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July 2, 1946.
F. w. H. MUELLER EI'AL
} 2,403,423
INTENSIFIGATION OF THE LATENT IMAGE
Filed Sept. 50, 1942
2 Sheets-Sheet l
722,0ed 7b Blower
Outlet
Acz'a’ Jodi-ed
INVENTORS
Fritz I44 Hellmut Mueller
'
.
BY James E Bates
AT ORNEY.
July 2; 1946.
F. w. H. MUELLER EI'AL
7
2,403,428
INTENSIFICATION OF THE LATENT IMAGE
Filed Sept. 50, 1942
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INVENTORS
Fritz ///./ l/ellmuZ Mueller
By James 15 Eates
A TTORNEY
I
Patented July 2,v 1946
2,403,428
UNITED STATES‘ PATENT OFFICE‘;
2,403,428
_
INTENSIFICATION OF THE LATENT IMAGE
Fritz W. Hellmut Mueller and James E. Bates,
Binghamton, N. Y., asslgnors/to General Aniline
& Film Corporation, New York, N. Y., a corpo
ration of Delaware
Application September 80, 1942, Serial No. 460,196
10 Claims. (Cl. 9546)
'
2
1
The present invention relates to a new photo
graphic process and more particularly to a meth
0d of intensifying or hyper-sensitizing exposed
photographic emulsions. The purpose of _such
intensi?cation is to increase the effective sensi
tivity of a photographic emulsion or a photo
culiar disadvantage that the increase in e?‘ec-‘
tive speed produced by such treatments is rather
small when applied to high-speed emulsion ?lms
while the greater speed increases are obtained
only with the low speed emulsion ?lms. Such
known methods are also cumbersome or involve
the use of expensive apparatus and unstable
In the art of photography it is often desirable
chemical compounds or solutions. It is, there
to increase the effective speed of photographic
fore, an object of the present invention to pro
emulsions as much as possible. This is partic 10 vide a simple method for treating photographic
ularly so when exposure must be made under
emulsions whereby the quality and speed of the
marginal light conditions. Intensifying the la
photographic emulsions and particularly medium
tent image obtained by exposure of a light sen
and high-speed ‘photographic emulsions are im
sitive silver halide emulsion under marginal light
proved to such a degree that the sensitivity of
conditions permits the photographer to obtain a 15 the emulsion is increased far beyond its original
fully graduated, shadow-detailed and well de?ned
value. It is a further object to provide a sim
picture where otherwise the quality of the neg
ple method of obtaining photographic records
ative would be poor because of under-exposure.
under extremely limited light conditions which
In motion picture photography where very in
would not produce a sufficiently developable la
tense illumination is employed, the cost of such 20 tent image on the high-speed commercially avail
illumination can be materially reduced ,and the
able ?lms to permit of obtaining proper photo
graphic element.
_
-
working conditions, rendered disagreeable by the
amount of illumination required, ‘can be materiq
graphic recording under ordinary conditions of
development. It is still another object of this
invention to provide a method of intensi?cation
25 of the latent image which does not necessitate
ally improved by the use of a process ‘for inten
si?cation of thelatent image. The results ob
tainable by press and aerial night photographers
the use of materials di?cult' to handle or un
working under conditions where the lighting is
stable under ordinary conditions.
4
limited can also be greatly improved by intensi
In the accomplishment of these andother ob
?cation of the latent image after exposure.
jects according to this invention, it has been dis
Various methods for intensifying the latent im 30 covered that the latent image produced on a
age-have beendescribed. In U. S. P. No. 2,168,971,
> photographic element by exposure can be inten
issued August 8, 1939, there is described a meth
. si?ed by treatment of the exposed and undevel
od of increasing the speed of photographic emul
oped material with the vapors of organic acids
sions by submitting exposed and undeveloped
or solutions of organic acids in suitable solvents.
