Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2002-11-07
2004-11-30
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S504000
Reexamination Certificate
active
06825612
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting diode (OLED) that can prevent a sealing material from overflowing and affecting normal operation of the OLED.
2. Description of the Prior Art
In various types of flat panel displays, since an OLED has many beneficial characteristics, such as having a spontaneous light source, a wide viewing angle, high response velocity, full-color, simpler structure, and a wide operating temperature, and saving power, the OLED has been used extensively in small and medium scale portable display fields.
Please refer to
FIG. 1
, which is a cross-sectional view of a conventional OLED
10
. As shown in
FIG. 1
, the conventional OLED
10
mainly includes a transparent glass substrate
12
, a transparent conductive layer
14
positioned on the glass substrate
10
, an organic layer
16
positioned on a predetermined region of the transparent conductive layer
14
, and a metal layer
18
positioned on the organic layer
16
. The transparent conductive layer
14
is used as an anode of the OLED
10
, and the metal layer
18
is used as a cathode of the OLED
10
.
In addition, the organic layer
16
further includes a hole transport layer (HTL)
20
, an emitting layer (EML)
22
, and an electron transport layer (ETL)
24
Positioned on the transparent conductive layer
14
, respectively. Furthermore, a hole injection layer (HIL, not show in
FIG. 1
) can be positioned between the transparent conductive layer
14
and the HTL
20
, and an electron injection layer (EIL, not shown in
FIG. 1
) can be formed between the metal layer
18
and the ETL
24
, for improving an adhesion problem of the transparent conductive layer
14
, the organic layer
16
, and the metal layer
18
, and benefiting electrons and holes being injected into the organic layer
16
. Moreover, another emitting layer (not shown in
FIG. 1
) that has an ability of transporting the electrons, or another HTL (not shown in
FIG. 1
) that has an ability of irradiating light, can be chosen to simply structure of the OLED. Typically, the transparent conductive layer
14
is composed of indium tin oxide (ITO) or indium zinc oxide (IZO). The organic layer
16
is formed by utilizing a thermal evaporation process, the HTL
20
is composed of diamine chemical Compound, and the metal layer
18
is composed of magnesium (Mg), aluminum (Al), lithium (Li) or an alloy of Mg, Al, and Li.
When a direct current (DC) voltage is applied to the OLED
10
, the electrons penetrate through the ETL
24
from the metal layer
18
(the cathode of the OLED
10
), and the holes penetrate through the HTL
20
from the transparent conductive layer
14
(the anode of the OLED
10
), and then the electrons and the holes are both injected into the emitting layer
22
. Further, the electrons and the holes move and re-combine together to form an electron/hole pair in the emitting layer
22
, and organic light emitting molecules of the emitting layer
22
are excited to an excitation state due to a potential difference caused by an external electric field. When the molecules discharge energy and return to a base sate, a fixed ratio of the discharging energy (i.e. the quantum efficiency, QE) is liberated in photon. Thereafter, the photon permeates the glass substrate
12
and illuminates downward. This is caused by electroluminescence of the OLED
10
.
However, the organic layer
16
and the metal layer
18
of the OLED
10
are very sensitive to moisture and oxygen gas. As soon as the organic layer
16
and the metal layer
18
are in touch with moisture and oxygen gas, the organic layer
16
could peel off the transparent conductive layer
14
and the metal layer
18
, the metal layer
18
could be oxidized, and dark spots could be generated in the OLED, reducing display quality, lowering glow of the OLED, and decreasing life of the OLED. Therefore, a passivation and encapsulation material of the OLED must have characteristics of perfect anti-abrasiveness, high thermal conductivity, and lower moisture permeability, to prevent the organic layer from contacting with the outside environment efficiently, and to increase the life of the OLED.
Please refer to
FIG. 1
again, an encapsulation process of the conventional OLED
10
utilizes a sealing material
26
, such as a binder composed of high polymer glue materials, to bind a container
28
made of glass or metal on the glass substrate
12
. Then, dry nitrogen gas is injected into a hollow part between the container
28
and the glass substrate
12
to accomplish the encapsulation process of the OLED
10
. In addition, a desiccating agent (not shown in
FIG. 1
) can be positioned in the OLED
10
for adsorbing moisture that permeates from outside into the OLED
10
caused by imperfect encapsulation of the OLED
10
, and preventing the organic layer
16
of the OLED
10
from moistening.
The conventional container
28
provides good isolation with the OLED
10
, moisture and oxygen gas. However, quantity of the sealing material
26
has to be properly measured during a lamination process of the encapsulation process. If an excess of the sealing material
26
is used for a better airtightness of the OLED
10
, the sealing material
26
could overflow into an inside of the OLED, due to improper distribution of the sealing material or unbalanced pressure during the lamination process. Therefore, the excess sealing materials are in touch with the organic layer
16
and affect the normal operation of the OLED
10
. Consequently, the conventional encapsulation process of the OLED always decreases the quality of the sealing material to prevent the above-mentioned problem. On the other hand, if an insufficient amount of sealing material
26
is used to bind the glass substrate
12
and the container
28
, the container
28
would not be sealed up with the glass substrate
12
closely, moisture and oxygen gas easily permeate the OLED
10
, and the container
28
is easily peeled off the glass substrate
12
. In addition, in order to increase the adhesion of the container
28
and the glass substrate
12
, a surface of the conventional container
28
that correspond to the glass substrate
12
can be sandblasted or etched to be a rough surface for raising adhesive area of the container
28
and the glass substrate
12
. However, illumination quality of the OLED is affected, and the container
28
with a rough surface cannot be applied in a top emission OLED (TOLED) display.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide an organic light emitting device to avoid the above-mentioned problems.
According to the preferred embodiment of the claimed invention, an organic light emitting diode (OLED) is introduced. The OLED comprises a bottom substrate including a bottom electrode positioned on an upper surface of the bottom substrate, an organic layer positioned on a predetermined region of the bottom electrode, a top electrode positioned on the organic layer, and a spot glue region positioned on the bottom substrate and outside the predetermined region of the bottom electrode, a top substrate positioned parallel with the bottom substrate, and a lower surface of the top substrate having at least one first ditch formed within the top substrate, and a sealing material positioned on the spot glue region of the bottom substrate for binding the top substrate and the bottom substrate together. The first ditch is used to prevent the sealing material from overflowing into the predetermined region of the bottom substrate and affecting normal operation of the OLED.
Since the OLED of the claimed invention has the ditches positioned within the top substrate of the OLED, an excess sealing material can flow into the ditches if an excess of the sealing material is utilized to bind the top substrate and the bottom substrate together. Therefore, the excess sealing material does not contact with the organic layer of the OLED and affect the normal
AU Optronics Corp.
Guharay Karabi
Hsu Winston
Patel Nimeshkumar D.
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