JPH04149447A - Electrophotographic photosensitive body - Google Patents

Abstract

PURPOSE:To attain high sensitivity, while minimizing residual potential, and to improve pre-exposure characteristics and repeated use characteristics by providing a photosensitive layer containing a specific azo pigment. CONSTITUTION:A photosensitive layer containing an azo pigment which is represented by a formula I is provided on an electrically conductive substrate. In the formula I, X represents organic residues with valences of 1 to 4, and n represents integers of 1 to 4. At the same time, R1 and R2 represent an hydrogen atom, an alkyl group, an alkyl group, an aryl group, a halogen atom, cyano group, or a nitro group, while l and m represent integers of 1 to 4. Thus, high sensitivity is attained, while residual potential is minimized, and pre-exposure characteristics and repeated use characteristics are improved.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer containing a novel azo pigment. More specifically, the present invention relates to a highly durable electrophotographic photoreceptor that has high sensitivity and is suitable for repeated use.

[Prior art and its problems]

Conventionally, electrophotographic photoreceptors having a photosensitive layer containing an inorganic photoconductor such as selenium, zinc oxide, or cadmium sulfide as a main component have been widely known. However, these are not necessarily satisfactory in terms of sensitivity, thermal stability, moisture resistance, durability, etc. (Also, in particular, selenium and cadmium sulfide have restrictions in manufacturing and handling due to their toxicity. On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture and generally have better thermal stability than selenium photoreceptors. Poly-N-
Vinyl carbazole is well known, and this and 2.4.
Electrophotographic photoreceptors having a photosensitive layer mainly composed of a charge transfer complex formed with a Lewis acid such as 7-hlinitro-9-fluorenone are not necessarily satisfactory in terms of sensitivity and durability. On the other hand, in laminated or dispersed function-separated photoreceptors, in which the carrier generation function and the carrier movement function are assigned to separate substances, each material has a wide selection range, and the charging characteristics, sensitivity, and durability are improved. It has the advantage that an electrophotographic photoreceptor having arbitrary electrophotographic properties can be produced relatively easily. Conventionally, various carrier-generating substances or carrier-transferring substances have been proposed. For example, an electrophotographic photoreceptor has been put into practical use that has a photosensitive layer that combines a carrier generation layer made of amorphous selenium and a carrier transfer layer mainly composed of poly-N-vinylcarbazole. However, the carrier generation layer made of amorphous selenium has the disadvantage of poor durability. In addition, various proposals have been made to use organic dyes and pigments as carrier-generating substances. Showa 52-42
Publication No. 41, JP-A-54-46558, JP-A No. 5
6-11945 and the like are already known. However, these azo pigments are not necessarily satisfactory in characteristics such as sensitivity, residual potential, and stability upon repeated use.

[Purpose of the invention]

An object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity, low residual potential, and excellent pre-exposure characteristics and repeated use characteristics.

[Structure of the invention]

