Abstract: A developing apparatus for developing an electrostatic image with light chromatic toner and dark chromatic toner which have the same hue, the developing device includes a light color developing device for accommodating a developer containing the light chromatic toner and carrier to develop the electrostatic image; a dark color developing device for accommodating a developer containing the dark chromatic toner and carrier to develop the electrostatic image; light color developer supply container accommodating a developer containing the light chromatic toner and the carrier to be supplied to the light color developing device; and dark color developer supply container accommodating a developer containing the dark chromatic toner and the carrier to be supplied to the dark color developing device, wherein the developer in the light chromatic toner supply container and the developer in the dark chromatic toner supply container have carrier weight ratios which are different from each other.

Abstract: An image forming apparatus that includes: a visible image forming unit that forms a visible image on a record material; and a retroreflective image forming unit that forms a retroreflective image having a retroreflection property on the record material.

Abstract: A color image forming system including a photosensitive drum, a charger which charges the photosensitive drum, and a laser scanning unit which is installed below the photosensitive drum and radiates light onto the charged photosensitive drum, to form an electrostatic latent image. The system further includes a plurality of developing units with toner of at least four colors such as yellow, magenta, cyan, and black, arranged at different heights along the outer surface of the photosensitive drum to develop the electrostatic latent image with the toner when a developing roller installed in each of the developing units is maintained at a developing gap with the photosensitive drum. A transfer unit transfers the developed image onto a piece of paper, and a fusing unit is installed above the photosensitive drum and fuses the transferred image onto the piece of paper. The developing units may be arranged in the order of magenta, cyan, yellow, and black.

Abstract: An image formation device has an image carrier in which are formed latent images, and a development device into which development units housing toner are detachably installed. When development units with a plurality of colors are installed in respective installation positions of the development device, the image formation device operates in color printing mode, and when at least one black development unit is installed in any among the plurality of installation positions, and at least one among the development units with the colors other than black is not installed, even if at least one development unit in the plurality of colors other than black is installed, the image formation device operates in monochrome printing mode. When any of the C, M, and Y development units is removed from color mode state, the image formation device operates in monochrome printing mode.

Abstract: A color electrophotographic image forming apparatus for forming an image on a recording material, includes (i) a mounting portion for detachably mounting process cartridges developing images with different colors and each including an electrophotographic photosensitive drum and a developing roller for developing an latent image formed on the drum, wherein roller is movable between a contact state contacting the drum and a spaced state spaced from the drum; (ii) a switching device switching the rollers between the contact and spacing states; (iii) a feeding belt for feeding the recording material along all of the drums; (iv) a controller for switching between a first monochrome mode in which the belt contacts all of the drums and a second monochrome mode in which the belt contacts only the drum of the cartridge which develops the latent image for image formation.

Abstract: A color image forming device includes a photosensitive unit, an exposing unit, a plurality of developing units, a first transfer body, a second transfer body and a fixing unit. The photosensitive unit includes a photosensitive member with a photosensitive layer. The exposing unit exposes the photosensitive layer to form a series of latent images on the photosensitive member. Each of the developing units includes a developing-agent bearing member bearing thereon a different color developing agent and supplies the developing agent to the photosensitive member to develop corresponding latent images into visible images. The first transfer body receives the visible images from the photosensitive member. The second transfer body receives transfer of the visible images from the first transfer body and transfers the visible images onto a recording medium. The fixing unit fixes the visible images onto the recording medium.

Abstract: In a tandem type image forming apparatus of this invention provided with image forming units arranged under an intermediate transfer medium and further, an exposure device arranged under the image forming units, developing devices are arranged so that exposure positions of image carriers and developing rollers come to the opposite sides with toner stirring mixers put between them. Further, there are guides extending under cleaning blades below the cleaning blades to receive falling toners. Further, suction ducts are provided to suck in the air around the developing devices. A slit area formed by the guides and an area of a laser beam projecting unit of the exposure device are arranged while they are shifted. Formed images are exposed at a sufficient exposure light intensity by preventing the laser beam injection unit of the exposure device from being stained and a toner image of high quality is obtained.

