Electro-conductive anti-reflection coating
The present invention relates to an electro-conductive, anti-reflection coating with the conventional half-wave, high-index layer sandwiched between two quarter-wave, low-index layers, in which the high-index, half-wave layer forms an electro-conductive layer, and in which the layer materials are selected such that an index ratio (high index/low index) is between 1.45 to 1.55 providing wide band widths for the anti-reflection coating. Preferably, the half-wave, electro-conductive, high index layer comprises indium titanium oxide providing a sheet resistance of less than 20 ohms/sq.
1. An electro-conductive, anti-reflection coating providing an anti-reflection effect for light having a central wavelength comprising:
a first ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a first low-index layer having a refractive index;
a ¼-wavelength stack, having an optical thickness of substantially one half of the central wavelength, comprising a first high-index layer, which is transparent and electrically conductive, and has a refractive index;
a second ½-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a second low-index layer, having a refractive index;
wherein a ratio of the refractive index of the first high-index layer divided by the refractive index of the first low-index layer is between 1.45 and 1.55;
wherein the first high-index layer comprises indium titanium oxide (ITiO) with a refractive index between 2.0 and 2.15, whereby the coating has a sheet resistance of less than 20 ohm/sq and provides less than 0.55% reflectance between 440 nm and 675 nm; and
wherein the ½-wavelength stack comprises a third low-index layer sandwiched between the first high-index layer and a third-high index layer.
2. The coating according to claim 1 , wherein the first ¼-wavelength stack comprises: the first low-index layer having an optical thickness of substantially ⅛ the central wavelength, and a second high-index layer having an optical thickness of substantially ⅛ the central wavelength.
3. The coating according to claim 2 , wherein the second high-index layer is comprised of substantially the same material as the first high-index layer to ensure that the coating has a sheet resistance of less than 20 ohm/sq.
4. The coating according to claim 1 , wherein the third high-index layer is comprised of substantially the same material as the first and second high-index layers to ensure that the coating has a sheet resistance of less than 20 ohm/sq.
5. The coating according to claim 1 , wherein the refractive index of the first high-index layer is greater than 2.05.
6. The coating according to claim 1 , wherein the refractive index of the first high-index layer is between 2.05 and 2.15.
7. The coating according to claim 1 , wherein the refractive index of the first high-index layer is between 2.05 and 2.10.
8. The coating according to claim 1 , wherein the refractive indexes of the first and second low-index layers are less than 1.40.
9. The coating according to claim 1 , wherein the refractive indexes of the first and second low-index layers are between 1.33 and 1.43.
10. The coating according to claim 1 , wherein the refractive indexes of the first and second low-index layers are between 1.36 and 1.40.
11. The coating according to claim 1 , wherein the first low-index layer is comprised of magnesium fluoride (MgF 2 ).
12. The coating according to claim 1 , wherein the ratio is between 1.48 and 1.52.
13. The coating according to claim 1 , further comprising a substrate supporting the first ¼-wavelength stack having a refractive index of between 1.45 and 1.55.
14. An electro-conductive, anti-reflection coating providing an anti-reflection effect for light having a central wavelength comprising:
a first ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a first low-index layer having a refractive index;
a ½-wavelength stack, having an optical thickness of substantially one half of the central wavelength, comprising a first high-index layer, which is transparent and electrically conductive, and has a refractive index;
a second ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a second low-index layer, having a refractive index;
wherein a ratio of the refractive index of the first high-index layer divided by the refractive index of the first low-index layer is between 1.45 and 1.55;
wherein the first high-index layer comprises indium titanium oxide (ITiO) with a refractive index between 2.0 and 2.15,
whereby the coating has a sheet resistance of less than 20 ohm/sq and provides less than 0.55% reflectance between 440 nm and 675 nm;
wherein the first ¼-wavelength stack comprises: the first low-index layer having an optical thickness of substantially ⅛ the central wavelength, and a second high-index layer having an optical thickness of substantially ⅛ the central wavelength; and
wherein the ½-wavelength stack comprises the first high-index layer sandwiched between two inner low-index layers, and two outer high-index materials.
15. The coating according to claim 14 , wherein the outer high-index layers are comprised of substantially the same material as the first high-index layer to ensure that the coating has a sheet resistance of less than 20 ohm/sq.
16. An electro-conductive, anti-reflection coating providing an anti-reflection effect for light having a central wavelength comprising:
a first ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a first low-index layer having a refractive index;
a ½-wavelength stack, having an optical thickness of substantially one half of the central wavelength, comprising a first high-index layer, which is transparent and electrically conductive, and has a refractive index;
a second ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a second low-index layer, having a refractive index;
wherein a ratio of the refractive index of the first high-index layer divided by the refractive index of the first low-index layer is between 1.45 and 1.55;
wherein the ½-wavelength stack comprises a central low-index layer sandwiched between the first high-index layer and a bottom high-index layer.
17. The coating according to claim 16 , wherein the bottom high-index layer is comprised of substantially a same material as the bottom high-index layer to ensure the coating has a sheet resistance of less than 20 ohm/sq.
18. The coating according to claim 16 , wherein the refractive index of the first high-index layer is between 2.05 and 2.10.
19. The coating according to claim 18 , wherein the first high-index layer comprises indium titanium oxide (ITiO).
20. The coating according to claim 19 , wherein the refractive indexes of the first and second low-index layers are between 1.36 and 1.40.
21. The coating according to claim 20 , wherein the first low-index layer is comprised of magnesium fluoride (MgF 2 ).
22. The coating according to claim 21 , wherein the ratio is between 1.48 and 1.52.
23. An electro-conductive, anti-reflection coating providing an anti-reflection effect for light having a central wavelength comprising:
a first ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a first low-index layer having a refractive index;
a ½-wavelength stack, having an optical thickness of substantially one half of the central wavelength, comprising a first high-index layer, which is transparent and electrically conductive, and has a refractive index;
a second ¼-wavelength stack, having an optical thickness of substantially one quarter of the central wavelength, comprising a second low-index layer, having a refractive index;
wherein a ratio of the refractive index of the first high-index layer divided by the refractive index of the first low-index layer is between 1.45 and 1.55;
wherein the ½-wavelength stack comprises the first high-index layer sandwiched between two inner low-index layers, and two outer high-index materials.
24. The coating according to claim 23 , wherein the two outer high-index layers are comprised of substantially the same material as the first high-index layer to ensure that the coating has a sheet resistance of less than 20 ohm/sq.
25. The coating according to claim 23 , wherein the refractive index of the first high-index layer is between 2.0 and 2.15.
26. The coating according to claim 23 , wherein the first high-index layer comprises indium titanium oxide (ITiO).