Title of Invention	A PROCESS FOR THE PREPARATION OF COLORED COATING ON SYBSTRATESWITH NATURAL ENVIRONMENTALLY BENIGN DYES
Abstract	Natural organic dye was extracted from flowers of hibiscus species. A silica based sol of these dye molecules was prepared using letraethyl orthosilicate, deionized water, dye solution and ethanol as precursors. Coloured coatings were prepared from this sol by dip coating technique. Optical properties of these films were studied. This final sol, doped with different cations was also investigated Conditions were found out for tailoring of colour and stability of the coating.

Title of Invention

A PROCESS FOR THE PREPARATION OF COLORED COATING ON SYBSTRATESWITH NATURAL ENVIRONMENTALLY BENIGN DYES

Abstract

Natural organic dye was extracted from flowers of hibiscus species. A silica based sol of these dye molecules was prepared using letraethyl orthosilicate, deionized water, dye solution and ethanol as precursors. Coloured coatings were prepared from this sol by dip coating technique. Optical properties of these films were studied. This final sol, doped with different cations was also investigated Conditions were found out for tailoring of colour and stability of the coating.

Full Text	The present invention relates to the preparation of color coated glass, fused silica, copper and stainless steel with natural, environmentally benign dyes particularly extracted from flowers of the hibiscus species for optical and luminescent including fluorescent systems-Coloured slabs or sheets of glass are used for their extensive application as colour filters in optical equipments including cameras or coloured glasses for architectural, industrial and other application. Colored glasses are generally obtained by melting glasses containing colouring ions (salts), homogenizing, casting etc. This is an old and wel1-known commerical process. Reference may also be made to the work of D. Kundu, P.K. Biswas and D. Ssnguli {J. Non-cryst. Solids 110 (1989) 133 interference coatings or colorless sheet glass for obtaining wavelength-selective reflection and consequent color format. A drawback of the known processes is the requirement of deposition of a large number of layers of controlled thickness and refractive index, i.e. a precise optical design for obtaining the required color purity; making it a complicated and an expensive process- Another drawback of the conventional process is the difficulty of ensuring the same homogenei ty in case of large area coatings. : 3 : Reference may be made to the work of A- Duran, J-Mo Fernandez Navarro, P. Casariego and A- Joglar O. Non-cryst. Solids 82 A drawback of the known processes is the generally poor intensity of colour. Another drawback is the color degradation and loss of homogenei ty due to uncontrolled precipi tat ion of certain transition metal o>iide above threshold levels, as also undesirable scattering of light-Reference may also be made to S. Sakka, K. Kamiya, K-Makita and Y. Yamamoto -CJ. Mater, Sc i . Letts. 2 395> in a Bimilar line, i.e. transition metal ions in silica sols for coloured coatings on glass. A drawback of this work is the generation of a large background absorption through the whole range of the spectrum apparently due to the precipitation of colloidal oxides of transition metals, and the consequent loss of control on the colour purity. Reference may be made to K.T. Bondarev CSteklo I Keramica 12 43 for the preparation of transparent and coloured glass by melting the raw materials. - 4 - The main drawback of the melt route fabrication of coloured 9 less is that the g j ass melting container (varying from a tank in a tank furnace) becomes contaminated with the colouring constituents and it becomes difficult or even impossible to melt other compositions, especially those for colourless glass, in the same set up unless repeated washing with suitable melts at high temperature is undertaken. This makes the process expensive and time consuming. Reference may be made to the work of Del Nero et al {Materials Research 6 (2003) 7633 dyes like crystal violet and malachite green werr incorporated in polyphosphate for the preparation of colored fi1ms. The drawback is that the system turned to s gel within a minute after completion of mixing, so that preparation of coatings on glass substrates was not possible. The main object of the present invention is to mitigate the above disadvantages of the known processes and provide preparation of colored coatings on sol id substrate with natural, environmentally benign dyes extracted from flowers of the hibiscus species for optical and luminescent systems. A further object of the present invention is to use the dyes in a simple wet chemical solgel technique for preparing the coatings. 