'Patented Mar. 8,1938 -
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UNITED STATES PATENT orFl-ce
PHOTOGRAPHIO EMULsIoNs
Martti Salo, Rochester, N. Y.,- assignor, by mesne .
assignments, to Eastman ‘Kodak Company,
Jersey City, N. J., a corporation of New Jersey _
No Drawing. Application April 16, 1936, ._
semi No.74,815
15 Claims;
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(C1. 95-7)
This invention relates to photographic emul-
mono-basic simple and mixed cellulose esters
sions and particularly to emulsions in which a
may be hydrolyzed and that as the degree of
hydrolyzed cellulose ester is used as the protec- . hydrolysis increases. the esters become soluble
tive colloid for the light-sensitive salt.'
in the more polar types of solvents such as 1,4
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5
Various substances have been suggested and
dioxane, beta-methoxy-ethyl alcohol and ethyl 6
tried as carriers or protective colloids for the
lactate. On further hydrolysis a stage is reached
light-sensitive salts used in photography, but, as where these esters become soluble in solvent mix-‘
is well-known, none has been found which pos-- tures containing as much as 50% water.
sess the unique chemical and physical properOn account ‘of the ‘presence of appreciable
l0 ties of gelatin. ‘Collodion was used for this pur-> amounts of water, a solvent mixture such as 10
pose before the discovery of the useful properties- ethyl lactate and water will dissolve the hydro
of gelatin as a photographic carrier and even up _ lyzed cellulose ester'and will also dissolve appre
to the present time, it is used in certain com-_ ciable quantities of inorganic salts such .as so-_
mercial processes.‘ Two methods of processing
dium chloride, sodium bromide, silver- nitrate,
l5 photographic plates were developed, namely, the
dry and the wet process.v According to the ?rst
method, the light sensitive halides were precipi-
etc. It is therefore possible to precipitate alight- 15 .
sensitive halide such as silver bromide in the
colloidal dispersion of the cellulose ester, some
tated in an alcohol-ether solution of‘ collodion
which was then coated onto a glass or other sup:
what similar to the manner in whichthe silver
bromide‘ is dispersed in gelatin. On coating' a
20 port and exposed and processed in a manner
similar to the present gelatin procedure. The
second process involves treating an iodized 001lodicn plate in a silver nitrate bath immediately
prior to exposure and development.
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solution containing the silver halide suspended 20
in the hydrolyzed cellulose ester onto a suitable
support, there is obtained a light-sensitive coat
‘ing which may be used to record photographic
images.
Of these two early processes employing collo-
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The cellulose esterswhich may be used as pro-_ 25
dion, only the wet plate process has, continued
to be of any importance. One objection to the
ccllodion process is the low water permeability
tective colloids for. the light-sensitive salts ac
‘cording to my invention, include the mono
basic simple and mixed acid esters of cellulose
of cellulose nitrate ?lms._ Coincident with this
an is the insolubility of cellulose nitrate in solvent
‘such as cellulose acetate, cellulose acetate pro- .
pionate, cellulose vacetate butyrate and others. 30
r mixtures containing appreciable amounts of‘wa-
' These are hydrolyzed to an acyl content of about
ter, which consequently prevents the use of
19 to about 33%.
water-soluble salts such as the common alkali
acyl content of 19 to 26% are particularly use
halides used in forming the light-sensitive hal-‘
3.1 ides of the present gelatin process.
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I The use of cellulose acetate as a carrier for
Hydrolyzed esters having an
ful, due to their high water permeability. ‘The
hydrolyzed esters used according to my inven- 35
tion have been prepared prior to the present in
light-sensitive salts, has also been suggested.
vention. Esters hydrolyzed to an acyl content
Eichengrun U. S. Patent No. 752,388, February
. 16, 1904, suggested alcohol solutions of cellulose
' 4o acetate, and Lederer British Patent No. 26,503
of 1906' suggested cellulose acetates soluble in
acetic acid ‘as carriers of light-sensitive salts.
of about 30% are described in Staud and Web
ber U: S.,Patents No. 1,896,145, granted February
7, 1933, and No. 1,954,336, granted April 10, 1934. '40
Cellulose esters ‘hydrolyzed to an acyl content
of below 30% are described in‘ the co-pending
- 'Up to the present time, however, photographic‘ ' application of Charles R. Fordyce Serial No.
