Organic thin film EL device and method for making the same

Stock material or miscellaneous articles – Composite – Of inorganic material

Reexamination Certificate

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C428S068000, C428S076000, C428S917000, C427S516000, C427S066000, C156S275500, C313S506000, C313S504000, C313S512000, C257S100000

Reexamination Certificate

active

06210815

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an organic thin film EL(electroluminescence) device and a method for making the same.
BACKGROUND OF THE INVENTION
Japanese patent application laid-open No. 2-73229 (1990) discloses a structure of liquid-crystal display panel where thermosetting sealing agent is used in side and ultraviolet-activated sealing agent is used outside.
The glass transfer temperature of organic materials used for organic thin film EL device is around 100° C., and it is generally necessary to apply a temperature of higher than 100° C. for several hours to harden thermosetting adhesives. Therefore, it may cause the deterioration in luminous characteristic.
Also, in organic thin film EL device, when bonding a glass substrate and a sealing cap using an ultraviolet-activated adhesive, hardening the adhesive, and then thermo-compression bonding a flexible print-circuit board, there may occur peeling between the hardened adhesive and the glass substrate due to a difference in thermal expansion coefficient between the hardened adhesive and the glass substrate. For example, when applying a temperature of higher than 200° C. at a distance of less than about 5 mm from the hardened adhesive, peeling is likely to occur between the hardened adhesive and the glass substrate.
When the distance between the flexible print-circuit and the ultraviolet-activated adhesive is widened to solve the above problem, there occurs the problem that the display area is reduced.
Japanese patent application laid-open No.62-231927 (1987) discloses a method that, in liquid-crystal display panel, temporary bonding is conducted by irradiating ultraviolet rays on part of sealing material, then hardening all parts thereof.
Also in organic thin film EL device, a method that part of the same adhesive is hardened, thermo-compression bonding the flexible print-circuit board, then hardening all parts of the adhesive as disclosed in Japanese patent application laid-open No.62-231927 can be imagined.
However, when unalteredly applying the technique disclosed in Japanese patent application laid-open No.62-231927 to the organic thin film EL device, different stresses, which are caused by the contraction of adhesive due to its hardening, are applied to first and second adhering parts. Therefore, the adhesive power is more reduced than the case that all part of adhesive is hardened at once.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an organic thin film EL device where the stress applied to adhering part is absorbed not to reduce the adhesive power.
It is a further object of the invention to provide a method for making an organic thin film EL device where the stress applied to adhering part is absorbed not to reduce the adhesive power.
According to the invention, an organic thin film EL device, comprises:
a transparent insulative substrate and a sealing cap which are bonded together by an ultraviolet-activated adhesive;
wherein the ultraviolet-activated adhesive is composed of a combination of adhesives with different hardening conditions to the irradiation of ultraviolet rays.
According to another aspect of the invention, an organic thin film EL device, comprises:
a transparent insulative substrate and a sealing cap which are bonded together by an ultraviolet-activated adhesive;
wherein the ultraviolet-activated adhesive is composed of a combination of a first adhesive to be hardened by a smaller irradiation amount of ultraviolet rays and a second adhesive to be hardened by a larger irradiation amount of ultraviolet rays.
According to another aspect of the invention, an organic thin film EL device, comprises:
a transparent insulative substrate and a sealing cap which are bonded together by an ultraviolet-activated adhesive;
wherein the ultraviolet-activated adhesive is composed of a combination of a first adhesive to be hardened by a smaller irradiation amount of ultraviolet rays, a second adhesive to be hardened by a larger irradiation amount of ultraviolet rays, and a third adhesive to be hardened by a medium irradiation amount of ultraviolet rays.
According to another aspect of the invention, a method for making an organic thin film EL device composed of a transparent insulative substrate and a sealing cap which are bonded together by an ultraviolet-activated adhesive, comprises the steps of:
disposing a plurality of the ultraviolet-activated adhesives with different hardening conditions to the irradiation of ultraviolet rays between the transparent insulative substrate and the sealing cap; and
irradiating ultraviolet rays with different irradiation conditions to the plurality of ultraviolet-activated adhesives in a plurality of separate steps so that the adhesives with different hardening conditions are hardened separately in each of the plurality of separate steps.


REFERENCES:
patent: 5356698 (1994-10-01), Kawamoto et al.
patent: 5909081 (1999-06-01), Eida et al.
patent: 5981092 (1999-11-01), Arai et al.
patent: 62-231927 (1987-10-01), None
patent: 2-73229 (1990-03-01), None
JPO abstract of JP 02073229 A, Mar. 1990.*
JPO abstract of JP 62231927 A, Oct. 1987.

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