WO2000066506A1

WO2000066506A1 - Highly tetrahedral amorphous carbon coating on glass

Info

Publication number: WO2000066506A1
Application number: PCT/US2000/011711
Authority: WO
Inventors: Vijayen S. Veerasamy
Original assignee: Guardian Industries Corporation
Priority date: 1999-05-03
Filing date: 2000-05-01
Publication date: 2000-11-09
Also published as: CA2368471A1; US7858150B2; DE60002060D1; PL195615B1; CZ20013760A3; HUP0200949A2; US7632538B2; DE60021627D1; AU4811300A; BR0008391B1; CA2368471C; WO2000066506A9; EP1338576A1; US6713178B2; US20060166009A1; EP1177156B1; EP1177156A1; ATE236860T1; US6261693B1; PL356132A1

Abstract

A soda inclusive glass substrate is coated with a highly tetrahedral amorphous carbon inclusive layer that is a form of diamond-like carbon (DLC). In certain embodiments, the amorphous carbon layer includes at least about 35 % sp3 carbon-carbon bonds, more preferably at least about 70 %, and most preferably at least about 80 % of the sp3 carbon-carbon bonds. The high density (e.g. greater than or equal to about 2.4 gm/cm3) of the amorphous carbon layer prevents soda from exiting the glass and reacting with water at surface(s) of the glass, thereby minimizing visible stains or (corrosion) on the glass. The high density amorphous carbon layer also may repel water. In some embodiments, the highly tetrahedral amorphous carbon layer is part of a larger DLC coating, while in other embodiments the highly tetrahedral layer forms the entirety of a DLC coating on the substrate.

Description

HIGHLY TETRAHEDRAL

AMORPHOUS CARBON COATING ON GLASS

This invention relates to a diamond-like carbon (DLC)

coating provided on (directly or indirectly) a glass or

other substrate. More particularly, in certain preferred

embodiments, this invention relates to a highly tetrahedral amorphous diamond like carbon coating on a soda inclusive

glass substrate (e.g. on a soda lime silica glass substrate) for purposes of repelling water and/or reducing corrosion on

the coated article. Ion beam and filtered carbon cathodic arc deposition are preferred methods of deposition for the coating.

BACKGROUND OF THE INVENTION

Soda inclusive glasses are known in the art . For example, see U.S. Patent No. 5,214,008, which is hereby

incorporated herein by reference.

Soda lime silica glass, for example, is used for

architectural glass, automotive windshields, and the like.

The aforesaid "008 patent discloses one type of soda lime silica glass known in the art. Unfortunately, conventional soda inclusive glasses are susceptible to environmental corrosion which occurs when

sodium (Na) diffuses from or leaves the glass interior.

This sodium, upon reaching the surface of the glass, may

react with water to produce visible stains or smears (e.g. stains of sodium hydroxide) on the glass surface. Such

glasses are also susceptible to retaining water on their surfaces in many different environments, including when used as automotive windows (e.g. backlites, side windows, and/or

windshields) . These glasses are also susceptible to fogging up on the interior surface thereof in automotive and other environments .

In view of the above, it is apparent that there exists a need in the art to prevent and/or minimize visible stains/corrosion on soda inclusive coated glass surfaces.

There also exists a need in the art to provide a strong

protective coating on window substrates. Other needs in the

art include the need for a coating on glass that reduces the coated article's susceptibility to fogging up in automotive

and other environments, and the need for a coated glass

article that can repel water and/or dirt . It is known to provide diamond like carbon (DLC)

coatings on glass. U.S. Patent No. 5,637,353, for example, states that DLC may be applied on glass. The '353 patent teaches that because there is a bonding problem between

glass and that type of DLC, an intermediate layer is

provided therebetween. Moreover, the '353 patent does not

disclose or mention the highly tetrahedral amorphous type of DLC used in many embodiments set forth below. The DLC of the ^Λ 353 patent would not be an efficient corrosion

minimizer on glass in many instances due to its low density (likely less than 2.0 gm/cm³) . Still further, the DLC of the ^v 353 patent is deposited in a less than efficient manner

for certain embodiments of this invention.

It is known that many glass substrates have small

cracks defined in their surface. The stress needed to crack

glass typically decreases with increasing exposure to water.

When water enters such a crack, it causes interatomic bonds at the tip of the crack to rupcure. This weakens glass. Water can accelerate the rate of crack growth more than a

thousand times by attacking the structure of the glass at

the root or tip of the crack. Strength of glass is in part controlled by the growth of cracks that penetrate the glass . Water, in these cracks, reacts with glass and causes it to

crack more easily as described in "The Fracturing of Glass,"

by T.A. Michalske and Bruce C. Bunker, hereby incorporated herein by reference . Water molecules cause a concerted chemical reaction in which a silicon-oxygen bond (of the

glass) at the crack tip and on oxygen-hydrogen bond in the water molecule are both cleaved, producing two silanol groups . The length of the crack thus increases by one bond rupture, thereby weakening the glass. Reaction with water

lowers the energy needed to break the silicon-oxygen bonds

by a factor of about 20, and so the bond-rupture allows

glass cracks to grow faster.

Thus, there also exists a need in the art for preventing water from reaching silicon-oxygen bonds at: tips

of cracks in a glass substrate, so as to strengthen the glass .

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 coated

article that can shed water (e.g. automotive windshield,

automotive backlite, automotive side window, architectural window, etc. ) .

Another object of this invention is to provide a system or means for reducing or minimizing corrosion on soda

inclusive coated glass articles.

Another object of this invention is to provide a coated glass article wherein a DLC coating protects the glass from

acids such as HF, nitric, and sodium hydroxide (the coating may be chemically inert) .

Another object of this invention is to provide a coated glass article that is not readily susceptible to fogging up. Another object is to provide a barrier layer with no

pin holes on a glass substrate.

