Multilayer Optical Film for Display Backlight Uniformity
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Solution Overview
Problem
Existing backlight systems for LCDs face challenges in achieving efficient and uniform illumination, particularly in reducing eye strain and extending the lifetime of optical film layers, while effectively managing blue, green, and red light spectra.
Innovation Solution
The implementation of an optical stack with one or more light converting layers that convert blue light into green and red light, combined with a multilayer optical film configuration that optimally transmits and reflects light across different wavelengths and angles, thereby enhancing the display system's illumination efficiency and reducing UV impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional backlight system uses blue LED light sources with simple optical films, then the device complexity is low, but the illumination uniformity and spectral quality are insufficient causing eye strain
Solution Approach 1:
The optical film is divided into multiple thin layers (at least 4 layers) with thicknesses less than 500 nm each. This segmentation allows precise control of optical properties at different wavelengths and angles, achieving superior illumination uniformity while managing the complexity through systematic layer design
Solution Approach 2:
The patent employs composite optical film structures combining multiple materials with different optical characteristics. Each layer is designed with specific refractive indices and optical densities to achieve wavelength-selective transmission and reflection, creating a composite system that optimizes illumination quality
2Reliability
If optical films are made thicker to improve durability and UV protection, then the reliability improves, but the light transmission efficiency decreases
Solution Approach 1:
The patent uses thin film structures (each layer < 500 nm) that provide sufficient mechanical durability and UV protection while maintaining optical transparency. The thin film design allows light to pass through with minimal absorption or scattering, preserving transmission efficiency while ensuring film longevity
Solution Approach 2:
Composite optical film structures combine materials optimized for different functions: some layers provide UV blocking and mechanical strength, while others are optimized for light transmission. This composite approach allows simultaneous achievement of reliability and energy efficiency
3Productivity
If the optical film transmits more blue light, then the energy efficiency improves, but the harmful UV effects on optical films increase
Solution Approach 1:
The patent incorporates UV-blocking layers within the optical film structure that convert harmful UV radiation into beneficial effects by protecting subsequent optical layers from degradation. The UV-blocking layers are positioned to intercept UV wavelengths while allowing visible blue light to pass through, thus maintaining backlight efficiency while eliminating UV damage
Solution Approach 2:
Intermediate layers are introduced between the blue LED source and the light-converting phosphor layers. These intermediary layers selectively block UV wavelengths while transmitting visible blue light, acting as a mediator that protects the optical system from UV damage without compromising the overall backlight efficiency
4Illumination intensity
If conventional optical films are used without angle-dependent design, then the manufacturing precision requirements are lower, but the illumination uniformity at different viewing angles deteriorates
Solution Approach 1:
Different layers of the optical film are designed with locally optimized properties: some layers have specific thicknesses and refractive indices tailored for normal incidence, while others are optimized for oblique angles. This local quality variation ensures uniform illumination across different viewing angles while managing manufacturing precision through targeted design
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 significantly improves the uniformity and efficiency of backlight illumination, reduces eye strain by managing UV light, and extends the lifespan of optical film layers by minimizing adverse UV effects.
Implementation Method 1
The one or more light converting layers are configured to receive a blue light including a blue wavelength spectrum having at least one blue peak at a corresponding blue peak wavelength and convert portions of the received blue light to green and red lights within the respective green and red emission spectra
Implementation Method 2
For an incident light incident at an incident angle of less than about 10 degrees, the first optical film transmits greater than about 50% of the incident light for the blue wavelength and reflects greater than about 60% of the incident light for each of the green and red peak wavelengths
Implementation Method 3
For an incident light incident at an incident angle of less than about 10 degrees, the first optical film transmits greater than about 50% of the incident light for the blue wavelength
Data Source
AI summary
A display system includes a light source emitting blue light including blue wavelength, and UV light including UV wavelength. A first multilayer optical film (MOF) is disposed between a display panel and a second MOF. Light conversion films receive and convert emitted blue light to green and red lights. At incident angles of less than 10 degrees, the first MOF transmits greater than 50% of light for the blue wavelength and reflects greater than 60% for green and red peak wavelengths. The second MOF transmits greater than 50% for blue, green and red peak wavelengths, and reflects greater than about 60% for the UV wavelength. At oblique incident angles, the first MOF reflects greater than 50% for the blue, green and red peak wavelengths, and the second MOF transmits greater than 50% for the blue, green and red peak wavelengths, and transmits greater than 60% for the UV wavelength.