EP1093598A1 - Polariseurs reflechissants a spectre reglable et a modes de fonctionnement electriquement commutables - Google Patents

Polariseurs reflechissants a spectre reglable et a modes de fonctionnement electriquement commutables

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Publication number
EP1093598A1
EP1093598A1 EP99927322A EP99927322A EP1093598A1 EP 1093598 A1 EP1093598 A1 EP 1093598A1 EP 99927322 A EP99927322 A EP 99927322A EP 99927322 A EP99927322 A EP 99927322A EP 1093598 A1 EP1093598 A1 EP 1093598A1
Authority
EP
European Patent Office
Prior art keywords
film
light
bandwidth
electric field
switchable
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Withdrawn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
EP99927322A
Other languages
German (de)
English (en)
Other versions
EP1093598A4 (fr
Inventor
Le Li
Bunsen Fan
Yingqiu Jiang
Sadeg Faris
Jian-Feng Li
Sameer D. Vartak
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.)
Reveo Inc
Original Assignee
Reveo Inc
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Filing date
Publication date
Priority claimed from US09/093,006 external-priority patent/US6369868B1/en
Priority claimed from US09/093,017 external-priority patent/US6473143B2/en
Application filed by Reveo Inc filed Critical Reveo Inc
Publication of EP1093598A1 publication Critical patent/EP1093598A1/fr
Publication of EP1093598A4 publication Critical patent/EP1093598A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y15/00—Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
    • E—FIXED CONSTRUCTIONS
    • E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
    • E06B—FIXED OR MOVABLE CLOSURES FOR OPENINGS IN BUILDINGS, VEHICLES, FENCES OR LIKE ENCLOSURES IN GENERAL, e.g. DOORS, WINDOWS, BLINDS, GATES
    • E06B9/00—Screening or protective devices for wall or similar openings, with or without operating or securing mechanisms; Closures of similar construction
    • E06B9/24—Screens or other constructions affording protection against light, especially against sunshine; Similar screens for privacy or appearance; Slat blinds
    • 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
    • G02F1/133365—Cells in which the active layer comprises a liquid crystalline polymer
    • 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
    • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
    • 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
    • G02F1/137—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/13718—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on a change of the texture state of a cholesteric liquid crystal
    • 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
    • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
    • G02F1/13345—Network or three-dimensional gels
    • 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
    • G02F1/133528—Polarisers
    • G02F1/133531—Polarisers characterised by the arrangement of polariser or analyser axes
    • 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
    • G02F1/133528—Polarisers
    • G02F1/133543—Cholesteric polarisers
    • 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
    • G02F2203/00—Function characteristic
    • G02F2203/07—Polarisation dependent

Definitions

  • the present invention relates generally to single-layer broadband reflective p olarizers having electrically controllable polarization efficiencies and reflection bandwidths, and more particularly to single- layer reflective polarizers which can be electrically switched from broadband operation to narrow band operation over the visible and infrared (IR) bands, as well as single-layer reflective polarizers which can b e electrically switched from narrow band operation to broadband operation over the visible and IR bands .
  • IR visible and infrared
  • polarizing device having electrically controllable transmission characteristics such as polarization, transmittance, and spectra is desired in order to actively control the display brightness as well as color balance, for example.
  • Electrically controllable polarizers can also serve as an enabling technology for other applications such as smart window, wherein the window transmission is electrically switchable from a totally reflective state to a totally transparent state by incorporating two switchable polarizers with opposite polarization states.
  • a window can provide lighting control and can additionally provide energy conservation benefits if externally mounted.
  • US Patent 5,691,789 discloses a single-layer reflective super broadband circular polarizer and method of fabricating the same b y producing a single layer having cholesteric liquid crystal (CLC) order where the pitch of the liquid crystal order varies in a non linear fashion across the layer.
  • CLC cholesteric liquid crystal
  • European Patent Application 0 643 121 A published March 1 5 , 1995 discloses a narrow band, switchable polarizing single layer reflector.
  • a primary object of the present invention is to provide a single layer polarizing film having a very wide bandwidth which is switchable.
  • Another object of the invention to provide a switchable reflecting polarizing filter having a very wide bandwidth which is controllable b y an electric field.
  • Another object of the invention to provide a switchable reflective film having little variation in the reflectivity outside of the reflective bandwidth of the film.
  • Another object of the invention to provide a "smart window" using a polarizing reflective film having a very wide bandwidth .
  • Another object of the invention to provide a "smart window" using a polarizing reflective film having a very wide bandwidth combined with a reflective multilayer polymer film having a very wide bandwidth.
  • Another object of the invention to provide a "smart window" using a polarizing reflective film having a very wide bandwidth combined with a reflective multilayer polymer film having little variation in the reflectivity outside of the reflective bandwidth of the film.
  • Another object of the invention to provide a "smart window" using a polarizing reflective multilayer polymer film having a very wide bandwidth combined with a light scattering layer for further control of transmitted light.
  • Another object of the invention to provide a reflective polarizing film having a bandwidth which is controllable by an electric field.
  • Another object of the invention to provide a "smart window" using a polarizing reflective film having a very wide bandwidth which is controllable by an electric field.
  • Another object of the present invention is to provide an electrically- switchable family of infrared reflective polarizers and filters, based on the remarkable properties of cholesteric liquid crystals (CLCs), having far- reaching dual-use aerospace and window-glazing applications.
  • CLCs cholesteric liquid crystals
  • Another object of the present invention is to provide electrically controllable polarizers and filters that can be remotely controlled an d involve no moving parts, to active-solar-control window glazings having the unheard-of property of infrared switchability while maintaining total visible transparency.
  • Another object of the present invention is to provide novel near- infrared switchable polarizers, filters, and reflectors, which fulfill a market need for remote-controlled, robust, thin-film, multiple-use optical components.
  • Another object of the present invention is to provide fast electrically-switchable infrared reflective polarizers capable of switching from broad-to-narrow band reflective operation over the IR band.
  • Another object of the present invention is to provide such a fast electrically-switchable infrared reflective polarizers, wherein its rise time is about 14.5 ms and its fall time about 8.5 ms .
  • Another object of the present invention is to provide fast electrically-switchable infrared reflective polarizers capable of switching from narrow-to-broad band reflective operation over the IR band .
  • Another object of the present invention is to provide a full understanding and comprehensive model of the chemical and physical switching mechanisms, verified through computer simulations.
