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(11) | EP 0 703 501 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Photoconductor for electro-photography and a method for fabricating the same |
| (57) A photoconductor for electrophotography (10) is fabricated by immersing an electroconductive
substrate (1, 11) made of an aluminum alloy in an aqueous mixed solution containing
an amine compound and sodium silicate to form a film (14) of aluminum oxide hydrate,
and applying a solution of an organic nitrogen compound, the solution containing iodine,
to the substrate after the film formation to form an intermediate layer (7, 12) on
the film of the aluminum oxide hydrate. A non-cut aluminum tube or cylinder fabricated
by extrusion and drawing can be used as the electroconductive substrate of the photoconductor. |
[0001] The present invention relates to a photoconductor for electrophotography and to a method for fabricating the same.
[0002] More particularly, the present invention relates to a photoconductor for electrography having an electroconductive substrate, especially a non-cut aluminum alloy substrate, and an intermediate layer provided thereon and to a method for fabricating the same.
[0003] Recently, photoconductors for electrophotography (hereafter, sometimes referred to simply as "photoconductors") made of organic materials have been used as photoconductors for printers, copying machines, and facsimiles instead of conventional inorganic photoconductor materials such as selenium, cadmium sulfide, and zinc oxide The organic photoconductors are taking the place of the inorganic photoconductors because of their various advantages such as no or less environmental pollution, improved productivity, and low cost.
[0004] Organic photoconductors for electrography include two types of photoconductors with different layer structures, i.e., a monolayer type photoconductor having an electroconductive substrate on which there is provided a layer containing a binder having dispersed therein a complex of polyvinylcarbazole and trinitrofluorophthalein or a phthalocyanine pigment, or a function-separated or laminated type photoconductor having in combination a layer containing a charge generating substance (i.e., a charge generating layer) and a layer containing a charge transporting layer (i.e., a charge transporting layer). Of these known photoconductors, the latter is given much attention. This is because the function-separated photoconductors not only can be made to have a sensitivity over a wide wavelength range of from visible light to infrared region by using various combinations of a charge generating substance and a charge transporting substance but also they have relatively high sensitivities.
[0005] Incidentally, the charge transporting substance used in organic photoconductors is mostly of a hole-migrating charge transporting substance because it is fabricated with ease and shows a less toxicity. Thus, the layer structure of such a photoconductor is mainly a so-called negative-charging type, i.e., including an electroconductive substrate and a charge generating layer and a charge transporting layer provided in this order on the substrate. The charge generating substance contained in the charge generating layer is an organic pigment which has a high optical absorption coefficient and a high, charge generation coefficient.
[0006] It is known that the properties of a photoconductor generally vary depending on the surface conditions of the aluminum substrate. That is, stain or contamination on the aluminum substrate or unevenness in the film formation of a charge generating layer due to unevenness in shape tend to cause defects of the photoconductor, for example, white spots, black spots, unevenness in concentration, fogging, and the like image defects.
[0007] As is well known, the charge generating layer is made into a very thin layer usually of a thickness on the order of several submicrons. This is because if the charge generating layer is unnecessarily thick, then the generated charges will not be injected in the charge transporting layer sufficiently, so that the photoconductor suffers from defects such as a decrease in memory or chargeability after prolonged use and an increase in the residual potential. As described above, in order to form a very thin charge generating layer on a substrate, the conditions of a surface of aluminum used as a substrate on which the charge generating layer is coated are particularly important.
[0008] There have been proposed various methods for cleaning the contamination of the surfaces of the substrate. In particular, various improvements have been recently proposed that use aqueous solvent instead of conventional halogen-containing cleaning solvents. For example, Japanese Patent Application Laying-open No. 188605/1993 describes the cleaning method in which cleaning is performed while electrolysis reaction is carried out in an aqueous solution. Japanese Patent Application Laying-open No. 150468/1993 describes the cleaning method which performs a cleaning with an alcoholic solvent after a cleaning with an aqueous solution. Japanese Patent Application Laying-open No. 127396/1993 describes the method which performs a rinsing with hot water.
[0009] Further, various methods are proposed to obtain improved cleaning effects by the use of a cleaning solution having improved properties. For example, Japanese Patent Application Laying-open No.3831/1994 and Japanese Patent Application Laying-open No. 281758/1993 disclose the methods in which there are used cleaning solutions having pH values controlled to be within a certain range. Japanese Patent Application Laying-open No. 59463/1994 discloses the method in which there is used a cleaning solution whose electroconductivity is controlled to be within a certain range.
