U.S. patent application number 10/055990 was filed with the patent office on 2002-06-13 for organic electroluminescent display device.
This patent application is currently assigned to NEC CORPORATION. Invention is credited to Ootsuki, Shigeyoshi, Yamaguchi, Yoshikazu.
Application Number | 20020072292 10/055990 |
Document ID | / |
Family ID | 11628464 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020072292 |
Kind Code |
A1 |
Ootsuki, Shigeyoshi ; et
al. |
June 13, 2002 |
Organic electroluminescent display device
Abstract
A method for manufacturing an organic electroluminescent display
device in which a patterning of an organic electro-luminescent
layer can be carried out without the use of photolithography or
metal masking. A transparent electrode and a hole transporting
layer are formed on an anode board. Three kinds of layer-stacked
devices each emitting light having one of primary colors of red,
green and blue, composed of a metal strip and an organic
electroluminescent layer covering around the metal strip are then
formed. These layer-stacked devices are mounted on an insulation
board in a manner that the organic electroluminescent layer faces
upward. Then, the anode board and the insulation board are overlaid
each other so that the transparent electrode intersects the
layer-stacked device and that the hole transporting layer and the
organic electro-luminescent layer are opposed to each other.
Inventors: |
Ootsuki, Shigeyoshi; (Tokyo,
JP) ; Yamaguchi, Yoshikazu; (Tokyo, JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NEC CORPORATION
|
Family ID: |
11628464 |
Appl. No.: |
10/055990 |
Filed: |
January 28, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10055990 |
Jan 28, 2002 |
|
|
|
09481875 |
Jan 12, 2000 |
|
|
|
Current U.S.
Class: |
445/24 ;
313/504 |
Current CPC
Class: |
H01L 51/56 20130101;
H01L 51/0008 20130101 |
Class at
Publication: |
445/24 ;
313/504 |
International
Class: |
H05B 033/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 1999 |
JP |
11-006075 |
Claims
What is claimed is:
1. An organic electroluminescent display device comprising: a
plurality of line-like transparent electrodes spreading in a first
direction; an anode board having a hole transporting layer formed
on said transparent electrode; an insulation board disposed
opposite to said anode board; and three kinds of layer-stacked
devices having organic electroluminescent layers each emitting a
different color light, which are disposed between said anode board
and said insulation board; whereby each of said three kinds of
layer-stacked devices is composed of a piece of strip-like metal, a
metal cathode formed on a surface of a piece of said strip-like
metal and organic electroluminescent layers, formed on said metal
cathode, each emitting a red, green or blue color light, wherein
said organic electroluminescent layers are arranged on the side of
said anode board in a second direction in which a longitudinal
direction of said organic electroluminescent layers intersects said
first direction.
2. The organic electroluminescent display device according to claim
1, wherein said layer-stacked device is composed of a piece of
strip-like metal, a metal cathode formed on a piece of said metal
and an organic electroluminescent layer formed on said metal
cathode emitting red, green or blue light.
3. The organic electroluminescent display device according to claim
1, wherein said metal electrode has a low work function.
4. The organic electroluminescent display device according to claim
2, wherein bumps and dips are formed on a surface of a piece of
said metal to cause light to be reflected irregularly.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application is a division of Application No.
09/481,875, filed Jan. 12, 2000, now pending, and based on Japanese
Patent Application No. 11-006075, filed Jan. 13, 1999, by
Shigeyoshi OOTSUKI and Yoshikazu YAMAGUCHI. This application claims
only subject matter disclosed in the parent application and
therefore presents no new matter.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an organic
electro-luminescent display device (hereinafter referred to as an
"organic EL display device") fabricated by using an organic
electroluminescent layer (hereinafter referred to an "organic EL
layer") and to a method for manufacturing the same.
[0004] 2. Description of the Related Art
[0005] An organic electroluminescent device is comprised of an
anode, a cathode and an ultra thin-film organic EL layer composed
of an organic electroluminescent compound disposed between the
anode and the cathode. When a voltage is applied between the anode
and the cathode, a hole and an electron from the anode and the
cathode are injected respectively into the organic EL layer and are
recombined therein. At this point, energy is produced which causes
a molecule of an organic electroluminescent compound constituting
the organic EL layer to be pumped and electroluminescence occurs
while the pumped molecule is deactivated to a ground state. The
organic EL display device is a layer-stacked device utilizing this
electroluminescent phenomenon.
