U.S. patent application number 11/117458 was filed with the patent office on 2005-11-17 for method for manufacturing organic el device, organic el device, and electronic apparatus.
This patent application is currently assigned to Seiko Epson Corporation. Invention is credited to Kobayashi, Hidekazu.
Application Number | 20050253131 11/117458 |
Document ID | / |
Family ID | 26597854 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050253131 |
Kind Code |
A1 |
Kobayashi, Hidekazu |
November 17, 2005 |
Method for manufacturing organic EL device, organic EL device, and
electronic apparatus
Abstract
The present invention provides reduced production cost in a
method for manufacturing an organic EL device including a step of
forming a light-emitting layer having a predetermined pattern by an
ink-jet method. The method achieves this objective by not forming a
bank which surrounds an area in a substrate surface other than an
area at which a light-emitting layer is formed. A
solution-repellent treatment is performed so that a droplet of a
liquid containing a light-emitting material has a contact angle of
15.degree. to 90.degree. with respect to the substrate surface
immediately before formation of the light-emitting layer.
Accordingly, a fluorine containing layer (a layer composed of a
material containing fluorine) is formed. Between a step of forming
the light-emitting layer and a step of forming a cathode, a step of
forming a hole blocking layer over the entire surface of the
substrate is performed.
Inventors: |
Kobayashi, Hidekazu;
(Hara-mura, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Seiko Epson Corporation
Tokyo
JP
|
Family ID: |
26597854 |
Appl. No.: |
11/117458 |
Filed: |
April 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11117458 |
Apr 29, 2005 |
|
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|
09925320 |
Aug 10, 2001 |
|
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6906458 |
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Current U.S.
Class: |
257/13 |
Current CPC
Class: |
H01L 51/0059 20130101;
H01L 51/0512 20130101; H01L 51/0037 20130101; H01L 51/0039
20130101; H01L 51/0005 20130101; H01L 27/3241 20130101 |
Class at
Publication: |
257/013 |
International
Class: |
H01L 029/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 2000 |
JP |
2000-244591 |
Aug 10, 2001 |
JP |
2001-244851 |
Claims
What is claimed is:
1. A method for manufacturing an organic EL device having at least
a first electrode layer, a light-emitting layer, and a second
electrode layer are sequentially formed above a substrate, and the
light-emitting layer is formed by supplying a liquid containing a
light-emitting material to a light-emitting area above the
substrate surface, the method comprising: performing a
solution-repellent treatment so that a droplet of the liquid has a
contact angle of 15.degree. to 90.degree. with respect to the
substrate surface immediately before the formation of the
light-emitting layer; and supplying the liquid to a predetermined
position above the substrate surface to which the
solution-repellent treatment is applied.
2. The method for manufacturing an organic EL device according to
claim 1, formation of the light-emitting layer being performed in a
plurality of the light-emitting areas above the substrate surface
by an ink-jet method.
3. The method for manufacturing an organic EL device according to
claim 1, the solution-repellent treatment being a plasma treatment
using a fluorocarbon gas.
4. The method for manufacturing an organic EL device according to
claim 1, the solution-repellent treatment being performed by
applying a fluorinated alkyl coupling agent.
5. The method for manufacturing an organic EL device according to
claim 1, further comprising performing a treatment that injects
oxygen radicals into the substrate surface immediately before the
solution-repellent treatment.
6. The method for manufacturing an organic EL device according to
claim 1, further comprising forming a hole blocking layer, which
allows electrons but not holes to pass therethrough, in the
light-emitting areas and therebetween above the substrate.
7. The method for manufacturing an organic EL device according to
claim 6, further comprising forming an electron blocking layer,
which allows holes but not electrons to pass therethrough, in the
light-emitting areas and therebetween above the substrate.
8. The method for manufacturing an organic EL device according to
claim 1, the first electrode layer being an anode, the second
electrode layer being a cathode, and the solution-repellent
treatment being performed in the light-emitting areas and
therebetween on the substrate immediately before formation of the
light-emitting layer.
9. The method for manufacturing an organic EL device according to
claim 1, the first electrode layer being an anode and the second
electrode layer being a cathode, and further comprising forming a
hole blocking layer, which allows electrons but not holes to pass
therethrough, in the light-emitting areas and therebetween above
the substrate after the formation of the light-emitting layers.
10. The method for manufacturing an organic EL device according to
claim 9, the hole blocking layer being a metal fluoride layer
comprising at least one of an alkali metal fluoride and an alkali
earth fluoride.
