Patent Application
20150037563
The invention relates to a coating material for glass or glass ceramic substrates, which may in particular be used for screen printing. The invention further relates to a composite material comprising a glass or glass ceramic substrate coated with the coating material.
Coating materials for glass or glass ceramic substrates are used, for example, for coating cooktops, for coating thermally loaded substrates, and for coating bullet-proof glass, in particular for vehicles.
The layers should be both heat-resistant during a bending process as is used for automotive glazing, for example, and should also meet the thermal requirements on a coated substrate for cooktops (induction, gas, and IR radiation).
At the same time, the layers should provide enough opaque color locations. In particular it is desired to provide black and white color locations.
However, on low-expansion substrates, color locations of a sufficiently low transmittance and a necessary thermal resistance have only been producible with limited success so far. This especially applies to glass and glass ceramic substrates having a low thermal expansion coefficient.
This is partly because either it is impossible to achieve a sufficiently high pigmentation level when using thermally resistant sol-gel paints, or because the alkali additives used have a negative impact on the color location of the pigments.
If a sol-gel matrix having a high organic content is used, as described in published patent application DE 19946712 A1, an excessive thermal load of the layers will entail a decomposition of organic residual constituents and the layers will flake off.
Also, in case of an insufficiently adapted expansion coefficient, it is only possible to produce layers of a smaller than desired thickness and of a higher than desired transmittance, because otherwise, at higher thicknesses, there will be flaking.
Therefore, an object of the invention is to at least mitigate the aforementioned drawbacks of the prior art.
In particular, a screen-printable coating material is to be provided, which is heat resistant and not prone to cracking nor peeling.
Another object of the invention is to provide a long-term stable one-component screen printing paint.
This object of the invention is already achieved by a coating material for coating glass or glass ceramics and by a composite material according to any one of the independent claims.
Preferred embodiments and modifications of the invention are set forth in the respective dependent claims.
The invention relates to a coating material for coating glass or glass ceramic substrates. The coating material is in particular provided in form of an ink, or paint, and is therefore referred to as “paint” below, for sake of simplification.
The coating material is especially used for heat loaded ceramic substrates such as cooktops, kitchen appliances, furnace and fireplace viewing windows.
The coating material enables to apply decorative coatings such as cooktop borders, control labeling, etc.
Another field of application is in particular that of special glasses and glass ceramics having a low coefficient of thermal expansion.
Especially, the invention is used for safety glass. One application is the coating of bullet-proof vehicle glass. A vehicle window pane is usually curved three-dimensionally and has a coating along its edge in the region in which the pane is bonded to the vehicle body, which coating is usually black.
The coating material or paint according to the invention should in particular be processable using a screen printing method.
The coating material comprises a sol-gel coating system, wherein a sol-gel coating system refers to a substance which at least partially solidifies by a sol-gel process. The coating material is in particular a single component paint, i.e. it is stable in storage for at least several weeks, especially exceeding 3 months, more preferably 6 months.
For screen-printable sol-gel materials, storage stability in particular means to exhibit a viscosity which ensures a durable, reliable application in a screen printing process over a period of at least several weeks. This involves that the coating material does not gel but remains liquid and processable. The viscosity of a processable, screen-printable coating material in the present case preferably ranges from 150 to 125,000 mPa·s, more preferably from 200 to 7,000 mPa·s, most preferably from 250 to 3,000 mPa·s.
In a particularly preferred embodiment, the viscosity of the screen printing paint is from 200 to 1000 mPa·s.
The coating material furthermore comprises pigments which define the color of the coating material. In particular black pigments are provided. More generally, however, pigments of any possible color may be added to the coating material.
According to the invention, the coating material comprises particles having a chain-like and/or fibrous morphology.
A chain-like or fibrous morphology refers to particles having a dimension along their longitudinal or main extension direction which is at least twice, preferably three times the dimension along the smallest extension of the particle, which in turn applies to the average of the particles used.
Particles of a chain-like morphology are secondary particles consisting of a plurality of concatenated smaller primary particles. It will be understood that the particles may be branched, at least partially.
In particular nanoparticles of an average length from 50 to 150 nm and an average size from 5 to 25 nm may be used. The size may be determined by means of scanning electronic micrographs, as will be described in detail below.
