JP2005300741A - Electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process cartridge which strikes a balance between downsizing and a long service life even when the ends of a developing member and an electrostatic charging member are in proximity with each other, and an electrophotographic device. <P>SOLUTION: In the electrophotographic photoreceptor having a conductive support and a photosensitive layer and a color electrophotographic process having an electrostatic charging means in contact with the electrophotographic photoreceptor and a developing means, the spacing between the end position of the electrostatic charging means and the end position of the developing means is within 8.0 mm and the surface layer of the electrophotographic photoreceptor contains a polyarylate having a specific structural unit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic apparatus that is an image forming apparatus using an electrophotographic system, such as a copying machine, a printer, and a FAX.

  For the sake of convenience, a description will be given of a charging process of a photosensitive member in an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, and an electrostatic recording apparatus.

  The image forming apparatus as described above includes a step of uniformly charging a chargeable member such as a photoconductor, a derivative, or a transfer material as an image carrier to a predetermined potential.

  Conventionally, corona charging in which corona discharge is performed by applying a high voltage of 5 to 10 KV to a charging wire of 60 μm to 100 μm has been widely used as the charging means.

  However, since the corona charging has various drawbacks such as ozone generation, contact charging has been proposed as an alternative.

  Contact charging is performed by pressing a charging member against the surface of the object to be charged and applying a voltage (such as a DC voltage or a superimposed voltage of a DC voltage and an AC voltage) to the charging member to obtain a predetermined polarity and potential on the surface of the object to be charged. It is to be charged.

  Such a contact-type charging device has advantages such as a low applied voltage and less ozone generation compared to a corona charging device.

  As a method for visualizing an electric latent image, a cascade development method, a magnetic brush development method, a pressure development method, and the like are known. Furthermore, there is also known a method in which a magnetic toner is used and a rotating developing sleeve containing a magnet is used as a toner carrier, and an electric field is formed between the sleeve and the photosensitive member to cause the magnetic toner to fly to the photosensitive member. It has been.

  Since the one-component development method does not require carrier particles such as glass beads and iron powder magnetic ferrite particles used in the two-component development method, the development device itself can be reduced in size and weight. Furthermore, since the two-component development method needs to keep the toner concentration in the developer constant, a device that detects the toner concentration and replenishes the necessary amount of toner is necessary, so that the developing device becomes large and heavy. . Since such a device is not required in the one-component development method, the developing device can be made small and light, which is preferable.

  In recent years, a contact one-component developing method has been proposed in which development is performed while pressing against the surface of a photoreceptor using a semiconductive developing roller or a developing roller having a dielectric layer on the surface. For example, Japan Hardcopy '89, 25-28, FUJITSU Sci. Tech. J. et al. , 28, 4, pp. 473-480 (December 1992), Japanese Patent Application Laid-Open No. 5-188756 and Japanese Patent Application Laid-Open No. 5-188752 describe techniques relating to one-component contact development.

  In the contact one-component development method, since the surface of the photoreceptor and the development electrode are very close to each other, there is an advantage that the edge effect of development can be reduced.

  However, when the contact one-component developing method is used, a configuration in which the surface of the photoreceptor is rubbed with toner and a toner carrier is essential, and in order to develop more toner on the photoreceptor than the surface of the toner carrier, the toner carrier Must be set faster than the peripheral speed of the photosensitive member. For this reason, there is a problem that the driving torque between the photosensitive member and the toner carrying member is increased, the surface of the photosensitive member is damaged and worn due to long-term use, and durability characteristics deteriorate.

On the other hand, the basic characteristics required for electrophotographic photoreceptors are that it can be charged to an appropriate potential in the dark, that there is little charge dissipation in the dark, and that the charge can be quickly dissipated by light irradiation. It is done.

  Conventionally, as a photoreceptor used in an electrophotographic apparatus, a photoconductive layer mainly composed of selenium or a selenium alloy is provided on a conductive support, and an inorganic photoconductive material such as zinc oxide or cadmium sulfide is contained in a binder. In general, those using an amorphous silicon-based material, etc. are known, but in recent years due to low cost, high degree of freedom in designing photoreceptors and non-polluting properties, etc. Organic photoconductors are becoming widely used.

