Abstract: A charge roller rotatable in contact with a photoconductive element in the form of a drum or a belt and applied with a voltage for charging the element, and an image forming apparatus using the same. The surface of the charge roller is ground in order to remove toner particles and other impurities firmly deposited thereon, as needed. The charge roller is capable of uniformly charging the photoconductive element at all times.

Abstract: An image forming apparatus capable of forming both of erasable images and images to be stored, and increasing the number of times that a single sheet with an image can be repetitively decolorized and reused. The apparatus includes a photoconductive element for electrostatically forming a latent image representative of image data. A developing device develops the latent image formed on the photoconductive element by either of an ordinary undecolorizable toner and a decolorizable toner.

Abstract: A method of controlling the density of images produced by an electrophotographic image forming apparatus to a constant value. A toner density sensor is provided with a first reference level variable in response to the output of an image density sensor, and a second reference level representative of a state associated with the optimum condition of a developer (e.g. immediately after replacement thereof). During usual control, the toner concentration of the developer is detected on the basis of the output of the toner density sensor, and the toner supply to the developer is controlled on the basis of the result of comparison of the detected toner concentration and the first reference level.

Abstract: A method applicable to an image forming apparatus which is implemented by an electrophotographic procedure for maintaining that the density of images to be produced by the apparatus is adequate at all times. When the density of a toner image of a reference image or a predetermined pattern sensed by the image density sensor lies in a predetermined adequate range, a sensing level associated with the toner density sensor responsive to the toner density of a developer is not changed. When the density of the toner image does not lie in the adequate range, it is determined that at least the sensing level of the toner density sensing being used at that time has to be changed. Then, whether or not the sensed density of the toner image of the reference image exists in a range in which the image density is controllable is determined.

Abstract: A toner density control device for an electrophotographic copier, facsimile apparatus, printer or similar image recorder of the type developing an electrostatic latent image formed on a photoconductive element, or image carrier, by using a developer in the form of a toner. The device includes a switch accessible for commanding a shift of an adjustable range of image density from a designed or standard range particular to the image recorder. The switch allows a person to select image density higher or lower than the standard adjustable range as desired.

Abstract: Liquid developers for use in electrostatic photography in which toner particles comprising pigment and specific polymer mixes having a particle size of from 0.2 to 0.8 .mu., and a particle size distribution such that about 90% of the particles are in the particle size range of from 0.3 to 0.6 .mu., are dispersed in a petroleum aliphatic hydrocarbon solvent having a solubility parameter of from 7.0 to 7.5, and method of preparation.