Light filtering lens film

A lens film is used in filtering visible, infrared, and ultraviolet light. The lens film has one or more metallized layers stacked together. Each metallized layer has a substrate with a metal coating covering one face of the substrate. One or more protecting layers are disposed over the stack of metallized layers to provide protection film. The lens film also has an ultraviolet absorbing material, such as an ultraviolet absorbing binder or substrate material. The lens film can be configured so that it meets the American National Standards Institute's shade standards for protection from harmful or intense light. The lens film can be mounted on a lens of an eye protection device. One method of mounting the lens is to provide an adhesive layer over a portion of the lens film and then binding the lens film to the lens with the adhesive layer.

FIELD OF THE INVENTION 
The present invention relates to a light filtering device for absorbing 
and/or reflecting visible, ultraviolet, and infrared light. In particular, 
the present invention relates to a light filtering lens film having 
multiple layers. 
BACKGROUND OF THE INVENTION 
Many activities require eye protection due to the presence or creation of 
harmful visible, ultraviolet, and infrared light. One example of such an 
activity is welding where intense light is generated by the welder's torch 
and the heated metal. Current safety standards for industrial eye and face 
protection for welding and other activities are published by the American 
National Standards Institute, Inc. (ANSI) in American National Standard 
Practice for Occupational and Educational Eye and Face Protection, ANSI 
Z87-1-1989, incorporated herein by reference. 
The ANSI standards define a set of shade ratings between 1 and 14 based on 
the weighted transmittance of luminous (380-780 nm), far ultraviolet 
(200-315 nm), near ultraviolet (315-385 nm), infrared (780-2000 nm), and 
blue (400-1400 nm) light. The ANSI standards also indicate the minimum 
shade protection recommended for certain specific activities. For electric 
arc welding, a protective lens should have a shade rating of 10-14, for 
gas welding, shades 4-8 are recommended, and for cutting or torch brazing, 
shades 3-6 are recommended. 
In meeting these standards, those engaged in these hazardous 
light-generating activities must often wear eye protection devices which 
are extremely limiting and usually dedicated to that particular activity. 
For example, a welder typically has a special helmet, mask, or pair of 
goggles that is worn only while welding. Furthermore, such a helmet, mask, 
or goggles often provides only a limited range of vision as the protective 
lenses of the eye protection device have only a small viewing area. 
These features of current eye protection devices are inconvenient for many 
wearers. For example, a worker on a job such as bridge repair, where 
welding is only one of the necessary activities, would find it convenient 
to have an eye protection device that could be used for both welding and 
other activities. Unfortunately, the lens shades required for eye 
protection devices appropriate for welding are usually too dark for other 
activities. Thus, there is a need for an eye protection device that can be 
used with activities that generate harmful light irradiation and can still 
be used with other activities that do not require such extreme light 
shielding. 
In addition, workers must often wear other protective gear such as 
respirators which may not be conveniently or cost-effectively combined 
with current protective helmets, masks, or goggles. There is a need for a 
lightweight, low-cost light filtering device that can be used in 
conjunction with other protective gear without requiring that such gear be 
dedicated for use only with harmful light-generating activities. 
The light filtering lens films of the present invention address these 
needs. The lens films of the present invention can be mounted on the lens 
or lenses of existing eye protection devices and are often detachable from 
these physical eye protection devices so that a worker can continue to 
wear the physical eye protection device while engaged in other activities. 
The lens films of the present invention provide a convenient, lightweight, 
low cost product for protecting wearers from harmful light arising from a 
wide variety of sources. 
SUMMARY OF THE INVENTION 
The present invention is directed to a light filtering lens film. The lens 
films of the present invention have one or more metallized layers formed 
in a stack. Each metallized layer is made of a substrate with a metal 
coating on at least one face of the substrate. The lens film includes one 
or more protecting layers to provide protection against damage to the 
film. The lens film also includes an ultraviolet light absorbing material. 
In one embodiment of the invention, the ultraviolet absorbing material is 
an ultraviolet (UV) absorbing binder that is provided between at least two 
of the metallized and protecting layers together. Alternatively, the 
ultraviolet absorbing material is an ultraviolet absorbing layer disposed 
in the lens film. 