Another object of this invention is to provide a coated glass article that is abrasion resistant, and/or can repel dirt and the like. Another object of this invention is to provide a glass

substrate with a DLC coating inclusive of a highly tetrahedral dense amorphous carbon layer, either in direct

or indirect contact with the substrate.

Another object of this invention is to provide a DLC

coating on a substrate, wherein the coating includes

different portions or layers with different densities and

different sp³ carbon-carbon bond percentages. The ratio of sp³ to sp² carbon-carbon bonds may be different in different layers or portions of the coating. Such a coating with varying compositions therein may be continuously formed by varying the ion energy used in the deposition process so that stresses in the coating are reduced in the interfacial portion/layer of the DLC coating immediately adjacent the

underlying substrate. Thus, a DLC coating may have therein an interfacial layer with a given density and sp³ carbon-

carbon bond percentage, and another layer with a higher density and higher sp³ carbon-carbon bond percentage.

Generally speaking, this invention fulfills certain of the above described needs/objects in the art by providing a

coated glass comprising:

a glass substrate including at least about 5% by weight soda/Na₂0; an amorphous carbon layer provided on the glass

substrate in order to reduce corrosion or stains on the

coated glass, wherein said amorphous carbon layer includes

sp² and sp³ carbon-carbon bonds; and

wherein the amorphous carbon layer has more sp³ carbon-

carbon bonds than sp² carbon-carbon bonds.

In other embodiments, this invention fulfills certain of the above described needs in the art by providing a

coated glass comprising: a soda inclusive glass substrate comprising, on a weight basis, from about 60-80% Si0₂, from about 10-20% Na₂0, from about 0-16% CaO, from about 0-10% K₂0, from about 0-10% MgO, and from about 0-5% Al₂0₃; and

a non-crystalline diamond-like carbon (DLC) coating

provided on the glass substrate, wherein the DLC coating includes at least one highly tetrahedral amorphous carbon

layer having at least about 35% sp³ carbon-carbon bonds.

In certain embodiments, the glass substrate is a soda lime silica float glass substrate. In preferred embodiments, the entire DLC coating or

alternatively only a layer within the DLC coating, has a density of from about 2.4 to 3.4 gm/cm³, most preferably

from about 2.7 to 3.0 gm/cm³.

In certain embodiments, the tetrahedral amorphous carbon layer has the aforesaid density range and includes at

least about 70% sp³ carbon-carbon bonds, and most preferably

at least about 80% sp³ carbon-carbon bonds.

In certain embodiments, the DLC coating includes a top layer (e.g. from about 2 to 8 atomic layers, or less than about 20 A) that is less dense than other portions of the DLC coating, thereby providing a solid lubricant portion at the top surface of the DLC coating. Layered graphene

connected carbon atoms are provided in this thin layer portion. The coefficient of friction is less than about 0.1 for this thin layer portion.

Another advantage of this invention is that the

temperature of the glass substrate is less than about 200°

C. , preferably less than about 150° C, most preferably from about 60-80° C, during the deposition of DLC material. This is to minimize graphitization during the deposition process.

This invention further fulfills the above described

needs in the art by providing a window having a substrate and a highly tetrahedral amorphous carbon layer thereon, wherein the substrate is or includes at least one of

borosilicate glass, soda lime silica glass, and plastic.

This invention will now be described with respect to

certain embodiments thereof, along with reference to the

accompanying illustrations.

IN THE DRAWINGS

Figure 1 is a side cross sectional view of a coated article according to an embodiment of this invention,

wherein a substrate is provided with a DLC coating including at least two layers therein.

Figure 2 is a side cross sectional view of a coated

article according to another embodiment of this invention, wherein a highly tetrahedral amorphous carbon DLC coating is

provided on and in contact with a substrate .

Figure 3 is a side cross sectional view of a coated

article according to yet another embodiment of this invention wherein a low-E or other coating is provided on a

substrate, with the DLC coating of either of the Fig. 1 or Fig. 2 embodiments also on the substrate but over top of the

intermediate low-E or other coating. Figure 4 illustrates an exemplar sp³ carbon atom hybridization bond.

Figure 5 illustrates an exemplar sp² carbon atom

hybridization bond.

Figure 6 illustrates exemplar sp hybridizations of a

carbon atom.

Figure 7 is a side cross sectional view of carbon ions

penetrating the substrate or DLC surface so as to strongly bond a DLC layer according to any embodiment herein. Figure 8 is a side cross sectional view of a coated glass substrate according to an embodiment of this

invention, illustrating DLC bonds penetrating cracks in the surface of a glass substrate.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION

Referring now more particularly to the accompanying

drawings in which like reference numerals indicate like elements throughout the accompanying views.

Figure 1 is a side cross sectional view of a coated

glass article according to ah embodiment of this invention,

wherein at least one diamond-like carbon (DLC) protective coating (s) 3 is provided directly on soda-inclusive glass substrate 1. DLC coating 3 in the Fig. 1 embodiment

includes at least one highly tetrahedral amorphous carbon (ta-C) layer 7 that has a high density (e.g. greater than

about 2.4 grams per cubic centimeter) and functions to repel

water and seal soda within the soda inclusive glass substrate. Coating 3 further includes at least one

interfacing layer 8 directly adjacent substrate 1, where layer 8 has a lesser density and a lesser percentage of sp³ carbon-carbon bonds than ta-C layer 7. Even though layer 8

differs from layer 7 in these manner (s), interfacing layer 8 may or may not qualify as ta-C with a density of at least

about 2.4 gm/cm³, as described below. It is noted that in certain embodiments, coating 3 may include multiple ta-C layers 7 and/or multiple layers 8. Layers 7 and 8 of the

coating may be formed in a continuous or non-continuous

deposition process in different embodiments of this

invention.