[0010] However, despite all the cares taken, aluminum tends to be influenced by the environment surrounding it and tends to be formed with an oxide film or a hydrated oxide film on its surface. The formation of such a film causes unevenness in coatability of a coating liquid. To solve this problem, the method of forming an Alumite film has been proposed to form a stable oxide film intentionally in order to improve coatability and film formability as described in Japanese Patent Application Laying-open No. 11610/1988, Japanese Patent Application Laying-open No 116161/1988, Japanese Patent Application Laying-open No. 616162/1988, and so on. However, this approach is disadvantageous from economical point of view since much cost is required for providing an anodizing installation as well as for coping with pollution of water.
[0011] For this reason, it was proposed to provide a layer of hydrated aluminum oxide chemically formed by hot water treatment as an oxide film for substituting Alumite and the provision of a hydrated aluminum oxide layer decreased light wear of the photoconductor for elecctrophotography (Japanese Patent Application Laying-open No. 29852/1989).
[0012] However, as is well known in the art, the aluminum used as an electroconductive substrate for a photoconductor for electrophotography is employed in the form of an alloy composition which contains one or more additional metals, e.g., iron (Fe), copper (Cu), manganese (Mn), or magnesium (Mg) in addition to aluminum (Al). A portion of the additional metal forms an alloy with aluminum and at the same time the other portion thereof crystallizes to form fine crystals. Formation of the fine crystals results in that the substrate is covered with a hydrated aluminum oxide layer insufficiently at the time of an Alumite treatment or a hydrated aluminum oxide treatment. This in turn leads to image defects. In order to avoid this defect, it was proposed to provide on the hydrated aluminum oxide layer an intermediate layer which contains an inorganic pigment dispersed therein (Japanese Patent Application Laying-open No. 19174/1994).
[0013] Although the above-described methods are applicable to electroconductive substrates made of commonly used aluminum alloys, for example, to aluminum cylinders subjected to precision surface-treated by cutting, it suffers from various problems as described below when it is applied to so-called non-cut aluminum tubes such as EI tubes fabricated by impact extrusion or ED tubes fabricated by extrusion and drawing, the methods being recently developed and well known as methods capable of fabricating aluminum cylinders for use in photoconductors for electrophotography at low cost.
[0014] That is, the non-cut aluminum tubes have many defects in the form of streaks or holes on its surface. Some of them are of several micrometers (µm) in depth. Such defects still exist or a part of which remains after a mechanical surface treatment such as honing or biting or a chemical surface treatment such as Alumite film formation or aluminum oxide hydrate film formation. In addition, metal crystals tend to form on the surface more apparently. In order to obviate the above-described defects, the approach of providing an intermediate layer having dispersed therein an inorganic pigment could also be applied to the non-cut aluminum tubes, which were subjected to Alumite film formation or aluminum oxide hydrate film formation. However, a considerably thick intermediate layer must be provided for completely covering or making up the configurational defects on the surface of the non-cut aluminum tube. In this occasion, care must be taken that if the intermediate layer has too large a thickness, the resulting photoconductor will have deteriorated performances such as an increased residual potential and decreased characteristics after repeated use for a long period of time.
[0015] With view to obviating the above-described disadvantages, the present inventors have made intensive investigation and as a result the present invention has been accomplished.
[0016] Now, it is an object of the present invention to provide a photoconductor for electrophotography which has an improved aluminum oxide hydrate film on its electroconductive substrate, which allows provision of an intermediate layer on the film in a thickness large enough to cover or make up the surface defects of a non-cut aluminum tube having cracks, flaws, streaks, holes or hollow portions, or otherwise undesirable irregularities or defects on its surface, which is free of an increase in residual potential, deterioration of characteristics after repeated use for a long time, and which shows less variation in its characteristics in varied environmental conditions ranging from high temperature and high humidity conditions to low temperature and low humidity conditions.
[0017] Another object of the present invention is to provide a method for fabricating such a photoconductor for electrophotography.
[0018] According to a first aspect of the present invention, there is provided a photoconductor for electrophotography comprising: an electroconductive substrate comprising an aluminum alloy; and an intermediate layer provided on the electroconductive substrate; a photosensitive layer provided on the intermediate layer; the electroconductive substrate having on a surface thereof a film of aluminum oxide hydrate containing nitrogen derived from an amine compound; and the intermediate layer containing a complex comprising an organic nitrogen compound and iodine.
[0022] The film of aluminum oxide hydrate may be a layer formed by immersing the electroconductive substrate in a solution of a mixture of the amine compound and sodium silicate.
[0023] According to a second aspect of the present invention, there is provided a method for fabricating a photoconductor for electrophotography, comprising the steps of: immersing an electroconductive substrate comprising an aluminum alloy in an aqueous mixed solution containing a mixture of an amine compound and sodium silicate to form a film of aluminum oxide hydrate on a surface of the substrate; and forming an intermediate layer on the film of aluminum oxide hydrate by applying to the electroconductive substrate after the film formation a coating liquid containing a complex organic nitrogen compound.
