JP2011186120A - Organic photoreceptor, image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic photoreceptor which has high durability and provides an electrophotographic image of high quality by improving a wear property of the organic photoreceptor up to the same level as an amorphous silicon photoreceptor and remedying image deletion and image blurring which is liable to be generated at a high temperature and high humidity or the like, and to provide an image forming apparatus using the photoreceptor, and a process cartridge. <P>SOLUTION: In the organic photoreceptor including a photosensitive layer on a conductive support and a protective layer thereon, the protective layer is formed by the reaction and curing of tin oxide particles containing at least 10 to 100 ppm of silicon atoms and subjected to hydrophobic treatment and a curable compound. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic photoreceptor used in an electrophotographic image forming apparatus and the like, an image forming apparatus using the organic photoreceptor, and a process cartridge.

  In recent years, an electrophotographic photosensitive member containing an organic photoconductive material (hereinafter also referred to as an organic photosensitive member or simply a photosensitive member) has been most widely used as the electrophotographic photosensitive member. Organic photoconductors have advantages over other photoconductors, such as easy development of materials suitable for various exposure light sources from visible light to infrared light, the ability to select materials without environmental pollution, and low manufacturing costs. However, there is a problem that the mechanical strength is weak, the surface of the photoreceptor is easily deteriorated or scratched when copying or printing a large number of sheets, and the durability is insufficient.

As a problem for improving the durability of the organic photoreceptor as described above, it has been strongly demanded to suppress wear due to abrasion of a cleaning blade or the like. As an approach for this purpose, a technique for incorporating inorganic fine particles on the surface of the photoreceptor has been studied. As one of them, a technique in which tin oxide doped with tungsten element is included in the surface layer of the photoreceptor has been reported (Patent Document 1). There is a disclosure that the tin oxide doped with the tungsten element further preferably contains 0.01 to 15 mol% (to tin oxide ratio) of niobium or silicon element as the third component, and as a result. The volume specific resistance of tin oxide doped with these elements is preferably 10 ² Ω · cm or less.

  The inventors of the present application have also started studying an organic photoreceptor having a protective layer containing tin oxide as described above, and conductive tin oxide having a small volume specific resistance as described above is used as a protective layer. When it is contained, the electrical resistance of the protective layer tends to decrease, and image blur and image flow are likely to occur.

  Moreover, as a curable resin applied to the protective layer, a protective layer of a curable resin obtained by photopolymerization using a compound having an acryloyl group or the like has been proposed (Patent Document 2). The protective layer also contains a filler such as a metal oxide in the curable resin, but the bond between the filler and the curable resin is weak, the strength as the protective layer is insufficient, and image blurring is also caused. However, it has not been able to solve the problem of image flow.

JP 2007-57992 A JP 2001-125297 A

  An object of the present invention is to solve the above-described problems, and to improve the wear resistance of an organic photoconductor to a level equivalent to that of an amorphous silicon photoconductor, and to easily generate an image stream under high temperature and high humidity. It is to provide an organic photoreceptor capable of improving image blur and improving durability and obtaining a high-quality electrophotographic image, and to provide an image forming apparatus and a process cartridge using the organic photoreceptor. .

  The inventors of the present application have found out the problems of the conventional protective layer for the protective layer applied to the organic photoreceptor, and as a result, the filler is uniformly dispersed in the curable resin in the protective layer, and the curable resin and the filler are It must be stronger and bonded to each other, and the curable resin must be hydrophobic in order to solve image wear, image blur, and poor cleaning at high temperature and high humidity. As a result, the present invention was completed. That is, the present invention is achieved by having the following configuration.

  1. In an organic photoreceptor having a photosensitive layer on a conductive support and a protective layer thereon, the protective layer contains at least 10 to 100 ppm of silicon atoms, and has been subjected to hydrophobic treatment with tin oxide particles and a curable compound. An organic photoreceptor characterized in that is a protective layer formed by reactive curing.

  2. 2. The organophotoreceptor according to 1 above, wherein the hydrophobized tin oxide particles are obtained by surface-treating tin oxide particles with a compound having a reactive functional group.

  3. 3. The organophotoreceptor according to 1 or 2 above, wherein the compound having a reactive functional group is a compound having a carbon-carbon double bond and a silyl group.

  4). 4. The organophotoreceptor according to any one of items 1 to 3, wherein the curable compound is a compound having a carbon-carbon double bond.

  5. 5. The organophotoreceptor according to 4 above, wherein the compound having a carbon-carbon double bond is a compound having an acryloyl group or a methacryloyl group.

  6). 6. The organophotoreceptor according to any one of 1 to 5, wherein a 50% particle size based on the number of the tin oxide particles is 10 to 100 nm.

  7). The organic photoreceptor according to any one of 1 to 6 above, wherein the organic photoreceptor has at least a charging unit, an exposing unit, and a developing unit around the organophotoreceptor and repeatedly forms an image. An image forming apparatus.

  8). The process cartridge used in the image forming apparatus described in item 7 integrally includes at least one of the organic photosensitive member described in any one of items 1 to 6 and a charging unit, an image exposing unit, and a developing unit. And a process cartridge configured to be removable from and into the image forming apparatus.

  By using the organophotoreceptor of the present invention, the strength against abrasion and scratching of the photoreceptor surface is remarkably improved, and electrostatic characteristics such as image blurring in a high temperature and high humidity environment and a rise in residual potential are remarkably improved. Is done.

1 is a schematic view in which functions of an image forming apparatus of the present invention are incorporated. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention. 1 is a cross-sectional view of a color image forming apparatus using an organic photoreceptor of the present invention.

  The organophotoreceptor of the present invention contains tin oxide particles containing at least 10 to 100 ppm of silicon atoms and subjected to a hydrophobic treatment in the protective layer.

  The hydrophobized tin oxide particles can be obtained by subjecting the surface of the tin oxide particles to a hydrophobic treatment on the surface of the tin oxide particles with a silane coupling agent or a titanium coupling agent that is generally well known.

