Manufacturing method for planographic printing plate for color printing - Patents

Manufacturing method for planographic printing plate for color printing

Patent Agent: Sughrue Mion, Pllc - Washington, DC, US
Patent Inventors: Fumikazu Kobayashi, Toshiharu Masuda
Applicaton #: 20070051261
Class: 101401100 (USPTO)
Related Patents: Printing, Printing Members, Blanks And Processes
03/08/07

The invention provides a method for forming planographic printing plates for color printing using a plurality of hues. The method includes at least: image-forming using an amplitude modulation screen only for a planographic printing plate used for printing black color used on a first drum of a printing machine; and image-forming using a frequency modulation screen for a planographic printing plate other than the planographic printing plate used for the first drum. The amplitude modulation screen preferably has a dot line number of 300 or less. The frequency modulation screen preferably has a dot size of 30 ¨µm or less. The planographic printing plates prepared in accordance with the method are preferably used for four-color printing of yellow, magenta, cyan and black.
SUMMARY OF THE INVENTION
[0009] The invention provides a method for manufacturing a planographic printing plate for color printing capable of suppressing defective transfer of the ink caused by transfer of ink components printed by a preceding drum onto the blanket of the second drum or thereafter, particularly onto the blanket of the final drum, during color printing, in order to print a high quality color image on a large number of printing sheets.
[0010] The invention has been completed by finding that in order to form a high quality image defective transfer of the ink can be suppressed by selectively using an FM screen, which is important for forming the high quality image, and an AM screen according to the hue to be printed.
[0011] Namely, the invention provides a method for forming planographic printing plates for color printing using a plurality of hues, comprising: image-forming using an amplitude modulation screen only for a planographic printing plate used for printing black color used on a first drum of a printing machine; and image-forming using a frequency modulation screen for a planographic printing plate other than the planographic printing plate used for the first drum.
[0012] In conventional full color printing, for example, a planographic printing plate for printing cyan, magenta and yellow colors, and other characteristic colors used when necessary, is manufactured using only an FM screen, and only the planographic printing plate used for the first drum, usually a drum for a black printing plate, is manufactured using an AM screen. This method allows the problem of defective color transfer in color printing to be solved without deteriorating the characteristics of the FM screen such as excellent reproducibility of the color, and enables stable printing.
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