JP3254996B2 - Aqueous ink composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording system, and more particularly to an aqueous ink composition capable of obtaining a printed matter having high robustness and a method for producing the same.

2. Description of the Related Art Conventional ink jet recording systems generate and eject ink droplets by an electrostatic suction system, a pneumatic feeding system, a system utilizing electric deformation of a piezoelectric element, a system utilizing pressure during heating and bubbling, and the like. Then, recording is performed by attaching the ink droplets to a recording sheet. The mainstream of the ink used in such a recording method is an aqueous ink composition containing an aqueous solution in which a water-soluble dye is dissolved, and a humectant such as glycol and a penetration enhancer such as alcohol and pyrrolidone dissolved therein. .

However, printing with an aqueous ink composition using a water-soluble dye inherently has a possibility of dissolving from a printed portion due to water solubility when contacted with water. Further, it is generally said that a water-soluble dye has poor light resistance as compared with a water-insoluble colorant because it has a water-soluble group such as a carboxylic acid group, a sulfonic acid group, and an amine group.

[0004] Various aqueous ink compositions and methods for producing the same have been proposed to solve these problems. For example, ink compositions using a dye that is insoluble in water but soluble in a water-soluble organic solvent are disclosed in JP-A-57-59970, JP-A-61-53372, and JP-A-63-162773. ing.

An aqueous ink composition using a disperse dye is proposed in JP-A-59-4665, and an aqueous ink composition in which a face insoluble in water is dispersed is disclosed in JP-A-56-147859. .

However, it can be said that these aqueous ink compositions still have room for improvement. In particular, when a colorant that is essentially insoluble or hardly soluble in water is used to improve the water resistance of the printed matter, it has been observed that the nozzles of the recording head tend to be clogged. This is due to the fact that it is not easy to stably present a water-insoluble or sparingly soluble colorant in the aqueous ink composition, and that a precipitate consisting of the sparingly soluble colorant is formed at the nozzle tip of the recording head. It was considered.

[0007]

SUMMARY OF THE INVENTION The present invention realizes a more excellent water resistance of a printed matter, while containing a coloring agent which is essentially insoluble or hardly soluble in water, and which hardly causes clogging of a recording head. It is an object of the present invention to provide an ink composition and a method for producing the same.

[0008] The present inventors have recently proposed that by adding a specific component to an ink composition, an ink composition containing a colorant that is essentially insoluble or hardly soluble in water can be obtained stably. Was found. The present invention is based on this finding.

That is, the ink composition according to the present invention comprises:
A poorly water-soluble or water-insoluble colorant, solid at room temperature, soluble in water, its heated melt or aqueous solution can dissolve the colorant, and can form a solid solution with the colorant It comprises at least a solid solvent and water.

The method for producing an ink composition according to the present invention comprises a step of melting a solid solvent by heating it to a temperature equal to or higher than its melting point and dissolving a colorant therein to obtain a colorant solution; Preparing a concentrated aqueous solution close to that, dissolving the colorant in the solution to obtain a colorant solution, mixing the colorant solution with an aqueous solution containing water or a water-soluble organic solvent, and forming the colorant particles therein. And a step of optionally adding an optional component for forming an ink composition to the dispersion.

Further, the ink composition according to the present invention can be obtained by the following production method, which comprises heating a solid solvent to a temperature higher than its melting point, melting the solid solvent, dissolving the colorant therein, and dissolving the colorant. Obtaining a solution, cooling the colorant solution to obtain a colorant solid solution comprising a colorant and a solid solvent,
Alternatively, a solid solvent and a volatile organic solvent are mixed, a colorant is dissolved therein to obtain a colorant solution, and the volatile organic solvent is removed by evaporation from the colorant solution to form a colorant solid solution. Obtaining, dissolving the colorant solid solution in water or an aqueous solution containing a water-soluble organic solvent to obtain a dispersion in which the colorant particles are dispersed, and forming an ink composition in the dispersion And optionally adding an optional component.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The aqueous ink composition according to the present invention is an aqueous ink composition comprising at least a hardly water-soluble or water-insoluble colorant, a solid solvent and water as described above.

Colorant The colorant used in the present invention is a poorly water-soluble or water-insoluble dye or pigment. Here, poorly water-soluble or water-insoluble means that the solubility in water at 20 ° C. is about 1 wt% or less, more preferably 0.1 wt% or less. Preferred examples thereof include oil-soluble dyes (Oil Dyes) and disperse dyes (Disperse Dyes).
), Or coloring agents classified as organic solvent-soluble pigments. By using these coloring agents, it is possible to obtain the fastness of the printed matter, particularly good water fastness and light fastness. These colorants may be used alone or in combination of two or more.

In the ink composition according to the present invention, the colorant is preferably present in a dispersed state. That is, the colorant is present as fine particles in the ink composition according to the present invention. In practice, it is not easy to demarcate whether a substance is dissolved or dispersed, but in a preferred embodiment of the present invention the presence of the colorant can be confirmed at least as particles. The color development of printed matter printed using the ink composition according to the present invention mainly depends on the colorant particles. According to a preferred embodiment of the present invention, the colorant particles have an average particle diameter of 10 nm to 10 nm.
μm, more preferably 25 nm
About 500 nm. Further, according to a preferred embodiment of the present invention, it is preferable to adjust the number of particles having a particle diameter of more than 20 μm to less than 1 ppm from the viewpoint of preventing clogging.

