Display assembly including two superposed display devices

1. A display assembly for a portable object, the display assembly comprising:

a first, at least partially transparent, emissive display device, and

a second reflective display device arranged underneath the first emissive display device,

wherein the second reflective display device is capable of switching between a transparent state, in which the device does not display any information, and a reflective state, when the device is activated,

wherein the first emissive display device includes a transparent emissive organic light-emitting diode display cell, and wherein the second reflective display device includes a reflective liquid crystal display cell,

wherein a circular polarizer, which is formed of an absorbing polarizer and a first quarter-wave plate, is placed above the transparent emissive organic light-emitting diode display cell, and

wherein a second quarter-wave plate is placed underneath the transparent emissive organic light-emitting diode display cell, the second quarter-wave plate being parallel to the first quarter-wave plate or arranged at 90° relative to the first quarter-wave plate.

2. The display assembly according to claim 1 , wherein the emissive display device is fixed to the reflective display device.

3. The display device according to claim 2 , wherein the emissive display device is bonded on the reflective display device by means of an adhesive film or a liquid adhesive layer.

4. The display assembly according to claim 3 , wherein the reflective liquid crystal display cell is devoid of polarizers.

5. The display assembly according to claim 2 , wherein the reflective liquid crystal display cell is devoid of polarizers.

6. The display assembly according to claim 1 , wherein the transparent emissive organic light-emitting diode display cell includes a stack of electroluminescent layers sandwiched between a transparent upper electrode and a transparent lower electrode.

7. The display assembly according to claim 6 , wherein the reflective liquid crystal display cell is selected from the group comprising twisted nematic liquid crystal cells, super twisted nematic liquid crystal cells and vertically aligned liquid crystal display cells and in that the addressing of these liquid crystal display cells may be of the direct type, the active matrix type or the passive matrix multiplexing type.

8. The display assembly according to claim 7 , wherein an absorbing polarizer is arranged on an upper face of the reflective liquid crystal display cell, and wherein an absorbing reflective polarizer is arranged underneath a lower face of the reflective liquid crystal display cell.

9. The display assembly according to claim 8 , wherein the absorbing reflective polarizer may be formed by an absorbing polarizer (a) disposed atop a reflector (b), or a reflective transmissive polarizer (c) disposed atop an absorption layer (d).

10. The display assembly according to claim 6 , wherein an absorbing polarizer is arranged on an upper face of the reflective liquid crystal display cell, and wherein an absorbing reflective polarizer is arranged underneath a lower face of the reflective liquid crystal display cell.

11. The display assembly according to claim 10 , wherein the absorbing reflective polarizer may be formed by an absorbing polarizer disposed atop a reflector, or a reflective transmissive polarizer disposed atop an absorption layer.

12. The display assembly according to claim 1 , wherein an absorbing polarizer is arranged on an upper face of the reflective liquid crystal display cell, and wherein an absorbing reflective polarizer is arranged underneath a lower face of the reflective liquid crystal display cell.

13. The display assembly according to claim 12 , wherein the absorbing reflective polarizer may be formed by an absorbing polarizer disposed atop a reflector, or a reflective transmissive polarizer disposed atop an absorption layer.

14. The display assembly according to claim 1 , wherein the reflective liquid crystal display cell is devoid of polarizers.

15. The display assembly according to claim 14 , wherein the reflective display cell is an electrophoretic display cell, a dichroic liquid crystal display cell or a cholesteric liquid crystal display cell.