AU1536600A - Coated lens to reduce visual perception of stains - Google Patents

Description

WO 00/31569 1 PCT/AU99/01025 COATED LENS TO REDUCE VISUAL PERCEPTION OF STAINS The present invention relates to optical articles bearing a coating which reduces the visual perception of stains. The optical articles according to the present invention are preferably 5 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 10 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-reflection coatings for reducing side glare or "mirror" (or 15 "interference") coatings for producing fashionable lens colours. Mirror coatings may also have other benefits such as contrast enhancement or the reduction of transmitted ultra-violet or infra-red light. Anti-reflection coatings known in the prior art enhance vision by reducing parasitic reflections that can disturb the wearer. They are generally deposited on 20 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 his eyes to others. Both mirror and anti-reflection coatings known in the art are multilayer 25 structures that achieve their optical properties by means of thin film interference effects. When stained, e.g. by facial oils or fingerprints, the stain on the surface of the lens is highly visible, as it contrasts greatly with adjacent clean areas of the lens. Because of this high visibility, the lens is perceived to be difficult to clean and to keep clean.

WO 00/31569 2 PCT/AU99/01025 2 The most common approach established in the prior art to make such lenses easier to clean is to coat the mirror or anti-reflection coating with an additional hydrophobic layer, which has a low surface energy and reduces the tendency for oily contaminants to attach to the coating. While this an 5 improvement, oils nevertheless still can soil the coating, and when they do, they are highly visible. The hydrophobic layer also has little effect on staining by greasy or fatty contaminants. Since it would not appear possible to completely eliminate soiling of the coating by oily or greasy contaminants, another approach might be to try to reduce 10 the visibility of stains when they do occur. Such a proposal is made in United States Patent 4,070,097 (Gelber). Gelber describes an anti-reflection coating for ophthalmic lenses that is designed to reduce the visibility of stains such as fingerprints and facial oils. The patent is restricted to a two-layer, metal-dielectric anti-reflection coating so is of limited application. 15 Similarly, United States Patent 5,847,876 (Ferrante and Ott) describes an anti-reflection coating that is "fingerprint-resistant". The patent is restricted to two dielectric layers on glass substrates, so is again of limited application. It would accordingly be a significant advance in the art if ophthalmic lenses could be provided with a coating or coatings of general applicability which could 20 reduce the visibility of stains such as fingerprints and facial oils. 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 a coated optical lens including 25 a lens element; and a stain masking coating on a surface of the lens element which coating WO 00/31569 3 PCT/AU99/01025 does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; is a multi-layer coating, the thickness and/or number of whose 5 layers are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating. In accordance with the present invention, one or more surfaces of an optical lens may be coated with the stain masking coating. The lens element may be either optically clear or tinted (light absorbing), 10 such as a sunglass lens, ophthalmic lens element, visor or the like. A sunglass lens is preferred. By the term "ophthalmic lens element", as used herein, we mean all forms of individual refractive optical bodies employed in the ophthalmic arts, including, but not limited to, lenses, lens wafers and semi-finished lens blanks requiring 15 further finishing to a particular patient's prescription. Where the lens element is an ophthalmic lens element, the ophthalmic lenses may be formed from a variety of different lens materials, including glass and particularly from a number of different polymeric plastic resins. A common ophthalmic lens material is diethylene glycol bis (allyl carbonate) or CR39 (PPG 20 Industries). 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 stain masking coating is a multi-layer or interference coating. By "stain masking," we mean that the appearance of the coating is substantially similar 25 either when it is clean or when it is stained by oily or greasy contaminants. The visual appearance of the coated optical lens in reflected light can be quantified by measuring its reflectance spectrum in a spectrophotometer. This spectral information may be reduced to three colour coordinates - a "lightness" WO 00/31569 4 PCT/AU99/01025 corresponding primarily to the luminous intensity of the reflected light, and two chromatic attributes, the "hue" and "chroma" corresponding to the general colour (eg. red, blue, green etc.) and its vividness. ("The Measurement of Appearance", 2 n d ed., R.S. Hunter and R.W. Harold, Wiley, New York, 1987). The term "colour" 5 as used here refers to all three colour coordinates. 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. A CMC colour variation of AEcMc(2:1)=1 iS the limit of acceptability for textiles. Applicants have found that this is too stringent a tolerance for changes in 10 appearance when anti-reflection or mirror coated lenses in the ophthalmic industry are stained. Applicants have observed that colour changes of up to 11 occurring when a mirror coated sunglass lens is stained are quite acceptable. Preferably the reflected colour shift (AE), when stained, is 8 or less, more preferably 6 or less. 15 It will be understood that optical interference coatings are designed to function in air, that is in a medium of refractive index equal to one. Accordingly, when stained, e.g. by body oils, and the like, the refractive index of which is approximately 1.3-1.6, there is normally a highly visible change in perceived colour. By calculating and minimising the colour difference AE between the clean 20 and stained reflectance of a hypothetical coating, it is possible to specifically design the stain masking coating of this invention. Accordingly, the stain masking coating may be designed by selecting the number and/or thickness and/or materials of the layers in a multilayer coating utilising suitable computer software. In a preferred form, the stain masking coating may function as a mirror 25 coating for a sunglass lens. Such a coating may preferably be applied to the convex surface of the lens. In another form, the stain masking coating may function as an anti-reflective coating, applied to the concave surface of a sunglass lens or on both surfaces of an ordinary lens. Accordingly, in one embodiment, wherein the stain masking coating 30 functions as a reflective (mirror) coating; and includes WO 00/31569 5 PCT/AU99/01025 a plurality of layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. 5 The lower and higher refractive index layers may be formed from any suitable material. The lower and higher refractive index layers may be formed of a dielectric material. Preferably the dielectric layers may be formed from metal oxides, fluorides or nitrides and diamond-like carbon. Preferably the dielectric material is selected from one or more of A1 2 0 3 , BaTiO 3 , Bi 2 0 3 , B 2 03, CeO 2 , 0r 2 0 3 , 10 Ga 2 03, GeO 2 , Fe 2 03, HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 03, MgO, Nd 2 03, Nb 2 0 5 , Pr 2 0 3 , Sb 2 03, Sc 2 03, SiO, SiO 2 , SnO 2 , Ta 2 05, TiO, TiO 2 , TiO 3 , W0 3 , Y 2 0 3 , Yb 2 03, ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF 2 , CeF 3 , HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3

