Radiation imagery chemistry: process – composition – or product th – Microcapsule – process – composition – or product
Reexamination Certificate
1996-12-11
2002-05-14
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Microcapsule, process, composition, or product
C430S336000, C430S337000, C430S351000, C430S348000, C430S350000, C503S219000, C503S225000, C503S216000, C503S226000
Reexamination Certificate
active
06387584
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photoimaging material containing a leuco dye which is capable of thermal image fixing. More particularly, the present invention relates to a photoimaging material which is not susceptible to background coloring (fogging) upon storage in dark or light environments after thermal image fixing. The photoimaging material of the invention can be used as a proof paper, a print-out paper, an overlay film, etc.
BACKGROUND OF THE INVENTION
Photoimaging materials which can be used as a proof paper, a print-out paper, an overlay film, and the like have hitherto been employed in various photographic applications. The image-wise exposed areas become visible in such as so-called free-radical photographic materials. Especially useful among these techniques are a method of forming color by radical oxidation of various leuco dyes to the corresponding dyes with a photooxidizing agent.
However, because of sensitivity to light, the above techniques are disadvantageous in that the dye image of a photoimaging material formed by exposure is prone to color formation upon further exposure to ordinary room light, sunlight, or white light or even upon storage in the dark. Several techniques for fixing the image after image-wise exposure have been proposed. Among these is a photoimaging material which comprises microcapsules containing both a leuco dye and a photooxidizing agent as encapsulated ingredients, and which further comprises a reducing agent arranged the outside of the microcapsules. In this photoimaging material, the image is fixed by heating after exposure (see JP-A-2-44). (The term “JP-A” as used herein means an “unexamined published Japanese patent application.”)
Hydroquinone reducing agents are known to improve the storage stability of the above-described photoimaging recording material after image fixing (see JP-A-3-191341). However, these hydroquinone reducing agents are disadvantageous in that after image fixing they tend to cause background coloring (fogging) during storage under light or dark conditions. As a result, the recording material has reduced contrast between the image areas and the background (white areas) to thereby impair quality. Thus, a fully satisfactory photoimaging material has not been obtained with the above technique.
The hydroquinone reducing agents mentioned above and the reducing agents described in JP-B-62-39728, including cyclic phenylhydrazide compounds, guanidine derivatives, alkylenediamine derivatives, hydroxyamine derivatives and phenylhydrazine compounds, further have another problem in that the reducing agents tend to vaporize or sublimate during thermal fixing or the molten reducing agent becomes oily and accumulates to foul the thermal fixing apparatus. (The term “JP-B” as used herein means an “examined Japanese patent publication.”)
SUMMARY OF THE INVENTION
An object of the present invention is to provide a photoimaging material capable of thermal image fixing and which is based on a method of forming color by radical oxidation of various leuco dyes to the corresponding dyes with a photooxidizing agent, which photoimaging material is not prone to background coloring (fogging) during storage under dark or light conditions after image fixing and which does not foul the inside of the apparatus during thermal image fixing.
The above object of the present invention is accomplished by providing a photoimaging material comprising a support having thereon a photoimaging layer comprising microcapsules and a reducing agent present outside the microcapsules, wherein the microcapsules contain a leuco dye capable of oxidative color formation, a photooxidizing agent, and an organosulfur antioxidant, and the reducing agent is 2,2′-methylenebis(4-methyl-6-t-butylphenol) or 2,2′-methylenebis(4-ethyl-6-t-butylphenol).
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in further detail below.
The reducing agent for use in the present invention is 2,2′-methylenebis(4-methyl-6-t-butylphenol) or 2,2′-methylenebis(4-ethyl-6-t-butylphenol). These compounds hitherto have not been used as fixing agents, because their ability to trap free radicals is inferior to that of other known reducing agents. Also, these compounds tend to cause background coloring (fogging) during storage in light or dark conditions when used as a fixing agent in an imaging material comprising a leuco dye and a photooxidizing agent. However, those two compounds are less prone to vaporize upon heating, and there is little fouling of the inside of the thermal fixing apparatus because the melts thereof do not change to an oily, sticky state but rather recrystallize.
