JP2754854B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, particularly to an electrophotographic photoreceptor having a function-separable type photosensitive layer.

(Prior Art) Conventionally, as a photosensitive layer of an electrophotographic photoreceptor, a so-called function separation type in which a charge generation layer for generating charge carriers by light irradiation and a charge transport layer for efficiently moving the charge carriers are separated. In photoconductors, both organic and inorganic materials have been used as charge transport materials. Examples of the organic material include a material using a polymer compound such as polyvinyl carbazole or a material in which a low molecular compound such as pyrazoline or triphenylamine is dispersed or dissolved in a polymer binder resin such as polycarbonate. In addition, examples of the inorganic material include chalcogenide compounds such as selenium and selenium / tellurium.

(Problems to be Solved by the Invention) However, in an electrophotographic photoreceptor using these charge transport materials, electrical repetition characteristics such as chargeability, dark decay, and residual potential are unstable, or hardness or Due to lack of mechanical strength such as adhesiveness, it is easy to be scratched or peeled off in the copier, it is difficult to form a stable image for a long time, and its lifespan is several thousand to tens of thousands Limited to the number of copies. When a surface layer or an adhesive layer is provided in order to improve these defects, defects may occur during the production of an electrophotographic photoreceptor due to an increase in residual potential or a complicated configuration of the photoreceptor. There was a problem such as increasing the number.

In addition, the electrophotographic photoreceptor using an organic charge transport material has insufficient transportability, in particular, a problem such as poor potential decay in a low-temperature environment, and is not suitable for high-speed copying operations. There was a problem.

Further, in the electrophotographic photoreceptor using the conventional charge transport material, heat resistance and light resistance are not sufficient, and the charge transport material which is a low molecular compound is crystallized or decomposed. It was necessary to restrict the conditions or environment for use or storage.

In addition, the electrophotographic photoreceptor having a charge-transporting layer provided as a part of the photoconductive layer in a function-separated type configuration generally has a thin charge-generating layer, so that absorption of light near the absorption edge is reduced, Light passing through the charge generation layer increased, and as a result, particularly in a printer using an infrared laser, generation of interference fringes due to multiple reflection with light reflected from a substrate was inevitable.

The present invention has been made in view of the above-described problems in the related art.

Accordingly, an object of the present invention is to provide an electrophotographic photoreceptor having a novel charge transport layer. That is, an object of the present invention is to provide a highly durable electrophotographic photoreceptor having a charge transport layer having high adhesiveness, high mechanical strength and hardness and few defects.

It is another object of the present invention to provide an electrophotographic photoreceptor having high sensitivity, rich color, high chargeability, low dark decay, and low residual potential after exposure.

Still another object of the present invention is to provide a high-quality electrophotographic photoreceptor capable of preventing occurrence of interference fringes in a laser printer using coherent light such as an infrared semiconductor laser as a light source.

(Means and Actions for Solving the Problems) The present inventors have conducted intensive studies on the charge transporting material that achieves the above-mentioned object, and as a result, the metal powder or the conductive metal oxide powder was mainly contained in the organic polymer compound. Are found to efficiently transport the photocarriers generated in the charge generation layer to the substrate side and have an excellent charge transport function, and a functionally separated photoreceptor using this charge transport material. However, the present invention has been found to physically, chemically, mechanically, and optically far exceed the photoreceptor using the conventional charge transport material, and completed the present invention.

Conventionally, there has been an example in which a conductive fine powder dispersed in an organic polymer compound is used for a surface protective layer.Such a surface protective film is provided on the outermost surface of a photoreceptor, and the surface charge is exposed in the dark. It is necessary to reach the surface of the layer, reduce the charge accumulation in the protective layer, and reduce the residual potential of the photoconductor,
With such a configuration, unlike the charge transport layer, the potential decay in darkness is reduced, and sufficient charge cannot be maintained as a photoconductor. In the case of a surface protective layer, its thickness is determined in relation to the resistance. For example, if the resistance of the protective layer is high, the thickness must be reduced.

