TECHNICAL FIELD OF THE INVENTION

The invention relates to an optical article suitable for improving the use of a digital device by an individual wearing said optical article in conditions where the display is submitted to natural light.

More precisely the invention relates to an optical article suitable for maximizing the transmission of light coming from a digital device and/or minimizing the transmission of natural light in a predetermined visible wavelength range depending on the emission spectrum of the digital device and on the emission spectrum of natural light, and to a process for the manufacture of such an article.

BACKGROUND INFORMATION AND PRIOR ART

The use of a digital device outdoor in conditions where the device is submitted to natural light, in particular sunlight, is often difficult because of the reflection of natural light on the digital device. When using the digital device outdoor, one needs to be able to discriminate the light emitted by the digital device from the natural light reflected by the device. Typical effects of natural light reflection are the reflection of surrounding, the reflection of self image and blinding glare. As example, a scheme of the different lights present when using a digital device, and photographs of the three types of reflections (reflection of surrounding, reflection of self image and binding glare) are presented on Figure 1.

In addition, the use of a digital device with sunglasses is also difficult because sunglasses, when absorbing or reflecting sunlight, also absorb or reflect at least part of the light emitted by the digital device.

It would thus be interesting to have an optical article affording efficient discrimination between light coming from the digital device and natural light reflected by said digital device, thus allowing the use of the digital device even in natural light such as sunlight.

US 2014/233105 discloses multi-band color vision filters. Some of the described filters aim at improving contrast for screen device. Said filters can be reflective, absorptive, or combination of both. All filters present very complex and sharp cut, and present three pass bands with interleave stop bands having transmission less than half transmission of adjacent pass band. The filters disclosed in this document are complex interferential filters comprising a large number of layers.

There is thus still a need in the art of an optical filter affording efficient discrimination between light coming from the digital device and natural light reflected by said digital device, which would be simple and easy to manufacture and afford a high ratio between the transmission of light coming from the device and the transmission of light reflected by the device.

SUMMARY OF THE INVENTION

The invention first relates to an optical article suitable for improving the use of a display by an individual wearing said optical article in conditions where the display is submitted to natural light, wherein the optical article comprises a substrate and an optical filter suitable for lowering the transmission of light in a predetermined wavelength range, the predetermined wavelength range being determined in function of the emission spectrum of the display and the emission spectrum of natural light, so as to maximize the transmission of light coming from the display and/or minimize the transmission of natural light in the visible wavelength range, wherein the ratio between the transmittance of the optical article for light coming from the display and the transmittance of the optical article for natural light is higher than 1.2 for a viewing angle of 25° through the optical article.

The second object of the invention is a process for the manufacture of an optical article according to the invention, comprising the steps of :

(a) Providing a substrate comprising at least a front side and a back side, optionally comprising at least one impact- resistance primer coating and/or at least one abrasion and/or scratch resistant coating on at least one of the front side and the back side,

(b) Depositing at least one absorbing layer onto the front side and/or the back side of the substrate provided in step (a) to obtain a first coated substrate, wherein the absorbing layer comprises at least one dye or dye mixture absorbing in a predetermined wavelength range determined in function of the emission spectrum of a display and of the emission spectrum of natural light, so as to maximize the transmission of light coming from the display and minimize the transmission of natural light, and

(c) Depositing at least one reflective stack onto the first coated substrate obtained at step (b).

BRIEF DESCRIPTION OF THE DRAWINGS

The following description with reference to the accompanying drawings will make it clear what the invention consists of and how it can be achieved. The invention is not limited to the embodiment/s illustrated in the drawings.

In the accompanying drawings:

Figure 1 presents a scheme of the different lights present when using a digital device (1a), and photographs of the three types of reflections: reflection of surrounding (1 b), reflection of self image (1 c) and binding glare (1 d).

Figure 2 presents the transmission spectrum of an optical article according to example 1. Figure 3 presents the transmission spectrum of an optical article according to example 2.

Figure 4 presents the transmission spectrum of an optical article according to example 3.

