U.S. patent application number 10/900080 was filed with the patent office on 2005-03-17 for organic el display device and method for fabricating the same.
This patent application is currently assigned to OPTREX Corporation. Invention is credited to Masumo, Kunio.
Application Number | 20050057154 10/900080 |
Document ID | / |
Family ID | 34279532 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050057154 |
Kind Code |
A1 |
Masumo, Kunio |
March 17, 2005 |
Organic EL display device and method for fabricating the same
Abstract
In one mode of the present invention, there is provided an
organic EL display device, which includes an organic light emitting
layer provided between sets of electrodes, comprising color filters
22 and an overcoat layer 23 provided on a substrate 21; an
inorganic solid layer 24 provided on the overcoat layer 23; a first
set of transparent electrodes 25 provided on the inorganic solid
layer 24; a light emitting layer 27 provided on the first set of
electrodes 25; and a second set of electrodes 28 formed on the
light emitting layer 27; wherein the inorganic solid layer 24 has
routes for moisture passage formed in regions between adjacent
electrodes of the first set so as to be uniform over an entire
active area.
Inventors: |
Masumo, Kunio;
(Yokohama-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
OPTREX Corporation
Tokyo
JP
116-0014
|
Family ID: |
34279532 |
Appl. No.: |
10/900080 |
Filed: |
July 28, 2004 |
Current U.S.
Class: |
313/512 ;
313/504; 313/506 |
Current CPC
Class: |
H01L 27/3281 20130101;
H01L 2251/558 20130101; H01L 51/524 20130101; H01L 27/322 20130101;
H01L 51/5253 20130101 |
Class at
Publication: |
313/512 ;
313/504; 313/506 |
International
Class: |
H05B 033/04; H05B
033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2003 |
JP |
2003-282344 |
Nov 28, 2003 |
JP |
2003-398762 |
May 31, 2004 |
JP |
2004-162506 |
Claims
What is claimed is:
1. An organic EL display device, which includes an organic light
emitting layer provided between a pair of electrodes, comprising:
an organic layer provided on a substrate; an inorganic solid layer
provided on the organic layer; a first set of transparent
electrodes provided on the inorganic solid layer; an organic light
emitting layer provided on the first set of electrodes; and a
second set of electrodes formed on the organic light emitting
layer; wherein the inorganic solid layer has routes for moisture
passage formed in regions between adjacent electrodes of the first
set so as to be substantially uniform over an entire active
area.
2. An organic EL display device, which includes a plurality of
pixels corresponding to an organic light emitting layer provided
between sets of electrodes, comprising: an organic layer provided
on a substrate; an inorganic solid layer provided on the organic
layer; a first set of transparent electrodes provided on the
inorganic solid layer; an organic light emitting layer provided on
the first set of electrodes; and a second set of electrodes formed
on the organic light emitting layer; wherein the inorganic solid
layer has routes for moisture passage formed in regions between
adjacent electrodes of the first set so as to correspond to
substantially all pixels.
3. The organic EL display device according to claim 2, wherein the
routes for moisture passage are formed at at least one location in
each of the regions between adjacent pixels.
4. An organic EL display device, which includes an organic light
emitting layer provided between sets of electrodes, comprising: an
organic layer provided on a substrate; an inorganic solid layer
provided on the organic layer; a first set of transparent
electrodes provided on the inorganic solid layer; an organic light
emitting layer provided on the first set of electrodes; and a
second set of electrodes formed on the organic light emitting
layer; wherein the inorganic solid layer has a layer thickness set
at such a thickness that allows routes for moisture passage to be
formed therein in order to avoid visible failure.
5. An organic EL display device, which includes an organic light
emitting layer provided between sets of electrodes, comprising: an
organic layer provided on a substrate; an inorganic solid layer
provided on the organic layer; a first set of transparent
electrodes provided on the inorganic solid layer; an organic light
emitting layer provided on the first set of electrodes; and a
second set of electrodes formed on the organic light emitting
layer; wherein the inorganic solid layer is provided so as to have
a layer thickness from 1 to 20 nm in regions between adjacent
electrodes of the first set.
6. The organic EL display device according to claim 5, wherein the
inorganic solid layer is provided so as to have a layer thickness
from 1 to 10 nm in the regions between adjacent electrodes of the
first set.
7. The organic EL display device according to claim 1, wherein the
inorganic solid layer is provided so as to have a substantially
equal thickness in an active area.
8. The organic EL display device according to claim 1, wherein the
inorganic solid layer has a greater thickness in regions with the
first set of electrodes therein than a thickness in the regions
between adjacent electrodes of the first set.
9. The organic EL display device according to claim 1, wherein the
inorganic solid layer includes a layer made of silicon oxide.
10. The organic EL display device according to claim 9, wherein the
inorganic solid layer includes a layer made of zirconium oxide
provided on the layer made of silicon oxide.
11. A method for fabricating an organic EL display device,
comprising: providing an organic layer on a substrate; providing an
inorganic solid layer on the organic layer; providing a first set
of transparent electrodes on the inorganic solid layer; providing
an organic light emitting layer on the first set of electrodes;
providing a second set of electrodes on the organic light emitting
layer provided on the first set of electrodes; and removing water
or an organic substance in the organic layer though routes for
moisture passage by drying the substrate before providing the
organic light emitting layer, the routes for moisture passage being
substantially uniformly provided in regions between adjacent
electrodes of the first set and in the inorganic solid layer over
an entire active area.
12. A method for fabricating an organic EL display device, which
includes a plurality of pixels corresponding to an organic light
emitting layer provided between sets of electrodes, comprising:
providing an organic layer on a substrate; providing an inorganic
solid layer on the organic layer; providing a first set of
transparent electrodes provided on the inorganic solid layer;
providing an organic light emitting layer on the first set of
electrodes; providing a second set of electrodes formed on the
organic light emitting layer provided on the first set of
electrodes; and removing water or an organic substance in the
organic layer though routes for moisture passage by drying the
substrate before providing the organic light emitting layer, the
routes for moisture passage being provided in regions between
adjacent electrodes of the first set so as to correspond to
substantially all pixels.
13. A method for fabricating an organic EL display device,
comprising: providing an organic layer on a substrate; providing an
inorganic solid layer on the organic layer; providing a first set
of transparent electrodes on the inorganic solid layer; providing
an organic light emitting layer on the first set of electrodes; and
providing a second set of electrodes on the organic light emitting
layer provided on the first set of electrodes; and further
comprising: removing water or an organic substance in the organic
layer though routes for moisture passage by drying the substrate
before providing the organic light emitting layer, the routes for
moisture passage being provided in the inorganic solid layer; and
forming the inorganic solid layer so as to have a layer thickness
set at such a thickness that allows the routes for moisture passage
to be formed therein in order to avoid visible failure when
providing of the organic light emitting layer.
14. A method for fabricating an organic EL display device, which
includes a plurality of pixels corresponding to an organic light
emitting layer provided between sets of electrodes, comprising:
providing an organic layer on a substrate; providing an inorganic
solid layer on the organic layer; providing a first set of
transparent electrodes provided on the inorganic solid layer;
providing an organic light emitting layer on the first set of
electrodes; and forming the inorganic solid layer so as to have a
layer thickness from 1 to 20 nm in regions between adjacent
electrodes of the first set when providing of the inorganic solid
layer.
15. The method according to claim 14, comprising forming the
inorganic solid layer so as to have a layer thickness from 1 to 5
nm when providing of the inorganic solid layer.
16. The method according to claim 15, comprising forming the
inorganic solid layer at a substrate temperature of 100.degree. C.
or below when providing of the inorganic solid layer.
17. The method according to claim 14, comprising forming the
inorganic solid layer at a substrate temperature of 200.degree. C.
or above when providing of the inorganic solid layer.
18. The method according to claim 11, further comprising removing
at least one part of portions of the inorganic solid layer in the
regions between adjacent electrodes of the first set before
providing of the organic light emitting layer.
