JP2003202732A - Electrostatic charging member and electrostatic charging device and electrostatic charging method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charging member which can perform uniform electrostatic charging with high efficiency and can prevent the generation of harmful ozone and the generation of a NOx giving rise to an image defect and has high reliability and performance maintenance characteristic by controlling the supply of water, etc., in an electrostatic charging method by injection of water and an electrostatic charging device and electrostatic charging method. <P>SOLUTION: The electrostatic charging member has a photocatalyst substance on its surface, in which the surface of the electrostatic charging member is made hydrophilic by irradiating the photocatalyst substance with light including a wavelength to excite the substance. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to a charging member, a charging device, and a charging method used for an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus such as a printer, a facsimile, and a compound OA device of these. More specifically, by pressing on the surface of a charged body such as a photoconductor or a dielectric,
The present invention relates to a charging member for uniformly charging the surface, a charging device using the same, and a charging method.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, the surface of an electrostatic latent image carrier (charged body) such as a photoconductor or a dielectric body is exposed before exposure in order to form an electrostatic latent image. Is being charged. As a method of performing the charging process, a non-contact charging method in which charging is performed by corona discharge generated by applying a high voltage to a tungsten wire is widely adopted. However, in this non-contact charging method, a large amount of ozone is generated due to discharge in the atmosphere by applying a high voltage, which causes environmental pollution around the image forming apparatus.

In contrast to the non-contact charging method, there is a contact charging method (Japanese Patent Laid-Open No. 54-150131) in which a charging member is brought into contact with an electrostatic latent image carrier to carry out a charging process. This contact charging method has the advantages that the voltage applied to the charging member is low and the amount of ozone generated is very small, and is being adopted recently.

However, since the conventional charging method using contact using discharge follows Paschen's law, a DC voltage obtained by adding a discharge start voltage and a desired charging potential is applied to the surface of the electrostatic latent image carrier. Therefore, there is a problem that the charging efficiency is extremely poor. Further, since the charging roll used as the charging member and the electrostatic latent image carrier are not completely in contact with each other, there is a problem that uniform charging cannot be performed.

A method (Japanese Patent Laid-Open No. 63-149668) of superposing an AC voltage component on an applied DC voltage component for the purpose of improving the non-uniform charging has been proposed, but it is not solved sufficiently. is not. In addition, although these contact charging methods can greatly reduce the ozone generation amount as compared with the non-contact charging method, they cannot be completely eliminated, and thus there is a problem to the environment. Further, there is a problem that the nitrogen oxide generated by the discharge contaminates the electrostatic latent image carrier and causes an image quality defect.

On the other hand, a magnetic brush, a roll-shaped charging member, or the like is used, and injection charging is performed in combination with an electrostatic latent image carrier having a charge injection layer to improve charging efficiency or to use ozone in an environment. There have been attempts to prevent contamination (Japanese Patent Laid-Open Nos. 59-133569 and 6-3).
921 and JP-A-8-69165). However, in the injection charging method as described above, the contact between the charging member and the electrostatic latent image carrier is not sufficient, so that there is a limit to the improvement of the charging efficiency, and in particular, the electrostatic latent image carrier that rotates at high speed is limited. A significant reduction in charging efficiency is observed when the is charged.

Further, a proposal using a charging member in which a sponge is impregnated with water has been made (JP-A-7-140729 and JP-A-8-62932). In the above method, the impregnated water in the sponge is used. Since it directly contacts the electrostatic latent image bearing member, it is difficult to control the amount of water supplied to the surface of the electrostatic latent image bearing member, and there is a problem that reliability and performance maintainability are lacking.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to control the supply of water in the injection charging method using water.
It is possible to perform high efficiency and uniform charging,
It is an object of the present invention to provide a charging member, a charging device, and a charging method that can prevent harmful ozone generation and nitrogen oxide generation that cause image quality defects, and have high reliability and high performance maintainability.

[0009]

The above objects can be achieved by the present invention described below. That is, the present invention provides a charging member having a <1> photocatalytic substance on its surface,
By irradiating the surface of the charging member with light having a wavelength that excites the photocatalytic substance, the surface of the charging member becomes hydrophilic.

<2> The charging member has the photocatalytic substance and silicon oxide on its surface. <1>
The charging member according to 1.

<3> The charging member has the photocatalytic substance and a silicone resin on its surface.
1> is the charging member.

<4> In any one of <1> to <3>, the contact angle of water on the surface of the charging member is 25 degrees or less when the photocatalytic substance is excited by the light irradiation. It is the charging member described.

<5> The charging member according to any one of <1> to <4>, wherein the photocatalytic substance is titanium oxide.

<6> The charging member is brought into contact with the member to be charged,
A charging device having means for applying a voltage to the charging member, wherein the charging member is the charging member according to any one of <1> to <5>.

<7> The charging member is the charging member according to any one of <1> to <5>, wherein a thin layer of water is formed on the surface of the charging member that contacts the member to be charged. By pressing on the charged body and applying a voltage,
This is a charging method characterized by charging an object to be charged.

