U.S. patent application number 11/336279 was filed with the patent office on 2006-06-01 for organic electroluminescence display device.
Invention is credited to Yih Chang, Tien-Rong Lu.
Application Number | 20060113902 11/336279 |
Document ID | / |
Family ID | 32986249 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060113902 |
Kind Code |
A1 |
Chang; Yih ; et al. |
June 1, 2006 |
Organic electroluminescence display device
Abstract
An organic electroluminescence display device is provided. The
OEL device includes a substrate, a first electrode layer, a second
electrode layer, an organic functional layer and at least one
electrochromic medium layer. The first electrode layer is disposed
on the substrate, the second electrode layer is disposed over the
first electrode layer, and the organic functional layer and the
electrochromic medium layer are disposed between the first
electrode layer and the second electrode layer. Accordingly, the
electrochromic medium layer is provided as a selective light valve
to improve the reflection of the external light, and thus the
contrast ratio of the organic electroluminescence display device is
enhanced.
Inventors: |
Chang; Yih; (Hsinchu,
TW) ; Lu; Tien-Rong; (Hsinchu, TW) |
Correspondence
Address: |
J.C. Patents
Suite 250
4 Venture
Irvine
CA
92618
US
|
Family ID: |
32986249 |
Appl. No.: |
11/336279 |
Filed: |
January 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10814217 |
Mar 30, 2004 |
|
|
|
11336279 |
Jan 20, 2006 |
|
|
|
Current U.S.
Class: |
313/504 |
Current CPC
Class: |
H01L 51/5281 20130101;
G02F 1/157 20130101; H01L 51/0077 20130101; H01L 51/0084 20130101;
H01L 51/0086 20130101; H01L 51/0078 20130101; H01L 51/0037
20130101 |
Class at
Publication: |
313/504 |
International
Class: |
H01J 1/62 20060101
H01J001/62; H01J 63/04 20060101 H01J063/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2003 |
TW |
92107664 |
Claims
1-16. (canceled)
17. A organic electroluminescence display device, comprising: a
first substrate, having a displaying surface; a first electrode
layer, disposed on the first substrate; a second electrode layer,
disposed over the first electrode layer; an organic functional
layer, disposed between the first electrode layer and the second
electrode layer; and a selective light valve, disposed over the
displaying surface.
18. The organic electroluminescence display device of claim 17,
wherein the selective light valve comprises a liquid crystal light
valve.
19. The organic electroluminescence display device of claim 18,
wherein the liquid crystal light valve comprises a second
substrate, a third substrate and a liquid crystal layer, the third
substrate is disposed over the displaying surface, and the liquid
crystal layer is disposed between the second substrate and the
third substrate.
20. The organic electroluminescence display device of claim 18,
wherein the liquid crystal light valve comprises a second substrate
and a liquid crystal layer, and the liquid crystal layer is
disposed between the displaying surface and the second
substrate.
21. The organic electroluminescence display device of claim 17,
wherein at least one electrochromic medium layer is further
disposed between the first electrode layer and the second electrode
layer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Taiwan
application serial no. 92107664, filed on Mar. 31, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to an organic
electroluminescence (OEL) display device. More particularly, the
present invention relates to organic electroluminescence display
device having selective light valve.
[0004] 2. Description of Related Art
[0005] In recent years, communication appliance has become more and
more important. Especially, portable communication appliance is the
major stream of the communication appliance. In the development of
the portable communication appliance, the flat panel display (FPD)
used for the communication interface between the user and the
appliance is important. The conventional flat panel display (FPD)
may be generally classified into plasma display panel (PDP), liquid
crystal display (LCD), inorganic electro-luminescent display, light
emitting diode (LED), vacuum fluorescence display and field
emission display (FED). However, in comparison with other flat
plane display device, the organic electroluminescence device has
the advantages of self-luminescence, non-viewing angle dependence,
power saving, easy process, low-cost, low temperature range of
operation, high response speed and full-color. Therefore, the
organic electroluminescence device has the potential to be the next
generation flat panel display (FPD).
