U.S. patent application number 14/119876 was filed with the patent office on 2015-02-05 for coating material for a glass or glass ceramic substrate, and coated glass or glass ceramic substrate.
This patent application is currently assigned to SCHOTT AG. The applicant listed for this patent is Andrea Anton, Matthias Bockmeyer, Vera Breier, Silke Knoche, Angelina Milanovska, Matthias Seyfarth. Invention is credited to Andrea Anton, Matthias Bockmeyer, Vera Breier, Silke Knoche, Angelina Milanovska, Matthias Seyfarth.
Application Number | 20150037563 14/119876 |
Document ID | / |
Family ID | 45999814 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150037563 |
Kind Code |
A1 |
Bockmeyer; Matthias ; et
al. |
February 5, 2015 |
COATING MATERIAL FOR A GLASS OR GLASS CERAMIC SUBSTRATE, AND COATED
GLASS OR GLASS CERAMIC SUBSTRATE
Abstract
A coating material is provided that includes a sol-gel coating
system, pigments, and chain-like or fibrous nanoparticles. The
coating system is stable at high temperatures and is suitable for
glass or glass-ceramic substrates having a low thermal expansion
coefficient.
Inventors: |
Bockmeyer; Matthias; (Mainz,
DE) ; Anton; Andrea; (Hueffelsheim, DE) ;
Seyfarth; Matthias; (Jena, DE) ; Breier; Vera;
(Lismore, AU) ; Knoche; Silke; (Saulheim, DE)
; Milanovska; Angelina; (Mainz, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bockmeyer; Matthias
Anton; Andrea
Seyfarth; Matthias
Breier; Vera
Knoche; Silke
Milanovska; Angelina |
Mainz
Hueffelsheim
Jena
Lismore
Saulheim
Mainz |
|
DE
DE
DE
AU
DE
DE |
|
|
Assignee: |
SCHOTT AG
Mainz
DE
|
Family ID: |
45999814 |
Appl. No.: |
14/119876 |
Filed: |
June 6, 2012 |
PCT Filed: |
June 6, 2012 |
PCT NO: |
PCT/EP2012/002418 |
371 Date: |
March 14, 2014 |
Current U.S.
Class: |
428/312.8 ;
106/286.3; 106/286.4; 428/429; 428/432; 428/433; 523/400;
524/560 |
Current CPC
Class: |
C03C 17/007 20130101;
C03C 2203/27 20130101; Y10T 428/24997 20150401; C09D 11/102
20130101; C03C 2217/475 20130101; C08K 3/28 20130101; C03C 17/326
20130101; C03C 2217/78 20130101; C03C 2203/28 20130101; C08K 3/36
20130101; C03C 17/001 20130101; C03C 17/30 20130101; C03C 1/008
20130101; C03C 2203/30 20130101; C03C 2218/119 20130101; C03C
2217/478 20130101; Y10T 428/31612 20150401; C03C 2217/44
20130101 |
Class at
Publication: |
428/312.8 ;
428/429; 428/433; 428/432; 106/286.3; 106/286.4; 524/560;
523/400 |
International
Class: |
C03C 17/00 20060101
C03C017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 2011 |
DE |
102011050872.4 |
Claims
1-15. (canceled)
16. A coating material for coating glass or glass ceramics,
comprising a sol-gel coating system which includes particles of a
chain-like morphology and pigments.
17. The coating material as in claim 16, wherein the particles are
nanoparticles having an average length from 50 to 150 nm and an
average size from 5 to 25 nm.
18. The coating material as in claim 16, wherein the coating
material is semi-transparent or opaque.
19. The coating material as in claim 16, wherein the sol-gel
coating system is a hybrid polymer sol-gel coating system.
20. The coating material as in claim 16, wherein the particles are
SiO.sub.2 particles.
21. The coating material as in claim 16, further comprising a mass
ratio of sol-gel to particles that ranges from 10:1 to 1:1.
22. The coating material as in claim 16, further comprising a mass
ratio of sol-gel to particles that ranges from 5:1 to 2:1.
23. The coating material as in claim 16, further comprising
absorbing pigments having a size from 1 to 200 nm.
24. The coating material as in claim 23, wherein the absorbing
pigments have a size from 10 to 50 nm.
25. The coating material as in claim 16, further comprising an
organic crosslinker.