AIF

6 , Na 5

AI

3 FI1 4 , NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3

N

4 , AIN. Polymeric materials or dielectric materials including dopants of metal compounds or other materials may 15 also be used. In a particularly preferred form the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material and the higher refractive index layers are formed from a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 0 3 ). 20 Accordingly, in a preferred aspect there is provided a coated optical lens including a lens element; and a stain masking reflective (mirror) coating on a surface of the lens element which coating 25 exhibits a reflected colour shift (AE) of 6 or less when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; and includes at least three layers of differing refractive index whose thickness is selected to provide a desired reflectance; 30 the lower refractive index layers including a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; WO 00/31569 6 PCT/AU99/01025 the higher refractive index layers including titanium dioxide (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 0 3 ). Preferably the stain masking coating includes a first adhesion layer. More preferably the adhesion layer is a metallic, e.g. Chromium (Cr) layer. 5 In a preferred form, the stain masking coating may include a total of 4 to 6 alternating higher and lower index layers, preferably 4 to 6 alternating layers. Alternatively the stain masking coating functions as a reflective (mirror) coating and includes a plurality of dielectric and metallic layers, wherein the thickness and/or 10 number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. Preferably the dielectric materials may be formed from metal oxides, fluorides or nitrides and diamond-like carbon. Preferably the dielectric material is selected from one or more of A1 2 0 3 , BaTiO 3 , Bi 2 03, B 2 0 3 , CeO 2 , Cr 2

O

3 , Ga 2 0 3 , GeO 2 , 15 Fe 2 0 3 , HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 03, MgO, Nd 2 0 3 , Nb 2 05, Pr 2 03, Sb 2 0 3 , Sc 2 03, SiO, SiO 2 , SnO 2 , Ta 2 05, TiO, TiO 2 , TiO 3 , WO 3 , Y 2 0 3 , Yb 2 03, ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF 2 , CeF 3 , HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3

AIF

6 , Na 5

A

3 FI1 4 , NdF3, PbF2, PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3

N

4 , AIN. Preferably the metallic materials may be selected from the metals, metal oxides or nitrides of one or more of Aluminium 20 (Al), Chromium (Cr), Niobium (Nb), Nickel (Ni), Palladium (Pd), Tin (Sn), Tantalum (Ta), Titanium (Ti), Tungsten (W) or Zirconium (Zr). A silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material is preferred for the dielectric layers. Chromium (Cr) or Niobium (Nb) is preferred for the light absorbing metallic 25 layers.

WO 00/31569 7 PCT/AU99/01025 Accordingly, in a particularly preferred embodiment there is provided a coated optical lens including a lens element; and a stain masking reflective (mirror) coating on a surface of the lens element 5 which coating exhibits a reflected colour shift (AE) of 6 or less when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; and includes at least three dielectric and metallic layers; 10 wherein the dielectric layers are formed of a dielectric material and include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the metallic materials include Chromium (Cr) or Niobium (Nb). In an alternative aspect of the present invention, the stain masking coating 15 functions as an anti-reflective coating and includes three or more layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained Preferably the lower and higher refractive index layers are formed of a 20 dielectric material selected from one or more of A1 2 0 3 , BaTiO 3 , Bi20 3 , B 2 0 3 , CeO 2 , Cr 2 03, Ga 2 03, GeO 2 , Fe 2 03, HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 03, MgO, Nd 2 03, Nb 2 05, Pr 2 03, Sb 2 03, Sc 2 03, SiO, SiO 2 , SnO 2 , Ta 2 05, TiO, TiO 2 , Ti 2 03, Ti 3 05, W03,

Y

2 0 3 , Yb 2 0 3 , ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF 2 , CeF3, HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3

AIF

6 , Na 5

AI

3 FI14, NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3

N

4 , AIN, or diamond-like 25 carbon. Polymeric materials or dielectric materials including dopants of metal compounds or other materials may also be used. More preferably the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the higher refractive index layers are formed from titanium dioxide (TiO 2 ) or 30 a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 0 3

).

