Optical Sheet BTDF Design for LED Backlight Uniformity
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Solution Overview
Problem
Conventional backlight modules using LEDs face challenges in achieving uniform illumination due to the point-source nature of light emitting diodes, leading to hot spots and inefficient heat dissipation, which can degrade the resin or lens units over time, especially with high-power elements.
Innovation Solution
A light source module incorporating a light emitting element with an optical sheet exhibiting bidirectional transmittance distribution function characteristics, featuring a depression and protrusion structure on one surface, and a diffusion sheet with dispersed particles, designed to distribute light uniformly and reduce optical distance, thereby enhancing light uniformity and reducing the number of light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional LED backlight modules are used, then the light source can be provided, but uniform illumination cannot be achieved due to hot spots from point light sources
Solution Approach 1:
The optical sheet is segmented into multiple regions with different refractive indices or optical properties, allowing different areas to control light distribution in specific directions. This segmentation enables the conversion of point source light into a more uniform area light source by directing light rays from different LED positions to cover the display area uniformly.
Solution Approach 2:
Different regions of the optical sheet are designed with locally optimized optical characteristics, such as varying refractive indices or micro-lens structures, to control light distribution directionally. This local quality variation allows each region to address specific hot spot areas and achieve overall uniform illumination.
2Reliability
If resin or lens units are used to encapsulate light emitting elements, then protection is provided, but heat dissipation becomes inefficient leading to degradation
Solution Approach 1:
The optical sheet serves as an intermediary component between the LED light sources and the display area. It not only controls light distribution but also facilitates heat management by providing thermal pathways while maintaining optical functionality, thus protecting LEDs from heat accumulation.
Solution Approach 2:
The optical sheet is constructed using composite materials that combine optical transparency with thermal conductivity properties. This allows the material to simultaneously perform light distribution and heat dissipation functions, protecting the LED from thermal degradation while maintaining illumination uniformity.
3Illumination intensity
If multiple light sources are used to achieve uniform illumination, then light uniformity improves, but the number of light sources and optical distance increase
Solution Approach 1:
The patent extracts the light distribution control function from the light sources themselves and transfers it to the optical sheet. This allows fewer LED sources to be used, as the optical sheet performs the additional function of redistributing light uniformly across the display area without requiring proportional increases in the number of LEDs.
Solution Approach 2:
The optical sheet is designed to perform multiple functions simultaneously: light distribution control, heat management, and uniformity enhancement. This multi-functionality allows a single component to replace what would otherwise require multiple separate components, reducing the overall number of light sources needed.
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 achieves excellent light uniformity in a thinner form factor, improving the lifespan and efficiency of the backlight unit by effectively distributing light and managing heat, suitable for applications like LCDs and televisions.
Implementation Method 1
an optical sheet disposed above the light source units and exhibiting bidirectional transmittance distribution function characteristics having first and second peaks at radiation angles less than 0° and greater than 0°
Implementation Method 2
The optical sheet may have a depression and protrusion structure formed on one surface thereof
Implementation Method 3
The depression and protrusion structure may have a plurality of structures having a pyramid shape
Implementation Method 4
a diffusion sheet disposed in a path of light transmitted through the optical sheet after being emitted from the light source unit
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4(a)~4(b)
AI summary
A light source module, a backlight unit, a display apparatus, a television set, and an illumination apparatus are provided. The light source module includes: one or more light source units (101) including a light emitting element (111) emitting light when electricity is applied thereto; and an optical sheet (103) disposed above the light source units (101) and exhibiting bidirectional transmittance distribution function characteristics having first and second peaks at radiation angles less than 0° and greater than 0°.