Curved Reflection Sheet Warpage Control in LCD Backlights
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Solution Overview
Problem
Large-size liquid crystal display devices face challenges in achieving uniform illumination due to warpage of reflection sheets when light emitting diodes are disposed in a concentrated manner, leading to increased manufacturing costs and weight with traditional light guide plates or Fresnel lenses.
Innovation Solution
A liquid crystal display device design featuring a curved reflection sheet with supports at its curved portions to maintain uniform illumination, including an outer frame and reinforcing members to prevent warpage, and an optical sheet with a tapered support column to minimize deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light emitting diodes are disposed in a concentrated manner to reduce substrate size and cost, then manufacturing cost is reduced, but uniform illumination across the image formation region deteriorates due to reflection sheet warpage
Solution Approach 1:
The reflection sheet is divided into different regions with different curvatures: a first curved region facing the light emitting diodes with a specific curvature radius, and a second curved region extending from the first region with a different curvature radius. This local differentiation of curvature properties allows the sheet to maintain structural integrity while achieving uniform light reflection across the entire image formation region, even with concentrated LED placement.
Solution Approach 2:
The reflection sheet employs a curved surface design with varying curvature radii in different regions. The first curved region has a curvature radius R1, while the second curved region has a curvature radius R2 where R1 < R2. This spherical/curved geometry enables the thin reflection sheet to maintain its shape and achieve uniform illumination without requiring a large substrate area, thus resolving the contradiction between cost reduction and illumination uniformity.
2Ease of manufacture
If a curved reflection sheet is used to reduce manufacturing cost and weight compared to light guide plates or Fresnel lenses, then manufacturing cost and weight are reduced, but warpage occurs in large-size devices making uniform illumination difficult
Solution Approach 1:
The reflection sheet is designed with a curved surface having different curvature radii in different regions. The first curved region has curvature radius R1 and the second curved region has curvature radius R2 (R1 < R2). This curvature design provides structural stability to the thin reflection sheet, preventing warpage in large-size devices while maintaining the cost and weight advantages of a curved sheet design.
Solution Approach 2:
Different regions of the reflection sheet have different curvature properties tailored to their specific functions. The first curved region near the LEDs has a tighter curvature (smaller R1) for effective light reflection, while the second curved region extending outward has a gentler curvature (larger R2) for structural stability and warpage prevention. This local quality differentiation resolves the contradiction between using a simple curved sheet and preventing warpage.
3Area of stationary object
If the size of the liquid crystal panel increases for large-size television sets, then display size is increased, but the reflection sheet becomes more prone to warpage reducing illumination uniformity
Solution Approach 1:
The reflection sheet employs a curved surface design with varying curvature radii that scales appropriately with panel size. The first curved region has curvature radius R1 and the second curved region has curvature radius R2, creating a gradient that maintains structural stability across large panel areas while ensuring uniform light reflection to all regions of the image formation area.
Solution Approach 2:
The reflection sheet is divided into multiple curved regions with different curvature characteristics. The first curved region handles the primary light reflection function near the concentrated LEDs, while the second curved region extends outward to provide structural support and maintain illumination uniformity across the entire large panel area. This segmentation allows the system to scale to large sizes without losing illumination 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
The solution effectively reduces warpage and ensures uniform illumination across the entire image formation region, reducing manufacturing costs and weight while maintaining high illumination quality.
Implementation Method 1
a plurality of light emitting diodes are disposed along a horizontal direction
Implementation Method 2
light beams emitted from the light emitting diodes are reflected or diffused
Implementation Method 3
light beams emitted from the light emitting diodes are reflected or diffused
Data Source
AI summary
In a liquid crystal display device including a backlight unit that irradiates the entire image formation region with light from light emitting diodes disposed in a concentrated manner, in order to reduce warpage of a reflection sheet to obtain uniform illumination, provided is a liquid crystal display device (1), including: a liquid crystal panel (3); a reflection sheet (6), which is disposed on a rear surface side of the liquid crystal panel (3) and is curved so as to have a concave surface facing the liquid crystal panel (3); a light emitting diode substrate on which a plurality of light emitting diodes (14) are disposed along a horizontal direction; and a support (21) for fixing the reflection sheet (6) at a curved portion of the reflection sheet (6).