Coated solar control glass articles

A coated solar control glass article includes a transparent substrate provided with a multilayer coating having solar control properties is disclosed. The multilayer coating includes a metal nitride functional layer sandwiched between two transparent dielectric layers. The thickness of the dielectric layer provided above the functional layer is greater than 60 nm and less than 150 nm and the thickness of the dielectric layer provided above the transparent substrate is greater than 10 nm and less than 45 nm. The coated solar control glass article exhibits gold/rose/purple colored reflection on the side opposite to the side provided with the multilayer coating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of PCT/IN2018/050587, filed Sep. 11, 2018, which in turn claims priority to Indian patent application number 201741032744 filed Sep. 15, 2017. The content of these applications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates, in general to a coated glass article, and more specifically to a heat treatable colored solar control glass article having a gold or rose/purple colored reflection and a method of making the same.

BACKGROUND

Solar control coatings are known in the art that are usually made of two or more layers of metal or metallic oxide (typical metals include titanium, zinc, copper, tin, and silver, and typical alloys include brass and stainless steel). These coatings are microscopically thin, yet give a slightly brown or gray color to the glass substrate bearing them. The exact form and thickness of the coating vary quite widely depending on the manufacturer. Early solar control coatings often had a layer of silver sandwiched between two layers of metal oxide. Later metal oxide layers made from metals other than silver were found to yield far better results. These improved coatings reduced emissivity and allowed high light transmission.

Solar control coatings having a layer stack of glass/Si3N4/Nb/Si3N4are known in the art, where the metallic Nb layer is the sole infrared (IR) reflecting layer in the coating. In certain instances, the Nb IR reflecting layer may be nitrided. While such layer stacks provide efficient solar control, the reflection color obtained by such layer stacks has never been worked upon. For example, a known solar control coating having a layer stack of glass/Si3N4/NbN/Si3N4has an external a* value in a range between −3 and +3; and b* value in a range between −20 and +10. This implies that a glass article with the above solar control layer stack would have a neutral to blue/green external reflection.

Referring to U.S. Pat. No. 6,994,910 describes a heat treatable coated article with NbN acting as the IR reflecting layer. Referring to PCT publication number 2005105687 relates to a solar control coating having a layer stack of glass/Si3N4/NbN/Si3N4that is heat treatable and bendable. The glass article coated with the solar control coating exhibits a blue/green color in external reflection. The solar control articles described in the cited references focus on achieving solar control properties and have either a neutral or a blue/green external reflection.

Notwithstanding all the past experience and technology which are available for producing solar control articles, it has been discovered that although these coated articles are effective in solar control, the solar control layer stack was never engineered to have different reflection colors. Hence there is scope for obtaining different reflection colors while retaining their solar control properties. For example, most of the solar control glass articles available currently in the market have a neutral or blue-green color in external reflection. A study on the emerging market trends revealed that bluish-green color is not to everyone's liking and may not be appropriate for every kind of building. Since these solar control articles are generally more expensive than their ordinary counterparts, it becomes more important to ensure that the extra cost is justified by multiple combined features of the coated articles.

Further, it has been found that the color of the external and internal refection of these articles can be improved upon by working on the dielectric layers of the solar control layer stack. The external reflection of the solar control coated articles can be varied by varying the coating thickness of the Si3N4layers of the solar control layer stack.

The present disclosure relates to a coated solar control glass article that comprises of a thin multilayer stack provided on one side of a transparent substrate. The thin multilayer stack comprising a metal nitride functional layer sandwiched between two transparent dielectric layers. The thickness of the metal nitride functional layer and the dielectric layer are designed in such a way that the solar control glass article exhibits a golden or rose/purple colored external appearance on the other side of the transparent substrate while retaining its solar control properties. Thus these coatings can block part of the solar spectra very efficiently in addition to having a golden or rose/purple colored appearance. The light transmission from exterior to interior of a building incorporated with these coated solar control glass articles is also decreased thereby reducing glare for the building occupants.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a transparent substrate comprising a multilayer coating having solar control properties is provided. The multilayer coating comprises of a metal nitride functional layer sandwiched between two transparent dielectric layers. The dielectric layer provided above the functional layer is thicker than the dielectric layer provided below the functional layer. Particularly, the thickness of the dielectric layer provided above the functional layer is greater than 60 nm and less than 150 nm and that of the dielectric layer provided above the transparent substrate is greater than 10 nm and less than 45 nm.

In one other aspect of the present disclosure, a heat treatable solar control glass article is disclosed. The heat treatable solar control glass article comprises of a transparent substrate provided with the multilayer coating and an enamel comprising glass frit, an organic polymer and a pigment. The enamel is provided above the multilayer coating. The heat treatable solar control glass article can be handled before the heat treatment.

