U.S. patent application number 17/007323 was filed with the patent office on 2020-12-24 for light valve films laminated between thin glass and plastic substrates.
The applicant listed for this patent is Research Frontiers Incorporated. Invention is credited to Steven M. Slovak, Seth Van Voorhees, Dongyan Wang.
Application Number | 20200398538 17/007323 |
Document ID | / |
Family ID | 1000005062719 |
Filed Date | 2020-12-24 |
United States Patent
Application |
20200398538 |
Kind Code |
A1 |
Van Voorhees; Seth ; et
al. |
December 24, 2020 |
LIGHT VALVE FILMS LAMINATED BETWEEN THIN GLASS AND PLASTIC
SUBSTRATES
Abstract
A laminated light valve film comprising: (a) a film having first
and second opposed outer surfaces; (b) a first layer of a polymeric
interlayer material upon at least a portion of each opposed outer
surface; (c) a first pair of substrates, one of which is adhered to
the interlayer material upon the first outer opposed surface of the
light valve film and the second is adhered to the interlayer
material upon the second outer opposed surface of the light valve
film, these substrates being formed from plastic or glass; (d) a
second layer of polymeric interlayer material applied to at least a
portion of an outer surface of each one of the first pair of
substrates; and (e) a second pair of substrates, one being adhered
to the interlayer upon the outer surface of one of the first pair
of substrates and a second one adhered to the interlayer material
on the outer surface of a second one of the first pair of
substrates, the second pair of substrates being formed from plastic
or glass, with the proviso that when the first pair of substrates
is formed of plastic, the second pair of substrates is formed of
glass, and vice-versa.
Inventors: |
Van Voorhees; Seth; (Short
Hills, NJ) ; Wang; Dongyan; (Ithaca, NY) ;
Slovak; Steven M.; (N. Massapequa, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Research Frontiers Incorporated |
Woodbury |
NY |
US |
|
|
Family ID: |
1000005062719 |
Appl. No.: |
17/007323 |
Filed: |
August 31, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15499508 |
Apr 27, 2017 |
10807347 |
|
|
17007323 |
|
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62330967 |
May 3, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/172 20130101;
G02F 1/1334 20130101; G02F 2001/133302 20130101; G02F 1/133305
20130101; B32B 17/10495 20130101; B32B 2551/00 20130101 |
International
Class: |
B32B 17/10 20060101
B32B017/10; G02F 1/1333 20060101 G02F001/1333; G02F 1/1334 20060101
G02F001/1334; G02F 1/17 20060101 G02F001/17 |
Claims
1. A laminated light valve film forming a light modulating element
of a light valve, said laminated film comprising: a) a light valve
film having first and second opposed outer surfaces; b) a layer of
a polymeric interlayer material applied to at least a portion of
said first and said second opposed outer surfaces of said light
valve film; and c) a pair of substrates wherein one of said pair is
applied upon and adhered to the interlayer material applied upon
the first outer opposed surface of said light valve film and a
second one of said substrates is applied upon and adhered to the
interlayer material applied upon the second opposed surface of the
light valve film, said substrates each formed of a plastic coated
on one or both sides with at least one layer of glass, said glass
coatings ranging in thickness from 0.5 microns to 2.4 microns.
2. The laminated light valve film according to claim 1 wherein a
plastic portion of each of said substrates has a thickness ranging
between 1.0 mm to 10.0 mm.
3. The laminated light valve film according to claim 2 wherein the
plastic portion of each of said substrates has a thickness ranging
from 1.0 mm to 5.0 mm.
4. The laminated light valve film according to claim 1, wherein the
glass coating on each said substrate has a thickness ranging from
0.5 microns to 1.5 microns.
5. The laminated light valve film according to claim 1, wherein the
film comprises: a) a cured suspended particle device emulsion
having a plurality of uncrosslinked droplets of a liquid light
valve suspension distributed throughout the cured emulsion; and b)
first and second plastic sheets, said sheets located outwardly from
and sandwiching said cured emulsion wherein, located upon an inner
surface of each said first and said second plastic sheet, adjacent
said cured emulsion, is a layer of a thin, transparent,
electrically conductive coating, said coatings serving as an
electrode to permit passage of an applied electric field through
said cured emulsion.
6. The laminated light valve film according to claim 1, wherein the
film comprises: a) droplets containing liquid crystals dispersed in
a cured polymer; and b) first and second plastic sheets, said
sheets located outwardly from and sandwiching said cured polymer
wherein, located upon an inner surface of each said first and said
second plastic sheet, adjacent said cured polymer, is a layer of a
thin, transparent, electrically conductive coating, said coatings
serving as an electrode to permit passage of an applied electric
field through said cured polymer.
7. The laminated light valve film according to claim 1, wherein the
light valve film further comprises a conductive material affixed to
the electrodes such that the material extends beyond the perimeter
of the laminated light valve film to permit connection of said film
to a suitable voltage source.
8. The laminated light valve film according to claim 1, wherein the
glass used in coating said plastic is selected from the group
consisting of tempered glass, annealed glass, low iron glass, low e
glass, UV blocking glass, chemically strengthened glass and
antimicrobial glass.
9. The laminated light valve film according to claim 1, wherein the
plastic used in forming the substrates is selected from the group
consisting of polycarbonate, polymethyl methacrylate, polystyrene
and polypropylene.
10. The laminated light valve film according to claim 1, wherein
the material used in forming the plastic substrates has a softening
point of at least 10.degree. C. higher than that of the polymeric
interlayer material.
11. The laminated light valve film according to claim 10, wherein
the polymeric interlayer material is selected from the group
consisting of ethylene vinylacetate (EVA), polyvinyl butyral (PVB)
and polyurethane.
