Electrophotographic photoreceptor, method of producing same, and electrophotographic apparatus

Abstract

An electrophotographic photoreceptor is provided that can achieve reductions in the amount of wear in the photoreceptor surface while producing an excellent image on a long-term basis. Also provided are a method of producing the electrophotographic photoreceptor and an electrophotographic apparatus. The electrophotographic photoreceptor includes a conductive substrate; and a photosensitive layer provided on the conductive substrate and being composed of a resin having a molecular structure optimized using molecular dynamic calculations that is a helical structure, and having a value for a ratio r/I between the diameter (r) and helix pitch (I) of the helical structure that ranges from 0.04 to 1.0.

Claims

1. An electrophotographic photoreceptor, comprising: a conductive substrate; and a photosensitive layer provided on the conductive substrate and being comprised of a polyarylate resin that has a molecular structure optimized using molecular dynamic calculations that is a helical structure, and that has a value for a ratio r/I between the diameter (r) and helix pitch (I) of the helical structure that ranges from 0.04 to 1.0, wherein the polyarylate resin has repeat units represented by a chemical structural formula 1 as follows: ##STR00023## where substructure formulas (A), (B), (C), and (D) each represent a structural unit that constitutes the resin; a, b, c, and d respectively represent mol % of the structural units (A), (B), (C), and (D); a+b+c+d is 100 mol %; R.sub.1 and R.sub.2 may be the same or different and represent a C.sub.2-8 alkyl group, a possibly substituted cycloalkyl group, or a possibly substituted aryl group; and R.sub.3 and R.sub.4 may be the same or different and represent a hydrogen atom, a C.sub.1-8 alkyl group, a possibly substituted cycloalkyl group, or a possibly substituted aryl group, or R.sub.3 and R.sub.4 may form a cyclic structure together with the carbon atom to which R.sub.3 and R.sub.4 may are bonded, and 1 or 2 arylene groups may be bonded to this cyclic structure.

2. The electrophotographic photoreceptor according to claim 1, wherein the c and d in the chemical structural formula 1 are 0 mol %.

3. The electrophotographic photoreceptor according to claim 1, wherein the b in the chemical structural formula 1 is a mol % that ranges from 65 mol % to less than 100 mol %.

4. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is comprised of at least a charge generation layer and a charge transport layer, and the charge transport layer contains the resin and a charge transport material.

5. The electrophotographic photoreceptor according to claim 4, wherein the charge generation layer and the charge transport layer are stacked in this sequence over the conductive substrate.

6. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains the resin, a charge generation material, and a charge transport material.

7. The electrophotographic photoreceptor according to claim 6, wherein the charge transport material contains a hole transport material and an electron transport material.

8. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is comprised of at least a charge transport layer and a charge generation layer, and the charge generation layer contains the resin, a charge generation material, and a charge transport material.

9. The electrophotographic photoreceptor according to claim 8, wherein the charge transport layer and the charge generation layer are stacked in this sequence over the conductive substrate.

10. An electrophotographic apparatus, comprising the electrophotographic photoreceptor according to claim 1.

11. A method of producing an electrophotographic photoreceptor, comprising: providing a conductive substrate; providing a coating liquid that contains at least a resin binder comprised of a a polyarylate resin that has a molecular structure optimized using molecular dynamic calculations that is a helical structure, and that has a value for a ratio r/I between the diameter (r) and helix pitch (I) of the helical structure that ranges from 0.04 to 1.0; and forming a photosensitive layer on the conductive substrate by coating the coating liquid thereon, wherein the polyarylate resin has repeat units represented by the following chemical structural formula 1: ##STR00024## where substructure formulas (A), (B), (C), and (D) each represent a structural unit that constitutes the resin; a, b, c, and d respectively represent mol % of the structural units (A), (B), (C), and (D); a+b+c+d is 100 mol %; R.sub.1 and R.sub.2 may be the same or different and represent a C.sub.2-8 alkyl group, a possibly substituted cycloalkyl group, or a possibly substituted aryl group; and R.sub.3 and R.sub.4 may be the same or different and represent a hydrogen atom, a C.sub.1-8 alkyl group, a possibly substituted cycloalkyl group, or a possibly substituted aryl group, or R.sub.3 and R.sub.4 may form a cyclic structure together with the carbon atom to which R.sub.3 and R.sub.4 are bonded, and 1 or 2 arylene groups may be bonded to this cyclic structure).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a schematic cross-sectional diagram that shows an example of a negative-charge, functionally separated stacked electrophotographic photoreceptor according to the present invention;

(2) FIG. 1B is a schematic cross-sectional diagram that shows an example of a positive-charge monolayer electrophotographic photoreceptor according to the present invention;

(3) FIG. 1(c) is a schematic cross-sectional diagram that shows an example of a positive-charge, functionally separated stacked electrophotographic photoreceptor according to the present invention;

(4) FIG. 2 is a schematic structural diagram that shows an example of the electrophotographic apparatus according to the present invention; and

(5) FIG. 3 is a .sup.1H-NMR spectrum of polyarylate copolymer resin (III-1).

DETAILED DESCRIPTION OF THE INVENTION

(6) Specific embodiments of the electrophotographic photoreceptor of the present invention are described in detail below with reference to the figures. The present invention is in no way limited by the description that follows.

