JP2018112704A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can achieve both extension of the lives of photoreceptors and improvement of the image quality of an output image.SOLUTION: An image forming apparatus comprises: photoreceptors; and charging means that are rotated in contact with the photoreceptors and charge the surfaces of the photoreceptors through discharge with a direct current. The photoreceptors each include a layer formed from an organic compound as an outermost surface layer, and the layer formed from the organic compound contains first filler particles having an average particle diameter of 50 nm or more and 500 nm or less in an amount of 1 mass% or more and 16 mass% or less. The charging means each include a resin layer as an outermost surface layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 15 μm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus.

  In the field of electrophotographic image forming apparatuses, one of the important themes is to extend the life of a photoconductor that forms an electrostatic latent image for the purpose of improving maintainability. As the photoreceptor, there are an inorganic photoreceptor using an inorganic compound material typified by amorphous silicon, and an organic photoreceptor using an organic compound material for the surface layer of the photoreceptor. Of these, organic photoreceptors that can be manufactured at lower cost are often employed.

  In addition, there is a charging means for charging the surface of the photoreceptor in order to form an electrostatic latent image on the photoreceptor. In recent years, a contact charging method in which a conductive rubber roller is brought into contact with a photosensitive member and charged is used from the viewpoint of saving space around the photosensitive member and reducing the size of an image forming apparatus.

  An image forming apparatus including such an organic photoreceptor and a contact-type charging unit has been proposed (for example, Patent Document 1).

JP 2008-262041 A

  However, in the conventionally known technique including the technique disclosed in Patent Document 1, when an alternating current is applied during contact charging, the surface layer is often worn out by discharge, and it is difficult to extend the life of the photoreceptor. In addition, when a direct current is applied instead of an alternating current, the surface layer is less worn by discharge, but a streak-like abnormal image is likely to be generated, so that it is difficult to improve the image quality.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of extending the life of a photoconductor and improving the quality of an output image.

  As a result of intensive studies by the inventor, it is extremely important to appropriately adjust the filler diameter and filler amount contained in the outermost surface layer of the photoreceptor and the surface roughness of the outermost layer of the charging unit in order to solve the above problems. As a result, the present invention has been completed.

  The present invention is an image forming apparatus comprising at least a photosensitive member and a charging unit that contacts the photosensitive member while rotating and charges the surface of the photosensitive member by discharging with a direct current, and the photosensitive member is an organic layer as the outermost layer. The layer formed from an organic compound includes a first filler particle having an average particle size of 50 nm to 500 nm in an amount of 1% by mass to 16% by mass, and the charging unit is an outermost layer. A resin layer is provided, and the resin layer provides an image forming apparatus containing second filler particles having an average particle diameter of 3 μm or more and 15 μm or less.

  The present invention is also an image forming apparatus comprising at least a photosensitive member and a charging unit that contacts the photosensitive member while rotating and charges the surface of the photosensitive member by discharging with a direct current, wherein the photosensitive member is an outermost layer. The layer formed from an organic compound contains 1% by mass to 16% by mass of first filler particles having an average particle size of 50 nm to 100 nm, and the charging means is the A resin layer is provided as a surface layer, and the resin layer provides an image forming apparatus containing second filler particles having an average particle diameter of 3 μm or more and 30 μm or less.

  The present invention further includes an image forming apparatus including at least a photosensitive member and a charging unit that contacts the photosensitive member while rotating and charges the surface of the photosensitive member by discharging with a direct current, wherein the photosensitive member is an outermost layer. And the layer formed from the organic compound contains 1% by mass to 12% by mass of the first filler particles having an average particle diameter of 50 nm to 500 nm. A resin layer is provided as a surface layer, and the resin layer provides an image forming apparatus containing second filler particles having an average particle diameter of 3 μm or more and 30 μm or less.

  In the present invention, the relative dielectric constant of the first filler particles is preferably not less than the relative dielectric constant of the organic compound.

  In the present invention, the first filler particles are at least one selected from the group consisting of silica particles, alumina particles, and titanium oxide particles, and the second filler particles are urethane resin particles, polyamide resin particles, and fluororesin particles. Preferably, at least one selected from the group consisting of nylon resin particles, acrylic resin particles, and urea resin particles. Among these, it is more preferable that the first filler particles are silica particles and the second filler particles are nylon resin particles.

  According to the present invention, it is possible to provide an image forming apparatus capable of achieving a longer life of a photoreceptor and a higher image quality of an output image. In the present invention, by using direct current contact charging advantageous for photoconductor surface wear, the amount of filler added to the photoconductor surface, the filler diameter, and the filler diameter added to the surface of the charging means are optimized to form an image. The life of the photosensitive member can be extended while maintaining the image quality of the apparatus at a high quality.

