U.S. patent application number 10/964677 was filed with the patent office on 2005-03-10 for organic electroluminescence device.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Furugori, Manabu, Kamatani, Jun, Moriyama, Takashi, Noguchi, Koji, Okada, Shinjiro, Takiguchi, Takao, Tsuboyama, Akira.
Application Number | 20050052125 10/964677 |
Document ID | / |
Family ID | 18837155 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050052125 |
Kind Code |
A1 |
Moriyama, Takashi ; et
al. |
March 10, 2005 |
Organic electroluminescence device
Abstract
A luminescence device is constituted by a substrate, a first
electrode disposed on the substrate, at least one organic
luminescence function layer disposed on the first electrode, a
second electrode disposed on the above at least one organic
luminescence function layer, and an oxygen absorbent disposed
between the substrate and the second electrode or between the first
and second electrodes. To the luminescence device, a voltage is
applied between the first and second electrodes to cause
phosphorescence from at last one layer constituting the
above-mentioned at least one organic luminescence function layer
preferably containing the oxygen absorbent. The oxygen absorbent
may be formed in a layer disposed at a region other than pixel
portions.
Inventors: |
Moriyama, Takashi;
(Kanagawa-ken, JP) ; Okada, Shinjiro;
(Kanagawa-ken, JP) ; Tsuboyama, Akira;
(Kanagawa-ken, JP) ; Takiguchi, Takao; (Tokyo,
JP) ; Noguchi, Koji; (Kanagawa-ken, JP) ;
Kamatani, Jun; (Kanagawa-ken, JP) ; Furugori,
Manabu; (Kanagawa-ken, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
18837155 |
Appl. No.: |
10/964677 |
Filed: |
October 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10964677 |
Oct 15, 2004 |
|
|
|
09996883 |
Nov 30, 2001 |
|
|
|
Current U.S.
Class: |
313/504 |
Current CPC
Class: |
H01L 51/5012 20130101;
Y10S 428/917 20130101; H01L 51/5072 20130101; H01L 51/5096
20130101; H01L 51/5016 20130101; H01L 51/5259 20130101; H01L
27/3281 20130101 |
Class at
Publication: |
313/504 |
International
Class: |
H01J 001/62; H01J
063/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2000 |
JP |
366549/2000 |
Claims
1-4. (Canceled)
5. A luminescence device array comprising a substrate and a
plurality of luminescence devices disposed on the substrate,
wherein each luminescence device comprises a first electrode
disposed on the substrate, at least one organic luminescence
function layer disposed on the first electrode, a second electrode
disposed on said at least one organic luminescence function layer,
and an oxygen absorbent, wherein a space is defined between a first
electrode of a first luminescence device and a first electrode of a
second luminescence device arranged next to the first luminescence
device in one surface direction of the substrate, and wherein the
oxygen absorbent is Mg and is disposed in the space.
6. A device array according to claim 5, wherein a voltage is
applied between the first and second electrodes to cause
phosphorescence from at least one layer constituting said at least
one organic luminescence function layer.
7. (Cancelled).
8. A device array according to claim 5, further comprising a
sealing housing disposed on the substrate in order to cover the
luminescence devices, and a hygroscopic agent which is sealed in a
space between the luminescence devices and the sealing housing.
9. A device array according to claim 8, wherein the hygroscopic
agent is CaO powder.
Description
FIELD OF THE INVENTION AND RELATED ART
[0001] The present invention relates to an organic
electroluminescence (EL) device used as a light-emitting device for
flat panel displays, projection displays, printers, etc.
[0002] Self-emission type devices for the flat panel display, such
as a plasma emission device, a field emission device, and an
electroluminescence (EL) device have attracted notice in recent
years.
[0003] Of these self-emission type devices, the EL device is
classified into an organic EL device and an inorganic EL
device.
[0004] The inorganic EL device is a self-emission device utilizing
luminescence based on collisional excitation. On the other hand he
organic EL device is a self-emissin device of a carrier
injection-type utilizing luminescence caused at the time of
recombination of electron and hole carried into a luminescence
layer.
