JPS6219734B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a novel photoreceptor having a photosensitive layer containing a disazo pigment. Conventionally, amorphous selenium,
Inorganic photoconductive materials such as selenium alloys, cadmium sulfide, and zinc oxide, polyvinyl carbazole, and derivatives thereof are widely known. It is well known that amorphous selenium or selenium alloys have extremely excellent properties as electrophotographic photoreceptors and are widely used in practical use. However, the sensitive wavelength region of amorphous selenium is the blue region and has almost no sensitivity in the red region. Various methods have been proposed to extend the photosensitivity to long wavelengths, but there are many restrictions on the selection of the sensitive wavelength range, and the photosensitivity to long wavelengths is not sufficient. Even when zinc oxide or cadmium sulfide is used as a photoreceptor, its sensitivity wavelength range is narrow, and it is necessary to add various sensitizers for practical use. Polyvinylcarbazole, which is widely known as an organic photoconductive material, has excellent transparency, film-forming properties, flexibility, and hole transport properties, but polyvinylcarbazole itself has a visible light range of 400 to 700 nm.
has the disadvantage of having almost no sensitivity. To improve these shortcomings, the special public service was developed in the 1970s.
No. 10496 describes polyvinylcarbazole and 2,
A photoreceptor is disclosed in which a charge transfer complex is formed with 4,7-trinitrofluorenone. Other photoreceptors in which amorphous selenium or a selenium alloy is used as a charge carrier generation layer and a charge transfer layer is laminated thereon, and each layer has a separate role, are disclosed in Japanese Patent Publication No. 45-5349 and Japanese Patent Publication No. 49-3168. , Japanese Patent Publication No. 50-14914, Japanese Patent Publication No. 10982-1982, etc. In addition, the following photoreceptors have been developed in which a charge carrier generation layer is made of various pigments and a charge transfer layer is provided thereon. USP 3837851 describes a photoreceptor having a charge carrier generation layer and a charge transport layer containing at least one triallylpyrazoline; USP 3850630 describes a photoreceptor comprising a transparent charge transport layer and a charge carrier generation layer comprising an indigoid pigment; USP 3871882 discloses a photoreceptor consisting of a charge carrier generation layer made of a perylene pigment derivative and a charge transfer layer made of a condensate of 3-bromopyrene and formaldehyde, JP-A-53
Japanese Patent No. 133445 discloses a photoreceptor comprising a transparent charge transfer layer and a charge carrier generation layer made of a disazo pigment having a stilbene skeleton. Although some of these photoreceptors are already in use on the market, the current situation is that a photoreceptor that satisfactorily satisfies various properties has not yet been obtained. As a result of various studies, the present inventors have found that a compound represented by the general formula below works effectively as a charge carrier generating substance for an electrophotographic photoreceptor, and has completed the present invention. The main object of the present invention is to provide an electrophotographic photoreceptor that has excellent reproducibility in the visible light region by providing a charge carrier generating material that has excellent sensitivity on the short wavelength side. That is, the present invention provides the following general formula on a conductive support: [However, A is

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[expression] or

[Formula] (where, A heterocyclic ring such as or a substituted product thereof, Ar2 and Ar3 are an aromatic ring such as a benzene ring or a naphthalene ring or a substituted product thereof, R ₁ and R ₃ are hydrogen, a lower alkyl group, a phenyl group or a substituted product thereof, R ₂ represents a lower alkyl group, a carboxyl group, or an ester thereof). ] The present invention provides an electrophotographic photoreceptor characterized by having a photosensitive layer containing a disazo pigment represented by the following as an active ingredient. Specific examples of the compounds having the above general formula used in the present invention are shown in the following structural formulas.

