GB1570576A

GB1570576A - Photosensitive material for electrophotography

Info

Publication number: GB1570576A
Application number: GB1714/78A
Authority: GB
Original assignee: Mita Industrial Co Ltd
Current assignee: Kyocera Mita Industrial Co Ltd
Priority date: 1977-01-17
Filing date: 1978-01-16
Publication date: 1980-07-02
Also published as: NL7800575A; JPS6148149B2; DE2801914A1; IT7819314A0; FR2377655A1; JPS5389433A; IT1092743B; FR2377655B1; CA1119449A; DE2801914C2

Description

(54) PHOTOSENSITIVE MATERIAL FOR ELECTROPHOTOGRAPHY (71) We, MITA INDUSTRIAL COMPANY LIMITED, a Japanese Body Corporate of 5, Miyabayashi-cho, Higashi-ku, Osaka, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to photosensitive materials for electrophotography.

In electrophotography, the generally adopted process comprises charging a photosensitive material which is provided with a photoconductive layer by, for example, corona discharge, exposing the photosensitive material imagewise to actinic rays to form an electrostatic latent image on the surface of the photoconductive layer, applying a developer to the surface of the photoconductive layer to form a toner image corresponding to the electrostatic latent image, and transferring this toner image formed on the surface of the photoconductive layer onto a copying paper. In this conventional process, after the transfer of the toner image, the photosensitive material is fed to a cleaning step where any residual toner is removed. The cleaned photosensitive materials then fed once again to the charging step indicated above and the process can then be repeated.

An electrophotographic photosensitive material which is to be used repeatedly in such a process must have some special properties different from those required of a photosensitive material employed in a process where a toner is directly fixed on the photosensitive layer. More specifically, in order to prevent fogging in the repeated copying operation and prolong the life of the photosensitive material, it is necessary for the photosensitive material of the former type to have a relatively quick dark decay (i.e. the surface potential of the non-exposed area of the photosensitive layer decays relatively quickly in the dark) and a negligible residual potential (i.e. the potential left on the exposed area of the photosensitive layer is negligible). When the residual potential of the photosensitive material is high, fogging is caused during the transfer step.Further, in the event of fogging or when the dark decay speed of the photosensitive material is low, the electrostatic charges of the electrostatic image formed on the surface of the photosensitive material, or other electrostatic charges generated for some different reason, remain on the surface of the photosensitive material even after the transfer and cleaning steps. Such charges cause fogging during the next copying cycle. Moreover, if the dark decay speed is low, even after the transfer step, toner particles are electrostatically attracted to the surface of the photosensitive material by a relatively strong attracting force. Consequently, the efficiency of the transfer of the toner to a copying paper is relatively low and the surface of the photosensitive material must be strongly wiped to remove any residual toner from the surface of the photosensitive material.

As a result, the surface of the photosensitive material is readily and quickly damaged and the life of the photosensitive material is shortened.

Photosensitive material of this type should also possess enhanced mechanical, electrical and chemical durability. Since the photosensitive material is repeatedly discharged or irradiated, and receives repeated wear through the use of a magnetic brush or cleaning member, the photoconductive layer of the photosensitive material can be easily damaged mechanically, or it can deteriorate electrically or chemically, readily. Moreover, in use of the photoconductive layer of the photosensitive material may peel away from the electrically conductive substrate.

Various organic or inorganic photoconductors are known for use in the formation of a pohtoconductive layer of a photosensitive material, for example phthaiocyanine and phthalocyanine derivatives which are readily available and cheap.

However, photosensitive materials which include phthalocyanine or its derivatives as a photoconductor fail to satisfy sufficiently the requirements outlined above for such materials. For example, a photosensitive material comprising a photoconductive layer composed of a dispersion of phthalocyanine or one of its derivatives in an electrically insulating binder, which is formed on an electrically conductive substrate, is still not satisfactory because its surface potential at the charging step is generally low, the rising speed of the surface potential is low, the residual potential at the exposure step is not negligible and the speed of reduction of the potential in the nonexposed area (i.e. the dark decay speed) is low.

We found that when an intermediate layer comprising a charge transfer complex of (A) an organic polymeric photoconductor and (B) a polycyclic aromatic nitro compound, in particular proportions, is formed on an electrically conductive substrate, and when a top layer comprising (C) phthalocyanine or a photoconductive phthalocyanine derivative incorporated in a binder with a particular proportion of a polycyclic aromatic nitro compound (B), which may or may not be the same polycyclic aromatic nitro compound present in the intermediate layer, is formed on the intermediate layer, the dark decay speed of the resulting photosensitive material is controlled to a range suitable for repeated copying operations and the residual potential can be reduced to a negligible level.Consequently, fogging can be prevented, the toner transfer efficiency can be improved and the life of the photosensitive material can be prolonged. It was also found that a photosensitive material having this layered structure possesses excellent mechanical, chemical and electrical durability.

