Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Antihalation or filter layer containing
Reexamination Certificate
2002-09-05
2003-12-30
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Antihalation or filter layer containing
C430S507000, C430S639000, C008S577000, C008S579000, C106S031360, C106S031940, C106S146100, C106S146400, C106S162100, C106S217500
Reexamination Certificate
active
06670111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a photographic dispersion comprising a sucrose derivative and a photographic compound.
2. Background of the Art
Hydrophobic compounds are introduced into hydrophilic photographic layers by the common practice in the photographic industry of dispersing a solution of the hydrophobic compounds in an organic solvent into a water medium, normally into a gelatin and surfactant water solution. In order to improve the stability of such dispersions, the hydrophobic compounds are frequently dissolved in high boiling organic solvents (also referred to in the art as permanent solvents, crystalloidal solvents, oil-type solvents, oil-formers and the like). In some cases, it may be advantageous to facilitate the dissolution of the hydrophobic compound by using an auxiliary water-immiscible or water-miscible low boiling organic solvent, which is removed afterwards by evaporation. Permanent high boiling solvents have a boiling point sufficiently high, generally above 150° C. at atmospheric pressure, such that they are not rapidly evaporated under normal dispersion making and photographic layer coating procedures. Permanent high-boiling solvents are primarily used in the conventional “oil-protection” dispersion method whereby the organic solvent remains in the dispersion, and thereby is incorporated into the emulsion layer coating solution and ultimately into the photographic element. Typical permanent solvent are, for example, tricresyl phosphate or dibutylphthalate.
Generally a photographic element comprises a plurality of layers, at least one of which comprises a silver halide emulsion, coated onto a support. During, or just prior to, the coating step, the dispersion may be heated to about 45° C. and maintained at that temperature for up to 24 hours. It has been noted that in certain cases the dispersed particles containing the photographically useful compound can undesirably grow in the dispersion as a result of relative dissolving and reprecipitation of particle material and solvent. This particle growth can cause the photographically useful compound to become less effective for its intended purpose.
One method of slowing the particle growth in photographic dispersions is disclosed in U.S. Pat. No. 4,181,527 to Toda et al. Toda et al. disclose that incorporation of organic solvent gelling agents, such as N-acylamino acid amides, N-acylamino acid amine salts, and dehydrated condensates of benzaldehydes and sorbitol or xylitol, into a photographic dispersion solidifies or “gels” the oil phase of the dispersion, thereby inhibiting particle growth. While this method does slow particle growth, the resulting viscosity increase of the dispersed phase containing the photographically useful compound can result in undesired decreases in performance such as reactivity or lubricity.
U.S. Pat. No. 5,468,604 discloses that certain hydrophobic, photographically inert compounds which do not solidify or gel the dispersed liquid organic phase can effectively inhibit undesired particle growth in photographic dispersions subject to such particle growth.
U.S. Pat. No. 6,045,985 and EP patent application No. 1,170,629, for example, disclose photographic dyes showing good solubility into the common permanent solvents. However, even a good dispersion of these molecules, obtained using tricresyl phosphate or dibuthylphtalate as permanent solvent, is unstable when stored for a long period of time with an evident change of the drop size distribution and a consequent increase of the average diameters.
U.S. Pat. No. 5,451,497 and European Patent Application EP 661,588 describe photographic dispersions containing photographically useful compounds, a main permanent solvent and a non-color forming, oil-soluble, monomeric or oligomeric organic compound having a glass transition temperature between 0° and 150° C., such as, for example, oil-soluble sucrose esters and rosin and derivatives thereof to inhibit the crystallization of the photographic useful compounds, in particular inhibiting crystallization of photographic couplers. U.S. Pat. Nos. 3,564,576; 3,676,142 and 3,516,833 also disclose sucrose esters as auxiliary solvents.
SUMMARY OF THE INVENTION
The present invention refers to a process for preparing a dispersion which comprises codispersing in an aqueous medium a sucrose derivative represented by general formula (1):
wherein substituents X
1
to X
8
, being the same or different, are represented by a hydrogen atom, an alkyl group or an acyl group, with the proviso that at least four of the X
1
to X
8
substituents are different from hydrogen and that the total sum of the carbon atoms of X
1
to X
8
substituents is at least sixteen;
and a photographic compound represented by general formula (2):
wherein R and R
1
each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted heterocyclic group or a substituted or unsubstituted aryl group; R
2
, R
3
and R
4
each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group and R
3
and R
4
may be combined to form a 6-membered ring.
The present invention also refers to a photographic dispersion comprising a sucrose derivative represented by previous general formula (1) and a photographic compound represented by previous general formula (2) dispersed in an aqueous medium and to a photographic element comprising a film support base having coated on at least one side thereof at least one hydrophilic colloid emulsion layer comprising said photographic dispersion.
Stable dispersions of these classes of photographic compounds, such as for example the compounds described in EP patent application No. 1,170,629, can be easily prepared using a sucrose derivative. The drop size distribution for these dispersed photographic compounds is narrow and change in drop size distribution is inhibited even when stored for a long period of time (e.g., 30 days) in a cold room (e.g., 5° C.).
DETAILED DESCRIPTION OF THE INVENTION
Accordingly, one aspect of the present invention relates to process for preparing a dispersion which comprises codispersing in an aqueous medium a sucrose derivative represented by the above described general formula (1) and a photographic compound represented by the above described general formula (2).
In particular, in formula (1),
X
1
to X
8
substituents, being the same or different, represent a hydrogen atom, an alkyl group (e.g., substituted or unsubstituted) or an acyl group (substituted or unsubstituted. Preferred alkyl groups include 1 to 8 carbon atom alkyl groups comprising linear or branched-chain alkyl groups, such as, for example, methyl group, trifluoromethyl group, ethyl group, propyl group, isopropyl group, butyl group, tert.-butyl group, neo-pentyl group, and octyl group. Preferred acyl groups include 1 to 8 carbon atom acyls comprising linear or branched-chain acyls, such as, for example, formyl group, acetyl group, chloroacetyl group, fluoroacetyl group, trichloroacetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, and pivaloyl group, or aromatic acyls, such as, for example, benzoyl group, phthaloyl group, naphthoyl group, toluoyl group. According to the substituent types from X
1
to X
8
, the sucrose derivatives useful in the present invention are therefore represented by sucrose ethers or esters. Preferably, the X
1
to X
8
substituents are acyl groups, and more preferably are acyl groups having from 2 to 7 carbon atoms, such as acetyl group, propionyl group, butyryl group, isobutyryl group or benzoyl group.
When in the present invention the term “group” is used to define a chemical compound or substituent, the described chemical material comprises the basic group, ring or residue and that group, ring or residue with conventional substitutions. When on the contrary the term “units” is used, only the chemical unsubstituted material is intended to be included. Fo
Balestra Corrado
Besio Mauro
Prosperi Emilio
Ferrania S.p.A.
Mark A. Litman & Assoc. P.A.
Schilling Richard L.
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