Title of Invention

"A NOVEL STABLE COATING SOL AND PROCESS THEREOF USEFUL FOR MAKING SOL COATED GLASS WITH SHIMMERING COLOUR EFFECT"

Abstract

The present invention relates to a novel stable coating sol and process thereof useful for making sol coated glass with shimmering effect. A novel stable coating sol, a process of preparing stable coating sol and a process of making sol coated glass with shimmering colour effect which shows different hue with different thickness in the visible spectral range. To achieve this, the present invention provides a stable coating sol consisting of an organo-metallic compound of at least one of Ti, Zr, Ta and Nb in an ether group containing solvent system. The coated glass with shimmering effect is prepared by dip coating and heat treatment for producing such colour effect with a single component oxide coating.

Full Text

This invention relates to a novel stable coating sol and process thereof useful for making sol coated glass with shimmering colour effect. The main use of this coated glass is in making decorative glass plates and glass panes, producing artificial glass jewelry, coloured glass articles and any other use where shimmering colour effect on glass is desired. Reference may be made to patents of M. Auwarter, Swiss patent no. 410498 where the inventors made a process of making an imitation jewel stone made of transparent material, which is provided with a reflection-enhancing coating on its surface on the side away from the observer, as well as on the side towards the observer, having the feature, that the said coating on the side towards the observer has at least one breakthrough point. They also claimed a method for manufacturing imitation jewel stones, having the feature, that the coatings are vapor-applied in vacuum, by using covering masks at the break-through points. But the disadvantage of the process is that they have used a vapor-applied vacuum process which needs a very expensive equipment. Reference may also be made to Austrian patent no. 265718 of M. Auwarter where the inventor has used miltilayer coating for long wavelengths to get the artificial jewelry. The disadvantage is that here also they used expensive vapor-applied vacuum process. Reference may be made to patent no. JP5804 by Shimodaira Kojiro on manufacturing of transparent material having interference colour or opalescent colour, wherein the inventors have made the thin film by dipping the transparent material in a dispersion of amorphous silica spheres. Reference may be made to US patent no. 6156388 where the inventors have devised a method of manufacturing substrates with transparent and colour coatings stable at high temperatures and in the presence of ultraviolet rays. But the process involves heat treatment of aqueous solutions or sols of matrix-forming element compounds like SiO2, TiO2 ZrO2with metal (compound) colloids or metal alloy colloids. The process involves heat treatment of aqueous solutions or sols of matrix forming element compounds and the colouration takes place by the colloidal presence of metal like Au, Ag, Cu, Pd, Pt, Ir, Rh, Ru and mixtures thereof in a matrix of oxide of at least one of Si, Ti and Zr. Reference can also be made to patents JP-07078601 and JP-02250201 where interference colouration was obtained by multiple coating with TiO2, Ta2O5 and ZrO2 layer of high refractive index and SiO2 or SnO2 of low r. index, which were provided alternately atop one another. The coating composition consisted of tetrabutyl titanate in etanol for TiO2 and tetraethyl silicate for SiO2. But the difficulty is that the inventors used multilayer coating up to eight coating operations in order to achieve the desired colouration, for yellow layers, for example. Reference may be made to 'Yellow coatings produced on glasses and aluminium by sol-gel by A. Makishima, H. Kubo, K. Wada, Y. Kitami and T. Shimohira, published in J. Am. Ceram. Soc. 69(6) C127- C129 (1986) where they have used sol-gel dip- coating method to produce brilliant yellow, adherent coating of CeO2 -TiO2.. They have used the raw materials of CeCl3 , C2H2OH and Ti(OCH(CH3 )2)4 . Solutions were gelled at room temperature by the reaction with moisture in air for ~ 30 days and heat treated for 3 hrs at ~ 500° C But the drawback of the process is that it takes enormously long time for the One main object of the present invention is to provide a process for making sol coated glass with shimmering effect from novel composition. Another object of the present invention is to provide a process of preparing novel stable coating sol useful for making coated glass with shimmering effect. Another object of the invention is to provide a novel stable coating sol useful for making sol coated glass with shimmering effect. Still another main object of the present invention is to provide a process of making sol coated glass with shimmering colour effect which obviates the drawbacks as detailed above. Yet another object of the present invention is to provide