Accordingly, the present invention provides a photosensitive material for use in electrophotography which comprises an electrically conductive substrate; an intermediate layer comprising a charge transfer complex of (A) an organic polymeric photoconductor and (B) a polycyclic aromatic nitro compound capable of acting as an electronacceptor, the weight ratio of (A) : (B) in said layer being from 6:1 to 1:6; and a top layer comprising (C) phthalocyanine or a photoconductive phthalocyanine derivative incorporated in a binder with a polycyclic aromatic nitro compound (B) in a weight ratio of (C):(B) of from 10:5 to 10:25.

Any organic polymer which is photoconductive may be used as the organic polymeric photoconductor (A) of the intermediate layer of the photosensitive material of the present invention. For example, poly N - vinylcarbazole, poly - N - acrylpheno- thiazine, poly - N - (p -acryloxyethylphenothiazine, poly-N-(2-acryloxypropyl)- phenothiazine, poly - N - allylcarbazole, poly - N - 2 - acryloxy - 2 - methyl - Nethylcarbazole, poly - N - (2 - p - vinylbenzoylethyl) - carbazone, poly - N - propenylcarbazole, poly - N - 2 - methylacryI- oxapropylcarbazole, poly - N - acrylcarbazole, poly - 4 - vinyl - p - (N - carbazyl) toluene, poly-vinylanisolacetophenone), polyindene and other known photoconductive organic polymeric substances may be empolyed.In particular poly-N-vinylcarbazole and nuclear substitution derivatives thereof, for example, halogen- and alkyl-substituted derivatives, which are easily available, may be employed.

Phthalocyanine and all of the known phthalocyanine derivatives which are photoconductive may be used as component (C) of the top layer of the photosensitive material of the present invention. For example, aluminum phthalocyanine, aluminum polychlorophthalocyanine, antimony phthalocyanine, barium phthalocyanine, beryllium phthalocyanine, cadmium hexadechlorophthalocyanine, cadmium phthalocyanine, cerium phthalocyanine, chromium phthalocyanine, cobalt phthalocyanine, cobalt chlorophthalocyanine copper - 4 - aminophthalocyanine, copper bromochlorophthalocyanine copper 4-chlorophthalocyanine, copper 4-nitrophthalocyanine, copper phthalocyanine, phthalocyanine, sulfonate, copper polychlorophthalocyanine, deuterio phthalocyanine dysprosium phthalocyanine, erbium phthalocyanine europium phthalocyanine, gadolinium phthalocyanine, gallium phthalocyanine, germanium phthalocyanine, holmium phthalocyanine, indium phthalocyanine, iron phthalocyanine, iron polyhalophthalocyanine, lanthanum phthalocyanine, lead phthalocyanine, lead polychlorophthalocyanine, cobalt hexaphenylphthalocyanine, copper pentaphenylphthalocyanine, lithium phthalocyanine, ruthenium phthalocyanine magnesium phthalocyanine manganese phthalocyanine, mercury phthalocyanine, molybdenum phthalocyanine, neodium phthalocyanine, nickel phthalocyanine, nickel polyhalophthalocyanine, osmium phthalocyanine, palladium phthalocyanine, palladium chlorophthalocyanine, alkoxyphthalocyanine, alkylaminophthalocyanine, alkylmercaptophthalocyanine, aryloxyphthalocyanine, arylmercaptophthalocyanine, copper phthalocyanine piperidine, cycloalkylaminophthalocyanine, dialkylaminophthalocyanine, diaralkylaminophthalocyanine, dicycloalkylaminophthalocyanine, hexadecahydrophthalocyanine, imidomethylphthal ocyanine, 12-naphthalo- cyanine, 2,3-naphthalocyanine, octa-azophthalocyanine, sulfur phthalocyanine, tetra azophthalocyanine, tetra - 4 - acetylaminophthalocyanine, tetra-4-aminobenzoylphthal phthalocyanine, tetra - 4 - aminophthalocyanine, tetra-4aminophthalocyanine, tetrachloromethylphthalocyanine. tetra - diazophthalocyanine, tetra-4,4-dimethylocta-azophthalocyanine, tetra-4,5-diphenylene-oxidephthalocyanine, tetra-4,5-diphenylocta-azophthalocyanine, tetra - (6 - methylbenzothiazoyl)phthalocyanine, tetra - p - methylphenylaminophthalocyanine, tetramethylphthalocyanine, tetranaphthotflazolylphthalo.

