Optical diffuser with high infrared clarity

An optical stack, comprising:

• an optical diffuser;
• and
• an optical film disposed on the optical diffuser and comprising a plurality of alternating polymeric first and second interference layers numbering greater than about 50, each interference layer having an average thickness less than about 250 nm,
• such that for nonoverlapping first and second wavelength ranges, the first wavelength range extending at least from about 450 nm to about 600 nm, and the second wavelength range extending at least from about 800 nm to about 1200 nm:
• the optical diffuser has a first scattering rate R1 for at least one wavelength in the first wavelength range, and a second scattering rate R2 for at least one wavelength in the second wavelength range, R1/R2≥2;
• and
• for light incident at an incident angle with respect to a direction perpendicular to the optical film, the optical film has an average optical transmission T0 in the first wavelength range when the incident angle is about zero degree, an average optical transmittance T60 when the incident angle is about 60 degrees, and an average optical transmission T1 in the second wavelength range when the incident angle is about zero degree, T60/T0<0.8, and T1>40%.

An optical stack, comprising:

• an optical diffuser having an average total transmission T1 and an average diffuse transmission T2 in a first wavelength range extending from about 450 nm to about 600 nm, T2/T1≥0.4;
• a multilayer optical film disposed on the optical diffuser and comprising a plurality of alternating first and second polymeric layers numbering at least 30, each first and second polymeric layer having an average thickness less than about 500 nm;
• and
• an optical reflector disposed on the multilayer optical film and reflecting at least 70% of light for each wavelength in the first wavelength range for each of orthogonal first and second polarization states, wherein the optical stack has a modulation transfer function (MTF) greater than about 0.4 at 2.2 line pairs per mm for at least one wavelength in a second wavelength range extending from about 800 nm to about 1200 nm.