DESC:Field of the Invention:
The present invention relates to high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates and more particularly to one component/pack, very thin (about 1-2 micron), highly transparent silicon based films/ coats adapted for higher UV and heat resistance coating material on glass or glass-like substrates.
Background Art:
The beneficial effects of solar energy are spanning over all spheres of life in the earth - still it exerts detrimental effects on the various kinds of paints and coatings. The Solar spectrum typically consists of 5% ultraviolet, 43% visible and almost 52% infrared rays/radiation. About 48% of the total 52% infrared radiation lies in between 780 nm to 2500nm. The human eye is sensitive to only a part of the total solar radiation. Different colours are detected by the optical human system in the wavelength range from 400 to 700 nm. Almost 90% of the total heat generated from the solar energy lies in the range of 780 nm to 2500 nm (see Figure 1). More precisely the heat-producing region of the infrared radiation ranges from 700 to 2500 nm. As mentioned above that almost 90% of the total heat generated from the solar energy lies in the range of 780 nm to 2500 nm i.e. in the IR region. The pigments used as colour component for coating or paints are commonly susceptible to degradation upon exposure to solar UV and/or IR radiation. Thus, methods for absorption of ultraviolet energy and of infrared energy are required for betterment of lifetime of both indoor and outdoor coatings and as well as the objects coated by it.
The primary objective of IR absorbing coating is to provide good absorption in the near-IR region of the solar spectrum and be transparent over a large region of the visible spectrum, thereby enabling the window of visible light to enter whilst absorbing the solar power from the near IR part of the spectrum. Such coatings are used as solar energy absorbers, as well as for producing hidden, machine-readable indicia on objects or documents, for the automated processing or authentication of the said objects or documents by machines.
Generally inorganic oxides are used as the thermal barrier material which also posses high durability and thermal barrier properties. A new class of selective solar absorption coatings, coat surface by a nano-structured layer which has high selective solar absorptivity consist of inorganic oxide particles. The inorganic oxides including antimony tin oxide (ATO), indium tin oxide (ITO), silica oxide (SiO2), aluminium oxide (Al2O3), molybdenum oxide (MoO3), niobium oxide (Nb2O5), vanadium oxide (V2O5), etc. are most commonly used. Particularly, in practice antimony tin oxide (ATO), indium tin oxide (ITO) and tungsten bronze etc. display most effective infrared blocking property. The inorganic metal derivatives can be synthesized by calcination of a mixture of oxides, nitrates, acetates and even metal oxides at temperatures above 1000 °C, alternatively by chemical methods like sol-gel method, solvo-thermal reaction etc. Coatings consisting of smaller particles or nanoparticles significantly improve the heat absorption and UV resistance properties [Malshe, V., et al. (2008). http://dx.doi.org/10.2174/ 2211334710801010067, Fang, V., et al. (2013). (GNSScience Report. New Zealand: Institute of Geological and Nuclear Sciences)]. In addition to their anti IR/UV properties, coatings can differ in their weatherability, chemical resistance, and other durability criteria.

Further the efforts directed to incorporate nanoparticles in different coating system led to the following:

US 2006/0008640 A1 teaches to provide a laminated structure for shielding against solar radiation having high solar radiation blocking characteristics with low manufacturing costs. A liquid composition to form a solar radiation blocking material is prepared by dispersing calcined and crushed tungstic acid fine particles with polymer based dispersing agents and solvent, and thus prepared liquid dispersion is added to vinyl resin. The viscous dispersed liquid is molded into a sheet shape to obtain an intermediate film. Thus obtained intermediate film is sandwiched between two sheets to be laminated selected from sheet-glass or plastic to obtain an intermediate layer, which upon heating become bonded with each other to prepare a laminated structure for shielding against solar radiation.

US 2014/0023860 A1 provides a liquid composition and its production process instrumental of forming a coating film which has sufficient ultraviolet-absorbing ability as well as infrared-absorbing ability. A liquid composition for forming a coating film comprising an infrared absorber selected from indium tin oxide, antinomy tin oxide and a composite tungsten oxide, an ultraviolet absorber selected from a benzophenone compound, a triazine compound and a benzotriazole compound, a dispersing agent having an acid value and/or an amine value, a binder component and a liquid medium, wherein the quantity of dispersing agent is used in such a fashion that the sum (mg KOH/g) of the acid value and the amine value of the dispersing agent, and the mass ratio of the dispersing agent to the infrared absorber, is from 2 to 30 (mg KOH/g).

US 8,980,381 B2 teaches a method of preparing coating compositions containing resins with dispersed nanoparticle precursors and methods for using said coatings as visual indicators of thermal and impact damage. The nanoparticle precursor/resin system reduces the nanoparticle precursor to its nanoparticle state when subjected to heat and/or physically impacted. The nanoparticles formed impart a color upon the coating at the point of exposure due to surface plasmon resonance. Microencapsulated leuco-dyes are utilized to impart color when the coating is struck. The dye within the microcapsule is released as the microcapsule wall bursts or melts. Solubilizing agents can be utilized to improve the solubility of the nanoparticle precursor in the resin.

