U.S. patent application number 10/950044 was filed with the patent office on 2005-02-17 for light-stable structures.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Castiglione, Stephanie B., Fischer, Richard M. JR..
Application Number | 20050037161 10/950044 |
Document ID | / |
Family ID | 33158592 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050037161 |
Kind Code |
A1 |
Castiglione, Stephanie B. ;
et al. |
February 17, 2005 |
Light-stable structures
Abstract
An assembly including a polymeric film in an inert environment
is provided. The inert environment is bounded on at least one side
by a pane comprising low emissivity glass.
Inventors: |
Castiglione, Stephanie B.;
(Hudson, WI) ; Fischer, Richard M. JR.; (Hudson,
WI) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
33158592 |
Appl. No.: |
10/950044 |
Filed: |
September 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10950044 |
Sep 24, 2004 |
|
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10413684 |
Apr 15, 2003 |
|
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6811841 |
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Current U.S.
Class: |
428/34 |
Current CPC
Class: |
E06B 3/6715 20130101;
B32B 2307/714 20130101; B32B 27/08 20130101; B32B 2315/08 20130101;
B32B 27/36 20130101; B32B 27/18 20130101; B32B 17/10018 20130101;
B32B 2398/00 20130101; B32B 3/30 20130101; Y10T 428/2457 20150115;
B32B 2307/71 20130101; B32B 17/10064 20130101 |
Class at
Publication: |
428/034 |
International
Class: |
E06B 003/24 |
Claims
We claim:
1. An assembly comprising a first pane; a second pane; a frame,
wherein the frame secures the first and second pane; an inert
environment between the first and second panes; and a polymeric
film positioned in the inert environment; wherein at least one pane
comprises a low emissivity glass.
2. The assembly of claim 1, wherein the low emissivity glass is
coated with at least one of a metal and an oxide.
3. The assembly of claim 1, wherein the inert environment comprises
a vacuum.
4. The assembly of claim 1, wherein the inert environment comprises
an inert gas.
5. The assembly of claim 4 wherein the inert gas is a noble
gas.
6. The assembly of claim 5, wherein the noble gas is argon.
7. The assembly of claim 1, wherein the inert environment comprises
less than about 3% oxygen.
8. The assembly of claim 1, further comprising a resin layer
comprising a first smooth surface and second structured surface
being formed of a plurality of spaced parallel grooves, each said
groove being formed by a first facet which is substantially
perpendicular to the first smooth surface and a second facet which
makes an angle between 1 to 60 degrees with the first smooth
surface, wherein the smooth surface is bonded to the polymeric
film.
9. The assembly claim 1, wherein the polymeric film is a
polyester.
10. The assembly of claim 9 wherein the polyester comprises a
polyester selected from the group consisting of polyethylene
naphthalate, polyethylene terephthalate, polycarbonates,
polyarylates, polybutylene naphthalate, polypropylene naphthalate,
polybutylene terephthalate, polypropylene terephthalate, and blends
and copolymers of any of the above with each other or with other
polymers.
11. The assembly of claim 1, wherein the structure exhibits a delta
b* yellowing value of less than 9 after exposure to a radiant dose
of 6000 kJ/m.sup.2 at 340 nm, according to ASTM G-155 test method,
employing a repeating test cycle of 8 hours of light at 88.degree.
C., black panel temperature, followed by 4 hours dark at 50.degree.
C., wherein the delta b* value is based on D-65, 10 degree
observer, specular included, reflectance measurements.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 10/413,684, filed Apr. 15, 2003, now allowed; the disclosure of
which is herein incorporated by reference.
BACKGROUND
[0002] The present invention relates to light-stable structures,
specifically structures comprising a polymeric film and an
ultraviolet light-absorbing compound that inhibits degradation of
the film despite exposure to ultraviolet light in an inert
environment.
[0003] A vast number of polymeric films are available for use in a
wide variety of applications. For example, polymeric films may be
used as decorative or protective layers. Use of some polymeric
films can be severely limited for outdoor applications and other
applications where the films are exposed to a source of light. For
example, many polymeric films degrade when subjected to prolonged
exposure to ultraviolet (UV) radiation (i.e., wavelengths less than
about 400 nanometers (nm), e.g., wavelengths between about 200 and
400 nm, e.g., wavelengths between about 315 and 400 nm). Exposure
to UV radiation occurs naturally during use outdoors or during
exposure to fluorescent light or other UV-emitting light
sources.
[0004] Polymeric films that have undergone UV degradation may show
detrimental changes in color and/or mechanical properties.
Color-fast films resist color degradation. Certain films are known
to have inherent color-fastness in the presence of UV light. Other
polymeric films do not exhibit color-fastness, for example, clear
films containing an aromatic moiety (e.g., some polyesters) may
yellow when exposed to UV light. These non-color-fast films may
require the addition of a modifier such as a UV stabilizer. The
modifier may be incorporated directly into the polymeric film, it
may be present in a coating applied to one or both surfaces of the
film, or it may be part of a layer positioned between the source of
the ultraviolet light and the polymeric film.
SUMMARY
[0005] Briefly, in one aspect, the present invention provides an
assembly comprising an inert environment bounded on at least one
side by a pane, wherein the pane is at least partially transparent
to ultraviolet light, a structure positioned in the inert
environment, the structure comprising a polymeric film and an
effective amount of a ultraviolet light-absorbing compound, wherein
the ultraviolet light absorbing compound comprises a triazine.
[0006] In another aspect, the present invention provides an
assembly comprising an inert environment bounded on at least one
side by a pane, wherein the pane is at least partially transparent
to ultraviolet light, a structure positioned in the inert
environment, the structure comprising a polymeric film, a resin
layer and an effective amount of a ultraviolet light-absorbing
compound, wherein the ultraviolet light absorbing compound
comprises a triazine.
[0007] In yet another aspect, the present invention provides an
assembly comprising an inert environment bounded on at least one
side by a pane, wherein the pane is at least partially transparent
to ultraviolet light, a structure positioned in the inert
environment, the structure comprising a polymeric film, a layer
comprising a first smooth surface and second structured surface
being formed of a plurality of spaced parallel grooves, each said
groove being formed by a first facet which is substantially
perpendicular to the first smooth surface and a second facet which
makes an angle between 1 to 60 degrees with the first smooth
surface, and an effective amount of a ultraviolet light-absorbing
compound, wherein the ultraviolet light-absorbing compound
comprises a triazine.
[0008] In yet another aspect, the present invention provides an
assembly comprising an inert environment bounded on at least one
side by a pane, wherein the pane is at least partially transparent
to ultraviolet light, a structure positioned in the inert
environment, the structure comprising a polymeric film and an
effective amount of a ultraviolet light-absorbing compound, wherein
the ultraviolet light absorbing compound comprises a triazine,
wherein the structure exhibits a delta b* yellowing value of less
than 9 after exposure to a radiant dose of 6000 kJ/m.sup.2 at 340
nm, according to ASTM G-155 test method, employing a repeating test
cycle of 8 hours of light at 88.degree. C., black panel
temperature, followed by 4 hours dark at 50.degree. C., wherein the
delta b* value is based on D-65, 10 degree observer, specular
included, reflectance measurements. The b* values are based on the
CIELab colorspace.
