A method of surface treating a polyimide film to impart improved adhesion to metal which comprises treating the surface of a polyimide film having a biphenyltetracarboxylic acid component by contact to a solution containing potassium permanganate andor sodium permanganate and potassium hydroxide andor sodium hydroxide and treating said surface with an acid. The backlight assembly includes a light source unit having a light source emitting light and a fixing member fixing the light source unit. The frame can include a first ear stem and a second ear stem that allows the frame to be worn on the wearer’s head.