EP4214170A1

EP4214170A1 - Antimicrobial and antiviral coating

Info

Publication number: EP4214170A1
Application number: EP21786548.4A
Authority: EP
Inventors: Simon James Hurst; Karikath Sukumar Varma; Andrew Oliver SMITH; Fiona BLACK; Simon JEFFREYS
Original assignee: Pilkington Group Ltd
Current assignee: Pilkington Group Ltd
Priority date: 2020-09-16
Filing date: 2021-09-16
Publication date: 2023-07-26
Also published as: AR123531A1; JP2023542156A; GB202014616D0; WO2022058734A1

Abstract

The present invention relates to an antimicrobial and/or antiviral coated glass substrate and to a process for preparing same and use thereof comprising: i) a glass substrate; and ii) a silica matrix coating layer wherein the silica matrix coating layer comprises: a) at least 50% by weight silica; and b) copper containing particles deposited on and/or embedded within the silica matrix coating layer in an amount of from 1 to 50 % by weight; and wherein growth of bacteria on the substrate is reduced by at least 10% compared with non-coated glass substrates; and wherein deactivation of viruses on the substrate is increased by at least 10% compared with non-coated glass substrates.

Description

ANTIMICROBIAL AND ANTIVIRAL COATING

The present invention relates to a process for producing an antimicrobial and/or antiviral coating on a glass substrate, to antimicrobial and/or antiviral coated glass substrates and to the use of such antimicrobial and/or antiviral coated glass substrates in a range of applications.

In addition, the present invention relates to a process for producing a toughenable antimicrobial and/or antiviral coating on a glass substrate, to toughenable antimicrobial and/or antiviral coated glass substrates and to the use of such toughenable antimicrobial and/or antiviral coated glass substrates in a range of applications.

That is, the present invention relates to a process for producing an antimicrobial and/or antiviral coating on a glass substrate and to glass substrates with such antimicrobial and/or antiviral coatings on at least one surface thereof. The invention also relates to antimicrobial and/or antiviral articles comprising antimicrobial coated glass substrates prepared in accordance with the present invention such as for example but not limited to architectural and automotive glazings, splash-backs, furniture, bottles, wall coverings and touchscreens.

As the extent to which glass substrates are used in the world increases, so the presence of micro-organisms which may reside on the surface of such substrates also increases, and therefore, the potential transfer of micro-organisms from one individual to another. Indeed, touch screens located for example in shops and supermarkets may have hundreds of individuals per hour using the touch screen terminal and therefore, potentially spreading microorganisms, in the form of bacteria, fungi, yeasts and viruses, from one user to another. For the purposes of the present invention, viruses are also considered to be micro-organisms.

In addition, as the threat of resistance to certain bacterial strains increases, and as epidemics arise from the transmission of some viruses, there is an ever-increasing need for individual glass substrates no matter the device or application, to be able to halt the spread of microorganisms, specifically bacteria and viruses.

It has been known for some time that microorganisms including bacteria, yeasts and viruses may be killed if brought into contact with a metallic surface. Indeed, in an attempt to stem the spread of microorganisms in nosocomial environments, copper has been used on surfaces such as door handles, bathroom fixtures, and beds. (Applied and Environmental microbiology 2011 , March, 77(5), 1541-1547). However, the ability to incorporate antimicrobial and antiviral properties into surfaces which are required to remain transparent to a required standard such as windows and doors, and which are also preferably resistant to for example wear and scratching has proved difficult. This is because, not only it is difficult to impart lasting antimicrobial and antiviral activity to glass substrates, but also, any coating applied to a glass substrate which provides antimicrobial and antiviral activity must still provide the required parameters of a glazing whilst retaining a pleasing aesthetic appearance at an acceptable cost. In addition, since it is desirable for glass substrates, especially windows and doors to preferably be heat treated or annealed, to comply with current glazing standards, providing glazing products which meet demanding performance in terms of being strengthened after the application of a coating, and which still are able to provide antimicrobial and antiviral properties, is understandably a challenge for glass manufacturers.

Attempts have been made to impart antimicrobial activity to a substrate surface. For example, in WO 2009/098655 there is described a method for conferring antibacterial properties to a substrate which comprises coating said substrate with a silver film by radio-frequency sputtering. However, the document is silent with respect to the properties of the glass substrate after treatment, specifically heat treatment.

KR 20130077630 A discloses the dispersion of nano-metal ions in a silica sol-gel for antifingerprint and antibacterial purposes. However, there is no consideration given to copper particles and instead, focuses on the production of nano-metal ions through the reaction of a strong metal salt, with a focus on silver. Likewise, CN 109534687 describes a process to provide a silica based sol-gel with incorporated metal ions, preferably silver, used to provide an antimicrobial function.

US 9,028,962 B2 discloses a complex, multi-stage, process whereby copper oxide particles are applied to a transparent substrate. The glass substrate is subjected to ion-exchange either before or after application of the particles to chemically strengthen the glass followed by reducing the copper oxide particles. The antimicrobial glasses are further coated with a fluorosilane layer.

In WO 2005115151. there is disclosed a functional sol-gel coating agent which comprises a nano-particulate additive and which is said to have both an antimicrobial function and a decorative function as a result of the surface of the particle being modified by attachment of a dispersing aid and/or an adhesion promotor in the formed of functional silanes, that is, oligomers with a high OH group content. US 2010/0015193 discloses a substrate with a plurality of antibacterial metal islands formed on the surface of the substrate and exposed to an external atmosphere with a view to forming a resistant coating. The average contact angle value between the substrate and the respective antibacterial metal islands is 90 degrees or less, when measured with a scanning electron microscope. The antibacterial metal islands are disposed by sputtering in an inert gas atmosphere.

DE 202005006784 generally describes articles such as doors, windows and/or inner linings for air conditioners or refrigerators which are suggested to be coated with a transparent, porous sol-gel-layer on at least a part of the surface, wherein the sol-gel layer comprises a matrix of organo-modified siloxanes with one or more alkyl groups and which is doped with at least one antimicrobially effective substance/compound. Unfortunately, no antimicrobial test data are provided in support.

However, none of the prior art documents described above detail a process according to the present invention, which is able to provide an antimicrobial coating on a substrate with the required microbial and/or viral resistance and optical properties, as well as wear and scratch resistance, to a level required of glass substrates and glazings used in the glass industry at reasonable cost, and which may be used for example in locations where the glass or glazings experience extensive public contact.

In addition, none of the documents above address the issues encountered when seeking to deliver antimicrobial and/or antiviral coatings to glass substrates on an industrial scale, or indeed, how to ensure that the antimicrobial and antiviral coatings applied to glass substrates at the end of and industrial coating run offer the same performance as antimicrobial and/or antiviral coatings applied to glass substrates at commencement of an industrial coating run. The above documents make no mention of the conditions required to deliver stability for both the active components and the resultant antimicrobial and/or antiviral coatings following application to glass substrates. In addition, the above documents are silent with respect to the problems associated with maintaining reproducibility of antimicrobial and/or antiviral coatings for glass substrates produced on an industrial scale; problems which the present invention seeks to address.

Therefore, there exists the need for a glass substrate to which has been applied a transparent coating which is able to reduce growth and transmission of microbial pathogens, especially bacteria and viruses, whilst maintaining optical performance and mechanical durability at reasonable cost and on an industrial scale. The anti-microbial and/or antiviral coated glass substrates prepared in accordance with the present invention may be used for example in but not limited to, automotive glazings and architectural glazings including commercial and residential applications as well as in food and healthcare applications. The present invention may also find application in for example but not limited to: electronic devices, such as touch screens, mobile phones, laptop computers, book readers, video gaming devices, automated teller machines, screens, medical containers, refrigeration applications or in transport or transportation applications and modes of transport. Indeed, the present invention is applicable to any application or situation where a glass substrate is used and may be touched, or where information displayed on a glass screen is retrieved by touch.

