WO2022195612A1

WO2022195612A1 - A heat treatble glass article with an enamel coating

Info

Publication number: WO2022195612A1
Application number: PCT/IN2022/050223
Authority: WO
Inventors: Jagadis S; Srinivas Prasad B.S
Original assignee: Saint-Gobain Glass France
Priority date: 2021-03-18
Filing date: 2022-03-10
Publication date: 2022-09-22

Abstract

The present application provides a heat treatable glass substrate coated with an enamel formulation. The enamel formulation comprises inorganic components, organic components and a ceramic precursor additive. The ceramic precursor during heat treatment of the glass substrate opacifies the glass substrate such that the glass substrate has substantially minimal visible light transmission. Further the application also provides a method of making the heat treatable glass substrate thereof.

Description

A HI M TREATBLE GLASS ARTICLE WITH AN ENAMEL COATING

TECHNICAL FIELD

The present disclosure in general relates to glass substrates coated with an enamel to improve opacity of the glass substrate. Specifically, the present disclosure relates to heat treatable glass substrates provided with an enamel coating comprising a ceramic precursor, such that the said coating during a heat treatment process opacifies the glass substrate. Further disclosed is a method of making a glass substrate thereof. BACKGROUND

Glass articles coated with enamel, finds its application in interior and exterior applications in buildings which must be opaque, optically distortion-free, tenaciously adherent, reasonably hard and resistant to sunlight, sun heat, chemicals and moisture, and several other functional properties. Specifically, glasses with opaque properties are intended for decorative building walls, or interior furniture fronts, and decorating glass sheets. For example, the enamel coatings on glass substrates may be used to form wardrobes, as privacy doors, decorative furniture, as partitions, in tables, shelves, in bathrooms, in shops displays, as wall covering, in outdoor environments, etc. It is very well established in the state of art to form an enamel coating layer on a glass sheet by applying a paste or paint prepared by dispersing an inorganic pigment and a finely powdered glass frit in a mixed solution of an organic binder and an organic solvent onto a surface of the glass sheet. And by further using the known techniques of screen-printing, a paint layer is formed on the glass surface which is further dried and fired to fuse the glass frit contained in the paint layer. Conventionally, enamel coated glass sheets for increasing the opacity may be produced according to various other processes. Conventional enamel-based commercial formulations are known to have high concentration of inorganic pigments and glass frits, with a relatively low concentration of organic binders or additives. The increased content of the inorganic pigments and extenders could improve opacity. However, the traditional enamel coatings systems are limited by the maximum amount of the pigments and extenders that can be used to allow for consistent deposition of the coatings on the glass substrate. Increased pigment usage to improve opacity also results in poor coating deposition.

Patent document WO2011051459A1 discloses enamel coatings with increased organic resin content in order to improve the green strength of the enamel coating with glass. The enamel coating in this application comprises between 11 and 40 % of organic material. However, such high organic content usually causes char residues which discolor the enamel coating after high-temperature heat treatment. Patent application EP3140261A1 discloses glass or glass-ceramic substrate, covered with an enamel layer. An organic resin is used as an undercoat underneath an enamel layer to impart higher adhesion and water resistance. Similarly, patent application US20090220778A1 teaches an organic resin being used as an overcoat on top of the enamel layer to impart higher green strength to the coating. The organic resin could potentially offer good green strength, but does not offer any further improvements in opacity over the conventional enamel systems.

Patent application US20090099287A1 teaches the use of polysiloxane coating in heat- treatable coating and is shown to withstand greater than 500°C exposure with no deterioration of the coating or the polysiloxane. The invention is intended towards a pyrolysis-resistant coating paint. The polysiloxane coating is entirely retained in its polymer form during the heat-treatment with the use of the heat-dissipating inorganic pigments. However, there is no suggestion of increase in opacity or hiding power of the coatings in this invention.

More recently, preceramic polymers or ceramic precursors have been known as starting materials for the manufacture of ceramic materials, but these materials have, however, not been known to be used in enamel formulations or coatings to increase the opacity.

In the established works in the state of art, there is a maximum limit on the inorganic pigments or extenders available for use, that can allow for a homogenous enamel coating deposition. This in turn limits the maximum achievable opacity (or hiding power) at a given enamel film thickness.

