Patent Description:
Ophthalmic tinted glasses are known for long time for protecting the eyes against excessive solar light intensity. To this purpose, a tinted glass is designed for absorbing and/or reflecting solar light so as to reduce light intensity to an amount which provides safety and comfortable vision to the wearer. Light which is involved in vision for a human being, called visible light, corresponds to the wavelength range from <NUM> (nanometer) to <NUM>, called visible wavelength range.

But it has been discovered more recently that light within the wavelength range from <NUM> to <NUM> is involved in maintaining circadian rhythms for the wearer. This range corresponds to medium-blue light. By significantly reducing retinal exposure to light which pertains to this wavelength range, tinted glasses may progressively have detrimental effects on the biological, hormonal and behavioural functions of the wearer. Such detrimental effects may appear after daily repeated and abusively prolonged wearing of the tinted glasses, and sleep troubles, seasonal affective disorders and mood disorders may result in long term. These effects are commonly described as chronobiological because of their consequences on the circadian rhythms of the wearer.

In addition, by significantly reducing the intensity of visible light which enters into the eyes, the tinted glasses cause the pupil diameter to increase, which affects visual acuity. In particular, the depth of field is decreased and the optical aberrations are more important. Also the increase in the pupil diameter leads to higher energetic exposure of the retina to non-filtered light wavelengths, in particular in case of non-filtered blue-violet wavelengths which are deemed to be noxious. Blue-violet wavelengths correspond to values between <NUM> and <NUM>.

Document <CIT> discloses ophthalmic filters to protect the eyes of the wearer.

From this situation, one object of the invention is to provide ophthalmic tinted glasses which produce protection against excessive light intensity but in which transmittance within the wavelength range from <NUM> to <NUM> is enriched.

Another object of the invention is to allow production of such tinted glasses with enriched transmittance within the wavelength range <NUM> - <NUM>, from base tinted glasses.

An additional object of the invention is to provide such tinted glasses which produce good protection against blue-violet light.

For meeting at one of these objects or others, a first aspect of the invention proposes an ophthalmic tinted glass which comprises:.

According to the invention, the base eyeglass and the first layered structure are such that a difference equal to a mean transmittance value of the tinted glass over a wavelength range from <NUM> to <NUM> minus a visual transmission value of the tinted glass is higher than <NUM>%, a spectral reflectance of said ophthalmic tinted glass for light impinging on the convex optical face (Cx) with incidence value of <NUM>°, having a value of more than <NUM>% for at least one first wavelength comprised between <NUM> and <NUM>, and another value of less than <NUM>% for at least one second wavelength comprised between <NUM> and <NUM>; and wherein the first layered structure (<NUM>) is a stack of eleven layers alternatively of zirconia and silica, starting and ending with two of said zirconia layers, with the zirconia layers (Z1-Z6) having respective thicknesses between <NUM> and <NUM>, and the silica layers (Q1-Q5) having respective thicknesses between <NUM> and <NUM>.

Put another way, TmB - Tv > <NUM>%, where TmB is the mean transmittance value of the tinted glass over the wavelength range from <NUM> to <NUM>, and Tv is the visual transmission value of the tinted glass as defined in standard ISO <NUM>-<NUM>:<NUM>, for taking into account the spectral sensibility to light of the retina cells, and using the illuminant D65 as defined by CIE standard ISO <NUM>:<NUM>/CIE S005/E-<NUM>. In the frame of the present invention, the mean transmittance value over the wavelength range from <NUM> to <NUM> denotes the calculation result of ∫<NUM><NUM> T(λ)·dλ/<NUM>, denoted TmB, where <NUM> is the length in nanometers of the wavelength range <NUM> - <NUM>, corresponding to medium-blue light, λ denotes the wavelength in nanometers and T(λ) denotes the spectral transmittance value at wavelength λ.

Possibly, in the whole description and appended claims, the wavelength range <NUM> - <NUM> may be replaced with range <NUM> - <NUM> while maintaining any threshold value unchanged. In such conditions, the mean transmittance value TmB to be considered is ∫<NUM><NUM> T(λ)·dλ/<NUM>, where <NUM> is the length in nanometers of the wavelength range <NUM> - <NUM>.

In this way, the proportion of the medium-blue light relative to the total amount of light which is effective for vision is increased by the first layered structure. But simultaneously, by selectively increasing light reflection, the first layered structure also produces a solar protection effect, with respect to the base eyeglass devoid of the first layered structure, since it reduces the total amount of visible light which enters into the wearer's eye.

