JPH1020536A - Electrophotographic photoreceptor and electrophotographic method using that - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such an electrophotographic photoreceptor having a low wearing protective layer that production of a blurred image or an out-of-focus image can be suppressed in a high humidity environment and the residual potential is not increased even in a low humidity environment, and to provide an electrophotographic method which uses this photoreceptor. SOLUTION: This electrophotographic photoreceptor has a photosensitive layer and a protective layer formed on a conductive base body. The protective layer is formed at least by dispersing and orienting fine particles containing a magnetic material in a binder resin. The binder resin used for the protective layer is preferably a polyurethane resin obtd. by the reaction of acrylpolyol and polyisocyanate. The fine particles containing a magnetic material are preferably dispersed and oriented in the perpendicular direction to the conductive base body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor used for an apparatus such as a copying machine, a printer, a facsimile and the like, and an electrophotographic method using the same.

[0002]

2. Description of the Related Art Various methods have conventionally been proposed for improving the printing durability of an organic electrophotographic photosensitive member. Among them, a method of improving the printing durability of a photoreceptor by separating a function of laminating an abrasion-resistant layer on a photosensitive layer and giving the abrasion-resistant layer the abrasion-resistant performance is disclosed. Kaisho 6
No. 0-3638. According to the method described in this publication, there is an advantage that durability can be greatly improved by providing a layer in which conductive fine powder is dispersed in a binder resin. Is inherent. That is, one of them is that the wear resistance is extremely good, so that the foreign matter which has been removed at the same time as the wear in the past remains on the surface, and therefore, this photoconductor has been used for a long time. In addition, there is a problem in that foreign matter presumed to be conductive ions adheres to the surface of the photoreceptor together with ozone generated at the time of charging, thereby causing image bleeding under high humidity conditions. Another is that even if conductive fine powder for resistance adjustment is dispersed in the binder resin, particularly under low humidity conditions, electric charges are accumulated in the binder resin and the residual potential is high. Problem. In order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. 7-181705 proposes to use needle-like fine particles made of titanium oxide so that the resistance of the protective layer has anisotropy. However, the orientation of the acicular fine particles is not always satisfactory.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances in the prior art, and has been made to solve the problems. That is, an object of the present invention is to provide an electrophotographic photoreceptor provided with a low-abrasion protective layer that suppresses the occurrence of image bleeding and image blurring under high-humidity conditions and has a low residual potential even under low-humidity conditions. And an electrophotographic method using the same.

[0004]

The electrophotographic photoreceptor of the present invention comprises an electrophotographic photoreceptor having a photosensitive layer and a protective layer provided on a conductive substrate. It is characterized in that fine particles containing a material are dispersed and oriented. The binder resin used for the protective layer is preferably a polyurethane resin obtained by a reaction between an acrylic polyol and a polyisocyanate. Further, the fine particles containing the magnetic material in the protective layer are preferably dispersed and oriented in a direction perpendicular to the conductive substrate. The electrophotographic method of the present invention includes a step of forming a latent image on an electrophotographic photoreceptor, a step of forming a toner image using a developer on the photoreceptor, and a step of transferring the toner image onto a transfer body. An electrophotographic method having a cleaning step of removing residual toner on the photoconductor is characterized in that a copied image is obtained by using the above electrophotographic photoconductor.

[0005]

Embodiments of the present invention will be described below in detail. The electrophotographic photoreceptor of the present invention is obtained by sequentially forming at least a photosensitive layer and a protective layer on a conductive substrate, and the protective layer contains fine particles containing a magnetic material oriented in a binder resin. Are dispersed. FIG. 1 is a schematic configuration diagram showing an example of the electrophotographic photoconductor of the present invention. In FIG. 1, 1 is a conductive substrate, 2 is an undercoat layer, 3 is a charge generation layer, 4 is a charge transport layer, 5 is a protective layer, and the protective layer 5 is made of a magnetic material oriented in a binder resin. It is formed by a dispersion of fine particles.

