JP2010049036A - Electrophotographic photoreceptor, developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the leak resistance of a photosensitive layer by directly bonding a fluorine atom to a binder resin in a charge transport layer; to avoid rise of residual potential due to increase in film thickness and deterioration of electric properties and leak resistance due to reduction in film thickness; to obtain stable image quality; and to reduce cost. <P>SOLUTION: Provided is an electrophotographic photoreceptor with a photosensitive layer 60 laminated on a conductive support 61, wherein a binder resin in a charge transport layer 64 as an uppermost layer of the photosensitive layer 60 includes a fluorine atom in at least one site of R1-R10 in formula (1). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrophotographic photosensitive member, a developing device, and an image forming apparatus.

  In recent years, since electrophotographic technology can obtain high-quality images immediately, it is widely used not only in the field of copying machines but also in the fields of various printers. The core of electrophotographic technology is a photoconductor, but in particular, a photoconductor using an organic photoconductive material that is pollution-free and easy to form and manufacture, that is, an organic photoconductor. Is now common.

  Furthermore, among organic photoreceptors, a function-separated photoreceptor having a photosensitive layer formed by laminating a charge generation layer and a charge transport layer is widely used. Function-separated type photoconductors can provide highly sensitive photoconductors by combining highly efficient charge generating materials and charge transport materials, respectively, and can provide photoconductors with a wide range of materials and high safety. In addition, since the productivity of coating is high and it is relatively advantageous in terms of cost, it has become the mainstream of photoreceptors.

  The mechanism of electrostatic latent image formation in the function-separated type photoreceptor is described. First, when the photoconductor is charged and then irradiated with light, the light passes through the charge transport layer and is absorbed by the charge generation material in the charge generation layer, thereby generating a charge. Then, the generated charges are injected into the charge transport layer at the interface between the charge generation layer and the charge transport layer, and further move in the charge transport layer toward the outermost surface by an electric field to neutralize the surface charge of the photoreceptor. By doing so, an electrostatic latent image is formed (see, for example, Patent Document 1).

  In recent electrophotographic apparatuses, instead of the corotron, a contact charging type charging apparatus that generates less ozone has been used. However, when a contact charging type charging device is used, an electrical pinhole is generated on the photoconductor due to a local high electric field applied during contact charging, and dielectric breakdown occurs on the pinhole. May appear.

  Such pinholes may occur due to coating film defects in the photosensitive layer, but other than that, conductive foreign matter generated in the electrophotographic apparatus may come into contact with or penetrate into the photosensitive member. In some cases, the conductive path is easily formed between the contact charging device and the photosensitive substrate.

  If it is noticeable, foreign matter such as carbon fiber or carrier powder mixed from other members in the electrophotographic apparatus or dust mixed in the electrophotographic apparatus pierces the photoconductor, and leak points from the charging device of the contact charging method May be formed.

  However, in order to conceal defects in the substrate by increasing the thickness of the undercoat layer of the photoconductor and to obtain stability in electrical characteristics, such problems are included. A method of applying and forming a layer to be applied on a substrate is employed. That is, a conductive powder-dispersed conductive layer is formed on an aluminum substrate, and an undercoat layer is further formed thereon. In this case, the conductive layer is used to conceal the substrate and the resistance is adjusted so that the undercoat layer has a blocking function.

Further, a method of improving leakage resistance by dispersing metal oxide fine particles having an appropriate powder resistance in the undercoat layer without increasing the thickness of the undercoat layer is also employed.
JP 2005-331567 A

  However, in the conventional photoreceptor, there is a problem that when the undercoat layer is made thick in order to suppress leakage of the photosensitive layer, the residual potential increases due to repeated use. Also, in the method of dispersing metal oxide fine particles in the undercoat layer, it is difficult to control the powder resistance value of the metal oxide fine particles, and if the powder resistance value is low, the leak resistance becomes insufficient and the powder resistance value is high. There was a problem that the residual potential increased. As described above, it is impossible to solve the problems of residual potential, stability of electrical characteristics, and leakage resistance by improving only the undercoat layer.

  The present invention solves the above-mentioned conventional problems, and by directly bonding fluorine atoms to the binder resin of the charge transport layer, the leakage resistance of the photosensitive layer can be improved, and the residual potential is increased by increasing the film thickness. It is another object of the present invention to provide an electrophotographic photosensitive member, a developing device, and an image forming apparatus that can obtain stable image quality without causing deterioration of electrical characteristics and leak resistance due to thin film formation.

