Derivative works — US Patent 8640498

Defensive Disclosure: Fining of Boroalumino Silicate Glasses - Derivative Works

This document details derivative works and technical disclosures related to US Patent 8640498, "Fining of boroalumino silicate glasses," with the objective of establishing prior art for potential future incremental improvements by competitors. The derivations are based on the core claims of the patent, specifically Claim 1, and explore variations across materials, operational parameters, cross-domain applications, integration with emerging technologies, and failure modes.

Core Claim Analyzed:

Claim 1: A method for producing alkali-free glass sheets by a downdraw process comprising:
(A) selecting, melting, and fining batch materials so that the glass making up the sheets comprises SiO2, Al2O3, B2O3, MgO, and CaO, and, on an oxide basis, has:
(i) a Σ[RO]/[Al2O3] ratio greater than or equal to 1.0, where [Al2O3] is the mole percent of Al2O3 and Σ[RO] is the sum of the mole percents of MgO, CaO, SrO, and BaO; and
(ii) a MgO content greater than or equal to 1.0 mole percent;
(B) producing the glass sheets from the melted and fined batch materials;
wherein:
(a) on an oxide basis, the glass making up the glass sheets comprises at most 0.005 mole percent As2O3;
(b) on an oxide basis, the glass making up the glass sheets comprises at most 0.005 mole percent Sb2O3;
(c) SnO2 is used in the fining and the glass making up the glass sheets has an SnO2 content which in mole percent on an oxide basis satisfies the relationship: 0.01≦SnO2; and
(d) the glass making up the glass sheets has a liquidus viscosity that is greater than or equal to 100,000 poise.

Derivative 1: Material & Component Substitution - Cerium Oxide and Zinc Oxide Fining

Enabling Description: The method for producing alkali-free glass sheets by a downdraw process is modified to utilize a cerium oxide (CeO2) fining agent in conjunction with a zinc oxide (ZnO) flux. The batch materials are selected such that the final glass comprises, on an oxide basis: SiO2: 64.0-71.0 mole percent, Al2O3: 9.0-12.0 mole percent, B2O3: 7.0-12.0 mole percent, MgO: 1.0-3.0 mole percent, CaO: 6.0-11.5 mole percent, SrO: 0-2.0 mole percent, BaO: 0-0.1 mole percent, ZnO: 0.5-3.0 mole percent, and CeO2: 0.1-0.5 mole percent. The Σ[RO]/[Al2O3] ratio is maintained at greater than or equal to 1.0, and the MgO content is greater than or equal to 1.0 mole percent. The As2O3 and Sb2O3 concentrations are each at most 0.005 mole percent, specifically excluding their use as primary fining agents. The CeO2 acts as a fining agent through redox reactions (Ce3+/Ce4+), releasing oxygen bubbles at elevated temperatures to coalesce and remove gaseous inclusions. Concurrently, ZnO acts as a flux to lower the overall melting temperature and melt viscosity, thereby facilitating fining and compensating for any subtle differences in fining efficiency compared to SnO2. The resulting glass sheets, produced via the downdraw process, exhibit a liquidus viscosity greater than or equal to 100,000 poise, suitable for display applications.

graph TD
    A[Select Batch Materials] --> B{Add ZnO as Flux & CeO2 as Fining Agent}
    B --> C[Melt Batch Materials]
    C --> D[Fining Process (CeO2 Redox)]
    D --> E{Check Composition & Properties}
    E -- Σ[RO]/[Al2O3] >= 1.0, MgO >= 1.0 mol%, As2O3 <= 0.005 mol%, Sb2O3 <= 0.005 mol%, CeO2 0.1-0.5 mol%, ZnO 0.5-3.0 mol% --> F[Downdraw Process]
    F --> G[Produce Alkali-Free Glass Sheets]
    G -- Liquidus Viscosity >= 100,000 poise --> H[Final Product (Enhanced Fining)]

Derivative 2: Material & Component Substitution - Germanium Dioxide for Optical Tuning

