Optical Member Hard Coat Composition for UV Crack Resistance
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Solution Overview
Problem
Hard coat layers on optical members, such as plastic eyeglass lenses, suffer from cracking under prolonged exposure to ultraviolet light and high-humidity conditions, particularly when containing inorganic oxides with an absorption edge at 300-450 nm.
Innovation Solution
Incorporating an ultraviolet absorber and an antioxidant into the hard coat layer, comprising inorganic oxides like titanium oxide, zirconium oxide, and a benzotriazole compound, enhances cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coat layer containing inorganic oxide with absorption edge at 300-450 nm is formed to enhance scratch resistance, then surface hardness is improved, but cracking occurs under ultraviolet irradiation and high-humidity conditions
Solution Approach 1:
An ultraviolet absorber compound (benzotriazole derivative) is introduced as an intermediary substance between the inorganic oxide and the hard coat layer matrix. This compound absorbs ultraviolet light before it can be absorbed by the inorganic oxide, preventing the inorganic oxide from reaching an excited state that would cause cracking. The intermediary thus blocks the harmful interaction between UV light and inorganic oxide while maintaining the scratch resistance provided by the inorganic oxide.
Solution Approach 2:
The invention converts the harmful effect of ultraviolet light absorption by inorganic oxide into a beneficial protective mechanism. By incorporating an ultraviolet absorber that preferentially absorbs UV light, the system prevents the inorganic oxide from absorbing UV energy and undergoing harmful excitation. The previously harmful UV absorption by inorganic oxide is thus converted into a controlled absorption process that protects rather than damages the hard coat layer.
2Duration of action of stationary object
If inorganic oxide is added to hard coat layer to improve durability, then scratch resistance is enhanced, but the layer becomes susceptible to cracking under prolonged ultraviolet exposure
Solution Approach 1:
The ultraviolet absorber acts as a mediator that intercepts ultraviolet light before it reaches the inorganic oxide. This intermediary layer of molecules absorbs the harmful UV radiation through their chromophoric groups, converting the energy into harmless forms (heat, vibrational energy) without allowing the inorganic oxide to absorb the UV energy and become excited. This protects the durability-enhancing inorganic oxide from UV-induced degradation.
Solution Approach 2:
The invention changes the optical parameters of the hard coat layer by introducing a compound with specific UV absorption characteristics. The benzotriazole derivative has absorption characteristics that complement the inorganic oxide, creating a layered absorption system where the organic compound handles UV absorption in the 280-400 nm range, preventing the inorganic oxide from experiencing harmful excitation while maintaining overall durability.
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 cracking resistance under ultraviolet irradiation and high-humidity conditions, maintaining durability and integrity.
Implementation Method 1
inclusion of an ultraviolet absorber and an antioxidant in a hard coat layer enables the hard coat layer to exhibit excellent cracking resistance under ultraviolet irradiation
Implementation Method 2
when the hard coat layer contains an inorganic oxide having an absorption edge at a wavelength of 300-450 nm, cracking tends to occur in the hard coat layer perhaps because of the inorganic oxide absorbing light energy and becoming an excited state
Implementation Method 3
a photopolymerization initiator
Data Source
Figure 1
AI summary
An optical member including a lens substrate and a hard coat layer, wherein the hard coat layer is a cured product of a curable composition including an inorganic oxide, an ultraviolet absorber, and an antioxidant, and wherein the curable composition contains an inorganic oxide having an absorption edge at a wavelength of 300 to 450 nm, [2] a curable composition including an inorganic oxide, an ultraviolet absorber, and an antioxidant, wherein the curable composition contains an inorganic oxide having an absorption edge at a wavelength of 300 to 450 nm, and [3] a method for producing an optical member, including a step of coating the curable composition as described in [2] onto a lens substrate and curing the composition to form a hard coat layer.