(7) As previously noted, electrophotographic photoreceptors can be generally classified into monolayer photoreceptors, which are primarily used as positive-charge types, and, within the realm of stacked (functionally separated) photoreceptors, into negative-charge stacked photoreceptors and positive-charge stacked photoreceptors. FIG. 1 is a schematic cross-sectional diagram that shows an example of the electrophotographic photoreceptor of the present invention, and shows, respectively, FIG. 1A a negative-charge stacked electrophotographic photoreceptor, FIG. 1B a positive-charge monolayer electrophotographic photoreceptor, and FIG. 1C a positive-charge stacked electrophotographic photoreceptor. As shown in the figures, in the negative-charge stacked photoreceptor, an undercoat layer 2 and a photosensitive layer, which has a charge generation layer 4 provided with a charge generation function and a charge transport layer 5 provided with a charge transport function, are successively stacked on a conductive substrate 1. In the positive-charge monolayer photoreceptor, an undercoat layer 2 and a monolayer photosensitive layer 3, which has both a charge generation function and a charge transport function, are successively stacked on a conductive substrate 1. In the positive-charge stacked photoreceptor, an undercoat layer 2 and a photosensitive layer having a charge transport layer 5 provided with a charge transport function and a charge generation layer 4 provided with both a charge generation function and a charge transport function are successively stacked on a conductive substrate 1. The undercoat layer 2 may be disposed as necessary in any of the photoreceptor types. In addition, the photosensitive layer of the present invention encompasses both a monolayer photosensitive layer and a stacked photosensitive layer in which a charge generation layer and a charge transport layer are stacked.

(8) The conductive substrate 1 fulfills the role of an electrode for the photoreceptor and at the same time is also a support for the individual layers that make up the photoreceptor, and it may have any shape, e.g., cylindrical, plate, film, and so forth. The material used for the conductive substrate 1, for example, may be a metal such as aluminum, stainless steel, or nickel or may be provided by the execution of a conductive treatment on the surface of, e.g., a glass or resin.

(9) The undercoat layer 2 is a layer for which the principal component is a resin or is composed of a metal oxide film such as alumite. This undercoat layer 2 is disposed on an optional basis for the purpose of, for example, controlling charge injection from the conductive substrate 1 into the photosensitive layer, covering over defects in the surface of the conductive layer, and/or improving the adherence between the photosensitive layer and the conductive substrate 1. The resin material used in the undercoat layer 2 can be exemplified by insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, cellulose, and so forth, and by conductive polymers such as polythiophene, polypyrrole, polyaniline, and so forth. A single one of these resins may be used by itself or a mixture of a suitable combination may be used. In addition, a metal oxide, e.g., titanium dioxide, zinc oxide, and so forth, may be used incorporated in these resins.

(10) The Negative-Charge Stacked Photoreceptor

(11) The charge generation layer 4 in the negative-charge stacked photoreceptor is formed by a method, for example, in which a coating liquid having particles of a charge generation material dispersed in a resin binder is applied, and it generates charge when irradiated with light. It is essential that the charge generation layer 4 have a high charge-generating efficiency and at the same time have the ability to inject the generated charge into the charge transport layer 5, while a low electric field dependence and good injection even in a low electric field are desirable. For example, phthalocyanine compounds, e.g., X-type metal-free phthalocyanine, -type metal-free phthalocyanine, -type titanyl phthalocyanine, -type titanyl phthalocyanine, Y-type titanyl phthalocyanine, -type titanyl phthalocyanine, amorphous titanyl phthalocyanine, and -type copper phthalocyanine; azo pigments; anthanthrone pigments; thiapyrylium pigments; perylene pigments; perinone pigments; squarylium pigments; quinacridone pigments; and so forth may be used individually or in appropriate combinations, and an optimal substance may be selected in correspondence to the light wavelength region of the exposure light source used for image formation. The content of the charge generation material in the charge generation layer 4, expressed with reference to the solids fraction in the charge generation layer 4, is preferably from 20 to 80 mass % and is more preferably from 30 to 70 mass %.

(12) The film thickness of the charge generation layer 4 is, as long as it exhibits a charge generation function, generally not more than 1 m and preferably not more than 0.5 m. The charge generation layer 4 used may also be mainly a charge generation material with, for example, a charge transport material and so forth added thereto. Suitable combinations of, for example, polycarbonate resin, polyester resin, polyamide resin, polyurethane resin, vinyl chloride resin, vinyl acetate resin, phenoxy resin, polyvinyl acetal resin, polyvinyl butyral resin, polystyrene resin, polysulfone resin, diallyl phthalate resin, and methacrylate ester resin polymers and copolymers can be used for the resin binder for the charge generation layer 4. In the case of a negative-charge stacked photoreceptor, the above-described helically structured resin may be used on an optional basis in the present invention as a resin binder for the charge generation layer 4.

(13) The charge transport layer 5 is constructed mainly from a charge transport material and a resin binder. In the case of a negative-charge stacked photoreceptor, the above-described helically structured resin must be used in the present invention as a resin binder for the charge transport layer 5 that is disposed on the surface side of the photosensitive layer. This makes it possible to obtain the expected effects of the present invention.

(14) The above-described helically structured resin may be used by itself or may be used mixed with another resin. The following can be used as this other resin: other polyarylate resins; various other polycarbonate resins, e.g., bisphenol A types, bisphenol Z types, bisphenol A-biphenyl copolymers, and bisphenol Z-biphenyl copolymers; polyphenylene resins; polyester resins; polyvinyl acetal resins; polyvinyl butyral resins; polyvinyl alcohol resins; vinyl chloride resins; vinyl acetate resins; polyethylene resins; polypropylene resins; acrylic resins; polyurethane resins; epoxy resins; melamine resins; silicone resins; polyamide resins; polystyrene resins; polyacetal resins; polysulfone resins; and methacrylate ester polymers and their copolymers. A mixture of resins of the same type, but with different molecular weights, may also be used.

