Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-01-19
2003-03-04
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031620
Reexamination Certificate
active
06527845
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an oil-based ink for ink-jet recording. More particularly, the invention relates to an oil-based ink for ink-jet recording which is excellent in ink spouting stability and storage stability without being influenced by temperature changes in printing circumstances, and causes little cockling.
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 high speed without decrease in density and without bleeding.
Currently, as printers, 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 excellent in availabilities from the viewpoint that the constitution of a recording head device therein 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 printer of this type, an oil-based type of ink in which a pigment is dispersed in a saturated hydrocarbon solvent has been recently put to practical use.
However, a pigment type of ink intrinsically has the so-called problem of low reliability as an ink-jet recording liquid, such as poor storage stability or spouting performance of the ink itself.
On the other hand, in order to increase the surface tension of ink so as to reduce clogging of a nozzle, it is more effective to contain a cycloparaffin (i.e., naphthene) in ink as a saturated hydrocarbon; however, when a printed matter as provided from ink containing a cycloparaffin is stored within a commercially available transparent document holder or the like, such a problem that the holder is swelled up to cause a cockling occurs.
Furthermore, such an attempt that an isoparaffin having a low melting point and a high boiling point is contained in ink in a large amount so as to maintain a liquid state thereof to a lower temperature and to prevent clogging of a nozzle which is caused by drying due to evaporation, has also been carried out. However, the surface tension of the resultant ink is lowered, and thus there exists a problem that a nozzle is easily clogged to cause a spouting failure.
Thus, an ink-jet recording ink in which a saturated hydrocarbon type organic solvent is used as a dispersing medium has various problems.
Accordingly, for example, as an improvement on the spouting performance of ink, a method in which an aliphatic hydrocarbon type organic solvent is used in combination with a polar solvent such as oleyl alcohol is disclosed in JP,A, 10-507487 and the like. According to this method, it is designed that the wettability of ink to a nozzle is controlled by combination use of the polar component so as to make a backward movement of ink after discharge from the front end of the nozzle to the interior thereof to prevent drying thereof.
However, when a saturated hydrocarbon solvent is used in combination with a polar solvent as in the aforesaid method, there is a problem that the storage stability of ink is still more decreased so that a pigment is precipitated during storage.
In view of the foregoing, it is an object of the invention to provide an oil-based ink for ink-jet recording which is excellent in spouting stability and storage stability over a wide temperature range from a low temperature to ordinary temperature or more, and furthermore low in cockling property.
DISCLOSURE OF THE INVENTION
Thus, the present invention provides an oil-based ink for ink-jet recording as follows:
(1) An oil-based ink for ink-jet recording comprising mainly an organic solvent, a pigment and a dispersing agent, said organic solvent comprising a saturated hydrocarbon solvent and a vegetable oil in a weight ratio of 100:(10 to 100).
(2) The oil-based ink for ink-jet recording of the above (1), wherein said saturated hydrocarbon solvent comprises both components of an isoparaffin solvent and a cycloparaffin solvent.
(3) The oil-based ink for ink-jet recording of the above (1) or (2), wherein said saturated hydrocarbon solvent comprises a liquid paraffin as a main component, said liquid paraffin having a viscosity of 20 mPa·s or less at a temperature of 25° C.
(4) The oil-based ink for ink-jet recording of the above (3), wherein said liquid paraffin is a liquid paraffin which passes at least one test selected from the group consisting of a purity test for liquid paraffin prescribed in the Japanese Pharmacopoeia, a purity test for liquid paraffin prescribed in the Japanese Standards of Food Additives, and a purity test for liquid paraffin prescribed in the Standards for Cosmetic Ingredients established in Japan.
(5) The oil-based ink for ink-jet recording of any one of the above (1) to (4), wherein said vegetable oil comprises at least one selected from the group consisting of a semidrying oil and a nondrying oil.
(6) The oil-based ink for ink-jet recording of any one of the above (1) to (5), wherein said vegetable oil comprises at least one selected from the group consisting of soybean oil, rape seed oil and olive oil.
(7) The oil-based ink for ink-jet recording of any one of the above (1) to (6), wherein said dispersing agent comprises a reaction product of an amine compound and a self condensation product of 12-hydroxystearic acid.
(8) The oil-based ink for ink-jet recording of any one of the above (1) to (7), which has a surface tension of 26 to 30 dyne/cm at a temperature of 25° C., and a contact angle to an ethylene fluoride/propylene copolymer film of 40° to 50°.
(9). The oil-based ink for ink-jet recording of any one of the above (1) to (8), which has a volume resistivity of 10
8
&OHgr;·cm or more.
Hereinafter, the present invention will be more particularly 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, and as particularly useful ones, 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 can be enumerated.
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, so as 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 suitable. Among others, as yellow, C.I. Pigment Yellow 138, 154, 180 and 185; as magenta, C.I. Pigment Red 122 and 202, and C.I. Pigment Violet 19; as cyan, C.I. Pigment Blue 15; as black, an acidic or neutral pigment of C.I. Pigment Black 7; as orange, C.I. Pigment Orange 43, 64 and 71; and as green, C.I. Pigment Green 7 and 36 are more suitable.
In the present invention, a suitable amount of a pigment is 0.5 to 30% by weight in an ink-jet recording oil-based ink, more suitably 1 to 10% by weight. When the amount of a pigment is too small, the color density of ink is lowered, while too large, printing becomes difficult due to ink viscosity or flowability.
Next, an organic solvent as used in the present invention mainly comprises a saturated hydrocarbon solvent and a vegetable oil.
As saturated hydrocarbon solvent utilized in the present invention, commercially available saturated hydrocarbon solvents which are used mainly in the existing ink-jet recording oil-based ink, for example, mixtures of isoparaffins such as Isopar E, Isopar G, Isopar H, Isopar L and Isopar M (each of the above made by Exxon Chemical Company), Shellsol (made by Shell Chemical Company), Soltrol (made by Philips Oil Co., Ltd.), Begasol (made by Mobil Petroleum Co., Inc.) and IP Solvent 2835 (made by IDEMIT
Kano Masanori
Tsuchiya Tatsurou
Armstrong Westerman & Hattori, LLP
Bell Mark L.
Faison Veronica F.
Sakata Inx Corp.
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