JPH0422268B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a photoreceptor for electrophotography. Prior Art There are inorganic photoreceptors for electrophotography, such as those using selenium and its alloys, or photoreceptors with dye-sensitized zinc oxide dispersed in a binder resin, and organic photoreceptors. For example, a typical method using a charge transfer complex of 2,4,7-trinitro-9-fluorenone (TNF) and poly-N-vinylcarbazole (PVK) is known. . However, while these photoreceptors have many advantages, they also have various disadvantages. For example, the currently widely used selenium photoreceptor has difficult manufacturing conditions and high manufacturing costs, is difficult to process into a belt due to its lack of flexibility, and is susceptible to heat and mechanical shock. It is sensitive and must be handled with care. Zinc oxide photoreceptors are low in cost because they can be manufactured by applying inexpensive zinc oxide to a support, but they generally have low sensitivity and poor surface smoothness, hardness, tensile strength, and abrasion resistance. It has mechanical disadvantages such as durability, and there are many problems with durability as a photoreceptor for plain paper copying machines that are usually used repeatedly. Furthermore, a photoreceptor using a charge transfer complex of TNF and PVK has low sensitivity and is unsuitable as a photoreceptor for high-speed copying machines. In recent years, extensive research has been carried out to eliminate the drawbacks of these photoreceptors, and in particular, various organic photoreceptors have been proposed. Among these, there is a layer (hereinafter referred to as "charge generation layer") containing a substance that generates charge carriers when irradiated with light (hereinafter referred to as "charge generation material"), and a layer that receives and transports the generated charge carriers. Substance (hereinafter referred to as "charge transport material")
A multilayer photoreceptor consisting of a layer mainly consisting of a charge transport layer (hereinafter referred to as a "charge transport layer") generally has higher sensitivity and stable chargeability compared to conventional organic photoreceptors. For this reason, it has attracted attention as a photoreceptor for plain paper copying machines, and some are in practical use. Conventional laminated photoreceptors of this type include: (1) one in which a thin layer of a perylene derivative vacuum-deposited is used as a charge generation layer and an oxadiazole derivative is used as a charge transport layer (see U.S. Pat. No. 3,871,882); ), (2) Using a thin layer formed by coating an organic amine solution of chlordian blue as the charge generation layer,
One in which a hydrazone compound is used in the charge transport layer (see Japanese Patent Publication No. 55-42380) is known. However, although conventional photoreceptors of this type have many advantages, they also have various drawbacks as described below. The photoreceptor using the perylene derivative and oxadiazole derivative shown in (1) above has a high manufacturing cost because its charge generation layer is formed by vacuum deposition. The photoreceptor using chlordiane blue and a hydrazone compound as shown in (2) above requires the use of an organic amine (e.g. ethylenediamine), which is generally difficult to handle, as a coating solvent for forming the charge generation layer. There are some flaws in the creation. Purpose The present invention provides an electrophotographic photoreceptor that can be easily manufactured and is suitable for repeated use. Structure The electrophotographic photoreceptor of the present invention has the following general formula () on a conductive support. (In the formula, R ¹ and R ² are hydrogen, lower alkyl group,
It represents a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group. R ¹ and R ² may be the same or different, or R ¹ and R ² may jointly form a ring. ) It is characterized by being provided with a photoconductive layer (photosensitive layer) containing a disazo compound represented by: Here, examples of lower alkyl groups in general formula () include methyl group, ethyl group, propyl group, etc., examples of aralkyl groups include benzyl group, phenethyl group, etc., and examples of aromatic groups include phenyl group, naphthyl group, anthryl group. , pyrenyl group, anthraquinonyl group, etc.; examples of heterocyclic groups include thienyl group, furyl group, pyridyl group, carbazolyl group, etc.; examples of the ring formed by R ¹ and R ² include hexylidene ring, pentylidene ring, Examples include a benzopentylidene ring and a dibenzopentylidene ring. Examples of substituents on the aralkyl group, aromatic group, heterocyclic group, or the ring formed by R ¹ and R ² include lower alkyl groups, lower alkoxy groups, halogen atoms, cyano groups, nitro groups, lower dialkylamino groups, etc. I can do it. Incidentally, the present invention is based on the inventor's extensive studies to achieve the above-mentioned object, and the discovery that the use of a specific disazo pigment (disazo compound) is extremely useful for electrophotographic photoreceptors. This was done based on the following. Furthermore, the electrophotographic photoreceptor of the present invention is not limited to a single-layer type, but rather is preferably a laminated type in which the photosensitive layer is composed of a charge generation layer and a charge transport layer. In such a laminated electrophotographic photoreceptor, the charge generation layer is formed of a layer containing a disazo pigment represented by the above general formula (). The present invention will be explained in more detail below. First, specific examples of the disazo compound represented by the general formula () used in the present invention are as follows.