[0006] The organic EL layer has a single layer structure or a
multi-layered structure containing at least one of organic layers
including an organic layer called an organic electroluminescent
layer which emits light when holes and electrons are combined
therein, an organic layer called a hole transporting layer into
which holes are easily injected and in which electrons are hardly
moved, and an organic layer in which electrons are easily injected
and in which holes are hardly moved.
[0007] The thin-film constituting the organic EL device is
ordinarily formed by a vacuum evaporation method and a thickness of
the film is not more than 1 m. There is, however, a problem in
that, if water, acids or alkali solutions are used while these thin
films are formed, since they soak into an interface between organic
EL layers, and also between the organic EL layer and the cathode,
electroluminescent performance and life characteristics of the
organic EL layer are remarkably degraded.
[0008] Therefore, photolithography using a conventionally known
wet-etching technique can not be used for high definition
separating process of the organic EL layer.
[0009] Moreover, a dry-etching technique also cannot be used
because a solvent, developer or release agent used for this
technique may cause damage to the organic EL layer or the cathode
during processes of applying a resist, of development and of
releasing.
[0010] To manufacture a color display device using such organic EL
devices, roughly three kinds of methods are available
conventionally.
[0011] A first method is to use an organic EL device emitting white
light which passes through a color filter having primary colors to
achieve color displaying. The color displaying technology using
such white layer-stacked devices and color filters is disclosed in,
for example, Japanese Laid-open Patent Application No.
Hei8-96959.
[0012] This first method disclosed above is the same in terms of
technological principles as that used widely for transmission type
color liquid crystal displays. Moreover, according to this method
disclosed, a color filter with high definition can be easily
implemented by using photolithography technology and a patterning
of the organic layer is not required if only one kind of the
organic EL device to emit white light is prepared. Therefore, there
is an advantage in that color display devices can be easily
manufactured by this method.
[0013] However, the above first method has a disadvantage in that,
since light having an unwanted wavelength is removed from emitted
white light with a filter, a major portion of the light emitted
from the organic EL device is discarded wastefully, thus making it
difficult to effectively utilize the electro-luminescence of the
organic EL device.
[0014] Furthermore, to put this first method to practical use, it
is necessary to develop white electroluminescent organic materials
having a high electroluminescent efficiency rate and a long life,
however, the actual development of such organic materials is
extremely difficult.
[0015] A second method is to use a color conversion technique
employing a blue electroluminescent organic EL device and color
conversion layers. A color display technique of the organic EL
device using this color conversion method is disclosed in, for
example, Japanese Laid-open Patent Application No. Hei3-152897.
[0016] In this color conversion method disclosed, blue light with a
short wavelength is produced by using the organic EL device and
then green light and red light each having a wavelength longer than
that of the blue light is produced by causing the blue light to
pass through the color conversion layer. If this method is used, it
is not necessary to scale down the organic EL device and the color
conversion layer with high definition can be implemented by using
photolithography, thus enabling easy fabrication of the color
display device with high definition.
[0017] However, this second method also has a disadvantage that it
is very difficult to actually increase the conversion rate of the
color conversion layer and therefore the efficiency rate of
effectively using electroluminescence of the organic EL device is
low.
[0018] Moreover, in this second method, it is also difficult to
obtain flatness of a surface of the color conversion layer when its
patterning is carried out and it is difficult to carry out the
patterning of a flattened layer without breaking the transparent
electrodes.
[0019] To overcome such shortcomings as described above in
implementing color display devices, a method for effectively using
electroluminescence of the organic EL device for displaying is
proposed in which organic EL devices each having one of primary
colors of red, green and blue are formed independently and
arranged.
SUMMARY OF THE INVENTION
[0020] In view of the above, it is an object of the present
invention to provide an organic electroluminescent display device
and a method for manufacturing the same wherein a patterning of the
organic electroluminescent layer can be carried out without a
process of photolithography or metal masking and wherein the
patterning of large area and/or with high definition is made
possible.
