WO2002014930A1

WO2002014930A1 - Anti-reflection coated lens

Info

Publication number: WO2002014930A1
Application number: PCT/AU2001/000940
Authority: WO
Inventors: Brandon Yip; Brian Douglas Adams
Original assignee: Sola International Holdings Ltd
Priority date: 2000-08-17
Filing date: 2001-08-01
Publication date: 2002-02-21
Also published as: AUPQ949600A0

Abstract

An optical lens has a light reflective or mirror coating on a rear or intermediate surface, and an anti-reflective coating on the front surface. This arragement helps protect the mirror coating from abrasion, while preventing ghost images due to internal reflections. THe lens is suitable for sunglasses, and may comprise back and front lens wafers.

Description

ANTI-REFLECTION COATED LENS

The present invention relates to an optical article including a surface which has been treated to reduce the intensity of parasitic internal reflections.

The optical articles according to the present invention are preferably employed in the preparation of articles such as optical lenses, including spectacle lenses, including sunglass lenses, visors, shields, glass sheets, protective screens, and the like.

Sunglasses generally serve to attenuate transmitted light, but aside from the level of light transmittance, there are other features that distinguish different sunglass lenses, such as material, transmitted colour, scratch resistance, reduction of side glare, ultra-violet transmittance, cosmetic appearance etc. Coatings, e.g thin films, may be applied to enhance the performance of sunglass lenses. Such coatings include scratch resistant coatings, hydrophobic coatings for easier cleaning, anti-reflective coatings for reducing side glare or "mirror" (or "interference") coatings for producing fashionable lens colours. General purpose sunglass lenses should meet certain standard specifications, including luminous transmittance, traffic signal recognition and UV transmittance (e.g. ANSI Z80.1- 1995).

Anti-reflection coatings are commonly deposited on ophthalmic and sunglass lenses in order to minimise spurious reflections, which both detract from the wearer's vision and are also cosmetically unpleasing. These coatings commonly consist of multi-layer, dielectric films of thicknesses chosen so that interference effects cause destructive cancellation of reflections over most of the visible spectrum. Due to cost and process control factors, these coatings are typically constructed from four to six layers, and exhibit a very weak, but visible residual reflection. They are generally deposited on both sides of transparent ophthalmic lenses and on the back (eye-side) surface of higher-quality sunglass lenses. For ophthalmic lenses, such coatings also increase the transmission of light through to the wearer and improve the visibility of the wearer's eyes to others. Another type of thin film coating is a "mirror" coating, applied to sunglass lenses to give them a cosmeticaily pleasing coloured or reflective appearance, which may also have other benefits such as contrast enhancement or the reduction of transmitted ultra-violet or infra-red light.

When mirror coatings are applied on the front (convex) surface of the lens, they are prone to damage by scratching. One way to protect the mirror coating from scratching and abrasion is to place it inside a laminated lens construction, rather than on an exposed exterior surface of the lens. Another possibility is to place the mirror coating on the rear surface of the lens, where it is protected from the outside world by the intervening body of the lens.

A problem with such internally mirrored lenses (where the reflective coating is not on the front surface) is that of internal reflections. They in fact contain multiple reflective surfaces - the front surface of the lens, the mirrored surface and (possibly) the rear surface. Multiple, internal reflections which may perturb the vision of the wearer are thus created. For normal sunglass lenses with no optical power the effect may not be severe, since the reflecting surfaces are parallel and closely spaced, leading to secondary reflections that are often superposed on the primary transmitted light rays. However, for corrective, ophthalmic (or prescription) lenses, the reflecting surfaces are no longer parallel and not necessarily closely spaced. "Ghost images" due to internal reflections may become very noticeable and detract from the optical performance of the lens.

It would accordingly be a significant advance in the art if such ophthalmic lenses could be modified to reduce or eliminate parasitic internal reflection.

Accordingly, it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties or deficiencies related to the prior art.

Accordingly, in a first aspect of the present invention there is provided an optical lens including a front surface; and a light reflective back surface; the front surface being rendered anti-reflective.

It will be understood that the provision of an anti-reflective front surface functions to reduce or eliminate the parasitic internal reflections generated by the light reflective rear surface.

In a preferred embodiment of this aspect of the present invention, the optical lens includes a light-reflective or mirror coating on the rear surface of the lens; and an anti-reflective coating on the front surface of the lens.

Preferably, the light reflective or mirror coating may be a light-absorbing coating. The absorbing coating may be an asymmetric reflectance, light absorbing coating. A multi-layer metal-dielectric coating is preferred, for example of the type described in International patent application PCT/AU98/00868, to

Applicants, the entire disclosure of which is incorporated by reference.

By the term "asymmetric reflectance", as used herein, we mean that the multi-layer coating renders the lens anti-reflective when viewed from one side of the coating and exhibits a selected colour or colourless reflection when viewed from the other side.

