CA1335086C - Multilayer heat-reflecting composite films and glazing products containing the same - Google Patents

Abstract

Visually transparent, preferably color corrected, infra-red reflecting films aredisclosed for solar heat control. The films employ Fabry-Perot sandwich interference filters which are characterized by having two or more transparent layers of sputter-deposited metal such as silver separated by dielectric spacer layers and optionally boundary layers. Methods for producing these materials by sputtering techniques as well as glazing materials incorporating these films are disclosed, as well. In preferred embodiments, these films are laminated into glazing structures.

Description

~ 33508~

MULTILAYER HEAT-REFLECTlNG COMPOSITE FILMS
AND GLAZING PRODUCTS CONTAINING THE SAME

Background of the Invention s 1. Field of the Invention This invention relates to heat-reflecting films. More particularly, it relates to composite films compri~in~ a series of dielectric and metal layers so as to create an infrared reflecting interference filter and to the use of such films in window gl~7in~
10 materials.

2. Description of the Prior Art In the 1890s, Fabry and Perot developed an interferometer consisting of a pair of parallel-sided, half-silvered ~ urs separated by a nonabsorbing layer. This device S had the property of prefelelllially passing energy of certain wavelengths and reflecting energy of other wavelengths. An embodiment of this principle known as the Fabry-Perot sandwich consists of two more or less transparent metal layers separated by a dielectric spacer layer. (See, for example, Knittl, Zdenek, OPTICS OF THIN FILMS, John Wiley & Sons, Ltd., London, 1976, at page 284.) Other filter products known as 20 "induced transmission filters" have been constructed of metal-dielectric sandwiches for use in window gl~7.ing structures. One such structure is described in USP
4,337,990 of Fan (July 6, 1982) as consisting of a transparent substrate, overlayered with a phase matching layer, a single metallic silver layer and an outer antireflection layer, with the three overlayers constit~lting a transparent heat reflector. While 25 generally effective, products of this general structure suffer from the disadvantage that to achieve high levels of heat reflection they must have relatively thick metal layers such as 15 to 25 nm in thickness which tend to have low transmittances of visible radiation, as well.
Another system which used a Fabry-Perot approach to achieve heat reflection 30 while tr~n~mitting visible radiation is shown in USP 3,682,528 of Apfel and Gelber (August 8, 1972). In this system, thinner layers of metal are employed but it is taught that to obtain such layers of an optically suitable metal, in particular silver, it is necessary to first lay down a thin "nucleation" precoat layer of nickel by vacuum deposition and then apply the silver to it, again by vacuum deposition methods. It is -1- ~

further taught that the deposited silver must then receive a thin postcoat layer of vapor-deposited nickel if another layer is to be applied over it. These extra coatings with nickel are time consuming and economically unattractive. This patent also discloses a filter having two silver layers but shows that each silver layer must be s accompanied by one, or two nickel layers and suggests only durability advantages to this more involved structure. The substrate upon which this m~ yer heat-reflecting film was constructed most commonly was glass. In one aspect this invention provides an improved version of Fabry-Perot-based g1~7.ing~ which need not contain these added protective layers.
It is also recognized that a wavelength selective filter can be achieved with a stack of altern~ting high/low index of refraction dielectrics. This would work but would require a large number of layers and be prohibitively expensive. This would not have the capability of low emissivity either.
In plerelled embodiments, this invention avoids other difficulties found in the application of the Fabry-Perot approach to g1~7ing products. While as a general class these materials perform the task of heat rejection with admirable efficiency, in some settings they present a strong color cast to their reflection when viewed from the incident light direction. This strong color is often objected to by some consumers. It is a preferred object of this invention to correct this failing in heat reflective g1~7ing~.
Another desired property of reflective g1~7in~ is that the appearance does not change as a function of viewing angle. This absence of angle sensitivity has not been easily achievable with prior materials used in Fabry-Perot configurations.
In studying gl~7in~ m~tçri~1~ employing these heat-reflecting filters we have discovered a number of configurations for plate glass and anti-lacerative glass which optimize the ef~ectiveness of the filter systems and/or simplify their fabrication.
These glass configurations find application in automotive and architectural settings.
ln some automotive settings, there is a desire to reflect as much heat as possible, but this must be done within the confines of various regulations setting light tr~n~mi~sion limits and the Fabry-Perot interference filter. In these Fabry-Perot filters are charact construction than materials employed like. For example, in the United States, automotive windshields must have a tr~n~mi.c.cion of visible light of at least 70% at normal incidence. The present invention can serve these needs.