Abstract: In the image forming apparatus of the present invention, a developing roller is press fit into the rotor at the edge of the rotary holder of the revolver type color developing device that is positioned against the photosensitive drum and a developing gap between the photosensitive drum and the developing roller is finely adjusted in parallel to a line connecting the center of the photosensitive drum and the rotary holder by sliding the developing roller in the rotor by the adjuster. Irrespective of the adjustment of the developing gap, the developing position on the photosensitive drum is always kept at a constant position and a developing image of high level of quality is obtained.

Abstract: An image forming apparatus includes plural toner image forming devices. Each of which has a rotating photoconductor, a charging device that uniformly charges a surface of the photoconductor, a latent image forming device that forms an electrostatic latent image on the surface of the charged photoconductor, a developing device that develops the electrostatic latent image on the surface of the photoconductor to a toner image, and a developing container that contains toner used by the developing device. A diameter of the photoconductor of at least one toner image forming device is formed larger than a diameter of the photoconductor of the other toner image forming devices. Each developing container of all the toner image forming devices is formed in equal-sized, and a center of rotation of a developing roll of each developing device is arranged in a position upper than a center of rotation of each photoconductor.

Abstract: In an image forming apparatus having at least an amorphous silicon photosensitive member, a magnetic toner developing means and a color developer developing means, the magnetic toner has a weight-average particle diameter (D4) of from 4.0 ?m to 10.0 ?m and a ratio thereof to number-average particle diameter (D1), D4/D1, of from 1.0 to 2.0, and the number of magnetic particles not passing through a mesh with an opening of 34 ?m which are contained in the unit volume of the magnetic toner is from 3.5 to 105. This image forming apparatus can not easily cause faulty cleaning performance even in using the magnetic toner and the non-magnetic color toners in combination and has superior environmental stability and running stability even where toners made to have small particle diameter are used or process speed is high.

Abstract: A color image forming system including a photosensitive drum, a charger which charges the photosensitive drum, and a laser scanning unit which is installed below the photosensitive drum and radiates light onto the charged photosensitive drum, to form an electrostatic latent image. The system further includes a plurality of developing units with toner of at least four colors such as yellow, magenta, cyan, and black, arranged at different heights along the outer surface of the photosensitive drum to develop the electrostatic latent image with the toner when a developing roller installed in each of the developing units is maintained at a developing gap with the photosensitive drum. A transfer unit transfers the developed image onto a piece of paper, and a fusing unit is installed above the photosensitive drum and fuses the transferred image onto the piece of paper. The developing units may be arranged in the order of magenta, cyan, yellow, and black.

Abstract: An image forming apparatus includes an image bearing member; an electrostatic image forming device for forming an electrostatic image on the image bearing member on the basis of an input signal; a developing device for developing the electrostatic image with toners having the same hue and having different densities; a toner image formation device for forming a toner image on a recording material; and a fixing device for fixing the toner image on the recording material, wherein a total of amounts per unit area of the toners which have the same hue and different densities and which constitute the toner image, is different when the toner image is formed on the basis of an input signal on a recording material which is a paper sheet and when the toner image is formed on the basis of the same input signal on a recording material which is an OHP sheet.

Abstract: An image forming system includes an image forming apparatus with attach/detach sections to/from which a developer container is attachable/detachable and an image bearing body. A driver instructs the apparatus to execute single-color or color-image formation. When a developer container is attached to each attach/detach section, the apparatus is usable as a color image forming apparatus. When a developer container is attached to only one attach/detach section, the apparatus is usable as a single-color image forming apparatus. The apparatus forms an image when the driver instructs the apparatus that is being used as the color image forming apparatus to execute single-color-image formation. The apparatus does not form an image when the driver instructs the apparatus that is being used as the single-color image forming apparatus to execute color-image formation.

