CN112840000B

CN112840000B - Coatings and coating formulations

Info

Publication number: CN112840000B
Application number: CN201980067619.5A
Authority: CN
Inventors: 卡米尔·查林·玛丽-塞西尔·卡库特; 西尔瓦娜·伦西娜·安东尼塔·迪西尔维斯特
Original assignee: Kostron Netherlands Co ltd
Current assignee: Kostron Netherlands Co ltd
Priority date: 2018-10-16
Filing date: 2019-10-15
Publication date: 2023-02-24
Anticipated expiration: 2039-10-15
Also published as: CN112840000A; TW202024247A; EP3867318A1; WO2020078977A1

Abstract

A coated substrate comprising a coating having an inorganic oxide and pores, said coating exhibiting improved anti-fouling performance. The coated substrate may be used, for example, in a solar module. Furthermore, a coating formulation and the use of a coating formulation are disclosed.

Description

Coatings and coating formulations

Technical Field

The present invention relates to an antireflective coating. More particularly, the present invention relates to antireflective coatings and coated substrates, coating formulations, and solar modules that exhibit stain resistance, as well as methods of improving the stain resistance of the coatings.

Disclosed herein are coated substrates comprising a coating comprising an inorganic oxide and pores, the coating exhibiting improved anti-fouling performance. The coated substrate can be used, for example, in a solar module. Furthermore, a coating formulation and the use of a coating formulation are disclosed herein.

Background

Anti-reflective (AR) coatings are coatings deposited on substrates that require high light transmittance, such as cover glass and greenhouse glass for solar modules, and that can reduce the reflectivity of the substrate. The performance of solar modules tends to degrade over time due to contamination of the surface through which light is transmitted, among other reasons. In areas with high contamination rates, it has been found that the accumulation of sand and dust particles substantially results in reduced performance.

Object of the Invention

It is an object of the present invention to provide an improved coating.

In another aspect of the present invention, it is an object of the present invention to provide an improved coating formulation.

In another aspect of the invention, it is an object of the invention to provide a method for improving the stain resistance of a coating.

The improvement may for example be to achieve an improved antifouling performance of the coating, or another feature of the invention.

Disclosure of Invention

In one aspect of the invention, this object is achieved by a coating formulation according to the claims, embodiments and aspects described herein.

In one aspect of the invention, this object is achieved by a coating formulation as described herein.

In other aspects of the invention, the object is achieved by a method, a coated substrate or a use according to the claims, embodiments and aspects described herein.

Drawings

The invention is explained below with reference to an exemplary embodiment and the accompanying drawings, in which

FIG. 1a schematically depicts an embodiment of an elongated particle for use in the present invention, having an elliptical shape (2D image of a long (elongated) ellipsoid), with a long (also referred to as principal) axis, with a length x1 perpendicular; a short (also referred to as minor) axis perpendicular to the long axis, having a length x2; and an aspect ratio (x 1/x 2) of at least 2.

Fig. 1b schematically depicts an embodiment of an elongated particle having a rod-like shape for use in the present invention, wherein the length of the major axis a is x1; minor axis (smaller diameter) perpendicular to major axis, length x2; and an aspect ratio (x 1/x 2) of at least 2.

Fig. 1c schematically depicts a spherical particle having: a first axis of length x1; a second axis perpendicular to the first axis and having a length x2; and the aspect ratio (x 1/x 2) is about 1.

Fig. 1d schematically depicts an embodiment of an elongated particle with an irregular shape for use in the present invention, having: a long axis of length x1; a minor axis perpendicular to the major axis (minor diameter, shortest dimension of the particle), with a length x2 (length of the longest straight line from one side of the particle to the other side of the particle); and an aspect ratio (x 1/x 2) of at least 2.

Fig. 2 shows the optical properties of the comparative sample.

Fig. 3 shows the optical properties of a sample according to the invention.

Disclosure of Invention

The present invention relates to an improved coating.

Such improved coatings may be obtained by converting the paint formulation into a functional coating, for example by heating.

Typically by converting the coating formulation on the substrate into a coated substrate.

Coated substrates, such as cover glasses for solar modules comprising an antireflective coating, often require cleaning at some point in time. In arid regions of the world, cleaning involves time and cost, and produces waste cleaning material. There is therefore a need to reduce the frequency of cleaning of coated substrates. The present invention solves the problem of reduced cleaning by improving the anti-fouling performance of the coated substrate. The present invention provides a coated substrate that exhibits improved stain resistance. The present invention provides a coating formulation that exhibits improved stain resistance after application of the formulation to a substrate and conversion of the dried coating formulation into a coated substrate. The present invention provides a solar module having improved anti-fouling performance.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

The improved anti-fouling performance can be demonstrated by: reduced frequency of cleaning while having the same power output over a period of time (e.g., 3 months). The improved anti-fouling performance can be demonstrated by: with improved power output at the same cleaning frequency over a period of time (e.g., 3 months).

The anti-fouling performance can be determined by measuring the transmittance of the anti-reflective coating on the transparent substrate by projection measurement using a spectrophotometer. The spectrophotometer can be any spectrophotometer suitable for analyzing a coated substrate. Suitable spectrophotometers include Shimadzu UV2600 spectrophotometer. Another suitable spectrophotometer includes the Optosol Transpec VIS-NIR spectrophotometer.

The improved anti-fouling performance may be demonstrated by an increased anti-fouling ratio (ASR) as defined herein. The improved anti-fouling performance can be demonstrated as an increased substrate-coating anti-fouling ratio ASR compared to a reference uncoated substrate. In one aspect, improved anti-fouling performance can be demonstrated as a substrate-coating anti-fouling ratio ASR of at least 50%. In one aspect, the ASR is at least 55%. In one aspect, the ASR is at least 60%. In one aspect, the ASR is at least 65%. In one aspect, the ASR is at least 70%. In one aspect, the ASR is at least 75%; in one aspect, the ASR is at least 80%. In one aspect at least 85%. In one aspect, the ASR is at least 90%.

In one aspect, the improved anti-smudge performance may be exhibited as an increased substrate-coating anti-reflective effect, ARE, as defined herein.

The improved anti-soil performance may be demonstrated as an increased ARE compared to a reference uncoated substrate. In one aspect, ARE is at least 2%; in one aspect, ARE is at least 3%; in one aspect, ARE is at least 4%; in one aspect, the ARE is at least 5%.

The coating formulation according to the invention provides improved antifouling properties.

The coating formulations according to the invention provide improved anti-fouling properties to coatings obtained from such formulations after curing, i.e. by converting the coating formulation on a substrate into a coated substrate, e.g. by heating to above 400 ℃.

The process according to the invention provides coated substrates which exhibit improved anti-fouling properties.

A coating formulation comprising:

i.2 to 18% by weight, based on the oxide equivalent of the inorganic substance, of elongated dense oxide particles having an aspect ratio of at least 2 and an average minor diameter in the range of 3 to 20nm, and

a porogen capable of forming pores with a diameter in the range of 10-120nm,

an inorganic oxide binder, and

(iii) a solvent, the solvent,

wherein the coating formulation comprises 0.5 to 15 weight percent alumina equivalent of an aluminum-containing compound based on the total ash residue after 2 minutes of combustion in air at 600 ℃.

The average smaller diameter referred to herein can be measured from at least one TEM image.

The aspect ratio referred to herein may be determined from at least one TEM image.

As mentioned herein, the amount of alumina equivalents of aluminum-containing compounds in the ash residue of the coating formulation product can be determined by ICP-MS.

In one aspect of the invention, the coating formulation comprises at least 2 wt.%, at least 2.5 wt.%, at least 3 wt.%, at least 3.5 wt.%, at least 4 wt.%, at least 4.5 wt.%, at least 5 wt.%, at least 5.5 wt.%, at least 6 wt.%, at least 7 wt.%, at least 8 wt.%, at least 9 wt.%, at least 10 wt.% of elongated dense inorganic oxide particles having an aspect ratio of at least 2 and an average minor diameter in the range of 3-20nm, based on inorganic oxide equivalent weight.

In one aspect of the invention, the coating formulation comprises at most 18 wt%, at most 17 wt%, at most 16 wt%, at most 15 wt%, at most 14 wt%, at most 13 wt%, at most 12wt%, based on inorganic oxide equivalent weight, of elongated dense inorganic oxide particles having an aspect ratio of at least 2 and an average minor diameter in the range of 3-20 nm.

The weight percent of elongated dense inorganic oxide particles having an aspect ratio of at least 2 and an average minor diameter in the range of 3-20nm (% by weight of the elongated particles) can be calculated as follows.

Weight% of elongated particles = weight% of inorganic oxide equivalents originating from elongated particles as compared to the total amount of silica equivalents in the coating formulation = m (SiO of elongated particles) ₂ )/m(SiO ₂ Total) · 100= wt% of elongated particles = wt% of elongated dense inorganic oxide particles having an aspect ratio of at least 2 and an average minor diameter in the range of 3-20nm, based on inorganic oxide equivalent weight. m is an elongated particulate solid in grams.

In one aspect of the invention, the coating formulation comprises at least 0.5 wt.%, at least 1 wt.%, at least 1.5 wt.%, at least 2 wt.%, at least 3 wt.%, at least 4 wt.%, at least 5 wt.%, at least 6 wt.%, at least 10 wt.%, at least 12 wt.% of the aluminum oxide equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises 15 wt.% or less, 14 wt.% or less, 13 wt.% or less, 12 wt.% or less, 11 wt.% or less, 10 wt.% or less, 9 wt.% or less, 8 wt.% or less of the aluminum oxide equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises 1 to 15 weight percent alumina equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises 1 to 10 weight percent alumina equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises from 2 to 10 weight percent alumina equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises from 1 to 8 weight percent alumina equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises 1.5 to 8 weight percent alumina equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises from 2 to 8 weight percent alumina equivalent of the aluminum-containing compound.

In another aspect of the invention, this object is achieved by a method for preparing a coated substrate, comprising the steps of:

-providing a substrate;

-providing a coating formulation according to any one of the embodiments as described herein;

-applying the coating formulation to a substrate;

-drying the coating formulation applied on the substrate; and is provided with

-converting the dried coating formulation on the substrate into a coated substrate.

