WO2004049047A1 - Film de vanne de lumiere pour arreter et commander la transmittance, et procede de fabrication associe - Google Patents

Film de vanne de lumiere pour arreter et commander la transmittance, et procede de fabrication associe Download PDF

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Publication number
WO2004049047A1
WO2004049047A1 PCT/KR2002/002205 KR0202205W WO2004049047A1 WO 2004049047 A1 WO2004049047 A1 WO 2004049047A1 KR 0202205 W KR0202205 W KR 0202205W WO 2004049047 A1 WO2004049047 A1 WO 2004049047A1
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Prior art keywords
resin
light
film
liquid crystal
transparent conductive
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PCT/KR2002/002205
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English (en)
Inventor
Byung-Seok Yu
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Spdi
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Priority to PCT/KR2002/002205 priority Critical patent/WO2004049047A1/fr
Priority to AU2002356457A priority patent/AU2002356457A1/en
Publication of WO2004049047A1 publication Critical patent/WO2004049047A1/fr

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    • 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 
    • G02F1/17—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 variable-absorption elements not provided for in groups G02F1/015 - G02F1/169
    • G02F1/172—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 variable-absorption elements not provided for in groups G02F1/015 - G02F1/169 based on a suspension of orientable dipolar particles, e.g. suspended particles displays
    • 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
    • G02F1/1347—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
    • G02F1/13476—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells in which at least one liquid crystal cell or layer assumes a scattering state

Definitions

  • the present invention relates to a film to be used as a flat display device for display panels or windows.
  • the present invention relates to a light valve which is for cut-off and controllability of light transmittance and a method of making the same.
  • a light valve was first disclosed in 1934 in US Patent Nos. 1,951,664 and 1,955,923 to E. H. Land.
  • the light valve comprises two transparent conductive substrates that are spaced apart by a small distance, and a liquid light-polarizing suspension or a liquid suspension of light-modulating particles (hereinafter, described as "a light-modulating suspension) injected between the substrates.
  • a liquid light-polarizing suspension or a liquid suspension of light-modulating particles hereinafter, described as "a light-modulating suspension
  • the light-modulating suspension reflects, scatters or absorbs most of the incident light due to Brownian movement of the particles dispersed in the suspension. Extremely small part of the incident light can pass through.
  • an electric field is applied through the substrates, the light-polarizing or light modulating particles in the suspension are polarized and aligned in parallel along the applied electric field.
  • the light can pass through between the aligned particles or along the major axe of particle and the light valve turns transparent.
  • Such early-stage light valves have various problems from a practical standpoint, which include aggregation and settling of light-polarizing particles in the suspension, thermal discoloration, change of optical density, performance deterioration due to ultraviolet radiation, difficulties in maintaining the space and injecting the suspension between the substrates.
  • Korean Patent No. 14,118, US Patent No. 5,409,734, European Patent No. 551,138, Japanese Patent Publication No. (Hei)4-303797 and US Patent No. 6,114,405 solved the above problems by forming a film wherein microdroplets of a light- modulating suspension are dispersed or by forming a separate, membrane-like film between two transparent conductive substrates.
  • microdroplets of the liquid light-modulating suspension dispersed in the film or light-modulating particles in the separate membrane-like body exhibit Brownian movement, and the light valve turns colored due to dichroism of the light-modulating particles.
  • the light valve rums colorless and transparent, with no scattering and transparency deterioration observed depending on the angle of view.
  • Such light valve films wherein microdroplets of a light-modulating suspension are dispersed or interconnected in a polymeric matrix can be produced by: 1) mechanically mixing a completely water- immiscible suspension with an aqueous solution of a water-soluble polymeric material to form an emulsion (the suspension is encapsulated in the polymeric solution), coating the emulsion and evaporating; 2) phase separation by polymerization; 3) thermal phase separation; and (4) phase separation by solvent evaporation.
  • Light-modulating particles are disclosed in US Patent Nos. 2,041,138 to E. H. Land, 2,306,108 to Land, et al, 2,375,963 to Thomas and 4,270,841 to R. L. Saxe, and UK Patent No. 433,455.
  • polyiodides are known and herapadite crystals which have been prepared by reacting quinine disulfates with iodine or HI.
  • Other salts of quinine alkaloids can react with iodine or HI to give polyiodides such as cinchonidine disulfate.
  • Hydrogen halide or alkaline or alkaline-earth halide such as, iodides, chlorides, bromides, are reacted with carboxylic acid of pyrazine or pyridine to produce polyhalide compound, such as, polyiodide, polychloride, polybromide, which are compounds of iodine atom and an organic or inorganics.
  • polyhalide compound such as, polyiodide, polychloride, polybromide, which are compounds of iodine atom and an organic or inorganics.
