TOP Reflective Polarizer Thickness Profile for Low Color
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Solution Overview
Problem
Conventional TOP reflective polarizers are not suitable for on-glass applications in modern liquid crystal display systems due to significant color generation at high oblique incidence angles, especially when used with high contrast absorbing polarizers.
Innovation Solution
A TOP reflective polarizer with a tailored thickness profile, where thicker optical repeat units face the front and thinner units face the back, is laminated directly to a high contrast absorbing polarizer without an air gap or high haze light diffusing layer, optimizing the layer orientation to minimize perceived color at oblique angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a TOP reflective polarizer is used in an on-glass configuration with a high contrast absorbing polarizer, then the display system achieves high contrast and simplified structure, but significant color is generated at high oblique incidence angles
Solution Approach 1:
The patent changes the physical parameter of layer thickness by implementing a thickness gradient across the microlayer packet, with thicker layers at the front surface and thinner layers at the back surface. This parameter modification allows the optical properties of the reflective polarizer to be tuned specifically for on-glass configurations, reducing perceived color at oblique angles while maintaining high contrast performance with high contrast absorbing polarizers.
Solution Approach 2:
The patent applies local quality by creating non-uniform thickness distribution within the microlayer packet. Different regions of the packet have different thicknesses - the front portion has thicker layers while the back portion has thinner layers. This spatial variation in local properties enables the polarizer to optimize performance for the specific on-glass application, reducing color generation at oblique angles where this configuration is most critical.
2Illumination intensity
If a TOP reflective polarizer with standard thickness profile is used, then broadband reflection is achieved, but excessive perceived color occurs at oblique angles requiring additional light diffusing layers
Solution Approach 1:
The patent modifies the thickness parameter of the microlayer packet to create a gradient profile that maintains broadband reflection capability while reducing perceived color at oblique angles. The thickness gradient is specifically designed to preserve the broad spectral reflection characteristics needed for display performance while correcting the angular color response through optimized layer thickness distribution.
Solution Approach 2:
The patent inverts the conventional approach by placing thicker layers at the front surface rather than the back surface. This inverted thickness profile reverses the optical path through the microlayer packet, changing how light interacts with the gradient and thereby reducing perceived color at oblique angles while preserving broadband reflection properties.
3Illumination intensity
If thicker microlayers are positioned at the back of the packet, then broadband reflection is optimized, but perceived color increases at high oblique angles
Solution Approach 1:
The patent inverts the conventional layer arrangement by positioning thicker microlayers at the front surface and thinner microlayers at the back surface, rather than the traditional configuration. This inversion fundamentally changes the optical interaction, reducing perceived color at high oblique angles while maintaining broadband reflection performance through the optimized gradient profile.
Solution Approach 2:
The patent changes the spatial distribution parameter of layer thickness, creating a gradient that decreases from front to back. This parameter modification optimizes the optical path for reduced perceived color at oblique angles while preserving the broadband reflection characteristics necessary for display performance.
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 allows for acceptable optical performance in liquid crystal displays, reducing unwanted color at high oblique angles and eliminating the need for additional light diffusing layers, thereby enhancing display brightness and color accuracy.
Implementation Method 1
The reflective polarizer is a multilayer optical film of alternating polymer layers that reflects and transmits light by optical interference
Implementation Method 2
Some of the microlayers are biaxially birefringent, and adjacent pairs of the first and second microlayers form optical repeat units
Data Source
AI summary
Multilayer optical film reflective polarizers previously considered to have excessive off-axis color can provide adequate performance in an LC display in an “on-glass” configuration, laminated to a back absorbing polarizer of the display, without any light diffusing layer or air gap in such laminate. The reflective polarizer is a tentered-one-packet (TOP) multilayer film, having only one packet of microlayers, and oriented using a standard tenter such that birefringent microlayers in the film are biaxially birefringent. The thickness profile of optical repeat units (ORUs) in the microlayer packet is tailored to avoid excessive perceived color at normal and oblique angles. Color at high oblique angles in the white state of the display is reduced by positioning thicker ORUs closer to the absorbing polarizer, and by ensuring that, with regard to a boxcar average of the ORU thickness profile, the average slope from an ORU(600) to an ORU(645) does not exceed 1.8 times the average slope from an ORU(450) to the ORU(600).