(19)
(11) EP 0 908 307 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
29.12.1999 Bulletin 1999/52

(43) Date of publication A2:
14.04.1999 Bulletin 1999/15

(21) Application number: 98203122.1

(22) Date of filing: 16.09.1998
(51) International Patent Classification (IPC)6B41C 1/10, B41M 5/36
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 08.10.1997 EP 97203131

(71) Applicant: AGFA-GEVAERT N.V.
2640 Mortsel (BE)

(72) Inventors:
  • Van Damme, Marc
    2640 Mortsel (BE)
  • Vermeersch, Joan
    2640 Mortsel (BE)
  • Deroover, GEERT
    2640 Mortsel (BE)

   


(54) A method for making positive printing plates from a heat mode sensitive imaging element


(57) According to the present invention there is provided a method for making lithographic printing plates including the following steps

a) preparing a heat mode imaging element having on a lithographic base with a hydrophilic surface a first layer including a polymer, soluble in an aqueous alkaline solution and a top layer on the same side of the lithographic base as the first layer which top layer is sensitive to IR-radiation and is unpenetrable for an alkaline developer containing SiO2 as silicates;

b) exposing imagewise said heat mode imaging element to IR-radiation;

c) developing said imagewise exposed heat mode imaging element with said alkaline developer so that the exposed areas of the top layer and the underlying areas of the first layer are dissolved and the unexposed areas of the first layer remain undissolved characterized in that said top layer includes an IR-dye in an amount between 1 and 100% by weight of the total amount of said IR-sensitive top layer selected from the group consisting of indoaniline dyes, cyanine dyes, merocyanine dyes, oxonol dyes, porphine derivatives, anthraquinone dyes, merostyryl dyes, pyrylium compounds, diphenyl and triphenyl azo compounds and squarylium derivatives.







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