JP2008275658A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus that is superior in wear resistance, cleaning property and electrical durability, even after a long-term repeated use and capable of outputting a high-quality image output having no abnormal image. <P>SOLUTION: The image forming apparatus includes an electrophotographic photoreceptor, containing filler particles in an outermost surface layer in a uniformly dispersed state satisfying the expression: 1.0×10<SP>-3</SP>≤(df×b<SP>3</SP>)/(dm×a<SP>3</SP>)≤2.5×10<SP>-2</SP>, where a is average distance (nm) between filler particles; b is the average diameter (nm) of the filler particles; df is the density (g/cm<SP>3</SP>) of the filler particles; and dm is the average density (g/cm<SP>3</SP>) of solid components in the outermost surface layer; a toner having an average circularity in a range of 0.95-0.98; and a cleaning means, having a contact member which is brought into contact with the electrophotographic photoreceptor under a contact pressure which is in a range of 0.13-0.25 N/cm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus. More specifically, the present invention relates to an image forming apparatus including a specific electrophotographic photosensitive member, a specific toner, and a specific cleaning unit.

An electrophotographic image forming apparatus (hereinafter also referred to as an electrophotographic apparatus) used as a copying machine, a printer, a facsimile apparatus, or the like forms an image through the following electrophotographic process.
First, a photosensitive layer of an electrophotographic photoreceptor (hereinafter also simply referred to as a photoreceptor) provided in the apparatus is uniformly charged to a predetermined potential by a charging unit. Next, exposure is performed by light such as laser light emitted from the exposure unit in accordance with image information to form an electrostatic latent image. A developer is supplied from the developing means to the formed electrostatic latent image, and colored particles called toner (dry toner), which is a component of the developer, are attached to the surface of the photoreceptor to cause electrostatic latent image. The image is developed and visualized as a toner image. The formed toner image is transferred from the surface of the photoreceptor to a transfer material such as recording paper by a transfer unit, and fixed by a fixing unit.

  At the time of the transfer operation by the transfer means, not all the toner on the surface of the photoconductor is transferred to the recording paper and transferred, but a part of the toner remains on the surface of the photoconductor. Further, the paper dust of the recording paper that comes into contact with the photoconductor during transfer may remain attached to the surface of the photoconductor. Such foreign matters such as residual toner and adhered paper dust on the surface of the photoreceptor adversely affect the quality of the formed image and are removed by the cleaning means. After cleaning the surface of the photoreceptor, the surface of the photosensitive layer is neutralized by a neutralizing unit, and the electrostatic latent image disappears.

An electrophotographic photoreceptor used in such an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a conductive substrate made of a conductive material.
Conventionally, an electrophotographic photosensitive member using an inorganic photoconductive material (hereinafter referred to as an inorganic photosensitive member) has been used as the electrophotographic photosensitive member. As a typical inorganic photoreceptor, a selenium photoreceptor using a layer made of amorphous selenium (a-Se) or amorphous selenium arsenic (a-AsSe) as a photosensitive layer, zinc oxide (ZnO) or sulfide. A zinc oxide-based or cadmium sulfide-based photoreceptor using a cadmium (CdS) dispersed in a resin together with a sensitizer such as a dye for the photosensitive layer, and a layer made of amorphous silicon (a-Si) are used for the photosensitive layer. Amorphous silicon photoconductor (hereinafter referred to as a-Si photoconductor).

However, inorganic photoreceptors have the following drawbacks.
Selenium photoreceptors and cadmium sulfide photoreceptors have problems with heat resistance and storage stability. Moreover, since selenium and cadmium are toxic to the human body and the environment, photoreceptors using these must be collected after use and disposed of properly.
Zinc oxide photoreceptors have the disadvantages of low sensitivity and low durability, and are rarely used today.
While a-Si photoreceptors that are attracting attention as non-polluting inorganic photoreceptors have advantages such as high sensitivity and high durability, they are manufactured using the plasma chemical vapor deposition method. However, it is difficult to form a film and image defects are likely to occur. The a-Si photoreceptor also has the disadvantages of low productivity and high manufacturing costs.

As described above, since the inorganic photoreceptor has many drawbacks, development of a photoconductive material used for the electrophotographic photoreceptor has progressed, and instead of the inorganic photoconductive material conventionally used, An organic photoconductive material, that is, an organic photoconductor (abbreviation: OPC) is frequently used.
An electrophotographic photoreceptor using an organic photoconductive material (hereinafter referred to as an organic photoreceptor) has some problems in sensitivity, durability, environmental stability, etc., but toxicity, manufacturing cost and material design. In terms of the degree of freedom, etc., there are many advantages over inorganic photoreceptors. The organic photoreceptor also has an advantage that the photosensitive layer can be formed by an easy and inexpensive method typified by a dip coating method.

Because of these many advantages, organic photoreceptors are gradually becoming the mainstream of electrophotographic photoreceptors. Also, due to recent research and development, the sensitivity and durability of organic photoreceptors have been improved, and at present, organic photoreceptors have been used as electrophotographic photoreceptors except in special cases. Yes.
In particular, the performance of organic photoreceptors has been remarkably improved by the development of function-separated photoreceptors in which a charge generation function and a charge transport function are assigned to different substances. In addition to the above-mentioned advantages of the organic photoconductor, the function-separated type photoconductor has an advantage that a photoconductor having an arbitrary characteristic can be relatively easily manufactured with a wide selection range of materials constituting the photosensitive layer. ing.

  There are two types of function-separated type photoreceptors: a laminated type and a single layer type. In the laminated type function separation type photoconductor, a laminated type constituted by laminating a charge generation layer containing a charge generation material responsible for a charge generation function and a charge transport layer containing a charge transport material responsible for a charge transport function. The photosensitive layer is provided. The charge generation layer and the charge transport layer are usually formed in a form in which the charge generation material and the charge transport material are each dispersed in a binder resin as a binder. On the other hand, in a single-layer type function dispersion type photoreceptor, a single-layer type photosensitive layer in which a charge generation material and a charge transport material are dispersed together in a binder resin is provided.

  In the electrophotographic apparatus, the above-described charging, exposure, development, transfer, cleaning, and charge removal operations are repeatedly performed on the photosensitive member under various environments. Therefore, the photosensitive member has high sensitivity and optical response. In addition to excellent properties, it is required to have excellent environmental stability, electrical stability, and durability against mechanical external forces (printing durability). Specifically, it is required that the surface layer of the photoconductor is not easily worn by rubbing by a cleaning means or the like.

  In recent years, a toner having a small particle size and a high degree of circularity has been adopted in order to improve the quality of a printed image. Since the transferability is clearly better than that of conventional toner, the image quality is improved, but the cleaning property is deteriorated. The reason is that if the toner becomes too round, it slips through between the photosensitive member and the cleaning means. As a countermeasure, the contact pressure of the cleaning means with respect to the photosensitive member may be increased. However, the large contact pressure causes damage to the photosensitive member. Therefore, improvement in the printing durability of the photoreceptor itself is more desired.

As an effort to improve the printing durability of the photosensitive layer, a technology for providing a protective layer on the outermost surface of the photoreceptor, a technology for imparting lubricity to the protective layer, a technology for curing the protective layer, and filler particles in the protective layer Technology is known.
These protective layers are basically desired to be as thin as possible from the viewpoint of not inhibiting the basic function of the photosensitive layer. In addition, the provision of the protective layer causes various harmful effects. For example, when the photosensitive layer and the protective layer have a discontinuous layer structure, the protective layer may be peeled off by long-term use, and the exposed area potential is increased by repeated use for a long time. On the contrary, when the protective layer and the photosensitive layer are dissolved in a continuous layer structure, that is, when the photosensitive layer is dissolved by the protective layer coating solution to be subsequently applied, the image characteristics of the photosensitive layer are deteriorated depending on the dissolution state.

  In particular, the use of a technique that contains filler particles adds a new influencing factor to the characteristics of the photoreceptor, such as controlling the dispersibility of the filler particles. That is, the characteristics of the photoreceptor are not defined only by the simple addition amount of filler particles. Patent Document 1 discloses that the printing durability is improved by adding filler particles up to about 0.1 to 10% by weight with respect to the total solid content of the outermost surface layer. However, it is easily assumed that the image characteristics / electrical characteristics / printing durability of the photoreceptor are affected by the difference in the dispersion state of the filler particles in the outermost surface layer. Also, if the dielectric constant of the outermost layer becomes non-uniform, the image thickness at the edge and the toner scattering at the time of black solid image output may occur. From this also, the dispersion state of the filler particles inside the outermost layer It can be seen that this greatly affects the characteristics of the photoreceptor. Nevertheless, Patent Document 1 makes no mention of these points.

  If a wear-resistant effect can be imparted to the outermost surface of a function-separated type photoreceptor, the production process will not include an extra step, so there are significant cost advantages compared to the case where a protective layer is added. There is. It is also possible to avoid the above-described adverse effects caused by stacking the photosensitive layer and the protective layer.

  On the other hand, when the printing durability is improved, as an adverse effect, image blur and image flow due to the influence of a charged product adhering to the surface of the drum (photosensitive member) occur particularly under high temperature and high humidity. In order to eliminate these adverse effects, an image forming apparatus is disclosed in which a cleaning unit is devised (Patent Document 2). However, in this apparatus, the tip portion of the cleaning blade has a V shape or a knife edge, and mechanical precision is required for manufacturing such a cleaning blade, which raises a problem of an increase in manufacturing cost.

