CA1134319A - Glass coated polycarbonate articles - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A polycarbonate substrate is provided with an adherent, hard, abrasion and organic solvent resistant thin glass top coat by initially priming the substrate with a primer coating comprised of the photoreaction products of certain polyfunction acrylic monomers and thereafter vapor depositing under vacuum onto the primer surface a thin glass top layer, the glass being evaporated by means of radio frequency induction heating.

Description

~ ~5 3~3 - ` 8CS 237 SUMMARY OF THE INVENTION
This invention relates to a method of applying a uniform, adherent, hard, abrasion and organic solvent resistant thin glass ; coating on a polycarbonate substrate. The method comprises first priming the polycarbonate substrate with a primer layer comprised of the photoreaction products of certain polyfunctlonal acrylate monomer and thereafter vapor depositing on said primed substrate a thin layer of glass, said glass being evaporated by means of radio frequency induction heating.

Polycarbonate resins are well known,commercially available materials possessing excellent physical and chemical properties which are useful in a wide variety of applications. Such polymers or resins, since they are less dense and more breakage resistant than glass, have been especially useful as substitutes for glass, as for example, in the manufacture of tail lights and stop light lenses, protective shields for fluorescent street lights, safety shields in inspection windows, windshields, windows, and the like.
However, these resins have relatively low mar and chemical solvent resistance.
In order to overcome this relatively low mar and chernical solvent resistance, polycarbonate articles have been coated with various organic and inorganic protective layers which increase the mar resistarlce of said polycarhonate articles. One type of inorganic protective layer is comprised of glass which has been vapor deposited onto the polycarbonate su~strate. Thus, for example, French Patent Specification No. 1,520,125 and the corres-ponding ~ritish Specification No. 1,144,099 teach that the surfaces of polycarbonates can be improved, especially rendered more scratch resistant, by vapor depositing an SiO2 layer of at least ~3~3~
~CS 2378 lu thickness onto ~he polycarbonate. This vapor deposition is accomplished by evaporating SiO2 with an electron beam evaporator source in a high vacuum in the presence of oxygen while regularly moving the polycarbonate article to be coated in the vapor jet and/
or the electron beam evaporator source in such a manner that at least 50 successive layers are evaporated onto the surface of the polycarbonate article.
~ owever, this electron beam vapor deposition method suffers from several disadvantages. One of these is due to the electron 10 beam source being, in effect, a point source of SiOx molecules. ;~
Thus, the area of the substrate immediately above the electron beam receives a thicker coating of glass than do the cross peri-pheral to the point of impingement of the SiOx molecules. Conse-quently, to provde a glass coating of uniform thickness a plurality of electron beam sources need be used or, alternately, the single electron beam qource must be rapidly oscillated along the width oi the substrate. Thus, it is generally difficult to obtain a glass layer of uniform thickness on large substrates utilizing an electron beam evaporator device.
Furthermore, the articles thus prepared have been found to be not entirely satisfactory since, under high stress or temperature ahanges, the SiO2 protective layer tends to crack and~or separate from the polycarbonate article. In order to overcome this crack-:iny ancl separa tion of the protective silicate glass layer, various modifications of the basic vapor deposition process have been proposed. Thus, British Patent 1,313,866 teaches a polycarbonate having a vapor deposited protective layer consisting of SiO2 and 5 to 10~ zirconium oxide. Similarly, U.S. Patent No. 3,645,779 teaches a synthetic polymer provided with a hard, abrasion-res~stant surface free of fine hairline cracks by vapor depositing ~3~ 8CS 2378 under vacuum onto the sur~ace of said polymer a B203-SiO2 glass containing less than S percent by weight of Na20. U.S. Patent No.
3,713,369 teaches disposing an in-termediate layer between the plastic substrate and the vapor deposi-ted glass layer for the purpose of improving the adherence of said glass layer. ~his intermediate layer comprises a polymerization layer which is formed by subjecting low-molecular organic vapors to a glow dis-charge operation and depositing the polymerization products on the substrate. The organic vapors are provided by organic compositions such as acetylene, xylol, and those compounds which contain Si, preferably in an SiO bond, such as silicate acid methyl or silicic acid ethy].ester, and low boiling siloxanes.
By the method of the instant invention it is possible to obtain vapor deposited glass coatings of uniform thickness and good adhesion on large substrates. By utillzing the method of the presen-t invention it is possible to produce a polycarbonate article having a protective top layer of vapor deposited glass which is free of cracks, is of a uniform thickness and is tenaciously and durably adhered to the polycarbonate substrate. The advantages ~0 of the instant invention include the fact that~the glass used to fo~m the protective layer need not be of any special composition, as is the case in the afore-mentioned U.S. Patent 3,645,779 and ~3ritish Patent 1,313,866; that the intermediate primer layer aids in providing solvent protection for the polycarbonate substrate;
and that the article produced by the instant method, since the polycarbonate substrate is already coated with the intermediate layer before it is exposed to the vapor deposition process, is relatively easy and simple to manufacture, i.e., the conditions existent during vapor deposition can be more variable than if there 30 were no intermediate layer and if radio frequency induction evapora- ;
tion were not used.

