JPH0553348A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body which suppresses reduction in the extent of electrification and the lowering of the sensitivity after repeated copying and gives a stable image. CONSTITUTION:An org. photosensitive layer contg. a fluorenone type bisazo pigment as an electric charge generating material and at least one kind of antioxidant selected among antioxidants represented by formulae I-VII is formed on an electric conductive substrate. This antioxidant prevents the oxidation of the org. photosensitive layer without deteriorating the high sensitivity characteristics of the bisazo pigment and improves the repetitive characteristics of the resulting sensitive body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor provided with an organic photosensitive layer on a conductive substrate, and more particularly to an electrophotographic photoreceptor using a fluorenone type bisazo pigment as a charge generating material.

[0002]

2. Description of the Related Art Recently, electrophotographic photoreceptors made of various materials have been proposed and used in image forming apparatuses such as copying machines utilizing the so-called Carlson process. One is an inorganic photoreceptor using an inorganic material such as selenium as a photosensitive layer, and the other is an organic photoreceptor using an organic material as a photosensitive layer. Organic photoconductors have many advantages such as being cheaper and higher in productivity than inorganic photoconductors and being non-polluting, and therefore extensive research has been conducted.

By the way, an organic photoconductor using a bisazo pigment as a charge generating material has been proposed. For example, in Japanese Patent Application Laid-Open No. 57-100434, an electrophotographic photoreceptor having a charge generating layer and a charge transporting layer provided on a conductive substrate has a charge generating layer composed of a layer containing a bisazo pigment. An electrophotographic photoreceptor having a layer containing a hydrazone compound is disclosed, and is disclosed in JP-A-63-11346.
No. 6, in an electrophotographic photoreceptor having a charge generating layer and a charge transporting layer provided on a conductive substrate, the charge generating layer comprises a layer containing a bisazo pigment, and the charge transporting layer contains a benzidine compound. An electrophotographic photoreceptor comprising layers is disclosed. In these publications, it is stated that by using a bisazo pigment as a charge generating material, it is possible to provide an electrophotographic photoreceptor having excellent charging characteristics and high sensitivity.

[0004]

However, in the electrophotographic photosensitive member prepared by using the bisazo pigment as the charge generating material as described above, when the image forming process such as charging, exposing and discharging is repeatedly performed, the surface is The potential tends to decrease significantly, and there is a drawback that the image density is not stabilized after long-term use. In particular, in an electrophotographic photosensitive member in which the organic photosensitive layer is formed of a single layer, the surface potential is remarkably lowered by the aging such as charging, exposure and charge elimination.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide an electrophotographic photoreceptor having excellent repeating characteristics.

[0006]

The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which an organic photosensitive layer containing a fluorenone type bisazo pigment as a charge generating material is provided on a conductive substrate. The photosensitive layer has the following formula
It is characterized by containing at least one kind selected from the group of antioxidants represented by (I) to (VII), and thereby the above object is achieved.

[0007]

[Chemical 8]

[0008]

[Chemical 9]

[0009]

[Chemical 10]

[0010]

[Chemical 11]

[0011]

[Chemical formula 12]

[0012]

[Chemical 13]

[0013]

[Chemical 14]

Next, the present invention will be described in detail.

The electrophotographic photoreceptor of the present invention contains a fluorenone type bisazo pigment as a charge generating material on a conductive substrate and further contains at least one of the antioxidants represented by the formulas (I) to (VII). An organic photosensitive layer containing one type is provided. The organic photosensitive layer may be a single layer,
Alternatively, it may be formed of a plurality of layers (for example, a charge generation layer and a charge transport layer). When the organic photosensitive layer has a plurality of layers, it is preferable that the fluorenone type bisazo pigment and the antioxidant represented by the formulas (I) to (VII) are contained in the same layer. Furthermore, a protective layer may be provided on the organic photosensitive layer, and an intermediate layer may be provided between the organic photosensitive layer and the conductive substrate.

In the present invention, as the fluorenone type bisazo pigment used as the charge generating material, conventionally known ones can be used, but the compound represented by the following formula (VIII) is preferably used. it can.

[0017]

[Chemical 15]

The fluorenone type bisazo pigment represented by the formula (VIII) is disclosed in JP-A-57-100434.