(15) The content of the resin binder in the charge transport layer 5, expressed with reference to the solids fraction in the charge transport layer 5, is preferably 10 to 90 mass % and more preferably 20 to 80 mass %. In addition, the content in this resin binder of the above-described helically structured resin is preferably in the range from 1 mass % to 100 mass % and is more preferably in the range from 5 mass % to 80 mass %.

(16) The weight-average molecular weight of the above-described helically structured resin, according to analysis by gel permeation chromatography (GPC) as polystyrene, is preferably 5,000 to 250,000 and is more preferably 10,000 to 200,000.

(17) Specific examples of the substructures (A) to (D), which are the structural units in chemical structural formula 1, are shown below as specific examples of the above-described helically structured resin. Moreover, specific examples of resins represented by chemical structural formula 1 are shown in the table below. However, the above-described helically structured resin according to the present invention is not limited to these exemplary structures.

(18) ##STR00002## ##STR00003## ##STR00004##

(19) TABLE-US-00001 TABLE 1 substructural unit designation structure No. A B C D (I-1) A1 B1 C1 D1 (I-2) A2 B2 C1 D1 (I-3) A3 B3 C1 D1 (I-4) A4 B4 C1 D1 (I-5) A5 B5 C1 D1 (I-6) A6 B6 C1 D1 (I-7) A7 B7 C1 D1 (I-8) A8 B8 C1 D1 (I-9) A9 B9 C1 D1 (I-10) A10 B10 C1 D1 (I-11) A11 B11 C1 D1 (I-12) A1 B1 (I-13) A2 B2 (I-14) A3 B3 (I-15) A4 B4 (I-16) A5 B5 (I-17) A6 B6 (I-18) A7 B7 (I-19) A8 B8 (I-20) A9 B9 (I-21) A10 B10 (I-22) A11 B11

(20) For example, the bisphenols given by the following M1 to M12 can be used as constituent monomers for these resins (I-1) to (I-22), but there is no limitation to these.

(21) ##STR00005## ##STR00006##

(22) Various hydrazone compounds, styryl compounds, diamine compounds, butadiene compounds, indole compounds, and so forth can be used, individually or mixed in a suitable combination, as the charge transport material in the charge transport layer 5. This charge transfer material can be exemplified by the charge transfer materials given by the following (II-1) to (II-22), but there is no limitation to these.

(23) ##STR00007## ##STR00008## ##STR00009##

(24) In order to maintain a surface potential that is effective from a practical standpoint, the film thickness of the charge transport layer 5 is preferably in the range from 3 to 50 m and more preferably in the range from 15 to 40 m.

(25) The Positive-Charge Monolayer Photoreceptor

(26) The monolayer photosensitive layer 3 in the positive-charge monolayer photoreceptor is composed mainly of a charge generation material, a hole transport material, an electron transport material (acceptor compound), and a resin binder.

(27) In the case of a positive-charge monolayer photoreceptor, the above-described helically structured resin must be used in the present invention as a resin binder for the monolayer photosensitive layer 3. This makes it possible to obtain the expected effects of the present invention. This helically structured resin can be exemplified by the same such resins as described above.

(28) The above-described helically structured resin may be used by itself as the resin binder for the monolayer photosensitive layer 3 or may be used mixed with another resin. The following can be used as this other resin: various other polycarbonate resins, e.g., bisphenol A types, bisphenol Z types, bisphenol A-biphenyl copolymers, and bisphenol Z-biphenyl copolymers; polyphenylene resins; polyester resins; polyvinyl acetal resins; polyvinyl butyral resins; polyvinyl alcohol resins; vinyl chloride resins; vinyl acetate resins; polyethylene resins; polypropylene resins; acrylic resins; polyurethane resins; epoxy resins; melamine resins; silicone resins; polyamide resins; polystyrene resins; polyacetal resins; other polyarylate resins; polysulfone resins; and methacrylate ester polymers and their copolymers. A mixture of resins of the same type, but with different molecular weights, may also be used.

(29) The content of the resin binder, expressed with reference to the solids fraction in the monolayer photosensitive layer 3, is preferably 10 to 90 mass % and is more preferably 20 to 80 mass %. The content in this resin binder of the above-described helically structured resin is preferably in the range from 1 mass % to 100 mass % and more preferably in the range from 5 mass % to 80 mass %.

(30) For example, a phthalocyanine pigment, azo pigment, anthanthrone pigment, perylene pigment, perinone pigment, polycyclic quinone pigment, squarylium pigment, thiapyrylium pigment, quinacridone pigment, and so forth may be used as the charge generation material in the monolayer photosensitive layer 3. A single one of these charge generation materials may be used by itself or two or more may be used in combination. In particular, a disazo pigment or trisazo pigment is preferably used for the azo pigment in the photoreceptor of the present invention; N,N-bis(3,5-dimethylphenyl)-3,4:9,10-perylenebis(carboxyimide) is preferably used for the perylene pigment in the photoreceptor of the present invention; and a metal-free phthalocyanine, copper phthalocyanine, or titanyl phthalocyanine is preferably used for the phthalocyanine pigment in the photoreceptor of the present invention. In addition, the use is preferred of X-type metal-free phthalocyanine, -type metal-free phthalocyanine, -type copper phthalocyanine, -type titanyl phthalocyanine, (-type titanyl phthalocyanine, Y-type titanyl phthalocyanine, amorphous titanyl phthalocyanine, or a titanyl phthalocyanine that has a maximum peak in the CuK x-ray diffraction spectrum at a Bragg angle 2 of 9.6 as described in Japanese Patent Application Laid-open No. H8-209023 and U.S. Pat. Nos. 5,736,282 and 5,874,570, because this provides substantially improved effects with regard to the sensitivity, durability, and image quality. The content of the charge generation material, expressed with reference to the solids fraction in the monolayer photosensitive layer 3, is preferably 0.1 to 20 mass % and more preferably 0.5 to 10 mass %.

