Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

This invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member.

Photosensitive layers of electrophotographic photosensitive members used in electrophotographic apparatus are known to include a single-layer type photosensitive layer and a multi-layer type photosensitive layer. The electrophotographic photosensitive members are also roughly grouped into a positive-chargeable electrophotographic photosensitive member and a negative-chargeable electrophotographic photosensitive member, depending on the polarity of electric charges produced when their surfaces are electrostatically charged. Of these, a negative-chargeable electrophotographic photosensitive member having a multi-layer type photosensitive layer is commonly used.

The negative-chargeable electrophotographic photosensitive member having a multi-layer type photosensitive layer commonly has on a support a charge generation layer containing a charge-generating material such as an azo pigment or a phthalocyanine pigment and a hole transport layer containing a hole-transporting material such as a hydrazone compound, a triarylamine compound or a stilbene compound which are in this order from the support side.

However, where the photosensitive layer (in particular, the charge generation layer in the case of the multi-layer type photosensitive layer) is directly provided on the support, it may often come about that the photosensitive layer (charge generation layer) comes to peel or that any defects (shape-related defects such as scratches or material-related defects such as impurities) of the surface of the support are directly reflected on images to cause problems such as black dot-like image defects and blank areas.

To resolve these problems, most electrophotographic photosensitive members are provided with a layer called an intermediate layer (also called a subbing layer) between the photosensitive layer and the support.

However, such electrophotographic photosensitive members are seen in some cases to become poor in electrophotographic performance as being presumably due to the intermediate layer. Accordingly, it has conventionally been attempted to improve properties of the intermediate layer by using various means, e.g., by incorporating the intermediate layer of the negative-chargeable electrophotographic photosensitive member with an electron-transporting material to make the intermediate layer into an electron-transport layer (Japanese Patent Applications Laid-open No. 2001-83726 and No. 2003-345044).

In recent years, there is a steady increase in a demand for the quality of electrophotographic images. For example, the tolerance limit for positive ghost has become remarkably severer. The positive ghost is a phenomenon that, where areas exposed to light appear as halftone images on the next-time round of an electrophotographic photosensitive member in the course of formation of images on a sheet, only the areas exposed to light come high in image density.

In this regard, it has not been the case that the above background art has attained a satisfactory level about how to lessen the positive ghost.

Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member that can reproduce good images with less positive ghost, and a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.

The present inventors have made extensive studies in order to provide an electrophotographic photosensitive member that can succeed at a high level in lessening the positive ghost. As the result, they have discovered that a copolymer having a specific structure may be incorporated in the photosensitive layer of the electrophotographic photosensitive member and this enables the electrophotographic photosensitive member to succeed at a high level in lessening the positive ghost.

More specifically, the present invention is an electrophotographic photosensitive member having a support and a photosensitive layer formed on the support, wherein

the photosensitive layer contains a copolymer having a repeating structural unit represented by the following formula (1) and a repeating structural unit represented by the following formula (2), or a copolymer having a repeating structural unit represented by the following formula (1) and a repeating structural unit represented by the following formula (3):

Z 1 -A-Z 2 -E 1   (1)

Z 3 -A-Z 4 —W 2 —B 2 —W 2   (2)

Z 5 —B 3 —Z 6 -E 4   (3)

where, in the formulas (1), (2) and (3);

Z 1 to Z 6 each independently represent a single bond, an alkylene group, an arylene group, or an arylene group substituted with an alkyl group;

E 1 represents a divalent group represented by —W 1 —B 1 —W 1 —, or a divalent group represented by the following formula (E11):

wherein X 1 represents a tetravalent group formed by removing four hydrogen atoms from a cyclic hydrocarbon;

E 4 represents a divalent group represented by —W 3 —B 4 —W 3 —, or a divalent group represented by the following formula (E41):

wherein X 4 represents a tetravalent group formed by removing four hydrogen atoms from a cyclic hydrocarbon;

W 1 to W 3 each independently represent a single bond, a urethane linkage, a urea linkage or an imide linkage;

A represents a divalent group represented by any of the following formulas (A-1) to (A-8):

where, in the formulas (A-1) to (A-8);

R 101 to R 104 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, or a cyano group, or represent a bonding or linking site; and R 105 and R 106 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with an alkyl group or halogen atom, or an alkyl group, or represent a bonding site; provided that any two of R 101 to R 106 are bonding sites;

R 201 to R 208 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, or a cyano group, or represent a bonding site; and R 209 and R 210 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with an alkyl group or halogen atom, or an alkyl group, or represent a bonding site; provided that any two of R 201 to R 210 are bonding sites;

R 301 to R 308 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; R 309 represents an oxygen atom or a dicyanomethylene group; and R 310 and R 311 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 304 and R 305 are not present; provided that any two of R 301 to R 308 are bonding sites;

R 401 to R 406 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; and R 407 represents an oxygen atom or a dicyanomethylene group; provided that any two of R 401 to R 406 are bonding sites;

R 501 to R 508 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; R 509 and R 510 each independently represent an oxygen atom or a dicyanomethylene group; and R 511 and R 512 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 501 and R 505 are not present; provided that any two of R 501 to R 508 are bonding sites;

