JPS6255663B2 - - 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. 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-generating 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 is disclosed that includes a charge generation layer made of a perylene pigment derivative and a charge transfer layer made of a condensate of 3-bromopyrene and formaldehyde. 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 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 generating material that has excellent sensitivity on the short wavelength side. That is, the electrophotographic photoreceptor of the present invention has the general formula [However, A is

[expression] or

[Formula] (where X is an aromatic ring such as a benzene ring or a naphthalene ring, an indole ring, a carbazole ring,
Represents a hetero ring such as a benzofuran ring or a substituted product thereof; Ar ₁ represents a hetero ring such as a benzene ring, an aromatic ring such as a naphthalene ring, or a dibenzofuran ring, or a substituted product thereof; Ar ₂ represents a benzene ring, a naphthalene ring, etc. represents an aromatic ring or a substituted product thereof; R ₁ represents 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. ). ] It is characterized by having a photosensitive layer containing a disazo pigment shown in the following. Specific examples of the disazo pigments represented by the above general formula used in the present invention are shown below in terms of structural formulas. During the ceremony About

It is written as [formula]. The above-mentioned disazo pigments are, for example, and,

[Formula] or

[Formula] (X, Ar ₁ , Ar ₂ , R ₁ and R ₂ are the same as above)
It can be easily produced by reaction with The electrophotographic photoreceptor according to the present invention is shown in FIGS.
It can take the form of a figure. The photoreceptor shown in FIG. 1 has a laminated photosensitive layer 2 on a conductive support 1, which is composed of a charge generation layer 5 mainly containing a disazo pigment 3 and a charge transfer layer 6 mainly containing a charge transfer substance. It is something that 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 generation of charges occurs in the disazo pigment 3, and on the other hand,
The charge transfer layer 6 receives and transfers charges, and the mechanism is such that the disazo pigment 3 generates the charges necessary for light attenuation, and the charge transfer layer 6 transfers the charges. The photoreceptor shown in FIG. 2 has a photosensitive layer 2' mainly composed of a disazo pigment 3, a charge transfer substance and an insulating binder on a conductive support 1. The photoreceptor shown in FIG. Again, the disazo pigment 3 is a charge generating substance. For other photoreceptors, it is also possible to reverse the charge generation layer and the charge transfer layer shown in FIG. The thickness of the photosensitive layer 2 is as shown in FIG. 1, and the thickness of the charge generation layer 5 is preferably 0.01 to 5 .mu.m, more preferably 0.05 to 2 .mu.m. If the thickness is less than 0.01 μm, charge generation will not be sufficient, and if it is more than 5 μm, the residual potential will be too high for practical use. The thickness of the charge transfer layer 6 is preferably 3 to 50 microns, more 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 charge generation layer 5 is mainly composed of a disazo pigment represented by the above general formula,
Furthermore, a binder, a plasticizer, etc. can be contained. Further, the proportion of the disazo pigment in the charge generation layer is preferably 30% by weight or more, more preferably 50% by weight or more. The charge transfer layer 6 is mainly composed of a charge transfer substance and a binder, and may further contain a plasticizer. The proportion of charge transport substance in the charge transport 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
If it exceeds 95% by weight, the mechanical strength of the photoreceptor film will be so poor that it cannot be put to practical use. In the case of the photoreceptor shown in FIG. 2, the thickness of the photosensitive layer 2' is preferably 3 to 50 μm, more preferably 5 μm.
~20μ. The proportion of the disazo compound in the photosensitive layer 2' is preferably 50% by weight or less, more preferably 20% by weight or less, and the proportion of the charge transfer substance is preferably 10 to 95% by weight, more preferably 30 to 90% by weight. Weight%. 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 deposited, or a conductive support. 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 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. 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-
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-
Brompyrene, 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) enyl)pyrazoline, 2-phenyl-4-(4-diethylaminophenyl)-5-phenyloxazole, triphenylamine, tris(4-diethylaminophenyl)methane, 3,6-bis(dibenzylamino)-9 -Ethylcarbazole and the like. These charge transfer substances may be used alone or in combination
It is used in combination of more than one species. 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, aluminum oxide, and the like, and the film thickness is preferably 1 μm or less. To create the photoreceptor shown in Figure 1, a disazo pigment is 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 are bonded if necessary. The agent is dispersed in a suitable solvent, coated on a conductive support and dried, and if necessary, the surface is polished by buffing or the like as shown in JP-A No. 51-90827. After finishing or adjusting the film thickness, a solution containing a charge transport substance and a binder is applied and dried. The photoreceptor shown in FIG. 2 can be prepared by dispersing fine powder of a disazo pigment in a solution containing a charge transfer substance and a binder, and coating the disazo pigment on a conductive support and drying it. In either case, 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. To perform copying using the photoreceptor of the present invention, the surface of the photosensitive layer is charged and exposed, and then developed.
This can be achieved by transferring to paper or the like, if necessary. 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. 1 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-diethylaminostyryl)anthracene 2
Parts by weight 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 dried at 120°C for 10 minutes. A charge transfer layer having a thickness of 16 .mu.m was formed using the above steps to obtain 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 potential is 20 lux, find the time (seconds) until the surface potential becomes 1/2 of Vpo, and calculate the halving exposure time. T = (seconds). The result was Vpo 1060 volts T = 1.3 seconds. Furthermore, similarly negatively charged, left in the dark, V′po
(volts), then irradiate the photosensitive layer with light that passes through a filter that cuts out light of 620 nm or more, and calculate the time (seconds) until the surface potential becomes 1/2 of V'po and reduce it by half. The exposure time was set as T′〓 (seconds).
The result was V′po 1060 volts T′〓 1.6 seconds. T′〓/T〓=1.23, indicating that the sensitivity on the short wavelength side is excellent. Furthermore, this photoconductor was used to make copies using a commercially available copying machine (P-500 manufactured by Ricoh Co., Ltd.), and the black original part (Kodatsu Grayscale 1.6) and the red original part (Kodatsu Color Control Patch, primary) were copied. The image density of the image (red) was measured using a Macbeth densitometer. Black manuscript section 1.1 Red manuscript section 0.6 Comparative example The procedure was exactly the same as in Example 1 except that Chlordiane Blue described in JP-A-47-37543 was used instead of the No. 1 disazo pigment of Example 1. A laminated photoreceptor was obtained. Next, using this photoreceptor, T'/T was determined. T′〓/T〓=1.83 In addition, the image density was 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 is achieved even in the red image area. Example 2 1 part by weight of No. 2 disazo pigment and 66 parts by weight of a 0.5 weight percent 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 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. It was applied onto the charge generation layer using a doctor blade and dried at 120°C for 10 minutes to form a charge transfer layer with a thickness of 14μ, thereby obtaining the laminated photoreceptor shown in FIG.
Then, T'/T was determined in exactly the same manner as in Example 1. T′〓/T〓=1.29 Examples 3 to 5 The procedure in Example 2 was repeated except that the disazo pigments shown in the numbers shown in Table 1 below were used instead of the No. 2 disazo pigment. A photoreceptor was prepared, and T'/T was determined using the same method, and the results shown in Table 1 were obtained.