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[Table] These disazo pigments are new compounds that use 1,2-bis(4-aminostyryl)benzene as a starting material, diazotize it and isolate it as a tetrazonium salt, and then dissolve it in an appropriate organic solvent, For example, in N,N-dimethylformamide,
It can be produced by carrying out a coupling reaction in the presence of a coupler corresponding to each of the above-mentioned pigments and an alkali. For example, the method for producing pigment No. 1 is as follows. Production example 1,2-bis(4-aminostyryl)benzene
After taking 15.0 g in 700 ml of water and adding 25 ml of concentrated hydrochloric acid, the resulting solution was cooled to 0°C, and a solution of 7.0 g of sodium sulfite dissolved in 25 ml of water was added to it at 0 to 5°C for 40 minutes. dripped. After stirring at the same temperature for 30 minutes, 30 ml of 42% borohydrofluoric acid was added to the reaction solution, and the precipitated crystals were separated, washed with water, and dried to produce 22.8 g (yield 93.1%) of tetrazonium. Difluoroborate was obtained as orange-red crystals. Decomposition point 122℃ or higher, IR absorption spectrum (KBr
In the tablet method), absorption based on N ₂ occurred at 2250 cm ^-1 . Next, the tetrazonium salt 2.0 obtained in this way
2-hydroxy-3- as g and coupler
2.2g of naphthoic acid anilide was cooled with N,N-
The mixture was dissolved in 370 ml of dimethylformamide, and a solution consisting of 3.9 g of sodium acetate and 62 ml of water was added dropwise thereto at a temperature of 4 to 8 DEG C. over an hour, followed by stirring at room temperature for about 3 hours. After that, remove the precipitate,
Wash three times with 300 ml of water and then eight times with 300 ml of N,N-dimethylformamide. Furthermore, the remaining N,N-dimethylformamide was washed away with acetone, and the resulting blue-black crystals were dried at a temperature of 70°C under a reduced pressure of 2 mmHg to form No. 1 disazo pigment.
Obtain 3.2 g (93% yield). Melting point is 300℃ or higher. The results of elemental analysis are as follows. Calculated value (%) Actual value (%) C 78.11 78.01 H 4.69 4.68 N 9.76 9.75 In addition, in the IR absorption spectrum (KBr tablet method)
Absorption due to secondary amide was observed at 1680 cm ^-1 . The photoreceptor of the present invention contains the above-mentioned disazo pigments, and can take the forms shown in FIGS. 1 to 3 depending on the application of these pigments. The photoreceptor shown in FIG. 1 comprises a conductive support 1, a charge carrier generation layer 5 mainly composed of a disazo pigment 3, and a charge transfer layer 6 mainly composed of a charge transfer substance. In the photoreceptor shown in FIG. 1, imagewise exposed light passes through the charge transfer layer and reaches the charge carrier generation layer 5, where charge carriers are generated in the disazo pigment 3 in that area, while the charge transfer layer 6 In this method, charge carriers are injected and transferred, and the mechanism is that the charge carriers necessary for light attenuation are generated by a disazo pigment, and the charge carriers are transferred by a charge transfer layer. The photoreceptor shown in FIG. 2 has a photosensitive layer 2' formed on a conductive support 1, which mainly comprises a disazo pigment 3, a charge transfer medium 4 consisting of a charge transfer substance and an insulating binder. Here again, the disazo pigment is a charge carrier generating substance. The first photoreceptor
It is also possible to reverse the charge carrier generation layer and the charge transfer layer shown in the figure. The photoreceptor shown in FIG. 3 has a photosensitive layer 2'' consisting of a disazo pigment 3 (here used as a photoconductive material) and an insulating binder on a conductive support 1. To create the photoreceptor shown in the figure, a disazo pigment can be vacuum deposited on a conductive support using the vacuum deposition method described in USP 3973959, USP 3996049, etc., or fine particles of a disazo pigment can be applied with a binder if necessary. Dispersed in a suitable solvent, coated and dried on a conductive support, and if necessary, the surface is finished by buffing or the like as shown in JP-A-51-90827. Alternatively, after adjusting the film thickness, a solution containing a charge transfer substance and a binder is coated and dried. The disazo pigment particles are dispersed in a binder solution, and the disazo pigment is dispersed in a binder solution, and then the disazo pigment is dispersed in a binder solution, and then the disazo pigment is dispersed in a binder solution, and then the disazo pigment is dispersed in a binder solution, and then the disazo pigment is dispersed in a binder solution. It may be applied and dried on a support. In any of the above cases, the disazo pigment used in the present invention is used after being ground to a particle size of 5 μ or less, preferably 2 μ or less, using a ball mill or the like. This is carried out using a doctor blade, dipping, wire bar, etc. The thickness of the photosensitive layer is as shown in Figure 1, and the thickness of the charge carrier generation layer is 0.01 to 5μ, preferably 0.05 to 2μ.This thickness is 0.01μ or less. If it is, the generation of charge carriers will not be sufficient, and if it is more than 5μ, the residual potential will be too high to be practical.The thickness of the charge transfer layer is 3 to 50μ, preferably 5 to 20μ. If it is less than 3μ, the amount of charge is insufficient, and 50μ