In another aspect of the invention, the lens film is mounted on a base lens 
to provide a lens that protects the eyes of a user from harmful light 
irradiation. 
In another embodiment of the invention, an eye protection device has a 
shield that covers at least the eyes of a wearer. The shield includes a 
lens upon which a lens film, described hereinabove, is mounted. The lens 
of the shield is positioned to allow the wearer of the eye protection 
device to look through the lens. 
The lens film is used by mounting the lens film on a lens and then 
positioning the lens in front of a wearer's eyes so that the wearer can 
view the work in which the wearer is engaged. In one embodiment of the 
invention, the lens film is adhesively mounted to the lens. 
In another aspect of the invention, a lens film is made by disposing one or 
more protecting layers on a metallized layer which has a metal coating 
disposed over a substrate. In addition, ultraviolet absorbing material is 
disposed in the lens film. 
These and various other features which characterize the invention are 
pointed out with particularity in the claims annexed hereto and forming a 
part hereof. However, for a better understanding of the invention, its 
advantages and objectives obtained by its use, reference should be made to 
the drawings which form a further part hereof and to the accompanying 
descriptive matter, in which there is illustrated and described a 
preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the Drawings, in general, FIG. 1 illustrates a lens film 20 of 
the invention mounted on a lens 22 of an eye protection device 24. Lens 
film 20 provides protection from harmful visible, infrared (IR), and 
ultraviolet (UV) light. In a preferred embodiment of the invention, lens 
film 20 meets or exceeds the transmittance requirements for a specific 
shade rating outlined by the American National Standards Institute, Inc. 
in the American National Standard Practice for Occupational and 
Educational Eve and Face Protection, ANSI Z87.1-1989. 
Lens film 20 can be shaped to fit the lens or lenses of almost any type of 
eye protection device including goggles, spectacles, face shields, masks, 
or helmets. In particular, lens film 20 can be used with goggles, masks, 
helmets, and other eye protection devices for welding applications. Lens 
film 20 can be configured to fit existing eye protection devices, 
including those associated with other protective devices such as 
respirators, to provide convenient protection against harmful or intense 
light. It is recommended that users of lens film 20 follow the ANSI 
guidelines with respect to the choice of an appropriate shade rating for 
their activity and the choice of appropriate eyewear to provide impact 
protection as well as other safety procedures and guidelines. 
Lens film 20 is mounted on lens 22 using an adhesive, clips, or other 
mounting method or device known to those skilled in the art. Lens film 20 
is configured to be either permanently or, preferably, detachably 
mountable on lens 22. More preferably, lens film 20 is detachably 
mountable and remountable on lens 22. A wearer of an eye protection device 
having a detachably mounted lens film 20 can conveniently switch from 
activities involving harmful light, such as welding, to other activities 
by removing the lens film. If lens film 20 is remountable, then lens film 
20 may be reused one or more times before it is discarded. 
Lens film 20 optionally includes a graspable tab 26 with which a user can 
easily detach lens film 20 from lens 22. Tab 26 may be made from the same 
material as lens film 20, or tab 26 may be formed from other materials, 
such as polymers or plastics, and attached to lens film 20. A tab is only 
one example of a device that may be attached to the lens film to 
facilitate the removal of the lens film from the lens. Those skilled in 
the art will recognize that there are many other methods or devices for 
removing the lens film from the lens which are within the scope of this 
invention. 
A further optional component that may be part of lens film 20 or may be 
separately applied to lens 22 is a light seal 28 which is disposed around 
the periphery of lens 22. When lens film 20 is applied to lens 22, lens 
film 20 should at least partially overlap light seal 28. The function of 
light seal 28 is to prevent harmful light from passing through points at 
the periphery of lens 22 which are not covered by lens film 20 due to, for 
example, an imprecise fit between lens film 20 and lens 22. Light seal 28 
is formed using an opaque material and positioned on lens 22 so that lens 
film 20 overlaps with light seal 28 at all or nearly all points along the 
periphery of the lens film. 
Light seal 28 can be made by painting a portion of the periphery of lens 22 
with an opaque material. Light seal 28 can also be formed by adhesively 
attaching opaque material to the periphery of lens 22. For example, opaque 
polyester may be cut in the form of a frame and attached to lens 22 or, 
alternatively, a clear polyester sheet with a printed opaque frame may be 
applied to lens 22. 
