JP2008070784A - Electrophotographic photoreceptor using asymmetric bishydroxy compound and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic photoconductive material excellent in solubility in a solvent and compatibility with a resin as well as in charge transport capacity, capable of producing an electrophotographic photoreceptor excellent in both of electric properties and durability, and useful also as a chemical precursor of various functional materials. <P>SOLUTION: An asymmetric bishydroxy compound represented by formula (1aa) is incorporated into a charge transport layer or a surface protective layer of an electrophotographic photoreceptor, whereby an electrophotographic photoreceptor excellent in electric properties and durability and capable of stably forming high-quality images free of image defects such as black spots is produced. An image forming apparatus equipped with the electrophotographic photoreceptor is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an asymmetric bishydroxy compound, an electrophotographic photosensitive member using the compound, and an image forming apparatus including the electrophotographic photosensitive member.

2. Description of the Related Art An electrophotographic image forming apparatus (hereinafter referred to as an electrophotographic apparatus) that forms an image using electrophotographic technology is widely used in a copying machine, a printer, a facsimile apparatus, and the like.
In an electrophotographic apparatus, an image is formed through the following electrophotographic process. First, a photosensitive layer of an electrophotographic photosensitive member (hereinafter also simply referred to as a photosensitive member) provided in the apparatus is charged and then exposed to form an electrostatic latent image. The formed electrostatic latent image is developed to form a toner image, and the formed toner image is transferred and fixed onto a transfer material such as a recording paper to form a desired image on the transfer material.

In recent years, electrophotographic technology has been used not only in the field of copying machines, but also in fields such as printing plate materials, slide films, and microfilms that previously used silver salt photographic technology. It is also applied to a high-speed printer using a light emitting diode (abbreviated as LED), a cathode ray tube (abbreviated as CRT), or the like as a light source.
With the expansion of the application range of electrophotographic technology, the demand for electrophotographic photoreceptors is becoming advanced and wide.

As an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly composed of an inorganic photoconductive material such as selenium, zinc oxide or cadmium sulfide has been widely used.
Although the inorganic photoreceptor has some basic characteristics as a photoreceptor, it has disadvantages such as difficulty in forming a photosensitive layer, poor plasticity, and high production cost. In addition, inorganic photoconductive materials are generally highly toxic and have significant limitations in manufacturing and handling.

As described above, since the inorganic photoconductive material and the inorganic photoreceptor using the inorganic photoconductive material have many drawbacks, research and development of the organic photoconductive material has been advanced.
Organic photoconductive materials have been extensively researched and developed in recent years, and are used not only for electrostatic recording elements such as electrophotographic photoreceptors, but also for sensor elements and organic electroluminescent (abbreviated EL) elements. Being started.

  Organic photoconductors using organic photoconductive materials have good film-forming properties, excellent flexibility, light weight, good transparency, and a wide wavelength range by appropriate sensitization methods. However, it has been developed as a mainstay of electrophotographic photosensitive members because it has an advantage that a photosensitive member exhibiting good sensitivity can be easily designed.

  Organic photoconductors initially had drawbacks in sensitivity and durability, but these disadvantages were separated into function-separated electrophotographic photoconductors in which the charge generation function and the charge transport function were respectively assigned to different substances. The development has improved significantly. Further, in addition to the above-mentioned advantages of the organic photoreceptor, this function-separated photoreceptor has a wide selection range of materials constituting the photosensitive layer, and an electrophotographic photoreceptor having arbitrary characteristics can be produced relatively easily. It also has advantages.

There are two types of function-separated type photoreceptors: a laminated type and a single layer type.
In the single layer type, there is provided a single layer type photosensitive layer in which a charge generating material responsible for charge generation and a charge transport material responsible for charge transport are co-dispersed in a binder resin called a binder resin. It is done.

  On the other hand, in a laminated type function separation type photoreceptor, a laminated type photosensitive material in which a charge generation layer in which a charge generation material is dispersed in a binder resin and a charge transport layer in which a charge transport material is dispersed in a binder resin are laminated. A layer is provided.

  Various materials such as phthalocyanine pigments, squarylium dyes, azo pigments, perylene pigments, polycyclic quinone pigments, cyanine dyes, squarate dyes, and pyrylium salt dyes have been studied as charge generating materials used in the functional separation type photoreceptor. Various materials having high light resistance and high charge generation ability have been proposed.

Examples of the charge transport material include pyrazoline compounds (for example, see Patent Document 1), hydrazone compounds (for example, see Patent Documents 2 to 4), triphenylamine compounds (for example, see Patent Documents 5 and 6), stilbene compounds ( For example, various compounds such as Patent Documents 7 and 8) are known.
Recently, compounds having a condensed polycyclic hydrocarbon system in the central mother nucleus, such as pyrene derivatives, naphthalene derivatives, terphenyl derivatives (see, for example, Patent Document 9) have been developed.

Charge transport materials include
(1) being stable to light and heat;
(2) being stable against active substances such as ozone, nitrogen oxides (general formula: NOx), and nitric acid generated by corona discharge when charging the surface of the photoreceptor;
(3) Excellent charge transport capability,
(4) Excellent compatibility with organic solvent and binder resin,
(5) There is a demand for easy and inexpensive manufacture.

However, although the charge transport materials satisfy some of these requirements, they have not met all at a high level.
In addition, the photoconductor has good sensitivity even when used in a low-temperature environment, small changes in characteristics due to changes in the surrounding environment, such as temperature and humidity, and excellent environmental stability. Although required, a charge transport material capable of realizing such characteristics has not been obtained yet.

On the other hand, recently, among the above requirements, in particular, it is required that the charge transport material has excellent charge transport capability.
For example, along with miniaturization of electrophotographic apparatuses such as copiers and printers and higher image forming speeds, higher sensitivity is required as the characteristics of the photosensitive member. As a means for realizing higher sensitivity of the photosensitive member, charge There is a need to improve the charge transporting ability of transport materials.

In a high-speed electrophotographic process, since the time from exposure to development is short, a photoconductor with good photoresponsiveness is required.
However, if the photoresponsiveness of the photoreceptor is poor, the rate of decay of the surface potential of the photosensitive layer due to exposure becomes slow, the residual potential rises, and it is repeatedly used in a state where the surface potential is not sufficiently attenuated. . For this reason, the surface charge of the portion to be erased is not sufficiently erased by exposure, and problems such as a decrease in image density occur at an early stage.

  On the other hand, in the function-separated type photoconductor, the charge generated by the charge generating material by light absorption is transported to the surface of the photosensitive layer by the charge transport material, so that the surface charge of the photosensitive layer in the irradiated portion is erased. The photoresponsiveness depends on the charge transport ability of the charge transport material.

Therefore, from the viewpoint of realizing a photoreceptor having sufficient photoresponsiveness and capable of forming a high-quality image even in a high-speed electrophotographic process, the charge transport material is required to have an excellent charge transport capability. It is done.
In recent years, electrophotographic apparatuses such as digital copying machines and printers have been miniaturized and speeded up, and high sensitivity corresponding to high speed has been demanded as a photosensitive member characteristic.

Therefore, as the characteristics of the photoreceptor, it is required that the sensitivity does not decrease even when used in a low temperature environment, and the change in characteristics is small and the reliability is high in various environments.
In addition, as a charge transport material, a higher charge transport capability is required.
Furthermore, since the time from exposure to development is short in a high-speed process, a photoconductor with good photoresponsiveness is required.

  As described above, since the photoresponsiveness depends on the charge transporting ability of the charge transporting substance, a charge transporting substance having a higher charge transporting ability is required from this point.

  Conventionally, various molecular designs have been performed for the purpose of developing charge transport materials that meet these requirements, and compounds that combine a hydrazone structure and a styryl structure to expand the conjugated system to a greater extent in the basic structure. Has also been proposed as a compound having an excellent charge transporting capability (see, for example, Patent Document 10).

  However, when these compounds are used in a low temperature environment, the sensitivity is lowered, and there is a problem that must be improved in terms of exhibiting sufficient charge transport ability. Therefore, in order to use the charge transport material as described above for a photoreceptor that can be used under various temperature environments, its performance is not yet sufficient.

Furthermore, the electrophotographic apparatus is also required to have high durability.
Therefore, in order to realize these, it is necessary that the electrophotographic photoreceptor is excellent in durability and can operate stably for a long period of time.
However, the durability of the photoreceptor is greatly affected by the printing durability of the outermost layer of the photoreceptor.

Usually, when the photoconductor is mounted and used in an electrophotographic apparatus, the outermost layer of the photoconductor is rubbed by a contact member such as a cleaning blade or a charging roller, and a part thereof is forced to be scraped off. If the amount of the outermost layer of the photoreceptor removed by rubbing, that is, the amount of film reduction is large, there arises a problem that the charge holding ability of the photoreceptor is lowered and the image quality is lowered.
For this reason, the outermost layer of the photoreceptor is required to be hard to be scraped off by the contact member, that is, to have excellent printing durability.

As a method for improving the printing durability of the outermost layer in the photoreceptor in which the charge transport layer is the outermost layer, it is conceivable to increase the content of the binder resin contained in the charge transport layer.
However, when the content of the binder resin is increased, the content of the charge transport material in the charge transport layer is relatively decreased, so that the charge transport capability of the charge transport layer is decreased and the photoresponsiveness is decreased. Arise.
Furthermore, when the compatibility between the charge transport material and the binder resin is poor, the charge transport material is partially crystallized at the time of film formation, so that there is a problem that a uniform charge transport layer cannot be obtained and image defects are caused. .

Therefore, it is difficult to realize a photoreceptor in which both electrical characteristics such as responsiveness and durability are compatible.
Therefore, in order to solve the above-mentioned problems in the electrophotographic photosensitive member, an attempt is made to impart a charge transport function to the binder resin and reduce the amount of the charge transport material added, and the structural unit having the charge transport function. The development of binder resins containing so-called polymeric photoconductive materials is underway.

  Specific examples thereof include polycarbonate resins having a triarylamine structure in the main chain or side chain (for example, see Patent Documents 11 to 15), and polyether resins having a triarylamine structure in the main chain (for example, see Patent Document 16). ) And the like.

These resins are synthesized by using a compound having a triarylamine structure and a hydroxyl group (for example, Patent Documents 17 to 20) as a monomer and homopolymerizing or copolymerizing these monomers.
However, the triarylamine compounds disclosed in Patent Documents 17 to 20 and the like do not have sufficient charge transport ability, and there are resins having a triphenylamine structure disclosed in Patent Documents 11 to 16 and the like obtained by polymerizing these compounds. However, it does not reach a sufficiently satisfactory level in terms of charge transport ability and mechanical strength.

  In order to solve such a problem of the polymer photoconductive material, an enamine structure, two hydroxyl groups, and a compound useful as a raw material compound for the polymer material and also useful as a charge transport material by itself There has been proposed a bishydroxy-substituted enamine compound (hereinafter also referred to as a bishydroxyenamine compound) having the formula (see Patent Document 21).

As another means for realizing high durability of the photosensitive member, the photosensitive layer is covered with a surface protective layer formed of a resin or the like. In a photoconductor provided with a surface protective layer, the surface protective layer is the outermost layer of the photoconductor, and therefore, the surface protective layer is required to have excellent charge transport capability and excellent wear resistance.
As a surface protective layer that satisfies such requirements, a surface protective layer made of a siloxane-based resin having a structural unit having a charge transport function has been proposed (see Patent Document 22).

  In the bishydroxyenamine compound described in Patent Document 21, the nitrogen atom contained in the enamine skeleton has the same substituent, the molecular structure is highly symmetric, and the crystallinity is good. There is a problem that the compatibility with the binder resin is poor. Therefore, for example, when the compound is used as a charge transport material for the charge transport layer, a part of the compound remains undissolved in the coating solution for forming the layer, and this insoluble matter exists in the charge transport layer in a crystalline state. This causes a bad effect such as causing an image defect.

  In addition, since the raw material compound used in producing the compound disclosed in Patent Document 21 and the intermediate product produced in the production process are also highly crystalline and poorly soluble in a solvent, the reaction is difficult to proceed smoothly. There is also. Further, when a polymer material is produced using the compound disclosed in Patent Document 21 as a raw material compound, there is a problem that the reactivity is deteriorated due to poor solubility. In addition, expensive raw materials must be used to construct the enamine structure, which is not preferable in terms of production.