  Therefore, the electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member in which a photosensitive layer is laminated on a conductive support, and the binder resin in the uppermost charge transport layer of the photosensitive layer is the following: A fluorine atom is contained in at least one of R1 to R10 shown in Formula (1).

  According to the present invention, in the electrophotographic photosensitive member, fluorine atoms are directly bonded to the binder resin of the charge transport layer. As a result, the leakage resistance of the photosensitive layer can be improved, the residual potential is not increased by increasing the thickness, and the electrical characteristics and leakage resistance are not deteriorated by reducing the thickness. Can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the first embodiment of the present invention.

  In the figure, reference numeral 10 denotes an image forming apparatus according to the present embodiment. For example, the image forming apparatus is a printer, a facsimile machine, a copying machine, a multi-function machine having various functions, or the like. Further, the image forming apparatus 10 may be a color printer that performs color printing by arranging image forming cartridges 20 that form images of respective colors in a multi-stage manner. A case of a monochrome printer that performs monochrome (for example, black) printing using the image forming cartridge 20 will be described.

  In this case, the image forming cartridge 20 is detachably attached to the image forming apparatus 10 and functions as a developing device. The image forming cartridge 20 includes an integrally formed cartridge case 21, a drum-type photosensitive drum 11 as an electrophotographic photosensitive member disposed in the cartridge case 21, and the photosensitive drum 11. A charging roller 12 as a charging device for charging the surface, a developing unit 13 for developing the surface of the photosensitive drum 11, and a cleaning unit 14 for cleaning the surface of the photosensitive drum 11 are provided.

  The charging roller 12 is in contact with the photosensitive drum 11 and is rotatably arranged.

  The developing unit 13 includes a developing roller 15 as a developer carrying member, a developing blade 16 as a toner layer forming member, a toner supply roller 17 as a developer supplying member, and an agitation member 18. A detachable toner cartridge 22 is mounted. The developing unit 13 develops the electrostatic latent image formed on the surface of the photosensitive drum 11 as an electrostatic latent image carrier by supplying toner as a developer to the surface of the photosensitive drum 11. To do.

  Here, the developing roller 15 includes a semiconductive elastic body formed around the conductive shaft, and rotates in contact with the photosensitive drum 11. The toner supply roller 17 also includes a semiconductive elastic body formed around the conductive shaft. The developing blade 16 thins the toner on the surface of the developing roller 15 and charges it. Note that the image forming apparatus 10 in the present embodiment employs a non-magnetic one-component contact developing method, and the toner is a non-magnetic one-component toner.

  The cleaning unit 14 includes a cleaning blade 23 and a spiral screw 24. The cleaning blade 23 scrapes off the toner remaining on the surface of the photosensitive drum 11, and the scraped toner is removed by the spiral screw 24. The toner is conveyed to a toner box (not shown).

  A transfer roller 25 as a transfer device for transferring the toner on the photoconductor drum 11 to a paper 31 as a transfer medium is disposed below the photoconductor drum 11.

  In the image forming apparatus 10, a sheet conveyance path 35 a through which the sheet 31 passes is disposed below the image forming cartridge 20. The paper transport unit 35 b that supplies the paper 31 to the paper transport path 35 a includes a hopper stage 32, and the paper 31 is stacked on the hopper stage 32. A spring 33 is disposed below the hopper stage 32, and the uppermost sheet 31 is pressed against the feeding roller 34 disposed above by the upward biasing force exerted by the spring 33. Is done. As the feed roller 34 rotates, the sheets 31 stacked on the hopper stage 32 are fed out one by one to the sheet conveyance path 35a.

  Conveying rollers 36a and 36b are disposed in the sheet conveying path 35a, and the sheet 31 fed to the sheet conveying path 35a is conveyed between the photosensitive drum 11 and the transfer roller 25 by the conveying rollers 36a and 36b. Is done.

  A fixing device 40 is disposed on the downstream side of the paper transport path 35a. The fixing device 40 includes a heating roller 40 a that heats the paper 31 and a pressure roller 40 b that presses the paper 31, and fixes the toner image on the paper 31. Further, discharge rollers 37a and 37b are disposed on the downstream side of the fixing device 40, and the sheet 31 on which the toner image is fixed is discharged out of the image forming apparatus 10 by the discharge rollers 37a and 37b.

