Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
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Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781118799499
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[10].

Schematic illustration of the float process: (a) for sheets thinner than the equilibrium thickness, where the glass is stretched, from its edges by top rolls and from its downstream part by conveyor rolls; (b) for sheets thicker than the equilibrium thickness, where water-cooled carbon fenders serve as slipping guides to glass flowing.

      5.4 A Complex Industrial Problem

      5.5 Trends in Float Production

      The float process is advantageous because it yields excellent flatness, high flexibility with regard to thickness and width, and high productivity owing to completely continuous operation during the whole lifetime of the melting furnace, which can now reach up to two decades. Ever since its conception, plenty of technological improvements have been conducted for achieving higher throughput, larger width, and higher still quality, the thickness currently extending down to less than 0.4 mm and up to around 25 mm.

Schematic illustration of the shape and thickness distribution of a 2 mm thick float-glass ribbon calculated with an integrated glass-forming model. Forming and the flow of molten tin are first calculated for a given temperature distribution of the glass ribbon. Heat transfer in the float bath then is simulated, and the whole calculation is iteratively repeated until convergence is reached for the three interrelated mechanisms. Graph depicts the simulated thickness distribution at the exit of the bath for 2 mm thick glass ribbon. The lateral distance is normalized. Schematic illustration of the complex interactions of impurities with the atmosphere, tin bath, and glass ribbon in the float process: (a) oxygen cycle, (b) sulfur cycle.

      Source: After Pilkington [9].

      In the early 1980s, the float process achieved production of ultrathin glass of less than 1.1 mm for twisted nematic (TN)/super TN (STN) liquid crystal display (LCD) substrates, touch panels, and other electronics products with a remarkably high quality for flatness, thickness constancy, defect level, etc. Beginning in the 1990s, the float process has been producing flat glass of various kinds of compositions other than the traditional soda‐lime silicate. Examples are alkali‐free glass for thin film transistor (TFT) LCD substrate, high strain‐point glass for plasma display panel (PDP) and solar panel substrates, specialty glasses for heat‐resistant products, hard disk drive (HDD) substrates, and other products such as touch panels and display covers that are then chemically strengthened.

      6.1 Slot Downdraw