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) a variable transmittance layer having a first spectrum in a dark state, and a second spectrum in a faded state; and
(b) a polymer color balancing layer having a third spectrum, wherein the variable transmittance layer and the color balancing layer are laminated together and comprise part of a stack;
(c) each of the first, second and third spectra comprising a visible portion;
(d) the first and third spectra combining to provide a dark state spectrum approximating a dark state target color; and
(e) the second and third spectra combining to provide a faded state spectrum approximating a faded state target color.
2. The optical filter of claim 1 further comprising a first glass layer that comprises part of the stack, wherein the variable transmittance layer and the color balancing layer are laminated to the first glass layer.
3. The optical filter of claim 2 further comprising a second glass layer that comprises part of the stack, wherein the variable transmittance layer and the color balancing layer are laminated to the second glass layer.
4. The optical filter of claim 1 wherein the color balancing layer comprises polyvinyl butyral (PVB).
5. The optical filter of claim 1 further comprising an ultraviolet (UV) blocking layer.
6. The optical filter of claim 5 wherein the UV blocking layer has a cutoff wavelength of about 435 nm or less.
7. The optical filter of claim 1 further comprising a light-attenuating layer.
8. 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.
9. The optical filter of claim 8 wherein the electromagnetic radiation is UV light.
10. The optical filter of claim 8 wherein the electromagnetic radiation has a component with a wavelength of 450 nm or less.
11. The optical filter of claim 8 wherein the voltage applied is from about 1.1 to about 2.5 V.
12. The optical filter of claim 1 further comprising an infrared (IR)-blocking layer.
13. The optical filter of claim 1 comprising any one or more of:
a. an LTA in a dark state of less than about 15%;
b. an LTA in a faded state of greater than about 5%; and
c. a contrast ratio of at least 5.
14. 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 light state.
15. 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 light state.
16. The optical filter of claim 1 wherein the target color of the dark state and color of the optical filter in the dark state provide a delta C value of from about 0 to about 20.
17. The optical filter of claim 1 wherein the target color of the dark state and color of the optical filter in the dark state provide a delta E value of from about 0 to about 20.
18. The optical filter of claim 1 wherein the target color of the faded state and color of the optical filter in the faded state provide a delta C value of from about 0 to about 20.
19. The optical filter of claim 1 wherein the target color of the faded state and color of the optical filter in the faded state provide a delta E value of from about 0 to about 20.
20. A device comprising the optical filter of claim 1 , wherein the device is a laminated glass, an ophthalmic device, an automotive glazing product or an architectural glazing product.