CA2090110A1 - Abrasion wear resistant polymeric substrate product - Google Patents

Abstract

2090110 9206843 PCTABS00011 A substantially optically transparent coated substrate product (1) with a highly adherent, abrasion-resistant diamond-like hard carbon coating (4) is disclosed. The substrate product is comprised of a polymeric substrate (1), and adhesion-mediating polysiloxane polymer layer (2), one or more intermediate layers (3) and an outer layer of diamond-like hard carbon (4). The invention also allows for the production of adherent thin film interference layer coatings (i.e. quarter wavelength stacks and anti-reflection coatings) using diamond-like hard carbon as the high refractive index layer and the interlayer(s) as the low refractive index layer or, alternatively, using diamond-like hard carbon as the low refractive index layer and the interlayer(s) as the high refractive index layer. The substrate product is useful as optical and sunglass lenses.

Description

W092/06843 PCT/US91/07~09 , :;
., ABRASION ~EAR RE~ISTANT
POLYMERIC ~UBST~E PRODUCT
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FIELD OF THE INVENTION
5This invention relates generally to coated - substrate products. More particularly, the invention relates to a s~bstantially optically transparent coated ;~ substrate product comprised of a polymeric parent substrate, one or more interlayers and a diamond-like carbon layer, and to a method for producing same.
BACKGROUND OF THE INVENTION
The properties of polymers (i.e., plastics) make -~ them ideal substrate materials for use in many applications. In particular, optically transparent plastics such as polycarbonate, CR-39 ~ ~allyl diglycol ~` carbonate) and acrylics have become widely accepted " materials for use as optical lenses because of their light weight and ease of molding compared to glass.
Polycarbonate also has superior impact resistance compared to glass. However, a major drawback with plastic substxates, particularly polycarbonate, is their poor scratch and abrasion resistance.
Various methods have been employed to enhance the abrasion wear resistance of plastic substrates. For - 25 example, many commercial plastic opthalmic and sunglass ; lenses are coated with either organic acrylat~-type ``; polymer coatings or polysiloxane~type polymer co~atings.
(See, S. ~erbPrt, Industrial Diamond Review, Feb. 1984, at p.77.) Althou~h these polymer coatings offer a significant improvement in abrasion resistance relative to the uncoated plastic lens, the perceived ahrasion resistance of the coated pl~stic lens compared to a glass -lens is still poor.
Glass and silicon dioxide have also ~een employ~d as coatings on plastic substrates to improve the ahrasion resistance. Illustrative are Great Britain Patent No.
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1,335,065, and U~S. Patent Nos. 3,458,342 and 4,328,646.
However, the absence of an intermediate layer between the glass or silicon dioxide layer and the plastic substrate often results in the glass or silicon dioxide coating spalling or cracking when the substrate is su~jected to thermal cycling.
- Several prior art techniques disclose the use of an intermediate layer between the substrate and the glass or silicon dioxide outer layer to improve adhesion of the outer layer. For example, U.S. Patent 4,190,681, issued to Hall, et al., discloses an evaporative deposition technique of a glass layer disposed on top of an intermediate layer of an acrylic-type polymer which has in turn been coated onto a polycarbonate substrate. U.S.
Patent No. 4,200,681, also issued to Hall, et al., discloses the vapor deposition of a top layer of silicon dioxide onto an intermediate primer layer which in turn has ~een deposited on the surface of a polycarbonate substrate. However, this partic:ular evaporative technique of applying a layer of silicon dioxide is o~ten undesirable for several reasons. First, this technique suffers from inadequate adhesion of the silicon dioxide ` or glass layer, due to (il the relatively low reactivity of the evaporated silicon oxide film-forming species, and -` 25 ~ii) insufficient bond strength between the silicon -- dioxide layer and the underlying carbonaceous acrylic polymer layer. Second, the individual particles of silicon dioxide may evaporate and later condense on the coating surface at rates which vary with the particular site-of deposition, resulting in a non-uniform glass surface often characterized by pits, pinholes, and other - -imperfections.
U.5. Patent No. 3,713,869, teaches the deposition of~an intermediate layer polymerized by glow discharge onto a polycarbonate surface. -A hard inorganic glass layer is then vaporized by an electron beam gun onto the ~ , ', ., i , ,,,,, , .,, , , .. , , , .... . . . . ., .. . . ... - - - - . - . - - - . . -. . .

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, intermediate layer in a manner similar to that used by Hall, et al. European Patent Application No. 0,266,225 further discloses a coating in which the plastic substrate is first coated with a silicon-based layer which is overcoated ~y a top layer of silicon dioxide.
~ U.S. Patent No. 4,8~2,g41 discloses a polycarbonate - substrate with an interfacial layer of resinous composition, and an abrasion-resistant top layer applied by plasma-enhanced chemical vapor deposition. U.S.
10 Patent No. 4,341,841 discloses an article with a multi-layer protective coating, comprising a substrate and two protective layers, one being a vacuum coated ceramic layer, and one being a resinous layer, coated in any order. ~lthough each of these prior art techniques have resulted in limited improvement in the adhesion between the glass or silicon dioxide coating and the substrate, and ultimately the wear resistance of tha coated substrate product, the prior art techniques do not contemplate a diamond-like carbon ("DLC") outer layer, nor address the optimum method for obtaining an adherent ` DLC layer on a polycarbonate substrate.
~`~ In all of the aforementioned prior art `~ techniques, the abrasion resistance of the coated plastic ~; substrate has been unsatisfactory because o~ the limited hardness of the silicon dioxide or glass coating.
Additional problems are also encountered by thin oxide coatings. Due to incomplete oxidation or inhomogeneous ~` - chemical bonding which is characteristic of oxide films, the films are susceptible to chemical reaction and damage ~` 30 by salt water. This is a particular disadvantage for eyeglass or sunglass lenses which are exposed to perspiration or ocean spray. Finally, under thermal cycling or flexing, the oxid~ coatings are susceptible to cracking and peeling.
There are also teachings of l'mixed phase" or "gradient" inorganic hard coatings for plastic substrates ;"

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Patent No. 4,~30,873, issued to Benz, et al., discloses a process for applying a transparent layer onto the surface of a plastic element by first polymerizing an organic vapor and subsequently introducing additives such as oxygen, hydrocarbon compounds, or nitrogen-containing compounds to the vapor to form a layer with increased hardness. International Patent Application No.
W089/01957 discloses a method for depositing an abrasion-resistant coating comprising the plasma-enhanced chemical vapor deposition of a coating characterized by a gradual transition from a composition consisting essentially of an interfacial material to a composition consisting essentially of an abrasion-resistant material. Further, U.S. Patent No. 4,777,090, discloses a product which has a disordered carbon coating at the substrate-coating interface and a relatively ordered portion composed of either carbon or silicon dioxide away from the substrate-coating interface. These prior art techniques similarly do not teach the deposition of a hard DLC layer, nor discuss the formation of a discrete multilayer coating structure with a polycarbonate substrate and an adherent DLC outer layer.
There are, however, sev2ral prior art references which teach the direct deposition of hard DLC films onto .. , ~ ~ .
pla~tic substrates to improve abrasion resistance.
- Illustrative are U.S. Patent Nos. 4,663,183, 4,770,940, 4,783,361, 4,698,256 and 4,877,677, and European Application Nos. 0,280,2l5 and 0,278,480. These prior art rèferences do not teach the use of interlayer materials which have been ~ound to be essential to - achieve satisfactory adherence of the DLC film.~ ~
- There are also prior art references which teach the deposition of hard DLC films onto plastic substrates ~` 35 with the use of limited interlayer materials. For example, U.S. Patent No. 4,661,409, issued to Kieser, et ~:`
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~5~ 2~ 3 al., discloses a substrate having an amorphous carbon coating and an adhesion-mediating interlayer of a ~' - siloxane or silazane polymer between the carbon film and ; the substrate. U.S. Patent No. ~,569,738, also issued to Xieser, et al., discloses a microwave discharge process for depositing the siloxane or silazane polymer and amorphous carbon layers on the substrate. 'However, in each of these references only intermediate layers of ' microwave discharge-deposited siloxane and silazane polymers are discussed.
~; Although DLC coatings possess excellent optical properties and exhibit excellent resistance to abrasion and chemical attack, DLC coatings have not been widely applied to plastic substrates (including lenses) to date for several reasons. First, while DLC coatings are in~eed very hard, they are also brittle when thin. Thus, when applied to soft substrates such as plastics, the DLC
'~ coating can crack and/or be crushed into the substrate - when a high load or force is applied to the surface of the substrate. This mechanism is also responsible for the apparent scratching of the DLC coating from the -` surface of plastic substrates in severe abrasive ;'~ environments.
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Second, the adhesion of DLC coatings to plastic substrates has been poor due to the high internal stress associated with the DLC coatings. This poor adhesion has been especially evident during cooling of DLC coated pla~tic substrat~s from elevated temperatures. There is also a significant difference in the thermal expansion coefficients between the-iDLC coating and~the plastic substrate. Thus, during thermal cycling the weak adhesive bonding strength''at the'DLC plasti'c interface is - overwhelmed by the forces generated by expansion and contraction, and hence,''the DLC'coating cracks and ~' 35 delaminates.
It is therefore an object of the present . .

