Backlight Unit Partition Wall and Reflective Sheet for Hot Spot Reduction
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Solution Overview
Problem
Direct-type backlight units in liquid crystal display devices face issues with mura such as hot spots and decreased image quality due to direct light emission from sources, and they also have thickness limitations that hinder a thin profile design.
Innovation Solution
A backlight unit design featuring a circuit board with LED packages, a partition wall that changes the light transmission direction by at least 40%, and a reflective pattern sheet to prevent vertical light emission and hot spots, along with a diffusion plate to ensure uniform light distribution, thereby reducing the optical gap and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If direct-type backlight unit is used to improve uniformity and brightness, then local dimming can be implemented and contrast ratio improved, but mura such as hot spot occurs and image quality decreases
Solution Approach 1:
The backlight unit is divided into multiple independent LED packages arranged in an array, allowing each package to be independently controlled for local dimming while maintaining overall brightness uniformity. This segmentation enables precise control of light emission from each location to prevent hot spots.
Solution Approach 2:
Different regions of the backlight unit are optimized with specific LED package arrangements and optical structures tailored to local requirements. The partition walls and reflective patterns are designed to address specific hot spot issues in different areas, providing localized solutions for image quality improvement.
2Adaptability or versatility
If light sources are disposed under the liquid crystal display panel to enable direct light emission, then local dimming method can be implemented, but the thickness of the backlight unit increases
Solution Approach 1:
The LED packages are nested within a compact structure that includes partition walls and reflective patterns integrated into the same space. The optical components are arranged in a stacked configuration where the reflective pattern sheet is positioned between the LED packages and the liquid crystal panel, maximizing space utilization and minimizing overall thickness.
Solution Approach 2:
The optical path is optimized by utilizing vertical space through the reflective pattern sheet that reflects light at specific angles. This dimensional arrangement allows the light to travel through a compact path, enabling local dimming functionality without significantly increasing the horizontal or vertical thickness of the backlight unit.
3Object-affected harmful factors
If partition wall height is increased to prevent vertical light emission, then hot spot prevention improves, but device complexity increases
Solution Approach 1:
The partition walls are integrated with the LED package mounting structure, combining the functions of structural support and optical light control into a single component system. This merging reduces the number of separate parts and simplifies manufacturing while maintaining effective control over vertical light emission.
Solution Approach 2:
Instead of increasing partition wall height, the invention optimizes other parameters such as the reflective pattern sheet properties, LED package orientation, and optical path lengths to achieve the same light control effect. This parameter optimization approach maintains simplicity while preventing hot spots and vertical light emission.
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 effectively prevents hot spots, improves image quality, and reduces the thickness of the backlight unit, enabling a thinner profile for liquid crystal display devices while allowing for local dimming and enhanced contrast ratio.
Implementation Method 1
a partition wall disposed among the plurality of LED packages to partially or entirely surround one or more LED packages, and changing a transmitting direction of at least 40% of the light incident on the partition wall
Implementation Method 2
a reflective pattern sheet over the encapsulation member and including a plurality of first reflective patterns corresponding to the plurality of LED packages, respectively
Implementation Method 3
an encapsulation member covering the plurality of LED packages and the partition wall
Data Source
AI summary
A liquid crystal display device includes a liquid crystal panel and a backlight unit under the liquid crystal panel and including a circuit board; a plurality of LED packages mounted on the circuit board; a partition wall on the circuit board and surrounding at least one LED package; an encapsulation member covering the plurality of LED packages and the partition wall; and a reflective pattern sheet over the encapsulation member and including a plurality of first reflective patterns corresponding to the plurality of LED packages, respectively, wherein a height of the partition wall is equal to or greater than a height of the at least one LED package and smaller than or equal to a thickness of the encapsulation member.