Liquid crystal display assembly for reducing optical defects

• US 7,102,703 B1
• Filed: 02/24/1999
• Issued: 09/05/2006
• Est. Priority Date: 02/24/1999
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Murray, Cade, Fridlyand, Tonya, Takiar, Hem, Mathew, Ranjan J.
• Primary Examiner(s): Nguyen, Dung T.
• Application Number:
  US09/256,702
• Time in Patent Office: 2,750 Days
• Field of Search: 349/58, 349/60, 349/150
• US Class Current: 349/60
• CPC Class Codes: G02F 1/133308 Support structures for LCD panels, e.g. frames or bezels
• CPC Class Codes: G02F 1/133385 with cooling means, e.g. fans
• CPC Class Codes: G02F 1/13452 Conductors connecting driver circuitry and terminals of panels

Abstract

An improved packaged liquid crystal display (LCD) assembly is described. A recess is used to house a support material while the LCD cell 609 is positioned at least partially within the containment structure. A plurality of spaced apart stabilizers are attached from the sides of the LCD cell 609 to the substrate without transmitting residual stresses induced during fabrication and operation. A support material is dispensed in the recess such that it provides support for the LCD cell 609 without transmitting residual stresses from the substrate. The described arrangements permit an LCD assembly which minimizes the amount of forces and stresses that lead to optical defects. The stabilizers, in addition to supporting the cell, also act to contain the encapsulating material used to protect the bonding wires. The support material, in addition to minimizing transmission of stresses, also provides improved heat dissipation from the LCD cell 609. In another embodiment, a method for constructing the LCD assembly is described.

Claims

1. A packaged liquid crystal display comprising:

a containment structure having a recess formed in a surface of the structure;

a liquid crystal cell including a die having a pixel array, a transparent plate attached to the die, and a liquid crystal material disposed in a gap region between the die and the transparent plate, the liquid crystal cell being positioned at least partially within the recess formed in the containment structure;

a thermal support layer formed of thermal support material arranged in the recess underneath the liquid crystal cell enabling the liquid crystal cell to float on the thermal support layer; and

a plurality of spaced apart stabilizers arranged to extend over the recess in the containment structure to couple edge portions of the liquid crystal cell to the containment structure without adhering the bottom surface of the liquid crystal cell to the bottom surface of the containment structure.

2. A packaged liquid crystal display as recited in claim 1 wherein the plurality of spaced apart stabilizers provide a mechanically stable system.

3. A packaged liquid crystal display as recited in claim 2 including four spaced apart stabilizers.

4. A packaged liquid crystal display as recited in claim 1 wherein the thickness of the thermal support material is between approximately 0.3 mm and 0.8 mm.

5. A packaged liquid crystal display as recited in claim 1 wherein thermal support material is a thermal grease.

6. A packaged liquid crystal display as recited in claim 1 wherein the plurality of spaced apart stabilizers prevent flow of an encapsulating material.

7. A packaged liquid crystal display as recited in claim 1 wherein each of the plurality of spaced apart stabilizers are anchored solely to the side of the liquid crystal cell.

8. A packaged liquid crystal display as recited in claim 1 wherein all the structures adhering to the cell have a rigidity less than the liquid crystal display.

9. A packaged liquid crystal display comprising:

a containment structure having a top surface;

a liquid crystal cell including a die having a pixel array, a transparent plate attached to the die, and a liquid crystal material disposed in a gap region between the die and the transparent plate, the liquid crystal cell being positioned at least partially within the containment structure;

a thermal support layer formed of thermal support material arranged between the liquid crystal cell and the containment structure enabling the liquid crystal cell to float on the thermal support layer; and

a plurality of spaced apart stabilizers arranged to couple edge portions of the liquid crystal cell to the containment structure without adhering the bottom surface of the liquid crystal cell to the bottom surface of the containment structure wherein the stabilizers are sufficiently compliant such that they do not induce substantial stresses in the LCD assembly.