If it is more than that, the residual potential is high and it is not practical. The proportion of the charge transfer substance in the charge transfer layer is 10 to 95% by weight, preferably 30 to 90% by weight. When the proportion of the charge transfer substance is less than 10% by weight, almost no charge transfer occurs, and when it is more than 95% by weight, the mechanical strength of the photoreceptor film is so poor that it cannot be put to practical use. Further, in the photoreceptor shown in FIG. 3, the thickness of the photosensitive layer is about 3 to 50 μm, preferably 5 to 20 μm, and the proportion of the disazo pigment in the photosensitive layer is 30 to 70% by weight, preferably about 50 μm. Weight % is appropriate. Note that a plasticizer can be used together with a binder when producing any of the photoreceptors shown in FIGS. 1 to 3. The conductive support used in the photoreceptor of the present invention may be a metal plate made of aluminum, copper, zinc, etc., a plastic sheet made of polyester, or a plastic film on which a conductive material such as aluminum or SnO ₂ is vapor-deposited, or a conductive support material such as aluminum, SnO2, etc. Treated paper, etc. is used. As a binder, polyamide, polyurethane,
Examples include condensation resins such as polyester, epoxy resin, polyketone, and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, and polyacrylamide, but all resins that are insulating and adhesive are used. Can be used. Examples of the plasticizer include halogenated paraffin, polychlorinated biphenyl, dimethylnaphthalene, and dibutyl phthalate. In addition, silicone oil or the like may be added to improve the surface properties of the photoreceptor. Examples of charge transfer substances include vinyl polymers such as poly-N-vinylcarbazole, polyvinylindoquinoxaline, polyvinyldibenzothiophene, polyvinylanthracene, and polyvinylacridine, bromopyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, Condensation resins such as 2,4,7-trinitro-
9-fluorenone, 2,6,8-trinitro-
4H-indeno[1,2-b]thiophene-4-
on, 2,8-dinitrodibenzothiophene,
1,3,7-trinitrodibenzothiophene-
5,5-dioxide, 1,3,7,9-tetranitrobenzo[c]cinnoline-5-oxide, 2,4,8-trinitrothioxanthone, 1
-Brompyrene, N-ethylcarbazole, 2-
Phenyl indole, 2-phenylnaphthalene,
2,5-bis(4-diethylaminophenyl)-
1,3,4-oxadiazole, 2,5-bis(4-diethylaminophenyl)-1,3,4-
Triazole, 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, 2-phenyl-4-(4
-diethylaminophenyl)-5-phenyloxazole, triphenylamine, tris(4-diethylaminophenyl)methane, 3,6-bis(dibenzylamino)-9-ethylcarbazole, 4,4'-bis(dimethylamino)-9-ethylcarbazole, benzylamino) diphenylmethane, 4,4'-bis(dibenzylamino)diphenyl ether, 1,1-bis(4-dibenzylaminophenyl)propane, 2-(α-naphthyl)-5-(4-diethylamino) phenyl)-
1,3,4-oxadiazole, 2-styryl-
5-(3-N-ethylcarbazolyl)-1,3,
4-Oxadiazole, 2-(4-methoxyphenyl)-5-(3-N-ethylcarbazolyl)-
1,3,4-oxadiazole, 2-(4-diethylaminophenyl)-5-(3-N-ethylcarbazolyl)-1,3,4-oxadiazole,
9-(4-diethylaminostyryl)anthracene, 9-(4-dimethylaminostyryl)anthracene, α-(9-anthryl)-β-(3-N
-Ethylcarbazolyl)ethylene, 5-methyl-
2-(4-diethylaminostyryl)benzoxazole, 9-(4-dibenzylaminobenzylidene)fluorene, N-ethyl-3-(9-fluorenylidene)carbazole, 2,6-bis(4
-diethylaminostyryl)pyridine, methylphenylhydrazono-3-methylidene-9-ethylcarbazole, methylphenylhydrazono-4-
Examples include methylidene-N,N-diethylaniline. These charge transfer substances may be used alone or in a mixture of two or more. The optimal charge transfer material will vary depending on the disazo pigment used. For unknown reasons, certain disazo pigments provide the most suitable electrophotographic photoreceptors when combined with certain charge transport materials. In any of the photoreceptors obtained as described above, an adhesive layer or a barrier layer may be provided between the conductive support and the photosensitive layer, if necessary. Suitable materials for these layers include polyamide, nitrocellulose, and aluminum oxide.
Further, the film thickness is preferably 1 μm or less. To perform copying using the photoreceptor of the present invention, the surface of the photosensitive layer is charged and exposed, and then developed.
If necessary, this can be achieved by transferring to paper or the like. The photoreceptor of the present invention has excellent advantages such as high sensitivity on the short wavelength side and high flexibility. Examples are shown below. Example 1 2 parts by weight of disazo pigment No. 8 and 98 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto an aluminum-deposited polyester film with a doctor blade and air-dried to a thickness of 1 μm. A single charge generation layer was formed. On the other hand 9
2 parts by weight of -(4-diethylaminostyryl)anthracene and 2 parts by weight of polycarbonate resin [Panlite L, manufactured by Teijin Co., Ltd.] were dissolved in 16 parts by weight of tetrahydrofuran, and this was applied onto the charge carrier generation layer with a doctor blade. The mixture was dried at 120° C. for 10 minutes to form a charge transfer layer of 11 μm, thereby obtaining the laminated photoreceptor shown in FIG. Next, a -6KV corona discharge was applied to the photosensitive layer surface of this photoreceptor using a commercially available electrostatic copying paper tester for 20 seconds to negatively charge it, and then it was left in a dark place for 20 seconds. ), then irradiate the photosensitive layer with light from a tungsten lamp so that the surface has an illuminance of 20 lux, find the time (seconds) until the surface potential becomes 1/2 of Vpo, and calculate the half-reduction exposure time. T _1/2 (seconds). the result

