Method and apparatus for leak-testing an electroluminescent device

• US 20030016361A1
• Filed: 06/17/2002
• Published: 01/23/2003
• Est. Priority Date: 06/19/2001
• Status: Active Grant

• Current Assignee: InnoLux Corporation
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van De Weijer, Peter, Mank, Adrianus Johannes Gerardus
• Granted Patent: US 6,816,255 B2
• Time in Patent Office: Days
• US Class Current: 356/432
• CPC Class Codes: H10K 50/846 comprising getter material or desiccants

Abstract

A method of detecting the leak-in of oxygen in an organic electroluminescent device via the extent of photo-degradation of the electroluminescent organic material is described. The photo-degradation of the electroluminescent organic material is induced by the presence of oxygen, and can be detected by comparing the photo luminescence of the material, before and after illumination of the material with light (e.g. form a laser).

Photo-degradation due to the presence of oxygen in an encapsulated organic electroluminescent device is evidence for a leak in the device, which leak will result in a shorter lifetime of the device.

The invention provides a fast, non-destructive method of inspecting organic electroluminescent devices on leakage, immediately after their production. Leak devices can be identified and discarded, even on-line.

Claims

1. A method of leak-testing an electroluminescent device having at least one organic light-emitting diode, the at least one LED being enclosed in a housing, said method involving photo-oxidation of the LED material.

2. A method as claimed in claim 1, comprising the steps of:

selecting a surface portion of the LED material which is in contact with the atmosphere in the housing,

irradiating said surface portion with light, whereby the irradiated material emits light,

detecting said emission,

generating an output signal which is proportional to an intensity of the detected emission,

analyzing said output signal on a decrease in time of an emission property.

3. A method as claimed in claim 1, characterized in that the analysis takes place in a predetermined period of time.

4. A method as claimed in claim 1, characterized in that the emission is detected by using a photo-electric detector.

5. A method as claimed in claim 1, characterized in that the irradiating light has a wavelength which brings the LED material to a luminescent state.

6. A method as claimed in claim 1, characterized in that the LED material is an organic polymer.

7. A method as claimed in claim 6, characterized in that the LED material is a PPV material.

8. A method as claimed in claim 1, characterized in that the housing accommodates a getter.

9. A method as claimed in claim 1, characterized in that the testing is carried out on-line during manufacture of the electroluminescent device.

10. A method as claimed in claim 1, characterized in that the electroluminescent device is rejected if the decrease surpasses a predetermined value.

11. An apparatus for leak testing an electroluminescent device having at least one light-emitting diode, the at least one LED being encapsulated in a housing, said apparatus comprising:

a source for emitting light in a predetermined wavelength range, said emitted light defining an optical path for irradiating a surface portion of the LED of the EL device to be tested,

means for collecting and detecting the photo-luminescent radiation emitted by said surface portion upon irradiation by the light from the source,

means for generating an output signal which is proportional to an intensity of the detected photo-luminescent radiation.

12. An apparatus as claimed in claim 11, further comprising means for processing the output signal and for generating a reject signal in the case of a leaky EL device.

13. An apparatus as claimed in claim 11, wherein the light source is a laser.

14. An apparatus as claimed in claim 13, wherein the laser produces light of a wavelength which predominantly excites the longest conjugated systems of the organic LED material.

15. An apparatus as claimed in claim 13, wherein the wavelength is longer than 450 nm.

16. An apparatus as claimed in claim 11, wherein one and the same lens is used for irradiating a surface portion of a LED and for collecting of the photo-luminescent radiation of said surface portion.

17. An apparatus as claimed in claim 11, further comprising a video system to determine whether a selected surface area of a LED is suited for leak-testing or not.

18. An apparatus as claimed in claim 11, further comprising a filter in the path of the photo-luminescent radiation, said filter transmitting the photo-luminescent radiation but being non-transmissive to the light emitted by the source.

22. A device as claimed in claim 19 or 20, wherein the LED comprises a PPV material.

23. A device as claimed in claim 19 or 20, wherein the LED comprises a fluorescence material.

19. An electroluminescent device having an organic light-emitting diode accommodated in a housing, said LED having a functional EL surface area and a restricted (localized) non-functional EL surface area which is in contact with the atmosphere in the housing and is reserved for a leak test on the basis of photo-oxidation.

20. An electroluminescent device having an organic light-emitting diode accommodated in a housing, said LED having a functional EL surface area and a restricted (localized) non-functional EL surface area which is in contact with the atmosphere in the housing and has been subjected to a photo-oxidation test.

21. A device as claimed in claim 20, wherein the area which has been subjected to a photo-oxidation test does not present any substantial photo-degradation.