WO2022090708A1

WO2022090708A1 - Use of coated substrates

Info

Publication number: WO2022090708A1
Application number: PCT/GB2021/052783
Authority: WO
Inventors: Nicola Joanne TEASDALE; Neil Mcsporran
Original assignee: Pilkington Group Limited
Priority date: 2020-10-26
Filing date: 2021-10-26
Publication date: 2022-05-05
Also published as: GB202016974D0; GB2600168A

Abstract

Use of a coated substrate as an antimicrobial substrate, wherein the substrate comprises a photocatalytically active titanium oxide coating on at least one surface thereof, wherein the coated surface of the substrate has a photocatalytic activity of greater than 5 x 10^-3cm^-1min^-1, and wherein the coated substrate has a visible light reflection measured from the coated surface of 35% or lower.

Description

Use of coated substrates

This invention relates to the use of coated substrates as antimicrobial substrates, in particular, but not exclusively, it relates to the use of coated glass.

It is known to deposit thin coatings having one or more layers, with a variety of properties, on to substrates including on to glass substrates. One property of interest is photocatalytic activity which arises by the photogeneration, in a semiconductor, of a hole-electron pair when the semiconductor is illuminated by light of a particular frequency. The hole-electron pair can be generated in sunlight and can react in humid air to form hydroxy and peroxy radicals on the surface of the semiconductor. The radicals oxidise organic grime on the surface. This property has an application in selfcleaning substrates, especially in self-cleaning glass for windows.

Titanium dioxide may be an efficient photocatalyst and may be deposited on to substrates to form a transparent coating with photocatalytic self-cleaning properties. Titanium oxide photocatalytic coatings are disclosed in EP 0901 991 A2, WO 97/07069, WO 97/10186, WO 98/41480, in Abstract 735 of 187th Electrochemical Society Meeting (Reno, NV, 95-1 , p.1102) and in New Scientist magazine (26 August 1995, p.19). In WO 98/06675 a chemical vapour deposition process is described for depositing titanium oxide coatings on hot flat glass at high deposition rate using a precursor gas mixture of titanium chloride and an organic compound as source of oxygen for formation of the titanium oxide coating.

There is also a need to prevent the transmission of potentially harmful microbes between humans and animals. In relation to the present invention, microbes include bacteria, viruses and fungi as well as yeasts and germs. One way in which microbes are transmitted is by “surface transmission”. This is where an individual interacts with a surface that has previously been seeded with microbes, for example by previous interaction with the surface by infectious individuals.

Transparent and semi-transparent surfaces, such as glazings, mirrors and displays are commonly found in environments which are shared by multiple individuals. As such, transparent and semi-transparent surfaces may act as a vector for the transmission of microbes, especially bacteria and viruses. This is particularly a problem in spaces which may be occupied by large numbers of people in succession, such as toilets, corridors, hospital rooms, shops and workplaces. In addition, as the extent to which electronic devices are used in the world increases, so the presence of micro-organisms which may reside on a screen surface also increases, and therefore, the potential transfer of micro-organisms from one individual to another. Indeed, touch screens and mirrors located for example in shops and supermarkets may have hundreds of individuals per hour using the touch screen terminal or touching the mirror surface and potentially spreading microbes from one user to another.

In addition, as the threat of resistance to antibiotics by certain bacterial strains increases, and as epidemics arise from the transmission of some viruses, there is an ever-increasing need for surfaces, no matter the device or application, to be able to halt the spread of micro-organisms.

Surface transmission can be significantly curtailed if, following seeding of the surface, the number of infectious microbes is reduced, preferably to a level where there is no risk of transmission to subsequent individuals.

Some surfaces are inhospitable to microbes, such that over time, microbes upon them are denatured and are no longer infectious. For example, it has been known for some time that microorganisms including bacteria, viruses and yeasts may be killed or rendered inactive if brought into contact with certain metallic or organic surfaces.

However, smooth surfaces, such as those typically used for glazing materials, are known to be environments upon which many microbes may survive for long periods of time. For example, whilst the SARS-Cov-2 virus is denatured to half the initial level on wood in around three hours, the same reduction on glass requires 24 hours, and on stainless steel requires 96 hours to attain the same level of reduction (“Stability of SARS-CoV-2 in different environmental conditions”, Chine et al, The Lancet Microbe, CORRESPONDENCE, Volume 1 , Issue 1 , E10, May 01 2020).

