Process for treatment by a beam of mono- or multicharged ions of a gas to produce antireflective glass materials

Abstract

A method of treatment using a beam of singly- and multiply-charged gas ions produced by an electron cyclotron resonance (ECR) source of a glass material in whichthe ion acceleration voltage of between 5 kV and 1000 kV is chosen to create an implanted layer of a thickness equal to a multiple of 100 nm; the ion dose per surface unit in a range of between 1012 ions/cm2 and 1018 ions/cm2 is chosen so as to create an atomic concentration of ions equal to 10% with a level of uncertainty of (+/)5%. Advantageously this makes it possible to obtain materials made from glass that is non-reflective in the visible range.

Claims

1. A process for imparting to a glass material a durable antireflective treatment that is antireflective to an incident wave having a wavelength in a visible region of a spectrum, comprising: subjecting the glass material to a bombardment by an ion beam of mono- and multicharged ions of a gas which are produced by an electron cyclotron resonance (ECR) source to form an implanted layer of ions in the glass material, wherein: a temperature for treatment of the glass material during the bombardment is less than or equal to a glass transition temperature of the glass material; the bombardment delivers to the glass material a dose of mono- and multicharged ions of the gas as measured per unit of surface area within a range of between 10.sup.12 ions/cm.sup.2 and 10.sup.18 ions/cm.sup.2, wherein the dose is selected to obtain an atomic concentration of mono- and multicharged ions of the gas such that the refractive index n of the implanted layer is approximately equal to (n1*n2).sup.1/2, where n1 is the index of the air and n2 is the index of the glass; an acceleration voltage of the ion beam is within a range of between 5 kV and 1000 kV and is selected to obtain an implanted thickness t equal to p*100 nm, where t is the implanted thickness corresponding to a region of implantation where the atomic concentration of implanted mono- and multicharged ions of the gas is greater than or equal to 1%, and p is an integer.

2. The process as claimed in claim 1, wherein the mono- and multicharged ions of the gas of the ion beam are ions of the elements selected from the group consisting of helium (He), neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe).

3. The process as claimed in claim 1, wherein the gas is selected from the group consisting of nitrogen (N.sub.2) and oxygen (O.sub.2).

4. The process as claimed in claim 1, wherein the ion beam of mono- and multicharged ions of the gas comprises at least 10% of multicharged ions.

5. The process as claimed in claim 1, wherein the dose of implanted mono- and multicharged ions of the gas per unit of surface area is selected to achieve an atomic concentration of implanted ions equal to 10% with an uncertainty of (+/) 5%.

6. The process as claimed in claim 5, wherein the dose of implanted mono- and multicharged ions of the gas per unit of surface area and the acceleration voltage are selected prior to subjecting the glass material to the bombardment to provide an atomic concentration of implanted ions equal to 10% with an uncertainty of (+/) 5% starting from an implantation profile of the mono- and multicharged ions of the ion beam as a function of a depth of the implanted layer.

7. The process as claimed in claim 1, wherein the glass material is movable with respect to the ion beam of mono- and multicharged ions of the gas at a rate, V.sub.D, of between 0.1 mm/s and 1000 mm/s.

8. The process as claimed in claim 7, wherein one and the same region of the glass material is moved under the beam of mono- and multicharged ions of the gas according to a plurality, N, of passes at the rate V.sub.D.

9. The process as claimed in claim 1, wherein the glass material is a soda-lime glass.

10. A glass part comprising at least one surface with an implanted ion layer formed by the process as claimed in claim 1, wherein the reflection of an incident wave in the visible region is reduced to less than half.

11. The process as claimed in claim 1, wherein the glass material is a bulk glass part selected from the group consisting of a touch screen, a spectacle lens, a lens of an optical device, a window of a building and an optical fiber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other distinguishing features and advantages of the present invention will emerge in the description below of nonlimiting implementational examples, illustrated by the appended figures, where:

(2) FIGS. 1.a and 1.b describe the propagation of an incident wave without and with an antireflective layer;

(3) FIGS. 2, 3, 5, 7 and 9 represent implantation profiles of various ions as a function of the implantation depth;

(4) FIGS. 4, 6 and 8 represent the variation in the gain G (as %) measured after the treatment as a function of the dose of ions for a given acceleration voltage.

DETAILED DESCRIPTION

(5) According to examples of the implementation of the present invention, samples of soda-lime glass material have formed the subject of studies with mono- and multicharged helium ions for some samples, with mono- and multicharged argon ions for other samples and with mono- and multicharged ions of nitrogen N.sub.2 for yet other samples.

