Optical Compensation Sheet for Liquid Crystal Display Tint Stability
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Solution Overview
Problem
Existing optical compensation sheets for liquid crystal displays suffer from significant tint changes under high temperature and humidity conditions, leading to deterioration of polarization properties and adhesion issues when used as protective films for polarizing plates, which affects the viewing angle and contrast performance.
Innovation Solution
A stretched polymer film with a cycloolefin polymer composition and an optical anisotropic layer having a liquid crystal compound aligned perpendicular to the stretching direction, providing specific retardation relationships and a low photoelastic modulus to maintain optical stability and adhesion under humid conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polymer film with wavelength dispersion different from in-plane retardation to thickness-direction retardation is used for optical compensation, then contrast can be enhanced and tint in black display can be close to gray, but tint viewing angle improvement is insufficient and tint change becomes remarkable after prolonged display under high temperature and humidity conditions
Solution Approach 1:
The patent changes the fundamental optical parameters of the compensation film by using a negative C-plate with specific retardation values (Rth between -100nm to -300nm at 550nm wavelength) and controlling the ratio between in-plane retardation (Re) and thickness-direction retardation (Rth). This parameter optimization resolves the contradiction by achieving both good contrast/tint control and stability under high temperature and humidity conditions.
2Manufacturing precision
If a laminate of retardation layers with positive refractive anisotropy and negative refractive anisotropy is used as protective film for polarizing plate, then contrast can be enhanced and tint in black display is close to gray, but the polarization properties of the polarizer deteriorate and the protective film peels off under high temperature and humidity conditions
Solution Approach 1:
The patent optimizes the retardation parameters of the compensation film (Re and Rth values and their ratio) to achieve the desired contrast and tint performance without requiring a complex laminate structure. This simplified single-film approach maintains good adhesion to the polarizer under high temperature and humidity conditions while still achieving excellent optical compensation.
3Reliability
If the adhesion of the polarizer is insufficient, then the protective film peels off the polarizer during preparation or storage under high temperature and humidity conditions, but improving adhesion may affect optical properties
Solution Approach 1:
The patent achieves both good adhesion and optical properties by optimizing the compensation film's retardation parameters and using appropriate adhesive layers with controlled thickness and properties. The balance between adhesion strength and optical performance is achieved through parameter optimization of both the compensation film and adhesive system.
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 solution effectively minimizes tint changes and maintains high fidelity images over extended periods under high humidity, preventing exfoliation and enhancing viewing angle contrast, thus ensuring stable polarization properties for liquid crystal displays.
Implementation Method 1
a stretched polymer film with a cycloolefin polymer composition
Implementation Method 2
an optical anisotropic layer having a liquid crystal compound aligned perpendicular to the stretching direction, providing specific retardation relationships
Implementation Method 3
an optical anisotropic layer having a liquid crystal compound aligned perpendicular to the stretching direction
Implementation Method 4
at least one optical anisotropic layer containing a liquid crystal compound
Implementation Method 5
providing specific retardation relationships and a low photoelastic modulus to maintain optical stability
Data Source
AI summary
An optical compensation sheet is provided and has a stretched polymer film or stretched cellulose acylate film and at least one optical anisotropic layer containing a liquid crystal compound, and has retardations satisfying the specific relationships defined in the specification.