On the other hand, according to a preferred embodiment of the present invention,
The ink composition according to the present invention contains substantially no dispersant. It is believed to be surprising to those skilled in the art that the colorant particles can be dispersed in the ink composition without substantially using a dispersant. Here, "substantially contains no dispersant" means that the ink composition does not contain any dispersant commonly used in the ink composition in the art or contains the dispersant at a concentration lower than its critical micelle concentration (CMC). Means that.
Generally, the critical micelle concentration is 0.01 to 3.6 depending on the dispersant.
Take the value of about wt% (New Edition Surfactant Handbook 1
19-127 (1991) Yoshida, Shindo, Ogaki, Nakayama,
Optical Books Co., Ltd.). Therefore, in a preferred embodiment of the present invention, it is preferable to include the dispersant at a concentration below these values.

The colorant used in the present invention needs to be soluble in a solid solvent, as described later.

The amount of the coloring agent to be added is preferably 0.5 to 20% by weight, more preferably about 1 to 10% by weight, based on the ink composition.

Preferred specific examples of the oil-soluble dye include the following.

As the yellow type, oil yellow 105 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), oil yellow 107 (trade name, manufactured by Orient Chemical Industry Co., Ltd.),
Oil Yellow 129 (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Yellow 29), Oil Yellow 3G (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Yellow 16), Oil Yellow GGS ( Product name, manufactured by Orient Chemical Co., Ltd.
C. I. Solvent Yellow 56), Varifast Yellow 1101 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Yellow 1105 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Yellow 41
20 (trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I.
I. Solvent Yellow 82), Oleosol Brilliant Yellow 5G (trade name, manufactured by Taoka Chemical Industry Co., Ltd.)
C. I. Solvent Yellow 150), Oleosol Fast Yellow 2G (trade name, manufactured by Taoka Chemical Industry Co., Ltd.)
C. I. Solvent Yellow 21), Oleosol Fast Yellow GCN (trade name, manufactured by Taoka Chemical Industry Co., Ltd.)
C. I. Solvent Yellow 151) and Eizenzot Yellow 1 (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.)
I. Solvent Yellow 56), Eizenzot Yellow 3 (trade name, CI Solvent Yellow 16 manufactured by Hodogaya Chemical Co., Ltd.), Eizenzot Yellow 6
(Trade name, CI Solvent Yellow 33, manufactured by Hodogaya Chemical Co., Ltd.), Aizen Spiron Yellow GRL
H (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Aizen Spiron Yellow 3RH (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Orazole Yellow 2GLN (trade name, manufactured by Ciba Geigy Corporation, CI Solvent Yellow) 88), Orazole Yellow 2RLN (trade name, manufactured by Ciba-Geigy,
C. I. Solvent Yellow 89), Orazole Yellow 3R (trade name, manufactured by Ciba Geigy, CI Solvent Yellow 25), Oraset Yellow GHS (trade name, manufactured by Ciba Geigy, CI Solvent Yellow 1)
63), Philamid Yellow R (trade name, manufactured by Ciba Geigy, CI Solvent Yellow 21) and the like.

Oil red 5B (trade name, CI Solvent Red 27, manufactured by Orient Chemical Industry Co., Ltd.), Oil Red RR (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Red) 2
4), Varifast Red 1306 (trade name, manufactured by Orient Chemical Co., Ltd., CI Solvent Red 10)
9), Varifast Red 1355 (trade name, manufactured by Orient Chemical Industries, Ltd.), Varifast Red 2303
(Trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Red 3304 (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Red 8), Varifast Red 3306 (trade name, manufactured by Orient Chemical Industry Co., Ltd.) ), Varifast Red 3320 (trade name, manufactured by Orient Chemical Industries, Ltd., CI Solvent Red 13)
2), Oil Pink 312 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Pink 2310N (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Red 218), Oleosol Fast Red BL (trade name) CI Solvent Red 132, manufactured by Taoka Chemical Industry Co., Ltd., Oleosol Fast Red RL (brand name, CI Solvent Red 122, manufactured by Taoka Chemical Industry Co., Ltd.), Oleosol Fast Red GL (brand name) ,
Made by Taoka Chemical Industry Co., Ltd., C.I. I. Solvent Red 1
32), Oleosol Red 2G (trade name, manufactured by Taoka Chemical Industry Co., Ltd.), Oleosol Fast Pink FB (trade name, manufactured by Taoka Chemical Industry Co., Ltd., CI Solvent Red 218), Eizen Zot Red 1 (trade name) Name, CI Solvent Red 2 manufactured by Hodogaya Chemical Industry Co., Ltd.
4), Eizen Zot Red 2 (trade name, CI Solvent Red 27, manufactured by Hodogaya Chemical Industry Co., Ltd.), Eizen Zot Red 3 (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd., CI Solvent Red) 18), Aizen Spiron Red BEH (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Aizen Spiron Red GEH (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Aizen Spiron Red C-G
H (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Eizen Zott Pink 1 (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.
C. I. Solvent Red 49), Orazole Red 3
GL (trade name, manufactured by Ciba Geigy, CI Solvent Red 130), Orazole Red 2BL (trade name, manufactured by Ciba Geigy, CI Solvent Red 132),
Orazole Red G (trade name, manufactured by Ciba Geigy, C.I.
I. Solvent Red 125), Orazole Red B
(Trade name, Ciba Geigy, CI Solvent Red 7), Philamid Red GR (trade name, Ciba Geigy, CI Solvent Red 225), Filester Red GA (trade name, Ciba Geigy, C.I.
Solvent Red 135), Filester Red RBA
(Trade name, CI Solvent Red 230, manufactured by Ciba Geigy), and Orazole Pink 5BLG (trade name, CI Solvent Red 127, manufactured by Ciba Geigy).

