Planar Illumination Device Narrow Picture-Frame Light Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional edge-light type backlight devices with narrowed picture-frames face issues of light leakage and reduced luminance due to the expansion of optical sheets, which can lead to deflection and insufficient strength of reflection structures, making it difficult to maintain efficient light usage and frame narrowing.
Innovation Solution
A planar illumination device with a reflection type polarizer longer than the light guide plate, positioned closer to the light sources, and a light-shielding portion on the optical sheets to absorb non-emitting region light, combined with a black chassis to suppress light leakage and enhance luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the optical sheets are made shorter than the light guide plate to prevent light leakage, then light leakage is suppressed, but the picture-frame cannot be narrowed
Solution Approach 1:
The optical sheets are divided into two functional segments: a light-shielding portion that extends beyond the light guide plate to absorb stray light, and a light-transmitting portion that maintains the narrowed picture-frame width. This segmentation allows each portion to perform its specific function independently, resolving the contradiction between preventing light leakage and narrowing the frame.
Solution Approach 2:
Different portions of the optical sheets are given different properties: the light-shielding portion has high light-absorbing capability to prevent leakage, while the light-transmitting portion maintains transparency for the display region. This local differentiation of properties allows the system to simultaneously achieve light leakage prevention and frame narrowing.
2Area of stationary object
If the optical sheets are made equal to the light guide plate length to narrow the picture-frame, then the picture-frame is narrowed, but light leakage occurs from the edge portion
Solution Approach 1:
The optical sheets are segmented into a light-shielding portion extending beyond the light guide plate and a light-transmitting portion covering the display region. This segmentation enables the light-shielding portion to capture stray light while the light-transmitting portion maintains the narrowed frame, resolving the contradiction.
Solution Approach 2:
The light-shielding portion acts as an intermediary element between the light guide plate and the outer environment. It intercepts stray light that would otherwise leak from the edge portion, preventing harmful light leakage while allowing the picture-frame to remain narrowed.
3Object-affected harmful factors
If black printing is provided on the optical sheets to absorb light, then light leakage is suppressed, but luminance is reduced
Solution Approach 1:
The optical sheets are segmented into a light-shielding portion and a light-transmitting portion. The light-shielding portion absorbs stray light to prevent leakage, while the light-transmitting portion maintains high transparency to preserve luminance in the display region. This segmentation resolves the contradiction by localizing light absorption away from the light-emitting area.
Solution Approach 2:
Different regions of the optical sheets have different optical properties: the light-shielding portion has high light-absorbing capability, while the light-transmitting portion has high transparency. This local quality differentiation ensures that light leakage is suppressed without compromising the luminance in the display region.
4Use of energy by moving object
If the reflection type polarizer is made longer than the light guide plate to reflect light back, then light usage efficiency is improved, but the device complexity increases
Solution Approach 1:
The light-shielding portion and light-transmitting portion are merged into a single integrated optical sheet structure. This merging achieves both light reflection/back-scattering functionality and light transmission functionality within one component, improving light usage efficiency while avoiding the complexity of multiple separate components.
Solution Approach 2:
The optical sheets are designed with multi-functionality: the light-shielding portion performs light absorption and reflection, while the light-transmitting portion performs light transmission. This universal design achieves multiple functions (light efficiency improvement and frame narrowing) within a single integrated structure, avoiding additional complexity.
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 configuration effectively suppresses light leakage and maintains high luminance while allowing for a narrowed picture-frame by reflecting absorbed light back into the light guide plate and using a black chassis to prevent further leakage, thus improving display quality.
Implementation Method 1
one of the plurality of optical sheets that is disposed in a position farthest from the light guide plate is a reflection type polarizer that allows some light to be transmitted therethrough and allows other light to be reflected thereby
Implementation Method 2
at least one of the plurality of optical sheets has a light-shielding portion provided in a part of a region corresponding to a non-light-emitting region of the planar illumination device
Implementation Method 3
a light guide plate for allowing light emitted from the light sources to exit in a planar manner
Data Source
AI summary
An object is to implement a narrowed picture-frame while suppressing the occurrence of light leakage and a reduction in luminance in an edge-light type backlight device. A backlight device is composed of LEDs (40); a side chassis (51) supporting a board having the LEDs (40) mounted thereon; a light guide plate (20) for allowing light emitted from the LEDs (40) to exit toward a liquid crystal panel in a planar manner; a reflection sheet (30) for allowing light traveling toward a back surface side within the light guide plate (20) to be reflected thereby; optical sheets (10) including a reflection type polarizer (11), a prism sheet (12), and a diffuser (13); and a top chassis (52) disposed on top of the optical sheets (10). Black printing (60) is provided in a part of the region of the diffuser (13). A length of the reflection type polarizer (11) is longer than a length of the light guide plate (20) such that an edge of the reflection type polarizer (11) is located closer to a side of the LEDs (40) than is an edge surface of the light guide plate (20).