| abstract |
An object of the present invention is to provide optical sheets having excellent heat resistance, moisture resistance, thermal dimensional stability and weather resistance, which hardly give rise to bending, yellowing and the like even though they receive generated heat from a lamp and ultraviolet ray irradiation, and to provide backlight units in which reduction of the occurrence of lack in uniformity of the brightness and lowering of the brightness is achieved using the optical sheet. The optical sheet of the present invention has a transparent substrate layer, and an optical layer overlaid to the front face side of the substrate layer. This optical layer includes a light diffusing agent in the binder. This binder is formed from a polymer composition containing (A) a copolymer and (B) a fine inorganic filler. This copolymer (A) includes at least one of a recurring unit derived from a (meth)acrylic ester having a cycloalkyl group, a recurring unit derived from an iso-butyl (meth)acrylate or a recurring unit derived from a tert-butyl (meth)acrylate. |