Oil blue 613 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), oil blue 2
N (trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I.
Solvent Blue 35), Oil Blue BOS (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Blue 1603 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Blue 1605 (trade name, manufactured by Orient Chemical Industry Co., Ltd.) , CI Solvent Blue 3
8), Varifast Blue 1607 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Blue 2606
(Trade name, CI Solvent Blue 70, manufactured by Orient Chemical Co., Ltd.), Varifast Blue 2610
(Trade name, manufactured by Orient Chemical Industry Co., Ltd.), Oleosol Fast Blue ELN (trade name, manufactured by Taoka Chemical Industry Co., Ltd., CI Solvent Blue 70), Oleosol Fast Blue GL (trade name, Taoka Chemical Industry Co., Ltd.) Made by company,
C. I. Solvent Blue 70), Oleosol Blue G
(Trade name, manufactured by Taoka Chemical Industry Co., Ltd.), Eizenzot Blue 1 (trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I.
I. Solvent Blue 25), Eizenzot Blue 2
(Trade name, CI Solvent Blue 14 manufactured by Hodogaya Chemical Industry Co., Ltd.), Eizen Spiron Blue GNH (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Eizen Spiron Blue 2BNH (trade name, Hodogaya Chemical Industry Co., Ltd.) Co., Ltd.), Aizen Spiron Blue BPNH (trade name, manufactured by Hodogaya Chemical Co., Ltd.), Orazole Blue GN (trade name, manufactured by Ciba Geigy, CI Solvent Blue 6)
7), Orazole Blue 2GLN (trade name, manufactured by Ciba Geigy, CI Solvent Blue 48), Oraset Blue 2R (trade name, manufactured by Ciba Geigy, CI Solvent Blue 68), Philamid Blue R ( Product name,
Ciba-Geigy, C.I. I. Solvent Blue 13
2), Filester Blue GN (trade name, manufactured by Ciba Geigy, CI Solvent Blue 67) and the like.

Examples of the black type include oil black HBB (trade name, CI Solvent Black 3 manufactured by Orient Chemical Industry Co., Ltd.) and oil black 860 (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Black) 3), Oil Black BS (trade name, manufactured by Orient Chemical Co., Ltd., CI Solvent Black 7),
Varifast Black 1802 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Varifast Black 1807
Varifast Black 3804 (trade name, manufactured by Orient Chemical Co., Ltd., CI Solvent Black 34), Varifast Black 3810 (trade name, manufactured by Orient Chemical Co., Ltd.) , CI Solvent Black 29), Varifast Black 3820 (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Black 27), Varifast Black 3830 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), Spirit Black SB (product name,
C. Orient Chemical Co., Ltd. I. Solvent Black 5), Spirit Black SSBB (trade name, CI Solvent Black 5 manufactured by Orient Chemical Industry Co., Ltd.), Spirit Black AB (trade name, manufactured by Orient Chemical Industry Co., Ltd., CI Solvent Black 5) , Nigrosine base (trade name, manufactured by Orient Chemical Co., Ltd., CI Solvent Black 7), Oleosol Fast Black RL (trade name, manufactured by Taoka Chemical Industry Co., Ltd., CI Solvent Black 27), Oleosol Black AR (trade name, manufactured by Taoka Chemical Industry Co., Ltd.),
Aizen Zotto Black 6 (trade name, CI Solvent Black 3 manufactured by Hodogaya Chemical Industry Co., Ltd.), Aizen Zotto Black 8 (trade name, CI Solvent Black 7 manufactured by Hodogaya Chemical Industry Co., Ltd.), Aizen Spiron Black MH (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Aizen Spiron Black GMH (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Orazol Black CN (trade name, manufactured by Ciba Geigy Co., Oil-soluble dyes such as CI Solvent Black 28) and Orazole Black RLI (trade name, manufactured by Ciba Geigy, CI Solvent Black 29).

