JP2567089B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a low molecular weight organic photoconductor that provides improved electrophotographic properties. .

[Prior art]

Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer containing selenium, zinc oxide, cadmium sulfide or the like as a main component has been widely used.

On the other hand, an organic photoreceptor having a photosensitive layer containing an organic light-guiding compound as a main component has many advantages such as compensating for the above-mentioned drawbacks of the above-mentioned inorganic photoreceptor and has been attracting attention in recent years. Has been put into practical use.

As such an organic photoreceptor, a photoconductive polymer represented by poly-N-vinyl carbazole and 2,4,7
An electrophotographic photoreceptor having a photosensitive layer mainly composed of a charge transfer complex formed with a Lewis acid such as -trinitro-9-fluorenone has been proposed. These organic photoconductive polymers are superior to inorganic photoconductive materials in terms of lightness and film formability, but they are superior to inorganic photoconductive materials in terms of sensitivity, durability, and stability due to environmental changes. Inferior and not always satisfactory.

On the other hand, the function-separated electrophotographic photosensitive member in which the charge generating function and the charge transporting function are shared by different substances has brought about a remarkable improvement in sensitivity and durability, which have been the drawbacks of the conventional functional photosensitive members. Such a function-separated type photoreceptor has the advantage that the material selection range of the charge generating substance and the charge transporting substance is wide and an electrophotographic photoreceptor having arbitrary characteristics can be relatively easily prepared.

Various azo pigments, polycyclic quinone pigments, cyanine dyes, squaric acid dyes, pyrylium salt dyes, and the like are known as charge generation materials. Among them, many structures have been proposed for azo pigments in terms of strong light resistance, large charge generation capability, easy material synthesis, and the like.

On the other hand, as the charge transport material, for example, Japanese Patent Publication No.
Pyrazoline compounds described in JP-B No. 52-42380 and JP-A No. 55-52063, hydrazone compounds described in JP-B No. 58-32372 and JP-A No. 61-132955, triphenylamine compounds. , JP-A-54-151955
The stilbene compounds described in JP-A No. 58-198043 and JP-A No. 58-198043 are known.

These charge transport materials require (i) light,
Stable to heat, (ii) stable to ozone, NO _X , nitric acid, etc. generated by corona discharge, (i
ii) High charge transporting ability, (iv) High compatibility with organic solvents and binders, (v) Easy and inexpensive production, and the like. However, conventional charge transporting materials for low molecular weight organic compounds satisfy some of the above-mentioned factors but none satisfy at a high level, and there are still points to be improved.

[Problems to be solved by the invention]

An object of the present invention is to eliminate various drawbacks of conventional photoconductors by providing an organic photoconductive compound that sufficiently satisfies the properties required for charge transport materials.

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

Another object of the present invention is to provide a novel organic photoconductive compound which is easy to manufacture and can be provided at low cost.

[Means for solving problems]

As a result of earnest studies on the organic photoconductive compound which provides the above-mentioned highly sensitive and highly durable electrophotographic photosensitive member, the present inventors have found that a biphenyl compound having a specific structure is suitable and arrived at the present invention.

That is, the present invention is an electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a biphenyl compound represented by the following general formula [I].

(However Shikichu, R ₁ and R ₂ .Ar ₁ illustrating methyl, ethyl, alkyl propyl, methoxy, ethoxy, alkoxy group propoxy, fluorine, chlorine, halogen atom such as bromine or a hydrogen atom, And Ar ₃ represent a phenyl group.
Ar ₂ and Ar _{4 each} represent a biphenyl group. ) Ar _{1 to} Ar ₄ may have a substituent, and as the substituent, an alkyl group such as methyl, ethyl, propyl or the like, an alkoxy group such as methoxy, ethoxy or the like, fluorine, chlorine,
Examples thereof include halogen atoms such as bromine.

Heretofore, biphenyl-based compounds in which Ar ₁ to Ar ₄ are all phenyl groups have been known in JP-B-58-32372 or JP-A-61-132955, but their electrophotographic properties are insufficient. However, there are problems such as a large potential fluctuation during durability.

By using Ar ₂ and Ar ₄ as biphenyl groups as in the biphenyl compound represented by the general formula [I] of the present invention, the above problems can be remarkably improved. It is speculated that this is because the introduction of a biphenyl group into Ar ₂ and Ar ₄ spreads the π-conjugated system, which is advantageous for carrier movement.

Further, the biphenyl compound represented by the general formula [I] is
If it is a biphenyl compound represented by the following general formula [II], the effect is more excellent.

However, in the formula, R ₃ and R ₄ represent a hydrogen atom or an alkyl group such as methyl, ethyl, or propyl.