US2010184901 (A1) relates to transparent and colorless compositions that absorb infrared radiation and that comprise nanoparticles comprising non-stoichiometric tungsten oxide particles. In certain respects, the prior art is directed to compositions that are transparent and colorless. In some embodiments, the compositions of the advancement comprise: (a) a binder; and (b) no more than 500 parts per million, based on the total weight of the composition, of non-stoichiometric tungsten oxide particles having an average primary particle size of no more than 300 nanometers dispersed in the binder.

Reference is also drawn to non-patent literature documents wherein utilization of photoactive and UV-blocking nanoparticles in transparent coatings and films are relied on the ability to avoid agglomeration and to adapt and optimize the film forming and deposition processes to ensure that the nanosized functional particles are distributed either homogeneously or in desired patterns [Satoru I. et al 2003 Sci. Technol. Adv. Mater. 4 269]. Providing robust methods to prepare colloidally stable dispersions in polar or non-polar media is of pivotal importance and a process that requires fundamental understanding of the nature and magnitude of the interparticle forces (Israelachvili, J. N.; 2011 Intermolecular and Surface Forces (San Diego, CA: Academic). The predominant interparticle forces in most nanoparticulate systems are the van der Waals, double layer (electrostatic), and steric (polymeric) forces. Controlling the compatibility between the nanoparticles and the matrix, either polymeric or inorganic, is also very important in order to tune the microstructure of the final material. [Faure, B. et al.; Sci. Technol. Adv. Mater. 14 (2013) (23pp) doi:10.1088/1468-6996/14/2/023001].

In addition to the above polymeric materials, such as, polystyrene, polycarbonate, polyvinyl chloride, polyvinyl alcohol, polyurethane, polyester, polyacrylates and silicone oxide matrix films are used either singular or in combination as the base material to form heat resistant coating layer on the glass or glass-like materials, in combination with the IR absorbing materials and UV absorbers. The prior materials are mostly two pack system. (US2010/0184901 Adochio et. al ;) Two component silica based coating materials lack the requisite clarity/transparency, heat cut-off efficiency and hardness required for everyday applications. Additionally, the coated films usually give a film thickness in the range of 10 microns.
The issue of compatibility and stability of all ingredients in the final formulated solution is the prime hurdle to overcome while developing polysiloxanes, polysilazane and titanium based coating materials to provide thin film coatable on glass and glass-like substrates. These polysiloxanes, polysilazane and titanium based coating materials have very high tendency of becoming hazy or cloudy i.e. undergoing agglomeration.

In the back drop of the above teachings and limitations in both patent and non-patent literatures for the development of effective IR and UV blocking transparent formulation coatable on glass and glass-like substrate to provide for very thin clear and hard films, there is therefore a continuing need in the art to explore for new kind of formulations of liquid coating material on glass or glass like objects which would on one hand block harmful radiations from sun like ultraviolet and infrared rays and on the other hand would also be one component, thin, highly transparent with higher UV and heat resistance coating material suitable for glass or glass-like substrates.
Objects of the invention:
The primary object of the present invention is to provide for high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates especially suited for glass and glass-like substrates such that advantages of inorganic paints could be realized of lower absorption of sun radiation, non-burning, absence of fouling and microcrystalline texture.

Another object of the present invention is to provide for high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates especially suited for glass and glass-like substrate involving nanoparticles that would be characterised by a high sintering activity.

Yet further object of the present advancement is directed to polymer coated and noncoated metal oxide nanoparticles adapted for photoactive applications especially IR-blocking enabling wide ranging applications and uses including high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates.
Another object of the present invention is directed to advancement in cesium tungsten bronze nanoparticles which would be adapted for photoactive applications especially IR-blocking and compatible with both polar and non polar solvents enabling wide ranging applications and uses including high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates.
Yet another object of the present invention is to provide for high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates that would be achievable by a sintering process at rather low temperatures suitable for glass or glass like substrates so as to realize the advantages of inorganic paints of lower absorption of sun radiation, non-burning, absence of fouling and microcrystalline texture.

Still another object of the present invention is to provide for high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates that would not become hazy or cloudy and would not undergo agglomeration in involving selective combination of components that would also make the film clear and hard.

Yet another object of the present invention is to provide for one component, very thin ( about 1-2 micron), high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates adapted to block harmful radiations like ultraviolet and infrared rays and serve as effective heat resistance coating material on glass or glass-like substrates and yet achieve hardness that would surpass the hardness obtained from the prior UV and heat resistance coating.
Yet another object of the present invention is to provide for one component, very thin (about 1-2 micron), high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates adapted to block harmful radiations like ultraviolet and infrared rays which will be capable of blocking the whole IR range, i.e., 700-2500.
Yet another object of the present invention is to provide for surfactant free inorganic nanoparticles based heat absorbing transparent coating especially suited for glass and glass-like substrates such that advantages of inorganic paints could be realized of lower absorption of sun radiation, non-burning, absence of fouling and microcrystalline texture.

