Abstract: A development device includes a developer container; a rotary cylindrical developer carrier including an outer electrode including multiple electrode portions arranged in a circumferential direction of the developer carrier, an inner electrode provided on an inner circumferential side of the developer carrier from the outer electrode, an insulation layer disposed between the outer electrode and the inner electrode, and a surface layer; and a bias power source to apply a first bias voltage and a second bias voltage to the inner electrode and the outer electrode, respectively. The first bias power source causes an electrical potential difference that changes with time between the inner electrode and the outer electrode to cause the developer to hop on a circumferential surface of the developer carrier. At least one of the first bias voltage and the second bias voltage has a cyclic waveform in which pulse-on time is reduced.

Abstract: A carrier including a magnetic core particle and a resin layer covering a surface of the magnetic core particle. The magnetic core particle is a ferrite particle including strontium in an amount of 0.005 to 3% by mass, measured by fluorescent X-ray spectroscopy. The resin layer comprises a resin obtained by heating a copolymer comprising a silicon-containing unit A and another silicon-containing specific unit B.

Abstract: A toner supplying roller which is used in a developing apparatus and has the following characteristics: (1) an average diameter of a foam cell opening portion on a surface of a foam elastic member is 100 to 800 ?m, (2) an unopened cell closed by a skin layer of a film thickness of 50 ?m or less is present in the surface of the foam elastic member, and (3) assuming that a surface area of the foam elastic member is A, a total area of the foam cell opening portions is B, and a surface area of the unopened cell is C, the following relationship is satisfied: B A + 0.2 ? B + C A ? 0.95 .

Abstract: The present invention provide a mold for forming a developer blade and a developer blade manufactured with such a mold which are able to give images of good quality even in the low-temperature low-humidity condition and to improve a mold releasability. A mold 10 for forming a developer blade has a plate accommodation space 14 in which the metal plate is accommodated and a belt-like cavity 15 for forming the elastic member adjacent to the plate accommodation space. At least a part 20a of a cavity surface 20 defining the cavity 15 in the cross section taken along the cavity width direction is finished to have a surface roughness Ry of not more than 10 ?m.

Abstract: An image forming apparatus includes a developer containing casing, a developer transport body, transport electrodes, and a developer vibrating section. The developer containing casing is a box-like member in which a developer is contained. The developer transport body has a developer transport surface, and is disposed within the developer containing casing. The plurality of transport electrodes are provided along the developer transport surface. These transport electrodes are configured such that they can transport the developer in a predetermined developer transport direction on the developer transport surface upon application of traveling-wave voltages. The developer vibrating section is configured to be able to vibrate the developer which is to be transported on the developer transport surface.

Abstract: In a system or method for development of potential images of images to be printed and generated on an intermediate image carrier using a developer fluid comprising charged toner particles and developer fluid in an electrographic printing or copying device, a feed device is provided comprising as function elements at least one chamber scraper, a raster element comprising cups to receiver the developer fluid, and at least one first flow element arranged in the chamber scraper. Between the at least one flow element and the raster element an electrical voltage is supplied such that a toner particle concentration in the cups of the raster element is increased. An application device accepts the developer fluid from the feed device and supplies it to the intermediate image carrier.

Abstract: An image forming apparatus, including a surface-traveling latent image bearer bearing a latent image on the surface thereof; an image developer feeding a toner in a two-component developer including the toner and a carrier to the latent image in a developing area facing the latent image bearer to develop the latent image to form a toner image, including a developer stirrer and feeder circulating the two-component developer in circulation paths while stirring the two-component developer, including a driver independently driving the first and the second stirring and feeding members; a transferer transferring the toner image onto a recording material; and a controller controlling the driver such that an amount of the two-component developer fed by the second stirring and feeding member per unit time is relatively larger than that of the two-component developer fed by the first stirring and feeding member when a predetermined increase condition of stirring is satisfied.

Abstract: The present invention is directed to a non-contact, single-component developing system for electrophotographic machines that effectively reduces the effect of adhesion forces on the development process. The developing system of the present invention uses a thin layer forming member where Rz is less than or equal to 6.65 ?m. Also, the system uses a predetermined length for the thin layer forming member, to control pressing force by the thin layer forming member on the toner and toner support member. The distance from the contact point to the edge is less than or equal to r×(tan ?). Angle ? is spanned by the contact point and the edge; r is the toner support member radius.

