JP6204230B2 - Electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to an electrophotographic photoreceptor.

  In an electrophotographic printer or a multifunction machine, an electrophotographic photosensitive member is used as an image carrier. In general, an electrophotographic photosensitive member includes a conductive substrate and a photosensitive layer provided directly or indirectly on the conductive substrate. A photoreceptor comprising a charge transport material, a charge generation material, and a photosensitive layer containing a resin (organic material) that binds these materials is called an electrophotographic organic photoreceptor. Among the electrophotographic organic photoreceptors, those that have separate layers for the charge transport function due to the inclusion of the charge transport material and the charge generation function mainly due to the inclusion of the charge generation material are the laminated electrophotographic photosensitive members. Called the body. An electrophotographic photoreceptor in which the charge transport material and the charge generation material are included in the same layer and both functions of charge generation and charge transport are realized in the same layer is referred to as a single layer type electrophotographic photoreceptor.

  On the other hand, examples of the photoreceptor include an electrophotographic inorganic photoreceptor using an inorganic material (for example, selenium or amorphous silicon photoreceptor). The electrophotographic organic photoreceptor has advantages such as relatively little influence on the environment and easy film formation and manufacture as compared with the electrophotographic inorganic photoreceptor, and is therefore used in many image forming apparatuses at present. Yes.

  Among the charge transport materials applicable to single-layer and multilayer-type organic photoreceptors, examples of the hole transport agent that transports holes include the butadienylbenzeneamine derivatives described in Patent Document 1. Butadienylbenzenamine derivatives are excellent in hole transport ability.

JP 2005-289877 A

  However, when a butadienylbenzenamine derivative is used as a hole transport agent in the photosensitive layer of an electrophotographic photoreceptor, sufficient electrical properties and abrasion resistance may not be obtained.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photosensitive member capable of imparting abrasion resistance while maintaining excellent electrical characteristics.

  The present invention relates to an electrophotographic photosensitive member having a photosensitive layer, wherein the photosensitive layer includes a charge generation layer containing a charge generation agent, a hole transport agent, a binder resin, a biphenyl derivative, and a charge containing silica particles. It is a laminated photosensitive layer in which a transport layer is laminated, or a single-layered photosensitive layer containing a charge generator, a hole transport agent, a binder resin, a biphenyl derivative, and silica particles. The charge transport layer is on the outermost surface of the multilayer photosensitive layer. Content of the said silica particle is 0.5 to 15 mass parts with respect to 100 mass parts of said binder resins.

  According to the present invention, it is possible to provide an electrophotographic photoreceptor capable of imparting abrasion resistance while maintaining excellent electrical characteristics.

It is a schematic sectional drawing which shows the structure of the laminated electrophotographic photoreceptor in this embodiment. It is a schematic sectional drawing which shows the structure of the single layer type electrophotographic photosensitive member in this embodiment.

  Embodiments of an electrophotographic photoreceptor according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments.

  The electrophotographic photosensitive member in this embodiment includes a base and a photosensitive layer provided on the base. In the electrophotographic photoreceptor, the photosensitive layer may be either a laminated type photosensitive layer or a single layer type photosensitive layer. The photosensitive layer contains a biphenyl derivative and silica particles.

  Hereinafter, the multilayer electrophotographic photoreceptor 10 and the single-layer electrophotographic photoreceptor 20 in this embodiment will be described in detail with reference to FIGS. 1 and 2.

<< Laminated electrophotographic photoreceptor 10 >>
FIG. 1 is a schematic cross-sectional view showing the structure of a multilayer electrophotographic photoreceptor 10 according to this embodiment.

As shown in FIG. 1A, the multilayer electrophotographic photoreceptor 10 includes a substrate 11 and a photosensitive layer 12. The photosensitive layer 12 includes a charge generation layer 13 and a charge transport layer 14.
The multilayer electrophotographic photoreceptor 10 can be produced by laminating the charge generation layer 13 and the charge transport layer 14 on the substrate 11 by coating or the like. The charge generation layer 13 contains a charge generation agent, and the charge transport layer 14 contains a hole transfer agent, silica particles, a biphenyl derivative, and a binder resin. The charge generation layer 13 may be a single layer or a plurality of layers. The charge transport layer 14 may be a single layer or a plurality of layers.

  In the multilayer electrophotographic photosensitive member 10, the charge transport layer 14 is generally thinner than the charge generation layer 13. In the multilayer electrophotographic photosensitive member 10, since the charge transport layer 14 is on the outermost surface, the charge generation layer 13 can be prevented from being worn or damaged even when used for a long time.

(Substrate)
As the substrate 11, various materials having conductivity can be used. As the substrate 11, for example, a substrate formed of metal (for example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, or brass). , A substrate made of a plastic material on which the above metal is deposited or laminated, or a glass substrate coated with aluminum iodide, anodized aluminum, tin oxide, indium oxide, or the like.

  That is, it is sufficient that the substrate 11 as a whole has conductivity, or at least the surface of the substrate 11 has conductivity. Moreover, it is preferable that the base | substrate 11 has sufficient mechanical strength in use.

  Further, the shape of the substrate 11 may be a sheet shape or a drum shape in accordance with the structure of the image forming apparatus in which the substrate 11 is used.