The base eyeglass may be a clear eyeglass, for example with visual transmission value higher than <NUM>%, or higher than <NUM>%, when measured in daylight conditions or using illuminant D65.

Alternatively, the material of base eyeglass may be light-absorbing, so that the base eyeglass produces a first solar protection effect. Then the first layered structure provides an additional solar protection so that the invention ophthalmic tinted glass has an overall solar protection efficiency which is improved with respect to that of the bare base eyeglass. And also in such case of light-absorbing base eyeglass, the first layered structure increases the relative proportion of medium-blue light with respect to the total light which is allowed by the base eyeglass to enter into the wearer's eye.

In particular, the base eyeglass may have a visual transmission value which is higher than <NUM>% when devoid of the first layered structure, and the first layered structure may be such that the visual transmission value of the tinted glass is less than or equal to <NUM>%. In this way, the invention allows transforming an initial ophthalmic tinted glass which is formed by the bare base eyeglass, and which pertains to class <NUM> as defined by the standard ISO <NUM>-<NUM>, into a final ophthalmic tinted glass which pertains to class <NUM>.

Advantageously, the base eyeglass and the first layered structure may be such that the mean transmittance value of the tinted glass over the wavelength range from <NUM> to <NUM>, or from <NUM> to <NUM>, is higher than <NUM>%, preferably higher than <NUM>%, more preferably higher than or equal to <NUM>%. Then, enough medium-blue light intensity enters into the wearer's eye to ensure that biological, hormonal and behavioural functions are not altered, and related circadian rhythms are maintained.

Generally for the invention, the base eyeglass may advantageously be such that its spectral transmittance when devoid of the first layered structure is less than <NUM>%, preferably less than <NUM>%, across the wavelength range from <NUM> to <NUM>. This means that the base eyeglass may be light-absorbing at least for visible light wavelengths below <NUM>. Thus, the base eyeglass provides protection against blue-violet light, and also the invention tinted glass.

The base eyeglass may also be such that its spectral transmittance when devoid of the first layered structure is less than <NUM>% across a wavelength range from <NUM> to <NUM>. This ensures that the invention tinted glass produces an efficient protection against dazzling for the wearer, because the maximum of the spectral sensibility of the human eye to light is close to <NUM>.

Alternatively or in combination, the base eyeglass may be such that its visual transmission value is less than <NUM>%, again when devoid of the first layered structure.

The base eyeglass material may be comprised of a transparent matrix with dyes and absorbers which are distributed therein. At least one of the dyes may have a light-absorption peak in the wavelength range from <NUM> to <NUM>, and at least two of the absorbers may have respective light-absorption peaks in another wavelength range from <NUM> to <NUM>.

According to the claimed invention, the spectral reflectance of the ophthalmic tinted glass for light impinging on the convex optical face with incidence value of <NUM>°, has a value of more than <NUM>% for at least one first wavelength comprised between <NUM> and <NUM>, and another value of less than <NUM>% for at least one second wavelength comprised between <NUM> and <NUM>. Thus, the first layered structure is less light-reflecting at the second wavelength in the medium-blue range with chronobiological effect, than for longer wavelengths corresponding to green, yellow or red colors.

Again generally for the invention, the ophthalmic tinted glass may further comprise:.

Such antireflection coating on the concave face of the tinted glass, as formed by the second layered structure, avoids that reflected light from behind the wearer's head, obliquely on each side, interferes with vision through the tinted glass. Preferably, the second layered structure may be such that the visual reflection value effective for light impinging from outside of the tinted glass onto the concave face of the ophthalmic tinted glass covered by the second layered structure is less than <NUM>%, preferably less than or equal to <NUM>%, for incidence value of <NUM>° (degree). The visual reflection values considered meet again the ISO standard indicated above for taking into account the spectral sensibility to light of the retina cells, using the illuminant D65.

Finally, a second aspect of the invention proposes a solar-protection eyewear, which comprises a frame and two ophthalmic tinted glasses mounted into the frame, each ophthalmic tinted glass being in accordance with the first invention aspect.

These and other features of the invention will be now described with reference to the appended figures, which relate to preferred but not-limiting embodiments of the invention.

For clarity sake, element sizes which appear in these figures do not correspond to actual dimensions or dimension ratios. Also, same reference labels which are indicated in some of these figures and in tables provided below denote identical elements of elements with identical function.