Figure 2 is a side cross sectional view of a coated

glass article according to another embodiment of this invention, wherein at least one DLC coating (s) 3 is provided on glass substrate 1. In the Fig. 2 embodiment, substantially the entire DLC coating 3 is made up of highly tetrahedral amorphous carbon (ta-C), similar to layer 7,

having a density of at least about 2.4 grams per cubic

centimeter and a high percentage (e.g. at least about 35%,

more preferably at least about 70%, and most preferably at least about 80%) of sp³ carbon-carbon bonds. In other words, ta-C layer 7 from the Fig. 1 embodiment forms the entirety of DLC coating 3 in the Fig. 2 embodiment. DLC coating 3 in the Fig. 2 embodiment may or may not have equal densities and/or the same percentages of sp³ carbon-carbon

bonds throughout the thickness of coating 3, as these parameters may be varied throughout layers 3 , 7 and 8 in the Fig. 1 and 2 embodiments by changing the ion energy used

during the deposition process of coating 3.

In the Fig. 3 embodiment, a low-E or other coating 5 is provided between substrate 1 and DLC coating 3 (i.e. the DLC coating of either the Fig. 1 or Fig. 2 embodiment) .

However, DLC coating 3 is still on substrate 1 in the Fig. 3 embodiment, along with a ta-C portion 7 of coating 3. Thus, the term "on" herein means that substrate 1 supports DLC coating 3 or any layer (e.g. 7, 8) thereof, regardless of

whether or not other layer (s) 5 are provided therebetween. Thus, protective coating 3 may be provided directly on

substrate 1 as shown in Figs. 1-2, or may be provided on

substrate 1 with a low-E or other coating (s) 5 therebetween

as shown in Fig. 3. Coating 5, instead of its illustrated

position in Fig. 3, may also be provided on top of DLC

coating 3 so that coating 3 (of either the Fig. 1 or Fig. 2

embodiment) is located between coating (s) 5 and substrate 1.

In still other embodiments, a DLC coating 3 may be provided

on both sides of a low-E coating 5.

Exemplar coatings (in full or any portion of these

coatings) that may be used as low-E or other coating (s) 5,

either on top of or below DLC coating 3 , are shown and/or

described in any of U.S. Patent Nos. 5,837,108, 5,800,933,

5,770,321, 5,557,462, 5,514,476, 5,425,861, 5,344,718,

5,376,455, 5,298,048, 5,242,560, 5,229,194, 5,188,887 and

4,960,645, which are all hereby incorporated herein by

reference. Simple silicon oxide and/or silicon nitride

coating (s) may also be used as coating (s) 5.

As will be discussed in more detail below, highly

tetrahedral amorphous carbon (ta-C) layer (s) 7 is a special

form of diamond-like carbon (DLC) , and includes at least

about 35% sp³ carbon-carbon bonds (i.e. it is highly tetrahedral) . In certain embodiments of this invention, ta-

C layer (s) 7 has at least about 35% sp³ carbon-carbon bonds of the total sp bonds in the layer, more preferably at least

about 70%, and most preferably at least about 80% sp³

carbon-carbon bonds so as to increase the density of layer 7 and its bonding strength. The amounts of sp³ bonds may be measured using Raman finger-printing and/or electron energy

loss spectroscopy. The high amount of sp³ bonds increases the density of layer thereby allowing it to prevent soda diffusion to the surface of the coated article.

Ta-C layer 7 forms the entirety of DLC coating 3 in the Fig. 2 embodiment, and ta-C layer 7 forms only a portion of

DLC coating 3 in the Fig..1 embodiment. This is because

interfacial amorphous carbon layer 8 in the Fig. 1 embodiment sometimes has a density less than about 2.4 grams per cubic centimeter and/or less than about 35% sp³ carbon-

carbon bonds. However, it is noted that DLC coating 3 has an interfacial layer immediately adjacent substrate 1 in each of the Fig. 1 and Fig. 2 embodiments, with the

difference being that the interfacial layer in the Fig. 2 embodiment has a density of at least about 2.4 grams per cubic centimeter and at least about 35% sp³ (more preferably at least about 70%, and most preferably at least about 80%) carbon-carbon bonds. Thus, layer 7 herein refers to both

layer 7 as illustrated in the Fig. 1 embodiment as well as

DLC coating 3 in the Fig. 2 embodiment.

At least some carbon atoms of DLC coating 3, and/or some sp² and/or sp³ carbon-carbon bonds, are provided in fissures or cracks in a surface (e.g. top surface) of the glass substrate, or may penetrate the glass surface of

substrate 1 itself or the surface of growing DLC, so as to strongly bond coating 3 to substrate 1. Subimplantation of

carbon atoms into the surface of substrate 1 enables coating 3 to be strongly bonded to substrate 1.

For purposes of simplicity, Figure 4 illustrates an

exemplar sp³ carbon-carbon or C-C bond (i.e. carbon to carbon diamond like bond) in coating 3 , Figure 4 an exemplar

sp² C-C bond in coating 3, and Figure 5 an exemplar sp .

The provision of dense (density of at least about 2.4 gm/cm³) ta-C layer 7 on soda inclusive glass substrate 1 reduces the amount of soda which can exit the substrate or reach the surface of the substrate or coated article (i.e.

ta-C limits sodium diffusion from the substrate) . Thus,

less soda is allowed to react with water or other material (s) on the surface of the article. The end result

is that the provision of ta-C layer 7 on the substrate

reduces stains and/or corrosion on the glass article which can form over time. The large number of sp³ carbon-carbon

bonds increases the density of layer 7 and allows the layer to repel water and minimize soda diffusion from soda

inclusive glass.

