JPH07271144A - Electrostatic charging member and electrophotographic device - Google Patents

Abstract

PURPOSE:To obviate the generation of sticking, fixing, etc., between the surface of an electrostatic charging member and the surface of a member to be electrostatically charged even if the electrostatic charging member is left standing in pressurized contact with the member to be electrostatically charged under a high temp. and high hunridity evrironment by specifying the ratio of the coeffts. of linear shrinkage of the base material and surface layer of the electrostatic charging member. CONSTITUTION:This electrophotographic device consists of a photoreceptor 1, the electrostatic charging member 2, a DC voltage device 3 for applying voltage to the electrostatic charging member 2, an optical device 4 for forming electrostatic latent images on the surface of this photoreceptor 1, a developing device 5, a corotron transfer device 6 for transferring the sensible image on the surface of the photoreceptor 1 by electrostatic attraction onto a material 7 to be transferred, a cleaning device 8 for removing residual toners and an optical destaticizer 9 for electrostatically initializing the photoreceptor 1. The electrostatic charging member 2 is formed by providing the surface of the base material with the surface layer and is so formed that the ratio of the coeffts. of linear shrinkage between the base material and the surface layer attains 1<(the coefft. of linear shrinkage of the surface layer)/(the coefft. of linear shrinkage of the base material)<2 or 1<(the coefft. of linear shrinkage of the base material)/(the coefft. of linear shrinkage of the surface layer<2.

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 an object 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 which occurs when a charging member is brought into contact with the object to be charged and a minute gap between the charging member and the member to be charged occurs. The technology that uses is becoming mainstream. When this charging means is used, the discharge current that flows during charging is small, so that harmful neutral active species such as ozone and nitrogen oxides are scarcely generated, and the chemical deterioration of the charged object and the human body It is possible to prevent adverse effects.

In order to uniformly charge the photoconductor,
It has been said that the surface layer of the above-mentioned charging member needs to be smooth. That is, if the surface of the charging member has large irregularities, the electric field is concentrated on the convex portions, so that the photosensitive portions are locally overcharged due to the convex portions and the photoreceptor is locally insufficiently charged due to the concave portions, and the solid portions are solid. It causes fog when a white image is output.

An example of the structure of the above charging means will be described below with reference to the drawings. FIG. 2 shows a photoconductive semiconductor (photoreceptor) 10 which is a member to be charged in the electrophotographic apparatus.
FIG. 6 is a cross-sectional view of a configuration in which a photosensitive member and a roller-shaped charging member that is driven to rotate are brought into contact with 0.

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 is used) and a photoconductive semiconductor layer (photosensitive layer) 100b. Here, the photosensitive layer is assumed to be a negative charging 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, the electrostatic latent image formed on the photoconductor is visualized by the charged colored resin powder (toner), and then the developed image is electrostatically transferred to the transfer material by the transfer device, Although the toner remaining on the body is removed by the cleaning device, all the toner remaining on the photoconductor is not cleaned, and a small amount of toner remains on the photoconductor without being cleaned. Therefore, the toner comes in contact with the surface of the charging member and adheres to the surface of the charging member.However, if charging is performed while the toner remains adhered, it may cause uneven charging. The adhered toner needs to be easily removed. Therefore, in order to improve the surface releasability of the charging member, for example, a surface layer made of a polyamide resin, a polyurethane resin, a fluororesin, or a mixture of these resins is provided to improve the toner cleaning property.

The charging operation of the charging member will be described below. As the photoconductor 100 rotates in the direction of the arrow in the figure, the charging member 101 also rotates following 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 photoconductor 100 is charged according to Equation 1.

[0008]

[Equation 1]

However, in (Equation 1), Vo is the surface potential of the photoconductor, Vin is the applied DC voltage, and Vth is the discharge start voltage between the photoconductor 100 and the charging member 101.