[0006] The organic electroluminescence component is used as a
displaying device by using the characteristic of the
self-luminescence of the organic functional material. The organic
electroluminescence component is classified into small molecular
organic light emitting component (SM-OLED) and polymer organic
light emitting component (PLED) according to the molecular weight
of the organic functional material. The structure for light
emitting of the organic electroluminescence component is mainly
constructed by a pair of electrodes and an organic functional
material layer. When a current is applied between the pair of
electrodes, exciton will be generated by the combination of
electron and hole in the organic functional material layer. Thus,
different color light is emitted by the exciton, and the color of
the light emitted is dependent on the characteristic of the
material of the organic functional material layer.
[0007] For any display device, the brightness discrimination is
dependent on the ratio of the brightness between fully turned on
and fully turned off, wherein the brightness ratio is generally
called a contrast ratio (CR). The brightness discrimination is
proportional to the contrast ratio. The conventional contrast ratio
is generally defined as below: CR = L sub , on + R amb L sub , off
+ R amb ( 1 ) ##EQU1##
[0008] In equation (1), L.sub.sub,on, is defined as the brightness
of the pixel being fully turned on, L.sub.sub,off is the brightness
of the pixel being fully turned off, and R.sub.amb is the reflected
brightness of the external light being incident into the display
device. When the L.sub.sub,on and the L.sub.sub,off of the pixel
are known (for example, L.sub.sub,on is about 100 nits and
L.sub.sub,off is about 1 nit), the relationship between the
contrast ratio and the reflected brightness of the external light
R.sub.amb can be calculated according to equation (1). It is noted
that, the larger the reflected brightness of the external light
R.sub.amb, the smaller the contrast ratio, i.e., the worse the
brightness discrimination. However, the only way is to enhance the
L.sub.sub,on of the pixel to increase the contrast ration and
obtain an applicable contrast ratio of the display device.
Alternatively, the smaller the reflected brightness of the external
light R.sub.amb, the larger the contrast ratio, thus the
L.sub.sub,on of the pixel may be decreased to obtain an applicable
contrast ratio. In general, the lower the L.sub.sub,on of the
pixel, the lower the power consumption and the lower harsh to the
eyes.
[0009] FIG. 1 is a drawing schematically illustrating a
conventional organic electroluminescence display device. Referring
to FIG. 1, a conventional organic electroluminescence display
device includes a substrate 100, a transparent electrode layer 102,
an organic functional layer 104 and a metal electrode layer 106.
The substrate 100 generally includes glass substrate. The
transparent electrode layer 102 is generally composed of
transparent conductive material such as indium tin oxide (ITO). The
organic functional layer 104 is generally an organic multilayer
comprising a hole injection layer, a hole transport layer, an
organic electroluminescence layer, an electron transport layer and
an electron injection layer. The metal electrode layer 106 is
generally composed of aluminum, calcium or alloy of magnesium and
silver. It is noted that, when current is applied between the
transparent electrode layer 102 and the metal electrode layer 106,
excitons will be generated by the recombination of electrons and
holes in the organic functional layer 104 and light will be
emitted. The mechanism of luminescence of different color of light
is dependent on the characteristic of the material of the organic
functional layer 104. In summary, the principle of displaying of
the organic electroluminescence display device is to convert
electric energy to photon energy by the driving of a current.
[0010] Referring to FIG. 1, the refractive index n.sub.1 of the
organic functional layer 104 is very close to the refractive index
n.sub.2 of the transparent anode layer 102. The refractive index
n.sub.1 of the organic functional layer 104 is, for example, larger
than the refractive index n.sub.3 of the transparent substrate 100.
In general, n.sub.1 is about 1.7, n.sub.2 is between 1.8 and 2.0,
and n.sub.3 is about 1.5 and larger than the refractive index of
air (.apprxeq.1).
[0011] In summary, the light of the organic electroluminescence
display device is emitted by the organic functional layer 104, and
the light has arbitrary propagation direction. However, the metal
electrode layer 106 may be provided as a reflection layer to
reflect the light, therefore, the light may only propagate in the
direction from the metal electrode layer 106 to the substrate 100.
