Silicon oxide coated polymer film and low pressure PECVD method for producing same

Abstract

The present invention relates to a stress-free, transparent silicon oxide-coated polymer substrate. The present invention further relates to a method for depositing a stress-free, transparent silicon oxide-based layer on a polymer substrate using a PECVD apparatus including at least one hollow cathode plasma source.

Description

[Technical Field]

[0001] The present invention relates to a stress-free, transparent silicon oxide-coated polymer substrate. The present invention also relates to a method for depositing a stress-free, transparent silicon oxide-based layer on a polymer substrate, particularly on a thin polymer film, more particularly on a polyethylene terephthalate (PET)-based thin polymer film, and promoting the adhesion of laminated materials to the polymer substrate. In particular, this method is adapted for use in a continuous coating process. [Background technology]

[0002] Silicon oxide-based layers can be used on polymer substrates for a variety of purposes. They can be used as barrier layers against water vapor or gases. They can also be part of more complex stacks of multiple layers used to modify the optical or optical energy properties of polymer films, such as anti-reflection layer stacks, low-emissivity insulating layer stacks, or solar radiation control layer stacks. They can also be used to improve the adhesion of polymer substrates to other substrates or adhesives or other coating layers.

[0003] To produce silicon oxide-based layers, so-called PECVD methods (plasma-enhanced chemical vapor deposition) can be used. These methods can be used to coat many different substrates for a variety of layer materials. A common problem encountered with polymer substrates is the increase in substrate temperature and etching of the polymer substrate surface by reactive species in the plasma. For example, it is known to deposit SiO2 and Si3N4 layers with thicknesses of 20-30 nm on 13 μm PET substrates using microwave excitation and / or high-frequency PECVD. Interesting barrier properties are obtained, while deposition rates of 10 nm·m·min -1 The dynamic deposition rate below 200 nm is very low for a coating of 200 nm thickness [ASda Silva Sobrinho et al., J. Vac. Sci. Technol. A 16(6), November / December 1998, p. 3190-3198].

[0004] When silicon oxide is deposited on a PET substrate by PECVD as a transparent barrier layer, oxygen and water vapor barrier properties can be obtained [R.J. Nelson and H. Chatham, Society of Vacuum Coaters, 34th Annual Technical Conference Proceedings (1991) pp. 113-117 and M. Izu, B. Dotter, SR Ovshinsky, Society of Vacuum Coaters, 36th Annual Technical Conference Proceedings (1993) pp. 333-340].

[0005] A drawback of known PECVD processes is, inter alia, that their deposition rates are too low for use in processes in which the substrate moves at high speed through one or more deposition processes, such as high-speed roll-to-roll processes. Furthermore, in known PECVD processes, higher deposition rates tend to result in higher substrate temperatures, thereby limiting the maximum deposition rate and / or requiring additional cooling measures for the polymer substrate. Furthermore, adhesion of these coatings to polymer substrates tends to be weak, and / or the inherent compressive stress in the coating is often high, resulting in deformation of the coated PET substrate.

[0006] Furthermore, it is known to apply silicon oxide-based layers by sputtering. A drawback of sputtered layers is the high cost caused by the low productivity of the silicon oxide sputtering process, i.e., the low dynamic deposition rate. More importantly for thin polymer films, except at minimum thicknesses, the inherent compressive stress of sputtered silicon oxide-based coatings causes deformation of the polymer substrate of the coated thin film. Summary of the Invention

[0007] One of the objectives of the present invention is to obtain silicon oxide-based layers on polymer substrates, particularly polymer films, using a low pressure PECVD method (for the present application, the pressure can be 0.005-0.025 Torr) that allows for one or more of high deposition rates, highly transparent silicon oxide-based films, and minimal deformation of the coated thin polymer substrate, particularly, and minimizing the amount of stress in the coating to minimize the risk of delamination.