Abstract: An image forming apparatus includes an image bearing member for carrying an electrostatic image; a developing device for developing the electrostatic image with a plurality of toners having the same hue and having different densities; a toner image formation device for forming on a recording material a toner image constituted by the toner having the same hue and different densities; and a fixing device for fixing the toner image on the recording material, wherein a total of amounts per unit area of the toners which have the same hue and different densities and which constitute a part of the toner image, is substantially the same as a total of amounts per unit area of the toners which have the same hue and different densities and which constitute another part of the toner image having a different density.

Abstract: This invention provides: a color toner to be fixed on a recording medium with a flash light comprising a binder resin, an infrared ray absorbent and a coloring agent for mainly developing a yellow color, wherein the coloring agent is C.I. Pigment Yellow 180 or C.I. Pigment Yellow 185; a color toner to be fixed on a recording medium with a flash light comprising a binder resin, an infrared ray absorbent and a coloring agent for mainly developing a magenta color, wherein the coloring agent is C.I. Pigment Violet 19; and a color toner to be fixed on a recording medium with a flash light comprising a binder resin, an infrared ray absorbent and a coloring agent for mainly developing a cyan color, wherein the coloring agent is C.I. Pigment Blue 15. Also disclosed are a color toner set comprising these color toners and an image forming apparatus employing at least one of the color toners or the color toner set.

Abstract: Even in case of using a hand-held personal computer, operability regarding a printing operation is improved and a print can be normally completed without allowing the print to be finished as an error. When a sufficient available area exists in an RAM 11 of a hand-held personal computer 1, image data sent from an application is converted into print data and, thereafter, the print data is temporarily stored as a spool file into the RAM 11. At the point when the whole print data is stored and the spool file is completed, a printing process in the application is released and the print data in the spool file is sent to a printer 5 by a background. If the sufficient available area does not exist in the RAM 11 of the hand-held PC 1, the whole print data is not temporarily stored as a spool file but the raster unit image data sent from the application is converted into the print data. The print data is sequentially sent to the printer 5 by the foreground and the printing process is executed.

Abstract: An electrostatic image forming apparatus is disclosed. The image forming apparatus contains a toner used in the developing means having saturated moisture content at a temperature of 30° C. and a relative humidity of 80% of within the range of from 0.1 to 2.0% by weight, and the photoreceptor contains a siloxane resin having an electric charge transfer ability and a crosslinked structure in the surface layer.

Abstract: An electrophotographic includes a main frame, a photosensitive drum unit having a photosensitive drum and vertically detachably installed on the main frame, a plurality of development units each having a developing roller and detachably installed on the main frame while sliding in a horizontal direction, and a first door openably installed for mounting or dismounting the plurality of development units.

Abstract: A developing apparatus including a developer container which contains a first developer having a first charging polarity and a second developer having a second charging polarity opposite to the first charging polarity, a developer bearing member which bears the first and the second developers, a layer forming device which forms a first layer substantially composed of the first developer on the developer bearing member and forms a second layer composed of the first and the second developers on the first layer, a separating member which is provided downstream of the layer forming device and upstream of a developing position in a developer bearing and conveying direction of the developer bearing member to separate the second layer from the developer bearing member, whereby plural kinds of developers can be selectively supplied for a development.

Abstract: A color printing system comprising a combination of at least four, and preferably six coloring materials, each of a different color, wherein these colors are selected from (1) an orange-red; (2) a violet-red; (3) a violet-blue; (4) a green-blue; (5) a green-yellow; and (6) an orange-yellow; as well as white and black. This system may be incorporated into a wide range of printing devices and provides a means of achieving a wide range of colors.

Abstract: An image forming apparatus includes a plurality of developing devices each including a developer carrying member for carrying a developer to develop an electrostatic latent image formed on an image bearing member, and a developer regulating member for regulating the developer carried on the developer carrying member; a common voltage applying device for applying a common voltage to the plurality of the developer regulating member. When a first one of the developer carrying members is rotating, and when a second one of the developer carrying members is not rotating, a potential difference between a potential of the second developer carrying member and the common voltage is smaller than a potential difference between a potential of the first developer carrying member and the common voltage.