The disperse dyes include Oraset Yellow 8GF (trade name, CI Disperse Yellow 82, manufactured by Ciba Geigy) and Eizenzot Yellow 5
(Trade name, CI Disperse Yellow 3 manufactured by Hodogaya Chemical Industry Co., Ltd.), Sumiplus Yellow HLR (trade name, CI Disperse Yellow 54 manufactured by Sumitomo Chemical Co., Ltd.), Kayaset Yellow AG (trade name, manufactured by Nippon Kayaku Co., Ltd., CI Disperse Yellow 5)
4), Sumipla Red B-2 (trade name, CI Disperse Red 191 manufactured by Sumitomo Chemical Co., Ltd.), Kaya Set Red B (trade name, manufactured by Nippon Kayaku Co., Ltd., C.I.
I. Disperse Red 60) and Filester Violet BA (trade name, manufactured by Ciba Geigy, CI Disperse Violet 57).

Further, pigments which are easily soluble in organic solvents include:
Hansa Yellow G (trade name, manufactured by Daido Kasei Co., Ltd., C.I.
I. Pigment Yellow 1), Hansa Yellow GR (trade name, manufactured by Daido Kasei Co., Ltd., CI Pigment Yellow 2), Hansa Yellow 10G (trade name, manufactured by Daido Kasei Co., Ltd., CI Pigment Yellow 3), fillet Star Yellow RNB (trade name, manufactured by Ciba Geigy, C.I.
I. Pigment Yellow 147), Kayaset Yellow E-AR (trade name, CI Pigment Yellow 147, manufactured by Nippon Kayaku Co., Ltd.), Kayaset Yellow E-L2
R (trade name, manufactured by Nippon Kayaku Co., Ltd., CI Pigment Yellow 142), permanent red 4R (trade name,
Daido Kasei Co., Ltd., C.I. I. Pigment Red 3),
Poppy Red (trade name, manufactured by Dainichi Seika Industry Co., Ltd., C.I.
I. Pigment Red 17), Brilliant Fast Scallet (trade name, manufactured by Daido Kasei Co., Ltd., CI Pigment Red 22), 3040 Red (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd., CI Pigment Red 2)
3), Fast Pin Crake 6G (trade name, Noma Chemical Industry Co., Ltd., CI Pigment Red 81), Eosin Lake (trade name, Arimoto Chemical Co., Ltd., CI Pigment Red 90), Kayaset Red E-CG (trade name, manufactured by Nippon Kayaku Co., Ltd., CI Pigment Red 250), Kayaset Red E-BG (trade name, manufactured by Nippon Kayaku Co., Ltd., CI Pigment Red 249), Carmine BS (trade name, manufactured by Dainippon Ink and Chemicals, Inc., CI Pigment Red 114) and Oraset Pink RF (trade name, manufactured by Ciba Geigy Corporation, CI Pigment Red 181).

Solid Solvent The solid solvent used in the present invention is a solid which is solid at room temperature and soluble in water, and its heated melt or aqueous solution is capable of dissolving the colorant, and forming a solid solution with the colorant. What can be formed.

The solid solvent is preferably solid at room temperature, but more preferably has a melting point of 30 ° C. or higher. Further, being soluble in water means that the solubility in water at 20 ° C. is preferably 15 wt% or more, more preferably 30 wt%.
t% or more.

In the present invention, the solid solvent has a property of dissolving the above-mentioned coloring agent when it is made into a heated melt or an aqueous solution. Here, that the heated melt dissolves the solid solvent means that the solubility of the colorant in the heated melt is preferably 1% by weight or more, more preferably 5w%.
t% or more.

In the present invention, forming a solid solution between the solid solvent and the colorant as described above means forming a mixed phase in which the colorant is dissolved in the crystal phase of the solid solvent.

By combining a solid solvent having such properties with the above-mentioned colorant, clogging of the nozzles of the recording head can be effectively prevented. The following theory is only an assumption, and it is not desired that the present invention be interpreted in a limited manner. However, the reason why clogging is effectively prevented is considered as follows. That is, when the ink composition according to the present invention dries at the tip of the nozzle to form a precipitate, the precipitate is mainly composed of a solid solution of a solid solvent and a colorant. The formation of a precipitate consisting essentially of only a slightly water-soluble or water-insoluble colorant is suppressed. This solid solution is easily dissolved and collapsed when the supply of the ink composition to the nozzle is started again. As a result, deposits that have blocked the nozzle are easily removed, and clogging of the nozzle is easily eliminated. On the other hand, in the ink composition according to the present invention, since the colorant is preferably present in the form of particles instead of being dissolved, when the ink composition is printed on a recording medium such as paper, the colorant is colored. The agent particles stop on the surface of the recording medium. However, since this solid solvent is dissolved in other solvent components such as water, it permeates into the recording medium together with these solvent components. As a result, the print formed on the surface of the recording medium consists essentially of only a slightly water-soluble or water-insoluble colorant. The amount of the solid solvent during printing becomes small, and its presence is such that the water resistance of the printing is not affected. Therefore, the water resistance of the poorly water-soluble or water-insoluble colorant is favorably maintained.

The addition amount of the solid solvent is preferably in the range of about 1 to 50% by weight, more preferably about 2.5 to 25% by weight, based on the whole ink composition.

According to a preferred embodiment of the present invention, preferred specific examples of the solid solvent include a carboxylic acid derivative, a urea derivative, and an alkylene carbonate.

Preferred specific examples of the carboxylic acid derivative include a compound having a melting point of 30 ° C. or higher and represented by the following formula (I).

