DISPLAY OPTICAL FILM AND BACKLIGHT UNIT

An optical stack for reflecting and transmitting light in a predetermined wavelength range includes stacked first and second optical films, the predetermined wavelength range defining a first wavelength range and a remaining wavelength range. For normally incident light and for each wavelength in a first wavelength range, the first optical film substantially reflects light having a first polarization state, and substantially transmits light having a second polarization state. For each of the first and second polarization states, for wavelengths in the first wavelength range, the second optical film has a maximum optical transmittance Tmax for light incident at a first incident angle, and an optical transmittance Tmax/2 for light incident at a second incident angle, where the second incident angle is greater than the first incident angle by less than about 50 degrees. For wavelengths in the remaining wavelength range, the second optical film reflects at least 80% of light.