Abstract:
The present invention provides electrophotographic sensitive materials having a high sensitivity as well as a high flexibility which comprise a conductive support and a photosensitive layer formed thereon, said photosensitive layer containing one disazo pigment, as an effective ingredient, which is selected from the group consisting of disazo pigments expressed by the following general formulas I, II, III, and IV, ##STR1## [(wherein A is selected from the group consisting of ##STR2## is selected from the group consisting of aromatic rings such as benzene ring, naphthalene ring, etc., hetero rings such as indole ring, carbazole ring, benzofuran ring, etc. and their substituents, Ar 1  is selected from the group consisting of aromatic rings such as benzene ring, naphthalene ring, etc., hetero rings such as dibenzofuran, etc. and their substituents, Ar 2  and Ar 3  are selected from the group consisting of aromatic rings such as benzene ring, naphthalene ring, etc. and their substituents, R 1  and R 3  are selected from the group consisting of hydrogen, lower alkyl radical or phenyl radical and their substituents and R 2  is selected from the group consisting of lower alkyl radical, carboxyl radical and their esters)].

Description:
This is a division, of application Ser. No. 925,157, filed July 17, 1978. 
    
    
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to electrophotographic sensitive materials, in particular novel sensitive materials which comprise a photosensitive layer containing a disazo pigment as an effective ingredient. 
     (b) Description of the Prior Art 
     As the electrophotographic sensitive material prepared by forming a photosensitive layer containing some azo pigment as an effective ingredient on a conductive support, one prepared by employing monoazo pigment (cf. Japanese Patent Publication No. 16474/1969), one prepared by employing benzidine-type disazo pigment (cf. U.S. Pat. No. 3,898,048 and U.S. Pat. No. 4,052,210), etc. are well known. These azo pigments are admittedly useful materials as an effective ingredient of the photosensitive layer as stated above, but when various requirements for photosensitive materials are taken into account from the viewpoint of the electrophotographic process, there has in fact not yet been obtained such a material as will sufficiently meet these requirements. Therefore, it is a matter of more importance to provide a wide variety of pigments, not limited to azo pigments, so as to afford a wide range of selection of pigments acting as an effective ingredient, thereby rendering it possible to provide a photosensitive material apposite to any specific process. In other words, it is desirable for the electrophotographic process that the variety of the pigments workable as an effective ingredient of photosensitive materials is as wide as possible. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide electrophotographic sensitive materials containing novel disazo pigments workable as an effective ingredient for a variety of electrophotographic processes. 
     A secondary object of the present invention is to provide electrophotographic sensitive materials which afford a wide range of selection of pigments workable as an effective ingredient. 
     Another object of the present invention is to provide electrophotographic sensitive materials having a high sensitivity as well as high flexibility and which contain the aforesaid disazo pigment. 
     In other words, the present invention provides electrophotographic sensitive materials characterized by having a photosensitive layer containing a disazo pigment, as an effective ingredient, which is selected from the group consisting disazo pigments expressed by the following general formulas I, II, III, and IV, ##STR3## [wherein A is selected from the group consisting of ##STR4## is selected from the group consisting of aromatic rings such as benzene ring, naphthalene ring, etc., hetero rings such as indole ring, carbazole ring, benzofuran ring, etc. and their substituents, Ar 1  is selected from the group consisting of aromatic rings such as benzene ring, naphthalene ring, etc., hetero rings such as dibenzofuran, etc. and their substituents, Ar 2  and Ar 3  are selected from the group consisting of aromatic rings such as benzene ring, naphthalene ring, etc. and their substituents, R 1  and R 3  are selected from the group consisting of hydrogen, lower alkyl radical or phenyl radical and their substituents and R 2  is selected from the group consisting of lower alkyl radical, carboxyl radical and their esters)]. 
     Hereinafter are shown concrete examples of the compounds expressed by the foregoing general formula I by means of structural formula. ##STR5## The portion ##STR6## being common to Compounds No. 2A-66A, is omitted and is expressed as --Y 1  -- in short hereinafter. ##STR7## 
     The disazo pigments expressed by the general formula I can be easily prepared through the process comprising first diazotizing the starting material 2,7-diaminofluoren-9-one which is readily available commercially or in accordance with conventional methods to precipitate tetrazonium salt and thereafter effecting coupling reaction of this tetrazonium salt with a coupler, such as Naphthol AS, corresponding to the aforedescribed various pigments within an appropriate organic solvent such as N,N-dimethyl formamide in the presence of alkali. For instance, the process of preparing the pigment No. 1A is as described in the following. Further, other disazo pigments can also be prepared by applying the same process excepting for changing the material used. 
     Preparation Example 
     5.5 g of 2,7-diaminofluoren-9-one is added to a dilute hydrochloric acid consisting of 46 ml of concentrated hydrochloric acid and 46 ml of water, and same is well stirred at 60° C. for about 30 minutes. Next, this mixture is cooled to about 0° C., and a solution obtained by dissolving 3.8 g of sodium nitrite in 6 ml of water is added dropwise to said mixture at a temperature of 0°-5° C. for about 30 minutes. Then, the same is stirred at the same temperature for about 30 minutes, a small amount of unreacted matter is filtered, the filtrate is poured in 40 ml of 42% borofluoric acid, the so separated crystals are removed by filtration, washed with water and dried to obtain 7.4 g (yield 70%) of cream-colored crystals of bisdiazonium-bistetrafluoroborate. Next, the thus obtained 2 g of bisdiazonium salt and 2.9 g of 2-hydroxy-3-phenylcarbamoyl naphthalene as a coupler are dissolved in 425 ml of cooled -N,N-dimethylformamide, a solution consisting of 4.1 g of sodium acetate and 60 ml of water is added dropwise thereto at a temperature of 4°-8° C. for 1 hour, and the same is stirred at room temperature for about 3 hours. Thereafter, precipitates are removed by filtration, washed 3 times with 300 ml of water, and further washed 7 times with 300 ml of N,N-dimethylformamide. Still residual N,N-dimethylformamide is washed away with acetone, and thus obtained golden-colored crystals are dried at 70° C. under reduced pressure of 2 mmHg to obtain 3 g (the yield 80%) of disazo pigment No. 1A. The melting point is over 300° C. 
     