10. A packaged liquid crystal display as recited in claim 9 wherein the containment structure includes a substrate having a recess therein, the liquid crystal cell being at least partially contained within the recess.

11. A packaged liquid crystal display as recited in claim 10 wherein the substrate includes one of aluminum or ceramic.

12. A packaged liquid crystal display as recited in claim 10 wherein the substrate is comprised of Alloy Ash 42.

13. A method of packaging a liquid crystal display assembly comprising:

dispensing a thermal support material in a containment structure;

disposing a liquid crystal cell at least partially within the containment structure and disposing the liquid crystal cell upon the thermal support layer so that the liquid crystal cell floats on the thermal support layer, the liquid crystal cell including a die having a pixel array, a transparent plate attached to the die, and a liquid crystal material disposed in a gap region between the die and the transparent plate; and

forming a plurality of spaced apart stabilizers arranged to couple an edge portion of the liquid crystal cell to the containment structure without adhering the bottom surface of the liquid crystal cell to the bottom surface of the containment structure.

14. The method of claim 13 further including wire bonding a plurality of leads from the die to a plurality of leads on the containment structure.

15. The method of claim 14 further including depositing encapsulating material over the plurality of leads.

16. The method of claim 15 wherein the encapsulating material is prevented from surrounding the liquid crystal cell.

17. The method of claim 15 wherein a cycle time for a single cell is less than five hours.

18. The method of claim 13 wherein the plurality of spaced apart stabilizers are arranged in manner such that substantially no stresses are imposed on the liquid crystal cell.

19. The method of claim 13 wherein the thermal support material is disposed such that none of the plurality of spaced apart stabilizers are dispensed below the liquid crystal cell.

20. The method of claim 13 wherein the plurality of spaced apart stabilizers are anchored solely to the side of the liquid crystal cell.

21. A packaged liquid crystal display comprising:

a containment structure having a bottom surface;

a liquid crystal cell including a die having a pixel array, a transparent plate attached to the die, and a liquid crystal material disposed in a gap region between the die and the transparent plate, the liquid crystal cell being positioned at least partially within the containment structure; and

a plurality of spaced apart stabilizers arranged to couple edge portions of the liquid crystal cell to the containment structure without adhering the bottom surface of the liquid crystal cell to the bottom surface of the containment structure, the stabilizers being sufficiently compliant such that they do not induce substantial stresses in the LCD assembly.

22. A packaged liquid crystal display as recited in claim 21 further comprising a support material arranged to support the liquid crystal cell in a floating manner within the containment structure.

23. A packaged liquid crystal display as recited in claim 22 wherein the support material includes a thermal grease.

24. A packaged liquid crystal display comprising:

a containment structure having a recess formed in a portion of a top surface of the structure;

a strip of tape mounted at an edge of the containment structure, the tape including a plurality of bond pads;

a raised barrier mounted at an edge of the containment structure on top of the strip of tape and arranged so that the bond pads are exposed;

a liquid crystal cell positioned at least partially within the recess formed in the containment structure, the cell including,

a die having a pixel array, the die being wire bonded to the bond pads of the tape,

a transparent plate attached to the die, and

a liquid crystal material disposed in a gap region between the die and the transparent plate;

a thermal support layer formed of thermal support material arranged in the recess underneath the liquid crystal cell enabling the liquid crystal cell to float on the thermal support layer; and

a plurality of spaced apart stabilizers arranged to couple at least two edge portions of the liquid crystal cell while leaving at least one edge of the cell open.

25. The display of claim 24 wherein the containment structure further includes a ground trace that extends along an edge of the containment structure and is in passive contact with the transparent plate.

26. The display of claim 25 wherein the ground trace is formed on a strip of tape that extends along an edge of the containment structure.

27. The display of claim 24 wherein the plurality of spaced apart stabilizers arranged to couple at least two edge portions of the liquid crystal cell are further configured to leave at least one edge of the cell open and not coupled with the cell to reduce induced stresses.

28. The display of claim 24 wherein the plurality of spaced apart stabilizers are arranged to extend over the recess in the containment structure.