JPH03211561A - Laminated electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent picture blurring under high-temp. and high-humidity conditions and to improve the wear resistance and durability of the sensitive body by successively laminating a charge transfer layer, a charge generating layer and a protective layer on a conductive substrate and incorporating a thermosetting silicone resin, a urethane elastomer and further a hydrophobic silica into the protective layer. CONSTITUTION:The charge transfer layer, charge generating layer and protective layer are successively laminated on the conductive substrate, and the thermosetting silicone resin, urethane elastomer and further hydrophobic silica are incorporated into the protective layer to obtain a high-hardness coating film excellent in light transmission which improves the wear resistance of the sensitive body. In addition, the moisture permeating characteristic of the silicone resin is prevented, the resistance of the protective layer is stabilized under high-temp. and high-humidity conditions, and picture blurring is improved. Consequently, a laminated electrophotographic sensitive body having sensitivity when positively charged, stable to environmental temp. and humidity, without picture flowing under high-temp. and high-humidity conditions and excellent in wear resistance and durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor containing an organic photoconductive substance, and particularly relates to a laminated electrophotographic photoreceptor used for positive charging. Conventional technology Photoreceptors made of inorganic photoconductive materials such as selenium, selenium-tellurium, cadmium sulfide, and zinc oxide have been widely used as laminated electrophotographic photoreceptors. Although research into organic photoconductive materials with characteristics such as the ability to select compounds that exhibit photoconductivity in a wavelength range is progressing, it is difficult to form a layered electrophotographic photoreceptor using an organic photoconductive material in the photosensitive layer. It has advantages such as being easy to use, highly flexible, and has a large degree of freedom in design.It is inexpensive and non-polluting. Therefore, in order to improve these problems, a laminated electrophotographic photoreceptor was proposed in which the photosensitive layer was formed by separating the functions of a charge generation layer and a charge transport layer.This laminated electrophotographic photoreceptor was put into practical use. The charge transport agents commonly used in the industry are electron-donating substances such as pyrazoline, hydrazone, and oxazole.The charge transport layer is of the hole transport type, so if the charge transport layer is laminated on the charge generation layer, it can be used with a negative charge. These electrophotographic photoreceptors are commonly used for charging, exposure,
Strength that is repeatedly used in the processes of development, transfer, cleaning, and static elimination In this series of processes, positive charging is more stable in corona discharge than negative charging, and the amount of ozone generated is small, resulting in less ozone oxidation. Inorganic photoreceptors such as selenium and selenium-tellurium alloys that have been used in the past are used with positive charging, but organic photoreceptors that can be used with positive charging have little deterioration of characteristics (~). There is a strong demand for photoreceptors (in order to achieve positive charging with a structure in which a charge transport layer is laminated on a normal charge generation layer), an electron-accepting substance such as trinitrofluorenone may be used as a charge transport agent. (b) These electron-accepting substances are not generally available because they have a high mobility, and they are chemically unstable and have carcinogenic and other harmful effects (l Therefore, they are not commonly used). In order to enable positive charging using a donor substance, a structure in which a charge transport layer and a charge generation layer are laminated in this order on a conductive support is proposed. In this case, charge transport from the charge generation layer Charge transport layer/charge generation A proposal is made for a three-layer structure with a protective layer of a thin resin film on top of this layer, or a four-layer structure consisting of a charge transport layer, a charge generation layer, a charge injection blocking layer, and a surface protection layer.Also, a charge transport layer and a charge generation layer. In the two-layer structure, proposals have been made to increase the resin ratio in the charge generation layer to make the film thicker to about 5 μm to improve mechanical strength, and to maintain sensitivity by adding a charge transport agent to the charge generation layer. For example, The 3rd International Combination of Advances in Non-Impact Printing
Congress on Advances in
Non-Impact Printing Tech
Proceedings) pH5, Electrophotography Society No. 59
In general, polyester resin polyvinyl butyral is used as a protective layer for photoreceptors in resin thin films, as reported in the Proceedings of the Annual Research Conference p184. M clothing phenolic resin Cellulose acetate Styrene maleic anhydride copolymer Polyamide resin 1g polyimide resin Melamine resin etc. (e.g.
Special Publication No. 38-15446 Special Publication No. 51-1574
Publication No. 8 Special Publication No. 52-24414 Special Publication No. 1983
-34860 Publication Special Publication No. 56-53756
Special Publication No. 60-55357 Publication No. 61-2234
No. 5, etc.) is proposed, but it is not sufficient in terms of durability and environmental stability, such as wear resistance, scratches due to repeated use, and image blur due to moisture absorption and permeation, especially under high temperature and high humidity conditions. Or, there may be problems with image blurring.Also, these protective layers of thin resin films do not have sufficient durability, and -X. However, there is a method of using a protective layer in which a metal oxide is dispersed in a binder resin as a protective layer (for example,
39846, Japanese Patent Publication No. 58-121044, Japanese Patent Publication No. 59-223445, etc.) have also been proposed (
The metal oxide in the binder resin is insoluble in the binder resin and solvent, and its shape is like a lump, so even if the content in the protective layer is constant, the resistance value varies depending on the state of dispersion. The problem that the invention aims to solve is that it becomes unstable, and if the blending ratio, particle size, etc. are not finely controlled, it can cause environmental or repeated fluctuations in chargeability and residual potential. There are not many products that have satisfactory characteristics in terms of sensitivity and durability, but they are stable in the usage environment such as temperature and humidity, and have high durability against scratches and abrasion.
Furthermore, although it is desired to develop a laminated electrophotographic photoreceptor that can be used with positive charging and has a longer lifespan that satisfies the characteristics required of a laminated electrophotographic photoreceptor, the present invention (in view of the above-mentioned problems) has been proposed. Sensitive to static electricity
We have created a laminated electrophotographic photoreceptor that is stable against temperature and humidity, does not cause image blurring especially under high temperature and high humidity conditions, has high hardness and film strength even with a thin protective layer, and has excellent abrasion resistance and durability. Means for Solving the Four Problems The present invention (1) A charge transport layer, a charge generation layer, and a protective layer are laminated in this order on a conductive support, and the protective layer is thermosetting. The laminated electrophotographic photoreceptor of the present invention contains a silicone resin, a urethane elastomer, and further hydrophobic silica. By stacking the layers in this order, it is positively charged and has sensitivity.