  Among such hydrophobizing treatments, the preferred hydrophobizing treatment of tin oxide particles of the present invention is a surface treatment with a compound having a reactive functional group.

  Below, the tin oxide particle | grains surface-treated with the compound which has a reactive functional group concerning this invention are demonstrated.

  Tin oxide particles surface-treated with the compound having a reactive functional group can be produced as follows.

  That is, the following general formula (1);

(Wherein R ³ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 1 to 10 carbon atoms, R ⁴ is an organic group having a polymerizable double bond, X is a halogen atom, an alkoxy group, an acyloxy group) A group, an aminoxy group, and a phenoxy group, and n is an integer of 1 to 3).

  The silane compound to be reacted with the tin oxide particles is not particularly limited as long as it is a compound having a silyl group, particularly a hydrolyzable silyl group, and capable of radical polymerization thereafter. Examples of the silane compound represented by the general formula (1) and the like will be given below.

_{S-1 CH 2 = CHSi (} CH 3) (OCH 3) 2
_{S-2 CH 2 = CHSi (} OCH 3) 3
S-3 CH ₂ = CHSiCl _{3
S-4 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5 CH 2 = CHCOO (} CH 2) 2 Si (OCH 3) 3
_{S-6 CH 2 = CHCOO (} CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-7 CH 2 = CHCOO (} CH 2) 3 Si (OCH 3) 3
_{S-8 CH 2 = CHCOO (} CH 2) 2 Si (CH 3) Cl 2
_{S-9 CH 2 = CHCOO (} CH 2) 2 SiCl 3
_{S-10 CH 2 = CHCOO (} CH 2) 3 Si (CH 3) Cl 2
S-11 CH ₂ = CHCOO (CH ₂ ) ₃ SiCl _{3
S-12 CH 2 = C (} CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13 CH 2 = C (} CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14 CH 2 = C (} CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15 CH 2 = C (} CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16 CH 2 = C (} CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17 CH 2 = C (} CH 3) COO (CH 2) 2 SiCl 3
_{S-18 CH 2 = C (} CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19 CH 2 = C (} CH 3) COO (CH 2) 3 SiCl 3
_{S-20 CH 2 = CHSi (} C 2 H 5) (OCH 3) 2
S-21 CH ₂ ═C (CH ₃ ) Si (OCH ₃ ) _{3
S-22 CH 2 = C (} CH 3) Si (OC 2 H 5) 3
_{S-23 CH 2 = CHSi (} OCH 3) 3
_{S-24 CH 2 = C (} CH 3) Si (CH 3) (OCH 3) 2
_{S-25 CH 2 = CHSi (} CH 3) Cl 2
_{S-26 CH 2 = CHCOOSi (} OCH 3) 3
_{S-27 CH 2 = CHCOOSi (} OC 2 H 5) 3
_{S-28 CH 2 = C (} CH 3) COOSi (OCH 3) 3
_{S-29 CH 2 = C (} CH 3) COOSi (OC 2 H 5) 3
_{S-30 CH 2 = C (} CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3

Etc. These silane compounds can be used alone or in admixture of two or more.

(Production method of tin oxide particles surface-treated with a compound having a reactive functional group and containing 10 to 100 ppm of silicon atoms)
The tin oxide particles according to the present invention can be obtained by surface-treating tin oxide particles containing 10 to 100 ppm of silicon atoms using the silane compound represented by the above general formula (1). In carrying out the surface coating treatment, 0.1-100 parts by mass of a silane compound as a surface treatment agent and 50-5000 parts by mass of a solvent are used with 100 parts by mass of tin oxide particles, using a wet media dispersion type apparatus. It is preferable to do.

  A surface treatment method for producing uniform and finer tin oxide particles whose surface is coated with a silane compound will be described below.

  By subjecting the slurry (suspension of solid particles) containing tin oxide particles and a surface treatment agent of a silane compound to wet pulverization, the surface treatment of the tin oxide particles proceeds simultaneously with the refinement of the tin oxide particles. Thereafter, the solvent is removed and the mixture is pulverized, so that the tin oxide particles according to the present invention surface-treated with a uniform and finer silane compound can be obtained.

  The wet media dispersion type apparatus, which is a surface treatment apparatus used in the present invention, is a method of aggregating tin oxide by filling beads in a container as a medium and rotating a stirring disk mounted perpendicularly to a rotation axis at high speed. It is an apparatus having a step of crushing and pulverizing / dispersing the particles, and as its configuration, there is no problem as long as the tin oxide particles are sufficiently dispersed and subjected to surface treatment when performing surface treatment on the tin oxide particles, For example, various types such as a vertical type, a horizontal type, a continuous type, and a batch type can be adopted. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersive devices are pulverized and dispersed by impact crushing, friction, cutting, shear stress, etc., using a grinding medium such as balls and beads.

  As the beads used in the sand grinder mill, balls made of glass, alumina, zircon, zirconia, steel, flint stone and the like can be used, but those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 1 to 2 mm are usually used, but in the present invention, those having a diameter of about 0.3 to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, the disk and container inner wall made of ceramic such as zirconia or silicon carbide are particularly used. Is preferred.

  By the wet treatment as described above, the tin oxide particles according to the present invention can be obtained by the surface treatment with the silane compound such as the general formula (1).

  The thus obtained tin oxide particles having a reactive functional group form a protective layer by reaction curing with a curable compound.

  That is, various compounds having a carbon-carbon double bond can be used as the compound that reacts with the reactive functional group of the tin oxide particles according to the present invention (the curable compound according to the present invention).

  The curable compound is preferably a monomer that is polymerized (cured) by irradiation with actinic rays such as ultraviolet rays or electron beams and becomes a resin generally used as a binder resin for a photoreceptor, such as polystyrene and polyacrylate. A monomer based on monomer, an acrylic monomer, a methacrylic monomer, a vinyl toluene monomer, a vinyl acetate monomer, and an N-vinyl pyrrolidone monomer are preferred.