In one aspect of this invention there is provided a method applying a thin relatively uniform protective glass coating on a poly-carbonate article by vapor depositing a thin layer of glass on said polycarbonate substrate using radio frequency induction heating to vapori2e the glass. In another preferred aspect of this invention the ~-~
method of priming the polycarbonate by ~i) applying to the polycarbonate substrate an ultraviolet light curable primer composition containing ;~
at least one certain polyfunctional acrylate monomer and a photo-initiator; (ii) curing said primer composition by exposure to ultra-violet light for a period of time effective to form a primer layer comprised of the photoreaction products of said polyfunctional acrylate.
In a still further aspect of the invention there is provided non-opaque polycarbonate articles having improved mar, abrasion, scratch and solvent resistance which may be suitably formed in accordance witl the preferred method above.
In the practice of this invention, any of the aromatic poly-carbonates can be employed herein. These are homopolymers and copolymers and mixtures thereof that are prepared by reacting a dihydric phenol with a carbonate precursor. Typical of some of the dihydric phenols that may be employed in the practice of this invention are bisphenol-A
(2,2-bis(4-hydroxyphenyl)propane), bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl) propane, 3,3-bis(4-hydroxyphenyl)pentane,

2,2-bis~3,5 dichloro-4-hydroxyphenyl)propane, 2,2-bis(4-3,5-dibromo-4-hydroxyphenyl) propane, bis(3-chloro-4-hydroxyphenyl)methane. Other dihydric phenols of the bisphenol type are also available and are disclosed in U.S. Patents 2,999,835 issued September 2, 1961, 3,028,365 issued April 3, 1972 and 3,334,154 issued August 1, 1967. ~ -It is, of course, possible to employ two or more different dihydric phenols or a copolymer of a dihydric phenol with a blycol or with hydroxy or acid terminated polyester, or with a dibasic acid in the event a carbonate copolymer or interpolymer rather ~ ~ 8CS 2378 than a homopolymer is desired for use in the preparation of the aromatic carbonate polymers of this invention. Also employed in the practice of this invention may be blends of any of the above materials to provide the aromatic carbonate polymer.
The carbonate precursor may be either a carbonyl halide, a carbonate ester or a haloormate. The carbonyl halides which can be employed herein are carbonyl bromide, carbonyl chloride and mixtures thereof. Typical of the carbonate esters which may be employed herein are diphenyl carbonate, di-(halophenyl) carbonates such as di-(chlorophenyl) carbonate, di-(bromophenyl) carbonate, di-(trichlorophenyl) carbonate, di-(tribromophenyl) carbonate, etc., di-(alkylphenyl) carbonate such as di(tolyl) carbonate, etc., di-(naphthyl) carbonate, di-(chloronaphthyl) carbonate, phenyl tolyl carbonate, chlorophenyl chloronaphthyl carbonate, etc., or mixtures thereof. The haloformates suitable for use herein include bis-haloformates of dihydric phenols (bischloro-formates of hydroquinone, etc.) or glycols (bishaloformates of ethylene glycol, neopentyl glycol, polyethylene glycol, etc.).
While other carbonate;precursors will occur to those skilled in the art, carbonyl chloride, also known as phosgene, is preferred.
Also included are the polymeric derivatives of a dihydric phenol, a dicarboxylic acid and carbonlc acid~. These are dis-closed in U.S. Patent 3,169,121 which igsued February 9, 1~65 ~ ;

E. P. Goldberg.
The aromatic carbonate polymers of this invention may be pre-pared by employing a molecular weight regulator, an acid acceptor and a catalyst. The molecular weight regulators which can be employed in carrying out the process of this invention include monohydric phenols such as phenol, chroman-I, para-tertiary-butyl-phenol, para-bromophenol, prlmary and secondary amines, etc.
Preferably, phenol is employed as the molecular weight regulator.

