U.S. patent application number 14/527167 was filed with the patent office on 2015-02-19 for organic electroluminescence device, display unit including the same, and method of manufacturing an organic electroluminescence device.
The applicant listed for this patent is SONY CORPORATION. Invention is credited to Mitsuhiro Kashiwabara.
Application Number | 20150048355 14/527167 |
Document ID | / |
Family ID | 43353490 |
Filed Date | 2015-02-19 |
United States Patent
Application |
20150048355 |
Kind Code |
A1 |
Kashiwabara; Mitsuhiro |
February 19, 2015 |
ORGANIC ELECTROLUMINESCENCE DEVICE, DISPLAY UNIT INCLUDING THE
SAME, AND METHOD OF MANUFACTURING AN ORGANIC ELECTROLUMINESCENCE
DEVICE
Abstract
An organic electroluminescence device includes a first
electrode, an organic layer formed on the first electrode and
including a light-emitting layer, an intermediate layer formed on
the organic layer; and a second electrode formed on the
intermediate layer and having a thickness of 6 nm or less.
Inventors: |
Kashiwabara; Mitsuhiro;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SONY CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
43353490 |
Appl. No.: |
14/527167 |
Filed: |
October 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13804162 |
Mar 14, 2013 |
8916861 |
|
|
14527167 |
|
|
|
|
12815017 |
Jun 14, 2010 |
8415658 |
|
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13804162 |
|
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Current U.S.
Class: |
257/40 |
Current CPC
Class: |
H01L 2251/558 20130101;
H01L 51/5253 20130101; H01L 2251/5315 20130101; H01L 51/5096
20130101; H01L 27/3244 20130101; H01L 51/5234 20130101; H01L
51/5265 20130101 |
Class at
Publication: |
257/40 |
International
Class: |
H01L 51/52 20060101
H01L051/52; H01L 27/32 20060101 H01L027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2009 |
JP |
2009-148888 |
Claims
1. An organic electroluminescence device comprising: a first
electrode; an organic layer formed on the first electrode and
including a light-emitting layer; an intermediate layer formed on
the organic layer; a second electrode formed on the intermediate
layer; and a protective layer formed on the second electrode,
wherein the intermediate layer is disposed between the second
electrode and the organic layer, wherein at least a portion of a
metal element contained in the intermediate layer is diffused into
the second electrode, and wherein the intermediate layer includes
at least one element selected from the group consisting of an
alkali metal, an alkali earth metal, a lanthanide metal, aluminum,
indium, tin, nickel, copper and zinc.
2. The organic electroluminescence device according to claim 1,
wherein the second electrode has a thickness of 6 nm or less.
3. The organic electroluminescence device according to claim 1,
wherein the intermediate layer directly contacts the organic layer
and the second electrode.
4. The organic electroluminescence device according to claim 1,
wherein the intermediate layer directly contacts the organic
layer.
5. The organic electroluminescence device according to claim 1,
wherein the intermediate layer directly contacts the second
electrode.
6. The organic electroluminescence device according to claim 1,
wherein at least a portion of a metal element contained in the
intermediate layer is diffused into the second electrode.
7. The organic electroluminescence device according to claim 1,
wherein the second electrode is made of a metal conductive film
including an alloy comprising one or more of aluminum, magnesium,
calcium and sodium.
8. The organic electroluminescence device according to claim 7,
wherein the alloy of the second electrode is a Mg--Ag alloy or an
Al--Li alloy.
9. The organic electroluminescence device according to claim 1,
wherein a thickness of the intermediate layer ranges from 0.1 nm to
5 nm.
10. The organic electroluminescence device according to claim 1,
wherein the intermediate layer includes at least one lanthanide
metal.
11. A display device comprising at least one organic
electroluminescent device including: a first electrode; an organic
layer formed on the first electrode and including a light-emitting
layer; an intermediate layer formed on the organic layer; a second
electrode formed on the intermediate layer; and a protective layer
formed on the second electrode, wherein the intermediate layer is
disposed between the second electrode and the organic layer,
wherein at least a portion of a metal element contained in the
intermediate layer is diffused into the second electrode, and
wherein the intermediate layer includes at least one element
selected from the group consisting of an alkali metal, an alkali
earth metal, a lanthanide metal, aluminum, indium, tin, nickel,
copper and zinc.
12. The display device according to claim 11, wherein the second
electrode has a thickness of 6 nm or less.
13. The display device according to claim 11, wherein the
intermediate layer directly contacts the organic layer and the
second electrode.
14. The display device according to claim 11, wherein the
intermediate layer directly contacts the organic layer.
15. The display device according to claim 11, wherein the
intermediate layer directly contacts the second electrode.
16. The display device according to claim 11, wherein at least a
portion of a metal element contained in the intermediate layer is
diffused into the second electrode.
17. The display device according to claim 11, wherein the second
electrode is made of a metal conductive film including an alloy
comprising one or more of aluminum, magnesium, calcium and
sodium.
18. The display device according to claim 17, wherein the alloy of
the second electrode is a Mg--Ag alloy or an Al--Li alloy.
19. The display device according to claim 11, wherein a thickness
of the intermediate layer ranges from 0.1 nm to 5 nm.
20. The display device according to claim 11, wherein the
intermediate layer includes at least one lanthanide metal.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/804,162, filed Mar. 14, 2013, which
application is a continuation of U.S. patent application Ser. No.
12/815,017, filed Jun. 14, 2010, which application issued as U.S.
Pat. No. 8,415,658 on Apr. 9, 2013, which claims priority to
Japanese Priority Patent Application JP 2009-148888 filed on Jun.
23, 2009, the entire contents of which is hereby incorporated by
reference.
BACKGROUND
[0002] The present disclosure relates to an organic
electroluminescence (EL) device suitable for a device including a
resonator structure and a display unit including the same.
[0003] The organic EL device in which electroluminescence of an
organic material is used has been already applied to an organic EL
display unit as a light emitting device capable of realizing high
luminance light emission by low voltage direct current drive. The
organic EL device has, for example, a structure in which a lower
electrode, an organic layer including a light emitting layer, and
an upper electrode are sequentially layered over a substrate. Light
generated in the light emitting layer is extracted from one of the
lower electrode side and the upper electrode side or both sides. In
the case where the light is extracted from the upper electrode, the
upper electrode is made of, for example, a transparent conductive
film. As a material of the transparent conductive film, for
example, a metal oxide conductive material such as an oxide of
indium and tin (ITO) and an oxide of indium and zinc (IZO) is
used.
[0004] However, in the case where the transparent conductive
material composed of the metal oxide is used, device
characteristics are lowered due to damage at the time of sputtering
deposition. Further, a sputtering film is strongly characterized by
intruding into and adhering to a projection and a defect section of
a deposition face. In addition, in order to express the electric
conductivity of the metal oxide, the film thickness thereof should
be about 15 nm or more. Thus, there is a high possibility that the
metal oxide conductive material adheres to a foreign matter or a
defect on the lower electrode or a defect section of the organic
film, and short circuit between the upper electrode and the lower
electrode is generated.
[0005] As a material of the upper electrode, a conductive film made
of a metal film is also used. For example, in Japanese Unexamined
Patent Application Publication No. 2004-164890, a description is
given that an electron injection metal having a refractive index of
1 or less and an extinction coefficient of 0.5 or more is
preferable as a material of the metal film in order to decrease
absorption loss. For example, Japanese Unexamined Patent
Application Publication No. 2004-164890 exemplifies a simple body
or an alloy of aluminum, magnesium, calcium, sodium and the
like.
[0006] The metal film has a thickness of about 10 nm, and functions
as an electrode. The film thickness of the metal film necessary for
expressing electric conductivity is small. Thus, there is a small
possibility that short circuit is generated in a foreign matter or
a defect on the lower electrode or a defect section of the organic
film. Further, in the case where the metal film is deposited by
vacuum evaporation method under high vacuum by using resistance
heating, evaporation particle scattering caused by collision with
gas molecules is hardly generated, and there is a small possibility
that the conductive material intrudes into a foreign matter or a
defect on the lower electrode or a defect section of the organic
film.
[0007] However, there has been a disadvantage that the electric
conductivity of the foregoing metal film is lowered by thinning the
metal film. In the case of an alloy of magnesium and silver (Mg--Ag
alloy), high electric conductivity is retained even if the film is
thinned, but thinning limit has been above 6 nm. That is, in the
past, there has been no known successful example that electric
conductivity is retained to the degree that an organic EL device is
able to be sufficiently driven with the use of a metal film having
a thickness of 6 nm or less.
[0008] For example, in Japanese Unexamined Patent Application
Publication No. 8-185984, a description is given that an upper
electrode is made of an oxide conductive material, and a
transparent Mg--Ag alloy film having a thickness of 2 nm is
provided between an organic layer and the upper electrode in order
to improve electron injection characteristics. The Mg--Ag alloy
film does not have a function as an electrode, and has only a
function as an electron injection layer. The oxide conductive
material is responsible for electric conductivity.
[0009] Therefore, it is desirable to provide an organic
electroluminescence device in which an upper electrode is made of a
metal film, and the thickness of the metal film is able to be
thinned down to 6 nm or less while electric conductivity of the
metal film is retained, and a display unit including the same.
SUMMARY
[0010] In an embodiment, an organic electroluminescence device
includes a first electrode, an organic layer formed on the first
electrode and including a light-emitting layer, an intermediate
layer formed on the organic layer, and a second electrode formed on
the intermediate layer and having a thickness of 6 nm or less. In
an embodiment, the organic layer includes an electron hole
injection layer, an electron hole transport layer, the
light-emitting layer, an electron transport layer, and an electron
injection layer that are layered in that order from a first
electrode side. In an embodiment, the second electrode is made of a
metal conductive film including an alloy comprising one or more of
aluminum, magnesium, calcium and sodium. In an embodiment, the
alloy of the second electrode is a Mg--Ag alloy or an Al--Li alloy.