In addition, the anti-microbial and/or antiviral coatings prepared in accordance with the present invention may be used for instance with coated and uncoated substrates, for example, glass substrates such as but not limited to float glass coated using chemical vapour deposition (CVD) and/or physical vapour deposition (PVD) to produce coating layers; the coating layers being located either above or below the antimicrobial and/or antiviral coatings.

Further, when the antimicrobial and/or antiviral coatings coatings prepared according to the present invention are applied to glass substrates, the glass substrates may comprise flat glass such as for example float glass or alternatively, the glass substrates may comprises alternative forms of glass such as for example but not limited to: borosilicate glass, rolled plate glass, ceramic glass, toughened glass, chemically strengthened glass, hallow glass or glass shaped for articles such as bottles, jars and medical containers.

According to a first aspect of the present invention there is provided a process for producing an antimicrobial and/or antiviral coating on a substrate, the process comprising the steps of: i) providing a glass substrate having a first surface and a second surface; ii) providing a silicon containing solution and a copper containing particle solution or powder; and iii) mixing together the silicon containing solution and the copper containing particle solution or powder in the presence of water and a hydrolysing material to form a silica and copper coating composition; wherein the hydrolysing material comprises: a) one or more polyol; b) one or more weak acid with a pKa value of at least 0.5; or c) one or more polyol and one or more weak acid, iv) contacting at least said first surface of the glass substrate with the silica and copper coating composition to deposit a layer of silica on the glass substrate; and iv) curing the silica and copper coating composition deposited on the glass substrate to form a silica matrix coating layer, wherein the copper containing particles are deposited on and/or are embedded within the silica matrix coating layer in an amount of from 1 to 50 % by weight.

In addition, in relation to the present invention, the process may additionally further comprise the step of: v) toughening the coated glass substrate at a temperature of at least 600 °C, more preferably at a temperature of at least 650 °C.

Preferably, the copper in the copper containing particle solution or powder may be in the form of micro-particles, clusters of nano-particles of copper, copper alloys, copper metal, or copper oxide, or mixtures thereof.

That is, the inventors have found that copper to be particularly compatible and beneficial in providing effective antimicrobial and/or anti-viral properties to a glass substrate when mixed and cured with a silicon containing solution to form a silica matrix coating layer. Indeed, in relation to the present invention the inventors have identified that the glass coating produced in accordance with the present invention is able to provide effective antimicrobial and/or antiviral properties both before and after toughening at a temperature of at least 600 °C.

The copper containing micro-particles or clusters of nanoparticles of copper comprise a size range of from 50nm to 15pm. More preferably, the copper particles are preferably provided in a size range of 75nm to 12 pm. Most preferably however, the copper particles are in a size range of 100nm to 10 pm.

In relation to the present invention, when present as a copper alloy, the copper alloy may comprise one of more of the elements selected from: zinc, tin, aluminium, silicon, nickel, manganese, beryllium, lead, iron, aluminium.

For the process for producing an antimicrobial or antiviral coating on a glass substrate according to the first aspect of the present invention, the hydrolysing material may comprise: a) one or more diol; b) one or more weak acid with a pKa value of at least 0.5; or c) one or more diol and one or more weak acid. That is, in relation to the present invention the inventors have found that the material used to hydrolyse the silicon to deposit a coating of silica onto the glass substrate, has an effect on the antimicrobial and antiviral properties of the coated glass substrate. When the hydrolysing material is a polyol, the polyol is preferably selected from: propylene glycol, ethylene glycol 1 ,3-propanediol, 1 ,4-butanediol or glycerol.

Preferably, the hydrolysing material is a diol. Most preferably propylene glycol is used as the hydrolysing material in connection with the process of the present invention.

When the hydrolysing material is a weak acid, that is, an acid with a pKa value of at least 0.5, the weak acid is preferably selected from the groups comprising one or more of: oxalic acid, phosphoric acid, chloroacetic acid, citric acid, lactic acid, ascorbic acid and propionic acid. Most preferably however, the inventors have found that citric acid is a preferred diol to use in connection with the present invention.

The copper containing particle solution or powder may comprise additional metal components such as for example: lead, tin, iron, antimony, nickel, zinc, cadmium, chromium, arsenic and tellurium. However, the additional metal components are preferably each present at low levels. For example, the additional metal components if present comprises less than 10% by weight of the silica matrix coating layer, more preferably, less than 5% by weight of the silica matrix coating layer, or less than 1 % by weight of the silica matrix coating layer.

Preferably the silica and copper coating composition applied to the glass substrate according to the present invention comprises at least 1 % by weight copper. Alternatively, the silica and copper coating composition applied to the glass substrate may comprise 1 to 10 % by weight copper. Alternatively, the silica and copper coating composition applied to the substrate may comprises up to 50 % by weight copper.

That is, the silica and copper coating composition deposited on the glass substrate and hence the silica matrix coating layer so formed on the substrate may comprise between 1 and 50 % by weight of copper. Alternatively, the silica matrix coating layer so formed on the substrate may comprise between 2 % by weight and 40% by weight of copper. Alternatively, the silica matrix coating layer so formed on the substrate may comprise between 5% by weight and 25 % by weight copper. Alternatively, the silica matrix coating layer so formed on the substrate may comprise between 10 and 25 % by weight of copper.

Alternatively, the silica and copper coating composition deposited on the glass substrate and hence the silica matrix coating layer so formed on the substrate may comprise between 1 to 40 % by weight of copper. More preferably, the silica matrix coating layer so formed on the substrate may comprise between 1 % and 25 % by weight of copper. Most preferably, the silica matrix coating layer so formed on the substrate may comprise between 1 % by weight and 20 % by weight.

Preferably, the copper in the silica matrix coating layer is in the form of copper metal, copper (I) oxide, or copper (II) oxide. More preferably, the copper in the silica matrix coating layer is in the form of copper metal or copper (I) oxide. Most preferably however, the copper is in the form of copper metal.

In relation to the first aspect of the present invention, the silicon containing solution and the copper containing particle solution or powder may each preferably comprise a solvent. The solvent used in the silicon containing solution and the copper containing particle solution or powder may be the same or different. The solvent is preferably selected from the group comprising for example: diacetone alcohol, propylene glycol, propylene glycol methyl ether (PGME), isopropanol, 3-methoxy-1 -butanol and mixtures thereof.

Preferably the silica coating composition applied to the glass substrate according to the present invention comprises at least 50 % by weight silica. Alternatively, the silica coating composition applied to the glass substrate may comprise at least 65 % by weight silica. Alternatively, the silica coating composition applied to the substrate comprises at least 75 % by weight silica.

That is, the silica coating composition deposited on the glass substrate and hence the silica matrix coating layer so formed on the substrate may comprise between 50 % by weight and 99 % by weight of silica. More preferably, the silica matrix coating layer so formed on the substrate may comprise between 65 % by weight and 98 % by weight of silica. Alternatively, the silica matrix coating layer so formed on the substrate may comprise between 50 % by weight and 80 % by weight of silica. Alternatively, the silica matrix coating layer so formed on the substrate may comprise between 50% by weight and 90 % by weight of silica.

