JP2507190B2 - Electrophotographic photoreceptor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member containing an organic photoconductive substance, and more particularly to a laminated electrophotographic photosensitive member used for positive charging.

[0002]

2. Description of the Related Art Conventionally, as electrophotographic photoconductors, photoconductors made of inorganic photoconductive substances such as selenium, selenium-tellurium alloy, cadmium sulfide and zinc oxide have been widely used, but in recent years, they are easy to synthesize. Research on organic photoconductive substances having characteristics such as selection of a compound exhibiting photoconductivity in an appropriate wavelength range is under way.

An electrophotographic photosensitive member using an organic photoconductive substance as a photosensitive layer has advantages such as easy film formation, high flexibility and a great degree of freedom in designing, inexpensive and non-polluting. However, the sensitivity and the photoreceptor life were inferior as compared with the inorganic photoconductive substance. Therefore, in order to improve them, a multi-layer type electrophotographic photoreceptor in which a charge generating layer and a charge transport layer are separated in function to form a photosensitive layer has been proposed and put into practical use. The charge-transporting agent generally used in this laminated type electrophotographic photoreceptor is an electron-donating substance such as pyrazoline, hydrazone, or oxazole, and therefore the charge-transporting layer is of the hole-transporting type, and therefore the charge-transporting layer is formed on the charge-generating layer. When is laminated, it is used with negative charging.

On the other hand, these electrophotographic photoconductors are usually repeatedly subjected to the processes of charging, exposing, developing, transferring, cleaning and neutralizing. In this series of processes, positive charging is more positive than negative charging. Corona discharge is stable, the amount of ozone generated is small, and the characteristic deterioration due to ozone oxidation is small. Further, since the conventionally used inorganic photoconductors such as selenium and selenium-tellurium alloy are used with positive charge, there is a strong demand for an organic photoconductor that can be used with positive charge because the electrophotographic process can be shared.

Here, in order to obtain positive charge in a structure in which a charge transport layer is laminated on an ordinary charge generation layer, an electron accepting substance such as trinitrofluorenone may be used as a charge transport agent. Receptive substances with a high mobility have not been obtained, and they are not generally used because they are chemically unstable and are harmful such as carcinogenicity. Therefore, in order to enable positive charging by using an electron-donating substance, a structure in which a charge transport layer and a charge generating layer are laminated in this order on a conductive support has been proposed. There are drawbacks such that the carrier injection into the charge transport layer is large and the chargeability is lowered, and generally the charge generation layer is a thin layer, so the mechanical strength is low and the durability is poor.

Therefore, there is proposed a three-layer structure in which a protective layer of a resin thin film is further provided on the charge transport layer / charge generation layer, or four layers of the charge transport layer / charge generation layer / charge injection blocking layer / surface protection layer. Proposal of structure, charge transport layer / charge generation layer 2
In the layer structure, the resin ratio of the charge generation layer is increased to 5 μm.
There have been proposals for increasing the mechanical strength by increasing the film thickness to the maximum, and further adding a charge transport agent to the charge generation layer to maintain sensitivity. (For example, The 3rd International Congress on Advanced in Non-Impact Printing Technology: The 3rd Intern
ational Congress on Advances in Non-Impact Printin
gTechnology Proceedings p115, The Electrophotographic Society 59th Research Symposium Proceedings p184, etc.) In general, as a protective layer for photoreceptors, polyester resin, polyvinyl butyral resin, phenol resin, cellulose acetate, styrene maleic anhydride Polymers, polyamide resins, polyimide resins, melamine resins, etc. (for example, Japanese Patent Publication No. 38-15
Japanese Patent Publication No. 446, Japanese Patent Publication No. 51-15748, Japanese Patent Publication No. 52-24414, Japanese Patent Publication No. 56-34860, Japanese Patent Publication No. 56-53756, and Japanese Patent Publication No. 60-55.
No. 357 and Japanese Patent Publication No. 61-22345, etc.) have been proposed, but they are not sufficient in terms of durability such as scratches and abrasion resistance due to repeated use, environmental stability, etc., especially after repeated use. There is a problem of image deletion or image blurring due to a decrease in surface resistance under high temperature and high humidity due to surface deposits such as paper dust.

