JP2012150164A - Electrophotographic photoreceptor, and image forming method, image forming apparatus and process cartridge for image forming apparatus using the photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor capable of outputting images of high picture quality with little fluctuation of image density in long-term printing or little unevenness of in-plane density of a printed material, in a photoreceptor having a protective layer formed by three-dimensionally crosslinking a radical polymerizable hole transporting compound or a radical polymerizable monomer by irradiation with UV rays or electron beams on a photoreceptor comprising sequentially deposited layers, and to provide an image forming method, an image forming apparatus and a process cartridge for an image forming apparatus, which employ the above electrophotographic photoreceptor and achieve high picture quality, a long service life and excellent cost performance.SOLUTION: The electrophotographic photoreceptor includes at least a charge generating layer 35, a hole transporting layer 37 and a hole transporting protective layer 39, sequentially layered on a conductive support 31. The hole transporting protective layer 39 comprises a three-dimensional crosslinked film obtained by chain polymerization of at least a radical polymerizable hole transporting compound by irradiation with UV rays or electron beams. The hole transporting protective layer contains a naphthoquinone compound.

Description

  The present invention relates to an image forming method, an image forming apparatus, an electrophotographic photosensitive member used in the image forming apparatus, an image forming apparatus, and a process cartridge for the image forming apparatus.

  In recent years, electrophotographic image forming apparatuses that have been widely spread in the office field due to the ease of on-demand printing have begun to spread in the commercial printing field. In the commercial printing field, high-speed printing, large-scale printing, high image quality, paper compatibility, and cost reduction of printed materials are required more than ever.

  In order to achieve high-speed printing, mass printing, and cost reduction of printed materials, the electrophotographic photoreceptor that is the central device of electrophotography needs to have a long life. As the photosensitive member, an inorganic photosensitive member represented by amorphous silicon and an organic photosensitive member made of an organic charge generating material and an organic charge transporting material are used. (I) Wide light absorption wavelength range and large absorption amount Optical characteristics such as (II) electrical characteristics such as high sensitivity and stable charging characteristics, (III) wide range of material selection, (IV) ease of manufacturing, (V) low cost, (VI) Organic photoreceptors are considered advantageous because of their non-toxicity. On the other hand, organic photoreceptors are vulnerable to scratches and wear, scratches cause image defects, and wear causes deterioration of sensitivity, chargeability and charge leakage, and causes abnormal images such as image density reduction and background stains.

  As a means for improving the scratch resistance and abrasion resistance of this organic photoreceptor, a photoreceptor having a mechanically strong protective layer formed on a conventional organic photoreceptor has been proposed. For example, Patent Document 1 proposes a photosensitive layer containing a compound obtained by curing a hole transporting compound having two or more chain polymerizable functional groups in the same molecule.

Patent Documents 2, 3 and 4 also provide protection to form a crosslinked film by irradiating a composition obtained by mixing a radical polymerizable charge transporting compound, a trifunctional or higher functional radical polymerizable monomer and a photopolymerization initiator with ultraviolet rays. Photoconductors with layers have been proposed.
Since this photoreceptor has excellent scratch resistance and abrasion resistance and is excellent in environmental stability, stable image output is possible without using a drum heater.
Further, in Patent Document 5, in order to prevent deterioration of electrical characteristics due to ultraviolet irradiation of a photoreceptor having the crosslinked film as a protective layer, the crosslinked film contains an ultraviolet absorber, and a photosensitive material during production of the photoreceptor. It has been proposed to prevent the deterioration of the material.

From these examinations, a radically polymerizable charge transporting compound (especially a charge transporting compound having an acrylic group) alone or mixed with another acrylic monomer, and a photoreceptor having a three-dimensionally crosslinked protective layer has excellent scratch resistance, It has been found that it has wear resistance and good electrical characteristics as a photoreceptor, and is suitable for commercial printing for printing in large quantities. However, in the recent commercial printing field, higher image quality than ever has been demanded. For this reason, it is necessary to suppress the potential fluctuation and the potential unevenness in the surface of the photoreceptor as much as possible. On the other hand, the photoconductor did not have sufficient characteristics.
As a cause, in order to form a protective layer having a high crosslinking density by a radical reaction, a photodegradable radical polymerization initiator is contained and light (particularly, ultraviolet rays) is irradiated, or an electron beam or radiation with higher energy is used. Irradiation requires direct excitation of the acrylic group to initiate polymerization, but in any case, the charge transport compound in the protective layer is simultaneously excited to partially decompose, and the decomposed product becomes a photoreceptor. It is considered that the charge transport function, which is an important function, is lowered.

For such problems, for example, it is conceived to contain an ultraviolet absorber as proposed in the above-mentioned Patent Document 5 in order to suppress degradation by ultraviolet rays. There is a problem that the transport function has a large side effect, and the charge transport function of the photoreceptor is greatly reduced, and the radical polymerization reaction is also suppressed at the same time, so that a protective layer having a sufficient crosslinking density cannot be formed. It has not been put into practical use.
A singlet oxygen quencher (for example, nickel dithiolate complex) is also known as an additive that suppresses the decomposition reaction of the dye. When such a material is added to the protective layer, the photoconductivity of the photoreceptor is known. Can not be used due to the harmful effect of completely disappearing.
In this way, at least the radically polymerizable charge transporting compound is cured with ultraviolet rays or electron beams to improve the problems caused by the protective layer of the photoreceptor having a protective layer as a three-dimensional crosslinked film, and high image quality required in the commercial printing field It has not been possible to cope with (stability of image density over time or density stability in the image plane).

  Therefore, an electrophotographic photosensitive member having a protective layer having a better charge transporting property and capable of outputting an image with higher image quality than before while having sufficient scratch resistance and abrasion resistance, and an image using the same Development of a forming method, an image forming apparatus, and a process cartridge for the image forming apparatus has been desired.

  An object of the present invention is to provide a photoreceptor having a protective layer in which a radically polymerizable hole transporting compound or radically polymerizable monomer is irradiated with ultraviolet rays or an electron beam and three-dimensionally crosslinked on a conventional normal layered photoreceptor. That is, in a photosensitive member in which at least a charge generation layer, a hole transport layer, and a hole transporting protective layer three-dimensionally cross-linked by radical polymerization are sequentially laminated on a conductive support), the hole is maintained while maintaining the mechanical strength of the protective layer. Further improve transportability, and reduce potential fluctuations over time and in-print potential fluctuations, enabling high-quality image output with less image density fluctuation and in-plane density unevenness over time. An image forming method, an image forming apparatus, and a process cartridge for an image forming apparatus using the electrophotographic photosensitive member, an image forming method, an image forming apparatus, and an image forming apparatus using the same It is.

The present inventors have no side effects on the basic functions such as chargeability and photoconductivity of the photoreceptor, do not inhibit radical chain polymerization, and can still suppress the decomposition of the hole transporting compound when forming the crosslinked protective layer, As a result of intensive studies on additives that can suppress the generation of charge traps (cause of reducing hole transportability) generated by decomposition, it was found that it is effective to contain a naphthoquinone compound in the protective layer.
That is, the said subject is solved by (1)-(9) of this invention.

［式中、Ｒ₁は、炭素数１〜４のアルキル基、または置換基を有してもよいフェニル基を示し、Ｒ₂は炭素数１〜４のアルキル基、または置換基を有してもよいフェニル基、または下記一般式（２）の置換基を表す。

Ｒ₄は、炭素数１〜４のアルキル基、または置換基を有してもよいベンジル基、フェネチル基、フェニル基を表す。］
（３）前記ナフトキノン化合物の含有量が、ラジカル重合性ホール輸送性化合物の０．５〜１０重量％であることを特徴とする（１）又は（２）に記載の電子写真感光体。
（４）前記ラジカル重合性ホール輸送性化合物のラジカル重合性反応基が、アクリロイルオキシ基であることを特徴とする（１）〜（３）のいずれか一項に記載の電子写真感光体。
（５）前記ホール輸送性保護層が、ラジカル重合性ホール輸送性化合物と共にホール輸送性を有しない３官能以上のラジカル重合性モノマーを連鎖重合させて得られる３次元架橋膜からなることを特徴とする（１）〜（４）のいずれか一項に記載の電子写真感光体。
（６）前記ホール輸送性保護層が少なくとも下記一般式（３）で表される１官能のラジカル重合性ホール輸送性化合物と共にホール輸送性を有しない３官能以上のラジカル重合性モノマーを連鎖重合させて得られる３次元架橋膜からなり、該ホール輸送性保護層中に前記一般式（２）で表されるナフトキノン化合物を含有させたことを特徴とする（５）に記載の電子写真感光体。

［式中、Ｒ₁₁、Ｒ₁₂、Ｒ₁₃、Ｒ₁₄、Ｒ₁₅は炭素数１〜４のアルキル基を表し、Ｒ₁₃とＲ₁₄は環を形成していてもよい。ｏ、ｐは０〜５の整数を、ｑ、ｒ、ｓは０〜４の整数を表し、ｏ、ｐ、ｑ、ｒ、ｓが２以上の場合は異なっていてもよい。ｍは０または１の整数を表す。Xは単結合、またはアルキレン基、アルキレンオキシ基の２価基を表す。］
（７）前記（１）〜（６）のいずれか一項に記載の電子写真感光体を用いて、少なくとも帯電、画像露光、現像、転写を繰り返し行なうことを特徴とする画像形成方法。
（８）前記（１）〜（６）のいずれか一項に記載の電子写真感光体を有することを特徴とする画像形成装置。
（９）前記（１）〜（６）のいずれか一項に記載の電子写真感光体と、帯電手段、現像手段、転写手段、クリーニング手段および除電手段よりなる群から選ばれた少なくとも一つの手段を有するものであって、画像形成装置本体に着脱可能としたことを特徴とする画像形成装置用プロセスカートリッジ。 (1) At least a charge generation layer, a hole transport layer, and a hole transport protective layer are sequentially laminated on a conductive support, and the hole transport protective layer irradiates at least a radical polymerizable hole transport compound with ultraviolet rays or an electron beam. An electrophotographic photosensitive member comprising a three-dimensional crosslinked film obtained by chain polymerization, wherein a naphthoquinone compound is contained in the hole transporting protective layer.
(2) The electrophotographic photosensitive member according to (1), wherein the naphthoquinone compound is a compound represented by the following general formula (1).

[Wherein, R ₁ represents an alkyl group having 1 to 4 carbon atoms or a phenyl group which may have a substituent, and R ₂ represents an alkyl group having 1 to 4 carbon atoms or a substituent. Or a substituent of the following general formula (2).

R ₄ represents an alkyl group having 1 to 4 carbon atoms, or a benzyl group, phenethyl group or phenyl group which may have a substituent. ]
(3) The electrophotographic photosensitive member according to (1) or (2), wherein the content of the naphthoquinone compound is 0.5 to 10% by weight of the radical polymerizable hole transporting compound.
(4) The electrophotographic photosensitive member according to any one of (1) to (3), wherein the radical polymerizable reactive group of the radical polymerizable hole transporting compound is an acryloyloxy group.
(5) The hole transporting protective layer is composed of a three-dimensional crosslinked film obtained by chain polymerization of a radical polymerizable monomer having a trifunctional or higher functionality that does not have hole transportability together with a radical polymerizable hole transportable compound. The electrophotographic photosensitive member according to any one of (1) to (4).
(6) The hole transporting protective layer is formed by chain polymerization of at least a monofunctional radical polymerizable hole transporting compound represented by the following general formula (3) with a trifunctional or higher functional radical polymerizable monomer having no hole transporting property. The electrophotographic photosensitive member according to (5), wherein the naphthoquinone compound represented by the general formula (2) is contained in the hole transporting protective layer.