Enabling Description: A method for producing alkali-free glass sheets by a slot-draw process (a type of downdraw) is utilized, wherein the batch materials are selected to include germanium dioxide (GeO2) as a partial substitute for silicon dioxide (SiO2). The resultant glass comprises on an oxide basis: SiO2: 50.0-60.0 mole percent, GeO2: 5.0-15.0 mole percent, Al2O3: 9.0-12.0 mole percent, B2O3: 7.0-12.0 mole percent, MgO: 1.0-3.0 mole percent, CaO: 6.0-11.5 mole percent, SrO: 0-2.0 mole percent, and BaO: 0-0.1 mole percent. The Σ[RO]/[Al2O3] ratio is maintained at greater than or equal to 1.0, and the MgO content is greater than or equal to 1.0 mole percent. Fining is performed using SnO2 at a concentration of 0.01-0.15 mole percent, ensuring As2O3 and Sb2O3 concentrations are each at most 0.005 mole percent. The inclusion of GeO2, known for its higher refractive index and lower dispersion compared to SiO2, allows for the tuning of the glass's optical properties while largely preserving its mechanical and thermal characteristics required for high-performance displays. The slot-draw process facilitates the production of thin, optically uniform sheets. The produced glass sheets exhibit a liquidus viscosity greater than or equal to 100,000 poise.

graph TD
    A[Select Batch Materials] --> B{Substitute GeO2 for part of SiO2}
    B --> C[Melt Batch Materials]
    C --> D[Fining Process (SnO2)]
    D --> E{Check Composition & Properties}
    E -- Σ[RO]/[Al2O3] >= 1.0, MgO >= 1.0 mol%, As2O3 <= 0.005 mol%, Sb2O3 <= 0.005 mol%, SnO2 >= 0.01 mol% --> F[Slot-Draw Process]
    F --> G[Produce Alkali-Free Glass Sheets (Optical Grade)]
    G -- Liquidus Viscosity >= 100,000 poise --> H[Final Product (Enhanced Optical Properties)]

Derivative 3: Operational Parameter Expansion - Micro-Scale Production with Ultra-High Vacuum Fining

Enabling Description: A method for producing alkali-free micro-glass sheets with a thickness less than 50 micrometers by a precision slot-draw process. This involves localized melting of the batch materials at a temperature exceeding 1700°C to ensure complete dissolution of SiO2, followed by rapid quenching to maintain the amorphous structure. The batch materials are selected to conform to the specified compositional ranges: SiO2: 64.0-71.0 mole percent, Al2O3: 9.0-12.0 mole percent, B2O3: 7.0-12.0 mole percent, MgO: 1.0-3.0 mole percent, CaO: 6.0-11.5 mole percent, SrO: 0-2.0 mole percent, BaO: 0-0.1 mole percent. The Σ[RO]/[Al2O3] ratio is maintained at greater than or equal to 1.0, and the MgO content is greater than or equal to 1.0 mole percent. Fining is accomplished using SnO2 (0.01-0.15 mole percent) under ultra-high vacuum conditions (e.g., 10^-5 Torr) during the melting phase. This vacuum fining actively extracts dissolved gases and reduces bubble nucleation, leading to exceptionally defect-free micro-glass sheets. As2O3 and Sb2O3 concentrations are each maintained at most 0.005 mole percent. The resulting micro-sheets possess a liquidus viscosity greater than or equal to 100,000 poise, enabling stable ultra-thin film formation for advanced micro-electronics.

graph TD
    A[Prepare Micro-Batch Materials] --> B{Melt at >1700°C in Ultra-High Vacuum}
    B --> C[Fining Process (SnO2 + Vacuum)]
    C --> D{Precision Slot-Draw}
    D --> E[Rapid Quenching]
    E --> F[Produce Alkali-Free Micro-Glass Sheets]
    F -- Thickness < 50 µm, Liquidus Viscosity >= 100,000 poise --> G[Final Product (Micro-electronics)]

Derivative 4: Operational Parameter Expansion - Continuous Large-Scale Production with Ultrasonic Fining

