JPH0738078B2 - Electrophotographic photoconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a photoconductor for electrophotography, and more specifically, in the photosensitive layer formed on a conductive substrate, the disazo compound represented by the general formula (I) is used. The present invention relates to an electrophotographic photoreceptor containing a compound.

[Conventional technology]

Conventionally, as a photosensitive material for an electrophotographic photoconductor (hereinafter also referred to as a photoconductor), an inorganic photoconductive substance such as selenium or a selenium alloy, or an inorganic photoconductive substance such as zinc oxide or cadmium sulfide is used in a resin binder. A dispersion, an organic conductive substance such as poly-N-vinylcarbazole or polyvinylanthracene, an organic photoconductive substance such as a phthalocyanine compound or a disazo compound, or these organic photoconductive substances are dispersed in a resin binder. It is used.

In addition, the photoreceptor must have the function of retaining surface charge in the dark, the function of receiving light to generate charge, and the function of receiving light to transport charge as well. A so-called single-layer type photoreceptor having a combined function, and a layer in which a function-separated layer is laminated mainly on a layer that contributes to charge generation and a layer that contributes to retention of surface charge in a dark place and charge transport during light reception There are laminated photoreceptors. For example, the Carlson method is applied to the image formation by the electrophotographic method using these photoconductors. Image formation by this method is performed by corona discharge to a photoconductor in a dark place, formation of an electrostatic latent image such as characters and pictures of an original by exposure on the charged photoconductor surface,
The electrostatic latent image thus formed is developed by toner, the developed toner image is transferred to a support such as paper, and fixed,
After the transfer of the toner image, the photoconductor is subjected to static elimination, removal of residuals, photostatic elimination, and the like, and then reused.

In recent years, electrophotographic photoreceptors using organic materials have been put into practical use due to advantages such as flexibility, thermal stability, and film-forming property. For example, poly-N-vinylcarbazole and 2,
A photoreceptor comprising 4,7-trinitrofluoren-9-one (described in U.S. Pat. No. 3,484,237), a photoreceptor containing an organic pigment as a main component (described in JP-A-47-37543), Examples thereof include photoconductors containing a eutectic complex of a dye and a resin as a main component (described in JP-A-47-10735). Furthermore, many new azo compounds and perylene compounds have been put to practical use.

[Problems to be solved by the invention]

As described above, the organic material has many advantages that the inorganic material does not have, however, the present situation is that one that does not sufficiently satisfy all the properties required for the electrophotographic photoreceptor has not yet been obtained. Especially, there was a problem in photosensitivity and characteristics in repeated continuous use.

The present invention has been made in view of the above-mentioned points, and by using a new organic material which has never been used as a charge generating substance in a photosensitive layer, an electrophotographic image having high sensitivity and excellent repeatability can be obtained. An object is to provide a photoconductor for use.

[Means for solving problems]

To achieve the above object, according to the present invention, there is provided an electrophotographic photoreceptor having a photosensitive layer containing at least one kind of the disazo compounds represented by the following general formula (I).

Cp-N = ND-N = N-Cp (I) [In the formula (I), -D- represents any one of the following general formulas (II) to (IV), and Cp represents a coupler. Indicates a residue.

(In the formulas (II) to (IV), Y _{1 to} Y ₁₈ are a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group, an acyl group, a halogen atom, a sulfonic acid group, and an optionally substituted alkyl group. , Cycloalkyl group, alkenyl group,
Represents an aryl group or an aromatic heterocyclic group, and Ar represents an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group. )] Further, it is preferable that the coupler residue Cp in the general formula (I) has a structure of any one of the following general formulas (V) to (VIII).

[In the formulas (V) to (VIII), Z is a residue which is condensed with a benzene ring to form a polycyclic aromatic ring or a heterocycle, and X ₁ is
OR ₁ or NR ₂ R ₃ (R ₁ , R ₂ and R ₃ represent a hydrogen atom, an alkyl group, an optionally substituted aryl group or an aromatic heterocyclic group), X ₂ and X ₅ are respectively substituted Optionally represents an alkyl group, an aryl group or an aromatic heterocyclic group, 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 represents a hydrogen atom, An optionally substituted alkyl group,
Represents a cycloalkyl group, an alkenyl group, an aryl group, or an aromatic heterocyclic group, X ₇ and X ₈ each represent a hydrogen atom, a halogen atom, a nitro group, or an optionally substituted alkyl group or an alkoxy group, X ₉ represents an alkyl group, an aryl group or a carboxyl group, and X ₁₀ represents an optionally substituted aryl group or aromatic heterocyclic group. [Operation] No example is known in which the disazo compound represented by the general formula (I) is used in the photosensitive layer. The present inventors have conducted extensive studies on various organic materials in order to achieve the above-mentioned object, and as a result of carrying out a number of experiments on these disazo compounds, the technical elucidation thereof has not yet been sufficiently conducted. It was found that the use of the specific disazo compound represented by the general formula (I) as a charge-generating substance is extremely effective for improving electrophotographic characteristics, and a photosensitive body having high sensitivity and excellent repeating characteristics is obtained. Was reached.

