JP2003316112A - Electrostatic charging member, image forming device, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charging member which can perform stable electrostatic charge for a long period of time in spite of use at different process speeds, an image forming device equipped with such electrostatic charging member, and a process cartridge. <P>SOLUTION: The electrostatic charging member comprising having a conductive elastic material base layer and a front surface layer on a conductive support, and having the front surface layer containing both of inorganic particles and organic particles, the image forming device equipped with such electrostatic charging member, and the process cartridge are provided. The inorganic particles are preferably silica powder and the primary particle size thereof is ≤0.5 μm. The silica powder is treated with a silane coupling agent. The organic particles are preferably a copolymer of ethylene glycol dimethacrylate and methyl methacrylate. The shape thereof is spherical, and is ≥0.95 in average circularity and <0.040 in standard deviation of the circularity. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member, an image forming apparatus using the charging member, and a process cartridge.
More specifically, the present invention relates to a charging member for applying a voltage to charge the surface of an electrophotographic photosensitive member, which is a member to be charged, to a predetermined potential, an image forming apparatus using the same, and a process cartridge.

[0002]

2. Description of the Related Art A contact charging method has been put into practical use as a primary charging method for an electrophotographic image forming apparatus. This uses a charging roller in which a conductive elastic layer is provided on the outer periphery of a conductive support (core bar) and a resistance layer is coated on the outer periphery of the conductive elastic layer, and a voltage is applied to the core bar. This is a method of charging the surface of the photoconductor by causing minute discharge near the contact nip between the charging roller and the photoconductor.

An example of a method that has actually spread is an AC + DC charging method in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied, as in Japanese Patent Laid-Open No. 1-204081. The voltage having a peak-to-peak voltage Vpp that is at least twice as high as the charging start voltage when a DC voltage is applied is used as the AC voltage that is superimposed to obtain the voltage.

The AC + DC charging method is a method capable of performing stable charging by applying an AC voltage. However, since an AC voltage source is used, compared with a DC charging method in which only a DC voltage is applied to a charging member. However, the cost of the image forming apparatus increases. Therefore, for example, Japanese Patent Laid-Open No. 5-341
In Japanese Patent No. 627, a DC charging method is proposed.

[0005]

The DC charging method is AC
The cost is generally lower than the charging method, but there are problems. That is, since there is no AC current uniforming effect unlike AC + DC charging, the charging uniformity is inferior to the AC + DC charging method. Further, since there is no uniform effect, there is also a problem that stains adhering to the surface of the charging roller and nonuniformity of electric resistance of the charging roller itself are likely to appear in an image.

For example, in the above-mentioned Japanese Unexamined Patent Publication No. 5-341627, in the case of the constitution of the charging roller, the electric resistance of the conductive elastic base layer is too large, especially in an environment of low temperature and low humidity such as 15 ° C./10% RH. Then, the ability to charge the photoconductor is insufficient. That is, in an environment of low temperature and low humidity, for example, 600 dp
When a high-definition image such as a halftone image of i is output, fine white streaks occur.

Therefore, when an electronically conductive conductive agent is added to the conductive elastic body to reduce the resistance, unevenness of the electric resistance due to the roller portion appears on the image this time, which is also sufficiently uniform. Charging becomes impossible. JP-A-1
JP-A 1-100549 discloses a member for office equipment in which an NBR rubber whose resistance is adjusted with carbon black is formed with a surface layer obtained by crosslinking a polyolefin-based polyol with two or more kinds of isocyanates. With the charging member having such a configuration, good charging characteristics cannot be obtained when it is used as a charging member for DC charging, which has a strict requirement for uniform resistance.

When the electrophotographic apparatus is driven at two or more different process speeds to output an image due to the thickness of the print medium, the DC charging method is compared with the AC charging method. There is also a problem in that the range of process speeds at which good charging characteristics are exhibited is narrow.
In other words, depending on the heat capacity of the print media, if you want to slow down the process speed and lengthen the time to pass through the fixing part in the case of thick print media, or when printing on a transparency sheet, The DC charging method is used in situations such as when it is desired to extend the time for passing through the fixing portion in order to sufficiently melt and mix the toner in the fixing portion in order to suppress light scattering as much as possible and to obtain an image with good light transmittance. However, there is a problem that it is more difficult to perform good charging as compared with the AC charging method.

The object of the present invention has been made in order to solve such a problem, and by the DC charging method, for example, 60
An object of the present invention is to provide a charging member that can perform stable charging for a long period of time even when used at different process speeds, even when a high-definition image such as a 0-dpi halftone image is output, due to its good charging characteristics.

Another object of the present invention is to provide an image forming apparatus and a process cartridge using the above charging member.

[0011]

Therefore, according to the present invention, in a charging member having a conductive elastic base layer and a surface layer on a conductive support, the surface layer contains both inorganic fine particles and organic fine particles. A charging member is provided.

According to the present invention, an image carrier, charging means for charging the image carrier to a predetermined potential, exposing means for forming an electrostatic latent image on the charged surface of the image carrier, and the image carrier. In the image forming apparatus including a developing unit that transfers toner to the electrostatic latent image formed thereon to visualize it, and forms a toner image, and a transfer unit that transfers the toner image to a transfer target member, the charging unit. Provides an image forming apparatus characterized in that it has the above charging member, and charges only the DC voltage to the charging member to charge the image carrier.

Further, according to the present invention, there is provided a process cartridge characterized in that the image carrier and the charging member are integrally supported and can be detachably attached to the main body of the image forming apparatus.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

In view of the constitution of the charging member for DC charging, the present inventors provide a conductive support, a conductive elastic base layer provided on the conductive support, and a conductive elastic base layer. Further, it has been found that a charging member having a surface layer containing at least inorganic fine particles and organic fine particles can provide a charging member capable of stable charging for a long period of time even when used at different process speeds. The present invention has been reached.

Conventionally, it has been difficult for the DC charging system to obtain stable charging in a low temperature and low humidity environment. Further, when one electrophotographic apparatus is used at two or more different process speeds due to the thickness of the printing medium, the DC charging method has better charging characteristics than the AC charging method. There was also a problem in that the range of process speeds at which the performance was exhibited was narrow. In the present invention, by using the surface layer containing at least inorganic fine particles and organic fine particles, good charging characteristics can be obtained even when a high-definition image such as a halftone image of 600 dpi is output by the DC charging method. Thus, a charging member capable of performing stable charging for a long time even when used at different process speeds is provided. By using such a roller, we have
It was discovered that a charging member that can be used at different process speeds and that can be used in a DC charging method that has a severe demand for uneven electric resistance can be obtained.
The present invention has been completed.

Next, the charging member of the present invention, the image forming apparatus using the charging member, the charging method and the process cartridge will be described.

<1> Charging Member The charging member of the present invention comprises a conductive support, a conductive elastic base layer provided on the conductive support, and at least an inorganic material provided on the conductive elastic base layer. It is composed of a surface layer containing fine particles and organic fine particles.

A specific structure of the charging member of the present invention is shown in FIG. (A) shows the cross-sectional view of a charging member, (b)
Shows a vertical sectional view.

The charging member of the present invention comprises a conductive support 1, a conductive elastic base layer 2 formed on the outer periphery of the conductive support 1, and a surface layer 3 covering the outer periphery of the conductive elastic base layer 2.

The electrically conductive support 1 of the present invention shown in FIG.
Is a cylinder having a carbon steel alloy surface coated with a nickel plating film having a thickness of 5 μm. As the material constituting the conductive support, other materials such as iron, aluminum, titanium,
Metals such as copper and nickel, stainless steel containing these metals, duralumin, alloys such as brass and bronze, and known materials that are rigid and conductive, such as carbon black and composite materials in which carbon fibers are fixed with plastic It can also be used. In addition to the cylindrical shape,
It is also possible to have a cylindrical shape having a hollow central portion.

In the present invention, first, the conductive elastic base layer 2 is formed on the outer periphery of the conductive support 1. The conductive elastic body base layer 2 is made of a conductive elastic body. Conductive elastic base layer 2
Is molded by mixing a conductive agent and a polymer elastic body. At least an ionic conductive agent is used as the conductive agent. Epichlorohydrin rubber is particularly preferably used as the elastic polymer. The epichlorohydrin rubber has some conductivity in itself, and can exhibit good conductivity even if the amount of the conductive agent added is small, and the variation in electric resistance due to environment and position can be reduced. So
It is preferably used as an elastic polymer.