         ______________________________________Elementary analysis (as C.sub.47 H.sub.30 N.sub.6 O.sub.5)      Calculated value                   Observed value______________________________________C (%)      74.39        74.01H (%)       3.99         4.06N (%)      11.08        11.39______________________________________IR Absorption Spectrum (NBr tablet)1675 cm.sup.-1    (Secondary amide)1720 cm.sup.-1    (Carbonyl)______________________________________ 
    
     Hereinafter will be shown concrete examples of compounds represented by the general formula II. ##STR8## The portion ##STR9## being common to Compounds No. 2B-66B, is omitted and represented as --Y 2  -- in short hereinafter. ##STR10## 
     The disazo pigments expressed by the general formula II can be easily prepared through the aforesaid process for preparing the disazo pigments expressed by the general formula I excepting the use of 3,7-diaminodibenzothiophene as the starting material. For instance, the process of preparing the pigment No. 1B is as described in the following. Further, other disazo pigments expressed by the general formula II can also be prepared in accordance with this preparation example excepting for changing the material used. Preparation Example 
     4.3 g of 3,7-diaminodibenzothiophene is added to a dilute hydrochloric acid consisting of 36 ml of concentrated hydrochloric acid and 36 ml of water, and same is well stirred at 60° C. for about 30 minutes. Next, this mixture is cooled to 0° C., and a solution obtained by dissolving 2.9 g of sodium nitrite in 10 ml of water is added dropwise to said mixture at a temperature of 0°-5° C. for about 30 minutes. Then, the same is stirred at the same temperature for about 30 minutes, a small amount of unreacted matter is filtrated, the filtrate is poured in 40 ml of 42% borofluoric acid, separated crystals are removed by filtration, washed with water and dried to obtain 80 g (the yield 98%) of yellow-colored crystals of bisdiazonium-distetrafluoroborate. The decomposition point is about 140° C. Next, the thus obtained 8.0 g bisdiazonium salt and 11.6 g of 2-hydroxy-3-phenylcarbamoyl naphthalene as a coupler are dissolved in 1.5 l of cooled N-N-dimethylformamide, a solution consisting of 16.4 g of sodium acetate and 160 ml of water is added dropwise thereto at a temperature of 4°-8° C. for 1 hour, and the same is stirred at room temperature for about 3 hours. Thereafter, precipitates are removed by filtration, washed 3 times with 500 ml of water, and further washed 8 times with 500 ml of N,N-dimethylformamide. Still residual N-N-dimethylformamide is washed away with acetone, and thus obtained pale and dark crystals are dried at 70° C. under reduced pressure of 2 mmHg to obtain 13.0 g (the yield 86%) of disazo pigment No. 1B. The melting point is over 300° C. 
     
         ______________________________________Elementary analysis results (as C.sub.46 H.sub.30 N.sub.8 O.sub.4 S)  Calculated value                 Observed value______________________________________C (%)    72.42            72.05H (%)    3.96             3.79N (%)    11.02            10.85IR Absorption Spectrum (KBr tablet)1680.sup.-1 (Secondary amide)______________________________________ 
    
     Hereinafter will be shown concrete examples of compounds expressed by the general formula III. ##STR11## The portion ##STR12## being common to Compounds No. 2C-66C, is omitted and represented as --Y 3  -- in short hereinafter. ##STR13## 
     The portion ##STR14## being common to Compounds No. 68C-C, is omitted and represented as --Z-- in short hereinafter. ##STR15## 
     The disazo pigments expressed by the general formula III can be easily prepared through the aforesaid process for preparing the disazo pigments expressed by the general formula I excepting the use of diamino derivatives of the corresponding stilbene as the starting material. For instance, the process of preparing the aforesaid pigment No. 1C is as described in the following. Further, other disazo pigments expressed by the general formula III can also be prepared in accordance with this preparation example excepting for changing the material used. 
     Preparation Example 1.5 g of 2,2&#39;-diaminostilbene is added to a dilute hydrochloric acid consisting of 12.6 ml of concentrated hydrochloric acid and 12.6 ml of water, and same is well stirred at 60° C. for about 30 minutes. Next, this mixture is cooled to about 0° C., and a solution obtained by dissolving 1.1 g of sodium nitrite in 1.7 ml of water is added dropwise to said mixture at a temperature of -1°˜0° C. for about 30 minutes. Then, the same is stirred at the same temperature for about 30 minutes, a small amount of unreacted matter is filtrated, the filtrate is poured in 11 ml of 42% borofluoric acid, the so separated crystals are removed by filtration, washed with water and dried to obtain 2.4 g (the yield 83%) of yellow-colored crystals of bisdiazonium-bistetrafluoroborate. The decomposition point is about 130° C. 
     Next, the thus obtained 2.0 g of bisdiazonium salt and 2.9 g of 2-hydroxy-3-phenylcarbamoylnaphthalene as a coupler are dissolved in 425 ml of cooled N,N-dimethylformamide, a solution consisting of 4.1 g of sodium acetate and 60 ml of water is added dropwise thereto at a temperature of 4°-8° C. for 1 hour, and then the same is stirred at room temperature for about 3 hours. Thereafter, precipitates are removed by filtration, washed 3 times with 300 ml of water, and further washed 8 times with 300 ml of N,N-dimethylformamide. Still residual N,N-dimethylformamide is washed away with acetone, and thus obtained pale and dark crystals are dried at 70° C. under reduced pressure of 2 mmHg to obtain 3.0 g (the yield 79%) of disazo pigment No. 1C. The melting point is over 300° C. 
     
         ______________________________________Elementary analysis (as C.sub.48 H.sub.34 N.sub.6 O.sub.4)    Calculated value               Observed value______________________________________C (%)      75.97        75.53H (%)      4.52         4.32N (%)      11.08        10.80IR Absorption Spectrum (KBr tablet)1680 cm.sup.-1 (Secondary amide)______________________________________ 
    
     Hereinafter will be shown concrete examples of compounds expressed by the general formula IV. ##STR16## The portion ##STR17## being common to Compounds No. 2D-66D, is omitted and represented as --Y 4  -- in short hereinafter. ##STR18## 
     The disazo pigments expressed by the general formula IV can be easily prepared through the aforesaid process for preparing the disazo pigment expressed by the general formula I excepting the use of 3,7-diaminodibenzothiophene-5,5-dioxide as the starting material. For instance, the process of preparing the aforesaid pigment No. 1D is as described in the following. Further, other disazo pigments expressed by the general formula IV can also be prepared in accordance with this preparation example excepting for changing the material used. 
     Preparation Example 
     1.3 g of 3,7-diaminodibenzothiophene-5,5-dioxide is added to a dilute hydrochloric acid consisting of 9 ml of concentrated hydrochloric acid and 9 ml of water, and same is well stirred at 80° C. for about 30 minutes. Next, this mixture is cooled to about 0° C., and a solution obtained by dissolving 0.8 g of sodium nitrite in 1 ml of water is added dropwise to said mixture at a temperature of 0°-5° C. for about 30 minutes. Then, the same is stirred at the same temperature for about 30 minutes, a small amount of unreacted matter is filtrated, the filtrate is poured in 10 ml of 42% borofluoric acid, the so separated crystals are removed by filtration, washed with water and dried to obtain 2.2 g (the yield 99%) of yellow-colored crystals of bisdiazoniumbistetrafluoroborate. The decomposition point is about 140° C. Next, the thus obtained 2.2 g of bisdiazonium salt and 2.9 g of 2-hydroxy-3-phenylcarbamoylnaphthalene as a coupler are dissolved in 425 ml of cooled, N,N-dimethylformamide, a solution consisting of 4.1 g of sodium acetate and 60 ml of water is added dropwise thereto at a temperature of 4°-8° C. for 1 hour, and then the same is stirred at room temperature for about 3 hours. Thereafter, precipitates are removed by filtration, washed 3 times with 300 ml of water, and further washed 8 times with 300 ml of N,N-dimethylformamide. Still residual N,N-dimethylformamide is washed away with acetone, and thus obtained pale and dark crystals are dried at 70° C. under reduced pressure of 2 mmHg to obtain 3.2 g (the yield 30%) of disazo pigment No. 1D. The melting point is over 300° C. 
     