R 601 to R 608 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, a nitro group, or a carboxylate group, or represent a bonding site; R 610 and R 611 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 604 and R 605 are not present; and R 609 represents a dicyanomethylene group; provided that any two of R 601 to R 608 are bonding sites;

R 701 to R 713 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, a nitro group, or a carboxylate group, or represent a bonding site; R 714 and R 715 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 704 and R 705 are not present; provided that any two of R 701 to R 713 are bonding sites; and

R 801 to R 808 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; provided that any two of R 801 to R 808 are bonding sites;

B 1 and B 4 each independently represent an arylene group, an alkylene group, an alkarylene group, an arylene group substituted with an alkyl group, halogen atom, cyano group or nitro group, an alkylene group substituted with a halogen atom, cyano group or nitro group, an alkarylene group substituted with an alkyl group, halogen atom, cyano group or nitro group, an arylene group interrupted by an ether or sulfonyl, or an alkylene group interrupted by an ether; and

B 2 and B 3 each independently represent an arylene group substituted with a carboxyl group only, an arylene group substituted with a carboxyl group and an alkyl group only, or an alkylene group substituted with a carboxyl group only.

The present invention is also a process cartridge which integrally supports the above electrophotographic photosensitive member and at least one device selected from the group consisting of a charging device, a developing device, a transfer device and a cleaning device, and is detachably mountable to the main body of an electrophotographic apparatus.

The present invention is still also an electrophotographic apparatus comprising the above electrophotographic photosensitive member, a charging device, an exposure device, a developing device and a transfer device.

According to the present invention, it can provide an electrophotographic photosensitive member that can succeed at a high level in lessening the positive ghost, and a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.

The reason why the electrophotographic photosensitive member having the photosensitive layer containing the above copolymer (copolymer resin) is superior in the effect of lessening positive ghost is unclear, and the present inventors presume it as stated below.

That is, the copolymer used in the present invention is a copolymer with a structure wherein structures having electron transport behavior and structures other than those are alternately present, and is a copolymer containing carboxyl groups. What the present inventors presume is that, in such a copolymer, the structures having electron transport behavior are present without being unevenly distributed and also the carboxyl groups mutually act with one another whereby probably the structures having electron transport behavior in the copolymer can take proper arrangement in a layer formed of such a copolymer and hence a superior effect of lessening positive ghost can be obtained.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

FIG. 1 is a view showing schematically the construction of an electrophotographic apparatus having a process cartridge provided with the electrophotographic photosensitive member of the present invention.

FIG. 2 is a view to illustrate ghost images (a print for evaluation on ghost).

FIG. 3 is a view to illustrate an image of one-dot “Keima” pattern (the “Keima” patter is similar to knight's move pattern).

The present invention is described below in detail.

In general, the electrophotographic photosensitive member has a support and a photosensitive layer formed on the support.

As the support, any support may be used as long as it has conductivity (a conductive support). It may include, e.g., a support made of a metal such as aluminum, nickel, copper, gold or iron, or an alloy of any of these; and an insulating support made of polyester, polyimide or glass and on which a thin film of a metal such as aluminum, silver or gold or of a conductive material such as indium oxide or tin oxide has been formed.

The support may have a surface having been treated by electrochemical treatment such as anodizing or by wet honing, blasting or cutting, in order to improve its electrical properties and prevent any interference fringes questioned when irradiated with coherent light such as semiconductor laser light.

A multi-layer type photosensitive layer has a charge generation layer containing a charge-generating material and a charge transport layer containing a charge-transporting material. The charge-transporting material includes a hole-transporting material and an electron-transporting material, where a charge transport layer containing the hole-transporting material is called a hole transport layer and a charge transport layer containing the electron-transporting material is called an electron transport layer. The multi-layer type photosensitive layer may be made to have a plurality of charge transport layers.

A single-layer type photosensitive layer is a layer incorporated with the charge-generating material and the charge-transporting material in the same layer.

It is preferable for the copolymer used in the present invention to be incorporated in the electron transport layer of a multi-layer type photosensitive layer having on the support the electron transport layer, the charge generation layer and the hole transport layer which are layered in this order from the support side.

The photosensitive layer is described below taking the case of the multi-layer type photosensitive layer of a negative-chargeable electrophotographic photosensitive member.

The charge generation layer contains a charge-generating material, and optionally contains a binder resin and other component(s).

The charge-generating material may include, e.g., azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments; perylene pigments such as perylene acid anhydrides and perylene acid imides; anthraquinone or polycyclic quinone pigments such as anthraquinone derivatives, anthanthrone derivatives, dibenzpyrenequinone derivatives, pyranthrone derivatives, violanthrone derivatives and isoviolanthrone derivatives; indigo pigments such as indigo derivatives and thioindigo derivatives; phthalocyanine pigments such as metal phthalocyanines and metal-free phthalocyanine; and perynone pigments such as bisbenzimidazole derivatives. Of these, azo pigments and phthalocyanine pigments are preferred. In particular, oxytitanium phthalocyanine, chlorogallium phthalocyanine and hydroxygallium phthalocyanine are preferred.

