JP2007538159A - Plasma enhanced chemical vapor deposition of metal oxides. - Google Patents

Abstract

  The metal oxide coating is produced by delivering a metal oxide precursor (10) and an oxidant through a corona discharge (40) or a dielectric barrier discharge to form a metal oxide and depositing it on a substrate. It can be applied to the substrate (60) at a relatively low temperature and at or near atmospheric pressure.

Description

  The present invention relates to plasma enhanced chemical vapor deposition of metal oxides on a substrate, particularly a plastic substrate.

Metal oxide coatings are deposited on glass substrates for a variety of applications. For example, in Patent Document 1, Jones describes chemical vapor deposition (CVD) coating of semiconductor SnO ₂ on a glass substrate at a temperature in the range of 250 ° C. to 400 ° C., atmospheric pressure or reduced pressure. Similarly, McCurdy describes a CDV method in US Pat. No. 6,057,836 for applying a tin or titanium oxide coating on a glass substrate at 630 ° C. and atmospheric pressure.

  In Patent Document 3, Shiozaki et al. Describe a method of depositing a transparent conductive zinc oxide coating on the back surface of a photoelectric converter using magnetron sputtering under high vacuum (2.2 mTorr).

  In Patent Document 4, Siddle et al. Is a method for producing a conductive low emissivity coating on a glass substrate, 1) depositing a reflective metal layer on the substrate, and then 2) oxygen scavenger. Describes a method comprising reactive sputter depositing a metal oxide layer on a reflective metal layer in the presence of, and then 3) heat treating the substrate at 400 ° C. to 720 ° C. is doing. The metal oxide is described as being an oxide of tin, zinc, tungsten, nickel, molybdenum, manganese, zirconium, vanadium, niobium, tantalum, cerium or titanium or a mixture thereof.

  Woo, in US Pat. No. 5,637,099, describes the preparation of an organic titanium precursor that can be used for metal-organic chemical vapor deposition (MOCVD). The thin film of titanium oxide is described as being formed on a glass substrate heated to 375 ° C to 475 ° C. On the other hand, Hitman et al., In Patent Document 6, on a variety of substrates including glass, sapphire, steel, aluminum and magnesium oxide, at a low temperature of about 268 ° C. but under reduced pressure (1 torr), rutile Describes depositing a thin film of type titanium dioxide.

US Pat. No. 5,830,530 US Pat. No. 6,238,738 US Pat. No. 6,136,162 US Pat. No. 6,540,884 US Pat. No. 6,603,033 International Publication No. 00/47797 Pamphlet

  As the prior art suggests, the deposition of metal oxides on a heat resistant substrate such as glass can be carried out at a relatively high temperature without degrading the quality of the glass. However, a considerably lower temperature is required for the deposition of the metal oxide on the plastic substrate. Moreover, for practical reasons, it is further desirable to perform such deposition at or near atmospheric pressure. Therefore, it would be advantageous to find a method for depositing metal oxides on a plastic substrate at a temperature below the glass transition temperature of the substrate, preferably at or near atmospheric pressure.

  The present invention 1) transports a metal-oxide precursor through a corona discharge or dielectric barrier discharge in the presence of an oxidant and converts the precursor to a metal oxide by plasma enhanced chemical vapor deposition (PECVD). The present invention addresses the needs in this technical field by providing a method comprising the steps of: 2) and 2) depositing the metal oxide on a substrate.

  Multi-layer compositions and / or composites on the substrate, optionally with other precursors conforming to PECVD, followed by metal oxide deposition or co-deposition of organosiloxane and SiOx coatings A composition can be provided.

  The present invention is a method of depositing a metal oxide on a substrate using plasma enhanced chemical vapor deposition. In the first step, the metal-organic precursor is delivered through a corona discharge or a dielectric barrier discharge in the presence of an oxidant and preferably a carrier gas. The discharge converts the precursor to a metal oxide and deposits it on the substrate.

  As used herein, the term “metal-oxide precursor” refers to a material capable of producing a metal oxide when subjected to plasma enhanced chemical vapor deposition (PECVD). Examples of suitable metal-oxide precursors include diethyl zinc, dimethyl zinc, zinc acetate, titanium tetrachloride, dimethyl tin diacetate, zinc acetylacetone salt, zirconium hexafluoroacetylacetone salt, zinc carbamate, trimethylindium, triethyl. Indium, cerium (IV) (2,2,6,6-tetramethyl-3,5-heptanedione salt) and mixtures thereof are included. Examples of metal oxides include zinc, tin, titanium, indium, cerium and zirconium oxides, and mixtures thereof. An example of a particularly useful metal oxide is indium-tin-oxide (ITO), which can be used as a transparent conductive oxide for electronics applications.

The method of the present invention can be advantageously carried out using the well-known corona discharge technique as illustrated in FIG. Referring now to FIG. 1 (a), the headspace (gas) from the precursor (10), the carrier for the precursor and the oxidant are passed through the first gas inlet (30) through the nozzle ( 20) and into the corona discharge (40) —it decomposes the gas between the two electrodes 50 (a) and 50 (b) —to produce the metal oxide and (60), preferably deposited on a heated plastic substrate for orderly distribution there. If a plastic substrate is used, the plastic is advantageously maintained at a temperature _close to its T _g , preferably no more than 50 ° C. above its T _g , prior to and during metal oxide deposition. . This process is preferably carried out at or near atmospheric pressure, typically in the range of 700-800 torr.