It has been said that the surface layer of the above-mentioned charging member needs to be smooth in order to uniformly charge the photoreceptor. That is, if the surface of the charging member has large irregularities, the electric field is concentrated on the convex portions, so that the photosensitive portions are locally overcharged due to the convex portions and the photoreceptor is locally insufficiently charged due to the concave portions, and the solid portions are solid. It causes fog when a white image is output.

In order to eliminate such uneven charging, in the past, measures were taken to smooth the surface of the charging member. Specifically, as disclosed in JP-A-2-222985, the 10-point average roughness Rz of the surface of the charging member.
Was 5 μm or less.

[0012]

However, when the above-mentioned conventional charging member is left in pressure contact with the photosensitive member, a phenomenon such as sticking or sticking of the charging member and the photosensitive member occurs especially in a high temperature and high humidity environment. There were cases. It is considered that the main reason for this is that a chemical bond due to hydrolysis of the resin on the surface of the charging member or the surface of the photoconductor occurs between the surface of the charging member and the surface of the photoconductor.

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 member to be charged even if the charging member is left in pressure contact with the member to be charged in a high temperature and high humidity environment. A charging member and an electrophotographic apparatus are provided.

[0014]

In order to solve the above problems, a charging member of the present invention is a charging member which contacts an object to be charged and charges the object, wherein the charging member is a base material. A surface layer is provided thereon, and the ratio of the linear shrinkage coefficient of the base material to the surface layer is 1 <(linear shrinkage coefficient of the surface layer) / (linear shrinkage coefficient of the base material) <2, or 1 <(base The charging member is characterized in that the linear shrinkage coefficient of the material) / (the linear shrinkage coefficient of the surface layer) <2.

Further, in the above charging member, the charging member has a roller shape. In order to solve the above-mentioned problems, the electrophotographic apparatus of the present invention includes a photoconductive semiconductor, a charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor, and a photoconductive semiconductor on the photoconductive semiconductor. An electronic device including an optical device for forming an electrostatic latent image on the surface, a developing device for visualizing the electrostatic latent image with charged colored resin powder, and a transfer device for transferring the visible image onto a transfer material. In the photographic device, the charging member has a surface layer provided on a base material, and a ratio of linear contraction coefficients of the base material and the surface layer is 1 <(linear contraction coefficient of surface layer) / (base material). Linear shrinkage coefficient) <2, or
1 <(Linear shrinkage coefficient of base material) / (Linear shrinkage coefficient of surface layer) <
2 is an electrophotographic apparatus.

In order to solve the above-mentioned problems, the charging member of the present invention is a charging member which contacts an object to be charged to charge the object, and the charging member is thermoset on a substrate. Of a polyisocyanate resin and a urethane polyol for forming the thermosetting polyurethane resin by providing a surface layer made of a hydrophilic polyurethane resin is 1/5 <(weight of polyisocyanate resin) / (weight of urethane polyol) The charging member is <1.

Further, the above charging member is characterized in that the charging member is roller-shaped. In order to solve the above-mentioned problems, the electrophotographic apparatus of the present invention includes a photoconductive semiconductor, a charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor, and a photoconductive semiconductor on the photoconductive semiconductor. An electronic device including an optical device for forming an electrostatic latent image on the surface, a developing device for visualizing the electrostatic latent image with charged colored resin powder, and a transfer device for transferring the visible image onto a transfer material. In the photographic apparatus, the charging member has a surface layer made of a thermosetting polyurethane resin on a substrate, and a weight ratio of polyisocyanate resin and urethane polyol for forming the thermosetting polyurethane resin is 1 / 5 <(weight of polyisocyanate resin) / (weight of urethane polyol) <
1 is an electrophotographic apparatus.

[0018]

According to the present invention, due to the above-mentioned constitution, even if the charging member and the body to be charged are left in pressure contact with each other in a high temperature and high humidity environment, the surface of the charging member does not stick or stick to the surface of the body to be charged. . Hereinafter, how the charging member of the present invention does not cause sticking, sticking, or the like with a member to be charged will be described.