As the oxytitanium phthalocyanine, preferred are oxytitanium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 9.0°, 14.2°, 23.9° and 27.1°, and oxytitanium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 9.5°, 9.7°, 11.7°, 15.0°, 23.5°, 24.1° and 27.3°, all in CuKα characteristic X-ray diffraction.

As the chlorogallium phthalocyanine, preferred are chlorogallium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 7.4°, 16.6°, 25.5° and 28.2°, chlorogallium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 6.8°, 17.3°, 23.6° and 26.9°, and chlorogallium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 8.7°, 9.2°, 17.6°, 24.0°, 27.4° and 28.8°, all in CuKα characteristic X-ray diffraction.

As the hydroxygallium phthalocyanine, preferred are hydroxygallium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 7.3°, 24.9° and 28.1°, and hydroxygallium phthalocyanine crystals with a crystal form having strong peaks at Bragg angles (2θ±0.2°) of 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3°, all in CuKα characteristic X-ray diffraction.

In the present invention, the Bragg angles in CuKα characteristic X-ray diffraction of the crystal form of the phthalocyanine crystals are measured under the following conditions.

Measuring instrument: Full-automatic X-ray diffractometer (trade name: MXP18; manufactured by Mach Science Co. X-ray tube: Cu; Tube voltage: 50 kV; Tube current: 300 mA; Scanning method: 2θ/θ scan; Scanning speed: 2°/min.; Sampling interval: 0.020°; Start angle (2θ): 5°; Stop angle (2θ): 40°; Divergent slit: 0.5°; Scattering slit: 0.5°; and Receiving slit: 0.3 mm. A concave monochromator is used.

The binder resin used in the charge generation layer may include, e.g., polymers, and copolymers, of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylate, methacrylate, vinylidene fluoride and trifluoroethylene, polyvinyl alcohol, polyvinyl acetal, polycarbonate, polyester, polysulfone, polyphenylene oxide, polyurethane, cellulose resins, phenol resins, melamine resins, silicon resins and epoxy resins. Of these, polyester, polycarbonate and polyvinyl acetal are preferred. In particular, polyvinyl acetal is much preferred.

The hole-transporting material may include, e.g., polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, benzidine compounds, triarylamine compounds and triphenylamine compounds, or polymers having in the backbone chain or side chain a group derived from any of these compounds.

The binder resin used in the hole transport layer may include, e.g., polyester, polycarbonate, polymethacrylate, polyarylate, polysulfone and polystyrene. Of these, polycarbonate and polyarylate are particularly preferred. Any of these may also preferably have as molecular weight a weight average molecular weight (Mw) ranging from 10,000 to 300,000.

In the hole transport layer, the hole-transporting material and the binder resin may preferably be in a proportion (hole-transporting material/binder resin) of from 10/5 to 5/10, and much preferably from 10/8 to 6/10.

In the case of the negative-chargeable electrophotographic photosensitive member, a surface protective layer may further be formed on the hole transport layer. The surface protective layer contains conductive particles or a charge-transporting material and a binder resin. The surface protective layer may further contain an additive such as a lubricant. The binder resin itself of the surface protective layer may have conductivity and/or charge transport properties. In such a case, the surface protective layer need not contain the conductive particles and/or the charge-transporting material. The binder resin of the surface protective layer may be either of a curable resin capable of curing by heat, light, radiations or the like and a non-curable thermoplastic resin.

An electron transport layer is formed between the charge generation layer and the support. The electron generation layer is constituted of a single layer or a plurality of layers. In the case when the electron generation layer is in plurality, at least one layer of the layers contains the above copolymer. Also, an adhesive layer for improving adherence or a layer for improving electrical properties, which is other than the electron generation layer containing the copolymer, such as a conductive layer formed of a resin with a metal oxide or conductive particles such as carbon black dispersed therein may be formed between the charge generation layer and the support.

The copolymer for the photosensitive layer, used in the present invention, is a copolymer having a repeating structural unit represented by the following formula (1) and a repeating structural unit represented by the following formula (2), or a copolymer having a repeating structural unit represented by the following formula (1) and a repeating structural unit represented by the following formula (3):

Z 1 -A-Z 2 -E 1   (1)

Z 3 -A-Z 4 —W 2 —B 2 —W 2   (2)

Z 5 —B 3 —Z 6 -E 4   (3)

where, in the formulas (1), (2) and (3);

Z 1 to Z 6 each independently represent a single bond, an alkylene group, an arylene group, or an arylene group substituted with an alkyl group;

E 1 represents a divalent group represented by —W 1 —B 1 —W 1 —, or a divalent group represented by the following formula (E11):

wherein X 1 represents a tetravalent group formed by removing four hydrogen atoms from a cyclic hydrocarbon;

E 4 represents a divalent group represented by —W 3 —B 4 —W 3 —, or a divalent group represented by the following formula (E41):

wherein X 4 represents a tetravalent group formed by removing four hydrogen atoms from a cyclic hydrocarbon;

W 1 to W 3 each independently represent a single bond, a urethane linkage, a urea linkage or an imide linkage;