Description
[0001] The present invention relates to an organic
electroluminescence (hereinbelow, referred as "organic EL" in
Description) display device and a method for fabricating the
same.
[0002] Research and development have been conducted on display
panels forming an organic EL display device (see, e.g.,
JP-A-2001-60495) on color filters. In order to prevent a minute
amount of moisture or a solvent contained in a color filter film
from deteriorating an organic EL display device, an inorganic solid
layer has been provided between the color filters and the organic
EL display device to prevent moisture or an organic substance
passing in an interlayer direction.
[0003] However, it is impossible for the inorganic solid layer to
serve for complete prevention in practice. There has been known a
problem that spot-like non-emissive areas are come out with the
lapse of time after device fabrication as shown in FIG. 1. FIG. 1
is a schematic plan view showing a state wherein non-emissive areas
2 have been caused in apertural areas (pixels) 1 of a light
emitting layer of an organic EL display device. Such spot-like
non-emissive areas are a potential cause of visible failure.
[0004] As stated earlier, the conventional organic EL display
devices have the problem that a display failure is caused with the
lapse of time.
[0005] The present invention is proposed in consideration of this
problem. It is an object of the present invention to provide an
organic EL display device and a method for fabricating the same,
which are hard to have the occurrence of visible failure caused by
the lapse of time or which have no occurrence of the visible
failure.
[0006] According to a first aspect of the present invention, there
is provided an organic EL display device, which includes an organic
light emitting layer provided between sets of electrodes,
comprising an organic layer provided on a substrate; an inorganic
solid layer provided on the organic layer; a first set of
transparent electrodes provided on the inorganic solid layer; an
organic light emitting layer provided on the first set of
electrodes; and a second set of electrodes formed on the organic
light emitting layer; wherein the inorganic solid layer has routes
for moisture passage formed in regions between adjacent electrodes
of the first set so as to be substantially uniform over an entire
active area. By this arrangement, it is possible to prevent visible
failure from causing in the organic EL display device with the
lapse of time.
[0007] According to a second aspect of the present invention, there
is provided an organic EL display device, which includes a
plurality of pixels corresponding to an organic light emitting
layer provided between sets of electrodes, comprising an organic
layer provided on a substrate; an inorganic solid layer provided on
the organic layer; a first set of transparent electrodes provided
on the inorganic solid layer; an organic light emitting layer
provided on the first set of electrodes; and a second set of
electrodes formed on the organic light emitting layer; wherein the
inorganic solid layer has routes for moisture passage formed in
regions between adjacent electrodes of the first set so as to
correspond to substantially all pixels. By this arrangement, it is
possible to prevent visible failure from causing in the organic EL
display device with the lapse of time.
[0008] According to a third aspect of the present invention, the
routes for moisture passage are formed at at least one location in
each of the regions between adjacent pixels in the organic EL
display device referred to in the second aspect.
[0009] According to a fourth aspect of the present invention, there
is provided an organic EL display device, which includes an organic
light emitting layer provided between sets of electrodes,
comprising an organic layer provided on a substrate; an inorganic
solid layer provided on the organic layer; a first set of
transparent electrodes provided on the inorganic solid layer; an
organic light emitting layer provided on the first set of
electrodes; and a second set of electrodes formed on the organic
light emitting layer; wherein the inorganic solid layer has a layer
thickness set at such a thickness that allows routes for moisture
passage to be formed therein in order to avoid visible failure. By
this arrangement, it is possible to prevent visible failure from
causing in the organic EL display device with the lapse of
time.
[0010] According to a fifth aspect of the present invention, there
is provided an organic EL display device, which includes an organic
light emitting layer provided between sets of electrodes,
comprising an organic layer provided on a substrate; an inorganic
solid layer provided on the organic layer; a first set of
transparent electrodes provided on the inorganic solid layer; an
organic light emitting layer provided on the first set of
electrodes; and a second set of electrodes formed on the organic
light emitting layer; wherein the inorganic solid layer is provided
so as to have a layer thickness from 1 to 20 nm in regions between
adjacent electrodes of the first set. By this arrangement, it is
possible to prevent visible failure from causing in the organic EL
display device with the lapse of time.
[0011] According to a sixth aspect of the present invention, the
inorganic solid layer referred to in the fifth aspect is provided
so as to have a layer thickness from 1 to 10 nm in the regions
between adjacent electrodes of the first set. It is preferred that
the inorganic solid layer is provided so as to have a layer
thickness of from 5 to 10 nm.
[0012] According to a seventh aspect of the present invention, the
inorganic solid layer referred to in the first to sixth aspects is
provided so as to have a substantially equal thickness in an active
area. By this arrangement, it is possible to avoid visible failure
with the lapse of time by a simple process.
[0013] According to an eighth aspect of the present invention, the
inorganic solid layer referred to in the first to sixth aspects has
a greater thickness in regions with the first set of electrodes
therein than a thickness in the regions between adjacent electrodes
of the first set.
[0014] According to a ninth aspect of the present invention, the
inorganic solid layer referred to in the first to eighth aspects
includes a layer made of silicon oxide. By this arrangement, it is
possible to provide the first set of electrode with improved
adhesive property.
[0015] According to a tenth aspect of the present invention, the
inorganic solid layer referred to in the ninth aspect may include a
layer made of zirconium oxide provided on the layer made of silicon
oxide. By this arrangement, it is possible to minimize the
roughness on the surface of the first set of electrodes.
[0016] According to an eleventh aspect of the present invention,
there is provided a method for fabricating an organic EL display
device, comprising providing an organic layer on a substrate;
providing an inorganic solid layer on the organic layer; providing
a first set of transparent electrodes on the inorganic solid layer;
providing an organic light emitting layer on the first set of
electrodes; providing a second set of electrodes on the organic
light emitting layer provided on the first set of electrodes; and
removing water or an organic substance in the organic layer though
routes for moisture passage by drying the substrate before
providing the organic light emitting layer, the routes for moisture
passage being substantially uniformly provided in regions between
adjacent electrodes of the first set and in the inorganic solid
layer over an entire active area. By this arrangement, it is
possible to fabricate an organic EL display device capable of
minimizing the occurrence of visible failure with the lapse of
time.
[0017] According to a twelfth aspect of the present invention,
there is provided a method for fabricating an organic EL display
device, which includes a plurality of pixels corresponding to an
organic light emitting layer provided between sets of electrodes,
comprising providing an organic layer on a substrate; providing an
inorganic solid layer on the organic layer; providing a first set
of transparent electrodes provided on the inorganic solid layer;
providing an organic light emitting layer on the first set of
electrodes; providing a second set of electrodes formed on the
organic light emitting layer provided on the first set of
electrodes; and removing water or an organic substance in the
organic layer though routes for moisture passage by drying the
substrate before providing the organic light emitting layer, the
routes for moisture passage being provided in regions between
adjacent electrodes of the first set so as to correspond to
substantially all pixels. By this arrangement, it is possible to
fabricate an organic EL display device capable of minimizing the
occurrence of visible failure with the lapse of time.
[0018] According to a thirteenth aspect of the present invention,
there is provided a method for fabricating an organic EL display
device, comprising providing an organic layer on a substrate;
providing an inorganic solid layer on the organic layer; providing
a first set of transparent electrodes on the inorganic solid layer;
providing an organic light emitting layer on the first set of
electrodes; and providing a second set of electrodes on the organic
light emitting layer provided on the first set of electrodes; and
further comprising removing water or an organic substance in the
organic layer though routes for moisture passage by drying the
substrate before providing the organic light emitting layer, the
routes for moisture passage being provided in the inorganic solid
layer; and forming the inorganic solid layer so as to have a layer
thickness set at such a thickness that allows the routes for
moisture passage to be formed therein in order to avoid visible
failure when providing of the organic light emitting layer. By this
arrangement, it is possible to fabricate an organic EL display
device capable of minimizing the occurrence of visible failure with
the lapse of time.
