Everywhere any time everyone sees glasses as materials for windows of houses and automobiles, substrates and cover glasses of TV sets, computers, smartphones and wristwatches, and glasses, bottles, art objects, etc. Glass has greatly contributed for development of mankind. For example, the invention of telescope using glass lenses developed astronomy, and microscope in similar manner progressed biology. In the 20th century, optical fiber of glass became the basis for today’s internet world. United Nations has declared the International Year of Glass 2022 to inform and accelerate the contribution of glass to the world.

In this lecture, “What is glass scientifically”and “Why do the unique characteristics of glass appears?” will be explained. Glass is amorphous substance, which is solidified without crystallization. The most typical and basic glass as an inorganic substance is SiO2 (silica) glass. Its atom structure consists of 3-dimensionally connected SiO4 tetrahedrons and does not have long-periodicity. Transparency, the most important characteristic of glass, comes into existence, because the substance does not absorb the visible light, and does not have grain boundaries.

Examples of epoch-making technologies and uses of glass will be shown. In old times, glass plates did not have high flatness and strength. Which technology changed the quality drastically? That is Float Process using a tin bath. Glass melt is floated on tin melt, and the glass layer becomes plate by cooling. For optical fiber, silica glass fiber with very high purity was invented. It is fabricated by chemical vapor deposition. In the fiber, attenuation of light is very small. Then it is used with a two-layer structure of fiber with different refract indexes. Network of optical fibers has been set in the whole world. Besides, other several uses of glass by new technologies will be mentioned, and future’s new possibility of glass will be touched.