JP2817811B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having excellent red reproducibility and light sensitivity.

[0002]

2. Description of the Related Art Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) include inorganic photoconductive substances such as selenium or selenium alloy, and inorganic photoconductive substances such as zinc oxide or cadmium sulfide. An organic photoconductive substance such as poly-N-vinylcarbazole or polyvinylanthracene, an organic photoconductive substance such as a phthalocyanine compound or a bisazo compound dispersed in a binder, dispersed in a binder. And vacuum-deposited ones are used.

A photoreceptor is required to have a function of retaining a surface charge in a dark place, a function of receiving light to generate a charge, and a function of receiving light and transporting a charge. A so-called single-layer type photoreceptor that combines these functions, and a layer that separates functions into a layer that mainly contributes to charge generation and a layer that contributes to surface charge in the dark and charge transport during photoreception. There is a so-called laminated photoconductor. For image formation by electrophotography using these photoconductors, for example, the Carlson method is applied. Image formation by this method involves charging a photoreceptor by corona discharge in a dark place, forming an electrostatic latent image such as a character or picture of an original on the charged photoreceptor surface, and forming the electrostatic latent image After the toner image is transferred, the photoreceptor is subjected to charge elimination, removal of residual toner, light charge elimination, etc., and then reused. Is done.

In recent years, electrophotographic photoreceptors using organic materials have been put to practical use due to their advantages such as flexibility, thermal stability, and film forming properties. Representative examples include a photoreceptor using a phthalocyanine compound as a charge generating substance (described in US Pat. No. 3,816,118), a photoreceptor using an azo compound (described in JP-A-47-37543), Photoreceptor using perylene compound (JP-A-63-27146)
No. 1), and a photoreceptor using a polycyclic quinone compound (described in JP-B-60-59588).

[0005]

By the way, when these organic photoconductors are applied to copying machines, they satisfy characteristics such as sensitivity, charge holding ability, printing durability, environmental resistance, and red reproducibility. There must be. In particular, improvements in sensitivity and red reproducibility under important conditions are desired. However, in order to improve these characteristics, an electron accepting substance and an electron donating substance are added to the charge generating layer, and a dye is added to the charge transporting layer. In addition, the charge transport ability of the charge transport layer itself is deteriorated. Therefore, azo compounds, perylene compounds, and polycyclic quinone compounds which are excellent in sensitivity, charge retention ability, printing durability, and environmental resistance and have no sensitivity to reflected light of a red image are being developed. The photoreceptor using the above material has not sufficiently satisfied the electrophotographic characteristics required for a copying machine.

The present invention has been made in view of the above points, and has as its object to provide an electrophotographic photoreceptor having high sensitivity and excellent red reproducibility by using a charge generating substance having a different general formula. .

[0007]

According to the present invention, there is provided an electroconductive substrate and a photosensitive layer, wherein the photosensitive layer comprises a bisazo compound represented by the general formulas (I) and (II). It is achieved by containing the compound as a charge generating substance or the bisazo compound represented by the general formulas (I) and (IX) as a charge generating substance.

[0008]

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Wherein Y is an optionally substituted heterocyclic residue,
R ₁ is an alkyl group which may be substituted, R ₂ is a hydrogen atom,
A cyano group, a carbamoyl group, a carboxyl group, an ester group or an acyl group, Z is an optionally substituted heterocyclic residue,
R ₃ is a halogen atom, an alkyl group or an alkoxy group,
R ₄ is an alkyl group which may be substituted, R ₅ is a hydrogen atom,
A cyano group, a carbamoyl group, a carboxyl group, an ester group or an acyl group, and Cp are coupler residues.

The following are specific examples of the bisazo compounds represented by the general formulas (I), (II) and (IX) used in the present invention.

