Novel direct‐view LED backlight unit with an aspheric microlens array and a rough‐texture sheet

Abstract— This study proposes a novel direct‐view light‐emitting‐diode (LED) backlight unit with a high‐fill‐factor aspheric microlens array and a rough‐texture sheet. An aspheric microlens array and a rough‐texture sheet made from polysiloxine were used as the grating element and optical diffuser, respectively, which increases light‐extraction efficiency and improves luminance uniformity. The specific aspheric microlens‐array mold was fabricated by using a heating encapsulated air process based on a glass wafer. This microlens array has the features of high fill factor and square‐foot boundary with a continuous surface‐relief profile. This unique out‐of‐plane surface profile creates a square light pattern with uniform luminance, and thus composes a uniform large‐sized light pattern exactly in accordance with the layout of the LED array. The rough‐texture sheet, which can scatter light uniformly, was formed by fine‐grit‐sandpaper molding. Experimental results show that by using an aspheric microlens array and rough‐texture sheet reported here as the backlight diffusing components is highly effective in improving light uniformity at a wide viewing angle. An increase in illuminance by more than 10% was achieved in comparison with commercial backlight modules. Low cost in fabricating the aspheric microlens array and rough‐texture sheet is anticipated due to the simplicity of the process.