A PROCESS FOR THE MANUFACTURE OF GLASS WITH MODIFIED RADIANT ENERGY CHARACTERISTICS AND THE PRODUCT SO OBTAINED

Abstract: A process for the manufacture of glass capable of transmitting and reflecting radiant energy in an amount different from that transmitted and reflected by the original glass, comprises an ion implantation of appropriate materials into one or more layers of the glass, thus producing a variation of density in the molecularre structure of the layers and consequently a variation of the refractive index. The so obtained glass can be commercially used with no restriction in the case of applications in contact with the external environment (figure 1).

Description: The present invention relates to sheets of grass having modified characteristics with respect to transmission and reflection of radiant energy. The sheets of glass conventionally used in motorcars, aeroplanes and generically in transportation means as well as in the building field, transmit and reflect an amount of heat and light energy different from that incident depending on the characteristics of the glass. These characteristics may be modified by depositing on one or both the outer surfaces, one or more thin layers of appropriate materials, by means of operations known in the art as cathodic sputtering and chemical deposition in a vapour state. The thin layers externally deposited on the glass show, however, a series of drawbacks. They can be scratched by solid bodies, can be abraded in unfavourable environmental conditions (dust, hail, polluting gases and the like), their adherence to the substrate can be impaired by chemical incompatibility with the substrate itself or by scarce cleanness. Operating disfunctions in the deposition apparatus can produce, moreover, disuniformity of the layer. A further disadvantage can be the fact that when the outer layers are subjected to high temperature they show a tendency to detatch or crack. The method of ion implantation to obtain a modification of the surface is well known. By this method it is possible to obtain in the treated materials, mechanical, electrical, optical, chemical and physical characteristics different from the original ones, with the object of improving such characteristics or obtaining new alloys having certain properties. A detailed description can be found in the text "Ion Implantation and Beam Technology" by J.S. Williams and J.M. Poate, issued by the Academic Press. In the production technology of microelectronics, a high energy ion implantation method is presently used, in which the ions are capable of penetrating to a depth of several micrometers below the surface in contact with the external surface of the silicium substrate, on which the microcircuits are built. By this method it is possible, by implantation of oxygen ions for instance, to obtain electrically insulated layers submerged into silicium and successively, by doping the silicium at a lower depth, to obtain conducting layers. In this manner microcircuits can be built inside the silicium substrate rather than outside. The microcircuits thus obtained are usually denominated "buried microcircuits". A method of ion implantation for obtaining buried multilayer filters has been described in US Patent No. 4262056. This document teaches that an implantation of nitrogen into silicium at a temperature between 600 and 1000°C, produces layers of Si₂N₄ at different levels, interlieved by pure silicium layers. In an article by Polato et al, J. Amer. Ceram. Soc. 70 (10) 775-79 (October 1987) some laboratory experiments are described in which nitrogen, neon, argon and krypton ions are implanted into glass. From the experimental results it appears that the percent reflectance of the glass is reduced as a consequence of the ion implantation. In this manner the creation of a new material is effected in the layer which has undergone implantation, which consequently shows a refractive index different from that of the original material. This filter can, however, only be used in the infrared range, being in any case opaque to white light. It has been found that the ion implantation technology can be advantageously used for the manufacture of sheets of glass capable of transmitting and reflecting appropriate amounts of energy, having any wave-length, different from that originally transmitted and reflected, to be used in transportation means and/or in the building field and/or in the optical industry. In particular it has been found that an ion implantation into internal layers of the glass, causes the ions to be inserted in the molecular structure of these layers, of which the density is modified, thus modifying the refractive index. The advantages of this process essentially consist in that as the layers having a modified refractive index are "buried" into the glass, they are altogether insensitive to any damage due to external sources and can consequently be used in all conditions. Object of the present invention is consequently a sheet of soda-lime glass with an energy reflection of 7% and a refractive index of 1,52 as an average for wavelengths of white light characterized in that it has a first layer containing nitrogen and carbonium ions in a ratio of 85:15 implanted at a glass temperature of 350°C with an energy of 100 KeV at a dose of 1 X 10¹⁷ ions/cm² through a thickness of 0,186 µm, a second layer underlying said first layer free of implanted ions having a thickness of 0,136 µm, and a third layer underlying said second layer containing nitrogen and carbonium ions in a ratio 85:15 implanted with a glass temperature of 350°C with an energy of 270 KeV at a dose of 1 X 10¹⁷ ions/cm² through a thickness of 0,234 µm, said glass having a maximum energy reflection of 15,9% at 1 µm wavelength. The features of the invention will be better illustrated referring to the accompanying drawing, in which: figure 1 shows, as an embodiment, a glass according to the invention. The invention is further illustrated in example 1. Referring to figure 1, layers which have various refractive indices are produced in the glass V by ion implantation within its thickness. The implantation is carried out by means of an apparatus for ion implantation capable of providing the ions with a sufficiently high energy, such as the apparatus EATON 1003 which can provide the ions with an energy up to 6 MeV. It is thus possible to select the refractive index of the implanted glass on the basis of the glass type and the ion type. In fact, argon, xenon, crypton, neon, helium ions can be advantagously implanted into layers "buried" in the glass. Ions of any other element can also be advantagously implanted, provided that temperature and pressure conditions are used such that they do not react with the elements of the glass composition. Further modifications of the energy transmission can be obtained by acting on the number of "buried" layers on which the ion implantation is effected. A variation in the combination of the number of layers and the type of ions, will obviously produce variations of the energy characteristics of the glass. Example 1 A glass which shows an increase of its energy reflection can be manufactured according to the invention. Referring to figure 1, on a sodium calcium glass V having an energy reflection 7% and a refractive index 1,52, measured as an average value of the values obtained at wave lengths of white light, a nitrogen and carbonium implantation was effected on the layer 3, at a ratio 85:15 with an energy 270 keV and a dose 1 x 10¹⁷ ions/cm² through a thickness of 0,234 micrometers. No implantation was effected on the layer 2 at 0,186 micrometers thickness. Successively, on the layer 1 a nitrogen and carbonium ion implantation was effected in a ratio 85:15 with a 100 keV energy and a dose of 1 x 10¹⁷ ions/cm² through a thickness of 0,234 micrometers. The glass temperature was about 350°C. A glass was thus obtained showing a maximum energy reflection of 15,9% at a 1 micrometer wavelength.

Claims: A sheet of soda-lime glass with an energy reflection of 7% and a refractive index of 1,52 as an average for wavelengths of white light characterized in that it has a first layer containing nitrogen and carbonium ions in a ratio of 85:15 implanted at a glass temperature of 350 °C with an energy of 100 KeV at a dose of 1 X 10¹⁷ ions/cm² through a thickness of 0,186 µm, a second layer underlying said first layer free of implanted ions having a thickness of 0,136 µm, and a third layer underlying said second layer containing nitrogen and carbonium ions in a ratio 85:15 implanted with a glass temperature of 350 °C with an energy of 270 KeV at a dose of 1 X 10 ¹⁷ ions/cm² through a thickness of 0,234 µm, said glass having a maximum energy reflection of 15,9 % at 1 µm wavelength.

Inventors: MASSARELLI, LIBERTO, SEBASTIANO, FRANCESCO
Applicants: SOCIETA' ITALIANA VETRO - SIV - S.P.A.
Application year: 1988
Main classification: C03C23
IPC codes: C03C21, C03C23, C23C14