DETAILED DESCRIPTION

Optical article

The invention first relates to an optical article suitable for improving the use of a display by an individual wearing said optical article in conditions where the display is submitted to natural light, wherein the optical article comprises a substrate and an optical filter suitable for lowering the transmission of light in a predetermined wavelength range, the predetermined wavelength range being determined in function of the emission spectrum of the display and the emission spectrum of natural light, so as to maximize the transmission of light coming from the display and/or minimize the transmission of natural light in the visible wavelength range, wherein the ratio between the transmittance of the optical article for light coming from the display and the transmittance of the optical article for natural light is higher than 1.2 for a viewing angle of 25° through the optical article.

The terms “optical article” refers to any optical article known in the art and that may be used by a wearer while using a digital device. Preferably, the optical article is an optical lens. In particular, the optical article is an ophthalmic lens. The ophthalmic lens may be mounted in an eyeglass frame.

As used herein, the term “optical lens” refers to any type of lens intended to be supported by a wearer's face, which may be for purposes of improving or enhancing visual acuity, for protecting against the environment, for fashion, or for adornment. The term may refer to ophthalmic lenses, such as non-corrective lenses, semi-finished lens blanks, and corrective lenses, such as progressive addition lenses, unifocal or multifocal lenses. The term may also include one or more of prescription, non-prescription, reflective, anti- reflective, magnifying, polarizing, filtering, anti-scratch, colored, tinted, clear, anti-fogging, ultraviolet (UV) light protected, or other lenses. Further examples of optical lens include electronic lens, virtual reality (VR) lens, and the like.

An optical lens may be manufactured in accordance with wearer specifications from an optical lens blank such as a semi-finished lens blank. A semi-finished lens blank generally has two opposite surfaces at least one of which is unfinished. The unfinished surface of the lens blank may be machined according to the wearer's prescription to provide the required surface of the optical lens. An optical lens having finished back and front surfaces may be referred to as an uncut optical lens. In the case of an ophthalmic lens for the correction or improvement of eyesight, for example, the ophthalmic lens may be manufactured according to a wearer prescription corresponding to the visual requirements of that wearer. At least one of the surfaces of the ophthalmic lens may be processed to provide an ophthalmic lens according to the wearer prescription. Alternatively, an ophthalmic lens may be directly injected or casted. In such manufacturing processes, the front and back sides are finished and the obtained lens is already according to the prescription of the wearer. They are ophthalmic stock lenses.

The shape and size of the spectacle frame supporting the optical lens may also be taken into account. For example, the contour of the uncut optical lens may be edged according to a shape of a spectacle frame on which the optical lens is to be mounted in order to obtain an edged or cut optical lens.

In an embodiment, the optical article is an ophthalmic lens which protects from sunlight.

The terms “maximize” and “minimize” respectively mean, when applied to the transmission of a type of light, that the relative transmission of said type of light is higher, respectively lower, when the optical article is used, compared to the transmission of said type of light in absence of the optical article.

Preferably, the optical article according to the invention maximizes the transmission of light coming from the display and minimizes the transmission of natural light in the visible wavelength range.

The terms “display” and “digital device” both refer to a device comprising at least one screen emitting light. Preferably, the display is a LED (Light-Emitting Diode) display, preferably an OLED (Organic Light-Emitting Diode) display. Examples of such displays are of course smartphones, but also digital tablets, or laptops. The emission spectrum of the display preferably presents a low emission around 580 nm, such as in the 550 nm-620 nm wavelength range.

The term “natural light” includes any type of natural light, especially daylight or sunlight. Sunlight has a bright emission in the whole visible spectrum, and especially in the 550 nm-620 nm wavelength range. In some embodiments, the term “natural light” also includes artificial light having a large spectrum, such as that emitted by some LED devices that mimic the sun.

In an embodiment, the display is a smartphone screen and/or natural light is sunlight. Preferably, the display is a smartphone screen and natural light is sunlight.

The substrate of the optical article can be any material known in the art as substrates of optical articles. The substrate may be made of thermosetting (cross-linked) organic glasses. Among appropriate thermosetting materials can be cited diethylene glycol bis(allylcarbonate) polymers and copolymers (in particular CR-39 ^® from PPG Industries, Essilor Orma ^® lenses), polyurethanes, polythiourethanes, polyepoxides, polyepisulfides, poly(meth)acrylates and copolymers based substrates, such as substrates comprising (meth)acrylic polymers and copolymers derived from bisphenol-A, polythio(meth)acrylates, as well as copolymers thereof and blends thereof.