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invention to provide a plastic substrate with hard coated surface layers, such as diamond-like carbon, firmly adhered thereto, thereby to prevent undesirable separation or crack formation, while at the same time providing excellent hardness and resistance to abrasion, chemical attack and impact.
It is a ~urther object of the present invention to provide an abrasion-resistant plastic substrate with increased ease o~ cleaning.
It is a further object of the present invention to provide a plastic substrate with a diamond-like hard carbon coating-which combines the ability to reflec~
decorative colors without sacrificing the aforementioned objects.
It is a further object of the present invention to provide a method for depositing an adherent coating incorporating high refractive index diamond-like hard - carbon layers in an alternating layer stack along with at ~` least one other material o~ substantially different refractive index in order to produce thin film interference coatings such as guarter wavelength stacks.
It is a further object of this invention to provide a low cost and efficient process for producing a pIastic substrate with superior abrasion wear resistance 2S and reduced chemical reactivity.
~ SUMMARY OF THE INVENTION
;~ The disclosed abrasion wear resistant coated substrate product substantially reduces or eliminates the disadvantag~s and shortc~mings associated with the prior art techniques. The invention discloses a substantially optically transparent composite structure which comprises - a polymeric parent substrate, one or more intermediate layers and a-diamond-like carbon layer.~ The invention al~o discloses a method for fabricating the coated substrate product.
According to the method, the substrate surface is . . .
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, initially chemically de-greased. In the second step, the substrate is coated with a polysiloxane polymer layer by a flow, dip, spray, or other conventional solution-based coating process. After the polysiloxane polymer layer is thermally cured, the coated surface is chemically cleaned. The substrate sur~ace is then sputter-etched with energetic gas ions to assist in the removal of residual hydrocarbons, as well as alkali metals and other additives. After sputter-etching, one or more interlayers are chemically vapor deposited on the substrate, followed by the deposition of a diamond-like `` carbon layer. Once the requisite number of interlayers and diamond-like carbon layers have been deposited, the coated substrate is cooled and removed from the reactor.
, 15 BRIEF DESCRIPTION OF THE DRAWTNGS
Further features and advantages will become apparent from the following and more-particular : `1 -~ description of the preferred embodiment of the invention, as illustrated in the accompanying drawings, in-whi~h like reference characters generally refer to the same `~ parts or elements throughout the views, and in which:
Figure 1 is a cross-sectional view of the c~ated substrate product in accordance with the present invention;
Figure 2 is a cross-sectional view of the coated substrate product in accordance with a furtheriembodiment of the prevent invention; and Figure 3 is a cross-sectional view of the coated substrate product in accordance with a still further ~ 30 embodiment of the present invention.-I DETAILED DESCRIPTION OF THE INVENTION - i In-accordance with~thé presentYinvention, the disclosed abrasion wear resistant~coated substrate product substantially reduces or eliminates the ~; 35 disadvantages and shortcomings associated with the prior art techniques. As illustrated in Figures 1-3, the '-.
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W09~/06843 PCT/US91tO72~9 ~'disclosed invention is a substantially optically transparent composite structure which comprises a polymeric parent substrate, one or more intermediate layers (interlayers) and a diamond-like carbon layer. By the term of "substantially optically transparent", it is ; intended to mean transparent to light in the visible region of the elactromagnetic spectrum, which is generally between 350 nanometers and approximately 750 nanometers wavelength. A highly important technical advantage of thè invention is that the resultant multilayer composite structure has all of the typical attributes of plasticsj such as high tensile and impact strength, while also exhibiting excellent resistance to wear and chemical attack.
~; 15 In the preferred embodiment form of the invention, as illustrated in Figure l, the polymeric parent substrate 1 is coated with an adhesion-mediating polysiloxane polymer layer 2 by a conventional dip, flow, spray, or other solution-hased coating process. In accordance with the invention, it has been found that adherence of diamond-like carbon t"DLC") film to a polymeric substrate is significantly improved, resulting in decidedly better product lifetime, when one applies an adherence transmitting intermediate layer, such as a polysiloxane polymer, between the polymeric substrate 1 ` and the diamond-like carbon~làyer 4 (i.e. inor~anic hard ~ layer). The enhanced adhesion ~etween the polymeric ;~ substrate and a diamond-like carbon layer 4 is due, in part! to the fact that the elastic modulus and thermal expansion coefficient of the polysiloxane layer 2 is - generally intermediate between that of the plastic substrate l and the diamond-like-carbon layer 4, resulting in reduced-expansion mismatch between the substrate l and the diamond-like carbon layer 4. -Polysiloxane polymers are formed from monomers such as bi-, tri-, and tetra-function silanes, in which silicon ~:;

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atoms are bonded to hydrogen atoms, alcohol functional groups, or alkoxy functional groups. By conventional condensation polymerization (so-called thermal curing process) these monomeric mixtures are converted to oligomers, and subsequently into a 3-dimensional network polymer by elimination (or condensation) of water or alcohols. The degree of crosslinking in the polysiloxane polymer coating is determined by the amount of tri-, and tetra-functional monomers and/or the amount of pre-polymerized crosslinking agents having reactive endgroups which are included in the mixture. Polysiloxane ~ polymer coatings can also incorporate additives such as ; resins (nylon, epoxy, melamine, etc.), hardners, flow control agents, diluents, thickeners, catalysts, dyes, pigments, colloidal suspensions of silicon dioxide and other oxide materials which can be used to modify the properties of the coating. Polysiloxane polymer layers are indeed known per se, but not known has been their excellent suitability as an intermediate layer for improving adherence (primer) be.tween plastics and DLC
coatings.
8y the term of "polysiloxane polymer", it is thus intended to mean a 3-dimensional network condensation polymer in which silicon atoms are bonded to 2-4 oxygen ~` 25 atoms. In the case of silicon bonded to 2 oxygen atoms, ; the oxygen a~oms ar~ inter-bonded to silicon atoms and these are a part of a ~: I ~- ' ' '.
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the polymer, and where-the third and fourth bonding ; positions on the silicon atoms are occupied ~y unreactive organic functional groups, either alkyl or aryl groups.
Furthermore, there will be some number of silicon atoms bonded to 3 oxygen atoms, and a lesser number of silicon ' ' W O 92/06843 PC~r/US91/07209 ~9~ -lo-atoms bonded to 4 oxygen atoms. In each case, those oxygen atoms bonded to silicon atoms are the cites for linking linear runs of the polymer to form a 3--dimensional network.
The adhesion-mediating polysiloxane polymer layer 2 can be from 1 to 20 microns in thickness. In the preferred embodiment form of the invention; the adhesion-mediating layer is at least 3 microns thick. It has been found that a critical polysiloxane layer thickness of at least 3 microns is necessary to provide the diamond-like - carbon layer 4 with adequate mechanical support under high loads. This~added support greatly reduces 'Icrushing" of the diamond-like carbon layer 4 into the substrate 1, allowing the amount of abrasion protection offered by the diamond-like carbon layer 4 to be greatly ~` increased.
Following deposition of the adhesion-mediating polysiloxane polymer layer, a first interlayer 3 is chemically vapor deposited onto the substantially optically transparent polymeric parent substrate 1. By `~ the term of "chemically vapor deposited", it is intended to mean materials deposited by vacuum deposition processes, including thermal evaporation, electron beam evaporation, magnetron sputtering, and ion beam -~ 25 sputtering from solid precursor materials, thermally-activated deposition from reactive gaseous precursor materials; and glow discharge, plasma, or ion beam -deposition from gaseous precursor materials. Preferably, the firs~ interlayer 3 is deposited onto the parent ~;~ 30 substrate 1 by ion beam sputtering or magnetron - sputtering when dense layers exhibiting compressive stress are desired, or by electron-beam evaporation when ; layers exhibiting tensile stress are desired, as discussed more fully herein.
The first interlayer 3 generally comprises a ~ substantially optically transparent material devoid of :

