CN1037702Y - Coating - Method and Apparatus for Glass Substrates - Google Patents

Abstract

Apparatus (10) for applying a coating to a substrate, comprising a gas distributor (14) with an outlet (30) located adjacent to the substrate for directing a gaseous reactant mixture to the substrate s surface. A set of downcomers (24) communicating and spaced along the length of the distributor are provided for supplying the gaseous reactant mixture to the distributor. The apparatus includes means for determining the thickness uniformity of the coating (38) applied to the substrate along the width. Finally, means are provided for supplying one or more reactants or an inert gas to the one or more downcomers to alter one or more reactions in the gaseous reactant mixture flowing through the one or more downcomers concentration of the substance. Consequently, the deposition rate of the coating near the downcomer is varied, thereby improving the uniformity of the deposited coating.

Description

Coating - method and apparatus for glass substrates

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for coating a substrate, particularly a glass substrate. More particularly, the present invention relates to a continuous chemical vapor deposition (CVD) process for producing coated glass for use in vehicle or architectural doors and windows, and an apparatus for producing the coated glass.

2. Overview of the Related Art Chemical vapor deposition processes are well known in the field of coating substrates. The substrate is coated by directing a beam of gaseous reactant mixture onto the surface of the substrate such that the reactant mixture deposits the desired coating on the surface of the substrate. The physical form of the coating reactants employed in this process can be liquids, vapors, liquids or solids dispersed in a gaseous mixture, suspended particles, or vaporized or aerosolized coating reactants dispersed in a gaseous mixture.

One of the problems associated with the CVD process involves producing a coating of uniform thickness along the width of the substrate. In some cases, such as applying a reflective metal oxide coating to a glass sheet, the requirement that the coating thickness must be uniform is particularly important because small variations in coating thickness can result in non-uniform glass sheet thicknesses. color. For example, a millionth of an inch variation in metal oxide coating can create an unattractive appearance on glass.

Generally speaking, in order to produce a coating of constant thickness, the gaseous reactant mixture must be uniformly spread over the entire glass sheet. Various devices have been proposed for coating a glass plate with a mixture of gaseous reactants in a uniform manner. For example, US Patent No. 4,504,526 discloses an apparatus comprising a series of individual passages interconnecting an inlet and an outlet located adjacent to a glass sheet. Each individual channel includes a portion with a cross-sectional area that differs from that of an adjacent channel, so that the velocity of fluid flowing through the channel varies.

In US Patent No. 4,535,000, Gordon describes a chemical vapor deposition process for coating a metal nitride film on a glass substrate. Gordon suggests using multiple applicators as a means of obtaining a uniform coating, since the non-uniformity of one applicator is usually not as good as that of the other applicators and tends to cancel out the differences from the different applicators Thickness error.

As taught by Sopko et al. in US Pat. No. 3,580,679, a gaseous mixture is distributed along the substrate by a gaseous manifold comprising a set of gaseous passages spaced from each other at their outlet ends, but these The vapor passages converge in a common passage at their inlets. To improve the uniformity of vapor deposition, it is recommended that each channel includes at least two opposing curved surfaces so that the vapor flowing through the channel changes direction at least twice. In addition, Sopko noted that baffles can be placed within the channels to further disrupt the gaseous flow stream and distribute the gasification along the length of the gasification manifold.

Despite the various devices previously proposed, some examples of which are listed above, there are still problems associated with applying a uniform thickness coating to a substrate using a chemical vapor deposition process. The reasons for this non-uniformity are variable, but may include exhaust gas balance, temperature differences across the substrate to be coated, dimensional changes in the coating equipment when heated, changes in the Reynolds number of the entry zone and consequent changes in total flow , and the accumulation of fouling in the applicator. Whatever the reason, it would be most advantageous to provide a method and apparatus to eliminate any problems of poor uniformity of coating thickness applied to a substrate in a chemical vapor deposition process.

SUMMARY OF THE INVENTION The present invention relates to an apparatus for applying a coating to a substrate using a chemical vapor deposition process. The apparatus includes a gas distributor with an outlet located adjacent the substrate to be coated for directing a gaseous reactant mixture to the surface of the substrate. The gaseous reactant mixture includes one or more reactants and an inert carrier gas. A set of downcomers communicating and spaced along the length of the distributor is provided for supplying the gaseous reactant mixture to the distributor. The apparatus includes means for determining the thickness uniformity of the coating applied to the substrate along the width. Finally, there is also a means for supplying one or more reactants or an inert gas to one or more downcomers to alter one or more reactants in the gaseous reactant mixture flowing through the downcomer concentration, that is, creates deliberate non-uniformity in the distribution of coating gas across the substrate to provide the desired uniform coating. The deposition rate of the coating near the downcomer is thus varied to improve the thickness uniformity of the deposited coating.