In general, the emitted light described above may be influenced by
the external light, and thus the brightness discrimination is
reduced. For example, referring to FIG. 1, when the external light
is incident to the organic electroluminescence display device, the
external light will be reflected by the interface between the air
and the transparent substrate 100, the interface between the
transparent substrate 100 and the transparent electrode layer 102,
and the interface between the organic functional layer 104 and the
metal electrode layer 106. All the reflected light will propagate
in the direction from metal electrode layer 106 to the substrate
100.
[0012] For example, referring to FIG. 1, the reflected light
W.sub.1 from the interface between the air and the transparent
substrate 100 is about 4% of the incident external light W. The
reflected light W.sub.2 from the transparent substrate 100 and the
transparent electrode layer 102 is about 0.8% of the incident
external light W. The reflected light W.sub.3 from the organic
functional layer 104 and the metal electrode layer 106 is over 90%.
Therefore, almost all the reflected light is reflected by the metal
electrode layer 106. In other words, almost all the reflected light
is generated by the interface between the organic functional layer
104 and the metal electrode layer 106. Thus, if the organic
electroluminescence display device is used outdoors with strong
external light, the contrast ratio is reduced obviously due to the
reflected external light. Therefore, how to reduce the incidence of
the strong external light to the interface between the organic
functional layer 104 and the metal electrode layer 106 is the most
important issue to be solved to enhance the contrast ratio of the
organic electroluminescence display device under strong external
light.
[0013] One of the conventional technologies provides a polarizer
attached to the surface of the display device, or provides a photo
sensor and an adjusting device of contrast ratio to solve the
problem described above. However, these two methods have the
disadvantages below. First, the reflected external light is reduced
by the polarizer, however, the light emitted by the device is also
reduced by the polarizer, therefore the contrast of the display
device is not enhanced and is not applicable for the display device
to be used outdoors. Next, the photo sensor and the adjusting
device of the contrast ratio are dependent on the intensity of the
external light, thus the cost is high.
SUMMARY OF THE INVENTION
[0014] Therefore, the present invention is directed to an organic
electroluminescence display device having a selective light valve.
The selective light valve is used to forbidden the transmission of
the external light to the pixel being turned off and used to allow
the transmission of the external light to the pixel being turned on
respectively. Therefore, the contrast ratio and the brightness
discrimination of the display device are enhanced.
[0015] In the present invention an organic electroluminescence
display device is provided. The display device comprises a
substrate, a first electrode layer, a second electrode layer, an
organic functional layer and at least one electrochromic medium
layer. The first electrode layer is disposed on the substrate, and
the second electrode layer is disposed over the first electrode
layer. The organic functional layer is disposed between the first
electrode layer and the second electrode layer. The electrochromic
medium layer is disposed between the first electrode layer and the
second electrode layer. Therefore, the transmittance of the
electrochromic medium layer is changed by the oxidation and
reduction reaction or the hydrogen bonding reaction of the
electrochromic medium when a current is applied. Thus, the
transmittance of the electrochromic medium layer may be used as a
selective light valve.
[0016] In one embodiment of the invention, the organic functional
layer is, for example but not limited to, disposed over the first
electrode layer, and the electrochromic medium layer is disposed
between the organic functional layer and the second electrode
layer. Or, the electrochromic medium layer is, for example but not
limited to, disposed over the first electrode layer, and the
organic functional layer is disposed between the electrochromic
medium layer and the second electrode layer. The organic functional
layer is, for example but not limited to, an organic
electroluminescence layer. In addition, a hole injection layer and
a hole transport layer may be further disposed between the first
electrode layer and the organic electroluminescence layer.
Moreover, an electron transport layer and an electron injection
layer may be selectively disposed between the second electrode
layer and the organic electroluminescence layer. The electrochromic
medium layer described above may be disposed between any two of the
hole injection layer, the hole transport layer, the organic
electroluminescence layer, the electron transport layer and the
electron injection layer described above.
[0017] In one embodiment of the invention, the electrochromic
medium layer material is composed, for example but not limited to,
transition metal oxide, Prussian compound, viologens, conductive
polymer, transition metal, lanthanide coordination complexes,
metallopolymers, metal phthalocyanines or the combination thereof.
