Viewing angle controllable liquid crystal display device

• US 7,639,328 B2
• Filed: 04/26/2007
• Issued: 12/29/2009
• Est. Priority Date: 12/28/2006
• Status: Expired due to Fees

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Jung, Mi Jun
• Primary Examiner(s): WONG, TINA MEI SENG
• Application Number:
  US11/790,623
• Publication Number:
  US 20080158484A1
• Time in Patent Office: 978 Days
• Field of Search: None
• US Class Current: 349/117
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: 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
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence

Abstract

The present invention relates to a viewing angle controllable liquid crystal display device. The purpose of the present invention is to provide a viewing angle controllable liquid crystal display device applied with TN mode LCD panel in which a narrow view angle mode is possible in bilateral symmetry. In order to achieve above mentioned purposes, the present invention comprises of: a first panel including a TN mode liquid crystal material having a lowest liquid crystal layer aligned to −45° direction from a lateral axis of the device and a upper most liquid crystal layer aligned to +45° direction from the lateral axis, and a upper polarizing plate disposing on the TN mode liquid crystal material and having a light transmission axis parallel to +45° direction from the lateral axis; a half wave plate disposing above the first panel and delaying a phase of light passing the first panel so that a polarization axis determined by the first panel is changed to perpendicular to the lateral axis; and a second panel disposing above the half wave plate, including ECB liquid crystal material and controlling a viewing angle in bilateral symmetry.

Claims

1. A viewing angle controllable liquid crystal display device, comprising:

a first panel including twisted nematic liquid crystal molecules oriented to transmit polarized light at an 45°

off-angle from a lateral axis of the device for preventing a gray inversion at side viewing angles;

a half wave plate structure for delaying a phase of the polarized light from the first type of liquid molecules so that the polarized light after passing the twisted nematic liquid crystal molecules is reoriented to be perpendicular to the lateral axis of the display device; and

a second panel disposing above the half wave plate, including electrically controlled birefringence liquid crystal molecules for selectively switching between narrow and wide viewing angles of the reoriented light after passing the half wave plate with a bilateral symmetry.

2. The viewing angle controllable liquid crystal display device according to claim 1, wherein the TN mode liquid crystal molecules are positioned between a common electrode and a pixel electrode of the first panel.

3. The viewing angle controllable liquid crystal display device according to claim 2, wherein the first panel includes an upper polarizer.

4. The viewing angle controllable liquid crystal display device according to claim 3, wherein the first panel includes an optical film between the upper polarizer and the pixel electrode.

5. The viewing angle controllable liquid crystal display device according to claim 3, wherein the first panel includes the half wave plate structure is disposed between the upper polarizer and the pixel electrode.

6. The viewing angle controllable liquid crystal display device according to claim 1, wherein the electrically controlled birefringence liquid crystal molecules are positioned between a first electrode and a second electrode of the second panel.

7. The viewing angle controllable liquid crystal display device according to claim 6, wherein the second panel includes a lower polarizing plate for receiving the polarized light at the 45°

off-angle from the lateral axis.

8. The viewing angle controllable liquid crystal display device according to claim 7, wherein the half wave plate structure is disposed between the second electrode and the lower polarizing plate.

9. The viewing angle controllable liquid crystal display device according to claim 1, wherein the half wave plate structure is between the first and second panels.

10. The viewing angle controllable liquid crystal display device according to claim 1, wherein the half wave plate structure has at least two half wave plates overlapped.

11. A viewing angle controllable liquid crystal display device according to claim 1, wherein

the twisted nematic liquid crystal molecules are positioned between an upper polarizer and a pixel electrode of the first panel;

the half wave plate structure delays a phase of the light from the twisted nematic liquid crystal molecules;

the electrically controlled birefringence liquid crystal molecules are positioned between an upper polarizing plate and a lower polarizing plate; and

the upper polarizer has first transmission axial direction different than a second transmission axial direction of the upper polarizing plate.

12. The viewing angle controllable liquid crystal display device according to claim 11, wherein the first transmission axial direction is parallel to the lateral axis of the display device.

13. The viewing angle controllable liquid crystal display device according to claim 11, wherein the second transmission axial direction is at 45°

with respect to the lateral axis of the device.

14. The viewing angle controllable liquid crystal display device according to claim 11, wherein the half wave plate structure is between the first and second panels.

15. The viewing angle controllable liquid crystal display device according to claim 11, wherein the half wave plate structure is between the electrically controlled birefringence liquid crystal molecules and the lower polarizing plate.

16. The viewing angle controllable liquid crystal display device according to claim 11, wherein the half wave plate structure is between the upper polarizer and the twisted nematic liquid crystal molecules.

17. A viewing angle controllable liquid crystal display device, comprising:

twisted nematic liquid crystal molecules positioned between an upper polarizer and a pixel electrode of a first panel for delaying a phase of light polarized at an 45°

off-angle from a lateral axis of the device to prevent a gray inversion at side viewing angles to change polarization direction of the light by 90°

;

a half wave plate structure for delaying a phase of the light from the twisted nematic liquid crystal molecules to further change polarization direction by 45°

; and

electrically controlled birefringence liquid crystal molecules positioned between an upper polarizing plate and a lower polarizing plate for selectively switching between narrow and wide viewing angles of the light after passing the half wave plate with a bilateral symmetry, wherein the upper polarizer has first transmission axial direction having a 45°

difference with a second transmission axial direction of the upper polarizing plate.

18. The viewing angle controllable liquid crystal display device according to claim 17, wherein the lower polarizing plate has a third transmission axial direction parallel to the a second transmission axial direction of the upper polarizing plate.