On the other hand, the surface protective layer described in Patent Document 22 does not have sufficient charge transport capability, and no surface protective layer excellent in both charge transport capability and mechanical strength has been realized at present.
Further, in the photoreceptor disclosed in Patent Document 22, the surface protective layer and the charge transport layer are incompatible with the charge transport material in the charge transport layer and the structural unit having the charge transport function of the siloxane resin constituting the surface protective layer. A potential barrier is formed at the interface with the layer, charge injection becomes insufficient, and there is a problem that sensitivity and photoresponsiveness are lowered.

  Charge transport materials having a hydrazone structure and a bisdiene structure or a bistriene structure to form an extended conjugated system are inherently excellent in electrical properties such as sensitivity and responsiveness and durability, but have poor printing durability when a photosensitive layer is formed. Printing durability is increased by increasing the content of the binder resin. However, since the electrical properties such as sensitivity and responsiveness are deteriorated by increasing the content of the binder resin, the present situation is that the advantages inherent in the hydrazone structure and the bisdiene structure or the bistriene structure are not fully utilized.

Japanese Patent Publication No.52-4188 JP-A-54-150128 Japanese Patent Publication No.55-42380 JP-A-55-52063 Japanese Patent Publication No.58-32372

JP-A-2-190862 JP 54-151955 A JP 58-198043 A JP 7-48324 A JP-A-5-66587

Japanese Patent Laid-Open No. 3-221522 JP-A-4-11627 JP-A-6-295077 JP 7-258399 A JP-A-8-62864

JP-A-8-176293 JP-A-7-228557 Japanese Patent Laid-Open No. 9-194442 JP 2000-136169 A JP 2002-249472 A JP 2004-269377 A JP 2000-241919

  Therefore, the present invention has excellent charge transport capability, excellent solubility in a solvent and compatibility with a resin, can prevent partial crystallization during film formation, and forms a broad conjugated system. Introducing a hydrazone structure and a bisdiene structure or a bistriene structure into an electrophotographic photoreceptor excellent in both electrical properties and durability at a lower cost and useful as a raw material compound for various functional materials It is an object of the present invention to provide a photoconductive material, an electrophotographic photoreceptor using the organic photoconductive material, and an image forming apparatus including the same.

  As a result of intensive researches, the present inventors have surprisingly found that the asymmetric bishydroxy compound is excellent in charge transporting ability and in both solubility in a solvent and compatibility with a resin. Further, the present inventors have found that it is extremely useful as an organic photoconductive material for an electrophotographic photosensitive member and an image forming apparatus including the same, and completed the present invention.

However, according to the present invention, the general formula (1):

(In the formula, Ar ₁ and Ar ₂ are an aryl group or a heterocyclic group which may optionally have a substituent, and Ar ₃ and Ar ₆ are different from each other and may optionally have a substituent. Or a divalent heterocyclic group, Ar ₄ is an optionally substituted arylene group or a divalent heterocyclic group, and Ar ₅ is a hydrogen atom or optionally substituted. An aryl group, an aralkyl group or an alkyl group, R ₁ is a hydrogen atom or an optionally substituted alkyl group, and R ₂ and R ₃ are a hydrogen atom or an optionally substituted group. An alkyl group, an aryl group, a heterocyclic group, or an aralkyl group, which may have a substituent, provided that R ₁ , R _2, and R ₃ may be the same or different groups, and n is 0 It is an integer of ~ 2)
An electrophotographic photoreceptor comprising the asymmetric bishydroxy compound represented by the formula:

According to the present invention, the asymmetric bishydroxy compound is a naphthylene group in which Ar ₃ optionally has a substituent in the general formula (1), and each of R ₁ , R ₂ and R ₃ Are both hydrogen, the following general formula (2):

(In the formula, Ar ₁ , Ar ₂ , Ar ₄ , Ar ₅ , Ar ₆ and n are as defined in the general formula (1), and a has a hydrogen atom or an optional substituent. An alkyl group or a dialkylamino group, provided that a plurality of a are present in the formula, they may be the same or different independently from each other, and m represents an integer of 1 to 6) There is provided an asymmetric bishydroxy compound (2) characterized in that it is shown.

（式中、式中、Ａｒ₁、Ａｒ₂、Ａｒ₆、ａ、ｍおよびｎは、前記一般式（１）において定義したものと同義である）
で示されることを特徴とする非対称ヒドロキシ化合物（３）が提供される。 Specifically, according to the present invention, Ar ₃ in the general formula (2) is an optionally substituted naphthylene group, Ar ₄ is a phenylene group, and Ar ₅ is hydrogen. And R ₁ and R ₂ and R ₃ are each hydrogen, the following general formula (3):

(In the formula, Ar ₁ , Ar ₂ , Ar ₆ , a, m, and n are as defined in the general formula (1)).
An asymmetric hydroxy compound (3) is provided, which is characterized in that

（式中、Ａｒ₁、Ａｒ₂、Ａｒ₆、ａおよびｍは、前記一般式（１）において定義したものと同義である）
で示されることを特徴とする非対称ヒドロキシ化合物（４）が提供される。 More specifically, according to the present invention, in the general formula (3), n is 0, and the following general formula (4):

(In the formula, Ar ₁ , Ar ₂ , Ar ₆ , a and m are as defined in the general formula (1)).
An asymmetric hydroxy compound (4) is provided, which is characterized in that

  According to the present invention, the photosensitive layer and the surface protective layer are laminated in this order on the conductive support, and at least one of the photosensitive layer and the surface protective layer comprises the asymmetric bishydroxy compound ( An electrophotographic photoreceptor characterized by containing any one of 1) to (4) alone or as a mixture thereof is provided.

  In addition, according to the present invention, a photosensitive layer containing any one of the asymmetric bishydroxy compounds (1) to (4) alone or as a mixture thereof is provided on a conductive support. An electrophotographic photoreceptor is provided.

  According to the invention, on the conductive support, there is provided a photosensitive layer and a surface protective layer containing any one of the asymmetric bishydroxy compounds (1) to (4) alone or as a mixture thereof. The electrophotographic photosensitive member is provided.

Furthermore, according to the present invention, the electrophotographic photoreceptor,
Charging means for charging the electrophotographic photoreceptor;
Exposure means for exposing the charged electrophotographic photosensitive member;
Developing means for developing an electrostatic latent image formed by exposure;
An image forming apparatus is provided.

  All of the asymmetric bishydroxy compounds according to the present invention have a hydrazone structure and a bisdiene structure or a bistriene structure, and form an extended conjugated system, so that they have a good charge transport function, particularly a hole transport function.

  Furthermore, the asymmetric bishydroxy compound according to the present invention not only has an excellent hole transport function, but also has excellent solubility in a solvent and compatibility with a resin. Therefore, the asymmetric bishydroxy compound is used as a photosensitive layer or a surface protective layer. Even when used in the above, it can be uniformly dispersed without causing partial crystallization.

Therefore, by including the asymmetric bishydroxy compound according to the present invention in, for example, a photosensitive layer or a surface protective layer of an electrophotographic photoreceptor, electrical characteristics such as charging property, sensitivity, and photoresponsiveness are good, and durability and An electrophotographic photoreceptor excellent in environmental stability can be provided.
Furthermore, the asymmetric bishydroxy compound according to the present invention is useful as an organic photoconductive material, and can be suitably used as a charge transport material for devices such as electrostatic recording elements such as electrophotographic photoreceptors, sensor elements, and EL elements. .

  The present invention also provides an electrophotographic photoreceptor containing the asymmetric bishydroxy compound according to the present invention in a surface protective layer. In the surface protective layer, the asymmetric bishydroxy compound according to the present invention is not crystallized and is dispersed in a uniform state, so that the charge transport function can be sufficiently exhibited.

Therefore, the electrophotographic photoreceptor according to the present invention is excellent not only in mechanical strength but also in electrical characteristics such as sensitivity and responsiveness. By using such an electrophotographic photosensitive member, a high-quality image free from image defects such as black spots can be formed even when used repeatedly over a long period of time.
Further, the electrophotographic photosensitive member according to the present invention can provide a high-quality image even when used in a high-speed electrophotographic process due to its excellent photoresponsiveness.

Furthermore, the asymmetric bishydroxy compound according to the present invention is also useful as a raw material compound for polymer materials such as polycarbonate resin, polyether resin, polyester resin, polyurethane resin, etc., and the asymmetric bishydroxy compound according to the present invention is used as a monomer. Thus, a polymer photoconductive material having an excellent charge transport function can be easily obtained.
In addition, according to the present invention, an image forming apparatus including the electrophotographic photosensitive member is provided.

  That is, since the electrophotographic photoreceptor according to the present invention contains the asymmetric bishydroxy compound according to the present invention in the photosensitive layer or the surface protective layer, the electrophotographic photoreceptor is excellent in electrical characteristics such as chargeability, sensitivity, and photoresponsiveness and durability. Further, the asymmetric bishydroxy compound according to the present invention is uniformly dispersed in the photosensitive layer or surface protective layer of the electrophotographic photoreceptor according to the present invention without being crystallized.

Therefore, the image forming apparatus according to the present invention can stably form a high-quality image free from image defects such as black spots over a long period of time under various environments.
In addition, since the electrophotographic photosensitive member according to the present invention has excellent photoresponsiveness and can provide a high-quality image even in a high-speed electrophotographic process, the image forming apparatus according to the present invention can increase the image forming speed. It is.

The asymmetric bishydroxy compound according to the present invention has a hydrazone structure and a bisene structure, a bisdiene structure or a bistriene structure, and has the general formula (1):

(In the formula, Ar ₁ and Ar ₂ are an aryl group or a heterocyclic group which may optionally have a substituent, and Ar ₃ and Ar ₆ are different from each other and may optionally have a substituent. Or a divalent heterocyclic group, Ar ₄ is an optionally substituted arylene group or a divalent heterocyclic group, and Ar ₅ is a hydrogen atom or optionally substituted. An aryl group, an aralkyl group or an alkyl group, R ₁ is a hydrogen atom or an optionally substituted alkyl group, and R ₂ and R ₃ are a hydrogen atom or an optionally substituted group. An alkyl group, an aryl group, a heterocyclic group, or an aralkyl group, which may have a substituent, provided that R ₁ , R _2, and R ₃ may be the same or different groups, and n is 0 It is an integer of ~ 2)
Indicated by

The aryl group optionally having a substituent represented by Ar ₁ and Ar ₂ in the general formula (1) is an alkyl group having 1 to 4 carbon atoms or a carbon atom having 1 to 4 carbon atoms. Examples include aryl groups such as phenyl, tolyl, naphthyl, and biphenylyl groups that may have an alkoxy group. Among these, phenyl, tolyl, naphthyl group and the like are preferable.

Moreover, as the heterocyclic group optionally having substituents represented by Ar ₁ and Ar ₂ in the general formula (1), furyl which may have an alkyl group having 1 to 4 carbon atoms as a substituent , Heterocyclic groups such as thienyl, thiazolyl, benzofuryl or indolyl groups.

Moreover, as an arylene group which may optionally have a substituent represented by Ar ₃ and Ar ₆ and Ar ₄ in the general formula (1), an alkyl group having 1 to 4 carbon atoms, Examples include arylene groups such as p-phenylene, m-phenylene, 1,4-naphthylene, pyrenylene, and biphenylylene groups that may have a substituent selected from the group consisting of an alkoxy group, a phenoxy group, and a phenylthio group.

  Among these, p-phenylene, m-phenylene, 1,4-naphthylene group and the like are preferable, and p-phenylene and 1,4-naphthylene group are particularly preferable.

In addition, as the divalent heterocyclic group optionally having a substituent represented by Ar _3, Ar ₆ and Ar ₄ in the general formula (1), an alkyl group having 1 to 4 carbon atoms, a carbon number 1,4-furandiyl, 1,4-thiophenediyl, 1,4-thiazoldiyl, 2,5-thinyl, which may have a substituent selected from the group consisting of 1-4 alkoxy groups, phenoxy groups and phenylthio groups Examples include benzofurandiyl, 2,5-benzothiophenediyl, indole-2,5-diyl, 2,5-benzothiazolediyl, 2,5-benzoxazolediyl, carbazole-3,6-diyl group.

In the general formula (1), as an aryl group represented by Ar ₅ and optionally having a substituent, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenoxy group, phenylthio, And aryl groups such as phenyl, tolyl, naphthyl, pyrenyl, and biphenylyl groups that may have a substituent selected from a group and a styryl group.

