Thermoset Polyurethane Polishing Pad for Glass Substrate Edge Flatness
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Solution Overview
Problem
Conventional polishing pads for rough and finish polishing of glass substrates and other materials often result in edge-subsidence, where the edge region is excessively polished, leading to uneven surfaces due to differences in hardness and polishing characteristics between rough and finish polishing pads.
Innovation Solution
A polishing pad with a thermoset polyurethane foam polishing layer, where the Asker C hardness value is 82 or less after immersion in water for 24 hours, and the tensile storage modulus is adjusted to satisfy the expression Y < 5X - 150, ensuring the edge region is made upheaved during rough polishing, allowing for even finish polishing across the entire surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hard polishing pad is used for rough polishing, then the matter can be made substantially flat at the edge region as well as the central region, but the work precision is low and edge-subsidence occurs during finish polishing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the storage modulus E' (30°C) to be 120 MPa or less and the temperature coefficient to be 2.5 or more. This specific parameter range allows the polishing pad to be soft enough to prevent edge-subsidence during finish polishing while still providing sufficient polishing pressure for effective rough polishing, thereby resolving the contradiction between rough polishing efficiency and edge region flatness
Solution Approach 2:
The patent applies local quality by creating a polishing pad with non-uniform density distribution, where the density gradually decreases from the central region to the edge region. This density gradient causes the pad to exert different polishing pressures locally - higher pressure at the center and lower pressure at the edges - which prevents edge-subsidence while maintaining overall polishing effectiveness
2Manufacturing precision
If a soft polishing pad is used to prevent edge-subsidence, then finish polishing quality improves, but rough polishing effectiveness decreases
Solution Approach 1:
The patent resolves this contradiction by optimizing the storage modulus E' (30°C) to be 120 MPa or less while maintaining a temperature coefficient of 2.5 or more. This parameter combination ensures the pad is soft enough for high-precision finish polishing that prevents edge-subsidence, yet still provides adequate polishing pressure for effective rough polishing operations
3Productivity
If the storage modulus E' (30°C) is increased to improve rough polishing performance, then polishing pressure increases, but edge-subsidence occurs during finish polishing
Solution Approach 1:
The patent applies parameter changes by setting the storage modulus E' (30°C) to 120 MPa or less and the temperature coefficient to 2.5 or more. This specific parameter range prevents edge-subsidence during finish polishing while maintaining sufficient polishing pressure for effective rough polishing, thereby resolving the contradiction between polishing rate and edge region flatness
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 prevents edge-subsidence by maintaining a lower polishing rate at the edge region, ensuring the edge and central regions are flattened uniformly during finish polishing, resulting in a glass substrate with excellent flatness and surface roughness.
Implementation Method 1
a polishing pad having a polishing layer comprising a thermoset polyurethane foam, wherein about the thermoset polyurethane foam, the Asker C hardness value thereof is 82 or less as a 60-second value, the hardness value being a value after the foam is immersed in water for 24 hours, and further the value of the tensile storage modulus E' (30° C.)
Data Source
AI summary
A polishing pad having a polishing layer comprising a thermoset polyurethane foam,wherein about the thermoset polyurethane foam, the Asker C hardness value thereof is 82 or less as a 60-second value, the hardness value being a value after the foam is immersed in water for 24 hours, and further the value of the tensile storage modulus E′ (30° C.) thereof at a frequency of 1.6 Hz satisfies the following expression (1):Y<5X−150 (1)wherein Y represents the tensile storage modulus E′ (MPa), and X represents the Asker C hardness value (60-second value) after the foam is immersed in water for 24 hours.