Backlight with Patterned Reflectors for Uniform Brightness
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Solution Overview
Problem
Direct-lit backlights face challenges in achieving thin profiles and uniform brightness due to the optical distance between LEDs and diffuser plates, leading to increased thickness and optical losses, while edge-lit backlights have minimal impact on dynamic contrast when turning off LEDs.
Innovation Solution
A backlight design incorporating a substrate, light sources, a reflective layer, a light guide plate with patterned reflectors and extractors, and a diffusive layer, which aligns patterned reflectors with light sources to enhance light hiding and uniformity, reducing the need for a diffuser plate and minimizing optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a diffuser plate is positioned at a distance from the LEDs to achieve desired light uniformity and avoid hot spots, then light uniformity is improved, but the overall display thickness increases
Solution Approach 1:
The backlight structure is segmented into distinct functional zones: a first reflective layer positioned close to LEDs for light extraction, a light guide plate with optical features for lateral light distribution, and a second reflective layer at the bottom for light redirection. This segmentation allows each component to perform its function optimally within a compact thickness, eliminating the need for a thick diffuser plate while maintaining uniformity.
Solution Approach 2:
The patent transitions from a single-plane diffuser approach to a multi-layered vertical structure. By stacking reflective layers at different positions (top and bottom) and incorporating optical features within the light guide plate, the solution utilizes the vertical dimension to achieve light uniformity without increasing overall thickness, effectively moving the problem from two-dimensional to three-dimensional space management.
2Length of stationary object
If the optical distance between LEDs and diffuser plate is reduced to decrease display thickness, then display thickness is improved, but optical losses increase
Solution Approach 1:
The patent extracts the light redirection function from the diffuser plate and assigns it to dedicated reflective layers positioned strategically near the LEDs. The first reflective layer is placed immediately adjacent to LED arrays to capture and redirect light before it enters the light guide plate, minimizing optical losses while allowing the diffuser plate to be positioned closer to the display surface, thereby reducing overall thickness without sacrificing optical efficiency.
Solution Approach 2:
The first reflective layer performs preliminary light redirection and extraction actions before light enters the main light guide plate. By pre-processing the light distribution close to the source, the system minimizes optical losses early in the light path, enabling subsequent components to operate more efficiently within a reduced thickness envelope.
3Length of stationary object
If edge-lit backlight is used to reduce display thickness, then display thickness is improved, but dynamic contrast ratio is minimized when turning off LEDs
Solution Approach 1:
The patent implements local quality by positioning reflective layers and optical features in specific locations relative to each LED. The first reflective layer is locally positioned adjacent to each LED array, and the light guide plate contains localized optical features that control light distribution from each LED independently. This localized control enables individual LED dimming and local dimming zones, preserving dynamic contrast ratio while maintaining a thin profile similar to edge-lit designs.
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 results in a thinner, more efficient direct-lit backlight with improved light uniformity and reduced 'hot spots, allowing for uniform brightness across the display without the thickness and optical losses associated with traditional designs.
Implementation Method 1
a first reflective layer is on the substrate... a second reflective layer is between the light guide plate and the first reflective layer
Implementation Method 2
a light guide plate, a pattern of light extractors, a plurality of patterned reflectors... Each patterned reflector is aligned with a corresponding light source
Implementation Method 3
a diffusive layer is on the light guide plate... improve the lateral spread of light
Data Source
AI summary
A backlight includes a substrate, a plurality of light sources, a reflective layer, a light guide plate, a pattern of light extractors, a plurality of patterned reflectors, and a diffusive layer. The plurality of light sources are proximate the substrate. The reflective layer is on the substrate. The light guide plate is proximate the plurality of light sources. The pattern of light extractors is on the light guide plate. The plurality of patterned reflectors are on the light guide plate. Each patterned reflector is aligned with a corresponding light source. The diffusive layer is on the light guide plate.