Abstract

Reflection graphs of four paper samples were recorded at room temperature in the wavelength range 400-700nm. From the UV-Vis data and using the Kubelka-Munk equation we calculated the indirect band gap energies of four different paper samples. The indirect band gap for tissue paper was estimated to be 1.169844796675eV, that of copy paper A4 axion sample of 1.169844772981780eV, of velvet board of 1.169844786551eV, and finally of Α4 copy paper maestro of 1.1698447698146900eV. The indirect band gap value was higher for tissue paper and proceeded decreasing from velvet board to copy paper A4 axion, and finally copy paper A4 maestro. The band gap energy was determined using the Tauc method. The Urbach energy for tissue paper was calculated to be 199.23meV. The Urbach energy for axion Α4 copy paper was calculated to be 324.23meV. The Urbach energy for velvet board was calculated to be 71.12meV. And finally, the Urbach energy for Α4 copy paper maestro was calculated to be 341.17meV. The Urbach energy varied inversely to the band gap for all four paper samples.

Keywords: Paper samples; Reflection graph; Kubelka-Munk equation; Indirect band gap; Tissue paper; Copy paper A4; Velvet board; Urbach energy