JP2010191161A - Electrophotographic photoreceptor, image forming apparatus, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor of high performance having high durability and obtaining excellent images continuously even under repeated use by improving problems of a conventional electrophotographic photoreceptor using polyarylate, i.e., improving wear resistance, solubility in a coating liquid solvent and electric characteristics (residual potential, bright part potential, etc.), and to provide an image forming apparatus compact with high reliability attaining high-speed printing by using the electrophotographic photoreceptor, and a process cartridge for the image forming apparatus. <P>SOLUTION: The electrophotographic photoreceptor having a photosensitive layer on a conductive support body is characterized in that the photosensitive layer contains a binder resin having specific structural units. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrophotographic photosensitive member having high durability and realizing high image quality over a long period of time. In addition, the present invention relates to an image forming apparatus and a process unit for the image forming apparatus that use those photoreceptors.

  An electrophotographic image forming method using an electrophotographic photosensitive member applied to a copying machine, a facsimile, a laser printer, or the like is performed by charging, image exposing and developing the electrophotographic photosensitive member, and then an image holding member (normally Each process includes transfer of a toner image onto a transfer of paper or the like, fixing, and cleaning of the surface of the electrophotographic photosensitive member.

  By the way, the electrophotographic photosensitive member has conventionally been provided with a photoconductive layer mainly composed of selenium or a selenium alloy on a conductive support, or an inorganic photoconductive material such as zinc oxide or cadmium sulfide in a binder. Dispersed and amorphous silicon-based materials are generally known, but in recent years they are organic due to their low cost, high degree of freedom in photoreceptor design, and non-polluting properties. Photoconductors are becoming widely used.

  As the organic photoreceptor, a photoreceptor having a function-separated type photosensitive layer structure in which a charge generation layer and a charge transport layer are laminated is excellent in various characteristics such as sensitivity, durability, and stability, and is widely put into practical use. Yes.

  However, in the organic photoreceptor having the above-described function-separated layer structure, the charge transport layer serving as the surface layer often contains a low-molecular compound charge transport material, so that the film formability of the charge transport layer is ensured. Therefore, a binder resin is used in combination with a charge transport material, but a charge transport layer composed of a low molecular charge transport material and a binder resin such as polycarbonate is generally soft, and when used repeatedly in an electrophotographic process, The disadvantage is the low wear resistance that the film is likely to be scraped by the mechanical load on the surface of the photoreceptor by the cleaning system. Actually, the film removal of the photoconductor may cause adverse effects such as deterioration of sensitivity and reduction of chargeability, and an abnormal image such as a decrease in image density and background stain may occur, resulting in the life of the photoconductor.

  In response to such problems, development of a technique capable of improving the binder resin and forming a charge transport layer having higher hardness has been advanced. For example, Patent Document 1 discloses a bisphenol Z type polycarbonate as a binder resin that improves the wear resistance of a photoreceptor.

  However, when using in a high-speed electrophotographic process, such a polycarbonate is often insufficient in terms of wear resistance, scratch resistance, etc., and a higher performance binder resin is currently desired.

  On the other hand, there is an example in which aromatic polyester is used as a binder resin in order to increase the mechanical strength of the photoreceptor. For example, Patent Document 2 discloses a technique of an electrophotographic photoreceptor using a polyarylate (aromatic polyester) resin, which is commercially available under the trade name “U-polymer”, as a binder. It is shown that the sensitivity is particularly excellent. Patent Document 3 discloses an electrophotographic photoreceptor comprising a polyarylate (aromatic polyester) copolymer having a structure using tetramethylbisphenol F and bisphenol A as a bisphenol component. Further, Patent Document 4 discloses an electrophotographic photosensitive member characterized by containing polyarylate (aromatic polyester) using bisphenol C as bisphenol.

  However, according to the technique using these aromatic polyesters as a binder for the photosensitive layer, there is a drawback that the solubility of the photosensitive layer in the coating solvent and the stability of the solution are poor, or these electrical characteristics are deteriorated. . In particular, in the technique described in the above-mentioned Patent Document 2, although slight improvement is seen in terms of wear resistance and sensitivity, the coating solution is poorly stable, so that coating production is impossible or possible. But slipperiness is poor. Further, in the technique described in Patent Document 3 described above, an improvement is seen in terms of wear resistance as compared with conventional polycarbonates, but no superiority is found in terms of slipping properties compared to polycarbonate. Furthermore, although the technique described in Patent Document 4 described above has the advantage that the wear resistance is improved as compared with the conventional polycarbonate and the life of the photosensitive member is extended, the electrical characteristics, particularly the responsiveness, are improved. It is inferior to the case where polycarbonate resin is used.

JP 59-71057 A JP-A-56-135844 Japanese Patent Laid-Open No. 3-6567 JP 7-333911 A

  The object of the present invention is to improve the electrophotographic photosensitive member using the conventional polyarylate, that is, the antiwear property, the solubility in the coating solution solvent, and the electrical properties (residual potential, bright portion potential, etc.). Another object of the present invention is to provide a high-performance electrophotographic photosensitive member having high durability and capable of continuously obtaining a good image even after repeated use. Another object of the present invention is to provide a highly reliable image forming apparatus and a process cartridge for an image forming apparatus that are small in size and capable of high-speed printing by using the electrophotographic photosensitive member.

  As a result of intensive studies, the present inventors have found that the object of the present invention can be achieved by using a novel polyarylate resin as a binder resin for an electrophotographic photosensitive member. It came.

  That is, the object of the present invention is achieved by having the following configuration.

  1. An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a binder resin having a structural unit represented by the following general formula (1).

(In the general formula (1), R represents a divalent organic group, and R ′ represents a divalent group having three or more aromatic rings.)
2. The binder resin having the structural unit represented by the general formula (1) is obtained by condensation polymerization of a dicarboxylic acid compound having R in the general formula (1) and a diol compound having R ′. 2. The electrophotographic photosensitive member according to 1.