  Further, the image forming apparatus 10 has a cover 38 attached to the upper portion thereof so as to be rotatable around a fulcrum 39. A support member 26 is disposed below the cover 38, and an LED (Light Emitting Diode) head 28 serving as an exposure apparatus is disposed on the support member 26 via a spring 27. The LED head 28 includes an LED array composed of a plurality of LED elements, a substrate on which a driver IC that drives the LED array is mounted, a rod lens array that collects light emitted from the LED elements, and the like. A control unit (not shown) of the image forming apparatus 10 drives the LED head 28 based on image data transmitted from a host device (not shown) and the like, and selectively causes the LED elements to emit light. An electrostatic latent image is formed on the surface. The LED head 28 is urged toward the photosensitive drum 11 by a spring 27 with the cover 38 closed.

  Next, a mechanism for driving the photosensitive drum 11 will be described.

  FIG. 3 is a cross-sectional view showing the overall structure of the photosensitive drum in the first embodiment of the present invention, and FIG. 4 is a perspective view showing a gear in the first embodiment of the present invention.

  As shown in FIG. 3, a metal shaft 30 that is a conductor is disposed inside the photosensitive drum 11. Further, a flange 41 is press-fitted into one end portion inside the photosensitive drum 11 and fixed with a non-conductive adhesive. The material of the flange 41 is a synthetic resin such as polyamide, polycarbonate, ABS (alkylbenzene sulfonic acid) resin, polyacetal, etc., and is made conductive by blending conductive powder such as metal powder, carbon black, and graphite. A synthetic resin is used. The flange 41 is rotatably attached to the shaft 30.

  A support member 42 is also disposed inside the photosensitive drum 11 on the opposite side of the flange 41. The support member 42 is rotatably attached to the shaft 30 and is fixed to the inside of the photosensitive drum 11. A gear 43 is fixed to the outside of the support member 42 with an adhesive. The gear 43 rotates the photosensitive drum 11 and meshes with the drive gear 44 as shown in the drawing. The drive gear 44 is rotatably attached to a fixed shaft 45 that is fixedly supported by the apparatus frame 51b. When the drive gear 44 is driven by a drive source (not shown) of the image forming apparatus 10, the photosensitive drum 11 rotates through the gear 43.

  The shaft 30 and the photosensitive drum 11 are attached to a cartridge case 21 of the image forming cartridge 20. Bearing holes 52a and 52b are formed in the cartridge case 21, and both end portions of the shaft 30 penetrate the bearing holes 52a and 52b. A collar 46 made of conductive metal is disposed between the cartridge case 21 on the left side and the flange 41 in the drawing. The collar 46 is rotatable with respect to the shaft 30 and is movable in the axial direction of the shaft 30. The collar 46 is in contact with the flange 41 and the cartridge case 21.

  The cartridge case 21 including the shaft 30 and the photosensitive drum 11 is mounted on the apparatus frames 51a and 51b. Slots 47a and 47b are formed in the device frames 51a and 51b, respectively, and the cartridge case 21 is mounted by engaging both ends of the shaft 30 in the slots 47a and 47b. At this time, one end 30a of the shaft 30 protrudes from the device frame 51a.

  A conductive spring member 48a is attached to the outside of the device frame 51a by a pin 48b. The spring member 48a is connected to a grounding member (not shown) and exerts a biasing force in the inner direction. When the image forming cartridge 20 is not attached to the apparatus frames 51a and 51b, the spring member 48a is located slightly inside the position shown in the figure, but the upper end portion of the spring member 48a is inclined outward. Therefore, the image forming cartridge 20 can be mounted from above. When the image forming cartridge 20 is mounted on the apparatus frames 51a and 51b, the one end 30a of the shaft 30 and the spring member 48a are in pressure contact.

  As shown in FIG. 4, the gear 43 and the drive gear 44 are made of helical gears, and the torsion (torsion) angles of the teeth are set in opposite directions. With such a helical gear structure, the gear 43 is urged in the left direction in FIG. 3, and thereby the contact between the one end 30 a of the shaft 30 and the spring member 48 a is improved.

  Next, the operation of the image forming apparatus 10 having the above configuration will be described.

