Reduction of intensity ringing in fluorescent displays
View Patent ↗Embodiments of fluorescent display screens having an intermediate layer between a light-emitting fluorescent layer and an excitation filter layer are disclosed. The intermediate layer includes (1) a low-index layer disposed between the light-emitting fluorescent layer and the excitation filter layer and (2) an index bridging layer disposed between the low-index layer and the excitation filter layer. The insertion of the low-index layer and the index bridging layer according to the above configuration reduces the sensitivity of the excitation coupling to the non-uniformities in the excitation filter layer and variability in the output frequency of the excitation source, leading to improved uniformity of display intensity without significant compromise in the excitation coupling efficiency. A index bridging region made of a hard coat also provides abrasion resistance and provides structure rigidity to the adjacent excitation filter layer.
1. A display screen, comprising:
a light-emitting layer configured to emit visible light in a first wavelength range under irradiation of excitation light in a second wavelength range distinct from the first wavelength range, the light-emitting layer having a first side facing a viewer side of the display screen, and a second side facing an excitation side of the display screen;
an excitation filter layer disposed on the excitation side of display screen relative to the light-emitting layer, and configured to selectively reflect the visible light in the first wavelength range and transmit the excitation light in the second wavelength range; and
an intermediate layer disposed between and adjacent to the light-emitting layer and the excitation filter layer, wherein the intermediate layer comprises one or more first regions in contact with the light-emitting layer, and a second region separating the one or more first regions from the excitation filter layer, and wherein the second region has a bridging refractive index between a first refractive index of the one or more first regions and a second refractive index of the excitation filter layer.
2. The display screen of claim 1 , wherein:
the second region of the intermediate layer is a layer of glass; and
the one or more first regions are one or more air gaps created by a plurality of stand-off elements separating the layer of glass from the light-emitting layer.
3. The display screen of claim 1 , wherein:
the second region of the intermediate layer is a layer of PET; and
the one or more first regions are one or more air gaps created by a plurality of stand-off elements separating the layer of PET from the light-emitting layer.
4. The display screen of claim 1 , wherein:
the display screen comprises a plurality of standoff elements separating the second region of the intermediate layer from the light-emitting layer;
the plurality of stand-off elements are a plurality of supporting ridges; and
the plurality of supporting ridges create a plurality of air gaps in a low-index layer separating the second region from the light-emitting layer.
5. The display screen of claim 1 , wherein:
the display screen comprises a plurality of standoff elements separating the second region of the intermediate layer from the light-emitting layer;
the light-emitting layer comprises a plurality of colored fluorescent stripes, and
the plurality of stand-off elements are stripe dividers each separating an adjacent pair of colored fluorescent stripes in the light-emitting layer.
6. The display screen of claim 1 , wherein:
the display screen comprises a plurality of standoff elements separating the second region of the intermediate layer from the light-emitting layer;
the plurality of stand-off elements are a plurality of supporting pillars; and
the plurality of supporting pillars create an air gap separating the second region from the light-emitting layer.
7. The display screen of claim 1 , wherein:
the display screen comprises a plurality of standoff elements separating the second region of the intermediate layer from the light-emitting layer; and
the plurality of stand-off elements each extend through the intermediate layer and at least part of the light-emitting layer.
8. The display screen of claim 1 , wherein:
the display screen comprises a plurality of standoff elements separating the second region of the intermediate layer from the light-emitting layer; and
the plurality of stand-off elements each extend between the light-emitting layer and the excitation filter layer.
9. The display screen of claim 1 , wherein:
the intermediate layer comprises a unitary structure having the bridging refractive index, the unitary structure having a flat first surface in contact with the excitation filter layer, and a ridged second surface in contact with the light-emitting layer, wherein one or more recessed areas on the ridged second surface of the unitary structure form the one or more first regions in the intermediate layer.
10. The display screen of claim 1 , wherein:
the excitation filter layer is a coextruded multi-layer film stack configured to create a transmission resonance for the excitation light in the second wavelength range.
11. The display screen of claim 1 , wherein:
the excitation filter layer is configured to create a transmission resonance for ultra-violet light of 405-415 nm wavelength.
12. The display screen of claim 1 , wherein:
the second region in the intermediate layer reduces intensity variations in the excitation light transmitted through the excitation filter layer to the light-emitting layer that have resulted from manufacturing variability in the excitation filter layer.
13. The display screen of claim 1 , wherein:
the excitation light is ultra-violet light of 405-415 nm wavelength.
14. The display screen of claim 1 , wherein:
the first refractive index is approximately 1.0, the second refractive index is approximately 1.67, and the bridging refractive index is approximately 1.43.
15. The display screen of claim 1 , wherein:
the second region in the intermediate layer has a thickness of approximately 5 microns and the bridging refractive index is approximately 1.4-1.5.
16. The display screen of claim 1 , wherein:
the light-emitting layer is a fluorescent layer having a thickness of approximately ten times a thickness of the second region in the intermediate layer.
17. The display screen of claim 1 , wherein:
the one or more first regions in the intermediate layer each have a thickness of approximately 20 microns and the second region in the intermediate layer has a thickness of approximately 5 microns.
18. The display screen of claim 1 , wherein:
the display screen further comprises a color filter layer on the viewer side of the display screen relative to the light-emitting layer, and the color filter layer comprises a periodic array of colored filter elements configured to transmit different colored light according to a predetermined sub-pixel pattern.
19. The display screen of claim 1 , wherein:
the light-emitting layer is a fluorescent layer emitting broad-spectrum visible light under irradiation of the excitation light.
20. The display screen of claim 1 , wherein:
the light-emitting layer is a fluorescent layer comprising a periodic array of colored fluorescent elements configured to emit different colored light according to a predetermined sub-pixel pattern when irradiated by the excitation light.
21. The display screen of claim 1 , further comprising:
one or more viewer-side layers disposed on the viewer side of the display screen relative to the light-emitting layer, the one or more viewer-side layers including one or more of: a UV block layer, a contrast enhancement layer, and an outer protective layer.
22. The display screen of claim 1 , further comprising:
an excitation source; and
one or more excitation-side layers disposed on the excitation side the display screen relative to the excitation filter layer, the one or more excitation-side layers including one or more of: a Fresnel layer, a servo layer, a mechanical support layer, and an antireflection coating layer.
23. A process for making a display screen, comprising:
applying a coating layer to a first side of an excitation filter layer, the excitation filter layer configured to selectively reflect visible light in a first wavelength range and transmit excitation light in a second wavelength range distinct from the first wavelength range, wherein the coating layer has a bridging refractive index smaller than a refractive index of the excitation filter layer;
applying an adhesive layer to a second side of the excitation filter layer;
laminating the excitation filter layer to a substrate by rolling the adhesive layer to the substrate; and
disposing a light-emitting layer over the coating layer on the first side of the excitation filter layer, wherein the light-emitting layer is separated from the coating layer by a plurality of air gaps.