U.S. patent application number 10/869728 was filed with the patent office on 2004-12-09 for organic el device and method for its manufacture.
Invention is credited to Fujimori, Masayuki, Kawaguchi, Yohei, Nakada, Hitoshi, Nishino, Atsushi, Nonaka, Yoshitaka, Ohata, Hiroshi, Ohyama, Kaneto.
Application Number | 20040248478 10/869728 |
Document ID | / |
Family ID | 18652109 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040248478 |
Kind Code |
A1 |
Nakada, Hitoshi ; et
al. |
December 9, 2004 |
Organic EL device and method for its manufacture
Abstract
An organic EL device comprising: 1) a laminate consisting of an
opposed pair of electrodes and an organic light-emitting layer
sandwiched between the electrode, 2) a gas-tight housing
accommodating the laminate and shielding off the external
atmosphere, and 3) a sheet-like preformed moisture-absorbing body
which is stretched and fabricated outside the gas-tight housing in
advance, disposed in isolation from the laminate within the
gas-tight housing, the preformed moisture-absorbing body being
fixedly secured to at least one part of the gas-tight housing, and
the preformed moisture-absorbing body comprising a desiccant and a
resin component.
Inventors: |
Nakada, Hitoshi;
(Yonezawa-shi, JP) ; Ohata, Hiroshi;
(Yonezawa-shi, JP) ; Nonaka, Yoshitaka;
(Yonezawa-shi, JP) ; Nishino, Atsushi;
(Neyagawa-shi, JP) ; Kawaguchi, Yohei; (Osaka-shi,
JP) ; Fujimori, Masayuki; (Shiga-ken, JP) ;
Ohyama, Kaneto; (Shiga-ken, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
18652109 |
Appl. No.: |
10/869728 |
Filed: |
June 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10869728 |
Jun 16, 2004 |
|
|
|
09854067 |
May 10, 2001 |
|
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Current U.S.
Class: |
439/894 |
Current CPC
Class: |
H01L 51/5259 20130101;
Y10T 428/231 20150115 |
Class at
Publication: |
439/894 |
International
Class: |
H01R 009/22 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2000 |
JP |
2000-145627 |
Claims
What is claimed is:
1. An organic EL device comprising: 1) a laminate consisting of an
opposed pair of electrodes and an organic light-emitting layer
sandwiched between the electrode, 2) a gas-tight housing
accommodating said laminate and shielding off the external
atmosphere, and 3) a sheet-like preformed moisture-absorbing body
which is stretched and fabricated outside the gas-tight housing in
advance, disposed in isolation from said laminate within said
gas-tight housing, said preformed moisture-absorbing body being
fixedly secured to at least one part of said gas-tight housing, and
said preformed moisture-absorbing body comprising a desiccant and a
resin component.
2. The organic EL device according to claim 1 wherein said
moisture-absorbing body is a body obtained by forming a mixture
consisting of a desiccant and a resin component.
3. The organic EL device according to claim 1 wherein the desiccant
comprises at least one member selected from the group consisting of
alkaline earth metal oxides and sulfate salts.
4. The organic EL device according to claim 1 wherein said resin
component is at least one kind of gas-permeable resin.
5. The organic EL device according to claim 1 wherein said resin
component is selected from the group consisting of polyolefins,
polyacrylic acids or esters, polyacrylonitrile, polyamides,
polyesters, epoxy resins and polycarbonates.
6. The organic EL device according to claim 1 wherein said resin
component is selected from the group consisting of polyethylene,
polypropylene, polybutadiene and polyisoprene.
7. The organic EL device according to claim 1 wherein the amount of
said desiccant is about 30 to 85 weight % and that of said resin
component is about 70 to 15 weight % based on 100 weight % of the
desiccant and resin component combined.
8. The organic EL device according to claim 1 wherein the amount of
said desiccant is about 40 to 80 weight % and that of said resin
component is about 60 to 20 weight % based on 100 weight % of the
desiccant and resin component combined.
9. The organic EL device according to claim 1 wherein the amount of
said desiccant is about 50 to 70 weight % and that of said resin
component is about 50 to 30 weight % based on 100 weight % of the
desiccant and resin component combined.
10. The organic EL device according to claim 1 wherein said resin
component is polyolefin.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of U.S. patent
application Ser. No. 09/854,067, filed May 10, 2001, which claims
priority to Japanese Patent Application No. 2000-145627, filed May
17, 2000. The disclosure of the United States Patent Application is
herein incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a novel organic
electroluminescent device and a method of manufacturing the
same.
