ULTRAVIOLET-LASER IRRADIATION OF THE POLYIMIDE, PMDA-ODA (KAPTON(TM)), TO YIELD A PATTERNABLE, POROUS, ELECTRICALLY CONDUCTING CARBON NETWORK

A beam of continuous-wave ultraviolet (275-363 nm) laser radiation, when focused to a spot such that its intensity is 10-100 kW/cm2, can be used to write a conducting pattern at speeds up to 90 cm/s on the surface of a film of polyimide, PMDA-ODA (Kapton(TM)). Analytical data show that the polyimide loses principally CO, CO2, C2H2 and HCN to give a black material that has C, 96.45, H, 0.29 and N, 2.85%. The product is very light (density about 0.1 g/cm3), porous and has an electrical conductivity of 20-25 S/cm. By the use of appropriate software, conducting patterns have been produced as lines of width as narrow as 15 mum or as uniform areas of up to 2 cm2. Free-standing filaments of the material have also been made. The conductivities of these specimens have not degraded over a period of several months in an ambient atmosphere. Raman spectra of the black material which was produced by raster scanning the laser beam over a PMDA-ODA surface show that the material is predominantly a 'glassy' carbon which is highly crystalline but with small crystallites.