JPS6219739B2 - - 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, inorganic photoconductive materials such as amorphous selenium, selenium alloys, cadmium sulfide, and zinc oxide, polyvinyl carbazole, and derivatives thereof are widely known as electrophotographic photoreceptors. 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, a photoreceptor made of amorphous selenium or a selenium alloy is used as a charge generation layer, and a charge transfer layer is laminated on this, each layer having its own role.
Publication No. 45-5349, Publication No. 49-3168, Publication No. 49-3168, Publication No. 49-3168, Special Publication Sho
50-14914, Japanese Patent Publication No. 51-10982, and the like. 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; discloses a photoreceptor comprising 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 discovered 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. A main object of the present invention is to provide an electrophotographic photoreceptor that has excellent reproducibility in the visible light region by using a charge carrier generating material that has excellent sensitivity on the short wavelength side. The present invention is based on the general formula [In the formula, A is

[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, a benzofuran ring, or a substituted product thereof;
Ar ₁ is an aromatic ring such as a benzene ring or a naphthalene ring,
A heterocycle such as a dibenzofuran ring and its substituted substances, _Ar2 is an aromatic ring such as a benzene ring and a naphthalene ring and its substituted substances, _R1 is hydrogen, a lower alkyl group or a phenyl group and its substituted substances,
_R2 represents a lower alkyl group, a carboxyl group, and an ester thereof. ] 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 disazo pigments represented by the above general formula used in the present invention are shown below in terms of structural formulas. Below, compounds No. 2 to 60 Since this part is common, we omit it and simply write this part as -
It is written as Y-. These disazo pigments are 3,4'-dinitro-
trans-3,4′- obtained by reducing stilbene
After diazotizing diamino-trans-stilbene by a known method and isolating it as a tetrazonium salt, a naphthol AS-based coupler corresponding to each of the above-mentioned pigments is added in an appropriate organic solvent such as N,N-dimethylformamide (DMF). It can be easily produced by coupling the compound and the like in the presence of an alkali. For example, the method for producing the pigment No. 1 is as follows. Incidentally, other diazo pigments can also be produced according to this production example, except that the raw materials are changed. Production example 3,4'-diamino-trans-stilbene (Ashley et al; J.Chem.Soc 1942.103,112 ,
3.97g was stirred with 100ml of water and 10ml of concentrated hydrochloric acid, and to this was added an aqueous solution of sodium nitrite (2.93g of NaNO ₂ + 10ml of water).
ml) was added dropwise at a temperature below 55°C, and the diazotization was completed by stirring at the same temperature for about 30 minutes. Add 42% hydroborofluoric acid to the reaction mixture, collect the precipitated crystals,
After washing with cold water and drying, it becomes yellow crystals.
6.97 g of trans-stilbene-3,4'-bisdiazonium bistetrafluoroborate was obtained. Next, 2.04g of the above tetrazonium salt and 2-hydroxy-3-phenylcarbamoylnaphthalene
2.63 g was dissolved in 300 ml of DMF, and an aqueous solution of sodium acetate (CH ₃ COONa 3.28 g + water 14 ml) was added dropwise thereto at room temperature, and the mixture was stirred at the same temperature for 2 hours to collect precipitated crystals. Next, 300 ml of DMF was added to the crystals, and after stirring at 80°C for 2 hours, the crystals were collected again. After repeating this operation twice, wash with water and dry.
