JP3186409B2 - Charging member and electrophotographic apparatus - 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 for charging a member to be charged and an electrophotographic apparatus.

[0002]

2. Description of the Related Art In recent years, particularly in the field of electrophotography, as a charging means for charging an object to be charged, an aerial discharge generated by a minute gap between the charging member and the member to be charged by contacting the charging member with the object to be charged. The technology that uses is the mainstream. If this charging means is used, the discharge current flowing at the time of charging is small, so that harmful neutral active species such as ozone and nitrogen oxides are hardly generated, thereby chemically deteriorating the material to be charged and causing human body damage. The adverse effects can be prevented.

In order to uniformly charge the photosensitive member,
It has been said that the surface layer of the charging member needs to be smooth. In other words, if there are large irregularities on the surface of the charging member, the electric field concentrates on the convex portions, causing local excessive charging of the photoconductor due to the convex portions and local insufficient charging of the photoconductor due to the concave portions. This causes fog when a white image is output.

Hereinafter, an example of the configuration of the above-mentioned charging means will be described with reference to the drawings. FIG. 2 shows a photoconductive semiconductor (photoconductor) 10 to be charged in an electrophotographic apparatus.
FIG. 3 is a cross-sectional view of a configuration in which a photosensitive member and a roller-shaped charging member that is driven and rotated contact the photosensitive member.

A DC voltage source 102 is applied to the charging member 101. The photoconductor 100 includes a grounded drum-shaped conductive support 100a (usually aluminum) and a photoconductive semiconductor layer (photosensitive layer) 100b. Here, the photosensitive layer was assumed to be of a negative charge type. The charging member 101 includes a conductive shaft 101a to which a voltage is applied, a semiconductive rubber layer 101b, and a surface layer 101c.

The surface layer 101c is provided mainly for the purpose of improving the surface releasability of the charging member. That is, in the electrophotographic process, an electrostatic latent image formed on a photoreceptor is visualized with a charged colored resin powder (toner), and then the developed image is electrostatically transferred to a transfer material by a transfer device. Although the toner remaining on the body is removed by the cleaning device, all the remaining toner on the photoconductor is not cleaned, and a small amount of toner remains on the photoconductor without being cleaned. Therefore, the toner contacts the charging member surface and adheres to the charging member surface.However, if charging is performed with the toner adhered, charging unevenness may be caused. The adhered toner needs to be easily removed. Therefore, in order to improve the surface releasability of the charging member, a surface layer made of, for example, a polyamide resin, a polyurethane resin, a fluororesin, or a mixture of these resins is provided to improve the cleaning property of the toner.

Hereinafter, the charging operation of the charging member will be described. As the photoconductor 100 rotates in the direction of the arrow in the figure, the charging member 101 also rotates in the direction of the arrow in the figure. Since a DC voltage is applied to the conductive shaft 101a by the DC voltage source 102, the surface of the photoreceptor 100 is charged according to Equation 1.

[0008]

(Equation 1)

In the equation (1), Vo is the surface potential of the photosensitive member, Vin is the applied DC voltage, and Vth is the discharge starting voltage between the photosensitive member 100 and the charging member 101.

It has been said that the surface layer of the charging member needs to be smooth in order to uniformly charge the photosensitive member. In other words, if there are large irregularities on the surface of the charging member, the electric field concentrates on the convex portions, causing local excessive charging of the photoconductor due to the convex portions and local insufficient charging of the photoconductor due to the concave portions. This causes fog when a white image is output.

In order to eliminate such charging unevenness, conventionally, a device for smoothing the surface of the charging member has been devised. More specifically, as disclosed in Japanese Patent Application Laid-Open No. 2-229885, a 10-point average roughness Rz
Was 5 μm or less.

[0012]

However, when the above-mentioned conventional charging member is left in pressure contact with the photosensitive member, phenomena such as sticking or sticking of the charging member to the photosensitive member occur particularly in a high-temperature and high-humidity environment. There was a case. This is considered to be mainly due to the fact that a chemical bond due to the hydrolysis of the resin on the surface of the charging member or the surface of the photosensitive member occurs between the surface of the charging member and the surface of the photosensitive member.

In view of the above problems, the present invention does not cause sticking or sticking between the surface of the charging member and the surface of the charging member even when the charging member is left in pressure contact with the member in a high temperature and high humidity environment. A charging member and an electrophotographic apparatus are provided.

[0014]

In order to solve the above-mentioned problems, a charging member according to the present invention is a charging member that contacts a member to be charged and charges the member to be charged. A surface layer is provided thereon, and the ratio of the linear shrinkage coefficient between the base material and the surface layer is 1 <(linear shrinkage coefficient of the surface layer) / (linear shrinkage coefficient of the base material) <2 or 1 <(base (Characteristic linear contraction coefficient) / (Linear contraction coefficient of surface layer) <2.

