Note: Descriptions are shown in the official language in which they were submitted.
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1085-31-00 '~
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TITLE: RADIATION CURABLE COATING FOR PHOTOGRAP~IC LAMINATE
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates to ultraviolet radiation E
curable compositions suitable for use as optical coatings
for use in photographic films.
Manufacturers of photographic films have been --
attempting to perfect three-dimensional-effect color films
for some time. One approach currently under investigation is ¦:
to deposit a clear, lenticulated optical coating onto
conventional photographic print material. The optical
coating is responsible for the three dimensional effect and
is usually composed of a cross-linked, ultraviolet-
radiation-cured acrylic polymer supported by a clear plastic ~:
base such as cellulose triacetate, polypropylene, or
polyester. The optical coating is typically 8-11 mils E
(0.008-0.011 inch) thick. Lenticulated optical coatings are [::
descrlbed in J. Nims et al, "Three Dimensional Pictures And
Method Of Composing Them," U.S. Patent No~ 3,852,787 ~F
(December 3, 1974). IE-
An optical coating should possess several char~ ~
acteristics; foremost among them is optical clarity. The b
optical coating must not be susceptible to yellowing or ,:
~ ~3~
other discoloration prior to, during, and after exposure and
developing of the color print material underlying the
optical coating.
In addition to optical clarity, the optical coating
must be sufficiently flexible so as not to crack when the
film is bent in half.
The physical characteris~ics of the optical coating
are highly dependent upon the choice of acrylate~terminated
oligomers employed in the manufacture of the optical
coating. In addition to providing a cured acrylic optical
coating which satisfies the requirements discussed above,
the uncured optical coating composition should possess a
rapid cure rate, thereby allowing processing speeds of at
least 15 feet per minute and preferably 30-60 feet per
minute.
Typically, acrylate-terminated oligomers which
possess polyester or polyether backbones have been employed
in the manufacture of optical coatings. Polyester based
acrylic coatln~s display poor hydrolytic stability.
Conventional water-based photographic developers can easily
penetrate polyester-based acrylic optical coatings, thereby
causing severe yellowing of the optical coating. Poly-
ether-based acrylic coatings suffer from poor oxidative
stability, and are also permeable to photographic
developers.
In European Patent No. 0104057, and in Canadian Patent
Application No. 437,003 filed September 19, 1983, which corres-
ponds thereto, we disclose optical coating compositions which
employ polyurethane-based acrylate-terminated oligomers.
E. Description of the Prior Art
H. Hisamatsu et al, "Photopolymerizable Iso-
cyanate-Containing Prepolymers," U.S. Patent No. 3,891,523
(June 24, 1975) discloses UV curable, acrylate-terminated
polyurethane prepolymers which have a free isocyanate
content of from 0~3 to 15 percent based on the total weight
~ 2 ~3~b~ ~
of the prepolymer and a cure initiator. The excess '
isocyanate groups are stated to impart superior adhesion to r
a substrate.
N. Miyata et al, "Photopolymerizable Vinylurethane
.........
Monomer," U.S. Patent No. 3,907,865 (September 23, 1975) :
discloses acrylate-terminated polyurethane oligomers which
are highly UV curable and which, upon curing, form a
non-yellowing acrylic film. The reference requires the use 'r'
of xylylene diisocyanate in the preparation of its
acrylate-terminated polyurethane oligomer.
D. Lorenz et al~ "Radiation Curable Coating :
Composition Comprising An Acryl Urethane Oligomer And An
Ultra-Violet Absorber," U.S. Patent No. 4,129,667 (December
12, 1978) discloses an acrylate-terminated, polyether or :
polyester-based polyurethane oligomer which is employed in _
combination with an acrylic ultraviolet radiation absorber.
D. Lorenz et al, "Radiation CurabIe Coating
Composition Comprising An Acryl Urethane Oligomer And An i::
Ultra-Violet Absorber," U.S. Patent No. 4,135,007 (January
17, 1979) discloses a radiation curable coating composition
comprising an acrylate-terminated, polyether or poly-
ester-based polyurethane oligomer and a benzylidene acid ~-
ester. :
H. Suzuki et al, "Thermosetting Resins," U.S. Patent _
No. 4,020,125 (April 26, 1977) discloses an acrylate-
terminated hydrogenated polybutadiene polymer which may be L:
cured by exposure to electron beam radiation. The thermoset
resin so produced has utility in electrical components.
