Whitening method for phosphor's color at off-state in lighting application

Patent metadata

Field	Value
Publication number	US-2019058091-A1
Application number	US-201615760459-A
Country	US
Kind code	A1
Filing date	Sep 20, 2016
Priority date	Sep 21, 2015
Publication date	Feb 21, 2019
Grant date	—

Abstract

A light-emitting device and method of producing a white appearance for a light-emitting device in an off-state are disclosed. The device includes a supporting member, an organic light emitting diode (OLED) disposed on the supporting member and a color conversion layer disposed on the OLED. The color conversion layer comprises phosphor and has a non-white appearance under ambient light when the device is in an off-state. The device further includes one or more whitening layers that have a plurality of whitening particles configured to reduce the absorption of ambient light by the color conversion layer and produce a white appearance for the device in the off-state under ambient light.

First claim

We claim:

1 . A light-emitting device comprising:
a supporting member; an organic light emitting diode (OLED) disposed on the supporting member; a color conversion layer disposed on the OLED, wherein the color conversion layer has a non-white appearance under ambient light; and one or more whitening layers disposed over the OLED and the color conversion layer, wherein the one or more whitening layers comprises a plurality of whitening particles and the one or more whitening layers is configured to reduce the absorption of ambient light by the color conversion layer and produce a white appearance for the device in an off-state under ambient light.

2 . The device of claim 1 , wherein the OLED is configured to emit light at a non-white color and the color conversion layer is configured to convert at least a portion of the non-white color to white.

3 . The device of claim 1 , wherein the total color conversion ratio of the device in the off-state under ambient light is at least half the total color conversion ratio of a comparator light-emitting device in the off-state under ambient light that does not comprise whitening layers.

4 . The device of claim 1 , wherein the one or more whitening layers reduces the color conversion ratio of the device in the off-state under ambient light by at least 50%.

5 . The device of claim 1 , wherein the one or more whitening layers reduces the color conversion ratio of the device in the off-state under ambient light up to 75%.

6 . The device of claim 1 , wherein the color conversion ratio of the device in the off-state under ambient light is less than 20.

7 . The device of claim 1 , wherein the color conversion ratio of the device in the off-state under ambient light is less than 10.

8 . The device of claim 1 , wherein the whitening particles comprise TiO 2 , Al 2 O 3 , ZrO, ZnO or mixtures thereof.

9 . The device of claim 1 , wherein the average diameter of the whitening particles is less than 50 microns.

10 . The device of claim 1 , wherein the supporting member comprises glass, acrylic, aluminum or combinations thereof.

11 . The device of claim 1 , wherein the OLED is a blue OLED comprising GaN and the color conversion layer comprises a YAG phosphor material.

12 . The device of claim 1 , wherein the transmittance of ambient light for the device in the off-state is at least 20% and the reflectance of ambient light for the device in the off-state is at least 70%.

13 . The device of claim 1 , wherein the transmittance and the reflectance of the light-emitting device as a variation of wavelength has a substantially linear relationship.

14 . The device of claim 1 , wherein the one or more whitening layers reduce the transmittance and increase the reflectance of ambient light when the device is in an off-state relative to a comparator light-emitting device that does not comprise a whitening layer.

15 . The device of claim 14 , wherein the transmittance for the device is reduced by at least 50% relative to the comparator light-emitting device.

16 . The device of claim 14 , wherein the reflectance for the device is at least 200% more than the reflectance for the comparator light-emitting device.

17 . A whitening component for a light-emitting device comprising a supporting member, an organic light emitting diode (OLED) disposed on the supporting member, and a color conversion layer disposed on the OLED, wherein the whitening component comprises one or more whitening layers disposed on the color conversion layer, each whitening layer comprising a plurality of whitening particles dispersed in a binder material and configured to whiten the appearance of the device in the off-state under ambient light.

18 . The method of producing a white appearance for a light-emitting device in an off-state, wherein the device comprises a supporting member, an organic light emitting diode (OLED) disposed on the supporting member, and a color conversion layer including an inorganic phosphor material disposed on the OLED, the method comprising:
(a) determining the total color conversion ratio of the light-emitting device; and (b) applying one or more whitening layers over the color conversion layer of the light-emitting device to form a modified light-emitting device, wherein the total color conversion ratio of the modified light-emitting device is at least 75% less than the color conversion ratio of the light-emitting device.

19 . The method of claim 18 , wherein the applying one or more whitening layers over the color conversion layer of the light-emitting device to form a modified light-emitting device further comprises:
(a) determining the total color conversion ratio of the modified light-emitting device; (b) comparing the color conversion ratios of the light-emitting device and the modified light emitting device; and (c) reapplying whitening layers over the color conversion layer until the total color conversion ratio of the modified light-emitting device is at least 75% less than the color conversion ratio of the light-emitting device.

20 . The method of claim 19 , wherein the determining the total color conversion ratio of the light-emitting device and determining the total color conversion ratio of the modified light-emitting device comprises:
(a) determining an initial color conversion ratio (CCR 0 ) using Equation 1 wherein C cof _ CCL 1 is the measured absorbance of the color conversion layer and Light represents a percentage of light exposed on the light-emitting device or the modified light-emitting device
(CCR 0 )=Light %×Ccof_CCL1  Equation 1; and

(b) determining the total color conversion ratio using Equation 2 by creating a geometric sequence having a plurality of terms each representing a value for the scattering of light inside the light-emitting device or the modified light-emitting device, wherein a represents the first term, r represents the common ratio and n represents the number of terms in the geometric sequence

CCRn
=

CCR
0

+

lim

n
→
∞





a


(

r
n

-
1

)

(

r
-
1

Assignees

• Sabic Global Technologies Bv

Inventors

• Kim Sang Hoon
• Chung Ho Kyoon
• Deok Su Jo
• Jung Subin

Classifications

• H01L33/504 Primary

  Electricity · mapped topic

• H01L33/62

  Electricity · mapped topic

• H01L2933/0091

  Electricity · mapped topic

• H01L33/32

  Electricity · mapped topic

• H10K50/854

  comprising scattering means · CPC title