R ¹ -CO-NH-R ² (I) (wherein R ¹ is an alkyl group which may be substituted, an alkoxy group which may be substituted, or 5 Or a 6-membered heteroaromatic ring,
² represents H or an alkyl group which may be substituted, or R ¹ and R ² together represent an alkylene group having 3 to 8 carbon atoms, and the alkylene group may be substituted In the formula (I), the alkyl group represented by R ¹ may be linear or branched, and is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms. is there. One or more hydrogen atoms of the alkyl group may be substituted. Preferred examples of the substituent include a hydroxyl group and an amino group.

The alkoxy group represented by R ¹ may be linear or branched, and is preferably an alkoxy group having 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms. One or more hydrogen atoms of the alkoxy group may be substituted. Preferred examples of the substituent include a hydroxyl group and an amino group.

Further, 5 containing one nitrogen represented by R ¹
Or, examples of the 6-membered heteroaromatic ring include pyrrolyl and pyridyl.

In the formula (I), the alkyl group represented by R ² may be linear or branched.
Preferably C1-8, more preferably C1-6
Is an alkyl group. One or more hydrogen atoms of the alkyl group may be substituted. Preferred examples of the substituent include a hydroxyl group and an amino group.

Further, R ¹ and R ² may together represent an alkylene group having 3 to 8 carbon atoms. One or more hydrogen atoms of the alkylene group may be substituted, and preferred examples of the substituent include a hydroxyl group and an amino group.

Preferred specific examples of the carboxylic acid derivative include lactamide (melting point 49-51 ° C.), acetamide (melting point 70 ° C.), N-methylacetamide (melting point 31
C), methyl carbamate (melting point 54 ° C), ethyl carbamate (melting point 48 ° C), ε-caprolactam (melting point 6
9 ° C.), δ-valerolactam (melting point 37 ° C.), nicotinamide (melting point 130 ° C.), glycolamide (melting point 11
6 ° C.), α-amino-ε-caprolactam (melting point 73
° C).

Preferred specific examples of the urea derivative as the solid solvent include a compound represented by the following formula (II).

R ³ —NH—CO—NH—R ⁴ (II) (wherein R ³ and R ⁴ each independently represent H or an optionally substituted alkyl group, or R ³ And R ⁴ together represent an alkylene group having 2 to 6 carbon atoms. Preferred specific examples of the compound of the formula (II) include dimethylol urea (melting point 138 ° C.), ethylene urea (melting point 131
° C) and monomethylol urea (melting point 110 ° C).

Preferred specific examples of the alkylene carbonate as the solid solvent include compounds represented by the following formula (III).

[0042] In ^{R 5 -O-CO-O-} R 6 (III) ( the above formulas, R ⁵ and R ⁶ are independently or each represent H or optionally substituted alkyl group, or R ⁵ And R ⁶ together represent an alkylene group having 2 to 6 carbon atoms) Preferred specific examples of the compound of the formula (III) include ethylene carbonate (melting point: 36 ° C).

Particularly, lactamide, acetamide, N-methylacetamide, methyl carbamate, ethyl carbamate, ε-caprolactam, δ-valerolactam, nicotinamide, dimethylol urea, ethylene urea, ethylene carbonate, glycol amide, α-amino -Ε-Caprolactam is preferred because of its high compatibility with the oil-soluble dyes, disperse dyes, and pigments readily soluble in solvents.

Water and Other Components The water used in the ink composition according to the present invention is preferably pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, or distilled water, or ultrapure water. In order to prevent the generation of mold and bacteria when the ink is stored for a long period of time, it is preferable to use water sterilized by ultraviolet irradiation, addition of hydrogen peroxide, or the like.

The ink composition according to the present invention can be used for water-based ink compositions, especially ink-jet recording ink compositions, such as penetration enhancement, viscosity adjustment, surface tension adjustment, hydrotropy adjustment, moisture retention, pH adjustment, Anti-mold,
Auxiliary agents for chelate formation, preservation, rust prevention and the like can be included as necessary.

Specifically, ethanol, isopropanol, butanol, pentanol, 2-pyrrolidone, N-
Methylpyrrolidone and the like can be added mainly as a penetration enhancer. According to a preferred embodiment of the present invention,
The penetration rate of the ink composition is preferably 20 seconds or less at a printing ink amount of 2.5 mg / cm ² with or without the addition of these penetration enhancers.

Further, a water-soluble resin such as polyvinyl alcohol, polyvinylpyrrolidone, casein, polyimine, carboxymethylcellulose and gum arabic can be added mainly as a viscosity modifier. According to a preferred embodiment of the present invention, the viscosity of the ink composition is 50 c at 5 ° C. with or without these viscosity modifiers.
It is preferably at most Ps.

Further, alcohols such as diethanolamine, triethanolamine, glycerin and diethylene glycol, nonionics, cations, anions and amphoteric surfactants can be added mainly as a surface tension modifier. According to a preferred embodiment of the present invention, the surface tension of the ink composition is preferably in the range of 25 to 70 dyn / cm with or without the use of these surface tension modifiers. When a surfactant is added to the aqueous ink composition according to the present invention for adjusting the surface tension, the surfactant is used to prevent the water resistance of the reprinted material from being lowered by solubilizing the coloring agent with water by the surfactant. It is preferable that the critical micelle concentration of the surfactant is not reached.

