JP2010170083A - Coating liquid for intermediate layer of electrophotographic photoreceptor having organic photosensitive layer, electrophotographic photoreceptor, image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating liquid for an intermediate layer of a photoreceptor having an organic photosensitive layer, the liquid using water, which is the most environmentally friendly, as a solvent and showing excellent long-term stability of liquid physical properties during production; to provide a photoreceptor having an intermediate layer formed by using the coating liquid and showing excellent characteristics in repeated use and environmental stability; and to provide an image forming apparatus equipped with the photoreceptor, and an image forming method using the apparatus. <P>SOLUTION: The coating liquid for an intermediate layer of an electrophotographic photoreceptor having an organic photosensitive layer contains: a block isocyanate compound; a resin having at least two active hydrogen-containing groups reactive with an isocyanate group in the block isocyanate compound; acicular titanium oxide fine particles; and an aqueous medium. The acicular titanium oxide fine particles are included by 30 to 90 wt.% based on the total amount of the block isocyanate compound, the resin and the acicular titanium oxide particles. The acicular titanium oxide fine particles have a minor axial length of not more than 0.5 μm, a major axial length of not more than 10 μm, and an average aspect ratio of 1.5 to 300. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating solution for an intermediate layer of an electrophotographic photosensitive member having an organic photosensitive layer, an electrophotographic photosensitive member having an intermediate layer formed using the same, an image forming apparatus having the same, and an image using the same It relates to the formality method.

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 clearly 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, techniques for adding metal fine particles or metal oxide fine particles to the intermediate layer have been proposed for the purpose of preventing image defects due to the influence of the conductive support and improving the residual potential. Examples of the metal oxide fine particles include titanium oxide fine particles having an untreated surface and titanium oxide fine particles having a surface coated with alumina or the like.
Since such titanium oxide powder is granular, contact between the particles is close to point contact, and the contact area is small. Therefore, if the content of the metal oxide does not exceed a certain amount, the resistance value of the intermediate layer is very high. The photosensitive member characteristics, particularly sensitivity and residual potential are deteriorated. Therefore, when using a granular metal oxide for an intermediate | middle layer, it is necessary to make the content very high.

However, even if the content of the metal oxide is increased to improve the characteristics, since the contact between the particles is weak, it is inevitable that the characteristics will gradually deteriorate due to repeated use of the photoreceptor for a long period of time.
Further, when the content of such a metal oxide is increased, there is a problem that the dispersibility and stability of the metal oxide in the resin are deteriorated and the storage stability of the coating liquid is deteriorated.

Japanese Patent No. 3657138 Japanese Patent No. 2707341 Japanese Patent No. 2790380 JP 2005-115351 A

  The present invention uses a coating solution for an intermediate layer of a photoreceptor having an organic photosensitive layer, which uses water having the smallest environmental load as a solvent and has excellent liquid property over time in production, and is formed using the same. Another object of the present invention is to provide a photoreceptor having an intermediate layer and excellent in repetitive characteristics and environmental stability, an image forming apparatus provided with the same, and an image formability method using the same.

  In order to realize a coating solution for an intermediate layer using water as a solvent, which does not generate a volatile organic compound (VOC) and does not cause a fire as described above, the present inventors have used a specific amount of a blocked isocyanate compound. And an intermediate layer coating solution comprising a resin having an active hydrogen-containing group capable of reacting with an isocyanate group, a specific amount of acicular titanium oxide fine particles, and an aqueous medium.

According to the present invention, including a blocked isocyanate compound, a resin having two or more active hydrogen-containing groups capable of reacting with an isocyanate group in the blocked isocyanate compound, acicular titanium oxide fine particles, and an aqueous medium,
The acicular titanium oxide fine particles are contained in a proportion of 30 to 90% by weight with respect to the total amount of the blocked isocyanate compound, the resin and the acicular titanium oxide fine particles,
An intermediate of a photoreceptor having an organic photosensitive layer, wherein the acicular titanium oxide fine particles have a minor axis length of 0.5 μm or less, a major axis length of 10 μm or less, and an average aspect ratio of 1.5 or more and 300 or less. A layer coating solution is provided.

  Further, according to the present invention, on the conductive support, at least an intermediate layer and an organic photosensitive layer are laminated in this order, and the intermediate layer is subjected to thermosetting from the intermediate layer coating solution. There is provided a photoreceptor characterized in that it is a formed layer.

  Further, according to the present invention, the above-described photoconductor, a charging unit for charging the photoconductor, an exposure unit for exposing the charged photoconductor to form an electrostatic latent image, and the exposure unit are formed by exposure. Developing means for developing the electrostatic latent image to form a toner image, transfer means for transferring the toner image formed by development onto a recording medium, and fixing the transferred toner image on the recording medium The image forming apparatus includes at least a fixing unit that forms an image, a cleaning unit that removes and collects toner remaining on the photoconductor, and a neutralizing unit that neutralizes surface charge remaining on the photoconductor. An apparatus is provided.

  In addition, according to the present invention, a charging step for charging the above-described photoconductor, an exposure step for exposing the charged photoconductor to form an electrostatic latent image, and the electrostatic latent image formed by exposure Developing the toner image to form a toner image; transferring the toner image formed by development onto a recording medium; and fixing the transferred toner image onto the recording medium to form an image. There is provided an image forming method comprising: a fixing step, a cleaning step of removing and collecting toner remaining on the photoconductor, and a static elimination step of neutralizing surface charges remaining on the photoconductor.

  According to the present invention, a coating solution for an intermediate layer of a photoreceptor having an organic photosensitive layer, which uses water having the smallest environmental load as a solvent and is excellent in stability of the liquid physical properties over time in production, A photoreceptor having a formed intermediate layer and excellent in repetitive characteristics and environmental stability, and an image forming apparatus including the photoreceptor can be provided.

That is, according to the present invention, the use of an aqueous medium as a solvent for the intermediate layer coating solution not only eliminates the problem of air pollution due to VOC in the production process, but also uses conventional petroleum-based solvents. Since there is no problem of CO ₂ emission, it contributes to the prevention of global warming, and furthermore, there is no risk of fire, so the manufacturing system can be simplified and the manufacturing cost can be reduced.

  When an aqueous medium is used as a solvent for the intermediate layer coating solution, a resin having a high affinity for water must be used, and an intermediate layer formed using such an intermediate layer coating solution is used. The photoreceptor having the moisture resistance is inferior. 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 two or more active hydrogen-containing groups capable of reacting with an isocyanate group such as a hydroxyl group or an amide group, it 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.

By adding acicular titanium oxide fine particles to the intermediate layer coating liquid, a coating liquid excellent in dispersibility and storage stability can be obtained, and the intermediate layer can be produced without coating unevenness. Therefore, even if it is used repeatedly, a photoconductor with little residual potential accumulation and little photosensitivity deterioration can be produced.
In addition, since the acicular titanium oxide fine particles are elongated, the particles are easily brought into contact with each other and the contact area is increased. Therefore, the resistance value of the intermediate layer can be made lower than when granular titanium oxide fine particles are used. Therefore, even if the content of titanium oxide fine particles in the intermediate layer is the same, an intermediate layer with better sensitivity characteristics can be easily produced.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the photoconductor of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the photoconductor of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the photoconductor of the present invention. 1 is a schematic side view illustrating a configuration of an image forming apparatus of the present invention.

