GB2404448A - Electrophoretic display device - Google Patents

Electrophoretic display device Download PDF

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Publication number
GB2404448A
GB2404448A GB0317911A GB0317911A GB2404448A GB 2404448 A GB2404448 A GB 2404448A GB 0317911 A GB0317911 A GB 0317911A GB 0317911 A GB0317911 A GB 0317911A GB 2404448 A GB2404448 A GB 2404448A
Authority
GB
United Kingdom
Prior art keywords
waveguide
waveguide plate
display device
particle
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0317911A
Other versions
GB0317911D0 (en
Inventor
Ian Charles Sage
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Qinetiq Ltd
Original Assignee
Qinetiq Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Qinetiq Ltd filed Critical Qinetiq Ltd
Priority to GB0317911A priority Critical patent/GB2404448A/en
Publication of GB0317911D0 publication Critical patent/GB0317911D0/en
Publication of GB2404448A publication Critical patent/GB2404448A/en
Withdrawn legal-status Critical Current

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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
    • 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
    • G02F1/1675—Constructional details
    • G02F1/1677—Structural association of cells with optical devices, e.g. reflectors or illuminating devices
    • 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 
    • G02F1/13—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 liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side

Landscapes

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

Abstract

An electrophoretic display device 2 is provided having a substrate 4 which comprises a waveguide plate and a light source 12 for side illuminating the waveguide plate. The waveguide plate generally guides light within the plane of the waveguide plate. Switching of the display to locate an electrophorectic particle 8 adjacent the waveguide substrate 4 couples light out of the waveguide which is then scattered by the particle out of the face of the substrate. The device therefore provides an emissive device that can work in low ambient lighting. In a refinement the particles are provided with luminescent material and so luminesce when located near the waveguide substrate. Different particle may luminesce at different wavelengths to provide a multi-coloured device.

