Acrylic Adhesive with Mesogen Core for LCD Stress Relief
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Solution Overview
Problem
Pressure-sensitive adhesive compositions used in liquid crystal display (LCD) devices face challenges in maintaining endurance reliability and preventing light leakage due to residual stress and birefringence under high temperature and humidity conditions, with existing solutions compromising on compatibility and durability.
Innovation Solution
A pressure-sensitive adhesive composition incorporating an acrylic copolymer and a liquid optically-anisotropic compound with a mesogen core, which relaxes stress and optically compensates for negative birefringence, enhancing compatibility and durability while preventing light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure-sensitive adhesive with a partially crosslinked viscoelastic structure is used to maintain high-temperature cohesive strength, then endurance reliability is improved, but residual stress and negative birefringence increase causing light leakage
Solution Approach 1:
A low molecular weight compound (molecular weight 1,000 to 30,000) is introduced as an intermediary substance to modify the adhesive layer. This compound reduces the negative birefringence caused by the crosslinked structure while maintaining the stress-relaxing capability, thereby preventing light leakage without sacrificing endurance reliability
Solution Approach 2:
The pressure-sensitive adhesive is formulated as a composite material combining a crosslinked viscoelastic polymer matrix with dispersed low molecular weight compounds. This composite structure provides both the high-temperature cohesive strength from the crosslinked network and the optical compensation from the low molecular weight additives, resolving the contradiction between reliability and light leakage prevention
2Productivity
If the size of LCD panels and polarizers is increased, then productivity is improved, but shrinkage and residual stress increase under heat resistance conditions leading to severe light leakage
Solution Approach 1:
The molecular weight parameter of the adhesive components is optimized. By using low molecular weight compounds (1,000 to 30,000) as additives in the adhesive composition, the material exhibits better stress-relaxing properties and reduced birefringence even in large-scale applications, allowing increased panel sizes without severe light leakage
3Object-generated harmful factors
If a pressure-sensitive adhesive with stress-relaxing feature is used to suppress light leakage, then optical performance is improved, but compatibility and durability may be compromised
Solution Approach 1:
The molecular weight parameter is precisely controlled within the range of 1,000 to 30,000 for the low molecular weight compounds added to the adhesive. This parameter optimization ensures that the compounds provide sufficient stress-relaxing effect to reduce birefringence while maintaining adequate compatibility and durability of the adhesive system
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 relaxes stress and optically compensates for negative birefringence, preventing light leakage and maintaining endurance reliability even under high temperature and humidity conditions, improving the performance of LCD devices.
Implementation Method 1
optically compensates for negative birefringence
Implementation Method 2
liquid optically-anisotropic compound with a mesogen core
Implementation Method 3
relaxes stress
Data Source
AI summary
The present invention relates to a pressure-sensitive adhesive composition, and a polarizer and a liquid crystal display (LCD) device using the pressure-sensitive adhesive composition, and more particularly, to a pressure-sensitive adhesive composition including (A) an acrylic copolymer and (B) a liquid optically-anisotropic compound having a mesogen core in its structure. The liquid optically-anisotropic compound having a mesogen core in its structure according to the present invention has superior solubility and compatibility with pressure-sensitive adhesive resin, and thus the pressure-sensitive adhesive composition including the liquid optically-anisotropic compound can relax stress caused by shrinkage of the polarizer and effectively compensate negative birefringence. Therefore, the polarizer and the LCD device using the pressure-sensitive adhesive composition can prevent light leakage originating from stress concentration in spite of long-term use.