JP5464025B2 - Organic photoreceptor and image forming apparatus - Google Patents

Description

  The present invention relates to an organic photoreceptor used for electrophotographic image formation and an image forming apparatus using the organic photoreceptor.

  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, techniques such as installing a high-strength protective layer on the surface of the photoreceptor have been studied. For example, it has been reported that a colloidal silica-containing curable siloxane resin is used as a protective layer of a photoreceptor (Patent Document 1). The colloidal silica-containing curable siloxane resin includes both a siloxane bond (Si—O—Si bond) curable resin and colloidal silica, which are highly hygroscopic, and the electric resistance of the protective layer is likely to decrease, resulting in image blur and image flow. Likely to happen.

  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, and the strength as the protective layer is insufficient. Even image blur and image flow that are likely to occur due to the installation of a protective layer cannot be sufficiently solved.

  In addition, as a filler to be contained in the protective layer, trigonal alumina particles are effective for improving image blurring (Patent Document 3). However, the protective layer also has a weak bond between the alumina particles and the binder resin in the protective layer, the uniform dispersion of the alumina particles in the protective layer is insufficient, the strength as the protective layer is weak, and the image blur is also sufficient. It has not been solved.

  In addition, when commercially available alumina particles are used as the alumina particles, there is a phenomenon that potential characteristic deterioration (particularly, increase in residual potential) is likely to occur along with the occurrence of image blur when the photoreceptor is used repeatedly, protecting the alumina particles. It is an obstacle to using as a filler in the layer.

Japanese Patent Laid-Open No. 6-118681 JP 2001-125297 A JP 2003-98712 A

  The inventors of the present invention have an object of the present invention as described above to solve the above-mentioned problems, and the deterioration of potential characteristics (especially the increase in residual potential) during repeated use in a protective layer containing alumina particles. ), An organic photoconductor having improved image blur and wear resistance, and an image forming apparatus using the organic photoconductor.

  As a result of identifying the problems of the conventional protective layer for the protective layer using alumina particles, the inventors of the present application have deteriorated the potential characteristics during repeated use in the protective layer containing alumina particles (particularly the residual potential). Rise), image blurring, and wear resistance characteristics, together with alumina particles in the protective layer, a metal oxide having a volume resistivity lower than that of the alumina particles is used together, and the curable resin in the protective layer is alumina. The present invention was completed by finding that it is important that the particles and metal oxide particles having a low volume resistivity are uniformly dispersed, and that the curable resin and the filler are more strongly bonded to each other.

  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 has alumina particles having a polymerizable unsaturated group, and has a volume resistivity of 1 × 10 ³ to 1 × 10 ¹⁰ Ω · An organic photoreceptor comprising a composition obtained by reacting metal oxide particles having a polymerizable unsaturated group of cm and a compound having a polymerizable reactive group.

  2. 2. The organophotoreceptor according to 1 above, wherein the metal oxide particles having a polymerizable unsaturated group are tin oxide having a polymerizable unsaturated group.

  3. The mass ratio in the protective layer of the alumina particles having a polymerizable unsaturated group and the metal oxide particles having a polymerizable unsaturated group is 1: 0.05 to 0.05: 1 The organic photoreceptor according to 1 or 2.

  4). Any one of the above 1-3, wherein the polymerizable unsaturated group of the alumina particle having a polymerizable unsaturated group and the metal oxide particle having a polymerizable unsaturated group is an acryloyl group or a methacryloyl group. The organic photoreceptor described in 1.

  5. 5. The organophotoreceptor according to any one of 1 to 4, wherein the compound having a polymerizable reactive group is a compound having a carbon-carbon double bond.

  6). In an image forming apparatus that has at least a charging unit, an exposure unit, and a developing unit around an organic photoreceptor, and repeatedly forms an image, the charging unit is a charging unit of a proximity discharge method using a charging roller, Is an organic photoreceptor according to any one of 1 to 5 above.

  By using the organic photoreceptor of the present invention, the strength against abrasion and scratching of the surface of the photoreceptor is remarkably improved, the surface scratch resistance and the amount of wear of the photoreceptor surface are improved, and a proximity discharge type charging roller is used. The residual potential rise in the image forming apparatus is also remarkably improved, and an electrophotographic image with high sensitivity and high image quality can be obtained.

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. FIG. 3 is a cross-sectional view illustrating a configuration example of a charging roller. It is the figure which showed the measuring method of volume resistance.

