Light switching device

• US 20020101413A1
• Filed: 01/08/2002
• Published: 08/01/2002
• Est. Priority Date: 01/12/2001
• Status: Abandoned Application

• 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, Van Der Sluis, Paul, Janner, Anna-Maria, Hunter, Iain Mcintosh
• Application Number:
  US10/042,449
• Publication Number:
  US 20020101413A1
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor
• 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
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 3/38 using electrochromic devices

Abstract

In an active matrix display (20) comprising pixels based on switching mirror display elements (30) the driving circuit provides continous current in two directions (charge/discharge) and prevents device degradation

Claims

1. Display device (20) being operable in a reflective mode (L) or in a transmissive mode (R) and having pixel elements for modulating light, each of said pixel elements comprising:

a stack of layers including a switchable layer (3) of an optically switchable material that switches the pixel elements from a first state to a second state, the second state being different from the first state, the first state and the second state being one of the following states;

a reflective or scattering state, a transmissive state, or an absorbing state and means for modulating light in the reflective mode (L) by switching from a reflective state to a non-reflective state, and for modulating light in the transmissive (R) mode by switching from a transmissive state to a non-transmissive state, the non-reflective state being the transmissive state or the absorbing state and the non-transmissive state being the reflective or scattering state or the absorbing state,

the means for modulating light comprising for each pixel element a first series connection of two complementary switches (31,32) between two voltage connections (35,36), the common point of said series connection being connected to a first connection (13) of the pixel element an intermediate voltage being provided to a second connection (11) of the pixel element, the complementary switches being controlled by storage means (33), the display device comprising further means(22, 23, 34) for controlling the storage means.

2. Display device according to claim 1 in which the optically switchable layer brings about switching by changing a concentration of hydrogen.

3. Display device according to claim 1 in which the second connection of the pixel element is a fixed reference voltage (29).

4. Display device according to claim 1 comprising a second series connection of two complementary switches (31′

,32′

) arranged in reverse sense with respect to the first series connection of two complementary switches (31,32) between said two voltages the second connection of the pixel element (11) being connected to the common point of said second series connection and the second series of complementary switches being controlled by said storage means.

5. Display device according to claim 1 in which the storage means comprise a capacitor element connected to the common point of said first series connection of complementary switches.

6. Display device according to claim 4 in which the storage means comprise a capacitor element connected to the common points of said first and second series connections of complementary switches.

7. Display device according to claim 1 in which the pixel elements are provided in a matrix structure and the further means comprise select switches (34) controlled by select lines (22), to which data is presented via data lines (23).

8. Display device according to claims 4 and 7 in which the complementary transistors have separate select switches.

9. Display device according to claim 1 in which the switches comprise thin film transistors