JP2728967B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer containing a low-molecular organic photoconductive compound that provides improved electrophotographic properties. It relates to a photoreceptor.

[Conventional technology]

Organic photoreceptors with organic photoconductive compounds are costly,
Since it has many advantages such as productivity, pollution-free properties, and future potential of materials, many proposals have been made and practical applications have been made so far.

For example, an electrophotographic photosensitive material mainly containing a charge transfer complex formed from a photoconductive polymer represented by poly-N-vinylcarbazole and a Lewis acid such as 2,4,7-trinitro-9-fluorenone. The body has been proposed. These organic photoconductive polymers are superior to inorganic photoconductive polymers in terms of lightness, film-forming properties, and the like, but are more sensitive to inorganic photoconductive materials in terms of sensitivity, durability, and stability due to environmental changes. And it is not always satisfactory.

On the other hand, a function-separated type electrophotographic photoreceptor in which the charge generation function and the charge transport function are respectively assigned to different substances has provided remarkable improvements in sensitivity and durability, which have been regarded as disadvantages of conventional organic photoreceptors. Such a function-separated type photoreceptor has an advantage that a material selection range of a charge generation material and a charge transport material is wide, and an electrophotographic photoreceptor having arbitrary characteristics can be relatively easily prepared.

As the charge generation material, various azo pigments, polycyclic quinone pigments, cyanine dyes, squaric acid dyes, pyrylium salt dyes, and the like are known. Among them, many structures of azo pigments have been proposed from the viewpoints of high light resistance, high charge generation ability, easy material synthesis, and the like.

On the other hand, as a charge transport material, for example, Japanese Patent Publication No. 52-4188
No. 55-42380 and Japanese Patent Application Laid-Open No. 55-52063.
No. 2372 and JP-A-61-132955, triphenylamine compounds, JP-A-54-151955 and JP-A-58-19
A stilbene compound disclosed in JP-A-8043 is known.

The requirements for these charge transport materials are (1)
(2) Stable against ozone, NO _x , nitric acid, etc. generated by corona discharge, (3) High charge transport ability, (4) Organic solvent High compatibility with the binder, and (5) easy and inexpensive synthesis. However, conventional charge transport materials using low-molecular-weight organic compounds satisfy some of the above requirements, but none satisfy all at a high level.
There are still points to be improved.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic photoconductive compound which sufficiently satisfies the characteristics required for the above-described charge transporting material, thereby solving various drawbacks of the conventional photoreceptor.

An object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity and capable of stably maintaining a potential upon repeated use.

[Means for solving the problem]

That is, the present invention relates to an electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a fluorene compound represented by the following general formula [1]. is there.

(In the formula, Ar ¹ , Ar ² , Ar ³ and Ar ⁴ each represent an aryl group which may have at least one group selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom as a substituent.) Examples of the alkyl group include methyl, ethyl, propyl and the like, examples of the alkoxy group include methoxy, ethoxy and propoxy, and examples of the halogen atom include fluorine, chlorine and bromine.

Hereinafter, typical examples of the compounds used in the present invention will be described. However, it is not limited to these compounds.

Next, a synthesis example of the compound will be described.

(Synthesis method of Exemplified Compound No. (2)) 5 g of 2,7-diiodofluorene, 4.82 g of N-phenyl-m-toluidine, 4.96 g of anhydrous potassium carbonate and 2.28 g of copper powder
Was added to 20 ml of nitrobenzene, and the mixture was heated and stirred at 190 to 200 ° C. for 15 hours. After cooling, filtration was performed, and the solvent of the filtrate was removed under reduced pressure. The residue was purified on a silica gel column to give the desired compound in 4.
6 g was obtained (72.7% yield).

Other compounds can be synthesized by a similar method.

The photoreceptor of the present invention is constituted by combining a charge transporting substance comprising a fluorene compound represented by the above general formula [1] and a suitable charge generating substance.

Examples of the configuration of the photosensitive layer include the following forms.