‘emulsions formed in this way have not ‘been’
62,333, ?led February 4, 1936.
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45 successful and have not gone‘ into general use.
The principal object of the present invention‘
‘As stated above, the solubility of the cellulose 45
esters in various solvents changes as the "degree
is to provide a carrier or protective colloid for _ of hydrolysis is increased. In order to form a
light-sensitive silver salts which has the physidispersion of light-sensitive inorganic salts in > '
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cal and photographic properties of gelatin.
the hydrolyzed cellulose ester‘solution, it is nec
This object is accomplished according to the
present invention by dispersing silver halides in
essary to use a solvent-water mixture which dis-. 50
solves both the cellulose ester and the inorganic '
the presence of a-water-susceptible, hydrolyzed,
salts used to precipitate the-light-sensitive 'salt.
mono-basic, simple or mixed acid ester of cellu- _ On ‘the basis of hydrolyzed cellulose acetate as a
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lose.
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, -It is known that cellulose acetate and other
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criterion, the following solvent-water mixtures
have been found suitable:
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2,110,401
soluble
Hydrolyzed
as follows:
cellulose acetate of - 33%‘ ' acetyl
Percent by weight
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water in mixture
‘Acetone '+ water-.. _____________________ __ 5-40
. 1,4-dioxane + water ___________ __,_. ____ __»_ 0-50
‘paper in an even coating of approximately .001"
thick and exposed in a contact printer using av
erage negatives. The paper carrying the emul
sion was then placed in a developing solution hav
- ing the following composition: _
Methyl-cellosolve + water ______________ __ 0-25 Water
Ethyl lactate .+ water__L__'___-__.._, ______ __ 0-50 v Monomethyl p-aminophenol sul10
Hydrolyzed cellulose acetate of 19 to 26% acetyl
is soluble as follows:
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Percent by ,weight
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This emulsion was coated onto baryta coated’.
water in mixture
Acetone + water __________ _'_ _________ ___ 35-80
_cc__ 500
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fate _______ _>_'___' ____ .._'____'__'___grams__
3.1
Sodium sul?te __________ __'_'______~_do____
Hydroquinone______________ _;_____do____
Sodium carbonate _________ ..'_ ____ __do_..__
Potassium bromide ______________ __do_..__
45.0
12.2
67.5
1.9
Ethyl lactate + water _____ __-.___' ______ ___35-70 ' Water to make____..>___‘ ________ __'__liter__ ' 1
Methyl cellosolve + water_v____________ __ 20-65. _ The penetration of the developer was found
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1.4 dioxane +_ water“, _______________ __ 30-65
be slow, but when the developer was diluted 1:1
Ethyl alcohol, + water ________________ __ 40-70
with water, the penetration was much more rapid.
n-propyl alcohol + water_____________ __ 50-80
The following examples illustrate methods of
The addition of ethyl carbamate to the developer
in the amount of 20 grams of ethyl carbamate
forming a light-sensitive coating according to
to 100cc. of developer and 100 cc. of water was
my invention:
found to’ further increase the‘ rate of penetration
of developer. The prints were ?xed for ten min
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Example‘!
' A-solution of 1.9 grams of potassium bromide
in>5 cc. ofa 1:1 ethyllactate-water_mixturenwas
mixed with a solution containing 3 grams-of cel
' lulose acetate hydrolyzed to an acetyl content of
about 33% dissolved in 21 grams of a solvent mix
ture containing 75% ethyl lactate and 25% water.
To this was then added slowly with good stirring,
utes in a bath containing 10 grams of sodium thlo
sulfate and 5 grams of potassium thiocyanate dis
solved in 50 cc. ofywater. It was found that the
potassium thiocyanate, in addition to being a sol-'
-vent for the silver halide, served as a swelling
agent forthe hydrolyzed esters and thereby. ac
celerated the ‘fixing process.
