Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M1/00—Inking and printing with a printer's forme
  • B41M1/14—Multicolour printing
  • B41M1/18—Printing one ink over another
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F3/00—Colour separation; Correction of tonal value
  • G03F3/04—Colour separation; Correction of tonal value by photographic means

Definitions

• the inventive method of color printing half-tone work is characterized by the use of plates or the like representing the combined blue and black components of the work, the combined red and black components of the work, and the combined yellow and black components of the work, the halftone work of the red, blue and yellow components having their dot sizes reduced sufficiently before combination with the black component such that the half-tone work is clearly reproduced in the required colors in the print.
• the method is also:characterized by the use of rubine red, a suitable process blue anda transparent process yellow (or equivalent inks).
• the invention provides a color printing method for forming a print including half-tone work and preferably including line work comprising separating the work into its primary red, primary blue, primary yellow and black components in any suitable manner, reducing the dot'sizes of the half-tone work in the primary color components such that the half-tone work is clearly reproduced in the required colors in the finished print, combining the separated black component with each of the separated primary color components and producing red/black, blue/black and yellow/- black combination plates or the like, and forming a print using said combined plates with rubine red ink, a suitable process blue ink and a transparent process yellow ink (or equivalent inks).
• the blue ink may be concentrated process blue or any other suitable blue ink.
• the method of the invention is based on the use of combination black/primary color plates or the like and the approximation of black line work by suitable balancing the primary color inks.
• the inks used are as follows:
• register marks are included on the copy prior to photography.
• Screen positives are prepared by use of a process screen enlarger using grey or magenta contact screens; the following screen angles are recommended: yellow red 45, blue and black 75. 1
• the screen ruling to be used is lines per inch, the yellow, red and blue positives are made with this screen and the black is made using a 133 screen ruling. Alternatively, using a 133 ruling for the three colors, the black will then be made on a 150 ruling.
• a normal set of screen positives for the yellow, red and blue are made.
• the black positive can be slightly flatter than normal; the reason for this will be apparent because of combining methods used.
• the dot etching will be increased slightly to enable the printer to increase the ink density readings above normal to achieve the best blacks.
• the increased etching found necessary is approximately: yellow 4-6% red 8 to 10% and blue 8 to 12%. This can vary with experience and will depend to some extent on the stock the job will be printed on. Any line work present is not etched.
• the black positive is then combined by registering carefully on to the back of the color positives and contacted to negative.
• the black positive will be out of contact by the thickness of the film used, normally 0.004 of an inch, but by experience and the use of a point source light, and having made a slightly lower contrast black positive, the gain in contrast can be controlled.
• the three color/black set of negatives are used to produce a proof and etching corrections can be made at this stage. A final set of positives will then be contacted from these negatives.
• the black screen positive is combined with the line type etc. prior to the final combination with the yellow, red and blue positives.
• the three combination plates produced as described above are used in the normal manner to print a four color job using the three primary inks defined above. It is preferred that the job is printed in the order blue, red and yellow. This allows the blue and red to fuse properly with the transparent yellow and ensures that no one color dominates, thus achieving black half-tone and line work closer to the spectrum than with conventional colors.
• the number of passes required to achieve the final print depends on the type of machine used but it will be appreciated that one pass and/or one deck will be saved by the present method. Thus, if a two color press is used, the second pass leaves one deck free for varnishing, special background or other special color, or any other suitable purpose. A three color press will produce a four color print in one pass while four or five color presses have one and two decks left free for any one of the above mentioned purposes.
• the resulting print includes line work which closely approximates black and includes half-tone. work having greater color depth and three dimensional properties.
• the better quality of the half-tone work is believed to be due to the fact that the usual black shading, which tends to mask the colors, is replaced by three balanced primary colors applied through the black part of the combined plates giving a pure color effect rather than a masking effect.
• An improved method of preparing half-tone combination primary color and black printing plates and using said plates in a half-tone primary color printing process including black line work where the black color is approximated by balancing the primary color components of the print and where the printing process involves using three primary color printing passes only, in a manner known generally per se, comprising, as the improvement, the steps of:

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Printing Methods (AREA)

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Cited By (12)

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Citations (4)

• 1974
  • 1974-04-10 JP JP4063274A patent/JPS557835B2/ja not_active Expired
  • 1974-04-11 US US460056A patent/US3926117A/en not_active Expired - Lifetime

Patent Citations (4)

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