Transflective liquid crystal display device with particular angle relationships between the half wave plate and polarizers

• US 7,307,680 B2
• Filed: 04/07/2003
• Issued: 12/11/2007
• Est. Priority Date: 04/17/2000
• Status: Expired due to Term

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Baek, Heum-Il
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): RUDE, TIMOTHY L
• Application Number:
  US10/407,247
• Publication Number:
  US 20030223022A1
• Time in Patent Office: 1,709 Days
• Field of Search: 349/121, 349/117, 349/102, 349/99, 349/119
• US Class Current: 349/102
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n

Abstract

A transflective LCD device improves a light transmittance in both the transmissive mode and the reflective mode and improves efficiency in the use of the light regardless of wavelength. To properly control the ON/OFF-switch of the blue wavelength band or the red wavelength band, the transflective LCD device adopts a half wave plate (λ/2) and changes the optic axes of the polarizers and the retardation film.

Claims

1. The transmissive LCD device, comprising:

first and second substrates facing and spaced apart from each other;

a first polarizer formed under the first substrate;

a half wave plate and a second polarizer that are formed in series on the second substrate;

a backlight device being adjacent to the first polarizer;

a liquid crystal layer interposed between the first and second substrates;

a common electrode on a surface of the second substrate facing the first substrate, the common electrode is formed of transparent conductive material;

wherein a slow axis of the half wave plate is disposed at an angle “

θ

”

from a transmissive axis of the second polarizer; and

wherein a transmissive axis of the first polarizer is disposed at the angle “

2θ

”

from the transmissive axis of the second polarizer.

2. The transmissive LCD device according to claim 1, further comprising alignment layers formed between the liquid crystal layer and the first and second substrates.

3. The transmissive LCD device according to claim 1, wherein molecules of the liquid crystal layer are arranged in a horizontal direction when a voltage is not applied to the common and pixel electrodes.

4. The transmissive LCD device according to claim 3, wherein an orientation direction of the liquid crystal layer is disposed at an angle “

2θ

+45°

”

from the transmissive axis of the second polarizer.

5. The transmissive LCD device according to claim 3, wherein an optical retardation of the liquid crystal layer between the common electrode and the pixel electrode ranges from 250 nm to 300 nm.

6. The transmissive LCD device according to claim 1, wherein molecules of the liquid crystal layer are arranged in a vertical direction when a voltage is not applied to the common and pixel electrodes.

7. The transmissive LCD device according to claim 6, wherein the molecules of the liquid crystal layer are arranged in a horizontal direction when the voltage is applied to the common and pixel electrodes.

8. The transmissive LCD device according to claim 6, wherein an optical retardation of the liquid crystal layer between the common electrode and the pixel electrode ranges from 250 nm to 300 nm.

9. The transmissive LCD device according to claim 6, wherein an orientation direction of the liquid crystal layer is disposed at an angle “

2θ

+45°

”

from the transmissive axis of the second polarizer.

10. The transmissive LCD device according to claim 1, wherein an optical retardation of the half wave plate ranges from 250 nm to 300 nm.

11. The transmissive LCD device according to claim 1, wherein the angle “

θ

”

ranges from 10°

to 17.5°

.