According to yet further aspect of the present invention the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays provide films having superior hardness compared to the reported compositions.
Yet another object of the present invention is directed to provide coats / formulations which would also overcome the issue of compatibility and stability of all ingredients in the final formulation since the presence of polysiloxanes, polysilazane and titanium based coating materials providing thin film coating on glass and glass-like substrates is known to have a high tendency of becoming hazy or cloudy i.e. undergoing agglomeration.

Summary of the invention

As discussed hereinbefore the present invention includes high transparency silicone based heat absorbing thin film/coating formulation for glass and glass like substrates and according to an embodiment the same is provided for in the form of single pack, silicon based coating material preferably liquid, more particularly including inorganic coating material and formulations thereof comprising polymer coated and noncoated metal oxide nanoparticles prepared by an improved process to provide for very thin ( about 1-2micron) transparent and hard coating on glass and glass-like substrates adapted to block harmful radiations like ultraviolet and infrared rays in one hand and on the other hand would be transparent to visible light.

In accordance with an aspect of the present invention it is surprisingly found that selective formulation/coating having the select combination of ingredients in select wt% could provide for the desired one component/ one pack film that is clear, hard and verythin (about 1-2 micron), highly transparent with higher UV and heat resistance when provided as a coating material on glass or glass-like substrates and even with hardness obtained which could surpass the hardness obtained from the prior UV and heat resistance coating.

According to another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays wherein the thin film comprises entirely inorganic/nano coating.
According to yet further aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays wherein said thin films about 1-2 or lesser micron in thickness.
In another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays provide films having superior hardness compared to the reported compositions.
In another aspect of the present invention the same is directed to thin film comprising metal oxides nanoparticles such as, cesium tungsten bronze, vanadium oxide, molybdenum oxide, indium tin oxide (ITO) and antimony-doped tin oxide (ATO) nanoparticles (NPs).
In another aspect of the present advancement there is provided for infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays comprise metal oxides nanoparticles comprise, cesium tungsten bronze, indium tin oxide (ITO) and antimony-doped tin oxide (ATO) nanoparticles, (NPs)are used as infrared blocking materials.
In another aspect of the present invention there is provided for infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays comprise metal oxides nanoparticles such as, cesiumtungsten bronze, vanadium oxide, molybdenum oxide, indium tin oxide (ITO) and antimony-doped tin oxide (ATO) nanoparticles (NPs) are transparent in the visible region.
In another aspect of the present invention there is provided for formulations comprising metal oxide nanoparticles including cesium tungsten bronze nanoparticles preferably about 2-15 wt % of the final composition.
In another aspect of the present invention there is provided for formulation comprising metal oxide nanoparticles including Indium tin oxide (ITO) nanoparticles preferably about 1-10 wt % of the final composition.
In certain respects, the present invention to the same is directed to compositions of matter that are transparent and colorless comprising metal oxide nanoparticles including antimony doped tin oxide (ATO) nanoparticles preferably about 1-10 wt % of the final composition.
In another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays comprise metal oxides nanoparticles also contains ultraviolet absorbers to absorb UV light completely.
In another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared including metal oxides nanoparticles involving benzotriazole or benzophenone based material preferably about 2-5 wt% as ultraviolet absorbers.
In another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays mixed with the base material to form heat resistant coating layer on the glass or glass-like materials.
In another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays are mixed with the base material in the final formulation to form heat resistant coating layer on the glass or glass-like materials and are selected from polysiloxanes, polysilazane either individually or both.
In another aspect of the present advancement the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared mixed with the base material in the final formulation to form heat resistant coating layer on the glass or glass-like materials is selected from polysiloxanes, polysilazane either individually or both titanium based coating materials for TiO2 NP.
In another aspect of the present advancement the same is directed to formulations capable of blocking harmful radiations like ultraviolet and infrared rays comprises TiO2 NPs sourced from Titanium butoxide or Titanium isopropoxide.
In another aspect of the present invention the same is directed to infrared coatings capable of blocking harmful radiations like ultraviolet and infrared rays comprise of ITO, TiO2, and cesium tungsten bronze NPs preferably in the size in the range of about 20 to 30 nm.
In another aspect of the present advancement the same is directed to process for manufacture of infrared pigment/coating formulation comprising cesium tungsten bronze were synthesized based on following the steps:
i. providing Cesium/sodium tungsten oxide and cesium chloride together in followed by addition of water;
ii. cooling the dispersion to about 0-50C;
iii. adjusting pH upto about pH 2;
iv. collecting precipitate and heating preferably about 170 to 190 0C preferably 180 0C for 4 hrs.
v. reducing at Cs2WO4 to CsxWO3-x preferably 4500 C for 3 to 5 hrs preferably 4 hr.
vi. cooling CsxWO3-x nanoparticles thus obtained; wherein x= 0.22-0.33 with size of the NP obtained in the range of 22 ± 5 nm.

