Optical stack including multilayer optical film and radio-wave anti-reflection sheet

Patent metadata

Field	Value
Publication number	US-12147066-B2
Application number	US-202118567823-A
Country	US
Kind code	B2
Filing date	Jun 28, 2021
Priority date	Jun 28, 2021
Publication date	Nov 19, 2024
Grant date	Nov 19, 2024

Abstract

An optical stack ( 100 ) includes a substrate ( 110 ), a radio-wave anti-reflection sheet ( 130 ) configured to reduce reflection from the optical stack ( 100 ) of radio waves at a predetermined operating frequency (f), and a visible light reflective, infrared light transmissive multilayer optical film ( 120 ) disposed between the radio-wave anti-reflection sheet ( 130 ) and the substrate ( 110 ). For radiation substantially normally incident on the radio-wave anti-reflection sheet ( 130 ) and for a first frequency range at least 20 GHZ wide, centered on the predetermined operating frequency (f), and disposed between about 1 GHZ and about 120 GHZ, a return loss of the optical stack ( 100 ) is asymmetric about the predetermined operating frequency (f) in the first frequency range. The optical stack ( 100 ) has a largest return loss S 11 L in the first frequency range of less than −10 dB and a difference between the largest return loss S 11 L and a smallest return loss S 11 S in the first frequency range is less than about 2 dB.

First claim

What is claimed is:

1. An optical stack comprising:
a substrate;
a radio-wave anti-reflection sheet configured to reduce reflection from the optical stack of radio waves emitted from a transmitter at a predetermined operating frequency; and
a multilayer optical film disposed between the radio-wave anti-reflection sheet and the substrate, such that for light substantially normally incident on the multilayer optical film and for at least one polarization state:
an average optical reflectance of the multilayer optical film is greater than about 70% in a first wavelength range of about 420 nm to about 680 nm; and
an average optical transmittance of the multilayer optical film is greater than about 70% in a second wavelength range at least about 100 nm wide and disposed between about 800 nm and about 1600 nm,

wherein for radiation substantially normally incident on the radio-wave anti-reflection sheet such that at least a portion of the radiation is transmitted through each of the radio-wave anti-reflection sheet, the multilayer optical film, and the substrate; and for a first frequency range at least 20 GHz wide, centered on the predetermined operating frequency, and disposed between about 1 GHz and about 120 GHz:
a return loss of the optical stack is asymmetric about the predetermined operating frequency in the first frequency range; and
the optical stack has a largest return loss S 11 L in the first frequency range of less than −10 dB and a difference between the largest return loss S 11 L and a smallest return loss S 11 S in the first frequency range is less than about 2 dB.

2. The optical stack of claim 1 , wherein the first frequency range is at least 25 GHz wide.

3. The optical stack of claim 1 , wherein the multilayer optical film comprises a plurality of optical repeat units numbering at least 10 in total, each of the optical repeat units comprising at least individual first and second polymeric layers, each of the first and second polymeric layers having an average thickness of less than about 500 nm.

4. The optical stack of claim 1 , wherein the radio-wave anti-reflection sheet comprises first and second layers having respective first and second densities, the first density being lower than the second density, the second layer being disposed between the first layer and the multilayer optical film.

5. The optical stack of claim 1 , wherein the smallest return loss S 11 S occurs at a frequency different from the predetermined operating frequency by at least about 2 GHz.

6. The optical stack of claim 1 , wherein for at least one frequency in a range of about 1 GHz to about 120 GHz, a dielectric loss tangent of the multilayer optical film is less than about 0.02 and a real part of a dielectric constant of the multilayer optical film is in a range of about 1.8 to about 4.

7. The optical stack of claim 1 , wherein for light substantially normally incident on the optical stack and for the at least one polarization state, an average optical transmittance of the optical stack is greater than about 20% in the second wavelength range.

8. The optical stack of claim 1 further comprising a polymeric cover layer disposed between the multilayer optical film and the radio-wave anti-reflection sheet.

9. The optical stack of claim 1 further comprising a heater film disposed between the substrate and the multilayer optical film.