cyanine, tetra - 4 - naphthylphthalocyanine, tetra - 4 - nitrophthalocyanine, tetraperinaphthylene - 4,5 - octa - azophthalocyanine, tetra - 2,3 - phenylene - oxide - phthalocyanine, tetra - 4 - phenylocta - azophthalocyanine, tetraphenylphthalocyanine, tetraphenylphthalocyanine-tetracarboxylic acid, tetraphenylphthalocyanin e tetrabariumcarboxylate, tetraphenylphthalocyanine - tetra4 - trifluoromethylmercaptophthalocyanine, tetrapyridine - phthalocyanine, tetra - 4 - tri fiuoromethylmercaptophthalocyanine, tetra4 - trifluoromethylphthalocyanine - 4,5thionaphthene - octa - azophthalocyanine, platinum phthalocyanine, potassium phthalocyanine, rhodium phthalocyanine, samarium phthalocyanine, silver phthalocyanine, silicon phthalocyanine, sodium phthalocyanine, sulfonated phthalocyanine, thorium phthalocyanine, thulium phthalocyanine, tin chlorophthalocyanine, tin phthalocyanine, titanium phthalocyanine, uranium phthalocyanine, vanadium phthalocyanine, ytteribium phthalocyanine, zinc chlorophthalocyanine, zinc phthalocyanine, and dimers, trimers, oligomers, polymers and copolymers thereof, may be used.

In particular, metal-free phthalocyanines and their nuclear substitution derivatives, for example, halogen-substituted derivatives, which are readily available, may be used.

Any polycyclic aromatic compound having at least one nitro substituuent in its nucleous may be combined with the organic polvmeric photoconductor (A) and the phthalocyanine or photoconductive phthalocyanine derivative (C) in the intermediate layer and top layer, respectively, of the photosensitive material of this invention.

For example 2,4-dinitro-l-chloronaphthalene.

1,4 - dinitronaphthalene, 1,5 - dinitronaphthalene. 3 - nitro - N - butylcarbazole, 4 - nitrobiphenyl, 4,41 - dinitrobiphenyl, 1 - chloro - 4 - nitroanthraquinone, 2,7 dinitroanthraquinone, 2,4,7 - trinitrofluorenone. 2.4.5.7 - tetranitrofluorenone, 9 - dicyanomethylene - 2,4,7 - trinitrofluorenone or 4 - nitroacenaDhthene, may be employed.

The use of 2,4,7 - trinitrofluorenone and 2,4.5,7-tetranitrofluorenone is preferred.

In the photosensitive material of this invention, it is important that the phthalocyanine or photoconductive phthalocyanine derivative (Cr and the polycyclic aromatic nitro compound (B) should be incorporated in a binder in a weight ratio of (C): (B) of from 10:5 to 10:25, preferably from 10:8 to 10:20.

It is known to use phthalocyanine or a photoconductive phthalocyanine derivative (C) in combination with a polycyclic aromatic nitro compound (B) as a photoconductive layer. In known photosensitive materials, however, the polycyclic aromatic compound is used in an amount much smaller than the amount specified in this invention.

When the polycyclic aromatic nitro compound is used in an amount smaller than that employed in the present invention, as will be seen from Comparative Example 1 and Table 1 below, the dark decay speed is too low and the residual potential is at a level that cannot be neglected. In such a photoconductive layer, fogging is readily caused by repeated high-speed copying operations. Additionally, since a large load is imposed on the photoconductive layer during the cleaning step, the resistance of the layer to the copying operation (i.e. the frequency of repeated copying operations which the photosensitive material can resist) is drastically lowered.When the polycyclic aromatic compound (B) is used in an amount larger than the amount specified in this invention, as will be seen from Comparative Example 2 and Table 1 below, the residual potential can be reduced substantially to zero, but the dark decay speed is too high and it is difficult to obtain a copied image having high contrast and density. In contrast, if the mixing ratio of the polycyclic aromatic nitro compound (B) to the phthalocyanine or photoconductive phthalocyanine derivative (C) is adjusted to a value within the range employed in this invention, for repeated high speed copying operations the residual potential can be reduced to a negligible level and the dack decay speed can be controlled so that the potential is abruptly lowered during a period from the toner transfer step to the point of initiation of the cleaning operation.Therefore, when a photosensitive material in accordance with this invention is used, it is possible to concurrently improve the toner image transfer efficiency, facilitate the cleaning operation, prevent fogging and improve the resistance of the material to the copying operation.

The use of polycyclic aromatic nitro compound to act as a dark decay speed controlling agent, in combination with the phthalocyanine or phthalocyanine derivative is believed to be new.