Coating (s) 3, and layer (s) 7, 8, also strengthen the glass article, reduce stress at the bonding surfaces between coating 3 and substrate 1, and provide a solid lubricant

surface on the article when coating 3 is located at a

surface of the article. Coating (s) 3 and/or layer 7 may o includes a top layer portion (e.g. the top 3 to 15 A) that

is less dense than central areas of coating 3, thereby providing a solid lubricant at the top surface of coating 3

furthest from the substrate so that the article is resistant

to scratching. Ta-C layer 7 also provides resistance to water/moisture entering or coming into substrate 1. Coating

3, and thus ta-C layer 7, are preferably formed/deposited continuously across glass substrate 1, absent any pinholes

or apertures . In certain embodiments, layer 7 and/or 8 adjacent the glass substrate is deposited at an ion energy that allows

significant numbers of carbon atoms to penetrate cracks in the glass surface as shown in Figure 8. The small size of

carbon atoms and the ion energy utilized prevent substantial water from reaching the tip of the crack (s) . This strengthens the glass in the long term by slowing down and/or stopping the rupture of silicon-oxygen bonds at crack tips caused by water exposure.

Advantages associated with certain embodiments of this invention include: (i) coated window articles that can shed

water in different environments (e.g. automotive windows such as backlites and windshields, or commercial and

residential windows) ; (ii) anti-fog coated articles that are

resistant to fogging up; (iii) strengthened coated windows; (iv) abrasion resistant coated windows; (v) coated articles that can repel dirt; and (vi) coated glass articles less susceptible to visible corrosion on surfaces thereof. For example, in automotive window embodiments, the outer surface

of substrate 1 exposed to the environment is coated with coating 3 in accordance with any of the Fig. 1-3

embodiments. In anti-fog automotive embodiments, the inner surface of automotive window substrates 1 may be coated with

coating 3 in accordance with any of the Fig. 1-3

embodiments .

In certain embodiments, coating 3 is at least about 70%

transparent to or transmissive of visible light rays,

preferably at least about 80%, and most preferably at least

about 90% transparent to visible light: rays.

In certain embodiments, DLC coating 3 (and thus layer 7

in the Fig. 2 embodiment) may be from about 30 to 3,000 A

thick, most preferably from about 50 to 300 A thick. As

for glass substrate 1, it may be from about 1.5 to 5.0 mm

thick, preferably from about 2.3 to 4.8 mm thick, and most

preferably from about 3.7 to 4.8 mm thick. Ta-C layer 7, in

certain embodiments, has a density of at least about 2.4

grams per cubic centimeter, more preferably from about 2.4

to 3.4 gm/cm³, and most preferably from about 2.7 to 3.0

gm/cm³.

Substrate 1 includes soda or Na₂0 in certain

embodiments of this invention. Thus, ta-C layer (s) 7

minimize the amount of soda that can reach the surface of

the coated article and cause stains/corrosion. In certain

embodiments, substrate 1 includes, on a weight basis, from about 60-80% Si0₂, from about 10-20% Na₂0, from about 0-16% CaO, from about 0-10% K₂0, from about 0-10% MgO, and from

about 0-5% Al₂0₃. In certain other embodiments, substrate 1 may be soda lime silica glass including, on a weight basis,

from about 66-75% Si0₂, from about 10-20% Na₂0, from about 5-15% CaO, from about 0-5% MgO, from about 0-5% Al₂0₃, and from about 0-5% K₂0. Most preferably, substrate 1 is soda lime silica glass including, by weight, from about 70-74% Si0₂, from about 12-16% Na₂0, from about 7-12% CaO, from about 3.5 to 4.5% MgO, from about 0 to 2.0% A1₂0₃, from

about 0-5% K₂0, and from about 0.08 to 0.15% iron oxide. Soda lime silica glass according to any of the above

embodiments may have a density of from about 150 to 160

pounds per cubic foot (preferably about 156) , an average short term bending strength of from about 6,500 to 7,500 psi (preferably about 7,000 psi), a specific heat (0-100 degrees C) of about 0.20 Btu/lbF, a softening point of from about 1330 to 1345 degrees F, a thermal conductivity of from about 0.52 to 0.57 Btu/hrftF, and a coefficient of linear

expansion (room temperature to 350 degrees C) of from about 4.7 to 5.0 x 10"⁶ degrees F. In certain embodiments, any

glass disclosed in U.S. Patent No. 5,214,008 or Patent No. 5,877,103, each incorporated herein by reference, may be used as substrate 1. Also, soda lime silica float glass

available from Guardian Industries Corp., Auburn Hills,

Michigan, may be used as substrate 1.

Any such aforesaid glass substrate 1 may be, for example, green, blue or grey in color when appropriate colorant (s) are provided in the glass.

In certain other embodiments of this invention, substrate 1 may be of borosilicate glass, or of

substantially transparent plastic. In certain borosilicate embodiments, the substrate 1 may include from about 75-85% Si0₂, from about 0-5% Na₂0, from about 0 to 4% Al₂0₃, from

about 0-5% K₂0, from about 8-15% B₂0₃, and from about 0-5% Li₂0.

In still further embodiments, an automotive window

(e.g. windshield or side window) including any of the above glass substrates laminated to a plastic substrate may combine to make up substrate 1, with the coating 3 of any of the Figs. 1-3 embodiments provided on either or both sides of such a window. Other embodiments would have substrate 1 made up of a sheet of soda lime silica glass laminated to a

plastic sheet for automotive window purpose, with coating (s) 3 of any of the Fig. 1-3 embodiments on the inner side of

the substrate bonded to the plastic. In other embodiments, substrate 1 may include first and second glass sheets of any

of the above mentioned glass materials laminated to one

another, for use in window (e.g. automotive windshield, residential window, commercial window, automotive side

window, automotive backlite or back window, etc.) and other similar environments.

In certain embodiments, coating 3 and/or ta-C layer 7 may have an average hardness of from about 30-80 GPa (most

preferably from about 40-75 GPa) , and a bandgap of from

about 1.8 to 2.2 eV. It is noted that the hardness and

density of coating 3 and/or layers 7, 8 thereof may be adjusted by varying the ion energy of the depositing apparatus or process described below.

