Title: Organic EL display device and method for fabricating the same using shadow mask
Abstract: An organic EL display device and a method for fabricating the same are disclosed, wherein an organic luminescence layer is formed at a crossing region of first and second electrodes using a shadow mask on which a plurality of holes are connected by bridges.
Patent Number: 6,884,139 Issued on 04/26/2005 to Kim
| Inventors:
|
Kim; Chang Nam (Seoul, KR)
|
| Assignee:
|
LG Electronics Inc. (Seoul, KR)
|
| Appl. No.:
|
185012 |
| Filed:
|
July 1, 2002 |
Foreign Application Priority Data
| Jul 03, 2001[KR] | 2001-39542 |
| Current U.S. Class: |
445/24; 445/25; 427/66; 427/468; 427/282 |
| Intern'l Class: |
H01J 009//24 |
| Field of Search: |
427/66,468,504,510,526,259,272,282
445/24,25
428/690
313/503,506,504
|
References Cited [Referenced By]
U.S. Patent Documents
| 5937272 | Aug., 1999 | Tang.
| |
| 6087772 | Jul., 2000 | Ootsuki et al.
| |
| 6501098 | Dec., 2002 | Yamazaki.
| |
| 6592933 | Jul., 2003 | Himeshima et al.
| |
| 6650044 | Nov., 2003 | Lowery.
| |
| 6686215 | Feb., 2004 | Yamada.
| |
| Foreign Patent Documents |
| 0 883 190 | Dec., 1998 | EP.
| |
| 0 955 791 | Nov., 1999 | EP.
| |
| 11-195490 | Jul., 1999 | JP.
| |
| 11-214154 | Aug., 1999 | JP.
| |
| 2000/-299190 | Oct., 2000 | JP.
| |
| 2001/-148291 | May., 2001 | JP.
| |
Primary Examiner: Glick; Edward J.
Assistant Examiner: Keaney; Elizabeth
Attorney, Agent or Firm: Fleshner & Kim, LLP
Claims
1. A method for fabricating a display device comprising:
forming a first electrode pattern on a substrate;
forming at least one organic luminescence layer on the first electrode pattern
at a plurality of pixels that is formed by aligning a mask having a plurality of
holes and a plurality of bridges that connect the holes; and
forming a second electrode pattern on the organic luminescence layer in a perpendicular
direction to the first electrode, wherein the bridges are formed on the same or
different plane as the mask and thicker than the mask.
2. The method of claim 1, wherein the mask is aligned three times so that each
organic luminescence layer of R, G, and B is alternatively arranged in a row direction.
3. The method of claim 1, wherein the substrate includes at least thin film transistors.
Description
This application claims the benefit of the Korean Application No. 2001-0039542
filed on Jul. 3, 2001, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device, and more particularly, to
an organic electroluminescence(EL) display device and a method for fabricating
the same.
2. Discussion of the Related Art
A method of using a shadow mask as shown in FIG. 1 is the most efficient method
to improve the luminescence efficiency among methods of forming R, G, and B pixels
in fabricating a full-color organic EL display device.
FIGS. 1A to 1D are diagrams showing a related art shadow mask and a
full-color organic EL display device according to a pixel array method.
As shown in FIG. 1A, an first electrode 2 is formed on a transparent substrate
1 and barriers 7 are additionally formed on the same to separate
between an insulating film 3 and a second electrode
Also, using a shadow mask 6, a common luminescence layer 5 of
R, G, and B, and each of organic luminescence layers 5-1 to 5-3
of R, G, and B is formed at a corresponding pixel on the insulating film 3.
Then, the second elecrode is formed on the entire surface.
There are three different types(i.e. a strip type as shown in FIG. 1B, a delta
type as shown in FIG. 1C, and an array type as shown in FIG. 1D) in forming an
organic luminescence layer using a shadow mask depending on the array method of
a pixel. In the array type, the size of R pixel is designed to be larger than G
or B pixel to supplement the luminescence efficiency of the R pixel.
The strip type is best among the above three pixel array types in terms of the
aperture ratio and first electrode resistance. In other words, because first electrodes
are formed in the form of strips, the device can be driven with low driving voltage.
On the other hand, in the strip type, the shadow mask 6 should also be
made in a strip form as shown in FIG. 1. In this instance, problems such
as the transformation or droop of the shadow mask 6 are caused in a large
degree because of an external pulling strength. Accordingly, in the process of
deposition, colors spread not only on the intended pixel region but also on other
areas because of shadow effect.
To obviate the above-mentioned problems, as shown in FIG. 2, a shadow mask on
which mask holes are made in turns while having the same pixel array structure
as that of the strip type of FIG. 1B is applied.
FIGS. 2A to 2D are deposition process diagrams of an organic luminescence
layer of a full-color organic EL display device using the related art shadow mask structure.
In this method, however, each organic luminescence layer displaying one of R,
G, and B colors should be formed by carrying out alignment and deposition twice
respectively. That is, to form three layers of R, G, and B, the deposition should
be carried out six times in all after the alignment being carried out six times
as well.
In other words, to form organic luminescence layers of R, G, and B, in case of
using the shadow mask 6 of FIGS. 1B to 1D, the shadow mask is aligned
and deposited three times respectively. In case of using a shadow mask shown in
FIG. 2, however, the shadow mask should be deposited 6 times.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an organic EL display
device and method for fabricating the same that substantially obviates one or more
problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a full-color organic EL display
device and a method for fabricating the same, in which an improved shadow mask
structure is provided to prevent a mask pattern from being transformed, thereby
obtaining high luminescence efficiency.
Another object of the present invention is to provide a full-color organic
EL display device and a method for fabricating the same which has a shadow mask
structure that provides a predetermined number of bridges formed over a long strip-shaped
holes so as to prevent transformation and droop caused by a pulling strength from
occurring, thereby obtaining high aperture ratio and low driving voltage.
Additional advantages, objects, and features of the invention will be
set forth in part in the description which follows and in part will become apparent
to those having ordinary skill in the art upon examination of the following or
may be learned from practice of the invention. The objectives and other advantages
of the invention may be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose
of the invention, as embodied and broadly described herein, a full-color organic
EL display device of the present invention includes organic luminescence layers
of R, G, and B formed in a strip shape at a plurality of pixels, which are defined
by a crossing region of first and second electrodes, on a transparent substrate
using a mask which has a plurality of strip-shaped holes and a plurality of bridges
crossing the holes.
In the preferred embodiment of the present invention, thin metal that act as
bridges
is formed over long strip-shaped holes of a shadow mask so as to prevent the shadow
mask from being transformed or drooped because of the pulling strength. The organic
luminescence layers of R,G,and B are alternately arranged in rows by three times'
alignments of the shadow mask.
It is to be understood that both the foregoing general description and the following
detailed description of the present invention are exemplary and explanatory and
are intended to provide further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding
of the invention and are incorporated in and constitute a part of this application,
illustrate embodiment(s) of the invention and together with the description serve
to explain the principle of the invention. In the drawings:
FIGS. 1A to 1D illustrate diagrams showing full-color organic EL display
devices in accordance with pixel array types and related art shadow masks;
FIGS. 2A to 2D illustrate deposition process diagrams of an organic
luminescence layer of a full-color organic EL display device using a shadow mask
structure of a related art;
FIGS. 3A to 3D illustrate deposition process diagrams of an organic
luminescence layer of a full-color organic EL display device using a shadow mask
structure of the present invention;
FIG. 4 illustrates a plane view of a shadow mask in accordance with the present
invention; and
FIGS. 5A to 5C are detailed diagrams showing a part ‘A’
of the shadow mask of FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the preferred embodiments of the
present invention, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numbers will be used throughout the drawings
to refer to the same or like parts.
FIGS. 3A to
3D illustrate deposition process diagrams of an organic
luminescence layer of a full-color organic EL display device using a shadow mask
structure of the present invention.
Referring to FIG. 3A, a first electrode
20 of a transparent electrode
material is formed on a transparent substrate
10. A supplementary electrode
may be applied to reduce the resistance of the first electrode
20. The substrate
includes at least thin film transistors.
Metals which have relatively lower resistance than the resistance of the first
electrode
20, such as Cr, Al, Cu, W, Au, Ni, and Ag, can be used as the
supplementary electrode.
An insulating film
30 is formed on the first electrode
20. Any
insulators,
regardless of inorganic materials or organic materials, can be used as the insulating
film
30.
A barrier
70 is formed on the insulating film
30 to insulate intervals
of each second electrode(not shown).
As shown in FIG. 4, a shadow mask
60 is used to form each organic luminescence
layer of R, G, and B and a common organic luminescence layer of the same at a plurality
of pixels on the transparent substrate
10. The pixels are defined by a region
crossed by the first and second electrodes.
FIG. 4 is a plane view of the shadow mask
60 in accordance of the present
invention. The shadow mask
60 has a plurality of strip-shaped holes and
a plurality of bridges
60-
1 which connect the holes.
The transformation of the shadow mask
60 is prevented by the bridges
60-
1
which connect the holes.
Referring to FIG. 3A, one bridge
60-
1 for each pixel is formed,
but the bridge
60-
1 is not necessarily formed at every pixel. In
consideration of the transformation of the shadow mask
60, the bridge may
be formed between every two or three pixels.
Preferably, the bridge
60-
1 has its width ‘a’
and thickness ‘b’ in the range of 1˜1000 μm.
FIGS. 5A to
5C illustrate a detailed view of the part ‘A’
of the shadow mask of FIG.
4. The bridge
60-
1 can be formed
either on the same plane and at the same thickness as the shadow mask
60
as shown in FIG. 5A, or on a different plane and at a different thickness from
the shadow mask
60 as shown in FIG.
5B. Alternatively, the bridge
60-
1 can also be formed on the same or different plane as or from
the shadow mask at a different thickness from the shadow mask
60 as shown
in FIG.
5C.
A common luminescence layer of R, G, and B (not shown) is deposited on the transparent
substrate
10 at a time using a blank mask which can deposit all the entire
luminescence region.
Subsequently, each organic luminescence layer of R, G, and B is alternately
arranged in rows at the pixel by three times aligning the shadow mask
60.
The common luminescence layer of R, G, and B may also be formed at each pixel
of R, G, and B using the shadow mask
60, not being deposited on the entire
luminescence region.
Subsequently, the second electrode (not shown) is formed by forming
a second electrode (Mg—Ag alloy, or Al, or other conductive materials) using
the blank shadow mask.
Then, passivation layers (oxygen adsorption layer, moisture adsorption layer,
and moisture-proof layer) are formed on the second electrode and encapsulation
is carried out.
The full-color organic EL display device in accordance with the present invention
has the following advantages.
By forming mask holes in the form of a bridge, the transformation and droop of
the shadow mask caused by the pulling strength is prevented. Thus, efficiency of
the full-color organic EL display device is maximized.
It will be apparent to those skilled in the art that various modifications and
variations can be made in the present invention. Thus, it is intended that the
present invention covers the modifications and variations of this invention provided
they come within the scope of the appended claims and their equivalents.
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