[0019] According to a fourteenth aspect of the present invention,
there is provided a method for fabricating an organic EL display
device, which includes a plurality of pixels corresponding to an
organic light emitting layer provided between sets of electrodes,
comprising providing an organic layer on a substrate; providing an
inorganic solid layer on the organic layer; providing a first set
of transparent electrodes provided on the inorganic solid layer;
providing an organic light emitting layer on the first set of
electrodes; and forming the inorganic solid layer so as to have a
layer thickness from 1 to 20 nm in regions between adjacent
electrodes of the first set when providing of the inorganic solid
layer. By this arrangement, it is possible to fabricate an organic
EL display device capable of reducing the occurrence of visible
failure with the lapse of time.
[0020] According to a fifteenth aspect of the present invention,
the method referred to in the fourteenth aspect comprises forming
the inorganic solid layer so as to have a layer thickness from 1 to
5 nm when providing of the inorganic solid layer.
[0021] According to a sixteenth aspect of the present invention,
the method referred to in the fifteenth aspect comprises forming
the inorganic solid layer at a substrate temperature of 100.degree.
C. or below when providing of the inorganic solid layer.
[0022] According to a seventeenth aspect of the present invention,
the method referred to the fourteenth aspect comprises forming the
inorganic solid layer at a substrate temperature of 200.degree. C.
or above when providing of the inorganic solid layer.
[0023] According to an eighteenth aspect of the present invention,
the method referred to in the eleventh to seventeenth aspects
further comprises removing at least one part of portions of the
inorganic solid layer in the regions between adjacent electrodes of
the first set before providing of the organic light emitting
layer.
[0024] In accordance with the present invention, it is possible to
provide an organic EL display device and a method for fabricating
the same, which are hard to have the occurrence of visible failure
caused by the lapse of time or which have no occurrence of the
visible failure.
[0025] In the drawings:
[0026] FIG. 1 is a schematic plan view of a conventional organic EL
display device;
[0027] FIG. 2 is a schematic cross-sectional view of the
conventional organic EL display device;
[0028] FIG. 3 is a schematic cross-sectional view of the organic EL
display device according to an embodiment of the present
invention;
[0029] FIG. 4 is a cross-sectional view of the conventional organic
EL display device, schematically showing a state wherein water or
an organic substance enters color filters or an overcoat layer;
[0030] FIG. 5 is a cross-sectional view of the conventional organic
EL display device, schematically showing a state wherein water or
an organic substance enters from the color filters or the overcoat
layer into an upper layer;
[0031] FIG. 6 is a cross-sectional view of the organic EL display
device according to the embodiment, schematically showing a state
wherein water or an organic substance enters color filters or an
overcoat layer;
[0032] FIG. 7 is a cross-sectional view of the organic EL display
device according to the embodiment, schematically showing a state
wherein water or an organic substance is removed from the color
filters or the overcoat layer;
[0033] FIGS. 8A and 8B are a cross-sectional views of the organic
EL display device according to an embodiment of the present
invention, schematically showing a state wherein after an inorganic
solid layer was once formed so as to have a thickness beyond 5 nm,
the portions of the inorganic solid layer between first patterned
electrodes are removed by etching;
[0034] FIG. 9 is a schematic cross-sectional view of the organic EL
display device according to an example of the present invention;
and
[0035] FIG. 10 is a schematic plan view of the organic EL display
device according to the example of the present invention.
[0036] Now, embodiments of the present invention will be described,
referring to examples, the accompanying drawings and the like. The
drawings, the examples and the like, and the description are
illustrative of the present invention but are not intended to limit
the scope of the present invention. It is to be understood that
other embodiments are included within the scope of the present
invention as long as they fall within the spirit of the present
invention. In the drawings, like reference numerals designate
identical or corresponding parts.
[0037] An organic EL display device is configured in a
multi-layered structure wherein, as an example, color filters are
provided on a substrate, an overcoat layer is formed on the color
filters and the substrate for flatness, an inorganic solid layer is
formed on the overcoat layer to prevent moisture or an organic
substance from passing in an interlayer direction, a first set of
transparent electrodes is provided on the inorganic solid layer, a
second set of electrodes is provided above the first set of
transparent electrodes (a side of the first set of electrodes
remote from the substrate), and an insulating layer with apertural
areas formed therein and a light emitting layer are provided
between the first set of electrodes and the second set of
electrodes.
[0038] This structure will be illustratively described, referring
to FIG. 2. The color filters 22, such as red color filters, blue
color filters and green color filters, are provided on the
substrate 21. The overcoat layer 23 is provided so as to cover the
color filters to form a flat surface. The inorganic solid layer 24
is provided on the overcoat layer. The first set of patterned
electrodes 25 is provided on the inorganic solid layer. The
insulating layer 26 with the apertural areas 29 formed therein, the
light emitting layer 27 and the second set of electrodes 28 are
provided on the first set of electrodes. The multi-layered
structure of the organic EL display device is configured in this
way. In general, the first set of electrodes is used as anodes, and
the second set of electrodes is used as cathodes. In the structure
stated earlier, the word "on" means not only that a layer or the
like is directly provided on another layer or a set of electrodes,
but also that a layer or the like is provided on another layer or a
set of electrodes with another layer or the like interposed
therebetween. In other words, another layer may be formed between
layers or between a layer and a set of electrodes.
[0039] The organic EL display device is usually driven by passive
matrix addressing, using the first set of transparent electrodes as
signal electrodes and the second set of electrodes as scanning
electrodes. This is because this type of structure can be easily
fabricated. Conversely, the first set of transparent electrodes may
be used as scanning electrodes, and the second set of electrodes
may be used as signal electrodes. The first set of electrodes and
the second set of electrodes may be respectively formed as scanning
electrodes and signal electrodes, which are connected to TFTs (thin
film transistors).
[0040] The color filters and the overcoat layer are layers made of
an organic material (organic layers) and are liable to hold water
or an organic substance, such as an organic solvent. In some cases,
good film formation of the first set of electrodes is inhibited by
water or an organic substance, which is generated from an organic
layer when the first set of electrodes is fabricated by, e.g.
sputtering. It has been known that the water or the organic
substance diffuses in the light emitting layer provided on the
first set of electrodes to disturb light emission.
[0041] In order to prevent the water or the organic substance from
diffusing, the formation of the first set of electrodes has been
performed so that the inorganic solid layer, which is made of,
e.g., silicon oxide, is provided under the first set of electrodes.
When the first set of electrodes is provided directly on the
organic layer, it is difficult to obtain a sufficient adhesive
force between the overcoat layer and the first set of electrodes in
many cases. The provision of the inorganic solid layer can solve
this problem as well.
[0042] However, the inorganic solid layer is susceptible to the
formation of a pinhole. When a pinhole is formed, water or an
organic substance contained in the organic layers passes through
the pinhole to disturb light emission in the light emitting layer.
The first set of electrodes is normally formed in a pattern having
a plurality of stripes. When the pinhole in the inorganic solid
layer exists in a region with a patterned stripe, it is possible to
prevent the movement of the water or the organic substance by the
first set of electrodes. However, when the pinhole is in a region
without a patterned stripe, it is impossible to inhibit the
movement of the water or the organic substance.
[0043] Even if the organic layers can be dried to completely remove
water or an organic substance before formation the inorganic solid
layer, water or an organic substance, which has been used during
fabrication of the organic EL display device, enters a color filter
or the overcoat layer through pinholes in the inorganic solid layer
as indicated by arrows in FIG. 4. This sort of trouble is caused at
the time of washing the first set of electrodes patterned by
etching, taking off a photoresist in a photolithographic treatment,
developing the insulating layer or washing the developed insulating
layer.
[0044] Even if a drying treatment is performed on a later stage,
the water or the organic substance, which has entered the color
filter or the overcoat layer, is insufficiently removed since there
is no other escape than the pinholes. After the organic EL display
device is finished, the water or the organic substance enters the
light emitting layer through the pinholes as indicated by arrows in
FIG. 5 to suppress light emission, causing non-emissive areas.