In order to prevent the charging member from sticking to, and sticking to, the charged member, it is conceivable to reduce the area of the nip portion due to the pressure contact between the charging member and the charged member. In order to reduce the area of the nip portion, the surface of the charging member may be roughened and the pressure contact between the charging member and the body to be charged may be changed from surface pressure contact to point pressure contact.

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

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

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

If the difference in the linear shrinkage coefficient between the substrate and the surface layer is too large, film peeling or cracking may occur during shrinkage, or the 10-point average surface roughness Rz of the surface layer after shrinkage is 15 μm.
It becomes more than m, which causes uneven charging. The inventors have found that the difference in linear shrinkage coefficient between the two is less than or equal to 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 uneven charging without film peeling and cracking during shrinking,
That is, it was found that a surface layer having an appropriate surface roughness (10-point average surface roughness Rz ≦ 15 μm) in which wrinkles having a smooth tip shape were formed was 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 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 surface layer has too strong film strength, wrinkles will be generated on the surface layer during contraction in the drying step after coating the surface layer. Without, 10
A smooth surface with a small point average surface roughness Rz is obtained. Therefore, when forming a surface layer made of a thermosetting polyurethane resin having an appropriate wrinkle (a smooth tip shape and a 10-point average surface roughness Rz of about 15 μm or less) on the surface, the amount of polyisocyanate resin to be mixed is The inventors have found that there is a maximum value, which is (weight of polyisocyanate resin) / (weight of urethane polyol) <1.

When the amount of polyisocyanate resin mixed is too small, the film strength is weak, and even if the linear shrinkage coefficient is slightly different from that of the base material, large wrinkles are generated, and the 10-point average surface after shrinkage. The roughness Rz becomes 15 μm or more, which causes uneven charging such as excessive charging and insufficient charging. Therefore, there is a minimum value for 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 out.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic apparatus which is a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of the electrophotographic apparatus of the first embodiment. Reference numeral 1 is a photoconductor, 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 photoconductor, and 5 is a resin for coloring the electrostatic latent image. Developing device for visualizing with powder (toner), 6
Is a corotron transfer device for transferring the visible image on the surface of the photoconductor to the transfer target material 7 by electrostatic attraction, 8 is a cleaning device for removing the toner remaining on the surface of the photoconductor after the transfer process, 9
Is an optical static eliminator for electrostatically initializing the photoconductor.

The photosensitive member 1 comprises a drum-shaped aluminum conductive support 1a having a diameter of 30 mm and a photosensitive layer 1b coated on the grounded conductive support 1a.

The conductive support 1a is not limited to aluminum and may be any one having a conventionally known conductivity, such as aluminum, a metal such as an aluminum alloy, tin oxide or indium oxide. It may be various plastics obtained by applying a metal oxide such as the above, or a metal and a metal oxide thereof by vacuum vapor deposition, sputtering, laminating, coating, or the like, and conductive treatment.

For the photosensitive layer 1a, a negative charging type laminated organic photoreceptor was used. Specifically, in the charge generation layer, 5 parts by weight of τ type metal-free phthalocyanine (manufactured by Toyo Ink Manufacturing Co., Ltd.) and acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name)
4 parts by weight of DIANAL HR664 ") and 1 part by weight of melamine resin (manufactured by Dainippon Ink and Co., Ltd., trade name" Super Beckamine L145-60 ") in 115 parts by weight of s-butyl alcohol are applied to the aluminum coating solution. The conductive support 1a was applied by dip coating and dried at 130 ° C. for 1 hour to have a film thickness of 0.2 μm.

The charge generation layer is not limited to the above materials and method. Examples of the charge generating substance used in the charge generating layer include various pigments or dyes such as phthalocyanine type, azo type, squarylium type, cyanine type, quinone type and perylene type pigments. The charge generation layer is prepared by adding and dispersing these pigments or dyes and a suitable binder resin to prepare a coating solution, and applying a conventional coating method such as a dip coating method, a spin coating method, a spray coating method, or an electrostatic coating method. It is applied and dried by heating to form a film having a thickness of several μm.
It is preferable to form the film with a thickness of 2 to 2 μm.

