IPS Polarizing Plate Retardation Control for Color Shift
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Solution Overview
Problem
In-plane switching (IPS) mode liquid crystal displays face significant challenges with color variation and light leakage, particularly as they become thinner and larger, leading to reduced image quality and increased light leakage issues.
Innovation Solution
A polarizing plate design that includes a polarizer with a first protective layer on the upper surface and a second protective layer on the lower surface, featuring specific retardation properties and axis orientations to improve contrast ratio, reduce lateral color shift, and suppress light leakage, thereby enhancing image quality and black visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional polarizing plates are used in IPS mode liquid crystal displays, then the basic polarization function is provided, but significant color variation (lateral color shift) occurs according to viewing angle
Solution Approach 1:
The polarizing plate is divided into multiple functional layers: a polarizer layer and two protective layers (first and second) with different optical properties. The first protective layer has low birefringence while the second protective layer has high birefringence, allowing each layer to perform its specific function in compensating for viewing angle color variation.
Solution Approach 2:
Different regions of the polarizing plate structure have different optical characteristics. The first protective layer is designed with low birefringence (Re≤100nm) to maintain polarization, while the second protective layer has high birefringence (Re>100nm) to provide optical compensation specifically for viewing angle effects, creating local optical quality variations.
2Volume of moving object
If the liquid crystal display is made thinner and larger, then the display size and thinness are improved, but color variation becomes more apparent and light leakage increases
Solution Approach 1:
The optical compensation function is built into the polarizing plate structure itself through the two protective layers with different birefringence properties. This preliminary design allows the plate to pre-compensate for viewing angle color variation before light reaches the liquid crystal layer, enabling thin and large displays to maintain color accuracy without adding separate compensation components.
3Strength
If conventional protective layers are used on the polarizer, then the polarizer is protected, but light leakage occurs and black visibility is reduced
Solution Approach 1:
The key parameter changed is the birefringence (Re) of the protective layers. The first protective layer is designed with Re≤100nm to minimize phase delay and prevent light leakage, while the second protective layer has Re>100nm for optical compensation. This parameter optimization allows the protective layers to protect the polarizer without causing light leakage that would reduce black visibility.
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 polarizing plate effectively improves front contrast ratio, reduces lateral color shift, and enhances black visibility by controlling in-plane retardation and axis orientations, resulting in improved image quality and reduced light leakage.
Implementation Method 1
the first protective layer has an in-plane retardation Re of about 5,000 nm or more at a wavelength of 550 nm
Implementation Method 2
where |Rth(450)|, |Rth(550)|, and |Rth(650)| are absolute values of out-of-plane retardations (unit: nm) of the second protective layer
Implementation Method 3
assuming an axis of the polarizer having a high index of refraction in an in-plane direction of the polarizer is a reference axis
Data Source
AI summary
A polarizing plate for IPS mode and an optical display apparatus including the same are provided. A polarizing plate includes: a polarizer; a first protective layer on an upper surface of the polarizer; and a second protective layer on a lower surface of the polarizer, wherein, assuming an axis of the polarizer having a high index of refraction in an in-plane direction of the polarizer is a reference axis (0°), an angle of an axis of the first protective layer having a low index of refraction in the in-plane direction thereof is in a range of about −5° to +5°, the first protective layer has an in-plane retardation Re of about 5,000 nm or more at a wavelength of 550 nm, the second protective layer includes a positive C plate layer, and the second protective layer satisfies at least one of Relations 1 and 2.