Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0601—Acyclic or carbocyclic compounds
  • G03G5/0605—Carbocyclic compounds
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0601—Acyclic or carbocyclic compounds
  • G03G5/0612—Acyclic or carbocyclic compounds containing nitrogen
  • G03G5/0616—Hydrazines; Hydrazones

Definitions

• This invention relates to an electrophotographic photosensitive element which is suitably used for an image-forming apparatus such as a copying machine.
• a photosensitive element which has a wide variation in function design, particularly such as a lamination type positive-charged electrophotographic photosensitive element which and has a charge generating layer (CGL) comprising a charge generating material which generates electrostatic charges by light irradiation and a charge transfer layer which contains a charge transfer material for transferring the charges formed in the charge generating layer.
• CGL charge generating layer
• electrostatic charges (holes) formed by the action of light near the surface of the charge generating layer travel through the charge generating layer and into the charge transfer layer to form electrostatic latent images.
• JP-A-2-222960 An example of such an electrophotographic photosensitive element is disclosed in JP-A-2-222960. (The term "JP-A" as herein used means an "unexamined published Japanese patent application”.)
• the electrophotographic photosensitive element comprises an electrically conductive substrate upon which is laminated, first, a charge transfer layer and, second, a charge generating layer, wherein the charge transfer layer contains a butadiene derivative represented by general formula (A); wherein A1 to A4 each represents an aryl group which may have a substituent and a hydrazone compound such as, e.g., 4-(N,N-diethylamino)benzaldehyde-N,N-diphenylhydrazone and 4-(N,N-dimethylamino) benzaldehyde-N,N-diphenylhydrazone, and the charge generating layer is formed by coating the conductive substrate with a charge transfer material dissolved in an alcohol series solvent.
• A1 to A4 each represents an aryl group which may have a substituent and a hydrazone compound such as, e.g., 4-(N,N-diethylamino)benzaldehyde-N,N-diphen
• the hydrazone compound has been used before as a charge transfer material. But the use of the hydrazone compound with the butadiene derivative shown by formula (I) described above has the following advantages.
• the present invention has been made to solve the problems discussed above.
• the object of this invention is to provide an electrophotographic photosensitive element having a long life and that is both highly stable and highly sensitive.
• an electrophotographic photosensitive element comprising an electrically conductive substrate having formed, first, a charge transfer layer, second, a charge generating layer, and, third, a surface protective layer.
• the charge transfer layer contains a butadiene derivative represented by formula (I): wherein Ar1, Ar2, Ar3 and Ar4 each represents an aryl group with a substituent and/or a hydrazone compound represented by formula (II): wherein R1, R2, and R3 each represents an alkyl group having from 1 to 5 carbon atoms or an alkoxy group having from 1 to 2 carbon atoms; R4 and R5 each represents an alkyl group having from 1 to 5 carbon atoms or a phenyl group; and P1, P2 and P3 each represents an integer of from 0 to 2.
• the charge generating layer contains the hydrazone compound represented by the above formula (II) as a charge transfer material in addition to a charge generating material.
• the charge generating layer is formed by coating the charge transfer layer with an alcoholic solvent in which is dissolved the coating composition of the charge generating layer.
• a surface protective layer is formed on the surface of the charge generating layer, which serves as a protective layer to increase the abrasion resistance. It also lengthens the life of the electrophotographic photosensitive element and decreases the thickness required of the charge generating layer.
• the charge generating layer of the electrophotographic photosensitive element also contains the hydrazone compound shown by aforesaid formula (II), which is a charge transfer material, the charges (holes) generated by the action of light near the surface of the charge generating layer are quickly transferred to the charge transfer layer, thereby increasing the sensitivity. It is therefore unnecessary in this invention to incorporate large amounts of the hydrazone compound into the charge transfer layer to increase the sensitivity. There is thus no need to risk causing the lowering of the glass transition point or the reduction of the mechanical strength of the charge transfer layer by adding too much of the hydrazone compound. It is also unnecessary to use a solvent in which the hydrazone compound is soluble during the formation of the charge generating layer.
• the hydrazone compound shown by aforesaid formula (II) which is a charge transfer material
• the thickness of the charge generating layer can be reduced, the probability of having such structural traps as thermal carriers and holes becomes very low, so that a stable photosensitive element can be designed.
