Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2000-09-07
2004-12-21
Williams, Joseph (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S512000
Reexamination Certificate
active
06833668
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display comprising an electroluminescence (hereinafter referred to as “EL”) element disposed on a substrate, and particularly to a sealing structure for an organic EL display device including an organic EL layer.
2. Description of the Related Art
A display device using organic EL comprises a self-emissive element which itself generates light when an electric current is made to flow through the element. Such a display device consumes less power compared to a CRT, and does not have the problem concerning viewing angle as in an LCD. Organic EL display devices are therefore regarded as devices that may replace both CRTs and LCDs.
FIG. 1A
is a plan view of a conventional organic EL display device, and
FIG. 1B
shows a cross-sectional view taken along line A—A′ of
FIG. 1A. A
plurality of selective drive circuits
2
are disposed for respective pixels on a transparent substrate
1
. Each selective drive circuit
2
is connected with a pixel electrode
4
. An organic EL layer
5
including an organic emissive material, and a counter electrode
6
are disposed covering the pixel electrodes
4
. Surrounding the pixel region constituted by the selective drive circuits
2
, pixel electrodes
4
, organic EL layer
5
, and counter electrode
6
, display driver circuits
7
a
,
7
b
are arranged for controlling the selective drive circuits
2
and applying predetermined voltages to the pixel electrodes
4
. The driver circuits
7
are connected to terminals
9
by wiring
8
. A cap
10
composed of a metal such as aluminum is arranged covering these structures, and is adhered to the transparent substrate
1
using a seal
51
. The space
12
between the cap
10
and the transparent substrate
1
is filled with dry nitrogen gas. A desiccant sheet
13
is disposed on the inner surface of the cap
10
.
A selective drive circuit
2
may comprise, for example, a plurality of semiconductor elements including thin film transistors (TFT). A first TFT switches between “on” (conductive state) and “off” (non-conductive state) in response to the output from the driver circuit
7
a
. When the first TFT of a selective drive circuit
2
is turned on by an output from the driver circuit
7
a
, the corresponding pixel electrode
4
is applied with a voltage according to an output from the driver circuit
7
b
via a second TFT. An electric current thereby flows between the pixel electrode
4
and the counter electrode
6
. The emissive layer
5
is the portion which emits light when a current is made to flow therein by the pixel electrode
4
and the counter electrode
6
. The emissive layer
5
emits light at an intensity according to the amount of current flowing between the pixel electrode
4
and the counter electrode
6
. The generated light transmits downward in the cross-sectional view through the transparent substrate
1
to be observed.
More specifically, holes injected from the anode and electrons injected from the cathode recombine within the organic EL layer
5
. As a result, organic molecules containing the organic EL layer
5
are excited, generating excitons. Through the process in which these excitons undergo radiation until deactivation, light is emitted from organic EL layer
5
. This light radiates outward through the side of the transparent anode via the transparent insulator substrate
1
, resulting in light emission.
The TFTs and organic EL layer
5
formed through lamination must be shielded from the external atmosphere. A cap
10
made of a metal such as aluminum is therefore adhered to the periphery of the insulating substrate
1
by a seal
51
composed of a sealing material such as epoxy. This arrangement is provided mainly for preventing deterioration of display quality when, for example, a defect such as a pinhole is present in the counter electrode
6
. In such a case, moisture entering from the pinhole may cause oxidation of the counter electrode
6
or a separation between the organic EL layer
5
and the counter electrode
6
, producing dark spots and resulting in degradation of display quality. In this light, the cap
10
not only protects the display region and the driver circuits
7
from physical shock, but also serves to prevent moisture from entering the device. The cap
10
is therefore formed in a shape of a tray covering the display region. Further, to prevent damage by penetrating moisture, the space
12
inside the cap
10
is filled with an inert gas such as dry nitrogen or helium, and the desiccant sheet
13
is disposed. A stepped portion may be provided in the location for arranging the desiccant sheet
13
. The structure as described above is disclosed, for example, in Japanese Patent Laid-Open Publication No. Hei 9-148066.
However, in a conventional sealing structure, moisture may still be present inside the device. For example, moisture may be present in the nitrogen gas filled in the space
12
. Moreover, as the desiccant sheet
13
is arranged on the cap
10
, it is possible that moisture may adhere to the organic EL layer without being adsorbed by the desiccant sheet
13
.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an element sealing structure for reliably preventing penetration of moisture into areas around self-emissive elements without increasing the device thickness.
Another object of the present invention is to enhance the aperture ratio of each pixel while realizing a reliable sealing structure.
A further object of the present invention is to simplify the device manufacturing process while realizing a reliable sealing structure.
The present invention for achieving the above objects provides a display device in which a display region having a self-emissive element is formed between a pair of substrates, wherein a resin having a desiccant mixed therein is disposed between the pair of substrates.
Another aspect of the display device of the present invention is that the pair of substrates are adhered to one another by a sealing material disposed surrounding at least the display region, so as to seal the display region including the self-emissive element.
A further aspect of the display device of the present invention is that the self-emissive element is an electroluminescence element, and especially an organic electroluminescence element.
According to the display device of the present invention as described above, a resin having a desiccant mixed therein is disposed between a pair of substrates. Moisture penetrating inside the display device can be adsorbed by the desiccant, thereby preventing deterioration of the display region by the moisture.
Furthermore, the pair of substrates are adhered to one another by a seal formed surrounding the display region, and a desiccant is mixed in the seal. The amount of moisture permeating through the substrates is negligible. The moisture permeating through the seal is adsorbed by the desiccant. Accordingly, almost no moisture penetrates inside the display device, and deterioration of the display region by moisture can effectively be prevented.
In another aspect of the display device of the present invention, the display region having the self-emissive element is formed on the first substrate among the pair of substrates, the second substrate is arranged facing the display region side of the first substrate and adhered to the first substrate, a color component is provided in the gap between the second substrate and the display region, and the second substrate is a transparent substrate which transmits at least visible light.
As described above, a color component is provided between the display region and the second substrate facing the first substrate having the display region formed thereon. Further, the second substrate is a transparent substrate which transmits visible light. According to this arrangement, the aperture ratio of the display pixels can be enhanced, and increased freedom is available in selecting the size and the driving capability of a TFT when using a TFT for driving
Komiya Naoaki
Yamada Tsutomu
Cantor & Colburn LLP
Williams Joseph
LandOfFree
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