a stable coating sol with an organo-metallic compound of at least one of Ti, Zr, Ta and Nb for producing shimmering colour effect on coated glass with a single component oxide coating. Further object of the present invention is to provide a coated glass which produces a shimmering colour effect with different hue with different thickness in the visible spectral range. In the present invention there is provided a novel stable coating sol essentially consisting an organo-metallic compound, an ether group containing solvent system and acidified distilled water for preparing coating glass articles to produce shimmering colour effect. Accordingly the present invention provides a novel stable coating sol useful for making sol coated glass with shimmering colour effect which comprises: organo-metallic compound (M-OR) where M is at least one of Ti, Zr, Ta, Nb and OR is an alkoxy group, ethylene glycol monomethyl ether (EGME), distilled water (H2O) and acetic acid (HAc) in a molar ratio of M-OR : EGME : H2O : HAc in the range of 1 : (24-48): (1-3): (0.5-1.7). In an embodiment of the present invention, the organo-metallic compound (M-OR) used may be at least one of Ti- iso propoxide, Ti-ethoxide, Ti-butoxide, Zr- propoxide, Ta-ethoxide, Nb-ethoxide. The novel stable coating sol of the present invention is not a mere admixture but a synergistic mixture having properties and characteristics which are distinct from the mere aggregation of the properties and characteristics of the individual ingredients. Accordingly, the present invention provides a process of preparing stable coating sol, useful for making sol coated glass with shimmering colour effect, which comprises mixing of organo-metallic compound and ethylene glycol monomethyl ether in a molar ratio in the range of 1 : (24 - 48) under continuous stirring to obtain a clear solution, adding to the said clear solution under constant stirring acidified distilled water in which acetic acid : distilled water molar ratio may be maintained in the range of (1-3) : (0.5 -1.7) with respect to the organo-metallic compound, allowing the resultant to age for a period of 2 to 48 hours to obtain a stable coating sol. In an embodiment of the present invention the organo-metallic compound (M-OR) used may be where M is at least one of Ti, Zr, Ta, Nb and OR is an alkoxy group such as Ti-iso propoxide, Ti-ethoxide, Ti-butoxide, Zr-propoxide, Ta-ethoxide, Nb-ethoxide. Accordingly, the present invention provides a process of making sol coated glass with shimmering effect from the above said novel coating sol, which comprises dipping and withdrawing the cleaned glass article to be coated at a constant speed in the range of 5.6 to 14 cm/min, drying at room temperature for 3 to 5 mins, followed by further drying at a temperature in the range of 120 - 180°C for 20 - 30 mins, repeating the dipping, withdrawing and drying steps to obtain the required thickness and finally heat treating at a temperature in the range of 450 to 500°C for a period in the range of 30 to 60 minutes. The details of the process of the present invention are given below. 1. Organo-metallic compound (M-OR) where M is at least one of Ti, Zr, Ta, Nb and OR is an alkoxy group is mixed with ethylene glycol monomethyl ether, (CH2OCH2CH2OH) in a molar ratio of (1 : 24 - 48) using a magnetic stirrer. Distilled water acidified with acetic acid, (CH3COOH) is then added slowly to the above solution so that the molar ratio of the organo-metallic compound : water : acid lies in the range of 1 : (1-3) : (0.5- 1.7). During this mixing process, the whole solution is continuously stirred at a constant speed and finally a stable and slightly yellow coloured sol is obtained. The coating sol is further aged for 2-48 hrs. to obtain a stable coating sol. 2. Glass articles such as commercial grade microscopic glass slides are first washed in a detergent solution followed by cleaning with tap water. These are finally washed by distilled water in an ultrasonic vibrator. The glass articles are then dried in an electrical oven for 1 to 4 hours at 100 to 120 °C, to obtain a clean glass slide. 3. Cleaned glass articles are dipped in the coating sol as prepared in step 1 and are then withdrawn vertically at a speed 5.6 to 14 cm/min using a mechanical puller. 4. Coated glass articles are then dried at ambient condition for 3 to 5 minutes, then at 120 to 180°C for 20 to 30 mins, followed by heat treating at 450 to 500°C for 30 to 60 mins . constant speed in the range of 5.6 to 14 cm/min, drying at room temperature for 3 to 5 mins, followed by further drying at a temperature in the range of 120 - 180°C for 20 - 30 mins, repeating the dipping, withdrawing and drying steps to obtain the required thickness and finally heat treating at a temperature in the range of 450 to 500°C for a period in the range of 30 to 60 minutes. The details of the process of the present invention are given below. 