Further, in the protective layer of these resin thin films, the durability is not sufficient with the thin film, while on the other hand, the thicker the film, the higher the residual potential and the poorer the repetitive characteristics are.

Therefore, a method using a protective layer in which a metal oxide is dispersed in a binder resin as the protective layer (for example,
Japanese Patent Publication No. 57-39846, Japanese Patent Publication No. 58-1210
No. 44, Japanese Patent Publication No. 59-223445, etc.), but the metal oxide in the binder resin is insoluble in the binder resin and the solvent, and its shape is lumpy, so that Even if the content is constant, the resistance value fluctuates depending on the dispersion state, the characteristics become unstable, and if the mixing ratio, particle size, etc. are not controlled finely, environmental change of charging property or residual potential or It has the drawback of causing repeated fluctuations.

[0009]

Therefore, in any case, very few products having satisfactory characteristics in terms of sensitivity and durability have been obtained, and have high durability against scratches and abrasion during repeated use. In addition, the surface resistance is not significantly reduced by surface deposits such as paper dust, it is stable in the environment of use such as temperature and humidity, and it can be used with positive charge and satisfies the characteristics required for electrophotographic photoreceptors. It is desired to develop an electrophotographic photoreceptor having a longer life.

[0010]

In view of the above problems, the present invention is formed by laminating a charge transport layer, a charge generation layer and a protective layer in this order on a conductive support, and the protective layer is thermosetting. Provided is an electrophotographic photoreceptor which comprises a silicone resin, a urethane elastomer, a hydrophobic silica and a silicone-based graft polymer, and is formed by laminating a charge transport layer and a charge generating layer in this order on a conductive support. It is a thing.

[0011]

The electrophotographic photoreceptor of the present invention has positive charge sensitivity by laminating a charge transport layer, a charge generation layer and a protective layer in this order on a conductive support.

In the electrophotographic photosensitive member of the present invention, by using a thermosetting silicone resin as the protective layer, a coating film having high hardness and excellent light transmission and weather resistance can be obtained. Further, the thermosetting silicone resin can be obtained. At the same time, by containing urethane elastomer, while improving wear resistance,
The original moisture permeability of the silicone resin is prevented, the resistance of the protective layer under high temperature and high humidity is stabilized, and image deletion can be improved.

Further, by containing the urethane elastomer, it is possible to prevent cracks due to curing shrinkage of the silicone resin at the time of film formation and to improve the adhesiveness to the lower layer.

The electrophotographic photosensitive member of the present invention comprises a protective layer,
By including hydrophobic silica in addition to the thermosetting silicone resin / urethane elastomer, the hardness of the surface of the photoconductor is improved and the friction coefficient of the surface is reduced, increasing the durability of the photoconductor and the toner filming resistance. The service life can be remarkably improved.

It is necessary that the silica contained at the same time be hydrophobic, and the hydrophobic treatment prevents the adsorption of ions such as water and ozone products, and improves the image flow under high temperature and high humidity. Is something that can be done.

The electrophotographic photoreceptor of the present invention further contains a silicone-based graft polymer in the protective layer to improve the water repellency of the surface of the photoreceptor and to reduce the friction coefficient of the surface, thereby adhering to the surface deposits. The adhesive strength to the protective layer is reduced, image deletion due to a decrease in surface resistance due to deposits such as paper dust during repeated use is prevented, and the actual service life can be significantly improved.

[0017]

EXAMPLES The electrophotographic photoreceptor of the present invention will be described in detail below.

The thermosetting silicone resin used in the protective layer of the electrophotographic photosensitive member of the present invention is obtained by thermosetting an alkoxysilane hydrolyzate, and the hydrolyzate is trifunctional or tetrafunctional. Any functional group having a silanol group may be used, and examples of the alkyl group include a methyl group.

These thermosetting silicone resins are preferably those which are soluble in alcoholic solvents as a hydrolyzate of alkoxysilane, and can be applied without eroding the lower layer, and after application formation, they are condensed by heat treatment. It hardens to obtain a film with high hardness and high durability.

Similarly, the urethane elastomer contained in the protective layer is preferably soluble in an alcohol solvent because it does not corrode the lower layer.

