JPS6318740B2 - - 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, is excellent in terms of 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 2,4,
A photoreceptor is disclosed in which a charge transfer complex is formed with 7-trinitrofluorenone. In addition, as a photoreceptor in which amorphous selenium or selenium alloy is used as a charge generation layer and a charge transfer layer is laminated on this, each layer has a role.
-5349 Publication, Special Publication No. 1977-3168, Special Publication No. 1973
-14914, Japanese Patent Publication No. 51-10982, etc. In addition, the following photoreceptors have been developed in which a charge generation layer is made of various pigments and a charge transfer layer is provided thereon. USP 3837851 describes a photoreceptor having a charge generation layer and a charge transfer layer containing at least one triallylpyrazoline; USP 3850630 describes a photoreceptor comprising a transparent charge transfer layer and a charge generation layer comprising an indigoid pigment; A photoreceptor consisting of a charge generation layer made of a perylene pigment derivative and a charge transfer layer made of a condensate of 3-frompyrene and formaldehyde, JP-A-53-133445 discloses a photoreceptor with a transparent charge transfer layer and a stilchen skeleton. A photoreceptor is disclosed comprising a charge generating layer comprising a disazo pigment. Some of these photoreceptors are already in use on the market;
At present, a photoreceptor that satisfactorily satisfies various properties has not yet been obtained. As a result of various studies, the present inventors have discovered that the compound represented by the general formula below works effectively as a charge-generating substance or a photoconductive substance for electrophotographic photoreceptors, and have completed the present invention. Ivy. 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

【formula】

【formula】 or

[Formula] (wherein,
Ar ₁ is an aromatic ring such as a benzene ring or a naphthalene ring,
Heterocycles such as dibenzofuran or substituents thereof, Ar ₂ and Ar ₃ are aromatic rings such as benzene rings and naphthalene rings or substituents thereof, R ₁ and
R ₃ represents hydrogen, a lower alkyl group, a phenyl group, or a substituted product thereof, and 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. These disazo pigments are new compounds,
After diazotizing 1,3-bis(2-aminostyryl)benzene and isolating it as a tetrazonium salt, it is mixed with couplers corresponding to each of the above-mentioned pigments in a suitable organic solvent, such as N,N-dimethylformamide. It can be produced by coupling reaction in the presence of an alkali. For example, the method for producing pigment No. 1 is as follows. Production example: Into dilute hydrochloric acid consisting of 1200ml of water and 60ml of concentrated hydrochloric acid,
1,3-bis(2-aminostyryl)benzene
After adding 28.0 g and stirring at 60°C for 30 minutes, the mixture was cooled to 0°C. Next, add 13.0g of sodium nitrite to this.
A solution prepared by dissolving . After stirring at the same temperature for 30 minutes, water
Then, 50 ml of 42% borofluoric acid was added to this solution, and the precipitated crystals were separated, washed with water,
After drying, 44.2 g (yield 94.0%) of yellow crystals of tetrazonium difluoroborate were obtained. Decomposition point 92
℃ or higher, infrared absorption spectrum (KBr tablet method)
In this case, an absorption band based on N ₂ at 2240 cm ^-1 and an absorption band based on trans -CH=CH- were observed at 965 cm ^-1 . Next, the tetrazonium salt 3.0 obtained in this way
g and 2-hydroxy-3- as coupler
3.3 g of naphthoic acid anilide was cooled with N,N-
The mixture was dissolved in 390 ml of dimethylformamide, and a solution consisting of 1.9 g of sodium acetate and 20 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,
After washing eight times with 300 ml of N,N-dimethylformamide and twice with 300 ml of water, the resulting dark red crystals were dried at a temperature of 70° C. under a reduced pressure of 2 mm Hg.
4.8 g (yield 93.0%) of No. 1 disazo pigment is obtained.
Melting point is 250℃ or higher. The results of elemental analysis are as follows. Calculated value (%) Actual value (%) C 78.11 77.90 H 4.69 4.56 N 9.76 9.55 In addition, in the IR absorption spectrum (KBr tablet method)
The absorption based on secondary amide at 1680cm ^-1 is 950cm ^-1
Absorption based on trans -CH=CH- was observed. 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 and a charge 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, the imagewise exposed light passes through the charge transfer layer and reaches the charge generation layer 5, where the disazo pigment 3 generates a charge, and on the other hand,
The charge transfer layer 6 receives and transfers charges, and the mechanism is such that the charges necessary for light attenuation are generated by the disazo pigment, and the charges are transferred by the 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. Again, the disazo pigment is a charge generating material. For other photoreceptors, it is also possible to reverse the charge generation layer and the charge transfer layer shown in FIG. 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 Figure USP 3973959, USP 3996049 disazo pigment on a conductive support.