[Wherein R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ represent an alkyl group having 1 to 4 carbon atoms, and R ₁₃ and R ₁₄ may form a ring. o and p represent integers of 0 to 5, q, r, and s represent integers of 0 to 4, and may be different when o, p, q, r, and s are 2 or more. m represents an integer of 0 or 1. X represents a single bond or a divalent group of an alkylene group or an alkyleneoxy group. ]
(7) An image forming method, wherein at least charging, image exposure, development, and transfer are repeated using the electrophotographic photosensitive member according to any one of (1) to (6).
(8) An image forming apparatus comprising the electrophotographic photosensitive member according to any one of (1) to (6).
(9) At least one means selected from the group consisting of the electrophotographic photosensitive member according to any one of (1) to (6) above, a charging means, a developing means, a transfer means, a cleaning means, and a static elimination means. A process cartridge for an image forming apparatus, characterized in that it is detachable from the main body of the image forming apparatus.

A photoconductor (that is, on a conductive support) in which a protective layer is formed by three-dimensionally cross-linking a radical polymerizable hole transporting compound or radical polymerizable monomer by irradiating ultraviolet rays or an electron beam on a conventional normal layer laminated photoconductor. In addition, at least a charge generation layer, a hole transport layer, and a hole transporting protective layer three-dimensionally cross-linked by radical polymerization are sequentially laminated), and a naphthoquinone compound is added to the protective layer. It is possible to provide an electrophotographic photosensitive member that is superior in hole transportability compared to the prior art by suppressing the decomposition of the hole transporting compound that occurs during the formation of the crosslinked film without degrading the physical characteristics, reducing the charge trapping of the protective layer. .
By improving the hole transportability of this protective layer, the potential fluctuations over time and the potential fluctuations in the printed surface are made smaller, resulting in high-quality image output with less fluctuations in image density and in-plane density unevenness over time. Is possible.
Accordingly, it is possible to provide an electrophotographic photosensitive member, an image forming method, an image forming apparatus, and a process cartridge for the image forming apparatus that enable image output with high image quality, long life, and excellent cost performance that are strongly demanded in the commercial printing field. .

1 is an example of a cross-sectional view of an electrophotographic photosensitive member of the present invention. 1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. 1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. FIG. 2 is a schematic diagram illustrating an example of a process cartridge for an image forming apparatus according to the present invention. It is the schematic which shows the measuring method of the elastic displacement rate with a micro surface hardness meter It is a figure which shows the relationship between the plastic displacement with respect to a load, and an elastic displacement. It is a figure which shows the X-ray-diffraction pattern of titanyl phthalocyanine.

  The present invention provides a protective layer having a three-dimensional cross-linked film obtained by initiating radical chain polymerization of a mixture of a radically polymerizable hole transporting compound or a polyfunctional radically polymerizable monomer on a conventional laminated photoconductor with high energy ray irradiation. When the protective layer is formed as a three-dimensional crosslinked film, a naphthoquinone compound is contained in the protective layer to suppress charge traps formed in the protective layer and the generation unevenness thereof. Prevents fluctuations in potential over time and variations in the light decay potential at various locations on the surface of the photoconductor, and is required for commercial printing with no change in image density during continuous printing or density unevenness in the image plane. This enables high-quality image formation.

  For photoconductors capable of forming high-quality images required for commercial printing, in-plane potential uniformity that allows the same potential everywhere when the same optical writing is performed, and charging and exposure over time. It is required to maintain the potential between printed sheets so that the potential is the same, and it is necessary to suppress not only the film thickness and homogeneity of the cross-linked protective layer but also the presence or non-uniformity of charge traps inside the protective layer.

  Irradiation unevenness due to equipment conditions, etc. when irradiating high-energy rays to start the crosslinking reaction of the protective layer, even if it prevents the elution etc. of the constituent materials of the lower layer to the crosslinked protective layer and forms a uniform coating film Will occur. For example, when UV irradiation is performed using a photopolymerization initiator, UV irradiation unevenness occurs on the surface of the photoreceptor due to the lamp boundary region of the UV irradiation device and light reflection in the device, affecting the film thickness and homogeneity of the crosslinked layer. Effect. Light irradiation unevenness is expected to lead to cross-linking density unevenness of the cross-linking protective layer, and an attempt was made to avoid cross-linking density unevenness by increasing the amount of light irradiation to bring the whole closer to complete cross-linking, but there was no clear effect. Rather, the increase in light irradiation caused deterioration of the photoreceptor characteristics. Therefore, it was speculated that the light irradiation unevenness led to unevenness in the amount of photodegradation product of the radical polymerizable hole transporting compound responsible for the hole transportability in the protective layer rather than the crosslink density unevenness. Therefore, it was considered that if this photodecomposition can be suppressed, the generation and unevenness of charge traps in the protective layer, which cause deterioration in potential uniformity and potential retention, can be suppressed.

Accordingly, the inventors have intensively studied an additive that prevents this photolysis and does not inhibit the curing polymerization reaction when irradiated with high energy rays such as ultraviolet rays, and found that the addition of a naphthoquinone compound is effective. Although the details of the mechanism are unknown, the excited state of the radical polymerizable hole transporting compound is quickly deactivated by the energy transfer from the radical polymerizable hole transporting compound excited by high energy rays to the naphthoquinone compound. It was speculated that the decomposition reaction from the excited state of the radical polymerizable hole transporting compound can be suppressed.
As can be seen from this, the naphthoquinone compound used in the present invention is also known to be used as an electron transport material in a photoreceptor, but the role in the present invention is not to impart electron transport properties but to transport holes. It suppresses the decomposition of the radically polymerizable hole transporting compound that is held during the curing reaction and over time.
Therefore, the addition amount is determined in consideration of them.

  Furthermore, the oxidation potential of the naphthoquinone compound is larger than the oxidation potential of the radically polymerizable hole transporting compound, and therefore there is an advantage that it does not become a hole trap even in the protective layer and does not reduce the hole transport ability. . Furthermore, since it is not intended to impart electron transport properties, the effect can be exerted even with a small addition amount, and the mechanical strength is reduced by adding a large amount of a compound that does not contribute to the polymerization reaction, and the high level necessary for the polymerization reaction. There is also an advantage that the transmission of energy rays into the layer is not hindered. In these respects, the naphthoquinone compound suppresses the photodecomposition of the radical polymerizable hole transporting compound at the time of irradiation with high energy rays such as ultraviolet irradiation without impairing the basic electrical and mechanical properties as a photoreceptor. It is presumed that the generation of charge traps in the protective layer can be suppressed.

Reduced generation of charge traps in the protective layer reduces the effects of UV irradiation unevenness in the surface, and improves the uniformity of the potential in the surface of the photoconductor and the potential stability over time. It is done.
By using such an electrophotographic photoreceptor, it is possible to output a high-quality image with excellent image density uniformity.

Hereinafter, the electrophotographic photosensitive member of the present invention will be described according to its layer structure.
FIG. 1 is a cross-sectional view showing an electrophotographic photoreceptor of the present invention. On a conductive support (31), a charge generation layer (35) having a charge generation function, a hole transport layer (37), and a hole are further provided. This is a photoreceptor having a normal layer laminated structure in which a transportable protective layer (39) is laminated. These four layers are indispensable components, and one or more subbing layers may be inserted between the conductive support (31) and the charge generation layer (35). Further, the layer constituting part including the charge generation layer (35), the hole transport layer (37) and the hole transport protective layer (39) is referred to as a photosensitive layer (33).

<Conductive support>
A conventionally well-known thing is used as an electroconductive support body (31).
Any material such as aluminum or nickel that has a volume resistance of 10 ¹⁰ Ω · cm or less may be used, and an aluminum drum, an aluminum vapor deposition film, a nickel belt, or the like is preferably used.
In order to achieve high image quality in the commercial printing field, the dimensional accuracy of the photoreceptor is strictly required. Therefore, the aluminum drum manufactured by the drawing method was cut and polished to increase the surface smoothness and dimensional accuracy. Those are preferred. As the nickel belt, an endless nickel belt disclosed in Japanese Patent Publication No. 52-36016 can be used.

<Charge generation layer>
As the charge generation layer (35), the charge generation layer used in the conventional organic electrophotographic photoreceptor can be used as it is. That is, in a layer mainly composed of a charge generation material having a charge generation function, a binder resin can be used in combination as necessary. Preferable charge generating materials include, for example, phthalocyanine pigments and azo pigments such as metal phthalocyanine and metal-free phthalocyanine. As the metal phthalocyanine, titanyl phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine and the like are used. These charge generation materials can be used alone or as a mixture of two or more.

  Examples of binder resins used as necessary include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, polyacrylamide, and the like. Can be mentioned. These binder resins can be used alone or as a mixture of two or more.

  The charge generation layer (35) is formed, for example, with the above charge generation material together with a binder resin if necessary, tetrahydrofuran, dioxane, dioxolane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, cyclopentanone, anisole, xylene, It can be formed by dispersing with a ball mill, attritor, sand mill, bead mill or the like using a solvent such as methyl ethyl ketone, acetone, ethyl acetate or butyl acetate, and applying the solution after diluting the dispersion appropriately. Moreover, leveling agents, such as a dimethyl silicone oil and a methylphenyl silicone oil, can be added as needed. The coating can be performed using a dip coating method, spray coating, bead coating, ring coating method or the like. The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, preferably 0.05 to 2 μm.

<Hole transport layer>
As the hole transport layer, a conventionally known charge transport layer in which a hole transport material is dispersed in a binder resin can be used as it is.
A conventionally known material can be used as it is as the hole transport material.
For example, oxazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Examples include derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, enamine derivatives, and the like. These can be used alone or in combination.

  Examples of the binder resin include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, poly Vinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, Examples thereof include thermoplastic or thermosetting resins such as phenol resins and alkyd resins. The amount of the hole transport material is 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. As the solvent used for the coating of the hole transport layer, the same solvent as the charge generation layer can be used, but a solvent that dissolves the hole transport material and the binder resin well is suitable. These solvents may be used alone or in combination of two or more. In addition, the same coating method as that for the charge generation layer (35) can be formed.

  If necessary, a plasticizer and a leveling agent can be added. As the plasticizer that can be used in combination with the hole transport layer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is 0 to 100 parts by weight of the binder resin. About 30 parts by weight is appropriate. Leveling agents that can be used in combination with the hole 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. The amount used is a binder resin. About 0 to 1 part by weight is appropriate for 100 parts by weight. The thickness of the hole transport layer is suitably about 5 to 40 μm, preferably about 10 to 30 μm. A hole transporting protective layer is formed on the hole transport layer thus formed.

