moisture permeable polyurethane resin. Parts by weight, particularly preferably about 30 parts by weight. When the amount of the poorly water-soluble inorganic salt is less than 2 parts by weight, the effect on the environmental change is small, and when the amount is more than 50 parts by weight, the strength of the surface layer 4 is weak and it is wasteful.

The poorly water-soluble inorganic salt is a solid pigment powder,
The hardly water-soluble inorganic salt is dispersed in the moisture-permeable polyurethane resin by kneading the moisture-permeable polyurethane resin and the slightly water-soluble inorganic salt. By mixing such a poorly water-soluble inorganic salt with a moisture-permeable polyurethane resin, the charging member of the present invention has a change in charging ability relative to a change in environment, as compared with a charging member having a surface layer of only synthetic resin. Can be made very small and stable. The reason for this is not clear, but the poorly water-soluble inorganic salt has the ability to constantly keep the moisture absorption constant even when the environment changes, that is, it keeps the water content in the surface layer moderately, and It is considered that a charging member having excellent stability will be realized. Even with a charging member having a surface layer composed of only a moisture-permeable polyurethane resin, good discharge can be generally performed at low temperature and low humidity. However, in the present invention, the poorly water-soluble inorganic salt is added as described above. By including, even in severe low temperature and low humidity,
It is possible to always generate a good discharge. as a result,
It is possible to perform uniform discharge with stable charging ability and without uneven charging.

The charging member may be formed by forming the surface layer on a metal supporting member with an intervening layer having elasticity such as conductive rubber interposed therebetween to form a charging roll. Alternatively, the surface layer may be formed to form a charging roll, or the charging member may be formed in a blade shape that contacts the member to be charged. A voltage of, for example, 600 to 2000 V is applied from a power source between the surface layer and the body to be charged, and the aforementioned discharge is performed to charge the body to be charged.

[0033]

1 is a sectional view of a roll-shaped charging member according to an embodiment of the present invention. The charging member 1 is preferably used in an electrophotographic process or an electrostatic recording process for forming an image in a copying machine or a recording device shown in FIG. The charging member 1 according to the present invention is provided in contact with the outer peripheral surface of a right columnar electrophotographic photosensitive member 11, and the electrostatic latent image is formed on the photosensitive member 11 thus charged by slit exposure by the exposure unit 5. Is formed, and then the developing means 6 is formed.
The electrostatic latent image is visualized as a toner image by the transfer path 1
The toner image is transferred onto the recording paper 7 conveyed by the transfer charging member 8 onto the recording paper 7. The toner remaining on the photoconductor 11 is removed by the cleaning unit 9. When charging the photoconductor 11 with the charging member 1,
When the residual potential exists on the photoconductor 11, it is preferable that the preexposure unit 10 irradiates the photoconductor 11 with light to remove the residual potential.

In the charging member 1 shown in FIG. 1, a rotatably provided conductive metal support member having a right circular column shape or a right cylindrical shape whose cross section perpendicular to the axis is a uniform circle in the axial direction. An electrically conductive intervening layer 3 having elasticity is fixed to the outer peripheral surface of 2, and a surface layer 4 according to the present invention is formed on the outer peripheral surface of the intervening layer 3. The support member 2 is made of metal such as iron, copper, and stainless steel.

As the intervening layer 3, a rubber material in which low resistance particles such as carbon black and metal powder are dispersed and adjusted to have conductivity is formed. As the rubber material, natural rubber, chloroprene rubber, styrene / butadiene rubber, ethylene / propylene rubber, butyl rubber, acrylic / nitrile / butadiene rubber, silicone rubber, urethane rubber, fluororubber,
Crosslinked rubbers such as halogenated butyl rubber, chlorosulfone polyethylene rubber, hydrogenated nitrile rubber, epichlorohydrin and their copolymers, blends, and polyolefins, polyesters, polyethers, polyamides, polyurethanes, etc. It can be appropriately selected from thermoplastic elastomers and the like. In addition, mineral oils such as aroma-based, naphthene-based, and paraffin-based oils and di- (2-ethylhexyl) phthalate (DOP), di- (2-ethylhexyl) adipate (DOA), di- (2- Plasticizers such as ethylhexyl) sebacate (DOS) and softeners such as rapeseed oil and vegetable oils such as coconut oil may be used. Other rubber chemicals, vulcanizing agents such as sulfur and peroxides as rubber additives, vulcanization accelerators such as zinc stearate, sulfenamide-based, thiuram-based, thiazole-based, guanidine-based vulcanization accelerators, amines -Based, phenol-based, sulfur-based, phosphorus-based anti-aging agents,
Reinforcing agents, inorganic fillers such as silica, talc, clay, etc. can be optionally selected. The conductive rubber forming the intervening layer 3 is made of oil or the like to have a low hardness (for example, 30 to 45 degrees) and has elasticity.