Additional examples of substrates suitable to the present invention are those obtained from thermosetting polythiourethane resins, which are marketed by the Mitsui Toatsu Chemicals company as MR series, in particular MR6 ^® , MR7 ^® and MR8 ^® resins. These substrates as well as the monomers used for their preparation are especially described in the patents US 4,689,387, US 4,775,733, US 5,059,673, US 5,087,758 and US 5,191,055. An example of polymerizable composition comprising a poly(thio)urethane resin that can be used in the present invention is disclosed in patent application W02007096425.

Preferred materials for the substrate are diethylene glycol bis(allylcarbonate) polymers. In a preferred embodiment, the substrate comprises, preferably is made of, diethylene glycol bis(allylcarbonate) polymer, marketed for instance as CR-39 ^® from PPG Industries.

In some embodiments, the substrate is an organic glass.

The ratio between the transmittance of the optical article for light coming from the display and the transmittance of the optical article for natural light is calculated in the visible wavelength range. Preferably, the ratio is normalized by the eye sensitivity based on CIE 1931 standard. Actually, as is well-known in the art, the eye sensitivity may be individually applied at each wavelength for both light sources (display and natural light) and then compounded to get a single value for each light. The ratio of both unitary values then results in the ratio as used in the present invention.

Said ratio is higher than 1.2 for a viewing angle of 25° through the optical article. In some embodiments, the ratio is higher than 1.25, preferably higher than 1.3, for a viewing angle of 25° through the optical article.

Preferaby, the ratio is low enough for the optical article to comply with the desired Qsignal values for the different colors according to standard values. Thus, preferably, the Qsignal values of the optical article for the different colors are as follows: Qsignal (red) >0.8 and/or Qsignal (green)>0.6 and/or Qsignal (yellow)>0.6 and/or Qsignal (blue)>0.6. In a preferred embodiment, the Qsignal values of the optical article for the different colors are as follows: Qsignal (red) >0.8 and Qsignal (green)>0.6 and Qsignal (yellow)>0.6 and Qsignal (blue)>0.6.

The optical filter can be any optical filter suitable for lowering the transmission of light in the predetermined wavelength range. Preferably, the optical filter comprises at least one dye or dye mixture absorbing light in the predetermined wavelength range. For instance, the optical filter may comprise a violet dye, such as a 1,4-diaminoanthraquinone, for instance “Disperse Violet 1” which CAS number is 128-95-0 or a phthalocyanine, for instance FHI 5936 marketed by Fabricolor Holding Int'l LLC.

The optical filter may further comprise at least one additional dye providing color balance properties and/or contrast increase to the optical article, for instance a dye absorbing in the 480 nm-520 nm wavelength range. Epolin E5841 is an example of additional dye which may be comprised in the optical filter.

In some embodiments, the optical filter comprises an absorbing layer comprising at least one dye absorbing at least part of natural light as detailed above and a reflective stack reflecting at least part of natural light, wherein the absorbing layer is the closest to the substrate.

The reflective stack can be any relective stack appropriate for reflecting at least part of natural light, especially sunlight. The reflective stack may be a mirror stack comprising alternate high refractive index (HI) layers and low refractive index (LI) layers. By HI layer is meant a layer with a refractive index of at least 1.55, preferably at least 1.60, in particular at least 1.65. HI layers may comprise, without limitation, one or more mineral oxides such as Ti0 ₂ , PrTi0 ₃ , LaTi0 ₃ , Zr0 ₂ , Ta ₂ 0 , Y2O3, Ce ₂ 0 ₃ , La ₂ 0 ₃ , Dy ₂ 0 , Nd ₂ 0 , Hf0 ₂ , Sc ₂ 0 ₃ , Pr ₂ 0 _3, Al ₂ 0 ₃ , or Si ₃ N ₄ , as well as suboxidations thereof, such as TiO _x with 1<x<2, and mixtures thereof. By LI layer is meant a layer with a refractive index lower than 1.55, preferably lower than 1.50, in particular lower than 1.45. Among the materials suitable for the LI layer can be cited for instance, without limitation, Si0 ₂ , SiO _x with 1<x<2, MgF ₂ , ZrF ₄ , Al ₂ 0 ₃ , AIF ₃ , chiolite (Na ₃ [AI ₃ F ₁₄ ]), cryolite (Na ₃ [AIF ₆ ]), or any mixture thereof, preferably Si0 ₂ or Si0 ₂ doped with Al ₂ 0 ₃ which contributes to raising the critical temperature of the stack. When Si0 ₂ /Al ₂ 0 ₃ mixtures are used, the LI layer preferably contains from 1 to 10%, more preferably from 1 to 8% by weight of Al ₂ 0 ₃ relative to the total weight of Si0 ₂ + Al ₂ 0 ₃ in said layer. A too high amount of alumina is detrimental to adhesion of the AR coating. In a preferred embodiment, the LI layer is a Si0 ₂ -based layer.