26. The coating material as in claim 25, wherein the organic
crosslinker is selected from the group consisting of an epoxide, an
acrylate, and combinations thereof.
27. The coating material as in claim 16, wherein the particles
comprise a plurality of primary particles and chain-like secondary
particles.
28. A coating material for coating glass or glass ceramics,
comprising in mass percent: sol-gel hydrolysate from 14 to 25%;
inorganic particles having a chain-like and/or fibrous morphology
from 11 to 20%; inorganic pigments from 18 to 44%; and solvents
from 23 to 45%.
29. The coating material as in claim 28, further comprising at
least one organic crosslinker in a proportion of less than 4%.
30. A composite material, comprising: a glass or glass ceramic
substrate, and a coating material comprising in mass percent: a
crosslinked sol-gel hydrolysate from 22 to 38%; and inorganic
particles from 18 to 31%, the inorganic particles having a
morphology selected from the group consisting of chain-like,
fibrous, and combinations thereof.
31. The composite material as in claim 30, wherein the crosslinked
sol-gel hydrolysate is an organically sol-gel hydrolysate, an
inorganically crosslinked sol-gel hydrolysate, and combinations
thereof.
32. The composite material as claim 30, wherein the crosslinked
sol-gel hydrolysate is an organically sol-gel hydrolysate having a
degree of organic crosslinking of more than 30%.
33. A composite material comprising a glass or glass ceramic
substrate and a baked coating material comprising, in mass percent,
from 30 to 55% of transparent semi-metal or metal oxides and from
45 to 70% of inorganic pigments.
34. The composite material as in claim 33, wherein the composite
material is selected from the group consisting of microporous,
mesoporous, and combinations thereof.
Description
FIELD OF THE INVENTION
[0001] 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.
BACKGROUND OF THE INVENTION
[0002] 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.
[0003] 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).
[0004] At the same time, the layers should provide enough opaque
color locations. In particular it is desired to provide black and
white color locations.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
OBJECT OF THE INVENTION
[0009] Therefore, an object of the invention is to at least
mitigate the aforementioned drawbacks of the prior art.
[0010] In particular, a screen-printable coating material is to be
provided, which is heat resistant and not prone to cracking nor
peeling.
[0011] Another object of the invention is to provide a long-term
stable one-component screen printing paint.
SUMMARY OF THE INVENTION
[0012] 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.
[0013] Preferred embodiments and modifications of the invention are
set forth in the respective dependent claims.
[0014] 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.
[0015] The coating material is especially used for heat loaded
ceramic substrates such as cooktops, kitchen appliances, furnace
and fireplace viewing windows.
[0016] The coating material enables to apply decorative coatings
such as cooktop borders, control labeling, etc.
[0017] Another field of application is in particular that of
special glasses and glass ceramics having a low coefficient of
thermal expansion.
[0018] 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.
[0019] The coating material or paint according to the invention
should in particular be processable using a screen printing
method.
[0020] 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.
[0021] 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 mPas, more preferably from
200 to 7,000 mPas, most preferably from 250 to 3,000 mPas.
[0022] In a particularly preferred embodiment, the viscosity of the
screen printing paint is from 200 to 1000 mPas.
[0023] 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.
[0024] According to the invention, the coating material comprises
particles having a chain-like and/or fibrous morphology.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] In particular a hybrid polymer sol-gel coating system is
used as a sol-gel material.
[0032] The pigments are preferably provided in form of particles
having a size of less than 2 .mu.m, preferably particles of less
than 200 nm, more preferably nanoparticles of less than or equal to
100 nm.
[0033] The particles of chain-like and/or fibrous morphology
preferably used include silicon oxide particles.
[0034] 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.
[0035] 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.
[0036] In one modification of the invention, an organic crosslinker
is added to the coating material, in particular an epoxy and/or an
acrylate.
[0037] 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.
[0038] The coating material has the following composition, based on
mass %: [0039] from 14 to 25%, preferably from 15 to 22%, more
preferably from 16 to 21% of sol-gel hydrolysate; [0040] from 11 to
20%, preferably from 12 to 18%, more preferably from 13 to 17% of
inorganic particles of a chain-like and/or fibrous morphology;
[0041] from 18 to 44%, preferably from 23 to 40%, more preferably
from 25 to 25% of inorganic pigments; [0042] from 23 to 45%,
preferably from 25 to 42%, more preferably from 27 to 41% of
solvents.