More specifically, the present invention relates to the injection charging method using water for directly injecting charges into the electrostatic latent image bearing member, which reduces the contact angle of water on the surface of the charging member, By uniformly forming a thin layer of water on the surface of the charging member, while maintaining the charging efficiency close to 100%, water spillage and member in the conventional case where a charging member in which sponge is impregnated with water is used. It is possible to achieve improvement of image defects caused by uneven charging due to surface drying and uneven water supply.

Further, according to the present invention, the adhesion between the charging member in the injection charging area and the electrostatic latent image carrier is improved, and stable injection charging is always possible regardless of the operating environment.
It is possible to obtain stable charging potential and charging efficiency in all environments without fluctuation of the charging potential due to humidity change which has been a problem in the conventional contact charging method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The charging member of the present invention has a photocatalytic substance on its surface, and the surface of the charging member becomes hydrophilic by irradiating with light having a wavelength that excites the photocatalytic substance. Is. The charging member is a member used in an apparatus that charges an electrostatic latent image bearing member (charged member) in an electrophotographic apparatus by charging.

<Charging Member> The charging member of the present invention has a photocatalytic substance on the surface as described above, but its form is such that it can be stably contacted with a member to be charged and can be irradiated with light. Any form can be used as long as the charge can be uniformly applied to the surface of the body to be charged. For example, roll
Although various shapes such as a plate shape, a block shape, a spherical shape, and a brush shape can be used, a roll shape is usually preferable.

FIG. 1 shows the roll appearance when the charging member of the present invention is used as a charging roll, and FIGS. 2 and 3 show examples of roll cross sections. In the charging roll shown in FIG. 2, on the surface of the solid cylindrical or hollow cylindrical conductive support 1a,
The conductive elastic body layer 1b is formed, and the photocatalytic substance layer 1d is further formed on the surface of the conductive elastic body layer 1b. Further, like the charging roll shown in FIG. 3, the resistance adjusting layer 1c is formed on the surface of the conductive elastic layer 1b, and the photocatalytic substance layer 1 is formed on the surface thereof.
You may provide d.

The conductive support 1a functions as an electrode and a support member of the charging member, and is, for example, a metal or alloy such as aluminum, copper alloy, stainless steel, etc .; iron plated with chromium, nickel, etc .; Conductive resin;
It is composed of a conductive material such as.

The conductive elastic layer 1b forms a nip between the charging member and the charging member so that the charging member is pressed against the surface of the charging member with an appropriate nip pressure and the charging member surface is uniformly charged. Further, the charging member is provided to have a predetermined resistance value.

The conductive elastic layer 1b is formed, for example, by dispersing a conductive agent in a rubber material. As the rubber material, isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, styrene-butadiene rubber,
Examples thereof include butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, ethylene-propylene-diene copolymer rubber, acrylonitrile-butadiene copolymer rubber, natural rubber and the like, and blended rubbers thereof. Of these, isoprene rubber, silicone rubber and ethylene propylene rubber are preferably used. These rubber materials may be foamed or non-foamed.

As the conductive agent, an electronic conductive agent or an ionic conductive agent is used. Examples of electronic conductive agents include carbon black such as Ketjen black and acetylene black;
Pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel and stainless steel;
Fine powders of various conductive metal oxides such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution; it can. Examples of ionic conductive agents include perchlorates such as tetraethylammonium and lauryltrimethylammonium, chlorates, etc .; alkali metals such as lithium and magnesium, perchlorates of alkaline earth metals, chlorates, etc. Can be mentioned.

These conductive agents may be used alone,
You may use it in combination of 2 or more type. Further, the addition amount thereof is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 to 50 parts by mass, and in the range of 5 to 35 parts by mass with respect to 100 parts by mass of the rubber material. More preferably. On the other hand, in the case of the above-mentioned ionic conductive agent, it is preferably in the range of 0.01 to 5 parts by mass, and more preferably in the range of 0.1 to 4 parts by mass with respect to 100 parts by mass of the rubber material. Thereby, it is preferable to adjust the volume resistance value of the conductive elastic layer 1b in the range of 2 × 10 ^{2 to} 5 × 10 ⁹ Ωcm. This volume resistance value is closely related to the volume resistance value of the resistance adjusting layer 1c described later. The hardness of the conductive elastic layer 1b is preferably 70 ° or less in Asker C hardness.

In the present invention, the conductive elastic layer 1b is used.
Although the photocatalyst material layer 1d may be formed directly on the surface of, the resistance adjusting layer 1c for adjusting the resistance of the charging member, and the protective layer provided from the viewpoint of preventing contamination of the surface of the member to be charged, The photocatalytic substance layer 1d may be formed on the surface of the resistance adjusting layer 1c or the protective layer. Moreover, you may provide an electrode layer between the electroconductive elastic layer 1b and the resistance adjustment layer 1c as needed. The electrode layer means the conductive elastic layer 1b.
It is provided in order to disperse the concentration of electric current due to the non-uniform dispersion of the conductive particles therein, and is composed only of a conductive inorganic substance.

