Meniscus Light Guide Plate for Thin Backlight Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large liquid crystal televisions face challenges in achieving a thin, efficient backlight unit with uniform brightness distribution, as existing solutions either result in lower light use efficiency, increased complexity, or high costs, and are prone to brightness unevenness due to thermal and humidity changes.
Innovation Solution
A planar lighting device featuring a meniscus-type light guide plate with a concave rectangular light exit plane, symmetrical inclined planes, and scattering particles, along with sliding mechanisms to absorb expansion and contraction, ensuring constant optical axis distance and preventing deformation towards the liquid crystal display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a direct illumination type backlight unit is used to achieve uniform light amount distribution, then brightness uniformity is improved, but the thickness increases to about 30 mm making further reduction difficult
Solution Approach 1:
The patent transitions from a direct illumination approach (light sources facing the display panel directly) to a light guide plate approach where light is admitted through the side surface and guided through a specific optical path to exit through the rear surface. This dimensional change in light propagation path enables thinner overall thickness while maintaining uniform brightness distribution across the display panel.
Solution Approach 2:
The light guide plate serves as an intermediary component between the light sources and the display panel. It receives light from the light sources, guides it through its internal structure with specific thickness variations, and outputs uniformly distributed light to the display panel. This intermediary function enables the system to achieve both thinness and brightness uniformity that cannot be accomplished with direct illumination alone.
2Length of stationary object
If the light guide plate is made thinner to reduce overall thickness, then brightness at locations immediately above the cold cathode tubes increases, causing uneven brightness on the light exit plane
Solution Approach 1:
The light guide plate is designed with non-uniform thickness distribution, where the thickness varies at different locations. Specifically, the thickness is greater at locations corresponding to cold cathode tubes and smaller at other locations. This local variation in thickness compensates for the brightness increase that would occur with uniform thinning, maintaining overall brightness uniformity across the light exit plane while still achieving a thinner overall design.
3Productivity
If complex light guide plate configurations with grooves for receiving cold cathode tubes are used, then light guiding performance is improved, but machining costs increase considerably
Solution Approach 1:
Instead of using complex geometric configurations like grooves or raised structures, the patent achieves improved light guiding performance by changing the parameter of thickness distribution. The light guide plate has a smoothly varying thickness profile that is greater at cold cathode tube locations and smaller elsewhere. This parameter-based approach maintains high light guiding efficiency while being much easier and less expensive to manufacture compared to complex geometric features.
4Ease of manufacture
If light guide plates with increased thickness at center than at ends are used to achieve stable manufacturing, then manufacturing stability is improved, but light use efficiency decreases due to light leakage through the opposite end
Solution Approach 1:
The light guide plate incorporates a light exit plane that is optically coupled to a light detector or control system. This dynamic feedback mechanism allows the system to detect light leakage and adjust the light guide plate thickness or other parameters in real-time to optimize light use efficiency. The dynamic adjustment compensates for the inherent light leakage issue in thicker plates while maintaining manufacturing stability.
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 a high light use efficiency with minimized brightness unevenness, a high-in-the-middle brightness distribution, and prevents deformation of the light guide plate, enabling a thinner and more efficient backlight unit for large liquid crystal displays.
Implementation Method 1
a light guide plate for guiding light emitted by an illuminating light source and admitted into the light guide plate in given directions and emitted through a light exit plane
Implementation Method 2
light guide plate formed by mixing scattering particles for diffusing light into a transparent resin
Data Source
AI summary
A planar lighting device comprises: a light guide plate including a concave rectangular light exit plane, two light entrance planes containing two opposite sides of the light exit plane and disposed opposite each other, two symmetrical inclined planes opposing to the light exit plane such that their distance from the light exit plane increases with the increasing distance from the two light entrance planes toward the center of the light exit plane, a curved portion connecting the two inclined planes; two light sources respectively disposed opposite the two light entrance planes for emitting light to enter the light into the light guide plate through the light entrance planes; and sliding mechanisms allowing the light sources to slide in a direction parallel to the light entrance planes of the light guide plate to absorb the expansion and contraction of the light sources along the length thereof.