[0043] 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 %: [0044] from 22 to 38%, preferably
from 18 to 31%, more preferably from 28 to 31% of organically
and/or inorganically crosslinked sol-gel hydrolysate; [0045] from
18 to 31%, preferably from 20 to 26%, more preferably from 23 to
25% of inorganic particles having a chain-like and/or fibrous
morphology; [0046] from 32 to 59%, preferably from 41 to 44%, more
preferably from 44 to 50% of inorganic pigments.
[0047] Organic crosslinking may be induced both thermally and
photochemically. Inorganic crosslinking through hydrolysis and
condensation reactions may also be induced thermally.
[0048] In its baked state, i.e. when the coating material was
heated to a temperature of above 300.degree. C. so that organic
components were largely removed, a composite material is provided
in which the coating has the following composition, based on mass
%: [0049] from 30 to 55%, preferably from 33 to 47%, more
preferably from 37 to 43% of transparent semi-metal or metal
oxides; [0050] from 45 to 70%, preferably from 53 to 67%, more
preferably from 57 to 63% of inorganic pigments.
[0051] The invention therefore in particular relates to a pigmented
hybrid polymer based printing paint which comprises chain-like
and/or fibrous SiO.sub.2 nanoparticles.
[0052] The paint comprises a sol-gel hydrolysate, nanoparticles,
optionally organic crosslinkers, inorganic pigments, high-boiling
solvents, initiators, and additives.
[0053] The viscosity of a paint according to the invention
preferably ranges from 150 to 125,000 mPas, more preferably from
200 to 7,000 mPas, most preferably from 250 to 3,000 mPas.
[0054] As a sol-gel precursor, metal alcoholates are preferably
used, in particular alkoxysilanes, for example TEOS
(tetraethoxysilane), or TMOS (tetramethoxysilane).
[0055] Preferably, a tetraalkoxysilane Si(OR1).sub.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).sub.3R2. R2=organic crosslinkable radical, in particular
glycidyloxypropyl, methacryloyloxypropyl, vinyl, allyl.
[0056] Optionally, another metal alcoholate is added, such as
Zr(OR).sub.4, Ti(OR).sub.4, Al(OR).sub.3, with OR=ethoxide,
propoxide, sec-butoxide, e.g. zirconium tetrapropoxide, titanium
tetraethoxide, aluminum sec-butoxide.
[0057] Optionally, another organosilane is used, e.g.
Si(OR1).sub.3R2, Si(OR1).sub.2R2.sub.2, wherein R2: methyl, phenyl,
ethyl, aminopropyl, mercapto, such as MTEOS
(methyltriethoxysilane), PhTEOS (phenyltriethoxysilane), DEMDEOS
(dimethyldiethoxysilane), mercaptosilane, APTES
(aminopropyltriethoxysilane).
[0058] Alkoxysilanes functionalized with organically crosslinkable
monomers may include, e.g., [0059] GPTES
(3-glycidyloxypropyltriethoxysilane), [0060] MPTES
(methacryloxypropyltriethoxysilane), [0061] GPTMS
(glycidyloxypropyltrimethoxysilane), [0062] MPTMS
(methacryloxypropyltrimethoxysilane), [0063] VIES
(vinyltriethoxysilane), and ATES (allyltriethoxysilane).
[0064] 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.
[0065] Preparation of the hydrolysate is accomplished by selective
reaction of the monomers with H.sub.2O. This is preferably
performed in the presence of an acid, in particular HCl,
H.sub.2SO.sub.4, paratoluenesulfonic acid, acetic acid.
[0066] The aqueous hydrolysis solution preferably has a pH of less
than 4, most preferably less than 2.5.
[0067] In a particular embodiment, the hydrolysis may be performed
in an alkaline environment, in particular using NH.sub.3.
[0068] In another embodiment, the hydrolysis is performed using an
aqueous nanoparticle dispersion.
[0069] The crosslinking degree of the hydrolysate may be adjusted
through the ratio of H.sub.2O to hydrolyzable monomers. The
crosslinking degree is preferably from 5 to 70%, more preferably
from 11 to 50%, most preferably from 15 to 35%.
[0070] The crosslinking degree may be determined by the .sup.29Si
NMR spectroscopy method known to those skilled in the art.
[0071] The proportion of TO groups is preferably >15%, and that
of T1 groups is preferably >35%.
[0072] The viscosity of the hydrolysate preferably ranges from 5 to
30 mPas, more preferably from 9 to 25 mPas.