11. The method for manufacturing an organic EL device according to
claim 8, further comprising forming a hole injection/transport
layer above the anodes, and performing a fluorination treatment on
the hole injection/transport layer.
12. A method for manufacturing an organic EL device having a
plurality of light-emitting areas above a substrate, the method
comprising: forming first electrode layers by patterning above the
substrate in the areas at which the light-emitting areas are to be
formed; forming a hole injection/transport layer above the first
electrode layers and between the first electrode layers; forming a
light-emitting layer above the hole injection/transport layer in
the areas at which the light-emitting areas are to be formed;
forming a hole blocking layer, which allows electrons but not holes
to pass therethrough, in the light-emitting areas and therebetween
including areas above the light-emitting layers; and forming a
second electrode layer above the hole blocking layer.
13. The method for manufacturing an organic EL device according to
claim 12, further comprising forming an electron blocking layer,
which allows holes but not electrons to pass therethrough, between
the hole injection/transport layer and the light-emitting layer and
in the light-emitting areas and therebetween.
14. The method for manufacturing an organic EL device according to
claim 12, formation of the light-emitting layer being performed by
an ink-jet method.
15. The method for manufacturing an organic EL device according to
claim 12, formation of the light-emitting layer being performed by
a deposition method.
16. The method for manufacturing an organic EL device according to
claim 12, the hole blocking layer being a metal fluoride layer
including at least one of an alkali metal fluoride and an alkali
earth fluoride.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a Division of Application Ser. No. 09/925,320 filed
Aug. 10, 2001. The entire disclosure of the prior application is
hereby incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to methods for manufacturing
organic EL (electroluminescence) devices. The organic EL devices
can be used, for example, as displays of a television and a
computer, and light sources, such as a backlight of a liquid
crystal display.
[0004] 2. Description of Related Art
[0005] Recently, as a self-luminous display used in place of a
liquid crystal display, organic EL devices (light-emitting devices
having a structure in which an organic light-emitting layer is
provided between an anode and a cathode) have rapidly been
developed. As a material for the light-emitting layer used for an
organic EL device, there are organic materials with low molecular
weight such as an aluminum quinolinol complex (Alq3), and organic
materials with large molecular weight such as polyparaphenylene
vinylene (PPV). A light-emitting layer composed of an organic
material with low molecular weight can be formed by a deposition
method as disclosed in, for example, Appl. Phys. Lett. 51(12), Sep.
21, 1987, p. 913. A light-emitting layer composed of an organic
material with large molecular weight is formed by a coating method
as disclosed in, for example, Appl. Phys. Lett. 71(1), Jul. 7,
1997, p. 34.
[0006] For example, in an organic EL device for use in a display,
it can be necessary to arrange a light-emitting layer at a position
on a substrate corresponding to each pixel. In addition, in the
cases of a color display and a white light source, it can be
necessary to arrange each of light-emitting layers having three
primary colors at each corresponding position on a substrate.
Accordingly, when the arrangement of light-emitting layers can be
performed by an ink-jet method, coating and patterning can be
simultaneously performed, and hence, patterning with high accuracy
can be performed in a short period of time. In addition, since a
material used in this method can be minimized, the material can be
efficiently used, and reduction in production cost can be
effectively achieved.
[0007] Previously, when light-emitting layers are formed into a
predetermined pattern by an ink-jet method, banks composed of an
insulating layer can be formed, and the light-emitting layers are
formed in areas surrounded thereby. Whether or not anodes are
patterned corresponding to the light-emitting area, the formation
of the insulating layers as described above can be performed.
SUMMARY OF THE INVENTION
[0008] The present invention provides a method for manufacturing an
organic EL device in which at least a first electrode layer, a
light-emitting layer, and a second electrode layer are sequentially
formed above a substrate, and the light-emitting layer can be
formed by supplying a liquid containing a light-emitting material
in a light-emitting area above the substrate surface. The method
for manufacturing the organic EL device includes forming no bank
which surrounds an area above the substrate surface other than an
area at which the light-emitting layer is formed, performing a
solution-repellent treatment so that a droplet of the liquid has a
contact angle in the range of 15.degree. to 90.degree. with respect
to the substrate surface immediately before the formation of the
light-emitting layer, and supplying the liquid to a predetermined
position above the substrate surface to which the
solution-repellent treatment is applied.
[0009] The present invention provides an organic EL device that can
include a plurality of light-emitting areas above a substrate, each
having a light-emitting layer provided between a first electrode
layer and a second electrode layer opposing thereto, and a hole
blocking layer, which allows electrons but not holes to pass
therethrough, in the light-emitting areas and therebetween.