  Patent Document 3 discloses that an electrophotographic photosensitive member having a specific surface layer containing at least a charge transport material and a nitrogen atom-free binder resin, and a photosensitive member surface with a contact pressure of 0.78 N / cm or more of linear pressure. A technique is disclosed that improves cleaning failure and achieves good electrophotographic characteristics by combining with a cleaning means comprising an abutting elastic blade. However, the sensitivity of this photoreceptor is inferior.

JP-A-1-205171 JP 2004-61560 A JP 2006-343658 A

  An object of the present invention is to provide an electrophotographic image forming apparatus that is excellent in mechanical / electrical durability even for repeated use over a long period of time and can output a high-quality image without occurrence of abnormal images. It is.

According to the present invention, an electrophotographic photosensitive member, a dry toner for developing and visualizing an electrostatic latent image formed on the electrophotographic photosensitive member, and an image visualized by the dry toner are transferred to a transfer material. Cleaning means for removing toner remaining on the electrophotographic photosensitive member after the cleaning,
The outermost surface layer of the electrophotographic photosensitive member contains filler particles, and the filler particles in the outermost surface layer have the following formula (1):
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² (1)
(In the formula, a means the average distance between filler particles (nm), b means the average filler particle diameter (nm), df means the density of filler particles (g / cm ³ ), and dm is the maximum. It is a uniform dispersion state that satisfies the average density (g / cm ³ ) of the solid content of the surface layer,
The dry toner has an average circularity ranging from 0.95 to 0.98;
The cleaning means has a contact member that contacts the electrophotographic photosensitive member, and the contact pressure of the contact member with respect to the electrophotographic photosensitive member is in the range of 0.13 to 0.25 N / cm. An image forming apparatus is provided.

  According to the present invention, it is possible to provide an image forming apparatus that is excellent in printing durability, retains electrical stability over a long period of use, has no defects such as the occurrence of abnormal images, and can form images with good sharpness. .

  The image forming apparatus of the present invention includes an electrophotographic photosensitive member, a dry toner for developing and visualizing an electrostatic latent image formed on the electrophotographic photosensitive member, and an image visualized by the dry toner. And at least cleaning means for removing toner remaining on the electrophotographic photosensitive member after being transferred to the electrophotographic photosensitive member. The components (that is, the electrophotographic photosensitive member, the dry toner, and the cleaning unit) and other components are not limited in any way except that the components have the following characteristics.

In the image forming apparatus of the present invention, the electrophotographic photosensitive member has an outermost surface layer containing filler particles, and the filler particles in the outermost surface layer are represented by the following formula (1):
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² (1)
(In the formula, a means the average distance between filler particles (nm), b means the average filler particle diameter (nm), df means the density of filler particles (g / cm ³ ), and dm is the maximum. It is characterized by a uniform dispersion state satisfying the average density (g / cm ³ ) of the solid content of the surface layer.
In the present invention, the outermost surface layer is a part of the charge transport layer constituting the photosensitive layer of the electrophotographic photosensitive member or a part (thickness direction) layer including the surface of the charge transport layer. From the viewpoint of ease of manufacture, the outermost surface layer is preferably the entire charge transport layer.

In the image forming apparatus of the present invention, the dry toner has an average circularity in the range of 0.95 to 0.98. Here, the circularity of the toner particles is expressed by (periphery of a circle having the same area as the projected area of the toner particles) / (peripheral length of the projected image of the toner particles).
In the image forming apparatus of the present invention, the cleaning unit includes a contact member that contacts the electrophotographic photosensitive member, and a contact pressure of the contact member with respect to the electrophotographic photosensitive member is 0.13 to 0.25 N. It is the range of / cm. An abutting member (which will be described in detail below, for example, a cleaning blade) rubs the surface of the photoreceptor to remove residual toner as the electrophotographic photoreceptor rotates.

  By adopting the above configuration, the image forming apparatus of the present invention can maintain good cleaning characteristics over a long period of time while achieving high image quality of a printed image, and can maintain a high-quality image for a long period of time. As a result, cost reduction and maintenance-free can be realized.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a partial cross-sectional view showing a simplified configuration of one embodiment of an electrophotographic photosensitive member used in the image forming apparatus of the present invention. The photoreceptor 1 includes a cylindrical conductive substrate 11 made of a conductive material, a charge generation layer 12 that is a layer laminated on the outer peripheral surface of the conductive substrate 11 and contains a charge generation material, and a charge generation layer. And a charge transport layer 13 containing a charge transport material. The charge generation layer 12 and the charge transport layer 13 constitute a photosensitive layer 14. That is, the photoreceptor 1 is a multilayer photoreceptor.
As shown in FIG. 3, the photoreceptor used in the image forming apparatus of the present invention is also a laminated photoreceptor (photoreceptor 2) in which an intermediate layer 15 is provided between the conductive substrate 11 and the charge generation layer 12. It may be.

(Conductive substrate)
The conductive substrate 11 serves as an electrode of the photoreceptor 1 and also functions as a support member for the other layers 12 and 13. The shape of the conductive substrate 11 is cylindrical in FIG. 1, but is not limited thereto, and may be a columnar shape, a sheet shape, an endless belt shape, or the like.

  As the conductive material constituting the conductive substrate 11, for example, a single metal such as aluminum, copper, zinc, nickel, or titanium, or an alloy such as an aluminum alloy or stainless steel can be used. Without being limited to these metal materials, a metal (aluminum, gold, silver, copper, zinc, nickel, titanium) foil is provided on the surface of a polymer material such as polyethylene terephthalate, nylon or polystyrene, hard paper or glass. Laminated, metal (aluminum, gold, silver, copper, zinc, nickel, titanium) deposited, or a conductive compound such as conductive polymer, tin oxide or indium oxide deposited or coated Etc. can also be used. These conductive materials are used after being processed into a predetermined shape.

  If necessary, the surface of the conductive substrate 11 is irregularly reflected within a range that does not affect the image quality, such as anodic oxide film treatment, surface treatment with chemicals or hot water, coloring treatment, or roughening the surface. Processing may be performed. In an electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform. For this reason, the laser beam reflected on the surface of the photoconductor and the laser beam reflected inside the photoconductor cause interference, and interference fringes due to this interference may appear on the image, resulting in an image defect. By performing the above-described treatment on the surface of the conductive substrate 11, image defects due to laser beam interference can be prevented.

(Charge generation layer)
The charge generation layer 12 contains, as a main component, a charge generation material that generates charges by absorbing light. Here, the main component means that the component contains an amount capable of expressing its main function. Substances effective as the charge generation substance include monoazo pigments, bisazo pigments, azo pigments such as trisazo pigments, indigo pigments such as indigo or thioindigo, perylene pigments such as peryleneimide or perylene anhydride, anthraquinone or Polycyclic quinone pigments such as pyrenequinone, phthalocyanine pigments such as metal phthalocyanine or metal-free phthalocyanine, triphenylmethane dyes represented by methyl violet, crystal violet, knight blue, victoria blue, erythrosine, rhodamine B, rhodamine 3R Acridine dyes typified by acridine orange, frappeosin, etc., thiazine dyes typified by methylene blue, methylene green, etc., oxazine dyes typified by capri blue, meldra blue, etc. Qualylium dyes, pyrylium salts and thiopyrylium salts, thioindigo dyes, bisbenzimidazole dyes, quinacridone dyes, quinoline dyes, lake dyes, azo lake dyes, dioxazine dyes, azurenium dyes, triallylmethane dyes, xanthenes Examples thereof include organic photoconductive materials such as cyano dyes, cyanine dyes, and triphenylmethane dyes, and inorganic photoconductive materials such as selenium and amorphous silicon. These charge generation materials may be used alone or in combination of two or more.

（式中、Ｘ¹、Ｘ²、Ｘ³及びＸ⁴は、それぞれハロゲン原子、アルキル基又はアルコキシ基を示し、ｒ、ｓ、ｙ及びｚは、それぞれ０〜４の整数を示す。）
で示されるオキソチタニウムフタロシアニン化合物を用いることが好ましい。 Among the above charge generation materials, the following general formula (A):

(Wherein, X ¹ , X ² , X ³ and X ⁴ each represent a halogen atom, an alkyl group or an alkoxy group, and r, s, y and z each represents an integer of 0 to 4)
It is preferable to use an oxotitanium phthalocyanine compound represented by the formula:

Examples of the halogen atom represented by X ¹ , X ² , X ³ and X ⁴ in the general formula (A) include fluorine, chlorine, bromine and iodine atoms.
Examples of the alkyl group represented by X ¹ , X ² , X ³ and X ⁴ include C _{1 to} C ₄ alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and t-butyl groups. It is done.
Further, the alkoxy groups represented by X ¹ , X ² , X ³ and X ⁴ include C ₁ -C ₄ alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and t-butoxy groups. Can be mentioned.

  Since the oxotitanium phthalocyanine compound represented by the general formula (A) is a charge generation material having high charge generation efficiency and high charge injection efficiency, the charge generation layer 12 using the compound absorbs light. As a result, a large amount of charge is generated, and the generated charge can be efficiently injected into the charge transport material contained in the charge transport layer 13 without being accumulated therein, and is smoothly transported to the surface of the photosensitive layer 14.

  The oxotitanium phthalocyanine compound represented by the general formula (A) is a known production method such as, for example, the method described in Phthhalocyanine Compounds, Reinhold Publishing Corp., New York, 1963 by Moser, Frank H and Arthur L. Thomas. Can be manufactured by.

