Antireflection coating film, and optical element, optical system, and optical apparatus having the same

1. An antireflection coating film formed on an optical base member comprising:

a first layer having a refractive index of N 1 and a film thickness of D 1 ;

a second layer having a refractive index of N 2 and a film thickness of D 2 ; and

a third layer formed of a fine concavo-convex structure, having a refractive index changing from N 3 to 1.0, and a film thickness of D 3 ,

wherein the first, second, and third layer are formed in order from the optical base member side having a refractive index of Nsub, and

wherein when the refractive indices Nsub, N 1 , N 2 , and N 3 are those taken for a light having a wavelength of 550 nm, the following conditions are satisfied;

1.43≦Nsub≦1.65

1.30≦N1≦1.50

22nm≦D1≦45 nm

1.42≦N2≦1.52

18 nm≦D2≦35 nm

1.35≦N3≦1.52

180 nm≦D3≦320 nm

N1<Nsub

N1<N2

N3≦N2.

2. The antireflection coating film according to claim 1 , where the following conditions are further satisfied:

1.30≦N1≦1.48

24 nm≦D1≦40 nm

1.43≦N2≦1.49

20 nm≦D2≦32 nm

1.36≦N3≦1.50

200 nm≦D3≦280 nm.

3. The antireflection coating film according to claim 1 , wherein the first layer includes an organic resin material.

4. The antireflection coating film according to claim 1 , wherein the first layer includes porous particles or hollow particles including silica (SiO 2 ) or magnesium fluoride (MgF 2 ) having grain diameters of 1 to 40 nm.

5. The antireflection coating film according to claim 1 , wherein the second layer is a layer including aluminum oxide.

6. The antireflection coating film according to claim 1 , wherein the third layer is a fine concavo-convex structure configured by containing aluminum oxide.

7. The antireflection coating film according to claim 1 , wherein the fine concavo-convex structure of the third layer has a plurality of protrusions, and wherein a distance between adjacent protrusions is 400 nm or smaller.

8. The antireflection coating film according to claim 1 , wherein the first layer includes an organic resin material having porous particles or hollow particles including silica (SiO2) or magnesium fluoride (MgF2) having grain diameters of 1 to 40 nm, wherein the second layer is a layer including aluminum oxide, and wherein the third layer is a fine concavo-convex structure containing aluminum oxide.

9. The antireflection coating film according to claim 1 , wherein when a refractive index of a center part in a film thickness direction of the third layer is Nc, and N 3 -Nc=ΔNa, and Nc- 1 =ΔNb, the following condition is satisfied;

ΔNa>ΔNb.

10. The antireflection coating film according to claim 1 , wherein the third layer including, in order from the optical base member side, a first region having a film thickness of D 31 and a refractive index change rate average R 1 , a second region having a film thickness of D 32 and a refractive index change rate average R 2 , and a third region having a film thickness of D 33 and a refractive index change rate average R 3 , the following conditions are satisfied;

D31<D32<D33

R1>R2>R3.

11. The antireflection coating film according to claim 10 , wherein the following condition is satisfied;

D 31 +D 32 +D 33 =D 3.

12. The antireflection coating film according to claim 1 , wherein, in a wavelength range having wavelengths from 400 to 700 nm, a reflectance with respect to a light incident at incident angles of 0 to 45° is 0.6% or lower, and a reflectance with respect to a light incident at incident angle of 60° is 2.5% or lower.

13. The antireflection coating film according to claim 1 , wherein, in a wavelength range having wavelengths from 400 to 700 nm, a reflectance with respect to a light incident at incident angles of 0 to 45° is 0.3% or lower, and a reflectance with respect to a light incident at incident angle of 60° is 1.8% or lower.

14. The antireflection coating film according to claim 1 , wherein the following condition is satisfied;

207.7nm≦D3≦267.8nm.

15. The antireflection coating film according to claim 1 , wherein the following condition is satisfied;

0.030 ≦N 2 −N 1≦0.133.

16. The antireflection coating film according to claim 1 , wherein the following condition is satisfied;

0.125 ≦N sub −N 1≦0.194.

17. The antireflection coating film according to claim 1 , wherein the optical base member and the first layer adhere with each other.

18. An optical element comprising:

an optical base member having a refractive index of Nsub;

an antireflection coating film including, in order from the optical base member side, a first layer having a refractive index of N 1 and a film thickness of D 1 , a second layer having a refractive index N 2 and a film thickness D 2 , and a third layer formed of a fine concavo-convex structure, having a refractive index changing from N 3 to 1.0, and a film thickness of D 3 , wherein when the refractive indices Nsub, N 1 , N 2 , and N 3 are those taken for a light having a wavelength of 550 nm, the following conditions are satisfied;

1.43≦Nsub≦1.65

1.30≦N1≦1.50

22nm≦D1≦45 nm

1.42≦N2≦1.52

18 nm≦D2≦35 nm

1.35≦N3≦1.52

180 nm≦D3≦320 nm

N1<Nsub

N1<N2

N3≦N2.

19. An optical system comprising:

an optical element including:

an optical base member having a refractive index of Nsub;

an antireflection coating film including, in order from the optical base member side, a first layer having a refractive index of N 1 and a film thickness of D 1 , a second layer having a refractive index of N 2 and a film thickness of D 2 , and a third layer formed of a fine concavo-convex structure, having a refractive index changing from N 3 to 1.0, and a film thickness of D 3 , wherein the optical element satisfies the following conditions when the refractive indices Nsub, N 1 , N 2 , and N 3 are those taken for a light having a wavelength of 550 nm;

1.43≦Nsub≦1.65

1.30≦N1≦1.50

22nm≦D1≦45 nm

1.42≦N2≦1.52

18 nm≦D2≦35 nm

1.35≦N3≦1.52

180 nm≦D3≦320 nm

N1<Nsub

N1<N2

N3≦N2.