In an embodiment, the intermediate layer includes calcium or
aluminum. In an embodiment, sheet resistance of a film comprising
the intermediate layer and the second electrode is
10,000.OMEGA./.quadrature. or less. In one embodiment, at least a
portion of a metal element contained in the intermediate layer is
diffused into the second electrode In another embodiment, the
intermediate layer is at least substantially diffused into the
second electrode.
[0011] In another embodiment, a display device includes at least
one organic electroluminescent device. In this embodiment, the
organic electroluminescent device includes a first electrode, an
organic layer formed on the first electrode and including a
light-emitting layer, an intermediate layer formed on the organic
layer, and a second electrode formed on the intermediate layer and
having a thickness of 6 nm or less.
[0012] In another embodiment, an organic electroluminescence device
includes an intermediate layer, and an electrode formed on the
intermediate layer and having a thickness of 6 nm or less. In this
embodiment, a sheet resistance of a film comprising the
intermediate layer and the electrode is 10,000.OMEGA./.quadrature.
or less.
[0013] In another embodiment, a method of manufacturing an organic
electroluminescence device includes: forming a first electrode;
forming an organic layer on the first electrode; forming a
laminated film including an intermediate layer and a second
electrode by forming the intermediate layer on the organic layer,
and forming the second electrode on the intermediate film, wherein
a thickness of the second electrode is 6 nm or less. In one
embodiment, the method further includes at least substantially
diffusing a material of the intermediate layer into the second
electrode, such that the laminated film is an integrated electrode
layer composed of the intermediate layer and the second
electrode.
[0014] According to another embodiment, an organic
electroluminescence device includes an intermediate layer composed
of a metal element such as an alkali metal provided between an
upper or second electrode and an organic layer in contact with the
upper electrode. In addition, in one embodiment, the thickness of
the intermediate layer is from 0.1 nm to 5 nm both inclusive.
According to another embodiment, an organic electroluminescence
device includes an upper or second electrode containing an alloy of
magnesium or the like as a main component, and containing a metal
element such as an alkali metal. Thus, lowering of electric
conductivity caused by degeneration of the upper electrode is
inhibited, and the thickness of the upper electrode is able to be
decreased down to 6 nm or less. In particular, the embodiments are
suitable for an organic electroluminescence device in which a
resonator structure is included, and light generated in the light
emitting layer is resonated between the lower electrode and the
upper electrode.
[0015] According to another embodiment, a display unit includes at
least one of the above-described embodiments. Thus, electric
conductivity of the upper electrode is maintained, and the organic
electroluminescence device is able to be favorably driven.
[0016] Additional features and advantages are described herein, and
will be apparent from the following Detailed Description and the
figures.
BRIEF DESCRIPTION OF THE FIGURES
[0017] FIG. 1 is a diagram illustrating a structure of a display
unit according to a first embodiment.
[0018] FIG. 2 is a diagram illustrating an example of the pixel
drive circuit illustrated in FIG. 1.
[0019] FIG. 3 is a cross sectional view illustrating a structure of
the organic EL device illustrated in FIG. 1.
[0020] FIGS. 4A and 4B are diagrams for comparing view angle
characteristics of the organic EL device having the resonator
structure illustrated in FIG. 3 to an existing example.
[0021] FIG. 5 is a cross sectional view illustrating a structure of
an organic EL device according to a first modified example.
[0022] FIG. 6 is a cross sectional view illustrating a structure of
an organic EL device according to a second embodiment.
[0023] FIG. 7 is a cross sectional view illustrating another
structure of the organic EL device illustrated in FIG. 6.
[0024] FIG. 8 is a plan view illustrating a schematic structure of
a module including the display unit of the foregoing
embodiments.
[0025] FIG. 9 is a perspective view illustrating an appearance of a
first application example of the display unit of the foregoing
embodiments.
[0026] FIG. 10A is a perspective view illustrating an appearance
viewed from the front side of a second application example, and
FIG. 10B is a perspective view illustrating an appearance viewed
from the rear side of the second application example.
[0027] FIG. 11 is a perspective view illustrating an appearance of
a third application example.
[0028] FIG. 12 is a perspective view illustrating an appearance of
a fourth application example.
[0029] FIG. 13A is an elevation view of a fifth application example
unclosed, FIG. 13B is a side view thereof, FIG. 13C is an elevation
view of the fifth application example closed, FIG. 13D is a left
side view thereof, FIG. 13E is a right side view thereof, FIG. 13F
is a top view thereof, and FIG. 13G is a bottom view thereof.
DETAILED DESCRIPTION
[0030] Embodiments will be hereinafter described in detail with
reference to the drawings. The description will be given in the
following order:
[0031] 1. First embodiment (example that a first resonator
structure is structured by a lower electrode and an upper
electrode)
[0032] 2. First modified example (example that an intermediate
layer 18 and an upper electrode 17 are integrated)
[0033] 3. Second embodiment (example that a second resonator
structure is structured by providing a resonance adjustment layer
on an upper electrode)
[0034] 4. Examples
First Embodiment
[0035] FIG. 1 illustrates a structure of a display unit according
to a first embodiment. The display unit is used as an organic EL
television device or the like. In the display unit, for example, as
a display region 110, an after-mentioned plurality of organic EL
devices 10R, 10G, and 10B are arranged in a matrix state over a
substrate 11. A signal line drive circuit 120 and a scanning line
drive circuit 130 that are drivers for displaying a video are
provided on the periphery of the display region 110.
[0036] In the display region 110, a pixel drive circuit 140 is
provided. FIG. 2 illustrates an example of the pixel drive circuit
140. The pixel drive circuit 140 is an active drive circuit that is
formed in a layer located lower than an after-mentioned lower
electrode 14. That is, the pixel drive circuit 140 has a drive
transistor Tr1, a writing transistor Tr2, a capacitor (retentive
capacity) Cs between the drive transistor Tr1 and the writing
transistor Tr2, and the organic EL device 10R (or 10G, 10B)
serially connected to the drive transistor Tr1 between a first
power line (Vcc) and a second power line (GND). The drive
transistor Tr1 and the writing transistor Tr2 are composed of a
general thin film transistor (TFT (Thin Film Transistor)). The
structure thereof is not particularly limited, and may be, for
example, inversely staggered structure (so-called bottom gate type)
or staggered structure (top gate type).
[0037] In the pixel drive circuit 140, a plurality of signal lines
120A are arranged in the column direction, and a plurality of
scanning lines 130A are arranged in the row direction. Each cross
section between each signal line 120A and each scanning line 130A
corresponds to one of the organic light emitting devices 10R, 10G,
and 10B (sub pixel). Each signal line 120A is connected to the
signal line drive circuit 120. An image signal is supplied to a
source electrode of the writing transistor Tr2 from the signal line
drive circuit 120 through the signal line 120A. Each scanning line
130A is connected to the scanning line drive circuit 130. A
scanning signal is sequentially supplied to a gate electrode of the
writing transistor Tr2 from the scanning line drive circuit 130
through the scanning line 130A.
[0038] Further, in the display region 110, the organic EL device
10R generating red light, the organic EL device 10G generating
green light, and the organic EL device 10B generating blue light
are sequentially arranged in a matrix state as a whole. A
combination of the organic EL devices 10R, 10G, and 10B adjacent to
each other composes one pixel.
[0039] FIG. 3 illustrates a cross sectional structure of the
organic EL devices 10R, 10G, and 10B illustrated in FIG. 1. The
organic EL devices 10R, 10G, and 10B respectively have a structure
in which the drive transistor Tr1 of the foregoing pixel circuit
140, a planarizing insulating film 12, the lower or first electrode
14 as an anode, an inter-electrode insulating film 15, an organic
layer 16 including a light emitting layer 16C described later, and
an upper or second electrode 17 as a cathode are layered in this
order from the substrate 11 side.
[0040] The organic EL devices 10R, 10G, and 10B as above are coated
with a protective layer 30. Further, a sealing substrate 50 made of
glass or the like is bonded to the whole area of the protective
layer 30 with an adhesive layer 40 in between, and thereby the
organic EL devices 10R, 10G, and 10B are sealed.
[0041] The substrate 11 is made of glass, a silicon (Si) wafer, a
resin or the like. The drive transistor Tr1 is electrically
connected to the lower electrode 14 through a connection hole 12A
provided in the planarizing insulating film 12.
[0042] The planarizing insulating film 12 is intended to planarize
a front face of the substrate 11 over which the pixel driving
circuit 140 is formed. Since the fine connection hole 12A is
provided, the planarizing insulating film 12 is preferably made of
a material having favorable pattern precision. Examples of
component materials of the planarizing insulating film 12 include
an organic material such as polyimide and an inorganic material
such as silicon oxide (SiO.sub.2).
[0043] The lower electrode 14 also has a function as a reflecting
layer, and desirably has high reflectance as much as possible in
order to improve light emission efficiency. In particular, in the
case where the lower electrode 14 is used as an anode, the lower
electrode 14 is desirably made of a material having high electron
hole injection characteristics. Such a lower electrode 14 has, for
example, a lamination direction thickness (hereinafter simply
referred to as thickness) from 100 nm to 1000 nm both inclusive.
Examples of material of the lower electrode 14 include a simple
substance or an alloy of metal elements such as chromium (Cr), gold
(Au), platinum (Pt), nickel (Ni), copper (Cu), tungsten (W), and
silver (Ag). A transparent conductive film composed of an oxide of
indium and tin (ITO) or the like may be provided on the surface of
the lower electrode 14. If an appropriate electron hole injection
layer is provided, it is able to use a material that has high
reflectance but has a disadvantage of an electron hole injection
barrier due to existence of an oxide film on the surface and a
small work function such as an aluminum (Al) alloy as the lower
electrode 14.
[0044] The inter-electrode insulating film 15 is intended to secure
insulation between the lower electrode 14 and the upper electrode
17, and to obtain a desired shape of the light emitting region. For
example, the inter-electrode insulating film 15 is made of a
photosensitive resin. The inter-electrode insulating film 15 is
provided with an aperture correspondingly to the light emitting
region. Though the organic layer 16 and the upper electrode 17 are
provided not only in the aperture but also over the inter-electrode
insulating film 15, light is emitted only in the aperture of the
inter-electrode insulating film 15.