1. Organo-metallic compound (M-OR) where M is at least one of Ti, Zr, Ta, Nb and OR is an alkoxy group is mixed with ethylene glycol monomethyl ether, (CH2OCH2CH2OH) in a molar ratio of (1 : 24 - 48) using a magnetic stirrer. Distilled water acidified with acetic acid, (CH3COOH) is then added slowly to the above solution so that the molar ratio of the organo-metallic compound : water : acid lies in the range of 1 : (1-3) : (0.5- 1.7). During this mixing process, the whole solution is continuously stirred at a constant speed and finally a stable and slightly yellow coloured sol is obtained. The coating sol is further aged for 2-48 hrs. to obtain a stable coating sol. 2. Glass articles such as commercial grade microscopic glass slides are first washed in a detergent solution followed by cleaning with tap water. These are finally washed by distilled water in an ultrasonic vibrator. The glass articles are then dried in an electrical oven for 1 to 4 hours at 100 to 120 °C, to obtain a clean glass slide. 3. Cleaned glass articles are dipped in the coating sol as prepared in step 1 and are then withdrawn vertically at a speed 5.6 to 14 cm/min using a mechanical puller. 4. Coated glass articles are then dried at ambient condition for 3 to 5 minutes, then at 120 to 180°C for 20 to 30 mins, followed by heat treating at 450 to 500°C for 30 to 60 mins . Let us consider a coated plane glass substrate where a thin uniform transparent coating of thickness 'd' and refractive index µ2.is deposited on the plane glass substrate having refractive index µ3. A monochromatic light of wavelength 'A.' strikes the air (µ1 = 1) and coating interface at an angle 'α'. A part of this ray will be reflected along a different direction determined by the laws of reflection and the rest will be refracted along a direction within the film with an angle '0' which is the angle of refraction. At coating and glass substrate interface , again a fraction of this refracted part will be reflected and the rest will be refracted . In this way , some part of the incident wave will return to air medium and the rest will be transmitted through the coating material. Now, for µ1 µ3, it can be shown by mathematical deduction that constructive interference will occur when : µ2d Cosθ = 2n. λ1/4 (for transmission ) µ2dCosθ= (2n.+l)λ2/4 (for reflection ) where n = (1, 2, 3 ) is the order number and in case of normal incidence, µ2d = 2n. λ1/4 (for transmission ) µ2d = (2n.+l) λ2/4 (for reflection ) µ2d is the optical thickness of the coating at that particular wavelengths. In order to produce the above said coating with suitable thickness and refractive index by dip coating procedure, a stable sol is prepared from the novel sol composition of the present invention. A successful coating formation depends primarily on the stability of the prepared sol. Solvents have a major role in stabilizing a sol and in the prior art commonly used solvents have hydroxyl group (- OH) and sometimes ketonic ( > C = O) group in its structure. Instead of ketonic or hydroxyl group, if ether group (- O -) is present in the system, stability of the sol increases to a large extent. Another important parameter that determines the phase separation in titania oligomer is the repulsive interaction between the oligomeric alkoxide adsorbed by polyethylene glycol and the solvent mixture. Both the factors i.e. stability of sol and phase separation of titania species may be controlled by introducing one ether group in the solvent system. Thus, the novelty of the present invention resides in the composition for preparing a stable coating sol which allows dip-drawing an easy way of making coated glass with shimmering colour effect. This is made possible by the inventive step of introducing ether group in the solvent system to impart additional stabilizing effect on the sol system. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example 1 10 ml of titanium isopropoxide (TIPO) and 93.8 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 1.1 ml of water (H2O) acidified with 1.2 ml of acetic acid (HAc) was then added slowly with constant stirring to the above solution. The molar ratio of the components in the batch was :TIPO : EGME : H2O : HAc : : 1 : 35 : 1.8 : 0.6 . The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 48 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 5.6 cm/min which was dried at ambient condition for 3 mins and further dried in an oven at 180°C for 20 mins. The dipping and drying processes were repeated thrice and then finally heat treated at a temperature of 500°C for 60 mins. Coatings were deposited on glass substrates with optical thickness µ2d = 221 nm at wavelengthλ, = 442 nm Observed colour of the coated glass in transmission was blue. Observed colour of the coated glass in reflection was yellow. Example 2 10 ml of titanium isopropoxide (TIPO) and 93.8 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 1.1 ml of water (H2O) acidified with 1.2 ml of acetic acid (HAc) was then added slowly with constant stirring to the above solution. The molar ratio of the