Cholesteric Liquid Crystal Layer With Tilted Helix for High Diffraction
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Solution Overview
Problem
The existing cholesteric liquid crystal layers in AR glasses suffer from low diffraction efficiency, leading to a decrease in the amount of reflected light.
Innovation Solution
A cholesteric liquid crystal layer with a liquid crystal alignment pattern where the optical axis direction continuously rotates in one in-plane direction, featuring specific tilt angles and retardation values, and a method of forming this layer through heating and exposure steps with a chiral agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional cholesteric liquid crystal layer is used, then the structure is simple, but the diffraction efficiency is low resulting in decreased reflected light amount
Solution Approach 1:
The patent applies parameter changes by precisely controlling the helical pitch of the cholesteric liquid crystal to match the wavelength of incident light, and by adjusting the tilt angle of the helical axis to optimize diffraction efficiency. These parameter optimizations resolve the contradiction by achieving high diffraction efficiency through controlled structural parameters rather than complex multi-layer designs.
Solution Approach 2:
The patent introduces a tilt angle dimension to the conventional planar cholesteric structure. By tilting the helical axis relative to the substrate normal, the patent creates a three-dimensional helical structure that enhances diffraction efficiency while maintaining the fundamental single-layer simplicity, thus resolving the contradiction between structural simplicity and optical performance.
2Illumination intensity
If the helical pitch is increased to reflect longer wavelengths, then the reflection wavelength range shifts, but the diffraction efficiency decreases
Solution Approach 1:
The patent simultaneously optimizes two parameters: the helical pitch determines the reflection wavelength range, while the tilt angle of the helical axis maintains high diffraction efficiency across different pitch values. This dual-parameter control allows the system to reflect longer wavelengths while preserving diffraction efficiency, resolving the contradiction between wavelength range and efficiency.
3Loss of energy
If a tilted helical structure is introduced to improve diffraction efficiency, then the optical performance improves, but the manufacturing complexity increases
Solution Approach 1:
The patent achieves tilted helical structures through parameter control during a single-step polymerization process. By controlling the polymerization conditions and chiral dopant concentration, the desired tilt angle is obtained without requiring additional manufacturing steps or complex multi-layer structures, thus maintaining ease of manufacture while achieving high diffraction efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed cholesteric liquid crystal layer achieves high diffraction efficiency for incident light, enhancing light reflection and guidance in AR glasses.
Implementation Method 1
The cholesteric liquid crystal layer achieves high diffraction efficiency for incident light
Implementation Method 2
a cholesteric liquid crystal layer that is obtained by immobilizing a cholesteric liquid crystalline phase
Implementation Method 3
heating the liquid crystal composition at a temperature T1 in a temperature range of a crystal-nematic phase transition temperature to a nematic-isotropic phase transition temperature of the liquid crystal compound
Implementation Method 4
a liquid crystal composition including a liquid crystal compound and a chiral agent
Data Source
AI summary
Provided are a cholesteric liquid crystal layer having high diffraction efficiency, method of forming the same, a laminate, light guide element, and image display device including the cholesteric liquid crystal layer. The cholesteric liquid crystal layer obtained by immobilizing a cholesteric liquid crystalline phase, in which the cholesteric liquid crystal layer has a liquid crystal alignment pattern having a direction of an optical axis from a liquid crystal compound changes while continuously rotating in at least one in-plane direction, in a cross-section observed with SEM, bright portions and dark portions are tilted, where a tilt angle of a direction in which in-plane retardation is minimum with respect to a normal line in a slow or fast axis plane is θ2, an absolute value of an optical axis tilt angle φ is “sin θ2=n·sin φ (n represents an average refractive index of the cholesteric liquid crystal layer)” is 5° or more.