Preferably the asymmetric reflectance light absorbing coating is a multilayer metal-dielectric coating; the dielectric materials being selected from one or more of SiO, Si0₂, Zr0₂, Al₂0₃, TiO, Ti0₂, Ti₂0_3! Y₂0₃, Yb₂0₃, MgO, Ta₂05, Ce0₂ and Hf0₂, MgF₂, AIF₃, BaF₂, CaF₂₎ Na₃AlF₆, Ta₂05 and Na5AI₃FI1₃, and Si₃N4 and AIN; and the metallic material selected from metals, metal oxides or nitrides of one or more of Niobium (Nb), Chromium (Cr), Tungsten (W), Tantalum (Ta), Tin (Sn), Palladium (Pd), Nickel (Ni) or Titanium (Ti).

More preferably the asymmetric reflectance, light absorbing coating further includes compatible dielectric layers of suitable thickness to provide a desired colour to the optical lens. In a particularly preferred form, the asymmetric reflectance light absorbing coating includes alternating layers of silica (Si0₂) and chromium (Cr) or Niobium (Nb) metal; and wherein the thickness and/or number of the respective layers are selected to provide an anti-reflective effect on the eye side of the optical lens and a desired colour on the other side of the optical lens.

Optionally the asymmetric reflectance, light absorbing coating includes an additional titanium dioxide layer or layers of such a thickness to provide a desired colour to the optical lens.

The anti-reflective coating on the front surface of the optical lens may be a standard multi-layer anti-reflective coating. The number and/or thickness of the layers may be selected utilising suitable computer software. The layers may include alternate high and low refractive index layers.

The low and high refractive index layers may be formed from any suitable material. The low and high refractive index layers may be formed of a dielectric material. Preferably the dielectric layers may be formed from metal oxides, fluorides or nitrides. Metal oxides which may be used for forming transparent layers include one or more of SiO, Si0_2l Zr0₂, Al₂0₃, TiO, Ti0₂, Ti₂0₃, Y2O3, Yb₂0₃, MgO, Pr₂0₃, Ta₂0₅, Ce0₂ and Hf0₂. Fluorides which may be used include one or more of MgF₂, AIF₃, BaF₂, CaF₂, Na₃AIF₆, Ta₂0_5> and Na₅AI₃Flι . Suitable nitrides include Si₃N and AIN.

A silica (Si0₂) or magnesium fluoride (MgF2) material is preferred for the low index layers.

A combination of titanium and praseodymium oxide (Ti0₂ + Pr2θ₃) is preferred for the high index layers. Such a combination may have a refractive index at 500 nm of approximately 2.15.

In a preferred form, the anti-reflection coating may include a total of 4 to 6 alternating high and low index layers, preferably 4 to 6 alternating layers. In a preferred aspect of the present invention the light reflective or mirror coating and/or the anti-reflective coating may be selected to provide a substantially balanced reflectance to the lens, for example, when applied to a surface of a lens of high curvature. The coating(s) may be prepared as described in International patent application PCT/AU99/01029, to Applicants, the entire disclosure of which is incorporated herein by reference.

By the term "substantially balanced reflectance" we mean that where the thickness of the coating varies across the surface of the lens, the lightness, hue and chroma of the reflectance vary in a balanced manner such that variations in visual appearance are either imperceptible or generally acceptable to an observer. For example, variations in chromatic attributes, such as hue, from the centre to the edge of the lens may be balanced by a reduction in lightness from the centre to the edge.

The substantially balanced reflectance coating, in use, may exhibit a substantially constant low photopic reflectance in the red-to-infra-red wavelength range of approximately 620 to 880 nm proximate the centre of the lens element.

Preferably, the photopic reflectance is less than approximately 3%. The reflectance is preferably low where the eye is most sensitive, in the region of approximately 550 nm.

The substantially balanced reflectance coating may function as an anti- reflection coating. The balanced reflectance coating may alternatively or in addition function as a light absorbing, or tint coating, in which case it may also have an asymmetric reflectance, such that from the wearer's side of- the lens element the coating is anti-reflective. The balanced reflectance coating may alternatively function as a light reflective or mirror coating.

The balanced reflectance coating may exhibit a substantially constant low photopic reflectance in the wavelength range of approximately 620 to 880 nm, the photopic reflectance preferably being less than approximately 1.5%. The balanced reflectance coating may, for example, exhibit a reflected colour difference from the centre to a radius of approximately 20 mm on the lens surface of less than approximately 11 CMC colour difference units. (Perceived variations in appearance may be quantified by calculating "CMC colour differences", as developed by the Colour Measurement Committee of the Society of Dyers and Colourists and explained in "The Measurement of Appearance", 2nd ed., R.S. Hunter and R.W. Harold, Wiley, New York, 1987).