  Of these, phenyl and naphthyl groups are preferred.

Similarly, the aralkyl group represented by Ar ₅ which may optionally have a substituent includes benzyl, phenethyl or 1-naphthylmethyl which may have an alkoxy group having 1 to 4 carbon atoms as a substituent. And an aralkyl group such as a group.

Furthermore, similarly, as the alkyl group optionally represented by Ar ₅ , which may have a substituent selected from a halogen atom and a thienyl group, methyl, ethyl, n-propyl, isopropyl C1-C4 linear or branched alkyl groups such as n-butyl, isobutyl and t-butyl groups, and cycloalkyl groups such as cyclohexyl and cyclopentyl groups.

In the general formula (1), the alkyl group represented by R ₁ , R ₂ and R ₃ which may optionally have a substituent is methyl, which may have a substituent selected from a halogen atom and a thienyl group, Examples thereof include linear or branched alkyl groups having 1 to 4 carbon atoms such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl and t-butyl groups.

Similarly, the aryl group optionally having a substituent represented by R ₂ and R ₃ is a substituent selected from an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. And aryl groups such as phenyl, tolyl and naphthyl. Of these, phenyl and naphthyl groups are preferred.

Similarly, the heterocyclic group optionally having substituents represented by R ₂ and R ₃ includes a furyl, thienyl, and thiazolyl group that may have an alkoxy group having 1 to 4 carbon atoms as a substituent. Etc.
Examples of the aralkyl group include aralkyl groups such as benzyl, phenethyl or 1-naphthylmethyl group.

（式中、Ａｒ₁、Ａｒ₂、Ａｒ₄およびＡｒ₅は式（１）で定義したとおりである）
で表される化合物が、好ましい。 In view of cost of raw materials, availability, ease of synthesis, and yield of synthesis, in general formula (1), either Ar ₃ or Ar ₆ is a p-phenylene group, and the other is 1 , 4-naphthylene group, and R ₁ , R ₂ and R ₃ are all hydrogen atoms, the general formula (2A):

(In the formula, Ar ₁ , Ar ₂ , Ar ₄ and Ar ₅ are as defined in formula (1)).
The compound represented by these is preferable.

（式中、Ａｒ₁およびＡｒ₂は一般式(１)で定義したとおりである）
で表される化合物がより好ましい。 Furthermore, in the general formula (2A), Ar ₄ is a phenylene group, and Ar ₅ is a hydrogen atom. General formula (3A):

(In the formula, Ar ₁ and Ar ₂ are as defined in the general formula (1))
The compound represented by these is more preferable.

（式中、Ａｒ₁およびＡｒ₂は一般式(１)で定義したとおりである）
で表される化合物がさらに好ましい。 In the general formula (3A), n = 0, general formula (4A):

(In the formula, Ar ₁ and Ar ₂ are as defined in the general formula (1))
Is more preferable.

The asymmetric bishydroxy compound (1) is prepared by preparing an intermediate of the asymmetric bishydroxyether compound (8a) or (8b) by, for example, the method shown in the following reaction scheme, and then removing the protecting group represented by R ₅ in the formula. It can be manufactured by deprotection.

Wherein Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ , Ar ₆ , R ₁ , R ₂ and R ₃ are as defined above, k is 0 or 1, R ₄ and R ₅ represents an optionally substituted alkyl group, aryl group, heterocyclic group or aralkyl group, and two R ₄ or R ₅ in the same molecule may be the same or different independently of each other. )

In the above reaction process formula, examples of the alkyl group which may have a substituent represented by R ₄ and R ₅ include methyl, ethyl, n-propyl, which may have a substituent selected from a halogen atom and a thienyl group, Examples thereof include linear or branched alkyl groups having 1 to 4 carbon atoms such as isopropyl, n-butyl, isobutyl and t-butyl groups. Of these, methyl and ethyl groups are preferred.

  In addition, as the aryl group which may have the above-described substituent, phenyl, tolyl, naphthyl group and the like which may have a substituent selected from an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms Of the aryl group.

  In addition, the heterocyclic group which may have the above-mentioned substituent is a furyl, thienyl or thiazolyl group which may have a substituent selected from an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. Etc.

  As the aralkyl group which may have a substituent, the alkyl portion is a linear or branched alkylene group having 1 to 3 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms is substituted with an aryl group. Examples include aralkyl groups such as benzyl, phenethyl or 1-naphthylmethyl group which may be present in the moiety.

（式中、Ａｒ₁、Ａｒ₂、Ａｒ₃およびＡｒ₆は一般式（１）における定義と同義である）で表されるヒドラゾン中間体をビスホルミル化して、下記一般式（６ａ） In the present invention, the general formula (1) to be contained in the photosensitive layer can be specifically produced by utilizing a known reaction, for example, as follows.
For example, the compound in which R ₁ is a hydrogen atom in the general formula (1) is represented by the following general formula (5)

(In the formula, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₆ have the same definitions as in general formula (1)), and bisformylation of the hydrazone intermediate represented by the following general formula (6a)

（式中、Ａｒ₁、Ａｒ₂、Ａｒ₃およびＡｒ₆は一般式（１）における定義と同義である）
で表されるヒドラゾン−ビスアルデヒド中間体（６ａ）を合成することができる。

(In the formula, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₆ have the same definitions as in general formula (1)).
The hydrazone-bisaldehyde intermediate represented by (6a) can be synthesized.

（式中、Ａｒ₁およびＡｒ₂は一般式（１）における定義と同義である）で表されるケトン化合物と、一般式（４ｂ）：

（式中、Ａｒ₃およびＡｒ₆は一般式（１）における定義と同義である）
で表されるヒドラジン化合物を、脱水縮合反応に付すことによって製造できる。 The hydrazone intermediate represented by the general formula (5) is, for example, the general formula (4a):

(Wherein, Ar ₁ and Ar ₂ have the same definitions as in general formula (1)), and general formula (4b):

(In the formula, Ar ₃ and Ar ₆ have the same definitions as in general formula (1)).
The hydrazine compound represented by these can be manufactured by attaching | subjecting to a dehydration condensation reaction.

The dehydration condensation reaction proceeds almost quantitatively by heating the ketone compound represented by the general formula (4a) and the hydrazine compound represented by the general formula (4b) in an alcohol solvent in the presence of an acid catalyst. To do.
The reaction temperature and reaction time of this dehydration condensation reaction are not particularly limited and are appropriately selected according to various conditions such as the type and amount of the ketone compound and hydrazine compound used. Preferably, the reaction temperature is 70-80. 4-8 hours at ° C.

Examples of alcohol solvents used in the dehydration condensation reaction include ethanol, isopropanol, and butanol.
Examples of the acid catalyst include p-toluenesulfonic acid, camphorsulfonic acid, acetic acid and the like. The addition amount of the acid catalyst is not particularly limited, but 0.001 to 0.01 molar equivalent is sufficient with respect to 1.0 molar equivalent of the ketone compound represented by the general formula (4a), for example.

For example, in the general formula (5), any one of Ar ₃ and Ar ₆ is a phenylene group, the other is a naphthylene group, and Ar ₁ and Ar ₂ are phenyl groups. ) Can be produced using benzophenone as the ketone compound represented by (1) and 1-naphthyl-1-phenylhydrazine as the hydrazine compound represented by the general formula (4b).

The bisformylation of the hydrazone intermediate represented by the general formula (5) can be performed by a known bisformylation reaction such as Vilsmeier formylation reaction.
The Virsmeier bisformylation reaction for the hydrazone intermediate represented by the general formula (5) is performed, for example, as follows.

  First, phosphorus oxychloride and N, N-dimethylformamide (DMF), N, N-diethylformamide, N, N-dibutylformamide, N-methyl-N-phenylformamide in a suitable solvent Or, N, N-diphenylformamide is added to prepare a Vilsmeier reagent.

  Examples of the solvent that can be used for this reaction include aprotic polar solvents such as N, N-dimethylformamide, halogenated hydrocarbons such as 1,2-dichloroethane, and aromatic hydrocarbons such as toluene. The above N, N-dimethylformamide may also be used as a solvent.

（式中、Ａｒ₁、Ａｒ₂、Ａｒ₃およびＡｒ₆は一般式（１）における定義と同義である）
で表されるヒドラゾン−ビスアルデヒド中間体が高収率で固体として得られる。 Next, 1.0 mole equivalent of the hydrazone intermediate represented by the general formula (5) is added to 2.0 to 2.3 mole equivalents of the prepared Vilsmeier reagent, and the mixture is heated at 80 to 120 ° C. for 2 hours. Stir for 10 hours to react. After completion of the reaction, hydrolysis is performed with an aqueous alkali solution to obtain a general formula (6a):

(In the formula, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₆ have the same definitions as in general formula (1)).
The hydrazone-bisaldehyde intermediate represented by is obtained as a solid in high yield.

Examples of the alkaline aqueous solution used for hydrolysis include 1 to 8 N sodium hydroxide or potassium hydroxide aqueous solution.
Further, instead of the above bisformylation reaction, for example, acetic anhydride or acetyl chloride is used for a bisacylation reaction well known to those skilled in the art, and subjected to the same treatment as the above reaction, whereby the reaction scheme described in the above reaction scheme is used. A biscarbonyl intermediate (6) is obtained.

  Further, the biscarbonyl intermediate (6) is subjected to a Wittig-Horner reaction, and an ether compound as a precursor of the asymmetric bishydroxy compound (1) is represented by the general formula (8a) or (8b). The ether compound represented (hereinafter referred to as ether compound (8a) or (8b)) is obtained.

Examples of the Wittig reagent include compounds represented by the general formula (7a) or (7b) (hereinafter referred to as Wittig reagent (7a) or (7b)).
In the Wittig reagents (7a) and (7b), the hydroxyl group of the substituent represented by Ar ₄ is protected by the substituent R ₅ .

By reacting the biscarbonyl intermediate (6) with the Wittig reagent (7a), an ether compound (8a) is obtained, and further by deprotecting the protected R ₅ group, the asymmetric bishydroxy compound (1) has n Is obtained (hereinafter referred to as asymmetric bishydroxy compound (1a)).

Further, by reacting the biscarbonyl intermediate (6) with the Wittig reagent (7b), an ether compound (8b) is obtained, and further, by removing the protecting group R ₅ , the asymmetric bishydroxy compound (1) In which n = 1 or 2 (hereinafter referred to as asymmetric bishydroxy compound (1b)).

The Wittig-Horner reaction for the biscarbonyl intermediate (6) can be carried out according to methods well known to those skilled in the art.
That is, the target substance can be obtained by reacting the biscarbonyl intermediate (6) with the Wittig reagent (7a) or (7b) in the presence of a basic catalyst such as a metal alkoxide in an appropriate solvent. it can.

  The solvent is not particularly limited as long as it is inert to the reaction and can dissolve or disperse the reaction substrate and catalyst. For example, aromatic hydrocarbons such as toluene and xylene, diethyl ether, tetrahydrofuran, Examples include ethers such as ethylene glycol dimethyl ether, amides such as N, N-dimethylformamide, and sulfoxides such as dimethyl sulfoxide, and these can be used alone or as a mixed solvent.

Further, the amount of the solvent used is not particularly limited, and the amount by which the reaction smoothly proceeds can be appropriately selected according to the reaction conditions such as the amount of the reaction substrate used, the reaction temperature, and the reaction time.
As said metal alkoxide basic catalyst, alkali metal alkoxides, such as well-known potassium t-butoxide, sodium ethoxide, sodium methoxide, can be used, for example. A metal alkoxide can be used individually by 1 type in the above, or in combination of 2 or more types.

  The use amounts of the reaction substrate and catalyst are not particularly limited and can be appropriately selected depending on the reaction conditions. However, considering the smooth progress of the reaction, for example, the Wittig reagent for 1 equivalent of the biscarbonyl intermediate (6) (7a) or (7b) can be used in an amount of about 2.0 to 2.3 equivalents, and the catalyst can be used in an amount of about 2.0 to 2.5 equivalents.

In this reaction, the ether compound (8a) or (8b) can be obtained by, for example, stirring at room temperature or heating at 30 to 60 ° C. for about 2 to 8 hours and treating according to a conventional method.
Deprotection of the ether compound (8a) or (8b) to obtain the asymmetric bishydroxy compound (1a) or (1b) can be carried out according to methods well known to those skilled in the art.

  That is, it can be carried out by reacting the ether compound (8a) or (8b) with a deprotecting agent in a suitable solvent.

