JPH02178667A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve sensitivity, electrophotographic characteristics, and variance between potentials in the light and in the dark and to enhance durability by incorporating a specified triarylamine compound in a photosensitive layer formed on a conductive substrate in an electrophotographic sensitive body. CONSTITUTION:The electrophotographic sensitive body is formed by laminating on the conductive substrate the photosensitive layer containing one of the triarylamine compounds represented by formula I in which each of Ar1 and Ar2 is a biphenyl group and Ar3 is a biphenyl or aromatic heterocyclic group and each of Ar1, Ar2, and Ar3 is optionally substituted by alkyl, such as methyl or ethyl, thus permitting the obtained electrophotographic sensitive body to be high in sensitive and small in variance between potentials in the light and in the dark at the time of successive image formation by repeating cycles of electric charging and exposure, and superior in durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to electrophotographic photoreceptors, and more particularly to low molecular weight organic photoconductive and inorganic photoconductive materials such as cadmium sulfide that provide improved electrophotographic properties. Although they are widely used, research into using organic photoconductive materials as electrophotographic photoreceptors has been actively conducted in recent years. Here, the basic characteristics required of an electrophotographic photoreceptor are: 1) It should be charged to an appropriate potential by corona discharge etc. in a dark place, 2) It should have good charge retention in a dark place, and 3) It should be exposed to light 4) The residual potential after irradiation with light is small.

Conventional electrophotographic photoreceptors using inorganic photosensitive materials such as selenium, zinc oxide, and cadmium sulfide have some basic characteristics, but they have difficulties in film formation, poor flexibility, and manufacturing costs. There are manufacturing problems such as high Furthermore, inorganic photosensitive materials are generally highly toxic, and from this point of view, it is desired to use organic materials instead of inorganic materials for photoreceptors. In general, organic compounds are lighter than inorganic compounds, have superior film-forming properties and flexibility, and are put into practical use at reduced manufacturing costs.

Until now, various organic photosensitive polymers including poly-N-vinylcarbazole have been proposed as typical organic electrophotographic photoreceptors.
These polymers are lighter than inorganic photoconductive materials,
Although they are excellent in terms of film-forming properties, they are inferior to inorganic photoconductive materials in terms of sensitivity, durability, stability against environmental changes, mechanical strength, etc., making it difficult to put them into practical use. In addition, hydrazone compounds disclosed in U.S. Pat. No. 4,150,987, triarylpyrazoline compounds described in U.S. Pat. No. 3,837,851, etc.,
Low-molecular organic photoconductors such as 9-styrylanthracene compounds described in JP-A-828 and JP-A-51-94829 have been proposed. By appropriately selecting the binder used, such low-molecular-weight organic photoconductors can overcome the drawbacks of film-forming properties that had been a problem in the field of organic photoconductive polymers. It cannot be said that the sensitivity is sufficient.

For these reasons, a laminated structure in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer has been proposed in recent years. Electrophotographic photoreceptors using this laminated structure as a photosensitive layer can now be improved in terms of sensitivity to visible light, charge retention, surface strength, and the like.

Many organic compounds have been proposed as charge transport materials. For example, pyrazoline compounds disclosed in JP-A No. 52-72231, hydrazone compounds disclosed in U.S. Pat. No. 842,431 and JP-A-55-52063,
Triphenylamine compounds of JP-A No. 7-195254 and JP-A-54-58445, JP-A-54-151
Stilbene compounds and the like are disclosed in Japanese Patent Application Laid-Open No. 955 and Japanese Patent Application Laid-Open No. 58-198043.

However, with conventional electrophotographic photoreceptors that use low-molecular-weight organic compounds as charge transport materials, the sensitivity and characteristics are not always sufficient (and when repeatedly charged and exposed, bright area potential and dark area potential change). Potential fluctuations are large and there are still points to be improved.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an electrophotographic photoreceptor that eliminates the various drawbacks of the conventional photoreceptors mentioned above.

Another object of the present invention is to provide a novel organic photoconductor that is easy to manufacture, relatively inexpensive, and has excellent durability.

[Means to solve the problem]

The present invention is an electrophotographic photoreceptor having a photosensitive layer on a conductive support.

Examples include alkyl groups such as pil, alkoxy groups such as methoxy, nidoxy, and propoxy, and halogen atoms such as fluorine, chlorine, and bromine. Note that Arl and Ar2 may be the same or different.