Abstract: A color image forming device includes a photosensitive unit, an exposing unit, a plurality of developing units, a first transfer body, a second transfer body and a fixing unit. The photosensitive unit includes a photosensitive member with a photosensitive layer. The exposing unit exposes the photosensitive layer to form a series of latent images on the photosensitive member. Each of the developing units includes a developing-agent bearing member bearing thereon a different color developing agent and supplies the developing agent to the photosensitive member to develop corresponding latent images into visible images. The first transfer body receives the visible images from the photosensitive member. The second transfer body receives transfer of the visible images from the first transfer body and transfers the visible images onto a recording medium. The fixing unit fixes the visible images onto the recording medium.

Abstract: The present invention relates to an image forming apparatus comprising a plurality of image forming units for forming images, the image forming units being detachably arranged in the image forming apparatus, and a plurality of developer supplying units arranged corresponding to each of the image forming units for supplying developing agents to the image forming units, the developer supplying units being detachably attached to the image forming apparatus. The image forming units and the developer supplying units are alternatively so disposed that one end in a longitudinal direction of the respective image forming units intersects with one end in a longitudinal direction of the respective developer supplying units.

Abstract: An image forming method is disclosed. The method comprises the steps of forming a latent image on a latent image carrying member, developing the latent image by a developer containing a toner, transferring the toner image onto an intermediate transfer member, transferring the toner image transferred on the intermediate transfer member onto a image forming support, and fixing the toner image formed on the image forming support, wherein the toner contains a resin and a colorant, and the toner is constituted by toner particles having a variation coefficient of the shape coefficient of not more than 16% and a number variation coefficient of the particle size distribution of not more than 27%.

Abstract: An image forming apparatus includes a plurality of developing devices, each of which includes a developer carrying member for carrying a developer to develop an electrostatic image formed on an image bearing member with a developer, and a developer regulating member for regulating the developer carried on the developer carrying member; a common voltage applying device for applying voltages to the developer regulating members, wherein the voltages are applied to the developer carrying members are variable independently from each other, and when at least one of the voltages varies, the voltage applied by the voltage applying device is capable of being changed.

Abstract: A color image forming apparatus forms an image using a deep toner and a pale toner at least for one color such that the pale toner is used to form an image in a high lightness area, and the pale toner and the deep toner are used in combination to form the image in a half tone area. A toner kit has a deep toner and a pale toner which are separated from each other. A method for forming an image uses the color image forming apparatus, the toner kit, and the deep toner and the pale toner. A high quality image can be formed while inhibiting graininess and roughness over a broad image area.

Abstract: In an image processing section, a foam toner signal generator generates a foam toner signal corresponding to a foam toner amount to be transferred to a three-dimensional print designation region discriminated at a three-dimensional print region discriminator, and a foam toner interpolation signal generator generates a foam toner interpolation signal corresponding to a foam toner amount to be transferred to an image region equal to or greater than a constant area in an ordinary print region discriminated at the three-dimensional print region discriminator. Foam toner of a predetermined amount corresponding to the foam toner signal is transferred to the three-dimensional print region, and foam toner of an amount that is less (of a lower height) than the predetermined amount and corresponds to the foam toner interpolation signal is transferred to the ordinary print region.

Abstract: A method for producing a toner of a custom color in a developer unit including a housing defining a reservoir for storing a supply of toner, a donor member for transporting toner to an imaging surface; including: identifying custom color requested; determining color of toner in the reservoir; detoning toner on the donor member if the color of toner in the reservoir is beyond a predefined value in color space from the custom color requested; calculating and dispensing primaries toner colors to be added to the reservoir to obtained the custom color requested; mixing the primary toner colors dispensed in the reservoir; and evaluating and comparing the color components of the toner being mixed to the custom color requested.