Further, the charging member is a roller-shaped charging member. According to another aspect of the invention, there is provided an electrophotographic apparatus, comprising: a photoconductive semiconductor; a charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor; An electronic device comprising: an optical device that forms an electrostatic latent image on the surface of the toner; a developing device that visualizes the electrostatic latent image with a charged colored resin powder; and a transfer device that transfers the visual image onto a material to be transferred. In a photographic apparatus, the charging member is provided with a surface layer on a substrate, and a ratio of a linear contraction coefficient between the substrate and the surface layer is 1 <(linear contraction coefficient of the surface layer) / (substrate of the substrate). Linear shrinkage coefficient) <2, or
1 <(linear shrinkage coefficient of substrate) / (linear shrinkage coefficient of surface layer) <
An electrophotographic apparatus, characterized in that:

In order to solve the above problems, a charging member of the present invention is a charging member that contacts a member to be charged and charges the member to be charged. A surface layer made of a conductive polyurethane resin is provided, and the weight ratio of the polyisocyanate resin and urethane polyol for forming the thermosetting polyurethane resin is 1/5 <(weight of polyisocyanate resin) / (weight of urethane polyol). <1. A charging member, characterized in that:

Further, the charging member is a roller-shaped charging member. According to another aspect of the invention, there is provided an electrophotographic apparatus, comprising: a photoconductive semiconductor; a charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor; An electronic device comprising: an optical device that forms an electrostatic latent image on the surface of the toner; a developing device that visualizes the electrostatic latent image with a charged colored resin powder; and a transfer device that transfers the visual image onto a material to be transferred. In a photographic apparatus, the charging member is provided with a surface layer made of a thermosetting polyurethane resin on a base material, and a weight ratio of a polyisocyanate resin and a urethane polyol for forming the thermosetting polyurethane resin is 1 / 5 <(weight of polyisocyanate resin) / (weight of urethane polyol) <
1. An electrophotographic apparatus, characterized in that:

[0018]

According to the present invention, the charging member does not stick to or adhere to the surface of the charging member even when the charging member and the charging member are allowed to stand under pressure in a high temperature and high humidity environment. . Hereinafter, how the charging member of the present invention does not cause sticking, sticking, or the like to the member to be charged will be described.

In order to make it difficult for the charging member to stick or stick to the member to be charged, it is considered that the area of the nip portion due to the pressure contact between the charging member and the member to be charged should be reduced. In order to reduce the area of the nip, the surface of the charging member may be roughened, and the pressure contact between the charging member and the member to be charged may be changed from surface pressure contact to point pressure contact.

Hereinafter, two types of surface roughening methods of the charging member presented in the present invention will be described in detail.

1. The ratio of the linear shrinkage coefficient between the base material of the charging member and the surface layer is defined as 1 <(linear shrinkage coefficient of the surface layer) / (linear shrinkage coefficient of the base material) <2, or 1 <(linear shrinkage coefficient of the base material) /
(Linear shrinkage coefficient of surface layer) <2.

In the drying step of the surface layer after the surface layer is applied on the base material, both the base material and the surface layer shrink according to the linear shrinkage coefficient specific to each material. If the linear shrinkage coefficient of the surface layer is different from the linear shrinkage coefficient of the substrate during this shrinkage, wrinkles are generated in the dried surface layer, and the surface is roughened. The wrinkles generated at this time have a smooth shape, and sharp wrinkles which are considered to cause uneven charging such as excessive charging and insufficient charging are unlikely to occur.

If the difference in linear shrinkage coefficient between the base material and the surface layer is too large, the film peels off and cracks occur during shrinkage, or the surface layer after shrinkage has a 10-point average surface roughness Rz of 15 μm.
m or more, causing charging unevenness. The inventors believe that the difference between the two linear contraction coefficients is less than twice, that is,
1 <(linear shrinkage coefficient of surface layer) / (linear shrinkage coefficient of base material) <
If 2, or 1 <(linear shrinkage coefficient of base material) / (linear shrinkage coefficient of surface layer) <2, the surface shape is less likely to cause charging unevenness without film peeling and cracking upon shrinkage,
That is, it has been found that a surface layer having moderate surface roughness (10-point average surface roughness Rz ≦ 15 μm) on which smooth wrinkles having a tip shape are formed can be obtained.

2. When a surface layer made of a thermosetting polyurethane resin is provided on a substrate, the weight ratio of the polyisocyanate resin and the urethane polyol forming the thermosetting polyurethane resin is set to 1/5 <(weight of polyisocyanate resin) / (urethane (Weight of polyol) <1.

It is well known that when a thermosetting polyurethane resin is formed, the film strength increases as the blending amount of the polyisocyanate resin increases. When a surface layer made of a thermosetting polyurethane resin is applied on the base material of the charging member, if the film strength of the surface layer is too strong, wrinkles are generated on the surface layer during shrinkage in a drying process after coating the surface layer. 10 without
A smooth surface having a small point average surface roughness Rz is obtained. Therefore, when forming a surface layer made of a thermosetting polyurethane resin having moderate wrinkles (smooth tip shape and 10-point average surface roughness Rz of about 15 μm or less) on the surface, the amount of the mixed polyisocyanate resin is The inventors have found that a maximum exists and that the maximum is (weight of polyisocyanate resin) / (weight of urethane polyol) <1.