  The coating solution for the intermediate layer of the photoreceptor having the organic photosensitive layer of the present invention includes a blocked isocyanate compound, a resin having two or more active hydrogen-containing groups capable of reacting with an isocyanate group in the blocked isocyanate compound, and a needle shape Containing fine titanium oxide particles and an aqueous medium, the acicular titanium oxide fine particles are contained in a proportion of 30 to 90% by weight with respect to the total amount of the blocked isocyanate compound, the resin and the acicular titanium oxide fine particles, The acicular titanium oxide fine particles have a minor axis length of 0.5 μm or less, a major axis length of 10 μm or less, and an average aspect ratio of 1.5 or more and 300 or less.

(Block isocyanate compounds and resins)
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. An addition reaction is initiated with the resin having a group, 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; and amine compounds such as diphenylaniline, aniline, carbazole, ethyleneimine, and polyethyleneimine. 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 two or more active hydrogen-containing groups capable of reacting with the isocyanate group in the blocked isocyanate compound is preferably a hydroxyl group or an amide group capable of reacting with the isocyanate group in a high yield.
That is, it has two or more hydroxyl groups or amide groups to form a crosslinked structure with the blocked isocyanate as a curing agent (if it has only one functional group, it does not have a crosslinked structure but has a high molecular weight). Polyol resins and polyamide resins are preferred. Moreover, by controlling the structure of these polyol resins and polyamide resins, they can be dispersed and dissolved in water well, and these resins have high adhesion to the substrate. Image defects due to poor contact with the substrate when used as a photoreceptor 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
Product name: Burnock WE-300, WE-304 and WE-306, manufactured by Asia Industry Co., Ltd., product name: WAP-473-FD and WAP-548, manufactured by DIC Corporation;

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.

The blocked isocyanate compound is preferably contained in a proportion having an isocyanate group in a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group in the resin. That is, the isocyanate group of the blocked isocyanate compound is preferably present in the blocked isocyanate compound at a molar ratio of 0.5 to 1.5 with respect to the active hydrogen-containing group of the resin. The molar ratio is preferably 0.5 or more and 1.2 or less, more preferably 0.6 or more and 1.1 or less.
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.

(Acicular titanium oxide fine particles)
The acicular titanium oxide fine particles adjust the volume resistivity of the intermediate layer when it is used as a photoconductor, prevent the injection of carriers from the conductive support to the photoconductive layer, and the electrical characteristics of the photoconductor in various environments. It has a function to maintain.
“Needle” is an elongated and unbranched shape including a rod, column, or spindle, and the ratio of the major axis length (L) to the minor axis length (S) L / S That is, the aspect ratio is 1.5 or more. Therefore, it does not necessarily have an extremely long and narrow shape, and the tip need not be sharp and sharp.

Since the acicular titanium oxide fine particles are elongated, the particles are easy to contact with each other and the contact area becomes large. Therefore, the resistance value of the intermediate layer can be lowered and the resistance is lower than when granular titanium oxide fine particles are used. Easy to control.
Therefore, an intermediate layer having equivalent performance can be easily produced even when the content of titanium oxide fine particles in the intermediate layer is reduced as compared with the case of using granular titanium oxide fine particles. The ability to reduce the content of fine titanium oxide particles is useful for improving the film strength of the intermediate layer and the adhesion to the conductive support. In addition, since the contact between the titanium oxide fine particles is strong, even when used repeatedly for a long period of time, characteristic deterioration does not occur and excellent stability is obtained.
In addition, when the content of the titanium oxide fine particles is the same, the resistance value of the intermediate layer can be lowered by using the acicular titanium oxide fine particles rather than the granular shape, so that the thickness of the intermediate layer is increased accordingly. This is advantageous for obtaining a smooth intermediate layer surface without surface defects of the conductive support appearing on the intermediate layer surface.
Further, in the case of acicular titanium oxide fine particles, even if no surface treatment is applied, the intermediate layer coating solution exhibits very stable dispersibility, and the stability is maintained for a long time.

The acicular titanium oxide fine particles of the present invention have a minor axis length of 1 μm or less, preferably 0.5 μm or less, more preferably 0.2 μm or less, 100 μm or less, preferably 10 μm or less, more preferably 5 μm or less, And an average aspect ratio of 1.5 to 300, preferably 2 to 20 and more preferably 2 to 10.
When the minor axis length and major axis length of the acicular titanium oxide fine particles are not within the above ranges, it is difficult to obtain an intermediate layer coating solution excellent in dispersibility and storage stability.
Further, when the average aspect ratio of the acicular titanium oxide fine particles is smaller than the above range, the titanium oxide fine particles are difficult to contact with each other, and the contact area becomes small. The effect of becomes difficult to express. On the other hand, when the average aspect ratio of the acicular titanium oxide fine particles is larger than the above range, the contact area between the titanium oxide fine particles becomes large, and improvement in the effect as the acicular shape cannot be expected.

In the present invention, the minor axis length (S), the major axis length (L), and the average aspect ratio (A = L / S) can take the following values, for example.
S = 0.01 μm, L = 0.015 μm, A = 1.5
S = 0.01 μm, L = 3 μm, A = 300
S = 0.1 μm, L = 0.15 μm, A = 1.5
S = 0.2 μm, L = 0.3 μm, A = 1.5
S = 0.033 μm, L = 10 μm, A = 300
S = 0.5 μm, L = 0.75 μm, A = 1.5

S = 0.01 μm, L = 0.02 μm, A = 2
S = 0.01 μm, L = 0.2 μm, A = 20
S = 0.1 μm, L = 0.2 μm, A = 2
S = 0.1 μm, L = 2 μm, A = 20
S = 0.2 μm, L = 0.4 μm, A = 2
S = 0.2 μm, L = 4 μm, A = 20
S = 0.25 μm, L = 5 μm, A = 20
S = 2.5 μm, L = 5 μm, A = 2

  The particle size (short axis length and long axis length) and aspect ratio of the acicular titanium oxide fine particles can be measured by a known method such as a weight sedimentation method or a light transmission type particle size distribution measuring method, but is acicular. Therefore, it is preferable to observe with an electron microscope and measure directly.

The crystal form of the acicular titanium oxide fine particles may be any one of anatase type, rutile type and brookite type, or a mixture thereof.
The volume resistance value of the acicular titanium oxide fine particles is 10 ⁵ Ω · cm or more and 10 ¹⁰ Ω · cm or less as a volume resistance value (hereinafter also referred to as “powder resistance value”) in a green compact with a press pressure of 100 kg / cm ² . A high resistance in the range is preferred.
When the powder resistance value of the titanium oxide fine particles is less than 10 ⁵ Ω · cm, the resistance value as the intermediate layer is lowered, and it may not function as a charge blocking layer. For example, the powder resistance value of titanium oxide subjected to a conductive treatment such as an antimony-doped tin oxide conductive layer is 10 ⁰ to 10 ¹ Ω · cm, and the intermediate layer using this does not function as an electrical blocking layer, Since the chargeability as a photoreceptor characteristic deteriorates, it cannot be used.
Further, if the powder resistance value of the titanium oxide fine particles exceeds 10 ¹⁰ Ω · cm, it becomes equal to or more than the volume resistance value of the resin, and the resistance value of the intermediate layer using this becomes too high, and light irradiation Since carrier transport that is sometimes generated is suppressed and prevented, the residual potential increases, which is not preferable.

