IPS Liquid Crystal Display Retardation Regions
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Solution Overview
Problem
IPS-mode liquid-crystal display devices face issues with color shift at oblique viewing angles due to unsuitable wavelength dispersion characteristics of the retardation layer, which compromises both viewing angle contrast and color fidelity.
Innovation Solution
The implementation of an IPS or FFS-mode liquid-crystal display device configuration that includes a first polarizing film, an optical compensatory film with specific retardation regions, and a liquid-crystal layer using a nematic liquid-crystal material, where the retardation characteristics of the retardation layers are optimized to reduce color shift and enhance viewing angle contrast by controlling the alignment and refractive indices of the liquid-crystal molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a retardation layer containing vertically-aligned discotic liquid-crystal molecules is used to improve viewing angle contrast, then viewing angle contrast is improved, but color shift occurs in oblique directions
Solution Approach 1:
The optical compensatory film is divided into two distinct retardation regions: a first retardation region containing vertically-aligned discotic liquid-crystal molecules and a second retardation region with specific retardation characteristics (Re(550) ≤ 20 nm, Rth(550) = 20-120 nm). This segmentation allows each region to contribute differently to optical compensation, improving viewing angle contrast while minimizing color shift through coordinated action.
Solution Approach 2:
Different regions of the optical compensatory film are assigned different optical properties. The first retardation region provides strong viewing angle compensation through vertically-aligned discotic molecules, while the second retardation region provides supplementary compensation with controlled retardation values. This local differentiation enables simultaneous optimization of both viewing angle contrast and color fidelity.
2Ease of manufacture
If the retardation characteristics of the retardation layer are optimized to reduce color shift, then color shift is reduced, but viewing angle contrast may be compromised
Solution Approach 1:
The optical compensatory film combines two different types of retardation regions with distinct optical characteristics. The first region uses discotic liquid-crystal molecules for strong viewing angle compensation, while the second region uses materials with specific retardation properties (Re(550) ≤ 20 nm, Rth(550) = 20-120 nm). This composite structure achieves both color accuracy and viewing angle contrast through synergistic optical compensation.
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 improves viewing angle contrast while minimizing color shift, providing a more stable and vivid display experience by optimizing the retardation characteristics and alignment of the liquid-crystal molecules within the display device.
Implementation Method 1
retardation in-plane at a wavelength of 550 nm, Re(550) of the second retardation region is equal to or less than 20 nm, and retardation along the thickness-direction at a wavelength of 550 nm, Rth(550) of the second retardation region is from 20 nm to 120 nm
Implementation Method 2
a first retardation region comprising a retardation layer containing a vertically-aligned discotic liquid-crystal compound
Implementation Method 3
liquid-crystal molecules of the nematic liquid-crystal material are aligned parallel to the surfaces of the pair of substrates at the black state
Data Source
AI summary
An IPS or FFS-mode liquid-crystal display device includes an optical compensatory film having a first retardation region and a second retardation region adjacent to the first retardation region, wherein a slow axis of the first retardation region is parallel to a slow axis of the second retardation region, retardation in-plane at a wavelength of 550 nm, Re(550) of the second retardation region is equal to or less than 20 nm, and retardation along the thickness-direction at a wavelength of 550 nm, Rth(550) of the second retardation region is from 20 nm to 120 nm, the first retardation region includes a retardation layer containing a vertically-aligned discotic liquid-crystal compound, and Re thereof at a wavelength of 450 nm, 550 nm and 650 nm, Re(450), Re(550) and Re(650) satisfy Re(450)/Re(550) of from 1 to 1.13 and Re(650)/Re(550) of from 0.94 to 1.