JP5286666B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming method applied to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile.

  Conventionally, an electrophotographic image forming apparatus such as a copying machine or a laser beam printer that uses an intermediate transfer member is known. These form images by the following process.

  The electrostatic latent image formed on the photoconductor as the image carrier is developed with toner and visualized. A primary transfer step of transferring the visualized toner image to the intermediate transfer member is performed, and this is sequentially repeated with a plurality of color toners to form a toner image of a plurality of colors on the intermediate transfer member.

  Next, the toner images of a plurality of colors on these intermediate transfer members are collectively transferred to a recording material. Finally, by fixing, a multicolor image and a color image are obtained on the recording material.

  In such an image forming apparatus using an intermediate transfer body, a toner image is once transferred to the intermediate transfer body and transferred in a superimposed manner, so that a part of a character image or a line image is not transferred. The phenomenon is often a problem. This void phenomenon is considered to occur as a result of concentration of mechanical pressure when transferring a character image or a line image to a recording material (such as paper) or an intermediate transfer member.

  Conventionally, various attempts have been made to prevent this hollow out phenomenon. For example, in Japanese Patent Application Laid-Open No. 2004-228561, when a character mode mainly consisting of a black image is selected, the force applied to the transfer roller is reduced to suppress a dropout phenomenon, and when an image mode mainly consisting of a natural image is selected, the transfer roller is A device was devised to give priority to transferability by increasing the pressure.

  Patent Document 2 discloses a method for improving the hollowing out by defining the toner aggregation rate when a specific overload is applied to the toner and defining the overload of the transfer portion.

  In Patent Document 3, toner agglomeration occurs by reducing the particle size of the toner by keeping the relationship between the surface roughness of the photoconductor, the surface roughness of the intermediate transfer member, and the volume average particle size of the toner used within a specific range. There has been proposed a device for preventing a void from occurring easily.

  Patent Document 4 discloses that the surface layer of a photoconductor contains fluorine atom-containing resin fine particles to reduce the surface energy of the photoconductor, thereby increasing the releasability of the toner pressed on the photoconductor during transfer. A method of preventing this is disclosed.

JP 2005-10389 A JP 2004-334004 A JP 2001-235946 A JP-A-6-250414

  However, none of the above-described conventional techniques has yet reached a sufficient solution.

  In general, the toner dropout phenomenon from the image carrier to the intermediate transfer member is caused by agglomerates in the toner layer during transfer compression, and the generated agglomerates are not transferred normally and remain on the image carrier side. Occurs. Conventionally, attempts have been made to suppress voids by lowering the transfer pressure, but in order to fill the unevenness of the toner layer height due to the image and the unevenness of the members in the paper width direction, a strong transfer pressure is required. In some cases, it was necessary to add, and it was not possible to sufficiently suppress voids or worms (hereinafter simply referred to as “voids”).

  SUMMARY OF THE INVENTION An object of the present invention is to prevent a transfer defect in a character or a linear image, particularly a so-called “collapse” phenomenon in which a non-transfer area appears in a character image or a linear image in an electrophotographic image forming apparatus. .

In order to solve the above-mentioned problem, an image forming apparatus according to claim 1, wherein after the toner image formed on the image carrier is primarily transferred onto the intermediate transfer member, the toner image on the intermediate transfer member is transferred to a recording material or the like. An image forming apparatus comprising transfer means for performing secondary transfer, wherein the intermediate transfer body has three layers of a base layer, an elastic layer, and a surface layer, wherein the surface layer is a non-foamed body layer, The elastic layer is a foam layer, and is located below the surface layer. The rebound resilience of the intermediate transfer member is 25 to 85%, which is smaller than the rebound resilience of the image carrier. The Young's modulus of the body is 3700 to 6000 Mpa.

  Here, the occurrence of the hollowing out phenomenon and the relationship between the intermediate transfer member and the image carrier used in the present invention will be described in detail. At the time of transfer from the image carrier to the intermediate transfer member, the toner layer is sandwiched between the image carrier and the intermediate transfer member, and a strong pressure is applied to the toner layer to generate aggregates in the toner layer. The stronger the pressure in the toner layer, the larger the aggregates in the toner layer, and the larger the amount of aggregates that are generated, adhere to the image carrier side and become hollow.

  The inventors of the present invention have intensively researched and found that “slow-out” can be suppressed by the following method. That is, by making the rebound resilience of the intermediate transfer member smaller than the rebound resilience of the image carrier, even if a strong pressure is generated in the toner layer, aggregates generated in the toner layer remain on the image carrier side. Therefore, the image is normally transferred to the intermediate transfer member side, and voids can be suppressed.