Abstract: Exemplary embodiments provide a roll member that includes one or more controllable cells and methods for making and using the roll member to control an image (or toner) state thereon. The controllable cells can be disposed on a roll substrate and configured in a manner that each controllable cell can be addressed individually and/or as groups. Each controllable cell can be addressable to provide a surface vibration to release toner particles adhered/attracted thereto and can also be capable of sensing the toner state of the roll member and thus to control the image or toner state. In an exemplary embodiment, the disclosed roll member can be used as a donor roll for a development system of an electrophotographic printing machine to create controlled and desired toner powder cloud for high quality image development.

Abstract: A toner including toner particles including a binder resin containing at least one polyester resin comprising an inorganic tin (II) compound and an external additive including a particulate inorganic material having a volume average particle diameter greater than 70 nm and less than 300 nm. The binder resin preferably includes a polyester resin having a weight average molecular weight of from 5,000 to 50,000 and another resin having a weight average molecular weight of from 200,000 to 400,000. A developer including the toner; and a developing device, an image forming apparatus and a process cartridge, which form toner images using the toner are also provided.

Abstract: There is provided an image formation device comprising an developer holding body having a holding surface parallel with a main scanning direction and holding thereon developer; an developer supplying unit to carry developer along a carrying path, wherein the developer supplying unit comprises first carrying electrodes arranged along the carrying path and serving to carry the developer in a carrying direction; second carrying electrodes arranged along the carrying path to face the first electrodes and serving to carry the developer in the carrying direction; a first voltage applying unit to apply a first carrying voltage having a first frequency to the first carrying electrodes; and a second voltage applying unit to apply, to the second carrying electrodes, a second carrying voltage having a second frequency different from the first frequency.

Abstract: A developing device includes a toner carrying member and an electric-field forming unit. The electric-field forming unit forms electric fields having different characteristics at a first area of the surface of the toner carrying member located within a developing area and a second area of the surface of the toner carrying member located out of the developing area such that a hopping height of toner at the first area is higher than that at the second area.

Abstract: A developing apparatus includes a developing roller, a first shaft, a second shaft, a belt, and a power supply. The developing roller is in contact with an image forming body. The first shaft is driven in rotation by an external drive source. The belt is entrained about the first and second shafts, and is partially at first and second portions in a wrapping contact with the developing roller. The power supply applies voltages to the first and second shafts such that a voltage drop appears in the belt in a direction of travel of the belt. The power supply applies a voltage to the developing roller such that a first electric field is developed across the developing roller and the first portion, and such that a second electric field in the opposite direction to the first electric field is developed across the developing roller and the second portion.

Abstract: An image forming method including forming a toner image on a transfer medium with a toner comprising a wax having a polar group, and applying a varnish to the toner image. The wax may be a plant wax having an ester group, a wax having a polar group derived from a fatty acid, an oxidized wax, or a mixture thereof. The varnish may include a surfactant, such as a polyoxyethylene glycol, and may be photocurable.

Abstract: A developer apparatus includes a toner carrier roller having convex and concave sections formed thereon. A restriction member including an elastic abutting member having an edge part that abuts the toner carrier roller removes toner from the convex sections such that the concave sections alone carry toner. Within a restriction nip created as the toner carrier roller and the restriction member abut abutting segments where the edge part abuts on the convex sections, and opening segments where the edge part and the concave sections are opposed to each other with a gap between each other, appear alternatingly along the width direction. In the opening segments, the edge part bulges toward bottom surfaces of the concave sections beyond linear lines connecting top surfaces of two adjacent convex sections which are on both sides to the concave sections which are opposed to the edge part.

Abstract: A developer apparatus, includes: a container which houses toner; a toner carrier roller that is provided, on a surface thereof, with a plurality of convex sections which are regularly arranged and a concave section which surrounds the convex sections, is shaped approximately like a cylinder, and rotates while carrying a toner layer of charged toner on the surface thereof; and a restriction member that abuts on the surface of the toner carrier roller to form a restriction nip, restricts a thickness of the toner layer carried on the surface of the toner carrier roller in the restriction nip, and removes the toner layer on the convex sections from among the toner layer carried on the surface of the toner carrier roller at an upstream-side end of the restriction nip in a rotation direction of the toner carrier roller, wherein a part of toner carried by the concave section moves to the convex sections to cover the convex sections with the toner at a downstream side to the restriction nip in the rotation direction

Abstract: In an image forming apparatus, a toner carrier roller rotatably mounted to a housing that stores toner rotates to convey toner to an opposed position facing a latent image carrier outside the housing. A plurality of convex sections are regularly arranged on a surface of the roller in an axial direction parallel to the rotational axis and in a circumferential direction orthogonal to the axial direction and parallel to a circumferential surface of the roller and a concave section surrounds the convex sections. A seal member abuts the surface of the roller moving from the outside toward the inside of the housing at a position downstream of the opposed position in a rotation direction of the roller to prevent toner leakage from inside the housing. The roller moves relative to the seal member in the axial direction.

