Abrasion-Resistant Coating Crack Reduction via Ether Additives

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Solution Overview

Problem

Existing abrasion- and scratch-resistant coatings for organic glass lenses tend to crack when deposited over a soft primer coating, compromising their mechanical and optical properties.

Innovation Solution

Incorporating specific organic ether additives with epoxy groups into the coating composition, specifically alkylene glycol diglycidyl ether or poly(alkylene glycol) diglycidyl ether, which enhances the coating's resistance to crack formation without affecting adhesion or optical clarity, even when applied over a soft primer coating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If hard coatings are deposited on soft primer coatings to improve abrasion resistance, then scratch resistance is improved, but crack formation increases

Engineering Contradiction:

Improvescratch resistanceVSAvoidcrack formation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the hard coating by incorporating specific epoxy compounds (diglycidyl ether of alkylene glycol or poly(alkylene glycol) diglycidyl ether) in controlled amounts (0.3-5 wt%). This compositional parameter change modifies the coating's flexibility and adhesion properties, allowing it to maintain scratch resistance while reducing crack formation on soft primer coatings

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite coating system by combining traditional hard coating components (silane hydrolysates, epoxy compounds) with specific ether additives. This composite approach integrates the hardness-providing elements with the flexibility-providing ether compounds, achieving a balanced coating that resists both scratching and cracking

Inventive Principle:

Principle #40Composite materials

2Reliability

If plasticizers are added to increase flexibility and reduce crack formation, then reliability is improved, but abrasion resistance decreases

Engineering Contradiction:

Improvecrack formationVSAvoidabrasion resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent precisely controls the concentration of plasticizing ether compounds within 0.3-5 wt% ranges. At these optimized levels, the ether compounds provide sufficient flexibility to reduce cracking while maintaining adequate abrasion resistance, unlike higher concentrations that would overly soften the coating

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies the plasticizing effect locally through targeted molecular interactions. The ether compounds selectively interact with the coating matrix to provide flexibility where needed while preserving the hard, abrasion-resistant network structure in other regions

Inventive Principle:

Principle #3Local quality

3Reliability

If high boiling temperature solvents are used to reduce crack formation, then reliability is improved, but manufacturing precision decreases due to reduced abrasion resistance

Engineering Contradiction:

Improvecrack formationVSAvoidabrasion resistance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical approach of using high-boiling solvents (which physically modify the coating matrix) with a chemical approach using ether compounds that provide flexibility through molecular interactions. This substitution achieves crack resistance without the side effect of reduced abrasion resistance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 significantly reduces crack formation in abrasion- and scratch-resistant coatings while maintaining high adhesion and optical transparency, achieving improved mechanical properties without increasing light diffusion or compromising scratch resistance.

Implementation Method 1

In order to increase the flexibility of the network and thus to reduce the tendency to crack formation under thermal stress, it has also been proposed in EP 0614957 to plasticize the matrix of the coating with organic silanes

Methodology Applied

Scientific EffectPlasticization:

Implementation Method 2

at least one epoxy compound bearing at least one silicon atom having at least one hydrolyzable group directly linked to the silicon atom

Methodology Applied

Scientific EffectHydrolysis: Hydrolysis

Implementation Method 3

at least one catalyst

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentEP3602149B1Optical article comprising an abrasion- and/or scratch-resistant coating having a low sensitivity to cracks

Publication Date: 2022.08.24 ESSILOR INTERNATIONAL(COMPAGNIE GENERALE D OPTIQUE)

AI summary

The present invention relates to an optical article comprising a substrate having at least one main surface successively coated with an impact-resistant primer coating and an abrasion- and/or scratch-resistant coating, which is formed from a composition comprising at least one epoxy compound bearing at least one silicon atom having at least one hydrolyzable group directly linked to the silicon atom and at least one group comprising an epoxy function, and/or a hydrolysate thereof, at least one alkylene glycol diglycidyl ether or poly(alkylene glycol) diglycidyl ether, colloidal particles of at least one metal oxide or metalloid oxide, at least one catalyst, the composition being devoid of comprise Si(X)4 compounds, or hydrolysates thereof, in which the X groups independently represent C1-C6 alkoxy groups.