Typical examples of the compound represented by the general formula [I] are shown below. However, it is not limited to these compounds.

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

(Synthesis Method of Compound Example No. (1)) N, N′-diphenylbenzidine 2.0 g (5.94 mmol), 4-
5.0 g (17.85 mmol) of iodobiphenyl, 2.46 g (17.80 mmol) of anhydrous potassium carbonate and 906 mg of copper powder were added to 1 of nitrobenzene.
The mixture was added to 5 ml and heated and stirred at about 190 ° C. for 10 hours. After cooling with suction filtration, nitrobenzene in the filtrate was distilled off under reduced pressure. The residue was separated and purified by a silica gel column to obtain 3.14 g of the objective compound (1). (Yield 82.5%) The melting point was 209 to 210 ° C. Elemental analysis was as follows for C ₄₈ H ₃₆ N ₂ .

C (%) H (%) N (%) Calculated value 89.97 5.66 4.37 Measured value 89.94 5.71 4.35 The infrared absorption spectrum (KBr tablet method) is shown in FIG.

The electrophotographic photosensitive member of the present invention is constituted by combining the charge transporting substance of the biphenyl compound represented by the above general formula [I] and an appropriate charge generating substance in the photosensitive layer.

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

(1) Layer containing charge generating substance / layer containing charge transporting substance (2) Layer containing charge transporting substance / layer containing charge generating substance (3) Layer containing charge generating substance and charge transporting substance (4) Layer Containing Charge Generating Material / Layer Containing Charge Generating Material and Charge Transporting Material The biphenyl compound represented by the general formula [I] of the present invention has a high ability to transport holes, and therefore has the above-mentioned form. Can be used as a charge transporting substance in the photosensitive layer.
When the form of the photosensitive layer is (1), it is preferably negatively charged, when it is (2), it is preferably positively charged, and when it is (3) or (4), both positive and negatively charged can be used.

Furthermore, in the electrophotographic photoreceptor of the present invention, an appropriate intermediate layer may be provided between the conductive support and the photosensitive layer, or a protective layer or an insulating layer may be provided on the surface of the photosensitive layer in order to improve adhesion and control charge injection. May be provided. The configuration of the photoconductor of the present invention is not limited to the above basic configuration.

In addition, especially the form of (1) is preferable among the said structures,
The details will be described below.

Examples of the conductive support in the invention include those having the forms shown below.

(1) Aluminum, aluminum alloy, stainless steel,
Plate-shaped or drum-shaped metal such as copper.

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

(3) Vapor deposition or application of a layer of a conductive compound such as a conductive polymer, tin oxide or indium oxide on a non-conductive support such as glass, resin or paper or the conductive support of (1) above. Formed by.

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) Phthalocyanine pigments such as metal phthalocyanine and non-metal phthalocyanine (3) Indigo pigments such as indigo and thioindico (4) Perylene anhydride, perylene imide, etc. Perylene pigments (5) Polycyclic quinone pigments such as anthraquinone and pyrenequinone (6) Squalilium dyes (7) Pyrylium salts, thiopyrylium salts (8) Triphenylmethane dyes (9) Selenium, amorphous silicon, etc. A layer containing an inorganic substance charge-generating substance, that is, a charge-generating layer, may be formed by dispersing the above-mentioned charge-generating substance in a suitable binder and applying it on a conductive support. it can.
It can also be formed by forming a thin film on the conductive support by a dry method such as vapor deposition, sputtering or CVD.

The binder can be selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyarylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, vinyl acetate. Resin, phenol resin, silicone resin, polysulfone resin, styrene-butadiene copolymer resin, alkyd resin, epoxy resin, urea resin, vinyl chloride-vinyl acetate copolymer resin and the like can be mentioned, but not limited to these. Absent. These may be used alone or in combination of two or more as a copolymer. The amount of the resin contained in the charge generation layer is 80% by weight or less, preferably 40% by weight or less. Further, the film thickness of the charge generation layer is preferably 5 μm or less, particularly preferably 0.01 μm to 1 μm.

Further, various sensitizers may be added to the charge generation layer.

The layer containing a charge-transporting substance, that is, the charge-transporting layer can be formed by combining the biphenyl compound represented by the general formula [I] with a suitable binder resin. Examples of the binder resin used in the charge transport layer include those used in the charge generation layer, and further include light-guiding polymers such as polyvinylcarbazole and polyvinylanthracene.

