Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2002-03-18
2004-11-09
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S506000, C313S504000
Reexamination Certificate
active
06815887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic electroluminescent (EL) display device, and more particularly, to an organic electroluminescent display device having improved structures of electrodes and an encapsulation layer and an external light reflection prevention structure.
2. Description of the Related Art
Recently, much attention has been paid to electroluminescent display devices because they have advantageous features suitable for next generation display devices, such as a wide viewing angle, a high contrast ratio and a high response speed. Electroluminescent display devices are classified into inorganic electroluminescent display devices and organic electroluminescent display devices according to materials to form emitter layers.
At the beginning of the development of inorganic electroluminescent display devices, they were put into commercial use as green-emitting display devices. However, inorganic electroluminescent display devices, like plasma display devices, are driven under an AC bias condition and require drive of several hundreds of volts. Also, since light-emitting materials for the inorganic electroluminescent display devices are inorganic matter, it is difficult to control light emission wavelength characteristics through molecular design, so that full-color display of a picture is not easily achieved.
On the other hand, organic electroluminescent display devices are spontaneous emission display devices that emit light by electrically exciting fluorescent organic compounds. Thus, it is expected that organic electroluminescent display devices can be applied to next generation display devices that can overcome shortcomings of liquid crystal display devices, with characteristics including low driving voltage, enabling the production of thin, small display panels, wide viewing angle, high response speed and so on. Organic electroluminescent display devices using a layered structure have been developed by Eastman Kodak Company and have been commercialized as green-emitting display devices having improved lifetime by Pioneer Electronic Corporation.
Recently, many kinds of new materials having various molecular structures that are advantageous in organic materials, and organic electroluminescent display devices (to be abbreviated as organic EL devices, hereinafter) as color display devices having excellent characteristics including lower DC drive voltage, small and thin structure, spontaneous emission and so on, have been the subjects of active research.
An example of an organic EL device is disclosed in Japanese Patent Publication No. Hei 10-335060 and is shown in FIG.
1
.
Referring to
FIG. 1
, an organic EL device
10
is configured such that an organic layered structure
11
is disposed between an anode
12
and a cathode
13
, and the cathode
13
is protected by an encapsulation layer
14
containing aluminum and at least one material having a work function greater than that of aluminum.
In the conventional organic EL device having the above-described configuration, external light is reflected by the cathode
13
and the encapsulation layer
14
, degrading readability of an image. In particular, in an outdoor environment in which the organic EL device is exposed to sunlight, relative luminance and contrast are sharply degraded by external light reflected by the cathode
13
.
U.S. Pat. No. 5,059,861 discloses an organic EL device having a cathode formed of various kinds of metals, excluding alkaline metals.
U.S. Pat. No. 5,047,687 discloses an organic EL device having a cathode formed of various kinds of metals including at least one metal having a low work function, excluding alkaline metals. Here, the metals include aluminum, vanadium and cobalt.
Japanese Patent Publication No. Hei 9-274990 discloses an organic EL device having an encapsulation layer that encapsulates an anode, an organic layered structure and a cathode, the encapsulation layer having at least one dehydrating agent selected from the group consisting of silica gel, zeolite, calcium chloride, activated carbon, nylon and polyvinyl alcohol.
U.S. Pat. No. 5,073,446, Japanese Patent Publication Nos. Hei 5-36475, Hei 8-222368 and Hei 7-161474 disclose organic EL devices having an anode, an organic layered structure, a cathode, an encapsulation layer to protect the cathode, and a sealing layer.
Most conventional EL devices use a polarizing film on the surface of a substrate in order to prevent reduction in the luminance of an image due to reflection of external light by electrodes and an organic layered structure. However, the use of a polarizing film results in shielding of some light generated from the organic layered structure, causing a substantial decrease in luminance.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an organic EL device which can enhance the contrast and luminance of an image and can remove the necessity of using a polarizing film to reduce the reflection of external light.
The foregoing and other objects of the present invention are achieved by providing an organic EL device comprising: a transparent substrate; a first electrode unit formed on the transparent substrate in a predetermined pattern and made of a transparent conductive material; an organic EL unit including organic layers having a predetermined pattern, stacked on the first electrode unit; a second electrode unit corresponding to the first electrode unit, formed on the organic EL unit in a predetermined pattern; and an encapsulation layer to encapsulate the first electrode unit, the organic EL unit and the second electrode unit to protect the same, the encapsulation layer consisting of a first component and a second component made of one or more metals selected from the group consisting of iron (Fe), cobalt (Co), vanadium (V), titanium (Ti), aluminium (Al), silver (Ag) and platinum (Pt).
In an embodiment of the present invention, the first component of the organic EL device is at least one transparent material selected from the group consisting of SiO
x
(x>1), SiN
x
(x>1), MgF
2
, CaF
2
, Al
2
O
3
, In
2
O
3
, and ITO (Indium Tin Oxide), and the encapsulation layer has a gradual component concentration gradient is distributed such that the light absorption efficiency of the encapsulation layer gradually increases along the thickness direction of the encapsulation layer as the distance of the encapsulation layer from the surface upon which external light is incident increases.
The foregoing and other objects of the present invention may also be achieved by providing an organic EL device comprising: a transparent substrate; a first electrode unit formed on the transparent substrate in a predetermined pattern and made of a transparent conductive material; an organic EL unit including organic layers having a predetermined pattern stacked on the first electrode unit; a second electrode unit formed on the organic EL unit consisting of a first component and a second component made of one or more metals selected from the group consisting of iron (Fe), cobalt (Co), vanadium (V), titanium (Ti), aluminium (Al), silver (Ag) and platinum (Pt); and an encapsulation layer to encapsulate the first electrode unit, the organic EL unit and the second electrode unit.
The foregoing and other objects of the present invention may also be achieved by providing an organic EL device comprising: a transparent substrate; an external light absorbing layer formed on the transparent substrate to absorb external light, a second electrode unit formed on the external light absorbing layer, an organic EL unit formed of organic layers having a predetermined pattern and stacked on the second electrode unit, and a first electrode unit formed on the organic EL unit in a predetermined pattern.
In an embodiment of the present invention, the external light absorbing layer includes a first component made of at least one transparent material selected from the group consisting of SiO
x
(x>1), SiN
x
(x>1), MgF
2
, CaF
2
, Al
2
O
3
, In
2
O
3
, an
Lee Joon-bae
Park Chang-won
Park Jin-woo
Shin Dong-chan
Dong Dalei
Patel Ashok
Samsung SDI & Co., Ltd.
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