In producing the surface layer 4, first, polyurethane is dissolved in a solvent and low resistance particles such as carbon black are dispersed in the solvent to adjust the resistance to 10 ⁶ to 10 ¹² Ω · cm.

In forming the surface layer 4, the moisture-permeable polyurethane resin prepared as described above is mixed with a poorly water-soluble inorganic salt in an amount of 2-5 per 100 parts by weight of the moisture-permeable polyurethane resin.
0 parts by weight, preferably 10 to 30 parts by weight, and most preferably 30 parts by weight are added, dispersed by a ball mill or the like, and coated on the intervening layer 3. The coating can be performed using a coating method such as a dip coating method or a spray coating method. The thickness of the surface layer is preferably 5 to 200 μm, particularly preferably 20 to 150 μm.

The reason why the surface layer 4 is adjusted to have a low resistance of 10 ⁶ to 10 ¹² Ω · cm is that it is effective against dielectric breakdown of the charged body such as the photoconductor 11. That is, in the case of contact charging, if a high voltage is applied to the charging member arranged in contact with the photoconductor, the defective portion inside the photoconductor will cause discharge breakdown. Therefore, the charging of the photoconductor 11 becomes non-uniform, and an excessive current flows from the charging member to the breaking point, and the voltage applied to the charging member drops. As a result, charging failure occurs over the entire area of contact with the photoconductor, which appears as a white belt in the regular development method and a black belt in the reversal development method. In order to prevent these, it is desirable that the voltage applied to the charging member be a low voltage. In order to apply this low voltage and perform uniform charging, the charging member 1
It is necessary to keep the surface layer of the low resistance.

Further, when a high voltage is applied by the DC power supply 13, a large amount of products such as ozone and NOx are generated during charging, and image blurring, image deletion, etc. occur on the charged body such as the photoconductor 11. It has an adverse effect.

Considering the above, the present invention is a charging member 1 having a surface layer 4 in which a poorly water-soluble inorganic salt is dispersed in a moisture-permeable polyurethane resin, and therefore carbon black or the like is contained in the surface layer 4. The resistance can be easily controlled by adding the required amount of the low resistance substance described above, and the hardness can be easily increased by adding oil to the inner conductive rubber layer or forming a foam. Since it can be controlled to, there is no particular problem. From the above, the voltage applied to the charging member 1 of the present invention is ± 6
It is possible to sufficiently uniformly charge an object to be charged such as the photoconductor 11 with a low voltage of 00V to ± 2000V.

One electrode of the DC power supply 13 is connected to the support member 2, and the other electrode is grounded. The photoreceptor 11 has a structure in which an electrically insulating photosensitive layer is formed on the surface of a metal straight cylinder, and the cylinder is grounded and connected to the other electrode of the power supply 13.

FIG. 3 is a graph showing the experimental results by the inventor of the embodiment shown in FIGS. 1 and 2. The voltage applied to the charging member 1 by the power source 13 and the surface potential of the photoconductor 11 charged by the charging member 1 are shown. The line L1 shows the characteristics in the environment of normal temperature and normal humidity and high temperature and high humidity, and the line L2 shows the low temperature and low humidity (for example, 10
C, 30% RH relative humidity) and high temperature and low humidity characteristics are shown. When the applied voltage is V1 = 1400V, for example, the difference voltage ΔV between the lines L1 and L2 is 50, for example.
It was confirmed that it was V and that it could be made smaller.
On the other hand, in the charging member described as the above-mentioned prior art, ΔV was, for example, 300V.

