DE102013009881B3 - Process for the preparation of an SiO 2 antireflective coating, SiO 2 antireflective coated substrate and its use - Google Patents

Abstract

Process for producing an SiO2 anti-reflective coating on a substrate, in particular a glass substrate, comprising producing an SiO2 coating precursor formulation, comprising a solution of metal salts and silica or silica sol or silane, solvent, water and thickening agent, applying the SiO2 coating precursor formulation to the substrate by screen printing , Roller coating or dipping, drying the SiO2 coating precursor formulation at a temperature in a range of 110-150 ° C for 5-15 minutes and baking the SiO2 coating precursor formulation at a temperature between 570-700 ° C for 1-5 minutes, the Metal salts are selected from the group consisting of elements of the first and second main group of the periodic table in the form of soluble salts and of MnO, ZnO, TiO2 in the form of soluble salts, the metal salts in an amount of 0.1 to 10 wt. %, and SiO2 from silica or silica sol or silane in an amount from 0.1 to 10% by weight, based on the total content of the SiO2 coating precursor formulation, are present, the metal oxides formed from the metal salts during the firing of the SiO2 coating precursor formulation effecting densification of the SiO2 anti-reflective coating.

Description

The present invention relates to mineralizer-containing SiO ₂ anti-reflection coatings and to processes for their preparation. In particular, the present invention relates to a novel process with which it is possible to prepare mineralizer-containing SiO ₂ antireflection coatings in a simple way, wherein the SiO ₂ antireflection coatings are selectively adjustable in their density, refractive index, mechanical strength and chemical resistance.

There are several approaches to reducing the reflection of light on glass surfaces. On the one hand, the application of a nanoporous layer to glass surfaces is known, which in addition to a self-cleaning effect (lotus effect) should also have a reflection-reducing effect. On the other hand, the application of antireflective (AR) coatings on glass surfaces is known. Furthermore, the principle of interference for glass antireflection is applied, with multiple layers of different refractive index being applied. Another surface treatment for anti-reflection of the glass is the etching. However, this is usually associated with the use of environmentally harmful substances such as hydrofluoric acid, which is disadvantageous.

There are numerous documents in the prior art which describe processes for the production of reflection-reducing coatings and reflection-reducing coatings.

The DE 10 2005 007 825 A1 describes a method for producing a reflection-reducing coating on a transparent substrate, in which at least one layer containing silicon, oxygen, carbon and hydrogen is deposited on at least one side of the substrate and subsequently reduces the carbon and hydrogen content in this at least one layer becomes. Deposition of the at least one layer containing silicon, oxygen, carbon, and hydrogen on the substrate may be accomplished by a PVD process, a CVD process, or a combination of both.

The DE 100 51 724 A1 describes a thermally cured, provided with an abrasion-resistant porous and sinter-stable SiO ₂ layer safety glass, wherein the SiO ₂ layer has a refractive index in the range of 1.25 to 1.40. This safety glass is obtained by coating a conventional soda-lime glass with an aqueous coating solution having a pH of from 3 to 8, containing 0.5-5.0 wt% of [SiO _x (OH) _y ] _n particles wherein 0 <y <4 and 0 <x <2, with a particle size of 10 to 60 nm and a surfactant mixture, drying the coated glass and thermal curing by heating to temperatures of at least 600 ° C for several minutes followed by thermal quenching of the coated glass by blowing off with air. The coating is applied by dipping method, spraying method or spin coating method, the dipping method being preferred.

The DE 1 941 191 A1 describes a process for producing transparent glassy crystalline or glassy-crystalline, inorganic multi-component materials, preferably in thin layers, without passing through a melt phase, wherein elements of the main groups I to III of the Periodic Table of the Elements are dissolved in solution in addition to other reactive metal compounds and reacted together in solution become. The solvent is then evaporated and heated well below the melting point or melting range of the multicomponent material to remove any volatile components. The layers are applied by dipping.

The DE 102 09 949 A1 describes a glass body for solar thermal energy, which contains a boron-containing glass tube, that at least on one of the sides inside or outside a porous SiO ₂ and phosphorus-containing layer on glass with boric oxide content. Also, the production of the glass body is described, wherein the glass body is immersed in a H ₃ PO ₄ and SiO ₂ -containing volatile solution.