In another aspect of the present advancement there is provided manner of manufacture of said infrared pigment/coating formulation comprising polymer coated cesium tungsten bronze nanoparticles synthesized following the steps:
a. involving the particles selectively in water, ethanol, isopropanol, xylene, cellosol acetate, butylacetate etc.;
b. dispersing the particles with the addition of various dispersing agent, such as, Triton X-100, CTAB, Nonoxynol-9, TERGITOL NP10 non-ionic surfactants
c. carrying out in situ polymerization with acrylic polyol on the surface of the NPs;
d. curing with polymeric diisocyanate
In another aspect of the present advancement there is provided manner of in situ polymerization with acrylic polyol following the steps:
dispersing the powder into the respective solvent;
heating on an oil bath with stirring;
mixing all the monomers and thermal initiator in rest of the solvent;
adding dropwise to the reaction mixture;
heating for another 1-2 hr; and
cooling to room temperature

In another aspect of the present advancement there is provided the process for synthesis of the said infrared pigment/coating formulation including Indium Oxide Nanoparticles following the steps:
i. dissolving indium acetate in 9-octadecene;
ii. adding different long chain aliphatic acids and long chain amines;
iii. heating at 110-150 ºC under N2 for about 20-40 mins;
iv. heating the mixture at about 200-300 ºC for about 5-8hrs;
v. finally collecting the ITO NPs using repeated precipitation and redispersion technique;
vi. the final ITO NPs dispersion being prepared in toluene/xylene/hexane for further applications.

In another aspect of the present advancement there is provided the process for synthesis of the said infrared pigment/coating formulation following the steps:
a) adding 1-5% of film base material in ethanol, isopropanol and butanol preferably isopropanol;
b) hydrolyzing by acid or alkali;
c) adding dispersion of 2-15wt% cesium tungsten bronze, 1-10wt% ITO and 1-10wt% ATO NP dispersions, 2-5 wt% UV absorbers;
d) adding polyol to make the formulation 100%;

Details of the invention
Thus the present advancement enables the one pack, very thin silicon based entirely inorganic coating formulation of the present advancement comprising ITO, ATO, TiO2, and cesium tungsten bronze NPs is directed to provide very thin film (1-2) micron on glass or glass like substrates exhibiting efficient blocking of UV and IR radiation with very good transparency and having higher hardness.
The advancement according to the present invention is discussed in greater detail in relation to the following non-limiting exemplary illustrations by way of following non-limiting Figures and Examples wherein
Figure 1: The relative solar energy distribution with respect to the wavelength. The above picture downloaded from Miracosta college library, USA (http://www.miracosta. edu).
Figure 2: The transmission electron microscopic image of the cesium tungstate bronze (CsxWO3-x) used in heat and UV resistant coating. The bar represents the 50nm scale. The average particle size of the materials as obtained from the dynamic light scattering was around 22 nm.
Figure 3: The average particle size of the ATO nanoparticle dispersions as obtained from the dynamic light scattering was around 250 nm.
Figure 4: The UV-Vis-NIR transmittance of a coated glass plate from the example 3.
Figure 5: The in-situ polymers synthesized in cellosolve acetate in the presence of the cesium tungstate dispersion have been characterized with FTIR. Strong –C-H stretching frequency (2970 cm-1) undoubtedly confirms the formation of polymers which also confirmed from the GPC results.
Figure 6: The in-situ polymers synthesized in ethyl cellosolve in the presence of the cesium tungstate dispersion have been characterized with FTIR. Strong –C-H stretching frequency (2970 cm-1) undoubtedly confirms the formation of polymers which also confirmed from the GPC results.
Figure 7: The in-situ polymers synthesized in butanol in the presence of the cesium tungstate dispersion have been characterized with FTIR. Strong –C-H stretching frequency (2970 cm-1) undoubtedly confirms the formation of polymers which also confirmed from the GPC results.
Figure 8: The in-situ synthesized polymeric dispersion of cesium tungstate in cellosolve acetate (A) as synthesized (B) after 7 days.
The UV and heat resistant transparent coating on glass and glass-like substrates comprise cesium tungsten oxide nanoparticles, ATO, ITO nano particles and in-situ generated TiO2 nanoparticles and the synthesis of them have been developed as follows:

