Note: Descriptions are shown in the official language in which they were submitted.
1;~2~5~2
PHOTOPOLYMERIZABLE THIOACRYLATE MONOMERS~ POLYMERS OF
SAME AND OPTICAL COMPONE~iTS CONTAINING SAID POLYMERS
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to novel thioacrylate
monomers, polymers of thioacrylates and optical components
containing these polymers.
Description Relakive to the Prior Art
Optical components, such as lenses, prisms, and
light guides, are known in the art. It is necessary that
materials used for making optical components be colorless
and transparent. It is also desirable that these materials
have a high refractive index. In the case of lenses, the
use of high refractive index materials makes possible the
use of thinner lenses having the same focal length as
thicker lenses made of materials with a lower refractive
index. The use of thinner lenses decreases the volume of
space required by the lens within an optical assembly.
Also, the manufacture of thinner lenses requires less
material, which constitutes a potential savings to the
manufacturer.
High refractive index materials have also been
shown to be desirable in light guides. U.S. Patent 3,809,686,
issued March 19, 1970, describes the method of producing
light guides by selectively irradiating polymethyl methacry-
late with ultraviolet light at given wavelengths. The
selective irradiation causes observable increases in the
refractive index of the polymer along the path of the
focused radiation. However, the index of refraction of
3 polymethyl methacrylate is only 1.49 to 1.50 and the
increases produced by irradiation are relatively small.
(The resulting change is refractive index equals 0.5 x 10 6
E, where E is the exposure in joules per square centimeter
for ultraviolet light `from a mercury arc.) The use of
polymers having a substantially higher refractive index
(over 1.60) in optical components would make possible the
use of optical components which are considerably thinner
than conventionally prepared components. It is thus seen
that transparent and colorless polymers of high refractive
4 indices are desirable for use in optical components.
~ Z2~S22
--2--
S~MMARY OF THE INVEN~IO~
Polymers of high refractive index are prepared
by photopolymerizing a monomer having the formula:
R O R
~ CH2~-S-CH-Ar-R
wherein:
Ar is arylene;
Rl is H, alkyl~ alkoxy, amino, halogen, sulfide,
sulfoxide, sulfonate 3 aryl or heterocyclic;
R ls H, alkyl, aryl or aralkyl, and
R is H or CH3.
The resulting polymer comprises from 5 to 100
percent of the above monomer and rrom O to 95 percent of a
copolymerizable ethylenically unsaturated monomer. The
polYmer is substantially colorless and transparent and has
a refractive index over 1.60. The high refractive index
renders the resulting polymer particularly useful in
optical components, such as lenses.
Deta~led Description Or Preferred Embodiments
The novel monomer is represented by the formula:
R O R
. C~2=C-C-S-CH-Ar-R
wherein:
Ar is arylene, preferably containing from about
6 to about 22 carbon atoms, such as phenylene, naphthalene~
anthracene, perylene, acenaphthene or rubrene;
l is H; alkyl, preferably containing from about
3 1 to about 20 carbon atoms, such as methyl, ethyl, iso-
propyI or hexyl; alkoxy, preferably containing from about
1 to about 20 carbon atoms, such as methoxy or ethoxy;
aminoj halogen such as chloride or bromide; sulfide;
sulfoxide; sulfonate; aryl, preferably conta~ning from
about 6 to about 18 carbon atoms, such as phenyl; or
heterocyclic, pre~erably a 5 to 7-membered ring which
may be saturated, such as pyrrolidine, morpholine,
piperidine, tetrahydrofurane, dioxane or quinaldine,
or un aturated, such as pyrrole, isoxazole, imldazole,
4 isothiazole, ~urazan or pyrazollne;
A
. ~
~22~2%
~ 2 is H, alkyl as described ror R1, aryl as
described for Rl or aralkyl such as benzyl and
is H or CH3-
It iS noted that thr~ughout the specificationand claims the terms "alkyl," 'laryl" and "arylene"
include substltuted alkyl, aryl and arylene, such as
methoxy ethyl, chlorophenyl and bromonaphthyl.
