Barrier layer for an article and method of making said barrier layer by ...

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BARRIER LAYER FOR AN ARTICLE AND METHOD OF MAKING SAID BARRIER LAYER BY EXPANDING THERMAL PLASMA

BACKGROUND OF THE INVENTION

The invention relates to a barrier layer that is resistant to the transmission of moisture and oxygen. More particularly, the present invention relates to an article having such a barrier layer and methods of applying such a barrier layer to an article.

Different types of electronic devices such as, but not limited to, light emitting diodes (also referred hereinafter as ^ "LEDs"), liquid crystal displays (also referred hereinafter as "LCDs"), photovoltaic articles, flat panel display devices, electrochromic articles, and organic electroluminescent devices (also referred hereinafter as "OELDs") share a common architecture: each device includes at least one 2o substrate and at least one "active" layer.

Many of the materials that are used in the active layers of such devices are sensitive to environmental factors. Electrode materials in LEDs and OELDs are sensitive to air and moisture, as are the polymeric and organic compounds that 25 are used in OELDs and the liquid crystal materials in LCDs. Exposure to the elements—particularly oxygen and water— may severely limit the lifetime of such devices.

Selection of a substantially impermeable substrate, such as glass, provides protection from environmental attack. 30 Polymeric substrates that are used in flexible versions of such devices, however, do not provide adequate protection against oxygen and moisture. Consequently, at least one coating that is substantially impermeable to oxygen and water vapor must be applied to the polymeric substrate to 35 achieve the desired level of protection.

Barrier materials have been applied to substrates using a variety of coating processes. Plasma enhanced chemical vapor deposition (PECVD), for example, has been used to deposit barrier materials. Typical PECVD processes, 40 however, are relatively slow; i.e. the barrier material is deposited on the substrate at a rate of about 30 to 60 nm/min or less. In order to be commercially viable, the barrier coating must be applied to the substrate at a significantly higher deposition rate. 45

While barrier materials are needed to extend lifetimes of flexible display devices such as LCDs, LEDs, and OELDs to acceptable levels, the methods that are currently used to apply the needed barrier materials to substrates are too slow. 5Q Therefore, what is needed is a method of forming a barrier layer on a substrate at a high rate of deposition. What is also needed is a method of forming a barrier layer on a substrate to form an article having acceptable water vapor and oxygen transmission rates. What is further needed is an article 5J having a barrier layer, the article having acceptable water vapor and oxygen transmission rates.

SUMMARY OF THE INVENTION

The present invention meets these and other needs by 60 providing an article comprising a substrate having a barrier layer disposed on the surface of the substrate and methods of depositing such a barrier layer on the substrate, wherein the barrier layer is resistant to transmission of moisture and oxygen therethrough. The article may include additional 65 layers, such as, but not limited to, an adhesion layer, abrasion resistant layers, radiation-absorbing layers,

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radiation-reflective layers, and conductive layers. Such articles Include, but are not limited to, light emitting diodes (LEDs), liquid crystal displays (LCDs), photovoltaic articles, electrochromic articles, organic integrated circuits, and organic electroluminescent devices (OELDs).

Accordingly, one aspect of the invention is to provide an article. The article comprises a substrate and at least one barrier layer disposed on at least one surface of the substrate, wherein the barrier layer comprises an inorganic material, and wherein the barrier layer is resistant to transmission of moisture and oxygen therethrough and has a water vapor transmission rate (WVTR) at 25° C. and 100% relative humidity of less than about 2 g/m2-day and an oxygen transmission rate (OTR) at 25° C. and 100% oxygen concentration of less than about 2 cc/m2-day.

A second aspect of the invention is to provide a barrier layer that is resistant to transmission of moisture and oxygen therethrough. The barrier layer comprises at least one of a metal oxide, a metal nitride, a metal carbide, and combinations thereof. Each of the metal nitride, the metal carbide, and the metal oxide contains at least one of silicon, aluminum, zinc, indium, tin, a transition metal, and combinations thereof. The barrier layer has a water vapor transmission rate (WVTR) at 25° C. and 100% relative humidity of less than about 2 g/m2-day and an oxygen transmission rate (OTR) at 25° C. and 100% oxygen concentration of less than about 2 cc/m2-day.

