Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to light-polarizing
materials, to set suspensions and fluid suspensions thereof,
and to light valves containing such fluid suspensions. In
particular, the present invention relates to organic light-
s polarizing materials that are derived from organic compounds
that do not have a nitrogen heteroatom, which is
characteristic of prior art organic light-polarizing
materials.
Light-polarizing materials, such as colloidal
suspensions of herapathite and herapathite-like light-
polarizing crystals, are described in U.S. Patents 1,951,664
(Land) and 2,178,996 (Land), respectively. U.S. Patent
2,237,567 (Land) discloses the production of light-
polarizing material in sheet form by various methods
including application of a solution of iodine and an iodide
to a sheet of polyvinyl alcohol which had been previously
stretched to orient the molecules therein. Numerous other
patents relating to light-polarizing materials, set
suspensions thereof and laminated products derived therefrom
and uses thereof are in the art including, for example, U.S.
Patent Nos. 2,041,138 (Land), 2,078,254 (Land), 2,168,220
(Land), 2,168,221 (Land), 2,185,018 (Sauer), 2,230,262
(Pollack), 2,246,087 (Bailey et al), 2,256,108 (Blake),
2,263,249 (Rogers), 2,306,108 (Land et al), 2,328,219
(Land), and 2,375,963 (Thomas). U.K. Patent 433,455
discloses the use of particles of purpureocobalt-
1
CA 02049869 2000-11-03
chloridesulphatepe=riod.ide in 1=he format=ion of light-
polarizing bodies.
At present, important uses for laminated set
suspensions of light-polarizing materials, often referred
to as "sheet polarizers", include lenses for polarized
sunglasses, components of the twisted nematic and other
types of liquid crysta_L displays and filters of various
types including contra:~t. enhancement filters for use in
conjunction with light E:missi~re displays. However, the
sheet polarizers thus employed are well. known to be
frequently subject to c~egradat:ion due t:o high levels of
heat, ultraviolet radiation and/or especially moisture.
Fluid suspensions of= light-polarizing and other
materials have been used in light valves, comprising a
cell containing a f=Lui<~ suspension of minute particles
which can be orient=ed by an e7_ectric or magnetic field to
change the transm:i~~sion of light through the suspension.
See for example, U. ;~. F?atent L~Ios. 3, 708, 219 (Forlini et
al), 3,743,382 (Rosenberg), 4,078,856 (Thompson et al),
4,113,362 (Saxe et al), 4,164,365 (Saxe), 4,407,565
(Saxe) , and 4, 422, 963 ;Thompsc>n et al) .
U.S. Patent 4,131,334 (Wi.tte et al) describes a
process for forming light-pol~:rizing particles by
hydrogenation of a nitrogen-containing organic compound,
which is then rear~t:ed with an appropriate acid to form a
salt. The salt may then be reacted, usually with iodine
and
-2-
an inorganic iodide, to produce stable polyiodide particles.
An object of the present invention is to provide
light-polarizing materials that have high stability with
respect to ultraviolet radiation, elevated temperatures and
high levels of moisture.
Polyhalides, including polyiodides, have been
known for quite some time. A polyiodide is a complex of
iodine atoms and an inorganic or organic matrix. Godina et
al discuss polyiodides and other polyhalides in detail in J.
Gen. Chem. USSR, 20, (1950), pages 1005-1016. Among the
known polyiodides is the light-polarizing crystalline
material, herapathite, which is formed by reaction of
quinine bisulfate, iodine and HI. Salts of other members of
the quinine alkaloid family also form light-polarizing
polyiodides by reaction with iodine and HI, such as
cinchonidine bisulfate. In these materials, the elemental
iodine combines with the alkaloid acid salt in the form of
the polyiodide anion, which has been variously described as
I3_ by Godina et al and as I5 by Teitelbaum et al, JACS, 100
(1978) pages 3215-3217. Godina et al show that the
polyiodide anion is formed by reaction between iodine and
HI, e.g.
