JPH02183259A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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, inorganic photoconductive materials such as selenium, zinc oxide, and cadmium sulfide have been widely used in electrophotographic photoreceptors, but in recent years, research using organic photoconductive materials has been actively conducted. The basic characteristics required of an electrophotographic photoreceptor are: ■) It must be charged to an appropriate potential by corona discharge in a dark place, 2) It must have good charge retention in a dark place, and 3) It must be able to resist light. Examples include rapid discharge of charges upon irradiation, and 4) low residual potential after irradiation with light.

Although electrophotographic photoreceptors using conventional inorganic photoconductive materials have some basic characteristics, they have manufacturing problems such as difficulty in film formation, poor flexibility, and high manufacturing costs. I am holding.

On the other hand, organic photoconductive materials have the advantages of being lightweight, having excellent film formability and flexibility, and having low manufacturing costs.
In recent years, many electrophotographic photoreceptors using organic photoconductive materials have been proposed and put into practical use.

A typical organic photoconductive material is poly-N-
Various organic photoconductive polymers including vinylcarbazole have been proposed, but these polymers are superior to inorganic photoconductive materials in terms of light weight and film formability, but they have poor sensitivity and It has been difficult to put it into practical use because it is inferior in terms of durability, stability against environmental changes, mechanical strength, etc. In addition, hydrazone compounds disclosed in U.S. Patent No. 4,150,987 and the like, U.S. Patent No. 3,837,851
Triarylpyrazoline compounds described in JP-A-51-94828, JP-A-51-94829, etc.
Low-molecular organic photoconductors such as the 9-styrylanthracene compound described in Japanese Patent Application Publication No. 2003-100000 have been proposed. These low-molecular-weight organic photoconductors have been able to overcome the film-forming problems that had been a problem in the field of organic photoconductive polymers by appropriately selecting the binder used. , cannot be said to be sufficient in terms of sensitivity.

For this reason, in recent years, a photosensitive layer having a laminated structure in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer has been proposed. An electrophotographic photoreceptor having this laminated structure as a photosensitive layer can now be improved in terms of sensitivity to visible light, charge retention power, surface strength, and the like.

Among these, many organic compounds have been cited as charge transport substances. For example, JP-A-52-722
Pyrazoline compound of Publication No. 31, U.S. Pat. No. 842,43
No. 1 and JP-A-55-52063 amine compounds,
JP-A-54-151955 and JP-A-58-19
A stilbene compound disclosed in Japanese Patent No. 8043 is known.

Also, JP-A-54-59142, JP-A-61-283
Carbazole compounds described in No. 341 and JP-A No. 63-58451 have also been reported as charge transport materials.

However, conventional electrophotographic photoreceptors using low-molecular-weight organic compounds as charge transport materials do not necessarily have sufficient sensitivity and characteristics, 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.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic photoreceptor that eliminates various drawbacks of conventional photoreceptors.

Another object of the present invention is to provide an electrophotographic photoreceptor 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, wherein the photosensitive layer contains a compound represented by the following general formula [■].

In the formula, RI r R2+ R3 and R4 represent an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. Alkyl groups include methyl and ethyl.

Examples of the aralkyl group include benzyl, phenethyl, etc.; examples of the aryl group include phenyl, diphenyl, naphthyl, etc.;
Examples of the heterocyclic group include pyridyl quinolyl, carbazolyl, thienyl, furyl, and the like. R6 represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group.

Specific examples of these groups are the same as above.

Each of the groups represented by R1 to R5 may have a substituent, and these substituents include a hydroxyl group, fluorine,
Halogen atoms such as chlorine, bromine, and iodine, alkyl groups such as methyl, ethyl, propyl, and butyl, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, aryl groups such as phenyl, diphenyl, and naphthyl, and aryloxy such as phenyloxy. group, amino group, dimethylamino,
Diethylamino, diphenylamino, ditolylamino.

Examples include substituted amine groups such as cyanidylamino, nitro groups, cyano groups, and acyl groups such as acetyl and benzoyl.

Furthermore, in the present invention, at least one of R3-R6 is an aryl group.