When substrate 1 of any of the aforesaid materials is coated with at least DLC coating 3 according to any of the Figs. 1-3 embodiments, the resulting coated article has the following characteristics in certain embodiments : visible transmittance (111. A) greater than about 60% (preferably

greater than about 70%) , UV (ultraviolet) transmittance less

than about 38%, total solar transmittance less than about 45%, and IR (infrared) transmittance less than about 35%

(preferably less than about 25%, and most preferably less than about 21%). Visible, "total solar", UV, and IR

transmittance measuring techniques are set forth in Pat. No. 5,800,933, as well as the ^Λ 008 patent, incorporated herein by reference.

Diamond-like carbon (DLC) and the special tetrahedral amorphous carbon (ta-C) form 7 of DLC utilized in certain

embodiments herein will now be described in detail . All DLC

3 shown in drawings herein is amorphous. Ta-C 7 is amorphous and yet has substantial C-C tetrahedral (sp³-type)

bonding and hence is termed tetrahedral amorphous carbon (ta-C) [or highly ta-C] as it has at least 35% sp³ C-C

bonds, preferably at least about 70% and most preferably at least about 80% sp³ C-C bonds. Diamond-like bonding gives

this ta-C material gross physical properties approaching those of diamond such as high hardness, high density and chemical inertness. However, ta-C also includes sp² C-C trigonal bonding and its optical and electronic properties

are largely determined by this bonding component. The

fraction of sp² bonding, and thus the density, in a ta-C

layer depends for example on the carbon ion energy used during deposition of coating 3 and/or layers 7 and 8.

Properties of a given DLC coating are a function of the

fraction of sp³ to sp² bonding throughout the coating and thus throughout layers 7 and 8.

It is noted that the sp³ bonds discussed herein are sp³ carbon-carbon bonds which result in a high density coating 3 and/or 7 and are not sp³ carbon-hydrogen bonds which do not

provide as high of density.

Depending on the technique of deposition, many ta-C

layers 7 herein contain amounts of H (up to about 4%) which

either include the C atom to take either a tetrahedral configuration or an sp² planar configuration or to be sp-

hybridised within a linear polymeric-like form. In other words C-C, C-H and H-H correlations all contribute to the average structure of layers 7 in some embodiments .

In the case of ta-C which is fully or at least about

90% hydrogen-free, C-C bonding describes the local structure. Ta-C films also have some fraction of sp² or graphic bonding. The spatial distribution of trigonal (sp²) and tetrahedral carbon atoms may determine the bonding

strength of layer (s) 3 to glass, as well as the layer's

density, strength, stress, etc. Tetrahedral amorphous carbon (ta-C) and its hydrogenated form ta-C:H (which contains no more than about 10 at% or so H) have the highest

percentage of carbon-carbon (C-C) sp³ bonding, and are used

as layer 7 in the Fig. 1 embodiment and coating 3 in the Fig. 2 embodiment, and either of these in the Fig. 3 embodiment. This diamond-like bonding confers upon ta-C 7 properties which are unrivaled by other forms of so called DLC which have lower densities and/or greater proportion of

graphitic sp² and polymeric sp C-C and C-H bonding. Ta-C 7 has high density (at least about 2.4 grams per

cubic centimeter), hardness, Young's modulus (700 - 800), as well as a low coefficient of friction (see Table 1 below) .

TABLE 1

Methods of depositing coating 3 on substrate 1 are described below for certain embodiments of this invention.

Prior to coating 3 being formed on the glass substrate,

the top surface of substrate 1 is preferably cleaned by way of an ion beam utilizing oxygen gas in each of the Fig. 1

and 2 embodiments. Oxygen gas physically cleans the surface due to its atomic weight of from about 28 - 40 amu, most preferably about 32. Substrate 1 may also be cleaned by,

for example, sputter cleaning the substrate prior to actual deposition of ta-C or other DLC material. This cleaning may utilize oxygen and/or carbon atoms, and can be at an ion

energy of from about 800 to 1200 eV, most preferably about 1,000 eV.

In plasma ion beam embodiments for depositing coatings

3, 7 and/or 8, carbon ions may be energized to form a stream from plasma toward substrate 1 so that carbon from the ions is deposited on substrate 1. An ion beam from gas phase produces a beam of C+, CH+, C₂H, and/or C₂H₂+ ions (i.e.

carbon or carbon based radicals) . Preferably, acetylene

feedstock gas (C₂H₂) is used to prevent or minimize polymerization and to obtain an appropriate energy to allow the ions to penetrate the substrate 1 surface and subimplant therein, thereby causing coating 3 atoms to intermix with the surface of substrate 1 a few atom layers thereinto.

Impact energy of ions for the bulk of coating 3 (e.g. layer 7 in the Fig. 1 and 2 embodiments) may be from about 100 to 200 eV per carbon atom, preferably from about 100-150 eV, to

cause dense sp³ C-C bonds to form in the DLC layer. The ions impact the substrate with this energy which promotes formation of sp³ carbon-carbon bonds. The impact energy of

the energetic carbon ions may be within a range to promote

formation of the desired lattice structure, such bonds in an interfacing portion (e.g. layer 8 in the Fig. 1 embodiment) of coating 3 apparently being formed at least in part by subimplantation into the substrate as shown in Figure 7. The stream may be optionally composed of ions having

approximately uniform weight, so that impact energy will be approximately uniform. Effectively, the energetic ions

impact on the growing film surface and/or substrate 1 and are driven into the growing film and/or substrate 1 to cause

densification. Coating 3, and especially layer 7, are preferably free of pinholes, to achieve satisfactory water repulsion and suppression of soda diffusion.

