Light Guide Plate Unit Shaped Elements Brightness Variation
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Solution Overview
Problem
Edge-light type surface light source devices exhibit in-plane variation of brightness due to the use of light guide plates with linear prisms, leading to a pattern of alternating bright and dark portions along the LED arrangement direction, which becomes more pronounced as the emission intensity of LEDs increases and LED spacing widens, affecting larger display surfaces.
Innovation Solution
A light guide plate design featuring unit shaped elements with a light exit surface angle between 10° and 30° in a specific zone, where the angle increases from the top to the end of the contour, and a ratio of height to width of 0.2 to 0.4, effectively diffusing and condensing light to reduce brightness variation near the light entrance surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide plate with linear prisms is used to achieve light condensing effects, then front-direction luminance is improved, but in-plane brightness variation occurs in the area near the light entrance surface
Solution Approach 1:
The patent applies local quality by providing different optical structures in different regions of the light guide plate. Specifically, the first optical structure (with larger light exit surface angle) is provided in the first region near the light entrance surface, while the second optical structure (with smaller light exit surface angle) is provided in the second region farther from the light entrance surface. This regional differentiation allows the plate to simultaneously achieve uniform brightness distribution and effective light condensing in different areas.
Solution Approach 2:
The light guide plate is segmented into multiple regions with different optical structures. The plate is divided into a first region and a second region along the light guide direction, with each region containing optically distinct structures. This segmentation enables independent optimization of brightness uniformity in the first region and light condensing efficiency in the second region.
2Productivity
If LED emission intensity is increased to reduce the number of LEDs, then cost is reduced, but in-plane brightness variation becomes more pronounced
Solution Approach 1:
The patent addresses this contradiction by implementing local quality through region-specific optical structures. The first optical structure in the first region is specifically designed to mitigate brightness variation caused by high-intensity LEDs, while the second optical structure in the second region maintains effective light extraction. This allows the use of fewer, higher-intensity LEDs without sacrificing brightness uniformity.
3Manufacturing precision
If the light exit surface angle is increased to diffuse light and reduce brightness variation, then in-plane brightness uniformity is improved, but light condensing effect is reduced
Solution Approach 1:
The patent resolves this contradiction through segmentation by dividing the light guide plate into two regions with different light exit surface angles. The first region has a larger light exit surface angle (10° to 30°) that diffuses light to reduce brightness variation, while the second region has a smaller light exit surface angle (0° to 10°) that maintains strong light condensing effects. This segmentation allows both requirements to be satisfied in their respective regions.
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 proposed light guide plate effectively obscures in-plane brightness variation and provides excellent light condensing effects, reducing the need for additional light condensing sheets and enhancing front-direction luminance, especially in larger display devices like home televisions.
Implementation Method 1
a light exit surface angle, which is an angle of a contour of each unit shaped element with respect to the one-side surface of the body portion, is more than 10° and not more than 30° in a zone of the contour of each unit shaped element
Data Source
AI summary
A light guide plate includes a body portion, and a plurality of unit shaped elements defining a light exit surface and arranged on one-side surface of the body portion side by side in an arrangement direction intersecting a light guide direction. Each unit shaped element extends in a direction intersecting the arrangement direction. A light exit surface angle θa, which is the angle of the contour of each unit shaped element with respect to the one-side surface, is more than 10° and not more than 30° in a zone of the contour of each unit shaped element, the width of the zone along the arrangement direction being not less than 35% and not more than 70% of the full width of the unit shaped element.