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Патент USA US2136176

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Patented Nov. 8, 1938
2,136,176
UNITED STATES . PATENT OFFICE
amass
vr'no'rormolm‘Into ‘
John M. Hammond, Washington, D. 0., claim
to The Varnish Products Company. Cleveland,
Ohio, a corporation of Ohio
No Drawing. Application October I0, 1887,
Serial No. 112,054
90mins. (C1- 41-33)
like mass; the jelly-like mass tamed by the dis
This invention relates to the art 0! photoen
graving and more particularly to what is known solved gelatin greatly retards evaporation of the
in the photoengraving industry as "stripping" solvent regardless of the solvent used; the nega
and to a new and improved stripping method
5 and a solution by means of which the method
of stripping may be e?ected.
-
In the photoengraving process a photographic
negative is produced. This negative comprises
a sensitized nitrocellulose ?lm, which is sup
10 ported on a suitable support such as a glass
plate. After the negative has been developed
it becomes necessary. because of the require
ments of the printing industry, to reverse this
image from left to right. Therefore, it be
comes essential to remove this image-bearing
I?lm of nitrocellulose from the glass plate and to
place it upon another supporting plate, usually
of glass, in a reverse position. This operation
of removing the image-bearing ?lm from the
20 glass plate is known in the photoengraving art
as "stripping.”
The ?lm of nitrocellulose is an extremely deli
cate one and does not of itself have sui?cient.
strength to withstand the operation of strip
ping. For this reason the practice in the craft
has been to coat the ?lm oi nitrocellulose with
a reinforcing-medium or layer 01' a character
which will give it the necessary strength to with
stand handling.
30
For a number of years in the early days oi!
photoengraving stripping was effected by coat
ing a nitrocellulose ?lm with a thick aqueous
solution of gelatin. This method consists of
pouring the gelatin solution onto the image
bearing surface of the nitrocellulose ?lm ad
herent to the glass plate, while the plate is
on a "leveling stand",-supporting the plate on
the leveling stand until the water has evaporated
from the gelatin, thereby forming a layer or ?lm
40 of dry gelatin over and in contact with the nitro
cellulose ?lm, and alter the gelatin has dried.
stripping the combined nitrocellulose and gelatin
film from the glass by immersing the negative
in a simple acetic acid solution.
The ?lm of
45 nitrocellulose is insoluble in water so that the"
tive has to be stripped with" extreme care to pre
vent tearing of the image—bearing ?lm and dis- ‘
tortion oi the image by stretching; the com
posite ?lm has to be placed on the second sup-,
port very carefully so that it will not stretch
or become distorted; it is di?icult to make the
composite ?lm adherent to the second support 1.
without tearing; the method also necessitates a
large amount of storage space wherein the plates
can be stored in leveled condition during the
drying of the gelatin: the gelatin deteriorates
very rapidly when it is‘ subjected to atmospheric 1;
conditions, fungi or bacteria, and it it is ?rst
prepared by a manufacturer, it is necessary to
use extreme care and a container with a type
of sp: clal lining for maintaining it in its original
useful condition until it reaches the hand of its no
consumer; and the ?lm formed does not have
the necessary properties of hardness, tensile
strength, and ?exibility to prevent distortion and
tearing under the usual conditions of present
day photoengraving practice.
Because oi’ the g5
disadvantages inherent in the gelatin method of
stripping, it was proposed that, instead’ 0!’ gela
tin, the reinforcing layer also be formed of nitro
cellulose. Since a solvent for nitrocellulose
would attack the original ?lm, it was not pos- m
sible to apply the second layer of nitrocellulose
directly to the image-bearing ?lm. ‘ Due to these
dii?culties, a stripping method was developed
which included the steps of ?rst coating the
negative with a solution 01' India rubber in 35
benzol, permitting evaporation of the benml so
as to leave a protective cover or coating of rub
her over theimage-bearing nitrocellulose ?lm.
then iorming a nitrocellulose ?lm on the rub
ber coating. by applying over the rubber coating 40
a nitrocellulose solution.‘
,_--
-‘> 1,
‘
This m‘ethodis much more satisfactory and
speedy than the earlier method using gelatin,
but it has certain disadvantages, particularly in
that two coating operations are required to strip 45
water of the gelatin solution has no e?ect on the
the image-bearing ?lm.
nitrocellulose ?lm.