1 is a diagram illustrating an image forming apparatus according to an exemplary embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

<Image forming apparatus>
A schematic configuration of the image forming apparatus according to the present embodiment will be described. As shown in FIG. 1, the image forming apparatus 1 is an apparatus that forms a color image using each color of magenta, yellow, cyan, and black. The image forming apparatus 1 includes an image formed on a peripheral surface, a conveying device 10 that conveys a sheet P, a developing device 20 that develops an electrostatic latent image, a transfer device 30 that secondarily transfers a toner image onto the sheet P, and the like. A photosensitive drum 40 (photosensitive member) that is an electrostatic latent image carrier (image carrier), a fixing device 50 that fixes the toner image on the paper P, and a discharge device 60 that discharges the paper P.

  The transport device 10 transports the paper P as a recording medium on which an image is formed on the transport path R1. The paper P is stacked and accommodated in the cassette K, picked up by the paper feed roller 11 and conveyed. The transport device 10 causes the paper P to reach the transfer nip region R2 via the transport path R1 at a timing when the toner image transferred to the paper P reaches the transfer nip region R2.

  Four developing devices 20 are provided for each color. Each developing device 20 includes a developing roller 21 that carries toner on the photosensitive drum 40. In the developing device 20, the toner and the carrier are adjusted so as to have a desired mixing ratio, and further mixed and stirred to uniformly distribute the toner and adjust the developer to which the optimum charge amount is given. The developer is carried on the developing roller 21. When the developer is transported to a region facing the photosensitive drum 40 by the rotation of the developing roller 21, toner in the developer carried on the developing roller 21 is formed on the peripheral surface of the photosensitive drum 40. The electrostatic latent image is developed and the electrostatic latent image is developed.

  The transfer device 30 conveys the toner image formed by the developing device 20 to the transfer nip region R2 where the toner image is secondarily transferred to the paper P. The transfer device 30 sandwiches the transfer belt 31 together with the transfer belt 31 on which the toner image is primarily transferred from the photosensitive drum 40, suspension rollers 34, 35, 36, and 37 that suspend the transfer belt 31, and the photosensitive drum 40. A primary transfer roller 32 and a secondary transfer roller 33 that sandwiches the transfer belt 31 together with the suspension roller 37 are provided.

  The transfer belt 31 is an endless belt that circulates and moves by suspension rollers 34, 35, 36, and 37. The suspension rollers 34, 35, 36, and 37 are rollers that can rotate around their respective central axes. The suspension roller 37 is a drive roller that is driven to rotate around the central axis, and the suspension rollers 34, 35, and 36 are driven rollers that are driven to rotate by the rotation drive of the suspension roller 37. The primary transfer roller 32 is provided so as to press the photosensitive drum 40 from the inner peripheral side of the transfer belt 31. The secondary transfer roller 33 is disposed in parallel with the suspension roller 37 with the transfer belt 31 interposed therebetween, and is provided so as to press the suspension roller 37 from the outer peripheral side of the transfer belt 31. As a result, the secondary transfer roller 33 forms a transfer nip region R <b> 2 with the transfer belt 31.

  Four photosensitive drums 40 are provided for each color. Each photoconductor drum 40 is provided along the moving direction of the transfer belt 31. On the periphery of the photosensitive drum 40, a developing device 20, a charging roller 41 (charging means), an exposure unit 42, and a cleaning unit 43 are provided.

  The charging roller 41 is a charging unit that uniformly charges the surface of the photosensitive drum 40 to a predetermined potential. The charging roller 41 moves following the rotation of the photosensitive drum 40. The exposure unit 42 exposes the surface of the photosensitive drum 40 charged by the charging roller 41 according to an image formed on the paper P. As a result, the potential of the portion exposed by the exposure unit 42 on the surface of the photosensitive drum 40 changes, and an electrostatic latent image is formed. The four developing devices 20 develop the electrostatic latent image formed on the photosensitive drum 40 with toner supplied from a toner tank N provided opposite to each developing device 20, and generate toner images. . Each toner tank N is filled with magenta, yellow, cyan and black toners. The cleaning unit 43 collects the toner remaining on the photosensitive drum 40 after the toner image formed on the photosensitive drum 40 is primarily transferred to the transfer belt 31.

  The fixing device 50 allows the toner image secondarily transferred from the transfer belt 31 to the paper P to adhere to the paper P and is fixed by passing the paper through a fixing nip portion that is heated and pressurized. The fixing device 50 includes a heating roller 52 (heating rotator) that heats the paper P, and a pressure roller 54 (pressure rotator) that presses and rotates the heating roller 52. The heating roller 52 and the pressure roller 54 are formed in a cylindrical shape, and the heating roller 52 includes a heat source such as a halogen lamp inside. A fixing nip portion which is a contact area is provided between the heating roller 52 and the pressure roller 54, and the toner image is melted and fixed on the paper P by passing the paper P through the fixing nip portion.

  The discharge device 60 includes discharge rollers 62 and 64 for discharging the paper P on which the toner image is fixed by the fixing device 50 to the outside of the device.

  Subsequently, a printing process by the image forming apparatus 1 will be described. When an image signal of a recorded image is input to the image forming apparatus 1, the control unit of the image forming apparatus 1 rotates the paper feed roller 11 to pick up and convey the paper P stacked on the cassette K. Based on the received image signal, the charging roller 41 uniformly charges the surface of the photosensitive drum 40 to a predetermined potential (charging process). Thereafter, the exposure unit 42 irradiates the surface of the photosensitive drum 40 with laser light to form an electrostatic latent image (exposure process).