Abstract: An image forming apparatus has a plurality of developing devices for developing an electrostatic image formed on an image bearing member, a rotary member holding the plurality of developing devices and rotated in a route including a developing position, the rotary member selectively positioning any one of the developing devices at the developing position, each of the plurality of developing devices having a first developer carrying member and a second developer carrying member for carrying a developer thereon and carrying it to the image bearing member, and a holding member holding the first developer carrying member and the second developer carrying member and pivotally movably provided.

Abstract: A color image forming apparatus includes a photoreceptor medium, an exposing unit, a plurality of developer units, and a power supply. The exposing unit scans light onto the photoreceptor drum to form a latent electrostatic image. The plurality of developer units include developer rollers supplying toner to the latent electrostatic image to develop the latent electrostatic image into a toner image. Each developer unit contains toner of a different color, and the developer units are arranged around the photoreceptor medium so that the developer rollers are separated by a development gap from the photoreceptor medium. The power supply selectively applies a first bias allowing toner to be supplied through the development gap to the photoreceptor medium on which the latent electrostatic image is formed and a second bias preventing toner from passing through the development gap.

Abstract: A color image forming device includes a housing, a photosensitive unit, an exposing unit, at least three developing units, a transfer unit, and a fixing unit. The housing has a recording medium discharge opening for discharging recording media in a forward direction. The photosensitive unit includes a photosensitive belt with a photosensitive layer. The exposing unit exposes the photosensitive layer to form a series of latent images on the photosensitive belt. The developing units are provided in a forward portion of the housing, each including a different color developing agent for supplying developing agent to the photosensitive belt to develop corresponding latent images into visible images. The transfer unit transfers the visible images onto a recording medium. The fixing unit is provided in a rear portion of the housing unit, fixes the visible images onto the recording medium and transports the recording medium toward the discharge opening.

Abstract: A tandem color laser printer 1 is provided with a photosensitive drum unit 15, a developing unit 14, and a scanning unit 13 for each color. The developing units 14, each including a main developer unit 25 and a toner hopper 24, and the scanning units 13, which irradiate laser beam, are alternately stacked vertically to overlap with each other in the vertical direction. This arrangement eliminates space required when arranging the developing units 14 and scanning units 13 side by side, thereby reducing the footprint of the color laser printer 1.

Abstract: An image forming device includes an image forming unit and a thermal fixing unit. The image forming unit uses a plurality of different color developing agents to form a color image on a recording medium. The plurality of different color developing agents are configured from binding resins with the same thermal properties. The plurality of different color developing agents include at least a high-resistance developing agent and a low-resistance developing agent. The high-resistance developing agent has a higher electrical resistance than the low-resistance developing agent and a lower charge-to-mass ratio than the low-resistance developing agent. The thermal fixing unit thermally fixes the color image onto the recording medium.

Abstract: A color image forming apparatus includes a photosensitive medium and developers in a fixed position, each having a developing gap with respect to the photosensitive medium to consecutively develop an image with color toners.

Abstract: An electrophotographic color image forming apparatus including a multiple number of photoreceptors for multiple development colors including black, is constructed such that the photoreceptors satisfy the following relation: 0.5<(X/Y)<0.8, where X represents the reduction in film thickness (?) per 1×107 mm of the traveling distance of the photoreceptor for black development and Y represents the reduction in film thickness (?) per 1×107 mm of the traveling distance of the photoreceptors for the other development colors. This limitation is aimed at differentiating the abrasion resistance of the photoreceptors between that for black and that for colors and designating the reduced amounts of the film thickness per unit traveling distance to fall within the predetermined ranges, whereby it is possible to prevent the drum for black development, which is used most frequently, alone, from being worn away at an earlier time.

