JP5492446B2 - Image forming apparatus and image forming method using the same - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member having an intermediate layer formed using a specific resin, an image forming apparatus including a contact charging type charging unit, and an image forming method using the same.

An electrophotographic photosensitive member (hereinafter also referred to as a “photosensitive member”) used in an electrophotographic image forming apparatus (also referred to as an “electrophotographic device”) that is frequently used in digital multi-function peripherals, printers, and the like is mounted on a conductive support. A photosensitive layer containing a photoconductive material is laminated on the surface, and an inorganic photoconductive material such as selenium has been conventionally used as the photoconductive material.
On the other hand, the organic photoconductive material is slightly inferior in terms of sensitivity, durability and stability to the environment as compared with the inorganic photoconductive material, but from the viewpoint of toxicity, manufacturing cost, freedom of material design, etc. In recent years, it has been widely used.

In addition, the structure of the photoreceptor has changed from a single layer type in which a charge generation material and a charge transport material are dispersed in a binder resin to a functional separation type in which the charge generation layer and the charge transport layer are separated, and the performance is also improved. It is improving.
At present, the mainstream is a configuration in which an intermediate layer, a stacked type (functional separation type) photosensitive layer in which a charge generation layer and a charge transport layer are stacked in this order are stacked in this order on a conductive support. It has become.
The intermediate layer can improve the adhesion of the photosensitive layer by coating defects on the conductive support, improve the film formability (coatability), prevent unnecessary charge injection from the conductive support, and improve the chargeability associated therewith. It has the function of.

An intermediate | middle layer is divided roughly into what consists of resin independent, and what consists of resin containing the pigment.
Examples of the resin used for the intermediate layer include water-soluble resins such as polyvinyl alcohol and casein, alcohol-soluble resins such as copolymer nylon resins, polyurethane, melamine resins, phenol resins, alkyd resins, epoxy resins, and siloxane resins. Examples thereof include a thermosetting resin that forms a network structure.

However, since water-soluble resins and alcohol-soluble resins are rich in moisture adsorption and affinity, there is a problem that physical properties are extremely dependent on the environment, and the characteristics of the photoreceptor are changed by humidity. In particular, since the intermediate layer absorbs a large amount of moisture at high humidity, repeated use of the photoreceptor at high temperature and high humidity or low temperature and low humidity greatly changes its characteristics and causes abnormal images such as black spots and density reduction.
Therefore, a thermosetting resin that forms a three-dimensional network structure excellent in solvent resistance and environmental stability was adopted.

  However, for example, melamine resins disclosed in Japanese Patent No. 3657138 (Patent Document 1), for example, resins such as phenol resin and methoxymethylated nylon disclosed in Japanese Patent No. 2707341 (Patent Document 2) Formaldehyde, which is said to be one of the causative substances of sick house syndrome at the time of resin production and is currently listed as a target substance in the Air Pollution Control Law, is used in large quantities. Therefore, there is a problem that unreacted substances during production are occluded in the resin, and formaldehyde is generated in the process of thermal crosslinking after the formation of the intermediate layer of the photoreceptor. In order to prevent the release of the generated formaldehyde into the atmosphere, a recovery facility is necessary, and it is obviously expensive to introduce the facility.

In addition, for example, in the urethane resin disclosed in Japanese Patent No. 2790380 (Patent Document 3), an active hydrogen-containing group such as a polyol compound and an isocyanate group of an isocyanate compound that is a curing agent have a three-dimensional network cross-linking reaction. No formaldehyde is generated since a cured film is formed. However, since the reactivity of the isocyanate group is very high, there is a problem that the pot life of the coating liquid using these is very short.
Therefore, a method using a blocked isocyanate compound in which an isocyanate group is protected with a blocking agent such as oxime has been reported, and the pot life of a coating liquid using an organic solvent has been considerably improved (for example, JP-A-2005-115351). Publication (refer patent document 4).

On the other hand, an image forming apparatus that forms an image by electrophotography forms an image through the following electrophotographic process.
First, a predetermined charging potential is supplied from the charging unit to the surface of the photoconductor to charge the surface of the photoconductor to a predetermined potential, and an image exposure unit (also referred to as an “exposure unit”) applies the photoconductor to the photoconductor according to image information. Image exposure is performed by irradiating light to form an electrostatic latent image. Next, a developer containing toner or the like is supplied to the electrostatic latent image formed from the developing unit to visualize the toner image (also referred to as “toner image”). Next, the toner image formed by the transfer unit is transferred from the surface of the photoreceptor to a recording medium such as paper, and is fixed by the fixing unit to form an image.

As the charging means, a corona charging method is generally used in which a charging potential is supplied from the wire electrode to the surface of the photoreceptor by corona discharge. In the charging method using corona discharge, a wire is stretched so as to face the surface of the photoconductor, and a high voltage is applied to the wire to generate a corona discharge between the photoconductor and the wire. Of charge. For example, in order to charge the surface of the photoreceptor to −700 V, a voltage of about −5 kV to −6 kV must be applied to the wire electrode.
Although this type of charger has excellent charging uniformity, it generates a large amount of discharge products such as ozone and NOx that adversely affect the human body and the environment. There is a problem that it is necessary to increase the size and cost of the apparatus. Another problem is that due to the generation of a large amount of ozone due to corona discharge, the material constituting the photoconductor is altered and the image is liable to deteriorate.

  Therefore, in recent years, instead of the corona discharge method, a charging device of a contact charging method has been developed in which a charging member is brought into contact with the photosensitive member for charging. For example, a charging device using a charging member in which a composite material in which conductive materials such as conductive fine particles are dispersed in an insulating elastic material is attached to the surface of a metal core formed in a roller shape is proposed (See, for example, JP-A-64-73365 (Patent Document 5) and JP-A-1-172857 (Patent Document 6)).

The composite material is formed so as to have a volume resistance of about 10 ⁶ to 10 ⁷ Ωcm. By applying a voltage to the metal core in a state in which the portion is in contact with the surface of the photoconductor, the conductive particles are formed. It is designed such that a potential is supplied to the surface of the photoreceptor through the via.
As the insulating elastic material, for example, polymer materials such as silicone rubber, polyurethane rubber, ethylene-propylene-diene copolymer rubber and nitrile rubber are used. As the conductive particles, for example, carbon powder, carbon fiber, metal Powder, graphite, etc. are used.

  In the contact charging device, a charging member on a semiconductive roller is disposed so as to contact the surface of the photosensitive member, and a voltage is applied to the charging member to generate a discharge in a gap on the image carrier at the contact site. As a result, a charge is imparted to the photoreceptor. In such an apparatus, the amount of ozone generated is extremely small, and the charging member is in contact with the photosensitive member. Therefore, the apparatus is suitable for reducing the size and weight of the apparatus.

However, in the contact charging device, it is important to use a photoconductor having a more uniform charging property than the photoconductor used in the non-contact charging device in order to apply the voltage by directly contacting the charging member with the photoconductor. This is one of the necessary conditions.
In addition, direct application of a high voltage by contact charging causes current to concentrate on the particles of the conductive material or semiconductive material in the photosensitive layer of the photoconductor, causing the photoconductor to be charged unevenly, resulting in discharge breakdown. May happen. When a discharge breakdown occurs in the photoconductor, the charging member becomes a ground potential, and the entire surface portion of the photoconductor that is in contact with the charging member becomes an uncharged portion. This uncharged portion becomes a black spot in reversal development, and as a result, a black streak image defect, a white spot in regular development, and a white streak image defect. In addition, the charging member and the high voltage application power source may be damaged.
As a means for solving the problems associated with such discharge breakdown, for example, in Japanese Patent No. 2614282 (Patent Document 7), the maximum particle size of particles contained in the photosensitive member is set to 1 μm or less, and the discharge breakdown is performed. A method for preventing (leak) has been proposed, but the image characteristics are still not sufficient.

Japanese Patent No. 3657138 Japanese Patent No. 2707341 Japanese Patent No. 2790380 JP 2005-115351 A JP-A-64-73365 Japanese Patent Laid-Open No. 1-172857 Japanese Patent No. 2614282

  In the present invention, when charging is performed by bringing a charging member into contact with the photoreceptor, the photosensitive layer does not cause dielectric breakdown due to leakage, and a high-quality image free from image defects due to leakage is obtained over a long period of time. It is an object of the present invention to provide an image forming apparatus that can be stably supplied and an image forming method using the same.

  The present inventors have found that the above problems can be solved by a photoconductor having an intermediate layer formed using a specific resin and an image forming apparatus having a contact charging type charging means, and complete the present invention. I reached.

Thus, according to the present invention, a photosensitive member, a charging unit that charges the photosensitive member, an exposure unit that exposes the charged photosensitive member to form an electrostatic latent image, and the static formed by exposure. Developing means for developing an electrostatic latent image to form a toner image, transfer means for transferring the toner image formed by development onto a recording material, and fixing the transferred toner image on the recording material A fixing unit that forms an image; a cleaning unit that removes and collects toner remaining on the photoconductor; and a static elimination unit that neutralizes surface charge remaining on the photoconductor.
The photoreceptor is a block isocyanate compound, a resin having an active hydrogen-containing group capable of reacting with an isocyanate group in the block isocyanate compound, an inorganic oxide fine particle, and an aqueous solution between a conductive support and a photosensitive layer. And the isocyanate group is formed by thermal curing from the intermediate layer coating liquid present in the blocked isocyanate compound at a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group. An intermediate layer,
An image forming apparatus is provided in which the charging unit is a contact charging method in which charging is performed by bringing a charging member into contact with the photosensitive member.

According to the present invention, the image forming apparatus is used to charge the photoconductor, to expose the charged photoconductor to form an electrostatic latent image, and to form the electrostatic latent image formed by the exposure. A latent image is developed to form a toner image, the toner image formed by development is transferred onto a recording material , and the transferred toner image is fixed onto the recording material to form an image. An image forming method is provided.

  According to the present invention, when charging is performed by bringing a charging member into contact with the photosensitive member, a high-quality image free from image defects due to leakage is generated for a long time without causing dielectric breakdown of the photosensitive layer due to leakage. And an image forming method using the same.

The intermediate layer of the photoconductor of the present invention uses water having the smallest environmental load as a solvent, and also uses an intermediate layer coating solution that is excellent in liquid physical properties over time in production. The production system not only eliminates the problem of pollution, but also contributes to the prevention of global warming and has no danger of fire because there is no problem of CO ₂ emissions like the conventional petroleum solvents. Can be simplified, and the manufacturing cost can be reduced.

  When an aqueous medium is used as the solvent for the intermediate layer coating solution, a resin having a high affinity for water must be used, and it has an intermediate layer formed using such an intermediate layer coating solution. The photoreceptor is inferior in moisture resistance. However, in the present invention, the resin is thermally cured with an isocyanate compound, the hydrophilic functional groups in the resin are reduced, and the coating film is densified as a cured film, so that the moisture resistance of the photoreceptor is improved and excellent. Environmental stability can be obtained.

The isocyanate group of the isocyanate compound reacts easily with water. However, in the present invention, since a blocked isocyanate compound in which an isocyanate group is protected with a stable protective group in water is used, a pot life equivalent to or higher than that of a conventional organic solvent-based coating liquid can be realized.
Further, by using a resin having an active hydrogen-containing group capable of reacting with an isocyanate group such as a hydroxyl group or an amide group, the resin can be easily thermoset with an isocyanate compound.
Furthermore, in the present invention, a dense cured film is formed by the presence of the isocyanate group in the blocked isocyanate compound at a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group in the resin. And excellent environmental characteristics as a photoreceptor.

  In addition, the intermediate layer coating liquid of the present invention has very good dispersibility of the inorganic oxide fine particles, does not produce local aggregates, and is less likely to leak even if contact charging is performed. Therefore, it is possible to stably provide a high-quality image free from image defects due to leakage over a long period of time without causing dielectric breakdown.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the photoreceptor of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the photoreceptor of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the photoreceptor of the present invention. 1 is a schematic side view illustrating a configuration of an image forming apparatus of the present invention. It is a figure which shows the X-ray-diffraction spectrum of the oxo titanyl phthalocyanine crystal | crystallization of the charge generation material used in the Example.

The image forming apparatus of the present invention includes a photoreceptor, a charging unit that charges the photoreceptor, an exposure unit that exposes the charged photoreceptor to form an electrostatic latent image, and the static formed by exposure. Developing means for developing an electrostatic latent image to form a toner image, transfer means for transferring the toner image formed by development onto a recording material, and fixing the transferred toner image on the recording material A fixing unit that forms an image; a cleaning unit that removes and collects toner remaining on the photoconductor; and a static elimination unit that neutralizes surface charge remaining on the photoconductor.
The photoreceptor is a block isocyanate compound, a resin having an active hydrogen-containing group capable of reacting with an isocyanate group in the block isocyanate compound, an inorganic oxide fine particle, and an aqueous solution between a conductive support and a photosensitive layer. And the isocyanate group is formed by thermal curing from the intermediate layer coating liquid present in the blocked isocyanate compound at a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group. An intermediate layer,
The charging unit is a contact charging method in which charging is performed by bringing a charging member into contact with the photosensitive member.
That is, the image forming apparatus of the present invention includes a photoconductor having an intermediate layer formed using a specific resin, and a contact charging type charging unit.

First, an intermediate layer formed using a specific resin in the photoreceptor will be described.
The intermediate layer includes a blocked isocyanate compound, a resin having an active hydrogen-containing group capable of reacting with an isocyanate group in the blocked isocyanate compound, inorganic oxide fine particles, and an aqueous medium between the conductive support and the photosensitive layer. And the isocyanate group is formed through thermal curing from the intermediate layer coating solution present in the blocked isocyanate compound at a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group. The

  A blocked isocyanate compound is a compound in which an isocyanate group of an aqueous isocyanate compound that can be dissolved or dispersed in water is protected with a blocking agent such as oxime, and contains active hydrogen that can react with an isocyanate group such as a hydroxyl group or an amide group by heating. Addition reaction with a resin having a group starts, the blocking agent is removed, and the crosslinking reaction proceeds. That is, the blocked isocyanate compound becomes a resin crosslinking agent.

  The aqueous isocyanate compound is a form in which an organic polyisocyanate having a plurality of isocyanate groups in one molecule is modified with various hydrophilic groups such as polyethylene oxide, a carboxyl group or a sulfonic acid group, or dissolved or made into a self-emulsifying type, or It is a compound in a form that is forcibly emulsified with a surfactant or the like so as to be dispersible in water.

Examples of the organic polyisocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hydrogenated toluene diisocyanate. Tetramethylene xylylene diisocyanate; and biuret, uretdione, carbodiimide, isocyanurate, and uretonimine modifications of the isocyanate. These organic polyisocyanates can be used alone or in combination of two or more.
Among these organic polyisocyanates, aliphatic diisocyanate-based organic polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate tend to have an affinity for water, so that they can be easily dissolved and dispersed in water and have a crosslinking density. It is particularly preferable because it is easy to increase the value.

In addition, various prepolymers derived from organic polyisocyanates, and further as blocking agents for blocking isocyanate groups in these organic polyisocyanates include active methylene compounds such as ethyl acetate and acetylacetone; butyl mercaptan , Mercaptan compounds such as dodecyl mercaptan, acid amide compounds such as acetanilide and acetic acid amide; lactam compounds such as ε-caprolactam, δ-valerolactam and γ-butyrolactam; acid imides such as succinimide and maleic acid imide Compounds: Imidazole compounds such as imidazole and 2-methylimidazole; Urea compounds such as urea, thiourea and ethyleneurea; Formamide oxime, acetoaldoxime, acetone oxime, methyl ethyl keto Oxime compounds such as shim, methyl isobutyl ketoxime, cyclohexanone oxime; amine compounds such as diphenylaniline, aniline, carbazole, ethyleneimine, polyethyleneimine, etc. These blocking agents may be used alone or in combination of two or more. Can be used in combination.
Among these blocking agents, oxime compounds such as methyl ethyl ketoxime and lactam compounds such as ε-caprolactam are particularly preferable from the viewpoint of versatility, ease of production, and workability.

Further, since the isocyanate group easily reacts with water, it is preferable to use a blocking agent having a dissociation temperature of 110 ° C. or higher so that the blocking agent dissociates after the water in the coating film volatilizes.
Therefore, the block isocyanate compound preferably has a structure in which hexamethylene diisocyanate or isophorone diisocyanate is blocked with an oxime or lactam blocking agent.

As the blocked isocyanate compound, for example,
Manufactured by Sumika Bayer Urethane Co., Ltd., product names: Bihijoule BL5140, BL5235 and VPLS2310;
Product name: Takenate WB-700WB-820 and WB-920, manufactured by Mitsui Chemicals Polyurethane Co., Ltd .;
Nippon Polyurethane Industry Co., Ltd., developed product name: BWD-102
Asahi Kasei Chemicals Corporation, developed product name: X1238, X1248 and X1258
Etc.

The active hydrogen-containing group in the resin having an active hydrogen-containing group that can react with the isocyanate group in the blocked isocyanate compound is preferably a hydroxyl group or an amide group that can react with the isocyanate group in a high yield.
That is, in order to form a crosslinked structure with the blocked isocyanate which is a curing agent, it has at least two equivalents of at least two isocyanate groups in the blocked isocyanate compound, that is, has at least two hydroxyl groups or amide groups (has only one functional group). If not, a polyol resin or a polyamide resin is preferable because it does not have a crosslinked structure but has a high molecular weight. Also, by controlling the structure of these polyol resins and polyamide resins, they can be dispersed and dissolved in water satisfactorily. Furthermore, these resins have high adhesion and are due to poor contact with the substrate when used as a photoreceptor. Image defects can also be effectively prevented.

As these polyol resin and polyamide resin, for example,
Product name: AQD-457 and AQD-473, Asahi Glass Co., Ltd., product name: Exenol 420 and 720, Sanyo Chemical Industries, Ltd., product name: Sannix GP-400, GP-700 And polyether polyol resins such as SP-750;
Hitachi Chemical Co., Ltd., product name: Phthalkid W2343, DIC Corporation, product name: Watersol S-118, CD-520 and BCD-3040, Harima Kasei Co., Ltd., product name: Hallidip WH-1188, etc. Polyester polyol resins of
DIC Corporation product name: Burnock WE-300, WE-304 and WE-306, Asia Industry Co., Ltd., product name: WAP-473-FD and WAP-548, Nuplex Industries Ltd. product name: SETAQUA6514 Such as polyacryl polyol resin;

Manufactured by Kuraray Co., Ltd., product name: polyvinyl alcohol resins such as modified polyvinyl alcohols such as Kuraray Poval PVA-203 and PVA-205;
Manufactured by Sekisui Chemical Co., Ltd., product name: polyvinyl acetal resins such as ESREC K KW-1 and KW-3;
Manufactured by Shin-Etsu Chemical Co., Ltd., product name: cellulose such as water-soluble cellulose ethers such as Metroles 65SH-50 and 65SH-400;
Made by Nagase ChemteX Corporation, product name: Water-soluble nylon (polyamide compound resin) such as Toresin FS-350 and FS-500
Etc.
Among these, a polyvinyl acetal resin is particularly preferable in terms of dispersibility of the intermediate layer coating solution.

The isocyanate group (H) of the blocked isocyanate compound is preferably present in the blocked isocyanate compound in a molar ratio of 0.5 or more and 1.5 or less with respect to the active hydrogen-containing group (B) of the resin. 1.2 or less is more preferable, and 0.6 or more and 1.1 or less is more preferable.
When the molar ratio (H / B) is less than 0.5 or exceeds 1.5, a large number of unreacted functional groups remain, the crosslinking density is lowered, and the photosensitive layer having the formed intermediate layer is formed. The environmental stability of the body may be reduced.

  The intermediate layer coating solution of the present invention contains fine particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum oxide, silicon oxide, and zirconium oxide. Among these metal oxide fine particles, fine particles of titanium oxide, zinc oxide and aluminum oxide are preferable from the viewpoint of conductivity and dispersibility, and fine particles of titanium oxide are particularly preferable.

The shape of the inorganic oxide fine particles may be any of dendritic, acicular and granular.
The average primary particle size of the inorganic oxide fine particles is preferably about 20 to 500 nm.

As inorganic oxide fine particles, for example,
Ishihara Sangyo Co., Ltd., product name: TTO-55D (shape: granular, average primary particle size: 30-50 nm), TTO-D-1 (shape: dendritic, average primary particle size: minor axis 40-70 nm, long Axis 200-300 nm), TTO-55A (shape: granular, average primary particle size 30-50 nm, alumina surface treatment), ST 21 (shape: granular, average primary particle size (measured by X-ray): 70 nm), PT 401M (Shape: granular, average primary particle size: 70 nm), CR-EL (shape: granular, average primary particle size: 250 nm) and STR-60A (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect Ratio 5, alumina, silica surface treatment),
Product name: GTR100 (shape: granular, average primary particle size: 260 nm), manufactured by Sakai Chemical Industry Co., Ltd.
Product name: MT-500SAS (shape: granular, average primary particle size: 35 nm) and JR 603 (shape: granular, average primary particle size: 280 nm)
Fine particles of titanium oxide such as

Ishihara Sangyo Co., Ltd., product name: FZO 50 (shape: granular, average primary particle size: 21 nm),
Product name: FINEX30 (shape: granular, average primary particle size: 35 nm), manufactured by Sakai Chemical Industry Co., Ltd.
Product name: MZ 300 (shape: granular, average primary particle size: 30-40 nm)
Product name: F 2 (shape: rod, average primary particle size: 65 nm), manufactured by Hakusui Tech Co., Ltd.
Zinc oxide fine particles such as;
Barium sulfate fine particles such as product name: Pastoran PC1 (shape: granular, tin oxide coating) manufactured by Mitsui Mining & Smelting Co., Ltd. may be mentioned.

The inorganic oxide fine particles are contained in a proportion of 30 to 90% by weight, preferably 50 to 90% by weight, based on the total amount of the blocked isocyanate compound, the resin and the inorganic oxide fine particles.
When this ratio is less than 30% by weight, the characteristics of the intermediate layer depend on the characteristics of the crosslinked resin, and there is a possibility that the characteristics of the photosensitive member may be greatly changed, particularly when the temperature and humidity are changed and repeated. In addition, when this ratio exceeds 90% by weight, the dispersibility of the inorganic oxide fine particles is reduced and the possibility of forming an aggregate is increased, and the adhesiveness with the conductive support is reduced, so that Image defects may occur.

The intermediate layer coating solution of the present invention may further contain an antifoaming agent.
The antifoaming agent is intended to suppress foam by adding a very small amount to the intermediate layer coating solution.
When water is used as a solvent as in the intermediate layer coating solution of the present invention, and particularly when a water-soluble resin is added, it is foamed by dispersion or stirring during preparation, and only the dispersion and stirring efficiency is lowered. Instead, it may foam during application and cause coating film defects. Antifoaming agents suppress these problems.

Examples of the antifoaming agent include a silicone system, a surfactant system, a polyether system, a higher alcohol system, an emulsion system, and an oil compound system. Among these, an oil compound system containing silica powder having a strong foam breaking property is particularly preferable.
Examples of antifoaming agents are San Nopco Corporation, product names: SN deformers 444, 470, 485, PC (polyether type), SN deformers 1311, 1316 (silicone type), SN deformers 777, 328, 480, H. -2 (oil compound system), manufactured by Nissho Sangyo Co., Ltd., product name: TSA750 (oil compound system), TSA770 (emulsion system), manufactured by Toray Dow Corning Co., Ltd .: product name: silicone such as DK Q1-1247 -Emulsions are listed.

The defoaming agent is preferably 0.0005 to 0.05 parts by weight with respect to 1 part by weight of the cross-linked resin (total of blocked isocyanate compound and resin: R).
If the defoamer is less than 0.0005 part by weight, an effective foam breaking effect may not be obtained, and if it exceeds 0.05 part by weight, the electrical characteristics of the photoreceptor may be deteriorated.

The intermediate layer coating solution of the present invention may contain additives such as a viscoelasticity adjusting agent, preservative, and curing catalyst as long as the effects of the present invention are not impaired.
As the viscoelasticity modifier, for example, manufactured by San Nopco Corporation, product names: SN thickener 601, A816 (polyether type), SN thickener 607 (urethane modified polyether type), SN thickener 617 (modified polyacrylic acid type), A product name: Water-soluble cellulose ether such as Metroze 65SH-4000 manufactured by Shin-Etsu Chemical Co., Ltd. can be mentioned.

As an antiseptic | preservative, the organic nitrogen sulfur type compound like the product made from San Nopco Co., Ltd. product name: Nopcoside SN-135W etc. are mentioned, for example.
Examples of the curing catalyst include amine compounds such as triethylamine, diethylethanolamine, and hexamethylenediamine; and organotin compounds such as dibutyltin dilaurate and dioctyltin dilaurate.

In addition, the intermediate layer coating solution of the present invention may contain an electron transporting material in order to adjust conductivity.
Examples of the electron transport material include perylene dyes, quinones such as diphenoquinone and naphthoquinone derivatives, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, aldehydes such as 4-nitrobenzaldehyde, anthraquinone and alizarin. Anthraquinones are mentioned.

The intermediate layer coating solution of the present invention is prepared by dissolving or dispersing a blocked isocyanate compound, a resin having an active hydrogen-containing group capable of reacting with an isocyanate group, inorganic oxide fine particles, and optional additives in an aqueous medium. be able to.
The aqueous medium means water or a mixed medium of water and a hydrophilic organic solvent such as a lower alcohol. In the present invention, only water is preferable. Water is more polar than organic solvents such as alcohol, so when dispersing fine particles (filler) such as titanium oxide, an intermediate layer coating solution with good dispersibility is prepared without aggregation of titanium oxides. It is considered possible.

  In order to disperse the components of the intermediate layer coating liquid, especially inorganic oxide fine particles, in water, common dispersers such as paint shakers, ball mills, sand mills, ball mills, sand mills, attritors, vibration mills, ultrasonic dispersers A general grinder such as may be used.

In order to stabilize this dispersion, a dispersion stabilizer may be added to the intermediate layer coating solution.
Examples of the dispersion stabilizer include Sanyo Kasei Co., Ltd., product names: Caribon L-400, Elestat AP-130, Sunspear PS-8, PDN-173, Ionette S-85, New Pole PE-61, and San Nopco shares. Product name: Roma PWA-40, Nobco Santo RFA, SN Dispersant 2060, 5020, 5029, 5468, 7347C and SN Wet P, manufactured by Nissin Chemical Industry Co., Ltd., product names: Surfinol 104E and Olphin PD-003 Product name: Poise 520, 530, Homogenol L 100, Daiichi Kogyo Seiyaku Co., Ltd., Charoru AN-103P, AH-144P, Discoat N-14, Toho Chemical Industries Co., Ltd., product name : Dibrozine A-100, Neoscope 30 And so on.

The intermediate layer is formed between the conductive support and the photosensitive layer through thermosetting from the above-described intermediate layer coating solution. The formation method will be specifically described together with the structure of the photosensitive member. .
1 to 3 are schematic cross-sectional views showing the structure of the main part of the photoreceptor of the present invention.
FIG. 1 shows the structure of the main part of a laminated photoreceptor in which the photosensitive layer is a laminated photosensitive layer in which a charge generation layer and a charge transport layer are laminated in this order (also referred to as “function-separated photosensitive layer”). It is a schematic cross section.
FIG. 2 is a schematic cross-sectional view showing the configuration of the main part of a laminated photoreceptor, which is an inverted two-layer laminated photosensitive layer in which a charge transport layer and a charge generation layer are laminated in this order.
FIG. 3 is a schematic cross-sectional view showing the configuration of the main part of a single-layer type photoreceptor that is a single-layer type photosensitive layer having a single photosensitive layer.
1 and 2 may be any, but the multilayer photosensitive layer of FIG. 1 is preferred.

In the photoreceptor of FIG. 1, an intermediate layer 2, a charge generation layer 3 containing a charge generation material, and a charge transport layer 4 containing a charge transport material are laminated in this order on the surface of a conductive support 1. The laminated photosensitive layer 5 is formed in this order.
In the photoreceptor of FIG. 2, an intermediate layer 2, a charge transport layer 4 containing a charge transport material, and a charge generation layer 3 containing a charge generation material are laminated in this order on the surface of the conductive support 1. The reverse two-layer type laminated photosensitive layer 5 is formed in this order.
In the photoreceptor of FIG. 3, an intermediate layer 2, a single-layer type photosensitive layer 5 ′ containing a charge generation material and a charge transport material are formed in this order on the surface of the conductive support 1.
Each configuration will be described sequentially.