〔Example〕

The above-mentioned disazo compound of the general formula (I) used in the present invention comprises a corresponding diazonium salt and a coupler,
Suitable organic solvent such as N, N-dimethylformamide (DM
It can be synthesized by reacting a base in F) to cause a coupling reaction.

Specific examples of the disazo compound of the general formula (I) thus obtained are as follows.

The photoconductor of the present invention is one in which the disazo compound represented by the general formula (I) is contained in the photoconductive layer.
Alternatively, it can be used as shown in FIG.

1 to 3 are conceptual sectional views of different embodiments of the photoconductor of the present invention, in which 1 is a conductive substrate, 2a, 2b and 2c are photosensitive layers, 3 is a charge generating substance, and 4 is charge generating. A layer, 5 is a charge transporting substance, 6 is a charge transporting layer, and 7 is a coating layer.

FIG. 1 shows a photosensitive layer 2a (usually referred to as a single layer type photoreceptor) in which a disazo compound which is a charge generating substance 3 and a charge transporting substance 5 are dispersed on a conductive base 1 in a resin binder (binder). The configuration) is provided.

FIG. 2 shows a photosensitive layer 2b formed by stacking a charge generation layer 4 containing a disazo compound as a charge generation substance 3 on a conductive substrate 1 and a charge transport layer 6 mainly composed of a charge transport substance 5.
(Generally referred to as a laminated type photoreceptor) is provided. The photoreceptor having this structure is usually used in a negative charging type.

FIG. 3 shows a layer structure opposite to that of FIG. 2 and is usually used in a positive charging system. In this case, it is general to further provide a coating layer 7 to protect the charge generation layer 4.

As described above, the reason why the laminated type photoconductor has two kinds of layer constitutions is that even if the photoconductor having the layer constitution shown in FIG. Because not. At the present stage, when the positive charging method is applied to the laminated type photoconductor, it is necessary to obtain the photoconductor having the layer structure shown in FIG.

The photoreceptor of FIG. 1 can be prepared by dispersing a charge generating substance in a solution in which a charge transporting substance and a resin binder are dissolved, and applying the dispersion on a conductive substrate.

The photosensitive member of FIG. 2 is obtained by coating a dispersion obtained by dispersing particles of a charge generating substance in a solvent or a resin binder on a conductive base, drying the solution, and dissolving the charge transporting substance and the resin binder thereon. It can be prepared by applying and drying the prepared solution.

The photoreceptor shown in FIG. 3 was obtained by coating a solution in which a charge transporting substance and a resin binder were dissolved on a conductive substrate, drying the solution, and dispersing particles of the charge generating substance in the solvent or the resin binder. The dispersion is applied and dried, and then the coating layer 7
It can be produced by forming.

The conductive substrate 1 serves not only as an electrode of the photoconductor but also as a support for other layers, and may be cylindrical, plate-shaped, or film-shaped, and is made of aluminum, stainless steel, nickel, or the like. A metal, glass, resin or the like that has been subjected to a conductive treatment may be used.

The charge generation layer 4 is formed by applying a material in which particles of the charge generation substance 3 represented by the disazo compound represented by the general formula (I) are dispersed in a resin binder, and receives light to generate charges. . In addition, it is important that the charge generation efficiency is high, and at the same time, the generated charge is injectable into the charge transport layer 6 and the coating layer 7, and the electric field dependence is small and it is desirable that the injection is good even in a low electric field. The charge generation layer may be mainly composed of a charge generation substance and a charge transporting substance or the like may be added thereto. Resin binders include polycarbonate, polyester, polyamide, polyurethane,
Epoxy, silicone resin, methacrylic acid ester polymers and copolymers can be used in appropriate combination.