The silica matrix coating layer prepared in accordance with the present invention is preferably based on tetraethyl orthosilicate, Si(OC2H5)4, (TEOS) and/or derivatives thereof, and is hydrolysed under mild reaction conditions to form a transparent coating. The silica matrix coating layer based on tetraethyl orthosiiicate is ideal for use on glass substrates such as float glass. In addition, the inventors have found that it is preferable to use tetraethyl orthosilicate in combination a copper containing particle solution or powder to form the silica matrix coating layer, and that the use of same provides excellent results in terms of both antimicrobial and antiviral reduction compared with no coated glass substrates.

In one embodiment of the process according to the present invention the silica and copper coating composition may be applied directly in contact with the glass substrate. Alternatively, the silica and copper coating composition may be applied atop another layer deposited on the glass substrate.

In addition, the silica and copper coating composition may further comprise zirconium. It is preferred that the amount of zirconium in the silica and copper coating composition is set for the required amount of zirconium in the silica matrix coating layer. More preferably, it is preferred that the amount of zirconium in the silica coating composition is set for the required amount of zirconium in the silica matrix coating composition once cured.

For example, the silica coating composition may further comprise at least 1% by weight zirconium. Alternatively, the silica coating composition may comprise less than 1 % by weight zirconium. In an alternative embodiment of the invention the silica and copper coating composition may comprise between 1 and 15 % by weight zirconium. Preferably, the silica coating composition may comprise between 2 and 10 % by weight zirconium. To improve the durability of the silica matrix coating layer, the silica and copper coating composition preferably comprises between 2 and 8% by weight zirconium.

The zirconium is preferably present in the silica coating composition in the form of an oxide of zirconium.

In relation to the process according to the present invention the silica coating composition may preferably be applied to the glass substrate by one or more of: roller coating; spray coating; hydraulically atomised spraying; air atomisation spraying; ultrasonic spraying; dip coating; spin coating; curtain coating; or slot-die coating. Most preferably, for the process according to the present invention the silica coating composition is applied to the glass substrate by roller coating or spray coating.

When following the process according to the present invention the surface of the glass substrate may be cleaned before applying the silica and copper coating composition to improve coating quality. Cleaning the glass substrate may preferably comprise one or more of: abrasion with ceria, washing with alkaline aqueous solution, rinsing with deionised water rinse and/or plasma treatment. Cleaning preferably removes any unwanted dust or dirt particles which may have collected prior to application of the silica layer.

Curing of the silica and copper coating composition may preferably be performed by heating to a temperature in the range 90 °C to 450 °C. More preferably, the process according to the present invention may preferably comprise curing the silica coating composition by heating to a temperature in the range 90 °C to 350 °C. More preferably, the process according to the present invention may preferably comprise curing the silica coating composition by heating to a temperature in the range 150 °C to 350 °C. Most preferably, the process according to the present invention may preferably comprise curing the silica coating composition by heating to a temperature in the range 180 °C to 300 °C, or 180 °C to 250 °C . Curing of the silica and copper coating composition is advantageous as it may improve the density of the silica matrix coating layer and the speed at which the silica matrix coating layer forms.

Preferably, the silica matrix coating layer is deposited to a thickness in the range 5nm to 250nm. Alternatively, the silica matrix coating layer is deposited to a thickness in the range 5nm to 200nm. More preferably, the silica matrix coating layer is deposited to a thickness in the range 10 to 100nm, or the silica matrix coating layer may be deposited to a thickness in the range 20 to 80nm. In addition, the silica matrix coating layer may be deposited to a thickness in the range 25 to 60nm, or even, 30 to 50nm.

The silica matrix coating layer comprising copper, may be used also in combination with coatings applied to glass substrates by for example chemical vapour deposition and/or physical vapour deposition, and which are applied either above or below the silica matrix coating layer. For example, in relation to the process according to the present invention, in an alternative embodiment a transparent conductive oxide coating may preferably be applied to the glass substrate before deposition of the silica and copper coating composition.

According to a second aspect of the present invention there is preferably provided an antimicrobial coated glass substrate preparing in accordance with the first aspect of the present invention comprising: i) a glass substrate; and ii) a silica matrix coating layer wherein the silica matrix coating layer comprises: a) at least 50% by weight silica; and b) copper containing particles deposited on and/or embedded within the silica matrix coating layer in an amount of from 1 to 50 % by weight; and wherein growth of bacteria on the substrate is reduced by at least 10% compared with non-coated glass substrates; and wherein deactivation of viruses on the substrate is increased by at least 10% compared with non-coated glass substrates.

Also in relation to the second aspect of the present invention the antimicrobial and/or antiviral coated glass substrate is preferably toughenable. That is, the coated glass substrate with the antimicrobial and/or antiviral coating applied may be heated to a temperature of at least 600 °C and still retain antimicrobial and/or antiviral properties. More preferably, the coated glass substrate with the antimicrobial and/or antiviral coating applied may be heated to a temperature of at least 650 °C and still retain antimicrobial and/or antiviral properties. Heat treated or annealed coated glass is desirable for a range of architectural and automotive glazing applications. The fact that the coated glass substrate according to the first and second aspect of the present invention retains both its antimicrobial and antiviral properties following heat treatment is beneficial and surprising.

Also in relation to the second aspect of the present invention there is preferably provided an antimicrobial coated substrate, wherein the antimicrobial coated substrate provides within 24 hours or less at least a 2 log reduction against gram positive and/or gram negative bacteria or a 2 log reduction against viruses.

More preferably, the antimicrobial coated substrate provides at least a 2-log reduction against gram positive and/or gram-negative bacteria within 2 hours. Even more preferably the antimicrobial coated substrate provides within 2 hours at least a 3 log reduction against gram positive and/or gram negative bacteria. A 2-log reduction or 2-log kill reduces a microbe colony to 10,000 bacteria after a 99.0% reduction and a 3-log kill reduces a microbe colony to 1 ,000 bacteria after a 99.9% reduction.

In addition, in relation to the second aspect of the present invention there is preferably provided an antiviral coated glass substrate, wherein the antiviral coated glass substrate provides within 24 hours or less at least a 2 log reduction against viruses. More preferably, the antiviral coated glass substrate provides at least a 2-log reduction against gram positive and/or gram-negative bacteria within 2 hours.

The antimicrobial coated glass substrate according to the second aspect of the present invention may further comprise at least 1.0% by weight zirconium. The zirconium is preferably present as an oxide. According to a third aspect of the present invention there is preferably provided an architectural or automotive glazing comprising an antimicrobial and/or anti-viral coated glass substrate in accordance with the second aspect of the present invention or prepared in accordance with the first aspect of the present invention.

According to a fourth aspect of the present invention there is preferably provided the use of an antimicrobial and/or anti-viral coated glass substrate prepared by the process according to the first aspect of the present invention, and/or an antimicrobial and/or anti-viral coated substrate according to a second aspect of the present invention used in the preparation of an insulated glazing unit, an automotive glazing unit, an electronic device, furniture, splash-backs or screens, medical containers, wall coverings, touchscreen, mirrors or glass bottles, refrigeration applications or in transport or transportation applications.

It will therefore be appreciated that all aspects of the present invention in relation to the first aspect of the present invention also apply in relation to the second, third and fourth aspects of the present invention as appropriate.

Embodiments of the present invention will now be described by way of example only with reference to the following examples and drawings in which:

Figures 1a, 1 b, 1c and 1d - illustrate progressive FTIR spectra over time for sol gel reactions conducted in diacetone alcohol, comparing the use of: (a) nitric acid, (b) hydrochloric acid, (c) citric acid at room temperature and (d) citric acid at 60 °C.

Figures 2a, 2b and 2c - illustrates how (a) the Si-O-C spectral peak at 788nm, (b) the Et-OH peak at 881nm, and (c) the Si-O-Si peak at 1140nm change over time when using different acid catalysts.