  Examples of the deprotecting agent include hydrogen halides such as hydrogen bromide and hydrogen iodide, aluminum halides such as aluminum chloride and aluminum bromide, boron tribromide, and ethanethiol sodium salt. it can.

The deprotecting agent can be used alone or in combination of two or more of the above compounds.
The amount of the deprotecting agent is not particularly limited, but considering that the reaction proceeds smoothly and that the target compound after the reaction can be easily isolated and purified, the ether compound (8a) or (8b) is reduced to 1 equivalent. On the other hand, it is preferable to use about 2.0 to 3.0 equivalents, and more preferably about 2.2 to 2.6 equivalents.

  The solvent for the above deprotection reaction can be used without particular limitation as long as it is inert to the reaction and can stably dissolve or disperse the reaction substrate. For example, aromatic hydrocarbons such as benzene and nitrobenzene, chlorobenzene, etc. Halogenated aromatic hydrocarbons such as N, N-dimethylformamide and the like, acetic anhydride, methylene chloride and the like are preferably used.

In addition, said solvent can be suitably selected and used according to the kind of deprotection agent.
For example, the reaction solvent is preferably acetic anhydride when a hydrogen halide is used as a deprotecting agent, and is preferably an aromatic hydrocarbon or a halogenated aromatic hydrocarbon when aluminum halide is used.

Further, as the reaction solvent, methylene chloride is preferable when boron tribromide is used as a deprotecting agent, and formamides are preferable when ethanethiol sodium salt is used.
The amount of the solvent used is not particularly limited, and can be appropriately selected according to the reaction conditions such as the kind of the reaction substrate and the deprotecting agent, the amount used, and the reaction temperature.

  This deprotection reaction is carried out under various reaction conditions, for example, under cooling or from room temperature to solvent reflux, depending on the activity of the deprotecting agent, and is completed in about 0.5 to 24 hours.

In addition, what is necessary is just to select suitably reaction temperature that the deprotection reaction advances smoothly.
The asymmetric bishydroxy compound (1) according to the present invention thus obtained can be easily extracted from the reaction mixture after completion of the reaction by general purification means such as extraction, chromatography, centrifugation, recrystallization, washing and the like. Can be isolated and purified.

  Specific examples of the asymmetric bishydroxy compound (1) according to the present invention that can be prepared according to the above method include those listed in Table 1 below.

  The asymmetric bishydroxy compound according to the present invention is useful as an organic photoconductive material because it has excellent charge transporting ability, solubility in a solvent, and compatibility with a resin, and is a photosensitive layer of an electrophotographic photoreceptor. It is particularly useful as a charge transport material in the above or as a charge transport material in the surface protective layer.

  In addition, since the asymmetric bishydroxy compound according to the present invention has two hydroxyl groups in the molecule, it can be used as a raw material compound for various polymer materials, particularly polymer materials derived from compounds having two hydroxyl groups. Useful.

  For example, by using the asymmetric bishydroxy compound according to the present invention as a monomer such as a polycarbonate resin, a polyether resin, a polyester resin, or a polyurethane resin, a polymer light having an excellent charge transport function and useful as a photoconductive material. A conductive material can be obtained.

  Conventional polymer manufacturing methods except that one or more of the asymmetric bishydroxy compounds according to the present invention are used as diols for polymer materials such as polycarbonate resin, polyether resin, polyester resin, and polyurethane resin. It can be manufactured in the same manner.

  For example, the polycarbonate resin is the same as the conventional polycarbonate resin except that one or more of the asymmetric bishydroxy compounds according to the present invention and one or more of the carbonate compounds are used as a raw material compound. Can be manufactured.

  As said carbonate compound, what is used for manufacture of polycarbonate resin can be used, for example, halogenated carbonyl compounds, such as phosgene and bis (trichloromethyl) carbonate (aka triphosgene), bisaryl carbonates, such as bisphenyl carbonate, and Examples thereof include bishalogenated formates such as bischloroformate derived from a dihydroxy compound having two hydroxyl groups.

  Examples of the dihydroxy compound used as a raw material for the bishalogenated formates include 4,4 ′-(1-methylethylidene) bisphenol, 4,4 ′-(1-methylethylidene) bis (2-methylphenol), and 4,4. Examples include '-cyclohexylidene bisphenol and 4,4-ethylidene bisphenol.

  The polymerization of the asymmetric bishydroxy compound and the carbonate compound according to the present invention can be carried out according to a known method. For example, when a carbonyl halide compound is used as the carbonate compound, a polycarbonate resin can be obtained by a solution polymerization method, an interfacial polymerization method, or the like.

  When bisaryl carbonates are used as the carbonate compound, a polycarbonate resin is obtained by a transesterification method.

  Since the asymmetric bishydroxy compound according to the present invention is excellent in solubility in a solvent, it is easily dissolved in a solvent used in the polymerization step.

  Therefore, by using the asymmetric bishydroxy compound according to the present invention as a raw material compound, the polymerization reaction can proceed smoothly, and a polymer material useful as a photoconductive material can be easily obtained as described above.

  The present invention will now be described in detail with reference to the accompanying drawings.

  1 to 8 are cross-sectional views schematically showing the configuration of the main part of an electrophotographic photosensitive member (hereinafter also simply referred to as “photosensitive member”) which is one of the embodiments according to the present invention.

  1-4 is a single layer type electrophotographic photosensitive member characterized in that the photosensitive layer 2 is a single layer type photosensitive layer 2 composed of a single layer.

  In the electrophotographic photoreceptors 15 to 18 shown in FIGS. 5 to 8, the photosensitive layer 7 is a laminated photosensitive layer (hereinafter also referred to as “function-separated photosensitive layer”) including the charge generation layer 3 and the charge transport layer 4. 7) a multilayer electrophotographic photosensitive member (hereinafter also referred to as “function-separated electrophotographic photosensitive member”).

  An electrophotographic photoreceptor 11 shown in FIG. 1 includes a conductive support (electrophotographic photoreceptor base tube) 1 and a photosensitive layer 2 formed on the surface of the conductive support 1.

  An electrophotographic photoreceptor 12 shown in FIG. 2 includes a conductive support 1, a photosensitive layer 2 formed on the surface of the conductive support 1, and a surface protective layer 5 formed on the surface of the photosensitive layer 2. .

  An electrophotographic photoreceptor 13 shown in FIG. 3 includes a conductive support 1, an intermediate layer 6 formed on the surface of the conductive support 1, and a photosensitive layer 2 formed on the surface of the intermediate layer 6.

  The electrophotographic photosensitive member 14 shown in FIG. 4 includes a conductive support 1, an intermediate layer 6 formed on the surface of the conductive support 1, a photosensitive layer 2 formed on the surface of the intermediate layer 6, and a photosensitive layer. 2 and a surface protective layer 5 formed on the surface of 2.

  An electrophotographic photoreceptor 15 shown in FIG. 5 includes a conductive support 1, a charge generation layer 3 formed on the surface of the conductive support 1, a charge transport layer 4 formed on the surface of the charge generation layer 3, and including.

  6 includes a conductive support 1, a charge generation layer 3 formed on the surface of the conductive support 1, and a charge transport layer 4 formed on the surface of the charge generation layer 3. And a surface protective layer 5 formed on the surface of the charge transport layer 4.

  7 includes a conductive support 1, an intermediate layer 6 formed on the surface of the conductive support 1, a charge generation layer 3 formed on the surface of the intermediate layer 6, and a charge. And a charge transport layer 4 formed on the surface of the generation layer 3.

  An electrophotographic photosensitive member 18 shown in FIG. 8 includes a conductive support 1, an intermediate layer 6 formed on the surface of the conductive support 1, a charge generation layer 3 formed on the surface of the intermediate layer 6, and a charge. A charge transport layer 4 formed on the surface of the generation layer 3 and a surface protective layer 5 formed on the surface of the charge transport layer 4 are included.

  The layers constituting the electrophotographic photoreceptors 11 to 18 shown in FIGS. 1 to 8 are specifically as follows.

[Conductive support]
The conductive support 1 is made of a metal material such as aluminum, aluminum alloy, copper, zinc, stainless steel, or titanium. Also, without being limited to these metal materials, a metal foil laminated on a substrate surface made of a polymer material such as polyethylene terephthalate, polyamide, polyester, polyoxymethylene, polystyrene, hard paper, glass, etc., metal material It is also possible to use a material in which a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide is evaporated or coated.

  The shape of the conductive support 1 is a sheet shape in the photoconductors 11 to 18 shown in FIGS. 1 to 8, but is not limited thereto, and may be a cylindrical shape, a columnar shape, an endless belt shape, or the like. .

  If necessary, the surface of the conductive support 1 is irregularly reflected within a range that does not affect the image quality, such as anodized film treatment, surface treatment with chemicals, hot water, coloring treatment, or roughening the surface. Processing may be performed.

  The irregular reflection treatment is particularly effective when the electrophotographic photosensitive member according to the present invention is used in an electrophotographic process using a laser as an exposure light source. That is, in the electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform, so the laser light reflected on the surface of the electrophotographic photosensitive member and the laser light reflected inside the electrophotographic photosensitive member are separated. In some cases, interference occurs, and interference fringes due to this interference appear in the image to cause image defects.

  However, by subjecting the surface of the conductive support 1 to the irregular reflection treatment as described above, it is possible to prevent image defects due to the interference of laser light having the same wavelength.

[Single-layer type photosensitive layer]
The photosensitive layer 2 which is a single-layer type photosensitive layer includes a charge generating material, an asymmetric bishydroxy compound according to the present invention, and a binder resin. In the photosensitive layer 2, the asymmetric bishydroxy compound according to the present invention functions as a charge transport material. The photosensitive layer 2 may contain an additive such as a charge transport material other than the asymmetric bishydroxy compound according to the present invention, an antioxidant, or the like, if necessary.

  The charge generating substance is a substance that generates charges by absorbing light. As the charge generation material, those commonly used in this field can be used, for example, azo pigments (monoazo pigments, bisazo pigments, trisazo pigments, etc.), indigo pigments (indigo, thioindigo, etc.), perylene pigments (peryleneimide). Organic compounds such as polycyclic quinone pigments (anthraquinone, pyrenequinone, etc.), phthalocyanine pigments (metal phthalocyanine, metal-free phthalocyanine, etc.), squarylium dyes, pyrylium salts, thiopyrylium salts, and triphenylmethane dyes. Examples thereof include pigments or dyes, and inorganic materials such as selenium and amorphous silicon.

One of the above charge generating materials can be used alone or in combination of two or more.
Among these charge generation materials, X-type metal-free phthalocyanine and metal phthalocyanine are preferable, and oxotitanium phthalocyanine is more preferable.

  X-type metal-free phthalocyanine and metal phthalocyanine, especially oxotitanium phthalocyanine, has high charge generation efficiency and charge injection efficiency, so it generates a large amount of charge by absorbing light and accumulates the generated charge in the molecule Without being injected efficiently into the asymmetric bishydroxy compound according to the present invention, which is a charge transport material contained in the photosensitive layer 2 or 7.

  Therefore, the charge generated in the charge generation material by light absorption is efficiently injected into the asymmetric bishydroxy compound according to the present invention used as a charge transport material and transported smoothly, so that high sensitivity and high resolution electrophotographic photosensitive You can get a body.

  Charge generation materials include triphenylmethane dyes represented by methyl violet, crystal violet, knight blue and Victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine dyes represented by acridine orange and frapeosin, methylene blue and methylene It may be used in combination with sensitizing dyes such as thiazine dyes typified by green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes or thiopyrylium salt dyes. .

As the asymmetric bishydroxy compound according to the present invention used as the charge transport material, one or more selected from the asymmetric bishydroxy compound (1) can be used.
For example, in order to further improve the electrical characteristics of the photosensitive layer 2, a charge transport material other than the asymmetric bishydroxy compound according to the present invention can be used in combination.
Such charge transport materials include hole transport materials and electron transport materials.

    As the above hole transporting substances, those commonly used in this field can be used, for example, carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidines. Derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triaryls Amine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene derivatives, enamine derivatives, benzidine derivatives, these A polymer having a group derived from a compound in the main chain or side chain (poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc.), Examples include polysilane.

