Patent ID: 6961106

Claim:
A retardation optical element having a function of reflecting ultraviolet light, comprising: a first retardation layer that has a cholesteric liquid crystalline molecular structure and acts as a negative C plate; and a second retardation layer laminated to the first retardation layer, the second retardation layer having a cholesteric liquid crystalline molecular structure and acting as a negative C plate, wherein the first and second retardation layers are made so that a direction of twisting of liquid crystalline molecules in the first retardation layer is opposite to that of twisting of liquid crystalline molecules in the second retardation layer, that at least part of the selective reflection wave range of the first retardation layer and at least part of the selective reflection wave range of the second retardation layer are both included in an ultraviolet region of 100 to 400 nm, and that a maximum reflectance for light in the ultraviolet region is 60% or more as a whole.