Image display device, and method for selecting combination of backlight light source and polarizing plate in liquid crystal display device

A method for selecting a combination of a backlight light source and a polarizer in a liquid crystal display device comprising a backlight light source, a light-source-side polarizer, a liquid crystal cell, and a viewing-side polarizer, the method comprising:

• (a) selecting a backlight light source having a plurality of peak groups in the range of 600 to 650 nm in an emission spectrum;
• and
• (b) selecting a polarizer comprising a polarizing element-protection film, the polarizer being at least one of a light-source-side polarizer and a viewing-side polarizer, wherein the polarizing element-protection film has a 45-degree light source fit index (FI(45)) of 0.4 or more and 0.62 or less as determined by the following formula 1:
• FI(45)=Wd/[Wc/(Rob(45)/Wc)] formula 1
• Rob(45):
• retardation when measuring the polarizing element-protection film from a direction inclined 50 degrees from a normal direction at incident angle and 45 degrees from a slow-axis direction to a fast-axis direction in a plane of the film
• Wd:
• peak-to-peak distance (nm) of the peak groups
• Wc:
• central wavelength (nm) of the peak groups.