A represents a divalent group represented by any of the following formulas (A-1) to (A-8):

where, in the formulas (A-1) to (A-8);

R 101 to R 104 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, or a cyano group, or represent a bonding site; and R 105 and R 106 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with an alkyl group or halogen atom, or an alkyl group, or represent a bonding site; provided that any two of R 101 to R 106 are bonding sites;

R 201 to R 208 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, or a cyano group, or represent a bonding site; and R 209 and R 210 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with an alkyl group or halogen atom, or an alkyl group, or represent a bonding site; provided that any two of R 201 to R 210 are bonding sites;

R 301 to R 308 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; R 309 represents an oxygen atom or a dicyanomethylene group; and R 310 and R 311 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 304 and R 305 are not present; provided that any two of R 301 to R 308 are bonding sites;

R 401 to R 406 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; and R 407 represents an oxygen atom or a dicyanomethylene group; provided that any two of R 401 to R 406 are bonding sites;

R 501 to R 508 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; R 509 and R 510 each independently represent an oxygen atom or a dicyanomethylene group; and R 511 and R 512 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 501 and R 505 are not present; provided that any two of R 501 to R 508 are bonding sites;

R 601 to R 608 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, a nitro group, or a carboxylate group, or represent a bonding site; R 610 and R 611 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 604 and R 605 are not present; and R 609 represents a dicyanomethylene group; provided that any two of R 601 to R 608 are bonding sites;

R 701 to R 713 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, a nitro group, or a carboxylate group, or represent a bonding site; R 714 and R 715 each independently represent a carbon atom or a nitrogen atom, and, in the case of the nitrogen atom, R 704 and R 705 are not present; provided that any two of R 701 to R 713 are bonding sites; and

R 801 to R 808 each independently represent a hydrogen atom, an aryl group, an aryl group substituted with a halogen atom, nitro group, cyano group, alkyl group or alkyl halide group, an alkyl group, a cyano group, or a nitro group, or represent a bonding site; provided that any two of R 801 to R 808 are bonding sites;

in the formulas (1), (2) and (3);

B 1 and B 4 each independently represent an arylene group, an alkylene group, an alkarylene group (i.e., a divalent group having both an arylene moiety and an alkylene moiety), an arylene group substituted with an alkyl group, halogen atom, cyano group or nitro group, an alkylene group substituted with a halogen atom, cyano group or nitro group, an alkarylene group substituted with an alkyl group, halogen atom, cyano group or nitro group, an arylene group interrupted by an ether or sulfonyl, or an alkylene group interrupted by an ether; and

B 2 and B 3 each independently represent an arylene group substituted with a carboxyl group only, an arylene group substituted with a carboxyl group and an alkyl group only, or an alkylene group substituted with a carboxyl group only. In other words, B 2 and B 3 each independently represent a substituted arylene group whose substituent(s) is/are a carboxyl group, a substituted arylene group whose substituents are a carboxyl group and an alkyl group, or a substituted alkylene group whose substituent(s) is/are a carboxyl group.

The electron transport layer may preferably contain the above copolymer in an amount of from 80% by mass to 100% by mass based on the total mass of the electron transport layer.

The electron transport layer may contain, besides the copolymer, a resin of various types, a cross-linking agent, organic particles, inorganic particles, a leveling agent and so forth in order to optimize film forming properties and electrical properties. These, however, may preferably be in a content of less than 50% by mass, and much preferably less than 20% by mass, based on the total mass of the electron transport layer.

In the above copolymer, the respective repeating structural units may be in any proportion selected as desired. The repeating structural unit represented by the formula (1) may preferably be in a proportion of from 50 mol % to 99 mol %, and much preferably from 70 mol % to 99 mol %, based on all the repeating structural units in the copolymer.

In the case when the copolymer is a copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2), the repeating structural unit represented by the formula (2) may preferably be in a proportion of from 1 mol % to 30 mol % based on all the repeating structural units in the copolymer. The repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2) in total may preferably be in a proportion of from 70 mol % to 100 mol % based on all the repeating structural units in the copolymer.

In the case when the copolymer is a copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3), too, the repeating structural unit represented by the formula (3) may preferably be in a proportion of from 1 mol % to 30 mol % based on all the repeating structural units in the copolymer. The repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3) in total may also preferably be in a proportion of from 70 mol % to 100 mol % based on all the repeating structural units in the copolymer.

Specific examples of the copolymer used in the present invention are shown below, by which, however, the present invention is by no means limited.

In the following Tables 1 to 16C, bonding sites are shown by dotted lines. Where the linkage is a single bond, it is shown as “sing.”.

The formulas (1), (2) and (3) are the same as the groups (structures) given in Tables 1 to 16C in terms of the right-to-left direction. As to the Exemplary Compounds 125-127, 209-211, 308-310, 322-357, 407, 408, 414-444, 509, 510, 513-549, 607-609, 612-646, 707-709, 712-745, 807-809 and 812-844, the groups of —NHCOO— as W 1 and W 3 are arranged in the direction such that the N's are bound to the B 1 and B 4 , respectively.

Table 1 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 2A and 2B (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3). Table 2C (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Table 3 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 4A and 4B (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3). Table 4C (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Table 5 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 6A, 6B, 6C and 6D (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3).

