U.S. patent application number 11/962015 was filed with the patent office on 2008-04-24 for dichroic filters on flexible polymer film substrates.
Invention is credited to Steven Allen Barth, Rocco John Fizzano, Charles Nicholas Van Nutt, Janet Sue Yeatts.
Application Number | 20080094703 11/962015 |
Document ID | / |
Family ID | 38619219 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080094703 |
Kind Code |
A1 |
Van Nutt; Charles Nicholas ;
et al. |
April 24, 2008 |
Dichroic Filters on Flexible Polymer Film Substrates
Abstract
Now, according to the present invention, dichroic filters are
provided that incorporate a flexible polymer film substrate, such
as poly(ethylene naphthalate), onto which a dielectric and/or
reflective metal stack has been formed. Filters of the present
invention are durable, flexible, and lightweight, and can be
advantageously used in many specialty lighting applications.
Inventors: |
Van Nutt; Charles Nicholas;
(Martinsville, VA) ; Fizzano; Rocco John;
(Bassett, VA) ; Yeatts; Janet Sue; (Ruffin,
NC) ; Barth; Steven Allen; (Martinsville,
VA) |
Correspondence
Address: |
BRENC LAW;ANDREW BRENC
P.O. BOX 155
ALBION
PA
16401-0155
US
|
Family ID: |
38619219 |
Appl. No.: |
11/962015 |
Filed: |
December 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11379774 |
Apr 21, 2006 |
7317576 |
|
|
11962015 |
Dec 20, 2007 |
|
|
|
Current U.S.
Class: |
359/487.05 |
Current CPC
Class: |
G02B 5/285 20130101 |
Class at
Publication: |
359/490 |
International
Class: |
G02B 5/30 20060101
G02B005/30 |
Claims
1. A dichroic filter comprising: a flexible polymer film substrate;
and, a stack formed on said polymer film substrate, wherein said
stack comprises at least 5 alternating layers of a first dielectric
or reflective metal and a second dielectric or reflective metal and
wherein said dichroic filter transmits only a subset of wavelengths
in the visible spectrum of wavelengths.
2. The filter of claim 1, wherein said filter further comprises a
polymer film adhered to said stack opposite said polymer film
substrate.
3. The filter of claim 2, wherein said polymer film is adhered to
said stack with a silicone adhesive.
4. The filter of claim 1, wherein said substrate comprises
poly(ethylene naphthalate).
5. The filter of claim 1, wherein said stack comprises at least 7
alternating layers of said first dielectric or reflective metal and
said second dielectric or reflective metal.
6. The filter of claim 1, wherein said stack comprises at least 11
alternating layers of said first dielectric or reflective metal and
said second dielectric or reflective metal.
7. The filter of claim 1, wherein said first dielectric or
reflective metal comprises a material having an index of refraction
of greater than 2 and said second dielectric comprises a material
having an index of refraction of less than 1.8.
8. The filter of claim 1, wherein said first dielectric or
reflective metal comprises titanium dioxide and said second
dielectric or reflective metal comprises silicon dioxide.
9. The filter of claim 1, wherein said layers are from 10
nanometers to 120 nanometers in thickness.
10. The filter of claim 1, further comprising a layer of pressure
sensitive adhesive disposed on said polymer film opposite said
stack.
11. The filter of claim 10, wherein said adhesive comprises
silicone.
12. The filter of claim 10, wherein said adhesive is removable.
13. The filter of claim 10, further comprising a release liner
disposed in contact with said pressure sensitive adhesive.
14. A dichroic filter comprising: a flexible polymer film
substrate; a stack formed on said polymer film substrate, wherein
said stack comprises at least 5 alternating layers of a first
dielectric or reflective metal and a second dielectric or
reflective metal and wherein said dichroic filter transmits only a
subset of wavelengths in the visible spectrum of wavelengths; and,
a polymer film adhered to said stack opposite said polymer film
substrate; wherein said first dielectric or reflective metal
comprises a material having an index of refraction of greater than
2 and said second dielectric comprises a material having an index
of refraction of less than 1.8 and wherein said layers are from 10
nanometers to 120 nanometers in thickness.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and is a continuation
application of copending U.S. application Ser. No. 11/379,774 filed
on Apr. 21, 2006, which is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention is in the field of light filters in
general, and, in particular, the present invention is in the field
of dichroic interference filters used to selectively transmit
desired wavelengths of light from a light source.
