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1. WO2007099025 - PLAQUES LITHOGRAPHIQUES POSITIVES

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

[CLAIMS]

1) A positive-working lithographic printing plate precursor
comprising on a grained and anodized aluminum support having a hydrophilic surface a coating comprising:
(i) an infrared absorbing agent and at least one colorant;
(ii) a first layer comprising a heat -sensitive oleophilic resin, (iii) and a second layer between said first layer and said hydrophilic support wherein said second layer comprises a polymer comprising at least one monomeric unit that comprises at least one sulfonamide group;
characterized in that the surface of said grained and anodized aluminum support has a mean pit depth equal or less than 2.2 μm.

2) A printing plate precursor according to claim 1 wherein the mean pit depth is equal or less than 2.0 μm.

3) A printing plate precursor according to claims 1 or 2 wherein the
2
mean pit area is equal or less than 25 μm .

4) A printing plate precursor according to any of the preceding claims wherein the mean pit volume is equal or less than 55 μm .

5) A printing plate precursor according to any of the preceding claims wherein the monomeric unit that comprises at least one sulfonamide group is represented by the following formula (I) :



formula ( I )
wherein:

R represents hydrogen or a hydrocarbon group having up to 12 carbon atoms ;
2 3
R and R independently represent hydrogen or a hydrocarbon group;

s X represents a single bond or divalent linking group;

Y is a bivalent sulphonamide group represented by -NR -SO2- or
k i k
-SO2-NR - wherein R and R each independently represent hydrogen, an optionally substituted alkyl, alkanoyl, alkenyl , alkynyl, cycloalkyl, heterocyclic, aryl , heteroaryl, aralkyl or heteroaralkyl
2 2
0 group or a group of the formula -C (=N) -NH-R , wherein R represents hydrogen or an optionally substituted alkyl or aryl group;
Z represents a terminal group or a bi-, tri- or quadrivalent linking group wherein the remaining 1 to 3 bonds of Z are linked to

Y .

5 6) A printing plate precursor according to any of the preceding
claims wherein the coating further comprises a barrier layer
above said first and second layer, comprising a development
inhibitor selected from the group consisting of

- a water-repellent polymer or copolymer;
0 - a bifunctional compound comprising a polar group and a hydrophobic group; or
- a bifunctional block-copolymer comprising a polar block and a hydrophobic block.

7) A printing plate precursor according to claim 6 wherein the 5 bifunctional compound comprising a polar group and a hydrophobic group is a surfactant and is present in an amount ranging from 10
2
to 100 mg/m relative to the coating weight.

8) A printing plate precursor according to claim 7 wherein the
bifunctional block-copolymer comprises a poly- or oligo (alkylene oxide) block and a hydrophobic block such as a long chain
hydrocarbon group, a poly- or oligosiloxane and/or a
s perfluorinated hydrocarbon group.

9) A printing plate precursor according to claim 8 wherein the
amount of the bifunctional block-copolymer is between 0.5 and 25 mg/m2 relative to the coating weight.

10) A method for making a positive-working heat-sensitive o lithographic printing plate comprising the steps of
(i) providing a printing plate precursor according to any of the preceding claims,
(ii) image-wise exposing said precursor to heat and/or IR-light, and
s (iii) developing said exposed precursor with an aqueous alkaline developing solution thereby removing the coating at the exposed areas while essentially not affecting the coating at the non- exposed areas .

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