Table 7 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 8A, 8B, 8C and 8D (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3).

Table 9 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 10A, 10B and 10C (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3).

Table 11 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 12A, 12B and 12 C (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3).

Table 13 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 14A, 14B and 14C (given later) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3).

Table 15 (given later) shows specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (2).

Tables 16A, 16B and 16C (given below) show specific examples (Exemplary Compounds) of the copolymer having the repeating structural unit represented by the formula (1) and the repeating structural unit represented by the formula (3).

The copolymer used in the present invention may preferably have a molecular weight in the range of, but not particularly limited to, from 5,000 to 15,000 in weight average molecular weight (Mw). The copolymer used in the present invention may also be synthesized through, but not particularly limited to, e.g., the following reaction process, in order to form the bonds or linkages of W 1 to W 3 in the formulas (1) to (3).

Where the linkages of W 1 to W 3 are urethane linkages, the copolymer may be formed by, e.g., allowing a compound having a hydroxyl group to react with a compound having an isocyanate group (“The Foundation and Application of Polyurethane”, CMC Publishing Co., Ltd., p. 3, 1986). In the present invention, however, the reaction is by no means limited to this reaction.

Where the linkages of W 1 to W 3 are urea linkages, the copolymer may be formed by allowing a compound having an amino group to react with a compound having an isocyanate group (“The Synthesis and Reaction of High Polymers (2)”, Kyoritu Shuppan Co., Ltd., p. 326, 1991). In the present invention, however, the reaction is by no means limited to this reaction.

Where the linkages of W 1 to W 3 are imide linkages, the copolymer may be formed by allowing a compound having an acid dianhydride group to react with a compound having an amino group (“The Dictionary of High Polymers”, Maruzen Co., Ltd., p. 1001, 1994). In the present invention, however, the reaction is by no means limited to this reaction.

Where the linkages of W 1 to W 3 are single bonds, the copolymer may be formed by, e.g., coupling reaction carried out using a urea compound and a boric acid derivative as raw materials, under basic conditions and making use of a palladium catalyst, e.g., tetrakis(triphenylphosphine)palladium (Angew. Chem. Int. Ed. 2005, 44, 4442). The single bonds, however, are known to be produced by other various reactions, and in the present invention the reaction is by no means limited to this reaction.

The copolymer used in the present invention may be synthesized by mutually polymerizing the compounds having the above polymerizable functional groups. Where the copolymer is synthesized in this way, it is necessary to first obtain a compound having a polymerizable functional group such as an amino group, a hydroxyl group, an isocyanate group, a halogen group, a boric acid group or an acid anhydride group and also having a skeleton corresponding to any of the above formulas (A-1) to (A-8). Then, it is necessary, using such a compound, to carry out polymerization reaction that forms the bonds or linkages represented by W 1 to W 3 .

Derivatives having the (A-1) structure as a main skeleton (which refers to compounds having the polymerizable functional group and also having the skeleton corresponding to the formula (A-1); the same applies alike hereinafter) may be synthesized by using a synthesis method disclosed in, e.g., U.S. Pat. No. 4,442,193, No. 4,992,349 or No. 5,468,583, or Chemistry of Materials, Vol. 19, No. 11, pp. 2703-2705, 2007). These may be synthesized by the reaction of a naphthalenetetracarboxylic dianhydride with a monoamine derivative; the both being commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as a reagent.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-1) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method which makes use of a naphthalenetetracarboxylic dianhydride derivative, or a monoamine derivative, having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group, or having a functional group which can combine with other compound having the polymerizable functional group.

A method is also available in which a naphthalenetetracarboxylic dianhydride derivative is allowed to react with a diamine derivative to produce a polymer directly. In this case, Z 1 to Z 6 and W 1 to W 3 in the formulas (1) to (3) are single bonds.

Derivatives having the (A-2) structure as a main skeleton may be synthesized by using a synthesis method disclosed in, e.g., Journal of the American Chemical Society, Vol. 129, No. 49, pp. 15259-78, 2007, and may be synthesized by the reaction of a perylenetetracarboxylic dianhydride derivative with a monoamine derivative; the both being commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as a reagent.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-2) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method which makes use of a perylenetetracarboxylic dianhydride derivative, or a monoamine derivative, having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group, or having a functional group which can combine with other compound having the polymerizable functional group.

A method is also available in which a perylenetetracarboxylic dianhydride derivative is allowed to react with a diamine derivative to produce a polymer directly. In this case, Z 1 to Z 6 and W 1 to W 3 in the formulas (1) to (3) are single bonds.

Some derivatives having the (A-3) structure as a main skeleton are commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as reagents. Then, these may also be synthesized, using a commercially available phenanthrene derivative or phenanthroline derivative as a material, by a synthesis method disclosed in Bull. Chem. Soc., Jpn., Vol. 65, pp. 1006-1011, 1992, Chem. Educator No. 6, pp. 227-234, 2001, Journal of Synthetic Organic Chemistry, Japan, Vol. 15, pp. 29-32, 1957, or Journal of Synthetic Organic Chemistry, Japan, Vol. 15, pp. 32-34, 1957. A dicyanomethylene group may also be introduced by the reaction with malononitrile.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-3) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method in which a structure having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group is introduced (e.g., a process carried out by cross-coupling reaction making use of a palladium catalyst, using a halide of a phenanthrene derivative or phenanthroline derivative as a material).