In addition, the laminated electrophotographic photoreceptor of the present invention uses a thermosetting silicone resin as a protective layer to obtain a coating film with high hardness and excellent light transmittance and weather resistance. The elastomer-containing material not only improves abrasion resistance but also prevents the inherent moisture permeability of silicone resin, stabilizes the resistance of the protective layer under high temperature and high humidity, and improves image fading. By containing the urethane elastomer, it is possible to prevent cracks caused by curing shrinkage of the silicone resin during film formation and to improve adhesion with the lower layer. With curable silicone resin and urethane elastomer
Furthermore, by including hydrophobic silica, the hardness of the photoconductor surface is improved and the surface friction coefficient is reduced, increasing the durability and toner filming resistance of the photoconductor, and significantly improving the actual service life. The silica contained at the same time must be hydrophobic, and hydrophobic treatment prevents the adsorption of ions such as moisture and ozone products and improves image blurring under high temperature and high humidity conditions. Examples The laminated electrophotographic photoreceptor of the present invention will be described in detail below. is a hydrolyzate of an alkoxysilane and has a bifunctional or trifunctional silanol group, and examples of the alkyl group include methyl and phenyl groups. !The monomer is preferably one that is soluble in alcoholic solvents, so that it can be applied without corroding the underlying layer, and after the coating is formed, it can be condensed and hardened by heat treatment, resulting in a highly hard and highly durable film. Similarly, the reason why the urethane elastomer contained in the protective layer does not corrode the lower layer is desirably one that is soluble in alcohol-based solvents. , n-hexane, ethyl acetate, etc., and then 1-propanono-L, which has a higher boiling point than these solvents.
/, 2-propano to 1-butano-/k 2-butano-k 2-methylpropano-/k 1-pentano-
Hydrophobic silica (Y-
Highly purified silica with an average particle size of 5 to 50 nm is treated with an organosilicon compound such as organosilane or silicone oil, and preferably has a water absorption rate of 1% or less at a relative humidity of at least 80%. For example, silica may be reacted with dimethyldichlorosilane to replace the silanol groups on the silica surface with dimethylsilyl groups, or trimethylsilyl groups may be used. Protective layer ζ A coating solution containing a thermosetting silicone resin and a urethane elastomer dissolved in a solvent that dissolves both and further dispersing hydrophobic silica is applied onto the photosensitive layer using a conventional coating method.
After drying and then curing and forming by heat treatment, the heat treatment temperature is 80°C to 200°C. Considering the heat resistance of the photosensitive layer, it is preferably about 80°C to 120°C.
The thickness of the protective layer is 0. Force length of 1 to 5 μm Electrophotographic properties, contact! Especially when considering wear resistance, 0. 2 to 2 μm is preferable. Also, the ratio method of thermosetting silicone resin and urethane elastomer in the protective layer is 2:8 in terms of solid content weight ratio after drying.
~8:2 is preferable; if the ratio of silicone resin is small, the surface hardness will be poor, and if the ratio of silicone resin is too high, environmental stability will deteriorate, and image blurring may occur at high temperature and high humidity. Hydrophobic silica dispersed in the protective layer (coating liquid stabilization method, coating film strength, film formability, etc.)
5 to 100 parts by weight of the total solid content of the protective layer
Weight starvation is preferably in the range of 10 to 50 parts by weight.The electron donating substance used in the charge transport layer of the multilayer electrophotographic photoreceptor of the present invention is 1. Alkyl group Alkoxy group
Amino compounds Compounds with electron-donating groups such as imide groups Polycyclic aromatic compounds such as anthracene, pyrene, and phenanthrene, or derivatives containing them Indo-&
Oxazo-) I < Oxacia Sheet K Carbachy/k Thiazo-) L < Heterocyclic compounds such as pyrazoline, imida sheet k Triazole, or derivatives containing them may be mentioned. These electron-donating substances and binder resin are mixed in a suitable solvent. When the electron-donating substance is a polymer compound, the charge transport layer may be formed by itself without mixing with a binder resin. ~ The thickness of the charge transport layer is from several μm to several tens of μm (preferably from 5 to 25 μm).