[0045] The organic layer 16 has, for example, a structure in which
an electron hole injection layer 16A, an electron hole transport
layer 16B, the light emitting layer 16C, an electron transport
layer 16D, and an electron injection layer 16E are layered from the
lower electrode 14 side. Of the foregoing layers, the layers other
than the light emitting layer 16C may be provided according to
needs. The organic layer 16 may have a structure varying according
to the light emitting color of the organic EL devices 10R, 10G, and
10B. The electron hole injection layer 16A is intended to improve
the electron hole injection efficiency and functions as a buffer
layer to prevent leakage. The electron hole transport layer 16B is
intended to improve efficiency to transport electron holes into the
light emitting layer 16C. The light emitting layer 16C is intended
to generate light due to electron-hole recombination by impressing
an electric field. The electron transport layer 16D is intended to
improve efficiency to transport electrons into the light emitting
layer 16C. The electron injection layer 16E is intended to improve
efficiency to inject electrons.
[0046] The electron hole injection layer 16A of the organic EL
device 10R has, for example, a thickness from 5 nm to 300 nm both
inclusive, and is composed of the hexaazatriphenylene derivative
shown in Chemical formula 1 or Chemical formula 2. The electron
hole transport layer 16B of the organic EL device 10R has, for
example, a thickness from 5 nm to 300 nm both inclusive, and is
composed of bis[(N-naphthyl)-N-phenyl]benzidine (.alpha.-NPD). The
light emitting layer 16C of the organic EL device 10R has, for
example, a thickness from 10 nm to 100 nm both inclusive, and is
composed of a material in which 40 volume % of
2,6-bis[4-[N-(4-metoxyphenyl)-N-phenyl]aminostyril]naphthalene-1,5-dicarb-
onitrile (BSN-BCN) is mixed with 8-quinolinol aluminum complex
(Alq.sub.3). The electron transport layer 16D of the organic EL
device 10R has, for example, a thickness from 5 nm to 300 nm both
inclusive, and is made of Alq3. The electron injection layer 16E of
the organic EL device 10R has, for example, a thickness about 0.3
nm, and is made of LiF, Li.sub.2O or the like.
##STR00001##
[0047] In Chemical formula 1, R1 to R6 respectively and
independently represent hydrogen; halogen; a hydroxyl group; an
amino group; an aryl amino group; a substituted/unsubstituted
carbonyl group having the carbon number of 20 or less; a
substituted/unsubstituted carbonylester group having the carbon
number of 20 or less; a substituted/unsubstituted alkyl group
having the carbon number of 20 or less; a substituted/unsubstituted
alkenyl group having the carbon number of 20 or less; a
substituted/unsubstituted alkoxyl group having the carbon number of
20 or less; a substituted/unsubstituted aryl group having the
carbon number of 30 or less; a substituted/unsubstituted
heterocyclic group having the carbon number of 30 or less; or a
substituted group selected from a group consisting of a nitrile
group, a cyano group, a nitro group, and a silyl group. Each Rm
(m=1 to 6) adjacent to each other may be bonded with each other
through an annular structure. Further, X1 to X6 respectively and
independently represent a carbon atom or a nitrogen atom.
[0048] Specifically, the electron hole injection layer 16A of the
organic EL device 10R is preferably made of the material shown in
Chemical formula 2.
##STR00002##
[0049] The electron hole injection layer 16A of the organic EL
device 10G has, for example, a thickness from 5 nm to 300 nm both
inclusive, and is composed of the hexaazatriphenylene derivative
shown in Chemical formula 1 or Chemical formula 2. The electron
hole transport layer 16B of the organic EL device 10G has, for
example, a thickness from 5 nm to 300 nm both inclusive, and is
composed of .alpha.-NPD. The light emitting layer 16C of the
organic EL device 10G has, for example, a thickness from 10 nm to
100 nm both inclusive, and is composed of a material in which 1
volume % of coumarin 6 is mixed with Alq3. The electron transport
layer 16D of the organic EL device 10G has, for example, a
thickness from 5 nm to 300 nm both inclusive, and is made of Alq3.
The electron injection layer 16E of the organic EL device 10G has,
for example, a thickness about 0.3 nm, and is made of LiF,
Li.sub.2O or the like.
[0050] The electron hole injection layer 16A of the organic EL
device 10B has, for example, a thickness from 5 nm to 300 nm both
inclusive, and is composed of the hexaazatriphenylene derivative
shown in Chemical formula 1 or Chemical formula 2. The electron
hole transport layer 16B of the organic EL device 10B has, for
example, a thickness from 5 nm to 300 nm both inclusive, and is
composed of .alpha.-NPD. The light emitting layer 16C of the
organic EL device 10B has, for example, a thickness from 10 nm to
100 nm both inclusive, and is composed of spiro 6.PHI.. The
electron transport layer 16D of the organic EL device 10B has, for
example, a thickness from 5 nm to 300 nm both inclusive, and is
made of Alq3. The electron injection layer 16E of the organic EL
device 10B has, for example, a thickness of about 0.3 nm, and is
composed of LiF, Li.sub.2O or the like.
[0051] The upper electrode 17 is made of a metal conductive film.
Specific examples thereof include an alloy of aluminum (Al),
magnesium (Mg), calcium (Ca), or sodium (Na). Specially, an alloy
of magnesium and silver (Mg--Ag alloy) is preferable, since the
Mg--Ag alloy has electric conductivity and small absorption in a
thin film. The ratio of magnesium and silver in the Mg--Ag alloy is
not particularly limited, but the film thickness ratio of Mg:Ag is
desirably in the range from 20:1 to 1:1. Further, the material of
the upper electrode 17 may be an alloy of aluminum (Al) and lithium
(Li) (Al--Li alloy).
[0052] The thickness of the second or upper electrode 17 is 6 nm or
less, and preferably from 2 nm to 6 nm both inclusive. If the
thickness thereof is 6 nm or less, it is possible to inhibit the
material of the upper electrode 17 from adhering to the surrounding
of a foreign matter on the lower electrode 14, and inhibit
generation of non-light emitting defect (so-called lost point) due
to electric short circuit between the lower electrode 14 and the
upper electrode 17. Further, if the thickness thereof is 2 nm or
more, it is possible to secure the electric conductivity of the
upper electrode 17 to the degree at which driving the organic EL
devices 10R, 10G, and 10B functions well. Further, the thickness of
the upper electrode 17 is more preferably from 2.5 nm to 6 nm both
inclusive, since thereby driving the organic EL devices 10R, 10G,
and 10B is sufficiently enabled.
[0053] The intermediate layer 18 is provided being contacted with
the upper electrode 17 between the upper electrode 17 and the
organic layer 16. The intermediate layer 18 has, for example, a
thickness from 0.1 nm to 5 nm both inclusive, and contains one
selected from the metal element group consisting of an alkali
metal, an alkali earth metal, a lanthanoid metal, aluminum, indium,
tin, nickel, copper, and zinc. Thereby, in the display unit, the
thickness of the upper electrode 17 may be decreased down to 6 nm
or less while electric conductivity of the upper electrode 17 is
retained.
[0054] "Thickness of the upper electrode 17" and "thickness of the
intermediate layer 18" in this specification are obtained by
optical method such as spectroscopic ellipsometry. Further,
"thickness of the upper electrode 17" and "thickness of the
intermediate layer 18" are measured in a state of a product after
being sealed with the sealing substrate 50 and being assembled.
[0055] The intermediate layer 18 has a function as a degeneration
preventive layer to inhibit the upper electrode 17 from being
directly contacted with the organic layer 16 and losing electric
conductivity. Thus, the intermediate layer 18 desirably has a
thickness with which degeneration preventive effect of the upper
electrode 17 is obtained. Specifically, as described above, the
intermediate layer 18 has a thickness of 0.1 nm or more. Further,
in the case where the thickness of the intermediate layer 18 is 5
nm or less, lowering of efficiency due to light absorption is able
to be small.
[0056] In the case where the upper electrode 17 is used as a
cathode, the intermediate layer 18 is preferably made of an
electron injection material. As described above, examples of such a
material include the alkali metal, the alkali earth metal, and the
lanthanoid metal. By providing the appropriate electron injection
layer 16E, a metal having a larger work function than that of
magnesium is able to be used. Examples of such a metal include a
metal such as aluminum, indium, and tin; and a transition metal
such as nickel, copper, and zinc.
[0057] Specifically, the intermediate layer 18 preferably contains
calcium. Calcium has favorable electron injection characteristics
to the organic layer 16, has high electric conductivity as a film,
and has small absorption. Further, calcium as a single material is
easily deposited onto the organic layer 16 comparatively, and
calcium is not subject to drastic oxidation and hydroxylation
reaction in the air differently from other material such as the
alkali earth metal and the alkali metal. Thus, handling calcium in
manufacturing is comparatively easy.
[0058] Otherwise, the intermediate layer 18 preferably contains
aluminum. If aluminum is layered after the appropriate electron
injection layer 16E such as lithium fluoride is formed thinly,
aluminum expresses favorable electron injection characteristics. In
addition, aluminum has effect to prevent degeneration of the upper
electrode 17 further provided thereon.
[0059] The sheet resistance of the film composed of the
intermediate layer 18 and the upper electrode 17 is preferably, for
example, 10000.OMEGA./.quadrature. or less. Thereby, in a panel
structure in which a contact section is arranged in the vicinity of
the pixel on the substrate, influence of voltage drop is able to be
lowered, and drive voltage rise or luminance gradient in the pixel
is able to be inhibited. For example, in a 100 inch full high
definition display unit, one pixel pitch is 1.15 mm. In such a
large pixel, if the white display light emitting efficiency is 20
cd/A and the display luminance is 200 cd/m.sup.2, voltage drop from
an end to the other end of the pixel is 0.13V, and there is a small
possibility to impair the display quality.