[0004] 2. Description of the Related Art
[0005] The organic EL (electroluminescent) device is a structural
entity comprising an organic light-emitting layer comprised of an
organic compound sandwiched between a pair of electrodes. The
organic EL, which is expected to find application in flat panel
displays and similar devices, has various characteristics such as
high-luminance emission, high-speed response, high
energy-converting rate, and high color development.
[0006] However, when an organic EL device is driven for long
periods of time, the device suffers a degradation in light emission
characteristics such as a decrease in overall emission luminosity
and a loss of uniformity that produces dark spots. For instance,
moisture may be adsorbed from the surfaces of component parts of
the organic EL device and propagate into the laminate, which
consists of a pair of electrodes with a light-emitting substance
sandwiched therebetween, via surface defects in the negative
electrode. The resulting delamination between the light-emitting
substance and the negative electrode blocks the flow of an electric
current to cause photoemission-free spots that appear as dark
spots.
[0007] To eliminate this drawback of dark spots, it is essential to
reduce the level of humidity within the organic EL device. One
means for reducing humidity in an organic EL is the use of a
protective layer containing a desiccant and a sealing layer that
are disposed adjacent to the laminate containing the positive
electrode, organic light-emitting substance, and negative electrode
(Japanese Unexamined Patent Publication H7-169567).
[0008] However, the use of such protective layers gives rise to
other problems. For instance, the protective layer results in an
increased risk leak currents and a cross talk, both of which tend
to produce undesired effects on the photoemission characteristics
of the device.
[0009] Another method that is used to resolve the moisture problem
is the use of an organic EL device comprising a gas-tight housing
containing a laminate consisting of a pair of electrodes and an
organic electroluminescent substance layer sandwiched between the
electrodes. A desiccating means is disposed apart from the laminate
comprising diphosphorus pentoxide (P.sub.2O.sub.5) in a
hermetically sealed condition (Japanese Unexamined Patent
Publication H3-261091).
[0010] However, with this technology, the desiccant P.sub.2O.sub.5
absorbs atmospheric moisture and dissolves to give phosphoric acid
which would adversely affect the laminate. Moreover, the method
which can be used for sealing the desiccant P.sub.2O.sub.5 into the
housing is limited so that the technology is not suited for
commercial-scale production.
SUMMARY OF THE INVENTION
[0011] A primary object of the present invention is to provide a
more expedient and positive desiccating means for use in an organic
EL device.
[0012] The inventor of the present invention did much research with
the above drawbacks of the prior art in mind and found that the
above object can be accomplished by fixing a preformed
moisture-absorbing body within a gas-tight housing. The present
invention has accordingly been developed.
[0013] The present invention, therefore, is directed to the
following organic EL devices and methods of manufacturing them.
[0014] 1. An organic EL device comprising 1) a laminate consisting
of a pair of electrodes and an organic light-emitting layer
sandwiched therebetween, 2) a gas-tight housing accommodating said
laminate and shielding off the external atmosphere and 3) a
desiccating means disposed apart from said laminate within said
airtight housing, characterized in that a preformed
moisture-absorbing body as said desiccating means is fixedly
secured to at least one part of said gas-tight housing.
[0015] 2. An organic EL device according to above paragraph 1
wherein said preformed moisture-absorbing body comprises a
desiccant and a resin component.
[0016] 3. An organic EL device according to above paragraph 1
wherein said preformed moisture-absorbing body is an artifact
obtained by shaping a mixture of a desiccant and a resin component
into a body.
[0017] 4. An organic EL device according to the above paragraph 2
or 3 wherein the desiccant comprises at least one member selected
from the group consisting of alkaline earth metal oxides and
sulfate salts.
[0018] 5. An organic EL device according to the above paragraph 2
or 3 wherein said resin component is at least one kind of
gas-permeable resin.
[0019] 6. A method of manufacturing an organic EL element
comprising 1) providing a laminate consisting of a pair of
electrodes and an organic light-emitting layer sandwiched
therebetween, 2) providing a gas-tight housing accommodating said
laminate and shielding off the external atmosphere and 3) disposing
a desiccating means apart from said laminate within said gas-tight
housing, characterized in that the method includes a step of fixing
said preformed moisture-absorbing body as desiccating means to at
least one part of said gas-tight housing.