  The organic photoconductive compound can freely select the photosensitive wavelength range of the electrophotographic photosensitive member depending on the compound. For example, in the case of an azo pigment, the following Patent Document 1 and Patent Document 2 show high sensitivity in the visible region. Compounds are disclosed, and Patent Documents 3 and 4 show compounds having sensitivity up to the infrared region. Among these materials, those showing sensitivity in the infrared region are used in LBP printers and LED printers that have made remarkable progress in recent years, and the demand frequency thereof is increasing. Electrophotographic photoreceptors using these organic photoconductive compounds are used as function-separated photoreceptors in which a charge transport layer and a charge generation layer are laminated in order to satisfy both electrical and mechanical characteristics. There are many cases. On the other hand, as a matter of course, the electrophotographic photosensitive member is required to have sensitivity, electrical characteristics, and optical characteristics according to the applied electrophotographic process. In particular, in the electrophotographic photoreceptor to be used repeatedly, the surface of the electrophotographic photoreceptor is directly subjected to electrical and mechanical external forces such as corona or direct charging, image exposure, toner development, transfer process and surface cleaning. , Durability against them is also required.

  Specifically, since electrical deterioration due to ozone and nitrogen oxides during charging, discharge during charging, and rubbing of the cleaning member may cause surface wear or scratches, mechanical and electrical deterioration may be prevented. Durability is required. The electrical deterioration is particularly a phenomenon in which carriers are accumulated in a portion irradiated with light and a potential difference is generated from a portion not irradiated with light, which occurs as a photo memory. In particular, organic photoreceptors, which are often materially soft unlike inorganic photoreceptors, are inferior in durability against mechanical deterioration, and improvement in durability is particularly desired. In addition, the surface which is an organic substance is easily contaminated by a substance such as an organic substance typified by toner or an oxide generated by discharge. Various attempts have been made to satisfy the durability characteristics required for the photoreceptor as described above.

  Resins that are often used for the surface layer and have good wear resistance and electrical properties include polycarbonates having a bisphenol A skeleton, polycarbonate Z, and polycarbonates copolymerized with bisphenol A skeleton, bisphenol Z, bisphenol C, and the like. Although attention has been paid to, the contact development method has a problem of deterioration of durability characteristics due to scratches or wear on the surface of the photoreceptor due to long-term use as described above.

Further, in recent years, a contact charging method in which a voltage is applied to the charging member arranged in contact as described above to charge the electrophotographic photosensitive member has become mainstream. This is a method of applying a charge by bringing a roller-shaped charging member made of conductive rubber or the like into contact with the electrophotographic photosensitive member, and the amount of ozone generated is significantly smaller than that of scorotron or the like. The scorotron has a merit that around 80% of the current flowing to the charger flows to the shield and is wasted, whereas direct charging has no waste and is very economical. However, since direct charging is due to discharge according to Paschen's law, it has the disadvantage that charging stability is very poor, causing slight discharge unevenness during charging, resulting in uneven charging potential, which is the normal development In this case, white stripes appear in the solid black image, and black stripes appear in the solid white image in the case of reversal development. As a countermeasure against this, a method has been adopted in which pre-exposure is performed on the upstream side of the nip portion between the charging member and the photosensitive member to eliminate minute discharge unevenness. A charging method has been devised (Japanese Patent Laid-Open No. 63-149668), and this method is currently mainstream. Although this charging system has improved the stability during charging, the amount of discharge on the surface of the electrophotographic photosensitive member is greatly increased due to the superposition of AC, and the electrophotographic photosensitive member is compared with DC charging with only DC voltage. The amount of shaving increases and the durability is inferior. Therefore, although DC charging is advantageous from the viewpoint of durability of the photoreceptor, the DC current increases the discharge current as the photosensitive layer becomes thinner. It has a disadvantage that it is further increased, and improvement in durability of the photoreceptor such as mechanical strength is desired.
JP-A-61-272754 JP 56-167759 A JP 57-19576 A Japanese Patent Laid-Open No. 61-228453

  However, recently, due to environmental issues and increased printer burden due to networking of computers, the demand for higher durability of cartridges is increasing, and cartridges using contact charging, contact development and organic photoreceptors are highly durable. The following problems were encountered when the system was changed.

