# US 7,410,678 B2 · Liquid crystal display using ferroelectric liquid crystal, and fabrication method thereof

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 7,410,678 B2
- Document ID: US7410678B2
- Status: Granted
- Kind: B2
- Application number: 11/157,791
- Filed: 2005-06-22
- Published: 2006-02-02
- Granted: 2008-08-12
- Earliest claimed: 2004-07-30
- Assignees: LG Display Co., Ltd.
- Inventors: Su Seok Choi
- Web page: https://patentgrep.com/patent/US7410678B2

## CPC

- G02F 1/13471: {in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells (G02F1/13475 takes precedence)}
- C09K 19/0225: {Ferroelectric}
- C09K 2323/00: Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
- C09K 2323/02: Alignment layer characterised by chemical composition
- G02F 1/133726: {made of a mesogenic material}
- G02F 1/1396: {the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell (G02F1/141 takes precedence)}
- G02F 1/141: using ferroelectric liquid crystals
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

A liquid crystal display utilizes ferroelectric liquid crystals in its construction. The liquid crystal display includes a first substrate, a first alignment layer over the first substrate, and a first ferroelectric liquid crystal layer over the first alignment layer, which has a polarity in a first direction. A second substrate faces the first substrate, a second alignment layer is over the second substrate, and a second ferroelectric liquid crystal layer is over the second alignment layer. Both ferroelectric layers have and a polarity in the same direction.

## Claims

### Claim 1

A liquid crystal display comprising:
a first substrate;
a first alignment layer over the first substrate;
a first ferroelectric liquid crystal layer over the first alignment layer, and having a polarity in a first direction;
a second substrate facing the first substrate;
a second alignment layer over the second substrate;
a second ferroelectric liquid crystal layer over the second alignment layer, and having a polarity of the same first direction as the first ferroelectric liquid crystal layer; and
a third liquid crystal layer formed between the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer,
wherein the third liquid crystal layer has a phase transition from a nematic phase to an isotropic phase when the temperature is raised.

### Claim 2 (depends on 1)

The display according to claim 1, wherein the first substrate has a pixel electrode, and the second substrate has a common electrode.

### Claim 3 (depends on 1)

The display according to claim 1, wherein the first and second ferroelectric liquid crystal layers have a phase transition from a chiral smectic C (SmC*) phase to a chiral nematic (N*) phase when a temperature is raised.

### Claim 4 (depends on 1)

The display according to claim 1, wherein the first and second ferroelectric liquid crystal layers have a phase transition from a chiral smectic C (SmC*) phase to a smectic A (SmA) phase when a temperature is raised.

### Claim 5 (depends on 1)

The display according to claim 1, wherein the third liquid crystal layer is formed of bulk nematic liquid crystal.

### Claim 6 (depends on 1)

The display according to claim 1, wherein the first and second ferroelectric liquid crystal layers have chiral smectic C (SmC*) phases at a temperature of T1 at which the third liquid crystal layer has a phase transition from a chiral nematic (N*) phase to an isotropic phase.

### Claim 7 (depends on 6)

The display according to claim 6, wherein the first and second ferroelectric liquid crystal layers have a phase transition from the chiral smectic C (SmC*) phase to a chiral nematic (N*) phase at a temperature T2 higher than the temperature of T1.

### Claim 8 (depends on 6)

The display according to claim 6, wherein the first and second ferroelectric liquid crystal layers have a phase transition from the chiral smectic C (SmC*) phase to a smectic A (SmA) phase at a temperature T2 higher than the temperature of T1.

### Claim 9

A method for fabricating a liquid crystal display, the method comprising:
forming first and second alignment layers over first and second substrates, respectively;
forming first and second ferroelectric liquid crystal layers over the first and second alignment layers, respectively;
filling a third liquid crystal layer between the first and second substrates to form a liquid crystal panel;
heating the liquid crystal panel to a temperature T1 to cause a phase transition of the first and second ferroelectric liquid crystal layers to nematic liquid crystal layers having a chiral nematic (N*) phase and to also cause a phase transition of the third liquid crystal layer to an isotropic liquid crystal layer;
cooling the liquid crystal panel to a temperature of T2 and applying a direct current voltage to the liquid crystal panel, to cause a phase transition of the first and second ferroelectric liquid crystal layers from the chiral nematic (N*) phase to a chiral smectic C (SmC*) phase and maintain the third liquid crystal layer in an isotropic phase; and
cooling the liquid crystal panel to a temperature T3, to maintain the first and second ferroelectric liquid crystal layers in the chiral smectic C (SmC*) phase and to cause a phase transition of the third liquid crystal layer from the isotropic phase to the chiral nematic (N*) phase.

### Claim 10 (depends on 9)

The method according to claim 9, wherein when the liquid crystal panel is cooled to the temperature T2 and has a direct current voltage applied thereto, the applied direct current voltage up to 10 volts.

### Claim 11 (depends on 9)

The method according to claim 9, wherein the first substrate has a pixel electrode, and the second substrate has a common electrode.

### Claim 12 (depends on 9)

The method according to claim 9, wherein when the liquid crystal panel is cooled to the temperature of T2 and has a direct current voltage applied thereto, the first and second ferroelectric liquid crystal layers have polarities in the same direction.

### Claim 13

A method for fabricating a liquid crystal display, the method comprising:
forming first and second alignment layers over first and second substrates, respectively;
forming first and second ferroelectric liquid crystal layers over the first and second alignment layers, respectively;
filling a third liquid crystal layer between the first and second substrates to form a liquid crystal panel;
heating the liquid crystal panel at a predetermined temperature of T1 to cause a phase transition of the first and second ferroelectric liquid crystal layers to smectic A (SmA) phase liquid crystal layers and cause a phase transition of the third liquid crystal layer to an isotropic liquid crystal layer;
cooling the liquid crystal panel to a temperature T2 and applying a direct current voltage to the liquid crystal panel, to cause a phase transition of the first and second ferroelectric liquid crystal layers from the smectic A (SmA) phase to a chiral smectic C (SmC*) phase and maintaining the third liquid crystal layer in an isotropic phase; and
cooling the liquid crystal panel to a temperature of T3, to maintain the first and second ferroelectric liquid crystal layers in the chiral smectic C (SmC*) phase and cause a phase transition of the third liquid crystal layer from the isotropic phase to a chiral nematic (N*) phase.

### Claim 14 (depends on 13)

The method according to claim 13, wherein when the liquid crystal panel is cooled to the temperature of T2 and has the direct current voltage applied thereto, the applied direct current voltage is up to 10 volts.

### Claim 15 (depends on 13)

The method according to claim 13, wherein the first substrate has a pixel electrode, and the second substrate has a common electrode.

### Claim 16 (depends on 14)

The method according to claim 14, wherein when the liquid crystal panel is cooled to the temperature T2 and has a direct current voltage applied thereto, the first and second ferroelectric liquid crystal layers have polarities in the same direction.