Epichlorohydrin rubber is a ring-opening polymer of a cyclic ether centered on epichlorohydrin, and the main monomers constituting the rubber include epichlorohydrin, ethylene oxide and acryl glycidyl ether.

Examples of the polymer epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-allyl glycidyl ether copolymer, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer and the like. To be Among these, an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer is particularly preferably used because it exhibits stable conductivity in the medium resistance region. The epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer can control conductivity and processability by arbitrarily adjusting the degree of polymerization and the composition ratio.

The polymer elastic body contains epichlorohydrin rubber as a main component, but other general rubber may be contained if necessary.

Other general rubbers include, for example,
EPM (ethylene / propylene rubber), EPDM (ethylene / propylene rubber), norbornene rubber, NBR
(Nitrile rubber), chloroprene rubber, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chlorosulphonated polyethylene, urethane rubber,
Examples thereof include styrene block copolymers such as SBS (styrene / butadiene / styrene-block copolymer) and SEBS (styrene / ethylene / butylene / styrene-block copolymer) and silicone rubber.

When the above-mentioned general rubber is contained, its content is preferably 1 to 50% by mass based on the total amount of the elastic polymer.

Examples of the conductive agent include perchlorates such as LiClO ₄ and NaClO ₄ , ionic conductive agents such as quaternary ammonium salts, and metal-based powders and fibers such as aluminum, palladium, iron, copper and silver. , Carbon black, metal powder or metal oxides such as titanium oxide, tin oxide and zinc oxide, metal compound powder such as copper sulfide and zinc sulfide, or tin oxide, antimony oxide, indium oxide, oxide on the surface of suitable particles Powder obtained by applying molybdenum, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, rhodium by electrolytic treatment, spray coating, mixed shaking, acetylene black, ketjen black , PAN
There are carbon powders such as (polyacrylonitrile) type carbon and pitch type carbon. These can be used alone or in combination of two or more.

The conductive agent preferably contains an ionic conductive agent for the purpose of reducing unevenness in the electrical resistivity of the conductive elastic base layer. The ionic conductive agent is uniformly dispersed in the elastic polymer, and the electronic resistivity of the conductive elastic material is made uniform, so that uniform charging is obtained even when the charging roller is applied with only DC voltage. be able to.

Examples of the ion conductive agent include LiCl
Examples thereof include perchlorates such as O ₄ and NaClO ₄ , quaternary ammonium salts and the like, and these can be used alone or in combination of two or more kinds. Among the ionic conductive agents, a quaternary ammonium salt of perchloric acid is particularly preferably used because it has stable resistance to environmental changes.

In addition to the ionic conductive agent, an electronically conductive conductive agent can be added in a range that does not cause unevenness in the electrical resistance of the conductive elastic body. The electronically conductive conductive agent can be used within a range in which the electronically conductive conductive agent has a lower conductivity than the ionic conductive agent. That is, the electronically conductive conductive agent has a volume resistivity of 1/1 when the electronically conductive conductive agent is added to the volume resistivity when only the ionic conductive agent is added to the polymer elastic body.
It can be used in a blending ratio of 2 or more.
Examples of the electrically conductive agent include aluminum,
Palladium, iron, copper, silver or other metal-based powder or fiber, carbon black, metal powder or titanium oxide, tin oxide, zinc oxide or other metal oxide powder, copper sulfide, zinc sulfide or other metal compound powder,
Or on the surface of suitable particles, tin oxide, antimony oxide,
Powder obtained by depositing indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, rhodium by electrolytic treatment, spray coating, mixed shaking, acetylene black , Ketjen black, PAN (polyacrylonitrile) -based carbon, pitch-based carbon and the like. These can be used alone or in combination of two or more.

In the present invention, the blending amount of these conductive agents is such that the volume resistivity of the conductive elastic body is low temperature / low humidity environment (L / L).
L: 15 ° C / 10% RH, normal temperature and normal humidity environment (N / N: 2)
3 ° C / 55% RH), high temperature and high humidity environment (H / H: 30 ° C /
80% RH, medium resistance region (volume resistivity is 1 × 10 ⁴
The amount is preferably about 1 × 10 ⁷ Ω · cm).

The volume resistance of the conductive elastic body is obtained by forming a sheet having a thickness of 1 mm, and then depositing a metal on both sides to form an electrode and a guard electrode, and then using a micro ammeter (ADVANTEST).
R8340A ULTRA HIGH REISTA
A voltage of 200 V was applied using NCE METER (manufactured by Advantest Co., Ltd.), and the current after 30 seconds was measured and calculated from the film thickness and the electrode area.

If the volume resistivity of the conductive elastic body is smaller than this, when a photoconductor as an image carrier has a pinhole, a large current concentrates on the pinhole at once, and the hole becomes larger. There is a possibility that such problems may occur that the current does not flow to a place other than the hole and a black band appears on the high-definition halftone image, and a portion having insufficient charging potential appears. On the other hand, if the volume resistivity is too high, the applied voltage drops in the conductive elastic layer, and it becomes impossible to uniformly charge the photoconductor to the desired potential without obtaining the necessary discharge current. is there.

In addition to these, the conductive elastic body may be a known plasticizer, filler, vulcanizing agent, vulcanization accelerator, antiaging agent, scorch inhibitor, dispersant, release agent, etc., if necessary. It is also preferable to add the compounding agent of.

As a method for molding the conductive elastic body, known methods such as extrusion molding, injection molding, compression molding and the like can be mentioned by mixing the above-mentioned raw materials of the conductive elastic body. Also,
The conductive elastic base layer may be produced by directly molding a conductive elastic body on a conductive support, or may be formed by coating the conductive support with a tube-shaped conductive elastic body. .
The surface may be polished to prepare the shape after the conductive elastic base layer is prepared.

The shape of the conductive elastic base layer is such that the diameter of the central portion of the conductive elastic base layer roller is such that the contact nip width between the completed charging roller and the photosensitive member is as uniform as possible in the longitudinal distribution of the roller. Preferably has a crown shape larger than the diameter of the end portion. Further, since the contact nip width of the completed roller becomes uniform, it is preferable that the runout of the conductive elastic base layer roller is small.

As shown in FIG. 2, the measured value of the runout is obtained by rotating the conductive elastic base layer roller with the conductive support as the rotation axis and making a non-contact laser length measuring device perpendicular to the rotation axis (in the present invention, The difference between the maximum value and the minimum value of the radius of the conductive elastic base layer roller measured by KEYENCE CORPORATION LS-5000) is obtained as a value. The difference between the maximum value and the minimum value of the radius is calculated at a pitch of 1 cm in the axial direction of the conductive elastic base layer roller, and the maximum value among them is taken as the value of the runout of the conductive elastic base layer roller.

Similarly, the diameter of the roller means that the conductive elastic base layer is measured by a non-contact laser length measuring machine perpendicular to the rotating shaft by rotating the conductive elastic base layer roller with the conductive support as the rotating shaft. The average of the maximum and minimum roller diameters is used.

The difference between the diameter of the central portion of the conductive elastic base layer roller in the axial direction and the average of the two diameters of the central portion 10 mm from both ends of the elastic body is determined as the value of the crown amount.

A preferable value of the runout of the conductive elastic base layer roller is 0.5% or less, more preferably 0.25% or less of the diameter of the central portion of the roller. The diameter of the roller of the present invention is 1
Since the value of 2 mm is preferable, the value of shake is specifically 60
It is preferably not more than μm, more preferably not more than 30 μm.

The value of the crown amount is determined so that the nip width of the finished roller is uniform, but preferably 0.1 to 5.0% of the roller diameter, specifically 12 μm to 600.
μm is preferred.

The Asker C hardness of the conductive elastic body is 85 °.
The following is preferable, and 80 ° or less is more preferable. When the Asker C hardness exceeds 85 °, the nip width between the charging member and the photoconductor becomes small, the contact force between the charging member and the photoconductor is concentrated in a small area, and the contact pressure becomes large.
As a result, the charging becomes unstable, and the adverse effects such as the easy adhesion of the developer and the like to the surfaces of the photoconductor and the charging member become remarkable.

