Light Guide Plate Diverging and Restricting Portions for Contrast
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Solution Overview
Problem
In direct-type backlights, brightness non-uniformity occurs due to leakage of luminous flux from one area to another, leading to a decline in contrast between areas, which is challenging to address with existing technologies.
Innovation Solution
A light guide plate with a diverging portion to direct light outward and a restricting portion to deflect light traveling outside the illuminated area, reducing light leakage and enhancing contrast by controlling the light distribution on the exit surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a plurality of LEDs are arranged in a matrix pattern on a surface directly underneath a display, then local dimming can be performed to partially change brightness of display regions, but brightness non-uniformity occurs and contrast between areas declines due to leakage of luminous flux from one area to another
Solution Approach 1:
The light guide plate is divided into multiple light guide regions, each corresponding to a specific LED and its intended illumination area. Each light guide region is further segmented into a light guide portion and a light-shielding portion, creating distinct functional zones that prevent cross-contamination of light between adjacent LED areas, thereby enabling local dimming while maintaining contrast.
Solution Approach 2:
Different regions of the light guide plate are assigned different optical properties: the light guide portion has high light transmission to illuminate the intended area, while the light-shielding portion has low light transmission to block stray light. This local differentiation of optical characteristics ensures that each LED's light remains confined to its designated area, preventing brightness non-uniformity and contrast loss.
2Illumination intensity
If light-scattering dots are provided on the rear surface of the light guide plate to diffuse light, then brightness non-uniformity within an illuminated area can be suppressed, but light leakage to adjacent areas increases causing contrast decline
Solution Approach 1:
The light guide plate is segmented into distinct light guide regions and light-shielding regions. The light-shielding portions act as barriers that contain the diffused light within each illuminated area, preventing it from leaking into adjacent areas. This segmentation allows aggressive light diffusion within zones while maintaining sharp boundaries between zones.
Solution Approach 2:
The light-shielding portion serves as an intermediary element between adjacent light guide portions. It intercepts and blocks light that attempts to travel from one illuminated area to another, acting as a mediator that preserves the independence of each local dimming zone while allowing the light guide portions to perform their light diffusion function.
3Illumination intensity
If a diverging portion is provided to cause luminous flux to diverge, then light distribution within the illuminated area improves, but light may travel outside the intended area reducing contrast
Solution Approach 1:
The light guide plate is divided into light guide portions that channel diverged light and light-shielding portions that block escaped light. The light-shielding portions are strategically positioned to intercept light that diverges beyond the intended illuminated area, containing the beneficial divergence effect within each zone while preventing harmful cross-zone light travel.
Solution Approach 2:
Different portions of the light guide plate have different light transmission properties tailored to their function: the light guide portions have high transmission to distribute light uniformly within the illuminated area, while the light-shielding portions have low transmission to block light that travels outside the intended area. This local optimization of optical properties resolves the contradiction between divergence benefits and light containment requirements.
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 solution effectively suppresses brightness non-uniformity and maintains contrast by reducing light leakage between areas, improving the overall brightness distribution and image quality in display devices.
Implementation Method 1
a diverging portion which is provided on an opposite side of a light exit surface from which light is emitted, the diverging portion causing a luminous flux emitted from a light emitting element to diverge
Implementation Method 2
a restricting portion which is provided, when a prescribed range from the light emitting element on the light exit surface is defined as an illuminated area illuminated by the light emitting element, in at least a periphery of the illuminated area on the light exit surface and which deflects or shields light traveling from inside toward outside of the illuminated area
Data Source
AI summary
To provide a technique for suppressing brightness non-uniformity of an area illuminated by a light source and also suppressing a decline in contrast between areas caused by incidence of a luminous flux of the area to another area. Provided is a light guide plate including: a diverging portion which is provided on an opposite side of a light exit surface from which light is emitted, the diverging portion causing a luminous flux emitted from a light emitting element to diverge; and a restricting portion which is provided, when a prescribed range from the light emitting element on the light exit surface is defined as an illuminated area illuminated by the light emitting element, in at least a periphery of the illuminated area on the light exit surface and which deflects or shields light traveling from inside toward outside of the illuminated area to restrict traveling, toward a side of the light exit surface, of light traveling toward the outside of the illuminated area.