<Hole transportable protective layer>
A feature of the present invention is a three-dimensional crosslinked film in which the hole transporting protective layer is formed by radical chain polymerization of at least a radical polymerizable hole transporting compound with high energy rays, and the crosslinked film contains a naphthoquinone compound. It is that.

The naphthoquinone compound, which is an essential material for the present invention, is synthesized by a known method such as an oxidation reaction of naphthalene with an oxidizing agent such as chromium oxide, an oxidation reaction of naphthol or naphthylamine, or a Diels-Alder reaction of benzoquinone and a butadiene derivative. Halogenated naphthoquinone can be directly introduced into the quinone ring by chlorine or bromine. A compound in which an ether group or a thioether group is substituted on the quinone ring of the naphthoquinone compound can be synthesized by the method described in JP-A-10-251194. These naphthoquinone compounds can be used effectively.
Further, the naphthoquinone compound represented by the general formula (1) is particularly effective because crystallization, LUMO level and LUMO / HOMO band cap can be controlled by selecting the substituents R ₁ and R ₂ .

式中、Ｒ₁は、炭素数１〜４のアルキル基、または置換基を有してもよいフェニル基を示す。Ｒ₁の炭素数１〜４のアルキル基としては、メチル基、エチル基、イソプロピル基、ｎ−プロピル基、ｔ−ブチル基などが挙げられ、フェニル基の置換基としては、同様な炭素数１〜４のアルキル基が用いられる。Ｒ₂は炭素数１〜４のアルキル基、または置換基を有してもよいフェニル基、または下記一般式（２）の置換基を表す。Ｒ₂の炭素数１〜４のアルキル基、及びフェニル基の置換基もＲ₁と同様なものが用いられる。

Ｒ₄は、炭素数１〜４のアルキル基、または置換基を有してもよいベンジル基、フェネチル基、フェニル基を表す。Ｒ₄の炭素数１〜４のアルキル基、及びベンジル基、フェネチル基、フェニル基の置換基もＲ₁と同様なものが用いられる。
特定の一般式（１）のナフトキノン化合物は、特開平９−１５１１５７号公報記載の一般的な合成方法により高収率で得られる。

In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms or a phenyl group which may have a substituent. Examples of the alkyl group having 1 to 4 carbon atoms of R ₁ include a methyl group, an ethyl group, an isopropyl group, an n-propyl group, a t-butyl group, and the like. ˜4 alkyl groups are used. R ₂ represents an alkyl group having 1 to 4 carbon atoms, a phenyl group which may have a substituent, or a substituent represented by the following general formula (2). The same alkyl group having 1 to 4 carbon atoms as R ₂ and a phenyl group substituent are the same as those for R ₁ .

R ₄ represents an alkyl group having 1 to 4 carbon atoms, or a benzyl group, phenethyl group or phenyl group which may have a substituent. The same alkyl group having 1 to ₄ carbon atoms as R ₄ and substituents for benzyl group, phenethyl group and phenyl group are the same as those for R ₁ .
The specific naphthoquinone compound of the general formula (1) can be obtained in a high yield by a general synthesis method described in JP-A-9-151157.

  Further, in JP-A-10-251206, JP-A-10-324658, JP-A-2001-13701, JP-A-2002-121167, JP-A-2006-36647, JP-A-2006-36677. A compound in which a plurality of the described naphthoquinone structures are bonded can also be used effectively.

Although the specific example of the naphthoquinone compound used for this invention below is shown in Table 1, it is not necessarily limited to these.

These naphthoquinone compounds are added in a proportion of 0.1 to 30% by weight in the hole transporting protective layer. When the amount is too small, the effect of reducing the in-plane potential fluctuation amount is not observed, and when the amount is too large, the sensitivity characteristic of the photoreceptor is deteriorated.
As described above, since these naphthoquinone compounds do not exhibit hole transport properties, if they are added excessively in the protective layer, the hole transport compounds are diluted, and the hole transport properties are lowered to cause sensitivity deterioration and the like. Moreover, since excessive addition will also reduce the crosslinking density by radical polymerization, the mechanical strength of a protective layer will be weakened and abrasion resistance will worsen. Therefore, it is desirable to add as little as possible within the effective range. According to experiments in which the addition amount was changed, the effect of suppressing the generation of charge traps was clearly seen when added in the range of 0.5 to 10% by weight with respect to the radically polymerizable hole transporting compound in the protective layer. It is more preferable in that it has fewer side effects.

Next, a method for forming a hole transporting protective layer and a composition other than the naphthoquinone compound will be described.
The hole transporting protective layer of the present invention is mainly obtained by polymerizing a radically polymerizable hole transporting compound and three-dimensionally cross-linking it.
(1) When the radical polymerizable hole transporting compound has one radical polymerizable functional group, the polymerization is performed by mixing with a polyfunctional radical polymerizable monomer having two or more radical polymerizable functional groups in one molecule.
(2) When the number of radical polymerizable functional groups of the radical polymerizable hole transporting compound is 2 or more, the radical polymerizable hole transporting compound can be polymerized alone, or one molecule of the radical polymerizable functional group It can also be polymerized by mixing with one or more radically polymerizable monomers.

A three-dimensional crosslinked film can be formed by radical chain polymerization under the above conditions. Even if a radical polymerization reaction is carried out with a compound having only one radical polymerizable functional group, it becomes only a linear polymer, and even if it is insolubilized by entanglement of molecular chains, it does not become a crosslinked film excellent in wear resistance of the present invention. Is appropriate.
In the above (1), when the radical polymerizable hole transporting compound has one radical polymerizable functional group, the polyfunctional radical polymerizable monomer having three or more radical polymerizable functional groups in one molecule; It is more preferable to mix and polymerize. In order to increase the hole transport property of the protective layer, it is necessary to increase the composition ratio of the radical polymerizable hole transport compound, and in order to obtain a film having a high crosslink density with excellent mechanical strength at such a composition ratio. This is because it is advantageous that the number of functional groups of the polyfunctional radical polymerizable monomer to be mixed is larger.

  In the present invention, the hole transporting protective layer is formed by irradiating a high energy beam such as an ultraviolet ray or an electron beam to initiate polymerization to form a crosslinked film. This is because a film having a high crosslink density and a high elastic work rate can be formed rather than being subjected to a polymerization reaction by heating using a thermal polymerization initiator or the like. Conditions necessary for ensuring the abrasion resistance of the protective layer of the present invention It is. However, since the irradiation energy is higher than that of heat, excitation of the hole transport structure occurs, but in the present invention, the decomposition of the hole transport compound can be suppressed by adding a naphthoquinone compound. Usually, in order to prevent the decomposition of the material due to such high energy beam irradiation, the oxygen concentration is lowered under nitrogen gas, or cooling is performed to prevent a temperature rise during irradiation. It can be crosslinked below.

In addition, as a radically polymerizable hole transporting compound having one functional group in a conventional study, a trifunctional or more radically polymerizable monomer having no hole transporting property is mixed with this, and a photopolymerization initiator is mixed. It is known that the radical reaction is initiated by UV irradiation and polymerized and cured to form a three-dimensional crosslinked film, which can form a hole transporting protective layer with excellent hole transporting properties and excellent wear resistance. In the present invention, this system can be applied as the most preferable system.
That is, a monofunctional radical polymerizable hole transporting compound, a trifunctional or higher functional radical polymerizable monomer having no hole transporting property, a photopolymerization initiator, and the naphthoquinone compound are dissolved in an appropriate solvent and coated on the hole transporting layer. Then, an optimum hole transporting protective layer can be formed by carrying out a crosslinking reaction by irradiating with ultraviolet rays.
When the radically polymerizable monomer is a liquid, such a coating liquid can be applied by dissolving other components in the liquid, but if necessary, it is diluted with a solvent as described above. Solvents used at this time include alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, tetrahydrofuran, dioxane and propyl ether. And ethers such as dichloromethane, dichloroethane, trichloroethane, and chlorobenzene, aromatics such as benzene, toluene, and xylene, and cellosolves such as methyl cellosolve, ethyl cellosolve, and cellosolve acetate. These solvents may be used alone or in combination of two or more. The dilution ratio with the solvent varies depending on the solubility of the composition, the coating method, and the target film thickness, and is arbitrary. The coating can be performed using a dip coating method, spray coating, bead coating, ring coating method or the like. Among the combinations of this solvent and coating method, the components of the lower hole transport layer are not mixed into the hole transport protective layer as much as possible, the adhesiveness at the interface between both layers is ensured, Coating with a spray coating method using tetrahydrofuran is most preferable.

For UV irradiation, a UV irradiation light source such as a high-pressure mercury lamp or a metal halide lamp can be used. Irradiation light amount is 50 mW / cm ² or more, preferably 1000 mW / cm ² or less, it takes time for the curing reaction is less than 50 mW / cm ^2. When it is higher than 1000 mW / cm ² , the reaction progresses unevenly, and the unevenness of the hole transporting protective layer and the deterioration of electrical characteristics become severe.

  Here, the radical polymerizable hole transporting compound, the trifunctional or higher functional radical polymerizable monomer, the photopolymerization initiator, the coating solvent, the coating method, the drying method, the ultraviolet irradiation condition and the like are disclosed in, for example, JP-A-2005-266513. , JP 2004-302452 and Japanese Patent No. 4145820, a charge transporting compound having a radical polymerizable functional group, a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure, and a bifunctional Radical polymerizable monomer, photopolymerization initiator can be used corresponding to the radical polymerizable hole transporting compound, polyfunctional radical polymerizable monomer, photopolymerization initiator of the present invention, coating solvents described in those prior application documents, The coating method, drying method, and ultraviolet irradiation conditions can be applied as they are.

  That is, the radical polymerizable hole transport compound used in the present invention is a compound having a hole transport structure such as triarylamine, hydrazone, pyrazoline, carbazole and the like and having a radical polymerizable functional group. Point to. As the radical polymerizable functional group, acryloyloxy group and methacryloyloxy group are particularly useful. The number of radically polymerizable functional groups in one molecule may be one or more, but it is easy to obtain a smooth surface property by suppressing the internal stress of the hole transporting protective layer and to maintain good electrical properties. It is preferable that the number of radically polymerizable functional groups is one. When the hole transporting compound has two or more radical polymerizable functional groups, the margin may be reduced due to large distortion due to the bulky hole transporting compound being fixed in the cross-linking by a plurality of bonds. Depending on the charge transporting structure and the number of functional groups, irregularities, cracks, and peeling may occur. In addition, this large strain cannot stably maintain the intermediate structure (cation radical) at the time of hole transport, so that the sensitivity is lowered due to charge trapping and the residual potential is likely to increase. As the hole transporting structure of the radical polymerizable hole transporting compound, a triarylamine structure is preferable because of its high mobility.

