DEPOSITION PROCESS

Abstract

The present invention relates to a process for producing a coated glass substrate, the process comprising providing a glass substrate having at least one surface, the surface having deposited thereon a layer of a transparent conductive material, providing a coating composition comprising a polysilazane, contacting the surface of the transparent conductive material with the coating composition and curing the coating composition to form a coating layer on the surface of the transparent conductive material the coating layer comprising silica, and to architectural and automotive glazing comprising coated glass substrates obtained using the process.

Claims

1.-33. (canceled)

34. A process for producing a silica coated glass substrate for use in automotive and architectural glazing, the process comprising: i) providing a glass substrate having at least one surface, the surface having deposited thereon a layer of a transparent conductive material; ii) providing a coating composition comprising a polysilazane; iii) contacting the layer of transparent conductive material with the coating composition; and iv) curing the coating composition to form a silica coating layer on the transparent conductive material layer, wherein the transparent conductive material layer comprises a transparent conductive oxide.

35. The process as claimed in claim 34, wherein the coating composition further comprises an aprotic solvent selected from the group consisting of: dibutyl ether, t-butyl methyl ether, tetrahydrofuran, butane, pentane, hexane, cyclohexane, 1,4-dioxane, toluene, xylene, anisole, mesitylene, 1,2-dimethoxybenzene, diphenyl ether and mixtures thereof.

36. The process according to claim 35, wherein the solvent comprises dibutyl ether, toluene, xylene, mesitylene and/or mixtures thereof.

37. The process as claimed in claim 34, wherein the transparent conductive oxide comprises indium tin oxide, doped tin oxide, doped zinc oxide or a mixture of two or more of these oxides, and wherein the transparent conductive oxide is deposited by chemical vapour deposition (CVD).

38. The process as claimed in claim 37, wherein the transparent conductive oxide of doped tin oxide comprises fluorine doped tin oxide.

39. The process as claimed in claim 34, wherein the layer of transparent conductive material has a sheet resistance in the range 5 /square to 400 /square.

40. The process as claimed in claim 34, wherein the polysilazane comprises a compound of formula [R.sup.1R.sup.2SiNR.sup.3].sub.n, wherein R.sup.1, R.sup.2, and R.sup.3 are each independently selected from H or C.sub.1 to C.sub.4 alkyl, and n is an integer.

41. The process as claimed in claim 34, wherein the polysilazane comprises perhydropolysilazane (PHPS) or methylpolysilazane (MPS).

42. The process as claimed in claim 34, wherein the layer of transparent conductive material is contacted with the coating composition by a method selected from: dip coating; spin coating; roller coating; spray coating; air atomisation spraying; ultrasonic spraying; and/or slot-die coating.

43. The process as claimed in claim 34, further comprising the step of cleaning the surface of the glass substrate.

44. The process as claimed in claim 43, wherein cleaning comprises one or more of: abrasion with ceria, washing with alkaline aqueous solution, deionised water rinse and/or plasma treatment.

45. The process as claimed in claim 34, wherein in step iv) curing the coating composition to form the silica coating layer on the layer of transparent conductive material comprises irradiating with ultraviolet radiation.

46. The process as claimed in claim 34, wherein in step iv) curing the coating composition to form the silica coating layer on the layer of transparent conductive material comprises heating to a temperature in the range 90 C. to 650 C.

47. The process as claimed in claim 34, wherein the polysilazane is at a concentration in the range 0.5% to 80% by weight in the coating composition.

48. The process as claimed in claim 34, wherein the silica coating layer is deposited to a thickness in the range 10 nm to 5 m.

49. The process as claimed in claim 34, wherein the silica coating layer comprises 1 at % to 8 at % nitrogen.

50. The process as claimed in claim 34, wherein the transparent Conductive oxide coating layer before contact with the silica coating layer, has an average surface roughness, (Sa1), greater than the average surface roughness, (Sa2), of the silica coated glass substrate.

51. The process according to claim 34, wherein the transparent conductive oxide coating layer before contact with the silica coating layer, has an average surface roughness, (Sa1), at least 5 nm greater than the average surface roughness, (Sa2), of the silica coated glass substrate.

52. The process according to claim 34, wherein the cured silica coating layer comprises an arithmetic mean height which is less than 50% of the transparent conductive material layer arithmetic mean height.

53. The coated glass substrate comprising a layer of transparent conductive oxide and a cured silica coating layer deposited on the layer of transparent conductive oxide by the process of claim 34.