[0020] 7. A method of manufacturing an organic EL element
comprising 1) providing a laminate consisting of a pair of
electrodes and an organic light-emitting layer sandwiched
therebetween, 2) providing a airtight housing accommodating said
laminate and shielding off the external atmosphere and 3) disposing
a desiccating means apart from said laminate within said airtight
housing, characterized in that the method includes a first step
comprising fabricating a preformed moisture-absorbing body
comprising a desiccant and a resin component and a second step
comprising fixing said preformed moisture-absorbing body as
desiccating means to at least one part of said gas-tight
housing.
[0021] 8. A manufacturing method according to the above paragraph 7
wherein said first step comprises providing a mixture consisting of
a desiccant and a resin component into the preformed
moisture-absorbing body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic diagram (sectional view) showing an
organic EL device according to embodiments of the present
invention.
[0023] FIG. 2 is a schematic diagram (sectional view) of the
organic EL device manufactured in accordance with one embodiment of
the present invention as described in Example 1.
[0024] FIG. 3 is an image of the organic EL device according to the
embodiment of the present invention described in Example 1 prior to
an accelerated moisture absorption test.
[0025] FIG. 4 is an image of the organic EL device according to the
embodiment of the present invention described in Example 1 after an
accelerated moisture absorption test.
[0026] FIG. 5 is an image of a prior art organic EL device
according -to Comparative Example 1 prior to an accelerated
moisture absorption test.
[0027] FIG. 6 is an image of a prior art organic EL device
according to Comparative Example 1 after an accelerated moisture
absorption test.
[0028] FIG. 7 is an image of a prior art organic EL device
according to Comparative Example 2 prior to an accelerated moisture
absorption test.
[0029] FIG. 8 is an image of a prior art organic EL device
according to Comparative Example 2 after an accelerated moisture
absorption test.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] An organic EL device according to the present invention
comprises an organic EL device comprising 1) a laminate consisting
of a pair of electrodes and an organic light-emitting layer
sandwiched between the two electrodes, 2) a gas-tight housing
accommodating said laminate and shielding off the external
atmosphere and 3) a desiccating means disposed apart from said
laminate within said gas-tight housing, wherein the desiccating
means is a preformed moisture-absorbing body. The preformed
moisture-absorbing body is fixedly secured inside the gas-tight
housing. Thus, except for the use of the preformed
moisture-absorbing body as desiccating means, the organic EL device
according to the present invention may be have the same structural
components as those of previously known organic EL devices [i.e.,
electrodes (positive and negative), organic light-emitting layer,
casing (gas-tight housing), substrate, carrier, etc.]. In certain
embodiments, an organic EL device (1), as depicted in FIG. 1,
comprises a glass substrate (2) attached to an ITO electrode (3),
an organic light-emitting layer (4), and a negative electrode (5).
The ITO electrode (3), the organic light-emitting layer (4), and
the negative electrode (5) together form a laminate (6). The device
(1) further comprises a desiccating means (8) not contacting said
laminate (6) and a glass seal can (7) that is attached to the glass
substrate (2) by a sealant (9).
[0031] While the laminate (6) for the organic EL device (1)
illustrated in FIG. 1 comprises a three-layer structure (i.e., the
ITO electrode (3), the organic light-emitting layer (4) and the
negative electrode (5)), the invention may optionally be embodied
as a multi-layer structure additionally comprising one or more
carrier transport layers, such as an electron transport layer, a
positive hole transport layer, or the like.
[0032] The desiccating means (8) is disposed apart from said
laminate (6). The laminate (6) and desiccating means (8) are sealed
inside a gas-tight housing defined by said glass substrate (2) and
the glass seal can (7) jointed with said sealant (9) in gas-tight
relation. The interior of the gas-tight housing is filled with a
dehumidified inert gas or maintained in a vacuum or substantially
vacuum condition.
[0033] In the present embodiment, said preformed moisture-absorbing
body (8) as desiccating means has been fixed to said gas-tight
housing in at least one location internally thereof.
[0034] The preformed moisture-absorbing body (8) is not
particularly restricted, insofar as the moisture within the
gas-tight housing may be reduced or removed. For example, a formed
body (8) comprising a desiccant and a resin component can be used
with advantage. The shape of the preformed moisture-absorbing body
(8) is not particularly restricted but can be judiciously selected
according to the intended use or application of the end product and
the location of use, among other variables. Thus, a sheet, pellet,
tablet, film, and grain(granule) can be cited as examples. The size
of the body can be judiciously selected with reference to the size
of the housing, among other variables.
[0035] The desiccant component of the preformed moisture-absorbing
body (8) is not particularly restricted in its capability for
adsorbing moisture. It is preferred, however, that the desiccant
component of the preformed moisture-absorbing body (8) comprise a
compound which is not only capable of chemical adsorption of
moisture but is also able to retain a solid state after the
adsorption. As examples of such compound, there can be mentioned
oxides of metals and salts of metals with inorganic acids or
organic acids. In the practice of the invention, it is particularly
preferred that the desiccant component of the preformed
moisture-absorbing body (8) comprise at least one member selected
from among alkaline earth metal oxides and sulfate salts.
[0036] The alkaline earth metal oxides include calcium oxide (CaO),
barium oxide (BaO) and magnesium oxide (MgO), among others.
[0037] The sulfate salts include lithium sulfate
(Li.sub.2SO.sub.4), sodium sulfate (Na.sub.2SO.sub.4), calcium
sulfate (CaSO.sub.4), magnesium sulfate (MgSO.sub.4), cobalt
sulfate (CoSO.sub.4), gallium sulfate (Ga.sub.2(SO.sub.4).sub.3),
titanium sulfate (Ti(SO.sub.4).sub.2), and nickel sulfate
(NiSO.sub.4), among others. Aside from the above, various
hygroscopic organic materials can also be used as the desiccant (8)
in the practice of the invention.
[0038] Also, the resin component of the preformed body (8) is not
particularly restricted so long as it does not interfere with the
moisture-removing action of the desiccant but is preferably a
highly gas-permeable material (that is to say a material with a low
gas barrier potential, particularly a gas-permeable resin). As
examples of such material, there can be mentioned polymeric
materials inclusive of polyolefins, polyacrylic acids or esters,
polyacrylonitrile, polyamides, polyesters, epoxy resins and
polycarbonates. Among them, polyolefin materials are preferred for
purposes of the invention. Specifically, polyethylene,
polypropylene, polybutadiene, polyisoprene, and the corresponding
copolymers can be mentioned.
[0039] In the present invention, the amounts of the desiccant and
resin component can be judiciously established according to the
respective types. Usually, however, based on 100 weight % of the
desiccant and resin component combined, the amount of the desiccant
component of the preformed body (8) may be about 30 weight % to
about 85 weight % and that of the resin component of the preformed
body (8) may be about 70 weight % to about 15 weight %. The
preferred proportions are about 40 weight % to about 80 weight % of
the desiccant and about 60 weight % to about 20 weight % of the
resin component. The most preferred are about 50 weight % to about
70 weight % of the desiccant component of the preformed body (8)
and about 50 weight % to about 30 weight % of the resin component
of the preformed body (8).
[0040] The preformed moisture-absorbing body (8) can be produced by
blending the above component materials evenly and forming the blend
into an optional shape. In such cases, the desiccant or gas
absorbent, is preferably dried thoroughly prior to formulation.
Moreover, the blending with the resin component of the preformed
body (8) may be carried out under heating as needed to prepare a
molten mass. A molding technology can be used, including any known
forming(molding) or granulation technology, such as press-forming
(inclusive of hot-pressing), extrusion, or granulation with a
rolling granulator, a twin-screw granulator, or the like.
[0041] In the present invention, the preformed moisture-absorbing
artifact (8) is preferably a body obtained by forming a mixture
consisting of a desiccant and a resin component. In order to avoid
untoward effects after installation into the organic EL device (1),
the preformed moisture-absorbing body (8) is preferably
substantially free of impurities such as solvents.
[0042] Furthermore, in case the preformed moisture-absorbing body
(8) is a sheet, this sheet can be stretched prior to use with
advantage. This stretching can be carried out according to known
methods, and may be uniaxial stretching or biaxial stretching.
Moreover, it is also possible to use, with advantage, a body
prepared using a fluororesin as the resin component by processing a
composition comprising the resin and a desiccant into a sheet and
subjecting the sheet to fibrillation.
[0043] When so formed into a sheet, the thickness of the preformed
moisture-absorbing body (8) can be judiciously selected according
to the intended use of the end product. For example, when the
organic EL device (1) of the invention is to be used as a portable
telephone display device, the usual thickness may be from about 50
.mu.m to about 400 .mu.m, preferably from 100 .mu.gm to 200 .mu.m
.