式中、Ｒ₁₁、Ｒ₁₂、Ｒ₁₃、Ｒ₁₄、Ｒ₁₅は炭素数１〜４のアルキル基を表し、Ｒ₁₃とＲ₁₄は環を形成していてもよい。この炭素数１〜４のアルキル基としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｔ−ブチル基などが挙げられる。Ｒ₁₃とＲ₁₄が形成する環状構造としては、フルオレン環などが挙げられる。
ｏ、ｐは０〜５の整数、ｑ、ｒ、ｓは０〜４の整数を表し、ｏ、ｐ、ｑ、ｒ、ｓが２以上の場合は異なっていてもよい。ｍは０または１の整数を表す。
Ｘは単結合、またはアルキレン基、アルキレンオキシ基の２価基を表す。このアルキレン２価基としては、メチレン基、１，２−エチレン基、１，３−プロピレン基、１，２−プロピレン基、２，２−プロピレン基、１，４−ブチレン基、１，５−ペンチレン基などの炭素数１〜６個の直鎖状又は分岐状アルキレン基が挙げられる。
また、このアルキレンオキシ２価基としは、エチレンオキシ基、プロピレンオキシ基、開環したカプロラクトン基などを表し、これらアルキレンオキシ２価基が２〜４回繰り返された２価の連結基も有効である。 A particularly effective compound as a radical polymerizable hole transporting compound has a structure of the following general formula (3), and it is excellent when used in combination with a trifunctional or higher functional radical polymerizable monomer having no hole transporting structure. It is possible to provide a hole transporting protective layer that has hole transportability and high mechanical strength, can be stably maintained at a low potential in the exposed area, and is excellent in wear resistance.

In the formula, R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , and R ₁₅ represent an alkyl group having 1 to 4 carbon atoms, and R ₁₃ and R ₁₄ may form a ring. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a t-butyl group. Examples of the cyclic structure formed by R ₁₃ and R ₁₄ include a fluorene ring.
o and p are integers of 0 to 5, q, r, and s represent integers of 0 to 4, and may be different when o, p, q, r, and s are 2 or more. m represents an integer of 0 or 1.
X represents a single bond or a divalent group of an alkylene group or an alkyleneoxy group. Examples of the alkylene divalent group include a methylene group, 1,2-ethylene group, 1,3-propylene group, 1,2-propylene group, 2,2-propylene group, 1,4-butylene group, 1,5-propylene group, Examples thereof include a linear or branched alkylene group having 1 to 6 carbon atoms such as a pentylene group.
The alkyleneoxy divalent group represents an ethyleneoxy group, a propyleneoxy group, a ring-opened caprolactone group, etc., and a divalent linking group in which these alkyleneoxy divalent groups are repeated 2 to 4 times is also effective. is there.

  The radical polymerizable hole transporting compound used in the present invention is important for imparting the hole transporting performance of the hole transporting protective layer, and this component is 20 to 80% by weight based on the total amount of the hole transporting protective layer, preferably The content of the coating liquid component is adjusted to be 30 to 70% by weight. If this component is less than 20% by weight, the hole transporting performance of the hole transporting protective layer cannot be sufficiently maintained, and repeated use causes deterioration of electrical characteristics such as a decrease in sensitivity and an increase in residual potential. On the other hand, if it exceeds 80% by weight, the content of the trifunctional monomer having no hole transport structure is lowered, and the crosslink density is lowered, so that high wear resistance is not exhibited. The required electrical characteristics and wear resistance differ depending on the process to be used, so it cannot be said unconditionally, but considering the balance of both characteristics, the range of 30 to 70% by weight is most preferable.

The polyfunctional radical polymerizable monomer used in the present invention is, for example, a monomer having no hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole and having three or more radical polymerizable functional groups. Point to. The radical polymerizable functional group may be any group as long as it has a carbon-carbon double bond and is capable of radical polymerization.
For example, trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, trimethylolpropane alkylene modified triacrylate, trimethylolpropane ethyleneoxy modified (hereinafter EO modified) triacrylate, trimethylolpropane propyleneoxy modified (hereinafter PO modified) Triacrylate, trimethylolpropane caprolactone modified triacrylate, trimethylolpropane alkylene modified trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETTA), glycerol triacrylate, glycerol epichlorohydrin modified (hereinafter ECH modified) triacrylate, Glycerol EO-modified triacrylate, glycerol P Modified triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), dipentaerythritol caprolactone modified hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkylated dipentaerythritol pentaacrylate, alkylated dipentaerythritol Tetraacrylate, alkylated dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, phosphoric acid EO-modified triacrylate, 2,2,5,5, -tetrahydroxymethylcyclopentanone tetraacrylate These may be used alone or in combination of two or more. .

  The polyfunctional radical polymerizable monomer preferably has a molecular weight ratio (molecular weight / functional group number) of 250 or less to the number of functional groups in the monomer in order to form a dense cross-linked bond in the hole transporting protective layer. Further, when this ratio is larger than 250, the hole transporting protective layer is soft and wear resistance is somewhat lowered. Therefore, in the monomers having a modifying group such as EO, PO, caprolactone, etc., extremely long modification It is not preferable to use a group having a group alone. Further, the proportion of the trifunctional or higher functional radical polymerizable monomer having no hole transporting structure used in the hole transporting protective layer is 20 to 80% by weight, preferably 30 to 70% by weight based on the total amount of the hole transporting protective layer. The content in the coating liquid solid content is adjusted so as to be%. When the monomer component is less than 20% by weight, the three-dimensional cross-linking density of the hole transporting protective layer is small, and a drastic improvement in wear resistance is not achieved as compared with the case of using a conventional thermoplastic binder resin. On the other hand, if it exceeds 80% by weight, the content of the hole transporting compound is lowered and the electrical characteristics are deteriorated. Since the required wear resistance and electrical characteristics differ depending on the process used, it cannot be said unconditionally, but considering the balance of both characteristics, the range of 30 to 70% by weight is most preferable.

  The photopolymerization initiator used in the present invention is not particularly limited as long as it is a polymerization initiator that easily generates radicals by light. For example, diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane- 1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpho Linophenyl) butanone-1,2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 1-phenyl-1,2 -Acetophenone-based or ketal-based photomultiplier such as propanedione-2- (o-ethoxycarbonyl) oxime Initiator, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, and other benzoin ether photopolymerization initiators, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, Benzophenone photopolymerization initiators such as 4-benzoylbiphenyl, 4-benzoylphenyl ether, acrylated benzophenone, 1,4-benzoylbenzene, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2, Thioxanthone photopolymerization initiators such as 4-diethylthioxanthone and 2,4-dichlorothioxanthone, and other photopolymerization initiators include ethyl anthraquino 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4-dimethoxybenzoyl) Examples include -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine compounds, triazine compounds, and imidazole compounds. These polymerization initiators may be used alone or in combination of two or more. The content thereof is 0.5 to 40 parts by weight, preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the total content having radical polymerizability in the solid content of the coating liquid.

  The hole transporting protective layer of the present invention is monofunctional and bifunctional radically polymerizable for the purpose of imparting functions such as viscosity adjustment during coating, stress relaxation of the hole transporting protective layer, lower surface energy, and reduction of friction coefficient. A monomer and a radically polymerizable oligomer can be used in combination. Known radical polymerizable monomers and oligomers can be used.

  Further, the case where the number of functional groups of the radical polymerizable group of the radical polymerizable hole transporting compound is 2 or more will be described in detail. As described above, the basic structure has a hole transport structure having a conventionally known aromatic tertiary amine structure such as triarylamine, hydrazone, pyrazoline, carbazole, etc. It has two or more inside. For example, Tables 3 to 86 of JP-A No. 2004-221959 describe many compound examples and can be used in the present invention. In particular, the radical polymerizable group is preferably the acryloyloxy group or methacryloyloxy group described above, and these polymerizable groups are bonded to the hole transport structure via an alkylene chain having 2 or more carbon atoms, more preferably 3 or more carbon atoms. Is particularly preferred. Thereby, generation | occurrence | production of the distortion mentioned above as a fault of the radically polymerizable hole transportable compound more than bifunctional can be relieved.

Specific examples of the monofunctional and bifunctional or higher functional radically polymerizable hole transporting compounds used in the present invention are shown in Table 2, but are not limited thereto.

Next, a method for producing a crosslinked film by electron beam irradiation will be described.
In the electron beam irradiation, it is not necessary to add a photopolymerization initiator, the radical polymerizable hole transporting compound alone or a mixture with the radical polymerizable monomer is dissolved in an appropriate solvent, applied on the hole transporting layer, and then irradiated. By doing so, a three-dimensional crosslinked film can be formed. These crosslinking conditions are also described in the above Japanese Patent Application Laid-Open No. 2004-221959, and known techniques can be used as they are. For example, the acceleration voltage of the electron beam is preferably 250 kV or less, the irradiation dose is preferably in the range of 1 Mrad to 20 Mrad, and the oxygen concentration during irradiation is preferably 10000 ppm or less.

  The film thickness of the hole transporting protective layer of the present invention is adjusted according to the required life of the photoconductor. On the contrary, if the film thickness is reduced, the potential of the exposed portion can be lowered, but the film shaving becomes rate-determining and the life is shortened. In the present invention, by adding a naphthoquinone compound, the potential of the exposed area can be kept low, and the margin for thickening is improved. The thickness of the hole transporting protective layer of the present invention is preferably 1 μm or more and 15 μm or less, more preferably 2 μm or more and 10 μm or less.

<Underlayer>
In the photoreceptor of the present invention, an undercoat layer can be provided between the conductive support (31) and the photosensitive layer (33). In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is coated with a solvent on these resins, the resin may be a resin having high solvent resistance with respect to a general organic solvent. desirable. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin. Further, a metal oxide fine powder pigment exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the undercoat layer in order to prevent moire and reduce residual potential. These undercoat layers can be formed using an appropriate solvent and a coating method like the above-mentioned photosensitive layer. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer of the present invention. In addition, in the undercoat layer of the present invention, Al ₂ O ₃ is provided by anodic oxidation, organic substances such as polyparaxylylene (parylene), SiO ₂ , SnO ₂ , TiO ₂ , ITO, CeO ₂ A material provided with an inorganic material such as a vacuum thin film can also be used favorably. In addition, known ones can be used. The thickness of the undercoat layer is suitably 1 to 15 μm.

<Addition of antioxidant to each layer>
In the present invention, in order to improve environmental resistance, in order to prevent a decrease in sensitivity and an increase in residual potential, oxidation is performed on each layer such as a hole transport layer, a hole transport protective layer, a charge generation layer, and an undercoat layer. An inhibitor can be added. A conventionally well-known material can be used for the antioxidant to add, and the following are mentioned.

(Phenolic compounds)
2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol), 4, 4'-thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3-tris- (2-methyl-4 -Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene- -(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] Crycol esters, tocopherols, etc.

(Paraphenylenediamines)
N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N, N'- Di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine and the like.
(Hydroquinones)
2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl) ) -5-methylhydroquinone and the like.

(Organic sulfur compounds)
Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like.
(Organic phosphorus compounds)
Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained.
The addition amount of the antioxidant in the present invention is 0.01 to 10% by weight based on the total weight of the layer to be added.

<Image Forming Method and Apparatus>
Next, the image forming method and the image forming apparatus of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a schematic diagram for explaining the electrophotographic process and the image forming apparatus of the present invention, and the following examples also belong to the category of the present invention.
The photoconductor (10) rotates in the direction of the arrow in FIG. 2, and around the photoconductor (10), a charging member (11), an image exposure member (12), a developing member (13), and a transfer member (16). ), A cleaning member (17), a charge removal member (18), and the like are disposed. The cleaning member (17) and the charge removal member (18) may be omitted.

