Display Polarizer Film Stack for Interference Rainbow Reduction
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Solution Overview
Problem
Existing polarizers for displays, particularly those using polyethylene terephthalate films with high in-plane retardation, cause interference rainbow patterns due to birefringence, affecting image quality and are unsuitable for flexible or thin devices.
Innovation Solution
A polarizer design featuring a polyester protective film with an in-plane retardation of less than 1200 nm, utilizing primers with specific refractive index relationships (np > n1 > n2 and (np−n1)/(np−n2) ≤ 0.7) to minimize birefringence and interference, combined with optional antiglare and anti-reflective layers to enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a polyester film with high in-plane retardation (R0≥3000 nm) is used to reduce interference rainbow patterns, then the occurrence of interference rainbow patterns is reduced, but the image quality and appearance of the display are significantly affected
Solution Approach 1:
The patent changes the key parameter of in-plane retardation from high (≥3000 nm) to low (<1200 nm) to eliminate interference rainbow patterns while maintaining good image quality. This parameter change fundamentally resolves the contradiction by finding a new operating point that satisfies both requirements.
Solution Approach 2:
The patent uses a composite structure combining polyester film with specific primer layers having controlled refractive indices. The primers form an intermediate layer that manages light interference through refractive index matching, allowing the use of low in-plane retardation film while preventing interference patterns.
2Object-affected harmful factors
If a polyester film with very high in-plane retardation (R0≥8000 nm) is used to further reduce interference rainbow patterns, then the occurrence of interference rainbow patterns is reduced, but high haze or high roughness coating layers are required which significantly affect image quality
Solution Approach 1:
The patent changes the in-plane retardation parameter to a low value (<1200 nm) and eliminates the need for high haze or high roughness coating layers. This dual parameter optimization resolves the contradiction by achieving interference pattern reduction through a different mechanism that doesn't compromise image quality.
Solution Approach 2:
The patent extracts and removes the problematic high haze or high roughness coating layers that were previously necessary. By using low in-plane retardation film combined with properly designed primers, the patent eliminates the need for these quality-degrading layers.
3Object-affected harmful factors
If the thickness of the polyester film is increased to obtain very high in-plane retardation, then the expected display quality is achieved, but the device becomes thicker and heavier contrary to current development trends
Solution Approach 1:
The patent changes the in-plane retardation parameter to low (<1200 nm) and achieves interference pattern reduction without increasing thickness. This allows the use of thin films that meet both the anti-interference requirement and the thinness trend of modern displays.
4Object-affected harmful factors
If a birefringent polyester film manufactured by high stretching rate is used to obtain very high in-plane retardation, then the expected display quality is achieved, but the tensile strength is reduced and heat shrinkage ratios differ between machine and transverse directions
Solution Approach 1:
The patent changes the in-plane retardation parameter to low (<1200 nm), which eliminates the need for high stretching rate manufacturing. This results in films with better tensile strength and more uniform heat shrinkage characteristics while still preventing interference patterns.
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 solution effectively reduces interference rainbow patterns without increasing haze or roughness, maintaining high light transmittance and mechanical strength, suitable for various display types including flexible devices.
Implementation Method 1
the polyester film, such as polyethylene terephthalate (PET) film, comprises benzene-ring structure with high crystallinity and has birefringence after stretch manufacturing process
Implementation Method 2
a first primer having a first refractive index (n1) disposed on one side of the polyester substrate, and a second primer having a second refractive index (n2) disposed on the other side of the polyester substrate and adjacent to the polarizing layer, wherein np>n1>n2
Data Source
AI summary
A polarizer applied for a viewing side of a display is disclosed. The polarizer comprises a polarizing layer, and a polyester protective film disposed on a front side of the polarizing layer. The polyester protective film comprises a polyester substrate with an in-plane retardation not greater than 1200 nm and having an average refractive index (np), a first primer layer disposed on one side of the polyester substrate and having a first refractive index (n1), and a second primer layer disposed on the other side of the polyester substrate and adjacent to the polarizing layer and having a second refractive index (n2), wherein the refractive indexes of the polyester protective substrate, the first primer layer and the second primer layer satisfy the relationships of np>n1>n2 and (np−n1)/(np−n2)≤0.7 to reduce interference rainbow patterns.