The DE 10 2008 006 785 B3 describes a method for producing a porous SiO ₂ -containing antireflection layer on a borosilicate glass body, wherein the body to be coated is wetted with a coating solution and then the coating is dried and fired. The wetting of the coated body with the coating solution is carried out by immersion in the coating solution.

The DE 10 2007 058 927 A1 describes a substrate having a sol-gel layer and a method for producing a composite material, wherein an SiO ₂ barrier layer is disposed between the sol-gel layer containing Al ₂ O ₃ as a curing agent and the substrate.

The WO 2005/049757 A1 describes a method of forming an SiO ₂ film on a substrate, comprising coating a glass with a silicic acid solution and curing the silicic acid solution on the substrate in an ammoniacal environment.

US 2010/0269901 A1 describes a method for producing a scratch-resistant antireflection coating by the sol-gel method by means of of a silica sol and additions of metal oxide sols such as Al ₂ O ₃ .SiO ₂ , MgAl ₂ O ₄ , ZrO ₂ , Al ₂ O ₃ , CaAl ₂ Si ₂ O ₈ .

WO 00/10934 A1 discloses a process for preparing an antireflective coating with metal oxide sols, silica sols, and a catalytic amount of aluminum acetylacetonate. Onto this cured coating is further applied a hydrophobic coating composition comprising an amorphous fluoropolymer, a perfluoroalkylorganosilane, a hydrolyzable silane or siloxane and a perfluorinated solvent, and the coating is cured.

In the DE 689 12 240 T2 For example, there is disclosed a method of making an optical viewing screen having a glossy or shimmer reducing viewer surface. In this case, a surface of a heated glass substrate is coated with an aqueous solution containing a lithium-stabilized silicate sol.

In the TW 000201020313 A The preparation of a manganese-activated zinc silicate film using the sol-gel technology is described. A multilayer structure mainly composed of transparent sol containing zinc chloride salts, silicon ethoxide and a manganese activator is formed on a plate. After a heat treatment with reducing gas, a monophasic zinc silicate film is obtained.

The WO 2005/115151 A1 describes a functional sol-gel coating agent comprising a nanoparticulate additive characterized by an antimicrobial function, using as antimicrobial component a nanoparticulate metal such as silver, copper, zinc and mixtures thereof.

In CN 000101870475 A discloses a process for the low temperature synthesis of zirconium silicate powder by non-hydrolytic sol-gel reaction using zirconium acetate as a zirconium source.

CN 000102180660 A describes a process for the preparation of magnesium manganese silicate nanopowders by means of a sol-gel process.

The DE 102 42 980 A1 describes a process for the replacement of organic and / or inorganic by-products of aqueous metal oxide and / or silicate sols by means of a dial filtration device, wherein the metal oxide and / or silicate sol an aqueous solution is added, which contains one or more exchange substances, against which By-products are to be exchanged and at the same time the dissolved by-products are removed from the metal oxide and / or silicate sol via a permeable membrane and wherein the membrane permeating permeate is discharged from the process, wherein the membrane is such that the colloidal components of the Metal oxide and / or silicate sols are retained by the membrane.

The US 8 003 194 B2 describes an antireflective coated touch screen comprising inorganic oxide particles forming surface structures in the range of greater than 2 microns to about 100 microns in a cured inorganic polymer matrix.

The JP 2001-278637 A describes a coating with a low reflection coefficient consisting of SiO ₂ particles and binder in a weight ratio of 60: 40-95: 5. As binders hydrolyzable metal compounds of Si, Al, Ti, Zr and Ta are given. The SiO ₂ granules are a mixture of non-aggregated SiO ₂ granules having an average grain diameter of 40-1000 nm and aggregated SiO ₂ particles having an average primary diameter of 10-100 nm.

The JP S57 100943 A discloses a durable SiO ₂ coating. In preparing this coating, a zirconium compound (eg, zirconium dichloride or zirconium tetranitrate) is added to an organic silicon compound (eg, ethyl silicate). The solution is then applied to the surface of a substrate and fired.

The object of the present invention is to provide a practical method for producing a SiO ₂ antireflection coating on a substrate, with which the density, the refractive index, the mechanical hardness and the chemical resistance of the SiO ₂ antireflection coating can be selectively adjusted.

