Patent ID: 8777438

Claim:
A direct type backlight unit, comprising: an optical film; a diffusion plate, for supporting the optical film; a bottom plate, disposed under the diffusion plate; a plurality of light emitted diodes, disposed between the diffusion plate and the bottom plate; and a plurality of support structures, disposed between the diffusion plate and the bottom plate and fixed on the bottom plate, wherein each support structure is disposed between two adjacent light emitting diodes, a height of each support structure is smaller than a distance between the bottom plate and the diffusion plate, wherein a distance between the bottom plate and the diffusion plate is a cavity height (Hc), a distance between the bottom plate and a top end of the support structure is a support structure height (Hs), a distance between the support structure and the light emitting diode is a spacing (S), wherein the cavity height (Hc), the support structure height (Hs), and the spacing (S) need to satisfy an equation of (Hc−Hs)×S/Hs≧3.5 mm, a surface of the support structure is a polishing surface, a frosting surface, a reflector surface, or a scattering surface, and a cross-section of the support structure is a circle shape, an elliptic shape, a regular polygon shape, an irregular polygon shape, or a saw-tooth shape.