The electrophotographic photoreceptor of the present invention is characterized in that at least a support, a charge transport layer and a charge generation layer are sequentially laminated, and the charge transport layer is composed of only a metal powder and an organic polymer compound in which the metal powder is dispersed. And It is surprising that what has been conventionally used as a low-resistance surface protective layer functions as a charge transport layer.

In the electrophotographic photoreceptor of the present invention, the metal powder dispersed in the organic polymer compound of the charge transporting layer may be selected from the group IIa of the periodic table.
An element selected from a group element, a group IIb element, a group IIIa element and a transition element, or an alloy or a mixture of two or more of these elements is used. These metal powders are both polarities capable of flowing both positive and negative charges, and the charge transport layer using them is bipolar.

 Hereinafter, the present invention will be described in detail.

FIG. 1 shows an example of a basic layer structure of the electrophotographic photoreceptor of the present invention. A charge transport layer 2 and a charge generation layer 3 are laminated on a support 1. In FIG. 2, an intermediate layer 4 is provided on a support, and a protective layer 5 is provided on the surface.

In the present invention, any of a conductive support and an insulating support may be used as the support. Examples of the conductive support include aluminum, stainless steel, nickel, metals such as chromium and alloys thereof, and examples of the insulating support include polyester, polyethylene, polycarbonate, polystyrene, polyamide, and a polymer film or sheet such as polyimide; Glass, ceramic and the like can be mentioned. When an insulating support is used, it is necessary that at least a surface in contact with another layer has been subjected to a conductive treatment. The conductive treatment is, in addition to the above metals, gold, silver,
Copper or the like can be formed by vapor deposition, sputtering, or ion plating.

In the electrophotographic photoreceptor of the present invention, irradiation of electromagnetic waves may be performed from the side of the support or from the side opposite to the support. In the case where the treatment is performed from the support side, the thickness of the metal layer formed by the conductive treatment may be at least enough to transmit the applied electromagnetic wave. Further, a transparent conductive film such as ITO can be used.

In the electrophotographic photoreceptor of the present invention, a charge generation layer and a charge transport layer are formed on a support. When a charge generation layer and a charge transport layer are sequentially laminated on a substrate, it is necessary to further provide an insulating layer on the surface of the charge transport layer in order to effectively retain charges in the dark. However, in this case, since the charge transport layer is provided on the charge generation layer,
The charge transport layer must be sufficiently transparent to sufficiently transmit the electromagnetic wave (light) used for exposure and reach the underlying charge generation layer, and the dispersion material used for the charge transport layer;
It is necessary to consider the film thickness and the like. In the present invention, since the charge generation layer is on the top, there is no need to particularly consider the transparency,
This is advantageous in material selection, film thickness, and the like.

In the present invention, an intermediate layer may be provided between the support and the charge generation layer or the charge transport layer for the purpose of preventing charge injection and improving adhesion.

The intermediate layer can be formed by applying a solution of an organic polymer compound such as polyamide, polyimide, or polyester, or an alkoxy compound such as silicon, titanium, or zirconium, followed by drying. In addition, Si by plasma CVD
N _X, SiC _X, SiO _X film, SiO _X by a PVD method such as ion plating, AlO _X, addition can be used ZrO _X film,
When the substrate is Al, an aluminum oxide layer may be formed by performing anodization.

As described above, the charge transport layer is formed by dispersing a metal powder in an organic polymer compound. As the metal powder, an element selected from Group IIa elements, Group IIb elements, Group IIIa elements and transition metals of the periodic table is used.
Group IIa elements include Be, Mg, Ca, Sr, Ba, and Ra; Group IIb elements include Zn and Cd;
Examples of group a elements include Al, Ga, In, and Tl.Examples of transition elements are Sc to Cu, Y to Ag, Hf to Au, which are main transition elements, and La to Lu, which are internal transition elements. , Ac to Lr. Of these, Al, Z
n, In and a main transition element can be preferably used.

The particle size of these metal powders needs to be smaller than the thickness of the charge transport layer, and is particularly preferably 1/10 or less of the thickness of the charge transport layer, specifically from 50 ° to 5 μm.
m, preferably in the range of 0.01 μm to 1 μm. When the particle size is smaller than 50γ, the charge transport function is reduced, and when the particle size is 5 μm or more, the surface property of the film is reduced,
It causes poor cleaning and lower resolution.

