Optical diffuser with high infrared clarity

Patent metadata

Field	Value
Publication number	US-2022091316-A1
Application number	US-201917309999-A
Country	US
Kind code	A1
Filing date	Feb 2, 2019
Priority date	Feb 2, 2019
Publication date	Mar 24, 2022
Grant date	—

Abstract

An optical stack (100) includes an optical diffuser (10) and a first reflective polarizer (40) disposed on the optical diffuser (10). For substantially normally incident light and for nonoverlapping first and second wavelength ranges, the optical diffuser (10) has a first scattering rate R1 for at least one wavelength in the first wavelength range, and a second scattering rate R2 for at least one wavelength in the second wavelength range, such that R1/R2 is greater than or equal to 2. The first reflective polarizer (40) may transmit at least 40% of light for a first polarization state for each wavelength in the first wavelength range, may reflect at least 70% of light for an orthogonal second polarization state for each wavelength in the first wavelength range, and transmit at least 40% of light for each of the first and second polarization states and for each wavelength in the second wavelength range.

First claim

1 . An optical stack, comprising:
an optical diffuser; and a first reflective polarizer disposed on the optical diffuser, such that for substantially normally incident light and for nonoverlapping first and second wavelength ranges, the first wavelength range extending at least from about 450 nm to about 600 nm, and the second wavelength range extending at least from about 800 nm to about 1200 nm: the optical diffuser has a first scattering rate R 1 for at least one wavelength in the first wavelength range, and a second scattering rate R 2 for at least one wavelength in the second wavelength range, R 1 /R 2 ≥2; and the first reflective polarizer transmits at least 40% of light for a first polarization state for each wavelength in the first wavelength range, reflects at least 70% of light for an orthogonal second polarization state for each wavelength in the first wavelength range, and transmits at least 40% of light for each of the first and second polarization states and for each wavelength in the second wavelength range.

2 - 3 . (canceled)

4 . The optical stack of claim 1 , wherein the optical diffuser comprises a binder defining a plurality of interconnected voids therein, such that for at least one cross-section of the optical diffuser along a thickness direction thereof, the voids cover at least 20% of the at least one cross-section, the optical diffuser and the binder having respective indices of refraction nd and nb at at least one wavelength in the first wavelength range, nd<nb.

5 - 9 . (canceled)

10 . The optical stack of claim 1 , wherein the first wavelength range extends from about 420 nm to about 650 nm.

11 . The optical stack of claim 1 , wherein the second wavelength range extends from about 800 nm to about 1550 nm.

12 - 16 . (canceled)

17 . The optical stack of claim 1 , wherein the optical diffuser has a first average scattering rate R 11 in the first wavelength range, and a second average scattering rate R 22 in the second wavelength range, R 11 /R 22 >about 2, R 11 /R 22 >about 2.5, R 11 /R 22 >about 3.0, R 11 /R 22 >about 3.5, R 11 /R 22 >about 4.0, R 11 /R 22 >about 4.5, R 11 /R 22 >about 5.0.

18 - 19 . (canceled)

20 . The optical stack of claim 1 , wherein the first reflective polarizer transmits at least 70% of light for the first polarization state for each wavelength in the first wavelength range.

21 - 23 . (canceled)

24 . The optical stack of claim 1 , wherein the first reflective polarizer transmits at least 50% of light for each of the first and second polarization states and for each wavelength in the second wavelength range.

25 . The optical stack of claim 1 having a first average optical haze H 1 in the first wavelength range and a second average optical haze H 2 in the second wavelength range, H 1 /H 2 >about 1.5, H 1 /H 2 >about 2.0, or H 1 /H 2 >about 2.5, or H 1 /H 2 >about 3.0, or H 1 /H 2 >about 3.5, or, H 1 /H 2 >about 4.0, or H 1 /H 2 >about 4.5, or H 1 /H 2 >about 5.0.