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[Table] These disazo compounds are
The diazonium salt described in the above publication and the corresponding coupler (2-hydroxy-3-naphthoic acid hydrazide) were mixed in a suitable organic solvent such as N,
It can be easily produced by reacting with a base in N-dimethylformamide (DMF) to cause a coupling reaction. By the way, as described above, the photoreceptor of the present invention contains a charge generating substance represented by the above general formula () in the photosensitive layer, but in an actual photoreceptor, the charge generating substance is and a charge transport material are combined to form a photosensitive layer (photoconductive layer). Although the charge transporting substance used in the present invention is not specified, typical examples thereof are as follows. [ ^R10 is an alkyl group such as a methyl group or an ethyl group, a substituted alkyl group such as a 2-chloroethyl group or a 2-hydroxyethyl group, ^R11 is an alkyl group such as a methyl group or an ethyl group, or an aralkyl group such as a benzyl group, Aryl group such as phenyl group, ^R12 is hydrogen atom, halogen atom such as chlorine, bromine, alkyl group such as methyl group, ethyl group, propyl group, butyl group, methoxy group, ethoxy group, propoxy group, butoxy group, etc. Represents an alkoxy group, dialkylamino group or nitro group. ] [Ar′ represents a naphthyl group, anthryl group, styryl group, or a substituted product thereof; R ¹³ represents an alkyl group such as a methyl group or an ethyl group, an aralkyl group such as a benzyl group, or an aryl group such as a phenyl group. Examples of substituents on naphthyl, anthryl, and styryl groups include alkyl groups such as methyl and ethyl groups, alkoxy groups such as methoxy and ethoxy groups, and dialkylamino groups such as dimethylamino and diethylamino groups. It will be done. ] [R ¹⁴ , R ¹⁵ or R ¹⁷ is a hydrogen atom, a methyl group,
It represents an alkyl group such as an ethyl group or a propyl group, an alkoxy group such as a methoxy group, an ethoxy group, or a propoxy group, a halogen atom such as chlorine or bromine, a nitro group or a hydroxyl group, and R ¹⁶ is a hydrogen atom, a methyl group, an ethyl group, Alkyl groups such as propyl groups, alkoxy groups such as methoxy, ethoxy, and propoxy groups, dialkylamino groups such as dimethylamino and diethylamino groups, dialkylamino groups such as dibenzylamino groups, and diarylamino groups such as diphenylamino groups. , a halogen atom such as bromine, a nitro group or a hydroxyl group, R ¹⁸ represents an alkyl group such as a methyl group or an ethyl group, an aralkyl group such as a benzyl group, or an aryl group such as a phenyl group. ] [R ¹⁹ , R ²⁰ , R ²¹ or R ²² is a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a propyl group,
It represents an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group, a dialkylamino group such as a dimethylamino group or a diethylamino group, a halogen atom such as chlorine or bromine, a nitro group, or a hydroxyl group. ] [ ^R23 is an alkyl group having 1 to 11 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted heterocyclic group, ^R24 or ^R25 is a hydrogen atom, methyl group, ethyl group, propyl group, butyl group represents an alkyl group, a chloro-substituted alkyl group, a hydroxy-substituted alkyl group, a substituted or unsubstituted aralkyl group, and R ²⁴ and R ²⁵ may be bonded to each other to form a nitrogen-containing heterocycle. R ²⁶ or R ²⁷ is a hydrogen atom,
It represents an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an alkoxy group such as a methoxy group or an ethoxy group, or a halogen atom such as chlorine or bromine. Examples of the heterocyclic group for R ²³ include pyridyl group, furyl group, thienyl group, indolyl group, pyrrolyl group,
Examples include quinolyl group and carbazolyl group.
Examples of the substituent on the phenyl group or heterocyclic group of R ²³ include alkyl groups such as methyl group and ethyl group, and alkoxy groups such as methoxy group and ethoxy group. Further, examples of the aralkyl group of R ²⁴ or R ²⁵ include benzyl group, and examples of substituents in the aralkyl group include chlorine,
Examples include halogen atoms such as bromine, alkyl groups such as methyl and ethyl groups, and nitro groups.
The heterocycle formed by bonding R ²⁴ and R ²⁵ to each other includes a morpholine ring. ] [ ^R23 is a hydrogen atom, a halogen atom such as chlorine or bromine, ^R29 is a hydrogen atom, a halogen atom such as chlorine or bromine, an alkyl group such as a methyl group or an ethyl group,
Alkoxy groups such as methoxy and ethoxy groups; dialkylamino groups such as dimethylamino, diethylamino and dibutylamino groups; dialkylamino groups such as dibenzylamino and chloro-substituted dibenzylamino groups; nitro and cyano groups. or

[Formula] R ³⁰ represents a hydrogen atom, a halogen atom such as chlorine or bromine, or an alkyl group such as a methyl group or an ethyl group. ] [R ³¹ is a hydrogen atom, a halogen atom such as chlorine or bromine, an alkyl group such as a methyl group, an ethyl group, a butyl group, an alkoxy group such as a methoxy group, an ethoxy group, a butoxy group, or a cyano group, R ³² or
R ³³ is a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a butyl group, a substituted alkyl group such as a 2-chloroethyl group or a 2-hydroxyethyl group, or a substituted or unsubstituted benzyl group, R ³⁴ or
R ³⁵ is a hydrogen atom, a halogen atom such as chlorine or bromine, an alkyl group such as a methyl group, an ethyl group or a butyl group, an alkoxy group such as a methoxy group, an ethoxy group or a butoxy group, or a dialkylamino group such as a dimethylamino group or a diethylamino group. represents a group. ^R32
Examples of the substituent on the benzyl group of R ³³ include alkyl groups such as methyl group and ethyl group, alkoxy groups such as methoxy group and ethoxy group, and nitro group. ] [Ar″ represents an N-alkylcarbazolyl group, and examples of the alkyl group include a methyl group, ethyl group, propyl group, and butyl group.] [R ³⁶ , R ³⁷ , R ³⁹ are hydrogen atoms, halogen atoms such as chlorine and bromine, alkyl groups such as methyl and ethyl groups, alkoxy groups such as methoxy and ethoxy groups, nitro groups or amino groups, R ³⁵ are hydrogen atoms, halogen atoms such as chlorine and bromine, methyl groups,
Alkyl groups such as ethyl groups, alkoxy groups such as methoxy groups and ethoxy groups, dialkylamino groups such as dimethylamino groups, diethylamino groups, and dibutylamino groups, dibenzylamino groups, chloro-substituted dibenzylamino groups, and methyl-substituted dibenzylamino groups. group, a substituted or unsubstituted dialkylamino group such as a methoxy-substituted dibenzylamino group, an N-alkyl-N-aralkyl amino group such as an N-methyl-N-benzylamino group, a carboxy group or its ester, an amino group, Represents a hydroxy group, a cyano group, and an acetylamino group. [R ⁴⁰ represents an N-alkylcarbazolyl group, pyridyl group, thienyl group, indolyl group, furyl group, or a substituted or unsubstituted naphthyl group, styryl group or anthryl group, respectively. Examples of substituents on naphthyl, styryl, and anthryl groups include alkyl groups such as methyl and ethyl groups, alkoxy groups such as methoxy and ethoxy groups, and dialkylamino groups such as dimethylamino and diethylamino groups. ] [R ⁴¹ and R ⁴² are hydrogen atoms, methyl groups, ethyl groups,
It represents an alkyl group such as a butyl group, an alkoxy group such as a methoxy group, an ethoxy group, a butoxy group, a halogen atom such as chlorine or bromine, or a dialkylamino group such as a dimethylamino group or a diethylamino group, and n ₁ represents 0 or 1. . ] [R ⁴³ and R ⁴⁴ are hydrogen atoms, alkyl groups such as methyl and ethyl groups, alkoxy groups such as methoxy and ethoxy groups, halogen atoms such as chlorine,
R ⁴⁵ and R ⁴⁶ are methyl group, ethyl group, propyl group,
An alkyl group such as a butyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, and R ⁴⁷ represents a hydrogen atom or a substituted or unsubstituted phenyl group. Examples of the aralkyl group for R ⁴⁵ and R ⁴⁶ include a benzyl group, and examples of the aryl group include a phenyl group. Substituents on aralkyl or aryl groups include alkyl groups such as methyl, ethyl, and butyl, alkoxy groups such as methoxy and ethoxy, halogen atoms such as chlorine, and dialkyl groups such as dimethylamino and diethylamino groups. An example is an amino group. ] [R ⁴⁸ and R ⁴⁹ represent an alkyl group such as a methyl group or an ethyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted benzyl group. Examples of the substituent include alkyl groups such as methyl group and ethyl group, and alkoxy groups such as methoxy group and ethoxy group. ] [R ⁵⁰ and R ⁵¹ represent the same groups as R ⁴⁸ and R ⁴⁹ above. ] [ ^R52 is a hydrogen atom, an alkyl group such as a methyl group or an ethyl group, a substituted or unsubstituted phenyl group,
n ₂ is an integer of 0 or 1, A is

