ENERGY COATING

TECHNICAL FIELD

The present disclosure relates in general to a device which controls the visibility with switchable transparency. More particularly the present disclosure provides a visibility controlling device with an efficient and improved switching time between transparent and non-transparent states, such that the light transmittance in transparent state and non-transparent state is substantially equivalent to their dry-frosted and wet-frosted state.

BACKGROUND

Generally, smart or switchable partitions involve a category of glazing materials that change their light-transmission properties in interaction to an external stimulus. It can be used in a wide range of everyday products such as windows, doors, skylights, partitions, sunroofs, sun visors and many more. Such smart or switchable partitions can also be referred as visibility controlling devices as per the present disclosure. The visibility controlling devices can be manually or automatically tuned to control the amount of light or optical transmittance through a transparent substrate.

At present, there is a huge demand for smart or switchable partition panels to serve as wide area of switchable gates for light transactions with the external world or space. It is quite common to find any polymer material or glass as partition without any additional functionality either in offices or houses or commercial or residential places. The control of light transmission to achieve privacy, however has been a challenge and quite often it varies with the specific nature of the partition used. The conventional methods of privacy setting, to block one's view to the outside, is performed using permanent fixtures such as blinds, screens, curtains, shutters, obscure glasses or any such combinations thereof. These methods although enhance privacy, they occupy internal space, require frequent and inconvenient cleaning and often requires artificial light despite high exterior light availability. Use of obscure glass offers no user control on the degree of transparency, thereby not making them customer or user friendly.

In the existing state of art, electrochromic glass uses varying colors of the different oxidation states of a material like tungsten oxide. The active material is sandwiched between two glass sheets using a laminate and an electrically conductive layer. The transparency can be tuned based on the applied voltage and can be tuned from a transparent state of about 80% to a translucent state of about 10%. However, such electrochromic glasses do not completely turn opaque and has a finite visibility in the switched OFF state, resulting in a lack of privacy.

Further known are Polymer-Dispersed Liquid Crystal (PDLC) based glasses and Suspended particle device (SPD) based glasses. In PDLC, the glasses have the liquid crystal orient along the applied electric field direction resulting in a complete transparent state. When the electric field is turned off, the liquid crystals randomize resulting in an opaque state. And in SPD, the glasses have a distribution of polar molecules that align in the direction of the applied electric field resulting in a transparent state. With the removal of the applied electric field, the glass turns opaque. However, the PDLC-based glasses only have binary states that can be either turned ON or OFF. The films are also expensive. Similarly, the SPD-based glasses also have fairly expensive components depending on the type of particles used to tune the transparency of glass.

Furthermore, smart windows or switchable transparency windows or visibility controlling devices have also been developed which become opaque or non-transparent to block or reflect sunlight on blazing days thereby saving energy and costs of cooling devices and thereafter return to a transparent state during low light conditions to enhance freely available natural light harvesting and to catch free warmth from the sun.

Inventions utilizing only the concept of refractive index matching to modulate the optical transmission has been described in US2783682A and CN103197438 to invent smart dimming glass using carbon tetrachloride as the base liquid which is a well- known greenhouse gas and a heap toxin along with o- dichlorobenzene which is known to cause sporadic irritation of the eyes and respiratory tract. These devices suffer from blemish pattern formation and produce ripping like appearance in the translucent state while switching between the on/off states.

None of the devices described in the above patents either attain complete reversal transparent and non-transparent states. Although such smart devices or visibility controlling devices exist in the art, for example, W02020070568A1 discloses visibility controlling device with a toggle option between translucent and transparent states in selected areas. Specifically, the smart visibility controlling device is involved in controlled transmission of light by refractive index matching of the components-etched panes of glass/polymer and liquid composition. When the liquid is removed from a cavity between two roughened sheets, the degree of opacity obtained depends on the efficiency of liquid removal. With the teachings disclosed in the aforesaid application the complete removal of liquid requires more time or extremely low de- wetting speeds, almost 40 to 48 hours or even more to achieve complete reversal in transparency or a steady state, which is a disadvantage to the end users who wish to achieve privacy or light transmittance in either states, instantly.