  In the developing device 20, the electrostatic latent image is developed to form a toner image (developing process). The toner image thus formed is primarily transferred from the photosensitive drum 40 to the transfer belt 31 in a region where the photosensitive drum 40 and the transfer belt 31 face each other (transfer process). On the transfer belt 31, toner images formed on the four photosensitive drums 40 are sequentially stacked to form one stacked toner image. The laminated toner image is secondarily transferred onto the paper P conveyed from the conveying device 10 in the transfer nip region R2 where the suspension roller 37 and the secondary transfer roller 33 face each other.

  The sheet P on which the laminated toner image is secondarily transferred is conveyed to the fixing device 50. The fixing device 50 melts and fixes the laminated toner image onto the paper P by heating and pressing the paper P between the heating roller 52 and the pressure roller 54 when the paper P passes through the fixing nip portion. (Fixing process). Thereafter, the paper P is discharged to the outside of the image forming apparatus 1 by the discharge rollers 62 and 64.

  Next, the photosensitive drum 40 (photosensitive member of this embodiment) and the charging roller 41 (charging means of this embodiment) will be described in further detail.

<Photosensitive drum>
The photosensitive drum has a configuration in which a photosensitive layer is provided on a conductive support.

(Conductive support)
The conductive support may be any material as long as it has conductivity. For example, a metal such as aluminum, copper, chromium, nickel, zinc, and stainless steel is formed into a drum shape, a sheet shape, or a belt shape. , Metal foil such as aluminum or copper laminated on plastic film, aluminum, indium oxide, tin oxide etc. deposited on plastic film, metal, plastic film, paper etc. Or what apply | coated with binder resin and provided the conductive layer is mentioned.

(Photosensitive layer)
As the photosensitive layer, either a negatively charged laminated type photosensitive layer or a positively charged single layer type photosensitive layer produced by a method known to those skilled in the art may be used. The negatively charged laminated photosensitive layer includes a charge generation layer and a charge transport layer provided on the charge generation layer.

(1) Negatively Charged Laminated Photosensitive Layer A negatively charged laminated photosensitive layer is configured by laminating a charge transport layer on a charge generation layer.
(1-1) Charge Generation Layer The charge generation layer is a layer mainly composed of a charge generation material having a charge generation function, and may contain a binder resin as necessary. A known charge generation material can be used for the charge generation layer. Examples of the charge generating substance include a monoazo pigment, a disazo pigment, an asymmetric disazo pigment, a trisazo pigment, an azo pigment having a carbazole skeleton, an azo pigment having a distyrylbenzene skeleton, an azo pigment having a triphenylamine skeleton, and a diphenylamine skeleton. Examples thereof include azo pigments, perylene pigments, and phthalocyanine pigments. These charge generation materials may be used alone or in combination of two or more. Among them, the charge generation layer preferably contains at least one selected from the group consisting of oxotitanyl phthalocyanine and gallium phthalocyanine because good electrical characteristics can be obtained.

  Examples of the binder resin used for the charge generation layer as needed include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, and polyvinyl ketone. These binder resins can be used alone or as a mixture of two or more.

  A charge generation material is dispersed in a solvent using a known dispersion method such as ball mill, attritor, sand mill, bead mill, and ultrasonic wave together with a binder resin as necessary to form a charge generation layer on a conductive support. The coating liquid for carrying out can be obtained.

  The layer thickness of the charge generation layer is preferably from 0.01 μm to 5 μm, and more preferably from 0.05 μm to 3 μm.

(1-2) Charge Transport Layer The charge transport layer is a layer having a charge transport structure, and is a layer containing a charge transport material and a binder resin as main components and further including first filler particles. That is, the charge transport layer is formed from an organic compound and further includes first filler particles. The charge transport layer contains a hole transport material as a charge transport material, but may contain an electron transport material as necessary.

  Binder resins include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polycarbonate. Examples thereof include thermoplastic or thermosetting resins such as resins and polyarylate resins.

  Examples of hole transport materials include poly (N-vinylcarbazole) and derivatives thereof, poly (γ-carbazolylethyl glutamate) and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, and oxazole derivatives. Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, aminobiphenyl derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9- Styryl anthracene derivative, pyrazoline derivative, divinylbenzene derivative, hydrazone derivative, indene derivative, butadiene derivative, pyrene derivative, bis-stilbene derivative Materials, distyrylbenzene derivatives, enamine derivatives and the like. These hole transport materials can be used alone or as a mixture of two or more.

  Examples of the electron transport material include benzoquinone series, cyanethylene series, cyanoquinodimethane series, fluorenone series, phenanthraquinone series, phthalic anhydride series, and thiopyrane series. , Naphthalene-based, diphenoquinone-based, and stilbenequinone-based compounds. Specific examples include electron-accepting substances such as chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, and 7-trinitro-9-fluorenone. These electron transport materials can be used alone or as a mixture of two or more.