         ______________________________________Elementary analysis results (as C.sub.46 H.sub.30 N.sub.6 O.sub.6 S)    Calculated value                  Observed value______________________________________ C (%)     69.51           68.95H (%)      3.80            3.79N (%)      10.57           10.85IR Absorption Spectrum (KBr tablet)1680 cm.sup.-1    (Secondary amide)______________________________________ 
    
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 through FIG. 4 illustrate, respectively, enlarged cross-sectional views of photosensitive materials according to the present invention. 
     Among the reference numerals in the drawings, 1 denotes a conductive support, 2, 2&#39;, 2&#34; and 2&#39;&#34; denote respectively a photosensitive layer, 3 denotes a binder, 4 denotes a disazo compound, 5 denotes a charge-transfer medium, 6 denotes a charge-carrier generating layer, and 7 denotes a charge-transfer medium layer. 
    
    
     The photosensitive materials according to the present invention contain the above mentioned disazo pigments represented by the general formulas I, II, III and IV and can assume such structures as illustrated in FIGS. 1-4 according to the way of application of these pigments. The photosensitive material illustrated in FIG. 1 is one prepared by forming a disazo pigment 4 (which serves herein as a photoconductive substance)-resinous binder 3 type photosensitive layer 2 on a conductive support 1. The photosensitive material illustrated in FIG. 2 is one prepared by forming a disazo pigment 4 (which serves herein as a charge-carrier generating substance)-charge transfer medium (which is a mixture of charge-transfer substance and a resinous binder) 5 type photosensitive layer 2&#39; on a conductive support 1. And the photosensitive materials illustrated in FIGS. 3-4 are modifications of the photosensitive material illustrated in FIG. 2 and the photosensitive layers 2&#34; and 2&#39;&#34; are each composed of a charge-carrier generating layer 6 consisting essentially of the disazo pigment 4 and a charge-transfer medium layer 7. The respective ingredients of these photosensitive materials are supposed to assume such function and mechanism as mentioned hereinafter. 
     First, in the photosensitive material of FIG. 1, the disazo pigment acts as a photoconductive substance, and generation and transfer of the charge-carrier necessary for light decay is performed through the pigment particles. In the case of the photosensitive material of FIG. 2, the charge-transfer substance forms a charge-transfer medium together with the binder (plus a plasticizer as occasion demands), while the disazo pigment acts as a charge-carrier generating substance. This charge-transfer medium has no charge-carrier generating ability as disazo pigments do, but it has an ability to accept and transfer the charge-carrier generated by disazo pigments. That is, in the case of the photosensitive material of FIG. 2, generation of the charge-carrier necessary for light decay is performed by the disazo pigment, while transfer of the charge-carrier is performed mainly by the charge-transfer medium. An additional essential condition required for the charge-transfer medium on this occasion is that the scope of absorption wavelength of the charge-transfer medium should not fall on mainly the scope of absorption wavelength of the visible region of the disazo pigment. The reason for this is that it is necessary to transmit the light to the surface of the disazo pigment in order to generate the charge carrier efficiently in the said pigment. This, however, is not applicable to the case of, for instance, a photosensitive material which is sensitive only to a specific wavelength. Therefore, it will do if the absorption wavelengths of both the charge-transfer medium and the disazo pigment do not completely overlap each other. Next, in the case of the photosensitive material of FIG. 3, the light after passing through the charge-transfer medium layer reaches to the photosensitive layer 2&#34; which acts as a charge-carrier generating layer, whereby generation of the charge-carrier is performed by the disazo pigment present in the portion, while the charge-transfer medium layer accepts the charge-carrier poured therein and transfers. The mechanism of this photosensitive material that generation of the charge-carrier required for light decay is performed by the disazo pigment and transfer of the charge-carrier is performed by the charge-transfer medium is the same as in the case of the photosensitive material illustrated in FIG. 2. The disazo pigment herein is likewise a charge-carrier generating substance. In this regard it is to be noted that the operation mechanism of the charge-transfer medium and charge-carrier generating layer in the photosensitive material of FIG. 4 is the same as in the case of the photosensitive material of FIG. 3. 
     In order to prepare the photosensitive material of FIG. 1, it suffices to coat a conductive support with a dispersion obtained by dispersing fine particles of a disazo pigment in a binder solution and then dry. In order to prepare the photosensitive material of FIG. 2, it suffices to disperse fine particles of a disazo pigment in a solution dissolved a charge-transfer substance and a binder therein, coat a conductive support with the resulting dispersion and then dry. And the photosensitive material of FIG. 3 can be obtained either by depositing a disazo pigment on a conductive support through vacuum evaporation or through the procedure comprising dispersing fine particles of a disazo pigment in an appropriate solvent dissolved a binder therein as occasion demands, coating the resulting dispersion on a conductive support and then drying and if further required, subjecting the thus formed photosensitive layer to the surface finishing, for instance, such as puff-grinding or the like or adjust the thickness of the coating film, thereafter coating thereon a solution containing a charge-transfer substance and a binder and drying. In this regard it is to be noted that in the case of the photosensitive material of FIG. 4 it can be obtained according to the procedure of preparing the photosensitive material of FIG. 3 wherein the order of forming the layers is reversed. In any case, the disazo pigment for use in the present invention is employed upon being pulverized into a particle size of less than 5μ, preferably less than 2μ, by means of a ball-mill or the like. Coating is effected using the conventional means such as doctor blade, wire bar, etc. The thickness of the photosensitive layers illustrated in FIGS. 1 and 2 is about 3-50μ, preferably 5-20μ. In the case of the photosensitive materials illustrated in FIGS. 3 and 4 the thickness of