Liquid Crystal Diffraction Element Angle Dependence
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Solution Overview
Problem
Liquid crystal diffraction elements exhibit significant angle dependence in diffraction efficiency and compromised heat resistance due to variations in liquid crystal composition components.
Innovation Solution
A liquid crystal diffraction element with an optically-anisotropic layer formed from a composition including at least one monofunctional polymerizable liquid crystal compound, where specific peak area ratios in the infrared absorbance spectrum satisfy predetermined expressions, reducing angle dependence and enhancing heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid crystal composition including polymerizable liquid crystal compounds is used to form an optically-anisotropic layer with continuous rotation of optical axis orientation, then diffraction function is achieved, but angle dependence of diffraction efficiency increases and heat resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the liquid crystal compounds. Specifically, it uses a combination of monofunctional polymerizable liquid crystal compounds (with specific polymerizable groups like acryloyl or methacryloyl) and polyfunctional polymerizable liquid crystal compounds in defined ratios. This compositional parameter control modifies the molecular structure and packing characteristics of the liquid crystal layer, thereby reducing angle dependence of diffraction efficiency and improving heat resistance while maintaining the continuous rotation of optical axis orientation.
Solution Approach 2:
The patent employs composite materials by combining multiple types of polymerizable liquid crystal compounds in a single liquid crystal composition. The composition includes both monofunctional and polyfunctional polymerizable liquid crystal compounds, each contributing specific properties. This composite approach allows the material to exhibit both the desired optical diffraction function and improved thermal stability, resolving the contradiction between angle dependence and heat resistance.
2Manufacturing precision
If liquid crystal composition components are varied to optimize diffraction performance, then diffraction efficiency improves, but angle dependence increases and heat resistance decreases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by establishing specific compositional ranges for the liquid crystal compounds. It specifies that the liquid crystal composition must contain monofunctional polymerizable liquid crystal compounds with particular polymerizable groups and defines the ratio relationship between monofunctional and polyfunctional compounds. These parameter specifications ensure optimal diffraction efficiency while simultaneously achieving improved heat resistance, eliminating the trade-off between the two performance aspects.
Solution Approach 2:
The patent applies local quality by ensuring that different regions of the liquid crystal layer have appropriate local composition characteristics. The specific combination of monofunctional and polyfunctional compounds creates localized molecular arrangements that optimize both diffraction performance and thermal stability in the optically-anisotropic layer, allowing simultaneous achievement of high diffraction efficiency and good heat resistance.
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 solution results in a liquid crystal diffraction element with reduced angle dependence of diffraction efficiency and improved heat resistance, suitable for applications in optical elements, image display units, head-mounted displays, beam steering, and sensors.
Implementation Method 1
an optically-anisotropic layer that is formed of a liquid crystal composition including a polymerizable liquid crystal compound, in which the polymerizable liquid crystal compound includes at least one monofunctional polymerizable liquid crystal compound having one polymerizable group, the optically-anisotropic layer has a liquid crystal alignment pattern in which an orientation of an optical axis derived from the polymerizable liquid crystal compound changes while continuously rotating in at least one in-plane direction
Implementation Method 2
in an infrared absorbance spectrum where a measurement sample obtained by powdering the optically-anisotropic layer is measured by Fourier transform infrared spectroscopy
Data Source
AI summary
Provided are a liquid crystal diffraction element having a small angle dependence of diffraction efficiency and excellent heat resistance, and a liquid crystal diffraction element, an optical element, an image display unit, a head-mounted display, a beam steering, and a sensor that include the liquid crystal diffraction element. A liquid crystal diffraction element according to the present invention includes an optically-anisotropic layer that is formed of a liquid crystal composition including a polymerizable liquid crystal compound, in which the polymerizable liquid crystal compound includes at least one monofunctional polymerizable liquid crystal compound having one polymerizable group, the optically-anisotropic layer has a liquid crystal alignment pattern in which an orientation of an optical axis derived from the monofunctional polymerizable liquid crystal compound changes while continuously rotating in at least one in-plane direction, and in an infrared absorbance spectrum where a measurement sample obtained by powdering the optically-anisotropic layer is measured by Fourier transform infrared spectroscopy, an area ratio of a specific peak satisfies a predetermined relational expression.