U.S. patent number 3,875,199 [Application Number 05/251,284] was granted by the patent office on 1975-04-01 for metal 1,2 dithiolenes.
This patent grant is currently assigned to Polaroid Corporation. Invention is credited to Stanley Morton Bloom.
United States Patent |
3,875,199 |
Bloom |
April 1, 1975 |
Metal 1,2 dithiolenes
Abstract
A metal complex of the formula: ##SPC1## Wherein Me is selected
from the group consisting of metals of the first, second, and third
transition metal series which will provide a complex that is an
effective infrared absorber and which is effectively transparent to
light in the visible region of the spectrum; and each R is selected
from the group consisting of alkyl, aromatic, heterocyclic and
nuclearly substituted aromatic and heterocyclic rings, provided
that at least two of said R moieties are different.
Inventors: |
Bloom; Stanley Morton (Waban,
MA) |
Assignee: |
Polaroid Corporation
(Cambridge, MA)
|
Family
ID: |
26941519 |
Appl.
No.: |
05/251,284 |
Filed: |
May 8, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
60982 |
Jul 6, 1970 |
3687862 |
|
|
|
577576 |
Sep 2, 1966 |
3588216 |
|
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|
Current U.S.
Class: |
556/136; 252/587;
351/49; 359/356; 359/359; 548/403; 549/3; 549/59; 549/210; 556/146;
568/331 |
Current CPC
Class: |
C07C
323/00 (20130101); C07C 321/00 (20130101) |
Current International
Class: |
G02C
7/10 (20060101); G02C 7/00 (20060101); C07f
015/00 (); C07f 015/04 () |
Field of
Search: |
;260/439R,429R |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Schrauzer et al., J. A. C. S. 87 (1965), pp. 1483-1489. .
Schrauzer et al., Ang. Chem. Int. Ed. English, 3 (1964), p.
381..
|
Primary Examiner: Demers; Arthur P.
Attorney, Agent or Firm: Morley; John P.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a division of U. S. Patent Application Ser. No.
60,982 filed July 6, 1970 now U.S. Pat. No. 3,687,862 which in turn
is a division of Application Ser. No. 577,576 filed Sept. 2, 1966
and now U.S. Pat. No. 3,588,216.
Claims
What is claimed is:
1. A compound of the following formula: ##SPC11##
2. A compound of the following formula: ##SPC12##
3. A compound of the following formula: ##SPC13##
4. A compound of the following formula: ##SPC14##
5. A compound of the following formula: ##SPC15##
Description
This invention relates to infrared (IR) absorption and, more
particularly to novel products and procedures directed thereto.
A primary object of this invention, therefore, is to provide novel
plastic products including means for absorbing in the infrared,
particularly in the near infrared, and novel processes employing
the same.
Another object is to provide novel products and processes for
diminishing to an appreciable extent transmission of light both in
the visible and in the infrared regions of the spectrum.
A further object is to provide novel plastic optical elements
including an infrared absorber.
Still another object is to provide novel light-polarizing elements
including means for absorption in the infrared.
Yet another object is to provide a novel sunglass structure having
a plastic optical system including light-polarizing means and means
for absorption in the infrared.
A still further object is to provide a class of compounds
particularly useful for precluding transmission of infrared and
novel processes employing the same.
Other objects of the invention will in part be obvious and will in
part appear hereinafter.
The invention accordingly comprises the processes involving several
steps and the relation and order of one or more of such steps with
respect to each of the others, and the products possessing the
features, properties and the relation of elements which are
exemplified in the following detailed disclosure, and the scope of
the application of which will be indicated in the claims.
For a fuller understanding of the nature and objects of the
invention, reference should be had to the following detailed
description taken in connection with the accompanying drawing
wherein:
FIG. 1 is an enlarged diagrammatic sectional view of a novel lens
system for sunglasses or the like according to this invention;
FIG. 2 is a partially exploded, perspective view of novel
sunglasses or the like having the lens system of FIG. 1;
FIG. 3 is a view similar to FIG. 1 of another lens system of this
invention;
FIG. 4 is a graphic presentation including superposed curves
showing the light transmittance of a plastic sunglass lens with and
without the IR absorbers of this invention; and
FIGS. 5 and 6 are graphic presentations of the light transmittance
curves of the IR absorbers illustrative of the class of absorbers
contemplated by this invention.
