Liquid crystal display device

• US 6,341,002 B1
• Filed: 10/14/1999
• Issued: 01/22/2002
• Est. Priority Date: 10/15/1998
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Shimizu, Masahiro, Itoh, Yasuhisa, Kubo, Masumi
• Primary Examiner(s): Ton, Toan
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US09/418,322
• Time in Patent Office: 831 Days
• Field of Search: 349/114, 349/113, 349/117, 349/119, 349/143, 349/179, 349/181, 349/180
• US Class Current: 349/119
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133557 Half-mirrors
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation

Abstract

A liquid crystal display device, includes: a first substrate, a second substrate, a liquid crystal layer interposed therebetween, and a plurality of pixel regions defined by a pair of electrodes for applying a voltage to the liquid crystal layer. Each of the plurality of pixel regions includes a reflection region and a transmission region, and the liquid crystal layer is made of a liquid crystal material having positive dielectric anisotropy. A first polarizing element is provided on the first substrate opposite to the liquid crystal layer; a second polarizing element is provided on the second substrate opposite to the liquid crystal layer; a first phase difference compensator is provided between the first polarizing element and the liquid crystal layer; and a second phase difference compensator is provided between the second polarizing element and the liquid crystal layer. A twist angle θ_t of the liquid crystal layer is in a range of 0° to 90°. Retardation Rd and the twist angle θ_t in a visible light region of the liquid crystal layer in the reflection region are in ranges within curves respectively represented by the following Formulae (1) and (2), and Formulae (3) and (4), in ranges within curves respectively represented by the following Formulae (5) and (6) and Formulae (7) and (8) at the twist angle θ_t in a range of 0°≦θ_t≦54.3°, and in ranges within curves respectively represented by prescribed Formulae.

Claims

1. A liquid crystal display device, comprising:

a first substrate, a second substrate, a liquid crystal layer interposed between the first substrate and the second substrate, and a plurality of pixel regions defined by a pair of electrodes for applying a voltage to the liquid crystal layer,

wherein each of the plurality of pixel regions includes a reflection region and a transmission region, and the liquid crystal layer is made of a liquid crystal material having positive dielectric anisotropy,

the device further including;

a first polarizing element provided on the first substrate opposite to the liquid crystal layer;

a second polarizing element provided on the second substrate opposite to the liquid crystal layer;

a first phase difference compensator provided between the first polarizing element and the liquid crystal layer; and

a second phase difference compensator provided between the second polarizing element and the liquid crystal layer,

a twist angle θ

_t of the liquid crystal layer being in a range of 0°

to 90°

,

wherein retardation Rd and the twist angle θ

_t in a visible light region of the liquid crystal layer in the reflection region are in ranges within curves respectively represented by the following Formulae (1) and (2), and Formulae (3) and (4), in ranges within curves respectively represented by the following Formulae (5) and (6) and Formulae (7) and (8) at the twist angle θ

_t in a range of 0°

≦

θ

_t≦

54.3°

, and in ranges within curves respectively represented by the following Formulae (5) and (8) at the twist angle θ

_t in a range of 54.3°

<

θ

_t≦

90°

, and

wherein the retardation Rd and the twist angle θ

_t in a visible light region of the liquid crystal layer in the transmission region are in ranges within curves respectively represented by the following Formulae (9) and (10) and Formulae (11) and (12);

2. A liquid crystal display device according to claim 1, wherein the retardation Rd is in a range within the curves respectively represented by Formulae (7) and (8) at the twist angle θ

_t in the reflection region in a range of 0°

≦

θ

_t≦

54.3°

, and in a range within the curves respectively represented by Formulae (5) and (8) at the twist angle θ

_t in the reflection region in a range of 54.3°

<

θ

_t≦

90°

, and

the retardation is in a range within the curves respectively represented by Formulae (11) and (12) at the twist angle θ

_t in the transmission region in a range of 0°

≦

θ

_t≦

90°

.

3. A liquid crystal display device according to claim 1, wherein the reflection region and the transmission region include a liquid crystal layer made of the same liquid crystal material, and

a thickness of the liquid crystal layer in the reflection region is smaller than a thickness of the liquid crystal layer in the transmission region.

4. A liquid crystal display device according to claim 2, wherein the first phase difference compensator has a first phase difference plate, the twist angle θ

_t of the liquid crystal layer is 0°

, the retardation Rd of the reflection region is 90 nm≦

Rd≦

187 nm, the retardation Rd of the transmission region is 110 nm≦

Rd≦

440 nm, and the retardation Rd of the first phase difference plate is 30 nm≦

Rd≦

250 nm.

5. A liquid crystal display device according to claim 4, wherein the first phase difference compensator further has a second phase difference plate, and the retardation Rd of the second phase difference plate is in a range of 220 nm≦

Rd≦

330 nm.

6. A liquid crystal display device according to claim 5, wherein the second phase difference compensator has a third phase difference plate, and the retardation Rd of the third phase difference plate is in a range of 120 nm≦

Rd≦

150 nm.

7. A liquid crystal display device according to claim 6, wherein the second phase difference compensator further has a fourth phase difference plate, and the retardation Rd of the fourth phase difference plate is in a range of 240 nm≦

Rd≦

310 nm.