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alkali metal atoms and fluorine, and capable of forming a strong chemical bond to the coated substrate 1 and the diamond-like carbon layer 4. By the term of "strong chemical bond", it is intended to mean that the interlayer is composed of a significant amount of an :~ element or elements which are capable of undergoing a chemical reaction with carbon to form carbide-bonding.
: The absence of alkali metals and fluorine is essential to . achieve a highly adherent interface between the first : 10 interlayer 3 and the diamond-like carbon layer 4. Thus, :~ the first interlayer 3 must also have the property of ,, providing a barrier to diffusion of alkali metals and additives from the parent substrate } to the diamond-like ~. carbon layer 4.
:. 15 The first interlayer 3 can be from 5 A to ~: 10,000 A in thickness, preferably at least 10 A thick, and may comprise silicon oxide, silicon dioxide, yttrium . oxide, germanium oxide, hafnium oxide, tantalum oxide, .` titanium oxide, zirconium oxide tungsten oxide, .: ` 20 molybdenum oxide, boron oxide or mixtures thereof. By the term "oxide", it is intended to mean a stoichiometrically oxidized material, or a partially oxidized material which contains excess metal atoms, or is deficient in oxygen. The first interlayer may further comprise silicon nitride, titanium nitride, tantalum .. nitride, hafnium nitride, zirconium nitride, boron .:; nitride, tungsten nitride, molybdenum nitride, silicon carbide, germanium carbide and mixtures thereof. By the ` ~ term "nitride", it is intended to mean a material composed of a stoichiometric amount of ni~rogen or a material which either contains excess nitrogen atoms, or : is de~icient in nitrogen. By the term "carbide", it is : intended to mean a material composed of a stoichiometric amount of carbon or a material which either contains - 35 excess carbon atoms, or is deficient in carbon.
In the preferred embodiment form of the ., , :
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invention, the first interlayer 3 comprises silicon dioxide. Silicon dioxide is the preferred interlayer material due to (i) its chemical similarity with the polysiloxane polymer adhesion-mediatiny layer 2 and the resultant affinity to form a strong chemical bond thereto and (ii) its ability to form an excellent chemical bond to diamond-like carbon. In accordance with the invention, it has been found that the thickness of the silicon dioxide first interlayer 3 should be from 200 A
to 2000 A to achieve optimum adhesion of the diamond-like carbon layer 4. Generally, the necessary thickness of the silicon dioxide interlayer 3 is dependent upon the nature of the polymeric substrate material, the physic l characteristics of the diamond-like carbon layer 4 bonded ~ 15 to the silicon dioxide first interlayer 3, and the degree ; of adhesion required for the particular application. For ;~ example, it has been found that when silicon dioxide layers less than approximately 400 A are employed as coatings over polycarbonate substrates, diamond-like carbon layers of thicknesses greater than 850 A will undergo adhesion failure when the substrate is thermally i cycled. However, silicon dioxide layers of approximately 200 A are sufficient to promote excellent adhesion with ; substrates exhibiting a lower thermal expansion ~` 25 coefficient (i.e. CR-3 ~ and acrylic plasticsj and/or diamond-like carbon layers of thickness less than 850 A.;~
In accordance with the invention, it is therefore ~ preferable that the silicon dioxide first interlayer 3 be - at least 200 A thick.
Following deposition of the first interlayer 3 onto the coated parent substrate 1, the diamond-like - carbon layer 4 is chemically vapor deposited onto the coated substrate. The diamond-like carbon layer 4 can be I ~rom 10 A to 10 micrometers in thickness. Preferably, the diamond-like carbon layer 4 is at least 200 A thick.
To ~urther enhance the abrasion wear resistance . .

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of the structure, more than one interlayer or a plurality of alternating interlayers 3 and diamond-like carbon layers 4 may be deposited onto the parent substrate 1, as ; shown in Figure 2. In a further envisioned embodiments - 5 of the invention not shown, the structure also may comprise a parent substrate 1, an adhesion-mediating layer 2, two or more different interlayers; a first diamond-like carbon layer 4, a first interlayer 3 and a second diamond-like carbon layer 4. It has been found that such arrangements allow for the deposition of a greater total thickness of DLC material, which provides a further increase in abrasion resistance.
~ owever, as the thickness of the coated substrate product increases, control of the stresses in the ` 15 respective diamond-like carbon layer(s) 4 and the interlayer(~) 3 becomes imperative. For example, if the interlayer 3 (e.g. silicon dioxide) is deposited onto the parent substrate 1 with an excessive tensile stress, the interlayer 3 may craze or crack. If the interlayer 3 is ~ 20 deposited onto the parent substrate 1 with an excessive `,!, compressive stress, problems, with the adherence o~ the ~` interlayer 3 and diamond-like carbon layer(s) 4 may be :..
encountered. Therefore in the preferred embodiment form of the invention, the compressive stress in the interlayer~s) 3 is less than the compressive stress in ~`~ the diamond-lik~ carbon layer(s) 4; more preferably, the compressive stress in the interlayer(s) 3 is intermediate between the compressive stress of the diamond-like carbon ~`~ layer(s) 4 and the adhesion-mediating layer 2.
Alternatively, the interlayer(s) 3 may be deposited onto the parent substrate 1 under tensile stress. This may be achieved by evaporative deposition of the interlayer(s) 3. The advantage of depositing the interlayer(s) 3 under tensile stress would be that the tensile stress in the interlayer(s) 3 would tend to cancel out the compressive stress in the diamond-like -: . , : :
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W O 92/06843 PC~r/US9l/07209 carbon layer( 5) 4, allowing for a much thicker composite structure.
In accordance with a further aspect of the ! invention, the modulus of elasticity and hardness of the 5 interlayer(s~ 3 is preferably less than the modulus of . elasticity and.hardness of the diamond-like carbon layer 4; more preferably, the modulus of elastic~ty of the : interlayer(s) 3 is intermediate that of the diamond-like . carbon layer 4 and the adhesion-mediating layer 2, and the hardness of the diamond-like carbon layer 4 is at least twice as hard as the underlying interlayer(s) ~.
~-~ With this particular arrangement, the impact resistance of the parent substrate 1 will be significantly enhanced.
In another embodiment of the invention, as ~ 15 illustrated in Figure 3, a second interlayer 5 is - chemically vapor deposited onto the coated substrate 1 ~ and positioned such that the second interlayer 5 is :- disposed between the first interlayer 3 and the diamond-like carbon layer 4. The second interlayer 5 would ;~ 20 similarly comprise a substantially optically transparent :~ - material devoid of alkali metal atoms and fluorine, and ;
i capable of forming a strong chemical bond to the first : interlayer 3 and the diamond-like carbon layer 4. The :~ second interlayer 5 may be from 5 A to 10,000 A in .~ 25 thickness, preferably at least 10 A thick, and comprise a substantially optically transparent silicon nitride, titanium nitride, tantalum nitride, tungsten nitride, molybdenum nitride, hafnium nitride, zirconium nitride,.
.: boron ~itride, yktrium oxide, qermanium oxide/ hafnium ; 30 oxide, silicon oxide, silicon dioxide, tantalum oxide, ~-i titanium oxide, zirconium oxide, tungsten oxide, . molybdenum oxide, boron oxide,~ silicon carbide, germanium carbide and mixtures thereof.
In the preferred embodiment form of the invention, the second interlayer 5 would similarly comprise silicon dioxide. As previously discussed, the ' ``' .
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-~; silicon dioxide second interlayer 5 may be from 200 A to 2000 A in thickness, preferably at least 200 A thick.
Since the second interlayer 5 provides a diffusion barrier for alkali metal atoms, fluorine and/or any additional additives which would adYersely effect the adherence of the diamond-like carbon layer 4 and since the second interlayer 5 is capable of forming a strong chemical bond with diamond-like carbon, the first - interlayer 3 could further comprise a substantially optically transparent aluminum oxide, cerium oxide, tin oxide, thorium oxide, lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, francium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, cerium oxide, radium oxide, barium fluoride, cerium fluoride, magnesium fluoride, thorium fluoride, calcium fluoride, neodymium fluoride, lead fluoride, sodium fluoride, lithium fluoride, ~inc selenide, zinc sulfide and mixtures thereof.
The second interlayer 5 may alternatively ~ 20 comprise a substantially optically transparent metallic - material capable o~ reflecting visible light and capable .
of forming a strong chemical bond with the first interlayer 3 and the diamond-like carbon layer 4, `$~ selected from the following two groups. In the first 25 group, the metallic material may consist of silicon, I
~` germanium, hafnium, molybdenum, tungsten, yttrium, ~ ¦
tantalum, titanium and zirconium. These metallic materials all form a strong chemical bond to the diamond- !
like carbon layer 4.
The second group of metallic materials comprises vanadium, niobium, chromium, manganese, rhenium, - technetium, iron, cobalt, iridium, rhodium, nickel, - palladium, platinum, copper, silver, gold, zlnc, ruthenium, indium, aluminum, tin, osmium, thallium, lead, antimony, bismuth and polonium. Preferably, the second interlayer 5 comprises rhenium, iridium, tin, indium, '' ' ,'`
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aluminum, nickel, iron, chromium, copper, gold, silver and platinum. Although these materials will provide a diffusion barrier to alkali metal atoms and fluorine, they will not form a strong carbide bond with the diamond-like carbon layer 4. Therefore, if any of these metallic materials are selected for the second interlayer 5, a third interlayer (not shown) must be disposed between the second interlayer 5 and the diamond-like ' carbon layer 4. The third interlayer would similarly ~e from 5 A to lO,OOO A in thickness, preferably at least lO
A thick, and comprise a substantially optically transparent material devoid of alkali metal atoms and fluorine and selected from the group consisting of silicon nitride, titanium nitride, tantalum nitride, tungsten nitride, molybdenum nitride, hafnium nitride, zirconium nitride, boron nitride, yttrium oxide, germanium oxide, hafnium oxide, silicon oxide, silicon ' dioxide, tantalum oxide, titanium oxide, zirconium oxide, ~' tungsten oxide, molybdenum oxide, boron oxide, silicon carbide, germanium carbide and mixtures thereof. In the preferred embodiment, the third interlayer would comprise silicon dioxide with a thickness of at least 200 A (as previously discussed). Although it is not necessary, this third interlayer may be employed with the ' 25 aforementioned first group o~ metallic materials.
;' The metallic second~lnterlayer 5 can be from 5 A
' to lOOO A in thickness. Preferably, the metallic second .
~'` interlayer 5 is at least 25 A thick.
~ The thickness'of the diamond-liXe carbon layer(s) `' 30 4, and''interlayer(s) 3 which are applied over the - metallic interlayer 5 can be precisely controlled to produce desired re~lected colors such as gold, pu~ple, blue, red, orange, green, etc. In this way, a plastic !~
substrate (such as an optical sunglass lens) can be produced which combines the features of a controlled reflected color with the abrasion wear resistance of the .
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diamond-like carbon coating of the present invention.
In yet another envisioned embodiment of the invention not shown, the embodiment illustrated in Figure