(Middle layer)
In the multilayer electrophotographic photoreceptor 10, as shown in FIG. 1B, an intermediate layer 15 containing a predetermined binder resin may be provided on the substrate 11. The intermediate layer 15 may be provided between the base 11 and the charge generation layer 13, or may be provided between the charge generation layer 13 and the charge transport layer 14.

  The multilayer electrophotographic photoreceptor 10 can improve the adhesion between the substrate 11 and the photosensitive layer 12 by including the intermediate layer 15. Further, by adding a predetermined fine powder in the intermediate layer 15, the incident light is scattered to suppress the generation of interference fringes and at the same time from the substrate 11 during non-exposure causing fogging and black spots to the photosensitive layer 12. It is possible to suppress charge injection into the.

  The fine powder added to the intermediate layer 15 is not particularly limited as long as it has light scattering properties and dispersibility. For example, white pigments (for example, titanium oxide, zinc oxide, zinc white, sulfide) Zinc, lead white, or lithopone), inorganic pigments as extender pigments (for example, alumina, calcium carbonate, or barium sulfate), fluorine resin particles, benzoguanamine resin particles, or styrene resin particles.

  In addition, it is preferable that the film thickness of the intermediate | middle layer 15 is 0.1 to 50 micrometer.

  As described above, the multilayer electrophotographic photosensitive member 10 includes the intermediate layer 15, so that charge injection from the substrate 11 side is suppressed and the effect of preventing partial dielectric breakdown is obtained.

(Charge generation layer)
In the multilayer electrophotographic photosensitive member 10, the charge generation layer 13 includes a charge generation agent. The charge generator is not particularly limited as long as it is a charge generator for an electrophotographic photoreceptor. Examples of the charge generator include X-type metal-free phthalocyanine (x-H ₂ Pc), Y-type titanyl phthalocyanine (Y-TiOPc), perylene pigment, bisazo pigment, dithioketopyrrolopyrrole pigment, metal-free naphthalocyanine pigment, metal Naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, cyanine pigments, powders of inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon, pyrylium salts, ansanthrone Pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, or quinacridone pigments.

A charge generator having an absorption wavelength in a desired region may be used alone, or two or more charge generators may be used in combination. Furthermore, for example, in a digital optical system image forming apparatus (for example, a laser beam printer or facsimile using a light source such as a semiconductor laser), it is preferable to use a photoconductor having sensitivity in a wavelength region of 700 nm or more. Therefore, for example, phthalocyanine pigments (for example, X-type metal-free phthalocyanine (x-H ₂ Pc) or Y-type titanyl phthalocyanine (Y-TiOPc)) are preferably used. The crystal shape of the phthalocyanine pigment is not particularly limited, and phthalocyanine pigments having various crystal shapes are used.

  For a photoreceptor applied to an image forming apparatus using a short wavelength laser light source (for example, a laser light source having a wavelength of about 350 nm or more and 550 nm or less), an ansanthrone pigment or a perylene pigment is suitable as a charge generator. Used for.

  The base resin for charge generation layer is not particularly limited as long as it is a resin for charge generation layer. Specific examples of the base resin for charge generation layer include styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene resin, Ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, polyurethane resin, polysulfone resin, diallyl phthalate resin, ketone Examples include resins, polyvinyl acetal resins, polyvinyl butyral resins, polyether resins, silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, epoxy acrylate resins, and urethane-acrylate resins. A polyvinyl butyral resin is preferably used as the base resin for the charge generation layer. The base resin for charge generation layer may be used alone or in combination of two or more.

  Usually, a charge generation layer and a charge transport layer are formed. Therefore, in the multilayer electrophotographic photosensitive member, the base resin for the charge generation layer is preferably a resin different from the binder resin so as not to be dissolved in the solvent used for the coating liquid when forming the charge transport layer. .

  The content of the charge generation agent is preferably 5 parts by mass or more and 1000 parts by mass or less, and preferably 30 parts by mass or less and 500 parts by mass or more with respect to 100 parts by mass of the base resin contained in the charge generation layer 13. More preferred. The film thickness of the charge generation layer 13 is preferably 0.1 μm or more and 5 μm or less.

(Charge transport layer)
In the charge transport layer 14, a biphenyl derivative, a hole transport agent, silica particles, a binder resin, and an electron acceptor compound are used.

  The biphenyl derivative used in the charge transport layer 14 is preferably a compound of “ADD-1” to “ADD-8” represented by the general formulas (1) to (8) or a derivative thereof.

  In the biphenyl derivative, the function of the binder resin can be effectively exhibited. That is, when a biphenyl derivative is used, it exhibits excellent crack resistance of the electrophotographic photosensitive member while maintaining excellent wear resistance and electrical characteristics of the electrophotographic photosensitive member by being selectively compatible with the binder resin. can do.

  The content of the biphenyl derivative is preferably 0.1 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The hole transporting agent preferably contains a compound having a styryltriarylamine structure (hereinafter referred to as a styryltriarylamine derivative).

  In the styryl triarylamine derivative, since the arylamine group is present, it can effectively contribute to suppression of electrical characteristics, particularly residual potential. The reason why such an effect can be obtained can be estimated as follows.

