Alkali-free glass and method for manufacturing alkali-free glass

Abstract

The invention relates to an alkali-free glass, wherein the strain point is above 725°C, the average coefficient of thermal expansion at 50-300°C is 30×10-7-40×10-7 / °C, and the temperature at which the glass viscosity reaches 102dPa·s T2 is below 1710°C, and the temperature T4 at which the glass viscosity reaches 104dPa·s is below 1320°C, expressed in mol% based on oxides, including SiO2: 66-70, Al2O3: 12-15, B2O3: 0-1.5, MgO: Greater than 9.5 and less than 13, CaO: 4~9, SrO: 0.5~4.5, BaO: 0~1 and ZrO2: 0~2, MgO+CaO+SrO+BaO is 17~21, MgO / (MgO+CaO+ SrO+BaO) is 0.4 or more, MgO / (MgO+CaO) is 0.4 or more, MgO / (MgO+SrO) is 0.6 or more, and does not substantially contain alkali metal oxides.

Description

technical field [0001] The present invention relates to an alkali-free glass that does not substantially contain alkali metal oxides and is capable of float forming, and is suitable as various substrate glasses for displays and substrate glasses for photomasks. Background technique [0002] Conventionally, various substrate glasses for displays, especially substrate glasses on which a metal or oxide thin film or the like has been formed on the surface, have required the following characteristics. [0003] (1) When an alkali metal oxide is contained, the alkali metal ions diffuse into the thin film to degrade the film properties, so the alkali metal ion should not be substantially contained. [0004] (2) When exposed to high temperature in the thin film forming process, in order to minimize the deformation of the glass and the shrinkage (thermal shrinkage) accompanying the structural stabilization of the glass, the strain point needs to be high. [0005] (3) To have sufficie...

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Problems solved by technology

[0019] However, although there is a solid-phase crystallization method as a method for producing high-quality p-Si TFTs, in order to implement this method, it is required to further increase the strain point.

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