[0027] The solution of the complex organic nitrogen compound may contain iodine in an amount of 3 to 30 parts by weight per 100 parts by weight of a film composition.
[0028] The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of the embodiment thereof taken in conjunction with the accompanying drawings.
Fig. 1 is a schematic cross sectional view showing a monolayer type photoconductor;
Fig. 2 is a schematic cross sectional view showing a laminate type photoconductor;
Fig. 3 is schematic cross sectional view showing another example of a laminate type photoconductor having a layer structure in reverse to that shown in Fig. 2;
Fig. 4 is a schematic perspective view showing a typical example of a photoconductor of the present invention in a cylindrical form; and
Fig. 5 is a schematic cross sectional view of the electroconductive substrate in each of the photoconductors shown in Figs. 1 to 4.
[0029] As shown in Fig. 1, a photosensitive layer 2A is provided on an electroconductive substrate 1 via one or more intermediate layers 7 such as a subbing layer and a barrier layer. The photosensitive layer 2A comprises a charge generating substance 3, and a charge transporting substance 5, both of which substances are dispersed in a resin binder matrix so that the photosensitive layer 2A functions as a photoconductor.
[0030] According to the arrangement shown in Fig. 2, a laminated photosensitive layer 2B is provided on an electroconductive substrate 1 via one or more intermediate layers 7 such as a subbing layer and a barrier layer. In this arrangement, a lower layer of the laminate is a charge generating layer 4 containing a charge generating substance 3, and an upper one is a charge transporting layer 6 containing a charge transporting substance 5 as a main component, so that the photosensitive layer 2B functions as a photoconductor. This photoconductor is usually used according to the negative charge mode.
[0031] According to the arrangement shown in Fig. 3, a laminated photosensitive layer 2C is provided on an electroconductive substrate 1 via one or more intermediate layers 7 such as a subbing layer and a barrier layer. In this arrangement, an lower layer of the laminate is a charge transporting layer 6 containing a charge transporting substance 5 as a main component, and an upper one is a charge generating layer 4 containing a charge generating substance 3, so that the photosensitive layer 2C factions as a photoconductor. This photoconductor is usually used according to the positive charge mode. In this case, a cover layer 8 may generally be further provided as shown in Fig. 3 to protect the charge generating layer 4.
[0032] The photoconductors as shown in Fig. 1 can be fabricated by forming one or more intermediate layers on an electroconductive substrate, dispersing a charge generating substance in a solution of a charge transporting substance and a resin binder, applying the resulting dispersion on the electroconductive substrate the on one or more intermediate layers, and then drying the resulting coating film.
[0033] The photoconductors as shown in Fig. 2 can be fabricated by forming one or more intermediate layers on an electroconductive substrate, applying a dispersion of a particulate charge generating substance in a solvent and/or a resin binder on the one or more intermediate layers to form a charge generating layer, drying the resulting coating film, applying a solution of a charge transporting substance and a binder resin on the charge generating layer, and then drying the resulting coating film.
[0034] The photoconductors as shown in Fig. 3 can be fabricated by applying one or more intermediate layers on an electroconductive substrate, applying a dispersion of a charge transporting substance and a binder resin on the one or more intermediate layers, drying the resulting coating film to form a charge transporting layer, applying a particulate charge generating substance in a solvent and/or a resin binder on the charge transporting layer, and then drying the resulting coating film.
[0035] Typically, the photoconductor of the present invention is fabricated in a cylindrical form as shown in Fig. 4. As shown in Fig. 4, a photoconductor 10 comprises a cylindrical electroconductive substrate 11 made of an aluminum alloy, which has on its outer surface an intermediate layer 12. On the intermediate layer 12 is provided a photosensitive layer 13. The photosensitive layer 13 may be a monolayer photosensitive layer having the same structure as the photosensitive layer 2A shown in Fig. 1, or may be of the same structure as the photosensitive layer 2B shown in Fig. 2 or the photosensitive layer 2C shown in Fig. 3. When the photosensitive layer 13 has the same structure as the photosensitive layer 2C shown in Fig. 3, a cover layer 8 may be provided on the photosensitive layer 13 similarly to the arrangement shown in Fig. 3.
[0036] As shown in Fig. 5, the electroconductive substrate 11 has on its surface a film 14 of aluminum oxide hydrate containing nitrogen derived from an amine compound used for forming the film 14. The photoconductor of the present invention has the intermediate layer 12 on the electroconductive substrate 11 via the film 14 of aluminum oxide hydrate.