It was [formula]. Furthermore, the photosensitive layer was charged negatively and left in a dark place to measure Vpo (volts), and then the photosensitive layer was irradiated with light that passed through a filter that cut out light of 620 nm or more, and the surface potential was _1/2 of V′po. The time (seconds) required for this to occur was determined as the half-reduction exposure time T' _1/2 (seconds). the result

It was [formula]. T' _1/2 /T _1/2 = 1.07, indicating that the sensitivity on the short wavelength side is excellent. Furthermore, this photoreceptor was used in a commercially available copying machine [P-500 manufactured by Ricoh Co., Ltd.] to make copies. The image density of (d) was measured using a Macbeth densitometer. Black original part 1.1 Red original part 0.7 Comparative example Lamination was carried out in exactly the same manner as in Example 1, except that Chlordiane Blue described in JP-A-47-37543 was used instead of disazo pigment No. 8 of Example 1. A type photoreceptor was obtained. Next, using this photoreceptor, T′ _1/2 /T
I asked for _1/2 . T' _1/2 /T _1/2 = 1.83 Image density was also determined in the same manner as in Example 1. Black image area: 1.1 Red image area: 0.4 From this, it is understood that by using the charge carrier generating substance of the present invention in an electrophotographic photoreceptor, excellent reproducibility is achieved even in the red image area. Example 2 1 part by weight of No. 1 disazo pigment and 66 parts by weight of a 0.5% by weight tetrahydrofuran solution of polyester resin [Vylon 200 manufactured by Toyobo Co., Ltd.] were ground and mixed in a ball mill, and the resulting dispersion was mixed with aluminum. It is applied onto the vapor-deposited polyester film using a doctor blade and dried at 80℃ for 2 minutes to a thickness of 0.7cm.
A charge carrier generation layer of μ was formed. Separately, 2 parts by weight of 1,1-bis(4-dibenzylaminophenyl)propane and 2 parts by weight of polycarbonate resin [Panlite K-1300 manufactured by Teijin Co., Ltd.] were dissolved in 16 parts by weight of tetrahydrofuran, and this was added to the charge carrier. Apply it on the generation layer with a doctor blade,
The mixture was dried at 120° C. for 10 minutes to form a charge transfer layer with a thickness of 13 μm, thereby obtaining the laminated photoreceptor shown in FIG. Next, T' _1/2 /T _1/2 was determined in exactly the same manner as in Example 1. T′ _1/2 /T _1/2 = 1.05 Examples 3 to 5 The same procedure as in Example 2 was used except that disazo pigments with numbers shown in Table 1 below were used instead of disazo pigment No. 1. The photoreceptor shown in Figure 1 was prepared, and T' _1/2 /T _1/2 was determined using the same method, and the results shown in Table 1 were obtained.

[Table] Example 6 2 parts by weight of No. 4 disazo pigment and 70 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto an aluminum-deposited polyester film with a doctor blade and air-dried. A charge carrier generation layer having a thickness of 1.5 μm was formed. On the other hand, 2 parts by weight of 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline and 3 parts by weight of polystyrene (Toporex, manufactured by Mitsui Toatsu Chemical Co., Ltd.) were added to 17 parts by weight of tetrahydrofuran. Dissolve and apply this onto the charge carrier generation layer using a doctor blade.
The mixture was dried for 10 minutes at 0.degree. C. to form a charge transfer layer with a thickness of 16 .mu.m, thereby obtaining the laminated photoreceptor shown in FIG. Next, T' _1/2 /T _1/2 was determined in exactly the same manner as in Example 1. T' _1/2 /T _1/2 = 1.03 Examples 7 to 10 The same procedure as in Example 6 was used except that disazo pigments with numbers shown in Table 2 below were used instead of disazo pigment No. 4. The photoreceptor shown in Figure 1 was prepared and T' _1/2 /T _1/2 was determined in the same manner and the results shown in Table 2 were obtained.