  The rebound resilience is a characteristic that represents the speed of deformation of an object when subjected to a load, whereas the hardness is a characteristic that represents the amount of deformation of an object when subjected to a load. The rate and hardness are different.

  In the primary transfer portion, as shown in FIG. 1, the toner layer is sandwiched between the photosensitive member (image carrier) and the transfer member, and the toner layer is transferred to the transfer member side by the force of the electric field, but is transferred to the transfer nip portion. When a strong pressure is applied, the photosensitive member and the transfer member are deformed, and the adhesion force with the aggregate generated in the toner layer is increased. If the adhesion force between the photosensitive member and the toner aggregate is larger than the adhesion force and electric field between the transfer member and the aggregate, a void occurs. At this time, as shown in FIG. 2, the remaining deformation of the photoconductor when the photoconductor and the transfer belt after the transfer nip are separated causes an increase in the adhesion force between the toner aggregate and the photoconductor. The inventors measured the rebound resilience in a combination of a photoconductor and a transfer belt having different properties, and found that the combination of a photoconductor and a transfer belt in which hollow defects frequently occur is higher than the rebound resilience of the photoconductor. It was found that the rebound resilience of the intermediate transfer member was higher. Therefore, in the image forming apparatus of the present invention, it is preferable that the rebound resilience of the photoconductor is higher than the rebound resilience of the intermediate transfer member.

  In the case of such a configuration, as shown in FIG. 3, since the deformation on the transfer belt side remains when the photoconductor after the transfer nip and the transfer belt are separated, the toner aggregate and the transfer belt are generated even when the toner aggregate is generated. The adhesion force to the toner side becomes larger than the adhesion force between the toner aggregate and the photosensitive member side, and transfer is normally performed. In addition, the measurement of a resilience elastic modulus is based on JISK6255-1999, and is measured in 25 degreeC environment. In addition, tan δ (loss tangent) measured by the dynamic viscoelasticity measuring apparatus has a correlation with the rebound resilience, and the lower the rebound resilience, the higher tan δ (loss tangent). In this case, tan δ (loss tangent) of the intermediate transfer member is preferably higher than tan δ (loss tangent) of the photosensitive member.

  The rebound resilience of the intermediate transfer member used in the image forming apparatus of the present invention is preferably in the range of 25 to 85%. If it is lower than 25%, the deformation of the intermediate transfer member is not recovered during the secondary transfer, and the transfer rate may deteriorate with respect to the transfer to the recording material. If the ratio is higher than 85%, the deformation of the intermediate transfer belt is recovered when the photoconductor and transfer belt after the transfer nip are separated, and the aggregate is pulled toward the photoconductor to cause a void.

  The Young's modulus of the intermediate transfer member used in the image forming apparatus of the present invention is preferably 6000 Mpa or less. If the Young's modulus of the intermediate transfer member is 6000 Mpa or more, the intermediate transfer member side is not deformed, so that a strong pressure is applied to the toner layer at the time of transfer, and the agglomerates are easily generated, and the agglomerates are likely to remain on the photosensitive member side. The occurrence of voids becomes noticeable.

  Further, the material and configuration of the intermediate transfer member used in the image forming apparatus of the present invention are not particularly limited, and all known materials and configurations can be used, but those composed of a plurality of layers having different properties are preferable.

An example of the material and configuration is shown below.
(1) A material having a high Young's modulus (tensile modulus) is used as a single-layer belt. PC (polycarbonate), PVDF (polyvinylidene fluoride), PAT (polyalkylene terephthalate), PC (polycarbonate) / PAT ( Polyalkylene terephthalate) blend materials, ETFE (ethylene tetrafluoroethylene copolymer) / PC, ETFE / PAT, PC / PAT blend materials, carbon black dispersed thermosetting polyimide, and the like. These single-layer belts with high Young's modulus have the advantage that the amount of deformation with respect to stress at the time of image formation is small, and in particular, it is difficult to cause misregistration at the time of color image formation. easy.

  (2) A belt having a two- to three-layer structure in which a belt having a high Young's modulus is used as a base layer and a surface layer or an intermediate layer is provided on the outer periphery thereof. These belts of two to three layers can adjust Young's modulus and resistance, and can prevent abnormal images derived from these characteristics. An elastic layer using rubber or elastomer can be used in the layer.

