Electrostatically-driven light modulator and display

• US 5,745,281 A
• Filed: 12/20/1996
• Issued: 04/28/1998
• Est. Priority Date: 12/29/1995
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Yi, You-Wen, Saito, Mitsuchika
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US08/771,566
• Time in Patent Office: 494 Days
• Field of Search: 359/290, 359/291, 359/295, 359/308
• US Class Current: 359/290
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

A light modulator having the small volume and low power consumption of LCD displays together with the higher resolution and faster response time of CRT displays. The light modulator includes a substrate pair, an opaque light shielding layer, a shutter assembly composed of a shutter plate and a shutter suspension, and electrodes. The substrate pair includes a first substrate and a second substrate positioned parallel to each other and spaced from one another to define a cavity. The opaque light shielding layer is located on one of the substrates, and defines a translucent window. The shutter assembly is located in the cavity. The shutter plate is movably mounted adjacent the window by the shutter suspension. The shutter suspension includes elastic support members disposed between the shutter plate and the substrate pair. The shutter suspension has a mechanically-stable position and deforms elastically from the mechanically-stable position in response to a change in overlap between the shutter plate and the mirror. The overlap between the shutter plate and the window controls the amount of light passing through the window. Finally, the electrodes are located on at least two of (a) the shutter assembly, (b) an inside surface of the first substrate, and (c) an inside surface of the second substrate, and are located to change the overlap between the shutter plate and the window by electrostatic force.

Claims

1. A light modulator, comprising:

a substrate pair including a first substrate and a second substrate positioned parallel to each other and spaced from one another to define a cavity;

an opaque light shielding layer located on at least one of the substrates, the light shielding layer defining a translucent window;

a shutter assembly located in the cavity, the shutter assembly including;

a shutter plate movably mounted adjacent the window,

a shutter suspension comprising elastic support members disposed between the shutter plate and the substrate pair to movably mount the shutter plate, the shutter suspension having a mechanically-stable position and deforming elastically from the mechanically-stable position in response to a change in overlap between the shutter plate and the window, the overlap between the shutter plate and the window controlling an amount of light passing through the window; and

electrodes located on at least two of;

the shutter assembly,

an inside surface of the first substrate, and

an inside surface of the second substrate,

the electrodes being located to change the overlap between the shutter plate and the window by electrostatic force.

2. The light modulator of claim 1, in which:

the light shielding layer is formed on the first substrate;

a first one of the electrodes is located on the inside surface of the first substrate and is translucent;

a second one of the electrodes is located on the inside surface of the second substrate and is translucent; and

the light passes through the first substrate and the second substrate.

3. The light modulator of claim 1, in which:

the light shielding layer is formed on the second substrate;

a first one of the electrodes is located on the inside surface of the first substrate and is translucent;

a second one of the electrodes is located on the inside surface of the second substrate and is translucent; and

the light passes through the first substrate and the second substrate.

4. The light modulator of claim 1, in which:

a first one of the electrodes is located on the inside surface of the first substrate and is translucent;

a second one of the electrodes is located on the inside surface of the second substrate and is reflecting; and

the light passes through the first substrate, and not through the second substrate.

5. The light modulator of claim 1, in which the shutter plate is formed from a polymer.

6. The light modulator of claim 1, in which the electrodes are formed only on the first and second substrates.

7. The light modulator of claim 1, additionally comprising spacers disposed between the first substrate and the second substrate, the shutter suspension being connected to the spacers.

8. The light modulator of claim 7, in which:

the shutter plate includes plural shutter plate segments;

the light shielding layer defines a window segment corresponding to each of the shutter plate segments; and

one of the electrodes is divided into an electrode segment corresponding to each of the shutter plate segments.

9. The light modulator of claim 8, in which:

the shutter plate is formed of a material having a resistivity; and

the cavity contains a fluid having a resistivity differing from the resistivity of the material of the shutter plate by a factor of greater than ten.

10. The light modulator of any one of claim 8, in which:

the shutter plate is formed of a material having a dielectric constant; and

the cavity contains a fluid having a dielectric constant differing from the dielectric constant of the material of the shutter plate by a factor of greater than two.

11. The light modulator of claim 1, additionally comprising a color filter mounted on one of the first substrate and the second substrate in alignment with the window.

12. The light modulator of claim 1, in which:

the shutter plate is formed of a material having a resistivity; and

the cavity contains a fluid having a resistivity differing from the resistivity of the material of the shutter plate by a factor of greater than ten.

13. The light modulator of any one of claim 1, in which:

the shutter plate is formed of a material having a dielectric constant; and

the cavity contains a fluid having a dielectric constant differing from the dielectric constant of the material of the shutter plate by a factor of greater than two.

14. A display comprising an array of light modulators according to claim 1.

15. The light modulator of claim 1, in which:

the shutter plate includes plural shutter plate segments;

the light shielding layer defines a window segment corresponding to each of the shutter plate segments; and

one of the electrodes is divided into an electrode segment corresponding to each of the shutter plate segments.

16. The light modulator of claim 15, in which:

the shutter plate is formed of a material having a resistivity; and

the cavity contains a fluid having a resistivity differing from the resistivity of the material of the shutter plate by a factor of greater than ten.

17. The light modulator claim 15, in which:

the shutter plate is formed of a material having a dielectric constant; and

the cavity contains a fluid having a dielectric constant differing from the dielectric constant of the material of the shutter plate by a factor of greater than two.

18. A light modulator, comprising:

a substrate pair including a first substrate and a second substrate positioned parallel to each other and spaced from one another to define a cavity;

an opaque light shielding layer located on one of the substrates, the light shielding layer defining a translucent window divided into window segments;

a shutter plate movably mounted in the cavity adjacent the window, the shutter plate including a shutter plate segment corresponding to each of the window segments;

a shutter suspension located in the cavity, the shutter suspension comprising elastic support members disposed between the shutter plate and the substrate pair to movably mount the shutter plate, the shutter suspension having a mechanically-stable position and deforming elastically from the mechanically-stable position in response to a change in overlap between the shutter plate and the window, the overlap between the shutter plate and the window controlling an amount of light passing through the window; and

a first electrode located on an inside surface of the first substrate;

a second electrode located on an inside surface of the second substrate , the electrodes being located to change the overlap between the shutter plate and the window by electrostatic force, at least one of the electrodes including an electrode segment corresponding to each of the window segments.

19. The light modulator of claim 18, in which:

the shutter plate is formed of a material having a resistivity; and

the cavity contains a fluid having a resistivity differing from the resistivity of the material of the shutter plate by a factor of greater than ten.

20. The light modulator claim 18, in which:

the shutter plate is formed of a material having a dielectric constant; and

the cavity contains a fluid having a dielectric constant differing from the dielectric constant of the material of the shutter plate by a factor of greater than two.