The compounding ratio of the binder and the biphenyl compound of the present invention is preferably 10 to 500 parts by weight of the 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 capable of transporting these charge carriers to the surface. ing. Since this charge transport layer has a limit for transporting charge carriers, the film thickness cannot be increased more than necessary, but a range of 5 μm to 40 μm, particularly 10 μm to 30 μm is preferable.

Further, in the charge transport layer, an antioxidant, a purple ray absorbing agent, a plasticizer or a known charge transport substance can be added as required.

When such a charge transport layer is formed, an appropriate organic solvent is used and a coating method such as a dipping 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. be able to.

The electrophotographic photoreceptor of the present invention is used not only for electrophotographic copying machines, but also for laser printers, CRT printers,
It can be widely used in electrophotographic application fields such as 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 according to examples.

Example 1 The following structural formula 4 g of the disazo pigment represented by 2 was dispersed in 100 ml of cyclohexanone for 2 g of butyral resin (degree of butyralization: 60 mol%) and dispersed in a sand mill for 24 hours to prepare a coating liquid.

This coating solution was applied onto an aluminum sheet with a Meyer bar so that the dry film thickness would be 0.2 μm to form a charge generation layer.

Next, 10 g of the above exemplified compound No. (8) as a charge transport material
And 10 g of polycarbonate resin (weight average molecular weight 20000) are dissolved in 70 g of monochlorobenzene, and this solution is applied on the above charge generation layer with a Meyer bar to provide a charge transport layer with a dry film thickness of 20 μm. A photoconductor was manufactured.

The electrophotographic photosensitive member manufactured in this manner 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. It was exposed at an illuminance of 20 lux and the charging characteristics were examined.

As the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E _1/5 ) required to attenuate the potential (V ₁ ) when dark-decayed for 1 second to 1/5 were measured.

Further, in order to measure the fluctuations in the light potential and the dark potential when repeatedly used, the photoconductor prepared in this example was attached to the cylinder for the photoconductive drum of the Canon PPC copier NP-3525. , 10,000 copies were made with the same machine, and fluctuations in the light potential (V _L ) and the dark potential (V _D ) at the initial stage and after 10,000 copies were measured. The initial V _D and V _L are −
It was set to 700V and -200V. The results are shown below.

Examples 2 to 10 and Comparative Examples 1 to 5 In each of these Examples, the exemplary compound N. (8) was used as the charge transporting substance used in Example 1 instead of the exemplary compound.
No. (1), (2), (3), (7), (13), (1
7), (25), (34), (35) are used, and the following structural formula is used as the charge generating substance. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the above pigment was used.

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

For comparison, an electrophotographic photosensitive member was manufactured by the same method using a compound having the following structure as a charge transport material, and the electrophotographic characteristics were measured. The respective effects are shown below.

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

Example 11 A solution prepared by dissolving 5 g of methoxymethylated nylon resin (number average molecular weight 32000) and 10 g of alcohol-soluble copolymerized nylon resin (number average molecular weight 29000) in 95 g of methanol on an aluminum substrate was applied using a Meyer bar, and dried. Film thickness is 1 μm
An undercoat layer was provided.

Next, the following structural formula 12 g of the charge generating substance represented by, 8 g of butyral resin (butyralization degree: 63 mol%) and 300 g of dioxane were dispersed for 48 hours with a ball mill disperser. This dispersion was applied onto the previously produced subbing layer by a blade coating method to form a charge generation layer having a film thickness after drying of 0.15 μm.

Next, 10 g of the above exemplified compound No. (10) and 10 g of polymethylmethacrylate resin (number average molecular weight of 50,000) were dissolved in 70 g of monochlorobenzene, and applied on the charge generation layer previously formed by the blade coating method, and after drying. The film thickness of
A 19 μm charge transport layer was formed.

A corona discharge of -5 KV was applied to the photoconductor thus manufactured. The surface potential at this time was measured (initial potential V ₀ ). Furthermore, the surface potential of this photoreceptor was measured after leaving it in the dark for 1 second. The sensitivity was evaluated by measuring the exposure dose (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;
An oscillation wavelength of 780 nm) was used. The results were as follows.

V ₀ : −681V V ₁ : −677V E _1/2 : 0.49 μJ / cm ² Next, laser beam printer (Canon LBP-CX), which is a reversal development type electrophotographic printer equipped with a semiconductor laser as above. The photoreceptor was set and an actual image forming test was used. The conditions are as follows.
Surface potential after primary charging; 7-700V, surface potential after image exposure;
-150V (exposure amount 0.6μJ / cm ² ), transfer potential; + 700V, developer polarity; negative polarity, process speed; 50mm / sec, development condition (development bias); -450V, image exposure scan method; image scan, primary Pre-charging exposure: 20 lux · sec full-color red exposure, image formation was performed by line scanning with a laser beam according to a character signal and an image signal, and good prints were obtained for both characters and images. Further, when images were continuously printed on 5000 sheets, stable and good prints were obtained from the initial stage to 5000 sheets.