The resistance adjusting layer 1c is provided for adjusting the charging member to a predetermined resistance value, and is composed of a thin film in which the above-mentioned conductive particles are dispersed in a resin. The resin used is not particularly limited, but resins belonging to the somewhat softer class such as polyurethane, polyamide, polyester and acrylic resin are suitable. As the conductive agent, the one used for the conductive elastic layer 1b is preferably used.

The amount of the conductive agent added is not particularly limited,
For example, in the case of an electronic conductive agent, it is preferably in the range of 1 to 50 parts by mass, more preferably in the range of 5 to 35 parts by mass with respect to 100 parts by mass of the resin used.
In this way, the volume resistance value of the resistance adjustment layer 1c is 3 × 10 ^{3 to} 5
It is preferably adjusted to a range of × 10 ¹⁰ Ωcm. Further, the thickness of the resistance adjusting layer is preferably in the range of 1 to 500 μm, and more preferably in the range of 5 to 400 μm. When the film thickness is less than 1 μm, not only the function as the resistance adjusting layer cannot be sufficiently exhibited, but also the leakage easily occurs and the surface of the charged body may be damaged. On the other hand, if the film thickness is thicker than 500 μm, the resistance value and hardness of the charging member may increase more than necessary.

In the present invention, a protective layer may be further provided on the surface of the resistance adjusting layer 1c. This protective layer is
It functions as a layer for preventing the charging member from sticking to the surface of the body to be charged. Further, the charging member is prevented from being contaminated by the toner remaining on the surface of the member to be charged and its external additive, and the adherence or sticking of paper powder or the like to the surface of the member to be charged is reduced, resulting in deterioration of charging performance and image quality defect caused by the deterioration. Is provided to prevent the occurrence of

The material constituting the above-mentioned protective layer is not particularly limited, and has a low contamination property to the charged body,
A relatively soft resin or rubber can be used.
Further, the surface of the resistance adjustment layer 1c may be subjected to UV irradiation, heat treatment, chemical treatment with a coupling agent or the like to form a layer having physical properties and compositions different from those of the resistance adjustment layer 1c to serve as a protective layer.

The photocatalytic substance used in the present invention is disposed on the outermost surface of the charging member, and the conductive elastic layer 1 is used.
b, the resistance adjusting layer 1c, or the surface of the protective layer is formed in layers. The photocatalytic substance is generally a substance that is excited by irradiation of light to generate an electron-hole pair, and causes an adsorbed molecule or the like to react by diffusion of the electron-hole pair. Its surface becomes hydrophilic by photoexcitation. In addition, since the wavelength range of light that is photoexcited differs depending on the substance, it is necessary that the light that is emitted includes a wavelength that excites the photocatalytic substance when the light is emitted.

The above-mentioned hydrophilic property means a property of being easily adapted to water and easily wetted, and generally, a contact angle to water (hereinafter, referred to as
It may be simply referred to as "water contact angle". The degree can be expressed by). The hydrophilic property in the present invention means a state where the contact angle to water is 30 degrees or less.

The water contact angle is the angle between the surface of the object to be measured and the liquid surface when water is dropped on the surface of the object to be measured. If this angle is large, it is difficult to wet the water. Means that when the angle is small, it easily wets water. The water contact angle can be measured using a goniometer or the like, but in the present invention, it is 23
The water contact angle after dropping for 10 seconds when water was dropped on the surface of the charging member in an environment of 55 ° C. and 55% RH was measured using a contact angle measuring device CA-X roll type (Kyowa Interface Science Co., Ltd.). did.

Further, since the surface of the charging member having the photocatalytic substance of the present invention becomes hydrophilic by light irradiation, the contact angle of the surface of the charging member with water is constant. It needs to be measured later. Therefore, with respect to the charging member of the present invention, the water contact angle was measured after irradiating the surface of the charging member with light having a wavelength for exciting the photocatalytic substance at a light intensity of 0.7 mW / cm ² for 10 minutes.

In the present invention, the surface of the charging member has a photocatalytic substance, and the surface of the charging member is made hydrophilic by the irradiation of light for exciting the photocatalytic substance, so that the surface of the charging member is kept constant. It is possible to stably and uniformly supply a certain amount of water, and as a result, it is possible to uniformly inject and charge an object to be charged without being affected by the use environment of the image forming apparatus.

From this point of view, it is desirable that the contact angle of the surface of the charging member with water is smaller, and the contact angle of the surface of the charging member with water is preferably 25 degrees or less, and preferably 15 degrees or less. More preferable.

The photocatalytic substance is not particularly limited as long as it has a small contact angle to water by the light irradiation, and examples thereof include titanium oxide, strontium titanate, zinc oxide, copper and the like. it can.
Of these, titanium oxide is particularly preferable because it has a large decrease in water contact angle with respect to light irradiation. Among the titanium oxides, anatase type titanium oxide is more preferable because it has higher activity than rutile type and amorphous type titanium oxides.