Alternatively, the coating may exhibit a reflected colour difference (Δ E) from the centre to a radius of approximately 20 mm on the lens surface of greater than approximately 11 CMC colour difference units, the colour difference being balanced by a complementary reduction in luminous intensity.

More preferably the coating exhibits a reflected colour difference (Δ E) of from approximately 11 to 20 CMC colour difference units.

In this embodiment the coating is preferably a multicoloured, anti-reflective coating.

In accordance with the present invention, one or both surfaces of an optical lens may be coated with the balanced reflectance coating.

In a preferred aspect, the lens includes a surface of high curvature and may be of generally ovaline shape and is located on the surface of a sphere whose radius of curvature corresponds to 11 D or above, a toroid where the horizontal radius of curvature corresponds to 11 D or above, or a surface where the radius of curvature changes across at least one section of the lens aperture.

In a preferred aspect, the balanced reflectance coating may be a multi-layer coating. The balanced reflectance coating may include a plurality of layers, the thickness and/or number of which being selected to reduce the phenomenon of

"colour rolloff". The balanced reflectance coating further provides an interference effect, e.g. an anti-reflective or light reflecting or mirror effect. More preferably the balanced reflectance coating includes a plurality of layers, wherein the thickness and/or number of the respective layers are selected to provide a substantially balanced reflectance in response to visual effects generated by variations in thickness of the coating in use, for example, as may occur when applied to a surface of a lens of high curvature.

In this embodiment, the coating may include a plurality of layers of differing refractive index wherein the thickness and/or number of the respective layers are selected to balance the variation of any combination of reflected lightness, hue and chroma.

The number and/or thickness of the layers may be selected utilising suitable computer software, adapted to minimise the variation of any combination of reflected lightness, hue or chroma accompanying variations in coating thickness.

Applicants have further noted that, where the balanced reflectance coating is applied to both surfaces of an ophthalmic lens element it is possible to improve optical performance, including colour uniformity, on highly curved substrates even further by balancing the colour variations between the two surfaces. It may further be possible to reduce or eliminate other optical aberrations, such as "ghost images" which may be generated by reflective coatings.

Accordingly, in a preferred aspect of the present invention, the light reflective or mirror coating and anti-reflective coating in combination exhibit a substantially balanced reflectance coating from the centre to a radius proximate the edge of the lens.

In a further preferred aspect of the present invention there is provided a front lens wafer for an optical lens including an anti-reflective front surface; and a reflective or mirror contact surface.

In a preferred embodiment of this aspect of the present invention, the front lens wafer includes an anti-reflective coating on the front surface, and a reflective or mirror coating on the contact surface thereof.

As will be discussed further below, the reflective or mirror contact surface of the front lens wafer generates ghost images through parasitic internal reflections. The anti-reflective front surface functions to reduce , or eliminate such parasitic reflections.

Preferably the light reflective mirror coating is an asymmetric reflectance light absorbing multi-layer metal-dielectric coating; and the anti-reflective coating is a multi-layer coating including alternate high and low refractive index layers, the high and low refractive index layers being formed of a dielectric material.

Accordingly, in a still further aspect of the present invention, there is provided a laminate optical lens including a front lens wafer including a front surface; and a first contact surface; a complementary back lens wafer including a second contact surface; the first and/or second contact surface being light reflective; and the front surface of the front lens wafer being rendered anti-reflective .

It will be understood that the provision of an anti-reflective front surface functions to reduce or eliminate the parasitic internal reflections generated by the light reflective internal contact surface of the laminate optical lens. This is discussed in more detail below.

In a preferred embodiment of this aspect of the present invention, the laminate optical lens includes a first light-reflective or mirror coating on a contact surface of the front or back lens wafer; and an anti- reflective coating on the front surface of the front lens wafer.

The light-reflective or mirror coating and anti-reflective coating may be as described above. The light-reflective or mirror coating may be an asymmetric reflectance, light absorbing coating. The anti-reflective coating may be a multi- layer dielectric coating.

More preferably, the light reflective or mirror coating is an asymmetric reflectance light absorbing multi-layer metal dielectric coating; and the anti-reflective coating is a multi-layer coating including alternate high and low refractive index, layers, the high and low refractive index layers being formed of a dielectric material.

As mentioned above, if it is not deposited on the front surface of the lens (as is most commonly done) the light-reflective surface or coating may generate ghost images which may disturb or distract wearer vision. Figure 1 illustrates how the ghost image effect occurs in a lens with a light reflective or internally-mirrored surface. The effect is basically a double-bounce reflection effect - depending on its reflectance, up to -30% of the incident light might be reflected away from the wearer by the internally-mirrored surface. Approximately 4 to 5% of this light (depending on the lens material) is then reflected back from the non-mirrored front surface of the front lens wafer, resulting in a ghost image of intensity up to 0.3 x 5 = 1.5% of the intensity of the primary image. Normally this would be difficult to see, but if the light source is bright and the background is much less bright (e.g. car headlights at night, reflections from water or reflections of the sun from a dark car) then a faint ghost image might be seen.

