Importance

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Abstract

A lithographic printing plate precursor comprises an electrochemically grained aluminium substrate, the grained surface of which is coated with a layer of gel-like amorphous colloidal oxides and hydroxides of aluminium and their hydrates incorporating metallic aluminium and inter-metallic aluminium alloys--generally at a level of below 5%--this layer being produced during the electrochemical graining process. The layer is typically present in an amount of from 0.1-20 g/m.sup.2 and at a layer thickness of 0.1-4.0 .mu.m, the particle sizes in the said layer generally falling in the range of from 10 to 2000 nm. Methods are disclosed for the preparation of said precursors via the electrochemical graining of aluminium substrates. The invention provides lithographic printing plate precursors which may be imagewise exposed by means of a high intensity laser beam to provide printing plates showing high durability on press and giving images which show good resolution and are free from background staining.

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First Claim