Enabling Description: A method for continuous, large-scale production of alkali-free glass sheets, specifically designed for Gen 10+ display substrates (e.g., 3000 mm × 3320 mm dimensions), using a fusion downdraw process. The melting system features a melter with a capacity exceeding 500 metric tons per day. The melting temperature is precisely controlled between 1600°C and 1650°C. Fining is significantly augmented by a combination of SnO2 (0.01-0.15 mole percent) and continuous ultrasonic cavitation applied within a dedicated refining zone of the melt. High-frequency ultrasonic transducers (e.g., >20 kHz) induce acoustic streaming and enhance the coalescence and rapid removal of microscopic gaseous inclusions. The glass composition adheres to SiO2: 64.0-71.0 mole percent, Al2O3: 9.0-12.0 mole percent, B2O3: 7.0-12.0 mole percent, MgO: 1.0-3.0 mole percent, CaO: 6.0-11.5 mole percent, SrO: 0-2.0 mole percent, BaO: 0-0.1 mole percent, with the Σ[RO]/[Al2O3] ratio greater than or equal to 1.0 and MgO content greater than or equal to 1.0 mole percent. As2O3 and Sb2O3 are present at concentrations of at most 0.005 mole percent each. The resulting glass maintains a liquidus viscosity greater than or equal to 100,000 poise, ensuring suitability for defect-free large format displays at high throughput.

graph TD
    A[Large-Scale Batch Preparation] --> B{Continuous Joule Melting (1600-1650°C)}
    B --> C[Fining with SnO2 + Ultrasonic Cavitation]
    C --> D{Fusion Downdraw (Gen 10+ Dimensions)}
    D --> E[Annealing & Cutting]
    E --> F[Produce Large Alkali-Free Glass Sheets]
    F -- High Throughput, Liquidus Viscosity >= 100,000 poise --> G[Final Product (Gen 10+ Display Substrates)]

Derivative 5: Cross-Domain Application - Photovoltaic Cover Glass

Enabling Description: A method for producing alkali-free glass sheets specifically adapted for use as high-transparency cover glass in photovoltaic solar panels, utilizing a downdraw process. The glass composition is precisely controlled within the specified ranges to enhance UV transmission properties and resist long-term environmental degradation, crucial for solar energy applications. The composition includes SiO2: 64.0-71.0 mole percent, Al2O3: 9.0-12.0 mole percent, B2O3: 7.0-12.0 mole percent, MgO: 1.0-3.0 mole percent, CaO: 6.0-11.5 mole percent, SrO: 0-2.0 mole percent, BaO: 0-0.1 mole percent. The Σ[RO]/[Al2O3] ratio is maintained at greater than or equal to 1.0, and the MgO content is greater than or equal to 1.0 mole percent. Fining is performed with SnO2 (0.01-0.15 mole percent), ensuring that As2O3 and Sb2O3 concentrations are each at most 0.005 mole percent to prevent any light absorption in the UV spectrum. The resulting glass sheets possess a liquidus viscosity greater than or equal to 100,000 poise, which is essential for uniform thickness and surface quality in the large-area glass required for cost-effective mass production of durable, highly transparent solar panel covers.

graph TD
    A[Select Batch Materials (Solar Grade, UV-optimized)] --> B[Melt & Fine (SnO2, low As/Sb)]
    B --> C{Downdraw Process}
    C --> D[Produce Alkali-Free Glass Sheets]
    D -- High UV Transparency, Environmental Durability, Liquidus Viscosity >= 100,000 poise --> E[Solar Panel Cover Glass]