  When an instruction to start printing is issued from the host apparatus to the image forming apparatus 10 and image data is transmitted from the host apparatus to the image forming apparatus 10, the control unit of the image forming apparatus 10 drives the feeding roller 34. Then, the paper 31 is fed out to the paper transport path 35a. The paper 31 fed out to the paper transport path 35a is transported between the photosensitive drum 11 and the transfer roller 25 by the transport rollers 36a and 36b.

  Further, the control unit drives the LED head 28 based on the transmitted image data, selectively causes the LED elements of the LED head 28 to emit light, and the photosensitive drum 11 charged in advance by the charging roller 12. Expose the surface. Thereby, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 11. Since the photosensitive drum 11 rotates in the direction indicated by the arrow in FIG. 2, when the electrostatic latent image reaches a position corresponding to the developing unit 13, the toner on the developing roller 15 is statically discharged by electrostatic force. Adhere to the electrostatic latent image. As a result, a toner image is formed on the photosensitive drum 11. Since the photosensitive drum 11 rotates in the direction indicated by the arrow in FIG. 2, the toner image moves to a contact position with the transfer roller 25.

  In this case, the toner image on the photoconductive drum 11 reaches the contact position with the transfer roller 25 in synchronization with the timing when the paper 31 reaches between the photoconductive drum 11 and the transfer roller 25, and the transfer roller 25 causes the toner to move. The image is transferred onto the paper 31. Then, the paper 31 on which the toner image is transferred is conveyed to the fixing device 40 and passes between the heating roller 40a and the pressure roller 40b of the fixing device 40, whereby the toner image is fixed on the paper 31. . The paper 31 on which the toner image is fixed is discharged out of the image forming apparatus 10 by the discharge rollers 37a and 37b.

  Next, the layer structure near the surface of the photosensitive drum 11 will be described.

  FIG. 1 is a sectional view showing a layer structure in the vicinity of the surface of the photosensitive drum in the first embodiment of the present invention.

  In the drawing, a cross section near the surface of the photosensitive drum 11 is shown, and 61 is a drum-shaped, ie, cylindrical, conductive support of the photosensitive drum 11, on the conductive support 61. A photosensitive layer 60 is formed. The conductive support 61 is made of a metal material such as aluminum, stainless steel, copper, or nickel, or a polyester film provided with a conductive layer such as aluminum, copper, palladium, tin oxide (tin), or indium oxide on the surface, paper It consists of insulating materials such as.

  An undercoat layer 62 may be formed between the conductive support 61 and the photosensitive layer 60 as in the example shown in the figure. The undercoat layer 62 is, for example, an inorganic layer such as an aluminum anodized film, aluminum oxide, aluminum hydroxide, or polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, It consists of an organic layer such as polyamide.

  In the example shown in the figure, the photosensitive layer 60 is formed on a conductive support 61 with an undercoat layer 62 interposed therebetween, and a charge generation layer 63 containing a charge generation material as a main component and a charge generation layer 63 on the charge generation layer 63. A charge transport layer 64 formed of a charge transport material and a binder resin as main components. That is, in the example shown in the figure, the photosensitive layer 60 is a laminated photosensitive layer in which a charge generation layer 63 and a charge transport layer 64 are sequentially laminated on a conductive support 61. The photosensitive layer 60 is formed by stacking the charge generation layer 63 and the charge transport layer 64 in reverse, that is, the charge transport layer 64 is stacked on the conductive support 61, and the charge transport layer 64 is charged on the charge transport layer 64. An inverted two-layer type photosensitive layer in which the generation layer 63 is laminated may be used. The photosensitive layer 60 may be a dispersion type photosensitive layer in which a charge generating material is dispersed in a charge transport layer 64.

  When the photosensitive layer 60 is a laminated type photosensitive layer or an inverted two-layer type photosensitive layer, the charge generation material used for the charge generation layer 63 includes selenium and its alloys, arsenic selenide compounds, cadmium sulfide, zinc oxide, Other inorganic photoconductive substances, phthalocyanines, azo dyes, quinacridones, polycyclic quinones, pyrylium salts, thiapyrylium salts, various organic pigments and dyes such as indigo, thioindigo, anthanthrone, pyranthrone, and cyanine can be used. Among them, metal-free phthalocyanine, copper indium chloride, gallium chloride, tin, oxytitanium, zinc, vanadium and other metals or oxides thereof, chloride coordinated phthalocyanines, monoazo, bisazo, trisazo, polyazos and other azo pigments Is preferably used.