[0009] In yet another aspect, the present invention provides an
assembly comprising a first pane, a second pane, a frame, wherein
the frame secures the first and second pane, an inert environment
between the first and second panes, a polymeric film positioned in
the inert environment, and an effective amount of a ultraviolet
light-absorbing compound, wherein the ultraviolet light absorbing
compound comprises a triazine.
[0010] The above summary of the present invention is not intended
to describe each discussed embodiment of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a side view of a structure in an inert environment
in accordance with an embodiment of the present invention.
[0012] FIG. 2 is a side view of a multilayer structure in
accordance with an embodiment of the present invention.
[0013] FIG. 3 is a side view of a multilayer structure with a
structured surface in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION
[0014] Some applications for polymeric films involve placing a
polymeric film in an inert environment. As used herein, the phrase
"inert environment" means an environment substantially free of
oxygen (e.g., less than about 3% by volume oxygen, e.g., less than
about 2.1% by volume oxygen, e.g., less than about 1.5% by volume
oxygen, e.g., less than about 1% by volume oxygen). The inert
environment may comprise one or more inert gases such as, for
example, noble gases (e.g., argon, krypton, neon), and nitrogen. In
some embodiments, the inert environment comprises at least about
80% by volume inert gas (e.g., at least about 90% by volume, e.g.,
at least about 95% by volume). The pressure may be less than
atmospheric pressure (e.g., less than about 1.times.10.sup.5
N/m.sup.2, e.g., less than about 0.6.times.10.sup.5 N/m.sup.2),
atmospheric (i.e., about 1.times.10.sup.5 N/m.sup.2), or greater
than atmospheric (i.e., greater than about 1.times.10.sup.5
N/m.sup.2).
[0015] One application where polymeric films are used in an inert
environment is as part of a protective or decorative structure in
an insulated window. An example of a polymeric film for protective
applications is the use of suspended films (e.g., films sold under
the trade names HEAT MIRROR 88 or HEAT MIRROR 66, manufactured by
Southwall Technologies, located in Palo Alto, Calif.) for reducing
thermal conductivity through the window, and improving the energy
rating of the window. Additional examples of films used for
protection include polyester films used for screening UV light, and
for preventing glass spread upon breakage in security applications.
Examples of such polyester-based products include films sold under
the trade names SCOTCHSHIELD Ultra Safety and Security Window Films
and SCOTCHTINT Sun Control Film, both available from 3M Company,
located in St. Paul, Minn.
[0016] One example of the use of polymeric films for decorative
purposes has been described in U.S. Pat. No. 5,840,407 (Futhey et
al.), incorporated herein by reference. Futhey et al. describe a
transparent optical film made of a polymeric material having a
first smooth surface and a second structured surface for providing
a simulated beveled appearance. The structured surface of the film
is formed of a plurality of spaced parallel grooves, each groove
being formed by a first facet, which is substantially perpendicular
to the first smooth surface and a second facet which makes an angle
between 1 to 60 degrees with the first smooth surface. The film may
be affixed to glass to simulate beveled glass. Futhey et al. also
describe the use of polymeric films to achieve other decorative
effects (e.g., V-groove cut effect, leaded glass, and textured
glass (e.g., ripple glass, hammered glass, moss glass, flemish
glass, glue chip glass, and baroque glass)).
[0017] FIG. 1 shows a cross-section of a multi-pane, insulated
window 30 comprising a frame assembly 32, and at least two panes of
gas-impermeable, light-transmitting material 34 and 40. The frame
assembly 32, secures the peripheral edges 52 and 54, of each pane
34 and 40, holding them in a substantially parallel relation to
each other. A hermetically sealed chamber 48, is formed between the
panes 34 and 40, bounded peripherally by the frame assembly 32. In
some applications, the hermetically sealed chamber 48, is evacuated
creating a vacuum. In other applications, the hermetically sealed
chamber 48, is filled with an inert gas. However, a hermetically
sealed chamber is not required so long as there is an inert
environment bounded on at least one side by a pane.
[0018] A pane may comprise glass, plastic or a combination thereof.
A pane may be transparent or translucent, and may be tinted and/or
contain printed images. A pane may have one layer or multiple
layers. A pane may, for example, be safety glass where two pieces
of glass are laminated to a polyvinyl butyral film such that the
film is between the two sheets of glass. A pane may be, for
example, laminated glass where two pieces of glass or plastic
(e.g., polymethylacrylate, polymethyl methacrylate) are laminated
to a polymer film (e.g., polyester film) such that the film is
between the two sheets of glass or plastic. Optionally, a resin
layer may be positioned between the polymer film and one or both
sheets of glass or plastic. A pane may optionally comprise
thermally tempered glass, where the glass has been heated and
rapidly cooled, or chemically tempered glass, where 2-10 microns of
each side of the glass are hardened by a chemical process. A pane
may be, for example, low emissivity glass where the glass is coated
with a metal or an oxide layer (e.g., glass available under the
trade names Lo{overscore (E)}.sup.2-140, Lo{overscore
(E)}.sup.2-170, Lo{overscore (E)}.sup.2-172, and Lo{overscore
(E)}.sup.2-178 from Cardinal IG, located in Minneapolis, Minn.). A
pane can alternatively comprise plastics such as, for example,
polycarbonate or polymethylmethacrylate based polymers.
[0019] Ultraviolet light 64, may pass through the first pane 34,
from the first surface 36, of the first pane 34, to the second
surface 38, of the first pane, 34. Alternatively, ultraviolet light
64, may pass through the second pane 40, from the second surface
44, of the second pane 40, to the first surface 42, of the second
pane, 40. In some applications, ultraviolet light 64, may pass
through both the first pane 34, and the second pane 40.
[0020] A structure 70, may be located between the panes 34 and 40,
thus positioned in the hermetically sealed chamber 48. The
structure 70, is shown adhered to the first surface 42, of the
second pane 40, by adhesive layer 50. In some embodiments, the
structure 70 may be adhered to the second surface 38, of the first
pane 34. In some embodiments, the structure 70, may be supported
between the two panes 34 and 40, by, for example, the frame
assembly 32.
[0021] In FIG. 1, the structure 70, is shown as comprising a first
layer 60, and an adhesive layer 50. In some embodiments, the
adhesive layer 50, may not be present. In some embodiments, the
first layer 60, may be bonded to, for example, the first surface
42, of the second pane 40.
[0022] The first layer 60, comprises at least one polymeric film.
The first layer 60, may be a multilayer film. For example, the
first layer 60, may comprise adhesive layer(s), resin layer(s),
bonding layer(s), primer layer(s), polymeric and/or non-polymeric
film(s). One or more layers of the structure 70, may optionally
further comprise additives such as, for example, dyes, flame
retardants, ultraviolet light absorbers, antioxidants, hindered
amine stabilizers, and combinations thereof.
[0023] FIG. 2 shows an exemplary multilayer structure 270. The
multilayer structure 270, comprises a first layer 216, and a second
layer 80. The first layer 216, is a polymeric film. The second
layer 80, may be, for example, a polymeric film, a resin layer, an
ink layer, or a metalized layer (e.g., vapor deposited metal). In
some embodiments, the second surface 84, of the second layer 80,
may be bonded directly to a first surface 206, of the first layer
216 (not shown). In some embodiments, a bonding layer 90, may be
present between the first surface 206, of the first layer 216, and
the second surface 84, of the second layer 80. In some embodiments,
a first primer layer 224, may be located between the bonding layer
90, and the first surface 206, of the first layer 216. In some
embodiments, a second primer layer 226, may be located between the
bonding layer 90, and the second surface 84, of the second layer
80.