Therefore, it is desirable to develop glass articles with enamel coatings having the desired opacity and as well ensuring that a homogeneous deposition of the coating is achieved. With the proposed invention, this problem is circumvented with the use of a heat-responsive additive that allows for good blending in the formulation and also homogenous deposition on glass. After high temperature heat-treatment, the heat- responsive additive improves the opacity of the coating. OBJECT OF INVENTION

The main object of the present invention is to provide a heat treatable glass article, said glass article coated with an enamel, the enamel specifically comprises a ceramic precursor. Said ceramic precursor when undergoing a heat treatment step, opacifies the glass substrate and provides a substantially opaque glass article, thereby ensuring nil or minimal visible light transmission.

Another object of the present invention is to provide a method for making a heat treatable glass article coated with an enamel in accordance with the disclosure. A glass article produced by the method in accordance with the disclosure has substantially minimal visible light transmission and also withstands the high tempering temperatures during the making of the glass substrate along with improving the opacity during the heat treatment.

Yet another object of the present invention is to provide a heat treatable glass article, in accordance with the method disclosed, such that the glass substrate can be handled and/or transported without mechanical damages to the enamel coating and further be tempered at temperatures as high as 750 °C after being handled and/or transported.

The present disclosure was developed by outlining the above objectives.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a heat treatable glass substrate coated with an enamel formulation is disclosed. The enamel formulation comprises inorganic component in the range of 0 to 70 weight %; organic component in the range of 0 to 40 weight %; a ceramic precursor additive in the range of 0.01 to 50 weight %; and a catalyst in the range of 0 to 20 weight % of the ceramic precursor additive. The ceramic precursor opacifies the glass substrate during heat treatment of the glass substrate, and such that the glass substrate after the heat treatment has substantially minimal visible light transmission. The glass substrate can be handled and/or transported without mechanical damages to the enamel coating and further be tempered at temperatures as high as 750 °C after being handled and/or transported.

In another aspect of the present disclosure, a method for making a heat treatable glass substrate is disclosed. The method involves the steps of: a) cleaning a glass substrate having a first surface and a second surface; b) applying the enamel in accordance with the present disclosure, on one of the surfaces of the glass substrate; c) drying in an infrared oven for about 10 - 20 minutes at a temperature of less than 250 °C; and heat treating the enamel coated glass substrate at a temperature of about 600 to 750 °C. The enamel comprising a ceramic precursor opacifies the glass substrate during the heat treatment such that glass substrate has substantially minimal visible light transmission after the heat treatment.

Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and are not limited in the accompanying figures.

FIG. 1 illustrates a cross-sectional view of a heat treatable glass article, in accordance with one embodiment of the present disclosure.

FIG.2 (a) illustrates a graphical representation of comparison of change in color values against black and white backgrounds as a function of dried enamel coating thickness prior to the high temperature tempering (>600 °C) for a comparative example 1 vs. the enamel coating, in accordance with one embodiment of the present disclosure.

FIG. 2 (b) illustrates a graphical representation of comparison of the light transmission values as a function of thickness for a comparative example 1 vs. the enamel coating, in accordance with one embodiment of the present disclosure.

FIG. 3 illustrates a graphical representation of comparison of the change in the color values against a white and black background as a function of the high-temperature heat treatment (tempering) for the heat treatable glass article coated with an enamel, with and without the use of the ceramic precursor, in accordance with one embodiment of the present disclosure.

FIG. 4 illustrates a graphical representation of comparison of change in color values against black and white backgrounds after tempering as a function of ceramic precursor incorporation, in accordance with one embodiment of the present disclosure.

FIG. 5 illustrates a graphical representation of comparison of light transmission values for the comparative example 1, silazane ceramic precursor alone and the enamel coating with the ceramic precursor used as an additive at 10% concentration, in accordance with one embodiment of the present disclosure.

FIG. 6 illustrates a graphical representation of the change in the colour due to the addition of the second black enamel coating, in accordance with one embodiment of the present disclosure.

Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts. Embodiments disclosed herein are related to a heat treatable enamel coated glass substrates and a method of making a heat treatable glass substrate provided with an enamel coating according to the teachings of the present disclosure. FIG. 1 illustrates a cross-sectional view of a heat treatable glass article 100 in accordance with one embodiment of the present disclosure. As shown, the heat treatable glass article 100 includes a glass substrate 101 having a first surface 102 and a second surface 103. The glass substrate 101 is directly provided with an enamel coating 104 on a first surface 102 of the glass substrate 101. In one embodiment of the present disclosure, the enamel coating provided on the first surface 102 of the glass substrate 101 comprises of inorganic materials, pigment, organic resins, ceramic precursor and a catalyst. In one embodiment of the present disclosure, the heat treatable glass substrate 101 is coated with an enamel 104 on the entire first surface 102 of the glass substrate 101 or in parts of the first surface 102 of the glass substrate 101. In a few other embodiments the enamel coating can be provided as a design pattern that can cover the surface area of the first surface 102 of the glass substrate 101 in varying extents, from 0.1 to 100%. In such an embodiment, the enamel coating 104 may be provided in the form of a decorative pattern using screen printing techniques to obtain various shapes and sizes. In an alternate embodiment, the enamel coating 104 can also be provided on the second surface 103 of the glass substrate 101. In one embodiment of the present disclosure, the heat treatable glass substrate 101 is provided with an enamel coating 104. The enamel coating formulation comprises the inorganic component in the range of 0 to 80 weight %; organic component in the range of 0 to 50 weight %; a ceramic precursor additive in the range of 0.01 to 50 weight %; and a catalyst in the range of 0 to 20 weight % of the ceramic precursor additive.

The glass substrate coated with an enamel 104 in accordance with the present disclosure comprising, the inorganic component further consisting of frits and pigments. The inorganic component is preferably present in the enamel coating 104 in the range of 10 to 60 weight%. In a most preferred embodiment, the inorganic material is present in the range of 0 to 50 weight%. The inorganic frit is selected from the group comprising but not limited to oxides of zinc, bismuth, lithium, boron, sodium, aluminum, silicon, potassium, calcium, titanium, chromium, iron, cobalt, copper, strontium, zirconium, barium or a combination thereof.

In accordance with an embodiment of the present disclosure, the pigment is selected from the group consisting of titanium oxide, barium sulfate, zinc sulfate, zinc phosphate, zinc sulfide, zinc oxide alumina, chromium oxide, copper oxide, iron oxide, carbon black, phthalocyanine or a combination thereof.

The organic component present in the enamel coating 104 is further comprised of a resin binder and a diluent. In a preferred embodiment the organic component in the enamel coating 104 is present in the range of 0 to 40 weight%. In a preferred embodiment the organic component is present in the range of 0 to 30 weight%. The resin binder is selected from the group comprising but not limited to acrylates, esters, acrylic esters, epoxies, polyols, urethanes, silicones, melamine and their combinations thereof. The diluent is selected from the group comprising but not limited to di-acetone alcohol, ether glycol, xylene or ethyl methyl ketone and their combinations thereof.

The enamel coating 104 provided on the heat treatable glass substrate 101 further comprises a catalyst. In an embodiment the catalyst used is dibutyltindilaurate present in a range of 0 to 3 weight% of the weight of the ceramic precursor. For certain ceramic precursor additives, the catalyst serves to increase the curing rate during the initial heat treatment at less than 250°C.

The heat treatable glass substrate 101 provided with the enamel coating 104 in accordance with the present disclosure further comprises a ceramic precursor 105. The ceramic precursor 105 additive in an embodiment is selected from the group consisting of polycarbosilanes, polysilazanes, polysiloxaness or polysilanes or their combinations or their derivatives thereof. The polysiloxanes include but are not limited to methyl silicone, phenyl methyl silicone, epoxy silicone, and their combinations or their derivatives thereof. In a preferred embodiment, the ceramic precursor 105 is a polysiloxane and, in a most preferred embodiment the ceramic precursor 105 is a methyl silicone polymer. The ceramic precursor 105 present in the enamel coating 104 is in the range of 0.01 to 20 weight%. In a preferred embodiment the ceramic precursor 105 is present in the range of 0.1 to 10 weight%.