The degree to which the water contact angle decreases (hydrophilization degree) with respect to the same light irradiation amount in the present invention is considered to be proportional to the photoexcitation efficiency of the photocatalytic substance, and generally, the photocatalytic substance has a small particle size and a large specific surface area. The higher the photoexcitation efficiency, the higher the degree of hydrophilicity. The average particle size of the photocatalytic substance used in the present invention is preferably in the range of 4 to 180 nm, more preferably in the range of 6 to 30 nm. When the average particle size is less than 4 nm, not only the production is difficult but also the handling property may become a problem. If the average particle size exceeds 180 nm, the activity as a photocatalytic substance may not be sufficient.

The specific surface area is almost inversely proportional to the average particle diameter, and in the present invention, it is 9 to 350 m ^2.
/ G is preferable and 50 to 260 m ² /
The range of g is more preferable.

The photocatalytic substance may be used alone,
You may mix and use 2 or more types of photocatalyst substances. Also,
When forming a layer on the surface of the conductive elastic layer 1b or the like, it may be mixed with another inorganic compound and / or a resin.

The above-mentioned inorganic compound is added mainly so as to maintain the hydrophilization state due to the above-mentioned light irradiation even after the light irradiation, and it is particularly preferable to use silicon oxide. The maintenance of the hydrophilic state after the light irradiation is remarkable when titanium oxide is used as the photocatalytic substance and silicon dioxide (silica) is used as the inorganic compound. The reason is that the water accumulated on the silica surface is the titanium oxide surface. It is considered that the titanium ions are stabilized because they are transported to.

The average particle size of the silicon oxide mixed with the photocatalyst substance is preferably in the range of 5 to 70 nm, and the mass ratio A / B of the mass A of the photocatalyst substance and the mass B of the inorganic compound is 95. It is preferably in the range of / 5 to 5/95.

On the other hand, the resin is added mainly for the purpose of reinforcing the photocatalyst material layer 1d and enhancing the durability of the charging member, and is not limited as long as it can uniformly disperse the photocatalyst material. Although it does not exist, it must be hard to decompose with active oxygen due to photoexcitation of the photocatalytic substance.
From this viewpoint, the resin is preferably a silicone resin.

The structure of the silicone resin is not particularly limited as long as it can be crosslinked and cured at a temperature at which the lower layer of the photocatalytic substance layer 1d is not decomposed. The curing temperature is preferably in the range of room temperature to 170 ° C, and 10
More preferably, it is in the range of 0 to 140 ° C.

The photocatalyst substance layer 1d can be formed by baking the photocatalyst substance on the surface of the conductive elastic body layer 1b or the like at high temperature in a powdery state, but the lower layer is often a non-heat-resistant material. From the standpoint that it can be formed as a more uniform layer, it is preferably formed by being dispersed in a liquid or the like and coated on the surface of the conductive elastic layer 1b or the like.

As the coating liquid, a sol-like slurry prepared by dispersing a photocatalytic substance having the above-mentioned average particle diameter in water, alcohol, toluene or the like may be used. It may be used after redispersion. In addition, the above-mentioned coating liquid may be used by mixing with the above-mentioned silicon oxide or silicone resin, or by mixing with other binders, surfactants, dispersants such as coupling agents and the like.

As a coating method, a spray method,
A usual coating method such as a dipping method or a spin coating method can be used. After coating, it may be dried at room temperature or may be dried by heating at 100 to 140 ° C. Further, a primer layer for improving adhesion may be formed before the coating. The layer thickness of the photocatalyst substance layer 1d after drying is preferably in the range of 0.01 to 20 μm.

Photocatalytic substance layer 1 formed in this way
On the surface of d, the photocatalyst substance directly controls the hydrophilicity of the surface of the charging member. Therefore, if the surface of the photocatalyst substance is covered with a binder or the like, the photocatalytic action is reduced depending on the coverage. Resulting in. Therefore, it is necessary that the photocatalyst substance is exposed to the outermost surface of the charging member at a certain rate or more, and the rate is preferably 10% or more as an area ratio in the entire surface.

The hardness of the charging member produced as described above is preferably 70 ° or less in terms of Asker C hardness. If the Asker C hardness is higher than 70 °, not only the nip uniformity with the member to be charged is impaired and image quality defects occur, but also the surface of the member to be charged may be gradually worn due to long-term use. is there. The Asker C hardness was measured under the condition of 1000 g load with a push needle of an Asker C type hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) in contact with the surface of the charging member.

The resistance value of the charging member is 2 × 10.
It is preferably in the range of ^{4 to} 5 × 10 ¹⁰ Ω. This can be adjusted within the above range by appropriately adjusting the volume resistance value of the conductive elastic layer, the volume resistance value of the resistance adjusting layer, and the film thickness. Resistance value is 2
When it is less than × 10 ⁴ Ω, an excessive current may flow on the surface of the body to be charged and a pinhole leak may easily occur on the surface of the body to be charged. On the other hand, when the resistance value is larger than 5 × 10 ¹⁰ Ω, it becomes difficult to charge the member to be charged at a low voltage, and an image quality defect occurs due to insufficient charging potential.