The charge transport layer 6 is formed by applying a material in which a hydrazone compound, a pyrazoline compound, a styryl compound, a triphenylamine compound, an oxazole compound, an oxadiazole compound, etc. are dissolved / dispersed in a resin binder as an organic charge transporting substance. In a dark place, it functions as an insulating layer that holds the charges of the photoconductor and transports the charges injected from the charge generation layer when receiving light. As the resin binder, polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, methacrylic acid polymer or copolymer, and the like can be used.

The coating layer 7 has a function of receiving and holding the electric charge of corona discharge in a dark place, and also has a property of transmitting the light to which the charge generating layer is sensitive. It is necessary to neutralize and eliminate the surface charge by receiving the generated charge and injecting the generated charge. As the coating material, an organic insulating film forming material such as polyester or polyamide can be applied. In addition, these organic materials and glass resins, SiO ₂
It is also possible to mix and use an inorganic material such as, or a material such as a metal or a metal oxide that reduces electric resistance. The coating material is not limited to the organic insulating film forming material, and an inorganic material such as SiO ₂ or a metal, a metal oxide, or the like can be formed by a method such as vapor deposition or sputtering. As described above, it is desirable that the coating material be as transparent as possible in the wavelength region of the maximum light absorption of the charge generating substance.

The thickness of the coating layer itself depends on the composition of the coating layer,
It can be arbitrarily set within a range in which there is no adverse effect such as an increase in residual potential when repeatedly and continuously used.

Hereinafter, specific examples of the present invention will be described.

Example 1 50 parts by weight of the disazo compound represented by the above compound No. 1 was added,
100 parts by weight of polyester resin (Vylon: Toyobo) and 1-phenyl-3- (p-diethylaminostyryl)-
100 parts by weight of 5- (p-diethylaminophenyl) -2-pyrazoline (ASPP) and a solvent of tetrahydrofuran (THF) are kneaded with a mixer for 3 hours to prepare a coating solution, and an aluminum vapor-deposited polyester film (Al −
On PET) by a wire bar method to form a photosensitive layer so that the film thickness after drying would be 15 μm, to prepare a photosensitive member having the structure shown in FIG.

Example 2 First, 100 parts by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) was dissolved in 700 parts by weight of tetrahydrofuran (THF), and 100 parts by weight of a polycarbonate resin (Panlite L-1250) was mixed with THF and dichloromethane. A coating solution prepared by mixing a solution dissolved in 700 parts by weight of a 1: 1 mixed solvent was applied on an aluminum vapor-deposited polyester film substrate by the wire bar method, and the film thickness after drying was 15 μm.
Was formed on the charge transport layer. On the charge transport layer thus obtained, 50 parts by weight of the disazo compound represented by the above compound No. 1, 50 parts by weight of a polyester resin (trade name: Byron 200: manufactured by Toyobo), 50 parts by weight of PMMA and 3 parts together with a THF solution were mixed. A coating solution is prepared by kneading with a time mixer and applied by a wire bar method, and a charge generation layer is formed so that the film thickness after drying is 0.5 μm. The body was made. However, a coating layer not directly involved in the present invention was not provided.

Example 3 The charge transporting material in Example 2 was changed from ABPH to styryl compound α-phenyl-4′-N, N-dimethylaminostilbene, and the charge transporting layer was formed in the same manner as in Example 2. Then, a charge generating layer was further formed to prepare a photoconductor.

Example 4 The charge-transporting substance in Example 2 was changed from ABPH to tri (p-tolyl) amine which is a triphenylamine compound, and other conditions were the same as in Example 2 to form a charge-transporting layer, and charge generation was further performed. A layer was formed to prepare a photoreceptor.

Example 5 The charge-transporting substance in Example 2 was changed from ABPH to oxadiazole compound 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, and Example 2 was changed. A charge transport layer was formed in the same manner as in 1. and a charge generation layer was further formed to prepare a photoconductor.

The electrophotographic characteristics of the thus obtained photoconductor were measured by using an electrostatic recording paper test device “SP-428” manufactured by Kawaguchi Electric. The results are shown in Table 1.

The surface potential V _s (volt) of the photoconductor is the initial surface potential when the surface of the photoconductor is positively charged by performing +6.0 kV corona discharge in the dark for 10 seconds, and then the corona discharge is stopped. Surface potential V _d (volt) when kept in the dark for 2 seconds
Was measured, and then the time (second) until V _d was halved by irradiating the surface of the photoconductor with white light with an illuminance of 2 lux was obtained and defined as the half-attenuation exposure amount E _1/2 (lux · second). . Further, the surface potential when white light having an illuminance of 2 lux was irradiated for 10 seconds was defined as the residual V _r (volt).