The alcohol-soluble urethane elastomer is
After condensation of isocyanate and an excess of polyol in excess of the equivalent amount in a solvent such as acetone having a low boiling point, n-hexane, and ethyl acetate, 1-propanol, 2-propanol, 1-butanol having a higher boiling point than these solvents are used. It can be obtained by substituting with an alcohol solvent containing at least one selected from 2-butanol, 2-methylpropanol, 1-pentanol, 2-pentanol, diacetone alcohol and the like.

At the same time, the hydrophobic silica contained in the protective layer is high-purity silica having a primary particle diameter of 5 to 50 nm and treated with an organosilicon compound such as organosilane or silicone oil. At least 80 relative humidity
It is preferable that the water absorption rate in% is 1% or less. For example, there may be mentioned those obtained by reacting silica with dimethyldichlorosilane to substitute silanol groups on the surface of silica with dimethylsilyl groups, and those substituted with trimethylsilyl groups.

At the same time, the silicone-based graft polymer contained in the protective layer has a silicone functional group in the side chain of the anchor polymer such as acryl having an average molecular weight of several tens to several hundreds, and at least the total solid content of the protective layer. It is preferable to add 10 parts by weight or less to 100 parts by weight so as to give water repellency such that the contact angle of the protective layer with respect to pure water becomes 90 ° or more.

In the protective layer of the electrophotographic photosensitive member of the present invention, the hydrolyzate of alkoxysilane and the urethane elastomer are dissolved in a solvent which dissolves both of them, hydrophobic silica is dispersed, and a silicone-based graft polymer is further added. The dissolved coating liquid is applied onto the photosensitive layer by a normal coating method,
It is dried and then cured by heat treatment to form. The heat treatment temperature is 80 ° C to 200 ° C, preferably 80 ° C to 120 ° C considering the heat resistance of the photosensitive layer. The thickness of the protective layer is 0.1 to 5 μm, but in consideration of electrophotographic characteristics, adhesiveness and abrasion resistance, it is particularly 0.2 to
2 μm is preferable.

The ratio of the thermosetting silicone resin to the urethane elastomer in the protective layer is preferably from 2: 8 to 8: 2 in terms of solid content weight ratio after drying, and when the ratio of the silicone resin becomes small, the surface hardness becomes small. In addition, if the ratio of the silicone resin is too large, the silicone resin may shrink due to curing during film formation, resulting in cracks or poor adhesion to the lower layer.

Further, the hydrophobic silica dispersed in the protective layer is, from the viewpoint of stability of coating liquid, coating strength, film forming property, etc.
The amount added is in the range of 1 to 100 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the total solid content of the protective layer.

The amount of the silicone-based graft polymer dissolved in the protective layer is 0.1 to 20 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the total solid content of the protective layer. It is a range of parts.

Examples of the electron-donating substance used in the charge-transporting layer of the electrophotographic photosensitive member of the present invention include compounds having an electron-donating group such as an alkyl group, an alkoxy group, an amino group and an imide group, anthracene, pyrene and phenanthrene. Polycyclic aromatic compounds or derivatives containing them, indole, oxazole, oxadiazole, carbazole,
Examples thereof include heterocyclic compounds such as thiazole, pyrazoline, imidazole and triazole, and derivatives containing them. The electron-donating substance and the binder resin are dissolved in an appropriate solvent and applied and dried by a normal coating method to form a charge transport layer.If the electron-donating substance is a polymer compound, the binder resin is mixed. Instead, the charge transport layer may be formed alone. The thickness of the charge transport layer is several μm to several tens μm, preferably 5 to 25 μm.

The charge generating material used in the charge generating layer of the electrophotographic photosensitive member of the present invention is a phthalocyanine-based material.
Azo series, square lilium series, cyanine series, quinone series,
Examples include various pigments or dyes such as perylene type.
The charge generation layer is formed by coating a coating solution prepared by adding and dispersing these pigments or dyes and a suitable binder resin by a conventional coating method, heating and drying, and forming a film having a thickness of several μm. Is preferably formed in a film thickness of 0.2 to 2 μm.

