JPH08314166A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] (Correction) [Objective] To provide an electrophotographic photoreceptor having little change in characteristics during repeated use over a long period of time and having excellent resistance to use especially under high temperature and high humidity. [Structure] In a function-separated laminated type photoreceptor, a benzidine compound having a specific structure as shown in the general formulas (I) to (II) is used as a charge transport material. General formula (I) General formula (II) [In the formula, A _{1 to} A ₄ are any _{one of} a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group, and a halogenated pyridyl group bonded at the 2-position, and B ₁ is an aryl group, an alkylaryl group, or an alkoxyaryl group. , R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group, and a halogen atom. ]

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor using a benzidine compound as a charge transport material.

[0002]

2. Description of the Related Art In the electrophotographic system based on Carlson's invention, the surface of a photoconductor is charged and exposed to form an electrostatic latent image, and the latent image is developed with toner to form a visible image. The toner image is transferred onto paper or the like and fixed to obtain an image. The photoconductor removes residual toner and eliminates charge, and is repeatedly used. The photoconductor used in such a process is excellent in charging property, charge retention property in a dark place, and charge dissipation property (sensitivity) at the time of light irradiation, and is also durable in repeated repeated use over a long period of time. It is required to be good, and further, it is required that the characteristics do not change even if the environment during use changes.

The photosensitive member is constructed by providing a photosensitive layer on a conductive substrate. Conventionally, inorganic photoconductors having an inorganic photoconductive material such as selenium, zinc oxide, or cadmium sulfide as a main material of the photosensitive layer have been widely used, but in recent years, the toxicity is generally lower than that of inorganic materials. , Transparency, flexibility,
Attention has been paid to organic photoconductors that use organic materials, which are excellent in terms of lightness and productivity, as the main material of the photosensitive layer.

As the organic photoreceptor, for example, Japanese Patent Publication No. 50
No. 10496 discloses a photoconductor using poly-N-vinylcarbazole and 2,4,7-trinitro-9-fluorenone, and Japanese Patent Publication No. 48-25658 discloses poly-N-vinylcarbazole as pyrylium. A photoreceptor sensitized with a dye has been proposed. However, these photoreceptors are not always sufficient in terms of sensitivity and durability. After that, a so-called function-separated type photoreceptor in which the photosensitive layer was separated into a charge generation layer and a charge transfer layer was proposed. For example, Japanese Patent Publication No. 55-42380 discloses a function-separated type photoreceptor in which chlorocyan blue and a hydrazone compound are combined. The body is proposed. In this way, the photosensitive layer is formed by stacking layers that are functionally separated into a charge generation layer that receives light to generate charge carriers and a charge transfer layer that moves injected charge carriers, so that each layer has its function. A combination of many charge generation layers and charge transfer layers is expected, as it is expected that a photoreceptor with various performances can be obtained by combining and combining optimal charge generation materials. Is proposed.

In the function-separated type photoreceptor, the charge generation layer has a large light absorption coefficient and a high photon efficiency, and the generated charge carriers efficiently flow to the substrate side and are efficiently injected into the charge transfer layer. It is important to be done. In the charge transfer layer, it is important that the charge carriers generated in the charge generation layer are efficiently injected, and the injected charge carriers are quickly moved without being trapped in the layer to cancel the surface charge. For this reason, research into a charge generating material and a charge transporting material having excellent performance, and research into a combination of a charge generating layer and a charge transfer layer having a high injection efficiency have been vigorously continued.

Suitable as a charge transport material as described above
As quality, N, N, N^', N^'Replacement benzine already known
Have been. For example, in JP-A-53-27033.
Is N, N^'-Diphenyl-N, N^'-Bis (2-methyl
Phenyl) -1,1^'Biphenyl-4,4^'-Diamine
Or N, N^'-Diphenyl-N, N^'-Bis (3-meth)
Ruphenyl) -1,1^'Biphenyl-4,4^'− Jami
Photoreceptor using a benzidine compound such as amine as a charge transport material
Have been proposed, and also JP-A-61-232955.
In the publication, the binder resin of the above-mentioned benzidine compound
In an attempt to improve the compatibility with the biphenyl skeleton
3,3^'3,3 with a substituent at the position ^'-Dimethyl-
N, N, N^', N^'Tetraphenyl-1,1^'-Bife
Nil-4,4^'A benzidine compound such as a diamine
It has been proposed to use it as a charge transport material.

