| abstract |
This invention relates to an improvement in a photochemical process for the preparation of printing plates wherein a printing plate comprising a photosensitive composition coated on a support is exposed to a pattern of laser light, the intensity of which light is modulated in accordance with an input source of information, and said printing plate is subsequently developed by removal from said support of that portion of the photosensitive coating composition which is not exposed to said pattern of laser light, the improvement comprising utilizing a pattern of laser light generated by a laser, and utilizing as a photosensitive composition a mixture consisting essentially of: (1) a negative-working condensate of a para-amino benzene diazonium compound present in an effective amount sufficient to sensitize said photosensitive composition to laser light, and (2) a colorant capable of absorbing light in the spectral range between about 450 -550 nm, said colorant selectively sensitizing the condensate to said laser light at a wavelength greater than about 450 nm, and being selected from the group consisting of azo, triarylmethane, xanthene and methine compounds. |