| 摘要 |
A letterpress printing plate in the form of an elongate, looped flexible band having a base layer, as of polyester, and a photosensitive layer. The photosensitive layer is exposed to ultraviolet light through a negative, and its unhardened portions are dissolved away, thereby leaving a printing image and one or two series of markings in relief on the base layer. Typically in the form of annular banks, the markings are arranged at constant spacings along one or, preferably, both sides of the base layer. Perforations are then formed in the base layer through the annular banks thereon. In its use on a web-fed rotary press the looped, perforated printing plate is to be wrapped around a plate cylinder and a guide cylinder spaced therefrom, with its perforations engaged with sprocket teeth on the plate cylinder, for printing the long image on a web against an impression cylinder.
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