Abstract:
A photoreceptor comprising a support and a photosensitive layer which contains an azo compound of the formula [I]: ##STR1## wherein Q is a halogen atom, a hydrogen atom, an alkyl group, an alkoxy group, an alkylsulfonyl group, an aryl group, an acetylamido group, ##STR2## (Q 1  is an alkyl group, an alkoxy group, a phenyl group, an amino group, a hydroxy group or a hydrogen atom) or ##STR3## (Q 2 , Q 3  and Q 4  independently are an alkyl group, an alkoxy group, a phenyl group, an acyl group, an ester group, a hydroxy group, a cyano group, a vinyl group, a halogen atom or a hydrogen atom), said alkyl group, alkoxy group, aryl group, amino group and vinyl group may have a substituent; Y 1  and Y 2  independently are a hydrogen atom, a halogen atom, a cyano group, a hydroxy group, an alkyl group or an alkoxy group; m and n each represent an integer of 0 to 2, and m and n cannot be both 0; A is any one of the following formulae: ##STR4## wherein Z is a group of atoms necessary for constituting a substituted or unsubstituted aromatic carbon ring or an aromatic heterocyclic ring, P 3  is a substituted or unsubstituted carbamoyl group or a substituted or unsubstituted sulfamoyl group, R 1  is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, a carboxyl group and its ester group or a cyano group, A&#39; is a substituted or unsubstituted aryl group, R 2  and R 3  independently are a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted aryl group.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a photoreceptor, particularly to a novel photoreceptor having a photosensitive layer containing an azo compound. 
     In the prior art, as electrophotographic receptors, there have widely been employed inorganic photoreceptors having photosensitive layers composed mainly of inorganic photoconductive compounds such as selenium, zinc oxide, cadmium sulfide, silicon, etc. However, these are not necessarily satisfactory in sensitivity, heat stability, humidity resistance, durabilty, etc. For example, selenium will be deteriorated in characteristics as the photoreceptor when crystallized and can be manufactured with difficulty, and also heat or fingerprint may cause crystallization to result in deterioration of performance as the photoreceptor. On the other hand, problems are involved in cadmium sulfide with respect to humidity resistance or durability, while zinc oxide poses problems in durability, etc. 
     In order to overcome the drawbacks possessed by inorganic photoreceptors, developments and researches have aggressively been made of organic photoreceptors having photosensitive layers composed mainly of various organic photoconductive compounds. For example, Japanese Patent Publication No. 10496/1975 discloses an organic photoreceptor having a photosensitive layer containing poly-N-vinylcarbazole and 2,4,7-trinitro-9-fluorenone. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability. For improving such drawbacks, an organic photoreceptor with higher performance has been attempted to be developed by having the carrier generating function and the carrier transporting function assigned to different materials. Many studies have been made on such a photoreceptor of the so-called function separation type, since the respective materials can be selected from a wide scope of materials and photoreceptors having any desired performance can be prepared with relative ease. 
     In such a photoreceptor of the function separation type, a large number of compounds have been proposed. As an example employing an inorganic compound as the carrier generating material, Japanese Patent Publication No. 16198/1968 discloses an amorphous selenium, which can be employed in combination with an organic photoconductive compound. However, the carrier generating layer comprising the amorphous selenium is not improved in the drawback of being crystallized by heat to be deteriorated in characteristics as the photoreceptor. 
     There have also been made many proposals about using organic dyes or organic dyes as the carrier generating material. For example, photoreceptors containing bisazo compounds or trisazo compounds in the photosensitive layer are already known as disclosed in Japanese Unexamined Patent Publication Nos. 22834/1979, 46558/1979, 46237/1981 and 196241/1982. However, these bisazo compounds or trisazo compounds are not necessarily satisfactory in characteristics of sensitivity, residual potential or stability during repeated uses, and also limited in scope of carrier transporting materials which can be selected, thus failing to satisfy sufficiently the wide range of requirements demanded by electrophotographic process. 
     Further, recourse has recently been made to gas lasers such as Ar laser, He-Ne laser, etc. or semiconductor lasers as the light source for photoreceptor. These lasers are characterized by capability of ON/OFF in time series, and expected to be promising as the light source for a copying having an image processing function, typically an intelligent copier as well as for a printer for output of a computer. Among them, semiconductor lasers are attracting attention, because they require no electrical signal/light signal transducing element such as acousatic optical element in nature, and also because they can be made to small scale and light weight. However, these semiconductor lasers are low in output as compared with gas lasers and the oscillated wavelength is longer (about 780 nm or longer), and therefore the photoreceptor of the prior art, of which spectral sensitivity is too much greater on the shorter wavelength side, can not be used as such as a photoreceptor using a semiconductor laser as the light source. 
     Moreover, an electrophotographic photosensitive member containing bisazo compounds in the photosensitive layer is already known as disclosed in Japanese Unexamined Patent Publication No. 194035/1983 (Our co-pending U.S. patent application Ser. No. 549,589, filed 11/7/83, now U.S. Pat. No. 4,515,881). However, bisazo compounds used in a photoreceptor of the present invention is excellent in dispersibility and coating characteristics than the above application, and the photoreceptor of the present invention is excellent in electrified potential, durabitlity and sensitivity than the above. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a photoreceptor containing a specific azo compound which is stable to heat and light, and also excellent in carrier generating ability. 
     Another object of this invention is to provide a photoreceptor which is high in sensitivity and small in residual potential, and also excellent in durability without change in those characteristics even when repeatedly used. 
     Still another object of this invention is to provide a photoreceptor containing an azo compound which can act effectively as the carrier generating material even when combined with a variety of carrier transporting materials. 
     It is also another object of this invention to provide a photoreceptor having sufficient practical sensitivity even to a long wavelength light source such as a semiconductor laser. 
     Further objects of this invention will become apparent from the following description in the specification. 
     The present inventors have made intensive studies to attain the objects as mentioned above and found that the azo compound represented by the following formula [I] can act as the effective component in the photoreceptor to accomplish this invention: ##STR5## wherein Q is a halogen atom, a hydrogen atom, an alkyl group, an alkoxy group, an alkylsulfonyl group, an aryl group, an acetylamido group, ##STR6## (Q 1  is an alkyl group, an alkoxy group, a phenyl group, an amino group, a hydroxy group or a hydrogen atom) or ##STR7## (Q 2 , Q 3  and Q 4  independently are an alkyl group, an alkoxy group, a phenyl group, an acyl group, an ester group, a hydroxy group, a cyano group, a vinyl group, a halogen atom or a hydrogen atom), said alkyl group, alkoxy group, aryl group, amino group, acyl group, acetylamino group, alkylsulfone group, phenyl group and vinyl group may have a substituent; 
     Y 1  and Y 2  independently are a hydrogen atom, a halogen atom, a cyano group, a hydroxy group, an alkyl group or an alkoxy group; m and n each represent an integer of 0 to 2, and m and n cannot be both 0; A represents a group represented by any one of the following formulae: ##STR8## wherein Z is a group of atoms necessary for constituting a substituted or unsubstituted aromatic carbon ring or an aromatic heterocyclic ring, P 3  is a substituted or unsubstituted carbamoyl group or a substituted or unsubstituted sulfamoyl group, R 1  is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, a carboxyl group and its ester group or a cyano group, A&#39; is a substituted or unsubstituted aryl group, R 2  and R 3  independently are a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted aryl group. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 through 6 show schematically sectional views of some examples of mechanical construction of photoreceptors of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The azo compound represented comprehensively, by the above formula [I] are inclusive of various embodiments, typically Embodiments A through E as described in detail below. 
     Embodiment A 
     This embodiment is represented by the following formula [IA]: ##STR9## wherein S is an alkyl group, or a substituted or unsubstituted benzene ring; and Y 1 , Y 2 , n and A are the same as defined in the above formula [I]. 
     In the above formula, P 3  is a substituted or unsubstituted carbamoyl group of the formula: ##STR10## or a substituted or unsubstituted sulfamoyl group of the formula: ##STR11## wherein R 4  represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted phenyl group; R 5  represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group (e.g. substituted or unsubstituted phenyl group, substituted or unsubstituted naphthyl group, substituted or unsubstituted anthryl group, etc.), or a substituted or unsubstituted aromatic heterocyclic group (e.g. substituted or unsubstituted carbazolyl group, substituted or unsubstituted dibenzofuryl group, etc.). 
     The substituents on these groups may include, for example, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms (e.g. methyl, ethyl, isopropyl, t-butyl, trifluoromethyl, etc.), a substituted or unsubstituted aralkyl group (e.g. benzyl, phenethyl, etc.), a halogen atom (chlorine, bromine, fluorine, iodine), a substituted or unsubstituted alkoxy group having 1 to 4 carbon atoms (e.g. methoxy, ethoxy, isopropoxy, t-butoxy, 2-chloroethoxy, etc.), a hydroxy group, a substituted or unsubstituted aryloxy group (e.g. p-chlorophenoxy, 1-naphthoxy, etc.), a acyloxy group (e.g. acetyloxy, p-cyanobenzoyloxy, etc.), a carboxyl group or its ester group (e.g. ethoxycarbonyl, m-bromophenoxycarbonyl, etc.), a carbamoyl group (e.g. amonocarbonyl, t-butylaminocarbonyl, anilinocarbonyl, etc.), an acyl group (e.g. acetyl, o-nitrobenzoyl, etc.), a sulfo group, a sulfamoyl group (e.g. aminosulfonyl, t-butylaminosulfonyl, p-tolylaminosulfonyl, etc.), an amino group, an acylamino group (e.g. acetylamino, benzoylamino, etc.), a sulfonamido group (e.g. methanesulfonamido, p-toluenesulfonamido, etc.), a cyano group, a nitro group and so on. Among them, preferable ones are a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms (e.g. methyl, ethyl, isopropyl, n-butyl, trifluoromethyl, etc.), a halogen atom (chlorine, bromine, fluorine, iodine), a substituted or unsubstituted alkoxy group having 1 to 4 carbon atoms (e.g. methoxy, ethoxy, t-butoxy, 2-chloroethoxy, etc.), a cyano group and a nitro group. 
     Z is a group of atoms necessary for forming a substituted or unsubstituted aromatic hydrocarbon ring or a substituted or unsubstituted aromatic heterocyclic ring, specifically representing, for example, a group of atoms for forming a substituted or unsubstituted benzene ring, a substituted or unsubstituted naphthalene ring, a substituted or unsubstituted indole ring, a substituted or unsubstituted carbazole ring, and the like. 
     As the substituents on the group of atoms for forming these rings, there may be enumerated a series of substituents as mentioned as the substituents for R 4  and R 5 , but preferably they are a halogen atom (chlorine, bromine, fluorine, iodine), a sulfo group and a sulfamoyl group (e.g. aminosulfonyl, p-tolylaminosulfonyl, etc.). 
     R 1  is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, a carboxyl group or its ester group, a substituted or unsubstituted carbamoyl group, a cyano group, preferably a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to b 4 carbon atoms (e.g. methyl, ethyl, isopropyl, t-butyl, trifluoromethyl, etc.) or a cyano group. 
     A&#39; is a substituted or unsubstituted aryl group, preferably a substituted or unsubstituted phenyl group, and the substituents on these groups may include a series of those as mentioned for R 4  and R 5 , but they are preferably a halogen atom (chlorine, bromine, fluorine, iodine), a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms (e.g. methyl, ethyl, isopropyl, t-butyl, trifluoromethyl, etc.), a substituted or unsubstituted alkoxy group having 1 to 4 carbon atoms (e.g. methoxy, ethoxy, isopropoxy, t-butoxy, 2-chloroethoxy, etc.). 
     R 2  and R 3  represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group and a substituted or unsubstituted aryl group, preferably a substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms (e.g. methyl, ethyl, isopropyl, t-butyl, trifluoromethyl, etc.) and a substituted or unsubstituted phenyl group (e.g. phenyl, p-methoxyphenyl, m-chlorophenyl, etc.). 
     Of the Embodiment A represented by the above formula [IA], particularly preferable compounds with respect to sensitivity and stability to heat and light have the structure as represented by the formula [IA]-II shown below: ##STR12## wherein A and S have the same meanings as defined in the formula [IA]. 
     Specific examples of useful azo compounds represented by the above formula [IA] may include, for example, those having the following formula: 
     Those having the formula [IA]-III: ##STR13##  wherein A, S, Y 1  and Y 2  have the same meanings as defined in the formula [IA]. 
     
