Patent ID: 7767929

Claim:
A method for removing a tin-containing foreign matter on a first and a second surface of a glass substrate, the method comprising applying to the surface of the glass substrate produced by a float process a pulse laser beam which has a transmittance of at least 70% through the glass substrate and which satisfies the following formulae (1) and (2), thereby removing the tin-containing foreign matter present on the first surface irradiated with the pulse laser beam and on a second side opposite to the first side irradiated with the pulse laser beam: 2.5×10 8 ≦E/t (1) E/ (λ× t 1/2 )≦1000 (2), wherein E is the energy density (J/cm 2 ) of the pulse laser beam per unit area on the surface of the glass substrate, t is a pulse width (sec) of the pulse laser beam, and λ is a wavelength (nm) of the pulse laser beam.