  The charge generation layer 63 may be formed of fine particles of these charge generation substances, for example, polyester resin, polyvinyl acetate, polyacrylate ester, polymethacrylate ester, polyester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy. It may be a dispersion layer in a form bound with various binder resins such as resin, epoxy resin, urethane resin, cellulose ester, and cellulose ether. In this case, the usage ratio of the charge generating material is in the range of 30 to 500 parts by weight with respect to 100 parts by weight of the binder resin, and the film thickness is usually 0.1 to 2 [μm].

  The charge generation layer 63 may contain various additives such as a leveling agent, an antioxidant, and a sensitizer for improving the coating property as necessary. The charge generation layer 63 may be a vapor deposition film of the charge generation material.

  Examples of the charge transport material used for the charge transport layer 64 include heterocyclic compounds such as carbazole, indole, imidazole, oxazole, virazole, oxadiazole, pyrazoline, thiadiazole, aniline derivatives, hydrazone compounds, and aromatic amines. An electron donating substance such as a derivative, a stilbene derivative, or a polymer having a group composed of these compounds in the main chain or side chain.

  The binder resin used for the charge transport layer 64 is polycarbonate and has a structure represented by the following formula (1).

  In addition, R1-R10 shown by said (1) shows a hydrogen atom, an alkyl group, and an aryl group each independently.

  In the binder resin, a part of hydrogen atoms in R1 to R10 represented by the formula (1) is substituted with fluorine atoms, and contains fluorine atoms having a molecular weight of 1% by weight or more.

  The binder resin includes vinyl polymers such as polymethyl methacrylate, polystyrene, polyvinyl chloride, polyester, polyester carbonate, polysulfone, polyimide, phenoxy, epoxy, silicone resin, and copolymers or partially cross-linked cured products thereof. Etc. may be used alone or as a mixture, but it is necessary to contain 1 [wt%] or more of fluorine atoms.

  As a method of bonding a fluorine atom to the polycarbonate which is the binder resin, a known method used for producing a polycarbonate from bisphenol A and a carbonate-forming compound, for example, a direct reaction between bisphenol A and phosgene ( Methods such as a phosgene method) and a transesterification reaction (transesterification method) between bisphenol A and bisaryl carbonate can be employed. By using bisphenol A in which hydrogen atoms are appropriately substituted with fluorine atoms, a polycarbonate having fluorine atoms bonded thereto can be produced. The fluorine atom substitution method is performed by a known method.

  In the phosgene method, bisphenol A and phosgene are usually reacted in the presence of an acid binder and a solvent. Examples of the acid binder include pyridine, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and the like as an aqueous solution. Moreover, as a solvent, a methylene chloride, chloroform, etc. are used, for example. Furthermore, a catalyst such as a tertiary amine such as triethylamine or a quaternary ammonium salt is used to promote the condensation polymerization reaction.

  In order to adjust the polymerization degree, it is preferable to add a monofunctional compound such as phenol, pt-butylphenol, p-cumylphenol, or a long-chain alkyl-substituted phenol as a molecular weight regulator. If necessary, a small amount of an antioxidant such as sodium sulfite or hydrosulfite, or a branching agent such as phloroglucin or isatin bisphenol may be added.

  The reaction temperature is usually in the range of 0 to 150 [° C], preferably in the range of 5 to 40 [° C]. The reaction time depends on the reaction temperature, but is usually 0.5 minutes to 10 hours, preferably 1 minute to 2 hours. Furthermore, it is desirable to maintain the pH of the reaction system at 10 or more during the reaction.

  On the other hand, in the case of transesterification, bisphenol A and bisaryl carbonate are mixed and reacted at high temperature under reduced pressure. The reaction is usually carried out at a temperature in the range of 150 to 350 [° C.], preferably in the range of 200 to 300 [° C.]. In addition, the degree of vacuum is preferably 1 [mmHg] or less at the end, and phenols derived from the bisaryl carbonate by-produced by the transesterification reaction are distilled out of the system. The reaction time depends on the reaction temperature, the reduced pressure, etc., but is usually about 1 to 10 hours. The reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon. Moreover, you may react by adding a molecular weight regulator, antioxidant, a branching agent, etc. as needed.

