Variable light-filtering device
First Claim
1. In a vehicle having at least one headlamp and a windshield, the improvement which comprises positioning in coextensive relationship with said windshield a variable light-filtering device comprising a pair of spaced, parallel, coextensive lighttransmitting electrodes, a layer of a light-transmitting redox compound capable of forming a stable colored free radical upon the addition of electrons confined between said electrodes and means for flowing an electric current in a predetermined direction through said device.
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Abstract
This invention relates to light filters employing redox compounds that are substantially light-transmitting in their oxidized state and capable of forming a stable colored free radical upon the addition of electrons. The colored free radical formed in response to the flow of electric current renders the device light-absorbing. To restore the original lighttransmitting properties, the colored free radical may be readily reoxidized, for example, by reversing the direction of current flow.
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Citations
14 Claims
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1. In a vehicle having at least one headlamp and a windshield, the improvement which comprises positioning in coextensive relationship with said windshield a variable light-filtering device comprising a pair of spaced, parallel, coextensive lighttransmitting electrodes, a layer of a light-transmitting redox compound capable of forming a stable colored free radical upon the addition of electrons confined between said electrodes and means for flowing an electric current in a predetermined direction through said device.
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2. A vehicle as defined in claim 1 wherein said redox compound is a 4,4'"'"''"'"'-dipyridylium compound, a diazapyrenium compound or a pyrazidinium compound.
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3. In a vehicle having at least one headlamp including a light bulb and a protective transparent cover and a windshield, the improvement which comprises positioning in coextensive relationship with said transparent cover a variable light-filtering device comprising a pair of spaced, parallel, coextensive light-transmitting electrodes, a layer of a light-transmitting redox compound capable of forming a stable colored free radical upon the addition of electrons confined between said electrodes and means for flowing an electric current in a predetermined direction through said device.
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4. A vehicle as defined in claim 3 which additionally includes a light-filtering device positioned in coextensive relationship with said windshield, said light-filtering device comprising a pair of spaced, parallel, coextensive light-transmitting electrodes, a layer of a light-transmitting redox compound capable of forming a stable colored free radical upon the addition of electrons confined between said electrodes, and means for flowing an electric current in a predetermined direction through said device.
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5. A vehicle as defined in claim 4 wherein said redox compound is a 4,4'"'"''"'"'-dipyridylium compound, a diazapyrenium compound or a pyrazidinium compound.
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6. A vehicle as defined in claim 1 wherein said redox compound is a polymer.
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7. A device according to claim 1 including means for reversing the direction of current flow.
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8. A device according to claim 7 including means for automatically predetermining said direction of current flow.
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9. A vehicle as defined in claim 6 wherein said headlamp contains light-polarizing means and said redox compound is a molecularly oriented redox polymer.
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10. A vehicle as defined in claim 9 wherein said headlamp light-polarizing means comprises a variable light-filtering device comprising a pair of spaced, parallel, coextensive light-transmitting electrodes, a layer of a light-transmitting molecularly oriented redox polymer capable of forming a stable colored free radical upon the addition of electrons confined between said electrodes, and means for flowing an electric current in a predetermined direction through said device.
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11. A vehicle as defined in claim 9 wherein said variable light-filtering device in coextensive relationship with said windshield includes a light-polarizing sheet substantially coextensive with and having one surface in juxtaposition with the outer surface of one of said electrodes.
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12. A vehicle as defined in claim 9 wherein said polymer is a 4, 4'"'"''"'"'-dipyridylium polymer.
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13. A vehicle as defined in claim 12 wherein said polymer is poly-N,n-butylene-4,4'"'"''"'"' -dipyridylium dibromide.
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14. A vehicle as defined in claim 1 wherein said redox compound is capable of functioning as its own electrolyte.
Specification