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Publication numberWO1982002961 A1
Publication typeApplication
Application numberPCT/GB1982/000059
Publication date2 Sep 1982
Filing date23 Feb 1982
Priority date24 Feb 1981
Also published asEP0072827A1
Publication numberPCT/1982/59, PCT/GB/1982/000059, PCT/GB/1982/00059, PCT/GB/82/000059, PCT/GB/82/00059, PCT/GB1982/000059, PCT/GB1982/00059, PCT/GB1982000059, PCT/GB198200059, PCT/GB82/000059, PCT/GB82/00059, PCT/GB82000059, PCT/GB8200059, WO 1982/002961 A1, WO 1982002961 A1, WO 1982002961A1, WO 8202961 A1, WO 8202961A1, WO-A1-1982002961, WO-A1-8202961, WO1982/002961A1, WO1982002961 A1, WO1982002961A1, WO8202961 A1, WO8202961A1
InventorsBenelux Nv Patscentre
ApplicantBassett Peter John, Verheijen Augustine Wilhelmus, Peeters Josephus Bonifacius
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
Display device
WO 1982002961 A1
Abstract
An electrophoretic display device utilizes transparent spheres (16) whose diameter is similar to that of visible light in place of the conventional pigment particles whereby to enhance the retro-reflective effect of the device. The spheres (16) may be glass or plastics or a combination of both with a specific gravity similar to that of the suspension medium (15) in which they are contained.
Claims  (OCR text may contain errors)
CLAIMS :
1. A display device comprising spaced electrodes and electrophoretically active particles in a liquid suspension medium disposed between said electrodes, the particles having a refractive index greater than that of the suspension medium characterised in that the particles are transparent to light in at least part of the visible spectrum and have an external diameter similar to or larger than the wavelength of visible light.
2. A display device according to claim 1, characterised in that the particles are spheres and are of glass or plastics materials or a combination thereof.
3. A display device according to claim 1 or 2 , characterised in that the particles are hollow.
4. A display device according to claim 1, 2 or 3 , characterised in that the particles have a specific gravity similar to that of the suspension medium.
5. A display device according to any one of the preceding claims characterised in that the particles include electretsto enhance the electrophoretic activity.
6. A display device according to any one of the preceding claims, characterised in that the liquid suspension medium includes a surfactant to enhance the electrophoretic activity.
Description  (OCR text may contain errors)

DISPLAY DEVICE

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.

In order that the present invention be more readily understood, an embodiment thereof will now be described by way of example with reference to the accompanying drawing which shows a cross-section through an electrophoretic display device. 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. 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.

In this embodiment, 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.

These two desiderata point to 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.

Preferably 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.

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. Alternatively, 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.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
EP0023741A1 *18 Jul 198011 Feb 1981Philips Electronics N.V.Electrophoretic image display device
GB1442360A * Title not available
US2792752 *1 Jul 195321 May 1957Rca CorpMethod of and means for controlling light
US3169163 *25 Mar 19599 Feb 1965Agfa Ag FaElectro-optical light valve utilizing charged particle migration
US3782932 *20 Sep 19721 Jan 1974Xerox CorpElectrophoretic imaging process using transparent particles
US3954465 *19 Aug 19744 May 1976Xerox CorporationElectrophoretic imaging members
US3972715 *29 Oct 19733 Aug 1976Xerox CorporationParticle orientation imaging system
US4126528 *26 Jul 197721 Nov 1978Xerox CorporationElectrophoretic composition and display device
Non-Patent Citations
Reference
1 *L'Onde Electrique, Volume 59, No. 10, October 1979 (Paris, FR) J.L. PLOIX et al "Afficheurs par Electrophorese" see pages 65-69, in particular page 66, right-hand column see paragraph III
2 *Optics Communications, Volume 15, No. 2, October 1975 (Amsterdam, NL) T. YOSHIMURA et al. "The Spectral Profile of Light Scattered by Particles in Electrophoretic Movement", see pages 277-280
3 *Proceedings of the SID, Volume 18, No. 3/4, 1977 (Los Angeles, US) I. OTA et al. "Developments in electrophoretic Displays", see pages 243-254, in particular page 244, paragraph B and page 245, paragraph III
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
WO1998041899A2 *12 Mar 199824 Sep 1998Massachusetts Institute Of TechnologyImproved microencapsulated electrophoretic display
WO1998041899A3 *12 Mar 199829 Oct 1998Massachusetts Inst TechnologyImproved microencapsulated electrophoretic display
WO1999010767A1 *27 Aug 19984 Mar 1999E-Ink CorporationElectrophoretic displays and materials
WO2003069403A1 *10 Feb 200321 Aug 2003Sipix Imaging, Inc.Core-shell particles for electrophoretic display
US5961804 *18 Mar 19975 Oct 1999Massachusetts Institute Of TechnologyMicroencapsulated electrophoretic display
US6118426 *27 Aug 199812 Sep 2000E Ink CorporationTransducers and indicators having printed displays
US625256427 Aug 199826 Jun 2001E Ink CorporationTiled displays
US645941827 Aug 19981 Oct 2002E Ink CorporationDisplays combining active and non-active inks
US663957827 Aug 199828 Oct 2003E Ink CorporationFlexible displays
US682582927 Aug 199830 Nov 2004E Ink CorporationAdhesive backed displays
US738251428 Nov 20053 Jun 2008Sipix Imaging, Inc.Core-shell particles for electrophoretic display
US77288113 Sep 20041 Jun 2010E Ink CorporationAdhesive backed displays
US885472115 Oct 20107 Oct 2014E Ink CorporationComponents and testing methods for use in the production of electro-optic displays
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US907528015 Oct 20107 Jul 2015E Ink CorporationComponents and methods for use in electro-optic displays
US917046723 Mar 201227 Oct 2015E Ink CorporationColor electro-optic displays, and processes for the production thereof
US918264628 Jan 201310 Nov 2015E Ink CorporationElectro-optic displays, and processes for the production thereof
US926819113 May 201323 Feb 2016E Ink CorporationMulti-color electrophoretic displays
US929351130 Oct 200922 Mar 2016E Ink CorporationMethods for achieving improved color in microencapsulated electrophoretic devices
US94709506 Nov 201518 Oct 2016E Ink CorporationElectro-optic displays, and processes for the production thereof
US956309920 Jan 20167 Feb 2017E Ink CorporationComponents and methods for use in electro-optic displays
US972695923 Sep 20158 Aug 2017E Ink CorporationColor electro-optic displays, and processes for the production thereof
US973354021 Jul 201415 Aug 2017E Ink CorporationComponents and methods for use in electro-optic displays
US97400764 Jan 201622 Aug 2017E Ink CorporationMulti-color electrophoretic displays
US977853620 Jan 20163 Oct 2017E Ink CorporationComponents and methods for use in electro-optic displays
Classifications
International ClassificationG02F1/167, G03G17/04
Cooperative ClassificationG02F1/167, G03G17/04
European ClassificationG02F1/167, G03G17/04
Legal Events
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2 Sep 1982AKDesignated states
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2 Sep 1982ALDesignated countries for regional patents
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