The binder resin used in the charge generation layer and the charge transport layer to be described later is, if necessary, for the purpose of improving the adhesiveness to other layers, improving the uniformity of the coating film, adjusting the fluidity during coating, and the like. Used specifically, polyester, polyvinyl chloride, polyvinyl butyral, polyvinyl acetate,
Examples thereof include polycarbonate, fluororesin, methacrylic resin, silicone resin, and copolymers of these resins. Further, as the solvent, a charge generating agent, a charge transporting agent,
Alternatively, it may be any as long as it dissolves 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. The solution was dissolved, the 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 materials and construction method. The electron-donating substance used in the charge-transporting layer may be a compound having an electron-donating group such as an alkyl group, an alkoxy group, an amino group, or an imide group, a polycyclic aromatic compound such as anthracene, pyrene, or phenanthrene, or a skeleton thereof. Having derivatives, indole, oxazole,
Examples thereof include heterocyclic compounds such as oxadiazole, carbazole, thiazole, pyrazoline, imidazole and triazole, and derivatives having a skeleton thereof. The electron donating substance and the binder resin are dissolved in an appropriate solvent, and the charge transporting layer is formed by coating and drying by a usual coating method such as a dip coating method, a spin coating method, a spray coating method and an electrostatic coating method. However, when the electron-donating substance is a polymer compound, the charge transport layer may be formed alone without mixing the binder resin. The thickness of the charge transport layer is several μm
~ Several tens of μm, but preferably 5 to 25 μm.

In the present embodiment, the photosensitive layer 1b is a negatively chargeable organic photosensitive layer, but the present invention is not limited to this. The voltage applied to the charging member 2, the bias voltage of the developing device 5, and the toner. A positive charging type may be used if the polarity of the corona wire current of the transfer device 6 is noted.
An inorganic photosensitive layer such as amorphous selenium or amorphous silicon may be used.

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

The semiconductive layer 2b is made of a thermoplastic polyurethane resin (Takelac E-360, manufactured by Takeda Pharmaceutical Co., Ltd., trade name.
A ″) is a conductive material such as lithium perchlorate (LiCl ₃
O ₄ ) was added internally in an amount of 5% by weight of solid content. Although the resistance value of the semiconductive layer was about 10 ⁷ Ω in this embodiment, it may be 10 ⁵ Ω or more and 10 ¹⁰ Ω or less, and preferably 10 ⁶ Ω or more and 10 ⁸ Ω or less.

The surface layer 2c comprises 25 parts by weight of xylene and n
-In a mixed solution consisting of 75 parts by weight of butyl alcohol,
Fluorine resin (made by Asahi Glass Co., Ltd., trade name "Lumiflon
It was prepared by applying a surface layer having a film thickness of 20 μm by a dip coating method using a solution prepared by mixing 100 parts by weight of the solid content of LF110 ″) and then drying with hot air at 100 ° C. for 3 hours.

The charging member 2 is 200 mm in the longitudinal direction of the photoconductor.
However, the pressure was applied to the photoconductor 1 at a total pressure of 700 g.

A DC constant voltage device 3 applied a negative constant 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 photoconductor 1 by the optical device 4. In this embodiment, the wavelength is 780 to 800n.
As a result of adjusting the output of the LED so that the photosensitive member surface potential of the latent image portion becomes −80 V using the m LED array,
The amount of light was 0.8 mW.

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

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

Plain paper having a basis weight of 60 g / m ² was used as the transfer material. The cleaning device 8 is configured such that a blade made of polyurethane resin rubs the surface of the photoconductor at a counter angle.

As the optical static eliminator 9, the same device as the optical device 4 was used, and the entire surface was always exposed while the photosensitive member was rotating.