Sangki Park and Sun-Kyu Lee (Applied Optics Vol. 55, Issue 9, pp. 2457-2462 (2016)) describe a micro-optical pattern-based selective transmission mechanism composed of a patterned plate and deionized water as liquid medium to get energy saving, environmentally benign switchable glass. However, the use of ultra-precision diamond-cutting machine to generate the patterns makes the invention costly and unsuitable for manufacturing larger sized partitions. Also, these journal articles on the micro-patterning of a solid surface to optimize transmission demonstrates the use of an oil-repellent coating to overcome the presence of residual liquid drops during dewetting. However, no understanding on the effect of the solid-liquid interactions on opacity and switching time speeds are provided.

Smart glass or switchable glass with an improved or quicker switching time speed from one state to another, will play an increasingly important role in the world's drive towards sustainability. Requiring very low amounts of power to operate, architects, designers and engineers can integrate smart glass into their projects in ways that offer unprecedented control over incoming light and glare. In doing so, electrical energy consumption can be lowered, cooling load is reduced, environmental impact mitigated, and occupant well-being is highly increased. These outcomes can be achieved by way of introducing smart partitions into various day lighting strategies with quicker time speed switchability requiring less amount of transparent liquid. Therefore, there certainly arises a need to develop a sustainable, smart or switchable partition or a visibility controlling device with a quicker switchable time speed, which in fact surprisingly and efficiently ensures that the full transparency and non-transparency is achieved during such switching. With the proposed invention, the customers are not only provided with a partition which provides privacy on demand but switching features at par with their costlier counterpart technologies.

OBJECT OF INVENTION

The main object of the present invention is to provide a visibility controlling device with switchable states of transparency and non-transparency. Another object of the present invention is to provide a visibility controlling device, said device ensures quicker switchable time speed between transparent and non-transparent state.

Yet another object of the present invention is to provide a visibility controlling device, said device during switchability between transparent state and non-transparent state, ensures that the light transmission is substantially equivalent to their dry-frosted and wet-frosted state.

The present disclosure was developed by outlining the above objectives.

SUMMARY OF THE DISCLOSURE

In an aspect of the present disclosure, a visibility controlling device with controlled regions of non-transparency and transparency is disclosed. Said device comprises, a framework formed by at least two transparent substrates juxtaposed to define a cavity and glued together and sealed by glue with a gap through a spacer and a hole for breathing. The at least two transparent substrates are roughened on one side and the cavity is filled with a transparent liquid of substantially equivalent refractive index as that of the transparent substrate. The roughened side of the at least one transparent substrate is coated with a material selected from the group consisting of siloxanes, silanes, silsesquioxanes hydrocarbon-terminated polymers and fluoropolymers, characterized in that the coating enables quicker liquid removal time by at least 1 order of magnitude to control the visibility.

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 (a) illustrates a visibility controlling device, in accordance with one embodiment of the present disclosure.

FIG. 1 (b) illustrates a roughened side of glass coated with low surface energy coating, in accordance with one embodiment of the present disclosure.

FIG. 1 (c) illustrates a visibility controlling device front view, in accordance with one embodiment of the present disclosure.

FIG. 2 represents a graphical representation of comparison of the light transmittance of the device in its transparent state with and without a low surface energy coating, in accordance with one embodiment of the present disclosure.

FIG. 3 (a) represents a graphical representation of comparison of the light transmittance in the non-transparent state and transparent state for the visibility controlling device with unmodified roughened glass sheets with no low surface energy coating as per comparative example 1, in accordance with one embodiment of the present disclosure.

FIG. 3 (b) represents a graphical representation of comparison of the light transmittance in the non-transparent state and transparent state for the visibility controlling device with modified roughened glass sheets with low surface energy coating as per inventive example 1, in accordance with one embodiment of the present disclosure. FIG. 4 represents a graphical representation of change in non-transparent state measured as a change in light transmittance from the time the liquid is withdrawn from the chamber, 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.