3 and discussed above may be provided with a second composite layer comprising a first interlayer 3 and a diamond~lika carbon layer 4~ The resultant multilayer structure would thus be a parent substrate l, an adhesion-mediating layer 2, a first interlayer 3, a second interlayer 5, a diamond-like carbon layer 4, a first interlayer 3 and a diamond-like carbon layer 4.
The structure may alternatively comprise a parent substrate 1, an adhesion-mediating layer 2, two first - interlayers 3, a diamond-like carbon layer 4, a first interlayer 3 and a diamond-like carbon layer 4; or a -15 parent substrate 1, and adhesion mediating layer 2, a Ifirst interlayer 3, a second interlayer 5, a first interlayer 3, a diamond-like carbon layer 4, a-first interlayer 3 and a diamond-like carbon layer 4. The aforementioned illustrative structures are not comprehensive, and other structure configurations may be employed within the scope of the invention to achieve the objectives of excellent resistance to abrasion, chemical attack and impact.
By choosing the appropriate interlayer 3, 5 and diamond-like carbon layer 4 thicknesses, criteria which are known in the art of op~ical coating design could be -employed in each of the aforementioned embodiments of the present invention to produce quarter wavelength ~tacks and other "dielectric stack" coating configurations. In these dielectric stack configurations, optical interference effects could be used to produce wavelength-selective mirrors or anti-reflection films.
Additionallyt the reflection of light at predetermined wavelength ranges may be either minimized or maximized by choosing the appropriate thickness of at least one of the interlayers 3,5 and diamond~like carbon layer 4.
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Superior abrasion wear resistance and environmental durability currently unavailable with conventional optical coatings could thus be realized by the incorporation of the dielectric stack configurations into the present invention.
The method of the present invention teaches those skilled in the art how to fabricate the transparent abrasion wear resistant coated polymeric substrate product. According to the method, the first step involves chemically de-greasing the surface of the parent " substrate 1. The substrate 1 is then coated with a polysiloxane polymer layer 2 (see Figure 1) by a conventional dip, flow, spray or other solution-based coating process. After the polysiloxane layer 2 is thermally cured, the coated surface of the substrate 1 is chemically cleaned. The substrate 1 is then placed into a chemical vapor deposition reactor vacuum chamber and the air evacuated from the chamber to less than approximately 5 x 10-6 Torr.
In the next step, the surface of the substrate 1 is sputter-etched with energetic ions or atoms to assist in the removal of residual hydxocarbons, as well as ~` alkali metals and other ad~itives which are commonly present on the surface of the substrate materials. In accordance with the invention, it has been found that the concentration of alkali metals (i.e. Na,Ca) at the surface of a substrate was significantly reduced as a -~ function of ion sputter-etching time and that increased sputter-etching time substantially improved the adhesion ` 30 of the diamond-like carbon layer 4. [See Examples 1-15]
- Therefore, it is concluded that the removal of alkali metals and other additives is also essential to a achieve a highly adherent interface betwee~ parent substrate 1 and the diamond-like carbon layer 4. -The sputter-etching may be performed with a beam of inert gas ions, hydrogen ions or oxygen ions, a glow '''`

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W092/06843 PCTtUS91/07209 discharge or a plasma of inert gas, hydrogen or oxygen.
In the preferred embodiment form of the invention, sputter-etching is performed with a beam of energetir gas ions at an energy of at least 200 eV.
Following the sputter-etching step, one or more interlayers are chemically vapor deposited onto the parent substrate 1. During a first cycle any of the aforementioned conventional chemical vapor deposition methods may be employed to deposit the interlayers 3,5 The deposition rate of each interlayer 3,5 is generally in the range of about 0.1-10 microns/hour. The total thickness of each interlayer can be in the range of about 5 A to 10,000 A. In the preferred embodiment form of the -~
invention, the total thickness for each interlayer 3,5 is at least 10 A, or at least 200 A if silicon dioxide is ; employed.
During the chemical vapor deposition of the interlayers 3,5 it is desirable to operate the reactor chamber at a temperature which is as low as possible. It has been found that decraasing the substrate 1 temperature generally improves the adherence of the diamond-like carbon layer 4 and also eliminates any danger of heating the plastic substrate 1 to a temperature which would be within the softening range for the plastic material. Therefore, in the preferred embodiment form of the invention, the temperature of the parent substrate 1 is maintained at less than 125 n C
during the chemical vapor deposition step(s).
-~ - After the chemical vapor deposition of one o-more interlayers onto the parent substrate 1, a diamond-~` like carbon layer 4 is deposited onto the coated substrate. The diamond-like carbon Iayer 4 can be deposited by the following conventional methods; (i) direct ion beam deposition, dual ion beam deposition, glow discharge, ~F-plasma, DC-plasma, or microwave plasma ~: deposition from a carbon-containing gas or a carbon-~ .

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WO9~/06843 PCT/US91/07209 `~

~containing vapor which can also he mixed with hydrogen, nitrogen-containing gases, oxygen containing gases and/or inert gas, (ii) electron beam evaporation, ion-assisted ~ evaporation, magnetron sputtering, ion beam sputtering, ; 5 or ion-assisted sputter deposition from a solid carbon target material, or (iii) combinations of (i) and ~ii).
In the preferred embodiment form of the invention, the diamond-like carbon layer(s) 4 is deposited by ion beam deposition from a hydrocarbon gas or carbon vapor. The ion beam deposition may also be performed in combination with an inert gas or hydrogen.
The deposition rate of the diamond-like carbon layer 4 is generally in the range of about 0.1-10 microns/hour. The total thickness of the diamond-like carbon layer 4 is generally in the range of about 10 A to 10 micrometers. Preferably, the thickness of the diamond like carbon layer 4 is at least 200 A thick.
After the deposition o~ the appropriate interlayers and diamond-like carbon layer(s) 4, a~
` 20 detailed in the aforementioned embodiments, the coated substrate product is cooled by extinguishing the deposition process and passing an inert gas over the `~ substrate until it has reached substantially room ~ temperature. The coated substrate product, exhibiting ; 25 superior resistance to abrasion and chemical attack, is then removed ~ro~ the reactor.
The examples which follow demonstrate that ~:, abrasion-resistant and highly adherent diamond-like hard ; carbon coatings can be applied to the surface of plastic substrates, such as optical lenses. The examples are for -i illustrative purposes only and are not meant to limit the scope of the claims in any way. - :
Example No. 1 illustrates that the invention can be used to apply adherent and abrasion-resistant diamond-like hard carbon coatings applied to polycarbonate and ~ CR-39 plastic lenses. Example No. 1 also illustrates '` .

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the critical i~fluence of the polysiloxane polymer layer thickness on the abrasion resistance of the diamond-like carbon coated substrate product. Example Nos. 2-6 illustrate the critical influence of the silicon dioxide interlayer thickness on the adhesion of the diamond-like carbon outer layer. Example Nos. 7-14 illustrate that a variety of reflected colors can be produce~ by including a metallic layer in the coating ~tack, a~d depositing different thicknesses of a silicon dioxide interlayer and diamond-like carbon over th~ metallic layer. Example No.
15 illustrates the deposition of alternating layers of ' silicon dioxide and diamond-like carbon over the polysiloxane polymer layer to form a quarter wavelength stack coating made of silicon dioxide and diamond-like carbon.
Table I is a summary of the Young's Modulus and Hardnes~ of the layers used in Examples 1-15.
-Table I
Young's Modulus and Hardness for typical layers used in the Examples 1-15.*
~aterial or Coating Hardness ~GPa) Young's Uodulus (Gi'a) .
___________________ __________ ___ _____________________ ~; Polycarbonate 0.23 3.8 25 Polysilo~ane (1~ 0.73 4.7 io2 (2) 8.6 ~ 88 DLC ~3) 12-21 100-170 .. . .
.:. ~otes: S1) Layer formed by dip coating~thermal curing ` 30 process ~- ~2) Lsyer formed by Ar ion beam sputter-, deposi~ion from a quart~ target. - I, ~3) Layer formed by direct ion beam deposition ..... .
from CH4/Ar gas.
~:~ 35 ~All values determined ~y nanoindentation measurement.
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W092/06~43 PCT/~S91/07209 ~ ~ -22-.