On the other hand, if the mixing amount of the polyisocyanate resin is too small, the film strength is low, so that even if the linear shrinkage coefficient with the substrate is slightly different, large wrinkles are generated, and the 10-point average surface after shrinkage is generated. The roughness Rz is 15 μm or more, which causes charging unevenness such as excessive charging and insufficient charging. Therefore, there is a minimum value in the amount of polyisocyanate resin to be mixed,
The minimum value is 1/5 <(weight of polyisocyanate resin) / (weight of urethane polyol),
The inventors have found.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrophotographic apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the configuration of the electrophotographic apparatus according to the first embodiment. 1 is a photoreceptor, 2 is a charging member, 3 is a DC constant voltage device for applying to the charging member 2, 4 is an optical device for forming an electrostatic latent image on the surface of the photoreceptor, 5 is a colored resin for forming the electrostatic latent image. Developing device for visualizing with powder (toner), 6
Is a corotron transfer device for transferring a visual image on the photoreceptor surface to the transfer material 7 by electrostatic attraction, 8 is a cleaning device for removing toner remaining on the photoreceptor surface after the transfer process, 9
Is an optical static eliminator for electrostatically initializing the photosensitive member.

The photosensitive member 1 is formed by coating a photosensitive layer 1b on a grounded aluminum conductive support 1a having a diameter of 30 mm and grounded.

The conductive support 1a is not limited to aluminum, but may be any one having a conventionally known conductivity. In addition to aluminum, a metal such as an aluminum alloy, tin oxide, and indium oxide may be used. And various kinds of plastics obtained by attaching a metal oxide such as, or a metal and a metal oxide thereto by vacuum deposition, sputtering, laminating, coating, or the like, and performing conductive treatment.

For the photosensitive layer 1a, a negatively charged laminated organic photoreceptor was used. Specifically, the charge generation layer contains 5 parts by weight of a τ-type metal-free phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd.) and an acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name “
The coating liquid obtained by dispersing 4 parts by weight of DIALAL HR664 ") and 1 part by weight of a melamine resin (trade name" Super Beckamine L145-60 "manufactured by Dainippon Ink Co., Ltd.) in 115 parts by weight of s-butyl alcohol was applied to the aluminum. Dip-coated on the conductive support 1a made and dried at 130 ° C. for 1 hour to form a film having a thickness of 0.2 μm.

The charge generation layer is not limited to the above materials and methods. Examples of the charge generation material used for the charge generation layer include various pigments or dyes such as phthalocyanine, azo, squarylium, cyanine, quinone, and perylene. The charge generating layer is prepared by adding and dispersing these pigments or dyes and an appropriate binder resin and preparing the prepared coating solution by a normal coating method such as dip coating, spin coating, spray coating, or electrostatic coating. It is coated and dried by heating to form a film having a thickness of several μm.
It is preferable to form a film having a thickness of 2 to 2 μm.

The binder resin used in the charge generation layer and the charge transport layer described below may be used, if necessary, for the purpose of improving the adhesion to other layers, improving the uniformity of the coating film, and adjusting the fluidity during coating. Used, specifically, polyester, polyvinyl chloride, polyvinyl butyral, polyvinyl acetate,
Examples thereof include polycarbonate, a fluororesin, a methacrylic resin, a silicone resin, and a copolymer of these resins. Further, as the solvent, a charge generating agent, a charge transporting agent,
Alternatively, any material may be used as long as it can dissolve the binder resin, and specifically, halogenated hydrocarbons, aromatics, hydrocarbons, ketones, esters, ethers and the like can be used.

In this embodiment, the charge transport layer has 1,1-
1 part by weight of bis (p-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene and 1 part by weight of polycarbonate (manufactured by Bayer, trade name "Macrohole N") in 9 parts by weight of methylene chloride After dissolution, this coating solution was applied onto the charge generation layer by dip coating and dried at 80 ° C. for 1 hour to form a film having a thickness of 20 μm.

The charge transport layer is not limited to the above-mentioned materials and methods. Examples of the electron-donating substance used for the charge transport layer include compounds having an electron-donating group such as an alkyl group, an alkoxy group, an amino group, and an imide group; polycyclic aromatic compounds such as anthracene, pyrene, and phenanthrene; or a skeleton thereof. Derivatives having, indole, oxazole,
Examples include heterocyclic compounds such as oxadiazole, carbazole, thiazole, pyrazoline, imidazole, and triazole, and derivatives having a skeleton thereof. These electron-donating substances and the binder resin are dissolved in an appropriate solvent, and applied and dried by a usual coating method such as dip coating, spin coating, spray coating, or electrostatic coating to form a charge transport layer. However, when the electron donating substance is a polymer compound, the charge transport layer may be formed alone without mixing the binder resin. Several μm as the thickness of the charge transport layer
To a thickness of several tens μm, preferably 5 to 25 μm.

