KR100287520B1 - Low emissivity coated light valves used as electrodes - Google Patents

Abstract

The light valves have opposing spaced cell walls, each of which carries an electrode for applying an electric field to the light valve and makes one or more electrodes of low-emissivity electroconductive material.

Description

Low emissivity-coated light valves used as electrodes

The present invention relates to a light valve, in particular a light valve having an electrode made of a low-emissivity, electrically conductive material.

Light valves have been used for more than 58 years for light control. The light valve is a cell composed of two walls separated by a small distance, at least one wall of which is transparent and both walls have electrodes in the form of a transparent electroconductive coating. There is a "light valve suspension" between the battery walls, which is a liquid in which a plurality of solid particles are suspended (U.S. Patent 4,407,565). Alternatively, the light valve suspension may be present in the form of a film in which the light valve suspension droplets are distributed in the film, and the suspension is composed of a plurality of small particles suspended in a liquid suspension medium (U.S. Patent 4,919,521). In this case the film is located between the opposing cell walls.

Without applying an electric field, the particles in the light valve suspension undergo Brownian motion, so the light that passes through the cell is reflected, transmitted or absorbed depending on the nature and concentration of the particles and the energy content of the light. When the electric field is applied through the light valve suspension in the light valve, the particles are aligned so that for many suspensions most of the light can pass through the cell.

Light valves are used to control light passing through alphanumeric displays, TV displays, windows, mirrors, filters, ski glasses and glasses.

The light valve suspension of the present invention consists of a liquid suspension medium in which a plurality of particles are dispersed. As is known, inorganic and organic particles such as mica, metals, graphite, metal halides, polyhalides of alkaloids (known in the literature as perhalides) and the like are used in the light valve suspension. Particles in liquid suspensions, such as halogen-containing polarizing materials, such as polyhalides of alkaloids, are polarizable (“alkaloids”; organonitride groups. Hackh's Chemical Dictionary Fourth Edition, McGraw-Hill Book Company.New York, 1969). In the case of using a polyhalide of an alkaloid salt, the alkaloid component may be quinine alkaloid (Hackh's Chemical Dictionary, supra). US Pat. Nos. 2,178,996 and 2,289,712 describe the use of polyhalides of quinine alkaloidates in detail. These particles are either absorbing or light-reflective.

The particles can also be polarized, for example, hydrogenated polyhalides of quinine alkaloids such as dihydrocinconidine sulfate polyiodide (US 4,131,334) or polarizing agents such as copper bromide or furfurocobalt chloride sulfate polyiodide (US 1,959,867). It may be metal halide or polyhalide particles. Particularly preferred are planar polyhalide particles which are more stable than known polyhalides (US Pat. No. 4,877,313, 5,003,701).

In theory, any particle capable of reflecting, absorbing or transmitting visible wavelengths can be used in the light valve suspension. The shape of the particles used in the light valve suspension should be "anisotropic". Particle structure or shape is that particles in one direction block more light than in the other. Particles such as needles, rods, laths or thin flakes are suitable.

Preferred are particle sized particles having an average dimension of less than 1 micron. Most particles have a size less than ½ of the blue light wavelength, for example, up to 2000 Hz, which can greatly reduce light scattering.

Light scattering and light absorbing particles oriented in an electric or magnetic field are usable. However, particles which absorb incident visible light are preferred because they show little light scattering. Polarizing particles are particularly preferred because they produce a good appearance.

Light absorbing particles include colored orientable pigments and dyes such as garnet red, conductive black or gray materials such as graphite or carbon black, dichromates, copper bromide and polyhalogens which are widely used in guest-host liquid crystal devices. Cargoes, especially polariodes such as polyiodes.

