Polarising plate for a planar-switch mode LCD, and a planar-switch mode LCD comprising the same
A polarizer for use in an IPS-LCD includes: a polarizing element; and a retardation film laminate attached to a surface of the polarizing element. The retardation film laminate includes a combination of a +B film and a −B film or a combination of a +B film and a +A film.
1. An IPS-LCD comprising:
a liquid crystal panel comprising a top substrate, a bottom substrate, and a liquid crystal cell disposed between the top substrate and the bottom substrate and filled with liquid crystals having a positive dielectric anisotropy, the liquid crystal panel operating in an IPS mode;
a first polarizer attached to one surface of the liquid crystal panel and in which an absorption axis of a polarizing element is arranged in parallel to an optical axis of the liquid crystal cell; and
a second polarizer attached to the other surface of the liquid crystal cell and having a polarizing element an absorption axis of which is arranged perpendicular to the optical axis of the liquid crystal cell,
wherein the second polarizer comprises a polarizing element and a retardation film laminate attached to a surface of the polarizing element, and the retardation film laminate includes a combination of a +B film and a −B film, said films being in direct contact and laminated on the polarizing element,
wherein the +B film is a film meeting nx>ny, nz>ny and nx≠nz, and the −B film is a film meeting nx>ny>nz,
wherein the +B film has a thickness retardation value Rth expressed as Equation (2) below,
R th=( nz−ny ) ×d (2)
wherein nx, ny and nz are, respectively, an x-axis refractive index, a y-axis refractive index and a z-axis refractive index of the +B film or the −B film and d is a thickness of the +B film, and
wherein the +B film has an in-plane retardation value of 50 nm to 150 nm and a thickness retardation value of 50 nm to 150 nm at a wavelength of 550 nm, and the −B film has an in-plane retardation value of 30 nm to 70 nm and a thickness retardation value of −30 nm to −120 nm at a wavelength of 550 nm.
2. The IPS-LCD of claim 1 , wherein Nz values of the +B film and the −B film are greater than 0 and equal to or less than 4, the Nz value being defined as
Nz= |1−( R th/ R in)|
where Rth denotes a thickness retardation value, and Rin denotes an in-plane retardation value.
3. The IPS-LCD of claim 1 , where the +B film and the −B film comprise a stretched polymer film or a liquid crystal film.
4. The IPS-LCD of claim 1 , wherein the first polarizer comprises:
a polarizing element; and
a protection film attached to one surface or both sides of the polarizing element, the protection film comprising a transparent isotropic film.
5. The IPS-LCD of claim 1 , wherein optical axes of the +B film and the −B film are parallel to each other.
6. The IPS-LCD of claim 5 , wherein optical axes of the +B film and the −B film are perpendicular to an absorption axis of the polarizing element of the second polarizer.
7. The IPS-LCD of claim 1 , wherein the +B film is a film meeting
nz>nx>ny, and the −B film is a film meeting nx>ny>nz.
8. The IPS-LCD of claim 1 , wherein the +B film is a film meeting
nx>nz>ny, and the −B film is a film meeting nx>ny>nz.
9. The IPS-LCD of claim 1 , wherein the +B film has an in-plane retardation value of 75 nm to 150 nm at a wavelength of 550 nm and a thickness retardation value of 75 nm to 150 nm at a wavelength of 550 nm, and the −B film has an in-plane retardation value of 40 nm to 70 nm and a thickness retardation value of −65 nm to −40 nm at a wavelength of 550 nm.