One or the principal objects of the present
invention is to provide a stripping solution and
method of stripping whereby the disadvantages
A disadvantage of the method just described
is that it requires a considerable period of ‘time
50 for the water to evaporate from the gelatin solu
tion and the plate has to be kept pertectlylevel
until the gelatin solution has lost its liquid char
acter. Further disadvantages of the method
utilizing the gelatin solution are that: it is dii’
It ?cult to make a proper solution of the jelly
‘
oi’ both oi’ the previous methods are eliminated 50
and the stripping operation is e?ected more
quickly and with a single coating operation, and
certain steps which are necessary in the prior
methods are eliminated.
An equally important object is to provide a so
2
2,186, 176
method oi’ stripping an image-bearing negative
photographic ?lm, which method includes the
steps of applying, directly on the image~bearing
?lm, a ?lm forming solution capable of deposit
ing, by simple evaporation, a dry, hard, tough.
transparent Stripping ?lm of adequate tensile
strength and ?exibility to permit handling un
der the usual conditions of work prevailing in
xylol is desirable in warm humid weather because
the lowering of temperature which would be
caused by the rapid evaporation of ethylene di
chloride under such conditions would be apt to
cause precipitation of water upon the ?lm. This
eifect is called "logging" and impairs the trans~
parency of the ?lm.
When the image-bearing nitrocellulose ?lm
has been coated with the
the solvent has evaporated, the image-bearing
?lm can be stripped irom the glass either by im
mersing it in water or in a weak aqueous solution of acetic acid. in some cases it may be de
15
sirable to combine a small amount of acetic acid
with the stripping solution to facilitate the strip
ably free from stretching, shrinking, and tearing.
20
A correlative object is to provide a method
of transferring an image-bearing negative photo
graphic ?lm from its original plate to another
plate and which comprises applying to the
ping of thl;3 ?lm in plain water. It‘ is not neces
sary, however, that acid be used at all,
Under some circumstances the
tion may have a dye substance incorporated
therein to render the resulting ?lm opaque to
actinic light.
image-bearing surface of the photographic ?lm
a. solution of cellulose derivative which is soluble
in and dissolved in hydrocarbon solvent or sol
vents which do not deleteriously affect the under
lying image-bearing ?lm and which may be
evaporated for depositing the cellulose derivative
as a ?lm on the image-bearing surface, and
30 stripping the resultant composite ?lm from the
original plate and depositing the same onto an
other supporting plate.
Another obicct is to
35
40
40
45
Other objects and advantages
parent from the following speci?cation, wherein
45
60
out my method,
be understood that the invention contem~
or an ester of cellulose, such as a product mar
keted commercially under the trade name "Her
cose C", by the Hercules Powder Company of
Wilmington, Delaware, and which is a cellulose
aceto-butyrate, and a solvent which may be a
plates the use of the recognized equivalents
therefore.
I claim:
1. The method of stripping an image-carrying
nitrocellulose ?lm from a
hydrocarbon solvent, for example, ethylene di
chloride or‘ xylol or any other suitable solvent
60' which does not deleteriously, a?ect the image
bearing ?lm. _A solution otthe foregoing char
mersing the plate in water.
‘
.
Oil
2. The method of stripping an image-carrying
solvent does nojtdissolve or attack the image
nitrocellulose ?lm from a glass plate which com
bearing ?lm, it is unnecessary to use, any pro~
tective layer ofIndiarubber or other protective
material.
,
,,
.
65
-
vllli‘i'iere extremeiy quick drying Tls desired
ethylene dichloride is preferred as a. solvent as
it evaporatesirom the stripping solution very
rapidly.
,
_.