Thus, the C-C sp³ bonding is preferably formed by having a predetermined range of ion energy prior to reaching substrate 1, or prior to reaching ta-C growing on the substrate. The optimal ion energy window for ta-C layer 7

formation in the Fig. 1 and 2 embodiments is from about 100-

200 eV (preferably from about 100-150 eV, and most

preferably from about 100-140 eV) per carbon ion. At these energies, films 7 (i.e. layer 3 in the Fig. 2 embodiment)

emulate diamond.

However, compressive stresses can develop in ta-C when being deposited at 100-150 eV. Such stress can reach as high as 10 Gpa and can potentially cause delamination from

many substrates. It has been found that these stresses can be controlled and decreased by increasing the ion energy the deposition process to a range of from about 200-1,000 eV. The plasma ion beam source enables ion energy to be controlled within different ranges in an industrial process

for large area deposition utilized herein. The compressive stress in amorphous carbon is thus decreased significantly at this higher ion energy range of 200-1,000 eV.

High stress is undesirable in the thin interfacing portion 8 of coating 3 that directly contacts the surface of a glass substrate 1. Thus, for example, the first 1-40% thickness (preferably the first 1-20% and most preferably the first 5-10% thickness) 8 of coating 3 is deposited on

substrate 1 using high anti-stress energy levels of from about 200-1,000 eV, preferably from about 400-500 eV. Then,

after this initial interfacing portion 8 of coating 3 has

been grown, the ion energy in the ion deposition process is decreased (either quickly or gradually while deposition

continues) to about 100-200 eV, preferably from about 100- 150 eV, to grow the remainder ta-C layer 7 of coating 3.

For example, assume for exemplary purposes only with reference to Fig. 1 that DLC coating 3 is 100 A thick. The first 10 A layer 8 of coating 3 (i.e. interfacing portion 8) may be deposited using an ion energy of from about 400 to

500 eV so that layer 8 of coating 3 that contacts the surface of substrate 1 has reduced compressive stresses relative to the remainder 7 of coating 3. Interfacing portion 8 of coating 3 at least partially subimplants into

the surface of substrate 1 to allow intermixing with the

glass surface. In certain embodiments, only C ions are used in the deposition of interfacing layer 8, with the graded composition interface being mainly SiC. This interface 8

between substrate 1 and coating 3 improves adhesion of coating 3 to substrate 1 and the gradual composition change

distributes strain in the interfacial region instead of narrowly concentrating it . Layer 8 of DLC coating 3 may or

may not have a density of at least about 2.4 grams per cubic centimeter in different embodiments, and may or may not have

at least about 35%, 70%, or 80% sp³ carbon-carbon bonds in different embodiments. After the first 10 A (i.e. layer 8)

of coating 3 has been deposited, then the ion energy is gradually or quickly decreased to 100 to 150 eV for the remainder [may be either ta-C or ta-C:H] 7 of coating 3 so

that layer 7 has a higher density and a higher percentage of sp³ C-C bonds than layer 8.

Thus, in certain embodiments, because of the adjustment in ion energy during the deposition process, ta-C coating 3

in Figs. 1-3 has different densities and different percentages of sp³ C-C bonds at different areas therein.

However, at least a portion of coating 3 is a highly

tetrahedral ta-C layer 7 having a__density of at least about 2.4 grams per cubic centimeter and at least about 35% sp³. The highly tetrahedral ta-C portion is the portion furthest from substrate 1 in Figure 1, but may optionally be at other areas of coating 3. In a similar manner, the portion of

coating 3 having a lesser percentage of sp³ C-C bonds is preferably the portion immediately adjacent substrate 1 (e.g. interfacing layer 8).

In certain embodiments, ₍ CH₄ may be used as a feedstock

gas during the deposition process instead of or in

combination with the aforesaid C₂H₂ gas. Referring to Figure 8, it is noted that the surface of

a glass substrate has tiny cracks or microcracks defined therein. These cracks may weaken glass by orders of magnitude, especially when water seeps therein and ruptures

further bonds. Thus, another advantage of this invention is that in certain embodiments amorphous carbon atoms and/or

networks of layer 7 or 8 fill in or collect in these small cracks because of the small size of carbon atoms (e.g. less

than about 100 pm radius atomic, most preferably less than about 80 pm, and most preferably about 76.7 pm) and because

of the ion energy of 200 to 1,000 eV, preferably about 400- 500 eV, and momentum. This increases the mechanical strength of the glass . The nano cracks in the glass surface

shown in Figure 8 may sometimes be from about 0.4 nm to 1 nm in width. The inert nature and size of the carbon atoms in these nonocracks will prevent water from attacking bonds at

the crack tip 14 and weakening the glass. The carbon atoms make their way to positions adjacent the tips 14 of these

cracks, due to their size and energy. Tips 14 of these cracks are, typically, from about 0.5 to 50 nm below the glass substrate surface. The top surface of layers 7 and/or 8 remains smooth and/or approximately flat within about less than 1.0 nm even above the cracks .

Carbon is now described generally, in many of its

forms, to aid in the understanding of this invention.

Carbon has the ability to form structures based on directed covalent bonds in all three spatial dimensions.

Two out of the six electrons of a carbon atom lie in the Is core and hence do not participate in bonding, while the four

remaining 2s and 2p electrons take part in chemical bonding to neighboring atoms. The carbon atom's one 2s and three 2p electron orbitals can hybridise in three different ways.

This enables carbon to exist as several allotropes. In nature, three allotropic crystalline phase exists, namely

diamond, graphite and the fullerenes and a plethora of non- crystalline forms.