[0021] According to a first aspect of the present invention, there
is provided a method for manufacturing an organic
electroluminescent display device comprising:
[0022] a first process of forming a patterned transparent electrode
on an anode board;
[0023] a second process of forming a hole transporting layer on
said transparent electrode;
[0024] a third process of forming three kinds of layer-stacked
devices by sequentially stacking a metal cathode, organic
electroluminescent layers each emitting red, green or blue color
light on a surface of a piece of strip-like metal;
[0025] a fourth process of arranging the above three kinds of
layer-stacked devices with each of the organic electro-luminescent
layers facing upward on an insulation board;
[0026] a fifth process of overlaying the anode board and the
insulation board each other so that the transparent electrode and
the layer-stacked devices intersect each other and that the hole
transporting layer and the organic electroluminescent layer are
opposed to each other; and
[0027] a sixth process of making sealing around the anode board and
the insulation board being overlaid each other.
[0028] In the organic EL display device of this aspect of the
present invention, the patterning of the organic
electro-luminescent layer constituting the layer-stacked device can
be carried out without a process of photolithography or metal
masking, thus allowing an easy production of color organic EL
display devices. Moreover, since the patterning of the organic
electroluminescent layer can be carried out without the use of a
shadow mask such as a metal mask, the patterning of large area
and/or with high definition is made possible.
[0029] In the foregoing, a preferable mode is one wherein the third
process further comprises a step of stacking a metal cathode and an
organic electroluminescent layer emitting red, green or blue light
on a surface of a piece of strip-like metal to form the
layer-stacked device. By forming the layer-stacked device, less
materials become waste compared with cases of using the
photolithography or metal masking, thus reducing production costs.
Moreover, since the organic electroluminescent layer is separately
evaporated for every electroluminescent color, a material for each
electroluminescent color is not mixed during evaporation, thus
avoiding mixing of colors. Also, each of defective layer-stacked
devices can be individually replaced even in the course of
manufacturing, thereby reducing losses caused by defective
layer-stacked devices, increasing yield of products and resulting
in the reduction of production costs. Furthermore, because a metal
strip can be used as a cathode, wiring resistance for the cathode
can be extremely lowered.
[0030] Also, a preferable mode is one that wherein the metal
electrode has a low work function.
[0031] Furthermore, a preferable mode is one that wherein further
comprises a step of forming bumps and dips on the surface of a
piece of the metal to cause light to be reflected irregularly.
[0032] According to a second aspect of the present invention, there
is provided an organic electroluminescent display device
comprising:
[0033] a plurality of line-like transparent electrodes spreading in
a first direction;
[0034] an anode board having a hole transporting layer formed on
said transparent electrode;
[0035] an insulation board disposed opposite to said anode board;
and
[0036] three kinds of layer-stacked devices having organic
electroluminescent layers each emitting a different color light,
which are disposed between the anode board and the insulation
board;
[0037] whereby each of the three kinds of layer-stacked devices is
composed of a piece of strip-like metal, a metal cathode formed on
a surface of a piece of the metal and organic electroluminescent
layers, formed on the metal cathode, each emitting a red, green or
blue color light, wherein the organic electroluminescent layers are
arranged on the side of said anode board in a second direction in
which a longitudinal direction of the organic electroluminescent
layers intersects the first direction.
[0038] In the foregoing, it is preferable that the layer-stacked
device is composed of a piece of strip-like metal, a metal cathode
formed on a piece of the metal and an organic electroluminescent
layer formed on the metal cathode emitting red, green or blue
light.
[0039] Also, a preferable mode is one that wherein the metal
electrode has a low work function.