[0060] The intermediate layer 18 and the upper electrode 17 are
formed as a laminated film in a manufacturing step as described
later. However, after the upper electrode 17 is formed, part of the
metal element contained in the intermediate layer 18 may be
distributed in the second electrode 17.
[0061] The upper electrode 17 also has a function as a translucent
reflecting layer. That is, the organic EL devices 10R, 10G, and 10B
have a resonator structure MC1 (first resonator structure MC1).
Light generated in the light emitting layer 16C is resonated
between the lower electrode 14 and the upper electrode 17 by the
resonator structure MC1. In the resonator structure MC1, the
interface between the lower electrode 14 and the organic layer 16
is a reflecting face P1, the interface between the intermediate
layer 18 and the electron injection layer 16E is a translucent
reflecting face P2, and the organic layer 16 is a resonance
section. The light generated in the light emitting layer 16C is
resonated and is extracted from the translucent reflecting face P2
side. In the case where the resonator structure MC1 is included,
the light generated in the light emitting layer 16C generates
multiple interference, the half bandwidth of spectrum of the light
extracted from the translucent reflecting face P2 side is
decreased, and the peak intensity is able to be increased. That is,
the light radiation intensity in the front face direction is able
to be increased, and the color purity of light emission is able to
be improved. Outside light entering from the sealing substrate 50
side is also able to be decayed by multiple interference. By
combining with an after-mentioned color filter 51, the reflectance
of outside light in the organic EL devices 10R, 10G, and 10B is
able to be significantly decreased.
[0062] To this end, an optical distance L1 between the reflecting
face P1 and the translucent reflecting face P2 preferably satisfies
Mathematical formula 1.
(2L1)/.lamda.+.PHI.)/(2.pi.)=m Mathematical formula 1
[0063] In the formula, "L1" represents the optical distance between
the reflecting face P1 and the translucent reflecting face P2. "m"
represents an order (0 or a natural number). ".PHI." represents a
sum of phase shift .PHI.1 of reflected light generated in the
reflecting face P1 and phase shift .PHI.2 of reflected light
generated in the translucent reflecting face P2
(.PHI.=.PHI.1+.PHI.2) (rad). ".lamda." represents a peak wavelength
of spectrum of light that is desirably extracted from the
translucent reflecting face P2 side. For L1 and .lamda. in the
Mathematical formula 1, the unit should be unified, and for
example, (nm) is used as the unit.
[0064] Between the reflecting face P1 and the translucent
reflecting face P2, a position where the extraction light emitting
strength becomes the maximum (resonance face) exists. The number of
resonance faces is m+1. Under the conditions of m=1 or more, in the
case where the light emitting face exists on a resonance face
closest to the reflecting face P1, the half bandwidth of light
emitting spectrum becomes widest.
[0065] In the organic EL devices 10R, 10G, and 10B having such a
resonator structure MC1, there is a tendency that as the order m
become larger, view angle dependence of luminance and chromaticity
becomes larger, that is, difference of luminance and chromaticity
between a case viewing in the front face direction and in a case
viewing in the oblique direction becomes larger. In the case where
assumption is made that the organic EL display unit is used for a
general television device or the like, luminance lowering and
chromaticity change according to view angle are desirably small.
Specifically, at the time of white light emission, the spectral
radiance ratio measured from 45 deg oblique direction with respect
to the spectral radiance ratio measured from the front face is
preferably 0.7 or more.
[0066] In view of only view angle characteristics, conditions m=0
are ideal. However, under such conditions, the thickness of the
organic layer 16 is small, and thus there is a possibility that
influence on light emitting characteristics and short circuit
between the lower electrode 14 and the upper electrode 17 are
generated. Thus, for example, by using the conditions m=1, view
angle dependence of luminance and chromaticity is avoided from
being increased, and lowering of light emitting characteristics and
short circuit generation are inhibited. For example, in the case
where the lower electrode 14 is composed of an aluminum alloy and
the upper electrode 17 is composed of an Mg--Ag alloy respectively,
the thickness of the organic layer 16 of the blue organic EL device
10B is about 80 nm if m is 0, and is about 190 nm if m is 1, and
accordingly generation of short circuit is inhibited.
[0067] Further, in this embodiment, as described above, the
thickness of the upper electrode 17 is decreased down to from 2 nm
to 6 nm both inclusive. Thus, luminance lowering and chromaticity
change according to the view angle are able to be more decreased
for the following reason. That is, in the case where the thickness
of the upper electrode 17 is decreased, the transmittance ratio of
the upper electrode 17 is increased and the reflectance is lowered.
In the result, out of light emission from the light emitting layer
16C, the ratio of light reflected by the upper electrode 17 toward
the lower electrode 14 side is decreased. Thereby, the resonator
structure MC1 is weakened, and angle dependence of light extracted
from the translucent reflecting face P2 is decreased. Accordingly,
for example, under the conditions that the order m is 1 or more,
view angle dependence of luminance and chromaticity is able to be
decreased, and an organic EL display unit having superior display
performance is able to be obtained.
[0068] FIG. 4A illustrates spectrums in the case where the
intermediate layer 18 composed of Ca having a thickness of 2 nm and
the upper electrode 17 composed of an Mg--Ag alloy having a
thickness of 4 nm are provided in the organic EL device having the
resonator structure MC1. The spectrums show results of viewing from
the front face and from 45 deg oblique direction by optical
simulation. FIG. 4B illustrates spectrums similarly obtained by
optical simulation in the case where the intermediate layer 18 is
not provided and only the upper electrode 17 composed of an Mg--Ag
alloy having a thickness of 8 nm is provided. As evidenced by FIG.
4A and FIG. 4B, in the former case in which the intermediate layer
18 is provided, the spectrum half bandwidth is wider, the peak
intensity is lower, and resonator effect is more modified than in
the latter case, but change of light emitting characteristics
according to the view angle is more decreased than in the latter
case.
[0069] The protective layer 30 illustrated in FIG. 3 is composed of
silicon nitride (SiN.sub.x), silicon oxide, a metal oxide or the
like. The adhesive layer 40 illustrated in FIG. 3 is composed of,
for example, a heat-hardening resin or a ultraviolet hardening
resin.
[0070] The sealing substrate 50 illustrated in FIG. 3 is located on
the upper electrode 17 side of the organic EL devices 10R, 10G, and
10B. The sealing substrate 50 seals the organic light EL devices
10R, 10G, and 10B together with the adhesive layer 40, and is made
of a material such as glass transparent to light generated in the
organic light EL devices 10R, 10G, and 10B. The sealing substrate
50 is, for example, provided with the color filter 51, which
extracts the light generated in the organic light EL devices 10R,
10G, and 10B, and absorbs outside light reflected by the organic EL
devices 10R, 10G, and 10B and the wiring in between to improve
contrast.
[0071] The color filter 51 may be provided on any face of the
sealing substrate 50, but is preferably provided on the side of the
organic EL devices 10R, 10G, and 10B. Thereby, the color filter 51
is not exposed on the surface, and is able to be protected by the
adhesive layer 40. Further, in this case, since the distance
between the light emitting layer 16C and the color filter 51 is
narrowed, it is possible to avoid an event that light emitted from
the light emitting layer 16C enters an adjacent color filter 51 of
other color to generate mixed color. The color filter 51 has a red
filter, a green filter, and a blue filter (not illustrated), which
are sequentially arranged correspondingly to the organic EL devices
10R, 10G, and 10B.
[0072] The red filter, the green filter, and the blue filter are
respectively formed in the shape of, for example, a rectangle with
no space in between. The red filter, the green filter, and the blue
filter are respectively made of a resin mixed with a pigment.
Adjustment is made by selecting a pigment so that light
transmittance in the intended red, green, or blue wavelength region
is high, and light transmittance in the other wavelength regions is
low.
[0073] Further, the wavelength range with high transmittance in the
color filter 51 corresponds with peak wavelength .lamda. of
spectrum of light that is desirably extracted from the resonator
structure MC1. Thereby, out of outside light entering from the
sealing substrate 50, only light having a wavelength equal to the
peak wavelength .lamda. of spectrum of light that is desirably
extracted passes through the color filter 51, and outside light in
other wavelengths is prevented from intruding into the organic
light EL devices 10R, 10G, and 10B.
[0074] The display unit is able to be manufactured, for example, as
follows.
[0075] First, the pixel drive circuit 140 including the drive
transistor Tr1 is formed on the substrate 11 made of the foregoing
material. After that, the planarizing insulating film 12 is formed
by coating the whole area of the substrate 11 with a sensitive
resin, and the planarizing insulating film 12 is patterned into a
given shape by exposure and development, the connection hole 12A is
formed, and the resultant is fired.
[0076] Next, the lower electrode 14 made of the foregoing material
is formed by, for example, sputtering method, and the lower
electrode 14 is selectively removed by wet etching. Thereby, the
respective organic light emitting devices 10R, 10G, and 10B are
separated individually.
[0077] Subsequently, the whole area of the substrate 11 is coated
with a photosensitive resin. An aperture is provided
correspondingly to the light emitting region by, for example,
photolithography method, and the resultant is fired. Accordingly,
the inter-electrode insulating film 15 is formed.
[0078] After that, the electron hole injection layer 16A, the
electron hole transport layer 16B, the light emitting layer 16C,
and the electron transport layer 16D of the organic layer 16 that
have the foregoing thickness and are made of the foregoing material
are formed by, for example, evaporation method.
[0079] After the organic layer 16 is formed, the laminated film
composed of the intermediate layer 18 and the upper electrode 17
that have the foregoing thickness and are made of the foregoing
material is deposited by, for example, evaporation method. After
the upper electrode 17 is formed, part of the metal element
contained in the intermediate layer 18 may be diffused and
distributed in the second electrode 17. Accordingly, the organic EL
devices 10R, 10G, and 10B as illustrated in FIG. 3 are formed.
