Patent GB-690476-A (GB)
Title: Improvements in or relating to methods of developing images in photographic layers to form developed images consisting of metal
IPC: G02F1/03
Filed: 1948-10-14
Abstract: 690,476. Physical development processes. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Oct. 14, 1948 [Oct. 17, 1947], No. 26749/48. Class 98 (ii). In a process for producing metal images by physical development of exposed photographic material in which the developer is supplied as two separate solutions stable in themselves, development is caused to proceed continuously, i.e. either a single continuous length or a series of separate pieces on a conveyer is introduced progressively to the treating bath or baths and is afterwards progressively removed therefrom. Preferably development is accelerated by heating either the developer or the material after it has absorbed developer and the material may be sensitized and exposed as a part of a single continuous process in which development comprises one stage. The first developer component may be applied to the exposed material by spraying and the second component by spraying or by means of a roller. If necessary the development may be accelerated by warming the material in moist air, e.g. on a roller having a porous moist covering, or by passing a heating current through a metal band which conveys the material, whereafter the material is washed and dried. The second developer component may be heated prior to application to the material or the heating and washing steps combined by passing the material into hot water. A regenerated cellulose film may be sensitized with a solution of 1-hydroxy 2-diazonium 6- methyl benzene 4-sulphonic acid, mercurous nitrate and nitric acid, dried, exposed and a developer applied by immersion successively in solutions of metol and of silver nitrate or in the reverse order. The film develops almost immediately and is then washed, passed into a bath containing glycerol, and wound up. A similarly sensitized and exposed paper is treated successively with metol and silver nitrate solutions, each containing nitric acid, and is then heated by means of steam or hot air to reduce its development time, or the paper may be developed to a mercury image first with the metol solution and heating, and this then converted to a silver image by the silver nitrate solution. Alternatively a regenerated cellulose film is sensitized by soaking it in silver nitrate followed by soaking in a solution of potassium bromide and nitric acid which has been heated to nearly boiling and then cooled, washed, dried, exposed, and developer is applied in two baths, first one containing silver nitrate and nitric acid and then a metol bath, followed by fixing, e.g. with hypo, and washing. In modifications of the above processes, one of the two physical developer components may be included in the sensitizer. Thus a paper support is sensitized with a solution containing the diazonium compound above-mentioned, mercurous nitrate, and nitric acid, and also includes silver nitrate. The paper is developed with hydroquinone, which may be boiling, or ferrous sulphate. A similarly sensitized regenerated cellulose film is developed with a metol solution containing a wetting agent while a silver bromide regenerated cellulose film prepared as set out above is soaked in a solution of silver nitrate and nitric acid, dried, exposed, and developed with metol, followed by fixing and washing. If desired, any of the physical development processes may be followed by fixing to remove residual silver salts, especially silver chloride produced by the action of washing water containing chlorides on the silver nitrate of the absorbed developer. Specifications 322,430, [Class 98 (ii)], 387,967, 439,005, 484,374, and 545,901 are referred to.