  In addition, as the above-mentioned electron transporting substances, those commonly used in this field can be used, for example, benzoquinone derivatives, tetracyanoethylene derivatives, tetracyanoquinodimethane derivatives, fluorenone derivatives, xanthone derivatives, phenanthraquinone derivatives, anhydrous phthales. Examples thereof include organic compounds such as acid derivatives and diphenoquinone derivatives, and inorganic materials such as amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloys, cadmium sulfide, antimony sulfide, zinc oxide, and zinc sulfide. These charge transport materials can be used alone or in combination of two or more.

  As the binder resin, those having binding properties are used. For example, the binder resin is used for the purpose of improving the mechanical strength and durability of the photosensitive layer 2.

  As the binder resin, those having excellent compatibility with the asymmetric bishydroxy compound according to the present invention are preferably used.

  Specific examples of such resins include, for example, vinyl resins such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, polycarbonate, polyester, polyester carbonate, polysulfone, polyarylate, polyamide, methacrylic resin, acrylic resin, polyether, poly Examples thereof include thermoplastic resins such as acrylamide and polyphenylene oxide, thermosetting resins such as phenoxy resin, epoxy resin, silicone resin, polyurethane and phenol resin, and partially crosslinked products of these resins.

Among the above resins, polystyrene, polycarbonate, polyarylate and polyphenylene oxide are particularly excellent in compatibility with the asymmetric bishydroxy compound according to the present invention, and further have a volume resistance of 10 ¹³ Ω or more and excellent electrical insulation, Moreover, since it is excellent in film formability, potential characteristics, etc., it can be suitably used as a binder resin, and polycarbonate can be particularly suitably used. Binder resin can also be used individually by 1 type or in combination of 2 or more types.

  The use ratio of the asymmetric bishydroxy compound according to the present invention and the binder resin is not particularly limited, but when used for the surface protective layer, it is 100 parts by weight to 2000 parts by weight with respect to 100 parts by weight of the asymmetric bishydroxy compound according to the present invention. It is preferable to use a binder resin.

  When the amount of the binder resin used is less than 100 parts by weight based on 100 parts by weight of the asymmetric bishydroxy compound according to the present invention, the amount of wear is large and the role as a protective layer may not be achieved.

  On the other hand, when the amount of the binder resin used exceeds 2000 parts by weight, the relative amount ratio of the binder resin to the charge transporting material may be increased, resulting in a phenomenon that sensitivity is lowered.

  When the binder resin is used in the charge transport layer, it is preferable to use 50 to 300 parts by weight of the binder resin with respect to 100 parts by weight of the asymmetric bishydroxy compound according to the present invention.

  When the amount of the binder resin used relative to 100 parts by weight of the asymmetric bishydroxy compound according to the present invention is less than 50 parts by weight, the amount of wear increases. On the other hand, when the amount of the binder resin used exceeds 300 parts by weight, the sensitivity decreases. Admitted to do.

  The antioxidant can reduce deterioration of the surface layer due to adhesion of active substances such as ozone and NOx generated when the electrophotographic photosensitive member is charged, and can further improve durability during repeated use of the electrophotographic photosensitive member. . Furthermore, as described below, the stability as a coating solution for forming a photosensitive layer is increased, the life of the solution is extended, and the electrophotographic photosensitive member produced with the coating solution is also durable because the oxidizing impurities are reduced. Will improve.

Examples of the antioxidant include hindered phenol derivatives and hindered amine derivatives.
The amount of the antioxidant used is not particularly limited, but is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the charge transport material. When the amount of the antioxidant used is less than 0.1 part by weight, the effect of improving the stability of the coating solution for forming a photosensitive layer described later and the durability of the electrophotographic photoreceptor is insufficient, and the amount exceeds 10 parts by weight. Adversely affects the electrical characteristics of the electrophotographic photosensitive member.

  The photosensitive layer 2 is prepared by dissolving a charge generating material, an asymmetric bishydroxy compound and a binder resin according to the present invention, and, if necessary, a charge transporting material other than the asymmetric bishydroxy compound according to the present invention and an antioxidant in a suitable organic solvent. It can be formed by dispersing to prepare a coating solution for forming a photosensitive layer, coating the coating solution on the surface of the conductive support 1 or the intermediate layer 6, and then drying to remove the organic solvent.

  Since the asymmetric bishydroxy compound according to the present invention is excellent in solubility in a solvent and compatibility with a binder resin, the asymmetric bishydroxy compound is dissolved in the coating solution or is uniformly dispersed, and is also crystallized in the process of forming the photosensitive layer 2. Do not turn.

  Therefore, in the present invention, a homogeneous photosensitive layer 2 having no crystallized portion can be formed.

  Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, and dichlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, tetrahydrofuran (THF), and dioxane. , Ethers such as dibenzyl ether and dimethoxymethyl ether, ketones such as cyclohexanone, acetophenone and isophorone, esters such as methyl benzoate and ethyl acetate, sulfur-containing solvents such as diphenyl sulfide, and fluorine-based solvents such as hexafluoroisopropanol Solvents and aprotic polar solvents such as N, N-dimethylformamide can be used, and one of these solvents can be used alone or as a mixed solvent of two or more. Furthermore, a mixed solvent obtained by adding alcohols, acetonitrile or methyl ethyl ketone to one or a mixture of two or more of these solvents can also be used.

  The film thickness of the photosensitive layer is not particularly limited, but is preferably 5 to 100 μm, and more preferably 10 to 50 μm. If the film thickness is less than 5 μm, the charge holding ability on the surface of the electrophotographic photosensitive member may be reduced. Conversely, if the film thickness exceeds 100 μm, the productivity of the electrophotographic photosensitive member may be reduced.

[Laminated photosensitive layer]
The photosensitive layer 7, which is a multilayer photosensitive layer, is a laminate including the charge generation layer 3 and the charge transport layer 4.

(Charge generation layer)
The charge generation layer 3 contains a charge generation material and a binder resin.

  As the charge generation material, one or more of the same charge generation materials as those contained in the photosensitive layer 2 can be used.

  As the binder resin, those commonly used as the matrix resin of the charge generation layer can be used, for example, thermoplastic resins such as polyester, polystyrene, acrylic resin, methacrylic resin, polycarbonate, polyarylate, polyurethane, phenol resin, alkyd resin, melamine resin. , Epoxy resins, silicone resins, phenoxy resins, polyvinyl butyral, polyvinyl formal, and other thermosetting resins, and copolymer resins containing two or more of the structural units contained in these resins (vinyl chloride-vinyl acetate copolymer) Insulating resins such as a coalesced resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin). Among these, polyvinyl butyral is preferable. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The content ratio of the charge generation material and the binder resin is not particularly limited, but preferably 10 to 99 wt% of the charge generation material is contained in the total amount of the charge generation material and the binder resin, and the balance is the binder resin. It is.

  If the ratio of the charge generation material is less than 10% by weight, the sensitivity may decrease. Conversely, if the ratio of the charge generation material exceeds 99% by weight, not only the film strength of the charge generation layer 3 is decreased but also the charge Since the dispersibility of the generated substance is reduced and coarse particles are increased, and the surface charge other than that which is to be erased by exposure is reduced, black spots where image defects, particularly toner, adheres to a white background and minute black spots are formed. A lot of image fogging is generated.

  In addition to the two essential components, the charge generation layer 3 may be one or more selected from a hole transport material, an electron transport material, an antioxidant, a dispersion stabilizer, a sensitizer, and the like as necessary. Each may contain an appropriate amount. As a result, the potential characteristics are improved, the stability of the coating solution for forming a charge generation layer, which will be described later, is increased, fatigue deterioration during repeated use of the electrophotographic photosensitive member can be reduced, and durability can be improved.

  The charge generation layer 3 is prepared by, for example, preparing a coating solution for forming a charge generation layer by dissolving or dispersing a charge generation material, a binder resin, and other additives as required in an appropriate organic solvent. It can form by apply | coating to the surface of the electroconductive support body 1 or the below-mentioned intermediate | middle layer 6, and drying and removing an organic solvent. Specifically, for example, a charge generation layer forming coating solution is prepared by dissolving or dispersing a charge generation material and other additives as required in a resin solution obtained by dissolving a binder resin in an organic solvent. .

  Examples of the organic solvent used herein include halogenated hydrocarbons such as tetrachloropropane and dichloroethane, ketones such as isophorone, methyl ethyl ketone, acetophenone, and cyclohexanone, esters such as ethyl acetate, methyl benzoate, and butyl acetate, tetrahydrofuran ( THF), dioxane, dibenzyl ether, ethers such as 1,2-dimethoxyethane and dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene and dichlorobenzene, diphenyl Sulfur-containing solvents such as sulfide, fluorine-based solvents such as hexafluoroisopropanol, aprotic polar solvents such as N, N-dimethylformamide or N, N-dimethylacetamide And the like. Moreover, these solvents can be used alone, or a mixed solvent in which two or more kinds are mixed can also be used.

Prior to dissolving or dispersing the charge generation material or the like in the resin solution, the charge generation material and other additives may be pre-ground.
The preliminary pulverization is performed using a general pulverizer such as a ball mill, a sand mill, an attritor, a vibration mill, or an ultrasonic disperser.

  The dissolution or dispersion of the charge generation material or the like in the resin solution is performed using a general dispersing machine such as a paint shaker, a ball mill, or a sand mill. At this time, it is preferable that the dispersion conditions are appropriately selected so that impurities are generated due to wear or the like from the container that contains the resin solution, the charge generation material, and the like and the members that constitute the disperser and are not mixed into the coating liquid.

  Examples of the method for applying the charge generation layer forming coating solution include roll coating, spray coating, blade coating, ring coating, and dip coating.

  The thickness of the charge generation layer 3 is not particularly limited, but is preferably 0.05 to 5 μm, and more preferably 0.1 to 1 μm. This is because if the thickness of the charge generation layer is less than 0.05 μm, the efficiency of light absorption is reduced and the sensitivity is lowered. Conversely, if the thickness of the charge generation layer exceeds 5 μm, This is because charge transfer becomes a rate-determining step in the process of erasing charges on the surface of the electrophotographic photosensitive member, and sensitivity is lowered.

(Charge transport layer)
The charge transport layer 4 contains an asymmetric bishydroxy compound according to the present invention and a binder resin having the ability to accept and transport charges generated by the charge generating material. Furthermore, the charge transport layer 4 may contain additives such as a charge transport material other than the asymmetric bishydroxy compound according to the present invention and an antioxidant, if necessary.

As the asymmetric bishydroxy compound according to the present invention, one or more selected from the asymmetric bishydroxy compound (1) can be used.
In addition, as the charge transport material, binder resin and antioxidant other than the asymmetric bishydroxy compound according to the present invention, the same materials as those used in the photosensitive layer 2 can be used in the same amounts.

  The charge transport layer 4 is prepared by, for example, dissolving or dispersing an asymmetric bishydroxy compound and a binder resin according to the present invention and, if necessary, a charge transport material other than the asymmetric bishydroxy compound according to the present invention and an antioxidant in a suitable organic solvent. The charge transport layer forming coating solution is prepared, the charge transport layer forming coating solution is applied to the surface of the charge generation layer 3, and the organic solvent is removed by drying.

Since the asymmetric bishydroxy compound according to the present invention does not crystallize in the process of forming the charge transport layer 4, the charge transport layer 4 in which the asymmetric bishydroxy compound according to the present invention is uniformly dispersed can be formed. As the organic solvent to be used, the same organic solvents as those used for forming the photosensitive layer 2 can be used.

  The method for applying the charge transport layer forming coating solution to the surface of the charge generation layer 3 is not particularly limited, and examples thereof include dip coating, roll coating, and inkjet coating. The drying may be performed by appropriately selecting a temperature at which the organic solvent contained in the coating solution is removed and the charge transport layer 4 having a uniform surface can be formed.

  The thickness of the charge transport layer 4 is not particularly limited, but is preferably 5 to 50 μm, more preferably 10 to 40 μm. This is because if the charge transport layer thickness is less than 5 μm, the charge holding ability of the surface of the electrophotographic photosensitive member may be reduced, but conversely if the charge transport layer thickness exceeds 50 μm, This is because the resolution may be lowered.

[Surface protective layer]
The surface protective layer 5 has a function of improving the durability of the electrophotographic photosensitive member. The surface protective layer 5 contains the asymmetric bishydroxy compound according to the present invention and a binder resin. Furthermore, the surface protective layer 5 may contain a charge transport material other than the asymmetric bishydroxy compound according to the present invention, if necessary.

