Organic light-emitting device

Details Organic light-emitting device Organic light-emitting device

2002-09-20

2004-04-20

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Solid-state type

C313S501000, C313S506000, C313S110000, C313S111000, C313S112000, C313S114000, C313S116000, C313S117000, C428S690000, C428S917000

Reexamination Certificate

active

06724140

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an organic light-emitting device (hereinafter abbreviated as OLED), particularly the device can be used preferably as an optical resonator type organic electroluminescence device with high directionality in light output.
BACKGROUND OF THE INVENTION
Optical resonator type OLEDs are characterized by high directionality showing sharp light emission spectra and are expected to be promising in applications such as liquid crystal projectors, optical telecommunications devices, and exposure sources for printers. Aiming at improved directionality, JP-A-9-180883 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposes an OLED comprising a pair of dielectric multilayer reflectors making up a resonator and having an active layer sandwiched therebetween, wherein the resonance wavelength is set in the shorter wavelength than the peak wavelength of the electroluminescence (EL) spectrum thereby to suppress light emitted in directions other than the vertical to the substrate. However, as long as there exists an emission spectrum in the wavelengths shorter than the resonance wavelength, it necessarily follows that shorter wavelength light is emitted with an angle, causing reduction in directionality or emission of light other than the vertical resonance wavelength.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly directional OLED.
The object of the present invention is accomplished by:
(1) An organic light-emitting device (OLED) comprising a substrate, a first reflective mirror, a transparent electrode, an organic light-emitting layer (OLE layer), and a back electrode in this order, which has on the reverse of the substrate a second reflective mirror having R
1
(&thgr;=0°) of 80 to 100% and R
2
(&thgr;=0°) of 0 to 40%, wherein R
1
(&thgr;) is an average reflectance at a wavelength &lgr; being 400 nm to (&lgr;
0
−&Dgr;&lgr;) (where &lgr;
0
is a resonance wavelength; and &Dgr;&lgr;=&lgr;max−&lgr;
0
, &lgr;max is a maximum wavelength that is obtained by measuring reflectance having the same value equal to R&agr; in a wavelength range about 400-700 nm. R&agr; is an average reflectance at a wavelength range from 400 nm to (&lgr;
0
−100) nm.) at an incidence angle &thgr;, and R
2
(&thgr;) is an average reflectance at a wavelength &lgr; is &lgr;
0
to 700 nm at an incidence angle &thgr;; and
(2) An organic light-emitting device comprising a substrate, a first reflective mirror, a transparent electrode, an OLE layer, and a back electrode in this order, which has on the reverse of the substrate a second reflective mirror having d&lgr;(&thgr;)/d&thgr; having an absolute value of 10 or smaller, wherein &lgr;(&thgr;) is a wavelength giving a reflectance (R
1
(&thgr;)+R
2
(&thgr;))/2; and R
1
(&thgr;) and R
2
(&thgr;) are as defined above.
The OLEDs of the present invention include the following preferred embodiments.
(3) An OLED according to (2) above, wherein the second reflective mirror has R
1
(&thgr;=0°) of 80 to 100% and R
2
(&thgr;=0°) of 0 to 40%.
(4) An OLED according to any one of (1) to (3) above, wherein the second reflective mirror is smaller in area than the first reflective mirror.
(5) An OLED according to anyone of (1) to (4) above, wherein the OLED further has third to (n+2)'th reflective mirrors having different reflection characteristics formed on the second reflective mirror.
(6) An OLED according to anyone of (1) to (5) above, wherein the substrate has a thickness of 5 &mgr;m to 10 cm.
(7) An OLED according to anyone of (1) to (6) above, wherein at least one of the first and second reflective mirrors is a multilayer thin film.
(8) An OLED according to (5) above, wherein at least one of the third to (n+2)'th reflective mirrors is a multilayer thin film.
(9) An OLED according to (7) or (8) above, wherein a difference between the highest and the lowest of the refractive indices of materials fabricating the multilayer thin film is 1.0 or smaller.
(10) An OLED according to any one of (7) to (9) above, wherein the number of layers making up the multilayer thin film is 6 or greater.
(11) An OLED according to any one of (7) to (10) above, wherein the multilayer thin film is a dielectric multilayer thin film.
(12) An OLED according to any one of (7) to (11) above, wherein the multilayer thin film contains at least one of ZrO
2
, Al
2
O
3
, TiO
2
, SiO
2
, CeO
2
, CaF
2
, LiF, MgF
2
, Na
3
AlF
6
, CeF
2
, MgO, ThO
2
, SiO, Sb
2
O
3
, In
2
O
3
, ZnO, SnO
2
, HfO
2
, Ta
2
O
5
, ZnS, CdS, CdTe, ZnSe, Sb
2
S
3
, Si, CdSe, and Ge.
(13) An OLED according to any one of (7) to (12) above, wherein the multilayer thin film contains at least one of ZrO
2
, Al
2
O
3
, TiO
2
, and SiO
2
.
(14) An OLED according to any one of (7) to (13) above, wherein the multilayer thin film contains at least one of ZrO
2
and Al
2
O
3
.
(15) An OLED according to any one of (7) to (14) above, wherein the multilayer thin film contains at least one transparent conductive layer.
(16) An OLED according to any one of (7) to (15) above, wherein the multilayer thin film contains at least one of In
2
O
3
, ZnO, and SnO
2
.


REFERENCES:
patent: 5478658 (1995-12-01), Dodabalapur et al.
patent: 5949187 (1999-09-01), Xu et al.
patent: 9-180883 (1997-07-01), None

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