Hard Coat Optical Member Composition Against UV Yellowing and Cracking
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Solution Overview
Problem
Optical members, such as plastic eyeglass lenses, suffer from yellowing and cracking issues under prolonged ultraviolet irradiation and high-humidity conditions, despite having hard coat layers.
Innovation Solution
Incorporating a predetermined amount of an ultraviolet absorber, such as a benzotriazole compound, into a curable composition for the hard coat layer, which is then cured with an inorganic oxide, enhances yellowing and cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coat layer is formed on a plastic optical member to enhance scratch resistance, then surface hardness is improved, but yellowing occurs under prolonged ultraviolet irradiation
Solution Approach 1:
An ultraviolet absorber is introduced as an intermediary substance within the hard coat layer to absorb harmful UV radiation before it can cause yellowing of the plastic substrate. The absorber acts as a mediator that protects the underlying material while allowing the hard coat to maintain its scratch resistance function.
Solution Approach 2:
The hard coat layer is formulated as a composite material containing both the hardening agents (silane compounds, epoxy compounds) and ultraviolet absorbers. This composite structure allows simultaneous achievement of surface hardness and yellowing resistance by combining materials with complementary functions.
2Strength
If a hard coat layer is formed on a plastic optical member to enhance scratch resistance, then surface hardness is improved, but cracking occurs under light irradiation in high-humidity environments
Solution Approach 1:
The ultraviolet absorber serves as a protective intermediary that reduces UV-induced degradation and hydrolysis in the hard coat layer. By absorbing UV energy, it prevents the formation of free radicals that would otherwise accelerate polymer degradation and cracking in high-humidity environments.
Solution Approach 2:
The chemical composition parameters of the hard coat layer are modified by incorporating ultraviolet absorbers with specific molecular structures and concentrations. This parameter change alters the photochemical stability and hydrolytic resistance of the coating, preventing cracking under combined light and humidity exposure.
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 optical member exhibits excellent resistance to yellowing under UV irradiation and cracking under light and high-humidity conditions, with improved durability and longevity.
Implementation Method 1
a curable composition comprising an inorganic oxide and an ultraviolet absorber... inclusion of a predetermined amount of an ultraviolet absorber in a hard coat layer enhances the yellowing resistance under ultraviolet irradiation
Implementation Method 2
JP-A-09-265059 describes an eyeglass lens containing... a hard coat layer formed thereon... JP-A-H05-287241 concerns a hard-coating agent for an optical article... a cationically polymerizable group containing silsesquioxane compound
Data Source
Figure 1
AI summary
An optical member including a plastic substrate and a hard coat layer, wherein the hard coat layer is a cured product of a curable composition including an inorganic oxide and an ultraviolet absorber, and wherein the content of the ultraviolet absorber in the cured product is 0.5 to 15% by mass, [2] a curable composition including an inorganic oxide and an ultraviolet absorber, wherein the content of the ultraviolet absorber is 0.5 to 15% by mass per 100% by mass of the total amount of the active ingredients of the curable composition, and [3] a method for producing an optical member, including a step of coating the curable composition as described in [2] onto a plastic substrate and curing the composition to form a hard coat layer.