Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-09-15
2003-09-02
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031590, C106S031860, C106S031890
Reexamination Certificate
active
06613136
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording ink composition, and more particularly to an aqueous recording color ink composition capable of producing color images on a sheet of plain paper by an ink-jet printing method, and suitable for an ink-jet printer, aqueous writing utensils, various kinds of recorders, and pen plotters. Also, the present invention relates to an ink-jet printing method using the above-mentioned recording ink composition.
2. Discussion of Background
Ink-jet printers have been widely utilized in recent years because of the advantages of low noise and low running cost, and color ink-jet printers capable of producing color images on a sheet of plain paper have also been on the market.
However, it is extremely difficult to obtain a color ink composition capable of meeting with the requirements for the produced image, for example, color reproduction, water resistance, light resistance, drying characteristics, prevention of blurring, and the reliability of ink-ejection. In particular, when the color images are produced using the ink-jet color printer, image blurring easily takes place in two-color-superimposed portions such as red, green, and blue color image portions, even though image clearness is sufficient in single color image portions formed by use of a yellow, magenta, or cyan color ink composition.
When the ink images deposited on a sheet of paper are dried without using any specific image fixing unit, the drying characteristics of the ink image are improved by increasing the penetrating properties of the ink through paper as described in Japanese Laid-Open Patent Application No. 55-29546. In this case, however, the improved penetrating properties of the ink through paper generate the problem of image blurring.
Japanese Patent Publication No. 60-23793 describes that a dialkylsulfosuccinic acid is contained in the ink composition as a surfactant, whereby the drying characteristics of the ink images can be improved and deterioration of image quality can be minimized. However, when such an ink composition is used for ink-jet printing, the diameters of picture elements of the obtained image considerably vary depending on the kind of image receiving sheet to be employed. The image density of the printed images is also considerably decreased. Further, if the ink composition is alkaline, this kind of surfactant is easily decomposed and the effect of the surfactant is diminishing during the storage of the ink composition.
Japanese Patent Publication No. 58-6752 discloses a quick-drying ink composition. By employing an ethylene oxide adduct having an acetylene bond as a surfactant in the ink composition, penetration of the ink is promoted to obtain quick-drying ink images with no image blur. However, the drying speed cannot be improved depending on the kind of dye used in the ink composition. For example, hydrophobic interaction between the surfactant and a direct dye such as “DBK168” (Trademark) inhibits the increase of drying speed.
Japanese Laid-Open Patent Application Ser. No. 56-57862 discloses an ink composition containing a strongly basic material. In the case where ink images are formed using this ink composition on an acidic paper which has been prepared using rosin as a sizing agent, the drying characteristics of the images can be improved. However, no improvement is observed in the drying characteristics of ink images when the ink images are formed on a paper manufactured using an alkyl ketene dimer or an alkenyl sulfosuccinic acid as the sizing agent. Even when acidic paper is employed, the drying characteristics of the two-color-superimposed image portion are not improved.
Japanese Laid-Open Patent Application No. 1-203483 discloses a recording ink composition comprising a polyhydric alcohol derivative and pectin. The pectin serves as a thickening agent for preventing the image blurring. However, the pectin is a nonionic material having hydroxyl group as a hydrophilic group, so that there is the shortcoming that ink ejection reliability is low when the printing operation is resumed after intermission.
Japanese Laid-Open Patent Application No.2-36276 discloses an ink composition comprising 2-propanol for improving the frequency response properties and the image fixing properties. However, this ink composition causes the problem of safety in terms of toxicity and flammability.
No pigment-containing ink composition of a penetrating type has been on the market. It has been considered that such a pigment-containing ink composition can be achieved only by using the commercially available surfactant “Surfy-nol” (Trademark), made by Air Products and Chemicals, containing a polysilanol group, and using butyl ether as a penetrating agent. However, butyl ether reacts with a pigment dispersant to form an agglomerate of pigment, and the above-mentioned surfactant “Surfy-nol” also tends to form an agglomerate of a pigment such as a functional-group-addition type carbon black.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a recording ink composition, in particular, an aqueous ink composition suitable for an ink-jet printing, with excellent penetrating properties, capable of producing ink images with excellent drying characteristics and minimum deterioration. Specifically, the first object is to provide a pigment-containing ink composition not by using “Surfy-nol” as a surfactant and butyl ether as a penetrating agent.
A second object of the present invention is to provide a method of recording images on an image-receiving medium. More specifically, the second object is to provide an ink-jet recording method with ink-ejecting reliability using a recording ink composition which is excellent from the view point of safety.
The first object can be achieved by a recording ink composition comprising a colorant insoluble and dispersible in water, water, a water soluble organic solvent, a wetting agent, 2-ethyl-1,3-hexanediol, and a surfactant selected from the group consisting of surfactants of formulas (I) to (V):
R
1
—O—(CH
2
CH
2
O)
m
CH
2
COO
−
M
+
(I)
wherein R
1
is a straight-chain or branched alkyl group having 6 to 14 carbon atoms, M
+
is a cation selected from the group consisting of alkali metal cation, quaternary ammonium cation, quaternary phosphonium cation, and alkanol amine cation, and m is an integer of 3 to 12,
wherein R
2
is a branched alkyl group having 5 to 16 carbon atoms, and M
+
is a cation selected from the group consisting of alkali metal cation, quaternary ammonium cation, quaternary phosphonium cation, and alkanol amine cation,
wherein R is a straight or branched carbon chain having 6 to 14 carbon atoms, and k is an integer of 5 to 20
R—(OCH
2
CH
2
)
n
OH (IV)
wherein R is a straight or branched carbon chain having 6 to 14 carbon atoms; and k is an integer of 5 to 20, and
wherein R′ is a carbon chain having 6 to 14 carbon atoms, and p and q are each an integer of 20 or less.
The second object can be achieved by a method of recording images on an image receiving medium, comprising the step of ejecting the above-described recording ink composition in the form of droplets from a recording head onto the image receiving medium, thereby forming images thereon.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The recording ink composition of the present invention comprises 2-ethyl-1,3-hexanediol, preferably in an amount of 0.1 to 7.0 wt. %, and at least one surfactant selected from the aforementioned surfactants of formulas (I) to (V), preferably in an amount of 0.1 to 5.0 wt. % of the total weight of the recording ink composition. As a result, the wettability of heating elements by the ink is improved, so that the ink ejection performance and the frequency response performance are stabilized. Furthermore, the problem of safety caused by the addition of 2-propanol, which would be used to achieve the ink ejection stability, can be solved by the present invention.
The surfactants (I) to (V) are as follows:
R
1
—O—(C
Arita Hitoshi
Bannai Akiko
Koyano Masayuki
Nagai Kiyofumi
Bell Mark L.
Faison Veronica F.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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