~ 5 -A suitable acid acceptor may be either an organic or an inorganic acid acceptor. A suitable organic acid acceptor is a tertiary amine and includes such materials as pyridine, triethyl-amine, dimethylaniline, tributylamine, etc. The inorganic acid acceptor may be one which can be either a hydroxide, a carbonate, a bicarbonate, or a phosphate of an alkali or alkaline earth metal.
The catalysts which are employed herein can be any of the suitable catalysts that aid the polymerization of bisphenol-A
with phosgene. Suitable catalysts include tertiary amines such as, for example, triethylamine, tripropylamine, N,N-dimethyl-aniline, quaternary ammonium compounds such as, for example, tetraethylammonium bromide, cetyl triethyl ammonium bromide, tetra-n-heptyl-ammonium iodide, tetra-n-propyl ammonium bromide, tetramethyl ammonium chloride, tetramethyl ammonium hydroxide, tetra-n~butyl-ammonium iodide, benzyltrimethylammonium chloride and quaternary phosphonium compounds such as, for example, n-butyltriphenyl phosphonium bromide and methyltriphenyl phos-phonium bromide. ~`
Also included herein are branched polycarbonates wherein a polyfunc~ional aromatic compound is reacted with the dihydric phenol and carbonate precursor to provide a thermoplastic randomly branched polycarbonate.
These polyfunctional aromatic compounds contain at least three functional groups with are carboxyl, carboxylic anhydride, haloformyl or mixtures thereof. Examples of these polyfunctional aromatic compounds which may be employed in the practice of this invention include: trimellitic ahhydride, trimellitic acid, trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyro-mellitic acid, pyromellitic dianhydride, mellitic acia, mellitic ~,3~
anhydride, trimesic acid, benzophenonetetracarboxylic acid, benzophenonetetracarboxylic anhydride and the like. The preferred polyfunctional aromatic compounds are trimellitic anhydride or trimellitic acid, or their haloformyl derivativesO
S Also included herein are blends of a linear polycarbonate and a branched polycarbonate.
The intermediate primer layer is formed by ~ust applying a coating composition containing at least one polyfunctional acrylic acid ester monomer onto ~he polycarbonate substrate and thereafter exposing said polycarbonate substrate with the coating composition thereon to ultraviolet light to cure said composition, thereby forming the intermediate primer layer which contains the polymer-ized photoreaction products of the polyfunctional acrylic acid ester monomer or monomers which are present in the photocurable `
coating composition.
The polyfunctional acrylic ester monomers of the present ~
invention are represented by the general formula ~ `

I. [H2C = C - C - O 3 R
n wherein n is an integer from 2 to 8, preferably from 2 to 6, and more preferab].y from 2 to 4; and R is an n valent hydrocarbon radical, an n valent substituted hydrocarbon radical, an n valent hydrocarbon radical containing at least one ether linkage, and an n valent substituted hydrocarbon radical containing at least one ether linkage. ~`
Preferred n valent hydrocarbon radicals are the n valent aliphatic, preferably saturated aliphatic, hydrocarbon radicals containing from 1 to about 20 carbon atoms and the n valent aromatic hydrocarbon radicals containing from 6 to about 10 carbon atoms.

: . .

~ 8CS 2378 Preferred n valent hydrocarbon radicals containing at least one ether linkage are the n valent aliphatic hydrocarhon radicals, preferably saturated aliphatic hydrocarbon radicals, containing from 1 to about 5 ether linkages and from 2 to about 20 carbon atoms.
Preferred n valent substituted hydrocarbon radicals are the n valent aliphatic hydrocarbon radicals, preferably the saturated aliphatic hydrocarbon radicals, contalning from 1 to about 20 carbon atoms, and the n valent aromatic hydrocarbon radicals con-taining from 6 to about 10 carbon atoms which contain substituent groups such as the halogens, i.e , fluorine, chlorine, bromine and iodine, hydroxyl, -COOH, and -COOR' groups wherein Rl represents alkyl groups containlng from 1 to about 6 carbon atoms. `
Preferred n valent substituted hydrocarbon radicals containing at least one ether linkage are the n valent aliphatic 7 preferably saturated aliphatic, hydrocarbon radicals containing from 2 to about 20 carbon atoms and from 1 to about 5 ether linkages which ; ~
contain substituent groups such as the halogen hydroxyl, -COOH, i and -COOR' groups wherein R' is as defined above.
It is to be understood that where substltuent groups are present, they should be such that they do not unduly hinder or interfere with the photocure of the polyfunctional acrylic monomers~
The more preferred polyfunctional acrylic monomers are those represented by foxmula I wherein R is selected from the group consisting of an n valent saturated aliphatic hydrocarbon radical containing from 1 to about 20 carbon atoms, a hydroxyl substituted n valent saturated aliphatlc hydrocarbon radlcal containing from l to about 20 carbon atoms, an n valent saturated aliphatic hydro-carbon radical containing from 2 to about 20 carbon atoms and from 1 to about 5 either linkages, and a hydroxyl substituted n valent ~ 8 -~ 8CS 2378 saturated aliphatic hydroca.rbon radical containing from 2 to about 20 carbon atoms and from l to about 5 e-ther linkages.
The preferred polyfunctional acrylate ester monomers are those wherein R is an alkyl, ether or.polyether group, with those 5 monomers wherein R is an alkyl group being more preferred.
More particularly, the difunctional acrylic monomers, or di-acrylates, are represented by ormula I wherein n is 2; the tri- . ;
functional acrylic monomers, or triacrylates, are represented by ~ ~
formula I wherein n is 3; and the tetra-functional acrylic mono- ~ `
mers, or tetraacrylates, are represented by formula I wherein n is 4.
Illustrative of suitable polyfunctional acrylate ester mono- ;
mers of formula I are those listed below in TABLE I.
TABLE I
Diacry~ates of Formula I
1. CH2=CHCOO-CH2--OOCCH--CH2 ~, 2. CH2=CHCOO-CH2-CH2-OOCCH=CH2