【formula】

[Formula] represents a 9-anthryl group or a substituted or unsubstituted N-alkylcarbazolyl group. Here, R ⁵³ is a hydrogen atom, an alkyl group,
Alkoxy group, halogen atom or

[Formula] Substituted amino group (R ⁵⁴ and R ⁵⁵ are methyl groups,
It represents an alkyl group such as an ethyl group, a propyl group, a butyl group, a substituted or unsubstituted aralkyl group such as a benzyl group, a substituted or unsubstituted aryl group such as a phenyl group, and R ⁵⁴ and R ⁵⁵ form a ring. You may. ), m represents an integer of 0, 1, 2 or 3, and when m is 2 or more, R ⁵³ may be the same group or different groups. As the substituent for the aralkyl group or aryl group in R ⁵⁴ or R ⁵⁵ ,
Examples include alkyl groups such as methyl, ethyl, propyl and butyl groups, alkoxy groups such as methoxy and ethoxy groups, halogen atoms such as chlorine, and dialkylamino groups such as dimethylamino and diethylamino groups. ] Further, specific examples of these charge transport substances are as follows.

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[Table] In addition to the above-mentioned exemplified compounds, polymer substances such as poly-
N-vinylcarbazole, halogenated-poly-N
- vinyl carbazole, polyvinylpyrene, or bromopyrene-formaldehyde condensation resin,
Condensation resins such as N-ethylcarbazole-formaldehyde condensation resin, and low molecular weight substances such as oxazole derivatives, oxadiazole derivatives, and nitro derivatives of fluorenone are all effective. The accompanying drawings are enlarged sectional views of two typical examples of electrophotographic photoreceptors according to the present invention, and FIG. FIG. 2 shows a photosensitive layer 41 provided with a charge generating layer 2 on a conductive support 11.
2. A charge transport layer 32 is provided to form a multilayer photosensitive layer 42. Compared to the former, the latter laminated type electrophotographic photoreceptor (as shown in FIG. 2) is more advantageous in various respects. It is also possible to form the photosensitive layer by dispersing a disazo compound represented by the general formula () in a binder resin, without using the above-mentioned charge transporting substance. As the conductive support 11 used in the present invention, metal plates, metal drums, or metal foils made of aluminum, nickel, chromium, etc., and plastics provided with a thin layer of aluminum, tin oxide, indium oxide, chromium, palladium, etc. Films and paper or plastic films coated or impregnated with conductive substances are used. In the laminated type photoreceptor, the charge generation layer 22 is made of a liquid in which a specific disazo compound represented by the general formula () shown above is made into fine particles by a means such as a ball mill and dispersed in an appropriate solvent, or as necessary. Accordingly, a dispersion in which a binder resin is dissolved is coated on the conductive support 11, and if necessary, the surface may be finished by a method such as buffing, or the film thickness may be adjusted. This is what I did. The thickness of the charge generation layer 22 is 0.01 to 5 μm, preferably 0.05 to 2 μm, and the proportion of the disazo compound in the charge generation layer 22 is 10 to 100% by weight, preferably 30 to 95% by weight. The thickness of the charge generation layer 22 is
Below 0.01 μm, sensitivity is poor, and above 5 μm, potential retention is poor. Furthermore, if the proportion of the disazo pigment in the charge generation layer 22 is less than 10% by weight, the sensitivity is poor. The charge generation layer 32 is made of a solution prepared by dissolving the various charge transport substances described above and a binder resin in a suitable solvent such as tetrahydrofuran.
It is formed by coating on top. Here, the proportion of the charge transport substance contained in the charge transport layer 32 is
10-80% by weight, preferably 25-75% by weight,
The film thickness is 2 to 100 μm, preferably 5 to 40 μm. If the proportion of the charge transport substance contained in the charge transport layer 32 is less than 10% by weight, the sensitivity will be poor;
Above this level, the film becomes brittle or crystals precipitate and the charge transport layer 32 becomes cloudy, which is not preferable. Further, if the thickness of the charge transport layer 32 is 2 μm or less, the potential is not maintained well, and if the thickness is 100 μm or more, the residual potential becomes high. Examples of the binder resin for the charge generation layer 22 used here include polyester resin, butyral resin, ethyl cellulose resin, epoxy resin, acrylic resin, vinylidene chloride resin, polystyrene,