DETAILED DESCRIPTION

As used herein, in every embodiment, it must be understood that the terms or phrases ‘smart partitions/glass’ or ‘switchable partitions/glass’ or ‘visibility controlling device’, can be used interchangeably. Said phrases refer to partitions/glasses which switch between transparent and non-transparent state, by allowing or blocking light/optical transmittance.

The term Tow surface energy coating’, as used herein, refers to a coating having characteristics of making the coated surface repulsive for liquids to stick or a weak molecular attraction which thereby allows quicker de-wetting of the surface.

The term ‘transparent liquid’ or ‘liquid’ can be used interchangeably and refers to a liquid filled in the cavity of at least two roughened transparent substrates, having substantially equivalent refractive index as that of the roughened transparent substrate and increases the transparency of the roughened transparent substrate by refractive index matching.

The term ‘ 1 order of magnitude’, as used herein, refers to an improvement in the liquid removal time. For example, T order of magnitude’, as referred herein the present application, shows the improvement in removal time of the transparent liquid, by at least 10 times faster than the existing device without low surface energy coating. As used herein, the term ‘transparent state’ is well known to a person skilled in the art, refers to a state which allows light to pass through so that objects on the other side can be distinctly seen. Similarly, the term ‘non-transparent’ or ‘opaque’ can be used interchangeably, referring to blocking light to pass through so that objects on the other side cannot be seen. Alternatively, ‘dry-frosted’ state corresponds to the nontransparent or opaque state before the liquid touches the substrate, whereas, the ‘wet- frosted’ state is the non-transparent or opaque state after the liquid has touched the surface at least once.

The term ‘transparent substrate roughened on one side’, as used herein, refers to a glass sheet where one side is roughened by means of grit blasting, coarse sand blasting, fine sand blasting, acid etching, laser etching, grinding, milling and loose particle machining or a combination thereof.

The present application provides a visibility controlling device with controlled regions of non-transparency and transparency. Referring to Figure 1(a) and 1(b) of the present application, the device comprises, a framework formed by at least two transparent substrates (1) juxtaposed to define a cavity and glued together and sealed by glue (5) with a gap through a spacer (4) and a hole for breathing. The at least two transparent substrates in accordance with the disclosure are roughened (2) on one side and the cavity between the two transparent substrates is filled with a transparent liquid of substantially equivalent refractive index as that of the transparent substrate (1). In accordance with the present disclosure, the roughened side (2) of the at least one transparent substrate is coated with a material selected from the group consisting of siloxanes, silanes, silsesquioxanes hydrocarbon-terminated polymers and fluoropolymers. Beneficially, the visibility controlling device in accordance with the present disclosure enables quicker liquid removal time by at least 1 order of magnitude to control the visibility. Further, beneficially, and surprisingly the disclosed visibility controlling device also ensures that a light transmittance in both transparent and nontransparent state is substantially equivalent to the respective dry-frosted and wet- frosted states.

Generally, the visibility controlling devices during their switch ON/OFF sates switch between transparent and non-transparent states. Usually during the transparent state, the light is transmitted through the device, while during the non-transparent state the light transmittance is not allowed through the device.

The visibility controlling device in accordance with the present disclosure, comprising a framework, such that the framework is formed by the at least two substrates juxtaposed, with both the substrates roughened on one side (2) glued together by glue (5) with a gap through a spacer and a hole for breathing. Said framework is connected through inlet/outlet (6) port to a liquid pumping station (7) filled with the transparent liquid of substantially equivalent refractive index as that of the transparent substrate.

In accordance with the present disclosure in order to form one-side roughened (2) of the transparent substrate material, the transparent substrate is selected from group comprising glass, polymer like polyethylene terephthalate, or acrylic sheet like polymethylmethacrylate. In a preferred embodiment, the at least two transparent substrates (1) in accordance with the present disclosure is selected from the group consisting of annealed glass, heat strengthened glass, tempered glass, non-tinted or tinted glasses. For exemplary purpose the device made of glass in accordance with the present disclosure is illustrated in Figure 1.

