A PHOTOCHROMIC FILM AND PROCESS FOR FORMING THE SAME

Abstract: A process of forming a photochromic film of predetermined thickness enabling the film to be affixed on a given surface of a blank, such as a lens, wherein the blank may be formed of glass, plastic, or any other applicable material. The resulting product comprises a lens blank or other product wich itself exhibits photochromic characteristics based on its exposure to ultraviolet rays.

Description: Description A PHOTOCHROMIC FILM AND PROCESS FOR FORMING THE SAME A- 5 Field of the Invention: This invention relates to a process for forming a film and a product such as a lens blank or any transparent or like material including glass, plastic which exhibits photochromic characteristics when the 10 subject film is adhered to a predetermined surface thereof. Background Art: Photochromic glass has been known in the prior 15 art for many years. This material is frequently found in the production of glass lenses wherein the photochromic effect of the glass from which the lens is formed will vary in shade based upon its exposure to ultraviolet rays such as sunlight. 20 Prior art attempts have been made to develop a plastic as versus a glass base material which is also capable of exhibiting photochromic characteristics. While such material has in fact been developed, it has been found to be less than totally satisfactory 25 from a commercial standpoint since such photochromic plastic exhibits a high degree of fatigue. Fatigue, in the optical or lens manufacturing industry, rep¬ resents the length of time a given material will retain its photochromic characteristics. The develop- 30 ment of photochromic plastic has not reached the point where it can be effective in ordinary every day usage for a significant period of time sufficient to justify widespread commercial application. Also, there have been attempts in the industry 3 to develop a photochromic film which ideally could be adhered to a given surface of a blank, such as a lens blank or the like, and thereby allow such blank to exhibit the desired photochromic characteristics. -2- However, this has been found to be less than feasible especially when coating plastic blanks, including plastic lenses with a photochromic film. The reason for this is that prior art attempts have resulted in the manufacture or production of films having a thickness of substantially 1.5 milimeters. When such a glass material film is disposed on a plastic blank, differences in the coefficience of expansion between the film and the plastic base has resulted in a cracking or breaking of the film thereby rendering 0 the lens blank worthless. The relatively great thickness of prior art photochromic film is based on the accepted concentration of silver halogenides in the film to accomplish the desired photochromic effects. 5 Even when dealing with glass material lens incorporating photochromic characteristics, the quality of lenses varies since lenses having a rela¬ tively great variation in curvature results in a lens of varying thickness. This in turn results in a o variation in tint or coloring of the lens which ideally should have a uniform tint when darkened due to the exposure of ultraviolet rays. This last limitation of inconsistency in color or tint has made the demand and necessity for an efficient and effec- tive photochromic film which would be capable of being adhered or disposed on the outer surface of any lens regardless of variations in its thickness or configuration. Ideally, such a film would result in a totally consistent tint or coloration of the lens 0 in that the thickness of the film would of course be uniform and be unrelated to any variations in the thickness or configuation of the lens itself. In addition, such a preferred photochromic film should be capable of being adhered to any material base including plastic, glass, or even infra-red filters. Such a photochromic film would not be limited to use in combination with optical lenses but could be applied to windshields, windows, or any application where photochromic characteristics would be desirable. The film also solves 'another problem in the industry by providing a relatively hard surface that is scratch resistant. Summary of the Invention: The present invention is directed towards a photochromic film which among other things provides a relatively hard surface which is not easily scratched and is also directed toward methods of forming such a 0 film and further including a resulting product such as a lens blank or like base on which the subject photochromic film has been disposed. More specific¬ ally, the subject photochromic film is produced by forming a mixture of a predetermined quantity of a 5 silica base material or phosphate base material and an additive of a silver halogenide compound. Such mixture is placed within a closed environment subject to a vacuum of predetermined negative pressures and a predetermined temperature defined within an activat- o ing temperature range. For purposes of explanation of the subject invention, activating temperature range is herein defined as a range of temperature at which evaporation of the formed mixture takes place dependent upon the existing negative pressure within the closed environment. Further, such activating temperature range has an upper limit at the tempera¬ ture at which a glass material, such as that material from which the mixture is formed, has its photo¬ chromic characteristics, if such exist, begin to deteriorate. Generally, it is well accepted that photochromic characteristics of a given glass material degenerate if such material is exposed to a temperature of 700°C. Accordingly, the upper limit of the activating temperature range is not to exceed any temperature at which such photochromic character¬ istics begin to deteriorate. The lower limit of such temperature range is again variable and depends upon the given and selected negative pressure of the OMPI closed environment. Similarly, the negative pressure of the closed environment in which the mixture is vaporized must be selected to always maintain the resulting temperature of evaporation to be less than the aforementioned temperature at which a glass material loses its photochromic characteristics. Adhering or disposing of the formed film is accomplished by condensing the vaporized compound of the mixture on a predetermined surface of a blank, such as a lens blank, prepositioned within the closed environment. While this description of the present invention will relate to the disposing of the formed film on lens blanks, it should be emphasized that the mate¬ rial can be formed on any given blank or base other than lens blanks and therefore used for a wide variety of commercial applications including wind¬ shields for automobiles, windows for houses and buildings, etc. Further, the process as generally described above is controlled such that the thickness of the formed photochromic film is such as to be preferably between 1 and 4 microns. This gives the formed film sufficient flexibility to be adhered to any given material base including plastic. Due to the extreme thinness of the formed photochromic film, any differ¬ ence in coefficience of expansion between a plastic base or blank and the film itself will not result in destruction of the film due to the inherent flexi¬ bility of a glass material film of a thickness of approximately 4 to 5 microns. In order to accomplish the above set forth process and control the parameters of temperature, negative pressure and thickness of the resulting film, it has been found that a machine can be util¬ ized of the type referred to as a "Sputtering Plant-DC/RF SPUTRON" if very low temperatures of evaporation have to be used. This machine while not the only type of machine capable of being utilized in the production of the subject photochromic film is representative of a type of machine capable of form¬ ing films of the degree of thickness required and more specifically is a plasma-beam sputtering equip¬ ment for the production of thin films of metals and dielectrics. Electron beam vacuum machine or vacuum machine on which the product will be evaporated by heat can also be used on special cases. Detailed Description of the Preferred Embodiment: The present invention relates to the production of a photochromic film of predetermined thickness capable of being applied to a lens blank or other material, either glass, plastic or other applicable material such that the resulting product itself demonstrates desired photochromic characteristics. In forming the subject photochromic film, a mixture is placed within a closed environment. The mixture is formed from a silica base material or a phosphate base material in predetermined proportions to an additive of a silver halogenide compound. More specifically, and one example of the forma¬ tion of the process, the mixture was formed by adding four parts by weight of silicium monoxide to an additive of one part by weight of the total resulting mixture of a silver halogenide compound. The halo¬ genide may be selected from any of the Halogen Group and preferably from the group consisting of silver chloride and/or silver bromide. Another example, the subject mixture was formed from three parts by volume silicium monoxide, one part by weight of a silver halogenide compound, and 1.5 parts by weight of a glass material previously structured to include photochromic characteristics before adding to the mixture. After blending or mixing the compounds, pre¬ ferably in particulate form, the mixture is placed within a closed environment of a vacuum in which both the negative pressure and temperature can be regu- lated. In producing the film, the mixture is vapor¬ ized at a temperature and negative pressure to ac¬ complish vaporization while at the same time main¬ taining the vaporization temperature within an acti¬ vating temperature range, as set forth above, and below an upper temperature limit at which glass material begins to lose its photochromic character¬ istics. The process is further controlled to cause condensation of the vaporized mixture on a predeter¬ mined surface of a blank which itself is predisposed or positioned within the closed environment prior to vaporization. The resulting formed film has a thick¬ ness of approximately 4 to 5 microns and, the thick¬ ness of the formed film may vary between 1 and 5 microns as desired. The parameters of the above set forth process can be regulated through the application of equipment of the type set forth above which is specifically designed for the production of thin films. The resulting product therefore exhibits substan¬ tially complete and in any event highly satisfactory photochromic characteristics from a commercial view¬ point when viewing therethrough regardless of any variations in the thickness of the blank or base on which it is formed.