Further, in JP-A-62-201447 and JP-A No. 1-315751, 1,1 ^{'- biphenyl-4,4'} - groups to be replaced by the 4,4 ^'diamine different , So to speak, it has been proposed to use a left-right asymmetric benzidine compound as a charge-transporting material, and as a result, it has better sensitivity than a photoreceptor using a left-right symmetric compound as a charge-transporting material, and has less fluctuation in characteristics due to repeated use. Furthermore, it is mentioned that a photoreceptor having less memory phenomenon during rest can be obtained.

[0008]

In the above-mentioned benzidine compounds, both or one of the diamines is a diaryl-substituted product. As a result of further studies on the photoconductors using these compounds as the charge transport material, the present inventors have found that
It has been found that the photoreceptors using these compounds have relatively good initial characteristics, but the performance gradually deteriorates when repeatedly used for a long period of time. In particular, such deterioration is severe when used in a high temperature environment. For this, in particular,
This is a serious problem when such a photoreceptor is used in a device whose internal temperature is high, such as a high-speed electrophotographic device.

The present invention has been made in view of the above points, and has little fluctuation in characteristics during repeated repeated use over a long period of time, and particularly has excellent resistance to use under high temperature and high humidity. The purpose is to provide.

[0010]

According to the present invention, the above-mentioned problems are solved in an electrophotographic photoreceptor comprising a photosensitive layer having a charge generation layer and a charge transfer layer laminated on a conductive substrate. It is solved by using a benzidine compound represented by the following general formula (I) as a charge transport material.

[0011]

[Chemical 6]

[In the formula (I), A ₁ , A ₂ , A ₃ and A
₄ is a pyridyl group bonded at the 2-position, an alkylpyridyl group,
It represents one of an alkoxypyridyl group and a halogenated pyridyl group, and R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group and a halogen atom. In addition, the above-mentioned problem is, in an electrophotographic photoreceptor comprising a photosensitive layer in which a charge generation layer and a charge transfer layer are laminated on a conductive substrate, a benzidine compound represented by the following general formula (II) is charged. It is solved by using it as a transport material.

[0013]

[Chemical 7]

[In the formula (II), A ₁ , A ₂ and A ₃ represent any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group and a halogenated pyridyl group bonded at the 2-position, and B ₁ is Aryl group, alkylaryl group,
It represents either an alkoxyaryl group or a halogenated aryl group, and R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group and a halogen atom. In addition, the above-mentioned problem is, in an electrophotographic photoreceptor comprising a photosensitive layer in which a charge generation layer and a charge transfer layer are laminated on a conductive substrate, a benzidine compound represented by the following general formula (III) is charged. It is solved by using it as a transport material.

[0015]

Embedded image

[In the formula (III), A ₁ and A ₂ represent any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group and a halogenated pyridyl group bonded at the 2-position, and B ₁ and B ₂ are It represents any one of an aryl group, an alkylaryl group, an alkoxyaryl group, and a halogenated aryl group, and R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group, and a halogen atom. In addition, the above-mentioned problem is an electrophotographic photoreceptor comprising a photosensitive layer formed by laminating a charge generation layer and a charge transfer layer on a conductive substrate, and a benzidine compound represented by the following general formula (IV) is charged. It is solved by using it as a transport material.

[0017]

[Chemical 9]

[In the formula (IV), A ₁ and A ₂ represent any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group and a halogenated pyridyl group bonded at the 2-position, and B ₁ and B ₂ are It represents any one of an aryl group, an alkylaryl group, an alkoxyaryl group, and a halogenated aryl group, and R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group, and a halogen atom. Further, the above-mentioned problem is that an electrophotographic photoreceptor comprising a photosensitive layer in which a charge generation layer and a charge transfer layer are laminated on a conductive substrate is charged with a benzidine compound represented by the following general formula (V). It is solved by using it as a transport material.

[0019]

[Chemical 10]

[In the formula (V), A ₁ is a pyridyl group bonded at the 2-position, an alkylpyridyl group, an alkoxypyridyl group,
Represents one of the halogenated pyridyl groups, B ₁ ,
B ₂ and B ₃ represent any of an aryl group, an alkylaryl group, an alkoxyaryl group and a halogenated aryl group, and R ₁ and R ₂ represent any of a hydrogen atom, an alkyl group, an alkoxy group and a halogen atom. Represents ] As a general method for the synthesis of benzidine compounds according to the invention, in the case of symmetrical structure in the compound represented by the general formula (I) and (III), the corresponding 4,4 ^'
- diiodo biphenyl compounds and 2,2 ^'- anhydrous potassium carbonate secondary amine, such as dipyridyl amine or 2-anilino pyridine, was heated with copper powder in a solvent such as sulfolane, synthesized by condensation. In the case of asymmetric structure with a compound represented by to the general formula (I) no (V), the corresponding 4,4 ^'- diiodo biphenyl compounds and ^2,2' - dipyridyl amine or 2-anilino pyridine A 4-nitro- ^4′ -N-substituted biphenyl compound obtained by reacting a secondary amine such as with is reacted with a halogenated benzene derivative such as iodobenzene or 2-iodopyridine, or a halogenated pyridine derivative to synthesize the compound. .