Abstract: A developing roller according to the invention includes a columnar magnet roller, and a cylindrical sleeve that houses the magnet roller. A plurality of fragmented micro recesses is formed on the surface of the sleeve. The micro recesses are arranged dispersively both in an axial direction and in a circumferential direction of the sleeve.

Abstract: Developing roller comprising a conductive mandrel with at least an elastic conductive base layer and a charge providing layer. The base layer is located closer to the mandrel than the charge providing layer. The base layer is roughened before the charge providing layer is applied to the base layer.

Abstract: An image forming apparatus is provided that has a developing agent holder arranged as opposed to an image holder having an electrostatic latent image formed thereon, the developing agent holder attaching the developing agent to the image holder, a developing agent supplying unit rotatably arranged in contact with the developing agent holder, the developing agent supplying unit supplying a developing agent to the developing agent holder, an adjustment unit capable of adjusting a contacting state between the developing agent holder and the developing agent supplying unit.

Abstract: A disclosed developing device includes a toner carrying member having electrodes, a toner supply unit supplying the toner to the toner carrying member, and a hopping electric field generator unit generating electric field to cause the toner hopping on the toner carrying member by applying a pulse voltage to the electrodes. The hopping electric field generator unit includes a pulse voltage generator circuit generating the pulse voltage, a first direct-current power source supplying bias to the pulse voltage generator circuit for regulating a peak value of the pulse voltage, and a second direct-current power source having a same polarity with a toner charging polarity, and outputting a variable voltage level. The hopping electric field generator unit controls the peak value of the pulse voltage by changing an output of the first power source and a mean thereof by changing an output of the second power source.

Abstract: A developer supply device, comprising a developer holding body having a cylindrical developer holding surface so that the developer holding surface moves in a direction perpendicular to the main scanning direction and a developer held on the developer holding surface is carried to a developer supply position; a developer amount limiting member that limits an amount of the developer held on the developer holding surface by contacting the developer holding surface on an upstream side in a moving direction of the developer holding surface with respect to the developer supply position; and a carrying substrate that carries the developer to the developer holding body through a traveling electric field, wherein the carrying substrate faces the developer holding surface at a developer holding position, and wherein a position to which the developer scraped off the developer holding surface falls is different from the developer holding position.

Abstract: A powder conveying device and an image forming apparatus having the same are disclosed. The powder conveying device to convey powder such as toner, includes a conveying plate to carry powder thereon, a vibration generating device to vibrate the conveying plate, and a plurality of conveying protrusions provided on a surface of the conveying plate to convey the powder loaded on the conveying plate. Each of the conveying protrusions has an incline of an upstream side and an incline of a downstream side on a powder conveying path. The incline of the upstream side is smaller than the incline of the downstream side. The powder conveying device can realized with smaller size and/or with lower cost.

Abstract: A developer carrier has concave portions regularly arranged on the surface thereof and being rotatable with a developer thereon. A contact member is made of an elastic rubber material, is in contact with the surface of the developer carrier, and vibrates with the rotation of the developer carrier. A value obtained by dividing a movement speed of the surface at the time of rotation of the developer carrier by a pitch of the concave portions in a peripheral direction of the developer carrier is smaller than a peak vibrational frequency of the contact member when a loss tangent obtained by dividing a loss elastic modulus of the contact member by a storage elastic modulus is the greatest.

Abstract: An aspect of the invention provides a development device including a rotatable development sleeve which supplies developer to a photosensitive drum, the development sleeve being disposed such that a rotational axis of the development sleeve is orientated toward a vertical direction; a conveying screw which conveys the developer along a rotational axis direction of the development sleeve; and a developer supply guide which guides the developer conveyed by the developer conveying device to the development sleeve. The plural developer supply guides are disposed at predetermined intervals in the rotational axis direction of the development sleeve and between the development sleeve and the conveying screw.

Abstract: A developing roller suppresses scattering of toner during a developing process and provides a further higher-quality electrophotographic image. The developing roller has a mandrel, an elastic layer provided on the circumference of the mandrel, and a surface layer provided on the circumference of the elastic layer. The surface layer contains a urethane resin serving as a binder and urethane resin particles dispersed in the binder, for forming convex portions on the surface of the surface layer. The surface of the urethane resin particles is partly covered with fine inorganic particles containing at least one element selected from silicon, titanium and aluminum and the urethane resin particles are in direct contact with the binder at the surface onto which the fine inorganic particles are not attached.