The "Asker C hardness" is the hardness of the charging member measured by using an Asker C type spring type rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) conforming to the Japan Rubber Association standard SRIS0101. Normal temperature and humidity (23 ℃
/ 55% RH), the hardness tester is left to stand for 12 hours or more in an environment of
The value is measured after 2 seconds.

To reduce the Asker C hardness, a plasticizer is added to the conductive elastic body. The compounding amount is the conductive elastic body 1
It is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 00 parts by mass. As the plasticizer, for example, an ester polymer plasticizer such as a copolymer of sebacic acid and propylene glycol can be used. Such an ester-based plasticizer has a polarity close to that of epichlorohydrin rubber, can be compounded in a relatively large amount, and has an advantage that the hardness of the base layer can be controlled to be small. The molecular weight of the polymer plasticizer is preferably 2,000 or more, more preferably 4,000 or more. If the molecular weight is less than 2,000, the plasticizer may seep out to the surface of the roller and contaminate the photoconductor.

The conductive elastic base layer is adhered to the conductive support through an adhesive, if necessary. In this case, the adhesive is preferably electrically conductive. A known conductive agent can be contained in the adhesive in order to make it conductive.

Examples of the binder for the adhesive include resins such as thermosetting resins and thermoplastic resins, and known adhesives such as urethane-based, acrylic-based, polyester-based, polyether-based and epoxy-based adhesives are used. You can

After the conductive elastic base layer is completed, the surface layer 3 is provided as a coating layer for the conductive elastic base layer. The surface layer of the charging member of the present invention contains at least inorganic fine particles and organic fine particles. The inorganic fine particles are preferably insulating fine particles, and specifically contain silica powder. If silica is contained, the absolute value of the charging potential becomes large and stable even when a high-resistance charging roller is used, so that it is particularly preferable for a DC charging roller.

The silica fine powder that can be used in the present invention includes dry silica produced by vapor phase oxidation of a silicon halogen compound or dry silica called fumed silica and wet silica produced from water glass. Both can be used, but dry silica, which has less silanol groups on the surface and inside and has no production residue, is preferred. It is preferable that the silica have a primary particle diameter of about 0.5 μm or less.

Further, in the present invention, it is preferable to use silica fine powder having a surface treated. The surface treatment is applied by chemically treating with an organosilicon compound that reacts with or physically adsorbs on the silica fine powder. As a preferred method, a method of treating dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound with a silane coupling agent, a method of treating with an organic silicon compound such as silicone oil, or a treatment with a silane coupling agent. Or after the treatment with a silane coupling agent and an organosilicon compound such as silicone oil.

Examples of the silane coupling agent used for the hydrophobic treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl. Phenyldichlorosilane, benzyldimethylchlorosilane,
Brommethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilylmercaptan,
Examples include triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane and 1,3-diphenyltetramethyldisiloxane. .

The organosilicon compound used for the hydrophobizing treatment includes silicone oil, and a preferable silicone oil has a viscosity of about 3 at 25 ° C.
The thing of 0-1,000 centistokes is used.
For example, it is preferable to use dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil or fluorine modified silicone oil.

The hydrophobic treatment with silicone oil may be carried out, for example, by directly mixing silica fine powder treated with a silane coupling agent and silicone oil with a mixer such as a Henschel mixer, or by using silica as a base. You may spray silicone oil. Alternatively, the silicone oil may be dissolved or dispersed in an appropriate solvent, then mixed with the silica fine powder of the base, and the solvent may be removed to perform the hydrophobic treatment.

The amount of the inorganic fine particles added is preferably 0.1 to 10% as a mass ratio in the surface layer after coating. If the amount is too small, the effect of adding the inorganic fine particles to stabilize the charging cannot be obtained, and if the amount is too large, it becomes difficult to control the viscosity of the surface layer coating composition and it becomes difficult to apply the composition uniformly, which is not preferable.

Next, as the organic fine particles contained in the surface layer, it is preferable to use crosslinked resin fine particles. If it is not crosslinked, it is not preferable because it may dissolve in a solvent generally used in the paint when it is used as a paint for coating the surface layer. The monomer for forming the crosslinked resin fine particles is not particularly limited, but a vinyl-based monomer is preferably used because of ease of polymerization and the like.

Examples of the vinyl-based monomer used in the present invention include acrylic acid esters such as methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and methacrylic acid such as methyl methacrylate, butyl methacrylate, and methacrylic acid hexyl. Aromatic vinyl monomers such as acid esters, styrene, p-methylstyrene and α-methylstyrene, vinyl acetate, acrylonitrile and the like can be mentioned.

In order to obtain crosslinked resin fine particles, in the present invention, a crosslinkable vinyl monomer having two or more vinyl groups in the molecule is used in addition to the above vinyl monomer. Examples of such crosslinkable vinyl-based monomers include ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate. The addition amount of these crosslinkable vinyl monomers is preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the non-crosslinkable vinyl monomer.

Although these crosslinked resin fine particles are polymerized by seed emulsion polymerization, dispersion polymerization, suspension polymerization, etc., they may be polymerized by suspension polymerization because there are few residual low molecular weight surfactants and the like. More preferable. The polymerization initiator is not particularly limited, and examples thereof include peroxide catalysts such as benzoyl peroxide and lauroyl peroxide, and azo catalysts such as azobisisobutyronitrile.

In the present invention, the organic fine particles are preferably composed of a copolymer of ethylene glycol dimethacrylate and methyl methacrylate.

The crosslinked resin fine particles used in the present invention more preferably have a shape closer to a true sphere. Specifically, the surface roughness of the charging roller is made uniform by precisely controlling the particle shape of the resin fine particles so that the average circularity is 0.95 or more and the standard deviation of the circularity is less than 0.040. Therefore, even if used at different process speeds, more uniform charging characteristics can be obtained. The circularity in the present invention is used as a simple method for quantitatively expressing the shape of particles, and in the present invention, the particle shape is measured using a flow type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics Co., Ltd. The circularity is calculated by the following formula. Further, as shown by the following formula, the value obtained by dividing the total sum of the measured circularity of all particles by the total number of particles is defined as the average circularity.

[0061]

[Equation 1]

[0062]

[Equation 2]

[0063]

[Equation 3] Here, the “particle projection area” is the area of the binarized toner particle image, and the “perimeter of the particle projection image” is the length of the contour line obtained by connecting the edge points of the toner particle image. Define.

The measuring device "FPIA-1000" used in the present invention was used after calculating the circularity of each particle.
In calculating the average circularity and the standard deviation of the circularity, the circularity of 0.400 to 1.0 is determined according to the circularity obtained.
00 at 0.010 intervals and divided into 61 divided ranges such as 0.400 or more and less than 0.410, 0.410 or more and less than 0.420 ... The calculation method of calculating the average circularity and the circularity standard deviation using the center value and frequency of the points is used.

Each value of the average circularity and the circularity standard deviation calculated by this calculation method, and each value of the average circularity and the circularity standard deviation calculated by the above-mentioned calculation formula that directly uses the circularity of each particle. Since the error between and is very small and can be substantially ignored, in the present invention, each of the above-mentioned factors is used for the reason of handling data such as short-circuiting of calculation time and simplification of calculation calculation formula. By utilizing the concept of a calculation formula that directly uses the circularity of particles, a partially modified calculation method like this is used.

The circularity in the present invention is an index showing the degree of unevenness of particles, and is 1. when the particles are perfectly spherical.
The circularity has a smaller value as the surface shape becomes more complicated.

As a specific measuring method, 10 ml of ion-exchanged water from which impure solids and the like have been removed beforehand is prepared in a container, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant into the water. Then, 0.02 g of a measurement sample is further added and uniformly dispersed. As a means for dispersing, an ultrasonic disperser "UH-50 type" (manufactured by SMT) equipped with a titanium alloy chip of 5φ as a vibrator was used, and a dispersion treatment for 5 minutes was performed using a dispersion treatment for 5 minutes. To do. At that time, the dispersion is appropriately cooled so that the temperature of the dispersion does not exceed 40 ° C.

For measuring the shape of the resin fine particles, the flow type particle image measuring device is used, and the toner particle concentration at the time of measurement is 3,
The concentration of the dispersion liquid is readjusted so as to be 000 to 10,000 particles / μl, and 1,000 or more toner particles are measured.