SUMMARY OF THE INVENTION
.
The applicants' invention is a composition of matter
comprising:
i) from 45 to 80 percent, based upon the total weight
of the composition, of an oligomer of the formula
O H H O O H H O
X-O-C-N~R2-N-C-O-Rl -O-C-N-R2-N-C -O-Q ........
~53~
where Rl is a linear or bra~ched hydrocarbo~ polymer of
from 1,000 to 4,000 ~olecular weight selected from the
group consi~ting of fully hydrogenated 1,2-polybuta- .-.-.diene; 1,2-polybutadiene hydrogenated to an iodine F
~umber of fr~m 9 to 21; and fully hydrogenated polyiso-
butylene;
R2 is a linear, branched or cyclic alkyl
of from six to twenty carbon atoms, .. :
X and Q are independently either
a) a radical of the formula
- R3 - O R5 ,
- ( ~ ) m~3FC~C=~H 2 ....
R4 .......
wherein R3, R4 and R5 are independently :
selected from the group consisting of ....
hydrogen, methyl, ethyl or propyl,m is an ......
integer from l to lO, and p is either .:.-.
zero or one, or ~
b) a saturated alkyl of from nine to twenty :
carbon atoms .... :-.
with the proviso ~hat said oligomer must possess ..:..
at least one acrylate or methacrylate
terminal group; - ~
ii) from 20 to 50 percent, based on total weight of ,--
the composition, of an acrylate or methacrylate ~.
terminated reactive diluent of from ~ to 22 carbon ;
ato~s; E'.'-.. ''.'
iii) from 0.~ to 5 percent~ based on total weight of
the composition, of a photoinitiator selected from ~
the group comprising 2-hydroxycyclohexylphenone,
diethoxyacetophenone, l-(4-dodecylphenyl)-2- i~.. :
hydroxy-2-methylpropan-l-one, 2-hydroxy-2-methyl- ~-
. l-phenyl-propa~ one and mixtures thereof.
When cur~, the ~0~05ition described above F
solidifies into a dry, water-impermeable film which is .
resistant to yellowing and suitable for use in a lenticu-
lated optic~l /oating. ~
E
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DETAILED DESCRIPTION OF THE INVENTION
The applicants have discovered that a composition
comprising an acrylate-terminated oligomer conforming to
formula I above, at least one reactive diluent, and a ::
5 specific photoinitiator satisfi~es the rigorou~ criteria
required of optical coatings.
A. THE ACRYLATE-TERMINATED OLIGOMER
The acrylate-terminated oligomer is composed of an
organic polymeric backbone which has been end-capped with a
diisocyanate which is itself then further reacted with an
acrylation agent.
1. The Organic Polymeric Backbone r
The organic polymeric backbone which is employed in
the applicants' invention is formed from a linear or
branched hydrocarbon polymer o~ from 1,000 to 4,000 mol~ar
weight. By "hydrocarbon" it is meant a non-aromatic compound t
containing a majority of methylene groups (-CH2-) and which
may contain both internal unsaturation (-CH=CH-) and pendant
unsaturation (-CH-CH~)~ Fully saturated hydrocarbons are
HC=CH2
preferred because the long-term flexibility of the cured
optical coating increases as the degree of unsaturation
decreases. Suitable hydrocarbon polymers include hydroxyl-
terminated, fully hydrogenated 1,2 polybutadiene or
polyisobutylene. ~ydrogenated 1,2-polybutadiene is
preferred due to its superior resistance to yellowing when
cured. It is commercially available from Nippon Soda, Ltd.
under the trademark GI-1000.