?lms to an atmosphere having a relative humid 35 This method gives substantial increases in the
ity of about 80% ‘and a temperature of 120° F.
for a predetermined length of time. U. S. P. No.
case of lowv and medium speed emulsions and
yields outstanding results in they case of high
speed emulsions. The e?ect of the intensi?ca
tion achieved by this method in the case of the
2,201,591, issued May 21, 1940, achieves a similar I
eilect by pro-bathing the exposed and undevel
oped ?lm in activating solutions, the activating 40 highest speed emulsion is to increase the sensi
agents of which are meta substituted amino and
tivity by 400% of its original value without pro
hydroxy derivatives of benzene such as resorcinol
ducing objectionable fog or any noticeable in
or meta. nitraniline.
According to U. S. P. No.’
2,146,802, issued February 14, 1939, the'effective
crease in the grain size of the silver halide.
It
is, therefore, possible to obtain pictures'possess
speed of photographic emulsions ‘before and after 45 ing a de?nition of detail and brilliance not here
exposure may be increased by treatment with
tofore obtainable with any known photographic
mercury vapor. G. S. Moore, in the Photo
‘material when making the exposure under ex
graphic Journal, volume 81, pages 27-32 (1941),
refers to exposure of the latent image to green
light and in U. S. P. No. 2,220,882, issued Novem
ber 12, 1940, ?ashing of the latent image with
tremely poor light conditions and developing the
?lm by known methods. In principle, this proc
. ess of intensi?cation is carried out as follows:
The exposed and undeveloped ?lm which may
be either black and white or color ?lm, hard
ened or non-hardened, sensitized or unsensitized,
For the most part these prior art processes for
is exposed to an atmosphere of organic acids in a
intensi?cation of the latent image have the pe 55 vapor state containing at least traces of water
infrared radiation is suggested for the same pur
2,408,428
3
sisting of ‘75% C. P. glacial acetic acid and 25%
C. P. formic acid. The cabinet was closed and
the fan put in operation. The conditioning with
rachloride which alcohol or non-polar solvent
contains at least traces of water but not more
than 1% by volume. By “traces 01’ water” we
the acid vapor occurred at an average room tem
perature of 70° F. and an average relative humid
ity of 50%. After 10 minutes’ treatment, the ma
mean to include amounts of water which are. for
instance, as low as two parts or water per mil
lion. . The treatment is carried out at room tem
perature or slightly elevated temperatures, pref
4
dish was charged with 25 cos. 0! a mixture con
vapor or is immersed in a bath consisting of a
solution of an organic acid in an alcohol or'a
non-polar solvent such as benzene or carbon tet
terial was developed at 68° F. in a metol hydro
quinone developer for 14 minutes.
A suitable
10 metol hydroquinone developer is one of the fol-
lowing composition diluted 1:1 (one part devel
oper and one part water).
,
atmospheric conditions or in vacuo. Increases
in the speed of the emulsion of some 50% to 400%
Hot water (125° F.) ________________ __cc__. 750
have been observed and in contrast to known
Metol _________________________ __grams__
1.5
methods 01' intensi?cation, the high-speed emul 15 Sodium sul?te, anhyd ____________ __do____ 45
sions show the greatest response to the treat
Sodium bisulfite ________________ __do____
1
,ment; that is, a greater increase in the sensitiv
Hydroquinone __________________ --do____
3
ity or high-speed emulsions is achieved than in
Sodium carbonate, monohydrated___do____ 6
erably not higher tha 85° to 90° F. under normal _
the low and medium speed emulsions.