  As the first filler particles, both organic filler particles and inorganic filler particles can be used. The organic compound that forms the charge transport layer becomes brittle when discharged by a charging roller, but by selecting a material made of a material that is less susceptible to discharge than the organic compound as the first filler particles, photoconductor wear Can be improved. Examples of such inorganic filler particles include those made of a metal oxide material such as silica, alumina, and titanium oxide. Preferred examples of the organic filler particles include fluorine-based polymers. For example, ETFE (tetrafluoroethylene / ethylene co-polymer) is preferable. Polymer), PFA (tetrafluoroethylene / perfluoroalkyl / vinyl ether copolymer), ECTFE (ethylene trifluoride chloride / ethylene copolymer), PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene) , PCTFE (polytrifluoroethylene chloride), PVF (polyvinyl fluoride), FEP (tetrafluoroethylene / hexafluoropropylene), EPE (tetrafluoroethylene / hexafluoropropylene / perfluoroalkyl / vinyl ether) And the like).

  A coating liquid for forming the charge transport layer on the charge generation layer can be obtained by dissolving the charge transport material and the binder resin in a solvent.

  The layer thickness of the charge transport layer is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 35 μm or less.

(2) Positively charged single layer type photosensitive layer The positively charged single layer type photosensitive layer includes at least the above charge generating substance, hole transporting substance, and electron transporting substance in a single layer formed of the above binder resin. Are distributed. Each of the substances can be used alone or as a mixture of two or more, as in the case of the negatively charged laminate type.

  A positively charged single layer type photosensitive layer is obtained by dispersing or dissolving these substances in a solvent containing the above binder resin in the same manner as in the case of a negatively charged laminated type to obtain a coating solution. It can be formed by solidifying the binder resin after coating on the conductive support.

  As the first filler to be added, the same filler as in the negatively charged laminated type can be used.

  The layer thickness of the positively charged single layer type photosensitive layer is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 35 μm or less.

(Other layers)
The above configuration of the photoconductor is merely an example, and the outermost layer may not necessarily be a photoconductive layer. That is, in this embodiment, the outermost layer of the photoreceptor only has to have a desired surface property by a filler as described later, and other layers such as a protective layer formed from an organic compound are further formed on the photosensitive layer. You may have. In this case, the first filler may not be included in the photosensitive layer, and the filler corresponding to the first filler may be included only in the protective layer.

  The protective layer is composed of the first filler described above and a curable resin obtained by curing a compound having a plurality of polymerizable functional groups. The protective layer is obtained by curing a coating film obtained from a coating solution for a protective layer obtained by dissolving at least a compound having a polymerizable functional group in a solvent and containing the first filler by using a crosslinking or polymerization reaction ( Polymerization). The compound having a polymerizable functional group may be an oligomer from a polymerizable monomer or a dimer in which a plurality of them are connected. Examples of the compound having a polymerizable functional group include compounds having a chain polymerizable functional group such as an acryloyloxy group, a methacryloyloxy group, and a styryl group. Moreover, the compound which has sequential polymerizable functional groups, such as a hydroxyl group, an alkoxy silyl group, an isocyanate group, and an epoxy group, is mentioned.

  For the curing reaction, for example, radical polymerization, ionic polymerization, thermal polymerization, photopolymerization, radiation polymerization (electron beam polymerization), plasma CVD method, photo CVD method and the like can be used.

  For the purpose of improving the charge transport capability of the protective layer, a charge transport material may be added to the protective layer coating solution. As the charge transport material, the above-described charge transport materials can be used. Additives can also be added for the purpose of improving various functions. Examples of the additive include conductive particles, an antioxidant, an ultraviolet absorber, a plasticizer, and a leveling agent.

  The thickness of the protective layer is preferably 0.1 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

<Charging roller>
The charging roller in the present embodiment functions as a charging unit that contacts the photosensitive drum while rotating and charges the surface of the photosensitive drum by discharging with a direct current. Note that the discharge stress on the outermost surface of the photosensitive member can be reduced by adopting a direct current as compared with a case where direct current and alternating current are superimposed. The charging roller can include a conductive support, a conductive elastic layer on the outer peripheral surface of the conductive support, and a resin layer on the outer peripheral surface of the conductive elastic layer.

[Conductive support]
The conductive support is not particularly limited as long as it is made of a conductive metal. For example, a metal hollow body (pipe-like) made of iron, copper, aluminum, nickel, stainless steel, etc. A solid (rod-like) or the like is used. The outer peripheral surface of the conductive support may be subjected to a plating treatment as necessary for the purpose of providing rust prevention and scratch resistance as long as the conductivity is not impaired. Moreover, in order to improve adhesiveness with a conductive elastic body layer, the adhesive agent, a primer, etc. may be apply | coated to the outer peripheral surface as needed. In that case, in order to ensure sufficient conductivity, these adhesives, primers and the like may be made conductive as necessary.

  The conductive support has, for example, a cylindrical shape having a diameter of 5 mm to 10 mm and a length of 250 mm to 360 mm.