  • Another object of the present invention is to provide an electrically- tunable infrared reflective polarizer.
  • Another object of the present invention is to provide an electrically switchable IR reflector based on an electrically switchable broadband reflective polarizer that operates in the IR region from 780nm to 4 microns.
  • Another object of the present invention is to provide a field- switchable broadband reflective polarizer operable in the spectral region from 700 to > 1000 nm, and having a polarizing bandwidth an d extinction ratio which are changeable via an applied electric field.
  • Another object of the present invention is to provide a novel method of optimizing the performance of such electro-optical structures in terms of extinction ratio, overall reflectivity, and reflection spectral cutting-off edge.
  • Another object of the present invention is to provide novel material recipes for making the switchable, broadband-to-narrow-band polarizers of the present invention, which enable further expansion of the polarizer bandwidth, shift to longer wavelengths, and increase the extinction ratio to the desired level.
  • Another object of the present invention is to provide a method of making such electrically-switchable IR reflective polarizers, using liquid crystal polymeric compounds having different pitch, cross-linking density, and polymerization rate.
  • Another object of the present invention is to provide an electrically- controllable narrow-band reflective polarizer which undergoes a shift in reflection band, rather than a broadening in bandwidth when a DC voltage is applied.
  • Another object of the present invention is to provide a novel method of precisely electrically tuning the CLC center wavelength b y applying an electric field, without affecting the other specifications of the polarizer, such as polarization, extinction ratio, and bandwidth.
  • a single layer spectrum-controllable reflective circular polarizer having spectral characteristics which can be electrically controlled by application of an external electric field.
  • the reflective polarizers are made from a cross-linkable cholesteric liquid crystal mixed with non-crosslinkable liquid crystal(s) and chiral dopant(s). These reflective polarizers reflect circularly polarized light matching its spiral sense.
  • the present invention embraces two different types of single-layer spectrum-controllable reflective polarizer: a first-type spectrum-controllable reflective polarizer which switches from broadband reflective operation at a given polarization state, to narrow-band reflective operation at the given polarization state; and a second-type spectrum-controllable reflective polarizer which switches from narrowband reflective operation at a given polarization state, to broadband reflective operation at the given polarization state.
  • the first type spectrum-controllable reflective polarizer realizable in a 1 O ⁇ m configuration, can be switched from a broadband polarizing mode (having a reflection bandwidth from about 440nm to about 660nm) to a narrow band polarizing mode (having a reflection bandwidth from about 420nm to about 460nm) by applying an AC electric field.
  • the first-type of polarizer according to the present invention can be realized in the form of a single layer polarizing reflective film comprising a cross linked polymer matrix mixed with low molecular weight liquid crystal molecules.
  • the liquid crystal molecules are oriented with respect to the surface of the film and to each other i n cholesteric order, and the pitch of the cholesteric order varies non- linearly across the thickness of the film so that the film reflects circularly polarized light having a broad bandwidth when no external electric field is applied across the film.
  • the ratio of the amount of liquid crystal molecules to the amount of cross-linked polymer is chosen so that the liquid crystal molecules may rotate reversibly in an electric field, an d hence destroy the cholesteric liquid crystalline order responsible for the broadband reflectivity of the polarized light.
  • the second-type of reflective polarizer can be switched from a narrow band m ode (having a reflection bandwidth from about 610nm to about 680nm) to a broadband mode (having a reflection bandwidth from about 480nm to about 830nm).
  • the second-type of reflective polarizer according to the present invention can be realized in the form of a single layer polarizing reflective film comprising a crosslinked polymer matrix mixed with low molecular weight liquid crystal molecules.
  • the low molecular weight liquid crystal molecules are oriented with respect to the surface of the film and to each other in cholesteric order.
  • the ratio of the amount of liquid crystal molecules to the amount of cross-linked polymer is chosen so that the liquid crystal molecules may move reversibly in a n electric field.
  • the composition of the film is uniform, the polarized reflectivity of the film has a very narrow bandwidth when there is no electric field impressed in the film. As the electric field is increased, the bandwidth of the polarized reflectivity increases.
  • Fig. 1 shows the reflective polarizing film according to the first generalized embodiment of the present invention.
  • Fig. 2 shows the device of Fig. 1 with the addition of a ⁇ /4 phase retardation plate.
  • Fig. 3 shows the device of Fig. 2 with an additional ⁇ /4 phase retardation plate.
  • Fig. 4 shows an embodiment of the reflective polarizing film of the first generalized embodiment of the present invention used for display purposes.
  • Fig. 5 shows an optical system using the reflective polarizing film of the first generalized embodiment of the present invention.
  • Fig. 6 shows an optical system for an optical communication fiber, made using the reflective polarizing film according to the first generalized embodiment of the present invention.
  • Fig. 7 shows the polarizing reflective film according to the first generalized embodiment of the present invention, employed as a cavity element in a laser cavity .
  • Fig. 8 shows the reflection spectrum of a typical switchable reflective polarizer according to the first generalized embodiment of the present invention.
  • Fig. 9 shows the transmission spectrum of a sample shown in Fig. 8.
  • Fig. 10 shows the transmission spectrum of opposite polarization from Fig. 9.
  • Fig. 11 shows the reflectivity of a sample of the first generalized embodiment for various voltages applied.
  • Fig. 12 is a transmission spectrum of the switchable reflective polarizer with the probing beam being left handed polarized.
  • Fig. 13 is the reflection spectrum of a switchable reflective polarizer in the visible band, made from Recipe #1 in Table III.
  • Fig. 14 is the transmission spectrum of a switchable reflective polarizer in the IR band, made from Recipe #2 in Table III.
  • Fig. 15 is the transmission spectrum of a switchable reflective polarizer in the visible band, made from Recipe #3 in Table III.
  • Fig. 16 shows the reflective polarizing film of the second generalized embodiment of the present invention.
  • Fig. 17 shows the device of Fig. 16 with the addition of a ⁇ /4 phase retardation plate.
  • Fig. 18 shows an additional embodiment of the device of Fig. 17.
  • Fig. 19 shows the film of Fig. 16 used for display purposes.
  • Fig. 20 shows an optical system using the film of the second generalized embodiment of the present invention.
  • Fig. 21 shows an optical system for injecting a controlled bandwidth polarized light beam into an optical communication fiber 164.
  • Fig. 22 shows the voltage controlled film of the second generalized embodiment of the present invention, employed as a cavity element in a laser cavity.
