Interferometric modulator with dual absorbing layers

• US 8,995,043 B2
• Filed: 11/29/2011
• Issued: 03/31/2015
• Est. Priority Date: 11/29/2011
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Ma, Jian J., Chang, Tallis Y., Hong, John H.
• Primary Examiner(s): Chapel, Derek S
• Application Number:
  US13/306,877
• Publication Number:
  US 20130135319A1
• Time in Patent Office: 1,218 Days
• Field of Search: None
• US Class Current: 359/290
• 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 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

This disclosure provides systems, methods and apparatus related to an electromechanical display device. In one aspect, an analog interferometric modulator includes a reflective display pixel having a reflector, and a movable first absorbing layer positionable at a distance d1 from the reflector, the first absorbing layer and the reflector defining a first gap therebetween. The apparatus also includes a second absorbing layer disposed at a distance d2 from the first absorbing layer, the first absorbing layer disposed between the second absorbing layer and the reflector, the second absorbing layer and the first absorbing layer defining a second gap therebetween. In addition, at least two of the reflector, the first absorbing layer and second absorbing layer are movable to synchronously either increase or decrease the thickness dimension of the first gap and the second gap.

Claims

1. An electromechanical display apparatus, comprising:

a reflective display pixel including

a reflector;

a first partially transmissive absorbing layer disposed from the reflector, the first absorbing layer and the reflector defining a first gap therebetween, the first gap having a thickness dimension of distance d1;

a second partially transmissive absorbing layer disposed from the first absorbing layer such that the first absorbing layer is between the second absorbing layer and the reflector, the second absorbing layer and the first absorbing layer defining a second gap therebetween, the second gap having a thickness dimension of distance d2; and

wherein at least two of the reflector, the first absorbing layer and second absorbing layer are movable to either increase or decrease the thickness dimension of the first gap and the second gap,

wherein the sum of the thickness of the first absorbing layer and the second absorbing layer is between about 3 nm and 12 nm.

2. The apparatus of claim 1, wherein the sum of the thickness of the first absorbing layer and the second absorbing layer is between about 5 nm and about 7 nm.

3. The apparatus of claim 1, wherein the display pixel is configured such that given a range of received light wavelengths λ

min to λ

max, distance d1<

λ

max, and d1+d2<

2λ

max.

4. The apparatus of claim 1, wherein at least two of the reflector, the first absorbing layer and second absorbing layer are movable such that the distances d1 and d2 place the first absorbing layer and the second absorbing layer, respectively, at consecutive dark fringes of a standing wave interference pattern of the desired display color resulting from the interference of the incident and reflected light.

5. The apparatus of claim 1, wherein the reflector and the first absorbing layer are movable by electrostatic forces when a first voltage is applied across the reflector and the second absorbing layer and a second voltage is applied across the reflector and the first absorbing layer.

6. The apparatus of claim 1, further comprising a substrate, wherein the second absorbing layer is disposed on the substrate.

7. The apparatus of claim 1, wherein the at least two absorbing layers are movable such that (|d2−

d1|)/((d1+d2)/2) is less than or equal to 0.25.

8. The apparatus of claim 1, wherein the first absorbing layer and the second absorbing layer include molybdenum-chromium (MoCr), vanadium (V), germanium (Ge), or tungsten (W).

9. The apparatus of claim 1, wherein the first absorbing layer is thicker than the second absorbing layer.

10. The apparatus of claim 1, wherein at least two of the reflectors, the first absorbing layer and second absorbing layer are movable such that the distances d1 and d2 place the first absorbing layer and the second absorbing layer at a distance of λ

/2±

15 nm and λ

±

15 nm, respectively, from the reflector, for a target primary color of light having wavelength λ

.

11. The apparatus of claim 1, wherein the display pixel further comprises a movable dielectric layer having a thickness of between about 100 nm and 300 nm, and wherein the first absorbing layer is deposed on the dielectric layer.

12. The apparatus of claim 1, wherein the display pixel further comprises a dielectric layer having a thickness of between about 100 nm and 300 nm, and wherein the second absorbing layer is disposed on the dielectric layer.