  In the contact-type charging device using discharge in a minute gap, since the charging member contacts the organic photoreceptor surface, the influence of the discharge near the contact surface of the charging member acts strongly on the organic photoreceptor, The surface of the member to be charged is deteriorated and easily scraped.

  Further, when the thickness of the organic photoreceptor is not constant, when the charging member comes into contact with the portion, discharge concentrates on the portion, and local shaving occurs. These effects are particularly likely to occur at both ends of the charging member.

  In the case of contact charging, since the discharge is generated at a portion slightly away from the contact portion with the organic photoreceptor, the conventional charging member has both ends of the charging member when the discharge portion is viewed from the drum circumferential direction. Since the discharge area from the portion becomes wider with respect to the drum circumferential direction, the discharge time becomes longer than the other portions, so that the deterioration of the organic photoreceptor occurs earlier.

  In view of this, as disclosed in Japanese Patent Laid-Open No. 4-157383, there has been proposed one in which the resistance of the end of the charging member is increased to prevent leakage at the end of the charging member.

  However, in this case, there is a sufficient effect when the current value flowing through the charging member is low, but when the current value is increased as the speed of the printer is increased, a high resistance body close to insulation is formed only in the non-image area. However, if the one-step discharge current is only reduced, the discharge at the part where the discharge current is switched may become strong, the effect may be insufficient, or the resistance difference at the part where the discharge current is switched. Even if a device having a resistance slightly higher than that of the image area is created instead of a high-resistance element, the effect of suppressing discharge from the extreme end is reduced, and thus the effect becomes insufficient.

  In addition, as shown in JP-A-63-2087773 and JP-A-1-179959, there has been proposed a technique in which the end portion is tapered or rounded to weaken the electric field strength at the end portion.

  However, in this case as well, there is a sufficient effect when the current value flowing through the charging member is low. However, when the current value is increased as the printer speed increases, a taper shape or an R shape is added at the outermost portion. In some cases, the discharge suppressing effect may be insufficient.

  As another method, for example, there is a method of reducing the influence of the surface deterioration portion by increasing the drum film thickness. However, increasing the film thickness makes it easier to be affected by environmental fluctuations, reducing the image quality, When the upper film thickness is increased, unevenness in thickness is likely to occur, and thus there is a disadvantage that unevenness in image density occurs.

  For the contact-type development system, a toner layer is formed on the electrophotographic photosensitive member and the developing roller, and the electrophotographic photosensitive member is rotated while the electrophotographic photosensitive member and the developing roller are mutually rotated. In order to develop a larger amount of toner on the photosensitive member than on the surface of the toner carrier, the peripheral speed of the toner carrier is required. Must be set faster than the peripheral speed of the photoreceptor. For this reason, the structure is such that abrasion due to friction is likely to occur between the photosensitive member and the toner carrying member. In particular, there is a problem that driving stress is easily applied to the end portion, and wear of the electrophotographic photosensitive member is accelerated.

  Furthermore, in recent years, the size of each component in the apparatus has been minimized because of the miniaturization of the electrophotographic apparatus. For this reason, the end of the charging member and the end of the developing member inevitably come close to each other, and wear of the end of the electrophotographic photosensitive member is accelerated synergistically, which seriously affects the life of the cartridge. It is a factor.

  The present invention has been made to solve the above-described problems of the prior art, and the object is to achieve a sufficient life even when the end of the developing member and the charging member are close to each other. It is an object of the present invention to provide a process cartridge and an electrophotographic apparatus that are both compact and have a long life.

In order to achieve the above object, the present invention provides an electrophotographic photosensitive member having a conductive support and a photosensitive layer, and a color electrophotographic process having a charging unit and a developing unit in contact with the electrophotographic photosensitive member. The distance between the end position and the end position of the developing means is within 8.0 mm, and
The surface layer of the electrophotographic photoreceptor has the following formula (1) or (2)

（１）

(1)

  (Wherein R11 to R14 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.)