  • Fig. 23 shows the reflection spectra for unpolarized light of the bandwidth changeable polarizer for different values of the voltage across the film of the second generalized embodiment of the present invention.
  • Fig. 24 shows the transmission spectra for right and left handed circularly polarized (RHCP and LHCP) light of a film of the second generalized embodiment of the present invention.
  • Fig. 25 is the reflection spectrum of the bandwidth changeable polarizer of the second type with the probing beam unpolarized.
  • Fig. 26 is the reflection spectrum of a switchable reflective polarizer of Recipe #1 in Table IV switched by AC voltage.
  • Fig. 27 is the reflection spectrum of a switchable reflective polarizer active in the IR band, switched by DC voltage, fabricated using Recipe # 1 in Table IV.
  • Fig. 28 is the transmission spectrum of a switchable reflective polarizer in the IR band, fabricated using Recipe #2 in Table IV.
  • Fig. 29 is the reflection spectrum of a switchable reflective polarizer in the IR band, fabricated using Recipe #3 in Table IV.
  • Fig. 30 is the reflection spectrum of a reflective polarizer switchable by an AC voltage, and fabricated using Recipe #4 in Table IV.
  • Fig. 31 is the transmission spectrum of a reflective polarizer switchable in the IR by DC voltage, and fabricated using Recipe #4 i n Table IV.
  • Fig. 32 is a schematic illustration of the pitch increase and mis- orientation evolution of the second-type of reflective polarizer under a n electric field.
  • Fig. 33 is a schematic illustration of the pitch increase and mis- orientation evolution of the second-type of reflective polarizer under a n electric field.
  • Fig. 34 is a schematic representation of a novel glazing structure incorporating the switchable reflective CLC polarizers of the present invention.
  • the switchable polarizers of the present i nvention can be classified into two distinct types by virtue of their modes of operation, namely : Broadband to narrow-band transition when field is applied; and Narrow- band to broadband transition when field is applied. These two types of switchable polarizers will be described in detail below.
  • the first type of reflective polarizer is made from a high molecular weight reactive cholesteric liquid crystal polymer material mixed with conventional low molecular weight liquid crystal(s) and a chiral dopant(s).
  • the resulting polarizers reflect circular polarized light matching their spiral senses.
  • a 10 micrometer thick polarizer, with a bandwidth from 440 nm to 660 nm, can be switched from a broadband reflection mode to a narrow-band transmission mode by applying a n electric field.
  • the switchable polarizer Using a material blend containing a reactive cholesteric liquid crystalline (CLC) compound, other non-reactive liquid crystal(s) an d chiral dopant(s), the switchable polarizer according to the first generalized embodiment is created by a mechanism termed as ultraviolet (UV) polymerization induced molecular re-distribution (PIMRD) which is responsible for creating a nonlinear helical pitch distribution along the CLC helical axis.
  • UV ultraviolet
  • PMRD photomerization induced molecular re-distribution
  • Polymerization induces segregation of the non-reactive compounds from the polymer. As a result, some diffusing non-reactive molecules are "trapped" in the polymer network during the polymerization.
  • the non linear pitch distribution may be attained by polymerizing with light, where the intensity of the light varies throughout the layer of material. This happens naturally if the material mixture absorbs the light strongly. The mixture is merely irradiated at a low enough intensity t o allow diffusion of the non-reactive nematic liquid crystalline molecules from one surface of the mixture to the other.
  • Appropriate light absorbing molecules may be added to the mixture, or a wavelength of the light may be chosen which is strongly absorbed in one of the constituents of the mixture which is necessary for the function of the broad band polarizer.
  • Other methods of polymerization as known in the art may be used as well, so long as the requisite non linear light absorption results. Such methods as electron o r other beam irradiation, or heating with a large temperature gradient across the material, could also be used.
  • the high molecular weight (HMW) polymer material forms a matrix holding the low molecular weight (LMW) liquid crystal material.
  • the high molecular weight polymer material is preferably itself a cholesteric liquid crystal (CLC) material, but it is not necessarily so.
  • the main function of the high molecular weight material is to form the matrix which stabilizes the low molecular weight material.
  • the low molecular weight material is aligned with respect to the surface, and has CLC order before polymerization and retains the order after polymerization. After polymerization, an electric field in the material may rotate the low molecular weight molecules if the density of the cross linking is low enough, and the CLC order will be changed or disrupted.
  • the polymer material acts somewhat like a spring to return the low molecular weight molecules to the original position, restoring the CLC order and the polarized reflectivity. If too little polymer is used, the material will be too liquid and the low molecular weight molecules may diffuse and reduce the non linearity of the pitch distribution, which would result in a narrow band polarizer. If too much polymer is used, the low molecular weight materials will no longer be able to rotate, and the material will not be switchable except under extremely high fields.
  • a general method for making the switchable polarizers of the present invention will be described below. Thereafter, particular recipes will be described for making such reflective polarizers.
  • a special right- handed reactive cholesteric liquid crystalline compound is mixed with a commercial nematic liquid crystal and certain amount of chiral dopant. The purpose of adding chiral dopant is to adjust the helical pitch.
  • Photo- initiator is also added to start the polymerization process.
  • a device made of two ITO glass sheets coated with rubbed polyamide and separated by 10 ⁇ m glass fiber spacers, is filled with the liquid crystal mixture, and then irradiated with UV light at an elevated temperature along the CLC helical axis.
  • Polymerization induces segregation of the non-reactive compounds from the polymer. As a result, some diffusing non-reactive molecules are "trapped" in the polymer network during the polymerization. At sites where more non-reactive nematic liquid crystalline molecules are accumulated, the helical pitch becomes longer.
  • this PIMRD mechanism yields a non-uniform helical pitch distribution throughout the mixture, resulting in a switchable broadband reflective polarizer.
  • polysiloxane liquid crystal materials from Wacker (Germany) and acrylate liquid crystal compounds from BASF (Germany) are effective in creating a field-switchable broadband reflective polarizer in the visible when mixed with E44 low molecular weight liquid crystal from EMI (Hawthorne, NY).
  • Tiso refers to isotropic transition temperature.
  • the cross-linking density for BASF liquid crystal materials is defined as follows:
  • Table II lists the collected non-polymerizable materials, primarily from EMI.