Some derivatives having the (A-4) structure as a main skeleton are commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as reagents. Then, these may also be synthesized, using a commercially available acenaphthenequinone derivative as a material, by a synthesis method disclosed in Tetrahedron Letters, 43(16), pp. 2991-2994, 2002, or Tetrahedron Letters, 44(10), pp. 2087-2091, 2003. A dicyanomethylene group may also be introduced by the reaction with malononitrile.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-4) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method in which a structure having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group is introduced (e.g., a process carried out by cross-coupling reaction making use of a palladium catalyst, using a halide of an acenaphthenequinone derivative as a material).

Some derivatives having the (A-5) structure as a main skeleton are commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as reagents. Then, these may also be synthesized, using a commercially available compound as a material, by a synthesis method disclosed in Synthesis, Vo. 5, pp. 388-389, 1988. A dicyanomethylene group may also be introduced by the reaction with malononitrile.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-5) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method in which a structure having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group is introduced (e.g., a process carried out by cross-coupling reaction making use of a palladium catalyst, using a halide of an anthraquinone derivative as a material).

Derivatives having the (A-6) structure as a main skeleton may be synthesized by using a synthesis method disclosed in U.S. Pat. No. 4,562,132, using a fluorenone derivative and malononitrile; the former being commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as a reagent.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-6) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method in which a structure having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group is introduced.

Derivatives having the (A-7) structure as a main skeleton may be synthesized by using a synthesis method disclosed in Japanese Patent Application Laid-open No. H05-279582 or No. H07-70038, using a fluorenone derivative and an aniline derivative; the both being commercially available from, e.g., Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co. or Johnson Matthey Japan Incorporated as a reagent.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-7) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method in which a structure having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group is introduced and a method which makes use of, as the above aniline derivative, an aniline derivative having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group, or having a functional group which can combine with other compound having the polymerizable functional group.

Derivatives having the (A-8) structure as a main skeleton may be synthesized by using a synthesis method disclosed in Japanese Patent Application Laid-open No. H01-206349 or PPCI/Japan Hardcopy '98 Papers, p. 207, 1998, and may be synthesized by using as a raw material a phenol derivative commercially available from, e.g., Tokyo Chemical Industry Co., Ltd. or Sigma-Aldrich Japan Co. as a reagent.

To make the compound have the polymerizable functional group, available are, e.g., a method in which a skeleton corresponding to the formula (A-8) of what has been synthesized by the above synthesis method is synthesized and thereafter the polymerizable functional group is introduced, and besides a method in which a structure having the polymerizable functional group or a functional group which can be a precursor of the polymerizable functional group is introduced.

Derivatives having as main skeletons the structures according to B 1 to B 4 (which refer to those into which the above polymerizable functional group has been introduced at the sites of bonding of the B 1 to B 4 divalent groups to the Z's; the B 1 to B 4 are hereinafter also “B's” collectively) are commercially available from, e.g., Tokyo Chemical Industry Co., Ltd. or Sigma-Aldrich Japan Co. as reagents. These may also be synthesized by introducing the polymerizable functional group into commercially available compounds. Such commercially available products may include, e.g., as commercially available products of isocyanate-containing compounds, TAKENATE and COSMONATE, available from Mitsui Takeda Chemicals, Inc.; DURANATE, available from Asahi Chemical Industry Co., Ltd.; and NIPPOLAN, available from Nippon Polyurethane Industry Co., Ltd. As commercially available products of amino group-containing compounds, they may include POLYMENT, available from Nippon Shokubai Co., Ltd.; and “2100 Series”, available from Three Bond Co., Ltd. Also, as commercially available products of hydroxyl group-containing compounds, they may include TAKELAC, available from Mitsui Chemicals Polyurethane, Inc.; and POLYLITE, available from DIC Corporation.

Of the B's, B 2 and B 3 are each required to have a carboxyl group. Accordingly, in order to incorporate such a structure into the copolymer, a method is available in which a compound having a structure containing the carboxyl group is further polymerized into the derivatives having as main skeletons the B 2 and B 3 structures each having the polymerizable functional group, or a compound having a structure containing a functional group which can be derived into the carboxyl group after being polymerized, such as a carboxylate group.

The copolymer and so forth used in the present invention were confirmed by the following methods.

Confirmation of raw materials for synthesizing copolymer:

Raw materials were confirmed by mass spectrometry.

Using a mass spectrometer (MALDI-TOF MS; ultraflex, manufactured by Bruker Daltonics Corp.), molecular weight was measured under conditions of accelerating voltage: 20 kV; mode: reflector; and molecular-weight standard molecule: C 60 fullerene. Confirmation was made by peak top values obtained.