  • light-polarizing material which has been prepared by reacting any one compound selected from the group of pyrazine 2,3- dicarboxylic acid, pyrazine 2,5-dicarboxylic acid, pyridine 2,5-dicarboxylic acid, 8- hydroxyquinolin, dihydrocinchonidine sulfate and 2-hydroxypryridine with a polyhalogen compound, phenanthrolin complex disclosed in U.S. Patent Nos. 5,646,284 and 5,710,273, phthalocyanin complex disclosed in U.S. Patent Nos. 4,968,425, 5,622,801 and 5,656,751, dichromatic light-polarizing particles disclosed in U.S. Patent Nos.
  • 5,710,273 and 5,106,533, and various pigments and dyes are used in the presence of a dispersing agent which is incompatible with the matrix forming polymeric resin and enhances dispersion of the light-modulating particles.
  • Novel metals such as Pt, Ag, Au, Pd, Rb, and metals such as Al, Cr, Ti, In can also be used.
  • Metal oxides such as brass tungsten can be used.
  • a dispersing agent which is sparingly compatible with polymeric film matrix and is capable of preventing overgrowth of light modulating particles is used. This helps the light-modulating particles or light-polarizing particles to be easily enclosed in microdroplets formed by phase separation during the film forming process.
  • polyhydroxyethyl methacrylate, polyacrylic acid, cellulose acetate, hydroxy propyl acrylate alone, or a block copolymer with neopentyl methacrylate, and nitrocellulose can be used.
  • Light-polarizing particles are generally suspended in a medium and can cut off light transmission.
  • the light-polarizing particles have polarization property, which enables them to be aligned and transmit light in the presence of an applied electric field, and makes them randomly positioned due to Brownian movement, thereby cut-off of light transmittance. This also makes it possible to control light transmittance.
  • the above structure maintains colored transparent state with no scattering even in the absence of an applied electric power, which gives a limitation to capability of light transmittance.
  • a low- voltage operation is difficult with the size of particle in a range of 0.1 [m to several ⁇ m, changing time of several hundreds of milliseconds and a higher threshold voltage of more than tens of volts.
  • the light valve comprises two transparent conductive substrates and a film having dispersed liquid crystal capsules between the substrates.
  • the liquid crystal in the dispersed spherical capsules is aligned along the interface of the capsules in the absence of an applied electric field, the incident light is doubly refracted at the interface of the capsules since refractive index of the liquid crystal is not the same as that of the polymeric resin surrounding the liquid crystal.
  • the film turns translucent and milky.
  • the refracted light is successively refracted and scattered in different directions at the interfaces of other capsules, the film turns translucent and milky.
  • the refractive index of the liquid crystal is the same as that of the polymeric resin matrix
  • thermoplastic resin such as, methyl methacrylate polymer or polyvinyl formal
  • liquid crystal material a homogeneous isotropic phase is maintained at a temperature above the melting point of the polymeric resin, but phase separation starts to occur at a certain degree of temperature as the temperature is lowered.
  • P ⁇ LC Polymer Network Liquid Crystal
  • the refraction index of liquid crystal such as nematic, smectic or cholesteric liquid crystal, is preferably identical to that of the polymeric resin to maximize light transmittance when an electric field is applied.
  • nematic liquid crystal showing a high degree of refraction anisotropy ( ⁇ « ) is used, scattering will be strong, and when liquid crystal showing a high degree of dielectric anisotropy is used, the light valve can be operated at low voltage.
  • a liquid crystal having a high refraction anisotropy and dielectric anisotropy is preferably used for a light-scattering type liquid crystal display device.
  • One of the methods of shortening operation time of such a polymeric dispersion type liquid crystal material is to reduce the surface attraction on the polymeric chain.
  • conventional polymeric dispersion type liquid crystal can be operated at a voltage in the range of 20-60N the threshold voltage can be lowered as down to around ION by using ferroelectric liquid crystal, recently commercially available, and by properly controlling the content of liquid crystal, the size of microdroplet of liquid crystal, and the thickness of the film.
  • threshold voltage can be lowered as below ION, and more surprisingly, as low as below 5N with sufficient contrast. This is possible because surface attraction on the wall of the microdroplets obtained by P ⁇ LC is weaker than that obtained by ⁇ CAP or PDLC.
  • the present invention employs the difference in the threshold voltages of light- modulating particles and liquid crystals to provide a light valve comprising a combined films thereof, which exhibit dark and colored state due to the behavior of the light- modulating particles when no electric field is applied, but varies the light transmittance by altering the amounts of light-polarizing or light-modulating particles or the magnitude of electric field.