As was mentioned previously, one aspect of the present invention is
directed to compounds which are especially useful for inhibiting
transmission of infrared radiation, particularly in the near
infrared, i.e., absorbing inrared radiation, and to products and
processes employing these compounds.
The infrared absorbers contemplated for use in the present
invention may be defined as a metal complex of a
bis-[cis-1,2-bis-(alkyl, hydrogen, aryl or heterocyclic)
ethylene-1,2-dithiolate]. They may also be defined more simply as
ene dithiol metal complexes.
These infrared absorbers may be represented by the following
formula: ##SPC2##
wherein:
Me is a metal of the first, second or third transition metal
series, i.e., those elements of Group VIII of the table of periodic
arrangement of the elements, e.g., nickel, palladium, or platinum,
which will provide a complex which is an effective IR absorber and
which is substantially or effectively transparent to light in the
visible region of the spectrum, e.g., from about 400-700.mu.;
each R, which may be the same or different, is hydrogen, alkyl, an
aromatic or heterocyclic ring, or a substituted derivative thereof,
e.g., alkoxyalkyl, alkyl and/or alkoxy-substituted aromatic and
heterocyclic rings, substituents of the foregoing description
containing electron withdrawing groups, etc.
As examples of useful alkyl radicals contemplated by said R
moieties, mention may be made of lower alkyl radicals containing
1-6 carbon atoms, e.g., methyl, ethyl, propyl, isopropyl, butyl,
etc. As examples of useful aromatic rings, including substituted
derivatives thereof, mention may be made of phenyl, naphthyl,
methyl-phenyl, methylnaphthyl, alkoxyphenyl and alkoxynaphthyl,
e.g., dodecyloxyphenyl, halo-substituted, particularly
fluoro-substituted, -alkyl-substituted, amino, including
dialkylamino -substituted, haloalkyl-substituted, e.g.,
trifluoromethyl-substituted phenyl and naphthyl radicals, etc.
As examples of useful heterocyclic rings, mention may be made of
those of the formula: ##SPC3##
where X is nitrogen, oxygen, or sulfur, and substituted derivatives
thereof, including benz-substituted derivatives.
The following compounds are illustrative of useful IR absorbers
within the scope of Formula (A): ##SPC4##
The compounds of Formula A are in general previously known in the
art, although certain of the disclosed species, particularly the
asymmetrical species, e.g., those of Formulae 3, 8, 9, 10, 13, 14,
16, 17, 18, and 19 are believed to be specifically novel. (See for
example, the article by Schrauzer and Mayweg, "Preparation,
Reactions, and Structure of Bisdithio-.alpha.-diketone Complexes of
Nickel, Palladium, and Platinum," J.A.C.S., 87:7, pp 1483-1489.)
The compounds of Formula A may accordingly in general be prepared
in the manner heretofore described in the literature.
For example, they may be prepared by reacting p.sub.4 S.sub.10 with
a compound of the formula: ##SPC5##
wherein R has the meaning heretofore noted, to form a compound of
the formula: ##SPC6##
which is then reacted with a suitable inorganic salt containing the
desired metal, Me, e.g., NiC1.sub.2 . 6H.sub.2 0, PtCl.sub.2,
PdCl.sub.2, K.sub.2 PtC1.sub.4, K.sub.2 PdC1.sub.4, etc., to
prepare the desired compound of Formula A. Symmetrical compounds,
i.e., where each R is the same, are obtained by using a single
compound of Forumla B wherein each R is the same. Asymmetrical
compounds (such as those of Formulae 8 and 9) may be obtained by
employing two different compounds of Formula B as starting
materials. In like manner, one or two compounds of Formula B in
which each R is different, may be exployed to pg,10 provide
compounds of Formula A wherein two or more of the R moieties are
different.