[0010] In addition, the present invention provides a method for
manufacturing an organic EL device that can include a plurality of
light-emitting areas above a substrate. The method for
manufacturing the organic EL device can include a step of forming
first electrode layers by patterning in areas above the substrate
at which the light-emitting areas are to be formed, a step of
forming a hole injection/transport layer above the first electrode
layers and between the first electrode layers, a step of forming a
light-emitting layer above the hole injection/transport layer in
the areas at which the light-emitting areas are to be formed, a
step of forming a hole blocking layer, which allows electrons but
not holes to pass therethrough, in the light-emitting areas and
therebetween including areas above the light-emitting layers, and a
step of forming a second electrode layer above the hole blocking
layer.
[0011] In addition, the present invention provides an electronic
apparatus provided with an organic EL device. The organic EL device
mentioned above includes a plurality of light-emitting areas above
a substrate, each having a light-emitting layer provided between a
first electrode layer and a second electrode layer opposing
thereto, and in the light-emitting areas and therebetween, a hole
injection/transport layer and a hole blocking layer which allows
electrons but not holes to pass therethrough.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will be described with reference to the
accompanying drawings, in which like elements are referenced to
with like numerals, and in which:
[0013] FIG. 1 illustrates manufacturing steps in a method for
manufacturing an organic EL device according to a first embodiment
of the present invention;
[0014] FIG. 2 is a cross-sectional view showing an organic EL
device formed by the method according to the first embodiment and
to a third embodiment;
[0015] FIG. 3 is a graph showing the results obtained by measuring
luminous characteristics and current characteristics at a position
corresponding to a light-emitting layer of the organic EL device
formed by the method according to the first embodiment;
[0016] FIG. 4 is a graph showing the results obtained by measuring
current properties at a position (non light-emitting area) between
adjacent light-emitting layers of an organic EL device curve A
shows the results of the organic EL device formed by the method
according to the first embodiment, curve B shows the results of the
device when a fluorine containing layer is not formed in the non
light-emitting area, curve C shows the results when a lithium
fluoride thin-film is not formed in the non light-emitting area,
and curve D shows the results when both the fluorine containing
layer and the lithium fluoride thin-film are not formed in the non
light-emitting area;
[0017] FIG. 5 is a cross-sectional view showing an organic EL
device formed by a method according to a second embodiment;
[0018] FIG. 6 is a perspective view showing an organic EL device
formed by a method according to a fourth embodiment;
[0019] FIG. 7 is a perspective view showing the structure of a
personal computer corresponding to an example of an electronic
apparatus to which the organic EL device of the present invention
is applied;
[0020] FIG. 8 is a perspective view showing the structure of a
mobile phone corresponding to an example of an electronic apparatus
to which the organic EL device of the present invention is applied;
and
[0021] FIG. 9 is a perspective view showing the structure of a
digital still camera corresponding to an example of an electronic
apparatus to which the organic EL device of the present invention
is applied.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] In the conventional techniques described above, when the
light-emitting layers each having a predetermined pattern are
formed by an ink-jet method, it is prerequisite to form bank
composed of an insulating layer. When the bank is formed, a
photolithographic step and an etching step must be performed, and
hence, there has been a problem in that the production cost is
increased.
[0023] The present invention is made in consideration of the
problems of the conventional techniques, and a feature of the
present invention is to provide a method for manufacturing an
organic EL device in which formation of the bank composed of an
insulating layer is not necessary even in the case that an ink-jet
method is used for forming light-emitting layers each having a
predetermined pattern.
[0024] In a first method for manufacturing an organic EL device
according to an embodiment of the present invention, at least a
first electrode layer, a light-emitting layer, and a second
electrode layer are sequentially formed above a substrate, and the
light-emitting layer is formed by supplying a liquid containing a
light-emitting material to a light-emitting area above a substrate
surface. The method including not forming a bank which surrounds an
area above the substrate surface other than the light-emitting
area, performing a solution-repellent treatment so that a droplet
of the liquid has a contact angle of 15.degree. to 90.degree. with
respect to the substrate surface immediately before formation of
the light-emitting layer, and supplying the liquid to a
predetermined position above the substrate surface to which the
solution-repellent treatment is applied.
[0025] In the method described above, by performing the
solution-repellent treatment so that the droplet of the liquid has
the contact angle of 15.degree. to 90.degree. with respect to the
substrate surface immediately before the formation of the
light-emitting layer, when the light-emitting layer is formed by an
ink-jet method without the bank, the liquid can be held at the
predetermined position.
