JP2003156865A - Electrophotographic photoreceptor and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor satisfying and maintaining good transfer performance and cleaning performance, and whose wear is suppressed, then, capable of obtaining an image of high quality free from abnormality such as surface staining, black dots and image missing, etc., irrespective of a long use, and to provide an image forming device using the electrophotographic photoreceptor. SOLUTION: As for the surface shape of the surface layer of the electrophotographic photoreceptor, the surface layer of the photoreceptor is formed to have a structure having a fine ruggedness in a large ruggedness, besides, the surface layer is formed to have a fractal structure.

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 used in copying machines, printers, facsimiles and the like, and an image forming apparatus using the same.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a printer or a facsimile, a photoconductor is uniformly charged, and then a latent image is formed by exposure, and the latent image is visualized with toner or the like. The converted image is transferred to a transfer material such as paper. After the transfer, if necessary, the residual toner is cleaned, the residual charge is eliminated, and the next cycle is performed again. On the other hand, the image transferred to the transfer material is fixed and output through a fixing process such as heating.

In such an image forming process, in order to repeatedly form a high quality image, the surface of the photoreceptor is uniformly exposed to light with high precision to faithfully form a latent image. It is conceivable that the developed toner image is efficiently transferred to a transfer material such as paper without disturbing it, and then quickly returned to the initial state. In particular, efficient transfer to the transfer material is required.

In the past, since the transfer rate of the toner image on the photosensitive member was poor, it was necessary to develop an excessive amount of toner in order to obtain a transferred image with sufficient image density. Further, it is necessary to clean the transfer residual toner with a cleaning member. Furthermore, the cycle of repeating the use decreases the transfer efficiency, further increases the developing amount, and increases the amount of toner to be cleaned.

When the amount of development increases, the toner consumption is accelerated and the toner runs out earlier than a predetermined life, and it is not preferable in terms of user cost to replace it with a new toner container. In addition, the amount of waste is increased, which is not preferable in terms of environmental load.

When the amount of toner to be cleaned increases, the amount of waste toner to be discarded increases, which is not preferable in terms of environmental load.
In recent years, the toner to be cleaned has a mechanism to be recycled again for development. However, the recycled toner contains foreign matter such as paper powder, and an increase in this ratio affects the charging property and the image quality. Must be kept to a minimum.

Further, when the amount of toner to be cleaned increases, the friction between the photoconductor, the cleaning member and the toner increases, the wear of the photoconductor increases, the load on the cleaning member increases, and defective cleaning occurs. And the toner agglomerates stick to the surface of the photoconductor and cause image loss.

The following have been proposed in order to improve transferability. As described in JP-A-6-95413, the contact angle with water is 10 by containing the fluorine-based fine particles.
As disclosed in JP-A-6-332215, containing fluorine-based fine particles and conductive fine powder, the temperature is set to 0 ° or more.
As disclosed in Japanese Patent Laid-Open No. 0-63027, it is proposed to reduce the amount of adhesion between the photoconductor and the toner and improve the transferability by a method of adhering the fine particles by a mechanism for adhering the fine particles to the surface of the photoconductor. .

Further, as in JP-A-1-193765, which defines the surface roughness of the surface of the photoreceptor with respect to the toner particle diameter, the surface of the photoreceptor is made to contain inorganic fine particles as in JP-A-8-262756. Roughness Rz is from 0.05 μm
1 μm, roughness of 0.1 to 2 μm and width of 3 by surface roughening as disclosed in JP-A-10-171132.
Proposals have also been made to improve the adhesion to the toner due to the surface roughness, such as those having a thickness of less than μm.

Furthermore, in recent years, in order to meet the demand for higher image quality in addition to higher speed, both toner and carrier have been made smaller in particle size. In the case of a toner having a small particle size, the fluidity of the powder is lowered because the total surface area is increased. In addition, the adhesive force with the surface of the photoconductor also increases, resulting in deterioration of transferability and cleaning performance.

When the transferability is deteriorated, a worm-eating image in which a part of the image is missing in a line image such as a character portion is generated. Further, since the required image density cannot be obtained, in order to avoid this, it is necessary to develop the toner in an excessive amount in advance.