For the diamond crystalline allotrope, in tetrahedral

or sp³ bonding all the four bonding electrons form σ bonds . The space lattice in diamond is shown in Figure 4 where each

carbon atom is tetrahedrally bonded to four other carbon

atoms by σ bonds of length 0.154 n and bond angle of 109°

53 " . The strength of such a bond coupled with the fact that

diamond is a macromolecule (with entirely covalent bonds) give diamond unique physical properties: high atomic density, transparency, extreme hardness, exceptionally high thermal conductivity and extremely high electrical

resistivity (10¹⁶ Ω-cm) . The properties of graphite are governed by its trigonal

bonding. The outer 2s, 2p_x and 2p_y orbitals hybridise in a manner to give three co-planar sp² orbitals which form σ

bonds and a p-type π orbital 2p_z perpendicular to the sp² orbital plane, as shown in Figure 5. Graphite consists of hexagonal layers separated from each other by a distance of

0.34 nm. Each carbon atom is bonded to three others by 0.142 nm long σ bonds within an hexagonal plane. These planes are held together by weak van der Waals bonding which explains why graphite is soft along the sp² plane. As for fullerenes, it is known that C₆₀ and C₇₀ are the most accessible members of the family of closed-cage

molecules called fullerenes, formed entirely of carbon in the sp² hybridised state. Each fullerenes C_n consists of 12

pentagonal rings and m hexagonal rings such that m = (n -

20) /2 (satisfying Euler's Theorem) . The σ bonds are wrapped

such that the fullerene has a highly strained structure and

the molecule is rigid. As for amorphous carbon, there exists a class of carbon in the metastable state without any long range order.

Material properties change when using different deposition

techniques or even by varying the deposition parameters within a single technique. In this category of materials on one extreme we have ta-C (e.g. layer 7) which is the most

diamond-like with up to 90% C-C sp³ bonding in certain

preferred embodiments and on the other a-C (amorphous carbon) , produced by thermal evaporation of carbon, in which more than 95% graphitic bonds are prevalent. In this respect, these two materials reflect the intrinsic diversity of non-crystalline forms of carbon.

Amorphous materials, such as layer (s) 3, 7 and 8, are metastable solids. In an amorphous solid there exists a set of equilibrium positions about which atoms oscillate. The atoms in an amorphous material are often extended into a

three dimensional network with the absence of order beyond

the second nearest neighbor distance .

Referring again to ta-C layer 7, the sp³/sp² C-C bonded fraction or percentage (%) , e.g. in a vacuum arc deposition technique or techniques used in the 77 patent or

deposition techniques discussed above, can be controlled by changing the energy of the incident C⁺ ions . The films deposited being metastable in nature are under high

compressive stress. The sp² hybridised carbon atoms are clustered and embedded within a sp³ matrix. The extent of

the latter bonding confers onto ta-C its diamond-like

physical properties. The fraction of the sp² hybridised atoms determines the extent of clustering. The degree of

clustering, which is seen as a strain relief mechanism, implies that the π and π* states become delocalised to such

an extent that they control the electronic and optical properties of the films. At high density of states, the π bands merge with the σ states to form the conduction and valence mobility band-edges. Their lower density tail states are localised giving a pseudo-gap. The term "tetrahedral amorphous carbon (ta-C) " is thus used to

distinguish this highly tetrahedral material from other

"diamond-like carbon" which have C-C correlations mostly of the sp² type .

The sp³ bonding in coatings 3 is believed to arise from

a densification process under energetic ion bombardment

conditions. Hybridisation of the carbon atom is expected to

adjust to the local density, becoming more sp³ if the density is high and more sp² if low. This can occur if an incident ion penetrates the first atomic layer and then enters an interstitial subsurface position. The local bonding then reforms around this atom and its neighbours to

adopt the most appropriate hybridisation. High energy ions in principle can penetrate the surface layer of the

substrate or growing DLC, increase the density of deeper layers which then forces sp³ bonding. Ions of lower energy than the penetration threshold only append to the surface

forming sp² bonded a-C.

Coated articles according to any of the aforesaid embodiments may be used, for example, in the context of automotive windshields, automotive back windows, automotive side windows, architectural glass, IG glass units, residential or commercial windows, and the like.

In any of the aforesaid embodiments, a layer of non- porous tungsten disulfide (WS₂) 12 may be provided on top of

layer 7 to prevent the DLC from burning off upon exposure to air if taken to high temperatures after the coating deposition. Layer 12 (e.g. see Figure 8) may be applied by

plasma spraying to a thickness of from about 300 to 10,000 A. WS₂ layer 12 is removeable in certain embodiments. Other suitable materials may instead be used for layer 12.

Once given the above disclosure, many other features, modifications, and improvements will become apparent to the

skilled artisan. Such other features, modifications, and improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the

following claims.

Claims

I CLAIM :

1. A coated glass comprising:

a soda inclusive glass substrate comprising, on a weight basis:

Si0₂ from about 60-80%,

Na₂0 from about 10-20%, CaO from about 0-16%, K_aO from about 0-10%,

MgO from about 0-10%, Al₂0₃ from about 0-5%; and a non-crystalline diamond-like carbon (DLC) coating provided on said glass substrate, wherein said DLC coating includes at least a first highly tetrahedral amorphous carbon layer having at least about 35% sp³ carbon-

carbon bonds and an average density of at least about 2.4 gm/cm³.

2. The coated glass of claim 1, wherein said DLC

coating further includes a second layer therein of amorphous

carbon that is in direct contact with said substrate so that said second layer is disposed between said substrate and

said first highly tetrahedral amorphous carbon layer, and wherein said first highly tetrahedral amorphous carbon layer has a greater density and a greater percentage of sp³

carbon-carbon bonds than said second layer of amorphous

carbon.

3. The coated glass of claim 1, wherein said first

highly tetrahedral amorphous carbon layer has at least about

70% sp³ carbon-carbon bonds, and wherein said glass substrate is a soda lime silica glass substrate including from about 66-75% Si0₂, from about 10-20% Na₂0, from about 5-15% CaO, from about 0-5% MgO, from about 0-5% Al₂0₃, and from about 0-5% K₂0.