[0026] The first method for manufacturing the organic EL device is
preferably used when the formation of the light-emitting layer is
performed in a plurality of light-emitting areas above the
substrate surface by an ink-jet method. The light-emitting area
means an area at which the light-emitting layer exists between the
first electrode layer and the second electrode layer opposing
thereto. For example, in a display unit, each pixel is the
light-emitting area.
[0027] In this method for manufacturing the organic EL device, as
the solution-repellent treatment, a fluorination treatment for
providing fluorine atoms above the substrate surface is preferably
performed. As this fluorination treatment, there may be mentioned
(1) a plasma treatment using a fluorocarbon gas (CF.sub.4 gas, for
example), (2) a method for applying a fluorinated alkyl coupling
agent (for example, perfluoroalkyl trimethoxy silane and "LP-8T"
manufactured by Shin-Etsu Silicone Co., Ltd., as an example of a
commercially available product), and (3) a method for exposing the
substrate to a vapor of a fluorinated alkyl coupling agent
(perfluoroalkyl trimethoxy silane or the like). In addition, when a
layer (for example, hole injection/transport layer) under the
light-emitting layer is formed by application of a liquid material,
the solution-repellent treatment may also be performed by mixing a
fluorinated alkyl coupling agent with the liquid material.
[0028] In the method for manufacturing the organic EL device having
the first feature described above, a treatment for injecting oxygen
radicals (oxygen plasma treatment or UV irradiation) into the
substrate surface is preferably performed immediately before the
solution-repellent treatment. As a result, adhesion of the
solution-repellent layer with respect to the substrate surface is
improved.
[0029] In this method for manufacturing the organic EL device, the
bank, which is provided in an area above the substrate surface
other than that at which the light-emitting layer is formed so as
to surround the light-emitting area, is not formed. Accordingly, by
another method other than the formation of the bank, it is
necessary to insulate two electrodes from each other located in the
area other than the light-emitting areas. As a method therefor,
there may be mentioned a method for forming a hole blocking layer,
which allows electron but not holes to pass therethrough, in the
light-emitting areas and therebetween above the substrate. Due to
the presence of this hole blocking layer, the two electrodes are
insulated from each other by the area between the light-emitting
areas above the substrate.
[0030] As the hole blocking layer, a metal fluoride layer composed
of an alkali fluoride or an alkaline earth fluoride (such as
lithium fluoride, sodium fluoride, cesium fluoride, magnesium
fluoride, calcium fluoride, strontium fluoride, or the like) may be
mentioned. In addition, an insulating thin-film having a thickness
of several nanometers may also be used.
[0031] In addition, an electron blocking layer, which allows holes
but not electrons to pass therethrough, is preferably further
formed in the light-emitting areas and therebetween above the
substrate surface.
[0032] In this method for manufacturing the organic EL device, the
first electrode layer is an anode, the second electrode layer is a
cathode, and the solution-repellent treatment may be performed
above the light-emitting areas and therebetween above the substrate
immediately before the formation of the light-emitting layer.
[0033] In this method for manufacturing the organic EL device, the
first electrode layer is an anode, the second electrode layer is a
cathode, and the hole blocking layer, which allows electrons but
not holes to pass therethrough, may be formed in the light-emitting
areas and therebetween above the substrate after the formation of
the light-emitting layer.
[0034] In this method for manufacturing the organic EL device, in
the case that the hole injection/transport layer is formed between
the anode and the light-emitting layer, a fluorination treatment is
performed above the hole injection/transport layer after the hole
injection/transport layer is formed above the anode.
[0035] In many cases, the hole transport layer is provided between
the light-emitting layer and the anode of the organic EL device.
Holes are injected into this hole transport layer from the anode,
and the hole transport layer transports these holes to the
light-emitting layer. When the light-emitting layer has hole
transporting characteristics, the hole transport layer may not be
provided in some cases. In addition, the hole injection layer and
the hole transport layer may be respectively provided in some
cases. Accordingly, in the present invention, a hole injection
layer and/or a hole transport layer formed between a light-emitting
layer and an anode are called a "hole injection/transport
layer".
[0036] An organic EL device according to an embodiment of the
present invention can include a plurality of light-emitting areas
above a substrate, each having a light-emitting layer provided
between a first electrode layer and a second electrode layer
opposing thereto, and a hole blocking layer, which allows electrons
but not holes to pass therethrough, provided in the light-emitting
areas and therebetween. An example of this organic EL device may be
an organic EL device in which a layer composed of a material
containing fluorine is provided between the first electrode layer
and the light-emitting layer.
