Patent GB-1302000-A (GB)
Inventor: SCHOOT C J
IPC: G02F1/1503
Filed: 1971-06-24
Abstract: 1302000 Luminescent materials and uses thereof PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 24 June 1971 [27 June 1970] 29703/71 Heading C4S Image display apparatus includes a solution of a reversibly reducible organic substance and an adjuvant in an inert solvent in contact with two inert electrodes, the substance being of formula where R and R<SP>1</SP> each represent an alkyl or cycloalkyl group with up to 18 carbon atoms or an unsaturated alkyl or cycloalkyl group with up to 12 carbon atoms or an aralkyl or alkaryl group with up to 10 carbon atoms or a phenyl group, which groups may be substituted in an aromatic nucleus with CF 3 , a halogen, CH 3 , OCH 3 , or NO 2 , a carbonamido-alkyl group in which the nitrogen atom may carry one or two alkyl groups which together with a hetero-atom may form a ring, which group may contain up to 16 carbon atoms, an alkoxy carbonylalkyl group containing up to 16 carbon atoms, a thienylalkyl group containing up to 10 carbon atoms, or a nitrile group, while R may be a group of formula in which in Formula I and II, R 1  and R<SP>1</SP> 1  are each a hydrogen atom or together, a -CH = CH- group, R 2  and R<SP>1</SP> 2  have the same meanings as R 1  and R<SP>1</SP> 1 , n is zero or unity and X is an electrochemically inert anion. Many examples are disclosed. X is preferably boron tetrafluoride or may be perchlorate, halides, or phosphate. Applied voltages may be D.C. rather than A.C., or square wave voltages, reduction at the cathode being reversed on change of polarity, or may be erased by voltage removal, and the image may be maintained by a smaller current. Erasure may be retarded by increasing electrode spacing, and chemical erasure precluded by a membrane separating oxidizable and reducible substances. Adjuvants may be substituted hydroquinones which in water have an oxidation reduction potential # 0À7 volts relative to the standard hydrogen electrode, e.g. substituted with a halogen, CN, CF 3 , CCl 3  or SCF 3 , and including tetra-substituted hydroquinones, e.g. 2,3-dichloro - 4,5 - dicyanohydroquinone and tetrachlorohydroquinone; ferrous salts, e.g. ferrous boron tetrafluoride, ferrous acetate or chloride, or 1,4-di-(dialkylamino) benzenes, and others as in Tables IV and V and are preferably colourless or only slightly coloured. The oxidizable and reducible substances are preferably in concentration # 0À01 mole/litre and substances added to a medium saturated with hydroquinone, for example, provides a white dispersion as background to a coloured image or a chemically inert, insoluble compound colour white or other contrast colour, such as titanium oxide, may be added. The inert solvents may be water and aprotic solvents such as acetonitrile, propioni. trile, glutarodinitrile, benzonitrile, propylene carbonate, nitromethane and acetic acid anhydride. Electrodes may be stannic oxide, indium oxide, platinum, palladium or gold and each may be of different material. A plurality of anodes and/or cathodes are disclosed and images may correspond to electrode shape or to the visible part screened by a mask. The electrode may be locally separated from the liquid by an insulating mask and the image made up of a plurality of components supplied by an equal number of electrodes or a text may be provided in a lacquer. Atmospheric gases or oxygen are preferably excluded and the device may be accommodated in an at least partially transparent easing of plastic or glass, one wall may be an electrode, e.g. stannic oxide on glass, and the image may be viewed through an anode aperture. Particular combinations include ethyl - viologen boron tetrafluoride and tetrachlorohydroquinone, each in amount 0À1 mol./litre, in acetonitrile containing 0À5 to 5% by wt. acetonitrile, 7À5% glutarodinitrile, or 10% by wt. propionitrile and others as in Tables IV and V using also ethylviologen chloride and bromide, and acids as in Table VI.