Multilayer, thin film barrier composites having alternating layers of barrier material and polymer material are known. For example, U.S. Pat. No. 6,268,695, entitled “Environmental Barrier Material For Organic Light Emitting Device And Method Of Making,” issued Jul. 31, 2001; U.S. Pat. No. 6,522,067, entitled “Environmental Barrier Material For Organic Light Emitting Device And Method Of Making,” issued Feb. 18, 2003; and U.S. Pat. No. 6,570,325, entitled “Environmental Barrier Material For Organic Light Emitting Device And Method Of Making”, issued May 27, 2003, all of which are incorporated herein by reference, describe encapsulated organic light emitting devices (OLEDs). These multilayer, thin film barrier composites are typically formed by depositing alternating layers of barrier material and decoupling material, such as by vacuum deposition.
Lateral diffusion into the exposed permeable decoupling layers of a multilayer barrier is an issue with respect to use of these structures for encapsulation. Current multilayer barriers are two dimensional structures: planar barrier layers separated by planar decoupling layers. As a result, they are subject to permeation in the plane of the decoupling layer. If the decoupling layers are deposited over the entire surface of the substrate, then the edges of the decoupling layers are exposed to oxygen, moisture, and other contaminants. This potentially allows the moisture, oxygen, or other contaminants to diffuse laterally into an encapsulated environmentally sensitive device from the edge of the composite, as shown in
Lateral diffusion is also an issue for the use of multilayer barriers on polymer films to create flexible substrates. Practical usage, either roll to roll or sheet based, will require sectioning, or cutting, to yield individual devices, an operation which leads to exposed edges.
Several methods have been proposed to protect the exposed edges. One method involves depositing multilayer barriers as an array of individual areas using methods that form edge sealing structures. An alternative method involves emplacing an edge sealing structure for each individual device subsequent to sectioning. Although both methods can be made to work, the impact of the additional processing steps and inventory logistics has prevented commercialization.
Therefore, there is a need for a multilayer barrier which provides protection against lateral diffusion, and for a method of making the multilayer barrier.
The present invention meets that need by providing a three dimensional multilayer barrier comprising a first continuous barrier layer adjacent to a substrate; a first discontinuous decoupling layer adjacent to the first continuous barrier layer, the first discontinuous decoupling layer having at least two sections; and a second continuous barrier layer adjacent to the first discontinuous decoupling layer, the second continuous barrier layer forming a wall separating the sections of the first discontinuous decoupling layer. By adjacent, we mean next to, but not necessarily directly next to. There can be additional layers between two adjacent layers.
Another aspect of the invention relates to a method of making the three dimensional multilayer barrier. The method involves depositing a first continuous barrier layer adjacent to a substrate; depositing a first discontinuous decoupling layer adjacent to the first continuous barrier layer, the first discontinuous decoupling layer having at least two sections; and depositing a second continuous barrier layer adjacent to the first discontinuous decoupling layer, the second continuous barrier layer forming a wall separating the sections of the first discontinuous decoupling layer.
The three dimensional multilayer barrier shown
The three dimensional multilayer barrier shown in
One solution to this situation is to maintain the mask placement within the decoupling layer/barrier layer pair, but shift the relative placement between one decoupling layer/barrier layer pair and the next. For example, shifting mask positions by ½ cell width in both the x and y directions to deposit third and fourth patterned decoupling layers would produce the structure shown in
The addition of a third decoupling layer/barrier layer pair made by shifting the mask position (e.g., ¼ cell width in both the x and y directions) will result in a structure having 3 decoupling layer/barrier layer pairs free of barrier material based structures that are continuous through the thickness.
The actual geometry of the deposited decoupling layer will not be as regular as is depicted in the preceding figures.