Figures 3a, 3b, 3c and 3d - illustrate progressive FTIR spectra over time for sol gel reactions refluxed at 60 °C with citric acid as the reaction catalyst in different solvents: (a) propylene glycol, (b) diacetone alcohol, (c) 3-methoxy-1 -butanol, (d) propylene glycol methyl ether).

Figures 4a, 4b, 4c and 4d - illustrate the comparison of the FTIR spectra for different solvents, using citric acid at 60 °C. (a) and (b) show the start and end points of the spectra respectively, (c) and (d) illustrate how the spectral peaks at: 788nm and 881 nm change over time respectively

Figures 5a and 5b - illustrate the progress of a reaction in which propylene glycol is used as solvent, using (a) precursor solution H and (b) precursor solution I

Figure 6 - illustrates the growth of the Et-OH peak at 881 nm, and hence the progression of the hydrolysis reaction, for different concentrations of citric acid where propylene glycol is used as the solvent. Figures 7a, 7b, 7c and 7d - illustrate the dissolution of copper in (a) a coating solution across the duration of a roller coating trial using, (b) different acids, (c) different copper particle size, and (d) different citric acid concentrations

Figures 8a and 8b - illustrate the particle size distributions in solution for suspensions of Nanotec and Promethean copper particles, with respect to the volume density

Figures 9a, 9b and 9c - illustrate the SEM cross-sectional images of copper particles showing the growth of the oxide shell for coated glass samples before and after simulated heat toughening treatment: (a) sample 9d, (b) sample 9c, (c) sample 9c.

Figure 10 - is an SEM image processed by Image J software, of sample 35a, highlighting the surface coverage of cooper in the sample.

Figure 11 - is a graph of copper surface coverage as a percentage (%) versus antiviral performance (%R), for samples 33a, 34a, 35a and 33c, 34c and 35c in Table 17c.

Figure 12 - is a graph of exposure time (hours) versus antiviral performance (%R), for samples 33a and 35a in Table 17c.

Materials

Metallic copper particles were obtained from Nanotec S.A. and Promethean Particles Ltd. Cuprous oxide particles were obtained from American Chemet Corporation and Nordox AS. TECS is tetraethyl orthosilicate, (also named tetraethoxysilane and abbreviated to TECS), it has the formula Si(OC2Hs)4 and is the ethyl ester of orthosilicic acid, Si(OH)4. It is available from Merck.

Experimental

Preparation of coating solutions

1. Preparation of tetraethyl orthosilicate sol gel precursor solutions under mild reaction conditions.

A series of precursor solutions comprising silica were prepared in connection with the present invention under mild reaction conditions. For each coating solution, Tetraethyl orthosilicate (TECS) was hydrolysed to produce a silica solution. Hydrolysis of the tetraethyl orthosilicate (TECS) was achieved using either: i) water in the presence of a weak acid; or ii) water in the presence of an organic solvent, for example diols.

The tetraethyl orthosilicate (TEOS) was combined with the water and either weak acid or diol with stirring at low temperature, that is, at a temperature between 20 °C and 80 °C. The weak acid was a carboxylic acid, specifically, citric acid. When the acid was used with water to hydrolyse the TEOS, the reaction was performed in an organic solvent. Suitable organic solvents were selected from: diacetone alcohol (DAA), propylene glycol methyl ether (PGME) or 3-methoxy-1 -butanol. When the hydrolysis reaction occurred in the absence of acid, that is, when a diol was utilized to hydrolyze the TEOS, the preferred organic solvent was preferably a diol, for example propylene glycol.

Details of component amounts for each of the precursor solutions exemplified and illustrated in Figures 1a to 1d, 2a to 2c, 3a to 3d, 4a to 4d, 5a, 5b and 6 are provided in Table 1.

Table 1

The progression of the TEOS hydrolysis reaction was followed using FTIR analysis. FTIR spectra for a series of TEOS hydrolysis reactions using different organic solvents and different acids are illustrated in the Figures 1 a to 1 d, 3a to 3d, 4a, 4b, 5a and 5b. The hydrolysis reaction was identified as complete when the spectral peaks at 881 nm (Et-OH) and 788nm (Si-O-C) stabilized. Figures 1a to 1d and 2a to 2c compare the progression of the hydrolysis reaction in citric acid (precursor solution C) to hydrochloric acid (precursor solution A) and nitric acid (precursor solution B), with diacetone alcohol as the chosen solvent.

The inventors observed that the reaction rate of the hydrolysis reaction may be modified according to the selected temperature. For example, it was observed that the rate of the hydrolysis reaction may be increased using an elevated temperature, specifically a temperature in the range 60 °C to 80 °C. Specifically, Figures 1 c and 1 d illustrate the difference in reaction rate for the hydrolysis of TEOS at room temperature (precursor solution C) and 60 °C (precursor solution D) respectively, using diacetone alcohol as the solvent and citric acid as the chosen organic acid. Where elevated temperatures were used for the TEOS hydrolysis reaction, the solution was heated under reflux to prevent evaporation of the solvent and water.

Figures 3a to 3d and 4a to 4d illustrate the difference in reaction rate for the hydrolysis of TEOS using different solvents with citric acid as the chosen organic acid. Precursor solutions D to G were used from Table 1. Propylene glycol was shown to have the highest reaction rate, with the hydrolysis reaction determined to be complete after 1 hour.

Figure 5a shows the progression of the FTIR spectra for the hydrolysis reaction of TEOS in propylene glycol, with a reduction in the amount of citric acid as described for precursor solution H in Table 1. The hydrolysis reaction was determined to be complete after 3 hours.

Figure 5b shows the progression of the FTIR spectra for the hydrolysis reaction of TEOS in the absence of any organic acid and a reduction in the amount of water as described for precursor solution I in Table 1. The hydrolysis reaction was determined to be complete after 3 hours.

Figure 6 shows the progression of the Et-OH peak at 881 nm over time for precursor solutions G to I.

2. Preparation of copper coating solutions.

Following the preparation of the precursor silica solutions described in section 1 , each solution was further diluted with solvent and copper containing particles added. In relation to the present invention, the inventors have found that the use of mild reaction conditions as described in section 1 above, produced coating solutions with improved stability in respect of the dissolution of copper in the coating solution. In contrast, the inventors have found that when using harsher conditions, for example, when using a strong inorganic acid such as for example hydrochloric acid as the sol gel reaction catalyst, the dissolution of copper commences upon addition of the inorganic acid and progresses rapidly.

Figure 7a illustrates the dissolution of copper in a silica coating solution over a two-hour period of a roller coating trial, in which the silica coating solution included hydrochloric acid. The inventors observed a colour change for the coating solution over the two hour period as a result of dissolution of the copper in the solution. Whilst not wishing to be bound by any particular theory, the inventors understand that the colour change may arise as a result of complexes formed with the copper.

The percentage of copper dissolved in the silica coating solution was determined by removing the undissolved copper particles and analysing the amount of copper in the remaining solution using inductively coupled plasma optical emission spectrometry (ICP-OES). The amount of copper remaining in solution is illustrated in Figure 7a.

The effect on the rate of copper dissolution using inorganic and organic acids for a silica coating solution with 0.1 weight percent copper with stirring for 15 hours with limited exposure to oxygen, that is, in a closed system, was investigated and the results are illustrated in Figure 7b.

The inventors have found that by reducing the concentration of organic acid used for the sol gel hydrolysis reaction of TEOS, it is possible to achieve a further reduction in rate of copper dissolution, as illustrated in Figure 7d.

In addition, the inventors noted that when the concentration of organic acid was reduced, as a result, it was preferable to increase in reaction time to sufficiently progress the sol gel hydrolysis reaction of TEOS described above in section 1 .

