GB1298462A - Recording information by forming fluorescent material images - Google Patents

Abstract

1298462 Luminescent materials and uses thereof; polycyclic aromatic hydrocarbons AMERICAN CYANAMID CO 30 Sept 1969 [1 Oct 1968 (3)] 48043/69 Headings C4S and C5E [Also in Division C2] A method of recording information on a substrate comprises providing a substrate carrying a substantially non-fluorescent substance as defined but which is convertible to a chemically different fluorescent substance on being heated and/or on the application of ultraviolet radiation, and heating or applying the above radiant energy in a pattern to effect conversion to a fluorescent substance capable of fluorescing under U.V. or visible radiation. The precursor is preferably completely non-fluorescent but may be a substance weakly fluorescent under U.V. or visible radiation and convertible to a fluorescent substance which fluoresces so much more strongly that an image pattern may be read out against the background. The converted fluorescent substance, which may be reversible on light application, may also be coloured and immediately visible or may be colourless like the precursor, and the information may be alphanumeric, code markings, e.g. dots or lines, or pictorial information, and in preferred embodiments no fixing is required. Applications include electronic storage and replay of sound and pictures, phonograph discs, numerical data collection and retrieval, production and validation of cards, stamps and passes, which may include superimposed information layers over part or all the card. Preferably the read out wavelength does not effect further conversion, but may be of the same wavelength as the information input radiation if of sufficiently short duration. Imaging duration may be as low as a millisecond, and with a laser, a nanosecond. The precursor may be coated on a substrate or incorporated in transparent or opaque plastics films, and sheets, belts, discs, drums, bottles or boxes. Many examples of precursor and fluorescent substances are given. For example, uranine and Rhodamine B and a wide range of chromere compounds are disclosed which being of differing spectral properties may be included in a coded alphabet and preparations of precursors are described. Other examples include o - chlorophenyl - 1 - naphthyl ether, polycyclic aromatic anhydrides undergoing photochemical decarbonylation, or the same reaction on heating to the melting point (specified m.p. disclosed), e.g. 9, 10 anhydride of 9, 10 diphenylanthracene, (others being disclosed); endoperoxides, e.g. 9,10-diphenyl anthracene endoperoxide, and halogen anthracene (others being disclosed), some of which may be initially weakly fluorescent, and undergo a chemical conversion, e.g. oxidation @rreduction, e.g. to quinone, under thermal contact, infrared or short wave U.V. and are reversible under U.V. and air or oxygen. Polycyclic aromatic hydrocarbons are formed by photochemical conversion of anhydrides or heating of the corresponding endoperoxides, e.g. 9,10-diphenylanthracene is prepared from 9,10-diphenyl-9,10- dihydro anthracene 9,10-anhydride. Other compounds prepared in examples include anthracene, diphenylphenylenenaphthacene 9,10-bis- (phenylethynyl) anthracene, 5,12-bis-(phenylethynyl) tetracene; 1,2,8,9 - dibenzpentacene. A hot die (e.g. keys, metal with raised letters) at 20‹ to 200‹ C. or higher may be applied and U.V. or infra-red input may be from lamps, arcs, or U.V. or infra-red lasers and the image may be by projecting a beam through a stencil, or by moving mirrors with lasers, specific examples being disclosed. A fluorescent material image formed from endoperoxide on paper was transferred to the substrate at higher conversion temperatures. Other combinations include polyethylmethacrylate containing a dibromo compound, plastic films containing DPA.O 2 (e.g. 40 mg./gm. of polymer) cast with various solvents on a microscope slide, e.g. PEMA, cellulose acetate butyrate, vinyl chloride-acetate copolymer, P.V.C., P.V.A., acrylite, and may include infra-red absorbers, such as charcoal, specific precursors being disclosed. The initial endoperoxide may be prepared by U.V. light in the presence of air or oxygen, with or without sensitizer, chemical synthesis or with active oxygen prepared by electrodeless discharge, other preparations being described (see Division C2). The amount of detectable fluorescence may be proportional to the input radiation, enabling tone variations to be achieved. Examples 1 to 26 disclose also conversions to fluorescent compounds by multistep chemical synthesis (e.g. Examples 3, 18, 19) and irradiation in solvents (e.g. Examples 1, 16, 19-22, 25) which are disclosed as not corresponding to the method of recording as claimed.