Examples of monomers useful herein include:
S~ naphthylcarbinyl)thioacrylate;
S-(2-naphthylcarbinyl)thioacrylate;
S-(l-naphthylcarbinyl)thiomethacrylate;
S~ naphthyl)ethylthioacrylate; and
l-bromo-2-naphthylthioacrylate.
The preferred monomers have the structures:
O
CH2= CH-C-S-CH2
and
CH2=CH-C-S-C~2 r ~
The monomers of the present in~ention are prepared
by heating the appropriate mercaptan, such as l-(naphthyl-
carbinyl)mercaptan with a 0-20% molar excess of bicyclo-
heptene carbonyl chloride ~n an organic solvent, suchas methylene chloride, at a temperature o~ 30-50C, while
an acid-accepting amine, such as diisopropylethylamine is
slowly added to the mixture. The prGduct is distilled
under condikions favorable to the splitting off of cyclo-
pentadiene, such as vacuum distillation at 200-300C,
resulting in a good yield of the monomers such as S-(l-
naphthylcarbinyl)thioacrylate.
~he starting material, bicycloheptene carbonyl
chloride, is prepared by stirring cyclopentadiene with a
0-20% molar excess o~ acryloyl chloride and an organic
solvent, such as methylene chloride, at a reduced tempera-
ture, such as -70 to -85C, and allowing the mixture to
warm slowly to room temperature. The acid chloride
product ls isolated by distlllation.
~ ~ ~ 2
--4--
The m~nomer of the present invention has a melt
in~ point less than or equal to 50C. Monomers having
meltin~ points over 50C form bubbles or exhibit non-
uniform crystallization when polymerized in situ. Bubbles
5 or crystals in the resulting polymers scatter light and
cause loss of image sharpness in the optical components
in ~hich they are used.
The polymer of this invention is one having:
(a) from 5 to 100 mole percent of recurring
units having the formula:
~3
-ct
C=O
S-CH-R2
Ar_Rl
where Ar, ~1, R and R3 are described above; and
(b) from 0 to 95 mole percent of a polymerized
copolymerizable ethylenically unsaturated
monomer.
Examples of copolymerizable ethylenically un-
saturated monomers useful herein include alkyl acrylates
and methacrylates such as methyl acrylate, ethyl acrylate,
propyl acrylate, butyl acrylate, and butyl methacrylate;
vinyl esters, amides, nitriles, ketones, halides, ethers~
olefins and diolefins, as exemplified by acrylonitrile,
methacrylonitrile, styrene, a-methyl styrene, acrylamide 3
methacrylamide, vlnyl chloride, methyl vinyl ketone,
fumaric, maleic and itaconic esters, 2-chloroethylvinyl
ether, dimethylaminoethyl methacrylate, 2-hydroxyethyl
methacrylate, N-vinylsuccinamide, N-vinylphthalimide,
~-vinylpyrrolidone, butadiene and ethylene.
Preferred monomers which are useful herein
include acrylates and methacrylates. A most preferred
3 monomer is benzyl methacrylate.
l'he novel polymer can be prepared by adding a
small amo~mt of photoinitiator (.001-1.0 weight percent)
such as benzoin methyl ether to the novel monomer or a
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~.~2~
mixture of preferably 50 to 100 mole percent of the novel
monomer and 0-50% of a copolymerizable ethylenically un-
saturated monomer described above. The mixture can be
polymerized at a temperature of 20-30C by irradiation
with a near-ultraviolet lamp. The resulting polymer has
an index of refraction above 1.60, typically in the
range from 1.60 to 1.70. The use of polymers having a
refractive index over 1.60 in optical components permits
the use of components which are considerably thinner
than conventionally prepared components. Other methods
of polymerization can similarly be used. Such methods
can include thermal polymerization, polymerization by
electron beam irradiation and polymerization by high
energy gamma irradiation. Examples of the polymers of
the invention include:
polytS-(1-naphthylcarbinyl)thioacrylate];
poly[S-(2-naphthylcarbinyl)thioacrylate]
poly[S-(l-naphthylcarbinyl)thioacrylate-
co-benzyl methacrylate];
polytS-(2-naphthylcarbinyl)thioacrylate-
co-benzyl methacrylate].
