Registered reflective element for a brightness enhanced TIR display
View Patent ↗The brightness of a TIR-based display is enhanced with a registered reflective element by recycling and reflecting light that passes through the dark pupil region of each hemi-spherical protrusion in the hemi-spherical surface back to the viewer. A method to fabricate a brightness enhanced TIR display comprising an apertured membrane with a thin conductive reflective metal layer facing and registered with the pupils of the hemi-spherical surface.
1. A totally internally reflective display with a brightness enhancing structure, the display comprising:
a transparent sheet comprising a plurality of transparent convex or hemi-spherical protrusions on the inward side of said sheet;
a backplane electrode;
a reflective element that is substantially aligned or registered below the dark center or pupil of each said convex or hemi-spherical protrusion to prevent light rays passing through said pupils from not substantially being recycled and reflected back to the display;
a low refractive index medium between the convex or hemi-spherical surface and backplane electrode;
a plurality of light absorbing electrophoretically mobile particles suspended in the low refractive index medium; and
a voltage source for applying a voltage across said low refractive index medium with said suspended light absorbing electrophoretically mobile particles, between the light reflecting electrode and the backplane electrode.
2. The totally internally reflective display with a brightness enhancing structure according to claim 1 , wherein the reflective element is an apertured membrane comprising a conductive reflective coating acting as a front electrode substantially aligned or registered below the dark center or pupil of each said convex or hemi-spherical protrusion to prevent light rays passing through said pupils from not substantially being recycled and reflected back to the display.
3. The totally internally reflective display with a brightness enhancing structure according to claim 2 , wherein the voltage source is switchable to apply:
a first voltage between the conductive light reflecting electrode aligned with the pupils of the convex or hemi-spherical protrusions on the inward surface of the transparent sheet and the backplane electrode, to move substantially all of the particles inwardly through the apertured membrane toward the backplane electrode to allow for total internal reflectance of light rays at the convex or hemi-spherical surface; and
a second voltage between the light reflecting electrode and the backplane electrode, to move substantially all of the particles outwardly through the apertured membrane toward the aligned or registered light reflecting electrode to frustrate total internal reflectance of light rays at the convex or hemi-spherical surface.
4. The totally internally reflective display with a brightness enhancing structure according to claim 3 , further comprising a color filter array.
5. The totally internally reflective display with a brightness enhancing structure according to claim 4 , further comprising a front light.
6. The totally internally reflective display with a brightness enhancing structure according to claim 3 , further comprising a front light.
7. The totally internally reflective display with a brightness enhancing structure according to claim 2 wherein the conductive reflective apertured membrane is substantially aligned with the pupils of the convex or hemi-spherical protrusions of the transparent sheet is fabricated by a photolithographic process.
8. A photolithographic process according to claim 7 comprising a combination of at least one or all of the following sub-processes:
coating a photoresist layer atop the metal layer of the membrane facing the hemispherical surface;
irradiating the photoresist layer with collimated high intensity light through the pupils of the hemi-spherical protrusions;
developing the photoresist layer to leave a desired geometric pattern using a positive or negative resist method;
etching and removing the exposed unneeded metal layer;
etching the membrane to form apertures;
etching the protective metal layer on the membrane facing the backplane electrode; and
stripping the remaining photoresist.
9. The totally internally reflective display with a brightness enhancing structure according to claim 1 further comprising a color filter array.
10. The totally internally reflective display with a brightness enhancing structure according to claim 1 , further comprising a front light.