Any known polymeric binder, especially an electrically insulating binder can be used as the binder in which the phthalocyanine or photoconductive phthalocyanine derivative (C) and the polycyclic aromatic nitro compound (Br are dispersed in the top layer of the photosensitive material of the present invention.For example, acrylic resins such as polyacrylic acid esters, polymeth acrylic acid esters, acrylic acid/methacrylic acid ester copolymers, acrylic acid/styrene copolymers and maleic anhydride/styrene/ methacrylic acid ester copolymers, vinyl aromatic polymers such as polystyrene and poly-methylstyrene, vinyl chloride resins such as vinyl chloridelvinyl acetate copolymers, partially saponified vinyl chloride/vinyl acetate copolymers, partially saponi fied and acetalized vinyl chloride/ vinyl acetate copolymers and vinyl chloride vinyl acetate/maleic anhydride copoly mers, vinyl ester polymers such as polyvinyl acetate, butadiene copolymers such as styrene/butadiene copolymers and acrylo nitrile/styrene/butadiene copolymers, olefin resins such as ethylene/vinyl acetate co polymers, ethylene/acrylic acid copolymers and ionomers, polyester resins such as ethylene/ butylene - terephthalate/isophthal ate, polyamide and copolyamide resins, polycarbonate resins, unsaturated polyester resins, urethane resins such as acrylic urethane, epoxy resins, phenol-formaldehyde resins, xylene resins and melamine-form aldehyde resins may be used. These binders may be used singly or in the form of a mixture of two or more of them. It is pre ferred that the volume resistivity of the binder used be at least 1 X 1011 R - cm. It is especially preferred to use an acrylic resin as a binder.

The amount of binder used is not par ticularly critical to the present invention.

However, in general, it is preferred to use from 100 to 1000 parts by weight, especially from 300 to 500 parts by weight, of binder per 100 parts by weight of the phthalo cyanine or photo conductive phthalocyanine derivative (C).

Preferably, a silicone oil is incorporated in the top layer of the photosensitive ma terial of the present invention. We found that when a silicone oil is incorporated in the top layer, during the exposure and de veloping steps the dark decay speed can be maintained at a relatively low level, and at the subsequent transfer or cleaning step the dark decay speed can be elevated to an extremely high level to thereby drastic ally reduce the residual potential of the non exposed area. In accordance with this pre ferred embodiment, the accumulation of charge can be effectively prevented and con sequently fogging prevented, the toner transfer efficiency improved, insulation break down prevented and the adaptability of the material to the cleaning operation improved.

Still further, in this preferred embodiment, the coating operation involved in the pro diction of the photosensitive material is made much easier, and the smoothness of the coating layer is noticeably improved.

Suitable silicone oils that can be used include polydimethylsiloxane, polymethylphenylsiloxane, polyhydrodienemethylsiloxane, polymethylaminopropylsiloxane, their copolymers, and dimethyIsiloxane/ethylene oxide block copolymers. Polydimethylsiloxane, which is readily available, is especially preferred.

A wide range of proportions of silicone oil may be incorporated in the top layer, but in general, it is preferred to employ from 5 to 150 parts by weight, especially 25 to 85 parts by weight, of silicone oil per 100 parts by weight of the phthalocyanine or photoconductive phthalocyanine derivative (C).

It is essential for an intermediate layer comprising an organic polymeric photoconductor (A) and a polycyclic aromatic nitro compound (B) mixed in the proportions indicated above to be interposed between the electrically conductive substrate and the top layer (first photoconductive layer) of the photosensitive material of the present invention.More specifically, in case of a photosensitive plate formed by coating a photoconductive layer, comprising phthalocyanine or a photoconductive phthalocyanine derivative, polycyclic aromatic nitro compound and binder, directly onto an electrically conductive substrate, as will be apparent from Comparative Example 5 and Table 1 below, the primary surface potential (the surface potential of the photosensitive material after charging but before exposure) is very low, the rising speed of the surface potential is low and the sensitivity expressed by the half life (seconds) of light decay is very low. Thus, this comparative photosensitive material is still insufficient in various respects.In contrast, when a layer (second photoconductive layer) comprising an organic polymeric photo conductor (A) and polycyclic aromatic nitro compound (B) is disposed between the top layer (first photoconductive layer) and the electrically this invention, the above properties can be this invention, the above propetries can be noticeably improved without detriment to the dark decay characteristics of the ma material. This will readily be appreciated when the results of Comparative Example 5 are compared those of Example 1.

It is also very important that in the intermediate layer used in the photosensitive material of the present invention, the organic polymeric photoconductor (A) should be combined with the polycyclic aromatic nitro compound (B) in a weight ratio of (A): (B) of from 6:1 to 1:6, especially from 1:1.7 to 1:2.2.