  The charge transport layer 64 may contain various additives such as an antioxidant and a sensitizer as necessary. The film thickness of the charge transport layer 64 is usually 5 to 30 [μm].

  Further, when the photosensitive layer 60 is a dispersion type photosensitive layer, the above-described charge generation material is dispersed in the charge transport medium having the above-described blending ratio by the combination of the above-described binder resin and the charge transport material. . In this case, it is necessary that the particle size of the charge generation material is sufficiently small, for example, 1 [μm] or less.

  If the amount of the charge generating material dispersed in the photosensitive layer 60 is too small, sufficient sensitivity cannot be obtained, and if it is too large, there are adverse effects such as a decrease in chargeability and a decrease in sensitivity. The range of ˜50 [% by weight] is preferable. The film thickness of the photosensitive layer 60 is preferably 5 to 30 [μm]. Also known plasticizers for improving film formability, flexibility, mechanical strength, additives for suppressing residual potential, dispersion aids for improving dispersion stability, coatability A leveling agent or a surfactant, for example, silicone oil or other additives may be added to improve the viscosity.

  As a method for forming each layer, a known method such as sequentially applying a coating solution obtained by dissolving or dispersing a substance contained in a layer in a solvent can be applied.

  Next, an experimental example in the present embodiment will be described.

  FIG. 5 is a diagram showing the relationship between the scratch opening diameter and the white spot on the image in the first embodiment of the present invention, and FIG. 6 shows the relationship between the load and the scratch opening diameter in the first embodiment of the present invention. FIG. 7 is a second diagram showing the relationship between the load and the flaw opening diameter in the first embodiment of the present invention, and FIG. 8 is the measured photosensitivity in the first embodiment of the present invention. It is a figure which shows the dimension of the flaw opening diameter on a layer, and the white spot diameter on an image.

  First, a method for evaluating leakage resistance will be described.

  In this experimental example, a laminated photosensitive layer is used as the photosensitive layer 60. The charge generation material used for the charge generation layer 63 is a bisazo compound and is bound by polyvinyl butyral which is a binder resin to form a dispersion layer. The film thickness of the charge generation layer 63 is 0.5 [μm].

  The charge transport material used for the charge transport layer 64 is a vidrazone compound. The initial film thickness of the charge transport layer 64 is 18 [μm]. The binder resin used for the charge transport layer 64 is a polycarbonate having a structure represented by the formula (1). There are two types of evaluation samples, a sample having a fluorine atom content of 1 [wt%] and a sample not containing a fluorine atom.

  Next, an experimental method will be described.

  First, a load of 50, 100, 150, 200 and 250 [g] is applied to the surface of the photosensitive layer 60 using a silk thread needle having a tip diameter of 0.05 [mm]. Next, using the photosensitive drum 11 having the photosensitive layer 60 and using the MICROLINE5900 manufactured by Oki Data Co., Ltd. as the image forming apparatus 10, a 100% density pattern and a blank paper pattern were printed. When a load was applied from the tip of the needle to the surface of the photosensitive layer 60, it was determined that a leak occurred when white spots occurred in the 100% density pattern and black spots occurred in the blank paper pattern. Further, the surface of the photosensitive drum 11 was observed with a laser microscope, and the opening diameter of the scratch formed on the surface of the photosensitive layer 60 was measured.

  The results of this experimental example are shown in FIGS.

  FIG. 8 shows the evaluation results. In FIG. 8, when the diameter of the white spot on the image is 100 [μm] or more, it is determined that a leak has occurred, and expressed as “×”, and when the diameter is less than 100 [μm], the white spot on the image is visually Because it is in a level that cannot be confirmed, “○” is indicated.

  5 and 8, in this experimental example, it can be confirmed that a leak has occurred when the scratch opening diameter is 50 [μm] or more. 6 and 8, when the load at which the flaw opening diameter is 50 [μm] or more is observed, if the binder resin of the charge transport layer 64 does not contain fluorine atoms, leakage occurs at a load of 150 [g]. On the other hand, when fluorine atoms are contained, it can be seen that no leak occurs up to a load of 200 [g].

  Further, FIG. 7 shows a graph in which the relationship between the load and the scratch opening diameter when the amount of fluorine atoms contained in the binder resin is 0.5 and 2 [g] is superimposed on FIG. . FIG. 7 shows that the effect is not so much seen when the fluorine atom content is 0.5 g.