It is known to modify surfaces to produce an antimicrobial effect. However, the ability to incorporate antimicrobial properties into surfaces which are required to remain transparent to a required standard such as the glazing in windows and doors and which are also resistant to for example wear and scratching, has proved difficult. This is because, not only it is difficult to impart lasting antimicrobial activity to glass substrates, but also, any modification or coating applied to a glass substrate which provides antimicrobial activity must still provide the required parameters of a glazing whilst retaining a pleasing aesthetic appearance at an acceptable cost.

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.

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.

Likewise, in JP 2005119026 there is described a substrate which provides antibacterial and anti-staining properties at the same time by way of a film comprising substituted siloxane molecules with surface hydroxyl groups on the entire surface of the substrate, the film further containing particles of silver.

WO 2007108514 A1 aims to provide a glass plate having an antibacterial film by forming an antibacterial film having a film thickness of 2 nm or more but not more than 100 nm on a glass plate either directly or via an undercoat film. Similarly, WO 2014112345 A1 aims to provide a base with an antiviral film. The antiviral film has a layer that is mainly composed of titanium oxide and an island part arranged on the surface of the layer and mainly composed of a Cu-based material.

However, there exists a need for a surface which even though located in areas of persistent human contact, may be readily cleaned to provide a safer environment.

In order to rapidly reduce the number of microbes adhered to a surface, it is usual to clean a surface with a detergent. However, such cleaning is often performed manually and is time consuming. In addition, common cleaning agents may erode surfaces, especially coated glass surfaces and mirrored surfaces leading to impaired appearance and performance. Surfaces which are modified to provide a self-cleaning effect are known. For example, WO 2000075087 A1 discloses a self-cleaning coated substrate, especially a glass substrate, having high photocatalytic activity and low visible light reflection and a durable self-cleaning coated glass and a process for making same.

Unfortunately, for some applications, a surface may not be sufficiently inhospitable to microbes, and traditional cleaning practices and products may not successfully remove sufficient levels of microbes. In such cases, it is common to use a “disinfection” process whereby the number of infectious microbes on a smooth surface is further reduced to a safe level by denaturing, rendering many of the microbes inactive.

One method of disinfection is by cleaning surfaces using a germicidal cleaner, such as a bleach. However, the use of bleach as a disinfectant may give rise to similar problems as stated above in respect of cleaning with a detergent, namely impaired appearance and performance of the substrate surface. However, cleaning performed manually with a germicidal product can often be more damaging and corrosive to the surface. Furthermore, germicidal cleaners may not sufficiently denature all microbes on the surface.

An alternative method of disinfecting surfaces is by UV disinfection. In this situation, UV light irradiation is used to denature microbes on a surface. UV is the term given to light in the wavelength range 10 to 400nm. UV light is commonly divided into UVA (320 to 400 nm), UVB (280 to 320 nm), and UVC (100 to 280 nm). UVC light is particularly effective for disinfecting surfaces, as the light penetrates microbes and alters their DNA structure, impairing and preventing replication.

In some cases, UV disinfection may be used in addition to disinfection with a germicidal cleaner. The additional UV disinfection step further reduces the prevalence of microbes on the surface, therefore reducing the likelihood of infection due to contact with the surface. An advantage of using UV disinfection in addition to disinfection with a germicidal cleaner is that this may allow the use of less corrosive cleaners, or may allow increased confidence that the surface is fully disinfected.

However, UV light may also be harmful to humans and animals, causing burns and DNA damage. Therefore UV disinfection if often only performed in a way that prevents humans and animals being exposed to UV light, thereby reducing the risk to individuals. UV light with a higher energy and therefore a shorter wavelength has the potential to be particularly harmful to individuals. As such, the exposure of individuals to UVB and UVC light is required to be much less than the exposure of individuals to UVA light.

Thus it would be advantageous to afford the use of a coated substrate as an antimicrobial substrate, e.g. the use of a substrate which may be effectively disinfected in an efficient manner and which minimises exposure and potential risk to individuals in the environment of the substrate. In addition, such a substrate may further provide desirable optical and durability properties of a glazing material, in particular a glass sheet, and thereby meet the standards and requirements of the glazing industry.

