Patent ID: 8760602

Claim:
A backlight device comprising: a light guiding plate having a light-emitting surface, a rear surface facing in a direction opposite that of said light-emitting surface, and side surfaces interconnecting the light-emitting surface and the rear surface; one or more concave portions formed into said rear surface and extending toward said light-emitting surface; and a light-emitting diode light source arranged within each of said one or more concave portions, wherein, at least (i) said light-emitting surface, (ii) said side surfaces of said light-guiding plate, and (iii) said rear surface of the light-guiding plate are configured as a reflective-angle modified portion comprising a rough reflective surface with minute convexities and concavities distributed uniformly across a whole surface of (i) said light-emitting surface, (ii) said side surfaces of said light-guiding plate, and (iii) said rear surface of the light-guiding plate but excludes surfaces of the one or more concave portions, wherein said reflective-angle modified portion modifies a reflective angle of light emitted from said light source so that light within the light-guiding plate having an angle of incidence with respect to the light emitting surface that is greater than a critical angle is reflected back from the light-emitting surface while light within the light-guiding plate having an angle of incidence with respect to the light-emitting surface that is equal to or smaller than the critical angle transmits through the light-emitting surface, the critical angle being that angle at which light totally reflects from said light-emitting surface, wherein the reflective-angle modified portion modifies light incident on the light-emitting surface such that light beams incident on the light-emitting surface have an angle different from a previous angle of incidence on the light-emitting surface; and wherein the backlight device further includes a reflective film on each of the side surfaces and the rear surface that is operable to reflect light transmitted through the rough reflective surface.