Multi-twist waveplate
AssigneeMerck Patent GmbH
InventorsStephen Mulcahy, Peter Wyatt, Owain Llyr Parri
Life of this patent
Estimating the term…
Abstract
A multi-twist waveplate comprising at least two layers of a polymerized chiral liquid crystal (LC) material on a substrate containing a surface grating, a method for its preparation, and its use in optical or electrooptical components or devices, especially for digital optics or augmented reality or virtual reality (AR/VR) applications like non-mechanical beam steering elements, optical waveguides, optical couplers, optical combiners, polarization beam splitters, partial mirrors or lenses.
Claims19
A waveplate comprising a substrate having a surface grating or a planar alignment layer, upon which substrate are provided two or more cholesteric liquid crystal (CLC) layers, the first CLC layer deposited directly on the substrate and the second and further CLC layers deposited directly onto the respective previous CLC layer, each CLC layer consisting of a polymerized chiral reactive mesogen (RM) mixture having an LC director exhibiting a helical twist with a defined twist angle along a helix axis in a thickness direction of the CLC layer, said chiral RM mixture comprising one or more RMs selected from mono-, di- and multireactive RMs, at least one chiral compound and a photoinitiator,
- wherein at least two CLC layers in the waveplate have a different twist angle, and
- wherein the surface grating induces a rotation of the LC director along an in-plane direction of the first CLC layer, or the planar alignment layer induces planar alignment in the first CLC layer,
- and
- wherein each chiral RM mixture has a proportion of direactive RMs of from 40 to 90% and the chiral compound is selected from chiral RMs.
A process of preparing a waveplate, comprising the steps of:
- A1) forming a surface grating or a planar alignment layer on the surface of a substrate,
- A2) depositing a first layer of a chiral RM mixture or an RM formulation comprising a chiral RM mixture, said chiral RM mixture comprising one or more RMs selected from mono-, di- and multireactive RMs, at least one chiral compound, a photoinitiator and a solvent or solvent blend, onto the surface grating or onto the planar alignment layer,
- A3) removing any solvents present,
- A4) optionally annealing the first layer of the chiral RM mixture,
- A5) polymerizing the chiral RM mixture of the first layer at a temperature where it is in the cholesteric phase,
- B1) depositing a second layer of a chiral RM mixture or an RM formulation comprising a chiral RM mixture, said chiral RM mixture comprising one or more RMs selected from mono-, di- and multireactive RMs, at least one chiral compound, a photoinitiator and a solvent or solvent blend, onto the polymerized first chiral RM layer,
- B2) removing any solvents present,
- B3) optionally annealing the chiral RM mixture of the second layer
- B4) polymerizing the chiral RM mixture of the second layer at a temperature where it is in the cholesteric phase,
- optionally repeating steps B1 to B4 one or more times with a subsequent third, fourth etc. layer of a chiral RM mixture which is provided and polymerized on the respective previously polymerized chiral RM layer,
- wherein the first CLC layer deposited directly on the substrate and the second and further CLC layers deposited directly onto the respective previous CLC layer each consist of a polymerized chiral reactive mesogen (RM) mixture having an LC director that exhibits a helical twist with a defined twist angle along a helix axis in a thickness direction of the CLC layer,
- wherein at least two CLC layers in the waveplate have a different twist angle,
- wherein the surface grating induces a rotation of the LC director along an in-plane direction of the first CLC layer, and the planar alignment layer induces planar alignment in the first CLC layer, and
- wherein each chiral RM mixture has a proportion of direactive RMs of from 40 to 90% and the chiral compound is selected from chiral RMs.
A chiral RM mixture comprising one or more RMs selected from mono-, di- and multireactive RMs, at least one chiral compound, and a photoinitiator, wherein the chiral RM mixture has a proportion of direactive RMs of from 40 to 90% and the chiral compound is selected from chiral RMs, and wherein the photoinitiator comprises one or more oxime esters.
Dependencies are inferred from the claim text.