In one embodiment of the invention, illustrated in FIGS. 5 and 6, light 
seal 28 is attached to lens 22 of an eye protection device 48, such as the 
full-protection respirator mask shown in FIG. 5. A typical full-protection 
respirator mask 48 is a 3M model 7800 respirator, available from Minnesota 
Mining and Manufacturing Company ("3M"), St. Paul, Minn. A lens assembly 
50, shown in detail in FIG. 6, includes lens 22, lens film 20, and light 
seal 28, and is held within a channel 54 of a clamping flange 52. The 
flange 52 is fastened to mask 48 by a flange securement means 58, such as 
screws or other fasteners, to prevent slippage of lens assembly 50. Light 
seal 28, in this embodiment of the invention, is typically a thin film 
which has an opaque region 56 that extends radially inward from the edge 
of light seal 28 to cover the exposed periphery of lens 22, as shown in 
FIG. 6. Lens film 20 is applied over light seal 28 so that it overlaps 
with the light seal. 
Light seal 28 is held in place by the clamping action of flange 52. 
Optionally, light seal 28 may also be adhesively bonded to lens 22. In 
addition, lens film 20 is adhesively bonded to light seal 28, although 
other means of binding lens film 20 to light seal 28 and/or lens 20 are 
also within the scope of this invention. 
In an alternative embodiment of the invention, light seal 28 is a layer of 
peripherally opaque material which is attached to or part of the layered 
structure of lens film 20, discussed hereinbelow. For example, light seal 
28 may be an opaque polymeric ring attached to the periphery of lens film 
20 so that when lens film 20 is mounted on lens 22, light seal 28 overlaps 
the periphery of both lens film 22 and lens 20. 
Lens film 20 is a layered composite as depicted in FIGS. 2-4. Preferably, 
the layers forming lens film 20 are thin so that the lens film is flexible 
and can conform to the contours of the lens to which the lens film is to 
be attached. Lens film 20 typically includes one or more metallized layers 
30 and one or more protecting layers 32. These layers are held together to 
form a stack of layers by a lamination adhesive 36 which may optionally be 
a UV absorbing binder 34. Optionally, a layer of mounting adhesive 38 is 
applied to a portion of lens film 20 so that lens film 20 can be 
adhesively mounted on a lens 22. 
The metallized layers 30 have a substrate 40 covered on at least one 
surface by a thin metal coating 42. The metal coating 42 typically 
reflects or absorbs visible and infrared light. Metal coating 42 is 
usually formed from a reflective metal or alloy such as aluminum, copper, 
gold, silver, titanium, inconel, or stainless steel, which is vapor-coated 
or sputtered on substrate 40. Suitable metallized layers are available 
commercially (for example, 3M-brand Scotchtint.TM. metallized films from 
3M). 
Substrate 40 of metallized layer 30 is often a polymer film although other 
suitable substrates may also be used. Suitable polymer films are made from 
acrylic polymers, such as acrylate, methacrylate, and copolymers thereof; 
polyethylene and copolymers thereof; polypropylene and copolymers thereof; 
polyvinylchloride and copolymers thereof; nylon; polycarbonate; and 
polyesters, such as polyethylene terephthalate, as well as other polymers 
known to those skilled in the art. Such polymeric films are well-known in 
the art and are commercially available in thicknesses ranging from less 
than 0.5 mils to more than 10 mils (1 mil equals 0.001 inch). 
In addition to providing support for metal coating 42, substrate 40 may 
also absorb harmful irradiation such as ultraviolet light. Moreover, 
substrate 40 may be tinted to provide further light absorption. 
Furthermore, lens film 20 may contain multiple metallized layers 30 stacked 
together, as shown in FIGS. 3 and 4, to increase the amount of eye 
protection beyond that of each individual metallized layer. The metal 
coatings and substrates of the multiple metallized layers of lens film 20 
need not be constructed of the same materials. These layers can be stacked 
together to produce a lens film having a specific shade rating. Typically, 
the stacking of metallized films produces a lens film that has light 
transmittance greater than initially expected based on the transmittance 
of each individual film. 
