MXPA98008231A - Ultraviolet radiation-curable light-modulating film for a light valve, and method of making same - Google Patents

Abstract

Se proporciona en la presente una película apropiada para usarse como una unidad moduladora de luz para una válvula de haz de luz que incluye una matriz polimérica que se ha reticulado mediante radiación ultravioleta. De preferencia, la matriz polimérica es un polímero que comprende grupos funcionales suspendidos que pueden reticularse con radiación ultravioleta en presencia de un fotoiniciador apropiado. La película puede formarse proporcionando una emulsión de la suspensión líquida de la válvula de haz de luz en un polímero y oligómero reticulable mediante luz ultravioleta líquido de preferencia polímero, seguido por una reacción de reticulación.

Description

"FILM OF MODULATION OF CURABLE LIGHT BY ULTRAVIOLET RADIATION, A VALVE OF BEAM OF LIGHT AND THE METHOD TO MANUFACTURE THE SAME" FIELD OF THE INVENTION The present invention relates to light beam valves or optical relays, variable light transmission plastic films for light beam valves and, more particularly, to improvements related to these films which can be cured with ultraviolet radiation, including methods to make them.

BACKGROUND For more than 60 years, light beam valves have been proposed to be used for light modulation. As used herein, the light beam valve comprises a cell formed of two walls that are spaced apart by a small distance, at least one being a transparent wall having the electrode walls therein usually in the form of transparent conductive coatings. . The cell contains an activatable light modulating material that can alter a liquid suspension or a plastic film where the droplets of a liquid suspension are distributed and encapsulated. The liquid suspension (sometimes referred to herein as a liquid light beam valve suspension) comprises small particles suspended in a liquid suspension medium. In the absence of the applied electric field, the particles in the liquid suspension exhibit a random Broian movement and therefore, a beam of light that passes to the cells is reflected, transmitted and absorbed, depending on the structure of the cell, the nature and concentration of the particles and the energy content of the light. When an electric field is applied through the suspension of the light beam valve in the light beam valve, the particles are aligned and during many suspensions most of the light can pass through the cell. Light beam valves have been proposed for many purposes including, e.g. alphanumeric presentation devices, television display devices, windows, sliding sunroofs, anti-sun visors, mirrors, glasses and the like to control the amount of light that passes through them. Light beam valves based on the use of a particle suspension to modulate light are known as "suspended particle devices" or "SPDs". For many applications it is preferred that the activatable material of a SPD light beam valve be a plastic film instead of a liquid suspension. For example, in a light beam valve used as a variable light transmission window, a plastic film in which droplets of the liquid suspension are distributed is preferred to a liquid suspension alone, because the effects of pressure hydrostatic eg, warped, associated with the high column of the liquid suspension can be avoided through the use of a film, and the risk of leakage or possible escape can also be avoided. Also, in a plastic film, the particles are present only within very small droplets, and therefore do not agglomerate significantly when the film is repeatedly activated with a voltage. One type of light beam valve film for an SPD light beam valve using microcapsules of dispersed suspended particles in a solid matrix layer is disclosed in U.S. Patent Number 4,919,521. A second type of SPD light beam valve film fabricated by phase separation of a homogeneous solution is disclosed in US Patent Number 5,409,734. SPD light beam valve films made by crosslinking a crosslinkable film forming material with a chemical crosslinking agent are disclosed in U.S. Patent Nos. 5,463,491 and 5,463,492 assigned to the concessionaire of the present invention. All those patents and other patents cited herein are incorporated herein by reference. There are several advantages of curing an SPD film by ultraviolet radiation instead of using heat to cure it., as disclosed in US Pat. Nos. 5,463,491 and 5,463,492. A heat-cured SPD film begins to cure as soon as the catalyst is added, while a UV curable film will cure only when it is "exposed to ultraviolet radiation. Healing by ultraviolet radiation also prevents prolonged exposure of the film to heat that could damage the film. Finally, healing by ultraviolet radiation can be achieved much more quickly than thermal curing. In the air, ultraviolet radiation healing can often be done in less than a minute, and in an oxygen-free atmosphere in just a few seconds.

COMPENDIUM OF THE INVENTION In one embodiment of the present invention, a film suitable for use as a light modulating unit of a light beam valve is provided, which comprises a matrix of the polymer that has been cross-linked by ultraviolet radiation. In particular, the polymer matrix is preferably a polymer comprising suspended functional groups that can be cross-linked with ultraviolet radiation in the presence of an appropriate photoinitiator. The film can be formed by providing an emulsion of a liquid suspension of the light beam valve in a liquid polymer or oligomer crosslinkable by ultraviolet radiation, or preferably a copolymer followed by a crosslinking reaction. In order to stabilize the emulsion it is preferred that there be either a separate emulsifier or, alternatively, one or more polymeric suspension blocks depending on the matrix polymer can act as an emulsifier, as disclosed in US Pat. No. 5,463,492. The film may comprise a crosslinked polyorganosiloxane polymer matrix, and the suspension of the liquid light beam valve distributed in the matrix of the crosslinked polymer may include in a fluorinated polymeric stabilizer, whereby light scattering or "haze" of The film of the light beam valve is considerably reduced. As used herein, the term "fluorinated" means a partially or fully fluorinated material. Further improvements in turbidity reduction can be obtained by providing the matrix of the polyorganosiloxane polymer crosslinked with aromatic groups or by mixing materials with the polymer matrix comprising aromatic groups, whose materials are miscible with the polymer matrix, but not miscible with the liquid suspension of the light beam valve. Alternatively, the fluorinated materials can be mixed with the liquid suspension of the light beam valve, which matrices are miscible with the liquid suspension of the light beam valve, but not miscible with the matrix of the polymer. The purpose of these actions is to produce the refractive index of the polymer matrix and that of the liquid suspension of the light beam valve equal or almost as equal as possible, whereby the turbidity and scattering of light can be considerably reduced or removed when the light beam valve is in the ON or ON state. As shown in U.S. Patent No. 5,463,492, the liquid suspension of the light beam valve has a liquid suspension means comprising, in whole or in part, a liquid polymeric stabilizer that allows the liquid suspension of the beam valve. of light is charged with a higher concentration of particles. The resultant light beam valve liquid suspension, whether used as such in a light beam valve or incorporated in a film, is stable and provides good contrast between the CONNECT and DISCONNECT states. The present invention also provides a light beam valve comprising a cell having separate cell walls and a film of the invention between the walls of the cell.

