JP2532803B2 - Method for producing electrophotographic photoreceptor and surface protective layer thereof - 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 photoreceptor containing an organic photoconductive substance, and more particularly to an electrophotographic photoreceptor having a protective layer provided on an organic photosensitive layer.

[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 photoconductor in which a photosensitive layer is formed by separating the functions of a charge generation layer and a charge transport layer has been proposed, which has been put into practical use, but still has a sufficient life. Not obtained. In particular, recently, due to the improvement of the sensitivity of the organic photoconductor and the digitalization of the copying machine, the organic photoconductor is used also in the copying machine having a relatively high speed, and the demand for longer life is increasing more and more.

In order to meet the demand for such a long life, as a protective layer for a photoreceptor, polyester resin, polyvinyl butyral resin, phenol resin, cellulose acetate, styrene-maleic anhydride copolymer, polyamide resin, and Polyimide resin, melamine resin, etc. (for example, Japanese Patent Publication No. 38-15446, Japanese Patent Publication No. 51-15)
Japanese Patent Publication No. 748, Japanese Patent Publication No. 52-24414, Japanese Patent Publication No. 56-34860, Japanese Patent Publication No. 56-53756, Japanese Patent Publication No. 60-55357, and Japanese Patent Publication No. 61-22.
No. 345, etc.) has been proposed, but it is not sufficient in terms of scratches due to repeated use, durability such as abrasion resistance, environmental stability, and the like.

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

Therefore, a method of 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
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 the shape thereof is lumpy. Even if the value is constant, the resistance value fluctuates depending on the dispersion state, the characteristics become unstable, and unless the compounding ratio, particle size, etc. are finely controlled, environmental changes or repetitive fluctuations of the charging property and residual potential. It has the drawback of causing

On the other hand, in general, a method using a diamond-like thin film as a protective layer for the photosensitive layer (see, for example, JP-A-62-20).
However, in the case of an organic photoreceptor, there are problems such as deterioration of the organic photosensitive layer and cracks in the synthesized diamond-like thin film by a synthesis method such as a normal plasma CVD method. .

[0008]

Therefore, as described above, few satisfactory properties have been obtained in terms of sensitivity, durability, etc., and they are stable to the environment of use such as temperature and humidity.
In addition, there is a demand for the development of an electrophotographic photoreceptor having a longer life, which satisfies the characteristics required for the electrophotographic photoreceptor.

[0009]

In view of the above problems, the present invention is formed by laminating an organic photosensitive layer and its protective layer in this order on a conductive support, and the protective layer has a high hardness and a near red color. Due to the photoconductor, which is a diamond-like thin film that is transparent and highly resistant to external light, the increase in residual potential due to repetition is small,
The present invention provides an electrophotographic photosensitive member which is stable against temperature and humidity and which is particularly excellent in abrasion resistance and durability.

Further, in a vacuum chamber connected to an exhaust device,
The organic photosensitive layer formed on the conductive support and the ground electrode are opposed to each other, and a negative DC voltage is applied to the conductive support,
Further, a high frequency electrode is arranged between the conductive support and the ground electrode, and a gas serving as a material for the protective layer is sprayed as a supersonic molecular beam from the ground electrode side to the organic photosensitive layer through the high frequency electrode at regular time intervals. According to the method, a diamond-like thin film having high hardness, transparency to near-infrared light, and high resistance can be formed as a protective layer without degrading the organic photosensitive layer without defects such as cracks.

[0011]

The electrophotographic photosensitive member of the present invention has a usual post-charge photosensitivity by laminating the organic photosensitive layer and its protective layer in this order on the conductive support.