The reflective stack of the optical article according to the invention may be for instance a mirror stack comprising alternate layers of Si0 ₂ and Zr0 ₂ , preferably a a mirror stack consisting of alternate layers of Si0 ₂ and Zr0 ₂ .

The optical filter is preferably a simple optical filter, which manufacture will not require too many or difficult steps. The optical filter may thus be a stack comprising from 1 to 14 layers, preferably from 1 to 12 layers, in particular from 1 to 10 layers. In some embodiments, the optical article is a stack comprising from 2 to 14 layers, preferably from 3 to 14 layers, in particular from 4 to 14 layers.

A further way to optimize both the visibility of the digital device and the protection towards natural light such as sunlight is to define different zones on the optical article, with different transmittances for light coming from the digital display and natural light. For instance, when the optical article is an ophthalmic lens, the optical filter on the top part of the lens may substantially absorb natural light, especially sunlight, whereas the optical filter on the bottom part of the lens does not substantially absorb the light coming from the digital display. For instance, the transmittance of the top part of the lens may be of less than 20%, for instance equal to 12%, for natural light, especially sunlight. For instance, the transmittance of the bottom part of the lens may be of more than 50%, for instance equal to 58%, for light coming from the digital display. The transmittance of the bottom part of the lens for natural light especially sunlight, may be higher than for the top part, as long as the ratio of more than 1.2 is maintained. For instance, the transmittance of of the bottom part of the lens for natural light especially sunlight, may be up to 50%, for instance equal to 45%.

Thus, in an embodiment, the concentration of the absorbing dye of the absorbing layer and/or the thickness of the reflective stack of the optical filter is not constant on the whole surface of the optical article.

The zones having different transmittances for light coming from the digital display and natural light may be discrete zones, but they may also be defined by a spatial gradient in the optical article transmission properties. When the optical article is an ophthalmic lens, the spatial gradient may be a gradient from the top to the bottom of the optical article. For instance, the reflective stack of the optical filter may present a thickness gradient from the top to the bottom of the optical article. For instance, the absorbing layer of the optical filter may present a concentration gradient of absorbing dye from the top to the bottom of the optical article.

In the present invention, the terms “absorbing” and “absorption” of a device in a wavelength range refer to a case where the mean emission value of the device in the wavelength range is lower than 50% of the mean emission value of the device in each of the adjacent 40 nm wavelength ranges.

In some embodiments, the light reflected by the reflective stack is at least partly absorbed by the optical article. For instance, at least 80%, preferably at least 90%, in particular at least 95%, of the light reflected by the reflective stack is absorbed by the optical article. This absorption of the light reflected by the reflective stack limits and/or suppresses undesirable reflections in the backside viewed by the wearer of the optical article. The absorption of the light reflected by the reflective stack further afford a pleasing aesthetic effect as the mirror reflection appears to people around the wearer but is not visible to the wearer himself.

In some embodiments, the chroma value of the optical article is lower or equal to 10, preferably lower or equal to 5. Actually, the general trends consist in lowering the chroma value of optical articles such as ophthalmic lenses so as to make the glass more neutral, that is to say so as to minimize the color perception. The chroma value is herein defined in the CIE La ^* b ^* 1976 system, with and observer at 10° and D65 as illuminant.

The chroma value c ^* _ab is defined as follows: c _a ^* _b = ^Ja* ² + b* ² , wherein a ^* and b ^* are the parameters of the CIE La ^* b ^* 1976 chromatic space.