  Further, when the powder resistance value of the titanium oxide fine particles is in the above range and the surface thereof is coated with alumina, silica, or zirconia, the effect of preventing black spots and the dispersibility of the intermediate layer coating liquid can be improved. Can be described. Furthermore, when the surface treatment is performed with methyl hydrogen polysiloxane or the like, the effect of preventing black spots can be further expected.

The acicular titanium oxide fine particles can be produced by a known method such as neutralization of a titanium tetrachloride solution and thermal hydrolysis of a titanyl sulfate solution.
The short axis length, the long axis length, and the average aspect ratio of the acicular titanium oxide fine particles can be adjusted by selecting raw materials and setting production conditions.
The produced acicular titanium oxide fine particles are preferably purified by alkali treatment or acid treatment.

Commercially available products can be used as the acicular titanium oxide fine particles, for example,
Product name: FTL-100 (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13), FTL-200 (short axis length 0.21 μm, long axis length 2.86 μm) , Average aspect ratio 5), FTL-300 (short axis length 0.27 μm, long axis length 5.15 μm, average aspect ratio 19)

Product name: STR-60A (short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, alumina, silica surface treatment), STR-60N (short axis length 0.01 μm) , Long axis length 0.05μm, average aspect ratio 5)
Product name: MT-150A (short axis length 0.01 μm, long axis length 0.1 μm, average aspect ratio 10), MT-100S (short axis length 0.01 μm, long axis length 0.02 μm) Average aspect ratio 2)
Etc.

The acicular titanium oxide fine particles are contained in a proportion of 30 to 90% by weight with respect to the total amount of the crosslinked resin (block isocyanate compound and resin) and acicular titanium oxide fine particles. The lower limit is preferably 35% by weight, more preferably 50% by weight. Moreover, the upper limit becomes like this. Preferably it is 80 weight%, More preferably, it is 70 weight%.
When this ratio is less than 30% by weight, the change in sensitivity of the photoconductor during continuous printing in a low-temperature and low-humidity environment becomes large, and the change in image density may increase. Moreover, when this ratio exceeds 90 weight%, there exists a possibility that the storage stability of the coating liquid for intermediate | middle layers may worsen, and a titanium oxide particle may settle.

The intermediate layer coating solution of the present invention may contain other metal oxide fine particles as long as the effects of the present invention are not impaired.
Examples of the metal oxide particles include zinc oxide, tin oxide, aluminum oxide, silicon oxide, and zirconium oxide. Among these, zinc oxide fine particles are particularly preferable from the viewpoint of dispersibility and specific resistance.

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

  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 electron transport materials 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 dissolves or disperses a blocked isocyanate compound, a resin having two or more active hydrogen-containing groups capable of reacting with an isocyanate group, acicular titanium oxide fine particles, and optional additives in an aqueous medium. Can be prepared.
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.

  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.

  In the photoreceptor of the present invention, at least an intermediate layer and an organic photosensitive layer are laminated in this order on a conductive support, and the intermediate layer is subjected to thermal curing from the intermediate layer coating solution of the present invention. It is a formed layer.

Next, the photoreceptor of the present invention will be specifically described with reference to the drawings.
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.

[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 the coating method, an optimum method may be selected in consideration of the physical properties and productivity of the coating liquid, and the dip coating method, the blade coater method, and the 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 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 (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, and 4-nitrobenzaldehyde. 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 the optical sensitizer 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 Copolymer resins containing two or more of the structural units contained in (vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, acrylo Tolyl - 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 those to be erased by exposure are reduced, and there is a risk that image defects, particularly an image fogging called black spots where toner adheres to a white background and minute black spots are formed, will 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 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 forming 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 or the like in the case of a sheet, and a spray method or a vertical ring in the case of a drum. Method, dip coating method and the like.

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 the ability to accept and transport charges generated by the charge generation material and a binder 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 derivative, dibenzothiophene derivative, indenothiophene derivative, phenanthrenequinone derivative, indenopyridine derivative, thioxanthone derivative, benzo [c] cinnoline derivative, phenazine oxide derivative, 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, polycarbonate-based resins, polyarylate resins and polystyrene resins are photochemically stable, excellent in compatibility with charge transport materials, and have a volume resistance of 10 ¹³ Ω or more. It is preferable because it is excellent in electrical insulation and has excellent film forming properties and potential characteristics.

  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, 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 is formed by exposure, the photosensitive member of the present invention, a charging unit for charging the photosensitive member, an exposure unit for exposing the charged photosensitive member to form an electrostatic latent image, and exposure. Developing means for developing the electrostatic latent image to form a toner image; transfer means for transferring the toner image formed by development onto a recording medium; and transferring the transferred toner image onto the recording medium. The image forming apparatus includes at least a fixing unit that fixes and 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 image forming apparatus of the present invention will be described with reference to the drawings, but is not limited to the following description.
FIG. 4 is a schematic side view showing the configuration of the image forming apparatus of the present invention.
The image forming apparatus 20 in FIG. 4 includes a photoreceptor 21 of the present invention (for example, one of the photoreceptors in FIGS. 1 to 3), a charging unit (charger) 24, an exposure unit 28, and a developing unit ( Development unit) 25, transfer unit (transfer unit) 26, cleaning unit (cleaner) 27, fixing unit (fixing unit) 31, and charge eliminating unit (not shown, attached to cleaning unit 27). Composed. Reference numeral 30 indicates a transfer sheet (also referred to as “recording sheet”) as a recording medium.

  The photosensitive member 21 is rotatably supported by the main body of the image forming apparatus 20 (not shown), and is driven to rotate in the direction of the arrow 23 around the rotation axis 22 by a driving unit (not shown). The drive means includes, for example, an electric motor and a reduction gear, and transmits the driving force to a conductive support constituting the core of the photoconductor 21, thereby rotating the photoconductor 21 at a predetermined peripheral speed. . The charger 24, the exposure unit 28, the developing unit 25, the transfer unit 26, and the cleaner 27 are arranged in this order along the outer peripheral surface of the photoconductor 21 from the upstream side in the rotation direction of the photoconductor 21 indicated by the arrow 23. It is provided toward the side.

  The charger 24 is a charging unit that charges the outer peripheral surface of the photoconductor 21 to a predetermined potential. Specifically, for example, the charger 24 is realized by a contact-type charging roller 24a, a charging brush, or a charger wire such as a corotron or a scorotron. Reference numeral 24b shows a bias power source.

  The exposure unit 28 includes, for example, a semiconductor laser as a light source, and is charged by irradiating light 28 a such as a laser beam output from the light source between the charger 24 and the developing unit 25 of the photosensitive member 21. The outer peripheral surface of the photoconductor 21 is exposed according to image information. The light 28a is repeatedly scanned in the main scanning direction in the direction in which the rotation axis 22 of the photoconductor 21 extends, and accordingly, electrostatic latent images are sequentially formed on the surface of the photoconductor 21.

