Polymer Substrate Hard Coat Layer Adhesion
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Solution Overview
Problem
Current polymer substrates with hard coating layers fail to achieve a balance of high abrasion resistance, boiling water resistance, and heat resistance, leading to issues such as peeling and cracking, especially when exposed to harsh environmental conditions like high humidity and temperature variations.
Innovation Solution
A polymer substrate with a hard coating layer is developed by laminating a cured underlayer and a silicon oxide layer using plasma-enhanced chemical vapor deposition (PE-CVD), where the underlayer comprises multi-functional acrylate and inorganic oxide fine particles, and the silicon oxide layer has specific chemical composition and thickness ranges to ensure strong adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high hardness hard coating layer is formed by PE-CVD on a resin substrate, then abrasion resistance is improved, but adhesion durability deteriorates due to interface stress
Solution Approach 1:
The hard coating layer is divided into multiple layers with different hardness and composition gradients. The layer closest to the resin substrate has lower hardness and different chemical composition to reduce interface stress, while outer layers progressively increase in hardness to provide abrasion resistance. This segmentation allows each layer to fulfill its specific function without causing adhesion failure.
Solution Approach 2:
The chemical composition parameters (SiO2 content, organic group types and ratios) and physical parameters (layer thickness, deposition conditions) are systematically varied across different layers. By controlling these parameters, the patent creates a gradient structure that transitions from low-stress near the substrate to high-hardness at the surface, resolving the contradiction between adhesion and abrasion resistance.
2Strength
If a hard coating layer is deposited to achieve high abrasion resistance, then surface hardness is improved, but resistance to boiling water and heat deteriorates
Solution Approach 1:
The hard coating layer is constructed as a composite material system combining inorganic SiO2 network with organic functional groups (alkyl, aryl, heteroatom-containing groups). This composite structure provides both the hardness from the inorganic network and the thermal/chemical stability from the organic components, enabling simultaneous achievement of surface hardness and resistance to boiling water and heat.
Solution Approach 2:
Different regions of the hard coating layer have different chemical compositions tailored to their specific functions. The inner layer near the substrate contains composition optimized for adhesion and stress relief, while outer layers contain composition optimized for hardness and environmental resistance. This local quality differentiation allows the coating to withstand both mechanical and thermal/chemical stresses.
3Weight of moving object
If polymer substrates are used instead of inorganic glass, then light weight and impact resistance are improved, but surface abrasion resistance and hardness deteriorate
Solution Approach 1:
The patent creates a composite structure where a polymer substrate (providing light weight and impact resistance) is combined with a specially designed hard coating layer (providing abrasion resistance). The coating layer uses a unique composition of SiO2 with controlled organic groups to achieve glass-like hardness while maintaining adhesion to the polymer substrate, thus compensating for the substrate's inherent softness.
4Reliability
If interface stress is reduced to improve adhesion, then durability is improved, but abrasion resistance deteriorates
Solution Approach 1:
The coating is segmented into multiple layers where the first layer (closest to substrate) is designed with lower hardness and different composition to minimize interface stress and improve adhesion. Subsequent layers progressively increase in hardness to provide the necessary abrasion resistance. This segmentation allows the system to achieve both good adhesion and high abrasion resistance by distributing functions across layers.
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 provides a polymer substrate with enhanced abrasion resistance, boiling water resistance, and heat resistance, comparable to inorganic glass, ensuring long-term reliability and durability in harsh environments.
Implementation Method 1
a hard coating layer, which demonstrates superior abrasion resistance, high hardness and heat resistance... obtained by depositing an organic silicon-based oxide polymer on a resin substrate by plasma-enhanced chemical vapor deposition (PE-CVD)
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
The present invention is a polymer substrate with a hard coat layer, which is obtained by directly laminating a polymer substrate, a base cured layer and a silicon oxide layer, wherein the base cured layer has a thickness of 1-20 µm and contains 10-90 parts by weight of a polyfunctional acrylate and 90-10 parts by weight of inorganic oxide fine particles and/or a hydrolytic condensation product of a silicon compound or contains a hydrolytic condensation product of an organic silicon compound as a primary component, and the silicon oxide layer satisfies requirement (a1) below at a position 0.04 µm in the thickness direction from the interface between the base cured layer and the silicon oxide layer and satisfies requirement (a3) below at the surface of the silicon oxide layer on the opposite side from the interface. Requirement (al): when the chemical composition is represented by SiOxCyHz, x falls within the range 1.93-1.98, y falls within the range 0.04-0.15 and z falls within the range 0.10-0.50. Requirement (a3): when the chemical composition is represented by SiOxCyHz, x falls within the range 1.94-2.02, y falls within the range 0.05-0.16 and z falls within the range 0.20-0.50.