(31) The following, for example, can be used as the hole transport material in the monolayer photosensitive layer 3: hydrazone compounds, pyrazoline compounds, pyrazolone compounds, oxadiazole compounds, oxazole compounds, arylamine compounds, benzidine compounds, stilbene compounds, styryl compounds, poly-N-vinylcarbazoles, polysilanes, and so forth. A single one of these hole transport materials may be used by itself or a combination of two or more may be used. The hole transport material used in the present invention preferably has an excellent transport capacity for the holes generated by irradiation with light and in addition is suitable for combination with the charge generation material. The content of the hole transport material, expressed with reference to the solids fraction of the monolayer photosensitive layer 3, is preferably 3 to 80 mass % and more preferably 5 to 60 mass %.

(32) The electron transport material (acceptor compound) in the monolayer photosensitive layer 3 can be exemplified by succinic anhydride, maleic anhydride, dibromosuccinic anhydride, phthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic anhydride, pyromellitic acid, trimellitic acid, trimellitic anhydride, phthalimide, 4-nitrophthalimide, tetracyanoethylene, tetracyanoquinodimethane, choranil, bromanil, o-nitrobenzoic acid, malononitrile, trinitrofluorenone, trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, thiopyran compounds, quinone compounds, benzoquinone compounds, diphenoquinone compounds, naphthoquinone compounds, anthraquinone compounds, stilbenequinone compounds, azoquinone compounds, and so forth. A single one of these electron transport materials may be used by itself or a combination of two or more may be used. The content of the electron transport material, expressed with reference to the solids fraction of the monolayer photosensitive layer 3, is preferably 1 to 50 mass % and more preferably 5 to 40 mass %.

(33) In order to maintain a surface potential that is effective from a practical standpoint, the film thickness of the monolayer photosensitive layer 3 is preferably in the range from 3 to 100 m and is more preferably in the range from 5 to 40 m.

(34) The Positive-Charge Stacked Photoreceptor

(35) The charge transport layer 5 in the positive-charge stacked photoreceptor is formed mainly from a charge transport material and a resin binder. The same materials as described in relation to the charge transport layer 5 of the negative-charge stacked photoreceptor can be used as the charge transport material and resin binder here. The content of each individual material and the film thickness of the charge transport layer 5 can also be the same as for the negative-charge stacked photoreceptor. In the case of the positive-charge stacked photoreceptor, the above-described helically structured resin may be used on an optional basis in the present invention as a resin binder in the charge transport layer 5.

(36) The charge generation layer 4 disposed on the charge transport layer 5 is composed mainly of a charge generation material, a hole transport material, an electron transport material (acceptor compound), and a resin binder. The same materials as described in relation to the monolayer photosensitive layer 3 of the monolayer photoreceptor may be used as the charge generation material, hole transport material, electron transport material, and resin binder. The content of each individual material and the film thickness of the charge generation layer 4 may be the same as for the monolayer photosensitive layer 3 of the monolayer photoreceptor. In the case of the positive-charge stacked photoreceptor, the above-described helically structured resin must be used in the present invention as a resin binder for the charge generation layer 4 disposed on the surface side of the photosensitive layer. This makes it possible to obtain the expected effects of the present invention.

(37) In order to enhance the environmental resistance and the stability with respect to harmful light, the photosensitive layer, in either the stacked or monolayer configuration, may contain a deterioration inhibitor such as an oxidation inhibitor and/or a photostabilizer. Compounds used for these purposes can be exemplified by chromanol derivatives such as tocopherol and their ester compounds, polyarylalkane compounds, hydroquinone derivatives, etherified compounds, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, phenylenediamine derivatives, phosphonate esters, phosphite esters, phenol compounds, hindered phenol compounds, straight-chain amine compounds, cyclic amine compounds, and hindered amine compounds.

(38) In addition, in order to enhance the leveling behavior of the film that has been formed and impart lubricity, these photosensitive layers may also contain a leveling agent, e.g., a silicone oil or fluorinated oil. The following may also be incorporated in order to adjust the film hardness and/or lower the coefficient of friction and impart lubricity: metal oxides such as silicon oxide (silica), titanium oxide, zinc oxide, calcium oxide, aluminum oxide (alumina), and zirconium oxide; metal sulfates such as barium sulfate and calcium sulfate; finely divided particles of a metal nitride such as silicon nitride and aluminum nitride; particles of a fluororesin such as a tetrafluoroethylene resin; and fluorinated comb graft polymer resins. Moreover, other known additives may also be incorporated as necessary within a range in which the electrophotographic characteristics are not significantly impaired.

(39) The Electrophotographic Apparatus

(40) The effects expected for the electrophotographic photoreceptor of the present invention are obtained by using it in the various machine processes. In specific terms, satisfactory effects can be obtained with charging processes such as contact charging configurations that use a roller or brush as well as noncontact charging configurations that use, for example, a corotron or scorotron, and with development processes such as noncontact developing regimes and contact developing regimes that use a nonmagnetic single-component, magnetic single-component, or magnetic two-component developing scheme.

