Patent GB-1169946-A (GB)
Title: Electrically Conductive Adhesive Tape
IPC: C09J7/20
Filed: 1966-09-12
Abstract: 1,169,946. Electrically conductive, pressuresensitive adhesive coating. MINNESOTA MINING & MFG. CO. 12 Sept., 1966 [13 Sept., 1965], No. 40712/66. Heading B2E. An electrically conductive adhesive tape comprises an electrically conductive flexible backing having thereon a pressure sensitive adhesive layer capable of passing an electric current therethrough to the backing, the adhesive layer comprising a chemically compatible mixture of adhesive and electrically conductive particles, the particles being uniformly distributed in a monolayer and having a volume of 0.1-40% of the volume of the adhesive, the tape having adhesion valves of at least 280g./in. and the electrical resistance measured from the adhesive surface to the backing being less than 100 ohms/sq. in. The backing may be metal foils e.g. copper, aluminium foils, metal coated synthetic or polymeric foils, conductive papers and cloths, metallized cloths. Pressure sensitive adhesive materials mentioned are polyacrylates, polyvinyl ethers, copolymers of polyvinyl acetate, and polyisobutylene, and natural neoprene, silicone rubbers. The electrically conductive particles may be spheres, spheroids, granules or discs and may be formed by starting with particles having a size range extending beyond the thickness of the adhesive layer and passing the particles in a vehicle through say a paint mill to flatten the particles. The particles may be metal such as copper, aluminium, antimony, bismuth, cadmium, chromium, cobalt, iron, lead, mercury amalgams, manganese, molybdenum, nickel, tin, titanium, tungsten, zinc, metal alloys or metal particles coded with metal the adhesive may contain antioxidants and chelating agents to prevent the degradation of the adhesive. Metallized plastics or glass beads particles, hollow spheres of graphite may be used, and different kind of particles can be mixed in one adhesive film. In the Examples: (1) aluminium foil is coated using a knife coater with adhesive comprising a copolymer of isooctylacrylate and acrylamide containing spherical silver particles and lined with a silicone treated glassine paper (2) copper foil is coated as in (1) and a backsize of a hydroxy terminated silicone polymer applied; (3) a tape is prepared as in (2) with copper particles; aluminium foil is coated with (5) adhesive mixtures comprising respectively the adhesive of (1) and graphite particles, (6) an adhesive comprising polyisobutylene, polybutene, hydrogenated methyl ester of resin, polyterpene and nickel spheres (7) an adhesive comprising polyvinyletho, phenol, modified alphapinene resin and tin granules, and an adhesive comprising natural rubber, polyterpene resin and aluminium spheres; (9) the adhesive of (1) and silver spheres are coated on the aluminium side of a polyester film coated with aluminium by vapour deposition and lined with the lining of (1); (10) the adhesive of (1) and silver spheres are coated on a silicone treated glassine paper which after drying is then wound up with a carbonaceous conductive cloth. After slitting the silicone treated paper is removed; (11) the adhesive coated paper of (9) is laminated to conductive paper made by beating the cloth of (10) with wood pulp in a water slurry and converting to paper on a papermaking machine. After slitting, the liner is removed. The tapes are useful as a wrapping material for electrical devices and circuit elements to give electrostatic shielding or to provide an envelope maintained at ground potential, low voltage conductors, replacements for soldered or other types of wire connections.