Protecting layers 32 are provided on lens film 20 to protect the underlying 
layers from scratching and damage. These layers are typically a polymer 
film formed from acrylic polymers, such as acrylate, methacrylate, and 
copolymers thereof; polyethylene and copolymers thereof; polypropylene and 
copolymers thereof; polyvinylchloride and copolymers thereof; nylon; 
polycarbonate; and polyesters, such as polyethylene terephthalate, as well 
as other suitable polymers known to those skilled in the art. Protecting 
layers 32 may be provided separately on lens film 20 or, alternatively, 
substrate 40 of one or more of the metallized layers may also act as a 
protecting layer. 
Typically, there is at least one protecting layer disposed over the surface 
of lens film 20 as shown in FIG. 2. This protecting layer 32 is preferably 
made of a material which is heat resistant to protect lens film 20 from 
heat generated by activities such as welding. Optionally, a protecting 
layer may be disposed on the other surface of lens film 20 as shown in 
FIGS. 3 and 4 to provide scratch resistance to this surface. 
Layers other than metallized layers and protecting layers may be included 
in lens film 20. For example, a tinted layer for removing visible light or 
an ultraviolet absorbing layer may be included among the metallized and 
protecting layers of lens film 20. These layers are typically made from 
the same materials as the protecting layers and/or metallized layers. 
Lens film 20 also includes ultraviolet absorbing material. In one 
embodiment of the invention, substrate 40 of one or more of the metallized 
layers 30 contains UV absorbing material. The substrate may be UV 
absorbing due to the inherent properties of the substrate material. For 
example, polyester absorbs some ultraviolet light. Alternatively, a UV 
absorbing compound may be added to the substrate material or coated on the 
substrate. 
Alternatively, as shown in FIG. 7, one or more separate UV absorbing layers 
44 might be provided within the stack of layers that make up lens film 20. 
This additional layer may be made of UV absorbing material or may contain 
one or more UV absorbing compounds as an additive to or coating on a 
substrate material. The UV absorbing layer can be made from the same 
polymeric materials as the protecting layers or the substrates of the 
metallized layers. 
In another embodiment of the invention, shown in FIGS. 2-4, the UV 
absorbing material is a UV absorbing binder 34. UV absorbing binder is 
typically an adhesive containing one or more UV absorbing compounds. 
Examples of UV absorbing compounds for use in a UV absorbing binder or for 
incorporation in a UV absorbing layer include substituted benzophenones 
and substituted benzotriazoles. Examples of suitable substituted 
benzophenones include 2,4-dihydroxy-benzophenone; 
2-hydroxy-4-acryloxyethoxy-benzophenone; 2-hydroxy-4-methoxy-benzophenone; 
2,2'-dihydroxy-4-methoxy-benzophenone; 
2,2'-dihydroxy-4,4'-dimethoxy-benzophenone; 
2-hydroxy-4-n-octyloxy-benzophenone; 2,2',4,4'-tetrahydroxy-benzophenone; 
and 4-dodecyloxy-2-hydroxy-benzophenone. Suitable benzotriazoles include 
2-[2'-hydroxy-3',5'-di(a,a-dimethyl-benzyl)phenyl]-benzotriazole, 
2-(2'-hydroxy-5'-methylphenyl)-benzotriazole, 
2-(3',5'-di-t-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, 
2-(3'-t-butyl-2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole, 
2-(2'-hydroxy-3',5'-di-t-butylphenyl)-benzotriazole, 
2-(2'-hydroxy-5'-t-octylphenyl)-benzotriazole, and 
2-(2'hydroxy-3',5'-di-tertiary amylphenyl)-benzotriazole. Any of these or 
other suitable UV absorbing compounds may be used alone or in combination 
to provide the desired UV absorption. 
In this embodiment of the invention, UV absorbing binder is provided 
between at least two of the protecting and metallized layers. Preferably, 
UV absorbing binder 34 is provided between all of the protecting and 
metallized layers, as shown in FIG. 4. 
Lens film 20 also optionally includes a mounting adhesive 38 applied to a 
portion of the lens film. Preferably, mounting adhesive 38 is applied to a 
portion of the periphery of lens film 20 to minimize the surface of lens 
22 in contact with mounting adhesive 38 as the adhesive may cause visual 
distortions. 
