Abstract:
An electrophotographic photoconductor is composed of an electroconductive support and a photoconductive layer formed thereon which contains a charge generating material and a charge transporting material. The charge generating material is composed of a particular triasazo compound and a particular disazo compound. A photoconductive composition useful as a photoconductive material is also composed of the trisazo compound and the disazo compound.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrophotographic photoconductor and a photoconductive composition for use in the electrophotographic photoconductor. This photoconductive composition is also useful as a photoconductive material for solar batteries, photosensors, and optical switching elements. 
     2. Discussion of Background 
     Recent development of information processing systems utilizing electrophotography is remarkable. In particular, a photoprinter which converts information to be recorded into digital signals and optically records the information is excellent in the printing quality and operational reliability. This digital recording technology is applied not only to such a photoprinter, but also to ordinary copying machines, so that a so-called digital copying machine has been developed. 
     A copying machine which employs the conventional analog copying technology, as well as this digital recording technology, can be provided with various information processing functions, so that it is expected that a demand for such a copying machine will be increased. 
     At present, semiconductor diodes (LD) and light emitting diodes (LED), which are small sized and inexpensive and have high operational reliability, are in general use as light sources for the optical printer. However, the wavelength of the light emitted from LED now in general use is 660 nm, while the wavelength range of the light emitted from LD is in a near infrared region, so that the development of an electrophotographic photoconductor having sensitivities in the range from a visible region to a near infrared region is desired. 
     The photosensitive wavelength range of an electrophotographic photoconductor is substantially determined by the photosensitive wavelength range of a charge generating material (CGM) employed in the electrophotographic photoconductor, so that varieties of charge generating materials have been developed. However, a single charge generating material (CGM) having a high photosensitivity in a broad wavelength range from visible through near infrared has not yet been developed. 
     Under such circumstances, various trials have been made for development of a photoconductor with such a broad photosensitive range by mixing a charge generating material having high photosensitivity to visible light (i.e., short wavelength CGM) and a charge generating material having high photosensitivity to near infrared light (i.e., long wavelength CGM). 
     For example, the following have been proposed: an electrophotographic printing plate having photosensitivities to white light, gas laser, and the light emitted from LED, prepared by mixing (a) a trisazo pigment, (b) at least one pigment selected from the group consisting of a perylene pigment and an anthanthrone pigments and (c) an electron-donating material (Japanese Laid-Open Patent Application 3-146957); an electrophotographic photoconductor having photosensitivities to white light and infrared laser, prepared by use of a disazo pigment and oxotitanium phthalocyanine (Japanese Laid-Open Patent Application 3-196049); and a photoconductor having photosensitivities to light from a visible region through an infrared region, which comprises a charge generating layer comprising a mixed pigment, and a binder agent which is composed of trigonal system selenium particles and phthalocyanine particles mixed in a styrene-butadiene copolymer (Japanese Laid-Open Patent Application 3-225346). 
     The above-mentioned photoconductors, however, have the shortcomings that the charging properties thereof are caused to deteriorate when exposed to ozone or NOx gases which are generated in a charger of a copying machine or a printer. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an electrophotographic photoconductor having (1) much higher photosensitivities to a broad wavelength range including a visible region through a near infrared region than a photoconductor designed by use of a mixture of a short wavelength charge generating material and a long wavelength charge generating material, and (2) high durability to ozone and NOx gases, with a minimized deterioration of the charging characteristics thereof even when exposed to ozone and Nox gases. 
     Another object of the present invention is to provide a photoconductive composition for use in the above-mentioned electrophotographic photoconductor. 
     The above objects of the present invention can be attained by use of a mixture of a particular trisazo compound and a particular disazo compound in the electrophotographic photoconductor and the photoconductive composition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The mixing ratio of a disazo compound to a trisazo compound for use in the present invention can be determined, depending upon the disazo compound and trisazo compound employed, and upon the characteristics required for the photoconductor, such as photosensitivity, charging characteristics, and resistance to gases. Generally, however, it is preferable that the mixing ratio of the disazo compound to the trisazo compound in terms of (Disazo Compound)/(Disazo compound+Trisazo Compound) be in the range of 0.01 to 0.99. 
     This is because when the above ratio is not less than 0.01, a sufficiently high sensitizing effect can be obtained effectively. On the other hand, even when the ratio is more than 0.99, the sensitizing effect and the resistance to gases cannot be improved any further. In order to obtain a uniform spectral photosensitivity in the visible region range through the near infrared region, it is preferable that the above ratio be in the range of 0.1 to 0.9. 
     There are two types of electrophotographic photoconductors. One is a laminated type or function-separated type electrophotographic photoconductor comprising an electroconductive support, a charge generation layer comprising a charge generating material which generates charge carriers upon the absorption of light, and a charge transport layer comprising a charge transporting material which facilitates the injection of the charge carriers and transports the charge carriers, formed on the electroconductive support. 
     The other is a single layer type or dispersion type electrophotographic photoconductor comprising an electroconductive support, and a photoconductive layer formed thereon comprising a charge generating material and a charge transporting material which are uniformly dispersed in a binder resin. 
     The present invention can be applied to any of the above electrophotographic photoconductors. 
     In the present invention, a mixture of a trisazo compound and a disazo compound serves as a charge generating material. In order that the charge generating material absorbs light with high efficiency and the generated charge carriers are effectively injected into the charge transporting material, it is preferable that the particle size of the charge generating material be minimized, specifically 1 μm or less. 
     A dispersion type electrophotographic photoconductor comprising the mixture of a trisazo compound and a disazo compound is prepared as follows: 
     (1-1) At least one trisazo compound and at least one disazo compound are separately dispersed in a dispersing medium, if necessary, together with a binder agent and a charge transporting material, in a dispersion mixer such as a ball mill, a vibration mill, a disk-vibration mill, an attritor, a sand mill or an ultrasonic dispersion mixer, whereby the trisazo compound and the disazo compound are ground to finely-divided particles with a particle size of 1 μm or less, and dispersed, whereby a trisazo compound dispersion and a disazo compound dispersion are separately prepared. The thus prepared trisazo dispersion and the trisazo dispersion were mixed, whereby a photoconductive layer coating liquid is prepared. The thus prepared photoconductive layer coating liquid is coated on an electronductive support, whereby a dispersion type electrophotographic photoconductor is fabricated. 
     (1-2) Alternatively, at least one trisazo compound and at least one disazo compound are mixed and dispersed in a dispersing medium, if necessary, together with a binder agent and a charge transporting material, in the above-mentioned dispersion mixer, so that the trisazo compound and the disazo compound are ground to finely-divided particles with a particle size of 1 μm or less, and dispersed, whereby a photoconductive layer coating liquid is prepared. The thus prepared photoconductive layer coating liquid is coated on the electroconductive support, whereby a dispersion type electrophotographic photoconductor is fabricated. 
     A function-separated type electrophotographic photoconductor comprising the mixture of a trisazo compound and a disazo compound can be fabricated as follows: 
     (2-1) At least one trisazo compound and at least one disazo compound are separately dispersed in a dispersing medium, if necessary, together with a binder agent, in the above-mentioned dispersion mixer, so that the trisazo compound and the disazo compound are ground to finely-divided particles with a particle size of 1 μm or less, and dispersed, whereby a trisazo compound dispersion and a disazo compound dispersion are separately prepared. The thus prepared trisazo dispersion and the trisazo dispersion were mixed, whereby a charge generation layer coating liquid is prepared. 
     (2-2) Alternatively, at least one trisazo compound and at least one disazo compound are mixed and dispersed in a dispersing medium, if necessary, together with a binder agent, in the above-mentioned dispersion mixer, so that the trisazo compound and the disazo compound are ground to finely-divided particles with a particle size of 1 μm or less, and dispersed, whereby a charge generation layer coating liquid is prepared. 
     Any of the above prepared charge generation layer coating liquids is coated on the electroconductive support and dried, whereby a charge generation layer is provided on the electroconductive support. 
     A charge transportation layer coating liquid comprising a charge transporting material is then coated on the above charge generation layer, whereby a function-separated type electrophotographic photoconductor is fabricated. 
     Electrophotographic photoconductors fabricated by the above-mentioned methods (1-1), (1-2), (2-1) and (2--2) have photosensitivities to light with a wavelength of 700 nm or more and have significantly improved resistance to gases such as Nox and ozone, with a significantly less deterioration of the charging characteristics thereof in comparison with a photoconductor comprising only a trisazo compound. 
     In particular, the photosensitivities to light with a wavelength of 700 nm or more of the electrophotographic photoconductors fabricated by the above-mentioned methods (2-1) and (2-2) are 1.5 to 2.5 times the photosensitivities of the photoconductor comprising only a trisazo compound. 
     The trisazo compound for use in the present invention is represented by formula (I) and the disazo compound for use in the present invention is represented by any of formulas (II) to (VIII): ##STR1##  wherein A, B and D each independently represent a coupler radical, and R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  each represent hydrogen, a halogen atom, an alkyl group, an alkoxyl group, or cyano group. 
     The coupler radical represented by A, B or D is selected from the group consisting of the radicals represented by formulas (IX-1) to (IX-6): ##STR2## wherein X 1  represents hydroxyl group, --N(R 11 )(R 12 ), or --NHSO 2  R 13 , in which R 11  and R 12  each represent hydrogen, an acyl group, or an alkyl group which may have a substituent, and R 13  represents an alkyl group which may have a substituent, or an aryl group which may have a substituent; 
     Y 1  represents hydrogen, a halogen atom, an alkyl group which may have a substituent, an alkoxyl group, carboxyl group, sulfonic acid group, benzimidazolyl group, a sulfamoyl group which may have a substituent, an allophanoyl group which may have a substituent, or --CON(R 14 )(Y 2 ), in which R 14  represents hydrogen, an alkyl group which may have a substituent, or a phenyl group which may have a substituent, Y 2  represents a cyclic hydrocarbon group which may have a substituent, a heterocyclic group which may have a substituent, or --N═C(R 15 )(R 16 ) in which R 15  represents a cyclic hydrocarbon group which may have a substituent, a heterocyclic group which may have a substituent, or a styryl group which may have a substituent, R 16  represents hydrogen, an alkyl group which may have a substituent, a phenyl group which may have a substituent, and R 15  and R 16  may form a ring in combination with a carbon atom to which R 15  and R 16  are bonded; and 
     Z represents a cyclic hydrocarbon group which may have a substituent, or a heterocyclic group which may have a substituent; ##STR3## wherein R 17  represents a hydrocarbon group which may have a substituent; ##STR4## wherein R 18  represents a hydrocarbon group which may have a substituent; ##STR5## wherein R 19  represents an alkyl group, carbamoyl group, carboxyl group or an ester group thereof; and Ar 11  represents an aromatic hydrocarbon group which may have a substituent; ##STR6## wherein X 2  represents a bivalent aromatic hydrocarbon group or a bivalent heterocyclic group; and ##STR7## wherein X 2  represents a bivalent aromatic hydrocarbon group or a bivalent heterocyclic group. 
     Specific examples of the coupler radicals represented by A, B or D in the trisazo compound represented by formula (I) and the disazo compound represented by any of formulas (II) to (VIII) are as shown in TABLE 1 to TABLE 16. 
     
                       TABLE 1______________________________________ ##STR8##CouplerNo.       R.sup.21     (R.sup.22).sub.n______________________________________ 1        H            H 2        H            2-NO.sub.2 3        H            3-NO.sub.2 4        H            4-NO.sub.2 5        H            2-CF.sub.3 6        H            3-CF.sub.3 7        H            4-CF.sub.3 8        H            2-CN 9        H            3-CN10        H            4-CN11        H            2-I12        H            3-I13        H            4-I14        H            2-Br15        H            3-Br16        H            4-Br17        H            2-Cl18        H            3-Cl19        H            4-Cl20        H            2-F21        H            3-F22        H            4-F23        H            2-CH.sub.324        H            3-CH.sub.325        H            4-CH.sub.326        H            2-C.sub.2 H.sub.527        H            4-C.sub.2 H.sub.528        H            2-OCH.sub.329        H            3-OCH.sub.330        H            4-OCH.sub.331        H            2-OC.sub.2 H.sub.532        H            3-OC.sub.2 H.sub.533        H            4-OC.sub.2 H.sub.534        H            4-N(CH.sub.3).sub.235        CH.sub.3     H36      ##STR9##    H37        H            2-OCH.sub.3, 5-OCH.sub.338        H            2-OC.sub.2 H.sub.5, 5-OC.sub.2 H.sub.539        H            2-CH.sub.3, 5-CH.sub.340        H            2-Cl, 5-Cl41        H            2-CH.sub.3, 5-Cl42        H            2-OCH.sub.3, 4-OCH.sub.343        H            2-CH.sub.3, 4-CH.sub.344        H            2-CH.sub.3, 4-Cl45        H            2-NO.sub.2, 4-OCH.sub.346        H            3-OCH.sub.3, 5-OCH.sub.347        H            2-OCH.sub.3, 5-Cl48        H            2-OCH.sub.3, 5-OCH.sub.3, 4-Cl49        H            2-OCH.sub.3, 4-OCH.sub.3, 5-Cl50        H            3-Cl, 4-Cl51        H            2-Cl, 4-Cl, 5-Cl52        H            2-CH.sub.3, 3-Cl53        H            3-Cl, 4-CH.sub.354        H            2-F, 4-F55        H            2-F, 5-F56        H            2-Cl, 4-NO.sub.257        H            2-NO.sub.2, 4-Cl58        H            2-Cl, 3-Cl, 4-Cl, 5-Cl59        H            4-OH______________________________________ 
    
     
                       TABLE 2______________________________________ ##STR10##CouplerNo.           R.sup.21  R.sup.22).sub.n______________________________________60            H         H61            H         2-NO.sub.262            H         3-NO.sub.263            H         4-NO.sub.264            H         2-Cl65            H         3-Cl66            H         4-Cl67            H         2-CH.sub.368            H         3-CH.sub.369            H         4-CH.sub.370            H         2-C.sub.2 H.sub.571            H         4-C.sub.2 H.sub.572            H         2-OCH.sub.373            H         3-OCH.sub.374            H         4-OCH.sub.375            H         2-OC.sub.2 H.sub.576            H         4-OC.sub.2 H.sub.577            H         2-CH.sub.3, 4-OCH.sub.378            H         2-CH.sub.3, 4-CH.sub.379            H         2-CH.sub.3, 5-CH.sub.380            H         2-CH.sub.3, 6-CH.sub.381            H         2-OCH.sub.3, 4-OCH.sub.382            H         2-OCH.sub.3, 5-OCH.sub.383            H         3-OCH.sub.3, 5-OCH.sub.384            H         2-CH.sub.3, 3-Cl85            H         2-CH.sub.3, 4-Cl86            H         2-CH.sub.3, 5-Cl87            H                    ##STR11##88            H         2-CH(CH.sub.3).sub.2______________________________________ 
    