[0045] The visible failure with the lapse of time stated earlier is
supposed to be caused by this mechanism. FIG. 4 shows a
cross-sectional structure when no layer is provided on a side of
the first set of electrodes remote from the substrate. However, a
similar problem is caused in a structure wherein another layer is
provided on the side of the first set of electrodes remote from the
substrate.
[0046] In other words, in the case of an organic EL display device
wherein a first set of transparent electrodes is provided on a
substrate, a second set of electrodes is provided on a side of the
first set of electrodes remote from the substrate, a light emitting
layer is provided between the first set of electrodes and the
second set of electrodes, an organic layer is provided between the
first set of electrodes and the substrate, and an inorganic solid
layer is provided between the first set of electrodes and the
organic layer to prevent water or an organic substance from passing
in an interlayer direction, when a pinhole exists in the inorganic
solid layer, spot-like non-emissive areas are formed with the lapse
of time as show in FIG. 1, causing visible failure. Although, as
one of the measures, there is a proposal to increase the thickness
of the inorganic solid layer, it is difficult to completely
eliminate the formation of the pinholes by this proposal. An
increase in the thickness also causes a problem, such as an
increase in production costs.
[0047] The problem of visible failure can be solved by providing
the inorganic solid layer so as to have a layer thickness from 0 to
5 nm between the first set of electrodes and the organic layer and
in at least a portion of each of regions without a patterned
electrode of the first set. By adopting this solution, it is
possible to fabricate an organic EL display device, wherein visible
failure with the lapse of time is not caused or is difficult to be
caused.
[0048] The structure of an organic EL display device with this
solution applied thereto will be described, referring to FIG. 3.
This figure is a schematic cross-sectional view of an organic EL
display device according to the present invention. Color filters
22, such as red color filters, blue color filters or green color
filters, are provided on a substrate 21, an overcoat layer 23 is
provided to cover the color filters so as to form a flat surface,
an inorganic solid layer 24 is provided on the overcoat layer, a
first set of patterned electrodes 25 are provided on the inorganic
solid layer, and an insulating layer 26, a light emitting layer 27
and a second set of electrodes 28 are provided on the first set of
electrodes. Although the multi-layered structure of the organic EL
display device is configured in this way, this figure
illustratively shows that the inorganic solid layer has a layer
thickness of 0 nm in regions without any one of the first set of
electrodes provided therein (hereinbelow, referred as "the pattern
spacings" or "the first electrode spacings" in some cases) since,
when patterning the first set of electrodes after having been
formed as a uniform layer, spacings between adjacent electrodes,
portions of the inorganic solid layer under the spacings, and
portions of the overcoat layer under the portions of the inorganic
solid layer are removed by etching. In the present invention, a
case wherein the inorganic solid layer is formed so as to have a
layer thickness of 0 nm includes a case wherein the inorganic solid
layer is not formed in all regions without any one of the first set
of electrodes provided therein.
[0049] By the provision of the inorganic solid layer 24, it is
possible to prevent water or an organic substance from diffusing
from the color filters 22 and the overcoat layer 23 onto the
inorganic solid layer 24 when fabricating the first set of
electrodes. Thus, it is possible to ensure an adhesive force
between the first set of electrodes 25 and the inorganic solid
layer 24.
[0050] Although water or an organic substance that has been used
when fabricating the respective layers after formation of the first
set of electrodes is likely to diffuse into the color filters 22
and the overcoat layer 23 as indicated by arrows in FIG. 6 since
the portions of the inorganic solid layer in the inter-patterns of
the first electrode spacings is removed, it is possible to easily
remove the water or the organic substance by, e.g., drying at a
later stage as indicated by arrows in FIG. 7. Although FIG. 6
shows, as in FIG. 4, a cross-sectional structure when no other
layer is not formed on the side of the first set of electrodes
remote from the substrate, the same holds for a structure wherein
another layer has been formed on the side of the first set of
electrodes remote from the substrate.
[0051] Accordingly, it is possible to prevent the occurrence of
visible failure with the lapse of time by sufficiently removing the
water or the organic substance of the organic EL display device
when finally sealing of the organic EL display device. Although
FIG. 7 shows a stage wherein the light emitting layer 27 and the
second set of electrodes 28 have been formed, the time for removing
water or an organic substance is not limited to this stage. The
removal of water or an organic substance may be performed one or
more times at an arbitrary stage up to final sealing of the organic
EL display device.
[0052] The inorganic solid layer does not necessarily need to have
a film thickness of 0 nm in the first electrode spacings. It is
sufficient that the inorganic solid layer has a layer thickness in
a range from 0 to 5 nm in the first electrode spacings. This is
because, even if the layer thickness is not 0 nm, it is possible to
remove water or an organic substance when the inorganic solid layer
is quite thin. For example, when the layer thickness is not greater
than about 2 nm, regions without the inorganic solid layer are
partly formed since it is difficult to obtain uniform film
deposition. The layer thickness of the inorganic solid layer
referred to here is an average value.
[0053] In many cases, it is preferred that the inorganic solid
layer has a layer thickness from 0.5 to 5 nm in the first electrode
spacings. This is because it is possible not only to prevent water
or an organic substance from entering but also to remove water or
an organic substance through the inorganic solid layer.
[0054] In consideration of the process tolerance of exposed
portions of the inorganic solid layer against, e.g., acids,
alkalis, organic solvents, plasma or a brush, a thicker layer of
the inorganic solid layer is preferred on condition that the
inorganic solid layer has a thickness in a range capable of
maintaining water permeability. In some cases, it is preferred that
the inorganic solid layer has a layer thickness from 5 to 10 nm in
consideration of the film deposition conditions of the inorganic
solid layer and the drying conditions before vapor deposition of
the device.
[0055] For example, in the case of depositing a film of SiO.sub.2
as the inorganic solid layer by sputtering, when the film
deposition is performed at a substrate temperature from 200 to
230.degree. C., it is possible to obtain sufficiently high water
permeability even if the layer thickness is about 10 nm. As stated
earlier, from the viewpoint of the process tolerance, it is
preferred that the inorganic solid layer has a greater layer
thickness. In this case, it was possible to obtain good results by
forming the inorganic solid layer so as to have a layer thickness
from 5 to 10 nm and performing a heating and drying process at 200
to 250.degree. C. as the drying process before vapor deposition of
the device.
[0056] Likewise, in a case wherein the inorganic solid layer is
made of a film of SiO.sub.2 deposited by sputtering at a substrate
temperature of 100.degree. C. or below, it is seen that the water
permeability is insufficient at a layer thickness of 10 nm. In this
case, it is sufficient that the inorganic solid layer has a layer
thickness of 1 to 5 nm.
[0057] In the present invention, in order to prevent water or an
organic substance from entering an organic layer before provision
of the first set of electrodes, it is preferred that the inorganic
solid layer is provided so as to have a layer thickness of 0 to 20
nm on a side of the first set of electrodes close to the substrate.
The inorganic solid layer may be fabricated as a single layer along
with the inorganic solid layer in each of the pattern spacings or
be fabricated separately from the inorganic solid layer in each of
the pattern spacings. Although all portions of the inorganic solid
layer does not need to exist on the same plane as each other, the
inorganic solid layer is provided between an organic layer and the
first set of electrodes in order to prevent water or an organic
substance from entering the organic layer. When the inorganic solid
layer is fabricated as the single layer, the inorganic solid layer
has a layer thickness from 0 to 5 nm in each of the pattern
spacings of the first set of electrodes, and the inorganic solid
layer has a layer thickness from 0 to 20 nm in the regions with the
first patterned electrodes (hereinbelow, referred to as "under the
first patterned electrodes" in some cases).
[0058] The inorganic solid layer may also have a layer thickness
from 0 to 5 nm in the regions with the first patterned electrodes
provided there.