12. A laminated light valve film forming a light modulating element
of a light valve, said laminated film comprising: a) a light valve
film having first and second opposed outer surfaces; b) a layer of
a polymeric interlayer material applied to at least a portion of
said first and said second opposed outer layers of said light valve
film; and c) a pair of substrates wherein one of said pair is
applied upon and adhered to the interlayer material applied upon
the first outer opposed surface of said light valve film and a
second one of said substrates is applied upon and adhered to the
interlayer material applied upon the second opposed surface of the
light valve film, said substrates each formed of glass coated on
one or both sides with at least one layer of plastic, the glass of
each said substrate ranging in thickness from 0.55 mm to 2.0
mm.
13. The laminated light valve film according to claim 12, wherein
the plastic coating on either side of the glass may have the same
thickness or wherein the thickness on one side may be different
from the thickness of the coating on the other side.
14. The laminated light valve film according to claim 12, wherein
the plastic coating on each said substrate has a thickness ranging
from 1 micron to 25 microns.
15. The laminated light valve according to claim 14, wherein the
plastic coating on each said substrate has a thickness ranging from
10 microns to 25 microns.
16. The laminated light valve film according to claim 12, wherein
the film comprises: a) a cured suspended particle device emulsion
having a plurality of uncrosslinked droplets of a liquid light
valve suspension distributed throughout the cured emulsion; and b)
first and second plastic sheets, said sheets located outwardly from
and sandwiching said cured emulsion wherein, located upon an inner
surface of each said first and said second plastic sheet, adjacent
said cured emulsion, is a layer of a thin, transparent,
electrically conductive coating, said coatings serving as an
electrode to permit passage of an applied electric field through
said cured emulsion.
17. The laminated light valve film according to claim 12, wherein
the film comprises: a) droplets containing liquid crystals
dispersed in a cured polymer; and b) first and second plastic
sheets, said sheets located outwardly from and sandwiching said
cured polymer wherein, located upon an inner surface of each said
first and said second plastic sheet, adjacent said cured polymer,
is a layer of a thin, transparent, electrically conductive coating,
said coatings serving as an electrode to permit passage of an
applied electric field through said cured polymer.
18. The laminated light valve film according to claim 12, wherein
the light valve film further comprises a conductive material
affixed to the electrodes such that the material extends beyond the
perimeter of the laminated light valve film to permit connection of
said film to a suitable voltage source.
19. The laminated light valve according to claim 12, wherein the
glass used in forming the substrates is selected from the group
consisting of tempered glass, annealed glass, low iron glass, low e
glass UV blocking glass, chemically strengthened glass and
antimicrobial glass.
20. The laminated light valve film according to claim 12, wherein
the plastic is formed from a material selected from the group
consisting of polycarbonate, polymethyl methacrylate, polystyrene
and polypropylene.
21. The laminated light valve film according to claim 12, wherein
the plastic material used in coating the substrates has a softening
point of at least 10.degree. C. higher than that of the polymeric
interlayer material.
22. The laminated light valve film according to claim 21, wherein
the polymeric interlayer material is selected from the group
consisting of ethylene vinylacetate (EVA), polyvinyl butyral (PVB)
and poly urethane.
23. A laminated light valve film forming a light-modulating element
of a light valve, said laminated film comprising: (a) a light valve
film having first and second opposed outer surfaces, said light
valve film comprising (i) a cured suspended particle device
emulsion having a plurality of uncrosslinked droplets of a liquid
light valve suspension distributed throughout the cured emulsion;
and (ii) first and second plastic sheets, said sheets located
outwardly from and sandwiching said cured emulsion wherein, located
upon an inner surface of each of said first and said second plastic
sheet, adjacent said cured emulsion, is a layer if a thin,
transparent, electrically conductive coating, said coating serving
as an electrode to permit passage of an applied electric field
through said cured emulsion; (b) a first layer of a polymeric
interlayer material applied to at least a portion of each said
first and said second opposed outer surface of said light valve
film; (c) a first pair of substrates, wherein one of said first
pair is applied upon and adhered to the interlayer material applied
upon said first outer opposed surface of said light valve film and
a second one of said first pair is applied upon and adhered to the
interlayer material applied upon said second outer opposed surface
of the light valve film, said first pair of substrates being formed
of a material selected from the group consisting of plastic and
glass, and wherein each of said first pair of substrates has a
thickness ranging from 0.1 to 0.55 mm; (d) a second layer of
polymeric interlayer material applied to at least a portion of an
outer surface of each one of said first pair of substrates; and (e)
a second pair of substrates, wherein one of said second pair is
applied upon and adhered to the interlayer applied upon the outer
surface of one of said first pair of substrates and a second one of
said second pair is applied upon and adhered to the interlayer
material applied upon the outer surface of a second one of said
first pair of substrates, said second pair of substrates being
formed of a material selected from the group consisting of plastic
and glass, wherein each of said second pair of substrates has a
thickness ranging from 0.10 to 0.55 mm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present patent application is a divisional of prior U.S.
patent application Ser. No. 15/499,508, filed Apr. 27, 2017, by
Seth Van Voorhees, Dongyan Wang and Steven M. Slovak, entitled
"LIGHT VALVE FILMS LAMINATED BETWEEN THIN GLASS AND PLASTIC
SUBSTRATES," which claims the benefit of and priority to U.S.
Provisional Patent Application No. 62/330,967, filed May 3, 2016,
by Seth Van Voorhees, Dongyan Wang and Steven M. Slovak, and
entitled "SUSPENDED PARTICLE DEVICE FILMS LAMINATED BETWEEN THIN
GLASS AND PLASTIC SUBSTRATES." The entire contents of each of these
patent applications are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention is directed to films and laminations of films
for use in light valves which comprise liquid particle suspensions.
Suspended Particle Devices are generally referred to herein as SPD
light valves, or simply as SPDs. Polymer dispersed liquid crystal
light valve films are generally referred to as PDLCs. The films are
laminated between a combination of thin glass and plastic
substrates.