(41) FIG. 2 shows a schematic structural diagram of an example of the structure of the electrophotographic apparatus according to the present invention. The electrophotographic apparatus 60 according to the present invention that is shown in the diagram is equipped with a photoreceptor 7 of the present invention that contains a conductive substrate 1, and, coated on the outer circumference thereof, an undercoat layer 2 and a photosensitive layer 300. This electrophotographic apparatus 60 is provided with a roller charging member 21 disposed at the outer periphery of the photoreceptor 7, a high-voltage power supply 22 that feeds an application voltage to this roller charging member 21, an imagewise exposure member 23, a developing device 24 provided with a developing roller 241, a paper feed member 25 provided with a paper feed roller 251 and a paper feed guide 252, a transfer charging device (direct charging type) 26, a cleaning apparatus 27 provided with a cleaning blade 271, and a neutralization member 28. The electrophotographic apparatus 60 of the present invention may also be a color printer.

EXAMPLES

(42) Specific embodiments of the present invention are more particularly described below using examples, but, insofar as its essential features are not exceeded, the present invention is not limited by the following examples.

(43) Resin Production

Production Example 1: Method of Producing Polyarylate Copolymer Resin (III-1)

(44) Into a 2-L four-neck flatbottom flask, 540 mL ion-exchanged water, 12.4 g NaOH, 0.459 g p-tert-butylphenol, 24.279 g of the above-described monomer M1 (2,6-bis(4-hydroxy-3-methylphenyl)methane), 4.95 g biphenol (abbreviated below as BP), and 0.272 g tetrabutylammonium bromide were introduced and a solution (i) was prepared. A solution (ii) was then prepared in which 12.27 g terephthaloyl chloride and 14.99 g isophthaloyl chloride were dissolved in 540 mL of dry methylene chloride. Solution (i) was first added dropwise to solution (ii) and stirring was performed for 2 hours to carry out a reaction. After the completion of the reaction, neutralization was carried out with 4.74 mL acetic acid and dilution was performed by the supplemental addition of 360 mL methylene chloride. The aqueous phase was separated and this was reprecipitated with 4-fold (volume) methanol. After drying for 2 hours at 60 C., washing was performed by making the obtained product into the 5% solution with methylene chloride and adding this to 3 L of ion-exchanged water and reprecipitating the resin. This washing was performed until the conductivity of the wash water reached 1 S/m or less. The recovered resin was again dissolved at 5 mass % in methylene chloride and reprecipitation was performed by dropwise addition to 5-fold acetone that was being stirred. The precipitate was filtered and dried for 2 hours at 60 C. to obtain 42.24 g of the target polymer. The .sup.1H-NMR spectrum in THF-d8 solution of this polyarylate copolymer resin (III-1) is given in FIG. 3, and its copolymerization ratio is as follows: a:b:c:d=36.0:44.0:9.0:11.0.

(45) A molecular weight of 150,000 was obtained when the weight-average molecular weight as polystyrene of this polyarylate copolymer resin (III-1) was measured by GPC analysis.

Production Example 2: Method of Producing Polyarylate Copolymer Resin (III-2)

(46) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M2 and adding 27.262 g thereof. The obtained polyarylate copolymer resin is designated (III-2).

Production Example 3: Method of Producing Polyarylate Copolymer Resin (III-3)

(47) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M3 and adding 30.245 g thereof. The obtained polyarylate copolymer resin is designated (III-3).

Production Example 4: Method of Producing Polyarylate Copolymer Resin (III-4)

(48) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M4 and adding 33.229 g thereof. The obtained polyarylate copolymer resin is designated (III-4).

Production Example 5: Method of Producing Polyarylate Copolymer Resin (III-5)

(49) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M5 and adding 36.212 g thereof. The obtained polyarylate copolymer resin is designated (III-5).

Production Example 6: Method of Producing Polyarylate Copolymer Resin (III-6)

(50) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M6 and adding 45.163 g thereof. The obtained polyarylate copolymer resin is designated (III-6).

Production Example 7: Method of Producing Polyarylate Copolymer Resin (III-7)

(51) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M7 and adding 33.229 g thereof. The obtained polyarylate copolymer resin is designated (III-7).

Production Example 8: Method of Producing Polyarylate Copolymer Resin (III-8)

(52) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M8 and adding 37.481 g thereof. The obtained polyarylate copolymer resin is designated (III-8).

Production Example 9: Method of Producing Polyarylate Copolymer Resin (III-9)

(53) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M9 and adding 53.667 g thereof. The obtained polyarylate copolymer resin is designated (III-9).

Production Example 10: Method of Producing Polyarylate Copolymer Resin (III-10)

(54) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M10 and adding 69.852 g thereof. The obtained polyarylate copolymer resin is designated (III-10).

Production Example 11: Method of Producing Polyarylate Copolymer Resin (III-11)

(55) The synthesis was carried out as in Production Example 1, but changing the monomer M1 in Production Example 1 to M11 and adding 38.767 g thereof. The obtained polyarylate copolymer resin is designated (III-11).

Production Example 12: Method of Producing Polyarylate Copolymer Resin (III-12)

(56) The synthesis was carried out as in Production Example 7, but using 37.383 g of the monomer M7 used in Production Example 7 and using 2.48 g BP. The obtained polyarylate copolymer resin is designated (III-12).

Production Example 13: Method of Producing Polyarylate Copolymer Resin (III-13)

(57) The synthesis was carried out as in Production Example 7, but using 41.536 g of the monomer M7 used in Production Example 7 and omitting the BP. The obtained polyarylate copolymer resin is designated (III-13).