(1) IZ + HI = H+ + I3_
Likewise, the IS_ polyiodide anion would be formed by the
reaction
(2) 2Iz + HI = H+ + IS
Godina et al explain that light-polarizing
polyiodides comprise the polyiodide anion and the acid salt
3
of quinine and the like as the cation. However, polyiodides
can also be formed without any apparent cation being
present, such as the starch-iodine complex and the stretched
or oriented polyvinyl alcohol-iodine complex. Teitelbaum et
al report that the starch-iodine complex contains adsorbed
iodine in the form of chains of iodine within the amylase
component of starch, the chains being made up of IS-
polyiodide anions as the dominant species. Godina et al
theorize that herapathite, starch-iodine and oriented PVA-
iodine complex are nadsorbing polyiodides~ in which
molecular iodine is adsorbed in layers on the polyiodide
chains.
The light-polarizing material of the present
invention is a complex that does not contain the nitrogen
heteroatom characteristic of prior art organic light
polarizing materials. This complex is obtained by reacting
(i) elemental iodine, (ii) a hydrohalide acid and/or an
ammonium or alkali metal or alkaline earth metal halide and
(iii) an ethylene diamine derivative of formula I below.
This complex contains adsorbed molecular iodine. When HI or
an iodide is used, we believe that the complex also contains ,.
the polyiodide anion, Ix, where x is 3 or 5, since Godina
et al and Teitelbaum et al both report that the polyiodide
anion is formed by reaction between (i) elemental iodine and
(ii) an iodide. Moreover, Godina et al report that crystals
containing adsorbed molecular iodine and the polyiodide
4
~~~43.~~?~'~'~
anion are light-polarizing.
In the Examples that follow, light polarizing
materials are prepared by reacting a compound I with iodine
and an iodide, bromide or chloride. In such cases, we
believe that the respective anions would be
-I_I_I_I_I_
-I-I-Br-I-I
_
-I-I-C1-I-I
using the structure elucidated by Teitelbaum et al as a
model.
Godina et al report that light-polarizing
complexes containing adsorbed molecular iodine cannot be
defined stoichiometrically by structural formula. Hence,
the light-polarizing material of the present invention is
defined in product-by-process format.
Compounds I that are useful in forming the light-
polarizing materials of the invention are compounds having
the formula:
R3 Ri R2 R3
R°OOCCHi N-CH-CH-N-CHZCOOR° ( I )
wherein R1 and RZ are independently hydrogen or lower alkyl,
R' is hydrogen or -CHZCOOR°, and each R° is independently
hydrogen or ~, where M is an alkali metal or alkaline earth
n
metal and n is the valence of M.
When Rl and/or RZ is lower alkyl, the lower alkyl
5
may be straight or branched chain alkyl, such as methyl,
ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl and the
like. Usually, the lower alkyl will have from 1 to about 6
carbon atoms, preferably from 1 to about 4 carbon atoms.
Compounds I are known her se or may be isomers,
homologues or analogs of known compounds and may be prepared
analogously to such known compounds.
Since the free acid form of compounds I, such as
ethylene diamine tetraacetic acid, ethylene diamine diacetic
acid, 1,2-diaminopropyl tetraacetic acid (i.e. R1 is methyl,
RZ is hydrogen and each R3 is -CHZCOOH) and the like, have
limited water solubility, compound I will either be used in
the form of a water-soluble alkali metal and/or alkaline
earth metal salt thereof, or the water-soluble salt can be
formed xn situ during the formation of the light-polarizing
material. Useful compounds I include ethylene diamine
tetraacetic acid or the disodium, dipotassium, tetrasodium,
tetrapotassium or disodium magnesium salts thereof, ethylene
diamine diacetic acid or the mono- or di- sodium or mono- or
di- potassium salts thereof, 1,2-diaminopropyl tetraacetic
acid or the disodium, dipotassium, tetrasodium or
tetrapotassium salts thereof and the like.
