Plastic ND Filter with Silane Coupling and Sandwich Structure
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Solution Overview
Problem
Neutral density (ND) filters with an Al2O3 layer on a thiourethane substrate face issues such as processing cracks, transmittance abnormalities, and outer appearance abnormalities due to moisture absorption and deformation, leading to potential cracks and strain during constant temperature and humidity tests.
Innovation Solution
A plastic base ND filter with a thiourethane substrate, incorporating a light absorbing film with a sandwich structure that includes a reverse stress layer between silica compound layers, which helps absorb visible light uniformly and prevent reflection, while enhancing durability by using a combination of NiOx, ZrO2, and SiO2+Al2O3 layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a light absorbing film including an Al2O3 layer is formed on a thiourethane substrate, then the ND filter can be manufactured with the desired optical properties, but processing cracks and transmittance abnormalities occur during constant temperature and humidity testing
Solution Approach 1:
A silane coupling agent layer is introduced as an intermediary between the thiourethane substrate and the Al2O3 light absorbing film. This coupling agent layer has affinity to both the substrate and the oxide layer, acting as a mediator that prevents direct adverse interaction while maintaining adhesion, thereby eliminating cracks and transmittance abnormalities during humidity testing
Solution Approach 2:
The patent creates a composite multi-layer structure consisting of the thiourethane substrate, silane coupling agent layer, Al2O3 light absorbing film, and NiOx layer. This composite structure combines materials with complementary properties, where the silane coupling agent provides both adhesive functionality and moisture barrier properties, enhancing overall reliability
2Adaptability or versatility
If the ND filter uses a thiourethane base that absorbs moisture readily, then the base can be deformed to follow external forces during lens shape processing, but outer appearance abnormalities occur during constant temperature and humidity testing
Solution Approach 1:
The silane coupling agent layer is applied beforehand to the thiourethane substrate before forming the light absorbing film. This layer acts as a protective cushion that prevents moisture from penetrating into the substrate during subsequent humidity testing, thereby preventing outer appearance abnormalities while allowing the substrate to maintain its deformability during lens shaping
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 provides ND filters with improved durability and resistance to moisture-induced cracks and strain, maintaining optical stability and uniform light absorption, thus ensuring consistent performance in various environmental conditions.
Implementation Method 1
incorporating a light absorbing film with a sandwich structure that includes a reverse stress layer between silica compound layers, which helps absorb visible light uniformly
Implementation Method 2
which helps absorb visible light uniformly and prevent reflection
Implementation Method 3
incorporating a light absorbing film with a sandwich structure that includes a reverse stress layer between silica compound layers
Data Source
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AI summary
Provided are a ND filter and a spectacle ND filter that have a base made of plastic and that have excellent durability. The ND filter has a base made of plastic, and a light absorbing film having a plurality of layers is provided on at least one surface of the base. The light absorbing film includes one or more NiOx layers made of NiOx, x being not less than 0 and not greater than 1, and includes a sandwich structure portion which is provided on an opposite side of at least one of the NiOx layers from the base and in which a reverse stress layer is sandwiched between silica compound layers.