The above-mentioned layers constituting the electrophotographic photosensitive member of the present invention will be described. As the conductive substrate, any known ones used for electrophotographic photoreceptors can be used. For example, aluminum, nickel, chromium,
Metals such as stainless steel, and aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium,
Examples include a plastic film provided with a thin film of tin oxide, indium oxide, ITO, or the like, or paper or a plastic film coated or impregnated with a conductivity imparting agent. These conductive supports are used in the form of a drum, a sheet, or an appropriate shape, but are not limited thereto. The surface of the conductive support may be further subjected to various treatments, if necessary, within a range that does not affect the image quality. For example, surface oxidation treatment, chemical treatment, coloring treatment, or the like, or irregular reflection treatment such as graining can be performed.

Next, an undercoat layer may be formed on the conductive substrate, if desired. As a material for forming the undercoat layer, polyvinyl butyral, polyvinyl pyridine, polyvinyl pyrrolidone, phenol resin, polyvinyl alcohol, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene-acrylate copolymer, polyamide, Any material known as a material for forming an undercoat layer such as casein, gelatin, and a silane coupling agent can be used. The thickness of the undercoat layer is generally set in the range of 0.2 to 2 μm.

A photosensitive layer is provided on the undercoat layer. When the photosensitive layer has a single-layer structure, the dye-sensitized Zn
Examples include an O photosensitive layer, a CdS photosensitive layer, and a photosensitive layer in which a charge generating material or the like is dispersed in a charge transporting material or a binder resin containing the same. Further, in the case of a laminated structure, a layer in which functions are separated into a charge generation layer and a charge transport layer may be mentioned. The order of lamination of the charge generation layer and the charge transport layer on the conductive substrate may be any order.

The charge generation layer is formed by dispersing a charge generation material in a binder resin as required. Examples of charge generation materials include selenium and selenium alloys; CdS, CdS
e, inorganic photoconductors such as CdSSe, ZnO and ZnS;
Metal or metal-free phthalocyanine pigment; bisazo pigment,
Azo pigments such as trisazo pigments; squarium compounds;
Azurenium compound; perylene pigment; indigo pigment; quinacridone pigment; polycyclic quinone pigment; cyanine dye; xanthene dye; Complexes and the like. Known binder resins include, for example, polycarbonate, polystyrene, polyester, polyvinyl butyral, methacrylate polymer or copolymer, vinyl acetate polymer or copolymer, cellulose ester or ether, polybutadiene, polyurethane, epoxy Resin or the like is used. The thickness of the charge generation layer is arbitrarily set in the range of 0.01 to 5 μm, and is preferably about 0.03 to 2 μm.

The charge transport layer is composed mainly of a charge transport material. The charge transport material is not particularly limited as long as it is transparent to visible light and has a charge transport ability.Specifically, imidazole, virazoline, thiazole, oxadiazole,
Oxazole, hydrazone, ketazine, azine, carbazole, polyvinyl carbazole and the like and derivatives thereof, triphenylamine derivatives, stilbene derivatives, benzidine derivatives and the like can be mentioned. As the binder resin used in combination with these if necessary, for example, polycarbonate, polyarylate, polyester, polystyrene, styrene-acrylonitrile copolymer, polysulfone, polymethacrylate, styrene-methacrylate copolymer and the like can give. The thickness of the charge transport layer is 10
A range of from 30 to 30 μm is preferred.

In the electrophotographic photoreceptor of the present invention, a protective layer is provided on the above-mentioned photosensitive layer. In this protective layer, it is necessary that fine particles containing an oriented magnetic material are dispersed in the binder resin. Examples of the binder resin used for the protective layer include general resins such as a polyurethane resin, a thermosetting silicone resin, a polyamide resin, a high-melting polyester resin, a phenol resin, a phosphazene resin, a polyarylate resin, and an epoxy resin. However, a polyurethane resin is preferable, and a polyurethane resin obtained by a reaction between an acrylic polyol and a polyisocyanate is more preferable. The protective layer of the present invention is such that fine particles of a magnetic material having a long axis are vertically oriented and dispersed in a conductive substrate in a binder resin containing a polyurethane resin obtained by a reaction between an acrylic polyol and a polyisocyanate. Is preferred. This orientation method is performed by dispersing a fine powder of a magnetic material in a binder resin, drying the obtained coating solution on the surface of the photoreceptor, and immediately applying a magnetic field almost immediately after the application.

