Planar Lighting Device With Inclined Light Guide Plate
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Solution Overview
Problem
Existing planar lighting devices face challenges in reducing thickness and weight while maintaining uniform illumination, as they require thicker light guide plates to accommodate longer light travel distances, leading to increased manufacturing costs and power consumption, and struggle with brightness unevenness near light entrance planes due to limited scattering particle density.
Innovation Solution
A planar lighting device with a light guide plate featuring inclined rear planes that increase thickness towards the center, paired with main and auxiliary LED light sources, and strategically placed reflection members to optimize light distribution and scattering, achieving a bell-curve illuminance distribution and reduced brightness unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the light guide plate thickness is reduced to achieve thinner backlight units, then the overall device thickness is improved, but the light travel distance becomes insufficient leading to uneven light amount distribution
Solution Approach 1:
The light guide plate employs varying thickness distribution where the central region is thicker than the peripheral regions. This local variation in thickness allows light to travel adequate distances for uniform distribution in the center while keeping the overall profile thinner at the edges, resolving the contradiction between reduced thickness and sufficient light travel distance.
Solution Approach 2:
Instead of uniformly reducing thickness in one dimension, the invention introduces thickness variation across different spatial dimensions of the light guide plate. By making the central region thicker and peripheral regions thinner, it creates a three-dimensional thickness profile that optimizes both overall thickness reduction and light distribution uniformity.
2Illumination intensity
If scattering particle density is increased near light entrance planes to improve illuminance distribution, then brightness unevenness is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The scattering particles are distributed non-uniformly within the light guide plate, with higher concentration in the central region and lower concentration near the light entrance planes. This local variation in particle density optimizes light scattering where needed while simplifying the manufacturing process in regions where less scattering is required.
Solution Approach 2:
The invention changes the parameter of scattering particle density from a constant value to a spatially varying value. By adjusting the particle density parameter across different regions of the light guide plate, it achieves improved illuminance distribution without requiring complex manufacturing processes.
3Weight of moving object
If the light guide plate is made thinner to reduce weight, then the device weight is improved, but the light travel distance decreases leading to brightness unevenness
Solution Approach 1:
The light guide plate features localized thickness variation with a thicker central region and thinner peripheral regions. This allows the plate to maintain sufficient weight and light travel distance in the central area where uniform brightness is most critical, while reducing overall weight through thinner edges.
Solution Approach 2:
The invention transitions from a uniform two-dimensional thin plate to a three-dimensional structure with varying thickness. This dimensional change enables the plate to be thinner on average (reducing weight) while maintaining adequate thickness in specific regions (ensuring uniform brightness distribution).
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 enables a thinner and more efficient planar lighting device with improved illuminance distribution and reduced manufacturing costs, capable of supporting larger display areas with uniform illumination and reduced brightness unevenness.
Implementation Method 1
light emitted by the light source and admitted through the light entrance plane into the light-diffusion light guide member receives a single or a multiple scattering effect at a given rate as the light propagates through the inside of the light-diffusion light guide member
Implementation Method 2
a significant proportion of light that reaches both end planes of the diffusion light guide member or a surface of the reflector receives reflection effect and is returned back into the diffusion light guide member
Data Source
AI summary
The planar lighting device includes, in addition to light sources, a light exit plane, a pair of light entrance planes formed on a pair of sides of the light exit plane, and a rear plane composed of a pair of inclined planes formed on a side opposite from the light exit plane such that the light guide plate grows thicker with an increasing distance from the light entrance planes toward the center. The light guide plate contains light scattering particles satisfying Npi>Np, where Npi is the particle density in a region of space within a given range of the light guide plate and Np the density in the other region of space. The planar lighting device with minimized brightness unevenness liable to develop near the light entrance planes when the light exit plane has great dimensions.