Further, the electrophotographic photosensitive member of the present invention can be remarkably improved in wear resistance and durability by using a diamond-like thin film having a high hardness, a transparent property against near infrared light and a high resistance as a protective layer. Is. Further, by forming the protective layer as a thin film, the electrostatic characteristics are relatively stable against temperature and humidity. In addition, the organic photosensitive layer is prevented from being continuously exposed to plasma by making the time interval of spraying the material gas as a supersonic molecular beam relatively long, and the temperature rise of the organic photosensitive layer is accompanied by water cooling of the conductive support. It is possible to suppress the deterioration of the organic photosensitive layer and to prevent the diamond-like thin film formed as the protective layer from cracking. In addition, by applying a negative voltage to the ground electrode facing the organic photosensitive layer to the conductive support, the material gas that is turned into plasma through the high-frequency electrode as a supersonic molecular beam and is sprayed has its positive ions. It accelerates and collides with the diamond thin film formed on the organic photosensitive layer to improve the hardness, transparency and resistivity of the diamond-like thin film formed as the protective layer. Here, supersonic molecular beam is the material gas.
Temperature of the gas due to adiabatic expansion when it is introduced into the vacuum chamber.
Of the material gas molecules due to the significant decrease in
The advance speeds are relatively uniform and there is little interference such as collisions with each other.
It is the flow of molecules in the absence. Generally such super sound
The fast molecular beam, when introducing the material gas into the vacuum device,
Use a nozzle that can obtain a sufficiently large pressure difference before and after that.
Can be obtained by Furthermore, the material gas is vacuumed.
A nozzle that can be opened and closed electrically
Then, the material gas is introduced into the vacuum device at regular time intervals.
This allows the pressure inside the vacuum device when the nozzle is closed.
Material gas molecules introduced by reducing the force and opening the nozzle
And the collision probability of the gas molecules remaining in the vacuum device
By making it small, in a wide range relatively far from the nozzle
It is possible to obtain supersonic molecular beams.

[0013]

EXAMPLES The method for producing the electrophotographic photosensitive member and the surface protective layer thereof according to the present invention will be described in detail below.

The conductive support used in the electrophotographic photosensitive member of the present invention may be any one having a conventionally known conductivity, such as a metal plate of aluminum or aluminum alloy, a metal drum, 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.

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.
Examples thereof include various pigments or dyes such as azo type, squarylium type, cyanine type and 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. It is preferable to form the film having a thickness of 0.2 to 2 μm. As the phthalocyanine-based pigment, ε-type, α-type, β-type copper phthalocyanine, other metal phthalocyanine, metal-free phthalocyanine and the like can be used.

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, and adjusting the fluidity during coating. , Specifically, polyester, polyvinyl chloride,
Polyvinyl butyral, polyvinyl acetate, polycarbonate, acrylic resin, methacrylic resin, silicone resin,
Alternatively, copolymers and mixtures of these resins may be mentioned. Further, as the solvent, in the case of the charge generation layer, a solvent that dissolves the binder resin and has good dispersibility of the charge generation substance is preferable, and in the case of the charge transport layer, a solvent that dissolves the charge transport agent and the binder resin may be used. More specifically, specifically, halogenated hydrocarbons, halogenated aromatics, aromatics, ketones, esters, ethers, alcohols and the like can be used.

In the electrophotographic photoreceptor of the present invention, a diamond-like thin film is formed as a protective layer on the thus-formed photosensitive layer composed of the charge generation layer and the charge transport layer. Hereinafter, a method for manufacturing the diamond-like thin film will be described with reference to a manufacturing apparatus illustrated in FIG. 1 as a conceptual system diagram.

An organic photosensitive drum 104 formed on a conductive support in a cylindrical ground electrode / vacuum chamber 101, an electromagnetic nozzle valve 106 for supplying a material gas, which faces the organic photosensitive drum 104, and a mesh shape for discharging and discharging the material gas. The electrode body 107 is arranged. The electromagnetic nozzle valve only needs to be capable of spraying the material gas as a supersonic molecular beam on the organic photoconductor for an arbitrary time by an electric signal, and a fuel jet nozzle of an automobile engine or the like is used. Further, the electrode body arranged between the electromagnetic nozzle valve and the organic photoconductor may be any one that can discharge-decompose the material gas ejected as a supersonic molecular beam.

The mesh electrode body 107 has a high frequency power source 1
08 is connected, and the DC power source 105 is connected to the organic photosensitive drum 104. The high-frequency power source connected to the mesh-shaped electrode may be any one capable of discharging and decomposing the material gas ejected as a supersonic molecular beam. Further, the DC power source connected to the organic photoconductor drum may be one that can apply a negative bias voltage to the organic photoconductor to accelerate and attract positive ions from the material gas that is discharged and decomposed into plasma. Good.

