GB598330A - Improvements in or relating to optical sheets or flexible reflex light reflecting sheets, and reflex light reflectors including the same - Google Patents

Abstract

598,330. Ornamenting. MINNESOTA MINING & MANUFACTURING CO. Aug. 9, 1945, No. 20413. Convention date, March 2. [Class 93] [Also in Groups VIII, XVIII and XX] A reflex reflector comprises a transparent sheet in which are embedded transparent spheres, the rear of the sheet being attachable to or forming a reflector, which may contact with or be spaced from the spheres, the spheres being covered at the front by a transparent covering having a flat front surface, and the refractive index of the spheres being at least 1.15 times that of the covering. The sheet may be flexible. Fig. 1 shows the spheres 13, which may be of glass, held in a binder layer 12 and a spacing film 11 which may be on a reflecting back 10. A solid transparent covering 14 having a flat front surface is provided. The reflector 10 may be rigid or flexible of cloth, paper or sheet metal or may comprise a reflecting coating on the film 11 deposited electrically or by spraying; it may comprise a further layer of binder material and pigment such as titanium dioxide or certain areas of the film 11 may be made reflecting by printing a design, the remaining areas being transparent. One or other or both the layers 11, 14 may be coloured as may the spheres. The reflector may be formed by successively depositing the layers on paper coated with ureaformaldehyde resin and from which the final sheet is stripped. A flexible reflector layer 10 comprising titanium dioxide pigment, N-butyl methacrylate polymer and iso-butyl methacrylate polymer with xylol as solvent is first deposited followed by a spacing layer 12 of N- butyl methacrylate polymer followed after drying by a further layer 12 of this polymer in which the glass beads are embedded. The final covering 14 comprises a mixture of N- and isobutyl methacrylate polymers. The layers may be deposited on the paper in the reverse order. A thermo- or pressure-sensitive adhesive may be provided on the film 11 instead of the reflecting back so that the flexible sheet, which may be stored in roll form, can be attached as desired. A suitable adhesive for laminating the sheet to aluminium foil comprises methyl acrylate and isobutyl acrylate (both monomers), diamylethylene dimaleate, benzoyl peroxide and emyl acetate. In the modification shown in Fig. 6 an opaque or translucent coloured layer 35 is provided, and Fig. 5 shows the spheres immersed directly in the reflecting layer 28 described above. Each sphere may be coated with a uniform layer of the same material as that comprising to layer 30 before being embedded in the reflecting layer 28. The sheet may be used for road traffic signs, advertisement posters or be attached to clothing and handbags for decoration and as warnings at night.