For example, among the oxotitanium phthalocyanine compounds represented by the general formula (A), in the case of unsubstituted oxotitanium phthalocyanine where r, s, y, and z are 0, phthalonitrile and titanium tetrachloride are heated and melted. Or dichlorotitanium phthalocyanine is synthesized by heating in a suitable solvent such as α-chloronaphthalene and then hydrolyzed with a base or water.
Alternatively, oxotitanium phthalocyanine can be produced by reacting isoindoline with titanium tetraalkoxide such as tetrabutoxytitanium in a suitable solvent such as N-methylpyrrolidone.

Examples of optional components other than the charge generation material contained as the main component include sensitizing dyes, binder resins, antioxidants, leveling agents, and plasticizers.
Examples of sensitizing dyes include triphenylmethane dyes such as methyl violet, crystal violet, knight blue and victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine dyes such as acridine orange and frapeosin, methylene blue and Examples include thiazine dyes typified by methylene green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes, and thiopyrylium salt dyes. The sensitizing dye is preferably used at a ratio of 10 parts by weight or less, more preferably at a ratio of 0.5 to 2 parts by weight with respect to 100 parts by weight of the charge generating substance.

  As a method for forming the charge generation layer 12, the above-described charge generation material is vacuum-deposited on the surface of the conductive substrate 11, or the charge generation layer coating obtained by dispersing the above-described charge generation material in a suitable solvent. The method etc. which apply | coat a liquid to the surface of the electroconductive base | substrate 11 are mentioned. Among these, in a binder resin solution obtained by mixing a binder resin as a binder in a solvent, a charge generating material is dispersed by a conventionally known method to prepare a coating solution for a charge generating layer, A method of applying the obtained coating solution to the surface of the conductive substrate 11 is preferably used. Hereinafter, this method will be described.

  Examples of the binder resin used for the charge generation layer 12 include polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, and polyarylate resin. , Phenoxy resins, polyvinyl butyral resins and polyvinyl formal resins, and copolymer resins containing two or more of the repeating units constituting these resins. Specific examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. Can do. The binder resin is not limited to these, and a commonly used resin can be used as the binder resin. One kind of these resins may be used alone, or two or more kinds thereof may be mixed and used.

  Examples of the solvent for the charge generation layer coating solution include halogenated hydrocarbons such as tetrachloropropane and dichloroethane, ketones such as acetone, isophorone, methyl ethyl ketone, acetophenone, and cyclohexanone, and esters such as ethyl acetate, methyl benzoate, and butyl acetate. , Tetrahydrofuran (THF), dioxane, dibenzyl ether, ethers such as 1,2-dimethoxyethane or dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, dichlorobenzene Sulfur-containing solvents such as diphenyl sulfide, fluorine-based solvents such as hexafluoroisopropanol, and aprotic polar solvents such as N, N-dimethylformamide or N, N-dimethylacetamide are used. Moreover, the solvent which mixed 2 or more types of these solvents can also be used. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.

  In the charge generation layer 12 including the charge generation material and the binder resin, the ratio W1 / W2 between the weight W1 of the charge generation material and the weight W2 of the binder resin is 10/100 or more and 200/100 or less. It is preferable that If the ratio W1 / W2 is less than 10/100, the sensitivity of the photoreceptor 1 may be lowered, which is not preferable. When the ratio W1 / W2 exceeds 200/100, not only the film strength of the charge generation layer 12 decreases, but also the dispersibility of the charge generation material may decrease and coarse particles may increase. For this reason, surface charges other than those that should be erased by exposure are reduced, and image fogging, particularly fogging of an image called black spots where toner adheres to a white background and minute black spots are formed may increase. The ratio W1 / W2 is more preferably 50/100 or more and 150/100 or less.

The charge generation material may be previously pulverized by a pulverizer before being dispersed in the binder resin solution. Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.
Examples of the disperser used when dispersing the charge generating substance in the binder resin solution include a paint shaker, a ball mill, and a sand mill. As a dispersion condition at this time, it is preferable to select an appropriate condition so that impurities are not mixed due to wear of members constituting the container and the disperser.

  Examples of the coating method for the charge generation layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these coating methods, an optimum method can be selected in consideration of the physical properties and productivity of coating. Among these coating methods, the dip coating method is a method in which a substrate is immersed in a coating tank filled with a coating solution, and then a layer is formed on the surface of the substrate by pulling it up at a constant speed or a sequentially changing speed. It is. As described above, the dip coating method is relatively simple and excellent in terms of productivity and cost. Therefore, it is frequently used for producing an electrophotographic photosensitive member. In addition, in order to stabilize the dispersibility of a coating liquid, the apparatus used for the dip coating method may be provided with a coating liquid dispersing apparatus represented by an ultrasonic generator.

  The film thickness of the charge generation layer 12 is preferably 0.05 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 1 μm or less. If the film thickness of the charge generation layer 12 is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor 1 may be lowered, which is not preferable. If the thickness of the charge generation layer 12 exceeds 5 μm, the charge transfer within the charge generation layer 12 becomes the rate-determining step in the process of erasing the surface charge of the photosensitive layer 14, and the sensitivity of the photoreceptor 1 may decrease. It is not preferable.

(Charge transport layer)
A charge transport layer 13 is provided on the charge generation layer 12. The charge transport layer 13 is mainly composed of a charge transport material having the ability to accept and transport the charge generated by the charge generation material contained in the charge generation layer 12, and filler particles that improve the durability of the photoreceptor. The binder resin can optionally be configured to bind the charge transport material and filler particles.
The binder resin is preferably contained in the range of 30 to 80% by weight with respect to the entire charge transport layer. In addition to the charge transport material, the filler particles, and the binder resin, an antioxidant, an ultraviolet absorber, a leveling agent, a plasticizer, and the like may be included.
As the charge transport material, a hole transport material and an electron transport material can be used.

  Examples of hole transport materials include carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, Polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene Derivatives, enamine derivatives, benzidine derivatives and the like. Polymers having groups derived from these compounds in the main chain or side chain, such as poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc. Or polysilane etc. are mentioned.

Examples of the electron transport material include organic compounds such as benzoquinone derivatives, tetracyanoethylene derivatives, tetracyanoquinodimethane derivatives, fluorenone derivatives, xanthone derivatives, phenanthraquinone derivatives, phthalic anhydride derivatives, and diphenoquinone derivatives.
The charge transport materials are not limited to those listed here, and can be used alone or in admixture of two or more.

（式中、Ｒ₁とＲ₂は、互いに同一か又は異なってもよい炭素数１〜４のアルキル基を表すか、又はＲ₁とＲ₂は互いに結合して窒素原子を含む複素環基を形成してもよく、ｎは１〜４の整数を表し、Ａｒはブタジエン基を有する芳香環基を表す）で示される化合物を用いることにより、繰り返し使用後においても、画像劣化の少ない安定した感光体を形成することが可能となる。 In particular, the following general formula (1) that is resistant to gases such as ozone and NOx generated in the electrophotographic process as a charge transport material.

(In the formula, R ₁ and R ₂ each represents an alkyl group having 1 to 4 carbon atoms which may be the same or different from each other, or R ₁ and R ₂ are bonded to each other to form a heterocyclic group containing a nitrogen atom. And n represents an integer of 1 to 4 and Ar represents an aromatic ring group having a butadiene group), and thus stable photosensitivity with little image deterioration even after repeated use. A body can be formed.

  The binder resin constituting the charge transport layer 13 is not particularly limited, and any resin known in the art can be used. In particular, a resin containing polycarbonate as a main component is preferable for reasons such as improved solubility in organic solvents and improved transparency of the coating film. Here, the main component means to occupy 50% by weight or more of the binder resin, and more preferably in the range of 60 to 100% by weight.

  Examples of resins other than polycarbonate include vinyl polymer resins such as polymethyl methacrylate resin, polystyrene resin, polyvinyl chloride resin, and the like, copolymer resins containing two or more of repeating units constituting these, and polyester resins, Polyester carbonate resin, polysulfone resin, phenoxy resin, epoxy resin, silicone resin, polyarylate resin, polyamide resin, methacrylic resin, acrylic resin, polyether resin, polyurethane resin, polyacrylamide resin, phenol resin, polyphenylene oxide resin, etc. . Moreover, the thermosetting resin which partially bridge | crosslinked these resin is also mentioned. These resins may be used alone or in a mixture of two or more.

When the charge transport layer 13 is the outermost surface layer, the charge transport layer contains filler particles.
The filler particles constituting the outermost surface layer are broadly classified into organic fillers and inorganic fillers centered on metal oxides. In general, organic fillers, mainly fluorine-based materials, are used for the purpose of controlling the wettability of the photoreceptor surface and suppressing the adhesion of foreign substances, etc., and inorganic fillers for the purpose of improving printing durability. Is mainly used. In the present invention, it is preferable to use an inorganic filler. As the inorganic filler, a material having a high hardness as a material is preferable, and when the outermost surface layer includes a binder resin, a material that is easily dispersed in the binder resin is more preferable. Examples of the inorganic filler include oxides such as silicon oxide (silica), titanium oxide, zinc oxide, calcium oxide, and aluminum oxide (alumina), or nitride compounds such as silicon nitride and aluminum nitride. In particular, as a result of considering light scattering in the charge transport layer, silicon oxide is preferable because it has a small difference from the refractive index of components other than the filler particles.

