With their sleek design and small footprint flat LCD screens are rapidly becoming the format of choice for televisions and monitors.
However, the manufacture of LCDs is a complex process, where the active substrates and the colour filters in a number of phases are arranged on the front and back of glass sheets. In most cases, 4-6 displays are produced on one glass plate.
It is crucial to identify even the smallest error in the plate or to detect the applied layers of quality control LCDs for trouble-free operation.
Microscopy is a key tool in the examination of LCD screens as techniques such as brightfield, differential interference contrast and interferometry provide the means to produce the high contrast images needed to spot small imperfections in the deposition layers, detect minute scratches on the glass screens and check the integrity of color filters.
Digital imaging technology enables record keeping and creates an audit trail for QC purposes.
Key techniques for QC in LCD manufacturing include: brightfield illumination; darkfield illumination; Nomarski DIC; diascopic illumination; episcopic illumination; digital imaging.