3. 2. The electrophotographic photosensitive member according to item 2, wherein the diol compound having R ′ is an aromatic diol compound represented by the following general formula (2):
HO−φ ₁ −A ₁ −φ ₂ −A ₂ −... −A _n−1 −φ _n −OH
Formula (2) phi _1, phi _2, the ... phi _n, a substituted or unsubstituted aromatic ring. (N is an integer of 3 or more)
A ₁ , A ₂ ,... A _n-1 represents a divalent group selected from the following group (n is an integer of 3 or more).
—CR ₁ R ₂ —, —R ₃ —, —O—, —S—, represents a direct bond. (Provided that the _R 1, _{R 2} is H, an alkyl group, an allyl group, an aryl group, an alkoxy group, a halogen, to make a bond with _{R 1} and _{R 2,} which may .R ₃ also form a ring, the carbon Represents an alkylene group of several 2 or more.)
4). 4. The electrophotographic photosensitive member as described in 2 or 3 above, wherein the diol compound having R ′ is at least one compound selected from the following d1 to d5.

d1: 4,4'-bis (3,5-dimethyl-4-phenylenediisopropylidene) bisphenol d2: 4,4 '-(1,4-phenylenediisopropylidene) bisphenol (bisphenol P)
d3: 4,4 '-(1,3-phenylenediisopropylidene) bisphenol (bisphenol M)
d4: 1,3-bis (4-hydroxyphenoxy) benzene d5: 1,4-bis (3-hydroxyphenoxy) benzene 5. The electrophotographic photoreceptor according to any one of items 2 to 4, wherein an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid is used for the dicarboxylic acid compound having R in the general formula (1).

  6). 6. The electrophotography as described in 5 above, wherein two or more dicarboxylic acid compounds selected from aromatic dicarboxylic acids or aliphatic dicarboxylic acids are used as the dicarboxylic acid compound having R in the general formula (1). Photoconductor.

  7). The electrophotographic photoreceptor has a charge generation layer and a charge transport layer laminated thereon as a photosensitive layer, and the surface layer of the electrophotographic photoreceptor has a structural unit represented by the general formula (1). The electrophotographic photosensitive member according to any one of the above items 1 to 6, further comprising a binder resin.

  8). 8. An image forming apparatus that has at least a charging unit, an exposure unit, and a developing unit around an electrophotographic photosensitive member, and repeatedly forms an image. An image forming apparatus characterized by being a photographic photoreceptor.

  9. The process cartridge used in the image forming apparatus described in item 8 includes at least one of the electrophotographic photosensitive member described in any one of items 1 to 7 and a charging unit, a cleaning unit, an image exposure unit, and a developing unit. A process cartridge which is integrally formed and configured to be able to be inserted into and removed from the image forming apparatus.

  By using the electrophotographic photosensitive member of the present invention, the wear resistance is improved, the solubility in the coating solution solvent at the time of manufacture, and the electrical characteristics (residual potential, bright part potential, etc.) are improved, and high durability is achieved. In addition, it is possible to provide a high-performance electrophotographic photosensitive member capable of continuously obtaining good images even after repeated use.

1 is a schematic view in which functions of an image forming apparatus of the present invention are incorporated. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention. 1 is a cross-sectional view of a color image forming apparatus using an organic photoreceptor of the present invention.

  Hereinafter, the present invention will be described in detail.

  The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a binder resin having a structural unit represented by the general formula (1). Features.

  Since the electrophotographic photoreceptor of the present invention has the above-described configuration, the photoreceptor has high durability and does not generate an image flow with repeated use, and a good image can be obtained continuously. .

  Next, main components constituting the present invention will be described below.

  The binder resin having the structural unit of the general formula (1) has a dicarboxylic acid compound having R (a divalent organic group) in the general formula (1) and R ′ (three or more aromatic rings). It can be obtained by condensation polymerization of a diol compound having a divalent group.

  As the diol compound having R ′, an aromatic diol compound represented by the following general formula (2) is preferably used.

General formula (2)
HO−φ ₁ −A ₁ −φ ₂ −A ₂ −... −A _n−1 −φ _n −OH
In general formula (2), φ ₁ , φ ₂ ,... Φ _n represent a substituted or unsubstituted aromatic ring. (N is an integer of 3 or more)
A ₁ , A ₂ ,... A _n-1 represents a divalent group selected from the following group (n is an integer of 3 or more).
_{-CR 1 R 2 -, - R} 3 -, - O -, - S-, represents a direct bond. (Provided that the _R 1, _{R 2} is H, an alkyl group, an allyl group, an aryl group, an alkoxy group, a halogen, to make a bond with _{R 1} and _{R 2,} which may .R ₃ also form a ring, the carbon Represents an alkylene group of several 2 or more.)
Specific examples of φ ₁ , φ ₂ ,..., Φ _n can be selected from, for example, the following groups, but the present invention is not limited to this and is within a range that does not impair the effects of the invention. Various selections may be made. φ _1, φ _{2, ...,} as the phi _n, all need not be the same _{substituent, φ 1, φ 2, ...} , a part or all of phi _n may be used with different substituents.

Among the substituents of A ₁ , A ₂ ,..., A _n-1 , particularly preferable examples can be selected from the following groups, for example, but the present invention is not limited thereto. Various selections may be made as long as the effects of the invention are not impaired. A _{1, A} 2, _..., as the _{A n-1,} all need not be the same _substituent, A _1, A 2, _..., a part or all of the _{A n-1} by using the different substituents Also good.

