Optical Glass Composition for Precision Press Molding
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Solution Overview
Problem
Existing optical glasses with high refractive indices and low dispersion struggle to maintain stability during precision press molding, leading to crystallization and devitrification issues, making it difficult to achieve refractive indices of 1.70 or higher with Abbé numbers of 50 or higher while maintaining low temperature softening properties.
Innovation Solution
The development of an optical glass composition with specific molar percentages of B2O3, SiO2, Li2O, La2O3, Gd2O3, Y2O3, and other components, optimized to prevent exothermic peaks within the glass transition temperature range and exhibit a single endothermic peak, ensuring high glass stability and low temperature softening properties, as measured by differential scanning calorimetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the refractive index is raised to 1.70 or higher while maintaining an Abbé number of 50 or higher, then optical performance is improved, but glass stability deteriorates and crystallization tendency intensifies
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition ratios of multiple oxides (B2O3: 40-75%, SiO2: 0-15%, Li2O: 1-10%, ZnO: 0-15%, La2O3: 5-22%, Gd2O3: 3-20%, Y2O3: 0-1%, ZrO2: 0-10%, MgO: 0-5%, CaO: 0-5%, SrO: 0-5%) to achieve the desired refractive index while suppressing crystallization. This systematic adjustment of compositional parameters resolves the contradiction between high refractive index and glass stability.
Solution Approach 2:
The patent uses composite materials by combining multiple oxide components with complementary properties. The base glass network (B2O3-SiO2) provides structural stability, while rare earth oxides (La2O3, Gd2O3, Y2O3) contribute to high refractive index and low dispersion. This composite approach allows simultaneous achievement of high refractive index (nd≥1.70), low dispersion (νd≥50), and resistance to crystallization.
2Ease of manufacture
If low temperature softening properties are imparted to the glass, then precision press molding becomes easier, but glass stability is diminished
Solution Approach 1:
The patent changes the thermal parameters of the glass by optimizing the ratio of softening agents (Li2O, ZnO, MgO, CaO, SrO) to network formers (B2O3, SiO2). This compositional parameter adjustment lowers the softening temperature for easier press molding while the specific ratio ranges prevent excessive softening that would compromise glass stability and cause devitrification during the molding process.
3Illumination intensity
If the glass composition is optimized for high refractive index and low dispersion, then optical performance is improved, but resistance to devitrification during precision press molding deteriorates
Solution Approach 1:
The patent employs composite materials strategy by integrating rare earth oxides (La2O3, Gd2O3, Y2O3) into a borate-silicate glass matrix. This composite structure provides high refractive index and low dispersion while the specific composition ratios and the presence of multiple stabilizing components (ZnO, ZrO2, MgO, CaO, SrO) work synergistically to suppress devitrification during precision press molding, thus maintaining both optical performance and reliability.
Solution Approach 2:
The patent uses intermediary substances (ZnO, ZrO2, MgO, CaO, SrO) that mediate between the optical requirements (high refractive index from rare earths) and the stability requirements (resistance to devitrification). These intermediary oxides modify the glass network structure to prevent crystal formation while allowing the rare earth components to provide the desired optical properties.
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 optical glass composition achieves high refractive indices and low dispersion while maintaining stability, allowing for successful precision press molding and the production of high-quality optical elements with improved thermal characteristics and reduced devitrification.
Implementation Method 1
measurement with a differential scanning calorimeter (DSC)... a temperature 120° C. higher than the glass transition temperature Tg will be denoted as 'Tg+120° C.'... no exothermic peak is present in a temperature range greater than or equal to the glass transition temperature Tg but not exceeding a temperature 120° C. higher than the glass transition temperature (Tg+120° C.)
Implementation Method 2
only one endothermic peak is present within a temperature range greater than or equal to a temperature 100° C. lower than the liquidus temperature LT (LT−100° C.) but not exceeding the liquidus temperature LT
Implementation Method 3
They discovered that the low temperature softening properties and glass stability of an optical glass could be evaluated by measurement with a differential scanning calorimeter (DSC). A differential scanning calorimeter scans the temperature of a glass sample over a broad temperature range, measuring the heat generation and heat absorption of the sample at a variety of temperatures.
Data Source
AI summary
The present invention relates to an optical glass having optical constants in the form of a refractive index nd of 1.70 or higher and an Abbé number nud of 50 or higher, a preform for precision press molding comprised of this glass, an optical element comprised of this glass, and methods for manufacturing the preform and the optical element.