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US 6,211,613 B1Granted
High contrast electroluminescent displays
AssigneeCambridge Display Technology Limited
InventorPaul May
Life of this patent
Estimating the term…
Abstract
The contrast of an electroluminescent display using an organic EL layer is improved by using a circular polariser in front of the surface. The polariser causes ambient light to be absorbed, while allowing transmission of emitted light and therefore improves the contrast of the display.
Claims40
An electroluminescent display, comprising:
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one colour arranged between first and second conductive layers which act as electrodes for said light-emitting device, and having a light reflective surface behind the surface of said at least one light-emissive layer opposed to a transparent viewing surface of said light-emitting device;
- a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- and
- a substrate on which said light-emitting device is disposed, wherein the numerical difference in the refractive indices of the materials of said substrate, said at least one light-emissive layer and said first conductive layer is not more than 0.3.
1 more element
An electroluminescent display, comprising
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one color arranged between first and second conductive layers which act as electrodes for said light-emitting device, and having a light reflective surface behind the surface of said at least one light-emissive layer opposed to a transparent viewing surface of said light-emitting device;
- a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- and
- a substrate on which said light-emitting device is disposed, wherein the refractive indices of the materials of said substrate, said at least one light-emissive layer and said first conductive layer are similar.
1 more element
An electroluminescent display comprising:
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one color arranged between first and second conductive layers which act as electrodes for said light-emitting device and having a light reflective surface behind the surface of said at least one light-emissive layer opposed to a transparent viewing surface of said light-emitting device;
- a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- and
- a substrate on which said night-emitting device is disposed, wherein the refractive index of said substrate is from 1.45 to 2.00, the refractive index of said at least one light-emissive layer is from 1.6 to 2.3 and the refractive index of said first conductive layer is from 1.5 to 2.5.
1 more element
An electroluminescent display, compromising:
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one color arranged between first and second conductive layers which act as electrodes for said light-emitting device, and having a light-reflective surface behind the surface of said at least on light-emissive layer opposed to a transparent viewing surface of said light-emitting device, and a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- wherein said light-emitting device further includes a layer of non-electroluminescent material disposed between said first conductive layer and said at least one light-emissive layer.
An electroluminescent display, comprising:
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one color arranged between first and second conductive layers which act as electrodes for said light-emitting device, and having a light reflective surface behind the surface of said at least one light-emissive layer opposed to a transparent viewing surface of said light-emitting device;
- and a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- wherein not more than 1% of on-axis ambient light is reflected.
An electroluminescent display, comprising:
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one color arranged between first and second conductive layers which act as electrodes for said light-emitting device, and having a light reflective surface behind the surface of said at least one light-emissive layer opposed to a transparent viewing surface of said light-emitting device;
- and a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- wherein the ratio of the emissive brightness of said display to the ambient illuminance is 1:10.
An electroluminescent display, comprising:
- an organic light-emitting device including at least one layer of an organic material for emitting radiation of at least one color arranged between first and second conductive layers which act as electrodes for said light-emitting device, and having a light reflective surface behind the surface of said at least one light-emissive layer opposed to a transparent viewing surface of said light-emitting device;
- and a circular polarizer disposed in front of the viewing surface of said light-emitting device;
- wherein the output brightness of said light-emitting device is not more than 10 cd/m2.
Dependencies are inferred from the claim text.