The light-polarizing materials of this invention
are formed by reacting a compound of formula I with
elemental iodine and a hydrohalide acid and/or an ammonium,
alkali metal or alkaline earth metal halide, in a suitable
6
solvent, such as water. See U.S. Patent Nos. 1,951,661,
2,176,516 and 2,289,712. The halide is usually an iodide,
but can also be a bromide or chloride. Preferably, the
reaction to form the polyhalide takes place in the presence
of a protective colloid, such as nitrocellulose or a
copolymer as disclosed in U.S. Patent No. 4,164,365, issued
August 14, 1979. It is presently preferred to provide
compound I in a first solution and a mixture of iodine and
ammonium or alkali metal or alkaline earth metal halide in a
l0 second solution, but, if desired, the halide can be in
either or both of the solutions. The solutions are then
mixed together, and the polyhalides are readily formed even
at room temperature. Light-polarizing polyhalide crystals
are then recovered by any suitable technique, such as by
filtering and the like.
Heretofore, organic light-polarizing materials
have been made only by reacting molecular iodine and an
iodide or the like with organic precursor compounds having
at least one heterocyclic ring containing a nitrogen
heteroatom, such as quinine bisulfate, dihydrocinchonidine
bisulfate and quinaldic acid anhydride and the precursor
compounds described in U.S. Patent 4,877,313. Surprisingly,
the present invention provides an organic light-polarizing
material obtained from the precursor compound (I), which
does not contain a nitrogen heteroatom.
For use in a light valve, the polyhalide particles
7
are suspended in a liquid suspending medium. As is known,
the liquid suspending medium may be virtually any
electrically resistive liquid so long as it suspends the
particles and dissolves the polymeric stabilizer.
Preferably, the liquid suspending medium has a relatively
high electrical resistivity and low vapor pressure, and does
not degrade or attack the particles or other components of
the suspension. See e.g. U.S. Patents 4,270,841 and
4,407,565 to Saxe.
For use in set suspensions, the polyhalide
particles are dispersed or distributed throughout a sheet
formed of suitable film-forming material, such as cellulose
acetate or polyvinylalcohol or the like. See e.g. U.S.
Patents 2,178,996 and 2,041,138.
ExamQles 1-3
Approximately 2 g. of disodium ethylene diamine
tetraacetic acid was dissolved in 5 g, of water and that
solution was then mixed with 5 g. of a solution of water in
which 0.8 g of iodine and 1 g. of calcium iodide were
dissolved. Blue-colored light-polarizing crystals formed
readily. The same procedure was followed and similar
results observed using dipotassium and disodium magnesium
ethylene diamine tetraacetic acid, respectively, in place of
disodium ethylene diamine tetraacetic acid.
Examples 4-5
8
Approximately 0.5 g of ethylene diamine diacetic
acid was dissolved in 5 g. of 2% aqueous sodium hydroxide
and that solution was then mixed with 5 g. of a solution of
water in which 0.8 g of iodine and 1 g. of calcium iodide
were dissolved. Blue-colored light-polarizing crystals
formed readily. The same procedure was followed and similar
results observed using 1,2-diaminopropyl tetraacetic acid in
place of ethylene diamine diacetic acid.
Comparative Examples 6-12
Comparative Examples 6-12 used compounds 6-12
below, respectively
6 - 1,6-Hexanediamine tetraacetic acid
7 - Nitrilotriacetic acid
8 - Ethylene (oxyethylenenitrilo)tetraacetic acid
(EGTA)
9 - Methyliminodiacetic acid
10 - Iminodiacetic acid
11 - 10-(2-Hydroxyethyl)ethylene diamine triacetic
acid
12 - N-(2-Hydroxyethyl)iminodiacetic acid.
Approximately 0.5 g of compound 6 was dissolved in
5 g. of 2% aqueous sodium hydroxide and that solution was
then mixed with 5 g. of a solution of water in which iodine
and calcium iodide were dissolved according to the same
amounts and procedures as in examples 4-5. No light-
polarizing crystals were produced. The same procedure was
9
followed and similar failure to produce polarizing crystals
observed using compounds 7-12 in place of compound 6.
The failure to form light-polarizing crystals in
comparative example 6, wherein 1,6-hexanediamine tetraacetic
acid was used, is in sharp contrast to the success described
above where EDTA was used under similar reaction conditions.
