IPS LCD having molecules remained parallel with electric fields applied

• US 6,285,428 B1
• Filed: 04/16/1998
• Issued: 09/04/2001
• Est. Priority Date: 04/18/1997
• Status: Expired due to Term

• Current Assignee: BOE HYDIS Technology Company Limited (SK Hynix Inc.)
• Original Assignee: Hyundai Electronics Industries Co. Ltd. (SK Hynix Inc.)
• Inventors: Park, Han Jun, You, Jae Geon, Lee, Seung Hee, Kim, Hyang Yul
• Primary Examiner(s): TON, MINH TOAN T
• Application Number:
  US09/061,054
• Time in Patent Office: 1,237 Days
• Field of Search: 349/141, 349/139, 349/96, 349/99, 349/123
• US Class Current: 349/141
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

A liquid crystal display device with an IPS mode having wide view angle characteristic and capable of improving response time and transmittance, is disclosed. A liquid crystal display device with an in-plane switching mode includes a first substrate having first and second electrodes formed thereon. A second substrate is disposed opposite to the first substrate with a selected distance. On a surface of the second substrate are also formed third and fourth electrodes. When a voltage is applied to the respective electrodes, a first electric field which is parallel to the planes of the substrates is generated between the first electrode and the second electrode, and a second electric field which is parallel to the planes of the substrates and is orthogonal to the first electric field is generated between the third electrode and the fourth electrode. A polarizer is arranged on the outside of the first substrate and a analyzer is arranged on the outside of the second substrate. A first homogeneous alignment film is applied to the first substrate on which the first and second electrodes are formed. A second homogeneous alignment film is also applied to the second substrate on which the third and fourth electrodes are formed. A liquid crystal layer having liquid crystal molecules is interposed between the both substrates, wherein the liquid crystal molecules are arranged in a homogeneous state in an absence of the electric field and are twisted in a presence of the electric field.

Claims

1. A liquid crystal display device with an in-plane switching mode, comprising:

a first substrate having a first electrode and a second electrode formed thereon, the first electrode being arranged parallel to the second electrode, a first electric field being generated between the first electrode and the second electrode when a voltage is applied to the first and second electrodes;

a second substrate having a third electrode and a fourth electrode formed thereon and disposed opposite to the first substrate, the third electrode being arranged parallel to the fourth electrode, a second electric field being generated between the third and fourth electrodes, the direction of the second electric field being substantially orthogonal to that of the first electric field; and

a liquid crystal layer having liquid crystal molecules interposed between the first substrate and the second substrate such that, in an absence of said first and second electric fields, the liquid crystal molecules are arranged homogeneously with the first and second substrates and, in a presence of the first and second electric fields, major axes of said liquid crystal molecules adjacent to the first and second substrates are parallel to said first and second electric fields, respectively, and wherein said liquid crystal molecules are twisted relative to each other while remaining parallel to said first and second substrates in the presence of said first and second electric fields.

2. The liquid crystal display device according to claim 1, further comprising:

a polarizer arranged on the outside of the first substrate;

an analyzer arranged on the outside of the second substrate;

a first homogeneous alignment film applied to the first substrate; and

a second homogeneous alignment film applied to the second substrate.

3. The liquid crystal display device according to claim 2, wherein the axes of the polarizer and analyzer are orthogonal to each other.

4. The liquid crystal display device according to claim 3, wherein the liquid crystal molecules substantially close to the first substrate deviate by an angle of about 45°

from the polarization of the polarizer and liquid crystal molecules substantially close to the second substrate deviate by an angle of about 45°

from the polarization axis of the analyzer, when a voltage is applied to the electrodes, respectively.

5. The liquid crystal display device according to claim 2, wherein the alignment direction of the first homogeneous alignment film substantially coincides with the polarization axis of the polarizer.

6. The liquid crystal display device according to claim 2, wherein the first and second homogeneous alignment films are anti-parallel to each other.

7. The liquid crystal display device according to claim 6, wherein the first and second homogeneous alignment films are rubbed in a direction of about 45°

with respect to the electrodes, respectively.

8. The liquid crystal display device according to claim 1, wherein the liquid crystal molecules has a pretilt angle of 1 to 5°

.

9. The liquid crystal display device according to claim 1, wherein the first electrode is a first pixel electrode, and the second electrode is a first counter electrode.

10. The liquid crystal display device according to claim 1, wherein the third electrode is a second pixel electrode, and the fourth electrode is a second counter electrode.