A two step vacuum process could be used to make the three dimensional multilayer barrier. The barrier layers can be deposited by reactive sputtering, with alternating patterned discontinuous decoupling layers deposited through masks. A possible cross-section of the resulting barrier structure is shown in
Various vacuum processes can be used to deposit the barrier layers including, but not limited to, sputtering, reactive sputtering, chemical vapor deposition, plasma enhanced chemical vapor deposition, evaporation, sublimation, electron cyclotron resonance-plasma enhanced vapor deposition (ECR-PECVD), and combinations thereof.
Barrier layers may be made from materials including, but not limited to, metals, metal oxides, metal nitrides, metal carbides, metal oxynitrides, metal oxyborides, and combinations thereof. Metals include, but are not limited to, aluminum, titanium, indium, tin, tantalum, zirconium, niobium, hafnium, yttrium, nickel, tungsten, chromium, zinc, alloys thereof, and combinations thereof. Metal oxides include, but are not limited to, silicon oxide, aluminum oxide, titanium oxide, indium oxide, tin oxide, indium tin oxide, tantalum oxide, zirconium oxide, niobium oxide, hafnium oxide, yttrium oxide, nickel oxide, tungsten oxide, chromium oxide, zinc oxide, and combinations thereof. Metal nitrides include, but are not limited to, aluminum nitride, silicon nitride, boron nitride, germanium nitride, chromium nitride, nickel nitride, and combinations thereof. Metal carbides include, but are not limited to, boron carbide, tungsten carbide, silicon carbide, and combinations thereof. Metal oxynitrides include, but are not limited to, aluminum oxynitride, silicon oxynitride, boron oxynitride, and combinations thereof. Metal oxyborides include, but are not limited to, zirconium oxyboride, titanium oxyboride, and combinations thereof.
The barrier layers can be graded composition barriers, if desired. Suitable graded composition barriers include, but are not limited to, those described in U.S. Pat. No. 7,015,640, which is incorporated herein by reference
Substantially opaque barrier layers can be made from opaque materials including, but not limited to, opaque metals, opaque polymers, opaque ceramics, opaque cermets, and combinations thereof. Opaque cermets include, but are not limited to, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, niobium nitride, tungsten disilicide, titanium diboride, zirconium diboride, and combinations thereof.
The decoupling layers can be deposited using vacuum processes, including but not limited to, flash evaporation with in situ polymerization under vacuum, or plasma deposition and polymerization.
Alternatively, the decoupling layers can be made using an atmospheric process. Suitable atmospheric processes include, but are not limited to, spin coating, ink jet printing, screen printing, spraying, or combinations thereof. Ink jet printing is advantageous because it is a non-contact process, which avoids damage and contamination caused by contact with the fragile barrier layers. In addition, it is capable of producing the required feature sizes, and it can achieve the necessary accuracy of registration over multiple deposition steps.
The decoupling layer could be deposited initially as a continuous layer using a process including, but not limited to, spin coating. The decoupling layer could then be divided into sections by a process including, but not limited to, mask etching. Alternatively, the surface of the substrate could be masked prior to the spincoating or other deposition process.
Decoupling layers can be made from materials including, but not limited to, organic polymers, inorganic polymers, organometallic polymers, hybrid organic/inorganic polymer systems, and silicates. Organic polymers include, but are not limited to, (meth)acrylates, urethanes, polyamides, polyimides, polybutylenes, isobutylene isoprene, polyolefins, epoxies, parylene, benzocyclobutadiene, polynorbornenes, polyarylethers, polycarbonate, alkyds, polyaniline, ethylene vinyl acetate, and ethylene acrylic acid. Inorganic polymers include, but are not limited to, silicones, polyphosphazenes, polysilazane, polycarbosilane, polycarborane, carborane siloxanes, polysilanes, phosphonitriles, sulfur nitride polymers, and siloxanes. Organometallic polymers include, but are not limited to, organometallic polymers of main group metals, transition metals and lanthanide/actinide metals (for example, polymetallocenylenes such as polyferrocene and polyruthenocene). Hybrid organic/inorganic polymer systems include, but are not limited to, organically modified silicates, ceramers, preceramic polymers, polyimide-silica hybrids, (meth)acrylate-silica hybrids, polydimethylsiloxane-silica hybrids.