A third aspect of the invention is to provide an article. The article comprises a substrate and at least one barrier layer, the at least one barrier layer comprising at least one of a metal oxide, a metal nitride, a metal carbide, and combinations thereof, wherein each of the metal nitride, the metal carbide, and the metal oxide contains at least one of silicon, aluminum, zinc, indium, tin, a transition metal, and combinations thereof, and wherein the barrier layer is resistant to transmission of moisture and oxygen therethrough and has a water vapor transmission rate (WVTR) at 25° C. and 100% relative humidity of less than about 2 g/m2-day and an oxygen transmission rate (OTR) at 25° C. and 100% oxygen concentration of less than about 2 cc/m2-day.

A fourth aspect of the invention is to provide a method of forming a coated article. The coated article comprises a substrate and a barrier layer disposed thereon, wherein the barrier layer is resistant to transmission of moisture and oxygen therethrough and has a water vapor transmission rate (WVTR) at 25° C. and 100% relative humidity of less than about 2 g/m2-day and an oxygen transmission rate (OTR) at 25° C. and 100% oxygen concentration of less than about 2 cc/m2-day. The method comprises the steps of: providing a substrate; generating a thermal plasma, the thermal plasma having an electron temperature of less than about 1 eV; injecting at least one reagent into the thermal plasma; reacting the at least one reagent in the thermal plasma to form at least one deposition precursor; and depositing the at least one deposition precursor on the substrate at a rate of at least about 200 nm/min to form the barrier layer on the substrate.

A fifth aspect of the invention is to provide a method of forming a barrier layer on a substrate. The barrier layer is resistant to transmission of moisture and oxygen therethrough and has a water vapor transmission rate (WVTR) at 25° C. and 100% relative humidity of less than about 2 g/m2-day and an oxygen transmission rate (OTR) at 25° C. and 100% oxygen concentration of less than about 2 cc/m2day, and comprises at least one of at least one of a metal oxide, a metal nitride, a metal carbide, and combinations 3

thereof, wherein each of the metal nitride, the metal carbide, and the metal oxide contains at least one of silicon, aluminum, zinc, indium, tin, a transition metal, and combinations thereof. The method comprises the steps of: generating a thermal plasma, the thermal plasma having an electron temperature of less than about 1 eV; injecting a first reagent into the thermal plasma, the first reagent comprising at least one of silicon, aluminum, zinc, indium, tin, a transition metal, and combinations thereof; injecting a second reagent into the thermal plasma, the second reagent comprising at least one of oxygen, nitrogen, and ammonia; decomposing the first reagent and the second reagent in the thermal plasma to form a plurality of decomposition products; reacting the at least one reagent in the thermal plasma to form at least one deposition precursor; and depositing the at least one deposition precursor on the substrate at a rate of at least about 200 nm/min to form the barrier layer comprising at least one of a metal oxide, a metal nitride, a metal carbide, and combinations thereof on the substrate.

A sixth aspect of the invention is to provide a method of forming a coated article. The coated article comprises a substrate and a barrier layer disposed thereon. The barrier layer is resistant to transmission of moisture and oxygen therethrough and has a water vapor transmission rate (WVTR) at 25° C. and 100% relative humidity of less than about 2 g/m2-day and an oxygen transmission rate (OTR) at 25° C. and 100% oxygen concentration of less than about 2 cc/m2-day, and comprises at least one of a metal oxide, a metal nitride, a metal carbide, and combinations thereof, wherein each of the metal nitride, the metal carbide, and the metal oxide contains at least one of silicon, aluminum, zinc, indium, tin, a transition metal, and combinations thereof. The method comprises the steps of: providing a substrate; generating a thermal plasma, the thermal plasma having an electron temperature of less than about 1 eV; injecting a first reagent into the thermal plasma, the first reagent comprising at least one of silicon, aluminum, zinc, indium, tin, a transition metal, and combinations thereof; injecting a second reagent into the thermal plasma, the second reagent comprising at least one of oxygen, nitrogen, and ammonia; reacting the first reagent and the second reagent in the thermal plasma to form at least one deposition precursor; and depositing the at least one deposition precursor on the substrate at a rate of at least about 200 nm/min, thereby forming the barrier layer comprising at least one of a metal oxide, a metal nitride, a metal carbide, and combinations thereof on the substrate.

