Optical member having low refractive index layer

1. An optical element comprising

a substrate; and

a low refractive index layer formed on the substrate, wherein the low refractive index layer has a refractive index of 1.50 or lower,

wherein the low refractive index layer comprises a resin layer that has a first surface and a second surface opposite to the first surface,

wherein the first surface is a undulating surface, and the second surface is located adjacent to the substrate,

wherein the resin layer comprises a first binder, hollow particles distributed in the first binder, and a fluorine-containing polymer immiscible with the hollow particles.

2. The optical element of claim 1 , wherein the first binder further comprises a silsesquioxane.

3. The optical element of claim 1 , wherein the resin layer further comprises a modified silicone compound, and a concentration of the modified silicone compound at the undulating surface is higher than a concentration of the modified silicone compound at a central part, in a thickness direction, of the resin layer.

4. The optical element of claim 1 , wherein a concentration of the fluorine-containing polymer at the undulating surface is higher than a concentration of the fluorine-containing polymer at the central part, in a thickness direction, of the resin layer, the hollow particles are hollow silica particles, and the hollow particles have a plurality of relative maximum points in a frequency-particle diameter curve which exhibits particle diameter distribution of the hollow particles.

5. The optical element of claim 1 , wherein the hollow particles have a photopolymerizable functional group and a hydroxyl group on a surface thereof, a median particle diameter of the hollow particles is in a range of about 10 nm to about 100 nm, and a refractive index of the hollow particles themselves is in a range of about 1.10 to about 1.40.

6. The optical element of claim 1 , wherein the fluorine-containing polymer immiscible with the hollow particles is a polymer of a monomer represented by Formula (6):

wherein, in Formula (6), Rf 1 represents a (per)fluoroalkyl group or a (per)fluoro polyether group; W 1 represents a linking group; RA 1 represents a functional group having a polymerizable unsaturated group; n is 1, 2, or 3; and m is 1, 2, or 3.

7. The optical element of claim 1 , wherein the first binder is a polymer formed of a photopolymerizable fluorine-containing monomer represented by Formulae (4) and (5):

wherein, in Formula (4), M is a structural unit derived from a fluorine-containing ethylene monomer represented by Formula (5), and A is a structural unit derived from a monomer which is co-polymerizable with the fluorine-containing ethylene monomer represented by Formula (5);

in Formula (5), X 1 and X 2 are H or F; X 3 is H, F, CH 3 , or CF 3 ; X 4 and X 5 are H, F, or CF 3 ; at least one of X 1 , X 2 , and X 3 comprises fluorine; Rf is an organic group having 1 to 3 Y 1 groups which are attached to a C1-C40 fluorine-containing alkyl group or a C2-C100 fluorine-containing alkyl group having an ether bond, wherein Y 1 is a C2-C10 monovalent organic group having an ethylene carbon-carbon double bond at an end thereof; a is 0, 1, 2, or 3; and b and c are 0 or 1;

the polymer comprises M at an amount in a range of about 0.1 mol % or higher to about 100 mol % or lower; and A at an amount in a range of about 0 mol % or higher to about 99.9 mol %, and

a number average molecular weight of the polymer is in a range of about 30,000 to about 1,000,000.

8. The optical element of claim 1 further comprising a hard coat layer located between the substrate and the low refractive index layer, the hard coat layer comprising a second binder that is a polymer of a monomer having a photopolymerizable functional group, and metal oxide particles distributed in the second binder.

9. The optical element of claim 8 , wherein the monomer having the photopolymerizable functional group comprises a first monomer represented by Formula (7) and a second monomer represented by Formula (8):

wherein, in Formulae (7) and (8), R 1 to R 4 each represent a photopolymerizable functional group that does not comprise a hydroxyl group, and R 5 in Formula (8) represents a functional group having a hydroxyl group at an end thereof.

10. The optical element of claim 8 , wherein the second binder comprises a photopolymerization product formed by photopolymerizing: at least one selected from a multibranched oligomer having a photopolymerizable functional group and a multibranched monomer having a photopolymerizable functional group; and the monomer having the photopolymerizable functional group.

11. The optical element of claim 8 , wherein the metal oxide particles comprise a tin oxide and a conducting material added to the tin oxide.

12. The optical element of claim 8 , wherein the metal oxide particles are unevenly distributed in the second binder with a greater concentration toward the second binder's surface portion adjacent to the substrate.

13. The optical element of claim 1 , wherein the low refractive index layer has a maximum thickness of about 200 nm, an average thickness in a range of about 90 nm to about 130 nm, an average surface roughness (Ra) in a range of about 10 nm to about 20 nm, a maximum height (Rmax) in a range of about 60 nm to about 150 nm, a 10-point average roughness (Rz) in a range of about 20 nm to about 60 nm, an average distance between adjacent peaks of the undulating surface (Sm) in a range of about 20 nm to about 80 nm, and visible light reflectance of about 0.3% or lower.

14. The optical element of claim 1 , wherein the substrate is a polarizing means.

15. An image display device comprising

an image display means; and

the an optical element disposed on a surface of the image display means,

wherein the optical element comprising

a substrate; and

a low refractive index layer formed on the substrate, wherein the low refractive index layer has a refractive index of 1.50 or lower,

wherein the low refractive index layer comprises a resin layer that has a first surface and a second surface opposite to the first surface,

the first surface is a undulating surface, and the second surface is located adjacent to the substrate, and

the resin layer comprises a first binder, hollow particles distributed in the first binder, and a fluorine-containing polymer immiscible with the hollow particles.

16. The image display device of claim 15 , wherein the first binder further comprises a silsesquioxane.

17. The image display device of claim 15 , wherein the resin layer further comprises a modified silicone compound, and a concentration of the modified silicone compound at the undulating surface is higher than a concentration of the modified silicone compound at a central part, in a thickness direction, of the resin layer.

18. The image display device of claim 15 , wherein a concentration of the fluorine-containing polymer at the undulating surface is higher than a concentration of the fluorine-containing polymer at the central part, in a thickness direction, of the resin layer, the hollow particles are hollow silica particles, and the hollow particles have a plurality of relative maximum points in a frequency-particle diameter curve which exhibits particle diameter distribution of the hollow particles.

19. The image display device of claim 15 , wherein the hollow particles have a photopolymerizable functional group and a hydroxyl group on a surface thereof, a median particle diameter of the hollow particles is in a range of about 10 nm to about 100 nm, and a refractive index of the hollow particles themselves is in a range of about 1.10 to about 1.40.

20. The image display device of claim 15 , wherein the fluorine-containing polymer immiscible with the hollow particles is a polymer of a monomer represented by Formula (6):

wherein, in Formula (6), Rf 1 represents a (per)fluoroalkyl group or a (per)fluoro polyether group; W 1 represents a linking group; RA 1 represents a functional group having a polymerizable unsaturated group; n is 1, 2, or 3; and m is 1, 2, or 3.