[0040] Furthermore, it is preferable that bumps and dips are formed
on a surface of a piece of the metal to cause light to be reflected
irregularly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The above and other objects, advantages and features of the
present invention will be more apparent from the following
description taken in conjunction with the accompanying drawings in
which:
[0042] FIG. 1 is a longitudinal sectional view of an organic EL
display device according to a first embodiment of the present
invention;
[0043] FIG. 2 is a flow chart showing a method of manufacturing the
organic EL display device of FIG. 1;
[0044] FIG. 3 is a sectional view illustrating an anode board used
in the organic EL display device of the first embodiment of the
present invention;
[0045] FIG. 4 is a top view of a metal mask for the organic EL
display device of the first embodiment of the present
invention;
[0046] FIG. 5 is a front view including a partially sectional view
illustrating a process of forming a layer-stacked device;
[0047] FIG. 6 is a sectional view of an insulation board used in
the organic EL display device of the first embodiment of the
present invention;
[0048] FIG. 7 is a sectional view illustrating a layer-stacked
device used in an organic EL display device of a second embodiment
of the present invention; and
[0049] FIG. 8 is a sectional view showing the organic EL display
device according to the second embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] Best modes of carrying out the present invention will be
described in further detail using various embodiments with
reference to the accompanying drawings.
[0051] First Embodiment
[0052] FIG. 1 is a longitudinal sectional view of an organic EL
display device according to a first embodiment of the present
invention.
[0053] As shown in FIG. 1, the organic EL display device is
comprised of an anode board 1, two or more line-like transparent
electrodes 2 formed on the anode board 1, a hole transporting layer
3 formed on each of the transparent electrodes 2.
[0054] The line-like transparent electrodes 2 is adapted to spread
in parallel with each other in the right and left direction on a
paper showing FIG. 1. The organic EL display device of this
embodiment is further comprised of an insulation board 10 on which
a layer-stacked device 16 emitting light having one of primary
colors is arranged.
[0055] Each layer-stacked device 16 is composed of a metal strip 11
spreading in a direction vertical to the paper showing FIG. 1, a
metal cathode (not shown) formed around the metal strip 11 and an
organic electroluminescent layer 12 composed of electroluminescent
organic compounds formed on the metal cathode. A metal such as Li
and Mg or the like, having a low work function, may preferably be
used as the metal cathode in this embodiment.
[0056] The metal cathode and organic electroluminescent layer 12
cover the metal strip 11 so that one side of a surface of the metal
strip 11 is exposed. Each of the layer-stacked devices 16 is
attached to each of the insulation boards 10 in a manner that one
side of a surface of the metal strip 11 is in touch with the
insulation board.
[0057] Each of the layer-stacked devices 16 is mounted, by turns,
on the insulation board 10 in the order of colors of red, green and
blue.
[0058] The anode board 1 and the insulation board 10 are stacked
together with an adhesive layer 13 interposed between the two
boards such that the hole transporting layer 3 is in touch with the
organic electroluminescent layer 12.
[0059] In the organic EL display device of this embodiment, the
patterning of the organic electroluminescent layer 12 constituting
the layer-stacked device 16 can be carried out without a process of
photolithography or metal masking, thus allowing an easy production
of color organic EL display devices.
[0060] Moreover, as depicted in FIG. 7, bumps and dips 1 la may be
formed on a surface of the metal strip 11 constituting the
layer-stacked device 16, which function as a light scattering layer
causing light to be reflected irregularly. By providing such bumps
and dips 11 a functioning as the light scattering layer, external
light radiated from the transparent electrode 2 does not reflect
specularly but irregularly on the surface of the metal strip 11. As
a result, external light from an illumination apparatus or sunlight
can be prevented and the image contrast can be improved
accordingly.
[0061] A method of manufacturing the organic EL display device of
this embodiment shown in FIG. 1 is hereafter described. FIG. 2 is a
flow chart showing the method of manufacturing the organic EL
display device of FIG. 1.
[0062] First, as shown in FIG. 3, an ITO (indium tin oxide) film is
formed on the anode board 1 composed of plate glass with a
thickness of 0.3 mm to 1.1 mm using a sputtering method in a manner
that the thickness of the above film becomes about 50 nm to about
300 nm (refer to Step 100 in FIG. 2).
[0063] The plate glass is preferably non-alkali glass adapted to
absorb less water such as 7059 or 1737 glass from Corning Co.,
however, unexpensive low-alkali glass or soda-lime glass may be
employed if sufficiently dried before use.