11. A liquid crystal display device with an in-plane switching mode, comprising:

a first substrate having a first electrode and a second electrode formed thereon, the first electrode being arranged parallel to the second electrode, a first electric field being generated between the first electrode and the second electrode when a voltage is applied to the first and second electrodes;

a second substrate having a third electrode and a fourth electrode formed thereon and disposed opposite to the first substrate, the third electrode being arranged parallel to the fourth electrode, a second electric field being generated between the third and fourth electrodes when the voltage is applied, the direction of the second electric field being substantially orthogonal to that of the first electric field;

a polarizer arranged on an outside of the first substrate;

an analyzer arranged on an outside of the second substrate;

a first homogenous alignment film applied to the first substrate;

a second homogeneous alignment film applied to the second substrate; and

a liquid crystal layer having liquid crystal molecules interposed between the first and second substrates such that, in an absence of said first and second electric fields, the liquid crystal molecules are arranged homogeneously with the first and second homogeneous alignment films and, in a presence of the first and second electric fields, major axes of said liquid crystal molecules adjacent to the first and second substrate are parallel to the first and second electric fields, respectively, and wherein said liquid crystal molecules are twisted relative to each other while remaining parallel to said first and second substrates in the presence of said first and second electric fields.

12. The liquid crystal display device according to claim 11, wherein the polarization axis of the analyzer is substantially orthogonal to that of the polarizer.

13. The liquid crystal display device according to claim 12, wherein the liquid crystal molecules substantially close to the first substrate deviate by an angle of 45°

from the polarization axis of the polarizer and liquid crystal molecules substantially close to the second substrate deviate by an angle of 45°

from the polarization axis of the analyzer, when the voltage is applied to the electrodes, respectively.

14. The liquid crystal display device according to claim 11, wherein the alignment direction of the first homogeneous alignment film substantially coincides with the polarization axis of the polarizer.

15. The liquid crystal display device according to claim 11, wherein the first and second homogeneous alignment films are anti-parallel to each other.

16. The liquid crystal display device according to claim 15, wherein the first and second homogeneous alignment films are rubbed in a direction of 45°

with respect to the electrodes, respectively.

17. The liquid crystal display device according to claim 11, wherein the liquid crystal molecules of the liquid crystal layer have a pretilt angle of about 1°

to 5°

.

18. The liquid crystal display device according to claim 11, wherein the first electrode is a first pixel electrode, and the second electrode is a first counter electrode.

19. The liquid crystal display device according to claim 11, wherein the third electrode is a second pixel electrode, and the fourth electrode is a second counter electrode.

20. A liquid crystal display device with an in-plane switching mode, comprising:

a first substrate having a first pixel electrode and a first counter electrode formed thereon, the first pixel electrode being arranged parallel to the first counter electrode, a first electric field being generated between the first pixel and counter electrodes when a voltage is applied to the first pixel and counter electrodes;

a second substrate having a second pixel electrode and a second counter electrode formed thereon and disposed opposite to the first substrate, the second pixel electrode being arranged parallel to the second counter electrode, a second electric field being generated between the second pixel electrode and the second counter electrode when the voltage is applied to the second pixel and counter electrodes, the direction of the second electric field being substantially orthogonal to that of the first electric field;

a polarizer arranged on an outside of the first substrate;

an analyzer on an outside of the second substrate, a polarization axis of the analyzer being substantially orthogonal to a polarization axis of the polarizer;

a first homogenous alignment film applied to the first substrate, an alignment direction of said first homogenous alignment film substantially coinciding with the polarization axis of said polarizer;

a second homogeneous alignment film applied to the second substrate, said first and second homogenous alignment films being anti-parallel to each other and being rubbed in a direction of 45°

relative to respective electrodes; and

a liquid crystal layer having liquid crystal molecules interposed between the first substrate and the second substrates such that, in an absence of said first and second electric fields, the liquid crystal molecules are arranged homogeneously with the first and second homogeneous alignment films and, in a presence of the first and second electric fields, major axes of said liquid crystal molecules adjacent to the first and second substrates are parallel to the first and second electric fields, respectively, and wherein said liquid crystal molecules are twisted relative to each other while remaining parallel to said first and second substrates in the presence of said first and second electric fields so that the liquid crystal molecules substantially close to the first substrate deviate by an angle of about 45°

from the polarization axis of the polarizer and liquid crystal molecules substantially close to the second substrate deviate by an angle of about 45°

from the polarization axis of the analyzer.