The above object of the present invention is to provide the following general formula C on a conductive support.
This was achieved by an electrophotographic photoreceptor characterized by having a photosensitive layer containing an azo pigment represented by T). General formula [■] In the c formula, X: represents a monovalent to tetravalent organic residue, represents an integer of n1 to 4, R7 and R2: hydrogen atom, alkyl group, alkoxy group, aryl group, halogen atom, cyano represents a group or a nitro group, and l and m represent an integer of 1 to 4. ] That is, in the present invention, by using the azo pigment represented by the general formula CI] as a photoconductive substance constituting the photosensitive layer of an electrophotographic photoreceptor, the azo pigment of the present invention can be used to generate excellent carriers. By using this as a carrier-generating material in so-called function-separated electrophotographic photoreceptors, in which carrier generation and transfer are performed using separate substances, the film has excellent physical properties, and has excellent charge retention, sensitivity, and residual properties. An electrophotographic photoreceptor that has excellent electrophotographic properties such as electric potential, has little fatigue deterioration even when used repeatedly, and does not change the above-mentioned properties even when exposed to heat or light, and can exhibit stable properties. can be created. In the general formula [I], X is benzene, naphthalene, fluorene, anthracene, anthraquinone,
Hydrocarbon aromatic rings such as fluorenone, pyrene, and phenanthrene; heteroaromatic rings such as furan, thiophene, pyridine, indole, benzothiazole, carbazole, pyrazole, and dibenzothiophene; Those bonded with family groups, such as triphenylamine, biphenyl, terphenyl, binaphthyl, diphenyloxadiazole,
Examples include diphenyl sulfone, diphenylmethane, diphenyl ether, stilbene, distyrylbenzene, distyrylcarbazole, and distyrylanthracene. Specific examples of R1 and R2 in general formula [I] include hydrogen atoms, alkyl groups such as methyl, ethyl, and isopropyl, alkoxy groups such as methoxy and ethoxy, and aryl groups such as phenyl, tolyl, chlorophenyl, and methoxyphenyl. Examples include halogen atoms such as , chloro, and bromine, cyano groups, and nitro groups. Specific examples of the azo pigment useful in the present invention represented by the above general formula include those having the following structural formula. (A) When n = 1 (monoazo compound), N=N-x (blank below) (B) When n = 2 (bisazo compound) (blank below) N2N X N=N (blank below) (below Margin) [Margin below] N=N In the case of (tetrakisazo compound) (white space below) (white space below) The azo pigment represented by the above general formula has the following - general formula [[] % formula %) (wherein, X and n are the same as in the general formula) ) is diazotized by a conventional method, and then a coupler represented by the following general formula % [ (wherein R1 and R2, and l and m are the same as in the general formula [I]) and an alkali are diazotized. or a diazonium salt of the amine of general formula (I[] in the form of a borofluoride salt or a zinc chloride double salt, etc.), -
Once isolated, the coupler of general formula (III) and the coupler are combined in a suitable solvent (e.g. N,N-dimethylformamide, dimethyl sulfoxide, ethanol, dioxa7) in the presence of an organic or inorganic alkali. It can be easily synthesized by ring reaction. Next, a method for synthesizing a representative example of the azo pigment used in the present invention will be shown. Synthesis Example (Exemplary Compound 58) (1) Synthesis of 6-hydroxybenzimidazo[2,1a]isoquinoline Homophthalic anhydride obtained from homophthalic acid (0,S,
Ca1l, Vol, 3.450110 g, o
- 8.68 g of phenylenediamine and 3 Qml of acetic acid
in 120 ml of nitrobenzene at 120°C.
Heat and stir for an hour. After returning to room temperature, the precipitated crystals were collected by filtration, washed with a small amount of nitrobenzene, further washed with methanol, and dried by heating under reduced pressure to obtain (a)
11.39 g of crystals were obtained. Melting point: 320°C or higher, yield: 79%. (b) Synthesis of Exemplified Compound 58 2.5-bis(4-aminophenyl)-1,3°4-oxadiazole (252 μ) was dissolved in 20 cc of DMF,