  In the styryl triarylamine derivative, since the arylamine group exists, the ionization potential can be lowered. Thereby, the energy gap of charge transfer between the styryl triarylamine derivative and the charge generator is reduced, and the charge transport efficiency can be effectively improved. In particular, when a styryl triarylamine derivative is used as a hole transport agent contained in a charge transport layer in a multilayer electrophotographic photoreceptor including a charge generation layer and a charge transport layer, the interface between these layers is used. Charge transfer can be effectively improved. Therefore, in the styryl triarylamine derivative, the presence of the arylamine group makes it possible to realize excellent electrical characteristics of the electrophotographic photosensitive member.

  And since a styryl triarylamine derivative has an arylamine group, the solubility to a solvent can be improved.

  The content of the hole transport agent containing the styryltriarylamine derivative is preferably 30 parts by mass or more and 60 parts by mass or less, and 30 parts by mass or more with respect to 100 parts by mass of the binder resin contained in the charge transport layer 14. More preferably, it is 55 parts by mass or less.

  By setting the content of the hole transporting agent including the styryltriarylamine derivative in such a range, the dispersibility of the styryltriarylamine derivative in the charge transport layer 14 is further improved, and further, the electrophotographic photosensitive member is further improved. Can obtain excellent electrical properties. When the content of the hole transporting agent including the styryltriarylamine derivative is less than 30 parts by mass, it may be difficult for the electrophotographic photosensitive member to obtain sufficient electric characteristics. On the other hand, when the content of the hole transporting agent including the styryltriarylamine derivative exceeds 60 parts by mass, the dispersibility of the styryltriarylamine derivative in the charge transporting layer 14 is lowered, and the charge of the electrophotographic photosensitive member is reduced. Transport efficiency may decrease.

  Below, the specific example of the hole transport agent containing a styryl triarylamine derivative is shown. Specific examples include hole transport agents represented by general formula (9) to general formula (12).

一般式（９）において、Ｒ₁〜Ｒ₇はそれぞれ独立に、水素原子、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基、又は炭素数１〜８のフェニル基であり、又は、Ｒ₃〜Ｒ₇のうち隣接したいずれか二つは、炭素数４〜６のアルキル環若しくはベンゼン環を形成する。ｄは、０〜５の整数である。

In General Formula (9), R _{1 to} R ₇ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group having 1 to 8 carbon atoms, or, two one adjacent of R ₃ to R ₇ form an alkyl ring or a benzene ring having 4 to 6 carbon atoms. d is an integer of 0-5.

一般式（１０）中、Ｒ₈〜Ｒ₁₅はそれぞれ独立に、水素原子、炭素数１〜８のアルキル基、炭素数１〜８のフェニル基であり、又は炭素数１〜８のアルコキシ基であり、ｅは、０〜５の整数であり、ｆは、０〜４の整数であり、ｎは、０又は１の整数である。

In General Formula (10), R _{8 to} R ₁₅ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. Yes, e is an integer of 0 to 5, f is an integer of 0 to 4, and n is an integer of 0 or 1.

一般式（１１）中、Ｒ₁₆〜Ｒ₂₂はそれぞれ独立に、水素原子、炭素数１〜８のアルキル基、炭素数１〜８のフェニル基、又は炭素数１〜８のアルコキシ基であり、ｇは、０〜４の整数であり、ｈは、０〜５の整数である。

In General Formula (11), R _{16 to} R ₂₂ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, g is an integer of 0 to 4, and h is an integer of 0 to 5.

一般式（１２）中、Ａｒ₁は、アリール基、又は共役ニ重結合を有する複素環基であり、Ａｒ₂は、アリール基であり、Ａｒ₁及びＡｒ₂はそれぞれ独立に、炭素数１〜６のアルキル基、炭素数１〜６のフェノキシ基、又は炭素数１〜６のアルコキシ基からなる群より選択される１以上の基に置換されてもよい。

In General Formula (12), Ar ₁ is an aryl group or a heterocyclic group having a conjugated double bond, Ar ₂ is an aryl group, and Ar ₁ and Ar ₂ are each independently a group having 1 to 1 carbon atoms. It may be substituted with one or more groups selected from the group consisting of 6 alkyl groups, C 1-6 phenoxy groups, or C 1-6 alkoxy groups.

  Further, the charge transport layer 14 may further contain a hole transport agent different from the styryltriarylamine derivative.

  Examples of typical nitrogen-containing cyclic compounds and condensed polycyclic compounds as hole transporting agents include styryltriarylamine compounds (excluding styryltriarylamine derivatives), oxadiazole compounds (for example, 2, 5-di (4-methylaminophenyl) -1,3,4-oxadiazole), styryl compounds (eg 9- (4-diethylaminostyryl) anthracene), carbazole compounds (eg polyvinyl carbazole), organic Polysilane compounds, pyrazoline compounds (for example, 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, Imidazole compounds, pyrazo Le-based compound, or triazole-based compounds. In addition, a hole transport agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  As described above, when the hole transport agent different from the styryl triarylamine derivative is further contained, the content of the hole transport agent is 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder resin. Preferably there is.

  In the multilayer electrophotographic photoreceptor 10 of this embodiment, the charge transport layer 14 of the multilayer photosensitive layer 12 contains silica particles. Silica particles and other particles (for example, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony or tantalum-doped tin oxide, or zirconium oxide). In comparison, silica particles can improve the abrasion resistance of the photosensitive layer. Further, the silica particles are easily surface-treated, are excellent in production cost, and are easy to prepare. The silica particles are preferably silica fine particles.

