Production of silver halide emulsions

Details Production of silver halide emulsions Production of silver halide emulsions

2000-07-14

2001-07-17

Le, Hoa Van (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Radiation sensitive product

Silver compound sensitizer containing

C430S567000

Reexamination Certificate

active

06261758

ABSTRACT:

This invention relates to a process for producing tabular silver bromide-iodide emulsions and silver bromide-chloride-iodide emulsions with an aspect ratio ≧2, an iodide content from 1 to 40 mol % and a chloride content from 0 to 20 mol %, by the process less steps. of (a) silver halide nucleus precipitation, and (b) at least one further precipitation of silver halide, in order to achieve an improved speed/grain size ratio and in order to achieve a higher stability of a photographic material which contains an emulsion produced in this manner.
The aspect ratio of a tabular silver halide emulsion is the ratio of the average diameter of the projected area of the equivalent circle to the average thickness of the grains.
It is known from U.S. Pat. No. 5,482,825 that a higher film speed and a reduced pressure sensitivity can be achieved by the addition of condensed dihydropyrimidines during the production of the emulsion.
In order to obtain a high speed/fogging ratio and good latent image stability, it is advantageous, during the production of the emulsion, to employ heterocycles which reduce fogging due to their substitution, as is described in JN 3,196,138 for thiosulphonate and as is described in JN 3,039,946 for mercapto-substituted heterocycles.
It is known from EP 337,370 that a silver halide zone with a low iodide content can be precipitated on to a silver halide zone with a high iodide content after the adsorption of surface-active substances (spectral sensitisers, stabilisers comprising SH groups, anti-fogging agents).
It is known from EP 462,579 that a silver halide zone with a higher iodide content can be formed in the presence of 5- or 6-membered ring heterocycles comprising an —SH group, in order to achieve a higher speed, low fogging, reduced granularity and good stability on storage.
The techniques described above are not capable of improving the speed/grain size ratio, or in other words of improving the speed whilst the grain size remains constant. The object of the present invention was to eliminate this disadvantage.
This object is achieved by the addition of at least one aromatic five- or six-membered, heterocyclic compound, which is free from —SH—, —SSO
2
H— and —SSO
2
R groups, in an amount from 10
−9
to 10
−4
mol/mol silver, during nucleus precipitation or during the precipitation of an inner zone of the silver halide grain which is different from the nucleus precipitate.
The present invention thus relates to the process cited at the outset, characterised in that the aforementioned measure is carried out.
Further silver halide precipitations which follow the precipitation of nuclei can be effected by adding soluble silver salts and soluble halides or by adding and depositing a fine-grained micrate emulsion.
Other preferred embodiments of the invention are given in the subsidiary claims.
The heterocyclic compound can also be a constituent of a condensed ring system.
Suitable compounds correspond to formulae I to VII given below:
wherein
R
1
denotes H, alkyl or aryl,
R
2
denotes —SR
3
or—NHCOR
3
, and
R
3
denotes alkyl;
wherein
R
4
denotes H, alkyl, aryl or —S—R
3
R
5
denotes H, alkyl, aryl, —SR
3
, —COR
6
, —COOR
6
, CN or hetaryl,
R
6
denotes alkyl or aryl, and
R
3
has the given meaning;
wherein
R
7
and R
8
, independently of each other, denote H, alkyl, —SR
3
, aryl or hetaryl,
R
9
denotes H or alkyl, and
R
3
has the given meaning;
wherein
R
10
and R
11
, independently of each other, denote H, alkyl or —SR
3
and
R
3
has the given meaning;
wherein the radicals
R
12
and R
13
are identical or different and denote H, alky, —NH
2
or —SR
3
, wherein R
3