The acrylic polyol forming the polyurethane resin used in the present invention includes, for example, those represented by the following general formula.

Embedded image (Wherein, R represents an alkyl group, and n is 10 to 1000
Is an integer. The acrylic polyol is, as a monomer component, in particular,
It is preferable to use an acrylic copolymer containing hydroxyethyl methacrylate. Specific examples include a styrene-methyl methacrylate-hydroxyethyl methacrylate copolymer, and a copolymer of hydroxyethyl methacrylate with a substituted or unsubstituted alkyl or phenyl ester of acrylic acid or methacrylic acid. Specific examples of acrylates and methacrylates used in these copolymers include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, Examples include pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, octyl acrylate, octyl methacrylate, phenyl acrylate, and phenyl methacrylate.

The polyisocyanate includes, for example, xylylene diisocyanate (XDI), tolylene diisocyanate (TDI), biuret type isocyanate represented by the following formula (2), and isocyanurate type represented by the following formula (3) And an adduct-type isocyanate represented by the following formula (4).

Embedded image

In the present invention, fine particles of a magnetic material are used for the protective layer.
Fe ₃ O ₄ , CrO ₂ , CoPt, CoFe ₂ O ₄ , C
rTe, FeCo, FeNi ₃ , Mn ₂ Sb and the like. The fine particles of these magnetic materials have a conductivity of 1
１．５1.5 × 10 ⁸ Ω · cm, and the particle size is 0.1 × 10 ⁸ Ω · cm.
It is preferable to use fine powder having a range of 01 to 0.3 μm and an aspect ratio of 1.0 to 9.5. As the shape of the fine powder of the magnetic material, the shape having an aspect ratio of less than 1.0 is not preferable because a sufficient effect on the orientation by the magnetic field cannot be obtained, while the shape of the fine powder of 9.5 or more is used for the protective layer. The viscosity of the binder resin is not preferred because a sufficient effect on the orientation by the magnetic field cannot be obtained.

When the magnetic material is black, such as Fe ₃ O _4, and the light absorption becomes large when forming a film,
If the surface is coated with SnO ₂ and whitened, the amount of light absorbed can be reduced. The amount of these magnetic materials is preferably in the range of 20 to 180 parts by weight based on 100 parts by weight of the binder resin. If the amount is less than 20 parts by weight, the residual potential increases under low-temperature and low-humidity conditions, resulting in a low-density image. Image bleeding occurs.

The formation of the above protective layer can be performed as follows. First, a fine powder of a magnetic material was added to a solution in which the above-mentioned acrylic polyol was dissolved in an appropriate solvent, and a polyisocyanate was added as a curing agent to a dispersion liquid dispersed by a ball mill. Immediately after coating on the photosensitive layer by, for example, drawing, dip coating, or the like, as shown in FIG. The protective layer is formed by drying in a state where is oriented. In FIG. 2, reference numeral 6 denotes an electromagnet for orientation, 7 denotes a reflecting mirror, 8 denotes a quartz lamp (infrared lamp), and 9 denotes an electrophotographic photosensitive member. The orientation electromagnet 6 is arranged in a direction perpendicular to the surface of the electrophotographic photosensitive member using a support or the like, and the quartz lamp 8 is irradiated with far-infrared rays using a halogen heater or the like to obtain magnetic properties. The curing is completed after orienting the fine powder of the material.