[0080] Subsequently, the protective layer 30 that is made of the
foregoing material is formed on the organic EL devices 10R, 10G,
and 10B by, for example, CVD method or sputtering method.
[0081] Further, for example, the sealing substrate 50 made of the
foregoing material is coated with a material of the red filter by
spin coating or the like, the resultant is provided with patterning
by photolithography technology, and fired. Thereby, the red filter
is formed. Subsequently, the blue filter and the green filter are
sequentially formed in the same manner as that of the red
filter.
[0082] After that, the adhesive layer 40 is formed on the
protective layer 30. The sealing substrate 50 and the protective
layer 30 are bonded with the adhesive layer 40 in between. At this
time, the face of the sealing substrate 50 on which the color
filter 51 is formed is preferably arranged on the side of the
organic EL devices 10R, 10G, and 10B. Accordingly, the display unit
illustrated in FIG. 1 to FIG. 3 is completed.
[0083] In the display unit, the scanning signal is supplied from
the scanning line drive circuit 130 to each pixel through the gate
electrode of the writing transistor Tr2, and the image signal from
the signal line drive circuit 120 is retained in the retentive
capacity Cs through the writing transistor Tr2. That is, the drive
transistor Tr1 is on-off controlled according to the signal
retained in the retentive capacity Cs, and thereby a drive current
Id is injected into the respective organic light emitting devices
10R, 10G, and 10B. In the result, electron-hole recombination is
generated to initiate light emission. The light is multiply
reflected between the lower electrode 14 (reflecting face P1) and
the upper electrode 17 (translucent reflecting face P2). After
that, the light passes through the upper electrode 17, the color
filter 51, and the sealing substrate 50, and is extracted.
[0084] In this case, the intermediate layer 18 is provided being
contacted with the upper electrode 17 between the upper electrode
17 and the organic layer 16. The intermediate layer 18 contains one
selected from the metal element group consisting of the foregoing
alkali metal and the like, and has a thickness from 0.1 nm to 5 nm
both inclusive. Thus, degeneration of the upper electrode 17 and
lowering of electric conductivity caused by direct contact between
the upper electrode 17 and the organic layer 16 are inhibited, the
organic EL devices 10R, 10G, and 10B are favorably driven, and
favorable display performance is able to be obtained for a long
term. Further, since the thickness of the upper electrode 17 is
small, generation of non-light emitting defect due to short circuit
between the lower electrode 14 and the upper electrode 17 is
inhibited.
[0085] Further, in the case where the organic EL devices 10R, 10G,
and 10B have the resonator structure MC1, by decreasing the
thickness of the upper electrode 17, the resonator structure MC1 is
weakened, and view angle dependence of light extracted from the
translucent reflecting face P2 is decreased. Accordingly, for
example, under the conditions that the order m is 1 or more and
view angle dependence of luminance and chromaticity is easily
significant, luminance and chromaticity change according to the
view angle is moderated.
[0086] As described above, in the organic EL devices 10R, 10G, and
10B of this embodiment, the intermediate layer 18 is provided being
contacted with the upper electrode 17 between the upper electrode
17 and the organic layer 16. The intermediate layer 18 contains one
selected from the metal element group consisting of the alkali
metal and the like, and has a thickness from 0.1 nm to 5 nm both
inclusive. Thus, lowering of electric conductivity caused by
degeneration of the upper electrode 17 is inhibited, and the
thickness of the upper electrode 17 may be decreased down to from 2
nm to 6 nm both inclusive. Thus, in the case where a display unit
is structured by using the organic EL devices 10R, 10G, and 10B,
electric conductivity of the upper electrode 17 is retained, the
organic EL devices 10R, 10G, and 10B are favorably driven, and
non-light emitting defect is able to be decreased. In particular,
the embodiments are suitable for the organic EL devices 10R, 10G,
and 10B in which the resonator structure MC1 is included, and light
generated in the light emitting layer 16C is resonated between the
lower electrode 14 and the upper electrode 17.
First Modified Example
[0087] FIG. 5 illustrates a cross sectional structure of the
organic EL devices 10R, 10G, and 10B of a display unit according to
a first modified example. The organic EL devices 10R, 10G, and 10B
have a structure similar to that of the foregoing first embodiment,
except that a material of the intermediate layer 18 is totally
diffused in the upper electrode 17, and the intermediate layer 18
is integrated with the upper electrode 17. Thus, a description will
be given by affixing the same referential symbols for the
corresponding elements.
[0088] The upper electrode 17 has a thickness from 2 nm to 6 nm
both inclusive. The upper electrode 17 contains an alloy containing
magnesium (Mg), aluminum (Al), calcium (Ca), or sodium (Na) as a
main component, and contains one selected from the metal element
group consisting of an alkali metal, an alkali earth metal, a
lanthanoid metal, aluminum, indium, tin, nickel, copper, and zinc.
Thereby, in the display unit, the thickness of the upper electrode
17 may be decreased down to 6 nm or less while electric
conductivity of the upper electrode 17 is retained.
[0089] As the alloy that is a main component of the upper electrode
17, for example, an alloy of magnesium and silver (Mg--Ag alloy) or
an alloy of aluminum (Al) and lithium (Li) (Al--Li alloy) is
preferable as in the upper electrode 17 of the first
embodiment.
[0090] The metal element contained in the upper electrode 17 has a
degeneration preventive function to inhibit the upper electrode 17
from being directly contacted with the organic layer 16 and losing
electric conductivity as the intermediate layer 18 of the foregoing
embodiment does. In the case where the upper electrode 17 is used
as a cathode, the metal element preferably has electron injection
characteristics. As described above, examples of such a material
include the alkali metal, the alkali earth metal, and the
lanthanoid metal. By providing the appropriate electron injection
layer 16E, a metal having a larger work function than that of
magnesium is able to be used. Examples of such a metal include a
metal such as aluminum, indium, and tin; and a transition metal
such as nickel, copper, and zinc.
[0091] Specifically, as the metal element contained in the upper
electrode 17, calcium or aluminum is preferable as in the
intermediate layer 18 of the first embodiment.
[0092] The thickness of the upper electrode 17 is more preferably
from 2.5 nm to 6 nm both inclusive as in the upper electrode 17 of
the first embodiment.
[0093] "Thickness of the upper electrode 17" in this specification
is obtained by optical method such as spectroscopic ellipsometry.
Further, "thickness of the upper electrode 17" is measured in a
state of a product after being sealed with the sealing substrate 50
and being assembled.
[0094] The sheet resistance of the upper electrode 17 is
preferably, for example, 10000.OMEGA./.quadrature. or less as in
the first embodiment.
[0095] The metal element contained in the upper electrode 17 is,
for example, diffused in the upper electrode 17. Further, the metal
element contained in the upper electrode 17 may be chemically
changed by being contacted with the electron transport layer 16D
and the electron injection layer 16E. The upper electrode 17 is
formed as a laminated film composed of the intermediate layer 18
and the upper electrode 17 in a manufacturing step as in the first
embodiment. However, after the upper electrode 17 is formed, the
metal element as the material of the intermediate layer 18 is
diffused and distributed in the upper electrode 17, and as a
result, an integrated electrode layer composed of the intermediate
layer 18 and the upper electrode 17 is structured. Therefore, if a
cross section is analyzed, the intermediate layer 18 is not
detected as a layer.
[0096] In this modified example, the translucent reflecting face P2
of the resonator structure MC1 is the interface between the upper
electrode 17 and the electron injection layer 16E.
[0097] A method of manufacturing the display unit is similar to
that of the foregoing first embodiment. That is, the intermediate
layer 18 and the upper electrode 17 are formed as a laminated film
as in the foregoing first embodiment. At this time, after the upper
electrode 17 is formed, the metal element as the material of the
intermediate layer 18 is diffused in the upper electrode 17, and as
a result, the upper electrode 17 is formed as the integrated
electrode layer composed of the intermediate layer 18 and the upper
electrode 17. Accordingly, the organic EL devices 10R, 10G, and 10B
illustrated in FIG. 5 are formed.
[0098] In the display unit, driving control is made for each pixel
and display is made in the same manner as that described in the
first embodiment. In this case, the upper electrode 17 contains the
alloy of magnesium (Mg) or the like as a main component, and
contains one selected from the metal element group consisting of
the foregoing alkali metal and the like. Thus, lowering of electric
conductivity caused by degeneration of the upper electrode 17 is
inhibited, the organic EL devices 10R, 10G, and 10B are favorably
driven, and favorable display performance is obtained for a long
term. Further, since the thickness of the upper electrode 17 is
small, generation of non-light emitting defect due to short circuit
between the lower electrode 14 and the upper electrode 17 is
inhibited.
[0099] As described above, in this modified example, the upper
electrode 17 contains the alloy of magnesium (Mg) or the like as a
main component, and contains one selected from the metal element
group consisting of the foregoing alkali metal and the like. Thus,
lowering of electric conductivity caused by degeneration of the
upper electrode 17 is inhibited, and the thickness of the upper
electrode 17 is able to be decreased down to from 2 nm to 6 nm both
inclusive. Thus, in the case where a display unit is structured by
using the organic EL devices 10R, 10G, and 10B, electric
conductivity of the upper electrode 17 is retained, the organic EL
devices 10R, 10G, and 10B are favorably driven, and non-light
emitting defect is able to be decreased. In particular, the
embodiments are suitable for the organic EL devices 10R, 10G, and
10B in which the resonator structure MC1 is included, and light
generated in the light emitting layer 16C is resonated between the
lower electrode 14 and the upper electrode 17.
Second Embodiment
[0100] FIG. 6 illustrates a cross sectional structure of the
organic EL devices 10R, 10G, and 10B according to a second
embodiment. The organic EL devices 10R, 10G, and 10B have a
structure similar to that of the foregoing first embodiment, except
that a resonance adjustment layer 19 is included between the upper
electrode 17 and the protective layer 30. Thus, a description will
be given by affixing the same referential symbols for the
corresponding elements.