  The intermediate transfer member used in the image forming apparatus of the present invention is preferably an intermediate transfer member in which a part of the layer is an elastic layer. The elastic layer is more preferably a foam layer. By setting it as a foam layer, it becomes easy to reduce the impact resilience. Furthermore, when the intermediate transfer member has a multilayer structure and includes a foam layer, it is preferable to form a non-foam layer on the surface layer. For example, in the three-layer structure as shown in FIG. 4, in the base layer 1, the intermediate layer 2, and the surface layer 3, the foam layer is formed in the intermediate layer and the non-foamed layer is formed in the surface layer. If the surface layer is a foam layer, there may be adverse effects such as toner entering the holes in the surface layer, or the adhesive force becomes too great and the transfer rate of secondary transfer decreases.

  The elastic belt (intermediate transfer material) resin is polycarbonate, fluororesin (ETFE, PVDF), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene. -Vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (for example, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer). Polymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (for example, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer) Polymer, styrene-phenyl methacrylate copolymer ), Styrene resins (monopolymer or copolymer containing styrene or a styrene substitution product) such as styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, methyl methacrylate resin , Butyl methacrylate resin, ethyl acrylate resin, butyl acrylate resin, modified acrylic resin (for example, silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate Polymer, vinyl chloride-vinyl acetate copolymer, rosin modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin , A silicone resin, a ketone resin, an ethylene-ethyl acrylate copolymer, a xylene resin, a polyvinyl butyral resin, a polyamide resin, a modified polyphenylene oxide resin, or a combination of two or more types can be used. . However, it is a matter of course that the material is not limited to the above materials.

  Elastic rubbers and elastomers include butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene Terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, ricone rubber, fluororubber, polysulfide rubber, polynorbornene rubber, hydrogenated nitrile Selected from the group consisting of rubber, thermoplastic elastomers (eg, polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyamide, polyurea, polyester, fluororesin) One type or a combination of two or more types can be used. However, it is not limited to the above materials.

  The material suitable for the foam layer is not particularly limited. For example, thermoplastic foam such as polyethylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, viscose, ionomer, or urethane, rubber foam, epoxy, phenol urea, pyranyl, silicone And thermosetting foams such as acrylic, among which urethane is most suitable. Further, when the material of the foam layer is urethane, any hydrophobic or hydrophilic polyol can be used as the polyol. Among these, polyether polyols of polypropylene glycol and ethylene oxide adducts are preferable. Further, the cell form of the foam layer can be used in any form such as single bubble or open cell, but open cell is preferable because the dimensional change due to temperature is small. When another layer is formed on the foam layer, the outer skin of the foam layer, that is, the skin layer may be removed by polishing, or another layer may be formed as it is without being polished. An adhesive layer can be provided between the other layer and the foam layer.

  There are no particular restrictions on the conductive agent for adjusting the resistance value. For example, carbon black, graphite, metal powder such as aluminum and nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, potassium titanate, antimony oxide-tin oxide composite Conductive metal oxides such as oxide (ATO) and indium oxide-tin oxide composite oxide (ITO) can be used. The conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. It is not limited to the conductive agent. Among these, carbon black is inexpensive and easy to control conductivity with a small amount. When used for urethane which is a foam layer, it is preferably used in an amount of 0.5 to 50 parts by weight, particularly 1 to 30 parts by weight, based on 100 parts by weight.

  The surface layer preferably has a small surface energy, and is a material that uses one or a combination of two or more of polyurethane, polyester, epoxy resin, etc. to improve lubricity, such as fluororesin, fluorine compound, carbon fluoride, 2 One kind or two or more kinds of powders such as titanium oxide and silicon carbide, or combinations of particles having different particle diameters can be dispersed and used. Further, it is also possible to use a material having a reduced surface energy by forming a fluorine-rich layer on the surface by performing a heat treatment like a fluorine-based rubber material. The method for producing the transfer layer is not limited. For example, a centrifugal molding method in which a material is poured into a rotating cylindrical mold to form a belt, a spray coating method in which a liquid paint is sprayed to form a film, a cylindrical shape Examples include the dipping method in which the mold is dipped in the material solution, the casting method in which the mold is poured into the inner mold and the outer mold, and the method in which the compound is wound around a cylindrical mold and vulcanized and polished. It is not limited to, but it is common to manufacture combining several manufacturing methods.

  As a method for preventing elongation in the case of a belt shape, there are a method of forming a rubber layer in a core resin layer with little elongation, a method of putting a material for preventing elongation in a core layer, etc., but it is limited to a specific production method. It is not something.