  As the diol compound having R ′, it is preferable to use one or more compounds selected from the following d1 to d5.

d1: 4,4'-bis (3,5-dimethyl-4-phenylenediisopropylidene) bisphenol d2: 4,4 '-(1,4-phenylenediisopropylidene) bisphenol (bisphenol P)
d3: 4,4 '-(1,3-phenylenediisopropylidene) bisphenol (bisphenol M)
d4: 1,3-bis (4-hydroxyphenoxy) benzene d5: 1,4-bis (3-hydroxyphenoxy) benzene Further, an aromatic dicarboxylic acid is added to the dicarboxylic acid compound having R in the general formula (1). Alternatively, it is preferable to use a dicarboxylic acid compound selected from aliphatic dicarboxylic acids.

  Examples of the aromatic dicarboxylic acid component include isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, methyl isophthalic acid, methyl terephthalic acid, diphenyl-4,4′-dicarboxylic acid, diphenyl-3, 3'-dicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, 1,1-diphenylethane-4,4'-dicarboxylic acid, 2,2-diphenylpropane-4,4'-dicarboxylic acid, benzophenone-4, 4'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic Acid, diphenylthioether-4,4'-dicarboxylic acid, diphenylsulfur De-4,4'-dicarboxylic acid, derived from an aromatic dicarboxylic acid compounds such as may be used in combination of two or more. Of these, isophthalic acid, terephthalic acid and mixtures thereof are particularly useful. In particular, a mixture of isophthalic acid and terephthalic acid is effective, and it is desirable that the molar ratio of isophthalic acid / terephthalic acid is in the range of 10/90 to 95/5, and a more preferable range is that the molar ratio is 25 / It is the range of 75-75 / 25.

  Examples of the aliphatic carboxylic acid component include adipic acid, glutaric acid, methylglutaric acid, succinic acid, methylsuccinic acid, pentanedicarboxylic acid, hexanedicarboxylic acid, heptanedicarboxylic acid, octanedicarboxylic acid, decanedicarboxylic acid, and dodecanedicarboxylic acid. Derived from acids, aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid.

The glass transition temperature of the binder resin of the general formula (1) according to the present invention is preferably 100 ° C. or higher and 180 ° C. or lower. The binder resin has an effective polystyrene average weight average molecular weight of 2 × 10 ^{4 to} 5 × 10 ⁶ , and particularly preferably has a polystyrene equivalent weight average molecular weight of 5 × 10 ⁴ to 1 × 10 ⁶ .

About the manufacturing method of the binder resin of the said General formula (1) of this invention As a manufacturing method of copolymer polyarylate resin which has a structural unit of this invention, each dicarboxylic acid compound which induces a polyarylate structure, a diol compound, or its A melt polymerization method, a solution polymerization method and an interfacial polymerization method using a derivative can be used, and among these, the interfacial polymerization method is effectively used. Moreover, the manufacturing method using the melt-kneading transesterification reaction of the other polyester resin is also possible.

  By using the binder resin of the general formula (1) according to the present invention for the surface layer of an electrophotographic photosensitive member, particularly an organic photosensitive member, the object of the present invention can be better achieved.

  Hereinafter, a preferable photoreceptor structure of the present invention will be described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor configured to have an organic compound having at least one of a charge generation function and a charge transport function indispensable for the configuration of the electrophotographic photoconductor, It contains all known organic photoreceptors such as a photoreceptor composed of a known organic charge generating material or organic charge transport material, a photoreceptor composed of a polymer complex with a charge generating function and a charge transport function.

  The organic photoreceptor may have a structure in which a photosensitive layer having a single layer structure is provided on a conductive support. However, in the present invention, a photoreceptor having at least the following layer structure is preferable, and the uppermost layer is among them. It is preferable to use the binder resin of the general formula (1) of the present invention for the protective layer or the photosensitive layer.

1) Layer structure in which a charge generation layer and a charge transport layer are sequentially laminated as an intermediate layer and a photosensitive layer on a conductive support,
2) Layer structure in which a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated as an intermediate layer and a photosensitive layer on a conductive support.
The layer structure of the organic photoreceptor of the present invention will be described focusing on the above 1) and 2).

[Conductive support]
The support used in the present invention may be any one as long as it has conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel formed into a drum or a sheet, aluminum or copper Metal foils such as those laminated on plastic films, aluminum, indium oxide and tin oxide deposited on plastic films, metals with conductive layers applied alone or with a binder resin, plastic films and For example, paper.

[Middle layer]
In the present invention, an intermediate layer having a barrier function and an adhesive function may be provided between the conductive layer and the photosensitive layer.

  The intermediate layer can be formed by dip coating or the like by dissolving a binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane and gelatin in a known solvent. Of these, an alcohol-soluble polyamide resin is preferred.

  Various conductive fine particles and metal oxides can be contained for the purpose of adjusting the resistance of the intermediate layer. For example, various metal oxides such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide. Ultrafine particles such as indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide can be used.

  You may use these metal oxides 1 type or in mixture of 2 or more types. When two or more types are mixed, it may take the form of a solid solution or fusion. The average particle diameter of such a metal oxide is preferably 0.3 μm or less, more preferably 0.1 μm or less.

  As the solvent used for the intermediate layer, a solvent in which inorganic particles are well dispersed and the polyamide resin is dissolved is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are excellent in solubility and coating performance of the polyamide resin. In addition, examples of co-solvents that can be used in combination with the above-described solvent to obtain favorable effects in order to improve storage stability and particle dispersibility include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

  The density | concentration of binder resin is suitably selected according to the film thickness and production rate of an intermediate | middle layer.

  When the inorganic particles are dispersed, the mixing ratio of the inorganic particles to the binder resin at the time is preferably 20 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  As a means for dispersing the inorganic particles, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The method for drying the intermediate layer can be appropriately selected according to the type of solvent and the film thickness, but thermal drying is preferred.

  The film thickness of the intermediate layer is preferably from 0.1 to 30 μm, more preferably from 0.3 to 20 μm.

(Charge generation layer)
The charge generation layer used in the present invention preferably contains a charge generation material and a binder resin, and is formed by dispersing and coating the charge generation material in a binder resin solution.

