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  Encapsulation of organic devicesRelated Patent Categories: Semiconductor Device Manufacturing: Process, Having Organic Semiconductive ComponentThe Patent Description & Claims data below is from USPTO Patent Application 20060105493. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATION [0001] This patent application claims the priority of U.S. provisional patent application Ser. No. 60/627,905, filed Nov. 15, 2004, the disclosure content of which is hereby incorporated by reference. FIELD OF THE INVENTION [0002] The present invention relates to the fabrication of organic electronic devices. In particular, the invention relates to a method for encapsulation of organic devices such as light-emitting diodes (OLEDs). BACKGROUND OF THE INVENTION [0003] Organic devices such as OLED-devices contain at least one active organic layer on a substrate sandwiched between two electrodes. To protect the active organic layer and other functional parts of the device, a cap is bonded to the substrate with the help of a bonding material. Usually the cap is bonded to the substrate using polymeric adhesives, for example epoxy adhesives, as bonding material. The bonding material fixes the cap on the substrate and acts as a barrier to harmful atmospheric gases such as oxygen and moisture. After mounting the cap on the substrate, the adhesive has to be cured. Many commonly used adhesives can be cured by heat treatment, for example on a hot plate or in an oven. However, heat treatment can damage the active organic layer or other functional parts of the device and can therefore adversely affect the performance of the device. To avoid damaging of the device during the heat treatment, the curing temperatures are generally adjusted to the temperature tolerance of the active organic layer or other functional parts of the device and not only to the curing properties of the bonding material. On the one hand, this can lead to enhanced permeation rates for harmful atmospheric gases of the cured bonding material and on the other hand, limits the number of bonding materials suited for sealing the device. Particularly, higher curing temperatures can allow the use of bonding materials with lower permeation rates for gases like oxygen and moisture. [0004] In U.S. Pat. No. 6,692,610, a method of fabricating devices such as OLED-devices is disclosed. The method includes applying an adhesive on a cap or substrate. The adhesive is partially cured to initiate the cross-linking process while remaining in the liquid phase. The cap is then mounted onto the substrate and the adhesive is cured to encapsulate the device. By partially curing the adhesive prior to mounting the cap, the curing of the adhesive can be achieved without prolonged exposure to UV-radiation or high temperatures, which can adversely impact the device. [0005] However, this method requires a further process step which makes the production of devices more complicated and expensive. Furthermore, the above-mentioned U.S. Pat. No. 6,692,610 does not disclose an alternative to the heat treatment which would allow the use of bonding material with improved barrier properties. SUMMARY OF THE INVENTION [0006] One object of the invention is to provide an improved method for encapsulation of a device. [0007] Another object of the invention is to provide an alternative to the heat treatment of the device for the curing of the bonding material. [0008] The invention relates to a method for encapsulating a device comprising the steps: [0009] depositing organic active material on an active region of a substrate; [0010] providing a cap to enclose said organic active material within a space defined by a cap periphery adapted to adhere to the substrate; [0011] applying a thermally curable bonding material to said cap periphery or to regions of the substrate adapted to adhere to said cap periphery; [0012] mounting said cap onto the substrate so that said bonding material is between said cap periphery and the substrate; and [0013] curing the bonding material with electromagnetic radiation in the near infrared range to encapsulate the device. [0014] In one embodiment, the active region comprises OLED cells. In accordance with the invention, the thermally curable bonding material is cured with the help of near infrared radiation, which replaces the heat treatment used according to the state of the art. The near infrared radiation stimulates specific vibrations within the bonding material (e.g. vibrations of C--H-bindings in polymeric materials, such as epoxy adhesives) and the energy of the radiation is almost completely transferred to the bonding material for curing in a direct way. Therefore, the curing of the bonding material occurs locally, and heating of other parts of the device, in particular of the active organic layer, can be avoided. [0015] By using near infrared radiation instead of heat treatment on a hot plate or in an oven, reduced process times can be achieved. It could be shown, for example, that a heat treatment of organic polymers for 30 minutes at 180.degree. C. in an oven can be replaced by an irradiation step of only a few seconds. As bonding materials, adhesives such as epoxy adhesives or adhesive foils, such as thermoplastic foils, suited particularly for flexible applications can be used. Furthermore, other bonding materials, which require a heat treatment at higher temperatures for curing, can also be used. One example for such a bonding material is solder glass. [0016] Compared to polymeric adhesives, solder glass shows improved barrier properties against atmospheric gases like oxygen and moisture. In one embodiment, the active organic layer is protected against residual near infrared radiation by means of a shadow mask. In a further embodiment, the near infrared radiation is focussed to be locally applied in the regions where the bonding material is applied. This ensures that the organic active layer of the device is not affected by the near infrared radiation. Preferably, the near infrared radiation is focussed in at least one line with a width of 1 to 2 mm. [0017] The use of line-focussed near infrared radiation for curing the bonding materials facilitates the integration of the encapsulation step in a batch process leading to improved process times. [0018] A method for encapsulating devices in a batch process comprises the steps: [0019] depositing organic active material on a plurality of active regions of a substrate; [0020] providing a plurality of caps for said plurality of active regions to enclose said organic active material within a space respectively defined by each cap periphery adapted to adhere to the substrate; [0021] applying a thermally curable bonding material to each said cap periphery or to regions of the substrate adapted to adhere to each said cap periphery such that said bonding material defines rectangular areas each containing one said active region, wherein said rectangular areas form a grid in such a way that the bonding material is arranged in parallel vertical lines and parallel horizontal lines; [0022] mounting said plurality of caps onto the substrate so that said bonding material is between each said cap periphery and the substrate; and [0023] curing said bonding material with electromagnetic radiation in the near infrared range focused in at least one line and applied sequentially across the substrate to encapsulate the devices. [0024] The caps can be separated or integrated on a cap substrate. The cap substrate can be a planar plate, comprising for example metal or glass. Furthermore, it is also possible that corresponding to the active regions of the substrate, the plate has cavities in order to protect the organic active material within the active region from damage due to direct contact with the cap. If the cap has a cavity bending over the active region of the device, getter material can be positioned inside the cavity of the cap, which binds oxygen and moisture. BRIEF DESCRIPTION OF THE DRAWINGS [0025] FIGS. 1 to 3 show schematic sectional views of an OLED-device according to the invention at different fabrication steps; [0026] FIGS. 4 to 6 show schematic sectional views of an OLED-device during curing of bonding material with the help of near infrared radiation; and [0027] FIGS. 7A to 7E show schematic top views of OLED-devices according to the invention at different fabrication steps of a batch process. DETAILED DESCRIPTION OF THE DRAWINGS [0028] In accordance with one embodiment of the invention, FIGS. 1, 2 and 3 show cross-sectional views of an OLED-device at different process steps. Referring to FIG. 1, the OLED-device comprises one or more active organic layers 1 with organic active material sandwiched between two electrodes 2, 3 formed on a substrate 4 in an active region 5. Electrical connections to the electrodes 2, 3 can be made by bond wires via bond pads 6. When an electrical current is applied to the OLED-device, electrons and holes are injected into the organic material of the active organic layer 1 by the electrodes 2, 3. The charge carriers recombine within the active organic layers 1 and the released energy is emitted as visible light. Continue reading... Full patent description for Encapsulation of organic devices Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Encapsulation of organic devices patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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