Varying LED Holes in Reflection Sheet for Thermal Expansion
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Solution Overview
Problem
The expansion and contraction of a resin reflection sheet in liquid crystal display apparatuses can cause light emitting diodes to be hidden, reducing luminance, as existing solutions either increase hole size to prevent hiding but compromise reflective area, or vice versa.
Innovation Solution
A liquid crystal display apparatus design featuring a reflection sheet with varying hole sizes and a fixing/retaining member system, where holes near the fixing member are smaller and those far from it are larger, allowing for differential movement to accommodate thermal expansion while maintaining light emitting diode visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of holes in the reflection sheet is increased to prevent light emitting diodes from being hidden during thermal expansion, then the light emitting diodes remain visible, but the reflective area decreases and luminance is reduced
Solution Approach 1:
The reflection sheet features holes with varying sizes distributed across its surface. Holes located far from the fixing hole have larger sizes to accommodate thermal displacement of light emitting diodes, while holes near the fixing hole have smaller sizes to maximize reflective area. This local differentiation resolves the contradiction by providing visibility assurance only where thermal displacement occurs, preserving luminance in regions where diodes remain stable.
2Ease of manufacture
If the reflection sheet is made of resin to achieve desired optical properties, then the reflection sheet can be formed with appropriate reflective characteristics, but it becomes prone to thermal expansion and contraction causing hole displacement
Solution Approach 1:
The invention utilizes the thermal expansion properties of resin materials by designing a hole size gradient that compensates for expected thermal displacement. The parameter change in hole sizes across the reflection sheet surface accounts for the dimensional instability of resin during thermal cycles, allowing the reflection sheet to maintain both its formability advantages and functional stability under temperature variations.
3Ease of manufacture
If uniform hole sizes are used across the reflection sheet, then manufacturing is simplified, but thermal expansion causes holes far from fixing points to displace and hide light emitting diodes
Solution Approach 1:
Rather than using uniform hole sizes, the invention implements a gradient hole size distribution where dimensions vary according to location. This local quality approach prioritizes reliability in regions most affected by thermal expansion (far from fixing holes) while accepting slightly more complex manufacturing processes, thereby preventing diode hiding without compromising overall manufacturability.
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 design prevents luminance reduction by ensuring light emitting diodes remain visible during reflection sheet expansion and contraction, maintaining optimal backlight performance.
Implementation Method 1
the reflection sheet is made of a resin, and hence the reflection sheet is prone to expand and contract due to heat
Data Source
AI summary
A reflection sheet is made of material having a coefficient of thermal expansion different from that of an LED substrate. A fixing member and a retaining member extend through the reflection sheet and the LED substrate so as to fix the reflection sheet and the LED substrate. The reflection sheet includes a fixing hole into which the fixing member is inserted, a retaining hole into which the retaining member is inserted, and LED holes within which light emitting diodes are disposed, respectively. Retaining of the reflection sheet by the retaining member has, compared to fixing of the reflection sheet by the fixing member, a higher degree of freedom of movement in a direction along a surface of the reflection sheet. The LED holes located in positions far from the fixing hole are larger than the LED holes located in positions close to the fixing hole.