Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2003-02-26
2004-05-04
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031720, C106S031730
Reexamination Certificate
active
06730153
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ink-jet recording oil-based ink. More particularly, the invention relates to an ink-jet recording oil-based ink which has satisfactory pigment dispersibility both at the beginning of storage and even during long-term storage and provides excellent spouting stability without being influenced by temperature changes in printing circumstances.
BACKGROUND ART
In the field of an ink-jet recording system, both sides of apparatus and ink have been studied so that an image having clear colors can be stably printed at a higher speed without decrease in density and without bleeding.
Currently, as a printing apparatus, a system using a piezo-vibrating element, a system using a thermal head, a system utilizing an electric attraction, and the like, are known.
Among them, the system using a piezo-vibrating element is highly useful from the viewpoint that the constitution of a recording head as a device is simple, and restrictions on electric and thermal performance to ink are less as compared with the other systems. Besides, as ink which is applied to a printing apparatus of this type, an oil-based type of ink in which a pigment is dispersed in a saturated hydrocarbon medium has been recently put to practical use.
However, a pigment type of ink intrinsically has the so-called problem of low reliability as an inkjet recording liquid, such as poor storage stability of the ink itself or poor ink spouting stability.
The main stream of currently available ink-jet recording oil-based ink is one wherein an isoparaffin solvent or a cycloparaffin solvent, the typical examples of which are Isopar series and Exxsol series, made by Exxon Chemical Company, is used alone as the saturated hydrocarbon solvent. However, the available ink has poor storage stability at low temperatures or is liable to cause clogging of nozzles, and thus does not have satisfactory performance.
In order to solve these problems, for example, a method in which a saturated hydrocarbon type organic solvent is used in combination with a highly polar solvent such as oleyl alcohol is disclosed in JP10-507487A and the like. However, when a saturated hydrocarbon solvent is used in combination with a highly polar solvent, there is a problem that the storage stability of ink is still more decreased so that a pigment is precipitated during storage.
Further, an inkjet recording oil-based ink wherein a liquid paraffin is used as a saturated hydrocarbon solvent and a compound having a long-chain alkyl group and a residual group of a dibasic acid is used as a dispersing agent is disclosed in International Publication No. WO099/38925. However, this system has the problem that it has poor spouting stability at low temperatures although it has spouting stability at ordinary temperatures.
The present inventors had discovered that an ink-jet recording oil-based ink which has satisfactory storage stability both in the beginning of storage and during long periods of storage and provides excellent spouting stability over a wide temperature range from a low temperature to a high temperature could be obtained by using 10 to 100 parts by weight of a vegetable oil relative to 100 parts by weight of a saturated hydrocarbon solvent as a solvent for an ink-jet recording ink, regardless of the type of materials such as saturated hydrocarbon solvent and dispersing agent, and disclosed this ink in International Application No. PCT/JP99/07243.
It is an object of the present invention to provide an ink-jet recording oil-based ink excellent in the above-mentioned properties by using a smaller amount of a vegetable oil than that in the ink-jet recording oil-based ink disclosed in the international application.
DISCLOSURE OF INVENTION
The present inventors have intensively conducted research to provide an ink-jet recording oil-based ink excellent in the above-mentioned properties by using a smaller amount of a vegetable oil and discovered that the object is accomplished by using a reaction product of a polyamine compound and a self condensation product of 12-hydroxystearic acid as a dispersing agent and a liquid paraffin as a main component of a saturated hydrocarbon solvent, thereby completing the present invention.
Thus, the present invention provides ink-jet recording oil-based inks as follows:
(1) An ink-jet recording oil-based ink comprising a pigment; a dispersing agent comprising a reaction product of a polyamine compound and a self condensation product of 12-hydroxystearic acid; a saturated hydrocarbon solvent comprising a liquid paraffin as a main component; and a vegetable oil, the ink having a surface tension of 26 to 30 dyne/cm at 25° C. and a contact angle on a polytetrafluoroethylene plate of 40° to 50° at 25° C., and satisfying the following relationship:
W
HC
/W
VC
>10
wherein W
HC
is the weight of the saturated hydrocarbon solvent and W
VC
is the weight of the vegetable oil.
(2) The ink-jet recording oil-based ink of (1) above, wherein the dispersing agent comprises a reaction product of polyallylamine and a self condensation product of 12-hydroxystearic acid.
(3) The ink-jet recording oil-based ink of (1) or (2) above, wherein the content of the liquid paraffin in the saturated hydrocarbon solvent is 70% by weight or more.
(4) The ink-jet recording oil-based ink of any one of (1) to (3) above, wherein the liquid paraffin contains 20% by weight or more of a monocyclic cycloparaffin, and has a surface tension of 26 to 30 dyne/cm at 25° C. and a viscosity of 20 mPa·s or less at 25° C.
(5) The ink-jet recording oil-based ink of any one of (1) to (4) above, wherein the saturated hydrocarbon solvent further contains an isoparaffin.
(6) The ink-jet recording oil-based ink of any one of (1) to (5) above, which further contains a petroleum resin and/or a rosin-modified maleic resin.
(7) The ink-jet recording oil-based ink of any one of (1) to (6) above, which has a solidifying point of −10° C. or less.
(8) The ink-jet recording oil-based ink of any one of (1) to (7) above, which has a volume resistivity of 10
8
&OHgr;·cm or more.
Hereinafter, the present invention will be more specifically explained.
First, as pigments used in the present invention, various inorganic or organic pigments which can be used in a common ink-jet recording ink can be used. Examples of particularly useful ones include C.I. Pigment Yellow 93, 95, 109, 110, 120, 128, 138, 139, 151, 154, 155, 173, 180, 185 and 193; C.I. Pigment Orange 34, 36, 43, 61, 63 and 71; C.I. Pigment Red 122, 202, and a solid solution of C.I. Pigment Red 122 and 202; C.I. Pigment Blue 15; C.I. Pigment Violet 19, 23 and 33; C.I. Pigment Black 7; and the like.
In an ink-jet recording system, the four colors of yellow, magenta, cyan and black are basically used, and recently the six colors in which orange and green are added thereto are used, and furthermore the eight colors in which light-magenta and light-blue are added thereto are used to form a color image, and the like.
In order to provide these hues, pigments which are excellent in weather resistance among the above-mentioned ones are preferable. Among others, C.I. Pigment Yellow 138, 154, 180 and 185 for yellow; C.I. Pigment Red 122 and 202, and C.I. Pigment Violet 19 for magenta; C.I. Pigment Blue 15 for cyan; an acidic or neutral C.I. Pigment Black 7 for black; C.I. Pigment Orange 43, 64 and 71 for orange; and C.I. Pigment Green 7 and 36 for green are more preferable.
In the present invention, a preferable amount of a pigment is 0.5 to 30% by weight, more preferably 1 to 10% by weight, in an ink-jet recording ink. When the amount of a pigment is too small, the color density of ink is lowered, while too large, printing becomes difficult due to the viscosity or flowability of ink.
In the present invention, as dispersing agents which are used to disperse a pigment into an organic solvent, reaction products of a polyamine compound and a self condensation product of 12-hydroxystearic acid can be used. Specific examples thereof include a reaction product of a polyallylamine and a self condensatio
Kano Masanori
Tsuchiya Tatsurou
Armstrong Kratz Quintos Hanson & Brooks, LLP
Faison Veronica F.
Koslow C. Melissa
Sakata Inx Corp.
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