Transflective LCD utilizing chiral liquid crystal filter/mirrors

• US 5,841,494 A
• Filed: 06/26/1996
• Issued: 11/24/1998
• Est. Priority Date: 06/26/1996
• Status: Expired due to Fees

• Current Assignee: Dennis R. Hall
• Original Assignee: Dennis R. Hall
• Inventors: Hall, Dennis R.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGUYEN, TIEP HUU
• Application Number:
  US08/670,451
• Time in Patent Office: 881 Days
• Field of Search: 349/98, 349/74, 349/162, 349/114, 349/115
• US Class Current: 349/98
• CPC Class Codes: G02F 1/133533 Colour selective polarisers G02F1/1347 takes precedence
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/133555 Transflectors

Abstract

A transflective Liquid Crystal Display (LCD) system is described, wherein the half silvered mirror is replaced by Chiral Liquid Crystal (CLC) reflectors/filters, which increase the reflected and transmitted brightness from over two times to as much as ten times. These principles are also applied to create an improved efficiency full color transflective LCD and a number of high brightness, limited color, displays.

Claims

1. A spatial display means composed of:

A first light polarizing filter, and

an array of polarization modulation cells, and

a multi-element chiral liquid crystal filter/mirror, and

a second light polarizing filter, and

a light source, wherein

ambient room light being polarized by said first light polarizing filter passes into said array of polarization modulating cells, said cells having a first switched state that transmits at least one color of said light in a first polarization state and said cells having a second switched state that transforms at least said one color of light to a second polarization state, with

light of said first or second polarization states being imposed upon said multi-element chiral liquid crystal filter/mirror, and

said liquid crystal filter/mirror providing transmission of said light of at least one color, being of said first polarization state, with

said transmitted light being either absorbed by said second polarizing filter or passed into said light source, and

said liquid crystal filter/mirror providing reflection of said light of at least one color, being of said second polarization state, with

said reflected light transiting said polarization modulation cell and said first polarizing filter to a viewer, and

said spatial display means having the option to activate said light source, whereupon,

light from said light source, being of at least one specific color, is polarized by said second polarizing filter, and

transits said multi-element chiral liquid crystal filter/mirror into,

said array of polarization modulation cells, said cells having a first switched state that transmits said light in a first polarization state and said cells having a second switched state that transforms said light to a second polarization state, with

said light of said first or second polarization states being imposed upon said first polarizing filter, whereupon

light of said first polarization state is absorbed by said first polarizing filter and light of said second polarization state is transmitted to a viewer.

2. A spatial display means according to claim 1, wherein said first and second polarizing filters are circularly polarizing filters, and

said array of polarization modulation cells are specifically an array of variable retardation cells, with

said cells switching between said first switched state of having substantially no retardation and intermediate states of retardation, up to and including said second switched state of having substantially a half wave of retardation, and

said intermediate states of retardation producing intermediate intensities or color variations of the light presented to said viewer.

3. A spatial display means according to claim 1, wherein said multi-element chiral liquid crystal filter/mirror and said second light polarizing filter are functionally combined, said combined element being comprised of at least two chiral liquid crystal species.

4. A spatial display means according to claim 3, wherein said combined element is disposed in an array, the specific elements of said array being incorporated within the cells of said array of polarization modulation cells.

5. A spatial display means according to claim 1, wherein said multi-element chiral liquid crystal filter/mirror is disposed in an array, the specific elements of said array being incorporated within the cells of said array of polarization modulation cells.

6. A spatial display means according to claim 5, wherein said combined element is disposed in at least two sets of combined elements, within the array of polarization modulation cells,

said sets forming sets of modulation cells, with

the individual sets of said combined elements, reflecting and transmitting light of substantially uniform color within each set, but of a color distinct from that respectively reflected and transmitted by other of said sets, and

having said sets of cells so disposed as to form color picture elements containing one cell of each of said sets.

7. A spatial display means according to claim 1, wherein said light source has a spectral distribution excluded by the accumulated reflective spectral response of said multi-element chiral liquid crystal filter/mirror.

8. A spatial display means according to claim 1, wherein said array of polarization modulating cells is disposed between said first light polarizing filter and said light source, and

said multi-element liquid crystal filter/mirror is disposed between said array of polarization modulating cells and said light source, and

said second polarizing filter is disposed between said multi-element liquid crystal filter/mirror and said light source.

9. A spatial display means composed of:

A first light polarizing filter, and

an array of polarization modulation cells, and

a quarter wave retardation element, and

a multi-element chiral liquid crystal filter/mirror, and

a second light polarizing filter, and

a light source, wherein

ambient room light being polarized by said first light polarizing filter passes into said array of polarization modulating cells, said cells having a first switched state that transmits said light in a first polarization orientation and said cells having a second switched state that transforms said light to a second polarization orientation, with

light of said first and second polarization orientations impinging upon said quarter wave retardation element, said quarter wave element transforming said light into polarized light having a substantial circular polarization component, and whereupon

light of said transformed first or second polarization orientations comprised light of a first and second polarization states, with said light being imposed upon said multi-element chiral liquid crystal filter/mirror, and

said liquid crystal filter/mirror providing transmission of said light of at least one color, being of said first polarization state, with

said transmitted light being either absorbed by said second polarizing filter or passed into said light source, and

said liquid crystal filter/mirror providing reflection of said light of at least one color, being of said second polarization state, with

said reflected light of said second polarization state, transiting said quarter wave element, whereupon said reflected light is transformed to its original polarization orientation, and

passed through said polarization modulation cell to said first polarizing filter to a viewer, with

said spatial display means having the option to activate said light source, whereupon,

light from said light source, being of at least one specific color, is polarized by said second polarizing filter, and

passes through said multi-element chiral liquid crystal filter/mirror to said quarter wave element, whereupon

the light is transformed to linearly polarized light, and

the orientation of said transformed linearly polarized light being controlled by said switched states of said polarization modulation cells, with

the orientation of said first switched state of said polarization modulation cells providing an orientation of said linearly polarized light that is substantially absorbed by said first polarizing filter, upon which said light impinges, and

the orientation of said second switched state of said polarization modulation cells providing an orientation of said linearly polarized light that is substantially transmitted by said first polarizing filter, upon which said light impinges, and

said transmitted light passing to a viewer.