Abstract: An image forming apparatus includes an image bearing member; a plurality of first developing devices for developing an electrostatic latent image formed on the image bearing member at a developing position using a developer which includes a toner and a carrier; a rotatable member rotatable in a path including the first developing position, for supporting the plurality of first developing devices, wherein each of the plurality of first developing devices is effective to discharge excess developer produced by receiving the developer including the toner and the carrier to outside of each of the plurality of first developer devices using a rotation of the rotatable member; and a second developer container for developing an electrostatic latent image formed on the image bearing member at a second developing position using a developer including a toner, wherein the second developing device is disposed at a position so as to be non-rotatably adjacent to the image bearing member.

Abstract: A color image formation apparatus includes a plurality of stages of photosensitive drums provided for respective developing agents, the photosensitive drums arranged in a predetermined direction; and developer units which are provided for respective photosensitive drums and which develop electrostatic latent images formed on the photosensitive drums, wherein an overlap exists in the predetermined direction between a portion of each photosensitive drum and a portion of the developer unit provided so as to correspond to an adjacent photosensitive drum.

Abstract: An image forming apparatus of the present invention includes two developing units each including two developing rollers facing a particular photoconductive drum and rotatable about respective axis parallel to the axis of the drum. Each developing unit is supported by a respective image forming unit and angularly movable about an axis substantially parallel to the axis of the drum. When each developing unit is angularly moved by a preselected angle, a gap for development is established between one of the developing rollers and the associated drum.

Abstract: A developer driving apparatus which drives a plurality of developing rollers via a gear chain including pivotable gears and one way gears. A reversible driving motor is coupled to a deceleration gear which directly drives a first swing drive gear and drives a second swing drive gear via an odd number of idler gears. Each swing drive gear is rotationally coupled with a respective swing gear having a center of rotation which is pivotable about a center of rotation of the respective swing drive gear. In a first position each swing gear drives one of the plurality of rollers via a respective one way gear and in a second position, each swing gear drives another of the plurality of rollers via a respective one way gear. A solenoid activated lever moves each swing gear between respective first and second positions.

Abstract: An image forming apparatus and associated method is provided and includes plural image forming mechanisms. Each forming mechanism includes an image carrying member, a development mechanism, and a toner storage. The image carrying member carries an electrostatic latent image. The development mechanism develops the electrostatic latent image into a visual image. The intermediate transfer member sequentially receives toner images into a composite toner image and transfers the composite toner image to a recording sheet. The toner storages have an approximately rectangular shape having a rectangular transverse section. At least one of the toner storages has a greater toner capacity than others of the toner storages, and a length of a short side of the rectangular transverse section of the toner storages having the greater toner capacity is approximately equal to lengths of long sides of the rectangular transverse sections of the others of the toner storages.

Abstract: In an image forming apparatus having at least an amorphous silicon photosensitive member, a magnetic toner developing means and a color developer developing means, the magnetic toner has a weight-average particle diameter (D4) of from 4.0 &mgr;m to 10.0 &mgr;m and a ratio thereof to number-average particle diameter (D1), D4/D1, of from 1.0 to 2.0, and the number of magnetic particles not passing through a mesh with an opening of 34 &mgr;m which are contained in the unit volume of the magnetic toner is from 3.5 to 105. This image forming apparatus can not easily cause faulty cleaning performance even in using the magnetic toner and the non-magnetic color toners in combination and has superior environmental stability and running stability even where toners made to have small particle diameter are used or process speed is high.

Abstract: The present invention provides a tandem-type image forming method using a trickle developing system, wherein the average circularity of a toner contained in at least a supplementary developer used for appropriately supplying a developer to a developing device is in the range of 0.940 to 0.980. In the toner, the ratio of the number of particles having an average circularity of 0.970 or greater, in a particle diameter range of a toner circle-equivalent diameter×⅗ or less, is 5% or less, and the ratio of the number of particles having an average circularity of 0.950 or less, in a particle diameter range of a toner circle-equivalent diameter×{fraction (7/5)} or greater, is 10% or less.