[0005] With respect to the organic EL device, T. W. Tang et al.
have substantiated in 1987 that it is possible to realize a
high-luminance luminance (1000 cd/m.sup.2) at a lower voltage (10
volts) by utilizing a lamination structure comprising a film of
fluorescent metal chelate complex and a film of diamine-based
molecules.
[0006] The self-emission device of carrier injection-type has
extensively studied and developed. Specifically, organic EL devices
using low-molecular weight materials for green luminescence or area
color-type luminescence of, e.g., red (R), green (G) and blue (B)
have been commercialized. Further, at present, a full-color organic
EL device has been extensively developed.
[0007] FIGS. 1 and 2 are respectively a schematic sectional view of
an embodiment of an ordinary organic EL device of lamination
organic luminescence function layer-type. Referring to FIGS. 1 and
2, the organic EL device comprises a cathode 11 or 21, an anode 14
or 25, and a lamination organic luminescence function layer,
including a luminescence layer 12 or 23 and a hole transport layer
13 or 24, disposed between the cathode 11 or 21 and the anode 14 or
25. In FIG. 2, an electron transport layer 22 is disposed between
the cathode 21 and the luminescence layer 23.
[0008] Examples of a material for the cathode 11 or 21 may
generally include metals having smaller work functions, such as
aluminum, aluminum-lithium alloy and magnesium-silver alloy.
Further, as a material for the anode 14 or 25 as a transparent
electrode, it is possible to use an electroconductive material
having a lager work function, such as ITO (indium tin oxide), thus
allowing light emission via the transparent electrode.
[0009] The organic luminescence function layers disposed between
the cathode 11 or 21 and the anode 14 or 25 may have a two-layer
structure including the luminescence layer 12 and the hole
transport layer 13 as shown in FIG. 1 and a three-layer structure
including the electron transport layer 22, the luminescence layer
23, and the hole transport layer 24 as shown in FIG. 2.
[0010] The hole transport layer 13 or 24 has a function of
efficiently injecting holes from the anode 14 or 25 to the
luminescence layer 12 or 23. The electron transport layer 22 has a
function of efficiently injecting electrons from the cathode 21 to
the luminescence layer 23. Further, the hole transport layer 13 or
24 and the electron transport layer 22 also have functions of
confining electrons and holes in the luminescence layer 12 or 23,
respectively (i.e., carrier blocking functions), thus enhancing a
luminescence efficiency.
[0011] A commercially available liquid crystal display device as a
full-color flat panel-type display device effects full-color image
display by using, e.g., color filters.
[0012] On the other hand, the organic EL device allows
self-emission of primary colors of red (R), green (G) and blue (B)
by appropriately selecting materials constituting luminescence
layers, thus advantageously provide a resultant EL device with a
high responsiveness and a wide viewing angle.
[0013] In order to realize a sufficiently practical full-color
display device, it is necessary to provide a luminescence device
excellent in luminance, chromaticity, and luminescence efficiency
for respective colors (R, G, B).
[0014] Generally, it is difficult to satisfy the above luminescence
characteristics in combination in the case of forming luminescence
layers for R, G, B of a single material. In order to obviate the
difficulty, an organic EL device of a colorant doping-type wherein
a host material is doped with a fluorescent organic compound
(fluorescent colorant) to shift its emission center wavelength is
generally employed. More specifically, referring again to FIGS. 1
and 2, at least one material for constituting organic luminescence
function layers (the hole transport layer, the electron transport
layer, the luminescence layer, etc.) is used as a host and is doped
with a small amount of the fluorescent colorant to utilize
luminescence from the fluorescent colorant. In this case, it is
possible to use a colorant exhibiting a higher fluorescence
efficiency, thus allowing improvement in quantum efficiency and a
wide latitude in selection of respective luminescence colors.
[0015] With respect to such a fluorescent colorant-doped organic EL
device, Murayama et al. has proposed a luminescence device using an
aluminum quinolinol complex doped with a quinacridone derivative,
whereby a maximum luminance of at least 100,000 cd/m.sup.2 has been
achieved (Preprint for 54th Meeting of the Applied Physics of
Japan, 1127 (1993).
[0016] In the organic EL device, as described above, holes and
electrons carried into a luminescence layer are recombined to form
an excitation state, thus causing luminescence.