Examples of the organic polymer compound include polyvinyl carbazole, acrylic resin, polycarbonate resin, polyester resin, vinyl chloride resin, fluorine resin, polyurethane resin, epoxy resin, unsaturated polyester resin, polyamide resin, and polyimide resin. Among them, a curable resin is preferable from the viewpoint of mechanical strength, adhesiveness, and moisture resistance.

In order to form the charge transport layer, the metal powder is dispersed in an organic solvent solution of the organic polymer compound or a liquid polymer compound, and the resulting dispersion is applied and dried.

The ratio between the metal powder and the organic polymer compound is arbitrarily determined depending on the particle size and specific resistance of the powder, the strength of the film, and the film thickness, but is generally preferably in the range of 2/98 to 40/60 by weight. . When the ratio of the metal powder is lower than 2% by weight, the charge transport function is insufficient, a high residual potential is exhibited, and the ratio is 40% by weight.
If it is higher than this, the chargeability is reduced and the function as a photoconductor cannot be achieved.

The thickness of the charge transport layer is 3 to 100 μm, preferably 5 to 50 μm.
It is set in the range of μm.

In the present invention, the charge transport layer can hold charges in the dark and, when charges are generated in the charge generation layer by irradiation with electromagnetic waves, quickly inject the charges to the substrate or the photosensitive layer. Charges can be transferred to the body surface. In the present invention, since the metal powder is dispersed and present in the charge transport layer, it is considered that a predetermined electrical path that is revealed only in the light is formed by the powder, and further, the charge transport layer and the charge generation layer The horizontal charge transfer occurs at the interface between the electrodes and no electric charge remains at the interface between the electrical paths.

In the present invention, the charge transport layer can transport both positive and negative charges, so that the photoreceptor can be used by positively charging or negatively charging.

Furthermore, since the chargeability of the function-separated type photoreceptor is determined by the charge transport layer having a large film thickness, the chargeability of the charge transport layer in the present invention needs to be in the range of about 15 V / μm to 100 V / μm. is there. Further, the ratio of the surface potential of the photoreceptor obtained based on the charge transport layer used in the present invention between dark and light irradiation shows at least 2 or more, which is a value which can be sufficiently applied to an electrophotographic process.

In the polymer matrix of the present invention, on the charge transporting layer formed by dispersing the metal powder, in order to effectively carry out charge retention in the dark, a film having high resistance at least in the dark is necessary, and the charge generating layer Is believed to perform this function. However, an insulating layer may be provided on the surface of the support, if necessary, in order to further enhance the charge holding ability.

As the charge generation layer, an inorganic material such as amorphous silicon, selenium, selenium arsenide, or selenium tellurium formed by a method such as CVD, vapor deposition, or sputtering can be used. Also, phthalocyanine, Cu phthalocyanine, Al phthalocyanine, V phthalocyanine, square phosphoric acid derivative,
A thin film obtained by dip coating or spray coating a dye or pigment such as merocyanine or bisazo dye, which is deposited or dispersed in a binder resin, can be used.

In the present invention, in order to make the charge generation layer an upper layer, Se, Se-Te
In the case of using a selenium-based charge generation layer such as an a-Si-based charge generation layer, compared with the case of using an organic charge generation material,
It is advantageous in terms of abrasion resistance and abrasion resistance.
The system charge generation layer has high hardness and is extremely advantageous as the outermost surface layer. Further, the a-Si based film can be effectively used as a surface layer from the above viewpoint.

Above all, when using amorphous silicon hydride, hydrogenated amorphous silicon to which germanium is added, and hydrogenated amorphous germanium, excellent mechanical and electrical properties are exhibited. In particular, silicon or germanium as a main component, 1 to 40
Those containing hydrogen at atomic%, especially 5 to 20 atomic%, are preferred.