3. CH2=CHCOO-CH2-CHOHCH2-OOCCH=CH2 ~ .

4. CH2=CHCOO-(CH2)6-OOCCH-CH2 20 5. CH2=CHCOO-CH2-CH2-CH-CH3 OOCCH=CH2 6- CH2=CHCOO-CH2CH2OCH2CH2-OOCCH=CH2 2 C O CH2cH2ocE~2cH2ocH2cH2ocH2cH2-ooccH=cH2 fH3 ~
8. CEl2=CHCOO-CH2-f-OOCCH=CH2 CH3 - :
CIH2OH : ~
9. CH2=CHCoO-CH2-f-cH20cH2cH2-OOccH=cH2 ~' ~ 8CS 2378 fH2H
10. CH2=CHCOO~CH2-C-OOCCH=CH2 fH2E~ ~
11. CH2=CHCOO-CH2-f-OOCCH=CH2 Triacrylates of E'ormula 1 IOOCCH=CH2 10 12. CH2=CHCOO-CH2CH2CHCEI-OOCCH=CH2 ~ ~
CH2=cHcoo-fH2 13. CH2=CHCOO-CH2-f~CH2-CEI3 CH2=CHCOO-CH2 fH2H
15 14- CH2=cHcoo-cH2-7-cH2-ooccH=cH2 CH2 -OOCCH=CH2 fH2H
15. CH2=CHCOO-CH2CH2-O-CH2-f-OOCCH=CH2 ~;
CH2-OOCCH=CH2 ::, Tetraacrylates of Form_la I ~
CH2=CHCOO-fEI2 16. CH2=CHCOO-CH2-f-CEI2-OOCCH=CH2 17. CH2=CHCOO-CH2-1CH-fH-CH2-OOCCH=CH2 ~ .
CH2=CHCOO-~H2CH2-OOCCH=CH2 IOH ' ~`' CH2 CHCOO-CH2THCH-CH2fEI-ooCCH=CH2 CH2=CHCOO-CH2 CH2-00CCH=cH2 These polyacrylate esters and thei.r production are well known to those skilled in -the art. One method of producing the di-, tri-, :

~ 8CS 2378 and tetraacrylate esters involves reacting acrylic acid with a di-, tri-, or te~rahydroxyl compound to produce the diester, triester or -tetraester. Thus, for example, acrylic acid can be reacted with ethylene glycol to produce ethylene glycol diacrylate (compound 2 in Table I).
Although the coating compositions may contain only one of said polyfunctional acrylate monomers, preferred coating composi-tions contain a mixture of two polyfunctional monomers, preferably a diacrylate and a triacrylate. When the coating compositions contain a mixture of acrylate monomers, it is preferred that the ratio, by weight, of the diacrylate to the triacrylate be from about 30/70 to about 70/30. Exemplary mixtures of diacrylates and triacrylates include mixtures of hexanediol diacrylate with pentaerythritol triacrylate, hexanediol diacrylate with trimethyl-olpropane triacrylater dlethyleneglycol diacrylate with pentaeryth-ritol triacrylate, and diethyleneglycol diacrylate with trimethyl-olpropane triacrylate.
Generally, the coating composition contains from about 70 to about 99weight percent of the polyfunctional acrylate monomer or mixtures of said monomers. ~he UV cured coating contains from about 70 to about 99 weight percent of the photoreaction products of the polyfunctional acrylate monomer or mixture of polyfunctional acrylate monomers present in the coating composition, The photocurable coating composition also contains a photo-~ensitizing amoun-t of photosensitizer, i.e., an amount effective to effect ~he photocure of the coating composition. Generally, this amount is from about 0.01% to about 10% by weight r preferably from about 0.1% to about 5% by weight of the photocurable coating composition. These additives and the cure thereof are generally well known in the art. Some nonlimiting examples of these UV

~ 11 -3~ cs 2378 radiation photosensitizers include ketones, such as benzophenone, acetophenone, benzil, benzyl methyl ketone; benzoins and substi-tuted benzoins such as benzoin methyl ether, ~ -hydroxymethyl benzoin isopropyl ether; halogen containing compounds such as C~-bromoacetophenone, p-bromoacetophenone, ~-chloromethyl-naphthalene, and the like.
The coating composition of the instant invention may also optionally contain various flatting agents, surface-active agents, thixotropic agents, and UV light absorbers. A11 of these addi-tives and the use thereof are well known in the art and do notrequire extensive discussions. Therefore, only a limited number will be referred to, it being understood that any compounds possessing the ability to function in such a manner, i.e., as a flatting agent, surface-active agent, UV light absorber, and the like, can be used so long as they do not deleteriously affect the photocuring of the coating compositions and do not adversely affect the non-opaque character of the coating.
The various sur~ace-active agents, including anionic, cationic and nonionic suriace-active agents are described in Kirk-Othmer Encyclopedia of Chemical Technology, Vol. l9, Interscience Pub--lishers, New York, 1969, pp. 507-593, and Encyclo~_i of Pol~mer Science and Technology, Vol. 13, Interscience Publishers, New York, 1970, pp. 477--486, both of which are references.