  The operation of the image forming apparatus is basically as follows. The charging member (11) charges the surface of the photoreceptor (10) almost uniformly. Subsequently, image light writing corresponding to the input signal is performed by the image exposure member (12) to form an electrostatic latent image. Next, the electrostatic latent image is developed by the developing member (13), and a toner image is formed on the surface of the photoreceptor. The formed toner image is transferred onto the transfer paper (15) sent to the transfer site by the transport roller (14) by the transfer member. This toner image is fixed on the transfer paper by a fixing device (not shown). Part of the toner that has not been transferred to the transfer paper is cleaned by the cleaning member (17). Next, the charge remaining on the photoreceptor is neutralized by the neutralizing member (18), and the process proceeds to the next cycle.

  As shown in FIG. 2, the photoconductor (10) has a drum shape, but may have a sheet shape or an endless belt shape. As the charging member (11) and the transfer member (16), in addition to corotron, scorotron, solid state charger (solid state charger), a roller-shaped charging member or a brush-shaped charging member is used. Are all usable.

On the other hand, light sources such as the image exposure member (12) and the charge removal member (18) include fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium lamps, light emitting diodes (LEDs), semiconductor lasers (LD), and electroluminescence (EL). ) And other luminescent materials can be used. Among these, a semiconductor laser (LD) and a light emitting diode (LED) are mainly used.
Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.

The light source or the like irradiates the photoconductor (10) with light by providing a transfer process, a static elimination process, a cleaning process, or a pre-exposure process using light irradiation together. However, the exposure of the photoconductor (10) in the static elimination process has a large influence of fatigue on the photoconductor (10), and may cause a decrease in charge and an increase in residual potential.
Therefore, there is a case where it is possible to eliminate static electricity by applying a reverse bias in the charging process or cleaning process instead of static elimination by exposure, which may be effective from the viewpoint of enhancing the durability of the photoreceptor.

  When the electrophotographic photosensitive member (10) is positively (negatively) charged and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member. A positive image can be obtained by developing this with negative (positive) toner (electrodetection fine particles), and a negative image can be obtained by developing with positive (negative) toner. A known method is applied to the developing unit, and a known method is also used for the charge eliminating unit.

  Among the contaminants that adhere to the surface of the photoconductor, discharge substances generated by charging and external additives contained in the toner are easy to pick up the effects of humidity and cause abnormal images. Paper powder is one of the causative substances, and when they adhere to the photoreceptor, abnormal images are more likely to occur, as well as a tendency to reduce wear resistance and cause uneven wear. Is seen. Therefore, it is more preferable from the viewpoint of high image quality that the photoconductor and the paper are not in direct contact for the above reason.

The toner developed on the photoconductor (10) by the developing member (13) is transferred to the transfer paper (15), but not all is transferred, and the toner remaining on the photoconductor (10). Also occurs. Such toner is removed from the photoreceptor (10) by the cleaning member (17).
As the cleaning member, a known member such as a cleaning blade or a cleaning brush is used. Moreover, both may be used together.

  The present invention can provide an electrophotographic photoreceptor useful for an electrophotographic system capable of on-demand printing in the commercial printing field. As an image forming apparatus or method for outputting high-quality color images at high speed in on-demand printing, each developing unit corresponding to a plurality of color toners is provided with a plurality of corresponding photoreceptors, thereby being arranged in parallel. It is very effectively used in a so-called tandem image forming apparatus that performs processing. The tandem image forming apparatus includes at least four color toners of yellow (C), magenta (M), cyan (C), and black (K) required for full-color printing and a developing unit that holds them. Further, by providing at least four photoconductors corresponding to them, full-color printing can be performed at an extremely high speed as compared with a conventional image forming apparatus capable of full-color printing.

FIG. 3 is a schematic view for explaining the tandem-type full-color electrophotographic apparatus of the present invention, and modifications as described below also belong to the category of the present invention.
In FIG. 3, photoconductors (10C (cyan)), (10M (magenta)), (10Y (yellow)), and (10K (black)) are drum-like photoconductors (10), and these photoconductors. (10C, 10M, 10Y, 10K) rotate in the direction of the arrow in the figure, around which at least the charging members (11C, 11M, 11Y, 11K), the developing members (13C, 13M, 13Y, 13K), Cleaning members (17C, 17M, 17Y, 17K) are arranged.

Laser light (12C, 12M) from an exposure member (not shown) from the outside of the photoreceptor (10) between the charging member (11C, 11M, 11Y, 11K) and the developing member (13C, 13M, 13Y, 13K). , 12Y, 12K), and electrostatic latent images are formed on the photoconductors (10C, 10M, 10Y, 10K).
Then, four image forming elements (20C, 20M, 20Y, 20K) centering on such a photoreceptor (10C, 10M, 10Y, 10K) are along a transfer conveyance belt (25) which is a transfer material conveyance unit. Are juxtaposed.

  The transfer / conveying belt (19) is disposed between the developing member (13C, 13M, 13Y, 13K) of each image forming unit (20C, 20M, 20Y, 20K) and the cleaning member (17C, 17M, 17Y, 17K). A transfer member (16C) for applying a transfer bias to the surface (rear surface) which is in contact with the photoconductor (10C, 10M, 10Y, 10K) and contacts the back side of the photoconductor (10) side of the transfer conveyance belt (19). , 16M, 16Y, 16K). Each of the image forming elements (20C, 20M, 20Y, 20K) is different in toner color inside the developing device, and the other components have the same configuration.

In the color electrophotographic apparatus having the configuration shown in FIG. 3, the image forming operation is performed as follows. First, in each of the image forming elements (20C, 20M, 20Y, and 20K), the charging member (11C, 11M, 11Y, and 11K) in which the photosensitive member (10C, 10M, 10Y, and 10K) rotates along with the photosensitive member 10 is rotated. ), And then an electrostatic image corresponding to the image of each color to be created by laser light (12C, 12M, 12Y, 12K) by an exposure unit (not shown) arranged outside the photoconductor (10). A latent image is formed.
Next, the latent image is developed by a developing member (13C, 13M, 13Y, 13K) to form a toner image. The developing members (13C, 13M, 13Y, and 13K) are developing members that perform development with toners of C (cyan), M (magenta), Y (yellow), and K (black), respectively. 10M, 10Y, and 10K) are overlaid on the transfer belt (19).

  The transfer paper (15) is sent out from the tray by the paper supply roller (21), temporarily stopped by the pair of registration rollers (22), and sent to the transfer member (23) in synchronization with the image formation on the photosensitive member. It is done. The toner image held on the transfer belt (19) is transferred onto the transfer paper (15) by an electric field formed by a potential difference between the transfer bias applied to the transfer member (23) and the transfer belt (19). . The toner image transferred onto the transfer paper is conveyed, the toner is fixed onto the transfer paper by the fixing member (24), and is discharged to a paper discharge unit (not shown). Further, residual toner that is not transferred by the transfer unit and remains on the photosensitive members (10C, 10M, 10Y, and 10K) is collected by cleaning members (17C, 17M, 17Y, and 17K) provided in the respective units. The

The intermediate transfer system as shown in FIG. 3 is particularly effective for an image forming apparatus capable of full-color printing. By forming a plurality of toner images once on an intermediate transfer body and transferring them to paper at once, It is easy to control the color shift and is effective for high image quality.
The intermediate transfer member includes various materials or shapes such as a drum shape and a belt shape. In the present invention, any conventionally known intermediate transfer member can be used. It is effective and useful for achieving high quality or high image quality.

  In the example of FIG. 3, the image forming elements are arranged in the order of colors of Y (yellow), M (magenta), C (cyan), and K (black) from the upstream side to the downstream side in the transfer sheet conveyance direction. However, it is not limited to this order, and the color order is arbitrarily set. Further, when a black-only document is created, it is particularly effective to use the present invention to provide a mechanism that stops the image forming elements (20C, 20M, 20Y) other than black.

  The present invention is an image forming method and an image forming apparatus using the electrophotographic photoreceptor according to the present invention for such image forming means. The image forming means may be fixedly incorporated in a copying apparatus, facsimile, or printer, but may be incorporated in these apparatuses in the form of a process cartridge and detachable. An example of the process cartridge is shown in FIG.

  The process cartridge for the image forming apparatus includes a photoreceptor (101), and in addition, a charging unit (102), a developing unit (104), a transfer unit (106), a cleaning unit (107), and a discharging unit (not shown). ), And an apparatus (part) that can be attached to and detached from the image forming apparatus main body. Referring to the image forming process by the apparatus illustrated in FIG. 4, the surface of the photoreceptor (101) is exposed by charging by the charging means (102) and exposure by the exposure means (103) while rotating in the direction of the arrow. An electrostatic latent image corresponding to the image is formed, and the electrostatic latent image is developed with toner by the developing means (104). The toner development is transferred to the transfer body (105) by the transfer means (106), and printed. Be out. Next, the surface of the photoconductor after the image transfer is cleaned by a cleaning unit (107), and further neutralized by a neutralizing unit (not shown), and the above operation is repeated again.

The present invention is an image in which a laminate type photoconductor having excellent wear resistance and scratch resistance and extremely high in-plane and repeated potential stability and at least one of charging, developing, transferring, cleaning and static eliminating means are integrated. A process cartridge for a forming apparatus is provided.
As is apparent from the above description, the electrophotographic photosensitive member of the present invention is not only used in electrophotographic copying machines, but also in electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making. Can also be used widely.

Details of the measurement method of the present invention will be described.
<Measurement of elastic displacement rate by micro surface hardness tester>
The elastic displacement rate τe of the present invention is measured by a load-unloading test of a micro surface hardness meter using a diamond indenter. As shown in FIG. 5, the indenter is pushed at a constant load speed from the point (a) where the indenter contacts the sample (loading process), and is stationary for a certain time at the maximum displacement (b) when the set load is reached. The indenter is pulled up at the unloading speed (unloading process), and the point at which no load is finally applied to the indenter is defined as the plastic displacement (c). At this time, the obtained indentation depth and load curve are recorded as shown in FIG. 6, and the maximum displacement (b) and plastic displacement (c) elastic displacement rate τe are calculated by the following equations.

かかる弾性変位率測定は、一定温湿度下で行われ、本発明で弾性変位率とは、温度２２℃、相対湿度５５％の環境条件下で、負荷速度０．３ｍＮ／秒、停止時間５秒、除荷速度０．３ｍＮ／秒（負荷速度と同じ）で行なわれた上記試験の測定値を示す。

Such elastic displacement rate measurement is performed under a constant temperature and humidity. In the present invention, the elastic displacement rate is a load speed of 0.3 mN / second and a stop time of 5 seconds under an environmental condition of a temperature of 22 ° C. and a relative humidity of 55%. The measurement value of the above test conducted at an unloading speed of 0.3 mN / sec (same as the loading speed) is shown.