The novel polymers of this invention are useful
in optical components. The term "optical component" is
defined as that portion of an optical assembly having
as its function the refraction of light. As used herein,
the term "optical component" refers to materials which
can also reflect, diffract and transmit light. However,
"optical components" is directed preferably toward
components in which changes in refractive capability
3 affect the overall utility of the component. "Refraction,"
as used herein, is defined as the deflection from a
straight path undergone by a light ray or energy wave
in passing obliquely from one medium (as air) into
another (as glass or other optical material) in which
its velocity is different. The term "optical assembly"
as used herein is defined as a collection of manufactured
parts in a complete machine, structure, or unit of a
machine relating to the scientific study or use of electro-
magnetic radiation. The term "optical components"
4 includes refractive materials, such as lenses, lens
z~
--6--adhesives, prisms, mirrors, solid light pipes, light
guides, fiber optics, phase-retardation plates and
twistels.
The term "prism" as used herein is defined as
a transparent body bounded in part by two plane faces
that are not parallel, said body being used to deviate
or disperse a beam of light. Prisms can be used in
telescopes, binoculars, beam splitters, rangefinders,
spectroscopes, spectrographs, spectrophotometers,
refractometers and anamorphic systems.
A "mirror" is definecl as a polished or smooth
surface (as glass) that forms images by reflection.
Mirrors can be used in telescopes, beam splitters, range-
finders, reflecting microscope objectives and condensing
systems-
A "solid light pipe" is defined as a transparentbody tapered to form a cone used to internally reflect a
meridional ray incident on the untapered end of the cone
from the conical wall at progressively lower angles of
incidence until it is delivered to the tapered end of
the cone, as described in Smith, Modern Optical Engineer-
ng, 1966, chapter 9. Light pipes can be used to enlarge
the field of view of a radiometer with a small detector.
A "light guide" is defined as a transparent body
having substantially tubular pathways of higher-refrac-
tive index material encased by a lower-refractive index
material used to internally reflect a meridional ray
incident on the entrance end from the walls of the
tubular pathways at substantially equal angles of
3 incidence until it is delivered to the exit end of the
guide, as described in U.S. Patent 3,809,686. Light
guides can be used in electronics to couple simple
circuits optically and without capacitative effects.
"Fiber opt~cs" are defined as transparent bodies
in the form of long polished cylinders in which light
strikes the walls of the cylinder with an angle of
incidence greater than the critical angle for total
internal reflection used to transmit light from one end
~ 122
--7--
to another without substantial leakage, either as a single
fiber or bound together in flexible bundles of fibers as
disclosed by Smith, Modern Optical Engineering, 1966,
chapter 9. Fiber optics are used in medical diagnostic
instruments such as flexible gastroscopes, in fire
detectors to relay signals to a sensor located behind
a heat shield, in data-processing equipment to sense
holes in punched cards or marks on examination forms,
and in photometers and colorimeters to serve as flexible
probes for a fixed sensor.
A "phase retardation plate" is defined as a
transparent body used to produce phase shifts in inci-
dent radiation resulting in elliptically or circularly
polarized light. Phase retardation plates may be a pair
of movable biaxial crystals in the form of wedges having
perpendicularly aligned optical axes, such as Babinet
compensators, Soleil compensators and the like. Or the
desired phase shifts may be produced by total internal
reflection in a phase retardation plate, such as a
Fresnel rhomb. Various phase retardation plates are
described by Kingslake, Applied Optics and Optical
Enrineerin~, 1965, volume I, chapter 9. Phase retarda-
tion plates are used in ellipsometers to study reflec-
tance characteristics of metals and properties of
surface films of liquids with polarized light.