[0017] Accordingly, in the organic EL device, excitation energy is
required to suppress consumption thereof in steps other than a
luminescence step in order to efficiently utilize the excitation
energy as that for luminescence in a step of transition of organic
material molecules contributing to luminescence from an excitation
state to a ground state.
[0018] There-are several factors for such energy consumption,
whereby device characteristics are adversely affected considerably.
For example, a luminescence efficiency is lowered to result in a
dark luminescence state or luminescence per se is not caused to
occur.
[0019] Generally, the organic EL device is considerably affected by
moisture (or water content). Specifically, the organic EL device is
accompanied with a defective region causing no luminescence therein
(called "dark spots") due to degradation or deterioration of a
metal electrode and/or adsorption of water content to impurities in
some cases. Such dark spots are gradually enlarged with time by the
influence of water content, thus adversely affecting the life of
the organic EL device.
[0020] Further, in addition to the influence of water content, it
has been generally known that oxygen entering the organic EL device
oxidizes electrodes and/or organic materials used therein, thus
lowering durability of the organic EL device.
[0021] In order to overcome the problem, Japanese Laid-Open Patent
Application (JP-A) 7-169567 has disclosed such a device structure
that a sealing structure including an oxygen absorbent layer for
oxygen absorption and an oxygen barrier layer with little oxygen
permeability is formed outside an organic EL device structure.
[0022] In the organic EL device of this type, however, a
fluorescence organic compound is used as a luminescence center
material as in the above-described conventional EL devices, thus
merely providing a lower quantum efficiency and a lower luminance
relative to power supply.
[0023] This may be attributable to the following mechanism.
[0024] Carriers, such as electrons and holes, injected from a pair
of oppositely disposed electrodes are recombined within a
luminescence layer formed of a organic luminescence function
material to place molecules of the organic luminescence function
material in an excited state (higher energy state) (herein, such
molecules are referred to as "excitons"). The excited state
includes an excited single state and an excited triplet state
determined based on a difference in spin state. In the case of an
ordinary fluorescent organic compound, only fluorescence from the
excited singlet state is observed at room temperature and no
phosphorescence from the excited triplet state is observed.
[0025] In this case, according to the statistical method, excitons
placed in the single state and those placed in the triplet state
may presumably be formed in a ratio of 1:3. For this reason, a
theoretical limit of an internal quantum efficiency in the case of
an organic EL device using a fluorescent material has been
considered to be 25%. Further, in the case of an organic EL device
of a simple lamination-type, an efficiency for taking emitted light
out is ca. 20%, thus resulting in an external quantum efficiency of
ca. 5% as an upper limit value. Indeed, the conventional organic EL
devices at best provide an external quantum efficiency of ca.
5%.
[0026] In order to improve the external quantum efficiency of the
organic EL device, Baldo et al. has proposed an organic EL device
exhibiting an external quantum efficiency increased up to ca. 8% by
using a metal complex containing iridium as a center metal and a
phenylpyrimidine ligand ("Applied Physics Letters", Vol. 75, No. 1,
pp. 4- (1999)). The higher external quantum efficiency may be
attributable to a particular triplet state of the iridium complex
exhibiting a stronger phosphorescence. Based on the stronger
phosphorescence, it is possible to efficiently utilize excitons in
the triplet state occupying the remaining 75% of all the excitons.
As a result, the internal quantum efficiency can be estimated to be
increased up to 100% as the theoretical limit.
[0027] As described above, in recent years, an organic EL device
using a phosphorescent material has attracted notice as a
high-efficiency self-emission device.
[0028] The organic EL device utilizing phosphorescence is, however,
accompanied with a serious problem of oxygen quenching (quenching
due to oxygen) causing deterioration in initial performance or that
with time of the resultant EL device. According to our study, this
problem is particularly noticeable in th case of the organic EL
device using a phosphorescent material compared with that using a
fluorescent material.
[0029] This may be attributable to the following factors (1) and
(2).
[0030] (1) A ground state of oxygen is a triplet state, thus
readily causing energy transfer or transition between the oxygen
triplet state and an excited triplet state of molecules of a
luminescent material to take the excitation energy of the
luminescence material molecules (i.e., oxygen quenching).