5 Still further object of the present invention is to use fs dip coating machine for clipping glass substrate into and pulling it from sol for obtaining coatings at predetermined rates to tailor the colour characteristics-Yet another object of the present invention is to tailor the colour characteristics of the coatings by doping the basic sol wi th sui table cations. A sti 11 further object of the present invention is to bake the coatings thus prepared at suitable temperature for fixing the colored coatings of the glass substrate. Accordingly, the present invention provides a process for the preparation of colored coatings on glass, fused silica, copper and ostainless steel with natural, environmentally benign dyes extracted from flowers of the hibiscus species for optical and luminescent systems which process comprises preparation of a silica based sol with or without dopant cations for tailoring color of the coatings, extraction of dye molecules from flowers-of the hibiscus species, dispersion of the dye molecules in the silica-based sol, dipping into and pulling from the sol glasE> substrates to obtain a coloured coatings to fi>: them on the glass substrate . : 6 : In an embodiment of the present invention, coloured coatings on solid substrates are prepared with natural, environmentally benign dyes extracted from flowers of the hibiscus species for optoelectronic and luminescent systems. In another embodiment of the present invention, silica based sol with or without dopant cations (for tailoring of color of the coatings) is prepared. In yet another embodiment of the present invention, dye molecules are extracted from flowers of the hibiscus species and dispersed in the sol mentioned above. In sti11 another embodiment of the present invention, solid substrate are dipped and pulled from the sol to obtain coatings of tailored color. In a further embodiment of the present invention, the coated substrates are baked for fixing the colored coatings on the glass substrate. The process steps were the following: : 7 : The coloring agent of the Hibiscus rosa-sinensis flower was extracted by boiling the flower petals in deionised water. At first only ten flowers were used for this purpose? and the net weight of the extracted dye is 0.066 gms. The extracted coloring agent was boiled to nearly six ml deionized water solution In another beaker 4-5 gm of tetraethyl ortho silicate different so3 id substrates by a known dip sol coating ^ technique which includes dip coating, spin coating and spray coating, (v) The coated films were heated in 373K, 423K and 473K for one hour. 8 (vi) The spectral responses of the films were examined using absorption and transmission spectra of the films. A very weak absorption peak was noticed near 535 nm and relatively strong absorption bands were found at 287 and 337 nm. The absorption band position and intensity did not change with the annealing temperature or time. The same experiment was repeated with 50 flowers with 0.329 gms of dyes but the only changp noticed was that the intensity of the absorption bands increased by five times. The abovementioned experiment was again repeated with 100 flowers (the weight of the extracted dye is 0.658 gms), this time the intensity of the absorption bands increased by eleven times. The colour of the films became redish violet. AX extracted dye in silica sol. The molar ratio of Al(NO ) 9H 0 and TEOS was varied from 1sX to 3 3. 2 1:8. A dip coated film was prepared from this : 9 : solution with annealing temperature fixed at 423K for one hour. This time the color of the fi1m became yel low- The absorption spectra of this film showed a strong absorption band near 306 nm- (viii) The above procedure was repeated replacing Al(NO ) 9H 0 with Mg (CH COO) . This time the O O . ^- o-> ¦£- the color of the film became gray and a strong absorption band was found at 600 nm associ ated wi th a second band st near 300 nm" (i>:) The same process was again repeated, where Mg (CH COO) was replaced by H BO .The color of 3 2 3 3 the fi1ms again became violet. The absorption bands appeared at 545 nm and 278 nm. The anorganic matri>: efficiently immobi lizes the dye molecules and maintains some defined separation between them, which in turn reduces the non-radiatIve relaxation processes of excited molecules in bulk dyes CM-A. Diaz-Garcia,S.F. De Avila, M.S. Kuzyk Applied Physics Letters,80, 4486 (2002)3. To overcome the problems stated earlier coloring agents present in the petals of the flowers of hibiscus species are used ss dye material. For this purpose, the dye is extracted from the mast common Indian 10 species of china rose with a scientific name Hibiscus rasa- sinensis. Eight flavonoid sglycones are found in the hibiscus flower extracts, including delphinidin, cyanidin, petun 