GENERAL BACKGROUND
[0003] Light valves have been known for more than eighty years for
use in the modulation of light. They have been proposed for use in
numerous applications during that time including, e.g.,
alphanumeric displays and television displays; filters for lamps,
cameras, displays and optical fibers; and windows, sunroofs, toys,
sunvisors, eyeglasses, goggles, mirrors, rearview mirrors, light
pipes and the like to control the amount of light passing
therethrough or reflected therefrom as the case may be. Examples of
windows include, without limitation, architectural windows for
commercial buildings, greenhouses and residences; windows, visors
and sunroofs for automotive vehicles, boats, trains, planes and
spacecraft; windows for doors including peepholes, and windows for
appliances such as ovens and refrigerators, including compartments
thereof.
[0004] As used herein, the term "light valve" refers to a cell
formed of two walls that are spaced apart by a small distance, with
at least one wall being transparent. The walls have electrodes
thereon, usually in the form of transparent, electrically
conductive coatings. Optionally, the electrically conductive
coatings can be deposited on the walls in patterns so that
different segments of the light valve can be selectively activated.
Additionally the electrodes on the walls may have thin transparent
dielectric overcoatings thereon. The cell contains a
light-modulating element (sometimes herein referred to as an
activatable material) which may, without limitation, be either a
liquid suspension of particles, or alternately, all or a portion of
the entire element may comprise a plastic film in which droplets of
a liquid suspension of particles are distributed.
[0005] For SPDs, the liquid suspension (sometimes herein referred
to as a liquid light valve suspension or simply as a light valve
suspension) comprises small particles suspended in a liquid
suspending medium. In the absence of an applied electrical field,
the particles in the liquid suspension of a SPD light valve may
assume random positions due to Brownian movement. Hence, a beam of
light passing into the cell is reflected, transmitted or absorbed
depending upon the cell structure, the nature and concentration of
the particles and the energy content of the light. The light valve
using this type of particle movement is thus relatively dark in the
OFF state. However, when an electric field is applied through the
liquid light valve suspension in the light valve, the particles
become aligned and for many suspensions most of the light can pass
through the cell. The light valve is thus relatively transparent in
the ON state. Alternatively, the particles in the liquid suspending
medium can achieve the ON and OFF states through other types of
electrophorectic particle movement. The .DELTA.T is defined as the
difference in visible light transmission between the ON and OFF
states.
[0006] For many applications it is preferable for all or part of
the activatable material, i.e., the light modulating element, to be
a plastic film rather than a liquid suspension. For example, in a
light valve used as a variable light transmission window, a plastic
film in which droplets of liquid suspension are distributed is
preferable to a liquid suspension alone because hydrostatic
pressure effects, e.g., bulging associated with a high column of a
light valve suspension, can be avoided through use of a film and
the risk of possible leakage can also be avoided. Another advantage
of using a plastic film is that, in a plastic film the particles
are generally present only within very small droplets and, hence,
do not noticeably agglomerate when the film is repeatedly activated
with a voltage.
[0007] The term SPD light valve film as used herein means a film or
sheet, or more than one thereof, comprising a suspension of
particles used or intended for use in a light valve. Such a light
valve film usually comprises a discontinuous droplet phase of a
liquid or liquids comprising dispersed particles (liquid light
valve suspension), such discontinuous phase being dispersed
throughout a solid continuous matrix phase, said phases enclosed
within one or more rigid or flexible solid films or sheets. The
combined aforesaid phases are referred to as the cured SPD
emulsion, which forms part of a light valve film, sometimes also
referred to as a film or film layer. The SPD light valve film
and/or laminate of the light valve film may also comprise one or
more additional layers such as, without limitation, a film,
coating, sheet or combination thereof, which may provide the light
valve film with one or more of, for example, (1) scratch
resistance, (2) protection from ultraviolet radiation, (3)
reflection of infrared energy, (4) electrical conductivity for
transmitting an applied electric or magnetic field to the
activatable material, (5) dielectric overcoatings, (6) color
tinting, (7) photovoltaic and (8) acoustic control. The additional
layers may be adhered to said light valve film with a pressure
sensitive adhesive (PSA) interlayer known to those skilled in the
art or with additional plies of interlayer during the lamination
procedure as discussed below in the Summary of the Invention.
[0008] A common (but non-limiting) construction for an SPD film has
five layers, namely, from one side to the other: (1) a first sheet
of polyethylene terephthalate ("PET") plastic, conveniently 5-7
mils in thickness, (2) a very thin transparent, electrically
conductive coating of indium tin oxide ("ITO") or alternative
conducting coating, acting or capable of acting as an electrode, on
an inner surface of said first sheet of PET, (3) a layer of cured
(i.e., cross-linked) SPD emulsion, usually 2-5 mils in thickness
and, (4) a second ITO coating acting or capable of acting as an
electrode on an inner surface of (5) a second PET plastic
substrate. As stated previously, additional layers which provide
other functions may optionally be added to the exemplary SPD film
described above. Typically, a material such as copper foil,
conductive fabric or the like is affixed to the electrodes such
that the material extends beyond the perimeter of the SPD film for
convenient connection of the film to a suitable voltage source.
Furthermore the SPD film can be laminated, for example, with
transparent hot melt adhesive films and/or glass or thicker
transparent plastic sheets to provide strength and rigidity and to
protect various parts of the combined unit from environmental
stresses which may, otherwise, damage its performance
characteristics. See, for example, U.S. Pat. No. 7,361,252 which is
assigned to the assignee of the present invention.
[0009] U.S. Pat. No. 5,409,734 exemplifies a type of
non-cross-linked light valve film that is made by phase separation
from a homogeneous solution. Light valve films made by
cross-linking (curing) of emulsions are also known. The films of
the present invention are specifically directed to the use of the
latter type of film, i.e., film comprising a layer formed by
cross-linking an emulsion, and to laminated films produced thereby.
