Optical Glass Composition for Precision Press Molding
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Solution Overview
Problem
High-refractive-index, low-dispersion optical glasses used in precision press molding face challenges such as volatility and striae formation due to high volatility components like B2O3, which affect the stability and quality of optical elements.
Innovation Solution
An optical glass composition with specific cation ratios and percentages of components like B2O3, La2O3, Gd2O3, ZnO, and WO3, optimized to maintain a low liquidus temperature and reduce volatility, allowing for stable production of high-quality optical elements with a refractive index of 1.86 or higher and an Abbé number of 28 to 36.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large quantities of high refractive index-imparting components such as Nb and rare earth components are incorporated, then the refractive index is raised and dispersion is lowered, but the liquidus temperature becomes excessively high (1020°C or above) and volatility increases causing striae formation
Solution Approach 1:
The patent changes the chemical composition parameters by introducing B2O3 at 20-40 wt% and adjusting the ratio of B3+ to other cations (B3+/(Si4++B3+) = 0.90-1.00, B3+/(La3++Gd3++Y3+) = 1.0-3.0, B3+/(Ti4++Nb5++Ta5++W6+) = 0.5-4.0). This parameter optimization lowers the liquidus temperature to 1000°C or below while maintaining high refractive index (nd ≥ 1.86) and low dispersion (vd = 28-36), thereby resolving the contradiction between optical performance and processing temperature.
2Temperature
If B3+ is used to lower the liquidus temperature, then the liquidus temperature is reduced, but B3+ is highly volatile causing striae and volatility problems during molding
Solution Approach 1:
The patent creates a composite glass system combining B2O3 with multiple other components (SiO2, La2O3, Gd2O3, ZnO, TiO2, Nb2O5, Ta2O5, WO3, and other metal oxides) in specific proportions. This composite approach allows B3+ to fulfill its function of lowering liquidus temperature while the other components compensate for its volatility, reducing striae formation and maintaining compositional homogeneity during molding operations.
Solution Approach 2:
The patent optimizes the concentration parameters of B3+ and other cations through precise ratio control (B3+/(Si4++B3+) = 0.90-1.00, B3+/(La3++Gd3++Y3+) = 1.0-3.0, B3+/(Ti4++Nb5++Ta5++W6+) = 0.5-4.0). This parameter optimization enables the glass to achieve low liquidus temperature (≤1000°C) while minimizing the harmful effects of B3+ volatility during processing.
3Ease of manufacture
If the glass transition temperature is lowered to enable precision press molding, then moldability is improved, but the thermal stability decreases
Solution Approach 1:
The patent adjusts the glass transition temperature parameter through compositional optimization, achieving Tg ≤ 590°C for improved moldability in precision press molding. Simultaneously, by controlling the liquidus temperature to ≤1000°C and optimizing the ratio of stabilizing components (Zn2+, Mg2+, Ca2+, Sr2+, Ba2+ with Zn2+/(Zn2++Mg2++Ca2++Sr2++Ba2+) = 0.8-1.0), the patent maintains adequate thermal stability during the molding process, resolving the contradiction between ease of manufacture and reliability.
Data Source
AI summary
The present invention relates to an optical glass having a refractive index nd of 1.86 or higher and an Abbé number v(nu)d of 28 to 36; a preform for precision press molding and an optical element that are comprised of this glass; and a method for manufacturing the optical element.