Radiation imagery chemistry: process – composition – or product th – Color imaging process – Using identified radiation sensitive composition in the...
Reexamination Certificate
2001-11-21
2003-03-11
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Color imaging process
Using identified radiation sensitive composition in the...
C430S350000, C430S543000, C430S546000, C430S552000, C430S556000, C430S561000, C430S566000, C430S613000, C430S614000, C430S619000, C430S631000, C430S502000, C430S944000
Reexamination Certificate
active
06531270
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the use of ionic liquids as coupler solvents in color photothermographic systems.
BACKGROUND OF THE INVENTION
Ionic liquids are salts characterized by their unusually low melting points, which salts can be molten even at room temperature. Ionic liquids were disclosed early on by Hurley and Wier in a series of U.S. Patents (U.S. Pat. Nos. 2,446,331; 2,446,339; 2,446,350). These patents disclosed room temperature melts, comprised of AlCl
3
and a variety of n-alkylpyridinium halides, which afforded an advantageous conducting bath, free of volatile solvents, for aluminum electroplating.
Over the past 15 years, work in room-temperature melts has been dominated by the use of varying proportions of AlCl
3
and 1-ethyl-3-methylimidazolium (EMI) chloride, as discussed in separate review articles by Wilkes and Osteryoung (Osteryoung, Robert A., (p. 329) and Wilkes, John S., (p. 217) in
Molten Salt Chemistry
, G. Mamantov and R. Marassi, eds., (D. Reidel Publishing, Dordrecht, Holland, 1987) and in Japanese patent Nos. 0574656 (Endo, 1993) and 0661095 (Kakazu, 1994). A disadvantage of these first molten salts, and a serious problem with any solvent-free ionic liquid containing a strong Lewis acid such as AlCl
3
, is the liberation of toxic gas when exposed to moisture. Additionally, the highly reactive nature of Lewis acids used to form room temperature melts limits the kinds of organic and inorganic compounds which are stable in these media.
Ionic liquids typically exhibit mixed organic and inorganic character. The cation is usually a heterocyclic cation such as 1-butyl-3-methyl imidazolium or n-butylpyridinium. These organic cations, which are relatively large compared to simpler organic or inorganic cations, account for the low melting point of the salts. The anions, on the other hand, determine to a large extent the chemical properties of the system. Tetrafluoroborate and hexafluorophosphate are among the types of anions that are attracting the interest of ionic-liquid research groups. These ions do not combine with their corresponding Lewis acids and therefore are not potentially acidic. They are air and water stable.
U.S. Pat. No. 5,827,602 to Koch et al. discloses ionic liquids having improved properties for application in batteries, catalysis, chemical separations, and other uses. The ionic liquids described in Koch et al. are hydrophobic in nature, being poorly soluble in water, and contain only non-Lewis acid anions. When fluorinated, they were found to be particularly useful as inert liquid diluents for highly reactive chemicals.
Ionic liquids are discussed, for example, by Freemantle, M.
Chem. Eng. News
1998, 76 [March 30], 32; Carmichael, H.
Chem. Britain,
2000, [January], 36; Seddon, K. R.
J. Chem. Tech. Biotechnol.
1997, 68, 351; Welton, T.
Chem. Rev.
1999, 99, 2071; Bruce, D. W., Bowlas, C. J., Seddon, K. R.
Chem. Comm.
1996, 1625; Merrigan, T. L., Bates, E. D., Dorman, S. C., Davis, J. H.
Chem. Comm.
2000, 2051; Freemantle, M.
Chem. Eng. News,
2000, 78 [May 15], 37. See also the following reviews of ionic liquids: Holbrey, J. D.; Seddon, K. R.
Clean Products and Processes
1999, 1, 223-236; and Dupont, J., Consorti, C. S. Spencer, J.
J. Braz. Chem. Soc.
2000, 11, 337-344.