  Examples of the charge generation material include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as bilenquinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and phthalocyanine pigments. It is not something. These charge generating substances can be used alone or in a form dispersed in a known resin.

  As the binder resin of the charge generation layer, a known resin can be used, for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, Polyurethane resins, phenol resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (eg, vinyl chloride-vinyl acetate copolymer resins, chlorides) Vinyl-vinyl acetate-maleic anhydride copolymer resin) and poly-vinylcarbazole resin, but are not limited thereto.

  The charge generation layer is formed by dispersing a charge generation material in a solution in which a binder resin is dissolved in a solvent using a disperser to prepare a coating solution, and applying the coating solution to a certain film thickness using a coating device. It is preferable to prepare the film by drying.

  Solvents for dissolving and coating the binder resin used in the charge generation layer include, for example, toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, Examples include butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine, but are not limited thereto.

  As a means for dispersing the charge generating material, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The mixing ratio of the charge generating material to the binder resin is preferably 1 to 600 parts by weight, more preferably 50 to 500 parts by weight based on 100 parts by weight of the binder resin. The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating. The pigment can also be formed by vacuum deposition.

(Charge transport layer)
The charge transport layer used in the photoreceptor of the present invention contains a charge transport material (CTM) and a binder resin, and is formed by dissolving and coating the charge transport material in a binder resin solution.

  Examples of charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds Oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1- A mixture of two or more of vinylpyrene, poly-9-vinylanthracene, triphenylamine derivatives and the like may be used.

  As the binder resin for the charge transport layer, it is preferable to use the binder resin represented by the general formula (1) of the present invention. A known resin may be used in combination with the binder resin of the general formula (1). Examples of the binder resin used in combination include polycarbonate resins, other polyacrylate resins, polyester resins, polystyrene resins, styrene-acrylonitrile copolymer resins, polymethacrylic acid ester resins, and styrene-methacrylic acid ester copolymer resins. .

  The charge transport layer is preferably formed by dissolving the binder resin and the charge transport material to prepare a coating solution, applying the coating solution to a certain film thickness with a coating machine, and drying the coating film.

  Examples of the solvent for dissolving the coating liquid containing the binder resin and the charge transport material for the charge transport layer include methylene chloride, 1,2-dichloroethane, toluene, xylene, benzene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetic acid. Examples include ethyl, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, N, N′-dimethylformamide, pyridine and the like. Among these, the binder resin of the general formula (1) according to the present invention is used. Solvents that improve the solubility of the coating solution and the stability of the coating solution when used are tetrahydrofuran, toluene, xylene, 1,4-dioxane, methyl isobutyl ketone, methylene chloride, 1,2- A solvent such as dichloroethane can be mentioned. That is, a good coating solution can be produced without necessarily using a halogen-containing solvent.

  The mixing ratio of the charge transport material to the binder resin is preferably 10 to 500 parts by mass, more preferably 20 to 150 parts by mass with respect to 100 parts by mass of the binder resin.

  The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 5 to 40 μm, more preferably 10 to 35 μm.

  An antioxidant, an electronic conductive agent, a stabilizer and the like may be added to the charge transport layer. For the antioxidant, those described in Japanese Patent Application No. 11-200135 and for the electronic conductive agent are described in Japanese Patent Application Laid-Open Nos. 50-137543 and 58-76483.

  In addition, a leveling agent can be added to the charge transport layer as necessary. Examples of leveling agents that can be used in the charge transport layer include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in the side chain. About 0-1 mass part is suitable with respect to a mass part.

  Next, an image forming apparatus using the organic photoreceptor of the present invention will be described.

  An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer material conveying unit D as a transfer material conveying unit. Yes.

  An automatic document feeder that automatically conveys the document is provided above the image reading unit A. The document placed on the document table 11 is separated and conveyed by the document conveyance roller 12 to the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including the two mirrors and the third mirror in the same direction at the speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the toner, developing means (developing process) 23, transfer / conveying belt device 45 serving as a transferring means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and light discharging means (light discharging process). PCL (precharge lamps) 27 are arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. As the photosensitive member 21, the organic photosensitive member according to the present invention is used, and the photosensitive member 21 is driven and rotated in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, an image based on an image signal called from the memory of the image processing unit B by an exposure optical system as an image exposure unit (image exposure step) 30 is used. Exposure is performed. The exposure optical system as the image exposure means 30 as the writing means uses a laser diode (not shown) as a light source, and the optical path is bent by the reflection mirror 32 via the rotating polygon mirror 31, the fθ lens 34, and the cylindrical lens 35, and main scanning is performed. Therefore, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In one example of the present embodiment, the character portion is exposed to form an electrostatic latent image.

  In the image forming apparatus of the present invention, it is preferable to use a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 800 nm as an image exposure light source when an electrostatic latent image is formed on a photoreceptor. Using these image exposure light sources, the exposure dot diameter in the writing direction is narrowed down to 10 to 100 μm, and digital exposure is performed on the organic photoreceptor, so that it is 400 dpi (dpi: the number of dots per 2.54 cm) or more. A high-resolution electrophotographic image of 2500 dpi can be obtained.

The exposure dot diameter refers to the length of the exposure beam along the main scanning direction (Ld: measured at the maximum length) in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a solid scanner such as the scanning optical system and LED using a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot diameter according to the present invention is used.

  The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method of the present invention, it is preferable to use a polymerized toner as a developer used in the developing means. By using a polymer toner having a uniform shape and particle size distribution in combination with the organic photoreceptor according to the present invention, an electrophotographic image with better sharpness can be obtained.

  The electrostatic latent image formed on the organic photoreceptor of the present invention is visualized as a toner image by development. The toner used for development may be a pulverized toner or a polymerized toner, but the toner according to the present invention is preferably a polymerized toner that can be prepared by a polymerization method from the viewpoint of obtaining a stable particle size distribution.