In the above-mentioned measurement of the volume resistance value, various compositions were formed into a sheet, and a measuring jig (R12702A / B resiliency chamber: manufactured by Advantest) and a high resistance measuring device (R8340A digital high resistance / Micro ammeter: Advantest Co., Ltd. and electric field (applied voltage /
The voltage adjusted so that the composition sheet thickness) was 1000 V / cm was calculated from the current value after applying for 30 seconds using the following formula (1). Volume resistivity (Ω · cm) = (19.63 × applied voltage (V)) / (current value (A) × composition sheet thickness (cm)) Equation (1)

For example, when the charging member is a charging roll, the resistance is measured by placing the roll on a metal plate and applying 500 g to both ends of the roll to measure a high resistance (R8340).
A digital high resistance / micro ammeter: manufactured by Advantest Corporation)
After applying a voltage of 100 V between the core metal of the roll and the metal plate for 10 seconds, the obtained current value was measured to obtain the roll resistance value.

<Image Forming Apparatus> FIG. 4 is an overall sectional view of an image forming apparatus in which the charging member of the present invention is incorporated as a charging roll. In FIG. 4, a cylindrical photosensitive drum (charged body) 11 that rotates in the arrow direction is arranged inside the image forming apparatus main body U, and functions as an electrostatic latent image carrier. A laser writing device 12 that writes an electrostatic latent image on the surface of the photosensitive drum 11 is arranged on the right side of the drawing inside the main body U of the image forming apparatus. Around the cylindrical photosensitive drum 11, a charger (charging device) that sequentially and uniformly charges the surface of the photosensitive drum 11 along the rotation direction thereof.
13, a developing device 14 that visualizes the electrostatic latent image, and a transfer device 1 that transfers the visualized toner image onto a sheet (transfer material)
5 and a cleaning device 16 for removing the residual toner on the surface of the photosensitive drum 11 are arranged.

The developing device 14 has a container 14a for containing toner. In the container 14a, a stirring member 14b for stirring toner and a rotatable developer carrier 1 are provided.
4c and a toner supply roller 14d for supplying toner to the developer carrying member 14c. The developer carrier 14c is supported by the container 14a with a slight gap from the surface of the photosensitive drum 11. Further, the cleaning device 16 includes a casing 16a. A blade holder 16b made of metal is fixed to the casing 16a, and a sheet-like cleaning blade 16c is fixed to the tip portion of the blade holder 16b. The edge portion of the cleaning blade 16c is in contact with the surface of the photosensitive drum 11.

At the bottom of the main body of the image forming apparatus U in the drawing, a paper feed tray 17 for accommodating paper is arranged. A paper take-out roller 18 for taking out the paper one by one from the paper feed tray 17 is arranged at an upper end portion of the paper feed tray 17. A pair of sheet guides 20 for guiding the sheet conveyed by the pair of sheet conveying rollers 19 are arranged above the left side of the sheet take-out roller 18. Inside the main body U of the image forming apparatus, a heating roller 21a is provided on the upper left side in the drawing.
A fixing device 21 having a pressure roller 21b is disposed between the fixing device 21 and the transfer device 15 to convey a sheet on which a toner image has been transferred.
Is provided. Further, above the fixing device 21, a pair of discharge rollers 23 and a conveyance path 24 for guiding the sheet on which the toner image is fixed from the fixing device 21 to the discharge roller 23 are provided. A discharge tray 25 on which the paper discharged from the discharge rollers 23 is placed is formed in the upper part of the main body of the image forming apparatus U in the drawing.

The image forming process of the image forming apparatus U will be briefly described as follows. First, the surface of the photosensitive drum 11 rotating in the direction of the arrow is uniformly injected and charged by the charging roll 1 to which a DC voltage is applied. An electrostatic latent image is written on the charged photoconductor drum 11 by the laser writing device 12. Photoconductor drum 11
The electrostatic latent image on the surface is developed into a toner image by the developing device 14. Then, the toner image is transferred by the transfer device 15 to the paper conveyed from the paper feed tray 17. After the transferred toner image is fixed on the sheet by the fixing device 21, the sheet is discharged onto the discharge tray 25 by the discharge roller 23. Further, after the toner image is transferred onto the sheet, the toner remaining on the surface of the photoconductor drum 11 is removed by the blade 16c of the cleaning device to prepare for the next image forming process.

<Charging Device and Charging Method> FIG. 5 is an enlarged view of the charging device (charging device) 13 in FIG. In FIG. 5, the charger 13 includes the charging roll 1. The charging roll 1 has a structure in which a conductive elastic body layer 1b, a resistance adjusting layer 1c, and a photocatalytic substance layer 1d are sequentially stacked on the surface of a conductive support 1a.

In the charging roll 1, both ends of the conductive support 1a are the casing 16 of the cleaning device 16.
It is supported by a support member 31 fixed to a. Also, two pressure springs 32, one end of which is fixed to the support member 31 and the other end of which is fixed to the end of the conductive support 1a, respectively.
The charging roll 1 is pressed and brought into contact with the surface of the photoconductor drum 11 by the urging force of. A metal pad holder 33 is fixed to the support member 31, and a water-containing sponge pad 34, which is a sheet-like cleaning member and a water supply member, is fixed to the tip end portion of the charging roll 1.
Even if a small amount of toner adheres to the surface, remove it,
At the same time, a fixed amount of water is supplied to form a thin layer of water on the surface of the charging roll 1.

