Side-Emitting LED Backlight Structure for Thin Local Dimming LCDs
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Solution Overview
Problem
Liquid crystal displays face challenges with non-uniform light distribution, high power consumption, and difficulty in achieving clear blackout effects and thin thickness in direct-lighting type backlight units due to the use of spot light sources and diffusion lenses, which are not suitable for local dimming.
Innovation Solution
The implementation of a light emitting device with a light reflection member on the upper surface, a light transmitting resin covering the side surface, and a light blocking member on the upper surface of the resin, along with a dam surrounding the lateral side of the light emitting diode chip, to enhance light distribution and suppress spot phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light emitting diodes are arranged in a matrix below the display panel to achieve uniform light distribution, then light uniformity is improved, but the thickness of the backlight unit increases due to the need for distance between light source and optical sheet
Solution Approach 1:
The patent transitions from a conventional bottom-emitting configuration to a side-emitting configuration by changing the emission direction of the light emitting diode. The light emitting diode chip is disposed to emit light in a lateral direction, and the optical sheet is positioned to receive light from the side surface of the light emitting diode package, thereby reducing the vertical thickness while maintaining light uniformity through lateral light distribution.
Solution Approach 2:
The patent introduces a light reflecting member positioned between the light emitting diode chip and the optical sheet to redirect light that would otherwise be lost upward. This intermediary component reflects light toward the optical sheet, improving light utilization efficiency and uniformity without requiring increased distance or additional thickness in the backlight unit.
2Illumination intensity
If a diffusion lens is used to spread light from light emitting diodes, then light distribution is improved, but the device complexity and thickness increase
Solution Approach 1:
The patent extracts and eliminates the diffusion lens from the optical system by adopting a side-emitting light emitting diode configuration. The lateral light emission naturally provides uniform light distribution without requiring additional diffusion components, thereby simplifying the overall device structure and reducing thickness while maintaining effective light spreading.
3Length of stationary object
If light emitting diodes are positioned close to the display panel to reduce thickness, then backlight unit thickness is reduced, but light uniformity deteriorates due to insufficient light spreading
Solution Approach 1:
The patent employs an asymmetric light emission geometry where the light emitting diode chip emits light primarily in a lateral direction toward the optical sheet, rather than uniformly in all directions. This asymmetric configuration, combined with the side-emitting package structure, enables effective light spreading at reduced distances, achieving both thinness and uniformity simultaneously.
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 improves luminous uniformity, reduces power consumption, and enables local dimming suitability without a diffusion lens, resulting in a thinner direct-lighting type backlight unit with improved contrast ratio.
Implementation Method 1
a light reflection member on an upper surface of the light emitting diode chip
Implementation Method 2
a light transmitting resin covering a side surface of the light emitting diode chip
Implementation Method 3
a light blocking member on an upper surface of the light transmitting resin
Data Source
AI summary
A display apparatus including a display panel, and a backlight to provide light toward the display panel, the backlight including a circuit board, an optical layer disposed on the circuit board, at least one light emitter disposed between the circuit board and the optical layer and including a light emitting structure disposed on the circuit board and having first and second conductivity type semiconductor layers and an active layer therebetween, first and second electrode pads electrically connected to the first and second conductivity type semiconductor layers, respectively, a reflector on the light emitting structure, a light transmitting layer disposed on the circuit board and contacting the light emitter, and a dam disposed on the circuit board and surrounding the light emitter and including a portion having a curved shape.