Example 1: Synthesis of cesium tungsten bronze
1-2g of cesium tungsten oxide and 0.2-0.5g cesium chloride was taken together in a round bottom flask followed by addition of 40-80 mL of water. Then, 5-10mL of conc. HCl was added drop wise to the reaction mixture until the pH of the solution reached around 2. The reaction was performed on an ice-bath. The temperature of the reaction mixture should be below 5?C during the addition. The reaction mixture was then stirred at room temperature for another 12h. The yellow precipitate thus obtained was collected by centrifugation and subsequently washed with water and ethanol. Finally, the material was heated in an oven at 180 ºC for 6hrs affording WO3 nanoparticles. The reduced WO3 nanoparticles CsxWO3-x, where; x= 0.22-0.33; were then obtained with the reaction of 10% H2 in nitrogen at 450ºC for 4h.
The material was dispersed using ultrasound sonication with the addition of various dispersing agent, such as, Triton X-100, CTAB, Nonoxynol-9, TERGITOL NP10 non-ionicsurfactants.(The dual compatibility of the non-ionic surfactant both in polar and non-polar solvents will help the nanoparticles to be dispersed well in polar or less polar solvents such as, isopropanol, xylene etc.)
Accordingly the resulting materials were dispersible in water, ethanol, isopropanol, xylene, cellosolve acetate, butylacetate etc. The average particle size of the synthesized CsxWO3-x; x= 0.22-0.33 were found to be around 22 ± 5 nm as obtained from transmission electron microscope and dynamic light scattering measurements (see Figure 2).
In-situ polymerization technique had been adapted to graft acrylic polyol on the surface of the cesium tungstate nanoparticles dispersions obtained in the above step. In-situ polymerization technique to graft acrylic polyols on the surface of cesium tungstate nanoparticles facilitated to obtain a stable dispersion of the nanoparticles in the solvents of choice. The resultant polymer-nanoparticle hybrids were eventually cured with polymeric diisocyanate to give a transparent bluish tinted coating on the glass or glass-like surfaces to obtain a highly transparent, UV and IR absorbing film.
The acrylic polyol grafted cesium tungstate nanoparticles as IR cut-off coats and its dispersion technique of the cesium tungstate nanoparticles and the in-situ polymerization along with the stabilization of the nanoparticles in the desired solvent is found to attain the desired attributes as targeted wherein the choice of solvent also plays an important role in the polymerization process. Above all, the grafted end products lead to the product stability as otherwise the NPs will not be stable in the solvents and will precipitate out of the solvents.
The cesium tungstate NPs solids are dispersed with the method discussed above. Then, the dispersions are coordinated with various amino silanes, such as, primary, secondary, tertiary and quaternary aminosilanes. The resultant materials are cured with various epoxy silanes.

Example 2: Synthesis of Indium tin oxide NP
Indium tin oxide (ITO) NPs dispersions were prepared using the modified methods by Gilstrapet. al; (Adv. Mater. 2008, 20, 4163–4166). In this synthesis, 0.5-1.5 mmol indium acetate and 0.05-0.25 mmol dibutyltindiacetate were dissolved in 20-50 mL of 9-octadecene. Different longchain aliphatic acids, such as, myristic acid, oleic acid etc. and long chain amines, such as, oleylamine, octadecylamine, dibutylamine also added to this solution. The solution was heated at 110-150 ºC under constant flow of N2 for 30 mins in the reaction medium. Finally, the mixture was heated at 200-300 ºC for 3-8hrs more precisely, 250-280 ºC for 4 hrs. The unreacted starting materials were cleaned and finally the ITO NPs were collected using repeated precipitation and redispersion technique using acetone and toluene or hexane with the aid of a high-speed centrifuge. The final ITO NPs dispersion was prepared in toluene/xylene/hexane for further applications.

Example 3: Synthesis of Antimony doped tin oxide NPS
Antimony doped tin oxide(ATO) NPs are synthesized using solvo - thermal synthesis methods (Modified method of Peters, Chem. Mater., 201527, 1090-1099). In this synthesis method, 0.5-1.5 mmol dibutyltin dilaurate/stannic (IV) chloride and 0.2-0.5 mmol antimony(III)acetate or antimony(III)chloride was dissolved in 20-50 mL of high boiling alcoholic solvents, such as, isopropanol, tertiary butyl alcohol, benzyl alcohol etc. Organic amines are used in this reaction mixture to act as bases thereby facilitate the decomposition of the metal complexes. The reaction mixture was transferred into a Teflon or glass-lined autoclave and the mixture was heated at 150-200 ºC for 4-10 hrs. Resulting light yellow to brownish suspensions were treated with dichloromethane causing flocculation which was separated by centrifugation, washed twice with acetone, and centrifuged.Final ATO NPs dispersion was prepared in toluene/xylene/hexane for further applications. The average particle size of the ATO nanoparticle dispersions as obtained from the dynamic light scattering was around 110 ± 10nm.
UV absorbers
UV absorbers, such as, benzotriazoleand benzophenone are used in the formulation of the coating for the light stabilization of the polymers or silane based coating used for heat and UV cut-off.
Example 4: Cesium tungstate dispersion and in-situ polymerization technique:
Preparation of cesium tungstate dispersion:
Cesium tungstate powder (0.6 g) was taken in 500 ml round bottom flask and then 75 g of solvent (butanol or cellosolve acetate or ethyl cellosolve) added in the flask. The powder was dispersed into the respective solvent using high energy sonication for 30 min.

