JPS6219736B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photoreceptor for electrophotography, and more particularly to a novel photoreceptor having a photosensitive layer containing a disazo pigment as an active ingredient. Conventionally, as an electrophotographic photoreceptor in which a photosensitive layer containing an azo pigment as an active ingredient is provided on a conductive support, for example, a photoreceptor using a monoazo pigment (Tokuko Showa)
44-16474) and one using a benzidine-based disazo pigment (Japanese Patent Application Laid-open No. 47-37543) are known. As mentioned above, these azo pigments are certainly useful materials as active ingredients in the photosensitive layer, but considering the various requirements for the photoreceptor from the point of view of the electrophotographic process, it is unlikely that they will fully satisfy these requirements. The reality is that we are not getting anything. Therefore, it is even more important to have a wide variety of pigments, not just azo pigments, that can serve as active ingredients, and only then can a photoreceptor suitable for a certain process be provided. becomes possible. That is, in the electrophotographic process, it is desirable to have as many types of pigments as possible that can act as active ingredients in the photoreceptor. A first object of the present invention is to provide an electrophotographic photoreceptor containing a novel disazo pigment that can serve as an active ingredient in various electrophotographic processes. A second object of the present invention is to provide an electrophotographic photoreceptor that allows a wide selection of disazo pigments that can serve as active ingredients. A third object of the present invention is to provide a new highly sensitive and highly flexible electrophotographic photoreceptor containing the above-mentioned disazo pigment. The present inventors produced a group of disazo pigments and studied their application to photoreceptors, and as a result, they found that disazo pigments having a carbazole skeleton represented by the general formula below can serve as an excellent active ingredient for photoreceptors. This knowledge led to the completion of the present invention. That is, the present invention provides the following general formula on a conductive support: [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;
Ar ₁ is an aromatic ring such as a benzene ring or a naphthalene ring,
A hetero ring such as a dibenzofuran ring or a carbazole ring or a substituted product thereof; Ar ₂ and Ar ₃ 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, or 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 of the above general formula used in the present invention are shown below in terms of structural formulas. These disazo pigments use 1,5-diaminonaphthalene as a starting material, which is first diazotized by a conventional method and isolated as a tetrazonium salt.
It can be easily produced by coupling a compound corresponding to A in the above general formula (a coupler such as naphthol AS) in an appropriate organic solvent such as N,N-dimethylformamide in the presence of an alkali. For example, the method for producing the No. 1 pigment is as follows. Note that other disazo pigments can also be produced according to this production example, except for changing the coupler. Production Example (Production of Disazo Pigment No. 1) 15.8g of 1,5-diaminonaphthalene was dissolved in concentrated hydrochloric acid.
Add to dilute hydrochloric acid prepared from 80 ml and 83 ml of water, and stir and mix thoroughly. Next, this mixture is cooled to about 0°C, and a solution of 15.2 g of sodium nitrite dissolved in 100 ml of water is gradually added dropwise at a temperature below 5°C. After dropping, stir at the same temperature for about 1 hour, remove trace amounts of insoluble matter, and add 110 ml of 42% borohydrofluoric acid aqueous solution to the liquid.
was added, and the precipitate was collected, washed with water, and dried to obtain 30.1 g (yield: 84.6%) of tetrazonium trifluoroborate as an off-white powder. Next, 7.1 g of this tetrazonium salt and 11.6 g of 2-hydroxy-3-naphthoic acid anilide as a coupling component were dissolved in 1700 ml of cooled N,N-dimethylformamide, and a solution of 20 g of sodium acetate and 300 ml of water was added to the solution. was added dropwise at a temperature of 12 to 15℃ for about 1 hour, and then added at room temperature for 3 more minutes.
Stir for hours. After that, remove the resulting precipitate and
After washing twice with water and then seven times with N,N-dimethylformamide 2, the
Disazo pigment of Compound No. 1 is dried under reduced pressure of
10.1g (yield 71.6%) was obtained. mp.300℃ or more. Elemental analysis (as C ₄₈ H ₃₀ O ₄ N ₆ ) Calculated value Actual value C (%) 74.77 74.53 H (%) 4.28 4.20 N (%) 11.89 11.59 The electrophotographic photoreceptor of the present invention uses the above disazo pigment Depending on how these pigments are applied, they can take the forms shown in Figures 1 to 3. 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 how these pigments are applied. The photoreceptor in FIG. 1 has a disazo pigment 4 on a conductive support 1.
(Here, it is used as a photoconductive substance.) A photosensitive layer 2 containing three resin binders is provided. Second
The photoreceptor in the figure has a disazo pigment 4 on a conductive support 1.
(here used as charge carrier generating material)
-A charge transfer medium (a mixture of a charge transfer substance and a resin binder) 5-based photosensitive layer 2' is provided.
The photoreceptor shown in Figure 3 is a modification of the photoreceptor shown in Figure 2.
The photosensitive layer 2'' consists of a charge carrier generation layer 6 mainly composed of a disazo pigment 4 and a layer 7 of a charge transport medium. In the photoreceptor of FIG. The generation and transfer of the charge carriers necessary for On the other hand, disazo pigments act as charge carrier generating substances.This charge transfer medium does not have the ability to generate charge carriers like disazo pigments, but it has the ability to accept and transfer charge carriers generated from disazo pigments. That is, in the photoreceptor of Fig. 2, the generation of charge carriers necessary for light attenuation is carried out by the disazo pigment, while the transfer of charge carriers is carried out mainly by the charge transfer medium. The basic condition required is that the absorption wavelength region of the charge transfer medium does not overlap with the absorption wavelength region of the disazo pigment, which is mainly in the visible region.This is necessary in order to efficiently generate charge carriers in the disazo pigment. This is because it is necessary to transmit light. However, this is not the case, for example, in the case of a photoreceptor that is sensitive only to a certain wavelength. Therefore, the absorption wavelengths of both the charge transfer medium and the disazo pigment must completely overlap. Next, in the photoreceptor shown in Figure 3, the light that has passed through the charge transfer medium layer reaches the photosensitive layer 2'', which is the charge carrier generation layer, and charge carriers are generated in the disazo pigment in that area. On the other hand, the charge transfer medium layer receives and transfers charge carriers, and the mechanism in which the charge carriers necessary for light attenuation are generated by the disazo pigment and the charge carriers are transferred by the charge transfer medium is a secondary mechanism. This is similar to the case of the photoreceptor shown in the figure. Here again, the disazo pigment is a charge carrier generating substance. In order to produce the photoreceptor shown in FIG. 1, a dispersion of disazo pigment particles dispersed in a binder solution may be coated on a conductive support and dried. To create the photoreceptor shown in Figure 2, fine particles of disazo pigment are dispersed in a solution containing a charge transporting substance and a binder, and the particles are coated on a conductive support and dried. good. The photoreceptor shown in Fig. 3 is made by vacuum-depositing a disazo pigment on a conductive support, or