54. A coated glass substrate comprising a layer of transparent conductive oxide and a cured silica coating layer deposited on the layer of transparent conductive oxide, wherein the transparent conductive oxide layer before deposition of the silica coating layer, has an average surface roughness (Sa1), greater than the average surface roughness (Sa2), of the silica coating layer.

55. The coated glass substrate according to claim 54, wherein the transparent conductive oxide layer has an average surface roughness (Sa1), at least 5 nm greater than the average surface roughness (Sa2), of the silica coating layer.

56. The coated glass substrate according to claim 54, wherein the layer of transparent conductive oxide comprises fluorine doped tin oxide deposited by chemical vapour deposition and wherein the arithmetic mean height of the cured silica coating layer is less than 50% of the arithmetic mean height of the fluorine doped tin oxide layer.

57. The coated glass substrate according to claim 54 comprising a cured silica layer with a thickness of between 15 and 100 nm.

Description

[0075] The present invention will now be described by way of example only, and with reference to, the accompanying drawings, in which:

[0076] FIG. 1 (a) is a scanning electron micrograph (SEM) of Example 1, FIG. 1 (b) is a scanning electron micrograph (SEM) of Example 6.

[0077] FIG. 2 (a) is a scanning electron micrograph (SEM) of Example 7, FIG. 2 (b) is a scanning electron micrograph (SEM) of Example 11.

[0078] FIG. 3a is a graph of transmission versus number of passes beneath a spray head for Examples 12 to 17 (diamondsExamples 12-14, squaresExamples 15-17) and

[0079] FIG. 3(b) is a graph of haze as a function of number of passes beneath a spray head for Examples 12 to 17 (diamondsExamples 12-14, squaresExamples 15-17).

[0080] FIG. 4 is a graph of surface roughness (Sa) as a function of silica coating thickness (nm) for spray deposited samples according to the invention.

[0081] As mentioned above, FIG. 1(a) is a scanning electron micrograph (SEM) of Example 1 prepared using a spray deposition method and wherein silica derived from PHPS is cured at a temperature of 500 C. for one hour. The glass substrate is indicated by 3, the fluorine doped tin oxide coating layer by 2 and the cured silica layer derived from a coating composition of PHPS is denoted by 1. As seen in FIG. 1a, the cured silica layer provides a smoothing layer on top of the fluorine doped tin oxide coating layer.

[0082] FIG. 1(b) is a scanning electron micrograph (SEM) of Example 6, also prepared using a spray deposition method but cured at a temperature of 150 C. for one hour. The glass substrate is indicated by 3, the fluorine doped tin oxide coating layer by 2 and the cured silica layer derived from a coating composition of PHPS is denoted by 1. As seen in FIG. 1a, the cured silica layer provides a smoothing layer on top of the fluorine doped tin oxide coating layer.

[0083] FIG. 2 (a) is a scanning electron micrograph (SEM) of Example 7, prepared using a spray deposition method and in which the silica layer derived from methylpolysilazane (MPS) is cured at a temperature of 150 C. for one hour. The glass substrate is indicated by 3, the fluorine doped tin oxide coating layer by 2 and the cured silica layer derived from a coating composition of methyl polysilazane is denoted by 1. As seen in FIG. 2a, the cured silica layer provides a smoothing layer on top of the fluorine doped tin oxide coating layer.

[0084] FIG. 2 (b) is a scanning electron micrograph (SEM) of Example 11 prepared using a spray deposition method and cured at a temperature of 500 C. for one hour. The glass substrate is indicated by 3, the fluorine doped tin oxide coating layer by 2 and the cured silica layer derived from a thicker coating composition of methylpolysilazane (MPS) is denoted by 1. As seen in FIG. 2b, the cured silica layer provides a smoothing layer on top of the fluorine doped tin oxide coating layer.

[0085] The invention will now be further illustrated, but not limited, by the following Examples.

Scanning Electron Microscopy

[0086] Scanning electron microscopy (SEM) was performed using a Philips XL30 FEG operating in plan and cross-section mode at varying instrument magnification and tilt angle.

Electrical Properties

[0087] The sheet resistance of the Examples was determined using a surface resistivity meter with a 4-point probe (Guardian Model SRM 232). Measurements were taken at the same thickness for each sample, and the mean of three measurements was taken.

Atomic Force Microscope

[0088] AFM (Bruker, Nanoscope Dimension Icon) was used to determine the roughness of samples including average surface roughness, Sa and Sq (as determined according to ISO 25178-No. 2 Aerial Specification Standard, published 2012, Sa being defined therein as the arithmetical mean height of the surface).