[0011]

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[0012]

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[0013]

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[0014]

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[0015]

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[0016]

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[0017]

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[0018]

The compound of the formula (I) has excellent red reproducibility, and the compound of the formula (II) has poor red reproducibility. However, by using both of them, a photoreceptor excellent in half-attenuation exposure amount (sensitivity) can be obtained without impairing red reproducibility. The compound of the general formula (IX) is inferior in sensitivity, but is more excellent in red reproducibility than the compound of the general formula (I). General formula (I) and general formula (IX)
By using the above compound in combination, a photoreceptor excellent in red reproducibility can be obtained without impairing the sensitivity.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are cross-sectional views showing a photoreceptor according to an embodiment of the present invention, and FIGS. 3 and 4 are cross-sectional views showing a photoreceptor according to a different embodiment of the present invention.
Is an undercoat layer, 3 is a charge generation layer, 4 is a charge transport layer, 5 is a photosensitive layer, 6 is a surface coating layer, 31, 32 and 31A, 32
A is a charge generation layer containing different charge generation substances, and the photosensitive layer is a function-separated type in which a charge generation layer and a charge transport layer are separated. 1 and 3 are laminated in the order of a charge generation layer and a charge transport layer. In some cases, six surface coating layers can be provided. The photosensitive layers in FIGS. 2 and 4 are laminated in the order of the charge transport layer and the charge generation layer, contrary to FIGS.

The conductive substrate 1 serves as an electrode of the photoreceptor and also serves as a support for the other layers, and may be cylindrical, plate-like or film-like. A conductive material may be applied to a metal such as nickel, glass, resin, or the like. The undercoat layer 2 improves the applicability of the charge generation layer and the charge transport layer, and has functions for preventing image defects, improving temperature / humidity characteristics, and preventing carrier injection from the substrate.

As the material, silicon, polyamide, polyester, acrylic, phenoxy, polystyrene, polyurethane resin, aluminum oxide, etc. are used. In order to control the conductivity of the resin, SiO ₂ , T
In some cases, metal oxides such as iO ₂ , In ₂ O ₃ , and ZrO ₂ are dispersed in a resin and used.

The thickness of the undercoat layer can be arbitrarily set within a range that does not adversely affect the function, though it depends on the composition. The charge generating layer 3 is formed by applying a material in which particles of an organic charge generating substance are dispersed in a resin binder, and receives light to generate charges. In addition, the charge generation efficiency is high, and at the same time, the injection property of the generated charge into the charge transport layer 4 is important.

Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance and is generally 5 μm or less, preferably 1 μm or less. The charge generation layer may be mainly composed of a charge generation substance, to which a charge transport substance or the like is added. Examples of the resin binder include vinyl chloride, vinyl chloride-vinyl acetate copolymer, diallyl phthalate, polyarylate, polystyrene, styrene-butadiene copolymer, polycarbonate, polyester, methacrylate, polyvinyl butyral polymer and copolymer. Can be used in combination as appropriate.

The charge transport layer 4 is a coating film made of a material in which an organic charge transport material is dispersed or dissolved in a resin binder. In a dark place, the charge transport layer 4 holds the charge of the photosensitive member as an insulator layer.
During photoreception, it functions to transport the charge injected from the charge generation layer. As the charge transport material, a hydrazone compound, a pyrazoline compound, a stilbene compound, an amine compound, a fluorenone compound, or the like is used. As the resin binder, the same resin as that of the charge generation layer is used, but mechanical, chemical, and electrical In addition to stability and adhesion, compatibility with the charge transport material is important.

The thickness of the charge transport layer is preferably in the range of 3 to 35 μm in order to maintain a practically effective surface potential.
More preferably, it is 10 to 30 μm.

The surface coating layer 6 has excellent durability against mechanical stress and is made of a chemically stable substance. The surface coating layer 6 has a function of receiving and holding the charge of corona discharge in a dark place. It is necessary for the generating layer to have the ability to transmit sensitive light, to transmit light at the time of exposure, to reach the charge generating layer, and to inject generated charges to neutralize and eliminate surface charges. Further, as described above, it is desirable that the coating material is as transparent as possible in the wavelength region of the maximum absorption of light of the charge generation substance.

As the coating material of the surface coating layer, modified silicone resin such as acrylic modified silicone, epoxy modified silicon, alkyd modified silicon, polyester modified silicon, urethane modified silicon, etc., and silicon resin, polyamide, polyester, Epoxy, phenoxy, acrylic resin and the like can be applied.
These resins can be used alone, but SiO ₂ , TiO ₂ , In ₂ O ₃ , Z
A mixed material with a condensate of a metal alkoxy compound capable of forming a film containing rO ₂ as a main component is preferable.

Although the thickness of the coating layer itself depends on the composition of the coating layer, it can be arbitrarily set within a range where adverse effects such as an increase in residual potential do not occur when used repeatedly and continuously.