Further, the organic photosensitive layer may contain a charge transport material. Examples of such charge transport materials include m-phenylenediamine compounds; tetracyanoethylene; fluorenone compounds such as 2,4,7, -trinitro-9-fluorenone; nitrated compounds such as dinitroanthracene; anhydrous amber. Acid; maleic anhydride; dibromomaleic anhydride; triphenylmethane compound; 2,5-di (4-dimethylaminophenyl)-
Oxadiazole compounds such as 1,3,4-oxadiazole; styryl compounds such as 9- (4-diethylaminostyryl) anthracene; carbazole compounds such as poly-N-vinylcarbazole; 1-phenyl-3 −
Pyrazoline compounds such as (p-dimethylaminophenyl) pyrazoline; 4,4 ′, 4 ″,-tris (N, N-)
Amine derivatives such as diphenylamino) triphenylamine; 1,1-bis (4-diethylaminophenyl) -4,
Conjugated unsaturated compounds such as 4-diphenyl-1,3-butadiene; hydrazone compounds such as 4- (N, N-diethylamino) benzaldehyde-N, N-diphenylhydrazone; indole compounds, oxazole compounds, isoxazole compounds Nitrogen-containing cyclic compounds such as compounds, thiazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, pyrazole-based compounds, pyrazoline-based compounds and triazole-based compounds; condensed polycyclic compounds and the like.

The following compounds are exemplified as the m-phenylenediamine compound. N, N, N ',
N'-tetraphenyl-1,3-phenylenediamine,
N, N, N ', N'-tetrakis (3-tolyl) -1,
3-phenylenediamine, N, N, N ', N'-tetraphenyl-3,5-tolylenediamine, N, N, N',
N'-tetrakis (3-tolyl) -3,5-tolylenediamine, N, N, N ', N'-tetrakis (4-tolyl) -1,3-phenylenediamine, N, N, N',
N'-tetrakis (4-tolyl) -3,5-tolylenediamine, N, N, N ', N'-tetrakis (3-ethylphenyl) -1,3-phenylenediamine, N, N,
N ', N'-tetrakis (4-propylphenyl)-
1,3-phenylenediamine, N, N, N ', N'-tetraphenyl-5-methoxy-1,3-phenylenediamine, N, N-bis (3-tolyl) -N', N'-diphenyl- 1,3-phenylenediamine, N, N'-bis (4-tolyl) -N, N'-diphenyl-1,3-phenylenediamine, N, N'-bis (4-tolyl) -N,
N'-bis (3-tolyl) -1,3-phenylenediamine, N, N'-bis (4-tolyl) -N, N'-bis (3-tolyl) -3,5-tolylenediamine, N , N '
-Bis (1-ethylphenyl) -N, N'-bis (3-
Ethylphenyl) -1,3-phenylenediamine, N,
N'-bis (4-ethylphenyl) -N, N'-bis (3-ethylphenyl) -3,5-tolylenediamine,
N, N, N ', N'-tetrakis (2,4,6, -trimethylphenyl) -1,3-phenylenediamine, N,
N, N ', N'-tetrakis (2,4,6, -trimethylphenyl) -3,5-tolylenediamine, N, N,
N ', N'-tetrakis (3,5-dimethyl) -1,3
-Phenylenediamine, N, N, N ', N'-tetrakis (3,5-dimethyl) -3,5-tolylenediamine,
N, N, N ', N'-tetrakis (3,5-diethyl)
-1,3-phenylenediamine, N, N, N ', N'-
Tetrakis (3,5-dimethyl) -3,5-tolylenediamine, N, N, N ', N'-tetrakis (3-chlorophenyl) -1,3-phenylenediamine, N, N,
N ', N'-tetrakis (3-bromophenyl) -1,
3-phenylenediamine, N, N, N ', N'-tetrakis (3-iodophenyl) -1,3-phenylenediamine, N, N, N', N'-tetrakis (3-fluorophenyl) -1, 3-phenylenediamine, N, N,
N ', N'-tetrakis (2-tolyl) -1,3-phenylenediamine, N, N, N', N'-tetrakis (2
-Methoxyphenyl) -5-methyl-1,3-phenylenediamine, N, N, N ', N'-tetrakis (2-chlorophenyl) -1,3-phenylenediamine, N,
N, N ', N'-tetrakis (2-aminophenyl)-
5-methyl-1,3-phenylenediamine, N, N,
N ', N'-tetrakis (3-tolyl) -5-methyl-
1,3-phenylenediamine, N, N, N ', N'-hexakis (4-tolyl) -1,3,5-benzenetriamine, N, N, N', N'-tetrakis (3-tolyl) -5-methoxy-1,3-phenylenediamine,
N, N, N ', N'-tetrakis (3-tolyl) -1,
3,5, -Benzenetriamine, N, N, N ', N'-
Tetrakis (3-tolyl) -5-allyl-1,3-phenylenediamine, N, N, N ′, N′-tetrakis (3
-Tolyl) -5-phenyl-1,3-phenylenediamine, N, N, N ', N'-tetrakis (3-tolyl)-
5-chloro-1,3-phenylenediamine, N, N,
N ', N'-tetrakis (3-tolyl) -5-nitro-
1,3-phenylenediamine, N, N, N ′, N′-tetrakis (3-tolyl) -5-sulfo-1,3-phenylenediamine, N, N, N ′, N′-tetrakis (3-
Tolyl) -5-cyano-1,3-phenylenediamine,
N, N, N ', N'-tetrakis (3-tolyl) -5-
Formyl-1,3-phenylenediamine, N, N,
N ', N'-tetrakis (3-tolyl) -5-acetyl-1,3-phenylenediamine, N, N, N', N'-
Tetrakis (3-tolyl) -5-carboxy-1,3-
Phenylenediamine, N, N, N ', N'-tetrakis (3-tolyl) -5-ethoxycarbonyl-1,3-phenylenediamine, N, N'-bis (3-tolyl)-
N, N'-bis (2,4,6, -trimethylphenyl)
-1,3-phenylenediamine.