[Conductive support 1]
The conductive support serves as an electrode for the photoreceptor and also functions as a support member for other layers.
The constituent material of the conductive support is not particularly limited as long as it is a material used in this field.
Specifically, metals and alloy materials such as aluminum, aluminum alloy, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum: polyethylene terephthalate, polyamide, polyester, polyoxy Polymer material such as methylene, polystyrene, cellulose, polylactic acid, hard paper, glass substrate laminated with metal foil, metal material or alloy material deposited, conductive polymer, tin oxide, oxidation Examples thereof include those obtained by depositing or applying a layer of a conductive compound such as indium or carbon black.

Examples of the shape of the conductive support include a sheet shape, a cylindrical shape, a columnar shape, and an endless belt (seamless belt) shape.
If necessary, the surface of the conductive support is subjected to irregular reflection treatment such as anodizing film treatment, surface treatment with chemicals, hot water, coloring treatment, and surface roughening within a range that does not affect the image quality. May be given.
The irregular reflection treatment is particularly effective when the photoreceptor according to the present invention is used in an electrophotographic process using a laser as an exposure light source. That is, in the electrophotographic process using a laser as an exposure light source, the wavelength of the laser beam is uniform, so the laser beam reflected on the surface of the photoconductor and the laser beam reflected inside the photoconductor cause interference, Interference fringes due to this interference may appear in the image and cause image defects. Therefore, by performing irregular reflection processing on the surface of the conductive support, it is possible to prevent image defects due to interference of laser light having a uniform wavelength.

[Intermediate layer (also called “undercoat layer”) 2]
The intermediate layer has a function of preventing charge injection from the conductive support to the single-layer type photosensitive layer or the laminated type photosensitive layer. That is, the decrease in chargeability of the single-layer type photosensitive layer or the multilayer type photosensitive layer is suppressed, the decrease in surface charge other than the portion to be erased by exposure is suppressed, and the occurrence of image defects such as fog is prevented. In particular, during image formation by the reversal development process, it is possible to prevent the occurrence of image fogging called black spots in which minute black dots made of toner are formed on a white background portion.

In addition, the intermediate layer covering the surface of the conductive support reduces the degree of unevenness, which is a defect on the surface of the conductive support, makes the surface uniform, and forms a single layer type photosensitive layer or a multilayer type photosensitive layer. And the adhesion (adhesiveness) between the conductive support and the single-layer type photosensitive layer or the multilayer type photosensitive layer can be improved.
An intermediate | middle layer is obtained by apply | coating the above-mentioned intermediate | middle layer coating liquid to the intermediate | middle layer surface formed on the electroconductive support body, and hardening the obtained coating film, for example.

In the case of a sheet, the application method of the intermediate layer coating solution is the Baker applicator method, the bar coater method (for example, the wire bar coater method), the casting method, the spin coating method, the roll method, the blade method, the bead method, and the curtain method. In the case of a drum, a spray method, a vertical ring method, a dip coating method, etc. are mentioned.
As an application method, an optimum method may be selected in consideration of physical properties and productivity of the coating liquid, and an immersion method, a blade coater method, and a spray method are particularly preferable.

  The dip coating method is a method of forming a layer on the conductive support 1 by immersing the conductive support 1 in a coating tank filled with a coating solution and then pulling it up at a constant speed or a speed that changes sequentially. is there. Since this method is relatively simple and excellent in terms of productivity and cost, it is widely used for manufacturing a photoreceptor. In addition, in order to stabilize the dispersibility of a coating liquid, you may provide the coating liquid dispersion | distribution apparatus represented by the ultrasonic generator in the apparatus used for a dip coating method.

When the coating agent of the blocked isocyanate compound is removed, the resin having two or more active hydrogen-containing groups that can react with the isocyanate group in the blocked isocyanate compound starts an addition reaction with the isocyanate compound, and the coating is cured. Thermal curing is preferable.
The heat curing can be performed using a known apparatus such as a hot air drying furnace and a far-infrared drying furnace, and the conditions may be appropriately set depending on the type of block isocyanate compound or resin used, the mixing ratio, etc. The temperature is 110 to 150 ° C, preferably 130 to 150 ° C, and the time is about 10 minutes to 1 hour.

  Although the film thickness of an intermediate | middle layer is not specifically limited, 0.1-20 micrometers is preferable and 0.5-10 micrometers is especially preferable. If the film thickness of the intermediate layer is less than 0.1 μm, it does not substantially function as an intermediate layer, and a uniform surface property cannot be obtained by covering defects of the conductive support, and carriers are injected from the conductive support. May not be prevented, and the chargeability may decrease. On the other hand, when the film thickness of the intermediate layer exceeds 20 μm, it is difficult to form a uniform coating film, and the sensitivity of the photoreceptor may be lowered.

The intermediate layer in the photoreceptor of the present invention may be not only a single layer but also a plurality of layers.
For example, a first intermediate layer (conductive layer) having a thickness of 2 to 20 μm containing conductive inorganic oxide fine particles and a second intermediate layer (insulating layer) having a thickness of 0.2 to 1 μm not containing inorganic oxide fine particles. A first intermediate layer (insulating layer or blocking layer) having a thickness of 0.2 to 1 μm containing no inorganic oxide fine particles and a second film having a thickness of 3 to 10 μm containing electrically conductive inorganic oxide fine particles. Examples include a combination with an intermediate layer (moire prevention layer).

[Laminated Photosensitive Layer 5]
The laminated photosensitive layer 5 includes a charge generation layer 3 and a charge transport layer 4. As described above, by assigning the charge generation function and the charge transport function to separate layers, the optimum material constituting each layer can be independently selected.
In the following description, a stacked photosensitive layer (FIG. 1) in which a charge generation layer and a charge transport layer are stacked in this order will be described. In the case of an inverted two-layer stacked photosensitive layer (FIG. 2), It is basically the same except that the stacking order is different.

[Charge generation layer 3]
The charge generation layer is mainly composed of a charge generation material having a charge generation capability of generating charges by absorbing irradiated light, and optionally contains a known additive and a binder resin resin (binder).
As the charge generation material, a compound used in this field can be used.
Specifically, an azo pigment (having a carbazole skeleton, a styryl stilbene skeleton, a triphenylamine skeleton, a dibenzothiophene skeleton, an oxadiazole skeleton, a fluorenone skeleton, a bis-stilbene skeleton, a distyryl oxadiazole skeleton, or a distyryl carbazole skeleton. , Monoazo pigments, bisazo pigments, trisazo pigments, etc.), perylene pigments (peryleneimide, perylene acid anhydride, etc.), polycyclic quinone pigments (quinacridone, anthraquinone, pyrenequinone, etc.), phthalocyanine pigments (metal phthalocyanine, no Metal phthalocyanine, halogenated metal-free phthalocyanine, etc.), indigo pigments (indigo, thioindigo, etc.), squarylium dyes, azurenium dyes, thiopyrylium dyes, pyrylium salts, triphenylmethane Organic pigments or dyes such as dyes, further selenium, inorganic materials such as amorphous silicon. These charge generating materials can be used alone or in combination of two or more.
Among these charge generation materials, phthalocyanine pigments, azo pigments, and perylene pigments are particularly preferable because of their high sensitivity.

  The charge generation layer is a chemical sensitizer, an optical sensitizer, an antioxidant, an ultraviolet absorber, a dispersion stabilizer, a sensitizer, a leveling agent, a plasticizer, as long as the preferable characteristics of the present invention are not impaired. An appropriate amount of one or more known additives selected from fine particles of inorganic compounds or organic compounds may be contained. These additives may be contained in the charge transport layer described later, or may be contained in both the charge generation layer and the charge transport layer.

The chemical sensitizer and the optical sensitizer improve the sensitivity of the photoreceptor, suppress an increase in residual potential and fatigue due to repeated use, and improve electrical durability.
Examples of chemical sensitizers include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride, and 4-chloronaphthalic anhydride; cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, 4-nitrobenzaldehyde, and the like. Aldehydes; anthraquinones such as anthraquinone and 1-nitroanthraquinone; polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitrofluorenone; diphenoquinone compounds Examples thereof include electron-withdrawing materials and those obtained by polymerizing these electron-withdrawing materials.

  Examples of optical sensitizers include xanthene dyes, quinoline pigments, organic photoconductive compounds such as copper phthalocyanine, triphenylmethane dyes typified by methyl violet, crystal violet, knight blue and victoria blue; erythrosin, Acridine dyes typified by rhodamine B, rhodamine 3R, acridine orange and frappeocin; thiazine dyes typified by methylene blue and methylene green; oxazine dyes typified by capri blue and meldra blue; cyanine dyes; styryl dyes; Examples include pyrylium salt dyes and thiopyrylium salt dyes.

Antioxidants can maintain sensitivity stability over a long period of time.
Antioxidants include phenolic antioxidants such as hindered phenols such as 2,6-di-t-butyl-4-methylphenol (2,6-di-t-butyl-p-cresol: BHT). , Amine antioxidants such as hindered amines, vitamin E, hydroquinone, paraphenylenediamine, arylalkanes and derivatives thereof, organic sulfur compounds, organic phosphorus compounds, etc., and these may be used alone or in combination of two or more. Can be used.

The addition amount of the antioxidant is preferably from 0.1 to 40 parts by weight, particularly preferably from 0.5 to 15 parts by weight, based on 100 parts by weight of the charge generation material.
If the addition amount of the antioxidant is less than 0.1 parts by weight, there is a possibility that sufficient effects cannot be obtained for improving the stability of the coating solution and improving the durability of the photoreceptor. On the other hand, if the amount of the antioxidant added exceeds 40 parts by weight, the photoreceptor characteristics may be adversely affected.

Leveling agents and plasticizers can improve film formability, flexibility and surface smoothness.
Examples of the leveling agent include a silicone leveling agent.
Examples of the plasticizer include dibasic acid esters such as phthalate esters, fatty acid esters, phosphate esters, chlorinated paraffins, and epoxy type plasticizers.

