High efficiency chiral nematic LC polarizer

Claim 2

A circular polarizer as claimed in Claim 1 wherein the liquid crystal is a thin film.

Claim 3

A circular polarizer as claimed in Claim 2 wherein the film is supported on a transparent substrate.

Claim 4

An assembly (30) for a direct view apparatus comprising: a light source (12); circular polarizing means in the optical path in a first, forward direction; rear reflecting means (32) adjacent the light source (12) in a second rearward direction; converting means (36) for converting circularly polarized radiation to linearly polarized radiation directly adjacent the circular polarizing means; display means adjacent the converting means for converting linearly polarized light to a direct view display; and polarization means (20) adjacent the display means for absorbing radiation not contributing to the direct view display image.

Claim 5

An assembly as claimed in Claim 4, wherein the circular polarizing means includes a polymer chiral nematic liquid crystal.

Claim 6

An assembly as claimed in Claim 5, wherein the polymer chiral nematic liquid crystal has a notch polarization bandwidth sufficient to allow transmission of circularly polarized light within the 100 nm to 250 nm band.

Claim 7

An assembly as claimed in Claim 5 or Claim 6 wherein the polymer chiral nematic liquid crystal comprises combinations of chiral and nematic liquid crystal monomers attached to backbones selected from the methacrylate/acrylate class of polymers.

Claim 8

An assembly as claimed in Claim 7, wherein the combinations exhibit birefringence characteristics of cyanotolane an (s)-(-)-1-phenylethanol.

Claim 9

An assembly as claimed in any one of claims 4 to 8, wherein the circular polarizing means includes a polymer chiral nematic liquid crystal configured as a film with less than full surface contact substrate support.

Claim 10

An assembly as claimed in any one of claims 4 to 8, wherein the polymer chiral nematic liquid crystal is supported through full surface contact with one or more substrates.

Claim 11

An assembly as claimed in any one of claims 4 to 10, wherein the rear reflecting means (32) includes a material which reverses the handedness of circular polarization of some portion of impinging light reflected from the circular polarizing means and which scavenges and returns to the circular polarizing means light from the light source which initially travelled in a direction away from the circular polarizing means.

Claim 12

An assembly as claimed in any one of claims 4 to 11, wherein the rear reflecting means (32) includes a metallic element.

Claim 13

An assembly as claimed in any one of the preceding claims when dependent upon Claim 9, wherein the polymer chiral nematic liquid crystal film is designed with birefringence and notch bandwidth sufficient to circularly polarize and transmit the entire visible light spectrum.

Claim 14

An assembly for illuminating a direct view apparatus including a light source, a liquid crystal device (LCD), and a front polarizer; the assembly including improved rear polarizer comprising: circular polarizing means for polarizing applied radiation within a selected and width in a first preferred direction and for reflecting radiation within the selected bandwidth polarized in a second direction interposed in the optical path between the light source (12) and the liquid crystal device in a first, forward direction; reflecting means (32) for returning to the circular polarizing means radiation reflected from the circular polarizing means and radiation directly received from the light source adjacent the light source in a second, rearward direction; and converting means (36) for converting circularly polarized light to linearly polarized light between the circular polarizing means and the liquid crystal device, whereby substantially all radiation from the light source within the selected bandwidth is ultimately converted by the front polarizer to linearly polarized light which displays the liquid crystal device display image.

Claim 15

An assembly as claimed in any one of claims 4 to 14, wherein the circular polarizing means comprises a plurality of chiral nematic liquid crystal films.

Claim 16

A means for circularly polarizing radiation of a selected bandwidth.

Claim 17

A means as claimed in Claim 16 comprising one or more liquid crystals exhibiting high birefringence.

Claim 18

Liquid crystals as claimed in Claim 17 of the chiral nematic variety.

Claim 19

Liquid crystals as claimed in Claim 18 including combinations of chiral and nematic liquid crystal monomers.

Claim 20

Liquid crystals as claimed in Claim 18 including combinations of chiral and nematic liquid crystal monomers attached t backbones comprised of polymers.

Claim 21

Liquid crystals as claimed in Claim 20 including polymers of the methacrylate/acrylate class.

Claim 22

Liquid crystals as claimed in Claim 21 exhibiting birefringence characteristics of cyanotolane and (s)-(-)-1-phenylethanol.

Claim 23

Liquid crystals as claimed in any one of claims 18 to 22 comprising a single film.

Claim 24

Liquid crystals as claimed in any one of claims 18 to 22 comprising one or more films fused into a single layer.

Claim 25

Liquid crystals as claimed in any one of claims 17 to 24 wherein the predetermined bandwidth of radiation which is circularly polarised is greater than 100 nm in the visible range.