2. The Diisocyanate
The choice of diisocyanate has an effect upon the
flexibility and optical clarity of the cured optical
coating. Non-aromatic diisocyanates of from six to twenty
carbon atoms may be employed in the preparation of the
isocyanate-~erminated precursor. Aromatic diisocyanates are
unacceptable due to their tendency to cause yellowing of the
cured optical coatin~ Suitable saturated, aliphatic
, ,, '7 ,
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6 ..
diisocyanates include dicyclohexylmethane-4,4'-diisocyanate,
isophorone diisocyanate, hexamethylene diis~cyanate and
trimethylhexamethylene diisocyanate. Isophorone diifiocyanate
is preferred because it provides superior surface hardness ;
in the cured acrylic film. :
The reaction between the hydroxyl-terminated
hydrocarbon and the diisocyanate generally requires a small
amount of catalyst, typically from 100 to 200 ppm. Suitable
catalysts include dibutyltin oxide, dibutyltin dilaurate,
stannous oleate, stannous octoate, and lead octoate.
Tertiary ~mines such as triethylamine, diethylmethylamine,
triethylene diamine, dimethylethylamine, morpholine, N-ethyl :
morpholine, and pipera~ine may also be employed. Dibutyltin ~
dilaurate is preferred because of its high reactivity. -
3. The Acrylation Agent
The acrylation agent is a hydroxyl-terminated .
aliphatic acrylate or methacryiate which must conform to the -
formula
R3 - O R5
HO- - (~)m~~ ~-c-c=cH2 e
wherein R3, R4, and R5 are independently selected from the ~:-
group consisting of hydrogen, methyl, ethyl, or propyl, m is E
an integer from 1 to 10, an~ p is zero or one. ~:
The choice of acrylation agent affects the degree of
crosslinking of the cured optical coating. The choice of F
acrylation agent also affects the cure rate of the
acrylate-terminated oligomer. Suitable hydroxyl-terminated
monoacry]ates include hydroxyethyl acrylate, hydroxyethyl :
methacrylate, hydroxypropy~ acrylate, and hydroxypropyl _
methacrylate. Hy~roxyethyl acrylate is preferred because it ~-
imparts a faster o~re rate to the polyurethane oligomer.
r~he acr~hati~n age~t shou~1d be ~d~ed to the
polyurethane precursor in the absence of light. To further
minimize the possibility of premature gellation, one or more
of the following precautions may b- taken:
11: ~!~ ' ' '
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l. Maintaining the reaction temperature at or
below 65C.
2. Adding 30 to lO0 ppm of an acrylate
stabilizer such as phenothiazine,
hydroquinone or methyl ether of
hydroquinone
3. Adding 15 to 20 weight percent of a -
reactive diluent to lower the reaction
mixture viscosity, thereby permitting ~ -
more efficient heat transfer. Suitable
reactive diluents include lauryl acrylate -
and 2-ethylhexyl acrylate~
4. Running the reaction under dried air. -
B. THE REACTIVE DILUENT ........
The oligomer formed by the acrylation of the
isocyanate-terminated precursor is a typically high ~:
viscosi~y liquid. A low molecular weight acrylic monomer is
added as a reactive diluent to lower the viscosity of the-
oligomer. Important considerations governing the selection l -
of the reactive diluent include toxicity, volatility, effect }
on the optical clarity of the cured optical coating, and ~'
cost. Acceptable reactive diluents include lauryl acrylate,
lauryl methacrylate, stearyl acrylate, stearyl methacrylate,
hexanediol diacrylate, trimethylolpropane triacrylate,
neopentyl glycol diacrylate, and ethylhexylacrylate. Lauryl iL:
acrylate is preferred because it imparts superior flexibil-
ity to the cured optical coating. Ethylhexylacrylate is
preferred due to its low cost.
Diacrylates or triacrylates may be employed as the t::
reactive diluent to impart enhanced surface hardness and r
adhesion to the cured optical coating composition. The cure
speed of the optical coating composition is usually more
rapid, and the cured film harder, when diacrylates or
triacrylates are employed as the reactive diluent.
`~.