According to this method, as the crosslinking reaction between the acrylic polyol and the polyisocyanate progresses,
A protective layer in which fine particles of a magnetic material are vertically oriented on a conductive substrate is formed. The magnetic field applied so as to be oriented is suitably about 2 to 4 times the coercive force Hc of the magnetic material. If the magnetic field is less than 2 times, the orientation ratio is insufficient, while if it exceeds 4 times, adhesion to the magnetic poles is observed. The thickness of the protective layer is preferably in the range of 0.5 to 10 μm. When the film thickness is smaller than 0.5 μm,
The function as a scratch-resistant and abrasion-resistant layer is poor, and the film surface is not smooth. On the other hand, if the thickness is more than 10 μm, the coating film will be drooped and cannot be applied uniformly. The protective layer obtained as described above has low friction,
It is excellent in abrasion resistance, and when an image is formed using the electrophotographic photoreceptor of the present invention having the protective layer, occurrence of image bleeding can be suppressed even under high humidity, and low humidity There is an advantage that the residual potential does not increase even below. For this reason, the electrophotographic photoreceptor of the present invention is particularly suitable for use in an electrostatic copying system.

Next, the electrophotographic method of the present invention will be described. The electrophotographic method of the present invention includes a step of forming a latent image on an electrophotographic photosensitive member, a step of developing the obtained latent image with toner, a step of transferring the obtained toner image to a transfer body, and a step of A process of thermally fixing the toner image, and further using an electrophotographic apparatus having a cleaning process for removing residual toner on the photoreceptor, repeatedly obtaining an image, wherein the photoreceptor is described above. An electrophotographic photosensitive member having a protective layer is used.

Hereinafter, description will be made with reference to the drawings. FIG. 3 is a schematic diagram showing an example of an electrophotographic copying apparatus used in the electrophotographic method of the present invention. Around the electrophotographic photosensitive member 12,
A contact charger 18, an exposure device 10, a developing device 11, a transfer device 14, a cleaning device 16, and a static eliminator 17 are provided. However, the static eliminator 17 is provided as needed. The electrophotographic photoreceptor 12 rotates in the direction of the arrow and is uniformly charged by the contact charger 18, and is then image-exposed by the exposure device 10, and the formed electrostatic latent image is
The image is visualized by the toner in the developing device 11. Next, the visualized toner image is transferred to a transfer device 1 such as a corona charger.
4, the toner image is fixed on the transfer paper 13 by the fixing device 15. The toner remaining on the surface of the electrophotographic photoreceptor 12 is cleaned by a cleaning device 16 including a blade cleaner and the like.
To eliminate the charge. Electrophotographic photosensitive member 12 after static elimination
Is uniformly charged again by the contact charger 18 in the next cycle, and image formation is repeatedly performed as described above. In the present invention, the charging method for the photoconductor may be any of contact charging by a cylindrical charging member in contact with the photoconductor and charging by a corotron.

[0020]

The present invention will be described below in detail with reference to examples. Note that “parts” means “parts by weight”. Example 1 n-butyl alcohol 170 in which 4 parts of polyvinyl butyral resin (Esrec BM-S, manufactured by Sekisui Chemical Co., Ltd.) was dissolved
In 30 parts, 30 parts of an organic zirconium compound (acetylacetone zirconium butyrate) and 3 parts of a mixture of organic silane compounds (γ-aminopropyltrimethoxysilane) were mixed and stirred to obtain a coating liquid for forming an undercoat layer. This coating solution was applied on a 30 mmφ ED tube aluminum substrate roughened by a honing treatment, air-dried at room temperature for 5 minutes, and then heated at 50 ° C. for 10 minutes. After placing in a constant temperature / humidity chamber of 85% RH (dew point 47 ° C.),
Dried in a hot air drier for 10 minutes at a temperature of 1.0 μm.
m was formed. Next, as a charge generation material,
15 parts of gallium chloride phthalocyanine, vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar) 1
A mixture consisting of 0 parts and 300 parts of n-butyl alcohol was dispersed using a sand mill for 4 hours. The obtained dispersion was dip-coated on the undercoat layer and dried to form a 0.2 μm-thick charge generation layer. Next, N, N'-
Diphenyl-N, N'-bis (3-methylphenyl)-
[1,1'-biphenyl] -4,4'-diamine (4 parts) and bisphenol Z-polycarbonate resin (molecular weight 4
(000) and 6 parts were dissolved in 80 parts of chlorobenzene. The obtained solution was applied and dried to form a charge transport layer having a thickness of 20 μm.