Substrates

[0089] In the Examples, substrates of float glass coated with fluorine doped tin oxide (as the outer layer) were prepared and subsequently coated with layers comprising silica using polysilazane in dibutyl ether.

[0090] The coated glass substrates were of the form glass/undoped SnO.sub.2/SiO.sub.2/F doped SnO.sub.2 and differed in the thickness of the doped tin oxide layer (as conveniently indicated by measuring sheet resistance, a thicker coating yielding lower sheet resistance). The following procedure describes the deposition of the doped tin oxide layer of the 15 /square substrate. The other substrates were produced in a similar way varying the thickness of the doped tin oxide coating and hence the sheet resistance.

[0091] The fluorine-doped tin dioxide layer is deposited using an on-line CVD coating process. This is done during the float glass production process with the temperature of the glass substrate at 600 to 650 C. A tin-containing precursor, in the form of dimethyltin dichloride (DMT), is heated to 177 C. and a stream of carrier gas, in the form of helium, is passed through the DMT. Gaseous oxygen is subsequently added to the DMT/helium gas stream. At the same time, a fluorine-containing precursor, in the form of anhydrous hydrogen fluoride (HF), is heated to 204 C. Additional water is added to create a mixture of gaseous HF and water. The two gas streams are mixed and delivered to the hot glass surface at a rate of around 395 litres/minute. The ratio of DMT to oxygen to HF is 3.6:61.3:1. The thickness of the resulting fluorine-doped tin oxide layer is approximately 3200 and it has a nominal sheet resistance of about 15 /square.

Silica Coatings

[0092] Silica coatings were deposited using a 20% by weight stock solution in dibutyl ether (DBE) of perhydropolysilazane (PHPS) or methylpolysilazane MPS available from Merck. During coating operations the stock solution was diluted with DBE at ratios ranging from 1:1 to 1:12. Adding DBE reduces the thickness of the resulting silica coating.

[0093] The glass substrate surface was cleaned prior to coating using combinations of ceria scrub, 2% KOH wash, deionised water rinse and air dry. Plasma treatment may also be required to remove remaining organic contaminants from the surface to reduce the contact angle (<5).

[0094] In the following comparative examples and examples the coating solution of polysilazane was applied to the substrate surface by either: [0095] i) spin coating; or [0096] ii) spray coating; or [0097] iii) roller coating; or [0098] iv) slot die coating, [0099] followed by curing using heat for example from IR lamps or at a temperature in the region of 200 C. for 1 hour, or ultraviolet radiation for example short wavelength UV 200 nm using a mercury or iron discharge lamp, to give a silica coating. The silica coated substrate was then tested for optical properties, durability (to architectural EN1096 and automotive TSR 7503G standards) and to show resistive heating.

Spin Coated Comparative Examples 1 to 8

[0100] These comparative Examples were conducted to evaluate coating thickness as a function of concentration of perhydropolysilazane (PHPS) solution.

[0101] Volumes of about 2 ml of PHPS solution in dibutyl ether (DBE) of varying concentration were applied to a float glass substrate. The substrate was spin coated at an acceleration of 1000 rpm/s to 2000 rpm. The substrates were subsequently heated for 1 hour at 500 C. which consisted of a 1 hour heating up period, a 1 hour holding period at 500 C., and a cool down period of around 8 hours. The results are presented in Table 1.

TABLE-US-00001 TABLE 1 Concentration of PHPS in Silica film Comparative coating solution. thickness Example (weight %) (nm) 1 7.6 21.7 2 9.7 26.1 3 15.8 40.2 4 18.9 46.5 5 32.3 83.8 6 37.3 97.7 7 48.7 132.7 8 55.7 153.2

Spray Coated Examples 1 to 20

[0102] Fluorine doped tin oxide (SnO.sub.2:F) coated glass substrates having a sheet resistances of either 6 /square, 10 /square or 15 /square were coated by a spray process from atomizer spray heads with 0.015 inch/0.06 mm fluid orifices, 0.2 bar to 3 bar liquid pressure range, and 2.6 to 10 litres/hour liquid delivery using a coating composition of PHPS in DBE or methylpolysilazane (MPS) in DBE, each of concentration 7.6 weight %. The substrates were at room temperature during deposition. Prior to deposition the substrates were cleaned using a ceria scrub and deionisied water. Spray deposition for each pass lasted for 2 or 3 seconds. Spray heads were 15 to 38 mm above the substrate during spraying. Curing of the silica after spraying was conducted by heating the coated glass to various temperatures (Examples 1 to 11), using a near-IR lamp (50% power) at a conveyor speed of 6 m/minute and 8 UV passes using a Jenton UV lamp (approximately 200 nm wavelength, 90% power) and conveyor with a speed of 2.1 m/minute. The volume of the spray was approximately 260 ml and the spray head separation was 10 to 15 cm. Pole to pole distance was 52 cm. The relative motion of the substrate and heads was 12 cm/minute.