See, for example, U.S. Pat. Nos. 5,463,491 and 5,463,492, and
7,361,252 all of which are assigned to the assignee of the present
invention. Various types of SPD emulsions, and methods of curing
the same, are described in U.S. Pat. Nos. 6,301,040, 6,416,827, and
6,900,923 B2, all of which are assigned to the assignee of the
present invention. Such films and variations thereof may be cured
through cross-linking brought about by exposing the films to (1)
ultraviolet radiation, (2) electron beams or (3) heat. A
non-limiting example of such a film from Example 5 of U.S. Pat. No.
6,900,923 B2 is produced as follows: 0.002 g of Irgacure 819 (Ciba
Specialty Chemicals) photoinitiator ("PI") was dissolved in 2 mL of
chloroform and added to 1 g of the matrix polymer described in
Example 1. The PI solution was thoroughly mixed with the matrix
polymer and the chloroform solvent was removed by placing the
mixture inside of a vacuum oven for 30 minutes at 60.degree. C. To
this was added 0.62 g of polyiodide crystal paste containing the
lauryl methacrylate/HEMA suspending polymer (0.56 g, as synthesized
in example 3 of the patent). The resulting mixture was thoroughly
mixed and the emulsion obtained was applied onto a conductive
coated polyester substrate as a 2 mil thick coating using a doctor
blade, mated with a blank conductive coated polyester substrate and
cured with ultraviolet radiation (8600 mJ/cm.sup.2/min) for 2 min
and 30 seconds. All of the patents and patent applications and
other references cited in this application are incorporated herein
by reference.
[0010] A variety of liquid light valve suspensions are well-known
in the art and such suspensions are readily formulated according to
techniques well-known to one of ordinary skill therein. The term
liquid light valve suspension, as noted above, when used herein
means a liquid suspending medium in which a plurality of small
particles are dispersed. The liquid suspending medium comprises one
or more non-aqueous, electrically resistive liquids in which there
is preferably dissolved at least one type of polymeric stabilizer
which acts to reduce the tendency of the particles to agglomerate
and to keep them dispersed and in suspension.
[0011] Liquid light valve suspensions useful in the present
invention may include any of the so-called prior art liquid
suspending media previously proposed for use in light valves for
suspending the particles. Liquid suspending media known in the art
which are useful herein include, but are not limited to, the liquid
suspending media disclosed in U.S. Pat. Nos. 4,247,175, 4,407,565,
4,772,103, 5,409,734, 5,461,506, 5,463,492, and 6,936,193 B2, the
disclosures of which are incorporated herein by reference. In
general one or both of the suspending medium and/or the polymeric
stabilizer typically dissolved therein is chosen so as to maintain
the suspended particles in gravitational equilibrium.
[0012] The polymeric stabilizer, when employed, can be a single
type of solid polymer that bonds to the surface of the particles,
but which also dissolves in the non-aqueous liquid(s) which
comprise the liquid suspending medium. Alternatively, there may be
two or more solid polymeric stabilizers serving as a polymeric
stabilizer system. For example, the particles can be coated with a
first type of solid polymeric stabilizer such as nitrocellulose
which, in effect, when dissolved provides a plain surface coating
for the particles, together with one or more additional types of
solid polymeric stabilizer that when dissolved, bond to or
associate with the first type of solid polymeric stabilizer and
also dissolve in the liquid suspending medium to provide dispersion
and steric protection for the particles. Also, liquid polymeric
stabilizers may be used to advantage, especially in SPD light valve
films, as described for example in U.S. Pat. No. 5,463,492.
[0013] Inorganic and organic particles may be used in a light valve
suspension, and such particles may be either light absorbing or
light reflecting in the visible portion of the electromagnetic
spectrum.
[0014] Conventional SPD light valves have generally employed
particles of colloidal size. As used herein the term colloidal
means that the particles generally have a largest dimension
averaging 1 micron or less. Preferably, most polyhalide or
non-polyhalide types of particles used or intended for use in an
SPD light valve suspension will have a largest dimension which
averages 0.3 micron or less and more preferably averages less than
one-half of the wavelength of blue light, i.e., less than 2000
Angstroms, to keep light scatter extremely low.
[0015] Another example of a light valve film is a PDLC film.
Similar to SPD films, PDLC films comprising liquid crystals are
dispersed into a liquid polymer, followed by solidification or
curing of the polymer. During the change of the polymer from a
liquid to solid, the liquid crystals become incompatible with the
solid polymer and form droplets throughout the solid polymer. The
curing conditions affect the size of the droplets that in turn
affect the final operating properties of a "smart window"
comprising such a film. Typically, the liquid mix of polymer and
liquid crystals is placed between two glass or plastic substrates
that include, on their inner aspect, a thin layer of a transparent,
conductive material, followed by curing of the polymer, thereby
forming the basic sandwich structure of the smart window. This
structure is in effect a capacitor.
[0016] In such case, electrodes from a power supply are attached to
the transparent electrodes. With no applied voltage, the liquid
crystals are randomly arranged in the droplets, resulting in
scattering of light as it passes through the smart window assembly.
This results in the translucent, "milky white" appearance. When a
voltage is applied to the electrodes, the electric field formed
between the two transparent electrodes on the glass causes the
liquid crystals to align, allowing light to pass through the
droplets with very little scattering and resulting in a transparent
state.
BACKGROUND OF THE INVENTION
[0017] In some cases, as mentioned above an SPD laminate or PDLC
laminate is desired wherein the film is sandwiched, using
transparent hot melt adhesive films (interlayers), between
transparent glass or plastic sheets. There are applications such
as, but not limited to, aircraft, architectural and automobile
windows where a light weight laminate that also prevents moisture
from entering the interior of the laminate via the face of the
substrates used to form the laminate is desired. Therefore, it is
the aim of the present invention to construct a laminate that
comprises both thin, light weight glass substrates and plastic
substrates on both opposing sides of the film.
Deficiencies of Prior Art Spd Films
[0018] SPD films, particularly those that comprise polyiodide
particles, are susceptible to moisture in that if moisture contacts
the cured SPD emulsion, it can lead to degradation of the SPD film,
including discoloration of the SPD film and a reduction in its
optical performance such as loss of .DELTA.T. The moisture can
enter the SPD laminate through the edge of the laminate. Thus
materials and methods have been developed for sealing the edge of
the SPD laminate to prevent the penetration of moisture
therethrough, as described for example in U.S. Pat. No. 8,670,173
and U.S. Patent Publication No. US 2016/0282645 A1.
[0019] Compared to glass, plastics such as acrylics and
polycarbonates are more susceptible to moisture penetration.
Therefore, SPD laminates comprised solely of plastic substrates may
allow moisture penetration through the opposing faces of the SPD
laminate. However, SPD laminates made with plastic substrates have
the benefit of light weight, improved UV protection and impact
resistance compared to an SPD laminate made with glass
substrates.
SUMMARY OF THE INVENTION
[0020] In one embodiment, light valve laminates comprise both thin,
light weight glass and plastic substrates. These were prepared and
tested in a high temperature, high humidity environment to show
that the thin glass prevented moisture from entering the laminate
through the face of the laminate. The location of the glass
substrates, as well as the plastic substrates, as the outer or
inner set of substrates comprising the light valve laminate, is
determined by the specific intended application as would be well
understood by one of ordinary skill in this field. Examples of
glass useful for this invention include, but are not limited to,
tempered glass, annealed glass, low iron glass, low e glass, UV
blocking glass and chemically strengthened glasses such as
Gorilla.RTM. glass produced by Corning Corporation and Willow.RTM.
glass, also produced by Corning. The thicknesses of the glass
substrates should have a range of 0.55 mm to 2.0 mm, preferably
0.55 mm to 1.10 mm.
[0021] In addition, the use of antimicrobial glass as the outer
substrate of the laminate in combination with one or more plastic
substrates, will impart beneficial health safety properties to the
resulting light valve. Antimicrobial agents destroy or inhibit the
growth of microorganisms, especially pathogenic microorganisms.
Antimicrobial glass is formulated with an ionic silver component as
the antimicrobial agent on the surface of the glass. Such health
safety properties are useful in a number of applications such as in
medical facilities and museum displays to reduce the transfer of
harmful bacteria by contact with the light valve. The plastic
substrates provided strength and rigidity, as well as UV protection
to the light valve laminate.
[0022] As used in this application plastics useful for this
invention include, but are not limited to, polycarbonate,
polymethyl methacrylate (acrylic), polystyrene and polypropylene.
The thicknesses of the plastic substrates should have a range of
1.0 mm to 10.0 mm, preferably 1.0 mm to 5.0 mm.
[0023] In cases where a flexible SPD laminate is required, the
glass and plastic substrates used for the lamination should each
have a thickness of 0.10 to 0.55 mm, preferably 0.10 mm to 0.20 mm
which allow for bending of the final light valve laminate for
curved applications without damage to the light valve laminate.
[0024] Sheets of a polymeric interlayer material are placed
between: (1) the film and the innermost substrate laminated
thereto, i.e., whether it be formed of glass or plastic, coated
glass or coated plastic (see below); as well as (2) between the
innermost and outermost substrates laminated to the film. The
purpose of this interlayer material is to hold the various laminate
components together during and following the formation of the
laminate. In the case of plastic substrates, the plastic substrates
are comprised of materials that have softening points significantly
higher, i.e. at least 10.degree. C., than those of the polymeric
interlayers that are heated and cooled during the lamination
process to form the laminate. This prevents the plastic sheets from
softening and deforming during the lamination process. For example,
an acrylic, polymethyl methacrylate substrate (Tg or softening
point of 105.degree. C.) might be used in a lamination with
ethylene vinylacetate (EVA) interlayers because the EVA melts at
80.degree. C. However, the acrylic substrate could not be used as
the substrate if the interlayer was polyvinyl butyral (PVB) because
the PVB melts at 120.degree. C. On the other hand, a polycarbonate
substrate (Tg or softening point of 157.degree. C.) could be safely
used with either EVA or PVB. Another material that may be used in
forming the polymeric interlayer in the present invention is
polyurethane.
[0025] Another embodiment involves the use of plastic substrates
incorporating plastics of the types and dimensions described above
that have been coated on one or both sides with at least one thin
layer of glass, each said glass layer having a thickness of 0.5
microns-2.4 microns, preferably 0.5 microns-1.5 microns, for
forming the substrates comprising a light valve laminate. The
literature reports that glass can be coated on plastic substrates.
For example, "Chamberless plasma deposition of glass coatings on
plastics" (G R Nowling, M Yajima, et. al., Plasma Sources Sci.
Technol., 14, (2005), 477-484) reports that "high-quality glass has
been deposited on plastic . . . ", " . . . an atmospheric plasma
process that operates without a chamber so that there is no
limitation on the substrate size or dimensions." and "Coating
plastics with thin films of glass by a "poor man's" ALD method"
states that "at ambient pressure, no vacuum systems are required .
. . " and "it can be run at low temperatures, at room temperature
and certainly below 100.degree. C." (See the website address:
otd.harvard.edu/explore-innovation/technologies/coating-plastics-with-thi-
n-films-of-glass-by-a-poor-mans-ald-method/). The plastic
substrates for this embodiment would have the same 1.0 mm to 10.0
mm, preferably 1.0 mm to 5.0 mm. range of thickness as discussed
above.
