SPD light valve film incorporating new suspending media, and light valve incorporating same

A film suitable for use as a light-modulating unit of a suspended particle device (SPD) light valve, said film comprising a matrix polymer material, which matrix polymer material is cross-linked in forming said film to produce a cross-linked polymer matrix, and having droplets of a liquid light valve suspension comprising a plurality of particles dispersed in a liquid suspending medium distributed within the cross-linked matrix, wherein said liquid suspending medium (a) is substantially immiscible with the matrix polymer material, (b) has a boiling point at atmospheric pressure greater than about 100° C., (c) has an electrical resistivity of at least about 0.8×106 ohms per square, and (d) has an index of refraction at 25° C. which differs from an index of refraction of the matrix polymer at substantially the same temperature by no more than about 0.002, and wherein said suspending medium comprises at least one liquid component selected from the group consisting of methyl pyrrolidinone, ethyl pyrrolidinone, dimethyl malonate, diethyl malonate, dimethyl succinate, di(propylene glycol)methyl ether, dimethyl phthalate, butyl phthalyl butyl glycolate, ethyl lactate, propylene carbonate, dimethyl perfluorosuberate, dimethyl tetrafluorosucciate, tetra(ethylene glycol)dimethyl ether, tri (ethylene glycol)dimethyl ether, di(ethylene glycol)dimethyl ether, ethylene glycol phenyl ether, epoxidized linseed oil, epoxidized soy oil, diethylisophthalate, a silicone copolyol-based laurate ester, a silicone copolyol copolymer, a silicone copolyol ester, a silicone copolyol-based isostearate ester, a silicone copolyol-based pelargonate ester, diethylisophthalate, dimethyl octofluoroadipate, and mixtures thereof.

An electro-optical device for controlling the transmission of radiation, said device comprising a cell formed of opposed cell walls, a light-modulating element between said cell walls and opposed electrode means operatively associated with said cell walls, said light-modulating element comprising a film, said film comprising a matrix polymer material and having droplets of a liquid light valve suspension comprising a plurality of particles dispersed in a liquid suspending medium distributed within the polymer matrix, said electrode means adapted for applying an electrical field across said suspension, wherein said liquid suspending medium (a) is substantially immiscible with the matrix polymer material, (b) has a boiling point at atmospheric pressure greater than about 100° C., (c) has an electrical resistivity of at least about 0.8×106 ohms per square, and (d) has an index of refraction at 25° C. which differs from an index of refraction of the matrix polymer at substantially the same temperature by no more than about 0.002, and wherein said suspending medium comprises at least one liquid component selected from the group consisting of methyl pyrrolidinone, ethyl pyrrolidinone, dimethyl malonate, diethyl malonate, dimethyl succinate, di(propylene glycol)methyl ether, dimethyl phthalate, butyl phthalyl butyl glycolate, ethyl lactate, propylene carbonate, dimethyl perfluorosuberate, dimethyl tetrafluorosucciate, tetra(ethylene glycol)dimethyl ether, tri(ethylene glycol)dimethyl ether, di(ethylene glycol)dimethyl ether, ethylene glycol phenyl ether, epoxidized linseed oil, epoxidized soy oil, diethylisophthalate, a silicone copolyol-based laurate ester, a silicone copolyol copolymer, a silicone copolyol ester, a silicone copolyol-based isostearate ester, a silicone copolyol-based pelargonate ester, diethylisophthalate, dimethyl octofluoroadipate, and mixtures thereof.

A method of preparing a film suitable for use as a light-modulating unit of an suspended particle device (SPD) light valve, the method comprising:

• preparing a quantity of a matrix polymer material;
• forming an emulsion from the combination of at least a portion of the matrix polymer material and a quantity of a liquid light valve suspension, said suspension comprising a plurality of particles suspended in a liquid suspending medium, wherein said liquid suspending medium (a) is substantially immiscible with the matrix polymer material, (b) has a boiling point at atmospheric pressure greater than about 100° C., (c) has an electrical resistivity of at least about 0.8×106 ohms per square, and (d) has an index of refraction at 25° C. which differs from an index of refraction of the matrix polymer at substantially the same temperature by no more than about 0.002, and wherein said suspending medium comprises at least one liquid component selected from the group consisting of methyl pyrrolidinone, ethyl pyrrolidinone, dimethyl malonate, diethyl malonate, dimethyl succinate, di(propylene glycol)methyl ether, dimethyl phthalate, butyl phthalyl butyl glycolate, ethyl lactate, propylene carbonate, dimethyl perfluorosuberate, dimethyl tetrafluorosucciate, tetra(ethylene glycol)dimethyl ether, tri(ethylene glycol)dimethyl ether, di(ethylene glycol)dimethyl ether, ethylene glycol phenyl ether, epoxidized linseed oil, epoxidized soy oil, diethylisophthalate, a silicone copolyol-based laurate ester, a silicone copolyol copolymer, a silicone copolyol ester, a silicone copolyol-based isostearate ester, a silicone copolyol-based pelargonate ester, diethylisophthalate, dimethyl octofluoroadipate, and mixtures thereof;
• and
• cross-linking the polymer matrix to solidify the matrix polymer and produce a film having droplets of the liquid light valve suspension distributed in the cross-linked polymer matrix.