  The developing unit 25 is a developing unit that develops an electrostatic latent image formed on the surface of the photoreceptor 21 by exposure with a developer. The developing unit 25 is provided facing the photoreceptor 21, and applies toner to the outer peripheral surface of the photoreceptor 21. A developing roller 25a to be supplied and a casing 25b for supporting the developing roller 25a so as to be rotatable around a rotation axis parallel to the rotation axis 22 of the photosensitive member 21 and containing a developer containing toner in the internal space thereof.

  The transfer device 26 supplies a toner image, which is a visible image formed on the outer peripheral surface of the photoconductor 21 by development, between the photoconductor 21 and the transfer device 26 from the direction of the arrow 29 by a conveying unit (not shown). It is a transfer means for transferring onto the transfer paper 30 as a recording medium. The transfer unit 26 is, for example, a non-contact type transfer unit that includes a charging unit and transfers the toner image onto the transfer paper 30 by applying a charge having a polarity opposite to that of the toner to the transfer paper 30.

  The cleaner 27 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface of the photoconductor 21 after the transfer operation by the transfer device 26, and includes a cleaning blade 27 a that peels off toner remaining on the outer peripheral surface of the photoconductor 21, and a cleaning device. A recovery casing 27b for storing the toner separated by the blade 27a. The cleaner 27 is provided together with a charge eliminating lamp (not shown).

  Further, the image forming apparatus 20 is provided with a fixing device 31 as fixing means for fixing the transferred image on the downstream side where the transfer paper 30 that has passed between the photoreceptor 21 and the transfer device 26 is conveyed. . The fixing device 31 includes a heating roller 31a having a heating unit (not shown), and a pressure roller 31b that is provided to face the heating roller 31a and is pressed by the heating roller 31a to form a contact portion.

  The image forming operation by the image forming apparatus 20 is performed as follows. First, when the photosensitive member 21 is rotationally driven in the direction of the arrow 23 by the driving means, the photosensitive member 24 is provided by the charger 24 provided on the upstream side in the rotational direction of the photosensitive member 21 with respect to the image forming point of the light 28a by the exposure means 28. The surface of 21 is uniformly charged to a predetermined positive or negative potential.

  Next, light 28 a corresponding to image information is irradiated from the exposure unit 28 to the surface of the photoconductor 21. With this exposure, the surface charge of the portion irradiated with the light 28a is removed from the photosensitive member 21, and a difference occurs between the surface potential of the portion irradiated with the light 28a and the surface potential of the portion not irradiated with the light 28a. An electrostatic latent image is formed.

  Next, toner is supplied to the surface of the photosensitive member 21 on which the electrostatic latent image is formed from a developing unit 25 provided on the downstream side in the rotation direction of the photosensitive member 21 with respect to the image forming point of the light 28a by the exposure unit 28. The electrostatic latent image is developed to form a toner image.

  In synchronization with the exposure of the photosensitive member 21, the transfer paper 30 is supplied between the photosensitive member 21 and the transfer device 26. The transfer device 26 applies a charge having a polarity opposite to that of the toner to the supplied transfer paper 30, and the toner image formed on the surface of the photoreceptor 21 is transferred onto the transfer paper 30.

  Next, the transfer paper 30 onto which the toner image has been transferred is conveyed to the fixing device 31 by the conveying means, and is heated and pressurized when passing through the contact portion between the heating roller 31a and the pressure roller 31b of the fixing device 31. The toner image is fixed on the transfer paper 30 and becomes a robust image. The transfer paper 30 on which the image is formed in this way is discharged to the outside of the image forming apparatus 20 by the conveying means.

  On the other hand, the toner remaining on the surface of the photoconductor 21 even after the transfer of the toner image by the transfer unit 26 is separated from the surface of the photoconductor 21 by the cleaner 27 and collected. The charge on the surface of the photoconductor 21 from which the toner has been removed in this manner is removed by the light from the static elimination lamp, and the electrostatic latent image on the surface of the photoconductor 21 disappears. Thereafter, the photosensitive member 21 is further driven to rotate, and a series of operations starting from charging is repeated to continuously form images.

  As described above, the image forming method of the present invention is formed by a charging step of charging the photoconductor of the present invention, an exposure step of exposing the charged photoconductor to form an electrostatic latent image, and exposure. A developing step for developing the electrostatic latent image to form a toner image, a transferring step for transferring the toner image formed by the development onto a recording medium, and the transferred toner image on the recording medium. The image forming apparatus includes: a fixing process for fixing and forming an image; a cleaning process for removing and collecting toner remaining on the photoconductor; and a static elimination process for neutralizing surface charges remaining on the photoconductor.

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

(Production Example 1)
Colloidal amorphous titanium hydroxide by neutralizing with an aqueous solution of sodium hydroxide (concentration 200 g / L) while maintaining an aqueous solution of titanium tetrachloride having a concentration of 200 g / L (manufactured by Osaka Titanium Technologies Co., Ltd.) at a temperature of 30 ° C. Was precipitated. The obtained colloidal amorphous titanium hydroxide was aged at 70 ° C. for 5 hours and then dried at 120 ° C. for 2 hours to obtain fine-particle hydrated titanium dioxide.
Next, 4 parts by weight of the fine water-containing titanium dioxide obtained as TiO ₂ , 4 parts by weight of sodium chloride and 1 part by weight of sodium hydrogen phosphate (Na ₂ HPO ₄ .2H ₂ O) were uniformly mixed to obtain a magnetic crucible. And baked in an electric furnace set at a temperature of 900 ° C. for 5 hours. The obtained fired product was put into water and boiled for 1 hour, followed by filtration and washing with water to remove soluble salts to obtain acicular titanium oxide fine particles.

(Alkali treatment)
The obtained acicular titanium oxide fine particles were subjected to alkali treatment.
That is, acicular titanium oxide was poured into water to obtain a suspension having a concentration of about 200 g / L, and an aqueous sodium hydroxide solution (concentration 200 g / L) was added to adjust the pH of the suspension to 13. . Next, the suspension was heated to 90 ° C. and stirred for 2 hours, and an aqueous hydrochloric acid solution (concentration 100 g / L) was further added to adjust the pH of the suspension to 7. Thereafter, the suspension was filtered, and the filter cake was washed with water until the specific resistance of the filtrate reached 50 μS.

(Acid treatment)
Subsequently, the obtained acicular titanium oxide fine particle filter cake was subjected to acid treatment.
That is, the filter cake was put into water again to obtain a suspension having a concentration of about 200 g / L, and an aqueous hydrochloric acid solution (concentration 100 g / L) was added to adjust the pH of the suspension to 1. The suspension was then heated to a temperature of 90 ° C. and stirred for 2 hours. Thereafter, the suspension was filtered, and the filter cake was washed with water until the specific resistance of the filtrate reached 50 μS.
Next, the obtained filter cake was dried overnight at a temperature of 120 ° C. and baked in an electric furnace set at a temperature of 600 ° C. for 1 hour to obtain a minor axis length of 0.01 μm, a major axis length of 2.5 μm, and an average aspect ratio of 250. 100 g of acicular titanium oxide fine particles A (fine particles A) were obtained.