In a preferred embodiment of the instant invention, the 25 coating compositions contain resorcinol monobenzoate. The resor-cinol monobenzoate is present in an amount, based upon the weight of the coating composition, exclusive of any additional solvent which may optionally be present, of from about 1 to about 20 weight percent, preferably from about 3 to about 15 weight percent.

~3~3~ 8CS 2378 The preferred UV cured coating thus contains, in addition to the afore-described photoreaction products of at least one polyfunc-tional acry]ic monomer, from about 1 to about 20% by weight of the photoreaction products of resorcinol monobenzoate, which products are formed during the UV cure of the UV curable coating composition.
The glass coated polycarbonate articles having the preferred -;
intermediate primer layers, i.e., those intermediate primer layers formed by the ultraviolet light cure of the intermediate coating composition containing resorcinol monobenzoate, have superior adhesion of the vapor deposited glass protective layer to the polycarbonate substrate, especially after exposure to weathering, ;
~ompared to glass coated polycarbonate articles having intermediate primer layers formed by the ultraviolet light cure of intermediate coating compositions wlthout the resorcinol monobenzoate.
In the practice of the present invention, the intermediate photocurable coating compositions are first formulated by adding together the polyfunctional acrylic monomer or mixtures thereof, the UV photosensitizer, resorcinol monobenzoate, and, optionally, `
any of the other aforementioned additives. Additionally, if so desired to reduce the viscosity of the coating formulation, an organic solvent, such as an alcohol, may optionally be incorpora-t~d into the fo.rmulation. Generally, the amount of solvent, if any, present shouldbesuch that evaporation of the solvent occurs before any deleterious effect on the substrate due to the aggres-siveness (in the chemical etching sense) of the coating composition ~
develops. The various components are thoroughly mixed so as to ; ~;
form a generally homogeneous coating composition. A thin, uniform coating of the coating solution is then applied onto the polycar~
bonate sllrface by any of the known means such as dipping, spraying, roll-coating and the like. The coating is then cured in an inert, :

~3~3~ 8CS 2378 e~g~, nitrogen~ atmosphere by irradiation with ultraviolet light which can have a wavelength of from 1849 A. to 4000 A. The lamp systems used to generate such radiation can consist of ultraviolet lamps which can consist of discharg~ lamps, as for example, xenon, metallic halide, metallic arc, such as low or high pressure mercury vapor discharge lamp, etc., having operating pressures of frorn as low as a few milli-torr up to about 10 atmospheres, can be employed.
By curing is meant both polymerization of the polyfunctional acrylic monomers and cross-lin~ing of the polymers to form hard, non-tacky intermediate primer coatings.
The cured intermediate primer layer has a thickness of from about 0.1 mils to about 10 mils, preferably from about0O2 mils to about 5 mils.
After the polycarbonate substrate has been primed by the application thereon of the intermediate primer coating composition and the cure of said coating composition by exposure to ultraviolet light, a thin layer of glass is vapor deposited onto said primed substrate using radio frequency induction heating to evaporate the glass.
The glass which can be deposited by vapor deposition OIltO the primed polycarbonate substrate generally consists mainly of SiO2.
0ther types of glass, however, can also be the protective top layer in accordance with the present invention. Examples of these other types o~ hard inoryanic glass include a glass consisting of SiO2, 25 B2O3~ A12O3 and N2O3; HfOX; ZrO2; and the like.
In describing the vapor deposition of the glass coating reference will be made to the two FIGURES of the drawings which illustrate in perspective and diagrammatically a preferred embodi-rnent of the arrangement for practicing the method of the invention. -~
The primed polycarbonate substrate 11, in this case a poly- -~

carbonate panel with the cured primer layer 20 in one side thereof ;