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a solution of 2.9 grams of silver nitrate dissolved
in 5 cc. of a 1:1 solution of ethyl lactate and
water. Finely divided silver bromide was thereby
produced in suspension in the solution.
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After diluting with 20' cc. of 1:1 ethyl lactate-.
water,,the emulsion was poured slowly into 200
to 300 cc. of water causing the acetateand the
occluded salts to be precipitated. The precipi
tated material was thoroughly washed with water
40 and then dried in an air drier,‘ following which
the dried material was dissolved in a solvent con
sisting of 54.5% ethylene chloride, 27.2 methyl
alcohol and 18.8% beta-methoxy-ethyl alcohol,
one part of the dried material being dissolved'in
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Example In '
A solution of 4.2 grams of potassium bromide
in, a _mixture of 5 cc. of beta-methoxyethyl alco
- 1101‘ and 9 cc. of waterw’asgadded to a solution
containing 6 grams of cellulose acetate hydrolyzed
to'an acetyl content of about 24.4% in 21.6 cc. of‘
betafme'thoxymethyl alcohol and 14.4 cc. of wa
ter. 5.4 grams of silver nitrate dissolved in 9 cc.
of water and 5 cc. of beta-methoxyethyl alcohol
'were then added with good stirring and silver
bromide precipitated in the solution. -'
This emulsion was coated on baryta paper, as
before, and exposed and developed. Good re
45 10 parts of the solvent mixture. This solution sults were obtained when the developer used in
. Example 11 wasdiluted with 4 parts of water.
" was then coated onto a glassplate in ‘a uniform
Emulsions formed from hydrolyzed cellulose
coating _of approximately --.001" thick.
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esters, as‘described above have numerous advan
The plate was exposed to light and ‘then im- ' tages' over ordinary gelatin emulsions. They
mersed in a developing bath of the following
composition:
-Water
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. Theyare insoluble in water and thereby permit
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Monomethyl p-aminophenol' sulI
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higher temperature baths to be'u‘sed in/process
ing, as'is frequentlyv required in tropical photo
4.5.0
graphic :work.
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vSodium sulphite _________ ___ _____ __do____.
Hydroquinone _______ _-_ _________ __;_do__»__ _ 12.0
' ‘Sodium carbonate_-__°_l___'. ______ __do____
67.5
' Potassium bromide_; _________ __-___do.____
1.9
Water to make; ________________ _'_liter_‘_
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Example 11
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have good mechanical strength and are not so
liable to breaking and rupturing in processing.
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A solution of ‘6.6 grams ‘of. potassium bromide
‘dissolved in 32 grams of a l :1 ethyl lactate-water
mixture was mixed with a solution containing 9
Emulsions formed in this way also '
have the advantage that greater uniformity may
be obtained in their manufacture.
The compounds and methods of procedure a.-.
‘scribed above maybe varied within wide limits.‘
Although I have found that the cellulose esters
"containing 19 to 24% acyl are most suitable for
the process of my invention due to their favor
able water susceptibility, emulsions may be made
with cellulose. esters having a greater acyl content ‘
grams of-cellulose acetate vbutyrate hydrolysed to ' even. though the water susceptibility of these
an acetyl content of 27% and butyryl content of Y emulsions is less favorable. A lower limit of 19%
4.5% in 111 gramsof a solvent mixture composed
of an ethyl lactate-water mixture in the propor-,
tion of 6 parts of ethyl lactate to 4 parts of water.
70 8.5 gramscf silver nitrate dissolved in 20 grams
in a 1:1 ethyl lactate-water mixture were added
with good stirring. To this emulsion there were
then added '9 grams ofthe cellulose acetate bu
tyrate dissolved in 111 grams 016:4 ethyl lactate
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75 water solution.
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has been placed on the acyl value of the hydro
' lyzed esters. This is an approximate value, since
esters of slightly lower acyl content may be used 5
.in applications where "the water solubility is not
a hindrance.