Eight polycarbonate sunglass lenses and two CR-39~ clear opthalmic lenses were vapor-degreased with Freon, and then dip-coated with a polysiloxane polymer layer which was thermally cured at approximately 250~F.
The polysiloxane layers on each substrate were prepared in an identical fashion, with the exception that the polysiloxane layer thickness was adjusted to be 1.3 microns for polycarbonate lens No. 1, 2.2 microns for polycarbonate lens No. 2, 3.0 microns for polycarbonate ~ lens NoO 3, 5.0 microns for polycarbonate lens No. 4, and 1 3 microns for CR-3 ~ lens No. 5. Rfter th~ curing process was complete, each lens was ultrasonically cleaned in a solvent bath of isopropyl alcohol, and then . blown dry with nitrogen gas. The lenses were mounted onto a substrate holder and inserted into a vacuum coating chamber which was evacuated to approximately

4 x 10 6 Torr. The substrates were sputter-etched for 20 minutes by a beam of Ar+ ions at an energy of 500 eV
and an ion beam current of 90 mA. Next, a 600-Angstroms - thick layer of silicon dioxide (SiO2) was deposited ont~
~ the lenses by Ar+ ion beam sputter deposition from a ``~ quartz target. The lenses were then coated with top layer of diamond-like carbon by direct ion beam deposition using an 11 cm ion beam source operated on 6 ~
sccm of CH4 and 3 sccm of Ar gas at a pressure of approximately 3 x 10 4 Torr. The ion energy was 50 eV
and the ion beam current was 150 mA. A transparent diamond-like hard carhon layer, 800 Angstroms thick, was deposited onto each lens.
After cooling under Ar gas flow for 5 minutes, the lenses were removed from~the reactor. Lenses lA, 2A, 3A, 4A, and 5A were tested ~or coating adhesion by immersion in a bath of boiling salt water (5% NaCl) for 20 minutes followed by rinsing in cold water. After . ~ .
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W092/06843 PCT/US91/07~09 -23- ~9 V.l 1 ~

removal of the lenses from the salt water bath, all of the coatings appeared undamaged, and did not crack, craze, or peel off the substrate~
: Lenses lB, 2B, 3B, 4B, and 5B wer tested for abrasion resistance by NFPA 1981 Standard on Open-Circuit Self~Contained Breathing Apparatus for Fire Fighters : (1987 Edition) Test Number 4-9, 'IFacepi~ce Lens ~brasion Resistance Test," using vertical weights of 4 and 12 pounds applied to ~0000 steel wool. The abrasion test results are summarized in Table II below.
.

Table II
Steel Wool Abrasion Test Results Lens No. Substrate Polysiloxsne 4-Pound 12-Pound Haterial Thickness Result Result _ 18 polycarbona~e 1.3 microns moderate heavy 2B polycarbonate 2.2 microns moderate hesvy 3B polycarbonaee 3.0 microns slight moderate/heavy 4B polycarbonate 5.0 m;crons none slight 5B CR-3 ~ 3.D microns none none/slight : , DefiniSions of Observed Damage Resul~s:
-: . .

Neavy = Many overlapping deep scratches visible to nsked eye. Microscopically t200x~, DLC
: "
;- coating removed; many scratches deep into substrate.
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~` ~oderate = Hany isolated scratches visible to naked eye.
Microscopically ~Z00x), D~C coating crushed :
into polysiloxane layer; feu deep scratches.

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W092/06~3 P~T/US91/07209 ~ -24-(Definitions of Observed D~mage Results): -S~ight = Fe~ isolated fine scratches visible to naked eye. Microscopically ~Z00~), "indentation scrfltches" observed, but DLC c~ating is not crack~d.

None = No damage visible to the naked eye.
Microscopically, feu isolated fine 1û "indeneation scrstch~s."
.
For reference, an uncoated polycarbonate lens exhibited heavy damage when abraded by the steel wool using a 4 pound vertical weight. The abrasion test results clearly demonstrated a dramatic improvemen~ in abrasion resistance when the polysiloxane polymer layer was at least 3 microns thick.

An 80 mm diameter x 2 mm thick ne.utral gray polycarbonate sunglass lens was coated by the following proa~dure. After molding, the lens was vapor-degreased with Freon, then dip-coated with a polysiloxane polymer layer which was thermally cured. The polysiloxane layer ` was 3 microns thick. After the curing process was complete, the lens was ultrasonically cleaned in a ; solvent bath of isopropyl alcohol, and blown dry with nitrogen gas. The lens was then mounted onto a substrate holder and inserted into a vacuum chamber which was evacuated to about l.~ x 1O-6 Torr. The sample was `; 30 sputter-etched for 3 minutes by a beam of Ar~ ions at an energy of 500 eV and an ion beam current of 90 mA. Next, a 850-Angstroms thick layer of sio2 was deposited onto the lens by Ar+ ion beam sputter deposition from a quartz target. The sample was then coated with diamond-like carbon by direct ion beam deposition from a quartz target. The sample was then coated with diamond-like , '; , . , ~... .. , ................. . . . . ... ,, ., i ., - , .. , : .

-25- 2~r3Vll~

carbon by direct ion beam deposition using an 11 cm ion beam source operated on 6 sccm of CH4 gas and 3 sccm of - Ar gas at a pressure of l.9 x 10 4 Torr. The ion energy was 75 eV and the ion beam current was 180 mA.
After cooling under Ar gas flow for 5 minutes, the lens was removed from the reactor. The coating was then tested for adhesion by immersing the sample in a bath of boiling salt water (5% NaCl) for 30 minutes. After removal of the sample from the salt water bath, the coating appeared undamaged, and did not crack, craze, or peel off the substrate. A cross-hatch/tape adhesion test indicated no adhesion failure of the coating.

A neutral gray polycarbonate sunglass lens coated with a 1.5-micron thick coating of polysiloxane polymer was prepared by the procedure in Example 2. Next, the lens was inserted into a vacuum coating chamber and evacuated to a pressure of 3 x 10 Torr. The lens was then sputter-etched for 3 minutes by a beam of Ar~ ions at an energy of 500 eV an an ion beam current of 67 mA.
Then, the vacuum coating procedure in Example 2 was ~- repeated, except no Sio2 coating was deposited between `~ the polysiloxane layer and the diamond-like carbon layer.
- The diamond~like carbon coating cracked and spalled from the substrate surface soon a~ter removal from the vacuum ~,f ~'- coating chamber, indicating very poor adhesion.

The procedure in Example 2 was repeated, except the vacuum coating chamber was evacuated to 1.2 x 10 6 Torr, and the SiO2 coating thickness was 200 Angstroms.
A~ter 30 minutes exposure to boiling salt water, the - coating exhibited some crazing (spalling), indicating inadequate adhesion. How~ver, th~ adhesion of the diamond-like carbon coating was much greater than that ` 35 found in Example 3.
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The procedure in Example 2 was repeated, except the vac^~um coating chamber was evacuated to 2.1 x 10 6 Torr, and the sio2 coating thickness was 550 Angstroms.
After 10 minutes exposure to boiling salt water, the diamond-likè carbon coating appeared undamaged~ and did not crack, craze, or peel off the substrate, indicating excellent adhesion.

The procedure in Example 2 was repeated, except the vacuum coating chamber was evacuated to 2.5 x 10 6 Torr and the SiO2 coating thickness was 650 Angstroms.
After 30 minutes exposure to boiling salt water, the diamond-like carbon coating appeared undamaged, and did not crack, craze, or peel off the substrate, indicating excellent adhesion.
~ ~' EXAMPLE .. ?
.:
An 80 mm diameter x 2mm thick neutral gray polycarbonate sunglass lens was coated by the following :;
`~ 20 procedure. After molding, the lens was vapor-degreased ;~ with Freon, then dip-coated with a polysiloxane polymer ?~ layer whi~h was thermally cured. The polysiloxane layer was 3 microns thick. After the curing process was ~; complete, the lens was ultrasonically cleaned in a "
solvent bath of isopropyl alcohol, and blown dry with nitrogen gas. The lens was then mounted onto a substrate holder and inserted into a vacuum chamber which was evacuated to 5 x 10 6 Torr. The s~bstrate was sputter-etched for 4 minutes by a beam of Ar+ ions at an energy 30 of 500 eV and an ion beam current oP 90 mA. Next, a 200--Angstroms thick layer of SiO2 was deposited onto the lens ~ by:Ar~ ion beam sputter deposition from a quartz target.
- Then, a 100-Angstroms thick layer of Cr was deposited on top of the SiO2 layer by Ar+ ion beam sputter deposition from a Cr metal target. Then, a 300-Angstroms thick layex of SiO2 was ion beam sputter-deposited on top of , - , '' ' ", ',' : ' . . .