BRIEF DESCRIPTION OF THE DRAWINGS Figures IA and IB are schematic views, in section, of a light beam valve of the invention in the DISCONNECTED and CONNECTED states, respectively.

THE LIQUID SUSPENSION OF THE LIGHT BEAM VALVE The liquid suspension of the light beam valve distributed in the matrix of the crosslinked polymer of the film of the present invention can be any liquid suspension of light beam valve known in the art and can be formulated according to known techniques. The term "liquid light beam valve suspension" as used herein means a "liquid suspension medium" wherein a plurality of small particles are dispersed. The "liquid suspension medium" comprises one or more non-aqueous electrically resistive liquids wherein preferably at least one type of polymeric stabilizer is dissolved which acts to reduce the tendency of the particles to agglomerate and to keep them dispersed. As is known, the inorganic and organic particles can be used in a light beam valve suspension, such as mica, metals, graphite, metal halides, polyhalides (which are sometimes referred to in the prior art as perhalides) of salts of alkaloid acid and the like. The particles in the liquid suspension can be light polarizers such as halogen-containing light polarizing materials, e.g. polyhalides of alkaloid acid salts. (The thermal "alkaloid" is used herein to mean an organic nitrogenous base as defined in Hackh's Chemical Dictionary, Fourth Edition, McGraw-Hill Book Company, New York, 1969). If a polyhalide of an alkaloid acid salt is used, the alkaloid residue may be a quinine alkaloid, as defined in the Chemical Dictionary of Hackh, supra. U.S. Patent Nos. 2,178,996 and 2,289,712 relate in detail to the use of polyhalides of quinine alkaloid acid salts. The particles can be light absorbing or light reflecting. Also, the particles may be particles of a hydrogenated polyhalide of a quinine alkaloid acid salt, such as dihydrocinconidine sulfate polyiodide, as described in U.S. Patent No. 4,131,334, or a light polarization metal halide or polyhalide, such as cupric bromide or purpurocobalt chloride sulfate, such as vg in U.S. Patent Number 1,956,867. Preferably, the particles are light polarization polyhalide particles, such as those described in U.S. Patent Nos. 4,877,313 and 5,002,701, which are more environmentally stable than the polyhalides of the prior art. In theory, any type of particle capable of reflecting, absorbing and / or transmitting the desired wavelengths of visible light can be used in the liquid suspension of the light beam valve, as long as the particle can be oriented by an electric field or magnetic. For the purposes of the present invention, however, particles that reflect a considerable amount of visible light can cause objectionable light scattering and therefore, are usually not desirable.

The shape of the particles used in the light beam valve suspension should preferably be "anisometric", ie the shape or structure of the particle such that in one orientation, the particle intercepts more light than in the other orientation. Particles that are needle-shaped, rod-shaped, ribbon-shaped or in the form of thin scales are appropriate. The light polarization crystals are especially useful because they produce a pleasant visual appearance, but any type of light absorbing particle can be used, preferably, exhibiting a very small light scattering. The particles are preferably of colloidal size, ie, the particles have a large dimension with an average of about 1 micron or less. It is preferred that most of the particles have large dimensions less than half the wavelength of the blue light, i.e., 2000 angstrom units or less, to keep the light scattering extremely low. The particles are also preferably light-absorbing, ie the particles absorb a significant portion of preference to most of the light incident on them and relatively little disperses of the light incident on them. The light absorbing particles comprise many types of material including pigments and colored orientable dyes, e.g. a garnet red, conductive black or gray material, such as graphite or carbon black, dichroic dyes such as are widely used in guest-guest liquid crystal devices, light biasing materials, e.g. cupric bromide and polyhalides, and especially polyiodides, e.g. those described together with the light beam valve devices of the prior art. The term "polyiodide" as used herein is used in the conventional sense and also in the same sense as the term "periodide" as used in the numerous light beam valve patents of the prior art e.g. see column 1 of U.S. Patent No. 1,951,664 (Land) entitled "Colloidal Suspensions and the Process of Making Same", to indicate a material that is a reaction product of a parent compound, which may be a sulfate (or certain other salts) as described in U.S. Patent Number 4,270,841) of heterocyclic nitrogen bases with iodine and an iodide. These reaction products are often referred to as polyiodide compounds. This type of particle is discussed in detail in "The Optical Properties and Structure of Polyiodides" by D.A.

