Glazing with a functional, especially hydrophobic,...

Details Glazing with a functional, especially hydrophobic,... Glazing with a functional, especially hydrophobic,...

2001-06-21

2003-09-30

Dawson, Robert (Department: 1712)

Stock material or miscellaneous articles

Composite

Of silicon containing

C428S304400, C428S312200, C428S315700, C428S428000, C428S429000, C428S446000, C428S447000, C428S688000, C428S696000, C428S702000

Reexamination Certificate

active

06627319

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a substrate, especially a transparent substrate, endowed with a property of hydrophobicity/oleophobicity for the purpose of obtaining certain anti-rain/anti-fouling effects or else the property of hydrophilicity/oleophilicity, or a photocatalytic characteristic, this being associated, respectively, with anti-misting/anti-frosting and also anti-staining effects, or with other properties: fragrance, etc. For this purpose, such a substrate, for example, is provided with a coating within the context of various applications, such as glazings for aeronautical, sea-going, land-borne (rail and road) transport vehicles, for building (windows), for urban furniture (display panels, bus shelters, etc.) or interior design (decorative panels, furnishings), domestic electrical appliances (refrigerator and oven doors, showcases, glass-ceramic plates), kitchen utensils, sanitaryware (washbasins, bathtubs, etc.), construction materials, etc.
BACKGROUND OF THE INVENTION
The substrate is therefore transparent or non-transparent and consists, in general, of glass, ceramic, glass-ceramic, metal, plastic (polymethyl methacrylate (PMMA), polyvinyl butyral (PVB), polycarbonate (PC) or polyurethane (PU), thermoplastic ethylene/vinyl acetate copolymer (EVA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate/polyester copolymers, cycloolefin copolymers of the ethylene
orbornene or ethylene/cyclopentadiene type, ionomer resins, for example an ethylen/(meth)acrylic acid copolymer neutralized by a polyamine, thermosetting or thermally crosslinkable polymers such as polyurethane, unsaturated polyester (UPE), ethylene/vinyl acetate copolymer, etc.) or of a combination of several of these materials.
The hydrophobicity/oleophobicity property to which reference has been made means that polar or nonpolar liquids do not adhere to the substrate so as to form an annoying film. A substrate having this property will have little or almost no tendency to retain dust or dirt of any type, fingermarks, insects, etc.
The presence of water and/or dirt results in an unattractive appearance and, as the case may be, a reduction in the transparency of the substrate together with an impairment of vision through it. Water and dirt are particularly annoying when the substrate is used for glazing in the transportation field.
The property of hydrophobicity/oleophobicity, or non-wettability, of a substrate means that the contact angles between a liquid and this substrate are high, for example, at least 90° in the case of water. The liquid therefore tends to flow off easily, in the form of drops, on the substrate simply under gravity if the substrate is inclined or due to the effect of aerodynamic forces in the case of a moving vehicle. Such known agents for imparting this hydrophobicity/oleophobicity property are, for example, fluoroalkylsilane such as those described in Patent Applications EP 0 492 417, EP 0 492 545 and EP 0 672 779.
Common hydrophobic/oleophobic agents are, in particular, alkyltrihalosilanes or alkyltrialkoxy-silanes, the alkyl group of which has at least one perfluorinated end group, that is to say one consisting of an F
3
C—(CF
2
)
n
— group in which n is a positive integer or zero, as described in Patent Application EP 0 719 743.
The hydrophobic/oleophobic agents are applied in a known manner as a solution using conventional deposition methods with or without heating.
One of the problems arising most acutely in the field of the invention is that of the durability of the hydrophobic/oleophobic coating. This is because durability is affected by the erosion which inevitably happens to some extent, for example during the periodically essential operations of cleaning the substrate when the latter is transparent, in order to restore satisfactory vision through the substrate. Thus, it is constantly endeavoured to slow down the rate of progressive removal of the hydrophobic/oleophobic coatings of the aforementioned types which takes place especially owing to the action of windscreen wipers, the more so as such removal may, in addition, result in degradation by ultraviolet radiation.
Two main approaches have hitherto been explored for increasing the durability of the coatings by limiting the erosion effects. Both these approaches consist in increasing the adhesion of the coatings to the substrates.
According to a first approach, Application EP 0 484 746 recommends the preparation of the substrate by a pre-treatment using a primer of the tetrahalosilane or tetralkoxysilane type.
Application EP 0 497 189 A2 proposes, according to a second approach, the prior creation on the surface of the substrate of irregularities having sizes, for example, of between 1 and 10 micrometers, either by adding particles or by various etching techniques such as chemical etching or sandblasting.
Moreover, it has been specified that, in all cases, there is no particular difficulty in reforming a new hydrophobic/oleophobic coating in order to remedy the erosion of the previous coating; this may be done on the old coating once it has been briefly cleaned. However, it is still obviously beneficial to delay this operation as long as possible.
SUMMARY OF THE INVENTION
The present invention is related to a substrate coated with a mesoporous film, wherein chemical molecules are bonded to the mesoporous film. In one embodiment, the substrate is made of a glass material or a plastic, and in another embodiment the substrate is made of glass. The mesoporous film may include at least one compound including at least one of the elements Si, W, Sb, Ti, Zr, Ta, V, Pb, Mg, Al, Mn, Co, Ni, Sn, Zn, In. The mesoporous film may have a periodic lattice on the scale of domains at least about 20 nm in size, and the mesoporous film may be electrically conducting. The chemical molecules may be hydrophobic/oleophobic and chosen from the group consisting of:
a) silicones; and
b) compounds satisfying the formulae:
 and R
p′
SiX
4-p′
  (II)
 wherein m=0 to 15, n=1 to 5, p=0, 1 or 2, R is a linear or branched alkyl group or a hydrogen atom, X is a hydrolysable group such a halogen, alkoxy, acetoxy, acyloxy, amino or NCO group, and p′=0, 1, 2 or 3.
The present invention also is related to a process for manufacturing a substrate including: bringing the substrate into contact with a composition formed from organic assembling groups and from at least one precursor for the material constituting a mesoporous film; precipitating the precursor around the organic assembling groups and growing the molecules of the precursor; and then removing the organic assembling groups, wherein chemical molecules, such as hydrophobic/oleophobic molecules, are then brought into contact, in the form of a solution or of a gas containing them, with the mesoporous film. The composition has a pH, and prior to bringing the substrate into contact with the composition, a layer having an isoelectric potential greater than or equal to the pH of the composition may be deposited on the substrate. In some embodiments, the organic assembling groups are micelles of cationic surfactant molecules, the precursor is a silicon alkoxide, and the organic assembling groups and precursor are in solution and possibly in hydrolysed form. The cationic surfactant may be cetyltrimethylammonium bromide, the precursor may be in solution due to hydrolysis in an acid medium of Si(OH)
4
, and the surfactant/Si molar ratio may be between 10
−4
and 0.5.
The present invention further is related to a glazing for buildings or transportation vehicles that has a transparent surface, wherein at least a portion of the transparent surface includes a substrate coated with a mesoporous film and chemical molecules bonded thereto.
In addition, the present invention is related to a substrate including a coating surface and a mesoporous film having hydrophobic/oleophobic molecules bonded thereto, wherein the mesoporous film is disposed on said coating surface. The molecules include at lea

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