  Fine particles of an inorganic compound or an organic compound can enhance mechanical strength and improve electrical characteristics. Examples of such fine particles include fine particles exemplified in an intermediate layer described later.

The charge generation layer can be formed by a known dry method and wet method.
Examples of the dry method include a method of vacuum-depositing a charge generating material on the surface of a conductive support.
As a wet method, for example, a charge generating material, and optionally additives and a binder resin are dissolved or dispersed in a suitable organic solvent to prepare a coating solution for forming a charge generating layer, and this coating solution is made conductive. The method of apply | coating to the intermediate | middle layer surface formed on the support body, and then drying and removing an organic solvent is mentioned.

The binder resin can improve the mechanical strength and durability of the charge generation layer, the binding property between layers, and the like, and a resin having a binding property used in this field can be used.
Specifically, vinyl resins such as polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate, polyester, polyester carbonate, polysulfone, polyarylate, polyamide, methacrylic resin, acrylic resin, polyether, polyacrylamide, polyphenylene oxide, etc. Thermoplastic resin: Thermosetting resin such as phenoxy resin, epoxy resin, silicone resin, polyurethane, phenol resin, alkyd resin, melamine resin, phenoxy resin, polyvinyl butyral, polyvinyl formal, partially cross-linked products of these resins, these resins Of the structural units contained in (vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, acrylonitrile) An insulating resin) such as styrene copolymer resin. These binder resins can be used alone or in combination of two or more.

The mixing ratio of the charge generation material and the binder resin is not particularly limited, but the charge generation material is usually about 10 to 99% by weight.
If the charge generation material is less than 10% by weight, the sensitivity of the photoreceptor may be lowered.
On the other hand, when the charge generation material exceeds 99% by weight, not only the film strength of the charge generation layer decreases, but also the dispersibility of the charge generation material decreases and coarse particles may increase. For this reason, surface charges other than the portion to be erased by exposure are reduced, and there is a risk that image defects, particularly an image called black spots where toner adheres to a white background and minute black spots are formed, increase.

  Examples of the organic solvent include aromatic hydrocarbons such as toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, and dichlorobenzene; halogenated hydrocarbons such as dichloromethane, dichloroethane, and tetrachloropropane; tetrahydrofuran (THF) and dioxane. , Ethers such as dibenzyl ether, dimethoxymethyl ether and 1,2-dimethoxyethane; ketones such as methyl ethyl ketone, cyclohexanone, acetophenone and isophorone; esters such as methyl benzoate, ethyl acetate and butyl acetate, and diphenyl sulfide Sulfur-containing solvents; Fluorine solvents such as hexafluoroisopropanol; aprotic polar solvents such as N, N-dimethylformamide and N, N-dimethylacetamide Etc., and these may be used alone or as a mixed solvent. A mixed solvent obtained by adding alcohols, acetonitrile, or methyl ethyl ketone to such a solvent can also be used. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.

Prior to dissolving or dispersing the constituent materials in the resin solution, the charge generating material may be pre-ground.
The preliminary pulverization can be performed using, for example, a general pulverizer such as a ball mill, a sand mill, an attritor, a vibration mill, or an ultrasonic disperser.
The dissolution or dispersion of the constituent materials in the resin solution can be performed using, for example, a general disperser such as a paint shaker, a ball mill, or a sand mill. At this time, it is preferable to appropriately set the dispersion conditions so that impurities are generated from the members constituting the container and the disperser due to wear and the like and are not mixed into the coating liquid.

The application method of the coating solution for the charge generation layer is a baker applicator method, a bar coater method, a casting method, a spin coating method, a roll method, a blade method, etc. for a sheet, and a spray method, a vertical ring method, for a drum. And a dip coating method.
As an application method, an optimum method may be selected in consideration of physical properties and productivity of the coating liquid, and an immersion method, a blade coater method, and a spray method are particularly preferable.

Although it will not specifically limit if the temperature in the drying process of a coating film is the temperature which can remove the used organic solvent, 50-140 degreeC is suitable and 80-130 degreeC is especially preferable.
When the drying temperature is less than 50 ° C., the drying time may be long. On the other hand, if the drying temperature exceeds 140 ° C., the electrical characteristics during repeated use of the photoreceptor may deteriorate and the resulting image may deteriorate.

  The thickness of the charge generation layer is not particularly limited, but is preferably 0.05 to 5 μm, particularly preferably 0.1 to 1 μm. When the thickness of the charge generation layer is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity may be lowered. On the other hand, if the thickness of the charge generation layer exceeds 5 μm, charge transport within the charge generation layer becomes a rate-limiting step in the process of erasing the charge on the surface of the photoreceptor, and the sensitivity may be lowered.

[Charge transport layer 4]
The charge transport layer contains, as main components, a charge transport material having an ability to accept and transport charges generated by the charge generation material and a binder resin resin (binder).

As the charge transport material, a compound used in this field can be used.
Specifically, poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives Imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline derivatives, phenylhydrazones, hydrazone derivatives, triphenylamine series Electron donating substances such as compounds, tetraphenyldiamine compounds, triphenylmethane compounds, stilbene compounds, azine compounds having a 3-methyl-2-benzothiazoline ring;

Fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyanoethylene, tetracyanoquinodimethane, promanyl, chloranil And electron accepting substances such as benzoquinone. These charge transport materials can be used alone or in combination of two or more.

The ratio (E / B) between the weight (E) of the charge transport material and the weight (B) of the binder resin is 10/12 to 10/25, preferably 10/16 to 10/20.
When the ratio (E / B) is less than 10/25, the relative amount ratio of the binder resin to the charge transport material is increased, and sufficient sensitivity may not be obtained.
On the other hand, if the ratio (E / B) exceeds 10/12, the printing durability of the charge transport layer and the durability of the photoreceptor may be lowered.

As the binder resin, one or more of the same binder resins as those contained in the charge generation layer can be used.
Among these resins, polyvinyl acetal resins are preferable because they are excellent in dispersibility with inorganic oxide fine particles, film formability, potential characteristics, and the like.
The charge transport layer may contain an appropriate amount of the same additive as that contained in the charge generation layer, if necessary, within the range not impairing the effects of the present invention.

The charge transport layer is prepared by dissolving or dispersing a charge transport material, a binder resin and other additives as required in an appropriate organic solvent to prepare a charge transport layer forming coating solution. It can be formed by applying to the surface of the layer and then drying to remove the organic solvent. More specifically, for example, by dissolving or dispersing a charge transport material and other additives as required in a resin solution obtained by dissolving a binder resin in an organic solvent, a charge transport layer forming coating solution is obtained. Prepare.
Other processes and conditions are in accordance with the formation of the charge generation layer.

  Although the film thickness of a charge transport layer is not specifically limited, 10-60 micrometers is preferable and 10-40 micrometers is especially preferable. If the thickness of the charge transport layer is less than 10 μm, the charge retention ability may be reduced. Conversely, if the thickness of the charge transport layer is more than 60 μm, sharpness decreases and residual potential increases, There is a risk that image deterioration will occur remarkably.

[Single layer type photosensitive layer 5 ']
The single-layer type photosensitive layer contains a charge generation material, a charge transport material, and a binder resin (binder) as main components.
The single-layer type photosensitive layer may contain an appropriate amount of the same additive as that contained in the charge generation layer, if necessary, within the range not impairing the effects of the present invention.

A single-layer type photosensitive layer is prepared by dissolving and / or dispersing a charge generation material, a charge transport material and, if necessary, other additives in an appropriate organic solvent to prepare a single-layer type photosensitive layer forming coating solution, This coating liquid can be formed by applying to the surface of the intermediate layer formed on the conductive support and then drying to remove the organic solvent.
Other processes and conditions are in accordance with the formation of the charge generation layer and the charge transport layer.

  The film thickness of the single-layer type photosensitive layer is not particularly limited, but is preferably 10 to 100 μm, and particularly preferably 15 to 50 μm. If the film thickness of the single-layer type photosensitive layer is less than 10 μm, the charge holding ability on the surface of the photoreceptor may be lowered, and if the film thickness of the single-layer type photosensitive layer exceeds 100 μm, the productivity may be lowered. is there.

[Protective layer (not shown)]
The photoreceptor of the present invention may have a protective layer (not shown) on the surface of the multilayer photosensitive layer 5 and the single-layer photosensitive layer 5 ′.
The protective layer has functions of improving the abrasion of the photosensitive layer and preventing chemical adverse effects caused by ozone, nitrogen oxides, and the like.

The protective layer is prepared by, for example, preparing a protective layer-forming coating solution by dissolving or dispersing a binder resin in an appropriate organic solvent and, if necessary, an additive such as an antioxidant or an ultraviolet absorber. The coating liquid can be applied to the surface of a single layer type photosensitive layer or a multilayer type photosensitive layer, and the organic solvent can be removed by drying.
Other processes and conditions are in accordance with the formation of the charge generation layer.

  Although the film thickness of a protective layer is not specifically limited, 0.5-10 micrometers is preferable and 1-5 micrometers is especially preferable. If the thickness of the surface protective layer 5 is less than 0.5 μm, the surface resistance of the photoreceptor is inferior and the durability may be insufficient. Conversely, if it exceeds 10 μm, the resolution of the photoreceptor may be reduced. There is.

