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Патент USA US2411546

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NOV. 26, 1946.
EB, KNOTT-
2,411,546
PHOTQGRAPHIG EMULSION
Filed April 12, 1945
l
-'
lbdl'de
FIG. I.
320
36 '
_
40
'
44
48
52
56
60
640/").4
FIG.4.
FIG.5.
EDWARD B; KNOTT
A'I'I'
3
Patented Nov. 26, 1946
' 2,411,546
- UNITED ‘IVSTATE 52,411,546PATENT OFFICE ’
PHOTO GRAPHIC EMULSION
Edward B. Knott, Wealdstone, England, assign
or to Eastman Kodak Company, Rochester,
N. Y., a corporation of New Jersey
Application April 12, 1945, Serial No, 587,916
_
'
In Great Britain May 18, ‘1944 '
'17 Claims‘.
.
1
(01. 95—7)
,
2
r
hydrazono group, a thiocarbamylhydrazono group
This invention relates to photographic emul
sions and more particularly to sensitized photo
graphic emulsions and to a process for preparing
and a guanylhydrazcno group.
' »
'
‘The compounds which I incorporate in the
spectrally sensitized emulsion include hydrazones,
semicarbazones, thiosemicarbazones, oximes and
aminoguanides. Typical examples of these ‘com;
the same;
' It is known that the distribution of spectral
sensitivity of certain spectrally sensitized (i. e.,
dye-sensitized) emulsions can be altered and an
increase in sensitivity obtained in some spectral
pounds
include:
'
_
'
4’-hydroxyi3'-acetyl-2-methylnaphtha -1',2',4,5
region, by incorporating certain additional sensi
tizing dyes in the spectrally sensitized emulsions.
(See United States Patents 2,158,882, dated May
16, 1939, and 2,159,565, dated May 23, I939.) The
thiazole phenylhydrazone having the formula:
O5H5HN—N-
0113
§
.
0
effect thus obtained has come to be known as
HO
supersensitization. Supersensitization of certain
vspectrally sensitized emulsions can also be effected
by incorporating certain substantially, colorless
heterocyclic bases, Yvizlrthose containing an
2C—CH
amino group, in the spectrallysensitized emul- , '
sions (see United States Patent "2,177,635, dated
October 31, 1939), Supersensitization- di?‘ers
from hypersensitization which’ involves bathing
of ?nished plates or ?lms, an operation which
normally reduces the pAg and/increases‘ the pH
20
of the emulsions with consequent decreased sta
bility.
,
v
4’-hydroxy-3’-acetyl-2-methylnaphtha -l’,2',4,5
thiazole semicarbazone.
a
I have now found a new method for supersensi¢
thiazole
aminoguanide.
thiazole ox'ime'.v
only does not reduce the stability of theemul-v
.
>
'
'
'
‘
'
-
‘
‘f
I
'
thiazole 'thiosemicarbazone.
sions, but is valuable as a means of securing spec
It is, accordingly, an object of my invention to
’
_
“
4'-hydroxy-3'-acetyl—2-methylnaphtha- 1’,~2',,¢l,5
tizing spectra-11y sensitized emulsions, which not
trally sensitized emulsions of increased speed.
,'
.4'ehydroXy-3’éacetyl-2-methylnaphtha -1’,2',4,5
25 4";hydroxy-3’-acety1—2-methylnaphtha- 1’,2’,4,5
‘
1
I The sensitizing dyes which I employ, in prace
80 ticing my invention fall within the class‘of 2'
cyanine dyes and thevclass of oxacarbocyanine
dyes. The supersensitizing e?ects obtained with
the 2’—cyanine dyes (especially the 1,1'-dialkyl
provide new supersensitized photographic emul
sions. A further object is to provide a process for
preparing such emulsions. ' Still other objects will
2,2’-cyanine salts) are much more marked than
35 the effects which can be obtained with the‘oxa
become apparent hereinafter.
In accordance with my invention, a photo
carbocyanine dyes. By the term Z’Tcyanine dye,
graphic‘ silver halide» emulsion spectrally sensi
I mean a monomethinecyanine dye containing a
tized with a 2"-cyanine dye or an oxacarbocyanine
quinoline nucleus linked through its '04- Or 2-po
dye is supersensitized by incorporating in the
sition to another heterocyclic nucleus through
emulsion at least one heterocyclic base‘selected 40 the a- or Z-position of the second heterocyclic
from those represented by the following general
nucleus. 'By the term oxacarbocyanine dyes, I
mean, a carbocyanine dye containing two benzox
azole nuclei. Among the 2'-cyanine dyes and
Z '
R1.
oxacarbocyanine dyes which I employ in prac
\ / .
