Removable PET Lens Stack With UV Blocking and Low Haze
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Solution Overview
Problem
Existing protective face shields for operating rooms suffer from high haze, inadequate UV blocking, and instability during sterilization processes, failing to meet the ANSI Z87.1-2020 standards and posing risks to surgical personnel.
Innovation Solution
A protective lens stack comprising a PET film with integrated UV blocking additive, matched refractive indices, and removable layers to achieve low haze and stability, using a hindered amine light stabilizer (HALS) and refractive index-matched PET films to ensure clarity and UV protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thin UV blocking layer (1-mil PET) is added to the base layer, then UV blocking is achieved with minimal haze (1%), but the total haze of the face shield increases to 2.05%, which is twice the ideal value
Solution Approach 1:
The patent combines UV blocking functionality with the base PET layer by incorporating UV absorbers and HALS stabilizers directly into the base layer formulation, eliminating the need for a separate UV blocking film. This integration reduces the total number of layers and minimizes cumulative haze while maintaining effective UV protection.
Solution Approach 2:
The base layer uses a composite formulation combining PET with UV-absorbing compounds and hindered amine light stabilizers (HALS), creating a multi-functional material that provides both structural integrity and UV protection without requiring additional separate layers.
2Object-affected harmful factors
If multiple layers are stacked to achieve UV blocking, then UV protection is improved, but the total haze increases and optical clarity deteriorates
Solution Approach 1:
The patent merges UV blocking functionality into the base layer itself through formulation modifications, eliminating the need for separate UV blocking layers. This reduces the total number of interfaces and layers, minimizing light scattering and maintaining high visible light transmission while providing effective UV protection.
3Manufacturing precision
If conventional PET film is used without UV blocking additives, then optical clarity is maintained with low haze, but UV radiation blocks poorly and transmits harmful rays to the wearer
Solution Approach 1:
The patent creates a composite PET material by incorporating UV absorbers and HALS stabilizers into the base layer formulation. This composite approach maintains the inherent optical clarity of PET while adding UV-blocking capabilities, achieving both low haze and effective UV protection in a single integrated layer.
Solution Approach 2:
The patent modifies the chemical composition parameters of the PET base layer by adding specific UV-absorbing compounds and stabilizers, changing the material's properties to provide UV blocking without significantly affecting its optical transmission characteristics in the visible range.
4Strength
If polycarbonate is used instead of PET for the face shield, then impact resistance is improved, but the material turns brown under gamma sterilization
Solution Approach 1:
The patent modifies the chemical composition of PET by incorporating HALS (hindered amine light stabilizers) and other stabilizers that specifically protect against gamma-induced degradation and color change, allowing the material to maintain its optical properties while achieving enhanced impact resistance through proper formulation.
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 achieves a protective lens stack with less than 2% haze, 87% visible light transmission, and effective UV blocking, maintaining optical clarity and sterility during gamma and EO sterilization, enhancing user safety and operational efficiency.
Implementation Method 1
a base layer including a polyethylene terephthalate (PET) film containing a UV blocking additive
Implementation Method 2
Refractive indices of the base layer and the one or more removable lens layers may be matched to within 0.2
Data Source
AI summary
A protective lens stack comprises a base layer including a polyethylene terephthalate (PET) film containing a UV blocking additive and one or more removable lens layers stacked on top of the base layer. Each of the removable lens layers may include a PET film and a first adhesive disposed on a bottom surface of the PET film. Refractive indices of the base layer and the one or more removable lens layers may be matched to within 0.2. Each layer of the protective lens stack, including the base layer and each of the removable lens layer(s), may have less than 0.5% haze. The protective lens stack may be used as a face shield or may be surface mountable using a second adhesive disposed on a bottom surface of the PET film containing the UV blocking additive.