Patent Publication Number: US-5296322-A

Title: Electrophotographic photosensitive member and apparatus using same

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an electrophotographic photosensitive member, particularly one having an improved intermediate layer disposed between an electroconductive support (hereinafter simply referred to as a &#34;support&#34;) and a photosensitive layer, and also an apparatus using such an improved electrophotographic photosensitive member. 
     For an electrophotographic photosensitive member of the Carlson type, it is generally important to ensure stability of a dark-part potential and a light-part potential in order to secure a constant image density on repetition of charging-exposure and provide images free from fog. 
     In order to ensure the potential stability, various proposals have been made, inclusive of, e.g., improvement in charge injection from the support to the photosensitive layer, improvement in adhesion between the support and the photosensitive layer, improvement in application characteristic of the photosensitive layer, and provision of an intermediate layer between the support and the photosensitive layer having a function of, e.g., covering defects on the support. 
     There has been also proposed a photosensitive member having a photosensitive layer of a laminated structure functionally separated into a charge generation layer and a charge transport layer. The charge generation layer is generally formed in a very thin layer of, e.g., about 0.5 micron, so that the thickness of the charge generation layer is liable to be nonuniform due to defects soiling, attachment or flaws on the surface of the support. Such a nonuniform thickness of the charge generation layer, however, results in a sensitivity irregularity of the photosensitive member, so that the charge generation layer is required to be as uniform as possible. 
     In view of the above circumstances, it has been proposed to dispose an intermediate layer, between the charge generation layer and the support, functioning as a barrier layer and an adhesive layer and also covering defects on the support. 
     Hitherto, as resins constituting such intermediate layers between the photosensitive layer and the support there have been known to use polyamide (Japanese Laid-Open Patent Application (JP-A) 48-47344, JP-A 52-25638), polyester (JP-A 52-20836, JP-A 54-206738), polyurethane (JP-A 53-89435, JP-A H2-115858), quarternary ammonium salt-containing acrylic polymer (JP-A 51-126148), and casein (JP-A 55-103556). 
     However, an intermediate layer composed of a material as described above changes its electric resistance corresponding to changes in environmental temperature and humidity, so that it has been difficult to ensure a stable potential characteristic over wide environmental conditions ranging from low temperature-low humidity to high temperature-high humidity by using an electrophotographic photosensitive member incorporating such an intermediate layer. 
     For example, when such a photosensitive member is repeatedly used under low temperature-low humidity conditions tending to increase the electric resistance of the intermediate layer, some charges remain in the intermediate layer to increase the light-part potential and the residual potential, thus resulting in fog in copied images. Further, in case where such a photosensitive member is used in an electrophotographic printer of the reversal development type, the resultant images are liable to be thin in density and fail to provide copies with a prescribed quality. 
     On the other hand, under high temperature-high humidity conditions, such an intermediate layer is liable to cause an inferior barrier function due to a lowering in electric resistance, thus resulting in a increase in carrier injection from the support side to cause a lowering in dark-part potential. As a result, under high temperature-high humidity conditions, copy images become thin. Ween such a photosensitive member is used in an electrophotographic printer of the reversal development type, the resultant images are liable to be accompanied with black spotty defects (black spots). Further, the above-mentioned photosensitive member of prior art having an intermediate layer comprising a cured layer of a polyurethane which is a reaction product between a polyether compound and a polyisocyanate compound, shows an effect of decreasing fog due to a lowering in electric resistance but is still accompanied with a problem that the resultant images are liable to be accompanied with black spotty defects (black spots). 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member capable of retaining a stable potential characteristic and thus stably forming images over wide environmental conditions ranging from low temperature-low humidity to high temperature-high humidity conditions. 
     Another object of the present invention is to provide an electrophotographic photosensitive member having an intermediate layer showing an excellent adhesion to the support and a good film characteristic and capable of forming good images free from defects under wide environmental conditions. 
     A further object of the present invention is to provide electrophotographic apparatus using such an improved photosensitive member. 
     According to the present invention, there is provided an electrophotographic photosensitive member, comprising: an electroconductive support, and an intermediate layer and a photosensitive layer disposed in this order on the support, wherein said intermediate layer comprises a reaction product of a polyol compound comprising at least one of a polyol compound [1] represented by Formula (1) shown below and a phosphated polyol compound with a polyisocyanate compound: ##STR3## wherein A denotes ##STR4## B denotes --R 4  --O--, A and B may be connected at random or in blocks with each other, Z denotes an active hydrogen compound residue; R 1  is an alkylene group having 1-9 carbon atoms; R 2  is an alkylene group having 1-10 carbon atoms; R 3  is an alkyl group, alkenyl group, aryl group or aralkyl group having 1-20 carbon atoms; R 4  is an alkylene group having 2-10 carbon atoms; k is a number of 1-12; m is a number of 1-250; n is a number of 0-100; and p is a number of 0-5. 
     These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic sectional view of a transfer-type copying machine loaded with an electrophotographic photosensitive member according to the present invention. 
     FIG. 2 is a block diagram of a facsimile system using a printer incorporating an electrophotographic photosensitive member according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The photosensitive member according to the present invention is provided with a stable potential characteristic and a good image forming characteristic over wide environmental conditions ranging from low temperature-low humidity to high temperature-high humidity conditions because it has an intermediate layer comprising a reaction product of at least one polyol compound selected from the polyol compound [I] and the phosphated polyol compound [II] with a polyisocyanate compound. The improved effects may be attributable to non-crystallization of the product polymer due to the presence of the side chain-type polyether unit (A) in the case of the reaction product of the polyol compound [I] with a polyisocyanate compound, and an increase in ionic conductivity due to the introduction of a phosphate group in the case of the reaction product of the phosphated polyol compound [II] with a polyisocyanate compound. Further, when the using the reaction product of both the polyol compounds [I] and [II] with a polyisocyanate compound, the non-crystallization and increased ionic conductivity of the product are considered to contribute to the effects of the present invention in combination. 
     The polyol compound [I] having a basic structure represented by the formula (1) may for example be formed by reacting an active hydrogen(--containing) compound with a glycidyl ether in the presence of a catalyst. 
     The active hydrogen compound may be a compound having two or more active hydrogen atoms in its molecule, and examples thereof may include: polyhydric alcohols, such as ethylene glycol, propylene glycol, 1,4-butanediol, glycerine, trimethylolpropane, pentaerythritol, sorbitol, sucrose, and polyglycerine; amines, such as monoethanolamine, butylamine, 2-ethylhexylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aniline, benzylamine, and phenylenediamine; and polyhydric phenols, such as bisphenol A, bisphenoI F, 1,1-bis(hydroxyphenyl)ethane, bisphenol AP, acetophenone, and hydroquinone. 
     Examples of the glycidyl ether reacted with the active hydrogen compound may include those having a substituent of an alkyl group, alkenyl group, aryl group or aralkyl group represented by the following formula (2): ##STR5## wherein R 2  is an alkylene group having 1-10 carbon atoms, such as methylene, ethylene, propylene, butylene, hexene, and nonene; R 3  is an alkyl group, alkenyl group, aryl group or aralkyl group having 1-20 carbon atoms, inclusive of alkyl groups, such as methyl, ethyl, isopropyl and butyl, alkenyl groups, such as vinyl and allyl, aryl groups, such as phenyl and naphthyl, and aralkyl groups, such as benzyl and phenethyl; and p is a number of 0-5. 
     At the time of the reaction of the active hydrogen compound with the glycidyl ether, it is possible to also react an alkylene oxide having 2-10 carbon atoms, examples of which may include: ethylene oxide, propylene oxide, butylene oxide, hexene oxide, cyclohexene oxide and nonene oxide. 
     In the case of reaction with the active hydrogen compound, the glycidyl ether and the alkylene oxide may be reacted in mixture or in any arbitrary order so as to provide a polyol compound [I] in the form of either a random polymer or a block polymer. 
     As the catalyst for the above reaction, basic catalysts, such as sodium methoxide, sodium hydroxide, potassium hydroxide, lithium carbonate and triethylamine, may generally be used, but a Lewis acid catalyst such as boron trifluoride can also be used. 
     Specific examples of the polyol compound [I] represented by the formula (1) used in the present invention are shown in the following Table 1. 
     