Production Example 14: Method of Producing Polyarylate Copolymer Resin (III-14)

(58) The synthesis was carried out as in Production Example 13, but using the monomer M13 indicated below for the monomer M7 used in Production Example 13 and adding 30.348 g thereof. The obtained polyarylate copolymer resin is designated (III-14) as follows.

(59) ##STR00010##

Production Example 15: Method of Producing Polyarylate Copolymer Resin (III-15)

(60) The synthesis was carried out as in Production Example 13, but using the monomer M14 indicated below for the monomer M7 used in Production Example 13 and adding 26.618 g thereof. The obtained polyarylate copolymer resin is designated (III-15) as follows.

(61) ##STR00011##

Production Example 16: Method of Producing Polyarylate Copolymer Resin (III-16)

(62) The synthesis was carried out as in Production Example 7, but using 24.922 g of the monomer M7 used in Production Example 7 and using 9.90 g BP. The obtained polyarylate copolymer resin is designated (III-16).

Production Example 17: Method of Producing Polyarylate Copolymer Resin (III-17)

(63) The synthesis was carried out as in Production Example 7, but using 20.768 g of the monomer M7 used in Production Example 7 and using 12.38 g BP. The obtained polyarylate copolymer resin is designated (III-17).

(64) Production of a Negative-Charge Stacked Photoreceptor

Example 1

(65) 5 mass parts of an alcohol-soluble nylon (product name CM8000 from Toray Industries, Inc.) and 5 mass parts of finely divided particles of an aminosilane-treated titanium oxide were dissolved and dispersed in 90 mass parts methanol to prepare a coating liquid 1. This coating liquid 1 was applied by dip coating as an undercoat layer 2 on the outer circumference of an aluminum cylinder having an outer diameter of 30 mm as a conductive substrate 1, and an undercoat layer 2 having a film thickness of 3 m was formed by drying for 30 minutes at a temperature of 100 C.

(66) A coating liquid 2 was prepared by dissolving and dispersing 1 mass parts of Y-titanyl phthalocyanine as a charge generation material and 1.5 mass parts of a polyvinyl butyral resin (product name S-LEC KS-1 from Sekisui Chemical Co., Ltd.) as a resin binder in 60 mass parts dichloromethane. This coating liquid 2 was applied by dip coating on the aforementioned undercoat layer 2, and a charge generation layer 4 with a film thickness of 0.3 m was formed by drying for 30 minutes at a temperature of 80 C.

(67) A coating liquid 3 was prepared by dissolving 90 mass parts of a compound with the following structural formula

(68) ##STR00012##
as a charge transport material and 110 mass parts of the polyarylate copolymer resin (III-1) of Production Example 1 as a resin binder in 1000 mass parts dichloromethane. The negative-charge stacked photoreceptor was then produced by applying the coating liquid 3 by dip coating on the aforementioned charge generation layer 4 and forming a charge transport layer 5 having a film thickness of 25 m by drying for 60 minutes at a temperature of 90 C.

Example 2

(69) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-2) of Production Example 2.

Example 3

(70) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-3) of Production Example 3.

Example 4

(71) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-4) of Production Example 4.

Example 5

(72) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-5) of Production Example 5.

Example 6

(73) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-6) of Production Example 6.

Example 7

(74) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-7) of Production Example 7.

Example 8

(75) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-8) of Production Example 8.

Example 9

(76) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-9) of Production Example 9.

Example 10

(77) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-10) of Production Example 10.

Example 11

(78) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-11) of Production Example 11.

Example 12

(79) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-12) of Production Example 12.

Example 13

(80) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-13) of Production Example 13.

Example 14

(81) A photoreceptor was produced by the same method as in Example 7, but changing the charge transport material used in Example 7 to the compound given by the following structural formula.

(82) ##STR00013##

Comparative Example 1

(83) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-14) of Production Example 14.

Comparative Example 2

(84) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-15) of Production Example 15.

Comparative Example 3

(85) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to a polycarbonate resin A (S-3000 from Mitsubishi Engineering-Plastics Corporation)(referred to below as III-18).

Comparative Example 4

(86) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-16) of Production Example 16.

Comparative Example 5

(87) A photoreceptor was produced by the same method as in Example 1, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 1 to the polyarylate copolymer resin (III-17) of Production Example 17.

(88) Production of a Positive-Charge Monolayer Photoreceptor

Example 15

(89) A coating liquid 4, prepared by the dissolution with stirring of 0.2 mass parts of a vinyl chloride-vinyl acetate-vinyl alcohol copolymer (product name Solbin TA5R from Nissin Chemical Industry Co., Ltd.) in 99 mass parts methyl ethyl ketone, was applied as an undercoat layer 2 by dip coating on the outer circumference of an aluminum cylinder having an outer diameter of 24 mm as a conductive substrate 1, and an undercoat layer 2 with a film thickness of 0.1 m was formed by drying for 30 minutes at a temperature of 100 C.

(90) A coating liquid 5 was prepared by the dissolution and dispersion in 350 mass parts tetrahydrofuran of 1 mass parts of a metal-free phthalocyanine with the following formula as a charge generation material,

(91) ##STR00014##
30 mass parts of a stilbene compound with the following general formula (II-1)

(92) ##STR00015##
and 15 mass parts of a stilbene compound with the following formula as hole transport materials,

(93) ##STR00016##
30 mass parts of a compound with the following formula as an electron transport material,

(94) ##STR00017##
and 55 mass parts of the polyarylate copolymer resin (III-1) of Production Example 1 as the binder resin; this coating liquid 5 was applied by dip coating on the aforementioned undercoat layer 2; and the monolayer photoreceptor was produced by drying for 60 minutes at a temperature of 100 C. to form a photosensitive layer 3 having a film thickness of 25 m.