Synthesis of polymer:
The cesium tungstate dispersion in the respective solvent underwent in-situ polymerization to get a stable dispersion of the cesium tungstate. Rest amount of the solvents (65 g) was added to the system. This RB flask containing the reaction mixture was placed on hot oil bath along with mechanical stirring and condenser. All the monomers MMA (24 g), BA (6 g), EHA (6 g), HEMA (24 g) and 2 g thermal initiators (TBPO) were mixed together and added dropwise into the reaction mixture very slowly (addition time almost 2-3 h). After complete addition of the monomer mixtures, the reaction mixture heating continued for another 60 mins and then kept out of the oil bath so that the temp of the solution will cool down to room temperature. Same reaction was performed for three different solvents (butanol, cellosolve acetate and ethyl cellosolve) without changing the other conditions.
One control experiment was also performed without the cesium tungstate dispersion but keeping all other conditions same using the solvent butanol.
All the synthesized polymers are characterized using GPC and NMR.

Sample Solvent Cesium Tungstate(%) Mn(Da) PDI
Sample-D1 Cellosolve Acetate 0.3 6500 10.5
Sample-D2 Ethyl Cellosolve 0.3 7000 12.0
Sample-D3 Butanol 0.3 27800 4.0
Sample-D4 Butanol - 7000 3.0

Final coating composition
The final coating was formulated using the above mentioned inorganic and organic additives. Well dispersed cesium tungsten bronze, ITO and ATO nanoparticle dispersions in the organic solvents along with the UV absorbers were used in the formulated coatings. 2-15wt.% cesium tungsten bronze, 1-10% ITO and 1-10% ATO NP dispersions, 2-5 wt.% UV absorbers were used in the final formulations. Polysiloxanes, polysilazane and titanium based coating materials were used in the final formulations to make a very thin and clear coating.
Example 5: 1-5 wt% tetraethoxyorthosilicate is hydrolysed under ammoniacal ethanol solution and 2-15wt% cesium tungsten bronze, 1-10wt% ITO and 1-10wt% ATO NP dispersions, 2-5 wt% UV absorbers are added to this resultant solution. Then 1-5 wt% polysilazane are added to the above solution. The rest of the 55-90% materials have been adjusted with polyols, such as, ethanol, isopropanol and butanol. All the solutions are mixed with strong stirring conditions using overhead stirrers at an average speed of 500 rpm for about one hour. The resultant materials are applied on a glass surface through a gun spray. The resultant material gave a clear film on the glass.
Thickness(µm) % UV block % IR block % Vis Transmission Haze%
1-2 99 75-77 73-75 2-3
Example 6: 1-5 wt% methoxy terminated polydimethylsiloxanes was taken in isopropanol. 1-10 wt% titanium tetraisopropoxidewas added to this solution. In this resultant solution, 2-15wt% cesium tungsten bronze, 1-10wt% ITO and 1-10wt% ATO NP dispersions, 2-5 wt% UV absorbers are added. The rest of the 55-90% materials have been adjusted with polyols, such as, ethanol, isopropanol and butanol. All the solutions are mixed with strong stirring conditions using overhead stirrers at an average speed of 500 rpm for about one hour. The resultant materials are applied on a glass surface through a gun spray. The resultant material provides a clear film on the glass.
Thickness(µm) % UV block % IR block % Vis Transmission Haze%
2-3 99 65-70 79-80 2-3
Example 7: 1-5 wt% tetraethoxyorthosilicate is hydrolysed under acidic water and ethanol solution using acetic acid or hydrochloric acids. 20wt% of the above solution is taken in isopropanol solution. In this resultant solution, 2-15 wt% cesium tungsten bronze, 1-10% ITO and 1-10% ATO NP dispersions, 2-5 wt% UV absorbers are added. Then 1-5 wt% titanium tetraisopropoxide is also added to the above solution. All the solutions are mixed with strong starring conditions. The resultant material gave a clear coating on the glass. Figure 4 shows the heat cut-off efficiency against the wavelength of light after preparing a thin film of the above mixture on a glass panel.
Thickness(µm) % UV block % IR block % Vis Transmission Haze%
2-3 99 80-82 75-77 1-2

Example 8: 1-5 wt% epoxysilanes, such as, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-metha-cryloxypropyl trimethoxysilane, etc. and 2-6 wt% amino- or cyanosilanes, such as, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyl dimethoxysilane, 2-cyanoethylmethyldimethoxysilane etc. were taken in isopropanol solution. 2-15wt% cesium tungsten bronze, 1-10% ITO and 1-10% ATO NP dispersions, 2-5 Wt% UV absorbers were added and the solution was mixed with strong stirring. The resultant material upon application gave a clear coating on the glass.
Thickness(µm) % UV block % IR block % Vis Transmission Haze%
2-3 99 68-70 78-79 1-2