[0044] In the organic EL device (1) according to the invention,
said preformed moisture-absorbing body (8) is fixedly secured to a
gas-tight housing in at least one position. The fixing method is
not particularly restricted so long as the artifact (8) can be
positively secured to the gas-tight housing. For example, method of
bonding the preformed moisture-absorbing body (8) to the gas-tight
housing may include the use of a known self-adhesive or adhesive
(preferably a solvent-free adhesive), thermal fusing, or fastener
means such as screws.
[0045] By way of illustration, the method of fixing the
moisture-absorbing body (8) may include: forming a self-adhesive
layer carrying a release sheet on the moisture-absorbing sheet,
peeling off the release sheet prior to bonding, and fixing the
moisture-absorbing sheet to the housing with the aid of the
self-adhesive layer. It is also possible to secure the artifact (8)
to the gas-tight housing with a solvent-free adhesive comprising an
ethylene-vinyl alcohol copolymer (EVOH) or the like. As the
solvent-free adhesive, a commercial product can be utilized.
[0046] In the practice of the present invention, the roughness of
inside surfaces of the gas-tight housing (defined by the glass
substrate (2) and the glass seal can (7)) may be may be increased
prior to fixing the preformed moisture-absorbing artifact in order
to provide a firmer bond between the preformed moisture-absorbing
body (8) and the gas-tight housing. The proper surface roughness
(Ra) can be judiciously selected according to the material
constituting the preformed moisture-absorbing body or the gas-tight
housing and may generally be about 0.2.about.0.6 .mu.m.
[0047] A method of manufacturing an organic EL device (1) according
to the invention is characterized by providing an organic EL device
comprising 1) a laminate (6) consisting of a pair of electrodes
(3), (5) and at least one organic light-emitting layer (4)
sandwiched the two electrodes (3), (5), 2) a gas-tight housing
accommodating said laminate (6), and 3) a desiccating means
disposed apart from said laminate within said gas-tight housing.
The method further comprises fixing a preformed moisture-absorbing
body (8) as desiccating means to at least one part of said
gas-tight housing.
[0048] Except that it includes a step of fixing a preformed
moisture-absorbing body (8) as desiccating means to at least one
part of said gas-tight housing, the manufacturing method of the
invention may follow the known manufacturing procedure or
protocol.
[0049] The manufacturing method of the invention preferably
comprises a first step comprising fabricating a preformed
moisture-absorbing artifact (8) composed of a desiccant and a resin
component and a second step comprising fixing said preformed
moisture-absorbing artifact (8) as desiccating means to at least
one internal part of said gas-tight housing.
[0050] Referring to the above first step, the preformed
moisture-absorbing body (8) is preferably an artifact fabricated by
forming (molding) a mixture of said desiccant and resin component.
Preferably, the preformed moisture-absorbing body (8) is
substantially free of impurities such as solvents, thus obviating
the trouble due to evaporation of solvent residues in the artifact
with the passage of time. The proportions of the desiccant and
resin component may be similar to those mentioned hereinbefore.
[0051] The fixing of the preformed moisture-absorbing body (8) can
be effected in the same manner as described above herein. The
fixing location is not particularly restricted as long as the
gas-tight housing can be successfully purged of moisture. When the
preformed moisture-absorbing body (8) is a sheet, for instance,
this sheet (8) may be secured in a location isolated from the
laminate (6), for example to a part of the internal wall (or all
over the wall) of the gas-tight housing as illustrated in FIG. 1.
In other words, all that is necessary is to insure that said sheet
be secured in such a manner that it will not come into contact with
the laminate (6). As the sheet is thus secured in position, the
moisture can be removed from the housing so that the formation of
non-emission areas (the so-called dark spots) can be suppressed or
precluded, thus providing a display device of high display
quality.
[0052] In the present invention, particularly because a preformed
moisture-absorbing body (8) is used as desiccating means, the
organic EL device (1) can be easily and positively provided with a
desiccating function.
[0053] The installation of desiccating means can be mechanized. As
a result, chances for moisture infiltrating into the internal
atmosphere are reduced so that an atmosphere with a highly
desiccated initial state can be established. Thus, it is not only
possible to manufacture a highly desiccated organic EL device but
also possible to effectively remove any moisture after manufacture
so that a more dependable organic EL device can be made available
on a commercial scale.