When the particle size of preferably used chain-like nanoparticles is determined in a 0.05 mass % dispersion using a method of dynamic light scattering (DLS) (Equipment: Deltanano HC; assessment according to the method of Conten), the particle size is approximately 91 nm, with a very broad distribution and a standard deviation of about 70 nm. For the chain-like particles measured in SEM (scanning electron microscope), the diameter of the primary particles is about 15 nm.
DLS measurements on dispersions without chain-like secondary particles, i.e. comprising only spherical primary particles (diameter of about 15 nm in SEM), however, reveal a diameter of 38 nm with a standard deviation of about 14 nm.
The coating material is preferably semi-transparent or opaque. An opaque coating refers to a coating that is lightproof to the human eye, whereas a semi-transparent coating refers to a coating that although having a clearly visible color effect, permits lighted indications behind a cooking surface, for example, to be recognizable with sharp contours and high contrast through the coating.
In particular a hybrid polymer sol-gel coating system is used as a sol-gel material.
The pigments are preferably provided in form of particles having a size of less than 2 μm, preferably particles of less than 200 nm, more preferably nanoparticles of less than or equal to 100 nm.
The particles of chain-like and/or fibrous morphology preferably used include silicon oxide particles.
In one embodiment of the invention, the mass ratio of sol-gel to particles ranges from 10:1 to 1:1, preferably from 5:1 to 2:1.
In one embodiment of the invention, the absorbing pigments have a size from 1 to 200 nm, preferably from 5 to 100 nm, and more preferably from 10 to 50 nm.
In one modification of the invention, an organic crosslinker is added to the coating material, in particular an epoxy and/or an acrylate.
The invention further relates to a coating material for coating glass or glass ceramic substrates, which is in particular provided as a screen-printable paint.
The coating material has the following composition, based on mass %:
In a dried state, i.e. in a predominantly solvent-free state in which the coating system is solidified, in particular organically crosslinked, but in which thermal decomposition of the organic components by baking has not yet occurred, a composite material may be provided in which the coating has the following composition, based on mass %:
Organic crosslinking may be induced both thermally and photochemically. Inorganic crosslinking through hydrolysis and condensation reactions may also be induced thermally.
In its baked state, i.e. when the coating material was heated to a temperature of above 300° C. so that organic components were largely removed, a composite material is provided in which the coating has the following composition, based on mass %:
The invention therefore in particular relates to a pigmented hybrid polymer based printing paint which comprises chain-like and/or fibrous SiO2 nanoparticles.
The paint comprises a sol-gel hydrolysate, nanoparticles, optionally organic crosslinkers, inorganic pigments, high-boiling solvents, initiators, and additives.
The viscosity of a paint according to the invention preferably ranges from 150 to 125,000 mPa·s, more preferably from 200 to 7,000 mPa·s, most preferably from 250 to 3,000 mPa·s.
As a sol-gel precursor, metal alcoholates are preferably used, in particular alkoxysilanes, for example TEOS (tetraethoxysilane), or TMOS (tetramethoxysilane).
Preferably, a tetraalkoxysilane Si(OR1)4, wherein OR1 is an organic radical, in particular methoxide, ethoxide, propoxide, butoxide, sec-butoxide, is used in combination with an alkoxysilane which has an organically crosslinkable functionality, Si(OR1)3R2. R2=organic crosslinkable radical, in particular glycidyloxypropyl, methacryloyloxypropyl, vinyl, allyl.
Optionally, another metal alcoholate is added, such as Zr(OR)4, Ti(OR)4, Al(OR)3, with OR=ethoxide, propoxide, sec-butoxide, e.g. zirconium tetrapropoxide, titanium tetraethoxide, aluminum sec-butoxide.
Optionally, another organosilane is used, e.g. Si(OR1)3R2, Si(OR1)2R22, wherein R2: methyl, phenyl, ethyl, aminopropyl, mercapto, such as MTEOS (methyltriethoxysilane), PhTEOS (phenyltriethoxysilane), DEMDEOS (dimethyldiethoxysilane), mercaptosilane, APTES (aminopropyltriethoxysilane).
Alkoxysilanes functionalized with organically crosslinkable monomers may include, e.g.,
In the sol-gel hydrolysate used for the coating material, the ratio of T (tertiary) to Q (quaternary) groups preferably ranges from 3:1 to 5:1, more preferably from 3.5:1 to 4.5:1. In a preferred embodiment, the sol-gel precursor does not include any M and/or D groups.