the charge-carrier generating layer is less than 5μ, preferably less than 2μ, and the thickness of the charge-transfer medium layer is about 3-50μ, preferably 5-20μ. In the case of the photosensitive material illustrated in FIG. 1, the proper amount of the disazo pigment contained in the photosensitive layer is 30-70% by weight, preferably about 50% by weight based on the weight of the photosensitive layer. (As above-described, in the case of the photosensitive material of FIG. 1 the disazo pigment acts as a photoconductive substance, and generation and transfer of the charge carrier required for light decay are performed through the pigment particles. Therefore, it is desirable that the contact between the pigment particles should be continuous from the photosensitive layer surface to the support. In view of this, it is desirable that the ratio of the disazo pigment to the photosensitive layer is as high as possible, but when taking both the strength and the sensitivity of the photosensitive layer into consideration, preferably it is about 50% by weight.) In the case of the photosensitive material illustrated in FIG. 2, the proper amount of the disazo pigment contained in the photosensitive layer is 1-50% by weight, preferably less than 20% by weight, and the proper amount of the charge-transfer substance therein is 10-95% by weight, preferably 30-90% by weight. And in the case of the photosensitive materials illustrated in FIGS. 3-4 the amount of the charge-transfer substance contained in the charge-transfer medium layer is 10-95% by weight, preferably 30-90% by weight as in the case of the photosensitive layer of the photosensitive material illustrated in FIG. 2. Further, in preparing all the photosensitive materials illustrated in FIGS. 1-4, it is possible to employ some plasticizer in combination with the binder. 
     In the photosensitive materials of the present invention there can be employed, as the conductive support, a plate or foil of a metal such as aluminum, etc., a plastic film deposited thereon a metal such as aluminum, etc. through vacuum evaporation, or a paper processed for conductivity. As binders suitably employed in the present invention, there are enumerated such condensation resins such as polyamide, polyurethane, polyester, epoxide resin, polyketone, polycarbonate, etc., vinyl polymers such as polyvinyl ketone, polystyrene, poly-N-vinyl carbazole, polyacrylamide, etc., and the like, but in spite of this, resins which are insulating and adhesive are all employable. As available plasticizers there can be enumerated halogenated paraffin, polyvinyl chloride, dimethyl naphthalene, dibutyl phthalate, etc. And as available charge-transfer substances there can be enumerated, as high molecular substances, vinyl polymers such as poly-N-vinyl carbazole, halogenated poly-N-vinyl carbazole, polyvinyl pyrene, polyvinyl indroquinoxaline, polyvinyl dibenzothiophene, polyvinyl anthracene, polyvinyl acridine, etc. and condensation resins such as pyrene-formaldehyde resin, bromopyrene-formaldehyde resin, ethyl carbazole-formaldehyde resin, chloroethyl carbazole-formaldehyde resin, etc., and as low molecular substances (monomers), fluorenone, 2-nitro-9-fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 4H-indeno[1,2-b]thiophen-4-one, 2-nitro-4H-indeno[1,2-b]thiophen-4-one, 2,6,8-trinitro-4H-indeno[1,2-b]thiophen-4-one, 8H-indeno[2,1-b]thiophen-8-one, 2-intro-8H-indeno[2,1-b]thiophen-8-one, 2-bromo-6,8-dinitro-4H-indeno[1,2-b]thiophene, 6,8-dinitro-4H-indeno[1,2-b]thiophene, 2-nitrodibenzothiophene, 2,8-dinitrodibenzothiophene, 3-nitrodibenzothiophene-5-oxide, 3,7-dinitrodibenzothiophene-5-oxide, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, 3-nitro-dibenzothiophene-5,5-dioxide, 3,7-dinitro-dibenzothiophene-5,5-dioxide, 4-dicyanomethylene-4H-indeno[1,2-b]thiophene, 6,8-dinitro-4-dicyanomethylene-4H-indeno[1,2-b]thiophene, 1,3,7,9-tetranitrobenzo[c]cinnoline-5-oxide, 2,4,10-trinitrobenzo[c]cinnoline-6-oxide, 2,4,8-trinitrobenzo[c]cinnoline-6-oxide, 2,4,8-trinitrothioxanthone, 2,4,7-trinitro-9,10-phenanthrene-guinone, 1,4-naphthoquinone-benzo[a]anthracene-7,12-dione, 2,4,7-trinitro-9-dicyanomethylene fluorene, tetrachlorophthalic anhydride, 1-bromopyrene, 1-methylpyrene, 1-ethylpyrene, 1-acetylpyrene, carbazole, N-ethylcarbazole, N-β-chloroethylcarbazole, N-β-hydroxyethyl carbazole, 2-phenyl indole, 2-phenylnaphthalene, 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2,5-bis(4-diethylaminophenyl)-1,3,4-triazole, 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, 2-phenyl-4-(4-diethylaminophenyl)-5-phenyloxazole, triphenyl amine, tris(4-diethylaminophenyl)methane, 3,6-bis(dibenzylamino)-9-ethyl carbazole, etc. These charge-transfer substances are employed either singly or in a combination of two or more of them. 
     Further, in every photosensitive material thus prepared an adhesive layer or a barrier layer can be disposed in between the conductive support and the photosensitive layer as occasion demands. The material suitably used in the formation of aforesaid layers includes polyamide, nitrocellulose, aluminum oxide, etc. and preferably the thickness of the layers is less than 1μ. 
     Reproduction using the photosensitive material according to the present invention can be achieved through the procedure comprising electrifying the photosensitive layer side of the photosensitive material, exposing and then developing, and if necessary, transferring onto an ordinary paper or the like. 
     The photosensitive materials according to the present invention have excellent advantages in that they are generally of high sensitivity and rich in flexibility. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Example 1 
     1 part by weight of polyester resin (namely, Polyester Adhesive 49000, the manufacture of Du Pont Inc.), 1 part by weight of the disazo compound No. 1A and 26 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 7μ-thick photosensitive layer and a structure illustrated in FIG. 1. 
     Subsequently, after charging positive electricity on the photosensitive layer of this photosensitive material by applying +6 KV corona discharge for 20 seconds by means of a commercial electrostatic copying paper testing apparatus, the photosensitive material was left alone in the dark for 20 seconds, and the surface potential Vpo(volt) at the time was measured. Next, light was applied to the photosensitive layer by means of a tungsten lamp so as to attain the illumination of 20 luxes on the surface thereof, and the time (unit:second) required for reducing said surface potential Vpo to half was sought, whereby the amount of exposure E1/2 (lux.sec.) was obtained. The result was as follows: 
     
         Vpo=590 V, E1/2=15 lux.sec. 
    