  • the present invention employing liquid crystals that scatter and cut off light transmittance in the absence of an applied electric field and transmit light instantly upon appliance of an electric field, to provide a light valve (1) which maintains an opaque-colored state in the absence of an applied voltage, maintains a transparent colored state at a certain level of voltage where the opacity due to scattering by the liquid crystal disappears but the light-polarizing particles are still not aligned, and shows an elevated light transmittance at a higher level of voltage where the light-modulating particles are gradually aligned in the suspension; (2) which, in another way, maintains a colorless, opaque state at a certain level of voltage where the light-polarizing or light-modulating particles start to be aligned and coloration disappears, and turns transparent at a higher level of voltage where liquid crystals are aligned along the electric field.
  • the present invention provides a light valve for cut-off and controllability of light transmittance, which comprises: a first transparent substrate; a first transparent conductive thin film formed on the first transparent substrate; a first resin film, formed on the top of the thin film, comprising microdroplets of a suspension of light-modulating particles; a second resin film, joined to the first resin film, comprising microdroplets of liquid crystal; a second transparent conductive thin film formed on the top of the second resin film; a second transparent substrate positioned on the top of the second transparent conductive thin film; and a power supply for connecting the first transparent conductive thin film and the second transparent conductive thin film.
  • the present invention provides a light valve for cut-off and controllability of light transmittance, which comprises: a first transparent substrate; a first transparent conductive thin film formed on the first transparent substrate; a resin film, formed on the top of the thin film, comprising microdroplets of a suspension of light-modulating particles and microdroplets of liquid crystal; a second transparent conductive thin film formed on the top of the resin film; a second transparent substrate positioned on the top of the second transparent conductive thin film; and a power supply for connecting the first transparent conductive thin film and the second transparent conductive thin film.
  • the present invention also provides a method of manufacturing a light valve for cut-off and controllability of light transmittance, which comprises the steps of: preparing a first resin solution comprising a suspension of light-modulating particles and a polymeric resin; forming a first resin film comprising microdroplets of the suspension of the light-modulating particles by applying the first resin solution on the first substrate; preparing a second resin solution comprising liquid crystal material and a polymeric resin; forming a second resin film comprising microdroplets of the liquid crystal by applying the second resin solution on the second substrate; and joining the first resin film and the second resin film.
  • the present invention still provides a method of manufacturing a light valve for cut-off and controllability of light transmittance, which comprises the steps of: preparing a first resin solution comprising a suspension of light-modulating particles and a polymeric resin; preparing a second resin solution comprising liquid crystal and a polymeric resin; and forming a resin film by sequentially applying the first and second resin solutions on the substrate.
  • the present invention further provides a method of manufacturing a light valve for cut-off and controllability of light transmittance, which comprises the steps of: preparing a first resin solution comprising a suspension of light-modulating particles and a polymeric resin; preparing a second resin solution comprising liquid crystal and a polymeric resin; preparing a mixed resin solution by mixing the first resin solution and the second resin solution; and forming a resin film by applying the mixed resin solution on a substrate.
  • the present invention still further provides a method of manufacturing a light valve for cut-off and controllability of light transmittance, which comprises the steps of: preparing a resin solution comprising a suspension of light-modulating particles, liquid crystal, and a polymeric resin; and forming a resin film by applying the resin solution on a substrate.
  • FIG. 1 is a cross-sectional view of a film-type light valve according to the conventional art
  • FIG. 2 is a cross-sectional view of a film-type light valve according to the present invention, wherein a light-modulating microdroplets-dispersed film is layered with a liquid crystal film.
  • FIG. 3 is a cross-sectional view of a film-type light valve according to the present invention, wherein light-modulating suspension microdroplets and liquid crystal microdroplets are contained in a single film.
  • FIG. 4 shows how incident light is cut off when no electric field is applied to the light valve in FIG. 2;
  • FIG. 5 shows how opacity disappears when a low electric field is applied to the light valve in FIG. 2;
  • FIG. 6 shows how light transmittance changes when a voltage higher than that in FIG. 5 is applied to the light valve in FIG. 2.
  • a light valve can be manufactured wherein a film comprising liquid crystal and a film comprising light- modulating particles are layered.
  • a first resin solution comprising a suspension of light-modulating particles and a polymeric resin or a monomer is prepared as a mixed solution which can be formed into a film after application and phase separation or as an emulsion which comprises microdroplets of the light-modulating suspension, and applied on a first substrate which is made of glass or a polymeric resin and coated with a conductive thin film to a thickness of 10-300 ⁇ m.
  • the mixed solution or the emulsion is formed into a first resin film comprising microdroplets of the light-modulating suspension by solvent evaporation or by phase separation via solvent evaporation, polymerization, thermosetting process or UN radiation.