[0024] In some embodiments, the bonding layer 90, may be an
adhesive (e.g., a pressure sensitive adhesive). In some
embodiments, the bonding layer 90, may be curable material (e.g.,
moisture curable, thermal curable, radiation curable).
[0025] In some embodiments, an adhesive layer (not shown) may be
applied to the second surface 208, of the first layer 216. In some
embodiments, an adhesive layer (not shown) may be applied to the
first surface 82, of the second layer 80.
[0026] In some embodiments, polymeric films exposed to UV radiation
in an inert environment show an objectionable color change. An
improvement over the existing structures is desirable if they are
to be used in an inert environment in applications requiring
extended exposure to ultraviolet light.
[0027] The yellowing caused by UV degradation often occurs by
photolysis. Photolysis occurs when a chemical species present in
the structure absorbs a photon initiating further reactions which
result in the formation of a chromophore. The chromophore absorbs
light in the visible region of the spectrum giving the film its
colored (i.e., yellow) appearance.
[0028] In an oxygen-containing environment, the structure may also
undergo photooxidation. Photooxidation is the normal degradation
process for organic materials exposed to ultraviolet light in an
oxygen-containing environment.
[0029] "Photo-bleaching" refers to photooxidation that alters the
chromophores formed by photolysis, thus reducing or eliminating
yellowing. The chromophores formed by photolysis absorb photons and
react with oxygen to form a new species. The presence of this new
species does not result in an objectionable color (e.g., yellow) in
the structure.
[0030] In an inert environment, photooxidation is expected to be
substantially reduced or eliminated. In such an environment,
materials that were rendered color-fast in an oxygen-containing
environment due to photobleaching may show unacceptable levels of
yellowing.
[0031] To prevent or inhibit photodegradation of a structure, an
ultraviolet light stabilizer can be incorporated into or applied to
one or more of the layers comprising the structure. A UV stabilizer
may also be incorporated into or applied to one or more surfaces of
a pane. UV stabilizers include materials that inhibit
photoinitiation (e.g., UV absorbers (UVAs) and excited state
quenchers), and materials that inhibit the subsequent oxidative
processes (e.g., radical scavengers and alkyl hydroperoxide
decomposers).
[0032] One factor affecting the selection of a photostabilizer is
the environment to which the structure will be exposed. In an
environment that is essentially free of oxygen, materials that
inhibit oxidative processes may be unnecessary. Other factors
affecting the selection of a photostabilizer include chemical
compatibility, processability, optical clarity, color, thermal
stability, and cost.
[0033] UVAs function by competitively absorbing the UV energy that
causes photodegradation of the structure. A wide variety of
ultraviolet light-absorbing compounds are available including, for
example, benzophenones (e.g., materials sold under the trade names
CYASORB UV-531 (available from Cytec Industries Inc., located in
West Paterson, N.J.), and UVINUL 3008 (available from BASF, located
in Mount Olive, N.J.)), benzotriazoles (e.g., materials sold under
the trade names CYASORB UV-5411 (available from Cytec Industries
Inc.), and TINUVIN 329, TINUVIN 360, and TINUVIN 571 (available
from Ciba Specialty Chemicals North America, located in Tarrytown,
N.Y.)), triazines (e.g., materials sold under the trade names
CYASORB UV-1164 (available from Cytec Industries Inc.), and TINUVIN
400 and TINUVIN 1577 (available from Ciba Specialty Chemicals North
America)), oxanilides (e.g., materials sold under the trade names
TINUVIN 312 (available from Ciba Specialty Chemicals North
America), and SANDUVOR VSU (available from Clariant AG, located in
Muttenz, Switzerland)), benzoxazinones (e.g., CYASORB UV-3638
(available from Cytec Industries Inc.), cyanoacrylates (e.g.,
UVINUL 3039 (available from BASF)), and benzilidine malonates
(e.g., HOSTAVIN PR-25 (available from Clariant AG).
[0034] The presence of a UVA can significantly improve the
durability of polymers exposed to UV light. In general, the
selection of a UVA is based on factors such as chemical
compatibility, processability, optical clarity, color, thermal
stability, and cost. In addition, some classes of UVA are known to
show accelerated loss rates when exposed to UV light in the
presence of oxygen (i.e., they undergo photooxidation), which may
make them less desirable for that reason.
[0035] If these UVAs were used in an inert environment, one would
expect that their loss rates would be significantly reduced. Thus,
for systems where the UV exposure occurs in an inert environment,
differences between classes of UVA based on susceptibility to
photooxidation would be substantially eliminated.
[0036] Surprisingly, even in an inert environment, specific classes
of UVA have superior resistance to photodegradation. For example,
the use of triazine (e.g., hydroxy-functional tris-aryl triazine
(e.g., 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxy-phenol and
2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-(octyloxy)phenol))
UVAs resulted in less color change when the films were exposed to
UV light in an inert environment.
[0037] The articles of the present invention generally comprise a
structure in an inert environment. In some embodiments, the inert
environment is bounded on at least one side by a pane. In some
embodiments, the inert environment is between two panes. In some
embodiments, the two panes are secured by a frame. In some
embodiments, the structure comprises at least one polymeric film
and an effective amount of at least one light stabilizing
composition. In some embodiments at least one of the panes
comprises the light stabilizing composition. The light stabilizing
composition comprises an ultraviolet light-absorbing compound.
[0038] The polymeric film of the invention may be virtually any
polymeric material. The polymeric material may be transparent,
translucent or opaque, uniaxially oriented, biaxially oriented or
unoriented.
[0039] The polymeric film may comprise, for example, polyolefins
(e.g., polyethylene, polypropylene, ethylene vinyl acetate
copolymers, ethylene acrylic acid copolymers, ionomers of ethylene
and mixtures thereof), polyesters, polyimides, polystyrenes,
acrylics, polyacrylates, polymethacrylates,
polymethylmethacrylates, polyurethanes, urethane acrylate polymers,
epoxy acrylate polymers, polyacetals, polycarbonate, polysulfone,
cellulose acetate butyrate, polyvinyl chloride, and blends
thereof.
[0040] If the polymeric film is a polyester film, it may
incorporate any polyester-containing polymer. Useful polyester
polymers include, for example, polymers having terephthalate,
isophthalate, and/or naphthalate comonomer units, e.g.,
polyethylene naphthalate (PEN), polyethylene terephthalate (PET)
and copolymers and blends thereof. Other suitable polyester
materials include polycarbonates, polyarylates, and other
naphthalate and terephthalate-containing polymers, such as, for
example, polybutylene naphthalate (PBN), polypropylene naphthalate
(PPN), and polybutylene terephthalate (PBT).
[0041] The polymeric film may comprise additives such as, for
example, lubricants and other melt processing aids, pigments, dyes
and other colorants, supplemental ultraviolet light stabilizers,
(e.g., hindered amine light stabilizers (i.e., HALS)),
antioxidants, nucleating agents, fillers, plasticizers, whitening
agents, flame retardants, antistatic and slip agents, and the
like.
[0042] Polymeric films may be prepared by known techniques
including casting or melt extrusion. The polymeric film may be
embossed by known techniques.