[0008] The present invention relates to a method for producing silicon oxide based layers on polymer substrates, in particular thin polymer films, by a PECVD method, comprising the steps of: a. providing a polymer substrate; b. providing a low-pressure PECVD apparatus for depositing a film on a polymer substrate, comprising at least one linear hollow cathode plasma source, wherein each plasma source comprises at least one pair of electrodes connected to an AC, DC, or pulsed DC generator; c. applying power to the plasma source such that the power density of the plasma is between 1 kW and 50 kW per linear meter of the plasma source; d. applying a gaseous precursor of an oxide of silicon to the polymer substrate at a flow rate of 50-700 sccm per linear meter of the plasma source, wherein the gaseous precursor is injected between the electrodes of each electrode pair at a flow rate of 1500-4000 sccm per linear meter of the plasma source between the two pairs of electrodes, each pair consisting of a respective electrode constituting each electrode pair, and a reactive gas injected into each electrode, the reactive gas being based on oxygen or an oxygen-containing derivative; The present invention also relates to a method comprising:

[0009] The present invention further relates to a silicon oxide-based layer that can be produced by the method of the present invention or any embodiment of this method or any combination of embodiments of this method.

[0010] The present invention further relates to a polymer substrate coated with a silicon oxide-based layer of the present invention, a coated polymer substrate that can be made by the method of the present invention or any embodiment of this method.

[0011] High dynamic deposition rates can be achieved by the method of the present invention. Specifically, by using this method, it is possible to obtain silicon oxide-based layers that are firmly adhered to polymer substrates at high dynamic deposition rates. Furthermore, the substrates coated in this manner may exhibit a limited amount of deformation. The inventors have discovered that this is possible by optionally combining the use of a linear hollow cathode PECVD apparatus, the use of a specific plasma power density, and the requirement that the ratio of the reactive gas flow rate to the gaseous precursor flow rate is preferably at least that required to obtain the layer. The layer, when deposited on a polymer substrate, can also be optimized with respect to its optical properties, specifically its transmittance. The silicon oxide-based layers deposited by the method of the present invention exhibit low stress, and the substrate is subjected to low thermal loads during the coating process. It is believed that the resulting coated substrates exhibit low deformation and high coating adhesion for these reasons.

[0012] The PECVD method of the present invention exhibits one or more of the above-listed processing advantages: high dynamic deposition rates of at least 200 nm×m / min, ease of processing on an industrial scale, excellent uniformity of the resulting layers (thickness variation <5%), low heat transfer to the polymer substrate, especially in the absence of substrate cooling, low deformation of the polymer substrate, particularly thin polymer film substrates, and modest installation costs.

[0013] The above and further aspects of the invention will now be described in more detail, by way of example, and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a low-pressure PECVD apparatus containing one linear hollow cathode plasma source, which contains a pair of electrodes to coat a polymer substrate with silicon oxide.

[0015] [Figure 2] 1 shows a cross-sectional view of a roll-to-roll coating apparatus for carrying out the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] These figures are not drawn to scale.

[0017] The method preferably requires a low pressure PECVD apparatus operating in an enclosure at a pressure of 0.005-0.025 Torr, preferably 0.010-0.020 Torr, more preferably 0.013-0.015 Torr, which apparatus comprises an AC or pulsed DC generator (the frequency of which is advantageously 5-150 kHz, preferably 5-100 kHz) or a linear hollow cathode plasma source connected to a DC generator.

[0018] Examples of PECVD devices are described below. The PECVD device may be provided in a vacuum chamber. This vacuum chamber is preferably arranged so that different devices providing different deposition modes or surface treatments can be placed next to each other. In some cases, these devices allowing different deposition modes are flat or rotating cathodes for magnetron sputtering deposition. This vacuum chamber may in particular be combined with a means for transporting the substrate. In particular, this vacuum chamber may be combined with a means for transporting thin polymer films along each deposition device in a roll-to-roll manner.

[0019] The PECVD apparatus of the present invention may consist of a hollow cathode plasma source, which includes, for example, at least one pair of electrodes connected to an AC or pulsed DC generator through which an electrical discharge occurs, and an opening in the electrodes through which the plasma is emitted. In preferred embodiments, the hollow cathode plasma source includes at least two, three, or four pairs of electrodes. Each electrode or cavity is connected to a pipe through which a gas or gas mixture that is ionized when an electrical discharge occurs can be introduced into the cavity.