WO 00/31569 8 PCT/AU99/01025 Accordingly, in a particularly preferred embodiment, there is provided a coated optical lens including a lens element; and a stain masking, anti-reflective coating on a surface of the lens element 5 which coating exhibits a reflected colour shift (AE) of 6 or less when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; and includes at least three layers of differing refractive index whose 10 thickness is selected to provide a desired reflectance; the lower refractive index layers including a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; the higher refractive index layers including titanium dioxide (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 0 3 ). 15 In an alternative embodiment of this aspect of the present invention, the stain masking coating functions as an anti-reflective coating and includes three or more dielectric and metallic layers, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. 20 Preferably, the dielectric layer(s) is formed from a dielectric material selected from one or more of A1 2 0 3 , BaTiO 3 , Bi20 3 , B 2 0 3 , CeO 2 , Cr20 3 , Ga 2 03, GeO 2 , Fe 2 03, HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 03, MgO, Nd 2 03, Nb 2 05, Pr 2 03, Sb 2 03, Sc 2 03, SiO, SiO 2 , SnO 2 , Ta 2 0 5 , TiO, TiO 2 , TiO 3 , WO 3 , Y 2 0 3 , Yb 2 0 3 , ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF2, CeF 3 , HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3

AIF

6 , Na 5

AI

3 FI14, NdF 3 , PbF 2 , 25 PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3

N

4 , AIN, or diamond-like carbon; and the metallic layer(s) is formed from a metallic material selected from the metals, metal oxides or metal nitrides of one or more of Aluminium (AI), Chromium (Cr), Niobium (Nb), Nickel (Ni), Palladium (Pd), Tin (Sn), Tantalum (Ta), Titanium (Ti), Tungsten (W) or Zirconium (Zr). 30 More preferably, the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the metallic material(s) is Niobium (Nb) or Chromium WO 00/31569 9 PCT/AU99/01025 (Cr). Accordingly, in a particularly preferred embodiment, there is provided a coated optical lens including a lens element; and 5 a stain masking, anti-reflective coating on a surface of the lens element which coating exhibits a reflected colour shift (AE) of 6 or less when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; and 10 includes at least three layers of differing refractive index whose thickness is selected to provide a desired reflectance; wherein the dielectric layers are formed of a dielectric material and include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and 15 the metallic materials include Chromium (Cr) or Niobium (Nb). The optical lens 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 lens element; and 20 a coating on surface of the lens element that does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; and a secondary coating which provides a desirable optical and/or mechanical property to the optical article. 25 The secondary coating may underlay the stain masking coating or be applied to a second surface of the lens element. The secondary coating may be of any suitable type. The secondary coating may be one or more of an anti-reflective, abrasion resistant, or impact-resistant hydrophobic and adhesion coatings. An abrasion-resistant coating is preferred.

WO 00/31569 10 PCT/AU99/01025 The combination of an abrasion resistant coating and an anti-reflective coating is particularly preferred. In a preferred embodiment of this aspect of the present invention, where the stain masking coating is a reflective coating, the secondary coating is an anti 5 reflective coating applied to the opposite surface of the lens element. In a further preferred embodiment, the stain masking coating functions as a reflective (mirror) coating or anti-reflective coating as described above. In a further preferred aspect, one or both surfaces of the optical article may be subjected to a surface treatment to improve bondability and/or compatibility of 10 the stain masking 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. 15 The surface treatment, alternatively or in addition, may include incorporating another adhesion 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. In a further aspect of the present invention, there is provided a method for 20 preparing a coated optical lens, which method includes providing a lens element; a metallic material or a higher refractive index material; and a lower refractive index material; 25 depositing overlapping layers of lower refractive index material and higher refractive index material or metallic material on a surface of the optical lens element, the number and/or thickness of the respective layers being selected to produce a stain masking coating which coating does not substantially vary in colour when stained by contaminants 30 having a refractive index in the range of approximately 1.3 to 1.6; WO 00/31569 11 PCT/AU99/01025 is a multi-layer coating, the thickness and/or number of which are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating. In a preferred aspect the high and low refractive index materials, preferably 5 TiO 2 or Pr 2 03/TriO 2 and SiO 2 , are deposited as alternating layers. Alternatively the metallic material and low refractive index materials are deposited as alternating layers. More preferably, the metallic material is Niobium (Nb) or Chromium (Cr). The deposition step may be a vacuum deposition step. The deposition step 10 may be conducted in a coating apparatus. A box coater or sputter coater may be used. 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. 15 In the figures: Figure 1 illustrates a known anti-reflective coating on the surface of a lens when contaminated by an oil droplet. Figure 2 illustrates a similar view to Figure 1 where the oil is able to wet the coating surface. 20 Figure 3 illustrates the measured reflectance spectra of a hard resin lens coated on both sides with a stain-masking coating according to the present invention. Figure 4 illustrates the measured reflectance spectra of a hard resin lens coated on both sides with a typical prior art anti-reflection coating. 25 Figure 5 illustrates the measured reflectance spectra of a hard resin lens WO 00/31569 12 PCT/AU99/01025 coated on one side with a stain-masking blue mirror coating according to the present invention. Figure 6 illustrates the measured reflectance spectra of a hard resin lens coated on one side with a typical, prior art blue mirror coating. 5 EXAMPLE 1 Figure 1 illustrates a typical known anti-reflective coating on the surface of a standard optical lens. For light incident from air onto a clean portion of the lens, the luminous reflectance (i.e. that visible to the human eye) is designed to be as low as possible (typically 0.5%). Only the front surface of the lens is shown - the 10 other surface of the lens would normally be coated identically. When the coating is stained by a liquid contaminant such as finger oil, the liquid either wets the surface of the lens or "beads up," depending on the contaminant and how it interacts with the surface of the coating. Commercial anti reflective ophthalmic lenses may be treated with a "hydrophobic" surface layer, 15 which has very low surface energy and is not easily wet by any liquid. It causes oily contaminants to bead on the surface of the lens, and they are easily removed by wiping, due to the low attraction of the liquid to the hydrophobic surface. This is the situation illustrated in Figure 1. However, if the contaminant is not a liquid, the hydrophobic coating is less effective in reducing soiling. 20 When the contaminant is able to soil the coating, either because the contaminant is a liquid able to spread on the surface or because it is a fatty solid, the situation is illustrated in Figure 2. The soiled area of the coating has two components of reflection - a first reflection from the surface of the contaminant and a second reflection from the coating underneath the contaminant. Typically 25 the layer of contamination on the surface of the coating will be at least of the order of several microns in thickness. Since this thickness is much greater than the wavelengths of visible light, the two reflections do not interfere coherently. The top reflection then is spectrally white, with an intensity given by WO 00/31569 13 PCT/AU99/01025 Rairicontaminant = (ncontaminant -1 )2/( ncontaminant +1) 2 Since ncontaminant ~ 1.3 for oily contaminants, the top reflection is of the order of 2%, as shown in the figure. This reflection is unavoidable and cannot be eliminated by interference effects. 5 The second reflection Rcontaminant/coating, from the coating underneath the oily or greasy contaminant, has an intensity determined by the way the coating behaves when light is incident from a medium of refractive index ncontaminant ~ 1.3. The reflection is determined by the way sub-reflections from the multiple layers of the coating interfere. According to the present invention, the intensity of the 10 second reflection may be minimised and made close to zero. Therefore, the minimal reflectance from the soiled coating is 2 + 0 = 2%, which is still less than that from the uncoated substrate (4% if nsubstrate = 1.5). Furthermore, the coating may be designed according to the present invention so that there is no perceptible change in colour of the coating whether it 15 is clean or stained. In this case, the stain is not easily seen on the lens. However, a compromise must be reached between designing the coating to best mask stains (which necessarily implies a reflectance of 2% when clean or soiled), and designing the coating to be as anti-reflective as possible when clean (which corresponds to a reflectance of 0%). 20 Table 1 illustrates the optical design for a stain-masking anti-reflection coating according to the present invention. Figure 3 illustrates the measured reflectance spectra of a hard resin lens coated on both sides with the coating, both when the coating is clean and when one surface of the coated lens is stained by a liquid of refractive index n=1.34. Clearly the reflectance is barely changed 25 when the coating is soiled, and consequently stains are difficult to see on the lens. The reflectance of the uncoated substrate is also shown in the figure, demonstrating that the coating is indeed anti-reflective.

