a photosensitive element of the present invention may have various layer structures , of which examples are illustrated in fig1 to 8 . these figures schematically show the structure in section . of course in practice , as in conventional devices , the shape and thickness of the layers is not as illustrated . fig1 to 4 show photosensitive layer structure comprising a charge generation substance layer 2 and a charge transport substance layer 3 formed directly onto a conductive substrate 1 ( fig1 ), a structure comprising a conductive substrate 1 , a blocking layer 4 which is formed on the conductive substrate , and a charge generation layer 2 and a charge transport layer 3 formed on the blocking layer ( fig2 ), a structure comprising a layer 2 of a charge generation substance , a layer 3 of a charge transport substance , and an intermediate layer 5 which locates between these two layers , all on a blocking layer 4 and substrate 1 ( fig3 ), and a structure comprising a layer of protective film 6 on the surface of a structure as shown in fig3 ( fig4 ). fig5 shows a layer 2 &# 39 ;, 3 &# 39 ; containing charge generation substance and charge transport substance mixed , on a conductive substrate 1 . fig6 shows a similar layer 2 &# 39 ;, 3 &# 39 ; beneath a surface protective film 6 and separated from the substrate 1 by a blocking layer 4 . fig7 is the same as fig3 but with the charge generating layer 2 and charge transport layer 3 reversed in order . fig8 shows a flexible sheet photosensitive element consisting of , as substrate , an organic high polymer film 7 with a coating film 8 of aluminium formed by vacuum deposition , and charge generating layer 2 and charge transport layer 3 formed on the substrate . the appropriate structure is selected in view of the intended use . when using a coated high polymer film described above as a conductive substrate , the photosensitive body obtained is useful as a photosensitive sheet for use in electrophotography ( fig8 ). in the present invention , the thickness of a layer or layers comprising a charge generation substance and a charge transport substance is determined essentially in dependence on charging characteristics which are necessary for the photosensitive element , but is preferably less than 100 μm . a layer having a thickness larger than 100 μm may decrease flexibility and photosensitivity of the layer . in the case of a single layer , the thickness is generally about 5 - 100 μm , while in the case of multi - layers , it is adequate to use generally a thickness of about 0 . 1 - 5 μm for a charge generation layer and about 5 - 100 μm for a charge transport layer . further , in the case of a single layer , the ratio of a charge generation substance to a charge transport substance is preferably about 10 % by weight , but the ratio is optionally selected depending on the types and properties of the substances . in the present invention , a blocking layer having a function as a barrier ( to improve the charging property and to avoid unintentional exposure by preventing leakage of a charge to the conductive substrate ) and a function as an adhesive can be formed between the conductive substrate and a photosensitive layer . for this blocking layer , polyamide resin , polyvinyl alcohol resin , polyurethane resin , aluminum oxide . etc . are among suitable materials . in the present invention , an intermediate layer can be formed between a charge generation layer and a charge transport layer . referring back to the discussion above , explanation of some preferred compounds used in the invention can be given as follows . a charge transport substance is required to have ( 1 ) ease of carrier injection from a charge generation substance , ( 2 ) a superior carrier transport property , ( 3 ) stability against external conditions such as light and ozone , etc . to fulfil requirement ( 1 ), the ionization potential of the charge transport substance should preferably be nearly equal to the ionization potential of the charge generation substance , and if the ionization potential of the charge transport substance is too small , deterioration of the charge transport substance by light and ozone etc . occurs easily and the requirement ( 3 ) is not satisfied . preferred chemical compounds used in the present invention have adequate ionization potential with a combination of the x -- ch ═ ch -- group and the aminoaryl group , and consequently , these chemical compounds are thought to fulfil requirements ( 1 ) and ( 3 ) concurrently . to fulfil requirement ( 2 ), electrons of the highest occupied molecular orbital are preferably concentrated to a part which has a superior ability to transport carriers . the preferred chemical compounds used in the present invention have difficulty in taking a planar structure and have an arylamino group which has a superior ability of carrier transport , and further , requirement ( 2 ) is satisfied as the part x -- ch ═ ch -- concentrates electrons of the highest occupied molecular orbital to the arylamino group . non - limitative examples of embodiments of the present invention are described below , with synthesis examples . a mixture of 11 . 