Backlight Unit Reflecting Layer Incident Angle Light Mixing
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Solution Overview
Problem
Conventional LCD backlight units using CCFLs suffer from environmental pollution, low response rate, and color reproducibility issues, and fail to produce uniform white light due to significant differences in light output between areas with and without optical devices, resulting in color stains.
Innovation Solution
A backlight unit with a surface light source and an optical sheet, featuring a reflecting layer with varying reflectivity based on incident angle, effectively disperses and mixes light beams from optical devices like LEDs, using PMMA for the optical sheet and transparent covers to ensure uniform light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pitch between optical devices is widened to reduce device complexity and cost, then the number of optical devices per unit area is reduced, but the light output uniformity deteriorates causing color stains
Solution Approach 1:
A light mixing sheet is introduced as an intermediary component between the optical devices and the optical sheet. This light mixing sheet receives light beams from multiple optical devices and mixes them through scattering and diffusion, then transmits the mixed light to the optical sheet. This mediator enables effective light mixing even when optical devices are spaced apart, maintaining uniformity while allowing reduced device density.
Solution Approach 2:
The patent introduces a new dimensional element by adding the light mixing sheet as a separate functional layer in the vertical stacking direction. This transforms the light mixing function from a two-dimensional surface issue to a three-dimensional volumetric process within the light mixing sheet, enabling more effective light redistribution across the display area.
2Ease of manufacture
If optical devices are arranged with large pitch to reduce cost, then manufacturing cost is reduced, but color blur increases due to insufficient light mixing
Solution Approach 1:
The light mixing sheet serves as a mediator that decouples the spacing between optical devices from the quality of light mixing. By introducing this intermediate layer with specific scattering and diffusion properties, the system can accommodate larger device pitch while maintaining color uniformity, thus reducing manufacturing cost without sacrificing color quality.
Solution Approach 2:
The patent changes the optical parameters of the light mixing sheet (scattering coefficient, diffusion angle, thickness) to optimize light mixing performance. By adjusting these parameters, the system achieves effective light redistribution even with widely spaced optical devices, maintaining color uniformity while allowing cost-effective device arrangement.
3Device complexity
If conventional optical sheet is used without light mixing layer, then device complexity is low, but light beams from optical devices are not effectively mixed causing color stains
Solution Approach 1:
The light mixing sheet is positioned as an intermediary layer between the optical devices and the conventional optical sheet. It performs the specialized function of light mixing through scattering and diffusion, while the upper optical sheet maintains its original light guiding and extraction functions. This layered mediator approach adds minimal complexity while achieving effective light mixing.
Solution Approach 2:
The patent segments the light management function into distinct layers: the light mixing sheet handles light redistribution and mixing, while the optical sheet above it handles light guiding and extraction. This functional segmentation allows each layer to be optimized for its specific purpose, achieving effective light mixing without compromising overall system performance.
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 uniform white light without color stains, enhancing product quality and competitiveness by minimizing light output differences between areas over and between optical devices, thereby reducing color blur.
Implementation Method 1
a reflecting layer disposed between the surface light source and the optical sheet and having reflectivity varied by an incident angle of light beams from the optical devices
Implementation Method 2
a reflecting layer disposed between the surface light source and the optical sheet and having reflectivity varied by an incident angle of light beams from the optical devices
Implementation Method 3
The diffuser sheet 236 diffuses the light beams incident from the optical devices 210 uniformly
Implementation Method 4
The light collecting sheet 238 collects the light beams diffused by the diffuser sheet 236 in a direction perpendicular to the plane of the LCD panel
Data Source
AI summary
Light beams are outputted from optical devices and mixed together to obtain uniform white light free from color stains, thereby achieving a backlight unit improved in light mixing feature. In the backlight unit, a surface light source has a reflecting surface with a plurality of optical devices mounted thereon. An optical sheet is disposed in front of the surface light source. A reflecting layer is disposed between the surface light source and the optical sheet and has reflectivity varied by an incident angle of light beams from the optical devices. The backlight unit enables the light beams from the optical devices to be mixed together. The light beams outputted from the optical devices are effectively mixed together by a reflecting layer having reflectively varied by an incident angle of the light beams from the optical devices, thereby achieving uniform white light without color stains.