Godina and G. P. Faerman published in The Journal of General Chemistry, U.S.S.R. Volume 20, pages 1005-1016 (1950). Herapatira, for example, is quinine bisulfate polyiodide and its formula is given under the heading "quinine iodosulfate" as 4C20H24N2O2.3H2SO4.2HI.I4.6H2O in the Merck index, Tenth Edition (Merck &Co. Inc. Rahway, NJ). In the most modern preferred types of polyiodides, the precursor compound need not be a salt, e.g. see U.S. Patent Nos. 4,877,313 and 5,002,701. In these polyiodide compounds, iodine is believed to form chains and the compounds are more intense light polarizers. The term "polyhalide" is used herein to mean a compound such as polyiodide, but wherein at least some amount of the iodide in the iodide is replaced by another halogen. The liquid light beam valve suspension distributed in the film of the present invention can include any liquid suspension medium proposed above for use in light beam valves for suspending the particles. Generally, the light suspending medium may comprise one or more electrically resistive, chemically inert liquids which both will suspend the particles and dissolve any polymer stabilizer used to reduce the tendency of the particles to agglomerate and therefore, to keep the particles in suspension. Liquid suspension media known in the art are useful herein such as the liquid suspension medium disclosed in US Pat. No. 4,247,175. Generally, one or both of the liquid suspension media or the polymeric stabilizer dissolved therein is selected in order to keep the suspended particles in gravitational equilibrium. A light beam valve suspension useful in the present invention is described in U.S. Patent No. 4,407,464 and is based on the use of the liquid suspension medium of an electrically resistive, chemically inert, low molecular weight fluorocarbon polymer having a low molecular weight. specific gravity at room temperature of at least about 1.5 having at least about 50 percent of its atoms constituted by halogen atoms, at least 60 percent of the halogen atoms being fluorine and the remainder being trialkyltrimellitate, etc. . to provide gravitational equilibrium to the suspended particles and to help disperse the particles in the liquid suspension medium. Other useful materials such as the electrically resistive or miscible organic liquid are disclosed in U.S. Patent Number 4,772,103, and details related to the liquid suspension material can be found in U.S. Patent Number 4,407,565. Other types of suspensions that do not incorporate these halogenated liquids can also be used and can keep the particles in gravitational equilibrium and a sufficient amount of the stabilization polymer is employed therein. As is known, another useful suspension for the light beam valve is based on the use as the liquid medium for suspension of minimally volatile or minimally volatile organic liquids, commonly classified as plasticizers. These "plasticizer" liquid suspension media may comprise one or more chemically inert, relatively nonvolatile, electrically resistive organic liquids (high boiling temperature) which will suspend the particles and dissolve the polymeric stabilizer but not the matrix polymer. For example, when the polymeric stabilizer includes a solid poly (meth) acrylate, useful liquid suspending media include liquid plasticizers for the poly (meth) acrylates, such as adipates, benzoates, glycerol triacetate, isophthalates, meltates, oleates, chloroparaffins. , phthalates, sebacatos and similar. The liquid suspension media for other solid polymeric stabilizers can be similarly selected from liquids useful as plasticizers for these polymers. Preferably, trialkyltrimelitates, such as tri-n-propyl, tri-n-butyl, tri-n-pentyl or tri-n-hexyl trimellitate and / or dialkyl adipates, for example, di-2- adipate, can be used. ethylhexyl, as the liquid suspension medium for solid polymeric stabilizers based on copolymers such as neopentyl (meth) acrylate copolymers. The polymeric stabilizer when employed can be of a single type of solid polymer that binds to the surface of the particles but that also dissolves in the non-aqueous liquid or liquids of the liquid suspension medium. Alternatively, there may be two or more solid polymeric stabilizers that serve as the polymeric stabilizer system. For example, the particles can be coated with a first type of solid polymeric stability such as nitrocellulose, which in fact provides a single surface coating for the particles and one or more additional types of solid polymeric stabilizer that binds or associates with the first type of solid polymeric stabilizer and also dissolves in the liquid suspension medium to provide dispersion and stearic protection for the particles.

Preferably, to maintain the particles in suspension, the liquid suspension medium may also comprise, the solid polymeric stabilizer, a block polymer of type A-B, as disclosed in US Patent Number 5,279,773. Nitrocellulose stabilizers and / or other solid polymeric stabilizers can also be provided in the liquid suspension medium in addition to the block polymer. It is preferred to use just enough block polymer A-B to keep the particles in suspension, the amount to be used being determined empirically for a suspension of the light beam valve determined as is known. Usually, the amount of the solid polymer stabilizer will be from about 1 percent to about 30 percent such as from 5 percent to about 25 percent by weight based on the total weight of the liquid suspension of the light beam valve. However, even when the use of a solid polymer stabilizer is preferred, it does not need to be used in all cases. Of course, liquid polymeric stabilizers can be used advantageously as will be described in detail below.

LIQUID POLYMERIC STABILIZERS Polymeric stabilizers previously used in a liquid suspension of the light beam valve have generally been glassy solids. A concentrate of a liquid suspension of the light beam valve made using a solid vitreous polymer as the polymeric stabilizer must also use a liquid suspension medium including a solvent, as described above, to allow the concentrate to be concentrated. process in a usable film, but the solvent imposes limitations on the amount of particles that can be included in the concentrate. However, when the polymeric stabilizer is a liquid polymer, as described in US Patent Number 5,463,492, the polymeric liquid stabilizer may provide part or preferably all of the liquid suspension medium and therefore, the concentrate may contain a much higher percentage of particles, which in turn allows the production of a thinner film, darker than otherwise. Also, when the matrix polymer and the polymeric stabilizer have been modified by the substitution of phenyl and fluorine, respectively, it would be very difficult to find a solvent that would dissolve one without dissolving the other. A further problem encountered with the use of a solvent for a solid polymeric stabilizer is that if the refractive index of the solvent is much higher than that of the matrix polymer and the solid polymeric stabilizer, the amount of turbidity in the film can increase. These problems are avoided by the use of a liquid polymer stabilizer. The polymeric liquid stabilizer is prepared in a conventional manner using a monomer or monomers that will provide the polymeric stabilizer with a low enough glass transition temperature so that the polymeric stabilizer is liquid within the operating temperature range of the valve. beam of light. For example, the proper selection of the alkyl groups suspended with respect to the number of carbon atoms as well as the presence or absence of branching as shown in the art allows the production of a polymer with a state transition temperature. vitreous default (which can be as low as -70 ° C). A low vitreous state transition temperature is desirable because the light beam valve in which the film is incorporated will only be capable of providing variable light transmission above the glass transition temperature of the liquid suspension medium. in the droplets. The molecular weight of the polymer will determine the viscosity of the polymeric stabilizer, the higher the molecular weight the higher the viscosity as it is known. An appropriate scale of molecular weight for the polymeric liquid stabilizer is from about Mw 1000 to about Mw 2 million. The monomers for the polymeric liquid stabilizer will be selected as described above so that the resulting polymeric liquid stabilizer will not dissolve the matrix polymer., but will bind to the surface of the particles and be miscible with any of the other liquids comprising the liquid suspension medium. When the particles are coated with nitrocellulose, the polymeric liquid stabilizer preferably includes a small percentage of functional groups that allow the polymeric stabilizer to be associated with the nitrocellulose, such as the groups derived from an unsaturated organic acid, ester or a ring thereof. , such as maleic acid anhydride, or other suitable functional groups such as methylol acrylamide, 2-hydroxyethyl (meth) acrylate, etc. Useful polymeric liquid stabilizers include polymerized units of alkyl (meth) acrylates, such as n-butyl acrylate and / or fluorinated alkyl (meth) acrylates, such as heptafluorobutylacrylate and the like, usually with a small percentage of an unsaturated acid, ester or ring thereof, methylol acrylamide, 2-hydroxyethyl (meth) acrylate or the like. Since the molecular weight of the polymeric liquid stabilizer can be controlled, its viscosity can be adjusted to produce a suspension of the light beam valve consisting only of a liquid polymeric stabilizer of lower viscosity and the particles, the liquid suspension medium separated and Polymeric stabilizers are not needed. This light beam valve suspension can then be encapsulated in a matrix polymer whose refractive index is matched to that of the polymeric liquid stabilizer to form a film with low haze. This is ideal for those cases where it is desirable to produce the film between glass rigid or flexible rigid plastic coated substrates without further processing (a sandwich cell). This would be particularly useful in those cases where a rapid decomposition time is not required, for example, architectural glazing.