3 din, mynretin, pelargodin, malvidin, quercetin and kaempf pro] (Trends in New Crops and New Uses J. Janick and A Wipkey has got some typical properties, this flavonol can make complex +3 3 +2 compounds wi th Al , B 5 Mg etc. which changes the absorption band (^f the f i 1ms £The Chemi st ry of F lavonoid Compounds , Edited by T.A - Ge i ssman, Pe rgamon Press, 1962 * A. D. Rosh a1,,AV" Brigc.jrovich,A.O.Doroshenko, V. Gpivovarenko and A.P. DemchenkoJournal of Photochemistry 127,89 The following examples are given by way of i ilustration and therefore should not be construed to 1ims t the scope of the present invention - EXAMPLE-1 The coloring agents of the flow (HGibiscus rosa™ ~>inensis) were extracted from the petals of the flowers by boiling them in del onized water. First, 10 tlowers 11 extracted dye 0.066 gros) were used for this purpose. The extracted solution mas boiled to nearly 5 ml in volume. Si 1 ica sol was prepared by using tetr'aethyl ortrhosi 1 icate (TEOS) , deionized water, ethyl alcohol &nd 0. IN HC1 as precursors, 4.5 gms of TEOS was mi>;ed with 2 gms of ethyl alcohol, 0.5 gm gms of deionized water and 10 drops of 0.1N HC1. The mixed precursors were stirred for one hour to obtain silica sol. The extracted solution was mixod with the silica sol and stirred for one hour to obtain the final sol. This sol was used to cost different solid substrates by dip costing technique. Coated films were annealed at temperatures ranging from 323 to 423K for one hour. The costings showed a violet hue. Absorption spectra showed a weak absorption peak at 532 nm. A strong pmJBsion peak was noticed at ~370 nm in the photoluminescence spectrum. EXAMPLE-2 The same experiment as in Example-1 was repeated with S0 flowers (weight of the extracted dye 0-330 gmss) . The absorption spectrum showed the peak at the same po&i tion through the same annealing temperature but the intensity of the peak : 12 : increased by five times,. The colour of the f i 1ms remained violet. A strong emission peak was noticed at ^370 nm in the photoluminescence spectrum. EXAMPLE - 3 The same experiment as in Example-1 was repeated with 100 flowers (weight of the extracted dye "" 0-658 gms), This time the absorption peak intensi ty increased by eleven times but the peak position and intensity did not change with the anneal ing temperature of the film's. The sol transformed into a gel within 12 hours. The colour of the films remained violet. This colour can be removed by dipping thp coating in cold water. A strong emission peak was noticed at ^370 nm in the photoluminpscence spectrum- EXAMPLE - 4 One silica so3-dye combination was prepared by the same process as mentioned in Example-3. Another 10 ml ethanol of Al(NO ) 9H O was prepared and i t was mixed with the dye dispersed silica sol end stirred for one hour. The molar ratio of 13 TEOS and AMNO ) 9H O was varied from l:l to 1:8. These sols 3 3. 2 were then used to coat different sol id substrates by dip coating technique. The film was annealed at temperatures ranging from 373 to 473K for one hour. The colour of the film became yellow. The color was stable and it did not wash out even in hot water EXAMPLE - 5 One si 1ica sol-dye combination was prepared by the same process 35 . mentioned in Example-3. Another 10 sol ethanol solution of 3 2 dye-dispersed silica sol and stirred for one hour. The molar ratio of TEOS and Mg(CA C00> was varied from 1:1 to ls8D This 3 2 sol was then used to coat different sol id substrates by dip coating technique. The fi1ms were annealed at temperatures ranging from 373 to 473K for one hour. The color of the film became gray. This color was also stable. The absorption spectrum 14 showed a single strong band near 600 nm associated with a second band at 300 nm. The coating and anneal ing operation was then repeat&d wi th soda 1ime glass as substrate. A gray-colored, relatively stable coating was obtained. A strong emission peak at ^387 nm associated with another relatively low intense peak at 423 nm were noticed in the photoluminescence spectrum. EXAMPLE-^ One si 1ica sol-dye combination was prepared by the same process as mentioned in E>;ample-3. Another 10 ml ethanol solution of H BD was prepared and it was mixed with the dye-dispersed 3 3 silica sol and stirred for one hour. The molar ratio of TE05 and H BO was varied from 1:1 to 1:8. This sol was then used to coat 3 3 the different solid substrates by dip coating technique. The film was annealed at temperatures ranging from 373 to 473K for one hour. The color of the film became violet. This color was also stable. The absorption spectrum showed a single strong band near 345 nm associated with a second band at 278 nm. The coating and anneal ing operation was then repeated with soda 1ime glass .as