Alternatively, fine particles of a disazo pigment are dispersed in a suitable solvent in which a binder is dissolved if necessary, and this is coated on a conductive support and dried. If necessary, the surface is finished by buffing as shown in JP-A-51-90827, or after adjusting the film thickness, a solution containing a charge-transfer substance and a binder is applied. Obtained by drying. The photoreceptor shown in FIG. 2 can be prepared by dispersing fine particles of a disazo pigment in a solution containing a charge transfer substance and a binder, and coating the dispersion on a conductive support and drying it. In order to produce the photoreceptor shown in FIG. 3, a dispersion of fine particles of a disazo pigment in a binder solution may be applied onto a conductive support and dried. 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 μm or less, preferably 2 μm or less, using a ball mill or the like. Application may be carried out by conventional means, such as a doctor blade, dipping, wire bar, etc. The thickness of the photosensitive layer is as shown in FIG. 1, and the thickness of the charge generating layer is 0.01 to 5 .mu.m, preferably 0.05 to 2 .mu.m. If the thickness is less than 0.01μ, charge generation will not be sufficient, and if it is more than 5μ, the residual potential will be too high for practical use. The thickness of the charge transport layer is 3 to 50 microns, preferably 5 to 20 microns. If the thickness is less than 3μ, the amount of charge will be insufficient, and if it is more than 50μ, the residual potential will be too high to be practical. The proportion of the charge transfer substance on 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 includes a composite 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 Conductive treated paper or the like 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 have connectivity can be 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. In addition, charge transfer substances include polymers such as vinyl polymers such as poly-N-vinylcarbazole, polyvinylindoquinoxaline, polyvinyldibenzothiophene, polyvinylanthracene, and polyvinylacridine, propylene-formaldehyde resin, ethylcarbazole-formaldehyde resin, etc. condensation resin, and low molecular weight (monomer) 2,4,7-trinitro-9-
Fluorenone, 2,6,8-trinitro-4H-
indeno[1,2-b]thiophen-4-one,
2,8-dinitrodibenzothiophene, 1,3,
7-trinitrodibenzothiophene-5,5-dioxide, 1,3,7,9-tetranitrobenzo[c]cinnoline-5-oxide, 2,4,
8-trinitrothioxanthone, 1-bromopyrene, N-ethylcarbazole, 2-phenylindole, 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(dibenzylamino)diphenylmethane, 4,4'-bis(dibenzylamino)diphenyl ether, 1,
1-bis(4-dibenzylaminophenyl)propane, 2-(α-naphthyl)-5-(4-diethylaminophenyl)-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-methylidene-N,N-diethylaniline, and the like. 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 are most effective when combined with certain charge transfer substances.