[0101] The resonance adjustment layer 19 is intended to control
resonator effect of the resonator structure MC1 by providing a
reflectance interface by using dielectric mirror principle on the
upper electrode 17, and has a refractive index different from the
refractive index of the protective layer 30. That is, the organic
EL devices 10R, 10G, and 10B have a resonator structure MC2 (second
resonator structure MC2). Light extracted from the resonator
structure MC1 is resonated between the interference between the
resonance adjustment layer 19 and the protective layer 30 and the
lower electrode 14 by the resonator structure MC2. In the resonator
structure MC2, the interface between the lower electrode 14 and the
organic layer 16 is the reflecting face P1, the interface between
the resonance adjustment layer 19 and the protective layer 30 is a
translucent reflecting face P3, and the organic layer 16, the
intermediate layer 18, the upper electrode 17, and the resonance
adjustment layer 19 are a resonance section. The light extracted
from the resonator structure MC1 is resonated and is extracted from
the translucent reflecting face P3 side. In the case where the
resonator structure MC2 is included as the second resonator
structure, if resonator effect of the resonator structure MC1 is
weakened by decreasing the thickness of the upper electrode 17,
resonator effect is able to be controlled.
[0102] An optical distance L2 between the reflecting face P1 and
the translucent reflecting face P3 preferably satisfies
Mathematical formula 2.
(2L2)/.lamda.+.PHI./(2.pi.)=m Mathematical formula 2
[0103] In the formula, "L2" represents the optical distance between
the reflecting face P1 and the translucent reflecting face P3. "m"
represents an order (0 or a natural number). ".PHI." represents a
sum of the phase shift .PHI.1 of reflected light generated in the
reflecting face P1 and a phase shift .PHI.3 of reflected light
generated in the translucent reflecting face P3
(.PHI.=.PHI.1+.PHI.3) (rad). ".lamda." represents a peak wavelength
of spectrum of light that is desirably extracted from the
translucent reflecting face P3 side. For L2 and .lamda. in the
Mathematical formula 2, the unit should be unified, and for
example, (nm) is used as the unit.
[0104] Further, the resonance adjustment layer 19 also has a
function as a protective film to prevent deterioration of the upper
electrode 17. That is, if the protective layer 30 is directly
layered on the upper electrode 17 by CVD method or sputtering
method after the upper electrode 17 is formed, there is a
possibility that the upper electrode 17 is degenerated by
introduced gas at the time of film forming, oxygen, high energy
particles, oxygen in a chamber or mobile environment, moisture or
the like, and function as an electrode is not able to be
maintained. However, if the resonance adjustment layer 19 is
provided by vacuum evaporation method continuously after the upper
electrode 17 is formed, the upper electrode 17 is able to be
protected.
[0105] The thickness of the resonance adjustment layer 19 is not
particularly limited. However, to prevent degeneration of the upper
electrode 17, for example, the thickness of the resonance
adjustment layer 19 is desirably 10 nm or more. The film thickness
setting is able to be adjusted as appropriate by optical design to
adjust the intensity of the resonator structure MC2. However, the
resonance adjustment layer 19 is supposed to be formed common to R,
G, and B. Thus, it is desirable that the refractive index and the
film thickness are set so that light extraction effect is favorable
for all three color. As a material of the resonance adjustment
layer 19, a material having small visible light absorption and
having a small possibility to degenerate the upper electrode 17 at
the time of film formation is desirable. It is able to select a
material having a refractive index according to adjustment request
of the resonator structure MC2. As a specific material, an vacuum
evaporative inorganic film or a vacuum evaporative organic film
represented by lithium fluoride (refractive index of 1.38 in 460
nm), potassium bromide (refractive index of 1.58), Alq3 (refractive
index of 1.84), MoO.sub.3 (refractive index of 2.22), ZnSe
(refractive index of 2.6) and the like are able to be used.
[0106] The refractive index of the resonance adjustment layer 19 is
preferably smaller than the refractive index of the protective
layer 30 for the following reason. That is, the translucent
reflecting face P3 of the resonator structure MC2 is formed by
refractive index difference of the interface between the resonator
adjustment layer 19 and the protective layer 30. Thus, if the
refractive index difference is increased, resonator effect is
intensified, while if the refractive index difference is decreased,
resonator effect is weakened. To intensify the resonator effect by
increasing the refractive index difference, the refractive index of
the resonance adjustment layer 19 is set smaller than that of the
protective layer 30, or is set larger than that of the protective
layer 30. If the refractive index of the resonance adjustment layer
19 is set smaller than that of the protective layer 30, as a result
of phase shift in the reflecting face P1, the order m of the
resonator structure MC2 is able to be identical with the order m of
the resonator structure MC1 composed of the lower electrode 14 and
the upper electrode 17. Further, in the case where the light
emitting position of each light emitting layer 16C of the organic
light emitting devices 10R, 10G, and 10B is located in the
resonance position that is most proximal to the lower electrode 14,
even if the resonance adjustment layer 19 is formed common to the
organic light emitting devices 10R, 10G, and 10B, resonance
intensity is able to be intensified for all the organic light
emitting devices 10R, 10G, and 10B.
[0107] In the case where there is no need to intensify resonator
effect, the refractive index of the resonance adjustment layer 19
is able to be set to a value close to the refractive index of the
protective layer 30. For example, in the case where the protective
layer 30 is composed of silicon nitride (refractive index from 1.8
to 1.9 both inclusive), the refractive index of the organic
material represented by Alq3 is about 1.9, and is suitable for the
resonance adjustment layer 19. In addition, other organic film or
other inorganic film may be used.
[0108] The display unit is able to be manufactured in the same
manner as that of the first embodiment, except that the resonance
adjustment layer 19 made of the foregoing material is formed by
vacuum evaporation method continuously after the upper electrode 17
is formed.
[0109] In the display unit, driving control is made for each pixel
and display is made in the same manner as that described in the
first embodiment. In this case, the resonance adjustment layer 19
is provided between the upper electrode 17 and the protective layer
30, and the resonator structure MC2 is structured. Thus, in the
case where resonator effect of the resonator structure MC1 is
weakened by decreasing the thickness of the upper electrode 17,
intensity of light extracted from the front face is increased.
[0110] As described above, in the organic EL devices 10R, 10G, and
10B of this embodiment, the resonance adjustment layer 19 is
provided between the upper electrode 17 and the protective layer
30, and the resonator structure MC2 is structured. Thus, in the
case where resonator effect of the resonator structure MC1 is
weakened by decreasing the thickness of the upper electrode 17, the
resonator effect is able to be controlled.
[0111] In this embodiment, as illustrated in FIG. 7, it is possible
that the metal element as a material of the intermediate layer 18
is diffused and distributed in the upper electrode 17, and as a
result, the upper electrode 17 is structured as an integrated
electrode layer composed of the intermediate layer 18 and the upper
electrode 17.
Module and Application Examples
[0112] A description will be given of application examples of the
display unit described in the foregoing embodiments. The display
unit of the foregoing embodiments is able to be applied to a
display unit of an electronic device in any field for displaying a
video signal inputted from outside or a video signal generated
inside as an image or a video, such as a television device, a
digital camera, a notebook personal computer, a portable terminal
device such as a mobile phone, and a video camera.
[0113] Module
[0114] The display unit of the foregoing embodiments is
incorporated in various electronic devices such as after-mentioned
first to fifth application examples as a module as illustrated in
FIG. 8, for example. In the module, for example, a region 210
exposed from the sealing substrate 50 and the adhesive layer 40 is
provided on a side of the substrate 11, and an external connection
terminal (not illustrated) is formed in the exposed region 210 by
extending the wirings of the signal line drive circuit 120 and the
scanning line drive circuit 130. The external connection terminal
may be provided with a Flexible Printed Circuit (FPC) 220 for
inputting and outputting a signal.
First Application Example
[0115] FIG. 9 is an appearance of a television device to which the
display unit of the foregoing embodiments is applied. The
television device has, for example, a video display screen section
300 including a front panel 310 and a filter glass 320. The video
display screen section 300 is composed of the display unit
according to the foregoing respective embodiments.
Second Application Example
[0116] FIGS. 10A and 10B are an appearance of a digital camera to
which the display unit of the foregoing embodiments is applied. The
digital camera has, for example, a light emitting section for a
flash 410, a display section 420, a menu switch 430, and a shutter
button 440. The display section 420 is composed of the display unit
according to the foregoing respective embodiments.
Third Application Example
[0117] FIG. 11 is an appearance of a notebook personal computer to
which the display unit of the foregoing embodiments is applied. The
notebook personal computer has, for example, a main body 510, a
keyboard 520 for operation of inputting characters and the like,
and a display section 530 for displaying an image. The display
section 530 is composed of the display unit according to the
foregoing respective embodiments.
Fourth Application Example
[0118] FIG. 12 is an appearance of a video camera to which the
display unit of the foregoing embodiments is applied. The video
camera has, for example, a main body 610, a lens for shooting an
object 620 provided on the front side face of the main body 610, a
start/stop switch in shooting 630, and a display section 640. The
display section 640 is composed of the display unit according to
the foregoing respective embodiments.
Fifth Application Example
[0119] FIGS. 13A to 13G are an appearance of a mobile phone to
which the display unit of the foregoing embodiments is applied. In
the mobile phone, for example, an upper package 710 and a lower
package 720 are jointed by a joint section (hinge section) 730. The
mobile phone has a display 740, a sub-display 750, a picture light
760, and a camera 770. The display 740 or the sub-display 750 is
composed of the display unit according to the foregoing respective
embodiments.
EXAMPLES
[0120] A description will be given of specific examples.