The compounds of Formula (A) have been found to possess
exceptionally desirable spectral absorption characteristics. As a
class, they have been found to be relatively "narrow band"
absorbers which have a .lambda..sub.max in the near infrared region
of the spectrum, substantially no absorption in the visible region,
i.e., are substantially transparent to visible light, and a
.lambda..sub.max in the ultraviolet region of the spectrum,
primarily in the far ultraviolet region. They are thus particularly
useful in optical systems wherein it is desired to transmit visible
light while absorbing light in the designated invisible regions of
the spectrum, that is, to reduce or minimize transmission in the
near infrared and/or in the ultraviolet region of the spectrum. The
spectral absorption characteristics of these compounds may be more
readily understood by reference to FIGS. 5 and 6 wherein spectral
absorption curves of two compounds illustrative of the class,
specifically, those of Formulae 5 (shown in dotted line) and 6
(shown in solid line) are superposed. It will be observed that the
.lambda..sub.max IR and .lambda..sub.max UV of the compounds are
shifted by substitution of the complexing metal. They may also be
shifted by changing the substituents of the R moiety, so that by so
doing it is possible to provide narrow band filters for various
portions of the IR and UV regions of the spectrum.
In addition to their exceptional spectral absorption
characteristics, the compounds have been found to be extremely
stable to the degradative forces of light, heat, and humidity.
Since IR absorbers as a class are quite unstable to such
conditions, this stability of those compounds of Formula A is quite
surprising.
A representative class of these compounds was tested for stability
to light, heat, and humidity by imbibing onto each of three sheets
of cellulose acetate butyrate a solution consisting of the compound
to be tested dissolved in a suitable organic solvent. Each of the
imbibed sheets was then subjected to one of the following standard
test procedures: (1) light stability under a xenon arc lamp; (2)
relative humidity (moisture plus heat); and (3) dry heat. Stability
was tested by determining the density before and after each test.
The following chart shows the results of these tests, the figures
given representing the percent of fading (loss of density) after
the recited time interval.
TABLE I
__________________________________________________________________________
Compound Solvent Xenon Arc Relative Humidity Dry Heat (Formula No.)
(U.V. Shield) (95% at 150.degree.F) (150.degree.F)
__________________________________________________________________________
1 tetrahydrofuran 2.4% (120 hrs) 0.0% (250 hrs) 8.2% (250 hrs) 2
CHCl.sub.3 0.0% (120 hrs) 2.0% (120 hrs) 0.0% (120 hrs) 4
CHCl.sub.3 2% (170 hrs) 3% (170 hrs) 5% (170 hrs) 7 tetrahydrofuran
3.5% (120 hrs) 2.3% (250 hrs) 3.5% (250 hrs) 8 CHCl.sub.3 2.6% (175
hrs) 1.7% (175 hrs) 1.3% (175 hrs) 12 CHCl.sub.3 3.0% (170 hrs)
3.4% (170 hrs) 0.0% (170 hrs)
__________________________________________________________________________
As was mentioned previously, the aforementioned infrared absorbers
are particularly useful in plastic optical products which, unlike
glass optical products, do not possess a molecular structure that
will inherently absorb in the infrared region. Of particular
interest in the practice of this invention are plastic sunglasses
such as those known in the art as polarizing sunglasses.
A typical plastic sunglass of this nature has an optical system
comprising a light polarizer laminated between two sheets of
transparent plastic, the outer or free surfaces of which may be
provided with an abrasive-resistant coating. The polarizing sheet
may for example be a molecularly oriented plastic sheet material
which has been stained or dyed to render it light polarizing, e.g.,
molecularly oriented polyvinyl alcohol stained with iodine; the
transparent plastic between which the polarizing sheet is laminated
may, for example, be a thermoplastic cellulose derivative, e.g.,
cellulose nitrate, cellulose triacetate, cellulose acetate
propionate, cellulose acetate butyrate, ethyl cellulose, etc.; and
the abrasive-resistant coating may, for example, be a completely
polymerized melamineformaldehyde resin, a thermosetting,
cross-linked polymer such as a diethylenic-substituted
polyalkyleneglycol, e.g., polymeric coatings formed by in situ
polymerization of polyalkyleneglycol diesters of
.alpha.-.beta.-unsaturated carboxylic acids on the plastic sheet
material, etc. Plastic laminations including materials of this
description are disclosed for example, in U.S. Pat. Nos. 2,237.567;
2,527,400; 2,554,850; 3,081,192; and 3,097,106.
