Microlayer Optical Stack for Privacy Viewing Without Color Shift
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Solution Overview
Problem
Conventional display technologies emit harmful ultraviolet (UV) light and low wavelength blue light, which can cause macular degeneration, and light control films used for privacy often result in undesirable color shifts and black displays for off-axis viewers.
Innovation Solution
An optical stack comprising a light control film with alternating visible light transmitting and absorbing regions, and an optical film with specific microlayers and reflection bands, designed to selectively transmit and reflect UV and blue light based on incidence angle, providing privacy and protection for on-axis viewers while allowing colored light transmission to off-axis viewers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a light control film with narrow viewing angle is used for privacy, then privacy protection is improved, but off-axis viewers see a black display which is undesirable
Solution Approach 1:
The optical film is segmented into multiple microlayers with different optical properties. Each microlayer has specific thickness and refractive index characteristics that collectively create wavelength-selective transmission. This segmentation allows the film to differentiate between on-axis and off-axis light paths while maintaining color transmission for off-axis viewers.
Solution Approach 2:
Different regions of the optical film have locally optimized properties - the microlayers are designed with specific thicknesses and refractive indices that create different optical responses for on-axis versus off-axis incident light. This local quality variation enables the film to provide privacy for on-axis viewers while allowing colored light transmission for off-axis viewers.
2Adaptability or versatility
If conventional light control films are used for privacy, then viewing angle control is improved, but undesirable color shifts occur
Solution Approach 1:
The optical film utilizes controlled changes in physical parameters - specifically the thickness of microlayers and their refractive indices - to achieve wavelength-selective optical responses. By precisely controlling these parameters, the film maintains accurate color transmission for off-axis viewers while providing the desired viewing angle control for privacy.
Solution Approach 2:
The optical film is constructed as a composite structure with multiple microlayers of different materials and thicknesses. This composite design enables simultaneous achievement of viewing angle control and color accuracy by combining materials with complementary optical properties that work together to filter wavelengths selectively.
3Use of energy by moving object
If backlight emits UV and blue light, then lighting efficiency is improved, but harmful effects on viewers occur
Solution Approach 1:
The optical film converts the harmful UV and blue light wavelengths into a beneficial filtering function. By designing microlayers with specific optical properties, the film reflects or absorbs these harmful wavelengths while transmitting visible light, thus protecting viewers without significantly compromising overall lighting efficiency.
Solution Approach 2:
The microlayer structure utilizes controlled changes in layer thickness and refractive index parameters to create wavelength-selective optical filtering. These parameter variations are designed to target specific harmful wavelengths (UV and blue light) for reflection or absorption while maintaining transmission of beneficial visible wavelengths.
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 optical stack effectively blocks harmful UV and blue light for on-axis viewers while allowing transmission of visible light, preventing undesirable color shifts and ensuring off-axis viewers see colored light rather than a black display, thus offering dual functionality of privacy and protection.
Implementation Method 1
The optical film includes a primary reflection band having a first band edge between about 600 nanometers (nm) and about 700 nm, and a secondary reflection band having a second band edge between about 350 nm and about 460 nm
Implementation Method 2
The optical film includes a transmission band including a first band edge, a second band edge, and a full width at half maximum (FWHM) extending from a first low wavelength to a first high wavelength greater than the first low wavelength
Data Source
AI summary
An optical stack includes a light control film and an optical film disposed on the light control film. The light control film includes a plurality of visible light transmitting regions separated from each other by one or more visible light absorbing regions. The optical film includes a plurality of microlayers having an F-ratio between about 0.25 to about 0.35 or about 0.65 to about 0.75. The optical film further includes a primary reflection band having a first band edge between about 600 nanometers (nm) and about 700 nm, and a secondary reflection band having a second band edge between about 350 nm and about 460 nm. The plurality of microlayers has an average optical reflectance of greater than about 80% across a FWHM of the primary reflection band for each of mutually orthogonal first and second polarization states.