Further, as shown in FIGS. 3 and 4, the charge generation layers can be laminated and used like the charge generation layer 31A and the charge generation layer 32A, and there is no problem in characteristics.

Example 1 7 parts by weight of a bisazo compound represented by the above formula I-1 as a charge generating substance, 3 parts by weight of a bisazo compound represented by the above formula II-1 and diallyl phthalate resin (trade name) as a binder resin 6 parts by weight of Dap K (manufactured by Osaka Soda) were mixed with 1280 parts by weight of methyl ethyl ketone, and kneaded with a mixer for 4 hours to prepare a coating solution to prepare a coating solution for a charge generation layer. Next, 1 part by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) as a charge transporting substance, 1 part by weight of a polycarbonate resin (trade name Panlite L-1225: manufactured by Teijin Chemicals) as a binder resin, and 6 parts by weight of dichloromethane To prepare a coating solution for the charge transport layer. Next, a coating solution prepared in the order of a charge generation layer (1 μm) and a charge transport layer (17 μm) was applied on a polyester terephthalate film on which aluminum was vapor-deposited, to prepare a photoreceptor for negative charging.

Example 2 The same as in Example 1 except that the charge generating substance of Example 1 was changed to 9 parts by weight of the bisazo compound represented by the above formula I-1 and 1 part by weight of the bisazo compound represented by the above formula II-1. A photoreceptor was prepared.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that the charge generating substance of Example 1 was changed to 10 parts by weight of the bisazo compound represented by the above formula I-1.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 1, except that the charge generating substance of Example 1 was changed to 10 parts by weight of the bisazo compound represented by the above formula II-1.

The electrophotographic characteristics of the photoreceptor thus obtained were evaluated by using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.
It measured using.

The surface potential V _s (volts) of the photosensitive member is an initial surface potential when the surface of the photosensitive member is negatively charged by performing a corona discharge of −6.0 kV for 10 seconds in a dark place, and subsequently the corona discharge. the surface potential of when kept dark for 2 seconds discontinued state of V _d was measured (volts), further followed by the photoreceptor surface to the irradiation of white light 2lux V _d the time to half seconds And the half-attenuation exposure amount E _1/2 (lux · s)
And Further, the surface potential when the surface of the photoreceptor was irradiated with 2 lux white light for 10 seconds was defined as the residual potential V _r (volt). Further, the half-attenuation exposure amount E _1/2 (5
50) and the half-attenuation exposure amount E _1/2 (6
50) to the red reproducibility E _1/2 (650) / E _1/2 (5
50). The larger the value of E _1/2 (650) / E _1/2 (550), the better the red reproducibility. Table 1 shows the measurement results.

[0036]

[Table 1]

As can be seen from Table 1, Examples 1 and 2 have almost the same surface potential and residual potential as Comparative Examples 1 and 2, and the half-attenuation exposure is improved without impairing the red reproducibility. Thus, the superiority of the present invention by mixing the bisazo compound represented by the general formula (I) and the bisazo compound represented by the general formula (II) is apparent.

Example 3 7 parts by weight of a bisazo compound represented by the above formula I-1 as a charge generating material, 3 parts by weight of a bisazo compound represented by the above formula II-1 and diallyl phthalate resin (trade name) as a binder resin (Dap K: Osaka Soda) 10 parts by weight was mixed with 2000 parts by weight of methyl ethyl ketone, and kneaded with a mixer for 4 hours to prepare a coating solution to prepare a coating solution for a charge generation layer. Next, 1 part by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) as a charge transporting substance, 1 part by weight of a polyarylate resin (trade name: U-Polymer P-5001: manufactured by Unitika) as a binder resin, and 6 parts by weight of dichloromethane To prepare a coating solution for the charge transport layer. Next, a coating liquid prepared in the order of a charge transport layer (17 μm) and a charge generation layer (1 μm) was applied on a polyester terephthalate film on which aluminum had been vapor-deposited to prepare a photoreceptor for positive charging.

Example 4 Same as Example 3 except that the charge generating material of Example 3 was changed to 9 parts by weight of the bisazo compound represented by the above formula I-1 and 1 part by weight of the bisazo compound represented by the above formula II-1. A photoreceptor was prepared.

Comparative Example 3 A photoconductor was prepared by the same way as that of Example 3 except that the charge generating substance of Example 3 was changed to 10 parts by weight of the bisazo compound represented by the above formula I-1.