  The average primary particle diameter of the silica fine particles is preferably 7 nm or more and 50 nm or less. When the particle diameter of the silica fine particles is less than 7 nm, the electrophotographic photosensitive member may be inferior in wear resistance or foreign matter may be generated on the surface of the photosensitive layer. On the other hand, when the particle diameter of the silica fine particles exceeds 50 nm, the dispersibility of the silica fine particles in the binder resin may be lowered.

  In the multilayer electrophotographic photoreceptor 10, the content of the silica fine particles is preferably 0.5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The silica fine particles are surface-treated with a surface treatment agent in order to improve the abrasion resistance and crack resistance of the electrophotographic photosensitive member. Examples of the surface treatment agent for silica fine particles include hexamethyldisilazane, N-methyl-hexamethyldisilazane, N-ethyl-hexamethyldisilazane, hexamethyl-N-propyldisilazane, dimethyldichlorosilane, or polydimethylsiloxane. Is mentioned. Since the reactivity with the hydroxyl group on the surface of the silica fine particles is good, it is particularly preferable to use hexamethyldisilazane as the surface treatment agent for the silica fine particles. When hexamethyldisilazane is used as the surface treatment agent, the reactivity with the hydroxyl groups on the surface of the silica fine particles is good, so that the hydroxyl groups on the surface of the silica fine particles are reduced. As a result, it is possible to suppress a decrease in electrical characteristics of the photoreceptor due to moisture (humidity).

  Furthermore, by using hexamethyldisilazane as the surface treatment agent, release of the surface treatment agent from the surface of the silica fine particles can be suppressed. For this reason, it is possible to suppress a decrease in sensitivity repeatability due to the liberated surface treatment agent becoming a trap of charges. Further, by including the silica fine particles and the biphenyl derivative in the charge transport layer 14, it is possible to improve the wear resistance and electrical characteristics of the electrophotographic photosensitive member.

  Examples of the binder resin contained in the charge transport layer 14 include known polycarbonate resins. Furthermore, examples of the binder resin contained in the charge transport layer 14 include “Resin-1” to “Resin-3” represented by the general formula (13) to the general formula (15).

  A resin different from the binder resin used in the charge transport layer 14 may be used. Examples of the binder resin include thermoplastic resins (for example, polycarbonate resins (polycarbonate resins other than polycarbonate resins having a skeleton of general formula (13) to general formula (15)), polyester resins, polyarylate resins, and styrene-butadiene copolymers. Polymer resin, styrene-acrylonitrile copolymer resin, styrene-maleic acid copolymer resin, acrylic copolymer resin, styrene-acrylic acid copolymer resin, polyethylene resin, ethylene-vinyl acetate copolymer resin, chlorination Polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, polyurethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, Is a polyether resin), a thermosetting resin (for example, a silicone resin, an epoxy resin, a phenol resin, a urea resin, or a melamine resin), or a photocurable resin (for example, an epoxy acrylate resin or a urethane-acrylate resin). It is done. These binder resins may be used individually by 1 type, and may be used in combination of 2 or more type.

  The viscosity average molecular weight of the binder resin is preferably 40000 or more, and more preferably 40000 or more and 60000 or less. If the viscosity average molecular weight of the binder resin is too low, the wear resistance of the binder resin cannot be increased, and the charge transport layer is likely to be worn. Moreover, when the viscosity average molecular weight of binder resin is too high, it will become difficult to melt | dissolve in a non-halogen system polar and a nonpolar mixed solvent. As a result, it becomes difficult to form a suitable charge transport layer, for example, it becomes difficult to prepare a coating solution for the charge transport layer.

  The charge transport layer 14 may use an electron acceptor compound in addition to the hole transport agent. Examples of the electron acceptor compound include a quinone derivative, anthraquinone derivative, malononitrile derivative, thiopyran derivative, trinitrothioxanthone derivative, 3,4,5,7-tetranitro-9-fluorenone derivative, dinitroanthracene derivative, dinitroacridine derivative, nitroant Araquinone derivatives, dinitroanthraquinone derivatives, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, or dibromomaleic anhydride Is mentioned. These electron acceptor compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  When it contains the electron acceptor compound mentioned above, it is preferable that content of an electron acceptor compound is 0.1 to 20 mass parts with respect to 100 mass parts of binder resins.

  The charge transport layer 14 may contain an antioxidant. Examples of the antioxidant include hindered phenol compounds, hindered amine compounds, thioether compounds, and phosphite compounds. Among these antioxidants, a hindered phenol compound or a hindered amine compound is preferable.

  The addition amount of the antioxidant in the charge transport layer 14 is preferably 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin. When the addition amount of the antioxidant is within such a range, it is possible to suppress a decrease in electrical characteristics of the electrophotographic photosensitive member due to oxidation of the electrophotographic photosensitive member.

  The thickness of the charge transport layer 14 is preferably 5 μm or more and 50 μm or less.

[Production Method of Laminated Electrophotographic Photoreceptor]
For example, the multilayer electrophotographic photoreceptor 10 can be manufactured by the following procedure. First, a charge generation layer, a base resin, and the like are mixed in a solvent to prepare a charge generation layer coating solution. The coating solution obtained in this way is applied to a conductive substrate (for example, an aluminum substrate) using a coating method such as a dip coating method, a spray coating method, a bead coating method, a blade coating method, or a roller coating method. On the tube). Thereafter, the charge generation layer 13 having a predetermined thickness can be formed by hot air drying.