[0020] A "PECVD apparatus including a linear hollow cathode plasma source" is understood to mean a linear plasma-enhanced chemical vapor deposition source including one or more pairs of electrodes configured to generate a hollow cathode discharge. An example of a hollow cathode plasma source is described in U.S. Pat. No. 8,652,586 to Maschwitz, which is incorporated herein by reference in its entirety. Figure 1 shows a hollow cathode-type plasma source that can be used in the present invention. The plasma source includes at least one pair of linear hollow cathode electrodes (1a) and (1b) arranged side-by-side in parallel and connected via an AC power supply (not shown). An electrically insulating material (9) is disposed around the hollow cathode electrodes. Plasma-generating gas is supplied through inlets (5a) and (5b). Precursor gas is supplied through precursor gas inlet (6) and directed into the plasma curtain (3) through a manifold (7) and a precursor injection slot (8) in the dark space between the electrodes. The AC power supply supplies a variable or alternating bipolar voltage to the two electrodes. The AC power supply first drives the first electrode to a negative voltage, enabling the formation of plasma, while the second electrode is driven to a positive voltage to function as the anode for the voltage application circuit. The power supply then drives the first electrode to a positive voltage, reversing the roles of cathode and anode. Because one of the electrodes is driven negative (1a), a discharge (2a) occurs in the corresponding cavity. The other electrode then forms the anode, causing electrons to escape the plasma through the outlet (10) and migrate to the anode side, completing the electrical circuit. In this way, a plasma with a curtain shape (3) is formed along the length of the electrodes in the region between the first and second electrodes above the substrate (4). While the substrate (4) is depicted here as a single polymer sheet, it could be, for example, a long ribbon shape in a roll-to-roll coating system. This method of driving the hollow cathode with AC power contributes to the formation of a uniform, linear plasma across the entire polymer substrate, perpendicular to the direction of movement (11) of the polymer substrate. In this patent, the electron emitting surface of the electrode is sometimes referred to as the plasma generating surface.

[0021] "Closed-circuit electron drift" is understood to mean electron flow caused by crossed electric and magnetic fields. In many conventional plasma-forming devices, closed-circuit electron drift forms a closed circuit or "racetrack" for electron flow. The hollow cathode PECVD device of the present invention operates without closed-circuit electron drift.

[0022] "AC power" is understood to mean power from an alternating current source whose voltage varies at a frequency in the form of a sine wave, square wave, pulse wave, or other waveform. The voltage variation often occurs from negative to positive relative to ground. In the bipolar form, the power output delivered by the two conductors is generally approximately 180 degrees out of phase.

[0023] The "electrodes" provide free electrons during plasma generation, for example, while they are connected to a power supply that provides a voltage. The two electron-emitting surfaces of the hollow cathode together are considered to be one electrode pair. The electrodes can be made from materials well known to those skilled in the art, such as steel, stainless steel, copper, or aluminum. However, in the case of plasma-enhanced deposition methods, these materials should be carefully selected, as different gases may require different electrode materials to ignite and maintain the plasma during operation. Coatings on the electrodes can also improve their performance and / or durability.

[0024] The PECVD apparatus may be particularly suitable for use in continuous coating processes in which the substrate is not fixed below the PECVD apparatus but is instead continuously moved below the PECVD apparatus, and the substrate may be moved in a direction perpendicular to the length of the plasma source.

[0025] The power density of a plasma is defined as the power dissipated in a plasma generated by one or more electrodes in relation to the size of the plasma.

[0026] The "linear meter of plasma," also referred to herein as the "total plasma length," is defined as the distance between the edges of the plasma generated by one pair of electrodes in a direction transverse to the direction of movement of the polymer substrate being coated. If the plasma source includes more than one pair of electrodes, the total plasma length is defined as the sum of the distances between the edges of the plasma generated by each pair of electrodes in a direction transverse to the direction of movement of the polymer substrate being coated.

[0027] In a linear hollow cathode plasma source, the "power density of the plasma" can be defined as the total power applied to the source divided by the total length of the plasma.