[0054] Moreover, unlike the conventional system in which a
desiccant (powders) is used as it is, the trouble of powders being
dislodged and scattered within the gas-tight housing can be
precluded. In addition, whereas the use of powders requires a
discrete packing space, this is no longer a requisite in the.
present invention, so that the invention contributes to device
down-sizing and weight reduction.
[0055] When a preformed moisture-absorbing body prepared by molding
a desiccant-resin mixture is used as desiccating means, the
performance aging of the organic EL device can be more positively
prevented. Since there are substantially no impurities such as a
solvent remaining in the preformed moisture-absorbing body, the
untoward effect of such impurities can be avoided.
[0056] In accordance with the manufacturing method of the present
invention, wherein a preformed moisture-absorbing body (8) is
secured to at least one part of a gas-tight housing, assembling of
the organic EL device (1) can be carried out at a temperature not
exceeding 50.degree. C. (preferably at room temperature) so that
the method is advantageous cost-wise, too. Moreover, it is not
necessary to pay attention to the heat resistance of the gas-tight
housing; thus, gas-tight housings made of various materials can be
utilized.
[0057] The organic EL device (1) of the present invention, which
has the above characteristics, is useful for such applications as
the flat panel displays of portable telephones, audio equipment and
various meters, as well as the computer display, television display
and other display devices.
EXAMPLES
[0058] The following examples are intended to delineate the
characteristics of the invention in further detail. It should,
however, be understood that these examples are by no means
definitive of the invention.
Example 1
[0059] A preformed moisture-absorbing body in the pellet form was
produced.
[0060] The desiccant CaO was thoroughly dehydrated by heating at
900.degree. C. for 1 hour, then cooled in a falling drying rate
atmosphere of 180.about.200.degree. C., and finally cooled to room
temperature. Then, 65 weight % of this CaO and 35 weight % of the
resin component polyethylene (mol. wt. ca 100,000) were dry-blended
and melt-kneaded under heating at about 230.degree. C. The
resulting mass was hot-pressed into a preformed moisture-absorbing
pellet (1.5 mm .O slashed..times.300 .mu.m thick).
[0061] The pellet was disposed in the cavity of an organic EL
device. FIG. 2 is a schematic cross-sectional view showing an
organic EL device equipped with the above preformed
moisture-absorbing artifact. FIG. 2 schematically illustrates an
organic EL display element (12) mounted on a glass substrate (11).
This display element is accommodated in the metallic cavity
(gas-tight housing) (13) and the preformed moisture-absorbing body
in a pellet form (14) is heat-bonded to the bottom of the cavity
(13). The cavity (13) mentioned above is sealed with a known
UV-curable epoxy sealant (15). An inert gas (e.g. argon gas),
dehumidified in advance, is sealed inside the cavity (16).
Accelerated Organic EL Test Method
[0062] The organic EL device fabricated in Example 1 was subjected
to an accelerated moisture-absorption test. In this accelerated
moisture-absorption test, the organic EL device was allowed to sit
in an atmosphere controlled at 60.degree. C. and 90% R.H. for 500
hours and the condition after exposure was compared with the
condition before exposure. The conditions before and after exposure
are shown in FIGS. 3 and 4, respectively.
Comparative Example 1
[0063] The accelerated organic test method described above was
performed with the organic EL device not equipped with the
preformed moisture-absorbing body. The conditions of the
Comparative Example 1 device before and after exposure are shown in
FIGS. 5 and 6, respectively.
Comparative Example 2
[0064] The accelerated organic test method described above was also
performed using an organic EL device equipped with the conventional
desiccating means (the same quantity of BaO powders as the CaO used
in Example 1). The conditions of the Comparative Example 2 device
before and after exposure are shown in FIGS. 7 and 8,
respectively.
Comparison of Test Results
[0065] It will be apparent from FIGS. 5 and 6 and FIGS. 7 and 8
that the device of Comparative Example 1 after exposure was dark
substantially throughout, with a pale gray area in the center being
the sole remaining light-emission zone, and that the device
according to Comparative Example 2 showed definite dark spots
before and after exposure, although the defects were not so
prominent as in Comparative Example 1.
[0066] In contrast, as shown in FIGS. 3 and 4, the organic EL
device according to the invention showed neither luminance aging
nor growth of dark spots, retaining the initial emission zone
intact and demonstrating the expected desiccation
characteristic.
* * * * *