  Various organic solvents can be used as a solvent for preparing the coating solution. Examples of the organic solvent include alcohols (eg, methanol, ethanol, isopropanol, or butanol), aliphatic hydrocarbons (eg, n-hexane, octane, or cyclohexane), aromatic hydrocarbons (eg, benzene, Toluene or xylene), halogenated hydrocarbons (eg, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, or chlorobenzene), ethers (eg, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether) 1,3-dioxolane, or 1,4-dioxane), ketones (for example, acetone, methyl ethyl ketone, or cyclohexanone), esthetics Class (e.g., methyl acetate, or ethyl acetate), dimethylformamide, dimethyl formamide, or dimethyl sulfoxide and the like. These organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

  Next, a biphenyl derivative, a hole transport agent, a binder resin, silica fine particles, and an electron acceptor compound are dispersed in the solvent described above to prepare a charge transport layer coating solution. Next, a charge transport layer coating solution is applied onto the charge generation layer 13 formed in advance and dried. The charge transport layer coating solution preparation method, coating method, and drying method can be performed in the same manner as the charge generation layer coating solution preparation method, coating method, and drying method for the charge generation layer 13.

  Silica fine particles can be dispersed in the charge transport layer 14 by a known method using a dispersing device. Examples of such a dispersing device include a roll mill, a bead mill, a paint shaker, and an ultrasonic dispersing device. Among these dispersing apparatuses, when an ultrasonic dispersing apparatus is used, silica fine particles can be favorably dispersed.

<< Single-layer type electrophotographic photoreceptor 20 >>
FIG. 2 is a schematic cross-sectional view showing the structure of the single-layer electrophotographic photoreceptor 20 in the present embodiment. For example, as shown in FIG. 2A, the single-layer electrophotographic photosensitive member 20 of the present invention includes a base 21 and a photosensitive layer 22 that is a single layer. The photosensitive layer 22 is formed on the substrate 21.

  In the single-layer electrophotographic photoreceptor 20, an intermediate layer 23 may be provided between the base 21 and the photosensitive layer 22 as shown in FIG.

  As the substrate 21 and the photosensitive layer 22 (charge generating agent, electron acceptor compound, hole transport agent, binder resin, biphenyl derivative, and silica fine particles), materials contained in the substrate 11 and the photosensitive layer 12 can be used.

  In the single-layer electrophotographic photosensitive member 20, the contents of the charge generator, hole transport agent, binder resin, biphenyl derivative, electron acceptor compound, and silica fine particles are not particularly limited. Specifically, for example, the content of the charge generating agent is preferably 0.2 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the binder resin. The content of the styryl triarylamine derivative as the hole transporting agent is preferably 30 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder resin. The content of the biphenyl derivative is preferably 0.1 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the binder resin. The content of the electron acceptor compound is preferably 10 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the binder resin. The content of the silica fine particles is preferably 0.5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The thickness of the photosensitive layer 22 is not particularly limited as long as it can sufficiently function as the photosensitive layer 22. Specifically, it is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[Method for producing single-layer electrophotographic photoreceptor]
The single-layer type electrophotographic photoreceptor 20 can be manufactured, for example, as follows. A charge generating agent, a hole transport agent, a binder resin, a biphenyl derivative, silica fine particles, and the like are mixed in a solvent to prepare a photosensitive layer coating solution. The photosensitive layer coating solution thus obtained is applied onto a conductive substrate using a coating method. Thereafter, the photosensitive layer 22 having a predetermined film thickness can be formed by hot air drying. In addition, about the preparation method of a coating liquid for photosensitive layers, a coating method, and a drying method, the preparation method, the coating method, and the drying method of the coating liquid for charge generation layers of the charge generation layer 13 of the laminated electrophotographic photosensitive member 10 The same can be done.

  Hereinafter, the present invention will be described more specifically using examples. In addition, this invention is not limited to the range of this Example.

<Method for Producing Photoreceptor A-1>
First, a surface-treated titanium oxide (manufactured by Teica Co., Ltd., “SMT-A”, number average primary particle diameter 10 nm) was prepared. In detail, after surface-treating with alumina and silica, a bead mill was used to prepare a surface treated with methylhydrogenpolysiloxane while performing wet dispersion. Next, 2 parts by mass of titanium oxide, 1 part by mass of nylon 6, nylon 12, nylon 66, nylon 610 four-dimensional copolymer polyamide resin (“Alamine CM8000” manufactured by Toray Industries, Inc.), 10 parts by mass of methanol, and 1 part by mass of butanol Part and a solvent containing 1 part by mass of toluene. These were then mixed for 5 hours using a bead mill to disperse the material in the solvent. This prepared the coating liquid for intermediate | middle layers.

  The obtained intermediate layer coating solution was filtered using a filter having an opening of 5 μm. Thereafter, an intermediate layer coating solution was applied to the surface of a drum-shaped aluminum substrate (supporting substrate) having a diameter of 30 mm and a length of 246 mm by a dip coating method. Subsequently, the intermediate layer coating solution was dried at 130 ° C. for 30 minutes to form an intermediate layer having a thickness of 2 μm on the substrate.