Here, ";polyiodide"; is conventionally used and has the same meaning in many documents as ";iodide"; a precursor compound that may be a sulfate of a heterocyclic nitrogen base (or published in US Pat. No. 4,270,841). Other salts) and reaction products of iodine and iodine ions. Such reaction products are called polyiodine compounds. Such particles are known ("; The Optical Properties and Structure of Polyiodides"; by DA Godina and GP Faerman published in The Journal of General Chemistry, USSR Vol. 20, pp. 1005-1016 (1950)). For example, hepatite is a quinine bisulfate polyiodide, whose structure is referred to as 4C ₂₀ H ₂₄ 0 ₂ SO ₄ · 3H ₂ SO ₄ · 2SHI · I ₄ · 6H ₂ O under the heading “; Merck & Co., Inc., Rahway, NJ. In more recent polyiodes, the linear compounds do not necessarily need to be salts (US Patent Nos. 4,877,313 and 5,002,701). In such a polyiodide compound, iodine forms a chain, so that the compound becomes a strong polarizing material. “; Polyhalide”; is used to mean a compound such as polyiodide, but iodine in the iodine compound may be replaced with another halogen element.

The light valve suspension of the present invention comprises a liquid suspension medium proposed for use in light valves for particle suspension. Generally, the liquid suspension medium consists of one or more electrically conductive, chemically inert liquids which dissolve a polymer stabilizer that suspends the particles and reduces the agglomeration tendency of the particles to keep the particles suspended. Known liquid suspending media can be used (U.S. Patent 4,247,175). In general, one or two of the liquid suspending media or polymer stabilizers dissolved therein are selected to maintain suspended particles in gravity equilibrium.

The light valve suspension of the present invention is known (US Patent 4,407,565) and based on its use as an electrically resistive liquid suspending medium, wherein the polymer has a specific gravity at room temperature of at least 1.5, at least 50% of valence halogen atoms and at least 60% of halogen atoms. Fluorine and the remainder are chlorine or bromine. Other suspensions that do not contain halogenated liquids may also be used, and the use of sufficient stabilizing polymers may maintain the particles in gravity equilibrium.

Polymer stabilizers are a single type of solid polymer that binds to the surface of the particles and also dissolves in the non-aqueous liquid of the liquid suspension medium. Alternatively, there are two or more solid polymer stabilizers that serve as polymer safety systems. One or more additional solid polymer stabilizations that are combined or combined with, for example, a first solid polymer stabilizer such as nitrocellulose that provides surface coatings to the particles and a first solid polymer stabilizer and are dissolved in a liquid suspension medium to provide dispersibility and steric protection to the particles. Zero particles can be coated.

Preferably the medium may contain an A-B type block polymer (European Patent 350,354) as a solid polymer stabilizer in order to keep the particles in suspension. Nitrocellulose or other solid polymer stabilizer can be added to the block polymer and fed to the medium. It is preferable to use an A-B block polymer in an amount sufficient to keep the particles suspended and the amount to be used for a given light valve suspension is determined experimentally. Generally the amount of solid polymer stabilizer is 1 to 30%, in particular 50 to 25%, based on the total weight of the suspension. However, although the use of a solid polymer stabilizer is preferred, it does not need to be used in all cases.

The publication (Joseph A. Check. III, Serial Nos. 972, 826 and 972, 830. both filed November 6, 1992) describes a recently preferred liquid and film type light valve suspension.

The light valve cell wall has an electrode. In some cases, for example mirrors or reflective displays, the electrode comprising the light valve back wall or deposited on the inner back wall is an opaque, reflective metal film. In a light valve to be used as a window, filter or glasses, the electrode contains a transparent electrically conductive coating and is deposited on the inside of both the front and rear cell walls of the light valve. Such a transparent electrode may include a transparent or translucent metal film such as gold or platinum, or may include a film made of a metal oxide, that is, tin oxide or indium tin oxide or other transparent electrically conductive material.

When the electrode is in direct contact with the light valve suspension, the light valve is called a resistive light valve. However, when the electrode has a non-conductor or dielectric overcoat in contact with the liquid light valve suspension, the light valve is referred to as a capacitive light valve. These types of light valves are known.

"Emissivity" of a surface is the ratio of radiation emitted by the surface to radiation emitted by a full blackbody copier at the same temperature. "Low emissivity"; The material reflects most of the incident thermal energy and absorbs and radiates only a small amount of thermal energy. For example, polished silver has an emissivity of about 0.02, which makes it an excellent heat energy reflector.