In multiple embodiments of the present disclosure, the ceramic precursor additive is a transparent additive. The ceramic precursor 105 in accordance with the present disclosure functions as a heat responsive opacifier. In the enamel coating of the present disclosure, the ceramic precursor exists in polymer form ensuring homogenous blending with the enamel coating formulation without altering the color and the appearance of the coating. The ceramic precursor polymer can withstand the initial heat treatment at less than 250°C without any degradation. During the high temperature treatment in excess of 600°C for the glass tempering operation, the organic component of the ceramic precursors burn-off leaving behind the inorganic remnants. In other words, the heat-responsive opacifier or the ceramic precursor additive incorporated in the enamel coating 104 is expected to undergo a physical transformation with the burning-off of the organic moieties leaving behind ceramic particles. Moreover, the burn-off process may also introduce voids in the enamel coating 104 during fusion of the inorganic enamel frits. The combination of the inorganic remnants of the ceramic precursor additive 105 and the introduction of voids in the enamel coating 104 lead to increase in opacity or the hiding power of the enamel coatings, at high temperatures during the heat-treatment of the glass substrate coated with the enamel. This transformation of the heat responsive opacifier or the ceramic precursor, while undergoing the heat treatment, results in an increase in the opacity of the glass substrate 101. In some embodiments the glass substrate the light transmission of the resultant glass article is much higher than that of its counterpart provided with a regular enamel. In multiple embodiments, the light transmission depends on the thickness of the enamel coating and the base enamel coating formulation.

The heat treatable glass substrate 101 coated with the enamel 104 comprising the ceramic precursor 105 provides a glass article with high opacity, thereby ensuring minimal visible light transmission. As stated earlier, the ceramic precursor when used in the enamel coating undergoes a physical transformation with the burning-off of the organic moieties leaving behind ceramic particles leading to increasing the opacity or the hiding power of the enamel coatings. However, the ceramic precursor inherently does not have the opacifying property or increase in hiding power, even upon heat treatment, when used in a standalone formulation containing only the ceramic precursor. Whereas when the ceramic precursor was used along with the other components described in enamel coating 104 of the present disclosure, it was surprisingly found that the ceramic precursor 105 was able to transform into a heat responsive opacifier, i.e., being able to transform into highly opaque particles resulting in the increased opacity of the glass substrate. Further the enamel coatingl04 containing the ceramic precursor 105 is found to be non-reactive and stable. In an alternate embodiment, the enamel coating 104 only reacts with moisture, which further aids in curing of the enamel coating.

Additionally, or optionally the enamel coating 104 of the present disclosure may contain other components conventionally used in the preparation of enamel coatings, for example, thickening agent, surface controlling agent, anti-foaming agent, and the like. In an alternate embodiment other ceramic precursor polymers, for example, carbosilanes can also be blended in the enamel coating 104 to achieve high opacity with nil or minimal visible light transmission. In yet another embodiment, different pigments based enamels could also be used.

In accordance with the present disclosure, the transparent substrate can be coated with multiple layers of enamel coating. In a specific embodiment a white enamel coating with different concentrations of the ceramic precursor additive is deposited on the heat treatable transparent substrate at varying dried film thickness. After the coating is dried, a second black enamel coating without a ceramic precursor is deposited on top of the white enamel coating and dried again to a dried film thickness of about 18um. The entire system is then heat treated in the furnace at temperatures in excess of 600°C and rapidly quenched to temper the glass and fuse the frits. The colour values are measured with and without the second black enamel coating against a white background. The change in the colour due to the addition of the second black enamel coating, AE*, is illustrated in Figure 6 as a function of the dried film thickness of the first white enamel coating.