A mixt~re of acrylic monomers is preferred as the
reactive diluent to achieve the optimum balance of
flexibility and mar resistance in the cured optical coating
while achieving the desired viscosity in the uncuxed optical
coating composition at the lowest cost and toxicity. A
reactive diluent comprising a mixture of ethylhexylacrylate
and hexanediol diacrylate, illustrated in Example III, is
preferred. r
C. THE PHOTOINITIATOR
The selection of photoinitiator is critical. It must
provide reasonable curing speed without causing premature
gellation of the optical coating composition. It must not
affect the optical clarity of the cured optical coating.
Only four photoinitiators - 2-hydroxycyclohexylphenone, :
lS diethoxyacetophenone, 1-(4-dodecylphenyl)-2-hydroxy-2-
methylpropan-l-one, and 2-hydroxy-2-methyl-l~phenyl-
propan-l-one - are acceptable for use as the photoinitiator.
2-hydroxycyclohexylphenone is commercially available from
Ciba-Geigy Corp., Dyestuffs and Chemicals Division,
Greensboro, North Carolina 27409 under the trad~E~k
CGI-184. 2-hy~}o~y-2~metbyl-1-phenyl~-propan-1-one is E
commercially available from Eff Chemicals Corporation, 500 ,~-
Executive Blvd., Elmsford, New York 10523, under the
trademark DAROCUR 1173. 1-(4-dodecylphenyl)-2-hydroxy- ,-
2-methylpropan-1-one is commercially available from EM
Chemicals Corporation under the trademark DAROCUR 953.
Diethoxyacetophenone is commercially available from the
UpJohn Company, Fine Chemicals Division, North Haven, :
Connecticut 06473.
.Cure of the optical coating composition is achieved
by depositing the coating composition onto a clear plastic
support and passing the supported coating composition under
an ultraviolet OF ionizing (electron beam) radiation source. -:
The coate2 side o~ the support is exposed to the radiation
~5 for a t;me sufficient to initiate addition polymerization of
the acrylate or methacrylate groups of the coating
composition. The polymerization process is preferably
!
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performed under an inert atmosphere such as nitrogen. The
resulting clear acrylic film bonded onto a clear plastic
support is termed a "cured optical coating."
By "ultraviolet radiation" it is meant any radiation
source which will emit ultraviolet radiation in wavelengths
of from 2000 to 4000 angstroms in sufficient intensity to
produce free radicals in the optical coating composition and ;
thereby induce addition polymerization of olefinic bonds, :
typically from 0~0004 to 6.0 watts/cm2. Suitable radiation
sources include Type RS sunlamps, carbon arc lamps, xenon
arc lamps, mercury vapor lamps, tungsten halide lamps,
fluorescent lamps with ultraviolet light emitting phosphors,
and lasers. :
D. HOW TO USE E::
The cured acrylic film of the optical coating may be
lenticulated by conventional processes. The clear plastic
support of the lenticulated optical coating is then bonded
to a conventional photoemulsion supported by backing
material. The resulting laminate, consisting of the
following layers -lenticulated acrylic film which is
resistant to yellowing, clear plastic support, photoemulsion !'~'~'''
and backing material - is termed an "unexposed color print
material." ~:
Unexposed color print material may be developed by
conventional photographic development processes, which ~::
typically comprise: '
1. Projecting the image of a color print ~
negative upon the surface of the color ~-
print material surface, thereby
"exposing" the color print material; L
2. Immersing the exposed color print
material in a "developer" solution for a
time sufficient to react the dyes and --
pigments in the color print photoemul-
sion, typically 4 minutes;
: .
3. Immersing the exposed color print
material in a "fixer" solution which
stops further reaction of the color print .
material photoemulsion;
4. Immersing the exposed color print
material in a water rinse for a time .::
sufficient to remove all traces of the
"developer" and "fixer" solutions, ;
typically 4 minutes at 91DF; and ..
5. Drying the developed color print .
material. ..
E. DESCRIPTION OF A PREFERRED EMBODIMENT _
The applicants have achieved optimum results from an
optical coating composition comprising .
i) approximately 59 percent, based upon .
total composition weight, of an oligomer ..
prepared by reacting hydrogenated NISSO ..