Further, the inventors have found that by reducing the exposure of the coating solution comprising copper to oxygen, the copper dissolution rate may be slowed. This was achieved by either enclosing the solution, capping the solution with nitrogen or sparging the solution with an inert gas.

The inventors have further found that the size of the copper particles was also shown to play a role in stabilising the dissolution of copper in the coating solution. Copper with a smaller average particle size was shown to dissolve faster than copper with a larger particle size when exposed to oxygen and stirred in the same solvent with constant agitation for two hours. The results of these findings are illustrated in Figure 7c. The size of copper particles in solution was determined using laser diffraction analysis, on a Malvern Mastersizer. The copper particle size distributions for two copper dispersions A and B used in the connection with the present invention are shown in Figure 8. Particles provided by copper dispersion A have a size range from 500nm to 8.5 microns, while particles provided by copper dispersion B have a size range from 200nm to 3 microns. Larger copper particles required increased stirring to remain suspended in the coating solution, whilst smaller copper particles remain suspended with reduced stirring. The need for reduced stirring in turn also reduces the rate of copper dissolution.

Table 2

3. Deposition of copper coating solutions by roller coating followed by heat treatment to obtain coated glass samples of a silica matrix layer comprising copper particles.

Coated glass samples were prepared to evaluate the potential anti-bacterial and antiviral effectiveness and durability of a silica matrix layer with embedded copper particles, formed from coating solutions derived from the sol gel reaction of tetraethyl orthosilicate (TEOS) described above with copper particles, and applied by roller coating to a float glass substrate as follows.

Coating solutions 1 to 7 were prepared using precursor solution C from Table 1 and stirred for four hours at room temperature. After stirring, these coating solutions were diluted with propylene glycol, diacetone alcohol and copper dispersion A or B to achieve silica and copper weight percentages as indicated in Table 3.

Coating solutions 8 to 12 were prepared using precursor solution D from Table 1 and stirred for four hours at 60 °C. After stirring, these coating solutions were diluted with propylene glycol, diacetone alcohol and copper dispersion A or B to achieve silica and copper weight percentages as indicated in Table 3.

Coating solution 13 using precursor solution I from Table 1 was stirred for 3 hours at 80 °C. After stirring, the coating solution was diluted with propylene glycol, diacetone alcohol and copperdispersion A or B to achieve silica and copper weight percentages as indicated in Table 3.

Copper dispersions A and B are described in Table 2 above.

Coating solutions 1 to 13 all comprised 41.55 % by weight propylene glycol.

Table 3

In each of the experiments, the roller coater apparatus used to produce the samples fortesting was a Burkle easy-Coater RCL-M 700, which comprises an application roller material made from smooth EPDM rubber and a doctor roller made was steel with a patterned engraving. Each of the coating solutions 1 to 13 were applied in turn to the roller coater by pumping the coating solution into a channel on the roller coater between the doctor roller and application roller, and recirculated. In each case, the coating solution was applied to a glass substrate, with dimensions 30cm by 40cm, by the application roller. The glass substrate used comprised soda-lime silicate glass such as float glass available from NSG. A typical soda-lime silicate glass composition comprises by weight for example: SiC>269-74%; AI2O3; Na2<D 10 - 16%; K2O 0 - 5%; MgO 0 - 6%; CaO 5 - 14%; SO₃ 0 - 2%; and Fe₂O₃ 0.005 - 2%.

Table 4 - Roller coating parameters used for coating solutions 1 to 13. where: pinch - is the compression between the application roller and doctor roller, offset - is the compression between the application roller and glass substrate, roller speeds - are the speeds of the application roller, doctor roller and transport conveyor.

After the coating was applied, the glass substrate was immediately heated in a convection oven at a temperature of 200 °C to 300 °C to cure the coatings. To further densify the silica matrix coating layer formed and simulate glass toughening processes, a heat treatment taking the glass surface to 650 °C was applied to some samples. Table 5 describes the curing conditions employed for each sample.

Table 5 - curing conditions to achieve coated glass samples 1 to 13.

4. Deposition of copper coating solutions by spray coating followed by heat treatment to obtain coated glass samples of a silica matrix layer comprising copper particles.

4.1. Samples made using single stationary spray head.

Coated glass samples were prepared to evaluate the antiviral effectiveness of a silica matrix layer with embedded copper particles, formed from coating solutions derived from the sol gel reaction of tetraethyl orthosilicate (TEOS) described above with copper particles, and applied by spray coating to a float glass substrate as follows.

Coating solutions 14 to 28 were prepared using precursor solution E from Table 1 , stirred for six hours at 60 °C. After stirring, these coating solutions were diluted with propylene glycol methyl ether, isopropanol and copper dispersions B to E as indicated in Table 6. Copper dispersions B to E are described in Table 2. Coating solutions 14 to 18 all comprised 75 % by weight isopropanol.

The spray coating apparatus used incorporated a stationary, hydraulically atomized spray nozzle with a spray angle of 72 °C, with the glass moving beneath the spray nozzle on a conveyor at room temperature.

Table 6

Each coating solution as indicated in Table 6, was applied individually to a glass substrate, with dimensions up to 30cm by 40cm, at room temperature.

Table 7 - Spray coating parameters used for coating solutions 14 to 28 The glass substrate used comprised soda-lime silicate glass such as float glass available from NSG. A typical soda-lime silicate glass composition comprises by weight for example: SiC>2 69-74%; AI₂O₃; Na₂O 10 - 16%; K₂O 0 - 5%; MgO 0 - 6%; CaO 5 - 14%; SO₃ 0 - 2%; and Fe₂O₃ 0.005 - 2%.

After the coating was applied, the substrate was dried at 40 to 50 °C on a heated conveyor for 1 to 2 minutes, before being transferred to a convection oven for a further 5 minute heat treatment up to 140 to 180 °C to cure the coatings. To further densify the silica matrix coating layer and simulate glass toughening processes, a further heat treatment to 650 °C was applied to a portion of the samples as described in Table 8.

Table 8

4.2. Samples made using multiple stationary spray heads and traversing spray heads

To simulate large scale production, samples were also made with multiple stationary spray heads or a traversing spray head, as required to coat larger substrate sizes. Each coating was applied individually to a glass substrate with a width of up to 70cm, and dried and cured as described above in 4.1 above.

Coating solutions 29 to 38 were prepared using precursor solution E from Table 1 and stirred for six hours at 60 °C. After stirring, these coating solutions were diluted with propylene glycol methyl ether, isopropanol and copper dispersion B, C and D as indicated in Table 8a. Coating solutions 29 to 32 comprised 75% by weight isopropanol. Coating solutions 33 to 35 comprised 25% by weight isopropanol.

Coating solutions 36 to 38 were prepared using precursor solution E from Table 1 and stirred for six hours at 60 °C. After stirring, these coating solutions were diluted with propylene glycol methyl ether, propylene glycol, isopropanol and copper dispersion B. Coating solutions 36 to 38 comprised 1 % by weight isopropanol and 5% by weight propylene glycol. Table 8a

For coating solutions 29 to 32, the spray coating apparatus used incorporated multiple stationary, hydraulically atomized spray nozzles each with a spray angle of 72 degrees, with the glass moving beneath the spray nozzles on a conveyor at room temperature.

For coating solutions 33 to 35, the spray coating apparatus used incorporated a single hydraulically atomized spray nozzle, with a spray angle of 110 degrees, attached to a traversing spray system.

For coating solutions 36 to 38, the spray coating apparatus used incorporated a single air atomized LVMP spray nozzle, attached to a traversing spray system.

Table 8b - Spray coating parameters used for coating solutions 29 to 32. Table 8c - Spray coating parameters used for coating solutions 33 to 35.