By using the charging member 1 in this manner, the surface of the member to be charged, which is the photoconductor 11, is not affected by scratches, etc., and in comparison with the conventional charging member having a surface layer of urethane only, the environment It was found that the change of the charging ability with respect to the change was very small and stable. Although the reason for this is not clear, the moisture-permeable polyurethane resin and the poorly water-soluble inorganic salt used in the surface layer 4 of the present invention have the ability to always keep the moisture absorption constant even when the environment changes. It is considered that this is because the environmental stability is excellent, and particularly good discharge always occurs even at low temperature and low humidity (for example, 10 ° C. and 30% RH relative humidity). As a result, it may be possible to perform uniform charging with stable charging ability and without uneven charging.

FIG. 4 is a sectional view showing a blade-shaped charging member 1a according to another embodiment of the present invention, and FIG. 5 is used to charge the photosensitive member 11 using the blade-shaped charging member 1a shown in FIG. The state is shown. In the charging member 1a, the base end of the intervening layer 3a is fixed to the metal plate-shaped supporting member 2a, and the surface layer 4a is formed on the outer peripheral surface of the intervening layer 3a. The surface layer 4a is located near the free end of the intervening layer 3a.
Touch 1. The intervening layer 3a is made of the same material as the intervening layer 3 in the above-described embodiment, and the surface layer 4a is made of the same material as the above-mentioned surface layer 4. Other configurations are the same as those in the above-mentioned embodiment.

The installation of the charging member to be brought into contact with the photosensitive member in the present invention is not limited to a specific method, and the charging member may be a fixed type or a moving type such as rotating in the same direction as the photosensitive member or in the opposite direction. Can be used. Further, it is possible to cause the charging member to function as a cleaning device for the developer on the photoconductor, especially in the embodiments of FIGS. 4 and 5. The voltage applied to the charging member in the direct charging of the present invention and the method of applying it depend on the use of each electrophotographic apparatus, but in addition to the method of instantly applying a desired voltage, the A method of applying the voltage stepwise for the purpose, a method of applying a direct current voltage, and a method of applying the direct current and the alternating current in a superimposed form can be used.

The charging members 1 and 1a of the present invention can also be used as the transfer charging means 8 shown in FIG.

The experimental results of the present inventor will be described.

Example 1 100 parts by weight of chloroprene rubber was kneaded with 10 parts by weight of conductive carbon black and 30 parts by weight of naphthenic mineral oil by an open roll and molded by a die, and the roller-shaped charging member 1 shown in FIG. The intervening layer 2 is provided. The volume resistance of the intervening layer 2 is 4 × 1 when measured in an environment of a temperature of 22 ° C. and a humidity of 60%.
It was 0 ⁷ Ω · cm and JIS A hardness was 40 degrees.

Next, 4500 parts by weight of a random copolymer polyol having an ethylene oxide / tetrahydrofuran molar ratio of 1.63 (average molecular weight 1.860, hydroxyl value 60) and 1-4-butanediol (abbreviation 1,4BD) 50.
0 parts by weight are well mixed and stirred, and heated at 60 ° C. At this time, the molar ratio of the polyol to the chain extender is 0.435. Then, 2030 parts by weight of diphenylmethane diisocyanate (MDI) heated to 50 ° C. (NCO / OH = 1.02) is added to this mixture and stirred. After the mixture becomes uniform, it is aged at 100 ° C. for 6 hours to obtain a block-shaped moisture-permeable polyurethane resin. This polyurethane resin was crushed and granulated with an extruder. The melt viscosity (200 ° C.) of this polyurethane resin was 12,000 poise. 100 parts by weight of this resin is dissolved in 600 parts by weight of dimethylformamide (DMF), and barium sulfate 20 is added.
By weight, 5 parts by weight of carbon black were sufficiently dispersed. The resin solution thus obtained on which the intervening layer 2 of the charging member 1 was formed was dipped to form the surface layer 4 having a film thickness of 40 μm. The volume resistance of the roller is 5 × 10 ⁷ Ω · cm.

This charging member 1 is attached as a primary charger of the reversal development type printer shown in FIG. 2, a DC voltage of 1400 V is applied by a power source 13, and the photoreceptor is kept at room temperature and normal humidity (abbreviated as N / N). 11 The potential on the surface was measured.
The results are shown in Table 1.