  In the present invention, a dynamic micro surface hardness tester DUH-201 (manufactured by Shimadzu Corporation) and a triangular pan indenter (115 °) are used, but values measured by any apparatus having equivalent performance may be used. The elastic displacement rate τe was measured at any nine locations on the sample, and two values were deleted from the maximum and minimum values, and the remaining five values were averaged. In the measurement, a photoconductor having the hole transporting protective layer of the present invention was prepared on an aluminum cylinder, and this was used after being appropriately cut. Since the elastic displacement rate τe is affected by the spring characteristics of the substrate, a rigid metal plate, slide glass, or the like is appropriate as the substrate. Furthermore, since the hardness and elasticity factors of the lower layer of the hole transporting protective layer (for example, hole transporting layer, charge generation layer) are also affected, the maximum displacement is less than the film thickness of the hole transporting protective layer so as to reduce these effects. The specified weight was adjusted to 1/10. If only the hole transporting protective layer is produced alone on the substrate, it is not preferable because mixing of the lower layer components and adhesiveness with the lower layer are changed and the surface cross-linked layer of the photoreceptor cannot be accurately reproduced.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. Note that “parts” used in the examples all represent parts by weight.

[Example 1]
As shown below, an undercoat layer, a charge generation layer, and a hole transport layer were sequentially formed on an aluminum cylinder having a surface polished of φ60 mm. Next, a hole transporting protective layer coating solution was spray-coated on the hole transporting layer as described below, dried naturally, then irradiated with ultraviolet rays, and dried to produce the electrophotographic photoreceptor of the present invention.
<Underlayer>
All materials having the following composition were mixed and ball milled with alumina balls for 48 hours. This dispersion was filtered through a 500 mesh stainless steel mesh to prepare a coating solution. This coating solution was dip coated and dried at 130 ° C. for 20 minutes to provide a 3.5 μm undercoat layer.
[Coating liquid for undercoat layer]
Alkyd resin 33.6 parts (Beckolite M-6401-50-S, solid content 50%, manufactured by Dainippon Ink & Chemicals, Inc.)
Melamine resin 18.7 parts (Super Becamine G-821-60, solid content 60%, manufactured by Dainippon Ink & Chemicals, Inc.)
84 parts of titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm)
100 parts of methyl ethyl ketone With the above composition, the volume ratio of the inorganic pigment to the binder resin is 1/1.
The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

<Charge generation layer>
(Synthesis of titanyl phthalocyanine crystal)
The synthesis was in accordance with Japanese Patent Application Laid-Open No. 2004-83859. That is, 292 parts of 1,3-diiminoisoindoline and 1800 parts of sulfolane are mixed, and 204 parts of titanium tetrabutoxide are added dropwise under a nitrogen stream. After completion of the dropwise addition, the temperature was gradually raised to 180 ° C., and the reaction was carried out by stirring for 5 hours while maintaining the reaction temperature between 170 ° C. and 180 ° C. After the reaction is complete, the mixture is allowed to cool, and then the precipitate is filtered, washed with chloroform until the powder turns blue, then washed several times with methanol, then washed several times with hot water at 80 ° C. and dried. Crude titanyl phthalocyanine was obtained. Crude titanyl phthalocyanine is dissolved in 20 times the amount of concentrated sulfuric acid, added dropwise to 100 times the amount of ice water with stirring, the precipitated crystals are filtered, and then ion-exchanged water (pH: 7. 0, specific conductivity: 1.0 μS / cm) Repeated washing with water (pH value of ion-exchanged water after washing was 6.8, specific conductivity was 2.6 μS / cm), wet of titanyl phthalocyanine pigment A cake (water paste) was obtained.
40 parts of this wet cake (water paste) thus obtained was put into 200 parts of tetrahydrofuran and stirred vigorously (2000 rpm) with a homomixer (Kennis, MARKIIf model) at room temperature, and the dark blue color of the paste turned pale blue. When changed (20 minutes after the start of stirring), stirring was stopped and filtration under reduced pressure was immediately performed. The crystals obtained on the filtration device were washed with tetrahydrofuran to obtain a wet cake of pigment. This was dried under reduced pressure (5 mmHg) at 70 ° C. for 2 days to obtain 8.5 parts of titanyl phthalocyanine crystals. The solid content concentration of the wet cake was 15% by mass. The crystal conversion solvent was used in a mass ratio of 33 times that of the wet cake. In addition, the halogen-containing compound is not used for the raw material of the synthesis example 1. When the obtained titanyl phthalocyanine powder was subjected to X-ray diffraction spectrum measurement under the following conditions, the Bragg angle 2θ with respect to CuKα ray (wavelength 1.542１．５) was 27.2 ± 0.2 °, and the maximum peak and the minimum angle 7.3. It has a peak at ± 0.2 °, and further has major peaks at 9.4 ± 0.2 °, 9.6 ± 0.2 °, 24.0 ± 0.2 °, and 7.3 A titanyl phthalocyanine powder having no peak between the peak at 0 ° and the peak at 9.4 ° and further having no peak at 26.3 ° was obtained. The result is shown in FIG.

<X-ray diffraction spectrum measurement conditions>
X-ray tube: Cu
Voltage: 50kV
Current: 30mA
Scanning speed: 2 ° / min Scanning range: 3 ° -40 °
Time constant: 2 seconds

[Coating liquid for charge generation layer]
Using the titanyl phthalocyanine crystal synthesized as described above, a dispersion having the following composition was prepared by bead milling under the conditions shown below.
・ Synthetic titanyl phthalocyanine crystal: 48 parts ・ Polyvinyl butyral (Sekisui Chemical Co., Ltd., BX-1): 32 parts ・ 2-butanone: 720 parts Commercially available bead mill disperser (VMA-GETZMANN GMBH) , DISPERMAT SL, the diameter of the rotor was 50 mm, and the volume of the dispersion chamber was 125 ml). A zirconia ball having a diameter of 0.5 mm was used.
First, a 2-butanone solution in which polyvinyl butyral was dissolved was put into a circulation tank and circulated, and it was confirmed that the resin liquid was filled in the circulation system and returned to the circulation tank.
Next, all the pigment was put into the circulation tank, and after stirring in the circulation tank, the rotor rotation speed was 3000 rpm. p. m. Circulated and dispersed for 300 minutes.
After completion of the dispersion, the mill base was discharged from the bead mill disperser, and further 2060 parts of 2-butanone was added, and all the mill base remaining in the disperser was discharged simultaneously with the dilution to prepare a dispersion.
This dispersion was used as a charge generation layer coating solution, dip-coated on the undercoat layer, and dried at 90 ° C. for 20 minutes to provide a 0.2 μm charge generation layer.

・１％シリコーンオイルのテトラヒドロフラン溶液 ０．２部
（ＫＦ５０−１００ＣＳ、信越化学工業製）
・酸化防止剤 ＢＨＴ ０．２部
・テトラヒドロフラン １００部 《Hall transport layer》
The following polycarbonate resin, hole transport material, silicone oil, and antioxidant were dissolved in tetrahydrofuran to prepare a hole transport layer coating solution. Using this coating solution, the charge generation layer was subjected to dip coating, and dried at 135 ° C. for 20 minutes to provide a 22 μm hole transport layer.
[Coating fluid for hole transport layer]
-10 parts of bisphenol Z polycarbonate resin (Panlite TS-2050, manufactured by Teijin Chemicals)
-10 parts of hole transport material (HTM-1) with the following structure (HTM-1 structural formula)

・ 0.2 parts of 1% silicone oil in tetrahydrofuran (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Antioxidant BHT 0.2 part ・ Tetrahydrofuran 100 parts

<Hole transportable protective layer>
The coating solution for the hole transporting protective layer was prepared by dissolving a polyfunctional radical polymerizable monomer, radical polymerizable hole transporting compound, naphthoquinone compound, and photopolymerization initiator having the following composition in tetrahydrofuran. This hole transporting protective layer coating solution was spray-coated on an aluminum cylinder in which the undercoat layer, the charge generation layer, and the hole transport layer were sequentially formed, and then air-dried for 20 minutes, followed by photocuring under the following conditions. .
The photocuring conditions were as follows: a metal halide lamp: 160 W / cm, irradiation distance: 120 mm, irradiation intensity: 500 mW / cm ² , irradiation time: 180 seconds, while rotating an aluminum cylinder and cooling with hot water at 30 ° C. from the inside. During the light irradiation, the oxygen concentration in the atmosphere was kept at 1% or less by replacing with nitrogen gas. After the light irradiation, in order to further remove the coating solvent, drying was performed at 130 ° C. for 30 minutes to provide a 4 μm hole transporting protective layer.

[Coating liquid for hole transporting protective layer]
-Multifunctional radical polymerizable monomer 10 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
Radical polymerizable hole transporting compound 10 parts Compound of the above specific example AD-3 Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
・ Naphthoquinone compound 0.5 part Compound of the above specific example NQ-12 (synthesized according to Synthesis Example 2 of JP-A-9-151157)
・ 100 parts of tetrahydrofuran

[Example 2]
In Example 1, the hole transport material in the hole transport layer coating solution is changed to 10 parts of the hole transport material (HTM-2) having the following structure, and the radical polymerizable hole transport compound in the hole transport protective layer coating solution is used. In the same manner as in Example 1, except that 10 parts of the compound of the specific example AD-2 and the naphthoquinone compound were changed to 0.1 part of the compound of the specific example NQ-1 (manufactured by Wako Pure Chemical Industries). A photographic photoreceptor was prepared.
(HTM-2 structural formula)

[Example 3]
In Example 2, the radically polymerizable hole transporting compound in the coating liquid for hole transporting protective layer was changed to 10 parts of the compound of Specific Example AD-12, and the naphthoquinone compound was changed to Compound 0.1 of Specific Example NQ-4. An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the parts were changed to those of Wako Pure Chemical Industries.

[Example 4]
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the formulation of the coating liquid for hole transporting protective layer was changed as follows.
[Coating liquid for hole transporting protective layer]
・ Multifunctional radical polymerizable monomer (1) 5 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
Polyfunctional radical polymerizable monomer (2) 5 parts Caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-120, manufactured by Nippon Kayaku Co., Ltd.)
Molecular weight: 1947, number of functional groups: 6 functions, molecular weight / number of functional groups = 325
-Radical polymerizable hole transporting compound 10 parts Compound of the above specific example AD-26-Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
・ Naphthoquinone compound 0.5 part Compound of the above specific example NQ-7 (manufactured by Wako Pure Chemical Industries, Ltd.)
Tetrahydrofuran 100 parts 0.2% 1% silicone oil tetrahydrofuran solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Example 5]
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transporting protective layer coating solution was changed as follows.
[Coating liquid for hole transporting protective layer]
・ Polyfunctional radical polymerizable monomer 10 parts Pentaerythritol tetraacrylate (SR-295, manufactured by Kayaku Sartomer)
Molecular weight: 352, number of functional groups: 4 functions, molecular weight / number of functional groups = 88
-Radical polymerizable hole transporting compound 10 parts Compound of the above specific example AD-18-Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
-Naphthoquinone compound 0.1 part Compound of the above specific example NQ-3 (manufactured by Wako Pure Chemical Industries)
Tetrahydrofuran 100 parts 0.2% 1% silicone oil tetrahydrofuran solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Example 6]
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transporting protective layer coating solution was changed as follows.
[Coating liquid for hole transporting protective layer]
・ Multifunctional radical polymerizable monomer (1) 5 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
Polyfunctional radical polymerizable monomer (2) 5 parts Caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-60, manufactured by Nippon Kayaku)
Molecular weight: 1263, number of functional groups: 6 functions, molecular weight / number of functional groups = 211
-Radical polymerizable hole transporting compound 10 parts Compound of the above specific example AD-17-Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
・ Naphthoquinone compound 0.5 part Compound of the above specific example NQ-9 (synthesized according to Synthesis Example 6 of JP-A-9-151157)
Tetrahydrofuran 100 parts 0.2% 1% silicone oil tetrahydrofuran solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Example 7]
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transporting protective layer coating solution was changed as follows.
[Coating liquid for hole transporting protective layer]
・ Multifunctional radical polymerizable monomer 8 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
Radical polymerizable hole transporting compound 12 parts Compound of the above specific example AD-37 Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
-Naphthoquinone compound 0.1 part Compound of the above specific example NQ-9 (synthesized according to Synthesis Example 6 of JP-A-9-151157)
・ 100 parts of tetrahydrofuran