Materials constituting the core layer for preventing elongation include, for example, natural fibers such as cotton and silk; polyester fibers, nylon (registered trademark) fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, poly Synthetic fibers such as vinylidene chloride fiber, polyurethane fiber, polyacetal fiber, polyfluoroethylene fiber, and phenol fiber; inorganic fiber such as carbon fiber, glass fiber, and boron fiber; selected from the group consisting of metal fibers such as iron fiber and copper fiber One or a combination of two or more types may be used to form a woven fabric or a yarn. Of course, the material is not limited to the above.
The filamentous body may be any twisting method such as a twist of one or a plurality of filaments, a single twisted yarn, various twisted yarns, a double yarn or the like. Further, for example, fibers of a material selected from the above material group may be blended. Of course, the yarn can be used after being subjected to an appropriate conductive treatment. On the other hand, the woven fabric can be any woven fabric such as knitted fabric, and of course, a woven fabric that is interwoven can also be used and can be subjected to a conductive treatment.

  The production method for providing the core layer is not particularly limited. For example, a method of providing a coating layer on a woven fabric woven in a cylindrical shape on a mold or the like, and a liquid woven woven fabric in a cylindrical shape. Examples thereof include a method of immersing in rubber or the like to provide a coating layer on one or both sides of the core layer, and a method of winding a thread spirally around a mold or the like at an arbitrary pitch and providing a coating layer thereon.

  The thickness of the elastic layer depends on the hardness of the elastic layer, but if it is too thick, the surface expands and contracts and cracks are likely to occur in the surface layer. In addition, since the expansion and contraction of the image increases as the amount of expansion and contraction increases, it is not preferable that the image is too thick (approximately 1 mm or more).

  Furthermore, the volume resistivity of the intermediate transfer member used in the present invention is preferably in the range of 107 to 1012 Ωcm. The intermediate transfer member used in the present invention preferably uses an elastic layer for controlling Young's modulus and rebound resilience, but resistance control is also important. If the volume resistivity of the intermediate transfer member exceeds the above range, the bias required for transfer becomes high, which increases the power supply cost. In addition, since the charging potential of the intermediate transfer member becomes high and self-discharge becomes difficult in the transfer process, the recording material peeling process, etc., it is necessary to provide a static eliminating means. If the volume resistivity is lower than the above range, the charge potential decays quickly, which is advantageous for static elimination by self-discharge, but toner scattering after transfer occurs.

  In addition, the image forming apparatus of the present invention preferably includes a lubricant application unit that applies a solid lubricant to the surface of the photoreceptor. By applying a solid lubricant to the surface of the photoconductor, the adhesion between the photoconductor and the toner is reduced, making it difficult for the toner to remain on the photoconductor side during separation of the photoconductor and the intermediate transfer body after transfer, preventing voids can do.

  Next, a photoconductor (image carrier) used in the image forming apparatus of the present invention will be described. First, the drum-shaped photoreceptor used in the present invention is one in which at least a photosensitive layer is formed on a conductive support, or one in which a charge generation layer or charge transport layer is formed, and further a photosensitive layer or charge transport. The thing in which the protective layer was formed on the layer is used. As the conductive support, the charge generation layer and the charge transport layer, any known one can be used. The material of the photoconductor of the present invention may be an inorganic photoconductor material such as selenium and its alloys and amorphous silicon, but an organic photoconductor material is preferred.

  Examples of the charge generating material constituting the charge generating layer of the organophotoreceptor include X-type metal-free phthalocyanine, π-type metal-free phthalocyanine, τ-type metal-free phthalocyanine, ε-type copper phthalocyanine, α-type titanyl phthalocyanine, β Phthalocyanine pigments such as type titanyl phthalocyanine, disazo trisazo pigments, anthraquinone pigments, polycyclic quinone pigments, indigo pigments, diphenylmethane pigments, trimethylmethane pigments, cyanine pigments, quinoline pigments, benzophenone pigments, naphthoquinone pigments, Perylene pigments, fluorenone pigments, squarylium pigments, azulenium pigments, perinone pigments, quinacridone pigments, naphthalocyanine pigments and porphyrin pigments can be used. The amount of these charge generation materials that can be used in combination with the organic acceptor compound in the entire photosensitive layer is usually 0.1 to 40% by weight, preferably 0.3 to 25% by weight. Examples of the charge transport material include a hole transport material and an electron transport material. As the hole transport material used in the present invention, known materials can be used, and examples of the inorganic material include selenium and its alloys, amorphous silicon and the like. Examples of organic substances include, for example, compounds having a triphenylamine moiety in the molecule, hydrazone compounds, triphenylmethane compounds, oxadiazole compounds, carbazole compounds, pyrazoline compounds, styryl compounds, butadiene compounds And a polymer donor compound such as a polysilane compound having a linear main chain made of Si, and polyvinylcarbazole. The amount of the hole transporting material in the entire photosensitive layer is usually 10% by weight or more, preferably 20 to 60% by weight.