Preparation of the hydrolysate is accomplished by selective reaction of the monomers with H2O. This is preferably performed in the presence of an acid, in particular HCl, H2SO4, paratoluenesulfonic acid, acetic acid.
The aqueous hydrolysis solution preferably has a pH of less than 4, most preferably less than 2.5.
In a particular embodiment, the hydrolysis may be performed in an alkaline environment, in particular using NH3.
In another embodiment, the hydrolysis is performed using an aqueous nanoparticle dispersion.
The crosslinking degree of the hydrolysate may be adjusted through the ratio of H2O to hydrolyzable monomers. The crosslinking degree is preferably from 5 to 70%, more preferably from 11 to 50%, most preferably from 15 to 35%.
The crosslinking degree may be determined by the 29Si NMR spectroscopy method known to those skilled in the art.
The proportion of TO groups is preferably >15%, and that of T1 groups is preferably >35%.
The viscosity of the hydrolysate preferably ranges from 5 to 30 mPa·s, more preferably from 9 to 25 mPa·s.
The residual solvent content of low-boiling solvents, e.g. ethanol, in the hydrolysate used is preferably less than 10 mass %.
The particles of chain-like and/or fibrous morphology are preferably prepared using a liquid phase synthesis process, especially a sol-gel-based alkali catalyzed process, or Stober process. Preferably, a non-aqueous solvent is used.
Preferably employed are products of colloidally dispersed chain-like silica sols from Nissan Chemicals (Organosilicasol™), or from FUSO Chemical Co.
In one particular embodiment, the fibrous nanoparticles are produced using a hydrothermal process and/or a fiber spinning process and/or gas-phase-based processes. Especially fibrous particles prepared by electrospinning processes are used.
High-boiling solvents having a vapor pressure of less than 1200 mbar, more preferably less than 500 mbar, most preferably less than 100 mbar at 20° C. are preferred.
The boiling point is preferably above 90° C., more preferably above 110° C.
Preferred solvents include ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, methyl isobutyl ketones, ethylene mono-n-propyl ether, propylene glycol monomethyl acetate, tripropylene glycol monomethyl ether, and terpineol.
When preparing the coating composition, a solvent exchange may be performed.
Preferable, a dispersion having a concentration of nanoparticles from 15 to 40 mass %, preferably 26 to 38 mass %, more preferably 35 to 37% is used.
In one embodiment of the invention, the viscosity of the nanoparticles containing dispersion is from 300 to 1500 mPa·s, preferably from 400 to 700 mPa·s.
The nanoparticles may have a mean size from 3 to 300 nm, a diameter from 3 to 70 nm, and a length from 50 to 300 nm, preferably from 70 to 150 nm.
The size and anisotropy may be determined using a scanning electron microscope. For this purpose, ten randomly selected particles are measured, and an average is calculated from the measured values.
In one embodiment, the nanoparticles are surface-stabilized. For example, cationic and/or anionic and/or neutral surfactants are used for this purpose. P-toluenesulfonic acid is preferably used, in particular with a mass fraction from 2 to 10 mass % (preferably from 3 to 9%) based on the total mass of nanoparticles.
The surface functionalization surprisingly achieves that the viscosity of the final paint remains stable and that the paint does not gel.
To increase scratch resistance of the intermediate product hybrid polymer layer, organic crosslinkers having a plurality of organic crosslinkable groups may be added to the coating material, in particular epoxides or acrylates, e.g. bis-epoxide, or bismethacrylate.
In a preferred embodiment, the coating composition comprises polyfunctional organic monomers and/or organosilanes. These monomers preferably have 2 or 3 or 4 organically crosslinkable functional groups.
Preferred compounds of this group include bismethacrylates, bis-epoxides, bismethacrylate silanes, bis-epoxy silanes, bismethacrylate urethane silanes, and mixtures of these substances.
The molar ratio of crosslinkable organic monomers to the monomer of the hardener or crosslinker used may range from 35:1 to 10:1, preferably from 25:1 to 15:1.
