Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-10-07
2002-02-26
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000, C430S569000, C430S600000, C430S603000, C430S605000, C430S607000, C430S613000, C430S614000
Reexamination Certificate
active
06350567
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to silver halide emulsions containing isothiazolone compounds and methods of making such emulsions.
BACKGROUND OF THE INVENTION
Problems with fogging have plagued the photographic industry from its inception. Fog is a deposit of silver or dye that is not directly related to the image-forming exposure, e.g., when a developer acts upon an emulsion layer, some reduced silver is formed in areas that have not been exposed to light. The fog sites on silver halide crystals can originate during emulsion manufacture or during aging of the photographic element. During the aging process, fog can become exaggerated by extremes in temperature and humidity. Fog can be defined as 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. Developed density, as normally measured, includes both that produced by fog and that produced by exposure to light.
Silver halide emulsions containing a high content of chloride, such as silver chloride or silver iodochloride, are known for their high photographic sensitivities and rapid processability as described in, for example, U.S. Pat. Nos. 5,736,310; 5,728,516; 5,726,005; and 5,674,674. Such emulsions are also prone to large degrees of fogging, especially in context with their use in reflective-support photographic display materials. To minimize this fog, mercuric salts and other antifoggants have been employed to satisfaction as described in, for example, U.S. Pat. Nos. 5,605,789; 5,550,013; and 5,547,827. Unfortunately, such fog-combating compounds are not without drawbacks. In recent years, it has become necessary to eliminate the need for mercuric salts in photographic products, especially in high chloride content emulsion formulations. Many other compounds which are useful as antifoggants also reduce speed. Even when using mercuric salts or other antifoggants during emulsion precipitation, where fog density is generally less than 0.10 reflection density, other means are needed to prevent the coated emulsion from undergoing changes during the aging processes.
In this invention it has been discovered that a specific group of isothiazolones is particularly useful in controlling fog in high chloride emulsions when added before or during precipitation of certain emulsions. Isothiazolones 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 isothiazolones as reducing fog when added during precipitation of a silver halide emulsion. However, nowhere has it been recognized or described that the specific group of isothiazolones of the invention confers significant advantageous sensitometric benefits when present during emulsion precipitation.
SUMMARY OF THE INVENTION
This invention provides a silver halide photographic element comprising a silver halide emulsion which is greater than 50 mole-% silver chloride, said emulsion containing an isothiazolone compound represented by the formula
wherein R
1
is a substituent; and Z contains the carbon atoms necessary to form a substituted or unsubstituted non-aromatic ring, wherein the isothiazolone compound was added before or during precipitation of the emulsion. It also provides a method of making the above described emulsion.
The isothiazolones used in this invention are highly effective at suppressing fog in silver halide emulsions when used during the precipitation stage of the emulsion manufacture. Not only do the isothiazolones reduce fog, they also stabilize the emulsion against sensitometric changes during aging of the emulsion. Further, they do so without significantly reducing speed.
DETAILED DESCRIPTION OF THE INVENTION
The isothiazolone 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 preferably 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 isothiazolone compound. Preferably R
1
is a substituted or unsubstituted aliphatic, aromatic or heterocyclic group.
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 groups 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 isothiazolones may be prepared as described in U.S. Pat. Nos. 4,708,959—Shroot et al; 4,851,541—Maignan et al; 5,082,966—Moffat; 5,336,777—Moffat et al; and 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.
It is understood throughout this specification and claims that any reference to a substituent by the identification of a group or a ring 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, sulfonylamino groups, acyloxy groups, carboxyl groups, cyano groups, sulfo groups and amino groups.
Useful levels of the isothiazolone compounds range from abou
Chen Benjamin T.
Klaus Roger L.
Mount Jeri L.
Baxter Janet
Eastman Kodak Company
Meeks Roberts Sarah
Walke Amanda C.
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