In another aspect of the disclosure, a composite glazing comprising a plurality of glass substrates is disclosed. One of the glass substrates of the plurality of glass substrates is the transparent substrate comprising a multilayer coating having solar control properties or a heat treatable solar control glass article or a heat treated solar control glass article of the present disclosure.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts. Embodiments disclosed herein are related to coated solar control glass articles.

A coated solar control glass article100according to one embodiment of the present disclosure is illustrated inFIG. 1. The coated solar control glass article100comprises of a glass substrate110provided with a multilayer coating200. The multilayer coating200comprises of a metal nitride functional layer120sandwiched between two transparent dielectric layers130a,130b. The dielectric layer130ais in direct contact with the glass substrate110and the dielectric layer130bis provided above the metal nitride functional layer120.

The metal nitride functional layer120comprises of at least one metal nitride selected from the group consisting of niobium, tantalum, molybdenum, nickel, chromium and zirconium. In a specific embodiment, the metal nitride functional layer120is niobium nitride (NbN). In another specific embodiment, the metal nitride functional layer120is nickel chromium nitride (NiCrN). The transparent dielectric layers130a,130bare based on aluminium nitride, aluminium oxynitride, silicon nitride or silicon oxynitride or silicon aluminium nitride. In one specific embodiment, the transparent dielectric layers130a,130bis silicon nitride.

In one embodiment of the present disclosure, the thickness of the metal nitride functional layer120is greater than 10 nm and less than 35 nm. The thickness of the metal nitride functional layer120is adjusted to obtain a desired light transmission through the coated solar control glass article100. In another embodiment of the present disclosure, the thickness of the transparent dielectric layers130a,130bis adjusted to optimize the reflectance and color of the transparent glass substrate110. In one embodiment, the thickness of the dielectric layer130bprovided above the metal nitride functional layer120is greater than 60 nm and less than 150 nm and the thickness of the dielectric layer130ain direct contact with the glass substrate110is greater than 10 nm and less than 45 nm.

In one embodiment, the multilayer coating200is applied on the transparent substrate110by physical vapor deposition using magnetron sputtering. In alternate embodiments, other suitable coating techniques may be used to obtain the multilayer coating200.

FIG. 2illustrates a coated solar control glass article100, according to another embodiment of the present disclosure. The coated solar control glass article100comprises of a glass substrate110provided with the multilayer coating200of the present disclosure. In multiple embodiments, the glass substrate110may be a clear glass or a tinted glass. The multilayer coating200is provided on the coating side (C)203of the transparent glass substrate110. When the coated solar control glass article100of the present disclosure is installed in a building the coating side203provided with the multilayer coating200faces the inside of a building. In such an arrangement, the glass side (G)202opposite to the coating side (C)203of the transparent glass substrate110exhibits a gold color reflection or a rose/purple color reflection depending on the thickness of the dielectric layer130a,130bwhen viewed from outside the building. The thickness of these dielectric layers130a,130bcan be engineered to obtain an aesthetically improved gold or rose/purple color reflection.

The thickness of the dielectric layer130bprovided above the metal nitride functional layer120is increased to increase the b* value (measured on the glass side (G)202) of the coated solar control glass article100. A positive b* (b*G>10) value gives a yellowish appearance on the glass side202opposite to the coating side203(provided with the multilayer coating200) of the transparent substrate110which contributes to the gold color reflection of the coated solar control glass article100on the glass side202. Similarly, a* value (measured on the glass side (G)202) is also engineered to be a positive value (0<a*G<4). A positive a* value in combination with the b* value results in golden color and helps avoiding greenish tint in the external reflection. However, in case of a*G>4 the red color dominates and hence should avoided for this particular application.

Similarly, a positive a* value (measured on the glass side (G) 202) (a*G>5) gives a reddish appearance on the glass side202opposite to the coating side203(provided with the multilayer coating200) of the transparent substrate110. This contributes to the rose/purple color reflection of the coated solar control glass article100on the glass side202. A positive b* value (measured on the glass side (G)202) results in rose color while a negative b* value (measured on the glass side (G)202) provides purple color reflection. However, in the case of rose/purple color reflection of the coated solar control glass article100b* value is maintained below the a* value (b*G<a*G). The light transmission of the coated solar control glass article100is 10%-55% depending on the thickness of metal nitride functional layer120.