MANUFACTURE OF THE FILM In accordance with the present invention, a film useful as a light modulating agent of the light beam valve can be prepared by forming an emulsion of the liquid suspension of the light beam valve in a liquid polymer or oligomer crosslinkable by radiation ultraviolet. As disclosed in U.S. Patent No. 5,463,492, the polymer matrix can be an emulsifier of liquid crosslinkable copolymers. The emulsifier of the crosslinkable copolymer serves the double function of providing the crosslinked matrix polymer and an emulsifier. The crosslinkable copolymer has a main chain that preferably includes terminates by crosslinkable groups at each end, the main chain being insoluble in the liquid suspension of the light beam valve. The emulsifier of the crosslinkable copolymer also has polymeric groups suspended depending on the main chain, the polymeric groups being soluble in a liquid suspension of the light beam valve. Alternatively, a separate emulsifier can be used. The polymer or oligomer crosslinkable by ultraviolet radiation, has a main chain comprising groups crosslinkable by ultraviolet radiation suspended from the main chain and / or at each end, the main chain being insoluble in the liquid suspension of the light beam valve. Any photoinitiator and any photosensitizer required to form the polymer matrix is included in the emulsion. The film of the invention can be prepared by mixing together the crosslinkable liquid polymer or oligomer with ultraviolet ratio, a photoinitiator, an emulsifier (if separated from the ultraviolet radiation crosslinkable copolymer) and a liquid suspension of light beam valve, to form an emulsion from a multitude of droplets of the liquid suspension of the light beam valve in the liquid copolymer crosslinkable by ultraviolet radiation. The emulsion can then be molded with a film and cured by irradiating with ultraviolet radiation thereby yielding a film containing encapsulated droplets of the liquid suspension of the light beam valve. The liquid oligomer polymer or crosslinkable by ultraviolet light and the liquid suspension of light beam valve are selected so that the components of one will not adversely affect the other. In addition, the by-products of the crosslinking reaction, if any, and the crosslinking conditions e.g. temperature, pressure, etc. they must also be compatible with and not detrimentally affect any material involved in the reaction, e.g. the polymer or oligomer crosslinkable by ultraviolet radiation, the emulsifier, the crosslinked polymer matrix and / or the light beam valve suspension. For example, if the particles are sensitive to heat, the crosslinking reaction should be carried out at a temperature at which the particles are stable. If the particles are detrimentally affected by water, the byproducts of the crosslinking reaction should not be aqueous. If the articulation with ultraviolet radiation is delayed by the presence of oxygen, as is often the case, the crosslinking reaction can be carried out in an atmosphere that does not contain oxygen, such as nitrogen or argon or in a vacuum. The main chain of the polymer crosslinkable by liquid ultraviolet irradiation can be or comprise a polyorganosiloxane, polybutadiene, polystyrene, poly (cyclopropene), polyamide, polyolefin, silicone rubber, polyacrylamide or polyurethane and the like. The liquid polymer or oligomer that is crosslinkable by ultraviolet radiation will inherently have functional groups that allow it to be crosslinked by ultraviolet radiation, such as acrylate, methacrylate or epoxide groups, may comprise a polymer chain that has been modified to include these functional groups. The polymer or oligomer crosslinkable by ultraviolet radiation must have a crosslinkable functionality in greater than two, as is known and can comprise a large number of crosslinkable groups, as long as the solubility requirements previously set forth herein have been met. These crosslinkable functional groups can be placed not only at or near the ends of the main chain, but also along the main chain and can be substituted either directly to the main chain or in groups suspended from the main chain. Suitable photoinitiators that will cause ultraviolet radiation to crosslink the functional groups crosslinkable by ultraviolet radiation are known such as benzoin isobutyl ether and the like. The crosslinking reaction can also be a condensation between the polyfunctional monomers that give rise to a crosslinked polymer. The crosslinkable liquid polymer or oligomer can be prepared by conventional copolymerization techniques. For example, a prepolymer (I) with functional groups, Y, such as (I) Y- | m-Y can be linked in a second prepolymer (II) having functional groups, X and B, such as (II) XLX I in order to form a liquid crosslinkable copolymer (II) having a main chain terminated by groups which may comprise an unsaturated polymerizable double bond curable by ultraviolet radiation or which are crosslinkable and which have polymeric or non-polymeric suspended groups curable by ultraviolet radiation such as [B] In the previous illustration, m, n and p are integers, A is the residue of a polymer that is insoluble in the liquid suspension of the light beam valve, L is a linking group and B is a functional group crosslinkable by suspended ultraviolet radiation or a chain that has this group substituted in it. It is possible that the main