  Among these, a curable compound having an acryloyl group or a methacryloyl group is particularly preferable because it can be cured in a small amount of light or in a short time.

  In the present invention, these curable compounds may be used alone or in combination.

  Examples of curable compounds are shown below.

In the present invention, the acrylic compound is a compound having an acryloyl group (CH ₂ ═CHCO—) or a methacryloyl group (CH ₂ ═CCH ₃ CO—). In addition, the number of Ac groups (the number of acryloyl groups) described below represents the number of acryloyl groups or methacryloyl groups.

  However, in the above, R and R 'are respectively shown below.

  In the present invention, the curable compound preferably has 2 or more functional groups, particularly preferably 4 or more. Further, the equivalent amount of the curable reactive group, that is, “curable compound molecular weight / number of functional groups” is preferably 1000 or less, and particularly preferably 500 or less. As a result, the crosslink density is increased and the wear resistance of the photoreceptor is improved. If the value is larger than this, a problem may occur in the high durability of the photoreceptor.

  In the present invention, two or more kinds of curable compounds having different curable reactive group equivalents may be mixed and used.

(Method for producing tin oxide particles containing 10 to 100 ppm of silicon atoms)
The tin oxide particles according to the present invention contain 10 to 100 ppm of silicon atoms. In addition to silicon atoms, the tin oxide particles contain sodium, potassium atoms, and the like as impurities. The content of these tin oxide particles is preferably controlled to 20 ppm or less. A particularly preferable range of the content of silicon atoms is 10 to 80 ppm. By subjecting such tin oxide particles containing a small amount of silicon atoms to a hydrophobization treatment, the volume specific resistance of tin oxide itself is increased to 10 ⁷ to 10 ¹² Ω · cm, and the protection containing the tin oxide particles is achieved. By using a photoreceptor having a layer, it is possible to stabilize potential characteristics during repeated use and to prevent occurrence of image blur.

  That is, by reducing the content of silicon atoms in the tin oxide particles, and also by hydrophobizing the surface of the tin oxide, the volume specific resistance of the tin oxide is increased, and a protective layer containing the tin oxide particles is provided. It is possible to stabilize the potential characteristics during repeated use of the photoreceptor and to prevent the occurrence of image blur.

  The tin oxide particles can be obtained as follows.

(Method for adjusting the content of silicon atoms)
Tin oxide particles containing a small amount of silicon atoms or the like according to the present invention can be produced by, for example, a thermal plasma method using an arc discharge plasma generator or the like. That is, tin metal purified to a high purity is used as one electrode material, and arc discharge is performed with the counter electrode while orienting an inert gas to the electrode, and tin is converted into a plasma flow vapor. Then, tin oxide containing silicon atoms of the present invention in a trace amount can be obtained by reacting plasma-like tin with an oxygen-containing gas containing silicon atoms in ppm.

  In addition, the tin oxide which adjusted content of a silicon atom can be obtained by requesting the manufacturer which can manufacture these professionally.

  The content of silicon atoms in the tin oxide can be measured by atomic absorption spectrometry.

  The tin oxide particles used in the present invention preferably have a number-based 50% particle size in the range of 10 to 100 nm. If the particle size is smaller than 10 nm, the wear resistance is not sufficient, and if the particle size is large, the writing light may be scattered or the particles may inhibit photocuring and the wear resistance may be insufficient. is there.

  The above-mentioned 50% particle size of the tin oxide particles is a photographic image (aggregated) of 300 tin oxide particles taken at random by a scanner taken with a scanning electron microscope (manufactured by JEOL Ltd.). Automatic image processing analyzer LUZEX AP (Nireco Corp.) software version Ver. The number-based 50% particle size was calculated using 1.32.

  The ratio of the tin oxide particles in the protective layer is 1 to 400 parts by mass, particularly preferably 50 to 250 parts by mass with respect to 100 parts by mass of the curable compound.

  In addition to the curable compound and tin oxide particles, the protective layer can be coated with a coating solution containing a polymerization initiator, filler, lubricant particles, antioxidant, etc., if necessary, and reacted to form a cured film. .

  When the curable compound of the present invention is reacted, a method of reacting by electron beam cleavage, a method of reacting with light and heat by adding a radical polymerization initiator, and the like are used. As the polymerization initiator, either a photopolymerization initiator or a thermal polymerization initiator can be used. Further, both light and heat initiators can be used in combination.

As a polymerization initiator of these photocurable compounds, a photopolymerization initiator is preferable, and among them, an alkylphenone compound or a phosphine oxide compound is preferable. In particular, a compound having an α-hydroxyacetophenone structure or an acylphosphine oxide structure is preferable. The photoinitiator used preferably below is illustrated.
Examples of α-aminoacetophenone series

Examples of α-hydroxyacetophenone compounds

Examples of acylphosphine oxide compounds

Examples of other photoinitiators

  In order to form a protective layer of these photocurable resins, after applying a coating solution (the above composition) for the protective layer on the photosensitive layer, first drying to the extent that the fluidity of the coating film is lost, and then applying ultraviolet rays. A method is preferred in which the protective layer is cured by irradiation, and in order to make the amount of volatile substances in the coating film a specified amount, secondary drying is performed.

  As a device for irradiating ultraviolet rays, a known device used for curing an ultraviolet curable resin can be used.

The amount of ultraviolet rays (mJ / cm ² ) for curing the resin with ultraviolet rays is preferably controlled by the ultraviolet irradiation intensity and irradiation time.

  On the other hand, as the thermal polymerization initiator, ketone peroxide compounds, peroxyketal compounds, hydroperoxide compounds, dialkyl peroxide compounds, diacyl peroxide compounds, peroxydicarbonate compounds, peroxyester compounds Compounds and the like are used, and these thermal polymerization initiators are disclosed in company product catalogs.