As can be seen from Table 1, the photoreceptors of Examples 1, 2, 3, 4, and 5 were good in surface potential V _s , half-attenuated exposure amount E _1/2 , and residual potential V _r .

Example 6 Disazo compound 100 represented by the above compounds No. 2 to No. 75
Polyester resin (trade name Byron 20
0) Knead with 100 parts by weight of THF solvent for 3 hours with a mixer to prepare a coating solution, and apply about 0.5 on an aluminum support.
The charge generation layer was formed by coating so as to have a thickness of μm. On top of this, the charge-transporting substance in Example 2 was added with ABPH.
Was changed to ASPP, and otherwise the coating liquid for charge transport layer obtained in the same manner as in Example 2 was applied so as to have a thickness of about 15 μm to form a charge transport layer to prepare a photoreceptor.

The electrophotographic characteristics of the thus obtained photoconductor were measured by using an electrostatic recording paper test device “SP-428” manufactured by Kawaguchi Electric. The results are shown in Table 2.

The surface potential V _d (volt) is measured when the surface of the photoconductor is negatively charged by applying a −6.0 kV corona discharge for 10 seconds in the dark to keep the corona discharge in the dark for 2 seconds. Then, the time (second) until _Vd is halved by irradiating the surface of the photoconductor with white light having an illuminance of 2 lux was obtained and defined as a half-attenuated exposure amount E _1/2 (lux · second). Also, the surface potential remains when the white light with an illumination of 2 lux is irradiated for 10 seconds.
It is V _r (volt).

As can be seen from Table 2, the photoconductors using the compounds No. 2 to No. 75 are also good in both the half-attenuation exposure amount E _1/2 and the residual potential V _r .

〔The invention's effect〕

According to the present invention, since the disazo compound represented by the general formula (I) is used as the charge generating substance on the basis of electroconductivity, a photoreceptor having high sensitivity even in positive charging and negative charging and excellent in repeating characteristics. Can be obtained.

Further, if necessary, a coating layer may be provided on the surface to improve durability.

[Brief description of drawings]

1, 2, and 3 are conceptual sectional views showing different embodiments of the photoconductor of the present invention. 1 ... Conductive substrate, 2a.2b.2c ... Photosensitive layer, 3 ... Charge generating material, 4 ... Charge generating layer, 5 ... Charge transporting material, 6
...... Charge transport layer, 7 …… Coating layer.

Claims (2)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing at least one of the disazo compounds represented by the following general formula (I). Cp-N = ND-N = N-Cp (I) [In the formula (I), -D- represents any one of the following general formulas (II) to (IV), and Cp represents a coupler. Indicates a residue. (In the formulas (II) to (IV), Y _{1 to} Y ₁₈ are a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group, an acyl group, a halogen atom, a sulfonic acid group, and an optionally substituted alkyl group. , Cycloalkyl group, alkenyl group,
Represents an aryl group or an aromatic heterocyclic group, and Ar represents an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group. )] 2. The photoconductor according to claim 1, wherein Cp in the general formula (I) is represented by the following general formulas (V) to (VI).
An electrophotographic photoreceptor, which is a disazo compound having any one of the structures of II). [In the formulas (V) to (VIII), Z is a residue which is condensed with a benzene ring to form a polycyclic aromatic ring or a heterocycle, and X ₁ is
OR ₁ or NR ₂ R ₃ (R ₁ , R ₂ and R ₃ represent a hydrogen atom, an alkyl group, an optionally substituted aryl group or an aromatic heterocyclic group), X ₂ and X ₅ are respectively substituted Optionally represents an alkyl group, an aryl group or an aromatic heterocyclic group, 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 represents a hydrogen atom, An optionally substituted alkyl group,
Represents a cycloalkyl group, an alkenyl group, an aryl group, or an aromatic heterocyclic group, X ₇ and X ₈ each represent a hydrogen atom, a halogen atom, a nitro group, or an optionally substituted alkyl group or an alkoxy group, X ₉ represents an alkyl group, an aryl group or a carboxyl group, and X ₁₀ represents an optionally substituted aryl group or aromatic heterocyclic group. ]