[0073] The residual solvent content of low-boiling solvents, e.g.
ethanol, in the hydrolysate used is preferably less than 10 mass
%.
[0074] 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.
[0075] Preferably employed are products of colloidally dispersed
chain-like silica sols from Nissan Chemicals (Organosilicasol.TM.),
or from FUSO Chemical Co.
[0076] 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.
[0077] 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.degree. C. are preferred.
[0078] The boiling point is preferably above 90.degree. C., more
preferably above 110.degree. C.
[0079] 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.
[0080] When preparing the coating composition, a solvent exchange
may be performed.
[0081] 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.
[0082] In one embodiment of the invention, the viscosity of the
nanoparticles containing dispersion is from 300 to 1500 mPas,
preferably from 400 to 700 mPas.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] The surface functionalization surprisingly achieves that the
viscosity of the final paint remains stable and that the paint does
not gel.
[0087] 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.
[0088] 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.
[0089] Preferred compounds of this group include bismethacrylates,
bis-epoxides, bismethacrylate silanes, bis-epoxy silanes,
bismethacrylate urethane silanes, and mixtures of these
substances.
[0090] 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.
[0091] 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.
[0092] Pigments that are preferably used are inorganic absorbing
pigments.
[0093] 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.
[0094] 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.
[0095] 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.
[0096] 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.
[0097] 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.RTM..
[0098] 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.
[0099] 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.
[0100] 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.
[0101] Amino functionalized silanes improve the crosslinking of the
layer and the adhesion of the layer to the substrate.
[0102] In order to avoid defects and unevenness of the layer,
segregation effects, bubbles, and/or foaming, additives are
preferably added to the coating solution.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] 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.
[0108] 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.
[0109] In N.sub.2 sorption, the cured layer (170.degree. C., 1 h)
preferably exhibits a BET multi-point surface area of less than 10
m.sup.2/g, more preferably less than 5 m.sup.2/g.
[0110] 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, SiO.sub.2 will be formed from
silicon based sol-gel precursors. ZrO.sub.2 may result from
Zr-based sol-gel precursors, and Al.sub.2O.sub.3 may result from
Al-based sol-gel precursors, or mixed oxides thereof.
[0111] For example, these include decomposition products of metal
alkoxysilanes and alkoxysilanes functionalized with or without
organically crosslinkable monomers.
[0112] 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.
[0113] Preferably, an LAS (lithium aluminum silicate glass ceramic:
Li.sub.2O.sup.-Al.sub.2O.sub.3-SiO.sub.2) with high-quartz mixed
crystals and/or keatite mixed crystals as the predominant crystal
phase is used.
[0114] LAS glass ceramics with TiO.sub.2 and/or ZrO.sub.2 and/or
SnO.sub.2 as nucleating agents are preferably used.
[0115] 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%.
[0116] 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.
[0117] 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.
[0118] Preferably, the gloss level is G1, according to EN ISO
2813.
[0119] 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.sup.-6/K, preferably less than 4*10.sup.-6/K, most preferably
less than 3.4*10.sup.-6/K.
[0120] The temperature resistance of the matrix used is preferably
more than 1000.degree. C., and therefore the thermal stability of
the inorganic coating depends mostly on the thermal stability of
the pigments that are used.
[0121] This advantage is primarily achieved by using a high
proportion of more than 11% of chain-like and/or fibrous
nanoparticles (preferably SiO.sub.2) .
[0122] The inventors have found that the chain-like nanoparticles
enhance internal cohesion of the inorganic composite layer and thus
prevent flaking of the layer.
[0123] 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.
[0124] A coating material according to the invention, in particular
in form of a paint, may be prepared as follows, by way of
example:
Hydrolysate 1:
[0125] First, 4 mol of GPTES (glycidoxypropyltriethoxysilane) is
hydrolyzed with 1 mol of TEOS and 2.3 g of H.sub.2O 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.
Hydrolysate 2:
[0126] First, 4 mol of MPTES (methacryloxypropyltriethoxysilane) is
hydrolyzed with 1 mol of TEOS and 2.3 g of H.sub.2O 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.
Hydrolysate 3:
[0127] 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 H.sub.2O 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.
Chain-like Nanoparticles 1:
[0128] 1000 g of a 15 mass % solution of chain-like SiO.sub.2
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.
