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Protected polymeric filmRelated Patent Categories: Stock Material Or Miscellaneous Articles, Composite (nonstructural Laminate), Of MetalProtected polymeric film description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060063015, Protected polymeric film. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] This invention relates to protected polymeric films and, more particularly, to polymeric films that have a reduced tendency to transmit moisture. This invention also relates to articles that incorporate such protected polymeric films. BACKGROUND [0002] Polymeric films tend to transmit moisture (e.g., water vapor), which can be undesirable if the transmission of moisture is detrimental to components that are secured to or subsequently formed on the film. As one example, organic electroluminescent devices may suffer reduced output or premature failure when exposed to moisture. Techniques have been developed to encapsulate and prolong the life of such devices, which may be sufficient if the device is formed on a glass substrate that is impermeable to moisture. Increasingly, however, it is desirable to form such devices on a polymeric film, but such films tend to inherently transmit moisture. A protected polymeric film that exhibited low permeability to moisture would be especially useful, but despite intense industrial effort to develop such a film, only limited success has been attained so far. SUMMARY OF THE INVENTION [0003] In one aspect, the present invention provides a protected polymeric film comprising a polymeric film substrate having a first major surface and a second major surface opposite the first major surface, and a protective structure that is provided on at least the first major surface of the substrate. The protective structure comprises a layer of boron oxide and an inorganic barrier layer. The layer of boron oxide may be disposed on the first major surface of the substrate with the inorganic barrier layer disposed over the layer of boron oxide. Alternatively, the inorganic barrier layer may be disposed on the first major surface of the substrate with the layer of boron oxide disposed over the inorganic barrier layer. A second protective structure (also comprising a layer of boron oxide and an inorganic barrier layer) may be provided on the second major surface of the substrate. The expressions "disposed on" and "disposed over" are not meant to suggest that direct, intimate contact is required between the layers that are in this relationship, but instead are relative terms of position. [0004] In some embodiments, the inorganic barrier layer cooperates with the first major surface of the substrate to encapsulate the layer of boron oxide. In other embodiments, the protective structure further comprises a second inorganic barrier layer. The layer of boron oxide may then be disposed between, and optionally be encapsulated by, the two inorganic barrier layers. [0005] The inorganic barrier layer preferably comprises an inorganic oxide, boride, nitride, carbide, oxynitride, oxyboride, or oxycarbide, such as silicon oxides, nitrides or carbides; diamond-like carbon layers; and metals such as silicon, aluminum or combinations thereof. Specific examples include silicon oxide (monoxide or dioxide), silicon nitride, aluminum oxide or silicon aluminum oxide. The inorganic barrier layer may be a multilayer construction comprising, for example, alternating polymeric and inorganic layers. In some instances, the inorganic barrier layer has low moisture permeability. [0006] Protected polymeric films according to the invention may further, and optionally, comprise a buffer layer such as an organometallic compound or a chelate compound. In these embodiments, the inorganic barrier layer may be disposed on the first major surface of the substrate, the layer of boron oxide may be disposed over the inorganic barrier layer, and the buffer layer may be disposed over the layer of boron oxide. [0007] The protective structures reduce the inherent, but potentially undesirable, tendency of polymeric films to transmit moisture. As a result, the protected polymeric films of the invention provide a good support on which an electroluminescent assembly (e.g., comprising a first electrode, a second electrode, and a light emitting structure disposed between the first and second electrodes) may be subsequently formed or attached. The electroluminescent assembly may be disposed on the surface of the polymeric film carrying the protective structure (either underneath it or over it), or on the opposite surface of the polymeric film. [0008] In another aspect, the present invention provides a method for reducing the transmission of moisture by a polymeric film by applying a protective structure, such as those described above, to at least a first major surface of the polymeric film. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The invention will be more fully appreciated with reference to the following non-limiting and not-to-scale drawings in which the same reference symbols designate like or analogous components throughout and in which: [0010] FIG. 1 is a schematic sectional view of a first embodiment of a protected polymeric film according to the invention; [0011] FIG. 2 is a schematic sectional view of a second embodiment of a protected polymeric film according to the invention; [0012] FIG. 3 is a schematic sectional view of a third embodiment of a protected polymeric film according to the invention; [0013] FIG. 4 is a schematic sectional view of a fourth embodiment of a protected polymeric film according to the invention; [0014] FIG. 5 is a schematic sectional view of a fifth embodiment of a protected polymeric film according to the invention; and [0015] FIG. 6 is a schematic sectional view of a sixth embodiment of a protected polymeric film according to the invention. DETAILED DESCRIPTION [0016] Broadly, and in one aspect, the invention provides a protected polymeric film comprising a polymeric film substrate having a first major surface and a second major surface opposite the first major surface, and a protective structure that is provided on at least the first major surface of the substrate. The protective structure comprises a layer of boron oxide and an inorganic barrier layer. Other layers may be optionally included in the protective structure, on the polymeric film substrate, or both. [0017] The protected polymeric films of the invention can be used to inhibit the transmission of moisture in a variety of applications. They are especially useful as substrates for use with organic electronic devices such as organic electroluminescent devices, organic transistors, liquid crystal displays, and other electronic components. [0018] Broadly, a "protected polymeric film" refers to a polymeric film substrate that has been provided with a protective structure as described herein, and a "protective structure" refers to the layer of boron oxide and the inorganic barrier layer that have been provided on the polymeric film substrate. Polymeric film substrates tend to transmit, or otherwise be permeable to moisture, which is undesirable if the transmission of moisture by the substrate is detrimental to components that are secured to or subsequently formed on the substrate. [0019] Thus, a "protected polymeric film" more specifically refers to a polymeric film substrate that has a reduced ability to transmit moisture relative to the same polymeric film substrate that does not have the protective structure. Similarly, a "protective structure" more specifically refers to a layered assembly comprising the layer of boron oxide and the inorganic barrier layer, and which reduces the undesirable, but inherent, tendency of a polymeric film to transmit moisture relative to the same polymeric film that does not have the protective structure. The protective structure is preferably adapted to reduce, often substantially, the inherent tendency of a polymeric film to transmit moisture through the surface(s) to which the protective structure has been applied. Continue reading about Protected polymeric film... Full patent description for Protected polymeric film Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Protected polymeric film 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. 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