Derivative 6: Cross-Domain Application - Medical/Laboratory Microscope Slides

Enabling Description: A method for producing alkali-free boroalumino silicate glass slides for high-precision microscopy and laboratory diagnostic applications. This involves an initial downdraw process to create a mother glass sheet, followed by a precision redraw process to achieve the final slide dimensions and thickness. The initial glass composition is fine-tuned for minimal auto-fluorescence under various excitation wavelengths and enhanced chemical resistance to a broad range of common laboratory reagents (acids, bases, organic solvents). The composition adheres to SiO2: 64.0-71.0 mole percent, Al2O3: 9.0-12.0 mole percent, B2O3: 7.0-12.0 mole percent, MgO: 1.0-3.0 mole percent, CaO: 6.0-11.5 mole percent, SrO: 0-2.0 mole percent, BaO: 0-0.1 mole percent. The Σ[RO]/[Al2O3] ratio is maintained at greater than or equal to 1.0, and the MgO content is greater than or equal to 1.0 mole percent. Fining uses SnO2 (0.01-0.15 mole percent), ensuring As2O3 and Sb2O3 concentrations are each at most 0.005 mole percent to minimize any intrinsic fluorescence. The primary downdrawn glass exhibits a liquidus viscosity greater than or equal to 100,000 poise, which is critical for enabling subsequent precision redraw into thin, high-quality, and dimensionally stable microscope slides.

graph TD
    A[Select Batch Materials (Low Auto-Fluorescence, Chemical Resistance)] --> B[Melt & Fine (SnO2, low As/Sb)]
    B --> C{Downdraw Process}
    C --> D[Initial Alkali-Free Glass Sheet]
    D -- Liquidus Viscosity >= 100,000 poise --> E[Precision Redraw Process]
    E --> F[Produce Alkali-Free Microscope Slides]
    F -- Minimal Auto-Fluorescence, High Chemical Resistance --> G[Medical/Lab Diagnostics]

Derivative 7: Integration with Emerging Tech - AI-Driven Real-time Optimization

Enabling Description: A method for producing alkali-free glass sheets by a downdraw process, wherein an AI-driven optimization system dynamically adjusts batch material selection, furnace temperature profiles, and fining parameters in real-time. IoT sensors, including high-temperature melt probes, optical defect detection systems, and spectroscopic analyzers, are embedded throughout the melting furnace and conditioning system. These sensors provide continuous feedback on melt temperature, viscosity, redox state, dissolved gas content, and real-time gaseous inclusion count. The AI model, leveraging machine learning algorithms trained on extensive historical production data and thermodynamic simulations, autonomously predicts and implements optimal adjustments to SiO2, Al2O3, B2O3, MgO, CaO, SrO, BaO concentrations (within specified ranges) and SnO2 fining agent levels (0.01-0.15 mole percent). The AI ensures the Σ[RO]/[Al2O3] ratio remains greater than or equal to 1.0, the MgO content greater than or equal to 1.0 mole percent, and minimal As2O3/Sb2O3 (at most 0.005 mole percent each). The system targets and maintains a consistent liquidus viscosity greater than or equal to 100,000 poise, proactively minimizing defect rates, reducing energy consumption, and optimizing material yield through continuous, data-driven process adjustments.

graph TD
    A[Batch Material Feedstock] --> B{IoT Sensors (Melt Temp, Viscosity, Redox, Inclusions)}
    B -- Real-time Data Stream --> C[AI Optimization Engine]
    C -- Dynamic Adjustments --> D[Melting & Fining System (SnO2)]
    D --> E{Downdraw Process}
    E --> F[Quality Control (Inline Sensors)]
    F --> G[Alkali-Free Glass Sheets]
    G -- Liquidus Viscosity >= 100,000 poise, Minimal Defects --> H[AI-Optimized Production]

Derivative 8: Integration with Emerging Tech - Blockchain for Supply Chain & Property Traceability

Enabling Description: A method for producing alkali-free glass sheets by a downdraw process, integrating blockchain technology to ensure transparent and immutable traceability of all raw material inputs and finished glass sheet properties. Each supplier of batch materials (SiO2, Al2O3, B2O3, MgO, CaO, SrO, BaO, SnO2) records a cryptographically signed certificate of analysis, including precise compositional data and origin, onto a distributed ledger. Throughout the melting and fining process, real-time sensor data (e.g., furnace temperature, energy consumption, fining agent dosage, molten glass elemental analysis, and gaseous inclusion levels) and final quality control measurements (e.g., composition verification, liquidus viscosity, CTE, strain point) are automatically hashed and added as transactions to the blockchain. This distributed ledger provides an auditable and tamper-proof record, ensuring end-to-end verification that the glass meets all specified requirements, including the Σ[RO]/[Al2O3] ratio (greater than or equal to 1.0), MgO content (greater than or equal to 1.0 mole percent), low As2O3/Sb2O3 (at most 0.005 mole percent each), and liquidus viscosity (greater than or equal to 100,000 poise). This enhances supply chain integrity, regulatory compliance, and product authentication.