The present invention also relates to a method of applying a coating of substantially uniform thickness to the surface of a substrate. A gaseous distributor is supplied with a gaseous reactant mixture including one or more reactants and an inert carrier gas by means of a set of communicating downcomers spaced along the length of the distributor. A coating is formed on the substrate by directing the gaseous reactant mixture from the outlet of the dispenser adjacent the substrate surface to the substrate surface. Then, the thickness uniformity of the coating applied to the substrate at various locations along the width of the substrate is determined and one or more reactants or an inert gas are supplied to one or more individual downcomers to vary The concentration of one or more reactants in the gaseous reactant mixture flowing through the downcomer. This changes the deposition rate of the coating near the downcomer to improve the thickness uniformity of the deposited coating. In addition, introducing a sufficient amount of an inert gas into a downcomer will increase the static pressure within the downcomer, thereby increasing the overall flow of the gaseous reactant mixture to the remaining downcomers.

Therefore, the present invention provides a relatively simple and inexpensive apparatus for correcting for variations in coating thickness obtained in a CVD process. Furthermore, regardless of the original cause of poor uniformity, a more uniform coating can be obtained.

The above and other advantages of the present invention will be more readily apparent to those skilled in the art from the following detailed description with reference to the accompanying drawings, in which: Figure 1 is a somewhat schematic, partially cutaway perspective view showing The coating apparatus of the present invention, and FIG. 2 is a schematic block diagram of the apparatus of the present invention.

According to the present invention there is provided a method of applying a coating to the surface of a moving heated glass ribbon, comprising: a) providing a coating gas distributor extending across the width of the glass ribbon to be coated, b) in Two or more supply locations spaced along the length of the distributor supply a gaseous paint mixture comprising at least one gaseous reactant from the manifold to the distributor, c) supply the gaseous paint mixture from the distribution d) detecting at least one optical property of the coated product at spaced locations across the coated width, said optical property as a function of the thickness of said coating; and e) the gaseous state supplied at one or more of said spaced supply locations based on poor uniformity of the coating as detected by measurements of said optical properties In the coating mixture, the concentration of the at least one gaseous reactant supplied relative to the other one or more of said spaced supply locations is selectively varied to improve said uniformity.

There is also provided in accordance with the present invention an apparatus for applying a coating to a substrate by a chemical vapor deposition process, comprising: a) a gas distributor with an outlet located near the substrate to be coated for applying a coating comprising A gaseous reactant mixture of one or more reactants and an inert carrier gas directed to the surface of the substrate; b) a set of downcomers communicating and spaced along the length of the distributor for mixing the gaseous reactants body is supplied to the dispenser; c) detection means for determining the uniformity of the thickness of the coating applied to the substrate along the width of the substrate; and d) flow control means for introducing one or more reactants Or an inert gas is supplied to one or more of the downcomers to alter the concentration of one or more reactants in the gaseous reactant mixture flowing through the downcomers, thereby altering the properties of the coating in the vicinity of the downcomer. deposition rate to improve the uniformity of the thickness of the deposited coating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method and apparatus of the present invention may be employed in conjunction with various substrates and coatings, and may be used to coat a continuous sheet or a series of discrete substrates. In the preferred embodiment of the invention, a continuous glass sheet is coated. The glass sheet can be a glass sheet produced by a glass sheet production process, any flat glass production process, or a float glass production process. The following description refers to the coating of a moving float glass ribbon that has just been formed, either in the kiln or secondly in an attached lehr.

Furthermore, the methods and apparatus of the present invention may be applied to chemical vapor deposition of any one or more reactants or coating precursors. In the preferred embodiment, the method and apparatus of the present invention is used to deposit a titanium nitride film on a freshly formed float glass ribbon while it is supported on a molten tin bath. A mixture of titanium tetrahalide and preferably a reducing agent such as titanium tetrachloride and anhydrous ammonia is reacted on or near the surface of the glass plate on which the titanium nitride coating is to be deposited. The two reactants are preferably supplied in helium as an inert carrier gas. This method of making titanium nitride coatings is more fully disclosed in US Patent Nos. 4,545,000 and 5,087,525, both of which are incorporated herein by reference in their entirety.

