Transmittance-variable device
A transmittance-variable device is disclosed herein. In some embodiments, the transmittance-variable device includes a retardation film, a liquid crystal alignment film, and a liquid crystal layer configured to implement a twist orientation mode, wherein the retardation film, the liquid crystal alignment film and the liquid crystal layer are sequentially arranged, wherein a twist angle (T) is in a range of 50 degrees to 180 degrees, and wherein the smallest angle A between a slow axis of the retardation film and an alignment direction of the liquid crystal alignment film satisfies Equation 1 when a product (Δnd) of a refractive index anisotropy (Δn) and a thickness (d) is 0.7 μm or less, and satisfies Equation 2 when the product (Δnd) is more than 0.7 μm. The transmittance-variable device can be applied to various applications without causing problems such as a crosstalk phenomenon, a rainbow phenomenon or a mirroring phenomenon.
1. A transmittance-variable device, comprising:
a retardation film having in-plane retardation of 5,000 nm or more for light having a wavelength of 550 nm;
a liquid crystal alignment film; and
a liquid crystal layer configured to implement a twist orientation mode,
wherein the retardation film, the liquid crystal alignment film and the liquid crystal layer are sequentially arranged,
wherein a twist angle (T) of the twist orientation mode is in a range of 50 degrees to 180 degrees, and
wherein the smallest angle A among angles between a slow axis of the retardation film and an alignment direction of the liquid crystal alignment film satisfies the following Equation 1 when a product (Δnd) of a refractive index anisotropy (Δn) and a thickness (d) is 0.7 μm or less, wherein Δn is the refractive index anisotropy of the liquid crystal layer for light having a wavelength of 550 nm and the thickness (d) is the thickness of the liquid crystal layer, and
wherein the smallest angle A among angles between a slow axis of the retardation film and an alignment direction of the liquid crystal alignment film satisfies the following Equation 2 when the product (Δnd) of (Δn) and the thickness (d) is more than 0.7 μm
0.05×Δ nd×T/μm+ 10≤ A≤ 0.16×Δ nd×T/μm+ 60 [Equation 1]
wherein the thickness (d) is in units of micrometers (μm), and T is in units of degree
0.16×Δ nd×T/μm− 10≤ A≤ 0.16×Δ nd×T/μm+ 20 [Equation 2]
wherein, Δn, the thickness (d), and T are in the same units as in Equation 1.
2. The transmittance-variable device according to claim 1 , wherein a ratio of the maximum transmittance (Tmax) relative to the minimum transmittance (Tmin) is in a range of 1.5 to 10.
3. The transmittance-variable device according to claim 1 , wherein the angle A is an angle measured along a twisting direction of the twist orientation mode from the alignment direction of the liquid crystal alignment film.
4. The transmittance-variable device according to claim 3 , wherein the twisting direction is clockwise or counterclockwise.
5. The transmittance-variable device according to claim 1 , wherein the liquid crystal alignment film is formed on a surface of the retardation film.
6. The transmittance-variable device according to claim 1 , further comprising:
a substrate, wherein the liquid crystal alignment film is formed on a surface of the substrate, and wherein the retardation film is attached to a surface of the substrate on which the liquid crystal alignment film is not formed.
7. The transmittance-variable device according to claim 1 , wherein the twist orientation mode is a horizontal twist orientation mode or an oblique twist orientation mode.
8. The transmittance-variable device according to claim 1 , wherein the liquid crystal layer comprises a dichroic dye.
9. The transmittance-variable device according to claim 1 , wherein the liquid crystal layer comprises a chiral agent.
10. The transmittance-variable device according to claim 1 , wherein the liquid crystal layer has a thickness of 20 μm or less.
11. Eyewear, comprising:
a left eye lens and a right eye lens; and
a frame configured to support the left eye lens and the right eye lens,
wherein each of the left eye lens and the right eye lens comprises the transmittance-variable device of claim 1 .