Retardation Layer Laminate for Diagonal Compensation and Thermal Stability
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Solution Overview
Problem
Existing polarizing plates with retardation layers suffer from breakage during fabrication, poor diagonal compensation, and inadequate thermal stability, especially when used in liquid crystal displays.
Innovation Solution
A polarizing plate is designed with a laminate structure of a first and second retardation layer stacked on a polarizer, where the second retardation layer includes a fluorene-based retardation layer, and the retardation values are controlled to achieve good diagonal compensation and thermal stability without breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a liquid crystal layer is provided to a retardation layer to reduce thickness, then the thickness of the polarizing plate is reduced, but the durability deteriorates due to brittle properties
Solution Approach 1:
The patent changes the material parameters of the retardation layer by using a copolymer composition with specific refractive index ratios (nx/ny between 1.01-1.05, nz/ny between 0.95-0.99) and controlled retardation values (Re: 50-150 nm, Rth: -200 to +200 nm). This parameter optimization allows achieving thin thickness (30-70 μm) while maintaining flexibility and preventing breakage, thus resolving the contradiction between thickness reduction and durability maintenance.
2Strength
If additives are added to prevent breakage of acrylic film, then breakage resistance is improved, but price increases and compatibility decreases
Solution Approach 1:
The patent employs a composite material approach by creating a copolymer consisting of a first polymer component and a second polymer component with specific functional groups. The second component (0.1-10 parts by weight per 100 parts of first component) provides flexibility and breakage resistance through molecular-level integration, eliminating the need for separate additives. This composite structure maintains material compatibility and avoids the complexity associated with multiple additive systems.
3Device complexity
If a single retardation layer is used, then the structure is simple, but diagonal compensation and thermal stability are poor
Solution Approach 1:
The patent segments the retardation function into two distinct retardation layers with different optical characteristics. The first layer has positive uniaxial birefringence (nx>ny= nz) while the second layer has negative uniaxial birefringence (nx= ny> nz). This segmentation allows each layer to contribute differently to the overall optical performance, achieving superior diagonal compensation and thermal stability while maintaining a relatively simple laminated structure.
4Ease of manufacture
If acrylic film is used as retardation layer, then refractive indexes nx, ny and nz are easy to realize, but thermal stability deteriorates in severe use environment
Solution Approach 1:
The patent changes the chemical composition parameters by using a copolymer system with specific functional groups (carboxyl, hydroxyl, amino, or carbonyl groups) and controlled molecular weights. The copolymer composition ratios and molecular weight parameters are optimized to achieve refractive indexes meeting the required ratios while simultaneously providing enhanced thermal stability through stronger molecular bonds and improved glass transition temperature, thus maintaining ease of manufacture while improving thermal performance.
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 proposed polarizing plate structure prevents breakage during fabrication, enhances diagonal compensation, and improves thermal stability, while maintaining a reduced thickness, thus addressing the limitations of existing technologies.
Implementation Method 1
the first retardation layer satisfies Equation 1 and the second retardation layer satisfies Equation 2: nx>nymz, nz>nx>ny, wherein Equation 1, nx, ny and nz are indexes of refraction of the first retardation layer at a wavelength of 550 nm in a slow axis direction, a fast axis direction and a thickness direction thereof
Data Source
AI summary
Provided is a polarizing plate and an optical display device comprising same, the polarizing plate comprising: a polarizer; and a stack body of a first phase difference layer and a second phase difference layer stacked on a lower surface of the polarizer, wherein the first phase difference layer satisfies Equation 1, the second phase difference layer satisfies Equation 2, the sum of an in-plane phase difference at a wavelength of 550 nm between the first phase difference layer and the second phase difference layer is about 100 nm to about 110 nm, the sum of a thickness direction phase difference at a wavelength of 550 nm between the first phase difference layer and the second phase difference layer is about −30 nm to about +10 nm, and the second phase difference layer comprises a fluorine-based phase difference layer.