     
                       TABLE 3______________________________________ ##STR12##CouplerNo.       R.sup.21       (R.sup.22).sub.n______________________________________ 89       H              H 90       H              4-N(CH.sub.3).sub.2 91       H              2-OCH.sub.3 92       H              3-OCH.sub.3 93       H              4-OCH.sub.3 94       H              4-OC.sub.2 H.sub.5 95       H              2-CH.sub.3 96       H              3-CH.sub.3 97       H              4-CH.sub.3 98       H              2-F 99       H              3-F100       H              4-F101       H              2-Cl102       H              3-Cl103       H              4-Cl104       H              2-Br105       H              3-Br106       H              4-Br107       H              2-Cl, 4-Cl108       H              3-Cl, 4-Cl109       H              2-CN110       H              4-CN111       H              2-NO.sub.2112       H              3-NO.sub.2113       H              4-NO.sub.2114       H              2-CH.sub.3, 4-CH.sub.3115       H              2-OCH.sub.3, 5-OCH.sub.3116       H              2-OCH.sub.3,                    3-OCH.sub.3, 4-OCH.sub.3117       CH.sub.3       H118      ##STR13##     H119      ##STR14##     H120       H                     ##STR15##______________________________________ 
    
     
                       TABLE 4______________________________________ ##STR16##CouplerNo.       R.sup.21             R.sup.22______________________________________121       CH.sub.3             CH.sub.3122       H              ##STR17##123       H              ##STR18##124       H              ##STR19##125       H              ##STR20##126       H              ##STR21##127       CH.sub.3              ##STR22##128       H              ##STR23##129       H              ##STR24##130       H              ##STR25##131       H              ##STR26##132       H              ##STR27##______________________________________ 
    
     
                       TABLE 5______________________________________ ##STR28##CouplerNo.                (R).sub.n______________________________________133                H134                2-OCH.sub.3135                3-OCH.sub.3136                4-OCH.sub.3137                2-CH.sub.3138                3-CH.sub.3139                4-CH.sub.3140                4-Cl141                2-NO.sub.2142                4-NO.sub.2143                2-OH144                2-OH, 3-NO.sub.2145                2-OH, 5-NO.sub.2146                2-OH, 3-OCH.sub.3______________________________________ 
    
     
                       TABLE 6______________________________________ ##STR29##CouplerNo.               (R).sub.n______________________________________147               4-Cl148               2-NO.sub.2149               3-NO.sub.2150               4-NO.sub.2151              ##STR30##152               H153               2-OCH.sub.3154               3-OCH.sub.3155               4-OCH.sub.3156               2-CH.sub.3157               3-CH.sub.3158               4-CH.sub.3159               2-Cl160               3-Cl______________________________________ 
    
     
                       TABLE 7______________________________________ ##STR31##Coupler No.  R.sup.21 (R.sup.22)n______________________________________161          H        2-OCH.sub.3, 4-Cl, 5-CH.sub.3162          OCH.sub.3                 H163          OCH.sub.3                 2-CH.sub.3164          OCH.sub.3                 2-OCH.sub.3, 5-OCH.sub.3, 4-Cl______________________________________ 
    
     
                       TABLE 8______________________________________ ##STR32##Coupler No.    X______________________________________165           ##STR33##166           ##STR34##167           ##STR35##______________________________________ 
    
     
                       TABLE 9______________________________________ ##STR36##CouplerNo.       R.sup.21______________________________________168      ##STR37##169      ##STR38##170      ##STR39##171      ##STR40##______________________________________ 
    
     
                       TABLE 10______________________________________ ##STR41##CouplerNo.       X          R______________________________________172      ##STR42##                 ##STR43##173      ##STR44##                 ##STR45##174      ##STR46##                 ##STR47##175      ##STR48##                 ##STR49##176      ##STR50##                 ##STR51##177      ##STR52##                 ##STR53##______________________________________ 
    
     
                       TABLE 11______________________________________ ##STR54##CouplerNo.        R.sup.1 R.sup.2______________________________________178        H       H179        CH.sub.3              H180        CH.sub.3              CH.sub.3181        H               ##STR55##______________________________________ 
    
     
                       TABLE 12______________________________________CouplerNo.    Structure______________________________________182   ##STR56##183   ##STR57##184   ##STR58##185   ##STR59##186   ##STR60##187   ##STR61##188   ##STR62##189   ##STR63##190   ##STR64##191   ##STR65##192   ##STR66##193   ##STR67##194   ##STR68##195   ##STR69##196   ##STR70##197   ##STR71##198   ##STR72##199   ##STR73##200   ##STR74##______________________________________ 
    
     
                       TABLE 13______________________________________ ##STR75##CouplerNo.           R.sup.21   (R.sup.22).sub.n______________________________________201           Cl         H202           Cl         2-OCH.sub.3203           Cl         3-OCH.sub.3204           Cl         4-OCH.sub.3205           Cl         2-CH.sub.3206           Cl         3-CH.sub.3207           Cl         4-CH.sub.3208           Cl         2-Cl209           Cl         3-Cl210           Cl         4-Cl211           Cl         2-NO.sub.2212           Cl         3-NO.sub.2213           Cl         4-NO.sub.2214           Cl         2-CH.sub.3, 4-Cl215           Cl         2-CH.sub.3, 4-CH.sub.3216           Cl         2-C.sub.2 H.sub.5217           CH.sub.3   H218           CH.sub.3   2-OCH.sub.3219           CH.sub.3   3-OCH.sub.3220           CH.sub.3   4-OCH.sub.3221           CH.sub.3   2-CH.sub.3222           CH.sub.3   3-CH.sub.3223           CH.sub.3   4-CH.sub.3224           CHI        2-Cl225           CH.sub.3   3-Cl226           CH.sub.3   4-Cl227           CH.sub.3   2-NO.sub.2228           CH.sub.3   3-NO.sub.2229           CH.sub.3   4-NO.sub.2230           CH.sub.3   2-CH.sub.3, 4-Cl231           CH.sub.3   2-CH.sub.3, 4-CH.sub.3232           CH.sub.3   2-C.sub.2 H.sub.5233           OCH.sub.3  H234           OCH.sub.3  2-OCH.sub.3235           OCH.sub.3  3-OCH.sub.3236           OCH.sub.3  4-OCH.sub.3237           OCH.sub.3  2-CH.sub.3238           OCH.sub.3  3-CH.sub.3239           OCH.sub.3  4-CH.sub.3240           OCH.sub.3  2-Cl241           OCH.sub.3  3-Cl242           OCH.sub.3  4-Cl243           OCH.sub.3  2-NO.sub.2244           OCH.sub.3  3-NO.sub.2245           OCH.sub.3  4-NO.sub.2246           OCH.sub.3  2-C.sub.2 H.sub.5______________________________________ 
    
     
                       TABLE 14______________________________________CouplerNo.      Structure______________________________________247     ##STR76##248     ##STR77##249     ##STR78##250     ##STR79##251     ##STR80##252     ##STR81##253     ##STR82##254     ##STR83##255     ##STR84##256     ##STR85##257     ##STR86##258     ##STR87##______________________________________ 
    
     
                       TABLE 15______________________________________ ##STR88##Coupler No.          (R.sup.22).sub.n______________________________________259                  2-Cl, 3-Cl260                  2-Cl, 4-Cl261                  3-Cl, 5-Cl______________________________________ 
    
     
                       TABLE 16______________________________________ ##STR89##Coupler No.          (R.sup.22).sub.n______________________________________262                  4-CH.sub.3263                  3-NO.sub.2264                  2-Cl265                  3-Cl266                  4-Cl267                  2-Cl, 3-Cl268                  2-Cl, 4-Cl269                  3-Cl, 5-Cl270                  2-Cl, 5-Cl271                  3-Cl, 4-Cl______________________________________ 
    
     Of the previously given trisazo compounds represented by formula (I), the following trisazo compounds (I-A), (I-B) and (I-C) are particularly preferable for use in the present invention: 
     Trisazo compound (I-A): ##STR90## wherein R 31  to R 39  each represent hydrogen, --CH 3 , --C 2  H 5 , --C 3  H 7 , chlorine, fluorine, bromine, iodine, CH 3  O--, C 2  H 5  O--, C 3  H 7  O--, --NO 2 , --CN, --CF 3 , or --OH. 
     The trisazo compound (I-A) is capable of generating charges with high efficiency when exposed to light in a near infrared region (with a wavelength of 700 nm or more), so that when the trisazo compound is mixed with a disazo compound to prepare a charge generating material, and a photoconductor is prepared by use of the charge generating material, the photoconductor has high photosensitivities in a wide wavelength range from a visible region through a near infrared region. 
     Trisazo Compound (I-B): ##STR91## 
     Trisazo Compound (I-C): ##STR92## 
     The trisazo compound (I-B) and trisazo compound (I-C) each have a broad photosensitive wavelength range, so that when a charge generating material is prepared by mixing any of these trisazo compounds with a disazo compound and a photoconductor is prepared by use of this charge generating material, the photoconductor has a high photosensitivity to an LD light with a wavelength of 780 nm to 850 nm. 
     Specific examples of a trisazo compound of the following formula (I-D) for use in the present invention are as follows: ##STR93## 
     wherein D represents any of the following: ##STR94## 
     More specifically, examples of the trisazo compounds of formula (I-D) for use in the present invention are shown in TABLES 17-(1) and 17-(2). In TABLES 17-(1) and 17-(2), R A  represents ##STR95## R B  represents --NR 3  R 4  ; and R C  represents --N═CR 3  R 4 . 
     
                       TABLE 17-(1)______________________________________CompoundNo.      D       R.sup.1                   R.sup.2  (R.sup.3).sub.n______________________________________I-D-1    D-1     H      R.sup.A  HI-D-2    D-1     H      R.sup.A  2-ClI-D-3    D-1     H      R.sup.A  3-ClI-D-4    D-1     H      R.sup.A  4-ClI-D-5    D-1     H      R.sup.A  2-FI-D-6    D-1     H      R.sup.A  3-FI-D-7    D-1     H      R.sup.A  4-FI-D-8    D-1     H      R.sup.A  4-OCH3I-D-9    D-1     H      R.sup.A  6-NO2I-D-10   D-1     H      R.sup.A  6-OC.sub.2 H.sub.5I-D-11   D-1     H      R.sup.A  4-CH.sub.3I-D-12   D-1     H      R.sup.A  4-NO.sub.2I-D-13   D-1     H      R.sup.A  4-OC.sub.2 H.sub.5I-D-14   D-1     H      R.sup.A  2-CH.sub.3, 4-CH.sub.3I-D-15   D-1     H      R.sup.A  2-CH.sub.3, 4-ClI-D-16   D-1     H      R.sup.A  2-CH.sub.3, 5-ClI-D-17   D-1     H      R.sup.A  2-OCH.sub.3, 5-BrI-D-18   D-1     H      R.sup.A  2-OCH.sub.3, 5-ClI-D-19   D-1     H      R.sup.A  2-CH.sub.3, 4-OCH.sub.3I-D-20   D-1     H      R.sup.A  2-OCH.sub.3I-D-21   D-1     H      R.sup.A  2-OCH.sub.3, 5-OCH.sub.3I-D-22   D-1     H      R.sup.A  4-COOHI-D-23   D-1     H      R.sup.A  4-SO.sub.3 NaI-D-24   D-1     H      R.sup.A  4-OC.sub.4 H.sub.9 (tert)I-D-25   D-1     H                              --I-D-26   D-1     H      R.sup.A  2-OCH.sub.3, 4-Cl,                            5-OCH.sub.3______________________________________ 
    
     
                                           TABLE 17-(2)__________________________________________________________________________CompoundNo.   D  R.sup.1      R.sup.2          (R.sup.5).sub.n                  R.sup.3                      (R.sup.5).sub.n                         R.sup.4                             (R.sup.5).sub.n                                 (R.sup.6).sub.1__________________________________________________________________________I-D-27 D-1    H R.sup.A          2-OCH.sub.3                  --  -- --  --  --          4-OCH.sub.3          5-ClI-D-28 D-1    H R.sup.A          4-N(CH.sub.3).sub.2                  --  -- --  --  --I-D-29 D-1    H R.sup.B          --      --  -- --  --  --I-D-30 D-1    H R.sup.A          4-CN    H   -- R.sup.A                             HI-D-31 D-1    H R.sup.B          --      --CH.sub.3                      -- R.sup.A                             H   --I-D-32 D-1    H R.sup.B          --      R.sup.A                      H  R.sup.A                             H   --I-D-33 D-1    H R.sup.B          --      --C.sub.2 H.sub.5                      -- --C.sub.2 H.sub.5                             --  --I-D-34 D-1    H R.sup.C          --      R.sup.A                      H  R.sup.A                             H   --I-D-35 D-1    H R.sup.C          --      H   -- R.sup.A                             H   --I-D-36 D-1    H R.sup.C          --      H   -- R.sup.A                             2-Cl                                 --I-D-37 D-1    H R.sup.C          --      H   -- R.sup.A                             4-  --                             OC.sub.2 H.sub.5I-D-38 D-1    H R.sup.A          H       --  -- --  --  HI-D-39 D-2    H R.sup.A          3-NO.sub.2                  --  -- --  --  8-ClI-D-40 D-2    H R.sup.A          4-CN    --  -- --  --  HI-D-41 D-2    H R.sup.A          2-OCH.sub.3                  --  -- --  --  HI-D-42 D-2    H R.sup.A          2-C.sub.2 H.sub.5                  --  -- --  --  HI-D-43 D-2    H R.sup.A          4-Cl    --  -- --  --  HI-D-44 D-2    H R.sup.A          2-Cl    --  -- --  --  HI-D-45 D-2    H R.sup.A          3-NO.sub.2                  --  -- --  --  HI-D-46 D-2    H R.sup.A          2-CH.sub.3                  --  -- --  --  HI-D-47 D-2    H R.sup.A          2-C.sub.2 H.sub.5                  --  -- --  --  8-ClI-D-48 D-2    H R.sup.A          5-NO.sub.2                  --  -- --  --  8-FI-D-49 D-2    H R.sup.C          --      R.sup.A                      H  R.sup.A                             H   HI-D-50 D-2    H R.sup.C          --      H   -- R.sup.A                             2-C.sub.2 H.sub.5                                 HI-D-51 D-2    H R.sup.B          --      --CH.sub.3                      -- --CH.sub.3                             --  HI-D-52 D-2    H R.sup.B          --      --CH.sub.3                      -- R.sup.A                             H   HI-D-53 D-2    H R.sup.B          --      R.sup.A                      H  R.sup.A                             H   8-FI-D-54 D-2    H R.sup.B          --      R.sup.A                      H  R.sup.A                             H   HI-D-55 D-2    H R.sup.A          4-CH.sub.3                  --  -- --  --  HI-D-56 D-2    H R.sup.A          4-C.sub.2 H.sub.5                  --  -- --  --  HI-D-57 D-2    H R.sup.A          2-CH.sub.3, 4-Cl                  --  -- --  --  8-ClI-D-58 D-2    H R.sup.A          2-OC.sub.2 H.sub.5                  --  -- --  --  HI-D-59 D-2    H R.sup.A          2-CH.sub.3, 5-OCH.sub.3                  --  -- --  --  HI-D-60 D-3    H R.sup.C          --      H   -- R.sup.A                             2-Br                                 --I-D-61 D-3    H R.sup.A          2-Cl    --  -- --  --  --I-D-62 D-4    --      --CH.sub.3          --      --  -- --  --  --I-D-63 D-4    --      R.sup.A          H       --  -- --  --  --I-D-64 D-5    --      --C.sub.2 H.sub.5          --      --  -- --  --  --I-D-65 D-6    --      --  --      --  -- --  --  --I-D-66 D-7    --      --  --      --  -- --  --  --I-D-67 D-8    --      --  --      --  -- --  --  --__________________________________________________________________________ 
    
