Light-switching device

• US 6,535,323 B2
• Filed: 09/27/2001
• Issued: 03/18/2003
• Est. Priority Date: 09/28/2000
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Johnson, Mark Thomas, Cornelissen, Hugo Johan, Van Der Sluis, Paul, Janner, Anna-Maria
• Primary Examiner(s): Schwartz, Jordan M.
• Assistant Examiner(s): STULTZ, JESSICA T
• Application Number:
  US09/965,415
• Publication Number:
  US 20020036816A1
• Time in Patent Office: 537 Days
• Field of Search: 359/242, 359/245, 359/247, 359/250-252, 359/254, 359/263, 359/267, 359/275, 359/315, 359/318, 359/320
• US Class Current: 359/275
• CPC Class Codes: G02F 1/1352 Light-reflecting layers
• CPC Class Codes: G02F 1/1523 comprising inorganic material
• CPC Class Codes: G02F 1/155 Electrodes
• CPC Class Codes: G02F 1/19 based on variable-reflection or variable-refraction elements not provided for in groups G02F1/015 - G02F1/169
• CPC Class Codes: G02F 2202/34 Metal hydrides materials

Abstract

The invention relates to a switching device having shorter switching times. The device comprises a switchable layer (3), which is switched between a reflecting and an absorbing state by changing a hydrogen content of the switchable layer (3). Applying a DC voltage on electroconductive layers (11, 13) changes the hydrogen content. These electroconductive layers (11, 13) sandwich a stack of layers comprising the switchable layer (3) and a hydrogen storage layer (9). The hydrogen storage layer comprises essentially the same compounds as the switchable layer (3), viz. LMgH_x and preferably GdMgH_x. The storage layer may be made thin, leading to relatively short hydrogen transportation times and a relatively fast display. The device may be further improved by applying a scattering foil.

Claims

1. A device which is reversibly switchable between at least a first state of reflecting light and a second state of absorbing light, said device comprising a stack of layers including a switchable layer (3) of an optically switchable material which brings about a switch from the first state to the second state of the device by changing a density of hydrogen, the stack further including a layer for storing hydrogen (9), separated from the switchable layer, which comprises a material comprising essentially the same compounds as the switchable layer (3).

2. A device as claimed in claim 1, wherein the device is a display device having pixel elements (20) which are reversibly switchable between the at least first state of reflecting light and the second state of absorbing light, said pixel elements (20) comprising said stack of layers.

3. A device as claimed in claim 2, wherein the device has a viewable side (24) which is provided with a scattering foil.

4. A device as claimed in claim 2, wherein a surface of the switchable layer is roughened so as to scatter light.

5. A device as claimed in claim 1, wherein the optically switchable material comprises LMgH_x, in which L represents Ni, Sc or Y or an element of the Lanthanide series.

6. A device as claimed in claim 2, wherein the display device has a viewable side (24) and electric switching means (22) for switching said switchable layer (3), and wherein the electric switching means (22) are positioned behind the switchable layer (3) with respect to the viewable side (24) of the display device.