Planar Lighting Device With Sliding Mechanism For Thermal Expansion
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Solution Overview
Problem
Large liquid crystal televisions face challenges in achieving a thin, cost-effective backlight unit with uniform brightness distribution, as existing solutions either compromise on light use efficiency, brightness uniformity, or increase manufacturing complexity, and are prone to unevenness due to temperature and humidity changes.
Innovation Solution
A planar lighting device featuring a light guide plate with a rectangular light exit plane, two opposite longer sides, inclined planes that taper inward, and scattering particles, along with a sliding mechanism to accommodate thermal expansion, ensuring constant light source positioning and high light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a direct illumination type backlight unit is used to achieve uniform light distribution, then brightness uniformity is improved, but the thickness increases to about 30 mm
Solution Approach 1:
The patent transitions from a direct illumination configuration (light source parallel to light guide plate) to a side illumination configuration (light source perpendicular to light guide plate). This dimensional change allows the light guide plate to be positioned closer to the display panel, reducing overall thickness while maintaining uniform brightness distribution through optimized light path geometry.
Solution Approach 2:
The light guide plate is segmented into multiple sections with different thicknesses - a first light guide plate section closer to the display panel and a second light guide plate section farther away. This segmentation allows optimization of light distribution in different zones, achieving uniform brightness while reducing the overall thickness requirement compared to a single thick plate design.
2Length of stationary object
If the light guide plate is made thinner to reduce thickness, then the thickness is reduced, but brightness unevenness increases at locations above cold cathode tubes
Solution Approach 1:
The patent applies local quality by creating different thickness zones in the light guide plate - a first section with greater thickness closer to the display panel and a second section with lesser thickness farther away. This local variation in thickness compensates for the brightness concentration effect, ensuring uniform illumination across the entire display area while maintaining an overall thin profile.
3Length of stationary object
If complex light guide plate configurations are used to achieve thin design and uniform brightness, then thickness is reduced and brightness uniformity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the thickness variation function from complex multi-component structures and implements it through a single integrated light guide plate with built-in thickness gradients. This extraction simplifies the overall structure by combining what would otherwise require multiple separate components into one manufacturable piece, reducing assembly steps and manufacturing complexity.
4Adaptability or versatility
If the light guide plate expands or contracts with temperature and humidity changes, then the light guide plate dimensions change, but positioning accuracy of light sources deteriorates
Solution Approach 1:
The patent implements a sliding mechanism that allows the light guide plate to dynamically adjust its position relative to the light sources as it expands or contracts with temperature and humidity changes. This dynamic adjustment capability maintains optimal positioning accuracy throughout environmental variations, preventing brightness non-uniformity that would result from fixed positioning.
Solution Approach 2:
The patent explicitly accounts for thermal expansion by designing a sliding mechanism that accommodates the light guide plate's dimensional changes due to temperature and humidity. The mechanism allows the plate to expand and contract freely while maintaining functional alignment with light sources, converting the harmful effect of thermal expansion into a manageable design parameter.
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 a thin configuration suitable for large-screen liquid crystal televisions, while maintaining stability across varying temperatures and humidity.
Implementation Method 1
scattering particles for scattering light propagating inside the light guide plate
Implementation Method 2
as the light guide plate expands or contracts
Data Source
AI summary
The planar lighting device includes a light guide plate including two symmetrical, inclined planes increasingly distanced from the light exit plane with the increasing distance from the light entrance planes toward the center, a curved portion joining the inclined planes, and scattering particles dispersed therein; light sources; a housing; a securing unit securing the light sources and light guide plate to keep their distance constant, and a sliding mechanism allowing the securing unit to slide. Distance between the light entrance planes, thicknesses at the light entrance planes and at the central curved portion, its radius of curvature and taper of the inclined planes are all held within respective given ranges as well as scattering particle diameter and density, light use efficiency and middle-high ratio of the brightness distribution.