  In the present invention, similar to the photopolymerization initiator, these thermal polymerization initiators are mixed with tin oxide particles having a reactive functional group according to the present invention, a curable compound, or the like to apply a protective layer. A coating solution is prepared, and the coating solution is coated on the photosensitive layer and then dried by heating to form the protective layer according to the present invention. In the examples described later, the following thermal polymerization initiator was used as an example of forming a curing protective layer by thermal polymerization.

  Thermal polymerization initiator used in the examples

  Also, as for the coating method of the protective layer, the dip coating in which the entire photoreceptor is immersed in the protective layer coating solution increases the diffusion of the polymerization initiator to the lower layer, so that the photosensitive layer film under the protective layer is not dissolved as much as possible. Therefore, it is preferable to use a coating processing method such as a volume regulation type (a circular slide hopper type is a typical example). The circular amount regulation type coating is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.

  These polymerization initiators may be used alone or in combination of two or more. Content of a polymerization initiator is 0.1-20 mass parts with respect to 100 mass parts of an acryl-type compound, Preferably it is 0.5-10 mass parts.

  The protective layer of the present invention can further contain various charge transport materials.

  Various lubricant particles can be added to the protective layer used in the present invention. For example, fluorine atom-containing resin particles can be added. Fluorine atom-containing resin particles include tetrafluoroethylene resin, trifluoroethylene chloride resin, hexafluorochloroethylene propylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and these One or two or more types are preferably selected from the copolymers, but tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferable. The ratio of the lubricant particles in the protective layer is preferably 5 to 70 parts by mass, more preferably 10 to 60% by mass with respect to 100 parts by mass of the acrylic resin. The average particle size of the lubricant particles is preferably 0.01 μm to 1 μm. Particularly preferably, it is 0.05 μm to 0.5 μm. The molecular weight of the resin can be appropriately selected and is not particularly limited.

  Solvents for forming the protective layer include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol, benzyl alcohol, toluene, xylene, methylene chloride, methyl ethyl ketone, cyclohexane, acetic acid. Examples thereof include, but are not limited to, ethyl, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine and diethylamine.

  The protective layer of the present invention is preferably subjected to reaction by irradiation with actinic radiation after natural drying or heat drying after coating.

  As the coating method, a known method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, and a slide hopper method can be used as in the case of the intermediate layer and the photosensitive layer. .

  The photoreceptor of the present invention is capable of generating a cured resin by irradiating actinic rays on the coating to generate radicals and polymerizing, and curing by forming a cross-linking bond between molecules and within the molecule. preferable. As the active ray, ultraviolet rays and electron beams are particularly preferable.

As the ultraviolet light source, any light source that generates ultraviolet light can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, or the like can be used. Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 5 to 500 mJ / cm ² , preferably 5 to 100 mJ / cm ² . The power of the lamp is preferably 0.1 kW to 5 kW, particularly preferably 0.5 kW to 3 kW.

  As an electron beam source, there is no particular limitation on the electron beam irradiation apparatus, and generally, an electron beam accelerator for electron beam irradiation is a curtain beam type that is relatively inexpensive and can provide a large output. Used. The acceleration voltage during electron beam irradiation is preferably 100 to 300 kV. The absorbed dose is preferably 0.5 to 10 Mrad.

  The irradiation time for obtaining the necessary amount of active ray irradiation is preferably from 0.1 second to 10 minutes, and more preferably from 0.1 second to 5 minutes from the viewpoint of curing efficiency or work efficiency of the acrylic compound.

  As the actinic radiation, ultraviolet rays are easy to use and are particularly preferable.

  The photoreceptor of the present invention can be dried before and after irradiating active rays and during irradiation with active rays, and the timing of drying can be appropriately selected by combining them.

  Drying conditions can be appropriately selected depending on the type of solvent, film thickness, and the like. The drying temperature is preferably room temperature to 180 ° C, particularly preferably 80 ° C to 140 ° C. The drying time is preferably 1 minute to 200 minutes, and particularly preferably 5 minutes to 100 minutes.

  The thickness of the protective layer is preferably 0.2 to 10 μm, more preferably 0.5 to 6 μm.

[Conductive support]
The support used in the present invention may be any one as long as it has conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel formed into a drum or a sheet, aluminum or copper Metal foils such as those laminated on plastic films, aluminum, indium oxide and tin oxide deposited on plastic films, metals with conductive layers applied alone or with a binder resin, plastic films and For example, paper.

[Middle layer]
In the present invention, an intermediate layer having a barrier function and an adhesive function may be provided between the conductive layer and the photosensitive layer.

  The intermediate layer can be formed by dip coating or the like by dissolving a binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane and gelatin in a known solvent. Of these, an alcohol-soluble polyamide resin is preferred.

  Various conductive fine particles and metal oxides can be contained for the purpose of adjusting the resistance of the intermediate layer. For example, various metal oxides such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide. Ultrafine particles such as indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide can be used.

  You may use these metal oxides 1 type or in mixture of 2 or more types. When two or more types are mixed, it may take the form of a solid solution or fusion. The average particle diameter of such a metal oxide is preferably 0.3 μm or less, more preferably 0.1 μm or less.

  As the solvent used for the intermediate layer, a solvent in which inorganic particles are well dispersed and the polyamide resin is dissolved is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are excellent in solubility and coating performance of the polyamide resin. In addition, examples of co-solvents that can be used in combination with the above-described solvent to obtain favorable effects in order to improve storage stability and particle dispersibility include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

  The density | concentration of binder resin is suitably selected according to the film thickness and production rate of an intermediate | middle layer.

  When the inorganic particles are dispersed, the mixing ratio of the inorganic particles to the binder resin at the time is preferably 20 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  As a means for dispersing the inorganic particles, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The method for drying the intermediate layer can be appropriately selected according to the type of solvent and the film thickness, but thermal drying is preferred.

  The thickness of the intermediate layer is preferably from 0.1 to 15 μm, more preferably from 0.3 to 10 μm.

