填料内添紙の空隙構造と光学特性

紙の構造と物性に及ぼす填料の効果第2報

抄録

Models for pore structure of paper have been proposed by some investigaters to elucidate the optical properties of paper. These models, however, are able to apply only to unloaded paper. In this paper, the relationship between the specific scattering coefficient and the characteristics representing the pore structure of loaded paper is discussed on the basis of a model of cylindrical pore structure. The pore size distribution was obtained from the results of both the mercury intrusion method and the nitrogen gas adsorption method.
The scattering coefficient of filler loaded paper is proportional to the surface area calculated from the intrusion measurement, while it is not proportional to the surface from the nitrogen adsorption method due to the presence of a large number of pores smaller than the wave length of light. The surface area of these paper shows that the fine grain filler (0.32.0 μm) forms void fractions consisting of pores of 0.11.0 μm diameter and that the coarse grain filler (10 μm) does not contribute to the increase in scattering coefficient because of its far greater diameter than the wave length of light.
These results reveal that the light scattering properties of filler loaded paper depend on the surface area of void over 0.1 μm of diameter and that the pores of less than 0.1 μm and of larger than 1 μm do not contribute to the light scattering properties of paper. In otherwords, the specific surface area of mercury intrusion method is optically effective. The scattering coefficient increases with an increase in fine grain filler content, while the void formed with the large filler is optically ineffective.
From Figs. 510 illustrating the wave length dependency of scattering coefficient, it is obviously recognized that as the wave length of incident light becomes shorter the smaller pore scatters more effectively the light.