The average particle size of the resin fine particles is preferably 100 μm or less. More preferably 0.5-50 μ
It is preferably m. More preferably, 1 to 25 μ
It is preferably m. Further, it is preferable that there is substantially no resin fine particles having a particle diameter of 3 times or more the weight average particle diameter. If the particle size is too large, the surface of the charging roller becomes too rough, resulting in non-uniform charging. On the other hand, if it is too small, the effect of stabilizing the charge in the low process speed region by adding the resin fine particles is not exhibited, which is not preferable.

Specific examples of the particle size measurement of the resin fine particles in the present invention will be shown below.

0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added to 100 to 150 ml of the electrolyte solution.
2 to 20 mg of the measurement sample is added thereto. The electrolytic solution in which the sample was suspended was dispersed for 1 to 3 minutes with an ultrasonic disperser, and then 17 times with a Coulter Counter Multisizer.
0.3 to 64 μm based on the volume using an aperture appropriately matched to the resin particle size such as μm or 100 μm
The particle size distribution of m, etc. shall be measured. The number average particle diameter and weight average particle diameter measured under these conditions are obtained by computer processing, and the cumulative ratio of the weight average particle diameter three times diameter cumulative distribution or more is calculated from the volume-based particle size distribution, and the three times diameter cumulative distribution or more is calculated. Calculate the cumulative value of.

The addition amount of the resin fine particles is preferably 1 to 80% by mass as a mass ratio in the surface layer after coating. If the amount is too small, the effect of stabilizing the charge by adding the resin fine particles cannot be obtained, and if the amount is too large, it becomes difficult to control the viscosity of the surface layer coating composition and it becomes difficult to apply the composition uniformly, which is not preferable.

Further, in the present invention, the ratio of the inorganic fine particles to the organic fine particles is preferably 1: 1 to 1: 100 (inorganic fine particles: organic fine particles) on a mass basis. Also,
The ratio of all particles to the entire surface layer is 3 to 7 on a volume basis.
It is preferably 0%, more preferably 5 to 50%.

As the binder for the surface layer, resins such as thermosetting resins and thermoplastic resins are used. As the binder for the surface layer of the present invention, a urethane resin is preferable, and among them, a urethane resin obtained by crosslinking a lactone-modified acrylic polyol with isophorone diisocyanate and hexamethylene diisocyanate is particularly preferably used.

When hexamethylene diisocyanate is used alone as the isocyanate for crosslinking the polyol of the surface layer, the surface layer is flexible and the surface of the roller after coating is uniformly finished, but on the other hand, in a severe high temperature and high humidity environment. However, the finished surface layer may not sufficiently prevent unvulcanized components (for example, an ionic conductive agent and a plasticizer) in the base layer from seeping out to the roller surface. The presence of such exudates can contaminate the photoreceptor.

On the other hand, when isophorone diisocyanate is used alone as the isocyanate for crosslinking the polyol of the surface layer, the surface layer has a great effect of preventing the exudation of the exuding substance from the base layer, but the surface layer becomes too hard. There is an adverse effect that the heat shrinkage of the base rubber cannot be followed, wrinkles occur on the surface of the finished roller, and the desired roller cannot be obtained in terms of surface roughness and shape of the roller.

The surface layer of the roller of the present invention provides a surface layer resin having good properties which have both the exuding substance blocking property of isophorone diisocyanate and the flexibility of hexamethylene diisocyanate, and the stain from an ionic base layer is provided. A charging roller having a good surface shape can be obtained while preventing the discharged substance from seeping out onto the roller surface.

That is, in the resin used for the surface layer in the present invention, the lactone-modified acrylic polyol, isophorone diisocyanate, and hexamethylene diisocyanate are blended and cured to give isophorone diisocyanate and hexamethylene diisocyanate to the lactone-modified acrylic polyol. A copolymer is formed by reacting randomly and forming a crosslinked structure.

The isocyanate used in the present invention is more preferably an isocyanurate type trimer.
The rigid trimer of the molecule serves as a cross-linking point, so that the surface layer can be more densely cross-linked, and the substance exuding from the ionic base layer can be more effectively prevented from exuding to the roller surface. be able to.

The isocyanate used in the present invention is more preferably a blocked isocyanate having an isocyanate group blocked with a blocking agent.
The reason for this is that the above-mentioned isocyanate groups are likely to react, and if the surface layer coating is left at room temperature for a long time, the reaction will gradually proceed and the characteristics of the coating may change. On the other hand, blocked isocyanate has an advantage that the coating material is easy to handle because the active isocyanate group is blocked and the blocked isocyanate does not react up to the dissociation temperature of the blocking agent. Blocking agents for masking include phenols, phenols such as cresol, lactams of ε-caprolactam and oximes such as methylethylketoxime, but in the case of the present invention, dissociation temperatures are relatively low oximes. preferable.

The trimer of lactone-modified acrylic polyol and blocked isocyanate constituting the surface layer of the present invention is illustrated.

[0082]

[Chemical 1] Lactone modified acrylic polyol

[0083]

[Chemical 2] Isophorone diisocyanate

[0084]

[Chemical 3] Hexamethylene diisocyanate On the other hand, the OH value of lactone-modified acrylic polyol is 80
It is preferably about KOHmg / g. If the OH value is low, it becomes difficult for the isocyanate to crosslink, which makes the resin too soft and sticks easily to the photoreceptor. If the OH group is too large, the coating film becomes too hard and easily cracks.

The lactone-modified acrylic polyol of the present invention is a copolymer of styrene and acrylic having a molecular chain skeleton, and has appropriate hardness and non-staining property. Further, the modified lactone group having a hydroxyl group at the terminal becomes a large number of crosslinking points,
It is possible to densely crosslink with an isocyanate, and it is possible to prevent the unvulcanized component from seeping out from the base layer.
As such a lactone-modified acrylic polyol,
For example, Praxel DC2016 (manufactured by Daicel Chemical Industries, Ltd.) can be mentioned.

Glass transition temperature Tg of resin used for surface layer
Is a viscoelasticity measurement method, and the peak temperature is preferably 45 ° C. or higher, and particularly preferably 50 ° C. or higher. If the temperature is lower than 45 ° C., it may adhere to the photoconductor when left in contact with the photoconductor for a long period of time, or the surface of the charging roller may be easily soiled with toner or the like, which is not preferable. .

The method of measuring the glass transition temperature Tg in the present invention is as follows. First, in the surface layer sample for measurement, the surface layer was peeled off from the roller state, and 5 mm × 40 m
Cut into strips of about m. A dynamic viscoelasticity measuring device RSA-II (manufactured by Rheometrics Scientific F.E. Co., Ltd.) is used as a measuring device, and a film tension fixture is used as a jig. The measurement was performed at a measurement frequency of 6.28 rad / sec and a temperature rising rate of 5 ° C./min. ,
Performed in auto tension mode with initial strain of 0.07 to 0.25%. The temperature dispersion of the loss tangent tan δ is measured, and the peak temperature is Tg.

Although not particularly limited, if the Tg is too high, the flexibility of the resin is lost and the coating film is easily cracked, which is not preferable. The Tg is adjusted by the ratio or amount of isocyanate crosslinked.

The compounding ratio of the lactone-modified acrylic polyol resin and the isocyanate is such that the ratio of the NCO group number (A) in the isocyanate in the coating composition and the OH group number (B) in the lactone-modified acrylic polyol resin is NCO / O.
The H ratio = A / B is preferably in the range of 0.1 to 2.0, particularly preferably adjusted to be in the range of 0.3 to 1.5.

By cross-linking the lactone-modified acrylic polyol with isocyanate, it is possible to prevent the low-molecular component from seeping out from the conductive elastic base layer, and the charging roller itself is unlikely to be contaminated with toner and the like, and the photoreceptor is contaminated. The surface layer which does not exist can be formed.

It is also preferable to mix various conductive agents and leveling agents with the resin coating material forming the surface layer. Examples of the leveling agent include silicone oil.

As the conductive agent used for the surface layer, for example,
Powders and fibers of metal such as aluminum, palladium, iron, copper, silver, carbon black, metal powder and metal oxides such as titanium oxide, tin oxide and zinc oxide, metal compounds such as copper sulfide and zinc sulfide, and oxidation Tin, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver,
Powder obtained by adhering copper, chromium, cobalt, iron, lead, platinum, rhodium, etc. to the surface by electrolytic treatment, spray coating, mixed shaking, acetylene black, Ketjen black, PAN-based carbon, pitch-based Carbon powder such as carbon may be used.