                                           TABLE 1                                 
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Polyol compound I                                                         
Z[ (A) .sub.m(B) .sub.nH].sub.k                                           
Active hydrogen                                                           
compound Z    (A) .sub.m                   (B) .sub.n                     
No. (residue) A component              .sup.-- m.sup.1)                   
                                           B component                    
                                                     - n.sup.2)           
                                                        k  -- Mn.sup.3)   
__________________________________________________________________________
 1  glycerine                                                             
               ##STR6##                7.4 --        0  3  4000           
 2  trimethylolpropane                                                    
               ##STR7##                2.6 --        0  3  2800           
 3  propylene glycol                                                      
               ##STR8##                1.1 --        0  2   700           
 4  pentaerythritol                                                       
               ##STR9##                7.3 CH.sub.2 CH.sub.2 O            
                                                     2.2                  
                                                        4  8000           
 5  ethylenediamine                                                       
               ##STR10##               9.5                                
                                            ##STR11##                     
                                                     1.0                  
                                                        4  6000           
 6  glycerine                                                             
               ##STR12##               7.5                                
                                            ##STR13##                     
                                                     0.7                  
                                                        3  4200           
 7  trimethylolpropane                                                    
               ##STR14##               3.4                                
                                            ##STR15##                     
                                                     1.5                  
                                                        3  3200           
 8  propylene glycol                                                      
               ##STR16##               1.1                                
                                            ##STR17##                     
                                                     0.7                  
                                                        2   900           
 9  pentaerythritol                                                       
               ##STR18##               6.1                                
                                            ##STR19##                     
                                                     5.5                  
                                                        4  8000           
10  ethylenediamine                                                       
               ##STR20##               3.8                                
                                            ##STR21##                     
                                                     11.6                 
                                                        4  7000           
11  glycerine                                                             
               ##STR22##               10.7                               
                                           --        0  3  10000          
12  glycerine                                                             
               ##STR23##               24.3                               
                                           --        0  3  6500           
13  trimethylolpropane                                                    
               ##STR24##               7.2 CH.sub.2 CH.sub.2 O            
                                                     2.5                  
                                                        3  5500           
14  trimethylolpropane                                                    
               ##STR25##               1.5 --        0  3  1400           
15  pentaerythritol                                                       
               ##STR26##               7.8 CH.sub.2 CH.sub.2 O            
                                                     2.0                  
                                                        4  6000           
16  glycerine                                                             
               ##STR27##               3.4 --        0  3  1600           
17  propylene glycol                                                      
               ##STR28##               14.6                               
                                           --        0  2  8500           
18  propylene glycol                                                      
               ##STR29##               93  --        0  2  19000          
19  propylene glycol                                                      
               ##STR30##               8.7 CH.sub.2 CH.sub.2 O            
                                                     47 2  6500           
20  sucrose                                                               
               ##STR31##               2.9           0  8  5500           
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 Notes:                                                                   
 .sup.1) .sup.-- m: average of m.                                         
 .sup.2) -n: average of n.                                                
 .sup.3) --Mn: numberaverage molecular weight                             
 
    
     Next, some specific examples of synthesis of the polyol compound [I] are shown below. 
     SYNTHESIS EXAMPLE 1--1 (EXAMPLE COMPOUND NO. 1) 
     70 g of glycerin as a starting material and 12 g of catalyst potassium hydroxide were placed in an autoclave, and 4000 g of methyldiethylene glycol glycidyl ether of the following formula was gradually added thereto in 6 hours for reaction at 120° C. ##STR32## 
     The reaction was completed by further 2 hours of reaction at the same temperature, and desalting and purification were performed to recover 3600 g of a polyol compound of Example Compound No. 1 having an Mn (number-average molecular weight calculated from the hydroxyl value) of 4000. 
     SYNTHESIS EXAMPLE 1-2 (EXAMPLE COMPOUND NO. 2) 
     134 g of trimethylolpropane as a starting material and 10 g of catalyst potassium hydroxide were placed in an autoclave, and 3100 g of n-butyltriethylene glycol glycidyl ether of the following formula was gradually added thereto in 6 hours for at 120° C. ##STR33## 
     The reaction was completed by further 2 hours of reaction at the same temperature, and desalting and purification were performed to recover 2900 g of a polyol compound of Example Compound No. 2 having an Mn of 2900. 
     On the other hand, the phosphated polyol compound [II] may be prepared from a polyoxyalkylene polyol compound (or polyether polyol), which in turn may be prepared through a process wherein one or more species of alkylene oxides each having 2-10 carbon atoms are polymerized or copolymerized together with an active hydrogen compound in the presence of a catalyst, and the product is treated for removal of the catalyst by an ordinary purification method, such as ion exchange, neutralization filtration or adsorption. The polyoxyalkylene polyol may preferably have a number-average molecular weight of 200-10,000. 
     Examples of the active hydrogen compound, the alkylene oxides having 2-10 carbon atoms and the catalyst may respectively be the same as those described above used for preparation of the polyol compound [1]. 
     The phosphated polyol Compound [II] may be obtained by reacting the polyoxyalkylene polyol compound with a phosphorus compound, preferably a phosphorus oxide, such as phosphorus pentoxide (P 2  O 5 ) and phosphorus oxytrichloride (POCl 3 ) in a manner which per se is known. In this instance, the oxyalkylene polyol compound and the phosphorus compound may preferably be reacted in a ratio suitable for providing a phosphated polyol compound [II] having a hydroxyl value of ordinarily 10-2000 mgKOH/g. 
     Some specific examples of the phosphated polyol compound [II] are shown in the following Table 2. 
     
                                           TABLE 2                                 
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Phosphated polyol compound [II]                                           
Polyoxyalkylene polyol                                                    
           Alkylene oxide                                                 
                    Copolymer Phosphorus                                  
           Number of carbon                                               
                    form      compound                                    
                                      phosphated polyol                   
Active hydrogen                                                           
           atoms *1, *2                                                   
                    BK RM         Ratio                                   
                                      Hydroxyl value                      
                                              Viscosity                   
compound   2  3  4  *3 *4 Mn  Species                                     
                                  *5  (mg KOH/g)                          
                                              (cps/25° C.)         
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A glycerine                                                               
           80 20       ∘                                      
                          600 P.sub.2 O.sub.5                             
                                  4   240     450                         
B glycerine                                                               
           50 50    ∘                                         
                          200 POCl.sub.3                                  
                                  15  785     360                         
C ethylene glycol                                                         
           100                                                            
               0          300 P.sub.2 O.sub.5                             
                                  12  324     200                         
D ethylene glycol                                                         
           60 40       ∘                                      
                          400 P.sub.2 O.sub.5                             
                                  9   253     310                         
E bisphenol A                                                             
           50 50    ∘                                         
                          500 P.sub.2 O.sub.5                             
                                  6   197     390                         
F trimethylol-                                                            
           90    10    ∘                                      
                          800 P.sub.2 O.sub.5                             
                                  3   118     520                         
  propane                                                                 
G trimethylol-                                                            
           70    30    ∘                                      
                          500 P.sub.2 O.sub.5                             
                                  3   311     410                         
  propane                                                                 
H penta-   40 60       ∘                                      
                          600 POCl.sub.3                                  
                                  9   303     400                         
  erythritol                                                              
I sorbitol 80 20       ∘                                      
                          600 POCl.sub.3                                  
                                  4   512     390                         
J sorbitol 50 50    ∘                                         
                          1500                                            
                              P.sub.2 O.sub.5                             
                                  8   161     620                         
K propylene glycol                                                        
              100         4000                                            
                              POCl.sub.3                                  
                                  8    19     710                         
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Notes of Table 2                                                          
*1:                                                                       
  Number of carbon atoms                                                  
  2: ethylene oxide                                                       
  3: propylene oxide                                                      
  4: butylene oxide                                                       
*2:                                                                       
  Numerals denote weight % values of the added alkylene oxides            
*3:                                                                       
  block copolymer                                                         
*4:                                                                       
  random copolymer                                                        
*5:                                                                       
  Amount (wt. parts) of the phosphorus compound reacted per 100 wt. parts 
  of the polyoxyalkylene polyol.                                          
 
