| abstract |
A dry-toner type coloured particle display ( fig. 13 ) is disclosed. In the image display panel, two or more groups of particles (103) having different colours and different charging characteristics are sealed in the space between two substrates (101,102), at least one of which is transparent. The particles move through the space in response to an applied electrostatic field produced by a pair of electrodes arranged on the substrates in order to display an image. Surface texture parameters R a (average roughness) and S m (usually an average peak to peak distance between neighbouring asperities on a surface) of the bounding substrates lie within specified ranges, defined relative to the particle size, in order to weaken attractive forces between the particles and the surface of the respective substrate. These attractive forces can be adhesion forces such as intermolecular and electrostatic image charge forces (as well as others), and are reduced by decreasing the effective particle to substrate contact area. As a result, the particles are more easily removed and the display driving voltage is reduced. nFurther display arrangements include the provision of bumps, dips or micro-cutouts on part of a substrate electrode to create a lateral electric field component, which again weakens attractive forces between the particles and the substrate electrode. Additionally, there is an arrangement disclosed in which an insulating member having a volume resistivity ρ of not less than 1 x 10 12 Ω.cm is coated thinly on to the surface of the substrate with which the particles are in contact in order to prevent leakage of charge away from the particles to the substrate. nFinally, there is an arrangement in which the display state of the image can be read-out by detecting the current due to the particles when these are moved inside a pixel. |