Self-aligned structures for improved wide viewing angle for liquid crystal displays

• US 6,256,080 B1
• Filed: 06/23/1999
• Issued: 07/03/2001
• Est. Priority Date: 06/23/1999
• Status: Expired due to Term

• Current Assignee: Infovision Optoelectronics Company Limited (Digital China Information Service Co., Ltd.), Shin Koh Den Technology Limited
• Original Assignee: International Business Machines Corporation
• Inventors: Colgan, Evan G., Lien, Shui-Chih A., Schleupen, Kai R.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): SCHECHTER, ANDREW M
• Application Number:
  US09/339,262
• Time in Patent Office: 741 Days
• Field of Search: 349/110, 349/111, 349/123, 349/129, 349/130, 349/191, 349/143, 349/139, 349/124, 349/160, 349/156
• US Class Current: 349/129
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/133707 Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes
• CPC Class Codes: G02F 1/133753 with different alignment orientations or pretilt angles on a same surface, e.g. for grey scale or improved viewing angle

Abstract

In accordance with the present invention, a liquid crystal display cell includes a first substrate having a light absorbent material patterned thereon. The light absorbent material includes a portion disposed within a pixel area. A conductive layer is formed on the light absorbent material for forming a first transparent electrode. A second electrode is spaced apart from the first electrode by a gap. The gap includes liquid crystal. A ridge or a trench is formed in the pixel area and projects into the liquid crystal. The ridge or trench is self-aligned to the portions of the light absorbent material in the pixel area. The first electrode and the second electrode provide an electric field therebetween wherein the ridge or trench provides pretilt control for the liquid crystal to provide an improved wide viewing angle and the portions of the light absorbent material absorb light leaked from the ridge. Other embodiments for active and passive displays are included as well as a method for employing the invention.

Claims

1. A liquid crystal display cell comprising:

a first substrate having a light absorbent material patterned thereon, the light absorbent material including a portion disposed within a pixel area;

a conductive layer formed in a position relative to the light absorbent material, the position being one of over the light absorbent material and below the light absorbent material for forming a first transparent electrode;

a second electrode spaced apart from the first electrode by a gap, the gap including liquid crystal;

a ridge formed in the pixel area and projecting into the liquid crystal, the ridge being self-aligned to the portions of the light absorbent material in the pixel area; and

the first electrode and the second electrode for providing an electric field therebetween wherein the ridge provides pretilt control for the liquid crystal to provide a viewing angle and the portions of the light absorbent material absorb light leaked from the ridge.

2. The cell as recited in claim 1, wherein the light absorbent material includes a black matrix.

3. The cell as recited in claim 1, wherein the first electrode is a common electrode and the second electrode is a pixel electrode.

4. The cell as recited in claim 3, wherein the pixel electrode includes a width and the ridge includes a width less than the width of the pixel electrode.

5. The cell as recited in claim 1, wherein the portions of the light absorbent material in the pixel area have a width and the ridge includes a width smaller than the width of the portions of the light absorbent material in the pixel area.

6. The cell as recited in claim 1, wherein the ridge includes one of a Y inverse Y structure, an X structure, a straight line structure, a T structure, multiple X or T structures and an I structure in the pixel area.

7. The cell as recited in claim 1, wherein the ridge includes tapered side walls.

8. The cell as recited in claim 1, wherein the liquid crystal includes a negative dielectric anisotropic liquid crystal.

9. A liquid crystal display cell comprising:

a first substrate having a first transparent electrode formed thereon;

an opaque material patterned on a portion of the first electrode;

a transparent insulation layer formed in a position relative to the first electrode, the position being one of over the first electrode and below the first electrode, insulation layer forming a trench;

a second electrode spaced apart from the first electrode by a gap, the gap including liquid crystal;

the trench opening to the liquid crystal, the trench being self-aligned to the patterned opaque material; and

the first electrode and the second electrode for providing an electric field therebetween wherein the trench provides a pretilt control for the liquid crystal to provide a viewing angle and the opaque material for preventing light leakage around the trench.

10. The cell as recited in claim 9, wherein the opaque material includes a same material as one of a data line and a gate line.

11. The cell as recited in claim 9, wherein the first electrode is a pixel electrode and the second electrode is a common electrode.

12. The cell as recited in claim 11, wherein the pixel electrode includes a width and the trench includes a width less than the width of the pixel electrode.

13. The cell as recited in claim 9, wherein the portion of the opaque material patterned on the first electrode includes a width and the trench includes a width smaller than the width of the opaque material patterned on the first electrode.

14. The cell as recited in claim 9, wherein the trench includes one of a Y inverse Y structure, an X structure, a straight line structure, a T structure, multiple X or T structures and an I structure.

15. The cell as recited in claim 9, wherein the trench includes tapered side walls.

16. The cell as recited in claim 9, wherein the first electrode is formed from a first conductive layer and the opaque material is formed from a second conductive layer such that the first conductive layer is electrically isolated from the second conductive layer for portions of the first and second conductive layers to form a storage capacitor.

17. The cell as recited in claim 9, wherein the liquid crystal includes a negative dielectric anisotropic liquid crystal.

18. A method for self-aligning pretilt control structures for liquid crystal displays comprising the steps of:

providing a first substrate having an opaque material patterned thereon, the opaque material having portions disposed in a pixel area;

forming a transparent conductive material in a position which is one of over the opaque material and below the opaque material in the pixel area;

forming a photosensitive resist on the conductive layer; and

exposing the resist to light by employing the opaque material as a mask to form self-aligned pretilt control structures in the pixel area.

19. The method as recited in claim 18, wherein the pretilt control structures include one of trenches and ridges.

20. The method as recited in claim 18, wherein the step of forming a transparent conductive material includes the step of forming the transparent conductive layer on the opaque material.

21. The method as recited in claim 20, wherein the photosensitive resist includes a positive resist, and the step of exposing the resist to light by employing the opaque material as a mask to form self-aligned pretilt control structures in the pixel area includes the step of forming ridges self-aligned to the opaque material in the pixel area.

22. The method as recited in claim 18, wherein the photosensitive resist includes a negative resist, and the step of exposing the resist to light by employing the opaque material as a mask to form self-aligned pretilt control structures in the pixel area includes the step of forming trenches self-aligned to the opaque material in the pixel area.

23. The method as recited in claim 18, further comprising the step of removing portions of the resist outside the pixel area.

24. The method as recited in claim 18, wherein the opaque material includes a black matrix.

25. The method as recited in claim 18, further comprising the step of developing the resist to form the pretilt control structures.