  In Cu-Kα characteristic X-ray diffraction spectrum, 1.5 parts by mass of titanyl phthalocyanine represented by the chemical formula (16) having one main peak at a Bragg angle 2θ ± 0.2 ° = 27.2 °, and a base resin 1 part by mass of a polyvinyl acetal resin (“SREC BX-5” manufactured by Sekisui Chemical Co., Ltd.) was added to a solvent containing 40 parts by mass of propylene glycol monomethyl ether and 40 parts by mass of tetrahydrofuran. Subsequently, these were mixed for 2 hours using the bead mill, the material was disperse | distributed in the solvent, and the coating liquid for charge generation layers was prepared. Next, the obtained filtrate was applied on the intermediate layer formed as described above using a dip coating method and dried at 50 ° C. for 5 minutes. As a result, a charge generation layer having a thickness of 0.3 μm was formed.

  42 parts by mass of CTM-1 represented by the chemical formula (17) as a hole transport agent and 2 parts by mass of a hindered phenol-based antioxidant (“Irganox 1010” manufactured by Ciba Japan Co., Ltd.) as an additive, 100 parts by mass of a polycarbonate resin (Resin-1, viscosity average molecular weight 51000) represented by chemical formula (18) as a binder resin, and 5 parts by mass of ADD-1 represented by chemical formula (19) as a biphenyl derivative, 5 parts by mass of silica fine particles (“RX200” manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle diameter of 12 nm and surface-treated with hexamethylene disilazane were added to a solvent containing 350 parts by mass of tetrahydrofuran and 350 parts by mass of toluene. . This was mixed for 12 hours using a circulating ultrasonic dispersion device, and each component was dispersed in a solvent to prepare a coating solution for a charge transport layer. The obtained charge transport layer coating solution was coated on the charge generation layer by the same operation as the charge generation layer coating solution. Thereafter, the film was dried at 120 ° C. for 40 minutes to form a charge transport layer having a thickness of 30 μm. As a result, Photoreceptor A-1 (Multilayer Electrophotographic Photoreceptor) was produced.

(Production method of photoconductor A-2)
A photoconductor A-2 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-2 represented by the chemical formula (20) as a hole transport agent.

(Method for Producing Photoreceptor A-3)
A photoconductor A-3 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-3 represented by the chemical formula (21) as a hole transport agent.

(Method for producing photoconductor A-4)
A photoconductor A-4 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-4 represented by the chemical formula (22) as a hole transport agent.

(Production method of photoconductor A-5)
A photoconductor A-5 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-5 represented by the chemical formula (23) as a hole transport agent.

(Method for producing photoconductor A-6)
A photoconductor A-6 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-6 represented by the chemical formula (24) as a hole transport agent.

(Production Method of Photoreceptor A-7)
A photoconductor A-7 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-7 represented by the chemical formula (25) as a hole transport agent.

(Production method of photoconductor A-8)
A photoconductor A-8 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-8 represented by the chemical formula (26) as a hole transport agent.

(Production Method of Photoreceptor A-9)
A photoconductor A-9 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-9 represented by the chemical formula (27) as a hole transport agent.

(Production Method of Photoreceptor A-10)
A photoconductor A-10 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-10 represented by the chemical formula (28) as a hole transport agent.

(Production Method of Photoreceptor A-11)
A photoconductor A-11 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-11 represented by the chemical formula (29) as a hole transport agent.

(Production Method of Photoreceptor A-12)
A photoconductor A-12 was produced in the same manner as the photoconductor A-1, except that CTM-1 was replaced with CTM-12 represented by the chemical formula (30) as a hole transport agent.

(Production Method of Photoreceptor A-13)
A photoconductor A-13 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced by ADD-2 represented by the chemical formula (31) as a biphenyl derivative.

(Method for Producing Photoreceptor A-14)
A photoconductor A-14 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-3 represented by the chemical formula (32) as a biphenyl derivative.

(Method for Producing Photoreceptor A-15)
A photoconductor A-15 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-4 represented by the chemical formula (33) as a biphenyl derivative.

(Method for Producing Photoreceptor A-16)
A photoconductor A-16 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-5 represented by the chemical formula (34) as a biphenyl derivative.

(Method for Producing Photoreceptor A-17)
A photoconductor A-17 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-6 represented by the chemical formula (35) as a biphenyl derivative.

(Production Method of Photoreceptor A-18)
A photoconductor A-18 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-7 represented by the chemical formula (36) as a biphenyl derivative.

(Production Method of Photoreceptor A-19)
A photoconductor A-19 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-8 represented by the chemical formula (37) as a biphenyl derivative.

(Method for Producing Photoreceptor A-20)
Except that Resin-1 was replaced with Resin-2 (viscosity average molecular weight 50500) represented by the chemical formula (38) as a binder resin, the same operation as that of the photoreceptor A-1 was performed to prepare the photoreceptor A-20. did.

(Production Method of Photoreceptor A-21)
Except that Resin-1 was replaced with Resin-3 (viscosity average molecular weight 50000) represented by the chemical formula (39) as a binder resin, the same operation as that of the photoreceptor A-1 was performed to prepare the photoreceptor A-21. did.

(Production Method of Photoreceptor A-22)
A photoconductor A-22 was produced in the same manner as the photoconductor A-1, except that the viscosity average molecular weight of Resin-1 was changed from 51000 to 40000 as a binder resin.