  The term “polymerized toner” means a toner in which a toner binder resin is formed and the toner shape is formed by polymerization of a raw material monomer of the binder resin and, if necessary, subsequent chemical treatment. More specifically, it means a toner formed through a polymerization reaction such as suspension polymerization or emulsion polymerization, and if necessary, a step of fusing particles between them.

  The volume average particle diameter of the toner, that is, the 50% volume particle diameter (Dv50) is preferably 2 to 9 μm, more preferably 3 to 7 μm. By setting this range, the resolution can be increased. In addition, by combining with the above range, the amount of toner having a fine particle diameter can be reduced while being a small particle diameter toner, the dot image reproducibility is improved over a long period of time, and the sharpness is excellent. In addition, a stable image can be formed.

  The toner according to the present invention may be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 80 μm.

  The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to.

  In the transfer material transport unit D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer material storage means in which transfer materials P of different sizes are stored. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer material P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer material P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer material P, and then re-feeded. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 are transferred. The toner image on the photosensitive member 21 is transferred to the transfer material P while being transferred to the transfer conveyance belt 454 of the transfer conveyance belt device 45 by the transfer electrode 24 and the separation electrode 25 at the transfer position Bo. Is, the transfer material P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer material P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image is fixed, the transfer material P is discharged onto the paper discharge tray 64.

  The above describes the state of image formation on one side of the transfer material. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the transfer material guide 177 is opened, and the transfer material P is indicated by a broken arrow. Conveyed in the direction.

  Further, the transfer material P is transported downward by the transport mechanism 178 and is switched back by the transfer material reversing unit 179, and the rear end portion of the transfer material P becomes the leading end portion and transported into the duplex copying paper supply unit 130. The

  The transfer material P moves a conveyance guide 131 provided in the duplex copying paper supply unit 130 in the paper supply direction, refeeds the transfer material P by the paper supply roller 132, and guides the transfer material P to the conveyance path 40. .

  Again, as described above, the transfer material P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer material P, fixed by the fixing unit 50, and then discharged onto the discharge tray 64.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge, and this unit is configured to be detachable from the apparatus main body. Also good. In addition, a process cartridge is formed by integrally supporting at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device together with a photosensitive member, and a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of an apparatus body.

  FIG. 2 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a feeding unit. It comprises a paper conveying means 21 and a fixing means 24. A document image reading device SC is disposed above the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit (charging step) 2Y, an exposure unit (exposure step) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A unit (developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (primary transfer step), and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk include charging means 2Y, 2M, 2C, and 2Bk that rotate around the photosensitive drums 1Y, 1M, 1C, and 1Bk, and image exposure means 3Y, 3M, 3C and 3Bk, rotating developing means 4Y, 4M, 4C and 4Bk, and cleaning means 5Y, 5M, 5C and 5Bk for cleaning the photosensitive drums 1Y, 1M, 1C and 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of toner images formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. explain.

  The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 5Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning means 5Y or the cleaning blade 5Y) is simply disposed, and a yellow (Y) toner image is formed on the photosensitive drum 1Y. In the present embodiment, in the image forming unit 10Y, at least the photosensitive drum 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 5Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photosensitive drum 1Y. In the present embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The image exposure unit 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y to form an electrostatic latent image corresponding to the yellow image. As the exposure means 3Y, the exposure means 3Y includes an LED in which light emitting elements are arranged in an array in the axial direction of the photosensitive drum 1Y and an imaging element (trade name; Selfoc lens), or A laser optical system or the like is used.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge (image forming unit). It may be configured to be detachable. In addition, at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge (image forming unit), which is detachable from the apparatus main body. A single image forming unit may be detachable using guide means such as a rail of the apparatus main body. Here, “supported integrally” means that the process cartridge can be attached or detached as one lump in the unit of the process cartridge when the process cartridge is attached or detached.

  The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. A transfer material P as a transfer material (a support for carrying a fixed final image: for example, plain paper, a transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and a plurality of intermediates. After passing through rollers 22A, 22B, 22C, 22D and registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto a transfer material P to transfer a color image all at once. The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing unit 24, is sandwiched between paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a transfer support for a toner image formed on a photosensitive member such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

  On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5b as the secondary transfer means, the residual toner is removed by the cleaning means 6b from the endless belt-shaped intermediate transfer body 70 in which the transfer material P is separated by curvature. The

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5b.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b. Consists of.

  Next, FIG. 3 shows a color image forming apparatus using the organic photoreceptor of the present invention (a copying machine having at least a charging means, an exposure means, a plurality of developing means, a transfer means, a cleaning means, and an intermediate transfer body around the organic photoreceptor. 1 is a cross-sectional view of a configuration of a laser beam printer). The belt-shaped intermediate transfer body 70 uses an elastic body having a medium resistance.

  Reference numeral 1 denotes a rotary drum type photoconductor that is repeatedly used as an image forming body, and is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed.

  In the rotation process, the photoreceptor 1 is uniformly charged to a predetermined polarity and potential by a charging means (charging process) 2, and then time-series electric digital of image information by an image exposure means (image exposure process) 3 (not shown). An electrostatic latent image corresponding to the yellow (Y) color component image (color information) of the target color image is formed by receiving image exposure by scanning exposure light or the like by a laser beam modulated in accordance with the pixel signal. The

  Then, the electrostatic latent image is developed with yellow toner as the first color by yellow (Y) developing means: developing step (yellow color developing device) 4Y. At this time, the second to fourth developing means (magenta developer, cyan developer, black developer) 4M, 4C, and 4Bk are turned off and do not act on the photosensitive member 1. The yellow toner image of the first color is not affected by the second to fourth developing devices.

  The intermediate transfer member 70 is stretched by rollers 79a, 79b, 79c, 79d, and 79e, and is driven to rotate in the clockwise direction at the same peripheral speed as the photosensitive member 1.