According to a first aspect of the present invention there is provided the use of a coated substrate as an antimicrobial substrate, wherein the substrate comprises a photocatalytically active titanium oxide coating on at least one surface thereof, wherein the coated surface of the substrate has a photocatalytic activity of greater than 5 x 10’³cm’¹min’¹, and wherein the coated substrate has a visible light reflection measured from the coated surface of 35% or lower.

It has surprisingly been found that the coated substrate specified in the first aspect of the present invention may be used as an antimicrobial substrate that reduces the prevalence of microbes on its surface to an unexpected degree.

In the context of the present invention, where a layer is said to be “based on” a particular material or materials, this means that the layer predominantly consists of the corresponding said material or materials, which means typically that it comprises at least about 50 at.% of said material or materials.

In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1% by weight of non-specified components.

The term “consisting of” or “consists of” means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of”, and also may also be taken to include the meaning “consists of’ or “consisting of”.

References herein such as “in the range x to y” are meant to include the interpretation “from x to y” and so include the values x and y.

In the context of the present invention a transparent material or a transparent substrate is a material or a substrate that is capable of transmitting visible light so that objects or images situated beyond or behind said material can be distinctly seen through said material or substrate.

In the context of the present invention the “thickness” of a layer (or coating) is, for any given location at a surface of the layer, represented by the distance through the layer, in the direction of the smallest dimension of the layer, from said location at a surface of the layer to a location at an opposing surface of said layer.

It should be noted that any refractive index values described herein are reported as average values across 400-780 nm of the electromagnetic spectrum.

In the context of the present invention the “film side” of the substrate means a surface of the substrate upon which a coating is located. In the context of the present invention the “glass side” of the substrate means a surface of the substrate opposing the surface upon which the coating is located.

Preferably the photocatalytically active titanium oxide coating is a titanium dioxide coating, more preferably titanium dioxide with a predominantly anatase crystal structure. More preferably, the titanium oxide coating comprises titanium dioxide with greater than or equal to 50% anatase. It has been found that the coated substrate specified in the first aspect has excellent antimicrobial properties, especially when illuminated with UV light. Furthermore, it has been found that, following irradiation of the coated substrate with UV light, an increased antimicrobial effect persists even in the absence of any light at all.

Said use according to the present invention may reduce the survival of one or more microbes on the coated surface of the substrate, such as for example bacteria and/or viruses, compared to an uncoated substrate that is otherwise the same as the coated substrate. Preferably, growth of bacteria on the coated surface of the substrate is reduced by at least 10%, more preferably 20%, even more preferably 30%, compared to an uncoated substrate that is otherwise the same as the coated substrate. Preferably, deactivation of viruses on the coated surface of the substrate is increased by at least 10%, more preferably 20%, even more preferably 30%, compared to an uncoated substrate that is otherwise the same as the coated substrate.

Particular microbes which may be denatured by the use according to the present invention include for example but are not limited to: gram positive and gram negative bacteria, including for example Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA), and corona viruses including SARS-CoV-2. Preferably the use according to the present invention provides a reduction 10% against one of Staphylococcus aureus, SARS-CoV-2, E.coli, P. gingivitis, or S.mutans, within 2 hours at 37° C. More preferably, the use according to the present invention provides a reduction of at least 20% against one of Staphylococcus aureus, SARS-CoV-2, E.coli, P. gingivitis, or S.mutans, more preferably at least 30%, and most preferably at least 40%, within 2 hours at 37° C.

Preferably said use occurs in an architectural glazing unit, automotive glazing unit, electronic device, furniture, splash-backs, bulkhead, door, blind, medical container, wall covering, touchscreen, mirror or glass bottle. Where the use occurs in a glazing unit, the coated substrate may be combined with one or more further substrates (e.g. one or two further glass substrates) to form the glazing unit. The coated substrate may be held in a spaced apart relationship with any adjacent further substrate to form an insulated glazing unit. Any further substrate may be held in a spaced apart relationship with any adjacent further substrate to form an insulated glazing unit.

Preferably, the coated surface is exposed, i.e. the coated surface contacts the surrounding environment. Preferably, where the use occurs in a glazing unit that is exposed to the external environment, the coated surface is exposed to the internal environment. Preferably, where the use occurs in a glazing unit, the coated surface is located on surface #2 in a monolithic glazing, surface #4 in a double glazing, or surface #6 in a triple glazing, where the surfaces are numbered sequentially starting from surface #1 which is exposed to the external environment.

