Polyester Optical Sheet Convex Features for Reduced Sticking
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Solution Overview
Problem
Existing polyester films used in optical sheets, while highly adhesive, suffer from poor handling properties during manufacturing, which affects the production efficiency and quality of backlight units and image display devices.
Innovation Solution
The optical sheet features a base layer made of polyester with a surface containing first convex parts, where the aspect ratio of these parts multiplied by 1,000 is less than 15, along with controlled ratios of ten-point average roughness SRz to average roughness SRa, enhancing handling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a polyester film with high surface crystallinity and adjusted thermal shrinkage is used to improve adhesion to other layers, then adhesive performance is improved, but handling properties during manufacturing deteriorate
Solution Approach 1:
The invention applies local quality by creating convex parts with specific aspect ratios at the surface of the base layer. These localized surface features (with aspect ratio × 1000 < 15) provide controlled adhesion points while the rest of the surface maintains properties suitable for handling. This resolves the contradiction by concentrating adhesive functionality in specific surface regions rather than uniformly across the entire surface.
2Strength
If the polyester film is made highly adhesive through plasma treatment and crystallinity adjustment, then bonding to functional layers is improved, but the film sticks to itself and other films during manufacturing
Solution Approach 1:
The invention segments the surface into convex parts and flat regions. The convex parts (with controlled aspect ratios) provide localized bonding strength, while the flat regions prevent excessive adhesion between films during handling. This segmentation allows the film to bond strongly to functional layers at convex points while minimizing self-sticking during manufacturing processes.
3Use of energy by moving object
If the surface crystallinity is increased to improve adhesion, then inter-layer bonding is enhanced, but surface friction resistance increases making handling difficult
Solution Approach 1:
The convex parts with specific aspect ratios create localized high-crystallinity regions that provide strong inter-layer bonding, while the overall surface maintains lower friction characteristics. The controlled geometry of convex parts ensures that high crystallinity is confined to specific locations rather than uniformly distributed, thus reducing overall surface friction resistance while maintaining bonding strength.
Data Source
Figure 1~2
Figure 3(a)~3(b)
AI summary
The present invention addresses the problem of providing an optical sheet having high light transmission property and light diffusion property, and having high handleability. An optical sheet according to one aspect of the present invention is provided with a base material layer having polyester as a main component, and has first protruding portions on at least one surface of the base material layer, and a value obtained by multiplying the aspect ratio of the first protruding portion by 1000 is less than 15. In a preferred aspect, the ratio SRz/SRa of ten point average roughness SRz to average roughness SRa of the one surface is 17-45.