Improvements in or relating to fluorescent devices

摘要

A coloured daylight signalling or display device comprises a diffusely-reflecting backing-sheet of a fabric such as cellulose acetate satin or crepe, paper or cardboard, and a dye which reflects and fluoresces in substantially the same colour, the dye being dispersed in or on the backing sheet in such dilution as to exhibit in daylight brightness greater than that given in daylight by reflection only by any dye or pigment of the same colour, under the same conditions. In one example, 6 oz. white cellulose acetate satin is dyed by immersion for 2 minutes at 180 DEG F. in an aqueous dye-bath comprising 15 per cent formic acid and 0.17 per cent meta diethylaminophenol phthalein hydrochloride and the dried dyed satin is passed through a aqueous solution of 40 per cent formic acid and 1 per cent zinc chloride to improve fastness to light and weathering. In a second example, 6 oz. white cellulose acetate satin is immersed in the dye bath of the first example and is then shaded by immersion for 15 minutes at 180 DEG F. in an aqueous dye-bath comprising 1 per cent Fluorescent Yellow HEB, 1 per cent of a higher fatty alcohol sulphate and 1 per cent sodium chloride. In other examples different concentrations, different fluorescent dyes such as meta diethylaminophenol phthalein ethyl ester hydrochloride, di-(dimethylaminophenyl)phenyl amino naphthyl methane chloride and 4-methyl-7-hydroxy coumarin sodium salt, and different fabrics such as silk crepe are used. The weathering properties of the fabrics can be enhanced by impregnating and coating them with a transparent lacquer such as vinyl resin or cellulose lacquer. In a further example, white paper, such as 140 pound basis photo-gelatine printing stock, is coated by air-spray equipment with a fluorescent composition comprising one part of the substance dissolved in 170 parts by weight of a 60 per cent butyl alcohol solution of urea formaldehyde resin. The evenly-coated paper is air-dried for at least 20 minutes and is finally baked for 2 hours at 200 DEG F. so as to condition the resinous content of the coating. Specifications 8449/10, [Class 37], 456,480, 483,662, [Group XL], and 560,143 are referred to.