Patent GB-712185-A (GB)
Title: Improvements in and relating to translucent coatings
Inventor: ANDERSON JAMES THOMSON
IPC: C03C17/00
Filed: 1951-05-11
Abstract: A light-diffusing coating of silica is produced on the surface of a light transmitting foundation, by applying a mixture of a solution of a binder and a colloidal solution of silica to produce a coating thereon, wholly or partially drying the coating, and heating the foundation to remove, wholly or in part, the binder and any remaining solvent.  The solution of colloidal silica may be produced by hydrolysis of ethyl silicate.  Specified binders are polymeric methyl methacrylate and nitrocellulose. Plasticizers such as butyl phthalate and camphor, additional solvents such as ethyl lactate, and colouring agents, e.g. cobalt chloride, may be added to the mixed solution.  In Examples I to III a colloidal solution of silica prepared by hydrolyzing a mixture of tetra ethyl silicate and acetone with water and hydrochloric acid is mixed with acetone solutions of a polymeric methyl methacrylate resin such as "Diakon" (Registered Trade Mark) type MC, additions of butyl phthalate, camphor, ethyl lactate or cobalt chloride being made.  The mixture is coated on to a base such as the inside of a filament lamp bulb, drained, dried and fired.  In Example IV an acetone solution of a "Diakon" type MC is mixed with dilute hydrochloric acid, distilled water and tetraethyl silicate and agitated until a clear solution is obtained to which acetone is added, the mixture then being applied as before.  In Example V a solution of high viscosity nitrocellulose in butyl acetate is mixed with a colloidal solution of silica prepared as in Examples I to III, applied to the foundation, dried and heated to burn off the binder.ALSO:A light-diffusing coating of silica is produced on the surface of a light transmitting foundation, by applying a mixture of a solution of a binder and a colloidal solution of silica to produce a coating thereon, wholly or partially drying the coating, and heating the foundation to remove, wholly or in part, the binder and any remaining solvent.  The solution of colloidal silica may be produced by hydrolysis of ethyl silicate.  Specified binders are polymeric methyl methacrylate and nitrocellulose. Plasticizers such as butyl phthalate and camphor, additional solvents such as ethyl lactate, and colouring agents, e.g. cobalt chloride, may be added to the mixed solution.  In Examples I to III a colloidal solution of silica prepared by hydrolyzing a mixture of tetra ethyl silicate and acetone with water and hydrochloric acid is mixed with acetone solutions of a polymeric methyl methacrylate resin such as "Diakon" (Registered Trade Mark) type MC, additions of butyl phthalate, camphor, ethyl lactate or cobalt chloride being made.  The mixture is coated on to a base such as the inside of a filament lamp bulb, drained, dried and fired.  In Example IV an acetone solution of a "Diakon" type MC is mixed with dilute hydrochloric acid, distilled water and tetra ethyl silicate and agitated until a clear solution is obtained to which acetone is added, the mixture then being as before. In Example V a solution of high viscosity nitrocellulose in butyl acetate is mixed with a colloidal solution of silica prepared as in Examples I to III, applied to the foundation, dried and heated to burn off the binder.