The organophotoreceptor of the present invention has a photosensitive layer on a conductive support and a protective layer thereon, the protective layer comprising at least alumina particles having a polymerizable unsaturated group, and a volume resistivity of 1. It contains a composition obtained by reacting a metal oxide particle having a polymerizable unsaturated group of × 10 ³ to 1 × 10 ¹⁰ Ω · cm and a compound having a polymerizable reactive group.

  The alumina particles and metal oxide particles having a polymerizable unsaturated group used in the present invention will be described.

  The alumina particles and metal oxide particles having a polymerizable unsaturated group used in the present invention 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 silane compound represented by a group, an aminoxy group and a phenoxy group, and n is an integer of 1 to 3), and alumina particles and metal oxide particles having a hydroxyl group on the surface (generally, alumina not subjected to surface treatment) The particles and the metal oxide particles can be produced by reacting with each other).

  The silane compound to be reacted with the alumina particles and the metal oxide particles is not particularly limited as long as it is a compound having a silyl group, particularly a hydrolyzable silyl group, and a polymerizable unsaturated group. Examples of the compound represented by the general formula (1) 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
In addition to the compound of the general formula (1), the following silane compound having a polymerizable unsaturated group capable of radical polymerization may be used.

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

  Hereinafter, a method for producing alumina particles having a polymerizable unsaturated group and metal oxide particles will be described using alumina particles as an example.

Method for Producing Alumina Particles Having Polymerizable Unsaturation Group Alumina particles having a polymerizable unsaturated group according to the present invention are obtained by subjecting the alumina particles to a surface treatment using the silane compound represented by the general formula (1). , You can get. In carrying out the surface coating treatment, 100 parts by mass of alumina particles are treated using a wet media dispersion type apparatus using 0.1 to 100 parts by mass of a silane compound as a surface treating agent and 50 to 5000 parts by mass of a solvent. It is preferable.

  A surface treatment method for producing uniform and finer alumina particles surface-coated with a silane compound will be described below.

  That is, by subjecting a slurry (a suspension of solid particles) containing alumina particles and a surface treatment agent of a silane compound to wet pulverization, the alumina particles are refined and the surface treatment of the alumina particles proceeds at the same time. Thereafter, the solvent is removed and the mixture is pulverized, so that alumina particles 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 metal oxide particle 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 a device having a step of crushing and pulverizing and dispersing the aggregated particles of the metal oxide, and the constitution thereof should be a type in which the metal oxide particles are sufficiently dispersed and surface-treated when the surface treatment is performed on the metal 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, alumina particles and metal oxide particles having a polymerizable unsaturated group can be obtained by surface treatment with a silane compound such as the general formula (1).

  The alumina particles and metal oxide particles having polymerizable unsaturated groups thus obtained are protected by the mutual reaction between the alumina particles and metal oxide particles and by reacting with compounds having polymerizable reactive groups. Layers can be formed.

(Metal oxide particles)
Examples of the metal oxide particles used in the present invention and having a polymerizable unsaturated group include metal oxide particles such as zinc oxide, tin oxide, and titanium oxide. Most preferred are particles of tin oxide or the like.

The volume resistivity of the metal oxide used in the present invention is in the range of 1 × 10 ³ to 1 × 10 ¹⁰ , and more preferably in the range of 1 × 10 ⁴ to 1 × 10 ⁹ . When the deposition resistivity particle size is large, the residual potential is not sufficiently suppressed, and when the volume resistivity is small, fogging due to a decrease in the photoreceptor surface potential may occur.

  The volume resistivity of the metal oxide fine particles is obtained as follows.

  An electrical resistance is generally used as a measure of the conductivity of a substance. A value indicating this resistance per unit volume (1 cm × 1 cm × 1 cm) is a volume resistivity (unit Ω · cm). This value is an absolute value specific to the substance.

FIG. 5 is a diagram showing a method for measuring volume resistance.
As shown in [Definition of volume resistivity (Ω · cm)], a constant current I (A) is passed through a cross-sectional area W × t, and the potential difference V (V) between electrodes separated by a distance L is measured. .

Definition of volume resistivity (Ω · cm) Cross-sectional area = W x t
Resistance R = V / I
Volume resistivity (Ω · cm) = V / I × W / L × t
The volume resistivity of the metal oxide fine particles described in the present invention is such that the metal oxide fine particles are filled in a container having electrodes arranged in parallel at intervals of 2 mm, and the direct current resistance at a potential difference of 500 V between both electrodes is represented by Yokogawa Hewlett-Packard Co. Measured with a 4329A High Resistance Meter manufactured by company.