substrate. A violet-colored, relatively stable coating was obtained. A strong emission peak at ^385 nm associated with another relatively low intensity peak at 425 was noticed in the photoluminescence spectrum- 15 EXAMPLE-7 One si1ica sol-dye combination was prepared by the same process as mentioned in Example-3. This sol was then used to coat different solid substrates by dip coating technique. The films were annealed at temperatures ranging from 373 to 473K for one hour- The color of the films became violet- Leaching of these films was performed using buffer solutions having pH values 4,6.5 rtnd 9.2. The leaching rate is almost same for all the buffer solutions. The colour of the films vanished within a mixture of dipping of the fi1ms in the leachant. EXAMPLE - 8 One alumina-doped silica sol-dye combination was prepared b y the same process as mentioned in Example-4. This sol was then used to coat different sol id substrates by dip coating technique. The films were annealed at temperatures ranging from 373 to 473K for one hour. The colour of the films became yellow. They were dipped in the leaching solutions having pH values 4, 6-5 and 9.2. The leaching rate of acidic 16 Extraction of dye (A): Preparation of silica sol (B): Petals of 10 to 100 hibiscus rosa-sinensis flower are collected. Petals are boiled in 500 ml hot deionized water. The temperature of the water maintained at 343 to 373K. The red colored water solution is filtered and Red solution was evaporated at 373K to obtain 5 ml concentrated dye solution (A). Tetraethyl orthosilicate (TEOS), water, ethanol and hydrochloric acid are mixed with a molar ratio 1: (0.5 to 3): (0.1 to 5): (0.00010 to 0.00045) and stirred for 5 mins to 5 hours (B). Preparation of cation doped silica sol (C): Different cations such as AF3, Mgf2 and BT3 are doped into the sol B for tailoring the color and stability of the final coating. In the final sol the molar ratio of TEOS and cation compound are varied from 1:1 to 1:16 (C). Solution A and sol C are mixed and stirred for 1 to 5 mins to obtain cation doped silica based dye sol for final coating. & Solution A and sol B are mixed and stirred for 1 to 5 mins to obtain silica based dye sol for final coating. The final sols are used to obtain coatings on glass, fused silica, copper and stainless steel by simple dip coating technique. The coated substrates are annealed at different temperature ranging from 323 to 473K to produce final coated substrate. IT Conclusions The main advantages of the present invention are: 1. It is a very low cost and simple process for the coloring of the glass and other solid surface. 2. The coatings are relatively scratch free, especially with silicate sols as the base. 3. The process may be used to colour a solid material and after that if needed this color may be washed out using simple cold water when the base is pure silica sol. 4. This type of coloring agent embedded in silica matrix shows possibilities in optoelectronic devices. 5. The coloured films are also fluorescent; i.e. have luminescent properties, which is useful for device applications. - 18 - WE CLAIM: 1. A process for the preparation of coloured coatings on substrates selected from glass, fused silica, high temperature plastics, metals and alloys, namely copper and stainless steel with natural, environmentally benign dyes which process comprises the following steps- a) extracting natural, environmentally benign dyes from flowers of hibiscus species by boiling said flower petals in deionized water for optical and luminescent systems; b) preparing a silica based sol preferably in the presence of dopant cations (A 1+3, Mg+2, B+3) for tailoring colour of the coating; c) dispersing said dye molecules of step (a) in said silica based sol of step (b); d) coating glass or other substrates by said dye dispersed sol; and e) annealing said coated substrate. 2. A process as claimed in Claim 1 wherein said coating is carried out by dip or spin or spray technique. 3. A process as claimed in Claim 1 wherein said sol is prepared from alkoxide-salts combinations (Si alkoxide and A1(NO3)3.9H2O, (CH3COO)2Mg and H3BO3). 19 4. A process for the preparation of coloured coatings substantially as herein described particularly with reference to the examples mentioned hereinabove. Natural organic dye was extracted from flowers of hibiscus species. A silica based sol of these dye molecules was prepared using letraethyl orthosilicate, deionized water, dye solution and ethanol as precursors. Coloured coatings were prepared from this sol by dip coating technique. Optical properties of these films were studied. This final sol, doped with different cations was also investigated Conditions were found out for tailoring of colour and stability of the coating.