In this embodiment, a negatively charged organic photosensitive layer is used as the photosensitive layer 1b. However, the present invention is not limited to this. The voltage applied to the charging member 2, the bias voltage of the developing device 5, the toner If attention is paid to the respective polarities of the corona wire current of the transfer device 6, a positive charging type may be used.
An inorganic photosensitive layer such as amorphous selenium and amorphous silicon may be used.

The photosensitive member 1 has a peripheral speed of 30 m in the direction of the arrow in FIG.
Rotated at m / sec. The charging member 2 has a thickness of 4 m on a conductive shaft 2a made of aluminum having a diameter of 3 mm to which a voltage is applied.
m of a semiconductive layer 2b made of polyurethane, and a surface layer 2c made of a fluororesin having a thickness of 20 μm was provided thereon.

The semiconductive layer 2b is made of a thermoplastic polyurethane resin (Takelac E-360, trade name, manufactured by Takeda Pharmaceutical Co., Ltd.).
A ″) is a conductive material such as lithium perchlorate (LiCl _3).
O ₄ ) with a solid content of 5% by weight was used. The resistance value of the semiconductive layer is about 10 ⁷ Ω in this embodiment, but may be 10 ⁵ Ω to 10 ¹⁰ Ω, and preferably 10 ⁶ Ω to 10 ⁸ Ω.

The surface layer 2c is composed of 25 parts by weight of xylene, n
-A mixed solution consisting of 75 parts by weight of butyl alcohol,
Fluororesin (trade name "Lumiflon" manufactured by Asahi Glass Co., Ltd.)
LF110 ″) was coated with a solid content of 100 parts by weight, and a 20 μm-thick surface layer was applied by dip coating, followed by hot-air drying at 100 ° C. for 3 hours.

The charging member 2 is 200 mm in the longitudinal direction of the photosensitive member.
, But pressed against the photoreceptor 1 with a total pressure of 700 g.

The DC constant voltage device 3 applied a negative voltage of 1.1 KV to the conductive shaft 2a of the charging member.

An electrostatic latent image is formed on the surface of the photoreceptor 1 by the optical device 4. In this embodiment, the wavelength is 780 to 800 n.
As a result of adjusting the output of the LED so that the photoconductor surface potential of the latent image portion becomes −80 V using the LED array of m,
The light amount was 0.8 mW.

As the developing device 5, a non-contact developing device using a magnetic one-component toner was used. A bias voltage in which an alternating electric field having a peak-to-peak voltage of 1.5 kV was superimposed on a DC voltage of -300 V was applied between the developing roller and the photoconductor. When this developing device was used, the charge amount of the toner was −6 μC / g.

As the transfer device 6, a corotron charger was used. A constant current of +300 μA was applied to the corotron wire.

As a material to be transferred, plain paper having a basis weight of 60 g / m ² was used. The cleaning device 8 has a configuration in which a polyurethane resin blade rubs the photoreceptor surface at a counter angle.

The same device as the optical device 4 was used as the light neutralizer 9, and the entire surface was exposed when the photosensitive member was rotating.

In order to measure the linear shrinkage coefficient of the semiconductive layer 2b, the above semiconductive layer 2b is dissolved in a mixed solution of toluene and isopropyl alcohol, the solution is applied on a glass preparation, dried, and then dried. It was peeled off and used as a measurement piece. The measurement is based on the standard "ASTM D696" for measuring the linear contraction coefficient (linear expansion coefficient).
Performed according to. As a result of the measurement, the linear shrinkage coefficient was about 15 × 10 ⁻⁵ / ° C. at room temperature.

In order to measure the linear shrinkage coefficient of the surface layer 2c, the above-mentioned surface layer 2c was applied on a glass preparation, dried and then peeled off from the glass preparation to obtain a test piece. The measurement was performed in accordance with the standard "ASTM D696" for measuring the linear contraction coefficient (linear expansion coefficient). The measurement result shows that the linear shrinkage coefficient is about 10 × 10 ⁻⁵ at room temperature.
/ ° C.

In this embodiment, (linear shrinkage coefficient of base material (semiconductive layer) of charging member) / (linear shrinkage coefficient of surface layer) = 1.5
(<2).

The surface layer of the charging member of this example shrank without peeling off and cracking in the drying step, and the surface had a 10-point average roughness Rz of 12 μm.

When the surface of the charging member was observed with a microscope, it was found that wrinkles having a smooth tip were formed.

Further, the electrophotographic apparatus of this embodiment is set at 50 ° C.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
No phenomenon such as sticking and sticking between the charging member and the photosensitive member occurred.

