Method and apparatus for front-lit semi-retro-reflective display
View Patent ↗The disclosure generally relates to a front-lit display having transparent and selectively emissive light directionality. The disclosed semi-retro-reflective, semi-specular and specular displays include directional front light systems that reflect light in a manner to preserve the non-Lambertian characteristic of the light output. This leads to brighter displays with a higher degree of luminance as compared to conventional microencapsulated electrophoretic displays with substantially Lambertian reflectance where much of the light is not reflected back towards the viewer.
1. A reflective display device, comprising:
a semi-retro-reflective display sheet having one or more convex protrusions to reflect light in a narrow angle relative to the direction of the incident light;
a light guide;
a light source to emit light to the light guide, the light guide configured to redirect light in a substantially perpendicular direction towards a surface of the semi-retro-reflective display sheet;
a front electrode;
a rear electrode;
an optically transparent fluid disposed between the front and the rear electrodes; and
a plurality of electrophoretically mobile particles suspended in the optically transparent fluid.
2. The display device of claim 1 , wherein the light source defines a light emitting diode (LED), cold cathode fluorescent lamp (CCFL) or a surface mount technology (SMT) incandescent lamp.
3. The display device of claim 1 , wherein the front electrode is transparent and disposed on the semi-retro-reflective display sheet.
4. The display device of claim 1 , wherein the rear electrode further comprises a thin film transistor or driven patterned array.
5. The display device of claim 1 , further comprising a voltage source to provide:
a first voltage to move substantially all of the electrophoretically mobile particles toward the rear electrode to allow incident rays to be totally internally reflected at the semi-retro-reflective display sheet towards the viewer; and
a second voltage to move substantially all of the electrophoretically mobile particles toward the front electrode and collect at the semi-retro-reflective surface to thereby frustrate total internal reflection.
6. The display device of claim 1 , further comprising one or more cross walls.
7. The display device of claim 1 , wherein the front light and the semi-retro-reflective display sheet are arranged relative to each other to provide a substantially non-Lambertian light display.
8. The display device of claim 1 , wherein the narrow angle defines an angle in the range of about 10° to about 30°.
9. The display device of claim 1 , wherein the light source and light guide are internal to the reflective display device.
10. The display device of claim 9 , wherein the light guide is configured to selectively redirect light in a direction substantially perpendicular to the surface of the outward sheet of the display.
11. The display device of claim 1 , wherein the light guide further comprises light extractor elements.
12. A reflective display, comprising:
a transparent outer sheet;
a light guide;
a light source to emit light into the light guide, the light guide configured to redirect light in a substantially perpendicular direction-towards a surface of the transparent outer sheet;
a rear electrode;
a perforated sheet situated between the light source and the rear electrode;
a front electrode disposed over the perforated sheet;
a semi-retro-reflective surface over the perforated sheet;
a medium disposed within the cavity formed between the transparent outer sheet and the rear electrode; and
a plurality of electrophoretically mobile particles suspended in the medium.
13. The display device of claim 12 , further comprising one or more cross walls.
14. The display device of claim 12 , wherein the light source, the light guide and the semi-retro-reflective surface are arranged relative to each other to provide a substantially non-Lambertian light display.
15. The display device of claim 12 , wherein the rear electrode further comprises a thin film transistor or driven patterned array.
16. The display device of claim 12 , further comprising a voltage source to communicate with the front and the rear electrodes to selectively move the electrophoretically mobile particles in the fluid, wherein the voltage source provides:
a first voltage to move substantially all of the electrophoretically mobile particles toward the rear electrode to allow incident rays to be reflected at the semi-retro-reflective display sheet towards the viewer; and
a second voltage to move substantially all of the electrophoretically mobile particles toward the front electrode and collect at the semi-retro-reflective surface to thereby absorb incident rays.
17. The display device of claim 12 , wherein the light guide further comprises light extractor elements.
18. A reflective display device, comprising:
a transparent outer sheet;
a light guide;
a light source to emit light into the light guide, the light guide to redirect light in a substantially perpendicular direction towards a surface of the transparent outer sheet;
a rear electrode;
a perforated sheet situated between the light guide and the rear electrode;
a reflective layer disposed over the perforated sheet;
a transparent front electrode disposed over the perforated sheet;
a medium disposed within the cavity formed between the transparent outer sheet and the rear electrode; and
a plurality of electrophoretically mobile particles suspended in the medium.
19. The display device of claim 18 , further comprising one or more cross walls.
20. The display device of claim 18 , wherein the light source and the semi-retro-reflective surface are arranged relative to each other to provide a substantially non-Lambertian light display.
21. The display device of claim 18 , wherein the rear electrode further comprises a thin film transistor or driven patterned array.
22. The display device of claim 18 , wherein the transparent front electrode is comprised of ITO or Baytron™ or electrically conductive particles dispersed in a polymer matrix or a combination thereof.
23. The display device of claim 18 , further comprising a voltage source to communicate a bias with the front and the rear electrodes to selectively move the electrophoretically mobile particles in the fluid, wherein the voltage source provides:
a first voltage to move substantially all of the electrophoretically mobile particles toward the rear electrode to allow incident rays to be reflected at the semi-retro-reflective display sheet towards the viewer; and
a second voltage to move substantially all of the electrophoretically mobile particles toward the front electrode and collect at the semi-retro-reflective surface to thereby absorb incident rays.
24. The display device of claim 18 , wherein the light guide further comprises light extractor elements.