Laminate with Polymerizable Liquid Crystal Layer for Thermal Stability
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Solution Overview
Problem
Polarizing plates with optically anisotropic layers formed using polymerizable liquid crystal compounds exhibit significant changes in in-plane retardation when exposed to high temperatures, leading to thermal instability and reddish unevenness, particularly due to moisture-induced decomposition.
Innovation Solution
A laminate configuration with a polarizer and optically anisotropic layer, where the polarizer contains a polyvinyl alcohol-based resin and the optically anisotropic layer is formed from a specific polymerizable liquid crystal compound, with controlled moisture permeability and water content, and a thickness of the polarizer less than 10 μm, ensuring thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a polarizing plate with an optically anisotropic layer formed of a polymerizable liquid crystal compound is used, then the device thickness can be reduced, but the in-plane retardation changes significantly when exposed to high temperature, causing reddish unevenness
Solution Approach 1:
The patent changes the chemical composition parameters of the optically anisotropic layer by introducing a specific polymerizable liquid crystal compound with a cyclic carbonate group. This compound has the formula: where R1 to R6 independently represent a hydrogen atom or a methyl group. By controlling the molecular structure and composition of the liquid crystal compound, the patent achieves both thin film formation and high thermal stability, preventing reddish unevenness while maintaining reduced device thickness.
Solution Approach 2:
The patent creates a composite optically anisotropic layer by combining the polymerizable liquid crystal compound (with cyclic carbonate group) with a polymerizable monomer or oligomer. This composite material system allows the liquid crystal molecules to maintain their optical anisotropy while the polymer network provides thermal stability. The composite structure prevents molecular rearrangement at high temperatures, thereby maintaining constant in-plane retardation and eliminating reddish unevenness.
2Volume of moving object
If the optically anisotropic layer is made thinner to reduce device thickness, then the overall device size is reduced, but the optical performance and thermal durability deteriorate
Solution Approach 1:
The patent achieves high thermal durability in thin films by precisely controlling the molecular parameters of the liquid crystal compound. The cyclic carbonate group in the compound structure provides enhanced thermal stability, allowing the layer to maintain its optical properties even at reduced thickness. This parameter optimization enables thin film formation (reducing device thickness) while preserving thermal durability through the unique molecular structure.
Solution Approach 2:
The patent applies local quality enhancement by introducing specific functional groups (cyclic carbonate) at critical positions in the liquid crystal molecule structure. This localized structural modification provides targeted thermal stability to the optically anisotropic layer, ensuring that even thin regions maintain their optical performance and resistance to thermal degradation.
3Ease of manufacture
If a conventional polymerizable liquid crystal compound is used, then the optically anisotropic layer can be formed, but moisture-induced decomposition occurs at high temperature, causing significant variation in in-plane retardation
Solution Approach 1:
The patent modifies the chemical parameters of the liquid crystal compound by incorporating a cyclic carbonate group, which fundamentally changes the compound's resistance to moisture-induced decomposition. This structural parameter change makes the compound stable under high-temperature humid conditions, preventing decomposition while maintaining ease of manufacture through standard polymerization processes.
Solution Approach 2:
The patent converts the potential harm of moisture exposure at high temperature into a benefit by using the cyclic carbonate group's inherent stability. This structural feature actually enhances the compound's resistance to hydrolysis and decomposition, transforming what would be a harmful environment into one that the material can withstand, thereby preventing in-plane retardation variation.
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 laminate exhibits excellent thermal durability by suppressing changes in in-plane retardation, maintaining optical performance even under high-temperature conditions, and is suitable for use in organic electroluminescent and liquid crystal display devices.
Implementation Method 1
the optically anisotropic layer is formed of a composition containing a polymerizable liquid crystal compound
Implementation Method 2
a polarizing plate having an optically anisotropic layer and a polarizer has been used for an organic electroluminescent device, a liquid crystal display device, or the like for the purpose of optical compensation
Implementation Method 3
a polymerizable liquid crystal compound having reciprocal wavelength dispersibility
Data Source
AI summary
Provided is a laminate, which has a polarizer and an optically anisotropic layer and is excellent in thermal durability, and an organic electroluminescent device and a liquid crystal display device, which include the laminate. The laminate has two substrates and a polarizing plate disposed between the two substrates, in which the polarizing plate has a polarizer and an optically anisotropic layer, the polarizer contains a polyvinyl alcohol-based resin, the optically anisotropic layer is formed of a composition containing a polymerizable liquid crystal compound represented by General Formula (I): L1-G1-D1-Ar-D2-G2-L2, a moisture permeability of the substrate is 10−3 g/m2·day or less, and a water content of the polarizing plate is 3.0 g/m2 or less.