Optical film and polarizing beam splitter

Patent metadata

Field	Value
Publication number	US-12455409-B2
Application number	US-202318342125-A
Country	US
Kind code	B2
Filing date	Jun 27, 2023
Priority date	Oct 20, 2017
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

Optical films and polarizing beam splitters including the optical films are described. In some cases, the optical film includes a first optical stack disposed on, and spaced apart by one or more spacer layers from, a second optical stack, each optical stack comprising a plurality of polymeric interference layers reflecting and transmitting light primarily by optical interference in a same predetermined wavelength range. Each optical stack has interference layers closer to the one or more spacer layers that reflect longer wavelengths and interference layers farther from the one or more spacer layers that reflect shorter wavelengths.

First claim

What is claimed is:

1. An optical film comprising a plurality of polymeric layers, the plurality of polymeric layers having an average optical transmittance of at least 80% of normally incident light having a first polarization state in a predetermined wavelength range extending at least from 450 to 600 nm and an average optical reflectance of at least 95% of normally incident light having an orthogonal second polarization state in the predetermined wavelength range, each polymeric layer of the plurality of polymeric layers having an average thickness less than about 200 nm, the plurality of polymeric layers comprising first and second polymeric layers as the two polymeric layers in the plurality of polymeric layers farthest apart from each other, the first and second polymeric layers having respective first and second thicknesses, a difference between the first and second thicknesses being less than about 10 nm.

2. The optical film of claim 1 defining an x-axis along the second polarization state, a y-axis along the first polarization state perpendicular to the x-axis, and a z-axis along a thickness direction of the optical film orthogonal to the x- and y-axes, wherein the plurality of polymeric layers comprise a plurality of alternating first and second interference layers, each first and second interference layer having an index nx along the x-axis, an index ny along the y-axis, and an index nz along the z-axis, for each first interference layer an absolute value of a difference between ny and nz less than 0.008 and a difference between nx and ny greater than 0.2, for each second interference layer an absolute value of a difference between ny and nz less than 0.005, and a difference between nx of the first interference layer and nx of the second interference layer greater than 0.2.

3. The optical film of claim 2 , wherein for each first interference layer, 1.8≤nx≤1.9, 1.5≤ny≤1.6, and 1.5≤nz≤1.6, and for each second layer, each of nx, ny and nz is between 1.5 and 1.6.

4. The optical film of claim 1 comprising first and second optical stacks spaced apart by one or more spacer layers, the first optical stack comprising a first plurality of layers in the plurality of polymeric layers, the second optical stack comprising a second plurality of layers in the plurality of polymeric layers, the first optical stack comprising the first polymeric layer, the second optical stack comprising the second polymeric layer.

5. The optical film of claim 4 , wherein the one or more spacer layers comprises a dichroic polarizer transmitting at least 80% of light having the first polarization state and absorbing at least 50% of light having the second polarization state.

6. A polarizing beam splitter (PBS) comprising:
a first prism comprising a first hypotenuse;
a second prism comprising a second hypotenuse facing the first hypotenuse; and
the optical film of claim 5 disposed between and adhered to the first and second hypotenuses, the first optical stack facing the first prism, the second optical stack facing the second prism, such that when the PBS is incorporated in an imaging system where an image light entering the PBS, exits the PBS after being sequentially reflected by the first optical stack, transmitted by the optical film, and reflected by the second optical stack, the dichroic polarizer absorbs at least 50% of image light scattered by at least one of the first and second optical stacks while absorbing less than 2% of the image light.

Assignees

• 3M Innovative Properties Company

Inventors

• Yun Zhisheng
• Nevitt Timothy J
• Le John D
• Kent Susan L

Classifications

• G02B5/3083

  Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001) · CPC title

• G02B27/283 Primary

  used for beam splitting or combining · CPC title

• G02B5/305 Primary

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