Table 8d - Spray coating parameters used for coating solutions 36 to 38.

The glass substrate used comprised soda-lime silicate glass such as float glass available from NSG. A typical soda-lime silicate glass composition comprises by weight for example: SiC>2 69-74%; AI₂O₃; Na₂O 10 - 16%; K₂O 0 - 5%; MgO 0 - 6%; CaO 5 - 14%; SO₃ 0 - 2%; and Fe₂O₃ 0.005 - 2%.

For coating solutions 31 to 32, after the coating was applied, the substrate was dried at 40 to 50 °C on a heated conveyor for 1 to 2 minutes, before being transferred to a convection oven for a further 5 minute heat treatment up to 140 to 180 °C to cure the coatings. To further densify the silica matrix coating layer and simulate glass toughening processes, a further heat treatment to 650 °C was applied to a portion of the samples as described in Table 8e.

For coating solutions 33 to 35, after the coating was applied, the substrate was dried at room temperature, before being transferred to a convection oven for a further 5 minute heat treatment to 150 °C or 200 °C as described in Table 8e.

For coating solutions 36 to 38, after the coating was applied, the substrate was dried in a convection oven set to 90 °C. To further cure the coating, a subsequent heat treatment to raise the surface temperature of the glass to 200 °C was applied to each sample.

Additional samples were made on a full-scale production line. Coatings were deposited on a glass substrate with a width of 2.25m and length of 3.21 m. For these samples, the spray coating apparatus used incorporated up to three air atomized LVMP nozzles attached to a traversing spray system. A line speed of up to 6m/min was used, with a two-stage curing process. After deposition, the coated substrate travelled down the line and dried in an IR oven set to a temperature between 50 and 100 °C. The dried coated substrate subsequently entered a second IR oven to further cure the coating, raising the surface temperature of the glass to 150 to 200 °C.

Table 8e - Details of post deposition treatments for coating solutions 29 to 38.

Anti-bacterial and anti-viral Testing

5. Anti-bacterial results for roller coated glass samples described in section 3 above.

The coated glass samples deposited by roller coating were assessed for antibacterial performance by University College London (UK), Saniter (Turkey), MGS Laboratories Ltd (UK) and Industrial Microbiological Services Limited (UK) using a standard protocol based on ISO22196. The samples were tested against Escherichia coli (E. Coli ATCC 8739) and Staphylococcus aureus (S. Aureus ATCC 6538P) over a 24-hour period.

In accordance with ISO22196, the anti-bacterial activity (or log reduction), R, was calculated according to Formula 1. In addition, the percentage of bacteria killed with respect to both the untreated test specimens immediately after inoculation (% I) and the untreated test specimens after incubation time, t, (% R) were calculated according to Formulae 2 and 3 respectively:

R = log_w U_t) - log_w(A_t) Formula 1 100 Formula 2 100 Formula 3 where

U_o is the average number of viable bacteria, in cells/cm², recovered from the untreated test specimens immediately after inoculation;

(J_t is the average number of viable bacteria, in cells/cm², recovered from the untreated test specimens after incubation time, t; A_t is the average number of viable bacteria, in cells/cm², recovered from the treated test specimens after incubation time, t.

Laboratory Results 1 .

Table 9 - Anti-bacterial results for 0.1 % by weight copper roller coated samples

Table 10 - Anti-bacterial results for 0.25 % by weight copper roller coated samples

Table 11 - Anti-bacterial results for 0.35 % by weight copper roller coated samples

Table 12 - Anti-bacterial results for 0.4 % by weight copper roller coated samples

The results in Tables 9 to 12 show an increase in anti-bacterial performance against E.Coli 8739 as the copper concentration in the coating solution increases. The results, for Table 10 in particular against E.Coli 8739, suggest that the performance improves for copper particles of smaller size. Sample 2a (using copper dispersion A) provided a percentage of bacteria killed relative to the uncoated reference of 94.75%, compared to 98.68% for sample 3a (using copper dispersion B).

Tables 9 and 10 show anti-bacterial performance against S. Aureus 6538 where over 99 % of the bacteria was killed relative to the uncoated reference (greater than 2 log reduction) even when using the lowest copper concentrations and the larger particles supplied by copper dispersion A (sample 1a).

Laboratory Results 2.

Table 13 - Anti bacterial results for 0.4 % by weight copper roller coated samples.

The results in Table 13 show that both sample 6a and sample 7a (using 0.4 % by weight copper using particle dispersion A and B in the coating) killed above 99.9 % of bacteria relative to the uncoated reference (greater than 3 log reduction).

Laboratory Results 3.

Table 14

Table 15

The results in Table 15 show that by increasing the copper concentration (from samples 11c to 9c), while keeping the curing methods constant, the anti-bacterial activity increases to an average of 1.87 (killing 98.67 % of bacteria relative to the uncoated reference), with multiple repeats killing above 99% of the bacteria relative to the uncoated reference.

The results in Tables 14 and 15, specifically samples 9a, 9b and 9c, also show that the temperature and duration of the initial cure (between 200 and 300 °C) have a significant effect on the anti-bacterial activity. Laboratory Results 3a.

Table 15a - Anti-bacterial results for samples 31 a to 32a and 31 b to 32b.

The results in Table 15a show that samples that have not undergone a 650 °C heat treatment (samples 31a and 32a) achieve greater than a log 4 reduction (99.99%) against E. Coli 8739 after 2 hours, and greater than a log 3 reduction (99.9%) against S. Aureus after 2 hours. For samples subjected to an additional 650 °C heat treatment (samples 31b and 32b), the time required to achieve anti-bacterial performance above a log 2 reduction (99%) was increased to 6 hours.

6. Anti-viral results for roller coated and spray coated glass samples described in sections 3 and 4

Laboratory Results 4.

The coated samples deposited by roller and spray coating were assessed for anti-viral performance by the University of Cambridge, using a protocol based on ISO21702. The viral strain used was Mouse Hepatitis Virus A59 (MHV-A59), a well-established coronavirus that can act as a SARS-CoV-2 surrogate. The viral strain belongs to the same betacoronavirus family as a SARS-CoV-2, is structurally nearly identical, and widely used in stability testing. The coated samples deposited by spray coating in section 4.2 were assessed for anti-viral performance by Virology Research Services Limited, using a protocol based on ISO21702. The viral strain used was Human Coronavirus NL63.

The infectivity was assessed by scoring samples’ virus induced cell death and expressed as remaining infectious titre (TCID50). These values were then used to calculate the log reduction, according to Formula 4. In addition, the percentage inactivation with respect to the untreated test specimens immediately after inoculation (%l) and the untreated test specimens after incubation time, t, (%R) were calculated according to Formulae 5 and 6 respectively:

R = log_w y_t~) - log_w Ct) Formula 4

%R = ( ) _{x 100} Formula 5 100 Formula 6 where

V_o is the average TCID50/m\ recovered from the untreated test specimens immediately after inoculation;

V_t is the average TCID50/m\ recovered from the untreated test specimens after incubation time, t;

C_t is the average TCID50/m\ recovered from the treated test specimens after incubation time, t;

TCID50 is the median tissue culture infectious dose - the concentration at which

50% of the cells are infected when the well plate upon which the cells have been cultured is inoculated with the diluted solution of viral fluid.

Table 16

The results in Table 16 show that sample 15c (spray coated sample using a coating solution consisting of 0.04 % by weight copper and 0.5 % by weight silica) deactivated 47.88 % of the Mouse Hepatitis Virus after 1 hour relative to the uncoated reference, and 94.52 % relative to the initial viral load Laboratory Results 5.