[0028] According to the present invention, a reactive gas based on oxygen (O2) or an oxygen-containing derivative can be used, the latter preferably being selected from the group consisting of ozone, hydrogen peroxide, water, and CO2. According to an embodiment, the reactive gas can advantageously further comprise an inert gas, such as helium, nitrogen, argon, neon, or krypton, to promote chemical dissociation of the precursor and control ion bombardment by the source. In an advantageous embodiment, the reactive gas is selected from O2 or an O2 inert gas mixture (e.g., an O2-Ar mixture). Such an ionizable reactive gas or gas mixture is introduced into the cavity of the electrode of the plasma source at a specific flow rate, which can be controlled by a mass flow meter that can be placed in the pipe between the gas reservoir and the plasma source. When an O2 inert gas mixture is used, the ratio of O2 to the inert gas (e.g., O2 to Ar), defined by the ratio of the flow rate of O2 to the flow rate of the inert gas, is in the range of 2 to 50, preferably 10 to 30, and very advantageously 15 to 25.

[0029] The precursor gas of silicon oxide is preferably injected uniformly along the length of the plasma source, preferably between at least two electrodes of the electrode pair of the plasma source. This precursor gas is activated when it comes into contact with the plasma. The substrate is brought close to the plasma source, thus being exposed to the activated precursor, and a thin silicon oxide-based layer is deposited on the substrate from the activated precursor gas. The precursor gas can be gaseous under standard temperature and pressure conditions, i.e., near room temperature and near atmospheric pressure. The precursor gas can be solid or preferably liquid under standard temperature and pressure conditions, and can also be an already vaporized precursor.

[0030] The amount, ie, flow rate, of the reactive gas or gas mixture and precursor gas injected into the plasma is controlled, for example, by liquid or vapor mass flow meters.

[0031] The operating pressure range of the plasma source is advantageously 0.005 to 0.025 Torr. The PECVD apparatus for the method of the present invention is advantageously provided in a vacuum chamber maintained at a pressure of 0.005 to 0.025 Torr, which pressure can be maintained by vacuum pumping means while injecting the various reactant and precursor gases. Vacuum pumping is preferably provided by a turbomolecular pump connected to the vacuum chamber surrounding the plasma source, preferably configured to provide uniform gas flow rates upstream and downstream of the PECVD apparatus. Preferably, pumping is provided at least on the side of the substrate being coated. Optionally, pumping is also provided on the side of the substrate opposite the side being coated.

[0032] In certain embodiments of the present invention, the ratio of reactive gas to precursor gas is sufficient to convert at least all of the C, H, and Si in the precursor molecules to CO, HO, and SiO. Specifically, the ratio of oxygen atoms in the reactive gas to precursor molecules is at least 2 O atoms per precursor molecule, and advantageously 5-30 O atoms per precursor molecule.

[0033] Furthermore, in advantageous embodiments of the present invention, the amount of oxygen or oxygen-containing derivative is sufficient to convert at least potentially all of the carbon, hydrogen, and / or silicon of the precursor to CO, HO, and SiO, i.e., the carbon, hydrogen, and silicon-containing portions of the precursor are converted to C x H y Si z where the amount of oxygen atoms provided, q, is preferably at least q=2x+0.5y+2z. Indeed, it has been found that lower amounts of oxygen increase absorption in silicon oxide-based films.

[0034] More specifically, the ratio of the power per linear meter of the plasma source to the pressure in the vacuum chamber (i.e., the power density) is preferably 1.5 (kW / m) / mTorr or less, more preferably 0.9 (kW / m) / mTorr or less, and even more preferably 0.8 (kW / m) / mTorr or less. It has been found that by limiting this power to pressure ratio, the temperature rise of the substrate during the coating process remains very moderate. Specifically, the substrate temperature can be maintained at 60°C or less, preferably 50°C or less, and more preferably 45°C or less, especially in the absence of additional substrate cooling means.

[0035] That is, in certain embodiments of the present invention, by controlling the ratio of power density to pressure as described above, the increase in substrate temperature due to the methods of the present invention in the absence of additional substrate cooling means is less than 40° C., advantageously less than 30° C., and more advantageously less than 25° C. The substrate temperature can be measured using thermocouples or otherwise estimated using irreversible temperature monitoring labels.