Claims: Claims 1. A process of forming a photochromic film comprising the steps of: a) preparing a base of a predetermined quant- 5 ity of the class which includes silica material and phosphate material, b) adding to said base a silver halogenide compound in sufficient quantity to define substan¬ tially at least about 10% by weight of the resulting 10 mixture, c) subjecting said mixture to a closed environ¬ ment under a vacuum within a predetermined negative pressure range and within a predetermined temperature range, ,5 d) regulating said negative pressure and temperature in cooperative relation to one another to accomplish vaporization of said mixture, e) further regulating said negative pressure and temperature to accomplish condensation of said 0 vaporized mixture as a film on a predetermined sur¬ face of a blank form prepositioned within said closed environment, f) controlling at least the parameters of negative pressure and temperature to the extent that 5 said film has a thicknes of no greater than substan¬ tially 5 microns thickness, and e) wherein said resulting formed film demon¬ strates photochromic characteristics. 0 2. A process as in claim 1 further comprising regulating said temperature relative to said pre¬ determined negative pressure to accomplish vapor¬ ization of said mixture, wherein said temperature may be regulated within a predetermined range having an 5 upper limit of about 600°C. and below 900°C. 3. A process as in claim 2 wherein said acti¬ vating temperature range comprises a variable lower OMPI limit dependent on an established negative pressure within said closed environment, said lower tempera¬ ture limit being sufficient to accomplish valori¬ zation of said mixture based on said established negative pressure. 4. A process as in claim 1 further comprising regulating said temperature within an activating temperature range, said activating temperature range including parameters of temperatures sufficient to accomplish vaporization dependent upon a predeter¬ mined established negative pressure within said closed environment and having an upper temperature limit less than an established temperature at which photochromic characteristics of a given material deteriorate_ 5. A process as in claim 4 wherein said acti¬ vating temperature range comprises a variable lower limit depending on an established negative pressure within said closed environment, said lower tempera¬ ture limit being sufficient to accomplish valori¬ zation of said mixture based on said established negative pressure. 6. A process as in claim 5 wherein said estab¬ lished negative pressure is sufficient to accomplish vaporization of said mixture at a temperature less than the temperature that will destroy photocromicity. 7. A process as in claim 1 wherein said mix¬ ture includes said base material comprising a pre¬ determined quantity of a base selected from the class which includes silica material and phosphate material and said additive comprising a silver halogenide compound in quantities sufficient to establish at least 10% by weight of said total mixture. OMP 8. A process as in claim 7 wherein said addi¬ tive compound comprises silver halogenide and defines at least 10% by weight of said resultant mixture. 9. A process as in claim 8 wherein said mix- ture includes said additive compound selected from the group consisting of silver bromide and silver chloride. 10. A process as in claim 1 further comprising said mixture including three parts by weight of a silica material base, one part by weight of a silver halogenide compound and 1.5 by weight of a glass material having photochromic characteristics prior to mixture. 11. A process as in claim 10 wherein said mixture includes a base selected from the class which includes silica material and phosphate material. 12. A process as in claim 1 wherein said mixture includes three parts by weight silica base or phosphate base, one part by weight silver halogenide and 1.5 part by weight of a glass material having photochromic characteristics prior to mixture. 13. A process as in claim 12 wherein said mixture includes said additive compound selected from the group consisting of silver halogenide. 14. A product comprising a transparent mate¬ rial base having a film of photochromic material disposed on a predetermined surface thereof, said product formed by the process of: a) preparing a mixture of silica base material with an additive of a silver halogenide compound of predetermined quantity such that said additive com¬ pound is substantially 10% by weight of said mixture, b) placing said mixture in a substantially closed environment and therein subjecting said mix¬ ture to a predetermined negative pressure and to an activating temperature range, c) selectively regulating said closed atmos¬ phere and said mixture to establish a determined negative pressure and temperature to accomplish evaporation of said mixture, d) condensing said varporized mixture on a predetermined surface of said base and further regu¬ lating the aforementioned process and said conden¬ sation to form said photochromic film having a pre¬ determined thickness on said predetermined surface. 15. A product as in claim 14 further comprising predisposing said transparent material base within said closed environment and regulating condensation of said mixture on said predetermined surface to produce a film thereon of between 1 and 5 microns. 16. A product as in claim 15 further com¬ prising establishing said predetermined negative pressure sufficient to cause evaporation of said mixture within said activating temperature range having an upper temperature limit at which evapora- tion occurs being less than an established tempera¬ ture at which photochromic characteristics of a given material degenerate. 17. A product as in claim 16 wherein said established negative pressure is sufficient to ac¬ complish vaporization of said mixture at a tempera¬ ture substantially less than 900°C. 18. A product as in claim 17 wherein said mixture comprises four parts by weight of a base material of silicium monoxide and said additive of one part by weight of silver halogenide compound. OMPI 19. A product as in claim 18 wherein said compound of silver halogenide is " selected from the group consisting of silver bromide and silver chloride. 20. A product as in claim 17 wherein said mixture includes three parts by weight of silicium monoxide, one part by volume silver halogenide compound, and 1.5 parts by weight of a glass material having photochromic characteristics prior to mixture. O_.ΓI

Inventors: MERLE JOSEPH EUGENE, MERLE, JOSEPH, EUGENE
Applicants: MERLE JOSEPH EUGENE, MERLE, JOSEPH, EUGENE
Application year: 1983
Main classification: G02B5
IPC codes: C03C17, G02B5