TWISTED ALIGNMENT MODE LIQUID CRYSTAL DISPLAY DEVICE

摘要

Provided is a liquid crystal display device in which the contrast is improved. The liquid crystal display device includes a first polarizing film, a second polarizing film, a twisted alignment mode liquid crystal and a backlight unit with a light-collecting prism sheet which is disposed on the back side of the liquid crystal cell, the first retardation film and the second retardation film each satisfy Formulae (I) and (II):;1 nm≦Re(550)≦50 nm   (I);120 nm≦Rth(550)≦220 nm   (II);;the liquid crystal cell has a depolarizing index (DI value) of 0.000800 or less.

主权项

1. A liquid crystal display device comprising:
a first polarizing film and a second polarizing film; a twisted alignment mode liquid crystal cell disposed between the first polarizing film and the second polarizing film; a first retardation film disposed between the first polarizing film and the liquid crystal cell; a second retardation film disposed between the second polarizing film and the liquid crystal cell; and a backlight unit with a light-collecting prism sheet which is disposed on the back side of the liquid crystal cell, wherein the absorption axis of the first polarizing film is orthogonal to the absorption axis of the second polarizing film; the liquid crystal cell includes a first substrate disposed nearer to the first polarizing film and a second substrate disposed nearer to the second polarizing film; at least one of the first substrate and the second substrate includes a transparent electrode; the transmission axis of the first polarizing film is parallel to the rubbing direction of the first substrate; the transmission axis of the second polarizing film is parallel to the rubbing direction of the second substrate; the first retardation film and the second retardation film each have an in-plane retardation Re(550) at a wavelength of 550 nm and a retardation Rth(550) across the thickness at a wavelength of 550 nm satisfying Formulae (I) and (II):
1 nm≦Re(550)≦50 nm   (I)120 nm≦Rth(550)≦220 nm   (II); the liquid crystal cell has a depolarizing index (DI value) of 0.000800 or less; and the backlight unit emits backlight such that averaged light quantity in the emission angle range of 50° to 85° inclined from a normal line of a display screen of the liquid crystal display device toward a direction giving a maximum in-plane retardation is 12% or less of the light quantity in the normal line direction; and the DI value is calculated by the following formula;
DI=2/(1+Tmax/Tmin) wherein Tmax represents a value of brightness in display mode of a black picture of the liquid crystal cell when the upper and lower polarizing plates are disposed in a parallel Nicol state and when the highest brightness is given by fine adjustment of the angle defined by the polarizing plates; and Tmin represents a value of brightness in a display mode of a black picture of the liquid crystal cell when the upper and lower polarizing plates are disposed in a cross Nicol state and when the lowest brightness is given by fine adjustment of the angle defined by the polarizing plates.