Since the dispersion state of the filler particles greatly affects the wear resistance and electrical stability, the following formula (1) in which the dispersion state is taken into consideration instead of simple addition:
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² (1)
(In the formula, a means the average distance between filler particles (nm), b means the average filler particle diameter (nm), df means the density (g / cm ³ ) of the filler particles, and dm is the maximum. Meaning the average density (g / cm ³ ) of the solid content of the surface layer)
It is added in an amount within the range specified in. When the amount is within this range, a photoreceptor showing good printing durability can be obtained.

The value of each parameter can be determined by the following method.
It is preferable to directly measure a by, for example, TEM cross-sectional observation. However, when a uniform dispersion state can be confirmed, a is indirectly calculated as a calculated value from the amount of filler particles added and the volume of the coating film as a medium. You may ask for.
Although b can be directly measured by, for example, cross-sectional observation by SEM, a catalog value may be cited when a commercially available product is used as filler particles.
df may be obtained by calculation from the volume and weight of the particles used, or when using a commercially available product, a catalog value may be cited.
The dm can be obtained by measuring and calculating the volume and weight of the coating film sample.
Here, the solid content of the outermost surface layer is a coating film of the outermost surface layer that has been solidified by applying a coating liquid and drying the solvent.

  The uniform dispersion state means that the state close to the primary particle size in FIG. 2 in the coating solution is fixed after solidifying as a coating film, and the average particle size of the particles in the coating film is the raw material before production. The state is almost equal to the primary particle size of the particles. In the formula (1), filler particles having a true sphere and no particle size distribution are assumed in a homogeneous solid medium, and these particles are uniformly dispersed in the medium. If the addition amount / particle diameter / density of the filler particles and the density of the medium (more precisely, the density of the entire solid content including the filler particles) are determined, the average distance a between the filler particles is determined. By substituting the obtained value a into the formula (1), it can be determined whether or not the filler particles satisfy the formula (1).

In other words, equation (1) assumes that the filler particles are uniformly “distributed”. Therefore, in this invention, the addition density | concentration of a filler particle is prescribed | regulated so that dispersion | distribution of the filler particle in a coating liquid / coating film may be uniform, and Formula (1) may be satisfy | filled.
Here, a is preferably small in order to minimize the adverse effects on light scattering and electrical carriers (electrons and / or holes) in the system. Specifically, 400 nm or less is suitable. More preferably, the range of a is 20 to 200 nm.
Since b (laser light) transmitted through the charge transport layer generates holes and electrons in the charge generation layer, b is desirably small in order to avoid light scattering and light absorption in the charge transport layer as much as possible. For example, the thickness is preferably 100 nm or less. Although a minimum is not specifically limited, From a viewpoint of handleability or expense, it may be about 5 nm. Therefore, the range of b is more preferably 5 to 100 nm, and further preferably 5 to 20 nm.
Preferably the range of df is 1.5~7g / cm ^3, more preferably 1.5~3g / cm ^3.
Preferably the range of dm is 1 to 2 g / cm ^3, more preferably 1-1.5 g / cm ^3.

  In adding the filler particles, various dispersion methods such as a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, or a paint shaker can be used to form a uniform particle dispersion state. In order to draw out the excellent characteristics of the electrophotographic photosensitive member, it is desired to grasp the dispersion state in the dispersion liquid for forming the coating film on the outermost surface of the electrophotographic photosensitive member or after the formation of the coating film.

  In FIG. 2, the same coating liquid formulation (1.55 g of polycarbonate resin PCZ-400 (manufactured by Idemitsu Kosan) and PCZ-800 (manufactured by Teijin Chemicals) and silica TS-610 (manufactured by Cabot Specialty Chemicals; primary particle diameter of 17 nm) ) When two types of dispersion were carried out by mixing 3.1 g with 55.9 g of tetrahydrofuran, the difference in particle size distribution in the coating solution after the dispersion treatment was compared. In FIG. 2, ◆ indicates the particle size distribution of the silica particles in the coating solution obtained by dispersing for 5 hours with a ball mill, and □ indicates the silica in the coating solution obtained by dispersing for 5 hours with a paint shaker. The particle size distribution of the particles is shown. ◆ shows that the silica particles are stably dispersed in the coating solution to a state close to the primary particle size, while from □, the silica particles form aggregates of micron order in the coating solution. I understand that. Although it is certain that □ indicates that an aggregate is formed by reaggregation, the detailed cause for obtaining this state has not been elucidated. The change in the aggregation state as shown in FIG. 2 directly corresponds to the electrical properties and surface uniformity of the final coating film, and the formation of a uniform dispersion close to the primary particle size in the dispersion is also reflected in the coating film. Is done. Therefore, the ◆ dispersion method is preferable because an outermost surface layer having excellent durability can be formed as a result.

In the above, preferred examples of unaggregated filler particles have been given. However, an aggregate of filler particles may be used as long as the formula (1) is satisfied. In the case of an aggregate, “a filler particle” is read as “aggregate” in a, b and df of the formula (1).
Moreover, although the dispersion process by a paint shaker is performed on the conditions in which an aggregate is formed in the above, it can also be made to disperse | distribute to the state close | similar to a primary particle diameter by changing conditions.
In addition, the dispersion state of the filler particles in the coating liquid can be evaluated using, for example, a light scattering particle size distribution measuring apparatus.

  Various additives may be added to the charge transport layer 13 as necessary. For example, a plasticizer or a leveling agent may be added to the charge transport layer 13 in order to improve the film formability, flexibility, or surface smoothness. Examples of the plasticizer include biphenyl, biphenyl chloride, benzophenone, o-terphenyl, dibasic acid ester (for example, phthalic acid ester), fatty acid ester, phosphate ester, various fluorohydrocarbons, chlorinated paraffin, and epoxy type plasticizer. Etc. Examples of the surface modifier include a silicone leveling agent such as silicone oil, a fluororesin leveling agent, and the like.

  The charge transport layer 13 is formed in the same manner as when the charge generation layer 12 is formed by coating, for example, in a suitable solvent, in a charge transport material, a binder resin, and filler particles (when the charge transport layer is the outermost layer). ), And if necessary, the aforementioned additives are dissolved or dispersed to prepare a coating solution for a charge transport layer, and the resulting coating solution is applied onto the charge generation layer 12.

  Examples of the solvent for the coating solution for the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, monochlorobenzene, dichlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, Ethers such as tetrahydrofuran, dioxane, dibenzyl ether and dimethoxymethyl ether, ketones such as cyclohexanone, acetophenone and isophorone, esters such as methyl benzoate and ethyl acetate, sulfur-containing solvents such as diphenyl sulfide, hexafluoroisopropanol, etc. And aprotic polar solvents such as N, N-dimethylformamide. One of these solvents may be used alone, or two or more thereof may be mixed and used. In addition, a solvent such as alcohols, acetonitrile or methyl ethyl ketone can be further added to the above-mentioned solvent as necessary. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.

  Examples of the coating method for the charge transport layer coating solution include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these coating methods, the dip coating method is particularly excellent in various respects as described above, and is often used when the charge transport layer 13 is formed.

  The film thickness of the charge transport layer 13 is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 30 μm or less. If the thickness of the charge transport layer 13 is less than 5 μm, the charge retention ability may be lowered, which is not preferable. If the thickness of the charge transport layer 13 exceeds 40 μm, the resolution of the photoreceptor 1 may be lowered, which is not preferable.

(Photosensitive layer)
Each layer of the photosensitive layer 14 is added with one or more sensitizers such as an electron accepting substance and a dye in order to improve sensitivity and further suppress an increase in residual potential and fatigue due to repeated use. Also good.

  Examples of the electron acceptor include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride, and 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, and 4-nitrobenzaldehyde. Aldehydes, anthraquinones, anthraquinones such as 1-nitroanthraquinone, polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, or diphenoquinone compounds An electron withdrawing material or the like can be used. Moreover, what polymerized these electron-withdrawing materials can also be used.

  As the dye, for example, an organic photoconductive compound such as xanthene dye, thiazine dye, triphenylmethane dye, quinoline pigment or copper phthalocyanine can be used. These organic photoconductive compounds function as optical sensitizers.

  Further, an antioxidant or an ultraviolet absorber may be added to each layer of the photosensitive layer 14. In particular, it is preferable to add an antioxidant or an ultraviolet absorber to the charge transport layer 13. As a result, deterioration of oxidizing gas such as ozone and nitrogen oxide can be reduced. Moreover, the stability of the coating liquid when forming each layer by coating can be enhanced.

  Moreover, it is preferable to contain antioxidant in the outermost surface layer containing a filler particle. The outermost surface layer containing filler particles is easily oxidized by an active gas during charging of the photoreceptor, such as ozone or NOx, and image blur is likely to occur. Therefore, the presence of an antioxidant can prevent the occurrence of image blur.

  As the antioxidant, a phenol compound, a hydroquinone compound, a tocopherol compound, an amine compound, or the like is used. Among these, a hindered phenol derivative, a hindered amine derivative, or a mixture thereof is preferably used. The total amount of these antioxidants used is preferably from 0.1 to 50 parts by weight, more preferably from 1 to 20 parts by weight, per 100 parts by weight of the charge transport material. If the amount of the antioxidant used is less than 0.1 part by weight, it may not be possible to obtain a sufficient effect for improving the stability of the coating solution and improving the durability of the photoreceptor. Further, if it exceeds 50 parts by weight, it may be adversely affected on the characteristics of the photosensitive member, so it is preferable to avoid it.