Representative examples of the above-mentioned benzidine compound according to the present invention include the following compounds.

[0022]

[Chemical 11]

[0023]

[Chemical 12]

[0024]

[Chemical 13]

[0025]

Embedded image

[0026]

[Chemical 15]

[0027]

Embedded image

[0028]

[Chemical 17]

[0029]

Embedded image

[0030]

[Chemical 19]

[0031]

Embedded image

[0032]

[Chemical 21]

[0033]

[Chemical formula 22]

As the conductive substrate of the photoreceptor according to the present invention, materials such as metal such as iron, nickel, copper and aluminum, plastic having metal deposited on the surface thereof, conductive plastic and the like are used. Sheet, belt, cylinder Used in shapes such as. On these substrates, if necessary,
An undercoat layer and a barrier layer can be provided. For the charge generation layer, a coating liquid prepared by kneading and dispersing the charge generation substance with a binder and a solvent that dissolves the binder in a sand mill, a paint shaker, an attritor, or the like is formed into a thin film, for example, 3 μm or less, preferably 0 μm. .0
It is formed by coating and drying so as to form a thin film of 1 μm to 1 μm. Examples of the charge generating substance include pyrylium salt, squarium salt, pyrrolopyrrole compound, ansanthuron compound, perylene compound, disazo compound, phthalocyanine compound, etc.
Alternatively, two or more kinds can be used as a mixture, and examples of the charge generating substance that can be particularly effectively used in the present invention include dibromoanthanthrone, an azo pigment, and a phthalocyanine pigment. Examples of the resin preferably used as the binder include polyvinyl formal, polyvinyl acetal, polyvinyl butyral, phenoxy resin, polyester resin, polycarbonate resin, epoxy resin, melamine resin, vinyl chloride copolymer and the like. The proportion of these binders in the charge generation layer is preferably 10% by weight or more and 60% by weight or less, and more preferably 30% by weight or more and 50% by weight or less.

The charge transfer layer has the above general formulas (I) to (V).
A coating solution prepared by dissolving a benzidine compound represented by the formula (1) as a charge transporting substance in a suitable solvent together with a binder is applied onto the charge generating layer by a known coating method, for example, spray coating, dip coating, curtain flow coating, etc. 5 μm to 50 μm, preferably 10 μm in film thickness
It is formed as a 40 μm coating film. As the binder used in the charge transfer layer, polyester resin, polysulfone resin, polyketone resin, polycarbonate resin,
(Poly) acrylic resin, styrene resin, etc. can be used,
The combination of the binder and the charge transport material is the binder 1
A preferable range is 300 parts by weight to 10 parts by weight with respect to 00 parts by weight. As the solvent, alcohols such as methanol, ethanol, butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone,
Ketones such as cyclohexanone, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, halogenated carbons such as chloroform, dichloromethane, dichloroethane, dichloroethylene and trichloroethane, toluene, xylene, diene Aromatic compounds such as chlorobenzene may be mentioned, and a suitable solvent is selected depending on the solubility of the binder used. The solid content concentration of the coating liquid is preferably 10% by weight to 60% by weight, more preferably 20% by weight to 40% by weight.

[0036]

The benzidine compounds represented by the above general formulas (I) to (V) have excellent compatibility with various binder resins. When such a compound is used as a charge transport material, it can be mixed well with a binder to form a uniform charge transfer layer, which has good charge retention characteristics, excellent sensitivity, small residual potential, and is repeatedly and repeatedly used over a long period of time. It is possible to obtain a photoconductor that has little variation in characteristics during use and has excellent resistance to use especially under high temperature and high humidity.