[0037] The aluminum substrate which can be used in the present invention includes, for example, JIS 1100, JIS 3003, and JIS 6063 materials. These materials can be fabricated into a cylindrical shape by impact extrusion, or by extrusion and drawing. The cylinders thus obtained may be used as they are or they may be surface treated as by honing or biting process before use by a suitable processing means.
[0038] According to the method of the present invention, an aluminum oxide hydrate film may be formed on the aluminum substrate by treating a surface of the aluminum substrate or non-cut aluminum cylinder with an aqueous solution containing a mixture of an amine compound and sodium silicate. The amine compound which can be used includes mono-, di- or trialkylamines having 1 to 4 carbon atoms in each alkyl moiety such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, and diethylamine, primary, secondary or tertiary alkylenediamines having 1 to 4 carbon atoms in each alkylene moiety such as ethylenediamine, propylenediamine, diethylenetriamine, triethylentetramine, triamines having 1 to 4 carbon atoms such as propanetriamine and butanetriamine, and alkylolamines having 1 to 4 carbon atoms in each alkylol moiety such as monoethanolamine, diethanolamine, and triethanolamine. Examples of the sodium silicate which can be used include sodium orthosilicate hydrates of the formula Na₂SiO₃·nH₂O where n=2 to 4, sodium metasilicate hydrates of the formula Na₄SiO₄·nH₂O where n=1 to 9, and sodium silicate anhydride of the formula Na₂SiO₃. The amine compound and the sodium silicate can be used in a molar ratio of 3:1 to 1:3. The aqueous solution of the amine compound and the sodium silicate is used at a temperature within the range of from 50°C to 90°C. It is desirable to control the ratio of the amine compound to the sodium silicate so that the aqueous solution has a pH within the range of from 9 to 12. At temperatures below 50°C, the rate of growth of the film of aluminum oxide hydrate is relatively low and, hence, the use of such low temperatures is disadvantageous from industrial-point of view. On the other hand, the use of temperatures above 90°C is also disadvantageous in that at such high temperatures, water evaporates more, which makes it difficult to control the concentration of the aqueous solution. At a pH of below 9, the film of aluminum oxide hydrate becomes coarse and there tends to occur a considerable corrosion by a decomposate at high humidities of an iodine complex added to the intermediate layer. Further, a pH of above 12 is undesirable since dissolution of aluminum proceeds preferentially to the formation of the film of aluminum oxide hydrate. An aluminum substrate which was cleaned to remove oil or dirt present on the surface thereof is immersed in the aqueous amine solution prepared as described above for 3 to 30 minutes to form a film of aluminum oxide hydrate on the substrate. The thus treated substrate is subsequently washed to remove the remaining aqueous amine solution and then dried The intermediate layer to be provided on the substrate with a film of aluminum oxide hydrate contains a complex of an organic nitrogen compound and iodine. The organic nitrogen compound which can be used includes, as high molecular weight substances, polymers such as polyamide resins, polyurethane resins, amino resins, aniline resins, polyanilines, and polypyrroles and, as low molecular weight substances, pyrrole, indole, indoline, toluenediamine, naphtalenediamine, ethylenediamine, hexamethylenediamine, tetramine, and pyrrolidone monoethanolamine and diethanolamine. The high molecular weight compounds can be used alone or in admixture with one or more other film forming thermoplastic or thermosetting resins or reactive oligomers. They can be dissolved in a solvent capable of dissolving them to form a solution, to which there is added a suitable amount of iodine to form a complex. The resulting solution is used for forming a film. Although suitable amount of iodine (I₂) to be added may vary depending on the kind of the high or low molecular weight compound used, it may suitably be within the range of 3 to 30 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the film composition. With below 3 parts by weight, the amount of the complex to be obtained is insufficient and as a result the resistance of the intermediate layer increases unacceptably and there occur defects such as an increase in the charging potential after repeated use and a decrease in the residual potential. On the other hand, with above 30 parts by weight, there exist free iodine (I) which does not participate in the formation of the complex. This causes defects such as a decrease in chargeability and a deterioration of the film at high humidities. The intermediate layer can be formed by applying a coating liquid of an organic nitrogen compound to which iodine is added in order to give a film forming property as described above to an aluminum tube whose surface has a film of aluminum oxide hydrate formed under specified conditions as described above, followed by heating, drying, and curing. The thickness of the intermediate layer is desirably not smaller than 0.2 µm and not greater than 20 µm. The intermediate layer of less than 20 µm thick is undesirable because it is difficult for the coating film thickness to follow minute protrusions and depressions on the surface of an aluminum tube having a film of aluminum oxide hydrate, go that pin-holes and runaways tend to occur. On the other hand, with the thickness of the intermediate layer greater than 20 µm, the coating layer has an unacceptably high resistance, resulting in an undesirably high residual potential. To the intermediate layer, there can be added organic or inorganic fillers in order to give the photoconductor a light scattering effect sufficient for its being useful as a photoconductor for electrophotography for printers using a laser beam, color the photoconductor, or cover the contamination, cracks or flaws on the surface of the aluminum tube, or hide defects in the appearance. Examples of the organic filler which can be used in the present invention includes finely divided polyethylene, polypropylene, polyurethane, silicone resin, fluorine containing rein, melamine resin, phenol resin, and so on. The inorganic filler which can be used is finely divided lead oxide, zinc oxide, titanium oxide, calcium oxide, silica, and so on. The particle diameter of the organic or inorganic filler is usually within the range of from 0.01 µm to 1 µm.
