Pressure-Sensitive Adhesive Composition for Liquid Crystal Display Polarizers
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Solution Overview
Problem
Conventional pressure-sensitive adhesive (PSA) compositions for polarizers in liquid crystal displays face challenges with dimensional stability at high temperatures and humidity, leading to stress concentration, birefringence, and light leakage, while also having reduced durability and slow curing processes that affect producibility and reworkability.
Innovation Solution
A PSA composition with an interpenetrating polymer network (IPN) structure, comprising an acrylic resin and a bifunctional crosslinking agent, which balances light leakage prevention and durability by controlling peel strength and curing time, allowing for rapid stabilization of adhesive strength and improved reworkability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the PSA is designed to be very hard by increasing bulk modulus, then dimensional stability and prevention of stress concentration are improved, but adhesive strength is greatly reduced, decreasing durability
Solution Approach 1:
The patent changes the chemical composition parameters of the PSA by incorporating specific functional groups (carboxyl, hydroxyl, amino groups) and controlling the glass transition temperature (Tg) within 0°C to 100°C. This allows the PSA to achieve both dimensional stability and adequate adhesive strength by adjusting molecular structure rather than simply increasing hardness.
Solution Approach 2:
The patent creates a composite adhesive system by combining PSA with specific additives including crosslinking agents, UV absorbers, and materials having specific functional groups. This composite approach allows the adhesive layer to simultaneously achieve dimensional stability, adhesive strength, and stress distribution properties that cannot be obtained with a single material.
2Object-affected harmful factors
If multi-functional acrylate and photoinitiator are added to increase bulk modulus by UV irradiation, then light leakage characteristics are improved, but the crosslinking reaction occurs too fast, greatly decreasing producibility and workability
Solution Approach 1:
The patent uses periodic or controlled action by selecting crosslinking agents with appropriate reactivity and controlling the curing process conditions. This allows the crosslinking reaction to proceed at a controlled rate rather than all at once, maintaining productivity while achieving the desired bulk modulus for light leakage prevention.
Solution Approach 2:
The patent introduces crosslinking agents as intermediaries that mediate between the PSA and the curing process. These crosslinking agents (isocyanate compounds, epoxy compounds, aziridine compounds, etc.) control the reaction kinetics and allow gradual buildup of bulk modulus without causing excessively fast crosslinking that would reduce productivity.
3Temperature
If the PSA is made hard to prevent contraction and expansion at high temperature and humidity, then stress concentration on the polarizer is minimized, but adhesive strength is reduced and durability decreases
Solution Approach 1:
The patent changes the thermal parameters of the PSA by controlling the glass transition temperature (Tg) to be between 0°C and 100°C and by incorporating functional groups that provide temperature-dependent flexibility. This allows the adhesive to maintain dimensional stability at high temperatures while retaining adequate adhesive strength through molecular structure design rather than simple hardening.
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 PSA composition effectively stabilizes adhesive strength within industry requirements, enhancing durability, reliability, and reworkability, while maintaining optical properties and reducing time-dependent changes, thus addressing the limitations of existing PSA compositions.
Implementation Method 1
a process of storing a PSA composition at a predetermined temperature for a predetermined period of time to terminate curing is referred to as an aging process
Implementation Method 2
a PSA composition, which includes an interpenetrating polymer network structure in a cured state, and comprises an acrylic resin and a crosslinking agent component
Data Source
AI summary
Provided are a pressure-sensitive adhesive (PSA) composition including an interpenetrating polymer network structure in a cured state, and including an acrylic resin and a crosslinking agent component that consists of a bifunctional crosslinking agent, a polarizer and a liquid crystal display. Provided are the PSA composition, the polarizer including a cured product of the PSA composition, and the liquid crystal display, which have excellent workability and optical properties, durability and reliability, at high temperature or humidity condition, and significantly increase productivity of optical members such as a polarizer, since the time-dependent change of the pressure-sensitive adhesive strength is rapidly ended after fabrication.