[0059] As a case wherein the inorganic solid layer does not have a
thin layer thickness in a range from 0 to 5 nm under the first
patterned electrodes, there is an example wherein the inorganic
solid layer is once deposited so as to have a layer thickness
beyond 5 nm as shown in FIG. 8A, and then the portions of the
inorganic solid layer in the patterned spacings of the first
electrodes are etched so as to have a layer thickness in the range
from 0 to 5 nm as shown in FIG. 8B. Or the portions of the
inorganic solid layer in the pattern spacings of the first
electrodes may be removed by polishing the substrate surface after
deposition of the first set of electrodes. In the latter case, the
total thickness decreases since the surfaces of the first set of
electrodes are also polished. FIG. 8B shows a case wherein the
portions of the inorganic solid layer between adjacent patterned
electrodes are all removed. A case wherein the portions of the
inorganic solid layer between adjacent patterned electrodes remain
so as to have a layer thickness in the range from 0 to 5 nm, or a
case wherein the portions of the overcoat layer between adjacent
patterned electrodes are also removed as shown in FIG. 3 are
included with the scope of the present invention.
[0060] As a case wherein the inorganic solid layer has a layer
thickness of 5 nm or below under the first patterned electrodes,
there is an example wherein the inorganic solid layer 24 shown in
FIG. 2 is deposited so as to have a layer thickness of 5 nm or
below from the start. In this case, although there is no need for
etching since the inorganic solid layer has already had a layer
thickness in the range from 0 to 5 nm in the pattern spacings of
the first electrodes, etching may be further performed for easy
removal of water or an organic substance.
[0061] It should be understood that one of the features of the
present invention that the inorganic solid layer has a layer
thickness from 0 to 5 nm in the pattern spacings of the first
electrodes is not limited to the cases stated earlier. A case
wherein the portions of the inorganic solid layer under the first
patterned electrodes partly have a layer thickness in the range
from 0 to 5 nm, and a case wherein the portions of the inorganic
solid layer in the pattern spacings partly have a layer thickness
in the range from 0 to 5 nm are also included within the scope of
the present invention. A specific preferred range for the layer
thickness or specific preferred portions of the inorganic solid
layer to have a layer thickness in the range from 0 to 5 nm may be
easily determined by performing a model experiment or the like and
reviewing whether the occurrence of visible failure with the lapse
of time can be avoided or not.
[0062] The advantage stated earlier may be regarded as being an
advantage offered by a feature that the layer thickness of the
inorganic solid layer in each of the pattern spacings of the first
electrodes is smaller than that under each of the first patterned
electrodes. In other words, it is possible to avoid difficulty in
fabrication of the first set of electrodes and to easily remove
water or an organic substance at a later stage by adding a process
wherein, after the inorganic solid layer has been once deposited,
the inorganic solid layer is processed so that the layer thickness
of the inorganic solid layer in each of the pattern spacings is
smaller than the layer thickness of the inorganic solid layer under
each of the first patterned electrodes. The layer thickness in this
case may be determined by an average value.
[0063] Strictly speaking, the layer thickness of the portions of
the inorganic solid layer in the first electrode spacings is
smaller than the layer thickness of the portions of the inorganic
solid layer at each of the intersections with the second set of
electrodes among the portions of the inorganic solid layer under
the first patterned electrodes, when seeing the organic EL display
device from a direction perpendicular to the substrate surface.
[0064] Such a structure may be obtained by preliminarily depositing
the inorganic solid layer so as to be at least partly formed at the
intersections between the first set of electrodes and the second
set of electrodes, and pattering the first set of electrodes,
followed by etching the portions of the inorganic solid layer
corresponding to the regions without the first patterned
electrodes. Or the portions of the inorganic solid layer
corresponding to the regions without the first patterned electrodes
may be removed by polishing the substrate surface.
[0065] Although any conventional method is applicable as a method
for processing the portions of the inorganic solid layer in the
pattern spacings so as to have a layer thickness from 0 to 5 nm,
the most rational method is to etch the portions of the inorganic
solid layer corresponding to the regions without the first
patterned electrodes after patterning the first set of electrodes.
Etching may be dry etching or wet etching, or a combination of
both. Although the portions of the inorganic solid layer under the
first patterned electrodes are partly etched to form undercuts in
some cases, no problem is caused as long as the formed undercuts
can be filled with, e.g., an insulating layer.
[0066] Or it is acceptable to remove the portions of the inorganic
solid layer in the regions of the first electrode spacings by
polishing the substrate surface after deposition of the first set
of electrodes. In this case, it is possible to minimize the
roughness of the surfaces of the first set of electrodes since not
only the organic layer in the regions of the first electrode
spacings but also the surfaces of the first set of electrodes are
removed by polishing. In this case, in consideration of a decrease
in the thickness of the first set of electrodes, it is preferred
that the first set of electrodes are deposited so as to have a
greater film thickness than desired.
[0067] The layer thickness of the portions of the inorganic solid
layer in the first electrode spacings, which is appropriate for
drying and removing of water or the like, is not limited to a value
in the range stated earlier. For example, the layer thickness
appropriate for drying and removing varies since the film quality
of the inorganic solid layer varies depending on the conditions of
film deposition of the inorganic solid layer and the first set of
electrodes. Specifically, when the film deposition temperature for
each of the inorganic solid layer and the first set of electrodes
is high, even a layer thickness beyond 5 nm is appropriate for
drying and removing moisture. On the other hand, when the film
deposition temperature for each of the inorganic solid layer and
the first set of electrodes is low, there is a tendency that even a
layer thickness below 5 nm is appropriate for drying and removing
moisture. The inorganic solid layer and the first set of electrodes
are normally deposited at substantially the same temperature since
both are deposited by the same sputtering system.
[0068] For example, when the film deposition temperature is as high
as about 200.degree. C., it is preferred that the portions of the
inorganic solid layer in the first electrode spacings has a layer
thickness from 0 to 20 nm. For example, when the first set of
electrodes is made of ITO, a polycrystal layer of ITO is formed by
film deposition at a temperature of 200.degree. C. or higher. On
the other hand, when the film deposition temperature is as low as
100.degree. C. or below, it is preferred that the layer thickness
is smaller than 5 nm. When film deposition is performed at a
temperature of 100.degree. C. or below, an amorphous layer of ITO
is formed. From the viewpoint of durability at a later process, it
is recommended that the layer thickness of the inorganic solid
layer is set at 1 nm or greater. The inorganic solid layer thus
formed is appropriate for drying and removing moisture or an
organic substance in an organic layer. The inorganic solid layer
may be formed so as to have a layer thickness in the range stated
earlier by film deposition or be formed by being partly removed by,
e.g., etching after having formed so as to have a greater film
thickness than the film thicknesses stated earlier.
[0069] The inorganic solid layer that is appropriate for drying and
removing has routes for moisture passage formed therein to pass
water or an organic substance in an organic layer from the organic
layer to an upper layer in the drying process. The routes for
moisture passage are routes, through which moisture or an organic
substance contained in the color filter 22 or the overcoat layer 23
passes through the inorganic solid layer in the drying process. In
the other words, moisture or the like in an organic layer can be
removed through the routes for moisture passage formed in the
inorganic solid layer since moisture or the like is movable between
layers through the routes for moisture passage in the drying
process. When the drying process is performed after formation of
the first set of electrodes, moisture or the like is removed
through the routes for moisture passage formed in the first
electrode spacings.
[0070] It is recommended that the routes for moisture passage are
uniformly formed in the inorganic solid layer over the entire
active area. When the drying process is performed after formation
the first set of electrodes, it is recommended that the routes for
moisture passage are uniformly formed in the pattern spacings of
the first electrodes. When the routes for moisture passage fail to
be uniformly formed with a certain density or more, it is
impossible to remove moisture or the like in an organic layer in a
sufficient way. As a result, it is observed that spot-like
non-emissive areas are formed in portions without the routes for
moisture passage as shown in FIG. 1.
