Planar Illumination Device with Segmented Light Guide Irregularities
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Solution Overview
Problem
Existing planar illumination devices face challenges in suppressing color unevenness on the emission surface, particularly due to the need for precise alignment of light sources and light guide plates, and the variation in chromaticity along the thickness direction caused by wavelength conversion materials.
Innovation Solution
A planar illumination device is designed with a light guide plate and multiple light sources arranged in the longitudinal direction of the light incident side surface. The light guide plate features a plurality of rows of first irregularities extending in the width direction to diffuse incident light in the thickness direction, specifically in the range opposing the blue LED chip, thereby mixing light with a large blue component and reducing color gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a yellow phosphor is disposed around a blue LED chip to obtain white light, then white light is emitted, but the chromaticity changes in the thickness direction depending on the distance for blue light to pass through the phosphor, causing color unevenness on the emission surface
Solution Approach 1:
The light guide plate is divided into multiple regions with different irregularity configurations. The first irregularities are disposed in a first region to address chromaticity variation in the thickness direction, while the second irregularities are disposed in a second region to address color unevenness in the width direction. This segmentation allows each region to independently optimize for its specific function.
Solution Approach 2:
Different types of irregularities are localized to specific regions of the light guide plate. The first irregularities (extending in width direction) are located in the first region opposing the blue LED chip to control thickness-direction chromaticity. The second irregularities (extending in thickness direction) are located in the second region to control width-direction color uniformity. Each region has optimized local properties for its specific chromaticity control need.
2Manufacturing precision
If an incident surface protrusion is formed to diffuse blue light in the width direction, then yellow tint on the emission surface is suppressed, but precise alignment between the blue LED chip and the protrusion is required
Solution Approach 1:
The irregularities are segmented into two distinct types with different orientations and locations. The first irregularities handle the chromaticity control for the blue LED chip region, while the second irregularities handle the color uniformity for the entire emission surface. This segmentation distributes the functional requirements and reduces the alignment sensitivity for any single feature.
Solution Approach 2:
The light guide plate acts as an intermediary medium that receives light from the blue LED chip and processes it through the two types of irregularities. The first irregularities serve as an intermediary to control the initial chromaticity variation, while the second irregularities serve as a secondary intermediary to further uniformize the color across the emission surface, reducing the direct alignment sensitivity.
3Stability of the object's composition
If light is diffused uniformly in both width and thickness directions, then uniform white light is emitted, but it is difficult to control the chromaticity in the emission surface
Solution Approach 1:
The light guide plate is designed with non-uniform irregularity distributions. The first irregularities are concentrated in the first region opposing the blue LED chip to specifically control chromaticity in the thickness direction. The second irregularities are distributed in the second region to control color uniformity in the width direction. This local quality differentiation allows independent optimization of chromaticity control for each spatial region.
Solution Approach 2:
The diffusion function is segmented into two independent subsystems: first irregularities for thickness-direction chromaticity control and second irregularities for width-direction color uniformity control. This segmentation allows each subsystem to be optimized for its specific function without interfering with the other, achieving both light uniformity and precise chromaticity control.
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 color unevenness on the emission surface by diffusing light in the thickness direction, reducing the blue tint gradient, and achieving balanced color emission without requiring precise alignment of light sources and light guide plates.
Implementation Method 1
a wavelength conversion material configured to emit second light having a wavelength longer than a wavelength of the first light by the light emitted by the light emitting element
Implementation Method 2
The light incident side surface is formed with a plurality of rows of first irregularities extending in a width direction of the light guide plate and configured to diffuse incident light in a thickness direction of the light guide plate
Data Source
AI summary
A planar illumination device of an embodiment includes a light guide plate for emitting light incident from a light incident side surface from one principal surface of two principal surfaces, and a plurality of light sources arranged in a longitudinal direction of the light incident side surface and emitting light incident on the light incident side surface. The light sources include a light emitting element for emitting first light and a wavelength conversion material for emitting second light having a wavelength longer than a wavelength of the first light by the light emitted by the light emitting element. The light incident side surface is formed with a plurality of rows of first irregularities extending in a width direction of the light guide plate and diffusing incident light in a thickness direction of the light guide plate in a partial range in the thickness direction of the light guide plate, the range opposing the light emitting element.