Examples include polybutadiene and copolymers thereof, which may be used alone or in a mixed state of two or more. Further, as the binder resin for the charge transport layer 32, polycarbonate resin, polyester resin,
Examples include polystyrene, polyurethane resin, epoxy resin, acrylic resin, silicone resin, and copolymers thereof, and these may be used alone or in a mixed state of two or more. Furthermore, various additives can be added to the charge transport layer 32 for the purpose of improving flexibility or durability. Additives used for this purpose include halogenated paraffins, dialkyl phthalates, silicone oils, and the like. Furthermore, in the photoreceptor of the present invention, if necessary, a barrier layer is provided between the conductive support 11 and the charge generation layer 22, an intermediate layer is provided between the charge generation layer 22 and the charge transport layer 32, and a layer is provided on the charge transport layer 32. An overcoat layer can also be provided. EXAMPLES Next, the present invention will be specifically explained using Examples, but the embodiments of the present invention are not limited thereby. Example 1 76 parts by weight of disazo compounds No. 1 to 32, polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.)
Tetrahydrofuran solution (solid content concentration 2%)
1,260 parts by weight and 3,700 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto the aluminum surface of an aluminum-deposited polyester base (conductive support) using a doctor blade, and air-dried. A charge generation layer with a thickness of about 1 μm was formed. On the other hand, charge transport material No. 2-29
2 parts by weight, polycarbonate resin (Panlite
After mixing and dissolving 2 parts by weight of K1300 (manufactured by Teijin Ltd.) and 16 parts by weight of tetrahydrofuran to form a solution, this was applied onto the charge generation layer using a doctor blade, and the mixture was heated at 80°C for 2 minutes and then at 100°C for 5 minutes. Dry to form a charge transport layer with a thickness of approximately 20 μm,
A laminated type photoreceptor No. 1 shown in FIG. 2 was prepared. Examples 2 to 10 Example 1 except that the disazo compound and charge transport substance shown in Table 1 below were used in place of disazo compound No. 1-32 and charge transport substance 2-29 used in Example 1. Photoreceptors Nos. 2 to 10 were prepared in the same manner as described above. These photoreceptors 1 to 10 were negatively charged by -6KV corona discharge for 20 seconds using an electrostatic copying paper tester (manufactured by Kawaguchi Electric Seisakusho Co., Ltd., model SP428). Leave it in a dark place for a second and measure the surface potential _Vpp () at that time. Then, irradiate the surface with light using a tungsten lamp at an illumination intensity of 4.5 lux until the surface potential is 1/1 of _Vpp . Find the time (seconds) until it becomes 2, and calculate the exposure amount E1/2
Table 1 shows the results of calculating (lux/second).

[Table] In addition, photoconductor No. 1 of the present invention was installed in a copier Ricopy P-500 manufactured by Ricoh Co., Ltd., and images were produced.
Repeated 10,000 times. As a result, clear images were obtained even after 10,000 repetitions. From this, it can be understood that the photoreceptor of the present invention is also excellent in durability. Effects As described above, the electrophotographic photoreceptor of the present invention is easy to manufacture and has excellent properties such as stable characteristics even after repeated use of the photoreceptor.

[Brief explanation of drawings]

1 and 2 are enlarged sectional views showing two typical examples of the electrophotographic photoreceptor of the present invention. 1... Conductive support, 21... Charge generating substance,
22... Charge generation layer, 31... Charge transport material, 3
2... Charge transport layer, 41, 42... Photosensitive layer.

Claims (1)

[Claims] 1. The following general formula () is formed on a conductive support. (In the formula, R ¹ and R ² are hydrogen, lower alkyl group,
It represents a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group. Here, R ¹ and R ² may be the same or different, and R ¹ and R ² may jointly form a ring. ) An electrophotographic photoreceptor comprising a photosensitive layer containing a disazo pigment represented by the following formula as an active ingredient.