Patent ID: 7527413

Claim:
A liquid crystal display device comprising a liquid crystal display panel and a backlight disposed on a side of said liquid crystal display panel opposite from a display screen of said liquid crystal display panel; wherein said backlight comprises: a plurality of line light sources arranged in parallel with each other; a transparent optical plate disposed on a side of said plurality of line light sources facing toward said liquid crystal display panel; and a plurality of minute optical controlling elements formed on a surface of said transparent optical plate facing toward said liquid crystal display panel; wherein said plurality of minute optical controlling elements extend in parallel with said plurality of line light sources, and said plurality of minute optical controlling elements are symmetrical in a cross section perpendicular to longitudinal axes of said plurality of line light sources, between two adjacent midplanes each of which passes midway between two adjacent ones of said plurality of line light sources and each of which is perpendicular to said transparent optical plate; wherein said transparent optical plate is formed of a material having a total luminous transmittance in a range of 90% to 100%; wherein each of said plurality of minute optical controlling elements has a triangular cross section in said cross section perpendicular to said longitudinal axes of said plurality of line light sources; wherein let αf be an angle between said liquid-crystal-display-panel-side surface of said transparent optical plate and a first oblique side of said triangular cross section of each of said minute optical controlling elements closer to a plane of symmetry of said minute optical controlling elements formed between said two adjacent midplanes; wherein let θf be an angle between said liquid-crystal-display-panel-side surface of said transparent optical plate and a second oblique side of said triangular cross section farther from said plane of symmetry; and wherein said plurality of minute optical controlling elements between said two adjacent midplanes have αf of a fixed value and θf increasing with increasing distance from said plane of symmetry.