Since the charge transport layer of the present invention has both polarities capable of transporting both positive and negative charges, the a-Si-based charge generation layer is optimal from the viewpoint of the charging polarity of the photoreceptor. This is because the a-Si film has a group V element of the periodic table in the film,
By adding a group III element, n-type, i-type, and p-type films can be easily formed, and when a positively charged photoreceptor is desired,
A p-type a-Si charge generation layer to which a group III element has been added may be used. If a negatively charged photoreceptor is desired, an n-type a-Si charge generation layer may be added by adding a group V element or as it is. If a bipolar photoreceptor is desired, a small amount of II
This is because the charge polarity of the photoreceptor can be easily controlled by adding a group I element to form an i-type a-Si charge generation layer.

Hereinafter, a case where hydrogenated amorphous silicon is used as the charge generation layer will be described as an example.

The charge generation layer containing amorphous silicon as a main component can be formed by a known method. For example, it can be formed by glow discharge decomposition, sputtering, ion plating, vacuum evaporation, or the like. These film forming methods are appropriately selected according to the purpose, but the plasma CV
The method of glow discharge decomposition of silane or a silane-based gas by the method D is preferable, and according to this method, 1 to 40
A film containing atomic% of hydrogen and having relatively high resistance and high photosensitivity is formed, and characteristics suitable as a charge generation layer can be obtained.

 Hereinafter, the plasma CVD method will be described as an example.

Examples of the raw material gas for forming the charge generation layer containing silicon as a main component include silanes such as silane and disilane. When forming the charge generation layer,
If necessary, a carrier gas such as hydrogen, helium, argon, or neon can be used. A dopant gas such as diborane (B ₂ H ₆ ) or phosphine (PH ₃ ) gas can be introduced into these source gases to add impurities such as boron or phosphorus into the film. Further, a halogen atom, a carbon atom, an oxygen atom, a nitrogen atom and the like may be contained for the purpose of increasing the light sensitivity. Furthermore, it is also possible to add elements such as germanium and tin for the purpose of increasing the sensitivity in the long wavelength region. The thickness of the charge generation layer is 0.1 to 30
μm, preferably in the range of 0.2 to 10 μm.

The electrophotographic photoreceptor of the present invention may be provided with a surface protective layer in order to prevent surface deterioration due to corona ions.
Plasma is used as a material for forming the surface protection layer.
Examples thereof include silicon oxide, silicon carbide, silicon nitride, amorphous carbon by the CVD method, alumina oxide by the ion plating method and the like, and a transparent organic polymer film in which an organic low molecular compound or conductive fine powder is dispersed.

(Example) Next, the present invention will be described with reference to examples.

Example 1 On a cylindrical aluminum pipe, 30 parts by weight of copper powder having an average particle diameter of about 0.5 μm or less, 70 parts by weight of polyurethane resin (Rethane 4000, manufactured by Kansai Paint Co.), 15 parts by weight of letan thinner (Kansai Paint Co., Ltd.) The mixture was mixed and dispersed for 20 hours using a ball mill, spray-coated with a solution containing 9 parts by weight of a urethane curing agent (manufactured by Kansai Paint Co., Ltd.), dried at 120 ° C. for 2 hours, and charged to a thickness of 15 μm. A transport layer was formed.

An electrophotographic photoreceptor was obtained by sequentially laminating a charge generation layer having the following composition and a surface protective layer thereon.

Charge generation layer (1 μm thickness) Square phosphoric acid derivative 30 parts by weight 70 parts by weight of polyester resin (Vylon-200, manufactured by Toyobo Co., Ltd.) Low-resistance surface protective layer (film thickness: 2 μm) 45 parts by weight of tin oxide powder 48 parts by weight of polyurethane resin (Rethane Clear, manufactured by Kansai Paint Co., Ltd.) 7 parts by weight The electrophotographic characteristics of the obtained electrophotographic photoreceptor were examined. When charged with a +6 KV corotron, the charged potential was maintained at 500 V. The residual potential after exposure to 550 nm light was 10V.

Example 2 An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generation layer was formed using crystalline selenium powder.

The charge generation layer was formed by dip coating a dispersion having the following composition.

70 parts by weight of crystalline selenium having a particle size of 0.05 to 0.5 μm 30 parts by weight of polyvinyl butyral (BM-1 manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight of butyl alcohol The electrophotographic characteristics of the obtained electrophotographic photoreceptor were measured. Charging potential of 460V when charged with a + 6KV corotron
Was held. The residual potential after exposure to 500 nm light was 10V. The light sensitivity was 6 erg / cm ² at half-exposure dose.

