Phase Difference Film Tint Stabilization via Layered Anisotropy
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Solution Overview
Problem
Phase difference films used in circularly polarizing plates exhibit significant changes in tint when viewed from oblique angles, affecting display device performance.
Innovation Solution
A phase difference film configuration comprising specific optically anisotropic layers, including C-plates and A-plates, with carefully aligned liquid crystal compounds and adhesion layers, to minimize tint changes when combined with a polarizer and viewed from various angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase difference film with optically anisotropic layers is combined with a polarizer to form a circularly polarizing plate, then the circular polarization function is achieved, but the tint changes significantly when viewed from oblique directions
Solution Approach 1:
The phase difference film is divided into four distinct optically anisotropic layers (first C-plate, second A-plate, third layer with twist-aligned liquid crystal compound, and fourth C-plate), each contributing specific optical characteristics. This segmentation allows precise control of light interaction at different stages, enabling stable tint appearance from oblique directions while maintaining circular polarization function.
Solution Approach 2:
The invention uses a composite structure combining different types of optically anisotropic layers with specific retardation values and orientation relationships. The combination of C-plates and A-plates with controlled in-plane retardation and thickness direction retardation creates a composite optical system that compensates for viewing angle dependencies, stabilizing tint appearance across various observation angles.
2Stability of the object's composition
If multiple optically anisotropic layers are laminated to improve tint stability, then the optical performance is enhanced, but the device complexity increases
Solution Approach 1:
The invention optimizes specific optical parameters of each layer including in-plane retardation (Re), thickness direction retardation (Rth), and the angle between slow axes. By precisely controlling these parameters within specified ranges and relationships, the four-layer structure achieves tint stability without requiring excessive layers, balancing performance enhancement with manageable complexity.
Solution Approach 2:
Each optically anisotropic layer is designed with specific local optical characteristics: the first and fourth layers are C-plates with specific Rth values, the second layer is an A-plate with specific Re and Rth values, and the third layer contains twist-aligned liquid crystal compound with controlled twisted angle. This local quality differentiation allows each layer to perform its specific function, achieving overall tint stability through coordinated local optimizations.
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 configuration stabilizes the tint appearance across all azimuthal angles, enhancing the performance of circularly polarizing plates in display devices.
Implementation Method 1
a third optically anisotropic layer which is a layer formed by fixing a liquid crystal compound twist-aligned along a helical axis extending in a thickness direction
Implementation Method 2
A phase difference film including a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order
Implementation Method 3
Phase difference film having refractive index anisotropy
Implementation Method 4
a phase difference film that has a small change in tint in a case where the phase difference film is combined with a polarizer
Data Source
AI summary
Provided are a phase difference film that has a small change in tint in a case where the phase difference film is combined with a polarizer and then applied as a circularly polarizing plate to a display device, and the display device is observed from an oblique direction at all azimuthal angles; as well as a circularly polarizing plate and a display device. The phase difference film includes a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order, in which the first optically anisotropic layer is a C-plate, the second optically anisotropic layer is an A-plate, the third optically anisotropic layer is a layer formed by fixing a liquid crystal compound twist-aligned along a helical axis extending in a thickness direction, and the first, second, third, and fourth optically anisotropic layers have a predetermined configuration.