  • a second resin film is prepared by a method similar to that used to prepare the first resin film, i.e., by preparing a second resin solution comprising liquid crystal and a polymeric resin or a monomer as a mixed solution or an emulsion which comprises encapsulated microdroplets of liquid crystal, and applied on a second substrate which is made of glass or a polymeric resin and coated with a conductive thin film to a thickness of 10-300 ⁇ m.
  • the mixed solution or the emulsion is formed into a second resin film comprising microdroplets of the liquid crystal by solvent evaporation or by phase separation via solvent evaporation, polymerization, thermosetting process or UN curation.
  • the first and second substrates which have been coated with the first and second resin films, respectively, are heated and joined to provide a light valve according to the present invention.
  • An adhesive layer can be inserted between the first and second resin films to join the two substrates.
  • the first resin solution comprises the light-modulating suspension and the polymeric resin in the ratio by weight of 1 : 1 to obtain homogenous microdroplets in the first solution.
  • the second resin solution comprises the liquid crystal and the polymeric resin in the ratio by weight of 1:1.25 to easily control the size of microdroplet and obtain homogenous microdroplets.
  • the first manufacturing method comprises the steps of preparing the first and second transparent conductive substrates having a transparent thin film thereon, and applying the first and second resin solutions on the first and second transparent conductive substrates.
  • a light valve by applying the first and the second resin solutions on a releasing agent-coated PET films 1 and 2(not coated with a transparent conductive thin film), forming and joining the first and the second resin films as described above, removing the releasing agent to obtain a film laminate and inserting the laminate between two transparent conductive substrates.
  • the second method of the present invention provides another manufacturing process, wherein a film of the light modulating suspension microdroplet and a film of liquid crystal are sequentially applied to make a laminated film.
  • This method comprises the steps of preparing a first resin solution comprising a light-modulating suspension and a polymeric resin and a second resin solution containing liquid crystal, applying the two solutions sequentially on a single transparent conductive substrate to obtain a layered film.
  • This sequential application method can be perforaied by multilayer extrusion die coating or multi-layer printing method.
  • the laminated film is covered with a second transparent conductive substrate having a transparent conductive thin film thereon to provide a light valve according to the present invention.
  • the substrate can be at room-temperature or thermally adhered.
  • the film matrixes used in the first and the second solutions should be immiscible or sparingly miscible.
  • the first resin solution comprises a light modulating suspension and, for example, methacrylate monomer or polymer in the ratio by weight of 1:0.5-1.25.
  • the second resin solution comprises liquid crystal and, for example, urethane monomer or polymer in the ratio by weight of 1:0.5-1.5 for the same reason.
  • the third method provides another manufacturing process wherein microdroplets of the light-modulating suspension and microdroplets of the liquid crystal are present in one single film layer.
  • This method comprises the steps of preparing a first resin solution comprising a light-modulating particles and a polymeric resin, preparing a second resin solution comprising liquid crystal and the same polymeric resin as used in the first resin solution, mixing the first and the second resin solutions to obtain a mixed solution, and applying the mixed solution onto a transparent conductive thin film-coated glass or polymeric film substrate to a thickness of 10-300 ⁇ m.
  • the light-modulating suspension and the liquid crystal can be mixed in a polymeric resin, employing the differences in phase separation characteristics, solubility characteristic, and miscibility characteristics.
  • Polymeric resins such as, silicone, urethane, or acrylic resin can be used for this purpose, i.e., since such resins are not reactive with light-modulating particles and can easily be separated from the light- modulating suspension phase and the liquid crystal phase.
  • the solution preferably comprises the light-modulating particles, liquid crystal, urethane polymeric resin in the ratio by weight of 3-5:4-6:10-12, more preferably 4:5:11.
  • polyiodine pyrazine 2,5-dicarboxylic acid for example, as light-polarizing material, which can be prepared by reacting polyhalogen compound with any one compound selected from the group consisting of pyrazine 2,3- dicarboxylic acid, pyrazine 2,5-dicarboxylic acid, pyridine 2,5-dicarboxylic acid, 8- hydroxyquinolin, dihydrocinchinidine sulfate, and 2-hydroxypyridine which are all known crystals in the background art.
  • a copolymer of polyhydroxyethyl methacrylate-polyhydroxyethyl methacrylate is used as a dispersing agent.
  • TL-213 which is one of the TL series optimized for PDLC products by Merck, is used.
  • thermoplastic resins which have refraction index of 1.4-1.55 and are incompatible or partially compatible with the suspension medium or liquid crystal can be used.
  • Preferable examples are polyvinyl butyral, polyvinyl acetate, polyethyl methacrylate, cellulose acetate.
  • the polymeric resin must be dissolved in a suitable solvent before the polymeric resin solution is mixed with the light-modulating suspension and the liquid crystal (hereinafter, described as "microdroplet forming material").
