Electroluminescent display with improved light outcoupling

• US 20060152150A1
• Filed: 09/23/2003
• Published: 07/13/2006
• Est. Priority Date: 10/01/2002
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Justel, Thomas, Boerner, Herbert
• Application Number:
  US10/530,149
• Publication Number:
  US 20060152150A1
• Time in Patent Office: Days
• US Class Current: 313/506
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/663 with alkaline earth metals
• CPC Class Codes: C09K 11/7716 Chalcogenides
• CPC Class Codes: C09K 11/7718 with alkaline earth metals
• CPC Class Codes: C09K 11/7729 Chalcogenides
• CPC Class Codes: C09K 11/7786 with alkaline earth metals
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• CPC Class Codes: H10K 2102/3026 Top emission
• CPC Class Codes: H10K 50/844 Encapsulations
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 50/865 comprising light absorbing layers, e.g. light-blocking layers
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]
• CPC Class Codes: H10K 59/873 Encapsulations
• CPC Class Codes: H10K 59/879 comprising refractive means, e.g. lenses
• CPC Class Codes: H10K 59/8792 comprising light absorbing layers, e.g. black layers

Abstract

A full color electroluminescent display is disclosed, the display including a common substrate and an array of electroluminescent devices disposed on the common substrate, wherein each of said electroluminescent devices comprises an electroluminescent layer that is sandwiched between a first and a second electrode, a color converting material that is capable of changing light emitted by the electroluminescent layer into light having a longer wavelength and a stack of 2n+1 transparent dielectric layers wherein n=0, 1, 2, 3, . . . and said transparent dielectric layers show alternating refractive indexes n. The electroluminescent display shows improved light outcoupling.

Claims

1. An electroluminescent display comprising a common substrate and an array of electroluminescent devices disposed on the common substrate, wherein each of said electroluminescent devices comprise an electroluminescent layer which is sandwiched between a first and a second electrode, a color converting material which is capable of changing light emitted by the electroluminescent layer into light having a longer wavelength and a stack of 2n+1 transparent dielectric layers wherein n =0, 1, 2, 3, . . . ,

said transparent dielectric layers having a high refractive index of n>

1.7 or a low refractive index of n<

1.7,

said transparent dielectric layers having a high refractive index n being arranged in alternating manner with said transparent dielectric layers having a low refractive index n,

said stack of 2n+1 transparent dielectric layers being arranged adjacent to one of the electrodes and a dielectric transparent layer having a high refractive index n adjoining said electrode.

2. An electroluminescent display as claimed in claim 1, wherein said transparent dielectric layers having a refractive index n>

1.7 is selected from the group consisting of TiO₂, ZnS and SnO₂.

3. An electroluminescent display as claimed in claim 1, wherein said transparent dielectric layers having a refractive index n<

1.7 is selected from the group consisting of SiO₂, MgF₂ and alumino silicates.

4. An electroluminescent display as claimed in claim 1, wherein said transparent dielectric layers having a high refractive index n is ZnS and said transparent dielectric layers having a low refractive index n is MgF₂.

5. An electroluminescent display as claimed in claim 1, wherein said electroluminescent device is an active matrix device having a pixelated first electrode.

6. An electroluminescent display as claimed in claim 1, wherein a capping layer is placed adjacent to the second electrode and wherein the color converter material is embedded in or placed on top of the capping layer.

7. An electroluminescent display as claimed in one of the claims 1 to 6, wherein the color converting material is selected from the group consisting of (Ba,Sr)₂SiO₄:

Eu, SrGa₂S₄;

Eu, CaS;

Ce, Ba₂ZnS₃;

Ce,K, Lumogen yellow ED206, (Sr;

Ca)₂SiO₄;

Eu, (Y,Gd)₃(Al,Ga)₅O₁₂;

Ce, Y₃Al₅O₁₂;

Ce, Lumogen F orange 240, SrGa₂S₄;

Pb, Sr₂Si₅N₈;

Eu, SrS;

Eu, Lumogen F red 300, Ba₂Si₅N₈;

Eu, Ca₂Si₅N₈;

Eu CaSiN₂;

Eu and CaS;

Eu.

8. An electroluminescent device comprising an electroluminescent layer which is sandwiched between a first and a second electrode, a color converting material which is capable of changing light emitted by the electroluminescent layer into light having a longer wavelength and a stack of 2n+1 transparent dielectric layers wherein n =0, 1, 2, 3, . . . ,

said transparent dielectric layers having a high refractive index of n>

1.7 or a low refractive index of n<

1.7,

said transparent dielectric layers having a high refractive index n being arranged in alternating manner with said transparent dielectric layers having a low refractive index n,

said stack of 2n+1 transparent dielectric layers being arranged adjacent to one of the electrodes and a dielectric transparent layer having a high refractive index n adjoining said electrode.