Example 12 10 g of titanyloxyphthalocyanine was added to cyclohexane 5
A solution prepared by dissolving 5 g of phenoxy resin in 00 g was added and dispersed in a ball mill for 1 hour. This dispersion is coated on an aluminum sheet with a Meyer bar and dried at 80 ° C for 2 hours to give a thickness of 0.6 μm.
The charge generation layer of was formed. Next, the exemplified compound No. (2
4) 10g, a solution of 10g of bisphenol Z type polycarbonate resin (weight average molecular weight 50,000) in 70g of monochlorobenzene was applied on the charge generation layer previously formed with a Meyer bar and dried at 110 ° C for 1 hour. , 16 μm charge transport layer was formed. The photoconductor thus prepared was measured in the same manner as in Example 11. The results are shown below.

V ₀ : −661V V ₁ : −651V E _1/2 : 0.52 μJ / cm ² Example 13 4- (4-dimethylaminophenyl) -2,6-diphenylthiapyrylium perchlorate 3 g and the above-mentioned exemplary charges 5 g of the transport compound No. (15) and 100 g of a toluene (50 parts by weight) -dioxane (50 parts by weight) solution of a polyester resin (weight average molecular weight 49,000) were mixed and dispersed in a ball mill for 5 hours. This dispersion was applied onto an aluminum sheet with a Meyer bar and dried at 100 ° C. for 2 hours to form a photosensitive layer of 16 μm. The photoconductor thus prepared was measured in the same manner as in Example 1. The results are shown below.

V ₀ : −691V V ₁ : −685V E _1/5 : 3.0lux ・ sec (initial) V _D : −700V V _L : −200V (after 10,000 sheets endurance) V _D : −690V V _L : −214V Example 14 Aqueous ammonia solution of casein (casein
11.2 g, 1 g of 28% aqueous ammonia, and 222 ml of water) were applied with a Meyer bar to form an undercoat layer having a dry film thickness of 1 μm. A charge transport layer and a charge generation layer of Example 3 are sequentially laminated on the layer,
A photoreceptor was formed in exactly the same manner as in Example 1 except that the layer structure was different, and the charging characteristics were measured in the same manner as in Example 1. However, the charging polarity was used. The results are shown below.

V ₀ : 698V V ₁ : 687V E _1/5 : 2.9lux · sec Example 15 A 5% methanol solution of soluble nylon (6-66-610-12 quaternary nylon copolymer) was applied on an aluminum plate, An undercoat layer having a dry film thickness of 0.5 μm was formed.

Next, the following structural formula 5 g of the pigment shown by was dispersed in 95 ml of tetrahydrofuran by a sand mill for 20 hours. Then the charge transport compounds exemplified above
5 g of No. (37) and 10 g of bisphenol Z-type polycarbonate resin (weight average molecular weight 50,000) were mixed with monochlorobenzene 3
The liquid dissolved in 0 ml was added to the dispersion liquid prepared above, and the mixture was further dispersed by a sand mill for 2 hours. This dispersion was applied on a previously prepared undercoat layer using a Meyer bar so that the film thickness after drying was 20 μm, and dried. The electrophotographic characteristics of the thus prepared photoconductor were measured by the same method as in Example 1. The results are shown below.

V ₀ : −682V V ₁ : −675V E _1/5 : 2.3lux · sec [Effects of the Invention] As described above, the electrophotographic photoreceptor containing the biphenyl compound according to the present invention has high sensitivity and can be repeatedly used. It is possible to provide an electrophotographic photosensitive member excellent in durability, in which fluctuations in the light portion potential and the dark portion potential are small during continuous image formation by charging and exposure.

[Brief description of drawings]

 FIG. 1 is a diagram showing an infrared absorption spectrum.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ryoji Yatsushiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-271355 (JP, A)

Claims (2)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a biphenyl compound represented by the following general formula [I]. (In the formula, R ₁ and R ₂ are an alkyl group, an alkoxy group,
Indicates a halogen atom or a hydrogen atom. Ar ₁ and Ar _{3 each} represent a phenyl group, and Ar ₂ and Ar _{4 each} represent a biphenyl group. ) 2. The electrophotographic photosensitive member according to claim 1, wherein the biphenyl compound represented by the general formula [I] is a biphenyl compound represented by the following general formula [II]. (However, in the formula, R ₃ and R ₄ represent a hydrogen atom or an alkyl group.)