_
In carrying out the process by treatment of 20
the exposed ?lm with the acid vapors .any con
venient enclosure, which will con?ne the vapors
and permit of intimate contact of all parts of the
Potassium bromide_._-___; ________ __do____
Water to make _________________ "liters"
0.8
1
The effective speed of the ?lm was tripled with
out appreciable increase in fog in comparison
with an untreated ?lm exposed and developed
emulsion surface of the ?lm with the acid va
pors, may be employed. For cut ?lm a wooden 25 under identical conditions.
cabinet 12" x 21" x 34" has been found suit
Example 2
able. This will hold a number of ?lm strips
which can be treated simultaneously. An electric
"Triple’S” Pan Portrait ?lm was exposed and
fan should be provided therein to give even cir
treated as above for 20 minutes. The e?‘ective
culation of the vapors rising from an open dish 30 speed was doubled in comparison with untreated
of the acid. With such an arrangement the
?lm exposed and developed under identical con
treatment requires from 10 minutes to 11/2 hours,
ditions.
depending upon the type and concentration of
Example 3
the acid. While all organic acids which possess
Exposed SS Pan Aerial ?lm was placed for 6
a su?lciently high vapor pressure at temperatures 35
minutes in a solution of commercial benzene con
which are not detrimental to the photographic
taining %% by volume of acetic acid and 1/r%
materials may be used, it has been found prac
by volume of formic acid at ‘72° F. Agitation was
tical in order to cut down the time of the treat
provided for 5 seconds every 2 minutes. After
ment to use lower molecular weight, aliphatic
acids and particularly formic acid, acetic acid, 40 removal of the ?lm from this solution and evapo
propionic acid or isobutyric acid; Mixtures of
ration of the benzene, the film was tank-devel
oped at 68° F. for 15 minutes in a metol X-ray
formic acid and acetic acid have in some in
?lm developer of the following composition:
stances been found to give more rapid results
than acetic acid alone and the selection of a suit
Hot water (125° F.) __________________ __cc 750
able ratio between the formic and acetic acids 45 Metol _____________________ __.___grams__ 3.5
enables the operator to choose the more conven
Sodi m sul?te, anhyd ___________ __do____ 60
ient length of time for the treatment. A par
Hyd oquinone __________________ __do____
9
ticularly advantageous container for carrying out
Sodium carbonate, monohydrated __do____ 40
the vapor treatment is the so-called Smith de
Potassium bromide ______________ __do_-__
2
veloping machine modi?ed to allow for acid va 50
Water to make _________________ __liters__"‘ 1
porization and circulation. This device is illus
The effective speed of the ?lm was tripled in
trated in the drawings wherein Figure I is a per
comparison with untreated ?lm exposed and de-'
spective view of the top and core of the Smith
veloped under identical conditions.
_
developing machine and Figure II is a perspec
tive view of the can or container for the core of 55
Example 4
Figure I. The legends on these’ ?gures adequate
ly explain the elements which have been added
Exposed “Triple S” Pan Aerial ?lm was placed
to the regular Smith developing machine to
for 32 minutes in a solution of commercial car
adapt it to this use. When the acid treatment
bontetrachloride, containing %% by volume of
is carried out by bathing the ?lm in, for instance, 60 acetic acid and 1A% by volume of formic acid at
a benzene solution of the organic acid, the solu
72° F. Agitation was provided for 5 seconds ev
tion should be placed in a tank provided with
ery 4 minutes. The ?lm was developed at 68° F.
agitating means to provide for circulation of the
for 15 minutes in a metol X-ray ?lm developer of
acid solution in contact with the ?lm.
the following composition:
The following examples will serve to speci?s 65.
Hot water (125° F.) ________________ __cc__ ‘750
cally describe the process as applied to particu
Metol ________________________ __grams__
3.5
lar types of ?lms. They should not be construed
Sodium sul?te, anhyd ___________ __do____ 60
as limiting or restricting this invention to the use
Hydroquinone __________________ __do____
9
of any of the containers or speci?c conditions
mentioned therein, but shall be considered as il 70 Sodium carbonate, monohydrated__do____ 40
lustrative.