WO 00/31569 14 PCT/AU99/01025 TABLE 1 Optical design for a stain-resistant anti-reflection coating Layer Thickness (nm) Hard resin substrate Cr adhesion layer 0.5 TiO2 (n(500 nm) =2.15) 5.9 SiO2 59.8 TiO2 (n(500 nm) =2.15) 12.5 SiO2 121 For comparison, Figure 4 shows the reflectance spectrum of a known 5 commercial anti-reflection coating, both when clean and when stained on one side by a liquid of refractive index n=1.34. While the coating is more anti-reflective than the stain-masking coating of Figure 3 when clean, stains affect the reflectance of the coating in a far more significant manner. It will be appreciated that on this optical lens, oily or greasy contaminants will be far more visible. 10 EXAMPLE 2 The first example of the invention is a multi-layer coating that achieves a satisfactory compromise between anti-reflectivity and stain minimisation and the corresponding coated article. For mirror coated lenses, (as opposed to anti-reflection coated lenses) the 15 same analysis for the optical effect of oily or greasy stains applies, but in desiring to minimise the visibility of stains, there is no longer the additional constraint of wishing to minimise the intensity of reflections. The coating may be designed to reflect with the same colour whether clean or stained so that stains are less visible. 20 Table 2 illustrates the optical design for a stain-masking, blue mirror coating WO 00/31569 15 PCT/AU99/01025 according to the present invention. Figure 5 illustrates the measured reflectance spectra of a hard resin lens coated on one side with the coating, both when the coating is clean and when stained by a liquid of refractive index n=1.34. The reflectance is only slightly changed when the coating is soiled, and particularly 5 near 550 nm where the human eye is most sensitive, the reflectance is almost unchanged when the coating is soiled. Consequently stains are difficult to see on the lens, as indeed is observed. TABLE 2 Optical design for a stain-resistant, blue mirror coating Layer Thickness (nm) Tinted hard resin substrate Cr adhesion layer 0.5 TiO2 (n(500 nm) =2.15) 162 SiO2 69 TiO2 (n(500 nm) =2.15) 149 SiO2 20 10 For comparison, Table 3 is the design for a prior art blue mirror coating that is identical to the previous coating (to the naked eye) when clean, but not having been specially designed for stain-masking performance, shows a more substantially modified reflectance spectrum when stained by a liquid of refractive 15 index n=1.34, as indicated in Figure 6. It will be appreciated that on this lens, greasy contaminants are more visible than for the previous example.

WO 00/31569 6 PCT/AU99/01025 TABLE 3 Optical design for a prior art, blue mirror coating Layer Thickness (nm) Tinted hard resin substrate Cr adhesion layer 0.5 TiO2 (n(500 nm) =2.15) 53 SiO2 63.6 TiO2 (n(500 nm) =2.15) 42.3 SiO2 147 EXAMPLE 3 5 The stain masking mirror coating is not limited in colour to blue. With appropriate coating design software, it is possible to specifically design stain masking mirror coatings of a wide variety of hues and lightnesses. Table 4 summarises the coating designs and measured colours of both stain masking and non-stain masking mirror coatings that have been variously produced on tinted 10 CR39, glass and polycarbonate lenses by the Applicants. The thicknesses of the SiO 2 , TiO 2 and TiO 2 /Pr 2 0 3 layers are indicated in nanometres. The colour coordinates are as measured for clean coatings and the AE is the colour shift when the coatings are stained by a liquid contaminant of refractive index n=1.466. The illuminant is the CIE Illuminant C. Also indicated are the stained colour shifts 15 expected from calculations, from which it can be seen that the design calculations give a good indication of the performance likely to be achieved in real coatings.

