JPH11305519A - Contact charging member and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a satisfactory image quality over a long period without causing a reduction in image quality such as black stripe or black spot or causing a bleed-out or the peeling of a conductive agent by including an amorphous metal oxide conductive agent in a contact charging member for charging in contact with a body to be charged. SOLUTION: A contact charging roller 1 which is a conductive member has the role of an electrode for applying an application voltage of DC voltage or DC voltage with AC voltage superposed thereon, and it is provided with a metal core material 2 for supporting the roller in a prescribed position and also forming a rotating shaft, a conductive elastic layer 3 for imparting elastic property to the roller surface provided thereon, and a resistance control layer 4 for controlling the resistance of the charging roller 1. The resistance control layer 4 contains an amorphous metal oxide conductive agent, and its volume resistance is set to preferably a volume natural resistance of 1×10<7> -1×10<11> Ω.cm, more preferably 1×10<8> -1×10<10> Ω.cm from the viewpoint of prevention of charge leak and prevention of image fogging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact-type charging member used for an electrophotographic image forming apparatus and the like.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus used for a copying machine, a printer, or the like, an image is formed through a process of uniformly charging an object to be charged.

[0003] In the charging step, a corona charging device has been widely used. However, the corona charging device requires a high-voltage power supply and uses corona discharge, and therefore has problems such as generation of ozone and active oxygen which are undesirable for the human body.

Therefore, recently, a contact charging device has been attracting attention as a charging device replacing the corona charging device. In this method, a charged member to which a voltage is applied is brought into contact with a charged body with a predetermined pressing force to charge the charged body, and the amount of generated ozone and the like is significantly reduced as compared with a corona charging device. Can be done. The voltage to be applied to the charging member is generally a DC voltage and an AC voltage, and the charging member needs to have a function of holding the member to be charged at a predetermined potential.
For that purpose, it is important to control the electric resistance of the charging member within a certain range.

In general, control of the electric resistance of a charging member is achieved by adding a conductive filler such as carbon black or metal oxide to a resin binder which is a main component of the charging member.

[0006] For example, Japanese Laid-Open 6-250494 discloses a particle size of at 0.1μm or less, the powder resistance of 10 ⁰ Ω · c
A contact charging device having a layer containing m or more conductive fillers is disclosed.

The charging member disclosed in JP-A-6-266207 contains an insulating metal oxide and a semiconductive binder.
A charging member having a surface layer containing a fluorine-based binder and a conductive pigment having a particle size of 0.5 to 5 μm and a powder resistance of 10 ⁻² to 10 ⁶ Ω · cm is disclosed.

[0008]

Generally, when the particle size of the above-mentioned powdery conductive filler is reduced, the surface energy increases and the powder tends to aggregate. As a result, it becomes difficult to uniformly disperse the conductive filler in the resin binder, so that microscopic resistance unevenness is likely to occur on the surface of the charging member, resulting in deterioration of image quality.

That is, even if the resistance value of the entire charging member is a desired value, a portion having a low resistance or a portion having a high resistance value is partially generated due to aggregation of the conductive filler.

[0010] Charging failure occurs at a portion where the resistance is partially high. Poor charging of the photoreceptor causes black streaks in a reversal developing electrophotography in which an exposed portion is developed with toner, and a cause of a decrease in image density in a regular developing type electrophotography in which an unexposed portion is developed. Become. Further, when a current flows from the charging member to the photoconductor, a pinhole is generated in the photoconductor, which causes black spots in reversal development.

In a part where the resistance value is partially low, the charging potential of the photosensitive member is locally increased, which causes black streaking and fogging in the regular developing system, and causes density reduction and white spots in the reversal developing system.

[0012] It is an object of the present invention that there is no micro-resistance unevenness, no charge leakage or current destruction, no deterioration of image quality such as black streaks and black spots, and the conductive agent is strongly bonded to the binder resin. An object of the present invention is to provide a contact charging member capable of maintaining good image quality for a long period of time without causing bleed-out or peeling of a conductive agent, and a method of manufacturing the same.