In the present invention, conductive tin oxide is preferably used as the conductive agent. In particular, conductive tin oxide obtained by doping tin oxide with antimony is preferably used. The reason is that conductive tin oxide obtained by doping tin oxide with antimony is relatively inexpensive, has a relatively large volume resistivity of the conductive agent itself, and has a difference from the volume resistivity of the resin in which the conductive agent is dispersed. Since it is smaller than the conductive agent, when the conductive agent is dispersed into a surface layer material having medium resistance, a slight difference in distribution of the conductive agent hardly causes a difference in resistance of the surface layer material,
This is because it is suitable as a conductive agent for the surface layer material of the present invention because the variation in resistance depending on the position can be suppressed to a relatively small value.

The compounding amounts of these conductive agents added to the surface layer resin are such that the volume resistivity of the surface layer resin is in a low temperature and low humidity environment (L
/ L: 15 ° C / 10% RH), normal temperature and normal humidity environment (N / N:
23 ℃ / 55% RH, high temperature and high humidity environment (H / H: 30 ℃)
/ 80% RH, medium resistance region (volume resistivity is 1 × 10
⁶ to 1 × 10 ¹⁵ Ω · cm).

When the volume resistivity of the surface layer is smaller than this, when used as a charging roller, when the photoconductor has a pinhole, an excessive current flows into the pinhole to cause leakage, and the leaked trace is an image. It is not preferable because it appears in. On the other hand, if the volume resistivity is too large, no current flows through the charging roller, the photosensitive member cannot be charged to a predetermined potential, and the image does not have the desired density. Further, even if charged to a certain potential, the charging becomes non-uniform and appears on the image, which is not preferable.

With respect to the volume resistance of the surface layer, the surface layer is peeled from the roller state and cut into a strip shape of about 5 mm × 5 mm.
An electrode and a guard electrode were prepared by vapor-depositing metal on both surfaces, and a micro ammeter (ADVANTEST R8340A ULT
RA HIGH RESISTANCE METER
A voltage of 200 V was applied using Advantest Co., Ltd., and the current after 30 seconds was measured and calculated from the film thickness and the electrode area.

The content of the conductive tin oxide is preferably 10 to 80% by mass, and more preferably 20 to 60% by mass, based on the surface layer after coating. The primary particle size of the conductive tin oxide is preferably 0.1 μm or less as observed by a differential scanning electron microscope. The secondary particles are dispersed in the surface layer coating material by a known method until the secondary particles become small. The secondary particle diameter is a value of volume average particle diameter MEDIAN measured by a centrifugal sedimentation type particle size distribution meter (CAPA700: manufactured by Horiba Ltd.), preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. If the secondary particle size is large, the variation in the resistance of the surface layer material depending on the position becomes large, which causes charging unevenness, which is not preferable.

The conductive tin oxide used in the present invention is preferably surface-treated. More preferably, the surface treatment is a coupling agent treatment. The surface treatment of the conductive tin oxide has an effect of suppressing the adhesion of water to the surface of the tin oxide and suppressing the environmental fluctuation of the volume resistivity of the finished surface layer. The coupling agent is
Having a hydrolyzable group and a hydrophobic group in the same molecule, silicon,
A compound bonded to a central element such as aluminum, titanium, or zirconium, which has a long-chain alkyl group in the hydrophobic group portion.

As the hydrolyzable group, for example, a relatively highly hydrophilic alkoxy group such as methoxy group, ethoxy group, propoxy group and butoxy group is used. Other,
An acryloxy group, a methacryloxy group, modified products thereof, halogen, and the like are also used. The hydrophobic group may be any group as long as it has a structure in which 6 or more carbon atoms are linearly connected in the structure, and in the bond form with the central element,
It may be directly bonded via a carboxylic acid ester, an alkoxy, a sulfonic acid ester or a phosphoric acid ester. Further, functional groups such as ether bond, epoxy group and amino group may be included in the structure of the hydrophobic group. By treating with a coupling agent, adsorption of moisture on the surface of tin oxide can be suppressed, and a surface layer material with less environmental fluctuation can be obtained. As the coupling agent used in the present invention, a silane coupling agent having high reactivity is preferable.

Examples of the silane coupling agent include:
Hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, trifluoropropyltrimethoxysilane and hexyltrimethoxysilane. However, trifluoropropyltrimethoxysilane is particularly preferable because it can suppress environmental fluctuations of the volume resistivity of the conductive agent to be small.

As the method for molding the surface layer, the materials constituting the above surface layer are dispersed by a known method using a conventionally known dispersing device using beads such as a sand mill, a paint shaker, a dyno mill and a pearl mill, The obtained resin coating material for forming the surface layer is applied by dipping or spray coating on the surface of the charging member, in the present invention, on the conductive elastic base layer. Considering the utilization efficiency of the surface layer coating material, the dipping method is preferable.

The surface layer thickness is preferably 5 to 100 μm.
m, more preferably 10 to 50 μm. When the thickness of the surface layer is larger than 50 μm, the uniformity of charging is impaired and fine white stripes are generated in the axial direction of the roller on the image, which is not preferable. The film thickness can be measured by cutting out the roller cross section with a sharp blade and observing it with an optical microscope or an electron microscope.

In order to adjust the surface layer film thickness, the resin solid content of the surface layer coating material and the coating pulling rate are controlled. Increasing the solid content of the resin in the surface coating increases the thickness of the surface layer, and decreasing the solid content decreases the thickness of the surface layer.
In the surface layer coating material of the present invention, the solid content of the resin with respect to the solvent that volatilizes is adjusted to 1 to 40 mass%. Also, increasing the coating pulling rate increases the surface layer thickness,
When the speed is reduced, the thickness of the surface layer is also reduced. Therefore, in the present invention, the coating pulling rate is 20 to 5000 mm /
min. Adjust to.

The surface roughness of the charging member of the present invention is preferably 0.5 μm or more and 40 μm or less in terms of ten-point average roughness Rz according to JIS B 0601-1994, and 0.1 μm or more and 5 μm or less in Ra. 10-point average roughness Rz is 1 μm or more and 30 μm or less, and Ra is 0.4 μm.
m or more and 6 μm or less. If the surface roughness is too large, uneven charging tends to appear in the output image, and if the surface roughness is too small, the effect of stabilizing the charging at a slow process speed by adding resin particles is not preferable.

As a method of measuring the average roughness (Ra, Rz), based on the surface roughness of JIS B 0601, a surf coder SE3400 manufactured by Kosaka Laboratory was used to measure 3 points in the axial direction.
A total of 6 points, 2 points in the circumferential direction, are measured, and the average value is taken. In the present invention, the contact needle is a diamond having a tip radius of 2 μm, the measurement speed is 0.5 mm / s, the cutoff λc is 0.8 mm, the reference length is 0.8 mm, and the evaluation length is 8.0 mm.

In order to obtain a charging member having a surface roughness within the above range, the surface roughness of the base layer, the film thickness of the surface layer, the average particle size of the resin fine particles and the addition amount are adjusted. The ten-point average roughness of the base layer is R
The z is 20 μm or less, more preferably 15 μm or less.

Further, the charging member of the present invention, as shown in FIG.
With the same stress as when used in an image forming device,
While abutting on a metal cylinder having the same curvature as the photoconductor, the metal cylinder is rotated at the same rotation speed as that in use (in the present invention, a force of 5N is applied to both ends of the shaft to obtain a diameter of 30 mm).
Of the metal cylinder, and the peripheral speed of the metal cylinder is 45 mm / s.
The electrical resistance of the charging member when a DC voltage of -250 V is applied is 1 × 10 ⁶ Ω or more in an environment of high temperature and high humidity of 30 ° C./80% RH and is 15 ° C./10%. It is preferably 1 × 10 ⁸ Ω or less in an environment of low temperature and low humidity. More preferably, it is 2 × 10 ⁶ Ω or more in an environment of high temperature and high humidity of 30 ° C./80% RH, and 15 ° C./10.
%, It is preferably 6 × 10 ⁷ Ω or less in a low temperature and low humidity environment.