(Production Method of Photoreceptor A-23)
A photoconductor A-23 was produced in the same manner as the photoconductor A-1, except that the viscosity average molecular weight of Resin-1 was changed from 51000 to 32500 as a binder resin.

(Production Method of Photoreceptor A-24)
A photoconductor A-24 was produced in the same manner as the photoconductor A-1, except that the type of silica fine particles was changed from RX200 to RX300 (average primary particle diameter: 7 nm).

(Production Method of Photoreceptor A-25)
A photoconductor A-25 was produced in the same manner as the photoconductor A-1, except that the type of silica fine particles was changed from RX200 to NAX50 (average primary particle size 50 nm).

(Production Method of Photoreceptor A-26)
The addition amount of CTM-1 was changed from 42 parts by mass to 50 parts by mass, and the silica fine particles (RX200) surface-treated with hexamethyldisilazane were replaced with silica fine particles (R974) surface-treated with dimethyldichlorosilane. The same operation as that of photoconductor A-1 was performed to prepare photoconductor A-26.

(Production Method of Photoreceptor A-27)
The amount of CTM-1 added was changed from 42 parts by weight to 50 parts by weight, and the silica fine particles treated with hexamethyldisilazane (RX200) from the silica fine particles treated with hexamethyldisilazane (RY200) were treated with polydimethylsiloxane. A photoconductor A-27 was produced in the same manner as the photoconductor A-1, except that the photoconductor A-27 was used.

(Production Method of Photoreceptor A-28)
Except that the addition amount of the silica fine particles was changed from 5 parts by mass to 0.5 parts by mass, the same operation as that of the photoreceptor A-1 was performed to prepare a photoreceptor A-28.

(Production Method of Photoreceptor A-29)
A photoconductor A-29 was produced in the same manner as the photoconductor A-1, except that the addition amount of the silica fine particles was changed from 5 parts by mass to 2 parts by mass.

(Method for Producing Photoreceptor A-30)
A photoconductor A-30 was produced in the same manner as the photoconductor A-1, except that the addition amount of silica fine particles was changed from 5 parts by mass to 10 parts by mass.

(Production Method of Photoreceptor A-31)
A photoconductor A-31 was produced in the same manner as the photoconductor A-1, except that the addition amount of the silica fine particles was changed from 5 parts by mass to 15 parts by mass.

(Production Method of Photosensitive Member B-1)
A photoconductor B-1 was produced in the same manner as the photoconductor A-1, except that the biphenyl derivative and silica fine particles were not used.

(Method for producing photoconductor B-2)
A photoconductor B-2 was produced in the same manner as the photoconductor A-1, except that silica fine particles were not used.

(Method for producing photoconductor B-3)
Except that the biphenyl derivative was not used, the same operation as that of photoconductor A-1 was performed to prepare photoconductor B-3.

(Method for producing photoconductor B-4)
A photoconductor B-4 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-9 represented by the chemical formula (40) as a biphenyl derivative.

(Production method of photoconductor B-5)
A photoconductor B-5 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-10 represented by the chemical formula (41) as a biphenyl derivative.

(Production method of photoconductor B-6)
A photoconductor B-6 was produced in the same manner as the photoconductor A-1, except that ADD-1 was replaced with ADD-11 represented by the chemical formula (42) as a biphenyl derivative.

  Table 1 shows materials contained in the charge transport layers of the photoreceptors A-1 to A-31 and the photoreceptors B-1 to B-6.

<Performance evaluation of electrophotographic photoreceptor>
(1) Electrical characteristic evaluation The number of revolutions of any one of photoconductors A-1 to A-31 and photoconductors B-1 to B-6 is measured using a drum sensitivity tester (manufactured by Gentec Corporation). Charging was performed at 31 rpm and −800V. Next, monochromatic light (wavelength: 780 nm, exposure amount: 1.0 μJ / cm ² ) was taken out from the light of the halogen lamp using a hand pulse filter, and irradiated onto the surface of the multilayer electrophotographic photosensitive member. The surface potential after 50 msec had elapsed after irradiation with monochromatic light was measured, and this surface potential was defined as the residual potential (V _L ). The measurement environment was a temperature of 23 ° C. and a humidity of 50% RH. When _VL is −120 V or more, the electric characteristics of each photoconductor are good, and when _VL is −100 V or more, the electric characteristics of each photoconductor are particularly good.

(2) Evaluation of crack resistance Oil and fat (oleic acid triglyceride) is attached to 10 locations on the surface of any of photoreceptors A-1 to A-31 and photoreceptors B-1 to B-6, and 2 Left for days. The measurement environment was a temperature of 23 ° C. and a humidity of 50% RH. Then, it observed using the optical microscope and confirmed the generation | occurrence | production condition of the crack. Each photoconductor was evaluated for crack resistance according to the following criteria.
Very good (◎): There are 0 cracks.
Good (O): The number of cracks is 1 or more and 3 or less.
Normal (Δ): The number of cracks is 4 or more and 5 or less.
Poor (x): There are 6 or more cracks.