The following substances or mixtures thereof are especially preferred: 3,4-epoxycyclohexane carboxylate, or dimethylene bisacrylamide, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, decanediol dimethacrylate, dodecanediol dimethacrylate, bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, ethoxylated bisphenol A dimethacrylate, bis-GMA(2,2-bis-4-(3-methacryloxy-2-hydroxypropyl)-phenylpropane), and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, as well as reaction products of isocyanates, especially diisocyanates and/or triisocyanates with OH groups-containing methacrylates.
Pigments that are preferably used are inorganic absorbing pigments.
Preferably, these absorbing pigments are provided in form of nanoscale particles of a primary particle size from 2 to 5000 nm, preferably from 8 to 1000 nm, more preferably from 10 to 500 nm.
These may include both non-oxide based pigments, such as TiN and/or ZrN, and/or TiC, and/or ZrC, or oxidic pigments such as manganese ferrite spinel, CrCu ferrite spinel, cobalt oxides/spinels, cobalt-aluminum spinels, cobalt-titanium spinels, cobalt-chromium spinels, cobalt-nickel-manganese-iron-chromium oxides/spinels, cobalt-nickel-zinc-titanium-aluminum oxides/spinels, iron oxides, iron-chromium oxides, iron-chromium-zinc-titanium oxide, copper-chromium spinels, nickel-chromium-antimony-titanium oxides, ZnO, titanium oxides, zirconium-silicon-iron oxides/spinels, etc.
In another embodiment, platelet-shaped pigments may be used as the pigments. Especially, these include effect pigments based on mica, aluminum, and/or glass flakes, which are coated with a multilayer interference coating.
To start the crosslinking reaction of the organic functional groups, thermally activatable initiators may be added to the coating solution. This may be aluminum acetylacetonate, or metylimidazole, for example.
It is also possible to add UV activatable initiators to the coating solution, such as e.g. iodonium, (4-methylphenyl)[4-(2-methylpropyl)phenyl], hexafluorophosphate(1−), or Irgacure 186®.
In one embodiment, adhesion promoters may be added to the coating material. These may include, for example, amino silanes and/or mercapto silanes, such as 3-aminopropyltriethoxysilane, or 3-mercaptopropyltrimethoxysilane.
The ratio of adhesion promoting silanes to the other alkoxysilanes may range from 1:30 to 1:10, preferably from 1:20 to 1:15.
In a preferred embodiment, one or more amino functionalized silanes are added to the coating material. Preferred amino functionalized silanes include 3-aminopropyl-trimethoxysilane, [3-(methylamino)propyl]trimethoxysilane, [3-(phenylamino)propyl]trimethoxysilane, [3-(diethylamino)propyl]trimethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylene diamine, 1-[3-(trimethoxysilyl)propyl]urea, bis(3-(methylamino)propyl)trimethoxysilane, and mixtures of these components.
Amino functionalized silanes improve the crosslinking of the layer and the adhesion of the layer to the substrate.
In order to avoid defects and unevenness of the layer, segregation effects, bubbles, and/or foaming, additives are preferably added to the coating solution.
These additives may amount up to 5 mass %, preferably up to 2 mass % of the coating solution, being referred to as deaerating agents, defoamers, leveling agents, dispersing agents, for example. They are commercially available, e.g. from TEGO (Evonic), and are known to those skilled in the art as typical paint additives.
Specifically, these are pure and/or organically modified low molecular weight polysiloxanes, organic polymers, fluorine functionalized polymers, polyether modified polymers, polysiloxanes, and/or polyacrylates, as well as basic and acidic fatty acid derivatives.
The dried and cured hybrid polymer layer produced from the coating material comprises an organically and inorganically crosslinked sol-gel material, nanoparticles, optionally organic crosslinkers, inorganic pigments, and additives.
The coating material of the invention may be used as a dried and/or cured coating, or may be baked on the substrate, whereby organic constituents of the coating material are removed at least partially. That means, baking in the context of the invention refers to a thermal treatment during which organic components are decomposed.
The dried and/or cured layer comprises an organic-inorganic network including chain-like nanoparticles and inorganic pigments. The pigmented layer (organic fraction of less than 25% by mass, preferably less than 15%) comprises an oxidic inorganic binder, crosslinked sol-gel material, and inorganic nanoparticles, and inorganic pigments.