Further, urea, alkyl urea, propylene urea and thiourea can be added mainly as a hydrotrope. It is preferable to add these in the range of 0.5 to 20% by weight based on the ink composition.

Further, polyols such as glycerin, diethylene glycol, maltitol, sorbitol,
It can be added mainly as a humectant. It is preferable to add these in the range of 1 to 25% by weight to the ink composition.

Further, when the ink composition is used in an ink jet recording system for charging the ink, a specific resistance adjusting agent selected from inorganic salts such as lithium chloride, sodium chloride and ammonium chloride can be added to the ink composition.

Production of Ink Composition The ink composition according to the present invention can be preferably produced by the following four methods. According to these methods, the ink composition in which the colorant is dispersed is ball milled,
It has an advantage that it can be easily obtained without performing a dispersion operation such as a sand mill, a roll mill, and a sand grinder.

Method (A) In the method (A) according to the first aspect of the present invention, first, a solid solvent is heated to a temperature equal to or higher than its melting point and melted, and a colorant is dissolved therein to prepare a colorant solution. . While the colorant solution is being heated and melted, water or an aqueous solution to which a water-soluble compound is added in the above-mentioned auxiliary agent to be added as necessary is added, mixed, and the colorant is coagulated and precipitated to form a colorant. Prepare a dispersion. As the water-soluble auxiliary agent, it is possible to use water-soluble organic solvents such as ethanol, isopropanol, butanol, and pentanol, alcohols such as 2-pyrrolidone, N-methylpyrrolidone, diethanolamine, triethanolamine, glycerin, and diethylene glycol. it can. The remaining auxiliaries are further added to this colorant dispersion at room temperature or under heating and mixed to obtain the aqueous ink composition according to the present invention.

In the present method, a colorant dispersion can be obtained only by mixing the above-mentioned colorant solution with water or an aqueous solution of an auxiliary agent. The following theory is merely an assumption, and it is not intended that the present invention be interpreted in a limited manner. The reason why the colorant dispersion is obtained is considered as follows. In the colorant solution, the colorant is dissolved molecularly. The solubility of the colorant decreases with the addition of water or aqueous auxiliaries to the colorant solution. Accordingly, the colorant shifts from a dissolved state to an insoluble state, and nuclei of the colorant ultrafine particles are generated. When the solubility further decreases, the colorant sequentially precipitates on the surface of the nucleus,
Growing into colorant particles. At this time, the colorant has a minimum particle diameter of about 25 nm and is considered to precipitate in a preferable state of a monodisperse state in which the particles do not aggregate.

Method (B) The ink composition according to the present invention may be produced by the following method which is a modification of the above method (A).

In the present method, a saturated aqueous solution of a solid solvent or a concentrated aqueous solution close to the saturated aqueous solution is prepared, and the colorant is dissolved therein to prepare a colorant solution. To this colorant solution, water or an aqueous solution to which the above-mentioned water-soluble auxiliary agent to be added as necessary is added, mixed, and the colorant is coagulated and precipitated to prepare a colorant dispersion. The remaining auxiliaries are further added to this colorant dispersion and mixed to obtain the aqueous ink composition according to the present invention. Thereafter, an ink composition can be obtained in the same manner as in the method (A).

Also in this method, a good colorant dispersion can be obtained. Regarding the reason, the above method (A)
It is considered almost the same.

Method (C) Further, the ink composition according to the present invention may be produced by the following method. In this method, first, a solid solvent is heated to a melting point or higher to form a melt, and a colorant is dissolved in the melt to prepare a colorant solution. The colorant solution is cooled to obtain a colorant solid solution containing the colorant and a solid solvent. Subsequently, the colorant solid solution is dissolved in water or an aqueous solution to which a water-soluble compound has been added in the above-mentioned auxiliary agent to be added as necessary. Here, this solid solution is dissolved in water or an aqueous solution of an auxiliary agent, but what is actually dissolved in water or the aqueous solution is a solid solvent component in the solid solution, and a colorant component in the solid solution is water or It is considered that they are dispersed as particles without being dissolved in the aqueous solution. As a result, a colorant dispersion can be obtained. Thereafter, the remaining auxiliaries are further added to this colorant dispersion at room temperature or under heating and mixed to obtain the aqueous ink composition according to the present invention.

Method (D) The ink composition according to the present invention may be produced by the following method which is a modification of the above method (C). In this method, a solid solvent and a volatile organic solvent are mixed, and a colorant is dissolved therein to prepare a colorant solution. Next, the volatile organic solvent was removed from the colorant solution by evaporation,
A colorant solid solution is prepared. The volatile organic solvent preferably dissolves the colorant and has a boiling point lower than that of the solid solvent. Specific examples thereof include alcohols such as methanol, ethanol and propanol,
Examples include ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene, esters such as methyl acetate and ethyl acetate, nitrogen compounds such as acetonitrile and triethylamine, and sulfur compounds such as thiophene. By dissolving this solid solution in water or an auxiliary aqueous solution in the same manner as in the above method (C), a colorant dispersion liquid and further an ink composition can be obtained.