Summaly of the Invention It is a general object of this invention to provide an improved gl~7,in~ materials employing a Fabry-Perot inl~lrelellce filter.
According to a first aspect of the invention there is provided a transpalellt, infrared reflecting composite film comprising a transparent support having a&ered to s one surface thereof the first layer of a seven layer i,llt;lrelellce filter each of the seven layers comprising a continuous discrete sputter-deposited layer directly contiguous with its adjacent layers, the first, third, fifth and seventh layers being dielectric layers and the second, fourth and sixth layers being transparent metal layers.
According to a second aspect of the present invention there is provided a o visually transparent, infrared reflecting composite film compri~ing a transparent support having a&ered to one surface thereof an interference filter having a plurality of continuous directly contiguous stacked layers, said layers comprising (a) a dielectric layer, (b) a discrete sputter-deposited transparent metal layer, (c) one or more pairs of layers, each pair comprising a dielectric spacer layer and a discrete 5 sputter-deposited transparent metal layer, and (d) a dielectric outer layer, wherein the dielectric is a sputter-deposited dielectric; the metal layers each comprise silver and each are from 4 to 17 nm in thickness and the dielectric layers each have an index of refraction of from about 1.75 to about 2.25 with the spacer layers having a thickness of from 70 to 100 nm an outer layers having a thickness of from about 30 nm to about 20 70 nm.
According to a third aspect of the present invention there is provided in a transparent, infrared-reflecting composite film including a transparent metal layer-dielectric layer filter adhered directly to one side of a transparent support, the improvement comprising employing as the transparent metal layer-dielectric layer25 filter a visible light-tr~n~mittin~ infrared-reflecting Fabry-Perot interference filter having five layers, wherein each of the five layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third and fifth layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm 30 thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second and fourth layers being transparent silver layers from about 4 to about 17 nm in thickness.
According to a fourth aspect of the present invention there is provided in a transparent, infrared-reflecting composite film including a transparent metal layer-dielectric layer filter adhered directly to one side of a transparent support, the improvement compri~ing employing as the transparelll metal layer-dielectric layer filter a visible light tr~n~mitting infrared-reflecting Fabry-Perot interference filter s having seven layers, wherein each of the seven layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third, fifth and seventh layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about alOO
o nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second, fourth and sixth layers being transparent silver layers form about 4 to about 17 nm in thickness.
According to a fifth aspect of the present invention there is provided in an infrared-reflecting gl~7ing material comprising a transparent gl~7ing m~t~ri~l having S an infrared-reflecting film adhered to its surface, the improvement comprising employing as the infrared-reflecting film a transparent plastic support carrying a visible light-tr~n~mit~in~ infrared-reflecting Fabry-Perot interference filter having five layers, wherein each of the five layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third and fifth layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second and fourth layers being transparent silver layers about 4 to about 17 nm in thickness.
2s According to a sixth aspect of the present invention there is provided in an infrared-reflecting gl~7ing material compri~in~ a transparent gl~7.ing material having an infrared-reflecting film adhered to its surface, the improvement comprising employing as the infrared reflecting film a transparent plastic support carrying a visible light-tr~n~mit~ing infrared-reflecting Fabry-Perot interference filter having seven layers, wherein each of the seven layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third, fifth and seventh layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second, fourth and sixth layers being transparenl silver layers from about 4 to about 17 nm in thickness.
According to a seventh aspect of the present invention there is provided in an s infrared-reflecting gl~7in~ m~terial comprising a transparent gl~7ing material having an infrared-reflecting film adhered to its surface the improvement comprising employing as the infrared reflecting film a visible light-tr~n~mittin~; infrared-reflecting Fabry-Perot interference filter having five layers, wherein each of the five layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent o layers without an intervening nucleation layer, the first, third and fifth layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second and fourth layers being transparent silver layers from about 4 to about 17 nm in thickness.
According to a further aspect of the present invention there is provided in an infrared-reflecting gl~ing material compri~in~ a transparent gl~7ing material having an infrared-reflecting film adhered to its surface the improvement compri~ing employing as the infrared reflecting film a visible light-transmitting infrared-reflecting 20 Fabry-Perot interference filter having seven layers, wherein each of the seven layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third, fifth and seventh layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from 25 about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second, fourth and sixth layers being transparent silver layers from about 4 to about 17 nm in thickness.
According to a still further aspect of the present invention there is provided aprocess for preparing a transparent, infrared-reflecting composite film including a 30 transparent metal layer-dielectric layer Fabry-Perot interference filter adhered to a transparent support, wherein the method comprises the steps of (a) directly sputter-depositing upon the transpal~nt support a discrete continuous boundary layer of dielectric; (b) directly sputter-depositing upon the boundary layer a discrete continuous first transparent metal layer; (c) directly sputter-depositing upon the first 1 335~

transparent metal layer a discrete continuous spacer layer of dielectric; (d) directly sputter-depositing upon the spacer layer a second discrete continuous transparent metal layer; and (e) directly sputter-depositing upon the second metal layer an outer layer of dielectric, wherein the metal layers are comprised of silver, and the dielectric s layers are comprised of indium oxide.
According to a still further aspect of the present invention there is provided avisually transparent, infrared reflecting composite film comprising a transparent support having adhered to one surface thereof an interference filter having a plurality of continuous directly contiguous stacked layers, said layers comprising: (a) a o dielectric layer; (b) a discrete sputter-deposited transparent metal layer; (c) one or more pairs of layers, each pair comprising a dielectric spacer layer and a discrete sputter-deposited transparent metal layer, and (d) a dielectric outer layer, wherein the dielectric is a sputter-deposited dielectric; the metal layers each comprise silver and each are from 4 to 17 nm in thickness and the dielectric layers each have an index of 15 refraction of from about 1.75 to about 2.25 with the spacer layers having a thickness of from 50 to 110 nm and outer layers having a thickness of from about 30 nm to about 70 nm.

Detailed Description of the Invention Brief Description of the Drawin~s In the drawings:
Figs. lA and lB are schematic cross-sectional views of two simple heat-reflecting filters of this invention employing two and three transparent layers of metal, 25 respectively;
Fig. 2 is a schematic cross-sectional view of a simple four-metal-layer heat reflector film of this invention;
Fig. 3 is a schematic cross-sectional view of a heat reflector film of this invention, such as shown in Fig. 1, having a physical protection layer covering its 30 Fabry-Perot filter;
Fig. 4 is a schematic cross-sectional view of a heat reflector film of this invention, such as shown in Fig. 1, having an optional hardcoat layer on its transparent support and a&ered to an additional transpalelll substrate via its filter layer stack which could serve as window gl~7.ing;