Internal reflections from the back of the back lens wafer may usually be ignored, because preferably, as discussed in more detail below, an absorbing material may be placed between the internally-mirrored surface and the back of the lens, so that internal reflections from the rear surface of the lens are attenuated twice by the absorber before arriving back at the wearer, as shown in Figure 2. Such internal reflections will be so weak that they will not be perceptible. The absorbing material may be a polarising film or other thin, absorbing layer. Alternatively, the entire rear lens wafer may be made of tinted plastic or glass. Without such a light-absorbing material, the wearer would see very disturbing reflections of his own eyes reflected back from the internal mirror.

Another possibility is that the mirror coating itself may act as the absorber where the internal mirror was an asymmetric reflectance light-absorbing coating, as discussed above.

If the mirrored surface is not inside the lens but on the back surface, ghost reflections are produced in a similar manner to that discussed above, as shown in Figure 3 below.

From this discussion, it will be appreciated that for mirrored lenses, (when the reflective coating is not placed on the front surface of the lens) ghost images may arise due to internal reflections between the front surface of the lens and the mirrored surface.

For normal sunglass lenses with no corrective power, the ghost images from an internal or back-surface mirror may not be noticeable to most wearers. The front lens wafer or lens (on the back of which the mirror coating is located) can be made very thin and its front and back surfaces parallel, so that any internal reflections will have almost no spatial separation from the primary light rays and ghost images will overlay the primary image and hence may not be perceptible. (If the front lens wafer is not thin, however, ghost images may become bothersome).

For corrective sunglass lenses, the front lens surface and the internal mirrored surface may not be parallel and may be many millimetres apart. In this case, rather than being superposed on the primary image, ghost image may be substantially separated from the primary image and hence may be very noticeable. Unacceptable disturbance to the vision of the wearer is likely to result.

It will be understood that the provision of the anti-reflective front surface of the invention functions to reduce or eliminate the parasitic internal reflections generated between the light reflective surface of the lens and the front surface of the lens.

The optical lens or lens wafer according to the present invention may be either optically clear or tinted (light absorbing), such as a sunglass lens, ophthalmic lens element, visor or the like. A sunglass lens is preferred. The optical lens may be a semi-finished lens blank requiring further finishing to a particular patient's prescription.

The lens element may be of the type described in International Patent

Application PCT/AU98/00872 "Spectacle Frames" to Applicants, the entire disclosure of which is incorporated herein by reference; or in Australian

Provisional Patent Application PP4748 "Optical Lens" to Applicants, the entire disclosure of which is incorporated herein by reference.

Where the lens element is an ophthalmic lens element, the ophthalmic lenses may be formed from a variety of different lens materials, and particularly from a number of different polymeric plastic resins. A common ophthalmic lens material is diethylene glycol bis (allyl carbonate) or CR39 (PPG Industries). Other high index lens materials are based on acrylic or allylic versions of bisphenols or allyl phthalates and the like. Other examples of lens materials that may be suitable for use with the invention include other acrylics, other allylics, styrenics, polycarbonates, vinylics, polyesters and the like.

The optical lens according to the present invention may further include one or more additional coatings. Accordingly in a further aspect of the present invention there is provided a multi-coated optical lens including a front surface; and a back surface; the multi-coated optical lens including a light reflective or mirror coating on the back surface thereof; and an anti-reflective coating on the front surface thereof; and one or more secondary coatings or films which provide a desirable optical and/or chemical and/or mechanical property to the optical lens.

Preferably the multi-coated optical lens includes a laminate optical lens including a front lens wafer including a front surface; and a first contact surface; a complementary back lens wafer including a second coated surface; the laminate optical lens including a first light-reflective or mirror coating on a contact surface of the front or back lens wafer; an anti-reflective coating on the front surface of the front lens wafer; and one or more secondary coatings which provide a desirable optical and/or chemical and/or mechanical property to the optical lens.

The secondary coating(s) may overlay or underlay the anti-reflective coating or be applied to a second surface of the lens.

The secondary coating(s) may be of any suitable type. The secondary coating(s) may be one or more of an anti-reflective, hydrophobic, abrasion resistant, or impact-resistant coating. An abrasion-resistant coating is preferred. The combination of an abrasion resistant coating and an anti-reflective coating is particularly preferred. A polarising or photochromic coating or film may be included. Where a laminate optical lens is used, a polarising film or coating may be included between the front and back lens wafers.