However, this is not preferable in terms of environmental load because the toner consumption is heavy and the user cost is large as described above, and the amount of waste toner container is increased. Further, since a large amount of toner needs cleaning, a large amount of waste toner is present, which is also undesirable from the environmental impact. In recent years, many cleaning toners use a mechanism that is recycled for development, but waste toner contains a large amount of foreign matter such as paper powder and toner agglomerates, which affects development characteristics and therefore the mixing amount. Need to be suppressed as much as possible.

In order to improve transferability, the surface of the toner is sufficiently covered with an inorganic filler to secure the fluidity of the toner. However, the toner having a small particle size needs an excessive amount, and such toner is cleaned. Abrasion during cleaning with a cleaning member such as a blade increases, and the life of the photoconductor is reduced. For this reason, it is desired to improve the transfer rate from the photosensitive member, develop the minimum necessary toner, and clean only the minimum residual toner. The conventional transfer rate is 80 to 90%, and 95% or more is desired to satisfy the above requirements.

[0014]

In the method of reducing the surface adhesive force by using the above-mentioned fluorine fine particles and the like, the transferability is improved but the wearability is inferior. In addition, streak-shaped image loss due to scratches may occur during long-term use, which is not preferable.

On the other hand, in the method of defining the surface roughness (Rz), it is necessary to reduce Rz in order to prevent cleaning failure. However, with such roughness, smoothing effect is immediately achieved with time. Disappear.

A system containing inorganic fine particles or the like has no effect because the surface roughness is too small when the particle size is small. The effect is obtained by containing a certain size of
Durability can also be improved, but only particles with a single particle size distribution
A part where the difference in height of the unevenness is large locally occurs, which causes a potential drop or a leak in that part in the charging step, and an abnormal image such as a background stain or a black spot is generated, which is not preferable. Furthermore, there is a problem that the residual potential of the photoconductor becomes large with an addition amount for expressing sufficient durability.

In the present invention, the above-mentioned problems are solved, that is, satisfactory transfer performance and cleaning performance are satisfied and maintained, photoreceptor wear is small, and even after long-term use, background stains, black spots, and image dropouts occur. SUMMARY OF THE INVENTION An object of the present invention is to provide a photoconductor that can obtain a high-quality image without abnormal images and an image forming apparatus using the photoconductor.

[0018]

In order to achieve the above object, the inventors of the present invention have achieved that the surface layer of the photoconductor has a surface shape having a fine uneven structure in large unevenness. I found it. That is, the present invention has the following configurations. (1) In the electrophotographic photoconductor, the surface layer of the photoconductor has a surface shape having a fine concavo-convex structure in large irregularities.

(2) The electrophotographic photoconductor according to (1), wherein the surface shape having a fine uneven structure in the large unevenness is a fractal structure.

(3) The surface layer of the electrophotographic photoreceptor is
The electrophotographic photoreceptor according to (1) or (2) above, which contains at least two kinds of particles having different average particle diameters.

(4) The particles having different average particle sizes are particles having an average particle size of 0.1 to 1 μm and particles having an average particle size of 0.001 to 0.1 μm. ) The electrophotographic photoreceptor as described above.

(5) The surface layer of the electrophotographic photoreceptor is
The electrophotographic photoreceptor according to (1) or (2) above, which contains at least a compound having high crystallinity, and the compound is crystallized during the process of producing the photoreceptor.

(6) The electrophotographic photoreceptor according to (5), wherein the compound having high crystallinity is a compound having at least a long-chain alkyl group.

(7) An image forming apparatus having at least a charging step for charging a photoreceptor, an exposure step for forming a latent image, a developing step for developing the latent image, and a transfer step for transferring the developed image to a transfer material. An image forming apparatus using the electrophotographic photoconductor according to any one of (1) to (6) above.

The large unevenness referred to in the present invention means that the mountain interval is 5
The ridges and valleys have a height of 1 to 5 μm and a large period. In addition, the fine irregularities have a mountain interval of 1
The height of the peaks and valleys is 0.1 μm or less, and the unevenness has a fine period.

The surface structure of the present invention is not formed by simply mixing particles having different particle sizes, and is achieved by the following. Since it is difficult to form the surface structure of the present invention with the same material, it is preferable to use particles made of different materials and having different particle sizes. The content ratio (number ratio) of particles of each particle size is set to the following range. 2 × 10 ² ≦ (number of small particles) / (number of large particles) ≦ 2 × 10 ⁵ Here, the number of particles is a value calculated as follows assuming that the particles are spheres. {(Added weight of particles) / (specific gravity of particles)} / {(4/3) × π
If the content ratio of x (average particle diameter / 2) ³ } particles is smaller or larger than this range, the surface structure of the present invention is not formed. The particles to be contained are preferably particles having an average particle size of 0.1 to 1 μm and particles having an average particle size of 0.001 to 0.1 μm.

