Optical path unit and liquid crystal display device

An optical path unit comprising, in sequence from a light incident direction:

• a light deflecting means;
• a first polarizing plate;
• a liquid crystal cell having a liquid crystal layer provided between a pair of substrates;
• and
• a second polarizing plate, wherein
• the first polarizing plate and the second polarizing plate are disposed such that transmission axes thereof have a crossed Nicols relationship;
• the light deflecting means has two prism films provided on a light incident surface with a plurality of linear prisms having a polygonal and tapered cross section and an endmost vertex angle of 90° to 110° at predetermined intervals;
• the light incident surfaces of the two prism films have a center-line average roughness Ra of 0.3 μm or less and a ten-point average roughness Rz of 1 μm or less;
• and
• one of the prism films is disposed such that a ridge line direction of the linear prisms is substantially in parallel with the transmission axis of the first polarizing plate, and the other prism film is disposed such that a ridge line direction of the linear prisms is substantially in parallel with the transmission axis of the second polarizing plate.