Fig. 5 is a schematic cross-sectional view of a filter as shown in Fig. l interposed between two rigid substrates such as glass.
Fig. 6 is a schematic cross-sectional view of a product as shown in Fig. 5 additionally including an antilacerative plastic layer for use in windshields and the s like.
Fig. 7 is a schematic cross-sectional view of a film such as shown in Fig. l adhered to an additional transparent substrate via its support layer. This too could serve as window g1~7in,~;
Fig. 8 is a cross-sectional view of a 1~min~te~ window p1~7.ing in which a film lO of the invention is 1~min~ted between two sheets of transparent substrate;
Figs. 9a, b and c are three cross-sectional views illustrating three film m~t~ri~1 prepared in the Example;
Fig. lO is a graph illustrating for comparison purposes the performance of a prior art reflecting film;
15Fig. l l is a graph illustrating the performance of a reflecting film having two transparent metal layers;
Fig. 12 is a graph illustrating the improved performance of a reflecting film ofthis invention having three transpalel1l metal layers;
Fig. 13 is an expanded-scale graph illustrating the spectral properties 20(transmittance, reflectance, and absorption) of an excellent 1~min~ted productincorporating a reflecting film having three transparent metal layers;
Fig. 14 is a color coordinant chart showing the color properties of filters of this invention using the CIE L*a*b* system; and Fig. 15 is a cross-sectional view of a flexible film-substrated filter of this 25invention employed as a suspended film in a double-pane window g1~7inp st~ucture.

Description of Preferred Embodiments Definitions 30As used in this specification and the appended claims, the following terms have defined me~ning~:
"Color neutral" and "color neutrality" are used herein in the normally accepted sense. That is, these terms mean that a 1~min~ted product of this invention has a reflectivity which is substantially invariant as a function of wavelength throughout the visible part of the spectrum and preferably independent of the angle of incidence. In preferred embodiments the l~min~ted product has a neutral tr~n~mitte~l color. This will follow if there is no wavelength-selective absorption.
"Visible radiation" or "light" means electromagnetic radiation having a s wavelength of from 380 nanometers to 750 nanometers. (CIE Standard) "Infrared radiation" or "heat" means electromagnetic radiation having a wavelength above 750 nanometers.
"Transparent" means having the property of transmitting visible radiation unless otherwise stated.
o "Tvis" or "Tv" or "Tr~n~mitt~nce visible" each refer to a measure oftransmittance over the visible wavelength. It is an integrated term covering the area under the tr~n.~ ce vs. wavelength curve throughout the visible wavelengths.
(1931 CIE Illllmin~nt C Standard). In automotive windshield gl~7ing Tvis should be 70% or greater.
"Tsol" or "Ts" or "Transmittance solar" each refer to a measure of tr~n~ ce over all solar energy wavelengths. (ASTM E 424A) It is an integrated term covering the area under the tr~n.cmitt~nce vs. wavelength curve for both visible and infrared wavelengths. In heat reflecting films and gl~7ings incorporating them it is a primary goal to decrease Tsol while m~ g Tvis as high as possible.
"SC" or "Shading Coefficient" is an accepted term in the field of architecture.
It relates the heat gain obtained when an environment is exposed to solar radiation through a given area of opening or ~l~7ing to the heat gain obtained through the same area of 1/8 inch single pane clear glass. (ASHRAE Standard Calculation Method) The clear glass is assigned a value of 1.00. An SC value below 1.00 indicates better heat rejection than single pane clear glass. A value above 1.00 would be worse than the baseline clear single pane. A similar term is "Rsol" or "reflectance solar" which is measure of total reflectance over the solar energy wavelength.
"Transparent metal layers" are homogeneous coherent metallic layers composed of silver gold pl~timlm palladium al~ copper or nickel and alloys thereof of a thickness which permits substantial transparency.
"Sputter deposit" or "sputter-deposited" refers to the process or the product ofthe process in which a layer of material is laid down by the use of a magnetron spulleler.
"Dielectrics" are nonmetallic m~tçri~l~ which are transparent to both visible 1 335û86 and infrared radiation. Generally, these m~t~ are inorganic oxides but other materials such as organic polymers may be included as well.
"Contiguous" has its usual meaning of being in actual contact, i.e. of being adjoining. From time to time the somewhat redlmd~nt term "directly contiguous" is 5 used for emphasis or clarification and has an identical meaning.
A "spacer layer" is a dielectric layer located between and contiguous with two transpalellt metal layers. In Fig. 1, 18 is a spacer layer.
A "boundary layer" is a layer contiguous with one and not two transparent metal layers. In Fig. 1, 20 and 22 are boundary layers.