  The yellow toner image of the first color formed and supported on the photosensitive member 1 is applied to the intermediate transfer member 70 from the primary transfer roller 5a in the process of passing through the nip portion between the photosensitive member 1 and the intermediate transfer member 70. Intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 70 by an electric field formed by the primary transfer bias.

  The surface of the photoreceptor 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer body 70 is cleaned by the cleaning device 6a.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black (black) toner image are sequentially superimposed and transferred onto the intermediate transfer body 70 to correspond to the target color image. A superimposed color toner image is formed.

  The secondary transfer roller 5b is supported in parallel with the secondary transfer counter roller 79b so as to be separated from the lower surface portion of the intermediate transfer body 70.

  The primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photoreceptor 1 to the intermediate transfer member 70 has a polarity opposite to that of the toner and is applied from a bias power source. The applied voltage is, for example, in the range of +100 V to +2 kV.

  In the primary transfer process of the first to third color toner images from the photosensitive member 1 to the intermediate transfer member 70, the secondary transfer roller 5b and the intermediate transfer member cleaning means 6b can be separated from the intermediate transfer member 70. .

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred onto the transfer material P, which is the second image carrier, the secondary transfer roller 5b is brought into contact with the belt of the intermediate transfer member 70. At the same time, the transfer material P is fed from the pair of paper registration rollers 23 through the transfer material guide to the contact nip of the intermediate transfer body 70 with the secondary transfer roller 5b at a predetermined timing. A secondary transfer bias is applied to the secondary transfer roller 5b from a bias power source. By this secondary transfer bias, the superimposed color toner image is transferred (secondary transfer) from the intermediate transfer body 70 to the transfer material P as the second image carrier. The transfer material P that has received the transfer of the toner image is introduced into the fixing means 24 and fixed by heating.

  The image forming apparatus of the present invention is generally applicable to electrophotographic apparatuses such as an electrophotographic copying machine, a laser printer, an LED printer, and a liquid crystal shutter type printer, and further displays, recordings, light printing, plate making, and facsimiles using electrophotographic technology. The present invention can be widely applied to such devices.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. In addition, "part" used in an Example represents a mass part altogether.

Production of Photoreceptor 1 Photoreceptor 1 was produced as follows.

  The surface of the cylindrical aluminum support was cut to prepare a conductive support having a surface roughness Rz = 1.5 (μm).

<Intermediate layer>
An intermediate layer coating solution having the following composition was prepared.
Polyamide resin X1010 (manufactured by Daicel Degussa Co., Ltd.) 1 part Titanium dioxide SMT500SAS (manufactured by Teika) 1.1 parts ethanol 20 parts Dispersion was carried out for 10 hours in a batch manner using a sand mill as a disperser.

  It apply | coated by the dip coating method on the said support body using the said coating liquid so that it might become a film thickness of 2 micrometers after drying for 20 minutes at 110 degreeC.

<Charge generation layer>
Charge generation material: titanyl phthalocyanine pigment (a titanyl phthalocyanine pigment having a maximum diffraction peak at a position of 5 at least 27.3 ° by Cu-Kα characteristic X-ray diffraction spectrum measurement)
20 parts polyvinyl butyral resin (# 6000-C: manufactured by Denki Kagaku Kogyo) 10 parts t-butyl acetate 700 parts 4-methoxy-4-methyl-2-pentanone 300 parts are mixed and dispersed for 10 hours using a sand mill. A charge generation layer coating solution was prepared. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.

<Charge transport layer>
Charge transport material: CTM (compound A below) 150 parts Binder: Copolymer polyarylate resin having the following structural units (with d1 and a mixture of isophthalic acid (a1) / terephthalic acid (a2) = 1/1 (parts) Copolymerization) 300 parts antioxidant (Irganox 1010: manufactured by Ciba Geigy Japan) 6 parts toluene / tetrahydrofuran = 1.5 / 8.5 (parts) 2000 parts silicon oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part mixed And dissolved to prepare a charge transport layer coating solution. The coating solution was dried on the charge generation layer using a dip coating method at 110 ° C. for 60 minutes to form a charge transport layer having a thickness of 30 μm.

Weight average molecular weight in terms of polystyrene: 290000
Production of Photoreceptor 2 In production of Photoreceptor 1, a copolymer polyarylate resin having the following structural units as a binder of the charge transport layer (the d2 and isophthalic acid (a1) / terephthalic acid (a2) = 1/1 (part) The photoconductor 2 was prepared in the same manner except that the copolymerization was carried out.

Weight average molecular weight in terms of polystyrene: 270000
Production of Photoreceptor 3 In production of Photoreceptor 1, a binder of the charge transport layer is a copolymer polyarylate resin having the following structural units (d3 and isophthalic acid (a1) / terephthalic acid (a2) = 1/1 (part). The photoconductor 3 was prepared in the same manner except that the copolymerization was carried out.

Weight average molecular weight in terms of polystyrene: 260000
Production of Photoreceptor 4 In the production of Photoreceptor 1, a copolymer polyarylate resin having the following structural units as the binder of the charge transport layer (the d4 and isophthalic acid (a1) / terephthalic acid (a2) = 1/1 (part) The photoconductor 4 was prepared in the same manner except that the copolymerization was carried out.

Weight average molecular weight in terms of polystyrene: 230000
Production of Photoreceptor 5 In the production of Photoreceptor 1, a copolymer polyarylate resin having the following structural units as the binder of the charge transport layer (the d5 and isophthalic acid (a1) / terephthalic acid (a2) = 1/1 (part) The photoconductor 5 was prepared in the same manner except that the copolymerization was carried out.

