Methods for reducing diffuse reflection of nanostructure-based transparent conductive films and touch panels made of the same
View Patent ↗The present disclosure relates to optical stacks having nanostructure-based transparent conductive films and low diffuse reflection. Also described are display devices that incorporate the optical stacks.
1. An optical stack, comprising a conductive film, the conductive film comprising:
at least one conductive nanostructure layer;
at least one substrate adjacent to the conductive nanostructure layer, wherein:
the conductive nanostructure layer comprises a plurality of conductive nanostructures and an insulating medium in which the plurality of conductive nanostructures are embedded,
the plurality of conductive nanostructures are a plurality of metal nanostructures, and
a diffuse reflection of an incident light, as viewed from a same side of the optical stack as the incident light, is less than 6% of the incident light; and
an overcoat immediately overlying the conductive nanostructure layer; and
an undercoat immediately underlying the conductive nanostructure layer, wherein:
a refractive index of the overcoat is less than 1.35, which is less than a refractive index of the insulating medium, and
the refractive index of the insulating medium is less than a refractive index of the undercoat.
2. The optical stack of claim 1 , wherein the insulating medium has a refractive index of less than 1.5.
3. The optical stack of claim 2 , wherein the insulating medium is air.
4. The optical stack of claim 1 , wherein individual nanostructures of the plurality of conductive nanostructures do not have an organic coating or have a low-index organic coating.
5. The optical stack of claim 1 , wherein:
the insulating medium is HPMC,
the plurality of conductive nanostructures are silver nanowires,
a weight ratio of HPMC and the plurality of conductive nanostructures is about 1:1, and
the conductive nanostructure layer has a sheet resistance of less than 100 ohms/sq.
6. The optical stack of claim 1 , wherein the optical stack is oriented such that the plurality of conductive nanostructures are more proximate to the incident light than the substrate.
7. The optical stack of claim 1 , wherein the overcoat has a refractive index of 1.34, 1.33, 1.32, or 1.21.
8. The optical stack of claim 1 , wherein the undercoat has a refractive index of at least 1.65.
9. The optical stack of claim 8 , wherein the undercoat comprises TiO 2 , polyimide, SiO 2 , or ZnO 2 .
10. The optical stack of claim 1 , further comprising an outermost cover layer that is most proximate to the incident light and has a refractive index of at least 1.7.
11. The optical stack of claim 10 , wherein the outermost cover layer comprises TiO 2 .
12. The optical stack of claim 1 , wherein:
the conductive nanostructure layer defines a conductive region and a non-conductive region,
the conductive region has a first sheet resistance,
the non-conductive region has a second sheet resistance, and
the first sheet resistance is at least 10 3 more than the second sheet resistance.
13. The optical stack of claim 1 , wherein the optical stack is oriented such that the substrate is more proximate to the incident light than the plurality of conductive nanostructures.
14. The optical stack of claim 13 , wherein the undercoat has a refractive index of at least 1.65.
15. The optical stack of claim 14 , wherein the undercoat comprises TiO 2 , polyimide, SiO 2 , or ZnO 2 .
16. The optical stack of claim 13 , further comprising an outermost cover layer that is most proximate to the incident light and has a refractive index of at least 1.7.
17. The optical stack of claim 16 , wherein the outermost cover layer comprises TiO 2 .
18. The optical stack of claim 13 , wherein:
the conductive nanostructure layer defines a conductive region and a non-conductive region,
the conductive region has a first sheet resistance,
the non-conductive region has a second sheet resistance, and
the first sheet resistance is at least 10 3 more than the second sheet resistance.
19. A display comprising the optical stack of claim 1 and an LCD module, wherein:
the optical stack and the LCD module define a space, and
the space is filled with an index fluid or a clear optical bonding material that has a refractive index of more than 1.
20. The optical stack of claim 1 , wherein a weight ratio of the plurality of conductive nanostructures to the insulating medium is between 1:5-1:1.
21. The optical stack of claim 1 , further comprising:
an outermost cover layer; and
a glass cover between the outermost cover layer and the overcoat, wherein a refractive index of the outermost cover layer is greater than a refractive index of the glass cover.
22. The optical stack of claim 21 , wherein the glass cover is separated from the overcoat by an optically clear adhesive.
23. The optical stack of claim 21 , wherein the outermost cover layer immediately overlies the glass cover.
24. The optical stack of claim 1 , wherein the refractive index of the undercoat is greater than the refractive index of the substrate.
25. An optical stack, comprising a conductive film, the conductive film comprising:
at least one conductive nanostructure layer;
at least one substrate adjacent to the conductive nanostructure layer, wherein the conductive nanostructure layer comprises a plurality of conductive nanostructures and an insulating medium in which the plurality of conductive nanostructures are embedded;
an overcoat in contact with the conductive nanostructure layer; and
an undercoat in contact with the conductive nanostructure layer and spaced apart from the overcoat by the conductive nanostructure layer, wherein:
a refractive index of the overcoat is less than 1.35, which is less than a refractive index of the insulating medium,
the refractive index of the insulating medium is less than a refractive index of the undercoat, and
the plurality of conductive nanostructures are a plurality of metal nanostructures.
26. The optical stack of claim 25 , further comprising:
an outermost cover layer; and
a glass cover between the outermost cover layer and the overcoat, wherein a refractive index of the outermost cover layer is greater than a refractive index of the glass cover.
27. The optical stack of claim 25 , wherein a weight ratio of the plurality of conductive nanostructures to the insulating medium is between 1:5-1:1.