Birefringence Compensation Layers for LCD Light Leakage
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Solution Overview
Problem
Electronic device displays often suffer from light leakage due to stress-induced birefringence when mounted in a housing, as materials like glass in the thin-film transistor and color filter layers undergo bending, causing undesirable changes in polarization that lead to light leakage, especially in dark states.
Innovation Solution
Incorporating birefringence compensation layers with photo-elastic constants opposite to those of the thin-film transistor and color filter layers, these layers can be made of glass or polymer materials like polystyrene, attached using optically clear adhesives, to counteract stress-induced birefringence effects, ensuring linearly polarized backlight remains linear, reducing light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If display components are mounted in the housing using standoffs and housing walls, then the display is securely positioned and supported, but stress-induced birefringence occurs in glass layers causing light leakage
Solution Approach 1:
The patent applies stress relief layers that intentionally introduce controlled stress to counteract the stress-induced birefringence caused by housing mounting. The stress relief layers are designed with specific photo-elastic properties to generate compensating birefringence that cancels out the harmful effects of mounting stress, converting the problematic stress into a beneficial compensation mechanism
Solution Approach 2:
The patent introduces stress relief layers as intermediary elements between the display glass layers and the housing mounting structure. These intermediate layers absorb and redistribute mounting stresses, preventing them from directly inducing birefringence in the optically critical glass layers while still allowing secure display mounting
2Ease of manufacture
If care is not taken during mounting, then manufacturing is simpler and faster, but optical effects cause undesired light leakage in dark state
Solution Approach 1:
The patent incorporates stress relief layers during the display assembly manufacturing process, before the display is installed in the housing. These layers are pre-positioned between specific display components to proactively compensate for mounting stresses that will occur during installation, ensuring reliable dark state performance without requiring special mounting procedures
3Reliability
If birefringence compensation layers are added to reduce light leakage, then dark state performance is improved, but device complexity increases
Solution Approach 1:
The patent applies stress relief layers selectively at specific locations within the display structure, between particular glass layers where stress-induced birefringence is most problematic. Rather than uniformly treating the entire display, the compensation is localized to the critical optical paths, reducing the overall complexity increase while maintaining effectiveness
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 birefringence compensation layers effectively mitigate light leakage by compensating for polarization changes caused by stress in the display layers, enhancing the display's ability to maintain a dark state without unwanted light emission.
Implementation Method 1
materials like glass in the thin-film transistor and color filter layers undergo bending, causing undesirable changes in polarization that lead to light leakage
Implementation Method 2
A birefringence compensation layer may be a glass layer having a photo-elastic constant that is opposite in sign to the photo-elastic constant of the thin-film transistor layer and/or the photo-elastic constant of the color filter layer
Data Source
AI summary
A display is provided that has upper and lower polarizers, a color filter layer, a liquid crystal layer, and a thin-film transistor layer. The color filter layer and thin-film transistor layer may be formed from materials such as glass that are subject to stress-induced birefringence. To reduce light leakage that reduces display performance, one or more birefringence compensation layers may be incorporated into the display to help compensate for any birefringence effects. The compensation layers may include a birefringence compensation layer attached to the color filter layer or the thin-film transistor layer. A display may include an upper compensation layer attached to the color filter layer and a lower compensation layer attached to the thin-film transistor layer. The compensation layer may be formed from glass or polymer materials that have a negative photo-elastic constant.