Moisture barrier coatings

This application is a divisional of U.S. Ser. No. 11/185,078, filed Jul. 20, 2005, which is pending, the disclosure of which is incorporated by reference in its entirety herein.

The present invention relates to barrier films for protection of moisture or oxygen sensitive articles.

Organic light emitting devices (OLEDs) can suffer reduced output or premature failure when exposed to water vapor or oxygen. Metals and glasses have been used to encapsulate and prolong the life of OLED devices, but metals typically lack transparency and glass lacks flexibility. Intense efforts are underway to find alternative encapsulation materials for OLEDs and other electronic devices. Examples include various types of vacuum processes are described in the patent and technical literature for the formation of barrier coatings. These methods span the range of e-beam evaporation, thermal evaporation, electron-cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD), magnetically enhanced PECVD, reactive sputtering, and others. Barrier performance of the coatings deposited by these methods typically results in a moisture vapor transmission rate (MVTR) in the range from 0.1-5 g/m² day, depending on the specific processes. Graff (WO0036665) demonstrates the importance of separating multiple inorganic oxide coatings with vapor deposited highly cross-linked polymer layers to achieve barrier performance necessary for OLED device substrates.

It is commonly accepted that multiple inorganic layers separated by polymer coatings are needed to achieve superior barrier performance. U.S. Pat. No. 5,320,875 teaches the importance of a plasma polymerized siloxane monomer and an adhesion promoter in addition to generating the plasma in an “oxygen excessive” mode and depositing the coatings in the “plasma reaction zone” to obtain improved barrier performance. The best barrier coatings made by this process still have an MVTR of 0.23 g/m² day. Da Silva Sobrinho et al. (Surface and Coatings Technology, 116-119, p 1204, 1999) report a microwave and radio frequency combined process for depositing barrier coatings. In U.S. Pat. No. 6,146,225, Sheats et al. claim that a high density plasma with low bias voltage results in superior quality barrier coatings.

References relating to flexible barrier films include U.S. Pat. No. 5,440,446 (Shaw et. al.), U.S. Pat. No. 5,530,581 (Cogan), U.S. Pat. No. 5,681,666 (Treger et al.), U.S. Pat. No. 5,686,360 (Harvey, III et al.), U.S. Pat. No. 5,736,207 (Walther et al.), U.S. Pat. No. 6,004,660 (Topolski et al.), U.S. Pat. No. 6,083,628 (Yializis), U.S. Pat. No. 6,146,225 (Sheats et al.), U.S. Pat. No. 6,214,422 (Yializis), U.S. Pat. No. 6,268,695 (Affinito), U.S. Pat. No. 6,358,570 (Affinito), U.S. Pat. No. 6,413,645 (Graff et al.), U.S. Pat. No. 6,492,026 (Graff et al.), U.S. Pat. No. 6,497,598 (Affinito), U.S. Pat. No. 6,497,598 (Affinito), U.S. Pat. No. 6,623,861 (Martin et al.), U.S. Pat. No. 6,570,325 (Graff et al.), U.S. Pat. No. 5,757,126, U.S. Patent Application No. 2002/0125822 A1 (Graff et al.), and PCT Published Application No. WO 97/16053 (Robert Bosch GmbH).

A first composite assembly for protection of a moisture or oxygen sensitive article includes a substrate, a first polymer layer overcoated on the substrate, and a second polymer layer overcoated on the first polymer layer. In this assembly, the first polymer layer is composed of a first polymer and the second polymer layer is composed of a second polymer different from the first polymer, and the second polymer comprises a plasma polymer.

A second composite assembly for protection of a moisture or oxygen sensitive article includes a substrate, a polymer layer overcoated on the substrate, and a diamond-like carbon layer overcoated on the polymer layer.

A third composite assembly for protection of a moisture or oxygen sensitive article includes a substrate, a polymer layer overcoated on the substrate, and a diamond-like glass layer overcoated on the polymer glass layer.

Processes include any method of fabricating these assemblies.

The words of orientation such as “atop”, “on”, “uppermost” and the like for the location of various layers in the barrier assemblies or devices refer to the relative position of one or more layers with respect to a horizontal support layer. We do not intend that the barrier assemblies or devices should have any particular orientation in space during or after their manufacture.

The term “overcoated” to describe the position of a layer with respect to a substrate or other element of a barrier assembly, refers to the layer as being atop the substrate or other element, but not necessarily contiguous to either the substrate or the other element.

The term “polymer” refers to homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction, including, e.g., transesterification. The term “polymer” also includes plasma deposited polymers. The term “copolymer” includes both random and block copolymers. The term “curable polymer” includes both crosslinked and uncrosslinked polymers. The term “crosslinked” polymer refers to a polymer whose polymer chains are joined together by covalent chemical bonds, usually via crosslinking molecules or groups, to form a network polymer. A crosslinked polymer is generally characterized by insolubility, but may be swellable in the presence of an appropriate solvent.

The term a “visible light-transmissive” support, layer, assembly or device means that the support, layer, assembly or device has an average transmission over the visible portion of the spectrum, T_vis of at least about 20%, measured along the normal axis.

The term “diamond-like glass” (DLG) refers to substantially or completely amorphous glass including carbon and silicon, and optionally including one or more additional components selected from the group including hydrogen, nitrogen, oxygen, fluorine, sulfur, titanium, and copper. Other elements may be present in certain embodiments. The amorphous diamond-like glass films may contain clustering of atoms to give it a short-range order but are essentially void of medium and long range ordering that lead to micro or macro crystallinity which can adversely scatter radiation having wavelengths of from 180 nanometers (nm) to 800 nm.

The term “diamond-like carbon” (DLC) refers to an amorphous film or coating comprising approximately 50 to 90 atomic percent carbon and approximately 10 to 50 atomic percent hydrogen, with a gram atom density of between approximately 0.20 and approximately 0.28 gram atoms per cubic centimeter, and composed of approximately 50% to approximately 90% tetrahedral bonds.