BACKGROUND
[0003] Devices that filter selected wavelengths of light are well
known and have been in use for many years. Typically, a source of
white light or light comprising components from wavelengths
throughout the visible spectrum is filtered so as to transmit only
the desired wavelengths. Among the various filters that are
conventionally available for use as a light filter, absorption
filters and interference filters are in common use.
[0004] Absorption filters are typically formed by imbuing a
substrate with a dye that functions to absorb a given subset of
visible light wavelengths. The result is that a portion of the
light that is incident upon the absorption filter will be absorbed,
and most of the remaining light will be transmitted through the
filter. While effective, absorption filters are not ideally suited
for many applications because the light that is absorbed is
converted to heat, which tends to shorten the life of the dye, the
filter substrate, or both. Absorption filters used in theatrical
lighting, which are also known as "filter gels" or "gels", for
example, are typically used for only a relatively short period of
time before the intensity of the light being filtered results in
the unacceptable degradation of the absorption filter.
[0005] Interference filters that filter visible light, which are
also known as dichroic filters, utilize very thin, alternating
layers of a material with a high refractive index and a material
with a low refractive index deposited on a substrate such as a
rigid glass substrate. These filters have little absorbance and
transmit some wavelengths, while reflecting other wavelengths and
causing destructive interference of out of phase wavelengths. This
results in a different apparent color on each side of the filter
(i.e. dichroic). Because dichroic filters do not absorb a
significant amount of light incident upon them, they do not suffer
from the same heat issues as absorption filters. Further, the
deposited layers of materials typically resist physical degradation
better than dyes, which often leads to longer and better
performance. Unfortunately, many conventional dichroic filters are
formed on glass substrates, which makes the filters relatively
heavy, subject to breakage, and relatively costly to produce and
distribute compared to gel filters.
[0006] What are needed in the art are improved optical filters that
can be used to filter light without degrading due to heat buildup
or dye instability, and that also can be produced, handled, and/or
distributed more easily and safely than glass based filters.
SUMMARY OF THE INVENTION
[0007] Now, according to the present invention, dichroic filters
are provided that incorporate a flexible polymer film substrate,
such as poly(ethylene naphthalate), onto which a dielectric and/or
reflective metal stack has been formed. Filters of the present
invention are durable, flexible, and lightweight, and can be
advantageously used in many specialty lighting applications.
BRIEF DESCRIPTION OF THE FIGURES
[0008] FIG. 1 is a graph of a light transmission spectrum of the
present invention.
[0009] FIG. 2 is a graph of a light transmission spectrum of the
present invention.
DETAILED DESCRIPTION
[0010] The present invention provides dichroic filters that can be
used in a wide variety of applications, including, for example, as
optical filters for use in theatre productions and as color filters
for any conventional lighting application.
[0011] Dichroic filters of the present invention comprise a
flexible polymer film substrate, as will be described in detail,
below, onto which alternating layers of two dielectric and/or
reflective metal materials with disparate refractive indices are
deposited, as will also be described in detail, below.
[0012] Dichroic filters of the present invention transmit only a
subset of wavelengths in the visible spectrum of wavelengths, which
results, for example, in the passing of colored light from a white
light source. Due to their special construction, filters of the
present invention reflect selective areas of the spectrum.
[0013] In various embodiments of the present invention, a flexible
polymer film substrate is provided as a base material onto which at
least five alternating layers of two dielectric and/or reflective
metal materials are deposited. In various embodiments, 7, 10, 15,
or 20 such layers, for example, can be used. The number of layers
can be chosen based on the desired light filtering characteristics
of the filter, as is well known in the art.
[0014] Flexible polymer film substrates of the present invention
can include one or more primer layers, as are known in the art, to
facilitate proper adhesion of the dielectric and/or reflective
metal layers to the flexible polymer film substrate.