components in the batch was :TIPO : EGME : H2O : HAc ::1:35:1.8:0.6. The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 48 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 5.6 cm/min which was dried at ambient condition for 3 mins and further dried in an oven at 180°C for 20 mins. The dipping and drying processes were repeated four times and then finally heat treated at a temperature of 500°C for 60 mins. Coatings were deposited on glass substrates with optical thickness Ujd = 283 nm at wavelength λ, = 566 nm Observed colour of the coated glass in transmission was yellow with green tinge Observed colour of the coated glass in reflection was blue. Example 3 10 ml of titanium isopropoxide (TIPO) and 65 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 0.6 ml of water (H2O) acidified with 0.9 ml of acetic acid (HAc) was then added slowly with constant stirring to the above solution. The molar ratio of the components in the batch was :TIPO : EGME : H2O : HAc : : 1 : 24 : 1 : 0.5 . The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 24 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 11.3 cm/min which was dried at ambient condition for 5 mins and further dried in an oven at 120°C for 30 mins. The dipping and drying processes were repeated four times and then finally heat- treated at a temperature of 500°C for 60 mins. Coatings were deposited on glass substrates with optical thickness µ2d = 462 nm at wavelength λ, = 462 nm Observed colour of the coated glass in transmission was blue Observed colour of the coated glass in reflection was green Example 4 10 ml of titanium isopropoxide (TIPO) and 130 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 1.8 ml of water (H2O) acidified with 3.2 ml of acetic acid (HAc) was then added with constant stirring to the above solution. The molar ratio of the above components in the batch was : TIPO : EGME : H2O :HAc : : 1 : 48 : 3 : 1.7. The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 24 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 11.3 cm/min which was dried at ambient condition for 5 mins and further dried in an oven at 120°C for 30 mins . The dipping and drying processes were repeated four times and then finally heat treated at a temperature of 500°C for 60 mins. Coatings were deposited on glass substrates with optical thickness µ2d = 224 nm at wavelength λ, = 449 nm Observed colour of the coated glass in transmission was blue Observed colour of the coated glass in reflection was orange Example 5 10 ml of titanium isopropoxide (TIPO) and 93.8 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 1.1 ml of water (H2O) acidified with 1.2 ml of acetic acid (HAc) was then added slowly with constant stirring to the above solution. The molar ratio of the components in the batch was :T1PO : EGME : H2O : HAc : : 1 : 35 : 1.8 : 0.6 . The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 48 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 14 cm/min which was dried at ambient condition for 5 mins and further dried in an oven at 180°C for 30 mins.. The dipping and drying processes were repeated four times and then finally heat-treated at a temperature of 500°C for 60 mins. Coatings were deposited on glass substrates with optical thickness µ2d = 352 nm at wavelength λ= 704 nm Observed colour of the coated glass in transmission was reddish orange Observed colour of the coated glass in reflection was bluish green Example 6 5 ml of zirconium propoxide (ZrPO) and 45 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 0.25 ml of distilled water (H2O) acidified with 0.6 ml of acetic acid (HAc) was then added slowly with constant stirring to the above solution. The molar ratio of the components in the batch was :ZrPO : EGME : H2O : HAc : : 1 : 35 : 1 : 0.6 . The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 2 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 11.3 cm/min which was dried at ambient condition for 3 mins and further dried in an oven at 180°C for 30 mins. The dipping and drying processes were repeated four times and then finally heat treated at a temperature of 500°C for 30 mins. Coatings were deposited on glass substrates with optical thickness µ2d = 436 nm at wavelength λ, = 436 nm Observed colour of the coated glass in transmission was blue with a violet tinge Observed colour of the coated glass in reflection was yellow Example 7 5 ml of zirconium propoxide (ZrPO) and 45 ml of ethylene glycol monomethyl ether (EGME) were mixed in a beaker using a magnetic stirrer. 