Weight average molecular weight in terms of polystyrene: 240000
Production of Photoreceptor 6 In production of the photoreceptor 1, a binder of the charge transport layer is a copolymerized polyarylate resin having the following structural units (diol of d6 and isophthalic acid (a1) / terephthalic acid (a2) = 1/1 ( The photosensitive member 6 was prepared in the same manner except that the copolymer was replaced with the copolymer of the component (1).

Weight average molecular weight in terms of polystyrene: 280000
Compound structure of d6

Production of Photoreceptor 7 The production of Photoreceptor 1 was carried out in the same manner except that the binder of the charge transport layer was replaced with a copolymerized polyarylate resin (copolymerization of d1 and dicarboxylic acid (a3) below) having the following structural units. Thus, a photoreceptor 7 was produced.

Weight average molecular weight in terms of polystyrene: 270000
a3 dicarboxylic acid compound structure

Production of Photoreceptor 8 Photoreceptor 8 was produced in the same manner as in production of Photoreceptor 1 except that the binder of the charge transport layer was replaced by a copolymerized polyarylate resin (copolymerization of d2 and a3) having the following structural units. Produced.

Weight average molecular weight in terms of polystyrene: 250,000
Production of Photoreceptor 9 In production of Photoreceptor 1, a binder of the charge transport layer was used as a copolymer polyarylate resin having the following structural units (1/1 of d1, (isophthalic acid (a1), terephthalic acid (a2) and a3). A photoconductor 9 was prepared in the same manner except that the copolymer was replaced with (a copolymer of 1/1 part).

l and m are molar ratios of components: l = 0.56: m = 0.44
Weight average molecular weight in terms of polystyrene: 250,000
Production of Photoreceptor 10 In the production of Photoreceptor 1, the binder of the charge transport layer was a copolymerized polyarylate resin having the following structural units (the above-mentioned d1, (isophthalic acid (a1), terephthalic acid (a2), and the following dicarboxylic acid (a4 The photoconductor 10 was prepared in the same manner except that the copolymer was replaced with a 2/2/1 (part) mixture).

l and m are molar ratios of components: l = 0.84: m = 0.16
Weight average molecular weight in terms of polystyrene: 260000
Structure of a4

Production of Photoreceptor 11 In the production of Photoreceptor 1, a binder of the charge transport layer is a copolymer polyarylate resin having the following structural units (the above-mentioned d1, (isophthalic acid (a1), terephthalic acid (a2) and adipic acid (a5) The photoconductor 11 was prepared in the same manner except that the copolymer was replaced with a 1 / 1.1 (part) mixture).

Structure of a5

l and m are molar ratios of components: l = 0.69: m = 0.31
Weight average molecular weight in terms of polystyrene: 270000
Production of Photoreceptor 12 (Comparative Photoreceptor) In production of Photoreceptor 1, the binder of the charge transport layer was replaced with a polyarylate resin having the following structural unit, and the coating solvent for the charge transport layer was replaced with 4000 parts of tetrahydrofuran. Similarly, a photoreceptor 12 was produced.

Weight average molecular weight in terms of polystyrene: 230000
Production of Photoreceptor 13 (Comparative Photoreceptor) In production of Photoreceptor 1, Photoreceptor 13 was prepared in the same manner except that the binder of the charge transport layer was changed to polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) having the following structural unit. Produced.

[Evaluation of photoconductor]
The photoconductor obtained as described above is basically a commercially available full-color MFP bizhub PRO C6500 having the configuration of FIG. 2 (manufactured by Konica Minolta Business Technologies, Inc .; using exposure light of a semiconductor laser of 600 dpi and 780 nm) Was used to evaluate. Since the full-color multifunction peripheral has four image forming units, the photosensitive members of each image forming unit are the same type of photosensitive member (for example, in the case of the photosensitive member 1, four photosensitive members 1 are provided. Prepared) and unified and evaluated. Each evaluation was performed under the conditions of 30 ° C. and 80% RH, and an A4 image with a YMCBk color printing ratio of 2.5% was printed on neutral A4 paper, and the printing durability test was performed. The environmental conditions were evaluated.

(Potential characteristics)
With the above evaluation, 100,000 images were printed, and the following surface potentials after the initial and 100,000 sheets were evaluated.

  The surface potential VL (V) of the exposed portion and the surface potential VH (V) of the unexposed portion were measured, and the potential fluctuations after initial and 100,000 sheets, ΔVL (V), ΔVH (V) were evaluated.

  Photoconductor charging potential (unexposed portion potential): The initial potential was set to -700V.

(Evaluation of color image)
After printing and printing durability test for 100,000 sheets at 30 ° C. and 80% RH, it was left for 12 hours under the environmental condition of 20 ° C. and 50% RH, and 4 sets of the full color multifunction machine bizhub PRO C6500 The image forming unit was activated, and a halftone image including a human face photograph was printed on A4 paper, and evaluated according to the following criteria.

◎: Halftone color image is smoothly reproduced and no image blur or image unevenness is found. ○: Image blur or image unevenness partially occurs in the halftone color image, but it is not conspicuous. Is reproduced smoothly (no problem in practical use)
○ △: Image blur and image unevenness are partially included in the halftone color image, and the reproducibility is at the acceptable boundary level. Δ: Image blur and image that are partially clear in the halftone color image. Unevenness is included and reproducibility is lost (practical problem)
X: Clear image blurring or image unevenness has occurred on the entire surface of the halftone color image (practically problematic).

(Amount of photoconductor wear)
In the above evaluation, 100,000 images were drawn and evaluated using the initial film thickness and the film thickness difference after 100,000 sheets. The thickness of the photosensitive layer is measured at 10 points at random (excluding 5 cm at both ends because the film thickness tends to be non-uniform at both ends of the photoconductor) at random, and the average value is the film of the photosensitive layer. Thickness. The film thickness measuring device was an eddy current type film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO), and the amount of wear from the initial film thickness was calculated.