The greater distance between the nitrogen atoms is the only
difference that could account for the failure described in
Examples 6 and 8.
The failure to form polarizing crystals in
comparative Examples 7, 9, 10 and 12 can be possibly
explained by the fact that these compounds contain only one
nitrogen atom. It appears that having two nitrogen atoms
separated by no more than two carbon atoms is essential to
the formation of light-polarizing crystals.
All of the compounds I used in the present
invention are known to form metal salts and/or to be metal-
chelating compounds, such as shown below, wherein R° is
calcium:
Accordingly, one possible explanation for the formation of
the light-polarizing materials of this invention is that
when the compounds I are reacted with iodine and a halide,
the halide and iodine enter into the reaction in an ionic
form. For example, if the halide is calcium iodide, CaIz,
iodine may enter the reaction as Ca+Z(Ix)z-, with the
positively charged calcium ion being chelated by the
compound I and the (IR)- anion being bonded to the positive
calcium ion, thereby forming a polyiodide crystal. While
this explanation seems reasonable, it is not intended that
this application be bound by this theory.
Liquid suspensions of the polyhalide particles of
this invention can be easily prepared by utilizing a
procedure somewhat similar to that for preparing liquid
suspensions of dihydrocinchonidine sulfate polyiodide
described in Example 2 of U.S. Patent No. 4,131,334 and in
Example 1 of U.S. Patent No. 4,407,565, but with compound I
of the present invention substituted for dihydrocinchonidine
sulfate and the quantities of the reactants adjusted as, for
example, given in the aforesaid examples.
Example 13
A. Preparation of Dipotassium Ethylene Diamine
Tetraacetic Acid Polyiodide - Nitrocellulose Complex.
Solution A was prepared by dissolving 3 g. of
dipotassium ethylenediamine tetraacetic acid in 15 g. of a
mixed solvent comprising 5 g. of water and 10 g. of 2-
ethoxyethanol.
Solution B was a 33-1/3% solution of
nitrocellulose in 2-ethoxyethanol. The nitrocellulose is a
mixed viscosity (18-25 cps and 15-20 sec) type.
11
Solution A and 22 g. of solution B were mixed to
form solution C.
Solution D was prepared by dissolving .48 g. of
calcium iodide hexahydrate in 10 g. of 2 ethoxyethanol and
then adding 1.4 g. of IZ and 20 g of tricresylphosphate
(TCP) and shaking for 10 minutes.
Solution C was combined with solution D with
vigorous mixing in a blaring blender while stirring with a
polyethylene spatula. After stirring for two minutes the
wet paste was spread as an 8 ml film on a glass plate and
allowed to dry overnight. The light-polarizing crystals
formed as the paste dried.
B. Preparation of the Liquid Suspension
The dried paste was scraped off the glass plate
and dispersed into 150 g. of isopentyl acetate (IPA) and
well shaken so as to disperse the paste to form a liquid
suspension. The suspension is then ultrasonically agitated
for 10 hours and centrifuged at 11,000 RPM for one hour.
The sediment is then resuspended in IPA and an effective
amount of a suitable polymer solution added thereto, e.g.
10-15 g. of a 15% solution of a 96.75%/3.25% copolymer of
neopanty1 acrylate/methylol acrylamide dissolved in
neopanty1 neopentanoate may be added. This new suspension
is placed in a vacuum apparatus for approximately five hours
to evaporate off nearly all of the IPA. Part of any other
solvent present that does not have too high a boiling point
12
2049~~0
may also evaporate. The suspension is then diluted to the
extent desired with Halocarbon Oil type 0.8/100
(manufactured by Halocarbon Products, Hackensack, New
Jersey) and any other desired solvents, such as neopentyl
neopentanoate, to provide the wanted off-state optical
density and response time. Additional polymer may be added.
Liquid suspensions of the type described above can
be used in light valves which utilize an AC electric field
to orient the particles in said suspensions to change and/or'
l0 control the transmission of light through the suspension.