As the binder resin contained in the above-mentioned organic photosensitive layer, all those which have been conventionally used in the photoreceptor coating liquid can be used, and examples thereof include thermosetting silicone resin, epoxy resin, urethane resin, and curing resin. Acrylic resin, acrylic modified urethane resin, alkyd resin, unsaturated polyester resin, diallyl phthalate resin, phenol resin, urea resin, benzoguanamine resin, melamine resin,
Olefin polymers such as styrene polymers, acrylic polymers, styrene-acrylic polymers, polyethylene, ethylene-vinyl acetate polymers, chlorinated polyethylene, polypropylene, ionomers; polyvinyl chloride; vinyl chloride-vinyl acetate copolymer Combined; polyvinyl acetate; saturated polyester; polyamide; thermoplastic urethane resin; polycarbonate such as bisphenol A type and bisphenol Z type; polyarylate; polysulfone; ketone resin; polyvinyl butyral resin; polyether resin and the like. When the organic photosensitive layer is formed of a plurality of layers, the binder resin can be used to form each layer.

When the organic photosensitive layer is formed of a single layer, the thickness of the organic photosensitive layer is preferably 10 to 50 μm, more preferably 15 to 30 μm.

When the organic photosensitive layer is formed of a single layer, the fluorenone type bisazo pigment is used as the binder resin 100 for the organic photosensitive layer.
The content is preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight. When the content of the fluorenone type bisazo pigment is less than 0.5 part by weight, the sensitivity of the photoconductor is lowered. On the contrary, when the content of the fluorenone type bisazo pigment exceeds 15 parts by weight, the abrasion resistance of the electrophotographic photosensitive member may be deteriorated.

The antioxidants represented by the formulas (I) to (VII) are used alone or in combination of two or more kinds. This antioxidant is
It is preferably contained in the range of 0.1 to 30 parts by weight, more preferably 5 to 2 parts by weight with respect to 100 parts by weight of the binder resin.
0 parts by weight. When the content of the antioxidant is less than 0.1 parts by weight, the repeating characteristics of the obtained photoreceptor tend to deteriorate, and conversely, when the content of the antioxidant exceeds 30 parts by weight, the initial sensitivity is low. May decrease, and the mechanical strength of the photosensitive layer may decrease.

When the organic photosensitive layer is composed of the charge generation layer and the charge transport layer, the thickness of the charge generation layer is 0.01 to 3.
μm is preferable, and 0.1 to 2 μm is more preferable. The thickness of the charge transport layer is preferably 2 to 100 μm, more preferably 5 to 30 μm.

In this case, the fluorenone type bisazo pigment is added in an amount of 20 to 30 with respect to 100 parts by weight of the binder resin in the charge generation layer.
The content is preferably 0 part by weight, more preferably 50 to 200 parts by weight. When the content of the fluorenone type bisazo pigment is less than 20 parts by weight, the charge generation ability is small, and conversely, when the content of the fluorenone type bisazo pigment exceeds 300 parts by weight, the mechanical strength of the organic photosensitive layer may decrease. is there.