3.19 g of Compound No. 1 disazo pigment was obtained. Red-purple crystal elemental analysis results Calculated value Actual value C% 75.98 75.67 H% 4.52 4.39 N% 11.07 10.82 The infrared absorption spectrum (KBr disK) is shown in FIG. Vco (secondary amide) 1675cm ^-1 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 consists mainly of a charge generation layer 5 mainly composed of a disazo pigment 3, a charge transfer substance and a binder (these materials form a charge transfer medium 4) on a conductive support 1. It consists of a charge transfer layer 6. In the photoreceptor shown in FIG. 1, imagewise exposed light passes through the charge transfer layer and reaches the charge generation layer 5, where charge carriers are generated in the disazo pigment 3, while the charge transfer layer 6 It receives and transfers charge carriers. That is, in the case of this photoreceptor, the generation of charge carriers necessary for light attenuation is performed by a disazo pigment, and the transfer of charge carriers is performed by a charge transfer medium. The photoreceptor shown in FIG. 2 has a photosensitive layer 2' mainly composed of a disazo pigment 3 and a charge transport medium 4 (a charge transport substance and an insulating binder) on a conductive support 1. The photoreceptor shown in FIG. Here again, the disazo pigment is a charge carrier generating substance, and the mechanism of generation and movement of charge carriers is the same as in the case of FIG. As other photoreceptors, it is also possible to reverse the charge generation layer and the charge transfer layer in the photoreceptor shown in FIG. 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 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 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. The thickness of the photosensitive layer is as shown in FIG. 1, and the thickness of the charge generation layer is 0.01 to 5 .mu.m, preferably 0.05 to 2 .mu.m. If the thickness is less than 0.01μ, charge carriers are not sufficiently generated, and if it is more than 5μ, the residual potential is too high for practical use. The thickness of the charge transfer layer is 3
-50μ, preferably 5-20μ. 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 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. On the other hand, in the case of the photoreceptor shown in FIG. 2, the thickness of the photosensitive layer is preferably 3 to 50 microns, preferably 5 to 20 microns. If it is less than 3μ, the amount of charge is insufficient, and if it is more than 50μ, the residual potential is high, which is not practical. The proportion of the disazo pigment in the photosensitive layer shown in FIG. 2 is 1 to 50% by weight, preferably 3 to 30% by weight. If this proportion is less than 1% by weight, the sensitivity will be low, and if this proportion is greater than 50% by weight, the mechanical strength of the photosensitive layer will be reduced. Further, the proportion of the charge transfer substance in this photosensitive layer is 10 to 95% by weight, preferably 30 to 95% by weight.
90% by weight is good. Outside this range, problems similar to those in the case of the charge transfer layer shown in FIG. 1 will occur. Note that a plasticizer can be used together with a binder when producing any of the photoreceptors shown in FIGS. 1 and 2. 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-
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-
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) phenyl) pyrazoline, 2-phenyl-4-(4-
Examples include diethylaminophenyl)-5-phenyloxazole, triphenylamine, tris(4-diethylaminophenyl)methane, and 3,6-bis(dibenzylamino)-9-ethylcarbazole. 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, aluminum oxide, etc.
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 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
Part by weight, polycarbonate resin [manufactured by Teijin Co., Ltd.]
Panlite L] 2 parts by weight, tetrahydrofuran
This was dissolved in 16 parts by weight and 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 10μ, thereby obtaining the laminated photoreceptor shown in Figure 1. . 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 make it negatively charged.The photoreceptor was then left in a dark place for 20 seconds, and the surface potential Vpo (volts) ), 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′ _1/2 seconds. the result

It was [formula]. 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 to 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. This photoconductor was then 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 Red) were copied. The image density of (d) was measured using a Macbeth densitometer. Black original portion 1.1 Red original portion 0.8 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' _1/2 /T _1/2 was determined. 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 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. Apply it on the generation layer with a doctor blade,
A charge transfer layer having a thickness of 13 μm was formed by drying at 120° C. for 10 minutes to obtain 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. 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 19 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 = 1.12 Examples 7 to 10 Same as Example 6 except that disazo pigments with the numbers shown in Table 2 below were used instead of disazo pigment No. 5. The photoreceptor shown in FIG. 1 was prepared by the same procedure, and T' _1/2 /T _1/2 was determined using the same method, 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), polyester resin (Example 2) ) was dissolved in 18 parts by weight of tetrahydrofuran and applied onto the charge generation layer using a doctor blade, dried at 120°C for 10 minutes to form a charge transfer layer with a thickness of 16μ, and
The laminated photoreceptor shown in the figure was obtained. Next, T' _1/2 /T _1/2 was determined in exactly the same manner as in Example 1. T′ _1/2 /T _1/2 = 1.08 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. The photoreceptor shown in FIG. 1 was prepared, and T' _1/2 /T _1/2 was determined in the same manner, 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. The same measurements as in Example 1 were carried out on this photoreceptor except that +6 KV corona discharge was used to determine T' _1/2 /T _1/2 . T' _1/2 /T _1/2 = 1.10 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. , create the photoreceptor shown in Figure 2,
T′ _1/2 /T _1/2 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 cross-sectional views of the photoreceptor of the present invention, respectively;
FIG. 3 is an infrared absorption spectrum of the disazo pigment of Compound No. 1. DESCRIPTION OF SYMBOLS 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 [In the formula, A is [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 substituent thereof;
Ar ₁ is an aromatic ring such as a benzene ring or a naphthalene ring,
Heterocycles such as dibenzofuran rings and their substituents, Ar ₂ is aromatic rings such as benzene rings and naphthalene rings and their substituents, R ₁ is hydrogen, lower alkyl groups or phenyl groups and their substituents, R ₂
is selected from the group consisting of lower alkyl groups, carboxyl groups and esters thereof). ] An electrophotographic photoreceptor comprising a photosensitive layer containing a disazo pigment represented by the following as an active ingredient.