The material gas is supplied from the material gas supply device 109 through the material gas supply nozzle valve 106. The material gas supply device 109 includes a material gas cylinder 112, a material gas flow rate control device 111, and a material gas selection valve 110,
The material gas selection valve 110 to be used is opened, and the material gas flow rate adjusting device 111 adjusts the flow rate to supply the material gas. The material gas supply nozzle valve 106 is opened and closed at appropriate time intervals by a nozzle valve opening / closing device 113, and is rotated by a drum rotating device 114 by a synchronous circuit 115.
Synchronize with 4.

The type and flow rate of the material gas used are, for example, 500 sccm of methane CH ₄ , but oxygen O ₂ , carbon dioxide CO _2, etc. may be added. As the carbon supply gas, hydrocarbon gas such as methane, ethane, propane, and acetylene, and vapor of organic solvent such as methanol, ethanol, and acetone can be used, but hydrogen, argon, helium, and the like are also used together. May be.

The photosensitive drum 104 is a drum rotating device 11
4, using a suitable rotation speed, for example 0.2-120 rpm
Rotate with. The rotation of the material gas supply nozzle valve 106 and the photoconductor drum 104 are synchronized by a synchronizing circuit 115. The pressure inside the vacuum chamber 101 is 0.001 to 1T on average
The discharge of the high frequency power supply 108 is such that discharge decomposition occurs only in a portion where the material gas is supplied from the material gas supply nozzle and the pressure is locally increased, and discharge decomposition does not occur in other portions. You can set it to. The DC voltage for accelerating positive ions is in the range of -100 to -1000V, and is usually about -200 to -600V.

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. An aluminum drum was used as a conductive support, and a charge generation layer, a charge transport layer, and a protective layer were prepared as follows.

As the charge generation layer, 5 parts by weight of τ-type metal-free phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd.) and acrylic resin (trade name DIANAL H, manufactured by Mitsubishi Rayon Co., Ltd.)
R664) 4 parts by weight and melamine resin (trade name: Super Beckamine L145-6 manufactured by Dainippon Ink and Chemicals, Inc.)
0) 1 part by weight was dispersed in 115 parts by weight of s-butyl alcohol. This coating solution is applied onto an aluminum drum having an outer diameter of 30 mm by dip coating and dried at 130 ° C. for 1 hour to give a film thickness of 0.2 μm.
m charge generating layer was formed.

Next, as a charge transport layer, 1,1-bis (p
-Diethylaminophenyl) -4,4-diphenyl-
1 part by weight of 1,3-butadiene 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 the coating solution is dip-coated on the charge generation layer to 80 ° C. And dry for 1 hour, film thickness 20μm
Was formed on the charge transport layer.

The photosensitive drum comprising the charge generation layer and the charge transport layer thus obtained is used as a photosensitive drum 104 inside the cylindrical vacuum chamber 101 of the apparatus shown in the conceptual system diagram of FIG. After arranging and evacuating the cylindrical vacuum chamber 101 to 10 ⁻³ Torr, the nozzle valve opening / closing device 11
3, the material gas supply nozzle valve 106 was opened every 1 second for 1 msec to supply the material gas. As for the timing of supplying the material gas, the five nozzles were sequentially opened, and the time interval was set so as to complete one cycle in exactly 1 sec. The material gas to be used was selected by the material gas selection valve 110 in the material gas supply device 109, and the material gas flow rate control device 111 set the flow rate of the material gas. The type and flow rate of the material gas used is methane CH ₄ 200
sccm.

13.56 MHz as the high frequency power source 108
A 500 W power supply was used, and the DC power supply 105 was set so that the DC bias voltage was -500V. The exhaust speed adjusting valve 102 was set so that the pressure in the cylindrical vacuum chamber 101 was 0.01 Torr on average. Exhaust device 10
For 3, a rotary pump having a mechanical booster pump in the front stage was used. The exhaust speed is 1800 m ³ / hr.