In order to measure the linear shrinkage coefficient of the semiconductive layer 2b, the above-mentioned semiconductive layer 2b is dissolved in a mixed solution of toluene and isopropyl alcohol, the solution is applied onto a glass preparation, dried and then removed from the glass preparation. It was peeled off and used as a measurement piece. The standard is "ASTM D696", which is a standard for measuring the coefficient of linear expansion (coefficient of linear expansion).
It was done according to. As a result of 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, which was used as a measurement piece. The measurement was performed according to the standard "ASTM D696" regarding the measurement of the coefficient of linear expansion (coefficient of linear expansion). 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 was peeled off in the drying process and shrunk without causing cracks, and the 10-point average roughness Rz of the surface was 12 μm.

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

Further, the electrophotographic apparatus of the present embodiment is set at 50 ° C. for 8 hours.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Phenomena such as sticking and sticking between the charging member and the photoconductor did not occur.

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

As in the present 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 that <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. Even if the electrophotographic apparatus equipped with this charging member that comes into pressure contact with the charged member (photoreceptor) is left in a high temperature and high humidity environment for a long period of time, sticking or sticking between the charging member and the charged member may occur. Therefore, it is possible to provide an electrophotographic apparatus capable of outputting a uniform image without uneven charging.

The electrophotographic apparatus according to the second embodiment of the present invention will be described below. It is the same as the first embodiment except that the surface layer 2c of the charging member 2 is a thermosetting polyurethane resin.

The surface layer 2c contains 250 parts by weight of toluene,
75 parts by weight of isopropyl alcohol and 10 parts of ethyl acetate
100 parts by weight of solid content of urethane polyol (manufactured by Takeda Chemical Industries, trade name "Takelac E-550A") and polyisocyanate resin (manufactured by Takeda Chemical Industry, trade name "Takenate D-140N") in a mixed solution consisting of parts by weight. 100 parts by weight of a surface layer having a thickness of 20 μm is applied by a dip coating method using a solution obtained by mixing 50 parts by weight of the solid content of
It was prepared by drying with hot air under the condition of ℃ 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 was peeled off in the drying process and shrunk without causing cracks, and the 10-point average roughness Rz of the surface was 10 μm.

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

Further, the electrophotographic apparatus of the present embodiment was set at 50 ° C. for 8 hours.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Phenomena such as sticking and sticking between the charging member and the photoconductor did not occur.

Further, when a white solid image or a halftone image is output using the electrophotographic apparatus of this embodiment, an image having a uniform density with no image abnormalities such as white spots, black spots, and fog can be obtained. It was It is considered that this is because the photoconductor 1 is uniformly charged by the charging member 2.

As in this example, the weight ratio of the polyisocyanate resin and the urethane polyol that make up the thermosetting polyurethane resin forming the surface layer of the charging member is 1/5 <(weight of polyisocyanate resin) / (urethane). If the weight of the polyol is less than 1, wrinkles having smooth tips are formed on the surface of the charging member, and the 10-point average surface roughness is 1
Even if the electrophotographic apparatus having the charging member of 5 μm or less and in pressure contact with the charged member (photoreceptor) is left in a high temperature and high humidity environment for a long time, the bonding between the charging member and the charged member It is possible to provide an electrophotographic apparatus capable of outputting a uniform image without uneven charging without causing sticking or sticking.

In this embodiment, the weight of the polyisocyanate resin used for forming the surface layer is the urethane polyol 1
Although 50 parts by weight is used with respect to 00 parts by weight, the present invention is not limited to this weight, and 20 parts by weight or more and 100 parts by weight or more.
It may be less than or equal to parts by weight.

The electrophotographic apparatus according to the third embodiment of the present invention will be described below. 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 mixing a mixed solution of 25 parts by weight of toluene and 75 parts by weight of isopropyl alcohol with a thermoplastic polyurethane resin (Takelac E-360A, manufactured by Takeda Pharmaceutical Co., Ltd., solids content: 50 parts by weight). And a silicone resin (manufactured by Toshiba Silicone Co., Ltd., product number “XR31-A2105”) with a solid content of 50 parts by weight are used to form a film having a thickness of 20 μm by a dip coating method.
It was prepared by applying a surface layer of m and drying with hot air under the condition of 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 slide, dried and then peeled off from the glass slide, and used as a measurement piece. The measurement was performed according to the standard "ASTM D696" regarding the measurement of the coefficient of linear expansion (coefficient of linear expansion). The measurement result shows that the linear shrinkage coefficient is about 25 × 10 ⁻⁵ at room temperature.
/ ° C.