(Charge generation layer)
The charge generation layer used in the present invention preferably contains a charge generation material and a binder resin, and is formed by dispersing and coating the charge generation material in a binder resin solution.

  Examples of the charge generating material include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as bilenquinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and phthalocyanine pigments. It is not something. These charge generating substances can be used alone or in a form dispersed in a known resin.

  As the binder resin of the charge generation layer, a known resin can be used, for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, Polyurethane resins, phenol resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (eg, vinyl chloride-vinyl acetate copolymer resins, chlorides) Vinyl-vinyl acetate-maleic anhydride copolymer resin) and poly-vinylcarbazole resin, but are not limited thereto.

  The charge generation layer is formed by dispersing a charge generation material in a solution in which a binder resin is dissolved in a solvent using a disperser to prepare a coating solution, and applying the coating solution to a certain film thickness using a coating device. It is preferable to prepare the film by drying.

  Solvents for dissolving and coating the binder resin used in the charge generation layer include, for example, toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, Examples include butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine, but are not limited thereto.

  As a means for dispersing the charge generating material, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The mixing ratio of the charge generating material to the binder resin is preferably 1 to 600 parts by weight, more preferably 50 to 500 parts by weight based on 100 parts by weight of the binder resin. The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating. The pigment can also be formed by vacuum deposition.

(Charge transport layer)
The charge transport layer used in the photoreceptor of the present invention contains a charge transport material and a binder resin, and is formed by dissolving and coating the charge transport material in a binder resin solution.

  Examples of charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds Oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1- Two or more kinds of vinylpyrene and poly-9-vinylanthracene may be mixed and used.

  As the basic structure of the charge transport material (CTM), a triphenylamine derivative, a styryl compound, a benzidine compound, a butadiene compound, and the like can be used, and among them, a styryl compound is preferable.

  A known resin can be used as the binder resin for the charge transport layer, and polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylic ester resin, and styrene-methacrylic acid. Examples include ester copolymer resins, and polycarbonate is preferred. Further, BPA, BPZ, dimethyl BPA, BPA-dimethyl BPA copolymer and the like are preferable in terms of crack resistance, wear resistance, and charging characteristics.

  The charge transport layer is preferably formed by dissolving the binder resin and the charge transport material to prepare a coating solution, applying the coating solution to a certain film thickness with a coating machine, and drying the coating film.

  Examples of the solvent for dissolving the binder resin and the charge transport material include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, and tetrahydrofuran. 1,4-dioxane, 1,3-dioxolane, pyridine, diethylamine, and the like, but are not limited thereto.

  The mixing ratio of the charge transport material to the binder resin is preferably 10 to 500 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the binder resin.

  The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  An antioxidant, an electronic conductive agent, a stabilizer and the like may be added to the charge transport layer. For the antioxidant, those described in Japanese Patent Application No. 11-200135 and for the electronic conductive agent are described in Japanese Patent Application Laid-Open Nos. 50-137543 and 58-76483.

  Next, an image forming apparatus using the organic photoreceptor of the present invention will be described.

  An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D as a transfer paper transport unit. Yes.

  An automatic document feeder that automatically conveys the document is provided above the image reading unit A. The document placed on the document table 11 is separated and conveyed by the document conveyance roller 12 to the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including the two mirrors and the third mirror in the same direction at the speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the toner, developing means (developing process) 23, transfer / conveying belt device 45 serving as a transferring means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and light discharging means (light discharging process). PCL (precharge lamps) 27 are arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. As the photosensitive member 21, the organic photosensitive member according to the present invention is used, and the photosensitive member 21 is driven and rotated in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, an image based on an image signal called from the memory of the image processing unit B by an exposure optical system as an image exposure unit (image exposure step) 30 is used. Exposure is performed. The exposure optical system as the image exposure means 30 as the writing means uses a laser diode (not shown) as a light source, and the optical path is bent by the reflection mirror 32 via the rotating polygon mirror 31, the fθ lens 34, and the cylindrical lens 35, and main scanning is performed. Therefore, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In one example of the present embodiment, the character portion is exposed to form an electrostatic latent image.

  In the image forming apparatus of the present invention, it is preferable to use a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 800 nm as an image exposure light source when an electrostatic latent image is formed on a photoreceptor. By using these image exposure light sources, the exposure dot diameter in the writing direction is narrowed down to 10 to 100 μm, and digital exposure is performed on the organic photoreceptor, so that it is 400 dpi (dpi: the number of dots per 2.54 cm) or more. A high-resolution electrophotographic image of 2500 dpi can be obtained.

The exposure dot diameter refers to the length of the exposure beam along the main scanning direction (Ld: measured at the maximum length) in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a solid scanner such as the scanning optical system and LED using a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot diameter according to the present invention is used.

  The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method of the present invention, it is preferable to use a polymerized toner as a developer used in the developing means. By using a polymer toner having a uniform shape and particle size distribution in combination with the organic photoreceptor according to the present invention, an electrophotographic image with better sharpness can be obtained.

  The electrostatic latent image formed on the organic photoreceptor of the present invention is visualized as a toner image by development. The toner used for development may be a pulverized toner or a polymerized toner, but the toner according to the present invention is preferably a polymerized toner that can be prepared by a polymerization method from the viewpoint of obtaining a stable particle size distribution.

  The term “polymerized toner” means a toner in which a toner binder resin is formed and the toner shape is formed by polymerization of a raw material monomer of the binder resin and, if necessary, subsequent chemical treatment. More specifically, it means a toner formed through a polymerization reaction such as suspension polymerization or emulsion polymerization, and if necessary, a step of fusing particles between them.

  The volume average particle diameter of the toner, that is, the 50% volume particle diameter (Dv50) is preferably 2 to 9 μm, more preferably 3 to 7 μm. By setting this range, the resolution can be increased. In addition, by combining with the above range, the amount of toner having a fine particle diameter can be reduced while being a small particle diameter toner, the dot image reproducibility is improved over a long period of time, and the sharpness is excellent. In addition, a stable image can be formed.