WO00/31569 17 PCT/AU99/01025 TABLE 4 Stain masking and non-stain masking mirror coatings Amber Pink Blue Orange Stain Normal Stain Normal Stain Normal Stain Normal mask mask mask mask Lens Cr 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 TiO 2 /Pr 2

O

3 95 42 165.5 94.7 TiO 2 31.6 60.1 117 98 SiO2 16 155 207 34.1 43.1 27.9 58 74 TiO 2 /Pr 2

O

3 180.8 40.7 156.2 TiO 2 47.5 178.5 110 97 SiO 2 94.6 58.7 152.2 170 111.6 10.5 52 Lightness L* 36 39 33 38 39 32 36 38 Chroma C* 20 21 51 60 40 54 36 40 Hue h* 63 71 307 317 275 293 34 45 Stained AE 8 17 4 15 6 30 6 26 (Measured) Stained AE 5 18 1 12 5 10 3 25 (Calculated) Figure 7 illustrates the colour changes seen when the mirrors are soiled by 5 a liquid contaminant of refractive index n=1.466. Observations suggest that colour changes of less than AE-6 are imperceptible and colour changes of less than AE-11 are perceptible but acceptable. Clearly it is possible to produce the stain masking coating of the invention in a broad range of colours, and for a given desired mirror colour, the visibility of 10 stains can be effectively minimised. Table 5 shows calculated designs for stain masking mirror coatings of different colours.

WO 00/31569 18 PCT/AU99/01025 TABLE 5 Further stain masking mirror coating designs Yellow Blue Green White Red Violet Lens Cr 0.5 0.5 0.5 0.5 0.5 0.5 TiO 2 90 123 125 67 101 142 SiO 2 125 154 160 115 129 63 TiO 2 102 120 264 67 87 47 SiO 2 170 106 81 176 137 159 TiO 2 107 94 SiO 2 83 80 Lightness L* 34 19 28 76 21 45 Chroma C* 49 42 35 72 44 64 Hue h* 71 292 173 103 7 292 Stained AE 7.1 3.6 7.3 4.9 4.1 3.4 It will be understood that the invention disclosed and defined in this 5 specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims (49)

1. A coated optical lens including a lens element; and a stain masking coating on a surface of the lens element which coating 5 does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; is a multi-layer coating, the thickness and/or number of which are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating. 10

2. A coated optical lens according to Claim 1 wherein the stain masking coating functions as a reflective (mirror) coating; and includes a plurality of layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; 15 the reflectance not varying substantially in colour when stained.

3. A coated optical lens according to Claim 2 wherein the reflected colour shift (A E), when stained, is 11 or less.

4. A coated optical lens according to Claim 3, wherein the reflected colour shift (AE), when stained, is 6 or less. 20

5. A coated optical lens according to Claim 2, wherein the layers of differing refractive index are formed of a dielectric material selected from one or more of A1 2 03, BaTiO 3 , Bi 2 03, B 2 0 3 , CeO 2 , Cr203, Ga 2 03, GeO 2 , Fe 2 0 3 , HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 0 3 , MgO, Nd 2 03, Nb 2 05, Pr 2 O 3 , Sb 2 0 3 , Sc 2 0 3 , SiO, SiO 2 , SnO 2 , Ta 2 05, TiO, TiO 2 , Ti 2 03, Ti 3 05, W0 3 , Y 2 0 3 , Yb 2 03, ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF 2 , CeF3, 25 HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3 AIF 6 , Na 5 A 3 FI14, NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3 N 4 , AIN, diamond-like carbon, polymeric materials or doped dielectric materials.

6. A coated optical lens according to Claim 5, wherein the stain masking coating includes four or more layers of differing refractive index. WO 00/31569 20 PCT/AU99/01025

7. A coated optical lens according to Claim 6, wherein the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; the higher refractive index layers are formed from titanium dioxide 5 (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 03); and the reflected colour shift (A E), when stained, is 6 or less.

8. A coated optical lens according to Claim 6, wherein the stain masking coating includes six or more layers of differing refractive index. 10

9. A coated optical lens according to Claim 8, wherein the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; the higher refractive index layers are formed from titanium dioxide (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium 15 oxide (Pr 2 0 3 ); and the reflected colour shift (AE), when stained, is 6 or less.

10. A coated optical lens according to Claim 1 wherein the stain masking coating functions as a reflective (mirror) coating and includes a plurality of dielectric and metallic layers, wherein the thickness and/or 20 number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained.