     Of the disazo compounds of formulas (II) to (VIII), the following disazo compounds (II-A) and (II-B) are particularly preferable for use in the present invention. This is because these disazo compounds have high photosensitivities in a visible light range and a stable coating liquid for preparing a photoconductive layer can be prepared from these disazo compounds: ##STR96## 
     Specific examples of a disazo compound having the following formula (II-1) for use in the present invention are as follows: ##STR97## wherein R 2  represents ##STR98## and Y represents ##STR99## 
     Specific examples of the disazo compound of formula (II-11) are shown in the following TABLES 18-(1) and 18-(2): 
     
                       TABLE 18-(1)______________________________________CompoundNo.       R.sup.1   (R.sup.4).sub.n (R.sup.3).sub.n______________________________________II-1-1    H         H               HII-1-2    H         2-CH.sub.3      HII-1-3    H         3-OCH.sub.3     HII-1-4    H         4-Cl            HII-1-5    H         3-NO.sub.2      HII-1-6    H         2-OC.sub.2 H.sub.5                               HII-1-7    H         4-NO.sub.2      HII-1-8    H         4-CH.sub.3      HII-1-9    N         3-Cl            HII-1-10   H         4-OC.sub.2 H.sub.5                               HII-1-11   H         2-CH.sub.3, 4-Cl                               HII-1-12   H         2-CH.sub.3, 5-Cl                               HII-1-13   H         2-CH.sub.3, 4-CH.sub.5                               HII-1-14   H         2-OCH.sub.3, 5-Cl                               HII-1-15   H         2-OCH.sub.3, 5-Br                               HII-1-16   H         2-CH.sub.3, 4-OCH.sub.3                               HII-1-17   H         2-OCH.sub.3, 5-OCH.sub.3                               HII-1-18   H         2-OCH.sub.3, 4-Cl, 5-OCH.sub.3                               HII-1-19   H         2-OCH.sub.3, 4-OCH.sub.3, 5-Cl                               HII-1-20   H         4-N(CH.sub.3).sub.2                               HII-1-21   H         4-CN            HII-1-22   H         4-COOH          HII-1-23   H         3-I             HII-1-24   H         4-OC.sub.4 H.sub.9 (tert)                               HII-1-25   H         2-OCH.sub.3     6-BrII-1-26   --CH.sub.3               H               H______________________________________ 
    
     
                       TABLE 18-(2)______________________________________CompoundNo.        R.sup.1        (R.sup.4).sub.n                               (R.sup.3).sub.n______________________________________II-1-27    C.sub.2 H.sub.5                     H         HII-1-28       ##STR100##    H         HII-1-29    CH.sub.3       2-CH.sub.3                               HII-1-30    C.sub.2 H.sub.5                     4-OCH.sub.3                               HII-1-31       ##STR101##    4-Cl      HII-1-32    H              2-Cl      H______________________________________ 
    
     
                       TABLE 18-(3)______________________________________CompoundNo.     R.sup.1                 R.sup.2                                 (R.sup.3).sub.n______________________________________II-1-33 CH.sub.3                H     HII-1-34 C.sub.3 H.sub.7 (iso)   H     HII-1-35    ##STR102##             H     HII-1-36    ##STR103##             H     HII-1-37    ##STR104##             H     HII-1-38    ##STR105##             H     H______________________________________ 
    
     Specific examples of a disazo compound having the following formula (II-2) for use in the present invention are shown in TABLE 19: ##STR106## 
     
                       TABLE 19______________________________________CompoundNo.         R.sup.1            R.sup.2______________________________________II-2-1                          HII-2-2        ##STR107##        H______________________________________ 
    
     Specific examples of a disazo compound having the following formula (II-3) for use in the present invention are shown in TABLE 20: ##STR108## wherein Y represents ##STR109## 
     
                       TABLE 20______________________________________CompoundNo.        R.sup.1    (R.sup.2).sub.n______________________________________II-3-1     --CH.sub.3 HII-3-2     --CH.sub.3 4-NO.sub.2II-3-3     --CH.sub.3 3-SO.sub.3 NH.sub.2II-3-4     --CH.sub.3 4-SO.sub.3 HII-3-5     --CH.sub.3 2-Cl, 3-SO.sub.3 H, 5-Cl, 6-ClII-3-6     --CH.sub.3 4-CH.sub.3II-3-7     --CH.sub.3 4-OCH.sub.3II-3-8     --CH.sub.3 4-ClII-3-9     --CH.sub.3 2-NO.sub.2, 4-NO.sub.2 II-3-10   --CH.sub.3 4-CN II-3-11   --CH.sub.3 4-N(CH.sub.3).sub.2 II-3-12   --CH.sub.3 4-NHCOCH.sub.3 II-3-13   --COOH     H II-3-14   --COOH     4-CH.sub.3 II-3-15   --COOH     4-OCH.sub.3 II-3-16   --COOC.sub.2 H.sub.5                 H II-3-17   --COOC.sub.2 H.sub.5                 4-CH.sub.3 II-3-18   --COOC.sub.2 H.sub.5                 4-OCH.sub.3______________________________________ 
    
     Specific examples of a disazo compound having the following formula (II-4) for use in the present invention are shown in TABLE 21: ##STR110## wherein Y is the same as in formula (II-3). 
     
                       TABLE 21______________________________________CompoundNo.            (R.sup.1).sub.n                      (R.sup.2).sub.n______________________________________II-4-1         2-CH.sub.3, 4-OCH.sub.3                      HII-4-2         4-OCH.sub.3 HII-4-3         4-Cl        HII-4-4         H           HII-4-5         3-NO.sub.2  HII-4-6         3-NO.sub.2  8-FII-4-7         3-NO.sub.2  8-ClII-4-8         3-NO.sub.2  10-Cl______________________________________ 
    
     Other disazo compounds for use in the present invention are shown in the following TABLE 22: 
     
                                           TABLE 22__________________________________________________________________________Compound No.   Chemical Structure__________________________________________________________________________II-5-1    ##STR111##II-5-2    ##STR112##II-5-3    ##STR113##II-5-4    ##STR114##__________________________________________________________________________ 
    
     In the above table, Y represents ##STR115## 
     Examples of unsymmetrical disazo compounds having following formula (II-6) for use in the present invention are shown in the following TABLE 23: ##STR116## 
     In the above formula (II-6), A represents any of A-1, A-2, A-3, A-4, A-5, A-6 or A-7 and B represents any of B-1, B-2, B-3, B-4, B-5, B-6 or B-7 shown below: ##STR117## 
     In TABLE 23, R A , R B , R C , R D  and R E  are respectively follows: 
     
                                           TABLE 23__________________________________________________________________________ ##STR118##            ##STR119##CompoundNo.   A   R.sup.1       R.sup.2           (R.sup.3).sub.n                B   R.sup.1                      R.sup.2                           (R.sup.3).sub.n__________________________________________________________________________II-5-1 A-1 R.sup.A       H   H    B-1 R.sup.A                       H   2-CH.sub.3II-5-2 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    3-CH.sub.3II-5-3 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    2-ClII-5-4 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    3-OCH.sub.3II-5-5 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    2-CH.sub.3,                           4-OCH.sub.3II-5-6 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    2-OCH.sub.3,                           5-OCH.sub.3II-5-7 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    3-III-5-8 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    2-OCH.sub.3II-5-9 A-1 R.sup.A       H   H    B-1 R.sup.A                      H    4-NO.sub.2II-5-10 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    2-CH.sub.3II-5-11 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    3-ClII-5-12 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    4-ClII-5-13 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    3-CH.sub.3II-5-14 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    3-III-5-15 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    2-III-5-16 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      H    2-OCH.sub.3II-5-17 A-1 R.sup.A       H   2-CH.sub.3                B-1 R.sup.A                      H    4-CNII-5-18 A-1 R.sup.B       H   --   B-1 R.sup.A                      H    3-OCH.sub.3II-5-19 A-1 R.sup.C       H   --   B-1 R.sup.A                      H    2-ClII-5-20 A-1 R.sup.C       H   --   B-1 R.sup.A                      H    2-CH.sub.3II-5-21 A-1 R.sup.E       H   --   B-1 R.sup.A                      H    2-ClII-5-22 A-1 R.sup.B       H   --   B-1 R.sup.C                      H    --II-5-23 A-1 R.sup.D       H   --   B-1 R.sup.A                      H    3-ClII-5-24 A-1 R.sup.C       H   --   B-1 R.sup.A                      H    3-ClII-5-25 A-1 R.sup.C       H   --   B-1 R.sup.A                      H    2-OCH.sub.3,                           5-OCH.sub.3II-5-26 A-1 R.sup.D       H   --   B-1 R.sup.A                      H    2-CH.sub.3II-5-27 A-1 R.sup.D       H   --   B-1 R.sup.C                      H    --II-5-28 A-1 R.sup.D       H   --   B-1 R.sup.A                      H    2-ClII-5-29 A-1 R.sup.A       H   2-Cl B-5 --                      --   --II-5-30 A-1 R.sup.A       H   2-Cl B-2 R.sup.A                      H    2-CH.sub.3II-5-31 A-1 R.sup.A       H   2-Cl B-3 R.sup.A                      CH.sub.3                           --II-5-32 A-1 R.sup.A       H   2-Cl B-7 R.sup.A                      H    4-OCH.sub.3II-5-33 A-1 R.sup.A       H   2-Cl B-1 R.sup.A                      CH.sub.3                           2-CH.sub.3II-5-34 A-1 R.sup.A       H   2-Cl B-4 --                      --   --II-5-35 A-1 R.sup.A       H   2-Cl B-5 --                      --   --II-5-36 A-1 R.sup.A       H   2-CH.sub.3                B-3 R.sup.A                      CH.sub.3                           --II-5-37 A-1 R.sup.A       H   3-Cl B-3 R.sup.A                      COOH 4-CH.sub.3II-5-38 A-1 R.sup.A       H   2-OCH.sub.3                B-1 R.sup.A                      C.sub.2 H.sub.5                           4-OCH.sub.3           5-OCH.sub.3II-5-39 A-7 R.sup.A       H   2-CH.sub.3                B-7 R.sup.A                      H    4-Cl           4-OCH.sub.3II-5-40 A-2 R.sup.B       H   --   B-1 R.sup.E                      H    --II-5-41 A-3 R.sup.A       CH.sub.3           4-SO.sub.3 H                B-3 R.sup.A                      CH.sub.3                           4-CH.sub.3__________________________________________________________________________ 
    
     The photoconductive layer of the electrophotographic photoconductor according to the present invention may be either of a dispersion type or of a function-separated type by use of a charge generating material and a charge transporting material in combination. 
     In the case of the dispersion type, a dispersion prepared by dispersing a charge generating material and a charge transporting material in a binder resin is applied to an electroconductive support to form a photoconductive layer thereon. 
     In the case of the function-separated type, a charge generation layer comprising a charge generating material and a binder resin is formed on an electroconductive support, and a charge transport layer comprising the charge transporting material and a binder resin is then formed on the charge generation layer. When a function-separated type electrophotographic photoconductor for positive charging is fabricated, the charge transport layer may be first formed on the electroconductive support and the charge generating layer is then formed on the charge transport layer. In the function-separated type electrophotographic photoconductor, the charge transporting material can be incorporated into the charge generation layer. In this case, the photosensitivity of the photoconductor for positive charging can be particularly improved. 
     In order to improve the adhesion and charge blocking properties of the photoconductor, an intermediate layer may be interposed between the electroconductive support and the photoconductive layer. Furthermore, a protective layer may be provided on the photoconductive layer in order to improve the resistance to wear and the mechanical durability of the photoconductive layer. 
     As the binder agent for use in the charge generation layer and the charge transport layer of the function-separated type electrophotographic photoconductor, and for use in the photoconductive layer of the dispersion type electrophotographic photoconductor of the present invention, any binder agents with excellent insulating properties which are conventionally employed in electrophotographic photoconductors can be employed. 
     Examples of such binder agents include polycarbonates (bisphenol A type and bisphenol Z type), polyester, methacrylic resin, acrylic resin, polyethylene, polyvinyl chloride, polyvinyl acetate, polystyrene, phenolic resin, epoxy resin, polyurethane, polyvinylidene chloride, alkyd resin, silicone resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, polyamide and phenoxy resin. These binder agents can be used alone or in combination. 
     In the case of a negative-charging type photoconductor comprising an electroconductive support, and a charge generation layer, and a charge transport layer, which are successively overlaid on the electroconductive support, it is preferable that the amount of the charge generating material be 20 wt. % or more of the weight of the binder agent contained in the charge generation layer, and that the thickness of the charge generation layer be in the range of 0.01 to 5 μm. It is preferable that the amount of the charge transporting material be 20 to 200 wt. % of the weight of the binder agent contained in the charge transport layer, and that the thickness of the charge transport layer be 5 to 100 μm. 
     In the charge generation layer, it is preferable that the amount of the charge generating material be 20 wt. % or more of the weight of the binder resin contained in the charge generation layer. Moreover, it is preferable to incorporate the charge transporting material into the charge generation layer, so that the increase of the residual potential can be minimized and the photosensitivity can be enhanced. In this case, it is preferable that the amount of the charge transporting material incorporated into the charge generation layer be preferably 20 to 200 wt. % of the weight of the binder resin contained in the charge generation layer. 
     In the case of the dispersion type electrophotographic photoconductor, it is preferable that the amount of the mixture of the trisazo compound and the disazo compound serving as a charge generating material be 5 to 95 wt. % of the weight of the binder agent contained in the photoconductive layer, and that the thickness of the photoconductive layer be in the range of 10 to 100 μm. In addition, it is preferable that the amount of the charge transporting material be 30 to 200 wt. % of the weight of the binder agent contained in the photoconductive layer. 
     Moreover, in order to improve the chargeability and the gas resistance of the photoconductive layer for use in the present invention, an antioxidant such as a phenolic compound, a hydroquinone compound, a hindered phenolic compound, a hindered amine compound, or a compound including hindered amine and hindered phenol within the molecules thereof can be added to the photoconductive layer of the electrophotographic photoconductive of the present invention regardless of the type thereof. 
     As the electroconductive support for the electrophotographic photoconductor of the present invention, a film, a cylindrical film, a belt-shaped film and a sheet of paper on which an electroconductive material with a volume resistivity of 10 10  Ω.cm or less is deposited or coated by vacuum deposition or sputtering can be employed. Examples of such an electroconductive material are metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum; metal oxides such as indium oxide; and copper iodide. 
     Furthermore, as the electroconductive support, a plate, a belt, and a base drum made of aluminum, aluminum alloy, nickel, or stainless steal can be employed. In particular, the base drum can be made by producing a tube by drawing and ironing (D.I.), impact ironing (I.I.), extrusion molding, or pultrusion, and then subjecting the tube to cutting superfinishing. 
     In the addition to the above, for instance, a plastic plate coated with a resin in which electroconductive finely-divided particles of carbon black, indium oxide or tin oxide are dispersed can also be used. 
     Any of conventionally known charge transporting materials can be employed as the charge transporting material for use in the present invention. 
     An example of the material is a compound of formula (IV) as disclosed in Japanese Laid-Open Patent Publication 1-302260: ##STR120## wherein R 1  and R 4  each represent hydrogen, an alkyl group, an alkoxyl group, a halogen atom, or a substituted amino group; R 2  and R 3  each represent hydrogen, an alkyl group or a substituted or unsubstituted phenyl group;  represents a benzene ring, a naphthalene ring, an anthracene ring, an indole ring or a carbazole ring; n is an integer of 0 or 1; and m is an integer of 0, 1, 2 or 3. 
     Specific examples of the compound of formula (IV) are as shown in TABLE 24. 
     