  The toner according to the present invention may be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 80 μm.

  The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to.

  In the transfer paper transport section D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer paper storage means for storing transfer paper P of different sizes. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer paper P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer paper P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer paper P to be transferred, and then fed again. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 The toner image on the photosensitive member 21 is transferred to the transfer paper P while being transferred to the transfer conveyance belt 454 of the transfer conveyance belt device 45 by the transfer electrode 24 and the separation electrode 25 at the transfer position Bo. Is, transfer sheet P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.

  The above describes the state in which image formation is performed on one side of the transfer paper. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the transfer paper guide 177 is opened, and the transfer paper P is indicated by a broken arrow. Conveyed in the direction.

  Further, the transfer paper P is transported downward by the transport mechanism 178 and switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P becomes the leading end portion and transported into the duplex copying paper supply unit 130. The

  The transfer paper P is moved in a paper feed direction by a conveyance guide 131 provided in the double-sided copy paper supply unit 130, the transfer paper P is re-fed by the paper supply roller 132, and the transfer paper P is guided to the conveyance path 40. .

  Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer paper P, fixed by the fixing unit 50, and then discharged onto the paper discharge tray 64.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge, and this unit is configured to be detachable from the apparatus main body. Also good. In addition, a process cartridge is formed by integrally supporting at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device together with a photosensitive member, and a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of an apparatus main body.

  FIG. 2 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a feeding unit. It comprises a paper conveying means 21 and a fixing means 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit (charging step) 2Y, an exposure unit (exposure step) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A unit (developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (primary transfer step), and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk include charging means 2Y, 2M, 2C, and 2Bk that rotate around the photosensitive drums 1Y, 1M, 1C, and 1Bk, and image exposure means 3Y, 3M, 3C and 3Bk, rotating developing means 4Y, 4M, 4C and 4Bk, and cleaning means 6Y, 6M, 6C and 6Bk for cleaning the photosensitive drums 1Y, 1M, 1C and 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of toner images formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. explain.

  The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 6Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning unit 6Y or the cleaning blade 6Y) is simply disposed, and a yellow (Y) toner image is formed on the photosensitive drum 1Y. In the present embodiment, in the image forming unit 10Y, at least the photosensitive drum 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 6Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photosensitive drum 1Y. In the present embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The image exposure means 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y, and forms an electrostatic latent image corresponding to the yellow image. As the exposure means 3Y, the exposure means 3Y includes an LED in which light emitting elements are arranged in an array in the axial direction of the photosensitive drum 1Y and an imaging element (for example, Cellhook lens (trademark)). Alternatively, a laser optical system or the like is used.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge (image forming unit), and this image forming unit is connected to the apparatus main body. It may be configured to be detachable. In addition, at least one of a charging device, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge (image forming unit), which is detachable from the apparatus main body. A single image forming unit may be detachable using guide means such as a rail of the apparatus main body. Here, “supported integrally” means that the process cartridge can be attached or detached as one lump in the unit of the process cartridge when the process cartridge is attached or detached.

  The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. The transfer paper P as a transfer material (support for supporting the final fixed image: for example, plain paper, transparent sheet, etc.) housed in the paper feed cassette 20 is fed by the paper feed means 21 and is a plurality of intermediates. After passing through the rollers 22A, 22B, 22C, 22D and the registration roller 23, they are conveyed to the secondary transfer roller 5b as the secondary transfer means, and are secondarily transferred onto the transfer paper P, and the color images are collectively transferred. The transfer paper P onto which the color image has been transferred is fixed by the fixing means 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a transfer support for a toner image formed on a photosensitive member such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

  On the other hand, after the color image is transferred onto the transfer paper P by the secondary transfer roller 5b as the secondary transfer means, the residual toner is removed by the cleaning means 6b from the endless belt-shaped intermediate transfer body 70 from which the transfer paper P is separated by curvature. The

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the transfer paper P passes through the secondary transfer roller 5b.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b. Consists of.

  Next, FIG. 3 shows a color image forming apparatus using the organic photoreceptor of the present invention (a copying machine having at least a charging means, an exposure means, a plurality of developing means, a transfer means, a cleaning means, and an intermediate transfer body around the organic photoreceptor. 1 is a cross-sectional view of a configuration of a laser beam printer). The belt-shaped intermediate transfer body 70 uses an elastic body having a medium resistance.

  Reference numeral 1 denotes a rotary drum type photoconductor that is repeatedly used as an image forming body, and is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed.

  In the rotation process, the photoreceptor 1 is uniformly charged to a predetermined polarity and potential by a charging means (charging process) 2, and then time-series electric digital of image information by an image exposure means (image exposure process) 3 (not shown). An electrostatic latent image corresponding to the yellow (Y) color component image (color information) of the target color image is formed by receiving image exposure by scanning exposure light or the like by a laser beam modulated in accordance with the pixel signal. The

  Then, the electrostatic latent image is developed with yellow toner as the first color by yellow (Y) developing means: developing step (yellow color developing device) 4Y. At this time, the second to fourth developing means (magenta developer, cyan developer, black developer) 4M, 4C, and 4Bk are turned off and do not act on the photosensitive member 1. The first color yellow toner image is not affected by the second to fourth developing units.

  The intermediate transfer member 70 is stretched by rollers 79a, 79b, 79c, 79d, and 79e, and is driven to rotate in the clockwise direction at the same peripheral speed as the photosensitive member 1.

  The yellow toner image of the first color formed and supported on the photosensitive member 1 is applied to the intermediate transfer member 70 from the primary transfer roller 5a in the process of passing through the nip portion between the photosensitive member 1 and the intermediate transfer member 70. The intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 70 by the electric field formed by the primary transfer bias.

  The surface of the photoreceptor 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer body 70 is cleaned by the cleaning device 6a.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black (black) toner image are sequentially superimposed and transferred onto the intermediate transfer body 70 to correspond to the target color image. A superimposed color toner image is formed.

