Light Guide Plate Positioning for Edge-Light Backlight Thermal Expansion
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Solution Overview
Problem
In edge-light type backlight devices for liquid crystal display devices, thermal expansion of the light guide plate causes light leakage, leading to reduced visibility and potential bright spots on the display surface due to the need for a space between recesses and projections, which can omit a cabinet and increase manufacturing costs.
Innovation Solution
A configuration where the light guide plate is positioned without recesses or projections on its edge surface, using positioning members that slide and elastic members to maintain the plate's position during thermal expansion and contraction, ensuring constant distance between the light source and light entrance surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If recesses and projections are used to position the light guide plate, then positioning is achieved, but thermal expansion causes light leakage and reduced visibility
Solution Approach 1:
The positioning member is designed with a through hole that allows it to slide dynamically in the plate surface direction. This dynamic capability enables the positioning member to adjust its position according to thermal expansion of the light guide plate, maintaining contact without creating gaps that would cause light leakage.
Solution Approach 2:
The positioning member's ability to change its position parameter (sliding along the inner surface) allows it to accommodate thermal expansion while maintaining proper positioning. The elastic member further enables parameter change through elastic deformation, absorbing dimensional changes without compromising positioning accuracy.
2Adaptability or versatility
If space is provided between recess and projection for thermal expansion, then thermal expansion is accommodated, but light leaks through the space
Solution Approach 1:
Instead of providing a fixed space gap, the positioning member is made dynamic through the through hole design, allowing it to slide and maintain contact with the light guide plate edge during thermal expansion, thus accommodating dimensional changes without creating light-leaking gaps.
Solution Approach 2:
The positioning member acts as an intermediary between the frame and the light guide plate, absorbing thermal expansion through sliding and elastic deformation while maintaining continuous contact that prevents light leakage.
3Object-affected harmful factors
If positioning members are added to position the light guide plate without recesses or projections, then positioning is achieved without light leakage, but device complexity increases
Solution Approach 1:
The invention extracts the positioning function from the light guide plate itself (no recesses or projections needed) and relocates it to separate positioning members attached to the frame. This separation allows the light guide plate to maintain its simple, continuous structure while positioning is handled by dedicated components with sliding capability.
Solution Approach 2:
The positioning member serves multiple functions: it positions the light guide plate in the plate surface direction, accommodates thermal expansion through sliding, and prevents light leakage by maintaining contact without gaps. This multi-functionality reduces the need for additional separate components.
4Ease of manufacture
If the light guide plate is positioned without recesses or projections, then manufacturing is simplified, but positioning accuracy during thermal expansion is compromised
Solution Approach 1:
The positioning member's sliding capability through the through hole design provides dynamic adjustment that maintains positioning accuracy during thermal expansion, compensating for the absence of recesses or projections in the light guide plate.
Solution Approach 2:
The positioning system uses parameter changes (sliding distance, elastic deformation) to maintain accurate positioning of the light guide plate despite thermal expansion, achieving both manufacturing simplicity and positioning precision.
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 prevents light leakage and maintains optimal optical properties by keeping the light guide plate positioned in the plate surface direction, reducing manufacturing costs and eliminating bright spots on the display surface.
Implementation Method 1
a space is required between the recess and the projection because the light guide plate increases its size at the edge surfaces thereof due to thermal expansion
Data Source
AI summary
A backlight unit includes a light guide plate 16, LEDs 17, a chassis 14, a frame 13 and positioning members 30. The light guide plate16 includes two edge surfaces that are light entrance surfaces 16b and a front surface that is a light exit surface. The LEDs 17 are arranged to be opposed to the light entrance surfaces 16b and in a portion of the light guide plate 16 except for four corner portions 16d of the light guide plate 16. The chassis 14 is arranged on an opposite side of the light guide plate 16 from the light exit surface. The frame 13 is arranged on a light exit surface side to have the light guide plate 16 and the LEDs 17 between the frame 13 and the chassis 14. The positioning members 30 are arranged on an inner surface of the frame 13 to be opposed to the respective four corner portions 16d of the light guide plate 16. Each of the positioning members 30 is in contact with an edge surface of the light guide plate 16 at each of the four corner portions 16d so as to position the light guide plate 16 in a plate surface direction. The positioning members are configured to slide to be away from the light guide plate 16 along the inner surface of the frame 13.