chain has suspended polymeric emulsifying groups and groups or chains crosslinkable by suspended ultraviolet radiation where these groups are substituted. Alternatively, the -sc & ^ ... r -. ^^ ss .. »- copolymerization of two or more monomers can be carried out, however, at least one of these monomers must comprise a functional group curable by ultraviolet radiation. It is currently preferred to use a polyorganosiloxane as the main chain of the crosslinkable polymer or oligomer. The polyorganosiloxanes comprise repeating units of silicon atoms bonded to the oxygen atoms, wherein the silicon atoms are substituted by one or usually two organic groups which may be substituted or unsubstituted and, of course, also comprise crosslinkable functional groups. Useful organic groups which may or may not have substituted crosslinkable functional groups therein include aliphatic, cycloaliphatic, aromatic, heterocyclic, aromatic, aliphatic and the like, this organic group is preferably aliphatic or saturated aromatic and more preferably is alkyl, aryl , aralkyl or alkaryl. Useful groups comprising crosslinkable functional groups include an acryloxyalkyl, methacryloxyalkyl and epoxy and other groups, preferably acryloxypropyl, methacryloxy, propyl, maleate, vinyl ether and epoxy groups. The difunctional vinyl ether or acrylate monomer can be mixed in the formulation in order to accelerate the curing process as well as to generate networks of the interpenetrating polymer. The polyorganosiloxane backbone can be a homo-polymer such as polymer of the Ri unit R2 or a copolymer such as wherein Ri, R2, R3 and R4 are identical or different organic groups at least one of which can be crosslinked with ultraviolet radiation, Ar is an aromatic group and wherein n and m are integers. A cross-linked polymer matrix derived from a polyorganosiloxane is preferred for use in the present invention due to many reasons. The crosslinked polyorganosiloxanes have excellent oxidation and ultraviolet radiation stability and are stable over a wide temperature range. Due to the wide availability of polyorganosiloxanes and the ease with which they can be crosslinked in the absence of harmful byproducts from the crosslinking reaction, these polymers are relatively inexpensive to manufacture and use. In addition, a crosslinked polyorganosiloxane polymer or oligomer can be used with a wide scale of liquid particles and polymeric stabilizers used in the suspensions of the light gas valve. Equally important, the matrix of the crosslinked polyorganosiloxane polymer provides the film with high dielectric strength which allows the use of large voltages through the light beam valve cell without arc formation, methacryloxy or epoxy groups and similar. In the presently preferred novelty of the invention, the suspended groups are or comprise the acryloxypropyl group. The properties of the crosslinkable functional groups by ultraviolet radiation are selected to ensure that the crosslinkable polymer or oligomer remains insoluble in the liquid suspension of the light beam valve so that the desired emulsion can be formed. For example, for a polyorganosiloxane crosslinkable by ultraviolet radiation, it is currently preferred that the crosslinkable groups by ultraviolet radiation are not more than about 20 mole percent of the matrix polymer, likewise, the aromatic content of a polyorganosiloxane crosslinkable by ultraviolet radiation is selected to ensure that the polymer or oligomer crosslinkable by ultraviolet radiation is insoluble in the liquid suspension of the light beam valve. For example, for a polyorganosiloxane crosslinkable by ultraviolet radiation, it is currently preferred that the aromatic groups constitute no more than about 30 weight percent of the matrix polymer. It is also known in the art that vinyl ether monomers and oligomers are additives and brighteners useful in photocurable cationic systems containing, for example, epoxide functionalities. For example, see U.S. Patent Number 5,650,453. If used in the present invention, a reactive vinyl ether monomer or oligomer can be independently crosslinkable due to the presence of the vinyl ether groups present in the monomer. The incorporation of these materials in the present invention, after curing will result in two interpenetrating polymerizable polymer networks that may or may not crosslink one into the other at certain points. While it is preferred to cure the matrix polymers of the present invention by exposing the uncured film to ultraviolet radiation, it is already known in the art that these ultraviolet radiation curable polymers and films can also be cured using electronic beam curing methods. A suitable process for preparing a crosslinkable liquid copolymer curable by ultraviolet radiation having a polyorganosiloxane backbone and suspended (meth) acryloxypropyl groups is a condensation copolymerization of hexamethylcyclotrisiloxane and 3-acryloxy-propylmethyldimethoxysilane. Suitably, the polyorganosilane residue of the liquid crosslinkable copolymer curable by ultraviolet radiation can have a molecular weight of from about Mw 17,000 to about Mw 3 million, preferably from about Mw 30,000 to about Mw 450,000. Furthermore, it is proposed here that the polyorganosiloxane backbone constitutes more than about 50 percent, preferably more than about 80 percent by weight of the emulsifier of the crosslinkable copolymer.