These and other aspects, advantages, and salient features of the present Invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic representation of an article of the present invention;

FIG. 2 is a schematic representation of a flexible liquid crystal display of the present invention;

FIG. 3a is a schematic representation of a light emitting diode of the present invention;

FIG. 3b is a schematic representation of a organic electroluminescent device of the present invention;

FIG. 4 is a schematic representation of an expanding thermal plasma deposition system; and

FIG. 5 is a plot of the water vapor transmission rate of a silicon nitride barrier layer of the present invention as a function of reagent flow rate.

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DETAILED DESCRIPTION

In the following description, like reference characters designate like or corresponding parts throughout the several views shown in the figures. It is also understood that terms 5 such as "top," "bottom," "outward," "inward," and the like are words of convenience and are not to be construed as limiting terms.

Several display devices such as, but not limited to, light emitting diodes (also referred hereinafter as "LEDs"), liquid crystal displays (also referred hereinafter as "LCDs"), photovoltaic articles, flat panel display devices, electrochromic articles, and organic electroluminescent devices (also referred hereinafter as "OELDs") share a common architecture: each device includes at least one substrate and at least one "active" layer. Light emitting diodes and organic electroluminescent devices, for example, may include a cathode layer, an electron transport layer, an emission layer, a hole transport layer, and an anode layer disposed on a substrate. 2Q Liquid crystal displays may include two substrates, each having an electrically conductive layer disposed thereon, and a liquid crystal layer sandwiched between the two substrates.

Many of the materials that are used in these devices may

25 be adversely affected by environmental factors. Electrode materials in LEDs and OELDs are sensitive to air and moisture, as are the polymeric and organic compounds that are used in OELDs and the liquid crystal materials in LCDs. Exposure to the elements—particularly oxygen and water—

3Q may severely limit the lifetime of such devices.

Selection of a substantially impermeable substrate, such as glass, provides protection from environmental attack. Polymeric substrates that are used in flexible versions of such devices, however, do not provide adequate protection

35 against oxygen and moisture. Consequently, at least one barrier layer that is substantially impermeable to oxygen and water vapor must be applied to the polymeric substrate to achieve the desired level of protection. Here, a coating, device, or coated substrate that is described as being "sub

40 stantially impermeable" is understood as having a water vapor transmission rate (also referred hereinafter as "WVTR") and an oxygen transmission rate (also referred hereinafter as "OTR") of less than about 2 g/m2-day at 25° C. and 100% relative humidity and less than about 2

45 cc/m2-day at 25° C. and 100% oxygen concentration, respectively.

Referring to the drawings in general and to FIG. 1 in particular, it will be understood that the Illustrations are for the purpose of describing a preferred embodiment of the

50 invention and are not intended to limit the invention thereto. FIG. 1 is a schematic representation of an article 100 of the present Invention. Article 100 comprises a substrate 102 and at least one barrier layer 106 disposed on a surface of substrate 102. An additional layer 104, such as, but not

55 limited to, an adhesion layer, may be optionally disposed between substrate 102 and the at least one barrier layer 106. Substrate 102 may comprise one of glass, a polymeric material, silicon, a metallic web, and fiberglass. Where substrate 102 is a polymeric material, substrate 102 com

60 prises at least one of a polycarbonate, a polyethylene terephtalene, a polyethylene naphthalene, a polyimide, a polyethersulfone, a polyacrylate, a polynorbornene, and combinations thereof. In another embodiment, substrate 102 is a metallic web comprising one of aluminum and steel.

65 The at least one barrier layer 106 comprises an inorganic material and is resistant to the transmission of moisture and oxygen therethrough. The at least one barrier layer 106 has