A gold colored solar control glass article300according to one specific embodiment of the present disclosure is illustrated inFIG. 3. The gold colored solar control glass article300comprises of a transparent substrate110provided with a multilayer coating200acomprising a niobium nitride layer302sandwiched between two transparent dielectric layers303a,303bbased on silicon nitride. The thickness of the niobium nitride layer302ranges between 10 nm and 35 nm. The niobium nitride layer302acts as the IR blocking layer of the multilayer coating200aand attributes to the solar control properties of the gold colored solar control glass article300.

While the solar control properties depend entirely on the thickness of the niobium nitride layer302, the light transmission (TL) of the gold colored solar control glass article300is invariably proportional to the thickness of the niobium nitride layer302. Hence it becomes important to have a balance between the solar control properties and the light transmission (TL) values of the solar control glass article300. Thus a thickness range between 10 nm and 35 nm of the niobium nitride layer302provides for the desired light transmission (TL) while also maintaining the solar control properties of the solar control glass article300.

The thickness of the silicon nitride layer303apresent above the transparent glass substrate110ranges between 15 nm and 45 nm and the thickness of the silicon nitride layer303bpresent above the niobium nitride layer302ranges between 60 nm and 100 nm. The silicon nitride dielectric layer303a,303bcontribute to the reflection color of the solar control glass article300and hence are designed in such a way that the glass side G of the transparent substrate110reflects a golden color and the coating side C of the transparent substrate110reflects a brilliant blue color. The multilayer coating200ais designed to have as low as 10% internal reflection. In one aspect of the embodiment, the gold colored solar control glass article300may be enamelled. In multiple aspects of the embodiment, the gold colored solar control glass article300may be strengthened, toughened or heated to a temperature ranging between 500° C. and 700° C.

In another embodiment of the present disclosure, the gold colored solar control glass article400is heat treatable.FIG. 4illustrates a heat treatable gold colored solar control glass article400comprising a transparent glass substrate110provided with a multilayer coating200aof the present disclosure and an enamel430. The enamel430is applied directly over the multilayer coating200aof the present disclosure. The enamel layer430comprises of glass frit, an organic material and a pigment. In one aspect of the embodiment, the weight percentage of the organic material ranges between 5-40% of the total weight of the enamel430upon drying. In one other aspect of the embodiment, the organic material comprises of at least one or more materials selected from the group consisting of polyols, alkyds, acrylic, polyacrylic, polyacrylates, polymethacrylates, acrylamides, melamine, polycarbonates, acrylic-styrenes, vinyl-acrylic, urethanes, polyurethanes, polyesters, polyolefins, urethane alkyds, polyurea, amino resins, polyamides, epoxies, epoxy esters, phenolic resins, silicon resins, PVC, PVB, water-based resins or reaction products of photocurable chemicals or thermally curable chemicals.

In another aspect of the present embodiment, the glass frit present in the enamel430contains a zinc-based material or bismuth-based material or their combinations thereof. In yet another aspect, the pigment present in the enamel430contributes to the color of the transparent glass substrate110and hence the pigment may be selected based on the desired color of the transparent glass substrate110. For example, titania provides white color, copper and cobalt oxide provide blue color and chromium oxide provides green color. In another example embodiment, grey/black colored enamel may be chosen to highlight the gold color external reflection of the heat treatable gold colored solar control glass article400.

In one other aspect of the embodiment, the enamel430protects the heat treatable gold colored solar control glass article400from external damage such as scratches and the multilayer coating200adoes not peel off or degrade during edge grinding, storage, transportation, etc. In another embodiment of the present disclosure, the enamel430is provided for temporary resistance of the heat treatable gold colored solar control glass article400prior to tempering and is intended to be removed or destroyed during tempering process.

The heat treatable gold colored solar control glass article400can be tempered and can be handled before tempering. This implies that the heat treatable gold colored solar control glass article400may be coated with the enamel430at the manufacturing site and can be transported to other locations without causing the multilayer coating200ato peel off or become damaged at the borders. Further the gold colored solar control glass article400coated with the enamel430may be cut, edge grind, beveled, drilled, sized and finished before being tempered. Here again the multilayer coating200adoes not peel off or get damaged at the borders of the cutting line.

In one other embodiment, the gold colored solar control glass article400coated with the enamel430can be tempered at a temperature above 600° C. During the tempering step the organic polymer present in the enamel430is completely burnt off. The other components of the enamel430fuse with the glass surface. The pigment present in the enamel430imparts colour to the glass substrate.

The heat treatable gold colored solar control glass article400has a ΔE* value (change in color of the heat treatable gold colored solar control glass article400before and after heat treatment) less than 2.5. The emissivity of the heat treatable gold colored solar control glass article400also does not undergo change after heat treatment. The heat treatable gold colored solar control glass article400exhibits a higher IR reflection compared to standard glass. The gold colored solar control glass article300and the heat treatable gold colored solar control glass article400exhibit high durability values.