[0026] In still another embodiment, glass substrates of the types
described above that have been coated on one or both sides with at
least one layer of plastic, each said coating layer having a
thickness of 1 micron-25 microns, preferably, 10 microns-25
microns, can be used as the substrates for forming the light valve
laminate. The thickness of the plastic coating on either side of
the glass substrate is usually, but not necessarily equal. As
disclosed above, the plastic(s) used to coat the glass substrates
are comprised of materials that have melting points significantly
higher (i.e., at least 10.degree. C.) than those of the polymeric
interlayers that are heated and cooled during the lamination
process to form the laminate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 provided herewith is a cross-sectional view through a
first embodiment of the laminated light valve film according to the
invention; and
[0028] FIG. 2 provided herewith is a cross-sectional view through a
further embodiment of the laminated light valve film according to
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] As indicated above, FIG. 1 is a cross-sectional view through
a first embodiment of the invention. Proceeding from the top of the
figure toward the bottom, the various layers of the laminate are
described as follows. Layer 10 is a first plastic substrate. Layer
12 is a first adhesive interlayer. Layer 14 is a first glass
substrate. Layer 12' is a second adhesive interlayer. The item
designated as 16 is a suspended particle device (SPD) light valve.
Next, 12'' is a third adhesive interlayer. Layer 14' is a second
glass substrate. Layer 12''' is a fourth adhesive interlayer.
Finally, layer 10' is a second plastic substrate.
[0030] FIG. 2 illustrates an alternate embodiment of the claimed
laminate. Again, beginning from the top of the figure, layer 18 is
a first glass or plastic substrate, having a thickness of from 0.1
mm to 0.55 mm. Layer 20 is a first adhesive interlayer. Layer 18'
is a second glass or plastic substrate, having a thickness of from
0.1 mm to 0.55 mm. Layer 20' is a second adhesive interlayer. Layer
22 is a suspended particle device (SPD) light valve. Layer 20'' is
a third adhesive interlayer. Layer 18'' is a third glass or plastic
substrate, having a thickness of from 0.1 mm to 0.55 mm. Layer
20''' is a fourth adhesive interlayer. Finally, layer 18' is a
fourth glass or plastic substrate, again having a thickness of from
0.1 mm to 0.55 mm.
[0031] Glass sheets with thicknesses of 0.55 mm and 1.10 mm were
obtained from Corning Glass, Corning, N.Y., under the trade name of
Gorilla.RTM. Glass. Furthermore, acrylic plastic sheets, 3.175 mm
thick, sold under the trade name Acrylite.RTM. OP-2, were obtained
from Evonik Performance Materials, Parsippany, N.J.
Impact-resistant clear polycarbonate plastic sheets, 1.5875 mm
thick, were obtained from McMaster-Carr, Dayton, N.J. Glass NMR
tubes with a thickness of 0.24 mm were obtained from Wilmad Glass,
Vineland, N.J. Standard glass sheets with a thickness of 2.38 mm
were used for the control laminations.
[0032] Initial heat/high humidity tests were performed on the NMR
glass tubes, standard 2.38 mm thick glass laminates and laminates
prepared with the glass and plastic substrates described above to
determine the ability of these samples to prevent moisture
penetration. The laminates so prepared incorporated a
moisture-sensitive indicator strip into the lamination stack that
was positioned adjacent to the SPD film within the laminate. The
indicator strips were also sealed inside of the NMR tubes. The
strips used for these laminations were Humidity Detection strips,
20%-80%, Part #33813-2080 obtained from Indigo Instruments,
www.indigo.com.
[0033] Standard SPD light valve laminates were prepared as
described in the aforementioned U.S. Pat. No. 7,361,252 patent. A
non-limiting summary of the procedure for laminating SPD films is
found in U.S. Pat. No. 7,361,252, assigned to the assignee of the
present invention, involves creating a "stack" comprising in
sequence a first glass sheet, a first sheet of interlayer, the SPD
film comprising cured SPD emulsion sandwiched between two
ITO-coated PET substrate sheets with copper foil bus bars attached
to and protruding from the ITO coatings, a second sheet of
interlayer and a second glass sheet, all positioned substantially
congruent to one another. The stack was placed in a vacuum bag
within a Carver Press and a strong vacuum was applied (greater than
29 inches of mercury). The platens of the press were then arranged
to touch the outsides of the unlaminated stack and their
temperature elevated to affect melting of the interlayers within
the stack. The platens were then cooled to solidify the interlayers
which adheres the stack into an SPD laminate.
[0034] In addition, laminates formed with glass and plastic
substrates were also prepared. A non-limiting example of the layup
for one of these laminates would be thin
glass/interlayer/plastic/interlayer/SPD
film/interlayer/plastic/interlayer/thin glass. As used herein a
"thin" glass sheet means a glass sheet with a thickness of <1.10
mm.
[0035] In order to prevent moisture from entering through the edge
of the sample laminates, frames of polyisobutylene (PIB) were
incorporated into the laminate, as described in US Publication No.
US 2016/0282645 A1. The frames of the polyisobutylene
moisture-resistant material were incorporated into the stack
beginning at the outer edge of the glass to a position adjacent to
the SPD film within the laminate. Taking into account, then, the
presence of the PIB frames, any moisture penetration into the
laminate would thus be attributable to moisture entering the
laminate through the face of the laminate, not through the edge of
the laminate. Two frames are used so that the copper foil
protruding outside the laminate is surrounded on both sides by the
PIB material.
[0036] The initial .DELTA.T or visible transmittance range (ON
state transmittance--OFF state transmittance) of each SPD light
valve laminate was measured with The Color Sphere Visible
Spectrophotometer, manufactured by Byk-Gardner, by applying an
electric field of 100V/60 Hz to the protruding busbars of the
laminate to obtain the ON-state transmittance. These optical
measurements were repeated periodically during the humidity
test.