If the resistance in a low temperature and low humidity environment is smaller than the above range, fine horizontal white stripes on a halftone image due to uneven charging hardly occur, which is preferable. If the resistance in a high temperature and high humidity environment is larger than the above range, the applied current does not leak even if there is a pinhole on the photoconductor, and uneven charging density does not appear on the halftone image, which is preferable.

In order to bring the electric resistance into the above range, the volume resistivity of the conductive elastic base layer of the charging member is 1 × 10 ⁴ to 1 × 1.
0 to ^{7 Ω} · cm, also the volume resistivity of the surface layer 1 × 10 ⁸ ~
1 × 10 ¹⁵ Ω · cm and surface layer film thickness of 10 to 50 μ
It may be adjusted so that m.

<2> Image Forming Apparatus FIG. 3 shows an image forming apparatus using the charging roller 6 which is one embodiment of the charging member of the present invention. The photosensitive drum 5, which is an image bearing member, is primarily charged by the charging roller 6 while rotating in the direction of the arrow, and then exposed by the exposing unit 1
1 is irradiated and an electrostatic latent image is formed. The toner in the thin layer on the developing roller 4, which is the developing means, is charged by the toner charging roller 29, and then contacts the surface of the photoconductor drum 5, whereby the electrostatic latent image is developed and visualized. Is formed.

The developed toner image is transferred from the photosensitive drum 5 to the print medium 7 which is the transferred member in the developing section between the transfer roller 8 which is a transfer member and the photosensitive drum 5, and then the fixing section. It is fixed by heat and pressure at 9,
It becomes a permanent image. The latent image remaining on the photoconductor drum 5 is exposed by the pre-charging exposure device, and the potential of the photoconductor drum 5 returns to the ground potential. The transfer residual toner that has not been transferred is collected by the cleaning blade 10.

Voltages are applied to the developing roller 4, toner charging roller 29, charging roller 6, and transfer roller 8 from power sources 18, 19, 20, and 22 of the image forming apparatus.

A DC voltage is applied from the power source 20 to the charging roller 6 which is the charging member of the present invention. By using a DC voltage as the applied voltage, there is an advantage that the cost of the power supply can be kept low. Further, there is an advantage that the charging sound generated when the AC voltage is applied is not generated.

The absolute value of the applied DC voltage is preferably the sum of the discharge start voltage of air and the primary charging potential of the surface of the member to be charged (photosensitive member surface). Normally, the discharge start voltage of air is about 600 to 700 V, and the primary charging potential of the surface of the photoconductor is about 300 to 800 V. Therefore, it is preferable to set the specific primary charging voltage to 900 to 1500 V.

When the color image forming apparatus is used,
As shown in FIG. 4, the photosensitive drums 5a to 5d, the transfer rollers 8a to
8d, charging rollers 6a to 6d, toner charging roller 29a
-29d, elastic regulation blades 30a-30d, exposure 11
a to 11d, toner containers 31a to 31d, etc.
Color components can be prepared and arranged in series.

<3> Charging Method In the present invention, by applying a DC voltage to the charging member,
A charging method for charging an object to be charged is provided.

<4> Process Cartridge The present invention relates to an image carrier, developing means for transferring toner to the electrostatic latent image formed on the image carrier to visualize it, and the transfer target. At least one selected from the cleaning means for removing the toner remaining on the image carrier after the toner image is transferred to the member is integrally supported with the charging member of the present invention, and is configured to be detachable from the image forming apparatus. It is a process cartridge.

In the process cartridge of the present invention, for example, as shown in FIG. 5, the photosensitive drum 5, the charging roller 6, the developing roller 4, the cleaning blade 10 and the like are integrally supported, and the process cartridge is detachable from the main body of the image forming apparatus. Is.

Before the electrophotographic process cartridge is used, it is preferable to avoid contact between the developing roller 4 and toner with a toner seal.

[0120]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples.

Example 1 <Preparation of Charging Roller> (1) Preparation of Conductive Elastic Base Layer Epichlorohydrin rubber (trade name: Epichromer CG1)
02, manufactured by Daiso Co., Ltd., 100 parts by mass, 30 parts by mass of calcium carbonate as a filler, 1 part by mass of zinc stearate as a lubricant, and colored grade carbon (trade name: Seast) as a reinforcing material for improving abrasiveness. SO, manufactured by Tokai Carbon Co., Ltd.), 5 parts by mass of zinc oxide, 5 parts by mass of a copolymer of sebacic acid and propylene glycol (molecular weight 8000) as a plasticizer, and perchloric acid of the following formula 4
2 parts by mass of primary ammonium salt,

[0122]

[Chemical 4] 1 part by mass of 2-mercaptobenzimidazole as an antioxidant is kneaded with an open roll for 20 minutes, and further 1 part by mass of DM (2-benzothiazolyl disulfide) as a vulcanization accelerator and as a vulcanization accelerator. 0.5 parts by mass of TS (tetramethylthiuram monosulfide) and 1.2 parts by mass of sulfur as a vulcanizing agent were added, and the mixture was further kneaded by an open roll for 15 minutes.

Using an rubber extruder, the outer diameter of this was 15 m.
m, internal diameter 5.5 mm, extruded into a cylindrical shape, cut into a length of 250 mm, primary vulcanized for 40 minutes in steam at 160 ° C. using a vulcanizing can, and primary vulcanization of conductive elastic base rubber A tube was obtained.

Next, a thermosetting adhesive of metal and rubber was applied to the central portion 231 mm in the axial direction of the cylindrical surface of a cylindrical conductive support (steel, surface plated with nickel) having a diameter of 6 mm and a length of 256 mm. Apply (Product name: Metalloc U-20),
After drying at 80 ° C. for 30 minutes, it was dried at 120 ° C. for 1 hour. This conductive support was inserted into the conductive elastic base layer rubber primary vulcanization tube, and then secondary vulcanization and curing of the adhesive were performed in an electric oven at 160 ° C. for 2 hours. A polishing layer was obtained.

Both ends of the rubber portion of this unpolished layer were cut off to make the length of the rubber portion 231 mm, and then the rubber portion was ground with a rotary grindstone to obtain an end diameter of 12.00 mm and a central diameter of 12.10 mm. A charging roller having a crown shape and a conductive elastic base layer having a surface ten-point average roughness Rz of 6 μm and a runout of 25 μm was obtained.

The charging roller having the conductive elastic base layer is N
/ N (normal temperature and humidity: 23 ° C./55% RH), the resistance of the charging roller having a conductive elastic base layer was measured after standing for 24 hours or more, and was 3.0 × 10 ⁵ Ω.
The Asker C hardness of the rubber portion was 74 °.

(2) Preparation of Surface Layer To 50 parts by mass of conductive tin oxide powder (trade name: SN-100P, manufactured by Ishihara Sangyo Co., Ltd.), 5% of a 1% isopropyl alcohol solution of trifluoropropyltrimethoxysilane was added.
300 parts by mass and glass beads 300 with an average particle size of 0.8 mm
After adding 70 parts by mass and dispersing with a paint shaker for 70 hours, the dispersion is filtered through a 500-mesh net, and then the solution is stirred in a Nauta mixer and warmed in a 100 ° C water bath to remove alcohol and dry. Then, a silane coupling agent was applied to the surface to obtain a surface-treated conductive tin oxide powder.

Lactone modified acrylic polyol (trade name: Praxel DC2009, Daicel Chemical Industries, Ltd.)
Manufactured by K.K.) 288 parts by mass was dissolved in 972 parts by mass of MIBK (methyl isobutyl ketone) to obtain a solution having a solid content of 16% by mass. 57 parts by mass of the surface-treated conductive tin oxide powder and 0.05 part by mass of silicone oil (trade name: SH-28PA, manufactured by Toray Dow Corning Silicone Co., Ltd.) with respect to 200 parts by mass of this acrylic polyol solution. , 1.0 part by mass of fine particle silica (primary particle diameter 0.015 μm) surface-treated with hexamethylene disilazane, average particle diameter 1
8 μm cross-linked polymethylmethacrylate (trade name: MB
16 parts by mass of X-20, manufactured by Sekisui Plastics Co., Ltd. was added, 200 parts by mass of glass beads having a diameter of 0.8 mm was added to the mixture, and the mixture was placed in a 450 ml mayonnaise bottle and dispersed for 6 hours using a paint shaker. did. A chart of the particle size distribution of the resin fine particles used is shown in FIG.

