Micromechanical displays and fabrication method

• US 20020000959A1
• Filed: 07/30/2001
• Published: 01/03/2002
• Est. Priority Date: 10/08/1998
• Status: Active Grant

• Current Assignee: Lenovo Singapore Pte Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Colgan, Evan G., Rosenbluth, Alan E., Kosbar, Laura L.
• Granted Patent: US 6,377,233 B2
• Time in Patent Office: Days
• US Class Current: 345/84
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2300/0473 Use of light emitting or modulating elements having two or more stable states when no power is applied
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• 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 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A display device, in accordance with the present invention includes a transparent substrate and an array of pixels formed on the substrate, each pixel comprises a transparent electrode and a deformable member electrically actuated between a first state and a second state, wherein in the first state a liquid including a dye is disposed in a gap between the transparent electrode and the deformable member and wherein in the second state the deformable member reduces the gap between the transparent electrode and the deformable member such that the liquid is substantially removed between the deformable layer and the transparent electrode in the area of contact. A plurality of switches are formed on the substrate for supplying control signals to the array of pixels to selectively actuate the deformable members of the pixels, wherein each switch comprises an actuating member movable between an active state and an inactive state, whereby in the active state any control signal supplied to the switch passes through the switch, and in the inactive state any control signal supplied to the switch is prevented from passing through the switch. Fabrication methods are also disclosed.

Claims

1. A display device comprising:

a transparent substrate;

an array of pixels formed on the substrate, each pixel comprises a transparent electrode and a deformable member electrically actuated between a first state and a second state, wherein in the first state a liquid including a dye is disposed in a gap between the transparent electrode and the deformable member and wherein in the second state the deformable member reduces the gap between the transparent electrode and the deformable member such that the liquid is substantially removed between the deformable layer and the transparent electrode; and

a plurality of switches formed on the substrate for supplying control signals to the array of pixels to selectively actuate the deformable members of the pixels, wherein each switch comprises an actuating member movable between an active state and an inactive state, whereby in the active state any control signal supplied to the switch passes through the switch, and in the inactive state any control signal supplied to the switch is prevented from passing through the switch.

2. The display device as recited in claim 1, wherein the deformable member includes a reflective surface which reduces the gap displacing a portion of the liquid when the deformable member is in the second state.

3. The display device as recited in claim 2, wherein the dye is black such that light is reflected from the deformable member, when the deformable member is in the second state and light is absorbed in the gap when the deformable member is in the first state.

4. The display device as recited in claim 3, wherein the dye includes Sudan Black.

5. The display device as recited in claim 3, wherein the dye includes Naphthol Blue Black.

6. The display device as recited in claim 1, wherein the deformable member includes a light absorbent surface which contacts an insulation layer over the transparent electrode in the second state.

7. The display device as recited in claim 6, wherein the dye is white such that light is reflected from the gap when the deformable member is in the second state and light is absorbed on the deformable member when the deformable member is in the first state.

8. The display device as recited in claim 1, wherein the deformable member is bistable having a hysteresis such that only the first and second states are permitted.

9. The display device as recited in claim 1, wherein the switches include microelectromechanical switches.

10. The display device as recited in claim 1, wherein the deformable member is actuated on hinges integrally formed with the deformable member.

11. The display device as recited in claim 1, further comprises an active area including the liquid therein and a first seal region for maintaining the liquid in the active area.

12. The display device as recited in claim 11, further comprises a second seal region for maintaining an inert gas therein between the first seal region and the second seal region such that the plurality of switches exist in the inert gas.

13. The display device as recited in claim 11, wherein the transparent electrode forms a data line for controlling the pixels and the deformable member forms a gate line for controlling the pixels such that voltage differences provided by control signals between the gate line and the data line provide a force for actuating the deformable member;

and

the plurality of switches formed on the substrate for supplying the control signals on gate lines and data lines to the array of pixels selectively actuate the deformable members of the pixels.

14. The display device as recited in claim 13, further comprises a shift register for addressing the gate lines, the shift register including a portion of the plurality of switches and another portion of the plurality of switches for demultiplexing the data lines.