A rose/purple colored solar control glass article500according to one specific embodiment is illustrated inFIG. 5. The rose/purple colored solar control glass article500comprises of a transparent substrate110provided with a multilayer coating200bcomprising a niobium nitride layer502sandwiched between two transparent dielectric layers503a,503bbased on silicon nitride. The thickness of the niobium nitride layer502ranges between 10 nm and 35 nm. The niobium nitride layer502acts as the IR blocking layer of the multilayer coating200band attributes to the solar control properties of the rose/purple colored solar control glass article500.

The thickness of the silicon nitride layer503apresent above the transparent substrate110ranges between 10 nm and 45 nm and the thickness of the silicon nitride layer503bpresent above the niobium nitride layer502ranges between 100 nm and 150 nm. The silicon nitride dielectric layer503a,503bcontribute to the reflection color of the rose/purple colored solar control glass article500and hence are designed in such a way that the glass side G of the transparent glass substrate110reflects a rose/purple color and the coating side C of the transparent glass substrate110reflects a bluish, greyish, greenish blue color with 30% of internal reflection. In one aspect of the embodiment, the rose/purple colored solar control glass article500may be enamelled. In multiple aspects of the embodiment, the rose/purple colored solar control glass article500may be strengthened, toughened or heated to a temperature ranging between 500° C. and 700° C.

In one embodiment of the present disclosure, a composite glazing comprising a plurality of glass substrates bonded together by a polymeric interlayer is disclosed. One of the glass substrates of the plurality of glass substrates can be a gold colored solar control glass article300or a heat treated gold colored solar control glass article400or a rose/purple colored solar control glass article500. In one aspect of the embodiment, the polymeric interlayer is made of polyvinyl butyral (PVB) and/or other organic polymers selected from the group consisting of polyurethane and/or ethylvinylacetate (EVA) and/or polyvinyl chloride and/or polyester and/or polyethylenevinylacetate (PET) and/or polycarbonate and/or polypropylene and/or polyethylene and/or polyurethacrylate or their combinations thereof.

In the following examples, the layer stacks were deposited by magnetically enhanced (magnetron) sputtering at room temperature on a transparent glass substrate having a thickness of 6 mm

Gold Colored Solar Control Glass Article

Two glass substrates were coated with the below shown layer stacks:

Optical properties of the two glass samples coated with layer stack 1 and layer stack 2 are summarized in Table 1.

TABLE 1Optical Properties of Gold Colored Solar Control Glass ArticleOutsideInsideEmissivityTLRexta*Gb*GRinta*Cb*CELayer26.326.42.722.712.6−0.9−38.80.65Stack1Layer33.325.5224.685−43.70.71Stack2Rext= External reflection;a*G, b*G = a*, b* values measured on glass side;Rint= Internal reflection;a*C, b*C = a*, b* values measured on coating side

Both the layer stacks exhibited a golden appearance on the glass side (that is on the building exterior) and a brilliant blue color on the coating side (that is on the building interior). It was evident that layer stack 2 having a decreased NbN thickness recorded an increased light transmission (TL) value. Transparent glass has an emissivity of 89%, whereas the gold colored solar control glass article according to this embodiment of the present disclosure has an emissivity value as less as 65% and 71%. Internal reflection (Rint) of the coated glass substrates was maintained below 15%.

Rose/Purple Colored Solar Control Glass Article

Two glass substrates were coated with the below shown layer stacks:

Optical properties of the two glass samples coated with layer stack 2 and layer stack 4 are summarized in Table 2.

Glass substrates coated with layer stack 3 exhibited a rose colored appearance and that coated with layer stack 4 exhibited a purple colored appearance on the glass side (G). The internal reflection (Rint) was found to be high at 31-37%. The external reflection (Rext) is much lower making the color subtle in appearance.

Durability Studies

The following durability studies were performed for the glass substrates coated with layer stack 1 to 4.

Erichsen Brush Test

The brush test was used to evaluate the resistance of the layer stacks to erosion caused by scrubbing. In this test a soft brush is rubbed against the coating where the coating is submerged in the water. This test is done to test mechanical robustness against washing machine brushes during processing.

The samples were tempered at a temperature above 600° C. after the Erichsen brush test. This step reveals the presence of any minor scratches that occurred during the test procedure. However, the tested samples did not show any sign of scratches.

In another experiment, the samples coated with layer stack 1 to layer stack 4 were first tempered at a temperature above 600° C. and then subjected to the Erichsen brush test procedure. Again the samples did not show any sign of minor scratch or coating erosion.