Furthermore, Table 1 shows the results of the same evaluation under a low temperature and low humidity condition (abbreviated as L / L) at a temperature of 10 ° C. and a humidity of 30%.

Example 2 The same as Example 1 except that the same members as in Example 1 were attached in a blade shape as shown in FIGS. 4 and 5.

Example 3 The same as Example 1 except that tribasic calcium phosphate was used instead of barium sulfate in Example 1.

Comparative Example 1 100 parts by weight of chloroprene rubber, 10 parts by weight of conductive carbon black, 30 parts by weight of naphthenic mineral oil, 5 parts by weight of zinc oxide, 4 parts by weight of magnesium oxide, 2 parts by weight of vulcanization accelerator, stearic acid. 1 part by weight was kneaded with an open roll and molded with a mold to provide the intervening layer 2 of the roller-shaped charging member 1 in FIG. The volume resistance of the intervening layer 2 is set to the temperature 22
4 × 10 ⁷ Ω when measuring resistance in an environment of ℃ and humidity of 60%
-Cm, JIS (Japanese Industrial Standard) A hardness was 40 degrees.

Next, polyester-based urethane resin solution Rezamin ME-3139LP (modified) manufactured by Dainichiseika Co., Ltd. (modified) (solvent composition MEK / DMF = weight ratio 40/60, nonvolatile content 30)
%) 6 parts by weight of poorly water-soluble inorganic salt (resin 10
If calculated to 0 parts by weight, it is about 20 parts by weight), 10 parts by weight of carbon black is added, 50 parts by weight of MEK and 50 parts by weight of DMF are added, and this is mixed in a ball mill to form a poorly water-soluble inorganic salt in the resin solution. , Carbon black was sufficiently dispersed. MEK is methyl ethyl ketone and DMF is dimethylformamide.

The intervening layer 3 was immersed in the resin solution thus obtained together with the supporting member 2 of the roller-shaped charging member 1 shown in FIG. 1 to form the surface layer 4 having a film thickness of 50 μm. When the volume resistance of the surface layer 4 was measured, it was 6 × 10 ⁷ Ωcm.

Comparative Example 2 In Example 1, no naphthenic mineral oil was added and the surface layer 4 was not covered, and only the intervening layer 3 was used. The intervening layer 3 is J
ISA hardness 70 degrees.

Comparative Example 3 Same as Comparative Example 2 except that the surface potential is different from Comparative Example 2.

[0059]

[Table 1]

In the image defect column of Table 1, "OK" indicates that no image defect has occurred. OK in the endurance test section
Indicates that the surface layers 4 and 4a are not scratched.

From the experimental results shown in Table 1, it was confirmed that the charging members 1 and 1a according to the present invention did not cause image defects and had excellent durability.

[0062]

As described above, according to the present invention, a moisture-permeable polyurethane resin which has both water-swelling resistance and moisture permeability and has a moisture permeability of 2000 or more and a water swelling degree of 5 or less at a thickness of 20 μm, and A charging member having a surface layer containing a poorly water-soluble inorganic salt is realized, and the charging member is brought into contact with a member to be charged, and a voltage is applied between the charging member and the member to be charged to remove the member to be charged. Since it is possible to be charged,
A charging member and a charging device that do not have an adverse effect such as scratches on the surface of the member to be charged and thus do not cause image defects and that are excellent in environmental stability are realized.

Further, according to the present invention, as described above, the surface of the body to be charged is not scratched, and even if the humidity changes, the charging can be performed uniformly without uneven charging. It becomes possible to obtain a good image.

Further, according to the present invention, the voltage supplied from the power source for charging can be charged at a relatively low voltage as compared with the prior art in which the wire is surrounded by the shield plate and corona discharge is performed. Become.

[Brief description of drawings]

FIG. 1 is a sectional view of a roller-shaped charging member 1 according to an embodiment of the present invention.

FIG. 2 is a simplified side view of an image forming apparatus such as a copying machine or a recording apparatus using the charging member 1.

FIG. 3 is a graph showing the characteristics of the charging member 1 showing the results of experiments conducted by the present inventors.

FIG. 4 is a blade-shaped charging member 1 according to another embodiment of the present invention.
It is sectional drawing of a.