[0013]

The object of the present invention is achieved by adopting the following constitution.

[1] A contact charging member for contacting and charging an object to be charged, wherein the contact charging member contains an amorphous metal oxide conductive agent.

[2] The metal oxide conductive agent has a particle size of 1 to 3.
The contact charging member according to [1], wherein the thickness is 100 nm.

[3] The contact charging member according to [1], further comprising a conductive agent made from a colloidal metal oxide sol.

[4] A method for producing a contact charging member, characterized by adding an amorphous conductive agent made from a colloidal metal oxide sol.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The metal oxide conductive agent contained in the contact charging member of the present invention is characterized by being amorphous. The term “amorphous” in the present invention mainly means an amorphous state, and a Bragg angle of 2 by X-ray diffraction using CuKα ray.
It has a broad scattering band having an apex between 20 ° and 70 °. In addition, it may have a crystalline diffraction line.

The conductive agent has a volume resistivity of 1 × 1.
0 ⁸ Ω · cm or less, preferably 10 ⁻⁵ Ω · cm or less.

The measurement of the volume resistivity is performed as follows. By applying a pressure of 100 kg / cm ^{2 to} the sample, a disc-shaped pellet having a diameter of 4 cm and a thickness of 0.2 cm is formed. The resistance (Ω · cm) of the pellet was measured using Hiresta AP (manufactured by Mitsubishi Yuka).

The metal oxide conductive agent of the present invention preferably employs a colloidal metal oxide sol. For example, ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In
_{2 O 3, SiO 2, MgO} , BaO, MoO 3, V 2 O 5 or the like colloids include, but are not particularly limited, preferably ZnO, is TiO _2, SnO ₂ Among these, SnO ₂
(Tin oxide) colloids are preferred.

The metal oxide particles have a diameter of 10 ^-5 to 10 ^-7 c.
Since the dispersed state of particles of m (1 to 100 nm) is stable, this size is referred to as colloidal dimension. Particles having a size of colloidal dimension are referred to as colloidal particles. It is called colloid in the invention.

The method for producing a colloidal metal oxide sol according to the present invention includes a method for producing a metal oxide particle by dispersing it in a suitable solvent, and a method for producing a metal compound soluble in a solvent from a decomposition reaction in the solvent. Either method can be adopted.

Hereinafter, the tin oxide sol will be described in detail.

When the solvent of the tin oxide sol dispersion at the time of production has poor compatibility with the protective colloid binder, the solvent is replaced with a solvent suitable for dispersing in the binder. Or a compound capable of stably dispersing a tin oxide sol is added as appropriate,
The tin oxide particles are dried and separated together with the compound added by heating to 0 ° C. or lower, further 150 ° C. or lower, and redispersed in water or water mixed with another solvent.

The tin compound used in the method for producing from the decomposition reaction of the tin compound soluble in the solvent in the solvent includes K
Compounds containing oxo anions such as ₂ SnO ₃ .3H ₂ O, water-soluble halides such as SnCl ₄ , R ′ ₂ SnR
(CH ₃ ) ₃ S having a structure of ₂ , R ₃ SnX and R ₂ SnX ₂
nCl · (pyridine), (C ₄ H ₉ ) ₂ Sn (OCC
₂ H ₅₎ organometallic compounds such as _{2, Sn (SO 4) 2} · 2H 2 O
And the like.

After dissolving a tin compound soluble in these solvents in a solvent, a tin oxide sol is produced by a physical method such as heating and pressurizing, or a chemical method such as oxidation, reduction and hydrolysis. Or a tin oxide sol is produced via an intermediate. For example, Japanese Patent Publication No. 35-6616 discloses that SnCl ₄
Dissolved in 00 volumes of distilled water to precipitate stannic hydroxide, then added ammonia water to make it slightly alkaline to dissolve the precipitate and heated until ammonia odor disappeared to produce colloidal tin oxide sol A method is described.