W092/06~43 PCT/US91/07209 -27- 2~

the Cr layer. Finally, a 500-Angstroms thick layer of transparent diamond-like hard carbon was deposited on top of the second sio2 layer by direct ion beam deposition using an 11 cm ion beam source operated on 6 sccm of CH4 and 3 sccm of Ar gas at a pressur~ of 4.8 x 10 5 Torr.
The ion energy was 75 eV and the ion beam current was 140 mA. The resultant lens was coated with an abrasion-resistant diamond-like carbon coating and exhibited a violet-blue reflected color.
EX~MPLE 8 An 80 mm diameter x 2 mm thick neutral gray sunglass lens was dip-coated with 3 microns of polysiloxane polymer, cleaned, and inserted into a vacuum chamber as described in Example 7. The vacuum chamber was then evacuated to a pressure of 4 . 5 x 10 7 Torr. The ~ substrate was sputter-etched for 4 minutes by a beam of -~ Ar+ ions at an energy of 500 eV and an ion beam current of 90 mA. Next, a 200-Angstroms thick layer of SiO2 was ~! deposited onto the lens by Ar+ :ion beam sputter ` 20 deposi~ion from a quartz target. Then, a 100-Angstroms thick layer of Si was deposited on top of the sio2 layer by Ar+ ion beam sputter deposition from a Si target.
~; Then, a 300-Angstrom thick layer of sio2 was ion beam sputter-deposited on top of the Si layer. Finally, a 2S 480-Angstroms thick layer of transparent diamond-like ~, hardicarbon was de~osited on top of the s~cond sio2 layer by direct ion beam deposition using the conditions d~scribed in Example 7. The resultant lens was coated with an abrasion-resistant diamond-like carbon coating :,................................................................. .
; 30 and exhibited a pink-gold reflected color.
EX~MPLE 9 -. . . ~ .
~ An 80 mm diameter x 2 mm thick neutraI gray sunglass lens was dip-coated with 3 microns- of ~;` polysiloxane polymer, cleaned, and inserted into a vacuum chamber as described in Example 7. The vacuum chamker was then evacuatPd to a pressure of 2.0 x 10 6 Torr. The '~ '' ' ' ' , . .
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W~92/06843 PCT/US91/072~9 . ~

~su~rate was sputter-etched for 4 minutes by a beam of Ar+ ions at an eneryy of 500 eV and an ion beam current of 90 mA. Next, a 500-Angstroms thick layer of SiO2 was deposited onto the lens by Ar~ ion beam sputter deposition from a quartz target. Then, a 100-Angstroms thick layer of Si was deposited on top of the sio2 layer by Ar+ ion beam sputter deposition from a Si target.
Finally, a 480-Angstroms thick layer of transparent diamond-like hard carbon was deposited on top of the Si layer by direct ion beam deposition using the conditions described in Example 7. The resultant lens was coated with an abrasion-resistant diamond-like carbon coating and exhibited a gold reflected color.

An 80 mm diameter x 2 mm thick neutral gray sunglass lens was dip-coated with 3 microns of polysiloxane polymer, cleaned, and inserted into a vacuum ` chamber as described in Example 7. The vacuum chamber was then evacuated to a pressure of 3.0 x 10 6 Torr. The substrate was sputter-etched for 4 minutes by a beam of Ar+ ions at an energy of 500 eV and an ion beam current of 90 mA. Next, a 200 Angstroms thick layer of SiO2 was deposited onto the lens by Ar+ ion beam sputter deposition from a quartz target. Then, a 100 Angstroms thick layer of Mo was deposited on top of the sio2 layer by Ar~ ion beam sputter deposition from a Mo target.
:, ;^ Then, a 300-Angstroms thic~ layer of SiO2 was ion beam sputter-deposited on top of the Mo layer. Finally, a 640-Angstroms thick layer of transparent diamond-like hard carbon was ~eposited on top of the second sio2 layer by direct ion beam deposition using the conditions described in Example 7. The resultant lens was coated with an abrasion-resistant diamond-like coating and exhibited a blue reflected color.

; A 2.5" wide x 6" long x 2 mm thick 6-base :
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-29- 2~9~

cylinder violet polycarbonate sunglass lens was dip-coated with 5 microns of polysiloxane polymer, cleaned, and inserted into a vacuum chamber as described in Example 2. Then, the vacuum chamber was evacuated to a pressure of 2 x lO 6 Torr. The substrate was sputter~
etched for 4 minutes by a beam of Ar~ ions at an energy of 500 eV and an ion beam current of 90 mA. Next, a 860-Angstroms thick layer of SiO2 was deposited onto the lens by Ar+ ion beam sputter deposition from a quartz target.
Then, a 100-Angstroms thick layer of Ge was deposited on top of the SiO2 layer by Ar+ ion beam sputter deposition from a Ge target. Thenl a 700-Angstroms thick layer of transparent diamond-like hard carbon was deposited on top of the Ge layer by direct ion beam deposition using the conditions described in Example 2.
~`The resultant lens was coated with an abrasion-resistant diamond-like carbon coating which exhibited a gold reflected color. The diamond-like carbon coating exhibited excellent adhesion aft:er tensile and compression flexing of the lens, and was not damaged after exposure to 30 minutes of boiling salt water.
EXAMPLE l2 A 2.5" wide x 6" long x 2 mm ~hick 6-base cylinder violet polycarbonate sunglass lens was dip-~`:!25 coated with 5 microns of polysiloxane polymer, cleaned, and inserted into a vacuum chamber as described in Example 2. The vacuum chal~er was then evacuated to a pressure of 2 x 10 6 Torr. The substrate was sputter-~tch~d for 4 minutes by a beam of Ar+ ions at an energy ` 30 of 500 eV and an ion beam current of ~0 mA. Next, a 860-Angstroms thick layer of SiO2 was deposited onto the lens by Ar+ ~on beam sputter deposition from a guartz target.
Then, a 100-Angstroms thick layer of Ge was deposited on top of the sio2 layer by Ar+ ion beam sputter deposition from a Ge target. Nextl a 500-Angstroms thick layer of sio2 was deposited on top of tha Ge layer using the .. .. ., .. ., . , . . .. ~ . .. . .. . .. . ....... ..
.
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W092/06843 PCT/~S91/07209 ~ -30- `

method described above. Finally, a 500-Angstroms thick layer of transparent diamond-like hard carbon was deposited on top of the second sio2 layer by direct ion beam deposition using the conditions described in Example 2.
The resultant lens was coated with an abrasion resistant diamond-like carbon coating which exhibited a purple reflected color. The diamond-like carbon coating exhibited excellent adhesion after tensile and compression flexing of the lens, and was not damaged after exposure to 30 minutes of ~oiling salt water.
, A 2.5" wide x 6" long x 2 mm thick 6-base cylinder violet polycarbonate sunglass lens was dip-coated with 5 microns of polysiloxane polymer, cleaned, and inserted into a vacuum chamber as described in Example 2. The vacuum chamber was then evacuated to a pressure of 5 x 10 6 Torr. The substrate was sputter-etched for 4 minutes by a beam of Ar+ ions at an energy of 500 eV and an ion beam current of 90 mA. Next, a 430-Angstroms thick layer of SiO2 was deposited onto the lens by Ar~ ion beam sputter deposition from a quartz target.
Then, a 100 Angstroms thick layer of Ge was deposited on top of the SiO2 layer by ~r+ ion beam sputter deposition --~ 25 from a Ge target. Next, a 400-Angstroms thick layer of ... .
SiO2 was deposited on top o~ the Ge layer using the method described above. Then, a 400-Angstroms thick - first layer of transparent diamond-like hard carbon was deposited on top of second SiO2 layer using the conditions described in Example 2. Nextl a third 400-Angstroms thick layer of SiO2 was deposited on top of the first diamond-like carbon layer using the method described above. Finally, a second 400-Angstroms thick layer of transparent diamond-like carbon was deposited on ~;~ 35 top of the third sio2 layer using the conditions described in Example 2.
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W092/0~843 PCT/US91/07209 The resultant lens was coat ~ ~ abrasion-resistant diamond-like carbon coating which exhibited a silver-blue reflected color. The diamond-like carbon coating exhibited ~xcellent adhesion after tensile and compression flexing of the lens, and was not damaged after exposure to 30 minutes of boiling salt water.

A 2.5" wide x 6" long x 2 mm thick 6-base cylinder violet polycarbonate sunglass lens was dip-coated with 5 microns of polysiloxane pol~er, cleaned,and inserted into a vacuum chamber as described in Example 2. The vacuum chamber was then evacuated to a pressure of 2 x 10 6 Torr. The substrate was sputter-etched for 4 minutes by a beam of Ar~ ions at an energy of 500 eV and an ion beam current of 90 mA. Next, a 425-Angstroms thick layer nf SiO2 was deposited onto the lens by Ar+ ion beam sputter deposition from a quartz target.
Then, a 100-Angstroms thirk layer of Ge was deposited on top of the SiO2 layer by Ar+ ion beam sputter deposition ; 20 from a Ge target. Next, a 440-Angstroms thick second layer of sio2 was deposited on top of the Ge layer using the method described above. Then, a 440-Angstroms thick first layer of transparent diamond-like carbon was deposited using the conditions describ2d in Example 2.
Next, a 440-Angstroms thick third layer of sio2 was deposited on top of the diamond-like carbon layer, using the method described above. Then, a 440-Angstroms thick second layer of transparent diamond-like car~on was deposited using the conditions described in Example 2.
Then, a 440-Angstroms thick fourth layer of sio2 was deposited as described above. Last, a 440-Angstroms thick third layer of transparent diamond-like carbon was deposited as the final layer of the stack, using the conditions described in Example 2.
The resultant lens was coated with an abrasion-resistant diamond-like carbon coating which exhibited a , ,. , .. .. . , -. . . .

.