Chain-like Nanoparticles 2:
[0129] 1000 g of a 15 mass % solution of chain-like SiO.sub.2
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.
Hybrid Polymer Paint 1:
[0130] 18 g of the hydrolysate 1 and 55 g of a 35 mass % solution
of chain-like SiO.sub.2 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.
[0131] Hybrid polymer paint 2:
[0132] 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.
Paint 3:
[0133] 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 (CoFe.sub.2O.sub.4 spinel). Subsequently, 0.5 g of a
foam-inhibiting paint additive is added. The paint is homogeneously
stirred using a dissolver disk.
Paint 4:
[0134] 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 (TiO.sub.2 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.
Paint 5:
[0135] 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.
Coating 1:
[0136] 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.sup.-6/K using a 140-mesh screen, and is
then dried at 170.degree. C. for 1 h.
[0137] Subsequently, the layer is baked at 420.degree. C. for 1 h.
The layer thickness is about 2.8 .mu.m. In this way, a
glass-ceramic substrate with a crack-free, porous, pigmented,
purely inorganic black layer will be obtained.
Coating 2:
[0138] 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.sup.-6/K using a 140-mesh screen, and is
then dried at 170.degree. C. for 1 h.
[0139] Subsequently, the layer is baked at 750.degree. C. for 1 h.
The layer thickness is about 3.0 .mu.m. 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.
Coating 3:
[0140] The hybrid polymer paint 1 is printed onto a borofloat glass
substrate (SCHOTT AG) having an expansion coefficient of
3.3*10.sup.-6/K using a 140-mesh screen, and is then dried at
170.degree. C. for 1 h. Subsequently, the layer is baked at
680.degree. C. for 4 min. The layer thickness is about 2.8
.mu.m.
[0141] The coated substrate is then bent in three dimensions at
about 590.degree. 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.
Coating 4:
[0142] The hybrid polymer paint 5 is printed onto a borofloat glass
substrate (SCHOTT AG) having an expansion coefficient of
3.3*10.sup.-6/K using a 140-mesh screen, and is then dried using IR
radiation and cured using UV light.
[0143] The layer is then baked at 680.degree. C. for 4 min. The
layer thickness is about 2.8 .mu.m.
[0144] The coated substrate is then bent in three dimensions at
about 590.degree. 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.
DESCRIPTION OF THE DRAWINGS
[0145] The invention will now be described in more detail by way of
schematically illustrated embodiments and with reference to the
drawings of FIG. 1 through FIG. 18.
[0146] FIG. 1 schematically shows a composite material 1 produced
according to the invention, which comprises a glass or glass
ceramic substrate 2.
[0147] 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.
[0148] 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.
[0149] With reference to FIGS. 2 to 4, an exemplary manufacturing
method for a coating material will now be explained in more
detail.
[0150] FIG. 2 shows, by way of example, the salient steps for
preparing a hydrolysate to form a sol-gel-based matrix.
[0151] 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.
[0152] 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.
[0153] In particular, an aqueous dispersion with oxidic
nanoparticles may be used. These nanoparticles may form an
additional filler in the sol-gel matrix.
[0154] Then, at least 90% of the low-boiling alcohol solvent used
herein is removed, and the hydrolysate is complete.
[0155] The coating material moreover comprises chain-like
nanoparticles, and the addition thereof will be explained with
reference to FIG. 3. The chain-like nanoparticles which are
prepared using a Stober process, for example, are provided in form
of a dispersion including a low-boiling solvent such as
isopropanol.
[0156] In order to perform a solvent exchange, first a high-boiling
solvent is added.
[0157] Subsequently, a surface-active stabilizing additive may be
added.
[0158] 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.
[0159] To prepare the coating material in form of a hybrid paint,
the hydrolysate as prepared according to FIG. 2 is provided, as
illustrated in FIG. 4.
[0160] Then the chain-like nanoparticles in high-boiling solvent as
prepared according to FIG. 3 are added.
[0161] Next, inorganic pigments are added, and the pigments are
mechanically dispersed, for instance using a stirrer.
[0162] Furthermore, organic crosslinkers, additives, and initiators
are added, and the hybrid polymer paint is complete.
[0163] An exemplary processing of the coating material is
illustrated in FIG. 5.
[0164] 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.
[0165] 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.degree. C.
[0166] A substantially purely inorganic layer is formed when baking
the coating material at a temperature above 350.degree. C.
