TITANIUM NITRIDE OR TIN OXIDE BONDING TO A COATER SURFACE

Abstract: A coater (10), which is used to deposit a compound on a glass sheet (12) has its surface (34, 56) roughened. That portion of the compound which tends to accumulate on the coater surface bonds to the roughened coater surface such that it does not peel away from the surface during application of the compound to the glass.

Description: TITLE Titanium nitride or tin oxide bonding to a coater surface BACKGROUND AND BRIEF SUMMARY OF THE INVENTION Glass and other transparent materials can be coated with transparent semi-conductor films such as tin oxide in order to reflect infra-red radiation. Such materials are useful in providing windows with enhanced insulating value (lower heat transport) for use in architectural windows, etc.; see for example, RE 31,708. The coating of glass with a titanium nitride coating for a solar control purposes is also known, see U.S. Patent 4,535,000. A glass coated first with titanium nitride and subsequently with tin oxide is disclosed in U.S. Patent 4,690,871. Coatings on glass of either tin oxide or titanium nitride or both, and also in combination with other coatings such as iridescence suppression coatings are now enjoying commercial acceptance. When a glass surface is to be coated first with titanium nitride and then overcoated with tin oxide, these coatings are applied in sequence. That is, a first coater will deposit the titanium nitride and subsequently a second coater will deposit the tin oxide. Ideally, it would be desirable to control the fluid flow characteristics of the reactants which form the titanium nitride and tin oxide and the spatial relationship between the coater surfaces overlying the moving glass surface, such that the titanium nitride and tin oxide which are formed, would only deposit on the moving glass surface. As a practical matter this has not been possible to achieve with the result that titanium nitride will build up or coat the coater surface overlying the glass surface on which the titanium nitride is deposited by reaction of titanium tetrachloride and ammonia. Similarly, the tin oxide coats the coater surface overlying the glass surface on which the tin oxide is deposited by reaction of tin tetrachloride and water vapor. The build-up of these coatings on the surfaces of the coaters is uneven and sometimes tends to peel or flake away from the coater surface during a production run. The peeling or flakes which remain attached to the surface disturb the reactant gas flow patterns and cause bands or other irregularities in the coating on the glass. Accordingly, it is an object of this invention to prevent these deposits of titanium nitride or tin oxide from peeling or flaking from the coater surfaces. Broadly the invention comprises treating the coater surface on which the build-up of these compounds occurs to enhance the bonding of the compounds to the surface and thereby prevent or inhibit the peeling and flaking. Prior to depositing a coating, the coater surface is prepared by roughening the surface. The roughened surface provides an increased surface area for an interlocking or keyed fit between the coating and the coater surface thereby strengthening the adhesive bond between the coating and the surface. The roughening can be carried out by sand blasting, filing, machining with a knurling tool or other methods that will be clear to those skilled in the art. Subsequent to the roughening of the surface, the surface is cleaned such as by blowing the remaining loose particulates away from the surface by compressed air. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross section side elevation of a coater used for depositing titanium nitride on a glass surface followed by an overcoating of tin oxide; and Figure 2 is a cross section view of a roughened surface. DESCRIPTION OF THE PREFERRED EMBODIMENT (S ) The invention will be described with reference to roughening coater surfaces of coaters which are used for the sequential deposition of titanium nitride and tin oxide on a moving glass surface. The coatings can be deposited using, for example, the reactant systems known in the art, i.e., those described in U.S. Patent No. 4,535,000 for titanium nitride and U.S. Patent No. 4,585,674 for tin oxide. In a production run, a coating of about 400 angstroms of titanium nitride can be followed by a coating of 300 angstroms of fluorine-doped tin oxide. Referring to Figure 1, an exemplary coater is shown generally at 10 installed between a float tank 14 and an annealing lehr (not shown) . Alternatively, one or both of the coaters may be positioned in the float tank, in which the glass floats on liquid tin. A glass sheet 12 exits from the float tank 14 and travels through a horizontal galley 16 while supported on rollers 18. Adjacent the exit end of the float tank is a first coating apparatus 20. Nitrogen; titanium tetrachloride and nitrogen; and ammonia and nitrogen are introduced into feed conduits 20, 22 and 24 and are discharged through transverse slots 26, 28 and 30. Downstream of the conduit 24 is an exhaust conduit 32. The surface of the underside of the coater section 34 is primarily affected by the build up of titanium nitride. A coater 40 similar to the coater 20 has three feed conduits 42, 44 and 46 into which gaseous reactants nitrogen; stannic chloride and nitrogen; and air, water vapor and hydrogen fluoride respectively are introduced. The gases are discharged through transverse slots 48, 50 and 52 respectively. At the downstream end of the coater 40 there is a discharge conduit 54. The surface of the underside of the coater section 56 is primarily affected by the build up of tin oxide. When the coaters start coating the glass, the surfaces of the sections 34 and 56 of the coaters 20 and 40 commence to build up layers of titanium nitride and tin oxide respectively. For a conventional smooth coater surface, when the titanium nitride reaches an average thickness of about 0.2 to 1 mm, then peeling, flaking and unevenness commences to develop causing irregularities in the coating deposited on the moving glass surface. When the tin oxide reaches an average thickness of between 0.5 to 2 mm on a smooth coater, then peeling, flaking and unevenness commences to develop causing irregularities in the coating deposited on the moving glass surface. For a typical production run with smooth coaters producing titanium nitride followed by an overcoating of tin oxide with the glass moving at 300 inches per minute, the run or coating operation can continue generally for about an hour before the peeling is severe enough to affect the quality of the coating. To enhance the adhesion of the coatings to the coater surfaces, such as metal or graphite surfaces, they are roughened such as by sand blasting with a sand blaster that is typically used to remove paint from metal and wood surfaces, until the coater has a uniform matte appearance. Subsequently the surface is blown clean with compressed air. It is then found that the length of the production runs can be increased to several hours. The term "roughened" or "roughness" as used in this disclosure means treating the surface of the coater such that at least twenty (20%) percent more surface area is available for bonding after roughening than before. The surface may be roughened in a uniform or non-uniform pattern. Preferably, the surface after roughening has a textured, grain-like, matte appearance. Alternatively, cuts can be formed defining recesses and projections, grooves forming islands can be cut into the surface, the islands being linear or non-linear, a knurled surface can be created, etc. A* roughened surface is shown in Figure 2. The size of the roughness, defined as the square root of the mean square distance of the surface from its average height, is typically in the range of 0.1 to 0.5 mm. Having described my invention, what I now claim is:

Claims: Claim 1. A method for enhancing bonding of a compound to the surface of a coater, which coater is used to deposit the compound on a glass surface which includes: roughening the surface of the coater to increase the surface area available for bonding by at least about 20%; depositing the compound from reactant gases onto the. roughened surface; and bonding the compound to the roughened surface such that as the deposited compound increases in thickness on the roughened surface it does not peel away from the surface wherein a corresponding thickness on a non-roughened surface would commence to peel. Claim 2. The method of Claim 1 wherein the compound is titanium nitride. Claim 3. The method of Claim 1 wherein the compound is tin oxide. Claim 4. The method of Claims 2 or 3 wherein the roughened surface is graphite. Claim 5. The method of Claims 2 or 3 wherein the roughened surface is graphite and which includes: removing particulate matter from the surface after roughening. Claim 6. The method of Claim 1. which includes roughening the surface by sandblasting. Claim 7. The method of Claim 1 which includes roughening the surface by machining the surface. Claim 8. The method of Claim 1 wherein the roughened surface has a coarse, non-uniform, grain-like appearance. Claim 9. The method of Claim 1 wherein the surface has a uniform, matte-like appearance. Claim 10. In a coater for depositing a compound on a glass surface, the coater having a surface in contact with the compound being deposited, the improvement which comprises: said surface roughened such that the surface area available for bonding is at least 20% greater than if the surface was non-roughened, to enhance the bonding of the deposited compound to the surface. Claim 11. The surface of Claim 10 wherein the roughened surface has a coarse, non-uniform, grain-like appearance. Claim 12. The surface of Claim 10 wherein the surface has a uniform, matte-like appearance.

Inventors: GORDON ROY G, GORDON, ROY, G.
Applicants: GORDON ROY G, GORDON, ROY, G.
Application year: 1991
Main classification: C23C16
IPC codes: C03C17, C23C16