In certain embodiments the coated substrate may further comprise a second coating located on an opposing surface of the substrate, i.e. the coating referred to in the preceding paragraphs is located on a first surface of the substrate and the second coating is located on an opposing surface of the substrate. The second coating may comprise an antireflection, low-emissivity and/or solar control coating.

In some embodiments an opposing surface of the substrate may be bonded to a second substrate by a ply of plastics interlayer. Preferably the plastics interlayer comprises polyvinyl butyral (PVB). Preferably the plastics interlayer does not comprise any UV- absorbers. Preferably the plastics interlayer is at least 70%, more preferably at least 80%, more preferably at least 90%, more preferably substantially, most preferably completely transparent to UV radiation. Any of the opposing surface of the substrate and either surface of the second substrate may be coated, for example with an antireflection, low-emissivity and/or solar control coating.

Preferably the use according to the present invention further comprises the step of irradiating the coated substrate with UV light from an artificial UV light source and/or from daylight. Preferably, the coated substrate is irradiated with UV light for at least 1 min, more preferably at least 20 min, even more preferably at least 1 hr, most preferably at least 2 hr. In relation to the present invention, UV light is electromagnetic radiation with a wavelength from 10 nm to 400 nm. Preferably, the UV light has a peak wavelength above 200 nm, more preferably above 220 nm, even more preferably above 250 nm. In relation to the present invention, the peak wavelength of light is the wavelength with the highest intensity in the light spectrum. For example, the peak wavelength of UV light is the wavelength with the highest intensity in the UV spectrum of 10 to 400 nm.

Preferably, the UV light is activated using an automated sensor process or a timer. According to the present invention, an automated sensor process may include a sensor device for sensing parameter information and a communication system for relaying the parameter information to a computational device which determines a response.

Preferably, the UV light source is a mobile UV light source. Preferably the mobile UV light source may be actuated between a position where light from the UV light source may impinge upon the coated substrate, and a position in which light from the UV light source does not impinge upon the coated substrate. Preferably, the mobile UV light source is attached to a robotic device. Preferably the robotic device is: an actuating arm; a wheeled, legged or tracked mobile carrier; or a retracting arm.

Preferably, the use according to the present invention further comprises a cleaning step, preferably wherein the coated substrate is cleaned with a cleaning product, preferably a detergent and/or a germicidal cleaning product. Preferably the cleaning step is an automated cleaning step, wherein the coated substrate is cleaned using sprayers, air knives and/or wipers. Alternatively, the cleaning step may be a manual cleaning step.

Photocatalytic activity for the purposes of this specification is determined by measuring the rate of decrease of the integrated absorbance of the infra-red absorption peaks corresponding to the C-H stretches of a thin film of stearic acid, formed on the coated substrate, under illumination by UV light from a UVA lamp having an intensity of about 32 W/m² at the surface of the coated substrate and a peak wavelength of 351 nm. The stearic acid film may be formed on samples of the coated substrate, 7 to 8 cm square, by spin casting 20 pl of a solution of stearic acid in methanol (8.8 x 10'³mol dm^-3) on the coated surface of the substrate at 2000 rpm for 1 minute. Infra-red spectra may be measured in transmission, and the peak height of the peak corresponding to the C-H stretches (at about 2700 to 3000 cm^-1) of the stearic acid film measured and the corresponding peak area determined from a calibration curve of peak area against peak height. A suitable UVA lamp is a UVA-351 lamp (obtained from the Q-Panel Co., Cleveland, Ohio, USA) having a peak wavelength of 351 nm and an intensity at the surface of the coated glass of approximately 32 W/m². The photocatalytic activity is expressed in this specification as the rate of decrease of the area of the IR peaks (in units of cm^-1 min^-1).

Preferably, the coated surface meets the EN1096-5-2016 standard test method and classification for the self-cleaning performances of coated glass surfaces.

Preferably the coated surface has a photocatalytic activity of greater than 1 x 10'² cm^-1 min^-1. More preferably the coated surface has a photocatalytic activity of greater than 3 x 10'² cm^-1 min^-1.

Low visible light reflection is advantageous because it is less distracting than high reflection and, especially for glass substrates, low visible light reflection corresponds to high visible transmission which is often required in architectural and especially automotive applications of glass. Preferably, the coated substrate has a visible reflection measured from the coated surface of 20% or lower, more preferably of 17% or lower and most preferably of 15% or lower.