Description of Filters The present invention involves heat reflecting filters. A basic embodiment of these filters is shown as film 10 in Fig. lA and as film 24 in Fig. lB. Films 10 and 24 include a multilayer interference filter 12 directly adhered to a transparent support 14.
Filter 12 operates according to the Fabry-Perot principle and includes two or three transpalelll metal layers 16, 16' and 16" separated by spacer layers 18 and 18' and bonded by two outer or boundary layers 20 and 22. Thus, it presents one or two cavities between metal layers. Fig. 2 shows a three-cavity film 25.
In preferred embodiments of this filter, the transparent metal layers are sputter-20 deposited. In addition, the spacer and boundary layers can be directly contiguous withthe transpa~elll metal layers. No nucleation layers are required when the transparent metal layers are sputter deposited. Nucleation layers may be present if desired,however.
As will be seen with reference to Figs. lA, lB and 2, two, three or more than 25 three transparent metal layers such as 16, 16', 16" and 16"', each separated from one another by a spacer layer such as 18, 18' and 18" can be employed. In theory, there is no limit to the number of transparent metal layers that can be used in these sandwich filters. In practice, however three to five trans~arellt metal layers are ple~-led, with three transparent metal layers being more ~)refe..ed.
The thickness of the various layers in the filter should be controlled to achieve an opl~ u"l balance between desired infra-red reflectance and desired visible radiation transmittance. The ideal thicknesses can also depend upon the nature of the transparent metal and dielectric employed.
Each of the transpalelll metal layers 16, 16' and 16" is from about 4 to about 40 nanometers (nm) in thickness, with the total thickness of metal generally being from about 12 to about 80 nm. With silver and silver alloyed with up to about 25% w of gold, which constitute preferred transparellt metals, excellent results are obtained with three or four layers of metal, each from 4 to 17 nm in thickness especially from about s 5toaboutl3nm.
In Figs. lA and lB, the transparent metal layers are depicted as of equal thickness. This is not a requirement of the present invention. Best results have been achieved with three-layer systems when the middle of the three metal layers is about 5% to 15%, especially about 10% thicker than each of the outer layers.
o The metal layers can be deposited by vapor deposition methods, electron-beam deposition, and the like. Magnetron s~ulle~ g is the plefe,led deposition method, but any methods which can deposit 10 nm layers with 2-3% accuracy in theory can be used.
The spacer layers, e.g., 18 and 18', between the transparent metal layers, e.g.,16, 16' and 16", can be the same or different and are each between about 30 and about 200 nm in thickness. The pler~lled thicknesses selected within this range will depend upon the index of refraction of the dielectric employed. Index of refraction values can be from about 1.4 to 2.7. In a general relationship, thicker layers are called for with low index material while thinner layers are used with higher index material. Spacer layers are preferably from about 50 to about 110 nm and especially from about 70 to about 100 nm in thickness for dielectrics having an index of refraction of from about 1.75 to about 2.25. Materials having an index of refraction within this range include the inorganic dielectrics such as metallic and semimetallic oxides, for example zinc oxide, indium oxide, tin oxide, titanium dioxide, silicon oxide, silicon dioxide, bismuth oxide, cl~-ollliulll oxide, as well as other inorganic metal compounds and salts, for example zinc sulfide and magnesium fluoride and llli2~ es thereof. Of these m~teri~l~7 preference is given to zinc oxide, indium oxide, tin oxide and mixtures thereof and titanium dioxide.
With materials having indices of refraction in the 1.4 to 1.75 range, spacer thicknesses are somewhat thicker. Suitable thicknesses in this embodiment are from about 75 to about 200 nm with thicknesses from about 100 to about 175 nm being preferred. Materials having these indices of refraction include hydrocarbon and oxyhydrocarbon organic polymers (1.55-1.65 index of refraction) and fluorocarbonpolymers (1.35-1.45 index of refraction).

1 33508~

With materials having indices of refraction in the 2.25 to 2.75 range, spacer thicknesses are somewhat thinner. Suitable thicknesses in this embodiment are from about 30 to about 90 nm with thicknesses from about 30 to about 80 nm being preferred. Materials having these indices of refraction include lead oxide, alul-~inu s fluoride, bismuth oxide and zinc sulfide.
Other typical inorganic dielectrics and their indexes of refraction are listed in sources such as M~lsik~nt Optical Materials~ Marcel Dekker, New York, 1985, pp.
17-96, and may be used.
As will be described below, the inorganic metallic and semimetallic oxide 10 dielectrics can be conveniently and preferably deposited by reactive spulle~ g techniques, although, if desired, chemical vapor deposit and other physical vapor deposition methods can be employed to apply the dielectric layers.
Filters 12, 24 and 25 in Figs. lA, lB and 2 are depicted with two boundary layers 20 and 22. These layers provide physical protection to the metal layers beneath S them and also serve to reduce visual reflections off of the metal surface to which they are contiguous. It is plerel.ed to have a symmetric sandwich with boundary layers on both outside surfaces. This will give rise to a series of two or more sequential Fabry-Perot inte,relence filters each of the filters comprising a continuous discrete sputter-deposited solar transparent metal layer directly sandwiched between continuous layers 20 of dielectric.
However, if desired, one or both of the boundary layers can be omitted. The boundary layers can be the same or different dielectric and can be identical to or different than the dielectric m~king up the spacers. The same preferences for materials recited for the spacer apply to the boundary layers and, for simplicity, it is 25 preferred if the boundary layers and the spacer layers are all made of the same materials and if they are all sputter-deposited.
The thicknesses of the boundary layers range from about 20 nm to about 150 nm. Boundary layers are preferably from about 25 to about 90 nm and especially from about 30 to about 70 nm in thickness for dielectrics having an index of refraction 30 of from about 1.75 to about 2.25. With m~teri~l~ having indices of refraction in the 1.4 to 1.75 range, preferred thicknesses are from about 30 to about 140 nm and especially from about 45 to about 100 nm. If, as shown in Fig. 2, three or more transparent metal layers are employed, the boundary layers will remain substantially unchanged.

To sum up the geometry of the presently preferred filters, they have 7 layers arranged in a stack as follows:
Boundary dielectric metal layer I
s Spacer layer I
Metal layer II
Spacer layer II
Metal layer III
Boundary dielectric o In this ~.lefelled configuration the three metal layers are plefelably silver and total from 25 to 35 nm in thickness with metal layer II being 110% % 5% of the metal layers I or III. The boundary layers and spacer layers are preferably indium oxide with boundary layer thicknesses of from 30 to 40 nm and spacer thicknesses of from 60 to 80 nm.
In a five-layer film, metal layer II and spacer II might be omitted.

