Patent ID: 7545561

Claim:
An evaluating method of a front-side glass substrate manufactured by a float method for an image display device, the evaluating method comprising: measuring reflection spectrum at a wavelength of 180 to 280 nm; dividing the measured reflection spectrum into two components by a curve fitting method using a following equation (2) M ⁢ ⁢ 1 ⁢ ⁢ exp ⁢ { - ( 1240 / λ - 1240 / M ⁢ ⁢ 2 ) 2 M ⁢ ⁢ 3 2 } + M ⁢ ⁢ 4 ⁢ ⁢ exp ⁢ { - ( 1240 / λ - 1240 / M ⁢ ⁢ 5 ) 2 M ⁢ ⁢ 6 2 } ( 2 ) one of the components being a component with Gaussian peak at a wavelength of 220 nm and a correlation to Sn ++ , and the other of the components being a component with no correlation to Sn ++ ; comparing areas of the components with Gaussian peak at a wavelength of 220 nm having a correlation to Sn ++ ; and analyzing Sn ++ content in the front-side glass substrate, wherein λ is a wavelength (nm), and M 1 to M 6 are fitting parameters.