  As the electron transport material used in the present invention, known materials can be used, for example, compounds having a fluorenone skeleton in the molecule, indenone compounds, indenoquinoxaline compounds, phthalimide compounds, naphthalimide compounds, pyrazine compounds. Examples thereof include compounds, indenopyrazine compounds, benzofluorenone compounds, pentadienone compounds, diphenoquinone compounds, benzoquinone compounds, and naphthoquinone compounds. In the present invention, the above electron transport materials can be used alone or in combination of several kinds.

  In addition, as the binder for the photosensitive layer, polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, Addition polymerization resins such as melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more of these repeating units, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-acetic acid Mention may be made of vinyl-maleic anhydride copolymer resins. The amount of these binders in the entire photosensitive layer is usually 20 to 90% by weight, preferably 30 to 70% by weight. In addition, an undercoat layer can be provided between the photosensitive layer and the conductive substrate for the purpose of improving the chargeability. As these materials, in addition to the binder material, known materials such as polyamide resin, polyvinyl alcohol, casein, and polyvinylpyrrolidone can be used.

  As the conductive support that can be used in the present invention, a known support can be used, such as a metal plate such as aluminum, nickel, copper, and stainless steel, a metal drum or metal foil, a thin film of aluminum, tin oxide, and copper iodide. Examples thereof include a plastic film or glass applied or pasted.

  In the case of using a belt-shaped photoconductor, the configuration is almost the same as the configuration of the above-mentioned photoconductor, but the material for the support uses a generally known engineering plastic base, such as polyethylene. Known materials such as terephthalate, polyethylene naphthalate, polyetherimide, polyethersulfone, polycarbonate, polyarylate and the like can be mentioned. However, this invention is not limited to these, What is necessary is just to have the characteristic as a belt support body. Among the materials for the support, polyethylene naphthalate particularly satisfies the requirements. The conductive layer may be formed by vapor deposition or sputtering of a metal or metal oxide, or conductive fine particles such as gold, silver, copper, zinc or the like and their oxides or alloys thereof and the base resin. Examples thereof include a method of coating or molding a conductive resin made of a mixture.

  The protective layer can contain inorganic fine particles. As the inorganic fine particles, for example, titanium oxide, silica, colloidal silica, aluminum oxide and the like are used, and silica and colloidal silica are particularly important. Is preferably made hydrophobic by coating with a titanium coupling agent or a silane coupling agent. The volume average particle size of the inorganic fine particles is preferably 0.01 to 5 μm, and if it is less than 0.01 μm, the contribution to the abrasion resistance and cleaning properties of the protective layer is insufficient. The particles protrude to damage the cleaning member, deteriorating the cleaning property, and the image quality is likely to be deteriorated.

  In order to produce the organic photoreceptor (image carrier) of the present invention, for example, a charge generation layer forming solution prepared by dissolving the charge generation substance in an organic solvent or dispersing it with a ball mill, ultrasonic waves, or the like is used. What is necessary is just to apply | coat and dry on the base | substrate which is an electroconductive support body by well-known methods, such as braid | blade application | coating and spray application | coating, and to apply | coat and dry the said charge transport material by the method similar to the above.

  Next, the toner used in the image forming apparatus of the present invention will be described. The toner used in the image forming apparatus of the present invention can be basically any known toner. As binder resin, styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, and substituted polymers thereof; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer Styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate Copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, Styrene-butadiene copolymer Styrene copolymers such as styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polychlorinated Vinyl, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, aromatic Group petroleum resin, chlorinated paraffin, paraffin wax and the like.

As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R) ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Se Red, parachlor ortho nitro Nirin Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH) Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R, Brilliant Red Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, poly Zored, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC) Indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalocyani Green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50% by weight with respect to 100% by weight of the binder resin.
The production method is not limited. For example, a resin or a colorant that is a constituent material of a toner is mixed and stirred, melt-kneaded, pulverized and classified, a method of dispersion polymerization, suspension polymerization, Examples thereof include a method of producing by a polymerization method such as an emulsion polymerization method.