  • a switchable polarizer according to the first generalized embodiment of the present invention has been obtained from samples of a liquid crystal mixture made from a first recipe consisting of 1.9% b y weight of a high molecular weight (HMW) CLC polymer CC4039R obtained from Wacker chemical , 96.6% of a low molecular weight (LMW) nematic material E7 from EMI chemical, 0.05% of a photoinitiator IG184 obtained from Ciba Geigy, 0.59% of a chiral additive S lOl l from EMI, and 0.82% of another chiral additive CB15 from EMI.
  • HMW high molecular weight
  • LMW low molecular weight
  • the intrinsic polarizing bandwidth before polymerization was estimated to be 60nm. After being polymerized at room temperature by a UV intensity of 0.72mW/cm2, the bandwidth was increased to 1 20nm . When no electric field is applied, the polarizer exhibits a high reflectivity to the right handed circularly polarized light within a bandwidth of 120nm. However, it is not reactive to the left-handed circularly polarized light. If a sufficient electric field was applied, the reflectivity drops t o almost zero and passes all polarizations of light.
  • the new polarizers are made from a reactive HMW cholesteric liquid crystal polymer mixed with conventional low molecular weight liquid crystal molecules and a chiral dopant(s).
  • the resulting polarizers reflect circular polarized light matching their spiral senses. When in the polarizing state, they exhibit a contrast ratio higher than 10: 1 and a bandwidth greater than 220nm in the visible region.
  • the polarizer When no electrical field is applied to the first type of broadband switchable polarizer, the polarizer exhibits a broadband polarizing reflective state in the visible from 440 nm to 660 nm. This polarizer can be switched from the polarizing reflection mode to a transmission mode by applying an AC o r DC electric field.
  • Second recipe 15% CM170*(504nm)(BASF), 28% CB15 (EMI), 55% E44(EMI), 2% IG184(Ciba Geigy).
  • Cell thickness d 8 , curing temperature 35oC, UV intensity lO-6mW/cm2. Bandwidth from 422 660nm (right-handed) when no voltage is applied.
  • Extinction ratio 10 1 , switching voltage 120V (rms) at lOOOHz.
  • CM170* cross-linking density is medium.
  • Cell thickness d 8 , curing temperature 35oC, UV 10- 6mW/cm2.
  • CM171 cross-linking density is medium.
  • Cell thickness d 8, curing temperature 35oC, UV 10-6mW/cm2. Bandwidth from 440 ⁇ 620nm (right-handed) when no voltage is applied, extinction ratio 6: 1 , switching voltage 120V (rms) at lOOOHz.
  • CM171 cross-linking density is medium .
  • d 8 , curing temperature 35oC, UV 1 0- 6mW/cm2. Bandwidth from 540 ⁇ 820nm (left-handed) when no voltage is applied, extinction ratio 6:1, switching voltage 120V (rms) at l OOOHz. CM171* cross-linking density is low.
  • the samples were made of two indium tin oxide (ITO) covered glass sheets coated with rubbed polyamide separated by glass fiber spacers a n d filled with liquid crystal mixture, and then irradiated with UV light at a elevated temperature.
  • ITO indium tin oxide
  • Fig. 1 shows the film 10 of the invention comprising a cross linked o r polymerized material having a high molecular weight component and a low molecular weight CLC component.
  • Film 10 is contacted by electrically conducting materials 12 and 14 which may have a voltage VI applied t o impress and electric field in the material of the invention.
  • the materials 12 and 14 may contact the film 10 or be closely adjacent film 1 0.
  • Unpolarized light 16 is shown incident on film 10 through conducting material 1 2, which is transparent to the light 16.
  • Right h an d circularly polarized light 18 is shown reflecting from film 10, while left hand circularly polarized light is shown transmitted through film 10 an d through material 14.
  • the device of Fig. 1 is a polarizer. If light 19 is transmitted, the device of Fig. 1 is a polarizing beamsplitter. When the field is impressed in film 1 0 by raising the voltage VI, the right hand circularly polarized light 1 8 disappears. If the light incident on to film 10 is right hand circularly polarized, the voltage may be used to change the device of Fig. 1 from a reflector of the light to a transmitter of the light.
  • Fig. 2 shows the device of Fig. 1 with the addition of a p /4 phase retardation plate 24. Unpolarized light incident on the device of Fig. 2 will be result in linearly polarized light being controllably reflected from the device. If linearly polarized light of the correct polarization is incident on the device of Fig. 2, the voltage may be used to controllably reflect or transmit the light.
  • Fig. 3 shows an additional embodiment of the device of Fig. 2. whereby an additional p 14 phase retardation plate 34 converts the circularly polarized light remaining from the initially unpolarized incident light to a linearly polarized light beam 32 which has opposite polarization to the reflected beam 22.
  • Fig. 4 shows an embodiment of the film of the invention used for display purposes.
  • the electric field in the film 10 of the invention is controlled to vary spatially across the area of the film 10 by a voltage controller 48 applying varying voltages to segmented electrodes 46.
  • Light 42 is reflected or not from the various areas of the film to give a display.
  • polarized light may be used for light 42, and the polarized light in transmission may also be used as a display.
  • Fig. 5 shows an optical system using the film of the invention, whereby the switchable broadband polarized light beam 58 may be used in further optical systems 54, and the transmitted light beam 59 may b e switched from polarized to unpolarized by the voltage applied across the conducting materials 10 and 12.
  • Fig. 6 shows one example of an optical system 54 for injecting a controlled polarized light beam 58 through a lens 62 into an optical communication fiber 64.
  • Fig. 7 an embodiment using the voltage controlled film of the invention as a cavity element in a laser cavity 70.
  • the switchable polarizing film is used here as cavity reflector 72 for a cavity comprising the switchable polarizing film, a broadband light amplifier 74, and a broadband mirror 76.
  • the device of Fig. 7 will lase and produce a broad bandwidth of laser light when the reflectivity of the mirror 72 reaches a threshold.
  • the laser output may be drawn either from the mirror 7 2 or from the mirror 76, or both, depending on the transmissions of the cavity reflectors.
  • Fig. 8 the reflection spectrum of a typical switchable polarizer made from recipe #2 is illustrated, which was measured with a n unpolarized light source. A reflection band from 440nm to 660nm with average reflectivity around 45% was obtained from the unpolarized probing beam. Upon applying an AC electric field ( l OV/micrometer), averaged reflectivity drops dramatically to a mere 2% (after correcting for the 4% surface reflection).
  • Fig. 9 presents the transmission spectrum of a sample made with recipe #2 with and without AC field applied to the polarizer, here the probing beam was right-handed polarized ("crossed" with the sample).