An abrasion-resistant (hard) coating including an organosilicone resin is preferred. A typical organosilicone resin that is suitable for use in the present invention has a composition comprising one or more of the following:

1) organosilane compounds with functional and/or non-functional groups such as glycidoxypropyl trimethoxy silane;

2) co-reactants for functional groups of functional organosilanes, such as organic epoxies, amines, organic acids, organic anhydrides, imines, amides, ketamines, acrylics, and isocyanates; colloidal silica, sols and/or metal and non-metal oxide sols; catalysts for silanol condensation, such as dibutylin dilaurate;

3) solvents such as water, alcohols, and ketones;

4) other additives, such as fillers.

Abrasion resistant coats of acrylic, urethane, melamine, and the like may also be used. These materials, however, frequently do not have the good abrasion resistant properties of organo-silicone hard coatings.

The abrasion-resistant (hard) coating may be coated by conventional methods such as dip coating, spray coating, spin coating, flow coating and the like or by newer methods such as Plasma Enhanced Chemical Vapour Deposition.

Coating thicknesses of between approximately 0.5 and 10 microns are preferred for abrasion and other properties.

The secondary abrasion resistant coating may be applied to the front and/or rear lens surfaces. The abrasion resistant coating may be of the type described in United States Patent 4,954,591 to the Applicants, the entire disclosure of which is incorporated herein by reference.

In a further preferred aspect, one or more surfaces of the optical article may be subjected to a surface treatment to improve bondability and/or compatibility of the anti-reflection and/or secondary coating. The surface treatment may be selected from one or more of the group consisting of plasma discharge, corona discharge, glow discharge, ionising radiation, UV radiation, flame treatment and laser, preferably excimer laser treatment. A plasma discharge treatment is preferred. The surface treatment, alternatively or in addition, may include incorporating another bonding layer, for example a layer including a metal or metal compound selected from the group consisting of one or more of Chromium, Nickel, Tin, Palladium, Silicon, and/or oxides thereof.

The optical article may be a sunglass lens of the wrap-around or visor type, for example of the type described in International Patent Application PCT/AU97/00188 "Improved Single Vision Lens" to Applicants, the entire disclosure of which is incorporated herein by reference.

Accordingly, the present invention provides spectacles including a spectacle frame; and a pair of optical lenses, each optical lens including a front surface; and a back surface; the optical lens including a light reflective or mirror coating on the rear surface of the lens; and an anti-reflective coating on the front surface of the lens.

Preferably the lens is a corrective sunglass lens.

In a preferred form, each optical lens is a corrective lens, more preferably a corrective sunglass lens.

In a further aspect of the present invention, there is provided a method for preparing a coated optical lens, which method includes providing an optical lens including a front surface; and a back surface; materials suitable to form an anti-reflective coating; materials suitable to form a light reflective or mirror coating; depositing the anti-reflective materials on the front surface to form an anti- reflective coating thereon; and depositing the light reflective materials on a second surface of the lens to form a light reflective or mirror coating.

The deposition steps may be conducted in any order.

The surface bearing the light reflective or mirror coating may be the back surface of the lens. Alternatively, where the optical lens is a laminate optical lens, the reflective or mirror coating may be deposited on a contact surface of the front or rear lens wafer.

Preferably the materials suitable to form an anti-reflective coating include a dielectric material of low refractive index and a dielectric material of high refractive index, the method further including depositing overlapping layers of low refractive index dielectric material and high refractive index dielectric material on the back surface of the optical lens, the number and/or thickness of the respective layers being selected to provide a desired anti-reflective effect.

In a preferred aspect, the high and low refractive index materials, preferably Pr₂θ₃/Ti0₂ and Si0₂, are deposited as alternating layers.

The deposition step may be a vacuum deposition step. The deposition step may be conducted in a coating apparatus. A box coater or sputter coater may be used.

In a further preferred aspect, the materials suitable to form a light reflective or mirror coating include a dielectric material selected from SiO, Si0₂, Zr0₂, Al₂0₃, TiO, Ti0₂, Ti₂0₃, Y₂0₃, Yb₂0₃, MgO, Ta₂05, Ce0₂ and Hf0₂, MgF₂, AIF₃, BaF₂, CaF₂, Na₃AIF₆, Ta₂05 and Na5AI FI1₃, and Si₃N4 and AIN; and a metallic material selected from metals, metal oxides or nitrides of one or more of Niobium (Nb), Chromium (Cr), Tungsten (W), Tantalum (Ta), Tin (Sn), Palladium (Pd), Nickel (Ni) or Titanium (Ti); the method further including depositing overlapping layers of dielectric material and metallic material to form an asymmetric reflectance light absorbing coating on the front surface of the optical lens.

