color tester sc 2 ch of suga test instruments co ltd a resin sheet was placed on top of the sample holder of the color tester and exposed to light from a light source for 10 min colorimetry was then conducted on the exposed sample and the measured values were subtracted from the initial t 0 min values l a b the differences u03b4l u03b4a u03b4b and u03b4e were used as indices of discoloration each resin sheet was cut into square 1 cm u00d7 1 cm strips which were coated with conductive silver paste on both top and bottom surfaces and dried for 24 h the electric resistance of each strip was measured with an lcr meter model 4261a or a high resist meter both by yokogawa hewlett packard ltd and the volume resistivity was calculated by the formula set forth below the thickness of the resin sheet was measured exactly with an electronic micrometer mh 100 of shinko denshi co ltd equ1 specimens of comparative white conductive resin composition were produced by repeating the procedure of example 9 except that a commercial grade of white conductive titanium dioxide that was coated with antimony doped tin dioxide ctr 72 of titan kogyo.