(Other photoconductor configuration examples)
FIG. 3 is a partial cross-sectional view showing, in a simplified manner, the configuration of another embodiment of the photoreceptor used in the present invention. The photosensitive member 2 is similar to the photosensitive member 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.
What should be noted in the photoreceptor 2 is that an intermediate layer (undercoat layer) 15 is provided between the conductive substrate 11 and the photosensitive layer 14.

(Middle layer)
If there is no intermediate layer 15 between the conductive substrate 11 and the photosensitive layer 14, charges may be injected from the conductive substrate 11 into the photosensitive layer 14. This charge lowers the chargeability of the photosensitive layer 14, thereby reducing the surface charge other than the portion to be erased by exposure, and as a result, defects such as fogging may occur in the image. In particular, when an image is formed using a reversal development process, a toner image may be formed by attaching toner to a portion where surface charge is reduced by exposure. For this reason, when the surface charge is reduced due to factors other than exposure, fogging of an image called black spot where toner adheres to a white background and a minute black spot is formed occurs, and as a result, the image quality may be significantly deteriorated. That is, when there is no intermediate layer 15 between the conductive substrate 11 and the photosensitive layer 14, the chargeability in a minute region is reduced due to a defect in the conductive substrate 11 or the photosensitive layer 14. The image may be fogged, resulting in a significant image defect.

  In the photoreceptor 2, since the intermediate layer 15 is provided between the conductive substrate 11 and the photosensitive layer 14 as described above, injection of charges from the conductive substrate 11 to the photosensitive layer 14 can be prevented. Accordingly, it is possible to prevent the chargeability of the photosensitive layer 14 from being lowered, to suppress the reduction of surface charges other than the portion to be erased by exposure, and to prevent the occurrence of defects such as fogging on the image.

Further, by providing the intermediate layer 15, the surface of the conductive substrate 11 can be covered and a uniform surface can be obtained, so that the film formability of the photosensitive layer 14 can be improved. Further, peeling of the photosensitive layer 14 from the conductive substrate 11 can be suppressed, and adhesion between the conductive substrate 11 and the photosensitive layer 14 can be improved.
For the intermediate layer 15, a resin layer or an alumite layer made of various resin materials is used.

  The resin material constituting the resin layer includes polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicone resin, polyvinyl butyral resin, and polyamide. Examples thereof include resins such as resins, and copolymer resins containing two or more of the repeating units constituting these resins. Moreover, casein, gelatin, polyvinyl alcohol, ethyl cellulose, and the like are also included. Among these resins, it is preferable to use a polyamide resin, and it is particularly preferable to use an alcohol-soluble nylon resin. Preferred alcohol-soluble nylon resins include, for example, so-called copolymer nylon obtained by copolymerizing 6-nylon, 6,6-nylon, 6,10-nylon, 11-nylon, 2-nylon and 12-nylon, and N Examples thereof include resins obtained by chemically modifying nylon such as -alkoxymethyl-modified nylon and N-alkoxyethyl-modified nylon.

The intermediate layer 15 may contain metal oxide particles. By containing these particles in the intermediate layer 15, the volume resistance value of the intermediate layer 15 can be adjusted, so that the effect of preventing charge injection from the conductive substrate 11 to the photosensitive layer 14 can be enhanced. In addition, the electrical characteristics of the photoreceptor can be maintained under various environments. The particle diameter is preferably in the range of 0.02 to 0.5 μm.
Examples of the metal oxide particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide particles.

  The intermediate layer 15 is formed by, for example, preparing the intermediate layer coating solution by dissolving or dispersing the above-described resin in a suitable solvent, and applying the coating solution to the surface of the conductive substrate 11. When the intermediate layer 15 contains the above-described metal oxide particles or the like, for example, these particles are dispersed in a resin solution obtained by dissolving the above-described resin in an appropriate solvent to form an intermediate layer coating solution. Prepare. Next, the intermediate layer 15 can be formed by applying this coating solution to the surface of the conductive substrate 11.

Water, various organic solvents, or a mixed solvent thereof is used as the solvent for the coating solution for the intermediate layer. For example, a single solvent such as water, methanol, ethanol or butanol, or water and alcohols, two or more alcohols, acetone or dioxolane and alcohols, chlorinated solvents such as dichloroethane, chloroform or trichloroethane and alcohols, etc. A mixed solvent is used. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.
As a method for dispersing the aforementioned particles in the resin solution, a general method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, a paint shaker, or the like can be used.

  In the intermediate layer coating solution, the ratio C / D between the total weight C of the resin and the metal oxide and the weight D of the solvent used in the intermediate layer coating solution is 1/99 to 40/60. The ratio is preferably 2/98 to 30/70. Further, the ratio E / F between the weight E of the resin and the weight F of the metal oxide is preferably 90/10 to 1/99, more preferably 70/30 to 5/95.

  Examples of the coating method of the intermediate layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these, the dip coating method is relatively simple and excellent in terms of productivity and cost, as described above, and is often used when the intermediate layer 16 is formed.

  The thickness of the intermediate layer 15 is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.05 μm or more and 10 μm or less. If the thickness of the intermediate layer 16 is less than 0.01 μm, it will be difficult to function as the intermediate layer 15 substantially, and it will be difficult to cover the defects of the conductive substrate 11 and obtain uniform surface properties. As a result, it is difficult to prevent the injection of charges from the conductive substrate 11 to the photosensitive layer 14, and the chargeability of the photosensitive layer 14 may be deteriorated. When the thickness of the intermediate layer 15 is formed by dip coating, it is difficult to form the intermediate layer 15 and the photosensitive layer 14 can be uniformly formed on the intermediate layer 15. This is not preferable because the sensitivity of the photoconductor may be lowered.

(Photoconductor manufacturing method)
In the production of the photoreceptor, it is preferable that a drying step is included in each formation of the charge generation layer 12, the charge transport layer 13, the intermediate layer 15, and the like. The drying temperature of the photoreceptor is suitably about 50 ° C. to about 140 ° C., and particularly preferably about 80 ° C. to about 130 ° C. When the drying temperature of the photoreceptor is less than about 50 ° C., the drying time is prolonged, or the solvent is not sufficiently evaporated and may remain in the photosensitive layer. If the drying temperature exceeds about 140 ° C., the electrical characteristics during repeated use deteriorate, and the image obtained using the photoreceptor may deteriorate, which is not preferable.

(Image forming device)
The image forming apparatus of the present invention includes at least the above-described photoreceptor according to the present invention, a toner having an average circularity in the range of 0.95 to 0.98, and 0.13 to 0.25 N on the photoreceptor. Other configurations are not limited as long as the cleaning unit has a contact member that contacts with a contact pressure in the range of / cm, and any known configuration can be employed.

  FIG. 4 is a layout side view showing a simplified configuration of one embodiment of the image forming apparatus of the present invention. An image forming apparatus 30 shown in FIG. 4 is a laser printer on which the photoreceptor 1 is mounted. Hereinafter, the configuration of the laser printer 30 and the image forming operation will be described with reference to FIG. The laser printer 30 illustrated in FIG. 4 is merely an example of the image forming apparatus of the present invention, and the image forming apparatus of the present invention is not limited by the following description.

A laser printer 30 as an image forming apparatus includes a photosensitive member 1, a semiconductor laser 31, a rotary polygon mirror 32, an imaging lens 34, a mirror 35, a corona charger 36 as a charging unit, a developing unit 37 as a developing unit, and transfer paper. A cassette 38, a paper feed roller 39, a registration roller 40, a transfer charger 41 as a transfer means, a separation charger 42, a conveyor belt 43, a fixing device 44, a paper discharge tray 45, and a cleaner 46 as a cleaning means. Is done.
The semiconductor laser 31, the rotary polygon mirror 32, the imaging lens 34, and the mirror 35 constitute an exposure unit 49. A light emitting diode may be used in place of the semiconductor laser.

  The photoreceptor 1 is mounted on the laser printer 30 so as to be rotatable in the direction of an arrow 47 by a driving unit (not shown). The laser beam 33 emitted from the semiconductor laser 31 is repeatedly scanned in the longitudinal direction (main scanning direction) with respect to the surface of the photosensitive member 1 by the rotary polygon mirror 32. The imaging lens 34 has f-θ characteristics, and the laser beam 33 is reflected by the mirror 35 to form an image on the surface of the photosensitive member 1 for exposure. By scanning the laser beam 33 as described above to form an image while rotating the photoconductor 1, an electrostatic latent image corresponding to image information is formed on the surface of the photoconductor 1.

  A corona charger 36 that is a non-contact charging means is provided upstream of the image forming point of the laser beam 33 in the rotation direction of the photosensitive member 1 and uniformly charges the surface of the photosensitive member 1. Therefore, the surface of the photosensitive member 1 that is uniformly charged with the laser beam 33 is exposed, and a difference occurs between the charge amount of the part exposed by the laser beam 33 and the charge amount of the part that is not exposed. Electrostatic latent image is formed.

  The developing device 37 is provided on the downstream side in the rotation direction of the photosensitive member 1 with respect to the image forming point of the laser beam 33, supplies toner to the electrostatic latent image formed on the surface of the photosensitive member 1, and converts the electrostatic latent image into toner. Develop as an image. Details of the toner that can be used in the image forming apparatus of the present invention will be described below.