The binder resin used in the charge generation layer and the charge transport layer is used, if necessary, for the purpose of improving the adhesiveness with other layers, improving the uniformity of the coating film, adjusting the fluidity during coating, and the like. , Specifically, polyester, polyvinyl chloride,
Examples thereof include polyvinyl butyral, polyvinyl acetate, polycarbonate, acrylic resin, methacrylic resin, silicone resin, and copolymers of these resins.
The solvent may be any solvent that can dissolve the charge generating agent, the charge transporting agent, or the binder resin, and specifically includes halogenated hydrocarbons, halogenated aromatics, aromatics, ketones, and esters. , Ethers and the like can be used.

The electroconductive support used in the electrophotographic photosensitive member of the present invention may be any one having a conventionally known electroconductivity, such as a metal plate and a metal drum of aluminum or aluminum alloy, tin oxide, Plates made of metal oxides such as indium oxide, or those metals and metal oxides are vacuum deposited, sputtered, laminated,
These are various plastic films and papers that have been made conductive by applying them by coating.

Further, the electrophotographic photoreceptor of the present invention is similar to a normal electrophotographic photoreceptor in that an adhesive layer of casein, polyvinyl alcohol, polyvinyl butyral, polyamide or the like is formed between the conductive support and the charge transport layer or A barrier layer can be provided.

In this way, the electrophotographic photoreceptor of the present invention formed by laminating the photosensitive layer composed of the charge transport layer and the charge generating layer and the protective layer on the conductive support is provided on the conductive support. A charge transport layer, a charge generation layer, and a protective layer are laminated in this order and are positively charged and sensitive.

Examples of the present invention will be specifically described below, but the present invention is not limited to the combinations shown in the following examples.

An electrophotographic photosensitive member according to an embodiment of the present invention will be described below. 1,1-bis (P-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene
1 part by weight and 1 part by weight of polycarbonate (trade name: Macrohole N manufactured by Bayer Co., Ltd.) are dissolved in 9 parts by weight of methylene chloride, and this coating solution is dip-coated on an aluminum drum having an outer diameter of 25 mm, and then at 80 ° C. for 1 After drying for an hour, a charge transport layer having a film thickness of 20 μm was formed.

Next, 5 parts by weight of τ type metal-free phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd.) and acrylic resin (product name DIANAL HR664 manufactured by Mitsubishi Rayon Co., Ltd.) 4
Parts by weight and melamine resin (manufactured by Dainippon Ink Co., Ltd.
1 part by weight of Super Beckamine L145-60) (trade name) was dispersed in 115 parts by weight of s-butyl alcohol. This coating solution is dip-coated on the charge transport layer, and the coating solution is applied at 130 ° C for 1 hour.
After drying for an hour, a charge generation layer having a thickness of 0.2 μm was formed.

Further, 70 parts by weight of a thermosetting silicone resin (manufactured by Toshiba Silicone Co., Ltd.) and a urethane elastomer (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name Orestar NL22).
49E) 30 parts by weight of n-butyl alcohol 1000
To the coating solution dissolved in 1 part by weight, 30 parts by weight of hydrophobic silica treated with a trimethylsilyl group was added and dispersed by ultrasonic dispersion, and further 5 parts by weight of a silicone-based graft polymer (GS-30 manufactured by Toagosei Co., Ltd.). A coating liquid was prepared by adding. This coating solution is dip-coated on the charge generation layer and heat-treated at 110 ° C. for 1 hour to be cured to a film thickness of 1
A protective layer having a thickness of μm was formed.

The electrophotographic photosensitive member thus obtained was mounted on a self-made image testing machine, and high temperature and high humidity (35 ° C., 85 R
H%) 1000, 2000, 3000, 400
The state of image deletion when 0 or 5000 sheets were printed was evaluated. FIG. 1 is a configuration diagram of an image tester for an electrophotographic photosensitive member according to an embodiment of the present invention.

In FIG. 1, 1 is a main charging unit, 2 is a laser exposure unit for writing an electrostatic latent image, 3 is a non-magnetic one-component DC flying developing unit, 4 is a paper and paper conveying unit, 5 is a transfer unit, and 6 is The fixing unit 7 is a toner cleaning unit using a urethane blade.

The evaluation results are shown in (Table 1).