-
Example 1
SS Pan Aerial ?lm was exposed and placed in a
wooden conditioning chamber (12" x 21" x 24")
Potassium bromide ______________ __do____
2
Water to make ____ __- ___________ __liters__
1
The effective speed after the treatment was
11/2 that of an untreated ?lm exposed and de
equipped with a small electric fan. A 4"-Petri 75 veloped under identical conditions.
2,403,42a
5
6
Example 5
it is necessary to give the absorbed acid an
opportunity to exert its speed increasing in?u
SS Pan Aerial ?lm was treated for 10 minutes
in a Smith developing machine modi?ed as
ence upon the latent image after exposure. It
development takes place too soon after exposure
of a ?lm which has 'been pretreated .with the
shown in the drawings discussed above. The
apparatus was prepared for the treatment by
placing a solution of 2 parts of glacial acetic acid
and 8 parts of formic acid on absorbing or
acid, desensitization invariably occurs since there
has been no opportunity for the acid to act on
the latent image. Development of a ?lm so
treated, therefore, should be delayed for several
blotter paper shown attached to a side wall of
the can. The cover ?tting over the winding
after exposure. Although this alternative
knobs and motor supports was taped tightly over 10 hours
procedure is of advantage where it is not
the can top during the treatment. Air was
blown into the can to circulate the acid vapors
- > possible to condition the already exposed ?lm by
treatment with the organic acid vapors, the pre
around‘the ?lm through the rubber inlet tube
taped to the blower outlet. This air circulates
past the acid-soaked blotter where it becomes
ferred practice is to submit the photographic
material after exposure to the treatment with the
acid vapors. In either case it will be apparent
» saturated with acid vapors. The humidity of the
that the latent image produced by exposure of
air itself supplies the necessary water content for
the photographic material is acted upon by the
the vapor mixture. It then circulates around the
acid vapors in the presence of moisture. Simi
?lm as the latter is run from spool to spool and
is carried. out of the tank or can through the 20 lar considerations apply to the treatment of the
photographic elements containing latent images
exhaust tube.
15 cc. of the acid mixture was
in solutions of the organic acids. Thus the ?lm
may be treated prior to exposure in a solution of
the organic acid in a suitable solvent.
su?icient for this treatment. The reels and ?lm
were removed and placed in another tank
containing a developer of the following com
position:
It has-‘been found that the solution methods
.
are more suitable for out ?lm or short lengths of
roll ?lm and, although any solvent which will
dissolve the organic acid with at least traces of
water is suitable for the solution treatment,
methanol and ethenol and such non-polar sol
Hot water (125° F.) _____________ __cc____ 750
Metol _________________________ "grams"
Sodium sul?te, anhyd ___________ __do____
3.5
60
Hydroquinone ___________________ __do____
9
Sodium carbonate, monohydrated__do____
40
vents as benzene and carbontetrachloride have
Potassium bromide ______________ __do____
Water to make _________________ "liters-"
2
1
been found most suitable. It is interesting to
note that whilepre-bathing of an exposed pho
tographic element containing a latent image in
Development was carried out in the usual Way
at 72° F. for 10 to 12 minutes. The eifective
speed of this ?lm was three times that of un
treated ?lm exposed and developed under
identical conditions.
' The conditions of the vapor treatment may be
varied and advantageously adapted according to
dilute aqueous solutions of organic acids such
as acetic acid does not produce intensi?cation
of the latent image and may lead to desensitiz
ing if the acid concentration increases, neverthe
less, pre-bathing in alcohol such as methanol and
40 ethenol containing up to 10% acetic acid or an
the speci?c results desired. The speed of acid
vapor intensi?cation of the latent image can also
be increased some ?ve times by carrying out the
process in vacuo. Also, formic acid reacts on the
latent image about ?ve times as rapidly as acetic
acid and higher concentrations of either acid
permit of shortening the time of the treatment
as does also more rapid circulation of the vapor
or increase of the temperature above room tem
acetic-formic acid mixture produces a substantial
intensi?cation of the latent image. The water
content of such an alcohol acid bath preferably
should not be more than 1% by volume. Obvi
ously. alcoholic bathing solutions can best be
practiced in accordance with the process of this
invention where the light-sensitive layer‘to be
treated rests upon a support which is not readily
attacked by that type of solvent. In. the case of
perature to approximately 85° to 90° F. The 50 non-polar solvent such as benzene or carbontetra
chloride which are not miscible with water in any
process is not limited to any particular type of
appreciable proportions the water necessary for
emulsion but is applicable to emulsions sensi
the process may be provided by the natural im
tized for any region of the spectral range, such
purities of the solvents. A water content of, for
as ortho, panchromatic and infrared emulsions.