[0036] In certain embodiments of the invention, the temperature reached by the substrate during the PECVD process is at least 20° C., alternatively at least 25° C., alternatively at least 30° C. This temperature reached by the substrate is maintained throughout the coating process in the absence of cooling means for the substrate.

[0037] In certain embodiments of the present invention, the ratio of power per linear meter of the plasma source to the pressure in the vacuum chamber is advantageously at least 0.2 (kW / m) / mTorr, more advantageously at least 0.4 (kW / m) / mTorr, and even more advantageously at least 0.6 (kW / m) / mTorr. Under these conditions, it has been found that substrate etching damage is very low or even completely absent.

[0038] Still other coating or surface treatment processes may, of course, require substrate cooling means either remote from the PECVD apparatus or close to the PECVD apparatus.

[0039] Preferably, in any embodiment of the present invention, the source of the PECVD apparatus may have dimensions of 250 mm to 4000 mm in length and 300 to 600 mm in width per pair of electrodes.

[0040] In any embodiment of the present invention, a power density is applied between the two electrodes such that the power density can be between 1 and 50 kW per linear meter of plasma, preferably between 2 and 30 kW per linear meter of plasma, and more preferably between 3 and 15 kW per linear meter of plasma. Above 50 kW per meter of plasma, powder formation in the gas phase can be observed, which is detrimental to the quality of the deposition.

[0041] The silicon oxide precursors that can be used in any embodiment of the present invention depend on the nature of the layer to be deposited. These are specifically gaseous or volatile products at the temperature and pressure at which the method is carried out. Silicon oxide precursors are commonly SiH4 (silane), TMDSO (tetramethyldisiloxane), and HMDSO (hexamethyldisiloxane), although this list is not comprehensive.

[0042] The flow rate of the gaseous precursor is 50-700 sccm (standard cubic centimeters per minute) per linear meter of the plasma source, preferably 150-500 sccm or 200-500 sccm per linear meter of the plasma source. This range is necessary to obtain the high deposition rates appropriate for this technique, preferably on the order of 200-400 nm×m / min.

[0043] The present invention further specifically relates to silicon oxide-based layers deposited using any embodiment or any combination of embodiments of the method of the present invention.

[0044] The present invention also relates to a polymer at least partially coated with a silicon oxide-based layer of the present invention.

[0045] The silicon oxide-based layer of the invention can have a geometric thickness of 2 to 1500 nm, preferably 20 to 800 nm, in particular 30 to 600 nm. The thickness selected depends on the desired technical effect of the substrate thus coated.

[0046] In certain embodiments of the present invention, the silicon oxide-based layer is in direct contact with the polymer substrate. In certain other embodiments of the present invention, other layers are present between the polymer substrate and the silicon oxide-based layer.

[0047] Preferably, the silicon oxide based layer of the present invention is SiO 2-x where x is 0 to 0.5. In certain embodiments, the silicon oxide-based layer comprises or consists essentially of SiO2. The silicon oxide-based layer of the present invention specifically contains H, C, N, Cl, CH z derivative, NH y Derivatives and OH yIt may contain up to 10 atomic % of precursor residues from the group consisting of derivatives (y is 1 to 4). This content is preferably determined by photoelectron spectroscopy (XPS) or secondary ion mass spectroscopy (SIMS), but it can also be determined by analytical techniques such as Raman spectroscopy, ion beam analysis such as NRA and RBS.

[0048] The silicon oxide-based layers of the present invention are amorphous and homogeneous throughout the thickness of the layer, as can be determined by cross-sectional transmission electron microscopy (TEM). Specifically, there is no detectable transition in the silicon oxide-based layer from a composition containing more organic residue to a composition with no organic residue at all.

[0049] The polymer substrates of the present invention can be homogeneous polymer sheets, although other shapes are possible. They may not contain fibers. Alternatively, they may contain glass fibers in an otherwise homogeneous polymer matrix. In particular, they may not be fiber-based woven or fabric-based. A silicon oxide-based layer may be present on at least a portion of the polymer, for example, on one side of a polymer sheet or on the entire polymer substrate.

