Method of suppressing fog in silver halide emulsions

Details Method of suppressing fog in silver halide emulsions Method of suppressing fog in silver halide emulsions

1999-10-12

2001-04-10

Letscher, Geraldine (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Nonradiation sensitive image processing compositions or...

C430S614000, C430S631000, C430S546000, C430S613000, C430S615000

Reexamination Certificate

active

06214529

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the use of isothiazolin-one compounds with light-sensitive silver halide emulsions.
BACKGROUND OF THE INVENTION
Problems with fogging of silver halide emulsions have plagued the photographic industry from its inception. Fog can be defined as a developed density that is not associated with the action of the image-forming exposure, and is usually expressed as “D-min,” the density obtained in the unexposed portions of the emulsion. Density, as normally measured, includes both that produced by fog and that produced as a function of exposure to light. It is known in the art that the appearance of photographic fog related to intentional or unintentional reduction of silver ion can occur during many stages of preparation of the photographic element including silver halide emulsion preparation, spectral/chemical sensitization of the silver halide emulsion, melting and holding of the liquid silver halide emulsion melts, subsequent coating of silver halide emulsions, and prolonged natural and artificial aging of coated silver halide emulsions.
The suppression of fog is, thus, a major concern when dealing with silver halide emulsions. A multitude of compounds involving many different chemical structures have been studied and used for this purpose. Examples can be found in
Research Disclosure
308119, published December 1989, and include mercaptotetrazoles, benzothiazoles, tetraazaindenes, disulfide compounds, and mercunic chloride to name a few. Despite the large number of materials available, few are able to reduce fog without also reducing speed.
There is an especially great need to control the tendency of emulsions to increase in fog while in the melted state. The demands of mass producing photographic film often require the pre-melting of large quantities of emulsion in preparation for long coating events. Emulsions may be held in the melted state for as long as 16 hours before completion of a particular job. During this period certain emulsions have a propensity to gain fog beyond an acceptable level and, therefore, require the addition of one or more antifoggants.
In this invention it has been discovered that a specific group of isothiazolin-ones is particularly useful in controlling fog which develops during melt-hold. Isothiazolin-ones are known as useful biocides for silver halide photographic elements as described in
Research Disclosure,
37026, February 1995; in U.S. Pat. Nos. 4,224,403,and 4,490,462; and in JP 09-329862 and JP 10-011739. JP 09-133977 describes one class of isothiazolin-ones as reducing fog when added during precipitation of a silver halide emulsion. However, nowhere has it been recognized or desciubed that a specific group of isothiazolin-ones is useful in reducing the fog which may develop during melt-hold of certain silver halide emulsions.
SUMMARY OF THE INVENTION
This invention provides a method of reducing fog in a silver halide emulsion comprising taking a high fogging emulsion which has been chemically sensitized and cooled, holding the high fogging emulsion in the form of a melt in preparation for coating on a support, and prior to or during said holding, contacting the emulsion with an isothiazolin-one compound represented by the following formula
wherein R
1
is a substituent, and Z contains the carbon atoms necessary to form a substituted or unsubstituted non-aromatic ling. This invention further provides a silver halide photographic element containing such an emulsion.
The particular isothiazolin-ones used in this invention are uniquely effective at suppressing fog in certain emulsions in the melted state. Not only do the isothiazolin-ones reduce fog, but they do so without reducing fresh speed or the speed observed after the emulsion has been held in the melted state. Other isothiazolin-ones which ale chemically very similar have little or no effect on the fog growth of photographic emulsions held in the melted state.