The carrier for the precursor is typically nitrogen or argon, preferably nitrogen; the oxidant is an oxygen-containing gas such as O ₂ , N ₂ O, air, O ₃ , CO ₂ , NO or N ₂ O ₄ and air is preferred. If the precursor is very reactive with the oxidant—for example, if the precursor is pyrophoric—separate the oxidant from the precursor as illustrated in FIG. 1 (b). Is preferred. According to this scheme, the carrier and precursor flow through a second gas inlet (70) provided directly above the corona discharge (40), and the oxidant flows through the first gas inlet (30). Flowing through. In addition, a second carrier may be used to further dilute the precursor concentration prior to introduction into the nozzle (20). The oxidant need not necessarily be actively supplied to the area if it is obtained from the atmosphere in the area of corona discharge or dielectric barrier discharge.

  The corona discharge (40) is preferably maintained at a voltage in the range of about 2-20 kV. The spacing between the corona discharge (40) and the substrate (60) typically varies between about 1 mm and 50 mm.

  The precursor can be delivered to the nozzle by partially filling the container with the precursor leaving a headspace and sweeping the headspace with a carrier to the nozzle (10). The vessel can be heated if necessary to generate the desired vapor pressure of the precursor. When the precursor is moisture sensitive, air-sensitive or both, the precursor is preferably contained in a container that is substantially free of moisture and oxygen.

  Dielectric barrier discharges, also known as “silent” and “atmospheric pressure glow” discharges, can also be used to practice the method of the present invention. FIG. 2 illustrates a schematic diagram of a dielectric barrier discharge device (100), including two metal electrodes (110 and 120), at least one of which is coated with a dielectric layer (130), over which A base material (150) is placed on top of each other. The gap between the electrodes (110 and 120) is typically in the range of 1-100 mm and the applied voltage is approximately 10-50 kV. The plasma (140) lasts for about 10-100 ns (nanoseconds) and is generated through a series of micro-arcs that occur randomly in space and time.

The concentration of precursor in the total gas mixture (precursor, oxidant and carrier gas) is preferably in the range of 10 ppm to 1% as volume / volume. The flow rate of the precursor is preferably in the range of 0.1 to 10 sccm, and the flow rate of the oxidant is preferably in the range of 10 to 100 scfm (2.7 × 10 ^{5 to} 2.7 × 10 ⁶ sccm). The thickness of the coating on the substrate depends on the application, but typically ranges from 10 nm to 1 μm.

  The substrate is not limited, but is preferably a plastic, examples of which include polycarbonate, polyurethane, thermoplastic polyurethane, poly (methyl methacrylate), polypropylene, low density polyethylene, high density polyethylene, ethylene-α-olefin. Copolymers, styrene (co) polymers, styrene-acrylonitrile copolymers, polyethylene terephthalate and polybutylene terephthalate. The method of the present invention can provide a UV protective coating to a plastic substrate at low temperatures and at or near atmospheric pressure.

  The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1-Attachment of tin oxide on polycarbonate substrate Dimethyltin diacetate was placed in a sealed precursor receptor and heated to 62 ° C. Nitrogen gas was flowed through the receiver at 3000 sccm, combined with air flow through 15 scfm (420,000 sccm). The incoming gas piping of the receiver was heated to 70 ° C. All of the gas mixture passed through a “PLASMA-JET®” corona discharge (apparatus) (available from Corotec Corp., Farmington, CT., Electrode spacing 1 cm) and led to a polycarbonate substrate. After 10 minutes, a clear monolithic coating of tin oxide was formed, as evidenced by a scanning electron microscope and X-ray photoelectron spectrophotometer (XPS).

Example 2-Titanium Oxide Adhesion on a Polycarbonate Substrate Titanium tetrachloride was placed in a sealed precursor receptor and cooled to 0 ° C. Nitrogen gas was passed through the receiver at 600 sccm, combined with a flow of dry air (TOC grade) passing through 20 scfm (570,000 sccm). All of the gas mixture passed through the plasma jet apparatus and was directed to the polycarbonate substrate. After 8 minutes, a clear monolithic coating of titanium oxide was formed, as evidenced by scanning electron microscopy and XPS.

Example 3-Zinc Oxide Adhesion on Polycarbonate Substrate Diethyl zinc was placed in a sealed precursor receptor. Nitrogen gas was passed through the receiver at 150 sccm and combined with another stream of nitrogen passing at 3500 sccm. This gas mixture was introduced into an air plasma stream generated by a plasma jet apparatus and directed onto a polycarbonate substrate. The air (TOC grade) flow rate was 20 scfm (570,000 sccm). After 10 minutes, a clear coating of zinc oxide was formed as evidenced by scanning electron microscopy and XPS.

