Lightguide with Line-Shaped Protrusions for LCD Luminance Uniformity
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Solution Overview
Problem
Side-light type liquid crystal display devices using LEDs suffer from luminance unevenness near the light entrance surface due to the use of point light sources, resulting in bright regions close to light sources and dark regions farther away, leading to uneven illumination.
Innovation Solution
The implementation of a lightguide with local-area and wide-area line-shaped protrusions on the reflection and exit surfaces, where the local-area protrusions weaken the light component orthogonal to their direction, reducing luminance unevenness by aligning light beams closer to the display region's intended direction, and allowing a narrower peripheral region for the liquid crystal display device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If point light sources (LEDs) are used in a side-light type backlight unit, then the light guide can effectively illuminate the display surface, but luminance unevenness occurs in the vicinity of the light entrance surface with bright regions near light sources and dark regions farther away
Solution Approach 1:
The light guide is segmented into multiple functional regions: a light entrance surface region, a display region, and an intermediate region containing line-shaped protrusions. This segmentation allows different regions to perform different functions - the protrusions in the intermediate region specifically address luminance uniformity by redirecting light, while the light entrance surface can maintain its structural role.
Solution Approach 2:
Line-shaped protrusions are strategically placed only in the intermediate region between the light entrance surface and display region, not uniformly across the entire light guide. This local modification creates specific optical effects where needed - the protrusions redirect light from bright regions toward dark regions - while leaving other regions unchanged to maintain their original functions.
2Manufacturing precision
If a clearance is maintained between the light entrance surface and display region to avoid luminance unevenness, then luminance uniformity improves, but the peripheral region size increases
Solution Approach 1:
Instead of solving the luminance uniformity problem by increasing the distance (one-dimensional solution) between the light entrance surface and display region, the invention introduces line-shaped protrusions that modify light propagation in a different dimensional approach. The protrusions create additional light redirection paths, achieving uniformity without requiring increased peripheral clearance.
3Manufacturing precision
If line-shaped protrusions are added to the light guide to reduce luminance unevenness, then luminance uniformity improves, but the device complexity increases
Solution Approach 1:
The light guide incorporates line-shaped protrusions that create a micro-structured surface topology. These protrusions function similarly to porous structures by providing multiple light interaction surfaces that redirect and diffuse light, achieving luminance uniformity through structural modification rather than adding separate optical components.
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 significantly reduces luminance unevenness in the display region, ensuring more uniform illumination and allowing for a narrower bezel size in liquid crystal display devices by effectively managing light distribution and alignment.
Implementation Method 1
When the light is reflected at the position of the line-shaped protrusion 221, the line-shaped protrusion 221 weakens the light component in a direction orthogonal to the extending direction of the line-shaped protrusion 221
Data Source
AI summary
A lightguide to be used in a liquid crystal display device includes a light exit surface, a reflection surface opposed to the light exit surface, and a light entrance surface, which is one side surface. In a region of the light exit surface or the reflection surface, which is on a front side of an intermediate portion between two light sources when viewed from the light entrance surface, a plurality of local-area line-shaped protrusions are arranged, which are extending in a first direction. Each of the local-area line-shaped protrusions reflects the entered light so that a component of the entered light which is orthogonal to the first direction is weakened. A length of a local-area line-shaped protrusion farthest from the two adjacent light sources, is larger than a length of a local-area line-shaped protrusion closest to any one of the two adjacent light sources.