Abstract: A developer supply apparatus is provided which supplies a toner to a supply object, the developer supply apparatus including a developer storage body which stores a powdery developer, and a transfer body which transfers the developer along the developer transfer path with traveling wave electric fields. The developer includes a toner having a predetermined charging characteristic and an electric neutralizer having an opposite charging characteristic, which is opposite to the predetermined charging characteristic.

Abstract: A developing device has a developer bearing member, a housing adapted to accommodate a developer, and a supply roller adapted to supply the developer within the housing for the developer bearing member. The supply roller has an outer circumferencial foam layer made of resin or rubber. The foam layer has an air permeability of 150-200 ml/cm2/s, a hardness of 50-200 N, and an average cell density of 20-40 per 25 mm width.

Abstract: A developing apparatus 130 is accommodated within a laser printer 100. The developing apparatus 130 includes a developing casing 131 and a toner electric field transport body 132. The toner electric field transport body 132 includes a transport wiring substrate 133 and a transport-substrate support member 134. A plurality of transport electrodes 133b are provided on the transport wiring substrate 133. The transport wiring substrate 133 is supported by the transport-substrate support member 134 in a state in which the transport wiring substrate 133 is deformed in a tubular shape. Further, the transport wiring substrate 133 is supported by the transport-substrate support member 134 such that margin areas of the transport wiring substrate 133, which are opposite end portions of the transport wiring substrate 133 with respect to a sub-scanning direction and in which the transport electrodes 133b are not formed, are separated from a tonner transport path.

Abstract: An image forming apparatus (100) includes a photoreceptor drum (1), a development unit (2), a pressing member (7), and a vibration absorption member (8). The development unit (2) is disposed adjacent to the photoreceptor drum (1), and supported movably toward and away from the photoreceptor drum (1). The pressing member (7) urges the development unit (2) toward the photoreceptor drum. The vibration absorption member (8) frictionally suppresses the movement of the development unit (2) toward and away from the photoreceptor drum (1). The vibration absorption member (8) attenuates a self-excited vibration of the development unit (2), by suppressing the movement of the development unit (2).

Abstract: A developing device includes a developing container in which a developer is contained; a developer carrying member for carrying the developer and feeding the developer by rotation thereof to a developing zone in which the developer carrying member opposes an image bearing member on which a latent image is formed and develops the latent image with the developer; and an electrode, disposed opposed to the developer carrying member, to which a bias for forming an electric field for moving regular-charge toner in the developer container toward the developer carrying member is to be applied. The electrode is provided downstream of the developing zone with respect to a rotational direction of the developer carrying member and is provided vertically above the developer carrying member. At least a part of the electrode is located downstream of a rectilinear line connecting a rotation center and top point of the developer carrying member with respect to the rotational direction of the developer carrying member.

Abstract: A developing apparatus, comprises an endless belt shaped donor member; a developer supporting member to carry developer including toner and magnetic carrier and to form a toner layer on the donor member; a first supporting member arranged in the inside of the donor member with a predetermined gap against the developer supporting member and to strain the donor member; a second supporting member arranged in the inside of the donor member with a predetermined gap against the developer supporting member and to strain the donor member; a toner supply bias applying section to apply onto the first supporting member a toner supply bias for supplying toner from the developer supporting member to the donor member; and a toner recovery bias applying section to apply onto the second supporting member a toner recovery bias for recovering toner from the donor member to the developer supporting member.

Abstract: A colorless transparent toner including a binder resin and a layered inorganic mineral, wherein the layered inorganic mineral is an organic modified layered inorganic mineral, in which at least part of ions present between layers are modified with an organic ion.

Abstract: A developing apparatus is accommodated within a laser printer. The developing apparatus includes a developing casing and a toner electric field transport body. The toner electric field transport body includes a transport wiring substrate and a transport-substrate support member. A plurality of transport electrodes are provided on the transport wiring substrate. The transport wiring substrate is supported by the transport-substrate support member in a state in which the transport wiring substrate is deformed in a tubular shape. Further, the transport wiring substrate is supported by the transport-substrate support member such that margin areas of the transport wiring substrate, which are opposite end portions of the transport wiring substrate with respect to a sub-scanning direction and in which the transport electrodes are not formed, are separated from a tonner transport path.