4 g of quinaldine , 20 . 0 g of p - di ( p - tolyl ) aminobenzaldehyde and 5 . 0 g of zinc chloride anhydride was heated for 8 hours in an oil bath which was kept at 160 °- 170 ° c . and , subsequently , was dissolved into 100 ml of n , n - dimethylformamide , and , after addition of 10 ml of water and 20 ml of concentrated ammonium aqueous solution , an oily product was dissolved into 200 ml of benzene . the oily layer was washed several times with water , and after drying with magnesium sulfate , benzene was distilled off . the obtained oily product was purified twice by silica gel column chromatography using a benzene - ethylacetate mixture as eluent and after distilling off of the solvent , a residual oily component was recrystallized with methyl alcohol containing water , and 2 -[ p - di ( p - tolyl ) aminostyryl ] quinoline ( the above - illustrated compound 22 ) was obtained . the yield was 15 . 5 g , and the melting point of the compound was 130 . 5 °- 132 . 5 ° c . a solution for a charge generation layer was prepared by mixing by ball milling for five hours of one part by weight of τ form metal free phthalocyanine ( reophoton ls made by toyo ink co . ), two parts by weight of denatured silicone resin ( kr - 5221 made by shinetsu chemical co ., solid component 60 %), and 37 parts by weight of tetrahydrofuran . the solution was applied to a thin aluminum foil 100 μm in thickness and 70 × 100 mm in size by an automatic applicator ( made by tokyo seiki co .) and , after drying for two hours at 130 ° c ., a charge generation layer was obtained . the thickness of the layer was less than 1 μm . subsequently , a solution for a charge transport layer was obtained by dissolving five parts by weight of the product of synthetic example 1 ( compound 22 ) and 10 parts by weight of polycarbonate resin ( lexan 141 made by general electric co .) into 84 parts by weight of a mixed solvent of methylene chloride / 1 , 2 - dichloroethane of 50 / 50 volume ratio . using this solution , a charge transport layer was prepared on the charge generation layer by the same method as for the charge generation layer , and a photosensitive element was obtained . the thickness of the charge transport layer was about 20 μm . electrophotographical characteristics of this photosensitive element were measured with an apparatus for testing of electrostatic recording paper ( sp - 428 type made by kawaguchi electric co .). the measurement included 10 seconds corona charging of - 5 kv ( the dynamic mode ), 30 seconds standing in the dark , and subsequent exposure with a tungsten bulb . during the measurement , the electric potential on the surface of the photosensitive body was recorded and a voltage at the end of corona charging v 0 , a voltage at the end of 30 seconds in the dark v 30 , and a half - decay exposure e 50 ( 1 ×. s ) were observed . the results were v 0 =- 1200 v , v 30 / v 0 = 82 %, and e 50 = 1 . 2 1 ×. s . further , image stability was evaluated by the following deterioration test . a piece of specimen was bonded on the circumferential surface of a rotary drum which rotated at circumferential speed of 190 cm / minute and a process of charging with a corona charger which was installed near the drum with voltage of - 5 . 2 kv during rotation and exposure with light of a tungsten lamp ( illuminance 50 1 ×) which was installed at a direction of 180 ° from the corona charger was repeated for three hours . subsequently , a resolution was evaluated by observing a resolution pattern which was obtained by contact exposure and development of a test chart published by the society of electrophotography ( tokyo ) ( no . 1 - r , 1975 edition ) with the naked eye . the photosensitive element of embodiment 1 showed no change in resolution which , when evaluated by the method described above after the deterioration test , was 12 . 5 lines / mm , comparing with an initial value of 12 . 5 lines / mm . when the electrophotographical characteristics were evaluated by the same method as at the initial stage of the deterioration test , the half decay exposure was 1 . 