| 摘要 |
PROBLEM TO BE SOLVED: To provide a backlight device for a liquid crystal display, in which the use efficiency of a light quantity from a light source is improved, and which has superior mass-productivity and performance stability by providing a λ/4 wavelength plate which can attain λ/4 in the broadband over the whole visible light region. SOLUTION: In the backlight device for a liquid crystal display, in which a light reflecting electrode, a luminescent layer, a transparent electrode, a 1/4 wavelength plate, and a circularly polarized light plate having a linearly polarized light film are arranged in this order, the 1/4 wavelength plate consists of a monolayer, and a retardation value Re (λ) in a wavelength λ has a characteristic, Re(450)<Re(550)<Re(650). It is preferable that the 1/4 wavelength plate consist of a mixture containing materials positive and negative in an intrinsic birefringence value, respectively, or a composition containing a copolymer (preferably, a graft copolymer) which has a chain part, whose intrinsic birefringence indicates positive uniaxiality and a chain part whose intrinsic birefringence indicates negative uniaxiality. |