• the charge transfer layer in this invention is formed by coating a conductive substrate with a coating composition comprising a charge transfer material, a binder resin, and a solvent and allowing the wet layer to dry.
• the charge generating layer is formed by coating a charge transfer layer coated conductive substrate with a coating composition comprising a charge generating material, a charge transfer material, a binder resin, and a binder on the charge transfer layer. The layer is then dried.
• the surface protective layer is formed by coating the already twice layered conductive substrate with a coating composition comprising an electric conductivity imparting agent and a binder on the charge generating layer and setting or hardening the layer.
• the charge transfer material being incorporated into the charge transfer layer is composed of the butadiene derivative represented by the formula (I) and/or the hydrazone compound represented by the formula (II).
• Preferred examples of Ar1, to Ar4 in the formula (I) include represents a methyl group or an ethyl group.
• butadiene derivatives include those disclosed in JP-A-62-30255.
• Preferred examples include Compounds (III) and (IV) shown below.
• the Compound (III) is more preferred as the butadiene derivative used in the present invention.
• the compound (III) has a plane structured electron system and also has a structure in which two phenyl groups are bonded to the 1-position of the butadiene and two 4-N,N-diethylaminophenyl groups are bonded to the 4-position of the butadiene, there are advantages in that the compound is largely polarized and has very excellent charge transfer capabilities. But, there are disadvantages in that the compound is not very soluble.
• R1, R2 and R3 in the formula (II) each preferably represents a methyl group, an ethyl group, a methoxy group or an ethoxy group.
• hydrazone compounds represented by the formula (II) 4-(N,N-diethyl-amino)benzaldehyde-N,N-diphenylhydrazone or 4-(N,N-dimethylamino)benzaldehyde-N,N-diphenylhydrazone can be used. These compounds have a relatively high solubility in alcoholic solvents as compared with other charge transfer materials and also have the nearest oxidation potential to the oxidation potential of the butadiene derivative shown by the formula (I). If there is a pronounced difference in oxidation potential between two charge transfer materials, trapped charges occurs.
• the ratio by weight of the hydrazone compound to the butadiene derivative is preferably between 10 and 300 parts, more preferably between 40 to 200 parts, of the hydrazone compound to 100 parts of the butadiene derivative. If the content of the hydrazone compound is larger than this range, the sensitivity of the electrophotographic photosensitive element is not improved and if the content is less than this range, it is difficult for charge transfer to occur between the charge transfer layer and the charge generating layer. This difficulty of charge transfer deteriorates the sensitivity and also causes crystallization and cracking to occur in the charge transfer layer. Thus, the presence of the hydrazone compound outside this range is undesirable in this invention.
• the compounds of formula (I) and/or formula (II) as charge transfer materials can also be used in combination with other conventionally known charge transfer materials.
• charge transfer materials examples include fluorenone series compounds such as tetracyanoethylene, 2,4,7-trinitro-9-fluorenone, etc.; nitro compounds such as 2,4,8-trinitrothioxanthone, dinitroanthracene, etc.; acid anhydrides such as succinic anhydride, maleic anhydride, dibromomaleic anhydride, etc,; oxadiazole series compounds such as 2,5-di-(4-dimethylaminophenyl)-1,3,4-oxadiazole, etc.; styryl series compounds such as 9-(4-diethylaminostyryl) anthracene, etc.; carbazole series compounds such as polyvinylcarbazole, etc.; pyrazoline series compounds such as 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline, etc.; amine derivatives such as 4,4' ,4"-tris(N,N-
• the ratio of the total content of the charge transfer materials to the binder resin for the charge transfer layer is preferably between 20 and 200 parts, more preferably between 50 to 200 parts, of charge transfer materials to 100 parts of binder resin of the charge transfer layer. If the total amount of the charge transfer materials is below this range, the charge transfer faculty becomes insufficient. If the total amount is above this range, the mechanical strength of the charge transfer layer is reduced.