Further, the conductive support 1a of the charging roll 1
A DC voltage is applied from the DC power supply 35. At the same time, by the ultraviolet irradiation device 26, the charging roll 1 is irradiated with ultraviolet rays.
Irradiate the surface of. Therefore, the charging roll 1 includes the conductive support 1a, the conductive elastic layer 1b, the resistance adjusting layer 1c,
By the photocatalyst material layer 1d and the thin layer of water uniformly formed on the surface thereof, the surface of the photosensitive drum 11 rotating in a predetermined direction while being in contact can be uniformly injected and charged.

The water-containing sponge pad is required especially when the environment in which the image forming apparatus is used is low humidity. For example, the temperature is 30 ° C. or higher and the humidity is 85% RH.
In the environment as described above, the surface of the charging member of the present invention can sufficiently retain water, so that the water-containing sponge pad may not be attached.

[0061]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 A conductive silicone rubber (X-34-2078) having a volume resistance of 5 × 10 ⁴ Ωcm and an Asker C hardness of 32 ° was mounted on a stainless (SUS) shaft having a diameter of 6 mm.
AB: manufactured by Toray Dow Corning Co., Ltd.) was injection-molded to a thickness of 3 mm to prepare a rubber roller having a diameter of 12 mm.
The surface of the obtained rubber roller was coated by a dipping method using a coating agent TKC-301 containing amorphous titanium oxide (titanium oxide 1.5% by mass, average particle size 6 nm, water solvent: manufactured by Teika). Done, then 110
Drying was performed for 30 minutes under the condition of ° C to form an undercoat layer of amorphous titanium oxide having a film thickness of 0.5 µm or less. Further, a coating agent TKC-304 (titanium oxide 5% by mass, water solvent: manufactured by Teika) diluted to 1.5% by mass of titanium oxide was used as a coating liquid, and the undercoat layer surface was used. Is coated by dipping method, and similarly at 30 ° C at 30 ° C.
After drying for a minute, a charging roll A having a photocatalytic substance layer having a film thickness of 0.5 μm or less was prepared.

The water contact angle of this roll surface in the dark was 49 degrees, but it was irradiated with black light (light intensity 0.7
The water contact angle of the roll surface after irradiation with mW for 10 minutes and the same in the following Examples and Comparative Examples) was 15 degrees. The roll resistance value of the roll was 2.1 × 10 ⁵ Ω and the Asker C hardness was 34 °.

-Charging Potential Evaluation Test- The charging roll A was replaced with an image forming apparatus (Able322).
(1: manufactured by Fuji Xerox Co., Ltd.) was attached with a water-containing pad pressed against a charger, and the image forming apparatus was modified so that the potential on the surface of the photoreceptor could be measured.
A direct current voltage of −420 V is applied to the conductive support of the charging roll, and while irradiating the surface of the charging roll A with ultraviolet rays, charges are injected onto the surface of the photoconductor having an outer diameter of 30 mm that comes into contact with the charging roll A, The image forming apparatus was operated, and the potential on the surface of the photosensitive member was continuously measured at the position of the developer carrying member. Table 1 shows the average value of the potentials for one round of the photosensitive member and the difference (potential variation) between the maximum potential and the minimum potential during one round at this time.

-Image quality evaluation test-A normal developing device was loaded in the same image forming apparatus as that used in the charging potential evaluation test, and a halftone image was output after the initial and 200,000 test charts were output. The density unevenness was confirmed. The judgment of the density unevenness was made according to the following criteria.・ Level with no unevenness ・ ・ ・ ○ ・ Level with slight unevenness but no problem with quality ・ ・ ・ △ ・ Level of unevenness with quality problem ・ ・ ・ × Table 1 shows the results.

(Example 2) Using the same material as in Example 1 and by the same method, a roll having an undercoat layer of amorphous titanium oxide formed on the surface of a conductive silicone rubber roll having a diameter of 12 mm was prepared. Furthermore, a coating agent TK containing anatase type titanium oxide on the roll surface
C-304: Silicon dioxide (R1
30: 1 primary particle diameter 7 nm: manufactured by Nippon Aerosil Co., Ltd.
1 part by mass of the dispersion liquid was coated by a dipping method and dried at 110 ° C. for 30 minutes to prepare a charging roll B having a photocatalytic substance layer having a film thickness of 1 μm.

The water contact angle of this roll surface in the dark was 53 degrees, but the water contact angle of the roll surface after black light irradiation was 20 degrees. The value of the contact angle was maintained even after the roll was left in the dark for 7 days. The roll resistance value of the roll was 4.3 × 10 ⁵ Ω and the Asker C hardness was 35 °. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.

(Example 3) In Example 2, in order to form a photocatalyst material layer, a coating agent containing anatase-type titanium oxide as a coating solution TKC-304: 100 parts by mass of silicon dioxide (OX50: primary: Particle size 50n
m: manufactured by Nippon Aerosil Co., Ltd.) was used to prepare a charging roll C having a photocatalytic substance layer having a film thickness of 1 μm in the same manner except that a dispersion liquid in which 0.2 part by mass thereof was dispersed.