The coating(s) may preferably be formed on the surfaces of the substrate according to the process and the box coaters as described in the Italian Patent No. 1.244.374 the entire disclosure of which is incorporated herein by reference.

In accordance with said method, the various layers of the uniform reflectance coating may be deposited in subsequent steps utilising a vacuum evaporation technique and exposing the growing layers to a bombardment of a beam of ions of inert gas.

Moreover, in accordance with the preferred method, the deposition of the layers may be achieved at a low temperature (generally below 80°C), using an ion beam having a medium intensity (meaning the average number of ions that reach the substrate) included between approximately 30 and 100 μA/cm2 and the energy included between approximately 50 and 100 eV.

The coated optical article may include a photochromic material or coating. The photochromic material may be incorporated into the optical article in any suitable manner, e.g. utilising an imbibing technique or by incorporation into the primer coating composition as discussed below.

The primer and/or secondary coating, when present, may alternatively or in addition include a photochromic material or coating. The photochromic material may include a photochromic dye.

The photochromic dye may be of any suitable type. A photochromic dye may be selected from one or more of the group consisting of anthraquinones, phthalocyanines, spiro-oxazines, chromenes, pyrans including spiro-pyrans and fulgides. A spiro-oxazine residue is preferred. The photochromic dye may be selected from any of those described above.

The selection of dyes which may be used may extend to conventional tinting dyes.

The photochromic material may be introduced to the coated optical article in any suitable manner. The photochromic dye may be incorporated into a polymer carrier or may be directly imbibed into the optical article, the primer, or other secondary coating or any combination thereof.

In a preferred aspect a photochromic monomer may be incorporated into the composition of the polymeric casting composition, the primer or secondary coating composition or any combination. The photochromic monomer may, fpr example, be of the type described in International Patent Application PCT/AU96/00466 to applicants, the entire disclosure of which is incorporated herein by reference.

Further characteristics and advantages of the present invention will be apparent from the following description of drawings and examples of embodiments of the present invention, given as indicative but not restrictive.

EXAMPLE 1

Lens with an asymmetric reflectance, light-absorbing coating on the back surface and an anti-reflective coating on the front surface

Figure 3 illustrates a preferred embodiment of a tinted optical lens according to the present invention. The lens is a hard resin plastic ophthalmic lens coated on both sides with a scratch resistant coating.

A light absorbing coating with asymmetric reflectance is applied to the back surface of the lens. The coating is designed to produce a neutral brown attenuation of transmitted light, as well as a fashionable silver colour when viewed from the front of the lens and the anti-reflection from the wearer-side of the lens, ie. the coating is a silver mirror from the front and is anti-reflective from the back.

Table 1 lists the materials and layer thicknesses used in the asymmetric reflectance, light absorbing coating. The coating was deposited using a commercial evaporative box coater (Satis 725). TABLE 1

Composition of silver-reflecting, light absorbing coating as deposited on the back surface of the sunglass lens. The sequence of layers is relative to a light ray entering the front surface of the optical lens.

The front surface of the front wafer is coated with a standard multi-layer anti- reflective coating as shown in Table 2.

TABLE 2

Composition of anti-reflective coating as deposited on front surface of a sunglass lens with an asymmetric reflectance, light-absorbing coating on the back surface.

EXAMPLE 2

Laminated lens with an internal light-absorbing coating and an anti- reflective coating on the front surface

Figure 4 illustrates another preferred embodiment of a tinted optical lens according to the present invention. The front and back lens wafers are hard resin plastic wafers from a commercial ophthalmic lens system (Sola International Matrix^® system). The back lens wafer is supplied with its external surface pre- coated with a scratch resistant and anti-reflective coating . The external surface of the front wafer is also treated with a scratch resistant coating. The internal surfaces of both wafers are of uncoated hard resin.

A light absorbing coating with asymmetric reflectance is applied to the contact surface of the front wafer. (It may equally well be applied to the coating surface of the back wafer instead. Only the first case will be discussed for simplicity.) The coating is designed so that when the wafers are laminated, neutral brown attenuation of transmitted light is achieved, as well as an aesthetically pleasing blue colour when viewed from the front of the lens and anti- reflection from the wearer-side of the lens, ie. the coating is a blue mirror from the front and is anti-reflective from the back.

Table 3 lists the materials and layer thicknesses used in the light absorbing coating. The coating was deposited using a commercial evaporative box coater (Satis 1200).

TABLE 3

Composition of blue-reflecting, light absorbing coating as deposited inside the laminated sunglass lens. The sequence of layers is relative to a light ray entering the front surface of the optical lens.

The front surface of the front wafer is coated with a standard multi-layer anti-reflective coating as shown in Table 4.

TABLE 4

Composition of anti-reflective coating as deposited on front surface of laminated sunglass lens with internal mirror.