Next, an acrylic polyol (G) comprising a styrene-methyl methacrylate-hydroxyethyl methacrylate copolymer having a composition ratio of about 4: 7: 2 (weight ratio)
R4026C, manufactured by Kansai Paint Co., Ltd., heating residue about 38%)
170 parts by weight of Fe ₃ O coated with SnO ₂ on the surface
₄ (MTA-740, manufactured by Toda Kogyo Co., Ltd.) Fine magnetic powder (volume resistivity: 7 × 10 ¹ Ω · cm, average particle diameter 5.8)
100 parts by weight of micron, aspect ratio of about 1: 6), 90 parts by weight of a thinner containing xylene as a main agent (Retanthinner, manufactured by Kansai Paint Co., Ltd.), and 4000 parts by weight of stainless steel spherical media having a diameter of 10 mm, a diameter of about 160 mm,
The mixture was placed in a stainless steel ball mill pot having a height of 170 mm, subjected to a dispersion treatment at 60 rpm for 24 hours, and mixed. Thereafter, the mixture subjected to the dispersion treatment is passed through a filter, a binder resin in which Fe ₃ O ₄ of a magnetic material coated with tin oxide is dispersed is taken out, and 400 parts by weight of the above-mentioned thinner is further mixed and further added thereto. Was added to obtain a coating liquid. Immediately after the obtained coating solution was provided on the charge transporting layer formed above with a drawing coating device to provide a coating layer for a protective layer having a thickness of about 3 μm, using the device shown in FIG.
A magnetic field (1110 Oe, which is three times the coercive force Hc of about 370 Oe) is applied, and the fine powder of the magnetic material is dried while being oriented vertically to the conductive substrate to form a protective layer. A photoreceptor was produced. The magnetic fine powder is Fe ₃ O ₄ (MTA-74).
0, manufactured by Toda Kogyo Co., Ltd.), prepared by adjusting a slurry with aluminum borate and an aqueous solution of a tin compound, and then reacting with an acid and an alkali, followed by filtration, washing, drying, crushing, and firing. The physical properties of this fine powder are as follows: specific surface area: 13.4 m ² / g, true specific gravity: 3.4 g / cc, tap density: 0.8, particle size distribution D ₁₀ = 1.46, D ₅₀ = 5.
78, it was a D ₉₀ = 19.26 microns. To coat tin oxide on the surface of the magnetic material, a fine powder of the magnetic material, an aluminum borate and an aqueous solution of a tin compound are mixed in a slurry, and the mixture is washed with an acid and an alkali in this order, and further washed with water and filtered. , Drying, crushing and firing. The mixing ratio of the tin oxide (SnO ₂ ) fine powder was 155 parts by weight with respect to 100 parts by weight of the binder resin.

The electrophotographic photoreceptor obtained above was applied to a printer (PC-PR1000 /
4R, manufactured by NEC Corporation) (Laser Write Se
select61C, manufactured by Macintosh)
Under high temperature and high humidity of 8 ° C and 85% RH, 1500 sheets /
The copying operation was performed for about 7,500 sheets for five consecutive days, but no image deletion or blurring was observed, and no other image quality problems occurred.
After completion of this copying operation, the surface of the photoreceptor was polished with KBr powder in order to identify the adhered matter on the surface of the photoreceptor, and the obtained surface attached matter was applied to an infrared absorption measuring instrument.