The transition metal oxide comprises, for example but not limited
to, WO.sub.3, MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5,
Ir(OH).sub.3, NiO.sub.xH.sub.y or the combination thereof. The
Prussian compound comprises, for example but not limited to,
[Fe.sup.IIIFe.sup.II(CN).sub.6].sup.-,
[Fe.sup.IIIFe.sup.III(CN).sub.6],
[Fe.sup.IIFe.sup.II(CN).sub.6].sup.2- or the combination thereof.
The viologens comprises, for example but not limited to,
1,1'-disubstituted-4,4'-bipyridinium salts. The conductive polymer
comprises, for example but not limited to, polypyrrole,
polythiophene, polyaniline, PEDOT or the combination thereof. The
transition metal, lanthanide coordination complexes and
metallopolymers comprises, for example but not limited to, metal
hydride, nitrosyl, oxo molybdenum complexes,
poly-[Ru.sup.II(vbpy).sub.2(Py).sub.2].sup.-Cl.sub.2 or the
combination thereof. The metal phthalocyanines comprises, for
example but not limited to, [Lu(Pc).sub.2].
[0018] In addition, the present invention provides an organic
electroluminescence display device. The display device comprises a
first substrate, a first electrode layer, a second electrode layer,
an organic functional layer and a selective light valve. The first
substrate comprises a displaying surface. The first electrode layer
is disposed on the first substrate, and the second electrode layer
is disposed over the first electrode layer. The organic functional
layer is disposed between the first electrode layer and the second
electrode layer. The selective light valve is disposed on the
displaying surface of the first substrate.
[0019] In one embodiment of the present invention, at least one
electrochromic medium layer is further disposed between the first
electrode layer and the second electrode layer.
[0020] In one embodiment of the present invention, the selective
light valve comprises, for example but not limited to, a liquid
crystal light valve. The liquid crystal light valve comprises a
second substrate, a third substrate and a liquid crystal layer. The
third substrate is disposed on the displaying surface of the first
substrate, and the liquid crystal layer is disposed between the
second substrate and the third substrate. In another embodiment of
the invention, the third substrate is optional and may be omitted,
and the liquid crystal layer is disposed between the displaying
surface of the first substrate and the second substrate. Thus, the
cost and the thickness of the organic electroluminescence display
device are all reduced.
[0021] In one embodiment of the present invention, the selective
light valve comprises, for example but not limited to, an
electrochromic medium layer. The electrochromic medium layer is
composed of, for example but not limited to, transition metal
oxide, Prussian compound, viologens, conductive polymer, transition
metal, lanthanide coordination complexes, metallopolymers, metal
phthalocyanines or the combination thereof. The transition metal
oxide comprises, for example but not limited to, WO.sub.3,
MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5, Ir(OH).sub.3,
NiO.sub.xH.sub.y or the combination thereof. The Prussian compound
comprises, for example but not limited to,
[Fe.sup.IIIFe.sup.II(CN).sub.6].sup.-,
[Fe.sup.IIIFe.sup.III(CN).sub.6],
[Fe.sup.IIFe.sup.II(CN).sub.6].sup.2- or the combination thereof.
The viologens comprises, for example but not limited to,
1,1'-disubstituted-4,4'-bipyridinium salts. The conductive polymer
comprises, for example but not limited to, polypyrrole,
polythiophene, polyaniline, PEDOT or the combination thereof. The
transition metal, lanthanide coordination complexes and
metallopolymers comprises, for example but not limited to, metal
hydride, nitrosyl, oxo molybdenum complexes,
poly-[Ru.sup.II(vbpy).sub.2(py).sub.2].sup.-Cl.sub.2 or the
combination thereof. The metal phthalocyanines comprises, for
example but not limited to, [Lu(Pc).sub.2].
[0022] Accordingly, the present invention provides a selective
light valve for the organic electroluminescence display device. For
the pixel being turned off, the selective light valve can avoid the
transmission of the external light, thus the reflected light of the
external light from the organic light emitting component is
reduced. For the pixel being turned on, the selective light valve
can allow the transmission of the external light, thus the
brightness of the pixel being turned on is enhanced. Thus, the
contrast ratio and the brightness discrimination of the organic
electroluminescence display device under strong light are
enhanced.
