Gradient permittivity film

1. A gradient permittivity film comprising:

a first permittivity layer comprising a first continuous matrix of a first material having a first relative permittivity (ε r1 ) and a second component having a second relative permittivity (ε r2 ) dispersed in the first continuous matrix, the first permittivity layer having a first effective layer relative permittivity (ε 1 ) and a thickness (T 1 ); and

a second permittivity layer having a second effective layer relative permittivity (ε 2 ) and a thickness (T 2 ) disposed on the first permittivity layer;

wherein the gradient permittivity film has a haze greater than 50% or a transmission of visible light less than 50%; and

wherein:

ε 1 is greater than ε 2 by at least 10% for at least one frequency (f) within a frequency range between 20 GHz and 300 GHz,

ε

1

=

1.1

to

⁢

10

⁢

ε

2

=

1.11

to

⁢

10

⁢

T

1

=

0.8

(

t

1

)

⁢

to

1.2

(

t

1

)

,

where

⁢

t

1

=

c

4

⁢

f

⁢

ε

1

⁢

T

2

=

0.8

(

t

2

)

⁢

to

1.2

(

t

2

)

,

where

⁢

t

2

=

c

4

⁢

f

⁢

ε

2

⁢

ε

r

⁢

1

⁢

is

⁢

greater

⁢

than

⁢

ε

r

⁢

2

⁢

for

⁢

the

⁢

frequency

⁢

f

.

2. The gradient permittivity film of claim 1 wherein the second permittivity layer is an adhesive.

3. The gradient permittivity film of claim 2 wherein the second permittivity layer is an acrylic foam adhesive.

4. The gradient permittivity film of claim 1 wherein the second permittivity layer comprises a second continuous matrix of a fourth material having a fourth relative permittivity (ε r4 ) and a fifth component having a fifth relative permittivity (ε r5 ) dispersed in the second continuous matrix.

5. The gradient permittivity film of claim 1 wherein ε 1 is from 1.3 to 1.6.

6. The gradient permittivity film of any claim 1 wherein ε 2 is from 1.9 to 2.6.

7. The gradient permittivity film of any of claim 1 wherein f is within a frequency range between 20 GHz and 120 GHz.

8. The gradient permittivity film of claim 7 wherein f is within a frequency range between 20 GHz and 100 GHz.

9. The gradient permittivity film of claim 8 wherein f is within a frequency range between 20 GHz and 81 GHz.

10. The gradient permittivity film of claim 9 wherein f is within a frequency range between 76 GHz and 81 GHz.

11. The gradient permittivity film of claim 9 wherein f is within a frequency range between 20 GHz and 30 GHz.

12. The gradient permittivity film of any of claim 1 wherein T 1 is from 700 μm to 1200 μm and T 2 is from 400 μm to 900 μm.

13. The gradient permittivity film of claim 12 wherein T 1 is from 800 μm to 900 μm and T 2 is from 600 μm to 800 μm.

14. The gradient permittivity film of claim 1 wherein the second component is disposed within a third component having a third relative permittivity (ε r3 ) and ε r2 ≤ε r3 for the frequency f.

15. The gradient permittivity film of claim 14 wherein the third component is glass and the second component is air.

16. The gradient permittivity film of claim 1 wherein the first component includes a polymeric material.

17. The gradient permittivity film of claim 1 wherein the first continuous matrix is a nonwoven material.

18. The gradient permittivity film of claim 1 wherein the second component is air.

19. The gradient permittivity film of claim 1 wherein the first permittivity layer is laminated to the second permittivity layer.

20. The gradient permittivity film of claim 1 further comprising a backing layer disposed on the second permittivity layer opposing the first permittivity layer.