Referring now to FIG. 1, an apparatus, generally designated 10, is shown for applying a coating to a substrate such as a continuous glass ribbon or sheet 12. As shown in FIG. The glass sheet 12 is typically supported on a molten tin bath (or rollers if coating is done in an annealing furnace) and moves along the trajectory shown by the lower right arrow in the figure. The production process requires that a glass substrate is typically formed during float glass production, and the glass sheet 12 is continuously fed while it is hot through the coating apparatus 10 shown in the figures. The coating equipment is usually located in a sealed area in which a non-oxidizing atmosphere is maintained. The non-oxidizing atmosphere is typically a gas comprising about 99% nitrogen by volume and 1% hydrogen by volume. However, other inert gases can be used in place of nitrogen, or the proportion of nitrogen can be increased or decreased, as long as the desired result, ie, prevention of oxidation of the tin bath, can be obtained.

More specifically, the coating apparatus 10 includes a vapor dispenser 14 positioned facing the glass sheet 12 and spanning the width of the glass sheet 12 . The gasification reactant mixture is supplied to the gasification distributor 14 by means of a supply assembly, which will be described in detail below. The first gasification reactant, usually mixed with an inert carrier gas such as nitrogen or helium, is supplied via supply line 16 to a mixing device 18 . In the mixing device 18 , the first gasification reactant is mixed with the second gasification reactant fed into the mixing device 18 via a supply line 20 . The second gasification reactant is also typically mixed with an inert carrier gas before being introduced into the mixing device 18 . Preferably the same carrier gas is used for both reactants.

A gaseous mixture consisting of the first and second reactants and a carrier gas (singular) or a mixture of carrier gases (plural) passes from the mixing device 18 to a jacketed manifold 22 . The jacketed manifold 22 can be used in a conventional manner to maintain the temperature of the gaseous compound mixture within the range required for the specific application conditions of any particular application and to provide a constant composition mixture along the length of the manifold. The gaseous compound mixture is supplied from the gas header 22 to the gaseous compound distributor 14 by means of a series of interconnected downcomers 24 . The downcomers 24 are generally spaced approximately evenly along the manifold 22 and the distributor 14 .

From the downcomer 24 , the gaseous mixture flows into a channel 26 formed in the distributor 14 . Channel 26 is preferably provided with a set of baffles 28 which force the gaseous compound mixture through a series of directional changes to distribute the gaseous compound mixture more uniformly along the length of distributor 14. This improves the uniformity of the coating deposited on the glass plate 12 . The gaseous mixture flows through the baffles 28 and out of the distributor 14 through the outlet 30, which is located adjacent to the glass plate 12. The first and second reactants within the gas mixture react on or near the surface of the glass sheet 12 , continuously depositing the desired coating on the glass sheet 12 as the glass sheet 12 passes through the distributor 14 .

The thickness of the coating deposited on the glass sheet 12 often varies across the width of the glass sheet 12, despite the provision of a series of spaced down pipes 24 that supply the gaseous compound mixture to the distributor 14, and a series of baffles 28 uneven. As mentioned above, this can be due to a number of factors, such as exhaust balance, temperature differences across the substrate to be coated, dimensional changes in the coating equipment when heated, changes in the Reynolds number of the entry zone and consequent changes in total flow, and build-up of scale on the equipment. When depositing a reflective coating on glass sheet 12, this non-uniformity can result in unacceptable variations in transmission and reflected color across the width of glass sheet 12.

To ameliorate any detectable non-uniformity in coating thickness, a connecting arm or side arm 32 is provided on a set of downcomers 24 of the coating apparatus 10 . In the preferred embodiment, all downpipes 24 are provided with a side arm 32 . Each side arm 32 communicates with a flow control device 36 via a separate supply line 34 . The flow control device 36 may be connected to a supply of one or more reactants. Alternatively, flow control device 36 may also be connected to a supply of inert gas (preferably the same inert gas used as the carrier gas for the reactants). In the preferred embodiment, flow control device 36 is connected to both a supply of one or more reactants and a supply of inert gas. Flow control device 36 controls the flow of one or more reactants or an inert gas (or both) through separate supply lines 34 (shown schematically). Flow control device 36 may be any suitable device for controlling this flow, such as a Dierra mass flow controller available from Sierra Instruments, Inc. of Montetey, California.