When a solid white image or a halftone image was output using the electrophotographic apparatus of this embodiment, an image having a uniform density without image abnormalities such as white spots, black spots, and fogging could be obtained. Was. This is considered because the photosensitive member 1 is uniformly charged by the charging member 2.

As in this embodiment, the ratio of the linear shrinkage coefficient of the base material (semiconductive layer) of the charging member to the surface layer is 1 <(linear shrinkage coefficient of the base material) / (linear shrinkage coefficient of the surface layer) If the materials of the base material and the surface layer are selected so as to satisfy <2, wrinkles having a smooth tip are formed on the surface of the charging member, and the 10-point average surface roughness is 15 μm or less, and Even if the electrophotographic apparatus having the charging member which is in pressure contact with the member to be charged (photoreceptor) is left in a high-temperature and high-humidity environment for a long time, sticking and sticking between the charging member and the member to be charged may occur. And an electrophotographic apparatus capable of outputting a uniform image without charge unevenness can be provided.

Hereinafter, an electrophotographic apparatus according to a second embodiment of the present invention will be described. This is the same as the first embodiment except that the surface layer 2c of the charging member 2 is made of a thermosetting polyurethane resin.

The surface layer 2c comprises 250 parts by weight of toluene,
75 parts by weight of isopropyl alcohol and 10 parts of ethyl acetate
100 parts by weight of a solid content of a urethane polyol (trade name “Takelac E-550A” manufactured by Takeda Pharmaceutical Co., Ltd.) and a polyisocyanate resin (trade name “Takenate D-140N” manufactured by Takeda Pharmaceutical Co., Ltd.) ), A surface layer having a thickness of 20 μm was applied by a dip coating method using a solution obtained by mixing 50 parts by weight of a solid content of
This was prepared by drying with hot air at 3 ° C. for 3 hours.

In this example, (1/5 <) (weight of polyisocyanate resin) / (weight of urethane polyol)
= 0.5 (<1).

The surface layer of the charging member of this example shrank without peeling off and cracking in the drying step, and the surface had a 10-point average roughness Rz of 10 μm.

When the surface of the charging member was observed with a microscope, it was found that wrinkles having a smooth tip were formed.

Further, the electrophotographic apparatus of this embodiment is set at 50 ° C.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
No phenomenon such as sticking and sticking between the charging member and the photosensitive member occurred.

When a solid white image or a halftone image is output using the electrophotographic apparatus of this embodiment, an image having a uniform density without image abnormalities such as white spots, black spots, and fog can be obtained. Was. This is considered because the photosensitive member 1 is uniformly charged by the charging member 2.

As in the present embodiment, the weight ratio of the polyisocyanate resin and the urethane polyol forming the thermosetting polyurethane resin forming the surface layer of the charging member is set to 1/5 <(weight of the polyisocyanate resin) / (urethane If the weight of the polyol is <1, a wrinkle having a smooth tip is formed on the surface of the charging member, and the ten-point average surface roughness is 1
Even if the electrophotographic apparatus having the charging member which is 5 μm or less and which is in pressure contact with the member to be charged (photoreceptor) is left in a high-temperature and high-humidity environment for a long time, the adhesion between the charging member and the member to be charged is It is possible to provide an electrophotographic apparatus capable of outputting a uniform image without uneven charging without causing sticking or sticking.

In the present embodiment, the weight of the polyisocyanate resin used for forming the surface layer was
The amount is 50 parts by weight with respect to 00 parts by weight, but the present invention is not limited to this weight.
What is necessary is just the weight part or less.

Hereinafter, an electrophotographic apparatus according to a third embodiment of the present invention will be described. This is the same as the first embodiment except that the surface layer 2c of the charging member 2 is a mixed resin of a thermoplastic polyurethane resin and a silicone resin.

The surface layer 2c was prepared by adding a thermoplastic polyurethane resin (trade name “Takerac E-360A” manufactured by Takeda Pharmaceutical Co., Ltd .; 50 parts by weight) to a mixed solution of 25 parts by weight of toluene and 75 parts by weight of isopropyl alcohol. And a solution obtained by mixing 50 parts by weight of a solid content of a silicone resin (product number “XR31-A2105” manufactured by Toshiba Silicone Co., Ltd.) with a thickness of 20 μm by a dip coating method.
After applying a surface layer having a thickness of 100 m, the resultant was dried with hot air at 100 ° C. for 3 hours.

In order to measure the linear shrinkage coefficient of the surface layer 2c, the above-mentioned surface layer 2c was applied on a glass preparation, dried and then peeled off from the glass preparation to obtain a test piece. The measurement was performed in accordance with the standard "ASTM D696" for measuring the linear contraction coefficient (linear expansion coefficient). The measurement result shows that the linear shrinkage coefficient is about 25 × 10 ⁻⁵ at room temperature.
/ ° C.

In this embodiment, (linear shrinkage coefficient of surface layer) /
(Linear shrinkage coefficient of base material (semiconductive layer) of charging member) = 1.7
(<2).