GI-1000*hydroxyl-terminated polybutadiene
with isophorone diisocyanate, followed by
endcappin~ with 2-hydroxyethyl acrylate,
ii) approximately 29 percent, based upon E.
total composition weight, of 1,6-hexane- g
diol diacrylate, employed as a reactive ~--
diluent, ..
iii~ approxima~ely 1~ percent, based upon -
total composition we~ght, of 2-ethyl- .:
hexylacrylate, als~ employed as a :
reactive diluent, ...
iv) approximately 2 percent, based upon .. :.
total composition weight, of 2-hydroxy- _
cyclohexylphenone, employed as a ._
photoinitiator~ ...
The prepaeation of this composition is illustrated by . --
Example III below.
~`Trademark t
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EXAMPLES:
The Examples which follow are intended to illustrate .....
the practice and advantages of the applicants' invention,
and are not intended to limit the scope of their invention ..
in any way. All concentration percentages are measured by ...
total weight of the composition unless otherwise stated.
k
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EXAMPLE I
50 grams (.45 equivalents) of isophorone diisocyanate
were added to a reactor vessel equipped with an agitator, a
thermometer, an inert gas inlet and a charging port. The
reaction vessel was continuously purged with dry air
throughout the oligomer preparation. The isophorone
diisocyanate was heated to 65C and agitated~ 0.04 grams of
dibutyltin dilaurate were added. 178 grams (0.225 e~uiva-
lents based on an equivalent weight of 791~ of "Exxon" :
hydroxyl-terminated, hydrogenated polyisobutylene (molecular
weight of 1582) were added. ::;
When the theoretical isocyanate content (0.225 :
equivalents) was reached, the temperature was raised to
75C. Over the course of 40 minutes, 26.43 grams (0.~25 ~-
e~uivalents) of 2-hydroxyethyl acrylate were added to the ~:
reaction mixture. The reaction required approximately three
hours to proceed to completion (final isocyanate concen- F~
tration less than 0.2%~ at a final temperature maintained
about 75-80C. E
54.~ grams of 2-ethylhexylacrylate and 3.6 grams of
2-hydroxycyclohexylphenone were added to 127.2 grams of the
oligomer, which was then mixed thoroughly to produce a ~r
clear, viscous, optical coating composition, which was
labelled IA.
54.5 grams of lauryl acrylate and 3.6 grams of
2-hydroxycyclohexylphenone were added to the remaining 127.2 :
grams of oligomer, and mixed thoroughly. The clear, viscous ::
optical co~ting composition so prepared was labelled IB.
*Trademark -
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EXAMPLE II
,.
Using the proced~re of Example I, 111.7 grams (0.14 '
equivalents, based upon an equivalent of 782 grams/equiva
lent) of hydrogenated NISSC GI-1000 hydroxyl-terminated
polybutadiene (approximately 1564 molecular weight) were
added to 30 grams (0.28 equiva:Lents) of trimethylhexa- ,:
methylene diisocyanate, in the presence of 0.03 grams of
dibutyltin dilaurate to form the isocyanate-terminated
precursor.
16.6 grams (0~14 equivalents) of 2-hydroxyethyl
acrylate were added to form the acrylate terminated
oligomer.
71.95 grams of the oligomer were mixed with 71.95
grams of 1,6-hexanediol diacrylate and 2.9 grams of
2-hydroxycyclohexylphenone to form a clear optical coating
composition, which was labelled IIA. _
The remaining 86.4 grams of the oligomer were mixed _
with 28.8 grams of 1,6-hexanediol diacrylate, 28.8 grams of
ethylhexylacrylate, and 2.9 grams of 2-hydroxycyclohexyl
phenone to form a clear optical coating composition which
was labelled IIB.
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,,,,:,.....
