Liquid Crystal Display with Optical Compensation Layers
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Solution Overview
Problem
Liquid crystal display apparatuses using homogeneously aligned liquid crystal cells face issues with insufficient black brightness when viewed from oblique directions due to varying polarization states of light depending on color.
Innovation Solution
The apparatus includes a liquid crystal cell with substrates having specific thickness direction retardations and optical compensation layers with specific refractive index characteristics, controlling the polarization direction and ellipticity of light emitted to minimize black brightness in oblique directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a homogeneously aligned liquid crystal cell is used, then the liquid crystal display apparatus can be manufactured with conventional structures, but the black brightness in oblique directions does not become sufficiently small
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness direction retardation Rth(550) of substrates to be within -10 nm to 100 nm and the product A×E to be 300 or less. These parameter specifications transform the conventional liquid crystal cell into one that achieves sufficiently small black brightness in oblique directions while maintaining manufacturability through standard homogeneous alignment processes.
Solution Approach 2:
The patent employs composite materials by combining the homogeneously aligned liquid crystal cell with specifically designed optical compensation layers. The substrates themselves act as optical compensation elements with controlled Rth values, creating a composite structure that addresses the oblique viewing angle issue without requiring complete redesign of the liquid crystal alignment mechanism.
2Illumination intensity
If optical compensation is attempted to reduce black brightness in oblique directions, then the display quality improves, but the device complexity increases due to additional optical compensation layers and precise retardation control
Solution Approach 1:
The patent applies universality by designing substrates that simultaneously serve as both structural components and optical compensation elements. The substrates with controlled Rth(550) values perform dual functions: providing mechanical support and acting as optical compensation layers to unify polarization states. This eliminates the need for separate compensation layers, reducing device complexity while maintaining display quality.
Solution Approach 2:
The patent uses parameter changes to simplify the optical compensation structure by precisely controlling the Rth(550) of substrates within -10 nm to 100 nm and the product A×E to 300 or less. These parameter specifications enable the substrates themselves to provide sufficient optical compensation, eliminating or reducing the need for additional complex compensation layers.
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
This configuration effectively reduces black brightness in oblique directions by unifying the polarization state of light, ensuring a sufficiently black display when viewed from angles, thereby improving the display's optical characteristics.
Implementation Method 1
the first optical compensation layer shows a refractive index characteristic of nx>nz>nym and the second optical compensation layer shows a refractive index characteristic of nz>nx=nym
Data Source
AI summary
There is provided a liquid crystal display apparatus having sufficiently small black brightness in an oblique direction. A liquid crystal display apparatus according to an embodiment of the present invention includes: a liquid crystal cell including a viewer-side substrate, a back surface-side substrate, and a homogeneously aligned liquid crystal layer sandwiched therebetween; a first polarizer arranged on a viewer side of the liquid crystal cell; a second polarizer arranged on a back surface side of the liquid crystal cell; a first optical compensation layer arranged between the liquid crystal cell and the first polarizer; and a second optical compensation layer arranged between the liquid crystal cell and the second polarizer. The viewer-side substrate and the back surface-side substrate each have a thickness direction retardation Rth(550) of from −10 nm to 100 nm, and a product A×E is 300 or less.