(1) A layer containing a charge generating substance / a layer containing a charge transporting substance is laminated in this order. (2) A layer containing a charge transporting substance / a layer containing a charge generating substance is laminated in this order. (4) Layer containing charge generating substance / containing charge generating substance and charge transporting substance The fluorene compound represented by the general formula [1] used in the present invention comprises: It has a high charge transporting ability for holes, and can be used as a transporting substance in the photosensitive layer of the above embodiment. In the case of (1), the photosensitive layer is preferably negatively charged, in the case of (2), positively charged, and in the case of (3), (4), both positively and negatively charged can be used.

 In the present invention, the configuration (1) is particularly preferable.

Further, in the electrophotographic photoreceptor of the present invention, a protective layer or an insulating layer may be provided on the surface of the photosensitive layer for improving adhesion and controlling charge injection. The configuration of the photoreceptor of the present invention is not limited to the above basic configuration.

Examples of the conductive support in the present invention include the following forms.

(1) Plates or drums made of metal such as aluminum, aluminum alloy, stainless steel, and copper.

(2) Aluminum, palladium, or the like on a non-conductive support such as glass, resin, paper, or the conductive support of (1).
A thin film formed by depositing or laminating metals such as rhodium, gold, and platinum.

(3) Depositing or applying a layer of a conductive compound such as a conductive polymer, tin oxide, or syndium oxide on a non-conductive support such as glass, resin, or paper or the conductive support described in (1) above. What was formed by

Further, an intermediate layer mainly composed of a resin having an adhesive property or a barrier property can be provided between the conductive support and the photosensitive layer.

Examples of effective charge generating substances used in the present invention include the following substances. These charge generating substances may be used alone or in combination of two or more.

(1) Azo pigments such as monoazo, bisazo and trisazo (2) Indigo pigments such as indigo and thioindigo (3) Phthalocyanine pigments such as metal phthalocyanine and nonmetal phthalocyanine (4) Perylene anhydride, perylene imide and the like (5) Polycyclic quinone pigments such as anthraquinone and pyrenequinone (6) Squarium dyes (7) Pyrylium salts and thiopyrylium salts (8) Triphenylphenyl dyes (9) Selenium, amorphous silicon, etc. A layer containing a charge generating substance, i.e., a charge generating layer, is formed by dispersing the above-described charge generating substance in an appropriate binder and applying the resultant onto a conductive support. Can be. Further, it can also be formed by forming a thin film on a conductive support by a dry method such as vapor deposition, sputter, CVD or the like.

As the binder, a wide range of binder resins can be selected, for example, a polycarbonate resin, a polyester resin,
Polyarylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, vinyl acetate resin,
Examples include, but are not limited to, phenolic resins, silicone resins, polysulfone resins, styrene-butadiene copolymer resins, alkyd resins, epoxy resins, urea resins, vinyl chloride-vinyl acetate copolymer resins. These can be used as homo- or copolymeric polymers.
Species or a mixture of two or more kinds may be used.

The amount of the resin contained in the charge generation layer is preferably 80% by weight or less, more preferably 40% by weight or less. The charge generation layer preferably has a thickness of 5 μm or less, more preferably 0.01 μm to 2 μm.

Various sensitizers may be added to the charge generation layer.

The layer containing the charge transport material, that is, the charge transport layer,
It can be formed by combining the fluorene compound represented by the general formula [1] and a suitable binder resin. Here, examples of the binder resin used for the charge transport layer include those used for the charge generation layer, and further include photoconductive polymers such as polyvinyl carbazole and polyvinyl anthracene.

The mixing ratio of the binder and the fluorene compound used in the present invention is preferably 10 to 500 parts by weight of the fluorene compound per 100 parts by weight of the binder.

The charge transport layer is electrically connected to the charge generation layer described above, and has a function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. Since the charge transport layer has a limit to transport the charge carrier, the film thickness cannot be increased more than necessary, but 5 μm to 40 μm,
In particular, a range of 10 μm to 30 μm is preferable.