11. A coated optical lens according to Claim 10 wherein the reflected colour shift (AE), when stained, is 11 or less.

12. A coated optical lens according to Claim 11 wherein the reflected colour 25 shift (AE), when stained, is 6 or less. WO 00/31569 21 PCT/AU99/01025

13. A coated optical lens according to Claim 10 wherein the dielectric layer(s) is formed from a dielectric material selected from one or more of A1 2 0 3 , BaTiO 3 , Bi 2 0 3 , B 2 0 3 , CeO 2 , Cr 2 03, Ga 2 0 3 , GeO 2 , Fe 2 03, HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 O0, MgO, Nd 2 03, Nb 2 05, Pr 2 0 3 , Sb 2 03, Sc 2 0 3 , SiO, SiO 2 , SnO 2 , Ta205, TiO, TiO 2 , TiO 3 , 5 WO 3 , Y 2 0 3 , Yb 2 03, ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF 2 , CeF 3 , HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3 AIF 6 , Na 5 A 3 FI1 4 , NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3 N 4 , AIN, diamond like carbon, polymeric materials or doped dielectric materials; and the metallic layer(s) is formed from a metallic material selected from the metals, metal oxides or metal nitrides of one or more of Aluminium (Al), Chromium 10 (Cr), Niobium (Nb), Nickel (Ni), Palladium (Pd), Tin (Sn), Tantalum (Ta), Titanium (Ti), Tungsten (W) or Zirconium (Zr).

14. A coated optical lens according to Claim 13, wherein the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material.

15. A coated optical lens according to Claim 14, wherein the metallic 15 material(s) is Niobium (Nb) or Chromium (Cr) and the reflected colour shift (AE), when stained, is 6 or less.

16. A coated optical lens according to Claim 10 wherein the thickness and/or number of the respective layers are selected to provide attenuation of transmitted light and an anti-reflective effect on the eye side 20 of the optical lens, as well as the desired reflectance on the other side of the lens; the reflectance not varying substantially in colour when stained.

17. A coated optical lens according to Claim 1, wherein the stain masking coating functions as an anti-reflective coating and includes three or more layers of differing refractive index, wherein the thickness and/or number of the respective 25 layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained.

18. A coated optical lens according to Claim 17 wherein the reflected colour shift (A E), when stained, is 11 or less. WO 00/31569 PCT/AU99/01025 22

19. A coated optical lens according to Claim 18, wherein the reflected colour shift (AE), when stained, is 6 or less.

20. A coated optical lens according to Claim 17 wherein the lower and higher refractive index layers are formed of a dielectric material selected from one or 5 more of Al 2 0 3 , BaTiO 3 , Bi 2 0 3 , B 2 0 3 , CeO 2 , 0r 2 0 3 , Ga 2 03, GeO 2 , Fe20 3 , HfO 2 , n 2 0 3 , Indium-tin oxide, La 2 03, MgO, Nd 2 03, Nb 2 0 5 , Pr 2 03, Sb 2 03, Sc 2 03, SiO, SiO 2 , SnO 2 , Ta 2 Os, TiO, TiO 2 , Ti 2 03, Ti 3 05, WO 3 , Y 2 0 3 , Yb 2 0 3 , ZnO, ZrO 2 , AIF 3 , BaF 2 , CaF 2 , CdF 2 , CeF 3 , HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3 AIF 6 , Na 5 AI 3 FI1 4 , NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3 N 4 , AIN, diamond-like carbon, polymeric materials or doped dielectric 10 materials.

21. A coated optical lens according to Claim 20 wherein the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material.

22. A coated optical lens according to Claim 21 wherein the higher refractive index layers are formed from titanium dioxide (TiO 2 ) or a combination of titanium 15 dioxide (TiO 2 ) and praseodymium oxide (Pr 2 0 3 ) and the reflected colour shift (AE), when stained, is 6 or less.

23. A coated optical lens according to Claim 1, wherein the stain masking coating functions as an anti-reflective coating and includes three or more dielectric and metallic layers, wherein the thickness and/or 20 number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained.

24. A coated optical lens according to Claim 23 wherein the reflected colour shift (A E), when stained, is 11 or less.

25. A coated optical lens according to Claim 24, wherein the reflected colour 25 shift (AE), when stained, is 6 or less.

26. A coated optical lens according to Claim 23, wherein the dielectric layer(s) is formed from a dielectric material selected from one or more of A1 2 0 3 , BaTiO 3 , WO 00/31569 23 PCT/AU99/01025 Bi 2 0 3 , B 2 0 3 , CeO 2 , Cr20 3 , Ga 2 0 3 , GeO 2 , Fe20 3 , HfO 2 , In 2 0 3 , Indium-tin oxide, La 2 03, MgO, Nd 2 03, Nb 2 Os, Pr 2 O 3 , Sb 2 03, Sc 2 O 3 , SiO, SiO 2 , SnO 2 , Ta 2 05, TiO, TiO 2 , TiO 3 , WO 3 , Y 2 0 3 , Yb 2 03, ZnO, ZrO 2 , AIF3, BaF 2 , CaF 2 , CdF 2 , CeF 3 , HfF 4 , LaF 3 , LiF, MgF 2 , NaF, Na 3 AIF 6 , Na 5 A 3 FI1 4 , NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF 4 , ZrF 4 , Si 3 N 4 , AIN, diamond 5 like carbon, polymeric materials or doped dielectric materials; and the metallic layer(s) is formed from a metallic material selected from the metals, metal oxides or metal nitrides of one or more of Aluminium (Al), Chromium (Cr), Niobium (Nb), Nickel (Ni), Palladium (Pd), Tin (Sn), Tantalum (Ta), Titanium (Ti), or Tungsten (W). 10

27. A coated optical lens according to Claim 26, wherein the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material.