Supporting the Filter In each of Figs. 1 through 6, the Fabry-Perot type filter is shown directly adhered to a transparent support 14. This support is shown in section because it is 20 many times as thick as the filter. This thick support is essential to the practice of this invention. The filter itself is at most only a few hundred nanometers thick and thus can have only minim~l physical strength without the added support. Support 14 can be selected from among the rigid and nonrigid but minim~lly stretchable transparent solids which can withstand the conditions of sputter deposition. Glass, both float or 25 plate glass and l~min~te~ glass and especially low iron float glass, and rigid plastics, such as poly(carbonate) and poly(acrylate) in thicknesses from about 50 mils to about 5 cm or more are representative examples of rigid supports. Poly(ester)s including poly(ethylene terphth~l~te) and other terphth~l~te ester polymers, poly(urethanes), cellulose ester polymers, acrylic polymers, and poly(vinyl fluoride)s from about 1 or 2 30 mils to about 50 mils in thickness are representative examples of nonrigid, minim~lly stretchable films which may be employed. Polylesters) and in particular poly(ethylene terphth~l~tes) such as the DuPont "Mylars" are a plerelled group of film supports.
The filter 12 is directly adhered to the support 14. This can be carried out by sequentially applying the various layers of the filter directly to the support. If the layers are applied by sputter deposition, this can involve first sputter depositing a boundary layer, then a transparent metal layer, a spacer layer, etc.
The macroscale transparent layers, be they a plastic or glass transparent support or an additional component (such as a glass layer l~min~ted to a plastic supported film), do contribute to the performance and visual optics of the final product as will be shown in the examples.

Optical Properties In some settings, the desired optical properties include maximum rejection (reflection) of heat (infrared wavelengths) with only less attention being paid to the amount of visible light tr~n~mitted or reflected. In other applications specific degrees of visible light tr~n.cmi~nce must be attained to meet government regulations, for example, in auto windshields the Tvis must be 70% or greater. Fig. 13 illustrates an excellent reflectance curve for such a product. In this product, reflectance is substantially constant at about 10% (i.e., the reflectance curves is substantially flat throughout the wavelengths between 350 nm and 700 nm. This means that the reflectance off of this product would be neutral in color without the strong tint that can be found objectionable. In this product, the reflectance increases substantially at the wavelengths outside the visible range to achieve good thermal rejection.
As previously noted, the present invention permits one to control the color of reflectance off of the filter. In many cases the property is used to attain color neutrality. with colored light this means a colored reflection or with white light a neutral reflection. This feature can be q~ ed by the CIE L*a*b* 1976 color coordinate system, in particular the ASTM 308-85 method.
Using the L*a*b* system the property is shown by values for a* and b* near 0 for example a* from -4 to +1 and b* from -2 to +2 when using an Illnmin~nt A light source. Fig. 14 is a L*a*b* color coordinant chart which shows the desired colorcoordinates and defines the desired color space.
This neutral color can also be illustrated by the shape of the absorbance/reflectance vs. wavelength curve. As shown in Fig. 13, products of this invention can achieve excellent constant low reflectances throughout the visiblespectrum. one can judge the quality of a product's color neutrality by the flatness of the reflectance curve over the visible spectrum as shown in that figure.
In general, it will be observed that when the ml1ltimetal layer films of this invention are l~min~ted to or between glass and/or plastic layers the overall optical properties are dirrelenl than the properties observed with the llnl~min~ted films. one achieves optical properties approaching the opLi,-,un- in ways not easily achieved by less complicated filter stacks. In particular, one can achieve l~min~ted filter products s having high Tvis/Tsol selectivity, neutral color, excellent heat rejection, high Tvis, high Rsol and an emissivity of less than 0.1.

Incorporation into Glazin~ Structures As may be seen by referring to Figs. 3 through 9, the multi-metal layer films of10 this invention may, if desired, contain a number of optional layers and may be incorporated into a great variety of gl~ing structures for architectural and transportation system uses. In Fig. 3 a film 30 is shown co"L~ g an optional protection layer 32 over filter 12, This layer 32 can typically be a hardcoat, such as a silicon-col~ coating which is applied as a liquid and thereafter cured with heat S and/or plasma or corona discharge to yield a hard scratch-resistant overcoating.
Typical hardcoats are the cured products resulting from heat or plasma treatment of a.) a hydrolysis and condensation product of methyltriethoxysilane; b.) lllixtules of poly(silicic acid) and copolymers of fluorinated monomers with compounds cont~ining primary and secondary alcohol groups as described in U.S. Patent Nos.20 3,429,845 and 3,429,845, respectively. Other hardcoat layers are described in U.S.
Pat. Nos. 3,390,203; 3,514,425; and 3,546,318. These hardcoat layers have thicknesses in the range of a few to a few hundred microns.
In Fig. 4, a preferred configuration 40 for employing the films of this invention is depicted. In this embodiment, the filter 12 is deposited on a support 14 as already 25 described. When the support 14 is a flexible plastic it can carry a previously applied hardcoat 42 for scratch resistance. The filter side of the film is then adhered to a transparent substrate 46 such as another film of flexible plastic or a layer of glass or rigid plastic, or the like using an optically acceptable adhesive 44 such as poly(vinyl butyral), ionomer resin, poly(urethane) resin, or polyvinyl chloride resin. Although 30 not wishing to be limited to a particular adhesive, preference is given to the commonly used glass adhesive, poly(vinyl butyral).
The configuration shown in Fig. 4 is of special interest in areas where the filmcomprises a filter 12 supported on plastic sheet 14 and this is applied to a surface such as the inside surface of a sheet of glass or other rigid m~tçri~l This can be used as architectural glass, as automotive windshields (when the glass is a suitable tempered or l~min~ted safety glass), automotive side or rear window glass (again with proper tempering, etc), as airclarl canopies, and the like. In these applications, the substrate 46 is the "outside" surface and support 14 can, if desired, be selected to provide s antilacerative properties to the resulting final product, as is disclosed in U.S. Pat. No.

