Multilayer organic solid thin films having a biaxial refractive index
A multilayer organic thin film includes a plurality of biaxially-oriented layers, where each layer is characterized by mutually orthogonal refractive indices, n 1 ≠n 2 ≠n 3 . In example structures, the corresponding in-plane refractive indices of adjacent layers may be rotated with respect to each other by a predetermined angle. Such a multilayer may be incorporated into a circular reflective polarizer, for example, which may be used in display systems to provide high broadband efficiency and high off-axis contrast. In an example process, individual organic thin films may be molded, and then oriented and stacked to form a multilayer.
1. A multilayer organic thin film comprising a plurality of biaxially-oriented layers, wherein each biaxially-oriented layer is equal in chemical composition and characterized by mutually orthogonal refractive indices, n 1 ≠n 2 ≠n 3 .
2. The multilayer organic thin film of claim 1 , wherein each biaxially-oriented layer comprises an optically anisotropic organic material.
3. The multilayer organic thin film of claim 1 , wherein each biaxially-oriented layer comprises a single crystal or polycrystalline material.
4. The multilayer organic thin film of claim 1 , wherein each biaxially-oriented layer comprises an optically anisotropic glassy material, the glassy material comprising molecules aligned along predetermined directions.
5. The multilayer organic thin film of claim 1 , wherein each biaxially-oriented layer directly overlies an adjacent biaxially-oriented layer.
6. The multilayer organic thin film of claim 1 , wherein in-plane refractive indices (n 2 , n 3 ) of a chosen biaxially-oriented layer are rotated by an angle (θ) with respect to corresponding in-plane refractive indices (n 2 , n 3 ) of a biaxially-oriented layer located adjacent to the chosen biaxially-oriented layer.
7. The multilayer organic thin film of claim 1 , wherein in-plane refractive indices (n 2 , n 3 ) of each biaxially-oriented layer are characterized by (n 2 +n 3 )/2>1.5.
8. The multilayer organic thin film of claim 1 , wherein in-plane refractive indices (n 2 , n 3 ) of each biaxially-oriented layer are characterized by |n 2 −n 3 |>0.05.
9. The multilayer organic thin film of claim 1 , wherein an out-of-plane refractive index (n 1 ) for a chosen biaxially-oriented layer is related to in-plane refractive indices (n 2 , n 3 ) for the chosen biaxially-oriented layer according to n 2 <n 1 <n 3 .
10. A circular reflective polarizer comprising the multilayer organic thin film of claim 1 .
11. A multilayer organic thin film comprising a stack of biaxially-oriented organic solid crystal layers, wherein each biaxially-oriented layer is equal in chemical composition, characterized by mutually orthogonal refractive indices, n 1 ≠n 2 ≠n 3 , and respective in-plane refractive indices (n 2 , n 3 ) of adjacent biaxially-oriented layers within the stack are rotationally offset by an angle (θ).