Patent GB-567675-A (GB)
Title: Improvements in or relating to the deposition on to supports of plastic material capable of forming a polarizer
IPC: G02B5/30
Filed: 1941-12-29
Abstract: 567,675. Light polarizers; coating surfaces. INTERNATIONAL POLAROID CORPORATION. Dec. 29, 1941, Nos. 16739 and 16740. Convention dates, Dec. 24, 1940, and Jan. 15, 1941. [Class 97 (i)] [Also in Groups III and XI] i In the production of a polarizing layer on a support, a mass of plastic material is rubbed on the support and heat, produced frictionally by the rubbing, or by preheating the support, causes the plastic material to adhere in a thin layer having its molecules oriented into substantial parallelism; the plastic material may be polyvinyl alcohol, polyvinyl acetal, &c., rendered dichroic by the heat as described in Specification 548,759, or by staining. The deposition may occur in flakes which coalesce and may be made on a spherical or other curved surface such as the surface of a motor car headlight, ophthalmic lens, &c., apparatus for this purpose being described. The mass of plastic material may be a bar manually wiped across the surface of a heated support, a disc 22, Fig, 2, rotated by a motor 24 on the surface of a support 20, the bristles 132, Fig. 12, of a brush reciprocated by a crank 136 and arm 138, or an endless belt 140, Fig. 13, carried by a driven roller 148 and a free roller 149. In all cases relative movement between the plastic and support may be at a speed high enough to produce heat sufficient to cause adhesion and orientation, the plastic, if narrower than the support, being also relatively movable laterally to produce contiguous layer strips which are coalesced together by the heat. Rollers and belts having various forms of separated plastic projections or flaps extending from their surfaces are described ; such projections &c. cause the plastic to be deposited in flakes which may overlap and are coalesced together by the heat. For curved supports, bristles 208, Fig. 19, projections &c. may be carried on roller 206 shaped to conform to the surface of the support 200, the support being carried on an axle 204 so as to be rotatable about its centre of curvature during deposition. Alternatively, a spherically-curved support 220, Fig. 21, may be mounted in a ring 230, rotatable about an axle 236 by a handle 240 during deposition, and laterally about an axle 234 by a crank 238 to change the strip upon which deposition is being effected, the two axes intersecting perpendicularly in the centre of curvature of the surface of the support. Deposition may be by an endless belt 222, roller, &c., to produce a complete covering for a head-light lens producing constant polarization in the light beam. Motor-operated apparatus embodying parts movable similarly to those of Fig. 21 is described in detail in the Specification. If the surface of the support is a toric surface, the two axles may pass respectively through the centres of curvature. For advertising purposes, the support and roller &c. may be moved relatively in circular and radial directions to produce circular orientations or rectilinear orientations radiating from a centre. The support may be glass, a plastic sheet, or other material ; it may be a reflector, and may have a low conductivity to increase the temperature resulting from the generated heat. The deposited layer may be rendered dichroic, and polarizing, by hydration of some of the molecules due to the heating, as described in Specification 548,759, or by the use of stains as described in Specifications 549,668, 549,698 and 556,578. Hydration and adhesion may be insured by further heating after deposition. Catalysts such as an acid, or a salt (ammonium iodide, ferric chloride, or sodium bisulphate, &c.) or dyes suitable for use as stains, may be provided in the polyvinyl alcohol mass, or be added to the deposited layer, as described in Specification 548,759, to assist the effect produced by the heating; dyes used as catalysts render unnecessary the use of inhibitors as described in Specification 548,759. The completed layer may comprise superposed layers having similar orientations and may have a thickness of 0.00015 inches approximately ; it may be protected by a thin cover glass secured by an adhesive, or by a resinous coating. Two supports having, completed layers may be secured together with the layers adjacent. The completed layer may be of sufficient thickness to serve as a quarterwave or other retardation plate which, used in conjunction with a polarizer on a head-light lens, circularly polarizes the light beam. In the Specification as open to inspection under Sect. 91, a layer of polyvinyl alcohol &c., deposited by pressing a softened sheet on to a head-lamp lens, or by coating thereon, has its molecules oriented by using a friction element such as a steel or fibre belt. This subjectmatter does not appear in the Specification as accepted.