Description

Electrophoretic Display Device This invention relates to an
electrophoretic display device, particularly to such a device having an illumination means.
Conventional electrophoretic displays are well known. Charged particles are suspended in a suspension medium between two substrates, at least one of which, the front of the display, is transparent. The particles and suspension medium are arranged to be different colours, for instance the particles may be white and the suspension medium black. Application of an electric field across the display will cause the particles to migrate towards either the front or the back of the display depending upon the polarity of the applied field. When a particle is located at the front of the display it displaces the suspension medium at that point and the display will appear white. When the particle is moved away however the suspension medium obscures the view of the particle and the display appears black. By dividing the display into a plurality of separately addressable pixels images can be written to the display. US patent 3,668, 106 describes a conventional electrophoretic display.
Displays of this sort are inherently reflective and therefore depend upon the level of ambient light. Such displays therefore are not good for low ambient light levels. The mode of action of electrophoretic displays determines that acceptable contrast is usually only achieved under illumination from the front or viewing side of the display. Such an illumination geometry presents a number of problems including reflection of light from the front surface or intermediate layers in the device which may reduce the contrast and cause undesirable glare, and the need for light sources to be mounted or arranged to provide substantially even illumination of the display without obscuring it which may add to the bulk weight and thickness of the system.
Thus according to the present invention there is provided a display device comprising at least one electrophoretic particle in a suspension medium located between a back substrate and a transparent front substrate characterized in that at least one substrate comprises a waveguide plate for guiding light substantially within the plane of the waveguide plate and the device further comprises a light source arranged to direct light into the waveguide plate.
The present invention therefore provides the device with a waveguide plate and a light source. The waveguide plate is arranged to generally guide light in the plane of the waveguide plate. In other words, when illuminated from the side, light is guided within the waveguide plate to the other side and there is no significant emission from the face of the waveguide plate. in use then the waveguide plate is side illuminated. When the display is switched so that the electrophoretic particles are located away from the waveguide substrate the light is guided within the plate to the other side where it may be incident on an absorbing material. Thus there is effectively no emission of light from the light source from the front plate of the device. When the display is switched however so that an electrophoretic particle is adjacent the waveguide substrate the optical loss from the waveguide is effectively increased in this region. This means that light will be coupled from the waveguide and scattered by the electrophorectic particle. Therefore there will be significant emission from the display in the vicinity of an electrophoretic particle.
In order to function effectively the electrophorectic particle should preferably have a higher refractive index than the suspension medium.
It should be noted that display devices are also known where particles are disposed continuously next to the front substrate but are arranged to have at least two colours.
Application of an appropriate field causes the particle to re-orientate so as to present a different colour. The present invention is equally applicable to such devices and in this specification reference to an electrophoretic display shall be taken to include reference to such devices and references to moving a particle close to the waveguide plate or away from the waveguide plate shall also be taken to mean reorientating such particle so that the part having a high refractive index is located adjacent or away from the waveguide plate respectively.
Preferably the waveguide plate has a higher refractive index than the suspension medium in order to promote optical waveguiding with low optical loss. Preferably the electrophoretic particle has a refractive index as least as high as the waveguide plate.
The present invention therefore provides a simple emissive device that can operate in low ambient lighting conditions. In high ambient lighting conditions the side illumination of the waveguide plate may not be required and the device may operate as a conventional electrophoretic device. In this case ambient light incident on the waveguide substrate passes therethrough and is reflected or not by the particle or suspension medium appropriately.
In another embodiment the electrophoretic particle may comprise a luminescent material.
In this embodiment activation of the device scatters light from the waveguide plate into the electrophoretic particle where it is absorbed. The particle can then be made to emit light at a different frequency depending upon the luminescent material employed.
Different electrophoretic particles may be provided with different luminescent materials so as to emit light at different frequencies and the particles may be arranged to provide a multicolour display. Conveniently the light source may be arranged to illuminate the waveguide plate with short wavelength radiation such as blue or ultra-violet light.
Conveniently the waveguide plate comprises the front substrate of the device. The presence or absence of an electrophoretic particle at the front substrate therefore determines whether there is scattering from the waveguide plate at that point. However in an alternative embodiment the waveguide plate could comprise the rear substrate of the device. The skilled person would realise that an appropriate electrophoretic particle could couple light from the rear substrate and direct it through the suspension medium to be emitted through the front substrate. Obviously in such an embodiment the suspension medium must be at least partially transmissive at the wavelength of operation. The invention therefore lies in ensuring the presence or absence of scattering particles adjacent a waveguide plate so as to couple light from the waveguide and out through the display surface of the device. In some embodiments it might even be desired to have waveguide plates at both the front and rear substrate.
The invention will now be described by way of example only with respect to the following drawings, of which; Figure 1 shows an electrophoretic display device according to the present invention, and Figure 2 shows an alternative electrophoretic display device according to the present invention.
Referring to figure 1 an electrophoretic display device is shown, generally indicated by the reference 2. The device has a transparent front substrate 4 and a rear substrate 6.
Electrodes (not shown) may be located on the front and rear substrates for driving the electrophoretic display. Disposed between the front and rear substrate 4, 6 are electrophoretic particles 8 located in suspension medium 10.
Eletrophoretic particles 8 may be any conventional electophoretic particle with a relatively high refractive index such as titanium dioxide, zirconium oxide, yttrium aluminium oxide, lead sulphide, polymer latex particles or microspheres comprising polymers such as, but not limited to, poly(styrene), poly(vinyl carbazole) and poly(2-vinyl naphthalene) and compositions including such polymers together with a luminescent material such as coumarin 6, Nile red, luminescent chelates of metals including but not limited to europium, terbium, dysprosium, chromium, zinc, manganese, aluminium and iridium, phosphor materials such as (optionally doped) zinc sulphide and cadmium sulphide in particulate or nanoparticulate form, anthracene, derivatives of perylene and decacyclene. The electrophoretic particles may also comprise materials which are both luminescent and exhibit a high refractive index including zinc sulphide and other luminescent materials such as doped oxides, sulphide, garnets, germanates and spinals.
Suspension medium 10 may again be any convention medium such as aliphatic alicyclic and aromatic hydrocarbon fluids and oils, ethers esters and ketone derivatives of hydrocarbons and combinations thereof together with fluorocarbon fluids and fluorocarbon ether derivatives such as the Fomblin fluids available from the Solvay Solexis company.
As will be well understood by those skilled in the art electrophoretic particles carry a charge and may be moved between the two substrates by application of an appropriate electric field between the electrodes. Figure 1 b shows the particles moved towards the front substrate.
Referring back to figure 1 a the display device further comprises a light source arranged to side illuminate the front substrate 4 which in this case is the waveguide plate. The light source 12 may be any convenient light sources such as an LED or LED array or a gas discharge lamp. The skilled person would be well aware how to couple light into the waveguide plate 4.
Waveguide plate 4 may conveniently be formed from glass or a transparent plastic.
In operation light from the light source 12 is coupled into the waveguide plate. The waveguide plate has a higher refractive index than air and also a higher refractive index than the suspension medium 10. Therefore in the situation shown in figure 1 a light coupled into the waveguide from the light source 12 is guided in the waveguide 4 with low loss to the other side where it is either allowed to escape the device, reflected back into the waveguide or absorbed.
Figure 1 b shows the situation when the electrophoretic particles are moved close to the front substrate 4. In the vicinity of the particles 8 the light no longer experiences a waveguide/suspension medium interface but a waveguide/particle interface. As the particle has a higher refractive index a proportion of the light will be coupled out of the waveguide where it will be scattered by the particle. Light scattered by the particle will be at a higher angle of incidence when it re-encounters the waveguide and so will be transmitted through the waveguide out of the front of the device.
Therefore any regions of the device where a particle is close to the front substrate will see light coupled out of the device whereas in the rest of the device no emission will occur.
In an alternative embodiment the electophoretic particle 8 comprise a luminescent material such as polystyrene doped with a fluorescent dye or silica doped with a rare earth such as erblum. In this case light coupled out of the waveguide is absorbed by the particle and then re-emitted at the intended wavelength. Different particles could comprise different luminescent materials with different luminescent wavelength to provide a multi-coloured device.
Figure 2 shows another type of device to which the invention can be applied. Instead of particles being moveable between two substrate bicoloured particles 20, 22 are used that can be rotated by application of a field. The particles would then be arranged to have one side having a high refractive index and the other side having a low refractive index. The waveguide plate arrangement is the same as that described with reference to figure 1. Particle 20 illustrates the situation with the low refractive index side adjacent the waveguide and particle 22 with the high refractive index side adjacent the waveguide.