instance, 0.0002% in benzene containing 1%
Simple experimental tests will establish the
acetic acid will give the intensi?cation of the la
optimum treatment for each particular type of
tent image as described in Example 3. ( The per
?lm. In general, shorter treatments produce less
centages given are by volume.) Immersion times
intensi?cation, but an insu?iciently hardened
for the liquid method treatment range from 5 to
emulsion may soften excessively under a more.
extended treatment. Also, the acid which the 60 30 minutes for optimum effects. The solvent
absorb-ed by the ?lm during immersion should
?lm absorbs in the conditioning chamber con
be removed from the ?lm before development
tinues to react after removing the ?lm from the
chamber until it has evaporated or becomes neu
tralized by the developer. Consequently, if a
?lm has received optimum conditioning in the
chamber there should be no delay in the develop
ment.
Otherwise, over-treatment _will result.
Conversely, a less than optimum treatment may
be corrected by withholding development for a
few hours. This same effect permits‘of submit
ting the ?lm before exposure to the organic acid
vapor treatment and employing the acid
absorbed by the ?lm during such treatment for
‘intensi?cation of‘ the latent image after
exposure. In following such a procedure as this, 75
since such solvents as benzene and carbontetra
chloride are immiscible with the usual devel
opers. This removal of the solvent after the acid
treatment can be effected by evaporation or rins
ing in an ethenol bath, care being taken in the
latter case to keep the rinsing time short enough
not to alfyect the ?lm base. In all of the liquid
methods or immersion treatments, vigorous agi
tation of the acid solution is desirable and the
temperature of the bath can be raised to ap
proximately 85° to 90° F. in order to speed up .
the action.
As further examples of the results which 'are
' 2,403,428
_
8
7
polar solvents containing up to 1% of water and
developing the latent image.
obtainable by this process, the following speed in
. creases are typical: “Ansco” Ultra Speed Pan, Su
persensitive Pan Aerial and Infrared emulsions
can be made 3 to 4 times faster‘; cine negative
2. The process of intensifying the latent image
of an exposed photographic silver halide emul
“Supreme,” “Triple S” Pan and “Triple S” Ortho
sion which comprises introducing the exposed
emulsion prior to development into an atmos
phere of organic acid vapors containing at least
traces of water vapor, removing it therefrom, and
when developed in developers conventionally used
developing the latent image.
for those ?lms. In cases where extreme speed
3. The process or intensifying the latent image
and contrast are of primary importance and a 10
of an exposed photographic silver halide emul
slight increase in graininess and fog less essen
sion which comprises immersing the exposed '
tial, the use of more energetic developers, for
emulsion prior to development in a bath con
instance those of the X-ray type, will produce
sisting of a solution of an organic acid in a
maximum speed. Increases obtained by the acid
vapor treatment were evidenced in most cases 15 volatile non-polar solvent containing such
amounts of water as are miscible with the sol
by an extension of the threshold sensitivity, but
vent, removing the emulsion from the bath, evap
gave a material increase of all the densities up
orating the solvent and developing‘the latent im
to approximately 1.0 or 1.2. At this point the
age.