[0043] The structures of the present invention may comprise one or
more layers in addition to the polymeric film. For example, the
structure may comprise an adhesive. The adhesive may be a pressure
sensitive adhesive or a non-pressure sensitive adhesive (e.g., a
thermally cured adhesive or a moisture cure adhesive). In some
embodiments, the adhesive is preferably a pressure sensitive
adhesive. In some embodiments, the adhesive layer is a clear
adhesive. In some embodiments, the adhesive layer contains low
amounts of residuals (e.g., a low outgassing adhesive).
[0044] One class of materials useful for the adhesive includes
acrylate and methacrylate polymers and copolymers. Such polymers
are formed, for example, by polymerizing one or more monomeric
acrylic or methacrylic esters of non-tertiary alkyl alcohols, with
the alkyl groups having from 1 to about 20 carbon atoms (e.g., from
3 to 18 carbon atoms). Suitable acrylate monomers include, for
example, methyl acrylate, ethyl acrylate, n-butyl acrylate, lauryl
acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, iso-octyl
acrylate, octadecyl acrylate, nonyl acrylate, decyl acrylate, and
dodecyl acrylate. The corresponding methacrylates are useful as
well. Also useful are aromatic acrylates and methacrylates, e.g.,
benzyl acrylate.
[0045] Optionally, one or more monoethylenically unsaturated
co-monomers may be polymerized with the acrylate or methacrylate
monomers. The particular type and amount of co-monomer is selected
based upon the desired properties of the polymer.
[0046] One group of useful co-monomers includes those having a
homopolymer glass transition temperature greater than the glass
transition temperature of the (meth)acrylate (i.e., acrylate or
methacrylate) homopolymer. Examples of suitable co-monomers falling
within this group include acrylic acid, acrylamides,
methacrylamides, substituted acrylamides (such as N,N-dimethyl
acrylamide), itaconic acid, methacrylic acid, acrylonitrile,
methacrylonitrile, vinyl acetate, N-vinyl pyrrolidone, isobornyl
acrylate, cyano ethyl acrylate, N-vinylcaprolactam, maleic
anhydride, hydroxyalkyl(meth)-acrylates, N,N-dimethyl aminoethyl
(meth)acrylate, N,N-diethylacrylamide, beta-carboxyethyl acrylate,
vinyl esters of neodecanoic, neononanoic, neopentanoic,
2-ethylhexanoic, or propionic acids (e.g., those available under
the trade name VYNATES, available from Union Carbide Corp., located
in Danbury, Conn.), vinylidene chloride, styrene, vinyl toluene,
and alkyl vinyl ethers.
[0047] A second group of monoethylenically unsaturated co-monomers
that may be polymerized with the acrylate or methacrylate monomers
includes those having a homopolymer glass transition temperature
(Tg) less than the glass transition temperature of the acrylate
homopolymer. Examples of suitable co-monomers falling within this
class include ethyloxyethoxy ethyl acrylate (Tg=-71 degrees
Celsius) and a methoxypolyethylene glycol 400 acrylate (Tg=-65
degrees Celsius; available under the trade name NK Ester AM-90G
from Shin Nakamura Chemical Co., Ltd.).
[0048] A second class of polymers useful in the adhesive includes
semicrystalline polymer resins, such as polyolefins and polyolefin
copolymers (e.g., polymer resins based upon monomers having between
about 2 and about 8 carbon atoms, such as low-density polyethylene,
high-density polyethylene, polypropylene, ethylene-propylene
copolymers, etc.), polyesters and co-polyesters, polyamides and
co-polyamides, fluorinated homopolymers and copolymers,
polyalkylene oxides (e.g., polyethylene oxide and polypropylene
oxide), polyvinyl alcohol, ionomers (e.g., ethylene-methacrylic
acid copolymers neutralized with a base), and cellulose acetate.
Other examples of polymers in this class include amorphous polymers
such as polyacrylonitrile, polyvinyl chloride, thermoplastic
polyurethanes, aromatic epoxies, polycarbonates, amorphous
polyesters, amorphous polyamides, ABS block copolymers,
polyphenylene oxide alloys, ionomers (e.g., ethylene-methacrylic
acid copolymers neutralized with salt), fluorinated elastomers, and
polydimethyl siloxane.
[0049] A third class of polymers useful in the adhesive includes
elastomers containing ultraviolet radiation-activatable groups.
Examples include polybutadiene, polyisoprene, polychloroprene,
random and block copolymers of styrene and dienes (e.g., SBR), and
ethylene-propylene-dien- e monomer rubber. This class of polymer is
typically combined with tackifying resins.
[0050] A fourth class of polymers useful in the adhesive includes
pressure sensitive and hot melt applied adhesives prepared from
non-photopolymerizable monomers. Such polymers can be adhesive
polymers (i.e., polymers that are inherently adhesive), or polymers
that are not inherently adhesive but are capable of forming
adhesive compositions when compounded with components such as
plasticizers, or tackifiers. Specific examples include
poly-alpha-olefins (e.g., polyoctene, polyhexene, and atactic
polypropylene), block copolymer-based adhesives, natural and
synthetic rubbers, silicone adhesives, ethylene-vinyl acetate, and
epoxy-containing structural adhesive blends (e.g., epoxy-acrylate
and epoxy-polyester blends).
[0051] In some embodiments, silicone based adhesives may be
particularly suited.
[0052] The adhesive layer may be radiation cured (e.g., thermally
cured, ultraviolet light cured, or electron beam cured) and can be
solvent-based, water-based or 100 percent solids.
[0053] In some embodiments, the adhesive layer has a thickness of
at least about 5 microns (e.g., at least about 10 microns). In some
embodiments, the adhesive layer is less than about 150 microns
(e.g., less than about 50 microns, e.g., less than about 25
microns).
[0054] The adhesive may comprise additives, such as fillers,
antioxidants, viscosity modifiers, pigments, tackifying resins,
fibers, and the like.
[0055] FIG. 3 shows an exemplary structure 370 useful in the
present invention. The structure 370, comprises a polymeric film
316, having a first surface 306, and a second surface 308. The
structure 370, further comprises a resin layer 10, having a smooth
surface 12, and a structured surface 14. The structured surface 14,
of the resin layer 10, may comprise grooves 18. The grooves 18, may
comprise a first facet 20, perpendicular to the smooth surface 12,
of the resin layer 10, and a second facet 22.
[0056] In some embodiments, the pitch of the grooves, the distance
between peaks of the grooves, is sufficiently small such that an
observer from a distance (e.g., about 3 meters) cannot discern the
individual grooves. In some embodiments, the pitch will be at least
about one micron (e.g., at least about five microns, e.g., at least
about ten microns). In some embodiments, the pitch will be less
than about 500 microns (e.g., less than about 250 microns, e.g.,
less than about 50 microns). In some embodiments, the depth of the
grooves will be less than about 200 microns (e.g., less than about
100 microns, e.g., less than about 75 microns).
[0057] In some embodiments, the smooth surface 12, of the resin
layer 10, may be bonded directly to the first surface 306, of the
polymeric film 316. In some embodiments, a first primer layer 326,
may be located between the resin layer 10, and the polymeric film
316.
[0058] The structure 370, further comprises an adhesive layer, 350.
In some embodiments, the adhesive layer 350, may be bonded directly
to the second surface 308, of the polymeric film 316. In some
embodiments, a second primer layer 324, may be located between the
adhesive layer 350, and the polymeric film 316.