The present disclosure, further provides a method for making a heat treatable glass substrate which is coated with the enamel, as per the teachings of the present disclosure. The method comprises the steps of cleaning a glass substrate having a first surface 102 and a second surface 103. The first surface 102 of the glass substrate 101 is applied with the enamel coating 104. The enamel coating 104 is applied directly on the glass substrate 101 covering its surface area in entirety or in parts using a variety of wet-coating deposition techniques including but not limiting to Meyer rod coating, screen printing, embossed roller coating, digital printing, curtain coating, gravure coating, ink-jetting, spray painting, spin coating, bar coating or dip coating. The enamel coating 104 can be provided in any form, size, shape and/or color in such a way that it covers the surface area of the glass substrate 101, in entirety or in parts thus making a patterned design. In an embodiment, the enamel coating 104 according to the present disclosure when applied by any of the known wet application processes such as spraying, dipping, flow coating, and electrodeposition, the coating is dried prior to firing. Drying is typically accomplished using IR lamps. The thickness of the enamel coating 104 typically depends on the requisite function and opacity to be achieved.

Further, the glass substrate coated with an enamel 104 is dried in an infrared oven for about 10 to 20 minutes at a temperature of less than 250 °C followed by heat treating the enamel coated glass substrate at a temperature of about 600 to 750 °C.

In accordance with the present disclosure, the thickness of the enamel coating 104 ranges from 1 to 200 pm. In a preferred embodiment the thickness of the enamel coating 104 ranges from 10 to 100 pm, and in a most preferred embodiment the thickness of the enamel coating 104 ranges from 10 to 50 pm. The enamel coating 104 can be used to cover the first surface 102 of the glass substrate in its entirety or in parts as a decorative pattern. The patterns formed by the enamel coating 104, printed on the glass substrate 101 are selected from the various patterns including but not limited to logos, lines, polka dots, circles, square, triangle, oval, rectangle, octagon, parallelogram, trapezoid, pentagon, hexagon, stars, gradients, abstract shapes or a combination thereof, with varying diameters and depths. The surface area to be covered by the enamel coating 104 in the present disclosure is varied based on the requirement and shape of the pattern. During the heat treatment step, the enamel coating 104 is fused onto the glass substrate 101. The ceramic precursor in accordance with the present disclosure undergoes a physical transformation with the burning-off of the organic moieties leaving behind ceramic particles. Moreover, the burn-off process may also introduce voids in the enamel coating 104 during fusion of the inorganic enamel frits. The combination of the inorganic remnants of the ceramic precursor 105 and the introduction of voids in the enamel coating leads to increasing the opacity or the hiding power of the glass substrate. The resulting glass articlelOO provided with the enamel coating 104 has reduced gloss and is highly opaque. The glass articles thus formed are substantially opaque with nil or minimal visible light transmission. The glass substrate with the enamel coating 104 of the disclosure does not yellow on curing and gives a hard, durable, scratch-resistant, gasoline-resistant, weather-resistant, alkali-resistant coating which is suitable for all interior glass applications including but not limited to partitions, wall cladding and decorative purposes that necessitate having bright, opaque colors and improved aesthetics.

Further the enamel coated glass substrate thus obtained according to the teachings of the present disclosure can be transported, cut, stored and/or washed and made to undergo other post-processing steps such as those not limited to edge grinding, bending etc., before subsequently being tempered or toughened at tempering temperature as high as 750°C for a specified duration of time. EXAMPLES

Inventive Example 1 (Sample A)

Preparation of an enamel coated glass substrate: Sample A is prepared in accordance with the present disclosure. Table 1 discloses Sample A, which was prepared following the steps produced below:

1) Cleaning a clear glass substrate having a first surface and a second surface. The clear glass substrate has a thickness of 6 mm.

2) Preparing an enamel coating, comprising inorganic component, organic component, and a ceramic precursor. The enamel coating formulation has about 70wt.% of inorganic components that include glass frits and pigments, 20wt.% of organic components that include a polymer binder resin and a diluent and about 10wt.% of the methyl silicone ceramic precursor. The curing of the ceramic precursor is enhanced with the use of diButylTindiLaurate (dBTdL) as a catalyst used at a concentration of about 3wt.% of the methyl silicone precursor.

3) Depositing an enamel coating inclusive of the methyl silicone ceramic precursor over one first surface of the clear glass substrate.

4) Drying in an infrared oven for less than 20 minutes at a temperature of less than 250 °C. After drying, the enamel coating has a thickness ranging from about 25 pm to about 60 pm.

5) Heat treating the coated clear glass substrate at a temperature of about 600 to 750 °C to obtain a glass substrate.