Abstract: A developing device is provided having a simple configuration by which a desired amount of developer can be delivered to an image bearing member, and there is provided an image forming apparatus having the developing device. A developing device includes a developing roller by which two-component developer is borne and delivered to a photoreceptor drum, a layer thickness-regulating member for regulating a layer thickness of the developer, and a magnetism-generating member for generating magnetism, and a control unit for controlling an amount of displacement of the magnetism-generating member. The control unit 23 controls an amount of displacement of the magnetism-generating member relative to the development sleeve.

Abstract: A developer has a molecular weight distribution of its tetrahydrofuran soluble portion measured by a gel permeation chromatography. In the molecular weight distribution, the main peak is in a range from 2×103 to 3×104 weight-average molecular weight (Mw), the shoulder peak is in a range from 200 to 500 Mw, and a half-value width of the main peak is equal to or less than 50000. A glass-transition temperature Tg of the developer is a range from 55° C. to 80° C.

Abstract: An image forming apparatus includes: a latent image bearing member on which an electrostatic latent image is to be formed; a developing unit which contains the developer and performs a development process to develop the electrostatic latent image formed on the latent image bearing member; and a movement mechanism which moves the developing unit toward the latent image bearing member when the development process is performed, and moves the developing unit away from the latent image bearing member and changes the attitude of the developing unit with, respect to the latent image bearing member when the development process is not performed.

Abstract: Each transport electrode has its longitudinal direction intersecting with a sub-scanning direction. Transport electrodes 133a are disposed in parallel with each other and are arrayed along the sub-scanning direction. A transport-electrode electricity supply wiring section is connected to root portions of the transport electrodes. The root portions are one end portions of the transport electrodes with respect to the longitudinal direction. Toner transport guide members are disposed in such a manner as to cover the transport-electrode electricity supply wiring section and opposite end portions of the transport electrodes; i.e., the root portions and distal end portions.

Abstract: An developer bearer conveys developer to a developing station under influence of an electric field created by an electric flux line. The developer bearer includes plural kinds of electrodes that receive different voltages from each other and collectively creates the electric flux line. The plural kinds of electrodes are arranged on different layers in a normal line of the developer bearer. The developer bearer includes an insulation layer that insulates the plural kinds of electrodes.

Abstract: A toner including toner particles including a binder resin, and a colorant, and an external additive present on a surface of the toner particles, wherein the external additive includes a silica having an average primary particle diameter of from 100 to 500 nm and a BET specific surface area of from 800 to 1000 m2/g. An image forming method including forming an electrostatic image on an image bearing member; developing the electrostatic image with the toner to form a toner image; and transferring the toner image on to a receiving material. An image forming apparatus including an image bearing member bearing an electrostatic image; a developing device developing an electrostatic image with the toner to form a toner image on the image bearing member; a transfer device transferring the toner image to a receiving material; and a fixing device fixing the toner image on the receiving material.

Abstract: A developing device configured to form toner cloud without making toner particles adhere to the electrostatic transport substrate having electrodes. By applying periodical voltages to electrodes, electrically charged toner particles float on the electrostatic transport substrate. Also, a rotatable toner transporter designed to carry toner particles floating on the electrostatic transport substrate. Also, a two-component developer bearer including a sleeve with magnets on which the two-component developer is borne. The two-component developer borne on the sleeve is sent to the toner transporter by rotation of the sleeve. There, toner particles are transported to the toner transporter because of the electric bias applied between the two-component developer bearer and the toner transporter. Toner particles electrically floating on the toner transporter are sent to the photoconductor for development.

Abstract: An image forming apparatus includes an image carrier that carries a latent image; a charging device that charges the image carrier with a charging voltage having an AC component; and a roller that carries a developer to be supplied to the image carrier in a developing position, with a surface of the roller provided with axially-formed grooves, the frequency of the AC component of the charging voltage and the number of the grooves provided on the roller being set so that non-uniformity in density of an output image becomes invisible, caused by interference between the frequency of the AC component of the charging voltage and the frequency at which the grooves pass the developing position.

Abstract: A developing unit for transferring toner onto a latent image on an image carrier so as to develop the latent image includes a toner carrier, an electric field generator and a separating force applicator. The toner carrier including a plurality of electrodes disposed along the surface thereof and insulated from each other transports the toner to a developing area facing the image carrier. The electric field generator applies a periodic voltage to the plurality of electrodes of the toner carrier so that an electric field is generated on the toner carrier surface to cause the toner charged to a given polarity and borne on the surface of the toner carrier to hop. The separating force applicator applies a separating force to separate the toner on the toner carrier from the surface thereof outside the developing area. The separating force applicator is disposed separately from the electric field generator.