Further, an antioxidant, an ultraviolet absorber, a plasticizer, or a known charge transport substance can be added to the charge transport layer as needed.

When such a charge transport layer is formed, an appropriate organic solvent is used, and a coating such as an immersion coating method, a beam coating method, a spray coating method, a spinner coating method, a roller coating method, a Meyer bar coating method, or a blade coating method is used. Method.

The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser printers, CRTs, printers, and electrophotographic plate making systems.

According to the present invention, a high-sensitivity electrophotographic photoreceptor can be provided, and there is an advantage that a change in a light portion potential and a dark portion potential upon repeated charging and exposure is small.

 Hereinafter, the present invention will be described with reference to examples.

Example 1 2 g of a bisazo pigment represented by the following structural formula was mixed with 1 g of a butyral resin (butyralization degree: 65 mol%) and 100 g of cyclohexanone.
The mixture was dispersed in a sand mill for 24 hours together with the solution dissolved in ml to prepare a coating solution.

The thickness of this coating liquid after drying on an aluminum sheet is 0.2μ.
m was applied by a Meyer bar to form a charge generation layer.

Next, as the charge transport material, the above-mentioned exemplified compound No. (5) 2
g and polycarbonate resin (weight average molecular weight 35,000) 2g
Was dissolved in 14 g of monochlorobenzene, and this solution was applied on the previous charge generation layer with a Meyer bar to a dry film thickness of 17 μm.
And a two-layer electrophotographic photoreceptor was prepared.

The electrophotographic photoreceptor thus prepared was corona-charged at −5 KV by a static method using an electrostatic copying paper tester Model-SP-428 manufactured by Kawaguchi Electric Co., Ltd., and held for 1 second in a dark place. Exposure was performed at an illuminance of 20 lux to examine the charging characteristics.

The surface potential (V ₀ ) and the exposure (E _1/5 ) required to attenuate the potential (V ₁ ) after dark decay for 1 second (V ₁ ) to 1/5 were measured.

Further, in order to measure the fluctuation of the light portion potential and the dark portion potential after repeated use, the photosensitive member prepared in this embodiment was attached to a cylinder for a photosensitive drum of a PPC copying machine NP-3825 manufactured by Canon Inc. 3,000 copies on the machine,
Fluctuations in the light potential (V _L ) and dark potential (V _D ) after 3000 copies were measured. Incidentally, the initial V _D and V _L each -700 V, -200 V
It was set to be. The results are shown in Table 1 below.

Examples 2 to 9, Comparative Examples 1 to 4 Instead of Exemplified Compound No. (5) as a charge transport material, Exemplified Compound Nos. (2), (3), (4), (8),
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that (9), (13), (20), (23), and (27) were used, and a pigment having the following structure was used as a charge generating substance. Created.

The electrophotographic characteristics of each photoconductor were measured by the same method as in Example 1.

For comparison, an electrophotographic photoreceptor was prepared by the same method using the following compound as a charge transport compound,
The electrophotographic properties were measured. The results are shown in Tables 2 and 3 below.

Comparative compound As is clear from Tables 2 and 3, the fluorene compound of the present invention is extremely excellent in sensitivity and potential stability upon repeated use as compared with the comparative compound.

Example 10 A solution prepared by dissolving 5 g of N-methoxymethylated 6 nylon resin (weight average molecular weight: 100,000) and 10 g of alcohol-soluble copolymerized nylon resin (weight average molecular weight: 80,000) in 95 g of methanol was coated on an aluminum substrate by a Meyer bar. An undercoat layer having a thickness of 1 μm after drying was provided.

Next, 10 g of a charge generating substance represented by the following structural formula, 6 g of a polyvinyl butyral resin (butyralization ratio: 68%, weight average molecular weight: 50,000) and 200 g of dioxane were dispersed by a ball mill disperser for 20 hours. This dispersion was applied on the undercoat layer manufactured previously by a blade coating method to form a charge generation layer having a thickness of 0.2 μm after drying.

