A backlight unit, comprising: a substrate; and at least one light assembly separately located on the substrate, wherein the light assembly comprises: a light source; and a lens configured to shield an upper surface and a side surface of the light source, wherein the lens comprises: a first portion separately located on the upper surface of the light source, wherein the first portion refracts light emitted from the light source; and a second portion separately located at the side surface of the light source; wherein the first portion comprises: a convex portion having hemisphere shape protruded upward; and a side portion extended from a lower portion of the convex portion and having a low surface facing the upper surface of the light source, wherein the low surface comprises a flat-shaped portion; wherein the second portion comprises: an inner portion facing the side surface of the light source and being inclined with respect to the side surface of the light source such that the inner portion reflects light from the light source toward the low surface of the first portion of the lens, and wherein the second portion includes a plurality of protrusions on the inner portion of the second portion. a substrate; and at least one light assembly separately located on the substrate, wherein the light assembly comprises: a light source; and a lens configured to shield an upper surface and a side surface of the light source, wherein the lens comprises: a first portion separately located on the upper surface of the light source, wherein the first portion refracts light emitted from the light source; and a second portion separately located at the side surface of the light source; wherein the first portion comprises: a convex portion having hemisphere shape protruded upward; and a side portion extended from a lower portion of the convex portion and having a low surface facing the upper surface of the light source, wherein the low surface comprises a flat-shaped portion; wherein the second portion comprises: an inner portion facing the side surface of the light source and being inclined with respect to the side surface of the light source such that the inner portion reflects light from the light source toward the low surface of the first portion of the lens, and wherein the second portion includes a plurality of protrusions on the inner portion of the second portion. a light source; and a lens configured to shield an upper surface and a side surface of the light source, wherein the lens comprises: a first portion separately located on the upper surface of the light source, wherein the first portion refracts light emitted from the light source; and a second portion separately located at the side surface of the light source; wherein the first portion comprises: a convex portion having hemisphere shape protruded upward; and a side portion extended from a lower portion of the convex portion and having a low surface facing the upper surface of the light source, wherein the low surface comprises a flat-shaped portion; wherein the second portion comprises: an inner portion facing the side surface of the light source and being inclined with respect to the side surface of the light source such that the inner portion reflects light from the light source toward the low surface of the first portion of the lens, and wherein the second portion includes a plurality of protrusions on the inner portion of the second portion. a first portion separately located on the upper surface of the light source, wherein the first portion refracts light emitted from the light source; and a second portion separately located at the side surface of the light source; wherein the first portion comprises: a convex portion having hemisphere shape protruded upward; and a side portion extended from a lower portion of the convex portion and having a low surface facing the upper surface of the light source, wherein the low surface comprises a flat-shaped portion; wherein the second portion comprises: an inner portion facing the side surface of the light source and being inclined with respect to the side surface of the light source such that the inner portion reflects light from the light source toward the low surface of the first portion of the lens, and wherein the second portion includes a plurality of protrusions on the inner portion of the second portion. a convex portion having hemisphere shape protruded upward; and a side portion extended from a lower portion of the convex portion and having a low surface facing the upper surface of the light source, wherein the low surface comprises a flat-shaped portion; wherein the second portion comprises: an inner portion facing the side surface of the light source and being inclined with respect to the side surface of the light source such that the inner portion reflects light from the light source toward the low surface of the first portion of the lens, and wherein the second portion includes a plurality of protrusions on the inner portion of the second portion. an inner portion facing the side surface of the light source and being inclined with respect to the side surface of the light source such that the inner portion reflects light from the light source toward the low surface of the first portion of the lens, and wherein the second portion includes a plurality of protrusions on the inner portion of the second portion.