Ionic liquids have generally been disclosed for use as solvents for a broad spectrum of chemical processes. These ionic liquids, which in some cases can serve as both catalyst and solvent, are attracting increasing interest from industry because they promise significant environmental benefits, since they are nonvolatile and therefore do not emit vapors. Hence they have been used, for example, in butene dimerization processes.
PCT publication WO 01/25326 to Lamanna et al. discloses an antistatic composition comprising at least one ionic salt consisting of a nonpolymeric nitrogen onium cation and a weakly coordinating fluoroorganic anion, the conjugate acid of the anion being a superacid, in combination with thermoplastic polymer. The composition was found to exhibit good antistatic performance over a wide range of humidity levels.
U.S. Pat. No. 6,048,388 to Schwarz et al. discloses an ink composition for ink-jet printing which comprises water, a colorant and an ionic liquid material. In a preferred embodiment, the ink is substantially free of organic solvents.
In contrast to ink-jet media, such as disclosed in Schwarz et al. U.S. Pat. No. 6,048,388, photographic color images are typically obtained by a coupling reaction between the development product of an incorporated developing agent (e.g., oxidized aromatic primary amino developing agent) and a color forming compound commonly referred to as a coupler. The dyes produced by coupling are typically indoaniline, azomethine, indamine or indophenol dyes, depending upon the chemical composition of the coupler and the developing agent. In multicolor photographic elements, the subtractive process of color formation is ordinarily employed and the resulting image dyes are usually cyan, magenta and yellow dyes which are formed in or adjacent silver halide layers sensitive to radiation complementary to the radiation absorbed by the image dye; i.e. silver halide emulsions sensitive to red, green and blue radiation.
Commonly, when intended for incorporation in photographic elements, couplers are commonly dispersed therein with the aid of a high boiling organic solvent, referred to as a coupler solvent. Couplers are rendered nondiffusible in photographic elements, and compatible with such coupler solvents, by including in the coupler molecule a group referred to as a ballast group. This helps to form the hydrophobic phase containing the coupler, which is subsequently dispersed as small oil droplets in the process of making the photographic dispersion of the coupler. This dispersion is in turn added to the balance of the components of the aqueous gelatin phase of the imaging layer. This ballast group is located on the coupler in a position other than the coupling position and imparts to the coupler sufficient bulk to render the coupler nondiffusible in the element as coated and during processing. It will be appreciated that the size and nature of the ballast group will depend upon the bulk of the unballasted coupler and the presence of other substituents on the coupler.
PROBLEM TO BE SOLVED BY THE INVENTION
Achieving adequate dye density has been a recurrent problem in photothermographic systems, especially photothermographic systems involving a dye-forming coupler. Photothermographic systems involve heat processable photosensitive elements that are constructed, so that they can be processed in a substantially dry state by applying heat. Because of the much greater challenges involved in developing a dry or substantially dry color photothermographic system, however, most of the activity to date has been limited to photothermographic systems that rely on silver development for image formation, especially in the areas of health imaging and microfiche.
Light-sensitive imaging elements which form colored dye records (for example, yellow, magenta and cyan records) of comparable density-forming ability and consistent stability in all three color records in a photothermographic system can be especially difficult. A major problem that remains in phototothermographic systems, wherein the dye images require the reaction of a blocked developer and a dye-forming coupler through substantially dry gelatin, is how to facilitate the speed and ease with which the dye images may be formed. In order to solve this problem, there is a need for a photothermographic element containing improved coupler systems that will exhibit a higher reactivity with oxidized developer than couplers heretofore discovered.
SUMMARY OF THE INVENTION
This invention involves the use of ionic liquids as coupler solvents in color or monochrome photothermographic systems. Dye-forming couplers used in photothermographic systems have been found to dissolve readily in ionic liquids. The couplers can be dissolved
Olson Leif P.
Reynolds James H.
Chea Thorl
Eastman Kodak Company
Konkol Chris P.
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