28. A coated optical lens according to Claim 27, wherein the metallic material(s) is Niobium (Nb) or Chromium (Cr) and the reflected colour shift (AE), when stained, is 6 or less. 15

29. A coated optical lens according to Claim 23 wherein the thickness and/or number of the respective layers are selected to provide attenuation of transmitted light and an anti-reflective effect on the eye side of the optical lens, as well as the desired reflectance on the other side of the lens; the reflectance not varying substantially in colour when stained. 20

30. A multi coated optical lens including a lens element, a stain masking coating on a surface of the lens element, which coating does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 25 1.3 to 1.6; is a multi-layer coating, the thickness and/or number of which are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating; and a secondary coating which provides a desirable optical and/or mechanical 30 property to the optical article. WO 00/31569 24 PCT/AU99/01025

31. A multi coated optical lens according to Claim 30 wherein the secondary coating underlays the stain masking coating or is applied to a second surface of the lens element.

32. A multi coated optical lens according to Claim 31 wherein the secondary 5 coating is selected from one or more of the group consisting of an anti-reflective, abrasion-resistant, impact-resistant, hydrophobic and adhesion coatings.

33. A multi-coated optical lens according to Claim 32 wherein the stain masking coating functions as a reflective coating and the secondary coating is an anti reflective coating applied to the opposite surface of the lens element. 10

34. A multi-coated optical lens according to Claim 30 wherein the reflected colour shift (A E), when stained, is 11 or less.

35. A multi-coated optical lens according to Claim 34 wherein the reflected colour shift (A E), when stained, is 6 or less.

36. A multi-coated optical lens according to Claim 30, wherein the stain 15 masking coating functions as a reflective (mirror) coating; and includes a plurality of layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained by 20 contaminants having a refractive index in the range of approximately 1.3 to 1.6.

37. A multi-coated optical lens according to Claim 36, wherein the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the higher refractive index layers are formed from of titanium dioxide (TiO 2 ) 25 or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 0 3 ).

38. A multi-coated optical lens according to Claim 30, wherein the stain masking coating functions as a reflective (mirror) coating and includes WO 00/31569 25 PCT/AU99/01025 a plurality of dielectric and metallic layers, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained.

39. A multi-coated optical lens according to Claim 38, wherein 5 the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the metallic material(s) is Niobium (Nb) or Chromium (Cr).

40. A multi-coated optical lens according to Claim 30, wherein the stain masking coating functions as an anti-reflective coating and includes three or more 10 lower and higher refractive index layers, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained.

41. A multi-coated optical lens according to Claim 40, wherein the lower refractive index layers include a silica (SiO 2 ) or magnesium 15 fluoride (MgF 2 ) material; and the higher refractive index layers are formed from titanium dioxide (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 03).

42. A multi-coated optical lens according to Claim 30, wherein the stain masking coating functions as an anti-reflective coating and includes 20 three or more dielectric and metallic layers, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained.

43. A multi-coated optical lens according to Claim 42, wherein the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) 25 material; and the metallic material(s) is Niobium (Nb) or Chromium (Cr).

44. A method for preparing a coated optical lens, which method includes providing WO 00/31569 26 PCT/AU99/01025 a lens element; a metallic material or a higher refractive index material; and a lower refractive index material; depositing overlapping layers of lower refractive index material and higher 5 refractive index material or metallic material on a surface of the optical lens element, the number and/or thickness of the respective layers being selected to produce a stain masking coating which coating does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; 10 is a multi-layer coating, the thickness and/or number of which are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating.

45. A method according to Claim 44 wherein the higher and lower refractive index materials are deposited as alternating layers. 15

46. A method according to Claim 45 wherein the high refractive index material is titanium dioxide (TiO 2 ) or a combination of praseodymium oxide (Pr 2 03) and titanium dioxide (TiO 2 ) and the low refractive index material is silica (SiO 2 ).