  The secondary transfer roller 5b is supported in parallel with the secondary transfer counter roller 79b so as to be separated from the lower surface portion of the intermediate transfer body 70.

  The primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photosensitive member 1 to the intermediate transfer member 70 has a polarity opposite to that of the toner and is applied from a bias power source. The applied voltage is, for example, in the range of +100 V to +2 kV.

  In the primary transfer process of the first to third color toner images from the photosensitive member 1 to the intermediate transfer member 70, the secondary transfer roller 5b and the intermediate transfer member cleaning means 6b can be separated from the intermediate transfer member 70. .

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred onto the transfer paper P as the second image carrier, the secondary transfer roller 5b is brought into contact with the belt of the intermediate transfer member 70. At the same time, the transfer paper P is fed from the pair of paper feeding registration rollers 23 through the transfer paper guide to the belt of the intermediate transfer body 70 to the contact nip with the secondary transfer roller 5b at a predetermined timing. A secondary transfer bias is applied to the secondary transfer roller 5b from a bias power source. By this secondary transfer bias, the superimposed color toner image is transferred (secondary transfer) from the intermediate transfer body 70 to the transfer sheet P as the second image carrier. The transfer paper P that has received the transfer of the toner image is introduced into the fixing means 24 and fixed by heating.

  The image forming apparatus of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers. The present invention can be widely applied to such devices.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the following text, “part” means “part by mass”.

Production of Photoreceptor 1 Photoreceptor 1 was produced as follows.

  The surface of the cylindrical aluminum support was cut to prepare a conductive support having a surface roughness Rz = 1.5 (μm).

<Intermediate layer>
An intermediate layer coating solution having the following composition was prepared.
Polyamide resin X1010 (manufactured by Daicel Degussa Co., Ltd.) 1 part Titanium oxide SMT500SAS (manufactured by Teika) 1.1 parts ethanol 20 parts Dispersion was carried out for 10 hours in a batch manner using a sand mill as a disperser.

  It apply | coated by the dip coating method so that it might become a film thickness of 2 micrometers after drying for 20 minutes at 110 degreeC on the said support body using the said coating liquid.

<Charge generation layer>
Charge generation material: titanyl phthalocyanine pigment (a titanyl phthalocyanine pigment having a maximum diffraction peak at a position of at least 27.3 ° in Cu-Kα characteristic X-ray diffraction spectrum measurement)
20 parts polyvinyl butyral resin (# 6000-C: manufactured by Denki Kagaku Kogyo) 10 parts t-butyl acetate 700 parts 4-methoxy-4-methyl-2-pentanone 300 parts are mixed and dispersed for 10 hours using a sand mill. A charge generation layer coating solution was prepared. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.

<Charge transport layer>
Charge transport material: CTM (compound A below) 150 parts Binder: Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical) 300 parts Antioxidant (Irganox 1010: manufactured by Ciba Japan) 6 parts Toluene / tetrahydrofuran = 1/9% by volume 2000 Part silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part was mixed and dissolved to prepare a charge transport layer coating solution. The coating liquid was dried on the charge generation layer by dip coating at 110 ° C. for 60 minutes to form a charge transport layer having a thickness of 20 μm.

<Protective layer>
Tin oxide particles surface-treated with a compound having a reactive functional group (the number-based 50% particle size is 20 nm when surface-treated with 30 parts of methacryloxypropyltrimethoxysilane (S-15) per 100 parts of tin oxide particles) Tin oxide particles containing 50 ppm of silicon atoms) 100 parts curable compound (Exemplary Compound No. 42) 100 parts Isopropyl alcohol 500 parts After dispersing the above components for 10 hours using a sand mill,
30 parts of a polymerization initiator 3-2 was added, mixed and stirred under light shielding to dissolve, and a protective layer coating solution was prepared (light-shielding during storage). A protective layer was applied using a circular slide hopper applicator on the photoreceptor on which the coating solution had been prepared up to the charge transport layer. After coating, after drying for 20 minutes at room temperature (solvent drying process), a metal halide lamp (500 W) is used for irradiation for 1 minute while rotating the photoreceptor at a position of 100 mm (ultraviolet curing process), and a protective layer having a thickness of 3 μm. Got.

Production of photoconductors 2 to 12 Photosensitive materials were similarly exposed except that the particle size of tin oxide, silicon atom content, surface treatment agent, curing conditions, etc. used in the protective layer of photoconductor 1 were changed as shown in Table 1. Body 2-12 was produced.
Curing conditions (light): A metal halide lamp (500 W) was irradiated for 1 minute while rotating the photoreceptor at a position of 100 mm to obtain a protective layer having a thickness of 3 μm.
Curing conditions (heat): Heated at 140 ° C. for 30 minutes to obtain a protective layer having a thickness of 3 μm.

Photoconductor 13
Photoconductor 13 was prepared in the same manner except that the surface treatment agent for the tin oxide particles of the protective layer was replaced with isobutyltrimethoxysilane (surface treatment agent having no reactive functional group) in the production of photoconductor 1.

Photoconductor 14
Photoconductor 14 was prepared in the same manner as in preparation of photoconductor 1, except that it contained 8 ppm of silicon atoms in the tin oxide particles of the protective layer.

Photoconductor 15
Photoconductor 15 was prepared in the same manner as in preparation of photoconductor 1, except that it contained 110 ppm of silicon atoms in the tin oxide particles of the protective layer.

Photoconductor 16
Photosensitive member 16 was prepared in the same manner as in preparation of photosensitive member 1, except that the tin oxide particles in the protective layer were removed.

Photoconductor 17
In the production of the photoreceptor 1, the surface treatment agent for the tin oxide particles of the protective layer is replaced with isobutyltrimethoxysilane (surface treatment agent having no reactive functional group), and the protective layer is formed by using polyarylate as the binder of the protective layer. A photoconductor 17 was produced in the same manner except that it was produced.