  The transfer paper 48 accommodated in the transfer paper cassette 38 is taken out one by one by the paper feed roller 39 and is given to the transfer charger 41 by the registration roller 40 in synchronism with the exposure of the photoreceptor 1. The toner image is transferred onto the transfer paper 48 by the transfer charger 41. A separation charger 42 provided in the vicinity of the transfer charger 41 discharges the transfer paper onto which the toner image has been transferred and separates it from the photoreceptor 1. The transfer paper 48 separated from the photoreceptor 1 is conveyed to the fixing device 44 by the conveying belt 43, and the toner image is fixed by the fixing device 44. The transfer paper 48 on which the image is formed in this manner is discharged toward the paper discharge tray 45.

After the transfer paper 48 is separated by the separation charger 42, the photoreceptor 1 that continues to rotate further removes foreign matters such as toner and paper dust remaining on the surface thereof by the cleaner 46.
The cleaner 46 includes at least an abutting member, and the abutting member abuts on the photosensitive member with an abutting pressure of 0.13 to 0.25 N / cm. The contact member is, for example, a cleaning blade or a cleaning brush, and is installed in the reverse rotation (counter) direction or the forward rotation (leading) direction (preferably the reverse rotation direction) with respect to the photoreceptor. The shape of the cleaning blade is not particularly limited, and may be various arbitrary shapes as long as it can be used for an electrophotographic photoreceptor (organic photoreceptor), for example, a plate shape. The thickness of the blade is, for example, 0.5 to 5 mm, preferably 1.5 to 3 mm. The blade can be made of various materials as long as it can be used for an electrophotographic photoreceptor (organic photoreceptor), such as a rubber elastic material, a foamed resin, preferably a rubber elastic material (eg, NBR), more preferably urethane. Made of rubber. The hardness of the blade is, for example, 50 to 90 in JIS-A hardness, and preferably 60 to 80. The rebound resilience (%) is, for example, 30 to 70, preferably 40 to 60. When the contact member is made of a rubber elastic material, the contact member may be attached to an end of a support such as iron or aluminum.

The contact pressure of the contact member on the surface of the photoreceptor can be measured, for example, as follows.
Two sheets of PET (polyethylene terephthalate) film (trade name: Mylar, manufactured by Teijin DuPont Films, Inc.) formed into a rectangular shape having a length of 300 mm and a width of 10 mm are stacked between the photoconductor and the cleaning blade. Pinch. Between the two rectangular PET films, one end in the longitudinal direction of the same PET film F2 formed in the shape of a strip having a length of 300 mm and a width of 20 mm is sandwiched, and a tension gauge G (product) is placed on the other end. Name: 2N, manufactured by Tech Jam Co., Ltd.). At this time, the two rectangular PET films and the photoreceptor are fixed to such an extent that they do not move when a force is applied to the strip-shaped PET film F2. A force is applied in the tangential direction of the photoreceptor and the cleaning blade to pull the strip-shaped PET film, and the value indicated by the tension gauge G is measured when the strip-shaped PET film slides between the two rectangular PET films.
The cleaner 46 may have a function of collecting the removed toner in a collection container.

  The surface of the photoreceptor 1 whose surface has been cleaned is neutralized by a neutralizer (not shown) (for example, a neutralization lamp) provided together with the cleaner 46, and is further rotated, and a series of image forming operations starting from the charging of the photoreceptor 1 are repeated. It is.

The image forming apparatus of the present invention can also employ a configuration in which a plurality of photosensitive members are provided so that a plurality of different toners can be used to form an overlapping image. This configuration is called a tandem system.
In the above description, the laser printer has been described as an example. However, the image forming apparatus of the present invention may be various printers, copiers, facsimiles, multi-function machines, etc. using an electrophotographic process regardless of monochrome or color.

(toner)
The toner usable in the present invention is colored particles containing at least a binder resin and a colorant, and has an average circularity in the range of 0.95 or more and 0.98 or less.
The average circularity can be measured by, for example, a flow type particle image analyzer FTIA-3000 (manufactured by Sysmex Corporation, measurement conditions: high magnification imaging unit, HPF measurement mode).

  Any binder resin that can be used for toners can be used. For example, addition polymerization resins such as styrene resin, styrene-acrylic resin, styrene-butadiene resin, and acrylic resin, polyester resin, polycarbonate resin, polyamide It may be a condensation polymerization type resin such as a resin, a polysulfonate resin and a polyethylene resin, or an epoxy resin. Among these, a polyester resin is preferable because the transparency of the resin is high and a clear color can be secured as a toner.

  The polyester resin is obtained, for example, by condensation polymerization of alcohol and carboxylic acid. Examples of the alcohol include diols such as polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol and 1,4-butenediol, Etherified bisphenols such as 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A, which are saturated or unsaturated with 3 to 22 carbon atoms. Examples thereof include a divalent alcohol simple substance substituted with a saturated hydrocarbon group and other divalent alcohol simple substance.

Examples of the carboxylic acid include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, Divalent organic acid monomers in which these are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, diacids of these acid anhydrides, lower alkyl esters and linolenic acid, and other divalents The organic acid monomer can be mentioned.
A preferred combination of the alcohol and carboxylic acid is 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, and a mixture of isophthalic acid and terephthalic acid.

The polyester resin may be a resin derived from a trifunctional or higher polyfunctional monomer as well as the divalent monomer. Examples of the trifunctional or higher polyfunctional monomer include glycerol and the like for alcohol, and trimellitic acid and the like for the carboxylic acid.
The styrene-acrylic resin can be obtained by polymerizing one or more monomers selected from, for example, styrenes, acrylic acids, methacrylic acids and derivatives thereof. Examples of monomers that can be used include styrenes such as styrene, α-ethylstyrene, vinyltoluene, and chlorostyrene.

  Acrylic acids and their derivatives include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, n-tetradecyl acrylate, n-hexadecyl acrylate, acrylic Acrylic acid esters such as lauryl acid, cyclohexyl acrylate, diethylaminoethyl acrylate and dimethylaminoethyl acrylate are listed.

  Methacrylic acid and its derivatives include methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, methacrylic acid. And methacrylic acid esters such as dodecyl acid, lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, and stearyl methacrylate. It is done.

  In addition to the above-mentioned monomers, a small amount of other monomers such as acrylonitrile, 2-vinylpyridine, 4-vinylpyridine, vinylcarbazole, vinylmethylether, butadiene, isoprene, and anhydrous maleate, as long as the effects of the styrene-acrylic resin are not impaired. Acid, maleic acid, maleic acid monoesters, maleic acid diesters, vinyl acetate and the like may be used.

  As a crosslinking agent used for polymerization of a styrene-acrylic resin, there are bifunctional and polyfunctional crosslinking agents. Examples of the bifunctional crosslinking agent include divinylbenzene, bis (4-acryloxypolyethoxyphenyl) propane, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5- Pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 200, # 400 and # 600 diacrylate , Dipropylene glycol diacrylate, polypropylene glycol diacrylate, polyester diacrylate (manufactured by MANDA Nippon Kayaku) and the like. In the cross-linking agent, the acrylate component may be replaced with a methacrylate component.

  Polyfunctional crosslinkers include pentaerythritol triacrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate and its methacrylate, 2,2-bis (4-methacryloxypolyethoxy) Phenyl) propane, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, and diaryl chlorendate.

  Any colorant that can be used for toner can be used. As the black colorant, for example, carbon black, aniline black, furnace black, lamp black and the like can be used. Examples of cyan colorants include phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue. As the magenta colorant, for example, rhodamine 6G lake, dimethylquinacridone, watch length red, rose bengal, rhodamine B, alizarin lake and the like can be used. As the yellow colorant, for example, chrome yellow, benzidine yellow, hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used.

  The toner may contain a charge control agent, a release agent, and other additives.

  For example, a toner is mixed with a binder resin in an amount of 20% by weight or less, and, if desired, a charge control agent, a release agent, and other additives are added to the resulting mixture, followed by melting, kneading, and cooling. It can be obtained by adjusting the circularity by applying heat treatment or mechanical treatment after each step of pulverization and classification. The circularity is preferably adjusted by heat treatment because it is relatively easy. The heat treatment is performed by raising the temperature above the softening point of the binder resin used for the toner.

Examples of the present invention will be described below, but the present invention is not limited to the following description.
First, an example of producing a photoreceptor in which a photosensitive layer is formed under various conditions on an aluminum cylindrical support having a diameter of 30 mm and a length of 340 mm will be described.
[Photosensitive body preparation example 1]

  Dispersing 3 g of titanium oxide (TTO-MI-1; manufactured by Ishihara Sangyo), 3 g of alcohol-soluble nylon resin (CM-8000; manufactured by Toray), 60 g of methanol, and 40 g of 1,3-dioxolane with a paint shaker for 10 hours. An undercoat layer coating solution was prepared. The prepared undercoat layer coating solution was formed by dip coating on an aluminum cylindrical support having a diameter of 30 mm and a length of 340 mm so as to have a film thickness of 1.0 μm, thereby forming an undercoat layer. .

  Next, 10 g of butyral resin (ESREC BM-2; manufactured by Sekisui Chemical Co., Ltd.), 1400 g of 1,3-dioxolane, titanyl phthalocyanine represented by the structural formula (A-1) (for example, the method described in Japanese Patent No. 3567422) The charge generation layer coating solution was prepared by dispersing 15 g by a ball mill for 72 hours. The charge generation layer was formed by depositing the coating solution on the aluminum cylindrical support provided with the undercoat layer so as to have a film thickness of 0.3 μm by a dip coating method.