The antioxidants represented by the formulas (I) to (VII) are preferably contained in an amount of 0.1 to 30 parts by weight, more preferably 5 parts by weight, based on 100 parts by weight of the binder resin. ~ 2
0 parts by weight. When the content of the antioxidant is less than 0.1 parts by weight, the repeating characteristics of the resulting photoreceptor tend to deteriorate, and conversely, when the content of the antioxidant exceeds 30 parts by weight, the initial sensitivity is low. May decrease, and the mechanical strength of the photosensitive layer may decrease.

The organic photosensitive layer may contain various additives such as a quencher.

Further, an antioxidant different from the above antioxidant may be used in combination. Examples of such antioxidants include antioxidants represented by the following formulas (IX) to (XVII).

[0030]

[Chemical 16]

[0031]

[Chemical 17]

[0032]

[Chemical 18]

[0033]

[Chemical 19]

[0034]

[Chemical 20]

[0035]

[Chemical 21]

[0036]

[Chemical formula 22]

[0037]

[Chemical formula 23]

[0038]

[Chemical formula 24]

The conductive substrate used in the present invention is formed in an appropriate shape such as a sheet shape or a drum shape according to the mechanism and structure of the image forming apparatus in which the electrophotographic photosensitive member is incorporated. The conductive substrate may be entirely formed of a conductive material such as metal, or the base material may be formed of a material having no conductivity and the surface thereof may be provided with a material having conductivity. Good. As the conductive material, for example, the surface is alumite-treated, or untreated aluminum,
Examples include copper, tin, platinum, gold, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, brass, etc. Especially, anodic oxidation by sulfuric acid alumite method and sealing with nickel acetate. Treated aluminum is preferably used. In the case of a conductive substrate formed by providing a conductive material on the surface of a base material made of a material having no conductivity, on the surface of a synthetic resin base material or a glass base material, the above-mentioned metal or A thin film made of a conductive material such as aluminum iodide, tin oxide, or indium oxide formed by a known film forming method such as a vacuum deposition method or a wet plating method, or a film of the metal material or the like on the surface of the base material. It is possible to employ, for example, a laminate of the above, a substrate in which a substance that imparts conductivity is injected into the surface of the base material, or the like. The conductive base material may be subjected to a surface treatment with a surface treatment agent such as a silane coupling agent or a titanium coupling agent, if necessary, to enhance the adhesiveness with the organic photosensitive layer.

In the electrophotographic photoreceptor of the present invention, at least the binder resin, the fluorenone type bisazo pigment and the antioxidant represented by the formulas (I) to (VII) are dispersed in tetrahydrofuran or the like as a solvent or a dispersion medium. This coating solution can be prepared by coating the conductive substrate with a conventional coating method such as a spray coating method, a dipping method or a flow coating method to form an organic photosensitive layer. It is preferable to perform a heat treatment in order to reduce the amount of tetrahydrofuran contained in the organic photosensitive layer. For example, the conductive substrate coated with the coating liquid is heated at a temperature of 120 ° C. or higher for 3 hours.
It is preferable to perform heat treatment for 0 minutes or more. When the heat treatment temperature is lower than the above conditions, the residual amount of tetrahydrofuran may not be sufficiently reduced.

As the solvent or dispersion medium used in the coating liquid, other solvent or dispersion medium may be used alone or in combination with tetrahydrofuran in addition to tetrahydrofuran.

Examples of such a solvent or dispersion medium include the following. Aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, xylene and toluene; halogenated hydrocarbons such as dichloromethane, carbon tetrachloride, chlorobenzene and methylene chloride; methyl alcohol, ethyl alcohol, isopropyl Alcohols such as alcohol, allyl alcohol, cyclopentanol, benzyl alcohol, furfuryl alcohol, diacetone alcohol; ethers such as dimethyl ether, diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, Ketones such as cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformamide; dimethylsulfoxide and the like.

The coating liquid is a conventionally known method, for example, a mixer, a ball mill, a paint shaker, a sand mill,
It can be prepared using an attritor, an ultrasonic disperser or the like. When preparing the above coating liquid, a surfactant, a leveling agent or the like may be added in order to improve dispersibility, coatability and the like.

[0044]

The antioxidants represented by the formulas (I) to (VII) can impart repetitive characteristics to the photoreceptor without inhibiting the high sensitivity characteristics of the fluorenone type bisazo pigment. That is, the photoreceptor having the organic photosensitive layer containing the fluorenone type bisazo pigment and not containing the antioxidant has excellent sensitivity at the initial stage, but the surface potential is lowered by repeated use. It is presumed that this is because the pigment in the organic photosensitive layer is oxidized during exposure. Therefore, when the organic photosensitive layer contains the antioxidants represented by the formulas (I) to (VII), it effectively prevents the oxidation during aging and maintains the high sensitivity characteristics of the fluorenone type bisazo pigment.