Confirmation of Copolymer:

Its structures were confirmed by NMR. The structures were confirmed by 1 H-NMR and 13 C-NMR analysis (FT-NMR: JNM-EX400 Model, manufactured by JEOL Ltd.) at 120° C. in 1,1,2,2-tetrachloroethane (d2) or dimethyl sulfoxide (d6). For the quantitative determination of carboxyl group content, the content of carboxyl groups in the copolymer was also quantitatively determined by using FT-IR, and preparing a calibration curve based on absorption of carboxyl groups, using samples in which benzoic acid was added to KBr powder in different amounts by using a KBr-tab method.

As methods for forming the layers that constitute the electrophotographic photosensitive member, such as the charge generation layer, the hole transport layer and the electron transport layer, methods are preferable in which coating fluids prepared by dissolving or dispersing materials making up the respective layers are coated to form the layers. Methods for coating may include, e.g., dip coating, spray coating, curtain coating and spin coating. From the viewpoint of efficiency and productivity, dip coating is preferred.

The process cartridge of the present invention is a process cartridge which integrally supports the electrophotographic photosensitive member of the present invention and at least one device selected from the group consisting of a charging device, a developing device, a transfer device and a cleaning device, and is detachably mountable to the main body of an electrophotographic apparatus.

The electrophotographic apparatus of the present invention is an electrophotographic apparatus comprising the electrophotographic photosensitive member of the present invention, a charging device, an exposure device, a developing device and a transfer device.

FIG. 1 schematically illustrates the construction of an electrophotographic apparatus provided with a process cartridge having the electrophotographic photosensitive member of the present invention.

In FIG. 1 , reference numeral 1 denotes a drum-shaped electrophotographic photosensitive member of the present invention, which is rotatingly driven around an axis 2 in the direction of an arrow at a stated peripheral speed. The electrophotographic photosensitive member 1 is, in the course of its rotation, uniformly electrostatically charged on its surface (peripheral surface) to a positive or negative, given potential through a charging device 3 (e.g., a contact primary charging device or a non-contact primary charging device). The electrophotographic photosensitive member thus charged is then exposed to exposure light 4 (e.g., laser light) emitted from an exposure device (not shown) for slit exposure or laser beam scanning exposure. In this way, electrostatic latent images are successively formed on the surface of the electrophotographic photosensitive member 1 .

The electrostatic latent images thus formed are then developed with a toner held in a developing device 5 (which may be either of a contact type and a non-contact type). The toner images thus formed are successively transferred through a transfer device 6 to a transfer material 7 (e.g., paper) fed from a paper feed section (not shown) to the part between the electrophotographic photosensitive member 1 and the transfer device 6 (e.g., a transfer charging assembly) in the manner synchronized with the rotation of the electrophotographic photosensitive member 1 .

The transfer material 7 to which the toner images have been transferred is separated from the surface of the electrophotographic photosensitive member, is guided into a fixing device 8 , where the toner images are fixed, and is then put out of the apparatus as a duplicate (a copy).

The surface of the electrophotographic photosensitive member 1 from which the toner images have been transferred is brought to removal of transfer residual toner through a cleaning device 9 . Thus the electrophotographic photosensitive member is cleaned on its surface, and is further subjected to charge elimination by pre-exposure light emitted from a pre-exposure device (not shown), and then repeatedly used for the formation of images.

The charging device 3 may be either of a scorotron charging assembly and a corotron charging assembly, which utilizes corona discharge. A contact charging device may also be used which makes use of, e.g., a roller-shaped, blade-shaped or brush-shaped charging member.

In the present invention, the above electrophotographic photosensitive member 1 and at least one device selected from the constituents such as the charging device 3 , the developing device 5 , the transfer device 6 and the cleaning device 9 may be so set up as to be integrally joined as a process cartridge. This process cartridge may be so set up as to be detachably mountable to the main body of an electrophotographic apparatus such as a copying machine or a laser beam printer.

For example, at least one device of the charging device 3 , the developing device 5 and the cleaning device 9 may integrally be supported together with the electrophotographic photosensitive member 1 to form a cartridge to set up a process cartridge 10 detachably mountable to the main body of the electrophotographic apparatus through a guide such as rails 11 and 12 provided in the main body of the electrophotographic apparatus.

In the case when the electrophotographic apparatus is a copying machine or a printer, the exposure light 4 is light reflected from, or transmitted through, an original; or light irradiated by the scanning of a laser beam, the driving of an LED array or the driving of a liquid crystal shutter array according to signals obtained by reading an original through a sensor and converting the information into signals.

The electrophotographic photosensitive member in the present invention is adaptable to electrophotographic apparatus in general, such as copying machines, laser beam printers, LED printers, and liquid-crystal shutter printers. It may further be widely applicable to display, recording, light printing, platemaking, facsimile and the like equipment to which electrophotographic techniques have been applied.

The present invention is described below in greater detail by giving specific working examples. Note, however, that the present invention is by no means limited to these.

Synthesis examples of the copolymer to be incorporated in the photosensitive layer of the electrophotographic photosensitive member of the present invention are given first. Note, however, that the synthesis of the copolymer used in the present invention is by no means limited to the following compounds and synthesis methods.