Such light valves can be used, for example, as variable
transmission windows, filters, mirrors, and eyeglasses, and
as electronic alphanumeric and graphic image displays.
By modifying the composition of the suspension,
however, it is possible to produce what is known in the
prior art as a set suspension, rather than a fluid
suspension or liquid suspension usable in a light valve as
described above. A set suspension of the particles of the
present invention would comprise, for example, a
light-polarizing sheet or film in which said particles would
be incorporated along with other materials.
There are many processes known in the art for
producing light-polarizing sheets and films. For example,
U.S. Patent 2,178,996 discloses a process for forming
certain light-polarizing particles, mixing said particles
into a dispersion medium which may include cellulose
13
acetate, and subjecting the dispersion of particles to flow
or extrusion or stretch, or rolling, so that the needle axis
of the dispersed polarizing crystals may be oriented to
substantial parallelism and a thin, sheet-like polarizing
body produced. U.S. Patent 2,041,138 discloses that
polarizing bodies may preferably be made in the form of a
relatively thin sheet or film comprising the suspending
medium and the minute particles dispersed therein. If
desired, the polarizing body may itself be permanently or
detachably fixed to a suitable support, preferably
transparent, as for example, to a plate of glass or to a
sheet of celluloid. Such a support may be desirable with
conditions where it is found that the polarizing body itself
may require some form of protection. It also discloses the
use of asymmetric particles, the flowing of the medium that
includes said particles past an edge, and retaining said
particles in an oriented position by setting or hardening
said medium.
U. S. Patent 2,168,220 discloses information
relating to polarizing material sold under the trade name
pPolaroid~. Use of plasticizers, adhesives and various types
of laminations and methods for forming said laminations are
disclosed.
Numerous types of polarizing films and uses for
polarizers are disclosed in U.S. Patent 2,246,087 including,
for example, use in windshields, windows, eyeglasses,
goggles, sunglasses, camera lenses, microscopes, mirrors and
in connection with three dimensional movies.
14
A process for transferring light-polarizing films
from one support to another and various materials used in
connection therewith are disclosed in U.S. Patent 2,256,108.
The information available from any of the
aforesaid patents and from numerous other patents and other
sources known in the art can be used to make
light-polarizing set suspensions, films and sheets which
include particles oriented in substantial parallelism, and
light-polarizing bodies and products made therefrom.
However, many light polarizers in commercial use
today do not incorporate films or sheets having solid
discrete particles oriented in parallel therein, but rather
use a sheet of polyvinyl alcohol polyiodide which has its
optic axis in the plane of the sheet and which transmits
with substantially no absorption only light vibrating
substantially perpendicularly to its optic axis, as
described in U.S. Patent 2,237,567 and 2,375,963 and other
sources known in the art. The commercially available
polarizers are known to be susceptible to degradation when
subjected for prolonged periods to harsh environmental
conditions such as high temperatures, high humidity,
ultraviolet radiation and especially combinations of such
conditions.
Despite the problems of commercially available
sheet polarizers with respect to environmental degradation,
it may be preferable or desirable from a manufacturing
viewpoint to react a stretched sheet of polymer with dyes or
stains or with iodine and an iodide to form a light-
CA 02049869 2000-11-03
polarizing complex,, rasher than tc use a plurality of
individual polariz=Lng crystal: as previously described.
To this end, usefu=L embc>diment:s of the present invention
also include compounds c:orr~prising compounds of this
invention, each mo_Lf~cu:Le of which has attached thereto a
polymerizable unsai~urav~ed group.
However, the polarizers made from set
suspensions of the par'~icles ~~nd ether materials of the
present invention will be stak~le to high levels of heat
1C and ultraviolet radiation and will tolerate water
excellently. According:Ly, the present invention makes
possible a substani=Lal improvement in t:he quality of
light-polarizing bodie:~ and products incorporating such
materials.
l~ Although specific erlbodiment~~ of the invention
have been described, it will be appreciated that many
modifications thereon may be rlade by one skilled in the
art, which fall wii=hin the sp::_rit and t>cope of this
invention.