Where slower evaporation is desired. the xylol
or some other solvent which does not delete
riously affect the image-bearing ‘?lm and which
evaporates 'less rapidly, is used. For example,
3. The method of
photographic
negative having an underlying image-bearing
?lm of ‘nitrocellulose compound which is super
imposed upon and adherent to a plate, which
comprises‘ in applying directly ‘on the surface of
the image-bearing nitrocellulose compound ?lm,
lil
3,186,176
a ?lm iorming solution oi’ a solute of essentially
water-insoluble material and an evaporable sol
vent- which does not a?'ect the nitrocellulose him
and image, and capable of depositing on the
Cl nitrocellulose compound ?lm without detrimen
tally affecting the nitrocellulose compound ?lm
and image, by evaporation of the solvent, an ad
herent, translucent film of adequate tensile
strength and flexibility to permit handling under
the usual conditions of photoengraving work,
effecting evaporation of the solvent, and strip
ping from the plate, the combined solute ?lm
and nitrocellulose compound image-bearing ?lm.
4. The method of stripping a photographic
negative having an image-bearing layer of nitro
cellulose which is superimposed upon a plate
which comprises applying directly on the sur
face 01' the negative a coating of solution essen;
tially of cellulose derivative and evaporable sol
vent which solution does not detrimentally affect
said layer of nitrocellulose and image, evaporat
ing the solvent, and thereby depositing on the
from the original supporting plate and disposing
negative, without detrimentally ‘affecting said
iayer a solution essentially of cellulose derivative
and evaporable solvent from the group consisting
of ethylene dichloride and xylol, which solution
does not detrimentally ai'lect the image-bearing‘
layer and the image, effecting evaporation of the
solvent to dispose the cellulose derivative as an
adherent coating on the surface of the image
nitrocellulose layer and image, an adherent strip—
ping ?lm, and then stripping the composite ?lm
and negative from the plate.
5. In the photoengraving process employing as
a negative a sensitized image-bearing nitrocel
lulose layer adherent to a support, the method
of stripping the negative from the support and
comprising applying on the negative a coating
of a solution essentially of cellulose derivative
and evaporable solvent, which solution does not
detrimentally a?’ect the nitrocellulose layer and
35 image, drying the coating to cause it to adhere
to the nitrocellulose layer as a tough ?exible film
and without detrimentally affecting the nitro
cellulose layer and image, and then stripping the
coating with the nitrocellulose layer adherent
40 thereto from the support.
it onto said other plate.
7. In the phcteengraving process empioying
an image-bearing nitrocellulose layer, the
method of transferring the image-bearing nitro (.1
cellulose layer from a supporting plate which
comprises applying directly on the image-bearing
surface of the nitrocellulose layer, a solution
essentially oi’ translucent cellulose derivative and
evaporable hydrocarbon solvent which does not . .
detrimentally a?ect the nitrocellulose layer and
the image, effecting evaporation of the solvent
to render the cellulose derivative adherent to the
nitrocellulose layer as a substantially uniform
coating on the said surface, and then stripping
the resultant combination from the plate and
transferring the combination to another support.
8. The method of stripping a photographic
negative having an underlying image-bearing
layer of nitrocellulose which is superimposed
upon and adherent to a plate. comprising apply
ing directly on the surface of the image-bearing
bearing layer without deterioration of the image
bearing layer and image, and then stripping
from the original supporting plate the combined
solute coating and image-bearing layer.
9. The method of stripping a photographic
negative having an underlying image-bearing
layer of nitrocellulose which is superimposed
upon and adherent to a plate, comprising apply
ing directly on the surface of the image~bearing
layer a ?lm forming solution essentially of
evaporable solvent, which does not detrimentally _
6. The method of transferring the image-bear
ing nitrocellulose layer from its original sup
porting plate to another supporting plate which
comprises applying on the image-bearing surface
affect the image-bearing layer, and cellulose
matter from the group consisting of ethyl-cel
lulose and cellulose aceto-butyrate, depositing
on the image-bearing layer by evaporation of the
of the nitrocellulose layer a solution essentially
of a hydrocarbon soluble cellulose derivative and
an evaporable hydrocarbon solvent which does
not detrimentaily affect the nitrocellulose and
tensile strength and ?exibility to permit handling
under the usual conditions of photoengraving
image, e?‘ecting evaporation of the solvent to
dispose the solute as an adherent coating on the
said surface of the nitrocellulose layer without
deterioration oi.’ the nitrocellulose layer and
image, then stripping the resultant combination
solvent, an adherent translucent ?lm of adequate
work and without detrimentally affecting the
image-bearing layer and image, and then strip
ping from the plate, the combined translucent
?lm and the image-bearing layer.
JOHN M. HAMMOND.
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