[Table] Example 6 2 parts by weight of No. 5 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 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 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 17 μm, thereby obtaining the laminated photoreceptor shown in FIG. Then, T'/T was determined in exactly the same manner as in Example 1. T′〓/T〓=1.23 Examples 7 to 10 The same procedure as in Example 6 was used except that disazo pigments with the numbers shown in Table 2 below were used instead of disazo pigment No. 5. The photoreceptor shown in Figure 1 was prepared and T'/T 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 generation layer having a thickness of 1 μm was formed. On the other hand, 2 parts by weight of 9-ethyl-3-carbazolaldehyde-1-methyl-1-phenylhydrazone, 1 part by weight of poly-N-vinylcarbazole (manufactured by BASF, Rubican M-170) and polyester resin (Example 2) ) was dissolved in 18 parts by weight of tetrahydrofuran, and this was applied onto the charge 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 laminated photoreceptor as shown in FIG. 1 was obtained. Then, T′〓/T〓 was determined in exactly the same manner as in Example 1. T′〓/T〓=1.35 Examples 12 to 15 The same procedure as in Example 11 was carried out except that disazo pigments with numbers shown in Table 3 below were used instead of disazo pigment No. 10. A photoreceptor was prepared and T'/T 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 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 18 μm as shown in FIG. 2 was prepared. below,
With respect to this photoreceptor, the same measurements as in Example 1 were carried out except that a +6 KV corona discharge was used to determine T'/T. T′〓/T〓=1.26 Examples 17 to 20 The same procedure as in Example 16 was carried out except that disazo pigments having the numbers shown in Table 4 below were used instead of disazo pigment No. 3. Create a photoreceptor of
T′〓/T〓 was determined using the same method and the results shown in Table 4 were obtained.

【table】 [Brief explanation of the drawing]

1 and 2 are enlarged sectional views of the photoreceptor of the present invention, respectively. 1... Conductive support, 2, 2'... Photosensitive layer, 3
... Disazo pigment, 4 ... Charge transfer medium, 5 ...
Charge generation layer, 6... Charge transfer layer.

Claims (1)

[Claims] 1. General formula [However, A is [Formula] or [Formula] (where X is an aromatic ring such as a benzene ring or a naphthalene ring, an indole ring, a carbazole ring,
Represents a hetero ring such as a benzofuran ring or a substituted product thereof; Ar ₁ represents a hetero ring such as a benzene ring, an aromatic ring such as a naphthalene ring, or a dibenzofuran ring, or a substituted product thereof; Ar ₂ represents a benzene ring, a naphthalene ring, etc. represents an aromatic ring or a substituted product thereof; R ₁ represents 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. ). ] An electrophotographic photoreceptor characterized by having a photosensitive layer containing a disazo pigment represented by the following.