In this example, (the linear shrinkage coefficient of the 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 example was peeled off during the drying process and shrunk without causing cracks, and the 10-point average roughness Rz of the surface was 11 μm.

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

In addition, the electrophotographic apparatus of this embodiment was set at 50 ° C. for 8 hours.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Phenomena such as sticking and sticking between the charging member and the photoconductor did not occur.

When a white solid image or a halftone image is output using the electrophotographic apparatus of this embodiment, it is possible to obtain an image having a uniform density with no image abnormalities such as white spots, black spots, and fog. It was It is considered that this is because the photoconductor 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 surface layer) / (linear shrinkage coefficient of the base material). If the materials of the base material and the surface layer are selected so that <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. Even if the electrophotographic apparatus equipped with this charging member that comes into pressure contact with the charged member (photoreceptor) is left in a high temperature and high humidity environment for a long period of time, sticking or sticking between the charging member and the charged member may occur. Therefore, it is possible to provide an electrophotographic apparatus capable of outputting a uniform image without uneven charging.

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 made of copolymerized nylon (manufactured by Toray Industries, Inc., trade number "C") in 80 parts by weight of methyl alcohol.
It was prepared by applying a surface layer having a film thickness of 20 μm by a dip coating method using a solution prepared by mixing 100 parts by weight of solid content of M8000 ″) and then drying 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, which was used as a measurement piece. The measurement was performed according to the standard "ASTM D696" regarding the measurement of the coefficient of linear expansion (coefficient of linear expansion). The measurement result shows that the linear shrinkage coefficient at room temperature is about 2 × 10 ⁻⁵ /
It was ℃.

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

The surface layer of the charging member of this comparative example was peeled off and cracked during the drying process. In addition, when the surface of the charging member was observed with a microscope, it was found that wrinkles having sharp tips, which are considered to cause uneven charging, were formed.

Further, the electrophotographic apparatus of this comparative example was set at 50 ° C. for 8 hours.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Adhesion between the charging member and the photoconductor occurred.

As in this comparative example, the ratio of the linear contraction coefficient of the base material (semiconductive layer) of the charging member to the surface layer is 1 <(linear contraction coefficient of base material) / (linear contraction coefficient of surface layer). If the material is selected out of the range of <2, the surface layer peels off during the drying process and cracks occur, and wrinkles having sharp tips that are considered to cause uneven charging are formed on the surface of the charging member. In addition, if the electrophotographic apparatus including this charging member that comes into pressure contact with the charged member (photoreceptor) is left in a high temperature and high humidity environment for a long period of time, the charging member and the charged member are fixed to each other.

Hereinafter, 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 is a silicone resin.

The surface layer 2c is made of isopropyl alcohol 9
Solid content of 12 parts by weight of silicone resin (manufactured by Toshiba Silicone Co., Ltd., product number "XR31-A2105") in 0 parts by weight.
It was prepared by applying a surface layer having a film thickness of 20 μm by a dip coating method using a solution prepared by mixing 0 parts by weight, and then drying with hot air under the condition of 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 according to the standard "ASTM D696" regarding the measurement of the coefficient of linear expansion (coefficient of linear expansion). The measurement result shows that the linear shrinkage coefficient is about 40 × 10 ⁻⁵ at room temperature.
/ ° C.

In this comparative example, (the linear shrinkage coefficient of the 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 during the drying process. In addition, when the surface of the charging member was observed with a microscope, it was found that wrinkles having sharp tips, which are considered to cause uneven charging, were formed.

Further, the electrophotographic apparatus of this comparative example was set at 50 ° C. for 8 hours.
When left in a high temperature and high humidity environment of 5% RH for 30 days,
Adhesion between the charging member and the photoconductor occurred.