Hence, the present inventors sought to develop a technique for improving fixing performance while maintaining reduced apparatus fouling. As a result, the present inventors discovered that by encapsulating an organosulfur antioxidant in microcapsules, background coloring (fogging) during storage in light or dark conditions after fixing can be prevented even when 2,2′-methylenebis(4-methyl-6-t-butylphenol) or 2,2′-methylenebis(4-ethyl-6-t-butylphenol) is used as a reducing agent. The present invention has been achieved based on this finding.
The organosulfur antioxidant for use in the present invention may be a known secondary antioxidant organosulfur compound for use in the field of polyolefins, styrene resins, and the like.
Examples of the antioxidant include dilauryl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3′-thiodipropionate, ditridecyl 3,3′-thiodipropionate and pentaerythrityl tetrakis(3-laurylthiopropionate). However, the organosulfur antioxidant for use in the present invention is not limited to these examples. The addition amount of the antioxidant is preferably from 0.01 to 2 mol, more preferably from 0.05 to 1 mol, per mol of the reducing agent .
Preferred examples of the leuco dye for use in the present invention include the following leuco dyes which are described in U.S. Pat. No. 3,445,234:
(A) aminotriarylmethanes, aminoxanthene, aminooxanthene, amino-9,10-dihydroacridine, aminophenoxazine, aminophenothiazine, aminodihydrophenazine, aminodiphenylmethane, and leucoindamine; and
(B) aminohydrocinnamic acid (cyanoethane), hydrazine, leucoindigoid dyes, amino-2,3-dihydroanthraquinone, tetrahalo-p,p-biphenols, 2-(p-hydroxyphenyl)-4,5-diphenylimidazole and phenethylaniline.
Of the leuco compounds enumerated above, those belonging to group (A) each loses one hydrogen atom to form a corresponding colored dye, while those belonging to group (B) each loses two hydrogen atoms to form a corresponding colored dye.
Specific examples of the leuco dye include tris(4-dimethylaminophenyl)methane, tris(4-diethylaminophenyl)-methane, tris(4-diethylamino-2-methylphenyl)methane, bis(4-diethylaminophenyl)(4-diethylamino-2-methylphenyl)methane, bis(4-diethylamino-2-methylphenyl)(4-diethylaminophenyl)-methane, bis(1-ethyl-2-methylindol-3-yl)phenylmethane, 2-N-(3-trifluoromethylphenyl)-N-ethylamino-6-diethylamino-9-(2-methoxycarbonylphenyl)xanthene, 2-(2-chlorophenyl)amino-6-dibutylamino-9-(2-methoxycarbonylphenyl)xanthene, 2-dibenzylamino-6-diethylamino-9-(2-methoxycarbonylphenyl)-xanthene, benzo[a]-6-N,N-diethylamino-9-(2-methoxycarbonyl-phenyl)xanthene, 2-(2-chlorophenyl)-amino-6-dibutylamino-9-(2-methylphenylcarboxamidophenyl)xanthene, 3,6-dimethoxy-9-(2-methoxycarbonyl)phenylxanthene, benzoyl leucomethylene blue and 3,7-bisdiethylaminophenoxazine.
The photooxidizing agent for use in the photoimaging material of the present invention preferably is a compound which is inert in its ordinary state. However, upon exposure to actinic radiation such as visible rays, ultraviolet rays, infrared rays, or X-rays, the photooxidizing agent generates a chemical species which oxidizes the leuco dye to a corresponding colored dye.
Representative examples of the photooxidizing agent include the lophine dimer compounds described in JP-B-62-39728 and JP-B-63-2099, such as 2,2′-bis(o-chlorop
Ikeda Kensuke
Ono Makoto
Angebranndt Martin
Fuji Photo Film Co. , Ltd.
Sughrue & Mion, PLLC
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