GB670473A - Improvements in or relating to reflex light reflectors - Google Patents

Abstract

670,473. Reflex reflectors. ROLLINSON, E. W. (Minnesota Mining & Manufacturing Co.). Nov. 23, 1949, No.. 30022/49. Class 97 (i). [Also in Group VIII] A reflex reflector has a single layer of transponent spheres whose refractive index is from 1.85 to 1.95 partially embedded in a reflective layer contacting the inner surfaces of the spheres and is characterized in that the reflective layer is formed of a transparent material admixed with smaller proportions, exceeding one per cent (by weight relative to the total) of reflective metallic flake pigment and transparent colour pigment, the metallic flakes being oriented in proximity to each embedded sphere surface so as to fan toward it, and the properties of the pigments being correlated so as to provide effective coloration and high brilliancy of reflex-reflected light. The reflector shown comprises several transparent spheres 25 of glass having a refractive index approximately equal to 1.90, partially embedded in a bonding layer 24, coated on a layer 23. This layer 23 is applied to a coating 22 which is cast on a sheet 21 and facilitates stripping thereof. The coatings 23, 24 are each composed of a transparent material containing a mixture of a finely-divided aluminium flake pigment and transparent colour pigment and the spheres are pressed into the coating 24, whereby the aluminium flakes face towards the spheres. The sheet 21 may be prepared by knife-coating a highly calendered Fourdrinier paper with a 40 per cent solution of isobutyl methacrylate polymer in xylol solvent. Thereafter, layer 22 is applied in two steps. Firstly; the dried paper is knife coated with a 10 per cent solution of polyvinyl butyral polymer in ethylene-glycol monoethyl-ether solvent and is then heated for one hour at 140‹ F. An overcoat of 12.5 per cent polyvinyl butyral polymer and 4.2 per cent of tricesyl phosphate plasticizer in the same solvent is then applied and dried. Coating 23 is then applied using a wet casting weight of 12-14 grains per 24 square inches and consists of 61.5 per cent of a solution of thermo-setting urea formaldehyde resin in a volatile solvent; 30.8 per cent heavy blown castor oil; 5 per cent ethylene-glycol monoethyl-ether; 7.7 per cent blue phthalocyanine pigment and 5 per cent aluminium pigment. This coating is dried and cured. Using the same mixture and a wet casting weight of 12-17 grains per 24 square inches, the coating 24 is then applied and the spheres 25 are pressed therein. Instead of using two coatings 23, 24, only one may be applied. Mixtures of reflective pigments and mixtures of transparent colour pigments may be used. The transparent material of layers 23, 24 may be dyed and the spheres 25 may be tinted. Reference has been directed by the Comptroller to Specification 556,935.