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Патент USA US3056686

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ire.
is
rates
3,056,676
Patented Get. 2, 1952
2.
1
The objects are accomplished by a photographic ?lm
comprising an oriented polyacrylonitrile ?lm, preferably
3,056,676
biaxially stretched at least 1.5 times its original dimen
sions in each of two mutually perpendicular directions,
impregnated with particles of a silver halide (silver bro
POLYMERIQ lFlLM AND PRQCESS OF
FREE’ARATEGN
Robert William Hendricks, Wilmington, Del, assignor to
E. I. du Pont de Nernours and Company, Wilmington,
lDel., a corporation of Delaware
No Drawing. Filed June 23, 1959, f‘ser. No. 822,199
5 Claims. (Cl. 96—8'7)
mide, silver iodide or silver chloride) to a depth of at
least 1% of the thickness of the polyacrylonitrile ?lm to
a maximum depth, the maximum depth being such as to
leave at least 50% of the thickness of the oriented poly
This invention relates to an improved photographic
?lm. More particularly, it relates to a new strong poly
\acrylonitrile ?lm free of impregnated particles. The im
portance of the lower limit, 1%, is in providing adequate
acrylonitrile photographic ?lm and the process for pre
paring it.
p‘ Films of acrylonitrile polymers have properties that
adhesion between the particles and the base ?lm and to
from the ?lm. The upper limit, 50%, is critical in avoid
preparation and storage of photographic ?lm. However,
free of impregnation.
avoid the danger of abrading the photosensitive particles
make them particularly desirable for use as photographic 15 ing unreasonable loss in the properties (strength, tough
ess, etc.) of the base ?lm, the polyacrylonitrile ?lm, due
?lm bases. Such ?lms, particularly those of the homo
to the destruction of the orientation of the ?lm. It should
polymer polyacrylonitrile, are notsubstantially affected
be understood that if impregnation of particles is per
by changes in temperature. They have an equally low
formed from both surfaces of the ?lm, then the maximum
sensitivity to changes in humidity. The use of acryloni
impregnation from each surface is 25% of the thickness
trile polymeric ?lm as a photographic ?lm base, there
of the ?lm, i.e., 50% of the ?lm’s thickness must be left
fore, would eliminate two very bothersome factors in the
The process of the invention comprises the steps, in
the polyacrylonitrile ?lms heretofore known to the trade
sequence, of treating at least one surface of an oriented
Processes for eliminating this drawback such as orienta 25 ?lm of an acrylonitrile polymer with an aqueous solution
of silver nitrate, preferably a solution containing a con
tion of the polyacrylonitrile ?lm have been dif?cult to
are much too brittle for use as a photographic ?lm base.
centration of 25-50% silver nitrate in water; removing
devise.
excess silver nitrate solution from the surface of the ?lm;
In a recent patent application, US. application Serial
exposing the treated surface of the ?lm to at least one
No. 739,181 ?led June 2, 1958, by M. F. Bechtold and
assigned to the assignee of the present application, a 30 halogen selected from the group consisting of bromine,
chlorine and iodine, said halogen in a form selected from
successful process for orienting polyacrylonitrile ?lms is
the group consisting of halogen acid, halogen salt and
presented. The process improves the toughness and
free halogen to convert the silver nitrate to silver halide
strength of polyacrylonitrile ?lms by orienting the mate
particles; and drying the particle~containing ?lm.
rial in the usual two directions but in an unusual sequence
of steps. Speci?cally, the process comprises dispersing
an acrylonitrile polymer in the form of discrete particles
having a size less than about 15 microns in a liquid
medium comprising water and a solvent metal salt for
said polymer dissolved therein, the salt being present in
an amount such that the molar ratio of polymer (calcu
lated as an equal weight of monomer) to solvent metal
salt is at least 0.5 but less than 6, but in an amount in
su?icient to form a salt solution which dissolves the poly
mer; forming the resulting dispersion into the shape of
a ?lm; evaporating water from the ?lm until coalescence
occurs; stretching the resulting ?lm containing the salt
35
The base ?lm is preferably a biaxially-oriented ?lm of
polyacrylonitrile. However, oriented copolymers of acry
ionitrile with alkyl acrylates (methacrylate), alkyl alk
acrylates (methylmethacrylate), styrene, butadiene meth
acrylonitrile, vinyl stearate, vinyl acetate, vinyl chloride,
N-vinyl pyrrolidone, Z-methyl-S-vinyl pyridine, vinyl
arine sulfonic acids and salts thereof, etc., wherein acry
lonitrile is the major component (at least 75% of the
copolymer is acrylonitrile) are also contemplated for ‘use
in the present invention.
