Optical filter comprising a variable transmittance layer
A optical filter comprising a variable transmittance layer having a first spectrum in a dark state, and a second spectrum in a faded state; and a color balancing layer having a third spectrum; each of the first, second and third spectra comprising a visible portion; the first and third spectra combining to provide a dark state spectrum approximating a dark state target color; and the second and third spectra combining to provide a fades state spectrum approximating a faded state target color. The optical filter may further comprise a light attenuating layer. The optical filter may further comprise part of a laminated glass.
1. An optical filter comprising:
a variable transmittance layer having a first spectrum in a dark state and a second spectrum in a faded state, wherein each of the first and second spectra comprise a visible portion;
an infrared (IR) blocking layer, wherein the variable transmittance layer and the infrared (IR) blocking layer comprise a stack; and
a color balancing layer having a third spectrum and comprising part of the stack, wherein the third spectrum comprises a visible portion, the first and third spectra combine to provide a dark state spectrum approximating a dark state target color, and the second and third spectra combine to provide a faded state spectrum approximating a faded state target color.
2. The optical filter of claim 1 wherein the variable transmittance layer comprises a switching material transitionable from a faded state to a dark state when exposed to electromagnetic radiation, and from a dark state to a faded state with application of a voltage.
3. The optical filter of claim 2 wherein the voltage applied is from 0.1 V to 2.5 V.
4. The optical filter of claim 1 further comprising an ultraviolet (UV) blocking layer that comprises part of the stack, wherein the UV blocking layer has a cutoff wavelength of between 370 nm and 435 nm.
5. The optical filter of claim 4 wherein the UV blocking layer blocks about 50% of incident UV light at the cutoff wavelength.
6. The optical filter of claim 1 comprising:
an LTA in a dark state of less than about 15%;
an LTA in a faded state of greater than about 5%; and
a contrast ratio of at least 5.
7. The optical filter of claim 1 comprising a light transmission value of 1% or less in the dark state and 6% or higher in the faded state.
8. The optical filter of claim 1 comprising a light transmission value of 5% or less in the dark state and 15% or higher in the faded state.
9. A device comprising the optical filter of claim 1 , wherein device comprises a laminated glass, an ophthalmic device, an automotive glazing product, or an architectural glazing product.