In most embodiments of the invention the substrate will be substantially transparent and in a preferred embodiment of the invention the substrate comprises a glass substrate. Usually the glass substrate will be a soda lime glass substrate.

Especially where the substrate is a soda lime glass substrate or other alkali metal ion containing substrate, the coated substrate preferably comprises an alkali metal ion blocking underlayer between the surface of the substrate and the photocatalytically active titanium oxide coating. This reduces the tendency for alkali metal ions from the substrate to migrate into the photocatalytically active titanium oxide coating which is advantageous because of the well-known tendency of alkali metal ions to poison semiconductor oxide coatings, reducing their activity.

The alkali metal ion blocking underlayer may comprise a metal oxide but preferably the alkali metal ion blocking underlayer is a layer of silicon oxide. The silicon oxide may be silica but will not necessarily be stoichiometric and may comprise impurities such as carbon (often referred to as silicon oxycarbide and deposited as described in GB 2,199,848B) or nitrogen (often referred to as silicon oxynitride).

It is advantageous if the alkali metal ion blocking underlayer is thin so that it has no significant effect on the optical properties of the coating, especially by reducing the transparency of a transparent coated substrate or causing interference colours in reflection or transmission. The suitable thickness range will depend on the properties of the material used to form the alkali metal ion blocking underlayer (especially its refractive index), but usually the alkali metal ion blocking underlayer has a thickness of less than 60 nm and preferably has a thickness of less than 40 nm, but preferably more than 20 nm, more preferably more than 30 nm. Where present, the alkali metal ion blocking underlayer should always be thick enough to reduce or block migration of alkali metal ions from the glass into the titanium oxide coating.

An advantage of the present invention is that the photocatalytically active titanium oxide coating may be thin (contributing to the low visible reflection of the coated substrate) but the coated substrate still has excellent photocatalytic activity. Preferably, the titanium oxide coating has a thickness of 30 nm or lower, more preferably the titanium oxide coating has a thickness of 20 nm or lower, more preferably the titanium oxide coating has a thickness in the range 2 nm to about 20 nm, and most preferably the titanium oxide coating has a thickness in the range 15 to 20 nm.

The present invention is also advantageous because depositing thin titanium oxide coatings requires less precursor and the layers can be deposited in a relatively short time. A thin titanium oxide coating is also less likely to cause interference colours in reflection or transmission. However, a particular advantage is that the visible light reflection of a thin titanium oxide coating is low which is especially important when the coated substrate is coated glass. Usually the required visible light transmission of the coated glass will determine the thickness of the titanium oxide coating.

In some preferred embodiments the coated substrate comprises: a clear transparent glass substrate, and a coating located on the glass substrate, wherein the coating comprises at least the following layers in sequence starting from the glass substrate: a first layer based on tin dioxide, wherein the first layer has a thickness of at least 5 nm, but at most 35 nm; a second layer based on silicon dioxide, wherein the second layer has a thickness of at least 15 nm, but at most 50 nm; a third layer based on antimony doped tin dioxide, wherein the third layer has a thickness of at least 100 nm, but at most 300 nm; a fourth layer based on silicon dioxide, wherein the fourth layer has a thickness of at least 5 nm, but at most 40 nm; and a photocatalytically active titanium dioxide coating, wherein the titanium dioxide coating has a thickness of at least 5 nm, but at most 30 nm.

These embodiments are advantageous in terms of providing solar control properties, lower film side and glass side reflectance and a superior colouration.

Preferably, the coated surface of the substrate has a static water contact angle of 20° or lower. Freshly prepared or cleaned glass has a hydrophilic surface (a static water contact angle of lower than about 40° indicates a hydrophilic surface), but organic contaminants rapidly adhere to the surface increasing the contact angle. A particular benefit of coated substrates (and especially coated glasses) of the present invention is that even if the coated surface is soiled, irradiation of the coated surface by UV light of the right wavelength will reduce the contact angle by reducing or destroying those contaminants. A further advantage is that water will spread out over the low contact angle surface reducing the distracting effect of droplets of water on the surface (e.g. from rain) and tending to wash away any grime or other contaminants that have not been destroyed by the photocatalytic activity of the surface. The static water contact angle is the angle subtended by the meniscus of a water droplet on a glass surface and may be determined in a known manner by measuring the diameter of a water droplet of known volume on a glass surface and calculated using an iterative procedure.