The image forming apparatus of the present invention includes a photoreceptor, a charging unit that charges the photoreceptor, an exposure unit that exposes the charged photoreceptor to form an electrostatic latent image, and the static formed by exposure. Developing means for developing an electrostatic latent image to form a toner image, transfer means for transferring the toner image formed by development onto a recording material, and fixing the transferred toner image on the recording material A fixing unit that forms an image; a cleaning unit that removes and collects toner remaining on the photoconductor; and a static elimination unit that neutralizes surface charge remaining on the photoconductor.
The photoreceptor has the intermediate layer described above,
The charging unit is a contact charging method in which charging is performed by bringing a charging member into contact with the photosensitive member.

An example of the image forming apparatus of the present invention will be described with reference to the drawings. However, the present invention is not limited to the contents described below.
FIG. 4 is a schematic side view showing the configuration of the image forming apparatus of the present invention.
The image forming apparatus 20 of FIG. 4 includes a photoreceptor 10 of the present invention (for example, any one of the photoreceptors of FIGS. 1 to 3), a charging unit (contact charger) 32, an exposure unit (“image exposure unit”). ) 30, developing means (developing device) 33, transferring means (transfer device) 34, fixing means (fixing device) 35, separating means 37, cleaning means (cleaner) 36, and discharging means ( (Not shown, provided with the cleaning means 36), and accommodated in the housing 38. Reference numeral 45 indicates a recording material (transfer paper or recording paper).

The photosensitive member 10 is rotatably supported by the main body of the image forming apparatus 20 (not shown), and is driven to rotate around the rotation axis 44 in the direction of the arrow 41 by a driving unit (not shown). The driving means is configured to include, for example, an electric motor and a reduction gear, and transmits the driving force to a conductive support constituting the core of the photoconductor 10, thereby rotating the photoconductor 10 at a predetermined peripheral speed. . The charging unit 32, the exposure unit 30, the developing unit 33, the transfer unit 34, the separation unit 37, and the cleaning unit 36 are arranged in this order along the outer peripheral surface 43 of the photoconductor 10 by the arrow 41. It is provided from the upstream side in the rotational direction to the downstream side.
Next, each means will be specifically described.

  The contact charger 32 is a charging unit that charges the outer peripheral surface 43 of the photoreceptor 10 to a predetermined potential. For example, the contact charger 32 includes a charging member 32 a including a charging brush (conductive brush) 50 and a support 51 and an external power source 39.

  The exposure unit 30 includes, for example, a semiconductor laser as a light source, and a light beam 31 such as a laser beam output from the light source is positioned between the contact charger 32 and the developing unit 33 in accordance with image information. The outer peripheral surface 43 is irradiated to form an electrostatic latent image on the outer peripheral surface 43.

  The developing unit 33 is a developing unit that develops the electrostatic latent image formed on the outer peripheral surface 43 of the photosensitive member 10 by exposure with a developer. The developing unit 33 is provided facing the photosensitive member 10 and supplies toner. 33a, and a casing 33b that supports the developing roller 33a so as to be rotatable about a rotation axis parallel to the rotation axis 44 of the photosensitive member 10 and accommodates a developer containing toner in an internal space thereof.

The transfer unit 34 supplies a toner image, which is a visible image formed on the outer peripheral surface 43 of the photoconductor 10 by development, between the photoconductor 10 and the transfer unit 34 from the direction of the arrow 42 by a conveying unit (not shown). The transfer unit is a transfer unit that transfers the image onto a transfer sheet 45 that is a recording material.
In this embodiment, the transfer unit 34 presses the transfer roller 34 a from the surface opposite to the contact surface between the outer peripheral surface 43 of the photoconductor 10 and the transfer paper 45, and the photoconductor 10 and the transfer paper 45 are in pressure contact with each other. It is a contact-type transfer unit that transfers onto the transfer paper 45 by driving the external power supply 40.
The transfer unit 34 may be, for example, a non-contact type transfer unit that transfers a toner image onto the transfer sheet 45 by applying a charge having a polarity opposite to that of the toner to the transfer sheet 45 from a corona discharger.

The separating unit 37 is a unit that separates the photoreceptor 10 and the transfer paper 45 that are in pressure contact with each other.
The cleaner 36 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface 43 of the photoconductor 10 after the transfer operation by the transfer device 34, and a cleaning blade 36 a that peels off toner remaining on the outer peripheral surface 43 of the photoconductor 10. And a recovery casing 36b for storing the toner separated by the cleaning blade 36a. Further, the cleaner 36 may be provided with a static elimination means (static elimination lamp) (not shown).

  A fixing device 35 for fixing the toner image transferred onto the transfer paper 45 is provided in the direction in which the transfer paper 45 separated from the photoreceptor 10 by the separating means 37 is conveyed. The fixing period 35 includes a heating roller 35a having a heating means (not shown), and a pressure roller 35b provided opposite to the heating roller 35a and pressed by the heating roller 35a to form a contact portion.

The image forming method of the present invention uses the image forming apparatus of the present invention to charge a photosensitive member, expose the charged photosensitive member to form an electrostatic latent image, and form an electrostatic latent image by exposure. The toner image is developed to form a toner image, the toner image formed by the development is transferred onto a recording material , and the transferred toner image is fixed onto the recording material to form an image.

An image forming operation by the image forming apparatus 20 will be described.
First, when the photosensitive member 10 is rotationally driven in the direction of the arrow 41 by the driving unit, the charging of the contact charger 32 provided on the upstream side in the rotational direction of the photosensitive member 10 with respect to the imaging point of the light 31 from the exposure unit 30 The member 32a is pressed against the outer peripheral surface 43 of the photoconductor 10 to form a contact portion. In this state, a predetermined power source is applied from the external power source 39 to the charging member 32a, and the outer peripheral surface 43 of the photoreceptor 10 is uniformly charged to a predetermined positive or negative potential.

  Next, light 31 is irradiated from the exposure unit 30 to the outer peripheral surface 43 of the photoconductor 10 according to image information. The light 31 from the light source is repeatedly scanned in the longitudinal direction of the photoconductor 10 that is the main scanning direction (the direction in which the rotation axis 44 extends), and the outer peripheral surface 43 of the photoconductor 10 is accompanied with this scanning and the rotation of the photoconductor 10. The electrostatic latent images are sequentially formed. That is, a difference occurs in the surface potential between the portion irradiated with the light 31 by the exposure and the portion not irradiated, and an electrostatic latent image is formed on the outer peripheral surface 43 of the photoreceptor 10.

  Next, the outer peripheral surface 43 of the photoconductor 10 on which an electrostatic latent image is formed from the developing roller 33a of the developing device 33 provided downstream of the imaging point of the light 31 from the light source in the rotation direction of the photoconductor 10. When the toner is supplied, the electrostatic latent image is developed, and a toner image is formed on the outer peripheral surface 43 of the photoreceptor 10.

  Next, in synchronization with the exposure of the photoconductor 10, the transfer paper 45 is supplied from the direction of the arrow 42 between the photoconductor 10 and the transfer device 34 by the conveying means, and the transfer roller 34 a of the transfer device 34 is moved to the photoconductor 10. Is pressed to form a contact portion, and the photoreceptor 10 and the transfer paper 45 are pressed against each other. In this state, a voltage is applied from the external power source 40 to the transfer roller 34a, that is, a toner image formed on the outer peripheral surface 43 of the photoconductor 10 is transferred onto the transfer paper 45 by applying a charge having a polarity opposite to that of the toner. The

  Next, the transfer paper 45 onto which the toner image has been transferred is peeled off from the outer peripheral surface 43 of the photoreceptor 10 by the separating means 37 and then transported to the fixing device 35 by the transporting means. When passing through the contact portion with the roller 35b, it is heated and pressurized. As a result, the toner image on the transfer paper 45 is fixed on the transfer paper 45 and a robust image is obtained. The transfer paper 45 on which the image is formed in this manner is discharged outside the image forming apparatus 20 by the conveying means.

  On the other hand, the toner remaining on the outer peripheral surface 43 of the photoconductor 10 after the transfer operation by the transfer device 34 is peeled off from the outer peripheral surface 43 of the photoconductor 10 by the cleaning blade 36a of the cleaner 36 and collected in the recovery casing 36b. The charge on the outer peripheral surface 43 of the photoconductor 10 from which the toner has been removed in this manner is removed by a static eliminator provided together with the cleaner 36, and the electrostatic latent image on the outer peripheral surface 43 of the photoconductor 10 disappears. Thereafter, the photoconductor 10 is further rotated and a series of operations starting from charging of the photoconductor 10 is repeated. As described above, images are continuously formed.

  In the image forming apparatus 20 of the present invention, the intermediate layer 2 of the photoreceptor 10 has almost no defects or aggregates, and the charge supplied from the charging member 32a is the charge transport layer 4 or the single-layer type photosensitive layer of the laminated photosensitive layer 5. When the charging member 32a is brought into contact with the photosensitive member 10 by the contact charger 32 and charging is performed, the stacked photosensitive layer 5 or the single-layer photosensitive layer is not concentrated on a part of 5 ′. Uniformly charged. That is, the multilayer type photosensitive layer or the single-layer type photosensitive layer 5 ′ is not broken down due to a local leak, and a high-quality image free from image defects caused by the leak can be stably supplied over a long period of time. And a highly reliable image forming apparatus 20 can be obtained (see FIGS. 1 to 3).

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

Example 1
As the conductive support, a cylindrical conductive support made of aluminum having a diameter of 30 mm, a length of 300 mm, and a thickness of 0.8 mm was used to produce the photoconductor of FIG.
First. Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) 12 parts by weight, polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3), and 3.2 parts by weight of a block isocyanate compound as a curing agent (Solid content: 37.5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310) 19.6 parts by weight, dispersion stable (manufactured by San Nopco, product name: SN deformer 470) ) 0.5 part by weight was added to 65 parts by weight of water and dispersed for 6 hours using a paint shaker to prepare an intermediate layer coating solution (total amount of 1 kg).
The isocyanate group (H) of the blocked isocyanate compound is 1.0 molar ratio (H / B) to the active hydrogen-containing group (B) of the resin, and the inorganic oxide fine particles (P) are crosslinked resin (block isocyanate). The weight ratio (P / R) was 6/4 with respect to the total of the compound and resin: R) (hereinafter referred to as “H / B” and “P / R”, respectively).
The obtained coating solution for the intermediate layer is filled in the coating tank, the conductive support is dipped and then pulled up, and the obtained coating film is dried and cured at a temperature of 150 ° C. for 30 minutes to obtain an intermediate film thickness of 1.0 μm. A layer was formed.