    
     Some specific examples of synthesis of the phosphated polyol compound [II] are shown below. 
     SYNTHESIS EXAMPLE 2-1 (EXAMPLE COMPOUND A) 
     550 g of ethylene oxide and 2200 g of propylene oxide were reacted together with 460 g of glycerine as a starting material in the presence of 9 g of catalyst potassium hydroxide in a 5000 ml-autoclave at 120° C. for 6 hours, followed by desalting purification, to recover 2950 g of a polyoxyalkylene polyol having an Mn (number-average molecular weight calculated from the hydroxyl value) of 600. 
     4 g of phosphorus pentoxide was added to 100 g of the polyoxyalkylene polyol, and the mixture was reacted for 6 hours at 70° C. under stirring to obtain phosphated polyol compound A (hydroxyl value: 240 mgKOH/g, viscosity: 450 cps/25° C.). 
     SYNTHESIS EXAMPLE 2-2 (EXAMPLE COMPOUND K) 
     3100 g of propylene oxide was reacted together with 53 g of propylene glycol as a starting material in the presence of 8 g of catalyst potassium hydroxide in a 5000 ml-autoclave at 120° C. for 6 hours, followed by desalting purification, to recover 2800 g of a polyoxyalkylene polyol having an Mn of 4000. 
     8 g of phosphorus oxytrichloride was added to 100 g of the polyoxyalkylene polyol, and the mixture was reacted for 6 hours at 70° C. under stirring to obtain phosphated polyol compound K (hydroxyl value: 19 mgKOH/g, viscosity: 710 cps/25° C.). 
     In the present invention, the polyol compound [I] and the phosphated polyol compound [II] can be used in combination for reaction with a polyisocyanate compound. 
     In the present invention, it is also possible to use another polyol compound in addition to the polyol compounds [I] and/or [II] for reaction with a polyisocyanate compound. Such another polyol compound may suitably be, e.g., a polyoxyalkylene polyol or a glycidyl ether represented by the above-mentioned formula (2), and also a polyester polyol or an acrylate polyol. A polyoxyalkylene polyol having a number-average molecular weight of 200-10,000 is particularly suitable. 
     The above-mentioned polyol compound (polyol compound [I] and/or [II] and optional another polyol compound) is reacted with a polyisocyanate compound to provide a reaction product constituting the intermediate layer of the photosensitive member according to the present invention. 
     Examples of the polyisocyanate compound to be used in the present invention may include: 2,4-toluene diisocyanate (2,4-TDI), 2-6-toluene diisocyanate (2,6-TDI), 4,4&#39;-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate, and mixtures and adducts thereof. 
     The polyisocyanate compound can also be used in a blocked isocyanate form (terminal-protected isocyanate). The blocking agent may for example be methyl ethyl ketoxime (MEKO), phenol, caprolactam, ethyl acetoacetate, methanol or sodium hydrogensulfite. 
     The blocking may be effected by adding such a blocking agent to the polyisocyanate compound and performing the reaction at 30°-90° C. for 0.5-2 hours. 
     The intermediate layer comprising a reaction product of the polyol compounds and polyisocyanate compound may be formed by applying a mixture including the above-mentioned polyol compound and polyisocyanate compound and then subjecting the resultant layer to curing under heating, or by synthesizing a polymer of the above-mentioned polyol compound and polyisocyanate compound in advance and then applying a solution of the polymer in an appropriate solvent, followed by drying. 
     It is also possible to form an intermediate product, such as a polyisocyanate compound prepared by reacting the above-mentioned polyol compound ([I]. II], etc.) with an excessive amount of an isocyanate compound, a blocked polyisocyanate compound prepared by protecting the terminals of such a polyisocyanate compound with a blocking agent, or an adduct prepared by adding a polyol compound such as a polyoxyalkylene polyol to such a polyisocyanate compound, formulate a paint containing such an intermediate product together with or in the absence of an additional polyol compound, and apply the paint, followed by curing under heating, to form the intermediate layer. 
     For the reaction between the polyol compound ([I], [II], etc.) and the polyisocyanate compound, it is possible to use a catalyst for accelerated reaction. The catalyst used for this purpose may for example include: amine catalysts, such as triethylamine, N,N-dimethylethanolamine, triethylenediamine N,N&#39;-dimethylpiperazine and N-methylmorpholine: and metal salt catalysts, such as zinc octylate, tin octylate, dibutyltin dilaurate and dibutyltin diacetate. 
     The polyol compound ([I], [II], etc.) and the polyisocyanate compound may preferably be reacted in a functional group molar ratio (NCO group/OH group) of 1/1-2/1 between the NCO and OH groups. 
     The intermediate layer of the photosensitive member according to the present invention may be composed of a single layer comprising a reaction product between the above-mentioned polyol compound and polyisocyanate compound, but can also assume a laminated structure including plural layers, at least one of which comprises the above-mentioned reaction product. In case where the intermediate layer is composed of plural layers, another layer not comprising the above-mentioned reaction product may comprise a resin material, such as polyamide, polyester or phenolic resin. 
     The intermediate layer used in the present invention can further contain, e.g., another resin, additive or electroconductive substance, according to necessity. 
     Examples of such an electroconductive substance may include: powder or short fiber of metals such as aluminum, copper, nickel, and silver; electroconductive metal oxides, such as antimony oxides, indium oxide and tin oxide; carbon film, carbon black and graphite powder; and electroconductive obtained by coating with such an electroconductive substance. 
     The thickness of the intermediate layer according to the present invention may be determined in view of electrophotographic characteristics and influence of defects on the support and may generally be set within the range of 0.1-50 microns, more suitably 0.5-30 microns. 
     The intermediate layer may be formed by an appropriate coating method, such as dip coating, spray coating or roller coating. 
     In the present invention, the photosensitive layer may be either of a single layer-type or of a laminated layer-type functionally separated into a charge generation layer and a charge transport layer. 
     An organic charge generation layer of the laminated layer-type photosensitive layer may for example be prepared by dispersing an organic charge-generating substance, such as azo pigment, quinone pigment, quinocyanine pigment, perylene pigment, indigo pigment, azulenium salt pigment or phthalocyanine pigment into a solution containing a resin such as polyvinyl butyral, polystyrene, polyvinyl acetate, acrylic resin, polyvinylpyrrolidone, ethyl cellulose acetate butyrate to form a coating liquid, and applying the coating liquid onto the above-mentioned intermediate layer. The charge generation layer may have a thickness of at most 5 microns, preferably 0.05-2 microns. 
     A charge transport layer may be formed on such a charge generation layer by dissolving a charge transporting substance of, e.g., a polycyclic aromatic compound having a structure of biphenylene, anthracene, pyrene, phenanthrene, etc., in its main chain or side chain, a nitrogen-containing cyclic compound such as indole, carbazole, oxadiazole or pyrazoline, triarylamine compound, hydrazone compound, or styryl compound into a solution of a film-forming resin to form a coating liquid, and applying the coating liquid. The film-forming resin may for example include polyester, polycarbonate, polymethacrylate and polystyrene. 
     The charge transport layer may ordinarily have a thickness of 5-40 microns, preferably 10-30 microns. 
     The laminated layer-type photosensitive layer can also assume a structure wherein the charge generation layer is disposed on the charge transport layer. 
     A single layer-type photosensitive layer may be formed as a layer containing both the charge generating substance and the charge transporting substance together in a resin. 
     In the present invention, it is also possible to constitute the photosensitive layer as a layer of an organic photoconductive polymer, such as poylvinylcarbazole or polyvinylanthracene, a vapor-deposition layer of a charge generation substance as described above, a vapor-deposited selenium layer, a vapor-deposited selenium-tellurium layer, or an amorphous silicon layer. 
     On the other hand, the support used in the present invention may be any one as far as it has an electroconductivity, inclusive of, e.g., a metal, such as aluminum, copper, chromium, nickel, zinc or stainless steel formed into a cylinder or sheet; a plastic film or paper laminated with a foil of a metal such as aluminum or copper, a plastic film provided thereon with a vapor-deposited layer of, e.g., aluminum, indium oxide or tin oxide, or a plastic film or paper coated with an electroconductive layer of an electroconductive substance alone or dispersed in an appropriate binder resin. 
     The electrophotographic photosensitive member according to the present invention may be applicable to an electrophotographic apparatus in general, inclusive of a copying machine, a laser printer, an LED printer and a liquid crystal shutter-type printer. and further widely applicable to apparatus, such as a display, a recording apparatus, a mini-scale printing apparatus, a plate production apparatus and a facsimile apparatus, utilizing electrophotography in an applied form. 
     FIG. 1 shows a schematic structural view of an ordinary transfer-type electrophotographic apparatus using an electrophotosensitive member of the invention. Referring to FIG. 1, a photosensitive drum (i.e., photosensitive member) 11 as an image-carrying member is rotated about an axis 11a at a prescribed peripheral speed in the direction of the arrow shown inside of the photosensitive drum 11. The surface of the photosensitive drum is uniformly charged by means of a charger 12 to have a prescribed positive or negative potential. The photosensitive drum 11 is exposed to light-image L (as by slit exposure or laser beam-scanning exposure) by using an image exposure means (not shown), whereby an electrostatic latent image corresponding to an exposure image is successively formed on the surface of the photosensitive drum 11. The electrostatic latent image is developed by a developing means 14 to form a toner image. The toner image is successively transferred to a transfer material P which is supplied from a supply part (not shown) to a position between the photosensitive drum 11 and a transfer charger 15 in synchronism with the rotating speed of the photosensitive drum 11, by means of the transfer charger 15. The transfer material P with the toner image thereon is separated from the photosensitive drum 11 to be conveyed to a fixing device 18, followed by image fixing to print out the transfer material P as a copy outside the electrophotographic apparatus. Residual toner particles on the surface of the photosensitive drum 11 after the transfer are removed by means of a cleaner 16 to provide a cleaned surface, and residual charge on the surface of the photosensitive drum 11 is erased by a pre-exposure means 17 to prepare for the next cycle. As the charger 12 for charging the photosensitive drum 11 uniformly, a corona charger is widely used in general. As the transfer charger 15, such a corona charger is also widely used in general. 
     According to the present invention, in the electrophotographic apparatus, it is possible to provide an apparatus unit which includes plural means inclusive of or selected from the photosensitive member (photosensitive drum), the charger, the developing means, the cleaner, etc. so as to be attached to or released from the apparatus body, as desired. The device unit may, for example, be composed of the photosensitive member and the cleaner to prepare a single unit capable of being attached to or released from the body of the electrophotographic apparatus by using a guiding means such as a rail in the body. The apparatus unit can be further accompanied with the charger and/or the developing means to prepare a single unit. 
     In case where the electrophotographic apparatus is used as a copying machine or a printer, exposure light-image L may be given by reading data on reflection light or transmitted light from an original or, converting the data on the original into a signal and then effecting a laser beam scanning, a drive of LED array or a drive of a liquid crystal shutter array. 
     In case where the electrophotographic apparatus according to the present invention is used as a printer of a facsimile machine, exposure light-image L is given by exposure for printing received data. FIG. 2 shows a block diagram of an embodiment for explaining this case. Referring to FIG. 2, a controller 21 controls an image-reading 20 and a printer 29. The whole controller 21 is controlled by a CPU (central processing unit) 27. Read data from the image-reading part is transmitted to a partner station through a transmitting circuit 23, and on the other hand, the received data from the partner station is sent to the printer 29 through a receiving circuit 22. An image memory memorizes prescribed image data. A printer controller 28 controls the printer 29, and reference number 24 denotes a telephone handset. 
     The image received through a line 25 (the image data sent through the circuit from a connected remote terminal) is demodulated by means of the receiving circuit 22 and successively stored in an image memory 26 after a restoring-signal processing of the image data. When image for at least one page is stored in the image memory 26, image recording of the page is effected. The CPU 27 reads out the image data for one page from the image memory 26 and sends the image data for one page subjected to the restoring-signal processing to the printer controller 28. The printer controller 28 receives the image data for one page from the CPU 27 and controls the printer 29 in order to effect image-data recording. Further, the CPU 27 is caused to receive image for a subsequent page during the recording by the printer 29. As described above, the receiving and recording of the image are performed. 
     Hereinbelow, the present invention will be explained based on Examples wherein &#34;part(s)&#34; means &#34;part(s) by weight&#34;. 
     EXAMPLE 1-1 
     A paint for an intermediate layer having the following composition was prepared by mixing. 
     
