Pressure-sensitive recording paper and colour developer therefor

摘要

An acid-treated smectite clay mineral which comprises, based on the oxides of the mineral when dried at 110 DEG C:… 75 to 92% by weight of SiO2;… 3.5 to 12.8% by weight of Al2O3;… 0.7 to 3.0% by weight of Fe2O3; and… 0.8 to 5.0% by weight of MgO;… the mineral having:… an X-ray diffraction pattern perpendicular to dioctahedral smectite in spacings of from 1.49 to 1.51 ANGSTROM ; a ratio SVI:SIV of the peak area (SVI) in the chemical shift range from 31 ppm to -50 ppm to the peak area (SIV) in the chemical shift range of from 31 ppm to 100 ppm in a <27>Al solid MAS-NMR measurement of from 60:40 to 85:15; a cation exchange capacity of from 20 to 60 meq/100g; and… a Hunter whiteness of at least 80%, is useful as a color developer for a pressure-sensitive recording paper.