New half-tone lithography uses for FPD proximity printing

Liquid Crystal Displays (LCDs), which are the current prevalent displays, can be roughly separated into two modules. Of these, the Color Filter (CF) module is frequently manufactured using a proximity exposure system also known as proximity printing, which offers relatively lower resolution and higher throughput. This is because the CF only functions as an optical filter and so only requires rough patterning with the width of large sub-pixel units. However, due to the recent rapid shrinkage of pixel units, the productivity of CF is worsening. This is particularly evident in Black Matrix (BM), which requires finer patterns than for other CF layers and therefore is becoming a bottleneck preventing the progress of displays, especially for manufacturers who have only proximity printing equipment. We demonstrated that it is possible to achieve practical optical image miniaturization in FPD lithography via the appropriate use of Half-Tone (HT) exposure which suppresses the light intensity, as per the Fresnel diffraction theory which governs proximity printing. Two desirable results were subsequently obtained in tests using actual BM processes: stable formation with fine BM lines of less than 6μm width, and an improvement in the corner shape using sub-resolution HT features.