In a particularly preferred embodiment Or this
invention, the monomers and polymers are useful as
materials for making lenses. A "lens" is a transparent
body having two opposite regular surfaces, either both
curved or one curved and the other plane, and which is
used either singly or combined in an optical instrument
for forming an image by focusing rays of light. It has
been found that, because of the higher refractive index
of these polymers, it is possible to produce lenses
which are thinner than lenses made with polymers having
refractive indices under 1.60, e.g., polymethyl-
methacrylate, n = 1.49 to 1.50~
t~
-8- ~222~2~
The lenses of this invention are not only
thinner than conventionally prepared lenses, but require
less curvature, occupy a smaller volume of space and thus
provide more freedom in assembly of multi-element lenses
than prior art lenses. They also require less polymer
to produce, constituting a potential cost savings to the
manufacturer.
Monomers of this invention are useful in pro-
ducing optical components by polymerization in situ.
Thus, the resulting polymer forms the final material of
which the optical component is comprised.
In a preferred embodiment, a lens is prepared
from the novel polymer in the following manner. A mixture
of from 5 to 100 mole percent of a preferred monomer,
such as S-(l-naphthylcarbinyl)thioacrylate, from 0 to 95
mole percent of a copolymerizable ethylenically unsaturated
monomer, such as benzyl methacrylate, and a small amount
of photoinitiator is prepared. A preferred molar ratio
for the mixture is about 84/16 S-(l-naphthylcarbinyl)-
thioacrylate:benzyl methacrylate. A mold of the desiredshape, such as a concave glass lens is filled with the
mixture and covered with a sheet of plate glass. The
assembly is polymerized by irradiation of near-ultra-
violet light. The resulting lens is clear and trans-
parent and contains the polymer of this invention having
a refractive index over 1.60.
The following examples are included for a
further understanding of the invention.
Example 1
3 A mixture of 66 g of cyclopentadiene and 500 ml
of methylene chloride was stirred with 90 g of acryloyl
chloride at dry ice temperature (-78.5C) and allowed to
warm slowly to room temperature over 24 hours. The
reaction product was then distilled. The resulting bi-
cycloheptene carbonyl chloride thus obtained was allowed
to react wikh l-(naphthylcarbinyl)mercaptan and refluxed
in methylene chloride (b.p. 40-41C) while one equivalent
of diisopropylethylamine was slowly added to the mixture.
,,;
~2;~Z~ii2~
g
The product was vacuum distilled, using a 250C oil bath,
under which conditlons the cyclopentadiene split off,
giving S~ naphthylcarbinyl)thioacrylate in good yield.
A thin-layer chromatograph (50:50 hexane/ether, silica
gel) of the resulting monomer indicated as Rf value of
o.69 to 0.72. An infrared spectrum made of the resulting
monomer showed the following bands: 1677 cm l(s), 1620
cm l(m), 1519 cm l(w), 1400 cm~l(s), 1175 cm l(m), 1014
cm l(s), and 780 cm l(s). A nuclear magnetic resonance
spectrum of the resulting monomer showed a complex
multiplet at 7.58 (7H), a doublet at 6.28 (2H), a triplet
at 5.48 (lH) and a singlet at 4.58 (2H).
Example 2
A mixture of 34 g of S~ naphthylcarbinyl)thio-
acrylate, 5 g of benzyl methacrylate, and 0.2 g of benzoinmethyl ether photoinitiator, and 0.3 g of aerosol OT mold
release, a product of American Cyanamid having the
formula:
o C H
" ,2 5
Na HO3S ~HCH2cOcH2cH 4 9
C=O
2~ 4 9
C 2H5
was prepared. A concave glass lens, used as a mold,
was filled with the mixture and covered with a sheet of
0.30-inch thick plate glass. The assembly was polymerized
at a distance of four inches from a 15-watt, near-ultra-
violet Blak-light for one hour at room temperature. The
resulting lens was clear and transparent.
The invention has been described in detail with
particular reference to certain preferred embodiments
thereof, but it will be understood that variations and
modifications can be effected within the spirit and
scope of the invention.