Alternatively, fine particles of disazo pigment may be dispersed in a suitable solvent in which a binder is dissolved, if necessary, and this may be applied and dried on a conductive support, and if necessary, the surface may be finished by a method such as buffing. After adjusting the film thickness, a solution containing a charge transporting substance and a binder is applied thereon and dried. In any 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 is carried out by conventional means, such as a doctor blade or wire bar.
The thickness of the photosensitive layer is about 3 cm in the ones in Figures 1 and 2.
-50μ, preferably 5-20μ. Further, in the case of FIG. 3, the thickness of the charge carrier generation layer is 5μ or less,
The thickness of the charge transport medium layer is preferably about 3 to 50 microns, preferably 5 to 20 microns. Further, in the photoreceptor shown in FIG. 1, the proportion of the disazo pigment in the photosensitive layer is 30 to 70% by weight, preferably about 50% by weight, based on the photosensitive layer. (As mentioned above, in the case of the photoreceptor shown in Figure 1, the disazo pigment acts as a photoconductive substance, and the generation and movement of charge carriers necessary for light attenuation occur through the pigment particles. It is preferable that the contact be continuous from the surface of the photosensitive layer to the support.For this reason, it is preferable that the proportion of the pigment in the photosensitive layer be relatively large, but considering the strength and sensitivity of the photosensitive layer, approximately 50% by weight is preferable. In the photoreceptor shown in FIG. 2, the proportion of the disazo pigment in the photosensitive layer is 50% by weight or less, preferably 20% by weight or less, and the proportion of the charge transfer substance is 10 to 95% by weight, preferably is 30-90% by weight. Further, the proportion of the charge transporting substance in the charge transport medium layer of the photoreceptor shown in FIG. 3 is 10 to 95% by weight, preferably 30 to 90% by weight, as in the case of the photosensitive layer of the photoreceptor shown in FIG. . Note that the first
In producing any of the photoreceptors shown in Figures 1 to 3, a plasticizer can be used in combination with a binder. In the photoreceptor of the present invention, the conductive support may be a metal plate or metal foil such as aluminum, a plastic film on which metal such as aluminum is vapor-deposited,
Alternatively, paper or the like that has been subjected to conductive treatment may be used. Examples of binders include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polyketone, and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, and polyacrylamide. In addition, any adhesive resin can be used. As a plasticizer, halogenated paraffin,
Examples include polychlorinated biphenyl, dimethylnaphthalene, and dibutyl phthalate. In addition, examples of charge-transferring substances include polymers such as poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylindoquinoxaline, polyvinyldibenzothiophene, polyvinylanthracene, and polyvinylacridine. Coalescence and condensation resins such as pyrene-formaldehyde resin, brompyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, chloroethylcarbazole-formaldehyde resin, and low molecular weight (monomer) resins such as fluorenone, 2-nitro-9-fluorenone, 2,7-dinitro-9-fluorenone,
2,4,7-trinitro-9-fluorenone,
2,4,5,7-tetranitro-9-fluorenone, 4H-indeno[1,2-b]thiophene-
4-one, 2-nitro-4H-indeno [1,2
-b] Thiophen-4-one, 2,6,8-trinitro-4H-indeno[1,2-b] Thiophen-4-one, 8H-indeno[2,1-b] Thiophen-8-one, 2 -Nitro-8H-indeno[2,1-b]thiophene-8-one, 2-bromo-6,8-dinitro-4H-indeno[1,
2-b] Thiophene, 6,8-dinitro-4H-
Indeno[1,2-b]thiophene, 2-nitrodibenzothiophene, 2,8-dinitrodibenzothiophene, 3-nitrodibenzothiophene-5
-oxide, 3,7-dinitrodibenzothiophene-5-oxide, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, 3
-Nitrodibenzothiophene-5,5-dioxide, 3,7-dinitrodibenzothiophene 5,
5-dioxide, 4-dicyanomethylene-4H
-Indeno[1,2-b]thiophene, 6,8-
Dinitro-4-dicyanomethylene-4H-indeno[1,2-b]thiophene, 1,3,7,9-
Tetranitrobenzo[c]cinnoline-5-oxide, 2,4,10-trinitrobenzo[c]cinnoline-6-oxide, 2,4,8-trinitrobenzo[c]cinnoline-6-oxide,
2,4,8-trinitrothioxanthone, 2,
4,7-trinitro-9,10-phenanthrenequinone, 1,4-naphthoquinonebenzo[a]anthracene-7,12-dione, 2,4,7-trinitro-9-dicyanomethylenefluorene, tetrachlorophthalic anhydride , 1-bromopyrene, tomethylpyrene, 1-ethylpyrene, 1-acetylpyrene, carbazole, N-ethylcarbazole, N
-β-chloroethylcarbazole, N-β-hydroxyethylcarbazole, 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, and the like. These charge transfer substances may be used alone or in combination of two or more. 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 generally has excellent advantages such as high sensitivity and flexibility. Examples are shown below. Example 1 1 part by weight of polyester resin (manufactured by DuPont, Polyester Adhesive 49000), 1 part by weight of No. 1 disazo pigment, and 26 parts by weight of tetrahydrofuran 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 100° C. for 10 minutes to obtain a photoreceptor having a photosensitive layer having a thickness of 7 μm as shown in FIG. 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 positively charge it, and then it was left in a dark place for 20 seconds, and the surface potential at that time was Vpo (volts). Then, the photosensitive layer is irradiated with light from a tungsten lamp so that the surface has an illumination intensity of 20 lux, and the time (seconds) until the surface potential becomes _1/2 of Vpo is determined, and the amount of light E _{1 /2} (lux seconds). The result is
Vpo=560V, E _1/2 25.5 Lux・sec. Examples 2 to 10 Photoreceptors were prepared according to the same photoreceptor preparation method as in Example 1, except that disazo pigments with the numbers shown in Table 1 below were used instead of disazo pigment No. 1 in Example 1. However, the same measurements as in Example 1 were carried out on these photoreceptors, and the results shown in Table 1 were obtained.