  The tin oxide used in the protective layers of the photoreceptors 1 to 17 changes the content of silicon atoms, but the content of other impurity metal atoms is adjusted to 10 ppm or less.

  The volume specific resistance (Ω · cm) of the hydrophobized tin oxide particles in Table 1 was measured as follows.

Measurement Method of Volume Specific Resistance (Ω · cm) As a measurement sample, a tin oxide fine particle powder was pressed to prepare a pellet having a diameter of 11 mm and a thickness of 2 mm. Using a TR8611A DIGITAL HIGH MEGOHM METER manufactured by Advantest, under the environment of 20 ° C. and 50% RH, a voltage of 100 V was applied and held for 30 seconds, and the value after 30 seconds was used as the resistance value. Measured.

[Evaluation of photoconductor]
(Repetitive potential characteristics)
Next, the initial dark part potential (Vd) and the initial bright part potential (Vl) are set around −700 V and −100 V, respectively, and charging and exposure are repeated 100000 times using monochromatic light of 780 nm, and the fluctuation amount of Vd and Vl ( ΔVd, ΔVl) were measured.

  Each variation amount ΔVd, ΔVl is practical if the change after the repetition (deviation from the initial value) is less than 150V.

A: Change in residual potential after actual shooting is less than 50 V (good)
○: Change in residual potential after actual shooting is less than 50 to 100 V (no problem in practical use)
Δ: Change in residual potential after actual shooting is less than 100 to 150 V (can be put to practical use)
X: The change in the residual potential after actual shooting is 150 V or more. (There are practical problems)
The results are shown in Table 1.

  The plus sign represents an increase in potential.

(Surface damage)
Each photoconductor produced was evaluated as follows.

  The photoconductor was modified to be able to evaluate bizhub PRO C6500 (laser exposure / reverse development / intermediate transfer tandem color composite machine with wavelength of 780 nm) manufactured by Konica Minolta Business Technologies, and mounted on an evaluation machine with optimized exposure. Then, the surface state of the photoreceptor was observed before and after printing 1 million sheets of A4 images with a YMCBk color printing rate of 2.5% at 20 ° C. and 50% RH on neutral paper, and the state of scratches was evaluated. The evaluation photoconductor is installed in the cyan position.

A: No surface damage after printing 1 million sheets (good)
○: 1 to 10 surface scratches after printing 1 million sheets (no problem in practical use)
X: 11 or more surface scratches occurred after printing 1 million sheets (practical problem)
(Amount of photoconductor wear)
One million images were obtained by the above evaluation, and the initial film thickness and the film thickness after 1 million sheets were evaluated. The thickness of the photosensitive layer is measured at 10 random locations where the thickness of the photosensitive layer is uniform (excluding the 3 cm at both ends because the film thickness tends to be non-uniform at both ends of the photoconductor), and the average value is the film thickness of the photosensitive layer. Thickness. The film thickness measuring device is an eddy current film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO).

A: The amount of wear is 1 μm or less (good)
○: Amount of wear is 1 μm to 3 μm (no problem in practical use)
X: The amount of wear is larger than 3 μm (there is a practical problem)
(Image blur)
Except for changing the environmental conditions to 30 ° C and 80% RH, 25,000 sheets of A4 images were printed on neutral paper under the evaluation conditions for surface scratches, and the main power of the actual machine was stopped 60 seconds after printing was completed. did. A halftone image (relative reflection density of 0.4 with a Macbeth densitometer) and a 6-dot lattice image of the entire A3 surface were printed on the entire surface of the A3 neutral paper immediately after the power was turned on 12 hours after the stop. The state of the printed image was observed and the following evaluation was performed.

◎: No blurring in halftone and grid images (good)
○: A thin strip-like density decrease in the longitudinal direction of the photoreceptor is observed only in the halftone image (no problem in practical use)
×: Lattice image loss or line width narrowing due to image blurring (practical problem)
The evaluation results are summarized in Table 2 below.

  As is clear from Table 2, the photoreceptors 1 to 13 in the invention of the present application have obtained results that are more than practical for each evaluation item, but any of the photoreceptors 14 to 17 of the comparative examples is evaluated. In the items, there is a problem in practicality.

10Y, 10M, 10C, 10Bk Image forming unit 1Y, 1M, 1C, 1Bk Photoconductor 2Y, 2M, 2C, 2Bk Charging unit 3Y, 3M, 3C, 3Bk Exposure unit 4Y, 4M, 4C, 4Bk Developing unit

Claims (8)

  In an organic photoreceptor having a photosensitive layer on a conductive support and a protective layer thereon, the protective layer contains at least 10 to 100 ppm of silicon atoms, and has been subjected to hydrophobic treatment with tin oxide particles and a curable compound. An organic photoreceptor characterized in that is a protective layer formed by reactive curing.   2. The organophotoreceptor according to claim 1, wherein the hydrophobized tin oxide particles are obtained by surface-treating tin oxide particles with a compound having a reactive functional group.   3. The organophotoreceptor according to claim 1, wherein the compound having a reactive functional group is a compound having a carbon-carbon double bond and a silyl group.   The organic photoconductor according to claim 1, wherein the curable compound is a compound having a carbon-carbon double bond.   5. The organophotoreceptor according to claim 4, wherein the compound having a carbon-carbon double bond is a compound having an acryloyl group or a methacryloyl group.   The organophotoreceptor according to claim 1, wherein a 50% particle size based on the number of the tin oxide particles is 10 to 100 nm.   The organic photoconductor according to any one of claims 1 to 6, wherein the organic photoconductor has at least a charging unit, an exposure unit, and a developing unit around the organic photoconductor to repeatedly form an image. An image forming apparatus characterized by being a body.   A process cartridge for use in the image forming apparatus according to claim 7 comprises at least one of the organic photosensitive member according to any one of claims 1 to 6 and at least one of a charging unit, an image exposing unit, and a developing unit. And a process cartridge configured to be removable from and into the image forming apparatus.

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