Table 17

The results in Table 17 show that roller coated sample 12d deactivated 99.91 % of the SARS- Cov-2 virus after 3 hours and 97.73 % after 24 hours, relative to both the uncoated reference and the initial viral load.

Additional anti-viral testing was conducted against Mouse Hepatitis Virus A49, SARS-Cov-2 (UK strain), Human Coronavirus 229E, Human Coronavirus NL63 and Influenza A.

Laboratory Results 6.

Table 17a

The results in Table 17a show that, for the same mass of copper, using Copper Dispersion B for sample 30a (relative to using Copper Dispersion C in sample 20a) improves the anti-viral performance from a 0.6 log reduction (74.85%) to 1.05 (91.02%). Whilst not wishing to be bound by any particular theory, the inventors believe that this may be due to the smaller particle size (as shown in Figure 8) that leads to a greater surface area coverage of copper particles.

The results also show that increasing the mass ratio of Copper to Silica in the coating solution from 0.08 (sample 9d) to 0.4 (sample 29a) improves the anti-viral performance from a 0.28 log reduction (47.91% kill) to 0.6 (74.85% kill). Table 17b

The results in T able 17b show that despite sample 32a having half the concentration of copper in the coating solution to sample 31a, the anti-viral performance is significantly greater. Whilst not wishing to be bound by any particular theory, the inventors believe that this may be due to the smaller particle size (as shown in Figure 8) which leads to a greater surface area coverage of copper particles (as shown in Table 22).

Table 17c

The results in Table 17c show that by linearly increasing the concentration of copper in the coating solution for samples cured at 200 °C (sample 33c to sample 35c), the anti-viral performance after 6 hours exposure time increases from a log reduction of 1 .20 (93.65% kill) to 1.79 (98.40% kill) to 3.20 (99.94% kill), as illustrated in Figure 11.

By linearly increasing the concentration of copper in the coating solution for samples cured at 150 °C (sample 33a to sample 35a) the anti-viral performance after 6 hours exposure time increases from a log reduction of 1.07 (91.45% kill) to 1.38 (95.84% kill) to 2.79 (99.84% kill), as illustrated in Figure 11.

By linearly increasing the length of exposure time, from 2 hours to 6 hours, samples cured at 150 °C (sample 33a and sample 35a) increases from a log reduction of 0.66 to 0.75 to 1.07 and a log reduction of 1.19 to 1.69 to 2.79, as illustrated in Figure 12.

The results for sample 35a plus laminating cycle and sample 35a plus treatment K, show that good anti-viral performance was maintained after the samples were subjected to a Laminating heat cycle and a rigorous cleaning agent via the ‘rub-rig test (described in Table 20).

Table 17d

The results in Table 17d show that by increasing the concentration of silica in the coating solution from 1.5 weight % to 2.5 weight % (samples 36c, 37c, 38c), while keeping the concentration of copper constant did not negatively affect the anti-viral performance. That is, increasing the thickness of silica around and over the copper particles did not negatively affect performance.

7. Durability testing of roller coated samples described in section 3

EN1096 Testing

The coated glass samples deposited by roller coating described in Table 5 were assessed for relative durability (or deterioration) by being subjected to cycles of SO2, condensation, salt and abrasion in accordance with EN1096 Class S and EN1096 Class B incorporated herein by reference. The results of the durability tests are summarized in Table 19. The classification system is based on the positioning of the coated surface when the coated glass is glazed. This glazed position determines the type and extent of attack, e.g. humidity, atmospheric pollution, abrasion, etc., that the coating will experience during its working life.

For EN1096 Class B - the coated glass may be used as monolithic glazing, but the coated surface should be on the inner face of the building. For EN1096 Class S - the coated surface of the glass may be positioned on the outer or the inner face of the building, but these types of coated glasses may only be used in specifically defined applications e.g. shop fronts.

Table 18 - Details of EN1096 tests.

Table 19

Cleaning agent compatibility

The coated glass samples deposited by roller coating described in Table 5 were assessed for relative durability (or deterioration) by being subjected to 3650 strokes of cleaning agent action from a modified oil rub rig with a load of 1 Kg on the coated surface, to simulate 3650 cleaning cycles. To apply the cleaning agent, a multi-purpose microfibre cloth, 8 x 9 cm pieces (88 % polyester / 12 % polyamide), were used, attached to a modified jig and wetted with cleaning agent as required during the run. For the synthetic sweat solution, a rubber strip was used in place of the micro-fibre cloth, 1000 strokes were conducted, and a 0.15 kg load was used. The results of the tests are described in Table 21. Table 20 - Description of cleaning agents used

Table 21

8. Surface analysis of roller coated and spray coated samples

ICP-OES analysis was conducted on coated samples to evaluate the total amount of copper in the coatings by the method steps described below:

• A 5x5 cm sample for testing was placed in a 90mm petri dish, coating face upwards;

• 2ml concentrated H2SO4 was pipetted onto the coating surface;

• The sample was then placed on a hotplate set at 100 °C for 10 minutes;

• The temperature was then increased to 150 °C for 10 mins, followed by 200 °C, until the sample was just fuming (usually in the region of around 5 minutes);

• The sample was then left to cool and then washed into a 50ml volumetric flask;

• The samples was then analysed by ICP-OES using matrix matched H2SO4 Cu standards

The method was used to evaluate the extent of damage to coatings following various durability tests, as shown in Table 23. Scanning electron microscopy studies were employed to analyse the appearance and distribution of the copper particles in relation to the silica matrix coating layer. Coated samples were taken and mounted onto aluminium stubs before coating with a thin layer of platinum (which provides a uniform conductive surface) prior to examination using a scanning electron microscope (SEM).

Figures 9a to 9c illustrate the size, shape and structure of the copper particles embedded the silica coating layer for sample 9c and sample 9d before and after simulated toughening process.

As backscattered electron (BSE) images highlighted difference in chemical composition, with higher atomic number material (that is, copper nanoparticles) appearing brighter, these images were processed with Imaged software (https://imagej.nih.gov/ij/index.html). An example of a processed image of sample 35a can be seen in Figure 10. The approximate size and number of brighter features on the surface of each sample could then be determined, and this data used to calculate the percentage of the two-dimensional surface covered by copper, as shown in Table 22.

Table 22

Figure 11 shows the relationship between the surface coverage of copper particles and the anti-viral performance relative to an uncoated reference (%R). Table 23

Table 23 shows that for sample 35a after test K, the minimum amount of copper retained was 76%. Table 17c in Section 5 showed that this sample 35a, maintained an anti-viral performance of 96.08% (1.41 log reduction).

9. Cosmetic Appearance Evaluation

Table 24 Table 25 - Example optical data

Therefore, in summary, there exists a large and expanding market for durable, antimicrobial and/or antiviral coatings on glass with high optical transparency and good aesthetic appearance. Whilst copper has been shown to possess some antimicrobial activity, copper- containing coatings which exhibit high antimicrobial efficacy commonly have durability or optical issues or simply cannot be produced on a sufficient scale or are not toughenable to the required extent. Whilst sol-gel formulations have been used to create durable coatings on glass, with the desired transparency, the methods of deposition use harsh reaction conditions and materials which are often incompatible with metal particles. In connection with the present invention, the inventors disclose herein a process which utilises a sol-gel method with considerably milder conditions whilst providing a coating which may be applied to a variety of substrates, whilst retaining durability and optical transparency alongside superior antimicrobial and antiviral properties, even on an industrial scale.

That is, the above findings described by the inventors, indicate that it is possible to formulate a coating solution suitable for the industrial preparation of anti-bacterial and/or anti-viral coated glass substrate. This was made possible by employing mild sol gel reaction conditions, that is, using a weak acid and/or a diol, to progress the hydrolysis reaction of tetraethyl orthosilicate to silica and thereby slow the rate of copper dissolution in the final coating solutions upon the addition of copper dispersions.

The inventors have demonstrated that silica and copper coating solutions may be applied to a glass substrate on an industrial scale by roller coating or spray coating resulting in coated glass substrates that display both anti-bacterial and anti-viral efficacy. That is, the results provided above have been shown to kill greater than 99.9 % of bacteria relative to uncoated references, against E.Coli 8739 and S. Aureus 6538 after 24 hours and also, the results provide evidence of the deactivation of over 99.9 % of the SARS-Cov-2 (UK Strain) virus after 3 hours, relative to an uncoated reference. In addition, it has been found that both anti-viral and anti-bacterial performance increases with increased mass of copper. Further, it has been found that anti-viral performance increases with increased surface coverage of copper. A greater surface coverage may be achieved with the same mass of copper by decreasing the particle size. For instance, Figure 11 indicates that for a viral exposure time of 6 hours, 1 .6% coverage of copper particles achieved a greater than 90% kill (log 1 reduction), whilst 3.1 % coverage of copper particles achieved a greater than 99% kill (log 2 reduction) against Human Coronavirus NL63.

A similar situation is experienced for anti-bacterial performance. For instance, for nontoughened glass samples, a greater than 99.9 % antibacterial reduction was achieved after 2 hours (log 3 reduction) against both gram positive and gram negative bacteria (Escherichia coli (E. Coli ATCC 8739) and Staphylococcus aureus (S. Aureus ATCC 6538P).

Toughened samples relative to non-toughened samples showed a decrease in performance, however, a greater than 99% antibacterial reduction was still achieved after 6 hours (log 2 reduction).

The coated substrates are also able to meet the demanding test requirements of the glazing industry and therefore may be used in a range of glass substrate applications.

Claims

1. A process for producing an antimicrobial and/or antiviral coating on a substrate, the process comprising the steps of: i) providing a glass substrate having a first surface and a second surface; ii) providing a silicon containing solution and a copper containing particle solution or powder; and iii) mixing together the silicon containing solution and the copper containing particle solution or powder in the presence of water and a hydrolysing material to form a silica and copper coating composition; wherein the hydrolysing material comprises: a) one or more polyol; b) one or more weak acid with a pKa value of at least 0.5; or c) one or more polyol and one or more weak acid, iv) contacting at least said first surface of the glass substrate with the silica and copper coating composition to deposit a layer of silica on the glass substrate; and iv) curing the silica and copper coating composition deposited on the glass substrate to form a silica matrix coating layer, wherein the copper containing particles are deposited on and/or are embedded within the silica matrix coating layer in an amount of from 1 to 50 % by weight.

2. A process according to claim 1 , further comprising the step of: v) toughening the coated glass substrate at a temperature of at least 600 °C, more preferably at a temperature of at least 650 °C.

3. A process according to claim 1 or 2 wherein the copper containing particle solution or powder comprises copper containing particles in the form of: micro-particles, clusters of nanoparticles of copper, copper alloys, copper metal, or copper oxide, or mixtures thereof.

4. A process according to claim 3 wherein the copper containing micro-particles or clusters of nanoparticles of copper comprise a size range of from 100nm to 10pm.

5. A process according to claim 3 wherein the copper alloys comprise one of more of the elements selected from: zinc, tin, aluminium, silicon, nickel, manganese, beryllium, lead, iron, aluminium.

6. A process according to any preceding claim wherein the silicon containing solution and the copper containing particle solution or powder comprise a solvent

37 selected from the group comprising: diacetone alcohol, propylene glycol, propylene glycol methyl ether (PGME), isopropanol, 3-methoxy-1 -butanol and mixtures thereof.

7. A process according to any preceding claim wherein the silica and copper coating composition comprises at least 50 % by weight silica, more preferably at least 65% by weight silica.

8. A process according to any preceding claim wherein the silica matrix coating layer is formed from a sol gel reaction involving the hydrolysis and polycondensation of tetraethyl orthosilicate, (TEOS) and/or derivatives thereof under mild reaction conditions.

9. A process according to any preceding claim wherein the silica and copper coating composition is applied directly to the glass substrate.

10. A process according to any preceding claim wherein the silica and copper coating composition further comprises at least 1.0% by weight zirconia relative to the amount of silica in the silica matrix coating layer.

11. A process according to claim 10 wherein the zirconia or aluminium present is in the form of an oxide.

12. A process according to any preceding claim wherein the silica and copper coating composition is applied to the glass substrate by means of one or more of: roller coating; spray coating; hydraulically atomised spraying; air atomisation spraying; ultrasonic spraying; dip coating; spin coating; curtain coating; or slot-die coating.

13. A process according to claim 12 wherein the silica-copper coating composition is applied to the glass substrate by roller coating or spray coating.

14. A process according to any preceding claim further comprising the step of cleaning the surface of the glass substrate before applying the silica and copper coating composition.

15. A process according to claim 14 wherein cleaning comprises the step of treating the surface of the glass substrate by means of one or more of: abrasion with ceria; washing with alkaline aqueous solution; rinsing with deionised water; and/or plasma treatment.

16. A process according to any preceding claim, wherein the step of curing the silica and

38 copper coating composition comprises heating to a temperature in the range 90 °C to 450 °C, more preferably to a temperature in the range 90 °C to 300 °C.

17. A process as claimed in any preceding claim wherein the silica matrix coating layer is deposited to a thickness in the range 5nm to 250nm.

18. A process according to any of claims 1 to 8 or any of claims 10 to 17 when dependent on claims 1 to 8, wherein a transparent conductive oxide coating is applied to the glass substrate before deposition of the silica and copper coating composition.

19. An antimicrobial and/or antiviral coated glass substrate prepared by the process according to any of claims 1 to 18 comprising: i) a glass substrate; and ii) a silica matrix coating layer wherein the silica matrix coating layer comprises: a) at least 50% by weight silica; and b) copper containing particles deposited on and/or embedded within the silica matrix coating layer in an amount of from 1 to 50 % by weight; and wherein growth of bacteria on the substrate is reduced by at least 10% compared with non-coated glass substrates; and wherein deactivation of viruses on the substrate is increased by at least 10% compared with non-coated glass substrates.

20. An antimicrobial and/or antiviral coated glass substrate according to claim 19 wherein the silica matrix coating layer further comprises at least 1 .0% by weight zirconia.

21 . An antimicrobial coated glass substrate according to claim 19 or 20 wherein the coated glass substrate provides within 24 hours at least a 2 log reduction against gram positive and/or gram negative bacteria or a 2 log reduction against viruses.

22. An antimicrobial coated glass substrate according to claim 19 or 20 wherein the coated glass substrate provides within 2 hours at least a 3 log reduction against gram positive and/or gram negative bacteria or within 2 hours a 2 log reduction against viruses.

23. An architectural or automotive glazing comprising an antimicrobial and/or anti-viral coated glass according to any of claims 19 to 22, and/or prepared by the process of any of claims 1 to 18.

24. Use of an antimicrobial and/or anti-viral coated glass substrate according to any of claims 19 to 22, and/or prepared by the process of any of claims 1 to 18 in the preparation of an insulated glazing unit or an automotive glazing unit.

25. Use of an antimicrobial and/or anti-viral coated glass substrate according to any of claims 19 to 22, and/or prepared by the process of any of claims 1 to 18 in the preparation of an electronic device, furniture, splash-backs or screens, medical containers, wall coverings, touchscreens, mirrors or glass bottles, refrigeration applications or in transport or transportation applications.