Next, 10 g of Exemplified Compound No. (6) and 10 g of polymethyl methacrylate resin (weight average molecular weight: 35,000) were dissolved in 70 g of monochlorobenzene, and coated on the previously formed charge generating layer by a blade coating method. A charge transport layer having a thickness of 17 μm after drying was formed.

The photoreceptor thus produced was subjected to a -5 KV corona discharge. At this time, the surface potential (initial potential V ₀ ) was measured. Further, the surface potential of this photoconductor after leaving it in a dark place for 1 second was measured. The sensitivity was evaluated by measuring the exposure amount (E _1/6 : μJ / cm ² ) required to attenuate the potential V ₁ after dark decay to _1/6 . At this time, a gallium / aluminum / arsenic ternary semiconductor laser (output: 5
mW; oscillation wavelength 780 nm). These results were as follows.

V ₀ : -699 (V) V ₁ : -695 (V) E _1/6 : 0.60 (μJ / cm ² ) Next, a laser beam printer which is an inversion-type electrophotographic printer equipped with a semiconductor laser as described above. The above photoreceptor was attached to (LBP-SX manufactured by Canon) and an actual image forming test was performed. The conditions are as follows.
Surface potential after primary charging; -700 V, surface potential after image exposure;
-150 V (exposure 2.0 μJ / cm ² ), transfer potential; +700 V, development polarity; negative polarity, process speed; 50 mm / sec, development conditions (development bias): -450, scan after image exposure; image scan, primary Exposure before charging; red lux exposure of 50 lux sec, and image formation were performed by laser scanning with a laser beam in accordance with a character signal and an image signal. Good prints were obtained for both characters and images.

In addition, when 3,000 images were continuously output, 30
Stable prints were obtained up to 00 sheets.

Example 11 4- (4-dimethylaminophenol) -2,6-diphenylthiapyrylium perchlorate (3 g) and the above-described exemplary charge transport compound No. (16) (5 g) were copolymerized with a polyester resin (weight average molecular weight: 45,000), toluene. (50 parts by weight) -dioxane (50 parts by weight) was mixed with 100 g of the solution, and dispersed in a ball mill for 10 hours. This dispersion was applied to an aluminum sheet with a Meyer bar, and dried at 110 ° C. for an hour to form a 16 μm photosensitive layer. The photoreceptor thus prepared was used in Example 1.
It was measured in the same manner as described above. The results are shown in Table 4 below.

Example 12 Alcohol-soluble nylon (6-66-610) on an aluminum substrate
A 5% methanol solution of (-12 quaternary nylon copolymer) was applied to form an undercoat layer having a thickness of 0.8 μm after drying.

Next, 5 g of a pigment represented by the following structural formula was dispersed in a sand mill in 90 ml of tetrahydrofuran.

Next, 5 g of the above-mentioned exemplified charge transporting compound No. (17) and bisphenol A type polycarbonate resin (weight average molecular weight 3
7 g of 5,000) was dissolved in 30 g of a monochlorobenzene (70 parts by weight) -dichloromethane (30 parts by weight) solution, added to the dispersion prepared above, and further dispersed by a sand mill for 5 hours.

The thickness of the dispersion after drying was 18
It was applied with a Meyer bar to a thickness of μm and dried.

The electrophotographic characteristics of the photoreceptor thus prepared were measured in Example 11.
It was measured in the same manner as described above. The results are shown below.

V ₀ : -700 (V) V ₁ : -690 (V) E _1/6 : 3.9 (μJ / cm ² ) [Effect of the Invention] As described above, the electrophotographic photoreceptor of the present invention has high sensitivity. In addition, when a continuous image is formed by repeated charging and exposure, fluctuations in the light portion potential and the dark portion potential are small and the durability is excellent.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takakazu Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-62-280554 (JP, A) JP-A-1 −105260 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a fluorene compound represented by the following general formula [1]. (In the formula, Ar ¹ , Ar ² , Ar ³ and Ar ⁴ each represent an aryl group which may have at least one group selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom as a substituent.)