Ar3 represents a phenyl group which may have a substituent or an aromatic heterocyclic group such as pyridyl, quinolyl, thienyl, furyl, etc. which may have a substituent. Substituents that Ar3 may have include alkyl groups such as methyl, ethyl, and propyl;
Alkoxy groups such as methoxy, ethoxy, propoxy, aryloxy groups such as phenoxy and naphthoxy, phenyl,
Examples include aromatic ring groups such as naphthyl, and halogen atoms such as fluorine, chlorine, and bromine.

In the formula, Ar1 and Ar2 represent a biphenyl group which may have a substituent. Examples of substituents that Arl and Ar2 may have include methyl, ethyl, and bro. Representative examples of the compounds represented by the general formula [1] are listed below.

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

(Synthesis method of compound example No. (2)) 4-iodobiphenyl 23.5g (83.9mmol
), P-toluidine 3. Og (28,0 mmol),
11.6 g (83.9 mmol) of anhydrous potassium carbonate and 15 g of copper powder were added to 50 ml of nitrobenzene, and the mixture was stirred and heated under reflux for 12 hours. After cooling, the mixture was filtered under suction, and nitrobenzene was removed from the filtrate under reduced pressure. Ethanol was added to the residue to precipitate crystals, and the crude crystals were separated and purified using a silica gel column to obtain 7.80 g of target compound (2) (yield 66.7%). The melting point was 187.0-188.0°C. The four element analysis was as follows for C, H and N.

C (%) H (%) N (%) Calculated value 90
．． 47 6.12 3.40 Actual value 90.45
6.16 3.39 Infrared absorption spectrum (KB
(Tablet method) is shown in FIG.

As described above, the compound of the present invention is easy to produce and can be synthesized at low cost.

Note that compounds other than those on the synthesis side can also be synthesized using a similar method.

In a preferred embodiment of the present invention, a compound represented by the above formula can be used as a charge transport substance contained in the charge transport layer of an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. .

The charge transport layer according to the present invention is preferably formed by applying a solution prepared by dissolving the compound represented by the above general formula and a binder in an appropriate solvent and drying the solution. Examples of the binder used here include polyarylate resin, polysulfone resin, polyamide resin, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin, polyester resin, alkyd resin, and polycarbonate. , polyurethane or copolymer resins such as styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and the like. In addition to such insulating polymers, organic photoconductive polymers such as polyvinylcarbazole, polyvinylanthracene, and polyvinylpyrene can also be used.

The blending ratio of the binder and the charge transport material of the present invention is preferably io to 500 parts by weight of the charge transport material per 100 parts by weight of the binder.

The charge transport layer is electrically connected to the charge generation layer below and has the 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. At this time, this charge transport layer may be laminated on or under the charge generation layer. However, it is desirable that the charge transport layer is laminated on the charge generation layer.

Since this charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary.

Generally, it is 5 μm to 40 μm, but the preferred range is 10 μm to 30 μm.

The organic solvent used when forming such a charge transport layer is
The binder varies depending on the type of binder used, and it is preferable to select one that does not dissolve the charge generation layer or underlying subbing layer. Specific organic solvents include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, and N.

Amides such as N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, and methylene chloride. , aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, and trichlorethylene, or aromatics such as benzene, toluene, xylene, monochlorobenzene, and dichlorobenzene.

Coating can be carried out using a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method, or a blade coating method.

For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying is generally preferably carried out at a temperature of 30° C. to 200° C. for a period of 5 minutes to 2 hours, either stationary or with ventilation.

The charge transport layer of the present invention may contain various additives. For example, plasticizers such as diphenyl, m-terphenyl, dibutyl phthalate, silicone oil, grafted silicone polymers, surface lubricants such as various fluorocarbons, potential stabilizers such as dicyanovinyl compounds, carbazole derivatives, β-carotene, Ni Examples include complexes, antioxidants such as 1,4-diazabicyclo[2,2,2]octane, and the like.

The charge generation layer used in the present invention is made of inorganic charge generation substances such as selenium, selenium-tellurium, amorphous silicon, pyrylium dyes, thiapyrylium dyes, azulenium dyes, thiacyanine dyes, quinocyanine dyes, azulenium dyes, etc. Organic charge generation in polycyclic bovine non-pigments such as cationic dyes, squbarium salt dyes, phthalocyanine pigments, anthonthrone pigments, dibenzpyrenequinone pigments, vilanthrone pigments, indigo pigments, quinacridone pigments, azo pigments, etc. Selected materials can be used alone or in combination as the evaporation layer or coating layer.

