| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method and an apparatus for lithography which prevent field interference between ejecting channels of a recording head and which are capable of meeting digital image data printing a large number of prints of a clear image inexpensively and at a high speed. SOLUTION: A plate material is mounted on a plate cylinder of a press. Based on signals of the image data, the image is formed directly on the plate material by an ink jet method of ejecting oil based ink from the recording head having the ejecting channels in a plurality, by utilizing an electrostatic field, so as to prepare a printing plate. With the plate material used in this state, lithographic printing is executed in succession. When the resolution of rendering on the plate material in the direction of rotation of the plate cylinder is made N (dots/25.4 mm) and the driving frequency of the individual ejecting channel of the recording head f (Hz), in this method for on-press lithography, the ejecting channels of the recording head are driven with the same phase at intervals of (n-1) pieces and, besides, a rotational speed V (mm/s) on the surface of the plate material mounted on the plate cylinder is set as a value described by the following equation. V=25.4×(f×n)/N.</p> |
