Three-Layer Retardation Polarizing Plate for Low Lateral Reflectivity
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Solution Overview
Problem
Existing polarizing plates for OLED displays suffer from high reflectivity and limited ellipticity, particularly at lateral sides, and have issues with processability and mechanical strength.
Innovation Solution
A polarizing plate design comprising a polarizer with a laminate of three retardation layers, where the first and second retardation layers have specific tilt angles and wavelength dispersions, and the third layer is a positive C plate, allowing for improved reflectivity and ellipticity while enabling roll-to-roll processing and enhanced mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative wavelength dispersion λ/4 retardation layer and a positive C plate are sequentially stacked on a lower surface of a polarizer to realize a circular polarizing plate, then the circular polarizing plate function is achieved, but the processability is poor due to difficulty in attachment through roll-to-roll processing and the retardation layer has insufficient strength
Solution Approach 1:
The patent changes the wavelength dispersion parameter from negative to positive for the first retardation layer, and adjusts the retardation values (50-100 nm for first layer, 180-240 nm for second layer) to achieve the circular polarizing plate function while improving processability and mechanical strength through roll-to-roll processing
Solution Approach 2:
The patent uses a composite structure of multiple retardation layers with different wavelength dispersions (first layer: positive wavelength dispersion, second layer: positive or flat wavelength dispersion) and specific retardation values to achieve the desired optical function while improving mechanical properties and processability
2Reliability
If a λ/2 retardation layer and a λ/4 retardation layer are sequentially stacked on the lower surface of the polarizer, then the circular polarizing plate function is achieved, but the reflectivity is high in all directions including lateral sides
Solution Approach 1:
The patent changes the retardation parameters from conventional λ/2 and λ/4 layers to specific in-plane retardation values (50-100 nm for first layer, 180-240 nm for second layer) with positive wavelength dispersion, which reduces reflectivity in all directions including lateral sides while maintaining the circular polarizing plate function
Solution Approach 2:
The patent introduces a third retardation layer (positive C plate) with specific out-of-plane retardation (-100 nm to -10 nm at 500 nm) to address the reflectivity issue specifically at lateral sides and improve ellipticity in all directions
3Reliability
If a liquid crystal layer is formed as the λ/4 retardation layer to achieve circular polarizing plate function, then the circular polarizing plate function is achieved, but an alignment layer is required and an additional process for sequentially transferring these layers to the polarizer is required after coating each of the layers
Solution Approach 1:
The patent extracts the liquid crystal layer and alignment layer from the conventional circular polarizing plate structure, replacing them with retardation layers formed by coating and stretching polymer films, which eliminates the need for alignment layers and sequential transfer processes
Solution Approach 2:
The patent replaces the liquid crystal molecular alignment mechanism with mechanical stretching of polymer films to induce birefringence and achieve the desired retardation properties, eliminating the need for alignment layers and complex sequential transfer processes
4Reliability
If conventional retardation layers are used, then the circular polarizing plate function is achieved, but the thickness of the polarizing plate is large and mechanical strength is insufficient
Solution Approach 1:
The patent uses retardation layers with specific in-plane retardation values (50-100 nm for first layer, 180-240 nm for second layer) achieved through controlled stretching, which reduces the required thickness of each layer while maintaining the circular polarizing plate function and improving mechanical strength
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 design achieves very low reflectivity and high ellipticity in all directions, including lateral sides, with reduced thickness and improved processability, while maintaining mechanical strength.
Implementation Method 1
the first retardation layer exhibits positive wavelength dispersion and has an in-plane retardation of 50 nm to 100 nm at a wavelength of 550 nm, and the second retardation layer exhibits positive wavelength dispersion or flat wavelength dispersion and has an in-plane retardation of 180 nm to 240 nm at a wavelength of 550 nm
Implementation Method 2
the first retardation layer may have a slow axis tilted at an angle of +40° to +50° or at an angle of −50° to −40° with respect to an absorption axis or a transmission axis of the polarizer, the slow axis of the first retardation layer is tilted at an angle of +80° to +100° or at an angle of −100° to −80° with respect to a slow axis of the second retardation layer
Implementation Method 3
the third retardation layer may be a positive C plate and may have an out-of-plane retardation of −100 nm to −10 nm at a wavelength of 500 nm
Data Source
AI summary
A polarizing plate and an optical display apparatus including the same. The polarizing plate includes: a polarizer; and a laminate of a first retardation layer and a second retardation layer, and a third retardation layer sequentially stacked on a lower surface of the polarizer, wherein the first retardation layer may have a slow axis tilted at an angle of +40° to +50° or at an angle of −50° to −40° with respect to an absorption axis or a transmission axis of the polarizer, the slow axis of the first retardation layer is tilted at an angle of +80° to +100° or at an angle of −100° to −80° with respect to a slow axis of the second retardation layer, the first retardation layer exhibits positive wavelength dispersion and has an in-plane retardation of 50 nm to 100 nm at a wavelength of 550 nm, and the second retardation layer has positive wavelength dispersion or flat wavelength dispersion and an in-plane retardation of 180 nm to 240 nm at a wavelength of 550 nm.