<FIG> shows a first possible configuration for an ophthalmic tinted glass <NUM> in accordance with the invention. It comprises a base eyeglass <NUM> which is self-supporting and has opposite optical faces Cx and Cc. The optical face Cx is convex and intended to be oriented towards a scene to be viewed when the tinted glass <NUM> is fitted within a spectacle frame and worn by a wearer. The optical face Cc is concave and intended to face an eye of the wearer. Both optical faces Cx and Cc may be such that the base eyeglass <NUM> does not produce any ametropia correction, namely it is of plano type, or may be such that the base eyeglass <NUM> produces an ametropia correction. In such latter case, the base eyeglass <NUM> may be of single vision type or a progressive addition lens.

The base eyeglass <NUM> is covered on its optical convex face Cx by a layered structure <NUM>. The layered structure <NUM> is based on thin-film technology so that the base eyeglass <NUM> forms a substrate for the layered structure <NUM>. Preferably, the layered structure <NUM> is multi-layered, and any coating deposition process or combination of several coating deposition processes may be used for producing the layered structure <NUM>, including physical vapour deposition (PVD), e.g. beam evaporation, thermal evaporation, sputtering, and also including chemical vapour deposition (CVD), atomic layer deposition (ALD), sol-gel, varnish deposition, etc. The structure <NUM> has been called first layered structure in the general part of this description.

Optionally, according to a second possible configuration for an ophthalmic tinted glass <NUM> in accordance with the invention, the base eyeglass <NUM> may also be covered on its optical concave face Cc with a layered structure <NUM>, as shown in <FIG>. In such case, the layered structure <NUM> is based on thin-film technology too, and may be multi-layered and deposited using the same deposition processes as recited above. The structure <NUM> has been called second layered structure in the general part of this description.

The base eyeglass <NUM> may be a clear eyeglass, corresponding to class <NUM> for tinted glasses as defined in standard ISO <NUM>-<NUM>. For example it may be an Orma™ eyeglass as supplied by Essilor, or a polycarbonate eyeglass. In such cases, the solar protection function of the ophthalmic tinted glass <NUM> is provided by the layered structure <NUM>.

Alternatively, the base eyeglass <NUM> may be of a light-absorbing material, still light-transmitting but with reduced transmission value, so that it produces per se a first contribution to the solar protection function of the ophthalmic tinted glass <NUM>. In such case, the layered structure <NUM> produces an additional solar protection contribution, so that the solar protection efficiency of the ophthalmic tinted glass <NUM> results from both contributions of the base eyeglass <NUM> and the layered structure <NUM>. For such alternative embodiments, the base eyeglass <NUM> may be based on Trivex™ matrix as supplied by PPG industries, which is well known and based on polyurethane polymer. The Trivex™ matrix is clear material per se, but dyes and absorbers can be incorporated therein for forming a tinted base eyeglass <NUM>. For example, Table <NUM> below indicates possible dye- and absorber concentrations which correspond to the spectral transmittance curve represented in <FIG>, for a <NUM> (millimeter) thick plano base eyeglass <NUM>. The dye- and absorber concentrations are expressed in mg (milligram) of each dye or absorber for <NUM> of the resulting blend of Trivex™ with the dyes and absorbers. Commercial suppliers are also indicated between parentheses.

The dyes indicated are mainly responsible for the shape of the eyeglass transmittance profile for wavelength values between <NUM> and <NUM>, whereas the absorbers are mainly responsible for the shape of the eyeglass transmittance profile for wavelength values between <NUM> and <NUM>. In the diagram of <FIG>, the horizontal axis indicates the wavelength λ in the visible range, i.e. from <NUM> (nanometer) to <NUM>, and the vertical axis indicates the spectral transmittance values T(λ) for light impinging perpendicular to the convex face Cx. As this appears from the transmittance curve, such base eyeglass <NUM> produces light absorption for wavelength values between <NUM> and <NUM>, and also between <NUM> and <NUM>. The absorption between <NUM> and <NUM> is beneficial for protecting the wearer's eye against harmful blue-violet radiation, and that between <NUM> and <NUM> is efficient for producing the solar protection function. Actually, as shown in the diagram of <FIG>, the spectral transmittance T(λ) is much less than <NUM>% in the range <NUM> - <NUM>, and less than <NUM>% in the range <NUM> - <NUM>. However, the transmission window between <NUM> and <NUM> allows enriching the total light which is transmitted for vision to the wearer's eye with medium-blue light beneficial for the chronobiological effects. The visual transmission value Tv, as defined by the standard ISO <NUM>-<NUM>:<NUM> with illuminant D65, is then <NUM>%, corresponding to class <NUM> for tinted glasses as defined in standard ISO <NUM>-<NUM>. The rear side visual reflection value Rv, for light impinging on the concave face Cc, is about <NUM>% at incidence value of <NUM>°, and the mean transmittance value over the medium-blue range from <NUM> to <NUM>, TmB = ∫<NUM><NUM> T(λ)·dλ/<NUM>, is <NUM>%. The rear side visual reflection value Rv which is considered here takes into account the absorption of the substrate.