Abstract: The toner includes at least a binder resin, and a colorant. The toner has properties such that the percentage W(3000) of components having a molecular weight of 3,000 or less in tetrahydrofuran-soluble components of the toner determined by a GPC-RALLS viscosity analysis is 20% by weight or less; the molecular weight Mp at the peak top of the main peak in the molecular weight distribution curve of the tetrahydrofuran-soluble components is from 4,000 to 10,000; and the ratio Rt(Mp)/Rs(Mp) of an inertia square radius Rt(Mp) at the molecular weight Mp to an inertia square radius Rs(Mp) of linear polystyrene at the molecular weight Mp is greater than 0.98, wherein the inertia square radius Rs(Mp) is determined from a working curve obtained by subjecting plural polystyrenes having different molecular weights to the GPC-RALLS viscosity analysis.

Abstract: A developing device, process cartridge, and image forming apparatus that use ETH development, and are capable of forming good multi-color images with a simple construction, and are capable of preventing the dispersal of powder. The developing device is for developing latent images on a latent image carrying member by applying powder to the latent image carrying member, and comprises: a transport member disposed in opposition to the latent image carrying member and having a plurality of transport electrodes that generate a progressive wave electric field to move the powder; a voltage supply device for applying a multi-phase voltage to the transport electrodes; and a transport member surface potential determination device for determining the surface potential of the transport member.

Abstract: A developer holding member includes a magnetic field generating device and a hollow body including the magnetic field generating device thereinside, and attracting a developer to an external surface thereof with magnetic force of the magnetic field generating device. The external surface of the hollow body is randomly provided with a large number of depressions, and a peak intensity of a spectrum within a range of wavelengths not more than 1 mm, which is figured out by performing a frequency analysis using a profile curve in a circumferential direction of the external surface, is not more than 12.

Abstract: A toner supply apparatus 6 is configured to be able to supply a charged toner T to a latent image forming surface LS of a photoconductor drum 3. The toner supply apparatus 6 houses a toner electric field transport body 62. The toner electric field transport body 62 has first portions and second portions which differ in toner T transport force. The first portions and the second portions differ in structural feature, such as relative dielectric constant or thickness. By means of such a structural difference, the state of transport of the toner T on the toner transport surface TTS is appropriately set.

Abstract: There is provided an image formation device, comprising a developer holding body having a developer holding surface; and a developer supply unit to supply the developer to a first position facing the developer holding surface by carrying the developer in a developer transport direction intersecting with the main scanning direction through use of effect of an electric field. The developer supply unit comprises a plurality of carrying electrodes each of which is formed to have a longer side extending along the main scanning direction. The carrying electrodes are arranged along the developer transport direction to carry the developer when a drive voltage is applied to the carrying electrodes. The developer supply unit has a developer carrying area formed such that, in the main scanning direction, the developer carrying area becomes narrower from an upstream side in the developer transport direction toward the first position along the developer transport direction.

Abstract: The present invention provides a magnetic mono-component toner which can suppress a selection development on a latent image carrier and can maintain favorable image properties for a long period by using a toner having the coarse powder distribution (S) within a given range in a jumping developing method and an image forming method which uses the toner. In the toner used in the jumping developing method which develops an electrostatic latent image formed on a latent image carrier using a developer carrier, the toner includes toner particles which contain at least a binding resin and a magnetic powder, and the coarse powder distribution (S) of the toner particles satisfies a following formula (1). Coarse powder distribution (S)=(50?A)/2?17 (volume %/?m)??(1) (wherein, A is a volume % of the coarse powder having particle sizes larger than D50 based on volume by 2 ?m or more).

Abstract: A development device includes an open-ended housing, a rotatable roller, an array of multiple primary electrodes, a voltage source, a sealing member, and a secondary electrode. The housing accommodates toner for application to the photoconductive surface through an end opening thereof. The roller has an outer circumferential surface to deliver the toner from within the housing to a development zone. The array of multiple primary electrodes are aligned with each other on the roller surface. The voltage source applies a periodic pulse voltage to at least a subset of the primary electrodes to generate an oscillating primary electric field. The sealing member seals clearance between the roller surface and an edge of the end opening downstream from the development zone. The secondary electrode generates a secondary electric field to force the toner from the sealing member toward the roller surface to prevent premature removal of the toner.