• Examples of the solvent which can be used for mixing the charge transfer material(s) with the binder resin are alcohols such as methanol, ethanol, propanol, isopropanol, butanol, etc.; cellosolves such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, etc.; esters such as ethyl acetate, methyl acetate, etc.; ketones such as acetone, methyl ethyl ketone, cyclohexanone, etc.; aliphatic hydrocarbons such as n-hexane, octane, cyclohexane, etc.; aromatic hydrocarbons such as benzen, toluene, xylene, etc.; halogenated hydrocarbons such as dichloroethane, carbon tetrachloride, methylene chloride, chlorobenzene
• binder resin for the charge transfer layer examples include olefinic polymers such as styrenic polymers, acrylic polymers, styrene-acrylic copolymers, polyethylene, an ethylene-vinyl acetate copolymer, chlorinated polyethylene, polypropylene, ionomer, polyvinyl chloride, a vinyl chloride vinyl acetate copolymer, polyester, alkyd resins, polyamide, polyurethane, epoxy resins, polycarbonate, polyarylate, polysulfone, diallylphthalate resins, silicone resins, ketone resins, polyvinylbutyral resins, polyether resins, phenol resins, melamine resins, benzoguanamine resins, and photosetting resins such as epoxy acrylate, urethane acrylate, polyester acrylate, etc. These resins can be used singly or as a mixture thereof.
• the coating composition composed of the charge transfer material (including the butadiene derivative (I) and the hydrazone compound (II), the binder resin, and the solvent described above is coated on an electrically conductive substrate at a thickness of from 10 to 40 ⁇ m, and particularly from 15 to 30 ⁇ m and dried.
• the electrically conductive substrate can be a sheet form material or a drum form material each having an electric conductivity.
• the substrates there are various materials having an electric conductivity.
• metals such as aluminum, aluminum alloys, copper, tin, platinum, gold, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steels, brass, etc., and plastics and glasses each having an electrically conductive layer of the metal, indium oxide, tin oxide, etc., formed thereon by a means such as a vapor deposition, etc.
• the materials having an oxide surface in particular, alumite-treated aluminum, and more particularly alumite-treated aluminum having the thickness of the alumite-treated layer of from 5 to 12 ⁇ m and having the surface roughness of 1.5S or less is preferred for increasing the adhesion with the photosensitive layer formed thereon.
• the conductive substrate can be treated with a surface treating agent such as a silane coupling agent, a titanium coupling agent, etc.
• Examples of the charge generating material being incorporated in the charge generating layer are selenium, selenium-tellurium, selenium-arsenic, amorphous silicone, pyrylium salts, azoic compounds, disazoic compounds, phthalocyanine compounds, ansanthrone series compounds, perylene series compounds, indigo series compounds, triphenylmethane series compounds, multi-rings condenced series quinone compounds, toluidine series compounds, pyrazoline series compounds, quinacridone series compounds, and pyrrolopyrrole series compounds. These charge generating materials can be used singly or as a mixture thereof.
• the most preferred materials are those containing phthalocyanine series compounds having various crystal types such as ⁇ -type, ⁇ -type and ⁇ -type, for example, aluminum phthalocyanine, copper phthalocyanine, and, in particular, metal free phthalocyanine, oxotitianyl phthalocyanine, etc.
• the use of a combination of the N-type pigment and the P-type pigment is preferred.
• the function of the P-type pigment is as follows.
• thermal holes existing in the P-type pigment are injected into the charge transfer layer and negative space charges are generated in the charge generating layer.
• the negative space charges increase the electric field of the light carriers in the charge generating layer to increase the generating efficiency of light carriers.
• both positive and negative charges are generated by the N-type pigment which absorbs light in the range of 550 to 600 nm.
• the positive charges are transferred through the charge generating layer by the P-type pigment which has a hole transferring property up to the interface between the charge generating layer and the charge transfer layer, after which the charges are injected into the charge transfer layer.
• the negative charges are neutralized with positive charges, which are induced on the surface layer of the electrophotographic photosensitive element by electrostatic charging.
• electrostatic latent images are formed at the light-exposed portions.
• the electric field for forming light carriers can be increased.
• the sensitivity of the photosensitive element can also be increased by improving the hole transferring property in the charge generating layer.
• N-type pigment/P-type pigment The weight ratio of N-type pigment and the P-type pigment (N-type pigment/P-type pigment, hereinafter referred to as "N/P ratio") is in the range of from 40/60 to 90/10. If the N/P ratio is over 90/10, the content of the P-type pigment in the layer is relatively less, so that there is less increase in the electric field, a weakening of the hole transferring property, and a deterioration of sensitivity. On the other hand, if there is an N/P ratio of less than 40/60, because the content of the N-type pigment is therefore less, therefore, the sensitivity and copying properties of a red original deteriorate.
