Plastic Lens λ/4 Layer Adhesion and Interference Control
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Solution Overview
Problem
Existing plastic lenses with hard coat layers face challenges in achieving uniform thickness, leading to interference fringes and inadequate adhesion between the hard coat layer and the plastic substrate, which affects their appearance and performance.
Innovation Solution
A plastic lens with a λ/4 layer formed by curing a composition containing a bifunctional or higher functional acrylate compound, a dendritic aliphatic compound, and metal oxide particles, applied in a thickness range of 50 to 100 nm, along with an impact absorbing layer, to enhance adhesion and prevent interference fringes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coat layer is applied to enhance abrasion resistance, then surface hardness is improved, but interference fringes are formed when thickness is uneven, impairing appearance
Solution Approach 1:
A λ/4 layer is introduced as an intermediary between the plastic substrate and the hard coat layer. This intermediate layer has a refractive index that is the geometric mean of the substrate and hard coat layer, creating gradual refractive index transitions that eliminate interference fringes while allowing the hard coat layer to achieve uniform thickness through standard coating processes.
Solution Approach 2:
The refractive index parameter of the λ/4 layer is specifically controlled to be the geometric mean of the substrate and hard coat layer refractive indices. This parameter optimization ensures that the wavelength of light in the λ/4 layer equals one-quarter of the wavelength in the hard coat layer, preventing interference fringes while maintaining manufacturing feasibility.
2Manufacturing precision
If a λ/4 layer is added to prevent interference fringes, then appearance is improved, but adhesion between hard coat layer and substrate becomes insufficient
Solution Approach 1:
The λ/4 layer is formulated as a composite material containing a dendritic aliphatic compound with acrylate groups at terminal positions, bifunctional or higher functional acrylate compounds, and metal oxide particles. This composite structure provides both the optical properties needed to prevent interference fringes and the chemical adhesion properties required for strong bonding to both the plastic substrate and hard coat layer.
Solution Approach 2:
The λ/4 layer is designed with specific local properties: the dendritic aliphatic compound provides adhesion at the substrate interface, the acrylate functional groups enable chemical bonding, and the metal oxide particles provide hardness and optical properties. This localized optimization of different material functions within the same layer resolves the contradiction between adhesion and interference prevention.
3Device complexity
If the λ/4 layer thickness is reduced to 1 µm or less, then manufacturing complexity is reduced, but adhesion may be compromised
Solution Approach 1:
The composition parameters of the λ/4 layer are optimized to achieve maximum adhesion within a thin thickness range of 50 to 100 nm. The dendritic aliphatic compound with terminal acrylate groups and the metal oxide particle concentration are specifically controlled to ensure sufficient adhesion even at these reduced thicknesses, eliminating the need for thicker layers while maintaining bonding reliability.
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 λ/4 layer exhibits excellent adhesion with a thickness of 1 µm or less, preventing interference fringes and improving the appearance and durability of the plastic lens, while maintaining high light fastness and weather resistance.
Implementation Method 1
forming a λ/4 layer (B) that is formed by curing a composition containing a bifunctional or higher functional acrylate compound, a dendritic aliphatic compound having an acrylate group at an end thereof, and metal oxide particles
Implementation Method 2
when the hard coat layer has an uneven thickness, interference fringes are formed to impair the appearance of the lens
Implementation Method 3
an impact absorbing layer (D) between the λ/4 layer (B) and the hard coat layer (C)
Data Source
AI summary
To provide a plastic lens having a λ/4 layer exhibiting excellent adhesion between a plastic substrate and a hard coat layer, and a method for producing thereof. A plastic lens containing: a plastic substrate (A); a λ/4 layer (B) that is formed on the plastic substrate, is formed by curing a composition comprising a bifunctional or higher functional acrylate compound, a dendritic aliphatic compound having an acrylate group at an end thereof, and metal oxide particles, and has a thickness of from 50 to 100 nm; and a hard coat layer (C) that is formed on the λ/4 layer directly or through another layer.