If it is determined that the coating deposited on the glass sheet 12 in a particular area is too thin, the flow control device 36 is activated to supply one or more reactants via the associated supply lines 34 and sidearms 32 to the chamber located at that particular area. One or more downcomers 24 . Since the reaction rate of film formation on the glass sheet 12 depends on the concentration of gas phase reactants above the glass sheet 12, an effective increase in the concentration of one of the reactants increases the deposition rate and thickness of the coating deposited in that particular area. In this manner, a more uniform coating thickness and color, and light transmission and/or solar coefficient, can be obtained over the entire width of the glass sheet 12 .

On the other hand, if it is determined that the coating deposited on the glass sheet 12 in a particular area is too thick, the flow control device 36 is activated to supply an inert gas via the associated supply line 34 and side arm 32 to the glass plate 32 located at that particular area. One or more downcomers 24 . Introducing an inert gas into a separate downcomer 24 reduces the concentration of reactants in the gaseous mixture passing through the downcomer 24, thereby reducing deposition on the glass sheet 12 in the area of the downcomer 24 rate. Furthermore, the introduction of additional inert gas into a downcomer 24, if sufficient in volume, will result in a certain static pressure increase in the downcomer 24 into which it is introduced. This reduces the total flow of gaseous-matter mixture to that downcomer 24 and increases the total flow of gaseous-matter mixture to the surrounding downcomers 24 . This again results in the deposition of a thinner coating near the downcomer 24 where the inert gas is introduced.

Figure 2 schematically shows the method of the present invention. The gasification reactants are supplied to jacketed header 22 via supply lines 16 and 20 and descend to distributor 14 via downcomer 24 . The gaseous mixture exits the distributor 14 through an outlet located near the glass plate 12. The first and second reactants in the gaseous mixture react at or near the surface of the glass sheet 12 , depositing the desired coating continuously thereon as the glass sheet 12 passes through the distributor 14 .

A thickness detection device 38 is preferably provided for detecting the thickness of the coating deposited on the glass plate 12. When depositing a reflective coating, the thickness is preferably detected by means of a photometer 38 located downstream of the coating apparatus 10. Thinner reflective coatings result in higher transmission coefficients and change the color of the reflection, which can be detected by a photometer. In the case of a titanium nitride coating deposited on a glass plate, a thinner coating results in a more negative value for the b* component of the reflected color, where b* measures the amount of color in the yellow basket on the CIE-Lab color scale . In this way, the uniformity of the coating thickness can be indirectly determined by measuring the b* component across the width of the glass sheet 12 . In a preferred embodiment, a profile scanning photometer is used to determine the thickness of the coating deposited along the width of the glass sheet 12.

The flow control device may be manually activated using manual control device 40 according to a visual output signal provided by any suitable device 38 for determining the thickness of the deposited coating. In another preferred embodiment, the thickness sensing device 48 is connected to a programmed controller 42 which is connected to the flow controller 36 and automatically activates the flow control device 36 in response to receiving a signal from the thickness sensing device 38. When the signal indicates that the non-uniformity of the coating thickness is outside a predetermined acceptable range programmed into the controller 42, the controller 42 activates the flow control device 36 to transfer one or more reactants or an inert gas Feed to one or more individual downcomers 24 to vary the concentration of one or more reactants in the gasification reactant mixture flowing through the downcomer 24 . Thus, the deposition rate of the coating near the downcomer is altered, thereby improving the thickness uniformity of the coating on the substrate.

In this application and the drawings, a preferred embodiment of the present invention is shown and described, and various modifications and changes are suggested, but it should be understood that they are not intended to be exhaustive and that other modifications may be implemented within the scope of the present invention and change. The recommendations contained herein have been chosen and included for purposes of illustration, so that those skilled in the art may more fully understand the invention and its principles, and be able to modify and implement it in various ways that are best suited to the conditions of a particular situation it. For example, it should be understood that any number of drop tubes and associated side arms, more than one, may be employed in accordance with the present invention, depending on the particular application.

Claims (25)

