Patent GB-1335962-A (GB)
Title: Deposition of metals onto organic materials
Inventor: ANDREWS T D
IPC: C23C18/18
Filed: 1969-11-26
Abstract: 1335962 Electroless plating active substrates IMPERIAL CHEMICAL INDUSTRIES Ltd 5 Nov 1970 [26 Nov 1969 26 May 1970] 57862/69 and 25203/70 Heading C7F [Also in Division G2]  Metal is deposited electrolessly in or on a substrate containing or consisting of an organic compound selected from (1) radical cations Z<SP>+</SP> or (2) neutral molecules Z derived by twoelectron reduction from a dication unit which is a salt containing N atoms at least two of which are quaternised and are contained in linked at least partially aromatic rings, the link providing a chain of conjugated unsaturation between the N atoms, and said dicationic unit being Z<SP>+</SP> in the equation where Z<SP>++</SP> is the normally stable state of the molecule in aqueous media. The radical cation may contain two unsaturated heterocyclic ring systems linked by a direct link or an azine or ethylene group, e.g. bis (indolizinium) ethylene, bis (benzothiazolinylidene) azine, bis (quinolyl) azine, bis (azulenyl) ethylene, and derivatives thereof, e.g. with C 1-10  alkyl or aryl substituents Associated anions may be halide, ClO 4 <SP>-</SP>, BF 4 <SP>-</SP>, CH 3  SO 4 <SP>-</SP>, HSO<SP>-</SP> 4  acetate, and polymeric ions such as poly (p-vinylbenzene sulphonate), poly (acrylate) and poly (styrylphosphonate). Preferred neutral compounds and radical cations are derived from dications of formula where R<SP>1-12</SP> are H, halogen, organic substituents, and n = 0 or an integer; various R may link to form rings. Examples are 4, 4'-bipyridilium; 4, 4'-biquinolinium; 1, 2-bis (4-pyridyl) ethylene; 2, 7-diazapyrinium; 2, 2'-bipyridyl; or 4, (4'- pyridyl) pyridinium, and their derivatives. The active compounds may be impregnated into paper, cloth, wood, or plastics foam, in an organic solvent or in water for type (3) compounds. The substrate may also be produced in the form of a film for silver-free photographic systems, by supporting a dicationic compound in a watersoluble or film-forming polymer matrix, e.g. of polyvinyl alcohol, poly (ammonium methacrylate), gelatine, alginates, maleic anhydride copolymers, polysaccharides, or polyvinyl pyrrolidone, or a 1, 6, diaminotrimethyl hexane/terephthalic acid copolymer cast into a film using DMF as a solvent may be employed. In use the film is exposed to radiation (UV, IR, visible or electronbeam) so that exposed parts are activated imagewise and are susceptible of development by selective electroless plating. The film is preferably a 0À001-0À1 mm film on a flexible support such as polyethyleneterephthalate, and may include (1) compounds for speed improvement (alcohols, phenols, carboxylic acids, sugars, glycerol, EDTA Na 2  picric acid, #-alamine, mellitic acid, triethanolamine, thiazine, or nicotinamide adenosine dinucleotide phosphate) (2) sensitisers, (riboflavin, Acronol (RTM) yellow, colophony, 3, 3' diethylthiacyanide iodide, proflavin, acridine orange, acriflavin, N-methylphenazinium methyl sulphate, 4-cyanoquinolinium methiodide or erythrosin (3) desensitizing agents (p-aminobenzoic acid, 6-amino-3, 4-phthaloy (acridone or urazole) and (4) other additives such as NH 4 Cl, urea, glycerol, or polyols to improve film pliability, or BaCl 2  to improve X-ray sensitivity. Development of the film image, or metallisation of a substrate, is by (1) optionally, if desired, treatment, e.g. for 0À5-5 mins at 15-30‹C, in 0À001 to 10 parts per 1000 in water of a salt of Ru, Rh, Pd, Os, Ir, Pt, Ag or Au, and (2) immersion in an electroless bath to provide a coating or image of Ag, Cu, Ni, Co, Co/Ni, or Fe, suitable baths being disclosed. Where the polymer of the film is water soluble or swellable, electroless plating is at room temperature or 1-30% of an alkali metal or ammonium salt, e.g. sulphate, is added to the bath to reduce damage to the film, or else same is pretreated with aqueous borax or glyoxal to induce cross-linking. The plating solution desirably contains a surfactant. Metal foam may be made by introducing the active compounds above into plastics foam, electroless plating, electro-plating, and optionally dissolving or burning out the plastics, and printed circuits may be made by circuit wise distribution of active compound followed by electroless plating, a 2- stage process using first Cu and then Fe-Ni for conductors and resistors in the circuit.