Among these, any one of R, -R4, and even R
If 1 and R3, especially R, , R2, R3 and R4 are all aryl groups, the electrophotographic properties will be even better.

Representative examples of the compounds represented by the general formula [I] are listed below.

(That's more than 100;) Next, a synthesis example of the above compound will be shown.

(Synthesis method of compound example No. 3) 3.6-cyamitsu-N-ethylcarbazole 3g (1
3゜3mmol), iodobenzene 30g (147m
mol), anhydrous potassium carbonate 12.5g (90.6m
mol) and 5 g of copper powder were stirred and heated under reflux for 10 hours. After cooling, the mixture was filtered with suction, and iodobenzene was removed from the filtrate under reduced pressure. Methanol was added to the residue to precipitate crystals, and the crude crystals were separated and purified using a silica gel column to obtain 4.2 g of the target compound (3) (yield 59.7%).
. The solid point was 219.4-220.5°C. The elemental analysis was as follows as C3aH3+N3.

Calculated value % Actual value % C86,1786,15 H5,905,91 N 7.93 7.94 The infrared absorption spectrum (KBr tablet method) is shown in FIG.

As mentioned above, this compound can be obtained in one reaction and can be produced at low cost.

Note that compounds other than those on the synthesis side are also synthesized using the same method.

In a preferred embodiment of the present invention, a compound represented by the above general formula can be used as a charge transport material in 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 is preferably formed by applying a solution prepared by dissolving the compound represented by the above general formula and a binder in a suitable solvent and drying the solution. Examples of the binder used here include polyarylate resin, polysulfone resin, polyamide resin, acrylic resin, and acrylonitrile resin.

Methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane or copolymer resin such as styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, etc. can be mentioned. In addition to such insulating polymers, polyvinylcarbazole.

Organic photoconductive polymers such as polyvinylanthracene and polyvinylpyrene can also be used.

The blending ratio of the binder and the charge transport material is 10 parts of the binder.
It is preferable that the charge transport material is 10 to 500 parts by weight per 0 parts by weight.

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, trichlorethylene, etc., or aromatics such as benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating can be carried out using a coating method such as a dip coating method, a spray coating method, a spinner 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 preferably carried out at a temperature of 30° C. to 200° C. for a period of 5 minutes to 2 hours, either stationary or under ventilation.

The charge transport layer can also 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 Complex, 1,
Examples include antioxidants such as 4-diazavinchlo[2,2,2]octane.

The charge generation layer used in the present invention includes selenium, selenite,
Inorganic charge-generating substances such as amorphous silicon, pyrylium dyes, thiapyrylium dyes, azulenium dyes, and thiacyanine dyes.

Cationic dyes such as quinocyanine dyes and azulenium dyes, polycyclic quinone pigments such as squbarium salt dyes, phthalocyanine pigments, anthorone pigments, dibenzpyrenequinone pigments, and pyranthrone pigments, indigo pigments, and quinacridone pigments. Materials selected from organic charge generating substances such as , azo pigments, etc. can be used.

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

As a general formula of an azo pigment, if we express the central skeleton as A1 A÷N = N Cp) n coupler part as Cp (here n = 2゜o
r3), first, specific examples of A include the following.

p' Specific examples of Cp include Cp-3 (R: alkyl, aryl, etc.). 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 variety of insulating resins and organic photoconductive polymers such as boryl 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
Preferably, the r' and 'i film layers have a film thickness of m x 14 m. This means that most of the incident light JIi is absorbed by the charge generation layer, generating many charge carriers.
Furthermore, this is due to the fact that the generated charge carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping.

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 embodiment of the present invention, the above-mentioned disazo pigment or the pyrylium dye disclosed in U.S. Pat. No. 3,554,745, U.S. Pat. Photoconductive pigments and dyes such as thiapyrylium dyes, selenapyrylium dyes, benzopyrylium dyes, benzothiapyryllium dyes, naphtopyrylium dyes, and naphthothiapyrylium dyes can also be used as sensitizers.