Comparative Example 4 A photoconductor was prepared by the same way as that of Example 3 except that the charge generating substance of Example 3 was changed to 10 parts by weight of a bisazo compound represented by the above formula II-1.

The electrophotographic characteristics of the photoreceptor thus obtained were measured by using an electrostatic recording paper tester "SP-428" manufactured by Kawaguchi Electric.
It measured using.

Surface potential V of photoreceptor_s(Bolt) is in the dark
+ 6.0kV corona discharge for 10 seconds, photoreceptor surface
Is the initial surface potential when positively charged, followed by
When corona discharge is stopped and kept in a dark place for 2 seconds
Surface potential V_d(Volts) and then the photoreceptor
Irradiate the surface with 2 lux white light to illuminate_dIs halved
And the half-attenuation exposure E_1/2(Lux
・ S) Also exposed to 2lux white light for 10 seconds
The surface potential when irradiating the body surface is the residual potential V _r(Bol
G). Furthermore, the half-attenuation exposure amount E of the monochromatic light of 550 nm
_1/2(550) and half-attenuation exposure amount E of monochromatic light of 650 nm
_1/2(650) ratio to red reproducibility E_1/2(650) / E
_1/2(550). E_1/2(650) / E_1/2(5
The larger the value of 50), the better the red reproducibility. Measurement
The results are shown in Table 2.

[0044]

[Table 2]

As can be seen from Table 2, Examples 3 and 4 have almost the same surface potential and residual potential as Comparative Examples 3 and 4, and improved the half-attenuated exposure without impairing the red reproducibility. Thus, the superiority of the present invention by mixing the bisazo compound represented by the general formula (I) and the bisazo compound represented by the general formula (II) is apparent.

Example 5 7 parts by weight of a bisazo compound represented by the above formula I-1 as a charge generating substance, 3 parts by weight of a bisazo compound represented by the above formula IX-1 and diallyl phthalate resin (trade name) as a binder resin 6 parts by weight of Dap K (manufactured by Osaka Soda) were mixed with 1280 parts by weight of methyl ethyl ketone, and kneaded with a mixer for 4 hours to prepare a coating solution to prepare a coating solution for a charge generation layer. Next, p-diethylaminobenzaldehyde-diphenylhydrazone (A
BPH) 1 part by weight, polycarbonate resin as a binder resin (trade name: Panlite L-1225: manufactured by Teijin Chemicals Limited) 1
Parts by weight were dissolved in 6 parts by weight of dichloromethane to prepare a coating solution for the charge transport layer. Next, a charge generation layer (1) was formed on a polyester terephthalate film on which aluminum was deposited.
μm) and a charge transport layer (18 μm) in this order to prepare a negatively charged photoreceptor.

Example 6 The same as Example 5 except that the charge generating material of Example 5 was changed to 5 parts by weight of the bisazo compound represented by the above formula I-1 and 5 parts by weight of the bisazo compound represented by the above formula IX-1. A photoreceptor was prepared.

Example 7 The same as Example 5 except that the charge generating material of Example 5 was changed to 3 parts by weight of the bisazo compound represented by the above formula I-1 and 7 parts by weight of the bisazo compound represented by the above formula IX-1. A photoreceptor was prepared.

Comparative Example 5 A photoconductor was prepared by the same way as that of Example 5 except that the charge generating substance of Example 5 was changed to 10 parts by weight of a bisazo compound represented by the above formula I-1.

Comparative Example 6 A photoconductor was prepared by the same way as that of Example 5 except that the charge generating substance of Example 5 was changed to 10 parts by weight of a bisazo compound represented by the above-mentioned chemical formula IX-1.

Electrophotography of the photoreceptor thus obtained
Characteristics of Kawaguchi Denki's electrostatic recording paper tester "SP-428"
It measured using. Photoreceptor surface potential V_s(Bolt)
Exposure to corona discharge of -6.0 kV for 10 seconds in dark place
This is the initial surface potential when the body surface is negatively charged,
Subsequently, it was kept in a dark place for 2 seconds with the corona discharge stopped.
Surface potential V_d(Volts) was measured. Further
Irradiating the surface of the photoreceptor with 2 lux white light_dBut
Obtain the time (second) until it becomes half, and obtain the half-attenuation exposure amount E_1/2
(Lux · s). In addition, 2lux of white light is 10
The surface potential when irradiating the photoconductor surface for 2 seconds is the residual potential V
_r(Volts). Furthermore, half attenuation of monochromatic light of 550 nm
Exposure E_1/2(550) and half attenuation of monochromatic light at 650 nm
Exposure E _1/2(650) ratio to red reproducibility E_1/2(65
0) / E_1/2(550). E_1/2(650) / E
_1/2The larger the value of (550), the better the red reproducibility.
You. Table 3 shows the measurement results.