While polarizing sunglasses of the foregoing description
effectively diminish transmission of visible light to a desired
comfortable level, e.g., to say from about 20-30% of the visible
solar energy, an appreciable amount of invisible radiation,
primarily in the ultraviolet and near infrared regions of the
spectrum, is transmitted. By way of illustration, the solar energy
at the lens of the eye is shown by one of the superposed curves on
FIG. 4. From this curve it will be seen that appreciable solar
energy both in the near infrared and in the ultraviolet regions of
the spectrum is present at the lens. The ultraviolet is
substantially absorbed at the lens, but the IR passes through.
In view of the foregoing discussion, it is quite surprising that
while it has heretofore been suggested to employ ultraviolet
absorbers in such optical products to protect the lens, it is
believed and understood that no one has heretofore employed an IR
absorber in such plastic optical products. The failure to do so is
believed to be at least in part due to the inherent instability to
light of IR absorbers as a class and may in part be due to the
failure to appreciate the advantages of employing such IR
absorbers. Infrared absorbers which also have good ultraviolet
absorption, as herein disclosed, thus minimize transmission of
radiation which may be harmful to the eye.
An important aspect of this invention, therefore, is the concept of
employing an infrared absorber in plastic optical products such as
sunglasses of the foregoing general description.
This aspect of the invention will be more readily understood by
reference to FIGS. 1-3 of the accompanying drawings.
As shown in FIG. 1, one embodiment of this aspect of the invention
comprises a plastic optical element 1, the outer surfaces of which
are provided with an abrasive-resistant coating 16, such as those
heretofore described. Between these outer layers are positioned, as
by lamination, a pair of substantially or effectively transparent
sheets of plastic 12, e.g., cellulose acetate butyrate, cellulose
nitrate, cellulose acetate propionate, cellulose acetate, ethyl
cellulose, etc; a pair of layers or coatings 14 containing an IR
absorber, e.g., one or more of the IR absorbers of Formula A, and a
polarizing sheet material 10, e.g., a molecularly oriented
polyvinyl alcohol sheet which has been stained with iodine to
render it light-polarizing and which may also have been borated in
the manner disclosed in any of U.S. Pat. Nos. 2,445,579, Re: 23,297
or 2,554,850.
The thicknesses of the various layers in the aforementioned plastic
optical elements are not critical and may vary over wide ranges. It
will be appreciated, however, that the layers are preferably as
thin as possible, for reasons of economy, weight and to minimize
distortion or refraction of transmitted light. By way of example
only, the abrasion-resistant coating layers each may be on the
order of 1 mi1 thick; the transparent plastic sheets may each be on
the order of 0.0120-0.0140 inch thick; the polarizer on the order
of 0.001 inch thick; and the IR absorber-containing layers each on
the order of about 0.1 to about 5.0 mils thick.
The IR absorber-containing layers may be applied as a coating
comprising a viscous solution containing the same or they may be
imbibed into the transparent plastic sheets by contacting them with
a solution containing one or more of the absorbers. The former
method of application is preferred, however, since it has been
found that greater amounts of the absorber can be added as a
coating than can be added by imbibition. It will be appreciated,
however, that even when applied as a coating, some of the absorber
may inherently be imbibed. Whether the IR absorber is added as a
coating or by imbibition, useful solvents for that purpose include
chloroform, methylene dichloride, toluene, tetrahydrofuran, etc.,
and mixtures of such solvents.
In addition to the layers or coatings shown in FIG. 1, the element
may contain other layers introduced to provide suitable bonding
surfaces to insure obtaining a strong lamination.
It will be appreciated that the plastic element is not restricted
to the relationship of layers shown in FIG. 1. For example, the IR
absorber may be present between the outer coating 16 and the
transparent plastic sheet 12. (In the event a scratch resistant
coating 16 is applied by in situ polymerization, care should be
exercised to avoid the use of polymerization catalysts, e.g.,
peroxides, which might attack the infrared absorber.) In lieu of
having two separate layers 14 of IR absorber, a single such layer
may be provided, as shown in FIG. 3. In any event, optical elements
of this invention may be employed in conventional eyeglass frames
18, as shown in FIG. 2.