         ______________________________________                                    
Polyol compound No. 1  9.6 wt. part(s)                                    
Hexamethylene diisocyanate (HMDI)                                         
                       1.4 wt. part(s)                                    
Dibutyltin dilaurate (DBTL)                                               
                       0.02 wt. part(s)                                   
Methyl ethyl ketone (MEK)                                                 
                       80 wt. part(s)                                     
______________________________________                                    
 
    
     The paint was applied onto an aluminum cylinder (OD (outer diameter)=30 mm, L (length)=360 mm) by dipping and then dried and cured at 150° C. for 30 min. to form a 3.0 micron-thick intermediate layer. 
     Separately, 4 parts of a disazo pigment represented by the following formula: ##STR34## 2 parts ofof a butyral resin (butyral degree=68% , Mw (weight-average molecular weight)=24000) and 34 parts of cyclohexanone were dispersed for 8 hours by means of a sand mill containing 1 mm-dia. glass beads and diluted with 60 parts of tetrahydrofuran (THF) to prepare a coating liquid for a charge generation layer. The thus prepared coating liquid was applied by dipping onto the above prepared intermediate layer and dried at 80° C. for 15 min. form a 0.2 micron-thick charge generation layer. 
     Then, 10 parts of a hydrazone compound of the formula: ##STR35## 10 parts of a bisphenol Z-type polycarbonate (Mw=30000), 10 parts of dichloromethane and 50 parts of monochlorobenzene were dissolved in mixture to form a coating liquid for a charge transport layer. The coating liquid was applied onto the above-formed charge generation layer by dipping and dried for 60 min. at 110° C. to form a 20 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a copying apparatus, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-development-transfer-cleaning were repeated at a cycle of 0.8 sec under low temperature-low humidity conditions (15° C.-15% RH). The results are summarized in Table 3 appearing hereinafter. 
     As is shown in Table 3, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further, as a result of 1000 sheets of successive image formation, images could be formed in a very stable state without causing an increase in light-part potential (V L ). 
     EXAMPLES 1-2-1-4 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 1-1 except that the following compositions were respectively used for preparing the intermediate layers. 
     
         ______________________________________                                    
[Example 1-2]                                                             
______________________________________                                    
Polyol compound No. 2) 18.1 part(s)                                       
2,4-TDI                1.9 part(s)                                        
DBTL                   0.02 part(s)                                       
MEK                    80 part(s)                                         
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 1-3]                                                             
______________________________________                                    
Polyol compound No. 5   17.6 part(s)                                      
HMDI in a blocked from with                                               
                        2.4 part(s)                                       
methyl ethyl ketoxime (MEKO)                                              
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 1-4]                                                             
______________________________________                                    
Polyol compound No. 7    8.7 part(s)                                      
Poly(oxyethylene)triol (Mn = 3000)                                        
                         8.7 part(s)                                      
MDI                      2.6 part(s)                                      
DBTL                     0.02 part(s)                                     
MEK                      80 part(s)                                       
______________________________________                                    
 
    
     The above-prepared photosensitive members were evaluated in the same manner as in Example 1-1. As a result, the respective photosensitive members showed a large difference between dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient potential contrast. Further, as a result of 1000 sheets of successive image formation, the respective photosensitive members provided images in a very stable state while causing almost no increase in light-part potential (V L ). 
     The results are also summarized in Table 3. 
     EXAMPLE 1-5 
     
         ______________________________________                                    
Example 1-5                                                               
______________________________________                                    
Polyol compound No. 8  41.6 parts                                         
2,6-TDI                8.4 parts                                          
______________________________________                                    
 
    
     The above ingredients were reacted under stirring for 4 hours at 90° C. to form a reaction product (polymer). 
     
         ______________________________________                                    
The above reaction product                                                
                        10 parts                                          
MEK                     60 parts                                          
Dichloromethane         30 parts                                          
______________________________________                                    
 
    
     A coating liquid was prepared by mixing the above ingredients, and an electrophotographic photosensitive member was prepared in the same manner as in Example 1-1 except that the coating liquid was used for preparing the intermediate layer. 
     The thus-prepared photosensitive member was evaluated in the same manner as in Example 1-1. As a result, the photosensitive member showed a large difference between dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient potential contrast. Further, as a result of 1000 sheets of successive image formation, the photosensitive member provided images in a very stable state while causing almost no increase in light-part potential (V L ). 
     The results are also shown in Table 3. 
     COMPARATIVE EXAMPLES 1-1 and 1-2 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 1-1 except that the following compositions were respectively used for preparing the intermediate layers. 
     
         ______________________________________                                    
[Comparative Example 1-1]                                                 
______________________________________                                    
Alcohol-soluble copolymer nylon                                           
                          5 part(s)                                       
(&#34;Amilan CM-8000&#34;, mfd. by Toray K.K.)                                    
Methanol                  95 part(s)                                      
______________________________________                                    
 
    
     
         ______________________________________                                    
[Comparative Example 1-2]                                                 
______________________________________                                    
Polyester polyol        14 part(s)                                        
(&#34;Nippolan 125&#34;, mfd. by Nihon                                            
Polyurethane Kogyo K.K.)                                                  
2,6-TDI                 6 part(s)                                         
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     The photosensitive members were evaluated in the same manner as in Example 1-1 . As a result, both photosensitive members showed an increase in light-potential part potential (V L ), thus resulting in images accompanied with fog after 1000 sheets of successive copying. 
     The results are also summarized in Table 3 below. 
     Separately, the intermediate layers were formed according to the above-described methods of 
     Examples 1-1-1-5 and Comparative Examples 1-1 and 1-2, and the adhesion strengths thereof were evaluated by a square matrix pattern (or checker pattern) peeling test according to JIS K5400 (general test method for paints). 
     As a result, the intermediate layers according to Examples 1-1-1-5 were all free from peeling, thus showing good adhesion to the aluminum substrate. On the other hand, the intermediate layers of Comparative Examples 1-1 and 1-2 showed peeling rates of 25% and 29% , respectively. 
     
                       TABLE 3                                                     
______________________________________                                    
                     After 1000 sheets of                                 
       Initial Stage sucessive copying                                    
       Dark-part                                                          
               Light-part                                                 
                         Light-part                                       
       potential                                                          
               potential potential Image                                  
       V.sub.D (-V)                                                       
               V.sub.L (-V)                                               
                         V.sub.L (-V)                                     
                                   evaluation                             
______________________________________                                    
Example                                                                   
1-1      685       170       190     Good                                 
1-2      660       175       190     Good                                 
1-3      680       180       200     Good                                 
1-4      670       165       180     Good                                 
1-5      675       185       195     Good                                 
Comparative                                                               
Example                                                                   
1-1      665       190       325     Fog                                  
                                     occurred                             
1-2      670       200       360     Fog                                  
                                     occurred                             
______________________________________                                    
 
    
     EXAMPLE 1-6 
     
         ______________________________________                                    
Resol-type phenolic resin                                                 
                         25 parts                                         
Electroconductive titanium oxide                                          
                         50 parts                                         
powder (coated with tin oxide                                             
containing 10% of antimony                                                
oxide)                                                                    
Methyl cellosolve        20 parts                                         
Methanol                 5 parts                                          
______________________________________                                    
 
    
     The above-ingredients were subjected to 2 hours of mixing and dispersion in a sand mill containing 1 mm-dia. glass beads to prepare a paint for a first intermediate layer. 
     The paint was applied onto an aluminum cylinder (OD=30 mm, L=260 mm) by dipping and then dried and cured at 140° C. for 30 min. to form a 20 micron-thick first intermediate layer. 
     