W092/068~3 PCT/VS91/07209 red-pink reflected color. The diamond-like carbon coating exhibited excellent adhesion after tensile and compression ~lexing o~ the lens, and was not damaged aftex exposure to 30 minutes of boiling salt watex.
-. 5 Table III
:~ Summary of results of polycarbonate :: lenses coated in Examples 8-14 . .:
. Ex. Polysiloxane Stack Layer/ Reflected Thickness Coating Structure Color ,`~"
: 7 . 3 mlcrons 200 A SiO2/100 A CrJ violet blue -~ 300 A SiO2/S00 1 DLC
' 8 3 microns 200 1 SiO2t100 A Si/ pink/gold , 300 1 SiO2/480 1 DLC

9 3 microns 500 A sio2/loo 1 Si/600 A DLC 3O1d ., 3 microns 200 A SiO2/100 A plo/ blue 300 1 SiO2/640 1 DLC

11 5 microns 860 A SiO2/100 A Ge/700 A DLC gold , .
i 25 12 5 microns 860 A SiOz/100 1 Ce/ purple S00 A SiO2/500 1 DLC
~' 13 5 microns 430 A SiO2/100 A Get400 A SiO2/ silver-blue . . 400 A DLC/400 A SiO2/400 A DLC
:~ 30 .. 14 5 microns 425 1 SiO2/100 1 Ge/200 1 SiO2/ red-pink ~ .: . 440 1 DLC/440 A SiO2/440 A SiO2/

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An adherent, abrasion-resistant quarter-`~ wavelength stack reflecting coating was ~ormed on -~ polycarbonate lenses. The layer thicknesses were chosen to maximize reflectance at 550 nanometers. The refractive index of the ~eposited SiO2 layer was 1.45, and the refractive index of the deposited diamond-like ; carbon layer was 2Ø The coating was formed as follows.
An 80 mm diameter x 2 mm thick neutral gray ~` 10 polycarbonate sunglass lens and an 80 mm diameter x 2 mm ~i thiek clear polycarbonate lens were dip-coated with 3 microns o~ polysiloxane polymer, cleaned, and inserted into a vacuum chamber as described in ~xample 2. The . . ~
chamber was evacuated to a pressure of 6.0 x lO ' Torr.
The substrates were sputter-etched for 3 minutes by a beam of Ar~ ions at an energy of 200 eV and an ion beam current of 40 mA. Next, a 945-Angstroms thick layer of sio2 was deposited onto the lenses by Ar+ ion beam sputter deposition ~rom a quartz target. Then, a 685-Angstroms thick layer of transparent diamond-like hard carbon was deposited on top of the ~irst SiO2 layer, using the conditions described in Example 2. Next, a second 945-Angstroms thick layer of SiO2 was deposited as described above. Finally, a second 685-Angstroms thick layer of transparent diamond-like hard carbon was `~ deposited on top of the second SiO2 layer using the `~ conditions described in Example 2. The coating was very adherent, had a high reflectance to visible light (550 nm) and exhibited a pale gold-blue reflected color on the neutral yray len~. `
From the foregoing descrip~ion, one of ordinary skill in the art can easily ascertain that the presen-~:
invention provides a novel method for producing a substantially optically transparent multilayer composite structure. A highly important technical advantage of the invention is that superior abrasion wear resistance is _ PCT/US91/072 achieved by use of a multilayer transparent structure comprised of a parent substrate, one or more interlayers ~; and a diamond-like carbon outer layer.
Without departing from the spirit and scope of this invention, one of ordinary skill can make various : changes and modifications to the invention to adapt it to various usages and conditions. As such, these changes and modifications are properly, equitably, and intended to be, within the full range of equivalents of the following claims.

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Claims (82)

WHAT IS CLAIMED IS:

1. A coated substrate product comprised of a substantially optically transparent polymeric substrate and a first composite layer, said first composite layer comprising a substantially optically transparent adhesion-mediating layer bonded to and disposed towards said substrate of a polysiloxane polymer having a high elasticity and capable of forming a strong chemical bond to said polymeric substrate, a chemically vapor deposited first interlayer bonded to and disposed immediately adjacent to said adhesion-mediating layer of a substantially optically transparent material devoid of alkali metal atoms and fluorine and capable of forming a strong chemical bond to said adhesion-mediating layer and diamond-like carbon, and a chemically vapor deposited first layer of substantially optically transparent diamond-like carbon bonded to and disposed immediately adjacent to said first interlayer and away from said substrate.

2. The product of Claim 1 wherein said adhesion-mediating layer is at least 3 microns thick.

3. The product of Claim 1 wherein said first diamond like carbon layer is at least 200 .ANG. thick.

4. The product of Claim 1 wherein said first interlayer comprises a substantially optically transparent material selected from the group consisting of silicon nitride, titanium nitride, tantalum nitride, tungsten nitride, molybdenum nitride, hafnium nitride, zirconium nitride, boron nitride, silicon oxide, silicon dioxide, yttrium oxide, germanium oxide, hafnium oxide, tantalum oxide, titanium oxide, zirconium oxide, tungsten oxide, molybdenum oxide, boron oxide, silicon carbide, germanium carbide and mixtures thereof.

5. The product of Claim 4 wherein said first interlayer is at least 10 .ANG. thick.

6. The product of Claim 1 wherein said first interlayer comprises silicon dioxide.

7. The product of Claim 6 wherein said first interlayer is at least 200 A thick.

8. The product of Claim 1 wherein the thickness of at least one of said first interlayer and said first diamond-like carbon layer is selected to minimize the reflection of light at predetermined wavelengths.

9. The product of Claim 1 wherein the thickness of at least one of said first interlayer and said first diamond-like carbon layer is selected to maximize the reflection of light at predetermined wavelengths.

10. The product of Claim 1 wherein the thickness of said first interlayer and said first diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

11. The product of Claim 1 wherein the compressive stress of said first interlayer is less than said first diamond-like carbon layer and greater than said adhesion-mediating layer.

12. The product of Claim 1 wherein said first interlayer exhibits a tensile stress and said first diamond-like carbon layer exhibits a compressive stress.

13. The product of Claim 1 including at least a second composite layer bonded to and disposed immediately adjacent to said first composite layer, said second composite layer comprising a second interlayer bonded to and disposed immediately adjacent to said first diamond-like carbon layer and away from said substrate and a second diamond-like carbon layer bonded to and disposed immediately adjacent to said second interlayer and away from said substrate.

14. The product of Claim 13 wherein said second interlayer comprises a substantially optically transparent material selected from the group consisting of silicon nitride, titanium nitride, tantalum nitride, tungsten nitride, molybdenum nitride, hafnium nitride, zirconium nitride, boron nitride, silicon oxide, silicon dioxide, yttrium oxide, germanium oxide, tungsten oxide, molybdenum oxide, boron oxide, hafnium oxide, tantalum oxide, titanium oxide, zirconium oxide, silicon carbide, germanium carbide and mixtures thereof.

15. The product of Claim 14 wherein the thickness of said second interlayer is at least 10 .ANG. thick.

16. The product of Claim 13 wherein said second interlayer comprises silicon dioxide.

17. The product of Claim 16 wherein said second interlayer is at least 200 .ANG. thick.

18. The product of Claim 13 wherein the thickness of said second diamond-like carbon layer is at least 200 .ANG.
thick.

19. The product of Claim 13 wherein the thickness of at least one of said first interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer is selected to minimize the reflection of light at predetermined wavelengths.

20. The product of Claim 13 wherein the thickness of at least one of said first interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer is selected to maximize the reflection of light at predetermined wavelengths.

21. The product of Claim 13 wherein the thickness of said first interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

22. The product of Claim 13 wherein the thickness of said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

23. The product of Claim 13 wherein the compressive stress of said second interlayer is less than said second diamond-like carbon layer.

24. The product of Claim 13 wherein said second interlayer exhibits a tensile stress and said first diamond-like carbon layer and said second diamond-like carbon layer exhibit a compressive stress.

25. The product of Claim 1 wherein said first composite layer includes a chemically vapor deposited third interlayer bonded to and disposed between said first interlayer and said first diamond-like carbon layer of a substantially optically transparent material capable of forming a strong chemical bond to said first interlayer and said first diamond-like carbon layer.

26. The product of Claim 25 wherein said first interlayer comprises a substantially optically transparent material selected from the group consisting of silicon nitride, titanium nitride, tantalum nitride, tungsten nitride, molybdenum nitride, hafnium nitride, zirconium nitride, boron nitride, silicon dioxide, silicon oxide, yttrium oxide, germanium oxide, tungsten oxide, molybdenum oxide, boron oxide, hafnium oxide, silicon oxide, silicon dioxide, tantalum oxide, titanium oxide, zirconium oxide, silicon carbide, germanium carbide, aluminum oxide, cerium oxide, tin oxide, thorium oxide, lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, francium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, radium oxide, barium fluoride, cerium fluoride, magnesium fluoride, thorium fluoride, calcium fluoride, neodymium fluoride, lead fluoride, sodium fluoride, lithium fluoride, zinc selenide, zinc sulfide and mixtures thereof.

27. The product of Claim 25 wherein said third interlayer comprises a substantially optically transparent material selected from the group consisting of silicon nitride, titanium nitride, tantalum nitride, hafnium nitride, tungsten nitride, molybdenum nitride, zirconium nitride, boron nitride, silicon dioxide, silicon oxide, yttrium oxide, germanium oxide, hafnium oxide, tungsten oxide, molybdenum oxide, boron oxide, tantalum oxide, titanium oxide, zirconium oxide, silicon carbide, germanium carbide, and mixtures thereof.