[0031] (2) The life of an excited triplet state is longer than that
of an excited single state by at least three digits. For this
reason, a time from the energy excitation step to a subsequent
luminescence step is longer in the case of utilizing
phosphorescence, thus resulting in an increased probability of
consumption of the excitation energy due to energy transition with
no luminescence including the oxygen quenching.
[0032] As a result of our study, it has been confirmed that the
presence of oxygen in an organic EL device particularly using a
phosphorescent material adversely affects not only an initial
luminescence luminance but also the life of the resultant EL
device, such as lowerings in luminescence luminance and
luminescence efficiency when the EL device is continuously or
discontinuously driven for a certain period of time. It has been
also found that such lowerings in luminescence luminance and
efficiency are considerably pronounced when compared with the
conventional organic EL device using a fluorescent material.
SUMMARY OF THE INVENTION
[0033] A principal object of the present invention is to provide an
organic electroluminescence device having solved the
above-mentioned problems.
[0034] A specific object of the present invention is to provide a
high-efficiency organic electroluminescence device using a
phosphorescent material capable of suppressing the influence of
oxygen to improve an initial luminance and present a deterioration
in performances with time in combination.
[0035] According to the present invention, there is also provided a
luminescence device, comprising: a substrate, a first electrode
disposed on the substrate, at least one organic luminescence
function layer disposed on the first electrode, a second electrode
disposed on said at least one organic luminescence function layer,
and an oxygen absorbent disposed between the substrate and the
second electrode.
[0036] According to the present invention, there is also provided a
luminescence device, comprising: a substrate, a first electrode
disposed on the substrate, at least one organic luminescence
function layer disposed on the first electrode, a second electrode
disposed on said at least one organic luminescence function layer,
and an oxygen absorbent disposed between the first electrode and
the second electrode.
[0037] In the luminescence device (organic EL device) of the
present invention, the above-mentioned oxygen absorbent may
preferably be contained in at least one layer constituting the
organic luminescence function layer by blending or co-vapor
deposition or disposed in proximity to the organic luminescence
function layer using a phosphorescent material, thus allowing
absorption and/or adsorption of oxygen within the luminescence
device to effectively suppress not only a lowering in initial
luminescence luminance but also a deterioration in performances
(e.g.,. luminescence efficiency) of the device with time at
repetitive use.
[0038] These and other objects, features and advantages of the
present invention will become more apparent upon a consideration of
the following description of the preferred embodiments of the
present invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIGS. 1 and 2 are respectively a schematic sectional view of
an ordinary organic electroluminescence device.
[0040] FIG. 3 is a schematic sectional view of an embodiment of the
luminescence device organic electroluminescence device according to
the present invention.
[0041] FIG. 4 is a schematic sectional view of an embodiment of the
luminescence device of a simple matrix-type according to of the
present invention.
[0042] FIG. 5 is a time chart of a drive waveform for driving the
luminescence device employed in Example 2 appearing
hereinafter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] The organic electroluminescence device according to the
present invention basically has a structure shown in FIG. 3.
[0044] Referring to FIG. 3, an organic EL device includes: a
substrate 1, an anode 2, at least one organic luminescence function
layer 2 including an organic luminescence function layer 4
containing an oxygen absorbent, a cathode 5, a sealing housing (or
casing) 6, an adhesive resin 7, and a hygroscopic agent 8. The
substrate 1, the sealing housing and the adhesive resin together
constitute a sealing means.
[0045] The substrate 1 may preferably be formed of a transparent
heat-resistant material, such as glass.
[0046] On the substrate 1, the anode 2 as a transparent electrode
is formed. Examples of a material for the anode (transparent
electrode) 2 may include those exhibiting a higher work function,
such as CuI, ITO (indium tin oxide) and SnO.sub.2, so as to improve
a hole injection efficiency from the anode.