As was mentioned earlier and illustrated in the spectral absorption
curves shown in FIGS. 5-6, while the compounds of Formula A are
extremely good absorbers in the near infrared region of the
spectrum and are substantially transparent to visible light, they
also absorb appreciably in the ultraviolet region. This latter
property makes it possible to eliminate or to materially reduce the
amount of ultraviolet absorber needed in such an element to protect
the lens of the eye. Thus, these compounds may be said to serve a
dual function in reducing the transmission of harmful invisible
radiation at both ends of the spectrum.
The amount of the IR absorber employed in the plastic optical
elements of this invention may vary over a wide range, the amount
employed being in part dependent upon the percent of transmission
in the region desired and is in part dependent upon the efficiency
of the absorber in the system employed. In a preferred embodiment,
however, the IR absorber is present in an amount such that the
amount of transmitted IR is not substantially greater, if greater
at all, than the amount of visible light transmitted. By not
"substantially greater," it is meant that the percent of IR
transmitted does not exceed the percent of visible light
transmitted by more than about 5percent.
Since the compounds of Formula A are relatively narrow band
absorbers, it may be desirable to employ a mixture of two or more
such compounds of varying .lambda..sub.max to provide effective
absorption over the necessary range of the infrared region of the
spectrum.
While the foregoing description of plastic optical elements has,
for purposes of illustration, been in terms of polarizing
sunglasses, it will be appreciated that the invention is not
limited thereto. Since an important aspect of this invention is the
discovery that compounds of Formula A effectively diminish
transmission of substantial amounts of unwanted invisible radiation
while being substantially transparent to visible light and
possessing extremely desirable stability to light, heat and
humidity, this invention also contemplates the use of the compounds
of Formula A in various systems wherein it is desired to transmit
visible light but to diminish or retard transmission of invisible
radiation in particular regions of the spectrum. Since these
compounds possess narrow absorption bands they may be employed
singly to provide absorption in a particular narrow band of the
spectrum or in combination to provide broader absorption. The
ability of the individual compounds to provide narrow absorption in
a desired region is a significant advantage which will be apparent
to those skilled in the art. Accordingly, the various other systems
to which this invention is applicable, e.g., in plastic lenses for
use in photography, will be readily suggested to those skilled in
the art in the light of this description.
The following examples show by way of illustration and not by way
of limitation the preparation of the novel compounds of this
invention, the .lambda..sub.max of each of the compounds being
determined in dichloromethane.
EXAMPLE 1
The IR absorber of Formula 1 was prepared by refluxing 1 mole of:
##SPC7##
with 1.25 mole of p.sub.4 S.sub.10 in dioxane (inert solvent) for
four hours. The mixture was then cooled and filtered, after which
was added 1 mole of NiCl.sub.2. 6H.sub.2 0 dissolved in water. The
resulting mixture was then heated on a steam bath for 2 hours to
form the compound of Formula 1 which was collected by cooling and
filtering to yield a crystalline product, m.p. 292.degree.C,
.lambda..sub.max = 920 .mu.; .epsilon. = 35,000.
EXAMPLE 2
Substitution of benzoin for the acyloin of Example 1 yielded the
compound of Formula 2, m.p. 282.degree.-283.degree.C
.lambda..sub.max = 865 .mu.; .epsilon. = 29,600.
EXAMPLE 3
Substitution of: ##SPC8##
in the procedure of Example 1 yielded the compound of Formula 7,
m.p. 255.degree.-256.degree.C; .lambda..sub.max = 773 .mu.;
.epsilon. = 19,600.
EXAMPLE 4
Repetition of Example 1, employing a large excess of benzoin to
avoid loss of the metal, and employing K.sub.2 PtC1.sub.4 yielded
the compound of Formula 6, m.p. 310.degree.; .lambda..sub.max = 800
.mu.; .epsilon. = 51,600.
EXAMPLE 5
Substitution of the acyloin in the procedure of Example 4 yielded
the compound of Formula 12, m.p. 303.degree.-305.degree.C;
.lambda..sub.max = 863 .mu.; 41,600.
EXAMPLE 6
Substitution of: ##SPC9##
in the procedure of Example 4 yielded the compound of Formula 11,
m.p. >350.degree.C; .lambda..sub.max = 740 .mu.; .epsilon. =
36,800.
EXAMPLE 7
Substitution of K.sub.2 PdC1.sub.4 in the procedure of Example 4
yielded the compound of Formula 5, m.p. 254.degree.C;
.lambda..sub.max = 885 .mu.; .epsilon. = 39,700.