[Conductive elastic layer]
The conductive elastic layer is not particularly limited as long as it has an appropriate elasticity in order to ensure uniform adhesion to the photosensitive member. For example, natural rubber; ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, polyurethane elastomer, epichlorohydrin rubber, isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR) , Synthetic rubber such as chloroprene rubber (CR); synthetic resin such as polyamide resin, polyurethane resin, and silicone resin; and the like as a base polymer. These may be used alone or in combination of two or more.

  For the base polymer, well-known additives such as a conductive agent, a vulcanizing agent, a vulcanization accelerator, a lubricant and an auxiliary agent are appropriately added as necessary for the purpose of imparting desired characteristics to the conductive elastic layer. You may mix | blend.

As the conductive agent, carbon black, graphite, potassium titanate, iron oxide, conductive titanium oxide (c-TiO ₂ ), conductive zinc oxide (c-ZnO), conductive tin oxide (c-SnO ₂ ) And quaternary ammonium salts. Examples of the vulcanizing agent include sulfur. Examples of the vulcanization accelerator include tetramethyl thiuram disulfide (CZ). Examples of the lubricant include stearic acid. Examples of the auxiliary agent include zinc white (ZnO).

  The thickness of the conductive elastic layer is preferably about 1.25 mm or more and 3.00 mm or less in order to develop appropriate elasticity.

[Resin layer]
The resin layer contains a matrix material and second filler particles.

  The matrix material is not particularly limited as long as it does not contaminate the photoreceptor to be charged. Fluorine resin, polyamide resin, acrylic resin, nylon resin, polyurethane resin, silicone resin, butyral resin, styrene- Examples thereof include base polymers such as ethylene / butylene-olefin copolymer (SEBC) and olefin-ethylene / butylene-olefin copolymer (CEBC). These may be used alone or in combination of two or more. In the present embodiment, the matrix material is at least selected from the group consisting of a fluororesin, an acrylic resin, a nylon resin, a polyurethane resin, and a silicone resin from the viewpoint of ease of handling, the degree of freedom in material design, and the like. One type is preferable, and at least one type selected from the group consisting of nylon resin and polyurethane resin is more preferable.

  Here, the thickness of the resin layer, that is, the layer thickness (layer thickness) of the portion formed of the matrix material alone is preferably 1.0 μm or more and 15.0 μm or less. The thickness of the resin layer can be measured by cutting the roller cross section with a sharp blade and observing with an optical microscope or an electron microscope.

  The second filler particles are not particularly limited as long as the second filler particles can form irregularities on the surface of the resin layer in order to ensure a sufficient discharge point. Suitable materials for the organic filler particles include urethane resin, polyamide resin, fluororesin, nylon resin, acrylic resin, urea resin and the like. Suitable materials for the inorganic filler particles include silica, alumina and the like. These may be used alone or in combination of two or more.

  The shape of the second filler particles is not particularly limited as long as it can form irregularities on the surface of the resin layer, and may be a true sphere, an oval sphere, an indefinite shape, or the like.

  In the base polymer, in addition to the particles exemplified above, various conductive agents (conductive carbon, graphite, copper, aluminum, nickel, iron powder, conductive tin oxide, conductive titanium oxide, ionic conductive agent) Etc.), a charge control agent and the like may be contained as required.

  In order to maintain the uniformity of charging by applying a direct current, it is preferable that the charging roller surface has an appropriate roughness. That is, the ten-point average roughness Rzjis on the surface of the resin layer is preferably 5 μm or more and 30 μm or less, and Sm is preferably 30 μm or more and 500 μm or less. Although there is a method of polishing the elastic rubber to roughen the surface, this method tends to cause streaky charging unevenness due to polishing marks. In this embodiment, particles are added to the surface of the charging roller. When particles are added in the vicinity of the elastic rubber surface, discharge easily occurs at the particle portions, and when particles are added uniformly, the discharge becomes uniform and streaky charging unevenness can be suppressed. The surface roughness can be measured according to JIS B0601-2001 using a surface roughness measuring device SE-3400 manufactured by Kosaka Laboratory.

  The charging roller can be manufactured as follows, for example. First, the material for the conductive elastic layer is kneaded using a kneader such as a kneader to prepare the material for the conductive elastic layer. Moreover, the resin layer coating liquid is prepared by kneading the material for the resin layer using a kneader such as a roll, adding an organic solvent to the mixture, mixing and stirring. Next, the material for the conductive elastic layer is filled in an injection mold in which a core metal serving as a conductive support is set, and heat crosslinking is performed under predetermined conditions. Thereafter, by removing the mold, a base roll having a conductive elastic body layer formed along the outer peripheral surface of the conductive support is manufactured. Next, a resin layer coating solution is applied to the outer peripheral surface of the base roll to form a resin layer. In this way, it is possible to produce a charging roller in which a conductive elastic layer is formed on the outer peripheral surface of the conductive support and a resin layer is formed on the outer peripheral surface of the conductive elastic layer.

  In addition, the formation method of a conductive elastic body layer is not limited to the injection molding method, You may employ | adopt the method which combined the casting method, the press molding method, the roll coat method, and grinding | polishing. Further, the coating method of the resin layer coating solution is not particularly limited, and a conventionally known dipping method, spray coating method, roll coating method, or the like may be employed.