                                           TABLE 24__________________________________________________________________________ No.CompoundTransportingCharge   n     R.sup.2      R.sup.3   R.sup.4                                ##STR121##__________________________________________________________________________ 1     0 H                  ##STR122##                           H                                ##STR123## 2     0 H                  ##STR124##                           H                                ##STR125## 3     0 H                  ##STR126##                           H                                ##STR127## 4     0 H                  ##STR128##                           H                                ##STR129## 5     0 H                  ##STR130##                           H                                ##STR131## 6     0 H                  ##STR132##                           H                                ##STR133## 7     0 H                  ##STR134##                           H                                ##STR135## 8     0 H                  ##STR136##                           H                                ##STR137## 9     0 H                  ##STR138##                           H                                ##STR139## 10    0 H                  ##STR140##                           H                                ##STR141## 11    0 H                  ##STR142##                           H                                ##STR143## 12    0 H                  ##STR144##                           H                                ##STR145## 13    0 H                  ##STR146##                           H                                ##STR147## 14    0 H                  ##STR148##                           H                                ##STR149## 15    0 H                  ##STR150##                           H                                ##STR151## 16    0 H                  ##STR152##                           H                                ##STR153## 17    0 H                  ##STR154##                           H                                ##STR155## 18    0 H                  ##STR156##                           H                                ##STR157## 19    0 H                  ##STR158##                           H                                ##STR159## 20    0 H                  ##STR160##                           H                                ##STR161## 21    0 H                  ##STR162##                           H                                ##STR163## 22    0 H                  ##STR164##                           H                                ##STR165## 23    0 H                  ##STR166##                           H                                ##STR167## 24    0 H                  ##STR168##                           H                                ##STR169## 25    0 H                  ##STR170##                           H                                ##STR171## 26    0     ##STR172##                  ##STR173##                           H                                ##STR174## 27    0     ##STR175##                  ##STR176##                           H                                ##STR177## 28    0     ##STR178##                  ##STR179##                           H                                ##STR180## 29    0 H                  ##STR181##                           H                                ##STR182## 30    0 H                  ##STR183##                           H                                ##STR184## 31    0 H                  ##STR185##                           H                                ##STR186## 32    0 H                  ##STR187##                           H                                ##STR188## 33    0 CH.sub.3                  ##STR189##                           H                                ##STR190## 34    0 CH.sub.3                  ##STR191##                           H                                ##STR192## 35    0 H                  ##STR193##                           H                                ##STR194## 36    0 H                  ##STR195##                           H                                ##STR196## 37    0 H                  ##STR197##                           H                                ##STR198## 38    0 H                  ##STR199##                           H                                ##STR200## 39    0 H                  ##STR201##                           H                                ##STR202## 40    0 H                  ##STR203##                           H                                ##STR204## 41    0 H                  ##STR205##                           H                                ##STR206## 42    0 H                  ##STR207##                           H                                ##STR208## 43    0 H                  ##STR209##                           H                                ##STR210## 44    0 H                  ##STR211##                           H                                ##STR212## 45    0 H                  ##STR213##                           H                                ##STR214## 46    0 H                  ##STR215##                           H                                ##STR216## 47    0 H                  ##STR217##                           H                                ##STR218## 48    0 H                  ##STR219##                           H                                ##STR220## 49    0 H                  ##STR221##                           H                                ##STR222## 50    0 H                  ##STR223##                           H                                ##STR224## 51    0 H                  ##STR225##                           H                                ##STR226## 52    0 H                  ##STR227##                           H                                ##STR228## 53    0 H                  ##STR229##                           H                                ##STR230## 54    0 H                  ##STR231##                           H                                ##STR232## 55    0 H                  ##STR233##                           H                                ##STR234## 56    0 H                  ##STR235##                           H                                ##STR236## 57    0 H                  ##STR237##                           H                                ##STR238## 58    0 H                  ##STR239##                           H                                ##STR240## 59    0 H                  ##STR241##                           H                                ##STR242## 60    0 H                  ##STR243##                           H                                ##STR244## 61    0 H                  ##STR245##                           H                                ##STR246## 62    0 H                  ##STR247##                           H                                ##STR248## 63    0 H                  ##STR249##                           H                                ##STR250## 64    0 H                  ##STR251##                           H                                ##STR252## 65    0 H                  ##STR253##                           H                                ##STR254## 66    0 H                  ##STR255##                           H                                ##STR256## 67    0 H                  ##STR257##                           H                                ##STR258## 68    0 H                  ##STR259##                           H                                ##STR260## 69    0 H                  ##STR261##                           H                                ##STR262## 70    0 H                  ##STR263##                           H                                ##STR264## 71    0 H                  ##STR265##                           H                                ##STR266## 72    0 H                  ##STR267##                           H                                ##STR268## 73    0 H                  ##STR269##                           H                                ##STR270## 74    0 H                  ##STR271##                           H                                ##STR272## 75    0 H                  ##STR273##                           H                                ##STR274## 76    0 H                  ##STR275##                           H                                ##STR276## 77    0 H                  ##STR277##                           H                                ##STR278## 78    0 H                  ##STR279##                           H                                ##STR280## 79    0 H                  ##STR281##                           H                                ##STR282## 80    0 H                  ##STR283##                           H                                ##STR284## 81    0 H                  ##STR285##                           H                                ##STR286## 82    0 H                  ##STR287##                           H                                ##STR288## 83    0 H                  ##STR289##                           H                                ##STR290## 84    0 H                  ##STR291##                           H                                ##STR292## 85    0 H                  ##STR293##                           H                                ##STR294## 86    0 H                  ##STR295##                           H                                ##STR296## 87    0 H                  ##STR297##                           H                                ##STR298## 88    0 H                  ##STR299##                           H                                ##STR300## 89    0 H                  ##STR301##                           H                                ##STR302## 90    0 H                  ##STR303##                           H                                ##STR304## 91    0 H                  ##STR305##                           H                                ##STR306## 92    0 H                  ##STR307##                           H                                ##STR308## 93    0 H                  ##STR309##                           H                                ##STR310## 94    0 H                  ##STR311##                           H                                ##STR312## 95    0 H                  ##STR313##                           H                                ##STR314## 96    0 H                  ##STR315##                           H                                ##STR316## 97    0 H                  ##STR317##                           H                                ##STR318## 98    0 H                  ##STR319##                           H                                ##STR320## 99    0 H                  ##STR321##                           H                                ##STR322##100    0 H                  ##STR323##                           H                                ##STR324##101    0 H                  ##STR325##                           H                                ##STR326##102    0 H                  ##STR327##                           H                                ##STR328##103    0 H                  ##STR329##                           H                                ##STR330##104    0 H                  ##STR331##                           H                                ##STR332##105    0 H                  ##STR333##                           H                                ##STR334##106    0 H                  ##STR335##                           H                                ##STR336##107    0 H                  ##STR337##                           H                                ##STR338##108    0 H                  ##STR339##                           H                                ##STR340##109    0 H                  ##STR341##                           H                                ##STR342##110    0 H                  ##STR343##                           H                                ##STR344##111    0 H                  ##STR345##                           H                                ##STR346##112    0 H                  ##STR347##                           H                                ##STR348##113    0 H                  ##STR349##                           H                                ##STR350##114    0 H                  ##STR351##                           H                                ##STR352##115    0 H                  ##STR353##                           H                                ##STR354##116    0 H                  ##STR355##                           H                                ##STR356##117    0 H                  ##STR357##                           H                                ##STR358##118    0 H                  ##STR359##                           H                                ##STR360##119    0 H                  ##STR361##                           H                                ##STR362##120    0 H                  ##STR363##                           H                                ##STR364##121    0 H                  ##STR365##                           H                                ##STR366##122    1 H                  ##STR367##                           H                                ##STR368##123    1 H                  ##STR369##                           H                                ##STR370##124    0 H            H         CH.sub.3                                ##STR371##125    0 H            H         H                                ##STR372##126    0 H            H         OCH.sub.3                                ##STR373##127    0 H            H         CH.sub.3                                ##STR374##128    0 H                  ##STR375##                           H                                ##STR376##__________________________________________________________________________ 
    
     In addition, as the charge transporting materials for use in the present invention, positive-hole-transporting materials and electron-transporting materials can be employed. 
     Furthermore, examples of the positive hole transporting materials are as follows: ##STR377## wherein R 1  represents methyl group, ethyl group, 2-hydroxyethyl group, or 2-chloroethyl group; R 2  represents methyl group, ethyl group, benzyl group or phenyl group; and R 3  represents hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, a dialkylamino group, or nitro group. ##STR378## wherein Ar represents a naphthyl group, an anthryl group, a styryl group, each of which may have a substituent, a pyridyl group, a furanyl group, or a thiophenyl group; and R represents an alkyl group or benzyl group. wherein R 1  represents an alkyl group, benzyl group, phenyl group, or naphthyl group; R 2  represents hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms, a dialkylamino group, a diaralkylamino group or a diarylamino group; n is an integer of 1 to 4; when n is 2 or more, R 2  may be the same or different; and R 3  represents hydrogen or methoxy group. ##STR379## wherein R 1  represents an alkyl group having 1 to 11 carbon atoms, a substituted or unsubstituted phenyl group, or a heterocyclic ring; R 2  and R 3  each independently represent hydrogen, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, a chloroalkyl group, or a substituted or unsubstituted aralkyl group, R 2  and R 3  in combination may form a heterocyclic ring containing nitrogen; and R 4  represents hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group or a halogen, and may be the same or different. ##STR380## wherein R represents hydrogen or a halogen atom; Ar represents a substituted or unsubstituted phenyl group, naphthyl group, anthryl group or carbazolyl group each of which may have a substituent. ##STR381## wherein R 1  represents hydrogen, a halogen atom, cyano group, an alkoxyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms; Ar represents ##STR382## wherein R 1  represents an alkyl group having 1 to 4 carbon atoms; R 2  and R 3  each represent hydrogen, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, or a dialkyl amino group; n is an integer of 1 or 2; when n is 2, R 3  may be the same or different; and R 4  and R 5  each represent hydrogen, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms or a substituted or unsubstituted benzyl group. ##STR383## wherein R represents carbazolyl group, pyridyl group, thienyl group, indolyl group, furyl group, a substituted or unsubstituted phenyl group, styryl group, naphthyl group, or anthryl group, each of which may have a substituent selected from the group consisting of a dialkylamino group, an alkyl group, an alkoxyl group, carboxyl group or an ester group thereof, a halogen atom, cyano group, an aralkylamino group, an N-alkyl-N-aralkylamino group, amino group, nitro group and acetylamino group. ##STR384## wherein R 1  represents a lower alkyl group, benzyl group or a substituted or unsubstituted aryl group; R 2  represents hydrogen, a lower alkyl group, a lower alkoxyl group, a halogen atom, nitro group, an amino group which may have as a substituent a lower alkyl group or benzyl group; and n is an integer of 1 or 2. ##STR385## wherein R 1  represents hydrogen, an alkyl group, an alkoxyl group or a halogen atom; R 2  and R 3  each represent an alkyl group, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted aryl group; R 4  represents hydrogen, or a substituted or unsubstituted phenyl group; and Ar represents phenyl group or naphthyl group. ##STR386## wherein n is an integer of 0 or 1; R 1 , R 2  and R 3  each represent hydrogen, an alkyl group or a substituted or unsubstituted phenyl group; 
     A represents ##STR387## 9-anthryl group represented by ##STR388## or a substituted or unsubstituted N-alkylcarbazolyl group, in which R 4  represents hydrogen, an alkyl group, an alkoxyl group, a halogen atom, or ##STR389## in which R 5  and R 6  each represents an alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group, and may form a ring; m is an integer of 0 to 3; and when m is 2 or more, R 4  may be the same or different. ##STR390## wherein R 1 , R 2  and R 3  each represent hydrogen, a lower alkyl group, a lower alkoxyl group, a dialkylamino group or a halogen atom; and n is an integer of 0 or 1. ##STR391## wherein R 1 , R 2  and R 3  each represent hydrogen, an alkyl group, an alkoxyl group or a halogen atom; and R 2  and R 3  may be the same or different. 
     Specific examples of the compound of formula (1) are 9-ethylcarbazole-3-aldehyde-1-methyl-1-phenylhydrazone, 9-ethylcarbazole-3-aldehyde-1-benzyl-1-phenylhydrazone, and 9-ethylcarbazole-3-aldehyde-1,1-diphenylhydrazone. 
     Specific examples of the compound of formula (2) are 4-diethylaminostyrene-β-aldehyde-1-methyl-1-phenylhydrazone, and 4-methyoxynaphthalene-1-aldehyde-1-benzyl-1-phenylhydrazone. 
     Specific examples of the compound of formula (3) are 4-methoxybenzaldehyde-1-methyl-1-phenylhydrazone, 2,4-dimethoxybenzaldehyde-1-benzyl-1-phenylhydrazone, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, 4-methoxybenzaldehyde-1-benzyl-1-(4-methoxy)phenylhydrazone, 4-diphenylaminobenzaldehyde-1-benzyl-1-phenylhydrazone, and 4-dibenzylaminobenzaldehyde-1,1-diphenylhydrazone. 
     Specific examples of the compound of formula (4) are 1,1-bis(4-dibenzylaminophenyl)propane, tris(4-diethylaminophenyl)methane, 1,1-bis(4-dibenzylaminophenyl)-propane, and 2,2&#39;-dimethyl-4,4&#39;-bis(diethylamino)-triphenylmethane. 
     Specific examples of the compound of formula (5) are 9-(4-diethylaminostyryl)anthracene, and 9-bromo-10-(4-diethylaminostyryl)anthracene. 
     Specific examples of the compound of formula (6) are 9-(4-dimethylaminobenzylidene)fluorene, and 3-(9-fluorenylidene)-9-ethylcarbazole. 
     Specific examples of the compound of formula (7) are 1,2-bis(4-diethylaminostyryl)benzene, and 1,2-bis(2,4-dimethoxystyryl)benzene. 
     Specific examples of the compound of formula (8) are 3-styryl-9-ethylcarbazole, and 3-(4-methoxystyryl)-9-ethylcarbazole. 
     Specific examples of the compound of formula (9) are 4-diphenylaminostilbene, 4-dibenzylaminostilbene, 4-ditolyllaminostilbene, 1-(4-diphenylaminostyryl)-naphthalene, and 1-(4-diethylaminostyryl)naphthylene. 
     Specific examples of the compound of formula (10) are 4&#39;-diphenylamino-α-phenylstilbene, and 4&#39;-methylphenylamino-α-phenylstilbene. 
     Specific examples of the compound of formula (11) are 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, and 1-phenyl-3-(4-dimethylaminostyryl)-5-(4-dimethylaminophenyl)pyrazoline. 
     Specific examples of the compound of formula (12) are N,N&#39;-diphenyl-N,N&#39;-bis(3-methylphenyl)-[1,1&#39;-bisphenyl]-4,4&#39;-diamine, N,N&#39;-diphenyl-N,N&#39;-bis(chlorophenyl)-[1,1&#39;-biphenyl]-4,4&#39;-diamine, and 3,3&#39;-dimethylbenzidine. 
     Examples of other positive hole transporting material are low-molecular compounds, for example, oxadiazole compounds such as 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2,5-bis[4-(4-diethylaminostyryl)phenyl]-1,3,4-oxadiazole, 2-(9-ethylcarbazolyl-3-)-5-(4-diethylaminophenyl)-1,3,4-oxadiazole, and oxazole compounds such as 2-vinyl-4-(2-chlorophenyl)-5-(4-diethylaminophenyl)oxazole, and 2-(4-diethylaminophenyl)-4-phenyloxazole, and polymers such as poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, pyrene formaldehyde resin and ethylcarbazole formaldehyde resin. 
     Specific examples of other charge transporting materials are chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, and 2,6,8-trinitro-4H-indeno[1,2-b]thiophene-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide. 
     Other features of this invention will become apparent in the course of the following description of exemplary embodiments, which are given for illustration of the invention and are not intended to be limiting thereof. 
     Example 1-1 
     [Formation of Charge Generation Layer] 
     A mixture of the following components was subjected to ball milling by use of PSZ balls in a 50 ml glass vessel for five days: 
     