The visibility controlling device fabrication, as per the present disclosure involves one side roughened transparent substrate facing the another one side roughened transparent substrate and fastened using transparent glue by putting a spacer (4) to create a void between the at least two transparent substrates (1) as illustrated in Figure 1. The transparent substrate (1) is sealed from the sides to block the cavity from all sides leaving a hole for air breathing and an option for inlet/outlet (6) to the flat surface of the substrate for flow of the transparent liquid. There is provided a liquid pumping station (7) connected via connector pipes to the inlet/outlet port (6) of the visibility controlling device. The device may be operated manually or through electrical means. In the present disclosure, the gap between the at least two transparent substrates ranges from 50 to 500 pm. In a preferred embodiment, the gap between the at least two transparent substrates is as less as 300 pm. The thickness of the spacer (4) in one embodiment of the present disclosure is ranging from 50 to 500 pm.

In another embodiment of present disclosure, the spacer (4) is selected from a group consisting of single side adhesive tapes, double side adhesive tapes, self-adhesive tapes, polymer strips, polyethylene terephthalate, polypropylene, teflon, polyacrylate, nylon, polystyrene, metal sheet strips or a combination thereof. In a preferred embodiment the spacer is made of made of polyvinyl chloride or polyethylene terephthalate. In another embodiment of present invention, the transparent glue is selected from a group consisting of polyurethane-based glue, epoxy-based glue, a- cyanoacrylate based glue and silicon- based glue.

The at least two transparent substrates (1) in accordance with the present disclosure are roughened (2) on the one side, where a cavity is formed between the two transparent substrates. In an embodiment the roughened sides (2) are created by various methods including but not limited to grit blasting, coarse sand blasting, fine sand blasting, acid etching, laser etching, grinding, milling and loose particle machining or a combination thereof. In a specific embodiment, the roughened sides on the transparent substrates are created by using fine sand blasting. The transparent substrates (1) in accordance with the present disclosure have a roughness ranging from 100 nm to 10000 nm. In a specific embodiment, the roughness is ranging from 1000 to 10000 nm. The at least two transparent substrates due to presence of roughness appears translucent in normal condition.

The at least two transparent substrates (1) forming a cavity, is filled with a transparent liquid of substantially equivalent refractive index as that of the transparent substrates. In an embodiment, the refractive index of the liquid is ranging from 1.480 to 1.580. In a preferred embodiment, the refractive index of the liquid is 1.5168. In a further embodiment of the present disclosure the visibility controlling device with controlled regions of transparent and non-transparent state comprises said liquid of aromatic amine ranging from 10%-90% by volume and polymer ranging from 90%-10% by volume. The transparent liquid in accordance with the present disclosure renders light transmission through the cavity, in spite of the internal wall roughness. When devoid of the transparent liquid, the cavity becomes translucent due to light scattering from the roughened internal wall surfaces.

In an embodiment in accordance with the present disclosure, the transparent liquid is selected from the group consisting of aniline and polyethylene glycol, dimethylpthalate, diethylpthalate, methyl salicylate, ethyl salicylate, butyl salicylate and methyl benzoate or their combination thereof. In a specific embodiment the liquid is dimethylphtalate or aniline and polyethylene glycol. The transparent liquid with substantially same refractive index as that of the transparent substrate partially blocks transmission of radiation in a selected spectral region of the ultraviolet from 200 to 300 nm as described in publication W02020070568A1.

The at least two transparent substrates (1) due to presence of roughness on one side (2) appears translucent in normal condition. When the transparent liquid of substantially equivalent refractive index as that of the transparent substrates starts being filled into the gap created due to spacer (4) the transparency gradually changes and when the gap is fully filled with the transparent liquid the substrate becomes fully transparent. The cavity formed is filled with the transparent liquid either manually or by electronic pumping. Surprisingly, in a specific preferred embodiment, the inventors of the present disclosure have coated the roughened side (2) of at least one transparent substrate with a hydroxyl terminated siloxanes. In a preferred embodiment of the present disclosure, the roughened side (2) of at least two transparent substrates facing each other is coated with a hydroxyl terminated siloxanes and have observed an efficient and quicker time for removal of the transparent liquid during the switching process. Such quicker removal of transparent liquid, by at least 1 order of magnitude, thereby achieved quicker switchable timings between transparent and non-transparent states.

