Glass Substrate with Notch Geometry for AR Optical Components
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Solution Overview
Problem
Existing glass substrates with high refractive index and high internal transmittance face challenges such as crystallization during processing, increased brittleness due to low fictive temperature, stress concentration at notches leading to breakage, and high manufacturing costs, which hinder the widespread adoption of AR glasses.
Innovation Solution
A glass substrate design with specific gravity of 3.00 or more, radius of 75 mm or more, refractive index of 1.800 or more, fictive temperature ratio less than 1.00, internal transmittance wavelength of 425 nm or less, and center of mass deviation within 0.05% to 1.2% of the radius, along with chamfered edges to reduce stress concentration and eccentric forces, enhancing damage resistance and handling operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If glass substrate with high refractive index is cooled and formed, then refractive index is improved, but crystallization occurs during processing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the cooling rate and temperature profile during glass formation. By optimizing the cooling rate parameter and maintaining specific temperature ranges, the patent achieves high refractive index glass formation while preventing crystallization, thus resolving the contradiction between improving refractive index and maintaining compositional stability.
2Illumination intensity
If reheating treatment is performed to control platinum ion valence, then internal transmittance is improved, but fictive temperature decreases and brittleness increases
Solution Approach 1:
The patent applies parameter changes by optimizing the reheating treatment parameters, specifically controlling the temperature range and duration. By maintaining the reheating temperature below the glass transition temperature and limiting exposure time, the patent achieves effective platinum ion valence control and improved internal transmittance while minimizing the decrease in fictive temperature and resulting brittleness.
3Ease of manufacture
If surface area of glass wafer is increased to reduce cost, then manufacturing cost is improved, but difficulty of manufacturing high refractive index glass increases
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the glass composition and establishing a standardized manufacturing process before large-scale production. By predetermined the glass composition ratios and process parameters that have been proven to work for high refractive index glass, the patent enables easier manufacturing of larger wafers, thus reducing cost while maintaining manufacturability.
4Measurement precision
If notch is formed at edge portion for alignment adjustment, then positioning accuracy is improved, but stress concentration increases and breakage risk increases
Solution Approach 1:
The patent applies local quality by creating a gradual transition zone at the notch rather than a sharp discontinuity. By designing the notch with a specific geometry that distributes stress more evenly, the patent maintains positioning accuracy while reducing stress concentration and breakage risk at the edge portion.
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 design significantly reduces breakage during handling and processing, allowing for larger, cost-effective production of glass substrates suitable for AR glasses with high refractive index and transmittance, addressing the limitations of existing technologies.
Implementation Method 1
a refractive index nd of the glass substrate is 1.800 or more
Implementation Method 2
an internal transmittance of the glass substrate to visible light is 80% or more
Data Source
AI summary
A circular glass substrate including first and second main surfaces opposite each other, an edge portion between the first and second main surfaces, and a notch at a part of the edge portion. The glass substrate has a specific gravity of 3.00 or more; a radius r of 75 mm or more; a refractive index nd of 1.800 or more; and a ratio (Tf/Tg) of a fictive temperature Tf (° C.) to a glass transition temperature Tg (° C.) of less than 1.00. In a relationship of an internal transmittance to a wavelength, when converted for a thickness of 10 mm, a shortest wavelength λ70 at which the internal transmittance becomes 70% is 425 nm or less; and a ratio (g/r) of deviation g (mm), of a center of mass (G) relative to a center (P), to the radius r, in a top view, is in a range of 0.05% to 1.2%.