Display backlight including optical film having a transmission peak wavelength greater than an emission peak wavelength of the backlight

A backlight for providing illumination to a display panel configured to display an image, the backlight comprising:

• an illumination system including red light emitting elements and configured to emit a light from an emission surface thereof, the emitted light comprising at least a red light comprising a red emission spectrum comprising a first red emission peak at a first red peak wavelength with a red full width at 70% maximum FWr1;
• and
• an optical film disposed on the red light emitting elements and comprising a plurality of polymeric layers, such that for a substantially normally incident light and for at least a first polarization state, an optical transmittance of the optical film versus wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength of greater than about 600 nm with a red-infrared full width at 70% maximum FWri1, wherein the first red-infrared peak wavelength is greater than the first red peak wavelength by at least 10 nm, and wherein FWri1/FWr1≥7.

A backlight for providing illumination to a display panel configured to display an image, the backlight comprising:

• an illumination system comprising red light emitting elements and configured to emit a light from an emission surface thereof, the emitted light comprising at least a red light comprising a red emission spectrum comprising a first red emission peak at a first red peak wavelength with a red full width at 70% maximum FWr1;
• and
• an optical film disposed on the red light emitting elements and comprising a plurality of polymeric layers, such that for an incident light incident on the optical film at an incident angle of greater than about 15 degrees and for at least a first polarization state, an optical transmittance of the optical film versus wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600 nm with a red-infrared full width at 50% maximum FW′2, wherein the red-infrared full width at 50% maximum FW′2 of the first red-infrared peak wavelength fully encompasses the red full width at 70% maximum FWr1 of the first red peak wavelength, and FW′2/FWr1≥2.