[0167] 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.degree. C.,
advantageously with the coating material already applied prior to
the bending of the glass.
[0168] FIG. 6 shows a table with a composition of the hybrid
polymer paint according to the invention in a simple embodiment,
and in preferred and more preferred exemplary embodiments.
[0169] First, the hybrid polymer coating comprises binder
components comprising a sol-gel hydrolysate, nanoparticles, and
organic crosslinkers.
[0170] Inorganic pigments are added as coloring components.
[0171] Furthermore, the hybrid polymer paint comprises a
high-boiling solvent.
[0172] Optionally, initiators and additives may be added in the
amount indicated in FIG. 6.
[0173] FIG. 7 schematically shows examples of the morphology of the
chain-like and fibrous nanoparticles used.
[0174] Illustrated are primary particles having a mean diameter
between 10 and 20 nm.
[0175] From these primary particles, chain-like secondary particles
are formed, which may reach a length of more than 100 nm.
[0176] Furthermore, fibrous nanoparticles may optionally be
used.
[0177] FIG. 8 and FIG. 9 show SEM images of dried chain-like
SiO.sub.2 nanoparticles. The primary particle size is approximately
15 nm, and chain length is at values between 39 and 89 nm.
[0178] FIG. 10 shows the DLS measurement of a very dilute alcoholic
dispersion with predominantly spherical primary and secondary
particles. The particles do not reveal a chain-like morphology in
SEM, given a primary particle size of about 15 nm. It can be seen
that the measured particle size is approximately 38 nm, with a
comparatively small variation (standard deviation of about 14 nm).
Differences between REM and DLS measurements of the particle size
are due to the fact, inter alia, that DLS measures the average
hydrodynamic radius of the particles.
[0179] FIG. 11 shows the DLS measurement of a very dilute alcoholic
dispersion with predominantly chain-like secondary particles based
on spherical primary particles. In SEM, the particles reveal a
chain-like morphology, with a primary particle size of about 15 nm
and an average chain length of 120 nm. It can be seen that the
particle size as measured by DLS is about 92 nm, with a
comparatively large variation (standard deviation of about 71 nm).
Differences between REM and DLS particle size measurements are due
to the fact, inter alia, that DLS measures the average hydrodynamic
radius of the particles. Also, the DLS evaluation method does not
permit to account for a chain-like geometry. Therefore, the
chain-like geometry is primarily reflected in the large variation
of the measured values.
[0180] FIG. 12 schematically shows the essential components of a
hybrid polymer layer according to the invention after drying at a
temperature between 140 and 250.degree. C.
[0181] The solvent now has been largely removed, so that the now
crosslinked organic and inorganic constituents of the coating
material remained.
[0182] FIG. 13 schematically shows the pore volume and the pore
size distribution of a hybrid polymer layer according to the
invention after drying at a temperature of 170.degree. C., as
determined according to the BET method by nitrogen adsorption.
[0183] 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.
[0184] FIG. 14 schematically shows the viscosity (y-axis) of two
exemplary embodiments of the invention, with the time in weeks
represented on the x-axis. It can be seen that after an initial
partly significant decrease in the first two weeks, the viscosity
is still at more than 20,000 mPas even after eight weeks. Thus, the
coating material is long-term stable.
[0185] FIG. 15 shows the composition of the coating material after
baking, in a simple embodiment, and in preferred and more preferred
exemplary embodiments.
[0186] Organic components have largely been removed, some inorganic
thermal decomposition products may at most have remained from
additives and initiators, if any.
[0187] 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.
[0188] The coating has a high proportion of inorganic pigments,
from 45 to 70%.
[0189] FIG. 16 shows a nitrogen adsorption porosimetry measurement
according to BET, on layer components scraped off from the baked
layer.
[0190] 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.
[0191] FIG. 17 shows the color of an exemplary layer in the Lab
color space, after drying on the one hand, after baking on the
other.
[0192] The values of a and b vary only slightly around zero.
[0193] Furthermore, the L-value is less than 30, preferably also
after baking, at least in one embodiment. Thus, the layer is
black.
[0194] FIG. 18 shows the transmission characteristic, with the
wavelength in nanometers plotted along the x-axis, and the
transmittance in % on the y-axis.
[0195] It can be seen that the transmittance is less than 0.5% over
the entire range of visible light. Thus, the layer is opaque.
[0196] 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.
* * * * *