6) Quenching the obtained coated clear glass substrate to toughen the glass.

Table 1

Inventive Example 2 (Sample B1

Sample B comprising an enamel coating prepared from an enamel formulation is prepared in accordance with the present disclosure with a ceramic precursor additive, following the steps as disclosed in inventive example 1 sample A. The ceramic precursor used in the formulation is a polysilazane instead of a silicone polymer, at the same concentration. Comparative Example 1 (Sample All

Preparation of an enamel coated glass substrate:

Sample A1 comprising an enamel coating prepared from an enamel formulation is prepared in accordance with the present disclosure, without a ceramic precursor additive, following the steps as disclosed in inventive example 1. Table 2 discloses the components of Sample Al.

Table 2

Comparative Example 2 (Sample B1 - Ceramic precursor additive alone on a glass substrate)

Sample B1 is prepared in accordance with the present disclosure with the following steps: 1. Cleaning a clear glass substrate having a first surface and a second surface. The clear glass substrate has a thickness of 6 mm.

2. A polysilazane ceramic precursor additive is wiped on the glass substrate.

3. Drying in an infrared oven for less than 20 minutes at a temperature of less than 250 °C.

4. Heat treating the coated clear glass substrate at a temperature of about 600 to 750 °C to obtain a glass substrate.

5. Quenching the obtained coated clear glass substrate to toughen the glass.

The two samples, Sample A and Sample Al, with and without the ceramic precursor, respectively are compared in Figure 2. Figure 2 (a) illustrates a graphical representation of comparison of the opacity of the enamel coatings expressed as a change in color values when measured against a black background and white background. The hiding power is plotted as a function of dried enamel coating thickness for the comparative Example 1 Sample Al vs. the Inventive Example 1, Sample A, in accordance with one embodiment of the present disclosure. Figure 2 (b) illustrates a graphical representation of comparison of the opacity of the enamel coatings expressed as light transmission values as a function of thickness for the comparative Example 1 Sample Al vs. the enamel coating (Inventive Example 1 , Sample A), in accordance with one embodiment of the present disclosure. The opacity of the samples (contrast AE* and light transmission) are measured after the high temperature (>600°C) glass toughening heat treatment, while the enamel coating thickness is measured before the high temperature (>600°C) glass toughening heat treatment. The color values L*, a* and b* were measured on toughened glasses with the fused enamel against a black background and a white background. The difference in the L*, a* and b* values against the two backgrounds are represented as the color change or contrast DE* , with a higher value denoting poorer opacity. Table 3 shows the difference in the contrast DE* and light transmission values for the Comparative Example 1, Sample A1 and the proposed enamel formulation (Inventive Example 1, Sample A), as a function of thickness.

Table 3

Figure 2 (b) and Table 3 clearly represent the difference in the light transmission values for the Comparative Example 1 Sample A1 and the Inventive Example 1 Sample A as a function of thickness of the dried enamel coating. The opacity or the hiding power of the enamel coating with the ceramic precursor is higher when compared to the Comparative Example 1 Sample A1 as indicated by the 2-fold lower transmission values for the enamel coating.

Figure 3 illustrates a graphical representation of comparison of the change in the color values against a white and black background as a function of the high-temperature heat treatment (tempering) for the heat treatable glass article coated with an enamel, with and without the use of the ceramic precursor, in accordance with one embodiment of the present disclosure. Figure 3 clearly shows change in the DE* values, for the enamel coating with and without the silicone heat-responsive opacifier before and after glass tempering. While the incorporation of the said ceramic precursor in the enamel coating decreases the opacity (increases DE*) before the heat treatment, the physical transformation of the ceramic precursor during the high temperature heat treatment results in increased opacity compared to the base Comparative Example 1 Sample Al. The data for Figure 3 is tabulated in Table 4. Table 4 represents the comparison of change in color values against black and white backgrounds as a function of the high temperature heat treatment for a comparative Example 1 Sample Al vs. the enamel coating (Inventive Example 1 Sample A).