In another specific example, U.S. Patent No. 3,684,50
A eutectic complex of a pyrylium dye and an electrically insulating polymer having an alkylidene diarylene moiety as disclosed in Publication No. 2 can also be used as a sensitizer. This eutectic complex combines, for example, 4-[4-bis-(2-chloroethyl)aminophenyl]-2,6-cyphenylthiapyrylium verchlorate and poly(4,4'-isopropylidene diphenylene carbonate) with a halogen Hydrocarbon solvents (e.g. dichloromethane, chloroform, carbon tetrachloride, 1.1-
Dichloroethane, 1,2-dichloroethane, 1,1.2
- trichloroethane, chlorobenzene, bromobenzene, 1,2-dichlorobenzene) and then dissolved in a non-polar solvent (e.g. hexane, octane, decane, 2-dichlorobenzene).
, 2.4 trimethylbenzene, obtained as a particulate eutectic complex by adding ligroin. The electrophotographic photoreceptor in this specific example includes styrene-butadiene copolymer silicone resin, vinyl resin, and vinylidene chloride.
Acrylonitrile copolymer Styrene-acrylonitrile copolymer, vinyl acetate-vinyl chloride copolymer, polyvinyl butyral, polymethyl methacrylate, poly-N-butyl methacrylate, polyesters,
Cellulose esters and the like can be contained as a binder.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines but also in a wide range of electrophotographic applications such as laser beam printers, CRT printers, and electrophotographic plate making systems.

According to the present invention, it is possible to provide a highly sensitive electrophotographic photoreceptor, and the present invention has the advantage that fluctuations in bright area potential and dark area potential are small when charging and exposure are repeatedly performed.

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.
A coating solution was prepared by dispersing the solution in a sand mill for 24 hours together with the solution dissolved in 1.

This coating solution was applied onto an aluminium root using a Mayer bar so that the dry film thickness was 0.2 μm to form a charge generation layer.

Next, as a charge transport substance, the above-mentioned exemplified compound Nα(2)lo
g and polycarbonate resin (weight average molecular fi2000
0) was dissolved in 70 g of monochlorobenzene, and this solution was applied onto the charge generation layer using a Mayer bar to form a charge transport layer having a dry thickness of 20 μm, thereby producing an 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 holding for a second, the illuminance was 20J! It was exposed to UV light and its charging characteristics were investigated.

The charging characteristics include the surface potential (V O) and the exposure f required to attenuate the potential when dark decaying for 1 second (■1).
f1 (E%) 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 was attached to the photosensitive drum cylinder of a copier (NP-3525: manufactured by Canon), and 5,000 copies were made using the same machine. Changes in bright area potential (VL) and dark area potential (VD) at the initial stage and after 5,000 copies were made. was measured. In addition, the early V.

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

Table 1 Examples 2-10. Comparative Examples 1 to 2 In each of these Examples, exemplified compounds Nα (3), (5), (12), (15 ), (19)
, (30).

An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that (34), (37), and (40) were used, and a pigment having the structural formula below was used as the charge generating substance.

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 using a compound having the following structural formula as a charge transport material, and its electrophotographic properties were measured.

The respective results are shown below.

Comparative compound (described in JP-A-63-58451) (JP-A-54-58451)
59142) (described in JP-A No. 62-283341) As is clear from the above examples and comparative examples, high sensitivity and high Durability can be achieved.

The dispersion of Example 11 was applied onto the previously prepared subbing layer by a blade coating method to form a charge generation layer having a thickness of 0.15 μm after drying.

A solution dissolved in 95 g of alcohol was applied using a Mayer bar to provide an undercoat layer having a thickness of 1 μm after drying.

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 were added.
Dispersion was carried out for 48 hours using a ball mill disperser. This was dissolved in 70 g of monochlorobenzene and coated on the previously formed charge generation layer by a blade coating method to produce a charge transport layer having a dry film thickness of <19 μm.

A corona discharge of 15 KV was applied to the photoreceptor thus produced. At this time, we want to measure the surface potential (initial potential Vo).

Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 1 second. Sensitivity is determined by the amount of exposure required to attenuate the potential v1 after dark decay (E 'iA + μJ/c
rrr). At this time, a gallium/aluminum/arsenic ternary semiconductor laser (output: 5 mW; oscillation wavelength: 780 nm) was used as a light source. These results were as follows.

Vo: -720V ■+Near 13V E H: 0.33 tl J/cm2 Next, we used a laser beam printer (LBP-C), which is a reversal development type electrophotographic printer equipped with the same semiconductor laser as above.
X: manufactured by Canon) was set in place of the above photoreceptor, and an actual image forming test was used. The conditions are as follows.

-Surface potential after next charging: -700V, surface potential after image exposure: -150V (Exposure f12.Op J/c ff
1), Transfer potential: +700V, Developer polarity: Negative polarity,
Process speed: 50mm/sec, development conditions (development bias): -450V, image exposure scanning method: image scan, - exposure before next charging: 501ux-5ec red full-surface exposure, image formation uses a laser beam to send character and image signals I performed a line scan according to the method and obtained good prints for both text 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 Titanyloxyphthalocyanine log to dioxane 48
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 and dried at 80° C. for 2 hours to produce a charge generation layer with a thickness of 0.5 μm. Next, 10 g of the exemplified compound No. (28), 10 g of bisphenol 2 type polycarbonate resin (weight average molecular weight 50.000)
A solution prepared by dissolving 70 g of monochlorobenzene was applied onto the previously formed charge generation layer using a Mayer bar, and heated at 110°C.
The mixture was dried for 1 hour to produce a charge transport layer with a thickness of 19 μm. The thus produced photoreceptor was measured in the same manner as in Example 11. The results are shown below.

Vo: -715V V,: -709V EH: 0.48 μJ/c n? Example 13 3 g of 4-(4-dimethylaminophenyl)-2,6-cyphenylthiavirylium perchlorate and 5 g of the above-mentioned exemplified compound No. (31) as a charge transport substance.

A polyester resin (weight average molecular weight 49,000) was mixed with 100 g of a toluene (50 parts by weight)-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
It was dried at 0° C. for 2 hours to produce a photosensitive layer with a thickness of 15 μm. The photoreceptor thus produced was measured in the same manner as in Example. The results are shown below.

Vo: -709V (initial)
(After 5000 sheets durability) V, ,: -702V
VD: -700V Vo: -690V
Ey2: 1.9fuxΦsec VL: -20
0V Vt,: -214V Example 14 Ammonia aqueous solution of casein (casein 1
1.2 g of 28% ammonia water and 222 ml of water were applied using a Meyer bar to form a subbing layer with a dry thickness of 1 μm. The charge transport layer and charge generation layer of Example 5 were sequentially laminated thereon, and a photoreceptor was prepared in exactly the same manner as in Example 1 except that the layer structure was different. It was measured. However, the charging polarity was O. The results are shown below.

vo: ■698v Vl: ■683v E! /6: 2.3 fuxesec Example 15 Soluble nylon (6-66-610-12
A 5% methanol solution of (quaternary nylon copolymer) was applied to prepare a subbing layer with a dry film thickness of 0.5 μm.

Next, 5 g of a pigment represented by the following structural formula was dispersed in 95 ml of tetrahydrofuran using a sand mill for 200 hours. Next, as a charge transport material, 5 g of the exemplary compound No. (25) and bisphenol Z type polycarbonate resin (weight average molecular weight 50.0
00) A solution of tog in 30 ml of monochlorobenzene was added to the previously prepared dispersion, and the mixture was further dispersed in 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: '716V V,: -705V Ej4: 2.81ux11sec [Effects of the Invention] As explained above, the electrophotographic photoreceptor containing the carbazole compound according to the present invention has high sensitivity, and also has high sensitivity due to repeated charging and exposure. It is possible to provide an electrophotographic photoreceptor with excellent durability and small fluctuations in bright area potential and dark area potential during image formation.

[Brief explanation of the drawing]

FIG. 1 shows an infrared absorption spectrum of the compound of the present invention measured by the KBr tablet method.

Claims (1)

[Claims] (1) An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a carbazole compound represented by the following general formula [I]. General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. , aralkyl group,
Indicates an aryl group or a heterocyclic group. However, R_1～
At least one or more of R_5 is an aryl group. )