3,900,673 which is incorporated herein by reference both for its teachings of antilacerative coatings and for its teachings of the fabrication of safety glassstructures.
Fig. 5 shows a variation 50 of the product of Fig. 1. Embodiment 50 includes a o filter 12 deposited on support 14 as previously described and this combination is attached via adhesive 51 to additional transparent layer 52. If layers 14 and 52 are both glass a very durable product results.
Fig. 6 depicts a variation 60 o f the product of Fig. 5 in which layers 14 and 52 are both glass. Embodiment 60 includes an antilacerative coating 62 adhered to the S inside surface of support 14 with adhesive layer 61.
Turning to Fig. 7, another embodiment 70 of the invention is depicted in which the film is adhered to a transparent substrate 72 with an adhesive 71, this time through the transparelll support 14. This embodiment has the disadvantage that the filter 12 is potentially physically accessible so that it can be physically damaged if great care is 20 not taken. This can of course be corrected by placing this surface in the interior of a double pane glass unit, or by providing other suitable protection.
Fig. 8 shows yet another embodiment 80. This embodiment 80 includes filter 12 deposited on transparent support (e.g., plastic film) 14. The filter and support are then l~min~ted between two transparent substrates 81 and 82 using adhesive layers 83 25 and 84, respectively. This configuration has the advantage, when 81 and 82 are glass, of presenting two glass surfaces.
The film products of the invention can also be used in nonl~min~ted structures, as shown in Fig. lS. In the figure, window unit 90 contains a sheet of film 10 stretched under tension between glass panes 65 and 64. 66 and 66' are air voids and 30 68 and 68' are spacer plugs for holding the film in proper position and properly under tension. This general window structure in which the present filters may be used and the materials and methods of its m~nuf~cture are shown in U.S. Patent No. 4,335,166.
An unexpected advantage of the films of the present invention which employ multiple transparent metal layers is their superior efficiency when l~min~ted to a transparent substrate in the configurations shown in Figs. 4, 5, 6, 7 or B.
In these configurations, the multiple transparent metal layer filters of this invention offer special advantages and efficiencies. When a transparent support-backed single metal layer sandwich filter (i.e. an induced tr~n~mi.~sion filter) is l~min~ted directly to a second sheet of transparent substrate to give a support-filter-substrate configuration, the filter undergoes a pronounced drop in efficiency. Fig. 9 illustrates that for a single metal layer filter this drop in efficiency is quite pronounced.
Fig. 10 depicts the tr~n~mission and reflectance of visible and infra-red wavelengths by a one metal layer filter with and without l~min~tion to a second transparent layer. In the case shown, this second layer is a second layer of plastic support. By difference, the energy absorbed by this filter with and without l~min~tion is shown as well. Line T is the tr~n.cmitt~nce curve for the lml~min~ted film. TL is the transl--ill~lce curve for the l~min~te~ film. R and RL are the reflectance curves.
A and AL are the absorption curves before and after l~min~ion respectively. Thisfilter has a 4 mil poly(ethylene terphth~l~te) (PET) backing having a directly deposited 46 nm thick indium oxide dielectric boundary layer; an 11.8 nm thick layer of sputter-deposited silver topped with another 46 nm thick indium oxide boundary layer. The layer to which this film is l~min~ted is a second sheet of the PET.
As can be seen, the l~min~tion causes tr~n~milt~nce in the visible region to drop markedly while substantially increasing tr~n~mit~nce of energy in the infra-red region. The Tvis value for the filter drops from 82% to 70% when it is l~min~ted. As the same time Tsol only drops from 62% to 55% This illustrates that the filter is not ~l~Çe~ llially passing visible wavelengths with the efficiency it did before l~min~ion.
This film when l~min~ted provides a Shading Coefficient of 0.67. This is little better than conventional green-tinted glass.
Turning to Fig. 11, comparable curves are presented for a filter of the invention having two metal layers. This filter uses the same materials and the same l~min~tion layer used in the filter characterized in Fig. 8. The filter layers are 35nIn of dielectric, 10.7 nm of silver, 75nm of dielectric, 10.7 nm of silver and 40 nm of dielectric. The curves are identified as in Fig. 10. One advantage is clear from the curves. In the infra-red region, this filter is much more efficient and does not change appreciably when l~min~ted. When Tvis and Tsol and SC values are delellnilled it is seen that the drop in Tvis is much less pronounced and in fact, relatively less or the same than the drop in Tsol. (Tvis went from 76% to 70%; Tsol went from 45% to 40%.) The SC
value for the l~min~ted material is a superior 0.53.
In Fig. 12 the same data are presented for a filter of this invention having three sputter-deposited transparent metal layers. This filter uses the same m~teri~l~ used in s the filters characterized in Figs. 10 and 9 in a 35 nm dielectric / 7 nm silver / 65 nm dielectric / 10 nm silver / 70 nm dielectric / 9 nm silver / 35 nm dielectric structure.
With this filter, the drop in Tvis is relatively less than the drop in Tsol so that the efficiency of the filter was subst~nti~lly unchanged by l~min~tion. (Tvis went from 74% to 70% and Tsol went from 42% to 38%.) Fig. 13 is an expanded-scale plot of o the spectral properties of a 7-layer (3-metal-layer) filter of this configuration repeated with greater precision and col~ri,.,~ g the excellent spectral properties which are obtained.