(3) Abrasion resistance evaluation The charge transport layer coating solution prepared in the preparation of any one of photoconductors A-1 to A-31 and photoconductors B-1 to B-6 was prepared using an aluminum pipe (diameter: 78 mm) was applied to a polypropylene sheet (thickness: 0.3 mm). This was dried at 120 ° C. for 40 minutes to produce a wear evaluation test sheet on which a charge transport layer having a thickness of 30 μm was formed.

  From this polypropylene sheet, the charge transport layer was peeled off and attached to a wheel S-36 (manufactured by Taber) to prepare a sample. The prepared sample is set in a rotary abrasion tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and is worn 1000 times under the conditions of a load of 500 gf and a rotational speed of 60 rpm using a wear wheel CS-10 (Taber Co., Ltd.), and evaluation of wear resistance. The test was conducted. The wear loss, which is a change in the mass of the sample before and after the wear resistance evaluation test, was measured, and the wear resistance of each photoconductor was evaluated based on this wear loss. When the wear loss exceeded 6.0 mg, the wear resistance of each photoconductor was insufficient. However, when the wear loss was 6.0 mg or less, the wear resistance of each photoconductor was good.

(4) Evaluation of abrasion resistance of the photoreceptor after the liquid life (using a coating liquid whose time has elapsed after production) In order to accelerate the liquid life of the coating liquid for the charge transport layer, a coating liquid for the charge transport layer is used using a roll mill. Circulated. The charge transport layer coating liquid 30 days after the preparation of the coating liquid was drummed to prepare a charge transport layer coating liquid after the liquid life. Using the coating liquid for the charge transport layer after the liquid life, the same operations as those for the sheet for the wear evaluation test before the liquid life were performed to perform the photoreceptors A-2 to A-31 and the photoreceptors B-1 to B-6. A sheet for a wear evaluation test after liquid life was prepared. Evaluation was performed in the same manner as the above-described wear resistance evaluation before the liquid life, using the sheet for wear evaluation test after the liquid life. The measurement environment was a temperature of 23 ° C. and a humidity of 50% RH. When the wear loss was 6.5 mg or more, the wear resistance after the liquid life of each photoconductor was insufficient. However, when the wear loss was less than 6.5 mg, the resistance of each photoconductor after the liquid life was low. Abrasion was good. Table 2 shows the evaluation results of the wear resistance after the liquid life of each photoconductor.

  Table 2 shows the electrical property evaluation, crack resistance evaluation, wear resistance evaluation before the liquid life, and wear resistance after the liquid life of the photoconductors A-1 to A-31 and the photoconductors B-1 to B-6. The result of evaluation is shown.

  In the electrophotographic photosensitive member according to the present invention, the residual potential in the electrical property evaluation was low, and the wear loss before and after the liquid life was small in the abrasion resistance test. Therefore, it is clear that the electrophotographic photoreceptor according to the present invention is excellent in wear resistance while maintaining excellent electrical characteristics.

  The electrophotographic photosensitive member according to the present invention can be suitably used for an image forming apparatus such as a multifunction peripheral.

DESCRIPTION OF SYMBOLS 10 Multilayer type electrophotographic photosensitive member 11 Base 12 Photosensitive layer 13 Charge generation layer 14 Charge transport layer 15 Intermediate layer 20 Single layer type electrophotographic photosensitive member 21 Base 22 Photosensitive layer 23 Intermediate layer

Claims (6)

An electrophotographic photoreceptor having a photosensitive layer,
The photosensitive layer is
A layered photosensitive layer in which a charge generation layer containing a charge generation agent and a charge transport layer containing a hole transport agent, a binder resin, a biphenyl derivative, and silica particles are laminated;
The charge transport layer is on the outermost surface of the multilayer photosensitive layer,
The content of the silica particles is state, and are less than 5 parts by mass or more 0.5 part by mass relative to the binder resin 100 parts by weight,
The electrophotographic photoreceptor , wherein the biphenyl derivative is a compound represented by chemical formula (4), chemical formula (6), chemical formula (7), or chemical formula (8) .

  The electrophotographic photosensitive member according to claim 1, wherein the silica particles are surface-treated with hexamethyldisilazane. The electrophotographic photosensitive member according to claim 1, wherein the binder resin is represented by a chemical formula (15).

The electrophotographic photosensitive member according to claim 1, wherein the hole transport agent is a compound represented by any one of the general formulas (9) to (12).

In the general formula (9), R _{1 to} R ₇ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group having 1 to 8 carbon atoms. Or any two adjacent R _{3 to} R _{7 form} a C 4-6 alkyl ring or a benzene ring. d is an integer of 0-5.

In the general formula (10), R _{8 to} R ₁₅ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. E is an integer of 0 to 5, f is an integer of 0 to 4, and n is an integer of 0 or 1.

In the general formula (11), R _{16 to} R ₂₂ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. , G is an integer of 0-4, and h is an integer of 0-5.

In the general formula (12), Ar ₁ is an aryl group or a heterocyclic group having a conjugated double bond, Ar ₂ is an aryl group, and Ar ₁ and Ar ₂ each independently have 1 carbon atom. It may be substituted with one or more groups selected from the group consisting of ˜6 alkyl groups, C 1-6 phenoxy groups, or C 1-6 alkoxy groups.   The electrophotographic photosensitive member according to claim 1, wherein the binder resin has a viscosity average molecular weight of 40000 or more. The electrophotographic photosensitive member according to claim 1, wherein the hole transport agent is a compound represented by the chemical formula (17).

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