The surface layer of the charging member of this embodiment shrank without peeling off and cracking in the drying step, and the surface had a 10-point average roughness Rz of 11 μm.

When the surface of the charging member was observed with a microscope, it was found that wrinkles having a smooth tip were formed.

Further, the electrophotographic apparatus of this embodiment was set at 50 ° C.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
No phenomenon such as sticking and sticking between the charging member and the photosensitive member occurred.

When a solid white image or a halftone image was output using the electrophotographic apparatus of this embodiment, it was possible to obtain an image of uniform density without image abnormalities such as white spots, black spots, and fog. Was. This is considered because the photosensitive member 1 is uniformly charged by the charging member 2.

As in this embodiment, the ratio of the linear shrinkage coefficient between the base material (semiconductive layer) of the charging member and the surface layer is 1 <(linear shrinkage coefficient of the surface layer) / (linear shrinkage coefficient of the base material). If the materials of the base material and the surface layer are selected so as to satisfy <2, wrinkles having a smooth tip are formed on the surface of the charging member, and the 10-point average surface roughness is 15 μm or less, and Even if the electrophotographic apparatus having the charging member which is in pressure contact with the member to be charged (photoreceptor) is left in a high-temperature and high-humidity environment for a long time, sticking and sticking between the charging member and the member to be charged may occur. And an electrophotographic apparatus capable of outputting a uniform image without charge unevenness can be provided.

The following is the same as the first embodiment except that the surface layer 2c of the charging member 2 described in the electrophotographic apparatus of the first comparative example is made of copolymer nylon.

The surface layer 2c was prepared by coating 80 parts by weight of methyl alcohol with a copolymer nylon (trade name “C” manufactured by Toray Industries, Inc.).
M8000 "), a surface layer having a thickness of 20 μm was applied by a dip coating method using a solution in which 100 parts by weight of a solid content was mixed, followed by hot-air drying at 100 ° C. for 3 hours.

In order to measure the linear shrinkage coefficient of the surface layer 2c, the above-mentioned surface layer 2c was applied on a glass preparation, dried, and then peeled off from the glass preparation to obtain a measurement piece. The measurement was performed in accordance with the standard "ASTM D696" for measuring the linear contraction coefficient (linear expansion coefficient). The measurement results show that the linear shrinkage coefficient at room temperature is about 2 × 10 ^-5 /
° C.

In this comparative example, (linear contraction coefficient of base material (semiconductive layer) of charging member) / (linear contraction coefficient of surface layer) = 7.5.
(> 2).

The surface layer of the charging member of this comparative example was peeled off and cracked in the drying step. In addition, when the surface of the charging member was observed with a microscope, it was found that wrinkles having a sharp tip, which would cause uneven charging, were formed.

The electrophotographic apparatus of this comparative example was heated at 50 ° C.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Sticking between the charging member and the photoconductor occurred.

As in this comparative example, the ratio of the linear shrinkage coefficient between the base material (semiconductive layer) of the charging member and the surface layer is 1 <(linear shrinkage coefficient of the base material) / (linear shrinkage coefficient of the surface layer). If the material is selected out of the range of <2, the surface layer will be peeled off during the drying step, cracks will be formed, and wrinkles having sharp tips which are considered to cause charging unevenness will be formed on the surface of the charging member. In addition, if the electrophotographic apparatus having the charging member which is in pressure contact with the member to be charged (photoreceptor) is left in a high-temperature and high-humidity environment for a long time, the charging member and the member to be charged are fixed.

The second embodiment is the same as the first embodiment except that the surface layer 2c of the charging member 2 described in the electrophotographic apparatus of the second comparative example is made of silicone resin.

The surface layer 2c is made of isopropyl alcohol 9
0 parts by weight of a solid content of a silicone resin (product number “XR31-A2105” manufactured by Toshiba Silicone Co., Ltd.) is 12
Using a solution in which 0 parts by weight was mixed, a surface layer having a thickness of 20 μm was applied by a dip coating method, followed by hot-air drying at 100 ° C. for 3 hours.

In order to measure the linear shrinkage coefficient of the surface layer 2c, the above-mentioned surface layer 2c was applied on a glass preparation, dried and then peeled off from the glass preparation to obtain a test piece. The measurement was performed in accordance with the standard "ASTM D696" for measuring the linear contraction coefficient (linear expansion coefficient). The measurement result shows that the linear shrinkage coefficient is about 40 × 10 ⁻⁵ at room temperature.
/ ° C.

In this comparative example, (linear shrinkage coefficient of surface layer) /
(Linear shrinkage coefficient of base material (semiconductive layer) of charging member) = 2.7
(> 2).

The surface layer of the charging member of this comparative example was peeled off and cracked in the drying step. In addition, when the surface of the charging member was observed with a microscope, it was found that wrinkles having a sharp tip, which would cause uneven charging, were formed.

The electrophotographic apparatus of this comparative example was heated at 50 ° C.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Sticking between the charging member and the photoconductor occurred.