[0060]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

EXAMPLE 1 150 g of lactamide was dissolved as a solid solvent by heating to 60 ° C., and Kayaset Yellow AG, a yellow disperse dye, was dissolved.
50 g of CI Disperse Yellow 54 (manufactured by Nippon Kayaku Co., Ltd.) was added with stirring and dissolved to prepare a colorant solution. Ethylene urea 1 as hydrotropic agent
800 g of the aqueous solution to which 2.5 wt% was added was heated to 60 ° C., and the colorant solution kept heated at 60 ° C. was added over 4 hours with stirring to prepare a colorant dispersion. After cooling the dispersion to room temperature, pentanol 5
g, 50 g of glycerin as a humectant was added with stirring, and further filtered through a filter having a pore size of 20 μm to prepare a yellow ink.

Examples 2 to 7 The same procedures as in Example 1 were carried out except that the amounts of the colorants and their additives, the amounts of the solid solvents and the auxiliaries were changed to those shown in Tables 1 and 2. An aqueous ink composition was prepared according to the procedure.

Example 8 165 g of ε-caprolactam as a solid solvent and 55 g of pure water were mixed and dissolved to prepare a 75 wt% ε-caprolactam aqueous solution. This is Eisenzod Pink 1, a red oil-soluble dye (manufactured by Hodogaya Chemical Co., Ltd.
C. I. Solvent Red 49) (35 g) was added with stirring, and dissolved by heating to prepare a colorant solution. After the colorant solution was cooled to room temperature, it was added to 800 g of water to which 12.5 wt% of urea was added as a hydrotropic agent over 4 hours with stirring to prepare a colorant dispersion. Further, 20 g of ethanol as a permeation enhancer and 30 g of multitoll as a humectant were added to the dispersion, and the mixture was filtered through a filter having a pore size of 20 μm to prepare a red ink.

Examples 9 to 11 The same procedures as in Example 8 were carried out except that the amounts of the colorants and their additives, the amounts of the solid solvents and the auxiliaries were changed to those shown in Tables 1 and 2. An aqueous ink composition was prepared according to the procedure.

Example 12 A mixed solvent was prepared by mixing 100 g of methyl carbamate as a solid solvent and 50 g of N-methylpyrrolidone as a penetration enhancer, and a blue disperse dye, Filester Violet BA ( Product name, Ciba-Geigy,
C. I. 30 g of Disverse Violet 57) was added with stirring and dissolved to prepare a colorant solution. This solution is used as a hydrotropic agent in propylene urea 10 w
It was added to 800 g of water to which t% had been added over 2 hours with stirring to prepare a colorant dispersion. Further, 30 g of sorbitol as a humectant was added to the dispersion, and the dispersion was filtered through a filter having a pore size of 20 μm to prepare a blue ink.

Examples 13 to 15 The same procedures as in Example 11 were carried out except that the amounts of the colorants and their addition, the amount of the solid solvent and the amount of the auxiliaries were changed to those shown in Tables 1 and 2. An aqueous ink composition was prepared according to the procedure.

Example 16 150 g of ε-caprolactam as a solid solvent was added at 80 ° C.
And 50 g of Kayaset Yellow AG (trade name, manufactured by Nippon Kayaku Co., Ltd., CI Disperse Yellow 54), which is a yellow disperse dyestuff, is heated and melted, and further cooled to room temperature The solution was cooled to prepare a colorant solid solution.
The colorant solid solution was added to 800 g of water to which 12.5 wt% of ethylene urea was added as a hydrotropic agent, and the mixture was stirred for 10 hours to prepare a colorant dispersion. 20 g of ethanol as a penetration enhancer and 50 g of glycerin as a humectant were added with stirring, and the dispersion was filtered with a filter having a pore size of 20 μm to prepare a yellow ink.

Examples 17 to 22 The same procedures as in Example 16 were carried out except that the amounts of the colorants and their additives, the amounts of the solid solvents and the auxiliaries were changed to those shown in Tables 1 and 2. An aqueous ink composition was prepared according to the procedure.

Example 23 A mixed solvent was prepared by mixing and dissolving 150 g of δ-valerolactam as a solid solvent and 100 g of acetone. 25 g of Spirit Black AB (trade name, CI Solvent Black 5 manufactured by Orient Chemical Industry Co., Ltd.), which is a black oil-soluble dye, is added and dissolved, and further heated to remove acetone to form a colorant solid solution. Prepared. 800 g of water to which 12.5 wt% of urea is added as a hydrotropic agent
This colorant solid solution was added thereto and stirred for 15 hours to prepare a colorant dispersion. Pentanol 5g as penetration enhancer
And 30 g of maltitol as a humectant were added with stirring, and the dispersion was filtered through a filter having a pore size of 20 μm to prepare a black ink.

Examples 24 to 26 The same procedures as in Example 23 were carried out except that the amounts of the coloring agent, the amount thereof added, the amount of the solid solvent and the amount of the auxiliary agent were changed to those shown in Tables 1 and 2. An aqueous ink composition was prepared according to the procedure.