To 370 parts by mass of this dispersion liquid, 25.6 parts by mass of a block type isocyanurate type trimer of isophorone diisocyanate (trade name: Vestanate B1370, manufactured by Degussa Hüls) and 3 parts of isocyanurate type hexamethylene diisocyanate type. 16.4 parts by mass of a body (trade name: Duranate TPA-B80E, manufactured by Asahi Kasei Corporation) were mixed, stirred for 1 hour with a ball mill, and finally the solution was filtered through a 200-mesh net to obtain a surface layer coating material. The viscosity of the paint was 7.8 mPa · s under the environment of 23 ° C.

The surface layer coating material was applied to the surface of the charging roller having the conductive elastic substrate by the dipping method. After coating at a pulling rate of 400 mm / min and air-drying for 30 minutes, the axial direction at the time of coating of the roller was reversed, coating was performed again at a pulling rate of 400 mm / min, air-drying for another 30 minutes, and then 100 at 160 ° C. Dry for minutes. The film thickness is 25 μm, and the volume resistivity of the surface layer is 1.3 × 1.
It was 0 ¹⁴ Ω · cm. The roller thus completed was used as the charging roller of Example 1.

<Evaluation of Charging Roller> Using the charging roller obtained as described above, evaluation was performed as follows.

The electrophotographic laser printer used in this test is a machine for A4 vertical output, the output speed of the recording medium is two kinds of 100 mm / sec and 30 mm / sec, and the image resolution is 600 dpi.

The photoconductor has a film thickness of 1 in an aluminum cylinder.
It is a reversal development type photosensitive drum coated with a 5 μm OPC layer, and the outermost layer is a charge transport layer using a modified polycarbonate as a binder resin.

The toner has a glass transition temperature of 6 in which a random copolymer of styrene and butyl acrylate containing a charge control agent, a dye, etc., centering on wax, is polymerized, and a polyester thin layer is further polymerized on the surface to externally add silica fine particles and the like.
A polymerized toner having a mass average particle diameter of 6 μm at 3 ° C.

For the primary charging, the charging roller of Example 1 obtained above was used and a DC voltage of -1150 V was applied to the charging roller.

All image evaluations were performed by outputting a halftone image (an image in which a horizontal line having a width of 1 dot and a spacing of 2 dots is drawn in the direction perpendicular to the rotation direction of the photoconductor).

Image Evaluation The electrophotographic laser printer used in this test was an A4 vertical output machine, and the output speed of the recording medium was 10.
There are two types, 0 mm / sec and 30 mm / sec, and the image resolution is 600 dpi.

The photoconductor has a film thickness of 1 in an aluminum cylinder.
It is a reversal development type photosensitive drum coated with a 6 μm OPC layer, and the outermost layer is a charge transport layer using a modified polycarbonate as a binder resin.

The toner has a glass transition temperature of 6 which is obtained by polymerizing a random copolymer of styrene and butyl acrylate containing a charge control agent, a dye and the like centering on a wax, and further polymerizing a thin polyester layer on the surface to which silica fine particles and the like are externally added.
A polymerized toner having a mass average particle diameter of 6 μm at 3 ° C.

For the primary charging, the charging roller of Example 1 obtained above was used and a DC voltage of -1150 V was applied to the charging roller.

All image evaluations were performed by outputting a halftone image (an image in which a horizontal line having a width of 1 dot and an interval of 2 dots is drawn in the direction perpendicular to the rotation direction of the photoconductor) image.

Low temperature and low humidity environment (L / L: 15 ° C / 10% R
H), fine horizontal white streaks are expected as initial image defects due to charging in a high temperature and high humidity environment (H / H: 30 ° C./80% RH), and therefore horizontal streaks did not occur at all. ⊚, only a little generated was ◯, a little generated was Δ, and a large amount was rated x.

Further, in each environment, a print density of 4% (an image in which a horizontal line having a width of 2 dots and an interval of 50 dots is drawn in the direction perpendicular to the rotation direction of the photoconductor) is continuously applied at a process speed of 100 m.
Durability was maintained at 4,000 sheets at m / sec, and halftone images were output in each environment. In this case, it was examined whether or not stains caused by unevenness in the distribution of the surface contact force of the charging roller would cause uneven charging. The case where the charging unevenness did not occur was marked with ⊚, the case where the charging unevenness occurred a little was marked with ◯, the case where the charging was moderate was marked with Δ, and the case where the charging was extremely large was marked with x.

In L / L and H / H, the resistance of the charging roller was measured before image formation. As a method of measuring the resistance, first, as shown in FIG. 7A, the charging roller 36 is charged to the metal cylinder 32 having the same curvature as that of the photosensitive member by the bearings 33a and 33b loaded with the shaft 31 at both ends thereof. 36
Contact them so that they are parallel to each other. Next, as shown in FIG. 7B, a metal cylinder 32 is rotated by a motor (not shown) at the same rotation speed as in the state where the charging roller is used, and the charging roller 36 is rotated.
The resistance of the charging roller 36 was calculated by measuring the current flowing through the charging roller 36 with an ammeter 35 when a DC voltage of −250 V was applied from the stabilizing power supply 34 while being rotated while being kept in contact with the metal cylinder 32. (In the present invention, a force of 5 N is applied to each end of the shaft to bring it into contact with a metal cylinder having a diameter of 30 mm, and the metal cylinder is rotated at a peripheral speed of 45 mm / s).

The charging roller of Example 1 has good surface properties,
Good images were output at two different process speeds in both high-temperature and high-humidity environments and low-temperature and low-humidity environments, and good images were output even after running. The evaluation results are shown in Table 1.

Examples 2 to 5 The amount of resin fine particles added to the surface layer was 8, 1 respectively.
The charging members of Examples 2 to 5 were obtained in the same manner as the charging member of Example 1, except that the charging members were changed to 2, 24, and 32 parts. The charging member thus obtained was evaluated in the same manner as in Example 1.

Examples 6 to 9 The amount of silica added to the surface layer was 0.3, respectively.
The charging members of Examples 6 to 9 were obtained in the same manner as the charging member of Example 1 except that the charging members were changed to 0.6, 2 and 4 parts. The charging member thus obtained was evaluated in the same manner as in Example 1.

Examples 10 and 11 The average particle size of the resin fine particles added to the surface layer was 3 respectively.
The charging members of Examples 10 and 11 were obtained in the same manner as the charging member of Example 1 except that the charging members were changed to μm and 30 μm. The charging member thus obtained was evaluated in the same manner as in Example 1.

Example 12 The resin fine particles added to the surface layer were changed. Acrylic resin lumps were crushed by a grinder, then further crushed at liquid nitrogen temperature, and classified by wind pressure to obtain an average particle diameter of 18 μm.
In addition, resin fine particles having an average circularity of 0.8 μm and a circularity standard deviation of 0.1 were obtained. Other than using the resin particles,
A charging member of Example 12 was obtained in the same manner as the charging member of Example 1. The charging member thus obtained was evaluated in the same manner as in Example 1.

Example 13 The procedure of Example 12 was repeated except that 2% by mass of conductive carbon black (trade name: Ketjen Black EC “made by Lion”) was added to the acrylic resin of Example 12. The charging member of Example 13 was obtained. The charging member thus obtained was evaluated in the same manner as in Example 1.

Example 14 A charging member of Example 14 was obtained in the same manner as in Example 12 except that the acrylic resin of Example 12 was changed to a polyamide resin. The charging member thus obtained was evaluated in the same manner as in Example 1.

Example 15 A charging member of Example 15 was obtained in the same manner as in Example 1 except that the methyl methacrylate of Example 1 was changed to styrene. The charging member thus obtained was evaluated in the same manner as in Example 1.

Example 16 Example 1 was repeated in the same manner as Example 1 except that methyl methacrylate in Example 1 was changed to butyl methacrylate.
A charging member 6 was obtained. The charging member thus obtained was evaluated in the same manner as in Example 1.