The organic crosslinking degree of the dried but not baked layer is preferably greater than 30%, more preferably greater than 50%. The degree of organic crosslinking is determined by IR and/or Raman spectroscopy.
In N2 sorption, the cured layer (170° C., 1 h) preferably exhibits a BET multi-point surface area of less than 10 m2/g, more preferably less than 5 m2/g.
After baking of the coating material, the oxidic decomposition products of the sol-gel hydrolysate are part of the skeleton-forming material comprising oxidic materials which resulted as decomposition products from molecularly dispersed sol-gel precursors. For example, SiO2 will be formed from silicon based sol-gel precursors. ZrO2 may result from Zr-based sol-gel precursors, and Al2O3 may result from Al-based sol-gel precursors, or mixed oxides thereof.
For example, these include decomposition products of metal alkoxysilanes and alkoxysilanes functionalized with or without organically crosslinkable monomers.
The coating material according to the invention in form of a paint is particularly useful for producing porous decorative inorganic coatings on special glass, such as borosilicate glass and lithium aluminum silicate (LAS) glass ceramics.
Preferably, an LAS (lithium aluminum silicate glass ceramic: Li2O-Al2O3-SiO2) with high-quartz mixed crystals and/or keatite mixed crystals as the predominant crystal phase is used.
LAS glass ceramics with TiO2 and/or ZrO2 and/or SnO2 as nucleating agents are preferably used.
An advantage of the printing paint according to the invention is that this paint permits to produce highly pigmented, high-temperature stable, crack-free layers with a transmittance of less than 5%, preferably less than 3%, more preferably less than 0.5%.
Using this paint, both light as well as gray to dark color locations may be produced. A particular advantage of the paint is that non-platelet-shaped pigments may be used for coloration.
A porous layer is produced whose color location is highly glossy, both before and following thermal loading, and which is not significantly affected by scattering at pores and cracks.
Preferably, the gloss level is G1, according to EN ISO 2813.
The coating material of the invention enables to apply inorganic layers of low transmittance onto substrates having a thermal coefficient of linear expansion a of less than 5*10−6/K, preferably less than 4*10−6/K, most preferably less than 3.4*10−6/K.
The temperature resistance of the matrix used is preferably more than 1000° C., and therefore the thermal stability of the inorganic coating depends mostly on the thermal stability of the pigments that are used.
This advantage is primarily achieved by using a high proportion of more than 11% of chain-like and/or fibrous nanoparticles (preferably SiO2) .
The inventors have found that the chain-like nanoparticles enhance internal cohesion of the inorganic composite layer and thus prevent flaking of the layer.
The coating material may in particular be used as a paint for producing decorative coatings for white goods or for automotive glass on the basis of special glasses.
A coating material according to the invention, in particular in form of a paint, may be prepared as follows, by way of example:
First, 4 mol of GPTES (glycidoxypropyltriethoxysilane) is hydrolyzed with 1 mol of TEOS and 2.3 g of H2O in which 0.344 g of p-toluenesulfonic acid has been dissolved. Then, on a rotary evaporator, the solvent is removed from this mixture to obtain the so-called hydrolysate.
First, 4 mol of MPTES (methacryloxypropyltriethoxysilane) is hydrolyzed with 1 mol of TEOS and 2.3 g of H2O in which 0.344 g of p-toluenesulfonic acid has been dissolved. Then, on a rotary evaporator, the solvent is removed from this mixture to obtain the so-called hydrolysate.
First, 3 mol of GPTES (glycidoxypropyltriethoxysilane) is hydrolyzed with 1 mol of TEOS (tetraethoxysilane), with 1 mol of MTEOS (methyltriethoxysilane) and 2.3 g of H2O in which 0.344 g of p-toluenesulfonic acid has been dissolved. Then, on a rotary evaporator, the solvent is removed from this mixture to obtain the so-called hydrolysate.
1000 g of a 15 mass % solution of chain-like SiO2 nanoparticles (mean length of 120 nm, mean spherical diameter of 15 nm) in isopropanol are mixed with 428 g of diethylene glycol monoethyl ether. Then, on a rotary evaporator at 40 mbar, the volatile solvent is removed. A 35 mass % dispersion is obtained. Subsequently, 10 g of a surface-active stabilizing agent is added.