         __________________________________________________________________________CompoundNo.   A                         S            Y.sub.1                                           Y.sub.2__________________________________________________________________________A-(1)  ##STR14##                            ##STR15##   H  HA-(2)  ##STR16##                            ##STR17##   H  HA-(3)  ##STR18##                            ##STR19##   H  HA-(4)  ##STR20##                            ##STR21##   H  HA-(5)  ##STR22##                            ##STR23##   H  HA-(6)  ##STR24##                OCH.sub.3    H  HA-(7)  ##STR25##                CH.sub.3     H  HA-(8)  ##STR26##                C.sub.3 H.sub.7                                        H  HA-(9)  ##STR27##                            ##STR28##   H  HA-(10)  ##STR29##                OCH.sub.3    H  HA-(11)  ##STR30##                C.sub.3 H.sub.7                                        H  HA-(12)  ##STR31##                            ##STR32##   H  HA-(13)  ##STR33##                C.sub.2 H.sub.5                                        H  HA-(14)  ##STR34##                OC.sub.2 H.sub.5                                        H  HA-(15)  ##STR35##                            ##STR36##   H  HA-(16)  ##STR37##                C.sub.3 H.sub.7                                        H  HA-(17)  ##STR38##                OCH.sub.3    H  HA-(18)  ##STR39##                            ##STR40##   H  HA-(19)  ##STR41##                C.sub.3 H.sub.7                                        H  HA-(20)  ##STR42##                C.sub.2 H.sub.5                                        H  HA-(21)  ##STR43##                            ##STR44##   Cl ClA-(22)  ##STR45##                            ##STR46##   H  HA-(23)  ##STR47##                C.sub.3 H.sub.7                                        H  HA-(24)  ##STR48##                OCH.sub.3    H  HA-(25)  ##STR49##                            ##STR50##   H  HA-(26)  ##STR51##                            ##STR52##   H  HA-(27)  ##STR53##                CH.sub.3     H  ClA-(28)  ##STR54##                            ##STR55##   Cl ClA-(29)  ##STR56##                            ##STR57##   H  HA-(30)  ##STR58##                OCH.sub.3    H  HA-(31)  ##STR59##                            ##STR60##   H  HA-(32)  ##STR61##                            ##STR62##   H  HA-(33)  ##STR63##                C.sub.3 H.sub.7                                        H  HA-(34)  ##STR64##                            ##STR65##   H  HA-(35)  ##STR66##                            ##STR67##   CN CNA-(36)  ##STR68##                            ##STR69##   H  HA-(37)  ##STR70##                C.sub.2 H.sub.5                                        H  HA-(38)  ##STR71##                C.sub.3 H.sub.7                                        CH.sub.3                                           CH.sub.3A-(39)  ##STR72##                            ##STR73##   H  HA-(40)  ##STR74##                            ##STR75##   H  H__________________________________________________________________________ 
    
     Those having the formula [IA]-IV: 
     
         __________________________________________________________________________ ##STR76##CompoundNo.   A                         S            Y.sub.1                                           Y.sub.2__________________________________________________________________________A-(41)  ##STR77##                            ##STR78##   H  HA-(42)  ##STR79##                            ##STR80##   H  HA-(43)  ##STR81##                            ##STR82##   H  HA-(44)  ##STR83##                            ##STR84##   H  HA-(45)  ##STR85##                            ##STR86##   H  HA-(46)  ##STR87##                            ##STR88##   H  HA-(47)  ##STR89##                            ##STR90##   H  HA-(48)  ##STR91##                            ##STR92##   H  HA-(49)  ##STR93##                            ##STR94##   H  HA-(50)  ##STR95##                            ##STR96##   H  HA-(51)  ##STR97##                            ##STR98##   Cl ClA-(52)  ##STR99##                CH.sub.3     Br CNA-(53)  ##STR100##               C.sub.2 H.sub.5                                        H  HA-(54)  ##STR101##               C.sub.3 H.sub.7                                        H  HA-(55)  ##STR102##                            ##STR103##  H  HA-(56)  ##STR104##                            ##STR105##  H  HA-(57)  ##STR106##                            ##STR107##  H  HA-(58)  ##STR108##               C.sub.3 H.sub.7                                        H  HA-(59)  ##STR109##               OCH.sub.3    H  HA-(60)  ##STR110##               CH.sub.3     H  HA-(61)  ##STR111##                            ##STR112##  CN CNA-(62)  ##STR113##                            ##STR114##  H  HA-(63)  ##STR115##               CH.sub.3     H  HA-(64)  ##STR116##               C.sub. 3 H.sub.7                                        H  HA-(65)  ##STR117##               OCH.sub.3    H  HA-(66)  ##STR118##                            ##STR119##  H  HA-(67)  ##STR120##               CH.sub.3     H  HA-(68)  ##STR121##               C.sub.3 H.sub.7                                        H  HA-(69)  ##STR122##               OCH.sub.3    H  HA-(70)  ##STR123##                            ##STR124##  H  HA-(71)  ##STR125##                            ##STR126##  H  H__________________________________________________________________________ 
    
     Others: ##STR127## 
     The azo compounds as set forth above can be synthesized easily according to the known method. A typical example is shown below. 
     Synthesis Example 1 [Synthesis of the Exemplary Compound A-(1)] 
     The synthesis route is schematically shown below: ##STR128## 
     That is, 2,7-dinitrofluorenone 1 (produced by Tokyo Kasei K.K.) was allowed to react with benzylcyanide 2 to be converted to a dinitro derivative 3, which was then reduced with iron to form a diamino derivative 4. The diamino derivative 4 (30.9 g, 0.1 mole) was dispersed by adding into a mixture of 1 liter of conc. HCl and 1 liter of water and a solution of 13.8 g (0.2 mole) of sodium nitrite dissolved in 0.1 liter of water was added dropwise at 5° C. under ice-cooling. After completion of the addition, the reaction mixture was filtered, and 1 liter of an aqueous 50% ammonium hexafluorophosphate solution was added to the filtrate. The resultant precipitate was recovered by filtration, washed with water and thoroughly dried. The salt obtained was dissolved in 1.5 liter of N,N-dimethylformamide (DMF) to provide a tetrazonium salt solution to be used in the subsequent reaction. 
     As the next step, 79.3 g (0.2 mole) of 2-hydroxy-3-(4-methoxy-2-methylphenylcarbamoyl)-benzo[a]carbazole (Naphthol AS-SR, produced by Hoechst AG) and 60 g of triethanolamine were dissolved in 4 liters of N,N-dimethylformamide, and the tetrazonium salt solution as prepared above was added dropwise under ice-cooling to the resultant solution, followed further by stirring for 2 hours to carry out the reaction. The crystal formed was recovered by filtration, and the crystal was washed twice with 5 liters of N,N-dimethylformamide and twice with 5 liters of acetone, followed by drying, to obtain 37.1 g of the desired bisazo compound A-(1) (33%). From the analytical results of m.p. 300° C. or higher, FD-MS spectrum which indicates a peak of M +  at m/Z 1124, and the elemental analysis of C=75.81%, N=11.17%, H=4.50% (Calcd. values, C=75.85%, N=11.21%, H=4.39%), it was confirmed that the desired substance was synthesized. 
     Embodiment B 
     This embodiment is represented by the following formula [IB]: ##STR129## wherein Y 1 , Y 2 , m, n and A are the same as defined in the above formula [I]. 
     The detailed description for the symbols Y 1 , Y 2  and A as given for the above embodiment [IA] are also applicable for this embodiment. 
     Of the Embodiment B represented by the above formula [IB], particularly preferable compounds with respect to sensitivity and stability to heat and light have the structure as represented by the formula [IB]-II shown below: ##STR130## wherein Y 1 , Y 2  and A are the same as defined above. 
     Specific examples of useful azo compounds represented by the above formula [IB] may include, for example, those having the following formula: 
     Those having the following formula [IB]-II: 
     
         __________________________________________________________________________ ##STR131##Com-                           Com-pound                          poundNo. Y.sub.1   Y.sub.2       A                  No. Y.sub.1                                  Y.sub.2                                      A__________________________________________________________________________B-(1)    H   H        ##STR132##        B-(2)                              H   H                                       ##STR133##B-(3)    H   H        ##STR134##        B-(4)                              H   H                                       ##STR135##B-(5)    H   H        ##STR136##        B-(6)                              H   H                                       ##STR137##B-(7)    H   H        ##STR138##        B-(8)                              H   H                                       ##STR139##B-(9)    H   H        ##STR140##        B-(10)                              H   H                                       ##STR141##B-(11)    H   H        ##STR142##        B-(12)                              H   H                                       ##STR143##B-(13)    H   H        ##STR144##        B-(14)                              H   H                                       ##STR145##B-(15)    H   H        ##STR146##        B-(16)                              H   H                                       ##STR147##B-(17)    H   H        ##STR148##        B-(18)                              H   H                                       ##STR149##B-(19)    H   H        ##STR150##        B-(20)                              H   H                                       ##STR151##B-(21)    H   H        ##STR152##        B-(22)                              H   H                                       ##STR153##B-(23)    H   CH.sub.3        ##STR154##        B-(24)                              OCH.sub.3                                  H                                       ##STR155##B-(25)    H   Cl        ##STR156##        B-(26)                              CN  H                                       ##STR157##B-(27)    H   H        ##STR158##        B-(28)                              H   H                                       ##STR159##B-(29)    H   H        ##STR160##        B-(30)                              H   H                                       ##STR161##B-(31)    H   H        ##STR162##        B-(32)                              H   H                                       ##STR163##B-(33)    H   H        ##STR164##        B-(34)                              H   H                                       ##STR165##B-(35)    H   H        ##STR166##        B-(36)                              H   H                                       ##STR167##B-(37)    H   H        ##STR168##        B-(38)                              H   H                                       ##STR169##B-(39)    H   H        ##STR170##        B-(40)                              H   H                                       ##STR171##B-(41)    H   H        ##STR172##        B-(42)                              H   H                                       ##STR173##B-(43)    H   H        ##STR174##        B-(44)                              H   H                                       ##STR175##B-(45)    H   H        ##STR176##        B-(46)                              H   H                                       ##STR177##B-(47)    H   H        ##STR178##        B-(48)                              CH.sub.3                                  H                                       ##STR179##B-(49)    H   OCH.sub.3        ##STR180##        B-(50)                              Br  Br                                       ##STR181##B-(51)    CN  Cl        ##STR182##        B-(52)                              OH  H                                       ##STR183##B-(53)    H   H        ##STR184##        B-(54)                              H   H                                       ##STR185##B-(55)    H   H        ##STR186##        B-(56)                              H   H                                       ##STR187##B-(57)    H   H        ##STR188##        B-(58)                              H   H                                       ##STR189##B-(59)    H   H        ##STR190##B-(60)    H   H        ##STR191##B-(61)    H   H        ##STR192##B-(62)    H   H        ##STR193##B-(63)    H   H        ##STR194##B-(64)    H   H        ##STR195##B-(65)    Cl  Cl        ##STR196##        B-(66)                              CN  CH.sub.3                                       ##STR197##B-(67)    OH  H        ##STR198##        B-(68)                              H   H                                       ##STR199##B-(69)    H   H        ##STR200##        B-(70)                              H   H                                       ##STR201##B-(71)    H   H        ##STR202##        B-(72)                              H   H                                       ##STR203##B-(73)    H   H        ##STR204##        B-(74)                              H   H                                       ##STR205##B-(75)    H   H        ##STR206##        B-(76)                              H   H                                       ##STR207##B-(77)    H   H        ##STR208##__________________________________________________________________________ 
    
     Those having the following formula [IB]-III: 
     
         __________________________________________________________________________ ##STR209##CompoundNo.   Y.sub.1     Y.sub.2        A__________________________________________________________________________B-(78) H   H         ##STR210##B-(79) H   H         ##STR211##B-(80) H   H         ##STR212##B-(81) H   H         ##STR213##B-(82) CH.sub.3     H         ##STR214##B-(83) OH  H         ##STR215##B-(84) H   H         ##STR216##B-(85) H   H         ##STR217##B-(86) H   H         ##STR218##B-(87) H   H         ##STR219##B-(88) H   H         ##STR220##B-(89) H   CN         ##STR221##B-(90) OCH.sub.3     H         ##STR222##B-(91) H   H         ##STR223##B-(92) H   H         ##STR224##B-(93) H   H         ##STR225##B-(94) H   H         ##STR226##B-(95) H   H         ##STR227##B-(96) H   H         ##STR228##B-(97) H   H         ##STR229##B-(98) H   H         ##STR230##B-(99) CH.sub.3     H         ##STR231##B-(100) OH  H         ##STR232##B-(101) H   H         ##STR233##B-(102) H   CH.sub.3         ##STR234##B-(103) H   H         ##STR235##B-(104) H   H         ##STR236##B-(105) H   H         ##STR237##B-(106) H   H         ##STR238##B-(107) H   H         ##STR239##B-(108) H   H         ##STR240##__________________________________________________________________________ 
    
     Those having the following formula [IB]-IV: 
     
         __________________________________________________________________________ ##STR241##CompoundNo.   Y.sub.1     Y.sub.2         A__________________________________________________________________________B-(109) H   H          ##STR242##B-(110) H   H          ##STR243##B-(111) H   H          ##STR244##B-(112) CH.sub.3     H          ##STR245##B-(113) OCH.sub.3     H          ##STR246##B-(114) C.sub.3 H.sub.7     H          ##STR247##B-(115) CN  H          ##STR248##B-(116) Cl  H          ##STR249##B-(117) Br  H          ##STR250##B-(118) I   H          ##STR251##B-(119) OH  H          ##STR252##B-(120) H   CH.sub.3          ##STR253##B-(121) H   H          ##STR254##B-(122) H   H          ##STR255##B-(123) H   H          ##STR256##B-(124) H   H          ##STR257##B-(125) H   H          ##STR258##B-(126) CH.sub.3     H          ##STR259##B-(127) Cl  H          ##STR260##B-(128) CH.sub.3     H          ##STR261##B-(129) C.sub.2 H.sub.5     H          ##STR262##B-(130) OCH.sub.3     OCH.sub.3          ##STR263##B-(131) CN  H          ##STR264##B-(132) Br  Br          ##STR265##B-(133) OH  H          ##STR266##B-(134) H   H          ##STR267##B-(135) CH.sub.3     H          ##STR268##B-(136) C.sub.2 H.sub.5     H          ##STR269##B-(137) Cl  H          ##STR270##B-(138) Br  H          ##STR271##B-(139) OH  H          ##STR272##__________________________________________________________________________ 
    
     Those having the following formula [IB]-V: 
     
         __________________________________________________________________________ ##STR273##Compound                       CompoundNo.     Y.sub.1      A                   No.     Y.sub.1                                     A__________________________________________________________________________B-(140) H       ##STR274##         B-(141) H                                      ##STR275##B-(142) H       ##STR276##         B-(143) H                                      ##STR277##B-(144) H       ##STR278##         B-(145) H                                      ##STR279##B-(146) H       ##STR280##         B-(147) H                                      ##STR281##B-(148) H       ##STR282##         B-(149) H                                      ##STR283##B-(150) H       ##STR284##         B-(151) H                                      ##STR285##B-(152) H       ##STR286##         B-(153) H                                      ##STR287##B-(154) H       ##STR288##         B-(155) H                                      ##STR289##B-(156) H       ##STR290##         B-(157) H                                      ##STR291##B-(158) CH.sub.3       ##STR292##         B-(159) H                                      ##STR293##B-(160) H       ##STR294##         B-(161) H                                      ##STR295##B-(162) H       ##STR296##         B-(163) H                                      ##STR297##B-(164) H  OHOO NCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2CH.sub.3__________________________________________________________________________ 
    