[Example 8]
In the same manner as in Example 1, an undercoat layer of 3.5 μm was formed on an φ60 mm aluminum cylinder, and the following charge generation layer coating solution was dip-coated on this undercoat layer, and dried at 130 ° C. for 20 minutes. A generation layer was formed. The film thickness of the charge generation layer was adjusted so that the transmittance of the charge generation layer at 655 nm was 20%. The transmittance of the charge generation layer was determined by applying a charge generation layer coating solution having the following composition to an aluminum cylinder wrapped with a polyethylene terephthalate film under the same conditions as the production of the photoreceptor, and the polyethylene without the charge generation layer applied Using a terephthalate film as a comparative control, the transmittance at 655 nm was evaluated with a commercially available spectrophotometer (Shimadzu: UV-3100). On this charge generation layer, a hole transport layer of 25 μm was formed in the same manner as in Example 1. Next, the hole transporting protective layer coating solution is spray coated and dried on the hole transporting layer as described below, and then provided with a hole transporting protective layer of 5 μm by electron beam irradiation. The body was made.

・ポリビニルブチラール（積水化学製：ＢＸ−１） ２部
・シクロヘキサノン ２５０部
・２−ブタノン １００部 [Coating liquid for charge generation layer]
Using a PSZ ball having a diameter of 10 mm in a ball mill disperser with a formulation having the following composition, a solvent in which polyvinyl butyral was dissolved and a bisazo pigment having the following structure were added, and the rotational speed was 85 r. p. m. For 7 days to prepare a charge generation layer coating solution.
-5 parts of bisazo pigment (CGM-1) with the following structure

Polyvinyl butyral (Sekisui Chemical: BX-1) 2 parts Cyclohexanone 250 parts 2-butanone 100 parts

<Hole transportable protective layer>
The coating solution for the hole transporting protective layer was prepared by dissolving a polyfunctional radical polymerizable monomer, a radical polymerizable hole transporting compound and a naphthoquinone compound having the following composition in tetrahydrofuran. The hole transporting protective layer coating solution is spray-coated on an aluminum cylinder in which the undercoat layer, the charge generation layer, and the hole transport layer are sequentially formed, and dried at 50 ° C. for 10 minutes. Line cured.
Electron beam curing conditions were as follows: the hole transport protective layer was formed by rotating the aluminum cylinder and cooling it with hot water of 30 ° C. from the inside while irradiating it with an acceleration voltage of 150 KV and an irradiation dose of 5 Mrad. During the electron beam irradiation, the atmosphere was replaced with nitrogen gas to keep the oxygen concentration in the atmosphere at 1% or less.
[Coating liquid for hole transporting protective layer]
・ Multifunctional radical polymerizable monomer 10 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
・ Radically polymerizable hole transporting compound 10 parts Compound of the above specific example AD-2 ・ Naphthoquinone compound 0.5 part Compound of the above specific example NQ-12 (Synthesis according to Synthesis Example 2 of JP-A-9-151157)
・ 100 parts of tetrahydrofuran

[Example 9]
In Example 8, an electrophotographic photoreceptor was produced in the same manner as in Example 8 except that the hole transporting protective layer coating solution was changed as follows.
[Coating liquid for hole transporting protective layer]
・ Polyfunctional radical polymerizable monomer Not used ・ Radical polymerizable hole transporting compound 20 parts Compound of the above specific example AD-35 ・ Naphthoquinone compound 0.5 part Compound of the above specific example NQ-9 (Japanese Patent Laid-Open No. 9-151157) Synthesis according to Synthesis Example 6)
・ 100 parts of tetrahydrofuran

[Example 10]
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transporting protective layer coating solution was changed as follows. At this time, the addition amount of the naphthoquinone compound (the compound of the specific example NQ-12) corresponds to 0.3% by weight with respect to the radical polymerizable hole transporting compound (the compound of the specific example AD-17).
[Coating liquid for hole transporting protective layer]
・ Multifunctional radical polymerizable monomer 10 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
-Radical polymerizable hole transporting compound 10 parts Compound of the above specific example AD-17-Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
-Naphthoquinone compound 0.03 parts Compound of the above specific example NQ-12 (synthesized according to Synthesis Example 2 of JP-A-9-151157)
Tetrahydrofuran 100 parts 0.2% 1% silicone oil tetrahydrofuran solution (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Example 11]
In Example 10, an electrophotographic photosensitive member was produced in the same manner as in Example 10 except that the amount of the naphthoquinone compound added to the hole transporting protective layer coating solution was 0.05 parts. At this time, the amount of the naphthoquinone compound (the compound of Specific Example NQ-12) is 0.5% by weight based on the radical polymerizable hole transporting compound (the compound of Specific Example AD-17).
[Example 12]
In Example 10, an electrophotographic photosensitive member was produced in the same manner as in Example 10 except that the amount of the naphthoquinone compound added to the hole transporting protective layer coating solution was 0.1 part. At this time, the amount of the naphthoquinone compound (the compound of the above specific example NQ-12) is 1% by weight with respect to the radical polymerizable hole transporting compound (the compound of the above specific example AD-17).

[Example 13]
In Example 10, an electrophotographic photosensitive member was produced in the same manner as in Example 10 except that the amount of the naphthoquinone compound added to the coating solution for hole transporting protective layer was 0.5 part. At this time, the addition amount of the naphthoquinone compound (the compound of the specific example NQ-12) corresponds to 5% by weight with respect to the radical polymerizable hole transporting compound (the compound of the specific example AD-17).
[Example 14]
In Example 10, an electrophotographic photoreceptor was produced in the same manner as in Example 10, except that the amount of the naphthoquinone compound added to the hole transporting protective layer coating solution was 1 part. At this time, the addition amount of the naphthoquinone compound (compound of the specific example NQ-12) corresponds to 10% by weight with respect to the radical polymerizable hole transporting compound (compound of the specific example AD-17).

[Example 15]
In Example 10, an electrophotographic photosensitive member was produced in the same manner as in Example 10 except that the amount of the naphthoquinone compound added to the hole transporting protective layer coating solution was 1.5 parts. At this time, the amount of the naphthoquinone compound (the compound of Specific Example NQ-12) is 15% by weight based on the radical polymerizable hole transporting compound (the compound of Specific Example AD-17).
[Example 16]
An electrophotographic photosensitive member was produced in the same manner as in Example 11 except that an aluminum cylinder with a diameter of 30 mm was used. At this time, the amount of the naphthoquinone compound (the compound of Specific Example NQ-12) is 0.5% by weight based on the radical polymerizable hole transporting compound (the compound of Specific Example AD-17).

[Example 17]
In Example 13, an electrophotographic photosensitive member was produced in the same manner as in Example 13 except that an aluminum cylinder with a diameter of 30 mm was used. At this time, the addition amount of the naphthoquinone compound (the compound of the specific example NQ-12) corresponds to 5% by weight with respect to the radical polymerizable hole transporting compound (the compound of the specific example AD-17).
[Example 18]
In Example 14, an electrophotographic photosensitive member was produced in the same manner as in Example 14 except that an aluminum cylinder with a diameter of 30 mm was used. At this time, the addition amount of the naphthoquinone compound (compound of the specific example NQ-12) corresponds to 10% by weight with respect to the radical polymerizable hole transporting compound (compound of the specific example AD-17).

[Comparative Examples 1 to 10]
In Examples 1 to 10, electrophotographic photosensitive members were produced in the same manner as in Examples 1 to 10 except that the naphthoquinone compound of the coating solution for hole transporting protective layer was not used.
[Comparative Example 11]
In Example 1, electrophotography was carried out in the same manner as in Example 1 except that 0.5 part of an ultraviolet absorber (UV-1) having the following structure was added in place of the naphthoquinone compound in the coating solution for hole transporting protective layer. A photoconductor was prepared.
(Structure of UV-1)

［比較例１３］
実施例１において、ホール輸送性保護層用塗工液のナフトキノン化合物の変わりに下記構造の電子移動剤（ＥＴＭ−１）０．５部を添加したこと以外は実施例１と同様にして電子写真感光体を作製した。
（ＥＴＭ−１の構造）

[Comparative Example 12]
In Example 1, electrophotography was performed in the same manner as in Example 1 except that 0.5 part of an ultraviolet absorber (UV-2) having the following structure was added instead of the naphthoquinone compound in the coating solution for the hole transporting protective layer. A photoconductor was prepared.
(Structure of UV-2)

[Comparative Example 13]
In Example 1, electrophotography was carried out in the same manner as in Example 1 except that 0.5 part of an electron transfer agent (ETM-1) having the following structure was added in place of the naphthoquinone compound in the coating liquid for hole transporting protective layer. A photoconductor was prepared.
(Structure of ETM-1)

[Comparative Example 14]
In Example 1, electrophotography was carried out in the same manner as in Example 1 except that 0.5 part of an electron transfer agent (ETM-2) having the following structure was added instead of the naphthoquinone compound in the coating solution for hole transporting protective layer. A photoconductor was prepared.
(Structure of ETM-2)

[Comparative Example 15]
In Example 1, the same procedure as in Example 1 was performed except that 0.5 part of a singlet oxygen quencher (Q-1) having the following structure was added in place of the naphthoquinone compound in the coating solution for the hole transporting protective layer. Thus, an electrophotographic photosensitive member was produced.
(Structure of Q-1)

[Comparative Example 16]
In Example 10, an electrophotographic photosensitive member was produced in the same manner as in Example 10 except that an aluminum cylinder with a diameter of 30 mm was used and the naphthoquinone compound of the coating solution for hole transporting protective layer was not used.
[Comparative Example 17]
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that an aluminum cylinder having a diameter of 30 mm was used, the thickness of the hole transport layer was 26 μm, and no hole transport protective layer was provided.

<Inhibition effect of charge trap generation by addition of naphthoquinone compound>
Charge traps generated in the protective layer cause the sensitivity of the photoconductor to decrease and the residual potential to increase because the movement of holes is slowed or stopped. When the photosensitive member negatively charged to the same potential is irradiated with light, holes generated in the charge generation layer move through the hole transporting layer and the hole transporting protective layer to reach the surface of the photosensitive member, and the surface potential disappears.
As the surface potential disappears, the electric field applied to the photosensitive layer decreases, so that the hole mobility gradually becomes slower and the surface potential no longer decreases. The potential at this time is defined as a saturation potential. Now, when charge traps are generated in the hole transporting protective layer, the surface potential cannot be lowered accordingly, so that the saturation potential is increased. Therefore, it was evaluated whether the generation of charge traps was suppressed by examining the saturation potential.