[0023] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The following drawings
illustrate embodiments of the invention and, together with the
description, serve to explain the principles of the invention.
[0025] FIG. 1 is a drawing schematically illustrating a
conventional organic electroluminescence display device;
[0026] FIG. 2 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention;
[0027] FIG. 3 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention;
[0028] FIG. 4 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention;
[0029] FIG. 5 is a drawing schematically illustrating comprises an
organic electroluminescence display device according to one
embodiment of the present invention; and
[0030] FIG. 6 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0031] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0032] FIG. 2 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention. Referring to FIG. 2, the organic
electroluminescence display device comprises, for example but not
limited to, a substrate 200, a first electrode layer 202, an
organic functional layer 204, a second electrode layer 206 and an
electrochromic medium layer 208. The substrate 200 comprises, for
example but not limited to, glass substrate or other transparent
substrate. The first electrode layer 202 is disposed on the
substrate 200. The first electrode layer 202 is, for example, a
transparent electrode layer composed of transparent conductive
material such as indium tin oxide (ITO). The second electrode layer
206 is disposed over the first electrode layer 202. The second
electrode layer 206 is, for example, a metal electrode comprises of
aluminum, calcium or alloy of magnesium and silver.
[0033] The organic functional layer 204 is disposed between the
first electrode layer 202 and the second electrode layer 206. The
organic functional layer 204 comprises, for example but not limited
to, organic multilayer comprising a hole injection layer 204a, a
hole transport layer 204b, an organic electroluminescence layer
204c, an electron transport layer 204d and an electron injection
layer 204e. It is noted that, since the light emitted by the
organic electroluminescence display device is generated from the
organic electroluminescence layer 204c, the above-described hole
injection layer 204a, hole transport layer 204b, electron transport
layer 204d and electron injection layer 204e are optional in the
manufacturing process.
[0034] For example, in a passive matrix display, the first
electrode layer 202 and the second electrode layer 206 comprise,
for example but not limited to, a plurality of mutually
perpendicular line structures, wherein a pixel region is
constructed by the intersection between the two electrode layers.
When a current is applied between the first electrode layer 202 and
the second electrode layer 206, and excitons is generated by the
recombination of electrons and holes in the organic functional
layer 204, a light is emitted. The mechanism of luminescence of
different color emitted light is dependent on the characteristic of
the material of the organic functional layer 204. In other words,
electric energy is converted to photon energy by the driving of a
current to emit a light for displaying of the organic
electroluminescence display device.
[0035] Referring to FIG. 2, the electrochromic medium layer 208 is
disposed between the organic functional layer 204 and the second
electrode layer 206. The electrochromic medium layer 208 is
comprised of, for example but not limited to, transition metal
oxide, Prussian compound, viologens, conductive polymer, transition
metal, lanthanide coordination complexes, metallopolymers, metal
phthalocyanines or the combination thereof.
[0036] The transition metal oxide comprises, for example but not
limited to, WO.sub.3, MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5,
Ir(OH).sub.3, NiO.sub.xH.sub.y or the combination thereof. The
Prussian compound comprises, for example but not limited to,
[Fe.sup.IIIFe.sup.II(CN).sub.6].sup.-,
[Fe.sup.IIIFe.sup.III(CN).sub.6],
[Fe.sup.IIFe.sup.II(CN).sub.6].sup.2- or the combination thereof.
The viologens comprises, for example but not limited to,
1,1'-disubstituted-4,4'-bipyridinium salts. The conductive polymer
comprises, for example but not limited to, polypyrrole,
polythiophene, polyaniline, PEDOT or the combination thereof. The
transition metal, the lanthanide coordination complexes and the
metallopolymers comprises, for example but not limited to, metal
hydride, nitrosyl, oxo molybdenum complexes,
poly-[Ru.sup.II(vbpy).sub.2(py).sub.2].sup.-Cl.sub.2 or the
combination thereof. The metal phthalocyanines comprises, for
example but not limited to, [Lu(Pc).sub.2].