A charge generating material was prepared in advance by the following method.
40 g of o-phthalodinitrile, 18 g of titanium tetrachloride and 500 ml of α-chloronaphthalene were reacted by heating and stirring at a temperature of 200 to 250 ° C. for 3 hours in a nitrogen atmosphere. Next, the reaction solution was allowed to cool to a temperature of 100 to 130 ° C., filtered while hot, and washed with 200 ml of α-chloronaphthalene heated to a temperature of 100 ° C. to obtain a crude dichlorotitanium phthalocyanine product.
The obtained crude product was washed with 200 ml of α-chloronaphthalene and then with 200 ml of methanol at room temperature, and further subjected to hot washing in 500 ml of methanol for 1 hour. After filtration, the obtained crude product was repeatedly washed with hot water in 500 ml of water until the pH reached 6-7. Then, it dried and the oxo titanyl phthalocyanine intermediate crystal was obtained.
Next, the obtained intermediate crystal was mixed with methyl ethyl ketone, milled with a glass bead having a diameter of 2 mm by a paint conditioner device (manufactured by Red Level), washed with methanol, and dried to obtain an oxotitanyl phthalocyanine crystal.
When the obtained crystal was analyzed by X-ray diffraction, it was found that the obtained crystal had a Bragg angle (2θ ± 0.2 °) of 7.3 °, 9.4 °, 9.7 ° and 27.3 °. It was found that it was a crystalline oxotitanyl phthalocyanine having a maximum diffraction peak in a peak bundle of 9.4 ° and 9.7 ° that overlapped with each other. FIG. 5 shows the X-ray diffraction spectrum.

2 parts by weight of the obtained oxotitanyl phthalocyanine crystal, 1 part by weight of polyvinyl butyral resin (product name: ESREC BBM-S, manufactured by Sekisui Chemical Co., Ltd.) as a binder resin, and dimethylpolysiloxane (Shin-Etsu) as a leveling agent Chemical Industry Co., Ltd., product name: KF-96) 0.06 parts by weight, dimethoxyethane 87.3 parts by weight as organic solvent and 9.7 parts by weight of cyclohexanone are mixed (mixing ratio = 90/10) Then, the mixture was dispersed using a paint shaker to prepare a charge generation layer coating solution (total amount: 1 kg).
The obtained charge generation layer coating solution was applied onto the previously formed intermediate layer by the same dip coating method as that for the intermediate layer, and the resulting coating film was naturally dried to obtain a charge having a thickness of 0.3 μm. A generation layer was formed.

Next, 10 parts by weight of a triphenylamine-butadiene derivative represented by the following structural formula (1) as a charge transport material and a polyvinyl acetal resin (solid content: 20%, OH value: 960, degree of acetalization) as a binder resin 9 mol%, manufactured by Sekisui Chemical Co., Ltd., product name: ESREC KW-1) 1.95 parts by weight, blocked isocyanate compound (solid content: 37.5%, NCO content: 3.7, Sumitomo Chemical Bayer Urethane) Manufactured product, product name: Bihijoule VPLS2310) 20.2 parts by weight and dimethylpolysiloxane as a leveling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-96) 0.004 parts by weight tetrahydrofuran as an organic solvent It was dissolved in 110 parts by weight of (THF) to prepare a charge transport layer coating solution (total amount: 1 kg).
The obtained charge transport layer coating solution was applied on the charge generation layer formed earlier by the same dip coating method as that for the intermediate layer, and the resulting coating film was dried at a temperature of 130 ° C. for 1 hour to form a film. A charge transport layer having a thickness of 23 μm was formed.
As described above, the electrophotographic photosensitive member of Example 1 was produced.

(Example 2)
A photoconductor of Example 2 was prepared in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 1.0, P / R = 3/7).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 6 parts by weight Polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 5.6 parts by weight Block isocyanate compound (solid content: 37. 5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 34.3 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: SN deformer 470): 0.5 weight Water: 54 parts by weight

(Example 3)
A photoconductor of Example 3 was prepared in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 0.6, P / R = 9/1).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 18 parts by weight Polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 0.8 part by weight Block isocyanate compound (solid content: 37. 5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 4.9 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: SN deformer 470): 0.5 weight Water: 76 parts by weight

(Example 4)
Instead of 12 parts by weight of titanium oxide fine particles (shape: needle, minor axis length 10 nm, major axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) Except that 12 parts by weight of granular titanium oxide fine particles (shape: granular, average primary particle size 30-50 nm, alumina surface treatment, manufactured by Ishihara Sangyo Co., Ltd., product name: TTO-55A) were used in the same manner as in Example 1. Thus, a photoconductor of Example 4 was produced (H / B = 1.0, P / R = 6/4).

(Example 5)
Instead of 12 parts by weight of titanium oxide fine particles (shape: needle, minor axis length 10 nm, major axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) The photoconductor of Example 5 was prepared in the same manner as in Example 1 except that 12 parts by weight of barium sulfate fine particles (shape: granular, tin oxide coated, manufactured by Mitsui Kinzoku Mining Co., Ltd., product name: Pastoran PC1) were used. It produced (H / B = 1.0, P / R = 6/4).

(Example 6)
Instead of 12 parts by weight of titanium oxide fine particles (shape: needle, minor axis length 10 nm, major axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) The photosensitivity of Example 6 was the same as Example 1 except that 12 parts by weight of zinc oxide fine particles (shape: granular, average primary particle size: 35 nm, manufactured by Sakai Chemical Industry Co., Ltd., product name: FINEX30) were used. A body was prepared (H / B = 1.0, P / R = 6/4).

(Example 7)
A photoconductor of Example 7 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 1.0, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 12 parts by weight Polyether polyol resin as a resin (water dispersion type, solid content: 35%, OH value: 60, manufactured by Nippon Polyurethane Industry Co., Ltd., product name: AQD-473): 14.3 parts by weight Block isocyanate Compound (solid content: 42%, NCO content: 7.5, manufactured by Nippon Polyurethane Industry Co., Ltd., developed product name: BWD-102): 7.1 parts by weight Dispersion stabilizer (manufactured by San Nopco Co., Ltd., product name: SN deformer) 470): 0.5 part by weight Water: 67 part by weight

(Example 8)
A photoconductor of Example 8 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 1.0, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 12 parts by weight Water-soluble cellulose as a resin (OH value: 360, manufactured by Shin-Etsu Chemical Co., Ltd., product name: Metroles 65SH-50): 0.96 parts by weight Block isocyanate compound (solid content: 37.5%, NCO Content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 18.8 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: SN deformer 470): 0.5 parts by weight Water: 68 Parts by weight

Example 9
A photoconductor of Example 9 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 1.0, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 12 parts by weight Water-soluble nylon (polyamide compound resin) as a resin (solid content: 20%, NH content: 10%, manufactured by Nagase ChemteX Corporation, product name: Toresin FS-350): 8.8 weight Part Block isocyanate compound (solid content: 45%, NCO content: 7.0%, manufactured by Mitsui Chemicals Polyurethanes, product name: Takenate WB-820): 13.9 parts by weight Dispersion stabilizer (manufactured by Sannopco, Product name: SN deformer 470): 0.5 parts by weight Water: 65.3 parts by weight

(Example 10)
A photoconductor of Example 10 was prepared in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 0.6, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 12 parts by weight Polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 5.1 parts by weight Block isocyanate compound (solid content: 37. 5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 18.6 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: SN deformer 470): 0.5 weight Water: 80 parts by weight

(Example 11)
A photoconductor of Example 11 was prepared in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 1.4, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 10 nm, long axis length 50 nm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A) : 12 parts by weight Polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 2.3 parts by weight Block isocyanate compound (solid content: 37. 5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 20.1 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: SN deformer 470): 0.5 weight Water: 65.6 parts by weight

(Comparative Example 1)
A photoconductor of Comparative Example 1 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components (organic solvent, no curing).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A): 12 parts by weight Copolymer nylon (made by Toray Industries, Inc., product name: Amilan CM8000): 8 parts by weight Methanol as an organic solvent: 100 parts by weight and 1,3-dioxolane: 80 parts by weight

(Comparative Example 2)
A photoconductor of Comparative Example 2 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components (aqueous, uncured).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A): 12 parts by weight Polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 20 parts by weight Water: 74 parts by weight

(Comparative Example 3)
A photoconductor of Comparative Example 3 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 0.4, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A): 12 parts by weight Polyvinyl acetal as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 7.2 parts by weight Block isocyanate compound (solid Minute: 37.5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 17.5 parts by weight Dispersion stabilizer (manufactured by Sannopco, product name: SN deformer 470): 0.5 parts by weight Water: 63 parts by weight

(Comparative Example 4)
A photoconductor of Comparative Example 3 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components (H / B = 1.6, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A): 12 parts by weight (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 2.1 parts by weight Block isocyanate compound (solid content: 37.5%, NCO content: 3.7, manufactured by Sumitomo Chemical Bayer Urethane, product name: Bihijoule VPLS2310): 20 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: SN deformer 470): 0.5 weight Water: 65.7 parts by weight

(Comparative Example 5)
A photoconductor of Comparative Example 3 was prepared in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components (an aqueous, non-block type isocyanate compound (NCO group at 20 ° C. for 20 hours). Completely decomposed), H / B = 1.0, P / R = 6/4).
Titanium oxide fine particles as inorganic oxide fine particles (shape: needle shape, short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, alumina, silica surface treatment, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60A): 12 parts by weight Resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 11.2 parts by weight Water-dispersed isocyanate (unblocked) Mold, NCO content: 16.5%, manufactured by Asahi Kasei Chemicals Corporation, product name: Duranate WB40-100): 5.8 parts by weight Antifoaming agent (polyether, manufactured by San Nopco, product name: SN deformer 470 ): 0.08 parts by weight Dispersion stabilizer (manufactured by San Nopco, product name: Roma PWA-40): 0.03 parts by weight Water: 71 parts by weight

[Evaluation]
As an image forming apparatus 20 according to one embodiment of the present invention shown in FIG. 4, a scorotron charger of a commercially available copying machine (manufactured by Sharp Corporation, model: AR-265S) is provided with a brush-like charging member 32a. A test copying machine obtained by modifying the charger 32 was prepared, and the characteristics of the photoreceptor were evaluated.