The polymeric material when treated in this invention
is usually in the form of a self-supporting ?lm. How
ever, it may be in the form of any shaped article. The
term “shaped article,” as used herein, is meant to include
and water in a gaseous atmosphere to elongate at least
one dimension of the ?lm while maintaining the molar
?lms, sheets, ?bers, fabrics, rods, tubes and the like.
ratio of polymer to salt in the ?lm within the range of
The ?rst step of the process must be critically con
at least 0.5 and less than 6 and maintaining the mole 50
trolled to provide the requisite amount of impregnation
percent water between about 30 and 80; and thereafter
of the silver nitrate solution into the polyacrylonitrile ar
washing salt from the resulting stretched ?lm and drying
ticle, i.e., impregnation to an extent of at least 1%, but
the stretched ?lm while maintaining said ?lm under ten
no more than 50% of the article’s thickness. To achieve
sion to restrict dimensional change of the ?lm during
washing and drying. The “mole percent water” is ex 55 this requires no special pretreatment. Silver nitrate solu
tion induces ‘swelling of the polyacrylonitrile article. By
pressed as part of the sum of the mole percentages of
causing the polymeric material to swell, the silver nitrate
water, salt and polymer, the total equaling 100%. The
tends to impregnate the polymeric material so that upon
solvent metal salts should be sufficiently soluble in water
conversion to insoluble silver halide particles the resulting
to yield 10% solutions, and preferably at least 30% solu
tions. Furthermore, concentrated aqueous solutions of 60 particles are ?rmly adhered to the acrylonitrile polymeric
material. However, the extent of impregnation depends
the salts must be capable of dissolving the acrylonitrile
on many factors. The concentration of silver nitrate in its
polymers at some temperature up to the boiling point of
solution, the duration of the impregnating treatment, the
the salt solution, e.g., from 0°—l75° C. and generally at
temperature of the treatment, etc., all have their effect.
25°-90° C.
The primary object of the present invention is to pro 65 Determining a suitable combination of conditions to pro
vide the required l—50% impregnation is not di?icult for
vide a photographic ?lm utilizing an oriented acryloni
one skilled in the art after a minimum of experience.
trile polymeric ?lm as the base ?lm. Another object is
Usually, a treatment time of 10 seconds-2 minutes is
a process for preparing such a photographic ?lm in which
adequate at a temperature slightly above room tempera
the toughness and strength of the base ?lm are not sacri
?ced. A further object is to provide a photographic ?hn 70 ture with the preferred concentrations of silver nitrate
from which ?aking or scratching o? of the photographic
salt is prevented. Other objects will appear hereinafter.
solution to attain the required impregnation. If desired,
an organic compound such as dimethylsulfoxide, dimethyl
3,056,676
3
4
formamide, butyrolaotone, dimethylacetamide, N-methyl
pyrrolidone and the like may be used along with the
silver nitrate solution to increase the rate of swelling of
the acrylonitrile polymeric material by providing better
wetting of the polymer and, thus, to increase the extent
of impregnation.
Although treatments involving immersion of the poly
machine stretcher. While in the stretcher, the ?lm was
placed in a pan to which was added water at 15° C. After
about 16 hours of soaking in the cold water, the ?lm was
washed for one hour with water at 65° C. and then dried
under tension for one hour at 120° C.
A sample of the two-way stretched polyacrylonitrile
?lm, 2 mils thick, was immersed in a solution prepared
meric material in a bath of silver nitrate are described
from equal parts by weight of silver nitrate, water and
in the subsequent examples, it should be understood that
dimethylsulfoxide for approximately 30 seconds. The
other modes are also useful. Brushing, spraying or paint 10 ?lm was next blotted dry with a paper towel and hydro
ing of the polymeric material in any manner with the
silver nitrate solution may be used successfully to im
( pregnate one or both surfaces of the ?lm.
The polyacrylonitrile ?lms impregnated with silver ni~
gen chloride gas was passed over the surface on one side
of the ?lm for approximately 30 seconds. The initially
clear surface became nearly opaque and white upon this
treatment with hydrogen chloride.