1. A method for applying a coating to the surface of a moving hot glass ribbon, comprising: a) a coating gas distributor extending across the width of the glass ribbon to be coated; b) along the distributor Two or more supply positions spaced apart by a length to supply a gaseous paint mixture comprising at least one gaseous reactant from the manifold to the distributor; c) directing the gaseous paint mixture from the distributor to the moving surface of the heated glass ribbon to form a coating on the heated glass surface; d) detecting at least one optical property of the coated product at spaced locations across the coated width, said optical property being dependent on said coating; varying in thickness of the layer; and e) in the gaseous paint mixture supplied at one or more of said spaced supply locations according to poor uniformity of the coating as detected by measurements of said optical properties , selectively varying the concentration of the at least one gaseous reactant supplied relative to the other one or more of said spaced supply locations to improve said uniformity. 2. The method of claim 1, wherein the gaseous coating mixture consists of one or more gaseous reactants and an inert carrier gas. 3. The method of claim 1, wherein selectively changing all of the reactants by adding additional reactants or inert gases to the mixture of gaseous reactants supplied at one or more of said spaced supply locations concentration of the at least one gaseous reactant. 4. The method of claim 1 wherein the gaseous paint mixture is supplied to the gas distributor by means of a set of downcomers that fluidly communicate the manifold with the gas distributor, the downcomers being along the distributor are spaced apart by the length of, and depending on the observed suboptimal uniformity, one or more reactants or an inert gas are supplied to one or more selected separate downcomers located between the manifold and the distributor to altering one or more reactants in the mixture of gaseous reactants flowing through the selected one or more downcomers relative to the one or more gaseous reactants flowing through the other one or more downcomers concentration, thereby changing the deposition rate of the coating in the vicinity of the selected one or more downcomers. 5. A method according to the preceding claim 4, characterized in that the thickness of the coating is determined indirectly by detecting the color of the reflection. 6. The method of claim 5, wherein the thickness of the coating is determined indirectly by detecting the color reflected from the side of the glass. 7. The method of claim 6, wherein the thickness of the coating is determined indirectly by detecting the b* component of the glass side reflected color. 8. The method of claim 1, wherein the thickness of the coating applied to the glass ribbon is indirectly determined by detecting the transmittance of the coated glass ribbon. 9. The method of claim 5, wherein a photometer is used to detect the reflected color. 10. The method of claim 9, wherein the reflected color is detected with a profile scanning photometer. 11. The method of claim 1, wherein one or more gaseous reactants or an inert gas are supplied to one or more separate supply locations by means of a mass flow controller. 12. The method of claim 4, wherein the one or more reactants or an inert gas is supplied to one or more downcomers by means of a mass flow controller. 13. The method of claim 12, wherein one or more gaseous reactants are supplied to one or more downcomers near an area where the thickness of the deposited coating is observed to be greater than that observed in other areas The resulting coating thickness should be thin. 14. The method of claim 12, wherein an inert gas is supplied to one or more of said downcomers in the vicinity of an area where the thickness of the deposited coating is observed to be greater than that observed in other areas The coating thickness should be thicker. 15. The method of claim 4, wherein a gaseous mixture comprising a titanium tetrahalide, a reducing agent and an inert carrier gas is supplied to the gas distributor via the downcomer. 16. The method of claim 4, wherein a gaseous mixture of titanium tetrachloride and ammonia contained in helium as an inert carrier gas is supplied to a gas distributor by means of the downcomer. 17. The method of claim 1 wherein the selective change is controlled by a programmable controller connected to a detection device arranged to detect said optical property. 18. A device for applying a coating to a substrate by a chemical vapor deposition process, comprising: a) a method for directing a gaseous reactant mixture comprising one or more reactants and an inert carrier gas to the substrate A gas distributor for the surface of the sheet with an outlet located near the substrate to be coated; b) a set of communicating gaseous reactant mixtures to supply the distributor and spaced along the length of the distributor an open downcomer; c) a detection device for measuring the uniformity of the thickness of the coating applied to the substrate along the width of the substrate; and d) for supplying one or more reactants or an inert gas to a flow control means for one or more of said downcomers to vary the concentration of one or more reactants in the gaseous reactant mixture flowing through said downcomer, thereby altering the deposition rate of the coating in the vicinity of said downcomer, Improve the uniformity of the thickness of the deposited coating. 19. Apparatus as defined in claim 18 including a manifold for initially delivering a constant composition gaseous precursor dope mixture to all of said downcomers. 20. The apparatus as defined in claim 18, further comprising a programmable controller coupled to said detection means, which automatically activates said flow control means in response to receipt of a signal from said detection means. 21. The apparatus as defined in claim 20, wherein said detection means comprises a photometer. 22. The apparatus as defined in claim 21, wherein the photometer comprises a profile scanning photometer. 23. The apparatus as defined in claim 18, wherein said flow control means comprises a mass flow controller. 24. The apparatus as defined in claim 18, wherein one set of said downcomers is provided with side arms connected to said flow control means by separate supply lines. 25. Apparatus as defined in claim 24, wherein each of said downcomers is provided with a side arm connected to said flow control means by a separate supply line.