While rotating the electrophotographic photoreceptors obtained in Examples 1 to 9 and the electrophotographic photoreceptors obtained in Comparative Examples 1 to 9 to which no naphthoquinone compound was added, at a linear speed of 160 mm / sec. The surface potential of the photosensitive member was measured by charging with a scorotron charger to −800 V, irradiating with a 655 nm semiconductor laser (aperture 70 × 80 μm, resolution 400 dpi), and 80 msec after irradiation. If this measurement is performed while gradually increasing the amount of irradiation light, the surface potential will no longer drop above a certain amount of light. This time, the surface potential when the light amount 1 μJ / cm ² sufficient for saturation was irradiated was measured as the saturation potential. The results are shown in Table 3.

As described above, when the correspondence with the system in which the naphthoquinone compound is not added in various photoreceptor configurations is seen, the saturation potential is lower in each case in which the naphthoquinone compound is added.
From this result, it can be seen that the added naphthoquinone compound suppresses the generation of charge traps.

<Influence of amount of naphthoquinone compound added>
The naphthoquinone compound used in the present invention does not have hole transportability and radical reactivity. Therefore, if the content is increased, it is expected that the hole transportability and the mechanical strength are reduced, and if the content is small, the effect of suppressing the generation of charge traps is expected to be reduced. Therefore, the elastic displacement rate τe, which is an index of the saturation potential and the mechanical strength of the electrophotographic photosensitive member with the addition amount changed, was measured in order to confirm that there is an appropriate range for the content.
Using the electrophotographic photoreceptors obtained in Examples 10 to 15 and Comparative Example 10, the saturation potential obtained in the same manner as described above and the elastic displacement rate τe obtained by the elastic displacement rate measurement method using the micro surface hardness tester. Is shown in Table 4.

From Table 2, the saturation potential depends on the amount of naphthoquinone compound added within a certain range.
Compared to the additive-free comparative example, when the addition amount is less than 0.5% by weight, the saturation potential hardly changes and the charge trap suppressing effect is not seen. On the other hand, when the addition amount is 10% by weight or more, it is understood that the saturation potential is no longer lowered and is excessive.
The elastic displacement rate shows a decreasing tendency as the addition amount increases. The presence of an additive having no radical reactivity indicates that the crosslinking density is reduced. However, it can be seen that when the addition amount is 10%, it has an elastic displacement rate of 40% or more, and it has sufficient mechanical strength as compared with a photoreceptor without a protective layer. However, if the added amount exceeds 10%, the elastic displacement rate is greatly reduced, and it cannot be said that the protective layer has sufficient strength.
In order to provide a photoconductor excellent in hole transportability with few mechanical traps as a protective layer, the amount of naphthoquinone compound added is 0.5% by weight relative to the radical polymerizable hole transportable compound. It can be seen that it is appropriate to add in the range of 10% to 10% by weight.

<In-machine potential change during continuous image output and effect on in-plane density unevenness>
It was found that the addition of a naphthoquinone compound can reduce the generation of charge traps in the protective layer, but it was evaluated how effective it is when outputting an actual image.
The electrophotographic photosensitive members produced in Examples 1 to 9, Example 13 and Comparative Examples 1 to 10 are mounted on a process cartridge of Ricoh's digital full-color composite machine imagio MP C7500 SP and attached to the main body at a resolution of 600 × 600 dpi. Using Ricoh My Recycled Paper GP A4 paper, the test patterns of yellow, magenta, cyan, and black halftone bands are output continuously at a printing speed of 60 sheets per minute. The 1st to 5th and 496 to 500th black images were arranged, and the in-plane unevenness of the image density was visually evaluated for rank. Further, the image density of the halftone pattern portion of the first sheet and the 500th sheet (black image portion of 1 by 1 dot) was measured with a Macbeth densitometer, and the change in image density at the start and end of printing was observed.
The image density was measured at five locations and the average was determined.
(In-plane unevenness rank level)
Rank 5: Unevenness is observed Rank 4: Unevenness is hardly observed Rank 3: Slight unevenness is observed in some images Rank 2: Slight unevenness is observed in all images Rank 1: Unevenness is observed in all images The results are shown in Table 5.

As described above, the electrophotographic photoreceptor of the present invention has less in-plane unevenness of image density compared to the electrophotographic photoreceptor to which no naphthoquinone compound is added, and enables high-quality image output. This characteristic is also maintained after a large amount of high-speed image output. It can also be seen that the density change in the halftone image portions of the first and 500th sheets is clearly small, and stable image output is possible over time.
Since this tendency appears not according to the magnitude of the previous saturation potential, but according to the presence or absence of additives, the amount of charge traps in the protective layer contributes to the density change over time and in-plane density unevenness during image output. It shows that.
Therefore, the electrophotographic photosensitive member of the present invention that can suppress the generation of charge traps by adding a naphthoquinone compound is an image output method, an image output device, and an image used in the image output method in the commercial printing field that require higher image quality and stability. It turns out that it is effective in providing the process cartridge for output devices.

<Comparison with other additive types>
An important function of the naphthoquinone compound of the present invention is to suppress decomposition when a radically polymerizable hole transporting compound is irradiated with high energy rays typified by ultraviolet rays or electron beams. The difference from the case of adding an ultraviolet absorber known to have the same function is evaluated.
Naphthoquinone compounds are well-known materials as electron transport materials. The difference from the case of adding an electron transport material known to have the same function is also evaluated.
Also, the difference from the case where a singlet oxygen quencher that is effective in preventing light fading of the dye material is added is evaluated.
For the photoreceptors obtained in Comparative Examples 11 to 15, the saturation potential was determined in the same manner as described above. The results are shown in Table 6.

As described above, it can be seen that not only the effect of lowering the saturation potential is not seen as compared with Comparative Example 10 of the additive-free system, but also there are some which become larger, and the side effect on the hole transport property is great.
From these facts, it can be seen that the effect of the naphthoquinone compound used in the present invention is unique.

<Evaluation of abrasion resistance of photoreceptor>
The photoconductors of Examples 16 to 18 and Comparative Examples 16 and 17 were mounted on a process cartridge for an electrophotographic apparatus, and 50,000 copies were made with an imaginary Neo 271 made by Ricoh. First, the initial dark portion potential was set to -850 V, and a 10-point character A4 chart with an image area of 6% was used as a copy original, and the image output after the initial copy and 50,000 copies was evaluated. In the image evaluation, the darkness of the characters, blurring, and dirt on the background were visually compared with the original copy. Further, the film thickness of all layers at the initial stage and after completion after copying 50,000 sheets was measured at intervals of 1 cm, and the wear amount was calculated from the difference. For film thickness measurement, an eddy current film thickness meter FISCHERSCOPE MMS (manufactured by Fischer) was used. The results are shown in Table 7.

  As described above, the wear amount of the photoconductor slightly increases with the amount of naphthoquinone compound added compared to the photoconductor in which the naphthoquinone compound is not added to the hole transportable protective layer of Comparative Example 16, but the hole transportability of Comparative Example 17 increases. Compared with a photoreceptor without a protective layer, it is possible to provide a long-life photoreceptor having a very high wear resistance, high image quality and high durability. The photoreceptor having no naphthoquinone compound added to the hole transporting protective layer of Comparative Example 16 itself has good durability, and it has been confirmed that the image quality is deteriorated in a 50,000-character chart copying test using this apparatus. Was not.

10, 10Y, 10M, 10C, 10K Photoconductor 11, 11Y, 11M, 11C, 11K Charging member 12, 12Y, 12M, 12C, 13K Image exposure member 13, 13Y, 13M, 13C, 13K Developing member 14 Transport roller 15 Transfer Paper 16, 16Y, 16M, 16C, 16K Transfer member 17, 17Y, 17M, 17C, 17K Cleaning member 18 Static eliminating member 20Y, 20M, 20C, 20K Image forming element 21 Paper feed roller 22 Registration roller 23 Transfer member (secondary transfer) Element)
24 fixing member 31 conductive support 33 photosensitive layer 35 charge generation layer 37 hole transport layer 39 hole transport protective layer 101 photosensitive drum 102 charging device 103 exposure 104 developing device 105 transfer body 106 transfer device 107 cleaning blade

JP 2000-66425 A JP 2006-113321 A Japanese Patent No. 4145820 JP 2004-302451 A JP 2004-302452 A

Claims (9)

  By laminating at least a charge generation layer, a hole transport layer, and a hole transport protective layer in this order on a conductive support, the hole transport protective layer irradiates at least a radical polymerizable hole transport compound with ultraviolet rays or an electron beam. An electrophotographic photosensitive member comprising a three-dimensional crosslinked film obtained by chain polymerization, wherein the naphthoquinone compound is contained in the hole transporting protective layer. The electrophotographic photoreceptor according to claim 1, wherein the naphthoquinone compound is a compound represented by the following general formula (1).

[Wherein, R ₁ represents an alkyl group having 1 to 4 carbon atoms or a phenyl group which may have a substituent, and R ₂ represents an alkyl group having 1 to 4 carbon atoms or a substituent. Or a substituent of the following general formula (2).

R ₄ represents an alkyl group having 1 to 4 carbon atoms, or a benzyl group, phenethyl group or phenyl group which may have a substituent. ]   The electrophotographic photosensitive member according to claim 1 or 2, wherein the content of the naphthoquinone compound is 0.5 to 10% by weight of the radical polymerizable hole transporting compound.   The electrophotographic photoreceptor according to claim 1, wherein the radical polymerizable reactive group of the radical polymerizable hole transporting compound is an acryloyloxy group.   The said hole transportable protective layer consists of a three-dimensional crosslinked film obtained by chain-polymerizing a radically polymerizable monomer having a trifunctional or higher functionality having no hole transportability together with a radically polymerizable hole transportable compound. The electrophotographic photosensitive member according to any one of 1 to 4. The hole transportable protective layer is obtained by chain polymerization of at least a trifunctional or more radical polymerizable monomer having no hole transportability together with a monofunctional radical polymerizable hole transportable compound represented by the following general formula (3). The electrophotographic photosensitive member according to claim 5, comprising a three-dimensional crosslinked film, wherein the naphthoquinone compound represented by the general formula (2) is contained in the hole transporting protective layer.

[Wherein R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ represent an alkyl group having 1 to 4 carbon atoms, and R ₁₃ and R ₁₄ may form a ring. o and p represent integers of 0 to 5, q, r, and s represent integers of 0 to 4, and may be different when o, p, q, r, and s are 2 or more. m represents an integer of 0 or 1. X represents a single bond or a divalent group of an alkylene group or an alkyleneoxy group. ]   An image forming method, wherein at least charging, image exposure, development, and transfer are repeated using the electrophotographic photosensitive member according to claim 1.   An image forming apparatus comprising the electrophotographic photosensitive member according to claim 1.   The electrophotographic photosensitive member according to any one of claims 1 to 6, and at least one means selected from the group consisting of a charging means, a developing means, a transfer means, a cleaning means, and a static elimination means. A process cartridge for an image forming apparatus, wherein the process cartridge is removable from the main body of the image forming apparatus.

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