Method for producing flexographic printing plates using direct laser engraving

A process for the production of flexographic printing plates which comprises a means of direct laser engraving, in which the starting material used is a laser-engravable flexographic printing element, at least comprising a dimensionally stable substrate and an elastomeric, relief forming layer having a thickness of at least 0.2 mm, and which process comprises at least the following steps:

• (1) engraving of a printing relief in the relief-forming layer with the aid of a laser, the height of the relief elements to be engraved by means of the laser being at least 0.03 mm, and
• (2) cleaning of the resulting printing plate by means of a liquid cleaning agent,
• wherein the cleaning agent comprises at least 50% by weight, based on the amount of all components of the cleaning agent, of one or more components (A) selected from the group consisting of
• (A1) lactones having 5, 6 or 7-membered rings,
• (A2) hydroxymonocarboxylic esters of the general formula R1—COO—R2, where R1 and R2, independently of one another, are a linear or branched alkyl, aralkyl, aryl or alkylaryl radical having 1 to 12 carbon atoms and at least one of the radicals R1 or R2 is substituted by at least one OH group, with the proviso that the esters have 5 to 20 carbon atoms,
• (A3) alkoxymonocarboxylic esters of the general formula R3—COO—R4, where R3 and R4, independently of one another, are a linear or branched alkyl, aralkyl or alkylaryl radical having 1 to 12 carbon atoms, and in which one or more, nonneighboring, nonterminal aliphatic carbon atoms in at least one of the radicals are replaced by an oxygen atom and the remainder can also have a terminal OH group, with the proviso that the esters have 5 to 20 carbon atoms,
• (A4) ketomonocarboxylic esters of the general formula R5-COO—R6, where R5 and R6, independently of one another, are a linear or branched alkyl, aralkyl or alkylaryl radical having 1 to 12 carbon atoms, and in which one or more, nonneighboring, nonterminal aliphatic carbon atoms in at least one of the radicals are replaced by a keto group >C═O, with the proviso that the esters have 5 to 20 carbon atoms,
• (A5) dicarboxylic esters of the general formula R7OOC—R8-COOR7 and/or R7COO—R8-OOCR7′, where R7 and R7′, independently of one another, are linear or branched alkyl radicals having 1 to 4 carbon atoms and R4 is a divalent hydrocarbon radical having 2 to 12 carbon atoms, with the proviso that the esters have 6 to 20 carbon atoms, and where the radicals R7 or R7′ and R8 are optionally further substituted with substituents selected from the group consisting of F, Cl, Br, OH and ═O and/or nonneighboring carbon atoms in the radicals may optionally be replaced by oxygen atoms, and
• (A6) ether alcohols of the general formula R9O—(—R10—O)nH, where n is a natural number from 2 to 5, R9 is H or a straight-chain or branched alkyl radical having 1 to 6 carbon atoms and R10 are identical or different alkylene radicals having 2 to 4 carbon atoms,
• with the proviso that the components (A1) to (A6) each have a boiling point in the range from 150° C. to 300° C.