Example 3 20 parts by weight of Ni powder having an average particle size of about 0.3 μm or less and 70 parts by weight of a polyurethane resin (manufactured by Kansai Paint Co., Ltd., Rethane 4000) and 15 parts by weight of letan thinner (manufactured by Kansai Paint Co., Ltd.) on a cylindrical aluminum pipe And use a ball mill to
Mix and disperse for 20 hours, and use a urethane curing agent (Kansai Paint Co., Ltd.)
Was spray-coated with a solution containing 9 parts by weight of
After drying for a time, a charge transporting layer having a thickness of 15 μm was formed.

The aluminum pipe on which only the charge transport layer was formed was placed in a vacuum chamber of a capacitively coupled plasma CVD apparatus.

The substrate temperature was maintained at 200 ° C, and 100% silane (Si
H ₄ ) 100cc gas per minute, 100ppm diborane diluted with hydrogen (B ₂ H
₆ ) 2 cc of gas was introduced per minute, and the inside of the reaction vessel was maintained at a pressure of 0.5 Torr. Then, high-frequency power of 13.65 MHz was supplied to generate glow discharge, and the power was maintained at 100 W. Thus, a high dark resistance containing hydrogen and a very small amount of boron, so-called i
A 1 μm charge generation layer made of amorphous silicon was formed. Continuously evacuated to high vacuum, SiH ₄ 30 sccm, NH ₃ 30 sccm
Was introduced into a reactor and discharged at 50 W to form a 0.1 μm SIN _x film, thereby producing an electrophotographic photosensitive member having a photosensitive layer having a thickness of about 16 μm.

When the electrophotographic characteristics of the obtained electrophotographic photoreceptor were measured, the charged potential was 450 V when charged with a corotron of +6 KV.
Was held. The residual potential after exposure to 550 nm light was 10V.

Using this electrophotographic photoreceptor, a copying operation of 100,000 sheets was performed by repeating normal charging, image exposure, development transfer, and cleaning steps according to a normal electrophotographic method, and a good image was obtained. When the photoreceptor was charged with a -6 KV corotron, -470 V was maintained. Upon exposure to light of 550 nm, the residual potential was -10 V, confirming that the photoreceptor was bipolar.

(Effect of the Invention) In the electrophotographic photoreceptor of the present invention, as described above, the charge transport layer is composed of only the metal powder and the organic polymer compound dispersed therein, so that the conventional charge transport layer material is used. As compared with the case, the mobility of electric charge is large and the heat resistance is excellent. In addition, it has the advantages of good adhesion and few defects. Therefore, the electrophotographic photosensitive member of the present invention
High durability, high sensitivity, rich color, high chargeability, low dark decay, and low residual potential after exposure.

Further, the electrophotographic photoreceptor of the present invention can be used for a device using coherent light such as an infrared semiconductor laser as a light source, and can obtain a high-quality image in which occurrence of interference fringes in a laser printer is prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment of the electrophotographic photosensitive member of the present invention, and FIG. 2 is a schematic sectional view of another embodiment of the electrophotographic photosensitive member of the present invention. 1 ... support, 2 ... charge transport layer, 3 ... charge generation layer,
4 ... Intermediate layer, 5 ... Surface protective layer.

Claims (5)

(57) [Claims] 1. An electrophotograph comprising at least a support, a charge transport layer and a charge generation layer sequentially laminated, wherein the charge transport layer comprises only metal powder and an organic polymer compound in which the metal powder is dispersed. Photoconductor. 2. The method according to claim 1, wherein the metal powder is a Group IIa element or a Group II element of the periodic table.
2. The electrophotographic photoreceptor according to claim 1, comprising an element selected from a group b element, a group IIIa element and a transition element, or an alloy or a mixture of two or more of these elements. . 3. The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains chalcogenide as a main component. 4. The electrophotographic photosensitive member according to claim 1, wherein the charge generation layer is mainly composed of amorphous silicon and / or amorphous germanium. 5. The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer mainly comprises an organic dye or an organic pigment.