Provided is a photoreceptor suitable for electrophotography. 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, aluminum oxide, and the like, and 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 No. 5 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 to a thickness of 1 μm. A charge generation layer was formed. On the other hand, 9-(4
2 parts by weight of (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 generation layer using a doctor blade and heated at 120°C for 10 minutes. Dry for minutes to a thickness of 11μ
A contact layer type photoreceptor as shown in FIG. 1 was obtained by forming a charge transfer layer. 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 potential is 20 lux, find the time (seconds) until the surface potential becomes 1/2 of Vpo, and calculate the halving exposure time. It was set as T1/2 (seconds). The result was {Vpo-1120 volts T1/2 1.8 seconds}. 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 was {V'po - 1120 volts T'1/2 1.9 seconds}. T′1/2/T1/2=1.06, indicating that the sensitivity on the short wavelength side is excellent. Furthermore, this photoconductor was used in a commercially available copying machine (P-500 manufactured by Ricoh Co., Ltd.) to make copies, and the black original part (Kodatsu Grayscale 1.6) and the red original part (Kodatsu Color Control Patch, Primary Red) were copied. The image density of (d) was measured using a Macbeth densitometer. Black original part 1.2 Red original part 0.8 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. 5 of Example 1. A type photoreceptor was obtained. Next, using this photoreceptor, T′1/2/T
I asked for 1/2. T'1/2/T1/2=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 generating substance of the present invention in an electrophotographic photoreceptor, excellent reproducibility can be 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 weight percent tetrahydrofuran solution of polyester resin (Pylon 200 manufactured by Toyobo Co., Ltd.) were ground and mixed in a ball mill, and the resulting dispersion was mixed with aluminum. It was applied onto the vapor-deposited polyester film using a doctor blade and dried at 80° C. for 2 minutes to form a charge generation layer with a thickness of 0.7 μm. 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 generating solution described above. Apply with a doctor blade on top of the layer and apply 120
The mixture was dried for 10 minutes at .degree. C. to form a charge transfer layer with a thickness of 13 .mu.m, thereby obtaining the laminated photoreceptor shown in FIG. Next, T'1/2/T1/2 was determined in exactly the same manner as in Example 1. T′1/2/T1/2=1.06 Examples 3 to 5 The same procedure as in Example 2 was used except that disazo pigments with the numbers shown in Table 1 below were used instead of disazo pigment No. 1. The photoreceptor shown in FIG. 1 was prepared and T'1/2/T1/2 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% 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 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) prazolin 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 generation layer using a doctor blade, and heat at 120°C.
The mixture was dried for 10 minutes to form a charge transfer layer with a thickness of 16 μm, thereby obtaining the laminated photoreceptor shown in FIG. Next, T'1/2/T1/2 was determined in exactly the same manner as in Example 1. T′1/2/T1/2=1.20 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/T1/2 was determined using the same method, and the results shown in Table 2 were obtained.

[Table] Example 11 2 parts by weight of disazo pigment No. 13 and 98 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, the resulting dispersion was applied onto an aluminum-deposited polyester film with a doctor blade, and air-dried. A charge generation layer with a thickness of 1 μm was formed. On the other hand, 2 parts by weight of methylphenylhydrazone-3-methylidene-9-ethylcarbazole, 1 part by weight of poly-N-vinylcarbazole (Lupican M-170 manufactured by BASF), 1 part by weight of polyester resin (same as in Example 2) 18 parts by weight of tetrahydrofuran, apply this onto the charge generation layer using a doctor blade, dry at 120°C for 10 minutes, and adjust the thickness.
A charge transfer layer of 16μ was formed to obtain a laminated photoreceptor as shown in FIG. Then, in exactly the same manner as in Example 1, T′1/2/T1/
I asked for 2. T′1/2/T1/2=1.19 Examples 12 to 15 The same procedure as in Example 11 was used except that disazo pigments with numbers shown in Table 3 below were used instead of disazo pigment No. 13. The photoreceptor shown in FIG. 1 was prepared and T'1/2/T1/2 was determined using 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 whole 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 of the form shown in FIG. 2 having a dried photosensitive layer with a thickness of 21 μm was prepared. Hereinafter, 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/T1/
I asked for 2. T′1/2/T1/2=1.07 Examples 17 to 20 The same procedure as in Example 16 was used except that disazo pigments with 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/T1/2 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. 10 disazo pigment, and 2.6 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill.
The resulting 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 with a photosensitive layer having a thickness of 7 μm as shown in Figure 3. . Below, the same measurements as in Example 1 were carried out on this photoreceptor except that +6KV corona discharge was used.
T′1/2/T1/2 was calculated. T′1/2/T1/2=1.18 Examples 22 to 25 The same procedure as in Example 21 was used except that disazo pigments with numbers shown in Table 5 below were used instead of disazo pigment No. 10. The photoreceptor shown in Figure 3 was prepared and T'1/2/T1/2 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 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, a heterocycle, or a substituent thereof, Ar ₁ is an aromatic ring, a heterocycle, or a substituent thereof,
Ar ₂ and Ar ₃ are aromatic rings or substituted products thereof,
R ₁ and R ₃ represent hydrogen, a lower alkyl group, a phenyl group, or a substituted product thereof, and R ₂ represents a lower alkyl group, a carboxyl group, or an ester thereof. 1. A photoreceptor for electrophotography, comprising a photosensitive layer containing a disazo pigment as an active ingredient.