[0047] On the anode 2, at least one organic luminescence function
layer 3 at least containing a luminescent material. The organic
luminescence function layer 3 may have a single-layer structure or
a lamination-layer structure which includes two layers comprising a
luminescence layer and an electron transport layer or a hole
transport layer; three layers comprising a luminescence layer, an
electron transport layer and a hole transport layer; and four or
more layers including the above layers. The organic luminescence
function layer 3 may be formed by vacuum deposition or spin
coating.
[0048] The luminescence layer contained in the organic luminescence
function layer 3 comprises a phosphorescent material, such as a
metal complex containing a heavy metal (as a center metal) having a
large spin-orbit interaction (e.g., Ru, Rh, Pd, Os, Ir Pt, Au,
etc.). Representative examples of the phosphorescent material may
include iridium complexes having a ligand, such as phenylpyridine o
or thienyl-pyridine; and platinum porphyrin derivatives.
[0049] The oxygen absorbent used in the present invention may be
contained in a part of the organic luminescence function layer 3 or
the entire organic luminescence function layer 3. In FIG. 3, the
oxygen absorbent is contained in the organic luminescence function
layer 4 constituting the three-layer type organic luminescence
function layer 3 as a part of the organic luminescence function
layer 3.
[0050] Examples of a material for the oxygen absorbent may include
metals having a lower work function such as alkali metal and alkali
earth metal; and compounds including metal oxides, such as iron
oxide.
[0051] Herein, the oxygen absorbent refers to a substance capable
of selectively absorbing and/or adsorbing oxygen physically or
chemically.
[0052] The organic luminescence function layer containing the
oxygen absorbent may be formed by co-vacuum deposition of the
oxygen absorbent with the organic luminescence function material
(such as a luminescent material) or by spin-coating a solution of
an oxygen absorbent powder in an appropriate solvent (such as
chloroform).
[0053] On the organic luminescence function layer 3, the cathode 5
as a metal electrode is formed, thus preparing an organic EL device
having a principal structure.
[0054] Examples of a material for the cathode 5 may preferably
include those having a lower work function, such as Mg-Ag ally, Al,
and Al-Li alloy, so as to improve an electron injection efficiency
from the cathode.
[0055] In order to hermetically seal up the above-prepared organic
EL device so as to block ambient air, the housing 6 is bonded to
the substrate 1 at a periphery thereof so as to enclose the organic
EL device by using the adhesion resin 7.
[0056] Examples of a material for the housing 6 may preferably
include a moisture barrier material, such as glass or metal.
Examples of a material for the adhesive resin 7 may preferably
include epoxy resin and UV (ultraviolet)-curable resin.
[0057] At the inner surface of the sealing housing 6, the
hygroscopic agent 8 may preferably be disposed in order to suppress
the influence of moisture (water content). Examples of a material
for the hygroscopic agent 8 may preferably include oxides, such as
calcium oxide and barium oxide.
[0058] With a spacing between the sealing housing 6 and the organic
EL device of the present invention, inert gas such as rare gas
(e.g., argon gas) or nitrogen gas may preferably be filled in order
to remove gases adversely affecting the organic EL device including
oxygen.
[0059] In the present invention, the oxygen absorbent may be
disposed not only within the organic EL device but also within the
sealing housing at the same time.
[0060] FIG. 4 shows another embodiment of the luminescence device
(organic EL device) according to the present invention.
[0061] Referring to FIG. 4, in this embodiment, the organic EL
device includes an oxygen absorbent 53 formed on a substrate 51 in
a stripe shape at a spacing between stripe-shaped first electrodes
52. On the first electrode 52, an organic luminescence function
layer 54 containing a luminescence layer is disposed. On the
organic luminescence function layer 54, stripe-shaped second
electrodes 55 ar disposed so as to intersect the first electrodes
52 to form a matrix of pixels each at an intersection.
[0062] Hereinbelow, the present invention will be described more
specifically based on Examples.
EXAMPLE 1
[0063] On a 1.1 mm-thick glass substrate (20.times.25 mm), a ca.
100 nm-thick transparent electrode (anode) of ITO (indium tin
oxide) was formed by sputtering, followed by patterning.
[0064] On the ITO electrode, four organic luminescence function
layers (first to fourth layers) were successively formed in the
following manner.