~3~3~ 8CS 2378 is placed in a vacuum vessel 10. The vacuum vessel contains a graphite crucible 12 demountably located in a ceramic receptacle 13 having radio frequency induction coils 14 mounted therein. The material to be volatilized l9,e.~,quartz, is placed in the crui-cible. The crucible is positioned so that its longitudinal axis `is transverse to the longitudinal axis and direction of travel of the polycarbonate panel thereby enabling the volatilized quartz material to be evenly deposited across the entire width of the polycarbonate panel as it passes over the crucible. Preferably, the crucible is positioned at a distance of about 10 inches below the polycarbonate sheet. The coils 14 are connected by means of power cells to a power supply service 16. The power supply source is a commercially available unit sold by Applied Materials, Inc., California, under the tradename Pachydyne~ 50 Induction Heating Power Supply rated at 50Kw/50 KHz. A vacuum system including a dif-fusion oil pump, is connected to the vacuum vessel to provide the necessary low pressures needed. Generally, these pressures are in the range of from about 10-4 to about 10-6 mm Hg. The vacuum vessel may optionally contain member 18 which may be in the shape of a hollow cyclindrical member having a plurality of small open-ings therein used for the introduction of oxygen into the vacuum chamber during the vapor deposition of the glass coating on the ~ `
primed polycarbonate panel.
In the practice of the method of the present invention the primed polycarbonate panel 11 is placed into the vacuum chamber 10 with the side of said panel containing the primer layer 20 disposed facing the crucible 12 which contains a supply of quartz. The chamber is then evacuated until a pressure of about 10-4 to about 10-6 mm of Hg is achieved. The coils 14 are then energized to melt the quartz and the polycarbonate panel is transported over the ~ 3g~ 8CS 2378 crucible in the direction indicated by the arrow, i.e., a direc-tion transverse to the longitudinal axis of the crucible. The stream of vaporized Si x particles then impinges upon and adheres to the primed polycarbonate panel. Oxygen can be in~
troduced into the vacuum chamber 10 by means of the hollow cylindri-cal member 18 to insure conversion of the SiOx stream to Sio2. The rate of movement of the poLycarbonate panel over the crucible can be varied so as to achieve the desired thickness of the SiO2 coat-ing thereon, i.e., the greater the rate of transport the thinner the SiO2 layer, the lower the rate of transpor~ the thicker the SiO2 layer. Generally, the thickness of the SiO2 layer ranges from about 1 to about 10 microns, preferably from about 2 to about 7 microns.
PREFERRED EMBODIMENTS OF THE INVENTION
_ _ In order to more fully and clearly illustrate the present invention, the following specific examples are presented. It is intended that the examples be considered as illustrative of rather than limiting the invention disclosed and claimed herein.

An aromatic polycarbonate is prepared by reacting 2,2-bis(4-hydroxyphenyl)propane and phosgene in the presence of an acid acceptor and a molecular weight reyulator and having an intrinsic viscosity of 0.57. The product is then fed into an extruder, whiah extruder is operated at about 265C and the extrudate is comminuted into pellets.

An intermediate coating composition is prepared by blending together 50 parts by weight of ethyleneglycol dlacrylate, 50 parts ~ -by weight of pentaerythritol triacry:Late, 2 parts by weight of ~, ~-diethoxyacetophenone, 5 parts by weight of resorcinol ~ - 16 , -~3~ 8CS 237~

monobenzoate, and 0.5 parts by weight of a silicone oil type surface-active agent produced by Mallincrodt Chemical Co. of New Jexsey under the designation, sYK-3oo. A film of about 12.5 microns thickness of this coating composition is applied to the polycarbonate panels prepared substantially in accordance with Example 1 using a wire-wound drawdown bar. The coated polycarbon~
ate panels are then passed through a Linde photocuring apparatus (this consists of a variable speed conveyor running through a chamber containing germicidal type mercury vapor lamps which emit light mainly at 2537A, 3150A and 3605A operating in air) wherein the nitrogen pressure is 25 psi nitrogen and the speed of the conveyor is 50 ft/min. The resulting primer coating is hard and tack~free.

A polycarbonate test panel prepared substantially in accord-ance with Example 1 is placed into a vacuum deposition chamber containing a crucible about which is disposed a radio frequency induction coil, said coil being connected to a power supply source.
The power supply source is a commercially available unit sold by Applied Materials, Inc., California, under the tradename, Pachy-dyne~ 50 Induction Heating Power Supply rated at 50 Kw 50 KHz.
This power supply source is operated at between 15-30 Kw. The cruicible, to which quartz is added, is located at a distance of 10 inches below the polycarbonate sheet. The crucible is posi-25 tioned so that its longitudinal axis is transverse to the longitu- ;
dinal axis and khe direction of travel of the polycarbonate test panel thereby enabling the volatilized quartæ material to be evenly deposited across the entire width of the test panel as it passes over the cruicible. The vacuum deposition chamber is maintained at a pressure of approximately 1 x 10-4 mm Hg and the -~3~ 8CS 2378 polycarbonate test panel is transported across the crucible at a rate of l foot per minute. A coating of silicon dioxide 3 microns thick is evenly and uniformly deposited on the polycarbonate pa~el.

A polycarbonate test panel prepared substantially in accord~
ance with Example l and precoated substantially in accordance with Example 3 is placed into a vacuum deposition chamb~r contain-ing a cruicible about which is disposed a radio frequency induction coil, said coil being connected to a Pachydyne~ 50 Induction ~eating Power Supply operating at between 15 30 Kw. The crucibler which contains quartz, is located lO inches below the polycarbonate test panel. The crucible~ is positioned so that its longitudinal axis is transverse to the longitudinal axis and the direction of travel of the polycarbonate test panel thereby enabling the vola-tilized quartz stream to evenly impinge upon the side of the poly-carbonate panel facing the crucible and resulting in a silicon dioxide layer which is evenly and uniformly deposited across the entire width of the test panel as it passes over the cruicible.
The vacuum deposition chamber is maintained at a pressure of ap-proximately l x 10-4 mm Hg and the polycarbonate test panel is transported across the crucibLe at a rate of l foot per minute.
A coating of silicon dioxide 3 microns thick is evenly and uniform-ly deposited on the precoated polycarbonate test panel.
The glass coated polycarbonate panels prepared in accordance with Examples 3 and 4 are subjected to a series of tests to determine the durability of adhesion of the glass coat, protection a~forded the polycarbonate substrate by the glass coating against attack by organic solvents, and the abrasion resistance of the glass coating.