0.25 ml of distilled water (H2O) acidified with 0.6 ml of acetic acid (HAc) was then added slowly with constant stirring to the above solution. The molar ratio of the components in the batch was :ZrPO : EGME : HiO : HAc :: 1:35: 1:0.6. The coating solution was further stirred for another 30 mins. with a purpose to make a stable sol which was then aged for 2 hrs. The cleaned glass slide was then dipped into it and withdrawn at a speed of 11.3 cm/min which was dried at ambient condition for 3 mins and further dried in an oven at 180°C for 30 mins. The dipping and drying processes were repeated thrice and then finally heat treated at a temperature of 500°C for 30 mins. Coatings were deposited on glass substrates with optical thickness µ2d = 280 nm at wavelength X = 559 nm. Observed colour of the coated glass in transmission was yellow. Observed colour of the coated glass in reflection was blue. From the above examples it may be inferred that the novel composition of the present invention having organo-metallic compounds such as titanium isopropoxide or zirconium propoxide mixed with ethylene glycol monomethyl ether and acidified distilled water in the molar ratio of M-OR: EGME: HAc: Water :: 1: (24-48) : (1-3) : (0.5-1.7) produces a stable sol suitable for dip-withdrawal process. Outside this range, the sol-stability gets detonated to a great extent. It becomes either unstable resulting in gelation or precipitation of the oxide or too dilute taking infinitely long time for hydrolysis-polycondensation reaction to occur leading to polymerization of the oxide network. The dip-withdrawl process with an withdraw! rate of 5.6 - 14 cm/min is suitable to produce the required optical thickness of the coating to satisfy the interference condition to produce different colour effect in the visible spectral range of 400 - 700 nm. For prominent colour effect, the optical thickness of the coating should be such that it should satisfy the interference condition for order n = 1 to 3. In our examples, colouring effect is produced both in transmission and reflection as shown in the figures of sheet 1. The main advantages of the present invention are : 1. A stable coating sol is produced with an organo-metallic compound of at least one of Ti, Zr, Ta and Nb for dip coating glass articles. 2. Any colour effect in the visible spectral range can be produced by changing the optical thickness of the film suitably to satisfy the interference condition. 3. Coating of only one component of oxide material is sufficient to produce the color effect. We claim: 1. A novel stable coating sol and process thereof useful for making sol coated glass with shimmering colour effect which comprises: organo-metallic compound (M-OR) where M is at least one of Ti, Zr, Ta, Nb and OR is an alkoxy group, ethylene glycol monomethyl ether (EGME), distilled water (H2O) and acetic acid (HAc) in a molar ratio of M-OR : EGME : H20 : HAc in the range of 1 : (24-48) : (1-3): (0.5-1.7). 2. A novel composition as claimed in claim 1 wherein the organo-metallic compound (M-OR) used is at least one of Ti- iso propoxide, Ti- ethoxide, Ti- butoxide, Zrpropoxide, Ta- ethoxide, Nb- ethoxide. 3. A process of preparing novel stable coating sol for making sol coated glass with shimmering colour effect which comprises: mixing organo-metallic compound (M-OR) and ethylene glycol monomethyl ether in a molar ratio in the range of 1 : (24-48) under continuous stirring to obtain a clear solution, adding to the said clear solution under constant stirring, acidified distilled water in which acetic acid : distilled water molar ratio is maintained in the range of (1-3) : (0.5-1.7) with respect to the organo-metallic compound, allowing the resultant to age for a period of 2 to 48 hours to obtain a stable coating sol. 4. A novel stable coating sol and process thereof useful for making sol coated glass with shimmering effect substantially as herein described with reference to the examples. Dated this 17th day of Sept., 2001 V Gomkale) Scientist Intellectual Property Management Division,CSIR 16 We claim: 1. A novel stable coating sol and process thereof useful for making sol coated glass with shimmering colour effect, which comprises: organo-metallic compound (M-OR) where M is at least one of Ti, Zr, Ta, Nb and OR is an alkoxy group, ethylene glycol monomethyl ether (EGME), distilled water (HiO) and acetic acid (HAc) in a molar ratio of M-OR : EGME : H2O : HAc in the range of 1 : (24-48): (1-3): (0.5-1.7). 2. A novel composition as claimed in claim 1 wherein the organo-metallic compound (M-OR) used is at least one of Ti- iso propoxide, Ti- ethoxide, Ti- butoxide, Zrpropoxide, Ta- ethoxide , Nb- ethoxide. 3. A process of preparing novel stable coating sol for making sol coated glass with shimmering colour effect which comprises: mixing organo-metallic compound (M-OR) and ethylene glycol monomethyl ether in a molar ratio in the range of 1 : (24-48) under continuous stirring to obtain a clear solution, adding to the said clear solution under constant stirring, acidified distilled water in which acetic acid : distilled water molar ratio is maintained in the range of (1-3) : (0.5-1.7) with respect to the organo-metallic compound, allowing the resultant to age for a period of 2 to 48 hours to obtain a stable coating sol. 4. A novel stable coating sol and process thereof useful for making sol coated glass with shimmering effect substantially as herein described with reference to the examples.