Also, a compound having high crystallinity may be contained, and appropriate conditions may be selected depending on the drying conditions, cooling conditions, addition amount, etc. in the process of producing the photoconductor to crystallize the surface structure to the above structure. To be achieved.

The layer having these surface structures may be the outermost surface layer constituting the photoconductor, and in the case of a photoconductor in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support, the charge transport layer is When the protective layer is formed on the protective layer as needed, the protective layer has this structure.

[0029]

1 is a schematic sectional view of an example of an image forming apparatus of the present invention. In FIG. 1, a photoconductor 11 is a photoconductor of the present invention. After being charged to a desired potential by a charger 12, a latent image is formed by exposure 13 and a toner image is formed by a developer 14. The toner image is transferred onto a transfer material (paper) by the transfer roller 15 to which a bias is applied.
Is transcribed to. The toner image remaining on the photoconductor without being transferred is cleaned by the cleaning member 16.
The static elimination member initializes the remaining electric charge to complete one cycle.

In the above process, a contact charging roller which generates less ozone can be suitably used as the charging member, and a semiconductor laser, an LED array or the like can be suitably used for the exposure. There are two-component developing systems, one is a two-component developer consisting of magnetic carrier and toner, the other is a non-magnetic one-component development using only non-magnetic toner and a magnetic one-component development using a magnetic toner containing magnetic powder. It can be used at process speeds. Similar to the charging member, a contact transfer roller that generates less ozone can be used as the transfer member, and a rubber blade-shaped cleaning member can be suitably used at a low cost. As the charge removing member, light charge removing using an LED or the like can be used.

The constitution of the photoreceptor of the present invention will be described in detail below. The photoconductor in FIG. 2 is one in which an intermediate layer 22, a charge generation layer 23, and a charge transport layer 24 are sequentially laminated on a conductive support 21. The conductive support 21 has a volume resistance of 10 ¹⁰ Ω · cm or less, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, indium oxide, or the like. The metal oxide of the above is coated on film or cylindrical plastic or paper by vapor deposition or sputtering, or a plate of aluminum, aluminum alloy, nickel, stainless steel or the like, and
It is possible to use a tube that has been surface-treated by cutting, superfinishing, polishing, etc., after forming it into a raw tube by a method such as extrusion or drawing. Further, the endless nickel belt and the endless stainless belt disclosed in JP-A-52-36016 can also be used as the conductive support 21.

In addition, the conductive support 21 of the present invention may be formed by coating the support with conductive powder dispersed in a suitable binder resin. As the conductive powder, carbon black, acetylene black, aluminum, nickel, iron, nichrome, copper, zinc,
Examples thereof include metal powder such as silver, conductive titanium oxide, conductive tin oxide, and metal oxide powder such as ITO.
Further, the binder resin used at the same time, polystyrene,
Styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer,
Polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly- Examples thereof include thermoplastic resins such as N-vinylcarbazole, acrylic resins, silicone resins, epoxy resins, melamine resins, urethane resins, phenol resins and alkyd resins, and thermosetting resins or photocurable resins.

Such a conductive layer can be provided by dispersing these conductive powders and a binder resin in a suitable solvent, for example, tetrahydrofuran, dichloromethane, 2-butanone, toluene or the like, and coating the dispersion. .

Further, heat shrinkage of a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, or Teflon (registered trademark) containing the conductive powder on a suitable cylindrical substrate. The one provided with a conductive layer by a tube,
It can be favorably used as the conductive support 21 of the present invention.

The intermediate layer 22 contains a binder resin together with titanium oxide. Examples of the resin include thermoplastic resins such as polyvinyl alcohol, casein, sodium polyacrylate, copolymerized nylon and methoxymethylated nylon. Thermosetting resins such as polyurethane, melamine, epoxy, alkyd, phenol, butyral and unsaturated polyester resins can be mentioned.