Comparison of laminated lenses with and without the anti-reflective coating on the front surface of the lens confirms that the anti-reflective coating of the invention is extremely effective in suppressing ghost images arising from internal reflections in the laminated, internally-mirrored sunglass lens.

Finally, it is to be understood that various alterations, modifications and/or additions may be made without departing from the spirit of the present invention as outlined herein.

Claims

1. An optical lens including a front surface; and a back surface; the optical lens including a light reflective or mirror coating on the rear surface of the lens; and an anti-reflective coating on the front surface of the lens.

2. An optical lens according to Claim 1 , wherein the light reflective or mirror coating is an asymmetric reflectance light absorbing coating.

3. An optical lens according to Claim 2, wherein the asymmetric reflectance light absorbing coating is a multi-layer metal-dielectric coating; the dielectric materials being selected from one or more of SiO, Si0₂, Zr0₂, AI2O3, TiO, Ti0₂, Ti₂0₃, Y₂0₃, Yb₂O_s, MgO, Ta₂05, Ce0₂ and Hf0₂, MgF₂, AIF₃, BaF₂, CaF₂, Na₃AIF₆, Ta₂05 and Na5AI₃FI1_3j and Si₃N4 and AIN; and the metallic material selected from metals, metal oxides or nitrides of one or more of Niobium (Nb), Chromium (Cr), Tungsten (W), Tantalum (Ta), Tin (Sn), Palladium (Pd), Nickel (Ni) or Titanium (Ti).

4. An optical lens according to Claim 3, wherein the asymmetric reflectance, light absorbance coating further includes compatible dielectric layers of suitable thickness to provide a desired colour to the optical lens.

5. An optical lens according to Claim 3, wherein the asymmetric reflectance light absorbing coating includes alternating layers of silica (Si0₂) and chromium (Cr) or Niobium (Nb) metal; and wherein the thickness and/or number of the respective layers are selected to provide an anti-reflective effect on the eye side of the optical lens and a desired colour on the other side of the optical lens.

6. An optical lens according to Claim 5, wherein the asymmetric reflectance, light absorbing coating includes an additional titanium dioxide layer or layers of such a thickness to provide a desired colour to the optical lens.

7. An optical lens according to Claim 1 , wherein the anti-reflective coating on the front surface includes alternating layers of low and high refractive index materials.

8. An optical lens according to claim 7, wherein the low and high refractive index layers are formed from dielectric materials selected from SiO, Si0₂, Zr0₂, Al₂0₃, TiO, Ti0₂, Ti₂0₃, Y₂0₃, Yb₂0₃, MgO, Ta₂05, Ce0₂ and Hf0₂, MgF₂, AIF₃, BaF₂, CaF₂, Na₃AIF_6l Ta₂05 and Na5AI₃FI1₃, and Si₃N4 and AIN.

9. An optical lens according to Claim 8, wherein the low refractive index layer is formed of silica (Si0₂) or magnesium fluoride (MgF₂); and the high refractive index layers are formed from a combination of titanium dioxide and praseodymium oxide (Ti0₂ + Pr₂0₃).

10. An optical lens according to Claim 1 , wherein the lens is a corrective lens.

.

11. An optical lens according to Claim 10, wherein the lens is a corrective sunglass lens.

12. An optical lens according to Claim 1 , wherein the light reflective or mirror coating functions as a substantially balanced reflectance coating from the centre to a radius proximate the edge of the lens.

13. An optical lens according to Claim 12, wherein the lens includes a surface of high curvature and the light reflective or mirror coating is deposited on the high curvature surface.

14. An optical lens according to Claim 1 , wherein the anti-reflective coating functions as a substantially balanced reflectance coating from the centre to a radius proximate the edge of the lens.

15. An optical lens according to Claim 14, wherein the lens includes a surface of high curvature.

16. An optical lens according to Claim 1 , wherein the light reflective or mirror coating and anti-reflective coating in combination exhibit a substantially balanced reflectance coating from the centre to a radius proximate the edge of the lens.

17. An optical lens according to Claim 16, wherein the lens includes a surface of high curvature.

18. A laminate optical lens including a front lens wafer including a front surface; and a first contact surface; a complementary back lens wafer including a second contact surface; the laminate optical lens including a first light reflective or mirror coating on a contact surface of the front or back lens wafer; and an anti-reflective coating on the front surface of the front lens wafer.

19. A laminate optical lens according to Claim 18, wherein the light reflective or mirror coating is an asymmetric reflectance light absorbing multi-layer metal-dielectric coating; and the anti-reflective coating is a multi-layer coating including alternate high and low refractive index layers, the high and low refractive index layers being formed of a dielectric material.