(Comparative Production Example 1)
A titanium sulfate solution having a concentration of 200 g / L was heated to a temperature of 30 ° C. to thermally hydrolyze the titanium sulfate, and the produced titanium dioxide hydrate was filtered. The obtained titanium dioxide hydrate filter cake was washed with water, aqueous ammonia (concentration 200 g / L) was added thereto to neutralize the sulfuric acid content, and the pH of the suspension was adjusted to 7. The obtained hydrate suspension was filtered, and the filter cake was washed with water until the H ₂ SO ₄ content in the hydrate was 0.5% by weight or less. The obtained filter cake was dried at a temperature of 70 ° C. for 5 hours and then at a temperature of 120 ° C. for 2 hours to obtain fine-particle hydrated titanium dioxide.
Subsequently, with respect to the obtained fine water-containing titanium dioxide, 1.2% by weight of ZnO, 0.55% by weight of K ₂ O and 0.5% by weight of P ₂ O _{5 based} on the TiO ₂ equivalent amount of the titanium content. % Addition, followed by firing at 900 ° C. for 3 hours. Thereafter, the fired product was put into water, boiled for 1 hour, filtered and washed to remove soluble salts. Thus, acicular titanium oxide fine particles were obtained.
Subsequently, in the same manner as in Production Example 1, the obtained acicular titanium oxide fine particles were subjected to alkali treatment and acid treatment, and the obtained filter cake was dried at a temperature of 120 ° C. for a whole day and night, and an electric furnace set at a temperature of 600 ° C. Was fired for 1 hour to obtain 100 g of acicular titanium oxide fine particles B (fine particles B) having a minor axis length of 0.3 μm, a major axis length of 11 μm, and an average aspect ratio of 37.

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, polyvinyl acetal of an aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3) and 6.3 parts by weight of a block isocyanate compound (solid content: 70%, NCO content: 7.9%, manufactured by Asahi Kasei Chemicals Corporation, product name: X1248, 9.6 parts by weight, acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13) , Ishihara Sangyo Co., Ltd., product name: FTL-100) 12 parts by weight and antifoaming agent (polyether antifoam, manufactured by San Nopco, product name: SN deformer 777) 0.02 part by weight of water In addition to 72 parts by weight, an intermediate layer coating solution (1 kg in total) was prepared by dispersing for 6 hours using a paint shaker.
The isocyanate group of the blocked isocyanate compound is in a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are based on the cross-linked resin (total of the blocked isocyanate compound and the resin: R). The weight ratio (P / R) was 6/4.
The obtained coating solution for forming an intermediate layer is filled in a coating tank, dipped in a conductive support, and then pulled up. The obtained coating film is dried and cured at a temperature of 150 ° C. for 30 minutes to obtain a film thickness of 1.0 μm. An intermediate layer was formed.

  Next, 2 parts by weight of Y-type oxotitanium phthalocyanine (manufactured by Sanyo Dye Co., Ltd.) as a charge generating substance, and polyvinyl butyral resin (product name: ESREC B BM-S, produced by Sekisui Chemical Co., Ltd.) as a binder resin 1 part by weight and 97 parts by weight of methyl ethyl ketone as an organic solvent were mixed and dispersed using a paint shaker to prepare a charge generation layer coating solution (total amount 1 kg). This charge generation layer coating solution was applied on the previously formed intermediate layer by the same dip coating method as that for the intermediate layer, and naturally dried to form a charge generation layer having a thickness of 0.4 μm.

Next, 10 parts by weight of a triphenylamine-butadiene derivative represented by the following structural formula (1) as a charge transport material and a polycarbonate resin (product name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) as a binder resin 18 parts by weight, 0.5 part by weight of 2,6-di-t-butyl-4-methylphenol as an antioxidant, and dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., product name) as a leveling agent : KF-96) 0.004 part by weight was dissolved in 110 parts by weight of tetrahydrofuran (THF) as an organic solvent to prepare a charge transport layer coating solution (total amount: 1 kg). This charge transport layer coating solution is applied onto the previously formed charge generation layer by the same dip coating method as that for the intermediate layer, and dried at a temperature of 130 ° C. for 1 hour to form a charge transport layer having a thickness of 23 μm. did.
The photoreceptor of Example 1 was produced as described above.

(Example 2)
A photoconductor of Example 2 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, surface untreated, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60N): 14 parts by weight Resin , 4.7 parts by weight of polyvinyl acetal (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3),
Block isocyanate compound (solid content: 70%, NCO content: 7.9%, manufactured by Asahi Kasei Chemicals Co., Ltd., developed product name: X1248) 7.2 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco Co., Ltd.) Product name: SN deformer 777): 0.02 part by weight Water: 74 part by weight The isocyanate group of the blocked isocyanate compound is in a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and acicular titanium oxide fine particles ( P) was a weight ratio (P / R) of 7/3 to the cross-linked resin (total of blocked isocyanate compound and resin: R).

(Example 3)
A photoconductor of 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.
Acicular titanium oxide fine particles (short axis length 0.27 μm, long axis length 5.15 μm, average aspect ratio 19, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-300): 10 parts by weight Polyvinyl acetal (solid) Minute: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 7.8 parts by weight Block isocyanate compound (solid content: 70%, NCO content: 7.9%, Asahi Kasei Chemicals Co., Ltd., developed product name: X1248): 12 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 70 parts by weight Block isocyanate The isocyanate group of the compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are crosslinked resin (block isocyanate). DOO compounds and resins Total: was 5/5 weight ratio with respect to R) (P / R).

Example 4
A photoconductor of Example 4 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles A prepared in Production Example 1 (short axis length 0.01 μm, long axis length 2.5 μm, average aspect ratio 250): 6 parts by weight Polyvinyl acetal (solid content: 20%, OH) as a resin Value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3: 11 parts by weight Block isocyanate compound ((solid content: 70%, NCO content: 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 16.9 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 66 parts by weight The isocyanate group of the blocked isocyanate compound is At a molar ratio of 1.0 to the active hydrogen-containing group of the resin, the acicular titanium oxide fine particles (P) are crosslinked resin (a combination of a blocked isocyanate compound and a resin). : A weight ratio with respect to R) 3/7 (P / R).

(Example 5)
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, 14.3 parts by weight of a polyether polyol (solid content: 35%, OH value: 60, manufactured by Nippon Polyurethane Industry Co., Ltd., product name: AQD-473) and a blocked isocyanate compound (solid content: 42%, containing NCO) Rate: 7.5%, Nippon Polyurethane Industry Co., Ltd., developed product name: BWD-102) 7.1 parts by weight, acicular titanium oxide fine particles (short axis length 0.21 μm, long axis length 2.86 μm, average aspect ratio) 14 parts by weight, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-200) and 0.5 parts by weight of antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 470) In addition to 67 parts by weight of water, a coating shaker was used for 6 hours of dispersion treatment to prepare an intermediate layer coating solution (total amount: 1 kg).
The isocyanate group of the blocked isocyanate compound is in a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are based on the cross-linked resin (total of the blocked isocyanate compound and the resin: R). The weight ratio (P / R) was 6/4.
The obtained coating solution for forming an intermediate layer is filled in a coating tank, dipped in a conductive support, and then pulled up. The obtained coating film is dried and cured at a temperature of 150 ° C. for 30 minutes to obtain a film thickness of 1.0 μm. An intermediate layer was formed.
Next, in the same manner as in Example 1, a charge generation layer and a charge transport layer were formed to produce a photoreceptor of Example 5.