This is inventively achieved by a method according to claim 1.

• – Herstellen einer SiO₂-Beschichtungsvorläuferformulierung, umfassend eine Lösung aus Metallsalzen und Kieselsäure oder Kieselsol oder Silan, Lösemittel, Wasser und Verdickungsmittel,
• – Auftragen der SiO₂-Beschichtungsvorläuferformulierung auf das Substrat mittels Siebdruck, Rollercoating oder Tauchen,
• – Trocknen der SiO₂-Beschichtungsvorläuferformulierung bei einer Temperatur in einem Bereich von 110–150°C für 5–15 Minuten und
• – Brennen der SiO₂-Beschichtungsvorläuferformulierung bei einer Temperatur zwischen 570–700°C für 1–5 Minuten,
• – wobei die Metallsalze aus der Gruppe ausgewählt werden, die aus Elementen der ersten und zweiten Hauptgruppe des Periodensystems in Form löslicher Salze besteht und aus MnO, ZnO, TiO₂ in Form löslicher Salze besteht,
• – wobei die Metallsalze in einer Menge von 0,1 bis 10 Gew.-%, und SiO₂ aus Kieselsäure oder Kieselsol oder Silan in einer Menge von 0,1 bis 10 Gew.-%, bezogen auf den Gesamtgehalt der SiO₂-Beschichtungsvorläuferformulierung, vorhanden sind.

The method for producing a SiO ₂ anti-reflection coating on a substrate, in particular a glass substrate, comprises

• Preparing an SiO ₂ coating precursor formulation comprising a solution of metal salts and silica or silica sol or silane, solvents, water and thickener,
• Applying the SiO ₂ coating precursor formulation to the substrate by screen printing, roller coating or dipping,
• Drying the SiO ₂ coating precursor formulation at a temperature in the range of 110-150 ° C for 5-15 minutes and
• Firing the SiO ₂ coating precursor formulation at a temperature between 570-700 ° C for 1-5 minutes,
• - wherein the metal salts are selected from the group consisting of elements of the first and second main group of the periodic table in the form of soluble salts and consists of MnO, ZnO, TiO ₂ in the form of soluble salts,
• - wherein the metal salts in an amount of 0.1 to 10 wt .-%, and SiO ₂ of silica or silica sol or silane in an amount of 0.1 to 10 wt .-%, based on the total content of the SiO ₂ coating precursor formulation , available.

The firing process produces metal oxides from the metal salts, which effect a densification of the SiO ₂ antireflective coating.

Thus, the density, the refractive index, the mechanical hardness and the chemical resistance of the SiO ₂ -antireflex coating can be selectively adjusted.

The SiO ₂ coating precursor formulation is prepared by mixing together the metal salts and silica or silica sol or silane, solvent, water and thickener. The solution is preferably rendered acidic, for example by addition of HNO ₃ , ie to a pH of less than 7.

As metal salts, chlorides, nitrates, sulfates, acetates, formates and other salts of organic acids can be used, this list is not exhaustive. Preferably, water of crystallization chlorides and nitrates are used.

Metal salts of lithium, magnesium, calcium and zinc are preferred as metal salts. In addition, mixtures of the metal salts mentioned can also be used. Quite conceivable is a mixture of metal salts of the first and the second main group, this list is not exhaustive.

The metal salts are present in an amount of from 0.1% to 10%, preferably from 0.15% to 8.5%, by weight, based on the total content of the SiO ₂ coating precursor formulation.

More preferably, the metal salts are present in an amount of from 0.2 to 5 percent by weight, based on the total content of the SiO ₂ coating precursor formulation. Still more preferably, the metal salts are present in an amount of 0.5 to 4.5 weight percent, based on the total content of the SiO ₂ coating precursor formulation. Still more preferably, the metal salts are present in an amount of 0.8-4.2 weight percent, based on the total content of the SiO ₂ coating precursor formulation.

Silica or silica sol or silane are used as the silicon oxide precursor. The silanes may be selected from the group consisting of tetraethoxysilane, silica sol, methylethoxysilane, ethylethoxysilane, methylmethoxysilane and tetramethylsilane, but this list is not exhaustive.