A method of preparing a coated substrate comprising the steps of:

-providing a substrate having a first surface;

-providing a coating formulation as described herein;

-applying the coating formulation on a first surface of a substrate;

-drying the applied coating formulation; and is

-converting the substrate with the dried coating formulation into a coated substrate comprising a coating on the first surface, e.g. by heating to above 400 degrees celsius.

In one aspect, a primer layer as described herein forms at least a portion of a first surface of a substrate. In one aspect, a primer layer as described herein forms a first surface of a substrate.

In another aspect of the invention, this object is achieved by a coated substrate obtainable by the process described herein, comprising a process comprising the steps of:

-providing a substrate;

-applying the coating formulation to a substrate;

-drying the coating formulation on the substrate; and is

-converting the coating formulation on the substrate into a coated substrate.

The invention further relates to a coated substrate comprising:

i. a substrate; and

a porous antireflective coating disposed on at least a portion of the substrate,

wherein the antireflective coating comprises:

pores with a diameter in the range of 10-120nm, preferably 30-100nm, as measured using ellipsometry and/or electron microscopy; and

-elongated dense inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3-20 nm; and

-0.5 to 15% by weight of alumina equivalent of an aluminium-containing compound.

In another aspect of the invention, the object is achieved by using a coating formulation comprising elongated inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3-20nm for improving the anti-fouling performance of a substrate, wherein the coating formulation comprises core-shell nanoparticles as porogen and 0.5-15 wt% of an aluminium-containing compound in alumina equivalents, wherein the core comprises an organic compound, e.g. a polymer such as a cationic polymer or an organic compound having a boiling point below 200 ℃, and the shell comprises an inorganic oxide.

In another aspect of the invention, the object is achieved by using a coating formulation comprising elongated compact inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3-20nm for improving the anti-fouling performance of a substrate, wherein the coating formulation comprises core-shell nanoparticles as porogens, wherein the core comprises an organic compound, such as a polymer or an organic compound having a boiling point below 200 ℃, and the shell comprises an inorganic oxide; and the formulation comprises 0.5 to 15 weight percent alumina equivalent of an aluminum-containing compound.

In one aspect of the invention, the polymer may be a cationic polymer.

The coatings disclosed herein are porous coatings. The coating can be made using a coating formulation that includes a binder and a porogen. The binder comprises inorganic binder particles, such as metal oxide particles, and/or inorganic oxide precursors. Porogens typically comprise organic materials that decompose, burn, evaporate, or are otherwise removed when exposed to high temperatures. Typically, the elevated temperature is 400 degrees celsius or more, such as 550 degrees celsius or more, such as 600 degrees celsius or more. Typically, the organic material is an organic polymer. In one aspect, a porogen comprises an organic material comprising an organic polymer, such as an organic neutral, organic cation, organic anionic polymer, polyelectrolyte, or a combination thereof. Porogens typically comprise an organic polymeric core and an inorganic oxide shell surrounding the core. The coating according to the invention comprises inorganic particles, for example elongated inorganic dense oxide particles. It should be noted that elongated inorganic dense oxide particles and elongated dense inorganic oxide particles are used interchangeably herein. It should be noted that elongated inorganic dense oxide particles and elongated bulk metal oxide particles are used interchangeably herein.

The coating according to the invention comprises pores having a diameter in the range of less than 1nm to about 120 nm. The pores may be open pores, e.g. openings along the boundary between two particles, and optionally connected to the surface of the coating, and/or the pores may be closed, e.g. (closed) hollow particles. The porogen-derived pores are also referred to herein as porogen pores. Preferably, the coating comprises pores with a diameter of 10-120nm, referred to as porogen pores. For pores with a diameter greater than 10nm, the pore size can be estimated by electron microscopy. For pores with diameters in the range of 2-50nm, ellipsometry can be used to determine the pore size distribution. The porogen pores preferably have a substantially regular shape, such as spherical or ellipsoidal (with one or two major axes) pores. In one aspect, the porogen pores preferably have a substantially regular shape, such as spherical or elliptical (with one or two major axes) pores, but should not have an aspect ratio greater than 5, as this may adversely affect the mechanical properties of the coating. Hollow particles such as hollow inorganic oxide particles can be defined as particles having a hollow core and an inorganic oxide shell. The porogen pores may be defined by hollow inorganic oxide particles, such as hollow inorganic oxide particles, and may be derived from core-shell particles having an inorganic oxide (or inorganic oxide precursor) shell and an organic polymer-based core to remove the polymer as the coating cures. After the coating formulation is cured, the polymer will decompose/remove and form a coating. The porogen pores may be defined by hollow inorganic oxide particles, such as hollow inorganic oxide particles, and may be derived from core-shell particles having an inorganic oxide (or inorganic oxide precursor) shell and a core material comprising an organic polymer and/or an organic compound, such that after curing of the coating, the core material will be removed. After the coating formulation is cured, the core material will be decomposed/removed, thereby forming a porous coating. The pores are typically derived from organic porogens that will typically be decomposed, burned, evaporated, or otherwise removed during conversion of the coating formulation into a functional coating.

In one aspect, a suitable curing temperature is at least 400 degrees celsius. In one aspect, a suitable curing temperature is at least 550 degrees celsius, and in one aspect at least 600 degrees celsius. The pores may also be defined by a combination of inorganic binder particles and/or dense inorganic oxide particles. In this case, the pores are typically derived from an organic porogen, such as polymer particles, or another porogen, which will typically be decomposed, burned, evaporated, or otherwise removed during conversion of the coating formulation into a functional coating. Porogens include organic neutral, cationic, and anionic polymers or polyelectrolytes (see, e.g., fuji, m.; takai, c.; river virtuzo, r.v.; adv.powder tech.,2014,25,91-100 zhang, x. Et al, app. Mater. Interfaces,2014,6, 1415-1423)

In the present invention, the pores are typically derived from an organic porogen, such as a polymer particle, or another porogen, which will typically be decomposed, burned, evaporated, or otherwise removed during conversion of the coating formulation into a functional coating. It should be observed that the conversion does not involve the polymerization of organic (monomeric) compounds, since the binder is an inorganic oxide-based binder, and thus the conversion is a sintering type conversion, in which organic matter is at least partially removed and the metal oxide particles are at least partially sintered together.

In addition to porogen pores, smaller pores are present at least in the binder. In the context of the present invention, adhesive pores are thus pores with a diameter of 1 to less than 10nm. The binder pores are generally not regular, but rather extend in non-contact regions between adjacent binder particles, dense inorganic oxide particles, and hollow nanoparticles (if present), and may form a network, which may or may not be connected to the surface of the coating or porogen pores.

The coating according to the invention is a porous coating. By "porous" is meant herein that the coating has pores and a porosity of at least 2%. The maximum porosity depends on the mechanical requirements of the coating and is generally 50% or less, preferably less than 45% porosity, more preferably less than 40% porosity. In one aspect, the porosity of such a coating is from 2 to 50%. High porosity generally increases the antireflective properties but may reduce the mechanical strength of the coating. In one aspect, the porosity of the porous antireflective coating is 2% or greater, 5% or greater, 10% or greater, 15% or greater, 20% or greater, 25% or greater, 30% or greater. In one aspect, the porous antireflective coating has a porosity of 50% or less, 45% or less, 40% or less. In one aspect, the porous antireflective coating has a porosity of 25-40%. In one aspect, the porous antireflective coating has a porosity of 30-40%.

The porous antireflective coating may also be referred to herein as a coating or an antireflective coating.

Image analysis may suitably be performed on SEM pictures, as is well known to those skilled in the art. One skilled in the art would be able to perform image analysis on SEM photographs of cross sections of the coating orthogonal to the substrate to determine that the number of pores having a minimum size of at least 10nm in the region of the AR coating closest to the substrate surface is less than the number of pores having a minimum size of at least 10nm in the region of the AR coating closest to the atmosphere.

Alternatively, one skilled in the art can calculate the porosity from the measured Refractive Index (RI). Knowing the RI of the coating material without any pores, one skilled in the art can calculate how much air/pore volume is present in the coating. The coating material herein is the total inorganic oxide material after conversion of the coating formulation into a functional coating, for example by heating. The total inorganic oxide material includes all of the inorganic oxide materials in the coating, such as the material of the binder, plus the material of the inorganic oxide shell, plus the aluminum-containing compound.

In one aspect, porosity is determined by image analysis on SEM photographs of a cross-section of the coating perpendicular to the substrate.

In one aspect of the invention, the coating of the coated substrate has a porosity of 2-50%.

The coating according to the invention further comprises elongated dense inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3 to 20 nm. Preferably, the smaller diameter is in the range of 5 to 20 nm. Elongate means that at least one dimension of the particle is much longer, for example at least 2, 3, 4, 5, 8, 10, 15 or 20 times the length of another dimension of the particle. Preferably, the length of the elongated dense inorganic oxide particles is less than 50 times the length of another dimension of the particles, such as up to 50, 30, 25, 20 or 15 times the length of another dimension of the particles. When the particles have an irregular shape, the aspect ratio is calculated as the length of the longest straight line from one side of the particle to the other side of the particle (even though this may mean that the straight line may be outside the particle) divided by the shortest dimension of the particle that is transverse to the longest straight line along that straight line anyway. Examples of elongated dense inorganic oxide particles are IPA-ST-UP (Nissan Chemical) and Levasil CS15/175 (Akzo Nobel), and the like, and are commercially available. Further examples include Levasil CS8-490 and Levasil CS15-150 (Akzo Nobel). Typically, the diameter of the elongated particles is less than their length. In one aspect, the elongated dense particles comprise elongated silica particles having a diameter of 1 to 30nm and a length of 10 to 200 nm.

In one aspect, the elongated dense particles comprise elongated silica particles having a diameter of 9-15nm and a length of 40-100 nm. IPA-ST-UP (Nissan chemical) is an example of an elongated silica particle with a diameter of 9-15nm and a length of 40-100 nm.

In one aspect, the elongated dense particles are elongated silica particles having a diameter of 1 to 30nm and a length of 10 to 200 nm.

