Patent GB-625823-A (GB)
Title: Improvements in or relating to the reproduction of sound track records cut into a carrier
IPC: G11B11/00
Filed: 1946-06-26
Abstract: 625,823. Optical sound records; printing processes. PHILIPS LAMPS, Ltd. June 26, 1946, No. 19075. Convention date, Oct. 23, 1939. [Class 100 (ii)] [Also in Group XXXVIII] For printing or duplicating sound tracks originally cut as V- shaped tracks in a master carrier, there is provided in or on a part of the master carrier a material adapted to be entirely or partly transferred by diffusion to a hydrophile material on a second carrier brought into contact with the master carrier, and to cause the formation in the contacting parts of said second carrier of a waterinsoluble compound which is less transparent or more transparent than the unaffected parts of the second carrier. As shown in Fig. 4, the master carrier A has a base layer 13 of celluloid, a layer 12 of gelatine and a black coating 11 in known manner, and also a layer 54 of celluloid lacquer. The V-shaped groove cut in this master carrier is filled with diffusible material at 18 such as a paste of silver nitrate and the master carrier is brought into contact with a second carrier B of a hydrophile material such as gelatine containing a reagent such as potassium chloride or hydrochloric acid. The diffusible material 18 is applied in a moist state or is moistened before the two carriers are brought together. The silver nitrate diffuses into the surface of carrier B when it forms silver chloride which is subsequently made fast by development. Alternative reagents are sodium sulphide and cobalt nitrate, and for these no development is required. If the master track is not required to produce sound, the black coating 11 may be omitted. In another form, Fig. 8, the diffusible reagent 18 is applied as a top coating on the gelatine layer 12 of the master carrier A and the V-shaped track is cut through this top coating, so that when the second carrier B is brought into contact with the master carrier, the diffusion and reaction occur at the outer parts. In a modification of this Fig. 10, the master carrier A has only a base layer of celluloid 13 covered with a layer 66 containing the diffusible reagent into which layer the V-shaped track is cut. When such a master carrier is brought into contact with the second carrier B, diffusion and reaction occur on the outer parts; but diffusion and reaction may be made to occur in the centre part by providing a top coating of lacquer 67 before the track is cut and filling up the track with a material 62 such as gelatine or agar through which the diffusion can occur from material 66 to the second carrier B. This process can thus produce positive or negative records according to whether the centre part is more transparent or less transparent than the outer parts. The process is applicable to the formation of a sound record alongside a kinematograph film. The carriers may be brought into contact by being passed between rollers or by being rolled into a spiral and after a certain time unrolled. The first method is suitable for materials diffusing and reacting comparatively quickly, and the second method for slow acting materials. Specification 331,278, [Class 40 (ii)], is referred to.