[0015] In various embodiments of the present invention, a flexible
polymer film substrate having dielectric and/or reflective metal
layers deposited thereon incorporates a second polymer film on the
top layer of dielectric and/or reflective metal. This second layer
functions to protect the dielectric and/or reflective metal layers
from mechanical damage that could otherwise cause degradation of
the interference filter. The second polymer film can comprise any
suitable material, as detailed below, and can be the same as or
different from the flexible polymer film substrate. The second
polymer film can be adhered to the dielectric and/or reflective
metal layers with any suitable adhesive, as is known in the art. In
various embodiments a spray on silicone adhesive is used. In other
embodiments, silicone adhesive can be applied using other means,
such as various gravure and slot die coating techniques. In various
embodiments the adhesive used is a high temperature adhesive, and,
in particular, is a high temperature silicone adhesive.
[0016] Flexible interference filters of the present invention can
further include a layer of a pressure sensitive adhesive and,
optionally, a release liner, disposed on the outer surface of one
of the polymer films, opposite the stack, with the first polymer
film preferred. In these embodiments, the filters can be applied to
any desired surface, including, for example, a frame, window, glass
panel, plastic panel, or other suitable support. The pressure
sensitive adhesive can be any suitable adhesive, and, in some
embodiments, the adhesive is a silicone pressure adhesive. The
adhesive itself can be a removable adhesive or a permanent
adhesive, and can be formed to completely cover the polymer film or
only a sub-portion thereof.
[0017] Flexible interference filters of the present invention are
useful in a wide variety of light filtering applications. As a
lightweight film, these filters can be used as a direct replacement
for standard gel filters. Further, because filters of the present
invention are flexible, they can be formed to match the curvature
of a light source, which eliminates or reduces gradients of colors
that can occur in conventional, flat filters for which distances
between the typically curved light sources and flat glass are not
constant. Filters can be formed to a non-planar shape at the time
of manufacture or at the point of application, as desired.
[0018] In other embodiments, filters of the present invention can
be combined to form a multiple filter roll or wheel that is useful
when the ability to quickly change filters is desired. Rolls and
wheels can easily be combined with an automatic control device to
allow for the rapid and automatic switching among several filters
in the roll or wheel.
Polymer Film
[0019] Polymer films of the present invention can be any suitable
thermoplastic film that is used in the performance film arts. In
various embodiments, the thermoplastic film can comprise
polycarbonates, acrylics, nylons, polyesters, polyurethanes,
polyolefins such as polypropylene, cellulose acetates and
triacetates, vinyl acetals, such as poly(vinyl butyral), polyimide,
vinyl chloride polymers and copolymers and the like, or another
plastic suitable for use in a performance film, for example,
PEEK.RTM. (polyetheretherketone). In various embodiments, the
thermoplastic film is a polyester film, for example poly(ethylene
naphthalate). In various embodiments, the thermoplastic film is
poly(ethylene terephthalate).
[0020] In various embodiments the thermoplastic film can have a
thickness of 0.012 millimeters to 0.40 millimeters, and preferably
0.07 millimeters to 0.17 millimeters.
[0021] The thermoplastic films, in some embodiments, are optically
transparent (i.e. objects adjacent one side of the layer can be
comfortably seen by the eye of a particular observer looking
through the layer from the other side). In various embodiments, the
thermoplastic film comprises materials such as re-stretched
thermoplastic films having the noted properties, which include
polyesters. In various embodiments, poly(ethylene naphthalate) is
used that has been biaxially stretched to improve strength, and has
been heat stabilized to provide low shrinkage characteristics when
subjected to elevated temperatures (e.g. less than 2% shrinkage in
both directions after 30 minutes at 150.degree. C.).
Dielectric and Reflective Layers
[0022] The alternating dielectric and/or reflective metal layers of
the present invention can comprise any suitable high/low pair, as
is known in the art. Useful pairs include titanium dioxide and
silicon dioxide and zinc sulfide and magnesium fluoride. High index
materials can include, but are not limited to: niobium pentoxide,
tantalum pentoxide, and reflective metals such as silver and
alloys, copper and alloys, and aluminum and alloys.