Because of this water solubility. v
' however, cellulose acetates of less than 19% acetyl
would not ilnd wide practical application. It is
:to'be understood that my invention is limited
onlyby thescope of the appendedclaims.
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I claim:
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in a solvent mixture containing approximately ‘
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\ 1. The method of making a sensitive photo—
50% water, dispersing a silver halide in the solu
graphic emulsion which comprises dispersing a
silver halide in a solution of a hydrolyzed cellu
tion, and curing the resulting dispersion. .
10. The method of making a sensitive photo
?lose‘organic acid ester of approximately 19% to ‘ graphic emulsion whichvcomprisesldissclving a
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approximately 33%
acyl. content. »
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- hydrolyzed cellulose organic acid ester of ap-'
2.. The‘method of making a sensitive photo v proximately 19% to approximately 33% acyl con
graphic emulsion which comprises dispersing a tent in a solvent mixture containing approximate
p‘ silver-halide ingv-a solution of a hydrolyzed cellu
ly 50% water, dispersing a silver halide in the
j - lose mixed organic acid ester of approximately
~'~ ,1 19% to‘ approximately 33% acyl content.
3.1 The method of making a sensitive photo
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solution, washing the excess salts from the dis 10
persion with water, redissolving the cellulosic ma
terial containing‘the silver halide in a solvent- 1
I graphic emulsion which' comprises dispersing a ' water mixture, and curing the resulting dispersion.
silver halide in a solution of hydrolyzed cellulose
15 acetate butyrate of approximately 19% to ap
proximately 33% acyl content.
4. The method of making a sensitive photo
graphic emulsion which comprises dispersing a
silver halide in a solution of hydrolyzed cellulose
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acetate or approximately -19% to approximately
33% acetylcontent.
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26%.
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12. The method of making a sensitive photo
graphic emulsion which comprises dispersing a.
silver halide in hydrolyzed cellulose acetate hav 20
ing an acetyl content of 19% to 26%‘.
13. The method of- making a sensitive photo
5. A sensitive photographic emulsion compris
ing a silver halide dispersed in ahydrolyzed cel
lulose organic acid ester of approximately 19%
25 to approximately 33% acyl content.
6-. A sensitive photographic emulsion compris
graphic emulsion which comprises ‘dissolving hy
drolyzed cellulose acetate of@19% to 26% .acetyl
ing a silver halide dispersed in a hydrolyzed cel
equal proportionsdisbérsing a silver halide in the
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i lulose mixed organic acid ester of approximately
19% to approximately 33% acyl content.
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11. A sensitive photographic emulsion compris- '
ing a silver 'halide dispersed in hydrolyzed cellu 15
lose acetate having an acetyl content of 19% to
so
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'7. A sensitive photographic emulsion compris
ing a. silver halide dispersed in hydrolyzed cel
content in a solvent. mixture /comprlsing p-meth 25
oxyethyl alcohol and water in approximately .
solutiomand curing the resulting dispersion.
14. The method of making a sensitive photo
graphic emulsion which comprises dispersing a 30
silver halide in hydrolyzed cellulose acetate bu
tyrate having an acyl content of 19% to 26%.
15. The method of making a sensitive photo»
v. lulose acetate butyrate of approximately 19% to
approximately 33% acyl content.
8. A sensitive photographic emulsion compris-' graphic emulsion which comprises dissolving hy
ing a silver halide dispersed in hydrolyzed cellu
drolyzed cellulose acetate butyrate of 19% to 26%
lose acetate 01 approximately 19% to approxi
acyl content in a solvent mixture comprising
' mately 33% jacetyl content.
p-methoxyethyl alcohol and water in approxi
9. The method of making’ a sensitive. photo
graphic emulsion which comprises dissolving a
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hydrolyzed cellulose organicacid ester of approxi- '
mately19% ‘to approximately 33% acyl content _
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mately equal proportions, dispersing 'a silver '
halide in the solution, and curing the resulting
dispersion.
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_ mam SALO.