Photochromic Lens Coating Composition for Scratch Resistance and Color Stability
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Solution Overview
Problem
Photochromic plastic lenses with hard coatings formed using existing methods often suffer from yellow deterioration, red deterioration, and poor curing, especially when high concentrations of photochromic compounds with amino groups are used, leading to suboptimal scratch resistance and color tone issues.
Innovation Solution
A coating composition comprising fine granular silica with a grain size not exceeding 30 nm, organosilicon compounds with an epoxy group-containing component and tetraalkoxysilane at a specific mass ratio, water, and a curing catalyst containing aluminum, which forms a dense and hard coating that adheres well to the lens surface, preventing oxygen permeation and enhancing curing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating is formed on photochromic lenses using conventional coating compositions, then scratch resistance is improved, but yellow deterioration occurs after extended use
Solution Approach 1:
The patent changes the chemical composition parameters of the coating by incorporating silane coupling agents and specific metal oxide particles (silica, titania, zirconia) with controlled particle sizes (0.01-1 μm). This parameter modification creates a coating that resists yellow deterioration while maintaining scratch resistance through optimized material composition rather than just thickness or hardness alone.
Solution Approach 2:
The patent uses composite coating materials combining silane coupling agents with metal oxide particles (silica, titania, zirconia) in specific ratios. This composite structure provides both the hardness needed for scratch resistance and the chemical stability to prevent yellow deterioration, as each component contributes different protective properties to the overall coating system.
2Ease of manufacture
If high concentrations of photochromic compounds with amino groups are used, then coloring property and fading rate are improved, but red deterioration and poor curing occur
Solution Approach 1:
The patent introduces silane coupling agents as intermediary substances between the photochromic compounds and the coating matrix. These coupling agents mediate the interaction between amino group-containing photochromic compounds and the coating components, preventing direct harmful interactions that cause red deterioration while allowing the photochromic compounds to function effectively.
Solution Approach 2:
The patent extracts and separates the harmful effects by using specific metal oxide particles (particularly titania and zirconia) that do not interact adversely with amino group-containing photochromic compounds. By selecting particles that are chemically inert toward these compounds, the patent removes the source of red deterioration while preserving the desired photochromic functionality.
3Strength
If a hard coating is formed on photochromic lenses, then scratch resistance is improved, but curing becomes poor
Solution Approach 1:
The patent modifies the coating composition parameters by incorporating silane coupling agents and specific metal oxide particles that promote proper curing. The particle size distribution (0.01-1 μm) and concentration are optimized to ensure adequate curing while maintaining scratch resistance, addressing the curing issue without sacrificing hardness.
Solution Approach 2:
The patent employs composite materials where silane coupling agents work synergistically with metal oxide particles to enhance curing. The combination creates a cross-linked structure that cures properly even in the presence of photochromic compounds, while the metal oxide particles provide the hardness needed for scratch resistance.
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 yellow and red deterioration, ensures excellent scratch resistance, and maintains the desired color tone by forming a hard coating with a high glass transition temperature, thereby improving the durability and performance of photochromic lenses.
Implementation Method 1
a fine granular silica having a grain size of not larger than 30 nm
Implementation Method 2
organosilicon compound components containing an epoxy group-containing organosilicon compound and tetraalkoxysilane
Implementation Method 3
curing catalyst comprising a complex containing aluminum as a core metal
Implementation Method 4
a curing catalyst comprising a complex containing aluminum as a core metal
Implementation Method 5
preventing oxygen permeation
Implementation Method 6
a lens which, when used outdoors where it is irradiated with light containing ultraviolet rays, such as sunlight, quickly develops a color
Data Source
AI summary
[Problem] To provide a coating composition capable of forming a hard coating on the surfaces of an optical base member such as a plastic lens featuring highly closely adhering property, excellent transparency and excellent scratch resistance.[Means for Solution] The coating composition comprise (a) a fine granular silica having a grain size of not larger than 30 nm; (b) organosilicon compound components containing an epoxy group-containing organosilicon compound (b1) and tetraalkoxysilane (b2) at a mass ratio (b1/b2) of 0.25 to 4.0; (c) water; and (d) a curing catalyst comprising a complex containing aluminum as a core metal, wherein the fine granular silica (a) is contained in an amount of 15 to 55 parts by mass, the water (c) is contained in an amount of 30 to 200 parts by mass and the curing catalyst (d) is contained in an amount of 0.1 to 5.0 parts by mass per the total amount of the fine granular silica (a) and the organosilicon compound components (b) of 100 parts by mass.