Comparative Example 1 An undercoat layer was formed on a conductive support in the same manner as in Example 1.
A charge generation layer and a charge transport layer were sequentially formed. Next, tin oxide fine powder (S-1, manufactured by Mitsubishi Materials Corporation) (particle size: 1.3 μm or less) was added to 47 parts by weight of an acrylic polyol composed of the styrene-methyl methacrylate-hydroxyethyl methacrylate copolymer used in Example 1. Is about 90%, 0.
58 parts by weight of about 30% for 15 μm or less and about 30% for 0.15 to 0.25 μm) were added in the same manner as in Example 1, and this was dispersed using a ball mill to obtain a coating solution. This coating solution was applied on the charge transport layer to a thickness of about 4 μm by the same drawing application apparatus as in Example 1, cured, and dried to form a protective layer having abrasion resistance. The obtained electrophotographic photoreceptor is connected to a printer (PC-
PR1000 / 4R, NEC Corporation) (Laser W
write Select 61C, manufactured by Macintosh), and about 7,500 copies were made at 28 ° C. and 85% RH at a high temperature and a high humidity for 1500 days / day for 5 consecutive days. , And thereafter image blurring and image blurring became noticeable. When the surface of the photoreceptor was wiped off with alcohol, no image blur could be seen, and it is considered that the surface deposits caused image blur and the like.
Using a KBr powder, the rubbed surface deposits were confirmed with an infrared absorption measuring instrument. As a result, peaks were observed at positions corresponding to nitrates and ammonium salts.
Matched what was seen in. FIG. 4 shows an infrared absorption spectrum of the rubbed surface deposit. From the comparison between Example 1 and Comparative Example 1, when the photoreceptor of Example 1 was used, image deletion and image blur were not observed because of the type and dispersion state of the fine particles dispersed in the protective layer. Is considered to be due to the difference from Comparative Example 1.

[0024]

According to the electrophotographic photoreceptor of the present invention, since the protective layer formed on the surface of the photoreceptor is formed by orienting and dispersing the fine powder of the magnetic material in the binder resin, the high temperature and high humidity Even if the discharge product adheres to the surface under, it is possible to suppress the occurrence of image deletion and image blur, and also to keep the residual potential low even under low temperature and low humidity. It has an excellent effect of improving abrasion resistance. Electrophotography using this photoreceptor, in any of the charging roller or corotron system,
Good electrophotographic performance can be exhibited over a long period of time, and an image with excellent image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of a layer configuration of an electrophotographic photoconductor of the present invention.

FIG. 2 is a conceptual diagram of an apparatus used for forming a protective layer in which fine particles of a magnetic material are oriented.

FIG. 3 is a schematic configuration diagram of an electrophotographic copying apparatus used in the electrophotographic method of the present invention.

FIG. 4 is an infrared absorption spectrum diagram of a surface adhered substance obtained by rubbing the surface of the photoreceptor prepared in Comparative Example 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive base, 2 ... Undercoat layer, 3 ... Charge generation layer, 4 ...
Charge transport layer, 5: protective layer, 6: electromagnet for orientation, 7: reflecting mirror, 8: quartz lamp (infrared lamp), 9, 12: electrophotographic photosensitive member, 10: exposure device, 11: developing device, 13: Transfer paper, 14: Transfer device, 15: Fixing device, 16: Cleaning device, 17: Static eliminator, 18: Contact charger.

Claims (6)

[Claims] 1. An electrophotographic photosensitive member having a photosensitive layer and a protective layer provided on a conductive substrate, wherein the protective layer is formed by dispersing and orienting at least fine particles containing a magnetic material in a binder resin. Photoconductor for electrophotography. 2. The electrophotographic photosensitive member according to claim 1, wherein the binder resin is a polyurethane resin obtained by a reaction between an acrylic polyol and a polyisocyanate. 3. The electrophotographic photoconductor according to claim 1, wherein the magnetic material is in a needle shape. 4. The photoconductor for electrophotography according to claim 1, wherein the surface of the magnetic material is coated with SnO ₂ . 5. The photoconductor for electrophotography according to claim 1, wherein the fine particles containing a magnetic material are dispersed and oriented in a direction perpendicular to the conductive substrate. 6. A step of forming a latent image on an electrophotographic photoreceptor, a step of forming a toner image on the photoreceptor using a developer, a step of transferring the toner image onto a transfer member, An electrophotographic method having a cleaning step for removing the residual toner, wherein a copied image is obtained using the electrophotographic photoconductor according to claim 1.