  Hereinafter, each aspect according to the image forming apparatus of the present invention including the above-described photoreceptor and charging unit will be described.

<First aspect>
The image forming apparatus according to this aspect is an image forming apparatus including at least a photosensitive member and a charging unit that rotates and contacts the photosensitive member and charges the surface of the photosensitive member by discharging with a direct current. A layer formed from an organic compound as the outermost layer, the layer formed from the organic compound contains 1% by mass to 16% by mass of first filler particles having an average particle diameter of 50 nm to 500 nm, and charging means Includes a resin layer as the outermost layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 15 μm or less.

  In this embodiment, the average particle diameter of the first filler particles is 50 nm or more and 500 nm or less from the viewpoint of reducing photoreceptor wear and obtaining good printing properties in relation to other configurations of this embodiment, but 100 nm The thickness is preferably 300 nm or less.

  The average particle diameter of the particles can be derived by arbitrarily extracting 100 particles from a population of a plurality of particles by SEM observation and taking the average value of the particle diameters. However, if the particle shape is not a perfect sphere and the particle diameter is not uniform, such as an elliptical sphere (a sphere with an elliptical cross section) or an indeterminate shape, the simple average value of the longest diameter and the shortest diameter is the particle size. The particle diameter can be made as follows.

  The content of the first filler particles is 1% by mass or more and 16% by mass or less from the viewpoint of obtaining reduction in photoreceptor wear and good printing characteristics in relation to the other configuration of this embodiment, but 5% by mass. % Or more and 12% by mass or less is preferable.

  The content of the filler particles can be quantified as follows. For example, by sampling a layer containing filler particles and heating it, the weight change (TG), differential heat (DTA), calorie (DSC), and mass of volatile components (MS) are measured. The content of the particles can be quantified (TG-DTA-MS, DSC (thermal analysis)).

  The average particle diameter of the second filler particles is 15 μm or less, preferably 12 μm or less, from the viewpoint of obtaining good printing characteristics in relation to other configurations of the present embodiment. In addition, since a moderate roughness is required for the resin layer surface, the lower limit can be 3 μm or more.

  The content of the second filler particles is preferably 5 parts by weight or more and 80 parts by weight or less, that is, 5 phr or more and 80 phr or less with respect to 100 parts by weight of the resin constituting the matrix material. When the content is 5 phr or more, there is a tendency that the charging performance is more easily satisfied. On the other hand, when the content is 80 phr or less, the particle sedimentation control when the paint is formed becomes easier and the coating stability is improved. There is a tendency not to get worse. From such a viewpoint, it is more preferably 10 phr or more and 70 phr or less.

<Second aspect>
The image forming apparatus according to this aspect is an image forming apparatus including at least a photosensitive member and a charging unit that rotates and contacts the photosensitive member and charges the surface of the photosensitive member by discharging with a direct current. The outermost layer includes a layer formed from an organic compound, and the layer formed from the organic compound contains 1% by mass to 16% by mass of first filler particles having an average particle diameter of 50 nm to 100 nm, and charging means Is provided with a resin layer as the outermost layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 30 μm or less.

  In this embodiment, the average particle diameter of the first filler particles is 50 nm or more and 100 nm or less from the viewpoint of reducing photoreceptor wear and obtaining good printing characteristics in relation to other configurations of this embodiment.

  The content of the first filler particles is 1% by mass or more and 16% by mass or less from the viewpoint of obtaining reduction in photoreceptor wear and good printing characteristics in relation to the other configuration of this embodiment, but 5% by mass. % Or more and 12% by mass or less is preferable.

  The average particle diameter of the second filler particles is 30 μm or less from the viewpoint of obtaining good printing characteristics in relation to other configurations of the present embodiment. The lower limit is 3 μm or more because an appropriate roughness is required on the surface of the resin layer, but 20 μm or more is preferable from the viewpoint of easy suppression of streaky abnormal images.

  The description of the first aspect can be applied to the content of the second filler particles.

<Third embodiment>
The image forming apparatus according to this aspect is an image forming apparatus including at least a photosensitive member and a charging unit that rotates and contacts the photosensitive member and charges the surface of the photosensitive member by discharging with a direct current. A layer formed from an organic compound as an outermost layer, the layer formed from an organic compound contains 1% by mass to 12% by mass of first filler particles having an average particle diameter of 50 nm to 500 nm, and charging means Is provided with a resin layer as the outermost layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 30 μm or less.

  In this embodiment, the average particle diameter of the first filler particles is 50 nm or more and 500 nm or less from the viewpoint of reducing photoreceptor wear and obtaining good printing properties in relation to other configurations of this embodiment, but 100 nm The thickness is preferably 300 nm or less.

  The content of the first filler particles is 1% by mass or more and 12% by mass or less from the viewpoint of obtaining reduction in photoreceptor wear and good printing characteristics in relation to other configurations of the present embodiment, but 2% by mass. % Or more and 5% by mass or less is preferable.