EXAMPLE I I I
Using the procedure of Example I, 106 grarns (0.135 ....
equivalents, based upon an equivalent weight of 782
grams/equivalent) of hydrogenated NISSO GI-1000 hydroxyl- ..
terminated polybutadiene were added to 30 grams (0.27 .::.
equivalents) of isophorone diisocyanate in the presence of a .:::
small amount of dibutyltin dilaurate to form the isocyanate-
terminated precursor. .,: :
15.7 grams (0.135 equivalents) of 2-hydroxyethyl ~:
acrylate were added to form the acrylate-terminated .... :.
oligomer. .~
75.9 grams of 1,6-hexanediol diacrylate, 25.3 grams .::
:::::::.
of ethylhexyl acrylate, and 5.1 grams of 2-hydroxycyclo- ...
hexylphenone were added to the oligomer, which was then
mixed thoroughly to produce a clear optical coating FL
composition labelled III. .....
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....
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, ........
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EXAMPLE IV !.:.
Using the procedure of Example I, 167.5 grams (0.225
equivalents, based upon a 744 equivalent weight) of
unsaturated NISSO G 1000 hydroxyl-terminated polybutadiene
were added to 50 grams (0.45 equivalents) of isophorone
diisocyanate in the presence of a small amount of dibutyltin ~-
dilaurate to form the isocyanate-terminated precursor.
26.1 grams (0.225 equivalents) of 2-hydroxyethyl
acrylate were added to form the acrylate-terminated
oligomer.
40.6 grams of 1,6-hexanediol diacrylate, 121.8 grams
of ethylhexyl a~rylate~ and 8.12 grams of 2-hydroxycyclo-
hexylphenone were added to the oligomer, which was then
mixed thoroughly to produce a clear optical coa~ing ~:
composition which was labelled IV.
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16
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....
EXAMPLE V IF.......... -
Using the procedure of Example I, 154 grams (0.135 !-.-.-.-.-.. --
equivalents, based upon an equivalent weight of 1141
grams/equivalent) of hydrogenated NISSO GI-2000 hydroxyl~
terminated polybutadiene (approximate molecular weight of
2282) were added to 30 grams (0.27 equivalents) of
isophorone diisocyanate in the presence of 0.04 grams of
dibutyltin dilaurate to form the isocyanate-terminated .....
precursor. ..
15.7 grams (0.135 equivalents) of 2-hydroxyethyl ..........
acrylate were added to form the acrylate terminated ::
::..:::
ollgomer. .......
93.19 grams of the oligomer were mixed with ~6.63 ~
..::..~.
grams of 1,6-hexanediol diacrylate, 13.31 grams of ..... -.
ethylhexyl acrylate, and 2.66 grams of 2-hydroxycyclo- ...
hexylphenone to produce a clear optical coating composition :.. :~.
labelled VA. .....
The remaining 106.5 grams of oligomer were mixed with ......
13.31 grams of trimethylolpropane triacrylate, 13.31 grams ~.~:-
of ethylhexyl acrylate, and 2.66 grams of 2-hydroxycyclo- -:-
hexylphenone to produce a clear optical coating composition .:.
labelled VB. t:~
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F....~
:::::::
.....
........
.._
,...........
.....
.... ...
........
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EXAMPLE VI ,,
.........
Using the procedure of Example I, 150.5 grams (0.19
equivalents, based upon an equivalent weight of 777
grams/equivalent) of hydrogenated NISSO GI-lO00 hydroxyl- ':.:
terminated polybutadiene were added to 50 grams (0.38 ~'",':
equivalents) of dicyclohexylmethane-4,4'-diisocyanate in the
presence of 0.04 grams of dibutyltin dilaurate to form,the ,.
isocyanate-terminated precursor. ..
22.5 grams (0.19 equivalents) of 2-hydroxyethyl ,
acrylate were added to form the acrylate-terminated .'.'
oligomer. ,':':':':
31.86 grams of trimethylolpropane triacrylate, 63.71 ,.. '.
grams of ethylhexyl acrylate, and 6.37 grams of 2-hydroxy- ':'
cyclohexylphenone were added to the oligomer, which was then ...
thoroughly mixed to produce a clear optical coating ",
composition labelled VI. "
.