Full Text

The present invention relates to the preparation of color coated glass, fused silica, copper and stainless steel with natural, environmentally benign dyes particularly extracted from flowers of the hibiscus species for optical and luminescent including fluorescent systems-Coloured slabs or sheets of glass are used for their extensive application as colour filters in optical equipments including cameras or coloured glasses for architectural, industrial and other application. Colored glasses are generally obtained by melting glasses containing colouring ions (salts), homogenizing, casting etc. This is an old and wel1-known commerical process. Reference may also be made to the work of D. Kundu, P.K. Biswas and D. Ssnguli {J. Non-cryst. Solids 110 (1989) 133 interference coatings or colorless sheet glass for obtaining wavelength-selective reflection and consequent color format.
A drawback of the known processes is the requirement of deposition of a large number of layers of controlled thickness and refractive index, i.e. a precise optical design for obtaining the required color purity; making it a complicated and an expensive process- Another drawback of the conventional process is the difficulty of ensuring the same homogenei ty in case of large area coatings.

: 3 :
Reference may be made to the work of A- Duran, J-Mo Fernandez Navarro, P. Casariego and A- Joglar O. Non-cryst. Solids 82 A drawback of the known processes is the generally poor intensity of colour. Another drawback is the color degradation and loss of homogenei ty due to uncontrolled precipi tat ion of certain transition metal o>iide above threshold levels, as also undesirable scattering of light-Reference may also be made to S. Sakka, K. Kamiya, K-Makita and Y. Yamamoto -CJ. Mater, Sc i . Letts. 2 395> in a Bimilar line, i.e. transition metal ions in silica sols for coloured coatings on glass.
A drawback of this work is the generation of a large background absorption through the whole range of the spectrum
apparently due to the precipitation of colloidal oxides of transition metals, and the consequent loss of control on the
colour purity.
Reference may be made to K.T. Bondarev CSteklo I Keramica 12 43 for the preparation of transparent and coloured glass by melting the raw materials.

- 4 -
The main drawback of the melt route fabrication of coloured 9 less is that the g j ass melting container (varying from
a tank in a tank furnace) becomes contaminated with the colouring constituents and it becomes difficult or even impossible to melt
other compositions, especially those for colourless glass, in the same set up unless repeated washing with suitable melts at high
temperature is undertaken. This makes the process expensive and time consuming.
Reference may be made to the work of Del Nero et al {Materials Research 6 (2003) 7633 dyes like crystal violet and malachite green werr incorporated in polyphosphate for the preparation of colored fi1ms. The drawback is that the system turned to s gel within a minute after completion of mixing, so that preparation of coatings on glass substrates was not possible.
The main object of the present invention is to mitigate the above disadvantages of the known processes and provide
preparation of colored coatings on sol id substrate with natural, environmentally benign dyes extracted from flowers of the
hibiscus species for optical and luminescent systems.
A further object of the present invention is to use the dyes in a simple wet chemical solgel technique for preparing the coatings.

5
Still further object of the present invention is to use fs dip coating machine for clipping glass substrate into and pulling it from sol for obtaining coatings at predetermined rates to tailor the colour characteristics-Yet another object of the present invention is to tailor the colour characteristics of the coatings by doping the basic sol wi th sui table cations.
A sti 11 further object of the present invention is to bake the coatings thus prepared at suitable temperature for fixing the colored coatings of the glass substrate.
Accordingly, the present invention provides a process for the preparation of colored coatings on glass, fused silica, copper and ostainless steel with natural, environmentally benign dyes extracted from flowers of the hibiscus species for optical and luminescent systems which process comprises preparation of a silica based sol with or without dopant cations for tailoring color of the coatings, extraction of dye molecules from flowers-of the hibiscus species, dispersion of the dye molecules in the silica-based sol, dipping into and pulling from the sol glasE> substrates to obtain a coloured coatings to fi>: them on the glass substrate .

: 6 :
In an embodiment of the present invention, coloured coatings on solid substrates are prepared with natural, environmentally benign dyes extracted from flowers of the hibiscus species for optoelectronic and luminescent systems.
In another embodiment of the present invention, silica based sol with or without dopant cations (for tailoring of color of the coatings) is prepared.
In yet another embodiment of the present invention, dye molecules are extracted from flowers of the hibiscus species and
dispersed in the sol mentioned above.
In sti11 another embodiment of the present invention, solid substrate are dipped and pulled from the sol to obtain
coatings of tailored color.
In a further embodiment of the present invention, the coated substrates are baked for fixing the colored coatings on the glass substrate.
The process steps were the following:

: 7 :
The coloring agent of the Hibiscus rosa-sinensis flower was extracted by boiling the flower petals in deionised water. At first only ten flowers were used for this purpose? and the net weight of the extracted dye is 0.066 gms. The extracted coloring agent was boiled to nearly six ml deionized water solution
In another beaker 4-5 gm of tetraethyl ortho silicate different so3 id substrates by a known dip sol
coating ^ technique which includes dip coating,
spin coating and spray coating,
(v) The coated films were heated in 373K, 423K and 473K for one hour.