[Table] Example 11 2 parts by weight of No. 10 disazo pigment and 98 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto an aluminum-deposited polyester film with a doctor blade and air-dried. A charge carrier generation layer having a thickness of 1 μm was formed. On the other hand, 2 parts by weight of methylphenylhydrazono-3-methylidene-9-ethylcarbazole, 1 part by weight of poly-N-vinylcarbazole (Rubican M-170 manufactured by BASF), 1 part of polyester resin (same as in Example 2) Part by weight was dissolved in 18 parts by weight of tetrahydrofuran, and this was applied onto the charge carrier generation layer using a doctor blade, and dried at 120°C for 10 minutes to form a charge transfer layer with a thickness of 16 μm. A photoreceptor was obtained. Then, in exactly the same manner as in Example 1, T′ _1/2 /T _1
/2 was calculated. T′ _1/2 /T _1/2 = 1.04 Examples 12 to 15 The procedure was carried out in exactly the same manner as in Example 11, except that disazo pigments with numbers shown in Table 3 below were used instead of disazo pigment No. 10. , a photoreceptor as shown in FIG. 1 was formed, and T' _1/2 /T _1/2 was determined by the same method, and the results shown in Table 3 were obtained.

[Table] Example 16 10 parts by weight of polyester resin (same as Example 2), 10 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole,
2 parts by weight of disazo pigment No. 3 and 108 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto a polyester film coated with aluminum using a doctor blade, and heated at 120°C for 10 minutes. A photoreceptor having a dry photoreceptor layer having a thickness of 21 μm as shown in FIG. 2 was prepared. The same measurements as in Example 1 were carried out on this photoreceptor except that +6KV corona discharge was used, and T' _1/2 /T _1/2
I asked for T′ _1/2 /T _1/2 = 1.09 Examples 17 to 20 The same procedure as in Example 16 was used except that disazo pigments with the numbers shown in Table 4 below were used instead of disazo pigment No. 3. The photoreceptor shown in Figure 2 was prepared and T' _1/2 /T _1/2 was determined using the same method, and the results shown in Table 4 were obtained.

[Table] Example 21 1 part by weight of polyester resin (same as in Example 2), 1 part by weight of No. 1 disazo pigment, and 26 parts by weight of tetrahydrofuran were ground and mixed in a ball mill.
The obtained dispersion was applied onto a polyester film coated with aluminum using a doctor blade, and dried at 100°C for 10 minutes to obtain a photoreceptor having a photosensitive layer having a thickness of 7 μm as shown in Fig. 3. . The same measurements as in Example 1 were carried out on this photoreceptor except that a +6KV corona discharge was used, and T _1/
2 /T _1/2 was calculated. T' _1/2 /T _1/2 = 1.07 Examples 22 to 25 The same procedure as in Example 21 was carried out except that the disazo pigments shown in Table 5 below were used instead of the No. 1 disazo pigment. The photoreceptor shown in Figure 3 was prepared and T' _1/2 /T _1/2 was determined using the same method, and the results shown in Table 5 were obtained.

【table】 [Brief explanation of the drawing]

1 to 3 are explanatory diagrams of the photoreceptor of the present invention, respectively. 1... Conductive support, 2, 2', 2''... Photosensitive layer, 3
... Disazo pigment, 4... Charge transfer medium, 5... Charge carrier generation layer, 6... Charge transfer layer.

Claims (1)

[Claims] 1. On a conductive support, the following general formula [However, A is [Formula] [Formula] or [Formula] (where X is an aromatic ring such as a benzene ring or a naphthalene ring, a hetero ring such as an indole ring, a carbazole ring, or a benzofuran ring, or a substituted product thereof;
Ar1 is an aromatic ring such as a benzene ring or a naphthalene ring,
Heterocycles such as dibenzofuran or their substituted substances, Ar2 and Ar3 are aromatic rings such as benzene rings and naphthalene rings or their substituted substances, _R1 and
R ₃ represents hydrogen, a lower alkyl group, a phenyl group, or a substitute thereof, and R ₂ represents a lower alkyl group, a carboxyl group, or an ester thereof. ] A photoreceptor for electrophotography, characterized in that it has a photosensitive layer containing a disazo pigment represented by the following as an active ingredient.