The polymer or oligomer crosslinked by ultraviolet radiation can be used to form a film with the aid of a separate emulsifier. The emulsifier ensures that each droplet of the light beam valve suspension will be surrounded by the polyorganosiloxane matrix polymer, thereby preventing shifting of the suspension of the light beam valve from the imperfectly enclosed droplets. The emulsionantre also prevents the coalescence of the droplets which allows the production of smaller capsules and a smaller size distribution of the capsules. Alternatively, polymeric groups, either polymerized through the polymerizable end groups polymerizable in the parent chain of the matrix, or suspended from the main chain, can serve as emulsifiers.

REDUCTION OF TURBIDITY IN THE FILM The light beam valves of the prior art described in many of the aforementioned patents e.g. US Patent No. 4,407,565 which uses light absorbing particles, exhibits excellent optical clarity and very low light scattering even when the Refractive index not of the liquid suspension medium of its liquid suspensions of light beam valve is much lower than the refractive index of the electrode material. For example, the refractive index of a commonly used electrode material, indium-tin oxide, is approximately 2: 0 at room temperature (although it may be somewhat higher or lower depending on the thickness of the layer) where the Index of refraction, nn for the liquid suspension medium will be within the range of 1.33 to 1.68 and usually falls within the range of approximately 1.38 to 1.56 at room temperature. Also, the non-liquid suspension medium can be considerably smaller or larger than that of the glass sheets usually used in the walls of the light beam valve. The refractive index of the glass varies according to the composition of the glass, but is commonly about 1.52 at room temperature. Even when a certain amount of light is lost in a light-beam valve by absorption or by reflection of the electrodes and walls, no scattering of objectionable light is normally caused by them despite the fact that their refractive indices usually differ. considerably from that of the liquid suspension medium. Therefore, the refractive indices of the electrode walls of the light beam valve can be ignored.

As is known from US Patent Number 4,563,492, the turbidity or light scattering of a film comprising a crosslinked polymer matrix having a liquid suspension of light beam valve incorporated therein, can be reduced by modifying the polymer matrix and / or the liquid portion of the liquid suspension of the light beam valve containing or being a polymeric stabilizer so that its refractive indices are more closely matched. In the preferred system of the present invention employing ultraviolet-cured polyorganosiloxane as the cross-linked polymer matrix, this can be achieved by using a liquid fluorinated polymer stabilizer in the liquid light beam valve suspension to lower the refractive index of the stabilizer. polymeric Alternatively, an improvement is possible if the polyorganosiloxane cured by ultraviolet radiation contains aromatic groups to raise the refractive index of the polymer matrix or if the polymeric or non-polymeric compound comprising aromatic groups is mixed with the polymer of the matrix and is miscible with the same but immiscible with the liquid suspension, or if a polymeric or non-polymeric fluorinated compound is mixed with the liquid suspension and is miscible with it but immiscible with the polymer matrix, or if any combination of the media is used described in this paragraph.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figure IA, a light beam 31 impinges on a film 27 of the present invention. The film 27 comprises a film 24 containing droplets 26, with the electrodes 28 in contact with the film 24. The protective layers 29 are in contact with each electrode 28. It is assumed that there is no potential difference, ie electric field between the electrodes 28. Therefore, particles 33 dispersed within microdroplets 26 of the liquid suspension, remain in random positions due to Brownian movement. Because the particles absorb light, a light beam 31 incident on the film is absorbed by the particles 33 within the microdroplets 26. FIG. IB assumes that there is an electric field (not shown) between the electrodes 28. As a result , the particles 33 are aligned within the microdroplets 26 and a considerable portion of the light beam 31 passes through the film, as indicated by the arrows 32. The electrodes for use in light beam valves and methods for depositing Electrodes on glass and plastic substrates are well known in the art. For example, see U.S. Patent Nos. 3,512,876 and 3,708,219 which disclose the use of electrodes in light beam valves and see U.S. Patent Nos. 2,628,927, 2,740,732, 3,001,901 and 3,020,376 which disclose articles having conductive coatings and especially coatings. transparent conductors in the glass and plastic substrates and the methods to form or deposit these coatings. Indium tin oxide ("ITO") or any other conductive metal can be used. It is currently preferred that the electrode 28 and the protective layer 29 be in the form of a prefabricated assembly. In this way the electrode 28 and the protective layer 29 can be provided by a film 29 such as a plastic film which has been coated with an electrode 28 before the application of the assembly to the film 24. As used herein, the The term "electrode" will be understood to mean not only electrically conductive metal oxide and other coatings used in the art for this purpose, but also coatings having dielectric overcoats therein, of materials such as a silicon device m. On the other hand, if the light beam valve were to be used as a display device, the electrodes would normally be deposited in patterns on discrete areas of the substrate. The terms "electrode" as used herein also comprise the use of semiconductor films and multiple layers of film, both transparent and colored, such as those used in presentation devices directed to an active matrix. In all cases, where a film of the present invention is used in a light beam valve device, it is assumed that there are appropriate electrical connections leading to an appropriate energy supply to operate the device. Although the usual type of liquid suspension of the light beam valve used in the light beam valve increases in light transmission when a voltage is applied, it should be understood that the present invention also comprises light beam valves, films and liquid suspensions of light beam valves that decrease in transmission of light when a voltage is applied, as disclosed in US Patent Number 4,078,856 or that when activated increases the transmission of radiation in a part of the electromagnetic spectrum and dimisnuye transmission in another part of the spectrum, as disclosed in US Patent Number 3,743,382.

The film of the present invention can itself function as a light beam valve as long as it has electrodes on its surface or protective layers. Nevertheless, if the film itself is going to function as a light beam valve, the electrodes should preferably be on the inner surface of each protective layer facing the inside of the film to prevent scratching and to minimize the voltage required to activate the movie. Also, the outer surfaces of the protective plastic layers can have on them an ultraviolet light absorbing lacquer filter such as the type sold by E.M. Chemicals from Hawthorne, N.Y. Numerous other crystalline surface coatings are commercially available to reduce abrasion and environmental attack especially in plastics. One of these systems is produced by Silicone Products Division of General Electrical Co. from Waterford, N.Y. comprising a hard coating primer material, Hard Coating Resin. A radiation curable crystalline coating that resists abrasion and ultraviolet radiation degradation is sold by The Sherwin Williams Company of Chicago, 111. Under the name of Permaclear UV. The same types of surface coatings may be useful with other embodiments of the present invention, particularly when the film is sandwiched between hard plastic substrates, such as polycarbonate. The present invention is illustrated by the following Examples. All parts and percentages are by weight, unless otherwise stated.

EXAMPLE 1 Preparation of Crosslinkable Siloxane Copolymer by Ultraviolet Radiation Containing Internal Phenyl Groups and Suspended Acryloxypropyl.