(Solvent solubility, coating solution storage stability)
Regarding the binder of the charge transport layer of the photoreceptors 1 to 12, the solvent solubility of the coating solution and the storage stability of the coating solution were evaluated. Solvent solubility evaluated the solubility of binder resin etc., when a coating liquid was produced on the following three conditions.

Condition 1:
Charge transport material: CTM (compound A) 150 parts Binder: 300 parts Antioxidant (Irganox 1010: manufactured by Ciba Geigy Japan) 6 parts Toluene / tetrahydrofuran = 1.5 / 8.5 (parts) 2000 parts Silicon oil (KF- 54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part Condition 2:
Charge transport material: CTM (compound A) 150 parts Binder: 300 parts Antioxidant (Irganox 1010: manufactured by Ciba Geigy Japan) 6 parts Tetrahydrofuran 2000 parts Silicon oil (KF-54: manufactured by Shin-Etsu Chemical Co.) 1 part Condition 3:
Charge transport material: CTM (compound A) 150 parts Binder: 300 parts Antioxidant (Irganox 1010: manufactured by Ciba Geigy Japan) 6 parts Methyl isobutyl ketone / xylene / tetrahydrofuran = 2/2/6 (parts)
2000 parts silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part The coating solution storability is that the coating solutions of conditions 1, 2 and 3 are stored at 5 ° C. for 48 hours (low temperature storage) and 30 ° C. Were stored for 48 hours (high temperature storage), and the presence or absence of changes after each storage was evaluated.

Evaluation criteria for solubility ◎: Easy and uniform dissolution is possible, no problem at all ○: Dissolution is somewhat difficult, lower limit of acceptance level △: Some have settled without dissolving, but slightly diluted This is a soluble result. However, since the concentration of the coating solution is slightly thin, it is disadvantageous for the production of the photoreceptor. ×: Clear solubility is insufficient, and dissolution requires 5 times or more and is not practical.

Evaluation criteria for coating solution storability ◎: No problem at all ○: Slight gelation tendency at low-temperature storage, but at a practical level △: Precipitation occurs at low-temperature storage ×: Fail level at any storage conditions Table 1 below summarizes the evaluation results.

  As is clear from Table 1, the photoreceptors 1 to 11 in the invention of the present application have obtained practical results or more in each evaluation item. However, in the photoreceptor 12 of the comparative example, the potential evaluation deteriorates. Also, the solvent solubility and the storage stability of the coating solution are greatly deteriorated, and in the photoreceptor 13, the potential evaluation is deteriorated, the color image is greatly deteriorated, and there is a problem in practical use.

10Y, 10M, 10C, 10Bk Image forming unit 1Y, 1M, 1C, 1Bk Photoconductor 2Y, 2M, 2C, 2Bk Charging unit 3Y, 3M, 3C, 3Bk Exposure unit 4Y, 4M, 4C, 4Bk Developing unit

Claims (9)

An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a binder resin having a structural unit represented by the following general formula (1).

(In the general formula (1), R represents a divalent organic group, and R ′ represents a divalent group having three or more aromatic rings.)   The binder resin having the structural unit represented by the general formula (1) is obtained by condensation polymerization of a dicarboxylic acid compound having R in the general formula (1) and a diol compound having R '. Item 2. The electrophotographic photosensitive member according to Item 1. 3. The electrophotographic photosensitive member according to claim 2, wherein an aromatic diol compound of the following general formula (2) is used as the diol compound having R ':
HO−φ ₁ −A ₁ −φ ₂ −A ₂ −... −A _n−1 −φ _n −OH
In general formula (2), φ ₁ , φ ₂ ,... Φ _n represent a substituted or unsubstituted aromatic ring. (N is an integer of 3 or more)
A ₁ , A ₂ ,... A _n-1 represents a divalent group selected from the following group (n is an integer of 3 or more).
—CR ₁ R ₂ —, —R ₃ —, —O—, —S—, represents a direct bond. (Provided that the _R 1, _{R 2} is H, an alkyl group, an allyl group, an aryl group, an alkoxy group, a halogen, to make a bond with _{R 1} and _{R 2,} which may .R ₃ also form a ring, the carbon Represents an alkylene group of several 2 or more.) 4. The electrophotographic photoreceptor according to claim 2, wherein the diol compound having R ′ is one or more compounds selected from the following d1 to d5.
d1: 4,4'-bis (3,5-dimethyl-4-phenylenediisopropylidene) bisphenol d2: 4,4 '-(1,4-phenylenediisopropylidene) bisphenol (bisphenol P)
d3: 4,4 '-(1,3-phenylenediisopropylidene) bisphenol (bisphenol M)
d4: 1,3-bis (4-hydroxyphenoxy) benzene d5: 1,4-bis (3-hydroxyphenoxy) benzene   5. The electrophotographic photosensitive member according to claim 2, wherein an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid is used as the dicarboxylic acid compound having R in the general formula (1).   6. The electron according to claim 5, wherein two or more dicarboxylic acid compounds selected from aromatic dicarboxylic acids or aliphatic dicarboxylic acids are used as the dicarboxylic acid compound having R in the general formula (1). Photoconductor.   The electrophotographic photoreceptor has a charge generation layer and a charge transport layer laminated thereon as a photosensitive layer, and the surface layer of the electrophotographic photoreceptor has a structural unit represented by the general formula (1). The electrophotographic photosensitive member according to claim 1, comprising a binder resin.   The image forming apparatus according to claim 1, wherein at least a charging unit, an exposing unit, and a developing unit are provided around the electrophotographic photoconductor, and the image forming apparatus repeatedly forms an image. An image forming apparatus comprising an electrophotographic photosensitive member.   A process cartridge used in the image forming apparatus according to claim 8 is at least one of the electrophotographic photosensitive member and the charging unit, the cleaning unit, the image exposing unit, and the developing unit according to any one of claims 1 to 7. A process cartridge comprising a single unit and configured to be able to be inserted into and removed from the image forming apparatus.

Images