Abstract: An image forming apparatus includes a plurality of image forming portions, and a first switching device and a second switching device that act on a plurality of clutch devices. The second switching device communicates with the first switching device and operates in association with an operation of the first switching device. This makes it possible to simplify the construction of the image forming apparatus and to suppress reduction of the service life of an image bearing member.

Abstract: In a developing device including a plurality of developing sections each including a developer carrier that causes a developer deposited thereon to form a magnet brush and contact an image carrier, the developer carrier including: a rotatable nonmagnetic sleeve; and a stationary magnet roller accommodated in the sleeve and including a magnetic pole for scooping up the developer to the sleeve, a magnetic pole for conveying the developer deposited on the sleeve, and a main magnetic pole for causing the developer to rise on the sleeve in a form of the magnet brush. The plurality of developing sections include at least one developing section in which a flux density of the main magnetic pole in a normal direction has an attenuation ratio of 40% or above and at least one developing section in which said flux density has an attenuation ratio of 30% or below.

Abstract: A colour printing system comprising a combination of at least four, and preferably six colouring materials, each of a different colour, wherein these colours are selected from

Abstract: A latent image is formed on a photoreceptor. Each of a plurality of toner carriers carries toner of a single color to be transferred onto the photoreceptor to make the latent image visible. Each of the toner carriers is fixed at a predetermined distance from a surface of the photoreceptor. A first bias supplier supplies a first bias required to transfer the toner to the photoreceptor to one of the toner carriers which is subjected to a developing operation. A second bias supplier supplies a second bias which is not enough to transfer the toner to the photoreceptor to the other toner carriers which are not subjected to the developing operation.

Abstract: This invention provides: a color toner to be fixed on a recording medium with a flash light comprising a binder resin, an infrared ray absorbent and a coloring agent for mainly developing a yellow color, wherein the coloring agent is C.I. Pigment Yellow 180 or C.I. Pigment Yellow 185; a color toner to be fixed on a recording medium with a flash light comprising a binder resin, an infrared ray absorbent and a coloring agent for mainly developing a magenta color, wherein the coloring agent is C.I. Pigment Violet 19; and a color toner to be fixed on a recording medium with a flash light comprising a binder resin, an infrared ray absorbent and a coloring agent for mainly developing a cyan color, wherein the coloring agent is C.I. Pigment Blue 15. Also disclosed are a color toner set comprising these color toners and an image forming apparatus employing at least one of the color toners or the color toner set.

Abstract: The present invention provides an image forming apparatus which, when switching operation from color image forming operation to monochromatic image forming operation, forms a monochromatic image on each of a prescribed number of sheets by stopping a part of the functions of yellow, magenta and cyan image forming sections of the color image forming operation, and thereafter, forms a monochromatic image only with a black-only image forming section, thereby permitting extension of service life of the image forming sections, while improving the productivity.

Abstract: An image forming apparatus includes a plurality of developing devices each including a developer carrying member for carrying a developer to develop an electrostatic latent image formed on an image bearing member, and a developer regulating member for regulating the developer carried on the developer carrying member; common voltage applying means for applying a common voltage to the plurality of develop our regulating members, wherein a first one of the developer carrying members is rotating, and a second one of the developer carrying members is not rotating, a potential difference between the second developer carrying member and the common voltage is smaller than a voltage difference between the first developer carrying member and the common voltage.

Abstract: An electrophotographic toner is formed as a blend of toner particles and external additives. The external additives include (1) first inorganic fine particles having an average primary particle size of 80-800 nm of oxide of a metal selected from the group consisting of titanium, aluminum, zinc and zirconium, (2) second inorganic fine particles other than silica having an average primary particle size of below 80 nm and (3) silica fine particles having an average primary particle size of below 30 nm. As a result, the toner can be made free from difficulties, such as melt-sticking onto an image-bearing member in a low humidity environment, roughening of halftone images in a low humidity environment, toner blot-down after storage at high temperatures or in continuous image formation on a large number of sheets, fog in continuous formations of images of low color area percentage in a low humidity environment, and re-transfer in multi-color image formation.