Table <NUM> below displays the configurations of five ophthalmic tinted glasses <NUM>, labelled D1 to D5, with their respective values for the visual transmission Tv, the visual reflection Rv of the concave face Cc for incidence value of <NUM>° (degree), and the medium-blue mean transmittance value TmB as defined by the integral equation above. For these tinted glasses D1 to D5, the base eyeglass <NUM> is that of <FIG> and Table <NUM>, denoted tinted as indicated in the column labelled <NUM>.

In this table, Z1, Q1, Z2, Q2 and Z3 denote the successive layers of the layered structures <NUM> (resp. <NUM>) borne by the optical faces Cx (resp. Cc) of the base eyeglasses <NUM>, when recited from the base eyeglass <NUM> to the air interface in front of (resp. behind) the tinted glass <NUM>. Z1, Z2 and Z3 are zirconia (ZrO<NUM>) layers with refractive index value of about <NUM> for the wavelength value of <NUM>, and Q1 and Q2 are silica (SiO<NUM>) layers with refractive index value of about <NUM> for the same wavelength value of <NUM>. The values displayed in the layer columns are the physical thicknesses of the individual layers, expressed in nanometers, and provided that the actual thickness values are within +/-<NUM>% of the values displayed. The layered structures <NUM> displayed in the Cx-lines are of selective mirror type, because of being reflection-enhancing for some wavelength values above <NUM> when comparing the base eyeglass <NUM> with and without the layered structure <NUM>. The mention "air" in two of the Cc-lines indicates that the concave optical faces Cc of the tinted glasses D1 and D3 do not have any layered structure <NUM>, and the layered structures <NUM> displayed in the Cc-lines for the tinted glasses D2 and D4 are of antireflection type. That for the tinted glass D5 is reflection-increasing. Tv-value being less than or equal to <NUM>% means that the tinted glass <NUM> is of class <NUM>. Thus, an appropriate layered structure <NUM> and a layered structure <NUM> when implemented can transform a base eyeglass <NUM> which pertains to class <NUM> of tinted glasses into a tinted glass <NUM> of class <NUM>. Rv-value being less than or equal to <NUM>% means that the tinted glass <NUM> is antireflective on its rear side.

Table <NUM> below displays the values for another tinted glass <NUM> according to the invention, which is labelled D6 and implements a base eyeglass <NUM> corresponding to <FIG> and Table <NUM>, with thickness of <NUM> for this base eyeglass <NUM>. The layered structure <NUM> on the convex face Cx is of selective mirror type again, and the layered structure <NUM> on the concave face Cc is antireflective. The layer thicknesses are expressed in nanometers again, and can vary within +/-<NUM>% with respect to the values indicated.

In Table <NUM>, UL denotes underlayers with refractive index value of about <NUM> at wavelength of <NUM>, and ITO denotes layers of indium-tin (In-Sn) oxide which are intermediate between layers Z2 and Q2. For example, the underlayers UL may be varnish layers which provide protection against impacts and scratches. <FIG> shows the layers of such tinted glass D6.

Table <NUM> below displays the values for another tinted glass <NUM> according to the invention, which is labelled D7 and implements an Orma™ base eyeglass <NUM> with thickness of <NUM>. The layered structure <NUM> on the convex face Cx is comprised of eleven layers alternatively of zirconia (Z1-Z6) and silica (Q1-Q5), but no layered structure <NUM> is on the concave face Cc. The layer thicknesses are expressed in nanometers again, and can vary within +/-<NUM>% with respect to the values indicated.

For the tinted glass D7, the visual transmission Tv equals <NUM>%, the visual reflection Rv for light impinging onto the concave side Cc with <NUM>° incidence value equals <NUM>%, and the medium-blue mean transmittance value TmB equals <NUM>%. <FIG> shows the layers of such tinted glass D7.

The diagrams of <FIG> relate to these latter tinted glasses D6 and D7. <FIG> exhibits the spectral transmittance curves for both tinted glasses. Spectral transmittance values are noted T(λ) again. For tinted glass D6, one can see the transmittance-lowering effect of the layered structure <NUM> when compared to the curve of <FIG>. For tinted glass D7, the large deepening effect between <NUM> and <NUM> is provided by the layered structure <NUM> of Table <NUM>. <FIG> shows the spectral reflectance values R(λ) for light impinging on the convex optical faces Cx with incidence value of <NUM>°. In particular, the spectral reflectance is <NUM>% at <NUM> and <NUM>% at <NUM> for the tinted glass D6. For the tinted glass D7, the spectral reflectance is <NUM>% at <NUM> and <NUM>% at <NUM>, again for light impinging on the convex optical faces Cx with incidence value of <NUM>°.