  As the asymmetric bishydroxy compound according to the present invention, one or more selected from the asymmetric bishydroxy compound (1) can be used. Further, as the charge transporting material and the binder resin other than the asymmetric bishydroxy compound according to the present invention, the same materials as those used in the photosensitive layer 2 can be used in the same usage amount.

  In the electrophotographic photoreceptor provided with the surface protective layer 5, the charge transport material contained in the photosensitive layer 2 or the charge transport layer 4 is preferably a butadiene compound. By using a butadiene compound, it is possible to prevent a potential barrier from being formed at the interface between the photosensitive layer 2 or the charge transport layer 4 and the surface protective layer 5, so that the surface protective layer 5 and the photosensitive layer 2 or the charge transport layer can be prevented. Therefore, it is possible to improve the sensitivity and photoresponsiveness of the photosensitive member.

  In the electrophotographic photoreceptor provided with the surface protective layer 5, the asymmetric bishydroxy compound according to the present invention may be used as the charge transport material contained in the photosensitive layer 2 or the charge transport layer 4. Since the asymmetric bishydroxy compound according to the present invention contains a similar structure to the butadiene compound, by using the asymmetric bishydroxy compound according to the present invention, the photosensitive layer 2 or the charge transport layer 4 and The transfer of charges with the surface protective layer 5 can be facilitated, and the sensitivity and photoresponsiveness of the photoreceptor can be improved.

  The surface protective layer 5 is obtained by, for example, dissolving or dispersing the asymmetric bishydroxy compound and binder resin according to the present invention and, if necessary, a charge transport material other than the asymmetric bishydroxy compound according to the present invention in a suitable organic solvent. It can be formed by preparing a coating solution for forming, applying the coating solution for forming the surface protective layer to the surface of the photosensitive layer 2 or 7, and removing the organic solvent by drying. As the organic solvent used here, the same organic solvent used for forming the photosensitive layer 2 can be used. Since the crystallization of the asymmetric bishydroxy compound according to the present invention does not occur in the process of forming the surface protective layer 5, the present invention forms the surface protective layer 5 in which the asymmetric bishydroxy compound according to the present invention is uniformly dispersed. Can do.

  Although the film thickness of the surface protective layer 5 is not particularly limited, it is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm. When the thickness of the surface protective layer 5 is less than 0.5 μm, the scratch resistance on the surface of the electrophotographic photosensitive member is inferior and the durability is insufficient. When it exceeds 10 μm, the resolution of the electrophotographic photosensitive member is lowered.

[Middle layer]
The intermediate layer 6 has a function of preventing charge injection from the conductive support 1 to the photosensitive layers 2 and 7. As a result, a decrease in chargeability of the photosensitive layers 2 and 7 is suppressed, a decrease in surface charge other than a portion to be erased by exposure is suppressed, and occurrence of image defects such as fog is prevented.

  In particular, during image formation by the reversal development process, it is possible to prevent the occurrence of image fogging called black spots in which minute black dots made of toner are formed on a white background portion. Further, by covering the surface of the conductive support 1 with the intermediate layer 6, the degree of unevenness which is a defect on the surface of the conductive support 1 is reduced, the surface is made uniform, and the film formability of the photosensitive layers 2 and 7 is improved. The adhesion between the conductive support 1 and the photosensitive layers 2 and 7 can be improved.

  For the intermediate layer 6, for example, a coating solution for forming an intermediate layer in which a resin material is dissolved in an appropriate solvent is prepared, this coating solution is applied to the surface of the conductive support 1, and the solvent in the coating solution is removed by heating. It can be formed by removing.

  The resin material constituting the resin layer includes polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyester, polycarbonate, polyester carbonate, polysulfone, polyvinyl butyral, polyamide, polyarylate and other thermoplastic resins, polyurethane , Epoxy resins, melamine resins, phenoxy resins, silicone resins, and other thermosetting resins, copolymer resins containing two or more of the structural units contained in these thermoplastic resins or thermosetting resins, casein, gelatin Natural polymer materials such as polyvinyl alcohol and ethyl cellulose.

  Examples of the solvent for dissolving or dispersing the resin material include water, alcohols such as methanol, ethanol, and butanol, glymes such as methyl carbitol and butyl carbitol, and a mixed solvent obtained by mixing two or more of these solvents. It is done.

  Furthermore, metal oxide particles may be added to the intermediate layer forming coating solution. By adding metal oxide particles, the volume resistance value of the intermediate layer 6 can be easily adjusted, charge injection from the conductive support 1 to the photosensitive layers 2 and 7 can be further suppressed, and the electrophotographic photosensitive member can be used in various environments. Electrical characteristics can be maintained.

  Examples of the metal oxide particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide. In order to disperse the metal oxide fine particles in the coating solution for forming the intermediate layer, a general particle dispersing device such as a ball mill, a sand mill, an attritor, a vibration mill, or an ultrasonic disperser can be used.

  When the total content of the resin material and the metal oxide particles in the coating solution for forming an intermediate layer containing the resin material and the metal oxide particles is C and the content of the solvent is D, the ratio of both (C / D ) Is preferably 1/99 to 40/60 (= 0.01 to 0.67, weight ratio), more preferably 2/98 to 30/70 (= 0.02 to 0.43, weight ratio). ).

  The ratio (E / F) between the resin material content (E) and the metal oxide particle content (F) is preferably 1/99 to 90/10 (= 0.01 to 9.0, weight ratio). And more preferably 5/95 to 70/30 (= 0.05 to 2.33, weight ratio).

  Although the film thickness of the intermediate layer 6 is not particularly limited, it is preferably 0.01 to 20 μm, and more preferably 0.1 to 10 μm. When the film thickness is less than 0.01 μm, the intermediate layer 6 does not substantially function, and a uniform surface cannot be obtained by covering the defects of the conductive support 1, and the conductive support 1 to the photosensitive layer 2, 7 becomes impossible to prevent the injection of electric charge to the photosensitive layer 2, and the chargeability of the photosensitive layers 2 and 7 is lowered. If the film thickness exceeds 20 μm, it is difficult to form the intermediate layer 6 uniformly, and the sensitivity of the electrophotographic photosensitive member also decreases.

  In addition, a layer containing alumite (alumite layer) may be formed on the surface of the conductive support 1 to form the intermediate layer 6.

  FIG. 9 is a side arrangement diagram showing a simplified configuration of an image forming apparatus 20 according to still another embodiment of the present invention. The image forming apparatus 20 includes an electrophotographic photosensitive member 21 according to the present invention having the same configuration as any of the electrophotographic photosensitive members 11 to 18 shown in FIGS.

  With reference to FIG. 9, an image forming apparatus 20 according to another embodiment of the present invention will be described. The image forming apparatus according to the present invention is not limited to the following description.

  The image forming apparatus 20 is an electrophotographic photosensitive member 21 according to the present invention, and is an electrophotographic photosensitive member 21 rotatably supported by a main body (not shown), a charger 24, an exposure unit 28, and a developing unit 25. And a transfer device 26, a cleaner 27, and a fixing device 31.

  The electrophotographic photosensitive member 21 is rotationally driven around the rotation axis 22 in the direction of the arrow 23 by a driving unit (not shown). The driving means includes, for example, an electric motor and a reduction gear, and transmits the driving force to a conductive support constituting the core of the electrophotographic photosensitive member 21, thereby causing the electrophotographic photosensitive member 21 to have a predetermined peripheral speed. To rotate.

  The charger 24, the exposure unit 28, the developing unit 25, the transfer unit 26, and the cleaner 27 are arranged in this order along the outer peripheral surface of the electrophotographic photosensitive member 21 in the rotation direction of the electrophotographic photosensitive member 21 indicated by an arrow 23. It is provided from the upstream side toward the downstream side.

  The charger 24 is a charging unit that charges the outer peripheral surface of the electrophotographic photosensitive member 21 to a predetermined potential. In the present embodiment, the charger 24 is realized by a contact-type charging roller 24a and a bias power source 24b that applies a voltage to the charging roller 24a. A charger wire can be used as the charging means, but in a charging roller that requires high abrasion resistance on the surface of the photoreceptor, the electrophotographic photoreceptor with the surface protective layer formed according to the present invention exhibits a great effect by improving durability. To do.

  The exposure unit 28 includes, for example, a semiconductor laser as a light source, and is charged by irradiating light 28 a such as a laser beam output from the light source between the charger 24 and the developing unit 25 of the electrophotographic photosensitive member 21. The outer peripheral surface of the electrophotographic photosensitive member 21 is exposed according to image information. The light 28a is repeatedly scanned in the main scanning direction in the direction in which the rotation axis 22 of the electrophotographic photosensitive member 21 extends, and accordingly, electrostatic latent images are sequentially formed on the surface of the electrophotographic photosensitive member 21.

  The developing unit 25 is a developing unit that develops an electrostatic latent image formed on the surface of the electrophotographic photosensitive member 21 by exposure with a developer, and is provided facing the electrophotographic photosensitive member 21. A developing roller 25a that supplies toner to the outer peripheral surface of the electrophotographic photosensitive member, and the developing roller 25a is rotatably supported around a rotation axis parallel to the rotation axis 22 of the electrophotographic photosensitive member 21, and a developer containing toner is accommodated in the internal space. Casing 25b.

  The transfer unit 26 transfers a toner image, which is a visible image formed on the outer peripheral surface of the electrophotographic photosensitive member 21 by development, between the electrophotographic photosensitive member 21 and the transfer unit 26 from the direction of the arrow 29 by a conveying unit (not shown). Transfer means for transferring onto a transfer paper 30 as a recording medium supplied to the printer. The transfer device 26 includes, for example, a charging unit, and is a non-contact type transfer unit that transfers a toner image onto the transfer paper 30 by applying a charge having a polarity opposite to that of the toner to the transfer paper 30.

  The cleaner 27 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface of the electrophotographic photosensitive member 21 after the transfer operation by the transfer device 26, and removes the toner remaining on the outer peripheral surface of the electrophotographic photosensitive member 21. 27a and a recovery casing 27b for storing the toner separated by the cleaning blade 27a. The cleaner 27 is provided together with a charge eliminating lamp (not shown).

  Further, the image forming apparatus 20 includes a fixing device 31 as fixing means for fixing the transferred image on the downstream side where the transfer paper 30 that has passed between the electrophotographic photosensitive member 21 and the transfer device 26 is conveyed. Provided. The fixing device 31 includes a heating roller 31a having a heating unit (not shown), and a pressure roller 31b that is provided to face the heating roller 31a and is pressed by the heating roller 31a to form a contact portion.

  The image forming operation by the image forming apparatus 20 is performed as follows. First, when the electrophotographic photosensitive member 21 is rotationally driven in the direction of the arrow 23 by the driving unit, the charger 24 provided on the upstream side in the rotational direction of the electrophotographic photosensitive member 21 with respect to the imaging point of the light 28a by the exposure unit 28. As a result, the surface of the electrophotographic photosensitive member 21 is uniformly charged to a predetermined positive or negative potential.

  Next, light 28 a corresponding to image information is irradiated from the exposure unit 28 to the surface of the electrophotographic photosensitive member 21. By this exposure, the surface charge of the part irradiated with the light 28a is removed from the electrophotographic photosensitive member 21, and the surface potential of the part irradiated with the light 28a is different from the surface potential of the part not irradiated with the light 28a. And an electrostatic latent image is formed.

  Toner is supplied to the surface of the electrophotographic photosensitive member 21 on which the electrostatic latent image is formed from a developing unit 25 provided downstream of the image forming point of the light 28a by the exposure means 28 in the rotation direction of the electrophotographic photosensitive member 21. The electrostatic latent image is developed to form a toner image.

  In synchronization with the exposure of the electrophotographic photosensitive member 21, the transfer paper 30 is supplied between the electrophotographic photosensitive member 21 and the transfer unit 26. The transfer device 26 applies a charge having the opposite polarity to the toner to the supplied transfer paper 30, and the toner image formed on the surface of the electrophotographic photosensitive member 21 is transferred onto the transfer paper 30.

  The transfer paper 30 onto which the toner image has been transferred is conveyed to a fixing device 31 by a conveying means, and is heated and pressurized when passing through a contact portion between a heating roller 31a and a pressure roller 31b of the fixing device 31, and toner The image is fixed on the transfer paper 30 and becomes a robust image. The transfer paper 30 on which the image is formed in this way is discharged to the outside of the image forming apparatus 20 by the conveying means.