As in this comparative example, the ratio of the linear contraction coefficient between the base material (semiconductive layer) and the surface layer of the charging member is 1 <(linear contraction coefficient of base material) / (linear contraction coefficient of surface layer). If the material is selected out of the range of <2, the surface layer peels off during the drying process and cracks occur, and wrinkles having sharp tips that are considered to cause uneven charging are formed on the surface of the charging member. In addition, if the electrophotographic apparatus including this charging member that comes into pressure contact with the charged member (photoreceptor) is left in a high temperature and high humidity environment for a long period of time, the charging member and the charged member are fixed to each other.

The electrophotographic apparatus of the third comparative example will be described below. The third embodiment is the same as the third embodiment except that the mixing weight of the polyisocyanate resin that forms the thermosetting polyurethane resin that forms 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
In a mixed solution of 0 parts by weight, 75 parts by weight of isopropyl alcohol, and 10 parts by weight of ethyl acetate, urethane polyol (Takelac E-5, trade name, manufactured by Takeda Pharmaceutical Co., Ltd.
50A ") solid content of 100 parts by weight, and polyisocyanate resin (Takenate D-1 manufactured by Takeda Pharmaceutical Co., Ltd.)
It was prepared by applying a surface layer having a film thickness of 20 μm by a dip coating method using a solution mixed with 10 parts by weight of a solid content of 40 N ″), followed by drying with hot air 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 tested at 50 ° C. and 85% R.
When left for 30 days in a high temperature and high humidity environment, sticking between the charging member and the photoconductor occurred. This phenomenon is because the amount of the mixed polyisocyanate resin is too small as compared with the amount of the urethane polyol, so that there are many hydroxyl groups remaining in the surface layer even after the drying step, and the surface molecules of the photoreceptor due to water molecules adsorbed by the hydroxyl groups It is thought that the cause is hydrolysis.

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

As in this comparative example, when the amount of polyisocyanate resin that makes up the thermosetting polyurethane resin that forms the surface layer is smaller than the amount of urethane polyol, that is,
When (weight of polyisocyanate resin) / (weight of urethane polyol) <1/5, when left in a high temperature and high humidity environment for a long period of time, sticking to a charged member (photoreceptor) that is in pressure contact with a charging member In addition to causing the above problem, sufficient film strength cannot be obtained, which is extremely unsuitable for practical use.

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

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

The 10-point average roughness of the surface layer has an 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 tested at 50 ° C. and 85% R.
When left for 30 days in a high temperature and high humidity environment, sticking between the charging member and the photoconductor occurred. It is considered that this phenomenon occurred because the surface area was small (Rz = about 7 μm) and the charging member and the photosensitive member were pressed against each other in a state close to the surface pressure contact, resulting in a large pressure contact area.

As in this comparative example, when the amount of polyisocyanate resin for forming the thermosetting polyurethane resin forming the surface layer is larger than the amount of urethane polyol (weight of polyisocyanate resin) / (weight of urethane polyol)>
1) Due to the increase of the film strength, the shrinkage in the drying process at the time of forming the surface layer is reduced, and the surface becomes smooth, and as a result, the pressure contact area between the charging member and the body to be charged is widened, and the environment is high temperature and high humidity. If it is left for a long period of time, phenomena such as sticking and sticking of the charging member and the body to be charged occur.

[0098]

INDUSTRIAL APPLICABILITY As described above, the present invention is a charging member for contacting a charged body and charging the charged body, wherein the charging member is provided with a surface layer on a base material, 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) / (surface layer It is a charging member characterized by a linear shrinkage coefficient) <2, and even if it is left in a high temperature and high humidity environment for a long period of time, sticking, sticking, etc. between the charging member and the body to be charged do not occur.

As described above, according to the present invention, the photoconductive semiconductor, the charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor, and the electrostatic latent image on the photoconductive semiconductor. An electrophotographic apparatus comprising: an optical device for forming an electrostatic latent image, a developing device for visualizing the electrostatic latent image with charged colored resin powder, and a transfer device for transferring the visible image onto a transfer material. The charging member has a surface layer provided on a base material, and the ratio of the linear contraction coefficients of the base material and the surface layer is 1 <(linear contraction coefficient of surface layer) / (linear contraction coefficient of base material) < 2 or
1 <(Linear shrinkage coefficient of base material) / (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 to each other or adhere to each other even when left in a high temperature and high humidity environment for a long time.