26 . The optical stack of claim 1 further comprising:
a first light redirecting film disposed between the first reflective polarizer and the optical diffuser and comprising a plurality of substantially parallel first microstructures extending along a first direction; and
a second light redirecting film disposed between the first reflective polarizer and the optical diffuser and comprising a plurality of substantially parallel second microstructures extending along a second direction different from the first direction;

such that for substantially normally incident light, each of the first and second light redirecting films absorbs less than about 10% of the incident light for each of the first and second wavelength ranges.

27 - 28 . (canceled)

29 . The optical stack of claim 1 , such that for the first wavelength range and for light incident at an incident angle with respect to a direction perpendicular to the first reflective polarizer, the first reflective polarizer has an average optical transmission T 0 when the incident angle is about zero degree, and an average optical transmittance T 60 when the incident angle is about 60 degrees, T 60 /T 0 <about 0.8, or T 60 /T 0 <about 0.75, or T 60 /T 0 <about 0.7, or T 60 /T 0 <about 0.65, or T 60 /T 0 <about 0.6, or T 60 /T 0 <about 0.55, or T 60 /T 0 <about 0.5.

30 . A backlight comprising:
a back reflector; the optical stack of claim 1 disposed on the back reflector; and a lightguide disposed between the back reflector and the optical stack, such that for substantially normally incident light and for each of the first and second polarization states, the back reflector reflects at least 70% of light for each wavelength in the first wavelength range, and transmits at least 70% of light for each wavelength in the second wavelength range.

31 . A display comprising the backlight of claim 30 disposed between a liquid crystal panel and an infrared-sensitive detector, such that when an infrared emitting source emitting light in the second wavelength range is disposed proximate the liquid crystal panel, the infrared-sensitive detector detects at least some of the light emitted by the infrared emitting source in the second wavelength range.

32 . A display comprising the backlight of claim 30 and configured to form a first image in the first wavelength range for viewing by a viewer, and a second image in the second wavelength range detectable by an infrared-sensitive camera.

33 . (canceled)

34 . An optical stack, comprising:
an optical diffuser; and an optical film disposed on the optical diffuser and comprising a plurality of alternating polymeric first and second interference layers numbering greater than about 50, each interference layer having an average thickness less than about 250 nm,
such that for nonoverlapping first and second wavelength ranges, the first wavelength range extending at least from about 450 nm to about 600 nm, and the second wavelength range extending at least from about 800 nm to about 1200 nm:
the optical diffuser has a first scattering rate R 1 for at least one wavelength in the first wavelength range, and a second scattering rate R 2 for at least one wavelength in the second wavelength range, R 1 /R 2 ≥2; and
for light incident at an incident angle with respect to a direction perpendicular to the optical film, the optical film has an average optical transmission T 0 in the first wavelength range when the incident angle is about zero degree, an average optical transmittance T 60 when the incident angle is about 60 degrees, and an average optical transmission T 1 in the second wavelength range when the incident angle is about zero degree, T 60 /T 0 <0.8, and T 1 >40%.

35 . An optical stack, comprising:
an optical diffuser having an average total transmission T 1 and an average diffuse transmission T 2 in a first wavelength range extending from about 450 nm to about 600 nm, T 2 /T 1 ≥0.4; a multilayer optical film disposed on the optical diffuser and comprising a plurality of alternating first and second polymeric layers numbering at least 30, each first and second polymeric layer having an average thickness less than about 500 nm; and an optical reflector disposed on the multilayer optical film and reflecting at least 70% of light for each wavelength in the first wavelength range for each of orthogonal first and second polarization states, wherein the optical stack has a modulation transfer function (MTF) greater than about 0.4 at 2.2 line pair

Assignees

• 3M Innovative Properties Co

Inventors

• Long Fan
• Xie Huijie
• Chen Jingfei
• Hu Zhe
• Wheatley John A
• Haag Adam D

Classifications

• G02B5/305

  including organic materials, e.g. polymeric layers · CPC title

• G02B5/0205

  characterised by the diffusing properties · CPC title

• G02B5/0294

  adapted to provide an additional optical effect, e.g. anti-reflection or filter · CPC title

• G02B5/0278

  used in transmission · CPC title

• G02B27/288

  Filters employing polarising elements, e.g. Lyot or Solc filters (G02B5/3016 takes precedence) · CPC title