     Those having the following formula [IB]-VI: 
     
         __________________________________________________________________________ ##STR298##Com-                           Com-pound                          poundNo. Y.sub.1 Y.sub.2    Y.sub.3      No.                 Y.sub.1                              Y.sub.2                                Y.sub.3__________________________________________________________________________B-(165)    H H  H       ##STR299##         B-(166)                              H H  H                                      ##STR300##B-(167)    H H  H       ##STR301##         B-(168)                              H H  H                                      ##STR302##B-(169)    H CH.sub.3    H       ##STR303##         B-(170)                              H H  Cl                                      ##STR304##B-(171)    H H  Br       ##STR305##         B-(172)                              H OH H                                      ##STR306##B-(173)    H H  H       ##STR307##         B-(174)                              H H  H                                      ##STR308##B-(175)    H H  H       ##STR309##         B-(176)                              H H  H                                      ##STR310##B-(177)    H H  H       ##STR311##         B-(178)                              H H  H                                      ##STR312##B-(179)    H H  H       ##STR313##         B-(180)                              H H  Cl                                      ##STR314##B-(181)    H H  Br       ##STR315##         B-(182)                              H CH.sub.3                                   H                                      ##STR316##B-(183)    H H  H       ##STR317##         B-(184)                              H H  H                                      ##STR318##__________________________________________________________________________ 
    
     Those having the following formula [IB]-VII: 
     
         __________________________________________________________________________ ##STR319##Com-                           Com-pound                          poundNo. Y.sub.1 Y.sub.2 Y.sub.3      A                   No. Y.sub.1                                Y.sub.2 Y.sub.3__________________________________________________________________________B-(185)    H HH       ##STR320##         B-(186)                              H HH                                      ##STR321##B-(187)    H HH       ##STR322##         B-(188)                              H HH                                      ##STR323##B-(189)    H HCH.sub.3       ##STR324##         B-(190)                              H HH                                      ##STR325##B-(191)    H HH       ##STR326##         B-(192)                              H HH                                      ##STR327##B-(193)    H H H       ##STR328##         B-(194)                              H HH                                      ##STR329##B-(195)    H HH       ##STR330##         B-(196)                              H HCl                                      ##STR331##B-(197)    H HH       ##STR332##         B-(198)                              H HH                                      ##STR333##B-(199)    H HH       ##STR334##         B-(200)                              H HH                                      ##STR335##B-(201)    H HCH.sub.3       ##STR336##         B-(202)                              H OHH                                      ##STR337##B-(203)    Cl HH       ##STR338##         B-(204)                              Cl                                ClCl                                      ##STR339##__________________________________________________________________________ 
    
     Others: ##STR340## 
     The azo compounds as set forth above can be synthesized easily according to the known method. A typical example is shown below. 
     Synthesis Example 2 [Synthesis of the Exemplary Compound B-(1)] 
     The synthesis route is schematically shown below: ##STR341## 
     That is, 2,7-dinitrofluorenone 1 (produced by Tokyo Kasei K.K.) was allowed to react with a phosphonate derivative 2 (Journal of American Chemical Society, 83, 1733 (1961)) to be converted to a dinitro derivative 3, which was then reduced with stannous chloride to form a diamino derivative 4 (Journal of Chemical Society, 870 (1954)). The diamino derivative 4 (23.3 g, 0.1 mole) was dispersed by adding into a mixture of 1 liter of conc. HCl and 1 liter of water and a solution of 13.8 g (0.2 mole) of sodium nitrite dissolved in 0.1 liter of water was added dropwise at 5° C. under ice-cooling. After completion of the addition, the reaction mixture was filtered, and 1 liter of an aqueous 50% ammonium hexafluorophosphate solution was added to the filtrate. The resultant precipitate was recovered by filtration, washed with water and thoroughly dried. The salt obtained was dissolved in 1.5 liters of N,N-dimethylformamide (DMF) to provide a tetrazonium salt solution to be used in the subsequent reaction. 
     As the next step, 79.3 g (0.2 mole) of 2-hydroxy-3-(4-methoxy-2-methylphenylcarbamoyl)-benzo[a]carbazole (Naphthol AS-SR, produced by Hoechst AG) and 60 g of triethanolamine were dissolved in 4 liters of N,N-dimethylformamide, and the tetrazonium salt solution as prepared above was added dropwise under ice-cooling to the resultant solution, followed further by stirring for 2 hours to carry out the reaction. The crystal formed was recovered by filtration, and the crystal was washed twice with 5 liters of N,N-dimethylformamide and twice with 5 liters of acetone, followed by drying, to obtain 70.3 g of the desired bisazo compound B-(1) (67%). From the analytical results of m.p. 300° C. or higher, FD-MS spectrum which indicates a peak of M +  at m/Z 1047,  and the elemental analysis of C=74.27%, N=11.95%, H=4.52% (Calcd. values, C=74.8%, N=12.03%, H=4.33%), it was confirmed that the desired substance was synthesized. 
     Embodiment C 
     This embodiment is represented by the following formula [IC]: ##STR342## wherein X is a halogen atom; Y 1 , Y 2 , m, n and A are the same as defined in the formula [I]. 
     In the above formula [IC], X represents a halogen atom (fluorine, chlorine, bromine or iodine), and other symbols have the same meanings as described in detail for the compound of the formula [IA]. 
     Of the Embodiment C represented by the above formula [IC], particularly preferable compounds with respect to sensitivity and stability to heat and light have the structure as represented by the formula [IC]-II shown below: ##STR343## wherein X, Y 1 , Y 2  and A are the same as defined in the above formula [IC]. 
     Specific examples of useful azo compounds represented by the above formula [IC] may include, for example, those having the following formula: 
     Those having the following formula [IC]-III: 
     
         __________________________________________________________________________ ##STR344##Com-                           Com-pound                          poundNo. A                   X Y.sub.1                       Y.sub.2                          No. A                   X Y.sub.1                                                      Y.sub.2__________________________________________________________________________C-(1)##STR345##         Cl                     H H  C-(2)                               ##STR346##         Cl                                                    H HC-(3)##STR347##         Cl                     H H  C-(4)                               ##STR348##         I H HC-(5)##STR349##         Cl                     H H  C-(6)                               ##STR350##         Cl                                                    H HC-(7)##STR351##         Br                     H H  C-(8)                               ##STR352##         Cl                                                    H HC-(9)##STR353##         Br                     H H  C-(10)                               ##STR354##         Cl                                                    H HC-(11)##STR355##         Cl                     H H  C-(12)                               ##STR356##         Cl                                                    H HC-(13)##STR357##         Br                     H H  C-(14)                               ##STR358##         Br                                                    H HC-(15)##STR359##         Cl                     H H  C-(16)                               ##STR360##         Cl                                                    HC-(17)##STR361##         Cl                     H CH.sub.3                          C-(18)                               ##STR362##         Cl                                                    H HC-(19)##STR363##         Br                     H H  C-(20)                               ##STR364##         Cl                                                    H HC-(21)##STR365##         Br                     H H  C-(22)                               ##STR366##         Cl                                                    H HC-(23)##STR367##         Br                     H H  C-(24)                               ##STR368##         I H HC-(25)##STR369##         F H H  C-(26)                               ##STR370##         Br                                                    H HC-(27)##STR371##         Cl                     H HC-(28)##STR372##         Br                     CNCN C-(29)                               ##STR373##         Br                                                    H HC-(30)##STR374##         Cl                     H H  C-(31)                               ##STR375##         Br                                                    H HC-(32)##STR376##         Br                     H H  C-(33)                               ##STR377##         Cl                                                    H HC-(34)##STR378##         Cl                     H H  C-(35)                               ##STR379##         Cl                                                    Cl                                                      ClC-(36)##STR380##         Br                     Br                       Br C-(37)                               ##STR381##         Cl                                                    H HC-(38)##STR382##         Cl                     Br                       Br C-(39)                               ##STR383##         Cl                                                    H HC-(40)##STR384##         Cl                     H H  C-(41)                               ##STR385##         Br                                                    H HC-(42)##STR386##         I H H  C-(43)                               ##STR387##         Cl                                                    H HC-(44)##STR388##         Br                     H H  C-(45)                               ##STR389##         Cl                                                    H HC-(46)##STR390##         Cl                     H H  C-(47)                               ##STR391##         Cl                                                    H HC-(48)##STR392##         Cl                     H H  C-(49)                               ##STR393##         Cl                                                    H HC-(50)##STR394##         Cl                     H H  C-(51)                               ##STR395##         Cl                                                    H HC-(52)##STR396##         Cl                     H H  C-(53)                               ##STR397##         Cl                                                    H HC-(54)##STR398##         Br                     H H  C-(55)                               ##STR399##         F H HC-(56)##STR400##         Cl                     H H  C-(57)                               ##STR401##         Cl                                                    H HC-(58)##STR402##         Cl                     H H  C-(59)                               ##STR403##         Cl                                                    H HC-(60)##STR404##         Br                     H H  C-(61)                               ##STR405##         Cl                                                    H HC-(62)##STR406##         Cl                     H H  C-(63)                               ##STR407##         Cl                                                    H H__________________________________________________________________________ 
    
     Those having the following formula [IC]-III 
     
         __________________________________________________________________________ ##STR408##CompoundNo.   A                          X Y.sub.1   Y.sub.2__________________________________________________________________________C-(64)  ##STR409##                Cl                              H         HC-(65)  ##STR410##                Br                              H         HC-(66)  ##STR411##                Cl                              H         HC-(67)  ##STR412##                Cl                              H         HC-(68)  ##STR413##                Cl                              H         HC-(69)  ##STR414##                Br                              H         CH.sub.3C-(70)  ##STR415##                Cl                              H         HC-(71)  ##STR416##                Br                              H         HC-(72)  ##STR417##                Cl                              H         HC-(73)  ##STR418##                Br                              H         HC-(74)  ##STR419##                Br                              CH.sub.3  CH.sub.3C-(75)  ##STR420##                F                               ##STR421##                                        HC-(76)  ##STR422##                Cl                              H         HC-(77)  ##STR423##                Cl                              H         HC-(78)  ##STR424##                Br                              H         H__________________________________________________________________________ 
    
     Others: ##STR425## 
     The azo compounds as set forth above can be synthesized easily according to the known method. A typical example is shown below. 
     Synthesis Example 3 [Synthesis of the Exemplary Compound C-(1)] 
     The synthesis route is schematically shown below: ##STR426## 
     That is, 2,7-dinitriofluorenone 1 (produced by Tokyo Kasei K.K.) was allowed to react with benzyl cyanide 2 to be converted to a dinitro derivative 3, which was then reduced with stannous chloride to form a diamino derivative 4 (Journal of Chemical Society, 870 (1954)). The diamino derivative 4 (267.7 g, 0.1 mole) was dispersed by adding into a mixture of 1 liter of conc. HCl and 1 liter of water and a solution of 13.8 g (0.2 mole) of sodium nitrite dissolved in 1 liter of water was added dropwise at 5° C. under ice-cooling. After completion of the addition, the reaction mixture was filtered, and 1 liter of an aqueous 50% ammonium hexafluorophosphate solution was added to the filtrate. The resultant precipitate was recovered by filtration, washed with water and thoroughly dried. The salt obtained was dissolved in 1.5 liters of N,N-dimethylformamide (DMF) to provide a tetrazonium salt solution to be used in the subsequent reaction. 
     As the next step, 79.3 g (0.2 mole) of 2-hydroxy-3-(4-methoxy-2-methylphenylcarbamoyl)-benzo[a]carbazole (Naphthol AS-SR, produced by Hoechst AG) and 60 g of triethanolamine were dissolved in 4 liters of N,N-dimethylformamide, and the tetrazonium salt solution was prepared above was added dropwise under ice-cooling to the resultant solution, followed further by stirring for 2 hours to carry out the reaction. The crystal formed was recovered by filtration, and the crystal was washed twice with 5 liters of N,N-dimethylformamide and twice with 5 liters of acetone, followed by drying, to obtain 81.2 g of the desired bisazo compound C-(1) (75%). From the analytical results of m.p. 300° C. or higher, FD-MS spectrum which indicates a peak of M +  at m/Z 1081, and the elemental analysis of C=72.00%, N=11.55%, H=4.15% (Calcd. values, C=72.11%, N=11.65%, H=4.10%), it was confirmed that the desired substance was synthesized. 
     Embodiment D 
     This embodiment is represented by the following formula [ID]: ##STR427## wherein Q 1 , Y 1 , Y 2 , m, n and A are the same as defined in the above formula [I]. 
     In the above formula, Q 1  represents, for example, an alkyl group (having desirably 1 to 5 carbon atoms), a phenyl group which may have a substituent or substituents, a hydrogen atom, an amino group, an alkylamino group, a phenylamino group or a hydroxyl group, and other symbols may be exemplified as detailed above. 
     Of the Embodiment D represented by the above formula [ID], particularly preferable compounds with respect to sensitivity and stability to heat and light have the structure as represented by the formula [ID]-II shown below: ##STR428## wherein Q 1 , W, Y 1 , Y 2  and A are the same as defined in the above formula [IC]. 
     Specific examples of useful azo compounds represented by the above formula [ID] may include, for example, those having the following formula: 
     Those having the formula [ID]-III: 
     