3 1 ×. s and significant change was not observed . instead of the charge transport substance used in embodiment 1 , the chemical compounds nos . ( 3 ), ( 4 ) and ( 9 ), were used for the preparation of photosensitive elements by the same method as embodiment 1 . the electrophotographic characteristics and resolution initially and after the deterioration test of the photosensitive bodies are shown in table 1 . table 1______________________________________embodi - compound v . sub . 0 v . sub . 30 / v . sub . 0 e . sub . 50 resolutionment no . (- v ) (%) ( lx · s ) ( lines / mm ) ______________________________________2 ( 3 ) 1100 75 1 . 1 12 . 5 1120 76 1 . 1 12 . 53 ( 4 ) 1190 80 1 . 3 12 . 5 1190 81 1 . 4 12 . 54 ( 9 ) 1200 85 1 . 3 12 . 5 1210 85 1 . 3 12 . 5______________________________________ for each embodiment , the upper line gives the initial results and the lower line the results after deterioration test . using oxotitanium phthalocyanine ( topa85 made by toyo ink . co .) instead of the charge generation substance used in embodiment 1 , a photosensitive element was prepared by the same method as embodiment 1 . the initial electrophotographic characteristics measured by the same method as in embodiment 1 were v 0 =- 1100 v , v 30 / v 0 = 75 %, e 50 = 1 . 2 1 ×. s , and the electrophotographic characteristics after the deterioration test were v 0 =- 1120 v , v 30 / v 0 = 74 %, e 50 = 1 . 2 1 . s , and significant change was hardly observed . the initial resolution was 12 . 5 lines / mm , and the resolution after the deterioration test was 12 . 5 lines / mm , and no change was observed . a solution for a blocking layer was prepared by dissolving 1 . 5 parts by weight of polyamide resin ( m - 1276 made by nihon rylsan co .) and 1 . 5 parts by weight of melamine resin ( ml - 2000 made by hitachi chemical co .) into a mixed solvent of 38 . 8 parts by weight of ethyl alcohol and 58 . 2 parts by weight of 1 , 1 , 2 - trichloroethane . a thin aluminum foil 100 μm in thickness , 70 × 100 mm in size , was immersed into the coating liquid , and a blocking layer was prepared by withdrawing the foil from the coating liquid at a speed of 5 mm / second and drying for one hour at 120 ° c . on the surface of the blocking layer , a charge generation layer and a charge transport layer were prepared by the same method as embodiment 5 and a photosensitive element was obtained . the electrophotographical characteristics of the photosensitive body before and after the deterioration test were evaluated in the same way as in embodiment 1 . in the result , the electrophotographical characteristics were initially v 0 =- 1155 v , v 30 / v 0 = 80 %, e 50 = 1 . 3 1 ×. s , and the resolution was 12 . 5 lines / mm . after the deterioration test , v 0 =- 1170v , v 30 / v 0 = 80 %, e 50 = 1 . 3 1 ×. s , and resolution 12 . 5 lines / mm . no significant change was observed . a mixture of 10 . o g of quinaldine , 19 . 0 g of p - diphenylaminobenzaldehyde and 5 . o g of zinc chloride anhydride was heated for 8 hours in an oil bath which was kept at 160 - 1 70 ° c . and subsequently the mixture was dissolved into 100 ml of n , n - dimethylformamide , and , after adding 10 ml of water and 20 ml of concentrated ammonium aqueous solution , an oily product was dissolved into 200 ml of benzene . the organic layer was washed several times with water and , after drying with magnesium sulfate , benzene was distilled off . the obtained oily product was purified twice with silica gel column chromatography using a benzene - ethylacetate mixture as eluent , and after distilling off of the solvent , a residual oily component was recrystallized with methyl alcohol containing water , and 2 -( p - diphenyl aminostyryl ) quinoline illustrated below was obtained . the yield was 5 . 7 g , and the melting point of the compound was 153 . 5 °- 154 . 5 ° c . ## str12 ## using 10 . 0 g of lepidine and 19 . 0 g of p - diphenylaminobenzaldehyde , 4 -( p - diphenylaminostyryl ) quinoline illustrated below was obtained by the same method as synthetic example 1 . they yield was 6 . 9 g , and the melting point was 92 . 0 °- 95 . 0 ° c . ## str13 ## using 17 . 0 g of lepidine and 30 . 0 g of p - di ( p - tolyl ) aminobenzaldehyde , 4 -[ p - di ( p - tolyl ) aminostyryl ] quinoline illustrated below was obtained by the same method as synthetic example 1 . the yield was 17 . 0 g , and the melting point was 90 . 5 °- 93 .° c . ## str14 ## using 5 . 4 g of 2 , 4 - dimethylthiazole and 12 . 