[0041]

[Table 1]

As described above, according to this embodiment, the electrophotographic photosensitive member is formed by laminating the charge transport layer, the charge generating layer and the protective layer in this order on the conductive support, and the thermosetting resin is used as the protective layer. By containing a silicone resin, urethane elastomer, hydrophobic silica, and further a silicone-based graft polymer, it has sensitivity to positive charge, is stable to temperature and humidity, and is especially a surface deposit such as paper powder after repeated use. by,
There is no image deletion due to the decrease in surface resistance under high temperature and high humidity,
Further, the present invention provides an electrophotographic photosensitive member having high hardness and film strength even when the protective layer is a thin layer, and having excellent abrasion resistance and durability.

The second embodiment of the present invention will be described below. In the protective layer of the first example, the coating liquid was prepared by adding 2 parts by weight instead of 5 parts by weight of a silicone-based graft polymer (GS-30 manufactured by Toagosei Kagaku Co., Ltd.) to prepare a coating liquid. A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in the example, and image evaluation was performed in the same manner as in the first example.

The evaluation results are shown in (Table 1). The third embodiment of the present invention will be described below.

In the protective layer of the first embodiment, a silicone-based graft polymer (GS manufactured by Toagosei Kagaku Co., Ltd.) is used.
-30) A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in Example 1 except that 1 part by weight was added instead of 5 parts by weight to prepare a coating liquid. Image evaluation was carried out in the same manner as in the example.

The evaluation results are shown in (Table 1). The fourth embodiment of the present invention will be described below.

In the protective layer of the first embodiment, 70 parts by weight of thermosetting silicone resin (manufactured by Toshiba Silicone Co., Ltd.) and urethane elastomer (manufactured by Mitsui Toatsu Chemicals, Inc.)
The charge transport layer, the charge generation layer, and the charge generation layer are the same as those in the first embodiment except that the thermosetting silicone resin 50 parts by weight and the urethane elastomer 50 parts by weight are used in place of the product name Olester NL2249E) 30 parts by weight. A protective layer was formed, and image evaluation was carried out in the same manner as in Example 1.

The evaluation results are shown in (Table 1). In addition, as a comparative example of the present invention, a sample was prepared by using only a thermosetting silicone resin, a urethane elastomer and hydrophobic silica as a protective layer.

In the first embodiment, the charge transport layer, the charge generating layer and the protective layer are the same as in the first embodiment except that the protective layer is made of only thermosetting silicone resin, urethane elastomer and hydrophobic silica. Was formed, and image evaluation was performed in the same manner as in the first example.

The evaluation results are shown in (Table 1).

[0051]

As described above, according to the present invention, the electrophotographic photosensitive member is formed by laminating the charge transport layer, the charge generating layer and the protective layer in this order on the conductive support, and the protective layer is thermosetting. By containing a silicone resin, urethane elastomer, hydrophobic silica, and further a silicone-based graft polymer, it has sensitivity to positive charge, is stable to temperature and humidity, and is especially a surface deposit such as paper dust after repeated use. As a result, there is no image deletion due to a decrease in surface resistance under high temperature and high humidity, and even if the protective layer is a thin layer, the hardness and film strength are high, and an electrophotographic photoreceptor having excellent wear resistance and durability can be obtained. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image tester for an electrophotographic photosensitive member according to a first embodiment of the present invention.

[Explanation of symbols]

 1 main charging section 2 laser exposure section for writing electrostatic latent image 3 non-magnetic one-component DC flying development section 4 paper and paper transport section 5 transfer section 6 fixing section 7 toner cleaning section with urethane blade

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinobu Murakami 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-2-151870 (JP, A) JP-A 64-- 79756 (JP, A) JP 60-57346 (JP, A) JP 61-95358 (JP, A) JP 54-44527 (JP, A) JP 62-75462 (JP, A) Japanese Patent Publication Sho 57-27453 (JP, B2)

Claims (2)

(57) [Claims] 1. An electrophotographic photosensitive member formed by laminating a photosensitive layer and a protective layer for the photosensitive layer on a conductive support, wherein the protective layer is a thermosetting silicone resin, a urethane elastomer and a hydrophobic silica. Further, an electrophotographic photoreceptor containing a silicone-based graft polymer. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is formed by laminating a charge transport layer and a charge generating layer in this order on a conductive support.