Alignment methods in fluid-filled MEMS displays

• US 9,229,222 B2
• Filed: 10/19/2007
• Issued: 01/05/2016
• Est. Priority Date: 02/23/2005
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Hagood, Nesbitt W., Fijol, John J., Steyn, Jasper Lodewyk, Payne, Richard S., Gandhi, Jignesh
• Primary Examiner(s): Niesz, Jamie C
• Application Number:
  US11/975,397
• Publication Number:
  US 20080037104A1
• Time in Patent Office: 3,000 Days
• Field of Search: 359/237, 359/290, 438/48, 438/26, 438/27, 438/34, 257/687
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0315 Cavities
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: B81C 2203/051 Active alignment, e.g. using internal or external actuators, magnets, sensors, marks or marks detectors
• CPC Class Codes: B81C 3/004 Active alignment, i.e. moving the elements in response to the detected position of the elements using internal or external actuators
• CPC Class Codes: G02B 26/00 Optical devices or arrangements for the control of light using movable or deformable optical elements control of light by modification of the optical properties of the media of the elements involved therein G02F1/00
• CPC Class Codes: G02B 26/023 comprising movable attenuating elements, e.g. neutral density filters
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0443 with several sub-pixels for the same colour in a pixel, not specifically used to display gradations G09G3/364 takes precedence
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means
• CPC Class Codes: H01L 2924/1461 MEMS

Abstract

This invention relates to MEMS display apparatus and methods for assembly thereof that include a plurality of light modulators having components substantially surrounded in a liquid that reduces the effects of stiction and improves the optical and electromechanical performance of the display apparatus. The invention also relates to methods for aligning components of a MEMS display to establish a correspondence between the plurality of light modulators and a plurality of apertures to regulate the transmission of light through the apparatus.

Claims

1. A display assembly comprising:

an array of MEMS light modulators formed on a first substrate, each of the MEMS light modulators including a shutter that moves in a plane substantially parallel to the first substrate;

a second substrate separated from the first substrate by a gap;

an array of spacers arranged between the first and second substrates, the number of spacers being proportional to the number of MEMS light modulators;

a hydrophobic liquid disposed between the first and second substrates substantially surrounding a movable portion of each MEMS light modulator, the movable portion including an actuator having a first flexible electrode and a second flexible electrode; and

a moisture resistant polymer seal surrounding the array of MEMS light modulators to contain the hydrophobic liquid between the two substrates, the polymer seal including a polymer that serves to adhere the first substrate to the second substrate.

2. The display assembly of claim 1, wherein the hydrophobic liquid comprises a lubricant.

3. The display assembly of claim 1, comprising a reflective aperture layer disposed on one of the first and second substrates.

4. The display assembly of claim 3, wherein the hydrophobic liquid has a first index of refraction and the substrate on which the reflective aperture layer is disposed has a second index of refraction, and wherein the first index of refraction is greater than or substantially equal to that of the second index of refraction.

5. The display assembly of claim 1, wherein the hydrophobic liquid is non-conductive.

6. The display assembly of claim 1, wherein the hydrophobic liquid has a dielectric constant greater than 2.0.

7. The display assembly of claim 1, wherein the hydrophobic liquid wets a surface of the MEMS modulators in the array of MEMS light modulators.

8. The display assembly of claim 7, wherein each of the MEMS light modulators includes a front side and a rear side, and wherein the hydrophobic liquid wets both the front and rear sides of the MEMS light modulators.

9. The display assembly of claim 1, wherein each of the MEMS light modulators includes a component that is controllably moved through the hydrophobic liquid.

10. The display assembly of claim 1, wherein the hydrophobic liquid is a single hydrophobic liquid.

11. The display assembly of claim 1, wherein the polymer seal is an epoxy.

12. The display assembly of claim 1, wherein each spacer of the array of spacers is arranged within or adjacent to a pixel of the display assembly.

13. The display assembly of claim 1, wherein each spacer of the array is arranged to maintain a substantially uniform pressure on the hydrophobic liquid.

14. The display assembly of claim 1, wherein each spacer of the array of spacers is associated with one or more MEMS light modulators.

15. The display assembly of claim 1, wherein each spacer of the array of spacers is associated with a group of two or more MEMS light modulators.

16. The display assembly of claim 1, wherein each spacer of the array of spacers is associated with a group of sixteen or more MEMS light modulators.

17. The display assembly of claim 1, wherein each MEMS light modulator is associated with one or more spacers of the array of spacers.

18. The display assembly of claim 1, wherein the density of the spacers of the array of spacers is arranged to maintain the second substrate at about a constant distance away from each of the MEMS light modulators of the array of MEMS light modulators.

19. The display assembly of claim 1, wherein the moisture resistant polymer seal is located within the gap.

20. The display assembly of claim 1, wherein the moisture resistant polymer seal adheres to a surface of the first substrate facing the gap and to a surface of the second substrate facing the gap.

21. The display assembly of claim 1, wherein the first flexible electrode includes a support beam connected to the shutter.

22. The display assembly of claim 1, wherein each spacer includes a first portion and a second portion, the first portion including a heat reflowable material.

23. The display assembly of claim 22, wherein the material functions as an adhesive to bond the first portion with the second portion.

24. The display assembly of claim 22, wherein the first portion is formed on the first substrate and the second portion is formed on the second substrate.

25. The display assembly of claim 22, wherein the material includes a metal alloy.

26. The display assembly of claim 25, wherein the metal alloy includes at least one of Pb—

Sn alloys, Pb—

In alloys, Tn—

Sn alloys, In—

Cu—

Sn alloys, Au—

Sn alloys, and Bi—

Sn alloys.

27. The display assembly of claim 22, wherein the material includes one of substantially pure In, Sn, Ga, and Bi.

28. The display assembly of claim 22, wherein the material is non-metallic.

29. The display assembly of claim 28, wherein the material includes glass.

30. The display assembly of claim 28, wherein the material includes at least one of barium-silicate, a lead-silicate glass, and a thermoplastic polymer.

31. The display assembly of claim 30, wherein the thermoplastic polymer includes at least one of polyethylene, polystyrene, polypropylene, and natural or synthetic waxes.