[0037] Another example of this organic EL device may be an organic
EL device in which the first electrode layer is an anode, the
second electrode layer is a cathode, a hole injection/transport
layer is provided above the anode, and a hole blocking layer
composed of an alkali fluoride or an alkaline earth fluoride is
provided.
[0038] In a method for manufacturing an organic EL device according
to an embodiment of the present invention, the organic EL device
can include a plurality of light-emitting areas above a substrate.
The method for manufacturing the organic EL device can include
forming first electrode layers by patterning above the substrate in
areas at which the light-emitting areas are to be formed, forming a
hole injection/transport layer above the first electrode layers and
between the first electrode layers, forming light-emitting layers
above the hole injection/transport layer in the areas at which the
light-emitting areas are to be formed, forming a hole blocking
layer, which allows electrons but not holes to pass therethrough,
in the light-emitting areas and therebetween including areas above
the light-emitting layers, and forming second electrode layers
above the hole blocking layer.
[0039] In the method for manufacturing the organic EL device
described in the above, it is preferable that an electron blocking
layer, which allows holes but not electrons to pass therethrough,
be further formed between the hole injection/transport layer and
the light-emitting layer and in the light-emitting areas and
therebetween.
[0040] In the method for manufacturing the organic EL device
described in the above, the formation of the light-emitting layers
may be performed by an ink-jet method or a deposition method.
[0041] In the method for manufacturing the organic EL device
described in the above, the hole blocking layer may be a metal
fluoride layer including an alkali fluoride or an alkali earth
fluoride.
[0042] An electronic apparatus according to an embodiment of the
present invention can include an organic EL device, wherein the
organic EL device includes a plurality of light-emitting areas
above a substrate, each having a light-emitting layer provided
between a first electrode layer and a second electrode layer
opposing thereto, and in the light-emitting areas and therebetween,
a hole injection/transport layer and a hole blocking layer which
allows electrons but not holes to pass therethrough.
[0043] Hereinafter, embodiments of the present invention will be
described with reference to the figures.
[0044] It is to be understood that the present invention is not
limited to the embodiments described below.
[0045] FIG. 1 illustrates exemplary manufacturing steps in a method
for manufacturing an organic EL device according to a first
embodiment of the present invention. In this method, first, an
IDIXO (In.sub.2O.sub.3--ZnO) thin-film is formed on a transparent
glass substrate 1, and by performing photolithography and etching
on this thin-film, transparent anodes (first electrode layers) 2
are formed at pixel positions (a plurality of positions) in a
substrate surface. FIG. 1(a) shows this state. As a material for
the transparent anode, ITO (In.sub.2O.sub.3--SnO.sub.2) may also be
used.
[0046] Next, on the surface of anode 2, irradiation treatment using
UV rays having a wavelength of 200 nm or less is performed. This
treatment increases the work function of the anode 2. An oxygen
plasma treatment may be performed instead. Subsequently, after
applying "Baytron" manufactured by Bayer AG to the entire surface
of the substrate 1 by spin-coating for forming a film, drying is
performed, whereby a hole injection/transport layer 3 is formed.
FIG. 1(b) shows this state. In this embodiment, although the hole
injection/transport layer 3 is formed over the entire surface of
the substrate, it may exist at least in light-emitting areas and
therebetween, that is, hole injection/transport layers may not be
connected to each other in the light-emitting areas and
therebetween.
[0047] Next, a plasma treatment using a CF.sub.4 gas (fluorocarbon
gas) is performed over the entire surface (the substrate surface
immediately before the formation of the light-emitting layer) of
the hole injection/transport layer 3, whereby the surface of the
hole injection/transport layer 3 is fluorinated
(solution-repellent). The conditions of the plasma treatment are
set such that the power is 300 W, the distance between the
substrate plane and the electrode is 1 mm, the transport speed of
the substrate is 10 mm/second, the carrier gas is helium, and the
environmental pressure is an atmospheric pressure.
[0048] Accordingly, as shown in FIG. 1(c), a fluorine containing
layer (a layer formed of a material containing fluorine) 4 is
formed on the hole injection/transport layer 3. By the plasma
treatment, fluorine atoms are bonded to molecules existing on the
surface of a polymeric material which forms the hole
injection/transport layer 3. The fluorine containing layer 4
indicates an area to which these fluorine atoms are bonded.
[0049] Next, a xylene solution containing poly(dioctyl fluorene) (a
light-emitting material) at a concentration of 1 wt % is discharged
using an ink-jet method at a position corresponding to each anode
2. Immediately before this discharge, since the fluorine containing
layer 4 exists on the topmost surface of the substrate 1, and a
contact angle of a droplet 50 of the solution is in the range of
15.degree. to 90.degree. with respect to the surface of this
fluorine containing layer 4, the solution remains in a
predetermined area corresponding to the area of the anode. FIG.