Tests were performed to evaluate the three dimensional multilayer barrier of the present invention using the calcium test. The calcium test is described in Nisato et al., “Thin Film Encapsulation for OLEDs: Evaluation of Multi-layer Barriers using the Ca Test,” SID 03 Digest, 2003, p. 550-553, which is incorporated herein by reference.
A three dimensional multilayer barrier comprised of an initial barrier layer of 400 Å with 4 decoupling layer/barrier layer pairs (0.5 μm of acrylate polymer and 400 Å of aluminum oxide) was formed over the calcium on a glass substrate. The mask used to form the decoupling layer had 480 μm diameter holes with a 200 μm distance between the holes, resulting in a 680 μm distance from the center of one hole to the center of the next.
Laser cuts 305 were made outside the calcium region 310 on 2 opposing sides, as shown schematically in
No edge effect was seen for any of the samples after 96 hrs. After 633 hrs, an edge effect was seen for the samples cut at 1360 μm (twice the center to center distance), as shown in
The results from the calcium test indicate that these samples have an oxygen transmission rate (OTR) of less than 0.005 cc/m2/day at 23° C. and 0% relative humidity, and less than 0.005 cc/m2/day at 38° C. and 90% relative humidity. The results also indicate that the samples have a water vapor transmission rate (WVTR) of less than 0.005 gm/m2/day at 38° C. and 100% relative humidity. These values are well below the detection limits of current industrial instrumentation used for permeation measurements (Mocon OxTran 2/20L and Permatran) (measured according to ASTM F 1927-98 and ASTM F 1249-90, respectively).
The barrier layers could be deposited as continuous layers across the entire substrate. This will be the most common situation. However, the barrier layers could also be deposited over only a portion of the substrate using a mask, for example, in order to form an array of devices in which each device is individually encapsulated. In this case, the barrier layer should be deposited over at least two sections of the discontinuous decoupling layer so that at least one wall of barrier material will be formed separating the sections of the discontinuous decoupling layer.
A continuous layer will not have any intentionally formed gaps in coverage. A discontinuous layer will have intentionally formed gaps in coverage.
The three dimensional multilayer barrier of the present invention can be used to encapsulate environmentally sensitive devices without the need to edge seal the barrier structures, as well as being used as barriers on flexible substrates. The three dimensional multilayer barrier of the present invention can be included on either side or both sides of the environmentally sensitive device, as desired. As shown in
Optionally, a conventional two dimensional barrier could be combined with the three dimensional multilayer barrier. For example, as shown in
If desired, one or more functional layers could be deposited before and/or after depositing the three dimensional multilayer barrier, and/or the two dimensional barrier. There could be functional layers on either or both sides of the environmentally sensitive device.
In addition, a discontinuous decoupling layer could be deposited before the first continuous barrier layer is deposited, if desired. This could be useful in encapsulating environmentally sensitive devices which have continuous cathodes as the top layer, including, but not limited to, active matrix devices and backlights. As shown in
While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the compositions and methods disclosed herein may be made without departing from the scope of the invention, which is defined in the appended claims.
This application is a continuation-in-part of U.S. application Ser. No. 11/068,356, filed Feb. 28, 2005, which is a Division of U.S. application Ser. No. 09/966,163, filed Sep. 28, 2001, now U.S. Pat. No. 6,866,901, which is a continuation-in-part of U.S. application Ser. No. 09/427,138, filed Oct. 25, 1999, now U.S. Pat. No. 6,522,067, all of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | 09966163 | Sep 2001 | US |
Child | 11068356 | Feb 2005 | US |
Number | Date | Country | |
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Parent | 11068356 | Feb 2005 | US |
Child | 11627583 | Jan 2007 | US |
Parent | 09427138 | Oct 1999 | US |
Child | 09966163 | Sep 2001 | US |