[0050] The polymer substrates of the present invention may include acrylic polymers, polymethyl methacrylate (PMMA) and its copolymers, CR-39 or allyl diglycol carbonate (ADC), polycarbonate, polypropylene (PP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene, cyclic olefin copolymers (COCs), and polyethylene terephthalate glycol (PETG), as well as combinations of the above. The polymer substrates of the present invention may include thermoplastic elastomers (TPEs), sometimes called thermoplastic rubbers, which are a class of copolymers or physical blends of polymers (usually plastics and rubbers) that consist of materials that have both thermoplastic and elastomeric properties. Specifically, the polymer substrate may include styrene block copolymers (TPS (TPE-s)), thermoplastic polyolefin elastomers (TPO (TPE-o)), thermoplastic vulcanizates (TPV (TPE-v or TPV)), thermoplastic polyurethanes (TPU (TPU)), thermoplastic copolyesters (TPC (TPE-E)), thermoplastic polyamides (TPA (TPE-A)).

[0051] The polymer substrate can be a thin polymer film having a thickness comprised between 5 μm and 300 μm, alternatively between 10 and 250 μm, alternatively between 20 and 200 μm, or alternatively between 25 and 150 μm. These thin polymer films can be processed, for example, in a roll-to-roll manner, as shown in FIG. 2. In FIG. 2, a polymer film substrate (29) is unwound from an unwind roll (21) and redirected on roll (27) toward a main roll (25) on which the inventive coating process occurs. The polymer film is then directed on roll (28) to be wound onto a take-up roll (22). The inventive coating process is carried out using a PECVD apparatus (23) that generates a plasma (26) on the surface of the polymer substrate, where a silicon oxide precursor is activated to form a silicon oxide coating on the polymer film substrate. The arrows in FIG. 2 indicate the direction of movement of the thin polymer film. The direction of the film can be reversed to repeat the coating process by moving the polymer film substrate in the opposite direction. Additional surface treatment or coating equipment (24) can be placed near the PECVD apparatus of the present invention. These thin polymer films can include, among others, PET, PMMA.

[0052] The application of the method is related to the properties of the layer deposited on the substrate.Various embodiments of the invention for different applications are described below.

[0053] The substrate is very advantageously a conventional polymer substrate or polymer film, such as a polyethylene-based polymer film. In the context of the present invention, the substrate may, for example, be a substrate already pre-coated with another layer that also has barrier layer properties.

[0054] In FIG. 1, the PECVD apparatus shown is a linear dual-beam plasma source (10) containing two cavities (13) where the discharge occurs and an opening (14) from which it is emitted. Each cavity contains an electrode (12) connected to a generator (11) that generates alternating current (AC) or pulsed DC. The plasma source includes a series of magnets (15) aligned along the cavity, facing each other. Gas injected into each cavity is thus ionized, forming an ion beam, known as the source of plasma (16), which is emitted out of the plasma source through the opening (14) toward the substrate (30) to be coated. The arrow indicates the forward direction of the substrate during deposition. The total width of the plasma is represented by "w," and the total length of the plasma refers to that portion measured perpendicularly, i.e., transversely to the substrate's direction of travel.

[0055] It is to be noted that the invention relates to all possible combinations of the features recited in the claims.

[0056] In the present invention, ranges of values ​​stated as lying between limits are intended to include those limits. [Example]

[0057] Silicon oxide-based coatings were deposited on PET sheets of different thicknesses using different precursors, as shown below. The sheet dimensions were approximately 210 mm x 297 mm. The PECVD apparatus used a hollow cathode plasma source containing two pairs of electrodes, each 40 cm long. Therefore, the total length of the generated plasma was 2 x 40 = 80 cm.

[0058] The indicated flow rates in sccm are for a temperature of 273.15 K (0 °C, 32 °F) and 10 5 Calculated in terms of absolute pressure in Pa (100 kPa, 1 bar).

[0059] Temperature was checked using THERMAX® irreversible temperature monitoring labels, which have sensitivity in the temperature range of 37-65°C.

[0060] The precursor used was SiH4 for Examples 1-15 and TMDSO for Examples 16-31. The substrates were attached to a 4 mm glass sheet and transported at a continuous speed on a roller conveyor below the PECVD source in a direction transverse to the length of the source. The reactant for Examples 1-31 was O2. Other deposition parameters are shown in Table 1 below.