1(d) shows this state.
[0050] Next, by evaporating the solvent of the droplet 50, a
light-emitting layer 5 is formed above each anode 2. FIG. 1(e)
shows this state.
[0051] In this embodiment, the formation of the light-emitting
layer is preformed by an ink-jet method, however, it is to be
understood that a printing method may also be used.
[0052] Next, a lithium fluoride thin-film (a hole blocking layer) 6
is formed by a vacuum deposition method over the entire surface of
the glass substrate 1. FIG. 1(f) shows this state. In this
embodiment, the lithium fluoride thin-film (hole blocking layer) 7
is formed over the entire surface of the substrate, however, it may
exist at least in the light-emitting areas and therebetween, that
is, lithium fluoride thin-films (hole blocking layers) may not be
connected to each other in the light-emitting areas and
therebetween.
[0053] Next, a lithium/aluminum laminated thin-film (cathode) 7 is
formed (the lithium thin-film is formed at the lithium fluoride
thin-film 6 side) over the entire surface of this lithium fluoride
thin-film 6 by a vacuum deposition method. FIG. 1(g) shows this
state. As the cathode, in addition to lithium, Ca, Mg, or an alloy
containing such metal is preferably used. In addition, a film
composed of a relatively stable metal, such as Al, Ag, or Au, may
also be used on the cathode described above. As a film-forming
method, in addition to a vacuum deposition method, a sputtering
method may also be used.
[0054] Next, by sealing the upper surface of the cathode 7, as
shown in FIG. 2, an organic EL panel (organic EL device) is
obtained. In this embodiment, a sealing material 8 composed of an
epoxy resin is provided over the entire surface of the cathode 7,
and a glass substrate 9 for sealing is provided thereon. In
addition, as a sealing method, can sealing using a metal or a glass
may also be performed. In both sealing methods, as required, a
desiccant or a deoxidizer may be enclosed in a sealed area. In
addition, there is a method for forming a thin-film having superior
gas barrier properties, such as aluminum nitride, silicon nitride,
or silicon oxide, by deposition or sputtering.
[0055] By connecting a driving circuit to the organic EL device
thus formed, an organic EL display unit can be obtained.
[0056] When the luminous properties and current properties are
measured at a position corresponding to the light-emitting layer 2
by applying a voltage to this organic EL panel, the graph shown in
FIG. 3 is obtained. In addition, when the current properties are
measured at a position (non light-emitting area) between the
adjacent light-emitting layers 5, the curve a shown in FIG. 4 is
obtained.
[0057] The measurement results of the current properties are shown
in FIG. 4 in which the curve b shows the results when the fluorine
containing layer 4 is not formed in the non light-emitting area.
The curve c shows the results when the lithium fluoride thin-film 6
is not formed in the non light-emitting area. The curve d shows the
results when the fluorine containing layer 4 and the lithium
fluoride thin-film 6 are not formed in the non light-emitting
area.
[0058] As can be seen from these results, it is understood that a
sufficient luminous properties can be obtained in the
light-emitting area (light-emitting layer 5) according to the
organic EL device of this embodiment. In addition, by forming both
the fluorine containing layer 4 and the lithium fluoride thin-film
6 without providing banks, which are previously formed in the non
light-emitting area, compared to the case (the curve d in FIG. 4)
in which the both the layer and the film are not formed, it is
understood that superior insulating properties can be obtained.
That is, in the organic EL device of this embodiment, the
light-emitting areas are separated from each other by the lithium
fluoride thin-film (hole blocking layer) 6 and the fluorine
containing layer (electron blocking layer) 4.
[0059] Concerning the insulating properties of the non
light-emitting area, compared to the result (the curve a) according
to this embodiment, superior insulating properties can be obtained
in the case (the curve b) in which the lithium fluoride thin-film
(hole blocking layer) 6 is formed in the non light-emitting area
without providing the fluorine containing layer 4. In addition, the
insulating properties obtained in the case (the curve c) in which
the fluorine containing layer 4 is formed in the non light-emitting
area without providing the lithium fluoride thin-film 6 are
approximately equivalent to those obtained in the case (the curve
d) in which the both are not formed.
[0060] FIG. 5 is a cross-sectional view showing an organic EL
device according to a second embodiment of the present invention.
In this embodiment, in a manner different from that in the first
embodiment, a TFT (thin-film transistor) element 15 is formed at
each pixel electrode (anode 2).
