Hydrophobic coating including DLC on substrate

Details Hydrophobic coating including DLC on substrate Hydrophobic coating including DLC on substrate

2000-06-01

2002-01-01

Turner, Archene (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including components having same physical characteristic in...

C428S212000, C428S408000, C428S428000, C428S426000, C428S446000

Reexamination Certificate

active

06335086

ABSTRACT:

This invention relates to a hydrophobic coating system including diamond-like carbon (DLC) provided on (directly or indirectly) a substrate of glass, plastic, ceramic, or the like, and a method of making the same. The coating system may include one or more layers and may be deposited on the substrate utilizing plasma ion beam deposition in certain embodiments.
BACKGROUND OF THE INVENTION
Conventional soda inclusive glasses are susceptible to environmental corrosion which occurs when, e.g., sodium (Na) diffuses from or leaves the glass interior, as well as to retaining water on their surfaces in many different environments, including when used as automotive windows (e.g. backlites, side windows, and/or windshields). When water is retained or collects on automotive windows, the water may freeze (i.e. forming ice) in certain environments. Additionally, the more water retained on a windshield, the higher power wiper motor(s) and/or wiper blade(s) required.
In view of the above, it is apparent that there exists a need in the art for (i) a coated article (e.g. coated glass, ceramic or plastic substrate) that can repel water and/or dirt, and a method of making the same, (ii) a coated soda inclusive glass where the coating(s) reduces the likelihood of visible stains/corrosion forming; and/or (iii) a protective hydrophobic coating system that is somewhat resistant to scratching, damage, or the like.
It is known to provide diamond like carbon (DLC) coatings on glass. U.S. Pat. No. 5,637,353, for example, states that DLC may be applied on glass. Unfortunately, the DLC of the '353 patent would not be an efficient hydrophobic coating and/or would not be an efficient corrosion minimizer on glass in many instances.
U.S. Pat. No. 5,900,342 to Visser et al. discloses a fluorinated DLC layer on an electrophotographic element. From about 25-65% fluorine content by atomic percentage is provided at an outermost surface, to provide for low surface energy in an attempt to make removal of xerographic toner easier. Unfortunately, this DLC inclusive layer of the '342 patent would be too soft for use on a glass substrate in automotive applications and the like. Its apparent lack of sp
3
C—C bonds and/or lack of Si—O bonds contribute to its softness. It is also believed that continuous exposure to sun, rain, humidity, dust, windshield wipers, and/or the environment in general would cause the '342 DLC layer to break down or degrade rather quickly over time.
Thus, there also exists a need in the art for a DLC inclusive coating that has sufficient hardness and durability to withstand the environment while still exhibiting satisfactory hydrophobic qualities.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.
SUMMARY OF THE INVENTION
An object of this invention is to provide a durable coated article that can shed or repel water (e.g. automotive windshield, automotive backlite, automotive side window, architectural window, bathroom shower glass, residential window, bathroom shower door, coated ceramic article/tile, etc.).
Another object of this invention is to provide a hydrophobic coating system including one or more diamond-like carbon (DLC) inclusive layers.
Yet another object of this invention, in embodiments where a hydrophobic coating system includes multiple DLC inclusive layers, is to form (e.g., via ion beam deposition techniques) a first underlying DLC inclusive layer using a first precursor or feedstock gas and a second DLC inclusive layer over the first underlying DLC inclusive layer using a second precursor or feedstock gas. In certain embodiments, the first underlying DLC inclusive layer may function as an anchoring and/or barrier layer while the second or overlying DLC inclusive layer may be more scratch resistant (i.e., harder) and more dense so as to improve the coated article's durability and/or scratch resistance characteristics.
Another object of this invention is to provide a DLC inclusive coating system including (i) an underlying DLC inclusive layer formed using a precursor/feedstock gas such as tetramethylsilane (TMS), and (ii) another DLC inclusive layer formed over the underlying layer (i) using another precursor/feedstock gas such as acetylene (C
2
H
2
), in a manner such that layer (i) functions as a barrier and/or anchoring layer and the overlying layer (ii) is of a more durable (e.g., scratch resistance and/or hard) nature. In such embodiments, the underlying DLC inclusive layer (i) may include silicon (Si) so as to provide improved bonding of the overlying layer (ii) to the substrate. The overlying layer may or may not include silicon (Si) in different embodiments.
Another object of this invention is to provide a coated substrate, wherein a coating system includes sp
3
carbon-carbon bonds and has a wettability W with regard to water of less than or equal to about 23 mN/m, more preferably less than or equal to about 21 mN/m, even more preferably less than or equal to about 20 mN/m, and in most preferred embodiments less than or equal to about 19 mN/meter. This can also be explained or measured in Joules per unit area (mJ/m
2
)
Another object of this invention is to provide a coated substrate, wherein a DLC inclusive coating system includes sp
3
carbon-carbon bonds and has a surface energy &ggr;
C
(on the surface of the coated article) of less than or equal to about 20.2 mN/m, more preferably less than or equal to about 19.5 mN/m, and most preferably less than or equal to about 18 mN/m.
Another object of this invention is to provide a coated substrate, wherein a DLC inclusive coating system has an initial (i.e. prior to being exposed to environmental tests, rubbing tests, acid tests, UV tests, or the like) water contact angle &thgr; of at least about 80 degrees, more preferably of at least about 100 degrees, even more preferably of at least about 110 degrees, and most preferably of at least about 125 degrees.
Another object of this invention is to provide a coating system for a glass substrate, wherein the coating system includes a greater number of sp
3
carbon-carbon (C—C) bonds than sp
2
carbon-carbon (C—C) bonds. In certain of these embodiments, the coating system need not include many sp
2
carbon-carbon (C—C) bonds.
Another object of this invention is to provide a coated glass article wherein a DLC inclusive coating system protects the glass from acids such as HF, nitric, and sodium hydroxide (the coating may be substantially chemically inert).
Another object of this invention is to provide a coated glass article that is abrasion resistant.
Another object of this invention is to provide a DLC coating system on a substrate, wherein the coating includes different portions or layers with different densities and different sp
3
carbon-carbon bond percentages. The ratio of sp
3
to sp
2
carbon-carbon bonds may be different in different layers or portions of the coating. Such a coating system with varying compositions at different portions thereof may be continuously formed (e.g., by varying feedstock and/or precursor gas(es) used, and/or by varying the ion energy used in the deposition process, using a single ion beam deposition device). Thus, a DLC inclusive coating system may have therein an interfacial layer with a given density and chemical makeup, and another outer or overlying layer portion having a higher density of sp
3
carbon-carbon (C—C) bonds and greater scratch resistance and/or durability.
Another object of this invention is to manufacture a coating system having hydrophobic qualities wherein the temperature of an underlying glass substrate may be less than about 200° C., preferably less than about 150° C., most preferably less than about 80° C., during the deposition of a DLC inclusive coating system. This reduces graphitization during the deposition process, as well as reduces detempering and/or damage to low-E and/or IR-reflective coatings already on the substrate

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