The water contact angle of the roll surface in the dark was 60 degrees, but the water contact angle of the roll surface after black light irradiation was 25 degrees. The value of the contact angle was maintained even after the roll was left in the dark for 7 days. The roll resistance value of the roll was 7.4 × 10 ⁵ Ω and the Asker C hardness was 35 °. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.

(Example 4) Using the same material as in Example 1 and in the same manner, a conductive silicone rubber roll having a diameter of 12 mm was prepared. Silicone resin solution Fressella P in which anatase type titanium oxide is dispersed as a coating liquid
(1 mass% active ingredient, methanol solvent: Matsushita Electric Works, Ltd.)
Was coated on the surface of the roll by a dipping method and dried and cured at 110 ° C. for 10 minutes to prepare a charging roll D having a photocatalytic substance layer having a film thickness of 0.5 μm or less.

The contact angle of the roll surface with water in the dark was 56 degrees, but the contact angle of the roll surface with water after black light irradiation was 15 degrees. The roll resistance value of the roll is 7.5 × 10 ⁵ Ω, Asker C
The hardness was 38 °. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.

(Example 5) In the formation of the surface layer of Example 6, 100 parts by mass of silicone resin solution Fressella N (resin solid content 20% by mass, methanol / toluene solvent: Matsushita Electric Works, Ltd.) as a coating liquid was used. Anatase type titanium oxide (ATM-100, average particle size 6 nm: manufactured by Teika) 1
Similarly, except that a dispersion liquid in which 0 parts by mass is dispersed is used,
A charging roll E having a photocatalytic substance layer having a film thickness of 0.5 μm or less was produced.

The water contact angle of this roll surface in the dark was 68 degrees, but the water contact angle of the roll surface after black light irradiation was 25 degrees. The roll resistance value of the roll is 8.5 × 10 ⁶ Ω and the Asker C hardness is 40 °.
Met. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.
Shown in.

(Example 6) A film thickness of 0.5 was obtained in the same manner as in Example 7 except that the amount of anatase-type titanium oxide was changed to 5 parts by mass relative to 100 parts by mass of the silicone resin solution.
A charging roll F having a photocatalytic substance layer having a thickness of μm or less was produced.

The water contact angle of the roll surface in the dark was 72 degrees, but the water contact angle of the roll surface after the black light irradiation was 30 degrees. The roll resistance value of the roll is 9.0 × 10 ⁶ Ω and the Asker C hardness is 41 °.
Met. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.
Shown in.

(Example 7) In the formation of the surface layer of Example 6, 100 parts by mass of a silicone resin solution SR2410 (resin solid content: 23% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) as a coating liquid was used for zinc oxide (average particle size). (20 nm: manufactured by Sakai Chemical Industry Co., Ltd.) A charging roll having a photocatalytic substance layer having a film thickness of 3 μm was prepared in the same manner except that a coating liquid was crosslinked for 10 minutes at 150 ° C. using a dispersion liquid in which 10 parts by mass was dispersed. G was made.

The water contact angle of this roll surface in the dark was 70 degrees, but the water contact angle of the roll surface after black light irradiation was 30 degrees. The roll resistance value of the roll is 5.6 × 10 ⁶ Ω and the Asker C hardness is 40 °.
Met. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.
Shown in.

(Example 8) Using the same material as in Example 1 and in the same manner, a conductive silicone rubber roll having a diameter of 12 mm was prepared. Polyurethane resin solution Nipporan 3113 made conductive with carbon black as a coating liquid
(Resin solid content 20% by mass: manufactured by Nippon Polyurethane Company) 10
With respect to 0 parts by mass, anatase type titanium oxide (AMT-1
00: manufactured by TAYCA Co., Ltd.) Using a dispersion liquid in which 10 parts by mass are dispersed, the roll surface is coated by a spray method, and 15
It was dried and cured at 0 ° C. for 30 minutes to prepare a charging roll H having a surface layer with a film thickness of 30 μm.

The water contact angle of the roll surface in the dark was 59 °, and the water contact angle of the roll surface after black light irradiation was 30 °. The roll resistance value of the roll was 4.4 × 10 ⁶ Ω and the Asker C hardness was 57 °. Using the above charging roll, a charging potential test and an image evaluation test were conducted in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1) The same materials as in Example 1 were used in the same manner to prepare conductive silicone rubber rolls having a diameter of 12 mm. Polyamide resin (C
M8000: Toray's methanol solution (resin solid content 10% by mass) 100 parts by mass, tin oxide (SN-1)
00P, average particle size 20 nm: manufactured by Ishihara Sangyo Co., Ltd.) Using a dispersion liquid in which 30 parts by mass are dispersed, the roll surface is coated by a spray method and dried at 130 ° C. for 10 minutes to form a surface layer having a film thickness of 25 μm. A charging roll I having

