Dope for glass

The present invention relates to coatings, particularly to the formation of a bottom layer, which is used to inhibit iridescence and protect the cover layer sensitive to alkali metal ions and prevent the migration of alkali metal ions from the glass surface of the bottom layer to the cover layer.

GB Patent No. 2031756B relates to a thin transparent semiconductor coating that reflects infrared rays. This coating is used to improve the insulating properties of window glass and is itself conductive. It can be used as a resistance heater, for example to remove ice or condensation on windows. According to GB Patent 2031756B, the application of this coating is limited due to the fact that it has an iridescent color tone, especially when the light is emitted; the beautiful angle of this iridescent effect is far from satisfactory, and due to the iridescence The color of the coating changes slightly with the thickness of the coating, which makes the problem more serious. GB2031756B has proposed a method to overcome the iridescence problem, that is, to layer a suitable underlayer to reduce iridescence under the semiconductor coating, and suggests that the preferred underlayer is the underlayer with a refractive index in the range of 1.7 to 18 and a thickness in the range of 64nm to 80nm. According to GB2031756B, the bottom layer can be formed by co-deposition of a suitable component mixture, such as a mixture of 84±3% silicon nitride and the remainder of silicon dioxide (called silicon oxynitride). This silicon oxynitride film can be used with silicon sources (such as SiH4, (CH3)2SiH2, (C2H5)2SiH2, (CH3)4Si, SiCl4, SiBr4), oxygen sources (such as O2, H2O, N2O) and nitrogen sources (such as N2H4). , NH3, NH3CH3NHNH2, (CH3)2NNH2) or oxygen source and nitrogen source together (NO, NH2OH, N2H4H2O) are formed by chemical vapor deposition on hot glass at a temperature of 500°C to 600°C.

Although there is a need for a suitable iridescent lightening underlayer, the underlayer proposed in the GB2031756B patent has not been applied to an important degree in commercial use. This is due to the following difficulties, especially the long deposition time required, using known methods It is difficult to form an underlayer of sufficient quality and thickness.

GB Patent Specification 2163146A is about forming a barrier coating on the surface of glass to prevent alkali metal ions from migrating from the glass to a covering layer sensitive to alkali metal ions such as tin oxide. This patent describes the formation of a transparent barrier coating by cleaving silane at a temperature higher than 600°C on the surface of a hot glass in the presence of a gas electron-donating compound to form a transparent barrier coating with good light permeability and excellent isolation It has been found that the presence of electron-donating compounds can allow oxygen on the glass to be incorporated into the coating, thus forming a transparent barrier coating up to 50nm thick on the glass surface.

The electron-donating compound used in the method of GB Patent Specification 2163146A either contains bonding electrons or acts as a unique pair of electrons, which can give the electron structure of the appropriate acceptor molecule. It has been found that the use of electron-donating compounds results in the formation of a transparent isolation layer between the oxygen in the glass and the silicon in the silane on the glass. Although the mechanism is not clear, it is believed that the process involves the adsorption of electron-donating compounds on the glass surface. It is generally preferred to use electron-donating compounds that do not contain oxygen, such as ethylene, or electron-donating compounds that contain some oxygen atoms, such as carbon monoxide and alcohol, which are generally considered as reducing agents.

Since the transparent barrier coating can be prepared in the absence of free oxygen and in the presence of compounds generally considered to be oxidizing agents, the barrier coating can be coated on a floating glass ribbon passing through a molten metal bath without the risk of accidental oxidation.

Unfortunately, when oxygen-free electron-donating compounds are used to alleviate the risk of silane being oxidized before reaching the glass surface and to alleviate the reaction gas oxidation of the molten metal bath carrying the glass ribbon, the formation of thicker iridescence recommended by GB Patent No. 2031756B reduces There is not enough oxygen in the bottom glass, and the thicker bottom layer is formed by oxygen-containing electron-donating compounds. For example, oxygen-containing electron-donating compounds such as carbon dioxide are used. It has been found that silane and carbon dioxide are used together, but the result is not a thin film with poor durability. Coating means that when trying to make the coating thicker, white mist-like deposits are formed.