The ?lm was then
trate are ?rst wiped gently to remove eXcess solution from 15 placed under a transparent sample of ?lm which had the
the surface and then converted to a photo-sensitive ?lm ' letter “B” inscribed on it in opaque ink, and the resulting
by conversion of the silver nitrate to insoluble particles
of silver bromide, silver iodide or silver chloride. The
?nal concentration of particles in the polymeric material
laminar structure was placed in front of a bank of ?uo
rescent sunlamps for approximately one minute with the
silver chloride-containing ?lm behind the lettered ?lm.
Upon removal from the lamps, the top ?lm was peeled
may range anywhere from 0.5% to as high as 65% of
the total weight of polymer plus particles without sub
stantially altering the physical properties of the polymeric
visible (as a semi-transparent white-unreduced portion)
material. However, a range of 15—45% of particles in
the polymeric material has been found to be most useful.
?lm.
off and it was found that the image of the letter was
on a black background of reduced silver in the bottom
The resulting ?lm was then washed thoroughly in
The conversion step may be accomplished by exposing 25 a bath of saturated sodium thiosulfate to remove unre
the impregnated ?lm to the vapors of the free halogen
duced silver chloride and silver nitrate to “?x” the image.
or the halogen acid. The conversion may also be ac
The excellent physical properties of the base polyacrylo
complished by using an aqueous solution of a soluble
nitrile ?lm were virtually unaffected by this treatment.
halide such as the alkali metal (sodium or potassium)
Example 2
halide or a solution of the halogen acid. This latter treat 30
A sample of the two-way stretched polyacrylonitrile
ment with an aqueous solution, surprisingly, does not
wash out silver salt from the ?lm. This is probably at
?lm, 2 mils thick, prepared as in Example 1, was im
tributable to the unexpected ability of the acrylonitrile
mersed in a saturated solution of silver nitrate for ap
groups of the polymeric ?lm to hold silver ions within the
proximately 30 seconds. The ?lm Was vblotted dry with
structure by coordination.
35 a paper towel and a 50/50 weight percent mixture of
hydrogen bromide gas and hydrogen iodide gas was
passed over the surface on one side of the ?lm for ap
The conversion treatments may be performed at room
temperature (20° C.) or slightly above. The duration
proximately 30 seconds. The initially clear surface be
of the treatments should be approximately equal to the
duration of the silver nitrate treatment in the previous step,
came nearly opaque and pale yellow. The ?lm was then
placed under a transparent sample of ?lm which had
. i.e., at least 10 seconds and as high as 2 minutes, depend
ing upon the thickness of the ?lm being treated.
If desired, sensitizers such as allyl diethylthiourea or
allylisothiocyanate may be added to the ?lm during or
subsequent to the conversion treatment to increase light
' with the silver bromide/silver iodide-containing ?lm be
sensitivity. These light sensitizers appear to be capable
hind the lettered ?lm. Upon removal from the lamps,
the letter “B” inscribed on it in opaque ink, and the re
sulting laminar structure was placed in front of a bank
of ?uorescent sunlamps for approximately one minute
of depositing silver sul?de on the silver halide grains to
the top ?lm was peeled off and it was found that the
increase the sensitivity of the silver halide grains to the
effect of light.
image of the letter was visible (as a semi-transparent
white-unreduced portion) on a black background of re
duced silver in the bottom ?lm.
The invention will be more clearly understood by re
The resulting ?lm was
ferring to the examples which follow, Example 1 repre 50 then Washed thoroughly in a bath of saturated sodium
thiosulfate to remove unreduced silver halide and silver
senting the best mode contemplated for performing the
nitrate to “?x” the image. The excellent physical prop
process of the invention. In the examples, all parts are
erties of the base polyacrylonitrile ?lm were virtually un
by weight unless otherwise speci?ed.
affected by the treatment.
Example 1
55
Example 3
Samples of two-way stretched polyacrylonitrile ?lm
were prepared in the following manner by photopolym
A sample of two-way stretched polyacrylonitrile ?lm,
erization from the following ingredients:
32.5 mole percent distilled acrylonitrile
15.2 mole percent zinc chloride
52.3 mole percent distilled water
Hydrochloric acid and benzoin, each in an amount less
than 1% based on the weight of the main ingredients,
2 mils thick, was immersed in a saturated solution of
60
silver nitrate for approximately 30 seconds. The ?lm
was blotted dry with a paper towel and placed on a
glass plate. A 10% aqueous solution of sodium chlo
ride was brushed onto the exposed surface of the poly
acrylonitrile ?lm with a cotton swab. The initially clear
surface become nearly opaque and white upon this treat
was also used in the preparation.