  The average particle diameter of the second filler particles is 30 μm or less from the viewpoint of obtaining good printing characteristics in relation to other configurations of the present embodiment. The lower limit is 3 μm or more because an appropriate roughness is required on the surface of the resin layer, but 20 μm or more is preferable from the viewpoint of easy suppression of streaky abnormal images.

  The description of the first aspect can be applied to the content of the second filler particles.

<Other aspects>
In the first to third embodiments, the relative dielectric constant of the first filler particles is preferably equal to or higher than the relative dielectric constant of the organic compound containing the first filler particles. For example, when polycarbonate (relative dielectric constant 3.1) is employed as the binder resin for the charge transport layer and silica particles (relative dielectric constant 3.6) are employed as the first filler particles, respectively, The relative dielectric constant of the filler particles is equal to or higher. This makes it difficult for the charging potential to decrease due to the local decrease in dielectric constant that occurs at the filler site. Therefore, even if the second filler particle diameter of the charging roller is large to some extent and the surface potential unevenness on the photosensitive member is somewhat uneven, the influence on the dot area deviation described later can be further reduced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

<Experiment 1>
The relationship between the amount and particle size of the first filler particles contained in the outermost layer of the photoreceptor and the photoreceptor wear rate was examined.
[Evaluation of photoreceptor wear rate]
A photoreceptor having the first filler particle content as shown in Table 1 was prepared, and incorporated in an image forming apparatus: MultiXpress X7600LX (manufactured by Samsung Electronics Co., Ltd.), and repeated image formation was performed under the following conditions.
Printing environment: Normal temperature and humidity environment (23 ° C./60% RH).
Printing conditions: printing speed (A4 horizontal feed 60 sheets / min), number of printed sheets (100,000 sheets).
Charging applied voltage: DC voltage -1400V.
Photoconductor initial film thickness: 30 μm.
Cleaning blade contact pressure: 30 gf / cm (the load cell is placed on the outer peripheral surface of the photoreceptor in contact with the cleaning blade, the load is measured, and the load cell and the cleaning blade are in contact with the photosensitive member in the rotation axis direction. The linear load was measured by dividing the measured load).

Next, the film thickness including the photosensitive layer laminated on the photosensitive conductive support in the image forming area is measured by Fischer's ISOSCOPE FMP30, and the photosensitive member is determined from the amount of film thickness change before and after repeated image formation. The amount of wear was obtained. This value was divided by the travel distance of the outer peripheral surface accompanying the rotation of the photoconductor to calculate the photoconductor wear rate. The results are shown in Table 1.

  In Table 1, OPC Filler means the first filler particles (silica particles) contained in the outermost surface layer of the photoreceptor.

  According to Table 1, it can be seen that OPC wear is improved by adding 1% by mass or more of a filler having a particle diameter of 50 nm or more as compared with the case of using a 20 nm filler corresponding to the conventional technology. When added in an amount of 20% by mass or more, the exposed area potential on the photoreceptor increased and the image density decreased.

<Experiment 2>
The relationship between the amount and the particle diameter of the first filler particles contained in the outermost layer of the photoreceptor, the particle diameter of the second filler particles contained in the outermost layer of the charging roller, and the dot area deviation was examined.
[Dot area deviation evaluation]
A photosensitive drum and a charging roller having the content of the first and second fillers as shown in Table 2 were incorporated into an image forming apparatus: MultiXpress X7600LX (manufactured by Samsung Electronics). Then, the toner image was developed on the photosensitive member by making the latent image shape of one dot into a square having a side of 85 μm. After development, the toner image was held on the photoconductor and left in the apparatus for 30 minutes or more. After the charge on the photoconductor was attenuated to some extent, the photoconductor was taken out of the apparatus. The area of 50 toner images obtained was measured with a microscope, and the standard deviation of the area was calculated. At this time, two-component development was adopted as the developing method, the toner particle diameter was 6 μm, and the toner charge amount was 50 μC / g. The results are shown in Table 2.

  In Table 2, CR Filler means second filler particles (nylon resin particles) contained on the outermost surface of the charging roller.

The dot area deviation is one of the indexes for evaluating the granularity of the image, and is obtained by measuring the area of one dot composed of the toner image on the photoconductor as described above. When the dot area deviation exceeds 650 μm ² , the graininess deteriorates in the halftone image. Therefore, the dot area deviation is preferably 650 μm ² or less. According to Table 2, the dot area deviation is mainly influenced by the OPC Filler particle amount and the CR Filler particle size. When the CR Filler particle size is 30 μm or less, the OPC Filler particle amount is preferably 12% by mass or less, and the CR Filler particle When the diameter was 15 μm or less, it was found that the OPC Filler particle amount is preferably 16% by mass or less. In particular, regarding CR Filler, if the particle size is large, the unevenness of the surface potential on the photoreceptor is large between the part where the particle is present and the part where the particle is not present, so that the unevenness of the charging potential is large and the dot area deviation is large. . In addition, even if the amount of OPC Filler particles is large, the unevenness of the potential of the exposed portion increases, so that the dot area deviation is considered to increase.