[0059] In some embodiments at least about 80 percent (e.g., at
least about 90 percent, e.g., about 100 percent) of the second
surface 308, the polymeric film 316, has the adhesive layer 350,
bonded thereto. In some embodiments, the adhesive layer 350, is
continuous. In some embodiments, areas of the polymeric film 316,
not covered by the adhesive layer 350, are margin(s) (i.e., the
peripheral edges of the polymeric film).
[0060] In some embodiments, an adhesive layer may be bonded to the
structured surface 14, of the resin layer 10. In some embodiments,
a primer layer may be located between the adhesive layer and the
resin layer.
[0061] There are numerous methods available for treating the
surfaces of a polymeric film to improve the adhesion of an adhesive
and/or resin layer thereto. Such methods include, for example,
chemical etching, electron-beam irradiation, corona treatment,
plasma etching, coextrusion of adhesion promoting layers, and
coating the polymeric film with adhesion promoting primer coatings,
some of which may be subsequently crosslinked. Exemplary primer
coatings include coatings comprising melamine acrylate based
primers and aqueous, cross-linked urethane polyester primers.
[0062] Application of the primer coating may be carried out by
standard coating techniques such as bar coating, roll coating,
curtain coating, rotogravure coating, spraying and dipping. In some
embodiments, the primer layer may be extruded onto the polymeric
film. In some embodiments, the primer layer may be coextruded with
the polymeric film. The polymeric film may be treated prior to the
application of the primer layer. Various known treatment techniques
include corona discharge, flame treatment, and electron beam
irradiation.
[0063] The resin layer may comprise a polymer (e.g., acrylic,
polycarbonate, polyester, polyethylene, polyurethane, and cellulose
acetate butyrate). In some embodiments, resins having one or more
of the following properties are particularly suitable: high thermal
stability, environmental stability, clarity, excellent release from
toolings or molds, and high receptivity for receiving a reflective
coating. Exemplary resins include: poly(carbonate),
poly(methylmethacrylate), polyethylene terephthalate, aliphatic
polyurethane, and cross-linked acrylate such as mono- or
multi-functional acrylates or acrylated epoxies, acrylated
polyesters, and acrylated urethanes blended with mono- and
multi-functional monomers. In some embodiments, resins that provide
highly effective refraction as well as sufficient durability and
weatherability, are particularly suitable.
[0064] One class of materials suitable for the resin layer is
reactive resin systems capable of being cross-linked by a free
radical polymerization mechanism by exposure to radiation, for
example, electron beam, ultraviolet light, or visible light.
Additionally, these materials may be polymerized by thermal means
with the addition of a thermal initiator such as, for example,
benzoyl peroxide. Radiation-initiated cationically polymerizable
resins also may be used. Reactive resins may be blends of
photoinitiator and at least one compound bearing an acrylate group.
In some embodiments, the resin blend contains a monofunctional, a
difunctional, or a polyfunctional compound to ensure formation of a
cross-linked polymeric network upon irradiation.
[0065] Illustrative examples of resins that are capable of being
polymerized by a free radical mechanism that can be used herein
include acrylic-based resins derived from epoxies, polyesters,
polyethers, and urethanes, ethylenically unsaturated compounds,
aminoplast derivatives having at least one pendant acrylate group,
isocyanate derivatives having at least one pendant acrylate group,
epoxy resins other than acrylated epoxies, and mixtures and
combinations thereof. The term acrylate as used herein encompasses
both acrylates and methacrylates. U.S. Pat. No. 4,576,850 (Martens)
discloses examples of crosslinked resins that may be used in the
present invention.
[0066] Ethylenically unsaturated resins, which include both
monomeric and polymeric compounds that contain atoms of carbon,
hydrogen and oxygen, and optionally nitrogen, sulfur, and the
halogens, may be used herein. Oxygen or nitrogen atoms, or both,
are generally present in ether, ester, urethane, amide, and urea
groups. In some embodiments, ethylenically unsaturated compounds
having a molecular weight of less than about 4,000 are particularly
suitable. In some embodiments, the ethylenically unsaturated
compounds are esters made from the reaction of compounds containing
aliphatic monohydroxy groups, aliphatic polyhydroxy groups, and
unsaturated carboxylic acids, such as acrylic acid, methacrylic
acid, itaconic acid, crotonic acid, iso-crotonic acid, maleic acid,
and the like. Such materials are typically readily available
commercially and can be readily cross-linked.
[0067] Some illustrative examples of compounds having an acrylic or
methacrylic group that are suitable for use in the invention are
listed below:
[0068] (1) Monofunctional compounds: ethylacrylate,
n-butylacrylate, isobutylacrylate, 2-ethylhexylacrylate,
n-hexylacrylate, n-octylacrylate, isooctyl acrylate, isobornyl
acrylate, tetrahydrofurfuryl acrylate, 2-phenoxyethyl acrylate, and
N,N-dimethylacrylamide;
[0069] (2) Difunctional compounds: 1,4-butanediol diacrylate,
1,6-hexanediol diacrylate, neopentylglycol diacrylate, ethylene
glycol diacrylate, triethyleneglycol diacrylate, tetraethylene
glycol diacrylate, and diethylene glycol diacrylate; and
[0070] (3) Polyfunctional compounds: trimethylolpropane
triacrylate, glycerol triacrylate, pentaerythritol triacrylate,
pentaerythritol tetraacrylate, and
tris(2-acryloyloxyethyl)isocyanurate.
[0071] Some representative examples of other suitable ethylenically
unsaturated compounds and resins include styrene, divinylbenzene,
vinyl toluene, N-vinyl formamide, N-vinyl pyrrolidone, N-vinyl
caprolactam, monoallyl, polyallyl, and polymethallyl esters such as
diallyl phthalate and diallyl adipate, and amides of carboxylic
acids such as N,N-diallyladipamide.
[0072] Illustrative examples of photopolymerization initiators that
can be blended with acrylic compounds in the resin layer include:
benzil, methyl o-benzoate, benzoin, benzoin ethyl ether, benzoin
isopropyl ether, benzoin isobutyl ether, etc.,
benzophenone/tertiary amine, acetophenones such as
2,2-diethoxyacetophenone, benzyl methyl ketal,
1-hydroxycyclohexylphenyl ketone,
2-hydroxy-2-methyl-1-phenylpropan-1-one- ,
1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one,
2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone,
2,4,6-trimethylbenzoyl-diphenylphosphine oxide,
2-methyl-1-4(methylthio), phenyl-2-morpholino-1-propanone,
bis(2,6-dimethoxybenzoyl)(2,4,4-trimethy- lpentyl)phosphine oxide,
etc. The compounds may be used individually or in combination.
[0073] Cationically polymerizable materials including, but are not
limited to, materials containing epoxy and vinyl ether functional
groups may be used herein. These systems are photoinitiated by
onium salt initiators, such as triarylsulfonium, and diaryliodonium
salts.
[0074] In some embodiments, particularly suitable materials to form
the resin layer include, for example, UV polymerizable polymers.
Exemplary resin layers include acrylate systems (e.g., hexanediol
diacrylate (e.g., SARTOMER SR238, available from Sartomer, located
in Exton, Pa.)), epoxy acrylate (e.g., CN104, available from
Sartomer), and phenoxyethyl acrylate (e.g., PHOTOMER 4035,
available from Cognis, located in Amber, Pa.). In some embodiments,
aliphatic systems are particularly suitable (e.g., aliphatic
urethane acrylate (e.g., PHOTOMER 6010 and 6210 available from
Cognis)).
