Joining the cut edges of photopolymerized flexographic printing plates

A method for joining the edges, which have been cut to size, of photopolymerized flexographic printing plates, which have relief layers and dimensionally stable base films, on printing cylinders comprising the following steps:

• (i) fixing the printing plates to make-ready cylinders by means of a first double-sided self-adhesive adhesive film having the same area as the printing plate,
• (ii) cutting the printing plates to size so that they fit the printing cylinders,
• (iii) removing the printing plates, which have been cut to size, from the make-ready cylinders and from the first self-adhesive films,
• (iv) fixing the printing plates which have been cut to size, by means of a second double-sided self-adhesive film, which has the same area as the printing plates and from 1.6 to 2.6 times the thickness of the first self-adhesive films to the printing cylinders, so that defined gaps result between the edges of the fixed printing plates,
• (v) filling the gaps between the edges to be joined, with a liquid photopolymerizable mixture consisting essentially of binders, photopolymerizable monomers which are compatible with these and photopolymerization initiators and
• (vi) partially polymerizing the mixture under a film cover which is transparent to light, by exposure to UV light until the elongation at break in the composite consisting of the solid gap closing compound and the printing plate material fulfils the condition
• R.sub.S <R.sub.S/F <<R.sub.F
• where
• R.sub.S is the elongation at break of the partially polymerized gap closing compound,
• R.sub.S/F is the elongation at break in the interface between the gap closing compound and the printing plate material and
• R.sub.F is the elongation at break of the printing plate material.