         ______________________________________Trisazo compound No. I-70                0.238 gDisazo compound No. II-17                0.012 g1% cyclohexanone solution                 4.75 gof polyvinyl butyral resin(Trademark &#34;XYHL&#34; made byUnion Carbide Japan K.K.)Cyclohexanone           7 g______________________________________ 
    
     Trisazo compound No. I-70 employed in the above formulation has the following chemical structure with a trisazo skeleton I and coupler radicals No. 70 in TABLE 2. ##STR392## 
     The number (I-70) assigned to the above trisazo compound indicates the trisazo skeleton thereof is indicated by the above formula (I), and the three coupler radicals represented by bonded to the trisazo skeleton is Coupler No. 70 in TABLE 2. 
     Furthermore, disazo compound No. II-17 in the formulation has the following chemical structure with a disazo skeleton II and coupler radicals No. 17 in TABLE ##STR393## 
     The number (II-17) assigned to the above disazo compound indicates the disazo skeleton thereof is indicated by the above formula (II) and the two coupler radicals represented by A is coupler No. 17 in TABLE 1. 
     The ball milling of the above mixture was continued for one day with the addition of methyl ethyl ketone, so that a charge generation layer coating liquid was prepared. 
     The above prepared charge generation layer coating liquid was coated by a blade on an aluminum-deposited polyester film with a thickness of 75 μm serving as a support, with a gap of 30 μm set between the tip of the blade and the surface of the aluminum-deposited polyester film, and dried by the application of heat at 80° C. for 2 minutes, so that a charge generation layer was provided on the support. 
     [Formation of Charge Transport Layer] 
     10 g of a Z type polycarbonate resin with a number-average molecular weight of about 50,000, 8 g of an α-phenylstilbene compound (1) of the following formula, and 72 g of toluene were mixed to prepare a charge transport layer coating liquid: ##STR394## 
     The above prepared charge transport layer coating liquid was coated by a blade on the charge generation layer, dried at 80° C., and then at 130° C. for 5 minutes, so that a charge transport layer with a thickness of about 20 μm was provided on the charge generation layer. 
     Thus, electrophotographic photoconductor No. 1-1 of the present invention was fabricated. 
     Examples 1-2 to 1-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-1 in Example 1-1 was repeated except that the amounts of trisazo compound No. I-70 and disazo compound No. II-17 employed in Example 1-1 were respectively changed as shown in the following TABLE 25, so that electrophotographic photoconductors Nos. 1-2 to 1-5 of the present invention were fabricated. 
     Comparative Examples 1-1 and 1-2 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-1 in Example 1-1 was repeated except that the amounts of trisazo compound No. I-70 and disazo compound No. II-17 employed in Example 1-1 were respectively changed as shown in the following TABLE 25, so that comparative electrophotographic photoconductors No. 1-1 and No. 1-2 were fabricated. 
     
                       TABLE 25______________________________________       Trisazo Compound                     Disazo CompoundExample No. No. I-70      No. II-17______________________________________Ex. 1-2     0.187 g       0.063 gEx. 1-3     0.125 g       0.125 gEx. 1-4     0.187 g       0.063 gEx. 1-5     0.238 g       0.012 gComp.        0.25 g          0 gEx. 1-1Comp.          0 g         0.25 gEx. 1-2______________________________________ 
    
     Evaluation 1 
     The electrophotographic characteristics of the thus fabricated electrophotographic photoconductors No. 1-1 to No. 1-5 of the present invention and comparative electrophotographic photoconductors No. 1-1 and No. 1-2 were evaluated by using an electrostatic-characteristics measuring apparatus (Trademark &#34;EPA8100&#34;, made by Kawaguchi Electro Works Co., Ltd.) in the following manner: 
     Each of the above electrophotographic photoconductors was negatively charged under the application of -5.5 kV for 2 seconds and the charging potential V 2  (volts) of the photoconductor was measured. The photoconductor was charged up to -800 V and then exposed to the light of a tungsten lamp at a color temperature of 2856° K. through a band-pass filter for 780 nm (a half-amplitude level of 20 nm), whereby the photosensitivity of each photoconductor was measured. 
     The exposure E 1/10  (μJ/cm 2 ) required to reduce the surface potential from -800 V to -80 V was measured as the index for the photosensitivity. Namely, the smaller the exposure E 1/10 , the higher the photoconductor. The results are shown in TABLE 26. 
     
                       TABLE 26______________________________________Example No.   V.sub.2 (volts)                   E.sub.1/10 (μJ/cm.sup.2)______________________________________Ex. 1-1       745       1.00Ex. 1-2       760       0.60Ex. 1-3       760       0.55Ex. 1-4       800       0.70Ex. 1-5       790       0.90Comp.         750       1.20Ex. 1-1Comp.         800       No sensitivityEx. 1-2______________________________________ 
    
     The evaluation results shown in TABLE 26 indicate that E 1/10  of each of electrophotographic photoconductors No. 1-1 to No. 1-5, each comprising the charge generating material which comprises the trisazo compound and the disazo compound, is smaller than that of comparative electrophotographic photoconductor No. 1-1, which comprises the trisazo compound alone as the charge generating material. 
     Comparative electrophotographic photoconductor No. 1-2, which comprises the disazo compound along as the charge generating material exhibited no photosensitivity. 
     Examples 1-6 to 1-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-3 in Example 1-3 was repeated except that disazo compound No. II-17 employed in Example 1-3 was replaced by disazo compounds No. II-29, No. II-19, No. II-12 and No. II-200, respectively, so that electrophotographic photoconductors Nos. 1-6 to 1-9 of the present invention were fabricated. 
     Disazo compounds No. II-29, No. II-19, No. II-12 and No. II-200 are such disazo compounds with the disazo skeleton II explained in Example 1-1 and coupler radicals No. 29, No. 19, and No. 12 in TABLE 1, and No. 200 in TABLE 12, respectively. 
     Examples 1-10 to 1-13 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-3 in Example 1-3 was repeated except that trisazo compound No. I-70 employed in Example 1-3 was replaced by trisazo compounds No. I-74, No. I-67, No. I-85 and No. I-82, respectively, so that electrophotographic photoconductors Nos. 1-10 to 1-13 of the present invention were fabricated. 
     Trisazo compounds No. I-74, No. I-67, No. I-85 and No. I-82 are such trisazo compounds with the trisazo skeleton I explained in Example 1-1 and coupler radicals No. 74, No. 67, No. 85 and No. 82 in TABLE 2. 
     Comparative Examples 1-3 to 1-6 
     The same procedure for fabrication of comparative electrophotographic photoconductor No. 1-1 in Comparative Example 1-1 was repeated except that trisazo compound No. 1-70 employed in Comparative Example 1-1 was replaced by trisazo compounds No. I-72, No. I-67, No. I-214 and No. I-77, respectively, so that comparative electrophotographic photoconductors Nos. 1-3 to 1-6 were fabricated. 
     Comparative Example 1-7 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-2 in Example 1-2 was repeated except that disazo compound No. II-17 in Example 1-2 was replaced by a perylene compound of the following formula, so that comparative electrophotographic photoconductor No. 1-7 was fabricated: ##STR395## 
     The charging potential V 2  and exposure E 1/10  of each of the electrophotographic photoconductors Nos. 1-6 to 1-13 of the present invention and comparative electrophotographic photoconductors Nos. 1-3 to 1-7 were measured in the same manner as in Evaluation 1. The results are shown in TABLE 27. 
     
                       TABLE 27______________________________________                    Trisazo                    Compound/                    Disazo  Trisazo  Disazo   Compound  Com-     Com-     (Weight  V.sub.2                                   E.sub.1/10Ex. No.  pound    pound    Ratio)   (volts)                                   (μJ/cm.sup.2)______________________________________Ex. 1-6  I-70     II-29    1/1      590   0.60Ex. 1-7  I-70     II-19    1/1      790   0.90Ex. 1-8  I-70     II-12    1/1      820   0.64Ex. 1-9  I-70      II-200  1/1      780   0.87 Ex. 1-10  I-74     II-17    1/1      660   5.00 Ex. 1-11  I-67     II-17    1/1      650   1.50 Ex. 1-12  I-85     II-17    1/1      700   0.65 Ex. 1-13  I-82     II-17    1/1      750   1.20Comp.  I-72     --       1/0      710   10.06Ex. 1-3Comp.  I-67     --       1/0      700   4.06Ex. 1-4Comp.   I-214   --       1/0      700   0.91Ex. 1-5Comp.  I-77     --       1/0      680   2.40Ex. 1-6Comp.  I-70     Perylene 1/1      750   1.58Ex. 1-7         Com-           pound______________________________________ 
    
     The evaluation results shown in TABLE 30 indicate that electrophotographic photoconductors Nos. 1-6 to 1-13 of the present invention, each comprising the charge generating material which comprises the trisazo compound and the disazo compound, are more significantly sensitized than comparative electrophotographic photoconductors Nos. 1-3 to 1-7, each comprising the charge generating material which comprises the trisazo compound alone. 
     More specifically, electrophotographic photoconductors Nos. 1-6 to 1-9 of the present invention comprising the charge generating material comprising trisazo compound No. I-70 and any of the previously mentioned disazo compounds have higher photosensitivity in comparison with the comparative electrophotographic photoconductor No. 1-1 comprising the charge generating material comprising trisazo compound No. I-70 alone. 
     In addition, electrophotographic photoconductors Nos. 1-10 to 1-13 of the present invention, each of which comprises the charge generating material comprising trisazo compound No. I-74, No. I-67, No. I-85, or No. I-82, and the disazo compounds, exhibited photosensitivities which are about twice higher than those of comparative electrophotographic photoconductors Nos. 1-3 to 1-6, each of which comprises the charge generating material comprising the trisazo compound alone. 
     In the comparative electrophotographic photoconductor No. 1-7 comprising the charge generating material comprising the perylene compound and trisazo compound No. I-70 in Comparative Example 1-7, the sensitizing effect was reduced rather than no sensitizing effect was exhibited, although it is reported that the perylene compound exhibits a sensitizing effect when used in combination with a phthalocyanine compound. 
     Examples 1-14 to 1-17 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-3 in Example 1-3 was repeated except that disazo compound No. II-17 employed in Example 1-3 was replaced by disazo compounds No. II-17.18, No. II-17.19, No. II-17.24, and No. II-1.200, respectively, so that electrophotographic photoconductors Nos. 1-14 to 1-17 of the present invention were fabricated. 
     Disazo compounds No. II-17.18, No. II-17.19, No. II-17.24 and No. II-1.200 are such disazo compounds with the disazo skeleton II indicated in Example 1-1 and a set of radicals No. 17 and No. 19, a set of coupler radicals No. 17 and No. 24, and a set of coupler radicals No. 1 and No. 200, respectively, each in an unsymmetrical configuration. For example, disazo compound No. II-17.18 is a disazo compound with the following chemical structure: ##STR396## 
     Hereinafter, the above nomenclature applies to compound numbers similar to the above. 
     Examples 1-18 and 1-19 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-12 in Example 1-12 was repeated except that disazo compound No. II-17 employed in Example 1-12 was replaced by disazo compounds No. II-17.24, and No. II-1.17, so that electrophotographic photoconductors No. 1-18 and No. 1-19 of the present invention were fabricated. 
     The charging potential V 2  and exposure E 1/10  of each of electrophotographic photoconductors No. 1-14 and No. 1-19 of the present invention were measured in the same manner as in Evaluation 1. The results are shown in TABLE 28. 
     