Taber Abrasion Test

Taber abrasion test was used for performing accelerated wear resistance testing. It involved mounting a flat sample of approximately 100 mm2to a turntable platform that rotate on a vertical axis at a fixed speed. The wear action was carried out by two rotating abrading wheels supported on a loading arm which applied 250-gram pressure against the sample, exclusive of the weight of the wheel in contact with sample. The weight before and after the test were measured to calculate the overall weight loss of the test samples. The results of the durability studies are summarized in Table 3.

The color change (ΔE*) after the tempering process was measured for transparent substrates coated with layer stack 1 and layer stack 2. The results are tabulated in Table 4. ΔE* value of the samples were found to be less than 2.5. Similarly, emissivity change after tempering process was measured for transparent substrates coated with layer stack 3 and layer stack 4. The samples did not record any change in emissivity.

Two 6 mm thick glass substrates (Planilux marketed by Saint-Gobain) were coated with the below shown layer stacks:

Optical properties of the two glass samples coated with layer stack 5 and layer stack 6 are summarized in Table 5.

TABLE 5Optical Properties of Layer Stack 5 and Layer Stack 6OutsideInsideTLRexta*Gb*GRinta*Cb*CLayer29.520.13207.67.4−40Stack5Layer44.522−0.522.34.611.9−43.2Stack6

The external appearance of glass substrates coated with layer stack 5 and layer stack 6 was observed to be golden color. However, the external reflection (Rext) was found to be lower than glass substrates coated with layer stack 1 and layer stack 2 thereby making the golden color less prominent.

Three 6 mm thick glass substrates (Planilux marketed by Saint-Gobain) were coated with the below shown layer stacks:

Optical properties of the three glass samples coated with layer stack 7, layer stack 8 and layer stack 9 are summarized in Table 6.

TABLE 6Optical Properties of Layer Stack7, Layer Stack 8 and Layer Stack 9OutsideInsideTLRexta*Gb*GRinta*Cb*CLayer22.613.57.23.636.5−9.7−7.7Stack7Layer2113.35.8−3.540.6−9.72.7Stack8Layer21205.92.332.6−9.1−9.9Stack9

Layer stacks 7, 8 and 9 exhibit different TLvalues compared to layer stack 3 and 4 shown in example 2. While layer stack 7 and 9 results in a rose colored external reflection, layer stack 8 results in a purple colored external reflection.

It should be noted that the above examples is only indicative and does not limit the scope of the invention in any manner. The brightness of the external color reflected by the coated glass substrates may be varied by varying the reflection values (Rintand Rext).

Comparative Example 1

The example given below illustrate various embodiments of the invention and allow the characteristics of the multilayer coatings obtained according to the prior art and according to the invention to be compared.

It was evident that the two prior art documents focus on a thicker dielectric layer above the transparent substrate. On the contrary the present disclosure provides a multilayer coating having a thicker dielectric layer above the metal nitride functional layer as shown in Table 7. This thicker dielectric layer provided above the metal nitride functional layer contributes to the gold or rose/purple color of the coated solar control article of the present disclosure.

The optical performance of the prior art references is tabulated in Table 8.

The variation obtained in a*, b* values both on the glass side (G) and coated side (C) of the present multilayer coating200are strikingly different from that recorded by the prior art references.

INDUSTRIAL APPLICABILITY

The coated solar control glass article100of the present disclosure can be used in a monolithic, double or triple glazing. These glazings are installed in such a way that the multilayer coating is preferably on face2, the faces of substrates being numbered from outside to the inside of the building or room which is equipped therewith, giving it a solar radiation protection effect. These glazings exhibit an emissivity value equal to or less than 80%. The coated solar control glass article100can also be used in building wall cladding panel of curtain walling for interior applications. Further the coated solar control glass article100can also be used as a side window, rear window or sunroof for an automobile or other vehicle.

The coated solar control glass article100of the present disclosure can also be enameled, strengthened or toughened and used for building interior applications. The durability studies of these coated solar control glass article100provide for a longer life of these articles. In embodiments where the coated solar control glass article100is heat treatable, the article can be handled before heat treatment. The major advantage being the transparent substrate may be provided with the multilayer coating, an enamel coating at a manufacturing site and can be transported to another job site without causing the coating to peel off or become damaged at the borders. Further the coated solar control glass article100coated with the enamel430may be cut, edge grind, beveled, drilled, sized and finished before being tempered. Here again the coating does not peel off or get damaged at the borders of the cutting line.

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.

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.

LIST OF ELEMENTS