In some cases, especially in windows, it is important that light valves reflect infrared radiation as well as control the amount of visible light. Therefore, since infrared rays take up most of the heat that enters a building or a car, it can reduce the use of air conditioners in the summer if it can effectively reflect infrared rays. What's more, if the heat in the building is reflected back into the building, the amount of heating in winter can be reduced.

Glass sheets, such as liquid crystal display substrates, used in the flat panel display industry generally have electrodes with indium tin oxide. These electrodes are "circle"; Can only partially reflect infrared light and a small amount of "; Only infrared light can be reflected. They are not low-emissivity electrodes and are therefore not useful for reflecting heat-causing infrared rays ("; far"; infrared is infrared at 2.5 to 300 microns and "; near"; infrared is infrared at 0.7 to 2.5 microns). ).

The modern flat glass industry sells a wide range of so-called low-emissivity or low-E-glass (sometimes called low-E coated glass) and these glasses have a special low emissivity coating on one side. Special coatings consist of a single layer of low emissivity material or a multilayer low emissivity coating. In some cases the purpose of low-E glass is to allow the glass to reflect heat more efficiently than when the glass alone.

As is known, the tin oxide coating can be conductive so that the coating audits the emissivity of the coated glass for far-infrared radiation with a wavelength of 3 microns or more. Low-E glass (Ford Motor Company, Detroit, Michigan) consists of a glass sheet having a fluorine-doped tin oxide layer on one side. U.S. Patent 4,900,634 also discloses a flat glass with a pyrolytic tin oxide coating comprising fluorine and a second dopant. Such low-E glass is useful in the present invention to provide a light valve cell wall having low-emissivity electrodes on the cell wall.

The second known low-E coating is a laminate consisting of a metal layer and an insulator. This multilayer stack provides a low E-coating capable of reflecting significant amounts of near infrared (U.S. Patents 2,519,722, 3,885,855, 4,799,745 and 5,183,700). Such low-E coatings are usually made of transparent metals, metal alloys or metal oxides such as silver, silver-gold alloys, copper, zinc sulfide, zinc oxide, tin oxide, tantalum oxide, etc., and n-layers of titanium dioxide, silicon dioxide, Multilayer laminates with n + 1 or n + 2 layers of transparent insulators such as magnesium and thorium fluoride are used. Three-layer low-E laminates of insulator-metal-insulators are useful, but at present, five-layer low-E laminates of insulator-metal-insulator-metal-insulators are preferred as electrodes of light valves.

Several other low-E coatings are known and are within the scope of the present invention for providing light valve electrodes.

The literature (1992, February, Glass Industry) describes the advantages of low-E glass as follows:

(1) Low-E glass not only reduces heat loss from the interior of the building during the heating season, but also reduces the inward movement of heat by reflecting some of the infrared heat to the infrared heat source during the cooling season,

(2) Metal oxides in low-E coatings can reflect 70% or more of long-wave infrared heat towards the heat source, but uncoated glass can only reflect 16% of long-wave infrared radiation:

(3) Efficient colored glass and low-E glass can reduce the solar heat gain by more than 1/3.

Low-E glass is far superior to infrared glass when compared to single glass or glass coated with tin oxide or indium tin oxide, but low-E glass having a low-emissivity monolayer doped with tin oxide is " one "; Mainly reflects infrared light, but "; Does not reflect infrared light efficiently As mentioned, the multilayer low-E coating of insulator / metal / insulation / metal / insulator is “; root”; It is preferred because it reflects infrared rays. The insertion of two silver layers between three insulating layers is currently commercially available (Cardinal I. G. of Minnetonka, Minnesota).

A list of low-emissivity glass manufacturers is in the publication (1992 Glass Industry Directory Issue, published by Glass Industry, P.O.Box 7636, Riverton, New Jersey).

Glass is a common substrate of low-E coating, but many low-E coatings can be applied on plastic substrates. (U.S. Patent No. 5,183,700 entitled "; Solar Control Properties in Low-Emissivity Coatings";)

The present invention provides a light valve having opposing spaced electron walls, each battery bottle having an electrode for providing an electric field to the light valve and at least one electrode made of a low-emissivity electroconductive material. Currently, cell walls made of low-emissivity electrically conductive materials have more than twice the amount of far-infrared reflectivity compared to cell walls that do not contain this material.