In the SiO ₂ antireflective coating, SiO _{2 is present} from silica or silica sol or silane in an amount of from 0.1 to 10% by weight, based on the total content of the SiO ₂ coating precursor formulation. Preferably, SiO _{2 is present} from silica or silica sol or silane in an amount of 0.15 to 8.5 weight percent, based on the total content of the SiO ₂ coating precursor formulation.

Further, preferably, SiO _{2 is available} from silica or silica sol or silane in an amount of 0.15 to 5.0% by weight, based on the total content of the SiO ₂ coating precursor formulation.

Very particular preference is given to SiO ₂ of silica or silica sol or silane in an amount of from 0.2 to 3.0% by weight, based on the total content of the SiO ₂ coating precursor formulation.

The thickener is selected from the group consisting of cellulose derivatives, methyl, ethyl, and hydroxypropyl cellulose. The thickener is present in an amount of from 0.5 to 10 weight percent, preferably from 1.0 to 7 weight percent, based on the total content of the SiO ₂ coating precursor formulation. The thickener has primarily the function of viscosity control.

The solvent is selected from the group consisting of dipropylene glycol monomethyl ether (Dowanol DPM), tripropylene glycol monomethyl ether (Dowanol TPM), ethanol, butyl diglycol, ethylene glycol, propylene glycol and dipropylene glycol. The solvent is present in an amount of 0 to 90% by weight, preferably 10 to 50% by weight, based on the total content of the SiO ₂ coating precursor formulation.

The water is present in an amount of 0 to 90% by weight, preferably 20 to 80% by weight, based on the total content of the SiO ₂ coating precursor formulation.

The substrate is selected from the group consisting of glass, solar glass, automotive glazing, window and glazing, desktops, touch panels, touchscreens.

The acidic solution of metal salts and silica, solvent, thickener and water is applied to the substrate by screen printing, roller coating or dipping, dried and fired.

The drying temperature is preferably in a range of 120-140 ° C, and more preferably in a range of 125-135 ° C. Very particular preference is 130 ° C.

The drying time is preferably in a range of 7-12 minutes, and most preferably 10 minutes.

The firing temperature is preferably in a range of 600-695 ° C, more preferably 650-695 ° C. Even more preferred is a range of 670-695 ° C. The firing time is preferably in a range of 2-4 minutes. Most preferably, the firing temperature is 690 ° C and the firing temperature is 3 minutes.

The metal salts have the function of mineralizers during firing, at the same time they suppress the hydrolysis of the baked layer, thus increasing the chemical resistance and the mechanical strength.

The antireflection properties are influenced depending on the metal oxides added, as well as the mechanical properties (scratch resistance, adhesion to the substrate, expansion coefficient).

In the method according to the invention a variable burn-in process and a shock firing for tempered safety glass (ESG) are feasible. After the firing, if necessary, a chemical hardening process can be carried out.

Another object of the invention is the SiO ₂ -antireflex-coated substrate, which is obtainable by the method described above.

The SiO ₂ antireflective coated substrate is used in glass, solar glasses, automotive glazings, window and architectural glazings, desktops, touch panels, and touchscreens, but this enumeration is not exhaustive.

The invention is explained in more detail below with reference to the examples, which do not limit the invention.

Examples

example 1

0.4 g of CaO is added in 5 g of water, 2.222 g of HNO ₃ (65%) are added and CaO is dissolved. 20 g of Hymocer ICG 400 (18% SiO ₂ in Dowanol TPM) from ETC Products GmbH Deggendorf and 15.7 g 808020 (7.5% Klucel L in Dowanol TPM) from Ferro GmbH, Frankfurt, are added and labeled with 40 g beads (diameter 0.8 mm) mixed for 0.5 hours. Then it is filtered off via a quick filter. It is printed with screen 120T on 4 mm flat glass, dried at 130 ° C for 10 min and fired at 690 ° C for 3 min. The result is a clear, firm, non-wipeable, dense layer with a scratch hardness to 20N Erichsen pen.