A crosslinkable copolymer was prepared by ultraviolet radiation in the following manner: In a 500 milliliter three-necked round bottom flask, equipped with a thermometer, condenser and a Teflon-coated magnetic stirrer, 44.40 grams of hexamethylcyclotrisiloxane, 18.20, were charged. grams of 1,4-bis (hydroxydimethylsilyl) benzene, 11.20 grams of 3-acryloxypropylmethyldimethoxysilane and 100 milliliters of anhydrous ethyl acetate. The combined reagents were heated to 64 ° C with stirring, forming a solution. During the addition of 4 milliliters of concentrated sulfuric acid, the temperature of the solution was raised to 79 ° C. The reaction solution was then refluxed for one and a half hours. The solution was allowed to cool to room temperature before 10 grams of sodium carbonate was added to neutralize the solution. The white solid was filtered and the solvent was removed using a rotary evaporator. The procedure yielded 55.94 grams of a colorless crystalline liquid with a refractive index of 1.4434 at 22.4 ° C and a viscosity of 423 centipoise at 22.9 ° C.

EXAMPLE 2 Preparation of n-Butyl Acrylate Fluorocopolymer A suspension liquid polymer was prepared as follows: to a 500 milliliter three-necked round bottom flask equipped with a thermometer, condenser, magnetic stirrer coated with Teflon and nitrogen blanket, loaded 33.20 grams of n-butyl acrylate, 16.23 grams of 2, 2, 3, 3, 4, 4-heptafluoro butyl acrylate, 1.0 gram of acrylate 2-hydroxyethyl and 8.38 grams of 1-hexanothiol. The mixture was dissolved in 90 milliliters of hexyl acetate. When the solution was heated to 120 ° C, 2.01 grams of t-butylperoxybenzoate dissolved in 20 milliliters of hexyl acetate was added through an addition funnel over a period of 1 minute. The temperature of the reaction solution amounted to 164.5 ° C in one minute. The reaction solution was then allowed to reflux at 168 ° C for one and a half hours. The residual monomers, the chain transfer agent and the solvent were removed using a rotary evaporator. This procedure yielded 57.28 grams of a yellow crystalline liquid with a refractive index of 1.4434 at 22.1 ° C and a viscosity of 147 centipoise at 22.5 ° C.

EXAMPLE 3 An emulsifier was prepared as follows: To a 250 milliliter three-necked round bottom flask, equipped with a condensing thermometer, Teflon-coated magnetic stirrer and nitrogen blanket, 17.71 grams of monometacryloxypropyl-terminated polydimethylsiloxane ( PS560-KG, United Chemicals Technologies, Inc.) and 90 milliliters of ethyl acetate. When the solution was heated to reflux temperature, the solution containing 17. 72 grams of n-butyl acrylate, 0.089 gram of 2,2'-azobisisobutyronitrile and 10 milliliters of ethyl acetate was added over a period of 30 minutes. The reaction solution was refluxed for two additional hours and half an hour after the addition of the initiator, the monomer was complete. The solvent and the residual monomer were removed using a rotary evaporator. This procedure yielded 29.88 grams of a very viscous crystalline colorless liquid with a refractive index of 1.4366 at 22.2 ° C.

EXAMPLE 4 An alternative emulsifier was prepared in two steps: Step (1) Siloxane Copolymer Terminated with Acryloxypropyl Containing Internal Phenyl Groups In a 250 milliliter three-necked round bottom flask equipped with a thermometer, condenser, Teflon-coated magnetic stirrer, 22.2 grams of hexamethylcyclotrisiloxane were charged, 9.1 grams of 1,4-bis (hydroxydimethylsilyl) benzene, 1.8 grams of 3-acryloxypropyl dimethylmethoxysilane and 50 milliliters of anhydrous ethyl acetate. The combined reagents were heated to 65 ° C with agitation forming a solution, after 2 milliliters of the concentrated sulfuric acid was added, the reaction solution is refluxed for one and a half hours. The solution is allowed to cool to room temperature before 5 grams of sodium carbonate is added to neutralize the solution. The white solid is filtered and the solvent is removed using a rotary evaporator. (2) n-Butyl acrylate siloxane copolymer: to a round bottom flask with a capacity of 250 milliliters of three necks, equipped with a thermometer, condenser, Teflon-coated magnetic stirrer and a blanket of nitrogen, 17.7 grams were charged of a siloxane copolymer terminated with acryloxyproyl (a product of step (1)) and 90 milliliters of ethyl acetate. When the solution was heated to reflux temperature, the solution containing 17.7 grams of n-butyl acrylate, 0.09 gram of 2,2'-azobisisobutyronitrile and 10 milliliters of ethyl acetate was added over a period of 30 minutes. The reaction solution was then refluxed for an additional two and a half hours after the addition of the initiator and the monomer was complete. The solvent and the residual monomer are removed using a rotary evaporator.

EXAMPLE 5 A crosslinkable emulsifier was prepared in the following manner: In a 100 milliliter three-necked round bottom flask, equipped with a thermometer, condenser, Teflon-coated magnetic stirrer and nitrogen blanket, 0.03 gram of liquid was charged. -acyloxypropyltrimethoxysilane, 0.45 gram of n-butyl acrylate, 0.23 gram of 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 0.02 gram of 2,2N-azobisisobutyronitrile and 20 milliliters of anhydrous ethyl acetate. The solution was heated to reflux at 78 ° C. After the reaction solution had been refluxed for four and a half hours, a solution containing 4.01 grams of the crosslinkable copolymer of Example 1, 0.03 gram of dibutyltin dilaurate and 20 milliliters of anhydrous ethyl acetate was added. The residual monomers and the solvent were removed using a rotary evaporator. This procedure yielded 3.94 grams of a colorless, near-crystalline liquid with a refractive index of 1.4451 to 21.7 ° C.

