Patent GB-544132-A (GB)
Title: Method of and means for producing colour separation records for colour photographic and photo-mechanical processes
IPC: G03F3/04
Filed: 1940-06-19
Abstract: 544,132. Photographic and photomechanical colour processes. KODAK, Ltd. (Eastman Kodak Co.). June 19, 1940, No. 10597. Drawings to Specification. [Class 98 (ii)] [Also in Group XL] A coloured original is painted with paints containing fluorescent ingredients whose fluorescences are separable in three spectral bands, and the red, green and blue colour separation records 'for photographic or photo-mechanical reproduction are made solely by means of the fluorescent light emitted in these bands when the picture is illuminated by fluoro-activating light. Each spectral band is used for recording one colour, the brighter the contents of such colour in the hue of a paint, the brighter being the fluorescence of the paint in the spectral band used for recording this colour. Colour separation positives may be made directly by recording the subtractive colour contents in the hues of the paints, i.e. the amounts of yellow, magenta, and bluegreen which subtractively produce the hues. For this purpose the three spectral bands A, B, C are used respectively for recording the subtractive colours yellow, magenta and blue-green, so that paints of these colours used in printing the original will fluoresce only in bands A, B, C respectively. A blue paint, which must record in the magenta and blue-green separation positives, must fluoresce in bands B and C but not in A; similarly a green paint fluorescing in bands A and C but not in B, and a red paint fluorescing in bands A and B but not C may be employed. White paint must fluoresce in none of the bands, and black in all three, unless a separate black printer is made as described below. The actual amounts of any one fluorescent ingredient employed in a paint depends on its fluorescent efficiency in that paint, some pigments absorbing the activating or the fluorescent light, or both, more than others. The light-source used for illuminating the original may be an ultra-violet arc with a filter to absorb visible light. Each of the three separation records is taken through a filter which absorbs all reflected and all fluorescent light other than that in the band representing the colour to be recorded. Alternatively, one of the records may be made by using a light source which causes only one of the fluorescent ingredients to fluoresce. For aqueous paints the fluorescent ingredients are preferably non- volatile, water-soluble, pulverable materials of relatively low optical density to its own visual colour and of high density to ultra-violet light. Suitable materials for use with a mercury-vapour lamp are chrysene, anthracene or chrysene with a trace, e.g. 1 per cent, of naphthacene, and Rhodamine G precipitated with a water-insoluble gum or resin. Chrysene when illuminated through a filter (e.g. of Corning Glass Co. No. 584) to cut off the visible light fluoresces with a violet light of about 400 to 450 millimicrons wavelength. A filter made of two "Wratten" (Registered Trade Mark) filters No. 3A and 2A transmitting this wave-band wholly or partially may be used in the optical system of the camera, together with a red absorbing filter unless the emulsion is orthochromatic or blue-sensitive. Anthracene with 1 per cent naphthacene similarly illuminated fluoresces in the green region from about 500 to 600 millimicrons, and a "Wratten" 61 filter may be employed to isolate this band. An alternative green fluorescent material consisting of chrysene recrystallized with 1 per cent naphthacene is described in Specification 542,006, [Group XL]. One per cent Rhodamine G illuminated by the mercury-vapour lamp without a filter fluoresces in the 600 to 700 millimicron band, and a Wratten No. 25 filter may be used with it. A table is given giving the quantitative composition of a pallette of colours for painting the originals. Blue-green, yellow, and magenta consist respectively of Patent Blue V Lake with chrysene Hansa yellow with anthracene containing 1 per cent naphthacene, and a mixture of Rhodamine B Lake and Goluidine Red with gum sandarac containing Rhodamine G, together in each case with silicon dioxide and Blanc Fixe (BaSO 4 ). Green consists of Brilliant Green and Rhodamine Lake with chrysene and anthacene with 1 per cent naphthacene. Orange red and light orange red consist of Hansa Yellow and Toluidine Red with gum sandarac containing Rhodamine G and anthracene containing 1 per cent naphthacene together with silicon dioxide and Blanc Fixe. Other colours are made by mixtures of these colours. In cases where a separate black record is made, the black paint contains no fluorescent material, and all the paints except black absorb infra-red light. An additional separation negative for the black printer is made by infra-red light, from incandescent tungsten for example. Thus a pen drawing may be made in black with colour washes and after the three colour records have been made a fourth exposure is made by tungsten light through a " Wratten " 38A filter on a high contrast infra-red sensitive plate, this recording only the black lines. From the four records printing plates may be prepared in the usual way. The process avoids the necessity for colour correction, and allows correct colour positives for photogravure and collotype to be made in a single step. Specifications 506,581 and 517,265 also are referred to.