Further, the ratio P / R of titanium oxide (P) and the binder resin (R) contained in the intermediate layer of the photoreceptor of the present invention is in the range of 0.9 / 1 to 2/1 by volume. Preferably there is. If the P / R ratio of the intermediate layer is less than 0.9 / 1, the characteristics of the intermediate layer are influenced by the characteristics of the binder resin, and the characteristics of the photoconductor greatly change especially with changes in temperature and humidity and repeated use. . Further, when the P / R ratio exceeds 2/1, the number of voids increases in the intermediate layer, and the adhesiveness with the charge generation layer decreases, and when it exceeds 3/1, air accumulates. , Causes air bubbles when coating and drying the photosensitive layer,
It will result in coating defects.

In addition to titanium oxide, fine powder pigments of metal oxides such as aluminum oxide, silica, zirconium oxide, tin oxide and indium oxide are added to the intermediate layer 22 in order to prevent moire and reduce residual potential. Is also good. Further, as the intermediate layer 33 of the present invention, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, a titanyl chelate compound, a zirconium chelate compound, a titanyl alkoxide compound, and an organic titanyl compound can also be used. These intermediate layers 22 can be formed by using an appropriate solvent, dispersion and coating method.

In addition, the intermediate layer 22 of the present invention contains Al
₂ O ₃ provided by anodic oxidation, organic substances such as polyparaxylylene, SiO ₂ , SnO ₂ , TiO ₂ , ITO, C
An inorganic substance such as eO ₂ provided by a vacuum thin film forming method can also be favorably used. The thickness of the intermediate layer 22 is preferably 0 to 20 μm. If necessary, a resin such as copolymerized nylon or methoxymethylated nylon may be further laminated thereon.

In the charge generation layer 23, as charge generation substances, in addition to metal-free phthalocyanine and titanyl phthalocyanine pigments, azo pigments such as monoazo pigments, bisazo pigments, asymmetric disazo pigments, trisazo pigments and tetraazo pigments, pyrrolopyrrole pigments, Anthraquinone pigment, perylene pigment, polycyclic quinone pigment, indigo pigment, squarium pigment, pyrene pigment, diphenylmethane pigment, azine pigment, quinoline pigment, perinone pigment, and other known materials can be used. In particular, azo and phthalocyanine pigments are preferably used. Further, in order to obtain a spectral sensitivity characteristic that can correspond to a wide light source wavelength, an azo pigment and a phthalocyanine-based pigment can be mixed and used.

As the solvent used here, isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane,
Examples include toluene, xylene, ligroin, and the like. The charge generation layer 33 is prepared by ball milling these components in a suitable solvent,
It is formed by dispersing using a sand mill, ultrasonic waves, etc., applying this on the intermediate layer 22, and drying. It is preferable to use an aliphatic ketone or an aromatic ketone.

The charge transport material used for the charge transport layer 24 includes a hole transport material and an electron transport material. Each is used properly depending on the charging polarity. Examples of the electron transport material include chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, and 2,4. , 5,7-Tetranitroxanthone, 2,4,8-Trinitrothioxanthone, 2,6,8-Trinitro-4H-indeno [1,2]
-B] Electron accepting substances such as thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide and benzoquinone derivative.

As the hole-transporting substance, poly-N-vinylcarbazole and its derivative, poly-γ-carbazolylethylglutamate and its derivative, pyrene-formaldehyde condensate and its derivative, polyvinylpyrene, polyvinylphenanthrene, polysilane, and the like. Oxazole derivative, oxadiazole derivative, imidazole derivative,
Monoarylamine derivative, diarylamine derivative,
Triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives,
Known materials such as a butadiene derivative, a pyrene derivative, a bisstilbene derivative, an enamine derivative and other polymerized hole transporting substances can be mentioned.

As the binder resin used in the charge transport layer 24, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride,
Vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin,
Polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, alkyd resin, JP-A-5- No. 158250 / JP-A-6-5
Examples thereof include thermoplastic or thermosetting resins such as various polycarbonate copolymers described in Japanese Patent No. 1544. The amount of the charge transport material is 20 to 30 with respect to 100 parts by weight of the binder resin.
0 parts by weight, preferably 40 to 150 parts by weight are suitable.

Further, in the photoreceptor shown in FIG. 2, since the charge transport layer 24 is the surface layer, the charge transport layer has the above uneven structure or fractal structure. In order to form these structures, the charge transport layer contains a material for forming a predetermined surface structure in addition to the above constituent materials.