[0037] For example, when the electrochromic medium layer 208 is
composed of transition metal oxide, it is divided into the two
types described below: ##STR1##
[0038] For a bottom emission organic electroluminescence display
device (light is emitted from the bottom surface of the substrate),
the electrochromic medium layer 208 is preferably composed of
P-type transition metal oxide, wherein for the NiO.sub.xM.sub.y,
M.sup.+ comprises H.sup.+, Li.sup.+, Na.sup.+, or K.sup.+. For
example, if the electrochromic medium layer 208 is composed of
Li.sub.xNi.sub.1-xO, the Li.sub.xNi.sub.1-xO thin film layer can be
deposited on the ITO glass substrate by sputtering or laser vapor
deposition process using target constructed by compressed mixture
of nickel oxide and lithium oxide powders. If the electrochromic
medium layer 208 is composed of NiO.sub.xH.sub.y, the
NiO.sub.xH.sub.y thin film can be manufactured by the following
steps. First, a nickel oxide thin film is manufactured by magnetron
sputtering process using pure nickel target under 10 mTorr O.sub.2.
Then the NiO.sub.xH.sub.y thin film layer is obtained by a reaction
of the nickel oxide thin film layer with 1M KOH solution.
[0039] According to the chemical reactions described above, when a
current is applied between the first electrode layer 202 and the
second electrode layer 206, the electrochromic medium layer 208
will be oxidized and reduced and thus has different color and
transmittance. In other words, the electrochromic medium layer 208
may be used as a selective light valve having different color and
transmittance according to the turning on and off of the pixel of
the organic electroluminescence display device.
[0040] For example, for the pixel being turned off, since the
current is not applied, the electrochromic medium layer 208 is
nearly non-transparent and has a light shielding effect. Therefore,
the incidence and the reflection of the external light to and from
the organic electroluminescence component are all reduced. For the
pixel being turned on, since the current is applied, the
electrochromic medium layer 208 is transparent, thus the external
light is incident to and reflected from the organic
electroluminescence component. Thus, the brightness of the pixel
being turned on is enhanced. In summary, for the whole organic
electroluminescence display device, the contrast ratio under a
strong light is enhanced, and thus the brightness discrimination of
the display device is also increased.
[0041] Accordingly, the present embodiment provides an
electrochromic medium layer 208 disposed between the organic
functional layer 204 and the second electrode layer 206. Thus, the
incidence of the strong external light to the interface between the
organic functional layer 204 and the second electrode layer 206 is
reduced. However, in another embodiment of the present invention,
the electrochromic medium layer 208 may also be disposed between
the first electrode layer 202 and the organic functional layer 204
(not shown), or may be disposed between any two of the
above-described hole injection layer 204a, hole transport layer
204b, organic electroluminescence layer 204c, electron transport
layer 204d and electron injection layer 204e (not shown). In any
one embodiment of the invention, the brightness discrimination of
the display device can be increased.
[0042] FIG. 3 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention. Referring to FIG. 3, the organic
electroluminescence display device comprises, for example but not
limited to, a first substrate 300, a first electrode layer 302, an
organic functional layer 304, a second electrode layer 306 and a
selective light valve 400. The first substrate 300 comprises, for
example but not limited to, glass substrate or other transparent
substrate. The first substrate 300 has a displaying surface 310.
The first electrode layer 302 is disposed on the first substrate
300, the first electrode layer 302 is, for example but not limited
to, a transparent electrode layer composed of, transparent
conductive material such as indium tin oxide (ITO). The second
electrode layer 306 is disposed over the first electrode layer 302.
The second electrode layer 306 comprises, for example but not
limited to, metal electrode layer composed of aluminum, calcium or
alloy of magnesium and silver. The organic functional layer 304 is
disposed between the first electrode layer 302 and the second
electrode layer 306 and comprises organic multilayer similar to the
embodiments described above. The selective light valve 400 is
disposed over the displaying surface 310 of the first substrate
300.