Examples 1-1 to 1-4
[0121] The intermediate layer 18 and the upper electrode 17 of the
foregoing first embodiment were formed. At this time, the
intermediate layer 18 was composed of calcium (Ca), and the
thickness thereof was 2.0 nm. The upper electrode 17 was composed
of an Mg--Ag alloy, and the thickness thereof was varied as
illustrated in Table 1. To match with the conditions of the organic
light emitting devices 10R, 10G, and 10B, as a foundation of the
intermediate layer 18, a vacuum evaporated film having a thickness
of 20 nm obtained by resistance heating of an electron transport
material was formed. The upper electrode 17 was deposited at a
vapor rate of 0.1 nm/sec by vacuum evaporation method by resistance
heating at a high vacuum degree of 1*10.sup.-5 Pa or less. The
co-evaporation ratio of magnesium and silver was Mg:Ag=10:1. To
prevent degeneration by air, a lithium fluoride film having a
thickness of 40 m was formed by vacuum evaporation on the upper
electrode 17. After that, the resultant was sealed with an
ultraviolet hardened resin.
Comparative Examples 1-1 and 1-2
[0122] An upper electrode composed of a Mg--Ag alloy was formed in
the same manner as that of the foregoing Examples 1-1 to 1-4,
except that the intermediate layer was not provided. At this time,
the thickness of the upper electrode was varied as illustrated in
Table 1.
[0123] For the obtained intermediate layer or the obtained upper
electrode of Examples 1-1 to 1-4 and Comparative examples 1-1 and
1-2, the thickness was measured by spectroscopic ellipsometry, and
the sheet resistance was examined. The results thereof are all
illustrated in Table 1.
TABLE-US-00001 TABLE 1 Material of intermediate layer
(thickness)/material of upper Sheet resistance electrode
(thickness) (.OMEGA./.quadrature.) Example 1-1 Ca (2.0 nm)/Mg--Ag
(2.0 nm) 585 Example 1-2 Ca (2.0 nm)/Mg--Ag (3.0 nm) 306 Example
1-3 Ca (2.0 nm)/Mg--Ag (4.0 nm) 215 Example 1-4 Ca (2.0 nm)/Mg--Ag
(5.0 nm) 162 Comparative Mg--Ag (10.0 nm) 86 example 1-1
Comparative Mg--Ag (4.0 nm) 28500 example 1-2
[0124] As evidenced by Table 1, in Comparative example 1-2 in which
the intermediate layer was not provided and the thickness of the
upper electrode was decreased, the sheet resistance was
significantly deteriorated compared to in Comparative Example 1-1
in which only the thick upper electrode was provided. Meanwhile, in
Examples 1-1 to 1-4 in which the thickness of the upper electrode
17 was decreased and the intermediate layer 18 was provided, the
sheet resistance was significantly improved compared to in
Comparative example 1-2 in which the intermediate layer was not
provided and the thickness of the upper electrode was decreased,
and a result close to that of Comparative example 1-1 in which only
the thick upper electrode was provided was obtained.
[0125] That is, it was found that in the case where the
intermediate layer 18 composed of calcium (Ca) was provided being
contacted with the upper electrode 17 between the upper electrode
17 and the organic layer 16, the thickness was able to be decreased
down to 6 nm or less while electric conductivity of the upper
electrode 17 was retained.
Examples 2-1 to 2-4
[0126] The organic EL device of the first embodiment was fabricated
by using the intermediate layer 18 and the upper electrode 17
illustrated in Table 1. First, as the lower electrode 14, an
aluminum-neodymium alloy film (film thickness: 150 nm) was formed
on the substrate 11 made of a glass plate sized 25 mm*25 mm.
Further, as a contact with the upper electrode 17 and a connection
section to a power line, a pad section (not illustrated) composed
of titanium was provided on the substrate 11.
[0127] Next, the lower electrode 14 was coated with a
photosensitive organic insulating material, and an aperture was
provided correspondingly to a light emitting region sized 2 mm*2 mm
in the central section of the lower electrode 14. Thereby, the
interelectrode insulating film 15 was formed.
[0128] Subsequently, a metal mask having an aperture was prepared.
The metal mask was arranged in the proximity of the substrate 11 in
a state that the aperture of the metal mask was aligned with the
light emitting region of the lower electrode 14. After that, the
electron hole injection layer 16A to the electron injection layer
16E were sequentially formed by vacuum evaporation method under
vacuum atmosphere of 1*10.sup.-5 Pa or less. At this time, the
optical distance L1 between the reflecting face P1 and the
translucent reflecting face P2 was adjusted to satisfy Mathematical
formula 1 by adjusting the thickness of the electron injection
layer 16A to the electron injection layer 16E to structure the
resonator structure MC1.
[0129] For the electron hole injection layer 16A, a film having a
thickness of 20 nm composed of the hexaazatriphenylene derivative
shown in Chemical formula 2 was formed. For the electron hole
transport layer 16B, a film having a thickness of 25 nm composed of
.alpha.-NPD was formed. The evaporation rate was 0.1 nm/sec. For
the light emitting layer 16C, a co-evaporated film having a
thickness of 30 nm in which Alq.sub.3 host was doped with 1%
coumarin 6 as a green light emitting material was formed. The
evaporation rate was 0.2 nm/sec. For the electron transport layer
16D, a film having a thickness of 175 nm composed of Alq.sub.3 was
formed. The evaporation rate was 0.2 nm/sec.
##STR00003##
[0130] After the electron transport layer 16D was formed, a metal
mask having an aperture corresponding to a pad section was
prepared. The metal mask was arranged in the proximity of the
substrate 11. As the electron injection layer 16E, a film having a
thickness of 0.3 nm composed of lithium fluoride was formed.
Subsequently, the intermediate layer 18 and the upper electrode 17
were formed in the same manner as that of Examples 1-1 to 1-4. The
film forming conditions were identical with those of Examples 1-1
to 1-4.
TABLE-US-00002 TABLE 2 (characteristics: value in current density
of 10 mA/cm.sup.2) Upper Intermedi- electrode Luminance ate layer
(nm) Front face Drive ratio (nm) Mg--Ag efficiency voltage (45
deg/front Ca alloy (cd/A) (V) face) Example 2-1 2.0 2.5 12.4 7.60
0.85 Example 2-2 2.0 3.0 12.5 7.49 0.84 Example 2-3 2.0 4.0 13.0
7.32 0.80 Example 2-4 2.0 5.0 13.4 7.38 0.75 Comparative Not 5.0
Not -- -- example 2-1 applicable conducted Comparative Not 6.0 13.6
9.54 0.70 example 2-2 applicable Comparative Not 7.0 13.8 7.74 0.65
example 2-3 applicable Comparative Not 9.0 13.9 7.58 0.57 example
2-4 applicable
[0131] After that, as the resonance adjustment layer 19, a film
having a thickness of 40 nm composed of Alq.sub.3 was formed on the
upper electrode 17 by vacuum evaporation method continuously after
the upper electrode 17 was formed. Subsequently, as the protective
layer 30, a silicon nitride film having a thickness of 1 .mu.m was
formed by plasma CVD method. In the examples, the resonance
adjustment layer 19 was used as a protective film to inhibit
degeneration of the upper electrode 17, and the resonator structure
MC2 was not structured. After that, the sealing substrate 50 made
of glass was bonded by using the adhesive layer 40 made of an
ultraviolet hardened resin.
Comparative Examples 2-1 to 2-4
[0132] An organic EL device was formed in the same manner as that
of the foregoing Examples 2-1 to 2-4, except that the intermediate
layer was not formed. At this time, the thickness of the upper
electrode was varied as illustrated in Table 2.
[0133] For the obtained organic EL devices of Examples 2-1 to 2-4
and Comparative examples 2-1 to 2-4, the initial characteristics
were measured. The result is also illustrated in Table 2. In Table
2, the luminance ratio is a ratio of the luminance measured from 45
deg oblique direction with respect to the front face luminance.
[0134] As evidenced by Table 2, in Examples 2-1 to 2-4 in which the
thickness of the upper electrode 17 was 2.5 nm or more, for all the
front face efficiency, the drive voltage, and the luminance ratio,
favorable results were obtained. In particular, the luminance ratio
was 0.7 or more in Examples 2-1 to 2-4, and the view angle
characteristics were improved. The reason thereof may be as
follows. That is, since the thickness of the upper electrode 17 was
decreased, the resonator effect of the resonator structure MC1 was
moderated. Further, continuous lighting was made for examples 2-1
to 2-4. In the result, lighting was enabled without any trouble for
all examples.
[0135] The thickness of the upper electrode 17 in Examples 2-1 to
2-4 was optically obtained by reflectance measurement. As a result,
it is not necessary to optically consider the intermediate layer 18
composed of calcium (Ca) as a metal film. In some cases, the
intermediate layer 18 composed of calcium (Ca) is chemically
changed by being contacted with the electron transport layer 16D
composed of Alq3 or the electron injection layer 16E composed of
LiF. In some cases, the intermediate layer 18 composed of calcium
(Ca) is diffused and distributed in the upper electrode 17.
[0136] Meanwhile, in Comparative example 2-1 in which the thickness
of the upper electrode was 5.0 nm, the resistance of the upper
electrode was high and conduction was not enabled. Similarly, in
the case where the thickness of the upper electrode was 5.0 or
less, conduction was not enabled. In Comparative examples 2-2 and
2-3 in which the thickness of the upper electrode was 6.0 nm or 7.0
nm, the initial conduction was enabled. However, in this case,
continuous lighting resulted in intense rise of a drive voltage,
and deterioration was significant. Accordingly, it was found as
follows. That is, it was only Comparative example 2-4 having the
thickness of the upper electrode of 9.0 nm that both the initial
driving and the continuous driving were stably enabled. In
addition, in the case where the intermediate layer was not
provided, the thickness of the metal film should be at least 9.0
nm. In Comparative examples 2-1 to 2-4, the luminance ratio was all
0.70 or less, and light emitting characteristics change according
to the view angle was large.
[0137] Further, in the case where comparison was made among
Examples 2-2 to 2-4, there was a tendency that as the thickness of
the upper electrode 17 was decreased, the front face efficiency was
lowered, while the luminance ratio was increased. The reason
thereof may be as follows. That is, since the thickness of the
upper electrode 17 was decreased, resonator effect of the resonator
structure MC1 was weakened.