The test to determine the durability of the glass coating in- `
volves subjecting the glass coated samples to a humidity test.

~ 18 -~.3~3~ 8CS 2378 This humidity test involves subjecting the glass coated samples to ~.
a number of humidity oven cycles, and after each cycle subjecting said samples to a scribed adhesion test. One humidity oven cycle consists of placing the sample into a cabinet maintained at 99~
relative humidity and 80-85F, raising the ~emperature to 140F, maintaining the temperature at 140F for 6 hours, and thereafter lowering the temperature to 80-85~, at which time one cycle is complete and the sample is removed and subjected to the scribed adhesion test. The scribed adhesion test consists of using a multiple blade tool to cut parallel grooves about 1 mm apart through the coating into the polycarbonate substrate, rotating the sample 90 and repeating the cutting process thereby forming a grid pattern of 1 mm squares cut into the coating and substrate, and applying an adhesive tape over the cross~hatched area and quickly lS pulling said tape off. A sample fails the adhesion test if any of the coating on any of the squares is pulled off. The results of this test are set forth in Table II~ -TABI,E II `
Humidity Test No. oE cycles in humidity oven `
after which sample fails scribed Example No. adhesion test 4 Passes adhesion test after 10 cycles The determination of the protection afforded against solvent attack of the polycarbonate substrate by the glass coating is accomplished by stressing an uncoated sample and -the glass coated ~amples to about 1,000 psi, and thereafter contacting for a period of 15 minutes the uncoated sample and the glass coated surface of the coated samples with a solvent mixture comprised, in parts by volume, of 100 parts methylene chloride, 100 parts chloroform, :
:

-~3~3~ 8CS 2378

5 parts methylethyl ketone, and 25 parts benzyl alcohol. After the15 minute exposure to the solvent mixtures, the samples are air dried and subjected to visual observation. The results are set forth in Table III.
TABLE III
Example No. Results of Visual Observation 1 Extreme cloudiness of sample due to etching and surface pitting as a result of surface chemical at-tack by solvent mixture.

3 Moderate cloudiness oE sample due to etching and surface pitting as a result of surface chemical at-tack by solvent mixture.

15 4 Clear sample indicating no etching or surface pitting of polycarbon-ate substrate by solvent mixture.
The abrasion test is one wherein test panels having a 1/4 inch diameter hole cut in the center are subjected to a Taber Abraser. The Taber Abraser is equipped with CS-lOF wheels which are resurfaced every 200 cycles by abrading for 25 cycles on an S-11 refacing disc. The weights used in combination with the CS-lOF wheels are 500 gm. weights. Initial measurements of the % Haze are made at follr places around -the future wear track of the sample using a Gardner Hazemeter. The sample is abraded for 100 cycles, cleaned with isopropanol, and the % Haze is remeasured at the same four places. The four differences in % Haze are calcu-lated and averayed to give the a % Haze. The results are set forth in Table IV.
T~sLE IV
Abrasion Resistance Example No. ~ % Haze , 3 4.1 . , .

~3~3~ 8CS 2378 , As can be seen from Table IV, the protection provided the pol~
carbonate substrate by a glass coating vapor deposited upon a primed polycarbonate panel i5 substantially the same as that pro vided by a glass coating vapor deposited on an unprimed polycar-bonate panel. However, as seen from Tables II and III, the glasscoating which is vapor deposited on a polycarbonate panel primed in accordance with the present invention results in a coating having a much superior durability after exposure to humidity and provides a much greater degree of solvent resistance than does a glass coating which is vapor deposited on a polycarbonate panel which is not primed. This results in a glass coated polycarbonate panel which can be utilized successfully in many commercial ap-plications.
Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifi-cations can be made thereto without departing from the spirit or scope of the invention as set forth herein.

`:

Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A shaped non-opaque polycarbonate article having improved mar, abrasion, scratch and organic solvent resistance comprising a polycarbonate substrate having deposited thereon (i) a primer coating layer comprised of the photoreaction product of at least one polyfunctional acrylic monomer represented by the general formula wherein n is an integer having a value of from 2 to 4, and R is a n valent hydrocarbon radical, n valent substituted hydrocarbon radical, n valent hydrocarbon radical containing at least one ether linkage, and a n valent substituted hydrocarbon radical containing at least one ether linkage; and (ii) a thin top layer of vapor deposited glass on said primer coating layer.