（２）

(2)

(Wherein R15 to R18 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.)
It contains polyarylate having a structural unit represented by

  It is an object of the present invention to provide a process cartridge and an electrophotographic apparatus that can achieve a sufficient life span in a configuration in which the end portions of the developing member and the charging member are close to each other, and achieve both downsizing and a long life.

Next, the general formula (1) used in the present invention will be described in detail.

（１）

(1)

(Wherein R11 to R14 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.)
In formula (1), examples of the alkyl group represented by R11 to R14 include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group include a phenyl group and a naphthyl group. Particularly preferable examples of R11 to R14 include a methyl group and an ethyl group, and two or more R11 to 14 are more preferably hydrogen atoms.

  Examples of the substituent that these groups may have include a halogen atom such as a fluorine atom, a chlorine atom and an iodine atom, an alkyl group such as a methyl group, an ethyl group and a propyl group, and an aryl group such as a phenyl group. Can be mentioned.

  Next, the general formula (2) used in the present invention will be described in detail.

（２）

(2)

(Wherein R15 to R18 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.)
In formula (2), examples of the alkyl group represented by R15 to R18 include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group include a phenyl group and a naphthyl group. Particularly preferred examples of R15 to R18 include a methyl group and an ethyl group, and two or more R15 to R18 are more preferably other than a hydrogen atom.

  Examples of the substituent that these groups may have include a halogen atom such as a fluorine atom, a chlorine atom and an iodine atom, an alkyl group such as a methyl group, an ethyl group and a propyl group, and an aryl group such as a phenyl group. Can be mentioned.

  Although the mechanism in the effect of the photoreceptor of the present invention has not been fully elucidated, these structures have crystallinity and bisphenol structure by having a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. This is thought to be because the structural rigidity is optimized in the charge transport layer, and it is speculated that this increases the scratch strength of the polymer chain.

  In addition, the polyarytes having the structural units (1) to (2) may be two or more kinds of structural units having a bisphenol structure other than the above or the above, even if they are homopolymers of the structures (1) to (2). Copolymerization of When copolymerizing with bisphenol structure other than the above, it is preferable that the content rate of the structural unit of said (1)-(2) is 5-95%. Two or more polyarylates may be mixed and used.

  In addition, the phthalic acid structure on the right side of the structural units (1) to (2) may be either tele / iso, but the ratio of the tele / iso mixture is 20/80 to 80/20. From the viewpoint of scratch strength and handling, it is more preferable.

  The molecular weight of the polyarylate resins of the above formulas (1) to (2) is preferably Mw = 20,000 to 200,000, and particularly preferably 50,000 to 150,000 in terms of scratch strength, productivity and the like.

  Specific examples of the structural units of the above formulas (1) to (2) are shown below. Moreover, the combination in a structure and mixing is not limited to a specific example.

（構成単位例１）

(Structural unit example 1)

（構成単位例２）

(Structural unit example 2)

（構成単位例３）

(Structural unit example 3)

（構成単位例４）

(Structural unit example 4)

（構成単位例５）

(Structural unit example 5)

（構成単位例６）

(Structural unit example 6)

  Among these structural unit examples, structural unit examples 1, 2, 3, and 4 are preferable, and structural unit examples 1 and 3 are particularly preferable.

  Examples of structural units of polyarylate used by copolymerizing or mixing with these structural units are shown below.

（構成単位例ａ−１）

(Structural unit example a-1)

（構成単位例ａ−２）

(Structural unit example a-2)

（構成単位例ａ−３）

(Structural unit example a-3)

（構成単位例ａ−４）

(Structural unit example a-4)

（構成単位例ａ−５）

(Structural unit example a-5)

（構成単位例ａ−６）

(Structural unit example a-6)

（構成単位例ａ−７）

(Structural unit example a-7)

（構成単位例ａ−８）

(Structural unit example a-8)

（構成単位例ａ−９）

(Structural unit example a-9)

（構成単位例ａ−１０）

(Structural unit example a-10)

  Among these structural unit examples, structural unit examples a-1, a-2, a-9, and a-10 are preferable as structural units of polyarylate to be copolymerized or mixed with the structural unit of the present invention. Unit examples a-1 and a-9 are particularly preferred.

  The polyarylate compound used in the present invention is synthesized by a conventional method. As an example, a synthesis example of a copolymer of structural unit example 3 / a-1 is shown below.

  A bisphenol monomer constituting the structural unit example 3 / a-1 (= 5/5) was added to and dissolved in a 10% aqueous sodium hydroxide solution. Further, trimethylbenzylammonium chloride was added as a polymerization catalyst and stirred. Separately, an equivalent mixture of terephthalic acid chloride / isophthalic acid chloride was dissolved in dichloromethane. This dichloromethane solution was added to the previously prepared aqueous sodium hydroxide solution with stirring to initiate polymerization.

  The polymerization was stirred for 3 hours while keeping the reaction temperature at 25 ° C. or lower. Thereafter, the reaction was terminated by adding acetic acid, and washing with water was repeated until the aqueous phase became neutral. After washing, the polymer was precipitated by dropwise addition to methanol with stirring. Furthermore, the polymer was vacuum-dried to obtain the compound of the present invention.

  Next, the compound of the present invention can be used by mixing with the polycarbonate represented by the general formula (3), and the productivity at the time of producing the photoreceptor, the stability of the solution, and the like are improved. The mixing ratio can be expressed by the above formulas (1) to (2) / general formula (3) = 5/95 to 95/5, and 50/50 to 95/5 in order to efficiently produce the effect. Is preferred.

  Although the molecular weight of General formula (3) is not specifically limited, Preferably it is Mv = 20000-80000. The specific example of the structural unit of General formula (3) is shown below. The structural unit may be a single unit or a copolymer of two or more types. Moreover, the combination in a structure and mixing is not limited to a specific example.

（３）

(3)

  (In the formula, X2 represents a carbon atom, a single bond (in this case, there is no R25 or R26), R21 to R24 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. , R25 and R26 are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, or R25 and R26, which are necessary to form a substituted or unsubstituted alkylidene group by bonding. Group.)

  Although the structural unit example of the polycarbonate shown by Formula (3) below is shown, it is not limited to these.

（構成単位例ｂ−１）

(Structural unit example b-1)

（構成単位例ｂ−２）

(Structural unit example b-2)

（構成単位例ｂ−３）

(Structural unit example b-3)

（構成単位例ｂ−４）

(Structural unit example b-4)

（構成単位例ｂ−５）

(Structural unit example b-5)

（構成単位例ｂ−６）

(Structural unit example b-6)

（構成単位例ｂ−７）

(Structural unit example b-7)

（構成単位例ｂ−８）

(Structural unit example b-8)

  Hereinafter, the structure of the electrophotographic photosensitive member used in the present invention will be described. The electrophotographic photoreceptor in the present invention has a photosensitive layer on a support. The photosensitive layer may be a single layer type containing the charge transport material and the charge generation material in the same layer, or may be a laminate type separated into the charge transport layer and the charge generation layer, but the laminate type is preferable in terms of electrophotographic characteristics. .

  The support to be used may be any one having conductivity, and examples thereof include metals such as aluminum and stainless steel, metals provided with a conductive layer, paper, plastics, etc., and examples of the shape include sheets and cylinders.

  When the image input such as LBP is laser light, a conductive layer may be provided for the purpose of preventing interference fringes due to scattering or covering the scratches on the substrate. This can be formed by dispersing conductive particles such as carbon black and metal particles in a binder resin. The thickness of the conductive layer is 5 to 40 μm, preferably 10 to 30 μm. In addition, interference fringe prevention can be performed by cutting a cylinder, anodizing, dry or wet blasting, and in that case, there is no need to provide a conductive layer.

  An intermediate layer having an adhesion function and a barrier function may be provided on the support or the conductive layer. Examples of the material for the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. These are dissolved in an appropriate solvent and applied. The thickness of the intermediate layer is 0.05 to 5 μm, preferably 0.3 to 1 μm. If the cylinder is directly anodized or a conductive film is formed by a sol-gel method, the intermediate layer may not be used.

  A charge generation layer is formed on the intermediate layer. Examples of the charge generating substance used in the present invention include selenium tellurium, pyrylium, thiapyrylium dyes, phthalocyanine, anthanthrone, dibenzpyrenequinone, trisazo, cyanine, disazo, monoazo, indigo, quinacridone, and asymmetric quinocyanine pigments.