[0061] Accordingly, when this organic EL device is formed, before
the step (step of forming the anode 2 on the glass substrate 1)
shown in FIG. 1(a) of the first embodiment is performed, a step of
forming the TFT element 15 at a predetermined position (position
corresponding to an area between the adjacent pixels) of the
substrate 1 corresponding to each pixel and a step of forming a
contact hole for connecting the TFT element 15 to the anode 2 are
performed. Reference numeral 16 indicates an insulating layer
(SiO.sub.2 film, for example) formed during the above-mentioned
steps.
[0062] The organic EL device shown in FIG. 5 is formed by using the
same method as that in the first embodiment except for the points
described above. This organic EL device is an active matrix type
organic EL display device. By using this device, when a
predetermined driving signal is input into the TFT element for each
pixel, a still image and a moving image can be displayed.
[0063] In a method for manufacturing an organic El device having a
structure in which a hole injection layer or a hole transport layer
and a light-emitting layer at a position corresponding to a
light-emitting pixel (a light-emitting area) are laminated on an
anode, and after a hole blocking layer is laminated on the front
surface, a cathode and a sealing layer are laminated, an example
using a mask deposition method will be described as means for
laminating the light-emitting layer at a position corresponding to
the light-emitting pixel. The cross-sectional view of the organic
EL device of this embodiment is the same as that shown in FIG.
2.
[0064] After ITO is patterned as the anode 2, a UV irradiation
treatment at a wavelength of 174 nm is performed, and m-MTDATA and
TPD are deposited as a hole injection layer or a hole transport
layer 3. In these steps, these layers may be formed by a mask
deposition at a position corresponding to the light-emitting pixel
through a physical mask. Next, mask deposition of Alq3, which is a
material for the light-emitting layer 5, is performed at the
position corresponding to the light-emitting pixel through a
physical mask. As a hole blocking layer 6, lithium fluoride is
deposited in an evacuated atmosphere. Next, as a cathode 7, calcium
and aluminum are sequentially deposited.
[0065] Furthermore, sealing and mounting are performed, thereby
forming an organic EL device. As the sealing method, in this
embodiment, a sealing material 8 composed of an epoxy resin is
provided over the entire surface of the cathode 7, and a glass
substrate 9 for sealing is provided thereon; however, can sealing
using a metal or a glass may be performed. In both sealing methods,
as required, a desiccant or a deoxidizer may be enclosed in the
sealed area. In addition, there is a method for forming a thin-film
having superior gas barrier properties, such as aluminum nitride,
silicon nitride, or silicon oxide, by deposition or sputtering.
[0066] FIG. 6 is a perspective view showing an organic EL device
according to a fourth embodiment of the present invention. This
organic EL device is a white plane light source, and except for the
two points described below, the cross-section perpendicular to a
glass substrate 1 is approximately equivalent to that in the first
embodiment shown in FIG. 2.
[0067] One difference is that instead of the glass substrate 9 for
sealing in the first embodiment, a housing 91 is used having
circular opening portions 91 a which are regularly provided in the
upper surface thereof. The other difference is that as a
light-emitting layer 5, a red light-emitting material (R), a green
light-emitting material (G), and a blue light-emitting material (B)
are repeatedly and regularly formed.
[0068] In addition, the individual R, Q and B light-emitting layers
5 are formed at pitch of 70.5 .mu.m to have each dot with 40 .mu.m
diameter. In this embodiment, in order to obtain white light when
the light-emitting layers are driven by the same voltage, the
diameter of each dot (circle forming the plan surface of the
light-emitting layer) is formed so as to be equal to each other,
and the ratio of the number of dots are R:G:B=2:1:4.
[0069] In the same manner as that in the first embodiment except
for the points described above, a white plane light source shown in
FIG. 6 is formed. When a voltage is applied to this white plane
light source, white luminescence can be obtained.
[0070] In the embodiments described above, the light-emitting layer
is formed by an ink-jet method, but it may also be formed by a
printing method such as a screen printing method.
[0071] In the method of the present invention, although a bank is
not formed which surrounds an area in the substrate surface other
than the area at which light-emitting layer is formed, a pattern
composed of an insulating material and having an aperture portion
in accordance with the pixel dimensions may be formed above the
substrate surface before the light-emitting layer is formed, and a
solution-repellent treatment defined in the present invention may
be performed in the substrate surface after this pattern is formed.
As a result, the dimensional accuracy of each pixel can be
improved. In the case described above, since the light-emitting
layer is formed in an area extending to the outside of the aperture
portion, the pattern does not correspond to the bank mentioned
above.