[0071] It is recommended that the inorganic solid layer has the
routes for moisture passage formed so as to correspond to all
pixels comprising the portions of the organic light emitting layer
formed between the first and second sets of electrodes.
Specifically, when the pixels are formed in a matrix pattern as
shown in FIG. 1, it is recommended that each of the pixels has at
least one route for moisture passage formed in a peripheral region
thereof (a region between the pixel and an adjacent pixel). It is
recommended that each of the pixels has one or more routes for
moisture passage formed in the region between the pixel and an
adjacent pixel. Since the moisture or the like in the organic
layers can be fully removed by this arrangement, it is possible to
avoid the occurrence of visible failure with respect to all
pixels.
[0072] In order to determine whether the routes for moisture
passage, which are appropriate for removal of water or the like in
the drying process, have been formed in the inorganic solid layer,
the substrate is put in a vacuum chamber and is heated therein for
instance. When the routes for moisture passage have been formed in
a sufficient way, an increase in the pressure in the chamber is
observed since the moisture or the like leaks out through the
routes for moisture passage. In other words, when the pressure in
the chamber increases, it is verified that the routes for moisture
passage have been formed in the inorganic solid layer in a
sufficient way, and that the routes for moisture passage are
appropriate for drying and removing. On the other hand, when the
pressure in the chamber does not increase, it is verified that the
routes for moisture passage are not appropriate for drying and
removing since the routes for moisture passage have been formed in
the inorganic solid layer in an insufficient way, and since the
routes for moisture passage cannot remove the moisture or the like
in a sufficient way. Thus, it is possible to determine whether the
routes for moisture passage have been formed so as to be
appropriate for drying and removing.
[0073] The inorganic solid layer, the thickness of which is as
extremely small as a few nm, may be deposited by lowering the power
supply for film deposition or reducing the time period for film
deposition. For example, it is possible to form the inorganic solid
layer as a thin layer by increasing the conveying speed for the
substrate to reduce the time period for film deposition in an
in-line sputtering system wherein the substance is subjected to
film deposition, being conveyed. For example, the film deposition
may be performed while the conveying speed is modified based on the
ratio of a desired film thickness of the extremely thin layer to be
actually deposited to a film thickness to be able to be accurately
measured. By this arrangement, it is possible to reduce the time
period for film deposition and to uniformly form the inorganic
solid layer as an extremely thin layer.
[0074] The film thickness of the inorganic solid layer, which is
formed as an extremely thin layer by the method stated below, may
be measured by a stylus method film thickness meter. A sample
wherein an organic layer, an inorganic solid layer and a
transparent electrode pattern are provided in layers, is used. The
inorganic solid layer is etched, using the transparent electrode
pattern as a mask. When the transparent electrodes is made of a
film of ITO, and when the inorganic solid layer is made of a film
of SiO.sub.2, only the film of SiO.sub.2 is etched away, and the
organic film as the lower layer is prevented to be etched by using
dilute hydrofluoric acid as the etchant.
[0075] After that, the film of ITO is etched away. Thus, the
patterned film of SiO.sub.2 remains on the organic film. The film
of SiO.sub.2 is measured by the stylus method film thickness meter.
It is normally difficult to measure a step from 1 to 10 nm with
good precision by the stylus method film thickness meter. However,
when a pattern for matrix elements of an organic EL display device
is used as the transparent electrode pattern, it is possible to
periodically measure a plurality of steps by the stylus method film
thickness meter since the steps are formed with a high density.
[0076] As a result, it is easy to distinguish between noise and a
step, and it is possible to improve measurement precision. Thus, it
is possible to measure a step having a difference of about 3 nm or
more with good reproducibility.
[0077] As the inorganic solid layer according to the present
invention, a material that has a function to prevent water or an
organic substance from diffusing is employed. Any inorganic
material, which preferably has a good adhesion property with
respect to the first set of electrodes, is applicable. Examples of
preferred inorganic compounds are silicon oxide (SiO.sub.2),
zirconium oxide (ZrO.sub.2), silicon nitride (SiNx), silicon
oxynitride (SiOxNy), tantalum oxide (TaOx) and aluminum oxide
(AlOx). A film of silicon oxide is particularly preferred. The
inorganic solid layer may be deposited by a conventional method,
such as sputtering. The inorganic solid layer may comprise a
plurality of layers made of different materials. When the inorganic
solid layer comprises a plurality of layers, it is preferred that
the inorganic solid layer includes a film of silicon oxide.
Additionally, when the inorganic solid layer has a multilayered
structure, it is recommended that a film of zirconium oxide be
formed on a film of silicon oxide. By this arrangement, it is
possible to reduce the roughness of the surfaces of the first set
of electrodes formed on the inorganic solid layer. The layer of
zirconium oxide may be deposited by a sputtering process wherein a
target of zirconium and an oxygen gas are employed.
[0078] The substrate to be employed in the present invention is a
supporter for the organic EL display device. A transparent
substrate, such as a glass sheet or a plastic film, is applicable
in general. More specifically, a soda lime glass substrate with an
alkali barrier or a non-alkali glass substrate is applicable in
many cases. A plastic substrate with a moisture-proof coating is
applicable. Examples of the plastic material are polycarbonate,
polymetacrylate and polysulfone.
[0079] As the material for the first set of electrodes, a thin film
of indium tin oxide (ITO) or a film of tin oxide is applicable. The
first set of electrodes may comprise a metal having a high work
function, such as silver or gold, a conductive inorganic material,
such as copper iodide, or a conductive polymer, such as
poly(3-methylthiophene), polypyrrole or polyaniline. Although the
layer thickness of the first set of electrodes is determined
depending on required transparency, the layer thickness is
generally from 5 to 1000 nm, preferably from 10 to 500 nm since the
transmittance ratio of visible light is set at 60% or higher,
preferably 80% or higher. In the case of metal electrodes, Al or Cr
or the like is applicable.
[0080] As the material for the second set of electrodes, various
electrode materials including electrode materials for the
conventional organic EL are applicable. Examples of the electrode
materials are an alloy of magnesium and aluminum, an alloy of
magnesium and silver, an alloy of magnesium and indium, an alloy of
aluminum and lithium, and aluminum.
[0081] As the material for the light emitting layer, a chemical
compound, which has a high fluorescence yield, a high injection
efficiency to electrons from the second set of electrodes, and a
high electron mobility, is effective. As such a chemical compound,
a known organic substance having a light emitting property, such as
8-oxyquinoline complex, tetraphenylbutadiene, styryl dye and
oxadiazole dye, is applicable.
[0082] The thickness of the light emitting layer is normally from
10 to 200 nm, preferably from 20 to 80 nm. The light emitting layer
may be accompanied by a hole transport layer, an interface layer,
an electron injection layer, an electron transport layer or the
like. When any one of these layers exists, the light emitting layer
according to the present invention is construed as one which
includes the layers.
[0083] As the organic layers according to the present invention,
any layer containing an organic composition may be included. In
other words, the organic layers are layers, which comprise a
substance capable of containing water or an organic substance.
Examples of the organic layers are the color filters, a color
conversion layer, a transparent film for interference control, the
overcoat layer and a black matrix. The present invention is
particularly preferred in practice when the color filters and the
overcoat layer are included as the organic layers.
[0084] It is preferred that the organic EL display device according
to the present invention further includes an insulating layer
having apertural areas corresponding to the intersections between
the first set of electrodes and the second set of electrodes in
order to delimit pixels for display.
[0085] As the material for forming the overcoat layer or the
insulating layer, a polymeric material, such as a polyimide resin,
is particularly applicable. There is no limitation to the material.
A known material having a sufficient insulating property is
applicable. However, the overcoat layer needs to be transparent in
order to make the light emitting parts visible from outside. As the
method for forming the overcoat layer or the insulating layer, a
known method is applicable.