         ______________________________________                                    
Polyol compound No. 14 14.0 part(s)                                       
2,4-TDI in a blocked form                                                 
                       6.0 part(s)                                        
with MEKO                                                                 
DBTL                   0.02 part(s)                                       
MEK                    80 part(s)                                         
______________________________________                                    
 
    
     The above ingredients were dissolved in mixture to form a paint for a second intermediate layer, which was then applied by dipping onto the first intermediate layer and dried and cured at 150° C. for 20 min. to form a 0.6 micron-thick second intermediate layer. 
     Then, 3 parts of a disazo pigment of the formula: ##STR36## 2 parts of polyvinyl benzal (benzal degree=80% , Mw=1000) and 35 parts of cyclohexanone were subjected to 12 hours of mixing and dispersion by a sand mill containing 1 mm-dia. glass beads and further dispersed after adding 60 parts of methyl ethyl ketone (MEK) to form a coating liquid for a charge generation layer. The coating liquid was applied by dipping onto the above second intermediate layer and dried at 80° C. for 20 min. to form a 0.2 micron-thick charge generation layer. 
     Then, 10 parts of a styryl compound of the formula: ##STR37## 10 parts of a bisphenol Z-type polycarbonate (Mw=30000), 15 parts of dichloromethane and 45 parts of monochlorobenzene were dissolved in mixture to form a coating liquid for a charge transport layer. The coating liquid was applied onto the above-formed charge generation layer by dipping and dried for 60 min. at 120° C. to form a 18 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a laser printer of the reversal development type, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-development-transfer-cleaning were repeated at a cycle of 1.5 sec under normal temperature-normal humidity conditions (23° C.-50% RH) and high temperature-high humidity conditions (30° C.-85% RH). The results are summarized in Table 4 appearing hereinafter. 
     As is shown in Table 4, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further, also under the high temperature-high humidity conditions, the dark-part potential was stable and good images free from black spots or fog could be formed. 
     EXAMPLES 1-7-1-10 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 1-6 except that the following compositions were respectively used for preparing the second intermediate layers. 
     
         ______________________________________                                    
[Example 1-7]                                                             
______________________________________                                    
Polyol compound [I] No. 3                                                 
                        12.8 part(s)                                      
HMDI in a phenol-blocked form                                             
                        7.2 part(s)                                       
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 1-8]                                                             
______________________________________                                    
Polyol compound No. 9   17.8 part(s)                                      
MDI in an MEKO-blocked form                                               
                        2.2 part(s)                                       
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 1-9]                                                             
______________________________________                                    
Polyol compound No. 1   10.3 part(s)                                      
Polyol compound No. 2   6.8 part(s)                                       
2,6-TDI in an MEKO-blocked form                                           
                        2.9 part(s)                                       
DBTL                    0.04 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 1-10]                                                            
______________________________________                                    
Polyol compound No. 11 19.4 part(s)                                       
HMDI in a trimerized form                                                 
                       0.6 part(s)                                        
isocyanurate                                                              
Tin octylate           0.02 part(s)                                       
MEK                    80 part(s)                                         
______________________________________                                    
 
    
     The above-prepared photosensitive members were evaluated in the same manner as in Example 1-6. As a result, each photosensitive member maintained a stable dark-part potential (V D ) even under high temperature-high humidity conditions and could provide good images free from occurrence of black spots or fog. 
     The results are summarized in Table 4. 
     COMPARATIVE EXAMPLES 1-3-1-5 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 6 except that the following compositions were respectively used for preparing the second intermediate layers. 
     
         ______________________________________                                    
[Comparative Example 1-3]                                                 
______________________________________                                    
N-methoxymethylated 6-nylon                                               
                        5 part(s)                                         
(Mw = 50000, methoxymethyl-                                               
substitution rate = 28%)                                                  
Methanol                95 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Comparative Example 1-4]                                                 
______________________________________                                    
Poly(oxypropylene)triol  15 part(s)                                       
(hydroxyl value = 170 mg KOH/g)                                           
2,4-TDI                  5 part(s)                                        
DBTL                     0.02 part(s)                                     
MEK                      80 part(s)                                       
______________________________________                                    
 
    
     
         ______________________________________                                    
[Comparative Example 1-5]                                                 
______________________________________                                    
Poly(oxyethylene)glycol (hydroxyl                                         
                        17.6 part(s)                                      
value = 37.5 mg KOH/g)                                                    
2,6-TDI in an MEKO-blocked form                                           
                        2.4 part(s)                                       
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     The photosensitive members were evaluated in the same manner as in Example 1-6. As a result, the photosensitive member according to Comparative Example 1-3 showed a decrease in chargeability to lower the dark-part potential (V D ) under the high temperature-high humidity conditions and also provided images accompanied with black spots and fog. On the other hand, the photosensitive members according to Comparative Examples 1-4 and 1-5 did not show a decrease in chargeability under the high temperature-high humidity conditions, but the resultant images were accompanied with black spots. 
     The results are summarized in Table 4. 
     Separately, the intermediate layers were formed according to the above-described methods of Examples 1-6-1-10 and Comparative Examples 1-3 and 1-5, and the adhesion strengths thereof were evaluated by a square matrix pattern (or checker pattern) peeling test according to JIS K5400. 
     As a result, the intermediate layers according to Examples 1-6-1-10 were all free from peeling, thus showing good adhesion to the aluminum substrate. On the other hand, the intermediate layers of Comparative Examples 1-3 to 1-5 showed peeling rates of 22% , 35% and 31% , respectively. 
     
                       TABLE 4                                                     
______________________________________                                    
       Environmental conditions                                           
       23° C., 50% RH                                              
                     30° C., 85% RH                                
       V.sub.D (-V)                                                       
               V.sub.L (-V)                                               
                         V.sub.D (-V)                                     
                                   Image                                  
______________________________________                                    
Example                                                                   
1-6      620       150       610     Good                                 
1-7      625       170       605     Good                                 
1-8      615       155       610     Good                                 
1-9      640       160       620     Good                                 
 1-10    630       165       625     Good                                 
Comparative                                                               
Example                                                                   
1-3      635       165       560     Black spots                          
                                     and fog                              
                                     occurred                             
1-4      630       165       610     Black spots                          
                                     occurred                             
1-5      630       180       615     Black spots                          
                                     occurred                             
______________________________________                                    
 
    
     EXAMPLE 1-11 
     
         ______________________________________                                    
Polyol compound No. 4   18.2 part(s)                                      
2,6-TDI in MEKO-blocked form                                              
                        1.8 part(s)                                       
Electroconductive titanium                                                
                        20 part(s)                                        
oxide powder (coated with tin                                             
oxide containing 8% of antimony                                           
oxide)                                                                    
Rutile-type titanium oxide powder                                         
                        20 part(s)                                        
DBTL                    0.02 part(s)                                      
MEK                     40 part(s)                                        
______________________________________                                    
 
    
     The above-ingredients were subjected to 3 hours of mixing and dispersion in a sand mill containing 1 mm-dia. glass beads to prepare a paint for a first intermediate layer. 
     The paint was applied onto an aluminum cylinder (OD=60 mm, L=260 mm) by dipping and then dried and cured at 150° C. for 30 min. to form a 15 micron-thick first intermediate layer. 
     Then, the paint for the second intermediate layer prepared in Example 1-6 was applied by dipping onto the above first intermediate layer, and dried and cured at 150° C. for 20 min. to form a 0.6 micron-thick second intermediate layer. 
     Then, 4 parts of a disazo pigment of the formula: ##STR38## 2 parts of polyvinyl butyral (butyral degree=71%, Mw=18000) and 34 parts of cyclohexanone were subjected to 6 hours of mixing and dispersion by a sand mill containing 1 mm-dia. glass beads and further dispersed after adding 60 parts of methyl ethyl ketone (MEK) to form a coating liquid for a charge generation layer. The coating liquid was applied by dipping onto the above second intermediate layer and dried at 80° C. for 15 min to form a 0.3 micron-thick charge generation layer. 
     Then, the coating liquid for a charge transport layer used in Example 1-6 was applied by dipping onto the charge generation layer and dried at 120° C. for 60 min to form a 22 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a copying apparatus, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-development-transfer-cleaning were repeated at a cycle of 0.6 sec under low temperature-low humidity conditions (10° C.-10% RH). The results are summarized in Table 5 appearing hereinafter. 
     As is shown in Table 5, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further, as a result of 1000 sheets of successive image formation, images could be formed in a very stable state without causing an increase in light-part potential (V L ). 
     EXAMPLE 1-12 
     
         ______________________________________                                    
Alcohol-soluble copolymer nylon                                           
                         3 parts                                          
(&#34;Amilan CM-8000&#34;, mfd. by                                                
Toray K.K.)                                                               
N-methoxymethylated 6-nylon                                               
                         3 parts                                          
(Mw = 150000, methoxymethyl                                               
substitution rate = 30%)                                                  
Methanol                 94 parts                                         
______________________________________                                    
 
    
     An electrophotographic photosensitive member was prepared in the same manner as in Example 1-11 except that a coating liquid prepared from the above ingredients was used for forming the second intermediate layer. 
     EXAMPLE 1-13 
     An electrophotographic photosensitive member was prepared in the same manner as in Example 1-11 except that the second insulating layer was omitted to form on the support a laminated structure composed of the first intermediate layer, the charge generation layer and the charge transport layer. 
     The above-prepared photosensitive members of Examples 1-12 and 1-13 were evaluated in the same manner as in Example 1-11. As a result, each photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient potential contrast. Further, as a result of 1000 sheets of successive image formation, the photosensitive members provided images in a very stable state while causing almost no increase in light-part potential (V L ). 
     The results are summarized in Table 5. 
     COMPARATIVE EXAMPLES 1-6 AND 1-7 
     
         ______________________________________                                    
Resol-type phenolic resin                                                 
                         20 parts                                         
Electroconductive titanium                                                
                         20 parts                                         
oxide powder (coated with tin                                             
oxide containing 8% of antimony                                           
oxide)                                                                    
Rutile-type titanium oxide powder                                         
                         20 parts                                         
Methyl cellosolve        25 parts                                         
Methanol                 15 parts                                         
______________________________________                                    
 
    
     A paint for the first intermediate layer was prepared from the above ingredients otherwise in the same manner as in Example 1-11. 
     Electrophotographic photosensitive members of Comparative Examples 1-6 and 1-7 were prepared in the same manner as in Examples 1-12 and 1-13, respectively, except that the above-prepared paint was used for forming the first intermediate layer. 
     The photosensitive members were evaluated in the same manner as in Example 1-11. As a result, the photosensitive member of Comparative Example 1-6 caused an increase in light-part potential (V L ) after 1000 sheets of successive image formation, thus providing images accompanied with fog. 
     On the other hand, the photosensitive member of Comparative Example 1-7 having the charge generation layer and Charge transport layer directly formed on the first intermediate layer showed only a low dark-part potential (V D ) due to insufficient barrier characteristic causing a large charge injection from the support side. As a result, it failed to provide a potential contrast necessary for image formation. 
     The results are summarized in Table 5. 
     