8
(vi) The spectral responses of the films were examined using absorption and transmission spectra of the films. A very weak absorption peak was noticed near 535 nm and relatively strong absorption bands were found at 287 and 337 nm. The absorption band position and intensity did not change with the annealing temperature or time. The same experiment was repeated with 50 flowers with 0.329 gms of dyes but the only changp noticed was that the intensity of the absorption bands increased by five times. The abovementioned experiment was again repeated with 100 flowers (the weight of the extracted dye is 0.658 gms), this time the intensity of the absorption bands increased by eleven times. The colour of the films became redish violet.
AX extracted dye in silica sol. The molar ratio of
Al(NO ) 9H 0 and TEOS was varied from 1sX to
3 3. 2 1:8. A dip coated film was prepared from this

: 9 :
solution with annealing temperature fixed at 423K for one hour. This time the color of the fi1m became yel low- The absorption spectra of this film showed a strong absorption band near 306 nm-
(viii) The above procedure was repeated replacing Al(NO ) 9H 0 with Mg (CH COO) . This time the
O O . ^- o-> ¦£-
the color of the film became gray and a strong absorption band was found at 600 nm associ ated wi th a second band st near 300 nm"
(i>:) The same process was again repeated, where
Mg (CH COO) was replaced by H BO .The color of
3 2 3 3
the fi1ms again became violet. The absorption
bands appeared at 545 nm and 278 nm.
The anorganic matri>: efficiently immobi lizes the dye
molecules and maintains some defined separation between them, which in turn reduces the non-radiatIve relaxation processes of
excited molecules in bulk dyes CM-A. Diaz-Garcia,S.F. De Avila, M.S. Kuzyk Applied Physics Letters,80, 4486 (2002)3. To overcome
the problems stated earlier coloring agents present in the petals of the flowers of hibiscus species are used ss dye material. For
this purpose, the dye is extracted from the mast common Indian

10
species of china rose with a scientific name Hibiscus rasa- sinensis. Eight flavonoid sglycones are found in the hibiscus flower extracts, including delphinidin, cyanidin, petun 3 din, mynretin, pelargodin, malvidin, quercetin and kaempf pro] (Trends in New Crops and New Uses J. Janick and A Wipkey has got some typical properties, this flavonol can make complex
+3 3 +2 compounds wi th Al , B 5 Mg etc. which changes the absorption
band (^f the f i 1ms £The Chemi st ry of F lavonoid Compounds , Edited by T.A - Ge i ssman, Pe rgamon Press, 1962 * A. D. Rosh a1,,AV" Brigc.jrovich,A.O.Doroshenko, V. Gpivovarenko and A.P. DemchenkoJournal of Photochemistry 127,89 The following examples are given by way of i ilustration and therefore should not be construed to 1ims t the scope of the present invention -
EXAMPLE-1
The coloring agents of the flow (HGibiscus rosa™ *~>inensis) were extracted from the petals of the flowers by boiling them in del onized water. First, 10 tlowers
11
extracted dye 0.066 gros) were used for this purpose. The extracted solution mas boiled to nearly 5 ml in volume.
Si 1 ica sol was prepared by using tetr'aethyl ortrhosi 1 icate (TEOS) , deionized water, ethyl alcohol &nd 0. IN HC1 as precursors, 4.5 gms of TEOS was mi>;ed with 2 gms of ethyl alcohol, 0.5 gm gms of deionized water and 10 drops of 0.1N HC1. The mixed precursors were stirred for one hour to obtain silica sol.
The extracted solution was mixod with the silica sol and stirred for one hour to obtain the final sol. This sol was used to cost different solid substrates by dip costing technique. Coated films were annealed at temperatures ranging from 323 to 423K for one hour. The costings showed a violet hue. Absorption spectra showed a weak absorption peak at 532 nm. A strong pmJBsion peak was noticed at ~370 nm in the photoluminescence spectrum.
EXAMPLE-2
The same experiment as in Example-1 was repeated with S0 flowers (weight of the extracted dye * 0-330 gmss) . The absorption spectrum showed the peak at the same po&i tion through the same annealing temperature but the intensity of the peak

