Backlight with collimating reflective polarizer

Patent metadata

Field	Value
Publication number	US-2025035984-A1
Application number	US-202418917254-A
Country	US
Kind code	A1
Filing date	Oct 16, 2024
Priority date	May 21, 2021
Publication date	Jan 30, 2025
Grant date	—

Abstract

A backlight including a front reflector disposed on a back reflector and defining a cavity therebetween. For a visible wavelength range and for a first incident angle of less than 5 degrees, the front reflector has an average transmittance of less than 20% for the incident light polarized along a first direction, and an average transmittance of between 20% and 85% for the incident light polarized along an orthogonal second direction. For a visible wavelength range and for a second incident angle of greater than 40 degrees, the front reflector has an average transmittance of less than 40% for each of the first and second directions. For at least a first wavelength in an infrared wavelength range, the front reflector has a transmittance of greater than about 40% for each of the first and second incident angles and for each of the first and second directions. For each of the first and second incident angles, for the incident light polarized along each of the first and second directions, the back reflector has a transmittance of greater than 30% for the first infrared wavelength, and an average transmittance of less than 20% in the visible range.

First claim

What is claimed is:

1 . A reflector for a backlight for providing illumination to a liquid crystal panel, the reflector comprising a plurality of polymeric layers numbering at least 50 in total, each of the polymeric layers having an average thickness of less than about 500 nm, such that for an incident light propagating in an incident plane and a visible wavelength range extending from about 420 nm to about 650 nm and an infrared wavelength range extending from about 900 to about 1500 nm, the front reflector has:
in the visible wavelength range: a first incident angle of less than about 5 degrees, an average transmittance of less than about 20% for the incident light polarized along a first direction, and an average transmittance of between about 20% and about 85% for the incident light polarized along an orthogonal second direction, and for a second incident angle of greater than about 40 degrees, an average transmittance of less than about 40% for each of the first and second directions lying in the incident plane and for each of a p-polarized and an s-polarized incident lights; and for at least a first wavelength in the infrared wavelength range: a transmittance of greater than about 40% for each of the first and second incident angles, for each of the p-polarized and an s-polarized incident lights, and for each of the first and second directions lying in the incident plane.

2 . The reflector of claim 1 , further comprising an optical diffuser.

3 . The reflector of claim 2 , wherein the optical diffuser comprises a plurality of protrusions on a major surface thereof.

4 . The reflector of claim 3 , wherein the protrusions in the plurality of protrusions form a regular array, an irregular array, or a substantially random array of protrusions.

5 . An optical system, comprising:
the reflector of claim 1 as a front reflector disposed on a back reflector and defining a cavity therebetween and substantially uniformly filled with a material; wherein the back reflector has: for each of the first and second incident angles, for the incident light polarized along each of the first and second directions, and for each of the first and second directions lying in the incident plane, a transmittance of greater than about 30% for the at least the first wavelength in the infrared wavelength range, and an average transmittance of less than about 20% in the visible wavelength range; wherein the material has an index of refraction of less than about 1.2 for at least one wavelength in the visible wavelength range.

Assignees

• 3M Innovative Properties Company

Inventors

• Stover Carl A
• Sousa Matthew E
• Acharya Bharat R
• Forsythe Benjamin J
• Taylor Robert D
• Sanford Quinn D

Classifications

• G02F2203/11

  involving infrared radiation · CPC title

• G02F1/133615

  Edge-illuminating devices, i.e. illuminating from the side · CPC title

• G02F1/133553

  Reflecting elements (associated to illuminating devices G02F1/133605) · CPC title

• G02F1/133504

  Diffusing, scattering, diffracting elements (associated to illuminating devices G02F1/133606) · CPC title

• G02F1/13338

  Input devices, e.g. touch panels · CPC title