EXAMPLE 8
Substitution of K.sub.2 PdCl.sub.4 in the procedure of Example 5
yielded the compound of Formula 4, m.p. >250.degree.C;
.lambda..sub.max = 948 .mu.; .epsilon. = 37,900.
EXAMPLE 9
4,4'-diisopropyl benzoin was prepared according to the synthesis
described in Ber., 77, 409 (1944). This compound was substituted
for the acyloin in the procedure of Example 1 to yield the compound
of Formula 13, m.p. 305.degree.-307.degree.C; .lambda..sub.max =
828 .mu.; .epsilon. = 49,200.
EXAMPLE 10
p-butoxybenzaldehyde was made by the method described in Stoermer,
Ber. 61,2328 (1928). This was in turn used to make
4,4'-dibutoxybenzoin in the manner described in Tadros, J. Chem.
Soc., (1963), 4527. Substitution of this benzoin for the acyloin of
Example 1 yielded the compound of Formula 14, m.p.
239.degree.-240.degree.C; .lambda..sub.max = 930; .epsilon. =
35,600.
EXAMPLE 11
Substitution of .alpha.-bromoacetophenone for the acyloin of
Example 1 yielded the compound of Formula 15 as an impure mixture
which was not purified. HBr gas was evolved during the reaction.
Analysis of the impure cpd; .lambda..sub.max = 815 .mu.; .epsilon.
= 7000.
EXAMPLE 12
The thenoin: ##SPC10##
was synthesized according to the procedure described in J. Org.
Chem. 14, 184 (1949). 20 g. of this compound (0.088 mole) and 57.5
g. of P.sub.2 S.sub.5 (0.13 mole) were refluxed with stirring for
six hours in 300 ml. of dioxane. The reaction mixture was cooled
and a black residue was filtered off. To the filtered solution was
then added 20.8 g. of NiC1.sub.2.6H.sub.2 O (0.088 mole) dissolved
in 100 m1. of H.sub.2 O. The mixture was heated on a steam bath for
one hour to form black crystals which were collected by cooling and
filtering to yield 1.1 g. of the compound of Formula 3. This
compound was purified by dissolving the crude product in 600 m1. of
CHC1.sub.3, filtering and evaporating the CHC1.sub.3 down to about
25 m1. and allowing the product to crystallize out. m.p.
250.degree.-251.degree.C; .lambda..sub.max = 970 .mu.; .epsilon. =
24,6000.
EXAMPLE 13
The procedure of Example 1 was repeated using as starting materials
a 3:1 ratio of benzoin to anisoin to yield the compound of Formula
8, m.p. 261.degree.-263.degree.C; .lambda..sub.max = 895 .mu.;
.epsilon. = 28,400.
EXAMPLE 14
Substitution of K.sub.2 PtC1.sub.4 in the procedure of Example 13
yielded the compound of Formula 10, m.p. 288.degree.-290.degree.C,
.lambda..sub.max = 838 .mu.; .epsilon. = 42,000.
The following example shows by way of illustration and not by way
of limitation the preparation of an optical element in accordance
with this invention.
EXAMPLE 15
To 100 cc of chloroform was added 7.5 g . of cellulose acetate
butyrate chips. To the resulting viscous solution was added a
second solution containing 0.1 g. of the IR absorber of Formula 1,
0.1 g. of the IR absorber of Formula 7, and 0.02 g. of "Calco Oil
Violet ZIRS" (tradename of American Cyanamid Company of a violet
dye which was employed to provide a neutral gray product) in 20 cc.