The material in accordance with the present disclosure is selected from the group consisting of siloxanes, silanes, silsesquioxanes hydrocarbon-terminated polymers and fluoropolymers (3). The coating material is a low surface energy based coating (3). In a specific embodiment the siloxanes are selected from the group consisting of, but not limited to poly dimethyl siloxane, amine functional siloxane, epoxy functional siloxane or combinations thereof. In a specific embodiment the silanes are selected from the group consisting of, but not limited to hydrocarbon-terminated or fluorocarbon- terminated silanes or combinations thereof. In a specific embodiment, the silsequioxanes are selected from the group consisting of, but not limited to hydrocarbon-terminated or fluorocarbon-terminated silsequioxanes or combinations thereof. In another embodiment the hydrocarbon terminated polymers are selected from the group consisting of, but not limited to acrylics, alkyds, epoxies, polyurethanes, or combinations thereof. Further, the fluoropolymers are selected from the group consisting of, but not limited to perfluorinated polymers and polyfluorinated polymers or combinations thereof. The visibility controlling device as per the present disclosure, the visibility is uniformly maintained by the flow of transparent liquid with speed ranging from 0.5 to 3 cm ³ /s. In yet another embodiment of the present disclosure, the pumping station is controlled by manual pumping and/or electrical pumping mechanism. As described in publication W02020070568A1 the bellow compression/expansion based pumping station (7) comprises rotation rod, metal gasket to prevent rotation rod from pulling off from the system due to natural bellow expansion, rotation rod holder to hold and rotate, outer casing for bellow compression/expansion pumping system, bellow holder, bellow, bellow mouth connector, rod holder, nut holder which holds nut with thread, nut with thread which allows rotation of rod, space inside the bellow where liquid is filled and hole in the glass where bellow mouth gets connected to the device. Rod holder on the glass which allows rod to rotate freely while rod rotation and bellow holder does UP/DOWN motion while rotating the rotation rod holder in clockwise and anticlockwise, respectively. This action reflects to the bellow compression/expansion mechanism with rod rotation. Further, according to the present disclosure the liquid pumping station (7) having air pressure induced flow mechanism comprises manual or electrical air compressor, non-returning valve, liquid container, air valve and T- junction of the pipe (8).

In accordance with an embodiment of the present disclosure the hydroxyl terminated siloxanes coating is a low surface energy based coating (3), which is provided on the roughened sides of the two glass substrates as shown in Figure 1(b). The low surface energy coating (3) in accordance with the present disclosure enables reduction of light transmission in the non-transparent state by at least two times when compared to the non-transparent state, without the low surface energy coating. The higher de-wetting of the surface is achieved during the transparent liquid removal,

The hydroxyl terminated siloxanes functioning as low surface energy coating (3), in an embodiment is selected from the group consisting of polydimethyl siloxane, amine functional polydimethyl siloxane and epoxy functional polydimethyl siloxane. In another embodiment, the low surface energy coating (3) is also selected from silanes including octadecyltrichlorosilane, tetraethoxysilane, hexamethyldisilazane or a combination thereof. In a further embodiment, the low surface energy coating is also selected from transparent hydrophobic coatings selected from aminopropylmethylsiloxane-dimethylsiloxane copolymer.

In a specific embodiment a solution comprising a solvent and an active material is sprayed on the roughened side of the glass substrate. The solvent is isopropyl alcohol and the active material in accordance with the present disclosure is aminopropylmethylsiloxane-dimethylsiloxane copolymer. Upon spraying of the solution, the solvent dries and the active material forms a thin film on the glass, referred as the low surface energy coating.