The water contact angle of this roll surface in the dark was 55 degrees, and the contact angle did not change even when irradiated with black light. The roll resistance value of the roll was 2.6 × 10 ⁵ Ω and the Asker C hardness was 61 °.
Using the above charging roll, a charging potential test and an image evaluation test (both initial only) were conducted in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2) In the formation of the surface layer of Comparative Example 2, a polyurethane resin solution Nipporan 3113 (resin solid content: 20) which was made conductive with carbon black as a coating liquid was used.
Mass%: made by Nippon Polyurethane Co., Ltd.)
Silicon dioxide (OX50: Nippon Aerosil Co., Ltd.) 0.5
Using a liquid obtained by adding 5 parts by mass of hexamethylene diisocyanate as a crosslinking agent to a dispersion liquid in which parts by mass are dispersed,
A charging roll J having a surface layer with a film thickness of 10 μm was produced in the same manner except that it was dried and cured at 150 ° C. for 30 minutes.

The water contact angle in the dark on the surface of this roll was 60 degrees, and the value of the contact angle did not change even when black light was irradiated. The roll resistance value of the roll is 7.9 × 10 ⁶ Ω and the Asker C hardness is 55.
It was °. Using the above charging roll, a charging potential test and an image evaluation test (both initial only) were conducted in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 In the surface layer formation of Comparative Example 1, 100 parts by mass of a silicone resin solution SR2410 (resin solid content 23% by mass: manufactured by Shin-Etsu Chemical Co., Ltd.) which was made conductive with tin oxide as a coating liquid was added. Using a dispersion liquid in which 0.2 parts by mass of silicon dioxide (R130: manufactured by Nippon Aerosil Co., Ltd.) is dispersed, and drying and curing are carried out at 150 ° C. for 10 minutes, the surface layer having a film thickness of 3 μm is similarly formed. A charging roll K was produced.

The water contact angle of the roll surface in the dark was 45 degrees, and the value of the contact angle did not change even after irradiation with black light. The roll resistance value of the roll is 3.5 × 10 ⁶ Ω and the Asker C hardness is 39 °.
Met. Using the above charging roll, a charging potential test and an image evaluation test (both initial only) were conducted in the same manner as in Example 1. The results are shown in Table 1.

[0085]

[Table 1]

[0086]

According to the present invention, it is possible to carry out highly efficient and uniform charging, and it is possible to prevent the generation of harmful ozone and the generation of nitrogen oxides which cause image quality defects.
Moreover, it is possible to provide a charging member, a charging device, and a charging method that have high reliability and high performance maintainability.

[Brief description of drawings]

FIG. 1 is an external view of a charging roll (charging member)

FIG. 2 is a sectional view of a charging roll (charging member)

FIG. 3 is a sectional view of another charging roll (charging member).

FIG. 4 is a sectional view of the image forming apparatus.

FIG. 5 is an enlarged view of a charger (charging device).

[Explanation of symbols]

1 Charging roll (charging device) 11 Photoconductor drum (charged body) 12 Laser writing device 13 Charging device (charging device) 14 Developer 15 Transfer device 16 Cleaning device 17 Paper tray 18 Paper ejection roll 19 Paper transport roll 20 Paper guide 21 Fixing device 22, 24 Transport path 23 Discharge roll 25 discharge tray 26 UV irradiation device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Kataoka             Fuji Zero, 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture             X Co., Ltd. F-term (reference) 2H200 FA02 FA07 GA23 GA44 HA02                       HA28 HB12 HB22 HB31 HB43                       HB45 HB46 HB47 HB48 LA17                       LA23 LA38 MA02 MB01 MC01                       NA06                 3J103 AA02 AA13 AA32 AA51 BA41                       CA02 FA18 FA30 GA02 GA57                       GA58 GA60 HA04 HA31 HA47                       HA51                 4G069 AA03 AA08 BA02A BA02B                       BA04A BA04B BA48A CD10                       EA08 EC22Y EC26 FB15                 4J038 DL001 HA216 KA04 NA06                       NA17 PB11

Claims (7)

[Claims] 1. A charging member having a photocatalytic substance on its surface, wherein the surface of the charging member is rendered hydrophilic by irradiating the surface of the charging member with light having a wavelength that excites the photocatalytic substance. A charging member characterized by the above. 2. The charging member according to claim 1, wherein the charging member has the photocatalyst substance and silicon oxide on a surface thereof. 3. The charging member has the photocatalytic substance and a silicone resin on a surface thereof.
The charging member according to 1. 4. The charging according to claim 1, wherein a contact angle of water on the surface of the charging member is 25 degrees or less when the photocatalytic substance is excited by the light irradiation. Element. 5. The charging member according to claim 1, wherein the photocatalytic substance is titanium oxide. 6. A charging device comprising: a charging member, which is brought into contact with a member to be charged, and which has means for applying a voltage to the charging member,
A charging device, wherein the charging member is the charging member according to any one of claims 1 to 5. 7. The charging member according to any one of claims 1 to 5, wherein a thin layer of water is formed on a surface of the charging member that is in contact with the member to be charged, and the charging member is charged. A charging method comprising charging a body to be charged by pressing the body and applying a voltage.