[0052]

[Table 3]

As can be seen from Table 3, Examples 5 to 7 have almost the same surface potential and residual potential as Comparative Examples 5 and 6, and improved red reproducibility without impairing the half-attenuated exposure amount. Thus, the superiority of the present invention by mixing the bisazo compound represented by the general formula (I) and the bisazo compound represented by the general formula (IX) is apparent.

Example 8 7 parts by weight of a bisazo compound represented by the above formula I-1 as a charge generating material, 3 parts by weight of a bisazo compound represented by the above formula IX-3, and diallyl phthalate resin (trade name) as a binder resin (Dap K: Osaka Soda) 10 parts by weight was mixed with 2000 parts by weight of methyl ethyl ketone, and kneaded with a mixer for 4 hours to prepare a coating solution to prepare a coating solution for a charge generation layer. Next, p-diethylaminobenzaldehyde-diphenylhydrazone (A
BPH) 1 part by weight, polyarylate resin (trade name: U-Polymer P-5001: manufactured by Unitika) as a binder resin 1
Parts by weight were dissolved in 6 parts by weight of dichloromethane to prepare a coating solution for the charge transport layer. Next, a charge transport layer (1) was formed on a polyester terephthalate film on which aluminum was deposited.
7 μm) and the coating solution prepared in the order of the charge generation layer (1 μm) to prepare a photoconductor for positive charging.

Example 9 The same as Example 8 except that the charge generating material of Example 8 was changed to 5 parts by weight of the bisazo compound represented by the above formula I-1 and 5 parts by weight of the bisazo compound represented by the above formula IX-3. A photoreceptor was prepared.

Example 10 The same as Example 8 except that the charge generating material of Example 8 was changed to 3 parts by weight of the bisazo compound represented by the above formula I-1 and 7 parts by weight of the bisazo compound represented by the above formula IX-3. A photoreceptor was prepared.

Comparative Example 7 A photoconductor was prepared by the same way as that of Example 8 except that the charge generating substance of Example 8 was changed to 10 parts by weight of a bisazo compound represented by the above formula IX-3.

Electrophotography of the photoreceptor thus obtained
Characteristics of Kawaguchi Denki's electrostatic recording paper tester "SP-428"
It measured using. Photoreceptor surface potential V_s(Bolt)
Exposure to corona discharge of + 6.0kV for 10 seconds in dark place
This is the initial surface potential when the body surface is positively charged,
Subsequently, it was kept in a dark place for 2 seconds with the corona discharge stopped.
Surface potential V_d(Volts) was measured. Further
Irradiating the surface of the photoreceptor with 2 lux white light_dBut
Obtain the time (s) until it becomes half and obtain the half-attenuation exposure amount E_1/2
(Lux · s). In addition, 2lux of white light is 10
The surface potential when irradiating the photoconductor surface for 2 seconds is the residual potential V
_r(Volts). Furthermore, half attenuation of monochromatic light of 550 nm
Exposure E_1/2(550) and half attenuation of monochromatic light at 650 nm
Exposure E _1/2(650) ratio to red reproducibility E_1/2(65
0) / E_1/2(550). E_1/2(650) / E
_1/2The larger the value of (550), the better the red reproducibility.
You. Table 4 shows the measurement results.

[0059]

[Table 4]

As can be seen from Table 4, Examples 8 to 10 have almost the same surface potential and residual potential as Comparative Example 7;
The red reproducibility is improved without impairing the half-attenuation exposure amount, and the superiority by mixing the bisazo compound represented by the general formula (I) of the present invention with the bisazo compound represented by the general formula (IX) Is clear.