     Examples 2 through 10 
     Varieties of photosensitive materials were prepared by applying the same procedure as in Example 1 save for employing the respective disazo compounds referred to by number in the following Table-1 in place of the disazo compound No. 1A used in Example 1. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 1, the result was as shown in Table-1, respectively. 
     
                       TABLE-1______________________________________       DisazoExample     compound    Vpo       El/2No.         No.         (volt)    (lux . sec.)______________________________________2            4A         630        83           17A         800        54           18A         700       155           32A         710       196           37A         725       307           49A         680       218           58A         695       259           62A         710       2510          65A         800       30______________________________________ 
    
     Example 11 
     10 parts by weight of polyester resin (the same as that in Example 1), 10 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of disazo compound No. 1A and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. Subsequently, measurement of Vpo and E1/2 of this photosensitive material was conducted through the same procedure as in Example 1 save for applying -6 KV corona discharge instead of +6 KV corona discharge employed in Example 1. The result was as follows: 
     
         Vpo=450 V, E1/2=10 lux.sec. 
    
     Examples 12 through 20 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 11 save for employing the respective disazo compounds referred to by number in the following Table-2 in place of the disazo compound No. 1A used in Example 11. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 11, the result was as shown in Table-2, respectively. 
     
                       TABLE-2______________________________________       DisazoExample     compound    Vpo       El/2No.         No.         (volt)    (lux . sec.)______________________________________12           3A         480       1013           5A         520       1514          11A         450       2015          23A         500       1516          25A         500       1517          35A         450       1018          38A         480       2019          41A         600       2020          60A         750       25______________________________________ 
    
     Example 21 
     10 parts by weight of polyester resin (the same as that in Example 1), 10 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of the disazo compound No. 1A and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 120° C. for 10 minutes, whereby there was prepared a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subsequently subjected to the same measurement as in Example 1, the result was as follows: 
     
         Vpo=830 V, E1/2=10 lux.sec. 
    
     Examples 22 through 30 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 21 save for employing the respective disazo compounds referred to by number in the following Table-3 in place of the disazo compound No. 1A used in Example 21. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 1, the result was as shown in the following Table-3, respectively. 
     
                       TABLE-3______________________________________       DisazoExample     compound    Vpo       El/2No.         No.         (volt)    (lux . sec.)______________________________________22           2A         900       1523           9A         850       1824          13A         880       1625          28A         800        926          33A         900       1527          45A         820       1728          47A         930       1029          52A         950       1530          66A         910       20______________________________________ 
    
     Example 31 
     200 parts by weight of poly-N-vinyl carbazole, 33 parts by weight of 2,4,7-trinitro-9-fluorenone, 20 parts by weight of polyester resin (the same as that in Example 1) and 20 parts by weight of the disazo compound No. 1A as added to 1780 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes and at a temperature of 120° C. for 5 minutes in succession, whereby there was obtained a photosensitive material having a 13μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subjected to the same measurement as in Example 1, the result was as follows: 
     
         Vpo=1,035 V, E1/2=5 lux.sec. 
    
     Examples 32 through 40 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 31 save for employing the respective disazo compound referred to by number in the following Table-4 in place of the disazo compound No. 1A used in Example 31. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 1, the result was as shown in the following Table-4, respectively. 
     
                       TABLE-4______________________________________       DisazoExample     compound    Vpo       El/2No.         No.         (volt)    (lux . sec.)______________________________________32           9A         1035      633          10A         1040      734          17A         1100      735          29A         1100      836          40A         1150      537          42A         1200      1538          51A         1280      1039          63A         1430      1940          64A         1500      15______________________________________ 
    
     Example 41 
     2 parts by weight of the disazo compound No. 1A and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of polycarbonate (namely, Panlite L, the manufacture of TEIJIN Co., Ltd.) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 100° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a photosensitive material having a structure illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement as in Example 1, the result was as follows: 
     
         Vpo=850 V, E1/2=15 lux.sec. 
    
     Examples 42 through 50 
     Varieties of photosensitive materials having a structure illustrated in FIG. 3 were prepared by applying the same procedure as in Example 41 save for employing the respective disazo compounds referred to by number in the following Table-5 in place of the disazo compound No. 1A used in Example 41. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 1, the result was as shown in Table-5, respectively. 
     
                       TABLE-5______________________________________    DisazoExample  compound       Vpo     E1/2-No. No. (volt) (lux .______________________________________                           sec.)42        8A            850     943       15A            880     1044       21A            880     1045       30A            870     846       33A            870     947       43A            855     1048       53A            865     1049       55A            880     1550       61A            880     15______________________________________ 
    
     Example 51 
     2 parts by weight of the disazo compound No. 1A and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of polycarbonate (the same as that in Example 41) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 120° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a laminate-type photosensitive material illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement of Vpo and E1/2 as in Example 1 save for applying -6 KV corona discharge instead of +6 KV corona discharge, the result was as follows: 
     
         Vpo=1,000 V, E1/2=8 lux.sec. 
    
     Examples 52 through 60 
     Varieties of photosensitive materials having the same structure as that of Example 51 were prepared by employing the respective disazo compound referred to by number in the following Table-6 in place of the disazo compound No. 1A used in Example 51. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 1, the result was as shown in Table-6, respectively. 
     
                       TABLE-6______________________________________    DisazoExample  compound       Vpo     E1/2No.      No.            (volt)  (lux.sec.)______________________________________52        6A            1000    553       14A            950     854       19A            980     555       22A            990     756       27A            990     957       36A            1020    1058       44A            990     1259       48A            1000    1560       53A            1100    20______________________________________ 
    
     Example 61 
     1 part by weight of polyester resin (namely, Polyester Adhesive 49000, the manufacture of Du Pont Inc.), 1 part by weight of the disazo compound No. 1B and 26 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 7μ-thick photosensitive layer and a structure illustrated in FIG. 1. 
     Subsequently, after charging positive electricity on the photosensitive layer of this photosensitive material by applying +6 KV corona discharge for 20 seconds by means of a commercial electrostatic copying paper testing apparatus, the photosensitive material was left alone in the dark for 20 seconds, and the surface potential Vpo(volt) at that time was measured. Next, light was applied to the photosensitive layer by means of a tungsten lamp so as to attain the illumination of 20 luxes on the surface thereof, and the time (unit:second) required for reducing said surface potential Vpo to half was sought, whereby the amount of exposure E1/2 (lux.sec.) was obtained. The result was as follows: 
     
         Vpo=500 V, E1/2=12 lux.sec. 
    