10. A vehicle assembly comprising a transmitter and the optical stack of claim 1 disposed proximate the transmitter, the radio-wave anti-reflection sheet facing the transmitter, the transmitter configured to transmit radio waves at the predetermined operating frequency.

11. An optical stack comprising:
a substrate;
a radio-wave anti-reflection sheet configured to reduce reflection from the optical stack of radio waves emitted from a transmitter at a predetermined operating frequency; and
a multilayer optical film disposed between the radio-wave anti-reflection sheet and the substrate, such that for light substantially normally incident on the multilayer optical film and for at least one polarization state:
an average optical reflectance of the multilayer optical film is greater than about 70% in a first wavelength range of about 420 nm to about 680 nm; and
an average optical transmittance of the multilayer optical film is greater than about 70% in a second wavelength range at least about 100 nm wide and disposed between about 800 nm and about 1600 nm,

wherein for radiation substantially normally incident on the radio-wave anti-reflection sheet such that at least a portion of the radiation is transmitted through each of the radio-wave anti-reflection sheet, the multilayer optical film, and the substrate:
for a first frequency range from f1 to f2, 1 GHZ≤f1<f2≤120 GHz, the predetermined operating frequency being an average of f1 and f2:
a return loss of the optical stack is asymmetric about the predetermined operating frequency in the first frequency range; and
the optical stack has a largest return loss S 11 L in the first frequency range of less than −10 dB and a difference between the largest return loss S 11 L and a smallest return loss S 11 S in the first frequency range is less than about 2 dB; and

for each of a second frequency range of about 0.1 f1 to f1 and a third frequency range of f2 to about 3 f2, the return loss of the optical stack comprises a least one peak and at least one valley, the at least one peak comprising a first local maximum greater than S 11 L+2 dB at a frequency fp1, the at least one valley comprising a first local minimum less than S 11 S−2 dB at a frequency fv1, f2−f1≥|fp1−fv1|.

12. The optical stack of claim 11 , wherein for each of the second and third frequency ranges, f2−f1≥1.5|fp1−fv1|.

13. The optical stack of claim 11 , wherein the multilayer optical film comprises a plurality of optical repeat units numbering at least 10 in total, each of the optical repeat units comprising at least individual first and second polymeric layers, each of the first and second polymeric layers having an average thickness of less than about 500 nm.

14. The optical stack of claim 11 , wherein the radio-wave anti-reflection sheet comprises first and second layers having respective first and second densities, the first density being lower than the second density, the second layer being disposed between the first layer and the multilayer optical film.

15. The optical stack of claim 11 , wherein the smallest return loss S 11 S occurs at a frequency different from the predetermined operating frequency by at least about 2 GHz.

16. The optical stack of claim 11 , wherein for at least one frequency in a range of about 1 GHz to about 120 GHz, a dielectric loss tangent of the multilayer optical film is less than about 0.02 and a real part of a dielectric constant of the multilayer optical film is in a range of about 1.8 to about 4.

17. The optical stack of claim 11 , wherein for light substantially normally incident on the optical stack and for the at least one polarization state, an average optical transmittance of the optical stack is greater than about 20% in the second wavelength range.

18. The optical stack of claim 11 further comprising a polymeric cover layer disposed between the multilayer optical film and the radio-wave anti-reflection sheet.

19. The optical stack of claim 11 further comprising a heater film disposed between the substrate and the multilayer optical film.

20. A vehicle assembly comprising a transmitter and the optical stack of claim 11 disposed proximate the

Assignees

• 3M Innovative Properties Company

Inventors

• Long Fan
• Acharya Bharat R
• Kim Jaewon
• Chen Jingfei
• Xie Huijie
• Hu Zhe

Classifications

• H01Q1/422

  comprising two or more layers of dielectric material (H01Q1/425 takes precedence) · CPC title

• G02B5/3008

  comprising dielectric particles, e.g. birefringent crystals embedded in a matrix · CPC title

• G02B5/208

  for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation · CPC title

• G02B1/04

  made of organic materials, e.g. plastics (G02B1/08 takes precedence) · CPC title

• G01S13/931

  of land vehicles · CPC title