In addition, when silane and ethylene are used in combination in accordance with GB2163146A to form a barrier coating with very high transparency (for example, the light transmittance is not less than 2% of the bottom glass), it has been found that the barrier properties of the coating cannot meet certain applications.

This requires a method suitable for industrial operation on a floating glass production line to produce an iridescent lightened bottom layer. This method has been proposed in GB Patent 2031756B. There is also a need for a method suitable for industrial operations on floating glass production lines to produce coatings that serve as an effective isolation layer. This coating is an effective barrier to the migration of alkali metal ions from the glass. At the same time, it has a very High transparency.

It has been found that these requirements can be met by the following method, which is to use a gas mixture of silane, ethylenically unsaturated hydrocarbon and carbon dioxide to aim at the hot glass surface, thereby depositing a transparent coating containing silicon and oxygen on the glass On the surface.

According to the method provided by the present invention, a useful underlayer is formed on the glass surface, which includes aligning a gas mixture of silane, unsaturated hydrocarbon compounds and carbon dioxide on the hot glass surface at a temperature of 600°C to 700°C. A transparent layer containing silicon and oxygen is deposited on the glass surface.

The bottom layer formed by the method of the present invention functions as an isolation layer for the migration of alkali metal ions from the glass. It is useful when the covering layer is sensitive to the migration of alkali metal ions from the glass. It can be directly or indirectly coated On the ground floor. According to another aspect of the present invention, the method further includes the step of coating a cover layer sensitive to the migration of alkali metal ions from the glass coating on the bottom layer.

Forms a conductive coating that reflects infrared and/or reduces iridescence. This infrared reflective and/or conductive layer is deposited on the bottom layer. Therefore, according to another aspect of the present invention, the method further includes the step of depositing a reflective infrared and/or conductive layer on the bottom layer. The cover layer may be a semiconductor metal oxide, such as tin-doped indium oxide, or doped tin oxide, especially fluorine-doped tin oxide.

Both the bottom layer and the cover layer can be coated on the floating glass on the glass production line. In this case, solid (as described in the embodiment in GB patent specification 2156386B, liquid (as described in GB patent specification 1523991) The pyrolysis of the fluorine-doped tin oxide deposits the fluorine-doped tin oxide as a cover layer by the pyrolysis of a vapor source (such as gaseous tin tetrachloride in the presence of water vapor and hydrogen fluoride) or a vapor source.

When the coating is used as an infrared reflective coating, the thickness of the infrared reflective layer is usually in the range of 200 nm to 500 nm. If necessary, thicker coatings can be made, for example up to 1000 nm thick, but from the perspective of the iridescent reduction properties of the underlying layer, it is usually unnecessary. When the coating is carrying current, such as in the case of resistance heaters or liquid crystal displays, the thickness of the coating will depend on the required conductivity, but the typical thickness range is 100 nm to 1000 nm.

If desired, although gaseous substituted or unsubstituted silanes such as dimethylsilane (CH3) 2SiH2 and disilane Si2H6 can be used, monosilane (SiH4) is preferred.

Although it is generally most convenient to use unsaturated hydrocarbons that are gaseous at room temperature, the unsaturated hydrocarbons may be ethylenically unsaturated hydrocarbon compounds, acetylene unsaturated compounds (such as acetylene) or aromatic compounds (such as toluene). Unsaturated hydrocarbons are preferably olefins, olefins containing 2 to 4 carbon atoms are more convenient, and ethylene is particularly preferred.

The ratio of the gaseous components in the gaseous mixture and the flow rate of the gaseous mixture on the glass surface can be adjusted to provide a bottom layer of required thickness and refractive index.

Carbon dioxide acts as an oxygen source. Therefore, although only limited oxygen is available on the glass surface, according to the instructions of GB Patent 2031756B, a transparent layer with a thickness of 80 nm can still be produced quickly. In addition, by appropriately adjusting the relative proportions of the gas components, the bottom layer with a refractive index in the range of 1.7 to 1.8 as described in GB Patent 2031756B can also be prepared. A preferred situation of the present invention is that the ratio of gas components in the gas mixture used to deposit the bottom layer and the flow rate of the gas mixture passing through the heated glass should be adjusted to form a thickness in the range of 60nm to 80nm and a refractive index of 1.6 to 1.8 sedimentary bottom layer.