Example 2

10 g Köstrosol 1540 (Chemiewerk Bad Köstritz) and 0.5 g LiNO ₃ are dissolved, 10 g 808020 (7.5% Klucel L in Dowanol TPM) from Ferro GmbH, Frankfurt, are added and it is stirred for 0.5 hours , It is printed with screen 120T on 4 mm flat glass, dried at 130 ° C for 10 min and fired at 690 ° C for 3 min. The result is a clear solid, non-wipeable, dense layer with a scratch hardness to 20N Erichsen pen. Resistant in acid test with 3% HCl after 2 hours.

Example 3

45.925 g of Dowanol TPM are initially charged and 2.102 g of Zn (NO ₃ ) ₂ .6H ₂ O are dissolved. 1.473 g of tetraethoxysilane and 1.5 g of Klucel L are added and dissolved in 2 hours. The result is a clear viscous solution. It is printed with Sieb 100T on 4 mm flat glass, dried at 130 ° C for 10 minutes, fired at 690 ° C for 3 minutes. The result is a very clear layer, which is scratch resistant to 20N Erichsen pen.

Claims (16)

A method for producing a SiO ₂ anti-reflection coating on a substrate, in particular a glass substrate, comprising preparing a SiO ₂ coating precursor formulation comprising a solution of metal salts and silica or silica sol or silane, solvent, water and thickener, applying the SiO ₂ coating precursor formulation to the Substrate by screen printing, roller coating or dipping, drying the SiO ₂ coating precursor formulation at a temperature in a range of 110-150 ° C for 5-15 minutes and firing the SiO ₂ coating precursor formulation at a temperature between 570-700 ° C for 1- 5 minutes, wherein the metal salts are selected from the group consisting of elements of the first and second main groups of the Periodic Table in the form of soluble salts and consisting of MnO, ZnO, TiO ₂ in the form of soluble salts, wherein the metal salts are present in an amount of 0.1 to 10 Wt .-%, and SiO ₂ of silica or silica sol or silane in an amount of 0.1 to 10 wt .-%, based on the total content of the SiO ₂ coating precursor formulation, are present, wherein in the firing of SiO ₂ - Coating precursor formulation resulting from the metal salts resulting metal oxides cause a densification of the SiO ₂ antireflective coating. The method of claim 1, wherein the SiO ₂ coating precursor formulation is prepared by mixing together the metal salts and silica or silica sol or silane, solvent, water and thickener. A method according to any one of claims 1-2, wherein the metal salts are present in an amount of from 0.15% to 8.5% by weight, based on the total content of the SiO ₂ coating precursor formulation. A method according to any one of claims 1-3, wherein SiO _{2 is present} from silica or silica sol or silane in an amount of 0.15 to 8.5% by weight, based on the total content of the SiO ₂ coating precursor formulation. A process according to any one of claims 1-4, wherein the thickening agent is selected from the group consisting of cellulose derivatives, methyl, ethyl, and hydroxypropyl cellulose. A process according to any one of claims 1-5 wherein the thickening agent is present in an amount of from 0.5% to 10% by weight, preferably 1.0% to 7% by weight, based on the total content of the SiO ₂ coating precursor formulation. The method of any of claims 1-6, wherein the solvent is selected from the group consisting of dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethanol, butyl diglycol, ethylene glycol, propylene glycol and dipropylene glycol. A method according to any one of claims 1-7, wherein the solvent is present in an amount of 0 to 90% by weight, preferably 10 to 50% by weight, based on the total content of the SiO ₂ coating precursor formulation. A process according to any one of claims 1-8, wherein the water is present in an amount of 0 to 90% by weight, preferably 20 to 80% by weight, based on the total content of the SiO ₂ coating precursor formulation. The method of any one of claims 1-9, wherein the substrate is selected from the group consisting of glass, solar glasses, automotive glazing, window and glazing, desktops, touch panels, touchscreens. A method according to any one of claims 1-10, wherein the drying temperature is in a range of 120-140 ° C. A method according to any one of claims 1-11, wherein the drying time is in a range of 7-12 minutes. A process according to any one of claims 1-12, wherein the firing temperature is in a range of 670-695 ° C. The method of any one of claims 1-13, wherein the firing time is in a range of 2-4 minutes. SiO ₂ -antireflex coated substrate obtainable according to any one of claims 1-14. Use of the SiO ₂ -antireflex-coated substrate according to claim 15 in glass, solar glass, glazing for motor vehicles, window and building glazings, desktops, touch panels, touchscreens.