[0065] First, on the ITO electrode, a 40 nm-thick first layer (hole
transport layer) of .alpha.-NPD (N4,N4'-di-naphthalene
-1-yl-N4,N4'-diphenylbiphenyl-4,4'-diamine) shown below was formed
by vacuum deposition (2.7.times.10.sup.-3 Pa). 1
[0066] On the first layer, a 40 nm-thick second layer (luminescence
layer) of a luminescent material comprising CPB
(4,4'-N,N'-dicarbazole biphenyl) shown below and Ir(ppy).sub.3 (fac
tris(2-phenylpyridine)iridium) (CBP: Ir(ppy).sub.3=93:7 by weight)
by co-vacuum deposition (2.7.times.10.sup.-3 Pa) at a controlled
deposition rate. 2
[0067] On the second layer, a 10 nm-thick third layer (exciton
diffusion prevention layer) of BCP
(2,9-dimethyl-4,7-diphenyl-1-,10-phenanthroline (Bathocuproin))
shown below doped with 1 wt. % of Mg (magnesium) by co-vacuum
deposition (2.7.times.10.sup.-3 Pa) at a controlled deposition
rate. 3
[0068] On the third layer, a 20 nm-thick fourth layer (electron
injection layer) of Alq3 (tris(8-hydroxyquinoline)aluminum
(aluminum-quinolinol complex)) shown below doped with 1 wt. % of Mg
by co-vacuum deposition (2.7.times.10.sup.-3 Pa) at a controlled
deposition rate. 4
[0069] In this example, as an oxygen absorbent, Mg was used in the
third and fourth layers in a form of co-deposited film.
[0070] On the thus-formed four organic luminescence function
layers, a 150 nm-thick Al electrode (cathode) was formed by vacuum
deposition (2.7.times.10.sup.-3 Pa) with a hard mask of stainless
steel so as to provide a matrix of pixels each having an area of 3
mm.sup.2 at each intersection with the patterned ITO electrode,
thus preparing an organic EL device according to the present
invention.
[0071] The thus-prepared organic EL device was placed in a glove
box filled with nitrogen gas, and a sealing housing of glass was
bonded thereto by using an epoxy resin adhesive. At that time, CaO
powder (hygroscopic agent) was sealed in a spacing between the EL
device and the sealing housing.
[0072] Characteristics of the EL deice were measured at room
temperature by using a microammeter ("Model 4140B", mfd. by
Hewlett-Packard Co.) for a current-voltage characteristic and a
luminance meter ("Model BM 7", mfd. by Topcon K. K.) for a
(luminescence) luminance. As a result, the EL device of the present
invention showed a good rectification characteristic.
[0073] More specifically, when the organic EL device was driven by
applying a voltage of 12 volts between the ITO electrode (anode)
and the Al electrode (cathode), the EL device showed a current
density of 9 mA/cm.sup.2 and a luminance of 1900 cd/m.sup.2. At
that time, a higher external quantum efficiency of 5.7% was
obtained.
[0074] Then, when a change in luminance from an initial luminance
of 100 cd/m.sup.2 of the EL device was measured by continuously
driving the EL device at a constant current, the EL device
exhibited a luminance half-life (a time for decreasing the initial
luminance ((100 cd/m.sup.2) to 1/2 thereof (50 cd/m.sup.2)) of 498
hours.
COMPARATIVE EXAMPLE 1
[0075] An organic EL device was prepared and evaluated in the same
manner as in Example 1 except that PCB (for the third layer) and
Alq 3 (for the fourth layer) were not doped with Mg (i.e., the
oxygen absorbent was not used at all).
[0076] The resultant organic EL device exhibited a current density
of 8.4 mA/cm.sup.2 (under application of a voltage of 12 volts), a
luminance of 1200 cd/m.sup.2, an external quantum efficiency of
3.9%, and a luminance half-lie of 272 hours, thus providing EL
characteristics inferior to those of the EL device prepared in
Example 1.
EXAMPLE 2
[0077] A simple matrix-type organic EL device as shown in FIG. 4
was prepared in the following manner.
[0078] On a 1.1 mm-thick glass substrate 51 (75.times.75 mm), a ca.