[0064] The ITO film formed on the glass board 1 is patterned using
a wet-etching method of photolithography so that each of the
patterned films is of a strip shape to allow it to spread in the
longitudinal direction (in the right and left directions in FIG.
3), each being disposed at intervals to form the transparent
electrode 2 (Step 1 10 in FIG. 2).
[0065] A patterned shape of the ITO film can be selected
arbitrarily. For example, according to this embodiment, a width of
each transparent electrode 2 is 330 m and an interval between
transparent electrodes 2 is 30 m.
[0066] The anode board 1 having the patterned transparent electrode
2 is put into a vacuum evaporation system, with the transparent
electrode 2 facing downward. That is, each of the transparent
electrodes 2 is adapted to face an evaporation source. Then,
N,N'-diphenyl-N,N'-bis(-naphthyl)1,1- '-biphenyl-4,4'-diamine
(hereafter referred to as "-NPD" being a hole-transportable organic
compound is weighed and put into a resistance heating board or a
crucible. A heater is built in the resistance heating board or
crucible. Air is exhausted from the vacuum evaporation system using
a vacuum pump so that the pressure therein becomes about
1.times.10.sup.-4Pa.
[0067] Then, as depicted in FIG. 4, a metal mask 14 is put between
the anode board 1 and the evaporation source so that it is fixed to
the anode board 1. Also, in FIG. 4, two or more slits 15 are formed
on the metal mask 14 by quadrangularly cutting an area of the metal
mask 14. Each slit 15 is so positioned that the slit 15 and the
transparent electrode 2 overlap each other when the metal mask 14
is overlaid on the anode board 1.
[0068] After the metal mask 14 is disposed between the anode board
1 and the evaporation source 17, a current is passed through the
heater built in the resistance heating board or the crucible, with
-NPD being put therein, and -NPD is heated and evaporated on the
transparent electrode 2 so that the thickness of the -NPD film
becomes 50 nm.
[0069] Thus, the hole transporting layer 3 is formed by causing
-NPD to be evaporated on the transparent electrode 2 (Step 120 in
FIG. 2).
[0070] Next, a metal strip 11 with a thickness of about 20 m and a
width of about 100 m is fabricated (Step 200 in FIG. 2).
[0071] As shown in FIG. 5, after the metal strip 11 is put into the
vacuum evaporation system, by heating an evaporation material 1 8
contained in the evaporation source 17, the evaporation material is
evaporated on a metal cathode (not shown), the organic
electroluminescent layer and the metal strip 11, resulting in the
formation of the layer-stacked device 16 (Step 210 in FIG. 2).
[0072] The metal strip 11 is fabricated by rolling, for example, a
copper cable with a diameter of about 50 m using a rolling
machine.
[0073] Metal other than copper, if electrically conductive, may be
used as a material for the metal strip 11. It includes iron,
silver, gold, aluminum, chromium, cobalt, tin, nickel, platinum or
an alloy thereof.
[0074] The method of processing metal so as to have a strip shape
is not limited to a rolling method of materials for lines. For
example, it may include a method of cutting a thin-plate, using a
mold and of pulling out molten metal from a fine and long hole.
[0075] The metal cathode is fabricated in such a manner as
described below. First, after aluminum is put into the resistance
heating board or crucible, the evaporation of aluminum on the metal
strip 11 is carried out within the vacuum evaporation system so
that a thickness of the aluminum film becomes 50 nm. Then, lithium
and aluminum separately put into the resistance heating board or
crucible are heated at the same time to be co-evaporated on the
metal cathode so that a thickness of the resulting film becomes 20
nm. Thus, the metal cathode having a structure, in which an
aluminum film is stacked on top of a film composed of a mixture of
lithium and aluminum, is formed. After the metal cathode is formed,
tris(8-quinolinolato) aluminum complex (hereinafter referred to
"Alq3") is weighed and put into the resistance heating board or
crucible. By the same method as described above, Alq3 is heated by
a heater to be evaporated so that a thickness of the Alq3 film
becomes 50 nm.