2N hydrochloric acid2. 2 cc of the mixture was added, and a solution of 145 ml of sodium nitrite dissolved in 1 cc of water was added dropwise at -10° C. while stirring, and the mixture was allowed to react for 30 minutes to form a tetrazonium salt. The tetrazonium salt solution thus obtained was added dropwise to a solution of 469 cc of crystals (a) and 9 cc of triethanolamine Q dissolved in 50 cc of DMF, which was being cooled and stirred, and after stirring for about 2 hours, the product was formed. The resulting crystals were collected by filtration and washed with DMF, water, and acetone to obtain crystals 119■ of the desired exemplified compound 58. Melting point: 330°C or higher, yield: 16%. Other azo pigments of the present invention can also be obtained according to the above synthesis examples. The electrophotographic photoreceptor of the present invention contains the azo pigment in the photosensitive layer, and the azo pigment can be used in various embodiments. For example, azo pigment is used as a binder.
It can be used as a photoconductive layer by coating the dispersion on a conductive support. Alternatively, a photosensitive layer can be formed by dispersing an azo pigment as a charge generating agent in a charge transporting material and coating this dispersed mixture on a conductive support. In yet another embodiment, it can be used as a laminated photoreceptor in which a charge generation layer containing an azo pigment as a charge generation agent is provided on a conductive support, and a charge transport layer is provided thereon. In this case, the charge generation layer may be formed by depositing an azo pigment on the conductive support, or by dispersing the azo pigment in a binder resin and coating the dispersion. . Examples of the binder resin used for dispersing the charge generating agent in the above embodiment include polyester resin, acrylic resin, styrene resin, silicone resin, alkyd resin, vinyl chloride-vinyl acetate copolymer resin, and styrene-butadiene copolymer. Coalescence, polyvinyl acetal resin, diallyl phthalate resin, polysulfone resin, polycarbonate resin, acetic acid-bicrotonic acid copolymer resin, polyarylate resin, butyral resin, styrene-maleic anhydride copolymer resin, rosin-phenol modified resin, casein etc.,
These can be used alone or in combination as a copolymer. The amount of these binders to be used is 0.1 to 5 times the weight of the azo pigment, but preferably 0.2 to 3 times the weight of the azo pigment. Further, as the charge transport material forming the charge transport layer, a known conductive compound can be used. For example, as the hole transport substance, polyvinylcarbazole, phenanthrene, N-ethylcarbazole, 2.5
-diphenyl-1,3,4-oxadiazole, 2,5
-bis(4-diethylaminophenyl) -1,3,4
-oxadiazole, 44'-bis(diethylamino)
-2,2-dimethyltriphenylmethane, 2,4.5-
tris(p-diethylaminophenyl)oxazole,
2.5-bis(p-diethylaminophenyl)-1,3
, 4-triazole, 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-2-pyrazoline, p-diethylaminobenzaldehydonidiphenylhydrazone, N-ethylcarbazole-3-carbaldehydonidiphenyl Examples include hydrazone, and examples of electron transport substances include 2-nitro-9-
Fluorenone, 2,7-sinitro-9-fluorenone,
Examples include 2,4.7-dolinitro-9-fluorenone, 2-nitrobenzothiophene, dinitroanthracene, dinitroacridine, and dinitroanthraquinone. These charge transport substances can be used by being dispersed or dissolved in a binder resin, and the resins mentioned above can be used as the binder resin. The amount of binder used is 0.0% by weight relative to the charge transport material. It is added at a ratio of 1 to 10 times the amount, preferably 0.2 to 5 times the amount. Examples of the conductive support used for producing the photoreceptor of the present invention include a metal plate, conductive paper, conductive plastic film, metallized film, metal cylinder, and plastic cylinder treated with metallization or metal foil. and so on. Examples of solvents used for coating these supports by dispersing or dissolving azo pigments and charge transport substances together with binders include toluene, xylene, monochlorobenzene, chloroform, dichloroethane, trichloroethylene, methylene chloride, Dioxane, tetrahydrofuran, ethyl acetate, butyl acetate, methyl cellosolve,
Methyl cellosolve acetate, cyclohexanone, methyl ethyl ketone, dimethyl formamide, dimethyl sulfoxide, ethyl alcohol, propyl alcohol,
Butyl alcohol etc.