21. A gradient permittivity film comprising:

a first permittivity layer comprising a first continuous matrix of a first material having a first relative permittivity (ε r1 ) and a second component having a second relative permittivity (ε r2 ) dispersed in the first continuous matrix, the first permittivity layer having a first effective layer relative permittivity (ε 1 ) and a thickness (T 1 ); and

a second permittivity layer having a second effective layer relative permittivity (ε 2 ) and a thickness (T 2 ) disposed on the first permittivity layer;

wherein the gradient permittivity film has a haze greater than 50% or a transmission of visible light less than 50%; and

wherein:

ε 1 is greater than ε 2 by at least 10% for at least one frequency (f) within a frequency range between 20 GHz and 300 GHz,

ε 1 =1.1 to 10

ε 1 =1.11 to 10

T 1 =0.8(t 1 ) to 1.2(t 1 ), where

t

1

=

c

2

⁢

f

⁢

ε

1

T 2 =0.8(t 2 ) to 1.2(t 2 ), where

t

2

=

c

4

⁢

f

⁢

ε

2

ε r1 is greater than ε r2 for the frequency f.

22. The gradient permittivity film of claim 21 wherein the second permittivity layer is an adhesive.

23. The gradient permittivity film of claim 22 wherein the second permittivity layer is an acrylic foam adhesive.

24. The gradient permittivity film of claim 21 wherein the second permittivity layer comprises a second continuous matrix of a fourth material having a fourth relative permittivity (ε r4 ) and a fifth component having a fifth relative permittivity (ε r5 ) dispersed in the second continuous matrix.

25. The gradient permittivity film of claim 21 wherein ε 1 is from 1.3 to 1.6.

26. The gradient permittivity film of any of claim 21 wherein ε 2 is from 1.9 to 2.6.

27. The gradient permittivity film of claim 21 wherein f is within a frequency range between 20 GHz and 120 GHz.

28. The gradient permittivity film of claim 27 wherein f is within a frequency range between 20 GHz and 100 GHz.

29. The gradient permittivity film of claim 28 wherein f is within a frequency range between 20 GHz and 81 GHz.

30. The gradient permittivity film of claim 29 wherein f is within a frequency range between 76 GHz and 81 GHz.

31. The gradient permittivity film of claim 29 wherein f is within a frequency range between 20 GHz and 30 GHz.

32. The gradient permittivity film of claim 21 wherein T 1 is from 1400 μm to 2400 um and T 2 is from 400 pm to 900 μm.

33. The gradient permittivity film of claim 32 wherein T 1 is from 1600 μm to 1800 μm and T 2 is from 650 μm to 900 μm.

34. The gradient permittivity film of claim 21 wherein the second component is disposed within a third component having a third relative permittivity (ε r3 ) and ε r2 ≤ε r3 for the frequency f.

35. The gradient permittivity film of claim 34 wherein the third component is glass and the second component is air.

36. The gradient permittivity film of claim 21 wherein the first component includes a polymeric material.

37. The gradient permittivity film of claim 21 wherein the first continuous matrix is a nonwoven material.

38. The gradient permittivity film of claim 21 wherein the second component is air.

39. The gradient permittivity film of claim 21 wherein the first permittivity layer is laminated to the second permittivity layer.

40. The gradient permittivity film of claim 21 further comprising a backing layer disposed on the second permittivity layer opposing the first permittivity layer.

41. An assembly comprising the gradient permittivity film of claim 1 or 21 attached to a vehicle bumper fascia.

42. The assembly of claim 41 wherein, at a location of attachment of the gradient permittivity film to the vehicle bumper fascia, a relative permittivity of the vehicle bumper fascia is within 10% of ε 1 .

43. The assembly of claim 42 wherein the relative permittivity of the vehicle bumper fascia is within 5% of ε 1 .

44. An assembly comprising the gradient permittivity film of claim 1 or 21 attached to an automobile radome.

45. The assembly of claim 44 wherein, at a location of attachment of the gradient permittivity tape and the automobile radome, a relative permittivity of the automobile radome is within 10% of ε 1.

46. The assembly of claim 45 , wherein the relative permittivity of the automobile radome is within 5% of ε 1 .