(6) These mono- and multicharged ions of a gas were emitted by an ECR source.

(7) The family of the soda-lime glasses combines glasses based on silica SiO.sub.2, on calcium and on sodium generally introduced in the manufacture in the form of CaO and Na.sub.2O. These glasses are the most widespread; they are used for the manufacture of bottles and glazings and represent of the order of 90% of glass production.

(8) The inventors have carried out a first series of tests with:

(9) A beam of mono- and multicharged helium ions with an intensity of 1 mA comprising He.sup.+ and He.sup.2+ ions; the acceleration voltage is 35 kV; the He.sup.+ energy is 35 keV and the He.sup.2+ energy is 70 keV. The treatment doses are equal to 10.sup.16, 310.sup.16 and 610.sup.16 ions/cm.sup.2. A beam of mono- and multicharged argon ions with an intensity of 1 mA comprising Ar.sup.+, Ar.sup.2+ and Ar.sup.3+ ions; the acceleration voltage is 35 kV; the Ar.sup.+ energy is 35 keV, the Ar.sup.2+ energy is 70 keV and the Ar.sup.3+ energy is 105 keV. The treatment doses are equal to 10.sup.16, 510.sup.16 and 10.sup.17 ions/cm.sup.2.

(10) The treated samples move with respect to the beam with a rate of movement of 120 mm/s and with a side advance at each return of 4 mm (10% of the diameter of the beam, which measures 40 mm). The treatment is carried out in several passes in order to achieve the necessary dose.

(11) The antireflective properties of the surface of the samples can be assessed qualitatively with the naked eye by observing the reflection of an image on a glass surface or also quantitatively by virtue of the use of an interferometric measurement process: for example, monochromatic light of 560 nm is projected through a thin glass strip treated on both faces, under a given angle of incidence, and the image obtained, in the form of a series of nested rings in the focal plane of a lens, is analyzed. The reflection coefficient of the diopters of the strip can be deduced by measuring the fineness of the bright rings (at mid-height of the maximum intensity).

(12) The inventors have carried out qualitative tests by observing, with the naked eye, the reflection of the light of a neon tube on a slightly inclined treated surface for different doses. The reflected image of this neon tube was observed under an angle of approximately 10.

(13) It emerges, from these qualitative tests, that the reflection of the neon in terms of lower contrast appears around a dose of 310.sup.16 ions/cm.sup.2 for argon and 10.sup.17 ions/cm.sup.2 for helium.

(14) A study carried out on a simulator of the implantation of multicharged ions, relying on semiempirical data developed by the inventors, gives, under the abovementioned treatment conditions, the following results recorded in table 1 for helium (see the implantation profile of FIG. 2) and table 2 for argon (see the implantation profile of FIG. 3).

(15) TABLE-US-00001 TABLE 1 Dose Antireflective He atomic Implanted (10.sup.16 ions effect concentra- layer He/cm.sup.2) observable tion (%) thickness 1 No 1% 200 nm 5 No 5% 200 nm 10 Yes 11% 200 nm

(16) TABLE-US-00002 TABLE 2 Dose Antireflective Ar atomic (10.sup.16 ions effect concentra- Implanted Ar/cm.sup.2) observable tion (%) thickness 1 No 2.5% 112 nm 3 Yes 12.5% 112 nm 6 No .sup.21% 112 nm

(17) As is recommended by the process of the invention, the adjusting of the acceleration voltage of the ions is calculated so as to adjust the implanted thickness over a multiple of approximately 100 nm. These extrapolated values (acceleration voltage, dose) can be more finely adjusted during an experimental adjustment phase using precise interferometric means which make it possible to evaluate the optimum reduction in the reflection coefficient (see abovementioned method).

(18) FIG. 1.a describes how an incident wave (I) is separated during passage through the diopter into a transmitted wave (T) and a strongly reflected wave (R), as a solid line. FIG. 1.b describes how an antireflective layer (AR) created by the process of the invention weakly returns the reflected wave (R), as a dotted line.

(19) FIG. 2 represents the implantation profile of helium ions corresponding to a dose of 10.sup.17 ions/cm.sup.2 obtained with a beam of He.sup.+ and He.sup.2+ ions and an acceleration voltage of 35 kV. The distribution of the He.sup.+/He.sup.2+ ions is 90%/10%. The implantation depth, expressed in angstroms, is found on the abscissa and the atomic concentration of implanted helium ions, expressed as %, is found on the ordinate. The atomic concentration of helium ions reaches approximately 10% (+/5%) over an implanted thickness of approximately 200 nm (i.e., 2 times 100 nm). The implanted thickness corresponds to the region where the atomic concentration of implanted helium ions is greater than or equal to 1%. As is confirmed by the experiment, these characteristics confer antireflective properties on the implanted layer.