[0061] TIFF0007730328000001.tif234170

[0062] Table 2 below shows the power / pressure ratio, substrate temperature, coating thickness and transmittance measured at an observer angle of 2° using illuminant D65. Coating thickness was measured using a Dektak® stylus profiler at the edge of the substrate area that was masked during coating deposition.

[0063] TIFF0007730328000002.tif235170

[0064] The silicon oxide layers of Examples 1-15 deposited above had carbon contents below the detection limit of X-ray photoelectron spectroscopy when deposited on glass samples for comparison. The silicon oxide layers of Examples 16-31 had carbon contents of 3-10 atomic percent. For samples deposited using a power density / pressure ratio greater than 0.5 (kW / m) / mTorr, the carbon content was 3-8 atomic percent.

[0065] The stress of the silicon oxide layer caused very little deformation of the thin PET substrate: all of the coated examples remained perfectly flat when observed with the naked eye with the coated sheet placed on a flat sheet of glass.

Claims

1. 1. A method for producing a silicon oxide based layer on a polymer substrate, the method comprising the steps of: a. providing a polymer substrate; b. providing a low-pressure PECVD apparatus for the deposition of silicon oxide-based layers on polymer substrates, comprising at least one linear hollow cathode plasma source, wherein each linear hollow cathode plasma source comprises at least one pair of electrodes connected to an AC, DC, or pulsed DC generator; c. applying power to the linear hollow cathode plasma source such that the power density of the plasma is between 1 kW and 50 kW per linear meter of length of the linear hollow cathode plasma source; d. applying to the polymer substrate a gaseous precursor of an oxide of silicon and a reactive gas based on oxygen or an oxygen-containing derivative, wherein the gaseous precursor is applied at a flow rate of 50-700 sccm per linear meter of length of the linear hollow cathode plasma source, the gaseous precursor being injected between the electrodes of each electrode pair of the linear hollow cathode plasma source, and the reactive gas is applied at a flow rate of 1500-4000 sccm per linear meter of length of the linear hollow cathode plasma source, the reactive gas being injected between the electrodes of the linear hollow cathode plasma source; Including, The PECVD apparatus is provided within a vacuum chamber maintained at a pressure of 5 to 25 mTorr, and the ratio of the power density per linear meter of length of the linear hollow cathode plasma source, expressed in kW / m, to the pressure in the vacuum chamber, expressed in mTorr, is 1.5 or less.

2. A method for producing a silicon oxide-based layer on a polymer substrate as described in claim 1, wherein the ratio of the power density per linear meter of length of the linear hollow cathode plasma source expressed in kW / m to the pressure in the vacuum chamber expressed in mTorr is 0.2 or more.

3. The reactive gas was pure O ２ and O ２ and a mixture of an inert gas, ２ When a mixture of inert gases is selected, the ratio of O to the flow rate of the inert gas in the mixture is ２ 3. The method for producing a silicon oxide based layer on a polymer substrate according to claim 1, wherein the ratio of the flow rates of:

4. The precursor of silicon oxide is SiH ４ 4. A method for producing a silicon oxide based layer on a polymer substrate according to any one of claims 1 to 3, wherein the silicon oxide based layer is selected from the group consisting of TMDSO, HMDSO and HMDSO.

5. 5. A method for producing a silicon oxide based layer on a polymer substrate according to any one of claims 1 to 4, wherein power is applied to the linear hollow cathode plasma source such that the power density of the plasma is between 2 kW and 30 kW per linear meter of length of the linear hollow cathode plasma source.

6. 6. A method for producing a silicon oxide based layer on a polymer substrate according to any one of claims 1 to 5, wherein power is applied to the linear hollow cathode plasma source such that the power density of the plasma is between 3 kW and 15 kW per linear meter of length of the linear hollow cathode plasma source.

7. 7. A method for producing a silicon oxide based layer on a polymer substrate according to any one of claims 1 to 6, wherein the flow rate of the gaseous precursor is between 150 and 500 sccm per linear meter of length of the linear hollow cathode plasma source.

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