  • Fig. 10 shows the transmission spectrum of a sample made with recipe #2 with the probing beam left-handed polarized ("parallel" with the sample.)
  • Fig. 11 shows the reflectivity in unpolarized light of a sample made from recipe #6 for various voltages applied.
  • the reflectivity for a specific wavelength could then be controlled by biasing the film, and a relatively small voltage added to the bias could be used t o switch the film from reflecting to nonreflecting for that specific wavelength. This is of great importance to control of light by low voltage signals from inexpensive electronic apparatus.
  • a two volt change in applied voltage would double the reflectivity of the film for unpolarized light around 600 nm, an d would change the reflectivity for the correct polarization by an even greater factor.
  • this type of polarizer has three well distinguished optical states, i.e. narrow band polarizing state, broadband polarizing state, and non- polarizing semi-clear state, depending on the voltage applied
  • narrow band polarizing state narrow band polarizing state
  • broadband polarizing state broadband polarizing state
  • non- polarizing semi-clear state depending on the voltage applied
  • liquid crystal compounds were first weighed and thoroughly mixed according to the pre-determined ratio.
  • IG 184 is the photo initiator from Cyba Geigy.
  • Tc is the curing temperature at which the sample is cured.
  • a switchable reflective polarizer in the visible range from 450 to 750 nm was obtained.
  • Fig. 13 shows the polarizer spectra as a function of applied voltage, obtained using the Perkin-Elmer Lambda 19 with an unpolarized light source.
  • Recipe #2 has been obtained by eliminating the chiral additives of R101 1 and R811 from Recipe #1. Shown in Fig. 14, this recipe produced the most successful result. If no voltage is applied, the polarizer spontaneously covers a broad spectral band from 600 - 1200 nm in the NIR region. Upon applying an AC electric field ( l OV/ ⁇ m at 1kHz), the averaged reflectivity drops dramatically to a mere 2% in the switched part in spectrum, and the polarizer is switched from the broadband to a narrow band. It is believed that the final field-on narrow reflection peak at around 600 nm is due to the cholesteric liquid crystal polymer network.
  • the second type of controllable bandwidth polarizer exhibits a narrow band (70nm) polarizing reflective state in the red spectral region when no electric field applied. However, when a low frequency or DC electric field is applied, this narrow band polarizer becomes a broadband reflective polarizer. Its bandwidth is extended to 350nm with a n averaged reflectivity no less than 40%.
  • a bandwidth changeable polarizer can b e created using a very fast UV curing process which is opposite to the PIMRD process.
  • a strong UV source (1 W/cm 2 ) and higher concentration of photo-initiator had been used.
  • diffusing was restricted during the polymerization.
  • a much more uniform helical pitch distribution throughout the mixture was obtained, resulting in a narrow band width (70 nm) reflective polarizer.
  • a special right-handed reactive cholesteric liquid crystalline compound was mixed with a commercially available nematic liquid crystal and certain amount of chiral dopant. The purpose of adding chiral dopant is again to adjust the helical pitch. Photo-initiator was also added to start the polymerization process. A commercial high power UV light source, wavelength centered at 365 nm, was used to polymerize reactive liquid crystal component in the mixture. Spectrometry was carried out with a Perkin-Elmer Lambda 1 9.
  • Fig. 25 presents the reflection spectrums of the bandwidth changeable polarizer. With electric field off, the bandwidth is narrow, only amounts to about 70 nm, after a low frequency electric field 7 V/ ⁇ m applied, the bandwidth is then broadened to 350 nm. From Fig. 25, we clearly see that the reflectivity is very high, even with the field applied, the reflectivity is still greater than 40% at normal direction, scattering plays an insignificant role here. By visual inspection, we found, with the low frequency electric field applied to the sample, that haze was n ot noticeable by naked eye.
  • the helical pitch distribution of the sample is narrow, and the distribution of the chiral polymer is also uniform though out the sample.
  • the polymer network with its own resulted helical structure was n ot affected due to its high cross-linking density.
  • the non-reactive cholesteric liquid crystal components are affected by the electric field.
  • the helical structure was untwisted.
  • the detailed first recipe is a mixture of 12% by weight of a high molecular weight (HMW) CLC polymer [BASF 1 81 (25 % bisacrylates)], 61% of a low molecular weight nematic material E44 obtained from Merck, 25% of a chiral additive CB15 obtained from Merck, and 1.9% of a photoinitiator IG 184 from Ciba Geigy.
  • HMW high molecular weight
  • CB15 chiral additive
  • IG 184 from Ciba Geigy.
  • a strong UV source (1 W/cm2) and higher concentration of photo-initiator had been used.
  • diffusion of the low molecular weight molecules was restricted during the polymerization.
  • a much more uniform helical pitch distribution throughout the mixture was obtained, resulting in a narrow band width (70 nm) reflective polarizer when the electric field impressed in the film was low.
  • a special right-handed reactive cholesteric liquid crystalline compound was mixed with a commercially available nematic liquid crystal and certain amount of chiral dopant. The purpose of adding chiral dopant is again to adjust the helical pitch. Photo-initiator was also added to start the polymerization process.
  • the sample made of two ITO glass sheets coated with rubbed polyimide and separated by a thinner glass bead spacers (8 mm), was filled with the new liquid crystal mixture, and then irradiated with a intense UV light source at room temperature for a short period of time (in the order of second).
  • d 10 micrometer, curing temperature 25oC, UV intensity lW/cm2.
  • Initial bandwidth 600 670nm when no voltage is applied; with a voltage of 26V(DC), the bandwidth broadens from 500 ⁇ 740nm (right- handed), switching voltage 26V (DC).
  • CM181 cross-linking density is low.
  • d 10 micrometer, curing temperature 25oC, UV intensity l W/cm2.
  • CM171 cross-linking density is medium.
  • FIG. 16 shows the film 1 10 of the second generalized embodiment of the present invention comprising a cross linked or polymerized material having a high molecular weight component and a low molecular weight CLC component.
  • Film 110 is contacted by electrically conducting materials 112 and 1 14 which may have a voltage VI applied to impress and electric field in the material of the invention.
  • the materials 112 an d 114 may contact the film 10 or be closely adjacent film 110.
  • Unpolarized light 1 16 is shown incident on film 10 through conducting material 1 12, which is transparent to the light 1 16.
  • Right hand circularly polarized light 1 18 is shown reflecting from film 1 10, while left hand circularly polarized light is shown transmitted through film 110 and through material 1 14.