(Example 6)
A photoconductor of Example 6 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.01 μm, long axis length 0.05 μm, average aspect ratio 5, surface untreated, manufactured by Sakai Chemical Industry Co., Ltd., product name: STR-60N): 12 parts by weight Resin , Aqueous polyacrylic polyol (solid content: 45%, OH value: 80, manufactured by DIC Corporation, product name: Burnock WE-300): 8.4 parts by weight Block isocyanate compound (solid content: 40%, NCO content: 5.4%, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd., product name: Takenate WB-920): 10.5 parts by weight Antifoaming agent (polyether antifoaming agent, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 69 parts by weight The isocyanate groups of the blocked isocyanate compound are in a molar ratio of 1.0 with respect to the active hydrogen-containing groups of the resin. Child (P) is, (sum of blocked isocyanate compound and a resin: R) crosslinked resin had a weight ratio of 6/4 with respect to (P / R). The weight ratio (P / R) was 6/4.

(Example 7)
A photoconductor of Example 7 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.21 μm, long axis length 2.86 μm, average aspect ratio 14, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-200): 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: 0.9 parts by weight Block isocyanate compound (solid content: 37.5%, NCO content: 3.7%, Sumika Bayer) Urethane Co., Ltd., product name: Bihijoule VPLS2310): 18.8 parts by weight Antifoaming agent (polyether foam suppressor, San Nopco Co., Ltd., product name: SN deformer 777): 0.02 parts by weight Water: 68 weights Part The isocyanate group of the blocked isocyanate compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) Resin (blocked isocyanate compound and resin Total: R) had a weight ratio of 6/4 with respect to (P / R).

(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.
Acicular titanium oxide fine particles (short axis length 0.01 μm, long axis length 0.1 μm, average aspect ratio 10, manufactured by Teika Co., Ltd., product name: MT-150A): 12 parts by weight Water-soluble nylon (solid) Minute: 20%, NH content: 10%, manufactured by Nagase ChemteX Corporation, product name: Toresin FS-350): 6.0 parts by weight Block isocyanate compound (solid content: 39.5%, NCO content: 4 .4%, manufactured by Sumika Bayer Urethane Co., Ltd., developed product name: BL-5140): 17.2 parts by weight Antifoaming agent (polyether antifoaming agent, manufactured by San Nopco, product name: SN deformer 777): 0 0.02 part by weight Water: 65 parts by weight The isocyanate group of the blocked isocyanate compound is 1.0 molar ratio to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are: Bridges resin (blocked isocyanate compound and resin Total: R) had a weight ratio of 6/4 with respect to (P / R).

Example 9
A photoconductor of Example 9 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.01 μm, long axis length 0.02 μm, average aspect ratio 2, manufactured by Teika Co., Ltd., product name: MT100S): 12 parts by weight Polyvinyl acetal (solid content: 20) as a resin %, OH value: 960, manufactured by Sekisui Chemical Co., Ltd., product name: KW-1): 2.3 parts by weight Block isocyanate compound (solid content: 70%, NCO content: 4.3%, Asahi Kasei Chemicals Corporation Made by company, developed product name: X1458): 10.8 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 75 parts by weight Block isocyanate The isocyanate group of the compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are crosslinked resin (block isocyanate). DOO compounds and resins Total: was a weight ratio of 6/4 with respect to R) (P / R).

(Example 10)
A photoconductor of Example 10 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particle acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 8 parts by weight as resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 9.4 parts by weight Block isocyanate compound (solid content: 70%, NCO content) : 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 14.5 parts by weight Antifoaming agent (Polyether antifoaming agent, manufactured by San Nopco, product name: SN deformer 777): 0.02 Part by weight Water: 68 parts by weight The isocyanate group of the blocked isocyanate compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) (Sum of blocked isocyanate compound and a resin: R) crosslinked resin had a weight ratio of 4/6 with respect to (P / R).

(Example 11)
A photoconductor of Example 11 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles Acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 16 parts by weight As resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 3.1 parts by weight Block isocyanate compound (solid content: 70%, NCO content) : 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 4.8 parts by weight Antifoaming agent (Polyether antifoaming agent, manufactured by San Nopco, product name: SN deformer 777): 0.02 Part by weight Water: 76 parts by weight The isocyanate group of the blocked isocyanate compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) (Sum of blocked isocyanate compound and a resin: R) crosslinked resin had a weight ratio of 8/2 with respect to (P / R).

Example 12
A photoconductor of Example 12 was produced in the same manner as Example 1 except that the thickness of the intermediate layer was 5 μm.

(Example 13)
A photoconductor of Example 13 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles Acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 12 parts by weight As resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 9.5 parts by weight Block isocyanate compound (solid content: 70%, NCO content) : 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 8.7 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 Part by weight Water: 70 parts by weight The isocyanate group of the blocked isocyanate compound is in a molar ratio of 0.6 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are (Total blocked isocyanate compound and a resin: R) crosslinked resin had a weight ratio of 6/4 with respect to (P / R).

(Example 14)
A photoconductor of Example 14 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared using the following components.
Acicular titanium oxide fine particles Acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 12 parts by weight As resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 5 parts by weight Block isocyanate compound (solid content: 70%, NCO content: 7 .9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 10 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 73 parts by weight The isocyanate group of the blocked isocyanate compound has a molar ratio of 1.3 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are crosslinked. Fat (blocked isocyanate compound and resin Total: R) had a weight ratio of 6/4 with respect to (P / R).

(Example 15)
A photoconductor of Example 15 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared using the following components.
Acicular titanium oxide fine particles Acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 12 parts by weight As resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 13 parts by weight Block isocyanate compound (solid content: 70%, NCO content: 7 .9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 7.8 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 68 parts by weight The isocyanate group of the blocked isocyanate compound has a molar ratio of 0.4 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are: Bridges resin (blocked isocyanate compound and resin Total: R) had a weight ratio of 6/4 with respect to (P / R).

(Example 16)
A photoconductor of Example 16 was produced in the same manner as Example 1 except that the intermediate layer coating solution was prepared using the following components.
Acicular titanium oxide fine particles Acicular titanium oxide (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 12 parts by weight As resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 4.1 parts by weight Block isocyanate compound (solid content: 70%, NCO content) : 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 10.2 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0.02 Part by weight Water: 74 parts by weight The isocyanate group of the blocked isocyanate compound is in a molar ratio of 1.6 to the active hydrogen-containing group of the resin, and acicular titanium oxide fine particles (P) (Sum of blocked isocyanate compound and a resin: R) crosslinked resin had a weight ratio of 6/4 with respect to (P / R).