Among the charge-generating substances used in the present invention, there are a wide variety of azo pigments, but typical structural examples of particularly effective azo pigments are shown below.

As a formula for azo pigments, the central skeleton is A1 as shown below. A(-N=N-Cp)l.

If we express a portion of the coupler as Cp (here n=2°o
r3), first, specific examples of A include the following.

A-5 p' 2H11 Specific examples of Cp include Cp-2 Cp-3 cp-5 (R: alkyl, aryl, etc.) p-6. The central skeleton A and the coupler Cp form a pigment serving as a charge-generating substance by appropriate combination.

The charge-generating layer can be formed by dispersing the above-mentioned charge-generating substance in a suitable binder and coating it on a support, or can be obtained by forming a vapor-deposited film using a vacuum evaporation device. Can be done. The binder can be selected from a wide range of insulating resins and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate,
Acrylic resin, polyacrylamide resin, polyamide,
Examples include insulating resins such as polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone.

The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. Organic solvents used during coating include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and amides such as N,N-dimethylformamide and N,N-dimethylacetamide. , sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, and aliphatics such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene. Halogenated hydrocarbons or aromatics such as benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, etc. can be used.

The charge generation layer contains as much of the organic photoconductor as possible in order to obtain sufficient absorbance and in order to inject carriers into the charge transport layer within the lifetime of the generated charge carriers, a thin film layer, e.g. 5 μm or less, preferably 0.01 μm
A thin film layer having a thickness of m-1 μm is preferable.

This means that most of the incident light is absorbed by the charge generation layer, generating a large number of charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, and are absorbed by the charge transport layer. This is due to the need to inject.

A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a conductive support.

As the conductive support, the support itself is conductive, such as aluminum, aluminum alloy, copper, zinc,
Stainless steel, etc. can be used, and in addition, plastics having a layer formed by vacuum evaporation of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc., conductive particles (for example, aluminum powder) can be used. , titanium oxide, tin oxide, zinc oxide, carbon black, silver particles, etc.) together with a suitable binder on a plastic or metal support, a support in which plastic or paper is impregnated with conductive particles, or a conductive support. For example, a plastic having a polymer with a chemical nature can be used.

A subbing layer having barrier and adhesive functions can also be provided between the conductive support and the photosensitive layer.

The subbing layer can be formed from casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. .

The thickness of the undercoat layer is 0.1 μm to 5 μm, preferably 0.1 μm to 5 μm.
A suitable thickness is 5 μm to 3 μm.

In another specific example of the present invention, the above-mentioned disazo pigment or pyrylium dyes, thiapyrylium dyes, selenapyrylium dyes, and benzopyrylium dyes disclosed in U.S. Pat. No. 3,554,745, U.S. Pat. , benzothiapyryllium dye, naphthopyryllium dye, naphthothiapyrylium dye, and other photoconductive pigments and dyes can also be used as sensitizers.

In another specific example, a eutectic complex of a pyrylium dye and an electrically insulating polymer having an alkylidene diarylene moiety, as disclosed in US Pat. No. 3,684,502, can also be used as a sensitizer. This eutectic complex is, for example, 4
-[4-bis-(2-chloroethyl)aminophenyl”
J-2,6-cyphenylthiapyrylium perchlorate and poly(4,4'-isobropylidene diphenylene carbonate) were mixed in a halogenated hydrocarbon solvent (e.g. dichloromethane, chloroform, carbon tetrachloride, l,!-dichloroethane). , 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, bromobenzene, l
, 2-dichlorobenzene) and then mixed with a non-polar solvent (e.g. hexane, octane, decane, 2,2.
A particulate eutectic complex is obtained by adding 4-trimethylbenzene and ligroin. The electrophotographic photoreceptor in this specific example includes styrene-butadiene copolymer, silicone resin, vinyl resin, vinylidene chloride-acrylonitrile copolymer styrene-acrylonitrile copolymer, vinyl acetate-vinyl chloride copolymer,
Polyvinyl butyral, polymethyl methacrylate, poly-N-nibutyl methacrylate, polyesters, cellulose esters, etc. can be contained as a binder.

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

Hereinafter, the present invention will be explained according to examples.