[Table] Example 11 10 parts by weight of polyester resin (same as Example 1), 2,4,7-trinitro-9-fluorenone
10 parts by weight, 2 parts by weight of No. 2 disazo pigment, and 198 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. Dry for 10 minutes at 10°C to a thickness of 10
A photoreceptor having the configuration shown in FIG. 2 having a photoreceptor layer of μ was prepared. Next, Vpo and E _1/2 of this photoreceptor were changed to -6KV instead of +6KV corona discharge in Example 1.
Measurements were made in exactly the same manner except that corona discharge was performed.
I got the results of Vpo = 550 volts and E _1/2 = lux seconds. Examples 12 to 20 In Example 11, the disazo pigments shown in the numbers shown in Table 2 below were used in place of the disazo pigment No. 2 to prepare a photoreceptor in the form shown in Figure 2.
Vpo and E _1/2 were determined using the same method as above, and the results shown in Table 2 were obtained.

[Table] Example 21 10 parts by weight of polyester resin (same as Example 1), 10 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole,
2 parts by weight of disazo pigment No. 3 and 198 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 10 μm as shown in FIG. 2 was prepared. Below, the same measurements as in Example 1 were performed on this photoreceptor,
The results were Vpo = 710 volts and E _1/2 = 12.3 lux-sec. Examples 22 to 30 A photoreceptor having the form shown in FIG. 2 was prepared in the same manner as in Example 21, except that disazo pigments shown in Table 3 below were used in place of disazo pigment No. 3 in Example 21, The same measurements as in Example 1 were carried out, and the results shown in Table 3 were obtained.

