Patent ID: 8632878

Claim:
A microporous material having improved laser marking capability, the microporous material comprising: (a) a polyolefin matrix; (b) finely divided, substantially water-insoluble filler distributed throughout the matrix, said filler comprising siliceous material and from 3 to 20 weight percent of titanium dioxide, based on the microporous material, said siliceous materiai being at least 50 weight percent of said filler; (c) a network of interconnecting pores communicating throughout the microporous material, the pores constituting 10 to 80 percent by volume of the microporous material; (d) 4 to 10 weight percent, based on the microporous material, of a particulate contrast enhancing material, other than titanium dioxide, that is distributed throughout the matrix; and wherein the particulate contrast enhancing material comprises reduced tungsten oxide, tin antimony oxide, tin antimony gray Cassiterite or mixtures thereof.