Optical Film With Gradient Microstructures For LED Backlight Uniformity
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Solution Overview
Problem
Conventional back light units for LCD displays face challenges in achieving uniform light distribution and hiding individual LEDs while maintaining a thin profile, as diffuser films either fail to provide adequate uniformity or increase thickness to achieve better results.
Innovation Solution
An optical film with spatially modulated microstructures, such as prisms, pyramids, or cones, is used above an array of LEDs to create a gradient structure that spreads light more effectively directly above LEDs and less so between them, enhancing on-axis luminance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a diffuser film is used to spread light from LEDs, then light uniformity is improved, but the individual LED points of light cannot be effectively hidden
Solution Approach 1:
The optical film implements local quality by having different microstructure configurations in different regions: regions directly above LEDs contain microstructures optimized for light extraction and spreading, while regions between LEDs contain different microstructures optimized for further diffusion and uniformity. This spatially varying local quality allows the film to simultaneously address light extraction from LEDs and hide the individual LED points.
Solution Approach 2:
The optical film is segmented into multiple regions with distinct microstructure patterns. Each region is independently optimized for its specific function: light extraction regions above LEDs and light spreading regions between LEDs. This segmentation allows the film to perform multiple functions that would be conflicting in a uniform structure.
2Illumination intensity
If the thickness of the diffuser film is increased to spread light further, then light uniformity is improved, but the back light unit thickness increases
Solution Approach 1:
Instead of increasing film thickness to achieve better light spreading, the invention changes the parameter of microstructure configuration. By optimizing the size, shape, and distribution of microstructures in different regions, the film achieves enhanced light uniformity within a thin profile, avoiding the need to increase overall thickness.
Solution Approach 2:
The invention transitions from solving the light spreading problem in the thickness dimension to solving it in the lateral dimension through spatially varying microstructure patterns. The microstructures are arranged and sized differently across the film surface to achieve the desired light distribution without increasing film thickness.
3Illumination intensity
If conventional optical films are used, then manufacturing is simpler, but light uniformity and brightness enhancement are insufficient
Solution Approach 1:
The invention merges multiple functions into a single optical film: light extraction, light spreading, and light uniformity enhancement. By integrating these functions into one film with spatially modulated microstructures, the design achieves superior performance without proportionally increasing manufacturing complexity, as all microstructures can be formed in a single molding or coating process.
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 film achieves a 50% enhancement in light uniformity and a 4% increase in brightness, effectively hiding individual LEDs and providing a brighter, more uniform light to the LCD panel while maintaining a thin profile.
Implementation Method 1
The spatially modulated microstructures have different sizes and/or shapes configured to create a gradient structure within each region. The gradient structure within each region is constructed and arranged to convert light beams emitted by the respective light emitting diode at different angles into a more uniform and higher on-axis luminance upon exiting the back light unit.
Data Source
AI summary
An optical film for a back light unit that includes an array of light emitting diodes. The optical film includes a substrate, and a plurality of regions of spatially modulated microstructures on at least one side of the substrate. The spatially modulated microstructures have different sizes and/or shapes configured to create a gradient structure within each region. The gradient structure within each region is constructed and arranged to cause more spreading of light when positioned directly above an individual light emitting diode and less spreading of light at locations not directly above an individual light emitting diode. Within the back light unit, the gradient structure converts light beams emitted by the respective light emitting diode at different angles into a more uniform and higher on-axis luminance upon exiting the back light unit.