Example 16

(95) A photoreceptor was produced by the same method as in Example 15, but changing the stilbene compound (II-1) used in Example 15 as a hole transport material to the compound given by the following formula (II-8).

(96) ##STR00018##

Comparative Example 6

(97) A photoreceptor was produced by the same method as in Example 16, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 16 to the polyarylate copolymer resin (III-16) of Production Example 16.

(98) Production of a Positive-Charge Stacked Photoreceptor

Example 17

(99) A coating liquid 6 was prepared by dissolving 50 mass parts of a compound with the following formula as a charge transport material

(100) ##STR00019##
and 50 mass parts of a Z-type polycarbonate (PCZ-500 from Mitsubishi Gas Chemical Company, Inc.) as binder resin in 800 mass parts dichloromethane. A charge transport layer 5 having a film thickness of 15 m was formed by applying this coating liquid 6 by dip coating on the outer circumference of an aluminum cylinder having an outer diameter of 24 mm as a conductive substrate 1, and then drying for 60 minutes at a temperature of 120 C.

(101) A coating liquid 7 was prepared by the dissolution and dispersion in 800 mass parts 1,2-dichloroethane of 1.2 mass parts of a metal-free phthalocyanine with the following formula as a charge generation material,

(102) ##STR00020##
10 mass parts of a stilbene compound with the following formula as a hole transport material,

(103) ##STR00021##
25 mass parts of a compound with the following formula as an electron transport material,

(104) ##STR00022##
and 60 mass parts of the polyarylate copolymer resin (III-1) of Production Example 1 as the binder resin; this coating liquid 7 was applied by dip coating on the aforementioned charge transport layer 5; and the positive-charge stacked photoreceptor was produced by drying for 60 minutes at a temperature of 100 C. to form a photosensitive layer 3 having a film thickness of 15 m.

Comparative Example 7

(105) A photoreceptor was produced by the same method as in Example 17, but changing the polyarylate copolymer resin (III-1) of Production Example 1 used in Example 17 to the polyarylate copolymer resin (III-16) of Production Example 16.

(106) Evaluation of the Photoreceptors

(107) The electrical properties of the photoreceptors produced in Examples 1 to 17 and Comparative Examples 1 to 7 were evaluated using the methods described below. The state of the coating fluid was also evaluated based on the solubility in the solvent of the resin binder during preparation of the coating liquid for the charge transport layer.

(108) Electrical Properties

(109) The electrical properties of the photoreceptors obtained in the examples and comparative examples were evaluated by the following method using a process simulator (CYNTHIA 91) from Gentec Co., Ltd. For the photoreceptors of Examples 1 to 17 and Comparative Examples 1 to 7, the surface of the photoreceptor was charged to 650 V by corona discharge in the dark in a 22 C. temperature/50% humidity environment, and the surface potential V.sub.0 was then measured immediately after charging. The surface potential V.sub.5 was subsequently measured after standing for 5 seconds in the dark, and the potential retention ratio Vk.sub.5 (%) at 5 seconds after charging was determined using the following formula (1).
Vk.sub.5=V.sub.5/V.sub.0100(1)
Then, at the time point when the surface potential had reached 600 V, the photoreceptor was irradiated for 5 seconds from a halogen lamp light source with 1.0 W/cm.sup.2 of exposure light spectrally separated to 780 nm using a filter, and the exposure dose required to photodecay the surface potential to 300 V was evaluated as E.sub.1/2 (J/cm.sup.2) and the residual potential of the photoreceptor surface at 5 seconds after exposure was evaluated as Vr.sub.5 (V).
Machine Evaluations

(110) Each of the photoreceptors produced in Examples 1 to 14 and Comparative Examples 1 to 5 was installed in an HP LJ4250 printer that had also been modified to enable measurement of the surface potential of the photoreceptor, and the amount of wear () post-printing was evaluated by printing 10,000 sheets of A4 paper and measuring the film thickness of the photoreceptor before and after printing. In addition, each of the photoreceptors produced in Examples 15 to 17 and Comparative Examples 6 and 7 was installed in a Brother HL-2040 printer that had also been modified to enable measurement of the surface potential of the photoreceptor and the exposure unit potential was evaluated. The amount of wear () post-printing was also evaluated by printing 10,000 sheets of A4 paper and measuring the film thickness of the photoreceptor before and after printing.

(111) Molecular Structure Calculations for the Resins

(112) With regard to the structure of the resins produced in the production examples, structure optimization calculations were carried out for the resins based on the charged molar ratios when the constituent monomers were polymerized. The structure optimization calculations were carried out using COGNAC, which is a molecular dynamics simulation program in J-OCTA (JSOL Corporation); the resin structure was formed using an all-atom model; Dreiding Model was selected for the force field parameters; the temperature condition was 300 K; the maximum number of repetitions was 10,000; the convergence criterion value was made 1%; and the optimized three-dimensional molecular structure (stable structure) was provided by RIS Monte Carlo calculations. The number of repeat monomers was made the minimum number of repetitions at which the total number of atoms exceeded 10,000.