(Comparative Example 1)
A photoreceptor of Comparative Example 1 was produced in the same manner as in Example 1 except that the intermediate layer coating solution (aqueous, uncured) was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 6 parts by weight Polyvinyl acetal (solid) Minute: 20%, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 20 parts by weight Water: 64 parts by weight

(Comparative Example 2)
A photoconductor of Comparative Example 2 was produced in the same manner as Example 1 except that the intermediate layer coating solution (organic solvent type, no curing) was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.13 μm, long axis length 1.68 μm, average aspect ratio 13, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): copolymer nylon (6 parts by weight resin) Toray Industries, Inc., product name: Amilan CM8000): 4 parts by weight

(Comparative Example 3)
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.
Acicular titanium oxide fine particles Granular titanium oxide fine particles (average primary particle size: 250 nm, manufactured by Ishihara Sangyo Co., Ltd., product name: CR-EL): 16 parts by weight Polyvinyl acetal of aqueous polyol as a resin (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 3.1 parts by weight Block isocyanate compound (solid content: 70%, NCO content: 7.9%, manufactured by Asahi Kasei Chemicals Corporation, Development name: X1248): 4.8 parts by weight Antifoaming agent (polyether antifoam, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 76 parts by weight Isocyanates of blocked isocyanate compounds The group has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are crosslinked resin (block isocyanate). DOO compounds and resins Total: was a weight ratio of 8/2 with respect to R) (P / R).

(Comparative Example 4)
A photoconductor of Comparative Example 4 was produced in the same manner as in Example 1 except that the intermediate layer coating solution was prepared with the following components.
Acicular titanium oxide fine particles (short axis length 0.05 to 0.1 μm, long axis length 3 to 6 μm, average aspect ratio 30 to 120, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 4 parts by weight as resin Polyvinyl acetal of aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 13 parts by weight Block isocyanate compound (solid content: 70%, NCO content) : 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 19 parts by weight Antifoaming agent (polyether antifoaming agent, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 64 parts by weight The isocyanate group of the blocked isocyanate compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) Resin (blocked isocyanate compound and resin Total: R) had a weight ratio of 2/8 with respect to (P / R).

(Comparative Example 5)
An intermediate layer coating solution was prepared in the same manner as in Example 1 except that the following components were used. However, soon after dispersion, titanium oxide started to precipitate, and a photoconductor could not be produced.
Acicular titanium oxide fine particles (short axis length 0.05 to 0.1 μm, long axis length 3 to 6 μm, average aspect ratio 30 to 120, manufactured by Ishihara Sangyo Co., Ltd., product name: FTL-100): 19 parts by weight Resin Polyvinyl acetal of an aqueous polyol (solid content: 20%, OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 0.78 parts by weight Block isocyanate compound (solid content: 70%, NCO Content rate: 7.9%, manufactured by Asahi Kasei Chemicals Corporation, developed product name: X1248): 1.2 parts by weight Antifoaming agent (polyether foam inhibitor, manufactured by San Nopco, product name: SN deformer 777): 0 0.02 part by weight Water: 79 parts by weight The isocyanate group of the blocked isocyanate compound has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and acicular titanium oxide fine particles (P It is (the sum of the blocked isocyanate compound and resin: R) crosslinked resin was 9.5 / 0.5 weight ratio with respect to (P / R).

(Comparative Example 6)
An intermediate layer coating solution was prepared in the same manner as in Example 1 except that the following components were used. However, soon after dispersion, titanium oxide started to precipitate, and a photoconductor could not be produced.
Acicular titanium oxide fine particles B prepared in Comparative Production Example 1 (short axis length 0.3 μm, long axis length 11 μm, average aspect ratio 37): 8 parts by weight Polyvinyl acetal of aqueous polyol as resin (solid content: 20%) , OH value: 570, manufactured by Sekisui Chemical Co., Ltd., product name: KW-3): 9.4 parts by weight Block isocyanate compound (solid content: 70%, NCO content: 7.9%, manufactured by Asahi Kasei Chemicals Corporation) , Developed product name: X1248): 14.5 parts by weight Antifoaming agent (polyether antifoam, manufactured by San Nopco, product name: SN deformer 777): 0.02 parts by weight Water: 68 parts by weight The isocyanate group has a molar ratio of 1.0 to the active hydrogen-containing group of the resin, and the acicular titanium oxide fine particles (P) are crosslinked resin (block isocyanate compound). And the total of the resin: a weight ratio of 40/60 with respect to R) (P / R).
Table 1 shows the materials and weight ratio P / R used in Examples 8 to 23 and Comparative Examples 6 to 11.

(Evaluation)
(1) Electrical characteristics and environmental stability of photoconductors The photoconductors obtained in Examples 1 to 16 and Comparative Examples 1 to 4 were developed so that the surface potential of the photoconductor at the developing portion in the image forming process can be measured. Mounted on a test digital copying machine (manufactured by Sharp Corporation, model: AR-625S) provided with a surface potentiometer (manufactured by Trek Japan Co., Ltd., model: model 344) instead of the device. Characteristics and environmental stability were evaluated.
First, in order to check the charging property, the surface potential VL of the black background portion when exposed in the dark excluding the exposure process in a low temperature / low humidity (L / L) environment having a temperature of 5 ° C. and a relative humidity of 10% ( V) was measured immediately after the first and 1000th copies, and the difference between them was determined as potential fluctuation ΔVL _1-1000 (V). In addition, image density evaluation was performed immediately after the first and 1000th copies in the L / L environment. Similarly, the first sheet in a room temperature / low humidity (N / L) environment at a temperature of 25 ° C. and a relative humidity of 5% and in a room temperature / high humidity (N / H) environment of a temperature of 25 ° C. and a relative humidity of 35%. The surface potential VL (V) immediately after copying was measured, and the difference in VL between the two environments was determined as the potential fluctuation ΔVL (V). It can be evaluated that the smaller the potential fluctuation ΔVL, the better the environmental stability (environmental characteristics).
The obtained results are shown in Table 2.

(2) Pot life (VL fluctuation of coating liquid after being left for 3 months)
The intermediate layer coating solutions prepared in Examples 1 to 16 and Comparative Examples 1 to 4 were stored for 3 months in a normal temperature and normal humidity (temperature 20 ° C., humidity 50%) environment, and then a photoconductor was prepared in the same manner. Then, the surface potential VL (V) immediately after the first copy in the L / L environment was measured for the obtained photoreceptor, and the surface potential VL (V immediately after the first copy in (1) above was measured. ) Was determined as a potential fluctuation ΔVLP (V) serving as a pot life index.
The obtained results are shown in Table 2.

(3) Curing degree of intermediate layer 0.5 g of the intermediate layer coating solution prepared in Examples 1 to 16 and Comparative Examples 1 to 4 was applied to the surface of a glass plate having dimensions of 50 mm × 50 mm × thickness 1.5 mm, respectively. The sample was obtained by uniformly coating by the wire bar method and drying and curing the obtained coating film at a temperature of 150 ° C. for 30 minutes.
The obtained samples were immersed in acetone at a temperature of 20 ° C. for 1 day while stirring at a rotation speed of 30 rpm, and the degree of cure (%) was obtained from the weight difference between the initial weight before immersion and the weight after immersion according to the following formula. It was.
Curing degree (%) = (1− (initial weight−weight after immersion) / (initial weight)) × 100
Moreover, (2) The intermediate layer coating solution prepared in the pot life study and stored for 3 months was also prepared in the same manner as described above, and the degree of cure (%) was determined.
The obtained results are shown in Table 2.