Example 1 5 g of a disazo pigment represented by the following structural formula was mixed with 2 g of butyral resin (degree of butyralization: 63 mol%) and 100 m of cyclohexanone.
j? A coating solution was prepared by dispersing the mixture in a sand mill for 24 hours together with a solution dissolved in the solution.

This coating solution was coated onto an aluminum sheet using a Mayer bar so that the dry film thickness was 0.2 μm to prepare a charge generation layer.

Next, as a charge transport substance, the above-mentioned exemplified compound Nα(6)10
g and polycarbonate resin (weight average molecular weight 20,000
) log was dissolved in 70 g of monochlorobenzene, and this solution was coated on the charge generation layer using a Mayer bar to form a charge transport layer with a dry film thickness of 20 μm, thereby producing a laminated electrophotographic photoreceptor.

The electrophotographic photoreceptor produced in this way was manufactured by Kawaguchi Electric Co., Ltd.
Electrostatic copying paper tester Model-3P-428 was used to statically charge the corona at 15 KV, and the test was carried out in the dark at 1
After being held for a second, it was exposed to light at an illuminance of 20fux and the charging characteristics were examined.

The charging characteristics include the surface potential (VO) and the amount of light exposure required to attenuate the potential (V,) when dark decaying for one second (
8%) was measured.

Furthermore, in order to measure the fluctuations in bright area potential and dark area potential during repeated use, the photoreceptor fabricated in this example was
c) Paste it on the photosensitive drum cylinder of a copying machine (NP-3525: Canon) and make 5,000 copies using the same machine. Changes in bright area potential (VL) and dark area potential (VD) at the initial stage and after 5,000 copies have been made. was measured. In addition, the early V.

and ■ were set to -700V and -200V, respectively. The results are shown below.

An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the pigments shown in Table 1 were used.

The electrophotographic properties of each photoreceptor were measured in the same manner as in Example 1.

For comparison, an electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that a compound having the following structural formula was used as a charge transport material, and its electrophotographic properties were measured. The results for each are shown below.

Examples 2-10. Comparative Examples 1 to 3 In each of these Examples, exemplified compounds Na (1), (2), (5), and (8) were used instead of exemplified compound Na (6) as the charge transport substance used in Example I. ,(10),
(12), (15).

, (20), and (23), and the following structural formula (% formula %) was used as a charge generating substance.As is clear from the above results, the compound of the present invention has superior sensitivity and potential stability during durability compared to the comparative compounds. It is clear that

Example 11 A solution prepared by dissolving 5 g of methoxymethylated nylon resin (number average molecular weight FF 132,000) and alcohol-soluble copolymerized nylon resin (number average molecular weight 29,000 log) in 95 g of methanol was applied onto an aluminum substrate using a Mayer bar.
Film thickness after drying (1 μm undercoat layer was provided.

Next, 10 g of a charge generating substance represented by the following structural formula, 5 g of butyral resin (degree of butyralization: 63 mol%), and 200 g of dioxane,
Dispersion was carried out for 48 hours using a ball mill disperser. This dispersion was applied onto the previously produced undercoat layer by a blade coating method to produce a charge generation layer having a thickness of 0.15 μm after drying.

Next, the above exemplary compound No. (3) 10 g, polymethyl methacrylate resin (weight average molecule i 50,000)
10 g of the solution was dissolved in 70 g of monochlorobenzene and coated on the previously formed charge generation layer by a blade coating method to prepare a charge transport layer having a thickness of 19 μm after drying.

A corona discharge of 15 KV was applied to the photoreceptor thus produced. The surface potential at this time was measured (initial potential V).

Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 1 second. Sensitivity was evaluated by measuring the exposure amount (8%, μJ/crrr) required to attenuate the potential v1 after dark decay to %. At this time, a gallium/aluminum/propylene ternary semiconductor laser (output 5 mWH oscillation wavelength 780 nm) was used as a light source. These results were as follows.

vo : -701V V, : -693V 8% : 0.51 pJ/cm"Next, a laser beam printer (LBP-C) which is a reversal development type electrophotographic printer equipped with the same semiconductor laser as above.
The above photoreceptor was set in a camera (X: manufactured by Canon), and an actual image forming test was conducted.

