Polarizing Plate Adhesive Curing Uniformity via Dual Photoinitiators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Polarizing plates face issues with curl occurrences and uneven curing rates due to the absorption of energy rays by the polarizer, leading to inadequate adhesive layer curing on the opposite surface, which affects the reliability and yield of the manufacturing process.
Innovation Solution
Incorporating a photoinitiator and photosensitizer represented by Chemical Formula 1 in the adhesive composition on the second protective film, which enhances sensitivity to long wavelength active energy rays, ensuring uniform curing and minimizing curl issues by improving the curing rate of the adhesive layer on the opposite surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If energy rays are irradiated on one surface of the laminate to cure the adhesive, then the adhesive on the irradiated surface is cured, but the polarizer absorbs the energy rays reducing the amount reaching the adhesive on the opposite surface, causing uneven curing rates and curl occurrences
Solution Approach 1:
The patent applies different photoinitiator systems to different surfaces of the adhesive layer. The surface facing the irradiation source contains photoinitiators sensitive to short wavelengths (200-400nm), while the opposite surface contains photoinitiators sensitive to long wavelengths (300-600nm). This local differentiation ensures that each region receives effective curing despite the polarizer's selective absorption characteristics, resolving the uneven curing problem.
Solution Approach 2:
The patent changes the wavelength sensitivity parameter of the photoinitiators based on their position in the laminate. By selecting photoinitiators with different absorption spectra (short-wave sensitive vs. long-wave sensitive), the system adapts to the varying energy ray transmission conditions at different depths, ensuring uniform curing throughout the adhesive layer despite the polarizer's absorption effects.
2Strength
If a water-based adhesive is used to attach the polarizer and protective film, then the adhesive provides initial bonding, but the adhesive strength is weak when using acryl-based or COP films, and curl occurrences occur due to the drying process
Solution Approach 1:
The patent replaces the water-based adhesive system (which relies on evaporation and drying) with a photopolymerizable adhesive system that cures through light-induced chemical reactions. This substitution eliminates the drying process that causes curling and provides superior adhesive strength for acryl-based and COP films, while maintaining manufacturing simplicity through single-step UV curing.
3Speed
If the adhesive composition uses a photoinitiator with high sensitivity to short wavelength light, then the adhesive on the irradiated surface cures quickly, but the adhesive on the opposite surface does not receive sufficient energy rays to cure properly
Solution Approach 1:
The patent implements a dual photoinitiator system where short-wave sensitive photoinitiators are positioned on the irradiation-facing surface to enable rapid initial curing, while long-wave sensitive photoinitiators are positioned on the opposite surface to ensure complete curing of the adhesive layer deep within the laminate. This spatial distribution of different photoinitiator types resolves the contradiction between fast surface curing and complete through-curing.
Solution Approach 2:
The adhesive composition functions as a composite photoinitiator system combining multiple types of photoinitiators with complementary absorption characteristics. This composite approach allows the adhesive layer to respond effectively to both short-wave and long-wave portions of the UV spectrum, ensuring uniform and complete curing throughout the entire adhesive thickness despite the polarizer's selective absorption.
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 method improves light efficiency and curing reliability, preventing curl occurrences and ensuring high curing efficiency even in long wavelength curing systems, thereby enhancing the overall quality of the polarizing plate manufacturing process.
Implementation Method 1
adhesive composition provided on one surface of the second protective film comprises a photoinitiator and a photosensitizer
Implementation Method 2
the adhesive composition provided on one surface of the second protective film comprises a photoinitiator and a photosensitizer represented by the following Chemical Formula 1
Data Source
AI summary
The present specification relates to a method for manufacturing a polarizing plate, and an adhesive composition for a polarizing plate.