Herein, the molecular weight of each copolymer having been synthesized was measured by GPC (measured with a gel permeation chromatograph “HLC-8120”, manufactured by Tosoh Corporation, and calculated in terms of polystyrene).

Synthesis Example 1

Copolymer of Exemplary Compound 101

To 200 parts by mass of dimethylacetamide, 5.4 parts by mass of naphthalenetetracarboxylic dianhydride, 2.1 parts by mass of 1,4-phenylenediamine and 0.15 part by mass of 3,5-diaminobenzoic acid were added in an atmosphere of nitrogen, and these were stirred at room temperature for 1 hour. After these raw materials became dissolved, reflux was carried out for 8 hours, and the precipitate formed was separated by filtration, followed by washing with acetone to obtain 6.2 parts by mass of an object copolymer (Exemplary Compound 101). The product obtained stood particulate.

Synthesis Example 2

Copolymer of Exemplary Compound 102

To 200 parts by mass of dimethylacetamide, 8.2 parts by mass of dibromonaphthalenetetracarboxylic dianhydride synthesized by the synthesis method described in Chemistry of Materials, Vol. 19, No. 11, pp. 2703-2705 (2007), 2.1 parts by mass of 1,4-phenylenediamine and 0.15 part by mass of 3,5-diaminobenzoic acid were added in an atmosphere of nitrogen, and these were stirred at room temperature for 1 hour. After these raw materials became dissolved, reflux was carried out for 8 hours, and the precipitate formed was separated by filtration, followed by washing with acetone to obtain 7.5 parts by mass of an object copolymer (Exemplary Compound 102). The product obtained stood particulate.

Synthesis Example 3

Copolymer of Exemplary Compound 125

To 200 parts by mass of dimethylacetamide, 5.4 parts by mass of naphthalenetetracarboxylic dianhydride and 4.4 parts by mass of 4-hydroxyaniline were added in an atmosphere of nitrogen, and these were stirred at room temperature for 1 hour. After these raw materials became dissolved, reflux was carried out for 8 hours, and the precipitate formed was separated by filtration, followed by recrystallization with ethyl acetate to obtain 5.0 parts by mass of a compound represented by the following structural formula.

To 4.3 parts by mass of the compound represented by the above structural formula, 1.6 parts by mass of 1,4-phenylene diisocyanate and 0.08 part by mass of 3,5-dihydroxybenzoic acid were added, and reflux was carried out for 8 hours in toluene, and the precipitate formed was separated by filtration, followed by washing with acetone to obtain 3.6 parts by mass of an object copolymer (Exemplary Compound 125). The product obtained stood particulate.

Synthesis Example 4

Copolymer of Exemplary Compound 304

To 20 parts by mass of diaminophenanthrenequinone synthesized by the synthesis method described in Journal of Synthetic Organic Chemistry, Japan, Vol. 15, pp. 29-32 (1957) and Journal of Synthetic Organic Chemistry, Japan, Vol. 15, pp. 32-34 (1957), 8 parts by mass of dicyanomethylene malononitrile was added, and reflux was carried out for 12 hours in tetrahydrofuran. After being left to cool, the purple crystals precipitated were separated by filtration, followed by recrystallization with ethyl acetate to obtain 4.8 parts by mass of a compound represented by the following structural formula.

To 200 parts by mass of dimethylacetamide, 4.5 parts by mass of the compound represented by the above structural formula, 0.15 part by mass of 3,5-diaminobenzoic acid and 4.4 parts by mass of pyromellitic anhydride were added in an atmosphere of nitrogen, and these were stirred at room temperature for 1 hour. After these raw materials became dissolved, reflux was carried out for 8 hours, and the precipitate formed was separated by filtration, followed by washing with acetone to obtain 5.2 parts by mass of an object copolymer (Exemplary Compound 304). The product obtained stood particulate.

Synthesis Example 5

Copolymer of Exemplary Compound 310

To a mixed solvent of 100 parts by mass of toluene and 50 parts by mass of ethanol, 2.8 parts by mass of 3-hydroxyphenylboric acid and 7.4 parts by mass of 3,6-dibromo-9,10-phenathrenedion synthesized by the synthesis method described in Chem. Educator No. 6, pp. 227-234 (2001) were added in an atmosphere of nitrogen. To the mixture obtained, 100 parts by mass of an aqueous 20% sodium carbonate solution was dropwise added, and thereafter 0.55 part by mass of tetrakis(triphenylphosphine)palladium (0) was added, followed by reflux for 2 hours. After the reaction, the organic phase was extracted with chloroform, and then washed with water, followed by drying with anhydrous sodium sulfate. The solvent was removed under reduced pressure, and thereafter the residue formed was purified by silica gel chromatography to obtain 5.2 parts by mass of a compound represented by the following structural formula.

To 3.7 parts by mass of the compound represented by the above structural formula, 1.6 parts by mass of 1,4-phenylene diisocyanate and 0.08 part by mass of 3,5-dihydroxybenzoic acid were added, and reflux was carried out for 12 hours in 100 parts by mass of toluene to obtain 2.2 parts by mass of an object copolymer (Exemplary Compound 310). The product obtained stood particulate.

Next, electrophotographic photosensitive members were produced and evaluated as shown below.