It is known that a polymeric photoconductor electron donor and a polycyclic aromatic nitro compound electron acceptor form a complex, and that a sensitized phoroconductive layer can be formed from these two compounds. In the intermediate layer of the photosensitive material of this invention, the polycyclic aromatic compound functions to control the charge characteristic of the surface of the photosensitive material (the first photo conductive layer).When the amount of the polycyclic aromatic nitro compound incorporated in the intermediate layer is smaller than that required in accordance with this invention, as will be- apparent from Comparative Example 3 and Table 1 below during repeated copying operations the residual potential accumulates on the surface of the photosensitive material, causing fogging, electrical deterioration of the photo conductive layer and a drastic reduction of the resistance of the material to the copying operation. When the amount of the polymeric photoconductor is larger than that required in this invention, as will be apparent from Comparative Example 4 and Table 1 below, the primary surface potential is drastically reduced and the rising speed of the surface potential is low. Accordingly, it is difficult to obtain satisfactory copied images.

In contrast, when the polymeric photoconductor is combined with the polycyclic aromatic nitro compound in the proportions required by this invention, the charge characteristics of the surface of the photoconductive layer can be controlled so that the residual potential can be reduced to a level that can be neglected while elevating the primary surface potential and the speed of rising of the surface potential by charging to sufficiently high levels. Detrimental effects owing to accumulation of the residual potential can be effectively eliminated.

In the photosensitive material of the present invention, a foil or plate of copper, aluminum, silver, tin or iron, in the form of a sheet or drum, may be used as the electrically conductive substrate. Additionally, a product formed by depositing such a metal in the form of a thin film on, for example, a plastic film by vacuum deposition or non-electrolytic plating can be used as the electrically conductive substrate.

In general, the photosensitive material of this invention is prepared by a process which comprises coating an electrically conductive substrate of the type mentioned above with a solution containing the organic polymeric photoconductor (A) and the polycyclic aromatic nitro compound (B) in the specific ratio indicated above to form an intermediate layer on the substrate, drying the intermediate layer, coating the intermediate layer with a liquid composition comprising phthalocyanine or a photoconductive phthalocyanine derivative (C) and a polycyclic aromatic nitro compound (B) incorporated into a binder of the type noted above in the specific proportions required by this invention, and drying the coating according to need.

The solvent employed in the preparation of a coating composition for the intermediate layer may be, for example, an aromatic hydrocarbon solvent such as benzene, toluene and xylene, a cyclic ether such as dioxane and tetrahydrofuran, a ketone such as acetone, methylethyl ketone, methylisobutyl ketone and cyclohexanone, an alcohol such as diacetone alcohol and ethylene glycol isobutyl ether, or an alicyclic hydrocarbon such as cyclohexane.

These solvents may be used singly or in the form of a mixture of two or more of them.

In general, it is preferred for this coating composition for the intermediate layer to be applied to the electrically conductive substrate at a solids concentration of from 1 to 80% by weight, especially from 5 to 30% by weight. The coated composition is ordinarily dried at a temperature of 10 to 200"C to form an intermediate layer.

During the course of the above process, a charge transfer complex is formed in the coating solution between the organic polymeric photoconductor (A) and the polycyclic aromatic nitro compound (B). However, it is also possible to adopt a process in which a solution of the organic polymeric photoconductor (A) and a solution of the polycyclic aromatic nitro compound B are prepared separately. These solutions are then coated onto the electrically conductive substrate in any order, and as a result a charge transfer complex is formed directly on the electrically conductive substrate. In this case, there is no particular disadvantage even if the complex is not formed uniformly throughout the intermediate layer.

In general, the coating composition used for the formation of the top layer is prepared by dissolving a binder. for example as mentioned above, in one or more of the previously-mentioned organic solvents, dispersing or dissolving the phthalocyanine or photoconductive phthalocyanine derivative and the polycyclic aromatic nitro compound in the binder solution, and homogenizing the resulting dispersion or solution. From the viewpoint of the adaptability as regards the coating operation, it is generally preferred for the solids concentration of this coating composition to be from 1 to 80% by weight, especially from 5 to 30% by weight.

The following considerations apply to the formation of the top layer. It is preferred to select for the coating composition forming the top layer a solvent which does not substantially dissolve the complex formed from the organic polymeric photoconductor and polycyclic aromatic nitro compound in the intermediate layer. A solvent capable of substantially dissolving the intermediate layer can be used, in which case it is preferable to solidify the composition forming the top layer within 5 minutes, especially 1 minute.

In the photosensitive material of the present invention, it is preferred for the thickness of the intermediate layer to be from 0.1 to 10F, especially from 1 to 8y and that the thickness of the top layer be from 0.1 to 30ss, especially from 1 to 15y. If the thickness of the intermediate layer is smaller than 0.1,a, the primary surface potential or its rising speed is often too low.