Examples of the solvent include, in addition to water, alcohol solvents such as methanol, ethanol, and isopropanol; ether solvents such as tetrahydrofuran, dioxane and diethyl ether; aliphatic organic solvents such as hexane and heptane;
Various solvents can be used according to the tin compound such as an aromatic organic solvent such as benzene and pyridine, and water and alcohols are preferable.

According to this method, it is also possible to add a compound containing an element other than a tin compound soluble in a solvent during the production, for example, a fluorine-containing compound or a metal capable of taking a trivalent or pentavalent coordination number. Compounds can be introduced.

As the fluorine-containing compound soluble in a solvent,
Either ionic fluoride or covalent fluoride may be used, and metal fluorides such as K ₂ TiF ₆ , HF, KHF ₂ Sb, and F ₃ MoF ₆ and fluoro complex anions such as NH ₄ MnF ₃ and NH ₄ BiF ₄ may be used. Compounds to be produced, BrF ₃ , SF ₄ , SF
Inorganic fluorides such as ₆ , CF ₃ I, CF ₃ COOH,
An organic fluorine compound such as P (CF ₃ ) ₃ can be used. Further, when the solvent is water, a combination of a fluorine-containing compound and a nonvolatile acid such as a combination of CaF ₂ and sulfuric acid may be used. it can.

Examples of the metal compound which can take a trivalent or pentavalent coordination number soluble in a solvent include Al, Ca, In, and Tl.
Or a group V element such as P, As, Sb, Bi, etc. Nb, V, which can take a trivalent or pentavalent coordination number
A group of compounds containing a transition metal such as Ti, Cr, Mo, Fe, Co, and Ni.

The content of the metal oxide conductive agent of the present invention is preferably 5 to 500 mg / m ² , more preferably 1 to 500 mg / m ^2.
It is a 0~350mg / m ^2. The weight ratio of the metal oxide conductive agent to the binder which is a main component of the contact charging member is 1
/ 300 to 100/1 is preferable, and more preferably 10
vol% or more. Generally, it is known that in a state in which a conductive agent is added to an insulating matrix in an amount of 10 vol% or more, percolation transition occurs and the conductivity of the conductive layer rapidly increases.

In the present invention, the contact charging roller 1, which is a charging member, is not limited to this, but a typical configuration is as shown in FIG. A role of an electrode for applying a DC voltage or an applied voltage obtained by superimposing an AC voltage on a DC voltage, a metal core material 2 that supports a roller at a predetermined position and also serves as a rotation axis, and has a resilient roller surface thereon. In addition, a conductive elastic layer 3 for controlling the resistance and a resistance control layer 4 for controlling the resistance of the charging roller are provided. The above amorphous metal oxide conductive agent is usually used by being contained in this resistance control layer. If necessary, a coating layer may be further provided thereon.

The metal core 2 is not particularly limited as long as it has sufficient conductivity and mechanical strength, but stainless steel is generally used.

The volume resistivity of the conductive elastic layer 3 for imparting elasticity to the contact charging roller 10 ² Omega · cm or more, 10 ¹⁰ Omega · cm or less, preferably 10 ³ Omega · cm or more, 10 ⁹ Ω · cm or less. If it is less than 10 ² Ω · cm, it may be difficult to control the resistance required as a charging member, and it may be necessary to add a large amount of a conductive agent. On the other hand, if it exceeds 10 ¹⁰ Ω · cm, it is difficult to obtain a resistance value necessary for forming a charging member exhibiting good charging characteristics.

The conductive elastic layer is capable of properly deforming the contact portion (nip portion) when contacting the member to be charged and suppressing vibration noise.
In order to prevent fusion of toner etc. to the photoreceptor, JIS
A hardness: 10 or more and 50 or less, preferably 15 or more and 40
It is as follows. JIS A hardness is measured by the method described in JIS K6301.