         __________________________________________________________________________ ##STR429##CompoundNo.   A                          Q.sub.1   Y.sub.1                                           Y.sub.2__________________________________________________________________________D-(1)  ##STR430##                CH.sub.3  H    HD-(2)  ##STR431##                CH.sub.3  H    HD-(3)  ##STR432##                CH.sub.3  H    HD-(4)  ##STR433##                             ##STR434##                                      H    HD-(5)  ##STR435##                             ##STR436##                                      H    HD-(6)  ##STR437##                C.sub.2 H.sub.5                                      H    HD-(7)  ##STR438##                CH.sub.3  H    HD-(8)  ##STR439##                C.sub.2 H.sub.5                                      H    HD-(9)  ##STR440##                OCH.sub.3 H    HD-(10)  ##STR441##                H         H    HD-(11)  ##STR442##                             ##STR443##                                      H    HD-(12)  ##STR444##                CH.sub.3  H    HD-(13)  ##STR445##                             ##STR446##                                      H    HD-(14)  ##STR447##                CH.sub.3  H    HD-(15)  ##STR448##                             ##STR449##                                      H    HD-(16)  ##STR450##                             ##STR451##                                      H    HD-(17)  ##STR452##                             ##STR453##                                      H    HD-(18)  ##STR454##                C.sub.3 H.sub.7                                      H    HD-(19)  ##STR455##                             ##STR456##                                      H    HD-(20)  ##STR457##                             ##STR458##                                      H    HD-(21)  ##STR459##                             ##STR460##                                      H    HD-(22)  ##STR461##                CH.sub.2OCH.sub.3                                      H    HD-(23)  ##STR462##                H         H    HD-(24)  ##STR463##                CH.sub.3  H    HD-(25)  ##STR464##                C.sub.2 H.sub.5                                      H    HD-(26)  ##STR465##                CH.sub.3  H    HD-(27)  ##STR466##                C.sub.2 H.sub.5                                      H    HD-(28)  ##STR467##                H         OCH.sub.3                                           CH.sub.3D-(29)  ##STR468##                CH.sub.3  H    HD-(30)  ##STR469##                C.sub.2 H.sub.5                                      H    HD-(31)  ##STR470##                H         H    HD-(32)  ##STR471##                CH.sub.3  H    HD-(33)  ##STR472##                C.sub.2 H.sub.5                                      H    HD-(34)  ##STR473##                H         H    HD-(35)  ##STR474##                C.sub.2 H.sub.5                                      H    HD-(36)  ##STR475##                CH.sub.3  H    HD-(37)  ##STR476##                OH        H    HD-(38)  ##STR477##                CH.sub.3  H    HD-(39)  ##STR478##                C.sub.2 H.sub.5                                      H    HD-(40)  ##STR479##                CH.sub.3  Cl   ClD-(41)  ##STR480##                OH        H    HD-(42)  ##STR481##                CH.sub.3  H    HD-(43)  ##STR482##                CH.sub.3  H    HD-(44)  ##STR483##                C.sub.2 H.sub.5                                      H    HD-(45)  ##STR484##                CH.sub.3  H    HD-(46)  ##STR485##                OH        H    HD-(47)  ##STR486##                CH.sub.3  H    HD-(48)  ##STR487##                CH.sub.3  H    HD-(49)  ##STR488##                C.sub.2 H.sub.5                                      OH   HD-(50)  ##STR489##                             ##STR490##                                      H    HD-(51)  ##STR491##                C.sub.2 H.sub.5                                      H    HD-(52)  ##STR492##                CH.sub.3  H    HD-(53)  ##STR493##                C.sub.2 H.sub.5                                      H    HD-(54)  ##STR494##                C.sub.2 H.sub.5                                      H    HD-(55)  ##STR495##                CH.sub.3  H    HD-(56)  ##STR496##                             ##STR497##                                      H    HD-(57)  ##STR498##                CH.sub.3  H    HD-(58)  ##STR499##                CH.sub.3  OCH.sub.2                                           HD-(59)  ##STR500##                             ##STR501##                                      H    HD-(60)  ##STR502##                NH.sub.2  H    HD-(61)  ##STR503##                CH.sub.3  H    HD-(62)  ##STR504##                             ##STR505##                                      H    HD-(63)  ##STR506##                CH.sub.3  H    HD-(64)  ##STR507##                C.sub.2 H.sub.5                                      H    HD-(65)  ##STR508##                OH        H    HD-(66)  ##STR509##                CH.sub.3  H    HD-(67)  ##STR510##                CH.sub.3  H    HD-(68)  ##STR511##                CH.sub.3  H    HD-(69)  ##STR512##                C.sub.2 H.sub.5                                      H    HD-(70)  ##STR513##                C.sub.2 H.sub.5                                      H    HD-(71)  ##STR514##                C.sub.2 H.sub.5                                      H    HD-(72)  ##STR515##                C.sub.2 H.sub.5                                      H    HD-(73)  ##STR516##                             ##STR517##                                      H    HD-(74)  ##STR518##                OCH.sub.3 H    HD-(75)  ##STR519##                CH.sub.3  H    HD-(76)  ##STR520##                H         H    HD-(77)  ##STR521##                OH        H    HD-(78)  ##STR522##                CH.sub.3  H    HD-(79)  ##STR523##                CH.sub.3  H    HD-(80)  ##STR524##                OCH.sub.3 Cl   HD-(81)  ##STR525##                C.sub.2 H.sub.5                                      H    BrD-(82)  ##STR526##                CH.sub.3  H    HD-(83)  ##STR527##                H         H    CH.sub.3__________________________________________________________________________ 
    
     Those having the formula [ID]-IV: 
     
         ______________________________________ ##STR528##Com-poundNo.   A                   Q.sub.1    Y.sub.1                                    Y.sub.2______________________________________D-(84)  ##STR529##         CH.sub.3   H   HD-(85)  ##STR530##                      ##STR531##                                H   HD-(86)  ##STR532##         C.sub.2 H.sub.5                                H   HD-(87)  ##STR533##         C.sub.2 H.sub.5                                H   HD-(88)  ##STR534##         OCH.sub.3  H   HD-(89)  ##STR535##                      ##STR536##                                H   HD-(90)  ##STR537##         OCH.sub.3  H   HD-(91)  ##STR538##         CH.sub.3   H   HD-(92)  ##STR539##                      ##STR540##                                H   HD-(93)  ##STR541##         CH.sub.3   H   H______________________________________ 
    
     Others: ##STR542## 
     The azo compounds as set forth above can be synthesized easily according to the known method. A typical example is shown below. 
     Synthesis Example 4 [Synthesis of the Exemplary Compound D-(1)] 
     The synthesis route is schematically shown below: ##STR543## 
     That is, 2,7-dinitrofluorenone 1 (produced by Tokyo Kasei K.K.) was allowed to react with cyanoacetone 2 to be converted to a dinitro derivative 3, which was then reduced with stannous chloride to form a diamino derivative 4 (Journal of Chemical Society, 870 (1954)). The diamino derivative 4 (27.5 g, 0.1 mole) was dispersed by adding into a mixture of 1 liter of conc. HCl and 1 liter of water and a solution of 13.8 g (0.2 mole) of sodium nitrite dissolved in 1 liter of water was added dropwise at 5° C. under ice-cooling. After completion of the addition, the reaction mixture was filtered, and 1 liter of an aqueous 50% ammonium hexafluorophosphate solution was added to the filtrate. The resultant precipitate was recovered by filtration, washed with water and thoroughly dried. The salt obtained was dissolved in 1.5 liters of N,N-dimethylformamide (DMF) to provide a tetrazonium salt solution to be used in the subsequent reaction. 
     As the next step, 79.3 g (0.2 mole) of 2-hydroxy-3-(4-methoxy-2-methylphenylcarbamoyl)-benzo[a]carbazole (Naphthol AS-SR, produced by Hoechst AG) and 60 g of triethanolamine were dissolved in 4 liters of N,N-dimethylformamide, and the tetrazonium salt solution as prepared above was added dropwise under ice-cooling to the resultant solution, followed further by stirring for 2 hours to carry out the reaction. The crystal formed was recovered by filtration, and the crystal was washed twice with 5 liters of N,N-dimethylformamide and twice with 5 liters of acetone, followed by drying, to obtain 68.7 g of the desired bisazo compound D-(1) (63%). From the analytical results of m.p. 300° C. or higher, FD-MS spectrum which indicates a peak of M +  at m/Z 1089, and the elemental analyis of C=73.72%, N=11.47%, H=4.37% (Calcd. values, C=73.81%, N=11.56%, H=4.35%), it was confirmed that the desired substance was synthesized. 
     Embodiment E 
     This embodiment is represented by the following formula [IE]: ##STR544## wherein Q 1 , Q 2 , Q 3 , Y 1 , Y 2 , m, n and A are the same as defined in the above formula [I]. 
     Of the Embodiment E represented by the above formula [IE], particularly preferable compounds with respect to sensitivity and stability to heat and light have the structure as represented by the formula [IE]-II shown below: ##STR545## wherein Q 1 , Q 2 , Q 3 , Y 1 , Y 2  and A are the same as defined in the above formula [ID]. 
     Specific examples of useful azo compounds represented by the above formula [IE] may include, for example, those having the following formula: 
     Those having the following formula [IE]-III: 
     
         __________________________________________________________________________ ##STR546##CompoundNo.   A                            Q.sub.1                                     Q.sub.2    Q.sub.3                                                   Y.sub.1                                                      Y.sub.2__________________________________________________________________________E-(1)  ##STR547##                  H      CH.sub.3   CH.sub.3                                                   H  HE-(2)  ##STR548##                  H      H          H  H  HE-(3)  ##STR549##                  H      CO.sub.2 CH.sub.3                                                H  H  HE-(4)  ##STR550##                  H      H          H  H  HE-(5)  ##STR551##                  H      H          H  H  HE-(6)  ##STR552##                  H      H          H  H  HE-(7)  ##STR553##                  H      H          H  H  HE-(8)  ##STR554##                  H      H          H  H  HE-(9)  ##STR555##                  H      H          H  H  HE-(10)  ##STR556##                  H      H          H  H  HE-(11)  ##STR557##                  H      CH.sub.3   H  H  HE-(12)  ##STR558##                  H      H          CH.sub.3                                                   H  CH.sub.3E-(13)  ##STR559##                  H      H          H  H  HE-(14)  ##STR560##                  H      H          H  H  OCH.sub.3E-(15)  ##STR561##                  H      CH.sub.3   H  CH.sub.3                                                      HE-(16)  ##STR562##                  H      H          CH.sub.3                                                   CH.sub.3                                                      HE-(17)  ##STR563##                  H      H          H  H  ClE-(18)  ##STR564##                  H                                      ##STR565##                                                H  H  HE-(19)  ##STR566##                  H      H          H  H  HE-(20)  ##STR567##                               ##STR568##                                      ##STR569##                                                H  H  HE-(21)  ##STR570##                  H      H          H  H  HE-(22)  ##STR571##                  H      CH.sub.3   H  H  HE-(23)  ##STR572##                  H      H          H  H  HE-(24)  ##STR573##                  H      H          H  H  HE-(25)  ##STR574##                  H      CHCHCH.sub.3                                                H  H  HE-(26)  ##STR575##                  H      H          H  H  HE-(27)  ##STR576##                  H      H          H  H  HE-(28)  ##STR577##                  H                                      ##STR578##                                                H  H  HE-(29)  ##STR579##                  H      OH         H  H  HE-(30)  ##STR580##                  H                                      ##STR581##                                                H  H  HE-(31)  ##STR582##                  H      CHCHCH.sub.3                                                H  H  HE-(32)  ##STR583##                  H      OC.sub.2 H.sub.5                                                H  H  HE-(33)  ##STR584##                  H                                      ##STR585##                                                H  H  HE-(34)  ##STR586##                  H                                      ##STR587##                                                H  H  HE-(35)  ##STR588##                  H      NHC.sub.6 H.sub.11                                                H  H  HE-(36)  ##STR589##                  H                                      ##STR590##                                                H  H  H__________________________________________________________________________ 
    
     Those having the following formula [IE]-IV: 
     
         __________________________________________________________________________ ##STR591##CompoundNo.   A                          Q.sub.1                                   Q.sub.2   Q.sub.3                                                Y.sub.1                                                  Y.sub.2__________________________________________________________________________E-(37)  ##STR592##                H      CHCHCH.sub.3                                             H  H HE-(38)  ##STR593##                H      CO.sub.2 CH.sub.3                                             H  H HE-(39)  ##STR594##                H      CH.sub.3  CH.sub.3                                                H HE-(40) &#34;                          H      H         H  H HE-(41)  ##STR595##                H      OC.sub.2 H.sub.5                                             H  H HE-(42)  ##STR596##                H                                    ##STR597##                                             H  H HE-(43)  ##STR598##                H      CO.sub.2 CH.sub.3                                             H  H HE-(44)  ##STR599##                H      H         H  H HE-(45)  ##STR600##                H      H         H  H HE-(46)  ##STR601##                H                                    ##STR602##                                             H  H HE-(47)  ##STR603##                H                                    ##STR604##                                             H  H HE-(48)  ##STR605##                H      H         H  H HE-(49)  ##STR606##                H      CHCHCH.sub.3                                             H  H HE-(50)  ##STR607##                H      OC.sub.2 H.sub.5                                             H  H HE-(51)  ##STR608##                H      H         H  H HE-(52)  ##STR609##                             ##STR610##                                    ##STR611##                                             H  H HE-(53)  ##STR612##                H      CH.sub.3  CH.sub.3                                                H HE-(54)  ##STR613##                H      CO.sub.2 C.sub.2 H.sub.5                                             H  H HE-(55)  ##STR614##                H      CO.sub.2 C.sub.2 H.sub.5                                             H  H HE-(56)  ##STR615##                H      H         H  H HE-(57)  ##STR616##                H                                    ##STR617##                                             H  H HE-(58)  ##STR618##                H      CHCHCH.sub.3                                             H  H HE-(59)  ##STR619##                H      OCH.sub.3 H  H H__________________________________________________________________________ 
    
     Those having the following formula [IE]-V: 
     
         __________________________________________________________________________ ##STR620##CompoundNo.   A                           Q.sub.1 Q.sub.2     Q.sub.3                                                    Y.sub.1                                                        Y.sub.2__________________________________________________________________________E-(60)  ##STR621##                 H       H           H  H   HE-(61)  ##STR622##                              ##STR623##                                      ##STR624## H  H   HE-(62)  ##STR625##                              ##STR626##                                      ##STR627## H  CH.sub.3                                                        HE-(63)  ##STR628##                 H       H           H  H   HE-(64)  ##STR629##                 H       CHCHCH.sub.3                                                 H  H   HE-(65)  ##STR630##                 H                                      ##STR631## H  H   HE-(66)  ##STR632##                 H       H           H  OCH.sub.3                                                        HE-(67)  ##STR633##                 H       H           H  H   HE-(68)  ##STR634##                 H       H           H  H   HE-(69)  ##STR635##                 H       CH.sub.3    CH.sub.3                                                    H   HE-(70)  ##STR636##                 H       CH.sub.3    CH.sub.3                                                    H   HE-(71)  ##STR637##                 H       CH.sub.3    CH.sub.3                                                    H   HE-(72)  ##STR638##                 H       H           H  H   HE-(73) &#34;                           H                                      ##STR639## H  H   HE-(74)  ##STR640##                 H       H           H  H   HE-(75)  ##STR641##                 H       OC.sub.2 H.sub.5                                                 H  H   HE-(76)  ##STR642##                 H       H           H  H   HE-(77)  ##STR643##                 H                                      ##STR644## H  H   HE-(78)  ##STR645##                 H                                      ##STR646## H  H   HE-(79)  ##STR647##                 H                                      ##STR648## H  H   H__________________________________________________________________________ 
    
     Those having the following formula [IE]-VI: 
     
         __________________________________________________________________________ ##STR649##CompoundNo.   A                          Q.sub.1                               Q.sub.2   Q.sub.3                                            Y.sub.1__________________________________________________________________________E-(80)  ##STR650##                H  H         H  HE-(81)  ##STR651##                H                                ##STR652##                                         H  HE-(82)  ##STR653##                H                                ##STR654##                                         H  HE-(83)  ##STR655##                H  H         H  HE-(84)  ##STR656##                H  CO.sub.2 CH.sub.3                                         H  HE-(85)  ##STR657##                H  CO.sub.2 CH.sub.3                                         H  HE-(86)  ##STR658##                H  H         H  HE-(87)  ##STR659##                H  CH.sub.3  CH.sub.3                                            HE-(88)  ##STR660##                CH.sub.3                               CH.sub.3  CH.sub.3                                            HE-(89)  ##STR661##                H  H         H  HE-(90)  ##STR662##                H  H         H  HE-(91)  ##STR663##                H  H         H  HE-(92)  ##STR664##                H  CHCHCH.sub.3                                         H  HE-(93)  ##STR665##                H                                ##STR666##                                         H  HE-(94)  ##STR667##                H                                ##STR668##                                         H  HE-(95)  ##STR669##                H  H         H  HE-(96)  ##STR670##                H  H         H  HE-(97)  ##STR671##                H                                ##STR672##                                         H  HE-(98)  ##STR673##                H                                ##STR674##                                         H  HE-(99)  ##STR675##                H                                ##STR676##                                         H  H__________________________________________________________________________ 
    
     Others: ##STR677## 
     The above azo compounds of this invention have excellent photoconductivity and, when a photoreceptor is to be prepared by use of this, it can be prepared by providing a photosensitive member dispersing the azo compound of this invention in a binder on an electroconductive support. A particularly excellent effect can be obtained when the photoreceptor of the so-called function separation type is constituted by use of the azo compound of this invention as the carrier generating material through utilization of the particularly excellent carrier generating ability of the photoconductivity possessed by the azo compound of this invention, together with a carrier transporting material which can act effectively in combination therewith. The function separation type photoreceptor may be a dispersion type, but it is more preferred to be a lamination type photoreceptor in which the carrier generating layer containing the carrier generating material and the carrier transporting layer containing the carrier transporting material are laminated. 
     The azo compound to be used invention may be employed either alone or as a combination of two or more compounds selected from the azo compounds represented by the above formula [I], or it can also be used in combination with other azo compounds. 
     Various forms have been known for mechanical constitution of photoreceptors, and any one of them can be used for the photoreceptor of this invention. 
     Generally, photoreceptors take the forms as shown in FIGS. 1 through 6. In FIG. 1 and FIG. 3, a photosensitive layer comprising a laminated product of a carrier generating layer 2 containing the above-described azo compound as the main component and a carrier transporting layer 3 containing a carrier transporting material as the main component is provided on an electroconductive support 1. As shown in FIG. 2 and FIG. 4, the photosensitive layer 4 may be provided also through an intermediate layer 5 provided on the electroconductive support. A photoreceptor with the most excellent electrophotographic characteristics can be obtained when the photosensitive layer 4 is thus constituted of the two layers. Also, in the present invention, as shown in FIG. 5 and FIG. 6, a photosensitive layer 4 comprising the above carrier generating material 7 dispersed in the layer 6 containing the carrier transporting material as the main component directly or through the intermediate layer 5. 
     When the azo compound of this invention is employed as the carrier generating material, the carrier transporting material which can be used in combination therewith may include, for example, electron acceptors which can readily transport electrons such as trinitrofluorenone or tetranitrofluorenone, and otherwise electron donors which can readily transport positive holes such as polymers having heterocyclic compounds as the side chains, typically poly-N-vinylcarbazole, triazole derivatives, oxadiazole derivatives, imidazole derivatives, pyrazoline derivatives, polyarylalkane derivatives, phenylenediamine derivatives, hydrazone derivatives, amino-substituted chalcone derivatives, triarylamine derivatives, carbazole derivatives, stilbene derivatives, and phenothiazine derivatives, but the carrier transporting material to be used in the present invention is not limited to these. 
     The carrier generating layer 2 constituting the photosensitive layer 4 with a double-layer constitution may be formed directly on the electroconductive support 1 or the carrier transporting layer 3, or on the intermediate layer such as an adhesive layer or a barrier layer optionally provided, according to the method as described below. 
     (M-1) The method in which a solution of an azo compound dissolved in an appropriate solvent, optionally mixed and dissolved with a binder, is coated. 
     (M-2) The method in which an azo compound is micropulverized in a dispersing medium by means of a ball mill or a homomixer, optionally together with a binder, and the resultant dispersion is coated. 
     The solvent or dispersing medium to be used for formation of the carrier generating layer may include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N,N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, 1,2-dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, etc. 
     When a binder is used in the carrier generating layer or the carrier transporting layer, any kind of materials may be available, but it is preferred to employ a film-forming polymer which is hydrophobic, high in dielectric constant and electrically insulating. Such polymers may include those as enumerated below, which are not limitative of this invention. 
     (P-1) Polycarbonate; 
     (P-2) Polyester; 
     (P-3) Methacrylic resin; 
     (P-4) Acrylic resin; 
     (P-5) Polyvinyl chloride; 
     (P-6) Polyvinylidene chloride; 
     (P-7) Polystyrene; 
     (P-8) Polyvinyl acetate; 
     (P-9) Styrene-butadiene copolymer; 
     (P-10) Vinylidene chloride-acrylonitrile copolymer; 
     (P-11) Vinyl chloride-vinyl acetate copolymer; 
     (P-12) Vinyl chloride-vinyl acetate-maleic anhydride copolymer; 
     (P-13) Silicone resin; 
     (P-14) Silicone-alkyd resin; 
     (P-15) Phenol-formaldehyde resin; 
     (P-16) Styrene-alkyd resin; 
     (P-17) Poly-N-vinylcarbazole. 
     These binders may be used either singly or as a mixture of two or more species. 
     The carrier generating layer 2 thus formed may have a thickness preferably of 0.01 μm to 20 μm, more preferably of 0.05 μm to 5 μm. When the carrier generating layer or the photosensitive layer is a dispersion system, the azo compound should preferably have particle sizes of 5 μm or less, more preferably 1 μm or less. 
     The electroconductive support to be used for the photoreceptor of this invention may include a material selected from plates or drums of metals or alloys, or papers or plastic films made electroconductive by coating, vapor deposition or lamination of metal thin films or thin films of electroconductive compounds or alloys thereon. As the intermediate layer such as adhesive layer or barrier layer, in addition to the polymers to be used as the aforesaid binder, it is also possible to employ organic polymeric materials such as polyvinyl alcohol, ethyl cellulose, carboxymethyl cellulose, etc. or aluminum oxide. 
     The photoreceptor of this invention has a constitution as described above and is excellent in charging characteristic, sensitivity characteristic and image forming characteristic, particularly excellent in durability without fatigue deteriortion when used repeatedly, as can also clearly be seen from the Examples as hereinafter described. 
     This invention is described in detail by referring to the following examples, by which the embodiments of this invention are not limited. 
     EXAMPLE 1 
     To 110 ml of 1,2-dichloroethane were added 2 g of the exemplary compound A-(21) and 2 g of a polycarbonate resin &#34;Panlite L-1250&#34; (trade name, produced by Teijin Kasei K.K.) and dispersed therein in a ball mill for 12 hours. The resultant dispersion was applied on a polyester film with aluminum vapor deposited thereon to a dried film thickness of 1 μm to provide a carrier generating layer, followed further by coating thereon with a solution of 6 g of 1-phenyl-(p-methylstyryl)-5-(p-methoxyphenyl)-pyrazoline (having the formula K-(1) shown below) and 10 g of a polycarbonate resin &#34;Panlite L-1250&#34; dissolved in 110 ml of 1,2-dichloroethane to a dried film thickness of 15 μm to form a carrier transporting layer, thus preparing a photoreceptor of this invention. ##STR678## 
     By use of the photoreceptor as described above, the following characteristic evaluations were conducted by means of an electrical paper testing machine Model SP-428 produced by Kawaguchi Denki Seisakusho K.K. After charging at a charged voltage of -6 KV for 5 seconds, the member was left to stand in dark for 5 seconds and then irradiated with a halogen lamp light to the luminosity of 35 lux on the surface of the photoreceptor, and the dose required for attenuating the surface potential to the half value (half-reduction dosage) E 1/2  was determined. Also, the surface potential after exposure at a dose of 30 lux.sec (residual potential) V R  was determined. Further, similar measurements were repeated for 100 times. The results are shown in Table 1. 
     
                       TABLE 1______________________________________    First measurement                100th measurement______________________________________E.sub.1/2 (lux · sec)      1.5           1.5V.sub.R (V)      0             0______________________________________ 
    
     COMPARATIVE EXAMPLE 1 
     A photoreceptor for comparative purpose was prepared in the same manner as in Example 1 except for employing the bisazo compound L-(1) shown below as the carrier generating material. ##STR679## 
     For this photoreceptor for comparative purpose, measurements were conducted similarly as in Example 1 to obtain the results as shown in Table 2. 
     
                       TABLE 2______________________________________    First measurement                100th measurement______________________________________E.sub.1/2  (lux · sec)      9.5           12.3V.sub.R (V)      -25           -140______________________________________ 
    
     As apparently seen from the above results, the photoreceptor of this invention is very superior to the photoreceptor for comparative purpose with respect to sensitivity, residual potential and stability in repeated uses. 
     EXAMPLES 2-4 
     Using the exemplary compounds A-(5), A-(6) and A-(7) as the carrier generating material, and 6-methyl-1-(1-ethyl-4-carbazolyl)methylideneamino-1,2,3,4-tetrahydroquinoline (the compound K-(1) shown below), 1-(1-ethyl-4-carbazolyl)methylideneamino-1,2,3,4-tetrahydroquinoline (the compound K-(2) shown below) and 4,4&#39;-dimethyl-4&#34;-(4-chloro)-styryltriphenylamine (the compound K-(3) shown below), respectively, following otherwise the same procedure as described in Example 1, photoconductive members of this invention were prepared and subjected to similar measurements to obtain the results shown in Table 3. ##STR680## 
     
                       TABLE 3______________________________________Ex-              First measurement                          100th measurementam-              E.sub.1/2 (lux ·                            E.sub.1/2 (lux ·ple  Azo compound            sec)     V.sub.R (V)                            sec)   V.sub.R (V)______________________________________2    Exemplary   1.3      0      1.3    0compoundA - (5)3    Exemplary   1.4      0      1.4    0compoundA - (6)4    Exemplary   1.6      0      1.6    0compoundA - (7)______________________________________ 
    
     EXAMPLE 5 
     On an electroconductive support comprising a polyester film on which aluminum foil is laminated, an intermediate layer with a thickness of 0.05 μm comprising a vinyl chloride-vinyl acetate-maleic anhydride copolymer &#34;Ethlec MF-10&#34; (trade name, produced by Sekisui Kagaku K.K.) was provided, and on the intermediate layer was further formed a carrier generating layer by coating with a dispersion prepared by dispersing a mixture of 2 g of the exemplary compound A-(11) and 110 ml of 1,2-dichloroethane in a ball mill for 24 hours to a dried film thickness of 0.5 μm. On the carrier generating layer, a solution of 6 g of 3,3&#39;,4-trimethyl-triphenylamine and 10 g of a methacrylic resin &#34;Acrypet&#34; (trade name, produced by Mitsubishi Rayon K.K.) dissolved in 70 ml of 1,2-dichloroethane was applied to a dried film thickness of 10 μm to form a carrier transporting layer, thus preparing an electrophotographic photoreceptor of this invention. 
     For this photoreceptor, the same measurements as in Example 1 were conducted to obtain the results of E 1/2  =2.2 lux.sec and V R  =0 V. 
     EXAMPLE 6 
     On the electroconductive support having the intermediate layer employed in Example 5 provided thereon, a 1% solution of the exemplary compound A-(40) in ethylenediamine was applied to a dried film thickness of 0.3 μm to form a carrier generating layer. 
     Subsequently, on the carrier generating layer was further applied a solution of 6 g of 4-methoxy-4&#39;-styryltriphenylamine (the compound K-(5) shown below) and 10 g of a polyester resin &#34;Byron 200&#34; (trade name, produced by Toyo Boseki K.K.) dissolved in 70 ml of 1,2-dichloroethane to a dried film thickness of 12 μm to form a carrier transporting layer. Thus, a photosensitive member of this invention was prepared. ##STR681## 
     For this photoreceptor, the same measurements as in Example 1 were conducted to obtain the results as shown in Table 4. 
     COMPARATIVE EXAMPLE 2 
     Example 6 was repeated except for substituting the bisazo compound L-(2) represented by the formula shown below for the exemplary compound A-(32) to prepare an electrophotographic photoreceptor for comparative purpose. 
     For this photoreceptor, the same measurements as in Example 1 were conducted to obtain the results as shown in Table 4. ##STR682## 
     
