Patent ID: 7629041

Claim:
A diffuser sheet for LCD applications comprising at least one light-scattering polymethyl methacrylate layer having a thickness in the range from 2 to 5 mm and an average surface roughness R Z in the range from 5 to 50 μm, wherein the polymethyl methacrylate layer comprises a polymethyl methacrylate matrix and also from 0.5 to 59.5% by weight, based on the weight of the light-scattering polymethyl methacrylate layer, of spherical scattering particles (A) whose median size V 50 is in the range from 0.1 to 40 μm, and whose refractive index differs from that of the polymethyl methacrylate matrix by a value in the range from 0.02 to 0.2, and from 0.5 to 59.5% by weight, based on the weight of the light-scattering polymethyl methacrylate layer, of spherical particles (B) whose median size V 50 is in the range from 10 to 150 μm and whose refractive index differs from that of the polymethyl methacrylate matrix by a value in the range from 0 to 0.2, where the total concentration of the spherical scattering particles (A) and particles (B) is in the range from 1 to 60% by weight, based on the weight of the light-scattering polymethyl methacrylate layer; wherein the median particle size V 50 of the spherical particles (B) is greater by at least 5 μm than the median particle size V 50 of the spherical scattering particles (A), wherein the transmittance of the diffuser sheet is in the range from 20 to 70% and its scattering power is greater than 0.3, and wherein the ratio of the square of average surface roughness of the polymethyl methacrylate layer R Z to the third power of the size of the spherical particles (B) R Z 2 /D PB 3 is in the range from 0.0002 to 0.1300 μm −1 .