The photosensitive drum 104 is a drum rotating device 11
4 was rotated at 75 rpm, and water-cooled from the inside of the conductive support before use.

Film deposition was carried out for 5 hours under the above synthesis conditions,
A surface protective layer having a thickness of about 0.1 μm was obtained. Got this way
Vickers hardness of the protective layer is 2000kg / mm²Higher hardness
The resistivity is 10^Ten High resistance of Ωcm or more, refraction
The ratio is about 2.2, and the optical band gap is about 1.6 eV.
Yes, the Raman scattering spectrum is mainly 1520 cm^-1
Broad scattering is observed only in the infrared absorption spectrum
2960 cm in Le ^-1Absorption coefficient α 1 and 3030
cm^-1The value of the ratio α1 / α2 of the absorption coefficient α2 at is about 3
there were. In addition, transmission electron diffraction TED and high-speed backscattered electrons
In line diffraction RHEED, with a halo ring pattern
And no significant signal was observed in X-ray diffraction XRD.
The film obtained from the fact that it did not have a specific crystal structure
Thought to be amorphous, sp³Mainly binding
It is considered to be a diamond-like thin film. Also this
The diamond-like thin film thus obtained has cracks and peeling.
It was a smooth film without any defects.

The characteristics of the electrophotographic photosensitive member thus obtained were measured by using a self-made characteristic tester. The test machine is shown in Figure 2.
With the configuration as shown in FIG. 5, the surface potential meter probe A203 measured the potential V0 after charging, and the surface potential meter probe B206 measured the potential VL after exposure. The surface electrometer is Trek
Model 344 manufactured by Japan Co., Ltd. was used, and the exposure light amount was 3 μJ / cm ² at 800 nm light. In addition, the same measurement was performed by repeating the cycle of charging, exposing and discharging 100 times. The characteristics of the electrophotographic photosensitive member thus obtained were little affected by temperature and humidity, and showed stable characteristics even after repeated up to 2,000,000 times. Also, there was almost no change compared to the characteristics of the photoconductor drum consisting of only the organic photosensitive layer without forming the diamond-like thin film protective layer, and it was confirmed that the organic photosensitive layer was not deteriorated by the formation of the diamond-like thin film protective layer. did it.

Further, the electrophotographic photosensitive drum obtained in the same manner is entirely developed by a usual two-component magnetic brush developing method, and then cleaned with a urethane rubber blade in two cycles.
After repeating 000000 times, the surface of the surface was smooth, no toner filming was observed, and scratches and abrasion were not observed.

Further, the electrophotographic photosensitive drum obtained in the same manner was mounted on a commercially available laser beam printer (Laser Shot A404 manufactured by Canon Inc.), and 20,000
Even after printing 0 sheets, no toner filming was observed on the surface, the surface was smooth, and scratches and abrasion were not observed, and a good image was obtained.

As described above, according to this embodiment, the electrophotographic photosensitive member is formed by laminating the charge generating layer, the charge transporting layer and the protective layer in this order on the conductive support, and the protective layer has a high hardness. The electrophotographic photosensitive member, which is a diamond-like thin film that is transparent to near-infrared light and has high resistance, has little increase in residual potential due to repetition, is stable against temperature and humidity, and is particularly excellent in abrasion resistance and durability. And an electrophotographic photosensitive member.

In a vacuum chamber connected to the exhaust device,
The organic photosensitive layer formed on the conductive support and the ground electrode are opposed to each other, and a negative DC voltage is applied to the conductive support,
Further, a high frequency electrode is arranged between the conductive support and the ground electrode, and a gas serving as a material for the protective layer is sprayed as a supersonic molecular beam from the ground electrode side to the organic photosensitive layer through the high frequency electrode at regular time intervals. According to the method, a diamond-like thin film having high hardness, transparency to near-infrared light, and high resistance can be formed as a protective layer without degrading the organic photosensitive layer without defects such as cracks.

As a comparative example of the present invention, a sample using a coating type surface protective layer made of a thermosetting silicone resin and a urethane elastomer was prepared below.