28. The product of Claim 27 wherein said third interlayer is at least 10 .ANG. thick.

29 The product of Claim 25 wherein said third interlayer comprises silicon dioxide.

30. The product of Claim 29 wherein the thickness of said third interlayer is at least 200 .ANG..

31. The product of Claim 25 wherein said third interlayer comprises a substantially optically transparent metallic material capable of reflecting visible light selected from the group consisting of silicon, germanium, hafnium, molybdenum, tungsten, yttrium, tantalum, titanium and zirconium.

32. The product of Claim 31 wherein said third interlayer is at least 25 .ANG. thick.

33. The product of Claim 25 wherein said third interlayer comprises a substantially optically transparent metallic material capable of reflecting visible light selected from the group consisting of vanadium, niobium, chromium, manganese, rhenium, technetium, iron, cobalt, iridium, rhodium, nickel, palladium, platinum, copper, silver, gold, zinc, ruthenium, indium, aluminum, tin, osmium, thallium, lead, antimony, bismuth and polonium.

34. The product of Claim 33 wherein said third interlayer is at least 25 .ANG. thick.

35. The product of Claim 25 wherein the thickness of at least one of said first interlayer, said third interlayer and said first diamond-like carbon layer is selected to minimize the reflection of light at predetermined wavelengths.

36. The product of Claim 25 wherein the thickness of at least one of said first interlayer, said third interlayer and said first diamond-like carbon layer is selected to maximize the reflection of light at predetermined wavelengths.

37. The product of Claim 25 wherein the thickness of said first interlayer, said third interlayer and said first diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

38. The product of Claim 25 wherein the thickness of said third interlayer and said first diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

39. The product of Claim 25 wherein the compressive stress of said third interlayer is less than said first diamond-like carbon layer and greater than said adhesion-mediating layer.

40. The product of Claim 25 wherein said third interlayer exhibits a tensile stress and said first diamond-like carbon layer exhibits a compressive stress.

41. The product of Claim 25 including a fourth interlayer disposed between said third interlayer and said first diamond-like carbon layer of a substantially optically transparent material devoid of alkali metal atoms and fluorine and capable of forming a strong chemical bond with said third interlayer and said first diamond-like carbon layer.

42. The product of Claim 41 wherein said fourth interlayer comprises a substantially optically transparent material selected from the group consisting of silicon nitride, titanium nitride, tantalum nitride, tungsten nitride, molybdenum nitride, hafnium nitride, zirconium nitride, boron nitride, silicon dioxide, silicon oxide, yttrium oxide, germanium oxide, hafnium oxide, tantalum oxide, tungsten oxide, molybdenum oxide, boron oxide, titanium oxide, zirconium oxide, silicon carbide, germanium carbide and mixtures thereof.

43. The product of Claim 42 wherein said fourth interlayer is at least 10 .ANG. thick.

44. The product of Claim 41 wherein said fourth interlayer comprises silicon dioxide.

45. The product of Claim 44 wherein the thickness of said fourth interlayer is at least 200 .ANG..

46. The product of Claim 41 wherein the thickness of at least one of said first interlayer, said third interlayer, said fourth interlayer and said first diamond-like carbon layer is selected to minimize the reflection of light at predetermined wavelengths.

47. The product of Claim 41 wherein the thickness of at least one of said first interlayer, said third interlayer, said fourth interlayer and said first diamond-like carbon layer is selected to maximize the reflection of light at predetermined wavelengths.

48. The product of Claim 41 wherein the thickness of said first interlayer, said third interlayer, said fourth interlayer and said first diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

49. The product of Claim 41 wherein the thickness of said third interlayer, said fourth interlayer and said first diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

50. The product of Claim 41 wherein the compressive stress of said fourth interlayer is less than said first diamond-like carbon layer and greater than said adhesion-mediating layer.

51. The product of Claim 41 wherein said fourth interlayer exhibits a tensile stress and said first diamond-like carbon layer exhibits a compressive stress.

52. The product of Claim 25 including at least one said second composite layer bonded to and disposed immediately adjacent to said first composite layer.

53. The product of Claim 52 wherein the thickness of at least one of said first interlayer, said third interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer is selected to minimize the reflection of light at predetermined wavelengths.

54. The product of Claim 52 wherein the thickness of at least one of said first interlayer, said third interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer is selected to maximize the reflection of light at predetermined wavelengths.

55. The product of Claim 52 wherein the thickness of said first interlayer, said third interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

56. The product of Claim 52 wherein the thickness of said third interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

57. The product of Claim 41 including at least one said second composite layer bonded to and disposed immediately adjacent to said first composite layer.

58. The product of Claim 57 wherein the thickness of at least one of said first interlayer, said third interlayer, said fourth interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer is selected to minimize the reflection of light at predetermined wavelengths.

59. The product of Claim 57 wherein the thickness of at least one of said first interlayer, said third interlayer, said fourth interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer is selected to maximize the reflection of light at predetermined wavelengths.

60. The product of Claim 57 wherein the thickness of said first interlayer, said third interlayer, said fourth interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

61. The product of Claim 57 wherein the thickness of said third interlayer, said fourth interlayer, said first diamond-like carbon layer, said second interlayer and said second diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

62. A chemical vapor deposition method for producing an abrasion wear resistant coated polymeric substrate product comprising: chemically degreasing the surface of a polymeric parent substrate; coating a substantially optically transparent polysiloxane polymer layer onto said parent substrate to a thickness of at least 3 microns; thermally curing said polysiloxane polymer coating; chemically cleaning the coated surface of said substrate; placing said substrate into a chemical vapor deposition reactor vacuum chamber and evacuating the air from said chamber to less than an approximately 5 x 10-6 Torr; sputter-etching the surface of said substrate with energetic gas ions at an energy of at least 200 eV to remove traces of residual hydrocarbon and to preferentially reduce the concentration of alkali metal atoms and alkali metal oxides at the substrate surface; chemically vapor depositing during a first cycle a substantially optically transparent first interlayer capable of forming a strong chemical bond to said substrate and diamond-like carbon onto to said substrate;
chemically vapor depositing during said first cycle a substantially optically transparent diamond-like carbon layer having a thickness of at least 200 .ANG. onto said coated substrate; cooling said coated substrate by extinguishing said deposition process and passing an inert gas over said substrate until the temperature of said substrate has reached substantially room temperature during said cool down step; recovering a coated substrate product exhibiting superior resistance to abrasion and chemical attack.

63. The method of Claim 62 wherein the polysiloxane polymer coating step comprises a dip coating process.

64. The method of Claim 62 wherein the polysiloxane polymer coating step comprises a flow coating process.

65. The method of Claim 62 wherein the polysiloxane polymer coating step comprises a spray coating process.

66. The method of Claim 62 wherein the temperature of said parent substrate is maintained at less than 125°C during said chemical vapor deposition steps.

67. The method of Claim 62 wherein the thickness of said diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

68. The method of Claim 62 wherein the thickness of said first interlayer and said diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

69. The method of Claim 62 wherein the compressive stress of said first interlayer is less than said diamond-like carbon layer and greater than said adhesion-mediating layer.

70. The method of Claim 62 wherein said first interlayer exhibits a tensile stress and said diamond-like carbon layer exhibits a compressive stress.

71. The method of Claim 62 wherein at least a second cycle is used to chemically vapor deposit at least a second interlayer and a second said diamond-like carbon layer onto said substrate.

72. The method of Claim 71 wherein the compressive stress of said first interlayer and said second interlayer is less than said diamond-like carbon layer and greater than said adhesion-mediating layer.

73. The method of Claim 71 wherein said first interlayer said second interlayer exhibit a tensile stress and said diamond-like carbon layer exhibits a compressive stress.

74. The method of Claim 71 wherein the deposition rate for said first interlayer, said second interlayer and said diamond-like carbon layer is generally in the range of about 0.1-10 microns/hour.

75. The method of Claim 62 wherein a third interlayer is chemically vapor deposited immediately adjacent to said first interlayer and away from said substrate of a substantially optically transparent material capable of forming a strong chemical bond to said first interlayer and a strong chemical bond to diamond-like carbon.

76. The method of Claim 75 wherein said diamond-like carbon layer is chemically vapor deposited immediately adjacent to said second interlayer and away from said substrate.

77. The method of Claim 75 wherein the deposition rate for said third interlayer is generally in the range of about 0.1-10 micron/hour.

78. The method of Claim 76 wherein the thickness of said third interlayer and said diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

79. The method of Claim 76 wherein the thickness of said first interlayer, said third interlayer and said diamond-like carbon layer corresponds to integer multiples of quarter wavelength optical thickness at predetermined wavelengths.

80. The method of Claim 75 wherein the compressive stress of said third interlayer is less than said diamond-like carbon layer and greater than said adhesion-mediating layer.

81. The method of Claim 75 wherein said third interlayer exhibits a tensile stress and said diamond-like carbon layer exhibits a compressive stress.

82. The method of Claim 75 wherein a second cycle is used to chemically vapor deposit at least a second said first interlayer and a second said diamond-like carbon layer onto said coated substrate.