(4) Image Density For the photoconductors obtained in Examples 1 to 16 and Comparative Examples 1 to 4, the reflection density of the black solid image immediately after the first and 1000th copies in the L / L environment was measured as Macbeth. Measurement was performed using a reflection densitometer (manufactured by Sakata Inx Corporation, model: Machbes RD918), and image density was determined according to the following criteria.
(Evaluation criteria)
◎ Good when the difference in image density between the 1st sheet and 1000th sheet is 0.3 or less. ○ The difference in image density between the 1st sheet and 1000th sheet is 0.3 or more and less than 0.6. X: The difference in image density between the first sheet and the 1000th sheet is not less than 0.6 and the image cannot be used. Table 2 shows the obtained results.
In Comparative Examples 5 and 6, since the titanium oxide fine particles in the intermediate layer coating solution settled and a photoconductor using the same could not be produced, the above (1) to (4) were not evaluated. It was.

The following can be seen from the results in Table 2.
(1) The photoreceptors of the present invention (Examples 1 to 16) are polyamide-based binders that are widely used in current photoreceptors, even though water is used as the solvent for the intermediate layer coating solution. Compared to organic solvent-based photoreceptors using resin (Comparative Example 2), they have equivalent or better performance in all of electric characteristics, environmental stability, fatigue characteristics, coating liquid stability (pot life) and image characteristics. is doing.

(2) The photoconductor of the present invention (Example 1) having an intermediate layer containing acicular titanium oxide fine particles is L / L more than the photoconductor (Comparative Example 3) having an intermediate layer containing granular titanium oxide fine particles. Sensitivity change during continuous printing in the environment is small. This is presumably because the acicular titanium oxide fine particles have a long and narrow shape, and thus the effect of suppressing the sensitivity change in continuous printing is larger than that of the granular titanium oxide fine particles. In addition, since the intermediate layer coating liquid containing acicular titanium oxide fine particles has sufficient sensitivity even when the P / R is lower than the intermediate layer coating liquid containing granular titanium oxide fine particles, P Since the / R is low, the coating solution stability is good.

(3) Photoreceptor of the present invention in which acicular titanium oxide fine particles are 30 to 90% by weight based on the total amount of cross-linked resin (block isocyanate compound and resin) and acicular titanium oxide fine particles (Examples 1 to 14) Can obtain the sensitivity in continuous printing under a good L / L environment and good coating solution stability of the intermediate layer coating solution. On the other hand, when the blending ratio of the acicular titanium oxide fine particles is less than 30% by weight (Comparative Example 4), the sensitivity in continuous printing under the L / L environment is significantly deteriorated, and the image density is also deteriorated. In the case of 90% by weight or more (Comparative Example 5), the storage stability of the intermediate layer coating solution is deteriorated and titanium oxide is precipitated.

(4) When the amount of the blocked isocyanate compound relative to the resin is less than 0.5 molar ratio, that is, when there are few NCO groups relative to the OH groups in the resin (Example 13), the degree of cure decreases, The proportion of OH groups (hydrophilic groups) in the film increases, and the environmental stability of the photoreceptor decreases.
On the other hand, when the amount of the blocked isocyanate compound relative to the resin is greater than 1.5 molar ratio, that is, when there are many NCO groups relative to the OH groups in the resin, the environmental characteristics are not significantly reduced, but the fatigue characteristics are reduced (moles). See Example 16 with a ratio of 1.6). This is presumably because an excess of isocyanate groups reacted with moisture to generate impurities that affect electrical characteristics.

(5) A photoreceptor (Comparative Example 2) using an intermediate layer coating solution containing an uncured aqueous binder resin has extremely deteriorated environmental characteristics.

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

20 Image forming apparatus 22 Rotating axis 23, 29 Arrow 24 Charging means (charger)
24a Charging roller 24b Bias power supply 25 Developing means (developer)
25a Developing roller 25b Casing 26 Transfer means (transfer device)
27 Cleaning means (cleaner)
27a Cleaning blade 27b Recovery casing 28 Exposure means 28a Light 30 Recording medium (transfer paper or recording paper)
31 Fixing means (fixing device)
31a Heating roller 31b Pressure roller

Claims (9)

A blocked isocyanate compound, a resin having two or more active hydrogen-containing groups capable of reacting with an isocyanate group in the blocked isocyanate compound, acicular titanium oxide fine particles, and an aqueous medium,
The acicular titanium oxide fine particles are contained in a proportion of 30 to 90% by weight with respect to the total amount of the blocked isocyanate compound, the resin and the acicular titanium oxide fine particles,
An electrophotographic photoreceptor having an organic photosensitive layer, wherein the acicular titanium oxide fine particles have a minor axis length of 0.5 μm or less, a major axis length of 10 μm or less, and an average aspect ratio of 1.5 or more and 300 or less. An intermediate layer coating solution.   The intermediate layer coating solution according to claim 1, wherein the acicular titanium oxide fine particles have a minor axis length of 0.2 μm or less, a major axis length of 5 μm or less, and an average aspect ratio of 2 or more and 20 or less.   The intermediate layer coating solution according to claim 1 or 2, wherein the active hydrogen-containing group is a hydroxyl group or an amide group.   The intermediate layer coating solution according to any one of claims 1 to 3, wherein the blocked isocyanate compound has a structure in which hexamethylene diisocyanate or isophorone diisocyanate is blocked with an oxime or lactam blocking agent.   5. The resin according to claim 1, wherein the resin is selected from a polyether polyol resin, a polyester polyol resin, a polyacryl polyol resin, a polyvinyl alcohol resin, a polyvinyl acetal resin, cellulose, and a polyamide resin. The coating liquid for intermediate | middle layers as described in 2.   The said block isocyanate compound is contained in the ratio which has the said isocyanate group by the molar ratio of 0.5-1.5 with respect to the said active hydrogen containing group in the said resin. The coating liquid for intermediate | middle layers as described in 2. On the conductive support, at least an intermediate layer and an organic photosensitive layer are laminated in this order,
An electrophotographic photoreceptor, wherein the intermediate layer is a layer formed by thermal curing from the intermediate layer coating solution according to claim 1.   8. The electrophotographic photosensitive member according to claim 7, a charging unit for charging the electrophotographic photosensitive member, an exposure unit for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image, and formed by exposure. Developing means for developing the electrostatic latent image formed thereon to form a toner image; transfer means for transferring the toner image formed by development onto a recording medium; and transferring the transferred toner image onto the recording medium At least a fixing unit that forms an image by fixing the toner, a cleaning unit that removes and collects toner remaining on the electrophotographic photosensitive member, and a neutralizing unit that neutralizes surface charges remaining on the electrophotographic photosensitive member. An image forming apparatus.   8. A charging step for charging the electrophotographic photosensitive member according to claim 7, an exposure step for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image, and the electrostatic latent image formed by exposure. Developing the toner image to form a toner image; transferring the toner image formed by development onto a recording medium; and fixing the transferred toner image onto the recording medium to form an image. An image forming method comprising: a fixing step for removing; a cleaning step for removing and collecting toner remaining on the electrophotographic photosensitive member; and a static eliminating step for neutralizing surface charges remaining on the electrophotographic photosensitive member.

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