  Further, as the toner used in the image forming apparatus of the present invention, a toner whose surface is coated with an external additive is suitable. As the material for the external additive, basically all known materials can be used, and examples thereof include silica fine powder, titania fine powder, alumina fine powder, acrylic fine powder and fluorine fine powder. By coating the surface of the toner with an external additive, the adhesive force between the toner and the photoconductor is reduced, so that voids are less likely to occur. The external additive coverage of the external additive is preferably 10 to 90%, and more preferably 30 to 60%. When the external additive coverage is less than 10%, it is difficult to make the adhesive force between the toner and the photoreceptor appropriate, and increase in the number of voids occurs. When the external additive coverage exceeds 90%, liberation of the external additive is likely to occur, and in particular, the constituent members of the image forming apparatus such as the photoreceptor may be easily damaged due to repeated image formation. The external additive coverage can be measured by image analysis of the electron microscope image of the toner surface to determine the ratio of the external additive coating area to the surface area of one toner particle.

  The external additive is preferably a mixture of fine particles having an average primary particle diameter of 50 nm to 150 nm and an external additive having a smaller particle diameter than the fine particles. The smaller the particle size of the external additive, the smaller the adhesion and the lower the cohesiveness. However, when the average particle size is less than 50 nm, the external additive is added to the surface of the toner base when the toner is stirred for a long time. Will be buried. By burying the external additive, the adhesive force of the toner changes, increasing the void and causing the image quality to deteriorate. When the external additive particles having an average particle size exceeding 150 nm are used, they are easily detached from the toner base material, and adhere to other members, causing abnormal images due to photoconductor filming. For this reason, the average particle size is reduced in order to reduce the cohesiveness by using an external additive having a small particle size, prevent an increase in adhesion when the toner is stirred for a long period of time, and stabilize the cohesiveness and fluidity. It is effective to use a mixture of external additive particles of 50 to 150 nm.

  Moreover, it is preferable that the external additive has a substantially spherical shape. By making the external additive into a spherical shape, it becomes difficult for the toner to be embedded in the toner base when it is stirred for a long time.

  For example, in the case of inorganic fine particles having hygroscopicity, the external additive is preferably subjected to a hydrophobization treatment in consideration of environmental stability and the like.

  There is no restriction | limiting in particular as the method of the said hydrophobization process, According to the objective, it can select suitably, For example, the method etc. with which a hydrophobization processing agent and the said fine powder are made to react at high temperature are mentioned.

  There is no restriction | limiting in particular as said hydrophobization processing agent, According to the objective, it can select suitably, For example, a silane coupling agent, silicone oil, etc. are mentioned.

  The external addition method of the external additive is not particularly limited and may be appropriately selected according to the purpose. For example, a method using various mixing devices such as a V-type blender, a Henschel mixer, and a mechano-fusion is preferable. It is done.

  According to the first aspect of the present invention, it is possible to provide an image forming apparatus capable of preventing the occurrence of voids during transfer and forming a high quality image.

  Hereinafter, the present invention will be described in detail based on the embodiment shown in FIG. 5 of the accompanying drawings. FIG. 5 is a schematic configuration diagram of a color image forming apparatus showing an embodiment of the present invention. In this embodiment, an intermediate transfer belt is used as an intermediate transfer body, but an intermediate transfer drum is used instead of the intermediate transfer belt. It can also be.

  The image forming apparatus shown in FIG. 5 has primary transfer portions (C1, C2, C3, C4) for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (BK). It has. Since each primary transfer portion (C1, C2, C3, C4) has substantially the same configuration, in the following description, the configuration of only one primary transfer portion (C1) will be described. The image carrier 11 is rotationally driven in the direction of arrow R1. At this time, the surface of the image carrier 11 is charged by the charging device 21 to a predetermined polarity, for example, a negative polarity. Next, the charged surface of the image carrier 11 is irradiated with light-modulated laser light L emitted from the image writing means, whereby an electrostatic latent image is formed on the surface of the image carrier 11. That is, the portion where the absolute value of the potential on the surface of the image carrier is lowered by the laser beam is an electrostatic latent image (image portion), and the portion where the absolute value of the potential is kept high without being irradiated with the laser beam is the background. Part. Next, the electrostatic latent image is developed with toner stored in the developing device 31 and charged to a predetermined polarity, and visualized as a toner image.