[Table] Example 31 200 parts by weight of poly-N-vinylcarbazole,
33 parts by weight of 2,4,7-trinitro-9-fluorenone, 20 parts by weight of polyester resin (same as in Example 1), and 20 parts by weight of No. 4 disazo pigment were added to 1780 parts by weight of tetrahydrofuran, and the mixture was ground and mixed in a ball mill. The resulting dispersion was applied with a doctor blade onto a polyester film on which aluminum had been vapor-deposited, and dried at 100°C for 10 minutes and then at 120°C for 5 minutes to form a photosensitive layer with a thickness of 13μ as shown in Figure 2. When a photoreceptor of the same type was prepared and the same measurements as in Example 1 were carried out, results of Vpo = 850 volts and E _1/2 = 12.9 lux·sec were obtained. Examples 32 to 40 In Example 31, the disazo pigments shown in Table 4 below were used in place of the disazo pigment No. 4 to prepare photoreceptors in the form shown in Figure 2, and the same method as in Example 1 was used.
Vpo and E _1/2 were determined and the results shown in Table 4 were obtained.

[Table] Example 41 2 parts by weight of disazo pigment No. 5 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 2,4,7-trinitro-9-fluorenone, 2 parts by weight of polycarbonate [Panlite L, manufactured by Teijin Co., Ltd.], and 46 parts by weight of tetrahydrofuran were mixed to prepare a dispersion liquid, and this was used as the charge carrier. Apply it on the generation layer with a doctor blade,
A charge transfer medium layer having a thickness of 10 μm was formed by drying at 100° C. for 10 minutes, and a photoreceptor having the form shown in FIG. 3 was obtained.
Example 1 Regarding the photoreceptor obtained as described above
Measured similarly, Vpo is 870 volts, E _1/2 is 14.1
I got the result of lux sec. Examples 42 to 50 A photoreceptor having the form shown in FIG. 3 was prepared in the same manner as in Example 41 except that disazo pigments shown in Table 5 below were used in place of disazo pigment No. 5. Table 5 shows the Vpo and E _1/2 of these photoreceptors.

[Table] Example 51 2 parts by weight of disazo pigment No. 6 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 form a thick film. A charge carrier generation layer having a thickness of 1 μm was formed. on the other hand,
2,5-bis(4-diethylaminophenyl)-
2 parts by weight of 1,3,4-oxadiazole, 2 parts by weight of polycarbonate (same as in Example 41) and 46 parts by weight of tetrahydrofuran were mixed to form a dispersion,
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 medium layer with a thickness of 10 μm, thereby obtaining the laminated photoreceptor shown in FIG. 3. The photoreceptor obtained as described above was measured in the same manner as in Example 1, except that -6KV corona discharge was performed, and the results were that the Vpo of this material was 730 volts and the E _1/2 was 3.7 lux·sec. I got it. Examples 52 to 60 Photoreceptors similar to Example 51 were prepared using the disazo pigments shown in Table 6 below in place of disazo pigment No. 6. Vpo and E _1/2 of these photoreceptors
is as shown in Table-6.

【table】 [Brief explanation of the drawing]

1 to 3 are enlarged sectional views of the photoreceptor of the present invention, respectively. 1... Conductive support, 2, 2', 2''... Photosensitive layer, 3
...binder, 4...disazo pigment, 5...charge transfer medium, 6...charge carrier generation layer, 7...charge transfer medium layer.

Claims (1)

[Claims] 1. General formula on a conductive support [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;
Ar ₁ is an aromatic ring such as a benzene ring or a naphthalene ring,
A hetero ring such as a dibenzofuran ring or a carbazole ring or a substituted product thereof; Ar ₂ and Ar ₃ 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, or a phenyl group or a substituted product thereof; 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.