# US 2013/0155359 A1 · Biaxial retardation film and fabrication method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0155359 A1 - Document ID: US20130155359A1 - Status: Published application - Kind: A1 - Application number: 13/491,369 - Filed: 2012-06-07 - Published: 2013-06-20 - Earliest claimed: 2011-12-14 - Assignees: Industrial Technology Research Institute - Inventors: Ching-Mao WU; Szu-Yin LIN - Web page: https://patentgrep.com/patent/US20130155359A1 ## CPC - G02B 5/3016: {involving passive liquid crystal elements (optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A biaxial retardation film is disclosed, including a substrate, wherein the substrate includes an alignment film thereon or an alignment-treated surface; and an optically anisotropic coating on the substrate, wherein the optically anisotropic coating includes a top layer and a bottom layer, wherein the bottom layer is a parallel aligned liquid crystal layer along an alignment direction of the substrate, and the top layer is a vertically aligned hexagonal pillar array liquid crystal layer, wherein three-dimensional refractive indices of the optically anisotropic coating satisfy a relationship nx>nz>ny. The disclosure also provides a fabrication method thereof. ## Claims ### Claim 1 A biaxial retardation film, comprising: a substrate, wherein the substrate comprises an alignment film thereon or an alignment-treated surface; and an optically anisotropic coating on the substrate, wherein the optically anisotropic coating comprises a top layer and a bottom layer, wherein, the bottom layer is a parallel aligned liquid crystal layer along an alignment direction of the substrate, and the top layer is a vertically aligned hexagonal pillar array liquid crystal layer, wherein three-dimensional refractive indices of the optically anisotropic coating satisfy a relationship nx>nz>ny. ### Claim 2 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein pillars of the hexagonal pillar array liquid crystal layer have a pitch (P) of 200-600 nm. ### Claim 3 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein pillars of the hexagonal pillar array liquid crystal layer have a diameter (D) of 100-300 nm. ### Claim 4 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein pillars of the hexagonal pillar array liquid crystal layer have an aspect ratio (length/diameter=H/D) of 1/2-2. ### Claim 5 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein a ratio of a thickness of the hexagonal pillar array liquid crystal layer to a thickness of the optically anisotropic coating is 8-60%. ### Claim 6 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein the hexagonal pillar array liquid crystal layer has a thickness of 50-600 nm. ### Claim 7 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein the biaxial retardation film has an in-plane retardation value R0 of 10-400 nm. ### Claim 8 (depends on 1) The biaxial retardation film as claimed in claim 1, wherein the biaxial retardation film has an out-of-plane retardation value Rth of 10-200 nm. ### Claim 9 A biaxial retardation film, comprising: a substrate, wherein the substrate comprises an alignment film thereon or an alignment-treated surface; and an optically anisotropic coating on the substrate, wherein the optically anisotropic coating comprises a top layer and a bottom layer, wherein the bottom layer and a pillar array of the top layer are orientation structures aligned perpendicular to one another, wherein three-dimensional refractive indices of the optically anisotropic coating satisfy a relationship nx>nz>ny. ### Claim 10 A fabrication method for a biaxial retardation film, comprising: providing a substrate, wherein the substrate comprises an alignment film thereon or an alignment-treated surface; forming an optically anisotropic coating on the substrate, and imprinting on the optically anisotropic coating so that the optically anisotropic coating is formed with a structure comprising a top layer and a bottom layer, wherein the bottom layer is a parallel aligned liquid crystal layer along an alignment direction of the substrate, and the top layer is a vertically aligned hexagonal pillar array liquid crystal layer, wherein three-dimensional refractive indices of the optically anisotropic coating satisfy a relationship nx>nz>ny. ### Claim 11 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein the step of imprinting is a step of nanoimprinting. ### Claim 12 (depends on 11) The fabrication method for biaxial retardation film as claimed in claim 11, wherein the step of nanoimprinting uses a mold comprising a silicon mold, a metallic mold, or a polymeric stamper. ### Claim 13 (depends on 11) The fabrication method for biaxial retardation film as claimed in claim 11, wherein the step of nanoimprinting comprises a batch process, a semi-batch process or a continuous roll-to-roll process. ### Claim 14 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, further comprising a step of irradiating the optically anisotropic coating with ultraviolet light. ### Claim 15 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein the pillars of the hexagonal pillar array liquid crystal layer have a pitch (P) of 200-600 nm. ### Claim 16 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein pillars of the hexagonal pillar array liquid crystal layer have a diameter (D) of 100-300 nm. ### Claim 17 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein pillars of the hexagonal pillar array liquid crystal layer have an aspect ratio (length/diameter=H/D) of 1/2-2. ### Claim 18 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein a ratio of a thickness of the hexagonal pillar array liquid crystal layer to a thickness of the optically anisotropic coating is 8-60%. ### Claim 19 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein the biaxial retardation film has an in-plane retardation value R0 of 10-400 nm. ### Claim 20 (depends on 10) The fabrication method for biaxial retardation film as claimed in claim 10, wherein the biaxial retardation film has an out-of-plane retardation value Rth of 10-200 nm.