  From this, it was confirmed that the leakage resistance of the photosensitive layer 60 is improved by directly bonding 1% by weight or more of fluorine atoms to the polycarbonate used as the binder resin.

  As described above, in this embodiment, 1% by weight or more of fluorine atoms are directly bonded to polycarbonate which is the binder resin of the charge transport layer 64 in the photosensitive layer 60 of the photosensitive drum 11 as the electrophotographic photosensitive member. As a result, the leakage resistance of the photosensitive layer 60 can be improved.

  When considering the leakage resistance of the electrophotographic photosensitive member, conventionally, it has been necessary to control several parameters, such as adjusting the film thickness of the undercoat layer 62 and adjusting the hardness or slipperiness of the surface of the photosensitive layer 60. Further, even when a fluorine-based resin is added to the binder resin on the surface of the photosensitive layer 60, it is difficult to disperse the fluorine-based resin, and it is difficult to effectively improve the leak resistance.

  The inventors of the present invention have found that leakage resistance is improved by improving the binder resin on the surface of the photosensitive layer 60. In the past, when taking countermeasures against leakage in an electrophotographic photosensitive member, it was necessary to prepare and evaluate samples by changing the materials of the undercoat layer 62 and the charge transport layer 64 in various ways. However, as in the present embodiment, it is understood that only the binder resin in the charge transport layer 64 may be replaced, and a reduction in the development cost of the electrophotographic photosensitive member can be expected.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 9 is a cross-sectional view showing a layer structure in the vicinity of the surface of the photosensitive drum according to the second embodiment of the present invention.

  Also in the present embodiment, an undercoat layer 62 is formed between the conductive support 61 and the photosensitive layer 60 as in the first embodiment. In the photosensitive layer 60, a charge transport layer lower layer 64a is formed on the charge generation layer 63 formed on the conductive support 61 with the undercoat layer 62 interposed therebetween. A charge transport layer upper layer 64b is formed thereon. That is, the charge transport layer 64 in the present embodiment includes a charge transport layer lower layer 64a and a charge transport layer upper layer 64b that are sequentially stacked.

  The binder resin used for the charge transport layer lower layer 64a is polycarbonate, and has substantially the same structure as the polycarbonate as the binder resin used for the charge transport layer 64 in the first embodiment. It is not necessary to contain a fluorine atom.

  On the other hand, the binder resin used for the charge transport layer upper layer 64b is polycarbonate, and, similar to the polycarbonate as the binder resin used for the charge transport layer 64 in the first embodiment, the above formula (1) And has a fluorine atom.

  The film thickness of the charge transport layer 64 was 18 [μm]. In this case, the film thickness of the charge transport layer upper layer 64b was set to 8 [μm] and the film thickness of the charge transport layer lower layer 64a was set to 10 [μm] in consideration of the film thickness reduction in actual use as the photosensitive drum 11.

  Since the structure of other points of the image forming apparatus 10 in the present embodiment is the same as that of the first embodiment, description thereof is omitted.

  Next, an experimental example in the present embodiment will be described.

  FIG. 10 is a diagram showing the relationship between the scratch opening diameter and the white spot on the image in the second embodiment of the present invention, and FIG. 11 shows the relationship between the load and the scratch opening diameter in the second embodiment of the present invention. FIG. 12 is a diagram showing the size of the flaw opening diameter on the photosensitive layer and the white spot diameter on the image measured in the second embodiment of the present invention.

  Also in the present embodiment, a load test similar to that in the first embodiment was performed. The result of the experimental example in the present embodiment is shown in FIGS.

  FIG. 12 shows the evaluation results. In FIG. 12, similarly to FIG. 8 in the first embodiment, when the diameter of the white spot on the image is 100 [μm] or more, it is determined that a leak has occurred and is expressed as “×”. If it is less than [μm], the white spot on the image is at a level where it cannot be visually confirmed, so “◯” is indicated.

  10 and 12, in this experimental example, it can be confirmed that a leak has occurred when the scratch opening diameter is 50 [μm] or more. 11 and 12, when the load at which the flaw opening diameter is 50 [μm] or more is observed, if the binder resin of the charge transport layer 64 does not contain fluorine atoms, leakage occurs at a load of 150 [g]. On the other hand, when fluorine atoms are contained, it can be seen that no leak occurs up to a load of 200 [g].