[0039] It is desirable that the finely divided organic or inorganic filler be added so that it may occupy 20% to 60% of the volume of the intermediate layer. If this value is below 20% by volume, the porosity of the filler in the intermediate layer is too large and the photoconductor tends to suffer from changes in the characteristics thereof due to variation or changes in the environment. On the other hand, if the value is above 60%, coatability of the coating liquid is too low. In order to prevent deterioration due to toxic substances, for example, ozone and nitrogen oxides, which are produced during the operation of the photoconductor, the intermediate layer may contain a phenol based antioxidant, a sulfur based antioxidant (for example, sulfide, disulfide), a phosphorus based antioxidant (for example, phosphite), an amine based antioxidant (for example, HALS, arylamines) and so on. These antioxidants may be added alone or in combination. Of course, a polyfunctional antioxidant which has a phenol group, a thioether group, a phosphite group and an amine group in the molecule can also be used. These additives can be added in amounts on the order of usually 0.1% to 20% by weight based on the weight of the film composition.
[0040] Organometal compounds such as ferrocene, copper acetylacetonate, cobalt acetylacetonate, copper naphthenate, and cooper acetate may also be added to the intermediate layer so far as they are uniformly dissolved in a coating liquid for forming the intermediate layer and remain dispersed uniformly in the coating film after film formation. Their amount is suitable within the range of 5 to 2% by weight based on the weight of iodine. The organometal compounds are believed to prevent oxidation of the amine compound and fix free iodine. They are particularly effective for preventing the occurrence of lifting of the intermediate layer under high humidity conditions.
[0041] The photosensitive layer provided on the intermediate layer may be a conventionally used photosensitive layer. Examples of the conventional photosensitive layer include the photosensitive layer containing a charge transporting complex comprising a combination of polyvinylcarbazole and trinitrofluorenone as described in U.S. Patent 3,484,237, the dye-sensitized photosensitive layer as described in Japanese Patent Application Publication No. 25685/1973, the monolayer type photosensitive layer containing a pigment dispersed in a hole transporting material or electron transporting material as described in Japanese Patent Application Laying-open No. 30328/1972 and Japanese Patent Application Laying-open No. 18545/1972, the function-separated type photosensitive layer including a charge generating layer and a charge transporting layer as the major components as described in Japanese Patent Application Laying-open No. 105537/1974. Of these, the function-separated type photosensitive layer including a charge generating layer and a charge transporting layer is widely put into practical use since it is highly sensitive and it can be fabricated from various materials depending on light source to be used and for some other reasons.
[0042] The charge generating layer can be prepared by dispersing a phthalocyanine pigment, an azo pigment, an anthanthrone pigment, a perylene pigment, a perinone pigment, a suquarylium pigment, a thiapyrylium pigment, or a quinacridone pigment in a binder resin solution such as a polyvinylbutyral, a vinyl chloride copolymer, an acrylic resin, a polyester, or a polycarbonate and applying the resulting coating composition on the intermediate layer. The thickness of the charge generating layer is preferably within the range of from 0.1µm to 2 µm.
[0043] The charge transporting layer can be prepared by mixing an enamine compound, a styryl compound, a hydrazone compound, or an amine compound with a resin which is compatible therewith, e.g., a polyester, a polycarbonate, a polymethacrylic acid ester, a polystyrene, or the like to form a solution and coating the solution on the charge generating layer to a thickness on the order of 10 µm to 40 µm. The order of laminating the charge generating layer and the charge transporting layer may be reversed.