20. A laminate optical lens according to Claim 18, wherein the lens is a corrective lens.

21. A laminate optical lens according to Claim 18, wherein the lens is a corrective sunglass lens.

22. A laminate optical lens according to Claim 19, wherein the light reflectance or mirror coating or anti-reflective coating or the coatings in combination exhibit(s) a substantially balanced reflectance coating from the centre to a radius proximate the edge of the lens.

23. A front lens wafer for an optical lens including a front surface; and a contact surface; the front lens wafer including an anti-reflective coating on the front surface; and a reflective or mirror coating on the contact surface thereof.

24. A front lens wafer according to Claim 23, wherein the light reflective or mirror coating is an asymmetric reflectance light absorbing multi-layer metal- dielectric coating; and the anti-reflective coating is a multi-layer coating including alternate high and low refractive index layers, the high and low refractive index layers being formed of a dielectric material.

25. A multi-coated optical lens including a front surface; and a back surface; the multi-coated optical lens including a light reflective or mirror coating on the back surface thereof; and an anti-reflective coating on the front surface thereof; and one or more secondary coatings or films which provide a desirable optical and/or chemical and/or mechanical property to the optical lens.

26. A multi-coated optical lens according to Claim 25, wherein the secondary coating is selected from one or more of an anti-reflective, hydrophobic abrasion resistant, impact resistant, or polarising or photochromic coating, the secondary coating(s) overlaying or underlaying the anti-reflective coating, or is applied to a second surface of the lens.

27. A multi-coated optical lens according to Claim 26, wherein the lens is a corrective sunglass lens.

28. A multi-coated optical lens including a laminate optical lens including a front lens wafer including a front surface; and a first contact surface; a complementary back lens wafer including a second coated surface; the laminate optical lens including a first light-reflective or mirror coating on a contact surface of the front or back lens wafer; an anti-reflective coating on the front surface of the front lens wafer; and one or more secondary coatings which provide a desirable optical and/or chemical and/or mechanical property to the optical lens.

29. A multi-coated optical lens according to Claim 28, wherein the secondary coating is selected from one or more of an anti-reflective, hydrophobic, abrasion resistant, impact resistant, or polarising or photochromic coating, the secondary coating(s) overlaying or underlaying the anti-reflective coating or is applied to a second surface of the lens.

30. A multi-coated optical lens according to Claim 29, wherein a polarising film or coating is included between the front and back lens wafers.

31. A method for preparing a coated optical lens, which method includes providing an optical lens including a front surface; and a back surface; materials suitable to form an anti-reflective coating; materials suitable to form a light reflective or mirror coating; depositing the anti-reflective materials on the front surface to form an anti- reflective coating thereon; and depositing the light reflective materials on a second surface of the lens to form a light reflective or mirror coating.

32. A method according to Claim 31 , wherein the materials suitable to form an anti-reflective coating include a dielectric material of low refractive index and a dielectric material of high refractive index, the method further including depositing overlapping layers of low refractive index dielectric material and high refractive index dielectric material on the front surface of the optical lens, the number and/or thickness of the respective layers being selected to provide a desired anti-reflective effect.

33. A method according to Claim 32, wherein a combination of praseodymium oxide and titanium dioxide (Pr θ₃ / Tiθ₂) and silica (Si0₂) are deposited as alternating layers.

34. A method according to Claim 32, wherein the materials suitable to form a light reflective or mirror coating include a dielectric material selected from SiO, Si0₂, Zr0₂, AI₂θ3, TiO, Ti0₂, Ti₂θ3, Y₂0₃, Yb₂0₃₎ MgO, Ta₂05, Ce0₂ and Hf0₂, MgF₂, AIF₃, BaF₂, CaF_2j Na₃AIF₆, Ta₂05 and Na5AI₃FI1₃, and Si₃N4 and AIN; and a metallic material selected from metals, metal oxides or nitrides of one or more of Niobium (Nb), Chromium (Cr), Tungsten (W), Tantalum (Ta), Tin (Sn), Palladium (Pd), Nickel (Ni) or Titanium (Ti); the method further including depositing overlapping layers of dielectric material and metallic material to form an asymmetric reflectance light absorbing coating on the front surface of the optical lens.

35. A method according to Claim 31 , wherein when the optical lens is a laminate optical lens, materials suitable to form the light reflective or mirror coating are deposited on a contact surface of the front or back lens wafer.

36. A method according to Claim 35, wherein the deposition step is a vacuum deposition step.

37. Spectacles including a spectacle frame; and a pair of optical lenses, each optical lens including a front surface; and a back surface; the optical lens including a light reflective or mirror coating on the rear surface of the lens; and an anti-reflective coating on the front surface of the lens.

38. Spectacles according to Claim 37, wherein each optical lens is a corrective lens.

39. Spectacles according to Claim 38, wherein each optical lens is a corrective sunglass lens.