Example 17 The resin fine particles added to the surface layer were changed. Equal amounts of resin fine particles having an average particle diameter of 30 μm, which were made in the same manner as the resin fine particles of Example 1, and resin fine particles having an average particle diameter of 10.5 μm, which were also made in the same manner as the resin fine particles of Example 1 were used. The mixture was mixed to obtain resin fine particles of Example 17. Example 1 in FIG.
7 shows a particle size distribution of resin fine particles of No. 7. The average particle diameter of the resin fine particles was 18 μm, but 3.5% or more of resin fine particle components having a particle diameter of 54 μm or more were contained. A charging member of Example 12 was obtained in the same manner as the charging member of Example 1 except that the resin fine particles were used. The charging member thus obtained was evaluated in the same manner as in Example 1.

Examples 18 and 19 Similar to the charging member of Example 1, except that the concentration of the acrylic polyol solution of the surface layer was changed and the thickness of the surface layer was changed to 10 μm and 35 μm. A charging member was obtained. The charging member thus obtained was evaluated in the same manner as in Example 1.

Examples 20 and 21 Example 20 and Example 21 were carried out in the same manner as the charging member of Example 1 except that the compounding amount of the conductive tin oxide as the conductive agent was changed to 50 parts by mass and 65 parts by mass. To obtain a charging member. The charging member thus obtained was evaluated in the same manner as in Example 1.

Comparative Example 1 A charging roller of Comparative Example 1 was obtained in the same manner as the charging roller of Example 1 except that the resin fine particles were not added. The charging member thus obtained was evaluated in the same manner as in Example 1.

Comparative Example 2 A charging roller of Comparative Example 2 was obtained in the same manner as the charging roller of Example 1 except that silica particles were not added. The charging member thus obtained was evaluated in the same manner as in Example 1.

The above examples and comparative examples are summarized in Tables 1 and 2.

[0160]

[Table 1]

[0161]

[Table 2] By including inorganic particles and organic particles in the surface layer, it is stable for a long period of time even when used at different process speeds
The reason why C charging can be performed is considered as follows.

That is, the inorganic fine particles serve as minute discharge points, and have the effect of stabilizing the charging.
There is an action to prevent lateral movement of charges in the surface layer, and the actions of both have a synergistic effect, so that stable DC charging can be performed for a long period of time even when used at different process speeds. It is thought that there is.

[0163]

According to the present invention, even when a high-definition image such as a halftone image of 600 dpi is output by the DC charging method, the good charging characteristics result in long-term stability even when used at different process speeds. It is possible to provide a charging member that can perform such charging.

By using the charging member of the present invention, even when a high-definition image is output by the DC charging method, the image forming apparatus can perform stable charging at different process speeds for a long period of time due to good charging characteristics. A charging method and a process cartridge can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross section of one embodiment of a charging member of the present invention. (A) shows a horizontal cross-sectional view of the charging member, and (b) shows a vertical cross-sectional view.

FIG. 2 is a schematic diagram showing a method for measuring shake of a conductive elastic base layer roller of the present invention.

FIG. 3 is a diagram showing an image forming apparatus using a charging roller 6 which is an embodiment of a charging member of the present invention.

FIG. 4 is a diagram showing a color image forming apparatus according to the present invention.

FIG. 5 is a view showing that the process cartridge of the present invention is configured such that a photosensitive drum, a charging roller, a developing roller, a cleaning blade, and the like are integrally supported, and that the process cartridge is detachable from the main body of the image forming apparatus.

6 is a diagram showing a particle size distribution of resin fine particles of Example 1. FIG.

FIG. 7 is a conceptual diagram for measuring the resistance of the charging roller of the present invention.

8 is a diagram showing a particle size distribution of resin fine particles of Example 17. FIG.

[Explanation of symbols]

1 Conductive support 2 Conductive elastic base layer 3 surface layer 4 developing roller 5 photoconductor drum 6 charging roller 7 print media 8 Transfer roller 9 fixing section 10 cleaning blade 18, 19, 20, 22 Power supply 29 Toner charging roller 31 axis 32 metal cylinder 36 charging roller 34 Stabilized power supply 35 ammeter 5a-5d photoconductor drum 6a to 6d charging roller 11a-11d exposure 29a to 29d toner charging roller 30a-30d Elasticity regulation blade 31a to 31d toner container 33a, 33b bearings

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Nagata             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Hiroshi Inoue             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Noriaki Kuroda             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Satoshi Taniguchi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Toshihiro Otaka             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Atsushi Ikeda             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Shinji Doi             1888-2 Kukizaki, Kukizaki-cho, Inashiki-gun, Ibaraki Prefecture             Within Kasei Co., Ltd. F term (reference) 2H077 AB03 AB13 AD06 AE04 EA14                 2H200 FA02 GA23 GA49 GB50 HA02                       HA28 HB12 HB22 HB43 HB45                       HB46 HB47 HB48 LA38 LC04                       LC08 MA02 MA03 MA11 MA12                       MA13 MA17 MA20 MB01 MB04                       MB06 MC01 MC02 MC15 NA02

Claims (23)

[Claims] 1. A charging member having a conductive elastic base layer and a surface layer on a conductive support, wherein the surface layer contains both inorganic fine particles and organic fine particles. 2. The charging member according to claim 1, wherein the organic fine particles are insulating fine particles. 3. The charging member according to claim 1, wherein the organic fine particles are crosslinked resin fine particles. 4. The average circularity of the organic fine particles is 0.95 or more, and the standard deviation of the circularity is less than 0.040, according to any one of claims 1 to 3. Charging member. 5. The organic fine particles do not include particles having a particle size three times or more the weight average particle size, and the organic fine particles according to any one of claims 1 to 4. Charging member. 6. The charging member according to claim 1, wherein the organic fine particles are composed of a crosslinked vinyl resin. 7. The organic fine particles are composed of a copolymer of ethylene glycol dimethacrylate and methyl methacrylate, and any one of claims 1 to 6 is provided.
The charging member according to the item. 8. The charging member according to claim 1, wherein the inorganic fine particles are insulating fine particles. 9. The charging member according to claim 1, wherein the inorganic fine particles are surface-treated. 10. The charging member according to claim 9, wherein the surface treatment is at least one of a coupling agent treatment and a silicone oil treatment. 11. The charging member according to claim 10, wherein the coupling agent is a silane coupling agent. 12. The charging member according to claim 1, wherein the inorganic fine particles are silica fine particles. 13. The electrically conductive elastic base layer contains epichlorohydrin rubber.
The charging member according to any one of 1. 14. The charging member according to claim 1, wherein the surface layer contains a urethane resin. 15. The charging member according to claim 14, wherein the urethane resin is a copolymer of isophorone diisocyanate, hexamethylene diisocyanate and a lactone-modified acrylic polyol. 16. The charging member according to claim 1, wherein the surface layer contains a conductive agent. 17. The charging member according to claim 16, wherein the conductive agent is conductive tin oxide. 18. The charging member according to claim 17, wherein the conductive tin oxide is surface-treated. 19. The charging member according to claim 18, wherein the surface treatment is a coupling agent treatment. 20. The charging member is brought into contact with a metal cylinder having the same curvature as that of the photoconductor drum under the same stress as in the use condition when used in an image forming apparatus, and the metal is rotated at the same rotation speed as in the use condition. The electric resistance of the charging member when a DC voltage of −250 V was applied while rotating the cylinder was 30 ° C./80% R
In the high temperature and high humidity environment of H, it is 1 × 10 ⁶ Ω or more,
20. It is 1 * 10 < ⁸ > (ohm) or less in low temperature low humidity environment (degreeC / 10% RH), The any one of Claims 1-19 characterized by the above-mentioned.
The charging member according to the item. 21. An image carrier, a charging unit that charges the image carrier to a predetermined potential, an exposing unit that forms an electrostatic latent image on a charged surface of the image carrier, and an exposing unit that is formed on the image carrier. In the image forming apparatus, the image forming apparatus includes a developing unit that transfers toner to the electrostatic latent image to visualize the electrostatic latent image to form a toner image, and a transfer unit that transfers the toner image to a transfer target member. 20 to 20 has a charging member according to any one of
An image forming apparatus characterized in that only a DC voltage is applied to the charging member to charge the image carrier. 22. The developing device is a contact developing device that develops the electrostatic latent image in a state of being in contact with the image carrier through the thin layer of the toner. 21. The image forming apparatus according to item 21. 23. A process cartridge, which integrally supports an image carrier and the charging member according to claim 1 and is detachable from a main body of an image forming apparatus.