• N-type pigment examples include perylene series compounds, ansanthrone series compounds, azoic compounds, methane, diphenylmethane, xanthene, and acridine, each having an amino group or a derivative thereof as a substituent.
• ansanthrone series compounds are suitably used owing to their efficiency in the formation of light carriers.
• P-type pigment examples include azo pigments, anthraquinone pigments, triphenylmethane pigments, nitro pigments, xanthene pigments, azine pigments, and quinoline pigments each having a sulfon group or a carboxyl group, and phthalocyanine series compounds.
• phthalocyanine series compounds which are non-toxic and excellent in workability, in particular, metal free phthalocyanine and oxotitanyl phthalocyanine are preferably used.
• hydrazone compounds shown by formula (II) above are used for the charge generating layer as well as the the charge transfer layer.
• Prefferred examples of the hydrazone compounds incorporated into the charge generating layer are the same as those preferably incorporated into the charge transfer layer in the present invention.
• Hydrazine compounds incorporated into the charge transfer layer and the charge generating layer may be the same or differnt.
• the hole transferring property is improved, and the sensitivity tends to increase, but, at the same time, thermal carriers are increased, which means that the stability necessary for repeated use is generally lowered.
• the contribution which the hydrazone compound gives to the photosensitive element of the invention differs according to the kinds and the structures of materials (i.e., the charge transferring agent, the charge transfer agent, the solvent, and other additives) being used. Therefore, the optimum amount of the hydrazone compound for the sensitivity and the repeating stability required in each formulation may be selected.
• the ratio by weight of the content of the hydrazone compound contained in the charge generating layer to the binder resin in the layer is between 0.1 and 100 parts hydrazone, preferably between 5 and 50 parts, to 100 parts of the binder resin. If the content of the hydrazone is over 100 parts, the solubility of the hydrazone compound becomes insufficient and the mechanical strength of the layer deteriorates, while if there is less than 0.1 part hydrazone, the desired addition effect of the hydrazone compound is not substantially obtained.
• binder resin for the charge generating layer the same binder resins described above for the charge transfer layer can be used.
• binder compounds polyvinyl acetal is suitably used in this invention since the binder is excellent in dispersibility for the components of the layer.
• a coating composition which contains the binder is excellent in storage stability.
• polyvinyl acetal contains a large amount of hydroxyl groups, the compound has a high hygroscopicity, which causes a decrease in resistance to surrounding conditions. Also, the hydroxyl groups act as traps for charge carriers (holes) generated at light exposure. This trapping characteristic of the hydroxyl groups lowers the sensitivity of the photosensitive element.
• polyvinyl acetal with a large amount of hydroxyl groups, has a high solubility in an organic solvent such as an alcohol.
• an organic solvent such as an alcohol.
• polyvinyl acetal in the charge generating layer is to a great extent swelled or dissolved by an organic solvent contained in the coating composition for the surface protective layer. This swelling or dissolving of the surface protective layer makes the interface indistinct between the charge generating layer and the surface protective layer. This in turn has a pronounced negative effect on the sensitivity characteristics, etc., of the photosensitive element. Additionally, it lowers the mechanical strength of the surface protective layer.
• an acetylacetone complex salt (metal acetylacetonate) is preferably added. Since the acetylacetone complex salt is hydrolyzed by drying the coating composition of the charge generating layer to cause a condensation reaction with the hydroxyl groups in the polyvinyl acetal, the amount of the hydroxyl groups remaining in the layer formed is decreased.
• acetylacetone complex salt which can be used in this invention, there are various chelate compounds selected from the group of (mono)acetyl acetonate complex salts composed of acetylacetone and a metal atom, a bisacetyl acetonate complex salt, a trisacetyl acetonate complex salt, and a tetracisacetyl acetonate complex salt.
• the complex salts represented by the following formulae (IV) or (V) are preferably used in this invention.
• M represents a trivalent or tetravalent metal
• Q1 represents an alkyl group or an alkoxy group
• n represents 3 when M is a trivalent metal or 4 when M is 4
• m represents an integer of 2 or lower.
• examples of M in the above formulae (V) and (VI) are aluminum and zirconium.
