Polarizing Plate Thermal Expansion Control
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Solution Overview
Problem
Polarizing plates experience severe curling and defects such as detachment and bubble-formation during stacking due to mismatched coefficients of thermal expansion between protective films, leading to inefficient attachment and durability issues.
Innovation Solution
A polarizing plate design featuring protective films with specific ratios of thermal expansion coefficients in the machine direction (MD) and transverse direction (TD), ranging from 0.5 to 2, to prevent curling and ensure proper attachment and protection of the polarizer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If protective films with mismatched coefficients of thermal expansion are used, then the polarizing plate can be manufactured with simple materials, but severe curling and defects occur during stacking
Solution Approach 1:
The patent applies parameter changes by precisely controlling the coefficients of thermal expansion of protective films to fall within specific ranges (0.01-0.06 ppm/°C in MD and 0.01-0.05 ppm/°C in TD at 25-120°C). This parameter control ensures that the protective films expand and contract at rates matching the polarizer, preventing curling and attachment defects while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs composite materials by selecting protective films with specific thermal expansion characteristics that complement the polarizer's properties. The use of materials like TAC, PET, COP, and their combinations creates a composite structure where each layer's thermal expansion is coordinated to prevent relative movement and curling during temperature variations
2Ease of operation
If protective films with high thermal expansion coefficients are used, then the films are easier to process and attach, but severe curling occurs during stacking
Solution Approach 1:
The patent changes the thermal expansion parameter of protective films to very low values (0.01-0.06 ppm/°C in MD and 0.01-0.05 ppm/°C in TD). This parameter modification allows the films to maintain dimensional stability during processing and stacking, preventing curling while remaining workable through standard attachment processes
3Adaptability or versatility
If protective films with different thermal expansion coefficients are used on each side, then design flexibility is improved, but detachment and bubble-formation occur
Solution Approach 1:
The patent applies parameter changes by establishing specific ranges for thermal expansion coefficients of protective films on both sides of the polarizer. By controlling these parameters to be within 0.01-0.06 ppm/°C in MD and 0.01-0.05 ppm/°C in TD, the patent achieves design flexibility in material selection while preventing detachment and bubble formation through matched thermal expansion behavior
Solution Approach 2:
The patent applies local quality by allowing different protective film materials on each side of the polarizer (such as TAC on one side and PET or COP on the other), each optimized for their specific position. However, both materials are selected to meet the thermal expansion criteria, ensuring local optimization without compromising overall attachment precision
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 controlled thermal expansion ratios between protective films reduce curling phenomena, enabling efficient stacking and attachment of polarizing plates to optical display devices while maintaining protection at high temperatures.
Implementation Method 1
a ratio t2/t1 or t1/t2 between coefficients t1 and t2 of thermal expansion of the first protective film and the second protective film ranges from about 0.5 to about 2, where t1 is a coefficient of thermal expansion of the first protective film and t2 is a coefficient of thermal expansion of the second protective film
Data Source
AI summary
A polarizing plate includes a polarizer, a first protective film attached to one side of the polarizer, and a second protective film attached to another side of the polarizer. A ratio between coefficients of thermal expansion of the first and second protective films, measured in a transverse direction (TD) at a temperature from about 25° C. to about 120° C., ranges from about 0.5 to about 2. A ratio between coefficients of thermal expansion of the first and second protective films measured in a machine direction (MD) at a temperature from about 25° C. to about 120° C. ranges from about 0.5 to about 2.