Vertically aligned liquid crystal display using polynorbornene based polymer film
Provided are a vertically aligned liquid crystal display (VA-LCD) with good viewing angle characteristics, which has liquid crystals with negative dielectric anisotropy (Δ∈<0). In the VA-LCD, a polynorbornene based polymer film is used as a protection film and/or as a negative C-plate retardation film for an upper polarization plate and/or a lower polarization plate. Therefore, high contrast characteristics for a front view and an oblique angle view are realized and color change for an oblique angle view can be minimized.
1. A vertically aligned liquid crystal display comprising at least one unstretched polynorbornene based negative C-plate retardation film for thickness retardation compensation between a vertically aligned panel and a polarization film, wherein a total thickness retardation value (R total ) of the vertically aligned liquid crystal display is defined as:
R total =R −C +R VA , (Equation 3)
30 nm≦ R total (= R VA +R −C )≦180 nm, (Equation 4)
wherein R −C is total thickness retardation value for all negative C-plate type films that can be used for optical compensation in the thickness direction, as given by:
R −C =(thickness retardation value of inner protection film of polarization plate)+(thickness retardation value of biaxial A-plate)+(thickness retardation value of negative C-plate);
R VA is the retardation value of the vertically aligned panel; and
R total is the sum of R VA and R −C .
2. The vertically aligned liquid crystal display of claim 1 , wherein the polynorbornene based negative C-plate retardation film is formed by solution casting.
3. The vertically aligned liquid crystal display of claim 1 , wherein the polynorbornene based negative C-plate retardation film has a refractive index satisfying the following Equation:
n x =n y >n z , (Equation 10)
wherein n x and n y are each an in-plane refractive index as measured at a wavelength of 550 nm; and
n z is a thickness refractive index as measured at a wavelength of 550 nm.
4. The vertically aligned liquid crystal display of claim 1 , which comprises, from bottom to top, a lower polarization plate, a vertically aligned panel, and an upper polarization plate, and
wherein at least one of the lower polarization plate and the upper polarization plate comprises at least one negative C-plate type retardation film made of a polynorbornene based polymer.
5. The vertically aligned liquid crystal display of claim 1 , which comprises, from bottom to top, a lower polarization plate, a vertically aligned panel, and an upper polarization plate, and
wherein at least one of the lower polarization plate and the upper polarization plate comprises an inner protection film made of a polynorbornene based polymer.
6. The vertically aligned liquid crystal display of claim 1 , further comprising a biaxial A-plate retardation film with refractive index satisfying one of the following Equations, obtained by stretching a polynorbornene based polymer film:
n x >n y =n z , (Equation 8)
n x >n y >n z , (Equation 9)
wherein n x and n y are each an in-plane refractive index as measured at a wavelength of 550 nm; and
n z is a thickness refractive index as measured at a wavelength of 550 nm.
7. The vertically aligned liquid crystal display of claim 6 , wherein the A-plate retardation film has normal wavelength dispersion, flat wavelength dispersion, or reverse wavelength dispersion.
8. The vertically aligned liquid crystal display of claim 1 , wherein the vertically aligned panel is an MVA (multidomain vertically aligned) mode panel, a PVA (patterned vertically aligned) mode panel, or a VA (vertically aligned) mode panel using a chiral additive, and
wherein a cell gap between liquid crystal cells constituting the vertically aligned panel is in the range from 3 to 8 μm.