As the material, at least two kinds of particles having different average particle sizes from each other can be mentioned. As the particles, it is possible to use inorganic particles such as metal, metal oxide, ceramic powder and silica, and organic resin particles such as silicon resin, fluororesin and acrylic resin. Considering the wear resistance of the surface, inorganic fine particles such as titanium oxide, zinc oxide, alumina, tin oxide and silica are preferable. Further, as the organic fine particles, silicon resin particles and fluororesin particles are also preferable because they can have a surface friction coefficient and a low surface energy. These particles are ultrasonic, ball mill,
Disperse into particles having a predetermined particle size distribution by a method such as a sand mill. A dispersion of these particles is prepared together with the above-mentioned charge transport substance, resin, solvent and the like, and this dispersion is applied by a method such as dip coating, spray coating or ring coating.

The plurality of particles to be contained preferably have different average particle diameters. One has an average particle size of 0.1 to 1 μm, the other 0.00
The average particle size is preferably 1 to 0.1 μm. 1μ
If particles of m or larger are used, the surface irregularities become too large and cleaning failure is caused, which is not preferable. By containing a plurality of particles having different average particle diameters, a surface structure having relatively large irregularities and fine irregularities formed therein is formed.

At the time of dispersing the particles, a dispersion aid such as various surfactants and coupling agents may be added, if necessary.

Next, inclusion of a compound having high crystallinity can be mentioned. As the compound having high crystallinity, a fatty acid compound having a long-chain alkyl group or a long-chain fluoroalkyl group, a fatty acid ester compound, a fatty acid ester amide compound, an aromatic fatty acid ester compound, an aromatic fatty acid ester amide compound and the like are preferably used. The long chain refers to one having a carbon length of 10 or more.

5 to 20 wt% of these compounds to the resin
%, The solution is applied and treated under predetermined drying / cooling conditions to crystallize the solution to a desired size. On the crystallized surface, due to various crystal sizes, moderately large irregularities and fine irregularities are formed in the surface.

It is particularly preferable that the irregularities formed by the above-mentioned particle dispersion and the crystalline compound form a fractal structure. A fractal structure is a structure that has a non-integer dimension that is a fractal dimension and that has self-similarity. This structure can evaluate the shape by calculating the fractal dimension.

The fractal dimension in the present invention can be obtained as follows. The surface shape is measured using an atomic force microscope (AFM). The fractal dimension is calculated from the following relational expression proposed by Majumdar et al. lnS (ΔX) = 2 (D-1) lnG + 2 (2-D) ln (ΔX) (ΔX is a measurement interval, lnS (ΔX) is a structural function, D is a fractal dimension, and G is a constant) Analysis using this As an example, a research paper by Shoji et al., “Preparation of superhydrophobic coating and its surface shape” (Journal of the Chemical Society of Japan 19
98 No. 12 p.837), and the present invention is evaluated in the same manner.

From the cross section of the surface roughness measured by AFM, the measurement interval is ΔX, the root mean square of the roughness at each measurement interval is S (ΔX), and the horizontal axis ln (ΔX) and the vertical axis lnS (ΔX) The fractal dimension of the cross section is determined on the assumption that the slope of the straight line of the graph obtained by plotting is equal to 2 (2-D). To this
Is added to the surface fractal dimension.

The charge transport layer 2 formed as described above
The film thickness of 4 is preferably about 5 to 50 μm.

FIG. 3 shows a protective layer 35 formed on the photoreceptor having the structure shown in FIG.
It shows what formed. In this case, since the protective layer serves as the surface layer, the protective layer forms a surface shape or a fractal structure having a fine uneven structure in the large unevenness. The protective layer 35 can be formed in the same manner as the above charge transport layer.

The photoreceptor of the present invention may be a laminate type photoreceptor as described above, or a single layer type photoreceptor provided with a single layer photosensitive layer containing a charge transport substance and a charge generating substance. The surface may have a surface shape or a fractal structure having a fine uneven structure in the large unevenness.

The method for forming the surface shape having fine irregularities in the large irregularities described above is not limited to the above method, and various methods may be used. For example, it can be manufactured by performing mechanical treatment such as cutting, polishing, blast treatment, or by chemically etching or vapor deposition. Further, a solution in which particles are dispersed may be sprayed onto the surface of the photoconductor to adhere only the particles.