  • the device of FIG. 16 is a polarizer. If light 1 19 is transmitted, the device of FIG. 16 is a polarizing beamsplitter. When the field is impressed in film 1 10 by raising the voltage VI, the bandwidth of the right hand circularly polarized light 1 18 broadens. If the light incident on to film 110 is right hand circularly polarized, the voltage may be used to change the device of FIG. 16 from a narrow band reflector of the light to a broad b and reflector of the light.
  • FIG. 17 shows the device of FIG. 16 with the addition of a p/4 phase retardation plate 124. Unpolarized light incident on the device of 17 will be result in linearly polarized light being controllably reflected from the device. If linearly polarized light of the correct polarization is incident o n the device of FIG. 17, the voltage may be used to control the bandwidth of the reflected light or the width of the "notch" in the transmitted light.
  • FIG. 18 shows an additional embodiment of the device of FIG. 1 7. whereby an additional p/ 4 phase retardation plate 134 converts th e circularly polarized light remaining from the initially unpolarized incident light to a linearly polarized light beam 132 which has opposite polarization to the reflected beam 122.
  • FIG. 19 shows an embodiment of the film of the invention used for display purposes.
  • the electric field in the film 110 of the invention is controlled to vary spatially across the area of the film 1 10 by a voltage controller 148 applying varying voltages to segmented electrodes 146.
  • the bandwidth of light 42 is changed from the various areas of the film to give a display.
  • polarized light may be used for light 142, and the polarized light in transmission may also be used as a display.
  • FIG. 20 shows an optical system using the film of the invention, whereby the controllable bandwidth light beam 158 may be used i n further optical systems 154, and the transmitted light beam 159 m ay have a "notch" controllable by the voltage applied across the conducting materials 1 10 and 1 12.
  • FIG. 21 shows one example of an optical system 154 for injecting a controlled bandwidth polarized light beam 158 through a lens 162 into an optical communication fiber 164.
  • FIG. 22 shows an embodiment using the voltage controlled film of the invention as a cavity element in a laser cavity 170.
  • the controllable bandwidth polarizing film is used here as cavity reflector 172 for a cavity comprising the controllable bandwidth polarizing film, a broadband light amplifier 174, and a broadband mirror 176.
  • the device of FIG. 22 will lase and produce a controllable bandwidth of laser light at wavelengths where the reflectivity of the mirror 172 reaches a threshold value.
  • the laser output may be drawn either from the mirror 172 or from the mirror 176, depending on the transmissions of the cavity reflectors.
  • FIG. 23 shows the reflection spectra for unpolarized light of the bandwidth changeable polarizer of recipe #1 for different values of the voltage across the film.
  • FIG. 24 shows the transmission spectra for right and left h anded circularly polarized (RHCP and LHCP) light for a sample of film made from recipe # 1 .
  • liquid crystal cells were fabricated using a method similar to that discussed in the previous section, but with several distinct differences .
  • the cells were made using two glass substrates having an ITO conductive coating.
  • the sample was annealed at a n elevated temperature (70 - 80°C).
  • the sample was then cooled to room-temperature and c ured (polymerized) at room temperature by a much more powerful broadb and (350 - 400 nm) UV light of intensity 4.4 W/c m 2 .
  • the curing time was about 5 seconds. There was no electric voltage applied during the curing process.
  • CM 181 and CM171 are liquid crystal polymers in cholesteric phase (BASF, Germany).
  • E44 is the low molecular weight nematic from EMI.
  • CB15 is the chiral additive from EMI.
  • IG 184 is a photo initiator from Cyba Geigy.
  • Tc is the curing temperature at which the sample is cured.
  • the first sample was made with 15 micron glass spacers. It is switchable using an AC voltage ( ⁇ 1 kHz). As shown in Fig. 26, the polarizer switches from broad bandwidth to narrow bandwidth when the AC field is switched on .
  • Figs. 28 and 29 show further improvements on Recipe #1 to shift the central wavelength of the switchable CLC polarizer to longer IR wavelengths by adding more chiral additives (S lOl l) which has a n opposite handedness to the original CLC mixture.
  • S lOl l chiral additives
  • the opposite handedness chiral untwists the original CLC helix and therefore shifts the center wavelength toward to longer side.
  • a switchable broadband polarizer has been created that starts reflecting from 700 n m to 1,000 nm.
  • the reflectivity of this polarizer is low. Therefore, Recipes #2 and #3 will be further optimized to achieve substantially higher extinction ratios.
  • Figs. 30 and 31 show the response to AC and DC fields of a CLC cell fabricated using Recipe #4.
  • the CLC polymer has been changed from CM181 to CM171 (both from BASF).
  • CM 171 has a medium cross-linking density and an intrinsic reflection wavelength at 507 n m .
  • CM181 has a low cross-linking density and reflects at 365 n m wavelength.
  • the broadband polarizer fabricated has a longer center wavelength.
  • the 15 micron polarizer shows reflection bandwidth reduction upon application of an AC field (1 kHz).
  • the 7.8 micron thick polarizer shows the opposite bandwidth switching behavior, i.e., i t exhibits a bandwidth broadening under a DC voltage. This observation is similar to that shown in Figs. 26 and 27.
  • switchable broadband polarizers Two different mechanisms have been identified for generating switchable broadband polarizers: (1) pitch gradient (for first-type reflective polarizers), and (2) helix lengthening and mis-orientation for second-type reflective polarizers).
  • the pitch gradient generally gives rise to a broadband effect when no electric field is applied, which corresponds to the first type of switchable broadband polarizer that is switched from broadband to narrow band.
  • the helix mis-orientation plus the pitch length increase that is induced by the DC electric field are responsible for the second-type of switchable broadband polarizer whose bandwidth can be switched from narrow to broad.
  • the first type of switchable IR polarizer is created by the same mechanism that governs other first type switchable polarizers, —a mechanism termed ultraviolet (UV) polymerization- induced molecular re-distribution (PIMRD), described hereinabove.
  • UV ultraviolet
  • PMRD photosensitive molecular re-distribution
  • a nonlinear helical pitch distribution induced along the CLC helical axis during the curing process is key.
  • the polymerization process of the active liquid crystal compound in this case, the liquid crystal polymer itself
  • the segregated liquid crystal molecules start to diffuse along the UV radiation direction.