65 ment with sodium chloride.
The resulting viscous solution was poured between
A photographic image was produced on this ?lm by
two thin glass plates spaced 20 mils apart. Ultraviolet
light from a bank of ?ve l5-watt ?uorescent sunlamps
following the procedure described in Example 2. The
?lm was washed with saturatedv sodium thiosulfate solu
tion to “?x” the image and then dried. The ?lm had
was radiated upon the solution for about 20 minutes.
The plates were separated to leave a salt-containing poly 70 excellent physical properties.
acrylonitrile ?lm.
The ?lm was stretched in two mutually perpendicular
directions at room temperature (23° C.) and 50% rela
tive humidity to about 3 times its original dimensions
Example 4
A sample of two-way stretched polyacrylonitrile ?lm,
2 mils thick, was immersed in a saturated solution of
(200% elongation) using simultaneous stretching in a 75 silver
nitrate for approximately 30 seconds. The ?lm
8,056,676
6
5
treating at least one surface of an oriented polyacrylo
nitrile ?lm with an aqueous solution of silver nitrate for
a time sui?cient to impregnate said ?lm to at least 1%,
but not more than 50%, of the thickness of said ?lm
with said solution; removing excess silver nitrate solu
tion from the surface of said ?lm; treating at least one
surface of said ?lm with an aqueous solution containing
was blotted dry with a paper towel and a 50/50 weight
percent mixture of chlorine and bromine was passed over
the surface on one side of the ?lm for approximately 30
seconds. The initially clear surface became nearly
opaque and slightly yellow in color.
A photographic image was produced on the ?lm by
following the procedure described in Example 2. After
at least one soluble halide selected from the group con
“?xing” the image and drying, the ?lm showed the same
sisting of alkali metal bromide, alkali metal iodide, a1
high level of physical properties as the original poly
10 kali metal chloride, hydrogen bromide, hydrogen iodide
acrylonitrile base ?lm.
and hydrogen chloride to convert said silver nitrate to
Having fully disclosed the invention, what is claimed
silver halide particles; and drying said particle-containing
is:
?lm.
4. A photographic ?lm comprising an oriented poly
treating at least one surface of an oriented polyacrylo
nitrile ?lm with an aqueous solution of silver nitrate for 15 acrylonitrile ?lm impregnated with 05-65% by weight
l. A process comprising the steps, in sequence, of
of particles of at least one silver halide selected from
a time su?icient to impregnate said ?lm to at least 1%,
but not more than 50%, of the thickness of said ?lm with
said solution; removing excess silver nitrate solution from
the group consisting of silver bromide, silver iodide and
silver chloride to a depth of 1—50% of the thickness of
said oriented polyacrylonitrile ?lm.
the surface of said ?lm; exposing said treated ?lm to at
5. A photographic ?lm as in claim 4 wherein said
least one halogen selected from the group consisting of 20
oriented polyacrylonitrile ?lm is biaxially oriented poly
bromine, chlorine and iodine, said halogen in a form
acrylonitrile ?lm which has been biaxially oriented by
selected from the group consisting of halogen acid, halo
stretching at least 1.5 times its original dimensions in
gen alkali metal salt and free halogen to convert said
each of two mutually perpendicular directions.
silver nitrate to silver halide particles; and drying said
particle-containing ?lm.
25
2. A process comprising the steps, in sequence, of
treating at least one surface of an oriented polyacryloni
trile ?lm with an aqueous solution of silver nitrate for a
time su?icient to impregnate said ?lm to at least 1%, but
not ‘more than 50%, of the thickness of said ?lm with 30
said solution; removing excess silver nitrate solution from
the surface of said ?lm; exposing said treated ?lm to at
least one gas selected from the group consisting of hy
drogen bromide, hydrogen iodide, hydrogen chloride,
bromine, iodine and chlorine to convert said silver ni 35
trate to silver halide particles; and drying said particle
containing ?lm.
3. A process comprising the steps, in sequence, of
References Cited in the ?le of this patent
UNITED STATES PATENTS
984,886
2,706,728
Brandenberger ________ __ Feb. 21, 1911
Coover et al. ________ __ Apr. 19, 1955
147,451
Japan _______________ __ Dec. 29, 1941
FOREIGN PATENTS
OTHER REFERENCES
Cyanamid’s Nitrogen Chemical Digest, The Chemistry
of Acrylonitrile, pp. 51-56, American Cyanamid Com
pany, New York, January 1951.
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