Composite polyester films and their use as protective layers for photopolymer plates, and photopolymer plates comprising said films
AssigneeRhone-Poulenc Films
InventorsJean-Pierre Assante, Philippe Corsi, Didier Veyrat
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Abstract
The invention relates to semicrystalline biorientated composite polyester films comprising a thick filled or unfilled layer and, on at least one of the faces of the layer (A), a coextruded polyester layer (B) whose thickness is less than that of the layer (A) and which has the following characteristics: Rt.ltoreq.3 .mu.m Rt/Ra.ltoreq.10 and contains a filler having the following characteristics: mean diameter D 50=1.5 to 2.5 .mu.m monodispersity I=D 75-D 25.ltoreq.1.2 These films can be used as protective sheets for the photopolymerizable layer of photopolymerizable elements.
Claims14
Semicrystalline biaxially oriented composite polyester film comprising a filled or unfilled polyester layer (A) and, on at least one of the faces of the layer (A), a coextruded polyester layer (B) whose thickness is less than that of the layer A, wherein the layer (B) has the following surface characteristics:
- (a) total roughness Rt.ltoreq.3 .mu.m;
- (b) peak density Rt/Ra.ltoreq.10 where Ra is the mean deviation roughness, and contains from 5 to 35% by weight of a filler having the following characteristics:
- (i) mean diameter D 50=1.5 to 2.5 .mu.m
- (ii) monodispersity I.ltoreq.1.2 .mu.m.
A method of using the semicrystalline biaxially oriented composite polyester film according to 1, 2, 3, 4, 5 or 6, as protective sheets for the photopolymerizable layer of photopolymerizable element for a printing plate by placing a face of the film containing layer (B) in contact with the photopolymerizable layer.
Photopolymerizable elements for a printing plate comprising at least one assembly which comprises a carrier, a photopolymerizable layer and a protective film, wherein the protective film comprises a coextruded biaxially oriented composite polyester film according to 1, 2, 3, 4, 5 or 6 and further wherein a face with of the film containing layer (B) is in contact with the photopolymerizable layer.
Photopolymerizable elements for a printing plate comprising two assemblies each comprising a carrier and a photopolymerizable layer, wherein the two photopolymerizable layers are separated by a protective sheet comprising a semicrystalline biaxially oriented composite polyester film according to 1, 2, 3, 4, 5 or 6, which has a layer (B) on each face of the layer (A).
Photopolymerizable elements for a printing plate comprising at least three assemblies each comprising a carrier, a photopolymerizable layer and a protective sheet, wherein each photopolymerizable layer of the element is separated from an adjacent photopolymerizable layer by a composite polyester film according to 1, 2, 3, 4, 5 or 6, in which layer (B) is on only one of the faces of the layer (A).
Dependencies are inferred from the claim text.