[0044] According to the present invention, the surface of the aluminum alloy substrate is provided with a fig of aluminum oxide hydrate under specified conditions and, hence, a photoconductor with a fine, hard aluminum oxide hydrate film can be obtained. The photoconductor shows a high mechanical stability even when the intermediate layer comprising a iodine-amine compound complex is relatively thick. Also, the photoconductor of the present invention shows mechanical stability when left to stand under high temperature and high humidity conditions for a long period of time. When the intermediate layer contains an antioxidant, deterioration due to ozone or the like can be prevented. Inclusion of organometal compounds in the intermediate layer fixes free iodine in the intermediate layer and prevents lifting of the intermediate layer under high humidity conditions.
EXAMPLES
[0045] Hereafter, the present invention will be described in more detail by examples. However, the present invention should not construed as being limited thereto in any sense.
Examples 1 to 3 and Comparative Examples 1 to 3
[0046] ED tubes each made of an aluminum alloy produced by extrusion and drawing having an outer diameter of 30 mm, an inner diameter of 28 mm, and a length of 260.5 mm, with a surface roughness in terms of maximum height (Rmax) of 2.0 µm were immersed in various aqueous mixed solutions containing various amine compounds and sodium silicate as shown in Table 1. As comparative examples, the same ED tubes were immersed in hot deionized water or a hot solution containing an amine compound alone, or provided with a aluminum oxide hydrate without a treatment with the mixed solution. Table 1 shows the compositions, pH, temperature of the mixed solutions for forming the aluminum oxide hydrate film.
[0047] In Table 1, Comparative Example 2 (abbreviated as "C.Ex.2" corresponds to the method described in Example 3 of Japanese Patent Application Laying-open No. 29852/1989, and SMSH stands for sodium metasilicate hydrate.
Table 1
| Example | Amine Compound | Sodium Silicate | pH | Temperature (°C) | Treating Time (Minute) |
| 1 | MEA 30 g/l | SMSH 15 g/l | 10.9 | 70 | 5 |
| 2 | DEA 15 g/l | SMSH 15 g/l | 11.1 | 70 | 3 |
| 3 | TEA 5 g/l | SMSH 15 g/l | 11.4 | 70 | 3 |
| C.Ex. 1 | TEA 15 g/l | None | 10.0 | 80 | 10 |
| C.Ex. 2 | - | - | 7.0 | 90 | 10 |
| C.Ex. 3 | No treatment | ||||
| Notes: MEA; monoethanolamine DEA; diethanolamine TEA; triethanolamine |
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[0048] The aluminum tubes each treated under the conditions shown in Table 1 to form an aluminum oxide hydrate film were provided with an intermediate layer thereon by applying a coating liquid having the composition A described below to a thickness of 15 µm.
Composition A:
[0049]
| Component | Parts by Weight |
| Iodine | 0.3 |
| Soluble Nylon: Toray, Corp. (AMILAN CM-8000 | 3 |
| Titanium oxide: Ishihara Sangyo K.K. (TTO-55(S)) | 3 |
| Methanol | 100 |
[0050] On each aluminum tube having the intermediate layer described above was dip-coated a coating liquid prepared by dispersing 1 part by weight of X type metal-free phthalocyanine ("Fastgen Blue 8120B", manufactured by Dai-Nippon Ink and Chemicals, Inc.) and 1 part by weight of a vinyl chloride copolymer ("MR-110", manufactured by Nippon Zeon Co., Ltd.) together with 100 parts by weight of methylene chloride in a paint shaker, to form a charge generating layer of a dry thickness of 0.2 µm. Subsequently, on the charge generating layer was dip-coated a coating liquid prepared by dissolving 10 parts by weight of a polycarbonate resin ("IUPILON PCZ-300", manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 10 parts by weight of N,N-diethylaminobenzaldehyde diphenylhydrazone in 80 parts by weight of tetrahydrofuran to form a charge transporting layer of a dry thickness of 20 µm. Thus, a photosensitive layer was formed.
[0051] The thus obtained photosensitive layers were examined for electric characteristics using a photoconductor process tester. More specifically, each photoconductor was attached to the photoconductor process tester, electrified to -600V using a corotron, rotated at a peripheral speed of 78.5 mm/sec., irradiated with a light at an exposure wavelength of 780 nm at an intensity of 2 µ/cm², and measured for an illuminated potential (Vi) after 0.2 second from the irradiation and a residual potential (Vr) after 1.5 seconds from the irradiation Also, the potential in the dark (V₀) was measured. Further, retention ratio of potential after standing in the dark for 5 seconds (Vk5(%)) was measured. This procedure was repeated in different environments, i.e., LL (low temperature and low humidity: 10°C, 20RH%), NN (normal temperature and normal humidity: 23°C, 50RH%), and HH (high temperature and high humidity: 40°C, 80RH%). Further, changes in the appearance of the photoconductors were observed when they were left to stand for a long period time in the HH environment. Tables 2, 3 and 4 show the results obtained.