  • esters such as, isoamyl acetate, benzyl acetate, ethyl acetate, methyl acetate, or aromatic hydrocarbons, such as, toluene, xylene, which does not have any influence on or is not reactive with the light-modulating particles or the liquid crystal.
  • aromatic hydrocarbons such as, toluene, xylene
  • a polymeric resin which has refraction index of 1.3-1.55 and is incompatible or partially compatible with the microdroplet forming material can be used.
  • thermoplastic monomers such as, methyl methacrylate, vinyl butyral, or heat cured or UN cured resins, such as, epoxy, silicone, urethane.
  • the same microdroplet forming material as used in solvent evaporation is used.
  • a commercially available epoxide is used for thermoset polymer resin matrix in condensation process, and methyl methacrylate is used with a polymerization initiator, benzoyl peroxide, in radical or condensation polymerization reaction.
  • ether linkage (-O- ) by reaction between the terminal hydroxyl (-OH) groups of the prepolymers and the functional groups of a cross linking agent to form a film.
  • a radical produced by UN radiation reacts with a pendant group of another monomer to produce a new radical.
  • radical reaction progresses, the chain length of resin polymer increases, and consequently, the solubility of microdroplet forming material decreases.
  • phase separation occurs and microdroplet forming material is dispersed in the polymeric resin in the form of microdroplets.
  • the size of microdroplet varies and can be controlled by the polymerization rate, concentrations of each components, characteristics of the liquid crystal used, viscosity and diffusion velocity of the light-modulating suspension and the polymeric resin, and compatibility of the plasticizer contained in the light-modulating suspension with the polymeric resin.
  • Phase separation can be carried out by thermal process, by heating a thermoplastic resin to a temperature above its melting point to obtain a melted solution and homogenously mixing in the microdroplet forming materials separately or together, cooling the mixed solution so that phase separation starts at a certain temperature to obtain a film having microdroplets dispersed therein.
  • microdroplets are uniformly dispersed or randomly interconnected in the polymeric resin. Physical parameters, such as, cooling speed or viscosity will determine the size and shape of microdroplet, and the form in which the microdroplets are interconnected.
  • a compatible plasticizer will be added before the polymeric resin is heated.
  • microdroplet forming material containing a plasticizer which is incompatible or partially compatible with the polymeric resin is used.
  • the mixture is applied on a transparent conductive substrate preheated to about 100°C and cooled in a cooling rate of 5-10°C per minute to provide a film.
  • the film thus obtained is covered with another transparent conductive substrate and attached with electrodes to provide a light valve according to the present invention.
  • Another transparent conductive substrate can be adhered before cooling the resin solution.
  • the resin film solution is prepared by homogenously mixing a light-modulating liquid suspension that is incompatible or partially compatible with the polymeric resin and contains a dispersing agent of similar refraction index and a polymeric resin solution dissolved in a solvent that has no influence on the optical characteristic of the light-modulating particles.
  • a mixed solution comprising liquid crystal is prepared in the same manner. The mixed solution is applied on a transparent conductive substrate to a predetermined thickness, and evaporated at room temperature or a certain degree of temperature, polymerized or thermally processed to initiate phase separation and solidification and thereafter obtain a film having microdroplets of light-modulating suspension and liquid crystal material dispersed in the polymeric resin.
  • the microdroplet forming material is dispersed or randomly interconnected in the polymeric resin.
  • a spherical microdroplet will form when the mixing ratio of the polymeric resin and the light-modulating suspension is up to 1:1, above which, however, microdroplets will be interconnected to assume a membrane-like structure.
  • the weight ration of the suspension to the polymeric resin is less than 0.5, the size of microdroplet will decrease to several ⁇ m s with deterioration of light transmittance modulation characteristics. This is true with a mixture of liquid crystal and a polymeric resin.
  • a preferable mixing ratio of liquid crystal and polymeric resin is 1.2:l(wt/wt).
  • a mixing ratio of the suspension, the liquid crystal and the polymeric resin is 3-5:4-6:10- 12, preferably, 4:5: 11.
  • a film thus obtained is attached with a film coated substrate or a transparent conductive substrate to provide a light valve according to the present invention.
  • the size of the dispersed microdroplet is 0.5-30 ⁇ m. Volatilization rate, concentrations of light transmittance suspension components, liquid crystals and light transmittance suspension, viscosities of the liquid crystal and the polymeric resin solution, and compatibility with the polymeric resin will determine the size, shape and irregularity of microdroplets.
  • the dispersed liquid crystal material When a relatively low level of electric field is applied to the light valve obtained as described above, the dispersed liquid crystal material is aligned to vanish scattering, whereby the light valve turns transparent.
  • the light-modulating particles in microdroplets or suspended in a membrane-like structure are aligned in parallel to the applied electric filed, whereby the light valve gradually turns transparent and almost colorless.