The conductive elastic layer includes EPDM, NBR, S
Rubber materials such as BR, CR, silicone rubber, polystyrene, polyolefin, polyvinyl chloride, polyurethane,
Any of polyester, polyamide-based thermoplastic elastomer and the like can be used.

However, silicone rubber is preferably used from the viewpoint of durability.

The resistance of the conductive elastic layer is adjusted by adding a predetermined amount of a conductive agent such as the above-described conductive metal oxide, carbon, metal powder, or solid electrolyte.

The volume resistivity of the resistance control layer 4 for controlling the resistance of the charging roller is from 1 × 10 ⁷ to 1 from the viewpoint of preventing charge leakage and preventing image fogging.
× 10 ¹¹ Ω · cm is good, more preferably 1 × 10 ⁸ to
It is 1 × 10 ¹⁰ Ω · cm.

The resistance control layer adjusts the resistance value by adding the above-described conductive metal oxide and, if necessary, a conductive agent such as carbon, metal powder, and solid electrolyte to a resin binder.

Examples of the resin binder used for the resistance control layer include ionomers (mainly composed of ethylene-unsaturated carboxylic acid), polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyurethane elastomer, celluloses, polyamide, polyvinyl chloride, acrylonitrile. −
Butadiene rubber, chloroprene rubber, acrylic rubber, hydrin rubber, urethane rubber and the like can be used.

When the dispersibility of the conductive metal oxide of the present invention in the resin used for the conductive elastic layer or the resistance control layer is not sufficient, the conductive metal oxide is dispersed in a resin having good dispersibility, and then sprayed. After solidifying a resin in which a conductive metal oxide is dispersed by a dry method, conductive resin fine particles can be prepared by a pulverizing method and dispersed in a resin used for a conductive elastic layer or a resistance control layer. By dispersing the conductive metal oxide in this manner, a conductive metal oxide that could not be used until now may be usable.

Next, an image forming method and an image forming apparatus used in the present invention will be described. However, the present invention is not limited to this method, but shows one typical example.

FIG. 2 is a sectional view of the image forming apparatus according to the present invention. In this embodiment, a monochrome image is formed, but a plurality of developing units may be used in order to form a color image instead of this embodiment.

The image forming apparatus of this embodiment uses a contact charging roller 1 as a contact charging member instead of a scorotron charger as the charging means.
To the photosensitive drum 1 by applying a charging bias in which a DC voltage (DC voltage) is superimposed on an AC voltage (AC voltage).
0 is charged.

As a transfer means, the transfer roller 14 is used to transfer the toner image on the photosensitive drum 10 to the surface of the recording paper P (transfer material).

The photosensitive drum 10 is formed by forming a photosensitive layer such as a-Si (amorphous silicon) or an organic photosensitive member (OPC) on the outer periphery of a base formed of, for example, a cylindrical aluminum member. It is rotated at a peripheral speed of 280 mm / sec in a clockwise direction indicated by an arrow 2.

The contact charging roller 1 as charging means is
It is a charging member that comes into contact with the photoconductor drum 10, and performs a charging operation on the photoconductor layer of the photoconductor drum 10 by a charging bias having the same polarity as the toner applied to the contact charging roller 1. Apply a uniform potential.

Exposure unit 120 as image exposure means
Denotes a semiconductor laser as a light emitting element (not shown), a rotary polygon mirror 120b for rotating and scanning a laser beam emitted from the semiconductor laser, an fθ lens 120c, and a reflection mirror 120.
d, the laser light emitted from the semiconductor laser is rotationally scanned by the rotating polygon mirror 120b, and is passed through the fθ lens 120c and the reflecting mirror 120d. Image exposure to form a latent image.