• the acetylacetone complex salt is usually supplied as a solid, such as a powder, which is advantageous in terms of storage stability. But since it takes a long time to uniformly disperse the complex salt in polyvinyl acetal, it is preferable to use the acetylacetone complex salt in a solution state (e.g., a solution of the acetylacetone complex salt dissolved in alcohol and water).
• a solution state e.g., a solution of the acetylacetone complex salt dissolved in alcohol and water.
• the alcohol which is used together with water to form a solution of the acetylacetone complex salt there are, for example, ethanol, methanol, isopropanol, butanol, ⁇ -oxyethyl methyl ether (methylcellosolve), ⁇ -oxyethyl ether (ethylcellosolve), ⁇ -oxyethyl propyl ether (propylcellosolve), and butyl- ⁇ -oxyethyl ether (butylcellosolve).
• methylcellosolve ⁇ -oxyethyl methyl ether
• ethylcellosolve ⁇ -oxyethyl propyl ether
• butyl- ⁇ -oxyethyl ether butylcellosolve
• butanol and butylcellosolve which are safe to use and have a low volatility are suitably used.
• concentration of the acetylacetone complex salt in a solution of the acetylacetone complex salt in an alcohol and water hereinafter, referred to as an acetylacetone complex salt solution.
• concentration of the acethylacetone complex salt is preferably in the range between 0.05 and 0.5 mol/liter. If the concentration of the acetylacetone complex salt is higher than 0.5 mol/liter, it takes a long time to dissolve the total amount of the acetylacetone complex salt and it takes time to prepare the solution of the complex salt. Also with a concentration higher than 0.5 mol/liter, uneven coating is liable to occur, which causes unevenness and lengthwise stripes on the specific layer formed, which results in the formation of defective images. Such unevenness also affects the sensitivity characteristics, the mechanical strength of the layer, the resistance to surrounding conditions, etc.
• the concentration of the acetylacetone complex salt is less than 0.05 mol/liter, a large amount of the acetylacetone complex salt solution must be added to the coating composition of the binder resin to sufficiently lower the amount of the hydroxyl groups of polyvinyl acetal remaining in the charge generating layer. This lowers the viscosity of the coating composition of the binder resin and deteriorates the coating and film-forming properties of the coating composition. It also increases the drying time for the coated layer.
• the concentration of water in the acetylacetone complex salt solution in this invention is in the range of from 1 to 10 mol/liter. If the concentration of water is larger than 10 mol/liter, the acetylacetone complex salt is hydrolyzed, whereby the amount of the hydroxyl groups remaining in the charge generating layer cannot be sufficiently decreased and also when a pigment, etc., is used, its dispersibility is decreased. Also, if the concentration of water is less than 1 mol/liter, the addition effect of water is not sufficiently obtained, it is difficult to dissolve the total amount of the acetylacetone complex salt in the solution, and it takes too much time to prepare the solution. Plus, when the water concentration is low, uneven coating, defective images, uneven sensitivity, decreased layer strength, and lowered resistance to surrounding conditions results.
• the concentration of the acetylacetone complex salt in the solution be adjusted so that the acetylacetone complex salt is combined with the coating composition in an amount of from 0.01 to 2.0 equivalent to the hydroxyl groups of the polyvinyl acetal contained in the coating composition. If the compounding ratio of the acetylacetone complex salt to the hydroxyl groups of the polyvinyl acetal is larger than 2.0 equivalent, each of the characteristics is improved but the stability is decreased with repeated use.
• the compounding ratio of the acetylacetone complex salt to the hydroxyl groups of the polyvinyl acetal is less than 0.01 equivalent, the added effect of the acetylacetone complex salt is not sufficiently obtained and large amounts of hydroxyl groups remain in the charge generating layer, whereby the lowering of the sensitivity, the deterioration of the resistance to surrounding conditions, and the resistance to an organic solvent are not sufficiently prevented.
• alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, etc. can be used.
• the reason of using these particular alcohols is because the hydrazone compound contained in the charge transfer layer has a solubility of from about 0.1 to 2% with these particular alcoholic solvents.
• part of the hydrazone compound contained in the charge transfer layer is dissolved while the coating composition for the charge generating layer is applied.
• the dissolved hydrazone diffuses into the charge generating layer formed.
• the occurrence of an electric barrier at the interface between the charge generating layer and the charge transfer layer can be prevented.