【Example】

Next, examples of the present invention will be shown. Example 1 1 part by weight of the exemplary pigment 58 according to the present invention and the following pigments R-1, R-2, R-3 and R-4 (hereinafter referred to as blank spaces) +2-1 Shaku-3 structural formula , 1 part by weight of polyarylate resin (U-100 manufactured by Unitika) were mixed with 100 parts by weight of dichloroethane, and dispersed together with glass beads in a paint conditioner device for 2 hours. The pigment dispersion thus obtained was coated with a wire bar onto an aluminum support for PS plates (anodized, manufactured by Agfa), and each charge generation layer was coated with a film thickness of approximately 0.2 to 0.3 microns. has been established. Next, a coating solution prepared by dissolving 1 part by weight of p-dibenzylaminobenzaldehyde=diphenylhydrazone and 1 part by weight of polyarylate resin in 10 parts by weight of dichloroethane as a charge transport material was applied onto the charge generation layer using a wire bar. A laminated photoreceptor having a charge transport layer with a thickness of 15 microns was prepared. Regarding this photoreceptor, an electrostatic recording tester (Kawaguchi Electric type 5P-
428), the following characteristic tests were conducted. That is, a voltage of -6 KV is applied to the charger to charge the photosensitive layer by corona discharge for 5 seconds, and the potential Vo (V) at that time is
, find the potential Vd (V) after leaving it for 10 seconds, DD=Vd
, /Vox100 (%) were measured. Also, the exposure amount El/2 (1111 seconds) required to attenuate the surface potential of the photosensitive layer by 1/2 by irradiating light from a halogen lamp with the illumination intensity on the photosensitive layer being 30 lux.
I asked for Next, this photoreceptor was exposed to the light of a fluorescent lamp with an illuminance of 50001111 for 5 minutes, left in a dark place for 30 seconds, and then subjected to the same characteristic test as above to determine the charging potential Vo (V).
, El/2 (Ioχ sec > DD C%) were determined. The results are shown in Table 1. The upper row of Table 1 shows the initial characteristics, and the lower row shows the characteristics after light irradiation. (The following is a blank space) From the results in Table 1, it can be seen that the photoreceptor using Azo Pigment 58 of the present invention has very good charging potential (■0), sensitivity, and pre-exposure characteristics. Next, the surface potential after exposing these photoreceptors at an exposure amount of 501 ux · seconds, that is, the residual potential E50 (V
) was sought. Similar measurements were repeated 500 times. In addition, irradiation exposure was further performed for 0.3 seconds at 300 fox using a tungsten lamp as a light source to eliminate residual potential, so that the residual potential was completely reduced to zero. The results are shown in Table 2. (The following is a blank space) From the results in Table 2, it can be seen that the photoreceptor using Azo Pigment 58 of the present invention has excellent repeated use characteristics. Example 2 Exemplary pigments 56, 60 and 66 of the present invention as described above,
For comparison, 2 parts by weight of each of the following pigments R-5, R-6, and R-7 (hereinafter referred to as margins), 1 part by weight of polycarbonate resin (Teijin Kasei Panlite-1250), and 50 parts by weight of dichloroethane were added.
In addition to parts by weight, it was dispersed in paint conditioner for 2 hours. This dispersion was applied onto the surface of an aluminum cylinder having an outer diameter of 60 cm by a cylindrical pull-up coating method. The film thickness was about 0.5 micron. On this charge generation layer, 1 part by weight of 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 2 parts by weight of polyester resin (Vylon-200) and 25 parts by weight of dichloroethane were added. A charge transport layer having a thickness of 15 microns was formed by applying the dissolved solution to produce a cylindrical photoreceptor. The charging potential Vo (V) and the general sensitivity Er/2 (lux - sec) were determined for this photoconductor in the same manner as in Example 1, and the initial charging potential after repeated charging exposure 10,000 times was determined. The difference ΔvO from the potential Vo was determined. The results are shown in Table 3. (The following is a blank space) From the results shown in the table, it was confirmed that all of the photoreceptors of the present invention have higher general sensitivity than the characteristics of comparative photoreceptors, and have excellent characteristics for repeated use. Example 3 Exemplary pigment 12.40.70.194 according to the invention as described above
, and 199, and for comparison, 1 part by weight of each of the following pigments J, polyarylate resin (Unitika U-
100) was mixed with 100 parts by weight of dichloroethane and dispersed in the same manner as in Example (1) above to obtain a coating dispersion. An aluminum support for PS plates (anodized, manufactured by Agfa) was coated in the same manner as the support, and a charge generation layer of 0.2 to 0.3 microns in film thickness was provided on each. A coating solution prepared by dissolving 21 parts by weight of p-dibenzylaminobenzaldehydonidiphenylhydrazo and 1 part by weight of polyarylate resin in 10 parts by weight of dichloroethane was applied onto the charge generating layer in the same manner to obtain a film thickness of 15 microns. A laminated photoreceptor with a charge transport layer was produced. The white light sensitivity of this photoconductor was measured in the same manner as in Example 2, and the charging potential after repeated charging exposure 10,000 times was as follows:
V. The difference ΔVo between the two electrodes and the residual potential ΔVr after static elimination were measured. The results are shown in Table 4. (Left below) From the results shown in the table, it can be concluded that the photoreceptors of the present invention have excellent characteristics such as higher general sensitivity, better repeatability, and lower residual potential than the comparative photoreceptors. was confirmed.

【Effect of the invention】

As is clear from the above, the method of the present invention provides high sensitivity,
It is possible to obtain an electrophotographic photoreceptor having a low residual potential and excellent pre-exposure characteristics and repeated use characteristics. Procedural amendment (voluntary) May 21, 1991

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing an azo pigment represented by the following general formula [I] on a conductive support. General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. are available▼ [In the formula, represents a group, an alkoxy group, an aryl group, a halogen atom, a cyano group, or a nitro group, and 1 and m represent an integer of 1 to 4. ]