Patent GB-1202330-A (GB)
Title: Retro-reflector and method of making the same
Inventor: GOLDMAN WILLIAM ABRAHAM
IPC: G02B5/128
Filed: 1968-07-04
Abstract: 1,202,330. Laminates. CANRAD PRECISION INDUSTRIES Inc. 4 July, 1968 No. 31930/68. Heading B5N. [Also in Divisions B2 and B6] A retro-reflector comprises a light reflective layer, a layer of transparent, tacky, dimensionally stable, pressure-sensitive adhesive resin adhered to the reflective layer by polar bonds, and a monolayer of a multiplicity of spaced glass beads adhered by polar bonds to the adhesive layer, the glass beads being neither partially nor totally embedded in the resin. In Fig. 2 the retro-reflective surface 5 consists of a backing layer 8 having deposited thereon a coating of reflective metal 10 such as aluminium, silver, gold. Electrostatically coated thereon is an adhesive layer 12 consisting of a tacky transparent pressure sensitive, dimensionally stable adhesive resin. Electrostatically coated on the resin layer 12 is a monolayer of glass beads 14 permanently adhered to and uniformly spaced upon the surface of the resin layer 12. Coated over the monolayer of glass beads 14 is a transparent protective covering layer 16. The backing layer can be of polyethylene terephthalate, paper, cloth and may be rigid or flexible. The reflective surface of metal may be coated on to the backing surface by spraying, electrodeposition or by coating an adhesive on the backing layer and then applying a thin metallic sheet or foil. The reflective surface may be bonded to a spacing film to produce a reflective surface having an integral back reflector. The reflecting surface on the backing layer may be formed by printing, stencilling or painting so that the surface presents desired insignia, designs or lettering, and certain areas may be non-reflective or black. The reflective layer then may be a paint or enamel type of coating containing reflective pigment particles, e.g. an aluminium paint containing flake aluminium pigment to cause a silvery appearance of a reflective light. The pressure-sensitive adhesive resin may be a resin containing at least one reactive hydroxy group partially cross-linked with a thermosetting resin containing one to three reactive hydrogen atoms. Pressuresensitive adhesive resins exemplified are polymers of esters formed from a carboxylic acid such as acrylic, methacrylic, succinic or itaconic acid with a polyhydroxy alcohol such as glycerol, glycol, methylene glycol, pinacone or erythritol. Thermosetting resins mentioned are the epichlorohydrin/bis phenol polymers, phenol/formaldehyde, melamine/formaldehyde, or urea/ formaldehyde resins. The top coating can be transparent flexible resins such as polyethylene terephthalate, or polymethyl- or polyethylmethacrylate, and may be applied in the form of a film-forming solution by knife coating, roller coating, electrostatic coating or as a preformed sheet. In another embodiment (Fig. 3, not shown), no backing layer is provided, but an adhesive coating is applied to the rear face of the reflective surface and is covered by a removable liner sheet. The adhesive coating may be solvent sensitive, heat sensitive or pressure sensitive.