The total mass ratio of the alumina particles in the protective layer and the metal oxide particles having a volume resistance of 1 × 10 ³ to 1 × 10 ¹⁰ is 1: 0.05 to 0.05: 1, more preferably 1 : 0.20 to 0.20-1.

  As described above, by containing alumina particles and metal oxide particles having a volume resistivity smaller than that of alumina in the protective layer, the protective layer is depleted when only high-resistance alumina is used, and charge transport is performed. Repeated increase in potential due to decrease in performance is prevented.

  Next, the compound having a polymerizable reactive group according to the present invention will be described.

The compound having a polymerizable reactive group according to the present invention has the above-described alumina particles having a polymerizable unsaturated group and a polymerizable unsaturated group having a volume resistivity of 1 × 10 ³ to 1 × 10 ¹⁰ Ω · cm. A composition for forming a protective layer is prepared by reaction curing with metal oxide particles.

  As the compound having a polymerizable reactive group according to the present invention, various compounds having a carbon-carbon double bond, epoxy compounds having a cyclic ether structure, and oxetane compounds can be used. In particular, various compounds having a carbon = carbon double bond are preferred.

  The compound having a polymerizable reactive group 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. In particular, styrene monomers, acrylic monomers, methacrylic monomers, vinyl toluene monomers, vinyl acetate monomers, and N-vinyl pyrrolidone monomers are preferable.

Among them, a curable compound having an acryloyl group (CH ₂ ═CHCO—) or a methacryloyl group (CH ₂ ═CCH ₃ CO—) is particularly preferable because it can be cured with a small amount of light or in a short time.

  Moreover, as a compound which has a polymerizable reactive group, an epoxy compound, a vinyl ether compound, an oxetane compound etc. are mentioned especially in a cation polymerizable monomer.

  In the present invention, these compounds having a polymerizable reactive group may be used alone or in combination.

  Examples of compounds having a polymerizable reactive group are shown below.

  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.

  Moreover, although the specific example of a preferable oxetane compound is shown below, this invention is not limited to these.

  Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  In the present invention, the compound having a polymerizable reactive group preferably has 2 or more functional groups, particularly preferably 4 or more. In the acrylic compound, the ratio of the molecular weight M of the compound having an acryloyl group or methacryloyl group to the number Ac of the acryloyl group or methacryloyl group; Ac / M is preferably in the following relationship. By using this ratio: Ac / M, the crosslink density is increased and the abrasion resistance of the photoreceptor is improved.

0.005 <Ac / M <0.012
In the present invention, the compound having a polymerizable reactive group may be used as a mixture of compounds having two or more kinds of polymerizable reactive groups having different reactive group equivalents.

  When reacting metal oxide particles having a polymerizable unsaturated group and a curable compound according to the present invention, a method of reacting by electron beam cleavage, a radical polymerization initiator or a cationic polymerization initiator is added, and light is added. A method of reacting with heat is 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 radical 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 compound that initiates cationic polymerization, e.g., diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds such as phosphonium ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 - , CF ₃ SO ₃ ^- ionic polymerization initiator or sulfonic acid sulfonated materials that generate a such as salts, halides or generates hydrogen halide, can be mentioned nonionic polymerization initiator such as iron arene complex. In particular, a sulfonate that generates a sulfonic acid that is a nonionic polymerization initiator and a halide that generates a hydrogen halide are 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 radical polymerization initiators

Nonionic polymerization initiator

Ionic polymerization initiator

  In order to form a protective layer of a photocurable resin, a protective layer coating solution (the above composition) is applied on the photosensitive layer, followed by primary drying until the fluidity of the coating film is lost, and then irradiation with ultraviolet rays. Then, the protective layer is cured, and a method of carrying out secondary drying to make the amount of volatile substances in the coating film a specified amount is preferable.

  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, in the same manner as the photopolymerization initiator, these thermal polymerization initiators are mixed with alumina particles having a polymerizable unsaturated group or a curable compound to prepare a coating solution for the protective layer. The coating solution is applied onto the photosensitive layer and then dried by heating to form the protective layer according to the present invention. As the thermal polymerization initiator, the above-mentioned other radical polymerization initiators can be used.

  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, and various lubricant particles, antioxidants, and the like can be added. 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 irradiation amount of active rays is preferably 0.1 second to 10 minutes, and more preferably 0.1 second to 5 minutes from the viewpoint of work efficiency.

  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.

  Below, the structure of organic photoreceptors other than the said protective layer is described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic photoconductors such as a photoconductor composed of an organic charge generating material or an organic charge transport material, a photoconductor composed of a polymer complex with a charge generating function and a charge transport function are contained.