of chloroform. The resulting mixture was coated onto each of two
sheets of clear cellulose acetate butyrate at a speed of 6
ft/minute to provide on each sheet a layer containing 0.020 g. of
combined IR absorbers per sq. ft. of surface area, the layer or
coating being approximately 0.3 mil thick. On the free surface of
each sheet of cellulose acetate butyrate (the surface opposite from
that containing the IR absorber coating) there was then applied an
abrasive-resistant coating such as described in Example 1 of the
aforementioned U.S. Pat. No. 3,097,106 containing 0.6percent by
weight of "Uvinul 490" (tradename of General Aniline Company for an
ultraviolet light absorber). The cellulose acetate butyrate on the
surface of each of the IR absorber-cellulose acetate butyrate
coating was converted back to cellulose by treating it with a 1:1:1
solution of sodium hydroxide, methanol and distilled water for 16
seconds at 46.degree.C. The converted surface of each sheet was
then washed and the two sheets were heated in an oven to drive off
excess moisture. A solution containing 1.5 g. of polyvinyl alcohol
(PVA) in 66.7 cc of water and 33.3 cc of methanol was coated on
each of the converted surfaces at 6 ft/minute to provide a suitable
bonding surface for the polarizer to be laminated therebetween. A
molecularly oriented PVA (stretched four times its original length)
was laminated to the PVA coating on one of the sheets at room
temperature by applying to the respective laminating surfaces a
laminating dope comprising a 2% PVA solution in water and pressing
the surfaces together. The molecularly oriented PVA was then
stained by imbibition in an iodine solution to render it
light-polarizing. It was then imbibed in a boric acid solution of
low concentration, dried in vacuo to remove excess liquid, and
baked in a heating chamber to dry. The other sheet was then
laminated in a similar manner to the free outer surface of the
polarizer to provide a plastic optical product containing two of
the IR absorbers.
The plastic sunglasses prepared in Example 15 were compared with a
similar pair prepared in substantially the same manner but
containing no IR absorbers. The latter sunglasses also contained a
substantially greater amount of ultraviolet absorber than that
which was added to the abrasive-resistant coating in the example.
For comparison purposes, the respective sunglasses were identical
in all other relevant components. The transmission curves of the
respective sunglasses are shown in FIG. 4 superposed with the
previously mentioned curve showing the solar energy at the lens of
the eye.
Looking first at the ultraviolet region (left sides of the graph),
it will be noted that the sunglasses without the IR absorber
greatly diminish the ultraviolet at the lens, transmitting 4% of
the total ultraviolet while the sunglasses with the IR absorber
nearly precluded any ultraviolet transmission, transmitting only
0.6% of the total ultraviolet thereby indicating the superiority of
the sunglasses of this invention in the ultraviolet region.
With reference next to the visible region of the spectrum, the
sunglasses without the IR absorber transmitted 24% of the Kv
(energy transmitted at middle visual range, i.e., about 550 .mu.);
whereas the sunglasses containing the IR absorber transmitted only
slightly less, 23%, thus indicating that there is no significant
difference in transparency to visible light as a result of the
incorporation of the infrared absorbers of this invention.
In the near IR region (right hand side), the sunglasses without the
IR absorber transmitted 59.5% of the total near infrared energy
otherwise available at the lens of the eye; whereas the sunglasses
with the absorber transmitted only 28% of the total radiation in
this region. It will thus be seen that the latter sunglasses
transmit no substantially greater per cent of the IR than they do
visible light. It will be appreciated, moreover, that by employing
one or more additional IR absorbers having a .lambda..sub.max more
towards the far infrared, the transmitted near infrared shown on
the chart may be further reduced to levels as low or lower than the
transmitted visible light.
As was mentioned previously, the asymmetrical compounds of Formula
A are specifically novel. These compounds provide the significant
advantage of making it possible to provide a particular compound
having absorption properties over a particular desired narrow band
of the infrared region. By way of illustration, it will be noted
from the illustrative examples that the symmetrical compounds of
Formulae 1 and 2 have .lambda..sub.max respectively of 920 .mu. and
865 .mu.. Assuming it is desired to obtain a compound having a
.lambda..sub.max intermediate these two points in the spectrum, one
may prepare the compound of Formula 8, which it will be noted has a
.lambda..sub.max of 895 .mu..
In Example 15 illustrating the preparation of a plastic optical
element in accordance with this invention, reference has been made
to the step of converting the cellulose acetate butyrate on the
surface of the IR absorber-cellulose acetate butyrate coating back
to cellulose. This concept is desecribed and claimed in the
copending application of Harold O. Buzzell, Ser. No. 577,578 filed
Sept. 2, 1966 and now U.S. Pat. No. 3,620,888.
Since certain changes may be made in the above product and
processes without departing from the scope of the invention herein
involved, it is intended that all matter contained in the above
description or shown in the accompanying drawings shall be
interpreted as illustrative and not in a limiting sense.
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