15. A display device comprising:

a substrate;

an array of pixels formed on the substrate, each pixel comprises an electrically actuated switch, a storage capacitor, a transparent substrate and a deformable member electrically actuated between a plurality of states, wherein in each of the states a liquid including a dye is disposed in a gap between a transparent substrate and the deformable member in an active area and wherein the gap is adjustable according to voltages applied to the deformable member and the storage capacitor thereby reflecting light from the active area according to different intensities.

16. The display device as recited in claim 15, wherein the deformable member includes a reflective surface for reflecting light through the transparent substrate and wherein the dye is black.

17. The display device as recited in claim 15, wherein the deformable member includes a light absorbent surface for absorbing light through the transparent substrate and wherein the dye is white.

18. The display device as recited in claim 15, wherein the deformable member is actuated on hinges integrally formed with the deformable member.

19. The display device as recited in claim 15, further comprises an active device area including the liquid therein and a first seal region for maintaining the liquid in the active area.

20. The display device as recited in claim 19, further comprises a second seal region for maintaining an inert gas therein between the first seal region and the second seal region such that the plurality of switches exist in the inert gas.

21. The display device as recited in claim 15, further comprises a shift register for addressing gate lines which are coupled to each pixel.

22. The display device as recited in claim 15, wherein the switches include microelectromechanical switches.

23. A method for fabricating a display device comprising the steps of:

patterning a black matrix layer on a transparent substrate;

depositing a first insulation layer on the patterned black matrix layer;

patterning a transparent conductor layer on the first insulation layer;

depositing a second insulation layer on the transparent conductor layer;

depositing a sacrificial layer on the second insulation layer for forming a gap of a predetermined distance between the second insulation layer and deformable members;

forming openings in the sacrificial layer for providing support points for the deformable members;

patterning a metal layer to form the deformable members; and

removing the sacrificial layer to provide the gap.

24. The method as recited in claim 23, further comprising the step of:

filling the gap with a liquid including a dye such that in a first state of the deformable member the liquid is disposed in the gap between the transparent electrode and the deformable member and wherein in a second state the deformable member reduces the gap between the transparent electrode and the deformable member such that the liquid is substantially removed between the deformable member and the transparent electrode.

25. The method as recited in claim 23, wherein the sacrificial layer includes copper and the step of removing the sacrificial layer includes the step of removing the sacrificial layer by a wet etch process.

26. The method as recited in claim 23, wherein the deformable members include deformable mirrors.

27. A method for fabricating a deformable display device comprising the steps of:

patterning a transparent conductor layer on a transparent substrate;

forming an insulation layer over the transparent conductor layer;

patterning a conductive black matrix layer on the insulation layer and outside the active area, the black matrix layer forming a drain electrode for switches;

providing a source electrode and a gate electrode for switches by patterning one of the black matrix layer and the transparent conductor layer outside the active area;

patterning a sacrificial layer for forming features in the sacrificial layer for providing support points for the deformable members and connections through the sacrificial layer; and

patterning a metal layer on the sacrificial layer to form the deformable members and support points for the deformable members, the deformable members including deformable display members in the active area and switches outside the active area; and

removing the sacrificial layer to provide a predetermined gap between the insulation over the transparent conductor and the deformable display members and to provide cantilevered conductors for the switches, the cantilevered conductors attaching to the source electrode and including a tip feature for contacting the drain electrode when the gate electrode is activated.

28. The method as recited in claim 27 wherein the step of patterning a sacrificial layer includes the steps of forming a via hole through the sacrificial layer to the source electrode;

and

forming a tip feature hole over the drain electrode such that upon patterning the metal layer the cantilevered conductor is attached to the source electrode and includes the tip feature for contacting the drain electrode.

29. The method as recited in claim 27, wherein the sacrificial layer includes a copper layer and further comprises the steps of:

forming dimples in the copper layer for forming the cantilevered conductors for switches; and

forming openings through the copper layer to form vias through the sacrificial layer.

30. The method as recited in claim 27, wherein the deformable display members include deformable mirrors.

31. The method as recited in claim 27, further comprising the step of:

filling the gap with a liquid including a dye such that in a first state of the deformable display member the liquid is disposed in the gap between the transparent electrode and the deformable display member and wherein in a second state the deformable display member reduces the gap between the transparent electrode and the deformable display member such that the liquid is substantially removed between the deformable display member and the transparent electrode.