US5061047A — Smectic liquid crystal devices

Claim 1

Independent Claim 141 words

A method of making a liquid crystal display device comprises the steps; providing two cell walls spaced apart by a spacer to contain a layer of a liquid crystal material, the wall inner surfaces having formed thereon electrode structures and at least one wall surface treated to provide a liquid crystal alignment, providing a tilted chiral smectic liquid crystal material having a cholesteric phase at an elevated temperature above ambient between the chiral smectic and isotropic phases with a cholesteric pitch p greater than half the layer thickness d at a temperature at least 0.1° C. above a cholesteric to smectic transition temperature and a significant spontaneous polarization Ps in the chiral smectic phase, heating the material to the cholesteric phase, introducing and sealing the material into the space between the walls, cooling the material to the tilted chiral smectic phase.

Claim 2

Independent Claim 141 words

A method of making a liquid crystal display device comprises the steps; providing two cell walls spaced apart by a spacer to contain a layer of a liquid crystal material, the wall inner surfaces having formed thereon electrode structures and at least one wall surface treated to provide a liquid crystal alignment, providing a tilted chiral smectic liquid crystal material having a cholesteric phase at an elevated temperature above ambient between the chiral smectic and isotropic phases with a cholesteric pitch p greater than half the layer thickness d at a temperature at least 0.1° C. above a cholesteric to smectic transition temperature and a significant spontaneous polarization Ps in the chiral smectic phase, heating the material to the cholesteric phase, introducing and sealing the material into the space between the walls, cooling the material to the tilted chiral smectic phase.

Claim 3

Dependent Claim 28 words

The method of claim 1 and comprising the further steps of reheating to above the smectic/cholesteric transition temperature and slowly cooling, whilst a unidirectional voltage pulse is applied.

Claim 4

Dependent Claim 26 words

The method of claim 1 wherein the material is cooled at a rate of less than 20° C./minute within +/-5° C. of the cholesteric/smectic phase transition.

Claim 5

Dependent Claim 26 words

The method of claim 1 wherein the material is cooled at a rate of less than 2° C./minute within +/-5° C. of the cholesteric/smectic phase transition.

Claim 6

Dependent Claim 26 words

The method of claim 1 wherein both walls are surface alignment treated and the cell is arranged with the alignment direction parallel in the same direction.

Claim 7

Dependent Claim 25 words

The method of claim 1 wherein both walls are surface alignment treated and the cell is arranged with the alignment direction parallel in opposite directions.

Claim 8

Dependent Claim 13 words

The method of claim 1 wherein the alignment is produced by unidirectional rubbing.

Claim 9

Dependent Claim 16 words

The method of claim 1 wherein the alignment is produced by oblique evaporation of silicon oxide.

Claim 10

Dependent Claim 119 words

A liquid crystal device comprising a layer of a tilted chiral smectic liquid crystal material contained between two cell walls each carrying electrode structures and at least one wall surface treated to give alignment to the liquid crystal molecules, a first linear polarizer and one of a second polarizer and an amount of dichroic dye in the liquid crystal material, the liquid crystal material having switched states and a tilted chiral smectic phase at normal device operating temperatures and a cholesteric phase at a higher, above ambient, temperature, with a cholesteric pitch greater than half the layer thickness d in the cholesteric phase for at least 0.1° C. above the cholesteric to smectic transition temperature, and a spontaneous polarization.

Claim 11

Dependent Claim 119 words

A liquid crystal device comprising a layer of a tilted chiral smectic liquid crystal material contained between two cell walls each carrying electrode structures and at least one wall surface treated to give alignment to the liquid crystal molecules, a first linear polarizer and one of a second polarizer and an amount of dichroic dye in the liquid crystal material, the liquid crystal material having switched states and a tilted chiral smectic phase at normal device operating temperatures and a cholesteric phase at a higher, above ambient, temperature, with a cholesteric pitch greater than half the layer thickness d in the cholesteric phase for at least 0.1° C. above the cholesteric to smectic transition temperature, and a spontaneous polarization.