  In the case of the functional separation type, the charge generation layer is composed of the former charge generation material 0.3 to 4 times the amount of binder resin and solvent, homogenizer, ultrasonic dispersion, ball mill, vibration ball mill, sand mill, attritor, roll mill and liquid collision. It is well dispersed by a method such as a mold type high-speed disperser, and the dispersion is applied and dried. It is also possible to add the binder resin after dispersing the charge generating material or not to use the binder resin. The film thickness of the charge generation layer is 5 μm or less, preferably 0.1 to 2 μm.

  The charge transport layer is mainly formed by dissolving the charge transport material and the above-described binder resin in a solvent, and coating and drying the obtained paint.

  Examples of the charge transport material used include triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, triallylmethane compounds, and thiazole compounds.

  The thickness of the charge transport layer is preferably 5 to 50 μm, more preferably 10 to 30 μm. The weight ratio of the charge transport material to the binder resin is about 5: 1 to 1: 5, preferably about 3: 1 to 1: 3. Examples of the application method include dip coating, spray coating, spinner coating, blade coating, and roll coating.

  The electrophotographic photosensitive member described above is used in an apparatus having a roller-shaped charging member in contact with the electrophotographic photosensitive member and a roller-shaped developing member. In the apparatus, the positional relationship between the charging member and the end of the developing member is such that the distance between the end position of the charging member and the end position of the developing member is within 8.0 mm. In the case of 8 mm or more, although the local end portion of the electrophotographic photosensitive member is less likely to be worn, the size of the device itself is also increased, so that the effects of the electrophotographic photosensitive member and the electrophotographic device of the present invention are obtained. It's hard to be done. Hereinafter, this relationship will be described with reference to the drawings.

  Hereinafter, the charging mechanism and the developing mechanism will be described. First, the charging mechanism will be described.

  As a contact-type charging member that is currently put into practical use, a roller-shaped charging member is generally used. For example, in this case, a conductive elastic layer, a resistance control layer, and a surface layer are sequentially arranged around a conductive metal core. In many cases, a laminated structure is used, but at least a core metal and an elastic body are required.

  Examples of the elastic material in this case include resins such as urethane, SBR, EVA, SBS, SEBS, SIS, TPO, EPDM, EPM, NBR, IR, BR, silicone rubber, epichlorohydrin rubber, and the like. Depending on the required resistance value, for example, a solid electrolyte such as carbon black, carbon fiber, metal oxide, metal powder, perchlorate, or a conductivity-imparting material such as a surfactant is added.

  Examples of the material for the resistance control body include polyamide, polyurethane, fluorine, polyvinyl alcohol, silicon, NBR, EPDM, CR, IR, BR, hydrin rubber, and the like, such as conductive or insulating material. There is a mixture of fillers and additives.

The material as described above is used, and the electric resistance value of the charging member is set to 1 × 10 ³ to 1 × 10 ¹⁰ Ω. However, the combination of the materials is not particularly limited as long as it finally becomes this value. .

  Next, the developing mechanism will be described.

  The electrophotographic apparatus of the present invention may be one that employs a system in which toner is coated as a one-component developer on the surface of an elastic roller, and this is brought into contact with the surface of the photoreceptor. The toner is preferably a non-magnetic toner, but may be a magnetic toner. It is important that the toner on the elastic roller is in contact with the surface of the photoreceptor. The toner carrier is substantially in contact with the surface of the photoreceptor, which means that the toner carrier is in contact with the photoreceptor when the toner is removed from the toner carrier. At this time, in order to obtain a toner image having no edge effect due to the electric field acting between the photosensitive member and the elastic roller facing the surface of the photosensitive member via the toner, the toner has a potential on the elastic roller surface or in the vicinity of the elastic roller surface, It is necessary to form an electric field between the photoreceptor surface and the toner carrier surface. For this reason, the elastic rubber of the elastic roller is resistance-controlled in the middle resistance region to form an electric field while preventing conduction with the surface of the photoreceptor, or a thin dielectric layer is provided on the surface layer of the conductive roller. Furthermore, a conductive resin sleeve in which the side facing the surface of the photoconductor is coated with an insulating material on the conductive roller, or a conductive layer is provided on the side of the insulating sleeve that does not face the photoconductor.