As in this comparative example, the ratio of the linear shrinkage coefficient between the base material (semiconductive layer) of the charging member and the surface layer is 1 <(linear shrinkage coefficient of the base material) / (linear shrinkage coefficient of the surface layer). If the material is selected out of the range of <2, the surface layer will be peeled off during the drying step, cracks will be formed, and wrinkles having sharp tips which are considered to cause charging unevenness will be formed on the surface of the charging member. In addition, if the electrophotographic apparatus having the charging member which is in pressure contact with the member to be charged (photoreceptor) is left in a high-temperature and high-humidity environment for a long time, the charging member and the member to be charged are fixed.

Hereinafter, an electrophotographic apparatus as a third comparative example will be described. The third embodiment is the same as the third embodiment except that the mixing weight of the polyisocyanate resin for forming the thermosetting polyurethane resin for forming the surface layer 2c of the charging member 2 is 10 parts by weight.

As described above, the surface layer 2c is made of toluene 25
A mixture of 0 parts by weight, 75 parts by weight of isopropyl alcohol, and 10 parts by weight of ethyl acetate was mixed with urethane polyol (Takerac E-5, trade name, manufactured by Takeda Pharmaceutical Co., Ltd.).
50A ") and 100 parts by weight of a solid content of a polyisocyanate resin (trade name" Takenate D-1 manufactured by Takeda Pharmaceutical Co., Ltd.)
A surface layer having a thickness of 20 μm was applied by a dip coating method using a solution obtained by mixing a solid content of 40 N ″) with 10 parts by weight of solid content, followed by hot-air drying at 100 ° C. for 3 hours.

In this comparative example, (weight of polyisocyanate resin) / (weight of urethane polyol) = 0.1 (<
1/5).

The electrophotographic apparatus of this comparative example was prepared at 50 ° C. and 85% R
When left in a high-temperature, high-humidity environment of H for 30 days, sticking between the charging member and the photosensitive member occurred. This phenomenon is because the amount of the mixed polyisocyanate resin is too small compared to the amount of the urethane polyol, so that many hydroxyl groups remain in the surface layer even after the drying step, and the photoreceptor surface resin is formed by water molecules surface-adsorbed by the hydroxyl groups. It is thought to be due to hydrolysis.

Further, when continuous images were formed using the electrophotographic apparatus of this comparative example, film peeling of the surface layer occurred when about 100 images were formed. This is probably because the amount of the mixed polyisocyanate resin was too small, the thermosetting polyurethane resin was not sufficiently crosslinked thermally, and the film strength of the surface layer was weak.

As in this comparative example, when the amount of the polyisocyanate resin forming the thermosetting polyurethane resin forming the surface layer is smaller than the amount of the urethane polyol,
In the case of (weight of polyisocyanate resin) / (weight of urethane polyol) <1/5, sticking to the charged member (photoreceptor) that is in pressure contact with the charging member when left in a high-temperature and high-humidity environment for a long period of time Not only does this cause sufficient film strength, but it is extremely unsuitable for practical use.

Hereinafter, an electrophotographic apparatus as a fourth comparative example will be described. The third embodiment is the same as the third embodiment except that the mixing weight of the polyisocyanate resin for forming the thermosetting polyurethane resin for forming the surface layer 2c of the charging member 2 is 150 parts by weight.

As described above, the surface layer 2c is made of toluene 25
A mixture of 0 parts by weight, 75 parts by weight of isopropyl alcohol, and 10 parts by weight of ethyl acetate was mixed with urethane polyol (Takerac E-5, trade name, manufactured by Takeda Pharmaceutical Co., Ltd.).
50A ") and 100 parts by weight of a solid content of a polyisocyanate resin (trade name" Takenate D-1 manufactured by Takeda Pharmaceutical Co., Ltd.)
A surface layer having a thickness of 20 μm was applied by a dip coating method using a solution obtained by mixing 150 N parts by weight of 40N ″) with a solid content, followed by hot-air drying at 100 ° C. for 3 hours.

The surface layer has a 10-point average roughness Rz of about 7 μm.
Met. In this comparative example, (1 <) 1.5 = (weight of polyisocyanate resin) / (weight of urethane polyol).

The electrophotographic apparatus of this comparative example was used at 50 ° C. and 85% R
When left in a high-temperature, high-humidity environment of H for 30 days, sticking between the charging member and the photosensitive member occurred. It is considered that this phenomenon occurred because the charging member and the photoreceptor were pressed against each other in a state close to the surface pressure contact because the roughness of the surface layer was small (Rz = about 7 μm), and the pressure contact area was large.

As in this comparative example, when the amount of the polyisocyanate resin forming the thermosetting polyurethane resin forming the surface layer is larger than the amount of the urethane polyol, (weight of the polyisocyanate resin) / (weight of the urethane polyol)>
1) Due to the increase in film strength, shrinkage in the drying step at the time of forming the surface layer is reduced, and the surface is smoothed. As a result, the pressure contact area between the charging member and the member to be charged is widened, and the For a long period of time, phenomena such as sticking and sticking between the charging member and the member to be charged occur.