100 nm-thick transparent electrode 52 of ITO (anode) was formed by
sputtering, followed by patterning in a stripe form including 100
lines each having a width of 100 .mu.m and a spacing (with an
adjacent line) of 40 .mu.m.
[0079] On the stripe ITO electrode 52, an oxygen absorbent of Mg
was formed by vacuum deposition with a mask in a stripe pattern 53
at respective center portions of the spacing of the stripe ITO
electrode 52 so as to have a width of 10 .mu.m and a thickness of
50 nm (for each stripe Mg layer).
[0080] On the ITO electrode 52 and the stripe pattern 53 of Mg,
four organic luminescence function layers 54 were formed in the
same manner as in Example 1 except that Mg (as the oxygen
absorbent) was not used at all.
[0081] Then, on the organic luminescence function layers 54, a
lamination metal electrode (cathode) 55 comprising a 10 nm-thick
Al-Li alloy layer (Li: 1.3 wt. %) and a 150 nm-thick Al layer
(disposed on the Al-Li alloy layer) was formed by vacuum deposition
(2.7.times.10.sup.3 Pa), followed by patterning in a stripe form
including 100 lines (each having a width of 100 .mu.m and a spacing
of 40 .mu.m) arranged so as to intersect the stripe ITO electrode
52 at right angles, thus preparing an organic EL device including a
matrix of pixels (100.times.100 pixels) each at an intersection of
the lines of ITO and metal electrodes.
[0082] The thus-prepared EL device was placed in a glove box filled
with nitrogen gas, and a sealing housing of glass (having an area
sufficient to enclose the entire EL device) was bonded to the EL
device by using an epoxy resin adhesive. At that time, CaO powder
(hygroscopic agent) was sealed in a spacing between the EL device
and the sealing housing.
[0083] The EL device (100.times.100 pixels) was then driven in a
simple matrix manner (frame frequency: 30 Hz, interlace scanning
manner) in the glove box by applying a drive waveform of 7-13 volts
(scanning signal voltage: 10 volts, data signal voltage: .+-.3
volts) as shown in FIG. 5.
[0084] As a result, it was confirmed that the EL device provided
smooth motion picture images.
[0085] When the EL device (including 100.times.100 lines) was
driven in a line-sequential manner, the EL device showed an initial
luminance of 34 cd/m.sup.2 in a whole area-luminance state.
Further, when the EL device was continuously driven, a resultant
luminance half-life was 460 hours.
COMPARATIVE EXAMPLE 2
[0086] A simple matrix-type organic EL device was prepared and
evaluated in the same manner as in Example 2 except that the stripe
Mg layer 53 was not formed (i.e., the oxygen absorbent was not used
at all).
[0087] The thus-prepared EL device exhibited an initial luminance
of 19 cd/m.sup.2 and a luminance half-life of 202 hours, thus being
considerably inferior in EL characteristics to those of the EL
device prepared in Example 2.
[0088] As described hereinabove, according to the present
invention, it is possible to provide a high-efficiency organic EL
device (luminescence device) expected to be further improved in
luminescence efficiency with an increased initial luminance and a
suppressed deterioration in performance with time while preventing
the adverse influence of oxygen.
[0089] The organic EL device according to the present invention may
be applicable to display apparatus, illumination apparatus, a light
source for a printer, a backlight of a liquid crystal display
apparatus, etc.
[0090] When the EL device was used in combination with a
simple-matrix electrode structure or active elements (e.g., TFTs
(thin film transistors)) to constitute a display apparatus, it
becomes possible to provide flat panel display with an energy
saving effect, a high visibility and lightweight properties.
[0091] When the EL device is used as a light source for a printer,
it becomes possible to utilize the EL device as a laser light
source for a laser beam printer. In this case, for example, the EL
device as the laser light source is arranged in array to effect a
desired light-exposure to a photosensitive drum, thus allowing
image formation.
[0092] By the use of the EL device of the present invention, it is
possible to remarkably reduce the size (or volume) of the
above-mentioned apparatus.
[0093] Further, with respect to the illumination apparatus and the
backlight, a good energy saving effect based on the use of a
high-efficiency luminescence device according to the present
invention can be expected.
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