The predetermined wavelength range is a wavelength range in the visible range, thus comprised between 380 nm and 700 nm, at which the natural light emission is important, and the light emitted by the digital device may be absorbed without substantially impacting on what is perceived by the digital device user. The predetermined wavelength range is determined on the basis of the emission spectra of the natural light and of the digital device, optionally normalized by the sensitivity of the eye based on CIE 1931 standard. In some embodiments, the predetermined wavelength range is a wavelength range comprised in the 550 nm-620 nm range. Actually, the 550 nm-620 nm range corresponds to a range wherein natural light such as sun light brightly emits, whereas digital displays such as OLED screens, especially smartphone OLED screens, have low emission. Absorbing light in this wavelength range will thus afford selective absorption of natural light which may be reflected by the digital display, in contrast with the light emitted by the display which will be only slightly affected. Preferably, the predetermined wavelength comprises the 580 nm wavelength. More preferably, the predetermined wavelength range is a wavelength range comprised in the 550 nm-620 nm range and comprising the 580 nm wavelength. In some embodiments, the predetermined wavelength range is the 550 nm-620 nm wavelength range.

Advantageously, the predetermined wavelength range is the only wavelength range of the visible spectrum wherein the optical article absorbs light. Thus, in some embodiments, the optical article does not absorb light in each wavelength range of the 380 nm-700 nm range out of the predetermined range. In these embodiments, the mean transmittance of the optical article in each wavelength range of the 380 nm-700 nm range out of the predetermined range is higher than 50% of the mean transmittance in both adjacent 40 nm wavelength ranges.

In some embodiments, the optical device does not absorb in the 520 nm-540 nm wavelength range, which corresponds to a wavelength range wherein OLED screens, especially smartphone OLED screens, strongly emit. In said embodiments, the mean transmittance of the optical article in the 520 nm-540 nm range is preferably higher than 40%, more preferably higher than 60%.

The optical article may comprise, in addition to the optical filter, additional coatings as classically in the art. Examples of a coating that may be disposed on an optical article include an anti-breakage coating, an anti-scratch coating, an anti-reflection coating, a tint coating, a color coating, an anti-static coating, an anti-smudge coating, a topcoat, an anti-reflective coating, an asymmetrical mirror and a hardcoat. In some embodiments, the optical article comprises, between the substrate and the optical filter, at least one impact-resistant primer coating and/or at least one abrasion and/or scratch resistant coating.

Process for the manufacture of an optical article

The invention further relates to a process for the manufacture of an optical article according to the invention, comprising the steps of :

(a) Providing a substrate comprising at least a front side and a back side, optionally comprising at least one impact- resistance primer coating and/or at least one abrasion and/or scratch resistant coating on at least one of the front side and the back side,

(b) Depositing at least one absorbing layer onto the front side and/or the back side of the substrate provided in step (a) to obtain a first coated substrate, wherein the absorbing layer comprises at least one dye or dye mixture absorbing in a predetermined wavelength range determined in function of the emission spectrum of a display and of the emission spectrum of natural light, so as to maximize the transmission of light coming from the display and minimize the transmission of natural light, and

(c) Depositing at least one reflective stack onto the first coated substrate obtained at step (b).

Step (b) may be performed by any appropriate technique known in the art. For instance, step (b) may be performed by a technique selected from the group consisting of vacuum deposition, vapor deposition, sol-gel deposition, spin coating, dip coating, spray coating, flow coating, film laminating, sticker coating, roller coating, brush coating, painting, sputtering, casting, Langmuir-Blodgett deposition, laser printing, inkjet printing, screen printing, pad printing, and any combination thereof.

In particular, step (b) may be performed by dip coating.

In some embodiments, when step (b) is performed by dip coating, the substrate is immersed into a dying bath comprising at least one dye dissolved in a solvent blend, and slowly withdrawn from the dip coating bath, so as to form an absorption gradient in the absorption layer. Such method is known in the art to obtain a gradient in properties of a layer and is disclosed for instance in US 5,453,100. The method disclosed in US 10,201,944 may also be used to form the absorption gradient in the absorption layer.

Step (c) may be performed by any appropriate technique known in the art. For instance, step (c) may be performed by a technique selected from the group consisting of vacuum deposition, vapor deposition, sol-gel deposition, spin coating, dip coating, spray coating, flow coating, film laminating, sticker coating, roller coating, brush coating, painting, sputtering, casting, Langmuir-Blodgett deposition, laser printing, inkjet printing, screen printing, pad printing, and any combination thereof.