10. A spatial display means according to claim 9, wherein said first and second polarizing filters are linearly polarizing filters, and

said array of polarization modulation cells are specifically an array of twisted nematic liquid crystal cells, with

said cells switching between said first switched state of having substantially no rotation of the plane of polarization of the light transiting said cell and intermediate states, wherein said plane of linear polarization is rotated up to and including said second switched state, providing substantially 90°

of rotation of said plane of linear polarization, and wherein

said intermediate states produce intermediate degrees of rotation providing intermediate intensities or color variations of the light presented to the viewer.

11. A spatial display means according to claim 9, wherein said multi-element chiral liquid crystal filter/mirror and said second light polarizing filter are functionally combined, said combined element being comprised of at least two chiral liquid crystal species.

12. A spatial display means according to claim 11, wherein said multi-element chiral liquid crystal filter/mirror or said combined element is disposed in an array comprised of at least two sets of combined elements, with the individual elements of each set being associated with individual polarization modulation cells,

the individual sets of said combined elements, reflecting and transmitting light of substantially uniform color within each set, but of a color distinct from that respectively reflected and transmitted by other of said sets, and

having said sets of cells so disposed as to form color picture elements containing one cell of each of said sets.

13. A spatial display means according to claim 9, wherein said light source has a spectral distribution excluded by the accumulated reflective spectral response of said multi-element chiral liquid crystal filter/mirror.

14. A spatial display means according to claim 9, wherein said array of polarization modulating cells is disposed between said first light polarizing filter and said light source, and

said multi-element liquid crystal filter/mirror is disposed between said array of polarization modulating cells and said light source, and

said second polarizing filter is disposed between said multi-element liquid crystal filter/mirror and said light source, and

said quarter wave retardation element is disposed between said array of polarization modulation cells and said multi-element liquid crystal filter/mirror.

15. A spatial display means composed of:

a first light polarizing filter, and

an array of polarization modulation cells, and

an array of multi-element chiral liquid crystal filter/mirror elements, disposed in at least two sets of color encoding elements, each set reflecting and transmitting light of substantially uniform color in at least one of two switched states of said polarization modulating cells and each element of each set being associated with individual cells of said array of polarization modulation cells, said sets of cells so disposed as to form color picture elements containing one cell of each of said sets, and

a second light polarizing filter, and

a light source, wherein

light from said light source is polarized to a first state by said second light polarizing filter, with

said light passing into said array of polarization modulation cells, said cells having a first switched state that transmits said light in a first polarization state and said cells having a second switched state that transforms said light to a second polarization state, with

said light of a said first and second polarization states being imposed upon said array of multi-element chiral liquid crystal filter/mirror elements, and

said light of said first polarization state in a first embodiment being reflected by said liquid crystal filter/mirror elements, returning said light to the light source where it is absorbed or in a second embodiment, having said light of said first polarization state being transmitted by said liquid crystal filter/mirror elements to said first light polarizing filter, where it is absorbed, and

having in said first and second embodiments, at least one color of said light of said second polarization state being reflected by said liquid crystal filter/mirror elements and returned to said light source, with the remainder of said light passing to a viewer, with

said light passing through said first light polarizing filter to a viewer in said second embodiment.

16. A spatial display means according to claim 15, wherein said array of multi-element chiral liquid crystal filter/mirror elements is disposed between said optional first light polarizing filter and said light source, and

said array of polarization modulation cells being disposed between said array of multi-element chiral liquid crystal filter/mirror elements and said light source, with

said second light polarizing filter being disposed between said array of polarization modulation cells and said light source.

17. A spatial display means according to claim 15, wherein said optional first and second light polarizing filters are circularly polarizing filters, and

said array of polarization modulation cells are specifically an array of variable retardation cells, with

said first switched state producing substantially no retardation and said second switched states constituting a half wave of retardation, and

having intermediate switched states that produce intermediate degrees of retardation, and

said intermediate degrees of retardation producing intermediate intensities or color variations of the light presented to said viewer.

18. A spatial display means according to claim 15, wherein said array of multi-element liquid crystal filter/mirror elements are in at least two sets of color elements, within the array of polarization modulation cells,

said sets of color elements forming sets of modulation cells, with

the individual sets of said color elements transmitting light of substantially uniform color and polarization within each set for a given switched state of said modulation cells, said color being distinct from the color of the light transmitted by color elements of other said sets, and

having said sets of cells so disposed as to form color picture elements containing one cell of each of said color element sets.

19. A spatial display means according to claim 15, wherein said light passing to a viewer is first projected upon a display screen, wherein said light reflected or transmitted to said viewer.

20. A spatial display means according to claim 15, wherein said viewer directly views said spatial display.

21. A spatial display means according to claim 15, wherein said array of multi-element chiral liquid crystal filter/mirror elements and said first light polarizing filter are functionally combined, said combined element being comprised of at least two chiral liquid crystal species.