In addition, various pigments or dyes such as perylene-based pigments or dyes may be used as the charge-generating substance used in the charge-generating layer of the multilayer electrophotographic photoreceptor of the present invention. A coating solution prepared by adding and dispersing a pigment or dye and a suitable binder resin is applied by a normal coating method.Heating and drying L.Forcing to form a film with a thickness of several μm.Preferably a film with a thickness of 0.2 to 2 μm. It is best to form it thickly (~ Charge generation layer Binder resin method used for charge transport layer Adhesiveness to other layers Ceramic clay Clay for uniformity of coating film As needed for the purpose of fluidity adjustment during coating, etc.) Examples of solvents used include Gi polyester) polyvinyl chloride/k polyvinyl butyler/k polyvinyl acetate/k polycarbonate, acrylic resin, methacrylic resin, silicone resin, and copolymers of these resins. Charge generation layer Any material may be used as long as it dissolves the charge transport agent or binder resin. Specifically, halogenated hydrocarbons, halogenated aromatics, aromatics, ketones, esters, ethers, etc. can be used. The conductive support used in the laminated electrophotographic photoreceptor of the invention (Table 1) Any conventionally known conductive support may be used, such as metal plates and metal drums such as aluminum, aluminum alloy, sulfur oxide, indium oxide, etc. These include plates made of metal oxides, or various plastic films and papers made of metals, metal oxides, etc. attached by vacuum evaporation, sputtering, lamination, coating, etc. and treated to make them conductive.

Laminated electrophotographic photoreceptor of the present invention (same number as ordinary laminated electrophotographic photoreceptor) Casein, polyvinyl alcohol-k
An adhesive layer or barrier layer such as polyvinyl butylar/k polyamide can be provided. In this way, a photosensitive layer consisting of a charge transport charge generating layer and a protective layer are laminated on a conductive support. The laminated electrophotographic photoreceptor J of the present invention has a charge transport layer, a charge generation layer, and a protective layer laminated in this order on a conductive support and is positively charged and sensitive.Examples of the present invention will be specifically described below. The present invention is not limited to the combinations shown in the following examples (Example 1) ■, 1-bis(P-diethylaminophenyl)-4,4
- 1 part by weight of diphenyl-1,3-butadiene and 1 part of polycarbonate (manufactured by Bayer AG, trade name Macrophor N)
80 parts by weight were dissolved in 9 parts by weight of methylene chloride, and this coating liquid was applied onto an aluminum drum with an outer diameter of 60 mm.
Dry at ℃ for 1 hour to form a charge transport layer with a thickness of 25 μm. 5 parts by weight of ζ τ-type metal-free phthalocyanine (manufactured by Toyo Ink Manufacturing Co., Ltd.), 4 parts by weight of acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name: DIANAL HR664), and melamine resin (manufactured by Inu Nippon Ink Co., Ltd., trade name: Super Beckamine) L145-60) 1 part by weight and S-
This coating solution, which was dispersed in 115 parts by weight of butyl alcohol, was applied onto the charge transport layer by drying at 100°C for 1 hour to form a charge generation layer with a thickness of 0.15 μm.
Thermosetting silicone resin (manufactured by Toshiba Silicone Corporation)
7 parts by weight of urethane elastomer (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: OLESTAR NL2249E) are dissolved in 100 parts by weight of n-butyl alcohol.Additionally, 3 parts by weight of hydrophobic silica treated with trimethylsilyl group is added to the coating solution. A coating solution is prepared by dispersing by ultrasonic dispersion,
Heat treated at 120℃ for 1 hour and cured to a film thickness of 1μ
The properties of the thus obtained laminated electrophotographic photoreceptor on which the protective layer of m was formed were measured using a self-made property testing machine. Measure the potential vO after charging with probe A (3), and the potential VL after exposure with surface electrometer probe B (6).1. X,
The exposure light amount was 3μJ/cm" with 800nm light, and the cycle of charging, exposing, and removing static electricity was repeated 1000 times.
Similar measurements were carried out. A laminated electrophotographic photoreceptor drum prepared in the same manner was developed over its entire surface using a normal two-component magnetic brush development method, and then cleaned with a urethane rubber blade for 20 cycles.
Repeatedly 000 times, observing the state of scratches and abrasion on the surface, the laminated electrophotographic photoreceptor drum obtained in the same manner was installed in a commercially available laser beam printer, and was heated at room temperature and humidity.
After printing 4,000 sheets at a temperature of 25 mm, 50 RH%) and leaving them at high temperature and high humidity (33 tons, 85 RH%) for 18 hours, further printing was performed to evaluate the state of image bleeding.The evaluation results are shown in Table 1.

