Agfa-gevaert

August Meisters

Luc H Leenders

Ludo Van Rompuy

A negative working non-ablative lithographic printing plate precursor is provided which includes a metal support such as an anodized aluminum plate and provided thereon a layer or a stack of layers, wherein at least one layer includes a near infrared light absorbing compound which is the main component of the layer(s). As the amount of other reactive compounds besides the near infrared light absorbing compound is less than 20% by weight, excellent-storage stability is obtained. In a highly preferred embodiment the layer or stack of layers is substantially free from the other reactive compounds. The material is very suitable for computer-to-plate and computer-to-press applications as it can be used as a printing master directly after exposure or may be processed by rinsing with plain water.

Thermal lithographic printing plate precursor with excellent shelf life

A method is provided for preparing a negative working lithographic printing plate precursor by applying a dry powder, containing a light absorbing compound in an amount not less than 50% by weight, on a metal support such as an anodized aluminum plate. The light absorbing compound is preferably carbon, soot or an infrared dye. In one embodiment of the invention, the dry powder may be rubbed in on the surface of the metal support. In another embodiment a layer of soot is applied on the metal support by contacting the surface of the support with a flame. In still another embodiment, a metal support is contacted with a transfer material consisting of a support and a dry layer of a light absorbing compound such as carbon. By applying heat or light, the dry powder is converted into a hydrophobic substance at the printing areas of the plate. The materials obtained by these methods are very suitable for computer-to-plate and computer-to-press applications as they can be processed by applying plain water, ink or fountain solution. Since the dry powder is preferably free from other reactive compounds besides the light absorbing compound, the materials are characterized by an excellent stability.

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Gentbrugge, Belgium

August Meisters