: 12 :
increased by five times,. The colour of the f i 1ms remained violet. A strong emission peak was noticed at ^370 nm in the photoluminescence spectrum.
EXAMPLE - 3
The same experiment as in Example-1 was repeated with 100 flowers (weight of the extracted dye "" 0-658 gms), This time the absorption peak intensi ty increased by eleven times but the peak position and intensity did not change with the anneal ing temperature of the film's. The sol transformed into a gel within 12 hours. The colour of the films remained violet. This colour can be removed by dipping thp coating in cold water. A strong emission peak was noticed at ^370 nm in the photoluminpscence spectrum-
EXAMPLE - 4
One silica so3-dye combination was prepared by the same process as mentioned in Example-3. Another 10 ml ethanol of Al(NO ) 9H O was prepared and i t was mixed with the dye
dispersed silica sol end stirred for one hour. The molar ratio of

13
TEOS and AMNO ) 9H O was varied from l:l to 1:8. These sols
3 3. 2 were then used to coat different sol id substrates by dip coating
technique. The film was annealed at temperatures ranging from 373 to 473K for one hour. The colour of the film became yellow. The color was stable and it did not wash out even in hot water EXAMPLE - 5
One si 1ica sol-dye combination was prepared by the same
process 35 . mentioned in Example-3. Another 10 sol ethanol
solution of 3 2 dye-dispersed silica sol and stirred for one hour. The molar
ratio of TEOS and Mg(CA C00> was varied from 1:1 to ls8D This
3 2 sol was then used to coat different sol id substrates by dip
coating technique. The fi1ms were annealed at temperatures ranging from 373 to 473K for one hour. The color of the film became gray. This color was also stable. The absorption spectrum

14
showed a single strong band near 600 nm associated with a second band at 300 nm. The coating and anneal ing operation was then repeat&d wi th soda 1ime glass as substrate. A gray-colored, relatively stable coating was obtained. A strong emission peak at ^387 nm associated with another relatively low intense peak at 423 nm were noticed in the photoluminescence spectrum.
EXAMPLE-^
One si 1ica sol-dye combination was prepared by the same process as mentioned in E>;ample-3. Another 10 ml ethanol solution
of H BD was prepared and it was mixed with the dye-dispersed
3 3 silica sol and stirred for one hour. The molar ratio of TE05 and
H BO was varied from 1:1 to 1:8. This sol was then used to coat
3 3 the different solid substrates by dip coating technique. The film
was annealed at temperatures ranging from 373 to 473K for one hour. The color of the film became violet. This color was also stable. The absorption spectrum showed a single strong band near 345 nm associated with a second band at 278 nm. The coating and anneal ing operation was then repeated with soda 1ime glass .as substrate. A violet-colored, relatively stable coating was obtained. A strong emission peak at ^385 nm associated with another relatively low intensity peak at 425 was noticed in the photoluminescence spectrum-

15
EXAMPLE-7
One si1ica sol-dye combination was prepared by the same process as mentioned in Example-3. This sol was then used to coat different solid substrates by dip coating technique. The films were annealed at temperatures ranging from 373 to 473K for one hour- The color of the films became violet- Leaching of these films was performed using buffer solutions having pH values 4,6.5 rtnd 9.2. The leaching rate is almost same for all the buffer solutions. The colour of the films vanished within a mixture of dipping of the fi1ms in the leachant.
EXAMPLE - 8
One alumina-doped silica sol-dye combination was prepared b y the same process as mentioned in Example-4. This sol was then used to coat different sol id substrates by dip coating technique. The films were annealed at temperatures ranging from 373 to 473K for one hour. The colour of the films became yellow. They were dipped in the leaching solutions having pH values 4, 6-5 and 9.2. The leaching rate of acidic
16

Extraction of dye (A):

Preparation of silica sol (B):

Petals of 10 to 100 hibiscus rosa-sinensis flower are collected.
Petals are boiled in 500 ml hot deionized water. The temperature of the water maintained at 343 to 373K. The red colored water solution is filtered and
Red solution was evaporated at 373K to obtain 5 ml concentrated dye solution (A).