‘formula:
‘
-
,
C
HO
-.
‘
‘
a
45
.
‘
S
\
'
1,1’-dialkyl-2,2"—cyanine salts, e. g., 1,1’-diethyl
/
2,2’-cyanine halides, such asjthe iodide. . '
0'31.
.
ticing my invention are the following:
N
3,1'-dialkylbenzothia-2’-cyanine salts, e. g., 3
50' methyL-l'-ethylbenzothia-2f 7 cyanine halides,
I,
such as the bromide.
'
,
3,1’-dialkylthia-2'ecyanine salts, e. g., 3-methyl
1’-ethy1thia-2'-cyanine halides, such as the
iodide.
and Z represents a h'ydrazono group, an alkylhy
' drazono
group, a 'dialkylhydrazono group,
an
’
_
iodide.
,
I
,
3,3’-dialkyloxacarbocyanine salts, e. g., 3,3'-di
aralkylhydrazono group, a diaralkylhydrazono
ethy1 or 3,3',9-triethyl oxacarbocyanine halides,
group, an arylhydrazono group, a diarylhy
Vdrazono ‘group, a hydroximino group, a earbamyl
.
3,1’-dialkylselena-2'-cyanine salts, e. g., 3,l’-di
ethylselena-z?cyanine halides, such as the‘
wherein R1 and R2 each represents an alkyl group .
60
such as the iodide.
2,41 1,546
3
4
The sensitizing dyes can be employed in any
desired condensation. Ordinarily from 10 to 30
I Example 2 I
_
To a gelatino-silver-bromiodide developing-Out
emulsion, dye-sensitized as in Example 1, ‘was add
mg. of dye per liter of emulsion (containing
about 0.25 gram-mole of silver halide) will suf
ed
flee to produce the optimum sensitizing e?ect.
4’ - hydroxy - 3’ - acetyl - 2 — methylnaphtha
1’,2’,4,5—thiazole semicarbazone in a concentra
The methods of incorporating sensitizing dyes 1n
tion of 100 mg. per that quantity of emulsion
equivalent to 200 grams of silver nitrate. The re
sulting emulsion showed an increase in green
sensitivity of 500 per cent over the green sensi
tivity of Example 1. This increase in green sen
sitivity is apparent from Fig. 2 of the accom
emulsions are well known to those skilled in the
art. Ordinarily, it is preferable to dissolve the
dye in a water-miscible solvent, such as- meth
anol, and incorporating the methyl alcoholic so
lution in the emulsion. Ethyl alcohol or acetone
may be employed instead of methanol.v One or"
panying drawing which depicts the sensitivity of
the instant emulsion.
Ordinarily, the heterocyclic base is incorpo~
rated in the emulsion which already contains the 15
Example 3
sensitizing dye or dyes. However, the hetero
To a gelatino-silver-bromicdide developing-out
cyclic base can be incorporated in the emulsion
emulsion, dye-sensitized as in Example 1, was add
before the sensitizing dye or dyes, or the hetero
more sensitizing dyes can be employed.
ed
cyclic base and the sensitizing dye or dyes can
4’ - hydroxy - 3' — acetyi - 2 - methylnaphtha
1’,2’,4,5-thiazole, aminoguanide in a concentra
tion of 100 mg. per that quantity of emulsion
equivalent to 200 grams of silver nitrate. The re
in the emulsion in a concentration equal to from
sulting emulsion showed an increase in green
about 10 to about 303 mg. for that- quantity of
sensitivity of 150 per cent over the green sensi
silver halide emulsion equivalent to 200 grams
of silver nitrate. The optimum concentration 25 tivity of Example 1. This increase in green sen
sitivity is apparent from Fig. 2 of the accom
for process-type emulsions is usually of the or
pany drawing which depicts the sensitivity of the
der of 100 mg. for that quantity of silver halide
instant emulsion.
.
emulsion equivalent to 200 grams of silver ni
be incorporated in the emulsion simultaneously.
