Circular Polarizing Plate Layout for Sunlight Black Tint Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing circularly polarizing plates exhibit black tint variation when displayed in black under severe conditions such as sunlight, which affects the visual quality of display devices.
Innovation Solution
A circularly polarizing plate configuration comprising a polarizer, a first optically anisotropic layer with a twist-aligned liquid crystal compound, and a second optically anisotropic layer as an A-plate, where specific relationships between the absorption axes and in-plane slow axes, along with refractive index anisotropy and retardation values, are defined to suppress black tint variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional circularly polarizing plate is used, then the basic polarization function is achieved, but black tint variation occurs under sunlight conditions
Solution Approach 1:
The circularly polarizing plate is divided into three distinct functional layers: a polarizing layer, a first optically anisotropic layer (twisted nematic liquid crystal layer), and a second optically anisotropic layer (A-plate). This segmentation allows each layer to be independently optimized for specific optical functions, enabling better control over light polarization and phase difference to suppress black tint variation under sunlight conditions while maintaining reliable polarization performance.
2Reliability
If the refractive index anisotropy and thickness of the first optically anisotropic layer are increased to improve polarization performance, then the black tint variation worsens under severe conditions
Solution Approach 1:
The patent optimizes specific parameters of the first optically anisotropic layer: the product of refractive index anisotropy (Δn) and thickness (d) at 550 nm wavelength is controlled within 150 nm < Δnd ≤ 450 nm, and the twisted angle of the liquid crystal compound is set between 20° and 70°. These parameter changes enable effective suppression of black tint variation under sunlight while maintaining reliable polarization performance.
Solution Approach 2:
The invention combines a twisted nematic liquid crystal compound in the first optically anisotropic layer with a specific A-plate (second optically anisotropic layer) having controlled in-plane retardation. This composite structure leverages the complementary optical properties of both materials to achieve superior performance in suppressing black tint variation under severe lighting conditions.
3Reliability
If the in-plane retardation of the second optically anisotropic layer is increased to enhance optical control, then the black tint variation increases when viewed from front direction
Solution Approach 1:
The in-plane retardation (Re) of the second optically anisotropic layer (A-plate) at 550 nm wavelength is precisely controlled within 30 nm ≤ Re(550) < 150 nm. This parameter optimization enables effective suppression of black tint variation when viewed from the front direction under sunlight conditions while maintaining the necessary optical control capability for circular polarization.
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 effectively reduces black tint variation in display devices when viewed under sunlight, enhancing visual clarity and quality.
Implementation Method 1
the first optically anisotropic layer 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 value of a product Δnd of a refractive index anisotropy Δn of the first optically anisotropic layer
Implementation Method 3
an in-plane retardation Re(550) of the second optically anisotropic layer at a wavelength of 550 nm
Data Source
AI summary
Provided are a circularly polarizing plate in which the black tint variation is suppressed in a case where a display device obtained by attaching the circularly polarizing plate to a display element is displayed in black and is then viewed from the front direction in a sunlight environment, and a display device. The circularly polarizing plate is has a polarizer, a first optically anisotropic layer, and a second optically anisotropic layer in this order, in which the first optically anisotropic layer is a layer formed by fixing a liquid crystal compound twist-aligned along a helical axis extending in a thickness direction, the second optically anisotropic layer is an A-plate, an absorption axis of the polarizer and an in-plane slow axis of the second optically anisotropic layer are parallel or orthogonal to each other, and the first optically anisotropic layer and the second optically anisotropic layer exhibit predetermined optical properties.