[0076] Thus, a layer-stacked device for emitting green light 16G,
in which the metal cathode fabricated by co-evaporation of aluminum
and the mixture of aluminum and lithium is stacked on top of the
organic electroluminescent layer emitting green light 12, is formed
on the metal strip 11.
[0077] As an organic compound constituting the organic
electroluminescent layer, Alq3 and
4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-- pyran
(hereafter referred to as "DCM") are employed. Alq3 and DCM are
co-evaporated on a metal cathode of each metal strip 11. Each of
Alq3 and DCM is individually provided from each evaporation source.
The co-evaporation is made in a manner that ALq3 contains 5% by
weight of DCM. The evaporation is continued until a thickness of
the film on the organic electroluminescent layer 12 becomes about
50 nm. Thus, a layer-stacked device for emitting red light 16R is
formed.
[0078] Similarly, perylene is used as an organic compound
constituting an organic electroluminescent layer 12. Perylene is
weighed and put into the resistance heating board or crucible. By
heating it by a heater, perylene is evaporated on a metal cathode
of each metal strip 11 until a thickness of its film becomes about
50 nm. Thus, a layer-stacked device for emitting blue light 16B is
formed as well.
[0079] As shown in FIG. 6, the organic electroluminescent layer 12
constituting the layer-stacked device 16 is mounted on the
insulation board 10. An exposed face of each metal strip 11
constituting the layer-stacked device 16 is adapted to be in touch
with the insulation board 10. Each of the layer-stacked device s
16R, 16G and 16B is arranged on the insulation board 10 in a
predetermined order of colors of red, green, blue, red, green and
blue and so on (Step 220 in FIG. 2).
[0080] An adhesive is applied in advance to the insulation board 10
and each layer-stacked device 16 is adhered to the insulation board
10, with the adhesive disposed therebetween.
[0081] As depicted in FIG. 1, the hole transporting layer 3 is
mounted on each of the layer-stacked device s 16R, 16G and 16B, and
the anode board 1 is then mounted on the insulation board 10, with
the transparent electrode disposed therebetween, in which the
transparent electrode intersects the metal strip 11 (Step 300 in
FIG. 2). That is, according to this embodiment, the transparent
electrodes 2 spread in the right and left directions on the paper
showing FIG. 3 while the metal strips 11 spread in the vertical
direction on the paper showing FIG. 6, resulting in the
intersection of the transparent electrode 2 and the metal strip 11.
Thus, the transparent electrode 2 and the metal strip 11 are formed
in a matrix manner. The anode board 1 is bonded to the insulation
board 10 by the adhesive layer 13. Then, sealing is made around the
anode board 1 and insulation board 10 (Step 310 in FIG. 2).
[0082] Next, operations of the organic EL display device according
to this embodiment are described below. When a voltage is applied
between the metal strip 11 and the transparent electrode 2 so that
the metal cathode is at a relatively negative potential, a hole and
an electron are injected from the transparent electrode 2 and from
the metal strip 11 into the organic electroluminescent layer 12
respectively. The hole and electron are re-combined within the
organic electroluminescent layer 12 and pump molecules constituting
the organic electroluminescent layer 12. When such pumped molecules
are returned to a ground state, electroluminescence occurs.
[0083] Accordingly, by supplying a signal sequentially scanning the
metal cathode to make the same at a negative potential and further
by matching timing of scanning of the metal cathode to that of
scanning of the clearing electrode 2 and by feeding a signal
corresponding to display data, an image corresponding to the
display data can be displayed.
[0084] Also, by setting a period in which a cathode is scanned to
60 hertz, the image is recognized to be a continuous moving image
owing to an afterimage of eyes of a human.
[0085] Furthermore, since the colors of light emitted from
layer-stacked devices 16R, 16G and 16B constitute primary colors, a
full color display can be possible by adjusting the brightness of
each of the above layer-stacked devices. To adjust the brightness,
methods are available including control on a current value flowing
through each of layer-stacked devices 16R, 16G and 16B, pulse width
modulation by which a time width of the display data is changed, or
the like.