                       TABLE 4______________________________________  First measurement                100th measurement  E.sub.1/2 (lux ·                    E.sub.1/2 (lux ·  sec)    V.sub.R (V)                    sec)      V .sub.R (V)______________________________________Example 6    1.5       0          1.6      0Comparative    7.0       0         11.3    -70example 2______________________________________ 
    
     EXAMPLE 7 
     A carrier generating layer was formed in the same manner as in Example 5 except for employing the exemplary compound A-(37) in place of the exemplary compound A-(11). On this layer was applied a solution of 6 g of 3-(p-methoxystyryl)-9-(p-methoxyphenyl)carbazole (Compound K-(6) shown below) and 10 g of a polycarbonate &#34;Panlite L-1250&#34; (trade name, produced by Teijin Kasei K.K.) dissolved in 70 ml of 1,2-dichloroethane to a dried film thickness of 10 μm to form a carrier transporting layer, thus preparing a photoreceptor of this invention. 
     For this photoreceptor, the same measurements as in Example 1 were conducted to obtain the results of E 1/2  =1.8 lux.sec and V R  =0 V. 
     EXAMPLE 8 
     On the surface of an aluminum drum of 100 mm in diameter was provided an intermediate layer with a thickness of 0.05 μm made of a vinyl choloride-vinyl acetate-maleic anhydride copolymer &#34;Ethlec MF-10&#34; (trade name, produced by Sekisui Kagaku K.K.), followed by coating thereon with a dispersion prepared by dispersing a mixture of 4 g of the exemplary compound A-(36) and 400 ml of 1,2-dichloroethane in a ball mill for 24 hours to a dried film thickness of 0.6 μm to form a carrier generating layer. 
     Further, on the carrier generating layer was applied a solution of 30 g of 3-(p-methoxystyryl)-9-(p-methoxyphenyl)carbazole (Compound K-(6) shown below) and 50 g of a polycarbonate resin &#34;Copiron S-1000&#34; (trade name, produced by Mitsubishi Gas Kagaku K.K.) dissolved in 400 ml of 1,2-dichloroethane to a dried film thickness of 13 μm to form a carrier transporting layer, thus preparing a drum-shaped electrophotographic photoreceptor. ##STR683## 
     The photoreceptor thus prepared was mounted on a modified electrophotographic copying machine &#34;U-Bix 1600 MR&#34; (trade name, produced by Konishiroku Photo Industry Co., Ltd.) and images were copied to obtain copied images which are high in contrast, faithful to original image and also clear. The quality was not changed at all even when repeated for 10,000 times. 
     COMPARATIVE EXAMPLE 3 
     A drum-shaped photoreceptor for comparative purpose was prepared similarly as in Example 8, except for using the triazo compound L-(3) represented by the structural formula shown below in place of the examplary compound A-(36), and the copied images were evaluated similarly as in Example 8. As the result, only images with much fogging were obtained. Further, as copying was repeated, the copied images were lowered in contrast, until substantially no copied image was obtained after repetition for 2,000 times. ##STR684## 
     EXAMPLE 9 
     On an electroconductive support comprising a polyester film on which aluminum foil is laminated, an intermediate layer with a thickness of 0.05 μm comprising a vinyl chloride-vinyl acetate-maleic anhydride copolymer &#34;Ethlec MF-10&#34; (trade name, produced by Sekisui Kagaku K.K.) was provided, and on the intermediate layer was further formed a carrier generating layer by coating with a dispersion prepared by dispersing a mixture of 5 g of the exemplary compound A-(17) and 3.3 g of a polycarbonate resin &#34;Panlite L-1250&#34; (trade name, produced by Teijin Kasei K.K.) in 100 ml of dichloromethane in a ball mill for 24 hours to a dried film thickness of 10 μm, to prepare a photoreceptor. 
     For the thus obtained photoreceptor, E 1/2  and V R  were measured similarly as in Example 1 except for changing the charging voltage to +6 KV. The results of the first measurement were E 1/2  =2.2 lux.sec and V R  =+5 V. 
     EXAMPLE 10 
     On a polyester film on which aluminum was vapor deposited, a solution of 6 g of of p-(N,N-diethylamino)-benzaldehyde-1,1-diphenylhydrazone and 10 g of a polyester resin &#34;Bryon 200&#34; (trade name, produced by Toyo Boseki K.K.) dissolved in 70 ml of 1,2-dichloroethane was applied as the carrier transporting layer to a dried film thickness of 10 μm. 
     Subsequently, on this layer was further formed a carrier generating layer by coating with a dispersion prepared by dispersing a mixture of 1 g of the exemplary compound A-(12) and 1 g of the exemplary compound A-(14) with 110 ml of 1,2-dichloroethane in a ball mill for 24 hours to a dried film thickness of 0.5 μm to prepare a photoreceptor of this invention. 
     The thus obtained photoreceptor was evaluated similarly as in Example 9 to obtain the results of E 1/2  =2.4 lux.sec and V R  =+5 V. 
     EXAMPLE 11 
     A 2% solution of the exemplary compound A-(10) in ethylenediamine was applied on a polyester film laminated with aluminum to a dried film thickness of 0.5 μm to form a carrier generating layer. Further, a carrier transporting layer was formed on the carrier generating layer by coating with a solution of about 10 g of 1-methyl-3-(p-diethylaminophenyl)-5-(p-diethylaminophenyl)pyrazoline (the compound K-(7) shown below), 1-phenyl-(p-methoxystyryl)-5-(p-diethylaminophenyl)pyrazoline (the compound K-(8) shown below) and 1-phenyl-(p-methylstyryl)-5-(p-methylphenyl)pyrazoline (the compound-(9) shown below) dissolved separately together with 14 g of a polycarbonate resin (trade name, Panlite L-1250, produced by Teijin Kasei K.K.) in 140 ml of 1,2-dichloromethane to a dried film thickness of 12 μm, followed by drying, to prepare photoreceptors with three kinds of different carrier transporting materials. ##STR685## 
     The three kinds of photoreceptors were subjected to the following characteristic evaluations by means of an electrical paper testing machine Model SP-428 produced by Kawaguchi Denki Seisakusho K.K. After charging at a charged voltage of -6 KV for 5 seconds, the member was left to stand in dark for 5 seconds and then irradiated with a halogen lamp light to the luminosity of 35 lux.on the surface of the photoreceptor, and the dose required for attenuating the surface potential to the half value (half-dosage) E 1/2  was determined. Also, the surface potential after exposure at a dose of 30 lux.sec (residual potential) V R  was determined. The results are shown in Table 5, which shows that good results can be obtained in each combination with any one of the carrier transporting materials. 
     
                       TABLE 5______________________________________Carrier transportingmaterial combinedwith exemplary com-pound A - (10)    E.sub.1/2 (lux · sec)                        V.sub.R (V)______________________________________K - (7)           1.3        0K - (8)           1.4        0K - (9)           1.5        0______________________________________ 
    
     COMPARATIVE EXAMPLE 4 
     A comparative photoreceptor was prepared in the same manner as in Example 11 except for substituting the bisazo compound shown below (L-(4)) for the exemplary compound A-(10) and subjected to characteristic evaluation. ##STR686## 
     As shown in Table 6, the results were found to be varied depending on the carrier transporting material. 
     
                       TABLE 6______________________________________Carrier transportingmaterial combinedwith the compoundL - (4)          E.sub.1/2 (lux · sec)                       V.sub.R (V)______________________________________K - (7)          4.1         2K - (8)          7.8        10K - (9)          12.3       50______________________________________ 
    
     EXAMPLE 12 
     On the electroconductive support having an intermediate layer provided thereon as employed in Example 5, a dispersion prepared by mixing well 2 g of the exemplary compound A-(2) and 100 ml of 1,2-dichloroethane was applied to a dried film thickness of 0.3 μm to prepare a carrier generating layer. 
     Subsequently, a carrier transporting layer was formed on the carrier generating layer by coating with a solution of carrier transporting materials of 6 g of 4-methyl-4&#39;-styryl-triphenylamine (the compound K-(10) shown below) and 10 g of a polycarbonate resin &#34;Panlite L-1250&#34; (trade name, produced by Teijin Kasei K.K.) dissolved in 90 g of 1,2-dichloroethane to a dried film thickness of 10 μm to prepare a photoreceptor of this invention. ##STR687## 
     For this photoreceptor, electrophotographic characteristics at room temperatures of 25° C. and 60° C. were measured similarly as in Example 7. The results are shown in Table 7. 
     
                       TABLE 7______________________________________        25° C.                60° C.______________________________________VA (V)         -890      -910E.sub.1/2  (lux · sec)          1.7       1.7V.sub.R (V)    0         0______________________________________ 
    
     As apparently seen from the above results, the electrophotographic photoreceptor has good sensitivity and residual potential characteristic even at higher temperature, indicating good stability to heat. 
     EXAMPLE 13 
     On the electroconductive support having an intermediate layer provided thereon as employed in Example 5, a dispersion prepared by mixing well 2 g of the exemplary compound A-(1) with 110 ml of 1,2-dichloroethane was applied to a dried film thickness of 0.3 μm to prepare a carrier generating layer. 
     For testing durability of the carrier generating layer against UV-ray, it was placed at a position at a distance of 30 cm from a ultra-high pressure mercury lamp (produced by Tokyo Shibaura Denki K.K.) and UV-ray was irradiated at 1500 cd/cm 3  for 10 minutes. 
     Next, a carrier transporting layer was formed on the UV-ray irradiated by coating with a solution of carrier transporting materials of 7 g of 4-methoxy-4&#39;-(4-methylstyryl)-triphenylamine (the compound K-(11) shown below) and 10 g of a polycarbonate resin (Panlite L-1250, trade name, produced by Teijin Kasei K.K.) dissolved in 90 g of 1,2-dichloroethane to a dried film thickness of 12 μm to prepare a photoreceptor of this invention. ##STR688## 
     For this photoreceptor, measurements were conducted similarly as in Example 5. The results are shown in Table 8. 
     EXAMPLE 14 
     Example 13 was repeated except for effecting no irradiation of UV-ray after formation of the carrier generating layer to prepare a photoreceptor, for which the same measurements as in Example 5 were conducted. The results are shown in Table 8. 
     
                       TABLE 8______________________________________        Example 13                Example 14______________________________________V.sub.A (V)    -1000     -980E.sub.1/2 (lux · sec)          1.4       1.3V.sub.R (V)       0        0______________________________________ 
    
     As apparently seen from the above results, it can be understood that the electrophotographic photoreceptor of this invention is excellent in sensitivity and residual potential characteristic relative to UV-ray irradiation, small in amount of variation of the receptor potential and also stable to light. 
     COMPARATIVE EXAMPLE 5 
     Photoreceptors were prepared in the same manner as in Example 13 and Example 14, except for changing the compound A-(1) to the bisazo compound (L-(5)) as shown below, and the same measurements as in Example 5 were conducted. ##STR689## 
     The results are shown in Table 9. 
     
                       TABLE 9______________________________________      With UV-ray               Without UV-ray      irradiation               irradiation______________________________________V.sub.A (V)  -1000      -920E.sub.1/2 (lux · sec)        12.6       9.3V.sub.R (V)   -14        -5______________________________________ 
    
     As apparently seen from the above results, the photoreceptor prepared by use of the above compound is deteriorated in sensitivity and residual potential characteristic by UV-ray irradiation with greater amount of variation of the receptor potential. 
     EXAMPLE 15 
     A drum-shaped photoreceptor was prepared in the same manner as in Example 5 except for using the exemplary compound A-(3) in place of the exemplary compound A-(11). The photoreceptor was found to have a spectral sensitivity of 0.42 μJ/cm 3  (half-reduction dosage). Practical copying test was conducted by means of a testing machine in which a semiconductor laser (780 nm) with a laser beam intensity of 0.85 mW on the surface of the photoreceptor of this invention was mounted. 
     After charging the surface of the photoreceptor to -6 KV, the member was exposed to laser beam and subjected to reversal development by a bias voltage of -250 V, whereby good images without fogging were obtained. 
     COMPARATIVE EXAMPLE 6 
     Example 15 was repeated except for employing the comparative bisazo compound L-(6) shown below in place of the exemplary compound A-(1) to obtain a comparative photoreceptor. ##STR690## 
     The photoreceptor was found to have a spectral sensitivity of 8.0 μJ/cm 3  (half-reduction dosage). When practical copying test by the semiconductor laser was conducted similarly as in Example 15, much fogging occurred to give no good image. 
     EXAMPLE 16 
     Example 1 was repeated except that the exemplary compound A-(21) was replaced with the exemplary compound B-(7) and 1-phenyl-(p-methylstyryl)-5-(p-methoxyphenyl)-pyrazoline with 1-(1-phenyl-4-carbazolyl)methylideneamino-1,2,3,4-tetra-hydroquinoline (having the formula K-(11) shown below). ##STR691## 
     The results are shown in Table 10. 
     
                       TABLE 10______________________________________    First measurement                100th measurement______________________________________E.sub.1/2 (lux · sec)      1.1           1.1V.sub.R (V)      0             0______________________________________ 
    
     COMPARATIVE EXAMPLE 7 
     A photoreceptor for comparative purpose was prepared in the same manner as in Example 16 except for employing the bisazo compound L-(7) shown below as the carrier generating material. ##STR692## 
     For this photoreceptor for comparative purpose, measurements were conducted similarly as in Example 16 to obtain the results as shown in Table 11. 
     
                       TABLE 11______________________________________    First measurement                100th measurement______________________________________E.sub.1/2 (lux · sec)      6.5           10.2V.sub.R (V)      -12           -100______________________________________ 
    
     As apparently seen from the above results, the photoreceptor of this invention is very superior to the photoreceptor for comparative purpose with respect to sensitivity, residual potential and stability in repeated uses. 
     EXAMPLES 17-19 
     Using the exemplary compounds B-(15), B-(17) and B-(18) as the carrier generating material, and 4-methoxy-4&#39;-(4-methoxy)styryl-triphenylamine (the compound K-(34) shown below), 4-methoxy-4&#39;-(4-methyl)styryl-triphenylamine (the compound K-(1) shown above) and 4-methoxy-4&#39;-styryl-triphenylamine (the compound K-(16) shown above), respectively, as the carrier transporting material following otherwise the same procedure as described in Example 16, photoconductive members of this invention were prepared and subjected to similar measurements to obtain the results shown in Table 12. ##STR693## 
     
                       TABLE 12______________________________________      First measurement                  100th measurement  Bisazo    E.sub.1/2 (lux ·                            E.sub.1/2 (lux ·Example  compound  sec)     V.sub.R (V)                            sec)   V.sub.R (V)______________________________________17     Exemplary 0.9      0      0.9    0  compound  B - (15)18     Exemplary 1.0      0      1.0    0  compound  B - (17)19     Exemplary 1.1      0      1.1    0  compound  B - (18)______________________________________ 
    
     EXAMPLE 20 
     Example 5 was repeated except that the exemplary compound A-(11) was replaced with the exemplary compound B-(32) and 3,3&#39;,4-trimethyl-triphenylamine with 4-methyl-4&#39;-styryl-triphenylamine. 
     For this photoreceptor, the same measurements as in Example 16 were conducted to obtain the results of E 1/2  =1.0 lux.sec and V R  =0 V. 
     EXAMPLE 21 
     Example 6 was repeated except that the exemplary compound A-(40) was replaced with the exemplary compound B-(65), and 4-methoxy-4&#39;-styryl-triphenylamine with 1-[4-(N,N-diethylamino)benzylidene]-amino-1,2,3,4-tetrahydroquinoline (the compound K-(15) shown below) to obtain the results shown in Table 13. ##STR694## 
     COMPARATIVE EXAMPLE 8 
     Example 21 was repeated except for substituting the bisazo compound L-(8) represented by the formula shown below for the exemplary compound B-(65) to prepare an electrophotographic photoreceptor for comparative purpose. ##STR695## 
     For this photoreceptor, the same measurements as in Example 16 were conducted to obtain the results as shown in Table 13. 
     
                       TABLE 13______________________________________  First measurement                100th measurement  E.sub.1/2 (lux ·                    E.sub.1/2 (lux ·  sec)    V.sub.R (V)                    sec)      V.sub.R (V)______________________________________Example 21    1.2       0          1.2      0Compara- 7.4       0         14.5    -40tiveexample 8______________________________________ 
    
     EXAMPLE 22 
     Example 7 was repeated except that the exemplary compound A-(37) was replaced with the exemplary compound B-(36) and 3-(p-methoxystyryl)-9-(p-methoxyphenyl)carbazone with 1-(1-ethyl-4-carbazolyl)methylideneamino-indoline (the compound K-(16) shown below) to prepare a photoreceptor of this invention. ##STR696## 
     For this photoreceptor, the same measurements as in Example 16 were conducted to obtain the results of E 1/2  =1.3 lux.sec and V 4  =0 V. 
     EXAMPLE 23 
     Example 8 was repeated except that the exemplary compound A-(36) was replaced with the exemplary compound B-(26), and 3-(p-methoxystyryl)-9-(p-methoxyphenyl)carbazone with 4,4&#39;-dimethyl-4&#34;-(4-methoxy)styryl-triphenylamine (the compound K-(17) shown below). Similar results as in Example 8 were obtained. ##STR697## 
     COMPARATIVE EXAMPLE 9 
     Example 23 was repeated except for using the bisazo compound L-(9) represented by the structural formula shown below in place of the exemplary compound B-(26), and the copied images were evaluated similarly as in Example 23. As the result, only images with much fogging were obtained. Further, as copying was repeated, the copied images were lowered in contrast, until substantially no copied image was obtained after repetition for 2,000 times. ##STR698## 
     EXAMPLE 24 
     Example 9 was repeated except that exemplary compound A-(17) was replaced with the exemplary compound B-(74) to prepare a photoreceptor. 
     For the thus obtained photoreceptor, E 1/2  and V R  were measured similarly as in Example 16 except for changing the charging voltage to +6 KV. The results of the first measurement were E 1/2  =2.0 lux.sec and V R  =0 V. 
     EXAMPLE 25 
     Example 10 was repeated except that p-(N,N-diethylamino)-benzaldehyde-1,1-diphenylhydrazone was replaced with 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazolone (the compound K-(18) shown below), and the exemplary compound A-(12) and A-(14) were replaced with the exemplary compounds B-(9) and B-(10), respectively. ##STR699## 
     The thus obtained photoreceptor was evaluated similarly as in Example 24 to obtain the results of E 1/2  =1.7 lux.sec and V R  =+5 V. 
     EXAMPLE 26 
     On an electroconductive support having aluminum foil laminated on a polyester film was provided an intermediate layer with a thickness of 0.05 μm made of a vinyl choloride-vinyl acetate-maleic anhydride copolymer &#34;Ethlec MF-10&#34; (trade name, produced by Sekisui Kagaku K.K.), followed by coating thereon with a dispersion prepared by dispersing a mixture of 4 g of the exemplary compound B-(54) and 8 g of 4-methoxy-4&#39;-methyl-4&#34;-(4-methyl)styryl-triphenylamine (the compound K-(19) shown below), 3 g of a polycarbonate resin &#34;Panlite L-1250&#34; (trade name, produced by Teijin Kasei K.K.) in 100 ml of dichloroethane in a sand grinder for 24 hours to prepare a photoreceptor. ##STR700## 
     For this photoreceptor, E 1/2  and V R  were measured in the same manner as in Example 16 except for changing the charged voltage to +6 KV to obtain the results of the first measurement of E 1/2  =1.0 lux.sec and V R  =0 V. 
     EXAMPLE 27 
     Example 11 was repeated except that the exemplary compound A-(10) was replaced with the exemplary compound B-(66), 1-methyl-3-(p-diethylaminophenyl)-5-(p-diethylaminophenyl)pyrazoline with 4-methoxy-4&#39;-(4-chloro)styryl-triphenylamine (the compound K-(20) shown below), 1-phenyl-(p-methoxystyryl)-5-(p-diethylaminophenyl)pyrazoline with 4,4&#39;-dimethyl-4&#34;-(4-bromo)styryltriphenylamine (the compound K-(21) shown below) and 1-phenyl-(p-methylstyryl)-5-(p-methylphenyl)pyrazoline with 4-(4-octyl)-styryl-triphenylamine (the compound K-(22) shown below) to obtain the results shown in Table 14. ##STR701## 
     
                       TABLE 14______________________________________Carrier transportingmaterial combinedwith exemplarycompound B - (66)            E.sub.1/2 (lux · sec)                       V.sub.R (V)______________________________________K - (20)         1.1        0K - (21)         1.0        0K - (22)         0.9        0______________________________________ 
    
     COMPARATIVE EXAMPLE 10 
     A comparative photoreceptor was prepared in the same manner as in Example 27 except for substituting the bisazo compound shown below (L-(10)) shown below for the exemplary compound B-(66) and subjected to characteristic evaluation. ##STR702## 
     As shown in Table 15, the results were found to be varied depending on the carrier transporting material. 
     
                       TABLE 15______________________________________Carrier transportingmaterial combinedwith the compoundL - (10)         E.sub.1/2 (lux · sec)                       V.sub.R (V)______________________________________K - (20)         16.7       40K - (21)         11.2       20K - (22)          6.2        7______________________________________ 
    
     EXAMPLE 28 
     Example 12 was repeated except that the exemplary compound A-(2) was replaced with the exemplary compound B-(59), and 4-methyl-4&#39;-styryl-triphenylamine with 4-methoxytriphenylamine (the compound K-(23) shown below) to obtain the results shown in Table 16. ##STR703## 
     
                       TABLE 16______________________________________          25° C.                60° C______________________________________V.sub.A (V)      -1000   -1010E.sub.1/2 (lux · sec)            1.0     1.0V.sub.R (V)         0       0______________________________________ 
    
     As apparently seen from the above results, the electrophotographic photoreceptor has good sensitivity and residual potential characteristic even at higher temperature, indicating good stability to heat. 
     EXAMPLE 29 
     Example 13 was repeated except that the exemplary compound A-(1) was replaced with the exemplary compound B-(3), and 4-methoxy-4&#39;-(4-methoxystyryl)-triphenylamine with 3-(p-methoxystyryl)-9-(p-methoxy-phenyl)carbazole (the compound K-(24) shown below), to obtain the results as shown in Table 17. ##STR704## 
     EXAMPLE 30 
     Example 29 was repeated except for effecting no irradiation of UV-ray after formation of the carrier generating layer to obtain the results shown in Table 17. 
     
                       TABLE 17______________________________________        Example 29                Example 30______________________________________V.sub.A (V)    -960      -940E.sub.1/2 (lux · sec)          1.1       1.1V.sub.R (V)      0         0______________________________________ 
    
     As apparently seen from the above results, it can be understood that the electrophotographic photoreceptor of this invention is excellent in sensitivity and residual potential characteristic relative to UV-ray irradiation, small in amount of variation of the receptor potential and also stable to light. 
     COMPARATIVE EXAMPLE 11 
     Photoreceptors were prepared in the same manner as in Example 29 and Example 30, except for changing the compound B-(3) to the bisazo compound (L-(11)) as shown below, and the same measurements as in Example 20 were conducted. ##STR705## 
     The results are shown in Table 18. 
     
                       TABLE 18______________________________________      With UV-ray               Without UV-ray      irradiation               irradiation______________________________________VA (V)       -910       -900E.sub.1/2 (lux · sec)        13.1       6.0V.sub.R (V)   -25        -5______________________________________ 
    
     As apparently seen from the above results, the photoreceptor prepared by use of the above compound is deteriorated in sensitivity and residual potential characteristic by UV-ray irradiation with greater amount of variation of the receptor potential. 
     EXAMPLE 31 
     Example 20 was repeated except for using the exemplary compound B-(1) in place of the exemplary compound B-(32). The drum-shaped photoreceptor obtained was found to have a spectral sensitivity at 9 nm of 950 volt.cm 2 .μW -1 .sec -1  (half-reduction rate). Copying test was conducted by means of a testing machine in which a semiconductor laser (9 nm) was mounted to give a laser beam intensity of 0.85 mW on the surface of the photoreceptor of this invention. 
     After charging the surface of the photoreceptor to -6 KV, the member was subjected to exposure to laser beam, followed by reversal development with a bias voltage of -250 V, whereby good images without fogging were obtained. 
     COMPARATIVE EXAMPLE 12 
     Example 31 was repeated except for employing the comparative bisazo compound L-(12) shown below in place of the exemplary compound B-(1) to obtain a comparative photoreceptor. ##STR706## 
     The photoreceptor was found to have a spectral sensitivity at 9 nm of 50 volt.cm 2 .μW -1 .sec -1  (half-reduction rate). When copying test by the semiconductor laser was conducted similarly as in Example 29, much fogging occurred to give no good image. 
     EXAMPLES 32-45 
     In Example 20, the exemplary compound B-(32) (charge generating material) and 4-methyl-4&#39;-styryl-triphenylamine (charge transporting material) were changed, respectively, to those as shown in Table 19, under otherwise the same conditions to prepare drum-shaped photoreceptors. These photoreceptors were found to have spectral sensitivities at 790 nm as shown in Table 19. In any of the copying tests conducted similarly as in Example 31 by use of these photoreceptors (Examples 32 to 45), good images without fog were obtained. 
     