Methods of Plepalalion S The films of this invention are prepared by laying down a series of uniform continuous layers of metal and dielectric in sequence on a support. The metal layers are laid down using magnetron spulleling. This technique can also be used to laydown the dielectric layers if they are of the inorganic oxide type which is plere,-ed.
Importantly, this technique can achieve the desired direct contiguous deposit of the various layers upon one another and upon the support layer without resort to nucleation layers and the like.
This technique and apparatus suitable for carrying out the production of the present materials are both described in detail in U.S. Patent No. 4,204,942 of Charroudi (May 27,1980).
2s Chemical coating or vapor deposition can be used to deposit the dielectric materials but are not prefel~ed. If these methods are used, conventional techniques of thermal evaporation, electron beam evaporation and chernical vapor deposition and the like known to those of skill in the art will be employed.
Examples Seven mllltil~yer filter stacks were prepared on plastic substrates. For purposes of the exarnple they were denominated sarnples A-G. These materials were then adhered to glass layers or l~rnin~ted between glass layers. in some cases the final products were designed to have anti-lacerative properties.

Desi~n Materials Substrate Substrate poly(ethylene terphth~l~te) (ICI 393, 4 mil) with a clear polysiloxanehardcoat was used for the anti-lacerative coatings, coated on the non-hardcoat side.
s Four mils was used to achieve anti-lacerative properties. ICI 393 was selectedbecause it m~ximi7.ed the a&esion of hardcoat. Encapsulated coatings were made on a dirrelellt (no hardcoat) 4 mil polyester (American Hoechst 4600). Encapsulatedanti-lacerative samples were made by l~min~ting an uncoated piece of ICI 393 onto an encapsulated sample.

Glass 3 mm clear float glass was used for all l~min~tions. In several later repeats, low iron glass l~min~tions were prepared which showed several percentage points improvement in Rsol.

Adhesive 15 mil and 30 mil Monsanto PVB were used for all spullered film l~min~tions for which data are presented. 15 mil and 30 mil DuPont PVB was examined and found to be optically similar. The tr~n~mis.cion spectra of l~min~tions without spulleled 20 coatings was measured to d~telll~ine the variability of absorption with l~min~tion temperature. T ~min~tions were made at 280*F and 300"F.

Sputtered Coatin~
Indium oxide and silver were used as dielectric and metal respectively. The 25 coatings were laid down in a magnetic spulleling appalalus.
The thickness of the filter layers in samples A-G was as shown in Table 1.

Table 1 Layer, thickness, nm 30Sample Layer (all prepared with hardcoated substrate) s G 29 10 58 11 58 10 29 (all prepared without haldcoat on substrate) D 1 = dielectric 1 Ml = metal 1, etc.

These seven filter stacks were then incorporated into gl~7in~ structures as shown in Fig. 9. A, B and C were l~min~ted into structures as shown in Fig. 9B. D, E, F and G were made up into 9A and 9C type structures.
In addition to these samples, three comparative samples of three composite l~min~tes were provided. One was a glass / 30 ml PVB / glass composite that had no s~ulleled filter coating and was intended to ~im~ te current l~min~ted windshields.
The second was a anti-lacerative version like 9B, dirrelellt only in having no spulleled film. The third was a sample of "Easy-Eye" brand, absorbing glass made up into aglass/PVB/glass geometry. These samples were also measured.
Visible tr~n.cmi~sion and reflection values were measured on a Spectrogard using Illllmin~nt "A" for the A-G materials with and without l~min~tion and for the three comparative materials.

Observations The results of the color measurements are given in Table 2. These results show that Tvis values of greater than 70% can be achieved with color neutrality using the present invention.

1 33508b Table 2 Color Sample Tvis,% Rsol,% of Reflected Light s L a*
b*
A* 72.6 36.7 33.255.47 6.72 B* 71.5 35.4 34.596.86 o 7.29 C* 70.3 37.0 33.6 6.45 5.44 A 73.8 24.1 33.040.55 1.16 B 71.8 23.3 33.15-1.19 1.87 C 72.8 23.5 33.27-1.11 1.65 D* 76.5 33.828.44 6.9 E* 75.9 34.688.27 5.11 F* 75.6 36.6 6.96 1.56 G* 74.9 37.6 36.846.19 0.12 D 73.0 29.3 34.61-3.28 1.42 E 71.5 29.8 34.57-3.26 1.0 F 71.9 29.9 33.34-3.11 1.1 G 71.9 32.1 34.36+4.81 1.12 1 ~35~86 Encap-sulated 84.0 7.1 33.46 -.82 0.36 s Antila-cerative 83.7 8.5 34.76 -2.05 3.08 Easy Eye 75.4 6.0 31.98 -2.62 1.05 *Before lamin~tion These results also showed that the lamin~tion of the films of this invention into composites gave improved color performance. Matçri~ls which were not acceptable 15 from a color point of view before l~min~tion were acceptable thereafter. The color properties are also shown in color charts such as Fig. 14.
Fig. 14 shows an L*a*b* color coordinate system and shows the general colors it represents together with the a* and b* values for materials of this invention before and after l~mination as taken from Table 1. As can be seen, the color properties20 became more neutral (that is, move closer to the 0,0 point of the coordinate system) with l~mination.
Additionally, when the reflection off of materials of this invention was inspected at a variety of angles, the materials were observed to have minim~l angle sensitivity. That is, the color of the reflection did not change with the angle.Although this invention has been described with reference to certain preferred embodiments, these are not to be construed as limit~tions upon the invention's scope which is as defined by the following claims:

Claims (20)

CLAIMS:

1. A transparent, infrared reflecting composite film comprising a transparent support having adhered to one surface thereof the first layer of a seven layer interference filter each of the seven layers comprising a continuous discrete sputter-deposited layer directly contiguous with its adjacent layers, the first, third, fifth and seventh layers being dielectric layers and the second, fourth and sixth layers being transparent metal layers.