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18
EXAMPLE VII
Portions of the optical coating composition of =
Example III were evaluated for various physico-chemical :,
properties. Results of these tests are listed in TABLE I
below:
TABLE I :
Viscosity @ 25@C1200-1400 cps
Refractive Index 1.470-1.475
Specific Gravity 1.01
~nsaturatlon 0.36 -:
Isocyanate Content <0.2
Base No. ~10.0 ~:
Acid No. <0.5
Portions of the optical coating composition of
Example III were cast as films and cured by exposure to
ultraviolet radiation. These films were then evaluated for
tensile strength and elongation. Results of these tests are
listed in TABLE II belowo 't
TABLE II
Tensile Strength1000-1200 psi - _
Elongation 15--20%
Tear Strength20-30 lb/inch
j
"Mar Resistance" is a measure of the surface hardness !,~
and surface lubricity ("slip") of the cured optical coating.
A cured optical coating passes this test if a fingernail ::
drawn across its suxface does not leave any scratches. ~
"Flexibility" is determined by manually bending a
sheet of cured optical coating in half (180) and observing
whether any cracks appear in the cured optical coating. A _-
"Good" rating means no cracks appeared. An "Acceptable"
1~ ............
rating means no cracks appeared, but the optical coating was .
harder to bend than optical coatings which were rated
"good". -::
The "Sun Light" exposure te!st consists of expssing a
cured optical coating to sun light: for a minimum of fuur ............
hours. ........
The "Sun Lamp" exposure test consis~cs of exposing a
cured optical coating to a 275 watt "Sy1vanial' sun lamp for a ~
minimum of twelve hours at a distance of one foot. ....
The "Fluorescent Lamp" exposure test consists of ....
exposing a cured optical coating to fluorescent light for a .~
minim~m of twelve hours a~ a distance of one foot. ~:.. ::
The "Incandescent Lamp" exposure test consists of ._
exposing the surface of a cured optical coating to a 100 ~.. ~
watt incandescent lamp for a minimum of twelve hours at a .-.^.. ~
distance of one ~ot.
The "140F Oven" exposure test consists of placing ~
the samples in an oven maintained at 140F for a minimum of ~::
eighteen hours. .
*Trademark ~
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EXAMPLE VIII ~:
The compositions of Examples I through VI were
deposited as films upon clear plastic supports (approxi- :-
mately six inches square), and cured by exposure to
ultraviolet radiation. The cured optical coatings so
::..:..
prepared were immersed in a photographic "developer" ,-
solution for approximately four minutes, immersed in a -
"fixer" solution for 1.5 minutes, immersed in a water rinse _
for approximately three minutes, and dried. ~
Some of the samples were then tested for mar _
resistance and flexibility while others were subjected to
various accelerated aging exposure tests to determine
resistance of the cured optical coatings to yellowing. ~
Results of these tests are set out in TABLE III below: _
.....
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EXAMPLE IX ::~
...........
The oligomer and reactive diluent of Example III were
mixed with the four permissible photoinitiators to produce ~.
the four optical coating compositions set out in TABLE IV .:.. :
below~
TABLE IV ,::
Component Composition Percentage `:
A B C D ....
oligomer 58.7 58.7 58.758~7 .....
reactive diluent ~
hexanediol diacrylate 29.5 29.5 29.529.5 ......
ethylhexyl acrylate 9.8 9.8 9.8 9.8 .....
photoinitiator .. _
2-hydroxycyclohexylphenone 2.0 .... _
diethoxyacetophenone 2.0 ....
2-hydroxy-2-methyl-1-phenyl- .......
propan-l-one 2.0 .... :
1-(4-dodecylphenyl)-2-hydroxy- ~
2-methylpropan-1-one _ 2.0 :
100~ 100% 100% 100% .... _
The four compositions described above were deposited ~.~
as films upon clear plastic supports (approximately six ~.::.. ::.-~.
inches square) and cured by exposure to ultraviolet L~
radiation. The cured optical coatings so prepared were rt._
immersed in a photographic developer solution for ~.~=
approximately four minutes, immersed in a fixer solution for ....
approximately three minutes, immersed in a water rinse for ,t .,
approximately three minutes, and dried. The samples were
then tested for yellowing resistance by exposure to various ~
accelerated aging exposure tests~ Results of these tests
are set out in TABLE V below~
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