In another embodiment of the present invention, the ratio of gas components in the gas mixture used to deposit the bottom layer and the flow rate of the gas mixture through the hot glass are adjusted to be able to deposit such a bottom layer whose thickness and refractive index make the coating The light transmittance of the glass with the bottom layer is less than 2% less than that of the uncoated glass, and it can provide an effective isolation layer for the migration of alkali metal ions from the glass. The light transmittance of the coated glass is better than that of the bottom. The light transmittance of the glass is less than 1%. The meaning of the term "effective isolation layer" is that when the method described in this article is used for testing, the sodium that can pass through the bottom layer is not more than 100 micrograms (preferably not more than 60 micrograms), and the sodium passed through is Na2O/decimeter 2 glass Said.

Generally speaking, the higher the ratio of unsaturated hydrocarbon to silane, the thinner the coating and the lower the refractive index of the coating. Usually the selected unsaturated hydrocarbon: silane operating volume ratio is 2:1 to 5:1, although outside this range, for example, 1:1 to 8:1 (or even higher) can also be used. It is believed that the role of unsaturated hydrocarbons is to adsorb on the surface of the glass, so generally speaking, the stronger the adsorption of unsaturated hydrocarbons on the glass, the ratio of unsaturated hydrocarbon to silane required for a given effect The lower. The volume ratio of carbon dioxide to silane is preferably 2:1 to 8:1, although outside this range, for example, 1:1 to 20:1 (or higher) can also be used. When operating under very low silane concentrations, usually only higher ratios are used.

The gas mixture used usually contains an inert carrier gas, such as nitrogen, in an amount of 10% to 90% of the volume of the gas mixture.

It can be expected that if the total flow rate of a gas mixture of a given composition is increased, the thickness of the bottom layer will increase as a result, and it has also been found that it can also increase the refractive index of the bottom layer.

The temperature of the glass is preferably 630°C to 720°C.

The method of the present invention is beneficial to the on-line production of an underlayer with reduced iridescence, an isolation underlayer for migration of alkali metal ions, and an underlayer with extremely high visible transmittance. In addition, the reactants used do not have a strong oxidizing effect. This method can be applied to the floating glass ribbon passing through the molten metal bath without the risk of accidental oxidation of the molten metal.

The present invention is only illustrative, and is not limited to the following examples. In the examples, all percentages are volume percentages unless otherwise noted, and the gas flow rate is measured at about 20°C under a pressure of 69 kPa (10 Psi). The quoted refractive index and thickness of the bottom layer are calculated from the maximum reflection wavelength and intensity of the bottom layer according to the film theory. The light transmittance of the coated glass is expressed as dT, which is the difference between the light transmittance (%) of the glass coated with the bottom layer and the light transmittance (%) of the uncoated glass. The efficiency of the bottom layer as a metal ion transport isolation layer was measured by the following method. Two pieces of coated glass samples, each cut into 10cm2, clamped between the two pieces of glass with an annular silicone rubber ring with an inner diameter of 8.5cm, thus forming an inner wall consisting of the coated glass surface and the silicone rubber ring Cylindrical pool defined on the surface. The cell was filled with deionized water through the hole of the rubber ring, and then the hole was closed. The closed cell was immersed in a water bath at 96°C for 48 hours, the solution was removed, and the sodium was analyzed by flame emission spectroscopy. The sodium extract was measured and the cell It is expressed in micrograms of Na2O/cm2 of glass exposed to water.