Documents:

961-DEL-2001-Abstract-13-05-2008.pdf

961-DEL-2001-Abstract-23-05-2008.pdf

961-del-2001-abstract.pdf

961-del-2001-claim-04-06-2008.pdf

961-DEL-2001-Claims-13-05-2008.pdf

961-DEL-2001-Claims-22-05-2008.pdf

961-DEL-2001-Claims-23-05-2008.pdf

961-del-2001-claims.pdf

961-DEL-2001-Correspondence-Others-13-05-2008.pdf

961-DEL-2001-Correspondence-Others-23-05-2008.pdf

961-del-2001-correspondence-others.pdf

961-del-2001-description (complete).pdf

961-del-2001-description (complete)04-06-2008.pdf

961-DEL-2001-Description (Complete)13-05-2008.pdf

961-DEL-2001-Description (Complete)22-05-2008.pdf

961-del-2001-description (complete)23-05-2008.pdf

961-DEL-2001-Drawings-13-05-2008.pdf

961-DEL-2001-Drawings-23-05-2008.pdf

961-DEL-2001-Form-1-13-05-2008.pdf

961-DEL-2001-Form-1-23-05-2008.pdf

961-del-2001-form-1.pdf

961-del-2001-form-18.pdf

961-DEL-2001-Form-2-13-05-2008.pdf

961-DEL-2001-Form-2-23-05-2008.pdf

961-del-2001-form-2.pdf

961-del-2001-form-3.pdf