Patent GB-585035-A (GB)
Title: Improvements in the production of articles comprising metal
IPC: C25D1/08
Filed: 1944-03-27
Abstract: 585,035. Photographic processes. KODAK, Ltd., GRESHAM, D. C., and LOENING, E. E. March 27, 1944, No. 5631. [Class 98 (ii)] [Also in Group XXXVI] - . A metal design on a non-metallic surface is made by coating a photographic light-sensitive layer comprising a hardenable colloid binder on a support formed of an electrically non-conducting substance on which an adherent layer of metal can be more readily deposited than on the binder, exposing to an image, removing the light-sensitive layer image-wise to form a stencil, making the areas of the support laid bare electrically conducting by depositing metal thereon, and preferably electroplating such metal with further metal. The support may be a cellulose ester such as cellulose acetate, a partially hydrolysed resin such as partially hydrolysed shellac, or wood or plaster coated with cellulose ester or hydrolysed shellac. A gelatino silver halide emulsion may be used and the gelatine removed image-wise with an etchbleach bath containing hydrogen peroxide. A bichromated colloid layer may also be used and the unhardened or the image-wise hardened areas removed. In example 1, a negative image of a wire mesh or electrical resistance is printed on to a gelatino silver halide emulsion on a cellulose acetate support, the image developed with a hydroquinone developer containing potassium hydroxide, and the gelatine removed image-wise. with a bath containing hydrogen peroxide, cupric sulphate, nitric acid, potassium bromide, and water. The film is then washed and bathed in stannous chloride solution, washed and treated with a silvering solution prepared from silver nitrate, ammonia and Rochelle salt, washed and rubbed vigorously with cotton wool in hot water to remove the - gelatine and adhering silver, and treated in a lead electro-plating bath containing lead carbonate, perchloric acid, gelatine and water. The metal mesh or resistance may be left on the support or stripped off. In example 2, a negative image of a wire mesh or electrical resistance is printed through a cellulose acetate support on to a gela,tino silver halide emulsion thereon, and after development in a tanning developer, the gelatine is removed image-wise in hot water. The support is hydrolysed in a caustic alkali bath and the hydrolysed layer is removed from the parts of the film unprotected by the gelatine stencil by rubbing with zinc chloride solution. The whole film is rubbed over with litho developing ink and the gelatine stencil removed with sodium hypochlorite solution. The support unprotected by ink is chemically silvered, further metal is electroplated on the silver, and the metal article is stripped off. In example 3, an emulsion-coated cellulose acetate film is exposed from the emulsion side and is developed in a non-tanning developer. The emulsion is removed imagewise in an etch-bleach bath, the film is treated with stannous chloride solution, and silver is chemically deposited, heavily on the bare areas and lightly on the gelatine stencil, from which latter it is removed by rubbing. Alternatively, the gelatine stencil is removed by hot water and rubbing. The silver deposited on the cellulose acetate is thickened by electro-plating and the metal article is stripped off. A mesh or resistance may be formed on'a cellulose nitrate support, sealed in a glass envelope to be evacuated, and the cellulose nitrate electrically fired by electrodes protruding through the envelope. A thermo-couple may'be formed on cellulose nitrate, which by first forming the design for the thermo-couple in silver and electro-plating this design first with copper and then with nickel, is provided with an auxiliary filament by means of which the cellulose nitrate may be fired when the thermo-couple is placed in an evacuated sealed glass envelope. Specification 573,771 is referred to.