Europa,schesP_ MM M M M MM II II I Ml Ml II I II J European Patent Office _ _ _ B4 © Publication number: 0 596 936 B1 Office europeen* des.. brevets , © EUROPEAN PATENT SPECIFICATION © Date of publication of patent specification: 11.10.95 © Int. CI.6: C03C 17/22 © Application number: 92915983.8 @ Date of filing: 20.07.92 © International application number: PCT/EP92/01649 © International publication number: WO 93/02981 (18.02.93 93/05) (54) DEPOSITION OF MAGNESIUM FLUORIDE FILMS. ® Priority: 29.07.91 US 736863 © Proprietor: FORD-WERKE AKTIENGESELL- SCHAFT @ Date of publication of application: 18.05.94 Bulletin 94/20 D-50725 Koln (DE) © Designated Contracting States: © Publication of the grant of the patent: DE 11.10.95 Bulletin 95/41 © Proprietor: FORD FRANCE S. A. © Designated Contracting States: B.P. 307 DE FR GB F-92506 Ruell-Malmalson Cedex (FR) © Designated Contracting States: © References cited: FR EP-A- 0 125 721 GB-A- 2 093 442 © Proprietor: FORD MOTOR COMPANY LIMITED US-A- 5 051 278 Eagle Way Brentwood, CHEMICAL ABSTRACTS, vol. 107, no. 20, No- Essex CM13 3BW (GB) vember 1987, Columbus, OH (US); no. © Designated Contracting States: 181929f GB 00 APPLIED OPTICS, vol. 27, no. 16, 15 August @ Inventor: PLATTS, Dennis, R. CO 1988, New York, NY (US); I.M. THOMAS, pp. 17217 Rougeway 00 3356-3358 Livonia, Ml 48152 (US) Oi CO m Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid (Art. 99(1) European patent convention). Rank Xerox (UK) Business Services (3. 10/3.09/3.3.3) EP 0 596 936 B1 0 Representative: Messulam, Alec Moses A. Messulam & Co. 24 Broadway Leigh on Sea Essex SS9 1BN (GB) 2 1 EP 0 596 936 B1 2 Description coatings on glass, utilizing reactive precursors which are easy to work with due to their good This invention relates to magnesium fluoride solubility properties. films and a process for deposition magnesium flu- Accordant with the present invention, a reactive oride films onto the surface of a hot glass sub- 5 precursor for preparing a magnesium fluoride film strate. on glass by a spray pyrolysis or chemical vapor Magnesium fluoride is well-known as a coating deposition process has surprisingly been discov- material which imparts anti-reflectivity to optical ered. The precursor comprises: articles and vision glazings, to increase the visible A) magnesium acetylacetonate; light transmissivity of same. Magnesium fluoride io B) trifluoroacetic acid; and films may conveniently be deposited onto transpar- C) optionally, a solvent. ent substrates, either singularly or in combination The inventive reactive precursor may be deliv- with other metal and dielectric layers, by conven- ered to the surface of a heated glass substrate as tional methods such as, for example, spray either a liquid (in the spray pyrolysis process) or as pyrolysis, chemical vapor deposition, vacuum 75 a vapor (in the chemical vapor deposition process). evaporation, sputtering, and the like. The reactive precursors of the present inven- The deposition of magnesium fluoride by spray tion are particularly well suited for placing magne- pyrolysis or chemical vapor deposition requires the sium fluoride anti-reflective films onto automotive preparation of a proper reactive precursor which is and architectural glazings. then directed onto the heated surface of the sub- 20 A magnesium fluoride film is deposited onto a strate to be coated. Spray pyrolysis utilises a liquid hot glass substrate by either of the well-known reactive precursor which is sprayed onto the sur- pyrolysis or chemical vapor deposition processes, face of the hot substrate whereat the precursor utilizing a reactive precursor comprising a mixture thermally decomposes and reacts to form a film. of magnesium acetylacetonate and trifluoroacetic Chemical vapor deposition utilises a gaseous reac- 25 acid. Conveniently, the reactive precursor may also tive precursor which is delivered to the surface of include a solvent. The magnesium fluoride film the hot substrate whereat the precursor reacts to deposited by the process of the present invention form the film. Conveniently, a continuous glass additionally contains a minor amount of magnesium ribbon being produced by the float glass process oxide which decreases as the reaction temperature possess sufficient heat to activate and react both 30 increases. spray pyrolysis and chemical vapor deposition pre- The glass upon which the magnesium fluoride cursors to form such films thereon. film is deposited may be in the form of individual U.S. Patent No. 3,475,192 to Langley discloses glass sheets, or in the form of a continuous glass a liquid reactive precursor which is coated onto a