Method for removing foreign matter on glass substrate surface
View Patent ↗It is to provide a method for removing a tin defect present on the surface of a glass substrate produced by a float process in a short time without the glass substrate surface being damaged regardless of the glass temperature. A method for removing a tin-containing foreign matter from the surface of glass, which comprises applying to the surface of a glass substrate produced by a float process a pulse laser beam having a transmittance of at least 70% through the glass substrate and having a pulse width, a wavelength and an energy density per unit area on the glass substrate surface which satisfy specific relations, to remove a tin-containing foreign matter present on the rear face opposite to the face irradiated with the pulse laser beam.
1. 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.
2. The method for removing a tin-containing foreign matter according to claim 1 , wherein the pulse laser beam has a transmittance of at least 75% through the glass substrate.
3. The method for removing a tin-containing foreign matter according to claim 1 , wherein the pulse laser beam has the wavelength of from 350 to 1200 nm.
4. The method for removing a tin-containing foreign matter according to claim 1 , wherein the pulse laser beam has the pulse width of at most 20 nsec.
5. The method for removing a tin-containing foreign matter according to claim 1 , wherein the pulse laser beam is applied to the glass substrate over the entire width.
6. The method for removing a tin-containing foreign matter according to claim 1 , wherein the glass substrate is a glass substrate for a flat panel display.
7. The method for removing a tin-containing foreign matter according to claim 1 , wherein the glass substrate has a thickness of at least 0.4 mm and at most 3 mm.
8. The method for removing a tin-containing foreign matter according to claim 1 , wherein the glass substrate has the following composition:
SiO 2 : 40 to 85 mass %
Al 2 O 3 : 0 to 35 mass %
B 2 O 3 : 0 to 25 mass %
MgO+CaO+SrO+BaO+ZnO: 1 to 50 mass %, and
Li 2 O+Na 2 O+K 2 O+Rb 2 O+Cs 2 O: 0 to 1 mass %.
9. The method for removing a tin-containing foreign matter according to claim 1 , wherein the glass substrate has the following composition:
SiO 2 : 40 to 85 mass %
Al 2 O 3 : 2 to 35 mass %
B 2 O 3 : 0 to 25 mass %
MgO+CaO+SrO+BaO+ZnO: 1 to 50 mass %, and
Li 2 O+Na 2 O+K 2 O+Rb 2 O+Cs 2 O: 1.1 to 30 mass %.
10. The method for removing a tin-containing foreign matter according to claim 1 , wherein the glass substrate has the following composition:
SiO 2 : 40 to 80 mass %
Al 2 O 3 : 0 to 2 mass %
MgO+CaO+SrO+BaO+ZnO: 1 to 50 mass %, and
Li 2 O+Na 2 O+K 2 O+Rb 2 O+Cs 2 O: 1.1 to 30 mass %.
11. The method for removing a tin-containing foreign matter according to claim 1 , wherein the tin-containing foreign matter is removed without damaging the glass substrate.