[0023] In a preferred embodiment, the high/low pair is titanium
dioxide and silicon dioxide. The alternating dielectric and/or
reflective metal layers of the present invention can be formed at
the appropriate thicknesses so as to provide the desired light
filtration. In various embodiments, the alternating dielectric
and/or reflective metal layers have a total thickness of 10 to 120
nanometers.
[0024] The alternating dielectric and/or reflective metal layers of
the present invention can have any suitable high/low combination of
refractive indices, for example, greater than 2 and less than 1.8
and greater than 2.2 and less than 1.6.
[0025] Alternating dielectric and/or reflective metal layers of the
present invention can be formed using any suitable method, as are
known in the art, for example, with physical vapor deposition such
as "sputtering", electron beam evaporation, and variations thereof.
In various embodiments, sputtering is the preferred method of
fabrication. Exemplary dielectric and/or reflective metal layer
forming techniques are well known in the art and include, for
example, those disclosed in U.S. Pat. No. 2,379,790, U.S. Pat. No.
6,859,323, and "Thin Film Optical Filters", 3.sup.rd Edition, by H.
Angus Macleod.
EXAMPLES
Example 1
[0026] A dichroic filter is prepared having the following
configuration--
[0027] Base Film--TK20 0.13 millimeters poly(ethylene naphthalate)
film (SKC Incorporated, Korea).
[0028] Stack Layers-- TABLE-US-00001 Layer Number Thickness
Material Layer 1 55 nm TiO.sub.2 Layer 2 95 nm SiO.sub.2 Layer 3 70
nm TiO.sub.2 Layer 4 95 nm SiO.sub.2 Layer 5 30 nm TiO.sub.2 Layer
6 95 nm SiO.sub.2 Layer 7 65 nm TiO.sub.2 Layer 8 90 nm SiO.sub.2
Layer 9 60 nm TiO.sub.2 Layer 10 45 nm SiO.sub.2 Layer 11 70 nm
TiO.sub.2 Layer 12 85 nm SiO.sub.2 Layer 13 65 nm TiO.sub.2
[0029] Laminating Adhesive--Dow Corning 7657 adhesive with Syloff
4000 catalyst (available from Dow Corning).
[0030] Protective Polymer--25.4 micron thickness poly(ethylene
terephthalate).
[0031] The light transmission characteristics of the resulting film
is shown in FIG. 1.
Example 2
[0032] A dichroic filter is prepared having the following
configuration--
[0033] Base Film--TK20 0.13 millimeters poly(ethylene naphthalate)
(SKC Incorporated, Korea).
[0034] Stack Layers-- TABLE-US-00002 Layer Number Thickness
Material Layer 1 10 nm TiO.sub.2 Layer 2 25 nm Silver-alloy Layer 3
95 nm TiO.sub.2 Layer 4 25 nm Silver-alloy Layer 5 110 nm TiO.sub.2
Layer 6 15 nm Silver-alloy Layer 7 75 nm TiO.sub.2
[0035] Laminating Adhesive--Dow Corning 7657 adhesive with Syloff
4000 catalyst (available from Dow Corning).
[0036] Protective Polymer--25.4 micron thickness poly(ethylene
terephthalate).
[0037] The light transmission characteristics of the resulting film
is shown in FIG. 2.
[0038] By virtue of the present invention, light, flexible,
dichroic filters are provided that effectively filter light and
resist degradation from heat buildup, which allows for longer
filter life and easier handling.
[0039] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiments disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
[0040] It will further be understood that any of the ranges,
values, or characteristics given for any single component of the
present invention can be used interchangeable with any ranges,
values, or characteristics given for any of the other components of
the invention, where compatible, to form an embodiment having
defined values for each of the components, as given herein
throughout.
[0041] Any figure reference numbers given within the abstract or
any claims are for illustrative purposes only and should not be
construed to limit the claimed invention to any one particular
embodiment shown in any figure.
[0042] Unless otherwise noted, drawings are not drawn to scale.
[0043] Each reference, including journal articles, patents,
applications, and books, referred to herein is hereby incorporated
by reference in its entirety.
* * * * *