The developing device 13 as a developing means contains, for example, a black one-component or two-component developer, and is kept at a predetermined gap from the photosensitive drum 10 by a striking roller (not shown). For example, thickness 0.5-1mm, outer diameter 1
Developing sleeve 131 as a developer carrier made of a non-magnetic stainless steel or aluminum material having a cylindrical shape of 5 to 25 mm
It has. The latent image on the photosensitive drum 10 is developed by applying a developing bias consisting of a DC voltage having the same polarity as the toner to the developing sleeve 131. As the developing bias, a bias obtained by superimposing an AC voltage (AC voltage) on a DC voltage (DC voltage) may be used.

In the present embodiment, the contact charging roller 1, the exposing unit 120 and the developing unit 13 are arranged in this order from the upstream side in the moving direction of the photosensitive drum 10. The photoconductor drum 10 is rotated clockwise by the arrow by the body drive motor, and at the same time, the contact charging roller 1 is operated, and the application of electric charge to the photoconductor drum 10 is started. Next, the photosensitive drum 10 to which the electric charge is applied is subjected to image exposure by a laser beam by the exposure unit 120, and the photosensitive drum 1
0, an electrostatic latent image is formed. The electrostatic latent image is then developed by the developing device 13 to form a toner image on the photosensitive drum 10.

The toner image is formed on the photosensitive drum 10 by the above-described image forming process, and the recording paper P is sent out by the secondary paper feed roller 15b at the same time. The toner image is transferred onto the recording paper P in a transfer area T by a transfer roller 14 which is a transfer unit to which a DC voltage having a polarity opposite to that of the toner is applied.

The separated and conveyed recording paper P is conveyed to a fixing device 17 as a fixing unit having two rollers 17a and 17b having a heater therein, where the toner is fixed by heat and pressure. Through the discharge roller 18,
It is discharged to a tray outside the device.

The toner remaining on the photosensitive drum 10 after transferring the toner image to the recording paper P is the photosensitive drum A
After the neutralization by the C neutralizer 16, the residual toner is removed by the cleaning device 19, and the next image forming cycle is started.

[0056]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto. In addition, "part"
Means "parts by weight".

(1) Synthesis of tin oxide sol (JP-A-9-13)
No. 8479) 65 g of stannic chloride hydrate was mixed with a water / ethanol mixed solution 20
The solution was dissolved in 00 cc to obtain a homogeneous solution. Next, the coprecipitate produced by boiling this is taken out by decantation and washed with distilled water many times. After confirming that there is no reaction of chloride ion by dropping silver nitrate into the distilled water from which the precipitate has been washed, distilled water is added to the washed precipitate to reduce the total amount to 2%.
000cc. Furthermore, 40cc of 30% ammonia water
In addition, the mixture was heated in an aqueous solution and concentrated to obtain a colloidal sol dispersion having a solid content of 8%.

(2) Formation of Conductive Elastomer Particles 1) A coating solution having the following constitution was prepared.

First liquid n-butyl acrylate 10 wt% t-butyl acrylate 35 wt% Styrene 27 wt% 2-hydroxyethyl acrylate 28 wt% copolymer latex liquid (solid content 30%) Second liquid n-butyl acrylate 40 wt% styrene 20 wt% glycidyl methacrylate 40 wt% copolymer latex liquid (solid content 30%) 2) The tin oxide sol dispersion synthesized in (1), the first liquid, and the second liquid are mixed at a volume ratio of 35:15:50. A latex solution was prepared.

In the latex, tin oxide sol 15 vol
%, Preferably 40 vol% or more, the conductive elastomer particles can be made conductive.

3) The latex liquid prepared in 2) was spray-dried to form latex particles having an average particle size of 0.04 μm.

After drying and solidifying the latex liquid, it is also possible to produce particles by a pulverization method.

(3) Production of Charging Roller (Example 1)
1) After thoroughly mixing and kneading the following rubber compound using a closed type mixer, 2 parts by weight of dicumyl peroxide was added by an open roll, and then compounded. Was prepared.

