Pressure Sensitive Adhesive for Polarizing Plate Light Leakage
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Solution Overview
Problem
Conventional polarizing plates with hydrophilic polymers like polyvinyl alcohol are prone to water and moisture, leading to performance deterioration when protective films are removed, resulting in light leakage and reduced durability in liquid crystal display devices.
Innovation Solution
A pressure sensitive adhesive composition with an acrylic polymer containing an alkyleneoxide group and an ultraviolet absorber, forming an interpenetrating polymer network structure, which provides different peel forces on both sides of the sheet and maintains optical properties and durability under high temperature and humidity conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If protective films are removed from polarizing plates to reduce thickness and weight, then the polarizing plate becomes thinner and lighter, but the performance is highly deteriorated due to water and moisture vulnerability
Solution Approach 1:
A pressure-sensitive adhesive layer is introduced as an intermediary between the polarizer and the substrate. This adhesive layer acts as a protective barrier that prevents water and moisture from reaching the hydrophilic polarizer, thereby maintaining performance stability even when protective films are removed. The adhesive layer has water resistance properties that protect the polarizer from environmental degradation.
Solution Approach 2:
The invention uses a composite adhesive layer composed of a acrylic polymer and a silane crosslinking agent. This composite structure provides both adhesion to the polarizer and water resistance properties. The silane crosslinking creates a three-dimensional network structure that enhances the adhesive's resistance to water and moisture, preventing performance deterioration of the polarizing plate.
2Ease of manufacture
If protective films are removed to achieve thin and light polarizing plates, then manufacturing simplicity is improved, but adhesion performance and durability are worsened
Solution Approach 1:
The adhesive layer undergoes a parameter change through UV irradiation or moisture curing, which transforms it from a liquid or soft state to a crosslinked gel state. This parameter change enables the adhesive to achieve strong adhesion to the polarizer and substrate while maintaining water resistance. The crosslinking density can be controlled to optimize both adhesion strength and durability.
3Reliability
If hydrophilic polymers like polyvinyl alcohol are used in polarizers, then polarizing performance is improved, but vulnerability to water and moisture increases
Solution Approach 1:
The pressure-sensitive adhesive layer serves as an intermediary barrier between the hydrophilic polarizer and the external environment. This adhesive layer has hydrophobic characteristics that prevent water and moisture from penetrating to the polarizer, thereby protecting the polarizing performance while allowing the use of effective hydrophilic polymers.
Solution Approach 2:
The invention extracts or removes the traditional protective films from the polarizing plate structure and replaces them with a functional pressure-sensitive adhesive layer that provides both adhesion and protection. This extraction simplifies the overall structure while maintaining or improving water resistance properties.
4Strength
If the adhesive layer modulus is increased to improve durability, then resistance to deformation is improved, but peel force becomes unsuitable
Solution Approach 1:
The adhesive layer exhibits dynamic properties through its crosslinking structure, where the three-dimensional network provides resistance to deformation (high modulus) while the flexible polymer chains maintain adequate peel force. The crosslinking density and polymer chain flexibility can be adjusted to achieve the optimal balance between durability and adhesion.
Solution Approach 2:
By controlling the crosslinking degree and polymer composition, the adhesive layer's mechanical parameters are optimized to achieve both high modulus for durability and appropriate peel force for proper bonding. The UV irradiation or moisture curing process allows precise control over these parameters.
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 adhesive composition effectively inhibits light leakage and maintains excellent durability and adhesion properties, even without protective films, by creating a gradient of tensile modulus and peel forces, enhancing the performance of polarizing plates in liquid crystal display devices.
Implementation Method 1
the composition in a hardened state comprises an interpenetrating polymer network structure (hereinafter, optionally referred to 'IPN') comprising said acrylic polymer in a cross-linked state
Implementation Method 2
A pressure sensitive adhesive composition comprising an acrylic polymer with an alkyleneoxide group and an ultraviolet absorber
Implementation Method 3
represents different peel forces in both sides of a sheet shape, on hardening the composition into the sheet shape
Data Source
AI summary
The present invention relates to a pressure sensitive adhesive composition. The present invention may effectively provide a pressure sensitive adhesive where peel forces for both sides are different and an modulus differs along the thickness direction. By applying the pressure sensitive adhesive as above, the present invention may provide, for example, an optical element, such as a polarizing plate, which can effectively inhibit light leakage and shows excellent durability, while being formed to have a thin thickness as well.