Claims (10)

1. A display device comprising at least one electrophoretic particle in a suspension medium located between a back substrate and a transparent front substrate characterized in that at least one substrate comprises a waveguide plate for guiding light substantially within the plane of the waveguide plate and the device further comprises a light source arranged to direct light into the waveguide plate.
2. A display device as claimed in claim 1 wherein the electrophoretic particle has a higher refractive index than the suspension medium.
3. A display device as claimed in claim 1 or claim 2 wherein the waveguide plate has a higher refractive index than the suspension medium.
4. A display device as claimed in any preceding claim wherein the electrophoretic particle has a refractive index at least as high as the waveguide plate.
5. A display device as claimed in any preceding claim wherein the at least one electrophoretic particle comprises a luminescent material.
6. A display device as claimed in claim 5 wherein a plurality of electrophoretic particles are provided and at least some particles have one of at least two luminescent materials, each luminescent material having a different wavelength of emission.
7. A display device as claimed in claim 5 or claim 6 wherein the light source is a short wavelength light source.
8. A display device as claimed in claim 7 wherein the light source is an ultraviolet light source.
9. A display device as claimed in any preceding claim wherein the waveguide plate comprises the front substrate. r
10. A display device as claimed in any preceding claim wherein the waveguide plate comprises the rear substrate.
GB0317911A 2003-07-31 2003-07-31 Electrophoretic display device Withdrawn GB2404448A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0317911A GB2404448A (en) 2003-07-31 2003-07-31 Electrophoretic display device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0317911A GB2404448A (en) 2003-07-31 2003-07-31 Electrophoretic display device

Publications (2)

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GB0317911D0 GB0317911D0 (en) 2003-09-03
GB2404448A true GB2404448A (en) 2005-02-02