A charge transport layer and a charge generation layer were prepared in the same manner as in the example, a surface protective layer was formed on the charge generation layer, and the characteristics were measured.

The surface protective layer is made of a thermosetting silicone resin (trade name Tosgard 52 manufactured by Toshiba Silicone Co., Ltd.).
0) 7 parts by weight of urethane elastomer and 3 parts by weight of urethane elastomer (trade name OLESTER NL2249E manufactured by Mitsui Toatsu Chemicals, Inc.) were dissolved in 115 parts by weight of n-butyl alcohol, and this coating solution was immersed on the charge generation layer. Apply and apply at 120 ° C for 1
It was heat-treated for a period of time and cured to form a surface protective layer having a film thickness of 1 μm.

The characteristics of the electrophotographic photosensitive member thus obtained are greatly affected by temperature and humidity, and show relatively stable characteristics under high temperature and high humidity even after repeated use. After repeated exposure, the potential after exposure doubled or more, and by 100 times, the potential increased to four times or more of the initial potential.

Further, the electrophotographic photosensitive drum obtained in the same manner is subjected to full-surface development by a usual two-component magnetic brush developing method and then cleaned with a urethane rubber blade in two cycles.
After repeating 000000 times, the protective layer and the photosensitive layer were completely worn away.

Further, the electrophotographic photosensitive drum obtained in the same manner was mounted on a commercially available laser beam printer (Laser Shot A404 manufactured by Canon Inc.), and 20,000
After printing 0 sheets, the protective layer was worn.

[0043]

As described above, the electrophotographic photosensitive member of the present invention is formed by laminating the charge generation layer, the charge transport layer and the protective layer in this order on the conductive support, and the protective layer has a high hardness. The electrophotographic photosensitive member, which is a diamond-like thin film that is transparent to near-infrared light and has high resistance, has little increase in residual potential due to repetition, is stable against temperature and humidity, and is particularly excellent in abrasion resistance and durability. And an electrophotographic photosensitive member.

In a vacuum chamber connected to the exhaust device,
The organic photosensitive layer formed on the conductive support and the ground electrode are opposed to each other, and a negative DC voltage is applied to the conductive support,
Further, a high frequency electrode is arranged between the conductive support and the ground electrode, and a gas serving as a material for the protective layer is sprayed as a supersonic molecular beam from the ground electrode side to the organic photosensitive layer through the high frequency electrode at regular time intervals. According to the method, a diamond-like thin film having high hardness, transparency to near-infrared light, and high resistance can be formed as a protective layer without degrading the organic photosensitive layer without defects such as cracks.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of an example of a manufacturing apparatus used for carrying out the present invention.

FIG. 2 is a schematic diagram of a self-made characteristic tester for measuring characteristics of a photosensitive drum.

[Explanation of symbols]

 101 Cylindrical Ground Electrode Body and Vacuum Tank 102 Exhaust Speed Control Valve 103 Exhaust Device 104 Organic Photoreceptor Drum Formed on Conductive Support 105 DC Power Supply 106 Material Gas Supply Electromagnetic Valve 107 Mesh for Discharge Decomposition of Material Gas Electrode body 108 high frequency power supply 109 material gas supply device 110 material gas selection valve 111 material gas flow rate controller 112 material gas cylinder 113 nozzle valve opening / closing device 114 drum rotating device 115 synchronous circuit 116 vacuum pressure gauge 201 photoconductor drum 202 corona charger 203 Electrometer probe A 204, 207 Tungsten lamp 205 Interference filter (800 nm) 206 Electrometer probe B 208 Colored glass filter (UV cut)

Claims (1)

(57) [Claims] 1. A negative DC voltage is applied to the conductive support by causing an organic photosensitive layer formed on the conductive support and a ground electrode to face each other in a vacuum chamber connected to an exhaust device. A high frequency electrode is arranged between a conductive support and the ground electrode, and a gas serving as a material for the protective layer is sprayed as a supersonic molecular beam from the ground electrode side to the organic photosensitive layer through the high frequency electrode at regular time intervals. method for producing an electrophotographic photoreceptor protective layer, characterized in that.