  The organophotoreceptor of the present invention is one in which at least a photosensitive layer and a protective layer as described above are sequentially laminated on a conductive support. Specifically, the layer configuration as shown below may be exemplified. it can.

1) Layer structure in which a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated as an intermediate layer and a photosensitive layer on a conductive support.
2) A layer structure in which an intermediate layer, a single layer containing a charge transport material and a charge generation material as a photosensitive layer, and a protective layer are sequentially laminated on a conductive support.

  The layer structure of the organic photoreceptor of the present invention will be described focusing on the above 1).

[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, alumina, 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 with respect to the binder resin 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 generation 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 (CTM) 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, poly-9-vinylanthracene, triphenylamine derivatives and the like may be mixed and used.

  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 according to the present invention, the charging unit uses a proximity discharge type charging unit using a charging roller.

  Here, the proximity discharge method is a region where the charging roller and the photosensitive member are closest (contact or non-contacting proximity region), and a charging potential is applied to the surface of the photosensitive member due to discharge between the charging roller and the photosensitive member. Means granted.

  As the charging roller used in the proximity discharge method of the present invention, the following charging roller is used.

FIG. 4 is a cross-sectional view illustrating a configuration example of the charging roller. As shown in FIG. 4, the charging roller 22 includes a cored bar 22a, a rubber layer such as chloroprene rubber, urethane rubber, and silicone rubber, or a sponge layer 22b, outermost layer, which is a conductive elastic member provided on the outer periphery thereof. And a protective layer 22c having a surface resistance of 10 ⁴ to 10 ⁷ Ω / □ is provided.

  The charging roller is preferably brought into contact with the photoreceptor 10 with a pressure contact force of 10 to 100 g / cm. The rotation of the charging roller is preferably 1 to 8 times the peripheral speed of the photosensitive drum 10.

  In the present invention, a charging bias voltage in which direct current and alternating current are superimposed is applied to the contact charging member such as the charging roller. By applying the DC and AC voltages, a uniform charging voltage can be applied to the organic photoreceptor according to the present invention, and the adhesion of dirt on the surface of the photoreceptor can be improved.

The contact charging member such as the charging roller has a DC voltage (DC) of 500 V to 1000 V, an AC voltage (AC) of a frequency in the range of an AC frequency of 0.5 to 3.0 kHz, and a center voltage of −0.1 to −. A range of 0.8 kV and V _p-p (voltage between peaks) of 1.2 to 2.0 kV is preferable.

  In the image forming apparatus of the present invention, a semiconductor laser or a light emitting diode having an oscillation wavelength of 350 to 800 nm is used as an image exposure light source when forming an electrostatic latent image 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.

<toner>
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.

<Developer>
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 onto the transfer paper P by the transfer pole 24, the separation pole 25, the nail separation means 250, and the like at the transfer position Bo. Separated from the body, After the transfer sheet P is placed conveyed to the transfer conveying belt 454 of the transfer conveyor belt device 45, 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 (trade name; Selfoc lens), or 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.

  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. A transfer material P as a transfer material (a support for carrying a fixed final image: for example, plain paper, a transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and a plurality of intermediates. After passing through rollers 22A, 22B, 22C, 22D and registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto a transfer material P to transfer a color image all at once. The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing unit 24, is sandwiched between 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 to the transfer material 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 in which the transfer material 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 material 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 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 first color yellow toner image 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 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. is there.

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred to the transfer material P, which is 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 material P is fed from the pair of paper 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 material P as the second image carrier. The transfer material P that has received the transfer of the toner image is introduced into the fixing means 24 and heated and fixed.

  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 alumina 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 5 at least 27.3 ° by 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>
Alumina particles having a polymerizable unsaturated group (alumina having a number average primary particle size of 20 nm surface-treated with the same mass of exemplified compound S-15 (surface treatment agent) (volume resistivity: 1.1 × 10 ¹¹ Ω · cm) 100 parts (number average primary particle diameter 20 nm of tin oxide A surface-treated with Exemplified Compound S-15 (surface treatment agent) of the same mass (volume resistivity: 1.1 × 10 ⁶ Ω · cm) Compound having 100 parts of polymerizable reactive group (Exemplary Compound No. 31) 100 parts isopropyl alcohol 500 parts After dispersing the above components using a sand mill for 10 hours,
Polymerization initiator 1-6 30 parts were 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 14 Photoconductors 2 to 14 were produced in the same manner except that the materials used for the protective layer of photoconductor 1 and the curing conditions were changed as shown in the list of Tables 1 and 2.
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.