Example 1 A 6mm floating glass ribbon is advancing at a conveying speed of 322 meters per hour. When it passes through a floating bath with a glass temperature of about 645°C, the gas mixture is brought into contact with the upper surface of the glass to coat it with a bottom layer. The gas mixture consists of 11% monosilane, 23% ethylene and 23% carbon dioxide, and uses 44% nitrogen as the carrier gas. The equipment described in GB Patent Specification 1507966 is used to make the gas mixture flow parallel to the surface of the glass along the moving direction of the glass under the condition of laminar flow, and the movement stroke of the gas mixture covering the glass surface is adjusted to close to 0.2m. The flow rate of the gas mixture is 22 liters/min/m (coated glass width).

A transparent, substantially haze-free base layer is formed on the glass surface with a thickness of 76.1 nm and a refractive index of 1.77.

In Examples 2 to 3, the experimental procedure of Example 1 was repeated with ethylene and carbon dioxide whose flow rate ratio was increased. As a result, an underlayer with a slightly reduced thickness and refractive index was formed. The conditions used and the results obtained are listed in Table 1. For comparison, the corresponding details of Example 1 are also listed.

Examples 4 to 8 repeat the experimental steps of Example 1, using different gas mixtures to change the ratio of ethylene to carbon dioxide while maintaining the ratio of silane: ethylene and adding carbon dioxide and keeping the total flow rate constant. The conditions used and the results obtained are listed in Table 2.

Using a high ratio of ethylene: silane, as in Examples 4 and 5, results in a very thin underlayer (less than 55 nm). Decreasing the ratio of ethylene: silane and increasing the ratio of carbon dioxide: silane initially caused the thickness of the bottom layer to increase (Examples 6 and 7), but when the ratio of carbon dioxide: silane increased to 8:1, the thickness of the bottom layer decreased.

Examples 9 to 13 repeat the experimental steps of Example 1, using a gas mixture containing 10% monosilane, 25% ethylene, 25% carbon dioxide, and 40% nitrogen and oxygen at different total flow rates. The results obtained are shown in Table 3 (Examples 9 to 11). It has been found that the thickness and refractive index of the bottom layer both increase with the increase of the total flow rate.

Repeat the steps of Example 9, using the same flow rate of silane ethylene and carbon dioxide, but increasing the flow rate of N2. The flow rates used and the properties of the resulting bottom layer are shown in Table 3 (Examples 9, 12 and 13). It was found that with the increase of the nitrogen flow rate. The thickness of the bottom layer decreases, and its refractive index increases.

Examples 14 to 19 These examples were carried out in a similar manner to Example 1. The bottom layer was formed on 6mm floating glass under the conditions listed in Table 4, and the measured refractive index thickness of the bottom layer is shown in the table. When the buoyant glass ribbon enters the annealing furnace, a gas mixture of tin tetrachloride, water and hydrogen fluoride is chemical vapor deposited, and then a fluorine-doped tin oxide layer is deposited on the entire bottom layer of the floating glass ribbon. Measure the thickness of the tin oxide layer and at the same time determine the color coordinates of the reflected light (CIEIllununat C) on the side of the glass coating. In the case of Examples 14 to 17, the color coordinates of the reflected light of the fluorine-doped tin oxide coating are similar to those of the fluorine-doped tin oxide coating without a bottom layer. comparing. (Use color coordinates to determine the color is described in the book "The Measurement of Ap-pearances" (John Wiley and sons, 1975) by RSHunter), and the results are shown in Table 5.

It can be seen that the effect of the bottom layer is to inhibit the tin oxide layer from reflecting the color.

Examples 20-23 repeat the steps of Example 1, using a gas mixture containing 10% silane, 20% ethylene, 30% carbon dioxide and 40% nitrogen, with a flow rate of 50 liters/min/m (glass), and coating On a 2.1mm glass ribbon with a speed of 1130 m/h. The position where the gas mixture passes through the glass is where the glass temperature is about 645°C.

It has been found that the uncoated glass is highly transparent, and the light transmittance of the coated glass is only 1.1% lower than that of the uncoated glass. It has been determined that the efficiency of the bottom layer for alkali isolation is 90 micrograms Na2O/dm2 (glass) (see above).