[0098]

As described above, the present invention relates to a charging member for charging an object to be charged by contacting the object, wherein the charging member is provided with a surface layer on a substrate, and The ratio of the linear shrinkage coefficient of the surface layer is 1 <(linear shrinkage coefficient of the surface layer) / (linear shrinkage coefficient of the base material) <2, or 1 <(linear shrinkage coefficient of the base material) / (of the surface layer) (Characteristic shrinkage coefficient) <2, and there is no sticking or sticking between the charging member and the member to be charged even when left in a high-temperature and high-humidity environment for a long time.

Further, as described above, the present invention provides a photoconductive semiconductor, a charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor, and an electrostatic latent image on the photoconductive semiconductor. An electrophotographic apparatus, comprising: an optical device that forms a latent image; a developing device that visualizes the electrostatic latent image with a charged colored resin powder; and a transfer device that transfers the visualized image onto a material to be transferred. The charging member is provided with a surface layer on a base material, and the ratio of the linear shrinkage coefficient between the base material and the surface layer is 1 <(linear shrinkage coefficient of surface layer) / (linear shrinkage coefficient of base material) < 2, or
1 <(linear shrinkage coefficient of substrate) / (linear shrinkage coefficient of surface layer) <
The electrophotographic apparatus is characterized in that the charging member and the member to be charged do not stick or adhere to each other even when left in a high-temperature and high-humidity environment for a long time.

Further, as described above, the present invention relates to a charging member for charging an object to be charged in contact with the object to be charged, wherein the charging member comprises a surface layer made of a thermosetting polyurethane resin on a substrate. And the weight ratio of the polyisocyanate resin and the urethane polyol for forming the thermosetting polyurethane resin is 1/5 <(weight of the polyisocyanate resin)
/ (Weight of urethane polyol) <1, and does not cause sticking or sticking between the charging member and the member to be charged even when left in a high-temperature and high-humidity environment for a long time. .

Further, as described above, the present invention provides a photoconductive semiconductor, a charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor, and an electrostatic latent image on the photoconductive semiconductor. An electrophotographic apparatus, comprising: an optical device that forms a latent image; a developing device that visualizes the electrostatic latent image with a charged colored resin powder; and a transfer device that transfers the visualized image onto a material to be transferred. The charging member is provided with a surface layer made of a thermosetting polyurethane resin on a base material, and the weight ratio of the polyisocyanate resin and the urethane polyol for forming the thermosetting polyurethane resin is 1/5 <(poly Weight of isocyanate resin) / (weight of urethane polyol) <
The electrophotographic apparatus is characterized in that the charging member and the member to be charged do not stick or adhere to each other even when left in a high-temperature and high-humidity environment for a long time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an electrophotographic apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration sectional view of a conventional charging device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 1a conductive support 1b photosensitive layer 2 charging member 2a conductive shaft 2b semiconductive layer 2c surface layer 3 DC voltage source 4 optical device 5 developing device 6 transfer device 7 transfer material 8 cleaning device 9 optical neutralizer 100 Photoconductor 100a Conductive support 100b Photosensitive layer 101 Charging member 101a Conductive shaft 101b Semiconductive layer 101c Surface layer 102 DC voltage source

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hisanori Nagase 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshio Umeda 1006 Odaka Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Akiyuki Naka 1006 Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshiki Yamamura 1006 Odoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) Reference Document JP-A-4-168452 (JP, A) JP-A-2-22985 (JP, A) JP-A-2-259186 (JP, A) JP-A-7-36302 (JP, A) JP-A-5 281831 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02-15/02 103 F16C 13/00

Claims (3)

(57) [Claims] An object to be charged is charged by contacting the object to be charged.
A charging member, wherein the charging member has a thermosetting property on a substrate.
Provided with a surface layer made of polyurethane resin, said thermosetting
Polyisocyanate for forming polyurethane resin
When the weight ratio between the resin and the urethane polyol is 1/5 <(poly
Weight of isocyanate resin) / (weight of urethane polyol)
(Weight) <1. 2. The method according to claim 1, wherein the charging member has a roller shape.
The charging member according to claim 1, wherein 3. A photoconductive semiconductor, and said photoconductive semiconductor.
A charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor;
An optical device for forming an electrostatic latent image on a photoconductive semiconductor;
Visualize the electrostatic latent image with charged colored resin powder
A developing device and a transfer device for transferring the visualized image onto a material to be transferred
An electrophotographic apparatus comprising:
A surface layer made of thermosetting polyurethane resin is provided on the substrate.
To form the thermosetting polyurethane resin.
Weight ratio of polyisocyanate resin to urethane polyol
Is 1/5 <(weight of polyisocyanate resin) / (c)
(Weight of the urethane polyol) <1.
Electrophotographic equipment.