0 g of p - di ( p - tolyl ) aminobenzaldehyde , 2 -[ p - di ( p - tolyl ) aminostyryl ] 4 - methylthiazole illustrated below was obtained by the same method as synthetic example 1 . the yield was 3 . 6 g , and the melting point was 100 . 0 °- 102 . 0 ° c . ## str15 ## a solution for a charge generation layer was prepared by ball milling for about 5 hours admixture of one part by weight of oxotitanium phthalocyanine , two parts by weight of denatured silicone resin ( kr - 5221 made by shinetsu chemical co ., solid content 60 %), and 37 parts by weight of tetrahydrofuran . a charge generation layer was prepared by applying the solution described above to a thin aluminum foil of 100 μm thickness with an automatic applicator ( made by tokyo seiki co .) and dried for two hours at 130 ° c . the thickness of the layer was less than 1 μm . subsequently , a solution for a charge transport layer was obtained by dissolving five parts by weight of the chemical compound of synthetic example 1 , that is 2 -[ p - di ( p - tolyl ) aminostyryl ] quinoline , and 10 parts by weight of polycarbonate resin ( lexan 141 made by general electric co .) to 84 parts by weight of a mixed solvent of methylene chloride / 1 , 2 - dichloroethane = 50 / 50 by weight . using this solution , a charge transport layer was prepared on the charge generation layer by the same method as the charge generation layer , and a photosensitive element was obtained . the thickness of the charge transport layer was about 20 μm . electrophotographical characteristics of the photosensitive body described above were measured by the test methods of embodiment 1 . the results were v 0 =- 1210 v , v 30 v 0 = 83 %, and e 50 = 1 . 3 1 ×. s . further , image stability was evaluated by the deterioration test of embodiment 1 . the photosensitive element showed no change in resolution after the deterioration test , that was 12 . 5 lines / mm , comparing with an initial value of 12 . 5 lines / mm . after the deterioration test , the half decay exposure e 50 was 1 . 3 1 ×. s and no significant change wa observed . using chemical compounds obtained in the synthetic examples 3 , 4 , 5 and 6 , instead of the charge transport substance in embodiment 7 , photosensitive elements were prepared and tested by the same methods as in embodiment 7 . electrophotographic characteristics and resolution initially and after the deterioration test of the photosensitive elements for electrophotography of these embodiments are shown in table 2 . table 2______________________________________ syntheticembodi - example v . sub . 0 v . sub . 30 / v . sub . 0 e . sub . 50 resolutionment compound (- v ) (%) ( lx · s ) ( lines / mm ) ______________________________________8 3 1080 78 1 . 7 12 . 5 1080 79 1 . 8 12 . 59 4 1190 80 1 . 3 12 . 5 1190 81 1 . 4 12 . 510 5 1200 85 1 . 3 12 . 5 1210 85 1 . 3 12 . 5______________________________________ for each embodiment , the upper line gives the initial results and the lower line the results after deterioration test . these embodiments show that the present invention can provide a superior photosensitive element for electrophotography which shows scarcely any deterioration in sensitivity and image stability even after repeated charging and exposure over long periods by using new chemical compound having a triarylamine group as a charge transport substance . by using 14 g of 6 - methylquinaldine and 25 g of p - di ( p - tolyl ) aminobenzaldehyde and in the same manner as in synthetic example 1 the compound 2 -[ p - di ( p - tolyl ) aminostyryl ]- 6 - methylquinoline was obtained . the yield was 24 g and the melting point thereof was 200 °- 202 . 5 ° c . this compound may also be used satisfactorily as a charge transport substance . a solution for a blocking layer was prepared by dissolving 2 . 0 parts by weight of polyamide resin ( h - 104 , product of nihon rylsan co .) and 0 . 5 parts by weight of melamine resin ( melan - 200 , product of hitachi chemical co .) into 100 parts by weight of a 1 / 1 ( by weight ) mixture solvent of 1 , 1 , 2 trichloroethane / ethanol . a thin aluminum sheet having a thickness of 0 . 1 μm was immersed into the coating liquid to coat the same , and thereafter the coated sheet was dried by heating at 120 ° c . for 30 minutes to obtain a blocking layer having a thickness of about 0 . 2 μm . next , a solution for an electrical charge generating layer was prepared by kneading with a ball mill for about 5 hours 1 part by weight of τ - type phthalocyanine ( reophoton ls , product of toyo ink co . ), 2 parts by weight of denatured silicon resin ( kr - 5221 , product of shinetsu chemical co ., solid component 60 %), and 37 parts by weight of tetrahydrofuran . the resultant solution was applied over the blocking layer prepared previously with an automatic applicator ( product of toyo seiki co .) and the coated sheet was dried at 130 ° c . for 2 hours to obtain an electrical charge generating layer . subsequently , a solution for an electrical charge transport layer was obtained by dissolving 5 parts by weight of the compound indicated in the above lists as ( d ) and 10 parts by weight of polycarbonate resin ( lexan 141 , product of general electric co .) into 84 parts of a 50 / 50 ( by volume ratio ) solvent mixture of methylene chloride / 1 , 2 - dichloroethane . by using the resultant solution , an electrical charge transport layer was formed over the electrical charge generating layer in the same manner as in the formation of the electrical charge generating layer and a photosensitive element of the structure shown in fig1 was obtained . the film thickness of the charge transport layer was about 20 μm . electrophotographic characteristics of the above photosensitive element were measured in the same manner as in embodiment 1 . the results were v 0 =- 1100 v , v 30 / v 0 = 0 . 90 , and e 50 = 1 . 1 1 ×. s . thereafter , for evaluating optical response property the following experiment was performed . the specimen was corona charged with a high speed light decay measurement apparatus ( cynthia 30hl , product of gentic co .) until the surface potential of the specimen photosensitive substance reached - 700 v , and the specimen was irradiated with a light beam having a wavelength of 780 nm and a light power of 40 mj / m 2 for 40 msec and the half decay exposure time t 50 until the surface voltage is reduced to half was measured to obtain a value t 50 = 18 ms . the percentage of electrons in the highest occupied molecular orbital of the compound ( d ) which locate on the triphenylamine skeleton was calculated by the mndo method defined above and found to be 91 . 4 %. subsequently , the durability of this element was evaluated by the deterioration test described in embodiment 1 , in which the photosensitive element of the present embodiment showed no change , in that the resolution was initially 12 . 5 lines / mm and after the deterioration test was also 12 . 5 lines / mm . further , after the deterioration test , the electrophotographic characteristics of the specimen was evaluated in the same manner as initially and was found out that no change was observed in the half decay exposure amount , in that it was 1 . 1 1 ×. s . in place of the compound ( d ) used in embodiment 11 the compound produced by synthetic example 3 was employed for the electrical charge transport material , and a photosensitive element was prepared in the same manner as in embodiment 11 . electron distribution in the highest occupied molecular orbital of the present compound was calculated by making use of the mndo method as defined above , and the percentage of electrons locating on the triphenylamine skeleton was found to be 75 . 2 %. the electrophotographic characteristics and optical response properties of this photosensitive element were evaluated as in embodiment 11 . the results were v 0 =- 1150v , v 30 / v 0 = 0 . 91 , e 50 = 1 . 5 1 ×. s , t 50 = 40 ms . furthermore , the electron distribution in the highest occupied molecular orbital of the compound a -( 19 ) disclosed in jp - a - 58 - 65440 ( 1983 ) on page 270 , second column was calculated . the electron location rate on the triphenylamine skeleton was 71 . 8 %. in place of the electrical charge transport material used in embodiment 11 , nine of the compounds illustrated above were employed in the manufacture of photosensitive elements in the same manner as in embodiment 11 . table 3 respectively shows initial values ( upper line for each compound ) and values after the deterioration test ( lower line for each compound ) of electrophotographic characteristics , optical response property and resolution of these photosensitive elements and the rate d at which electrons in the highest occupied molecular orbital locate on the triphenylamine skeleton of the compound . in table 3 the first column is the embodiment number and the second column indicates the illustrated compound table 3______________________________________d v . sub . 0 e . sub . 50 t . sub . 50 resolution (%) (- v ) v . sub . 30 / v . sub . 0 ( lx · s ) ( ms ) ( line / mm ) ______________________________________13 ( b ) 85 . 5 1100 0 . 91 1 . 1 18 . 0 12 . 5 1120 0 . 92 1 . 1 18 . 0 12 . 514 ( f ) 81 . 8 1110 0 . 89 1 . 1 20 . 0 12 . 5 1130 0 . 90 1 . 09 20 . 0 12 . 515 ( k ) 82 . 0 1115 0 . 90 1 . 11 19 . 5 12 . 5 1130 0 . 92 1 . 10 19 . 5 12 . 516 ( l ) 80 . 8 1140 0 . 92 1 . 15 22 . 5 12 . 5 1160 0 . 93 1 . 20 23 . 0 12 . 517 ( p ) 81 . 5 1130 0 . 92 1 . 10 21 . 0 12 . 5 1140 0 . 93 1 . 11 21 . 0 12 . 518 ( c ) 80 . 0 1120 0 . 90 1 . 20 20 . 0 12 . 5 1100 0 . 89 1 . 18 20 . 0 12 . 519 ( e ) 90 . 0 1100 0 . 91 1 . 14 19 . 0 12 . 5 1050 0 . 85 1 . 12 18 . 5 12 . 520 ( m ) 82 . 0 1060 0 . 90 1 . 20 20 . 0 12 . 5 1000 0 . 86 1 . 20 20 . 0 12 . 521 ( o ) 81 . 1 1020 0 . 89 1 . 23 21 . 0 12 . 5 1000 0 . 87 1 . 22 21 . 0 12 . 5______________________________________ further the respective values d for the illustrated compounds ( a ), ( g ), ( h ), ( i ), ( j ) and ( n ) were calculated to be 80 . 2 %, 80 . 5 %, 84 . 5 %, 87 . 0 %, 82 . 0 % and 82 . 5 % respectively , and these compounds also exhibited excellent electrophotographic characteristics . in the same manner as in embodiment 11 , a photosensitive element was prepared using oxotitaniumphthalocyanine for the electrical charge generating material . the electrophotographic characteristics , optical response property and resolution of this photosensitive element were evaluated in the same way before and after the deterioration test . the initial electrophotographic characteristics and optical response property were v 0 =- 11oov , v 30 / v 0 = 0 . 86 , e 50 = 1 . 09 1x . s , t 50 = 18 . o ms , and the resolution 12 . 5 lines / mm and after the deterioration test the electrophotographic characteristics , and optical response property were v 0 =- 1120v , v 30 / v 0 = 0 . 89 , e 50 = 1 . 10 1x . s , and t 50 = 18 . o ms and the resolution was 12 . 5 lines / mm . a photosensitive element was prepared by subsequently laminating an electrical charge generating layer and an electrical charge transport layer on a sheet of mylar film on which aluminum was evaporated , in the same manner as in embodiment 11 . before and after the deterioration test the electrophotographic characteristics , optical response property and resolution of this photosensitive element were evaluated in the same way . the initial electrophotographic characteristics and optical response property were v 0 =- 1050v , v 30 / v 0 = 0 . 84 , e 50 = 1 . 09 1x . s , t 50 = 18 . o ms , and the resolution was 12 . 5 lines / mm . after the deterioration test , the results were v 0 =- 1070 v , v 30 / v 0 = 0 . 86 e 50 = 1 . 10 1x . s . t 50 = 18 . o ms and the resolution was 12 . 5 lines / mm . a solution for a surface protective layer was prepared of 60 parts by weight of butyl etherealized melamine formaldehyde resin , 40 parts by weight of isopropylalcohol and 0 . 03 parts by weight of silane coupling agent , and was applied to the photosensitive element of embodiment 11 in the same manner as was used for forming the electrical charge transport layer , and was cured at 120 ° c . to obtain a photosensitive element provided with a protective layer . before and after the same deterioration test , the electrophotographic optical response property and resolution of this photosensitive element were evaluated in the same way . the initial electrophotographic characteristics and optical response property were v 0 =- 1150 v , v 30 / v 0 = 0 . 95 , e 50 = 1 . 15 1x . s , t 50 = 19 . o ms and the resolution was 12 . 5 lines / mm . after the deterioration test the results were v 0 =- 1160 v , v 30 v 0 = 0 . 96 , e 50 = 1 . 16 1x . s and t 50 = 19 . 0 ms and the resolution was 12 . 5 lines / mm . in the same manner as in embodiment 11 , a photosensitive layer structure was formed on a bare aluminum cylinder . this photosensitive drum was loaded into an electrophotographic device having the constitution as shown in fig9 and tested , and even after output of 100 , 000 prints of a4 size , an excellent picture image print was obtained . fig9 shows a laser printer having a photosensitive drum 7 , a developing device 10 applying developing agent 8 to the drum , a corona discharge charger 12 and a fur brush 13 for cleaning the drum . paper 15 is moved past an image transfer device 14 at the drum to a fixing device 16 . in operation , the drum 7 is charged by the charger 12 , given an electrostatic image by the laser beam 11 , toner is applied by developing device 10 to give a toner image 9 , which is transferred to the paper by transfer device 14 and fixed . such apparatus is generally known and need not be described further . electrophotographic apparatuses according to the invention employ photosensitive elements which can have excellent response and high durability . excellent image printing can be achieved , and maintenance requirements can be reduced .