  • the speed at which the light transmittance changes the disappearance of scattering depends on the property of the liquid crystal material used, and the speed of transparency depends on the viscosity of the light-transmitting suspension, the amount of the dispersing agent added, the concentration of the plasticizer, and the size and concentration of the light- modulating particles.
  • liquid crystal material TL series and ZLI series (Merck) can be used for this process, ZLI- 2427, 2777 for emulsion process, TL-202, 205, 213, 216 for phase separation process, alone or together.
  • the kind of liquid crystal and suspension used, the size of particles, the thickness of film will determine the operation property of the liquid crystal.
  • the light valve according to the present invention can cut off and control the light transmittance by maintaining opaque colored state in the absence of an applied electric field, and initially maintaining a colored transparent state and gradually turning colorless and transparent when an electric field is applied thereafter.
  • a light valve can be structured otherwise such that it turns opaque but colorless when light-modulating particles preferentially are aligned in parallel to the applied electric filed in the absence of an electric field, but when a higher level of the electric field is applied thereafter, the dispersed liquid crystal material is aligned to disappear scattering, whereby the light valve turns transparent.
  • the light transmittance change can be reversibly repeated more than two hundred thousand times.
  • the increase of light transmittance in a colorless, transparent state and the increase of clarity in colored state can be achieved by coinciding the refraction index of the suspension medium with that of the polymeric resin and adding a suitable amount of a dispersing agent.
  • a periodic signal (alternating current) is used, and the film can be operated in the range of 15-300N (effective value) and a frequency range of 30Hz-10kHz.
  • the shift of state occurs depending on the applied electric field, and the response time to electric field is within hundreds of millisecond in colorless state and within tens of millisecond in colored state,
  • a transparent conductive film-coated glass or polymeric film can be used as transparent conductive substrate
  • a transparent conductive substrate with a transparent insulating layer of about 2-100 ⁇ m can be used to prevent short-circuit due to foreign materials between narrowly spaced substrates.
  • a conductive thin metal film such as, aluminum, gold or silver, can be used as electrode.
  • the film according to the present invention When no electric power is supplied, the film according to the present invention is opaque due to scattering by liquid crystal and colored due to dichroism of the light- modulating particles exhibiting Brownian movement. However, when electric power is supplied, the film initially turns transparent but still colored as the liquid crystal material is aligned, and when the light-modulating particles are aligned in parallel to the electric field, the film turns transparent and colorless. Since the suspension medium has the refraction index similar to that of the polymeric resin, scattering and transparency change is low. In an optical standpoint, while a conventional light valve cannot completely cut off light transmittance, a light valve according to the present invention can obtain a milk-white opaque state caused by scattering in the absence of an electric filed and the clarity in the presence of electric filed.
  • FIG. 1 is a cross-sectional view of a prior art light valve wherein a film having a liquid light-modulating suspension dispersed in a polymeric resin is interposed between two transparent conductive substrates.
  • FIG. 2 is a cross-sectional view of a light valve wherein two films, in which microdroplets of light-modulating suspension and microdroplets of liquid crystal is respectively dispersed in a polymeric resin, are layered.
  • FIG. 3 is a cross-sectional view of another film according to the present invention, wherein microdroplets of light-modulating particles and microdroplets of liquid crystal are dispersed together in a single polymeric resin.
  • FIG. 4 shows how light is transmitted in the light valve of FIG. 2 when no electric field is applied.
  • FIG. 5 shows how light is transmitted in the light valve of FIG. 2 when a low electric field is applied.
  • FIG. 6 shows how light is transmitted in the light valve of FIG. 2 when a higher level of electric field is applied.
  • FIG. 1 depicts a prior art light valve, wherein film 1 having microdroplets 5 of a liquid light-modulating suspension are dispersed by phase separation in a polymeric resin film matrix is interposed between two transparent substrates 9 on which a transparent conductive thin film 8 is coated, with no sealing and spacers. The valve is operated by AC power supply 10 and switch 12.
  • FIG. 2 shows a light valve according to the present invention, wherein film 1 having microdroplets 5 of a liquid light-modulating suspension dispersed in a polymeric resin and film 2 having microdroplets 7 of liquid crystal are dispersed, are interposed between two transparent substrates 9 on which a transparent conductive thin film 8 is coated.
  • the valve turns opaque colored — » transparent colored — > colorless transparent or opaque colored -» opaque colorless - colorless transparent, depending on operation mode with switch.
  • FIG. 3 is a cross-sectional view of a structure, wherein film 11 having microdroplets 5 of a liquid light-modulating suspension and microdroplets 7 of liquid crystal are dispersed together in a polymeric resin is interposed between two transparent substrates 9 on which a transparent conductive thin film 8 is coated.