                       TABLE 28______________________________________                    Trisazo                    Compound/                    Disazo  Trisazo           Compound  Com-     Disazo   (Weight  V.sub.2                                   E.sub.1/10Ex. No.  pound    Compound Ratio)   (volts)                                   (μJ/cm.sup.2)______________________________________Ex. 1-14  I-70     II-17.18 1/1      750   0.55Ex. 1-15  I-70     II-17.19 1/1      790   0.60Ex. 1-16  I-70     II-17.24 1/1      660   0.51Ex. 1-17  I-70     II-1.200 1/1      780   0.65Ex. 1-18   I-214   II-17.24 1/1      660   0.50Ex. 1-19   I-214   II-1.200 1/1      650   0.45______________________________________ 
    
     The evaluation results shown in TABLE 28 indicate that electrophotographic photoconductors Nos. 1-14 to 1-17, each of which comprises the charge generating material comprising trisazo compound No. I-70 and any of the previously mentioned disazo compounds, exhibit an apparently higher sensitizing effect in comparison with comparative electrophotographic photoconductor No. 1-1. In Electrophotographic photoconductors No. 1-18 and No. 1-19, the respective charge generating materials comprise trisazo compound No. I-214 and disazo compound II-17.24, and trisazo compound II-214 and disazo compound II-1.200. These electrophotographic photoconductors have an apparently higher sensitizing effect in comparison with comparative electrophotographic photoconductor No. 1-5, indicating the advantage of the use of the trisazo compound and the disazo compound in combination over the single use of the trisazo compound. 
     Example 1-20 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-3 in Example 1-3 was repeated except that the α-phenylstilbene compound (1) employed in Example 1-3 serving as a charge transporting material was replaced by an α-phenylstilbene compound of the following formula (2), whereby electrophoto-graphic photoconductor No. 1-20 of the present invention was fabricated: ##STR397## 
     Comparative Example 1-8 
     The same procedure for fabrication of comparative electrophotographic photoconductor No. 1-1 in Comparative Example 1-1 was repeated except that the α-phenylstilbene compound (1) employed in Comparative Example 1 serving as a charge transporting material was replaced by the α-phenylstilbene compound (2) employed in Example 1-20, whereby comparative electrophotographic photoconductor No. 1-8 was fabricated. 
     Example 1-21 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-4 3 in Example 1-3 was repeated except that the α-phenylstilbene compound (1) employed in Example 1-3 serving as a charge transporting material was replaced by a hydrazone compound of the following formula (3), whereby electrophotographic photoconductor No. 1-4 21 of the present invention was fabricated: ##STR398## 
     Comparative Example 1-9 
     The same procedure for fabrication of comparative electrophotographic photoconductor No. 1-1 in Comparative Example 1-1 was repeated except that the α-phenylstilbene (1) employed in Comparative Example 1-1 serving as a charge transporting material was replaced by the hydrazone compound (3) employed in Example 1-21, whereby comparative electrophotographic photoconductor No. 1-9 was fabricated. 
     Evaluation 2 
     The electrophotographic properties of the above-prepared electrophotographic photoconductors No. 1-20 and No. 1-21 of the present invention and comparative electrophotographic photoconductors No. 1-8 and No. 1-9 were evaluated in the same manner as in Evaluation 1. The results are shown in TABLE 29. 
     
                       TABLE 29______________________________________ Trisazo  Disazo    ChargeEx.   Com-     Com-      Transporting                             V.sub.2                                   E.sub.1/10No.   pound    pound     Material (volts)                                   (μJ/cm.sup.2)______________________________________Ex.   I-70     II-17     Stilbene 820   0.801-20                     CompoundComp. I-70     --        Same as  800   1.90Ex.                      above1-8Ex.   I-70     II-17     Hydrazone                             805   0.651-21                     CompoundComp. I-70     --        Same as  780   1.35Ex.                      above1-9______________________________________ 
    
     Example 1-22 
     An alcohol-soluble polyamide resin (Trademark &#34;Amilan CM8000&#34; made by Toray Industries, Inc.) was coated on an aluminum-deposited polyester film serving as a support, whereby an intermediate layer with a thickness of 0.3 μm was provided on the support. 
     [Formation of Photoconductive Layer] 
     A mixture of the following components was subjected to ball milling by use of agate balls in a glass vessel for 3 days, whereby an azo compound mixture was prepared: 
     
         ______________________________________Trisazo compound No. I-70               1.25 gDisazo compound No. II-17               1.25 gCyclohexanone         30 g______________________________________ 
    
     A mixture of the following components was mixed, whereby a photoconductive layer coating liquid was prepared: 
     
         ______________________________________Polycarbonate resin   5 g(Trademark &#34;C-1400&#34; made byTeijin Chemicals Ltd.)α-phenylstilbene compound (1)                 5 gemployed in Example 1-12,5-di-tert-butylhydro-                0.05 gquinoneAzo compound mixture 15 gprepared aboveTetrahydrofuran      30 g______________________________________ 
    
     The thus prepared photoconductive layer coating liquid was coated by a doctor blade on the intermediate layer provided on the aluminum-deposited polyester film with a gap of 250 μm set between the surface of the intermediate layer and the tip of the doctor blade, dried at 80° C. for 5 minutes, and then at 120° C. for one hour, whereby a photoconductive layer with a thickness of about 20 μm was provided on the intermediate layer. 
     Thus, electrophotographic photoconductor No. 1-22 of the present invention was fabricated. 
     The thus obtained electrophotographic photoconductor No. 1-22 was evaluated in the same manner as in Evaluation 1, provided that the electric charge applied to the photoconductor was changed to +5.5 V. As a result, the charge potential V 2  was 850 V, and the exposure E 1/10  was 0.68 μJ/cm 2 . 
     Comparative Example 1-10 
     An alcohol-soluble polyamide resin (Trademark &#34;Amilan CM8000&#34; made by Toray Industries, Inc.) was coated on an aluminum-deposited polyester film serving as a support, so that an intermediate layer with a thickness of 0.3 μm was provided on the support. 
     [Formation of Photoconductive Layer] 
     A mixture of the following components was subjected to ball milling by use of agate balls in a glass vessel for 3 days, whereby an azo compound mixture was prepared: 
     
         ______________________________________Trisazo compound No. I-70                2.5 gCyclohexanone         30 g______________________________________ 
    
     A photoconductive layer coating liquid was prepared by mixing the following components: 
     
         ______________________________________Polycarbonate resin   5 gTrademark &#34;C-1400&#34; made byTeijin Chemicals Ltd.)α-phenylstilbene compound (1)                 5 gemployed in Example 1-12,5-di-tert-butylhydro-                0.05 gquinoneAzo compound mixture 15 gprepared aboveTetrahydrofuran      30 g______________________________________ 
    
     The thus obtained photoconductive layer coating liquid was coated by a doctor blade on the thus prepared intermediate layer provided on the aluminum-deposited polyester film by a doctor blade, dried at 80° C. for 5 minutes, and then at 120° C. for one hour, so that a photoconductive layer with a thickness of about 20 μm was provided on the intermediate layer. 
     Thus, comparative electrophotographic photoconductor No. 1-10 was fabricated. 
     The thus fabricated comparative electrophotographic photoconductor No. 1-10 was evaluated in the same manner as in Evaluation 1, provided that the electric charge applied to the photoconductor was changed to +5.5 V. As a result, the charge potential V 2  was 900 V, and the exposure E 1/10  was 1.50 μJ/cm 2 . 
     Electrophotographic photoconductors Nos. 1--1 to 1-21 of the present invention and comparative electrophotographic photoconductors Nos. 1--1 to 1-6 and Nos. 1-8 to 1-10 were exposed to a 5 ppm NO gas for 5 days, and the charging potential V 2  and E 1/10  thereof were measured in the same manner to investigate the resistance thereof to the NO gas. 
     The results are shown in TABLE 30. 
     
                                           TABLE 30__________________________________________________________________________                    V.sub.2 (volts)                                E.sub.1/10 (μJ/cm.sup.2)             Trisazo                    Before                          After Before                                      After             Compound/                    Exposure                          Exposure                                Exposure                                      Exposure             Disazo to    to    to    toPhoto-            Compound                    Nitrogen                          Nitrogen                                Nitrogen                                      Nitrogenconductor Trisazo       Disazo             (Weight                    Monoxide                          Monoxide                                Monoxide                                      MonoxideNo.   Compound       Compound             Ratio) Gas   Gas   Gas   Gas__________________________________________________________________________No. 1-1 1-70  II-17 20/1   750   500   1.00  0.80No. 1-2 I-70  II-17 3/1    760   650   0.60  0.55No. 1-3 I-70  II-17 1/1    760   700   0.55  0.52No. 1-4 I-70  II-17 1/3    800   760   0.70  0.67No. 1-5 I-70  II-17  1/20  800   780   0.90  0.90No. 1-6 I-70  II-29 1/1    590   550   0.60  0.58No. 1-7 I-70  II-19 1/1    790   700   0.90  0.80No. 1-8 I-70  II-12 1/1    820   780   0.64  0.60No. 1-9 I-70   II-200             1/1    780   750   0.87  0.82No. 1-10 I-72  II-17 1/1    680   660   5.00  4.90No. 1-11 I-67  II-17 1/1    650   600   1.50  1.40No. 1-12  I-214       II-17 1/1    700   650   0.65  0.63No. 1-13 I-77  II-17 1/1    750   700   1.20  1.15No. 1-14 I-70        1/1    750   700   0.55  0.54No. 1-15 I-70  II-17.19             1/1    790   770   0.60  0.59No. 1-16 I-70  II-17.24             1/1    660   650   0.51  0.50No. 1-17 I-70  II-1.200             1/1    780   760   0.65  0.61No. 1-18  I-214       II-17.24             1/1    720   680   0.50  0.49No. 1-19  I-214       II-1.200             1/1    750   700   0.45  0.42No. 1-20 I-70  II-17 1/1    800   800   0.80  0.80No. 1-21 I-70  II-17 1/1    805   750   0.65  0.63No. 1-22 I-70  II-17 1/1    850   800   0.68  0.66Comp. No. I-70  --    1/0    750   200   1.20  **1-1Comp. No. I-72  --    1/0    720   200   10.06 **1-3Comp. No. 1-67  --    1/0    720   150   4.06  **1-4Comp. No.  I-214       --    1/0    700   150   0.91  **1-5Comp. No. I-77  --    1/0    680   200   2.40  **1-6Comp. No. I-70  --    1/0    800   350   1.90  **1-8Comp. No. I-70  --    1/1    780   100   1.35  **1-9Comp. No. I-70  --    0/1    900   400   1.50  1.50 1-10__________________________________________________________________________ Mark (**) in the above table denotes that measuring the photosensitivity of the photoconductor was impossible because it was impossible to charge the photoconductor up to 800 V. 
    
     The evaluation results shown in TABLE 30, the reduction of the charging potential V 2  of each of the electrophotographic photoconductors Nos. 1-3 to 1-22 of the present invention, each of which comprises the charge generating material comprising the respective trisazo compound and disazo compound, when exposed to the NO gas, was significantly less than that of comparative electrophotographic photoconductors No. 1--1, Nos. 1-3 to 1-6, No. 1-9, and No. 1-10. 
     Example 1-23 
     [Formation of Charge Generation Layer] 
     [Preparation of Dispersion A] 
     A mixture of 0.25 g of trisazo compound No. I-70, 4.75 of a 1% cyclohexanone solution of polyvinyl butyral resin (Trademark &#34;XYHL&#34; made by Union Carbide Japan K.K.) and 7 g of cyclohexanone was subjected to ball milling by use of 100 g of PSZ balls having a diameter of 5 mm in a 50 ml glass vessel for 5 days, and further subjected to ball milling with the addition of methyl ethyl ketone for one day, whereby a dispersion A was prepared. 
     [Preparation of Dispersion B] 
     A mixture of 0.25 g of disazo compound No. II-17, 4.75 g of a 1% cyclohexanone solution of a polyvinyl butyral resin (Trademark &#34;XYHL&#34; made by Union Carbide Japan K. K.) and 7 g of cyclohexanone was subjected to ball milling by use of 100 g of PSZ balls having a diameter of 5 mm in a 50 ml glass vessel for 5 days, and further subjected to ball milling with the addition of methyl ethyl ketone for one day, whereby a dispersion B was prepared. 
     [Fabrication of Electrophotographic Photoconductor No. 1-23] 
     The thus obtained dispersions A and B were mixed with a ratio by weight of 1:1, whereby a charge generation layer coating liquid was obtained. 
     The same procedure for fabrication of the function-separated type electrophotographic photoconductor No. 1-1 in Example 1-1 was repeated except that the charge generation layer coating liquid employed in Example 1-1 was replaced by the above prepared charge generation layer coating liquid, so that electrophotographic photoconductor No. 1-23 of the present invention was fabricated. 
     The thus fabricated electrophotographic photoconductor No. 1-23 of the present invention was exposed to a 5 ppm NO gas for 5 days, so that the resistance to the gas of electro-photographic photoconductor No. 1-23 of the present invention was evaluated. The chargeability and photosensitivity thereof before and after the exposure to the nitrogen monoxide gas were measured in the same manner as in Evaluation 1. The results are shown in TABLE 31. 
     
                       TABLE 31______________________________________V.sub.2 (volts)     E.sub.1/10 (μJ/cm.sup.2)  Before    After      Before  After  Exposure  Exposure   Exposure                               Exposure  to        to         to      to  Nitrogen  Nitrogen   Nitrogen                               NitrogenEx. No.  Monoxide  Monoxide   Monoxide                               Monoxide______________________________________Ex. 23 750       710        1.30    1.20Comp.  750       200        1.20    **Ex. 1-1______________________________________ Mark (**) in the above table denotes that measuring the photosensitivity of the photoconductor was impossible because it was impossible to charge the photoconductor up to 800 V. 
    
     The evaluation results shown in TABLE 31 indicate that the deterioration of the photosensitivity of electrophotographic photoconductor No. 1-23 of the present invention was little and the resistance to the gas thereof was much better in comparison with comparative electrophotographic photoconductor No. 1-1 comprising the charge generation layer comprising the trisaso compound alone. 
     Examples 1-24 to 1-30 
     The same procedure for fabrication of electrophotographic photoconductor No. 1-3 of the present invention in Example 1-3 was repeated except that disazo compound No. II-17 employed in Example 1-3 was replaced by disazo compounds No. II-1, II-6, II-8, II-20, II-28, II-31, and II-40, respectively, and that the about 20 μm-thick charge transport layer employed in Example 1-3 was replaced by a 30 μm-thick charge transport layer, whereby electrophotographic photoconductors Nos. 1-24 to 1-30 of the present invention were fabricated. 
     The charge potential V 2  and exposure E 1/10  of each of the electrophotographic photoconductors Nos. 1-24 to 1-30 of the present invention were measured in the same manner as in Evaluation 1. The results are shown in TABLE 32. 
     
                       TABLE 32______________________________________                    Trisazo                    Compound/                    Disazo Trisazo  Disazo    CompoundEx.   Com-     Com-      (Weight  V.sub.2                                   E.sub.1/10No.   pound    pound     Ratio)   (volts)                                   (μJ/cm.sup.2)______________________________________Ex. 24 I-70     II-1      1/1      1010  0.43Ex. 25 I-70     II-6      1/1      926   0.39Ex. 26 I-70     II-8      1/1      984   0.67Ex. 27 I-70     II-20     1/1      1025  0.30Ex. 28 I-70     II-28     1/1      964   0.42Ex. 29 I-70     II-31     1/1      997   0.42Ex. 30 I-70     II-40     1/1      956   0.45______________________________________ 
    
     Example 2-1 
     [Formation of Charge Generation Layer] 
     A mixture of the following components was subjected to ball milling by use of PSZ balls with a diameter of 5 mm in a 50 ml glass vessel for 7 days: 
     
         ______________________________________Trisazo compound No. I-70                 0.19 gDisazo compound No. III-60                 0.01 g2 wt. % cyclohexanone solution                  4.0 gof polyvinyl butyral resin(Trademark &#34;XYHL&#34;, made byUnion Carbide Japan K.K.)______________________________________ 
    
     In the above formulation, disazo compound No. III-60 has the following chemical structure with disazo skeleton III, and coupler radical No. 60 in TABLE 2: ##STR399## 
     With the addition of 6.0 g of cyclohexanone, the above mixture was subjected to ball milling for 3 days. With a further addition of 13.0 g of cyclohexanone, the mixture was further subjected to ball milling for one day, whereby a charge generation layer coating liquid was prepared. 
     The thus prepared charge generation layer coating liquid was coated by a doctor blade on an aluminum plate (produced in accordance with JIS 1080) with a thickness of 0.2 mm serving as a support, with a gap of 50 μm set between the tip of the doctor blade and the surface of the aluminum plate, and dried at 120° C. for 10 minutes, whereby a charge generation layer with a thickness of about 0.2 μm was provided on the support. 
     [Formation of Charge Transport Layer] 
     The following components were mixed and dissolved, whereby a charge transport layer coating liquid was prepared: 
     
         ______________________________________                  Parts by Weight______________________________________α-Phenylstilbene compound (1)                     9with the following formula: ##STR400##Bisphenol Z type polycarbonate                    10resin (Trademark &#34;TS2050&#34; madeby Teijin Chemicals, Ltd.;Viscosity-average molecularweight: 40,000)______________________________________ 
    
     The thus prepared charge transport layer coating liquid was coated by a doctor blade on the above charge generation layer, and dried at 120° C. for 20 minutes, so that a charge transport layer with a thickness of about 28 μm was provided on the above charge generation layer. 
     Thus, electrophotographic photoconductor No. 2-1 of the present invention was fabricated. 
     Examples 2-2 to 2-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-1 in Example 2-1 was repeated except that the amounts of trisazo compound No. I-70 and disazo compound No. III-60 in the charge generation layer coating liquid employed in Example 2-1 were respectively changed as shown in TABLE 33, so that electrophotographic photoconductors Nos. 2-2 to 2-5 of the present invention were fabricated. 
     Comparative Examples 2-1 and 2-2 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-1 in Example 2-1 was repeated except that the amounts of trisazo compound No. I-70 and disazo compound No. III-60 in the charge generation layer coating liquid employed in Example 2-1 were respectively changed as shown in TABLE 33, so that comparative electrophotographic photoconductors No. 2-1 and No. 2-2 were fabricated. 
     Evaluation 3 
     The electrophotographic characteristics of the above fabricated electrophotographic photoconductors No. 2-1 to No. 2-5 of the present invention and comparative electrophotographic photoconductors No. 2-1 and No. 2-2 were evaluated as follows by using an electrostatic characteristics measuring apparatus, (&#34;EPA8100&#34;, made by Kawaguchi Electro Works Co., Ltd.), which was set in a dynamic mode: 
     Each of the above electrophotographic photoconductors was negatively charged under the application of -6 Kv for 2 seconds and the charging potential V 2  (-V) of the photoconductor was measured. The photoconductor was charged up to -800 V and then exposed to the light of a tungsten lamp at a color temperature of 2856° K. through a band-pass filter for 780 nm (with a half-amplitude level of 13 nm). The exposure E (μJ/cm 2 ) required to reduce the surface potential from -800 V to -100 V was measured as an index for the photosensitivity S. The photosensitivity S was calculated by dividing 700 by the value of the exposure E (i.e., S=700/E). The larger the value of S, the higher the photosensitivity. The results are shown in TABLE 33. 
     
                                           TABLE 33__________________________________________________________________________             Trisazo             Compound [I]/             Disazo  V.sub.2 (--V)                               S (V · cm.sup.2 /μJ)Photo- Trisazo       Disazo             Compound [III]                     Before                          After                               Before                                    Afterconductor Compound       Compound             (Weight Exposure                          Exposure                               Exposure                                    ExposureNo.   [I]   [III] Ratio)  to Ozone                          to Ozone                               to Ozone                                    to Ozone__________________________________________________________________________No. 2-1 I-70  III-60             19/1    770  320  1160 **No. 2-2 I-70  III-60             3/1     780  450  1170 1310No. 2-3 I-70  III-60             1/1     790  490  1210 1300No. 2-4 I-70  III-60             1/3     780  600  1200 2170No. 2-5 I-70  III-60              1/19   770  650  1110 1150Comp. No. I-70  --    1/0     780  170   964 **2-1Comp. No. --    III-60             0/1     780  700  No Sensi-                                    No Sensi-2-2                                 tivity                                    tivity__________________________________________________________________________ Mark (**) in the above table denotes that measuring the photosensitivity of the photoconductor was impossible because it was impossible to charge the photoconductor up to 800 V. 
    
     The evaluation results shown in TABLE 33 indicate that electrophotographic photoconductors No. 2-1 to No. 2-5 of the present invention, each comprising the charge generation layer comprising trisazo compound No. I-70 and disazo compound No. III-60, have a higher photosensitivity and are more sensitized in comparison with comparative electrophotographic photoconductors No. 2-1 and No. 2-2, each comprising the charge generation layer comprising either trisazo compound No. I-70 or disazo compound No. III-60. 
     Moreover, the deterioration of the charging potential V 2  of comparative electrophotographic photoconductor No. 2-2 in Comparative Example 2-2, comprising disazo compound No. III-60 alone, when exposed to ozone, was less than that of comparative electrophotographic photoconductor No. 2-1 in Comparative Example 2-1 comprising trisazo compound No. I-70 alone. 
     In addition, the deterioration of the charging potential V 2  and the photosensitivity of electrophotographic photoconductors No. 2-1 to No. 2-5 in Examples 2-1 to 2-5, each comprising trisazo compound No. I-70 and disazo compound No. III-60, when exposed to ozone, were much less than those of comparative electrophotographic photoconductor No. 2-1 in Comparative Example 2-1 comprising trisazo compound No. I-70 alone. 
     Examples 2-6 to 2-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that trisazo compound No. I-70 employed in Example 2-3 was replaced by trisazo compounds No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby electrophotographic photoconductors Nos. 2-6 to 2-9 of the present invention were fabricated. 
     Examples 2-10 to 2-13 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that disazo compound No. II-60 employed in Example 2-3 was replaced by disazo compounds No. III-1, No. III-201, No. III-217, and No. III-233, respectively, whereby electrophotographic photoconductors Nos. 2-10 to 2-13 of the present invention were fabricated. 
     Comparative Examples 2-3 to 2-6 
     The same procedure for fabrication of comparative electrophotographic photoconductor No. 2-1 in Comparative Example 2-1 was repeated except that trisazo compound No. I-70 employed in Comparative Example 2-1 was replaced by trisazo compounds No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby comparative electrophotographic photoconductors Nos. 2-3 to 2-6 were fabricated. 
     Example 2-14 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that the α-phenylstilbene compound (1) employed in Example 2-3 serving as a charge transporting material was replaced by an α-phenylstilbene (2) of the following formula, whereby electrophotographic photoconductor No. 2-14 of the present invention was fabricated: ##STR401## 
     Example 2-15 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that the α-phenylstilbene compound (1) employed in Example 2-3 serving as a charge transporting material was replaced by a hydrazone compound of the following formula, whereby electrophotographic photoconductor No. 2-15 of the present invention was fabricated: ##STR402## 
     The charging potential V 2  and the photosensitivity S conductors No. 2-6 to No. 2-15 of the present invention and comparative electrophotographic photoconductors No. 2-3 to No. 2-11 were measured in the same manner as in Evaluation 3. 
     The results are shown in TABLE 34. 
     
                                           TABLE 34__________________________________________________________________________             Trisazo             Compound/             Disazo Charge                          V.sub.2 [--V]                                    S [V · cm.sup.2                                    /μJ]Photo-            Compound                    Trans-                          Before                               After                                    Before                                         Afterconductor Trisazo       Disazo             (Weight                    porting                          Exposure                               Exposure                                    Exposure                                         ExposureNo.   Compound       Compound             Ratio) Material                          to Ozone                               to Ozone                                    to Ozone                                         to Ozone__________________________________________________________________________Comp.  I-205       --    1/0    Same as                          760  150  520  **No. 2-3                  aboveComp. I-88  --    1/0    Same as                          750  120   80  **No. 2-4                  aboveComp.  I-214       --    1/0    Same as                          770   90  1700 **No. 2-5                  aboveComp. I-67  --    1/0    Same as                          760  160   260 **No. 2-6                  above No. 2-14 I-70  III-60             1/1    α-phenyl-                          790  680   650  680                    stilbene                    Compound No. 2-15 I-70  III-60             1/1    Hydrazone                          780  710   800  840                    CompoundNo. 2-6  1-205       III-60             1/1    α-phenyl-                          780  450   600  680                    stilbene                    CompoundNo. 2-7 I-88  III-60             1/1    Same as                          780  420   140  180                    aboveNo. 2-8  I-214       III-60             1/1    Same as                          770  400  1810 1990                    aboveNo. 2-9 I-67  III-60             1/1    Same as                          790  490   360  410                    above No. 2-10 I-70  III-1 1/1    Same as                          780  500  1350 1470                    above No. 2-11 I-70   III-201             1/1    Same as                          790  480  1150 1260                    above No. 2-12 I-70   III-217             1/1    Same as                          800  470  1220 1310                    above No. 2-13 I-70   III-233             1/1    Same as                          780  470  1110 1250                    above__________________________________________________________________________ Mark (**) in the above table denotes that measuring the photosensitivity of the photoconductor was impossible because it was impossible to charge the photoconductor up to 800 V. 
    
     Example 3-1 
     The procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that disazo compound No. III-60 employed in Example 2-3 was replaced by disazo compound No. IV-1, whereby electrophotographic photoconductor No. 3-1 of the present invention was fabricated. 
     Disazo compound No. IV-1 has the following chemical structure with a disazo skeleton IV and coupler radicals No. 1 in TABLE 1: ##STR403## 
     The charging potential V 2  (-V) and the photosensitivity S (V.cm 2  /μJ) of the electrophotographic photoconductor No. 3-1 were respectively 780 volts and 1410 V.cm 2  /μJ. 
     Examples 3-2 to 3-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 3-1 in Example 3-1 was repeated except that trisazo compound No. I-70 employed in Example 3-1 was replaced by trisazo compound No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby electrophotographic photoconductors No. 3-2 to No. 3-5 of the present invention were fabricated. 
     Examples 3-6 to 3-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 3-1 in Example 3-1 was repeated except that disazo compound No. IV-1 employed in Example 3-1 was replaced by disazo compounds No. IV-4, No. IV-19, No. IV-25, and No. IV-30, respectively, whereby electrophotographic photoconductors No. 3-6 to No. 3-9 of the present invention were fabricated. 
     Examples 3-10 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-14 in Example 2-14 was repeated except that disazo compound No. III-60 employed in Example 2-14 was replaced by disazo compound No. IV-1, whereby electrophotographic photoconductor No. 3-10 of the present invention was fabricated. 
     Example 3-11 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-15 in Example 2-15 was repeated except that disazo compound No. III-60 employed whereby electrophotographic photoconductor No. 3-11 of the present invention was fabricated. 
     The thus fabricated electrophotographic photoconductors Nos. 3-2 to 3-11 of the present invention was exposed to a 5 ppm NO gas for 5 days, so that the resistances thereof to the gas were evaluated. The chargeability and photosensitivity thereof before and after the exposure to the NO gas were measured in the manner as in Evaluation 1. The results are shown in TABLE 35. 1 
     
                                           TABLE 35__________________________________________________________________________             Trisazo             Compound/             Disazo Charge                          V.sub.2 [--V]                                    S [V · cm.sup.2                                    /μJ]Photo-            Compound                    Trans-                          Before                               After                                    Before                                         Afterconductor Trisazo       Disazo             (Weight                    porting                          Exposure                               Exposure                                    Exposure                                         ExposureNo.   Compound       Compound             Ratio) Material                          to Ozone                               to Ozone                                    to Ozone                                         to Ozone__________________________________________________________________________No. 3-2  I-205       IV-1  1/1    α-phenyl-                          780  610   740  850                    stilbene                    Compound                    (1)No. 3-3 I-88  IV-1  1/1    Same as                          770  590   170  280                    aboveEx. 3-4  I-214       IV-1  1/1    Same as                          780  560  2100 2290                    aboveNo. 3-5 I-67  IV-1  1/1    Same as                          790  580   370  450                    aboveNo. 3-6 I-70  IV-4  1/1    Same as                          770  570  1310 1400                    aboveNo. 3-7 I-70   IV-19             1/1    Same as                          780  590  1290 1350                    aboveNo. 3-8 I-70   IV-25             1/1    Same as                          780  550  1420 1490                    aboveNo. 3-9 I-70   IV-30             1/1    Same as                          790  520  1350 1410                    above No. 3-10 I-70  IV-1  1/1    α-phenyl                          800  690  1050 1090                    stilbene                    compound                    (2) No. 3-11 I-70  IV-1  1/1    Hydrazone                          780  700  1100 1170                    compound__________________________________________________________________________ 
    
     Example 4-1 
     The procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that disazo compound No. III-60 employed in Example 2-3 was replaced by disazo compound No. V-17, so that electrophotographic photoconductor No. 4-1 of the present invention was fabricated. 
     Disazo compound No. V-17 has the following chemical structure with a disazo skeleton V and coupler radicals No. 17 in TABLE 1: ##STR404## 
     The charging potential V 2  (-V) and the photosensitivity S (V.cm 2  /μJ) of electrophotographic photoconductor No. 4-1 were respectively 790 V and 1350 V.cm 2  /μJ. 
     Examples 4-2 to 4-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 4-1 in Example 4-1 was repeated except that trisazo compound No. I-70 employed in Example 4-1 was replaced by trisazo compounds No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby electrophotographic photoconductors No. 4-2 to No. 4-5 of the present invention were fabricated. 
     Examples 4-6 to 4-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 4-1in Example 4-1 was repeated except that disazo compound No. V-17 employed in Example 4-1 was replaced by disazo compounds No. V-11, No. V-14, No. V-23, and No. V-60, respectively, whereby electrophotographic photoconductors No. 4-6 to No. 4-9 of the present invention were fabricated. 
     Examples 4-10 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-14 in Example 2-14 was repeated except that disazo compound No. III-60 employed in Example 2-14 was replaced by disazo compound No. V-17, whereby electrophotographic photoconductor No. 4-10 of the present invention was fabricated. 
     Example 4-11 
     The same procedure for fabrication of electrophotographic, photoconductor No. 2-15 in Example 2-15 was repeated except that disazo compound No. III-60 employed in Example 2-15 was replaced by disazo compound No. V-17, whereby electrophotographic photoconductor No. 4-11 of the present invention was fabricated. 
     The formulation and the properties of each of electrophotographic photoconductors No. 4-1to No. 4-11 measured in the same manner as with electrophotographic photoconductors No. 3-2 to No. 3-11 are shown in TABLE 36. 
     
