Method for bending a glass sheet

A method of bending a glass sheet which has been heated to have a viscosity of not lower than 105 Pa·s and not higher than 108 Pa·s, comprising the steps of:

• bending the glass sheet by pressing portions of the heated glass sheet having a viscosity of not lower than 105 Pa·s and not higher than 108 Pa·s against a bending surface, wherein the portions of the heated glass sheet having a viscosity of not lower than 105 Pa·s and not higher than 108 Pa·s are pressed against the bending surface in the bending step;
• and
• controlling a bending temperature T and a bending time period t for the glass sheet so as to satisfy the following formulas 1 and 2:
• 0.05<φ<2.00 Formula 1
• ϕ
• =
• ∫
• 0
• t
• ⁢
• P
• ⁡
• (
• τ
• )
• η
• ⁡
• (
• T
• )
• ⁢
• ⅆ
• τ
• Formula
• ⁢
• ⁢
• 2
• where P(τ) is a surface pressure difference (unit:
• Pa) between a pressure applied on a primary surface of the glass sheet and a pressure applied on a rear surface of the glass sheet at a time τ, t is a bending time period (unit:
• s), η(T) is the viscosity (unit:
• Pa·s) of the glass sheet at a temperature T, and T is a bending temperature (unit:
• ° C.) at a time τ.