In some embodiments, step (c) is performed by using a deposition mask, so as to form different zones with different anti-reflective properties. The different zones may be, as exposed above, discrete zones or may form a spatial gradient of anti-reflective properties on the surface of the optical article. The shape of the deposition mask depends on the desired zones. When a thickness gradient of the anti-reflective stack is desired, a triangular deposition mask can be for instance used. The use of such a deposition mask for creating a thickness gradient of the anti-reflective stack is well-known in the art and may be implemented for instance with an apparatus for vapor deposition comprising a distribution mask as disclosed in WO 2018/087090. The gradient of the anti-reflective stack, obtained by lowering the thickness of each layer of the anti-reflective stack, triggers an already described rainbow mirror effect which is aesthetically interesting.

For instance, step (c) may be implemented by simple application of the deposition mask on the lens in the thin film deposition chamber during the rotation.

The following examples are provided only for illustrative purposes and do not aim at limiting the scope of the invention.

EXAMPLES

Example 1: Optical article comprising an absorbing dve and a mirror stack

An optical article comprising an Orma® substrate, an abrasion-resistant and/or anti-scratch Mithril 1.5 hard coat, an anti-reflective Crizal Sun coating and an iPhone mirror, dipped for 10 minutes in a solution of disperse violet 1 (Lumacel Heliotrope R, LG Chemicals Ltd) was simulated and its transmission spectrum was established. The mirror stack is a 10 layer stack made of Si0 ₂ and Zr0 ₂ based layers. The transmission spectrum of the obtained optical article is presented on Figure 2.

This optical article presents a ratio between the transmittance of the optical article for light coming from an iPhone X screen and the transmittance of the optical article for natural light at a 25° angle of 1.41. The structure of the iPhone mirror is an alternate of Si0 ₂ and Zr0 ₂ layers as detailed in table 1 below:

Additional similar optical articles comprising 50%, 60%, 70%, 80% and 90% of the tint of the above optical article were simulated in similar conditions. They respectively afforded ratios of 1.27, 1.30, 1.33, 1.36 and 1.38.

All six articles satisfied the required Qsignal values for the standard for red, yellow and blue. The articles comprising 50%, 60%, 70%, and 80% of the tint also satisfied the required Qsignal values for the standard for green.

Example 2 : Optical article comprising an absorbing dve and a mirror stack An optical article comprising an Orma® substrate, an abrasion-resistant and/or anti-scratch Mithril 1.5 hard coat, an anti-reflective Crizal Sun coating and an iPhone mirror, dipped for 10 minutes in a solution of disperse violet 1 (Lumacel Heliotrope R, LG Chemicals Ltd) was simulated and its transmission spectrum was established. The structure of the iPhone mirror is an alternate of Si0 ₂ and Zr0 ₂ layers as detailed in table 2 below:

Table 2: Mirror stack of the optical article of example 2

The transmission spectrum of the obtained optical article is presented on

Figure 3. This optical article presents a ratio between the transmittance of the optical article for light coming from an iPhone X screen and the transmittance of the optical article for natural light at a 25° angle of 1.38.

This optical lens presents the advantage that the reflection from the mirror is mostly absorbed in the lens, thus the wearer does not get undesirable reflections in the backside. The wearer would indeed get 1.4% reflection from the front side and 1.1% reflection from the mirror on the back side. A pleasing aesthetic effect is obtained, where the mirror reflection appears to other people but not to the wearer himself.

Example 3 : Optical article comprising an abosrbing dve and a mirror stack An optical article comprising an MR8® substrate, an abrasion-resistant and/or anti-scratch Mithril 1.6 hard coat, an anti-reflective Crizal Sun coating and an iPhone mirror, dipped for 10 minutes in a solution comprising a mixture of Epolin E5841 (75%) and FHI5936 (105%) dyes was simulated and its transmission spectrum was established. The structure of the iPhone mirror is the same as presented above in table 1 for example 1.

The transmission spectrum of the obtained optical article is presented on

Figure 4.

This optical article presents a ratio between the transmittance of the optical article for light coming from an iPhone X screen and the transmittance of the optical article for natural light at a 25° angle of 1.28.

This optical article presents the further advantage of a low chroma equal to 3, avoiding an undesirable coloration of the optical article.