Example 11 The charge generation layer 31 was formed of the above-mentioned formula I-
10 parts by weight of the bisazo compound represented by No. 1 and 6 parts by weight of a diallyl phthalate resin (trade name: Dap K: manufactured by Osaka Soda) as a binder resin were mixed with 1280 of methyl ethyl ketone.
Parts by weight and kneading with a mixer for 4 hours to prepare a coating solution to prepare a coating solution for the charge generation layer.
Is obtained by adding 10 parts by weight of a bisazo compound represented by the above chemical formula IX-1 as a charge generating substance, 6 parts by weight of a diallyl phthalate resin (trade name: DAP K, manufactured by Osaka Soda) as a binder resin, 2560 parts by weight of methyl ethyl ketone, The mixture was mixed and kneaded with a mixer for 4 hours to prepare a coating solution to prepare a coating solution for the charge generation layer. Next, p as a charge transport material
1 part by weight of -diethylaminobenzaldehyde-diphenylhydrazone (ABPH) and 1 part by weight of a polycarbonate resin (trade name: Panlite L-1225: manufactured by Teijin Chemicals Ltd.) as a binder resin are dissolved in 6 parts by weight of dichloromethane to form a charge transport layer. Was prepared. Next, the charge generation layer 32 (0.7 μm) and the charge generation layer 31 (0.3 μm) were formed on a polyester terephthalate film on which aluminum was deposited.
m) and the coating solution prepared respectively in the order of the charge transport layer (18 μm) were applied to prepare a photoreceptor for negative charging.

Example 12 The charge generation material of the charge generation layer 31 in Example 11 was changed to the bisazo compound represented by the above-mentioned chemical formula IX-1, and the charge generation material of the charge generation layer 32 was changed to the bisazo compound represented by the above-mentioned chemical formula I-1. A photoconductor was prepared in the same manner as in Example 11, except that the compound was changed.

Comparative Example 8 A photoconductor was prepared in the same manner as in Example 11 except that the charge generating substance of Example 11 was changed to only 10 parts by weight of the bisazo compound represented by the above-mentioned chemical formula I-1 to form the layer structure shown in FIG. Created.

Comparative Example 9 A photoconductor was prepared in the same manner as in Example 11, except that the charge generating substance of Example 11 was changed to only 10 parts by weight of the bisazo compound represented by the above-mentioned chemical formula IX-1 to form the layer structure shown in FIG. Created. The electrophotographic characteristics of the photoreceptor thus obtained were measured using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.

The surface potential V _s (volt) of the photosensitive member is an initial surface potential when the surface of the photosensitive member is negatively charged by performing a corona discharge of −6.0 kV for 10 seconds in a dark place. Was stopped, and the surface potential V _d (volt) was measured when kept in a dark place for 2 seconds. Further subsequently photoconductor time until V _d is halved to white light illumination of 2lux illuminance on the surface (s) of the calculated half-attenuation exposure E _1/2 (lu
x · s). Further, the surface potential when the surface of the photoreceptor was irradiated with 2 lux white light for 10 seconds was defined as residual potential V _r (volt).

Further, as a method for evaluating red reproducibility, 550 nm
Half-attenuation exposure E1 _{/ 2} (550) of monochromatic light and 650 nm
The ratio of the half-attenuated exposure amount E _1/2 (650) of the monochromatic light was defined as red reproducibility E _1/2 (650) / E _1/2 (550). E
_The larger the value of _1/2 (650) / E1 / ₂ (550), the lower the sensitivity to red light, and the better the red reproducibility in an actual copying machine image. Table 5 shows the measurement results.

[0067]

[Table 5]

As can be seen from Table 5, Examples 11 and 12
Is a bisazo compound represented by the general formula (I) of the present invention in which the surface potential and the residual potential are almost the same as in Comparative Examples 8 and 9, and the red reproducibility is improved without impairing the half-attenuated exposure amount. And the bisazo compound represented by the general formula (IX) is simultaneously laminated and used.

Example 13 The charge generation layer 31A was formed by using the above-mentioned chemical formula I as a charge generation material.
1 part by weight of a bisazo compound represented by -1 and 1 part by weight of diallyl phthalate resin (trade name: DAP K: manufactured by Osaka Soda) as a binder resin are mixed with 200 parts by weight of methyl ethyl ketone, and kneaded by a mixer for 4 hours. To prepare a coating solution for the charge generation layer, and the charge generation layer 32A
Is 1 part by weight of a bisazo compound represented by the above-mentioned chemical formula IX-3 as a charge generating substance, 1 part by weight of diallyl phthalate resin (trade name: DAP K, manufactured by Osaka Soda) as a binder resin, 400 parts by weight of methyl ethyl ketone Mix 4
The coating solution was adjusted by kneading with a time mixer to prepare a coating solution for the charge generation layer. Next, 1 part by weight of P-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) as a charge transport material, 1 part by weight of a polyarylate resin (trade name: U-Polymer P-5001: manufactured by Unitika) as a binder resin, and 6 parts by weight of dichloromethane To prepare a coating solution for the charge transport layer. Next, a charge transport layer (17 μm), a charge generation layer 32A (0.7 μm) on a polyester terephthalate film on which aluminum was deposited,
The coating solutions prepared respectively in the order of the charge generation layer 31A (0.3 μm) were applied to prepare a photoconductor for positive charging.