graph LR
    A[Raw Material Suppliers] -- CoAs via API --> B(Blockchain Ledger)
    C[Batch Preparation System] -- Composition Data --> B
    D[Melting & Fining (SnO2)] -- Real-time Sensor Data --> B
    E[Downdraw Process] --> F[Glass Sheet Production]
    F -- Final QC Data (Viscosity, CTE) --> B
    B -- Immutable Traceability --> G[Manufacturers / Consumers]
    G -- Verify: Σ[RO]/[Al2O3] >= 1.0, MgO >= 1.0 mol%, As/Sb <= 0.005 mol%, Liquidus Viscosity >= 100,000 poise --> H[Trust & Compliance]

Derivative 9: The "Inverse" or Failure Mode - Low-Power Maintenance Mode

Enabling Description: A method for producing alkali-free glass sheets by a downdraw process, incorporating a "low-power fining and holding mode" for energy conservation during periods of reduced demand, process hold points, or system maintenance. In this mode, the batch materials are continuously melted at a reduced temperature range (e.g., 1500°C - 1550°C), resulting in a slightly higher melt viscosity and slower dissolution rates. The concentration of the fining agent (SnO2) is reduced (e.g., 0.01-0.05 mole percent) or a less potent, yet environmentally friendly, auxiliary fining agent like SO3 (0.01-0.05 mole percent) is partially substituted for SnO2. This results in an intentionally higher, but acceptable, gaseous inclusion level (e.g., up to 0.5 inclusions/cm3) and a slightly lower liquidus viscosity (e.g., 50,000-90,000 poise), sufficient to maintain the melt in a workable state without full production quality. The fundamental compositional requirements for SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO, and the Σ[RO]/[Al2O3] ratio (greater than or equal to 1.0) and MgO content (greater than or equal to 1.0 mole percent), as well as low As2O3/Sb2O3 (at most 0.005 mole percent each), are maintained to ensure material integrity and rapid ramp-up to full operational mode without requiring a complete cold start.

stateDiagram-v2
    [*] --> Startup: Initiate Process
    Startup --> Low_Power_Maintenance_Mode: Activate Low-Power for Efficiency/Hold
    Low_Power_Maintenance_Mode --> Full_Production_Mode: Ramp Up for Production
    Full_Production_Mode --> Low_Power_Maintenance_Mode: Transition to Standby
    Low_Power_Maintenance_Mode --> Shutdown: Terminate Process
    Low_Power_Maintenance_Mode : Reduced Temp (1500-1550°C)\nReduced SnO2/SO3 Fining\nHigher Inclusions (0.5/cm3 target)\nLiquidus Viscosity (50k-90k poise target)
    Full_Production_Mode : Optimal Temp (1600-1650°C)\nOptimal SnO2 Fining (>=0.01 mol%)\nLow Inclusions (<=0.05/cm3)\nLiquidus Viscosity (>=100k poise)

Derivative 10: The "Inverse" or Failure Mode - Automated Compositional Deviation Diversion

Enabling Description: A method for producing alkali-free glass sheets by a downdraw process, which incorporates an automated safe-failure mechanism to handle batch materials or molten glass that deviate from critical compositional specifications. An inline, real-time elemental analysis system (e.g., X-ray fluorescence (XRF) or Laser-Induced Breakdown Spectroscopy (LIBS)) continuously monitors the molten glass composition upstream of the downdraw process. If the analysis detects that the Σ[RO]/[Al2O3] ratio falls below 1.00 or the MgO content drops below 1.0 mole percent (which indicates a high probability of undesirable liquidus phases or inadequate fining efficacy, as described in the patent), the system automatically triggers a diversion of the off-specification molten glass stream to a dedicated waste collection and recycling system. This prevents the production of defective glass sheets and safeguards the downdraw forming equipment from potential damage due to crystallized glass. The fining process with SnO2 (0.01-0.15 mole percent) and adherence to minimal As2O3/Sb2O3 (at most 0.005 mole percent each) are maintained until the diversion point. The diverted waste glass can then be either re-batched after analysis or repurposed for less stringent applications.