[0037]

EXAMPLES First, examples of synthesis of the benzidine compound according to the present invention will be shown, and then examples will be described. Synthesis Example necked flask of compound examples (1) 4-4 ^'- di-iodophenyl 20g
r, 2, 2 ^'- dipyridyl amine 17Gr, placed anhydrous potassium carbonate 21Gr, copper powder 3GR, sulfolane 50 ml, was continued for 60 hours at a temperature 220 ° C.. After cooling, 500 ml of water was added, and the mixture was stirred and then separated. The above operation was repeated 3 times. Methanol was added to the obtained residual liquid, the solid content was separated by filtration, extracted with a mixed solvent of toluene and n-hexane, recrystallized and dried under reduced pressure to obtain 12 gr of a white powder. The thus obtained compound is a fully automatic elemental analyzer 24 manufactured by Perkin Elmer Co., Ltd.
As a result of measurement with 00IICHNS / O, the numerical values shown in Table 1 were obtained.

[0038]

[Table 1]

The molecular weight of the synthesized product measured by a mass spectrometer JMS-AX500 manufactured by JEOL Ltd. is theoretically 4
It was 492 against 92.6. Compound Example (15) Synthesis Example necked flask 4-nitro-4 ^'- putting di iodophenyl 16GR, 2-anilino pyridine 8.5Gr, anhydrous potassium carbonate 11gr, copper powder 2 gr, sulfolane 30 ml, the temperature The reaction was continued by stirring at 220 ° C. for 60 hours. Then, purification was carried out in the same manner as in the synthesis example of compound example (1) to obtain 4-nitro- ^4′- N-substituted biphenyl, which was reduced with metallic tin and hydrochloric acid and neutralized to give 4
A -amino- ^4'- N-substituted biphenyl was obtained.

4-amino-4 ^' thus obtained
20-gr of 2-iodopyridine, 2 gr of iron powder, and 30 ml of sulfolane were added to -N-substituted biphenyl, and the mixture was heated to 30 ° C.
The reaction was carried out at the temperature of 40 hours. Then, purification was performed in the same manner as in the synthesis example of compound example (1), and white powder 7 g
r was obtained. Table 2 shows the elemental analysis results of the thus obtained synthesized product, which was analyzed in the same manner as in the case of the synthesis example of the compound example (1).

[0041]

[Table 2]

The molecular weight analyzed in the same manner as in the case of the synthesis example of the compound example (1) was 491 with respect to the theoretical value of 491.6. Compounds other than the above can be synthesized by the method according to the above-mentioned synthesis example. Example 1 A peripheral surface mirror-finished aluminum cylinder having an outer diameter of 60 mm, a length of 348 mm, and a thickness of 1 mm was used, and a polyamide resin (made by Toray Industries, Inc .; Alamin CM-8000) was used on the outer peripheral surface.
Dip coated with 3% methanol solution of
An undercoat layer of μm was provided. On this undercoat layer, 2.4 parts by weight of a disazo pigment represented by the following structural formula (A), 0.6 parts by weight of a polyvinyl acetal resin (Sekisui Chemical Co., Ltd .; S-Rex KS-5Z), and 10 parts of methyl ethyl ketone were used.
Disperse with a paint shaker together with 20 parts by weight of cyclohexanone, and further add 70 parts of methyl ethyl ketone.
A coating solution prepared by diluting by adding parts by weight was applied to form a charge generation layer having a dry film thickness of 0.4 μm.

[0043]

[Chemical formula 23]

On this charge generation layer, a coating solution prepared by dissolving 10 parts by weight of the above compound example (1) as a charge transport material and 10 parts by weight of bisphenol Z type polycarbonate (molecular weight 80,000) in 140 parts by weight of dichloromethane. Example 1 was applied to form a charge transfer layer having a dry film thickness of 24 μm.
A photoconductor was manufactured. Examples 2 to 10 In Example 1, the charge transport material used in the charge transport layer is the compound examples (8), (15), (22), (29),
Photoreceptors of Examples 2 to 10 were produced in the same manner as in Example 1 except that (36), (43), (50), (57) and (64) were used, respectively.

Comparative Example 1 In Example 1, the charge transport material used in the charge transport layer was represented by the following structural formulas (B-1), (B-2), (B-3), (B).
Comparative Examples 1, 2, 3 and 4 were prepared in the same manner as in Example 1 except that the compounds shown in -4) were used instead.

[0046]

[Chemical formula 24]

[0047]

[Chemical 25]

Each of the photoconductors of Examples 1 to 10 and Comparative Examples 1 to 4 is a commercially available copying machine (Matsushita Electric Industrial Co., Ltd .; FP-
3270) and the characteristics were evaluated. The initial dark potential and light potential of the photoconductor are -800V and -100V, respectively.
And the amount of light from the dark potential to the bright potential (l
x.s) is the sensitivity. Also, 10l after the start of exposure
The potential after irradiation with light of x · s is defined as the residual potential V _r . The charging and exposure processes as described above are performed at room temperature and normal humidity (temperature 25 ° C., relative humidity 50%), high temperature and high humidity (temperature 40
Repeatedly for 3 hours each at ℃, relative humidity 90%,
Changes in properties were measured and at the same time changes in images were observed. The results are shown in Tables 3 and 4.

