Optical Element Resin Thickness Warpage Control
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Solution Overview
Problem
Conventional lenticular lens sheets made of UV curable resin on glass substrates face issues with dimensional stability and warpage due to differences in thermal expansion coefficients, leading to poor reliability and alignment challenges in display devices.
Innovation Solution
The optical element is designed with specific resin thickness ratios (RTmax/RTmin ≤ 9/5 or ≤ 5/3) and internal stress management (σ/Es×RTmax/T ≤ 13.0 ppm or ≤ 3.0 ppm) to prevent curvature changes and warpage, using a glass substrate with a thickness of 200 μm or more and a low elastic modulus resin, and incorporating a stress-release resin layer to accommodate volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a resin lens sheet is used to reduce cost, then manufacturing cost is reduced, but thermal expansion mismatch causes misalignment and loss of pixel positioning accuracy
Solution Approach 1:
The patent uses a composite structure combining a glass substrate with a resin lens layer. The glass substrate provides thermal stability and dimensional accuracy, while the resin lens provides optical functionality. This composite approach resolves the contradiction by integrating materials with complementary properties - the glass substrate's low thermal expansion coefficient prevents misalignment, while the resin lens maintains cost-effectiveness and optical performance.
2Adaptability or versatility
If UV curable resin is patterned on glass substrate to create lenticular lens, then optical functionality is achieved, but difference in mechanical properties causes substrate warpage
Solution Approach 1:
The patent controls the thickness of the UV curable resin layer within specific ranges (5-50 μm for certain embodiments, or 10-30 μm in others). By optimizing this critical parameter, the resin layer provides sufficient optical functionality while minimizing the stress differential that causes warpage. The controlled thickness ensures the resin layer is thin enough to maintain substrate flatness yet thick enough to provide the required lens optical effects.
Solution Approach 2:
The resin layer is applied locally only where lens functionality is required, rather than covering the entire substrate uniformly. This localized application reduces the overall stress imbalance on the substrate, minimizing warpage while still providing the necessary optical functions in specific regions.
3Reliability
If resin thickness is increased to improve light fastness, then resistance to light-induced deformation is improved, but curing shrinkage causes greater warpage
Solution Approach 1:
The patent identifies and controls multiple parameters including resin thickness (5-50 μm or 10-30 μm), resin composition (specific UV curable resin formulations), and substrate thickness. By optimizing these parameters within specific ranges, the patent achieves a balance where the resin layer has sufficient thickness to provide light fastness and resistance to deformation, while remaining thin enough to minimize warpage caused by curing shrinkage.
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 enhances the reliability and productivity of the optical element by preventing deformation and warpage, ensuring stable performance in light fastness and thermal tests, and facilitating easier attachment to display devices.
Implementation Method 1
injecting a UV curable liquid resin between a transparent substrate and a lens mold and irradiating the resin with UV rays to form a lens array
Data Source
AI summary
An optical element includes a substrate and a resin and satisfies the following formula, RTmax/RTmin≤9/5, wherein RTmin represents the resin thickness at the thinnest regions of a major patterned component that is made of the resin, and RTmax represents the resin thickness at the thickest regions of the major patterned component which is made of the resin.