GB1313412A - Electrophoretic image reproduction device - Google Patents

Abstract

1313412 Matrix displays MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 23 April 1970 [23 April 1969 (2) 12 June 1969 (4) 29 July 1969] 19611/70 Heading G5C [Also in Divisions H1 and H4] A display device comprises a colloid layer and means for applying an electric field thereto so that the colloidal particles move electrophoretically to one side of the layer thereby varying the optical reflectivity of the layer. The field may be applied by two electrodes adjacent the entire major faces of the colloid layer, or one of the electrodes may be shaped or segmented, Figs. 5 and 6 (not shown), or both electrodes may be in the form of orthogonal sets of parallel strips, Fig. 7 (not shown), e.g. for sequential scanning purposes. An insulating coating between the electrode and colloid improves the operating life of the device, Fig. 11 (not shown). Alternatively the electrode may be placed, permanently or temporarily, on the outer surface of a container for the colloid, Figs. 6b and 8a (not shown), e.g. being shaped, or an electrode "pen". The electric field may also be applied using ions or a beam of electrons which scan an insulating plate, or a conductor mosaic plate, adjacent the colloid, Fig. 9 (not shown). The display produced may be erased in each case by application of a direct or alternating field, e.g. using a conductive roller on one surface of a housing for the colloid, or by directing charged particles thereto. The colloid may comprise particles of a single type, or of types having different mobilities or charge polarities, in a closed or colourless medium. Thus a grey colloid formed of black and white oppositely charged particles will give white and black opposed surfaces when a field is applied. The colloid layer may include a layer of porous material such that the colloid particles may pass through but which obscures the particles when they have passed through, Fig. 2 (not shown). In such a device, on reversing the applied field, the colour may change from that of the colloid to that of the porous layer. The colloid may also be contained in a layer of porous material which serves to space the electrodes apart, particularly if the device has flexible walls, and which may be colourless or be constituted by the coloured porous layer mentioned above if it is of a suitable thickness, or a spacer may be incorporated which divides the layer into individual cells. Figs. 12 and 13 (not shown). A display panel , Fig. 12c (not shown), uses such a spacer together with orthogonal sets of strip electrodes. Successive cells have colloids capable of giving red, green and blue reflectances, respectively, or are provided with red, green and blue filters and have colloids capable of giving black or white reflectances. The display may be "fixed" if the suspension medium is suitable, e.g. by heating a thermosetting medium, by cooling a molten medium, or by evaporating off solvent which has previously been used to soften the medium. Details of materials used for the colloid and in the construction of the device are given in the Specification.