  Therefore, even when the charge transport layer 64 has a two-layer structure and contains a binder resin in which fluorine atoms are bonded only to the charge transport layer upper layer 64b, the film thickness of the charge transport layer upper layer 64b is not less than a predetermined value. It was confirmed that the leakage resistance of the photosensitive layer 60 was improved by directly bonding 1 [wt%] or more of fluorine atoms to polycarbonate which is a binder resin.

  Thus, in the present embodiment, fluorine atoms are not included in the entire binder resin of the charge transport layer 64, but fluorine atoms are included only in the charge transport layer upper layer 64b. Since the charge transport layer 64 has a two-layer structure, the upper charge transport layer upper layer 64b has a structure with excellent leakage resistance, and the lower charge transport layer lower layer 64a is made of a material having excellent electrical characteristics. It became possible to do.

  In the first and second embodiments, an example in which the image forming apparatus 10 using an electrophotographic photosensitive member is a printer has been described. However, the present invention is not limited to an electronic device such as a copying machine or a facsimile machine. The present invention can be applied to all image forming apparatuses 10 using a photographic photoreceptor.

  The present invention is not limited to the above-described embodiment, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

FIG. 2 is a cross-sectional view showing a layer structure near the surface of the photosensitive drum in the first embodiment of the present invention. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view showing an overall structure of a photosensitive drum in a first embodiment of the present invention. It is a perspective view which shows the gear in the 1st Embodiment of this invention. It is a figure which shows the relationship between the flaw opening diameter and the white point on an image in the 1st Embodiment of this invention. It is a 1st figure which shows the relationship between the load in the 1st Embodiment of this invention, and a crack opening diameter. It is a 2nd figure which shows the relationship between the load and flaw opening diameter in the 1st Embodiment of this invention. It is a figure which shows the dimension of the flaw opening diameter on the photosensitive layer and the dimension of the white spot diameter on an image which were measured in the 1st Embodiment of this invention. It is sectional drawing which shows the layer structure of the surface vicinity of the photoconductive drum in the 2nd Embodiment of this invention. It is a figure which shows the relationship between the crack opening diameter and the white spot on an image in the 2nd Embodiment of this invention. It is a figure which shows the relationship between the load and flaw opening diameter in the 2nd Embodiment of this invention. It is a figure which shows the dimension of the flaw opening diameter on the photosensitive layer and the dimension of the white spot diameter on an image which were measured in the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Photoconductor drum 12 Charging roller 20 Image forming cartridge 25 Transfer roller 28 LED head 31 Paper 60 Photosensitive layer 61 Conductive support 64 Charge transport layer 64a Charge transport layer lower layer 64b Charge transport layer upper layer

Claims (6)

(a) an electrophotographic photosensitive member in which a photosensitive layer is laminated on a conductive support,
(B) The binder resin in the uppermost charge transport layer of the photosensitive layer contains a fluorine atom in at least one of R1 to R10 represented by the following formula (1). body.

The electrophotographic photosensitive member according to claim 1, wherein the binder resin has a hydrogen atom, an alkyl group, and an aryl group independently bonded to each of R 1 to R 10 represented by the formula (1). The uppermost charge transport layer of the photosensitive layer has a two-layer structure,
The upper layer of the charge transport layer contains the binder resin,
The electrophotographic photosensitive member according to claim 1, wherein the lower layer of the charge transport layer contains a binder resin in which fluorine atoms of the binder resin are substituted with hydrogen atoms. The photosensitive layer has a scratch opening diameter of 50 [μm] or less when a load of 150 [g] is applied to a silk needle having a tip diameter of 0.05 [mm] on the surface, and the photosensitive layer is exposed to light. The electrophotographic photosensitive member according to claim 1, wherein no image defect due to layer leakage occurs. A developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member according to claim 1. (a) the electrophotographic photosensitive member according to any one of claims 1 to 4;
(B) a charging device for charging the surface of the electrophotographic photosensitive member;
(C) an exposure device that exposes the charged surface of the electrophotographic photosensitive member to form an electrostatic latent image;
(D) a developing device for developing the electrostatic latent image;
(E) An image forming apparatus comprising: a transfer device that transfers an image developed by the developing device to a transfer medium.

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