The thin film/coatings according to the present advancement as disclosed above advantageously directs to development of cesium tungsten bronze nanoparticles treated with non-ionic surfactant to make it compatible with both polar and non polar solvents for the subsequent steps. Moreover, application of in-situ polymerization on cesium tungsten bronze nanoparticles made it stable in the form of dispersion.
With the obtained thickness of the coating according to the advancement it displayed substantially improved % absorption of the intended IR and UV radiation and simultaneously offered better visibility compared to other reported coatings.
Kodaira et al. reported infrared radiation cut off of about 60 % along with the UV cut off of about 99%. The visible transmittance can be obtained in the range of 74% with 4 micron film thickness. (PCT/US2014/0023860 Kodaira et. al;). On the other hand the coating according to the present advancement of 1-2 micron films exhibits to cut more than 70% IR radiation along with the 99% UV radiation. The visible transparencies of the said films obtained according to the advancement are also above 75% with lower amount of haze and yellowness index.
It is thus possible by way of the present advancement to provide for one component/pack, very thin (about 1-2micron), superior UV and heat resistance coating material with the following characteristics and advantages:
(i) high transparency silicon based films/ coats and formulation suitable on glass or glass like substrates;
(ii) a hybrid of inorganic binders, inorganic and organic additives displaying superior hardness as compared to the existing coatings;
(iii) overcoming the issue of compatibility and stability of all ingredients in the final formulation since the presence of polysiloxanes, polysilazane and titanium based coating materials providing thin film coating on glass and glass-like substrates is known to have a high tendency of becoming hazy or cloudy i.e. undergoing agglomeration.
(iv) easy application of the composition on the intended surface such as gun spray; and
(v) green composition with zero VOC emission (the alcohols used- methanol, ethanol or isopropanol are not considered VOCs) and easy drying.
,CLAIMS:We Claim:
1. Stable cesium tungstate nanoparticles suitable for stable dispersion in solvents comprising:
acrylic polyol grafted on the surface of cesium tungstate nanoparticles.

2. Stable cesium tungstate nanoparticles as claimed in claim 1 wherein in-situ polymerisation graft acrylic polyols on surface of said cesium tungstate nanoparticles.

3. Stable cesium tungstate nanoparticles as claimed in anyone of claims 1 or 2 having average particle size of the synthesized CsxWO3-x; x= 0.22-0.33 was around 22 ± 5 nm.

4. Stable cesium tungstate nanoparticles as claimed in anyone of claims 1 to 3 favour stable dispersion in solvents including water, ethanol, isopropanol, xylene, cellosolve acetate, butylacetate.

5. Stable silicone based high transparency thin film /coating formulation comprising: acrylic polyol grafted cesium tungstate nanoparticles stable in formulation with base materials selected from polysiloxanes, polysilazane either individually or both in amounts of 1 to 5 % by wt. or 1-5 wt% epoxy silanes with 2-6 wt% amino- or cyano silanes.

6. Stable silicone based high transparency thin film /coating formulation as claimed in claim 5 which is a “single pack” formulation comprising metal oxides nanoparticles including cesium tungsten bronze, vanadium oxide, molybdenum oxide, indium tin oxide (ITO) and antimony-doped tin oxide (ATO) nanoparticles (NPs).

7. Stable silicone based high transparency thin film /coating formulation as claimed in anyone of claims 5 to 6 comprising in situ polymerised graft acrylic polyols on surface of said cesium tungstate nanoparticles having average particle size of the synthesized CsxWO3-x; x= 0.22-0.33 were around 22 ± 5 nm.

8. Stable silicone based high transparency thin film /coating formulation as claimed in claim anyone of claims 5 to 7
Thickness(µm) % UV block % IR block % Vis Transmission Haze%
1 to 3 98.5 to 99.5 65 to82 73 to 80 1 to 3

9. Stable silicone based high transparency thin film /coating formulation as claimed in anyone of claims 5 to 8 suitable for coating on glass or glass like substrates,
wherein said coatings is capable of blocking harmful radiations like ultraviolet and infrared rays wherein the thin film comprises entirely inorganic/nano coating.

10. Stable silicone based high transparency thin film /coating formulation as claimed in anyone of claims 5 to 9 comprising metal oxides nanoparticles (NPs) selectively cesium tungsten bronze 2 to 15 % by wt, indium tin oxide (ITO) 1 to10 % by wt. and antimony-doped tin oxide (ATO) 1 to 10 % by wt.

11. Stable silicone based high transparency thin film /coating formulation as claimed in anyone of claims 5 to 10 which is heat resistant and comprising ultraviolet absorbers to absorb UV light and including benzotriazole or benzophenone based material preferably about 2-5 wt% as ultraviolet absorbers.