  On the other hand, the toner remaining on the surface of the electrophotographic photosensitive member 21 even after the transfer of the toner image by the transfer device 26 is separated from the surface of the electrophotographic photosensitive member 21 by the cleaner 27 and collected. The charge on the surface of the electrophotographic photosensitive member 21 from which the toner has been removed in this manner is removed by the light from the static elimination lamp, and the electrostatic latent image on the surface of the electrophotographic photosensitive member 21 disappears. Thereafter, the electrophotographic photosensitive member 21 is further rotationally driven, and a series of operations starting from charging is repeated to continuously form images.

  Since the image forming apparatus 20 according to the present invention includes the electrophotographic photosensitive member 21 having the photosensitive layer or the surface protective layer in which the asymmetric bishydroxy compound according to the present invention is uniformly dispersed, a high-quality image without image defects such as black spots. Can be formed.

  EXAMPLES Hereinafter, although a manufacture example, an Example, and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to the following description content.

Production Example 1:
Exemplified Compound No. Preparation of 1 Exemplified compound subjected to dehydration condensation reaction using benzophenone (4aa) as a ketone compound and 1-phenyl-1-naphthylhydrazine (5aa) as a hydrazine compound, and passing through a hydrazone intermediate (5aa) No. 1 shows a synthesis scheme of 1.

  In 100 mL of ethanol, 18.2 g (1.0 molar equivalent) of benzophenone (4aa), 24.6 g (1.05 molar equivalent) of 1-naphthyl-1-phenylhydrazine (4bb) and 0.06 mL (0 0.01 mole equivalent) was added and stirred for 6 hours while heating to 80 ° C. After allowing the reaction solution to cool, 100 mL of hexane was added thereto, and the precipitated crystals were collected by filtration and dried under reduced pressure to obtain 35.8 g of hydrazone intermediate (5aa) as yellow crystals (yield 90.0%). .

  Next, 16.86 g (2.2 molar equivalents) of phosphorus oxychloride is slowly added to 100 mL of anhydrous N, N-dimethylformamide (abbreviated DMF) under ice cooling, and the mixture is stirred for about 30 minutes to prepare a Vilsmeier reagent. did. To this solution, 19.92 g (1.0 molar equivalent) of the hydrazone intermediate (5aa) obtained above was gradually added under ice cooling. Thereafter, the reaction solution was gradually heated to raise the temperature of the reaction solution to 80 ° C., and stirred for 6 hours while maintaining the reaction solution at 80 to 90 ° C. for reaction. After completion of the reaction, the reaction solution was allowed to cool and gradually added to 800 mL of a cooled 4N (4N) aqueous sodium hydroxide solution to cause precipitation. The resulting precipitate was collected by filtration and sufficiently washed with water, and then recrystallized with a mixed solvent of ethanol and ethyl acetate to obtain 18.4 g of a yellow powdery compound.

As a result of analyzing the obtained crystals by liquid chromatography-mass spectrometry (abbreviation LC-MS), the target compound, hydrazone-bisaldehyde intermediate (6aa) (theoretical molecular weight: 454. A peak corresponding to the molecular ion [M + H] ⁺ with a proton added to 17) was observed at 455.6. From this, it was confirmed that the obtained compound was a hydrazone-bisaldehyde intermediate represented by the structural formula (6aa) (yield: 81%).

  Further, from the analysis result of LC-MS, it was found that the purity of the obtained hydrazone-aldehyde intermediate (6aa) was 99.0%.

  7.26 g (1.0 eq) of the hydrazone-bisaldehyde intermediate (6aa) and 14.571 g (2.4 eq) of diethyl-p-methoxybenzylphosphonate (7aa) were dissolved in 80 ml of anhydrous DMF and dissolved in this solution. Under stirring, 5.6 g (2.5 equivalents) of potassium t-butoxide was gradually added at 0 ° C. Thereafter, the mixture was allowed to stand at room temperature for 1 hour, further heated to 50 ° C., and stirred for 5 hours while heating to maintain 50 ° C. The reaction mixture was allowed to cool and then poured into excess methanol. The precipitate was collected and dissolved in toluene to obtain a toluene solution. The toluene solution was transferred to a separatory funnel, washed with water, and the separated organic layer was dried over magnesium sulfate. After drying, solids were removed, the organic layer was concentrated under reduced pressure, and silica gel column chromatography was performed to obtain 9.0 g of yellow crystals.

As a result of analyzing the obtained yellow crystals by LC-MS, a peak corresponding to the molecular ion [M + H] ⁺ in which a proton was added to the compound represented by the chemical structural formula (8aa) (theoretical molecular weight: 662.83). Was observed at 663.91. From this fact, the crystals are exemplified by Compound Nos. 1 was found to be an asymmetric bisalkoxyhydrazone compound (8aa) which is a precursor of No. 1 (yield: 85%).

  Moreover, the purity of the obtained compound was 97.7% from the analysis result of HPLC at the time of LC-MS measurement.

[Synthesis of Asymmetric Bishydroxy Compound (1aa) (Exemplary Compound No. 1)]
6.58 g (1.0 equivalent) of the asymmetric bisalkoxyhydrazone compound (8aa) and 6.39 g (7.0 equivalent) of ethanethiol sodium salt were suspended in 130 ml of N, N-dimethylformamide and stirred under a nitrogen gas stream. While gradually heating, foaming started at 130 ° C. After the foaming subsided, the temperature was further raised and the mixture was refluxed with heating for 4 hours. The reaction mixture was allowed to cool to room temperature, poured into 600 ml of ice water, and neutralized by adding 3.2 ml of concentrated hydrochloric acid with stirring. This was extracted with 400 ml of ethyl acetate, the extract was washed with water, dried over anhydrous magnesium sulfate, filtered, and then the solvent was distilled off under reduced pressure to obtain 6.71 g of crude crystals. This was recrystallized with a mixed solvent of ethanol and ethyl acetate (ethanol: ethyl acetate = 8: 2 to 7: 3) to obtain 5.55 g of a yellow powdery compound.

The elemental analysis values of this yellow powdery compound were as follows.
<Exemplary Compound No. Elemental analysis value of 1>
Theoretical value C: 85.15%, H: 5.4%, N: 4.41%, O: 5.04%
Measured value C: 85.0%, H: 5.31%, N: 4.38%, O: 5.02%
Moreover, as a result of analyzing the obtained yellow powdery compound by LC-MS, molecular ion obtained by adding proton to the compound represented by the target chemical structural formula (1aa) (calculated molecular weight: 634.78) [ A peak corresponding to M + H] ⁺ was observed at 635.89.

  From the results of elemental analysis and LC-MS analysis, the obtained yellow powdery compound was identified as Exemplified Compound No. 1 asymmetric bishydroxyhydrazone compound (1aa) was found (yield: 88%).

  Moreover, the purity of the obtained compound (1aa) was 99.0% from the analysis result of HPLC at the time of LC-MS measurement.

Production Examples 2-3
Synthesis of Exemplified Compounds No. 6 and 10 Except for using each of the raw material compounds shown in Table 2 below instead of the ketone compound (4aa) and Wittig reagent (7aa) in Production Example 1, the same operation as in Production Example 1 And Exemplified Compound No. 6 and 10 were produced respectively. Table 2 also shows the raw material compounds of Exemplary Compound No. 1.

Below, the structure of the asymmetric bishydroxy enamine obtained by manufacture example 1-3, the result of elemental analysis, and the result of LC-MS are shown.

Production Example 4
Synthesis of Comparative Symmetric Bishydroxy Enamine Compound Same as Production Example 1 except that 16.9 g (1.0 equivalent) of an enamine compound synthesized from diphenylamine and diphenylacetaldehyde is used as the amine compound instead of the hydrazine compound in Production Example 1. Thus, a symmetrical bishydroxyenamine compound represented by the following chemical structural formula (11) which is an exemplary compound (EA-14) described in Example 1 of JP-A-2004-269377 (hereinafter, “symmetrical bishydroxyenamine”). 4.21 g of compound (11) ”is obtained.

The elemental analysis values of the obtained symmetric bishydroxyenamine compound (11) were as follows.
<Elemental analysis value of symmetrical bishydroxyenamine compound (11)>
Calculated value C: 86.42%, H: 5.70%, N: 2.40%
Actual value C: 85.97%, H: 5.38%, N: 2.27%

As a result of analyzing the obtained symmetric bishydroxyenamine compound (11) by LC-MS, protons were added to the compound represented by the target chemical structural formula (11) (theoretical value of molecular weight: 583.73). The peak corresponding to the molecular ion [M + H] ⁺ was observed at 584.9.

  From the results of elemental analysis and LC-MS analysis, it was confirmed that the obtained compound was a symmetric bishydroxyenamine compound (11) of the exemplified compound (EA-14) described in JP-A-2004-269377. (Yield: 83%). Moreover, the purity of the obtained compound (11) was 98.3% from the analysis result of HPLC at the time of LC-MS measurement.

Example 1
Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention produced in Production Example 1 as follows. An electrophotographic photoreceptor using 1 as a charge transport material for the charge transport layer was prepared.
As the conductive support, a polyethylene terephthalate (abbreviated as PET) film having a thickness of 100 μm deposited with aluminum (hereinafter referred to as “aluminum-deposited PET film”) was used.

  7 parts by weight of titanium oxide (trade name: Taibake TTO55A, manufactured by Ishihara Sangyo Co., Ltd.) and 13 parts by weight of copolymer nylon resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.), 159 parts by weight of methyl alcohol and 1,3- In addition to a mixed solvent with 106 parts by weight of dioxolane, dispersion treatment was performed for 8 hours with a paint shaker to prepare 100 g of an intermediate layer forming coating solution. This coating solution for forming an intermediate layer was applied to the aluminum surface of an aluminum vapor-deposited PET film, which is a conductive support, by an applicator and naturally dried to form an intermediate layer having a thickness of 1 μm.

  Next, 1 part by weight of X-type metal-free phthalocyanine (Fastogen Blue 8120, manufactured by Dainippon Ink) and 1 part by weight of butyral resin (trade name: # 6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.) were added to 98 parts by weight of methyl ethyl ketone. The mixture was mixed and dispersed with a paint shaker to prepare 50 g of a charge generation layer forming coating solution. This charge generation layer forming coating solution was applied to the surface of the previously provided intermediate layer in the same manner as the above intermediate layer, and naturally dried to form a charge generation layer having a thickness of 0.4 μm.

  Subsequently, Exemplified Compound No. 1 produced in Production Example 1 was used. 100 parts by weight of asymmetric bishydroxy compound 1 and 100 parts by weight of polycarbonate resin (trade name: Iupilon Z400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) are mixed, and a coating solution for forming a charge transport layer having a solid content of 10% by weight using toluene as a solvent. 50 g was prepared. This charge transport layer forming coating solution is applied to the surface of the charge generation layer previously provided in the same manner as the intermediate layer, and then dried at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 20 μm. did.

  Thus, like the electrophotographic photosensitive member 17 shown in FIG. 7, the stacked electron according to the present invention has a stacked structure in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially stacked on a conductive support. A photographic photoreceptor was prepared.

Examples 2-3
Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention. A laminate according to the present invention having a laminated structure in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support in the same manner as in Example 1 except that Exemplified Compounds 6 and 10 were used instead of Example 1. Type electrophotographic photosensitive member was produced.

Example 4
Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention produced in Production Example 1 was used. As in Example 1, an electrophotographic photosensitive member using 1 as a charge transport material for the surface protective layer was prepared, and the aluminum surface of a conductive support formed by depositing aluminum on the surface of a PET film having a thickness of 100 μm was used. Then, an intermediate layer having a thickness of 1 μm and a charge generation layer having a thickness of 0.4 μm were sequentially formed.

  Subsequently, Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention. In place of 1, butadiene compound represented by the following chemical structural formula (12) (1,1-bis (p-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene, trade name: T405, Inc. A charge transport layer was formed in exactly the same manner as in Example 1 except that Takasago Chemical Co., Ltd. (hereinafter referred to as butadiene compound (12)) was used.

  Next, 60 parts by weight of a curable siloxane resin (trade name: KP-854, manufactured by Shin-Etsu Chemical Co., Ltd.) and 60 parts by weight of isopropanol were mixed and dissolved uniformly. 6 parts by weight of the asymmetric bishydroxy compound 1 was added and mixed to prepare 50 g of a coating solution for forming a surface protective layer. This surface protective layer forming coating solution was applied to the surface of the charge transport layer in the same manner as in the case of forming the intermediate layer in Example 1, and dried at 120 ° C. for 1 hour to form a surface protective layer having a thickness of 1 μm. . Thus, like the electrophotographic photosensitive member 18 shown in FIG. 8, the present invention has a laminated structure in which an intermediate layer, a charge generation layer, a charge transport layer, and a surface protective layer are sequentially laminated on a conductive support. A laminated electrophotographic photosensitive member was prepared.