Table 2
| Environment | |||||||||
| LL | NN | HH | |||||||
| Example | 1 | 2 | 3 | 1 | 2 | 3 | 1 | 2 | 3 |
| V0(V) | -660 | -670 | -650 | -620 | -630 | -600 | -640 | -630 | -610 |
| Vi(V) | -80 | -100 | -90 | -60 | -70 | -75 | -40 | -30 | -50 |
| Vk5(%) | 94 | 96 | 95 | 96 | 97 | 96 | 91 | 90 | 92 |
| Vr(V) | -35 | -46 | -42 | -20 | -25 | -30 | -15 | -17 | -14 |
Table 3
| Environment | |||||||||
| LL | NN | HH | |||||||
| Comparative Example | 1 | 2 | 3 | 1 | 2 | 3 | 1 | 2 | 3 |
| V0(V) | -650 | -680 | -670 | -630 | -650 | -640 | -620 | -600 | -570 |
| Vi(V) | -95 | -90 | -100 | -50 | -60 | -65 | -20 | -40 | -20 |
| Vk5(%) | 95 | 97 | 96 | 95 | 96 | 93 | 86 | 81 | 80 |
| Vr(V) | -80 | -60 | -70 | -20 | -20 | -30 | -10 | -20 | -10 |
Table 4
| Standing Time | |||
| Example | 100 Hours | 200 Hours | 500 Hours |
| 1 | No change | No change | Small bubbles |
| 2 | No change | No change | Small bubbles |
| 3 | No change | No change | No change |
| C.Ex. 1 | No change | Fine bubbles | Small bubbles |
| C.Ex. 2 | No change | Small bubbles | Large inflation |
| C.Ex. 3 | Small bubbles | Large inflation | |
[0052] As shown in Tables 2, 3 and 4, the photoconductors of the examples of the present invention show increased durabilities.
Examples 4, 5 and 6
[0053] Photoconductors were fabricated in the same manner as in Examples 1, 2 and 3 except that an intermediate layer of a dry thickness of 15 µm was formed by using composition B below and drying at 120°C for 15 minutes.
Composition B
[0054]
| Parts by Weight | |
| Melamine resin: YUBAN 20HS, manufactured by Mitsui Toatsu Co., Ltd. | 100 |
| Iodine | 5 |
| a-Tocopherol | 5 |
| Anhydrous ammonium itaconate | 3 |
| Titanium oxide: TTO-55(S), manufactured by Ishihara Sangro K.K. | 100 |
| Blocked isocyanate: BARNOK D-500, manufactured by Dai-Nippon Ink and Chemicals, Inc. | 5 |
| Tetrahydrofuran | 200 |
| Methanol | 100 |
[0055] The photoconductors were left to stand in the HH environment (45°C, 80RH%) and changes in the appearance were observed. Table 5 shows the results obtained.
Table 5
| Standing Time | |||
| Example | 100 Hours | 200 Hours | 500 Hours |
| 4 | No change | Small bubbles | Inflations |
| 5 | No change | No change | Small bubbles |
| 6 | No change | No change | Small bubbles |
[0056] Replacement of the composition A by the composition B results in an improved durability due to the use of thermosetting resin.
Examples 7, 8 and 9
[0057] Photoconductors were fabricated by providing the aluminum tube treated in the same manner as in Example 3 with the same intermediate coating liquid compositions C, D and E, respectively, as shown in Table 6, drying the coating liquid on each aluminum tube at 130°C for 10 minutes to form an intermediate layer of a dry thickness of 17 µm, and forming a charge generating layer and a charge transporting layer by repeating the procedure of Example 1.
Table 6
| Coating Liquid Composition of Intermediate Layer (Part by Weight) | |||
| C | D | E | |
| Benzoguanamine resin: SUPERBECKAMINE TD-26, manufactured by Dai-Nippon Ink and Chemicals, Inc. | 10 | 10 | 10 |
| Blocked isocyanate : BARNOCK D:500, manufactured by Dai-Nippon Ink and Chemicals, Inc. | 10 | 10 | 10 |
| Iodine | 2 | 2 | 2 |
| Copper acetate | 0.4 | ||
| Ferrocene | 0.5 | ||
| Cobalt naphthenate | 0.4 | ||
| Tetrahydrofuran | 20 | 20 | 20 |
| Ethanol | 10 | 10 | 10 |
[0058] The photoconductors thus obtained were left to stand in the HH environment as in Examples 4 to 6 and changes in the appearance thereof were observed. Table 7 shows the results obtained.