Preferably, the coated substrate has a haze of 1% or lower, which is beneficial because this allows clarity of view through a transparent coated substrate.

In preferred embodiments, the coated surface of the substrate is durable to abrasion, such that the coated surface remains photocatalytically active after it has been subjected to 300 strokes of the European standard abrasion test. Preferably, the coated surface remains photocatalytically active after it has been subjected to 500 strokes of the European standard abrasion test, and more preferably the coated surface remains photocatalytically active after it has been subjected to 1000 strokes of the European standard abrasion test.

This is advantageous because coated substrates of the present invention may be used with the coated surface exposed to the outside (e.g. coated glasses with the coated surface of the glass as the outer surface of a window) where the coating is vulnerable to abrasion. Likewise, interior locations can be exposed to wear and tear, especially in public places, and touchscreens and the like must also be resistant to abrasion.

The European standard abrasion test refers to the abrasion test described in European standard BS EN 1096 Part 2 (1999) and comprises the reciprocation of a felt pad at a set speed and pressure over the surface of the sample. In the present specification, a coated substrate is considered to remain photocatalytically active if, after being subjected to the European abrasion test, irradiation by UV light (e.g. of peak wavelength 351 nm) reduces the static water contact angle to below 15°. To achieve this contact angle after abrasion of the coated substrate will usually take less than 48 hours of irradiation at an intensity of about 32 W/m² at the surface of the coated substrate. Preferably, the haze of the coated substrate is 2% or lower after being subjected to the European standard abrasion test.

The coated substrates used in the present invention may also be durable to humidity cycling (which is intended to have a similar effect to weathering). Thus, in preferred embodiments of the invention, the coated surface of the substrate is durable to humidity cycling such that the coated surface remains photocatalytically active after the coated substrate has been subjected to 200 cycles of the humidity cycling test. In the present specification, the humidity cycling test refers to a test wherein the coating is subjected to a temperature cycle of 35°C to 75°C to 35°C in 4 hours at near 100% relative humidity. The coated substrate is considered to remain photocatalytically active, if, after the test, irradiation by UV light reduces the static water contact angle to below 15°.

In a further preferred embodiment, the present invention uses a durable coated glass comprising a glass substrate having a coating on one surface thereof, said coating comprising an alkali metal ion blocking underlayer and a photocatalytically active titanium oxide layer, wherein the coated surface of the substrate is durable to abrasion such that the coated surface remains photocatalytically active after it has been subjected to 300 strokes of the European standard abrasion test. In this embodiment, the coated glass preferably has a visible light reflection measured on the coated side of 35% or lower, and the photocatalytically active titanium oxide layer preferably has a thickness of 30 nm or lower. Thin coatings are durable to abrasion which is surprising because previously it has been thought that only relatively thick coatings would have good durability.

In a still further embodiment, the present invention uses a coated glass comprising a glass substrate having a photocatalytically active titanium oxide coating on one surface thereof, characterised in that the coated surface of the glass has a photocatalytic activity of greater than 4 x 10'² cm^-1 min^-1, preferably greater than 6 x 10'² cm^-1 min^-1 and more preferably greater than 8 x 10'² cm^-1 min^-1 and in that the coated glass has a visible light reflection measured from the coated surface of less than 20%.

In addition the use of the present invention may comprise reducing the concentration of atmospheric contaminants. For example, the coated substrate under irradiation by light of UV wavelengths (including UV wavelengths present in sunlight) may destroy atmospheric contaminants for example, nitrogen oxides, ozone and organic pollutants, adsorbed on the coated surface. This use is particularly advantageous in the open in built-up areas (for example, in city streets) where the concentration of organic contaminants may be relatively high (especially in intense sunlight), but where the available surface area of substrate is also relatively high. Alternatively, the coated substrate (with the coated surface on the inside) may be used to reduce the concentration of atmospheric contaminants inside buildings, especially in office buildings having a relatively high concentration of atmospheric contaminants.

Any feature set out above in relation to the first aspect of the present invention may also be utilised in relation to any other aspects of the present invention.

Any invention described herein may be combined with any feature of any other invention described herein mutatis mutandis.