Usually the heterocyclic bases are incorporated
trate. The heterocyclic bases are preferably but
.
E 26617712713 4
not necessarily dissolved in a water-miscible 30
A gelatino~silver-bromiodide developing-out
solvent, such as methanol before incorporation
emulsion was sensitized with 3,3’-diethyl0Xa
in the emulsion. One or more of the heterocyclic
bases can be employed and the heterocyclic
bases as well as the sensitizing dyes can be added
to the emulsion during any suitable stage of its 35
carbocyanineiodide having the formula:
preparation. Usually both the heterocyclic bases
and the supersensitizing dyes are advantageously
added to the washed, ?nished emulsions.
> .
To determine the optimum concentration of
any of the heterocyclic bases, a batch of emulsion
is ?rst sensitized with the sensitizing dye in such
quantity as to give optimum speed. Another
batch of the same emulsion is similarly sensitized
and several portions of this batch of emulsion
are treated with various concentrations of the
heterocyclic base. Each of the portions of emul
in a concentration equal to 100 mg. of the carbo
cyanine iodide per that quantity of emulsion
equivalent to 200 grams of silver nitrate. The
cyclic’ bases of the present invention. The com
sensitizing effect of this quantity of dye is de
picted in Fig. 4 of the accompanying drawing. _
Example 5
To a gelatino-silver-bromiodide developing-out
emulsion, dye-sensitized as in Example 3, was
added ¢l'- hydroxy -' 3'- acetyl-2-methylnaphtha
1',2',4,5-thiazole semicarbazone in a concentra
tion of 100 mg. per that quantity of emulsion
equivalent to 200 grams of silver nitrate. The
resulting emulsion showed an increase in green
sensitivity of 30 per cent over the green sensitivity
of Example 4. This increase'in' green sensitivity
positions of the emulsions are given in the fol
lowing examples which are numbered to corre
drawing which depicts the sensitivity of the in
stant emulsion.
sion is then coated and exposed and processed as
usual. The increase in the minus blue speed of
the emulsion at optimum supersensitizer con
centration is taken as a measure of the super
sensitizing action of the compound. Wedge spec
trograms also indicate this measure.
,
.
The accompanying drawing shows diagram
‘matically the spectrograms of emulsions contain
ing sensitizing dyes with and Without the hetero- \_
can be seen from Fig. 5 of the accompanying
spond to the ?gure numbers in the drawing.
In a manner similar to that illustrated in the
Example 1
foregoing examples, other 2'-cyanine dyes and
A gelatino-silver-bromiodide developing-out
‘emulsion was sensitized with 1,l'—diethy1—2,2’
oxacarbocyanine dyes can be supersensitized with
one or more of the heterocyclic bases represented
by the foregoing general formula:
My invention is primarily directed to the cus
cyanine iodide having the formula:
'65 tomarily employed gelatino-silver-halide devel
oping-out emulsions, such as gelatino-silver
chloride, gelatino-silver-chlorobromide, gelatino
silver-bromide
N
C2115
C2H5
emulsions.
I
70
in a concentration of 100 mg. per that quantity
of emulsion equivalent to 200 grams of silver ni
.
Emulsions prepared in accordance with my in
any desired support, such as cellulose nitrate ?lm,
cellulose acetate ?lm, polyvinyl acetal resin ?lm,
metal support, glass support or paper support.
dyelis depicted in Fig. 1 of the accompanying
'
gelatino-silver-bromiodide
vention can be coated in the usual manner upon
trate. The sensitizing e?ect of this quantity of
drawing.
and
75
The carbonylic compounds, such as 4'-hydroxy
2,411,540
3'- acetyl - 2 - methylnaphtha - 1',2',4,5 -thiazole,
from which the compounds I employ in practicing
my invention are prepared, are obtained as illus-j
trated in the following example.