[0043] The selective light valve 400 comprises, for example but not
limited to, a second substrate 410, a third substrate 420 and a
liquid crystal layer 430. The second substrate 410 and the third
substrate 420 comprise, for example but not limited to, glass
substrate or other transparent substrate. The third substrate 420
is disposed on or over the displaying surface 310 of the first
substrate 300, and the liquid crystal layer 430 is disposed between
the second substrate 410 and the third substrate 420. The selective
light valve 400 is provided for controlling the passing through of
the external light or not. For example, for the pixel being turned
off, the transmission of the external light to the displaying
device is forbidden, thus the reflected light due to the reflection
of the external light incident to the organic electroluminescence
component is reduced. However, for the pixel being turned on, the
transmission of the external light to the display device is
allowed, thus the brightness of the pixel being turned on is
enhanced. Therefore, the contrast ratio of the organic
electroluminescence display device under a strong external light is
enhanced, and the brightness discrimination of the display device
is also enhanced.
[0044] It is noted that, for the selective light valve 400 (i.e., a
so-called liquid crystal light valve) of the present invention, it
is not necessary to dispose an upper and a lower polarizers on the
external surface of the second substrate 410 and the third
substrate 420 as disposed in conventional LCD device. In the
present invention, only the liquid crystal layer 430 is used as a
light valve to selective shield the external light under a driving
voltage. Thus, the brightness discrimination of the organic
electroluminescence display device is enhanced.
[0045] FIG. 4 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention. Referring to FIG. 4, the structure of the
organic electroluminescence display device is similar to that shown
in FIG. 3 except for that the third substrate 420 in FIG. 3 is
omitted in FIG. 4. Therefore, the liquid crystal layer 430 is
disposed on or over the displaying surface 310 of the first
substrate 300. In other words, the thin film transistor (TFT) and
the alignment film may be disposed on or over the displaying
surface 310 of the first substrate 300, and thus the liquid crystal
layer 430 and the OEL device are disposed on the same substrate.
Thus, the thickness of the organic electroluminescence display
device may be further reduced.
[0046] In the embodiments described above, a selective light valve
such as an electrochromic medium layer or a liquid crystal light
valve is provided for the organic electroluminescence display
device. However, in another embodiment of the invention described
hereinafter, more than one type of selective light valve may be
disposed in the organic electroluminescence display device.
[0047] FIG. 5 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention. It is noted that, the display device shown
in FIG. 5 comprising the electrochromic medium layer 208 shown in
FIG. 2 and the selective light valve 400 (i.e., the liquid crystal
light valve) shown in FIG. 3 simultaneously. Therefore, the organic
electroluminescence display device shown in FIG. 5 has the
advantages and characteristics of the electrochromic medium layer
208 and the selective light valve 400 (liquid crystal light valve)
described above. Thus, the brightness discrimination of the organic
electroluminescence display device is further enhanced.
[0048] FIG. 6 is a drawing schematically illustrating an organic
electroluminescence display device according to one embodiment of
the present invention. It is noted that, the display device shown
in FIG. 6 comprising the electrochromic medium layer 208 shown in
FIG. 2 and the selective light valve 400 (i.e., the liquid crystal
light valve) shown in FIG. 4 simultaneously. Therefore, the organic
electroluminescence display device shown in FIG. 6 has the
advantages and characteristics of the electrochromic medium layer
208 and the selective light valve 400 (liquid crystal light valve)
described above. Thus, the brightness discrimination of the organic
electroluminescence display device is further enhanced and the
thickness of the electroluminescence display device is further
reduced.
[0049] Accordingly, the organic electroluminescence display device
of the invention at least has the following advantages. First, the
organic electroluminescence display device of the present invention
provides at least one selective light valve to forbidden the
transmission of the external light to the pixel being turned off.
Thus, the reflection of the external light due to the interface
between the metal electrode layer and the organic functional layer
is reduced. In addition, the contrast ratio, the brightness
discrimination and the displaying quality of the organic
electroluminescence component under strong light is enhanced.
[0050] Next, the organic electroluminescence display device of the
present invention provides a selective light valve to allow the
transmission of the external light to the pixel being turned on.
Thus, the reflected light of the external light may be used to
enhance the luminous efficiency and the contrast of the organic
light emitting component.
[0051] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *