BACKGROUND

Infrared reflectors may be polymeric multilayer optical films formed by coextruding tens to hundreds of molten polymer layers and subsequently orienting or stretching the resulting film. These microlayers have different refractive index characteristics and sufficient thinness so that light is reflected at interfaces between adjacent microlayers. Infrared reflectors typically reflect over part of the near-infrared spectrum and may be useful for solar heat rejection applications.

SUMMARY

In one aspect, the present description relates to an infrared reflecting film. In particular, the infrared reflecting film includes a multilayer optical core having a plurality of optical repeat unit including a first birefringent polymer layer and a second polymer layer. The infrared reflecting film also includes a visible absorbing layer disposed adjacent a major surface of the multilayer optical core, the visible absorbing layer not being an adhesive layer. The plurality of optical repeat units each have an optical thickness, and the optical thicknesses of the plurality of optical repeat units are configured such that the plurality of optical repeat units exhibits a reflection band having a left bandedge and a right bandedge, each bandedge of a reflection band defined as the point nearest to the center of the reflection band, at which transmission crosses 45 percent. The reflection band shifts as a function of incidence angle and produces a maximum color shift, the maximum color shift being the largest distance, ignoring lightness, between two points in a L*a*b* color space, of reflected color, over a range of incidence angles from 0 to 85 degrees measured at 5 degree increments. At a 60 degree angle of incidence, the left bandedge is at or below 750 nm, and the maximum color shift with and through the visible absorbing layer is reduced by at least 25% compared with the maximum color shift without the visible absorbing layer.

In another aspect, the present description relates to an infrared reflecting film. The infrared reflecting film includes a multilayer optical core having a plurality of optical repeat units, each optical repeat unit including a first birefringent polymer layer and a second polymer layer, and a visible absorbing layer disposed adjacent a major surface of the multilayer optical core, the visible absorbing layer not being an adhesive layer. The plurality of optical repeat units each have an optical thickness, the optical thicknesses of the plurality of optical repeat units are configured such that the plurality of optical repeat units exhibits a reflection band having a left bandedge and a right bandedge, the reflection band shifts as a function of incidence angle, and where at a 60 degree angle of incidence, the left bandedge is at or below 750 nm. The ratio of the visible light reflection from 400 nm to 700 nm at 50° angle of incidence versus 8° angle of incidence is at least 150%.