Claim 12

Dependent Claim 29 words

The device of claim 9 wherein the cell walls are surface treated to align liquid crystal molecules in the same direction with a splayed configuration across the layer thickness.

Claim 13

Dependent Claim 36 words

The device of claim 9 wherein the electrodes on each wall are formed as strip electrodes with strip electrodes on one wall forming an angle with strip electrodes on another wall thereby forming a matrix format.

Claim 14

Dependent Claim 18 words

The device of claim 9 wherein the electrodes are formed as strip electrodes arranged in a segment format.

Claim 15

Dependent Claim 13 words

The device of claim 9 wherein the electrodes are formed as sheet electrodes.

Claim 16

Dependent Claim 16 words

The device of claim 9 wherein the liquid crystal layer thickness is up to 15 μm.

Claim 17

Dependent Claim 25 words

The device of claim 9 wherein the cholesteric pitch p is greater than d/2 at a temperature at least 5° C. above the transition temperature.

Claim 18

Dependent Claim 34 words

The device of claim 9 wherein one polarizer is a neutral polarizer and a second polarizer is comprised of two differently coloured polarizers arranged with their optical axis orthogonal with respect to each other.

Claim 19

Dependent Claim 44 words

The device of claim 9 wherein said first polarizer is arranged with an optical axis parallel to the liquid crystal molecular alignment in one of said switched states, and another polarizer is arranged with an optical axis crossed with respect to the first polarizer.

Claim 20

Dependent Claim 26 words

The device of claim 9 wherein the cholesteric pitch within 0.1° C. of the cholesteric/smectic trasition is greater than four times the liquid crystal layer thickness.

Claim 21

Dependent Claim 32 words

The device of claim 9 and further comprising means for applying the two d.c. voltages of opposite polarity to the electrode structures to switch the liquid crystal material into two different states.

Claim 22

Dependent Claim 71 words

A liquid crystal material mixture for use in a liquid crystal display device comprising a material having a tilted chiral smectic phase at normal device operating temperatures and a cholesteric phase at an elevated temperature, the mixture having a cholesteric pitch greater than 4 μm in the cholesteric phase at least 0.1° C. above a cholesteric to smectic transition temperature, and a substantial spontaneous polarization coefficient Ps, in the smectic phase.

Claim 23

Dependent Claim 71 words

A liquid crystal material mixture for use in a liquid crystal display device comprising a material having a tilted chiral smectic phase at normal device operating temperatures and a cholesteric phase at an elevated temperature, the mixture having a cholesteric pitch greater than 4 μm in the cholesteric phase at least 0.1° C. above a cholesteric to smectic transition temperature, and a substantial spontaneous polarization coefficient Ps, in the smectic phase.

Claim 24

Dependent Claim 17 words

The material of claim 20 wherein the material has the following phases with temperature: isotropic⃡cholesteric⃡smectic A⃡chiral smectic⃡solid.

Claim 25

Dependent Claim 16 words

The material of claim 20 wherein the material has the following phases with temperature: isotropic⃡cholesteric⃡chiral smectic⃡solid.

Claim 26

Dependent Claim 31 words

The material of claim 20 wherein the pitch in the cholesteric phase is greater than 4 μm over a temperature range up to 5° C. above the cholesteric smectic phase transition.

Claim 27

Dependent Claim 14 words

The material of claim 20 wherein the smectic pitch is greater than 2 μm.

Claim 28

Dependent Claim 16 words

The material of claim 20 wherein the spontaneous polarization is greater than 0.1 nC/cm 2 .

Claim 29

Dependent Claim 14 words

The material of claim 20 wherein the cholesteric/smectic phase transition is above 40° C.

Claim 30

Dependent Claim 15 words

The material of claim 20 wherein the cholesteric smectic phase transition is above 100° C.

Claim 31

Dependent Claim 14 words

The material of claim 20 and further including an amount of a dichroic dye.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-10-28	1995-04-29	1995-10-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-10-28	1999-04-29	1999-10-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-10-28	2003-04-29	2003-10-29	$7700.00	Window Closed / Lapsed

Smectic liquid crystal devices

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag