Heat Affected Zone Analysis of Flexible OLED Display Film by Photoluminescence and Raman Imaging Microscopy

Abstract

The impurities and heat affected zones (HAZ) in flexibl e organic light emitting diode (OLED) display films were measure d using Raman imaging and photoluminescence (PL). The flexible OLED display is a relatively thin, multi-layer structure of highly complex materials. A multi-layer film of polyethylene terephthala te (PET) and polyimide (PI) with an adhesive is a key component of flexible structures that replace rigid glass substrates. Recently, laser cutting is the most common method for the processing of mu lti-Iayer polymers. In this study, a confocal line imaging Raman microscope was operated at 532-nm and 785-nm, a max power of 500-mW, with 400 × 1340 pixels with a TE cooled CCD. A sample area of 80 μm x 80 μm can be measured within 5 min with 100 x magnification lens with a 1 sec exposure time at a resolution of 20 0nm pixels via line imaging technology. Raman imaging spectros copy and PL were performed to measure the HAZ and impurities at the surface as well as inside the multi-layer films. The most do minant impurities were carbon and adhesives which may have ori ginated from an adhesive layer between two polymer films. Impu rities near the laser cutting zone were identified as the thermal ch anges of PET and PI materials themselves by Raman imaging an d PL. The PL intensity increased as the thermal effect on PI and PET increased.