Finally, a last invention embodiment is provided in Table <NUM> below and <FIG>. The base eyeglass <NUM> is that of <FIG> and Table <NUM>. Table <NUM> displays the layer thicknesses in nanometers for both layered structures <NUM> and <NUM> of this another tinted glass <NUM>, called Prototype. The actual thickness values may vary again within +/-<NUM>% with respect to the values indicated. The layered structure <NUM> on the convex face Cx has four layers, and is again of selective mirror type. The layered structure <NUM> on the concave face Cc has six layers, including one of tin oxide (SnO<NUM>) which is intermediate between the layers Z3 and Q3, and is antireflective.

The diagram of <FIG> compares the spectral transmittance curve of the base eyeglass <NUM> as used for the tinted glass Prototype, but devoid of the layered structures <NUM> and <NUM>, and that of the completed tinted glass Prototype. Actually, the spectral transmittance values are modified in a limited extent when the layered structure <NUM> is suppressed from the tinted glass Prototype. Put another way, a tinted glass which would be comprised only of the tinted base eyeglass <NUM> according to Table <NUM> and <FIG> and the layered structure <NUM> according to the Cx-line of Table <NUM>, almost meets the invention. In particular, such tinted glass Prototype devoid of the layered structure <NUM> on its concave face Cc has the following values: Tv = <NUM>% and TmB = <NUM>%. The antireflective layered structure <NUM> as implemented in the tinted glass Prototype mainly has the function of reducing the reflection for light rays which impinge laterally from behind the wearer's head onto the concave face Cc of the tinted glass.

Alternatively, the layered structure <NUM> as displayed in the Cx-line of Table <NUM> may be combined with many base eyeglasses of different types. In particular, it may be applied on the convex face of a Trivex™-based clear base eyeglass <NUM>. Then, the following values are obtained without implementing any layered structure <NUM> on the concave face Cc: Tv = <NUM>% and TmB = <NUM>%.

In <FIG>, the solar-protection eyewear <NUM> comprises two tinted glasses <NUM> each according to the invention, which are mounted in a frame <NUM> so as to fit on the wearer's face. Thanks to the invention, the eyewear <NUM> provides efficient solar protection to the wearer, while avoiding biological, hormonal and behavioural disorders for him.

Claim 1:
An ophthalmic tinted glass (<NUM>) comprising:
- a substrate-forming base eyeglass (<NUM>), comprised of a self-supporting portion of a light-transmitting material intermediate between a convex face (Cx) and a concave face (Cc), and
- a first layered structure (<NUM>) covering the convex face (Cx) of the base eyeglass (<NUM>), and adapted for increasing a reflection effective for light impinging from outside of the tinted glass (<NUM>) onto the convex face covered by the first layered structure, when compared to a reference reflection effective for light impinging also from outside onto the convex face but without the first layered structure, the reflection increase being effective for at least one light wavelength higher than <NUM>,
the base eyeglass (<NUM>) and the first layered structure (<NUM>) being such that a difference equal to a mean transmittance value of the tinted glass (<NUM>) over a wavelength range from <NUM> to <NUM>, defined as <MAT>
where <NUM> is the length in nanometers of the wavelength range <NUM> - <NUM>, λ denotes the wavelength in nanometers and T(λ) denotes the spectral transmittance value at wavelength λ, or from <NUM> to <NUM>, defined as <MAT>
where <NUM> is the length in nanometers of the wavelength range <NUM> - <NUM>,
minus a visual transmission value of the tinted glass is higher than <NUM>% , a spectral reflectance of said ophthalmic tinted glass for light impinging on the convex optical face (Cx) with incidence value of <NUM>°, having a value of more than <NUM>% for at least one first wavelength comprised between <NUM> and <NUM>, and another value of less than <NUM>% for at least one second wavelength comprised between <NUM> and <NUM>; and wherein the first layered structure (<NUM>) is a stack of eleven layers alternatively of zirconia and silica, starting and ending with two of said zirconia layers, with the zirconia layers (Z1-Z6) having respective thicknesses between <NUM> and <NUM>, and the silica layers (Q1-Q5) having respective thicknesses between <NUM> and <NUM>.