[0075] In some embodiments, particularly suitable initiators
include, for example, long wavelength curable materials (e.g.,
LUCIRIN TPO, available from BASF; or IRGACURE 819, available from
Ciba Specialty Chemicals North America).
[0076] The ultraviolet light absorbing compounds of the present
invention are preferably triazine compounds, and in particular
hydroxy-functional tris-aryl triazine compounds. Generally, these
compositions will correspond to the chemical formula: 1
[0077] wherein each R.sup.1 is independently selected from the
group consisting of hydrogen and substituted or unsubstituted,
branched or unbranched alkyl, aryl, or alkaryl groups having from 1
to about 18 carbon atoms. In some embodiments, the carbon chains of
any such alkyl, aryl, or alkaryl group are free of interruption by
one or more oxygen atoms and are not substituted by a hydroxy
substituent. In some embodiments, the carbon chains of any such
alkyl, aryl, or alkaryl group have one or more reactive functional
groups (e.g., hydroxyl groups).
[0078] Particularly preferred ultraviolet light absorbing compounds
include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxy-phenol and
2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-(octyloxy)phenol.
Suitable ultraviolet absorbing compounds are available
commercially, including, e.g., those available under the trade
names CYASORB UV-1164, available from Cytec Industries Inc., and
TINUVIN 1577, available from Ciba Specialty Chemicals North
America.
[0079] An effective amount of UVA should be present in one or more
layers of the structure. An effective amount of UVA is amount
sufficient to maintain the delta b* value at less than about 9
after an exposure of 6000 kJ/m.sup.2 at 340 nanometers (e.g., less
than about 5.5 after 6000 kJ/m.sup.2 at 340 nanometers), where the
exposure is a repeating test cycle of 8 hours of light at
88.degree. C., black panel temperature, followed by 4 hours dark at
50.degree. C., in accordance with ASTM G-155 test method, and where
the b* value is based on D-65, 10 degree observer, specular
included, reflectance measurements. In some embodiments, the delta
b* is less than about 11 after 8400 kJ/m.sup.2 at 340 nanometers
(e.g., less than about 4 after 8400 kJ/m.sup.2 at 340 nanometers).
Delta b* is the difference between the b* value measured after the
exposure and the initial b* value.
[0080] In some embodiments, the ultraviolet light-absorbing
compound is present in the light stable structure in an amount
between about 0.25% (e.g., 0.5%, e.g., 1%) and about 5% (e.g., 4%,
e.g., 3%) by weight of the polymeric film. In some embodiments,
about 1.5% by weight of the ultraviolet light-absorbing compound is
present. In some embodiments, about 2% by weight of the ultraviolet
light-absorbing compound is present. In some embodiments, about 3%
by weight of the ultraviolet light-absorbing compound is
present.
[0081] In addition to the UVA, the structure of the present
invention may comprise a hindered amine light stabilizing (HALS)
composition. Many useful HALS are known in the art. Generally, the
most useful HALS compositions are those derived from a tetramethyl
piperidine, and those that can be considered polymeric tertiary
amines. Broadly, these include high molecular weight (i.e., above
about 500), oligomeric, and polymeric compounds that contain a
polyalkylpiperidine constituent, including polyesters, polyethers,
polyamides, polyamines, polyurethanes, polyureas,
polyaminotriazines and copolymers thereof. Preferred HALS
compositions are those containing polymeric compounds made of
substituted hydroxypiperidines, including the polycondensation
product of a hydroxypiperidines with a suitable acid or with a
triazine. A particularly preferred HALS compound is the
polycondensation product of
1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine with
succinic acid. Suitable HALS compositions are available
commercially, for example, under the TINUVIN trade name from Ciba
Specialty Chemicals North America. One such useful HALS composition
is TINUVIN 622.
[0082] The UVA may be present in one or more layers of the
structure. In some embodiments, the UVA is present in the polymeric
film. An effective amount of the UVA compound can be incorporated
into the polymeric film in any manner that facilitates the ability
of the structure to retard deleterious effects of exposure to
unwanted radiation, in particular ultraviolet radiation. The UVA
can, for example, be incorporated along with any additional
additives and adjuvants directly into the polymeric resin(s)
either, before, during, or after its formation into a film. Such
incorporation can take place using any conventional method of
mixing or dispersing additives into a polymer resin, such as, for
example, milling or extrusion.
[0083] In some embodiments, the UVA may be applied to one or both
surfaces of the polymeric film. For example, in some embodiments
the UVA may be coextruded with the polymeric film. In some
embodiments, the UVA may be coated onto one or both surfaces of the
polymeric film, using any known coating technique (e.g., roll
coating, gravure coating).
[0084] In some embodiments, the UVA may be incorporated into a
primer layer, a resin layer, and/or an adhesive layer. Such
incorporation can take place using any conventional method of
mixing or dispersing additives into a polymer resin, such as, for
example, milling or extrusion.
EXAMPLES
[0085] The following examples are offered to aid in the
understanding of the present invention and are not to be construed
as limiting the scope thereof. Unless otherwise indicated, all
parts and percentages are by weight.
[0086] Film Making Procedure
[0087] Polyester film was prepared for use in the Examples in a
batch reactor using ethylene glycol and dimethyl terephthalate as
starting materials. The polyester resin was made using 0.02% cobalt
acetate (available from The Shepherd Chemical Company, located in
Cincinnati, Ohio), 0.02% zinc acetate (available from Mallinckrodt
Baker, Inc., located in Phillipsburg, N.J.), and 0.03% antimony
triacetate (available from Atofina Chemicals, located in
Philadelphia, Pa.). The polyester resin also contained 0.04%
triethyl phosphonoacetate (TEPA) (available from Albright and
Wilson Co., located in Glen Allen, Va.). TEPA is believed to serve
as a catalyst scavenger during subsequent extrusion processing,
stabilizing the polyester resin and preventing the formation of
chemically reactive sites on the polymer chains.
[0088] The films were made on a continuous pilot-plant-sized
sequential biaxial orientation film manufacturing line. A 40 mm
twin screw extruder, equipped with high shear mixing screws to
enhance mixing of the polymer and additives, was used. A twin screw
powder feeder was used to meter the additives to the extruder. A
film die having manual die bolt adjustments was used. A chilled
(20.degree. C.) casting wheel was used. Electrostatic pinning was
used to aid in quenching the cast web and providing even caliper.
The cast web was stretched in the machine direction using a length
orienter having preheating rolls and IR heating in the stretching
gap. Transverse direction stretching and heat setting was performed
in a tenter oven.
[0089] Resin Casting Procedure
[0090] The resin system contained 75 parts PHOTOMER 6210 (available
from Cognis), 25 parts hexanediol diacrylate, SR238 (available from
Sartomer), and 0.5% of LUCIRIN TPO (available from BASF). The
materials were blended with a high-speed mixer, and then heated in
an oven at 160.degree. F. (71.degree. C.) for 24 hours. The
compounded resin was subsequently cooled to room temperature.
[0091] The resin system was coated onto the film using a slot die.