If the thickness of the intermediate layer is larger than 10g, the residual potential reaches a level that cannot be neglected, and consequently fogging readily occurs or there is a reduction in resistance to the copying operation. When the thickness of the top layer is smaller than O.l;u, the primary surface potential or its rising speed is often too low. When the thickness of the top layer is larger than 30,a, sensitivity, i.e., the light decay speed, is reduced and insulation breakdown readily occurs.

By use of the photosensitive material of this invention, electrical and photoconductive characteristics can be noticeably improved during repeated copying operations.

Furthermore, the mechanical properties of the material, such as its resistance to peeling, can be much improved. More specifically, in the case of a photosensitive material formed by applying a photoconductive layer comprising phthalocyanine or a photoconductive phthalocyanine derivative, a polycyclic aromatic nitro compound and a binder directly onto a metal substrate, the photoconductive layer can be easily peeled off during a pressure-sensitive tape peel test, as described below. However, peeling of the photoconductive layer is not caused at all when the same test is carried out on the photosensitive material of the present invention.

The photosensitive material of this invention is especially valuable and useful as a photosensitive material for an electrophotographic copying machine in which the surface of the photosensitive material is positivelv charged and the photosensitive material is used repeatedly for the copying operation.

The following Examples 1 to 9 illustrate the present invention.

Example I In tetrahydrofuran were homogeneously dissolved 10 g of polyvinvlcarbazole (here inafter referred to as "PVK") (Luvican M-170 manufactured by BASF AG.) and 20 g of 2,4,7-trinitrofiuorenone (hereinafter referred to as "TNF"), and the solution was coated on an aluminum foil having a thickness of 40p so that the dry thickness was 4a, whereby an intermediate layer was formed.Then, 3 g of Phthalocyanine Blue (hereinafter referred to as "PC") (Heliogen Blue 7800 manufactured by BASF AG.), 3 g of TNF and 35 g of an acrylic resin (FR-1112D manufactured by Mitsubishi Rayon K.K., solid content = 40% by weight) were homogeneously dispersed in 139 g of toluene, and the dispersion was coated on the intermediate layer so that the dry coating thickness was lOlL as a whole. Then, the coating was dried at 100"C. for 10 minutes.

Thus, a photosensitive plate of the present invention was prepared.

Comparative photosensitive plates were prepared for evaluating the properties of the photosensitive plate of this invention.

Comparative Example I A photosensitive plate was prepared in the same manner as described in Example 1 except that the amount of TNF in the top layer-forming coating composition was changed to 0.3 g.

Comparative Example 2 A photosensitive plate was prepared in the same manner as described in Example 1 except that the amount of TNF in the top layer-forming coating composition was changed to 10 g.

Comparative Example 3 A photosensitive plate was prepared in the same manner as described in Example 1 except that the amount of TNF in the intermediate layer-forming coating composition was changed to 1 g.

Comparative Example 4 A photosensitive plate was prepared in the same manner as described in Example 1 except that the amount of TNF in the intermediate layer-forming coating composition was changed to 100 g.

Comparative Example S In 139 g of toluene were homogeneously dispersed 3 g of PC. 0.5 g of TNF and 35 g of an acrylic resin (FR-1112D), and the dispersion was coated on an aluminum foil having a thickness of 40 y so that the drv thickness was the same as in Example 1 (lOa). Then, the coating was dried at 100"C.

for 10 minutes to form a photosensitive plate.

The photosensitive plate obtained in -Example 1 was tested by using a tester of the nositive charginFexposure-develoning transfer-fixing type. Clear images having a high resolving power were obtained. Several thousand prints could be obtained when the copying operation was repeated by using this photosensitive plate.

Electric characteristics of the photosensitive plate obtained in Example 1 were examined by using an electrostatic paper analyser manufactured by Kawaguchi Denki K.K. to obtain results shown in Table 1.

The comparative photosensitive plates were similarly subjected to the copying test and their eletcric properties were similarly examined. Obtained results are shown in Table 1.