                       TABLE 19______________________________________                             Spectral                             sensitivityExample Charge generat-                Charge transport-                             volt · cm.sup.2 ·No.     ing material ing material μW.sup.-1 · sec.sup.-1______________________________________Example 32   Exemplary com-                Compound K-(25)                             950   pound B-(5)Example 33   Exemplary com-                Compound K-(26)                             880   pound (B-6)Example 34   Exemplary com-                Compound K-(27)                             1020   pound (B-12)Example 35   Exemplary com-                Compound K-(28)                             990   pound (B-13)Example 36   Exemplary com-                Compound K-(29)                             900   pound (B-14)Example 37   Exemplary com-                Compound K-(30)                             800   pound (B-19)Example 38   Exemplary com-                Compound K-(31)                             780   pound (B-20)Example 39   Exemplary com-                Compound K-(32)                             990   pound (B-21)Example 40   Exemplary com-                Compound K-(33)                             1000   pound (B-22)Example 41   Exemplary com-                Compound K-(34)                             920   pound (B-23)Example 42   Exemplary com-                Compound K-(35)                             930   pound (B-24)Example 43   Exemplary com-                Compound K-(36)                             940   pound (B-25)Example 44   Exemplary com-                Compound K-(37)                             620   pound (B-78)Example 45   Exemplary com-                Compound K-(38)                             710   pound (B-111)______________________________________ ##STR707## 
    
     EXAMPLES 46-47 
     Using the exemplary compounds C-(70) and C-(10) as the carrier generating material, and the compounds shown below K-(39) and K-(40), respectively, as the carrier transporting material following otherwise the same procedure as described in Example 46, photoconductive members of this invention were prepared and subjected to similar measurements to obtain the results shown in Table 20. ##STR708## 
     
                       TABLE 20______________________________________      First measurement                  100th measurement  Bisazo    E.sub.1/2 (lux ·                            E.sub.1/2  (lux ·Example  compound  sec)     V.sub.R (V)                            sec)   V.sub.R (V)______________________________________46     Exemplary 1.2      0      1.2    0  compound  C - (70)47     Exemplary 1.5      0      1.5    0  compound  C - (10)______________________________________ 
    
     EXAMPLE 48 
     Example 7 was repeated except that the exemplary compound A-(37) was replaced with the exemplary compound C-(59) and the compound K-(41) shown below was employed as the carrier transporting material to prepare a photoreceptor of this invention. ##STR709## 
     For this photoreceptor, the same measurements as in Example 91 were conducted to obtain the results of E 1/2  =1.5 lux.sec and V R  =0 V. 
     EXAMPLE 49 
     Example 12 was repeated except that the exemplary compound A-(2) was replaced with the exemplary compound C-(61) and the compound K-(42) shown below was used as the carrier transporting material to obtain the results shown in Table 21. ##STR710## 
     
                       TABLE 21______________________________________          25° C.                60° C.______________________________________VA (V)           -990    -1010E.sub.1/2 (lux · sec)            1.0     1.0V.sub.R (V)        0        0______________________________________ 
    
     As apparently seen from the above results, the electrophotographic photoreceptor has good sensitivity and residual potential characteristic even at higher temperature, indicating good stability to heat. 
     EXAMPLE 50 
     Example 13 was repeated except that the exemplary compound A-(1) was replaced with the exemplary compound C-(53) and the compound K-(43) shown below was employed as the carrier transporting material to obtain the results as shown in Table 22. ##STR711## 
     EXAMPLE 51 
     Example 50 was repeated except for effecting no irradiation of UV-ray after formation of the carrier generating layer to obtain the results shown in Table 22. 
     
                       TABLE 22______________________________________        Example 50                Example 51______________________________________VA (V)         -950      -920E.sub.1/2 (lux · sec)          1.3       1.3V.sub.R (V)      0         0______________________________________ 
    
     As apparently seen from the above results, it can be understood that the electrophotographic photoreceptor of this invention is excellent in sensitivity and residual potential characteristic relative to UV-ray irradiation, small in amount of variation of the receptor potential and also stable to light. 
     COMPARATIVE EXAMPLE 13 
     Photoreceptors were prepared in the same manner as in Example 50 and Example 51, except for changing the compound C-(53) to the bisazo compound (L-(13)) as shown below, and the same measurements as in Example 20 were conducted. ##STR712## 
     The results are shown in Table 23. 
     
                       TABLE 23______________________________________      With UV-ray               Without UV-ray      irradiation               irradiation______________________________________VA (V)       -850       -800E.sub.1/2 (lux · sec)        11.3       3.7V.sub.R (V)   -20        -5______________________________________ 
    
     As apparently seen from the above results, the photoreceptor prepared by use of the above compound is deteriorated in sensitivity and residual potential characteristic by UV-ray irradiation with greater amount of variation of the receptor potential. 
     EXAMPLE 52 
     Example 5 was repeated except for using the exemplary compound A-(11) in place of the exemplary compound C-(63). The drum-shaped photoreceptor obtained was found to have a spectral sensitivity at 790 nm of 920 volt.cm 2 .μW -1 .sec -1  (half-reduction rate). Copying test was conducted by means of a testing machine in which a semiconductor laser (790 nm) was mounted to give a laser beam intensity of 0.85 nW on the surface of the photoreceptor of this invention. 
     After charging the surface of the photoreceptor to -6 KV, the member was subjected to exposure to laser beam, followed by reversal development with a bias voltage of -250 V, whereby good images without fogging were obtained. 
     COMPARATIVE EXAMPLE 14 
     Example 52 was repeated except for employing the comparative bisazo compound L-(14) shown below in place of the exemplary compound C-(63) to obtain a comparative photoreceptor. ##STR713## 
     The photoreceptor was found to have a spectral sensitivity at 790 nm of 50 volt.cm 2 .μW -1 .sec -1  (half-reduction rate). When copying test by the semiconductor laser was conducted similarly as in Example 106, much fogging occurred to give no good image. 
     EXAMPLES 53-57 
     In Example 5, the exemplary compound A-(11) (charge generating material) and the compound for charge transporting material were changed, respectively, to those as shown in Table 24, under otherwise the same conditions to prepare drum-shaped photoreceptors. These photoreceptors were found to have spectral sensitivities at 790 nm as shown in Table 24. In any of the copying tests conducted similarly as in Example 52 by use of these photoreceptors (Examples 53-57), good images without fog were obtained. 
     
                       TABLE 24______________________________________                             Spectral                             sensitivityExample Charge generat-                Charge transport-                             volt · cm.sup.2 ·No.     ing matertial                ing material μW.sup.-1 · sec.sup.-1______________________________________Example 53   Exemplary com-                Compound K-(44)                             900   pound C-(8)Example 54   Exemplary com-                Compound K-(45)                             800   pound C-(15)Example 55   Exemplary com-                Compound K-(46)                             720   pound C-(18)Example 56   Exemplary com-                Compound K-(47)                             730   pound C-(26)Example 57   Exemplary com-                Compound K-(48)                             980   pound C-(37)______________________________________ ##STR714## 
    
     EXAMPLES 58-59 
     Using the exemplary compounds D-(56) and D-(2) as the carrier generating material, and the compounds shown below K-(49) and K-(50), respectively, as the carrier transporting material following otherwise the same procedure as described in Example 1, photoconductive members of this invention were prepared and subjected to similar measurements to obtain the results shown in Table 25. ##STR715## 
     
                       TABLE 25______________________________________      First measurement                  100th measurement  Bisazo    E.sub.1/2 (lux ·                            E.sub.1/2 (lux ·Example  compound  sec)     V.sub.R (V)                            sec)   V.sub.R (V)______________________________________49     Exemplary 1.4      0      1.4    0  compound  D - (56)50     Exemplary 1.5      0      1.5    0  compound  D - (2)______________________________________ 
    
     EXAMPLE 60 
     Example 9 was repeated except that exemplary compound A-(17) was replaced with the exemplary compound D-(35) to prepare a photoreceptor. 
     For the thus obtained photoreceptor, E 1/2  and V R  were measured similarly as in Example 1 except for changing the charging voltage to +6 KV. The results of the first measurement were E 1/2  =1.8 lux.sec and V R  =+5 V. 
     EXAMPLE 61 
     Example 10 was repeated except that the compound K-(51) shown below was employed as the carrier transporting material, and the exemplary compound D-(57) and the following bisazo compound were employed as the carrier generating materials, respectively. ##STR716## 
     The thus obtained photoreceptor was evaluated similarly as in Example 60 to obtain the results of E 1/2  =2.0 lux.sec and V R  =+7 V. 
     EXAMPLES 62-65 
     In Example 5, the exemplary compound A-(5) (charge generating material) and the compound for charge transporting material were changed, respectively, to those as shown in Table 26, under otherwise the same conditions to prepare drum-shaped photoreceptors. These photoreceptors were found to have spectral sensitivities at 790 nm as shown in Table 26. In any of the copying tests conducted similarly as in Example 5 by use of these photoreceptors (Examples 62-65), good images without fog were obtained. 
     
                       TABLE 26______________________________________                             Spectral                             sensitivityExample Charge generat-                Charge transport-                             volt · cm.sup.2 ·No.     ing material ing material μW.sup.-1 · sec.sup.-1______________________________________Example 62   Exemplary com-                Compound K-(52)                             1020   pound D-(4)Example 63   Exemplary com-                Compound K-(53)                             970   pound D-(7)Example 64   Exemplary com-                Compound K-(54)                             960   pound D-(15)Example 65   Exemplary com-                Compound K-(55)                             880   pound D-(23)______________________________________ ##STR717## 
    
     EXAMPLE 66 
     Example 9 was repeated except that exemplary compound A-(17) was replaced with the exemplary compound E-(27) to prepare a photoreceptor. 
     For the thus obtained photoreceptor, E 1/2  and V R  were measured similarly as in Example 1 except for changing the charging voltage to +6 KV. The results of the first measurement were E 1/2  =1.7 lux.sec and V R  =+4 V. 
     EXAMPLE 67 
     Example 11 was repeated except that the exemplary compound A-(10) was replaced with the exemplary compound E-(35), and the carrier transporting materials were changed to the compounds shown below K-(56), K-(57) and K-(58), respectively, to obtain the results shown in Table 27. ##STR718## 
     
                       TABLE 27______________________________________Carrier transportingmaterial combinedwith exemplarycompound E - (35)            E.sub.1/2 (lux · sec)                       V.sub.R (V)______________________________________K - (56)         1.8        0K - (57)         1.5        0K - (58)         1.1        0______________________________________ 
    
     COMPARATIVE EXAMPLE 15 
     A comparative photoreceptor was prepared in the same manner as in Example 67 except for substituting the bisazo compound shown below (L-(15)) shown below for the exemplary compound E-(35) and subjected to characteristic evaluation. ##STR719## 
     As shown in Table 27, the results were found to be varied depending on the carrier transporting material. 
     
                       TABLE 27______________________________________Carrier transportingmaterial combinedwith the compoundL - (15)         E.sub.1/2 (lux · sec)                       V.sub.R (V)______________________________________K - (56)         10.1       33K - (57)         7.8        24K - (58)         5.7        15______________________________________ 
    
     EXAMPLE 68 
     Example 12 was repeated except that the exemplary compound A-(2) was replaced with the exemplary compound E-(72) and the compound K-(59) shown below was used as the carrier transporting material to obtain the results shown in Table 28. ##STR720## 
     
                       TABLE 28______________________________________          25° C.                60° C.______________________________________VA (V)           -1020   -1040E.sub.1/2 (lux · sec)            1.3     1.3V.sub.R (V)         0       0______________________________________ 
    
     As apparently seen from the above results, the electrophotographic photoreceptor has good sensitivity and residual potential characteristic even at higher temperature, indicating good stability to heat. 
     EXAMPLE 69 
     Example 13 was repeated except that the exemplary compound A-(1) was replaced with the exemplary compound E-(57) and the compound K-(60) shown below was employed as the carrier transporting material to obtain the results as shown in Table 29. ##STR721## 
     EXAMPLE 70 
     Example 69 was repeated except for effecting no irradiation of UV-ray after formation of the carrier generating layer to obtain the results shown in Table 29. 
     
                       TABLE 29______________________________________        Example 69                Example 70______________________________________VA (V)         -980      -950E.sub.1/2 (lux · sec)          1.3       1.3V.sub.R (V)      0         0______________________________________ 
    
     As apparently seen from the above results, it can be understood that the electrophotographic photoreceptor of this invention is excellent in sensitivity and residual potential characteristic relative to UV-ray irradiation, small in amount of variation of the receptor potential and also stable to light. 
     COMPARATIVE EXAMPLE 16 
     Photoreceptors were prepared in the same manner as in Example 69 and Example 70, except for changing the compound E-(57) to the bisazo compound (L-(16)) as shown below, and the same measurements as in Example 5 were conducted. ##STR722## 
     The results are shown in Table 30. 
     
                       TABLE 30______________________________________      With UV-ray               Without UV-ray      irradiation               irradiation______________________________________VA (V)       -950       -920E.sub.1/2 (lux · sec)        -9.8       -5.1V.sub.R (V)   -40        -21______________________________________ 
    
     As apparently seen from the above results, the photoreceptor prepared by use of the above compound is deteriorated in sensitivity and residual potential characteristic by UV-ray irradiation with greater amount of variation of the receptor potential. 
     EXAMPLES 71-75 
     In Example 5, the exemplary compound A-(11) (charge generating material) and the compound for charge transporting material were changed, respectively, to those as shown in Table 31, under otherwise the same conditions to prepare drum-shaped photoreceptors. These photoreceptors were found to have spectral sensitivities at 790 nm as shown in Table 31. In any of the copying tests conducted similarly as in Example 5 by use of these photoreceptors (Examples 71-75), good images without fog were obtained. 
     
                       TABLE 31______________________________________                             Spectral                             sensitivityExample Charge generat-                Charge transport-                             volt · cm.sup.2 ·No.     ing material ing material μW.sup.-1 · sec.sup.-1______________________________________Example 71   Exemplary com-                Compound K-(61)                             1010   pound E-(1)Example 72   Exemplary com-                Compound K-(62)                             950   pound E-(14)Example 73   Exemplary com-                Compound K-(63)                             960   pound E-(30)Example 74   Exemplary com-                Compound K-(64)                             850   pound E-(33)Example 75   Exemplary com-                Compound K-(65)                             910   pound E-(33)______________________________________ ##STR723## 
    
     As apparently seen from the examples and comparative examples, the photoreceptors of this invention are markedly excellent in characteristics such as stability, sensitivity, durability, combiantion with a wide variety of carrier transporting materials. 
     By use of the azo compounds represented by the above formula [I] as the photoconductive material constituting the photosensitive layer of the photoreceptor according to this invention, it is possible to prepare a photoreceptor as intended by this invention, which is stable to heat and light, excellent in electrophotographic characteristics such as charge retentive force, sensitivity, residual potential, etc., also small in fatigue deterioration when used repeatedly, and further has sufficient sensitivity in the long wavelength region of 780 nm or longer.