• the alcoholic solvent By properly selecting the alcoholic solvent, the occurrence of the electric barrier at the interface between the charge generating layer and the charge transfer layer can be effectively prevented. Choosing such a solvent also results in the prevention of cracks by solvate shock, the crystallization of the charge transfer material, the dissolving off of the binder resin, etc. To produce the above-mentioned effects, the use of n-butanol is particularly preferred.
• the ratio of the charge generating material to the binder in the charge generating layer is in the range preferably between 5 and 500 parts of charge generating material (more preferably between 10 and 250 parts) to 100 parts of binder resin. If the content of the charge generating material is less than 5 parts, the charge generating faculty is less, while if the content is over 500 parts, the adhesion between layers is lowered.
• the thickness of the charge generating layer is suitably from 0.01 to 3 ⁇ m, and particularly suitable from about 0.1 to 2 ⁇ m.
• a conventionally known coating composition such as a silicone resin series coating composition, an alkyd resin series coating composition, etc.
• a silicone resin series coating composition forming a silicone resin film having excellent electric characteristics can be most preferably used as the coating composition for the surface protective layer in this invention.
• the silicone resin series coating composition is a coating composition prepared by dissolving or dispersing in a solvent the hydrolyzed product(s) (so-called organosiloxane oligomer) of silane series compounds, e.g., organosilanes such as tetraalkoxysilane, trialkoxyalkylsilane, dialkoxydialkylsilane, diphenyldiethoxysilane, diphenyldimethoxysilane, diphenylmethylethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, etc., and organohalosilanes such as trichloroalkylsilane, dichlorodialkylsilane, etc., singly or as a mixture thereof, or the initial condensation reaction product(s) of the hydrolyzed product(s) as a non-volatile solid component.
• organosilanes such as tetraalkoxy
• alkoxy group and alkyl group of the silane compound there are groups having from 1 to about 4 carbon atoms, such as methoxy, ethoxy, isopropoxy, t-butoxy, glycidoxy, methyl, ethyl, etc.
• the electrical conductivity imparting agent described above there are fine particles of a metal oxide such as tin oxide, titanium oxide, indium oxide, antimony oxide, etc., or a solid solution of tin oxide and antimony oxide.
• a metal oxide such as tin oxide, titanium oxide, indium oxide, antimony oxide, etc.
• a solid solution of tin oxide and antimony oxide are preferably used in this invention.
• the coating composition for the surface protective layer and the electrical conductivity imparting agent can be mixed by using a conventionally known means such as a ball mill, an ultrasonic dispersing apparatus, etc.
• the thickness of the surface protective layer is preferably in the range of from 0.01 to 3 ⁇ m. If the thickness of the surface protective layer is less than 0.01 ⁇ m, the sensitivity of the electrophotographic photosensitive element is lowered, while if the thickness is over 3 ⁇ m, there is a possibility of reducing the stability during repeated use.
• the charge transfer layer, the charge generating layer, and the surface protective layer may contain, if necessary, sensitizers such as terphenyl, halonaphthoquinones, acenaphthylenes, etc.; fluorene series compounds such as 9-(N,N-diphenylhydrazino) fluorene, 9-carbazolyliminoflurene, etc.; antioxidants such as hindered phenols, hindered amines, etc.; ultraviolet absorbants such as benzotriazole, etc.; plasticizers; radical uptaking agents; etc.
• sensitizers such as terphenyl, halonaphthoquinones, acenaphthylenes, etc.
• fluorene series compounds such as 9-(N,N-diphenylhydrazino) fluorene, 9-carbazolyliminoflurene, etc.
• antioxidants such as hindered phenols, hindered amines
• a leveling agent such as a silicone oil, etc., a surface active agent, a thickener, etc., may be used together.
• each coating composition can be prepared by a conventional method using, for example, a mixer, a ball mill, a paint shaker, a sand mill, an attritor, a ultrasonic dispersing means, etc.
• the following coating composition for a charge transfer layer was prepared.