Table 1 Comparative Comparative Comparative Comparative Comparative Copying Characteristics Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 sharpness O X # # # X density O O X O X X fogging O X O X O X cleaning property O X O X # # resistance to copying operation O X # # # X transfer efficiency O X O # O X Electric Characteristics sensitivity (Lux. sec) 16 30 17 25 18 27 initial potential (Volt) 460 450 455 470 350 380 charge quantity (Volt) 500 560 480 520 400 410 residual potential (Volt) 10 30 7 40 9 41 dark decay (Volt/sec) 60 25 100 10 51 7 Other adhesiveness O O # O # X Notes Sharpness: Reproducibility of fine lines, meshes, halftones and small letters, which was evaluated according to the following scale: 0: good A: slightly bad X: bad Density: The density of the image area (nonexposed area), which was evaluated according to the following scale: 0: dense A: slightly thin X: thin Fogging: Contamination of the background in the non-image area (exposure area), which was evaluated according to the following scale: O: not observed h slight X: conspicuous Cleaning Property: Easiness in removing the toner left on the photosensitive plate after transfer, which was evaluated according to the following scale: 0: very easy h slightly difficult X: difficult Resistance to Copying Operation: The number of good quality prints ob tained at the repeated copying operation, which was evaluated according to the following scale: 0: more than 1000 prints : 500-1000 prints X: less than 500 prints Transfer Efficiency: The ratio of the toner transferred to copying paper after development, which was evaluated according to the following scale: O: more than 80% of the toner was transferred A: 50 to 80% of the toner was trans ferred X: less than 50% of the toner was trans ferred Conditions for Measurements by Electro static Paper Analyzer: Light: 40 Lux Charge: 5 KV (positive) Sensitivity: quantity of light (Lux.sec) at which the potential just before exposure decayed to 1/2, which was determined according to the static method Initial potential: saturation charge voltage (V) as deter mined according to the static method Charge quantity: saturation voltage (V) observed when charging was effected for 10 seconds, which was determined according to the dynamic method Residual potential: voltage (V) observed 3 seconds after exposure, which was determined ac cording to the static method Dark decay: average value of the potential decay (V/sec) over a period of 3 seconds from charge-off, which was determined according to the static method Adhesiveness:: The adhesion strength of the photosensitive layer to the aluminum substrate (the peel resistance observed when an pressuresensitive adhesive tape was applied to the photosensitive layer and the tape was then peeled off), which was evaluated according to the following scale: 0: strong A: ordinary X: weak Example 2 In 80 g of a mixed solvent of toluene/ cyclohexanone (3/1 weight ratio) were homogeneously dissolved 10 g of PVK (Tuvical 210 manufactured by Takasago Koryo K. K.) and 10 g of TNF, and the solution was coated an aluminum foil having a thickness of 40 so that the dry thickness was 5aa, whereby an intermediate layer was formed. Then, 3 g of Phthalocyanine Blue (Heliogen Blue 7800 manufactured by BASF AG.), 4 g of TNF and 30 g of an acrylic resin (Acrydic A-196 Manufactured by Dai-Nippon Ink Kagaku Kogyo K.K., solid content = 50% were homogeneously dispersed in 100 g of toluene, and the dispersion was coated on the intermediate layer so that the dry coating thickness was 10 as a whole. The coating was then dried at 1000 C. for 10 minutes to obtain a photosensitive plate.

When this photosensitive plate was tested in the same manner as described in Example 1, good results similar to the results obtained in Example 1 were obtained.

Example 3 A photosensitive plate was prepared in the same manner as described in Example 1 except that an epoxy resin (Epikote 1009 manufactured by Shell Chemical Co.) was used instead of the acrylic resin in such an amount that the amount of the solids was the same as in the acrylic resin used in Example 1 and acetone was used as the solvent instead of toluene. When this photosensitive plate was tested, good results similar to the results obtained in Example 1 were obtained.

Example 4 A photosensitive plate was prepared in the same manner as described in Example 1 except that a polyester resin (Vylon 113 manufactured by Toyo Boseki K. K.) was used instead of the acrylic resin usde in Example 1. When this photosensitive plate was tested, good results similar to the results obtained in Example 1 were obtained.

Example 5 When a curing agent (Epicure manufao tured by Shell Chemical Co.) was added in forming the top layer in Example 3 in an amount of 5% by weight based on Epikote 1009, the durability was further improved in the resulting photosensitive prate.

Example 6 A photosensitive plate was prepared in the same manner as described in Example 1 except that 1 g of a silicon oil (KF-96 manufactured by Shinetsu Kagaku Kogyo K. K.) was added to the top layer-forming coating composition. When this photosensitive plate was tested in the same manner as described in Example 1, it was found that the resistance to the copying operation, and the cleaning property of this photosensitive plate were further improved over the photosensitive plate obtained in Example 1.

Example 7 A photosensitive plate was prepared in the same manner as described in Example 1 except that in the intermediate layerforming coating composition, TNF was replaced by the same weight of 2,4,7-tetranitro fluorenone. When this photosensitive plate was tested in the same manner as described in Example 1, good results similar to the results obtained in Example 1 were obtained.

Example 8 A photosensitive plate was prepared in the same manner as described in Example 1 except that in the intermediate coatingforming composition, poly - N - 2 - acrylcarbazole was used instead of PVK. When this photosensitive plate was tested, good results similar to the results obtained in Example 1 were obtained.

Example 9 A photosensitive plate was prepared in the same manner as described in Example 1 except that Resino Blue RSP (cooper phthalocyanine manufactured by Resino Color Kogyo K. K.) was used instead of Heliogen Blue 7800. When this photosensitive plate was tested in the same manner as described in Example 1, good results similar to the results obtained in Example 1 were obtained.