                                           TABLE 5                                 
__________________________________________________________________________
Resin components for                                                      
intermediate layers                                                       
                Initial stage                                             
                          After 1000 sheets                               
1st       2nd   V.sub.D (-V)                                              
                     V.sub.L (-V)                                         
                          V.sub.L (-V)                                    
                               Image                                      
__________________________________________________________________________
Ex.                                                                       
1-11                                                                      
    Polyether                                                             
          Polyether                                                       
                725  165  197  Good                                       
    urethane                                                              
          urethane                                                        
1-12                                                                      
    Polyether                                                             
          nylon 730  175  185  Good                                       
    urethane                                                              
1-13                                                                      
    Polyether                                                             
          none  715  155  165  Good                                       
    urethane                                                              
Comp.                                                                     
Ex.                                                                       
1-6 phenolic                                                              
          nylon 705  155  295  Fog occurred                               
    resin                                                                 
1-7 phenolic                                                              
          none  385  180  (evaluation impossible)                         
    resin                                                                 
__________________________________________________________________________
 
    
     EXAMPLE 2-1 
     A paint for an intermediate layer having the following composition was prepared by mixing. 
     
         ______________________________________                                    
Phosphated polyol compound A                                              
                       14.3 wt. part(s)                                   
Hexamethylene diisocyanate (HMDI)                                         
                       5.7 wt. part(s)                                    
Dibutyltin dilaurate (DBTL)                                               
                       0.02 wt. part(s)                                   
Methyl ethyl ketone (MEK)                                                 
                       80 wt. part(s)                                     
______________________________________                                    
 
    
     The paint was applied onto an aluminum cylinder (OD (outer diameter)=30 mm, L (length)=360 mm) by dipping and then dried and cured at 150° C. for 30 min. to form a 3.0 micron-thick intermediate layer. 
     Separately, 4 parts of a disazo pigment represented by the following formula: ##STR39## 2 parts of of a butyral resin (butyral degree=68%, Mw (weight-average molecular weight)=24000) and 34 parts of cyclohexanone were dispersed for 8 hours by means of a sand mill containing 1 mm-dia. glass beads and diluted with 60 parts of tetrahydrofuran (THF) to prepare a coating liquid for a charge generation layer. The thus prepared coating liquid was applied by dipping onto the above prepared intermediate layer and dried at 80° C. for 15 min. form a 0.2 micron-thick charge generation layer. 
     Then, 10 parts of a hydrazone compound of the formula: ##STR40## 10 parts of a bisphenol Z-type polycarbonate (Mw=30000), 10 parts of dichloromethane and 50 parts of monochlorobenzene were dissolved in mixture to form a coating liquid for a charge transport layer. The coating liquid was applied onto the above-formed charge generation layer by dipping and dried for 60 min. at 120° C. to form a 20 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a copying apparatus, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-development-transfer-cleaning were repeated at a cycle of 0.8 sec under low temperature-low humidity conditions (15° C.-15% RH). The results are summarized in Table 6 appearing hereinafter. 
     As is shown in Table 6, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further, as a result of 1000 sheets of successive image formation, images could be formed in a very stable state without causing an increase in light-part potential (V L ). 
     EXAMPLES 2--2-2--4 
     electrophotographic photosensitive members were prepared in the same manner as in Example 2-1 except that the following compositions were respectively used for preparing the intermediate layers. 
     
         ______________________________________                                    
[Example 2-2]                                                             
______________________________________                                    
Phosphated polyol compound B                                              
                        8.5 part(s)                                       
2,4-TDI                 11.5 part(s)                                      
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 2-3]                                                             
______________________________________                                    
Phosphated polyol compound C                                              
                        9.8 part(s)                                       
HMDI in a blocked form with                                               
                        10.2 part(s)                                      
methyl ethyl ketoxime (MEKO)                                              
DBTL                    0.02 part(s)                                      
MEK                     80 part(s)                                        
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 2-4]                                                             
______________________________________                                    
Phosphated polyol compound D                                              
                         3.2 part(s)                                      
Poly(oxyethylene)triol (Mn = 3000)                                        
                         12.9 part(s)                                     
MDI                      3.9 part(s)                                      
DBTL                     0.02 part(s)                                     
MEK                      80 part(s)                                       
______________________________________                                    
 
    
     The above-prepared photosensitive members were evaluated in the same manner as in Example 2-1. As a result, the respective photosensitive members showed a large difference between dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient potential contrast. Further, as a result of 1000 sheets of successive image formation, the respective photosensitive members provided images in a very stable state while causing almost no increase in light-part potential (V L ). 
     The results are also summarized in Table 6. 
     EXAMPLE 2-5 
     
         ______________________________________                                    
Phosphated polyol compound E                                              
                         76    parts                                      
2,6-TDI                  24    parts                                      
______________________________________                                    
 
    
     The above ingredients were reacted under stirring for 4 hours at 90° C. to form a reaction product (polymer). 
     
         ______________________________________                                    
The above reaction product                                                
                        10    parts                                       
MEK                     60    parts                                       
Dichloromethane         30    parts                                       
______________________________________                                    
 
    
     A coating liquid was prepared by mixing the above ingredients, and an electrophotographic photosensitive member was prepared in the same manner as in Example 2-1 except that the coating liquid was used for preparing the intermediate layer. 
     The thus-prepared photosensitive member was evaluated in the same manner as in Example 2-1. As a result, the photosensitive member showed a large difference between dark-part potential (V D ) and light-part part potential (V L ), thus providing a sufficient potential contrast. Further, as a result of 1000 sheets of successive image formation, the photosensitive member provided images in a very stable state while causing almost no increase in light-part potential (V L ). 
     The results are also shown in Table 6. 
     COMPARATIVE EXAMPLES 2-1 AND 2-2 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 2-1 except that the following compositions were respectively used for preparing the intermediate layers. 
     
         ______________________________________                                    
[Comparative Example 2-1]                                                 
______________________________________                                    
Alcohol-soluble copolymer nylon                                           
                         5     part(s)                                    
(&#34;Amilan CM-8000&#34;, mfd. by Toray K.K.)                                    
Methanol                 95    part(s)                                    
______________________________________                                    
 
    
     
         ______________________________________                                    
[Comparative Example 2-2]                                                 
______________________________________                                    
Polyester polyol       14     part(s)                                     
(&#34;Nippolan 125&#34;, mfd. by Nihon                                            
Polyurethane Kogyo K.K.)                                                  
2,6-TDI                6      part(s)                                     
DBTL                   0.02   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     The photosensitive members were evaluated in the same manner as in Example 2-1. As a result, both photosensitive members showed an increase in light-part potential (V L ), thus resulting in images accompanied with fog after 1000 sheets of successive copying. 
     The results are also summarized in Table 6 below. 
     Separately, the intermediate layers were formed according to the above-described methods of Examples 2-1-2-5 and Comparative Examples 2-1 and 2--2, and the adhesion strengths thereof were evaluated by a square matrix pattern (or checker pattern) peeling test according to JIS K5400 (General test method for paints). 
     As a result, the intermediate layers according to Examples 2-1-2-5 were all free from peeling, thus showing good adhesion to the aluminum substrate. On the other hand, the intermediate layers of Comparative Examples 2-1 and 2--2 showed peeling rates of 25% and 29% , respectively. 
     
                       TABLE 6                                                     
______________________________________                                    
                   After 1000 sheets                                      
Initial stage      of successive copying                                  
Dark-part    Light-part                                                   
                       Light-part                                         
potential    potential potential Image                                    
V.sub.D (-V) V.sub.L (-V)                                                 
                       V.sub.L (-V)                                       
                                 evaluation                               
______________________________________                                    
Example                                                                   
2-1    670       175       180     Good                                   
2-2    665       165       195     Good                                   
2-3    660       185       200     Good                                   
2-4    675       160       185     Good                                   
2-5    680       190       195     Good                                   
Comp.                                                                     
Example                                                                   
2-1    665       190       325     Fog occurred                           
2-2    670       200       360     Fog occurred                           
______________________________________                                    
 
    
     Example 2-6 
     
         ______________________________________                                    
Resol-type phenolic resin                                                 
                         25    parts                                      
Electroconductive titanium oxide                                          
                         50    parts                                      
powder (coated with tin oxide                                             
containing 10% of antimony                                                
oxide)                                                                    
Methyl cellosolve        20    parts                                      
Methanol                 5     parts                                      
______________________________________                                    
 
    
     The above-ingredients were subjected to 2 hours of mixing and dispersion in a sand mill containing 1 mm-dia. glass beads to prepare a paint for a first intermediate layer. 
     The paint was applied onto an aluminum cylinder (OD=30 mm, L=260 mm) by dipping and then dried and cured at 140° C. for 30 min. to form a 20 micron-thick first intermediate layer. 
     