[0086] In accordance with a method for fabricating the organic EL
display device according to the present invention, a first set of
transparent electrodes are provided on a substrate, a second set of
electrodes are provided on a side of the first set of electrodes
remote from the substrate, a light emitting layer is formed so as
to be located between a layer of the first set of electrodes and a
layer of the second set of electrodes, an organic layer is formed
between the first set of electrodes and the substrate, and an
inorganic solid layer for, which is capable of preventing water or
an organic substance from passing in an interlayer direction, is
provided so as to have a layer thickness from 0 to 5 nm so that the
inorganic solid layer is located between the layer of the first set
of electrodes and the organic layer, and in at least one portion of
each of regions without the patterned electrodes of the first
electrodes. Then, water or an organic substance is removed. The
removal of water or an organic substance means a reduction in the
mass of water or an organic substance contained, and does not
necessarily means the nonexistence of water or an organic
substance.
[0087] As stated earlier, the removal of water or an organic
substance may be performed one or more times at an arbitrary stage
up to a stage wherein a display area comprising collection of
pixels is sealed to finally seal the organic EL display device. The
removal is preferably performed before formation of the second set
of electrodes. This is because, after formation of the second
electrodes, the second electrodes works as a barrier to deteriorate
the removal efficiency of water or an organic substance in many
cases. The removal is more preferably performed before formation of
the organic film as the light emitting element layer. This is
because in many cases, it is difficult to perform drying by heating
after formation of the organic film. Specifically, when the removal
is performed may be determined, depending on the fabrication
processes of an actual organic EL display device.
[0088] The removal of water or an organic substance is preferably
performed by a drying treatment. The drying treatment may be
performed in any drying mode, such heating, introduction of a dry
gas, or depressurization. The drying treatment may be performed in
a combination of modes.
[0089] More specifically, it is preferred in terms of
simplification and high reliability that the drying treatment is
performed by heating in a dry atmosphere using introduction of a
dry gas or in depressurization. In this case, the degree of
depressurization may be appropriately selected. To replace an
atmosphere by a dry gas before depressurization is effective. As
the dry gas, dry air, a nitrogen gas, an argon gas or the like is
applicable. It is preferred that the drying treatment is performed
before formation of the light emitting layer. It is preferred from
the viewpoint of the time period required for process treatment
that the drying treatment is performed by depressurization and
heating.
[0090] It is preferred that required treatments are performed in an
environment of a drying gas of atmospheric pressure or a drying gas
of decompressed pressure up to sealing of the display area after
removal of water or an organic substance by the drying treatment or
the like. As the dry gas, dry air, a nitrogen gas, an argon gas or
the like is applicable.
[0091] When the display area is sealed to complete the organic EL
display device according to the present invention, it is preferred
from the viewpoint of avoiding aged deterioration by invasion of
external air to perform the sealing in an atmosphere of a dry gas.
As the dry gas, it is preferred to employ a gas inactive against
the employed materials, such as a nitrogen gas, or an argon
gas.
[0092] Thus, the organic EL display device according to the present
invention is provided as an electronic device, which is capable of
avoiding the occurrence of display failure with the lapse of time
or making the occurrence of display failure difficult. In other
words, the organic EL display device can maintain the initial
display properties at substantially the same level.
[0093] The present invention has been mainly described in about a
case wherein the inorganic solid layer exists under each of the
first patterned electrodes. When the inorganic solid layer, which
disturbs the diffusion of water or an organic substance, does not
exist between adjacent first patterned electrodes, the advantage of
the present invention is offered irrespective of whether the
inorganic solid layer exists under the first patterned electrodes.
In other words, an organic EL display device, which includes a
first set of transparent electrodes on a substrate, a second set of
electrodes provided on a side of the first set of electrodes remote
from the substrate, a light emitting layer formed so as to be
located between a layer of the first set of electrodes and a layer
of the second set of electrodes, and an organic layer is formed
between the layer of the first set of electrodes and the substrate,
and wherein an inorganic solid layer, which is capable of
preventing water or an organic substance from passing in an
interlayer direction, does not exist under the first patterned
electrode or between adjacent patterned electrode, is also included
in the category of the organic EL display device according to the
present invention.
EXAMPLES
[0094] Now, examples of the present invention and comparative
examples will be described in detail. Examples 1, 2, 3, 6, 7, 8, 9,
10, 11 and 12 are examples of the present invention, and Examples 4
and 5 are comparative examples.
Example 1
[0095] Color filters having a thickness of 1.5 .mu.m were formed on
a glass substrate by photolithography. An overcoat layer, which
comprised an acryl resin provided on a glass substrate base and
having a thickness of 2 .mu.m, was formed by photolithography. An
inorganic solid layer, which had a thickness of 20 nm and is made
of SiO.sub.2, was formed by sputtering. An ITO film as a layer of
the first set of electrodes was deposited so as to have a thickness
150 nm by sputtering. The inorganic solid layer of SiO.sub.2 was
deposited by RF sputtering under such conditions that the substrate
temperature was 220.degree. C., SiO.sub.2 was employed as the
target, an argon gas was employed as the sputtering gas, and the
gas pressure is 0.7 Pa. The ITO film was deposited by DC sputtering
under such conditions that the substrate temperature was
220.degree. C., an argon gas with 0.8% of oxygen gas added was
employed as the sputtering gas, and the gas pressure was 0.7
Pa.
[0096] Then, the first set of electrodes (anodes) made of ITO was
patterned by wet etching, using a solution of hydrochloric acid and
ferric chloride. By this treatment, the portions of the inorganic
solid layer made of SiO.sub.2 between adjacent first patterned
electrodes were exposed. The width of each of the first patterned
electrodes was set at 320 .mu.m, and the width of the exposed
portions of the inorganic solid layer of SiO.sub.2 between adjacent
patterned electrodes was set at 30 .mu.m.
[0097] Next, the exposed portions of the inorganic solid layer of
SiO.sub.2 between adjacent first patterned electrodes were wet
etched by dilute hydrofluoric acid. Since the overcoat layer was
not wet etched by dilute hydrofluoric acid, etching was performed
only to the inorganic solid layer of SiO.sub.2. By this treatment,
the portions of the overcoat layer between adjacent first patterned
electrodes were exposed, and a structure wherein the portions of
the inorganic solid layer did not substantially exist between
adjacent first patterned electrodes was obtained a shown in FIG.
8B.
[0098] On this structure, an insulating layer, which had apertural
areas and was made of photosensitive polyimide, was formed by
photolithography. Cathode separator, which were made of a cresol
resin, were formed as an upper layer. The apertural areas of the
insulating layer had an apertural width in a width direction of the
first patterned electrodes set at 300 .mu.m. Additionally, a light
emitting element layer was formed by vapor deposition of copper
phthalocyanine having a thickness of 10 nm, .alpha.-NPD
(4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) having a thickness
of 100 nm and Alq3 (tris(8-quinolinorate)aluminum) having a
thickness of 60 nm. On the light emitting element layer, a film of
LiF having a thickness of 0.5 nm and Al electrodes having a
thickness of 80 nm were deposited by a vapor deposition method to
form an electron injection layer and cathodes (second set of
electrodes).
[0099] As shown in FIG. 9, the organic EL display device was
completed by providing a seal 91 manufactured by Three Bond Co.,
Ltd. and an opposed substrate 92 made of glass with a desiccant 94
manufactured by Saes Getters Co., Ltd. being affixed thereon,
sealing a dry nitrogen gas in a space 93, and sealingly
encapsulating the active area in a layered structure, which
comprised the substrate 21, the color filters 22, the overcoat
layer 23, the inorganic solid layer 24, the first set of electrodes
25, the insulating layer 26, the light emitting layer 27 and the
second set of electrodes 28. In FIG. 9, the patterned portions of
the color filters, the insulating layer, and the inorganic solid
layer are omitted.