Table 7
| Standing Time | |||
| Example | 100 Hours | 500 Hours | 1000 Hours |
| 7 (Coating liquid C) | No change | No change | No change |
| 8 (Coating liquid D) | No change | No change | No change |
| 9 (Coating liquid E) | No change | No change | No change |
[0059] As can be seen from Examples 7, 8 and 9 (Table 7), the inclusion of an organometal compound in the intermediate layer prevents lifting of the intermediate layer and increases the durability of the photoconductor to 1000 hours.
[0060] According to the present invention, the electroconductive substrate has an aluminum oxide hydrate film formed by dip-coating of an aqueous mixed solution containing an amine compound and sodium silicate and, hence, the electroconductive substrate is covered with a film of aluminum oxide hydrate which is dense and hard. Therefore, when an intermediate layer containing a complex of an organic nitrogen compound and iodine is formed to a considerable thickness on the substrate, or when left to stand under high temperature and high humidity conditions for long period of time, the photoconductor of the present invention has high mechanical stability. As a result, according to the present invention, aluminum tubes extruded and drawn only can be used for the fabrication of photoconductors for electrophotography. In other words, the photoconductor of the present invention can be fabricated at low cost. Inclusion of an antioxidant or an organometal compound in the intermediate layer prevents deterioration of the intermediate layer with ozone or lifting of the intermediate layer under high humidity conditions, so that reliable photoconductors can be obtained.
[0061] Further, according to the method of the present invention, a film of aluminum oxide hydrate and an intermediate layer are formed so that a dense, hard film of aluminum oxide hydrate can be obtained with ease at optimum temperature and pH conditions. The present invention enables one to obtain a photoconductor having excellent characteristics by the formation of a relatively thick intermediate layer on the surface of a non-cut aluminum tube.
[0062] The present invention has been described in detail with respect to an embodiment, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.
1. A photoconductor for electrophotography characterized by comprising:
an electroconductive substrate comprising an aluminum alloy;
an intermediate layer provided on said electroconductive substrate;
a photosensitive layer provided on said intermediate layer;
said electroconductive substrate having on a surface thereof a film of aluminum oxide hydrate containing nitrogen derived from an amine compound;
said intermediate layer containing a complex comprising an organic nitrogen compound and iodine.
an electroconductive substrate comprising an aluminum alloy;
an intermediate layer provided on said electroconductive substrate;
a photosensitive layer provided on said intermediate layer;
said electroconductive substrate having on a surface thereof a film of aluminum oxide hydrate containing nitrogen derived from an amine compound;
said intermediate layer containing a complex comprising an organic nitrogen compound and iodine.
2. The photoconductor for electrophotography as claimed in claim 1, characterized in
that said intermediate layer contains an antioxidant.
3. The photoconductor for electrophotography as claimed in claim 1, characterized in
that said intermediate layer contains an organic metal compound.
4. The photoconductor for electrophotography as claimed in claim 1, characterized in
that said intermediate layer contains an organic or inorganic filler.
5. The photoconductor for electrophotography as claimed in claim 1, characterized in
that said film of aluminum oxide hydrate is a layer formed by immersing said electroconductive
substrate in a solution of a mixture of said amine compound and sodium silicate.
6. A method for fabricating a photoconductor for electrophotography, characterized by
comprising the steps of:
immersing an electroconductive substrate comprising an aluminum alloy in an aqueous mixed solution containing a mixture of an amine compound and sodium silicate to form a film of aluminum oxide hydrate on a surface of said substrate; and
forming an intermediate layer on said film of aluminum oxide hydrate by applying to said electroconductive substrate after said film formation a coating liquid containing a complex organic nitrogen compound.
immersing an electroconductive substrate comprising an aluminum alloy in an aqueous mixed solution containing a mixture of an amine compound and sodium silicate to form a film of aluminum oxide hydrate on a surface of said substrate; and
forming an intermediate layer on said film of aluminum oxide hydrate by applying to said electroconductive substrate after said film formation a coating liquid containing a complex organic nitrogen compound.
7. The method for fabricating a photoconductor for electrophotography as claimed in claim
6, characterized in that said aqueous mixed solution has a pH within the range of
from 9 to 12.
8. The method for fabricating a photoconductor for electrophotography as claimed in claim
6, characterized in that said mixed solution is at a temperature within the range
of from 50°C to 90°C.
9. The method for fabricating a photoconductor for electrophotography as claimed in claim
6, characterized in that said solution of said complex organic nitrogen compound contains
iodine.
10. The method for fabricating a photoconductor for electrophotography as claimed in claim
9, characterized in that said solution of said complex organic nitrogen compound contains
iodine in an amount of 3 to 30 parts by weight per 100 parts by weight of a film composition.