The resin-coated film was brought into contact with a tool or mold
bearing a prismatic structure using pressure provided by a rotating
nip roll. While the resin was in contact with the tool, the resin
was cured using a high intensity Fusion Systems "D" lamp (available
from Fusion UV Curing Systems, located in Rockville, Md.) with a
UV-A (315-400 nm) dose in the range of 100-1000 mJ/cm.sup.2.
[0092] Acrylic Pressure Sensitive Adhesive
[0093] The adhesive used in the examples was a vinyl acetate
scavenged 90/10 isooctylacrylate (IOA), acrylic acid (AA)
blend.
[0094] A master solution is prepared including 216 parts of
isooctylacrylate, 24 parts of acrylic acid, 0.48 parts of
2,2'-azobis(isobutyronitrile) initiator (available under the trade
name VAZO 64, from E.I. du Pont de Nemours and Company, located in
Wilmington, Del.) and 360 parts of ethyl acetate solvent. A four
ounce (about 120 ml) bottle is filled with 60 parts of the master
solution. After purging with nitrogen to remove oxygen, the bottle
is sealed and tumbled for sixteen (16) hours at 55.degree. C. in a
rotating water bath to effect 90 to 95% conversion. The bottle is
opened and an additional initiator charge of 2.4 parts of a 1%
solution of VAZO 64 in ethyl acetate is added. Fifteen percent
(15%) vinyl acetate scavenger, based on the initial monomer charge,
is added to the bottle. The bottle is repurged, sealed, and placed
in the rotating water bath at 60.degree. C. for 20 additional hours
to obtain the adhesive solution.
[0095] The adhesive solution is taken from the bottle and knife
coated onto a 2 mil (50.8 micron) thick, silicone coated polyester
film (available under the trade name T-50, from Courtaulds Film,
located in Martinsville, Va.) to a 2 mil (50.8 micrometer) dried
coating thickness. The adhesive solution thus coated is immediately
dried for ten minutes in a 65.degree. C. oven.
[0096] Sample Mounting Procedure
[0097] Sealed multilayer assemblies simulating double-glazed
insulated glass window units were prepared to test examples of
films containing ultraviolet light absorbing compounds under
exposure to ultraviolet light, while in an inert gas environment.
Using the ACRYLIC PRESSURE SENSITIVE ADHESIVE, a film sample was
laminated to a 6.times.12 inch (15.24.times.30.45 cm) glass plate
of 1/8-inch (3.2 mm) thickness. This was designated as the bottom
glass. A silicone rubber gasket was formed by cutting a 6.times.12
inch (15.24.times.30.45 cm) rectangular shape from 1/4-inch (6.35
mm) thick, Shore 60 A durometer sheet stock (available as part No.
8632K96 from McMaster-Carr Supply Company, located in Chicago,
Ill.) and then cutting out a 5.times.11 inch (12.7.times.27.9 cm)
center portion to form a 1/2-inch (12.7 mm) wide gasket at the
periphery of the glass window unit. This gasket was placed on the
bottom glass plate with the film sample attached inside the
rectangle formed by the cut gasket. A similar sized 6.times.12 inch
(15.24.times.30.45 cm) glass plate (cover glass) was placed on top
of the silicone gasket to form a sealed chamber between the two
panes of glass, simulating a double-glazed insulated glass window
unit. The cover glass was 1/8-inch (3.2 mm) thick float glass
available from White Bear Glass, located in White Bear, Minn.
[0098] Aluminum foil tape (SCOTCH ALUMINUM FOIL TAPE 425, available
from 3M Company) was applied around the periphery of the assembly
to further seal the chamber and to protect the silicone gasket. The
aluminum tape covered the side edges of the bottom glass, the cover
glass, and the side edge of the silicone gasket. The aluminum tape
also partially covered the face of the bottom glass and cover glass
by 1 inch (2.54 cm) in from the edge. Binder Clips (2-inch wide,
BC-100, stock number 99100, available from Officemate International
Corporation of Edison, N.J.) were also covered with aluminum tape
and placed at the edge of the window unit to hold the assembly
together.
[0099] Two holes were drilled in opposite side edges of the
silicone rubber gasket to provide access and egress for an argon
gas purge. The atmosphere inside the window unit was maintained at
greater than about 98.5% argon during exposure in the accelerated
weathering device. The argon concentration was measured using a
GasGlass-1000 (available from SparkLike, located in Helsinki,
Finland).
[0100] UV Exposure Procedure
[0101] Each test window unit was placed into a Q-SUN/3000 test
chamber, available from Q-Panel Lab Products of Cleveland, Ohio,
with air-cooled xenon arc lamps equipped with daylight filters.
Light passed through the top cover glass to the film samples, in
the argon gas environment, attached to the bottom glass. The units
were exposed to a repeating test cycle of 8 hours of light at
88.degree. C., black panel temperature, followed by 4 hours dark at
50.degree. C., in accordance with ASTM G-155 test method.
[0102] Color Measurement Procedure
[0103] Color changes of the samples, specifically yellowing, was
measured as a b* value using a ColorEye 2180 Spectrophotometer,
available from GretagMcBeth of New Windsor, N.Y. (D-65, 10 degree
observer, specular included). Specimens were measured in
reflectance mode (on glass) using a white ceramic standard white
tile as background for the sample/glass plate. Measurements were
based on the CIElab colorspace. Measurements and color differences
were determined following D2244-02 Standard Practice for
Calculation of Color Tolerances and Color Differences from
Instrumentally Measured Color Coordinates.
[0104] Sample Descriptions
[0105] Comparative Example C1 is a 2 mil (51 micrometer) polyester
film containing TINUVIN 360, a benzotriazole UV stabilizer. This
film is available under the trade name MELINEX 943 from Dupont
Teijin, located in Wilmington, Del. The ACRYLIC PRESSURE SENSITIVE
ADHESIVE was laminated to one surface of the film for subsequent
mounting to the bottom glass.
[0106] Comparative Example C2 is a 100 gauge (25.4 micrometer)
polyester film containing CYASORB UV-3638, a benzoxazinone UV
absorber. This film is available under the trade name HB3 from
Dupont Teijin Films. The ACRYLIC PRESSURE SENSITIVE ADHESIVE was
laminated to one surface of the film for subsequent mounting to the
bottom glass.
[0107] Example 1 is a 1 mil (25.4 micrometer) polyester film made
according to the FILM MAKING PROCEDURE. The film contains 2% by
weight CYASORB UV-1164, a triazine UV absorber available from Cytec
Industries Inc. The ACRYLIC PRESSURE SENSITIVE ADHESIVE was
laminated to one surface of the film for subsequent mounting to the
bottom glass.
[0108] Example 2 is a 5 mil (127 micrometer) polyester film made
according to the FILM MAKING PROCEDURE. The film contains 2% by
weight CYASORB UV-1164. The ACRYLIC PRESSURE SENSITIVE ADHESIVE was
laminated to one surface of the film for subsequent mounting to the
bottom glass.
[0109] Example 3 is a 1 mil (25.4 micrometer) polyester film made
according to THE FILM MAKING PROCEDURE. The film contains 1.5% by
weight TINUVIN 1577, a triazine UV absorber available from Ciba
Specialty Chemicals Corporation. The ACRYLIC PRESSURE SENSITIVE
ADHESIVE was laminated to one surface of the film for subsequent
mounting to the bottom glass.