Photoreceptor 15 (without alumina particles having a polymerizable unsaturated group in the protective layer)
Photoreceptor 15 was produced in the same manner as Photoreceptor 1 except that in the production of Photoreceptor 1, alumina particles having polymerizable unsaturated groups in the protective layer of the protective layer were removed.

Photoconductor 16 (without tin oxide particles having a polymerizable unsaturated group in the protective layer)
Photoreceptor 16 was produced in the same manner as Photoreceptor 1, except that in the production of Photoreceptor 1, tin oxide particles having a polymerizable unsaturated group in the protective layer of the protective layer were removed.

In Table 1,
Tin oxide A, tin oxide B, and tin oxide C are different types of tin oxide due to differences in sintering temperature during the production of tin oxide.

Zinc oxide (passet AK) and zinc oxide (23-K) are zinc oxides manufactured by Hakusui Tech Co., Ltd.
[Evaluation of photoconductor]
Each photoconductor produced was evaluated as follows.

  The photoconductor was modified so that the bizhub PRO C6500 (780 nm laser exposure / reverse development / intermediate transfer tandem color multi-function machine) manufactured by Konica Minolta Business Technologies, Inc. can be evaluated (the charging means is changed to the charging roller shown in FIG. 4). Change), mounted on an evaluation machine with optimized exposure amount, and evaluated A4 images with Y, M, C, and Bk color printing rates of 2.5% on neutral paper for evaluation.

(Measurement of exposure part potential (VL))
In an environment of 30 ° C. and 85% RH, 100,000 A4 size prints were output continuously. The exposed portion potential VL (VL of the Bk photoconductor) before and after the continuous printing was measured. In addition, the exposure part electric potential was made into the electric potential of the exposed part which maximized the laser light quantity with the said evaluation machine.

(Surface damage)
Under the environment of 20 ° C. and 50% RH, the surface state of the photoconductor was observed before and after outputting 1 million sheets of images to evaluate the state of scratches. 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 (practically problematic).

(Amount of photoconductor wear)
One million images were printed in an environment of 20 ° C. and 50% RH, 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), and the difference in the photosensitive layer thickness before and after the actual shooting test is defined as the film thickness depletion amount.

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 problem in practical use).

(Image cover)
The environmental conditions were changed to 10 ° C. and 20% RH, and a character chart image was printed on A3 coated paper. The state of the white background of the printed image was observed and the following evaluation was performed.

A: No fogging on the white background (good)
○: Slight fogging is observed on the white background (no problem in practical use)
×: Severe fogging is observed on the white background (practical problem)
The evaluation results are summarized in Table 3 below.

  As is apparent from Table 3, the photoreceptors 1 to 13 in the invention of the present application have obtained practical results or more in each evaluation item. In the photoreceptor 14 of the comparative example, the oxidation in the protective layer is achieved. In the photoreceptor 14 having a low zinc volume resistance, image fogging is large, and even in the photoreceptor 15 not containing alumina in the protective layer, image fogging occurs, and the photoreceptor in which the particles in the protective layer are only alumina. In No. 16, the VL (exposure part potential) after printing 1 million sheets greatly increases, resulting in 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 (6)

In an organic photoreceptor having a photosensitive layer on a conductive support and a protective layer thereon, the protective layer has alumina particles having a polymerizable unsaturated group, and has a volume resistivity of 1 × 10 ³ to 1 × 10 ¹⁰ Ω · An organic photoreceptor comprising a composition obtained by reacting metal oxide particles having a polymerizable unsaturated group of cm and a compound having a polymerizable reactive group.   2. The organophotoreceptor according to claim 1, wherein the metal oxide particles having a polymerizable unsaturated group are tin oxide having a polymerizable unsaturated group.   The mass ratio in the protective layer of the alumina particles having a polymerizable unsaturated group and the metal oxide particles having a polymerizable unsaturated group is 1: 0.05 to 0.05: 1. Item 3. The organic photoreceptor according to item 1 or 2.   The polymerizable unsaturated group of the alumina particle having a polymerizable unsaturated group and the metal oxide particle having a polymerizable unsaturated group is an acryloyl group or a methacryloyl group. The organic photoreceptor described in the item.   The organophotoreceptor according to any one of claims 1 to 4, wherein the compound having a polymerizable reactive group is a compound having a carbon-carbon double bond.   In an image forming apparatus that has at least a charging unit, an exposure unit, and a developing unit around an organic photoreceptor, and repeatedly forms an image, the charging unit is a charging unit of a proximity discharge method using a charging roller, and the organic photoreceptor An image forming apparatus comprising the organic photoreceptor according to claim 1.

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