Agc Inc.

Madoka Ono

Setsuro Ito

Suguru Murayama

Satoshi Kanasugi

Yousuke Amino

Osamu Honma

A glass for chemical strengthening has a Young's modulus E of 70 GPa or more. The glass satisfies X+X+Xbeing 1760 or less. Here, Xis a numerical value equivalent to a value [unit: kPa/&#xb0; C.] obtained by multiplying the Young's modulus E by an average coefficient &#x3b1; of thermal expansion at 50&#xb0; C. to 350&#xb0; C., Xis a numeral value equivalent to a value of a temperature Tf [unit: &#xb0; C.] at which a viscosity of the glass reaches 100 MPa&#xb7;s, and Xis a numerical value equivalent to a value of a difference [unit: 10Pa&#xb7;s] between the viscosity (100 MPa&#xb7;s) at the Tf and a viscosity &#x3b7;at a temperature 10&#xb0; C. higher than the Tf.

Glass for chemical strengthening, chemically strengthened glass and method for manufacturing chemically strengthened glass

A strengthened glass has a mirror constant A of 1.97 MPa&#xb7;mor less, a surface compressive stress (CS) of 10 MPa or more. A product (t&#xd7;CS) of a sheet thickness t (unit: mm) and the CS (unit: MPa) is less than 230. The strengthened glass may have a fictive temperature at a central portion in a sheet thickness t direction of not lower than a glass transition temperature Tg and Tg+100&#xb0; C. or lower.

Reinforced glass

Provides is low scattering silica glass suitable as a material of an optical communication fiber. Silica glass has a fictive temperature of at least 1,000&#xb0; C. and a void radius of at most 0.240 nm, as measured by positron annihilation lifetime spectroscopy. A method for heat-treating silica glass is also provided, which comprises holding silica glass to be heat-treated in an atmosphere at a temperature of at least 1,200&#xb0; C. and at most 2,000&#xb0; C. under a pressure of at least 30 MPa, and cooling the silica glass at an average temperature-decreasing rate of at least 40&#xb0; C./min during cooling within a temperature range of from 1,200&#xb0; C. to 900&#xb0; C. A method for heat-treating silica glass also comprises holding silica glass to be heat-treated in an atmosphere at a temperature of at least 1,200&#xb0; C. and at most 2,000&#xb0; C. under a pressure of at least 140 MPa, and cooling the silica glass in an atmosphere under a pressure of at least 140 MPa during cooling within a temperature range of from 1,200&#xb0; C. to 900&#xb0; C.

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Tokyo, Japan

Madoka Ono