Optical Filter Hafnium Oxide Adhesion
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Solution Overview
Problem
Conventional optical filters with dielectric multi-layer films containing hafnium oxide tend to separate from transparent substrates after heat treatment, compromising their structural integrity and functionality.
Innovation Solution
The optical filter design includes a transparent glass substrate with a dielectric multi-layer film containing hafnium oxide, where the surface roughness of both the substrate and the film is controlled, and an optional silicon oxide adhesion layer is introduced between the substrate and the film to enhance adhesion, preventing separation during heat treatment and curved form usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is applied to crystallize hafnium oxide in the dielectric multi-layer film, then the optical filter achieves desired optical properties, but separation occurs at the interface between the transparent substrate and the dielectric multi-layer film
Solution Approach 1:
The patent applies preliminary surface treatment to the transparent substrate before forming the dielectric multi-layer film. Specifically, the substrate surface is subjected to plasma treatment or chemical treatment to create a roughened surface with increased surface area and enhanced adhesion properties. This preliminary action ensures that when heat treatment is later applied to crystallize the hafnium oxide, the dielectric film remains firmly attached to the substrate without separating at the interface.
2Manufacturing precision
If the dielectric multi-layer film is made smooth to improve optical performance, then light transmission is enhanced, but adhesion to the substrate deteriorates during heat treatment
Solution Approach 1:
The patent segments the surface characteristics into two distinct zones: the substrate-film interface region and the film outer surface region. At the interface, the substrate surface is deliberately roughened through plasma or chemical treatment to maximize adhesion. At the outer film surface, the patent maintains smoothness by controlling the deposition process and selecting appropriate materials, ensuring optimal optical transmission. This spatial segmentation of surface properties resolves the contradiction between adhesion and optical performance.
Solution Approach 2:
The patent applies different quality characteristics to different locations within the dielectric multi-layer structure. The inner surface of the dielectric film that contacts the substrate is designed with high adhesion quality through interface treatment, while the outer surface is optimized for optical quality with smooth finish. This local differentiation of properties allows the system to simultaneously achieve strong adhesion during heat treatment and high optical transmission performance.
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 effectively prevents separation of the dielectric multi-layer film from the transparent substrate, ensuring the optical filter's stability and performance, particularly in sterilization devices that utilize ultraviolet radiation for microbial inactivation.
Implementation Method 1
an optical filter (interference filter) is used which includes a dielectric multi-layer film where hafnium oxide layers and silicon oxide layers are alternately layered one on top of another in order to transmit, among light emitted from a light source, light in a wavelength range of 190 nm to 230 nm and block light of wavelengths other than the above wavelength range
Implementation Method 2
an optical filter may be produced by forming a dielectric multi-layer film on a transparent substrate and then subjecting the obtained laminate product to heat treatment in order to crystallize hafnium oxide
Implementation Method 3
a sterilization device that allows ultraviolet radiation to act on DNA in cells of organisms to be sterilized, such as bacteria, without harming human cells, to selectively inactivate the organisms to be sterilized
Data Source
AI summary
Provided is an optical filter in which a dielectric multi-layer film is less likely to separate from a transparent substrate. An optical filter 1 includes: a transparent substrate 2 made of glass; and a dielectric multi-layer film 3 provided on the transparent substrate 2 and containing hafnium oxide, wherein a surface of the transparent substrate 2 on the dielectric multi-layer film 3 side has an arithmetic mean height Sa of 0.22 nm or less.