2. The article of claim 1 wherein said n valent hydrocarbon radical is an n valent aliphatic hydrocarbon radical, said n valent substituted hydrocarbon radical is a n valent substituted aliphatic hydrocarbon radical, said n valent hydrocarbon radical containing at least one ether linkcage is a n valent aliphatic hydro-carbon containing at least one ether linkage, and said n valent substituted hydrocarbon radical containing at least one ether linkage is a n valent substituted aliphatic hydrocarbon radical containing at least one ether 1inkage.

3. The article of claim 2 wherein said n valent aliphatic hydrocarbon radical and n valent substituted aliphatic hydrocarbon radical contain irom 1 to about 20 carbon atoms.

4. The article of claim 2 wherein said n valent aliphatic hydrocarbon radical containing at least one ether linkage and n valent substituted aliphatic hydrocarbon radical containing at least one ether linkage contain from 2 to about 20 carbon atoms and from 1 to about 5 ether linkages.

5. The article of claim 1 wherein said primer coating layer is comprised of the photoreaction product of ethyleneglycol diacrylate and pentaerythritol triacrylate.

6. The article of claim 1 wherein said vapor deposited layer of glass is comprised substantially of SiOx wherein x ranges from 1 to 2.

7. The article of claim 6 wherein x is 2.

8. A shaped, non-opaque polycarbonate article having improved mar, abrasion, scratch and organic solvent resistance, said article comprising a polycarbonate substrate bearing a photocurable primer coating composition comprised of (a) a photosensitizer, and (b) at least one photocurable, polyfunctional acrylic monomer represented by the general formula wherein n is an integer having a value of from 2 to 4, and R is a n valent hydrocarbon radical, n valent substituted hydrocarbon radical, n valent hydrocarbon radical containing at least one ether linkage, and a n valent substituted hydro-carbon radical containing at least one ether linkage; said primer coating composition having been exposed to ultraviolet light for a period of time sufficient to photocure said primer coating composition and thereby producing a hard primer coating layer on said poIycarbonate substrate; said article further including a thin layer of vapor deposited glass on said primer coating layer.

9. The article of claim 8 wherein said n valent hydrocarbon radical is a n valent aliphatic hydrocarbon radical, said n valent substituted hydrocarbon radical is a n valent substituted aliphatic hydrocarbon radical, said n valent hydrocarbon radical containing at least one ether linkage is a n valent aliphatic hydrocarbon radical containing at least one ether linkage, and said n valent substituted hydrocarbon radical containing at least one ether linkage is a n valent substituted aliphatic hydrocarbon radical containing at least one ether linkage.

10. The articles of claim 9 wherein said n valent aliphatic hydrocarbon radical and n valent substituted aliphatic hydrocarbon radical contain from 1 to about 20 carbon atoms.

11. The article of claim g wherein said n valent aliphatic hydrocarbon radical containing at least one ether linkage and said n valent substituted aliphatic hydrocarbon radical containing at least one ether linkage contain from 2 to about 20 carbon atoms and from 1 to about 5 ether linkages.

12. The article of claim 8 wherein said primer coating composition contains ethyleneglycol diacrylate and pentaerythritol triacrylate.

13. The article of claim 8 wherein said glass layer is comprised substantially of SiOx wherein x ranges from 1 to 2.

14. The article of claim 13 wherein x is 2.

15. The article of claim 8 wherein said glass layer is vaporized by means of radio frequency induction heating.

16. A method of providing an adherent thin glass film of relative uniform thickness on a poly-carbonate substrate which comprises the steps of:
(i) producing a stream of vaporized glass by heating a source of glass by radio frequency induction in an evacuated chamber; and, (ii) passing a polycarbonate substrate through said stream of vaporized glass with the longi-tudinal axis of said substrate transverse to said stream of vaporized glass such that said stream of vaporized glass contacts and is uniformly deposited on the polycarbonate substrate surface exposed thereto.

17. The method according to claim 16wherein said evacuated chamber is maintained at a pressure of from about 10-4 to about 10-6 mm Hg.

18. The method according to claim 16 wherein oxygen is introduced into said stream of vaporized glass.

19. The method according to claim 16 wherein the thickness of the glass film is varied by varying the rate of passage of said polycarbonate substrate through said stream of vaporized glass.

20. The method according to claim 19 wherein the thickness of said glass film ranges from about 1 to about 10 microns.

21. The method according to claim 16 wherein said glass film is comprised substantially of SiO2.
22. The method according to claim 16, 17 or 18 wherein said polycarbonate substrate is primed with a primer coating layer comprised of the photoreaction product of at least one polyfunctional acrylic monomer

Claim 22 continued:
represented by the general formula wherein n is an integer having a value of from 2 to 4, and R is a n valent hydrocarbon radical, n valent substituted hydrocarbon radical, n valent hydrocarbon radical containing at least one ether linkage, and a n valent substituted hydrocarbon radical containing at least one ether linkage.