Table 4

Figure 4 illustrates a graphical representation of comparison of change in color values against black and white backgrounds after tempering as a function of ceramic precursor incorporation, in accordance with one embodiment of the present disclosure. Figure 4 clearly shows the change in AE* values, for the comparative Example 1 Sample Al without ceramic precursor and with two different ceramic precursor additives: silicone and polysilazane, in accordance with the present disclosure. With the use of both silicone (Inventive Example 1 Sample A) and polysilazane ceramic precursors (Inventive Example 2 Sample B), the opacity of the paint improves after the high temperature heat treatment compared to the comparative Example 1 Sample Al. Similar improvements in opacity with the use of any ceramic precursor that can transform from a transparent polymer state to an opaque ceramic state during the high temperature heat treatment, can be achieved. The data for Figure 4 is tabulated in Table 5. Table 5 represents the change in color values against black and white backgrounds.

Table 5

Figure 5 illustrates a graphical representation of comparison of light transmission values for the

Comparative Example 1 Sample Al,

Polysilazane ceramic precursor (Comparative Example 2 Sample Bl). Silazane ceramic precursor alone is coated on a glass substrate, and

Enamel coating (Inventive Example 1 Sample B) with the ceramic precursor at

10% concentration, in accordance with one embodiment of the present disclosure. Comparative Example 1 Sample Al, Comparative Example 2 Sample B1 and the Inventive Example 2 Sample B in a concentration of 10wt.% of the polysilazane ceramic precursor are deposited on clear glass sheets. As can be seen in Figure 5, Sample B1 (or the polysilazane ceramic precursor) when deposited on its own, demonstrates very high light transmission values or low hiding power after the high temperature toughening operation. Thus, the hiding power or the opacity is not an inherent property of the ceramic precursor alone. However, when the polysilazane precursor is incorporated in the enamel formulation there is unforeseen surprising results (Inventive Example 1 Sample A), where an almost 0 light transmission is achieved and with respect to Inventive Example 2, Sample B, the light transmission drops several fold compared to the comparative Sample Al.

Figure 5 further clearly shows the synergistic effect of the addition of the ceramic precursor to the base enamel coating. Without the addition of the ceramic precursor polymer, the glass coated with the comparative Example 1 Sample Al displays about 18% light transmission, while a coating of the polysilazane ceramic precursor (Comparative Example 2 Sample Bl) is transparent with a light transmission value as high as 89%. However, with the incorporation of the ceramic precursor into the enamel coating (Inventive Example 1 Sample A), the light transmission value drops to around 3-4%. This observed effect can be attributed to the scattering of light by the transformed ceramic particles and the voids created in the enamel matrix during the high temperature physical transformation of the ceramic precursor. This is in contrast to the uniform film that forms on the surface when the polysilazane ceramic precursor is used as a standalone coating (Comparative Example 2 Sample Bl). The data for Figure 5 is tabulated in Table 6. Table 6 represents the light transmission values for the 3 different coatings.

Table 6

Figure 6 represents the change in the colour due to the addition of the second black enamel coating, DE*, as a function of the dried film thickness of the first white enamel coating on X axis. It is clearly inferred from the figure 6, the difference in the colour values with and without a second enamel coating is most apparent at lower thicknesses without the use of the ceramic precursor in the first white enamel layer. Increasing the thickness of the first enamel layer increases its hiding power and reduces the impact of the second black enamel coating. Moreover, even at low thicknesses of the first enamel layer, incorporation of a ceramic precursor additive reduces DE* thereby improving the hiding power and resulting in limited influence of the second black enamel coating on the aesthetics of the heat treatable transparent substrate. Thus from the above inventive and comparative examples the glass article 100 of the present disclosure is very unique with significantly high opacity and substantially nil or minimal light transmission, thereby making it highly opaque, and suitable for various applications such as lift lobbies, spandrels, interiors, wardrobes, kitchen shutters, bathrooms and could also be possibly used as dinning and coffee table surfaces, depending on customers’ interest. More and more of these applications necessitate the glass article to achieve aesthetic appeal to customers, along with opaque properties, in order to hide the fixing solutions used or the mechanical installation in the buildings.

Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.

The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Certain features, that are for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in a sub combination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.