increase became relatively smaller, until at the
v4. The process of intensifying the latent image
shoulder region either no increase or a slight de
of an exposed photographic silver halide emul
crease of density resulted. Such extension of the
sion which comprises immersing the exposed
toe produced an overall ?attening of the grada
emulsion prior to development in a bath consist
tion, but for miniature camera work where low
ingiof a volatile- alcohol solution of an organic
density negatives are customary this ?attening
is not a disadvantage. The flattening of the 25 acid containing up to 1% of water, removing the
cut ?lm can be doubled in speed; Finopan and
“Fluorapid” film can be made 11/2 times as fast
emulsion from the bath, evaporating the solvent
> gradation may also, if desired, be counteracted by
a slight extension of the developing time. Figure
and developing the latent image.
5. The process of treating an exposed photo-t
graphic silver halide emulsion containing a latent
III of the accompanying drawings, illustrates typ
ical speed increases obtained by the organic acid
treatment. In said Figure III, wherein the ordi 30 image which comprises contacting said exposed
emulsion prior to development with an organic
nates represent densities and the abscissae rep
acid vapor ‘containing at least traces of water
resent the log of exposure. “A” is the density
curve for “Ansco” Ultraspced Pan ?lm which has
vapor for at least 10 minutes at a temperature
been exposed and developed in the ordinary
of‘ from room temperature to 90° F. and develop
manner, “B” is the density curve for the same 35 ing the latent image.
6. The process of treating an exposed photo
type of ?lm exposed under the same conditions
graphic silver halide emulsion containing a latent
and treated with acetic acid vapor prior to de
velopment in accordance with the method of the
present invention. A similar curve is obtained
by treating the exposed film with a solution of
image which comprises contacting said exposed
emulsion with an organic acid vapor containing
at least traces of water vapor for from 10 min
utes to 11/2 hours while circulating the said va
pors in contact with the emulsion at a tempera
ture of from room temperature to 90° F. and
acetic acid in benzene containing water as an im
purity of the solvent.
_
'
In .contrast to other known methods for in
tensi?cation of the latent image the increase in 45 developing the latent image.
7. The process of claim 6 wherein the organic
sensitivity obtained by the acid vapor treatment
acid vapor is a mixture of acetic and formic acid
of this invention is quite permanent. In fact, if
vapors.
~
development is somewhat delayed after treat
8. The process of intensifying the latent image
ment, the increase in sensitivity progresses for
several days, then does not noticeably change for 50 of an exposed photographic silver halide emul
two or three weeks.
sion which comprises immersing the exposed
After four to seven weeks’
emulsion prior to development in a bath con
storage the increase will be reduced only to ap
sisting of a 1% solution of an organic acid in
proximately %2 its original value and the increased
benzene containing at least traces of water at a
sensitivity will not be completely lost until it has
been stored for approximately 10 months. The 55 temperature of from room temperature to 90°
F. and removing the emulsion from the bath,
increased sensitivity of ?lms submitted to other
evaporating the benzene and developing the la
known methods of intensi?cation in some in
tent image.
stances begins to diminish shortly after the
9. The process of claim 8 wherein the organic
treatment and in most cases has been completely
lost in a few weeks’ time.
‘
Having thus described our invention, what we
60
acid is a mixture of acetic-and formic acids.
10. The process of intensifying the latent im
claim as new and desire to secure by Letters. Pat
age of an‘ exposed photographic silver halide
cut is:
emulsion which comprises immersing the exposed
.
'
‘
v
emulsion prior to development in a bath consist
1. The process of intensifying the latent image
of an exposed photographic silver halide emulsion 65 ing of a 10% acetic acid methanol solution con
taining not more than 1% water, removing the
which comprises contacting the exposed emul
emulsion from the bath, evaporating the meth
sions prior to development with a member of the
anol and developing the latent image.
group consisting of organic acid vapors contain
_
'
FRITZ W. HELLMUT MUELLER. ing at least traces of water and solutions of or,
JAMES E. BATES.
ganic acids in volatile alcohols and volatile non 70 .
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