                                           TABLE 36__________________________________________________________________________             Trisazo             Compound/             Disazo Charge                          V.sub.2 [--V]                                    S [V · cm.sup.2                                    /μJ]Photo-            Compound                    Trans-                          Before                               After                                    Before                                         Afterconductor Trisazo       Disazo             (Weight                    porting                          Exposure                               Exposure                                    Exposure                                         ExposureNo.   Compound       Compound             Ratio) Material                          to Ozone                               to Ozone                                    to Ozone                                         to Ozone__________________________________________________________________________No. 4-2  I-205       V-17  1/1    α-phenyl                          780  600   660  730                    stilbene                    Compound                    (1)No. 4-3 I-88  V-17  1/1    Same as                          770  610   210  290                    aboveNo. 4-4  I-214       V-17  1/1    Same as                          760  580  2050 2200                    aboveNo. 4-5 I-67  V-17  1/1    Same as                          770  630   380  470                    aboveNo. 4-6 I-70  V-11  1/1    Same as                          770  610  1250 1330                    aboveNo. 4-7 I-70  V-14  1/1    Same as                          780  620  1210 1320                    aboveNo. 4-8 I-70  V-23  1/1    Same as                          770  650  1360 1450                    aboveNo. 4-9 I-70  V-60  1/1    Same as                          770  620  1180 1280                    above No. 4-10 I-70  V-17  1/1    α-phenyl-                          780  680  1100 1150                    stilbene                    compound                    (2) No. 4-11 I-70  V-17  1/1    Hydrazone                          780  690  1220 1230                    compound__________________________________________________________________________ 
    
     Example 5-1 
     The procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that disazo compound No. III-60 employed in Example 2-3 was replaced by disazo compound No. VI-63, whereby electrophotographic photoconductor No. 5-1 of the present invention was fabricated. 
     Disazo compound No. VI-63 has the following chemical structure with a disazo skeleton VI and coupler radicals No. 63 in TABLE 2: ##STR405## 
     The charging potential V 2  and the photosensitivity S (V.cm 2  /μJ) of electrophotographic photoconductor No. 5-1 were respectively 780 V and 1420 V.cm 2  /μJ. 
     Examples 5-2 to 5-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 5-1 in Example 5-1 was repeated except that trisazo compound No. I-70 employed in Example 5-1 was replaced by trisazo compounds No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby electrophotographic photoconductors No. 5-2 to No. 5-5 of the present invention were fabricated. 
     Examples 5-6 to 5-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 5-1 in Example 5-1 was repeated except that disazo compound No. V-17 employed in Example 5-1 was replaced by disazo compounds No. II-1, No. II-64, No. II-223, and No. II-224, respectively, whereby electrophotographic photoconductors No. 5-6 to No. 5-9 of the present invention were fabricated. 
     Examples 5-10 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-14 in Example 2-14 was repeated except that disazo compound No. III-60 employed in Example 2-14 was replaced by disazo compound No. VI-63, whereby electrophotographic photoconductor No. 5-10 of the present invention was fabricated. 
     Example 5-11 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-15 in Example 2-15 was repeated except that disazo compound No. III-60 employed in Example 2-15 was replaced by disazo compound No. VI-63, whereby electrophotographic photoconductor No. 5-11 of the present invention was fabricated. 
     The formulation and the properties of each of electrophotographic photoconductors No. 5-1 to No. 5-11 measured in the same manner as with electrophotographic photoconductors No. 3-2 to 3-11 are shown in TABLE 37. 
     
                                           TABLE 37__________________________________________________________________________             Trisazo             Compound/             Disazo Charge                          V.sub.2 [--V]                                    S [V · cm.sup.2                                    /μJ]Photo-            Compound                    Trans-                          Before                               After                                    Before                                         Afterconductor Trisazo       Disazo             (Weight                    porting                          Exposure                               Exposure                                    Exposure                                         ExposureNo.   Compound       Compound             Ratio) Material                          to Ozone                               to Ozone                                    to Ozone                                         to Ozone__________________________________________________________________________No. 5-2  I-205       VI-63 1/1    α-phenyl-                          760  520   720  910                    stilbene                    Compound                    (1)No. 5-3 I-88  VI-63 1/1    Same as                          750  500   180  270                    aboveNo. 5-4  I-214       VI-63 1/1    Same as                          760  490  1910 2040                    aboveNo. 5-5 I-67  VI-63 1/1    Same as                          770  530   350  490                    aboveNo. 5-6 I-70  VI-1  1/1    Same as                          780  510  1430 1510                    aboveNo. 5-7 I-70  VI-64 1/1    Same as                          770  500  1380 1470                    aboveNo. 5-8 I-70   VI-223             1/1    Same as                          790  540  1310 1420                    aboveNo. 5-9 I-70   VI-224             1/1    Same as                          780  520  1410 1500                    above No. 5-10 I-70  VI-63 1/1    α-phenyl-                          780  600   950 1010                    stilbene                    compound                    (2) No. 5-11 I-70  VI-63 1/1    Hydrazone                          780  620  1060 1200                    compound__________________________________________________________________________ 
    
     Example 6-1 
     The procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that disazo compound No. III-60 employed in Example 2-3 was replaced by disazo compound No. VII(1)-1, whereby electrophotographic photoconductor No. 6-1 of the present invention was fabricated. 
     Disazo compound No. VII(1)-1 has the following chemical structure with a disazo skeleton VII(1) with a disazo skeleton VII in which R 1  is CN and coupler radical represented by A is coupler radical No. 1 in TABLE 1: ##STR406## 
     Examples 6-2 to 6-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 6-1 in Example 6-1 was repeated except that trisazo compound No. I-70 employed in Example 6-1 was replaced by trisazo compounds No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby electrophotographic photoconductors No. 6-2 to No. 6-5 of the present invention were fabricated. 
     Examples 6-6 to 6-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 6-1 in Example 6-1 was repeated except that disazo compound No. VII(1)-1 employed in Example 6-1 was replaced by disazo compounds No. VII(1)-89, No. VII(1)-19, No. VII(2)-19, and No. VII(3)-19, respectively, whereby electrophotographic photoconductors No. 6-9 of the present invention were fabricated. 
     Disazo skeleton VII(2) is a disazo skeleton VII in which R 1  is Cl, and disazo skeleton VII(3) is a disazo skeleton VII in which R 1  is Br. 
     Examples 6-10 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-14 in Example 2-14 was repeated except that disazo compound No. III-60 employed in Example 2-14 was replaced by disazo compound No. VII(1)-1, whereby electrophotographic photoconductor No. 6-10 of the present invention was fabricated. 
     Example 6-11 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-15 in Example 2-15 was repeated except that disazo compound No. III-60 employed in Example 2-15 was replaced by disazo compound No. VII(1)-1, whereby electrophotographic photoconductor No. 6-11 of the present invention was fabricated. 
     The formulation and properties of each of electrophotographic photoconductors No. 6-1 to No. 6-11, measured in the same manner as with electrophotographic photoconductors No. 3-2 to No. 3-11, are shown in TABLE 38. 
     
                                           TABLE 38__________________________________________________________________________             Trisazo             Compound/             Disazo Charge                          V.sub.2 [--V]                                    S [V · cm.sup.2                                    /μJ]Photo-            Compound                    Trans-                          Before                               After                                    Before                                         Afterconductor Trisazo       Disazo             (Weight                    porting                          Exposure                               Exposure                                    Exposure                                         ExposureNo.   Compound       Compound             Ratio) Material                          to Ozone                               to Ozone                                    to Ozone                                         to Ozone__________________________________________________________________________No. 6-1 I-70  VII-1 1/1    α-phenyl-                          780  580  1620 1750                    stilbene                    Compound                    (1)No. 6-2  I-205       VII-1 1/1    Same as                          790  590   820  910                    aboveNo. 6-3 I-88  VII-1 1/1    Same as                          780  600   310  400                    aboveNo. 6-4  I-214       VII-1 1/1    Same as                          800  550  2210 2400                    aboveNo. 6-5 I-67  VII-1 1/1    Same as                          780  560   470  520                    aboveNo. 6-6 I-70   VII-89             1/1    Same as                          780  600  1510 1710                    aboveNo. 6-7 I-70   VII-19             1/1    Same as                          790  620  1550 1650                    aboveNo. 6-8 I-70   VII-19             1/1    Same as                          770  630  1360 1400                    aboveNo. 6-9 I-70   VII-19             1/1    Same as                          760  590  1290 1390                    above No. 6-10 I-70  VII-1 1/1    α-phenyl-                          800  600  1150 1290                    stilbene                    compound                    (2) No. 6-11 I-70  VII-1 1/1    Hydrazone                          780  620  1320 1370                    compound__________________________________________________________________________ 
    
     Example 7-1 
     The procedure for fabrication of electrophotographic photoconductor No. 2-3 in Example 2-3 was repeated except that disazo compound No. III-60 employed in Example 2-3 was replaced by disazo compound No. VIII-195, whereby electrophotographic photoconductor No. 7-1 of the present invention was fabricated. 
     Disazo compound No. VIII-195 has the following chemical structure with a disazo skeleton VIII and coupler radicals No. 195 in TABLE 12: ##STR407## 
     Examples 7-2 to 7-5 
     The same procedure for fabrication of electrophotographic photoconductor No. 7-1 in Example 7-1 was repeated except that trisazo compound No. I-70 employed in Example 7-1 was replaced by trisazo compounds No. I-205, No. I-88, No. I-214, and No. I-67, respectively, whereby electrophotographic photoconductors No. 7-2 to No. 7-5 of the present invention were fabricated. 
     Examples 7-6 to 7-9 
     The same procedure for fabrication of electrophotographic photoconductor No. 7-1 in Example 7-1 was repeated except that disazo compound No. VIII-195 employed in Example 7-1 was replaced by disazo compounds No. VIII-1.195, No. VIII-1, No. VIII-191, and No. VIII-17, respectively, whereby electrophotographic photoconductors No. 7-6 to No. 7-9 of the present invention were fabricated. 
     Disazo compound No. VIII-1.195 has the following chemical structure: ##STR408## in which A is coupler radical No. 1 in TABLE 1 and B is coupler radical No. 195 in TABLE 12. 
     Examples 7-10 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-14 in Example 2-14 was repeated except that disazo compound No. III-60 employed in Example 2-14 was replaced by disazo compound No. VIII-195, whereby electrophotographic photoconductor No. 7-10 of the present invention was fabricated. 
     Example 7-11 
     The same procedure for fabrication of electrophotographic photoconductor No. 2-15 in Example 2-15 was repeated except that disazo compound No. III-60 employed in Example 2-15 was replaced by disazo compound No. VII-195, whereby electrophotographic photoconductor No. 7-11 of the present invention was fabricated. 
     The formulation and the properties of each of electrophotographic photoconductors No. 7-1 to No. 7-11, measured in the same manner as with electrophotographic photoconductors No. 3-2 to No. 3-11, are shown in TABLE 39. 
     
                                           TABLE 39__________________________________________________________________________             Trisazo             Compound/             Disazo Charge                          V.sub.2 [--V]                                    S [V · cm.sup.2                                    /μJ]Photo-            Compound                    Trans-                          Before                               After                                    Before                                         Afterconductor Trisazo       Disazo             (Weight                    porting                          Exposure                               Exposure                                    Exposure                                         ExposureNo.   Compound       Compound             Ratio) Material                          to Ozone                               to Ozone                                    to Ozone                                         to Ozone__________________________________________________________________________No. 7-1 I-70  II-195             1/1    α-phenyl                          790  400  1410 1850                    stilbene                    Compound                    (1)No. 7-2  I-205       VIII-195             1/1    Same as                          790  410   700  900                    aboveNo. 7-3 I-88  VIII-195             1/1    Same as                          780  390   250  320                    aboveNo. 7-4  I-214       VIII-195             1/1    Same as                          800  390  2200 2410                    aboveNo. 7-5 I-67  VIII-195             1/1    Same as                          790  420   450  600                    aboveNo. 7-6 I-70  VIII-1.195             1/1    Same as                          780  430  1450 1550                    aboveNo. 7-7 I-70  VIII-1             1/1    Same as                          790  410  1120 1210                    aboveNo. 7-8 I-70  VIII-191             1/1    Same as                          800  420  1210 1310                    aboveNo. 7-9 I-70  VIII-17             1/1    Same as                          800  420  1170 1290                    above No. 7-10 I-70  VIII-195             1/1    α-phenyl-                          800  650  1110 1200                    stilbene                    compound                    (2) No. 7-11 1-70  VIII-195             1/1    Hydrazone                          780  610  1150 1290                    compound__________________________________________________________________________