Repeat the above steps to coat 6mm and 4mm glass with gases of different composition. The coating location, the temperature of the glass, the conveying speed of the glass ribbon, the gas composition and flow rate used, and the properties of the coated product are shown in Table 6. Comparing Examples 21 and 22, it can be seen that increasing the glass temperature and silane concentration, and reducing the ratio of ethylene and carbon dioxide to silane can better compensate for the loss caused by reducing the gas flow rate (from 55 to 24 L/min/m) Therefore, the thickness of the coating formed in Example 22 is about twice that of Example 21. All the examples showed good isolation performance, but the bottom layer of Example 22 had the highest light transmittance (relative to the light transmittance of uncoated glass).

Examples 24-30 These examples illustrate the use of butene as an unsaturated hydrocarbon, which is used with silane and carbon dioxide to form a color-inhibiting underlayer and barrier layer in accordance with the method of the present invention. These examples were carried out according to the procedure described in Example 1 but only coated on the shuttle of the narrow glass ribbon. The glass is 6 mm thick, moves at a conveying speed of 360 m/h, and the temperature at the coating position is 685°C. The coating conditions used, gas composition and gas flow rate, and the properties of the bottom layer formed are listed in Table 7.

In Examples 25-27, satisfactory color suppression layers with a thickness of 60 nm to 80 nm and a refractive index of 1.6 to 1.8 can be obtained (Example 24 is outside the above range to a certain extent). Examples 28-30 conducted at low gas flow rates resulted in a thinner coating with excellent isolation properties, and the light transmittance of the coated glass was close to that of the uncoated glass. Comparing Examples 24-30 with the previous examples, it can be seen that a higher total gas flow rate is obviously required to form a coating of similar thickness. It is believed that this is due (at least in part) to the method of Examples 24-30 being performed on a narrow glass ribbon, with most of the gas escaping from the edge of the ribbon to be coated.

Example 31-3 610cm×10cm 3mm floating glass static sample, the glass coating was heated to 650°C in a silica tube in the laboratory, and a coating containing silane, carbon dioxide, unsaturated hydrocarbon and nitrogen was passed on the surface of the hot glass. The coating mixed gas, the gas composition and processing time, as well as the light transmittance and the isolation performance of the coated product are listed in Table 8. Good isolation performance and high transparency can be obtained for each unsaturated hydrocarbon used (The light transmittance difference with uncoated glass is within 1%).

Examples 37-40 repeat the steps of Example 1, using a gas mixture of silane, ethylene, carbon dioxide, and nitrogen to coat 2 mm floating glass with a conveying speed of 1100 m/h.

The light transmittance of the glass is measured and compared with the light transmittance of the uncoated glass to obtain the difference dT, and the isolation performance of the glass is measured according to the above method. The thickness of the coating is too small to be measured by the above-mentioned optical method. It is measured by the argon ion etching technique.

The coating conditions and the results obtained are shown in Table 9.

Examples 37-40 are examples of the formation of the isolation layer. The glass coated in this manner has a light transmittance that is less than 1.5% (dT) lower than that of the uncoated glass. The final comparative sample shows that in the absence of carbon dioxide, although the bottom layer is actually thicker than the bottom layer formed in Examples 38 and 40, the light transmittance is significantly lower (dT=2.3%). The comparison between Examples 37 and 38 shows that increasing the ratio of dopants (ethylene and carbon dioxide) to silane will reduce the thickness of the bottom layer, which in turn improves the light transmittance but reduces the isolation performance. A slight decrease in the ratio of dopant to silane (Comparative Examples 37 and 39) will reduce the light transmittance, but the thickness and isolation properties remain unchanged. Reducing ethylene and increasing carbon dioxide can significantly reduce the thickness (Example 40) and increase the light transmittance, but the insulation performance is greatly reduced.

The above examples show that by adjusting the ratio of gas components in the gas mixture used in the method of the present invention and the flow rate of the gas mixture passing through the surface of the heated glass, an underlayer with a desired thickness and refractive index can be obtained. Therefore, the method of the present invention is not only useful for forming the color suppression underlayer of the type described in GB Patent 2,031,756B, but also for forming other color suppression underlayers known in the art and the underlayer with high transparency and isolation performance. useful.