Optical film, backlight and display system

An optical film comprising a plurality of layers numbering less than about 600 in total, the plurality of layers comprising a plurality of first layers numbering at least 3 in total disposed on a plurality of polymeric second layers numbering at least 20 in total, each of at least 30% of the first layers comprising at least 30% by weight of an inorganic material, each of the first and the polymeric second layers having an average thickness of less than about 500 nm, such that for a substantially unpolarized substantially normally incident light:

• an optical reflectance of the polymeric second layers versus wavelength comprises a first reflection band comprising a first full width at half maximum FWHM1 that is at least 100 nm wide and comprises at least one wavelength in a red wavelength range extending from about 590 nm to about 670 nm, but no wavelengths in a green wavelength range extending from about 490 nm to about 560 nm, the plurality of first layers extending the FWHM1 so that the optical film has a second reflection band comprising a second full width at half maximum FWHM2 greater than FWHM1 by at least 20 nm and including at least one wavelength in the green wavelength range, wherein the optical film and the plurality of second layers have respective average optical reflectances Rof(r) and R2(r) in the red wavelength range, a magnitude of a difference between Rof(r) and R2(r) less than about 3%.

An optical film comprising a plurality of first layers numbering between 3 and 50 in total disposed on a plurality alternating polymeric second and polymeric third layers numbering at least 20 in total, each of at least 30% of the first layers comprising at least 30% by weight of an inorganic material, each of the polymeric second layers having at least 80% by weight of polyethylene terephthalate, each of the first, second and third layers having an average thickness of less than about 500 nm, such that for a substantially unpolarized substantially normally incident light:

• optical reflectances of the optical film, the plurality of first layers, and the plurality of alternating polymeric second and polymeric third layers comprise respective first, second, and third reflection bands comprising respective first, second, and third full width at half maxima that extend between respective smaller wavelengths and respective larger wavelengths, wherein, each of the first, second, and third full width at half maxima is at least 50 nm wide, and wherein:
• a magnitude of a difference between the smaller wavelengths of the first and third full width at half maxima is less than about 20 nm;
• the smaller wavelength of the third full width at half maxima is less than the smaller wavelength of the second full width at half maxima by at least 20 nm;
• and
• the larger wavelength of the first full width at half maxima is greater than the larger wavelength of the second full width at half maxima by at least 5 nm.

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

• a plurality of light emitting elements arranged two-dimensionally and spaced apart from each other and configured to emit light having an emitted wavelength;
• one or more light converting films disposed on the light emitting elements and comprising first, second and third emission spectra comprising respective first, second and third peaks at corresponding respective first, second and third peak wavelengths and corresponding non-overlapping first, second, and third full width at half maxima (FWHMs), the second FWHM disposed between the first and third FWHM, the one or more light converting films configured to receive the emitted light from the light emitting elements and convert at least portions of the received emitted light to second and third lights having respective second and third wavelengths disposed in the respective second and third FWHMs;
• and
• an optical film disposed between the light emitting elements and the one or more light converting films and comprising a plurality of inorganic first layers numbering less than 50 in total and a plurality of polymeric second layers numbering at least 20 in total, each of the inorganic first and the polymeric second layers having an average thickness of less than about 500 nm, such that for a substantially unpolarized substantially normally incident light, the optical film has an optical transmittance of greater than about 60% at the emitted wavelength and an optical reflectance of greater than about 70% at each of the second and third wavelengths.