(Rubber compounding) Silicone rubber 100 parts Zinc oxide 5 parts Conductive agent (carbon black) 7 parts Industrial paraffin 20 parts Plasticizer (aromatic process oil) 40 parts 2) Stainless steel cylinder 10 mm in diameter and 320 mm in length Roll the rubber compound on the roller surface at 150 ° C for 1
The mixture was heated and vulcanized for 5 minutes to obtain a silicone rubber roller having a 3 mm-thick elastic layer.

3) Next, the following coating layer coating material for obtaining a coating layer on the roller was kneaded using a small bead mill to obtain a coating layer coating material.

(Blending of coating material for coating layer) Polyamide resin 100 parts Elastomer particles obtained from (2) 150 parts Methanol 100 parts Toluene 300 parts 4) The above coating material is spray-coated on the roller, and then heated at 120 ° C. for 2 hours. By doing so, the residual solvent was removed, and a charging member having a tough coating layer having a thickness of 10 μm was obtained.

(4) Production of Charging Roller (Example 2)
(According to the method described in JP-A-6-250494) 1) The coating material for a coating layer described below for obtaining a coating layer on a roller was kneaded using a small bead mill to obtain a coating material for a coating layer.

(Blending of coating material for coating layer) 100 parts of methylolated nylon 100 parts of colloidal sol dispersion obtained in (1) 150 parts of methanol 150 parts of toluene 2) The above coating material is spray-coated on the roller, and then 120 ° C. For 1 hour to remove the residual solvent to obtain a charging member having a tough coating layer having a thickness of 10 μm.

(5) Comparative Example A coating material for a coating layer for obtaining a coating layer on a roller having an elastic layer obtained by rubber compounding of Example 1 was prepared according to the following formulation.

(Coating of coating material for coating layer) Polyamide resin 100 parts Tin oxide powder 30 parts Methanol 100 parts Toluene 300 parts The above coating material was spray-coated on the roller, and then 12
By heating at 0 ° C. for 2 hours, the residual solvent was removed, and a charging member having a tough coating layer having a thickness of 10 μm was obtained.

(6) Performance comparison (Evaluation of image)
3015 (manufactured by Konica Corp.)
Image evaluation was performed under a bias condition of -1800 VDC in an environment of 60 ° C. and 60% RH.

Example 1 Example 2 Comparative Example Halftone Image (Initial) Evaluation of ○ ＊ * 1 * 1 Image density unevenness in halftone portion Also, after continuous printing of 5000 sheets, peeling of conductive agent in Comparative Example The contamination of the photoreceptor was suspected as a cause.

[0073]

According to the present invention, there is no unevenness of resistance in the micro-area, no electric charge leakage or destruction of electric current occurs, no deterioration of image quality such as black stripes, black spots, etc., and the conductive agent is strongly bonded to the binder resin. And a contact charging member capable of maintaining good image quality for a long period of time without causing bleed-out or peeling of the conductive agent, and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a contact charging roller of the present invention.

FIG. 2 is a cross-sectional configuration diagram illustrating an image forming method and apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact charging roller 2 Metal core material 3 Conductive elastic layer 4 Resistance control layer (coating layer of Example) 10 Photoconductor drum 13 Developing device 14 Transfer roller 17 Fixing device P Transfer material (recording paper)

Claims (4)

[Claims] 1. A contact charging member for contacting and charging an object to be charged, comprising an amorphous metal oxide conductive agent. 2. The metal oxide conductive agent has a particle size of 1 to 100.
2. The contact charging member according to claim 1, wherein 3. The contact charging member according to claim 1, further comprising a conductive agent made of a colloidal metal oxide sol. 4. A method for manufacturing a contact charging member, comprising adding an amorphous conductive agent made from a colloidal metal oxide sol.