  • the recipe for the polarizer in the IR was obtained b y shifting the polarizer's center wavelength to longer wavelength, as shown by the narrow band curve in Fig. 14. To lengthen the center wavelength, higher concentrations of the nematic liquid crystal (E44) have been added to the mixture.
  • the switching of this type of polarizer from broadband to narrow band is realized through molecular reorientation induced by the electric field.
  • the broadband polarizer inherently has a pitch gradient across the film thickness that corresponds to the liquid crystal component gradient; at the site where the pitch is longer, the low molecular weight nematic (e.g. E44) concentration is higher. Therefore, the helix at the longer pitch site becomes easier to untwist to a homeotropic orientation due to the easier reorientation of the E44 molecules by the electric field, since the nematic E44 has a larger positive dielectric anisotropy and lower viscosity. As a result, the polarizer reflectivity at longer wavelength disappears first when the voltage reaches to a certain level.
  • the shorter pitch is more difficult to untwist under the same electric field because of the higher concentration of the polymer network.
  • the electric field In order to switch the shorter pitch, the electric field must be further increased. Therefore, the polarizer bandwidth further reduces.
  • concentration of the liquid crystal polymer is so high that molecular reorientation by the electric field becomes impossible. This corresponds to the shortest pitch or the shortest reflection wavelength since the liquid crystal polymer used in the mixture has a short intrinsic pitch.
  • Fig. 32 schematically illustrates this switching mechanism.
  • the switching mechanism for the second type of polarizer is more complicated. It is important to point out that a DC electric field is necessary in order to realize such switching.
  • this type of polarizer is in a rather narrow bandwidth state.
  • t o the liquid crystal component gradient that is caused by the faster UV polymerization of the mixture.
  • th e homeotropic transition threshold field Under a sufficient field, but still below th e homeotropic transition threshold field, the reorientation of the low molecular weight nematic E44 material takes place, which increases the pitch length. As a result there is a wavelength shift toward to longer wavelength.
  • the i ncrease of the pitch length will cause some of the pitches to be mis-oriented.
  • the mis-oriented pitch has a helical axis no longer parallel to the film surface normal.
  • normally-incident light experiences a shorter pitch. Therefore, the reflection wavelength is shifted to the shorter side.
  • the tilt of the liquid crystal molecules reduces the average refractive index. This, in part, causes the further expansion toward to the shorter wavelength side as the reflected wavelength depends on both the pitch of the CLC and the average index of refraction.
  • the pitch length increase due to the liquid crystal reorientation by the electric field is responsible for the reflection band expansion toward longer wavelengths.
  • Both types of polarizers are made from liquid crystal blends containing cross-linkable and non-cross-linkable compounds.
  • the first type polarizer with a 10 micron thickness, can be switched from a broadband (about 220nm) to a narrow band (40nm) by an electric field.
  • the second type polarizer with a 8 micron thickness, can be switched from a narrow band (70nm) to broadband (350nm). Both polarizers exhibit an extinction ratio over 15 : 1 .
  • Another application of the present invention would be in a reflective-type display structure, wherein there are no color filters and n o other polarizers other than the switchable circular reflective polarizers of the present invention.
  • the novel polarizers of the present invention can be used for m an y other applications including IR switchable glazing for energy conservation.
  • IR switchable glazing for energy conservation.
  • Today's advanced glazing market there are several new technologies that effectively manage the solar radiation into buildings.
  • One example is the 20% low-e IGU glazing which has special metal deposition film that rejects the solar radiation from entering into buildings.
  • such product has the following disadvantages.
  • First, it has a very low transmittance in the visible because of the broader cutoff spectral tail in the reflection of the metal film. As a result, the electric power is increased for interior lightening.
  • the switchable IR polarizers of the present invention By adjusting the voltage applied onto the switchable reflective polarizers hereof, the electro- optical glazing embodying the same, as shown in Fig. 34, for example, can transmits IR radiation between 0 and 100%. Therefore, such electro- optical glazings will be effective in any location despite of the local weather condition.
  • the new switchable polarizer can be used to build IR detection and imaging system that allows a temporal management of the IR radiation transmittance and wavelength selection.
  • the switchable/controllable reflective polarizers of the present invention can be used in many scientific research activities where temporal IR polarization management becomes important.
  • the switchable/controllable reflective polarizers of the present invention can also be used to construct an IR polarimeter which fully analyze the IR radiation polarization state.
  • this instrument When this instrument is jointly used with an IR detection or imaging system, it will further enhance the detectability as well as the accuracy of the detection system.
  • the switchable/controllable reflective polarizers of the present invention can be used in automotive vehicles, maritime vessels, aircrafts and spacecrafts.

Abstract

La présente invention concerne une pellicule de réglage de la lumière (10) comprenant un réseau de polymère polymérisé variant spatialement dans une direction normale par rapport à la surface de la pellicule, le réseau de polymère polymérisé étant constitué par un matériau polymère réticulé de poids moléculaire élevé mélangé à un matériau nématique de faible poids moléculaire présentant un ordre de cristal liquide cholestérique, un champ électrique imprimé sur la pellicule permettant de régler la largeur de bande de réflexion d'une lumière à polarisation circulaire.