In accordance with the present disclosure, the low surface energy coating (3) provided on the roughened side (2) of the two transparent substrates (1) controls the transparent liquid removal time which is in turn linked to the switchability between transparent and non-transparent state. The roughened surfaces (2) of the transparent substrates (1) in accordance with the present disclosure are modified with a low surface energy coating (3). The cavity formed between the two transparent substrates filled with a refractive index-matched liquid as stated earlier in the disclosure. The choice of the transparent liquid and the solid surface chemistry is such that the static contact angle of the liquid on the roughened glass is at least 80°. The low liquid wettability surface allows for a more efficient and quicker removal of the transparent liquid from within the cavity during the transition from the wet-transparent state to a dry non-transparent state. The low-surface energy coating (3) in accordance with the present disclosure is considered wherein the contact angle of the liquid on the roughened glass surface after coating is greater than or at least 80°. When the roughened sides (2) are treated with the low- surface energy coating (3) according to the present disclosure, the efficiency of liquid removal from within the roughened features is far higher. The retraction of the transparent liquid from within the cavity due to the presence of the low surface energy coating (3) on the roughened side (2) of the glass, yields a higher opacity or nontransparency which is surprisingly beneficial.

In an embodiment the thickness of the low surface energy coating (3) is ranging from 1 to 200 nm. In a preferred embodiment, the thickness of the low surface energy coating (3) ranging from 100 to 200 nm. In an alternate embodiment the low surface energy coating (3) can also be provided in the form of a pattern.

In an embodiment the low surface energy coating (3) in accordance with the present disclosure is non-toxic, non-fluorinated emulsion-based formulation which is low in preparation cost. It was surprisingly found by the inventors of the present application, that while the roughened sides (2) of the transparent substrates (1) are coated with a low surface energy coating (3), the time required for removal of the liquid has been more efficient. This has been indicative while switching between transparent to nontransparent state in less than 60 seconds and at the same time ensuring that light transmittance in respective transparent and non-transparent states is substantially equivalent to their dry-frosted and wet-frosted states. The transparent liquid removal time achieved by using a low surface energy coating (3) in accordance with the present disclosure, is way less than currently existing smart or switchable partitions/glasses. Also, as per the present disclosure during the switching complete privacy is ensured or light is allowed as per the end users wish instantaneously without having to wait for hours together.

In yet another embodiment of the present disclosure, the device transmits light ranging from 60% to 90% in transparent state and 0% to 20% in non-transparent state, with the low surface energy coating provided on one side of the transparent substrate. In a preferred embodiment, the device transmits light ranging from 80 % to 100% in transparent state and 0% to 7% in non-transparent state, with the low surface energy coating provided on one side of the transparent substrate. In a most preferred embodiment, the device transmits light ranging from 98% to 100% in transparent state and 0% to 1% in non-transparent state, with the low surface energy coating provided on one side of the transparent substrate after the switching between transparent and non-transparent state. In, yet another specific embodiment of the present disclosure, the device blocks 99% to 100% of UV rays and 20% to 30% of IR rays.

The visibility controlling device in accordance with the present disclosure ensures that the complete opacity and the transparency of the system is obtained when the roughened side of the transparent substrate is provided with a low surface energy coating. When the transparent liquid is removed from the cavity between the two roughened sheets, the degree of opacity obtained depends on the efficiency of liquid removal. With present disclosure, the time taken for complete removal of transparent liquid has drastically decreased and also achieves complete reversal in transparency and increase the opacity of the liquid-free unit.

In one embodiment of the present disclosure, the visibility is controlled from top to bottom, bottom to top, sideways, or a combination thereof.

Thus, the visibility controlling device in accordance with the present disclosure, is beneficial in ways, that it helps the customers to achieve privacy by increased transparent liquid removal time or efficient switching time, and in some cases even instantly, thereby gaining technical and economic significance.