12. Stable silicone based high transparency thin film /coating formulation as claimed in anyone of claims 5 to 11 wherein base material is selected from polysiloxanes, polysilazane either individually or both or epoxy silanes with amino- or cyano silanes titanium based coating materials for TiO2 NP preferably including Titanium butoxide or Titanium isopropoxide.

13. A process for the manufacture of stable cesium tungstate nanoparticles suitable for stable dispersion in solvents comprising:
providing cesium tungsten nanoparticles ;
subjecting the said cesium tungsten nanoparticles to in situ polymerisation with acrylic polyols.

14. A process for the manufacture of stable cesium tungstate nanoparticles as claimed in claim 13 comprising synthesising cesium tungsten bronze nanoparticles comprising the steps of:
i. providing cesium/sodium tungsten oxide and cesium chloride together in followed by addition of water;
ii. cooling the dispersion to about 0-50C;
iii. adjusting pH upto about pH 2;
iv. collecting precipitate and heating preferably about 170 to 190 0C preferably 180 0C for 4 hrs.
v. reducing at Cs2WO4 to CsxWO3-x preferably 4500 C for 3 to 5 hrs preferably 4 hr.
vi. cooling CsxWO3-x nanoparticles thus obtained; wherein x= 0.22-0.33 with size of the NPs obtained in the range of 22 ± 5 nm

15. A process for manufacture of stable silicone based high transparency thin film /coating formulation as claimed in anyone of claims 5 to 12 comprising:

comprising providing metal nanoparticles including polymer coated cesium tungsten bronze nanoparticles in base materials selected from polysiloxanes, polysilazane either individually or both or epoxy silanes with amino- or cyano silanes in amounts of 1 to 5% by wt.

16. A process as claimed in anyone of claims 13 to 15 comprising providing
metal oxides nanoparticles (NPs) selectively cesium tungsten bronze 2 to 15% by wt, indium tin oxide (ITO) 1 to10 % by wt. and antimony-doped tin oxide (ATO) 1 to 10% by wt.

17. A process for manufacture of stable silicone based high transparency thin film /coating formulation as claimed in claim 16 wherein polymer coated cesium tungsten bronze nanoparticles are obtained following;
a) involving the particles selectively in water, ethanol, isopropanol, xylene, cellosol acetate, butylacetate etc.;
b) dispersing the particles with the addition of various dispersing agent, such as, Triton X-100, CTAB, Nonoxynol-9, TERGITOL NP10 non-ionic surfactants
c) carrying out in situ polymerization with acrylic polyol on the surface of the NPs;
d) curing with polymeric diisocyanate.

18. A process for manufacture of stable silicone based high transparency thin film /coating formulation as claimed in claim 16 and 17 wherein in situ polymerization with acrylic polyol follows the steps:
a. dispersing the powder into the respective solvent
b. heating on an oil bath with stirring;
c. mixing all the monomers and thermal initiator in rest of the solvent;
d. adding dropwise to the reaction mixture;
e. heating for another 1-2 hr; and
f. cooling to room temperature

19. A process as claimed in anyone of claims 16 to 18 wherein said indium tin oxide (ITO) is obtained following:
i. dissolving indium acetate in 9-octadecene;
ii. adding different long chain aliphatic acids and long chain amines
iii. heating at 110-150 ºC under N2 for about 20-40 mins;
iv. heating the mixture at about 200-300 ºC for about 5-8hrs;
v. finally collecting the ITO NPs using repeated precipitation and redispersion technique;
vi. the final ITO NPs dispersion being prepared in toluene/xylene/hexane for further applications.

20. A process as claimed in anyone of claims 16 to 19 wherein said antimony-doped tin oxide (ATO) is obtained following the steps:
a. dissolving antimony(III)acetate or antimony(III)chloride and dibutyltin dilaurate/stannic (IV) chloride in isopropanol;
b. adding organic bases;
c. heating at 150-2000C for 4- 10 hrs in Teflon or glass lined autoclave;
d. separating the precipitate by centrifugation and washing providing antimony doped tin oxide NPs.

21. A process as claimed in anyone of claims 16 to 20 for high transparency “single pack” silicone based heat absorbing thin film/coating formulation comprises the steps:
a) adding 1-5% of film base material in ethanol, isopropanol and butanol preferably isopropanol;
b) hydrolyzing by acid or alkali;
c) adding dispersion of 2-15wt% cesium tungsten bronze, 1-10wt% ITO and 1-10wt% ATO NP dispersions, 2-5 wt% UV absorbers;
d) adding polyol to make the formulation 100%;

22. A process as claimed in anyone of claims 16 to 21 wherein said base material used include epoxy silane, amino silane and for TEOS instead of TiO2, titanium tetraisopropoxide .

Dated this the 28th day of February, 2019 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)