Example 6.—4'-hydroa:y-3'acetyl-z-methylnaph
tha-1',2',4,5—thiazole
V
4-phenyl-2-methylthiazole-5-acetic acid (11.66
grams) anhydrous sodium acetate (3 grams) and
acetic anhydride (60sv cc.) were re?uxed gently 10
for 3 hours. Acetic acid (10 cc.) was added and
the mixture poured into water. The solid was
collected and washed with water then a little
wherein R1 and R2 each represents an alkyl group
and Z represents a hydrazono group, an alkyl
hydrazono group, a dialkylhydrazono group, an
methanol. On recrystallization from methanol,
aralkylhydrazono grounp, a diaralkylhydrazono
5.8 grams of 4’-acetoxy-2-methylnaphtha-1’,2',-_ 15 group, an arylhydrazono group, a diarylhydrazono
4,5-thiazole crystallizedout. The mother liquor
group, a carbamylhydrazono group, a thiocar
was then mixed with the ?rst methanol washings
and concentrated. On standing several days, 3.1
bamylhydrazono group and a guanylhydrazono
grains of 4’-acetoXy-3'-acetyl-2—methylnaphtha
l',2',4,5-thiazole crystallized out. R/ecrystallized
gI'OU-P- .
2. A photographic gelatino-silver-halide emul
from methanol, it formed gleaming colorless
sion, spectrally sensitized with at least one sensi
tizing dye selected from the group consisting of
needles M. P. 205° C.
2'-cyanine dyes and oxacarbocyanine dyes, said ‘
' I
(a) On adding an excess of aqueous caustic
soda to a spirit solution of the acetoxy compound
emulsion containing, as a supersensitizer, at least
one heterocyclic base selected from those repre
described above a deep yellow color developed.
sented by the following general formula:
Acidi?cation with dilute acetic acid gave yellow ,
?ocks of 4'-hydroxy-3'-acetyI-Z-methylnaphtha
V
.
_
Z\ /R2 ._
l',2',4,5—thiazole which were recrystallized from
methanol forming yellow needles M. P. 126° to
127° C. ?uorescing intensely green in ultraviolet 30
light.
U
H0
\
0
.
'
/
s
'
‘
C---R1
. (b) 4’ - hydroxy- 2 - methylnaphtha -1',2',4,5
thiazole (0.5 gram), obtained above, was dissolved
N
in nitrobenpene (5 cc.) with acetylchloride (0.2
gram) or aceticanhydride (0.3 gram). _Alumin
ium chloride (1 gram) was then added at room
temperature, then heated on the water bath for
4 hours. The deep yellow solution was decom
posed with dilute hydrochloric acid forming yel
low ?ocks. These were'collected, the nitroben
wherein R1 and R2 each represents an alkyl group
and Z represents a hydrazono group, an alkyl
hydrazono group, a dialkylhydrazono group, an
40 aralkylhydrazono group, a .diaralkylhydrazono
zene layer taken up in' ether, separated from the
group,xan arylhydrazono'group, a diarylhydra
aqueous layer and ‘extracted several times with I
zono vgroup, a carbamylhydrazono group, a thio
ZN-aqueous sodium'carbonate until the extracts
were almost colorless. On neutralization ‘with
carbamylhydrazono group and a guanylhydrazono
acetic acid; a‘ further yield-of yellow flocksjwas
given. Yield 0.35 gram. Recrystallized from.
methanoLthey formed yellow needles M. P. 126°_
group.
‘ '
.
C; . A mixed melting point with the product from
group consistingof 2'-cyanine dyes andoxacarbo
'(a) showed no depression.
cyanine dyes, said emulsion containing, as a
supersensitizer,v at least one heterocyclic base se
3. Avv photographic gelatino-silver-halide , de
veloping-out emulsion spectrally sensitized with
at least one sensitizing dye selected from the
,
(c) 4:’-acetoxy—2emethylnaphtha-lf',2',4,5-thi-,
‘azole (0.5 gram) in nitrobenzene (5 cc.) were
lected from-those represented by the following
heated on the water bath for'4 hours with alu- .
general formula:
minium chloride (2 grams). ‘On working up as
~
g
1
1'
usual 0.2 gram of the same product as from (a) .
was obtained.
55
.
Similarly other acyloxy compounds can be pre
pared using, propionic compounds, butyric com
pounds, etc., instead of acetic compounds.
The hydrazones,= semicarbazones, oximes and
aminoguanides of the carbonylic compounds can 60
be prepared by refluxing the carbonylic com
pound with a hydrazine salt, a semicarbazide
salt, a hydroxylamine salt or an aminoguanidine
wherein R1 and R2 each represents an alkyl group
salt in ethyl alcohol in the. presence of sodium
and’ Zrepresents a hydrazono group, an alkyl
_acetate.~
hydrazono group, adialkylhydrazono group, an
' Whatl claim as my invention and desire to
'aralkylhydrazono group, a diaralkylhydrazono
be securedby Letters Patent of the .United
‘ group, an arylhydrazono group, adiarylhydrazono
States
is:
"
.