In co-pending Application No. 1713/78 (Serial No. 1,570,575) we have described and claimed a photosensitive material for use in electrophotography, which comprises an electrically conductive substrate; an intermediate layer comprising (A) phthalocyanine or a photo conductive phthalocyanine derivative incorporated in a binder with (B) a polycyclic aromatic nitro compound; the weight ratio of (A) : (B) in said intermediate layer being from 10.5 to 10:40; and a top layer comprising a charge transfer complex of (C) an organic polymeric photo conductor and a polycyclic aromatic nitro compound (B), the weight ratio of (C): (B) in said top layer being from 6:1 to 1:6.

WHAT WE CLAIM IS: 1. A photosensitive material for use in electrophotography which comprises an electrically conductive substrate; an intermediate layer comprising a charge transfer complex of (A) an organic polymeric photoconductor and (B) a polycyclic aromatic nitro compound capable of acting as an electron-acceptor, the weight ratio of (A): (B) in said layer from 6:1 to 1:6, and a top layer comprising (C) phthalacyanine or a photo conductive phthalocyanine derivative incorporated in a binder with a polycyclic aromatic nitro compound (B) in a weight ratio of (C):Q3) or from 10:5 to 10:25.

2. A photosensitive material according to claim 1 wherein the organic polymeric photoconductor (A) is poly-n-vinyl carbazole or a nuclear substitution derivative thereof.

3. A photosensitive material according to claim 1 or 2 wherein the polycyclic aromatic nitro compound (B) is 2,4,7-trinitrofluorenone or 2,4,5,7-tetranitrofluorenone.

4. A photosensitive material according to any one of claims 1 to 3 wherein the phthalocyanine or photo conductive phthalocyanine derivative is a metal-free phthalocyanine or a nuclear substitution derivative thereof.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. in the same manner as described in Example 1, good results similar to the results obtained in Example 1 were obtained. Example 3 A photosensitive plate was prepared in the same manner as described in Example 1 except that an epoxy resin (Epikote 1009 manufactured by Shell Chemical Co.) was used instead of the acrylic resin in such an amount that the amount of the solids was the same as in the acrylic resin used in Example 1 and acetone was used as the solvent instead of toluene. When this photosensitive plate was tested, good results similar to the results obtained in Example 1 were obtained. Example 4 A photosensitive plate was prepared in the same manner as described in Example 1 except that a polyester resin (Vylon 113 manufactured by Toyo Boseki K. K.) was used instead of the acrylic resin usde in Example 1. When this photosensitive plate was tested, good results similar to the results obtained in Example 1 were obtained. Example 5 When a curing agent (Epicure manufao tured by Shell Chemical Co.) was added in forming the top layer in Example 3 in an amount of 5% by weight based on Epikote 1009, the durability was further improved in the resulting photosensitive prate. Example 6 A photosensitive plate was prepared in the same manner as described in Example 1 except that 1 g of a silicon oil (KF-96 manufactured by Shinetsu Kagaku Kogyo K. K.) was added to the top layer-forming coating composition. When this photosensitive plate was tested in the same manner as described in Example 1, it was found that the resistance to the copying operation, and the cleaning property of this photosensitive plate were further improved over the photosensitive plate obtained in Example 1. Example 7 A photosensitive plate was prepared in the same manner as described in Example

1 except that in the intermediate layerforming coating composition, TNF was replaced by the same weight of 2,4,7-tetranitro fluorenone. When this photosensitive plate was tested in the same manner as described in Example 1, good results similar to the results obtained in Example 1 were obtained.

5. A photosensitive material according

to any one of claims 1 to 4 wherein the binder is an acrylic resin.

6. A photosensitive material according to any one of claims 1 to 5, wherein the wegiht ratio of (A) : (B) is from 1:1.7 to 1:2.2.

7. A photosensitive material according to any one of claims 1 to 6, wherein the weight ratio of (C) : (B) is from 10:8 to 10:20.

8. A photosensitive material according to any one of claims 1 to 7, wherein the top layer further comprises a silicone oil in an amount of from 5 to 150 parts by weight per 100 parts by weight of the phthalocyanine or photoconductive phthalocyanine derivative (C).

9. A photosensitive material according to any one of claims 1 to 8 wherein the intermediate layer has a thickness of from 0.1 to 101b and the top layer has a thickness of from 0.1 to 30cur.

10. A photosensitive material according to claim 9, wherein the intermediate layer has a thickness of from 1 to 8,a and the top layer has a thickness of from 1 to 15.

11. A photosensitive material according to claim 1, substantially as described in any one of Examples 1 to 9.