Thin Multilayer Reflector Uniform Left Bandedge
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Solution Overview
Problem
Conventional multilayer reflectors exhibit caliper variations and nonuniformities during manufacturing, leading to unsuitable performance in precision applications, particularly in displays where uniform backlight illumination and high efficiency are challenging due to large variations in the left bandedge of the reflector.
Innovation Solution
A multilayer optical reflector design featuring a plurality of optical repeat units with a specific f-ratio and minimum optical thickness, ensuring high transmission of unpolarized light between 400 nm to 480 nm and low transmission between 550 nm to 800 nm, with a uniform left bandedge greater than or equal to 500 nm and minimal variation across dimensions, achieving a thickness of less than 55 micrometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multilayer reflectors are manufactured, then production can proceed with standard processes, but caliper variations and nonuniformities occur leading to large variations in left bandedge
Solution Approach 1:
The patent applies parameter changes by specifying precise optical thickness ranges (20-40 nm per layer) and controlled layer composition ratios (birefringent polymer to total polymer) to achieve uniform left bandedge. By controlling the optical parameters and thickness parameters of each layer, the invention resolves the contradiction between manufacturing precision and ease of manufacture.
Solution Approach 2:
The patent uses composite materials by combining birefringent polymer layers with isotropic polymer layers in a multilayer structure. This composite approach enables precise control over optical properties while maintaining manufacturability through the use of polymer materials that can be processed using standard coating techniques.
2Productivity
If the reflector thickness is reduced to improve display performance, then efficiency increases, but manufacturing variations become more significant
Solution Approach 1:
The patent changes the parameter of layer thickness to an optimized range (20-40 nm per layer) that achieves thin overall structure while maintaining manufacturing control. The total thickness is controlled to be less than 50 micrometers, and by specifying the optical thickness and composition ratio parameters, the invention achieves both thinness and manufacturing precision.
Solution Approach 2:
The patent applies local quality by ensuring that each individual layer within the multilayer structure meets specific thickness and composition criteria. By controlling the local properties of each layer (optical thickness, birefringent polymer content), the overall uniformity is achieved even in thin structures.
3Reliability
If standard multilayer structures are used, then manufacturing is straightforward, but transmission characteristics vary across the bandedge region
Solution Approach 1:
The patent employs composite materials with specific optical properties (birefringent and isotropic polymers) arranged in alternating layers. This composite structure provides consistent transmission characteristics by leveraging the complementary optical properties of the different materials, achieving reliability without excessive structural complexity.
Solution Approach 2:
The patent optimizes parameters such as the refractive index contrast between layers, the optical thickness of each layer, and the composition ratio of birefringent to total polymer. By carefully adjusting these parameters, the invention achieves reliable and consistent transmission characteristics across the bandedge region.
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 ensures uniform backlight illumination and high efficiency in displays by maintaining a consistent left bandedge across the reflector, enhancing display performance and reducing material waste through precise control of optical properties.
Implementation Method 1
each optical repeat unit having a total optical thickness and including a birefringent polymer and a second polymer
Implementation Method 2
The plurality of optical repeat units have a minimum optical thickness and an f-ratio such that the average transmission of unpolarized normally incident light from 400 nm to 480 nm is greater than 40%
Data Source
AI summary
Thin multilayer reflectors are described. In particular, thin multilayer reflectors that partially transmit blue light and reflect green and red light are described. The thin multilayer reflectors have a uniform left bandedge across each dimension of the film, wherein the location of the left bandedge varies in a range of no more than 10% of the average left bandedge across that dimension.