  Untransferred toner remaining on the image carrier without being transferred to the transfer belt (intermediate transfer member) is scraped off by the cleaning device 41 to clean the surface of the image carrier. The toner removed from the image carrier can be transported to a developing device by a toner recycling device (not shown) to recycle the toner.

  The transfer means (transfer section) for performing the secondary transfer is arranged to face the image carriers 11 to 14 and the image carriers 11 to 14, is wound around a plurality of rollers and is driven to rotate in the direction of the arrow, The toner images carried by the image carriers 11 to 14 are arranged to face the roller 73 via the intermediate transfer belt 50 and the intermediate transfer belt 50 for transferring the toner images, and the intermediate transfer belt 50 is subjected to a predetermined nip pressure. A secondary transfer roller 80 that abuts and transfers the toner image formed on the intermediate transfer belt 50 to the recording material P is provided.

  The intermediate transfer belt 50 is stretched by rollers 71 to 73 and primary transfer bias rollers 61 to 64, and is driven to rotate in the direction of the arrow in the drawing by a drive motor (not shown). The speed of the surface of the intermediate transfer belt 50 is driven at a speed substantially equal to the speed of the surfaces of the image carriers 11 to 14, but it is also possible to make a speed difference. The primary transfer bias rollers 61 to 64 are pressed in the direction of the photoconductors 11 to 14 by pressure springs (not shown). The intermediate transfer belt 50 is adjusted so that its volume resistivity is in the range of 107 to 1012 Ωcm. The volume resistivity of the intermediate transfer belt was measured according to JIS-K6911. The yellow toner image, the magenta toner image, the cyan toner image, and the black toner image respectively formed on the image carriers 11 to 14 are sequentially transferred onto the intermediate transfer belt 50. On the other hand, the recording material P is conveyed from the sheet feeding device (not shown) between the intermediate transfer belt 50 and the secondary transfer roller 80 at a predetermined timing from the direction of the arrow F. At this time, the toner images of the respective colors formed on the intermediate transfer belt 50 are electrostatically collectively transferred onto the recording material P. The recording material P to which the toner image of each color is transferred is heated and pressurized by a fixing device (not shown), and the toner image is fixed on the recording material P. Thereafter, the recording material fixed by a fixing device (not shown) is discharged from a paper discharge unit (not shown). The color image forming apparatus of this embodiment superimposes a single color mode for forming an image of any one color of yellow, magenta, cyan or black and an image of any two colors of yellow, magenta, cyan or black. There are two-color mode to form, three-color mode to superimpose images of any one of yellow, magenta, cyan, and black, and a full-color mode to form a four-color superimposed image as described above. The mode can be specified by an operation unit (not shown).

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
4. An intermediate transfer belt (intermediate transfer member) having a rebound resilience of 34% and a Young's modulus of 3800 Mpa, and a photoreceptor having a rebound resilience of 53%, having the same configuration as FIG. The (image carrier) was mounted on the color image forming apparatus having the configuration shown in FIG. 5, a full color image was printed, and the void was evaluated by the following evaluation method.
-Evaluation of hollow holes-
Using the intermediate transfer belt and the photosensitive member of the combination of Example 1, evaluation of the void at the time of the transfer pressure spring force 16N was performed.

One pressure spring of this apparatus is installed at each end of the transfer roller, and the transfer pressure spring force is the total value of the spring force at both ends. The transfer pressurizing spring force 16N is conventionally large enough to cause hollowing out. The degree of hollowing out is determined in five stages (5 is 5) for the state of hollowing out for an image output using a test chart in which fine lines of 3 dots in the main operation direction and 60 dots in the secondary operation direction are evenly arranged. A good 1 is bad). Rank 4 or higher is an image-free range.
-Result-
When an intermediate transfer belt having a rebound resilience of 34% including a conductive foamed elastic layer and a Young's modulus of 3800 Mpa and a photoreceptor having a rebound resilience of 53% were used, the hollowness degree was 5. The results are shown in Table 1.

(Example 2)
An intermediate transfer belt (intermediate transfer member) having a rebound resilience of 45% and a Young's modulus of 4000 Mpa using a non-foamed elastic layer as an intermediate layer, and a photosensitivity of 53% rebound resilience. As a result of evaluating in the same manner as in Example 1 except that the body (image carrier) was used, the hollowness degree was 4. The results are shown in Table 1.