     Examples 62 through 70 
     Varieties of photosensitive materials were prepared by applying the same procedure as in Example 61 save for employing the respective disazo compounds referred to by number in the following Table-7 in place of the disazo compound No. 1B used in Example 61. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 61, the result was as shown in Table-7, respectively. 
     
                       TABLE-7______________________________________    DisazoExample  compound       Vpo     E1/2No.      No.            (volt)  (lux . sec.)______________________________________62        4B            620     1063       17B            600     1264       18B            680     1065       32B            620     1566       37B            630     2067       49B            690     1968       58B            680     2569       62B            680     2570       65B            690     30______________________________________ 
    
     Example 71 
     10 parts by weight of polyester resin (the same as that in Example 61), 10 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of disazo compound No. 1B and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. Subsequently, measurement of Vpo and E1/2 of this photosensitive material was conducted through the same procedure as in Example 61 save for applying -6 KV corona discharge instead of +6 KV corona discharge employed in Example 61. The result was as follows: 
     
         Vpo=520 V, E1/2=9 lux.sec. 
    
     Examples 72 through 80 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 71 save for employing the respective disazo compounds referred to by number in the following Table-8 in place of the disazo compound No. 1B used in Example 71. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 61, the result was as shown in Table-8, respectively. 
     
                       TABLE-8______________________________________    DisazoExample  compound       Vpo     E1/2No.      No.            (volt)  (lux.sec.)______________________________________72        3B            480     1073        5B            500     1074       11B            480     1275       23B            500     976       25B            500     1577       35B            490     1578       38B            520     1579       41B            500     2080       60B            580     18______________________________________ 
    
     Example 81 
     10 parts by weight of polyester resin (the same as that in Example 61), 10 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of the disazo compound No. 1B and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 120° C. for 10 minutes, whereby there was prepared a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subsequently subjected to the same measurement as in Example 61, the result was as follows: 
     
         Vpo=790 V, E1/2=5 lux.sec. 
    
     Examples 82 through 90 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 81 save for employing the respective disazo compounds referred to by number in the following Table-9 in place of the disazo compound No. 1B used in Example 81. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 61, the result was as shown in the following Table-9, respectively. 
     
                       TABLE-9______________________________________    DisazoExample  compound       Vpo     E1/2No.      No.            (volt)  (lux.sec.)______________________________________82        2B            950     1083        9B            920     1284       13B            900     1085       28B            920     1586       33B            900     1387       45B            920     1988       47B            990     1989       52B            1000    2090       66B            950     25______________________________________ 
    
     Example 91 
     200 parts by weight of poly-N-vinyl carbazole, 33 parts by weight of 2,4,7-trinitro-9-fluorenone, 20 parts by weight of polyester resin (the same as that in Example 61) and 20 parts by weight of the disazo compound No. 1B as added to 1780 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes and at a temperature of 120° C. for 5 minutes in succession, whereby there was obtained a photosensitive material having a 13μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subjected to the same measurement as in Example 61, the result was as follows: 
     
         Vpo=1,020 V, E1/2=3 lux.sec. 
    
     Examples 92 through 100 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 91 save for employing the respective disazo compound referred to by number in the following Table-10 in place of the disazo compound No. 1B used in Example 91. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 61, the result was as shown in the following Table-10, respectively. 
     
                       TABLE 10______________________________________     DisazoExample   compound    Vpo        El/2No.       No.         (volt)     (lux . sec.)______________________________________92         9B         1020       593        10B         1000       394        17B         1120       595        29B         1100       596        40B          980       897        42B         1000       1098        51B         1100       1299        63B         1000       15100       64B         1100       20______________________________________ 
    
     Example 101 
     2 parts by weight of the disazo compound No. 1B and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of polycarbonate (namely, Panlite L, the manufacture of TEIJIN Co. Ltd.) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 100° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a photosensitive material having a structure illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement as in Example 61, the result was as follows: 
     
         Vpo=900 V, E1/2=15 lux.sec. 
    
     Examples 102 through 110 
     Varieties of photosensitive materials having a structure illustrated in FIG. 3 were prepared by applying the same procedure as in Example 101 save for employing the respective disazo compounds referred to by number in the following Table-11 in place of the disazo compound No. 1B used in Example 101. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 61, the result was as shown in Table-11, respectively. 
     
                       TABLE 11______________________________________     DisazoExample   compound    Vpo        El/2No.       No.         (volt)     (lux . sec.)______________________________________102        8B         800        10103       15B         820        10104       21B         870        12105       30B         900        15106       33B         910        18107       43B         880        20108       53B         900        15109       55B         920        20110       61B         900        20______________________________________ 
    
     Example 111 
     2 parts by weight of the disazo compound No. 1B and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of polycarbonate (the same as that in Example 101) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 120° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a laminate-type photosensitive material illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement of Vpo and E1/2 as in Example 61 save for applying -6 KV corona discharge instead of +6 KV corona discharge, the result was as follows: 
     
         Vpo=1,020 V, E1/2=10 lux.sec. 
    
     Examples 112 through 120 
     Varieties of photosensitive materials having the same structure as that of Example 111 were prepared by employing the respective disazo compound referred to by number in the following Table-12 in place of the disazo compound No. 1B used in Example 111. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 61, the result was as shown in Table-12, respectively. 
     
                       TABLE 12______________________________________     DisazoExample   compound    Vpo        E1/2No.       No.         (volt)     (lux . sec.)______________________________________112        6B         1000       9113       14B          990       10114       19B          980       8115       22B         1000       12116       27B         1020       15117       36B         1030       10118       44B         1000       9119       48B         1100       20120       53B         1200       25______________________________________ 
    
     Example 121 
     1 part by weight of polyester resin (namely, Polyester Adhesive 49000, the manufacture of Du Pont Inc.), 1 part by weight of the disazo compound No. 1C and 26 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 7μ-thick photosensitive layer and a structure illustrated in FIG. 1. 
     Subsequently, after charging positive electricity on the photosensitive layer of this photosensitive material by applying +6 KV corona discharge for 20 seconds by means of a commercial electrostatic copying paper testing apparatus, the photosensitive material was left alone in the dark for 20 seconds, and the surface potential Vpo(volt) at that time was measured. Next, light was applied to the photosensitive layer by means of a tungsten lamp so as to attain the illumination of 20 luxes on the surface thereof, and the time (unit: second) required for reducing said surface potential Vpo to half was sought, whereby the amount of exposure E1/2 (lux.sec.) was obtained. The result was as follows: 
     
         Vpo=700 V, E1/2=10 lux.sec. 
    
     Examples 122 through 130 
     Varieties of photosensitive materials were prepared by applying the same procedure as in Example 121 save for employing the respective disazo compounds referred to by number in the following Table-13 in place of the disazo compound No. 1C used in Example 121. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 121, the result was as shown in Table-13, respectively. 
     