(1) Initial image quality An image in which the photoconductors obtained in Examples 1 to 11 and Comparative Examples 1 to 5 are mounted on a test copying machine, and the gradation of the image is expressed by gradations of black and white on a transfer sheet. A so-called halftone image was formed.
The reflectance density as the image density of the halftone image obtained for each photoconductor was measured using a Macbeth densitometer (Macbeth model: RD914) and compared with the set allowable range of image density. Further, the presence or absence of black spots and white spots in the halftone image obtained by visual observation was observed.
From the obtained results, the image quality of the halftone image was evaluated based on the following criteria.

○: Good (the image density is almost equal to the median of the allowable range, and there are no image defects such as black spots and white spots)
Δ: No problem in practical use (the image density is lower than or slightly lower than the standard allowable range, but is within the allowable range, and there are no image defects such as black spots and white spots)
×: Unusable for actual use (image density is out of the allowable range or low, or there are image defects such as black spots, white spots)

(2) Initial electrical characteristics Instead of the developing device of the test copying machine (reversal development process), a surface potential meter (manufactured by Trek, model: Model 344) is mounted at the development site, and a white original is printed on each photoconductor. Photoreceptor surface potential V0 (-V) when copying, halftone original surface potential VH (-V), photoconductor surface potential VL (-) V) was measured and used as the initial evaluation result.

(3) Image quality and electrical characteristics after repeated use Next, the surface electrometer of the test copying machine is taken out and mounted again, and an image of a predetermined pattern is defined in Japanese Industrial Standard (JIS) P0138. After copying on 30,000 sheets of A4 size transfer paper, a halftone image was further formed, and the image quality was evaluated in the same manner as in (1).
Further, in the same manner as (2), the surface potentials V0, VH and VL of the photoconductor were measured and used as the evaluation results after repeated use.
The above results are shown in Table 1 together with the constituent materials of the intermediate layer coating solution used for forming the intermediate layer of the photoreceptor.

(Example 12)
For the photoconductor of Example 1, after evaluating (1) initial image quality and (2) initial electrical characteristics, an aerial image of 500,000 sheets in terms of A4-size transfer paper was obtained without a developing device of a test copying machine. did. Thereafter, a developing device was mounted again to form a halftone image, and the image quality was evaluated in the same manner as in (1). Further, in the same manner as (2), the surface potentials V0, VH and VL of the photoconductor were measured and used as the evaluation results after repeated use. The obtained results are shown in Table 2.

(Comparative Example 6)
The contact charger 32 provided with the brush-like charging member 32a of the test copying machine is taken out and mounted again with the scorotron charger (non-contact charger). As for the photoconductor of Example 1, as in Example 12, Initial image quality, initial electrical characteristics, image quality after repeated use (after aerial photography) and electrical characteristics were evaluated. The obtained results are shown in Table 2.

The following can be seen from the results in Table 1.
The photoconductors of Examples 1 to 11 are organic solvent systems using polyamide-based binder resins that are often used in current photoconductors, even though water is used as the solvent for the intermediate layer coating solution. Compared to Comparative Example 1, the electrical characteristics, fatigue characteristics, and image characteristics are all equivalent or better. This is because the dispersibility of the aqueous intermediate layer coating liquids of Examples 1 to 11 is better than that of the organic solvent intermediate layer coating liquid of Comparative Example 1, so that the leak point in contact charging is reduced. This is considered to be because stable electrical characteristics and image characteristics can be obtained without causing discharge breakdown.

In the copying machine on which the photoconductors of Comparative Examples 1 to 5 were mounted, damage of the photosensitive layer due to leakage appeared as black spots in the image after repeated use.
Further, when the resin is polyvinyl acetal, more stable image characteristics can be obtained (comparison between Example 1 and Examples 7 to 9). This is because the polyvinyl acetal coats the surface of the inorganic oxide fine particles (filler), thereby improving the dispersibility of the inorganic oxide fine particles in the coating solution for the intermediate layer, reducing local aggregates, and making contact. It is presumed that leaks are less likely to occur even when charged.

  Further, when the isocyanate group has a molar ratio of 0.5 to 1.5 with respect to the active oxygen group of the resin, more stable image characteristics can be obtained (Examples 1, 10 and 11 and Comparative Example 3 and Comparison with 4). This is because when the amount of isocyanate group is outside the above range, the curing agent or resin cannot be reacted completely and remains in the film, and when it is contact-charged, the unreacted part becomes a leak point, and the image density is extremely low. Therefore, it is presumed that the black spots are caused.

The photoconductor of Comparative Example 2 is markedly deteriorated in sensitivity during repeated use, probably because it uses an intermediate layer coating solution that is not thermally cured.
In Comparative Example 5, the non-block type isocyanate was used as a curing agent, so the image density was extremely low and black spots were observed. This is because unblocked isocyanate groups are very easy to react with water, and it is difficult to prepare a stable coating solution for an intermediate layer. This is thought to be because it is difficult to obtain a layer.

  In Example 12, the photosensitive member of Example 1 and the contact charging method are used. On the other hand, in Comparative Example 6, the photoreceptor of Example 1 and a non-contact charging type charger are used. If it is a non-contact charging method, it receives ozone damage and the like, and the chargeability after repeated fatigue, sensitivity characteristics, and image quality deteriorate.

1 conductive support 2 intermediate layer (undercoat layer)
3 Charge Generation Layer 4 Charge Transport Layer 5 Multilayer Type Photosensitive Layer 5 ′ Single Layer Type Photosensitive Layer

DESCRIPTION OF SYMBOLS 10 Electrophotographic photoreceptor 20 Image forming apparatus 30 Exposure means 31 Light 32 Charging means (contact charger)
32a charging member 33 developing means (developing device)
33a developing roller 33b casing 34 transfer means (transfer device)
34a transfer roller

35 Fixing means (fixing device)
35a heating roller 35b pressure roller 36 cleaning means (cleaner)
36a Cleaning blade 36b Recovery casing 37 Separating means 38 Housing 39, 40 External power supply 41, 42 Arrow 43 Outer surface 44 Rotating axis 45 Recording material (transfer sheet or recording sheet)
50 Charging brush (conductive brush)
51 Support

Claims (8)

An electrophotographic photosensitive member; a charging unit that charges the electrophotographic photosensitive member; an exposing unit that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image; and the electrostatic latent image formed by exposure. A developing unit for developing the image to form a toner image, a transfer unit for transferring the toner image formed by the development onto the recording material, and fixing the transferred toner image on the recording material to form an image. A fixing unit for forming; a cleaning unit for removing and collecting the toner remaining on the electrophotographic photosensitive member; and at least a static eliminating unit for neutralizing surface charges remaining on the electrophotographic photosensitive member,
The electrophotographic photoreceptor comprises a blocked isocyanate compound, a resin having an active hydrogen-containing group capable of reacting with an isocyanate group in the blocked isocyanate compound, and inorganic oxide fine particles between a conductive support and a photosensitive layer. A medium containing only water, and the isocyanate group is heated from the intermediate layer coating solution present in the blocked isocyanate compound at a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group. Having an intermediate layer formed through curing,
An image forming apparatus, wherein the charging unit is a contact charging method in which charging is performed by bringing a charging member into contact with the electrophotographic photosensitive member.   The image forming apparatus according to claim 1, wherein the active hydrogen-containing group is a hydroxyl group or an amide group.   The image forming apparatus according to claim 1, wherein the blocked isocyanate compound has a structure in which hexamethylene diisocyanate or isophorone diisocyanate is blocked with an oxime or lactam blocking agent.   The said resin is any one of Claims 1-3 selected from polyether polyol resin, polyester polyol resin, polyacryl polyol resin, polyvinyl alcohol resin, polyvinyl acetal resin, cellulose, and polyamide resin. The image forming apparatus described in 1.   The image forming apparatus according to claim 4, wherein the resin is a polyvinyl acetal resin.   The image forming apparatus according to claim 1, wherein the inorganic oxide fine particles are fine particles of titanium oxide.   The said inorganic oxide microparticles | fine-particles are contained in the said intermediate layer coating liquid in the ratio of 30 to 90 weight% with respect to the total amount of the said block isocyanate compound, resin, and inorganic oxide microparticles. The image forming apparatus according to any one of the above.   An image forming apparatus according to any one of claims 1 to 7, wherein the electrophotographic photosensitive member is charged, the charged electrophotographic photosensitive member is exposed to form an electrostatic latent image, and exposure is performed. The electrostatic latent image formed by developing is developed to form a toner image, the toner image formed by development is transferred onto a recording material, and the transferred toner image is fixed onto the recording material. An image forming method comprising forming an image.

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