(20) FIG. 3 represents the implantation profile of argon ions corresponding to a dose of 3*10.sup.16 ions/cm.sup.2 obtained with a beam of Ar.sup.+, Ar.sup.2+ and Ar.sup.3+ ions and an acceleration voltage of 35 kV. The distribution of the Ar.sup.+/Ar.sup.2+/Ar.sup.3+ ions is 60%/30%/10%. The implantation depth, expressed in angstroms, is found on the abscissa and the atomic concentration of implanted helium ions, expressed as %, is found on the ordinate. The atomic concentration of argon ions reaches approximately 10% (+/5%) over an implanted thickness of approximately 100 nm (i.e., 1 times 100 nm). The implanted thickness t corresponds to the region where the atomic concentration of implanted helium ions is greater than or equal to 1%. As is confirmed by the experiment, these characteristics confer antireflective characteristics on the implanted layer.

(21) Furthermore, a second series of tests was undertaken in order to evaluate the antireflective treatment with characterization means in order to quantify, with greater accuracy, the gain in transmission of the light G (as %) obtained after treatment through a diopter made of glass belonging to the soda-lime family. By definition, G refers to the gain, expressed as %, corresponding to the increase in the light transmission coefficient obtained after treatment (in other words, the difference between the transmission coefficient after and before treatment).

(22) Two types of ions were employed: nitrogen (N.sub.2) and argon (Ar).

(23) For the nitrogen, two treatment depths were studied by adjusting the acceleration voltage to 20 and 35 kV.

(24) For the argon, just one acceleration voltage of 35 kV was employed.

(25) Several doses were employed for each type of ion at different acceleration voltages. The results are recorded in the following tables:

(26) For nitrogen (N.sub.2) at 20 kV:

(27) TABLE-US-00003 Doses (10.sup.17 ions/cm.sup.2) Gain G (%) 0 0 0.01 0.4 0.05 0.6 0.1 0.5 0.5 2.3 1 2.3

(28) For nitrogen (N.sub.2) at 35 kV:

(29) TABLE-US-00004 Doses (10.sup.17 ions/cm.sup.2) Gain G (%) 0 0 0.05 0.5 0.1 0.6 0.3 0.7 0.6 1.4 0.75 1.7 1 0.4 2.5 1.2 5 0.2

(30) For argon (Ar) at 35 kV:

(31) TABLE-US-00005 Doses (10.sup.17 ions/cm.sup.2) Gain G (%) 0 0 0.75 1.9 1 2.1 2.5 2.4

(32) FIG. 4 represents, on the axis of the ordinates, the gain G (in %) measured after treatment with nitrogen (N.sub.2) at 20 kV and according to different doses represented on the axis of the abscissa and expressed in 10.sup.17 ions/cm.sup.2. A dose of 0.410.sup.17 ions/cm.sup.2 appears particularly indicated in order to reduce by half the light reflection coefficient, which changes from 4% to 2%, whereas the light transmission coefficient, which increases by 2%, changes from 96% to 98%. The line referenced A corresponds to the dose for which the atomic concentration of implanted ions is equal to 10% and the lines referenced B and C respectively correspond to the doses for which the atomic concentration of implanted ions is equal to 5% and 15%. The saturation threshold of the curve corresponding to a maximum gain in light transmission which is located on the line A. The lines B and C frame this threshold.

(33) FIG. 5 represents the implantation profile simulated with nitrogen ions corresponding to a dose of 0.5*10.sup.17 ions/cm.sup.2 obtained with a beam of N.sup.+, N.sup.2+ and N.sup.3+ ions and an acceleration voltage of 20 kV. The distribution of the N.sup.+/N.sup.2+/N.sup.3+ ions is estimated equal to 58%/31%/11%. The implantation depth, expressed in angstroms, is found on the abscissa and the atomic concentration of implanted nitrogen ions, expressed as %, is found on the ordinate. The atomic concentration of nitrogen ions reaches approximately 10% over an implanted thickness of approximately 200 nm (i.e., 2 times 100 nm). The implanted thickness t corresponds to the region where the atomic concentration of implanted nitrogen ions is greater than or equal to 1%. The experiment proves that these treatment characteristics in terms of maximum concentration of implanted ions and in terms of treatment depth confer antireflective characteristics on the layer implanted with nitrogen ions.