[0072] In addition, in the individual embodiments described above,
since the transparent glass substrate 1 is used as the substrate,
the transparent anode 2 is provided at the substrate side, and the
cathode 7 is opaque, light generated in the light-emitting layer is
reflected at the cathode 7 and is then emitted to the glass
substrate 1 side. However, by forming an opaque electrode (first
electrode) at the substrate side and a transparent second
electrode, light generated in the light-emitting layer may be
emitted to the side opposite to the substrate. The material used
for the cathode may be, in addition to ITO, a metal material such
as gold, silver, copper, or a metal having a low work function,
i.e., calcium, magnesium, cesium, strontium, or rubidium, that is
formed into a transparent thin-film. In addition, a thin-film alloy
composed of magnesium and silver or composed of aluminum and
lithium may also be used.
[0073] In the case described above, since the first electrode is
opaque, the TFT element can be formed in the pixel position in the
substrate surface, and hence, compared to the structure shown in
FIG. 5 in which the TFT element must be formed at the position
between the pixels, the ratio of the entire pixel area to the
substrate area can be increased. In addition, since an opaque
substrate can be used, a semiconductor substrate such as a silicon
substrate can also be used.
[0074] Furthermore, in the individual embodiments described above,
the electrode (first electrode) at the substrate side is used as an
anode, and the electrode (second electrode) at the side opposite to
the substrate is used as a cathode, but the first electrode may be
used as a cathode, and the second electrode may be used as an
anode. In the case described above, the positional relationship
between the layers with respect to the substrate is opposite to
that described in the first embodiment.
[0075] Furthermore, the organic EL device of the present invention
may be applied to various electronic apparatuses, such as a mobile
personal computer, a mobile phone, a digital still camera and the
like.
[0076] FIG. 7 is a perspective view showing the structure of a
mobile personal computer. In FIG. 7, a personal computer 100 has a
structure composed of a main body 104 provided with a keyboard 102
and a display unit 106 formed of the organic EL device of the
present invention.
[0077] FIG. 8 is a perspective view of a mobile phone. In FIG. 8, a
mobile phone 200 comprises, in addition to a plurality of operation
buttons 202, an ear piece 206, a mouthpiece 204, and a display
panel 208 formed of the organic EL device of the present
invention.
[0078] FIG. 9 is a perspective view showing the structure of a
digital still camera 300. In the figure, the connection with
external apparatuses is also briefly shown. Compared to a typical
camera which exposes a film to an optical image of an object, the
digital camera 300 produces image signals by performing
photoelectric conversion of an optical image of an object using an
imaging element such as a CCD (Charged Coupled Device).
[0079] A display panel 304 composed of the organic EL device of the
present invention is provided on the back surface of a case 302 of
the digital still camera 300, and the structure is formed so as to
perform display in accordance with the image signals provided from
the CCD. Accordingly, the display panel 304 serves as a viewfinder
for displaying the object. In addition, a light-receiving unit 306
containing an optical lens, and the CCD, for example, is provided
on an observing side (the back surface side in the figure) of
302.
[0080] When a picture taker views an object image displayed on the
display panel 304 and then presses a button 308, an image signal of
the CCD at that time is transferred to and stored in a memory of a
circuit substrate 310. In addition, in this digital still camera
300, a video signal output terminal 312 and an input/output
terminal 314 for data communication are provided on the side
surface of the case 302.
[0081] In addition, as shown in the figure, as required, a
television monitor 430 and a personal computer 440 are connected to
the video signal output terminal 312 and the input/output terminal
314 for data communication, respectively. Furthermore, the
structure is formed so that the image signal stored in the memory
of the circuit substrate 310 is output on the television monitor
430 or to the personal computer 440 by a predetermined
operation.
[0082] As an electronic apparatus to which the organic EL device of
the present invention can be applied as a display unit, in addition
to the personal computer in FIG. 7, the mobile phone in FIG. 8, and
the digital still camera in FIG. 9, there may be mentioned a
television, a viewfinder type and a direct viewing video tape
recorder, a car navigation apparatus, a pager, an electronic
notebook, an electronic calculator, a word processor, a
workstation, a television phone, a point of sales (POS) terminal,
and an apparatus provided with a touch panel.
[0083] As has thus been described, according to the present
invention, since the organic EL device is formed without forming
banks (banks surrounding the areas at which the light-emitting
layers are formed) which have been conventionally required to be
formed, the production cost can be reduced. In particular, the
insulating properties in the non light-emitting area can reliably
be obtained.
* * * * *