Mounting adhesive 38 may be a contact adhesive, such as adhesive tape or 
pressure sensitive adhesive, or may require water or another solvent to 
activate or expose the adhesive. Preferably, mounting adhesive 38 provides 
for detachable mounting of lens film 20 to lens 22 and more preferably, 
mounting adhesive 38 provides for remounting of lens film 20. Optionally, 
a removable adhesive protection strip, not shown, is provided over the 
mounting adhesive 38 to prevent unwanted adhesion of the lens film to 
other objects. 
EXAMPLES 
The following examples demonstrate the principles of the invention. It is 
to be understood that these examples are merely illustrative and are in no 
way to be interpreted as limiting the scope of the invention. 
Three lens films having a shade rating of 4 or better were made following 
the principles of the invention. The three lens films had the following 
configurations: 
______________________________________ 
Film 1 Film 2 Film 3 
______________________________________ 
SCLARL400 SCLARL400 SCLARL400 
LE30CUARL LE30CUARL LE30CUARL 
LE30CUARL LE30CUARL LE30CUARL 
LE30CUARL LE20SIAR NR35SMARL 
Mylar.TM. Mylar.TM. LE30CUARL 
Mylar.TM. 
______________________________________ 
SCLARL400 (3M) is a 0.005" thick polymeric protecting layer which provided 
scratch and heat resistance to the lens film. LE30CUARL and LE20SIAR are 
Scotchtint.TM. metallized films (3M) with copper and aluminum coatings, 
respectively, on a tinted polyester substrate. NR35SMARL is a tinted 
polyester film (3M). A.0.004" Mylar.TM. film was applied to the back 
surface of the stack of metallized layers to provide protection against 
scratching. The layers were held together by a UV absorbing binder which 
is provided on the commercially available films. An adhesive transfer tape 
(3M, No. Y920XL) was applied over a portion of the Mylar.TM. layer so that 
the lens film could be adhesively mounted on a lens. The lens film was cut 
using scissors in an approximately oval shape for use with lenses of a 
full-face respirator providing eye protection. When the lens film was cut, 
a tab of material was left attached to the oval lens film to provide a 
convenient method for detaching the lens film from a lens. 
The transmittance of these lens films was measured over the range of 200 to 
2000 nm. The weighted transmittances of the films were then calculated as 
described in the ANSI standards, ANSI Z87.1-1989, 24-25, for the luminous 
(380-780 nm), far ultraviolet (200-315 nm), near ultraviolet (315-385 nm), 
infrared (780-2000 nm), and blue (400-1400 nm) spectra. The results, as 
well as the requirements for a Shade 4 and 5 protective lens, are 
presented in Table 1. 
TABLE 1 
______________________________________ 
Weighted Transmittances (%) for Films 1-3 
Shade 4 
Shade 5 Film 1 Film 2 Film 3 
______________________________________ 
T.sub.L 3.16-8.50 
1.18-3.16 4.8 2.7 1.5 
(380-780 nm) 
T.sub.NUV 
&lt;T.sub.L /10 
&lt;T.sub.L /10 
&lt;0.1 &lt;0.1 &lt;0.1 
(315-385 nm) 
T.sub.FUV 
&lt;0.04 &lt;0.02 &lt;0.01 &lt;0.01 &lt;0.01 
(200-315 nm) 
T.sub.IR &lt;5.0 &lt;2.5 0.6 0.5 0.6 
(780-2000 nm) 
T.sub.blue 
&lt;T.sub.L &lt;T.sub.L 2.1 2.1 0.7 
(400-1400 nm) 
______________________________________ 
The test data shown in Table 1 show that lens film 1 meets the requirements 
for a Shade 4 rating and lens films 2 and 3 meet the requirements for a 
Shade 5 rating. In addition, these lens films were flexible and could be 
cut to a desired shape to fit a lens of an eye protection device. The 
mounting adhesive applied to these lens films also provided for detachable 
mounting and remounting of the lens film on an appropriate lens. 
The invention has been described with reference to various specific and 
preferred embodiments and techniques. However, it will be apparent to one 
of ordinarily skill in the art that many variations and modifications may 
be made while remaining within the spirit and scope of the invention. 
All publications in this specification are indicative of the level of 
ordinary skill in the art to which this invention pertains. All 
publications are herein incorporated by reference to the same extent as if 
each individual publication or patent application was specifically and 
individually indicated by reference.