In one aspect, the elongated dense particles are elongated-silica particles having a diameter of 9-15nm and a length of 40-100 nm. IPA-ST-UP (Nissan chemical) is an example of an elongated silica particle with a diameter of 9-15nm and a length of 40-100 nm.

IPA-ST-UP as used herein refers to ORGANOSILICAL ^TM IPA-ST-UP。

The elongated particles have an aspect ratio of at least 2 and may, but are not limited to, have an elliptical, rod-like or irregular shape. The elongated particles used in the present invention have a major axis (which may also be referred to as a major axis) having a length x1; and has a shorter axis (which may also be referred to as a minor axis) perpendicular to the major axis of length x2; and an aspect ratio (x 1/x 2) of at least 2.

The aspect ratio is calculated by: the length of the longest axis is divided by the length of the smaller axis. The longest axis may also be referred to as the major axis. The smaller axis may also be referred to as the minor axis, minor diameter, or shortest dimension of the particle.

Typically, to determine the length of the axis of the particle, the outer surface of the particle is used.

By dense is meant that the inorganic oxide particles have low porosity or no porosity, e.g., less than 5 volume percent porosity or no porosity. In one aspect, the elongated dense inorganic oxide particles have a porosity of 0.5 to 5 volume percent, in one aspect 1 to 4 volume percent, and in one aspect 1 to 3 volume percent.

Porogens here means entities capable of forming pores in the final coating with a diameter of 10 to 120nm, preferably 30 to 100nm, and may be, for example, hollow particles; core-shell particles whose core has a boiling point below the curing temperature of the coating formulation or whose core is combustible or depolymerizable below the curing temperature; particles which are combustible or depolymerizable below the curing temperature. Porogens may also be referred to as porogens. The core having a boiling point lower than the curing temperature has a decomposition temperature lower than the curing temperature. A burnable or depolymerizable core below the curing temperature is a core that decomposes or depolymerizes or a combination thereof during curing, i.e., at a temperature below the curing temperature. As a result, the core is removed and pores are formed. Thus, a porogen or pore-forming agent herein refers to an entity capable of forming pores with a diameter of 10 to 120nm, preferably 30 to 100nm, in the final coating. The porogens may be polymer particles, for example, polystyrene particles, pluronic P123 and/or PMMA particles. The porogen may be, for example, a hollow particle. The porogen may be, for example, hollow silica particles. The porogen may be, for example, a core-shell particle whose core has a boiling point below the curing temperature of the coating formulation. The porogen may be a core-shell particle whose core is combustible or depolymerizable below the curing temperature; or particles which are combustible or depolymerizable below the curing temperature. The core having a boiling point lower than the curing temperature contains a substance having a boiling point lower than the curing temperature. The core, which is combustible or depolymerizable below the curing temperature, comprises a material that decomposes or depolymerizes or a combination thereof during curing, i.e. at a temperature below the curing temperature. As a result, the compound is removed and pores are formed.

Oxide equivalent of inorganic substance means herein a metal oxide comprising silicon oxide, irrespective of the actual compound present of the inorganic substance, so that for example tetraethoxysilane will be considered as SiO ₂ Whether tetraethoxysilane, partially hydrolyzed tetraethoxysilane or SiO is present ₂ That is, the oxide equivalent of an inorganic substance refers herein to the equivalent of a metal oxide containing silicon oxide, which may be formed from the actual compound or inorganic oxide precursor used. Thus, for example, whether tetraethoxysilane, partially hydrolyzed tetraethoxysilane or SiO is present ₂ The tetraethoxysilane is expressed by SiO ₂ And (3) equivalent weight. Similarly for alumina, one calculates the pure Al that can be formed ₂ O ₃ The amount of (c). Calculating the alumina equivalent to theoretical Al based on the alumina precursor added to the formulation ₂ O ₃ Amount of the compound (A).

In the examples, the weight% of alumina in the coating formulation is defined as: m (Al 2O 3)/(m (Al 2O 3) + m (SiO 2)) × 100= Al2O3 by weight%, where m is the number of grams used.

Wherein weight percent of alumina equivalents refers to weight percent compared to the total amount of inorganic oxide equivalents in the coating formulation.

It can also be expressed by a phrase wherein the weight% of Al2O3 is expressed as

The alumina precursor may comprise

Al (III) complexes, for example halogen-based salts of Al (III) in the form of AlX3, where X can be in the form of F, cl, br, I and hydrates thereof;

al (III) inorganic salts, such as aluminum (III) nitrate, nitrite, sulfite, sulfate, phosphate, chlorate, perchlorate, carbonate and hydrate forms thereof;

al (III) complexes with oxygen-or nitrogen-donor-based ligands, which are hydrolysable, such as alkoxides or amides; and

-combinations thereof.

The alumina precursor may include any one of Al (isopropoxide) 3 (Al (isopropoxide) 3), al (sec-butoxide) 3 (Al (sec-butoxide) 3), al (NO 3) 3, alCl3, or a combination thereof.

The silica precursor can include TEOS (tetraethoxysilane), TMOS (tetramethoxysilane), an alkylsilane such as (R) x) Si (OCH 3) 4-x, where R = CH3, C2H5, OC2H5, OCH3, or a combination thereof.

In one aspect, the inorganic oxide equivalents of the coating formulation are based on the total ash residue after 2 minutes of combustion in air at 600 ℃. The skilled person knows that the total ash residue after 2 minutes of combustion in air at 600 ℃ is the total residual solid matter after 2 minutes of combustion in air at 600 ℃.

For example, for silica, starting from alkoxysilanes. When referring to oxide equivalents, it is assumed that only pure SiO is formed ₂ . Similarly, for alumina, if starting from Al (NO 3) 3, the calculation can beTo form pure Al ₂ O ₃ The amount of (c).

For example, for 10 grams of tetraethyl orthosilicate (TEOS), the amount of inorganic oxide equivalents is calculated as follows:

i.e. SiO ₂ Equivalent = oxide equivalent of inorganic =10/208.33 × 60.08=2.88g

For example, for 1 gram of elongated dense inorganic oxide particles having an aspect ratio of at least 2 and an average minor diameter in the range of 3 to 20nm, the inorganic oxide equivalent weight is calculated as follows:

the elongated particles used in the examples are considered to be pure SiO2. Thus 1 gram of elongated particles corresponds to 1 gram of inorganic oxide (here 1 gram of SiO 2).

In one embodiment, the porogen comprises a significant portion of the total amount of inorganic oxides in the coating formulation. Preferably, the porogen comprises from 10 to 75 weight percent of the total inorganic oxides in the coating formulation, more preferably the porogen comprises from 20 to 50 weight percent of the total inorganic oxides in the coating formulation. This may be the case, for example, where the porogen is core shell particles or hollow particles.

The inorganic oxide may be any oxide known in glass coatings. The inorganic oxide may be any known in glass coatings, including metal oxides, such as Al ₂ O ₃ 、SiO ₂ 、TiO ₂ 、ZrO ₂ Oxides of the lanthanide series elements, and mixtures thereof (including mixed oxides). The inorganic oxide may be any known in glass coatings, including metal oxides, compounds and mixtures, including, for example, al ₂ O ₃ 、SiO ₂ And optionally one or more of Li2O, beO, baO, mgO, K2O, caO, mnO, niO SrO, feO, fe2O3, cuO, cu2O, coO, znO, pbO, geO2, snO2, sb2O3, bi2O 3. In one aspect, the inorganic oxide comprises Al ₂ O ₃ 、SiO ₂ 、TiO ₂ 、ZrO ₂ And/or combinations thereof.

Preferably, the inorganic oxide comprises silica, preferably the inorganic oxide comprises at least 50 wt% silica, more preferably the inorganic oxide comprises at least 90 wt% silica, for example the inorganic oxide consists of silica.

The coated substrate according to the invention can be prepared, for example, by a process comprising the steps of: providing a substrate; providing a coating formulation according to the present invention; coating the coating formula product on a substrate; drying the coating formulation on the substrate; and converting the coating formulation on the substrate into a coated substrate. It should be observed that the conversion does not involve polymerization of the organic polymer, but rather consolidation of the binder and/or conversion of the porogen to pores in the coating. This may be combined with, for example, a tempering treatment of the glass substrate by heating, but may also involve evaporation of the solvent in the solvent templated particles, which may be performed at a much lower temperature.

Where the core comprises a solvent, for example, in a solvent-templated particle, the conversion of the porogen to the pores may involve evaporation of the solvent, for example, at a temperature of less than 250 ℃. The boiling point of the solvent may be at most 250 ℃, or at most 200, 175, or 150 ℃. In this case, a substrate comprising a coated coating formulation according to the present invention is converted into a coated substrate comprising a coating on a first surface by exposing the coated coating formulation to a temperature of less than 250 ℃. In one aspect, the coating formulation is applied by exposing the coating formulation to a temperature of less than 200 ℃, less than 175 ℃, or less than 150 ℃.

Anti-reflective coatings comprising IPA-ST-UP particles (elongated particles) and an inorganic binder are disclosed in WO 2007/093341. However, WO2007/093341 does not show any correlation with the antifouling properties and does not disclose the presence of pores with a diameter of 10-120nm, in particular 30-100nm, in the coating.

When the coating is applied to a substrate (e.g., a glass sheet), the coating will have an inner surface facing the substrate and an outer surface facing away from the substrate. In one embodiment, the elongated dense inorganic oxide particles are non-uniformly distributed in the coating. In particular, it has been found advantageous that the mass ratio of inorganic oxide originating from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating is higher in or near the outer surface of the coating. Here, the outer surface refers to the surface of the coating layer remote from the substrate, which is typically exposed to the atmosphere.

The distribution may be determined, for example, by STEM-EDX or depth profiling. Thus, the distribution of elongated dense inorganic oxide particles in the coating can be determined, for example, by STEM-EDX or by depth profiling. This is particularly advantageous when the chemical composition of the dense inorganic oxide particles and the overall formulation are not the same.

In one aspect of the coating according to the invention, the mass ratio of inorganic oxide originating from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating is higher in or near the outer surface of the coating compared to the reference coating. A suitable reference coating may be one without elongated dense inorganic oxide particles.