The description in combination with the figures is provided to assist in understanding the teachings disclosed herein, is provided to assist in describing the teachings, and should not be interpreted as a limitation on the scope or applicability of the teachings. However, other teachings can certainly be used in this application.

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the use of "a" or "an" is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, where more than one item is described herein, a single item may be substituted for that more than one item. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent that certain details regarding specific materials and processing acts are not described, such details may include conventional approaches, which may be found in reference books and other sources within the manufacturing arts.

While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

List of Elements

TITLE: A HEAT TREATBLE GLASS ARTICLE WITH AN ENAMEL COATING

100 Glass Article

101 Glass substrate

102 First Surface

103 Second Surface

104 Enamel coating

105 Ceramic precursor

Claims

We Claim:

1) A heat treatable glass substrate coated with an enamel formulation, the enamel formulation comprising: inorganic component in the range of 0 to 70 weight %; organic component in the range of 0 to 40 weight %; a ceramic precursor additive in the range of 0.01 to 50 weight %; and a catalyst in the range of 0 to 20 weight % of the ceramic precursor additive, wherein the ceramic precursor opacifies the glass substrate during heat treatment of the glass substrate, characterized in that the glass substrate can be tempered at temperatures as high as 750 °C.

2) The heat treatable glass substrate as claimed in claim 1, wherein the glass substrate can be handled and/or transported without mechanical damages to the enamel coating and further be tempered at temperatures as high as 750 °C, after being handled and/or transported.

3) The heat treatable glass substrate as claimed in claim 1, wherein the inorganic component further comprises frits and pigments.

4) The heat treatable glass substrate as claimed in claim 3, wherein the frits are selected from the group comprising but not limited to oxides of zinc, bismuth, lithium, boron, sodium, aluminum, silicon, potassium, calcium, titanium, chromium, iron, cobalt, copper, strontium, zirconium, barium.

5) The heat treatable glass substrate as claimed in claim 3, wherein the pigment is selected from the group comprising but not limited to titanium dioxide, zinc oxide, iron or other metal ion doped titania, copper oxide, chromium oxide, cobalt oxide, lithium niobate, manganates, berilium oxide, cadmium sulfide or cadmium telluride.

6) The heat treatable glass substrate as claimed in claim 1, wherein the organic component further comprises a polymer resin and a diluent.

7) The heat treatable glass substrate as claimed in claim 6, wherein the polymer resin is selected from the group comprising but not limited to acrylates, esters, acrylic esters, epoxies, polyols, urethanes, silicones, melamine and their combinations thereof.

8) The heat treatable glass substrate as claimed in claim 6, wherein the diluent is selected from the group comprising but not limited to di-acetone alcohol, ether glycol, xylene or ethyl methyl ketone and their combinations thereof.

9) The heat treatable glass substrate as claimed in claim 1, wherein the ceramic precursor is a heat responsive opacifier.

10) The heat treatable glass substrate as claimed in claim 9, wherein the ceramic precursor is selected from the group consisting of polycarbosilanes, polysilazanes, polysiloxanes, polysilanes, organometallics, or combinations thereof.

11) The heat treatable glass substrate as claimed in claim 10, wherein the ceramic precursor is a polysiloxane comprising a methyl silicone polymer.

12) The heat treatable glass substrate as claimed in claim 1, wherein the catalyst is selected from a group comprising but not limited to dibutyltindilaurate,

13) A method for making a heat treatable glass substrate, comprising the step of: cleaning a glass substrate having a first surface and a second surface; applying the enamel as claimed in claim 1 on one of the surfaces of the glass substrate; drying in an infrared oven for about 10 - 20 minutes at a temperature of less than 250 °C; and heat treating the enamel coated glass substrate at a temperature of about 600 to 750 °C; wherein the enamel comprises a ceramic precursor that opacifies the glass substrate during the heat treatment such that glass substrate has substantially minimal visible light transmission, characterized in that the glass substrate can be handled and/or transported without mechanical damages to the enamel coating and further be tempered at temperatures as high as 750 °C after being handled and/or transported.

14) The method as claimed in claim 13, wherein the enamel is applied over the glass substrate by screen printing, embossed roller coating, digital printing, curtain coating, gravure coating, ink-jetting, spray painting or dip coating.