1000 g of a 15 mass % solution of chain-like SiO2 nanoparticles (mean length of 120 nm, mean spherical diameter of 15 nm) in isopropanol are mixed with diethylene glycol monoethyl ether. Then, on a rotary evaporator at 40 mbar, the volatile solvent is removed. A 30 mass % dispersion is obtained. Subsequently, 10 g of a surface-active stabilizing agent is added.
18 g of the hydrolysate 1 and 55 g of a 35 mass % solution of chain-like SiO2 nanoparticles in diethylene glycol monoethyl ether are mixed with 30 g of a nanoscale (<100 nm) black pigment (manganese ferrite spinel). Subsequently, 0.4 g of a flow-promoting paint additive is added. The paint is homogeneously stirred using a dissolver disk.
Hybrid polymer paint 2:
18 g of the hydrolysate 1 and 55 g of the chain-like nanoparticles 1 are mixed with 38 g of a nanoscale (<100 nm) black pigment (manganese ferrite spinel). Subsequently, 0.4 g of a flow-promoting paint additive and 0.7 g of a cationic thermal initiator are added. The paint is homogeneously stirred using a dissolver disk.
18 g of hydrolysate 1 and 55 g of the chain-like nanoparticles 1 are mixed with 38 g of a nanoscale (30 nm) black pigment (CoFe2O4 spinel). Subsequently, 0.5 g of a foam-inhibiting paint additive is added. The paint is homogeneously stirred using a dissolver disk.
18 g of the hydrolysate 3 and 55 g of the chain-like nanoparticles 1 are mixed with 38 g of a nanoscale (100 nm) white pigment (TiO2 rutile). Subsequently, 0.4 g of a defoaming paint additive and 0.5 g of a cationic thermal initiator are added. The paint is homogeneously stirred using a dissolver disk.
18 g of the hydrolysate 2 and 55 g of the chain-like nanoparticles 2 are mixed with 30 g of a nanoscale (<100 nm) black pigment (manganese ferrite spinel). Subsequently, 0.4 g of a leveling paint additive and 0.5 g of a radical photoinitiator are added. The paint is homogeneously stirred using a dissolver disk.
The hybrid polymer paint 1 is printed onto a transparent lithium aluminum silicate (LAS) glass ceramic having an expansion coefficient of 0±0.3*10−6/K using a 140-mesh screen, and is then dried at 170° C. for 1 h.
Subsequently, the layer is baked at 420° C. for 1 h. The layer thickness is about 2.8 μm. In this way, a glass-ceramic substrate with a crack-free, porous, pigmented, purely inorganic black layer will be obtained.
The hybrid polymer paint 4 is printed onto a transparent lithium aluminum silicate (LAS) glass ceramic having an expansion coefficient of 0±0.3*10−6/K using a 140-mesh screen, and is then dried at 170° C. for 1 h.
Subsequently, the layer is baked at 750° C. for 1 h. The layer thickness is about 3.0 μm. In this way, a glass-ceramic substrate will be obtained which is provided with a crack-free, porous, thermally resistant, pigmented, purely inorganic white layer.
The hybrid polymer paint 1 is printed onto a borofloat glass substrate (SCHOTT AG) having an expansion coefficient of 3.3*10-6/K using a 140-mesh screen, and is then dried at 170° C. for 1 h. Subsequently, the layer is baked at 680° C. for 4 min. The layer thickness is about 2.8 μm.
The coated substrate is then bent in three dimensions at about 590° C. in combination with other substrates. The coating does not melt during this process nor does it adhere to the other substrates it is in contact with. Neither does the coating flake off.
The hybrid polymer paint 5 is printed onto a borofloat glass substrate (SCHOTT AG) having an expansion coefficient of 3.3*10-6/K using a 140-mesh screen, and is then dried using IR radiation and cured using UV light.
The layer is then baked at 680° C. for 4 min. The layer thickness is about 2.8 μm.
The coated substrate is then bent in three dimensions at about 590° C. in combination with other substrates. The coating does not melt during this process nor does it adhere to the other substrates it is in contact with. Neither does the coating flake off.
The invention will now be described in more detail by way of schematically illustrated embodiments and with reference to the drawings of
A coating material 3 provided in form of a paint has been applied onto the glass or glass ceramic substrate 2 by a screen printing method.