It will be appreciated that optional features applicable to one aspect of the invention can be used in any combination, and in any number. Moreover, they can also be used with any of the other aspects of the invention in any combination and in any number. This includes, but is not limited to, the dependent claims from any claim being used as dependent claims for any other claim in the claims of this application.

The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention will now be further described by way of the following specific embodiments, which are given by way of illustration and not of limitation:

Coated glasses applicable to the present invention were produced using an on-line CVD process as described in the Examples, below. The layers of the coatings were applied on line to the glass substrate by chemical vapour deposition during the glass manufacturing process, as is well known in the art. In the Examples two-layer coatings were applied to the glass ribbon.

Examples

A ribbon of 1 mm thick soda lime float glass advancing at a lehr speed of 300 m/hour was coated with a two-layer coating as the ribbon advanced over the float bath at a position where the glass temperature was in the range of about 650°C to about 670°C. The float bath atmosphere comprised a flowing gaseous mixture of nitrogen and 9% hydrogen at a bath pressure of approximately 0.15 mbar.

Layer 1 (the first layer to be deposited on the glass) was a layer of silicon oxide. Layer 1 was deposited by causing a gaseous mixture of monosilane (Si H4, 60 ml/min), oxygen (120 ml/min), ethylene (360 ml/min) and nitrogen (8 litres/min) to contact and flow parallel to the glass surface in the direction of movement of the glass using coating apparatus as described in GB patent specification 1 507 966 (referring in particular to Fig. 2 and the corresponding description on page 3 line 73 to page 4 line 75) with a path of travel of the gaseous mixture over the glass surface of approximately 0.15 m. Extraction was at approximately 0.9 to 1.2 mbar. The glass ribbon was coated across a width of approximately 10 cm at a point where its temperature was approximately 670°C. The thickness of the silica layer was around 35 nm. Layer 2 (the second layer to be deposited) was a layer of titanium dioxide. Layer 2 was deposited by combining separate gas streams comprising titanium tetrachloride in flowing nitrogen carrier gas, ethyl acetate in flowing nitrogen carrier gas and a bulk flow of nitrogen of 8 l/min (flow rate measured at 20 psi) into a gaseous mixture and then delivering (through lines maintained at about 250°C) the gaseous mixture to coating apparatus consisting of an oil cooled dual flow coater. The pressure of the nitrogen carrier and bulk nitrogen gases was approximately 20 pounds per square inch. The gaseous mixture contacted and flowed parallel to the glass surface both upstream and downstream along the glass ribbon. The path of travel of the gaseous mixture downstream was about 0.15 m and upstream was about 0.15 m with extraction of about 0.15 mbar. Titanium tetrachloride and ethyl acetate were entrained in separate streams of flowing nitrogen carrier gas by passing nitrogen through bubblers containing either titanium tetrachloride or ethyl acetate. The titanium tetrachloride bubbler was maintained at a temperature of 69°C and the ethyl acetate bubbler was maintained at a temperature of 42°C. The thickness of the titanium dioxide layer was around 17 nm. The thickness values for the layers were determined using high resolution scanning electron microscopy and optical modelling of the reflection and transmission spectra of the coated glass. The thickness of the coatings was measured with an uncertainty of about 5%.

Anti-Viral Testing

The Examples were tested according to ISO Standard 21702 (2019) (specifies proper methods for measuring antiviral activity on plastics and other non-porous surfaces of antiviral-treated products against specified viruses).

Several Examples were tested for antiviral activity according to the above standard against Mouse Hepatitis Virus. These samples were not overlaid with the cover film specified in the above standard. Such cover films help ensure that the viral medium does not dry out, eliminate the effect of contact angle and ensure the medium is in contact with the surface. However, a cover film would not be present in a “real life” scenario and therefore was omitted for these samples. Samples were pre-activated for 4 hours under 360 nm UV illumination (at an intensity of about 32 W/m² at the surface of the coated substrate) that replicated daylight in average summer conditions. The samples were then tested in the presence of the virus after 15 min and 30 min, again under 360 nm UV light. A control of 1 mm thick uncoated soda lime float glass was also tested in the same manner. The results shown in Table 1 below are averages taken from five repeats of the test.

Table 1 : Antiviral activity of Examples according to the present invention and a control sample against Mouse Hepatitis Virus

As can be seen from Table 1 , the Examples of the invention demonstrated a significant viral reduction compared to the control. It is worth noting that the control also showed antiviral activity because the UV light alone inactivates the virus.