                       TABLE 13______________________________________     DisazoExample   compound    Vpo        E1/2No.       No.         (volt)     (lux . sec.)______________________________________122        3C         720        10123        5C         700        8124       18C         680        10125       30C         700        12126       44C         800        15127       49C         890        10128       55C         800        20129       67C         800        10130       93C         790        5______________________________________ 
    
     Example 131 
     10 parts by weight of polyester resin (the same as that in Example 121), 10 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of disazo compound No. 1C and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. Subsequently, measurement of Vpo and E1/2 of this photosensitive material was conducted through the same procedure as in Example 121 save for applying -6 KV corona discharge instead of +6 KV corona discharge employed in Example 121. The result was as follows: 
     
         Vpo=430 V, E1/2=12 lux.sec. 
    
     Examples 132 through 140 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 131 save for employing the respective disazo compounds referred to by number in the following Table-14 in place of the disazo compound No. 1C used in Example 131. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 121, the result was as shown in Table-14, respectively. 
     
                       TABLE 14______________________________________     DisazoExample   compound    Vpo        E1/2No.       No.         (volt)     (lux . sec.)______________________________________132        3C         450        12133        5C         480        13134       12C         490        12135       25C         520        15136       27C         450        10137       48C         440        11138       69C         450        10139       71C         440        10140       110C        440        20______________________________________ 
    
     Example 141 
     10 parts by weight of polyester resin (the same as that in Example 121), 10 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of the disazo compound No. 1C and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 120° C. for 10 minutes, whereby there was prepared a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subsequently subjected to the same measurement as in Example 121, the result was as follows: 
     
         Vpo=820 V, E1/2=8 lux.sec. 
    
     Examples 142 through 150 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 141 save for employing the respective disazo compounds referred to by number in the following Table-15 in place of the disazo compound No. 1C used in Example 141. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 121, the result was as shown in the following Table-15, respectively. 
     
                       TABLE 15______________________________________    DisazoExample  compound      Vpo     E 1/2No.      No.           (volt)  (lux. sec.)______________________________________142      17C           800      5143      27C           800      9144      56C           790     35145      62C           800     30146      67C           820     10147      71C           820     10148      83C           800      8149      101C          810     10150      126C          830     20______________________________________ 
    
     Example 151 
     200 parts by weight of poly-N-vinyl carbazole, 33 parts by weight of 2,4,7-trinitro-9-fluorenone, 20 parts by weight of polyester resin (the same as that in Example 121) and 20 parts by weight of the disazo compound No. 1C as added to 1780 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes and at a temperature of 120° C. for 5 minutes in succession, whereby there was obtained a photosensitive material having a 13μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subjected to the same measurement as in Example 121, the result was as follows: 
     
         Vpo=1,000 V, E1/2=5 lux.sec. 
    
     Examples 152 through 160 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 151 save for employing the respective disazo compound referred to by number in the following Table-16 in place of the disazo compound No. 1C used in Example 151. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 121, the result was as shown in the following Table-16, respectively. 
     
                       TABLE 16______________________________________    DisazoExample  compound      Vpo     E 1/2No.      No.           (volt)  (lux. sec.)______________________________________152       3C           1100    5153       5C           1100    3154      19C           1000    8155      55C            900    15156      67C            980    5157      91C           1020    3158      110C          1040    8159      123C          1080    18160      127C          1200    25______________________________________ 
    
     Example 161 
     2 parts by weight of the disazo compound No. 1C and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of polycarbonate (namely, Panlite L, the manufacture of TEIJIN Co., Ltd.) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 100° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a photosensitive material having a structure illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement as in Example 121, the result was as follows: 
     
         Vpo=920 V, E1/2=15 lux.sec. 
    
     Examples 162 through 170 
     Varieties of photosensitive materials having a structure illustrated in FIG. 3 were prepared by applying the same procedure as in Example 161 save for employing the respective disazo compounds referred to by number in the following Table-17 in place of the disazo compound No. 1C used in Example 161. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 121, the result was as shown in Table-17, respectively. 
     
                       TABLE 17______________________________________    DisazoExample  compound      Vpo     E 1/2No.      No.           (volt)  (lux. sec.)______________________________________162       3C           980     15163       5C           920     12164      19C           900     10165      55C           950     20166      67C           930     10167      91C           990      8168      110C          990     10169      123C          920     19170      127C          1000    30______________________________________ 
    
     Example 171 
     2 parts by weight of the disazo compound 1C and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of polycarbonate (the same as that in Example 151) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 120° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a laminate-type photosensitive material illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement of Vpo and E1/2 as in Example 121 save for applying -6 KV corona discharge instead of +6 KV corona discharge, the result was as follows: 
     
         Vpo=990 V, E1/2=8 lux.sec. 
    
     Examples 172 through 180 
     Varieties of photosensitive materials having the same structure as that of Example 171 were prepared by employing the respective disazo compound referred to by number in the following Table-18 in place of the disazo compound No. 1C used in Example 171. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 121, the result was as shown in Table-18, respectively. 
     
                       TABLE 18______________________________________    DisazoExample  compound      Vpo     E 1/2No.      No.           (volt)  (lux. sec.)______________________________________172       3C           900     10173       5C           890     10174      19C           910     12175      55C           910     25176      67C           900     12177      91C           880     18178      110C          870     15179      123C          890     20180      127C          900     35______________________________________ 
    
     Example 181 
     1 parts by weight of polyester resin (namely, Polyester Adhesive 49000, the manufacture of Du Pont Inc.), 1 part by weight of the disazo compound 1D and 26 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosensitive material having a 7μ-thick photosensitive layer and a structure illustrated in FIG. 1. 
     Subsequently, after charging positive electricity on the photosensitive layer of this photosensitive materials by applying +6 KV corona discharge for 20 seconds by means of a commercial electrostatic copying paper testing apparatus, the photosensitive material was left alone in the dark for 20 seconds, and the surface potential Vpo(volt) at that time was measured. Next, light was applied to the photosensitive layer by means of a tungsten lamp so as to attain the illumination of 20 luxes on the surface thereof, and the time (unit: second) required for reducing said surface potential Vpo to half was sought, whereby the amount of exposure E1/2 (lux.sec.) was obtained. The result was as follows: 
     
         Vpo=500 V, E1/2=15 lux.sec. 
    
     Examples 182 through 190 
     Varieties of photosensitive materials were prepared by applying the same procedure as in Example 181 save for employing the respective disazo compounds referred to by number in the following Table-19 in place of the disazo compound No. 1D used in Example 181. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 181, the result was as shown in Table-19, respectively. 
     