Tetraethyl orthosilicate (TEOS), water, ethanol and hydrochloric acid are mixed with a molar ratio 1: (0.5 to 3): (0.1 to 5): (0.00010 to 0.00045) and stirred for 5 mins to 5 hours (B).
Preparation of cation doped silica sol (C):
Different cations such as AF3, Mgf2 and BT3 are doped into the sol B for tailoring the color and stability of the final coating. In the final sol the molar ratio of TEOS and cation compound are varied from 1:1 to 1:16 (C).

Solution A and sol C are mixed and stirred for 1 to 5 mins to obtain cation doped silica based dye sol for final
coating.
&
Solution A and sol B are mixed and stirred for 1 to 5 mins to obtain silica based dye sol for final coating.
The final sols are used to obtain coatings on glass, fused silica, copper and stainless steel by simple dip coating technique. The coated substrates are annealed at different temperature ranging from 323 to 473K to produce final coated substrate.

IT
Conclusions
The main advantages of the present invention are:
1. It is a very low cost and simple process for the coloring of the glass and other solid
surface.
2. The coatings are relatively scratch free, especially with silicate sols as the base.
3. The process may be used to colour a solid material and after that if needed this color
may be washed out using simple cold water when the base is pure silica sol.
4. This type of coloring agent embedded in silica matrix shows possibilities in
optoelectronic devices.
5. The coloured films are also fluorescent; i.e. have luminescent properties, which is
useful for device applications.

- 18 -
WE CLAIM:
1. A process for the preparation of coloured coatings on substrates selected from glass, fused silica, high temperature plastics, metals and alloys, namely copper and stainless steel with natural, environmentally benign dyes which process comprises the following steps-
a) extracting natural, environmentally benign dyes from flowers of
hibiscus species by boiling said flower petals in deionized water for optical
and luminescent systems;
b) preparing a silica based sol preferably in the presence of dopant
cations (A 1+3, Mg+2, B+3) for tailoring colour of the coating;
c) dispersing said dye molecules of step (a) in said silica based sol of
step (b);
d) coating glass or other substrates by said dye dispersed sol; and
e) annealing said coated substrate.
2. A process as claimed in Claim 1 wherein said coating is carried out
by dip or spin or spray technique.
3. A process as claimed in Claim 1 wherein said sol is prepared from
alkoxide-salts combinations (Si alkoxide and A1(NO3)3.9H2O, (CH3COO)2Mg and H3BO3).

19
4. A process for the preparation of coloured coatings substantially as
herein described particularly with reference to the examples mentioned hereinabove.
Natural organic dye was extracted from flowers of hibiscus species. A silica based sol of these dye molecules was prepared using letraethyl orthosilicate, deionized water, dye solution and ethanol as precursors. Coloured coatings were prepared from this sol by dip coating technique. Optical properties of these films were studied. This final sol, doped with different cations was also investigated Conditions were found out for tailoring of colour and stability of the coating.

Documents:

00219-kol-2004 abstract.pdf

00219-kol-2004 claims.pdf

00219-kol-2004 correspondence.pdf

00219-kol-2004 description (complete).pdf

00219-kol-2004 form-1.pdf

00219-kol-2004 form-13.pdf

00219-kol-2004 form-18.pdf

00219-kol-2004 form-2.pdf

00219-kol-2004 form-26.pdf

00219-kol-2004 form-3.pdf

00219-kol-2004 letters patent.pdf

00219-kol-2004 reply f.e.r.pdf

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Patent Number

203285

Indian Patent Application Number

219/KOL/2004

PG Journal Number

10/2007

Publication Date

09-Mar-2007

Grant Date

09-Mar-2007

Date of Filing

30-Apr-2004

Name of Patentee

INDIAN ASSOCIATION FOR THE CULTIVATION

Applicant Address

2 AND 3 RAJA S C MULLICK ROAD, JADAVPUR KOLKATA 700032

Inventors:

#	Inventor's Name	Inventor's Address
1	GUHA PINAKI	INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE ,JADAVPUR KOLKATA 700032
2	GANGULY PROF DIBYENDU	INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE ,JADAVPUR KOLKATA 700032
3	CHAUDHURY PROF SUBHADRA	OF INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE ,JADAVPUR KOLKATA 700032

PCT International Classification Number

C 03 C 17/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA