Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
1998-10-15
2001-07-10
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S504000, C313S506000, C313S493000
Reexamination Certificate
active
06259204
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an organic EL (electroluminescent) device using an organic compound, and more specifically to an improvement in or relating to a sealing sheet used therewith
In recent years, organic EL devices have been under intensive investigation. One such device is basically built up of a thin film form of hole transporting material such as triphenyldiamine (TPD) deposited by evaporation on a hole injecting electrode, a light emitting layer of fluorescent material such as an aluminum quinolinol complex (Alq
3
) laminated thereon, and a metal (electron injecting) electrode of a metal having a low work function such as Mg and formed on the light emitting layer. This organic EL device now attracts attentions because a very high luminance ranging from several hundreds to tens of thousands cd/m
2
can be achieved with a voltage of approximately 10 V.
A grave problem with an organic EL device is that it is acutely sensitive to moisture. Exposure of the organic EL device to moisture, for instance, causes a light emitting layer to peel off electrode layers, or materials forming part thereof to degenerate. This results in another problem that non-light emission spots called dark spots occur or any consistent light emission cannot be kept.
One approach known to solve this problem is to fix an airtight case, a sealing layer or the like closely on a substrate to cover an organic EL multilayer structure, thereby shielding it from the outside, as typically disclosed in JP-A's 5-36475, 5-89959 and 7-169567.
However, the provision of such a sealing layer in a box form is not suitable for the mass production of organic EL devices because of a production cost increase. For such a sealing layer, inexpensive glasses are usually employed. When a glass sheet is used with no modification thereto, however, it is likely to come into contact with, or abutment on, an organic EL multilayer structure (as seen in FIG.
3
), resulting in a breakdown of the organic EL structure. In an effort, a spacer or the like is used to bond a glass sealing sheet to an organic EL structure while the glass sealing sheet is kept at a height higher than the organic EL structure. Even when the portion of the glass sealing sheet bonded to the organic EL structure is kept at the required height, however, it is likely that the undulations of the glass sealing sheet and a substrate with an organic EL device stacked thereon cause the glass sealing sheet to come into contact with, or abutment on, an organic EL device structure, resulting in a breakdown of the organic EL structure or the occurrence of dark spots. When the sealing sheet is kept at a height higher than required, on the other hand, a problem arises in conjunction with airtightness, and no suitable spacer is available.
SUMMARY OF THE INVENTION
An object of the invention is to provide an organic EL device comprising a sealing sheet that can be produced at low costs yet with high productivity, and can be located in neither contact with nor abutment on an organic EL structure while there is a proper clearance between them.
As a result of studies of the contact or abutment of such a glass sealing sheet with or on an organic EL structure, the inventors have found that such contact or abutment is ascribable to the irregularities or undulations of the glass sheet. The inventors have also found that the more inexpensive the glass, the more noticeable the irregularities or undulations of the glass become, and that if a glass sealing sheet is located at a height larger than the size of an irregularity or undulation thereof, the contact or abutment of the glass sealing sheet with or on an organic EL structure can then be provided with a necessary minimum height.
The aforesaid object is achieved by the inventions defined below as (1) to (8).
(1) An organic EL device, which comprises a substrate, an organic EL structure provided on the substrate, and a sealing sheet located at a position above said substrate, where said sealing sheet is in no contact with said organic EL structure, and in which a height from a surface of said substrate, on which a film form of organic EL device structure is formed, to a junction of said sealing sheet with said substrate has a value larger than a value obtained by adding a size of an irregularity or undulation of said sealing plate to a height of said organic EL structure.
(2) The organic EL device according to (1), wherein said sealing sheet is an unground flat sheet.
(3) The organic EL device according to (1) or (2), wherein the size of said irregularity or undulation of said sealing sheet is within 60 &mgr;m.
(4) The organic EL device according to any one of (1) to (3), wherein the height from the surface of said substrate, on which said film form of organic EL structure is formed, to the junction of said sealing sheet with said substrate is up to 120 &mgr;m.
(5) The organic EL device according to any one of (1) to (4), wherein a spacer is interleaved between the surface of said substrate on which said film form of organic EL structure is formed and the junction of said sealing sheet with said substrate.
(6) The organic EL device according to any one of (1) to (5), wherein a recess is provided in a lower side of said sealing sheet and in at least an area of said sealing sheet that opposes to said organic EL structure, so that the height from the surface of said substrate, on which said film form of organic EL structure is formed, to the junction of said sealing sheet with said substrate is adjusted by a depth of said recess.
(7) The organic EL device according to (6), wherein the recess in said sealing sheet is formed by sandblasting or cutting.
(8) The organic EL device according to (6) or (7), wherein said sealing sheet is bonded to said substrate using an adhesive agent having a spacer of 3 to 10 &mgr;m.
REFERENCES:
patent: 5821692 (1998-10-01), Rogers et al.
patent: 5874804 (1999-02-01), Rogers
patent: 5909081 (1999-06-01), Eida et al.
patent: 6049167 (2000-04-01), Onitsuka et al.
patent: 6111357 (2000-08-01), Fleming et al.
patent: 0 776 147 (1997-05-01), None
patent: 0 859 539 (1998-08-01), None
patent: 56-30287 (1981-03-01), None
patent: 60-81797 (1985-05-01), None
patent: 4-212284 (1992-08-01), None
patent: 8-302340 (1996-11-01), None
patent: 9-274990 (1997-10-01), None
patent: 10-3988 (1998-01-01), None
patent: 10-41067 (1998-02-01), None
patent: 10-106746 (1998-04-01), None
Ebisawa Akira
Endo Hiroyuki
Onitsuka Osamu
Someya Taku
Yasukawa Kouji
Guharay Karabi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Ashok
TDK Corporation
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