[0037] The procedure used to test the samples in a high
temperature/humidity environment, as disclosed in US Publication
No. US 2016/0282645 A1, assigned to the assignee of the present
invention, is as follows: SPD laminates, laminates without SPD film
and other samples with different configurations were placed in an
upper portion of a desiccator that had a reservoir of water in the
lower section thereof. A ceramic plate with holes prevented the
samples from coming in direct contact with the water in the bottom
section of the desiccator. Placing this desiccator in a 60.degree.
C. oven creates a high temperature, high humidity environment that
SPD films and SPD laminates would not normally be exposed to in the
field. However, these extreme conditions were created so that
meaningful test results would be obtained in a reasonable period of
time. The moisture-saturated desiccator containing the samples was
placed in a 60.degree. C. oven and the samples were periodically
evaluated for one or more of 1) the presence of moisture within the
laminate as detected by the moisture indicator strips, 2) the
change in the appearance of the clear interlayer within the
laminate from clear to cloudy/hazy and 3) the .DELTA.T change of
the SPD film within the laminate. A positive (+) .DELTA.T change
indicates that the range of light transmission for the SPD film has
increased during exposure to the 60.degree. C. temperature during
the test. This is due to the improved dispersion of the polyiodide
particles within the SPD film and should not be viewed as a loss in
functionality.
Results and Discussion
TABLE-US-00001 [0038] TABLE 1 Results of 60.degree. C. High
Humidity Test (glass, glass/plastic laminates) Days of 60.degree.
C., Clear High Moisture Interlayer Humidity Indicated Became
Laminate Details Exposure From Strip Hazy NMRtube 0.24 mm, flame
sealed, 435 No -- indicator only Gorilla .RTM. Glass 0.55 lam, 247
Yes Yes indicator only Gorilla .RTM. Glass 1.10 lam, 247 Yes Yes
indicator only Standard glass/Standard glass lam, 260 Yes Yes
indicator only (Leads) Gorilla .RTM. Glass 0.55-Standard Glass 284
Yes Yes lam, indicators only (thin-thick) Acrylite .RTM./Acrylite
.RTM. lam, 6 Yes Yes indicator only Polycarbonate/Polycarbonate
lam, 2 Yes Yes indicator only Gorilla .RTM. Glass 0.55/Acrylite
.RTM./ 163 Yes Yes Acrylite .RTM./Gorilla .RTM. Glass 0.55 lam,
indicator only Gorilla .RTM. Glass 0.55/Acrylite .RTM./ 181 Yes Yes
Acrylite .RTM./Gorilla .RTM. Glass 0.55 lam, indicator only
(Leads)
All laminations (lam) are PIB frame protected "Gorilla.RTM. Glass
0.55-Regular Glass lam" is also marked as "thin-thick glass lam".
"Gorilla.RTM. Glass 0.55" is Gorilla.RTM. Glass of 0.55 mm
thickness. "Gorilla Glass 1.10" is Gorilla.RTM. Glass of 1.10 mm
thickness. "Standard glass" is 2.38 mm thickness "Acrylite.RTM." is
acrylic plastic of 3.175 mm thickness "Polycarbonate" plastic is
1.5875 mm thick
[0039] Table 1 provides the 60.degree. C. high humidity test
results for non-SPD film containing laminates and other samples.
The tests with the NMR glass tubes show that glass thicknesses as
low as 0.24 mm are still very effective as moisture barriers. For
example, the flame sealed 0.24 mm thick NMR glass tube has been in
the 60.degree. C. high humidity chamber for 435 days with no color
change observed for the moisture strip and the test continues.
[0040] Two laminates made with Gorilla.RTM. Glass substrates, 0.55
mm thick and 1.10 mm thick, were exposed in the 60.degree. C. high
humidity chamber for 247 days before a color change was observed
and the moisture strip and the clear interlayer in these laminates
became hazy. The laminate in Table 1 labeled, "(thin-thick)" is
comprised of 0.55 mm thin glass and 2.38 mm standard glass and a
separate moisture indicator strip was placed adjacent to each of
the glass substrates. If moisture passes through the thin glass
substrate first, the moisture strip adjacent to the thin glass will
change color before the moisture strip adjacent to the thick glass
substrate changes color. This laminate was exposed in the
60.degree. C. high humidity chamber for 284 days before a color
change was observed for both moisture strips. Conversely, the
indicator strip within the laminates made with acrylic substrates
(Acrylite.RTM./Acrylite.RTM.) and polycarbonate substrates
(polycarbonate/polycarbonate) turned color after 6 days and 2 days
of exposure in the 60.degree. C. high humidity chamber
respectively. The clear interlayer in both of these laminates
turned hazy. This demonstrates that plastic substrates of varying
thicknesses allow moisture penetration after a short time.
[0041] Finally, the acrylic and glass hybrid laminates made with
the following configuration: Gorilla.RTM. Glass
0.55/Acrylite.RTM./Acrylite.RTM./Gorilla.RTM. Glass 0.55, were
exposed in the 60.degree. C. high humidity chamber for 163 days and
181 days respectively before color change was observed for the
moisture strip and the clear interlayer in these laminates became
hazy. One of the hybrid laminates described above also had copper
foil busbars protruding from the laminate to simulate the presence
of an SPD film inside the laminate. As mentioned above, this
laminate had been in the 60.degree. C. high humidity chamber for
181 days before a color change was observed for the moisture strip.