EP99927322A 1998-06-05 1999-06-07 Polariseurs reflechissants a spectre reglable et a modes de fonctionnement electriquement commutables Withdrawn EP1093598A4 (fr)

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US09/093,006 US6369868B1 (en) 1998-06-05 1998-06-05 Liquid crystal polarizer with electrically controllable bandwidth
US09/093,017 US6473143B2 (en) 1991-11-27 1998-06-05 Broadband switchable polarizer
US93017 1998-06-05
US93006 1998-06-05
PCT/US1999/012759 WO1999063400A1 (fr) 1998-06-05 1999-06-07 Polariseurs reflechissants a spectre reglable et a modes de fonctionnement electriquement commutables

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2504003A (en) * 2012-07-11 2014-01-15 Alphamicron Inc Continuous wave directional emission liquid crystal structures and devices

Families Citing this family (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2003224809A1 (en) 2002-03-27 2003-10-13 Avery Dennison Corporation Switchable electro-optical laminates
US7068344B2 (en) * 2003-02-24 2006-06-27 3M Innovative Properties Company Cholesteric liquid crystal optical bodies and methods of manufacture and use
WO2006046832A1 (fr) * 2004-10-26 2006-05-04 Ha, Kyoungsu Corps optique polarisant et procede de fabrication associe
ZA200705619B (en) 2005-01-10 2009-01-28 Avery Dennison Corp Removable curl labels
FR2890396B1 (fr) 2005-09-08 2009-01-23 Centre Nat Rech Scient Procede d'elaboration d'un materiau a cristaux liquides a taux de reflexion accru
FR2890397B1 (fr) 2005-09-08 2009-02-27 Centre Nat Rech Scient Procede d'elaboration d'un materiau a cristaux liquides a bande de reflexion elargie
JP4894214B2 (ja) * 2005-09-29 2012-03-14 独立行政法人物質・材料研究機構 高効率レーザー発振装置
EP2094799B1 (fr) 2006-11-02 2013-08-28 Avery Dennison Corporation Adhésif en émulsion pour film lavable
WO2010038175A2 (fr) 2008-10-02 2010-04-08 Koninklijke Philips Electronics N.V. Détecteur spectral
US20120034402A1 (en) 2009-03-30 2012-02-09 Avery Dennison Corporation Removable Adhesive Label Containing Polymeric Film Layer Having Water Affinity
RU2635037C1 (ru) 2009-03-30 2017-11-08 Авери Деннисон Корпорейшн Удаляемая самоклеящаяся этикетка, включающая слой полимерной пленки с высоким модулем упругости при растяжении
US20120018098A1 (en) 2009-03-30 2012-01-26 Avery Dennison Corporation Removable Adhesive Label Containing Inherently Shrinkable Polymeric Film
EP2442160A4 (fr) * 2009-06-11 2012-11-07 Fujifilm Corp Procédé de production d'un film réfléchissant
CN102575959B (zh) 2009-10-16 2015-01-28 皇家飞利浦电子股份有限公司 用于检测接收光光谱成分的可调谐光谱检测设备
EP2742383B1 (fr) * 2011-08-08 2018-01-17 Merck Patent GmbH Agencement de couches pour la régulation de transmission de lumière
JP6165750B2 (ja) * 2011-10-24 2017-07-19 メルク パテント ゲゼルシャフト ミット ベシュレンクテル ハフツングＭｅｒｃｋ Ｐａｔｅｎｔ Ｇｅｓｅｌｌｓｃｈａｆｔ ｍｉｔ ｂｅｓｃｈｒａｅｎｋｔｅｒ Ｈａｆｔｕｎｇ 液晶媒体を含む切換素子
US9302452B2 (en) * 2012-03-02 2016-04-05 Ppg Industries Ohio, Inc. Transparent laminates comprising inkjet printed conductive lines and methods of forming the same
JP2015045679A (ja) * 2013-08-27 2015-03-12 国立大学法人大阪大学 光学素子の製造方法、光学素子、偏光無依存型位相変調素子
CN103676327B (zh) * 2013-12-13 2016-08-17 北京科技大学 有光响应特性的多反射带层状胆甾相液晶复合薄膜及工艺
CN105487157A (zh) * 2014-08-13 2016-04-13 南京晶多新材料科技有限公司 一种兼作散射偏光片的电控调光膜的构造和应用
BR112017013196B1 (pt) 2014-12-30 2022-02-22 Kimberly-Clark Worldwide, Inc Artigo absorvente com camada de folha superior em contato com a pele, parcialmente separável
KR102268665B1 (ko) * 2020-03-17 2021-06-23 사회복지법인 삼성생명공익재단 실내 감정 조절 블라인드, 실내 감정 조절 블라인드의 동작 방법, 및 컴퓨터 프로그램
US20230393317A1 (en) * 2022-06-02 2023-12-07 Meta Platforms Technologies, Llc Tunable reflective polarizer

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0643121A1 (fr) * 1993-09-08 1995-03-15 Koninklijke Philips Electronics N.V. Filtre cholestérique commutable et luminaire ayant un tel filtre
WO1997023580A1 (fr) * 1995-12-21 1997-07-03 Philips Electronics N.V. Procede de fabrication d'un filtre cholesterique commutable et d'un luminaire le comportant

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5691789A (en) * 1995-10-30 1997-11-25 Li; Le Single-layer reflective super broadband circular polarizer and method of fabrication therefor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0643121A1 (fr) * 1993-09-08 1995-03-15 Koninklijke Philips Electronics N.V. Filtre cholestérique commutable et luminaire ayant un tel filtre
WO1997023580A1 (fr) * 1995-12-21 1997-07-03 Philips Electronics N.V. Procede de fabrication d'un filtre cholesterique commutable et d'un luminaire le comportant

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
HIKMET R A M ET AL: "Electrically switchable mirrors and optical components made from liquid-crystal gels" NATURE, MACMILLAN JOURNALS LTD. LONDON, GB, vol. 392, no. 6675, 2 April 1998 (1998-04-02), pages 476-479, XP002103849 ISSN: 0028-0836 *
LI J-F ET AL: "SINGLE-LAYER REFLECTIVE POLARIZERS WITH ELECTRICALLY CONTROLLED SPECTRUM" 1999 SID INTERNATIONAL SYMPOSIUM DIGEST OF TECHNICAL PAPERS. SAN JOSE, CA, MAY 18 - 20, 1999, SID INTERNATIONAL SYMPOSIUM DIGEST OF TECHNICAL PAPERS, SAN JOSE, CA: SID, US, vol. 30, 18 May 1999 (1999-05-18), pages 1066-1069, XP000894830 *
LI L ET AL: "SINGLE-LAYER SUPER BROADBAND REFLECTIVE POLARIZER" SID INTERNATIONAL SYMPOSIUM. DIGEST OF TECHNICAL PAPERS. SAN DIEGO, MAY 12 - 17, 1996, SANTA ANA, SID, US, vol. 27, 12 May 1996 (1996-05-12), pages 111-113, XP002922397 ISSN: 0097-966X *
See also references of WO9963400A1 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2504003A (en) * 2012-07-11 2014-01-15 Alphamicron Inc Continuous wave directional emission liquid crystal structures and devices
GB2504003B (en) * 2012-07-11 2015-08-12 Alphamicron Inc Continuous wave directional emission liquid crystal structures and devices

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KR20010071415A (ko) 2001-07-28
CA2333871A1 (fr) 1999-12-09
CN1179233C (zh) 2004-12-08
JP2002517784A (ja) 2002-06-18
CN1312918A (zh) 2001-09-12
WO1999063400A1 (fr) 1999-12-09
AU4425699A (en) 1999-12-20
EP1093598A4 (fr) 2002-07-24

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