4. The coated glass of claim 3 , wherein said highly tetrahedral amorphous carbon layer has at least about 80% sp³ carbon-carbon bonds.

5. The coated glass of claim 3 , wherein said DLC

coating has an average hardness of at least about 40 Gpa, and an average density of at least about 2.4 gm/cm³.

6. The coated glass of claim 1, wherein said DLC

coating has a thickness of from about 30 to 3,000 A.

7. The coated glass of claim 6, wherein said DLC

coating has a thickness of from about 50 to 300 A.

8. The coated glass of claim 1, wherein said DLC coating has a bandgap of from about 1.8 to 2.2 eV.

9. The coated glass of claim 1, wherein the coated

glass comprises the following characteristics : visible transmittance (111. A) : > 60% UV transmittance: < 38% IR transmittance: < 35%.

10. The coated glass of claim 1, wherein said DLC

coating includes at least about 70% sp³ carbon-carbon bonds.

11. The coated glass of claim 1, wherein said DLC coating includes at least about 80% sp³ carbon-carbon bonds.

12. The coated glass of claim 1, wherein said DLC coating is from about 30 to 3,000 A thick, and wherein said first highly tetrahedral amorphous carbon layer of said DLC coating is from about 30 to 2,900 A thick.

13. The coated glass of claim 1, wherein said DLC coating includes sp³ carbon-carbon bonds subimplanted in a surface of said glass substrate so as to strongly bond said DLC coating to said glass substrate.

14. The coated glass of claim 1, further comprising a low-E coating system having at least one layer provided between said glass substrate and said DLC layer.

15. A coated glass comprising: a glass substrate including at least about 5% by weight Na₂0;

a highly tetrahedral amorphous carbon layer, for reducing corrosion on the substrate, having a density of at

least about 2.4 gm/cm³ provided on said glass substrate in order to reduce corrosion or stains on the coated glass, wherein said highly tetrahedral amorphous carbon layer

includes sp² and sp³ carbon-carbon bonds; and

wherein said highly tetrahedral amorphous carbon

layer has more sp³ carbon-carbon bonds than sp² carbon-

carbon bonds .

16. The coated glass of claim 15, further comprising

another amorphous carbon layer located between said

substrate and said highly tetrahedral amorphous carbon

layer, and wherein said another amorphous carbon layer has a

density less than said highly tetrahedral amorphous carbon

layer and a lesser percentage of sp³ carbon-carbon bonds

than said highly tetrahedral amorphous carbon layer.

17. The coated glass of claim 15, wherein said highly

tetrahedral amorphous carbon layer has at least about 70%

sp³ carbon-carbon bonds, and a thickness of from about 30-

300 A.

18. The coated glass of claim 17, wherein said highly

tetrahedral amorphous carbon layer is in direct contact with

said glass substrate.

19. A coated glass comprising:

a soda inclusive glass substrate comprising, on a

weight basis :

Si0₂ from about 60-80%,

Na₂0 from about 10-20%,

CaO from about 0-16%,

K₂0 from about 0-10%,

MgO from about 0-10%,

A1₂0₃ from about 0-5%;

a diamond-like carbon (DLC) coating provided on

said glass substrate for reducing visible corrosion, wherein

said DLC coating has an average density of at least about

2.4 gm/cm³ and a thickness of from about 50 to 300 A; and

wherein the coated glass comprises the following

characteristics:

visible transmittance: > 60%

UV transmittance: < 38%

IR transmittance: < 35%.

20. A method of making a coated glass article, the

method comprising the steps of : providing a glass substrate comprising, on a weight basis, 60-80% Si0₂, 10-20% Na₂0, 0-16% CaO, 0-10% K₂0, 0-10% MgO, and 0-5% Al₂0₃; and

forming at least one highly tetrahedral amorphous

carbon layer having more sp³ carbon-carbon bonds than sp² carbon-carbon bonds on the glass substrate for reducing potential for corrosion.

21. The method of claim 20, wherein said forming step includes using a plasma ion beam and using acetylene gas to form the at least one carbon layer on the glass substrate.

22. The method of claim 20, wherein said forming step includes using a plasma ion beam to form the highly tetrahedral amorphous carbon layer, and varying the ion energy from about 200 to 800 eV during the deposition of an

interfacial portion of the amorphous carbon layer deposited immediately adjacent the substrate to a lower level of from about 100 to 150 eV during the deposition of a higher density portion of the carbon layer that is deposited over

the interfacial portion.

23. An automotive window comprising:

a substrate transparent to at least about 70% of

visible light rays;

a highly tetrahedral amorphous carbon inclusive

coating provided on said substrate, wherein said coating has

a thickness of from about 50 to 300 A and a substantial

number of sp³ carbon-carbon bonds; and

wherein the automotive window comprises the

following optical characteristics:

visible transmittance: > 70%

UV transmittance: < 38%

IR transmittance: < 35%.

24. The automotive window of claim 23 , wherein said

substrate includes one of soda lime silica glass,

borosilicate glass, and substantially transparent plastic,

and wherein said coating has an average density of at least

about 2.4 gm/cm³.

25. The automotive window of claim 23, wherein the

window is an automotive windshield.

26. A method of coating a glass substrate to improve

long-term strength of the glass substrate, the method

comprising the steps of:

providing a glass substrate having at least one

crack with a tip defined therein;

depositing a layer of diamond-like carbon directly

on the glass substrate at an energy level so that carbon

atoms make their way into the crack to a location proximate

the tip of the crack; and

the carbon atoms in the crack preventing some

water molecules from reaching a silicon-oxygen bond at the

tip of the crack thereby improving the long-term strength of

the glass .

27. The method of claim 26, wherein said energy level

is an ion energy level of from about 200 to 1,000 eV.