Backlight LED Orientation for LCD Brightness Uniformity
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Solution Overview
Problem
Backlight systems for liquid crystal display devices using LEDs suffer from brightness variations due to the spacing of LEDs on the light guide plate, leading to reduced display quality and increased costs when the number of LEDs is minimized.
Innovation Solution
The solution involves arranging LEDs at an angle relative to the normal of the light guide plate's surface, using a positioning pin to secure a flexible printed-circuit board, and incorporating reflection grooves on the light guide plate to optimize light distribution and reduce brightness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the number of LEDs is reduced to lower cost, then manufacturing cost decreases, but brightness uniformity deteriorates due to larger spacing between LEDs
Solution Approach 1:
The patent applies local quality by creating asymmetric LED arrangements where LEDs at different positions (edge portions vs central portion) have different orientations relative to the light guide plate. Specifically, LEDs at edge portions are inclined at a first angle while central LEDs are inclined at a second angle, optimizing light extraction locally at each position to compensate for spacing effects and maintain uniform brightness across the illuminating surface.
Solution Approach 2:
The patent changes the orientation parameter of LEDs based on their position on the light guide plate. By varying the inclination angle parameter - using a first inclination angle for edge LEDs and a second inclination angle for central LEDs - the system optimizes light distribution to maintain brightness uniformity even with reduced LED count and larger spacing between them.
2Device complexity
If LEDs are arranged with larger spacing to reduce component count, then device complexity decreases, but brightness uniformity worsens due to reduced light coverage
Solution Approach 1:
The patent addresses the brightness uniformity issue caused by larger LED spacing by implementing local quality optimization. LEDs at edge portions are oriented at a first inclination angle to maximize light extraction at edges, while central LEDs use a second inclination angle optimized for central light distribution. This localized optimization ensures uniform brightness across the entire illuminating surface despite reduced LED density.
Solution Approach 2:
The patent employs asymmetry by using different inclination angles for LEDs at different positions. The asymmetric arrangement - with edge LEDs inclined at one angle and central LEDs at another - compensates for the non-uniform light distribution that would normally result from larger spacing between fewer LEDs, thereby maintaining brightness uniformity.
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 effectively suppresses in-plane brightness variations, maintaining display quality while reducing costs by minimizing the number of LEDs used, ensuring a consistent illuminating surface even with fewer LEDs.
Implementation Method 1
light emitted from the LED is introduced onto a side face (light-receiving surface) of the light guide plate and goes out from an illuminating surface which is a top surface of the light guide plate
Implementation Method 2
a plurality of light-emitting diodes (each referred to as LED hereinafter) are provided as light sources, light emitted from the LED is introduced onto a side face (light-receiving surface) of the light guide plate
Implementation Method 3
incorporating reflection grooves on the light guide plate to optimize light distribution
Data Source
AI summary
A liquid crystal display device having includes a light guide plate having a surface thereof serving as an illuminating surface region opposite to a liquid crystal display panel, light sources mounted on a flexible printed-circuit board and provided on a side face of the light guide plate, an optical sheet member interposed between the liquid crystal display panel and the light guide plate. The side surfaces of the light guide plate with the light sources provided thereon have a ridge-like inclined surface formed thereon, when viewed from the illuminating surface, and the ridge-like inclined surfaces serve as a light-receiving surface with the light source arranged thereon.