  • FIG. 4 shows how incident light is transmitted in the light valve of FIG. 2 when no electric filed is applied. In the absence of an applied electric field, light-modulating particles 4 in the suspension microdroplets 5 exhibit Brownian movement and liquid crystal 6 is randomly oriented, whereby incident light 13 is absorbed, scattered or reflected by light-modulating particles 4 and not transmitted.
  • FIG. 5 shows how the opacity disappears when a low electric field is applied.
  • liquid crystal microdroplets 7 dispersed in film 2 are aligned in the presence of an applied electric field, incident light 13 passes through liquid crystal film layer 2.
  • Light-modulating particles 4 in film layer 1 are still not aligned but exhibit Brownian movement at a relatively low electric field, whereby incident light 13 is absorbed, scattered or reflected by light-modulating particles 4 and not transmitted.
  • FIG. 6 shows how light is transmitted in the light valve of FIG. 2 when an electric field higher than that of FIG. 5 is applied. Since liquid crystal microdroplets 7 dispersed in film 2 are aligned in the presence of an applied electric field, incident light 13 passes through liquid crystal film layer 2, and, further, between light-modulating particles 4 and/or through light-modulating particles 4, if the refraction index of the polymeric resin coincides with that of the microdroplet forming material, no scattering occurs and light is transmitted.
  • Example 1 lOg of polymethyl methacrylate (as film matrix) is dissolved in 40g of toluene to give a polymeric resin solution. 5g of a liquid suspension consisting of 20 wt% of light-modulating particles, 65 wt % of suspension medium, and 15 wt% of a dispersing agent is added to the polymeric resin solution, mixed mechanically for 30 minutes and thereafter ultrasonically mixed for about 2 hours. This mixing procedure is repeated two times and the solution is defoamed. The mixed solution is applied on a transparent conductive film -coated glass or PET film substrate in thickness of 200 ⁇ m. After solvent evaporation at room temperature or in a heating bath of 50 to 90 C, a film of about 50 ⁇ m having microdroplets of light modulating suspension dispersed in the polymer resin is obtained.
  • Example 2 lOg of polymethyl methacrylate(as film matrix) is dissolved in 40g of toluene
  • the mixed solution is applied on a transparent conductive film-coated glass or PET film substrate in a thickness of 200 ⁇ m. After solvent evaporation at room temperature or in a heating bath of 50 to 90 C, a film of about 22 ⁇ m having microdroplets of liquid crystal dispersed in the polymer resin is obtained.
  • the film-coated substrate of Example 1 is covered with the film-coated substrate of Example 2.
  • the two film layers are thermally bonded to produce a light valve.
  • Films are prepared as described in Example 1 , except that the amount of the light-modulating suspension in the polymeric resin varies from 6g up to lOg. As the amount of the liquid light-modulating suspension increases, microdroplets are more interconnected, and not in the form of spherical microdroplets in the films.
  • Films are prepared as described in Example 2, except that the amount of the liquid crystal in the polymeric resin varies from 2g up to lOg. As the amount of the liquid crystal increases, microdroplets are more interconnected, and not in the form of spherical microdroplets in the films.
  • a solution for polymerization phase separation is prepared by using urethane for a film matrix, adding a light modulating suspension (corresponding to 20 wt% of the film matrix), and 5 wt % of benzoate peroxide as polymerization initiator and a small amount of ethyleneglycol dimethylmethacrylate as crosslinking agent.
  • the homogenous solution is coated in a thickness of 10-100 ⁇ m, put in a reactor for polymerization of 90°C to give a film.
  • a solution for polymerization phase separation is prepared by using polymethylmethacrylate and methylmethacrylate (1:2) for film matrix, adding liquid crystal TL-213 (40 wt% of the film matrix), and 5 wt% of lauryl peroxide as polymerization initiator and a small amount of divinyl benzene.
  • the homogenous solution is coated in a thickness of 10-100 ⁇ m, put in a reactor for polymerization of 70°C to give a film.
  • the film-coated substrate of Example 6 is covered with the film-coated substrate of Example 7.
  • the two film layers are thermally bonded to produce a light valve.