EXAMPLE 6 A film was prepared as follows: in a 28 gram capacity bottle, 2.00 grams of the ultraviolet radiation curable matrix polymer of Example 1, 1.60 grams of suspension polymer of Example 2, 0.31 gram of a concentrate consisting of 25 weight percent calcium pyroxy-2, 5-dicarboxylic acid polyiodide crystals with trace amount of SS-type microcellulose of 1/4 sec, and 75 mole percent of a random copolymer of 78.2% one hundred mole of n-butyl acrylate / 19.2 mole percent of 2,2,3,3,4,4,4-heptafluorobutyl acrylate / 2.6 mole percent of 2-hydroxyethyl acrylate, 0.39 gram of the emulsifier of Example 3 and 0.06 gram of benzoin isobutyl ether. The mixture was manually homogenized for more than 4 minutes. The mixture was spread in a thickness layer of .0762 millimeter on a piece of glass coated with ITO. The film was then degassed and intercalated by a second piece of glass coated with ITO in a vacuum. The film was exposed in an ultraviolet radiation lamp (Healing Zone, 80 mw / square centimeter, at 365 nanometers, ADAC Technologies, Inc. .), for 30 seconds. The transmission of the disconnection state of the cell formed in this way was 31.77 percent and the transmission of the connected state (50 V, 400 Hz) was 65.20 percent. The turbidity of the DISCONNECT status of the cell was 27.5 percent, and the turbidity of the CONNECT status was 14.7 percent.

EXAMPLE 7 A film was prearranged as follows: to a 28 gram capacity bottle was added 1.00 gram of the crosslinkable emulsifier of Example 5, 0.80 gram of the suspension polymer of Example 2, 0.18 gram of a concentrate consisting of 25 percent of weight of crystals of the pyrazine-2,5-dicarboxylic acid calcium polyiodide with a trace amount of 1/4 sec. of SS-type nitrocellulose and 75 mole percent of a random copolymer of 78.2 mole percent n-butyl acrylate / 19.2 mole percent 2, 2, 3, 3, 4, 4, 4-hepfluorobutyl / 2.6 acrylate mole percent of 2-hydroxyethyl acrylate, and 0.03 gram of benzoin isobutyl ether. The mixture was manually homogenized for more than 4 minutes. The mixture was dispersed in a layer of a thickness of 0.762 millimeter in a piece of glass coated with ITO.1 The film was exposed to an ultraviolet radiation lamp (Healing Zone, 80 mw / square centimeter at 365 nanometers, ADAC, Technologies, Inc.) for 50 seconds. 1 The film was then degassed and intercalated by a second piece of glass coated with ITO in a vacuum.

The transmission of the DISCONNECT status of the cell formed in this manner was 20.93 percent, whose transmission of the CONNECT status (50 V, 400 HZ) was 62.71 percent. The turbidity of the DISCONNECT status of the cell was 31.0 percent and the turbidity of the CONNECT status was 7.3 percent.

Claims (14)

R E I V I N D I C A C I O N E S:

1. A method for preparing a film suitable for use as a light modulating unit of a light beam valve SPD, comprising a crosslinked polymer matrix having droplets of a liquid suspension of light beam valve distributed in the matrix of crosslinked polymer, the suspension of the light beam valve comprises particles suspended in a liquid suspension medium; which comprises mixing a liquid oligomer or polymer crosslinkable by ultraviolet radiation and a liquid suspension of light beam valve, emulsifying the resulting mixture to form an emulsion of the liquid suspension of light beam valve in the oligomer or polymer or liquid crosslinkable by ultraviolet radiation, and crosslink the oligomer or liquid polymer crosslinkable by ultraviolet radiation while the mixture is in the form of a thin layer of the emulsion exposing the thin layer of the emulsion for ultraviolet radiation or to an electronic beam, the oligomer or polymer of the particles being free from detrimental effects with respect to each other.

2. The method according to claim 1, wherein the emulsion contains an emulsifier.

3. The method according to claim 1, wherein the crosslinkable liquid oligomer or polymer has a backbone which is insoluble in the liquid suspension medium and suspended polymeric groups which are soluble in the liquid suspension medium, whereby the oligomer or polymer works as an emulsifier.

4. The method according to claim 3, wherein the main chain comprises a polyorganosiloxane.

5. The method according to claim 4, wherein the suspended polymer groups are polyacrylates and / or polymethacrylates.

6. The method according to claim 4, wherein the polyorganosiloxane contains internal aromatic groups. The method according to claim 1, wherein the emulsion includes a photoinitiator to initiate crosslinking. The method according to claim 1, wherein the liquid oligomer or polymer crosslinkable by ultraviolet radiation includes acrylate or methacrylate or epoxy groups. The method according to claim 1, wherein the polymer or oligomer crosslinkable by liquid ultraviolet radiation is a polyorganosiloxane, polybutadiene, polystyrene, poly (cyclopropene), polyolefin of polilamide, silicone rubber, polyacrylamide or polyurethane. A method for preparing a film suitable for use as a light modulation unit as a SPD light beam valve, comprising a crosslinked polyorganosiloxane polymer matrix having droplets of a liquid suspension of the light beam valve and distributed in the matrix of the crosslinked polyorganosiloxane polymer, the light beam valve suspension comprises particles suspended in a liquid suspension medium; which comprises mixing an oligomer or polymer polyorganosiloxane liquid or crosslinkable by ultraviolet radiation in the liquid suspension of the light beam valve, emulsifying the resulting mixture to form an emulsion of the liquid suspension of light beam valve in the oligomer or polymer of liquid polyorganosiloxane crosslinkable by ultraviolet radiation and crosslink the oligomer or polymer of liquid polyorganosiloxane crosslinkable by ultraviolet radiation while the mixture is in the form of a thin layer of the emulsion to ultraviolet radiation or electron beam. The method according to claim 10, wherein the polymer or oligomer of polyorganosiloxane crosslinkable by liquid ultraviolet radiation has suspended (meth) acryloxypropyl groups or acryloxypropyl groups. 12. The method according to claim 10, wherein the polyorganosiloxane contains internal phenyl groups. The method according to claim 10, wherein the emulsion contains a liquid polymeric stabilizer to prevent agglomeration of the particles. 14. The method according to claim 13, wherein the liquid polymeric stabilizer is fluorinated.