Next, 1.8 g of a polycarbonate resin (PCZ-400; manufactured by Mitsubishi Gas Chemical) represented by the following structural formula (B) and 1.8 g of silica (TS-610; manufactured by Cabot Specialty Chemicals) were added to 32.4 g of tetrahydrofuran. Mixed. The obtained mixture was subjected to a dispersion treatment with a ball mill for 7 hours using ZrO ₂ beads (φ3 mm) as a medium to prepare a primary dispersion coating solution for a charge transport layer. At this stage, silica (filler particles) are uniformly dispersed, and the dispersion state corresponding to the primary particle diameter (about 17 nm) is maintained. A light scattering particle size distribution measuring device (Microtrac UPA-150; Nikkiso) ) To confirm.

（式中、Ｒ₅〜Ｒ₁₂は水素原子、ハロゲン原子、又は置換若しくは末置換の脂肪族基若しくは炭素環基を表し、Ｚは置換又は未置換の炭素環又は複素環を形成するのに必要な原子群を表し、ｎは１０〜１０００の数を表す。

(Wherein R _{5 to} R ₁₂ represent a hydrogen atom, a halogen atom, or a substituted or terminally substituted aliphatic group or carbocyclic group, and Z is necessary to form a substituted or unsubstituted carbocyclic or heterocyclic ring. N represents a number of 10 to 1000.

  Next, 100 g of a butadiene compound (Takasago Fragrance Co., Ltd.) represented by the following structural formula (I) as a charge transport material, 1 g of a polycarbonate resin (PCZ-400), 5 g of an antioxidant (K-NOX BHT; manufactured by Degussa) Was dissolved in 984 g of tetrahydrofuran. To this solution, 3.6 g of the primary dispersion coating liquid for charge transport layer was mixed and stirred for 15 hours to prepare a secondary dispersion coating liquid for charge transport layer. This coating solution was applied onto the above-described charge generation layer by a dip coating method and dried at 130 ° C. for 1 hour to form a charge transport layer having a layer thickness of 25 μm, thereby producing a photoreceptor according to the present invention.

(Photosensitive member production example 2)
After forming the charge generation layer in the same manner as in Production Example 1, 0.62 g each of two types of polycarbonate resins PCZ-400 and PCZ-800 having the same structural formula and different weight average molecular weights and silica (TS-610) 1 A primary dispersion coating solution for a charge transport layer was prepared by mixing .25 g with 22.5 g of tetrahydrofuran and dispersing the mixture with a ball mill for 7 hours. Next, 100 g of the butadiene compound represented by the structural formula (I) as a charge transport material, 69.9 g of each of the polycarbonate resins PCZ-400 and PCZ-800, and 5 g of an antioxidant (K-NOX BHT) are added to tetrahydrofuran. The mixture was dissolved in 984 g. A photoconductor according to the present invention was produced in the same manner as in Production Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Photoconductor Preparation Example 3)
After forming the charge generation layer in the same manner as in Production Example 1, 2.0 g and 1.1 g of two types of polycarbonate resins PCZ-400 and PCZ-800 and 3.1 g of silica (TS-610) were added to 55.9 g of tetrahydrofuran. Then, the mixture was dispersed in a ball mill for 7 hours to prepare a primary dispersion coating solution for a charge transport layer. Next, 100 g of the butadiene compound represented by the structural formula (I) as a charge transport material, 88.4 g and 48.6 g of the polycarbonate resins PCZ-400 and PCZ-800, respectively, and an antioxidant (K-NOX BHT). 5 g was mixed with 992 g of tetrahydrofuran and dissolved. A photoconductor according to the present invention was produced in the same manner as in Production Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Photosensitive member production example 4)
After forming the charge generation layer in the same manner as in Production Example 1, 4.66 g of polycarbonate resin (PCZ-400) and 4.65 g of silica (TS-610) were mixed in 83.7 g of tetrahydrofuran and dispersed for 7 hours in a ball mill. The primary dispersion coating liquid for charge transport layers was prepared by processing. Next, 100 g of a butadiene compound represented by the above structural formula (I), 135.4 g of a polycarbonate resin (PCZ-400) and 5 g of an antioxidant (K-NOX BHT) are mixed and dissolved in 998 g of tetrahydrofuran as a charge transport material. did. A photoreceptor according to the present invention was produced in the same manner as in Production Example 1 except that the obtained solution was used as the secondary dispersion coating solution for the charge transport layer.

(Photosensitive member preparation example 5)
A photoconductor according to the present invention was produced with the same content as in Production Example 3 except that the type of filler particles was changed to alumina (Sumicorundum AA-04; manufactured by Sumitomo Chemical Co., Ltd.).

(Photoconductor Preparation Example 6)
A photoconductor according to the present invention was produced with the same content as in Production Example 3 except that the type of filler particles was changed to silica (X-24-9163A; manufactured by Shin-Etsu Chemical Co., Ltd.).

(Photoconductor Preparation Example 7)
A photoconductor according to the present invention was produced with the same content as in Production Example 3 except that the type of filler particles was changed to silica (SO-E5; manufactured by Admatex).

(Photosensitive member production example 8)
Other than changing the charge transport material to 90 g of a triarylamine compound (manufactured by Nippon Distilled Industries Co., Ltd.) represented by the following structural formula (II) and 10 g of a butadiene compound (manufactured by Takasago Fragrance Co., Ltd.) represented by the following structural formula (III). Produced a photoreceptor according to the present invention in the same manner as in Production Example 3.

(Photoreceptor Production Example 9)
A photoconductor was prepared in the same manner as in Preparation Example 3, except that the charge transport material was changed to 100 g of the triarylamine compound represented by the above structural formula (II) (manufactured by Nippon Distilled Industries).

(Photoconductor Preparation Example 10)
A photoconductor according to the present invention was produced in the same manner as in Production Example 3, except that the charge transport material was changed to 100 g of a styryl compound (Hodogaya Chemical Co., Ltd.) represented by the following structural formula (IV).

(Photoreceptor Production Example 11)
A photoconductor according to the present invention was produced in the same manner as in Production Example 3 except that the antioxidant was not added to the primary dispersion coating solution for the charge transport layer.

(Photoconductor Preparation Example 12)
A primary dispersion coating solution for a charge transport layer was prepared by mixing 3.1 g of polycarbonate resin (PCZ-800) and 3.1 g of silica (TS-610) with 55.8 g of tetrahydrofuran and dispersing the mixture for 7 hours with a paint shaker. Prepared. Thereafter, when the particle size distribution of silica in the coating solution was measured, it was confirmed that a coarse aggregate that was clearly larger than the primary particle size was formed. A photoconductor was produced in the same manner as in Production Example 3 except that this primary dispersion coating solution was used.

(Photoconductor Preparation Example 13)
A polycarbonate resin (PCZ-800) (0.12 g) and silica (TS-610) (0.12 g) were mixed with tetrahydrofuran (1.66 g) and dispersed in a ball mill for 7 hours to prepare a primary dispersion coating solution for a charge transport layer. . Next, 100 g of a butadiene compound (manufactured by Takasago Fragrance Co., Ltd.) represented by the above structural formula (I) as a charge transport material, 69.9 g of each of polycarbonate resins PCZ-400 and PCZ-800, an antioxidant (K-NOX). 5 g of BHT) was mixed with 980 g of tetrahydrofuran and dissolved. A photoconductor was produced in the same manner as in Production Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Photoconductor Preparation Example 14)
Polycarbonate resins PCZ-400 and PCZ-800, 2.5 g each, silica (TS-610) 5.0 g mixed with 90 g tetrahydrofuran, and dispersed in a ball mill for 5 hours to be a primary dispersion coating solution for a charge transport layer. Adjusted. Next, 100 g of a butadiene-based compound (manufactured by Takasago Fragrance Co., Ltd.) represented by the above structural formula (I) as a charge transport material, 67.5 g each of polycarbonate resins PCZ-400 and PCZ-800, and an antioxidant (K-NOX). 5 g of BHT was mixed with 1005.6 g of tetrahydrofuran and dissolved. A photoconductor was produced in the same manner as in Production Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Photoreceptor Preparation Example 15)
After preparing the primary dispersion coating liquid for the charge transport layer, 100 g of a butadiene compound (manufactured by Takasago Fragrance Co., Ltd.) represented by the above structural formula (I) as a charge transport material, polycarbonate resin (PCZ-400) and polytetrafluoroethylene ( PTFE: Lubron L-2 (manufactured by Nisshinsei) was mixed with 123.3 g and 13.7 g, respectively, and antioxidant (K-NOX BHT) 5 g was mixed with tetrahydrofuran 984 g. A photoconductor was produced in the same manner as in Production Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Photoreceptor Production Example 16)
As a charge transport material, 100 g of a butadiene compound represented by the above structural formula (I) (manufactured by Takasago Fragrance Co., Ltd.), 63 g of each of polycarbonate resins PCZ-400 and PCZ-800, and 5 g of an antioxidant (K-NOX BHT) in tetrahydrofuran. The mixture was dissolved in 980 g. A photoconductor was produced in the same manner as in Production Example 1 except that the obtained solution was used as a coating solution for forming a charge transport layer.

Types of filler particles, compositions, average filler particle distance a (nm), average filler particle diameter b (nm), density of filler particles df (g / cm ³ ), outermost surface layer Table 1 shows the average density dm (g / cm ³ ), the Rf value (df × b ³ ) / (dm × a ³ ), and the content (% by weight) in the charge transport layer. In addition, the measuring method of a, b, df, and dm is described below. Table 1 shows the types of charge transport materials (CTM) and antioxidants.

[Measuring method of a, b, df and dm]
In Production Examples 1 to 11 and 13 to 15 in which a uniform dispersed state could be confirmed, a was obtained as a calculated value from the amount of filler particles added and the volume of the coating film as a medium.
Since b is a commercially available filler particle, it quoted from the catalog value.
Since df is a commercially available filler particle, the catalog value was quoted.
The dm was obtained by measuring and measuring the volume and weight of the coating film.

(Embodiment of the image device of the present invention)
Each photoconductor of Production Examples 1, 3, 4 and 11 is mounted on a color digital multifunction machine MX-4500N (manufactured by Sharp) modified so that the developing device can be replaced with a surface potential measuring device for testing, and is defined by ISO19752. An image of 100,000 character test charts was formed. Sensitivity, printing durability and images were evaluated by the following methods.
In the evaluation, the toner having different circularity and the contact pressure (blade linear pressure) of the cleaning blade to the photosensitive member were combined.

[Production of toner]
85 parts of a polyester resin (trade name: Toughton, manufactured by Kao Corporation, glass transition temperature 70 ° C., softening temperature 130 ° C.) as a binder resin, and copper phthalocyanine (CI Pigment Blue 15: 3) as a colorant 5 Parts, a release agent (carnauba wax melting point 82 ° C.) 8 parts, and a charge control agent (Bontron E84, Orient Chemical Industry Co., Ltd.) 2 parts were mixed and dispersed in a Henschel mixer for 3 minutes to obtain a raw material. The obtained raw material was melt-kneaded and dispersed using a twin-screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.) to produce a toner having a center particle size of 6.7 μm by a normal pulverization method. A surface modification treatment with hot air was performed to obtain a toner having an average circularity of 0.94, 0.95, 0.98 or 0.99. The heat treatment conditions were 250 ° C. for 2 minutes, 250 ° C. for 3 minutes, 250 ° C. for 4 minutes, and 250 ° C. for 5 minutes for average circularity of 0.94, 0.95, 0.98 and 0.99, respectively. It was. The average circularity was measured using FPIA-3000 (manufactured by Sysmex).

[Cleaning means]
As the cleaning blade as a cleaning means, the one (2 mm thick urethane rubber blade) provided in the color digital multifunction peripheral MX-4500N (manufactured by Sharp) was used. The blade contact pressure was adjusted by changing the blade biting angle. The contact pressure was measured using a tension gauge G (trade name: 2N, manufactured by Tech Jam Co., Ltd.).

Next, a method for evaluating each performance will be described.
[Sensitivity (electric property) evaluation]
The developing device was removed from the copying machine, and a surface potential meter (model 344; manufactured by Trek Japan) was attached instead. Using this copier, the surface potential of the photoconductor when not exposed to laser light in a normal temperature / normal humidity (N / N) environment at a temperature of 25 ° C. and a relative humidity of 50% is shown. Adjusted to -650V. In this state, exposure is performed with a laser beam (0.4 μJ / cm ² ), the initial surface potential of the photoconductor is defined as exposure potential VL1 (−V), and the surface potential after forming 100,000 sheets of images using the test chart is determined. It measured as exposure potential VL2 (-V). The sensitivity was evaluated from the obtained VL according to the following criteria. Note that the smaller the absolute value of the exposure potential VL, the higher the sensitivity of the photoconductor.

<Criteria>
○: | VL | <90 (V)
Δ: 90 (V) ≦ | VL | <130 (V)
×: 130 (V) ≦ | VL |

[Cleanability evaluation]
By using the above-described character test chart and A4 size recording paper, and after the initial image formation (≈0k) and after 100,000 sheets of image formation, the formed image is visually observed, and the sharpness and sensitivity of the boundary between two black and white colors are detected. The presence or absence of black streaks due to toner leakage in the direction of body rotation was tested. Further, the fogging amount Wk was obtained by a measuring device to be described later, and the cleaning property was evaluated. The fogging amount Wk of the formed image was determined by measuring the reflection density using Z-Σ90 COLOR MEASURING SYSTEM (manufactured by Nippon Denshoku Industries Co., Ltd.). Specifically, first, the reflection average density Wr of the recording paper before image formation was measured. Next, an image was formed on the recording paper, and after the image formation, the reflection density of each portion of the white background portion of the recording paper was measured. The reflection density Ws of the portion judged to be the most fogged, that is, the portion with the highest density while being a white background portion, was measured. Wk obtained from Wr and Ws by the formula {100 × (Wr−Ws) / Wr} was defined as the fogging amount. The cleaning properties were evaluated from the obtained Wk according to the following criteria.

○: Good. There is no black streak with good clarity. Fog amount Wk is less than 5%.
Δ: No practical problem. The sharpness is at a level that causes no problem in practice, and the length of black streaks is 2.0 mm or less and 5 or less. Fog amount Wk is 5% or more and less than 10%.
X: Not practical. There is a practical problem with sharpness. Exceeding the above Δ range of black lines. Fog amount Wk is 10% or more.

[Image degradation evaluation]
Density unevenness was evaluated according to the following criteria by outputting a halftone image in which the degradation level of the image quality after the printing durability test was 80 tones corresponding to 255 tones by modulating the pulse width of the semiconductor laser. The greater the density unevenness, the more the image is degraded.

○: There is no density unevenness in the image visually. Good picture.
Δ: Density unevenness in image visually. There is no problem in actual use.
X: Density unevenness in image visually. A level that causes problems in actual use.

[Comprehensive evaluation]
Based on the determination results of the above three items, the determination is made as follows.
◎: All three items ○
○: One or more items with only ○ or △ out of 3 items △
×: At least one of the three items ×

  The evaluation results are shown in Tables 3 and 4.

From Tables 2 and 3, a photoreceptor containing filler particles in the outermost surface layer so as to satisfy 1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² In an image forming apparatus, a dry toner having a circularity of 0.95 or more and 0.98 or less and a cleaning unit having a contact member contact pressure of 0.13 to 0.25 N / cm. It was confirmed that there was no problem in actual use in sensitivity stability, cleaning performance and image degradation evaluation at the time of actual shooting.
On the other hand, even if the filler particles in the outermost surface layer satisfy the range of 1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ^−2. Image formation in combination with dry toner having a circularity outside the range of 0.95 to 0.98 and / or cleaning means in which the contact pressure of the contact member is outside the range of 0.13 to 0.25 N / cm In the apparatus, there were problems in practical use in terms of cleaning properties or image deterioration.

1 is a schematic partial cross-sectional view of an electrophotographic photosensitive member that can be used in the present invention. It is a graph which shows the difference of the aggregated particle diameter by the dispersion conditions of a filler particle. 1 is a schematic partial cross-sectional view of an electrophotographic photosensitive member that can be used in the present invention. 1 is a schematic side view of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Electrophotographic photoreceptor 11 Conductive substrate 12 Charge generation layer 13 Charge transport layer 14 Photosensitive layer 15 Intermediate layer 30 Laser printer (image forming apparatus)
DESCRIPTION OF SYMBOLS 31 Semiconductor laser 32 Rotating polygon mirror 34 Imaging lens 35 Mirror 36 Corona charger 37 Developing device 38 Transfer paper cassette 39 Paper feed roller 40 Registration roller 41 Transfer charger 42 Separation charger 43 Conveyor belt 44 Fixing device 45 Paper discharge tray 46 Cleaner 47 Arrow 48 Transfer paper 49 Exposure means

Claims (8)

An electrophotographic photosensitive member, a dry toner for developing and visualizing an electrostatic latent image formed on the electrophotographic photosensitive member, and the electrophotographic image after transferring an image visualized by the dry toner to a transfer material At least cleaning means for removing toner remaining on the photoreceptor,
The outermost surface layer of the electrophotographic photosensitive member contains filler particles, and the filler particles in the outermost surface layer have the following formula (1):
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² (1)
(In the formula, a means the average distance between filler particles (nm), b means the average filler particle diameter (nm), df means the density of filler particles (g / cm ³ ), and dm is the maximum. It is a uniform dispersion state that satisfies the average density (g / cm ³ ) of the solid content of the surface layer,
The dry toner has an average circularity ranging from 0.95 to 0.98;
The cleaning means has a contact member that contacts the electrophotographic photosensitive member, and the contact pressure of the contact member with respect to the electrophotographic photosensitive member is in the range of 0.13 to 0.25 N / cm. An image forming apparatus. The image forming apparatus according to claim 1, wherein the filler particles are made of silicon oxide. The image forming apparatus according to claim 1, wherein the filler particles have an average particle diameter of 100 nm or less. The electrophotographic photoreceptor is represented by the following general formula (1) as a charge transport material:

(In the formula, R ₁ and R ₂ each represents an alkyl group having 1 to 4 carbon atoms which may be the same or different from each other, or R ₁ and R ₂ are bonded to each other to form a heterocyclic group containing a nitrogen atom. N may represent an integer of 1 to 4, Ar represents an aromatic ring group having a butadiene group)
The image forming apparatus according to claim 1, comprising an amine compound represented by the formula: The image forming apparatus according to claim 1, wherein the outermost surface layer further contains an antioxidant. The image forming apparatus according to claim 1, wherein the dry toner is made of a polyester resin. The image forming apparatus according to claim 1, wherein the dry toner is surface-modified by heat treatment. The image forming apparatus according to claim 1, wherein the contact member is made of urethane rubber.

Images