A double frame of PIB was used on this laminate to prevent moisture
from entering the edge of the laminate where the copper foil exits
the laminate. The data clearly shows that the 60.degree. C.
temperature and high humidity environment of this test allowed
moisture to pass through the face of the plastic substrate
laminates after only several days of exposure. The fact that the
thinnest all-glass 0.24 mm NMR tube sample tested lasted over 435
days without allowing moisture penetration confirms that glass is
ideal for moisture prevention. Although the laminates made with
glass alone or glass and plastic eventually showed the presence of
moisture within the laminates, the fact that a minimum of 161 days
was required for detection by the moisture strips strongly suggests
that the moisture entered the laminates through the edges of the
laminates. Although, as described above, PIB frames were
incorporated into the laminates to prevent moisture ingress via the
edge of the laminates, the severity of the test conditions likely
allowed the moisture to eventually pass between the substrates and
through the edge of the laminates. The same explanation also
applies to the applicable results below for Table 2.
TABLE-US-00002 TABLE 2 Results of 60.degree. C. High Humidity Test
(SPD: glass, glass/plastic laminates) Moisture Indicated Cloudy
.DELTA.T change- from Interlayer days and Laminate Details Strip
Appearance status Std. Glass/SPD/Std. No No +5.60, Glass, lam 306
days Yes Yes -14.02, 392 days Acrylite .RTM./SPD/ 6 days Yes -6.50,
Acrylite .RTM. lam 27 days Yes Yes Malfunction, discontinued at 83
days Gorilla .RTM. Glass 0.55/ No No +4.18, Acrylite
.RTM./SPD/Acrylite .RTM./ 141 days Gorilla .RTM. Glass 0.55 lam Yes
Yes +5.30, 212 days Yes Yes Malfunction, discontinued at 227 days,
Acrylite .RTM./Gorilla .RTM. Glass No Yes -2.82, 0.55/SPD/Gorilla
.RTM. Glass 0.55/ 55 days Acrylite .RTM. lam, (reverse) No Yes
-8.70, 306 days Yes Yes Malfunction, discontinued at 392 days
All laminations (lam) were double PIB frame protected and had
copper leads protruding from the edge "Gorilla Glass 0.55" is
Gorilla.RTM. Glass of 0.55 mm thickness. "Gorilla Glass 1.10" is
Gorilla.RTM. Glass of 1.10 mm thickness. "Std. Glass" is a standard
glass of 2.38 mm thickness "Acrylite.RTM." is acrylic plastic of
3.175 mm thickness
[0042] Table 2 provides the 60.degree. C. high humidity test
results for SPD film-containing laminates. The results are similar
to those obtained for the non-SPD-containing laminates in Table 1.
For example, the SPD laminate made with glass substrates
(Glass/SPD/Glass) exposed in the 60.degree. C. high humidity
chamber for 306 days had no color change observed for the moisture
strip, the clear interlayer in these laminates had not become hazy
and the SPD film within the laminates has gained 5.60 transmittance
points. After 392 days of exposure, a color change was observed for
the moisture strip, the clear interlayer in the laminate became
hazy and the SPD film within the laminate lost 14.02 transmittance
points. As described for the Table 1 results above, moisture
entering through the edge of the laminate was responsible for the
392 day exposure results.
[0043] The glass and acrylic hybrid laminate made with the
following configuration: Gorilla.RTM. Glass
0.55/Acrylite/SPD/Acrylite/Gorilla Glass 0.55, had been in the
60.degree. C. high humidity chamber for 141 days with no color
change observed for the moisture strip, the clear interlayer in the
laminate did not become hazy and the SPD film within the laminate
gained 4.18 transmittance points. After 212 days of exposure color
change was observed for the moisture strip, the clear interlayer in
the laminate became hazy but the SPD film within the laminate still
had gained 5.30 transmittance points. Finally, after 227 days of
exposure, the SPD film within the laminate no longer functioned
when the voltage was applied. It is believed that the moisture
present inside the laminate for 15 days eventually caused a
malfunction, such as a short-circuit, which rendered the SPD sample
inoperable and had we been able to measure the visible
transmittance of the SPD film there would have been a significant
loss of transmittance points.
[0044] In the case of the acrylic and glass hybrid laminate made
with the following configuration: Acrylite.RTM./Gorilla.RTM. Glass
0.55/SPD/Gorilla.RTM. Glass 0.55/Acrylite.RTM., the laminate had
been in the 60.degree. C. high humidity chamber for 55 days and no
color change was observed for the moisture strip, but the clear
interlayer in the laminate became hazy and the SPD film within the
laminate lost 2.82 transmittance points. Since this laminate has
Acrylite.RTM. plastic as the outermost substrates, moisture was
able to penetrate through the Acrylite.RTM. and cause the clear
interlayer between the Acrylite.RTM. and the Gorilla.RTM. Glass to
become cloudy, which is believed to be responsible for the measured
loss of transmission for the SPD film. However, the Gorilla.RTM.
Glass prevented the moisture from penetrating any further into the
laminate where the SPD film is positioned. After 306 days of
exposure still no color change was observed for the moisture strip,
the clear interlayer in the laminate remained hazy and the SPD film
within the laminate now lost 8.70 transmittance points. Finally,
after 392 days of exposure, color change was observed for the
moisture strip and the SPD film within the laminate no longer
functioned when the voltage was applied presumably due to a
short-circuit. For applications where an SPD laminate with an
impact and scratch resistant outer surface is desired this
configuration is preferred.
[0045] Finally, for an Acrylite/SPD/Acrylite laminate, after just 6
days of exposure in the 60.degree. C. high humidity chamber, color
change was observed for the moisture strip, the clear interlayer in
the laminate became hazy and after 27 days of exposure the SPD film
within the laminate had lost 6.50 transmittance points. This
confirms that SPD laminates made with only plastic substrates
quickly allow moisture to pass through the face of substrates and
adversely affect the appearance and performance of the SPD
laminate. These results show that SPD laminates made with a
combination of thin glass and plastic laminates protect the SPD
film from degradation due to moisture exposure while, at the same
time, providing, light weight, strength, impact resistance and UV
protection.
* * * * *
References