(113) When the molecular structure obtained for the polymer assumed a helical structure, the diameter (r) (angstrom) and the helix pitch (I) (angstrom) of the helical structure were determined from the corresponding molecular coordinates and the value of r/I was then calculated. The results of these evaluations are given in the following Tables 2 and 3.

(114) TABLE-US-00002 TABLE 2 amount image after resin molecular of film printing structure Production weight Vk.sub.5 E.sub.1/2 Vr.sub.5 wear durability calculation Example Example resin Mw (10.sup.4) solubility (%) (J/cm.sup.2) (V) m test r/l Example 1 Production (III-1) 15.0 soluble 96.7 0.14 16 1.8 good 0.041 Example 1 Example 2 Production (III-2) 15.5 soluble 97.1 0.13 15 1.7 good 0.070 Example 2 Example 3 Production (III-3) 14.2 soluble 97.2 0.13 14 1.5 good 0.099 Example 3 Example 4 Production (III-4) 15.2 soluble 96.5 0.13 16 1.8 good 0.128 Example 4 Example 5 Production (III-5) 14.8 soluble 96.7 0.13 15 1.9 good 0.151 Example 5 Example 6 Production (III-6) 14.2 soluble 96.8 0.13 14 1.8 good 0.172 Example 6 Example 7 Production (III-7) 15.1 soluble 97.0 0.15 29 1.7 good 0.160 Example 7 Example 8 Production (III-8) 14.4 soluble 97.1 0.14 23 2.0 good 0.264 Example 8 Example 9 Production (III-9) 14.0 soluble 96.6 0.13 20 1.7 good 0.274 Example 9 Example Production (III-10) 14.2 soluble 96.8 0.13 14 1.6 good 0.290 10 Example 10 Example Production (III-11) 15.3 soluble 96.4 0.13 13 1.7 good 0.189 11 Example 11 Example Production (III-12) 14.9 soluble 96.5 0.13 12 1.6 good 0.171 12 Example 12 Example Production (III-13) 13.8 soluble 96.7 0.14 21 1.9 good 0.196 13 Example 13 Example Production (III-7) 15.1 soluble 96.6 0.13 14 1.8 good 0.160 14 Example 7 Comp. Production (III-14) 14.0 soluble 97.0 0.15 28 3.0 streak 0.009 Example 1 Example defects are 14 present Comp. Production (III-15) 14.4 soluble 96.3 0.13 25 2.8 streak nonhelical Example 2 Example defects are structure 15 present Comp. (III-18) 6.3 soluble 96.5 0.18 19 6.0 streak nonhelical Example 3 defects are structure present Comp. Production (III-16) 14.0 soluble 96.5 0.16 29 2.5 streak 0.015 Example 4 Example defects are 16 present Comp. Production (III-17) could not insoluble nonhelical Example 5 Example be structure 17 measured

(115) TABLE-US-00003 TABLE 3 amount image after resin molecular of film printing structure Production weight Vk.sub.5 E.sub.1/2 Vr.sub.5 wear durability calculation Example Example resin Mw (10.sup.4) solubility (%) (J/cm.sup.2) (V) m test r/l Example Production (III-1) 15.0 soluble 88.8 0.75 44 2.7 good 0.041 15 Example 1 Example Production (III-1) 15.0 soluble 87.2 0.69 35 2.8 good 0.041 16 Example 1 Comp. Production (III-16) 14.0 soluble 87.9 0.77 46 4.8 streak 0.015 Example 6 Example defects are 16 present Example Production (III-1) 15.0 soluble 87.2 0.61 29 2.0 good 0.041 17 Example 1 Comp. Production (III-16) 14.0 soluble 87.9 0.64 31 3.5 streak 0.015 Example 7 Example defects are 16 present

(116) According to the results in the preceding tables, low values were obtained in Examples 1 to 17 for the amount of film wear after a printing durability test in an actual machine, and were obtained without impairing the electrical properties in the role as a photoreceptor. In Comparative Examples 1 to 4, 6, and 7, on the other hand, a large amount of film wear was observed and streak image defects were seen in the image after the printing durability test. The evaluations could not be carried out in Comparative Example 5 due to an inadequate solubility by the resin. In Examples 1 to 14, the r/I value for the structure calculated based on the monomer ratio in resin synthesis exhibits numerical values from 0.04 to 1.0 and it is thus shown that the wear resistance is improved by the intertwining effect of the resin structure. The printing durability was unsatisfactory in Comparative Example 4, which used resin (III-16) which had a molar ratio (a+b):(c+d) (M7:BP)=60:40, while a photoreceptor could not be produced due to a lack of solubility in Comparative Example 5, which used resin (III-17) which had a molar ratio (a+b):(c+d) (M7:BP)=50:50.

(117) It was thus confirmed in accordance with the preceding that the use of the helically structured resin according to the present invention can provide an excellent electrophotographic photoreceptor that undergoes little wear while not suffering from a loss in electrical properties.

EXPLANATION OF REFERENCE NUMERALS

(118) 1 conductive substrate

(119) 2 undercoat layer

(120) 3 monolayer photosensitive layer

(121) 4 charge generation layer

(122) 5 charge transport layer

(123) 7 photoreceptor

(124) 21 roller charging member

(125) 22 high-voltage power source

(126) 23 imagewise exposure member

(127) 24 developing device

(128) 241 developing roller

(129) 25 paper feed member

(130) 251 paper feed roller

(131) 252 paper feed guide

(132) 26 transfer charging device (direct charging type)

(133) 27 cleaning apparatus

(134) 271 cleaning blade

(135) 28 neutralization member

(136) 60 electrophotographic apparatus

(137) 300 photosensitive layer