DETAILED DESCRIPTION OF THE INVENTION
The isothiazolin-one compounds utilized in this invention are represented by the formula
Z contains the carbon atoms necessary to form a substituted or unsubstituted non-aromatic ring. Preferably Z is a substituted or unsubstituted five or six-membered non-aromatic ring, and more prefererably Z is a substituted or unsubstituted five-membered non-aromatic ring. In one suitable embodiment Z is an unsubstituted non-aromatic five-membered ring.
R
1
can be any substituent which is suitable for use in a silver halide photographic element and which does not interfere with the fog restraining activity of the isothiazolin-one compound. Preferably R
1
is a substituted or unsubstituted aliphatic, aromatic or heterocyclic groups.
When R
1
is an aliphatic group, preferably, it is an alkyl group having from 1 to 20 carbon atoms, or an alkenyl or alkynyl group having from 2 to 20 carbon atoms. More preferably, it is an alkyl group having 1 to 6 carbon atoms, or an alkenyl or alkynyl group having 3 to 5 carbon atoms. Most preferably it is an alkyl group having 1 to 3 carbon atoms. These groups may or may not have substituents. Examples of alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, isopropyl and t-butyl groups. Examples of alkenyl groups include allyl and butenyl groups and examples of alkynyl groups include propargyl and butynyl groups.
The preferred aromatic groups have from 6 to 20 carbon atoms and include, among others, phenyl and naphthyl groups. More preferably, the aromatic groups have 6 to 10 carbon atoms and most preferably the aromatic groups are phenyl. These groups may be substituted or unsubstituted. The heterocyclic groups are 3 to 15-membered rings or condensed rings with at least one atom selected from nitrogen, oxygen, sulfur, selenium and tellurium. More preferably, the heterocyclic groups are 5 to 6-membered rings with at least one atom selected from nitrogen. Examples of heterocyclic groups include pyrrolidine, piperidine, pyridine, tetrahydrofuran, thiophene, oxazole, thiazole, imidazole, benzothiazole, benzoxazole, benzimidazole, selenazole, benzoselenazole, tellurazole, triazole, benzotriazole, tetrazole, oxadiazole, or thiadiazole rings.
Nonlimiting examples of substituent groups for R
1
and Z include alkyl groups (for example, methyl, ethyl, hexyl), aryl groups (for example, phenyl, naphthyl, tolyl), acyl groups (for example, acetyl, propionyl, butyryl, valeryl), sulfonyl groups (for example, methylsulfonyl, phenylsulfonyl), ether groups (for example methoxy, ethoxy, propoxy, butoxy), hydroxyl and nitrile groups. Preferred substituents are lower alkyl groups, i.e., those having 1 to 4 carbon atoms (for example, methyl), hydroxyl groups, and halogen groups (for example, chloro).
The isothiazolin-ones may be prepared as described in U.S. Pat. No. 4,708,959—Shroot et al; U.S. Pat. No. 4,851,541—Maignan et al; U.S. Pat. No. 5,082,966—Moffat; U.S. Pat. No. 5,336,777—Moffat et al; and U.S. Pat. No. 5,466,814—Moffat et al, all of which are incorporated herein by reference. Some of them are also available commercially from Zeneca Biocides, Inc., Wilmington, Del. 19850-5457.
It is understood throughout this specification and claims that any reference to a substituent by the identification of a group or a ling containing a substitutable hydrogen (e.g., alkyl, amine, aryl, alkoxy, heterocyclic, etc.), unless otherwise specifically described as being unsubstituted or as being substituted with only certain substituents, shall encompass not only the substituent's unsubstituted form but also its form substituted with any substituents which do not negate the advantages of this invention. Nonlimiting examples of suitable substituents are alkyl groups (for example, methyl, ethyl, hexyl), aryl groups (for example, phenyl, naphthyl, tolyl), acyl groups (for example, acetyl, propionyl, butyryl, valeryl), sulfonyl groups (for example, methylsulfonyl, phenylsulfonyl), alkoxy groups, hydroxy groups, alkylthio groups, arylthio groups, acylamino groups, sulfo

Affiliated with

Also associated with

Rating

Method of suppressing fog in silver halide emulsions does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of suppressing fog in silver halide emulsions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of suppressing fog in silver halide emulsions will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2552283