[0103] The spray coated samples all formed excellent silica coatings, exhibiting significantly reduced roughness of the surface of the substrates. Further results are described below.

Examples 1 to 11

[0104] In examples 1 to 11 silica was spray deposited onto coated glass substrates with a sheet resistance of 15 /square. Examples 1 to 6 were deposited using perhydropolysilazane (PHPS) in dibutylether (DBE). Examples 7 to 11 were deposited using methylpolysilazane (MPS) in dibutylether (DBE). The results of analysis of Examples 1 to 6 are shown in Table 2 and the results for Examples 7 to 11 in Table 3.

TABLE-US-00002 TABLE 2 Actual(averaged) 1 Hour ISO9050 Contact AFM Sa AFM Sq SEM Thickness Cure Temp Tvis Haze Angle (nm) (nm) Example (nm) ( C.) (%) (%) () 5 m.sup.2 5 m.sup.2 1 170 500 85.0 0.39 43.3 0.93 1.20 2 189 500 85.2 0.41 51.3 0.82 1.02 3 156 300 84.6 0.44 82.4 0.92 1.23 4 176 300 86.7 0.46 76.7 1.25 1.68 5 106 150 84.3 0.44 102.1 1.18 1.60 6 148 150 87.3 0.36 88.2 1.06 1.47 SnO.sub.2:F 0 0 84.4 0.95 55.8 12.94 16.13 Substrate Float 0.25 glass AFM SaAtomic Force Microscope average surface roughness value AFM SqAtomic Force Microscope average root mean square height

TABLE-US-00003 TABLE 3 Actual (averaged) 1 Hour ISO9050 AFM Sa AFM Sq SEM Thickness Cure Temp Tvis Haze Contact (nm) (nm) Example (nm) ( C.) (%) (%) Angle 5 m.sup.2 5 m.sup.2 7 187 150 85.8 0.38 76.7 0.64 0.95 8 195 300 87.0 0.35 88.2 0.94 1.85 9 482 300 87.6 0.33 82.4 0.67 1.19 10 187 500 86.5 0.38 82.4 0.76 1.14 11 632 500 87.6 0.39 47.1 0.36 0.67 SnO.sub.2:F 0 0 84.4 0.95 55.8 12.94 16.13 Substrate Float 0.25 Glass

[0105] In examples 12 to 17, silica was spray deposited onto coated glass substrates with sheet resistances of 6 /square (Examples 12, 13 and 14) or 10 /square (Example 15, 16, 17) respectively using perhydropolysilazane (PHPS) in dibutylether (DBE) over 1, 2 or 3 spray deposition passes. The results of analysis of Examples 12 to 17 are shown in Table 4 including the analysis of nitrogen content of the layer comprising silica and data for the substrates (Subs. 6 and Subs. 10).

TABLE-US-00004 TABLE 4 Layer Sheet Nitrogen Thick- Resis- Vis- Vis- No. of content ness Haze tance ible ible Example Passes (at %) (nm) (% T) (/sq) % T % R Subs. 6 0 1.46 6.07 81 10.1 12 1 1.6 38 1.01 6.05 80.6 10.2 13 2 2.2 58 0.81 6.28 83.1 8.4 14 3 4 88 0.68 5.80 84.2 7.1 Subs. 10 0 1.05 9.12 83.1 10.4 15 1 3.4 62 0.63 9.11 83.4 10.2 16 2 3.5 65 0.48 8.93 85.5 7.9 17 3 2.4 85 0.39 9.03 86.8 6.9

Electrically Heatable Demonstrators: Example 18, 19 and 20

[0106] Perhydropolysilazane (PHPS) in dibutylether (DBE) was used to apply coatings by spray deposition onto substrates with sheet resistances of 6 /square, 10 /square and 15 /square. An electrical contact was made to the samples and a voltage applied. The temperature of the samples was measured using a temperature probe. The results for each Example are indicated in Table 5.

TABLE-US-00005 TABLE 5 Sheet Resistance Applied of Substrate Voltage Current Temperature Example (/square) (V) (A) ( C.) 18 6 42 5.1 100 48 5.8 133 19 10 42 3.4 90 48 3.9 105 20 15 42 2.6 54 48 2.9 81

Roller Coated Examples

[0107] Roller coated examples were produced to evaluate coating thickness and surface roughness as a function of coating solution concentration and roller speed and direction using a Burckle easy-Coater RCL-M 700 Roller Coater. A PHPS silica coating solution was pumped into the channel formed between the doctor roller, application roller and sealing end plates. The solution coated the application roller which in turn applied the solution to the substrate. The substrates were doped tin oxide coated float glass. Prior to coating the substrates were cleaned in a flat-bed washing machine. Following coating the samples were cured either using mercury discharge lamps and/or thermally cured at 200 C. for an hour in a convectively heated oven. The results are presented in Table 6.

TABLE-US-00006 TABLE 6 PHPS AFM Sa SEM Coating Solution Application Application (nm) Thickness Silica Concentration Roller Speed Roller 5 5 Range Ex Precursor Solvent (%) (m/min) Direction micron (nm) 1 PHPS 1:1 Mesitylene:Toluene 3.0 3 Reverse 10.8 21 to 32 2 PHPS 1:1 Mesitylene:Toluene 6.7 10 Forward 7.1 20 to 60 3 PHPS 1:1 Mesitylene:Toluene 6.7 3 Forward 8.8 33 to 59 4 PHPS 1:1 Mesitylene:Toluene 13.4 3 Forward 6.4 19 to 74 5 PHPS 1:1 Mesitylenc:Toluene 16.0 3 Forward 6.1 12 to 83 6 PHPS 1:1 Mesitylene:Toluene 18.0 3 Forward 4.7 16 to 86 Float Glass 0.3

Slot Die Coated Examples

[0108] PHPS slot die coated examples were produced to evaluate coating thickness and roughness as a function of coating solution flow rate using a nTact nDeavor slot die coating system. The coating solution was delivered to a reservoir within a die, the coating solutions exited the die through a narrow slot forming a bead. The die was positioned above the substrate and moved along the substrate to form a coating. The substrates were fluorine doped tin oxide coated float glass, with the fluorine doped tin oxide applied by CVD. Prior to coating with PHPS the fluorine doped tin oxide coated float glass substrates were cleaned in a flat-bed washing machine. Following coating the samples were thermally cured at 200 C. for an hour in a convectively heated oven. The results are presented in Table 7.

TABLE-US-00007 TABLE 7 Coating Die to AFM Sa SEM Solution Flow Slot Substrate (nm) Thickness Silica Concentration Rate Width Gap 5 5 Range Ex Precursor Solvent (%) (ml/min) (micron) (micron) micron (nm) 1 PHPS DBE 10.0 0.7 50 20 9.1 13 to 28 2 PHPS DBE 10.0 1.5 50 40 7.9 12 to 53 3 PHPS DBE 10.0 2.9 50 50 6.6 18 to 50 4 PHPS DBE 10.0 5.8 50 75 4.5 16 to 49 5 PHPS DBE 10.0 11.6 50 100 2.3 33 to 100 Float 0.3 Glass

Marking Resistant Demonstrators; Examples 1 to 4

[0109] Fluorine doped tin oxide coated glass substrates were over-coated with a layer of silica formed from PHPS by roller coating and slot die coating. The resistance of the PHPS applied silica coating to marking was assessed by manually marking the applied silica coating using pencils and a coin followed by visual inspection of resulting marks. The results are provided in Table 8.

TABLE-US-00008 TABLE 8 Over- SEM Coating AFM Surface Coating Thickness Range Roughness, Sa Resistance Ex Method (nm) (nm) to Marking SnO2:F 0 13.6 Very Low coating only Float Glass 0 0.3 1 Slot Die 16 to 49 4.5 High 2 Slot Die 33 to 100 2.3 Very High 3 Roller 33 to 59 8.8 High 4 Roller 16 to 86 4.7 Very High 5 Spin 18 to 28 2.4 High 6 Spin 30 to 39 1.7 Very low 7 Spray 34 to 38 12.3 Low 8 Spray 30 to 32 12.0 Low

[0110] Therefore it can be seen from the results in Table 8 that when a silica layer derived from a polysilazane such as PHPS is provided and cured above a transparent conductive oxide such as fluorine doped tin oxide (SnO.sub.2:F) applied by chemical vapour deposition (CVD) to float glass, not only does the silica layer have an improved smoothing effect on the surface of the transparent conductive oxide but in addition, the silica layer provides an increased level of resistance to marking, especially when the silica layer is applied by a slot die, roller coating, spray coating or spin coating process.

[0111] Furthermore, improved levels of resistance to marking by the silica layer are provided when the thickness of the silica layer is between 15 and 110 nm.