2. A visually transparent, infrared reflecting composite film comprising a transparent support having adhered to one surface thereof an interference filter having a plurality of continuous directly contiguous stacked layers, said layers comprising:
a. a dielectric layer, b. a discrete sputter-deposited transparent metal layer, c. one or more pairs of layers, each pair comprising a dielectric spacer layer and a discrete sputter-deposited transparent metal layer, and d. a dielectric outer layer, wherein the dielectric is a sputter-deposited dielectric; the metal layers each comprise silver and each are from 4 to 17 nm in thickness and the dielectric layers each have an index of refraction of from about 1.75 to about 2.25 with the spacer layers having a thickness of from 70 to 100 nm and outer layers having a thickness of from about 30 nm to about 70 nm.

3. The composite film of claim 2 wherein there are two metal layers each from 10 to 12 nm in thickness.

4. The composite film of claim 2 wherein there are three metal layers each from 5 to 10 nm in thickness.

5. In a transparent, infrared-reflecting composite film including a transparent metal layer-dielectric layer filter adhered directly to one side of a transparent support, the improvement comprising employing as the transparent metal layer-dielectric layer filter a visible light-transmitting infrared-reflecting Fabry-Perot interference filter having five layers, wherein each of the five layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third and fifth layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second and fourth layers being transparent silver layers from about 4 to about 17 nm in thickness.

6. The improved composite film of claim 5, wherein the transparent support is plastic.

7. The improved composite film of claim 6, wherein the plastic is poly(ethylene terephthalate).

8. In a transparent, infrared-reflecting composite film including a transparent metal layer-dielectric layer filter adhered directly to one side of a transparent support, the improvement comprising employing as the transparent metal layer-dielectric layer filter a visible light transmitting infrared-reflecting Fabry-Perot interference filter having seven layers, wherein each of the seven layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third, fifth and seventh layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about a100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second, fourth and sixth layers being transparent silver layers form about 4 to about 17 nm in thickness.

9. The improved composite film of claim 8, wherein the transparent support is plastic.

10. The improved composite film of claim 9, wherein the plastic is poly(ethylene terephthalate).

11. In an infrared-reflecting glazing material comprising a transparent glazing material having an infrared-reflecting film adhered to its surface, the improvement comprising employing as the infrared-reflecting film a transparent plastic support carrying a visible light-transmitting infrared-reflecting Fabry-Perot interference filter having five layers, wherein each of the five layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third and fifth layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second and fourth layers being transparent silver layers about 4 to about 17 nm in thickness.

12. In an infrared-reflecting glazing material comprising a transparent glazing material having an infrared-reflecting film adhered to its surface, the improvement comprising employing as the infrared reflecting film a transparent plastic support carrying a visible light-transmitting infrared-reflecting Fabry-Perot interference filter having seven layers, wherein each of the seven layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third, fifth and seventh layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second, fourth and sixth layers being transparent silver layers from about 4 to about 17 nm in thickness.

13. In an infrared-reflecting glazing material comprising a transparent glazing material having an infrared-reflecting film adhered to its surface the improvement comprising employing as the infrared reflecting film a visible light-transmitting infrared-reflecting Fabry-Perot interference filter having five layers, wherein each of the five layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third and fifth layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second and fourth layers being transparent silver layers from about 4 to about 17 nm inthickness.

14. In an infrared-reflecting glazing material comprising a transparent glazing material having an infrared-reflecting film adhered to its surface, the improvement comprising employing as the infrared reflecting film a visible light-transmitting infrared-reflecting Fabry-Perot interference filter having seven layers, wherein each of the seven layers is a continuous, discrete sputter-deposited layer directly contiguous with its adjacent layers without an intervening nucleation layer, the first, third, fifth and seventh layers being dielectric layers comprising indium oxide, the first and fifth dielectric layers being from about 30 to about 70 nm thick and said third dielectric layer being from about 70 to about 100 nm thick, each of said dielectric layers having an index of refraction of from about 1.75 to about 2.25, and the second, fourth and sixth layers being transparent silver layers from about 4 to about 17 nm in thickness.

15. A process for preparing a transparent, infrared-reflecting composite film including a transparent metal layer-dielectric layer Fabry-Perot interference filter adhered to a transparent support, wherein the method comprises the steps of:
a. directly sputter-depositing upon the transparent support a discrete continuous boundary layer of dielectric;
b. directly sputter-depositing upon the boundary layer a discrete continuous first transparent metal layer;
c. directly sputter-depositing upon the first transparent metal layer a discrete continuous spacer layer of dielectric;
d. directly sputter-depositing upon the spacer layer a second discrete continuous transparent metal layer; and e. directly sputter-depositing upon the second metal layer an outer layer of dielectric, wherein the metal layers are comprised of silver, and the dielectric layers are comprised of indium oxide.

16. A visually transparent, infrared reflecting composite film comprising a transparent support having adhered to one surface thereof an interference filter having a plurality of continuous directly contiguous stacked layers, said layers comprising:
a. a dielectric layer;
b. a discrete sputter-deposited transparent metal layer;
c. one or more pairs of layers, each pair comprising a dielectric spacer layer and a discrete sputter-deposited transparent metal layer, and d. a dielectric outer layer, wherein the dielectric is a sputter-deposited dielectric; the metal layers each comprise silver and each are from 4 to 17 nm in thickness and the dielectric layers each have an index of refraction of from about 1.75 to about 2.25 with the spacer layers having a thickness of from 50 to 110 nm and outer layers having a thickness of from about 30 nm to about 70 nm.

17. The visually transparent infrared reflecting composite film of claim 16 wherein said one or more pairs of layers is one pair of layers.

18. The visually transparent infrared reflecting composite film of claim 17 wherein the metal layers are from 10 to 12 nm in thickness.

19. The visually transparent infrared reflecting composite film of claim 16 wherein said one or more pairs of layers is two pairs of layers.

20. The visually transparent infrared reflecting composite film of claim 19 wherein the metal layers are from 5 to 10 nm in thickness.