Example 4-Adsorption of UV-absorbing zinc oxide on polycarbonate substrate Diethyl zinc was placed in a sealed precursor receptor. Nitrogen gas was flowed through the receiver at 100 sccm and combined with another nitrogen flow passing at 3800 sccm. This gas mixture was introduced into a stream of air plasma generated by a plasma jet device and directed onto a polycarbonate substrate. The flow rate of air (low humidity adjusted air) was 15 scfm (570,000 sccm). The electric power applied to the electrode was 720 W, and the distance from the injection port to the substrate was 20 mm. After 15 minutes, a clear coating of about 0.6 μm thick zinc oxide was formed on the polycarbonate sheet, as evidenced by scanning electron microscopy and XPS. As evident from XRD analysis, the polycarbonate sheet (T _g = 150 ° C.) was heated to a temperature of 180 ° C. during deposition to induce crystallization in the coating. The zinc oxide coating was still inactive after 1000 hours of the “QUV-B” weathering test according to ASTM G53-96. The coating exhibited a yellowness index <5, δ haze <18%, light transmission 85%, and UV absorption about 360 nm blocking.

Example 5 Adhesion of Zinc Oxide on a Polycarbonate Substrate Using Dielectric Barrier Discharge Diethyl zinc was placed in a sealed receiver. Nitrogen gas was passed through the receiver at 150 sccm, combined with another nitrogen flow of 60 scfm. This gas mixture was led downstream and exited the electrode and mixed with air before entering the discharge zone in contact with the polycarbonate substrate. The air flow rate was 11357 sccm. The electric power applied to the electrode was 1,000 W, and the distance from the electrode to the substrate was about 4 mm. After 10 minutes, a clear coating of zinc oxide was formed on the polycarbonate film as evidenced by scanning electron microscopy and XPS.

Example 6 SiOxCyHz or SiOx / Zinc Oxide Multilayer Coating An organosiloxane coating, similar to VPP according to US Pat. No. 5,718,967, was deposited on a polycarbonate substrate. The precursor tetramethyldisiloxane flowing at 6000 sccm is mixed with N ₂ O at a flow rate of 1000 sccm. This gas mixture was introduced into a stream of nitrogen plasma generated by a plasma jet device and directed onto a polycarbonate substrate. The remaining nitrogen gas (balance gas of nitrogen) was flowed at 25 scfm. The electric power applied to the electrode was 78 W, and the distance from the injection port to the base material was 5 mm.

  A zinc oxide coating was deposited on top of the organosiloxane coating according to Example 4. If necessary, another organosiloxane layer was deposited on the zinc oxide layer.

FIG. 1 shows a corona discharge method in which a metal oxide is generated and deposited on a substrate. FIG. 2 shows a dielectric barrier discharge device.

Claims (13)

  1) a step of conveying a metal-oxide precursor through a corona discharge or a dielectric barrier discharge in the presence of an oxidant and converting the precursor to a metal oxide by plasma enhanced chemical vapor deposition; and 2) the metal oxidation A method comprising the step of depositing an object on a substrate.   The method of claim 1, wherein the metal-oxide precursor is conveyed through a corona discharge at or near atmospheric pressure. The method of claim 2 wherein the substrate is a plastic heated to a temperature not exceeding a temperature above its _{Tg of} greater than 50C.   The metal-oxide precursor is diethyl zinc, dimethyl zinc, zinc acetate, titanium tetrachloride, dimethyl tin diacetate, zinc acetylacetonate, zirconium hexafluoroacetylacetonate, trimethylindium, triethylindium, cerium (IV) ( The method according to claim 3, selected from the group consisting of 2,2,6,6-tetramethyl-3,5-heptanedionate) and zinc carbamate.   4. The method of claim 3, wherein the metal-oxide precursor is selected from the group consisting of diethyl zinc, titanium tetrachloride, trimethylindium, triethylindium and dimethyltin diacetate. The method according to oxidant, _{air, O 2, N 2 O,} CO 2, H 2 O, CO, N 2 O 4 and O ₃ or claim 3 selected from the group consisting of combinations thereof.   4. A process according to claim 3, wherein an inert gas carrier is used for the precursor and the oxidant is from the atmosphere.   The method of claim 2, wherein the metal oxide is selected from the group consisting of zinc oxide, titanium oxide, tin oxide, zirconium oxide and cerium oxide.   The method of claim 2 wherein the metal oxide is indium-tin-oxide. 1) the step of conveying the metal-oxide precursor and oxidant through corona discharge or dielectric barrier discharge to convert the precursor to metal oxide by plasma enhanced chemical vapor deposition; and 2) the base material of the metal oxide. Depositing on a metal on a plastic substrate that maintains the discharge at or near atmospheric pressure and heats the substrate to a temperature not exceeding 50 ° C. above its T _g A method of depositing an oxide coating.   10. The method of claim 9, wherein the metal oxide is deposited simultaneously with or subsequent to plasma enhanced chemical vapor deposition of another material on the plastic substrate.   An article made by the method of claim 11.   Articles wherein said another substance is an organosilane or SiOx deposit.

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