An example will be described below. (Example 1) Titanium oxide (CREL: manufactured by Ishihara Sangyo) 70
Parts by weight, alkyd resin (Beckolite M6401-5
0-S (solid content 50%): Dainippon Ink and Chemicals, Inc. 1
5 parts by weight, melamine resin (Super Beckamine L-12
1-60 (solid content 60%): manufactured by Dainippon Ink and Chemicals, Inc.
A mixture of 10 parts by weight and 100 parts by weight of methyl ethyl ketone was dispersed in a ball mill for 72 hours to prepare an intermediate layer coating solution, which was applied on an aluminum cutting drum having a diameter of 30 mm and a length of 340 mm, and dried at 130 ° C. for 20 minutes. Then, an intermediate layer having a film thickness of 3 μm was produced.

Next, a mixture of 10 parts by weight of the disazo pigment of the following formula (Formula 1) and 200 parts by weight of methyl ethyl ketone was dispersed in a ball mill for 10 days, and then 2 parts by weight of polyvinyl butyral resin (Eslec BL-1 manufactured by Sekisui Chemical Co., Ltd.) Department,
100 parts by weight of methyl ethyl ketone and cyclohexanone 3
It was diluted with a mixed solvent consisting of 00 parts by weight to prepare a charge generation layer coating liquid. This was applied onto the intermediate layer to form a charge generation layer.

[0059]

[Chemical 1]

Next, 70 parts by weight of a charge transporting material represented by the following structural formula (Formula 2), 100 parts by weight of polycarbonate (Z type: viscosity average molecular weight 50000), silicone oil (KF-50: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.02 parts by weight was dissolved to prepare a charge transport layer coating liquid.

[0061]

[Chemical 2] This was applied onto the charge generation layer and dried at 135 ° C. for 20 minutes to form a charge transport layer having a thickness of 20 μm. Each of the intermediate layer, charge generation layer and charge transport layer was applied by dip coating.

Next, alumina (density 3.8 g / cm ³ )
20 parts by weight was put into a mixed solvent consisting of 80 parts by weight of tetrahydrofuran and 20 parts by weight of cyclohexanone, and a dispersion A was prepared by a ball mill. The average particle size of this dispersion A was 0.5 μm. In addition, silica particles (density 2.
10 parts by weight of 2 g / cm ³ ) was added to a mixed solvent of 80 parts by weight of tetrahydrofuran and 20 parts by weight of cyclohexanone, and a dispersion B was prepared by a ball mill. The average particle size of this dispersion B was 0.02 μm. Alumina 15
The charge transport material 70 of the above (Chemical Formula 2)
By weight, 100 parts by weight of polycarbonate (Z type: viscosity average molecular weight 50,000) was dissolved to prepare a coating liquid for protective layer. The main coating solution was applied onto the charge transport layer by spray coating and dried at 150 ° C. for 20 minutes to form a protective layer having a film thickness of 3 μm, and the photoreceptor of the present invention was obtained.

The surface roughness profile obtained by measuring the surface of the obtained photoreceptor with a stylus type surface roughness meter is as shown in FIG. In this way, the large unevenness had a large number of fine unevenness.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the protective layer in Example 1 was a protective layer containing no alumina particles. The surface roughness profile obtained by measuring the surface of the obtained photoreceptor with a stylus surface roughness meter is shown in FIG.
There was no large unevenness (mountain interval 5 to 100 μm, height of peaks and valleys 1 to 5 μm), and the shape was only fine unevenness.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 1 except that the protective layer in Example 1 was a protective layer containing no silica particles. The surface roughness profile obtained by measuring the surface of the obtained photoconductor with a stylus type surface roughness meter is as shown in FIG. 6, and there are large irregularities, but fine irregularities (mountain intervals of 1 μm or less, peak and valley heights of 0. .1 to 5 μm) was not observed.

Comparative Example 3 A photoconductor was prepared in the same manner as in Example 1 except that the protective layer in Example 1 was a protective layer containing neither alumina particles nor silica particles. The surface roughness profile obtained by measuring the surface of the obtained photoreceptor with a stylus surface roughness meter is as shown in FIG. 7, and the surface was smooth.

Example 2 A photoconductor was prepared in the same manner as in Example 1 except that the following protective layer was used instead of the protective layer in Example 1. <Preparation of protective layer> 70 parts by weight of the charge-transporting substance of the above (Chemical Formula 2), polycarbonate (Z type: viscosity average molecular weight 50
000) 100 parts by weight and 10 parts by weight of the following compound (Chemical Formula 3) were dissolved in 500 parts by weight of tetrahydrofuran and 50 parts by weight of cyclohexanone to give a protective layer coating solution.