[0138] That is, it was found that in the case where the
intermediate layer 18 composed of calcium (Ca) was provided being
contacted with the upper electrode 17 between the upper electrode
17 and the organic layer 16, even if the thickness of the upper
electrode 17 was decreased down to 6 nm or less, electric
conductivity was retained, and the organic EL device was favorably
driven for a long term.
Comparative Example 2-5
[0139] An organic EL device was formed in the same manner as that
of Examples 2-1 to 2-4, except that the upper electrode was
composed of silver (Ag) instead of the Mg--Ag alloy, and the
thickness thereof was 7 nm. At this time, the intermediate layer
was formed in the same manner as that of Examples 2-1 to 2-4. For
the obtained organic EL device, the reflective spectrum of the
upper electrode was examined. The result was largely different from
the assumed result of the simple silver (Ag). Further, when the
organic EL device was tried to be lighted, conduction was not
enabled. The reason thereof may be as follows. That is, in the
silver (Ag) thin film, the film quality was not stable.
Comparative Example 2-6
[0140] An organic EL device was formed in the same manner as that
of Examples 2-1 to 2-4, except that the upper electrode was
composed of aluminum (Al) instead of the Mg--Ag alloy, and the
thickness thereof was 7 nm. At this time, the intermediate layer
was formed in the same manner as that of Examples 2-1 to 2-4. When
the obtained organic EL device was tried to be lighted, conduction
was not enabled.
[0141] That is, it was found that in the case where the upper
electrode 17 was composed of the Mg--Ag alloy, the organic EL
device was able to be favorably driven.
Examples 3-1 to 3-4
[0142] An organic EL device was formed in the same manner as that
of Examples 2-1 to 2-4, except that the thickness of the upper
electrode 17 was 5.0 nm, and the thickness of the intermediate
layer 18 was varied as illustrated in Table 3. Example 3-3 was
identical with Example 2-4. For the obtained organic EL device, the
initial characteristics were examined. The results thereof are also
illustrated in Table 3.
TABLE-US-00003 TABLE 3 Upper Intermedi- electrode Luminance ate
layer (nm) Front face Drive ratio (nm) Mg--Ag efficiency voltage
(45 deg/front Ca alloy (cd/A) (V) face) Example 3-1 0.5 5.0 13.9
7.75 0.83 Example 3-2 1.0 5.0 13.8 7.36 0.78 Example 3-3 2.0 5.0
13.4 7.38 0.75 Example 3-4 4.0 5.0 12.9 7.93 0.72
[0143] As evidenced by Table 3, for all the front face efficiency,
the drive voltage, and the luminance ratio, favorable results were
obtained not depending on the thickness of the intermediate layer
18. In particular, the luminance ratio was 0.7 or more in Examples
3-1 to 3-4, which was favorable. Further, luminance deterioration
characteristics in driving at a certain current was examined. The
result was almost equal to that of Comparative example 1-1 in which
the thickness of the metal film composed of the Mg--Ag alloy was 10
nm.
[0144] That is, it was found that in the case where the thickness
of the intermediate layer 18 was from 0.5 nm to 4 nm both
inclusive, the organic EL device was able to be favorably
driven.
Example 4
[0145] As the resonance adjustment layer 19, a film composed of
lithium fluoride having a thickness of 20 nm was formed. The
thickness of the organic layer was adjusted so that the optical
distance L2 between the reflecting face P1 and the translucent
reflecting face P3 satisfied Mathematical formula 2. Accordingly,
the resonator structure MC2 was structured. At this time, the phase
shift .PHI..sub.3 in the translucent reflecting face P3 in the
resonator structure MC2 was different from the phase shift
.PHI..sub.2 in the translucent reflecting face P2 in the resonator
structure MC1, and thus the optical distance L1 is different from
the optical distance L2, but the order m was identical. The organic
EL device was formed in the same manner as that of Example 2-4 as
for the rest.
[0146] For the obtained organic EL device, the extraction intensity
in the front face was examined. In the result, the extraction
intensity was improved than that of Example 2-4 by 6%.
[0147] That is, it was found that in the case where the resonator
structure MC2 was structured by providing the resonance adjustment
layer 19 between the upper electrode 17 and the protective layer
30, if resonator effect of the resonator structure MC1 is weakened
by decreasing the thickness of the upper electrode 17, the
resonator effect is able to be controlled.
Example 5
[0148] An active matrix organic EL display unit having a pixel
count of 960*540 was fabricated in the same manner as that of
Example 2-4, except that the intermediate layer 18 was composed of
calcium (Ca) (thickness: 2 nm) and the upper electrode 17 was
composed of an Mg--Ag alloy (thickness: 5 nm).
Comparative Example 5
[0149] An active matrix organic EL display unit having a pixel
count of 960*540 was fabricated. The intermediate layer was not
provided, and the upper electrode was composed of an Mg--Ag alloy
(thickness: 8 nm).
[0150] For the obtained organic EL display units of Example 5 and
Comparative example 5, the average number of non-light emitting
defects per panel was examined. In Example 5, the result was one
twenty-fifth ( 1/25) of Comparative example 5, which means the
average number of non-light emitting defects was able to be
significantly decreased. The reason thereof may be as follows. That
is, in Example 5, the thickness of the upper electrode 17 was
small. Thus, in a manufacturing step, the upper electrode 17
intrudes into around a foreign matter on the lower electrode 14,
and thereby a leak pass formation between the lower electrode 14
and the upper electrode 17 was inhibited.
[0151] That is, it was found that in the case where a display unit
was structured by using the organic EL device in which the
intermediate layer 18 was provided being contacted with the upper
electrode 17 between the upper electrode 17 and the organic layer
16, the thickness of the upper electrode 17 was able to be
decreased, and the number of non-light emitting defects was able to
be decreased.
Example 6
[0152] An organic EL device was formed in the same manner as that
of Examples 2-1 to 2-4, except that the intermediate layer 18 was
composed of aluminum (Al) (thickness: 1 nm) and the upper electrode
17 was composed of an Mg--Ag alloy (thickness: 5 nm). For the
obtained organic EL device, the initial characteristics were
examined. The obtained result is illustrated in Table 4.
TABLE-US-00004 TABLE 4 Upper Intermedi- electrode Luminance ate
layer (nm) Front face Drive ratio (nm) Mg--Ag efficiency voltage
(45 deg/front Al alloy (cd/A) (V) face) Example 6 1.0 5.0 12.9 7.35
0.76
[0153] As evidenced by Table 4, in the case where aluminum (Al) was
used instead of calcium (Ca) as the intermediate layer 18,
favorable light emission was obtained as well. Further, luminance
deterioration characteristics in driving at a certain current were
examined. The result was equal to that of Comparative example
2-4.
[0154] That is, it was found that in the case where the
intermediate layer 18 composed of aluminum (Al) was provided being
contacted with the upper electrode 17 between the upper electrode
17 and the organic layer 16, even if the thickness of the upper
electrode 17 was decreased down to 6 nm or less, electric
conductivity was retained, and the organic EL device was favorably
driven for a long term.
[0155] In the foregoing second embodiment and the foregoing
examples, the description has been given of the case that the
resonance adjustment layer 19 was provided between the upper
electrode 17 and the protective layer 30, and the interface between
the resonance adjustment layer 19 and the protective layer 30 was
the translucent reflecting face P3. However, the resonance
adjustment layer 19 may be provided in other position. For example,
if the protective layer 30 is not provided, the resonance
adjustment layer 19 is able to be provided between the upper
electrode 17 and the adhesive layer 40. Further, the resonance
adjustment layer 19 may be provided between the protective layer 30
and the adhesive layer 40.
[0156] Further, for example, the material, the thickness, the
film-forming method, the film-forming conditions and the like of
each layer are not limited to those described in the foregoing
embodiments and the foregoing examples, but other material, other
thickness, other film-forming method, and other film-forming
conditions may be adopted.
[0157] Further, for example, in the foregoing embodiments and the
foregoing examples, the description has been given of the case that
the lower electrode 14, the organic layer 16, and the upper
electrode 17 are sequentially layered from the substrate 11 side
over the substrate 11, and light is extracted from the sealing
substrate 50 side. However, it is possible that the lamination
order is reversed, that is, the upper electrode 17, the organic
layer 16, and the lower electrode 14 are sequentially layered from
the substrate 11 side over the substrate 11, and light is extracted
from the substrate 11 side.
[0158] In addition, for example, in the foregoing embodiments and
the foregoing examples, the description has been given of the case
that the lower electrode 14 is an anode, and the upper electrode 17
is a cathode. However, it is possible that the lower electrode 14
is a cathode, and the upper electrode 17 is an anode. Further, it
is possible that the lower electrode 14 is a cathode, the upper
electrode 17 is an anode, and the upper electrode 17, the organic
layer 16, and the lower electrode 14 are sequentially layered from
the substrate 11 side over the substrate 11, and light is extracted
from the substrate 11 side.
[0159] Furthermore, in the foregoing embodiments and the foregoing
examples, the description has been specifically given of the
structure of the organic light emitting devices 10R, 10G, and 10B.
However, it is not always necessary to provide all layers, and
other layer may be further provided.
[0160] In addition, in the foregoing embodiments and the foregoing
examples, the description has been given of the active matrix
display unit. However, the embodiments are also able to be applied
to a passive matrix display unit. Furthermore, the structure of the
pixel drive circuit for driving the active matrix is not limited to
the structure described in the foregoing embodiments and the
foregoing examples. If necessary, a capacity device or a transistor
may be added. In this case, according to the change of the pixel
drive circuit, a necessary drive circuit may be added in addition
to the foregoing signal line drive circuit 120 and the foregoing
scanning line drive circuit 130.
[0161] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications can be made without departing from the spirit and
scope of the present subject matter and without diminishing its
intended advantages. It is therefore intended that such changes and
modifications be covered by the appended claims.
* * * * *