Patent GB-425126-A (GB)
Title: Improvements in or relating to the copying of opaque originals by contact printing
IPC: G03C5/10
Filed: 1933-09-07
Abstract: 425,126. Reproducing opaque originals by diazotype processes. NAAMLOOZE VENNOOTSCHAP CHEMISCHE FABRIEK L. VAN DER GRINTEN, Venlo, Limburg, Holland. Sept. 7, 1933, No. 24836. Convention date, Sept. 14, 1932. [Class 98 (ii)] In a process for making reflex copies by a diazotype process the original to be copied is impinged upon by a radiation after this has passed through the sensitive diazo material, the radiation being divided into small areas of greater and less actinic intensity. Preferably parallel rays are employed. The division of the radiation may be effected by means of a screen, such as one made by ruling cross-lines in a material intercepting actinic rays, placed in close proximity to or in contact with the sensitive sheet. The screen may be applied to or form part of the sensitive sheet and preferably is of such a material that it may be removed mechanically, by washing with solvents, or by combined washing and mechanical action. The sensitive material may be distributed in the form of a screen. In the example shown in Fig. 3, the rays pass through slots b of a screen R laid over the sensitive layer E placed in contact with the original O to be copied. The black parts (indicated by cross-hatching) of the original do not reflect the rays so that only the sensitive material in the path of the rays is decomposed, whereas in the white parts the scattered reflected light decomposes the sensitive material. Fig. 5 shows a screenlike arrangement of the sensitive material E, no separate screen being used. Fig. 7 shows a screen with an upper surface formed with lens-like areas L or with polygonal lenses S. Fig. 8 shows a screen with the upper surface divided into prisms P. In the screens the ratio of the area of the covering parts to the total area of the surface is termed the " covering factor " ; and the breadth of the covering parts expressed in millimeters is termed the coarseness. Examples are given as follows :-I. A crossed line screen obtained from a silver bromide plate of coarseness À1 and covering factor of À6 is placed in contact with a sheet of cellulose acetate having a layer of para-diazoethylbenzyl-aniline, the other side of the sheet being in contact with a printed original. After exposure to an arc lamp at a distance of 30 cm. development is carried out with a thin layer of alkaline solution of an azo dye component to obtain a positive on a colourless background. II. A screen of coarseness À2 and covering factor À8 is made by covering one side of a glass plate with a layer of silver foil and scraping away the silver with a tracing machine to form transparent lines. The sensitive sheet is a gelatine foil coated on both sides with an alcoholic solution of diazo-1- dimethylamino-4-methyl-2 benzene. An alkaline solution of phloroglucinol is used for development. III. A cellulose film is coated on both sides with a diazo-1-dimethylamino-4- benzene solution and a line screening of coarseness À5 and covering factor À8 printed on one side, the material being 6 parts of casein and 6 parts of sugar to 100 parts of water with sufficient aluminium powder to obtain the required covering power. Radiation is carried out by a mercury-vapour lamp, the screened side of the sensitive sheet being towards the lamp. The sheet may be exposed before use to a preliminary radiation with the screen side towards the source and an absorbing background on the other side. IV. A thin celluloid film is formed on one side with cylindrical lenses of radius À03 mm. with focal lines separated by distances of À04 mm. and the other side coated with para-diazo-diphenylamine. V. A transparent carrier sensitized in the mass with diazo-1-diethylamino-4-benzene is placed in contact with a screen of coarseness of À1 and covering factor À8 and irradiated through the screen with a black absorbing background on the other side before being used for copying an original. VI. A transparent sheet coated on both sides with para-diazo-diphenylamine is perforated with oblong openings of 1 cm. in length and À1 mm. in breadth with intermediate spaces of À1 mm. The series of lines may be staggered. The Specification as open to inspection under Sect. 91, describes the use with the example III of a transparent film between the sensitive film and the original to be copied. This subject-matter does not appear in the Specification as accepted.