47. A method according to Claim 44 wherein the metallic material(s) and low refractive index material(s) are deposited as alternating layers. 20 48. A method according to Claim 47, wherein the metallic material(s) is Niobium (Nb) or Chromium (Cr). WO 00/31569 PCT/AU99/01025 27 AMENDED CLAIMS [received by the International Bureau on 20 March 2000 (20.03.00); original claims 30-48 replaced by new claims 30-49; remaining claims unchanged (4 pages)] Bi 2 0 3 , B 2 0 3 . CeO 2 , Cr20 3 , Ga 2 03. GeO 2 , Fe 2 0 3 , HfO 2 . In 2 0 3 . Indium-tin oxide, La 2 0 3 , MgO, Nd 2 03. Nb 2 05, Pr 2 03. Sb 2 03. Sc 2 03, SiO, SiO 2 . SnO 2 . Ta20 5 .TiO, TiO 2 ' TiO 3 , WO 3 , Y 2 0 3 , Yb 2 03, ZnO, ZrO 2 , AIF3. BaF 2 . CaF 2 , CdF 2 , CeF 3 , HfF 4 LaF 3 , LiF, MgF2. NaF, Na 3 AIF 6 . Na 5 A 3 FI 1 4 , NdF 3 , PbF 2 , PrF 3 , SrF 2 , ThF4, ZrF 4 , Si 3 N 4 , AIN, diamond 5 like carbon, polymeric materials or doped dielectric materials; and the metallic layer(s) is formed from a metallic material selected from the metals, metal oxides or metal nitrides of one or more of Aluminium (AI), Chromium (Cr), Niobium (Nb), Nickel (Ni), Palladium (Pd), Tin (Sn), Tantalum (Ta), Titanium (Ti), or Tungsten (W). 10 27. A coated optical lens according to Claim 26, wherein the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material. 28. A coated optical lens according to Claim 27, wherein the metallic material(s) is Niobium (Nb) or Chromium (Cr) and the reflected colour shift (AE), when stained, is 6 or less. 15 29. A coated optical lens according to Claim 23 wherein the thickness and/or number of the respective layers are selected to provide attenuation of transmitted light and an anti-reflective effect on the eye side of the optical lens, as well as the desired reflectance on the other side of the lens; the reflectance not varying substantially in colour when stained. 20 30. A coated optical lens including a lens element; and a stain masking coating on a surface of the lens element which coating does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; 25 is a multi-layer coating, the thickness and/or number of which are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating; wherein when the stain masking coating functions as a reflective (mirror) coating; the coating includes AME7NDED CHEWT ADrTr'y r iol WO 00/31569 PCT/AU99/01025 28 a plurality of layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained; and 5 when the stain masking coating functions as an anti-reflective coating the coating includes three or more layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. 10 31. A multi coated optical lens including a lens element, a stain masking coating on a surface of the lens element, which coating does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 15 1.3 to 1.6; is a multi-layer coating, the thickness and/or number of which are selected to reduce the visibility of stains; and functions as an anti-reflective or reflective (mirror) coating; and a secondary coating which provides a desirable optical and/or mechanical 20 property to the optical article. 32. A multi coated optical lens according to Claim 31 wherein the secondary coating underlays the stain masking coating or is applied to a second surface of the lens element. 33. A multi coated optical lens according to Claim 32 wherein the secondary 25 coating is selected from one or more of the group consisting of an anti-reflective, abrasion-resistant, impact-resistant, hydrophobic and adhesion coatings. 34. A multi-coated optical lens according to Claim 33 wherein the stain masking coating functions as a reflective coating and the secondary coating is an anti reflective coating applied to the opposite surface of the lens element. AMENDED RUFTT fA RTTrT V 101 WO 00/31569 PCT/AU99/01025 29 35. A multi-coated optical lens according to Claim 31 wherein the reflected colour shift (A E), when stained, is 11 or less. 36. A multi-coated optical lens according to Claim 35 wherein the reflected colour shift (AE), when stained, is 6 or less. 5 37. A multi-coated optical lens according to Claim 31, wherein the stain masking coating functions as a reflective (mirror) coating; and includes a plurality of layers of differing refractive index, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; 10 the reflectance not varying substantially in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6. 38. A multi-coated optical lens according to Claim 37, wherein the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and 15 the higher refractive index layers are formed from of titanium dioxide (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 03). 39. A multi-coated optical lens according to Claim 31, wherein the stain masking coating functions as a reflective (mirror) coating and includes a plurality of dielectric and metallic layers, wherein the thickness and/or 20 number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. 40. A multi-coated optical lens according to Claim 34, wherein the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and 25 the metallic material(s) is Niobium (Nb) or Chromium (Cr). 41. A multi-coated optical lens according to Claim 31, wherein the stain masking coating functions as an anti-reflective coating and includes three or more AMENDED SHIEF.T AARTTrT.W 101 WO 00/31569 PCT/AU99/01025 30 lower and higher refractive index layers, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. 42. A multi-coated optical lens according to Claim 41, wherein 5 the lower refractive index layers include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the higher refractive index layers are formed from titanium dioxide (TiO 2 ) or a combination of titanium dioxide (TiO 2 ) and praseodymium oxide (Pr 2 03). 43. A multi-coated optical lens according to Claim 31, wherein the stain 10 masking coating functions as an anti-reflective coating and includes three or more dielectric and metallic layers, wherein the thickness and/or number of the respective layers are selected to provide a desired reflectance; the reflectance not varying substantially in colour when stained. 44. A multi-coated optical lens according to Claim 43, wherein 15 the dielectric layer(s) include a silica (SiO 2 ) or magnesium fluoride (MgF 2 ) material; and the metallic material(s) is Niobium (Nb) or Chromium (Cr). 45. A method for preparing a coated optical lens, which method includes providing 20 a lens element; a metallic material or a higher refractive index material; and a lower refractive index material; depositing overlapping layers of lower refractive index material and higher refractive index material or metallic material on a surface of the optical lens 25 element, the number and/or thickness of the respective layers being selected to produce a stain masking coating which coating does not substantially vary in colour when stained by contaminants having a refractive index in the range of approximately 1.3 to 1.6; is a multi-layer coating, the thickness and/or number of which are 30 selected to reduce the visibility of stains; and AMENDED RI VWT (ARTTr.rt 1OI' WO 00/31569 PCT/AU99/01025 31 functions as an anti-reflective or reflective (mirror) coating. 46. A method according to Claim 45 wherein the higher and lower refractive index materials are deposited as alternating layers. 47. A method according to Claim 46 wherein the high refractive index material 5 is titanium dioxide (TiO 2 ) or a combination of praseodymium oxide (Pr 2 03) and titanium dioxide (TiO 2 ) and the low refractive index material is silica (SiO 2 ).

48. A method according to Claim 45 wherein the metallic material(s) and low refractive index material(s) are deposited as alternating layers.

49. A method according to Claim 48, wherein the metallic material(s) is 10 Niobium (Nb) or Chromium (Cr). AMENDED SHEET (ARTWT.F 101 WO 00/31569 PCT/AU99/01025 32 STATEMENT UNDER ARTICLE 19 New Claim 30 has been formed by a combination of original Claims 1, 2 and 7.