EXAMPLES

Inventive Example 1 Table 1 discloses a static contact angle of two transparent liquids used on two roughened glasses with the low surface energy coating modification according to an inventive Example 1 :

Table 1

Two roughened glass sheets were washed and dried to eliminate dirt and grime from the surface. An amino modified hydroxyl terminated siloxane was used as the low surface energy coating. A solvent based spray formulation was realized with 10% by weight of active content in isopropyl alcohol. The active material is deposited on the glass by spray and excess has been wiped off using a microfiber cloth. The glass was then allowed to dry overnight and the dimethylpthalate contact angle was checked as shown in Table 1 before assembling the microfluidic chamber. The low surface energy coating is a non-toxic, non-fluorinated emulsion-based formulation which is low in preparation cost.

Comparative Example 1

Table 2 discloses a static contact angle of two representative liquids used on two roughened glasses without the low surface energy coating modification according to comparative Example 1 :

Table 2

Inference:

The increase in contact angle of the liquid on the surface coated with low surface energy coating implies repulsion of the liquid to the coated surface. As a result, when an outlet is provided for the liquid to leave the cavity when the walls of the cavity are coated with the said low surface energy coating, the withdrawal of the liquid is faster and more efficient owing to the repulsion of the liquid to the walls of the cavity. In turn, complete withdrawal of the liquid ensures that the wet-frosted opacity of the device is as much as the dry-frosted opacity thereby allowing repeatability in achieving the non-transparent state.

It was clearly observed from graphical representation in Figure 2, that the difference in light transmittance between glass sheets with no surface energy coating and modified glass sheets with the low surface energy coating is small with a maximum loss of 10%. This slight decrease in transparency could be due to the haziness associated with the thickness of the coating deposited on the roughened glass.

Further, from Figure 3(a) which indicates the light transmittance of a device in accordance with comparative example 1, it can be inferred that the non-transparent state has a light transmission of only about 2-3%, which jumps to close 40% in the transparent state, leading to loss in privacy. While in figure 3(b), which indicates the light transmittance of a device in accordance with inventive example 1, it can be inferred that when a low surface energy coating is applied, the retraction of the liquid from within the cavity is more efficient and the light transmission in the wet-frosted state is a lot closer to that of the dry-frosted state and is about 4%. A 10-fold improvement in the non-transparent state is observed with the application of a low surface energy coating. Hence, it is surprisingly found that the low surface energy coating improves the non-transparency in the privacy state of the glass system. The switching speed to go to this state is equally important and the rate at which the maximum non-transparency is reached for a coated as compared to an uncoated glass.

Inventive Example 1

Table 3 discloses a switching time for roughened glasses with the low surface energy coating modification according to inventive Example 1 :

Table 3

Comparative Example 1

Table 4 discloses a switching time for roughened glasses without the low surface energy coating modification according to comparative Example 1 :

Table 4

Inference:

It is inferred from the graphical representation in Figure 4, which depicts the comparison for liquid withdrawn at the highest speed of 2 cm/s. The coated glass in accordance with inventive example 1, reaches the maximum non-transparency instantly post liquid withdrawal, whereas, the uncoated glass (comparative example 1) takes 48 hours to reach steady state or to come back to its original state of transparency and non-transparency. Furthermore, the steady state non-transparency is three times lower in the uncoated glass, thereby proving the clear advantage of the low surface energy coating for the privacy glass application, with a quicker switching time of as less as 60 seconds.

INDUSTRIAL APPLICABILITY

Thus, from the above inventive and comparative examples, the visibility controlling device or the smart partition of the present disclosure is very unique with significantly improved privacy to the end user, by ensuring quicker switchability between transparent and non-transparent state. The visibility controlling device as per the present disclosure is sustainable, and find its application in various commercial and residential places such as office partitions, interior partitions for privacy in health and hospitality sector, smart windows, facades etc.

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. 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. 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. 1 Reference Numerals:

1 - transparent substrate

2 - roughened side

3 - low surface energy coating

4 - spacer

5 - sealant / glue

6 - inlet/outlet

7 - pumping station

8 - pipe