The main advantage of using a low-E coating around one or the light valve electrodes is that they reflect a significant amount of infrared light from the light valve electrode itself.

The second advantage is that low-E coated glass is much cheaper than glass coated with tin oxide or indium tin oxide. This is because low-E coatings are applied to the glass during the glass making process or to large volumes of glass, but the glass coated with tin oxide or indium tin oxide is coated in a relatively expensive batch process. Therefore, the use of low-E coated glass sheets as battery walls of light valves is very economical.

Example 1

Light valves are fabricated using cell walls, which are low-E glass sheets, having a fluorine-doped tin oxide layer as an electrode. The cap between the electrodes is 5 millimeters. A dihydrocinconidating sulfate plioid ("; DCSI";) liquid suspension, prepared according to the known method (U.S. Patent No. 4,131,334), is filled between the electrodes. Applying a 150 volt RMS voltage to the electrode makes the light valve transparent as observed when using a standard light valve electrode.

Example 2

Example 1 is repeated using a liquid suspension of pyrazine 2.5-dicarboxylic acid calcium iodide particles as described in US Pat. No. 5,002,701. Applying a 150 volt effective voltage, the light valve is very transparent, as obtained using standard light valve electrodes.

Example 3-4

Examples 1 and 2 are repeated using a cell wall made of low-E coated glass having a low-E coating of insulator-silver metal-insulator-silver metal-insulator.

Example 5

Example 1 was repeated using a transparent plastic sheet coated with an electrode in the form of fluorine-doped tin oxide on the plastic sheet. The result is the same.

Example 6

Example 1 was repeated using a laminated transparent sheet of plastic and glass coated with an electrode in the form of fluorine-doped tin oxide on one side of the sheet. The result is the same.

Claims (15)

A light valve comprising a pair of opposed and spaced cell walls, a light valve suspension comprising particles suspended in a liquid suspension medium and disposed between the cell walls, and an electrode disposed on the cell wall for applying an electric field to the light valve suspension To At least one of the electrodes comprises a low emissivity electroconductive material in addition to the metal. 2. The light valve of claim 1, wherein all of the electrodes comprise a low-emissivity, electrically conductive material in addition to the metal. 3. The light valve of claim 1 or 2, wherein the metal low emissivity material is a fluorine-doped tin oxide, dielectric-metal-dielectric or dielectric-metal-dielectric-metal-dielectric stack. The light valve of claim 1, wherein the cell wall is made of glass, plastic or glass-plastic laminate. The light valve according to claim 1, wherein the electrode and the battery wall are transparent when in the form of a window. The light valve according to claim 1, wherein the low-emissivity electroconductive material other than the metal can reflect far infrared rays at least twice as compared with the cell wall without the low-emissivity electroconductive material other than the metal. The light valve according to claim 2, wherein the battery wall is made of a glass or plastic laminate. 4. The light valve of claim 3, wherein the cell wall is made of glass, plastic or glass-plastic laminate. The light valve according to claim 2, wherein the electrode and the cell wall are transparent when in the form of a window. 4. The light valve according to claim 3, wherein the electrode and the battery wall are transparent when in the form of a window. The light valve according to claim 4, wherein the electrode and the battery wall are transparent when in the form of a window. 3. The light valve according to claim 2, wherein the low-emissivity electroconductive material other than the metal can reflect far infrared rays at least twice as compared to the cell wall without the low-emissivity electroconductive material other than the metal. 4. The light valve according to claim 3, wherein the low-emissivity electroconductive material other than the metal can reflect far infrared rays at least twice as compared with the cell wall without the low-emissivity electroconductive material other than the metal. 5. The light valve according to claim 4, wherein the low-emissivity electroconductive material other than the metal can reflect far infrared rays at least twice as compared with the cell wall without the low-emissivity electroconductive material other than the metal. 6. The light valve according to claim 5, wherein the low-emissivity electroconductive material other than the metal can reflect far infrared rays at least twice as compared with the cell wall without the low-emissivity electroconductive material other than the metal.