[0110] Example 4 is a 1 mil (25.4 micrometer) polyester film made
according to the FILM MAKING PROCEDURE. The film contains 2%
CYASORB UV-1164. One surface of the film was primed with Primer A,
a primer containing 99% cyclohexanone, 0.5% vinyl chloride/vinyl
acetate/vinyl alcohol terpolymer resin (available under the trade
name UCAR VAGH, from Union Carbide, located in South Charleston, W.
Va.), and 0.5% polyester resin. Primer A was applied using gravure
coating and was dried at 250.degree. F. (121.degree. C.) for about
45 seconds. The ACRYLIC PRESSURE SENSITIVE ADHESIVE was laminated
to the unprimed surface of the film for subsequent mounting to the
bottom glass.
[0111] Comparative Examples C1 and C2, and Examples 1-4 were
mounted in simulated double-glazed insulated glass window units
according to the SAMPLE MOUNTING PROCEDURE. The samples were
subject to UV exposure according to the UV EXPOSURE PROCEDURE.
Samples were periodically removed from the test chamber after
exposures of approximately 2600, 3600, 6000, 7200 and 8400
kJ/m.sup.2 at 340 nanometers, as indicated in Table 1. Color
measurements were conducted using the COLOR MEASUREMENT PROCEDURE.
Values of b* are reported in Table 1.
1TABLE 1 Values of b* Exposure (kJ/m.sup.2 at 340 nanometers)
Example Initial 2636 3618 6030 7236 8442 C1 2.0255 4.797 5.559
7.535 10.5 13.135 C2 1.77 6.25 7.97 15.18 23.87 35.42 1 2.05 3.339
3.765 4.5 5.15 5.37 2 3.999 4.9885 5.523 8.46 6.865 7.335 3 3.29
5.85 N/A 3.61 N/A N/A 4 1.82 4.8925 6.0875 10.645 14.995 24.72 (N/A
= no measurement made)
[0112] Examples of the present invention show improved resistance
to UV degradation (yellowing) at 3618 kJ/m.sup.2 at 340 nanometers,
and more preferably at 8442 kJ/m.sup.2. The yellowing observed for
Example 4 is believed to be a result of the photodegradation of the
vinyl polyester primer present on that sample.
[0113] Comparative Example C3 is a decorative, resin-coated,
polyester film, available under the trade name ACCENTRIM B200
(available from 3M Company).
[0114] Example 5 is a 2 mil (50.8 micrometer) polyester film made
according to THE FILM MAKING PROCEDURE. The film contains 2.5%
TINUVIN 1577. The one surface of the film was primed with Primer B,
a primer containing: 82.9% deionized water, 15.1% NEOREZ R-960
(aqueous urethane from Neoresins, located in Wilmington, Del.),
0.3% NEOCRYL CX-100 (aziridine crosslinker from Neoresins), 1.5%
TRITON X-100 (surfactant from Union Carbide), and 0.2% polystyrene
beads (30% by weight dispersed in water, available from 3M
Company). Primer B was applied pre-tenter using gravure coating and
was dried at 150.degree. F. (66.degree. C.) for about 30 seconds. A
1.7 mil (43.2 micrometer) thick resin layer was applied to the
primed surface of the polyester film using the RESIN CASTING
PROCEDURE. The ACRYLIC PRESSURE SENSITIVE ADHESIVE was laminated to
the unprimed surface of the film for subsequent mounting to the
bottom glass.
[0115] Example 6 is a 2 mil (50.8 micrometer) polyester film made
according to the FILM MAKING PROCEDURE. The film contains 3%
TINUVIN 1577. Primer B was applied using gravure coating and was
dried at 150.degree. F. (66.degree. C.) for about 30 seconds. A 1.7
mil (43.2 micrometer) thick resin layer was applied to the primed
surface of the polyester film using the RESIN CASTING PROCEDURE.
The ACRYLIC PRESSURE SENSITIVE ADHESIVE was laminated to the
unprimed surface of the film for subsequent mounting to the bottom
glass.
[0116] Example 7 was made according to the procedure of Example 6,
except that the film was UV post-cured in order to cure the resin
layer fully. UV post-cure was conducted after the microstructured
web was removed from the tool. UV post-cure was performed using a
high intensity Fusion Systems "D" spectrum lamp with a UV-A
(315-400 nm) dose in the range of 100-1000 mJ/cm.sup.2. The UV
post-cure light directly impinged on and UV post-cured the resin
layer.
[0117] Comparative Example C3, and Examples 5-7 were mounted in
simulated double-glazed insulated glass window units according to
the SAMPLE MOUNTING PROCEDURE. The samples were subject to UV
exposure according to the UV EXPOSURE PROCEDURE. Samples were
periodically removed from the test chamber after exposures of
approximately 2600, 4800, 6000 kJ/m.sup.2 at 340 nanometers, as
indicated in Table 2. Color measurements were conducted using the
COLOR MEASUREMENT PROCEDURE. Values of b* are reported in Table
2.
2TABLE 2 Values of b* Exposure (kJ/m.sup.2 at 340 nanometers)
EXAMPLE Initial 2636 4824 6030 C3 2.54 12.93 N/A 40.99 5 2.07 2.99
5.11 6.43 6 3.13 4.42 5.73 5.19 7 3.28 4.49 5.76 5.32 (N/A = no
measurement made)
[0118] Examples of the present invention showed improved resistance
to photodegradation (yellowing).
[0119] Comparative Examples C1-C3, and Examples 1-7 were mounted in
simulated double-glazed insulated glass window units according to
the SAMPLE MOUNTING PROCEDURE, except that the cover glass plate
was replaced with a {fraction (3/32)}-inch (2.4 mm) thick, low
emissivity glass plate (available under the trade name Lo{overscore
(E)}.sup.2-172, from Cardinal IG, located in Minneapolis,
Minn.).
[0120] The samples were subject to UV exposure according to the UV
EXPOSURE PROCEDURE. Samples were periodically removed from the test
chamber after exposures of approximately 2600, 3600, 4800, 6000,
7200 and 8400 kJ/m.sup.2 at 340 nanometers, as indicated in Table
2. Color measurements were conducted using the COLOR MEASUREMENT
PROCEDURE. Values of b* are reported in Table 3.
3TABLE 3 Values of b* Exposure (kJ/m.sup.2 at 340 nanometers)
Example Initial 2636 3618 4824 6030 7236 8442 C1 2.7 2.888 3.0055
N/A 3.065 3.15 3.155 C2 2.07 2.80 2.92 N/A 3.48 3.76 3.93 C3 2.08
2.46 2.76 N/A 2.92 3.29 3.52 1 2.895 3.101 3.312 N/A 3.68 3.77
3.815 2 4.23 4.42 4.67 N/A 4.985 5.115 5.255 3 3.29 3.43 N/A 5.23
3.61 N/A N/A 4 2.135 2.634 2.903 N/A 3.335 3.64 3.835 5 2.06 2.57
N/A 2.60 2.64 N/A N/A 6 3.49 3.58 N/A 3.70 3.71 N/A N/A 7 3.66 3.68
N/A 3.77 3.75 N/A N/A (N/A = no measurement made)
[0121] The use of low emissivity glass results in reduced rates of
yellowing.
[0122] Various modifications and alterations of this invention will
be apparent to those skilled in the art without departing from the
scope and spirit of this invention, and it should be understood
that this invention is not limited to the illustrative embodiments
set forth herein.
* * * * *