[0049]

[Table 3]

[0050]

[Table 4]

As shown in Tables 3 and 4, the characteristics of the photoconductors of the examples are more stable than those of the photoconductors of the comparative examples, especially in a high temperature and high humidity environment. The effect of using such a compound as a charge transport material is clear.

[0052]

According to the present invention, the above-mentioned general formulas (I) to
By using the benzidine compound represented by (V) as a charge transport material, the charge retention characteristics are good, the sensitivity is excellent, the residual potential is small, and the characteristics do not fluctuate during repeated use over a long period of time, especially at high temperatures. It is possible to obtain an electrophotographic photoreceptor having excellent resistance to use under high humidity. Such a photoreceptor can be preferably used in a high speed electrophotographic apparatus.

Claims (5)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer comprising a conductive substrate and at least a charge generation layer and a charge transfer layer laminated on the conductive substrate, and a benzidine compound represented by the following general formula (I) is used for charge transport. An electrophotographic photoreceptor, which is used as a substance. Embedded image [In the formula (I), A ₁ , A ₂ , A ₃ and A ₄ represent any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group and a halogenated pyridyl group bonded at the 2-position, and R ₁ and R ₂ represents any one of a hydrogen atom, an alkyl group, an alkoxy group and a halogen atom. ] 2. An electrophotographic photoreceptor comprising a photosensitive layer comprising a conductive substrate and at least a charge generation layer and a charge transfer layer laminated on the conductive substrate, wherein a benzidine compound represented by the following general formula (II) is charge-transported. An electrophotographic photoreceptor, which is used as a substance. Embedded image [In the formula (II), A ₁ , A ₂ and A ₃ represent any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group and a halogenated pyridyl group bonded at the 2-position,
B ₁ represents any _one of an aryl group, an alkylaryl group, an alkoxyaryl group and a halogenated aryl group, and R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group and a halogen atom. . ] 3. An electrophotographic photoreceptor comprising a photosensitive layer comprising a conductive substrate and at least a charge generation layer and a charge transfer layer laminated on the conductive substrate. The benzidine compound represented by the following general formula (III) is used for the charge transport. An electrophotographic photoreceptor, which is used as a substance. Embedded image [In the formula (III), A ₁ and A ₂ represent any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group, and a halogenated pyridyl group bonded at the 2-position, and
₁ and B ₂ represent any of an aryl group, an alkylaryl group, an alkoxyaryl group and a halogenated aryl group, and R ₁ and R ₂ represent a hydrogen atom, an alkyl group,
Represents either an alkoxy group or a halogen atom. ] 4. An electrophotographic photoreceptor comprising a photosensitive layer comprising a conductive substrate and at least a charge generation layer and a charge transfer layer laminated on the conductive substrate, and a benzidine compound represented by the following general formula (IV) is used for charge transport. An electrophotographic photoreceptor, which is used as a substance. [Chemical 4] [In the formula (IV), A ₁ and A ₂ are a pyridyl group bonded at the 2-position, an alkylpyridyl group, an alkoxypyridyl group,
Represents any one of halogenated pyridyl groups, B ₁ and B ₂ represent any one of an aryl group, an alkylaryl group, an alkoxyaryl group and a halogenated aryl group, R ₁ and R ₂ represent a hydrogen atom, Represents one of an alkyl group, an alkoxy group, and a halogen atom. ] 5. An electrophotographic photoreceptor comprising a photosensitive layer comprising a conductive substrate and at least a charge generation layer and a charge transfer layer laminated on the conductive substrate, and a benzidine compound represented by the following general formula (V) is used for charge transport. An electrophotographic photoreceptor, which is used as a substance. Embedded image [In the formula (V), A ₁ represents any one of a pyridyl group, an alkylpyridyl group, an alkoxypyridyl group, and a halogenated pyridyl group bonded at the 2-position, and B ₁ , B ₂ and B _2
3 represents any one of an aryl group, an alkylaryl group, an alkoxyaryl group and a halogenated aryl group, and R ₁ and R ₂ represent any one of a hydrogen atom, an alkyl group, an alkoxy group and a halogen atom. ]