light the individual spectral lines are then passed to a two dimensional ccd chip 7 as photodetector which is used to measure the band intensity different depths can be established by changing the distance between sample and objective with an analogous setup of the measurement apparatus it is also possible to determine the depth resolved degree of crosslinking of psa films by confocal fluorescence spectroscopy for this purpose the light source in the apparatus according to fig1 is judiciously a uv light source and a cutoff filter is advantageously used in place of the notch filter 2 evaluation of the fluorescence emission spectrum of the sample can be made conventionally in analogy to the above described raman spectroscopy the adhesive properties of two dimensional substrates having a psa film can be detected by measuring the shear strength as a measure of the cohesion and the peel strength as a comprehensive measure of cohesion and adhesion for the purposes of testing polyethylene terephthalate or aluminum sheets are coated with a psa film so as to give a dry film thickness of from 25 to 80 u03bcm for the testing of solvent free hotmelt psas polyethylene terephthalate sheets are coated with the psa compositions on a heated coating bench at from 85 to 120 u00b0 c to give a film thickness of about 25 u03bcm where copolymer solutions are employed for the test the solvents are evaporated off at 70 u00b0 c and 1 bar for 1 minute the coated and dried sheets are irradiated with the light from medium pressure mercury.