Acrylic Adhesive with Meta-Substituted Mesogen for LCD Light Leakage
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Solution Overview
Problem
Traditional acrylic pressure-sensitive adhesive layers in LCD devices suffer from light leakage due to negative birefringence caused by residual stress, especially under high temperature and high humidity conditions, which is exacerbated by the shrinkage of polarizers, and existing solutions fail to completely suppress this issue while maintaining endurance reliability.
Innovation Solution
An acrylic pressure-sensitive adhesive composition incorporating an optically anisotropic compound with alkyl, alkenyl, or alkynyl groups in a meta position of mesogen, which enhances compatibility and optical anisotropy, introducing a crosslinking structure to maximize stress release and convert negative birefringence to positive birefringence, thereby improving light leakage without compromising endurance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a partially crosslinked viscoelastic pressure-sensitive adhesive layer is used to maintain high-temperature cohesive strength and endurance reliability, then reliability is improved, but residual stress and negative birefringence occur under high temperature and humidity conditions, causing light leakage
Solution Approach 1:
The invention changes the optical parameter (birefringence) of the pressure-sensitive adhesive layer by incorporating an optically anisotropic compound. This compound has positive birefringence that compensates for the negative birefringence generated by residual stress in the crosslinked adhesive structure, thereby suppressing light leakage while maintaining the crosslinked structure's high-temperature cohesive strength and endurance reliability
Solution Approach 2:
The invention creates a composite pressure-sensitive adhesive system by combining a crosslinked acrylic polymer matrix with an optically anisotropic compound. The crosslinked structure provides mechanical strength and reliability, while the optically anisotropic compound provides positive birefringence to counteract the negative birefringence from residual stress, achieving both reliability and light leakage suppression
2Productivity
If the size of LCD panel and polarizer is increased to meet market demands, then productivity is improved, but shrinkage of the polarizer increases under high temperature conditions, leading to increased residual stress and severe light leakage
Solution Approach 1:
The invention changes the optical parameter (birefringence) of the pressure-sensitive adhesive layer by incorporating an optically anisotropic compound. This compound has positive birefringence that compensates for the negative birefringence generated by residual stress in the crosslinked adhesive structure, thereby suppressing light leakage while maintaining the crosslinked structure's high-temperature cohesive strength and endurance reliability
Solution Approach 2:
The invention applies preliminary optical compensation by incorporating the optically anisotropic compound with positive birefringence into the pressure-sensitive adhesive layer before the polarizer shrinkage occurs. This pre-established positive birefringence counteracts the negative birefringence that will be generated by residual stress when the large-sized polarizer shrinks under high temperature and humidity conditions, preventing light leakage before it occurs
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 composition effectively controls birefringence and reduces light leakage in LCD devices by converting residual stress-induced negative birefringence to positive birefringence, maintaining the adhesive's endurance reliability and optical performance under varying conditions.
Implementation Method 1
it is necessary to perform optical compensation which regulates negative birefringence of the pressure-sensitive adhesive resulting from the residual stress into positive birefringence
Implementation Method 2
an optically anisotropic compound having one or more substituents containing one of an alkyl group, an alkenyl group, and an alkynyl group in a meta position of mesogen
Implementation Method 3
The light leakage phenomenon can be suppressed by preventing generation of residual stress with regulation of a stress releasing characteristic of the pressure-sensitive adhesive fixed on the polarizer
Data Source
AI summary
Disclosed are (A) an acrylic pressure-sensitive adhesive; and (B) an acrylic pressure-sensitive adhesive comprising an optically anisotropic compound having at least one substituent which contains an alkyl group, alkenyl group or alkynyl group at a meta-position of a mesogen. A polarizing plate and a liquid crystal display using the same are also disclosed. The optically anisotropic compound ensures excellent compatibility with the adhesive and high birefringence. Thus, main properties such as adhesion, reliability and durability in the conditions of high temperatures or high temperatures and high humidity are not worsened. Moreover light leakage is prevented by efficiently controlling the birefringence caused by shrinkage stress of the polarizing plate.