Thin Optical Filter with Compressive Multi-Layer Films
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Solution Overview
Problem
Conventional optical filters struggle to achieve a balance between thinness and strength, with existing solutions either compromising on optical properties or substrate reinforcement, and are prone to warping and breakage due to thin substrates.
Innovation Solution
A thin substrate coated on both sides with multi-layer films having compression stress, where the strength ratio is optimized using conditional formulas to achieve high strength and thinness, with specific film deposition processes and materials like TiO2 and SiO2 to enhance optical properties and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the substrate thickness is reduced to achieve a slim profile, then the optical filter becomes thinner, but the substrate becomes more liable to break and warp
Solution Approach 1:
The patent applies composite materials by bonding two glass substrates together with an infrared-cut layer in between. This composite structure provides both the thinness required for slim profiles and the strength needed to prevent breaking and warping, as the bonded structure distributes mechanical stress across multiple components rather than relying on a single thick substrate
Solution Approach 2:
The patent changes the physical parameters of the substrate by controlling the thickness to be 0.5 mm or less while maintaining strength through the composite structure. This parameter optimization allows achieving the slim profile requirement without compromising mechanical integrity
2Shape
If dielectric multi-layer films are formed on opposite sides of an extremely thin substrate with symmetrical structure, then the warp resulting from film stress is reduced, but the strength of the optical filter cannot be increased
Solution Approach 1:
The patent uses a composite structure of two bonded glass substrates with an infrared-cut layer between them. This composite design provides inherent resistance to warping through the bonded joint while maintaining overall strength, unlike single-substrate approaches where symmetrical film structures alone cannot compensate for the weakness of extremely thin substrates
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 results in an optical filter that is both thin and strong, suitable for low-profile digital appliances, with improved resistance to bending and breakage, and enhanced optical performance by fulfilling specific strength and stress conditions.
Implementation Method 1
the multi-layer films on both sides of the substrate both have compression stress
Implementation Method 2
a multi-layer film deposited by multi-layer film sputtering
Data Source
AI summary
In this optical filter, each side of a substrate that is at most 0.3 mm in thickness is coated with a multilayer film. Both of the multilayer films are under compressive stress, and the optical filter satisfies the relation F≥−1.25t+1.525 (where F represents the ratio of the strength of the optical filter to the strength of the substrate (the strength of the optical filter with the substrate coated divided by the strength of the uncoated substrate) and t represents the thickness of the substrate (in mm)).