ribbon produced by the well-known float glass pro- glass surface then fired to form a magnesium flu- 35 cess. Suitable glass substrates for use according to oride film. The precursor comprises magnesium the present invention may include any of the con- fluoride dissolved in a mixture of an organic solvent ventional glass compositions known in the art as and a film forming material, e.g., an oil. useful for preparing automotive or architectural U.S. Patent No. 4,492,721 to Joosten et al. glazings. The various chemical compositions which discloses a method of providing magnesium flu- 40 produce different glass substrates, e.g., borosilicate oride layers on substrates by the disproportionation glass or soda-lime-silica glass, generally do not of fluorine-containing organic magnesium com- structurally nor chemically affect the deposited lay- pounds containing at least six fluorine atoms per er of magnesium fluoride. A preferred glass is magnesium atom. A reactive precursor, comprising commonly known in the art as soda-lime-silica a fluorine-containing compound, e.g., magnesium 45 glass, and may be of any thickness generally trifluoroacetate, magnesium known as useful for providing support for a coating trifluoroacetylacetonate, magnesium hex- such as magnesium fluoride. afluoroacetylacetonate, etc., and an organic solvent Where the glass to be coated with magnesium is contacted with a hot glass substrate utilizing fluoride is being produced by the float glass pro- either spray pyrolysis or chemical vapor deposition, 50 cess, the temperature of the glass is already suffi- depending upon the vaporisation temperature of ciently high to either pyrolyze the liquid spray or the fluorine-containing compound used. Such pre- react together the vaporised components of the cursors, however, are generally difficult to work chemical vapor deposition reactive precursors of with due to their limited solubility in various sol- the present invention. Pyrolysis or chemical vapor vents, and additionally produce coatings on glass 55 deposition utilizing the inventive reactive precursors having relatively limited anti-reflection properties. generally is carried out at a temperature from about It would be desirable to devise a process for 482 • C (900 • F) to about 649 • C (1 ,200 • F). Individ- depositing highly anti-reflective magnesium fluoride ual glass sheets which are to receive a coating of 3 3 EP 0 596 936 B1 4 magnesium fluoride must be heated to approxi- film thicknesses from about 5 nm (50 Angstroms) mately this specified temperature range to effect to about 500 nm (5,000 Angstroms) have been the pyrolysis or chemical vapor deposition reaction. found to be useful for various automotive and ar- Magnesium acetylacetonate is a well-known, chitectural glazing applications, depending on the commercially available chemical reagent which 5 intended purpose for the magnesium fluoride film. may be obtained from Amspec, Gloucester City, The inventive process is not only useful for New Jersey. Trifluoroacetic acid likewise is a well- forming a magnesium fluoride film directly on a known commercially available chemical reagent, glass surface, but also for forming a magnesium generally available in concentrations from about fluoride film on a previously deposited coating 97% to about 98.5%, from suppliers such as Fisher io which is adhered to the glass surface. Thus, the Scientific, Pittsburgh, Pennsylvania. present invention may be used to apply a magne- Solvents which may optionally be included in sium fluoride film over a previously applied dielec- the reactive precursors of the present invention tric or metal layer. Accordingly, the term "glass include a wide variety of organic materials such as, substrate" as used herein is intended to include for example, methanol, dimethylformamide, ben- is glass having one or more of the aforementioned zene, toluene, xylene, hexane, heptane, methanol, dielectric or metal layers adhered thereto. Exam- ethanol, methylene chloride, perchloroethylene, ples of dielectric layers upon which a magnesium chloroform, carbon tetrachloride, fluoride film may be necessarily limited to, ZnO, dimethylacetamide, acetonitrile, nitrobenzene, ace- Sn02, MgF2, Al203, TiN, Si02, MgO, Ti02, and the tic acid, ethylene diamine, propanol, butanol, etc., 20 like, as well as mixtures thereof. Contemplated and water, as well as mixtures thereof. A preferred metal layers having the same operability and utility solvent is a mixture of methanol and water. upon which a magnesium fluoride film may be The ingredients may be admixed in any con- deposited include, but are not necessarily