Example 14 The charge generation material of the charge generation layer 31A of Example 13 was changed to the bisazo compound represented by the chemical formula IX-3, and the charge generation material of the charge generation layer 32A was changed to the bisazo compound represented by the chemical formula I-1. A photoconductor was prepared in the same manner as in Example 13, except that the compound was changed.

Comparative Example 10 A photoconductor was prepared in the same manner as in Example 13, except that the charge generating substance of Example 13 was changed to only 10 parts by weight of the bisazo compound represented by the above-mentioned chemical formula I-1 to form a layer as shown in FIG. Created.

Comparative Example 11 A photoconductor was prepared by the same way as that of Example 13 except that the charge generating substance of Example 13 was changed to only 10 parts by weight of bisazo compound represented by the above-mentioned chemical formula IX-3, and the layer configuration was changed as shown in FIG. Created.

The electrophotographic characteristics of the photoreceptor thus obtained were evaluated by using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.
It measured using. The surface potential V _s (volts) of the photoreceptor is an initial surface potential when the surface of the photoreceptor is positively charged by performing a corona discharge of +6.0 kV for 10 seconds in a dark place,
Subsequently, the surface potential V _d (volt) when the corona discharge was stopped and the device was kept in a dark place for 2 seconds was measured. Further subsequently semi attenuation exposure determined the time (seconds) until V _d is halved by the illuminance on the surface of the photosensitive member and white light illumination of 2lux E _1/2
(Lux · s). In addition, 2lux of white light is 10
The surface potential when irradiating the photoconductor surface for 2 seconds is the residual potential V
_r (volt).

Further, as a method for evaluating red reproducibility, 550 nm
Half-attenuation exposure E1 _{/ 2} (550) of monochromatic light and 650 nm
The ratio of the half-attenuated exposure amount E _1/2 (650) of the monochromatic light was defined as red reproducibility E _1/2 (650) / E _1/2 (550). E
_The larger the value of _1/2 (650) / E1 / ₂ (550), the lower the sensitivity to red light, and the better the red reproducibility in an actual copying machine image. Table 6 shows the measurement results.

[0075]

[Table 6]

As can be seen from Table 6, Examples 13 and 14
Is a bisazo compound represented by the general formula (I) of the present invention in which the surface potential and the residual potential are almost the same as in Comparative Examples 10 and 11, and the red reproducibility is improved without impairing the half-attenuated exposure amount. And the bisazo compound represented by the general formula (IX) is simultaneously laminated and used.

[0077]

According to the present invention, the bisazo compound represented by the general formula (I) and the bisazo compound represented by the general formula (II) or the general formula (IX) are used as the charge generating material.
In combination with the bisazo compound represented by the formula (1), a photoreceptor having high sensitivity and excellent red reproducibility can be obtained as a photoreceptor for electrophotography for a copying machine, even when positively and negatively charged.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a negatively charged photoconductor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a positively charged photoconductor according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a negative charging type photoconductor according to another embodiment of the present invention;

FIG. 4 is a cross-sectional view showing a positively charged photoconductor according to another embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 charge generation layer 4 charge transport layer 5 photosensitive layer 6 surface coating layer 31 charge generation layer 32 charge generation layer 31A charge generation layer 32A charge generation layer

Claims (10)