• CC agent A dibromoansanthrone
• CG agent B metal free phthalocyanine
• CG agent C oxotitanyl phthalocyanine
• CT agent A as a charge transfer agent
• the coating composition for a charge transfer layer was coated on an aluminum substrate by dip coating and dried for 30 minutes at 90°C to form a charge transfer layer having the thickness shown in Table 1 below. Then, the coating composition for a charge generating layer was coated on the charge transfer layer by dip coating and dried for 30 minutes at 110°C to form a charge generating layer having a thickness of 0.5 ⁇ m. Furthermore, the coating composition for a surface protective layer was coated on the charge generating layer by dip coating and dried for 60 minutes at 110°C to form a surface protective layer having a thickness of 2.0 ⁇ m.
• each charge transfer layer and each charge generating layer having the thicknesses shown in Table 2 below were formed using one or two kinds of charge transfer materials being contained in the charge transfer layer selected from the CT agent A described above, 4-(N,N-dimethylamino)benzaldehyde-N,N-diphenylhydrazone (hereinafter referred to as CT agent B), and 1,1-bis(4-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene (hereinafter referred to as CT agent C) at the ratios shown in Table 2 below, using the CG agent A and the CG agent C as the charge generating agent being contained in the charge generating agent at the ratios shown in Table 2, and using the CT agent A or the CT agent B as the charge transfer agent being contained in the charge generating layer at the ratio shown in Table 2, 12 kinds of electrophotographic photosensitive elements were prepared.
• CT agent B 4-(N,N-dimethylamino)benzaldehyde-N,N-diphen
• Each electrophotographic photosensitive element was positively charged using a drum-form sensitivity test machine (Gentec Cynthia 30M Type, made by Gentec) and the charged potential (V) was measured.
• a halogen lamp was used such that the exposure intensity thereof was adjusted to be 0.1 mW/cm2 per unit area of the photosensitive element, the photosensitive element was exposed to the halogen lamp for 0.3 second, and the potential (V) after the light exposure was measured.
• the glass transition temperature (°C) of the electrophotographic photosensitive element was measured using a thermal analysis apparatus DT-30 made by Shimazu Seisakusho Ltd.
• the sample in which no abnormality was observed in the appearance of both the charge transfer layer and charge generating layer was shown by A and the sample in which the abnormality was observed in the appearance of at least one of the charge transfer layer and the charge generating layer was shown by B.
• the sample in which the lowering of the potential after 300 cycles was less than 20 V was shown by A
• the sample in which the lowering of the potential after 300 cycles was from 20 V to 50 V was shown by B
• the samples in which the lowering of the potential after 300 cycles was 50 V or higher was shown by C.
• IPA isopropyl alcohol
• n-BuOH represents n-butyl alcohol
• MIBK represents methyl isobutyl ketone
• CH3CN represents acetonitrile
• the glass transition temperature of the photosensitive element in Comparative Example 13 is 54°C, which is 20°C lower than the glass transition temperature (74°C) of the photosensitive element in Example 23 having the same compositions of the charge transfer layer and the charge generating layer except for the CT agent A in both layers, which shows that the mechanical strength of the photosensitive element in Comparative Example 13 is greatly lowered. This is based on the content of the charge transfer material (CT agent A) in the charge transfer layer of the photosensitive element in Comparative Example 13.
• the electrophotographic photosensitive element having a charge transfer layer containing the CT agent A and the CT agent C and a charge generating layer containing the N type pigment (CG agent A) and the P type pigment (CG agent B or CG agent C), with the charge generating layer being formed using an alcoholic solvent, shows a low potential after light exposure and has an excellent sensitivity as compared with other photosensitive elements.
• a hydrazone compound CT agent A or CT agent B
• the sensitivity is even more improved.
• the charge generating layer contains the hydrazone compound shown by formula (II) described above and the thickness of the charge generating layer is thin, the transfer of charges from the charge generating layer to the charge transfer layer is smoothly conducted and the photosensitive element has a high performance stability without causing thermal carriers and traps. Also, by forming the surface protective layer, the abrasion resistance is increased, whereby the life of the photosensitive element is prolonged so that the sensitivity is increased and images having a high quality can be obtained.

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• 1990
  • 1990-11-29 DE DE1990625455 patent/DE69025455T2/de not_active Expired - Fee Related
  • 1990-11-29 ES ES90122848T patent/ES2082816T3/es not_active Expired - Lifetime
  • 1990-11-29 EP EP19900122848 patent/EP0430235B1/fr not_active Expired - Lifetime
  • 1990-11-30 CA CA 2031269 patent/CA2031269A1/fr not_active Abandoned

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