Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-11-30
2001-04-24
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S306600
Reexamination Certificate
active
06221194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of an electroluminescent display panel in which a plate or another electroluminescent substrate is laminated over an electroluminescent substrate.
2. Description of Related Art
An electroluminescent (hereinafter referred to as EL) display panel in which two EL substrates are laminated has been known hitherto. One EL substrate emits light of a certain color, and the other EL substrate emits light of a different color, thereby providing a multi-color or full color display when the two substrates are combined as a single unit. One example of the EL display panel of this kind is disclosed in JP-A-64-60993. Two EL substrates, each comprising a pair of electrode layers and a luminescent layer interposed between the pair of electrodes layers, are laminated over each other with a space therebetween. The periphery of the laminated EL substrates is sealed by epoxy resin or a film carrying a connector wiring thereon, thereby forming a single display panel having a space between the two EL substrates which is sealed at its periphery. The peripherally-sealed spacing, (also, termed “closed space” in some references) is brought under vacuum and filled with insulation oil such as silicone oil to protect an active area (an area from which light is emitted) of the EL panel from moisture. To fill the peripherally-sealed spacing with insulation oil, the spacing has to be brought under vacuum, and then the insulation oil has to be introduced. This requires additional manufacturing steps, and moreover there is a possibility that the insulation oil will leak out of the spacing under an extreme environment.
Also, in a single EL display panel which has only one EL substrate and is covered by a cover plate such as a glass plate, a space between the EL substrate and the cover plate has to be filled with insulation oil in the same manner as in the EL panel having two EL substrates. Therefore, the same aforementioned problems are unavoidable.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned problem. An object of the present invention is to provide an effective and efficient method of bonding two EL substrates or bonding an EL substrate and a cover plate. Another object of the present invention is to provide a method of forming a sealing structure to protect the active area of the EL display panel from moisture.
According to the present invention, a first EL substrate having an electroluminescent layer sandwiched between a pair of electrodes and a second EL substrate having the same structure as the first EL substrate are laminated so that both luminescent layers face each other. Both EL substrates are bonded together with an adhesive layer interposed therebetween under pressure and heat. An insulation film made of resin such as epoxy resin is placed between both EL substrates and is deformed into the adhesive layer under pressure and heat. The adhesive layer serves not only to firmly bond both substrates but also to prevent moisture or water from permeating into the bonded EL display panel. The EL display panel having two EL substrates can be manufactured in a simple and inexpensive manufacturing process.
Preferably, two EL substrates, each emitting different color of light are bonded so that a multi-color display is realized. For example, an EL substrate emitting green light is used as the first substrate and an EL substrate emitting orange light is used as the second substrate. A simple cover plate such as a glass plate having no EL elements may be used in place of the second EL substrate. The adhesive layer can serve as a humidity-protection layer as long as it covers at least an active area of the EL display panel, but it is preferable that the humidity-protection layer covers the entire surface of the EL substrates containing the adhesive layer.
A pair of the electrodes of each EL substrate are connected to outside driving circuits through connector sheets having wiring printed thereon. The connector sheets are attached to the insulation film before the insulation film is deformed into the adhesive layer under pressure and heat, and the electrodes are electrically connected to the connector sheets at the same time both EL substrates are bonded by the adhesive layer. The bonding process may be carried out in the following order. The insulation film to which the connector sheets for the first EL substrate are attached is bonded to the first EL substrate. Then, the connector sheets for the second EL substrate are attached to the insulation film, and the second EL substrate is bonded to the first EL substrate with the adhesive layer deformed from the insulation film interposed therebetween. Alternatively, connector sheets for both EL substrates are first attached to the insulation film, and then both EL substrates are bonded with the insulation film interposed therebetween.
The surface of both EL substrates may be covered by resin to be hardened by ultraviolet radiation before the surface is covered by the insulation film, so that the surface is flattened to prevent the enclosure of bubbles between the surface and the adhesive layer. The resin is hardened by radiating ultraviolet light at the same time the insulation film forms the adhesive layer under pressure and heat. Additional use of the resin to be hardened by ultraviolet radiation further improves humidity-protection ability of the EL display panel. As the insulation film, a resin film having tackiness, preferably, an epoxy resin film is used.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.
REFERENCES:
patent: 4767679 (1988-08-01), Kawachi
patent: 4954746 (1990-09-01), Taniguchi et al.
patent: 5194027 (1993-03-01), Kruskopf et al.
patent: 5883465 (1999-03-01), Inoguchi et al.
Goto Shoichi
Inoguchi Kazuhiro
Watanabe Yusuke
Ball Michael W.
Denso Corporation
Haran John T.
Pillsbury & Winthrop LLP
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