,
'
,
"
l. A photographic silver halide emulsion spec
trally sensitized with at least one sensitizing dyer
selected from the group consisting of 2’.-cyanine
dyes and oxacarbocyanine dyes, said emulsion
containing,v as ' a supersensitizer,
at leastione
group, a‘carbamylhydrazono group,‘ athiocar
bamylhydrazono' group and aguanylhydrazono
4. A photographic gelatino-silver;bromiodide
"developing-out emulsion, 'spectrally: "sensitized
heterocyclic base selected from those represented {.with-vatrleast. one sensitizing dye selected ;from'
~=by the following generalformula;
_} g2...
¢the;g1foup,::consisting. or Zf-Qcyanine, dyesiand
2,411,546:
7
8
oxacarbocyanine dyes, said emulsion containing,
and containing, as a supersensitlzer, at least one
as a supersensitizer, at least one heterocyclic base
heterocyclic ‘base selected from, those represented
by the: following; general vrormula:
selected from those represented by the following
general formula:
3
10
wherein R1 andRz each represents an alkyl group
wherein R1 and R2 each represents an'alkyl group
and Z represents’ a hydrazono group, an alkyl
and-[Z represents a hydrazono group, an alkyl
hydrazono group, a dialkylhydrazono group, an
hydrazono group, a dialkylhydrazono. group, an
aralkylhydrazono group, a diaralkylhydrazono
aralkylhydrazono group, a diaralkylhydrazono
group, an arylhydrazonogroup, a diarylhydrazono 2
group, an arylhydrazono group, a diarylhydra
zono group, a carbamylhydrazono group, ‘a thio
group,
a
carbamylhydrazono group,
a
thio
carbamylhydrazono group and a guanylhydra
carbamylhydrazono group and a guanylhydrazono
group.
.
zono group.
8. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized
'
_5. A photographic igelatino-silyer-halide vde
veloping-rout emulsion ‘spectrally sensitized with
with at least one 3,1'r-di-alkylbenzothia-Z'-cyanine
at least one 2'-cyanine sensitizing dye and con- ‘25 salt and containing, as a supersensitizer, at least
taining, as a supersensitizer, at least one hetero
one heterocyclic base selected from those repre
cyclic base selected from. those represented by
the following general formula:
sented by the. following general formula:
30
35
wherein R1 and R2- each represents an alkyl
‘wherein R-rand- R2 each represents an alkyl .group 40 group and Z. represents a hydrazono group, an
and Z represents. a hydrazono group, an alkyl
alkylhydrazono group, a dialkylhydrazono group,
hydrazono group, a rdialkylhydrazono group, an
an aralkylhydrazono group, a diaralkylhydrazono
aralkylhydrazono group, a‘ .diaralkylhydrajzono
group, an .arylhydrazono group, a diarylhy
drazono group, a carbamylhydrazono group, a
thiocarbamylhydrazono group and .a guanylhy
drazono.‘ group.
group, an arylhydrazono group, a diarylhydrazono
‘group, a‘ oar-bamylhydrazono- group, a thio
'carb amyllhydrazono group and ‘a' guanylhydrazono
group;
9. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized
~
6. A photographic gelatino~si1ver-bromiodide
developing-out emulsion spectrally-sensitized with _
with at least one 3,1'-dialkylthia-2'-cyanine salt
0
and containing, as a supersensitizer, at least one
walt least one 2'-cyanine sensitizing .dye and con
taining, as a supersensitizer, at least one hetero
cyclic base selected from those represented :by
the following general formula:
heterocyclic base selected from those represented
by the. following general formula:
HO
\
S
C-Ri
wherein R1 and R2- each represents an alkyl
' wherein R1" and 1R2 each represents an alkyl group 65 group and Z represents a hydrazono group, an
and Z represents a hydrazono group, an valkyl
hydrazono group, a dialk-ylhydrazono group, an
aralkylhydraz'ono. group, a. diaralkylhydrazono
group, an arylhydrazono group, a diarylhydra
zono group, a carbamylhydrazono group, a thic
carbamylhydrazono group and a guanylhydra
' zono . group.
7-...A photographic gelatinor'silver-bromiodide
.id‘eveloping-out emulsion spectrally sensitized
alkylhydrazono "group, a diallgylhydrazono group,
an aralkylhydrazono group, a diaralkylhydrazono
group, an arylhydrazono group, a diarylhydr'a
"zono .group, a carbamylhydrazonov group, a thio
70 carbamylhydrazono group and a guanylhydra
' zono. group.
10. A photographic gelatino-silver-bron?odide
developing-out emulsion spectrally sensitized
, with at least :one l,l'-dialkyl-2,2'-cyanine salt
.‘f-with-aat leastone Llt-xlialkykZBk-cyanlne salt 75 in which the;
slollhsg?gh. ‘contain from
2,411,546
10
a vsupersensitizer, at least one heterocyclic base
1 to 2 carbon atoms, the emulsion containing, as
a supersensitizer, at least one heterocyclic'bas'e
selected from those represented by the following
general formula:
selected from those represented by the following '
general formula:
wherein R1 and R2 each represents an alkyl group I
and Z represents a hydrazono group, an alkylhy
wherein R1 and R2 each represents an alkyl group
and Z represents a hydrazono group, an alkyl
drazono group, a dialkylhydrazono group, an ar
alkylhydra'zono
group,
a
diaralkylhydrazono
hydrazono group, a dialkylhydrazono group, an
group, an arylhydrazono group, a diarylhydra
aralkylhydrazono group, a diaralkylhydrazono
group, an arylhydrazono group, a diarylhydra 20 zono group, a carbamylhydrazono group, a thio
carbamylhydrazono group and a guanylhydrazono
zono group, a carbamylhyclrazono group, a thio
carbamylhydrazono group and a guanylhydra
zono group.
group.
‘
11. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized
,
13. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized
25 with a 1,1’-dialkyl-2,2’-cyanine salt in which the
alkyl groups each contains from 1 to 2 carbon
atoms, the emulsion containing, as a supersensi
with at least one 3,1'-dialkylthia-2’-cyanine salt
in which the alkyl groups each contains from
1 to 2 carbon atoms, the emulsion containing,
tizer, 4’-hydroXy-3’-acetyl-2-methylnaphtha-1’,
as a supersensitizer, at least one heterocyclic
2’,4,5-thiazole semicarbazone.
'
14. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized with
base selected from those represented by the
following general formula:
a 1,1’-dialky1-2,2'-cyanine salt in which the alkyl
groups each contains from 1 to 2 carbon atoms,
the emulsion containing, as a supersensitizer, 4'
35 hydroxy-3'-acetyl - 2 - methylnaphtha-1',2’,4,5
thiazole aminoguanide.
15. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized with
a 1,1’-diethyl-2,2’-cyanine salt, the emulsion
40 containing, as a supersensitizer, 4'-hydroxy-3’
acety1-2 —methylnaphtha- 1' ,2 ' ,4,5-thiazole
carbazone.
16. A photographic gelatino-si1ver-bromiodide
wherein R1 and R2 each represents an alkyl group
and Z represents a hydrazono group, an alkyl
hydrazono group, a dialkylhydrazono group, an
developing-out emulsion spectrally sensitized with
a 1,1'-diethyl42,2’-cyanine salt, the emulsion con-,
taining, as a supersensitizer, 4'-hydroxy-3’-ace
1..
aralkylhydrazono group, a diaralkylhydrazono
tyl - 2 - methylnaphtha-l',2’,4,5-thiazole
group, an arylhydrazono group, a diarylhydra
zono group, a carbamylhydrazono group, a thio
carbamylhydrazono group and a guanylhydra
zono group.
'
12. A photographic gelatino-silver-bromiodide
developing-out
emulsion
spectrally
sensitized '
with at least one 3,1'-dialkylbenzothia-2’-cyanine
salt in which the alkyl groups each contains from
1 to 2 carbon atoms, the emulsion containing, as
semi
'
'
guanide.
amino
,
.17. A photographic gelatino-silver-bromiodide
developing-out emulsion spectrally sensitized
with a 3-methyl-1’-ethylthia-2’-cyanine salt, the
emulsion containing, as a supersensitizer, 4'-hy_
droxy-3'-acetyl-2-methylnaphtha - 1’,2',4,5-thi
azole semicarbazone.
EDWARD B, KNOTT.
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