[0086] In the method for manufacturing the organic EL display
device described above, the transparent electrode 2 and the hole
transporting layer 3 are formed first on the anode board 1 and then
each layer-stacked device 16 is formed on the insulation board 10,
however, this fabrication order may be changed arbitrarily, i.e.,
each layer-stacked device 16 is firstly formed on the insulation
board 10 and then the transparent electrode 2 and the hole
transporting layer 3 may be formed on the anode board 1.
[0087] As described above, according to the method for
manufacturing the organic EL display device of the present
invention, the patterning of the organic electroluminescent layer
12 can be carried out without using methods such as
photolithography or metal masking, thus allowing easy fabrication
of a color organic EL display device.
[0088] Since the layer-stacked device 16 to be formed by stacking
the metal cathode and organic electroluminescent layer 12 on the
fine and long metal strip 11 is manufactured by vacuum evaporation
for every electroluminescent color, less materials become waste
compared with cases of using photolithography or metal masking,
thus reducing production costs.
[0089] Moreover, since the organic electroluminescent layer 12 is
separately evaporated for every electroluminescent color, a
material for each electroluminescent color is not mixed during
evaporation, thus avoiding mixing of colors.
[0090] Each of defective layer-stacked devices 16 can be
individually replaced even in the course of manufacturing, thereby
reducing losses caused by defective layer-stacked device s,
increasing yield of products and resulting in the reduction in
production costs.
[0091] Furthermore, because a metal strip can be used as a cathode,
wiring resistance for the cathode can be extremely lowered.
[0092] Second Embodiment
[0093] FIG. 7 is a sectional view illustrating a layer-stacked
device used in an organic EL display device of a second embodiment
of the present invention. FIG. 8 is a sectional view showing the
organic EL display device according to the second embodiment of the
present invention.
[0094] As shown in FIG. 7, in the organic EL display device of this
embodiment, a surface facing toward the anode board 1 of the metal
strip 11 is not smooth and bumps and dips 1 la are formed. As
depicted in FIG. 8, external light, while being incident on the
bumps and dips, is reflected irregularly.
[0095] The bumps and dips 11 a on the surface of the metal strip 11
can be formed by in advance providing bumps and dips on the surface
of one roller while the metal strip 11 is being rolled with a
rolling machine.
[0096] The organic EL display device of the second embodiment has
the same configuration as those of the first embodiment except that
the bumps and dips are formed on the surface of the metal strip 11
and can be manufactured in the same manner as in the first
embodiment.
[0097] According to this embodiment, the surface facing toward the
organic electroluminescent layer 12 of the metal strip 11 has a
light scattering property and accordingly external light 19
radiated from the transparent electrode 2 is reflected not
specularly but irregularly. As a result, external light from an
illumination apparatus or sunlight can be prevented and excellent
image contrast can be obtained accordingly.
[0098] As described above, according to the present invention, the
patterning of the organic medium constituting the layer-stacked
device can be carried out without the use of methods such as the
photolithography or metal masking, thus allowing easy fabrication
of a color organic EL display device.
[0099] Also, since the patterning of the organic
electro-luminescent layer can be carried out without the use of a
shadow mask such as a metal mask, the patterning of large area
and/or with high definition is made possible.
[0100] Furthermore, in this method, the patterning is carried out
by putting the shadow mask including the metal mask between the
board and the evaporation source and by causing a substance to be
evaporated to be passed through an opening of the shadow mask and
to be accumulated on the board. Therefore, loss of
electroluminescence is reduced because light produced by the
organic EL device does not pass through a filter or the color
conversion layer, which therefore allows the color display device
using the organic EL device to be implemented at a high conversion
rate.
[0101] However, this method has a big disadvantage that, since the
wet-etching process cannot be used as a method for independently
arranging the organic EL devices emitting light each having one of
primary colors, the patterning has to be carried out by using the
shadow mask including the metal mask, thus making it impossible to
implement the patterning of large area and/or with high
definition.
[0102] It is thus apparent that the present invention is not
limited to the above embodiments but may be changed and modified
without departing from the scope and spirit of the invention.
[0103] Finally, the present application claims the priority of
Japanese Patent Application No. Hei 11-006075 filed on Jan. 13,
1999, which is herein incorporated by reference.
* * * * *