  In the case of the one-component contact development method, the roller carrying the toner may be rotated in the same direction as the peripheral speed of the photosensitive member, or may be rotated in the opposite direction. When the rotation is in the same direction, the peripheral speed ratio is preferably set to 100% or more, more preferably 110 to 300%, and still more preferably 120 to 250% with respect to the peripheral speed of the photosensitive member. It is good. If it is less than 100%, there is a problem in image quality such as poor line cutting. As the peripheral speed ratio increases, the amount of toner supplied to the development site increases, the frequency of toner desorption with respect to the latent image increases, and unnecessary portions are scraped off and applied to the necessary portions. An image faithful to the latent image can be obtained. However, if the peripheral speed difference is too large, wear of the electrophotographic photosensitive member is promoted. Particularly, if the peripheral speed difference exceeds 250%, wear near the contact position of the end of the developing roller is extremely accelerated. Absent.

  Hereinafter, it demonstrates according to an Example. “Parts” means parts by weight.

(Example 1)
A 30φ357 mm Al cylinder was used as a support, and a coating material composed of the following materials was applied on the support by a dipping method and thermally cured at 140 ° C. for 30 minutes to form a 15 μm conductive layer.
Conductive pigment: SnO ₂ Coated barium sulfate 10 parts Resistance adjusting pigment: Titanium oxide 2 parts Binder resin: Phenol resin 6 parts Leveling agent: Silicone oil 0.001 part Solvent: Methanol, methoxypropanol 0.2 / 0.8 20 parts Next, a solution obtained by dissolving 3 parts of N methoxymethylated nylon (registered trademark) and 3 parts of copolymer nylon (registered trademark) in a mixed solvent of 65 parts of methanol and 30 parts of n-butanol was applied by dipping. An intermediate layer of 0.5 μm was formed.

  Next, 9 parts of a HOGaPc crystal having a strong peak at 7.4 ° ± 0.2 and 28.2 ° ± 0.2 in the Bragg angle 2θ in X-ray diffraction of CuKα and polyvinyl butyral (trade name S-REC BX-1, A solution prepared by dissolving 3 parts of Sekisui Chemical Co., Ltd. in 100 parts of tetrahydrofuran was dispersed for 3 hours in a sand mill using 1 mmφ glass beads. 200 parts of butyl acetate was added thereto, diluted and recovered, and this was dip-coated on the undercoat layer and dried at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.30 μm. .

Next, in order to form a charge transport layer, a paint for charge transport was prepared. Copolymer polyarylate resin of structural unit example 3 / a-1 (= 5/5) (weight average molecular weight 125000), amine compounds A and B represented by the following formula
Amine compound A

  Amine compound B

  Was prepared to be polyarylate resin 10, amine compound A7, amine compound B1 and solvent 80 in the final weight ratio.

  The solvent was prepared such that the final weight ratio of monochlorobenzene: dimethoxymethane was 6: 4. This paint was applied by a dip coating method and dried at 130 ° C. for 1 hour to form a charge transport layer having a thickness of 15 μm.

  Next, evaluation will be described. The apparatus used was a modified LBP5500 (17 sheets per minute) manufactured by Canon. In the modification, the peripheral speed difference of the developing roller with respect to the electrophotographic photosensitive member was set to 200%. Further, the contact pressure of the developing roller to the electrophotographic photosensitive member was set to 1.5 times. The contact pressure of the charging roller was doubled.

  The evaluation was performed using the above apparatus. As for durability, 10,000 full-color images with a printing rate of 5% were printed intermittently. Evaluation evaluated the image after printing 10,000 sheets. Further, after the endurance, the difference ΔD (μm) between the film thickness at the center of the photoconductor and the film thickness at the most worn portion near the end of the developing roller and the end of the charging roller was measured.

(Example 2)
Same as Example 1 except that the binder in the charge transport layer in Example 1 is a copolymer polyarylate resin of Example 3 / a-1 (copolymerization ratio 3/7, weight average molecular weight Mw = 132000). Was evaluated. The results are shown in Table 1.

(Example 3)
Example 1 is the same as Example 1 except that the binder in the charge transport layer is a copolymerized polyarylate resin of Example 2 / a-9 (copolymerization ratio 5/5, weight average molecular weight Mw = 112000). Was evaluated. The results are shown in Table 1.

Example 4
Evaluation was performed in the same manner as in Example 1 except that the binder in the charge transport layer in Example 1 was changed to the polyarylate resin in the structural unit example 1 (weight average molecular weight Mw = 138000). The results are shown in Table 1.

(Example 5)
Same as Example 1 except that the binder in the charge transport layer in Example 1 was a copolymer polyarylate resin (copolymerization ratio 5/5, weight average molecular weight Mw = 132000) of structural unit example 4 / a-1. Was evaluated. The results are shown in Table 1.

(Example 6)
In Example 1, the binder in the charge transport layer is composed of the polyarylate resin of constituent unit example 1 / a-1 (copolymerization ratio 5/5, weight average molecular weight Mw = 112000) and the polycarbonate resin of constituent unit example b-1 (weight). Evaluation was performed in the same manner as in Example 1 except that a mixture (mixing ratio 7/3) having an average molecular weight Mw = 89000 was used. The results are shown in Table 1.

(Example 7)
In Example 1, the binder in the charge transport layer was replaced with the polyarylate resin of constituent unit example 3 / a-1 (copolymerization ratio 5/5, weight average molecular weight Mw = 112000) and the polyarylate resin of constituent unit example a-1 ( Evaluation was performed in the same manner as in Example 1 except that the mixture was a mixture having a weight average molecular weight Mw = 110000 (mixing ratio 7/3). The results are shown in Table 1.

(Examples 8 to 14)
In Examples 1 to 7, the evaluation was performed in the same manner as in Examples 1 to 6 except that an evaluator was further modified so that it was driven at twice the speed. The results are shown in Table 1.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 except that the binder in the charge transport layer in Example 1 was changed to the polyarylate resin of the structural unit example a-1 (weight average molecular weight Mw = 110000). The results are shown in Table 2.

(Comparative Example 2)
Evaluation was performed in the same manner as in Example 1 except that the binder in the charge transport layer in Example 1 was the polycarbonate resin of the structural unit example b-1 (weight average molecular weight Mw = 110000). The results are shown in Table 2.

The figure which shows the positional relationship of the electrophotographic photoconductor which concerns on this invention, a charging member, and the edge part of a developing member. The figure which shows the positional relationship of the electrophotographic photoconductor which concerns on this invention, a charging member, and the edge part of a developing member.

Explanation of symbols

a Electrophotographic photosensitive member b Charging roller c Developing roller d Distance between end portions of developing roller and charging roller

Claims (6)

In an electrophotographic photosensitive member having a conductive support and a photosensitive layer, and a color electrophotographic process having a charging unit and a developing unit in contact with the electrophotographic photosensitive member, an end position of the charging unit and an end position of the developing unit Is within 8.0 mm, and
The surface layer of the electrophotographic photoreceptor has the following formula (1)

(1)
(Wherein R11 to R14 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.)
An electrophotographic apparatus comprising polyarylate having a structural unit represented by: In an electrophotographic photosensitive member having a conductive support and a photosensitive layer, and a color electrophotographic process having a charging unit and a developing unit in contact with the electrophotographic photosensitive member, an end position of the charging unit and an end position of the developing unit Is within 8.0 mm, and
The surface layer of the electrophotographic photoreceptor has the following formula (2)

(2)
(Wherein R15 to R18 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.)
An electrophotographic apparatus comprising polyarylate having a structural unit represented by:   3. The electrophotographic apparatus according to claim 1, wherein the charging means is a contact charging method using a roller.   3. The electrophotographic apparatus according to claim 1, wherein the developing means is a contact developing system using a roller.   The electrophotographic apparatus according to claim 1, wherein a peripheral speed difference of the developing roller with respect to the electrophotographic photosensitive member is 120% or more and less than 300%.   3. The electrophotographic apparatus according to claim 1, wherein the electrophotographic photoreceptor is a laminated photoreceptor having a charge transport layer, a charge generation layer, and an underlayer on a conductive support.

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