It was found to be advantageous if the ratio at 20nm of the coating closest to the outer surface is higher than the average mass ratio of the inorganic oxide originating from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating. In one aspect, at 20nm of the coating nearest the outer surface, a ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to total inorganic oxide of the coating is at least 50% higher than an average ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to total inorganic oxide of the coating. In particular, it was found to be advantageous when the ratio at 20nm of the coating closest to the outer surface is higher than the average mass ratio of the inorganic oxide originating from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating. Preferably, the ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to total inorganic oxide of the coating is at least 50% higher than the average ratio of total inorganic oxide derived from the elongated dense inorganic oxide particles to the coating at 20nm of the coating closest to the outer surface, more preferably, the ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to total inorganic oxide of the coating is at least 2 times higher than the average ratio of total inorganic oxide derived from the elongated dense inorganic oxide particles to the coating at 20nm of the coating closest to the outer surface. It can be theorized, but not limited thereto, that the improved anti-fouling performance associated with such distribution of elongated dense inorganic oxide particles is related to the slight changes in surface morphology observed when the elongated dense inorganic oxide particles are disposed near or at the coating surface.

In one aspect, the coated substrate according to the invention exhibits a higher mass ratio of inorganic oxide originating from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating layer than the average mass ratio of inorganic oxide originating from the dense inorganic oxide particles to the total inorganic oxide of the coating layer in the top layer of the coating layer closest to the outer surface of the coated substrate, which is 20nm thick.

In one aspect, in the top layer of the coating, the mass ratio of inorganic oxide derived from the dense inorganic oxide particles to the total inorganic oxide of the coating is at least 50% higher than the average mass ratio of the total inorganic oxide derived from the elongated dense inorganic oxide particles to the coating.

In one aspect, in the top layer of the coating, the mass ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating is at least twice as high as the average mass ratio of inorganic oxide particles derived from the dense inorganic oxide to the total inorganic oxide of the coating.

The coatings according to the invention show improved antifouling properties. The improved anti-fouling performance may be demonstrated as an increased anti-fouling ratio (ASR), defined as follows:

where "T" is the average transmission of 380-1100nm as measured by a spectrophotometer, "substrate" refers to the substrate without the coating, "coating" refers to the substrate with a double-sided coating. "0" refers to the transmission measured before the contamination test and "contamination" refers to the transmission after the contamination test. 380-1100nm means herein the wavelength region of 380 to 1100nm, including 1100nm. In one aspect, "T" is the average transmission of 380-1100nm as measured by a Shimadzu UV2600 spectrophotometer. In one aspect, "T" is the average transmittance of 380-1100nm as measured by an Optosol Transpec VIS-NIR spectrophotometer. In one aspect, the coated substrate exhibits ASR of at least 50%. In one aspect, the coated substrate exhibits an ASR of at least 75%. In one aspect, the coated substrate exhibits an ASR of at least 80%. In one aspect, the coated substrate exhibits an ASR of at least 90%.

Contamination testing was performed as described in the experimental section.

Contamination testing may include:

a) Providing a substrate with a surface to be measured;

b) Cleaning a surface to be measured to obtain a clean surface;

c) Measuring the transmittance of the cleaned surface at 380-1100nm prior to contamination and determining an average transmittance (T0) in the range 380 to 1100 nm;

d) Soiling the surface to be tested with dust to obtain a dust-soiled surface;

e) Oscillating the substrate having the dusty surface;

f) Removing excess dust from the dust surface to obtain a contaminated surface; and

g) Measuring the transmittance of the contaminated surface after contamination at 380-1100nm (transmittance after contamination)

And the average transmission (T) in the range of 380-1100nm was measured _{Pollution (b) by} )。

The following values can thus be obtained:

t in step c) _{Base material, 0} : average transmission of 380-1100nm of the uncoated glass surface (uncoated substrate) before the contamination test;

t in step g) _{Substrate, contamination} : an average transmission of 380-1100nm of the uncoated glass surface after the contamination test;

t in step c) _{Coating layer, 0} : average transmission of 380-1100nm of the coated glass surface (double-sided coating) before the contamination test;

t in step g) _{Coating, contamination} : average transmission of 380-1100nm of the coated glass surface after the contamination test.

T _{Coating layer, 0} May also be referred to herein as T _{Coated substrate, 0} Or T _{Coated substrate with Al, 0} Or T _{Coated substrate without Al, 0} 。

T _{Coating, contamination} May also be referred to herein as T _{Coated substrates, contamination} Or T _{Coated substrates with Al, contamination} Or T _{Coated substrates without Al, contamination} 。

In step e) of the contamination test, the shaking may be carried out at a speed of 100 revolutions per minute for 300 cycles; one cycle is defined as one complete rotation of the circular drive disk: a full reciprocating motion of the Taber shaker table tray.

In step f) of the contamination test, excess dust can be removed by manually tapping the thin edge of the substrate (side of the glass plate) lightly on a hard surface (e.g. table top).

After removing the excess dust, the back surface (the front surface is a surface receiving incident light in the spectrophotometer) of the contaminated substrate (contaminated glass plate) can be cleaned by lightly wiping the back side surface with a soft cloth;

in one aspect, the cleaning comprises: clean with deionized water and soft cloth, rinse with laboratory grade ethanol and dry overnight.

Preferably, the cleaning is performed at a relative humidity of less than 40%.

Soil test (soil test and soil test) are used interchangeably herein.

Here, the average transmittance of 380-1100nm means an average transmittance value in a wavelength range of 380 to 1100nm.

In one aspect, the transmittance is measured using an Optosol Transpec VIS-NIR spectrophotometer.

In one aspect, the transmittance is measured using a Shimadzu UV2600 spectrophotometer.

In one aspect, contamination testing is performed using a Taber oscillatory wear tester (e.g., model 6160), particularly steps d) and e) above.

ASR indicates the extent to which the coating improves the stain resistance of the substrate. Thus, a 50% ASR means that the coating only loses half the transmission compared to the transmission loss of the bare substrate. The bare substrate here is a substrate without a coating, for example, a piece of uncoated glass. Preferably, the coated substrate-coated ASR is at least 75%, more preferably the substrate-coated ASR is at least 80%, and most preferably the substrate-coated ASR is at least 90%. ASR cannot be higher than 100% because this means better coating after fouling, so ASR should be 100% maximum.

In one aspect, the present invention provides a coated substrate, obtainable by the process for preparing a coated substrate according to the present invention, exhibiting improved anti-fouling performance.

In one aspect, the present invention provides a coated substrate comprising:

i. a substrate; and

wherein the antireflective coating comprises:

-0.5 to 15% by weight of an aluminium-containing compound, preferably 0.5 to 30% by weight of an aluminium-containing compound.

The weight percent alumina equivalent of the aluminum containing compound in the antireflective coating can be determined using STEM EDX. Or may be determined using ToF-SIMS.

In one aspect of the invention, the coating formulation comprises at least 0.5 wt.%, at least 1 wt.%, at least 1.5 wt.%, at least 2 wt.%, at least 3 wt.%, at least 4 wt.%, at least 5 wt.%, at least 6 wt.%, at least 10 wt.%, at least 12 wt.% of an aluminum oxide equivalent of the aluminum-containing compound.

In one aspect of the invention, the coating formulation comprises 15 wt.% or less, 14 wt.% or less, 13 wt.% or less, 2 wt.% or less, 11 wt.% or less, 10 wt.% or less, 9 wt.% or less, 8 wt.% or less of the aluminum oxide equivalent of the aluminum-containing compound.

The porous antireflective coating may also be referred to herein as a coating.

The substrate is a solid material, such as a polymer sheet or a glass member. The substrate may comprise quartz or a polymer foil, such as a glass foil. Examples of polymeric substrates are plastic foils and polymers based on one or more polymers selected from the group consisting of polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polyethylene naphthalate (PEN), polycarbonate (PC). Another example of a polymeric substrate includes Polyimide (PI). The polymer substrate is advantageous for flexible solar cells. Preferably, the substrate is transparent. In one aspect, the substrate has an average transmission of at least 80% in the range of 380-1100 nm.

Preferably, the substrate is a glass member selected from the group consisting of float glass, chemically strengthened float glass, borosilicate glass, structured glass, toughened glass and thin flexible glass (having a thickness in the range of, for example, 20 to 250 μm, for example 50 to 100 μm) and substrates comprising glass members, such as partially or fully assembled solar modules and assemblies comprising glass members. The glass member may be SM glass or MM glass. Commercially available MM glass includes interboat GMB SINA 3.2MM solar glass for photovoltaic applications.

In one aspect of the invention, the coated substrate is a cover glass for a solar module.

The invention also relates to a solar module comprising a coated substrate as described herein.

Solar modules typically comprise a glass member forming at least a portion of a first surface of a substrate and at least one member selected from the group consisting of thin film transparent conductive and/or semiconductive layers, a backsheet, a sealant, a conductive film, a solar cell, wiring, a controller box, and a frame. The glass member may be selected from float glass, chemically strengthened float glass, borosilicate glass, structured glass, toughened glass and thin flexible glass (having a thickness in the range of, for example, 20 to 250 μm, for example 50 to 100 μm). Preferred substrates for the process according to the invention are therefore tempered glass, chemically strengthened glass and substrates comprising temperature-sensitive elements, such as partially or fully assembled solar cell modules. In one embodiment, the substrate comprises a transparent solid panel member having a primer layer on a first side of the panel member such that the primer layer forms at least a portion of the first surface of the substrate to apply the single layer, non-laminate layer coating. Preferably, the base coat is selected from barrier coatings, such as sodium barrier coatings and anti-reflective coatings.

In one aspect, the coated substrate according to the present invention comprises a transparent solid plate member, and an undercoat layer interposed between the first surface and the coating on the first coating layer, preferably, the undercoat layer is selected from a barrier coating and an anti-reflective coating.

In one aspect, the substrate is a transparent solid plate member having a primer layer on a first side of the plate member, whereby the primer layer forms at least a portion of the first surface of the substrate. In one aspect, the substrate is a transparent solid plate member having a primer layer on a first side of the plate member, whereby the primer layer forms a first surface of the substrate.

The coating according to the invention is preferably an anti-reflective coating. In one aspect according to the invention, the coated substrate exhibits an ARE of at least 2%, at least 3%, at least 4%, at least 5%.

In one aspect, the coated substrates according to the invention exhibit a substrate-coating antireflection effect ARE, wherein

ARE＝T _{Coated substrate, 0} -T _{Base material, 0}

Is at least 2%, preferably ARE at least 3%, more preferably ARE at least 4%, wherein "T" is the average transmission in the wavelength range of 380-1100nm, "substrate" refers to a substrate without a coating, "coated substrate" refers to a substrate with a double-sided coating, and 0 refers to prior to the contamination test. In one aspect, T is an average transmission of 380-1100nm as measured by a Shimadzu UV2600 spectrophotometer. In one aspect, T is the average transmittance of 380-1100nm as measured by an Optosol Transpec VIS-NIR spectrophotometer.

The coating according to the invention is particularly suitable for reducing the reflectivity of a substrate, for example any type of glass substrate, and is therefore used as an anti-reflective coating.

Another aspect of the invention relates to a coating formulation comprising a porogen capable of forming pores with a diameter of 10-120nm, elongated dense inorganic oxide particles with an aspect ratio of at least 2 and a minor diameter in the range of 3 to 20nm, an inorganic binder, a solvent and 0.5 to 15 wt% of an aluminium containing compound in alumina equivalents. "aluminum" and "aluminum" are used interchangeably herein. In one aspect, the alumina equivalent of the aluminum-containing compound is based on the total ash residue after 2 minutes of combustion in air at 600 ℃. The aluminium may be provided, for example, as a metal oxide powder, but more preferably as an organic or inorganic salt, optionally in solution or suspension. In a preferred embodiment, the coating formulation comprises 1.0 to 15% by weight of aluminum oxide equivalent of the aluminum-containing compound, since the stability in terms of shelf life is found to be optimal at aluminum concentrations in this range. Stability refers to the stability of the product of the coating formulation. The stability of a coating formulation can be evaluated by observing the homogeneity of the coating formulation. Heterogeneous coating formulation products show low stability and low shelf life. The heterogeneity of a formulation can be directly observed by the presence of precipitates or gels in a liquid formulation, or can be measured by DLS (dynamic light scattering) by the growth or aggregation of colloidal particles in suspension over time. The use of non-uniform coating formulations often results in non-uniform coatings.

In a preferred embodiment, the coating formulation comprises from 2 to 10% by weight of aluminium-containing compound in terms of aluminium oxide equivalents, since it was found that it provides very good antifouling properties.

In one aspect, a coating formulation according to the present invention comprises:

i.2 to 18% by weight (based on inorganic oxide equivalents) of an inorganic substance having an aspect ratio of at least 2, an average minor diameter in the range 3 to 20nm (measured by TEM), and

a porogen capable of forming pores with a diameter in the range of 10-120nm,

an inorganic oxide binder, and

(iv) a solvent, wherein,

wherein the coating formulation comprises 0.5 to 15 wt.% of an aluminium-containing compound in an aluminium oxide equivalent based on the total ash residue after combustion in air at 600 ℃ for 2 minutes.

Porogens may be, for example, hollow inorganic oxide particles, or core-shell particles having an inorganic oxide (or inorganic oxide precursor) shell and a core comprising an organic compound (e.g., an organic compound having a boiling point less than 200 ℃ or a cationic polymer). The porogen may also be an organic porogen, such as an organic nanoparticle, e.g., an organic polymer nanoparticle, or another porogen that will typically decompose, burn, evaporate, or otherwise be removed during conversion of the coating formulation into a functional coating. Organic nanoparticles refer herein to particles comprising one or more organic molecules and having a size in the range of 50-150 nm. Examples of organic molecules are polymers, such as acrylic polymers and latexes; and an oligomer. Elongated dense inorganic oxide particles are discussed above.

In one aspect of the invention, a porogen comprises

Core-shell nanoparticles, wherein the core comprises an organic compound, for example an organic compound or a polymer with a boiling point below 200 ℃, and the shell comprises an inorganic oxide; and

-hollow inorganic nanoparticles.

In one aspect of the invention, a porogen comprises core-shell nanoparticles, where the core comprises an organic compound, such as an organic compound or polymer with a boiling point below 200 ℃, and the shell comprises an inorganic oxide.

In one aspect, the core-shell nanoparticles herein comprise

(a) A core material comprising a cationic polymer; and

(b) A shell material comprising an inorganic oxide.

In one aspect, the core-shell nanoparticles herein comprise

(a) A core material comprising a cationic polymer; and

(b) A shell material comprising silica.

In one aspect, the core material comprises a polymeric material (e.g., a homopolymer, a random copolymer, a block copolymer, etc.). In one aspect, the polymer is selected from the group consisting of polyesters, polyamides, polyurethanes, polystyrenes, poly (meth) acrylates, copolymers, and combinations thereof. In one aspect, the core comprises a poly (meth) acrylate. In one aspect, the polymer is selected from the group consisting of latex, diblock copolymer, triblock copolymer, and combinations thereof. In one aspect, the polymer is a cationic copolymer comprising a partially or fully quaternized amine functional vinyl monomer.

In one aspect, the core-shell nanoparticles herein comprise:

(a) A cationic core material comprising a latex; and

(b) A shell material comprising an inorganic oxide.

In one aspect, the core-shell nanoparticles herein comprise

(a) A cationic core material comprising a latex; and

(b) A shell material comprising silica.

As used herein, the term "latex" refers to a stable suspension of polymer particles. Preferably, the suspension is an emulsion. Preferably, the latex is cationic. The cationic groups may be incorporated into the polymer, or may be added in any other form, for example by addition of a cationic surfactant. In one aspect, the cationic group is at least partially bound to the polymer. In one aspect, the cationic groups are incorporated into the polymer during polymerization. In one aspect, the latex comprises a polymer and a cationic surfactant. In one aspect, the surfactant comprises an ammonium surfactant. Any suitable polymer may be used, such as homopolymers, random copolymers, block copolymers, diblock copolymers, triblock copolymers, and combinations thereof. The latex preferably comprises an aqueous cationic vinyl polymer. Preferably, the latex comprises a polymer comprising styrene monomers, (meth) acrylic monomers, copolymers thereof, or combinations thereof.

In one aspect, the porogen has an average particle size of 300nm or less, preferably 200nm or less, more preferably 150nm or less. In one aspect, the porogen has an average particle size of 100nm or less. In one aspect, the porogen has an average particle size of 1nm or more. Preferably, the average particle size of the porogen is 10nm or more. In one aspect, the porogen has an average particle size of 30nm or greater. The average particle size of the porogens can be measured by Dynamic Light Scattering (DLS). Alternatively, the size of the porogen can be measured using Transmission Electron Microscopy (TEM).

In one aspect, the average size of the porogens is g, where g =1/2 x (length + width), measured using TEM. In one aspect, g is 300nm or less. In one aspect, g is 200nm or less. In one aspect, g is 150nm or less. In one aspect, g is 100nm or less. In one aspect, g is 1nm or greater. In one aspect, g is 10nm or greater.

The core-shell nanoparticles herein generally have an average particle size of 300nm or less, preferably 200nm or less, more preferably 150nm or less. In one aspect, the nanoparticles have an average particle size of 100nm or less. The core-shell nanoparticles have an average size of 1nm or greater. Preferably, the core-shell nanoparticles have an average size of 10nm or greater. In one aspect, the core-shell nanoparticles have an average particle size of 30nm or greater. The average particle size can be measured by Dynamic Light Scattering (DLS). Alternatively, transmission Electron Microscopy (TEM) can be used to measure particle size.

In one aspect, the core-shell nanoparticles have an average size g, where g =1/2 x (length + width), as measured using TEM. In one aspect, g is 300nm or less. In one aspect, g is 200nm or less. In one aspect, g is 150nm or less. In one aspect, g is 100nm or less. In one aspect, g is 1nm or greater. In one aspect, g is 10nm or greater.

Preferably, the average size of the core-shell nanoparticle is 1nm or greater, more preferably 3nm or greater, and even more preferably 6nm or greater. Preferably, the average size of the cores is 100nm or less, more preferably 80nm or less, even more preferably 70nm or less. The size of the core can be measured using TEM.

In one aspect, the cores have an average size of 6nm or greater and 100nm or less as measured using TEM. In one aspect, the average size of the cores is 6nm or greater and 80nm or less as measured using TEM. In one aspect, the cores have an average size of 10nm or greater and 70nm or less as measured using TEM.

Preferably, the thickness of the shell of the core-shell nanoparticle is at least 1nm, more preferably at least 5nm, even more preferably at least 10nm. Preferably, the shell has a thickness of 75nm or less, more preferably 50nm or less, even more preferably 25nm or less. The thickness of the shell can be measured using TEM.

In one aspect, the shell has a thickness of 1nm or more and 50nm or less as measured using TEM. In one aspect, the shell has a thickness of 5nm or more and 25nm or less as measured using TEM. In one aspect, the shell has a thickness of 10nm or more and 25nm or less as measured using TEM.

In one aspect of the invention, the porogen comprises from 10 to 75 weight percent of the total amount of inorganic oxide equivalents in the coating formulation. In one aspect, the porogen comprises from 20 to 50 weight percent of the total amount of inorganic oxide equivalents in the coating formulation.

The inorganic binder typically comprises inorganic oxide particles having a diameter in the range of 0.1 to 7nm and/or inorganic oxide precursors having a diameter in the range of 0.1 to 7nm. The inorganic binder is preferably inorganic oxide particles or inorganic oxide precursors having a diameter of about 0.1 to 7nm.

It should be noted that the inorganic oxide particles may have a diameter greater than 7nm, for example, in the range of 7 to 10nm. It should be noted that the inorganic oxide precursor may have a diameter greater than 7nm, for example, in the range of 7 to 10nm.

In one aspect of the invention, the inorganic binder comprises inorganic oxide nanoparticles having an average diameter in the range of 0.1 to 7nm.

In one aspect, the inorganic binder typically comprises inorganic oxide particles having a diameter in the range of 0.1 to 5nm and/or inorganic oxide precursors having a diameter in the range of 0.1 to 5 nm.

The diameter of the inorganic oxide particles and/or inorganic oxide precursors can be measured by Dynamic Light Scattering (DLS). Examples are pre-oligomeric silicon alkoxides (silicon alkoxides), such as pre-oligomeric tetraethoxysilane, pre-oligomeric titanium alkoxides and metal oxide sols. Examples of inorganic oxide particles and/or inorganic oxide precursors include metal oxide sols. Pre-oligomerized silicon alkoxides (silicon alkoxides) are also known to the skilled worker as pre-oligomerized silicon alkoxides (silicon alkoxides). The inorganic binder may be prepared, for example, as described in WO2009/106456 (incorporated herein by reference).

The coating formulation according to the invention comprises a solvent. The solvent can be any solvent, combination of solvents, or combination of solvents and additives, such as surfactants and stabilizers, that can achieve stable dispersion of the coating formulation. Typically, the solvent comprises 80-98% of the mass of the coating formulation product. Very suitable solvents are Isopropanol (IPA), water or a combination of solvents comprising IPA and/or water.

The coating formulation according to the invention comprises elongated dense inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3-20nm for improving the anti-fouling performance of a substrate in a coating on the substrate. It is highly unexpected that the shape of the dense inorganic oxide particles seems to have a major influence on the anti-fouling properties of the coating, and thus the sensitivity of the substrate to fouling can be reduced by coating the substrate with a coating comprising elongated dense inorganic oxide particles. Coatings prepared from coating formulations comprising non-spherical particles (e.g., elongated particles, particularly elongated dense inorganic oxide particles) exhibit improved anti-fouling performance as compared to coatings prepared from coating formulations without elongated dense inorganic oxide particles. In one aspect, coatings prepared from coating formulations comprising non-spherical particles (e.g., elongated particles, particularly elongated dense inorganic oxide particles) exhibit improved anti-fouling performance compared to coatings prepared from coating formulations comprising spherical particles. In other words, the method of reducing the susceptibility of a substrate to contamination comprises the steps of: coating formulations containing elongated dense inorganic oxide particles are applied to a substrate, and the coating formulation is converted into a functional coating, such as by heating.

Another aspect of the invention relates to a solar module comprising a coated substrate according to the invention. Another aspect of the invention relates to a solar module comprising a coated substrate as described herein. The solar module shows significantly better performance at lower operating costs. The reason for this is that the cleaning frequency is reduced or the power output is increased at the same cleaning frequency, all of which may significantly reduce the fouling of the solar module due to the enhanced fouling resistance of the inventive coating. Other advantageous devices comprising the coated substrate according to the invention are greenhouse glasses (or polymer films), concentrating solar modules, windows, displays. In some applications, such as roof coatings or container surfaces, the substrate can be opaque and the advantages of the present invention are focused on the ability of the anti-smudge coating to reduce the collection of soil on the substrate or to enhance the cleanability of the coated substrate as compared to an uncoated substrate.

The coating formulation may be applied to the substrate by any technique known in the art, such as dipping, brushing, spraying, spin coating, slot die coating, aerosol coating, or by using a roller. The spray coating may be airless or applied using conventional air, or electrostatic, or high volume/low pressure (HVLP) or aerosol. Preferably, the coating formulation is applied by roll coating, aerosol coating or dip coating.

A functional coating refers to a coating that enhances the mechanical, optical, and/or electrical properties of a substrate to which the functional coating is attached. Examples of possible enhanced mechanical properties of a substrate coated with a coating according to the invention are increased surface hardness, increased stiffness or wear properties compared to the mechanical properties of an uncoated substrate. Examples of possible enhanced optical properties of substrates coated with the coatings of the present invention are increased light transmission from air through the functional coating and substrate compared to light transmission directly from air through the substrate, and decreased reflectance from air to the functional coating and functional coating to the substrate at the interface compared to reflectance directly from air to the uncoated substrate. An example of a possible enhanced electrical property of a substrate coated with a coating of the present invention is increased electrical conductivity compared to an unconverted coating and/or an uncoated substrate.

Another aspect of the invention relates to the use of a coating formulation comprising elongated inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter of 3-20nm for improving the stain resistance of a substrate. In particular, this embodiment relates to a coating formulation comprising core-shell nanoparticles as porogens, wherein the core comprises an organic compound, such as an organic compound having a boiling point below 200 ℃ or a cationic polymer, the shell comprises an inorganic oxide, and the coating formulation comprises 0.5 to 15 wt% of an aluminum-containing compound in alumina equivalents, based on the total ash residue burned in air at 600 ℃ for 2 minutes. Another aspect of the invention includes the use of a coating formulation as described herein to improve the stain resistance of a substrate, such as a cover glass for a solar module.

Another aspect of the invention includes the use of a coating formulation comprising elongated compact inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3-20nm for improving the stain resistance of a substrate, wherein the coating formulation comprises core-shell nanoparticles as porogens, wherein the core comprises an organic compound, such as an organic compound or polymer having a boiling point below 200 ℃, and the shell comprises an inorganic oxide; the formulation contains 0.5 to 15% by weight of an aluminium-containing compound in terms of alumina equivalents.

Another aspect of the invention includes the combination of:

-an aluminium-containing compound,

use to improve the stain resistance of a substrate.

Another aspect of the invention includes the use of elongated dense inorganic oxide particles having an aspect ratio of at least 2 and a smaller diameter in the range of 3-20nm to reduce contamination of solar modules.

Another aspect of the invention includes the combination of:

-an aluminium-containing compound,

to reduce contamination of the solar module.

Embodiments of the invention include the following:

1. a coating formulation comprising:

-2-18 wt.% (based on inorganic oxide equivalent) of elongated inorganic dense oxide particles having an aspect ratio of at least 2, an average minor diameter in the range of 3-20nm (measured by at least one TEM image), and

-a porogen capable of forming pores with a diameter in the range of 10-120 nm;

-an inorganic oxide binder; and

-a solvent, which is a mixture of water and a solvent,

2. The coating formulation according to any one of the preceding embodiments, wherein the amount of alumina equivalents of the aluminum-containing compound based on the total ash residue after 2 minutes of combustion in air at 600 ℃ is measured using ICP-MS.

3. The coating formulation according to any one of the preceding embodiments, wherein the elongated dense oxide particles comprise elongated silica particles having an average diameter of 3-20nm and an average length of 10-150nm, preferably as measured by at least one TEM image.

4. The coating formulation according to any one of the preceding embodiments, wherein the elongated dense oxide particles are elongated silica particles having an average diameter of 3-20nm and an average length of 10-150nm, preferably as measured by at least one TEM image.

5. The coating formulation according to any one of the preceding embodiments, wherein the elongated dense oxide particles comprise elongated silica particles having an average diameter of 2-20nm and an average length of 10-60nm, preferably as measured by at least one TEM image.

6. The coating formulation according to any one of the preceding embodiments, wherein the elongated dense oxide particles comprise elongated silica particles having an average diameter of 2-20nm and an average length of 10-40nm, preferably as measured by at least one TEM image.

7. The coating formulation according to any one of the preceding embodiments, wherein the elongated dense oxide particles are elongated silica particles having an average diameter of 2-20nm and an average length of 10-40nm, preferably measured by at least one TEM image.

8. The coating formulation according to any one of the preceding embodiments, wherein the elongated dense oxide particles comprise elongated silica particles having an average diameter of 4-15nm and an average length of 40-100nm, preferably as measured by at least one TEM image.

9. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 14 weight percent alumina equivalent of the aluminum-containing compound.

10. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 13 weight percent alumina equivalent of the aluminum-containing compound.

11. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 12 weight percent alumina equivalent of the aluminum-containing compound.

12. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 11 weight percent alumina equivalent of the aluminum-containing compound.

13. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 10 weight percent alumina equivalent of the aluminum-containing compound.

14. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 9 wt.% of the aluminum-containing compound in an alumina equivalent.

15. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1 to 8 weight percent alumina equivalent of the aluminum-containing compound.

16. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 1.5 to 12 weight percent aluminum oxide equivalent of the aluminum-containing compound.

17. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 1.5 to 10 weight percent aluminum oxide equivalent of the aluminum-containing compound.

18. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 1.5 to 9 weight percent aluminum oxide equivalent of the aluminum-containing compound.

19. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 1.5 to 8 weight percent aluminum oxide equivalent of the aluminum-containing compound.

20. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 2 to 10 weight percent aluminum oxide equivalent of the aluminum-containing compound.

21. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 2 to 9 wt.% of the aluminum-containing compound in an alumina equivalent.

22. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises from 2 to 8 weight percent alumina equivalent of the aluminum-containing compound.

23. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 2 to 15 wt% of elongated inorganic dense oxide particles based on oxide equivalents of inorganic.

24. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 2 to 14 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic.

25. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 2 to 13 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

26. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 2 to 12wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

27. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 3 to 15 wt% of elongated inorganic dense oxide particles based on oxide equivalents of inorganic material.

28. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 3 to 14 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic.

29. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 3 to 13 wt% of elongated inorganic dense oxide particles, based on the oxide equivalents of the inorganic.

30. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 3 to 12wt% of elongated inorganic dense oxide particles based on oxide equivalents of inorganic.

31. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 4 to 15 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

32. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 4 to 14 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

33. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 4 to 13 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

34. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 4 to 12wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

35. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 5 to 15 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

36. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 5 to 14 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic.

37. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 5 to 13 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

38. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 5 to 12wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

39. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 6 to 14 wt% of elongated inorganic dense oxide particles, based on oxide equivalents of inorganic material.

40. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 6 to 13 wt% of elongated inorganic dense oxide particles, based on the oxide equivalent of the inorganic.

41. The coating formulation according to any one of the preceding embodiments, wherein the coating formulation comprises 6 to 12wt% of elongated inorganic dense oxide particles based on oxide equivalents of inorganic material.

42. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises core-shell nanoparticles, wherein the core comprises an organic compound and the shell comprises an inorganic oxide.

43. The coating formulation according to any one of the preceding embodiments, wherein the organic compound comprises a polymer, preferably a cationic polymer.

44. The coating formulation according to any one of the preceding embodiments, wherein the organic compound has a boiling point of less than 200 ℃.

45. The coating formulation according to any one of the preceding embodiments, wherein the organic compound comprises a cationic polymer.

46. The coating formulation according to any one of the preceding embodiments, wherein the cationic polymer comprises a poly (meth) acrylate and/or a copolymer thereof.

47. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises cationically stabilized copolymer micelles.

48. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises a cationically stabilized di-block or tri-block copolymer.

49. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises a latex.

50. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises a cationically stabilized latex.

51. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises hollow inorganic particles, such as hollow silica particles.

52. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises a block copolymer obtained from ethylene oxide and propylene oxide.

53. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises a tri-block copolymer comprising polyethylene oxide (PEO) and polypropylene oxide (PPO).

54. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises core-shell nanoparticles and hollow inorganic nanoparticles, wherein the core comprises an organic compound, such as an organic compound having a boiling point below 200 ℃ or a cationic polymer, and the shell comprises an inorganic oxide.

55. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises from 10 to 75 weight percent of the total inorganic oxides in the coating formulation.

56. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises 18 to 50 weight percent of the total inorganic oxides in the coating formulation.

57. The coating formulation according to any one of the preceding embodiments, wherein the porogen comprises 18 to 40 weight percent of the total inorganic oxide in the coating formulation.

58. The coating formulation according to any one of the preceding embodiments, wherein the inorganic binder comprises inorganic oxide nanoparticles having a number average diameter in the range of 0.1 to 7nm.

59. The coating formulation according to any one of the preceding embodiments, wherein the porogen has an average size measured using DLS of 20-150 nm.

60. The coating formulation according to any one of the preceding embodiments, wherein the porogens have an average size of 20-120nm as measured using DLS.

61. A method of preparing a coated substrate comprising the steps of:

-providing a substrate;

-providing a coating formulation according to any one of the preceding embodiments;

-applying the coating formulation to a substrate;

-drying the coating formulation applied on the substrate; and is

-converting the coating formulation on the substrate into a coated substrate.

62. A method of preparing a coated substrate comprising the steps of:

a. providing a substrate having a first surface;

b. providing a coating formulation according to any one of the preceding embodiments;

c. applying a coating formulation to a first surface of a substrate;

d. drying the applied coating formulation; and is

e. The substrate with the dried coating formulation is converted to a coated substrate comprising a coating on a first surface, for example by heating to above 400 degrees celsius.

63. A coated substrate obtainable by the method of any one of the preceding embodiments.

64. A coated substrate obtainable by the process of any one of the preceding embodiments, which exhibits improved anti-fouling performance.

65. A coated substrate comprising:

i. a substrate; and

wherein the antireflective coating comprises:

-pores with a diameter in the range of 10-120nm, preferably 30-100 nm; and

-elongated dense inorganic oxide particles having an aspect ratio of at least 2 and a minor diameter in the range of 3-20nm as measured by at least one TEM image; and

-0.5 to 15% by weight of aluminium oxide equivalent of an aluminium-containing compound.

66. The coated substrate according to any one of the preceding embodiments, wherein the substrate comprises a transparent solid plate member, and a primer layer interposed between the first surface and the coating on the first surface, preferably the primer layer is selected from a barrier coating and an anti-reflective coating.

67. The coated substrate according to any one of the preceding embodiments, wherein the substrate is a polymer sheet or a glass member, preferably the glass member comprises a structured glass, such as MM or SM glass.

68. The coated substrate according to any one of the preceding embodiments, wherein the substrate comprises a transparent solid plate member having an undercoat layer on a first face of the plate member, whereby the undercoat layer forms at least a portion of the first surface of the substrate, preferably the undercoat layer is selected from a barrier coating and an anti-reflective coating.

69. The coated substrate according to any one of the preceding embodiments, wherein at 20nm of the coating closest to the outer surface of the coated substrate, the mass ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to total inorganic oxide of the coating is higher than the average mass ratio of inorganic oxide derived from the dense inorganic oxide particles to total inorganic oxide of the coating,

preferably, the mass ratio of inorganic oxide derived from the dense inorganic oxide particles to the total inorganic oxide of the coating is at least 50% higher than the average mass ratio of inorganic oxide derived from the dense inorganic oxide particles to the total inorganic oxide of the coating at 20nm of the coating closest to the outer surface,

more preferably, the mass ratio of inorganic oxide derived from the dense inorganic oxide particles to total inorganic oxide of the coating is at least 2 times higher than the average mass ratio of the dense inorganic oxide particles to total inorganic oxide of the coating at 20nm of the coating closest to the outer surface.

70. The coated substrate according to any of the preceding embodiments, wherein the substrate exhibits a substrate-to-coating anti-contamination ratio ASR,

at least 55%, wherein "T" is an average transmission of 380 to 1100nm, "substrate" refers to a substrate without a coating, "coating" refers to a substrate with a double-sided coating, "0" refers to before the contamination test, "contamination" refers to after the contamination test.

71. A coated substrate according to any of the preceding embodiments, said substrate exhibiting a substrate-to-coating anti-contamination ratio, ASR, of at least 60%.

72. A coated substrate according to any one of the preceding embodiments exhibiting a substrate-to-coating anti-contamination ratio ASR of at least 65%.

73. The coated substrate according to any of the preceding embodiments, which substrate exhibits a substrate-to-coating anti-contamination ratio, ASR, of at least 70%.

74. A coated substrate according to any one of the preceding embodiments exhibiting a substrate-to-coating anti-contamination ratio ASR of at least 75%.

75. A coated substrate according to any one of the preceding embodiments exhibiting a substrate-to-coating anti-contamination ratio ASR of at least 80%.

76. A coated substrate according to any of the preceding embodiments, said substrate exhibiting a substrate-to-coating anti-contamination ratio, ASR, of at least 85%.

77. A coated substrate according to any one of the preceding embodiments exhibiting a substrate-to-coating anti-contamination ratio ASR of at least 90%.

78. The coated substrate according to any one of the preceding embodiments, wherein the coated substrate exhibits a substrate-coating antireflective effect ARE,

ARE＝T _{coated substrate, 0} -T _{Base material, 0}

At least 2%, preferably at least 3% ARE, more preferably at least 4% ARE, wherein "T" is the average transmission of 380 to 1100nm, "substrate" refers to the substrate without coating, "coated substrate" refers to the substrate with double-sided coating, "0" refers to before the soiling test.

79. The coated substrate according to any one of the preceding embodiments, wherein the coated substrate exhibits a substrate-coating antireflective effect, ARE, of at least 3%.

80. The coated substrate according to any one of the preceding embodiments, wherein the coated substrate exhibits a substrate-coating antireflective effect, ARE, of at least 4%.

81. The coated substrate according to any one of the preceding embodiments, wherein the coated substrate exhibits a substrate-coating antireflective effect, ARE, of at least 5%.

82. A coated substrate according to any one of the preceding embodiments, wherein in the top layer of 20nm thickness of the coating layer closest to the outer surface of the coated substrate the mass ratio of inorganic oxide originating from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating layer is higher than the average mass ratio of inorganic oxide originating from the dense inorganic oxide particles to the total inorganic oxide of the coating layer,

preferably, the mass ratio of inorganic oxide derived from the dense inorganic oxide particles to the total inorganic oxide of the coating layer in the top layer of the coating layer is at least 50% higher than the average mass ratio of inorganic oxide derived from the elongated dense inorganic oxide particles to the total inorganic oxide of the coating layer,

more preferably, the mass ratio of inorganic oxide derived from the elongated dense elongated inorganic oxide particles to the total inorganic oxide of the coating in the top layer of the coating is at least 2 times higher than the average mass ratio of inorganic oxide derived from the dense inorganic oxide particles to the total inorganic oxide of the coating.

83. The coated substrate according to any one of the preceding embodiments, wherein the substrate is a cover glass for a solar module.

84. A solar module comprising the coated substrate according to any of the preceding embodiments.

85. Use of a composition according to any of the preceding embodiments to reduce the frequency of cleaning of a substrate, preferably glass.

86. Use of a composition according to any of the preceding embodiments to improve the stain resistance of a substrate, preferably glass.

87. Use of a composition according to any one of the preceding embodiments for reducing the cleaning frequency of a cover glass of a solar module.

88. Use of a composition according to any one of the preceding embodiments for reducing the cleaning frequency of a cover glass of a solar module.

Testing

Optical measuring method

The optical properties were measured in the wavelength range 380-1100nm using an Optosol Transpec VIS-NIR spectrophotometer equipped with an integrating sphere. The average transmission and the maximum T% (at maximum λ) were determined. The results are listed below.

Pollution measuring method

And (3) pollution procedure: the antifouling properties of the coatings were tested by means of a Taber oscillatory wear tester (model 6160) using commercial Arizona test dust of quartz A4 roughness (varying in size from 1 to 200 μm), commercially available from KSL Staubtechnik GMBH, as fouling medium. The 100X 100mm glass plate to be tested was first washed with deionized water and soft cloth, rinsed with laboratory grade ethanol and left to dry overnight. The coated sample was then placed in the tray of a Taber shaker table so that the top surface of the glass plate was at the same height as the sample holder within the tray. Next, 20g of Arizona test dust was gently dispersed over the glass plate using a brush. The contamination procedure (300 cycles at a rate of 100 cycles per minute; one cycle is defined as one complete rotation of the circular drive disc: one complete reciprocation of the tray). The test sample is then removed from the tray and gently tapped to remove excess sand on its surface. The back of the test glass plate was lightly wiped with a soft cloth to remove any dust adhering under the plate. Relative humidity in the test environment was 36% RH, temperature was 21 ℃.

And (3) pollution evaluation: the degree of contamination of the coating was determined by the relative loss of transmission after contamination, measured with an Optosol Transpec VIS-NIR spectrophotometer. For this purpose, transmission spectra were recorded before and after artificial contamination by means of the Taber oscillatory wear test. Subsequently, the average transmission of the spectrum between 380-1100nm is established. Based on the resulting difference between the previous and subsequent values of the average transmission between 380-1100nm recorded in the spectrum, conclusions can be drawn about the contamination level and thus the effectiveness of the anti-soiling coating.

Method for determining inorganic oxide composition

The cured sample was scraped from the substrate with a razor blade. The scrapings were rinsed from the substrate with ethanol and collected. A drop of the ethanol suspension was transferred to a carbon mesh and dried before the elemental composition was determined by STEM EDX on shavings arranged on the edges of the carbon mesh. At least the components Si, O and Al were measured and quantified by means of the software Esprit 1.9.

Method for determining pore size

The pore diameter of the porogen pores, i.e. pores with a diameter in the range of 10-120nm, is defined as the length of the line representing the longest distance between the walls of the pores in a cross-section perpendicular to the substrate surface, measured by SEM. For irregular holes, the line representing the longest distance may reach outside the hole. As is well known, SEM stands for scanning electron microscope.

For binder pores having a pore size of 1 to 10nm, the pore size was measured by ellipsometry using the methods described herein. Since the method utilizes the adsorption of water in the pores, the measured dimensions correspond to the smallest diameter of the pores.

Method for determining particle size

The size of the binder particles and the size of the elongated dense inorganic particles were measured using CryoTEM. The average size is based on the number average size of 10 randomly selected particles.

Ellipsometry

The volume fraction of the binder pores and the pore size distribution were determined by water adsorption under a change in the relative partial pressure of water. In the pore size range in the 2-50nm range, the saturation pressure (and hence the condensation/evaporation of water in the pores) is a function of the minimum size of the pores described by the kelvin equation. Due to the density difference between water and air, the condensation of water in the pores greatly changes the optical properties of the coating, which are measured by ellipsometry.

Sample preparation depends on the type of substrate. For float glass, a transparent tape is applied to the back of the glass to reduce back reflection. For SM glass, measurements were made using a focusing probe to reduce light scattering caused by sample roughness. In the case of SM glass, no scotch tape was applied to the back.

The ellipsometer used was Woollam M-2000UI running complete Ease (Woollam) version 5.20. Typically, the refractive indices herein are reported at an optical wavelength of 600 nm.

Data analysis/modeling method

Experimental data were analyzed by fitting an optical model constructed using CompleteEase. The bare uncoated substrate was first measured and then fitted using a b-spline model. The coating was described by the Cauchy model using the first two items A and B of the series development. For the evaluation of the model, the data measured at 35% rh were used.

Examples

Example 1: preparation of core-shell particle solutions

The core-shell particles were prepared by the same method disclosed in WO2009/030703 with isopropanol instead of ethanol. The solution was further diluted with isopropanol to a concentration of 10.0 wt.% silica equivalent and had a particle size of 135 nm.

Example 2: preparation of inorganic Binders

The silica-based inorganic binder prepared from tetraethoxysilane is prepared by the same method as disclosed in WO2011/157820 and further diluted with isopropanol to obtain a binder solution of about 2wt% silica equivalent and 3-5nm particle size.

Example 3: preparation of stock solutions

By mixing Al (NO) ₃ ) ₃ ·9H ₂ Al-Stock solutions were prepared by dissolving O (Fluka, 06275Lot SZBG0830V) in a mixture of isopropanol (Brenntag, lot I/103/3ju 15/13333, ref 2427801) and methoxypropanol (Sigma Aldrich, lot K49958738820) to a solids content of 5%. The solution was then further diluted with isopropanol to 2 wt.% alumina equivalent.

Stock solutions of elongated IPA-ST-UP particles were prepared by diluting IPA-ST-UP (Nissan Chemical, lot 111002) with isopropanol to a concentration of 2 wt.% oxide equivalents. This stock solution was used to prepare the samples in table 1.

Example 4: preparation of coating formulation products

All formulations were prepared in 500ml translucent HDPE bottles with caps. The amounts of the components are shown in table 1. The weighed core-shell solution and 2-propanol were added and the bottle was shaken. To this mixture was added the inorganic binder and the bottle was shaken. Then the diluted Al stock solution is added and finally the stock solution of elongated particles. The amounts of the components are shown in table 6.

Example 5: sample coating

Coatings were prepared with the coating formulation used for up to 48 hours. All samples were contaminated within 48 hours after the coating was prepared. The formula was filled into a rectangular container having inner dimensions of 2.5X 11 cm. Approximately 200g of the coating formulation was filled.

The glass used was a 10X 10cm sheet cut from 3.2mm Pilkington Optiwhite S float glass. The panels were washed and dried prior to application of the coating. The dipping conditions are as follows: 18.5-21.4 ℃; relative humidity <20% rh; the impregnation speed was varied between 4 and 5mm/s, as shown in Table 1. The immersion speed was set such that an optical thickness of about 600nm was obtained.

Table 1:

example 6: converting a coated coating formulation into a functional coating

The coated samples listed in table 1 were dried at room temperature for at least 15 minutes and then cured by heating in an oven at 650 ℃ for 3 minutes. This process is similar to the thermal conversion achieved during the tempering process of cover glasses typically used in PV solar modules. The results of the optical measurements are shown in Table 2.

Examples of transmittance measurements for sample A2 before and after contamination are shown in fig. 1. Contamination was observed to significantly reduce the transmission. In fig. 2, the transmittance measurement of sample E according to the invention is shown. Here, the transmittance before and after contamination is very close.

It was observed that for coating formulations containing core-shell particles and inorganic binder, a stable coating formulation was obtained, resulting in a uniform coating, whereas the same coating formulation became unstable when elongated particles were added, resulting in an uneven coating and the coating formulation starting to settle within a few days. When the formulation further contains an aluminum species, the resulting coating formulation is stable and the resulting coating exhibits anti-reflective and anti-fouling properties.

TABLE 2

0 (comparative) denotes uncoated glass

* AS loss is the transmission loss after contamination on the same plate, T _{Before pollution} Minus T _{After pollution} (380-1100 nm based on the average T%).

% IPA-ST-UP is the weight% inorganic oxide equivalent weight from IPA-ST-UP particles compared to the total amount of silica in the coating formulation: m (IPA-ST-UP)/m (SiO) ₂ ) 100= wt.% IPA-ST-UP

% Al2O3 is weight% based on alumina equivalents compared to the total amount of inorganic oxides in the coating formulation: m (Al 2O 3)/(m (Al 2O 3) + m (SiO 2)). 100= wt% Al2O3, m being the grams used.

Claims

1. A coating formulation comprising:

6 to 13 wt% of elongated dense inorganic oxide particles based on oxide equivalents of inorganic material, said particles having an aspect ratio of at least 2 and an average smaller diameter in the range of 3 to 20nm, as measured by at least one TEM image,

a porogen capable of forming pores with diameters in the range of 10-120nm, wherein the porogen comprises core-shell nanoparticles, wherein the core comprises an organic compound and the shell comprises an inorganic oxide, and wherein the porogen comprises 10 to 75 weight percent of the total amount of inorganic oxides in the coating formulation,

an inorganic oxide binder, and

a solvent, a water-soluble organic solvent,

wherein the coating formulation comprises 0.5 to 15% alumina equivalent of an aluminium containing compound as determined by ICP-MS, based on total ash residue after 2 minutes of combustion in air at 600 ℃.

2. The coating formulation of claim 1, wherein the coating formulation comprises 6-12 wt% elongated dense inorganic oxide particles based on the oxide equivalent weight of the inorganic substance.

3. The coating formulation according to claim 1 or 2, wherein the elongated dense inorganic oxide particles comprise elongated silica particles having an average diameter of 3-20nm and an average length of 10-150nm, as measured by TEM.

4. The coating formulation of claim 1 or 2, wherein the organic compound comprises a cationic polymer.

5. The coating formulation of claim 4, wherein the cationic polymer comprises a poly (meth) acrylate and/or a copolymer thereof.

6. The coating formulation of claim 1 or 2, wherein the porogen comprises 18 to 50 weight percent of a total amount of inorganic oxides in the coating formulation.

7. The coating formulation of claim 1 or 2, wherein the porogen comprises 18 to 40 weight percent of the total amount of inorganic oxides in the coating formulation.

8. The coating formulation of claim 1 or 2, wherein the porogen comprises from 20 to 50 wt% of a total amount of inorganic oxides in the coating formulation.

9. The coating formulation of claim 1 or 2, wherein the coating formulation comprises 1 to 10% aluminum oxide equivalent of the aluminum-containing compound.

10. The coating formulation of claim 1 or 2, wherein the inorganic binder comprises inorganic oxide nanoparticles having a number average diameter in the range of 0.1 to 7nm.

11. A method of preparing a coated substrate comprising the steps of:

-providing a substrate;

-providing a coating formulation according to any one of claims 1 to 10;

-applying a coating formulation on said substrate;

-drying the coating formulation on the substrate; and is

-converting the coating formulation on the substrate into a coated substrate.

12. A coated substrate obtainable by the process of claim 11.

13. A coated substrate comprising:

a substrate; and

a porous antireflective coating disposed on at least a portion of a substrate, wherein the antireflective coating is formed from the coating formulation of any one of claims 1 to 10,

wherein the antireflective coating comprises:

pores with a diameter in the range of 10-120nm, measured by SEM; and

-0.5 to 15% by weight of alumina equivalent of an aluminium-containing compound, determined by ToF-SIMS.

14. The coated substrate of claim 13, wherein the antireflective coating comprises pores having diameters in the range of 30-100 nm.

15. The coated substrate of any one of claims 12-14, wherein the substrate exhibits a substrate-to-coating anti-contamination ratio (ASR),

at least 80%, wherein "T" is the average transmission in the wavelength range of 380-1100nm, "substrate" refers to the substrate without the coating, "coating" refers to the substrate with the double-sided coating, "0" refers to before the soiling test, and "soiling" refers to after the soiling test.

16. The coated substrate according to any one of claims 12 to 14, wherein the coated substrate has a substrate-coating antireflection effect ARE,

at least 4%, wherein "T" is the average transmission in the wavelength range of 380-1100nm, "substrate" refers to the substrate without the coating, "coated substrate" refers to the substrate with the double-sided coating, "0" refers to before the contamination test.

17. A coated substrate according to claim 16, wherein the ARE is at least 5%.

18. The coated substrate of any one of claims 12-14, wherein the substrate is a cover glass for a solar module.

19. A solar module comprising a coated substrate according to any one of claims 12 to 18.

20. Use of a coating formulation according to any one of claims 1 to 10 for improving the stain resistance of a substrate.

21. The use of claim 20, wherein the substrate is glass.

22. Use according to claim 20 or 21, wherein the substrate is a cover glass for a solar module.