(57) [Claims] 1. A photosensitive layer comprising a conductive substrate and a photosensitive layer, wherein the photosensitive layer comprises at least one of a bisazo compound represented by the general formula (I) and at least one of a bisazo compound represented by the general formula (II). An electrophotographic photoreceptor characterized in that the photoreceptor contains one kind as a charge generating substance. Embedded image (Where Y is an optionally substituted heterocyclic residue, R ₁ is an optionally substituted alkyl group, R ₂ is a hydrogen atom, a cyano group,
A carbamoyl group, a carboxyl group, an ester group or an acyl group, Z is an optionally substituted heterocyclic residue, R ₃ is a halogen atom, an alkyl group or an alkoxy group, R ₄ is an optionally substituted alkyl group, and R ₅ is Hydrogen atom, cyano group,
Represents a carbamoyl group, a carboxyl group, an ester group or an acyl group. ) 2. A photosensitive layer comprising a conductive substrate and a photosensitive layer, wherein the photosensitive layer comprises at least one of a bisazo compound represented by the general formula (I) and at least one of a bisazo compound represented by the general formula (IX). An electrophotographic photoreceptor characterized in that the photoreceptor contains one kind as a charge generating substance. Embedded image (Where Y is an optionally substituted heterocyclic residue, R ₁ is an optionally substituted alkyl group, R ₂ is a hydrogen atom, a cyano group,
A carbamoyl group, a carboxyl group, an ester group or an acyl group, and Cp are coupler residues. ) 3. The photoreceptor according to claim 1, wherein
An electrophotographic photoconductor, wherein the photosensitive layer is formed by laminating a charge generation layer and a charge transport layer. 4. The photoreceptor according to claim 3, wherein the two kinds of bisazo compounds represented by different general formulas form different charge generating layers, respectively, and the charge generating layers are laminated on each other. A photoconductor for electrophotography, comprising: 5. The electrophotographic photoconductor according to claim 2, wherein the coupler residue Cp is represented by any one of formulas (III) to (VIII). Embedded image (In the general formulas (III) to (VIII), Q is a residue condensed with a benzene ring to form a polycyclic aromatic ring or a heterocyclic ring; X ₁
Is OR or NR'R "(R, R 'and R" each represent a hydrogen atom, an alkyl group which may be substituted, an aryl group or an aromatic heterocyclic group), and X ₂ and X ₅ are each substituted X ₃ and X ₆ represent a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group or an acyl group, and X ₄ and X ₁₁ represent a hydrogen atom an alkyl group which may be substituted, a cycloalkyl group, an alkenyl group, an aryl group or an aromatic heterocyclic group, X ₇
And X ₈ are each a hydrogen atom, a halogen atom, a nitro group or an optionally substituted alkyl or alkoxy group, X ₉ represents an alkyl group, an aryl group, a carboxyl group, an ester group, X ₁₀ is optionally substituted Represents an aryl group or an aromatic heterocyclic group, and G represents a residue forming a heterocyclic ring. ) 6. The photoreceptor according to claim 1, wherein the compounds of the general formulas (I) and (II) each have R ₁ as CH ₃
A compound wherein R ₂ is a CN group, Y is a residue forming pyrido [1,2-a] benzimidazole, R ₃ is a Cl atom, R ₄ is a CH ₃ group, R ₅ is a CN group, and Z is Pyrido [1,2
-A] a compound which is a residue forming benzimidazole; 7. The photosensitive member according to claim 6, wherein the weight ratio of the compound represented by the general formula (I) to the compound represented by the general formula (II) is in the range of 7: 3 and 9: 1. A photoconductor for electrophotography, comprising: 8. The photoreceptor according to claim 2, wherein each of the compounds of the general formulas (I) and (IX) has R ₁ as CH ₃
A compound wherein R ₂ is a CN group, Y is a residue forming pyrido [1,2-a] benzimidazole, a coupler residue C
p is a general formula (VI), X ₅ is a CH ₃ group, and X ₆ is C
A photoreceptor for electrophotography, comprising a compound having an N group, X ₇ being a hydrogen atom and X ₈ being a hydrogen atom. 9. The photoreceptor according to claim 2, wherein the compounds of the general formulas (I) and (IX) each have R ₁ as CH ₃
A compound wherein R ₂ is a CN group, Y is a residue forming pyrido [1,2-a] benzimidazole, a coupler residue C
A photoreceptor for electrophotography, wherein p is a compound of the general formula (III), and R ₁ and R ″ of X ₁ are an aryl group substituted with a hydrogen atom and a methyl group, respectively. 10. The photoreceptor according to claim 8, wherein the weight ratio of the compound represented by the general formula (I) to the compound represented by the general formula (IX) is 7: 3 and 3: 7. A photoreceptor for electrophotography, characterized in that: