Fabrication of anti-moiré filters using hollow glass microspheres by slot-die coating.

When photographing a display panel with a digital camera, moire' fringes appear due to the interference between the black matrix (BM) of the display panel and the grid line in an image sensor of the digital camera. With an attempt to suppress the moire' effect, we have fabricated rigid and flexible anti-moire' filters by large-area uniform coating of hollow glass microspheres (HGMs) using table and roll slot-die coaters. It is addressed that the manifold volume of the slot-die head is critical for uniform coating of non-aqueous solutions with micrometer-sized particles added. Such an anti-moire' filter is shown to suppress the moire' phenomenon (aliasing) to a great extent by breaking the periodicity of the panel, which is induced by light diffusion. To quantify the moire' strength, we have calculated the brightness ratio from the measured moire' patterns. In the presence of the filter with 7 wt% HGM, the brightness ratio of an ultra-high-definition TV is decreased from 123.79 % to 103.5 %, indicating that the moire' phenomenon is considerably suppressed. It is also found that the moire' suppression capability of the filter depends sensitively on the BM structure (i.e., the narrower the BM, the weaker the moire' fringes), which is in qualitatively good agreement with simulation results by ray tracing algorithm.