         ______________________________________                                    
Phosphated polyol compound A                                              
                       11.0   part(s)                                     
2,4-TDI in a blocked form                                                 
                       9.0    part(s)                                     
with MEKO                                                                 
DBTL                   0.02   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     The above ingredients were dissolved in mixture to form a paint for a second intermediate layer, which was then applied by dipping onto the first intermediate layer and dried and cured at 150° C. for 20 min. to form a 0.6 micron-thick second intermediate layer. 
     Then, 3 parts of a disazo pigment of the formula: ##STR41## 2 parts of polyvinyl benzal (benzal degree=80%, Mw=11000) and 35 parts of cyclohexanone were subjected to 12 hours of mixing and dispersion by a sand mill containing 1 mm-dia. glass beads and further dispersed after adding 60 parts of methyl ethyl ketone (MEK) to form a coating liquid for a charge generation layer. The coating liquid was applied by dipping onto the above second intermediate layer and dried at 80° C. for 20 min. to form a 0.2 micron-thick charge generation layer. 
     Then, 10 parts of a styryl compound of the formula: ##STR42## 10 parts of a bisphenol Z-type polycarbonate (Mw=30000), 15 parts of dichloromethane and 45 parts of monochlorobenzene were dissolved in mixture to form a coating liquid for a charge transport layer. The coating liquid was applied onto the above-formed charge generation layer by dipping and dried for 60 min. at 120° C. to form a 18 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a laser printer of the reversal development type, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-development-transfer-cleaning were repeated at a cycle of 1.5 sec under normal temperature-normal humidity conditions (23° C.-50% RH) and high temperature-high humidity conditions (30° C.-85% RH). The results are summarized in Table 7 appearing hereinafter. 
     As is shown in Table 7, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further, also under the high temperature-high humidity conditions, the dark-part potential was stable and good images free from black spots or fog could be formed. 
     EXAMPLES 2-7-2-10 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 2-6 except that the following compositions were respectively used for preparing the second intermediate layers. 
     
         ______________________________________                                    
[Example 2-7]                                                             
______________________________________                                    
Phosphated polyol compound F                                              
                       14.0   part(s)                                     
HMDI in a phenol-blocked form                                             
                       6.0    part(s)                                     
DBTL                   0.02   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 2-8]                                                             
______________________________________                                    
Phosphated polyol compound G                                              
                       8.7    part(s)                                     
MDI in an MEKO-blocked form                                               
                       11.3   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 2-9]                                                             
______________________________________                                    
Phosphated polyol compound A                                              
                       8.0    part(s)                                     
Phosphated polyol compound K                                              
                       5.4    part(s)                                     
2,6-TDI in an MEKO-blocked form                                           
                       6.6    part(s)                                     
DBTL                   0.04   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     
         ______________________________________                                    
[Example 2-10]                                                            
______________________________________                                    
Phosphated polyol compound H                                              
                       13.4   part(s)                                     
HMDI in a trimerized form                                                 
                       6.6    part(s)                                     
isocyanurate                                                              
Stannous octylate      0.02   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     The above-prepared photosensitive members were evaluated in the same manner as in Example 2-6. As a result, each photosensitive member maintained a stable dark-part potential (V D ) even under high temperature-high humidity conditions and could provide good images free from occurrence of black spots or fog. 
     The results are summarized in Table 7. 
     COMPARATIVE EXAMPLES 2-3-2-5 
     Electrophotographic photosensitive members were prepared in the same manner as in Example 6 except that the following compositions were respectively used for preparing the second intermediate layers. 
     
         ______________________________________                                    
[Comparative Example 2-3]                                                 
______________________________________                                    
N-methoxymethylated 6-nylon                                               
                        5     part(s)                                     
(Mw = 50000, methoxymethyl-                                               
substitution rate = 28%)                                                  
Methanol                95    part(s)                                     
______________________________________                                    
 
    
     
         ______________________________________                                    
[Comparative Example 2-4]                                                 
______________________________________                                    
Poly(oxypropylene)triol 15     part(s)                                    
(hydroxyl value = 170 mg KOH/g)                                           
2,4-TDI                 5      part(s)                                    
DBTL                    0.02   part(s)                                    
MEK                     80     part(s)                                    
______________________________________                                    
 
    
     
         ______________________________________                                    
[Comparative Example 2-5]                                                 
______________________________________                                    
Poly(oxyethylene)glycol (hydroxyl                                         
                       15     part(s)                                     
value = 37.5 mg KOH/g)                                                    
2,6-TDI in an MEKO-blocked form                                           
                       5      part(s)                                     
DBTL                   0.02   part(s)                                     
MEK                    80     part(s)                                     
______________________________________                                    
 
    
     The photosensitive members were evaluated in the same manner as in Example 2-6. As a result, the photosensitive member according to Comparative Example 2-3 showed a decrease in chargeability to lower the dark-part potential (V D ) under the high temperature-high humidity conditions and also provided images accompanied with black spots and fog. On the other hand, the photosensitive members according to Comparative Examples 2-4 and 2-5 did not show a decrease in chargeability under the high temperature-high humidity conditions, but the resultant images were accompanied with black spots. 
     The results are summarized in Table 7. 
     Separately, the intermediate layers were formed according to the above-described methods of Examples 2-6-2-10 and Comparative Examples 2-3 and 2-5, and the adhesion strengths thereof were evaluated by a square matrix pattern (or checker pattern) peeling test according to JIS K5400. 
     As a result, the intermediate layers according to Examples 2-6-2-10 were all free from peeling, thus showing good adhesion to the aluminum substrate. On the other hand, the intermediate layers of Comparative Examples 2-3 to 2-5 showed peeling rates of 22% , 35% and 31% , respectively. 
     
                       TABLE 7                                                     
______________________________________                                    
       Environmental conditions                                           
       23° C., 50% RH                                              
                   30° C., 85% RH                                  
       V.sub.D (-V)                                                       
              V.sub.L (-V)                                                
                       V.sub.D (-V)                                       
                                Image                                     
______________________________________                                    
Example                                                                   
2-6      615      160      610    Good                                    
2-7      630      165      620    Good                                    
2-8      640      170      615    Good                                    
2-9      625      165      615    Good                                    
2-10     615      160      610    Good                                    
Comparative                                                               
Example                                                                   
2-3      635      165      560    Black spots and                         
                                  fog occurred                            
2-4      630      165      610    Black spots                             
                                  occurred                                
2-5      630      180      615    Black spots                             
                                  occurred                                
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     EXAMPLE 2-11 
     
         ______________________________________                                    
Phosphated polyol compound J                                              
                       13.1   part(s)                                     
2,6-TDI in MEKO-blocked form                                              
                       6.9    part(s)                                     
Electroconductive titanium                                                
                       20     part(s)                                     
oxide powder (coated with tin                                             
oxide containing 8% of artimony                                           
oxide)                                                                    
Rutile-type titanium oxide powder                                         
                       20     part(s)                                     
DBTL                   0.02   part(s)                                     
MEK                    40     part(s)                                     
______________________________________                                    
 
    
     The above-ingredients were subjected to 3 hours of mixing and dispersion in a sand mill containing 1 mm-dia. glass beads to prepare a paint for a first intermediate layer. 
     The paint was applied onto an aluminum cylinder (OD=60 mm, L=260 mm) by dipping and then dried and cured at 150° C. for 30 min. to form a 15 micron-thick first intermediate layer. 
     Then, the paint for the second intermediate layer prepared in Example 2-6 was applied by dipping onto the above first intermediate layer, and dried and cured at 150° C. for 20 min. to form a 0.6 micron-thick second intermediate layer. 
     Then, 4 parts of a disazo pigment of the formula: ##STR43## 2 parts of polyvinyl butyral (butyral degree=71% , Mw=18000) and 34 parts of cyclohexanone were subjected to 6 hours of mixing and dispersion by a sand mill containing 1 mm-dia. glass beads and further dispersed after adding 60 parts of methyl ethyl ketone (MEK) to form a coating liquid for a charge generation layer. The coating liquid was applied by dipping onto the above second intermediate layer and dried at 80° C. for 15 min to form a 0.3 micron-thick charge generation layer. 
     Then, the coating liquid for a charge transport layer used in Example 2-6 was applied by dipping onto the charge generation layer and dried at 120° C. for 60 min to form a 22 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a copying apparatus, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-development-transfer-cleaning were repeated at a cycle of 0.6 sec under low temperature-low humidity conditions (10° C.-10% RH). The results are summarized in Table 8 appearing hereinafter. 
     As is shown in Table 8, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further, as a result of 1000 sheets of successive image formation, images could be formed in a very stable state without causing an increase in light-part potential (V L ). 
     EXAMPLE 2-12 
     
         ______________________________________                                    
Alcohol-soluble copolymer nylon                                           
                         3     parts                                      
(&#34;Amilan CM-8000&#34;, mfd. by                                                
Toray K.K.)                                                               
N-methoxymethylated 6-nylon                                               
                         3     parts                                      
(Mw = 150000, methoxymethyl                                               
substitution rate = 30%)                                                  
Methanol                 94    parts                                      
______________________________________                                    
 
    
     An electrophotographic photosensitive member was prepared in the same manner as in Example 2-11 except that a coating liquid prepared from the above ingredients was used for forming the second intermediate layer. 
     EXAMPLE 2-13 
     An electrophotographic photosensitive member was prepared in the same manner as in Example 2-11 except that the second insulating layer was omitted to form on the support a laminated structure composed of the first intermediate layer, the charge generation layer and the charge transport layer. 
     The above-prepared photosensitive members of Examples 2-12 and 2-13 were evaluated in the same manner as in Example 2-11. As a result, each photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient potential contrast. Further, as a result of 1000 sheets of successive image formation, the photosensitive members provided images in a very stable state while causing almost no increase in light-part potential (V L ). 
     The results are summarized in Table 8. 
     COMPARATIVE EXAMPLES 2-6 AND 2-7 
     
         ______________________________________                                    
Resol-type phenolic resin                                                 
                         20    parts                                      
Electroconductive titanium                                                
                         20    parts                                      
oxide powder (coated with tin                                             
oxide containing 8% of antimony                                           
oxide)                                                                    
Rutile-type titanium oxide powder                                         
                         20    parts                                      
Methyl cellosolve        25    parts                                      
Methanol                 15    parts                                      
______________________________________                                    
 
    
     A paint for the first intermediate layer was prepared from the above ingredients otherwise in the same manner as in Example 2-11. 
     Electrophotographic photosensitive members of Comparative Examples 2-6 and 2-7 were prepared in the same manner as in Examples 2-12 and 2-13, respectively, except that the above-prepared paint was used for forming the first intermediate layer. 
     The photosensitive members were evaluated in the same manner as in Example 2-11. As a result, the photosensitive member of Comparative Example 2-6 caused an increase in light-part potential (V L ) after 1000 sheets of successive image formation, thus providing images accompanied with fog. 
     On the other hand, the photosensitive member of Comparative Example 2-7 having the charge generation layer and charge transport layer directly formed on the first intermediate layer showed only a low dark-part potential (V D ) due to insufficient barrier characteristic causing a large charge injection from the support side. As a result, it failed to provide a potential contrast necessary for image formation. 
     The results are summarized in Table 8. 
     
                                           TABLE 8                                 
__________________________________________________________________________
Resin components for                                                      
intermediate layers                                                       
                Initial stage                                             
                          After 1000 sheets                               
1st       2nd   V.sub.D (-V)                                              
                     V.sub.L (-V)                                         
                          V.sub.L (-V)                                    
                               Image                                      
__________________________________________________________________________
Ex.                                                                       
2-11                                                                      
    Polyether                                                             
          Polyether                                                       
                720  155  165  Good                                       
    urethane                                                              
          urethane                                                        
2-12                                                                      
    Polyether                                                             
          nylon 725  180  195  Good                                       
    urethane                                                              
2-13                                                                      
    Polyether                                                             
          none  710  150  155  Good                                       
    urethane                                                              
Comp.                                                                     
Ex.                                                                       
2-6 phenolic                                                              
          nylong                                                          
                705  165  295  Fog occurred                               
    resin                                                                 
2-7 phenolic                                                              
          none  385  180  (evaluation impossible)                         
    resin                                                                 
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     EXAMPLES 2-14 
     
         ______________________________________                                    
Phosphated polyol compound A                                              
                         7.2    part(s)                                   
Polyol compound of the following                                          
                         9.8    &#34;                                         
structure:                                                                
 ##STR44##                                                                
(a + b + c)/3 = 7.4                                                       
Mw = 4000                                                                 
 ##STR45##                                                                
HMDI                     3.6    &#34;                                         
DBTL                     0.02   &#34;                                         
MEK                      80     &#34;                                         
______________________________________                                    
 
    
     The above ingredients were mixed with each other to prepare a paint for an intermediate layer. 
     The paints was applied onto an aluminum cylinder (OD=30 mm, L=360 mm) by dipping and then dried and cured at 150° C. for 30 min. to form a 3.0 μm-thick intermediate layer. 
     The, 4 parts of a titanyl oxyphthalocyanine pigment of the following formula: ##STR46## 2 parts of polyvinyl butyral (butyral degree=68% , Mw=24000) and 34 parts of cyclohexanone were mixed and dispersed with each other for 8 hours in a sand mill containing 1 mm-dia. glass beads and then diluted with 60 parts of tetrahydrofuran to form a coating liquid for a charge generation layer. The coating liquid was applied by dipping onto the above intermediate layer and dried at 80° C. for 15 hours to form a 0.2 micron-thick charge generation layer. 
     Then, 4 parts of a triphenylamine derivative of the following formula: ##STR47## 10 parts of polycarbonate Z (Mw=30,000), 10 parts of dichloromethane and 50 parts of monochlorobenzene were mixed with each other to form a coating liquid for a charge transport layer. 
     The coating liquid was applied onto the above charge generation layer and dried at 120° C. for 60 min to form a 20 micron-thick charge transport layer. 
     The thus-prepared electrophotographic photosensitive member was incorporated in a copying apparatus, and the electrophotographic performances thereof were evaluated by a process wherein steps of charging-exposure-transfer-cleaning were repeated at a cycle of 0.8 sec. under low temperature-low humidity conditions (15° C.-15% RH). The results are summarized in Table 9 appearing hereinafter. 
     As is shown in Table 9, the photosensitive member showed a large difference between the dark-part potential (V D ) and light-part potential (V L ), thus providing a sufficient contrast. Further as a result of 1000 sheets of successive image formation, images could be formed in a very stable state without causing an increase in light-part potential (V L ). 
     EXAMPLES 2-15 
     
         ______________________________________                                    
Phosphated polyol compound B                                              
                         4.3    part(s)                                   
Polyol compound of the following                                          
                         9.1    &#34;                                         
structure:                                                                
 ##STR48##                                                                
(d + e + f)/3 = 2.6                                                       
Mw = 2800                                                                 
 ##STR49##                                                                
2,4-TDI                  6.7    &#34;                                         
DBTL                     0.02   &#34;                                         
MEK                      80     &#34;                                         
______________________________________                                    
 
    
     The above ingredients were mixed with each other to prepare a paint for an intermediate layer. 
     A photosensitive member was prepared and evaluated in the same manner as in Example 2-14 except that the intermediate layer was formed by using the above paint. The results are also shown in Table 9. 
     EXAMPLES 2-16 
     
         ______________________________________                                    
Phosphated polyol compound C                                              
                          4.9    part(s)                                  
Polyol compound of the following                                          
                          6.4    &#34;                                        
structure:                                                                
 ##STR50##                                                                
(g + h + i)/3 = 1.1                                                       
Mw = 700                                                                  
 ##STR51##                                                                
HMDI in an MEKO-blocked form                                              
                          8.7    &#34;                                        
DBTL                      0.02   &#34;                                        
MEK                       80     &#34;                                        
______________________________________                                    
 
    
     The above ingredients were mixed with each other to prepare a paint for an intermediate layer. 
     A photosensitive member was prepared and evaluated in the same manner as in Example 2-14 except that the intermediate layer was formed by using the above paint. The results are also shown in Table 9. 
     EXAMPLE 2-17 
     
         ______________________________________                                    
Resol-type phenolic resin                                                 
                         25     parts                                     
Electroconductive titanium oxide                                          
                         50     parts                                     
powder (coated with tin oxide                                             
containing 10% of antimony                                                
oxide)                                                                    
Methyl cellosolve        20     parts                                     
Methanol                 5      parts                                     
______________________________________                                    
 
    
     The above-ingredients were subjected to 2 hours of mixing and dispersion in a sand mill containing 1 mm-dia. glass beads to prepare a paint for a first intermediate layer. 
     The paint was applied onto an aluminum cylinder (OD=30 mm, L=860 mm) by dipping and then dried and cured at 140° C. for 30 min. to form a 20 micron-thick first intermediate layer. 
     Then, the paint for an intermediate layer prepared in Example 1-14 was applied by dipping onto the above first intermediate layer to form a 3.0 μm-thick second intermediate layer. 
     A charge generation layer and a charge transport layer were formed successively on the second intermediate layer in the same manner as in Example 2-14 to prepare a photosensitive member, which was then evaluated in the same manner as in Example 2-14. The results are also shown in Table 9. 
     
                                           TABLE 9                                 
__________________________________________________________________________
Resin components for                                                      
intermediate layers                                                       
                  Initial stage                                           
                              After 1000 sheets                           
Ex. 1st    2nd    V.sub.D (-V)                                            
                        V.sub.L (-V)                                      
                              V.sub.L (-V)                                
                                    Image                                 
__________________________________________________________________________
2-14                                                                      
    Polyether                                                             
           none   725   110   125   Good                                  
    urethane                                                              
2-15                                                                      
    Polyether                                                             
           none   725   105   105   Good                                  
    urethane                                                              
2-16                                                                      
    Polyether                                                             
           none   720   115   125   Good                                  
    urethane                                                              
2-17                                                                      
    Phenolic                                                              
           Polyether                                                      
                  725   105   105   Good                                  
    resin  urethane                                                       
__________________________________________________________________________
 
    
     As described above, the electrophotographic photosensitive member according to the present invention having an intermediate layer comprising a reaction product of a polyol compound ([I] and/or [II]) and a polyisocyanate compound can retain a stable potential characteristic and thus stably form good images over wide environmental conditions ranging from low temperature-low humidity to high temperature-high humidity conditions.