Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/166—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
  • G02F1/167—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G17/00—Electrographic processes using patterns other than charge patterns, e.g. an electric conductivity pattern; Processes involving a migration, e.g. photoelectrophoresis, photoelectrosolography; Processes involving a selective transfer, e.g. electrophoto-adhesive processes; Apparatus essentially involving a single such process
  • G03G17/04—Electrographic processes using patterns other than charge patterns, e.g. an electric conductivity pattern; Processes involving a migration, e.g. photoelectrophoresis, photoelectrosolography; Processes involving a selective transfer, e.g. electrophoto-adhesive processes; Apparatus essentially involving a single such process using photoelectrophoresis

Definitions

• the present invention relates to display devices and more particularly to electrophoretic or dielectricphoretic display devices.
• Electrophoretic display devices are known and a feature of these devices is that they are passive, i.e. they do not emit light rather they reflect or transmit incident light.
• An object of the present invention is to provide an electrophorectic or dielectricphoretic display device with enhanced reflectance in the direction of illumination.
• An electrophoretic display device 10 comprises a non-conductive substrate 11 to which is applied an electrode 12 and an electrode 13 spaced from the electrode 12.
• the space between the electrode 12 and the electrode 13 is filled by a liquid material 15 containing small particles 16.
• a liquid material 15 containing small particles 16 When an electric field is applied across the space by a voltage applied to the electrode 12 and electrode 13, the particles migrate to either the electrode 12 or the olectrodo 13.
• Either or both of the electrodes 12, 13 can be an array so as to produce any desired pattern depending on the disposition and shape of the or each array.
• the device is designed for viewing in the direction of the arrow A in which case the electrode 13 will be formed of a transparent material and provided with a transparent protective cover 17.
• the particles 16 are specifically selected for their reflective properties and it has been found that they should be optically transparent in at least part of the visible spectrum. Further, they should have a diameter similar to or larger than the wavelength of visible light, e.g. from 0.5 to 20 microns. It is advantageous if they have a specific gravity similar to that of the liquid material so that they exhibit neutral buoyancy in the liquid material and can move relatively easily under the action of an electric field.
• glass or plastics particles being used.
• a combination of glass and plastics is also possible such as glass coated with plastics.
• the preferred plastics are polyamide, polyimide, polyester, polypropylene or polycarbonate.
• the particles are spherical but may be either solid or hollow spheres.
• the refractive index of the material of the spheres should preferably be higher than that of the liquid material. Such particles are known to exhibit good reflectance in the direction of illumination.
• the electrophoretic activity can be enhanced by adding a surfactant to the liquid material and/or by forming electrets within the particles.
• the above construction may be used as an addressable sign such as a road sign, a warning display or an information panel and has the additional advantages that dye absorption on reflective glass particles would be lower than absorption on conventional organic pigments. This provides increased perceived contrast. Also, chemical and light-induced degradation is lower for glass particles than for organic pigments. Thus, the life of the device would be increased.
• glass particles With glass particles, it may be necessary to process them so that they exhibit an electrophoretic effect.
• a number of processes are available such as exposing molten glass to an electrical discharge and cooling the glass to trap charged particles in the glass matrix.
• glass at .room temperature could be exposed to ionizing radiation such as cathode rays or X-rays to form charged particles in the glass. Both these processes form electrets but it is also possible to activate the surface of the glass particles chemically and then coat the particles with long chain molecules to cause a charge to be present.

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• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Molecular Biology (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)

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• 1982
  • 1982-02-23 WO PCT/GB1982/000059 patent/WO1982002961A1/en not_active Application Discontinuation
  • 1982-02-23 EP EP82900555A patent/EP0072827A1/de not_active Withdrawn

Non-Patent Citations (1)

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