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005057261A2 (en) * 2003-12-08 2005-06-23 University Of Cincinnati Light emissive display based on lightwave coupling
WO2008032248A1 (en) * 2006-09-12 2008-03-20 Koninklijke Philips Electronics N.V. Controllable light guide
US7430355B2 (en) 2003-12-08 2008-09-30 University Of Cincinnati Light emissive signage devices based on lightwave coupling
WO2009027915A1 (en) 2007-08-27 2009-03-05 Koninklijke Philips Electronics N.V. Light output device
WO2010142843A1 (en) * 2009-06-08 2010-12-16 Marimils Oy Display system and display apparatus
WO2011005792A1 (en) * 2009-07-07 2011-01-13 Dolby Laboratories Licensing Corporation Edge-lit local dimming displays, display components and related methods
WO2015000380A1 (en) * 2013-07-04 2015-01-08 杨文君 Method for manufacturing display screen
CN108027543A (en) * 2015-12-07 2018-05-11 伊英克公司 Three dimensional display
US10309615B2 (en) 2015-02-09 2019-06-04 Sun Chemical Corporation Light emissive display based on lightwave coupling in combination with visible light illuminated content

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4147932A (en) * 1977-09-06 1979-04-03 Xonics, Inc. Low light level and infrared viewing system
US5317667A (en) * 1992-11-23 1994-05-31 Ford Motor Company Electrophoretic switch for a light pipe
WO2000075720A2 (en) * 1999-06-02 2000-12-14 The University Of British Columbia Electrophoretic, high index, or phase transition control of total internal reflection in high efficiency variable reflectivity image displays
US6512626B1 (en) * 1999-06-16 2003-01-28 Creavis Gesellschaft Fuer Technologie Und Innovation Mbh Composite sheets with electrically switchable optical properties made of light-scattering base material

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4147932A (en) * 1977-09-06 1979-04-03 Xonics, Inc. Low light level and infrared viewing system
US5317667A (en) * 1992-11-23 1994-05-31 Ford Motor Company Electrophoretic switch for a light pipe
WO2000075720A2 (en) * 1999-06-02 2000-12-14 The University Of British Columbia Electrophoretic, high index, or phase transition control of total internal reflection in high efficiency variable reflectivity image displays
US6512626B1 (en) * 1999-06-16 2003-01-28 Creavis Gesellschaft Fuer Technologie Und Innovation Mbh Composite sheets with electrically switchable optical properties made of light-scattering base material

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005057261A2 (en) * 2003-12-08 2005-06-23 University Of Cincinnati Light emissive display based on lightwave coupling
WO2005057261A3 (en) * 2003-12-08 2005-10-06 Univ Cincinnati Light emissive display based on lightwave coupling
US7123796B2 (en) 2003-12-08 2006-10-17 University Of Cincinnati Light emissive display based on lightwave coupling
US7430355B2 (en) 2003-12-08 2008-09-30 University Of Cincinnati Light emissive signage devices based on lightwave coupling
WO2008032248A1 (en) * 2006-09-12 2008-03-20 Koninklijke Philips Electronics N.V. Controllable light guide
EP2188668A1 (en) * 2007-08-27 2010-05-26 Koninklijke Philips Electronics N.V. Light output device
WO2009027915A1 (en) 2007-08-27 2009-03-05 Koninklijke Philips Electronics N.V. Light output device
WO2010142843A1 (en) * 2009-06-08 2010-12-16 Marimils Oy Display system and display apparatus
WO2011005792A1 (en) * 2009-07-07 2011-01-13 Dolby Laboratories Licensing Corporation Edge-lit local dimming displays, display components and related methods
US8786643B2 (en) 2009-07-07 2014-07-22 Dolby Laboratories Licensing Corporation Edge-lit local dimming displays, display components and related methods
WO2015000380A1 (en) * 2013-07-04 2015-01-08 杨文君 Method for manufacturing display screen
US10309615B2 (en) 2015-02-09 2019-06-04 Sun Chemical Corporation Light emissive display based on lightwave coupling in combination with visible light illuminated content
CN108027543A (en) * 2015-12-07 2018-05-11 伊英克公司 Three dimensional display
EP3387487A4 (en) * 2015-12-07 2018-12-05 E Ink Corporation Three-dimensional display
US10209530B2 (en) 2015-12-07 2019-02-19 E Ink Corporation Three-dimensional display

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Publication number Publication date
GB0317911D0 (en) 2003-09-03

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