  • a light valve according to the present invention can be used in indoor partitions, window glass for buildings, various flat display elements in electronic appliances and image instrument, as substitutes for a variety of instrumental panels and conventional liquid crystal display elements, light shutter, a variety of billboards or information display board for indoor or outdoor, windowpane, rear vision mirror and automobile sun roof, and also as glasses and safety glasses.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Mathematical Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Liquid Crystal (AREA)
  • Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)

Abstract

L'invention concerne un film pour une vanne de lumière. Ce film comprend des micro-gouttelettes de cristal liquide dispersées dans une matrice polymère, et des micro-gouttelettes d'une suspension liquide de particules polarisant la lumière dispersées dans une matrice polymère. Le film est formé par émulsification, ou par des procédés de séparation de phase impliquant une évaporation de solvant et un traitement thermique. Ce film maintient et arrête la transmittance en l'absence de tension appliquée. Cependant, une fois qu'une tension est appliquée, la capacité d'arrêt de transmittance disparaît, et en outre, la transmittance peut être commandée continuellement par la magnitude d'une tension appliquée. Ainsi, grâce à la capacité d'arrêt et de commande de la transmittance, le film peut être utilisé pour une variété de fenêtres et de dispositifs d'affichage.
PCT/KR2002/002205 2002-11-25 2002-11-25 Film de vanne de lumiere pour arreter et commander la transmittance, et procede de fabrication associe WO2004049047A1 (fr)

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PCT/KR2002/002205 WO2004049047A1 (fr) 2002-11-25 2002-11-25 Film de vanne de lumiere pour arreter et commander la transmittance, et procede de fabrication associe
AU2002356457A AU2002356457A1 (en) 2002-11-25 2002-11-25 A light valve for cut-off and controllability of light transmittance and a manufacturing method thereof

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PCT/KR2002/002205 WO2004049047A1 (fr) 2002-11-25 2002-11-25 Film de vanne de lumiere pour arreter et commander la transmittance, et procede de fabrication associe

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WO2006005968A1 (fr) * 2004-07-14 2006-01-19 House-Building Society #887 'paupio Murai' Procede et dispositif permettant de reguler et de controler la transparence et la translucidite d'un vitrage ou d'une toile ciree
CN102902098A (zh) * 2012-09-28 2013-01-30 北京三五九投资有限公司 可调色阶印刷型柔性显示屏
CN109856884A (zh) * 2018-11-19 2019-06-07 浙江精一新材料科技有限公司 一种悬浮粒子可控光阀的制备方法
WO2019205501A1 (fr) * 2018-04-28 2019-10-31 华南师范大学 Fenêtre intelligente à réponse électrique multi-stable et son procédé de préparation

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US5670978A (en) * 1993-12-28 1997-09-23 Shimadzu Corporation Light modulator using an asymetrically-driven ferroelectric liquid crystal thick cell
KR20020033987A (ko) * 2000-10-31 2002-05-08 서경도 팽윤/상분리법을 이용한 고분자-액정 마이크로캡슐의 제조
US6486928B1 (en) * 1998-06-10 2002-11-26 Saint-Gobian Glass France Electrically controllable system having a separate functional component for controlling light transmission that includes at least one transparent layer slowing photo reduction degradation of an active element

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KR960014118B1 (ko) * 1992-01-10 1996-10-14 한국유리공업 주식회사 광편광현탁액이 고분자수지내에 분산된 투과도 가변창용 필름 및 그 제조방법
US5670978A (en) * 1993-12-28 1997-09-23 Shimadzu Corporation Light modulator using an asymetrically-driven ferroelectric liquid crystal thick cell
US6486928B1 (en) * 1998-06-10 2002-11-26 Saint-Gobian Glass France Electrically controllable system having a separate functional component for controlling light transmission that includes at least one transparent layer slowing photo reduction degradation of an active element
KR20020033987A (ko) * 2000-10-31 2002-05-08 서경도 팽윤/상분리법을 이용한 고분자-액정 마이크로캡슐의 제조

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006005968A1 (fr) * 2004-07-14 2006-01-19 House-Building Society #887 'paupio Murai' Procede et dispositif permettant de reguler et de controler la transparence et la translucidite d'un vitrage ou d'une toile ciree
EA011200B1 (ru) * 2004-07-14 2009-02-27 Нодар Майсурадзе Способ и устройство для регулирования светопроницаемости/прозрачности остекления или пленки
US8031277B2 (en) 2004-07-14 2011-10-04 Nodar Maisuradze Method and device for regulation and control of transparence and translucence of glazing or oilcloth
CN102902098A (zh) * 2012-09-28 2013-01-30 北京三五九投资有限公司 可调色阶印刷型柔性显示屏
WO2019205501A1 (fr) * 2018-04-28 2019-10-31 华南师范大学 Fenêtre intelligente à réponse électrique multi-stable et son procédé de préparation
US11067866B2 (en) 2018-04-28 2021-07-20 South China Normal University Multi-stable electroresponsive smart window and preparation method thereof
US11209711B2 (en) 2018-04-28 2021-12-28 South China Normal University Method for preparing multi-stable electroresponsive smart window
CN109856884A (zh) * 2018-11-19 2019-06-07 浙江精一新材料科技有限公司 一种悬浮粒子可控光阀的制备方法

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