[0068]

[Chemical 3]

The main coating liquid was applied onto the charge transport layer by spraying, dried at 150 ° C. for 20 minutes, and then cooled at a rate of 10 ° C./minute to form a protective layer. AF on the surface of the obtained photoreceptor
The surface shape was measured with M, and the fractal dimension of the cross section was calculated from the cross section, and was 1.3. Therefore,
The fractal dimension of the surface is 2.3.

Comparative Example 4 A photoconductor was prepared in the same manner as in Example 2 except that the compound of (Chemical Formula 3) in the protective layer was changed to the following compound (Chemical Formula 4).

[0071]

[Chemical 4]

The fractal dimension of the surface of the obtained photoconductor was determined in the same manner as in Example 2. The abscissa ln of the root mean square S (ΔX) of roughness at each measurement interval with respect to the measurement interval ΔX.
The graph obtained by plotting (ΔX) on the vertical axis lnS (ΔX) did not show linearity and was not a fractal shape. The surface roughness profile obtained by measuring the surface of the obtained photoconductor with a stylus type surface roughness meter has a shape similar to that shown in FIG. 6, and there are large irregularities, but fine irregularities (mountain intervals of 1 μm or less, peaks and valleys). Height of 0.1 to 5 μm) was not observed.

In each of the photoconductors of the above Examples and Comparative Examples,
The transfer rate when a black solid image was copied and output to a postcard was measured with a Ricoh copy machine Imagio MF2200. Further, the line omission when the 2-dot vertical and horizontal lattice lines were copied and output to the postcard was observed. The same evaluation was performed after outputting 5,000 sheets. The results are shown in Table 1. Further, the number of printable sheets up to the toner end with the same toner filling amount was compared. The results are shown in Table 2.

[0074]

[Table 1]

[Table 2]

[0075]

As can be seen from the above results, the transfer rate of the present invention is excellent because of the constitution of the present invention, that is, the photoconductor surface has fine irregularities in the large irregularities and further has the fractal shape. In addition, it is possible to maintain the image quality even during long-term use, and it is possible to continue to provide a high-quality image with no image loss during long-term use. Furthermore, the life of the replenishment toner can be extended without developing unnecessary toner, leading to a reduction in user cost. Further, since the toner to be cleaned is reduced, the waste toner is reduced and the environmental load can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a general image forming apparatus.

FIG. 2 is a cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor of the present invention.

FIG. 3 is a cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor of the present invention.

FIG. 4 is a surface roughness profile of the photoconductor obtained in Example 1.

5 is a surface roughness profile of the photoconductor obtained in Comparative Example 1. FIG.

6 is a surface roughness profile of the photoconductor obtained in Comparative Example 2. FIG.

7 is a surface roughness profile of the photoconductor obtained in Comparative Example 3. FIG.

[Explanation of symbols]

11: photoconductor 12: Charger 13: Exposure 14: Developing device 15: Transfer roller 16: Cleaning member 21, 31: conductive support 22, 32: Middle layer 23 and 33: charge generation layer 24, 34: charge transport layer 35: protective layer

Claims (7)

[Claims] 1. An electrophotographic photoreceptor, wherein the surface layer of the photoreceptor has a surface shape having a fine concavo-convex structure in large irregularities. 2. The electrophotographic photoreceptor according to claim 1, wherein the surface shape having a fine uneven structure in the large unevenness is a fractal structure. 3. The electrophotographic photosensitive member according to claim 1, wherein the surface layer of the electrophotographic photosensitive member contains at least two kinds of particles having different average particle sizes from each other. 4. The particles having different average particle diameters are particles having an average particle diameter of 0.1 to 1 μm and an average particle diameter of 0.1.
4. The electrophotographic photoconductor according to claim 3, wherein the photoconductor is a particle of 001 to 0.1 μm. 5. The surface layer of the electrophotographic photoconductor contains at least a compound having high crystallinity, and the compound is crystallized during the photoconductor production process.
Alternatively, the electrophotographic photoreceptor according to item 2. 6. The electrophotographic photoreceptor according to claim 5, wherein the compound having high crystallinity is a compound having at least a long-chain alkyl group. 7. An image forming apparatus having at least a charging step for charging a photoconductor, an exposure step for forming a latent image, a developing step for developing the latent image, and a transfer step for transferring the developed image to a transfer material. An image forming apparatus using the electrophotographic photoconductor according to claim 1.