Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-04-26
2003-11-18
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031900
Reexamination Certificate
active
06648953
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink composition for ink jet recording, a process for the preparation of such an ink composition, and an ink jet recording process using such an ink composition.
BACKGROUND OF THE INVENTION
A composite black comprising a cyan ink, a yellow ink and a magenta ink can be used as a black ink in the ink jet recording process. In general, however, the composite black provides low density. Further, the image printed from the composite black has a deteriorated light fastness. Thus, as the coloring agent, carbon black has heretofore been mainly used. However, since the single use of carbon black as a coloring agent may impair the stability of ink jetting from the recording head, attempts have heretofore been made to overcome these difficulties.
For example, JP-A-4-57861 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses an aqueous black ink comprising carbon black and a dye. This ink allegedly exhibits excellent print fastness (e.g., water fastness, marker resistance, abrasion resistance), as well as excellent jetting stability.
Further, JP-A-6-287492 discloses an aqueous black comprising an inorganic pigment (particularly carbon black), a dispersant and particulate titanium dioxide or alumina. This ink allegedly enables a recording process with excellent reliability that provides excellent print density and quality.
Although the prior art ink jet recording process using the foregoing ink exhibits excellent jetting stability over a short period of time, there arise two problems concerning unstable jetting when printing is carried out over a long period of time.
One of these problems is a phenomenon that, in the case of continuously printing over a long period of time of several hours or longer, ink droplets fly irregularly in randomly deflected directions (hereinafter referred to as “malalignment”), and thus it becomes impossible to achieve recording on a recording paper as expected. This phenomenon of malalignment is a critical defect in recent recording processes with a requirement for high image qualities and in the so-called plural copy-recording process, which will be in great demand in the future where a printer should be operated over an extended period of time.
Another problem is a phenomenon that, when allowed to stand over a long period of time of ten days or longer after the completion of printing, the ink jet head is clogged, and thus ink cannot be jetted therefrom any longer, i.e., so-called fill-in.
Between these phenomena concerning unstable jetting, malalignment occurs particularly in the case of using carbon black as a colorant for a black ink.
Further, the above-described black ink comprising a dye is disadvantageous in that the resulting printed matter leaves something to be desired in light fastness.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to eliminate the foregoing malalignment which can occur when the ink jet recording process is used over an extended period of time while maintaining the desired print quality required for an ink composition for the ink jet recording process.
The foregoing object can be accomplished with the ink composition for ink jet recording process of the present invention, comprising
(1) a carbon black,
(2) an organic pigment and
(3) a dispersant and
(4) at least one saccharide incorporated in an aqueous medium.
DETAILED DESCRIPTION OF THE INVENTION
Suitable examples of the carbon black incorporated in the ink composition include those which have heretofore been commonly used in conventional ink compositions for ink jet recording process. Specific examples of suitable carbon blacks include furnace black, lamp black, acetylene black, and channel black.
The organic pigments are not particularly restricted so long as the organic pigments are dispersible in aqueous media. Examples of yellow organic pigments include C.I. Pigment Yellow 1 (Hanza yellow G), 2, 3 (Hanza yellow 10G), 4, 5 (Hanza yellow 5G), 6, 7, 10, 11, 12, 13, 14, 16, 17, 24 (flavanthron yellow), 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108 (anthrapyrimidine yellow), 109, 110, 113, 117 (copper complex salt pigment), 120, 124, 128, 129, 133 (quinophthalone), 138, 139 (isoindolinone), 147, 151, 153 (nickel complex pigment), 154, 167, 172 and 180.
Examples of Magenta organic pigments include C.I. Pigment Red 1 (Para-red), 2, 3 (toluidine red), 4, 5 (ITR Red), 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38 (pyrazolone red), 40, 41, 42, 88 (thioindigo), 112 (naphthol AS-type), 114 (naphthol AS-type), 122 (dimethylquinacridone), 123, 144, 146, 149, 150, 166, 168 (anthoanthorone orange), 170 (naphthol AS-type), 171, 175, 176, 177, 178, 179 (prylene maroon), 185, 187, 202, 209 (dichloroquinacridone), 219, 224 (perylene type), 245 (naphtol AS-type) or C.I. Pigment Violet 19 (quinacridone), 23 (dioxazine violet), 32, 33, 36, 38, 43 and 50.
Examples of organic cyan pigments include C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 16 (metal-free phthalocyanine), 18 (alkali blue toner), 25, 60 (Threne Blue), 65 (Violanthrone) and 66 (indigo).
As a black organic pigment, use can be made of, for example, aniline black (C.I. Pigment Black 1).
It is also possible to use organic color pigments other than magenta, cyan and yellow such as C.I. Pigment Green 7 (phthalocyanine green), 10 (green gold), 36, 37; C.I. Pigment Brown 3, 5, 25 and 26; or C.I. Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43 and 63.
The ink composition according to the present invention is suitable as long as it comprises, as pigments, a carbon black and at least one organic pigment incorporated therein. In order to adjust the color tone, the carbon black and two or three or more organic pigments may be combined. In the case of a combination of a carbon black and one organic pigment, the organic pigment is preferably selected from the group consisting of organic pigments having a color tone close to black, more preferably C.I. pigment black 1 (aniline black), C.I. pigment brown 26 (perylene black), C.I. pigment violet, C.I. pigment green, and C.I. pigment blue. In order to properly mix color tones, organic pigments respectively selected from the group consisting of carbon black and C.I. pigments Y, M and C may be added to the carbon black.
The total amount of pigment, i.e., the sum of the amount of the carbon black and the organic pigment, is determined to achieve the color and density required for printed material or desired physical properties of ink and the amount varies with the specific gravity or bulk density of the pigment. Thus, the amount is not specifically limited. In practice, however, it is preferably from 0.5 to 30% by weight, more preferably from 1 to 12% by weight, based on the total weight of the ink composition. If the total amount of the pigment falls below 0.5% by weight, the desired print density may not be obtained. On the contrary, if the total amount of the pigment exceeds 30% by weight, the ink composition exhibits a structural viscosity that makes it impossible to secure the desired jetting stability. If the total amount of the pigment falls within the range of from 1 to 12% by weight, a high print density can be obtained and the resulting ink composition is quite suitable for the ink jet recording process.
The ratio of the amount of carbon black to the amount of organic pigment (carbon black:organic pigment) (w/w) varies with the various properties of the carbon black used and the organic pigment selected, and thus is not specifically limited. In practice, however, it is preferably from 95:5 to 30:70, more preferably from 90:10 to 50:50. If the amount of carbon black exceeds 9 times by weight that of the organic pigment, long-term jetting stability can be impaired. On the contrary, if the amount of carbon black falls below 3/7 times by weight that of the organic pigment, sufficient print density cannot be achieved, or the light fastness of the printed material can be impaired. If the fore
Komatsu Hidehiko
Nakamura Hiroto
Tsukahara Michinari
Yamazaki Hideo
Bell Mark L.
Faison Veronica F.
Seiko Epson Corporation
Sughrue & Mion, PLLC
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