5 is a side view of a part of an image forming apparatus using the charging member 1a shown in FIG.

[Explanation of symbols]

1,1a Charging member 2,2a support member 3,3a intervening layer 4,4a surface layer 5 Exposure means 6 developing means 8 Transfer charging means 9 Cleaning means 10 Pre-exposure means for removing residual potential

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-241364 (JP, A) JP-A-6-289738 (JP, A) JP-A-6-313422 (JP, A) JP-A-6- 248174 (JP, A) International publication 91/010942 (WO, A1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103 G03G 15/08 501

Claims (8)

(57) [Claims] 1. The moisture permeability when the thickness is 20 μm is 20.
A charging having a surface layer containing a moisture-permeable polyurethane resin having a water swelling degree of 00 or more and 5 or less, and 2 to 50 parts by weight of a poorly water-soluble inorganic salt with respect to 100 parts by weight of the moisture-permeable polyurethane resin. Parts. 2. A moisture-permeable polyurethane resin is a resin obtained by reacting a polyol and a polyisocyanate in the presence of a chain extender if necessary, and the polyol is a random copolymer of ethylene oxide and tetrahydrofuran. And the molar ratio of ethylene oxide and tetrahydrofuran in the copolymer is 40/60 to 80/20.
The charging member according to claim 1, wherein 3. The random copolymer has a molecular weight of 600 to 3.
The charging member according to claim 2, wherein the charging member has a range of 000. 4. The poorly water-soluble inorganic salt is calcium phosphate,
2. One or more selected from the group consisting of barium sulfate, calcium sulfate, barium carbonate, calcium carbonate and magnesium carbonate.
The charging member described. 5. A metal support member, a conductive intervening layer provided on the outer peripheral surface of the support member and having elasticity, and a moisture permeability of 2000 or more when formed on the outer peripheral surface of the intervening layer and having a thickness of 20 μm. And a moisture permeable polyurethane resin having a water swelling degree of 5 or less, and the moisture permeable polyurethane resin 100.
Including 2 to 50 parts by weight of a poorly water-soluble inorganic salt with respect to parts by weight,
A charging member having a surface layer in contact with an object to be charged and formed in a roll shape. 6. A metal supporting member, a conductive intervening layer having a base end fixed to the supporting member and having elasticity, and a moisture permeability of 2000 when formed on the outer peripheral surface of the interposing layer and having a thickness of 20 μm. As described above, a moisture-permeable polyurethane resin having a water swelling degree of 5 or less, and the moisture-permeable polyurethane resin 100.
Including 2 to 50 parts by weight of a poorly water-soluble inorganic salt with respect to parts by weight,
A charging member having a surface layer in contact with a body to be charged in the vicinity of a free end portion of the intervening layer and formed in a blade shape. 7. (a) an object to be charged, (b) a charging member, (b1) a metal supporting member, (b2) provided on an outer peripheral surface of the supporting member, and having elasticity and conductivity. An intervening layer, and (b3) a moisture-permeable polyurethane resin formed on the outer peripheral surface of the intervening layer and having a water vapor permeability of 2000 or more and a water swelling degree of 5 or less when the thickness is 20 μm, and 100 parts by weight of the moisture-permeable polyurethane resin. On the other hand, a charging member (2) having a surface layer that contains 2 to 50 parts by weight of a poorly water-soluble inorganic salt and is in contact with an object to be charged and is formed in a roll, and (c) an object to be charged and a supporting member. A charging device comprising a power supply for applying a voltage therebetween. 8. An electrically conductive body, comprising: (a) a body to be charged; (b) a charging member; (b1) a metal supporting member; and (b2) a base end portion fixed to the supporting member. (B3) a moisture-permeable polyurethane resin having a moisture permeability of 2000 or more and a water swelling degree of 5 or less when formed on the outer peripheral surface of the intermediate layer (b3) and having a thickness of 20 μm, and 100 weight of the moisture-permeable polyurethane resin. (2) to 50 parts by weight of a poorly water-soluble inorganic salt, and a surface layer that comes into contact with the body to be charged near the free end of the intervening layer, and is formed into a blade shape. c) A charging device comprising a power source for applying a voltage between the member to be charged and the supporting member.