Examples 5-6
Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention. Except for using Exemplified Compounds 6 and 10 in place of Example 1, it has a laminated structure in which an intermediate layer, a charge generation layer, a charge transport layer and a surface protective layer are sequentially laminated on a conductive support in the same manner as in Example 4. A multilayer electrophotographic photosensitive member according to the present invention was produced.

Comparative Example 1
Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention. Structural formula 10 instead of 1:

A laminated electrophotographic photosensitive member according to the present invention having a laminated structure in which an intermediate layer, a charge generating layer, a charge transporting layer and a surface protective layer are sequentially laminated on a conductive support in the same manner as in Example 1 except that Was made.

Comparative Example 2
Exemplified Compound No. 1 which is an asymmetric bishydroxy compound according to the present invention. A laminate in which an intermediate layer, a charge generation layer, a charge transport layer, and a surface protective layer were sequentially laminated on a conductive support in exactly the same manner as in Example 1 except that the symmetric bishydroxyenamine compound (11) was used instead of 1. A multilayer electrophotographic photoreceptor according to the present invention having a structure was prepared.

<Electrical characteristics evaluation>
About each electrophotographic photosensitive member obtained in Examples 1 to 6 and Comparative Examples 1 and 2, using an electrostatic paper test apparatus (trade name: EPA-8200, manufactured by Kawaguchi Electric Co., Ltd.), the following is performed. The electrical characteristics were evaluated.

The surface of the photoreceptor was charged by applying a minus (−) 5 kV voltage to the photoreceptor, and the surface potential of the photoreceptor at this time was measured as a charged potential V0 [V]. Next, the charged photoreceptor surface was exposed to light, and the exposure amount required to halve the surface potential of the photoreceptor from the charging potential V0 was measured as a half exposure amount E1 / 2 [μJ / cm ² ]. . Further, the surface potential of the photosensitive member at the time when 10 seconds passed from the start of exposure was measured as a residual potential Vr [V]. For the exposure, light having a wavelength of 780 nm and intensity of 1 μW / cm ² obtained by spectroscopy with a monochromator was used.

<Image evaluation>
About each electrophotographic photosensitive member obtained in Examples 1-6 and Comparative Examples 1-2, the state of the image formed as follows was evaluated.

  The photosensitive drum is taken out from a commercially available digital copying machine (trade name: LIBRE AR-451, manufactured by Sharp Corporation), and a part of the photosensitive layer of the photosensitive drum is peeled off. In order to prevent leakage in the developing device by connecting between the aluminum vapor-deposited surface of the electrophotographic photosensitive member (PET film) obtained in 1-6 or Comparative Example 1 and the conductive support with an aluminum foil, the conductive portion The surface of was protected with cellophane tape or the like, and was mounted again on the copying machine AR-451.

  Using this copying machine, a halftone image was formed on A3 size paper defined in Japanese Industrial Standard (JIS) P0138: 1998, and this was used as an evaluation image. Here, the halftone image is an image in which gradation of the image is expressed by gradation using black and white dots. Table 4 below shows the evaluation results obtained by visually observing the obtained image for evaluation and evaluating the image state of the portion formed of the electrophotographic photosensitive member obtained in Examples 1 to 6 or Comparative Example 1.

The photoreceptors of Examples 1 to 3 using the asymmetric bishydroxy compound according to the present invention for the charge transport layer and Examples 4 to 6 using the surface protective layer have half-exposure E1 / 2 compared to Comparative Examples 1 and 2. It was also found that the absolute values of the residual potential Vr were both small and excellent in sensitivity and responsiveness.
In Examples 1 to 6, the image state was good, and image defects such as black spots, white spots, black bands, and image blur did not occur.

  On the other hand, in Comparative Example 1 in which the symmetric bishydroxyenamine compound (11) was used for the charge transport layer, many black spots were generated in the image. This is because the symmetric bishydroxyenamine compound (11) has high chemical structural symmetry, so the solubility in the solvent is low, and the insoluble part in the solvent remains in the charge transport layer in a crystalline state, and the part is It is thought that it appeared as a black spot in the image.

  All of the asymmetric bishydroxy compounds according to the present invention have a hydrazone structure and a bisdiene structure or a bistriene structure, and form an extended conjugated system, so that they have a good charge transport function, particularly a hole transport function.

  Furthermore, the asymmetric bishydroxy compound according to the present invention not only has an excellent hole transport function, but also has excellent solubility in a solvent and compatibility with a resin. Therefore, the asymmetric bishydroxy compound is used as a photosensitive layer or a surface protective layer. Even when used in the above, it can be uniformly dispersed without causing partial crystallization.

  Therefore, by including the asymmetric bishydroxy compound according to the present invention in, for example, a photosensitive layer or a surface protective layer of an electrophotographic photoreceptor, electrical characteristics such as charging property, sensitivity, and photoresponsiveness are good, and durability and An electrophotographic photoreceptor excellent in environmental stability can be provided.

  Furthermore, the asymmetric bishydroxy compound according to the present invention is useful as an organic photoconductive material, and can be suitably used as a charge transport material for devices such as electrostatic recording elements such as electrophotographic photoreceptors, sensor elements, and EL elements. .

  Furthermore, the asymmetric bishydroxy compound according to the present invention is also useful as a raw material compound for polymer materials such as polycarbonate resin, polyether resin, polyester resin, polyurethane resin, etc., and the asymmetric bishydroxy compound according to the present invention is used as a monomer. Thus, a polymer photoconductive material having an excellent charge transport function can be easily obtained.

  In addition, according to the present invention, an image forming apparatus including the electrophotographic photosensitive member is provided.

  That is, since the electrophotographic photoreceptor according to the present invention contains the asymmetric bishydroxy compound according to the present invention in the photosensitive layer or the surface protective layer, the electrophotographic photoreceptor is excellent in electrical characteristics such as chargeability, sensitivity, and photoresponsiveness and durability. Further, the asymmetric bishydroxy compound according to the present invention is uniformly dispersed in the photosensitive layer or surface protective layer of the electrophotographic photoreceptor according to the present invention without being crystallized.

  Therefore, the image forming apparatus according to the present invention can stably form a high-quality image free from image defects such as black spots over a long period of time under various environments.

  In addition, since the electrophotographic photosensitive member according to the present invention has excellent photoresponsiveness and can provide a high-quality image even in a high-speed electrophotographic process, the image forming apparatus according to the present invention can increase the image forming speed. It is.

1 is a cross-sectional view schematically showing a configuration of a main part of a single-layer electrophotographic photoreceptor 11 that is one embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of a main part of a single-layer electrophotographic photosensitive member 12 that is one embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of a main part of a single-layer electrophotographic photoreceptor 13 that is one embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of a main part of a single-layer electrophotographic photoreceptor 14 that is one embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of a main part of a multilayer electrophotographic photoreceptor 15 which is one embodiment of the present invention.

1 is a cross-sectional view schematically showing a configuration of a main part of a multilayer electrophotographic photosensitive member 16 which is one embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a configuration of a main part of a multilayer electrophotographic photoreceptor 17 that is one embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of a main part of a multilayer electrophotographic photoreceptor 18 that is one embodiment of the present invention. FIG. 6 is a side layout diagram illustrating a simplified configuration of an image forming apparatus 20 that is still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 and 7 Photosensitive layer 3 Charge generation layer 4 Charge transport layer 5 Surface protective layer 6 Intermediate layer 11-18, 21 Electrophotographic photosensitive member 20 Image forming apparatus 24 Charger 25 Developer 26 Transfer device 27 Cleaner 28 Exposure means 30 Transfer paper 31 Fixing device

Claims (11)

General formula (1):

(In the formula, Ar ₁ and Ar ₂ are an aryl group or a heterocyclic group which may optionally have a substituent, and Ar ₃ and Ar ₆ are different from each other and may optionally have a substituent. Or a divalent heterocyclic group, Ar ₄ is an optionally substituted arylene group or a divalent heterocyclic group, and Ar ₅ is a hydrogen atom or optionally substituted. An aryl group, an aralkyl group or an alkyl group, R ₁ is a hydrogen atom or an optionally substituted alkyl group, and R ₂ and R ₃ are a hydrogen atom or an optionally substituted group. An alkyl group, an aryl group, a heterocyclic group, or an aralkyl group, which may have a substituent, provided that R ₁ , R _2, and R ₃ may be the same or different groups, and n is 0 It is an integer of ~ 2)
An electrophotographic photoreceptor comprising an asymmetric bishydroxy compound represented by the formula: In the general formula (1), Ar ₃ is an optionally substituted naphthylene group in the general formula (1), and R ₁ , R _2, and R ₃ are both hydrogen, General formula (2):

(In the formula, Ar ₁ , Ar ₂ , Ar ₄ , Ar ₅ , Ar ₆ and n are as defined in the general formula (1), and a has a hydrogen atom or an optional substituent. An alkyl group or a dialkylamino group, provided that a plurality of a's are present in the formula, they may be the same or different independently from each other, and m represents an integer of 1 to 6.)
The electrophotographic photosensitive member according to claim 1, which is represented by: In the asymmetric bishydroxy compound, Ar ₃ in the general formula (1) is an optionally substituted naphthylene group, Ar ₄ is a phenylene group, Ar ₅ is hydrogen, R ₁ And R ₂ and R ₃ are each hydrogen, the following general formula (3):

(In the formula, Ar ₁ , Ar ₂ , Ar ₆ , n, a and m are as defined in the general formula (2)).
The electrophotographic photosensitive member according to claim 1, which is represented by: In the asymmetric bishydroxy compound, Ar ₃ in the general formula (1) is an optionally substituted naphthylene group, Ar ₄ is a phenylene group, Ar ₅ is hydrogen, R ₁ Is hydrogen and n is 0, the following general formula (4):

(In the formula, Ar ₁ , Ar ₂ , Ar ₆ , a and m are as defined in the general formula (2)).
The electrophotographic photosensitive member according to claim 1, which is represented by: In the asymmetric bishydroxy compound, in the general formula (1), either Ar ₃ or Ar ₆ is a naphthylene group, the other is a phenylene group, and R ₁ , R _2, and R ₃ are both hydrogen. The following general formula (2A):

(In the formula, Ar ₁ , Ar ₂ , Ar ₄ , Ar ₅ and n are as defined in the general formula (1)).
The electrophotographic photosensitive member according to claim 1, which is represented by: In the asymmetric bishydroxy compound, in the general formula (1), either Ar ₃ or Ar ₆ is a naphthylene group, the other and Ar ₄ are phenylene groups, Ar ₅ is hydrogen, R ₁ and R ₂ and R ₃ are each hydrogen, the following general formula (3A):

(In the formula, Ar ₁ , Ar ₂ and n have the same meaning as defined in the general formula (1)).
The electrophotographic photosensitive member according to claim 1, which is represented by: In the asymmetric bishydroxy compound, in the general formula (1), either Ar ₃ or Ar ₆ is a naphthylene group, the other and Ar ₄ is a phenylene group, Ar ₅ is hydrogen, and R ₁ is hydrogen. And n is 0, the following general formula (4A):

(In the formula, Ar ₁ and Ar ₂ have the same meaning as defined in the general formula (1)).
The electrophotographic photosensitive member according to claim 1, which is represented by:   A photosensitive layer and a surface protective layer are laminated in this order on a conductive support, and at least one of the photosensitive layer and the surface protective layer is asymmetric according to any one of claims 1 to 7. An electrophotographic photoreceptor comprising a bishydroxy compound.   The photosensitive layer has a stacked structure of a charge generation layer containing a charge generation material and a charge transport layer containing an asymmetric bishydroxy compound according to any one of claims 1 to 7. Electrophotographic photoreceptor. An electrophotographic photosensitive member according to claim 8 or 9,
Charging means for charging the electrophotographic photoreceptor;
Exposure means for exposing the charged electrophotographic photosensitive member;
Developing means for developing an electrostatic latent image formed by exposure;
An image forming apparatus comprising:   The image forming apparatus according to claim 10, wherein the charging unit is contact charging.

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