flowchart LR
    A[Batch Material Feed] --> B{Melt & Fine}
    B --> C{Real-time Compositional Analysis (XRF/LIBS)}
    C -- Σ[RO]/[Al2O3] < 1.0 OR MgO < 1.0 mol% --> D{Divert to Waste System}
    D --> E[Waste Glass Collection/Recycling]
    C -- Σ[RO]/[Al2O3] >= 1.0 AND MgO >= 1.0 mol% --> F[Downdraw Process]
    F --> G[Quality Alkali-Free Glass Sheets]
    G -- Liquidus Viscosity >= 100,000 poise --> H[Final Product]

Combination Prior Art Scenarios:

US8640498 + Open-Source CFD (Computational Fluid Dynamics) Software (e.g., OpenFOAM):
- The method of US8640498 for producing alkali-free glass sheets with specific compositional and fining parameters is enhanced by employing open-source Computational Fluid Dynamics (CFD) software, such as OpenFOAM. This combination allows for sophisticated numerical modeling and simulation of the complex molten glass flow dynamics, heat transfer, and gaseous inclusion transport mechanisms within the melting furnace, fining zone, and downdraw forming apparatus. By integrating the patent's specific glass properties (e.g., liquidus viscosity, temperature-dependent viscosity profiles, gas solubilities based on Σ[RO]/[Al2O3] ratio) into the CFD model, engineers can virtually optimize furnace geometries, burner placements, fining agent (SnO2) injection strategies, and flow rates to predict and ensure uniform glass composition, minimized defects, and consistent liquidus viscosity, without costly physical prototyping. This approach enables a predictive understanding of the process from batch charging to sheet formation.
US8640498 + Open-Source Data Analytics Platform (e.g., Apache Spark with Zeppelin Notebooks):
- The manufacturing process described in US8640498 is integrated with an open-source data analytics platform, specifically utilizing Apache Spark for distributed data processing and Zeppelin Notebooks for interactive data exploration and visualization. This system ingests vast amounts of real-time operational data from the glass production line, including batch material feed rates, melting furnace temperatures, energy consumption, SnO2 dosing levels, and inline quality control measurements (e.g., optical defect detection, viscosity sensors). Leveraging Spark's machine learning libraries, correlations are identified between subtle variations in raw material inputs (e.g., trace contaminants impacting As2O3/Sb2O3 levels), process parameters, and the resulting glass properties (e.g., Σ[RO]/[Al2O3] ratio, MgO content, actual liquidus viscosity, and gaseous inclusion levels). This platform facilitates continuous process improvement, anomaly detection, predictive maintenance, and ensures stringent adherence to the patent's compositional and physical property requirements for alkali-free glass sheets.
US8640498 + Open-Source Industrial Control System (e.g., OpenPLC or Node-RED with industrial protocols):
- The method for producing alkali-free glass sheets by a downdraw process, as described in US8640498, is automated and controlled using an open-source industrial control system framework, such as OpenPLC or Node-RED. This system provides a flexible and modular approach to orchestrate the entire production line. OpenPLC can be programmed to manage the sequence and timing of batch material feeding, precise control of Joule heating electrodes to maintain specific melt temperatures (e.g., for optimal SiO2 dissolution and fining agent reactivity), and control of the downdraw machine's speed and tension to achieve desired sheet dimensions and liquidus viscosity. Node-RED can visually link sensors (e.g., temperature, flow, level sensors using Modbus TCP or OPC UA protocols) to actuators, implementing control logic that ensures the molten glass composition consistently meets the Σ[RO]/[Al2O3] ratio (greater than or equal to 1.0) and MgO content (greater than or equal to 1.0 mole percent), while strictly regulating SnO2 fining agent addition and minimizing undesirable As2O3/Sb2O3 levels to at most 0.005 mole percent each. This enables robust and adaptable automation of the glass manufacturing process.