From the above results, it was found that the dot area deviation was 650 μm ² or less under the following conditions, and good image quality was obtained.
Condition 1: first filler particle diameter of 500 nm or less, first filler particle amount of 16% by mass or less, and second filler particle diameter of 15 μm or less.
Condition 2: The first filler particle size is 100 nm or less, the first filler particle amount is 16% by mass or less, and the second filler particle size is 30 μm or less.
Condition 3: First filler particle diameter of 500 nm or less, first filler particle amount of 12% by mass or less, and second filler particle diameter of 30 μm or less.

<Experiment 3>
The type of the first filler particles contained in the outermost layer of the photoconductor was changed, and the relationship with the photoconductor wear rate and the relationship with the dot area deviation were examined. Specifically, various evaluations were performed in the same manner as in Experiment 1 and Experiment 2, except that polytetrafluoroethylene particles (average particle diameter 200 nm) were used as the first filler particles instead of silica particles. The results are shown in Tables 3 and 4.

  From the above results, when polytetrafluoroethylene particles having an average particle diameter of 200 nm are used as the first filler, the first filler particle amount is 16% by mass or less, and the second filler particle diameter is 15 μm or less. Further, it has been found that the wear resistance of the photoreceptor and the image quality can be improved.

  In addition, when the dot area deviation is compared between the case where silica particles having an average particle diameter of 200 nm are added to the charge transport layer in Experiment 1 and the present experiment, the value when the second filler particle diameter is 30 μm in this experiment. Is getting worse. The inventor infers this cause as follows. In Experiment 1, the relative dielectric constant of polycarbonate, which is the binder resin of the charge transport layer, is 3.1, that of silica particles is 3.6, and the relative dielectric constant of the first filler particles is equal to that of the binder resin. Because of the above, it is considered that the charging potential is unlikely to decrease due to the local decrease in dielectric constant that occurs in the filler region. On the other hand, in this experiment, the relative dielectric constant of polycarbonate, which is the binder resin of the charge transport layer, is 3.1, and that of polytetrafluoroethylene particles is 2.1. It is considered that the local surface potential unevenness on the photosensitive member is promoted because the charged potential is liable to be lowered and the second filler particle size is 30 μm.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Conveying device, 11 ... Feeding roller, 20 ... Developing device, 21 ... Developing roller, 30 ... Transfer device, 31 ... Transfer belt, 32 ... Primary transfer roller, 33 ... Secondary transfer roller ( (Transfer roller), 34, 35, 36 ... suspension roller, 37 ... suspension roller, 40 ... photosensitive drum, 41 ... charging roller, 42 ... exposure unit, 43 ... cleaning unit, 50 ... fixing device, 52 ... heating roller, 54 ... pressure roller, 60 ... discharge device, 62, 64 ... discharge roller, K ... cassette, N ... toner tank, P ... paper, R1 ... transport path, R2 ... transfer nip area.

Claims (6)

An image forming apparatus comprising at least a photosensitive member, and a charging unit that contacts the photosensitive member while rotating and charges the surface of the photosensitive member by discharging with a direct current,
The photoreceptor includes a layer formed from an organic compound as an outermost layer, and the layer formed from the organic compound contains 1% by mass to 16% by mass of first filler particles having an average particle diameter of 50 nm to 500 nm. Contains,
The charging means includes a resin layer as an outermost layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 15 μm or less.
Image forming apparatus. An image forming apparatus comprising at least a photosensitive member, and a charging unit that contacts the photosensitive member while rotating and charges the surface of the photosensitive member by discharging with a direct current,
The photoreceptor includes a layer formed from an organic compound as an outermost layer, and the layer formed from the organic compound contains 1% by mass to 16% by mass of first filler particles having an average particle diameter of 50 nm to 100 nm. Contains,
The charging means includes a resin layer as an outermost layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 30 μm or less.
Image forming apparatus. An image forming apparatus comprising at least a photosensitive member, and a charging unit that contacts the photosensitive member while rotating and charges the surface of the photosensitive member by discharging with a direct current,
The photoreceptor includes a layer formed from an organic compound as an outermost layer, and the layer formed from the organic compound contains 1% by mass to 12% by mass of first filler particles having an average particle diameter of 50 nm to 500 nm. Contains,
The charging means includes a resin layer as an outermost layer, and the resin layer contains second filler particles having an average particle diameter of 3 μm or more and 30 μm or less.
Image forming apparatus.   The image forming apparatus according to claim 1, wherein a relative dielectric constant of the first filler particle is equal to or higher than a relative dielectric constant of the organic compound.   The first filler particles are at least one selected from the group consisting of silica particles, alumina particles and titanium oxide particles, and the second filler particles are urethane resin particles, polyamide resin particles, fluororesin particles, nylon The image forming apparatus according to claim 1, wherein the image forming apparatus is at least one selected from the group consisting of resin particles, acrylic resin particles, and urea resin particles.   The image forming apparatus according to claim 1, wherein the first filler particles are silica particles, and the second filler particles are nylon resin particles.

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