(Example 3)
An intermediate transfer belt (intermediate transfer member) having a rebound resilience of 30% and a Young's modulus of 3700 MPa using a foam layer as an intermediate layer, and a photoconductor (image bearing member) having a rebound resilience of 53% are the same as in FIG. As a result of performing the evaluation in the same manner as in Example 1 except that the body) was used, the hollowness degree was 5. The results are shown in Table 1.

Example 4
An intermediate transfer belt (intermediate transfer body) having a rebound resilience of 80% and a Young's modulus of 3600 Mpa using a non-foamed elastic layer as an intermediate layer, and a photosensitivity of 90% rebound resilience. As a result of evaluating in the same manner as in Example 1 except that the body (image carrier) was used, the hollowness degree was 4. The results are shown in Table 1.

(Example 5)
An intermediate transfer belt (intermediate transfer member) having a rebound resilience of 22% and a Young's modulus of 4000 Mpa using a foam layer as an intermediate layer and a photoreceptor having a rebound resilience of 53% are the same as in FIG. As a result of evaluating in the same manner as in Example 1 except that the degree of hollowness was 2. The results are shown in Table 1.

(Example 6)
The intermediate transfer belt 50 (see FIG. 5) is a belt having a two-layer structure, and an intermediate transfer belt (intermediate transfer member) having a rebound elastic modulus of 88% and a Young's modulus of 3600 MPa using a non-foamed elastic layer as a surface layer. As a result of evaluating in the same manner as in Example 1 except that a photoconductor (image carrier) having an elastic modulus of 90% was used, the hollowness degree was 2. The results are shown in Table 1.

(Comparative Example 1)
An intermediate transfer belt (intermediate transfer member) having a rebound resilience of 60% and a Young's modulus of 3600 Mpa using a non-foamed elastic layer as an intermediate layer, and a photosensitivity of 53% rebound resilience. As a result of evaluating in the same manner as in Example 1 except that the body (image carrier) was used, the hollowness degree was 1. The results are shown in Table 1.

(Comparative Example 2)
The intermediate transfer belt 50 (see FIG. 5) is a single-layer belt mainly composed of polyimide. The intermediate transfer belt (intermediate transfer member) having a rebound resilience of 60% and a Young's modulus of 6800 Mpa and a rebound resilience of 53%. As a result of evaluating in the same manner as in Example 1 except that the body (image carrier) was used, the hollowness degree was 1. The results are shown in Table 1.

  As shown in Table 1, each of Examples 1 to 6 in which the rebound resilience of the intermediate transfer member is smaller than the rebound resilience of the image carrier has a degree of hollow loss of 2 or more. Good results were obtained compared to degree 1.

  In particular, Examples 1 to 4 in which the rebound resilience of the intermediate transfer member is smaller than the rebound resilience of the image bearing member and the rebound resilience of the intermediate transfer member is in the range of 25 to 85% are all in the middle. The degree was 4 or more and there was no problem, and a good image was obtained.

  On the other hand, Comparative Example 1 in which the rebound resilience of the intermediate transfer member is larger than the rebound resilience of the image carrier has a hollowness degree of 1, and the rebound resilience of the intermediate transfer member is the same as that of the image carrier. 2 also had a hollowness of 1.

It is sectional drawing explaining the effect | action in a primary transfer part. FIG. 6 is a cross-sectional view for explaining a void in a primary transfer portion. It is sectional drawing explaining the effect | action in the primary transfer part concerning this invention. FIG. 3 is a cross-sectional view showing a layer structure of an intermediate transfer member according to the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus applied to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base layer 2 Intermediate | middle layer 3 Surface layer 11, 12, 13, 14 Image carrier 21, 22, 23, 24 Charging device 31, 32, 33, 34 Developing device 41, 42, 43, 44 Cleaning device 50 Intermediate transfer belt 61, 62, 63, 64 Primary transfer roller 71, 72, 73 Roller 80 Secondary transfer roller P Transfer material

Claims (1)

An image forming apparatus comprising transfer means for performing a primary transfer of a toner image formed on an image carrier onto an intermediate transfer member and then performing a secondary transfer of the toner image on the intermediate transfer member onto a recording material or the like, In the image forming apparatus in which the intermediate transfer member has three layers of a base layer, an elastic layer, and a surface layer,
The surface layer is a non-foamed layer, the elastic layer is a foam layer, and is positioned below the surface layer,
The rebound resilience of the intermediate transfer member is 25 to 85%, which is smaller than the rebound resilience of the image carrier,
An image forming apparatus, wherein the intermediate transfer member has a Young's modulus of 3700 to 6000 MPa.

Images