The conditions are as follows. −Surface potential after next charging; −7
00V, surface potential after image exposure; -150V (exposure amount 2.0 μJ/crrr), transfer potential; +700V, developer polarity; negative polarity, process speed; 50mm/
5ees development conditions (development bias), -450V, image exposure scan method; image scan, -exposure before next charging;
Full red exposure of 501ux-8eC and image formation were carried out by line scanning a laser beam in accordance with character signals and image signals, and good prints were obtained for both characters and images. Furthermore, when 3,000 images were printed continuously, stable and good prints were obtained from the initial stage up to 3,000 images.

Example 12 10 g of titanyloxyphthalocyanine was mixed with 48 g of dioxane.
The mixture was added to a solution of 5 g of phenoxy resin dissolved in 5 g of phenoxy resin, and dispersed in a ball mill for 2 hours. This dispersion was applied onto an aluminum sheet using a Mayer bar, dried at 80°C for 2 hours, and then dried at 80°C.
A charge generation layer having a thickness of 5 μm was prepared. Next, the exemplified compound N
o, (7) l Og , bisphenol 2 type polycarbonate resin (weight average molecular fi 50000) lo
g dissolved in 70 g of monochlorobenzene was applied onto the previously formed charge generation layer using a Mayer bar, and
It was dried at ℃ for 1 hour to produce a 19 μm charge transport layer. The photoreceptor thus produced was measured in the same manner as in the example. The results are shown below.

Vo: -699V V,: -693V E'4: 0.61 μl crd Example 13 3 g of 4-(4-dimethylaminophenyl)-2,6-cyphenylthiapyrylium perchlorate and Exemplary Compound No. as a charge transport substance, 5 g of (18), polyester resin (weight average molecular fi 49000) toluene (
50 parts by weight) - 100 g of dioxane (50 parts by weight) solution
and dispersed in a ball mill for 6 hours. This dispersion was applied onto an aluminum sheet using a Mayer bar, and heated at 100℃ for 2 hours.
It was dried for a period of time to produce a 15 μm photosensitive layer. The photoreceptor thus produced was measured in the same manner as in Example 1. The results are shown below.

Vo: -701V V,: -697V E'4: 2,11ux*5ec (Initial) VD: -700V VL: -200V (After 5000 sheets durability) VD: -682V Vt: -215V Example! 4 Place casein ammonia aqueous solution (casein 1) on an aluminum plate.
1.2 g of 28% ammonia water, 1 g of 28% ammonia water, and 222 ml of water were applied using a Meyer bar to form a subbing layer with a dry film thickness of 1 μm. A photoreceptor was prepared in the same manner as in Example 1, except that the charge transport layer and charge generation layer of Example 3 were sequentially laminated thereon, and the layer structure was different, and the charging characteristics were measured in the same manner as in Example 1. did. However, the charging polarity was set to ■. The results are shown below.

vo: ■697v vl: ■685v Ey2: 2.51ux・sec Example 15 Soluble nylon (6-66-610-12
A 5% methanol solution of (quaternary nylon copolymer) was applied to prepare a subbing layer having a dry film thickness of 0.5 μm.

Next, 5 g of the pigment represented by the following structural formula was added to 95 ml of tetrahydrofuran.
The mixture was dispersed in a medium sand mill for 200 hours. Next, 5 g of Exemplified Compound No. (14) and bisphenol 2 type polycarbonate resin (weight average molecular weight 50.00
0) 10g to 30ml of monochlorobenzene! The solution was added to the previously prepared dispersion and further dispersed using a sand mill for 2 hours. This dispersion was applied onto the previously formed subbing layer using a Mayer bar so that the film thickness after drying would be 20 μm, and then dried. The electrophotographic properties of the photoreceptor thus produced were measured in the same manner as in Example 1.

The results are shown below.

Vo: -700V V,: -691V Ey2: 3.01ux*sec [Effects of the Invention] As explained above, the electrophotographic photoreceptor containing the triarylamine compound according to the present invention has high sensitivity and can be repeatedly charged. - It is possible to provide an electrophotographic photoreceptor with excellent durability and small fluctuations in bright area potential and dark area potential during continuous image formation by exposure.

[Brief explanation of the drawing]

FIG. 1 is an infrared absorption spectrum diagram (KBr tablet method) of compound example No. (2) obtained in the synthesis example.

Claims (1)

[Scope of Claims] An electrophotographic photoreceptor having a photosensitive layer on a conductive support, characterized in that the photosensitive layer contains a triarylamine compound represented by the following general formula [I]. . General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. or an aromatic heterocyclic group that may have a substituent.)