Several Examples were tested for antiviral activity according to the above standard against Human Coronavirus. UV light of 390 nm wavelength (at an intensity of about 32 W/m² at the surface of the coated substrate), which does not affect this virus, was utilised for these tests. Samples were overlaid with a cover film according to the above standard and pre-activated for 4 hours under 390 nm UV illumination. The samples were then tested in the presence of the virus after 30 min and 60 min, some under 390 nm UV light during this period and some in the dark. A control of 1 mm thick uncoated soda lime float glass was also tested in the same manner. The results shown in Table 2 below are averages taken from five repeats of the test.

Table 2: Antiviral activity of Examples according to the present invention and a control sample against Human Coronavirus Table 2 shows that the Examples of the invention demonstrated a significant viral reduction compared to the control, and that this activity was also present for samples that were tested in the dark, i.e. the activity in the absence of the influence of UV light confirms the antimicrobial properties of the Examples of the invention. The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1 . Use of a coated substrate as an antimicrobial substrate, wherein the substrate comprises a photocatalytically active titanium oxide coating on at least one surface thereof, wherein the coated surface of the substrate has a photocatalytic activity of greater than

5 x 10’³cm’¹min’¹, and wherein the coated substrate has a visible light reflection measured from the coated surface of 35% or lower.

2. The use according to claim 1 , wherein growth of bacteria on the coated surface of the substrate is reduced by at least 10% compared to an uncoated substrate that is otherwise the same as the coated substrate, and/or deactivation of viruses on the coated surface of the substrate is increased by at least 10% compared to an uncoated substrate that is otherwise the same as the coated substrate..

3. The use according to any preceding claim, wherein said use occurs in an architectural glazing unit, automotive glazing unit, electronic device, furniture, splashbacks, bulkhead, door, blind, medical container, wall covering, touchscreen, mirror or glass bottle.

4. The use according to any preceding claim, wherein the coated surface is exposed.

5. The use according to any preceding claim, wherein, where the use occurs in a glazing unit that is exposed to the external environment, the coated surface is exposed to the internal environment.

6. The use according to any preceding claim, wherein the coated substrate further comprises a second coating located on an opposing surface of the substrate, wherein the second coating comprises an antireflection, low-emissivity and/or solar control coating.

7. The use according to any preceding claim, wherein an opposing surface of the substrate is bonded to a second substrate by a ply of plastics interlayer, wherein the plastics interlayer does not comprise any UV-absorbers.

8. The use according to any preceding claim, further comprising the step of irradiating the coated substrate with UV light from an artificial UV light source and/or from daylight for at least 1 min, preferably at least 20 min, more preferably at least 1 hr, most preferably at least 2 hr.

9. The use according to claim 8, wherein the UV light has a peak wavelength above 200 nm, preferably above 220 nm, more preferably above 250 nm.

10. The use according to claim 8 or claim 9, wherein the UV light is activated using an automated sensor process or a timer.

11 . The use according to any preceding claim, wherein the substrate is a transparent glass substrate.

12. The use according to any preceding claim, wherein the coated substrate comprises an alkali metal ion blocking underlayer between the surface of the substrate and the photocatalytically active titanium oxide coating, wherein the alkali metal ion blocking underlayer is a layer of silicon oxide.

13. The use according to claim 12, wherein the alkali metal ion blocking underlayer has a thickness of more than 20 nm, but less than 40 nm.

14. The use according to any preceding claim, wherein the titanium oxide coating has a thickness of 30 nm or lower.

15. The use according to any preceding claim, wherein the coated substrate comprises: a clear transparent glass substrate, and a coating located on the glass substrate, wherein the coating comprises at least the following layers in sequence starting from the glass substrate: a first layer based on tin dioxide, wherein the first layer has a thickness of at least 5 nm, but at most 35 nm; a second layer based on silicon dioxide, wherein the second layer has a thickness of at least 15 nm, but at most 50 nm; a third layer based on antimony doped tin dioxide, wherein the third layer has a thickness of at least 100 nm, but at most 300 nm; a fourth layer based on silicon dioxide, wherein the fourth layer has a thickness of at least 5 nm, but at most 40 nm; and a photocatalytically active titanium dioxide coating, wherein the titanium dioxide coating has a thickness of at least 5 nm, but at most 30 nm.