(34) FIG. 6 represents, on the axis of the ordinates, the gain G (as %) measured after treatment with nitrogen (N.sub.2) at 35 kV and according to different doses represented on the axis of the abscissa and expressed in 10.sup.17 ions/cm.sup.2. Here also, a dose of 0.7510.sup.17 ions/cm.sup.2 appears particularly indicated in order to reduce virtually by half the light reflection coefficient, which changes from 4% to 2.3%, whereas the light transmission coefficient, which increases by 1.7%, changes from 96% to 97.7%. The line referenced A corresponds to the dose for which the atomic concentration of implanted ions is equal to 10% and the lines referenced B and C respectively correspond to the doses for which the atomic concentration of implanted ions is equal to 5% and 15%. The peak of the curve corresponding to the maximum gain in light transmission is located on the line A. The lines B and C frame this peak.

(35) FIG. 7 represents the implantation profile simulated with nitrogen ions corresponding to a dose of 0.75*10.sup.17 ions/cm.sup.2 obtained with a beam of N.sup.+, N.sup.2+ and N.sup.3+ ions and an acceleration voltage of 35 kV. The distribution of the N.sup.+/N.sup.2+/N.sup.3+ ions is estimated equal to 58%/31%/11%. The implantation depth, expressed in angstroms, is found on the abscissa and the atomic concentration of implanted nitrogen ions, expressed as %, is found on the ordinate. The atomic concentration of nitrogen ions reaches approximately 10% over an implanted thickness of approximately 300 nm (i.e., 3 times 100 nm). The implanted thickness t corresponds to the region where the atomic concentration of implanted nitrogen ions is greater than or equal to 1%. The experiment proves that these treatment characteristics in terms of maximum concentration of implanted ions and in terms of treatment depth confer antireflective characteristics on the layer implanted with nitrogen ions.

(36) FIG. 8 represents, on the axis of the ordinates, the gain G (as %) measured after treatment with argon (Ar) at 35 kV and according to different doses represented on the axis of the abscissa and expressed in 10.sup.17 ions/cm.sup.2. A dose of 0.7510.sup.17 ions/cm.sup.2, indeed even less, appears particularly indicated in order to reduce virtually by half the light reflection coefficient, which changes from 4% to 2.1%, whereas the light transmission coefficient, which increases by 1.9%, changes from 96% to 97.9%. The line referenced A corresponds to the dose for which the atomic concentration of implanted ions is equal to 15% and the lines referenced B and C respectively correspond to the doses for which the atomic concentration of implanted ions is equal to 10% and 20%. The saturation threshold corresponding to a maximum gain in light transmission is located instead on a line A where the concentration is 15%, slightly greater than that expected at 10%. However, it will be pointed out that the curve is the product of an extrapolation with a finite number of results acquired with doses greater than or equal to 0.510.sup.17 cm.sup.2. It would be necessary to supplement and refine this extrapolation with results acquired with lower doses located below 0.7510.sup.17 ions/cm.sup.2 (for example 0.1, 0.2 and 0.510.sup.17 ions/cm.sup.2). It is highly probable that, on this occasion, the saturation threshold is carried over into a region of lower doses located approximately around 0.510.sup.17 ions/cm.sup.2 corresponding to an atomic concentration of implanted ions located around 10%, which would be more in accordance with the predictions.

(37) FIG. 9 represents the implantation profile simulated with argon ions corresponding to a dose of 0.75*10.sup.17 ions/cm.sup.2 obtained with a beam of Ar.sup.+, Ar.sup.2+ and Ar.sup.3+ ions and an acceleration voltage of 35 kV. The distribution of the Ar.sup.+/Ar.sup.2+/Ar.sup.3+ ions is estimated equal to 66%/24%/10%. The implantation depth, expressed in angstroms, is found on the abscissa and the atomic concentration of implanted argon ions, expressed as %, is found on the ordinate. The atomic concentration of argon ions reaches approximately 15% over an implanted thickness of approximately 100 nm (i.e., 1 times 100 nm). The implanted thickness t corresponds to the region where the atomic concentration of implanted nitrogen ions is greater than or equal to 1%. The experiment proves that these treatment characteristics in terms of maximum atomic concentration of implanted ions and in terms of treatment depth confer antireflective characteristics on the layer implanted with argon ions.

(38) From this treatment campaign, it emerges that nitrogen makes it possible to obtain antireflective properties comparable to those obtained with noble ions, such as helium or argon. Without going too far, this might possibly be explained, as for the noble gases, by the formation of nanocavities filled with nitrogen N.sub.2 molecules. Preliminary studies show that the same effects are obtained with another diatomic gas, such as oxygen (O.sub.2).