Glass Substrate

The glass substrate of an LCD (Liquid Crystal Display) is made from aluminosilicate and other components. It is an electronic-grade material that needs to have low alkalinity, high flatness, high-temperature resistance, and a low coefficient of thermal expansion.

 

Display glass can be categorized based on its alkali content into alkali glass, low-alkali glass, and alkali-free glass. Different compositions result in varying material characteristics such as softening point, thermal expansion rate, and density.

Glass Substrate Properties

Glass Substrate Properties

Property	Alkali Glass	Low-Alkali Glass	Alkali-Free Glass
Alkali Content %	13.5	7	0
Softening Point (°C)	510	535	593-667
Thermal Expansion Rate (x 10^-7/K)	85 @ 50~350℃	51 @ 50~385℃	37-48 @ 0~380℃
Density (g/cm³)	2.49	2.36	2.49-2.78
Production Method	Float Method	Float Method, Stretch Method	Fusion Method, Stretch Method
Applications	TN, STN	STN	TFT

Alkali Glass: This type has the highest alkali content (13.5%) and a relatively lower softening point (510°C). Its thermal expansion rate is 85 x 10^-7/K at 50~350°C, and its density is 2.49 g/cm³. Alkali glass is typically produced using the float method and is used for TN and STN displays.

 

Low-Alkali Glass: This glass contains 7.0% alkali, with a softening point of 535°C. Its thermal expansion rate is 51 x 10^-7/K at 50~385°C, and it has a density of 2.36 g/cm³. Low-alkali glass can be produced using both the float and stretch methods and is primarily used for STN displays.

 

Alkali-Free Glass: With no alkali content, this glass has the highest softening point range (593-667°C) and the lowest thermal expansion rate (3748 x 10^-7/K at 0380°C). Its density ranges from 2.49 to 2.78 g/cm³. Alkali-free glass is manufactured using the fusion and stretch methods and is used in TFT displays.