[0045]

EXAMPLES The present invention will be described below with reference to examples and comparative examples.

Examples 1 to 7 and Comparative Examples 2 to 5 5 parts by weight of the antioxidant shown in Table 1, 4 parts by weight of the fluorenone type bisazo pigment represented by the formula (VIII), N, N,
For a single-layer type photosensitive layer, 100 parts by weight of N ', N'-tetrakis (3-tolyl) -1,3-phenylenediamine, 100 parts by weight of a polycarbonate resin and a predetermined amount of tetrahydrofuran are dispersed in a ball mill for 24 hours or more. A coating liquid was prepared. This coating solution was applied on an aluminum sheet with a wire bar to a thickness of about 24 ± 2 μm, and heat-treated at about 100 ° C. for 1 hour to prepare an electrophotographic photoreceptor.

Comparative Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the antioxidant was not used.

The charging characteristics and photosensitive characteristics of the electrophotographic photosensitive members obtained in Examples 1 to 7 and Comparative Examples 1 to 5 were evaluated according to the following methods. The results are shown in Table 1.

1) Measurement of initial surface potential V1sp A single layer type electrophotographic photosensitive member was loaded in an electrostatic copying tester (EPA-8100, manufactured by Kawaguchi Electric Co., Ltd.), and the surface potential was positively charged to give a surface. The potential V1sp (V) was measured.

2) Measurement of half-exposure amount E1 / 2 and residual potential Vrp Using the halogen lamp which is the exposure light source of the electrostatic copying test apparatus, the photosensitive member in the above charged state was measured 1 second after the start of charging.
Exposure was performed at an exposure intensity of 50 lux for 1/15 seconds, the time until the initial surface potential V1sp became 1/2 was determined, and the half-exposure amount E1 / 2 (lux · sec) was calculated. In addition, the surface potential after 0.2 seconds from the exposure is measured to measure the residual potential Vrp.
(V).

3) Repeatability characteristic ΔV in the electrostatic copying tester
Measurement of sp After measuring the initial surface potential V1sp, the half-exposure amount E1 / 2, and the residual potential Vrp with the above electrostatic copying tester, an exposure intensity of 2 was measured using a halogen lamp as the static elimination light source of the above tester.
The electricity was removed with 00lux for 1 second. The surface potential V2sp (V) after repeated use 300 times was measured, and the surface potential V1sp
The difference between (V) and the surface potential V2sp (V)) was calculated as the surface potential change value ΔVsp.

[0052]

[Table 1]

From Table 1, the electrophotographic photosensitive members obtained in Examples 1 to 7 were found to have good repeating characteristics.

Examples 8 to 13 5 parts by weight of the antioxidant shown in Table 2, 4 parts by weight of the fluorenone type bisazo pigment represented by the formula (VIII), N, N,
100 parts by weight of N ′, N′-tetrakis (4-tolyl) -3 ′, 3-dimethylbenzidine (6Me-TPD),
100 parts by weight of N-ethylcarbazole-3-aldehyde-diphenylhydrazone, 20 parts by weight of full orange phenylhydrazone, and polycarbonate resin 10
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 using 0 part by weight.

Comparative Example 6 An electrophotographic photosensitive member was prepared in the same manner as in Example 8 except that the antioxidant was not used.

The ΔVsp of the electrophotographic photoconductors obtained in Examples 8 to 13 and Comparative Example 6 after repeated use of 300 times was measured in the same manner as in Example 1. The results are shown in Table 2.

[0057]

[Table 2]

From Table 2, the electrophotographic photosensitive members obtained in Examples 8 to 13 had good repeating characteristics.

[0059]

As is apparent from the above description, according to the present invention, since the organic photosensitive layer contains a specific antioxidant, the electrophotographic photosensitive member has good sensitivity even after repeated use. Can be provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuneo Oki 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd.

Claims (1)

[Claims] 1. An electrophotographic photosensitive member comprising an electrically conductive substrate and an organic photosensitive layer containing a fluorenone type bisazo pigment as a charge generating material, the organic photosensitive layer further comprising the following formulas (I) to (VII): ) An electrophotographic photoreceptor containing at least one selected from the group of antioxidants represented by [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] [Chemical 5] [Chemical 6] [Chemical 7]