                       TABLE 19______________________________________    DisazoExample  compound      Vpo     E 1/2No.      No.           (volt)  (lux. sec.)______________________________________182       4D           620     10183      17D           620     10184      18D           700     12185      32D           710     14186      37D           700     25187      49D           690     30188      58D           690     30189      62D           700     20190      65D           800     35______________________________________ 
    
     Example 191 
     10 parts by weight of polyester resin (the same as that in Example 181), 10 parts of weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of disazo compound No. 1D and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes, whereby there was obtained a photosenitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. Subsequently, measurement of Vpo and E1/2 of this photosensitive material was conducted through the same procedure as in Example 181 save for applying -6 KV corona discharge instead of +6 KV corona discharge employed in Example 15. The result was as follows: 
     
         Vpo=500 V, E1/2=8 lux.sec. 
    
     Examples 192 through 200 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 191 save for employing the respective disazo compounds referred to by number in the following Table-20 in place of the disazo compound No. 1D used in Example 181. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 181, the result was as shown in Table-20, respectively. 
     
                       TABLE 20______________________________________    DisazoExample  compound      Vpo     E 1/2No.      No.           (volt)  (lux. sec.)______________________________________192       3D           490      8193       5D           480      5194      11D           500      9195      23D           500     15196      25D           480     18197      35D           520     20198      38D           500     20199      41D           490     18200      60D           630     18______________________________________ 
    
     Example 201 
     10 parts by weight of polyester resin (the same as that in Example 181), 10 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of the disazo compound No. 1D and 198 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 120° C. for 10 minutes, whereby there was prepared a photosensitive material having a 10μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subsequently subjected to the same measurement as in Example 181, the result was as follows: 
     
         Vpo=800 V, E1/2=6 lux.sec. 
    
     Examples 202 through 210 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 201 save for employing the respective disazo compounds referred to by number in the following Table-21 in place of the disazo compound No. 1D used in Example 201. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 181, the result was as shown in the following Table-21, respectively. 
     
                       TABLE 21______________________________________     DisazoExample   compound    Vpo        E1/2No.       No.         (volt)     (lux . sec.)______________________________________202        2D         950        10203        9D         900        12204       13D         920         8205       28D         930        15206       33D         890        16207       45D         900        19208       47D         900        20209       52D         890        21210       66D         950        25______________________________________ 
    
     Example 211 
     200 parts by weight of poly-N-vinyl carbazole, 33 parts by weight of 2,4,7-trinitro-9-fluorenone, 20 parts by weight of polyester resin (the same as that in Example 181) and 20 parts by weight of the disazo compound No. 1D as added to 1780 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was dried at a temperature of 100° C. for 10 minutes and at a temperature of 120° C. for 5 minutes in succession, whereby there was obtained a photosensitive material having a 13μ-thick photosensitive layer and a structure illustrated in FIG. 2. When this photosensitive material was subjected to the same measurement as in Example 181, the result was as follows: 
     
         Vpo=1,000 V, E1/2=3 lux.sec. 
    
     Examples 212 through 220 
     Varieties of photosensitive materials having a structure illustrated in FIG. 2 were prepared by applying the same procedure as in Example 211 save for employing the respective disazo compounds referred to by number in the following Table-22 in place of the disazo compound No. 1D used in Example 211. When these photosensitive materials were subsequently subjected to the same measurement of Vpo and E1/2 as in Example 181, the result was as shown in the following Table-22, respectively. 
     
                       TABLE-22______________________________________    SisazoExample  compound       Vpo     E1/2No.      No.            (volt)  (lux.sec.)______________________________________212       9D            1020    5213      10D            1000    3214      17D            1120    8215      29D            1000    6216      40D             995    10217      42D            1150    8218      51D            1200    12219      63D            1200    15220      64D            1210    15______________________________________ 
    
     Example 221 
     2 parts by weight of the disazo compound No. 1D and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,4,7-trinitro-9-fluorenone, 2 parts by weight of polycarbonate (namely, Panlite L, the manufacture of TEIJIN Co. Ltd.) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 100° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a photosensitive material having a structure illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement as in Example 181, the result was as follows: 
     
         Vpo=800 V, E1/2=15 lux.sec. 
    
     Examples 222 through 230 
     Varieties of photosensitive materials having a structure illustrated in FIG. 3 were prepared by applying the same procedure as in Example 221 save for employing the respective disazo compounds referred to by number in the following Table-23 in place of the disazo compound No. 1D used in Example 221. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 181, the result was as shown in Table-23, respectively. 
     
                       TABLE-23______________________________________       DisazoExample     compound    Vpo       El/2No.         No.         (volt)    (lux . sec.)______________________________________222          8D         850        9223         15D         800       10224         21D         870        8225         30D         880       15226         33D         890       20227         43D         900       10228         53D         865       10229         55D         880       18230         61D         900       25______________________________________ 
    
     Example 231 
     2 parts by weight of the disazo compound No. 1D and 98 parts by weight of tetrahydrofuran were pulverized and mixed together within a ball-mill, and the resulting dispersion was coated, by means of a doctor blade, on a polyester film deposited with aluminum through vacuum evaporation and was subjected to natural drying, whereby there was formed a 1μ-thick charge-carrier generating layer. Meanwhile, another dispersion was prepared by mixing 2 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of polycarbonate (the same as that in Example 221) and 46 parts by weight of tetrahydrofuran together, and this dispersion was coated on the foregoing charge-carrier generating layer by means of a doctor blade and then dried at a temperature of 120° C. for 10 minutes to form a 10μ-thick charge-transfer medium layer, whereby there was obtained a laminate-type photosensitive material illustrated in FIG. 3. When the thus obtained photosensitive material was subjected to the same measurement of Vpo and E1/2 as in Example 181 save for applying -6 KV corona discharge instead of +6 KV corona discharge, the result was as follows: 
     
         Vpo=1,000 V, E1/2=8 lux.sec. 
    
     Examples 232 through 240 
     Varieties of photosensitive materials having the same structure as that of Example 231 were prepared by employing the respective disazo compound referred to by number in the following Table-24 in place of the disazo compound No. 1D used in Example 231. When these photosensitive materials were subjected to the same measurement of Vpo and E1/2 as in Example 181, the result was as shown in Table-24, respectively. 
     
                       TABLE-24______________________________________       DisazoExample     compound    Vpo       El/2No.         No.         (volt)    (lux . sec.)______________________________________232          6D         1000      8233         14D          990      8234         19D          980      10235         22D          990      8236         27D         1000      10237         36D          990      15238         44D         1000      8239         48D         1020      19240         53D         1100      25______________________________________