As described above, the present invention is a charging member for contacting a charged body to charge the charged body, wherein the charging member is a surface layer made of a thermosetting polyurethane resin on a base material. And the weight ratio of polyisocyanate resin and urethane polyol for forming the thermosetting polyurethane resin is 1/5 <(weight of polyisocyanate resin).
/ (Weight of urethane polyol) <1, and the charging member does not stick or adhere to the member to be charged even when left in a high temperature and high humidity environment for a long time. .

As described above, according to the present invention, the photoconductive semiconductor, the charging member that contacts the photoconductive semiconductor to charge the photoconductive semiconductor, and the electrostatic latent image on the photoconductive semiconductor. An electrophotographic apparatus comprising: an optical device for forming an electrostatic latent image, a developing device for visualizing the electrostatic latent image with charged colored resin powder, and a transfer device for transferring the visible image onto a transfer material. In the charging member, a surface layer made of a thermosetting polyurethane resin is provided on a base material, and a weight ratio of polyisocyanate resin and 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 it 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 period of time.

[Brief description of drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 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 Transferred 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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hisanori Nagase 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshio Umeda, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Akiyuki Naka, 1006 Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Toshiki Yamamura, 1006, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial

Claims (6)

[Claims] 1. A charging member for charging a charged body by contacting the charged body, wherein the charging member has a surface layer provided on a base material, and the surface shrinkage coefficient of the linear shrinkage coefficient of the base material and the surface layer. Ratio is 1 <
(Linear shrinkage coefficient of surface layer) / (Linear shrinkage coefficient of base material) <2,
Alternatively, the charging member is characterized in that 1 <(linear shrinkage coefficient of base material) / (linear shrinkage coefficient of surface layer) <2. 2. The charging member according to claim 1, wherein the charging member is roller-shaped. 3. A photoconductive semiconductor, a charging member for contacting the photoconductive semiconductor to charge the photoconductive semiconductor, an optical device for forming an electrostatic latent image on the photoconductive semiconductor, An electrophotographic apparatus comprising: a developing device that visualizes an electrostatic latent image with charged colored resin powder; and a transfer device that transfers the visualized image onto a transfer material, wherein the charging member is a base material. A surface layer is provided thereon, and the ratio of the linear shrinkage coefficient of the base material to the surface layer is 1 <(linear shrinkage coefficient of the surface layer) / (linear shrinkage coefficient of the base material) <2, or 1 <(base An electrophotographic apparatus, wherein the linear shrinkage coefficient of the material) / (the linear shrinkage coefficient of the surface layer) <2. 4. A charging member for contacting a charged body to charge the charged body, wherein the charging member comprises a surface layer made of a thermosetting polyurethane resin on a base material, the thermosetting polyurethane. A charging member, wherein the weight ratio of the polyisocyanate resin and the urethane polyol for forming the resin is 1/5 <(weight of polyisocyanate resin) / (weight of urethane polyol) <1. 5. The charging member according to claim 4, wherein the charging member has a roller shape. 6. A photoconductive semiconductor, a charging member for contacting the photoconductive semiconductor to charge the photoconductive semiconductor, an optical device for forming an electrostatic latent image on the photoconductive semiconductor, An electrophotographic apparatus comprising: a developing device that visualizes an electrostatic latent image with charged colored resin powder; and a transfer device that transfers the visualized image onto a material to be transferred, wherein the charging member is a base material. A surface layer made of a thermosetting polyurethane resin is provided on the surface, and the weight ratio of the polyisocyanate resin and the urethane polyol for forming the thermosetting polyurethane resin is 1/5 <(weight of polyisocyanate resin) / (urethane). An electrophotographic apparatus, wherein the weight of the polyol) is <1.