has the given meaning;
wherein
R
3
and R
7
have the given meanings;
wherein
R
14
denotes H, alkyl, —SR
3
or NHCOR
3
,
R
15
denotes H, alkyl, NH
2
or OH, and
R
3
, R
9
and R
12
have the given meanings.
The alkyl, aryl and hetaryl groups can be unsubstituted or substituted, wherein SH groups, SSO
2
H groups and SSO
2
—R groups are excluded.
Examples include:
Formula I
I-1: R
1
=phenyl; R
2
=—S—CH
2
—COOH
I-2: R
1
=H; R
2
=—S—CH
2
—COOH
I-3: R
1
=H; R
2
=—NHCOCH
3
Formula II
II-1: R
4
=—S—C
5
H
11
; R
5
=phenoxycarbonyl
II-2 R
4
=CH
3
; R
5
=4-ethoxycarbonylphenoxycarbonyl
II-3: R
4
=CH
3
; R
5
=—COOC
9
H
19
II-4: R
4
=—C(CH
3
)
3
; R
5
=—CN
II-5: R
4
=4-chlorophenyl; R
5
=4-methyl-1, 3-thiazolyl-2-
II-6: R
4
=H; R
5
=1-(2-tolyloxycarbonyl)-propylmercapto
II-7: R
4
=H; R
5
=—S—CH(C
4
H
9
)COOCH
2
CF
3
II-8: R
4
=H; R
5
=—S—CH
2
COOC
6
H
13
II-9: R
4
=CH
3
; R
5
=—COOC
6
H
13
Formula III
III-1: R
9
=H; R
7
=—S—C
6
H
13
; R
8
=2-furyl
III-2: R
9
=H; R
7
=—SCH
2
COOH; R
8
=H
III-3: R
9
=H; R
7
=—SCH(CH
3
)COOH; R
8
=H
III-4: R
9
=CH
2
OH; R
7
=H; R
8=H
III-5: R
9
=CH
2
COOH; R
7
=—SCH
3
, R
8
=—CH
3
Formula IV
IV-1: R
10
=H; R
11
=C
2
H
5
IV-2: R
10
=SCH
2
COOH; R
11
=CH
2
CH
2
COOC
5
H
11
Formula V:
V-1: R
12
NH
2
; R
13
=SCH
2
COOH
V-2: R
12
=SC
2
H
5
; R
13
=SCH
2
COOH
V-3: R
12
=H; R
13
=SCH
2
COOH
V-4: R
12
=SCH
2
COOH; R
13
=SCH
2
COOH
V-5: R
12
=SC
2
H
5
; R
13
=S—CH
2
COOC
5
H
11
Formula VI:
VI-1: R
7
=H
VI-2: R
7
=SCH
2
COOH
VI-3: R
7
=SC
6
H
13
Formula VII
VII-1: R
14
=SCH
2
COOH; R
15
=CH
3
; R
9
=H; R
12
=SCH
2
COOH
VII-2: R
14
=SCH
2
COOH; R
15
=OH; R=H; R
12
=NH
2
VII-3: R
14
=NHCOCH
2
CH
2
COOH; R
15
=CH
3
; R
9
=H: R
12
=H
VII-4: R
14
=SCH
2
COOH; R
15
=CH
3
; R
9
=H; R
12
=H
Compounds of formulae I and II are particularly preferred. The following were tested as comparison compounds:
The silver halide emulsions which are produced according to the invention are used in particular in photographic films, preferably in colour negative films.
Photographic films consist of a support on which at least one light-sensitive silver halide emulsion layer is deposited. Thin films and foils are particularly suitable as supports. A review of support materials and of the auxiliary layers which are deposited on the front and back thereof is given in Research Disclosure 37254, Part 1 (1995), page 285 and in Research Disclosure 38957, Part XV (1996), page 627.
Photographic films usually contain at least one red-sensitive, at least one green-sensitive and at least one blue-sensitive silver halide emulsion layer, and optionally contain intermediate layers and protective layers also.
Depending on the type of photographic film, these layers may be arranged differently. This will be illustrated for the most important products:
Colour photographic films such as colour negative films and colour reversal films comprise, in the following sequence on their support: 2 or 3 red-sensitive, cyan-coupling silver halide emulsion layers, 2 or 3 green-sensitive, magenta coupling silver halide emulsion layers, and 2 or 3 blue-sensitive, yellow-coupling silver halide emulsions layers. The layers of identical spectral sensitivity differ as regards their photographic speed, wherein the less sensitive partial layers are generally disposed nearer the support than are the more highly sensitive partial layers.
A yellow filter layer is usually provided between the green-sensitive and blue-sensitive layers, to prevent blue light from reaching the layers underneath.
The options for different layer arrangements and their effects on photographic properties are described in J. Inf Rec. Mats., 1994, Vol. 22, pages 183-193, and in Research Disclosure 38957, Part XI (1996), page 624.
Departures from the number and arrangement of the light-sensitive layers may be effected in order to achieve defined results. For example, all the high-sensitivity layers may be combined to form a layer stack and all the low-se

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