[0100] The drying treatment was performed at a temperature of
200.degree. C. under vacuum for 1 hour after formation of the
cathode separator. Additionally, the drying treatment was performed
at a temperature of 200.degree. C. for 10 minutes in a dry nitrogen
atmosphere having a dew point of about -80.degree. C. just before
vapor deposition of the light emitting element layer. The vapor
deposition of the light emitting layer was performed under vacuum
without contact with atmospheric air during the process from the
drying step to the deposition step. The sealing treatment was
performed by using the seal in an atmosphere of a dry nitrogen
gas.
[0101] After the organic EL display device was stored at a
temperature of 105.degree. C. for 24 hours, the apertural areas of
the light emitting layer of the organic EL display device were
observed. No spot-like non-emissive areas were observed as shown in
FIG. 10.
Example 2
[0102] This example was performed as in Example 1 except that,
instead of the inorganic solid layer made of SiO.sub.2 and having a
thickness of 20 nm, an inorganic solid layer, which was only
different in terms of a thickness of 5 nm and was deposited under
the same film deposition conditions as Example 1, was used, the
inorganic solid layer made of SiO.sub.2 was not subjected to
etching by dilute hydrofluoric acid, and that the drying time was
changed.
[0103] It was supposed that the drying time needed to be extended
in comparison with Example 1 since the entire surface of the
overcoat layer was covered with the inorganic solid layer made of
SiO.sub.2 so as to have every portion covered with the inorganic
solid layer. For this reason, although the second drying treatment
and the sealing treatment were performed as in Example 1, the first
drying treatment was performed at a temperature of 200.degree. C.
in vacuum for 2 hours.
[0104] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
Example 3
[0105] This example was performed as in Example 1 except that,
instead of the inorganic solid layer made of SiO.sub.2 and having a
thickness of 20 nm, an inorganic solid layer, which comprised a
layer made of SiO.sub.2 and having a thickness of 20 nm and a layer
made of ZrO.sub.2, having a thickness of 5 nm and layered thereon,
was used, the layered portions were collectively etched by dry
etching using a gas mixture of CF.sub.4 and O.sub.2.
[0106] Although portions of the overcoat layer were also etched to
a depth of about 1 .mu.m as shown in FIG. 6, there was no trouble
with respect to layer formation on the etched portions since the
etched portions were filled with the insulating layer.
[0107] Although it was supposed that the drying time was able to be
shortened in comparison with Example 1 since the dry etching
treatment was adopted and since the overcoat layer was only partly
etched, the drying treatments and the sealing treatment were
performed as in Example 1.
[0108] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
Example 4
[0109] This example was performed as in Example 1 except that the
inorganic solid layer was not subjected to etching by dilute
hydrofluoric acid, and that the drying treatments and the sealing
treatment were performed as in Example 2.
[0110] Evaluation, which was performed as in Example 1, revealed
that spot-like non-emissive portions were observed as shown in FIG.
1.
Example 5
[0111] This example was performed as in Example 1 except that,
instead of the inorganic solid layer made of SiO.sub.2 and having a
thickness of 20 nm, an inorganic solid layer, which comprised a
layer made of SiO.sub.2 and having a thickness of 20 nm and a layer
made of SiN, having a thickness of 200 nm and layered thereon, was
used, the inorganic solid layer made of SiO.sub.2 was not subjected
to etching by dilute hydrofluoric acid, and that the drying
treatments and the sealing treatment were performed as in Example
2.
[0112] Evaluation, which was performed as in Example 1, revealed
that nearly half as many spot-like non-emissive portions as the
non-emissive portions in Example 4 were observed.
Example 6
[0113] The treatments up to fabrication of the first patterned
electrodes made of ITO by etching using a liquid mixture of
hydrochloric acid and a solution of ferric chloride to expose the
portions of the inorganic solid layer of SiO.sub.2 between adjacent
patterned electrodes are performed as in Example 1. Then, the
surface of the ITO film is flattened by polishing. At this time, it
is sufficient that the film thickness of the ITO film is reduced by
about 15 nm.
[0114] The film thickness of the portions of the inorganic solid
layer of SiO.sub.2 between adjacent ITO patterns is also reduced to
about 5 nm by a decrease of about 15 nm. The subsequent processes
may be performed as in Example 1. The dry treatments before vapor
deposition, and the sealing treatment may be performed as in
Example 1.
Example 7
[0115] This example was performed as in Example 1 except following
conditions as below.
[0116] An inorganic solid layer was used, being comprised of a
ZrO.sub.2 layer with 2.5 nm thickness on a SiO.sub.2 layer with 2.5
nm thickness, which was deposited under the same conditions as
Example 1 instead of a SiO.sub.2 layer of 20 nm thickness.
[0117] The SiO.sub.2 inorganic solid layer was not subjected to
etching by dilute hydrofluoric acid and the drying time was
changed.
[0118] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
Example 8
[0119] This example was performed as in Example 2 except that the
thickness of the color filters was set at 1.2 .mu.m, the overcoat
layer was formed so as to have a thickness of 1.5 .mu.m, the
pattern width of the first electrodes was set at 70 .mu.m, the
width of the exposed portions of the inorganic solid layer of
SiO.sub.2 between adjacent patterned electrodes was set at 20
.mu.m, the apertural width of the insulation layer was set at 60
.mu.m, and the light emitting layer was replaced by a white light
emitting element layer having a total film thickness of 140 nm.
[0120] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
Example 9
[0121] This example was performed as in Example 8 except that after
formation of the cathode separator and the washing treatment, the
drying treatment was performed at a temperature of 200.degree. C.
for 60 min in a dry nitrogen atmosphere having a dew point of about
-80.degree. C., and that the light emitting element layer was
formed by vapor deposition without contact with atmospheric
air.
[0122] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
Example 10
[0123] This example was performed as in Example 9 except that after
formation of the cathode separator and the washing treatment, the
drying treatment was changed to be performed at a temperature of
200.degree. C. for 60 min in a dry an atmosphere having a dew point
of about -50.degree. C.
[0124] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
Example 11
[0125] This example was performed as in Example 8 except that after
formation of the cathode separator and the washing treatment, a
heating drying treatment was performed at a temperature of
200.degree. C. for 1 hour in vacuum with subsequent cooling to room
temperature in vacuum, and that the light emitting element layer
was formed by vapor deposition after being passed through
atmospheric air. In this case, the atmospheric air had a
temperature of 23.degree. C. and a humidity of about 5.0% RH, and
the residence time in the atmospheric air was about 5 min.
[0126] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
However, when examined microscopically how light was emitted, each
of the pixels had a non-emissive portion formed in a width of about
3 .mu.m on a portion of the relevant first electrode close to an
end thereof in common with other pixels.
[0127] When examined microscopically how light was emitted in
Examples 1, 2, 3, 6, 7, 8, 9 and 10, any non-emissive portions were
not observed.
Example 12
[0128] This example was performed as in Example 8 except that after
formation of the cathode separator and the washing treatment, the
light emitting element layer was formed by vapor deposition without
performing any heating treatment or other treatment.
[0129] Evaluation, which was performed as in Example 1, revealed
that any spot-like non-emissive portions were not observed.
However, when examined microscopically how light was emitted, each
of the pixels had a non-emissive portion formed in a width of about
12 .mu.m on a portion of the relevant first electrode close to an
end thereof in common with other pixels. Although it was
microscopically seen that the light emitting part of each of the
pixels was quite thinned, neither chrominance non-uniformity, stain
nor the like was observed as viewing the entire screen with the
naked eye. It is supposed that the pixels were uniformly contracted
over the entire screen.
[0130] The entire disclosures of Japanese Patent Application No.
2003-282344 filed on Jul. 30, 2003, Japanese Patent Application No.
2003-398762 filed on Nov. 28, 2003 and Japanese Patent Application
No. 2004-162506 filed on May 31, 2004 including specifications,
claims, drawings and summaries are incorporated herein by reference
in their entireties.
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