The coating material 3 may only be dried and cured. Furthermore, the coating material 3 is high-temperature resistant, and upon baking of the coating material 3 organic components of the coating material 3 are largely removed.
With reference to
First, a mixture is prepared from a silane with at least one organically crosslinkable component and a tetravalent alkoxysilane. Optionally, one or more other organosilane monomeres or organosilane oligomeres may be added.
By selectively adding water with an acid catalyst, with a pH of less than 4, an inorganic condensation degree of between 10 and 40% is adjusted.
In particular, an aqueous dispersion with oxidic nanoparticles may be used. These nanoparticles may form an additional filler in the sol-gel matrix.
Then, at least 90% of the low-boiling alcohol solvent used herein is removed, and the hydrolysate is complete.
The coating material moreover comprises chain-like nanoparticles, and the addition thereof will be explained with reference to
In order to perform a solvent exchange, first a high-boiling solvent is added.
Subsequently, a surface-active stabilizing additive may be added.
Then, at least 90% of the low-boiling solvent is removed, and the solvent exchange is completed, preferably a dispersion of between 25 and 40 mass% of oxide nanoparticles is obtained.
To prepare the coating material in form of a hybrid paint, the hydrolysate as prepared according to
Then the chain-like nanoparticles in high-boiling solvent as prepared according to
Next, inorganic pigments are added, and the pigments are mechanically dispersed, for instance using a stirrer.
Furthermore, organic crosslinkers, additives, and initiators are added, and the hybrid polymer paint is complete.
An exemplary processing of the coating material is illustrated in
First, the coating material in form of the pigmented paint is applied onto a glass or glass ceramic substrate by screen printing, inkjet, etc. In this way, a wet film of the hybrid polymer is formed.
Subsequently, the coating material is dried, and/or organic crosslinking is performed. This may already be accomplished at room temperature, or at a temperature of up to 250° C.
A substantially purely inorganic layer is formed when baking the coating material at a temperature above 350° C.
In preferred exemplary embodiments, the coating material is used either as a cooking surface, or for vehicle glass which is bent at a temperature between 500 and 700° C., advantageously with the coating material already applied prior to the bending of the glass.
First, the hybrid polymer coating comprises binder components comprising a sol-gel hydrolysate, nanoparticles, and organic crosslinkers.
Inorganic pigments are added as coloring components.
Furthermore, the hybrid polymer paint comprises a high-boiling solvent.
Optionally, initiators and additives may be added in the amount indicated in
Illustrated are primary particles having a mean diameter between 10 and 20 nm.
From these primary particles, chain-like secondary particles are formed, which may reach a length of more than 100 nm.
Furthermore, fibrous nanoparticles may optionally be used.
The solvent now has been largely removed, so that the now crosslinked organic and inorganic constituents of the coating material remained.
It can be seen that the dried and organically crosslinked coating material is substantially dense, i.e. it does not has any microporous or mesoporous structures.
Organic components have largely been removed, some inorganic thermal decomposition products may at most have remained from additives and initiators, if any.
The coating comprises oxidic components which may be divided into predominantly transparent oxidic components resulting from the sol-gel hydrolysate and the binder. Other oxidic components result from the chain-like and/or fibrous nanoparticles added.
The coating has a high proportion of inorganic pigments, from 45 to 70%.
Apparent therefrom is a mean pore diameter ranging from 1 to 10 nm on the average. The layer exhibits a clearly microporous and mesoporous structure. Also, a bi-modal pore size distribution can be seen. Both micropores (radius of about 1 nm) and mesopores of a radius from 3 to 5 nm may be determined. However, the total volume of mesopores is significantly larger than the total volume of micropores. The total surface area of the pores has increased to more than the 50 to 100-fold value as compared to that of the layer that has only been dried.
The values of a and b vary only slightly around zero.
Furthermore, the L-value is less than 30, preferably also after baking, at least in one embodiment. Thus, the layer is black.
It can be seen that the transmittance is less than 0.5% over the entire range of visible light. Thus, the layer is opaque.
The invention provides a screen-printable coating system for glass or glass ceramic substrates, which does not crack even under high-temperature stress, and which does not peel off.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102011050872.4 | Jun 2011 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/002418 | 6/6/2012 | WO | 00 | 3/14/2014 |