(Example 2) A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in Example 1 except that in the protective layer of Example 1, the ratio of thermosetting silicone resin and urethane elastomer was set to 5=5. Characteristics were measured in the same manner as in Example 1 and the results are shown in Table 1.

(Example 3) A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in Example 1 except that in the protective layer of Example 1, the ratio of thermosetting silicone resin and urethane elastomer was set to 3=7. The characteristics were measured in the same manner as in Example 1, and the results are shown in Table 1.

(Example 4) In the protective layer of Example 1, the amount of hydrophobic silica added was 5
A charge transport layer was prepared in the same manner as in Example 1 except that parts by weight were changed.
Charge generation layer A protective layer was formed and the characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1) As Comparative Example 1, a sample was prepared with only a thermosetting silicone resin as a protective layer, a charge transport layer and a charge generation layer were formed in the same manner as in Example 1, and the protective layer was made of thermosetting silicone resin. A protective layer was formed with the same composition as in Example 1, except that only silicone resin was used, and the characteristics were measured. Table 1 shows the results.

(Comparative Example 2) Similarly, as Comparative Example 2, a sample was prepared using only urethane elastomer as a protective layer, a charge transport layer and a charge generation layer were prepared in the same manner as in Example 1, and a protective layer was formed using only urethane elastomer. A protective layer was formed with the same composition as in Example 1, except for the above, and the characteristics were measured. The results are shown in Table 1.

(Comparative Example 3) Similarly, as Comparative Example 3, a sample was prepared using untreated silica in which the silica contained in the protective layer was not substituted with a trimethylsilyl group. A protective layer was formed with the same composition as in Example 1, except that the silica contained in the protective layer was untreated silica that was not substituted with trimethylsilyl groups, and the characteristics were measured. Shown in the table.

Effects of the Invention (5) Nails Detailed Description of the Laminated Electrophotographic Photoreceptor of the Present Invention Laminated electrophotographic photoreceptor Ji of the present invention A charge transport layer, a charge generation layer, and a protective layer are laminated in this order on a conductive support. Because the protective layer contains thermosetting silicone resin, urethane elastomer, and hydrophobic silica, it is positively charged and sensitive, and is stable against environmental conditions of temperature and humidity, especially under high temperature and high humidity conditions. This is a laminated electrophotographic photoreceptor with no image blurring at the bottom and excellent wear resistance and durability.

[Brief explanation of drawings]

Fig. 1: Schematic diagram of a self-made characteristic testing machine for measuring the characteristics of photoreceptor drums Fig. 2 is a characteristic comparison diagram between the performance of the embodiment of the present invention and the performance of a comparative example.・To photoconductor drive 2...corona charger 3...
Electrometer probe A, 4.7... Tungsten lamp, 5... Interference filter (800 nm), 6...
Electrometer probe & 8... Colored glass filter (UV cut).

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor formed by laminating a photosensitive layer and a protective layer for the photosensitive layer on a conductive support,
A laminated electrophotographic photoreceptor, wherein the protective layer contains a thermosetting silicone resin, a urethane elastomer, and further hydrophobic silica. (2) The laminated electrophotographic photoreceptor according to claim (1), wherein the photosensitive layer is formed by laminating a charge transport layer and a charge generation layer in this order on a conductive support.