Example 27 150 g of ethylene carbonate as a solid solvent was heated and melted at 40 ° C., and Kayaset Yellow A, a yellow disperse dyestuff, was produced.
50 g of -G (trade name, manufactured by Nippon Kayaku Co., Ltd., CI Disperse Yellow 54) was added with stirring, and dissolved by heating to prepare a colorant solution. 800 g of water to which 12.5 wt% of propylene urea was added as a hydrotropic agent was heated to 40 ° C., and the colorant solution was added with stirring over 4 hours while heating to prepare a colorant dispersion. 5 g of pentanol as a penetration enhancer and 50 g of glycerin as a humectant were added with stirring, and the dispersion was filtered with a filter having a pore size of 20 μm to prepare a yellow ink.

Examples 28 to 30 The same procedures as in Example 27 were carried out except that the amounts of the coloring agent, the amount thereof added, the amount of the solid solvent and the amount of the auxiliary agent were changed to those shown in Tables 1 and 2. An aqueous ink composition was prepared according to the procedure.

The auxiliary A in the table is a hydrotrope,
B is a penetration enhancer and C is a humectant.

[0074]

[Table 1]

[0075]

[Table 2] Comparative Example 1 This is an example in which N-methylpyrrolidone was used instead of the solid solvent. That is, to 350 g of N-methylpyrrolidone, 45 g of black oil-soluble dye, Spirit Black AB (trade name: CI Solvent Black 5, manufactured by Orient Chemical Co., Ltd.) was added and dissolved, and then 50 g of ethylene glycol and 30 g of urea were added. And pure water is added to make the total amount of ink 10
The mixture was added with stirring until the amount became 00 g. Thereafter, the solution was filtered with a filter having a pore size of 20 μm to prepare an oil-dissolving dye black ink.

Comparative Example 2 This is an example in which 1,3-dimethyl-2-imidazolidinone was used in place of the solid solvent. That is, 30 g of Kayaset Yellow AG (trade name, CI Disperse Yellow 54 manufactured by Nippon Kayaku Co., Ltd.) which is a yellow disperse dye, and 1,
100 g of 3-dimethyl-2-imidazolidinone, 10 g of ethylene glycol as a humectant, and sodium dodecylbenzenesensulfonate 5 as an anionic surfactant
0 g were mixed. Pure water is added to this mixture to make the total amount of ink 10
After the addition, the dispersion was dispersed in a ball mill for 24 hours, followed by filtration through a filter having a pore size of 20 μm to prepare a disperse dye-dispersed yellow ink.

Comparative Example 3 This is an example using N-methylpyrrolidone instead of the solid solvent. That is, 50 g of Sumiton Cyanine Blue (trade name, manufactured by Sumitomo Chemical Co., Ltd., CI Pigment Blue 15) as a blue pigment, and N-methylpyrrolidone 150
g, 100 g of ethylene glycol as a humectant, 100 g of SMA resin 1440H (trade name, manufactured by Alcochemical Co., Ltd., styrene-maleic acid copolymer) as a water-soluble resin dispersant, and 10 g of dimethylaminoethanol. Pure water is added to this mixture to make the total amount of ink 1000 g.
After addition, the mixture was dispersed in a ball mill for 18 hours, and subsequently filtered through a filter having a pore size of 20 μm to prepare a pigment-dispersed blue ink.

Performance Evaluation Test The aqueous ink compositions of Examples and Comparative Examples were printed using an ink jet recording apparatus, and the print stability against dry clogging of the printed matter and the fastness of the printed matter were evaluated.

The printing stability was determined by restoring the ink discharge level after leaving the ink-jet recording apparatus filled with ink for 1 week at room temperature without a rubber cap for preventing ink drying.

The evaluation of the fastness was made on the water fastness and light fastness. The water resistance was determined according to the water drop test of JIS L0853 according to JIS test method JIS L0853, by dropping one drop of water on the printed surface and leaving it to dry, and then determining the amount of fading on the printed surface. The light fastness was determined by exposing the printed matter to sunlight day and night, based on the day and night method of the daylight test of JIS L0841 in accordance with JIS test method JISL0841, and determining the fading amount.

In each of the inks of the above Examples, the ink ejection was recovered even after being left at room temperature for one week, and the printing stability was good. As for the water resistance, no colorant was eluted out of the printed portion on the paper, or only traces of the colorant did not fade, and good fastness was obtained. The light resistance is such that the decrease in optical density is 10 to 4
At 0%, printed characters could be read even after exposure, and good fastness was obtained.

Further, the ink compositions of the above Examples exhibited stable continuous ejection, good paper permeability, and storage stability of the ink.

On the other hand, the water resistance and light resistance of the ink of the comparative example were almost the same as those of the ink of the above example.
Regarding the printing stability, no ink could be ejected after one week of standing.

Continuation of front page (56) References JP-A-60-118770 (JP, A) JP-A-6-41484 (JP, A) JP-A-6-264015 (JP, A) JP-A-5-59313 (JP) JP-A-6-100831 (JP, A) JP-A-5-194886 (JP, A) JP-A-6-313138 (JP, A) JP-A-6-100825 (JP, A) 6-172690 (JP, A) JP-A-7-138510 (JP, A) JP-A-8-127746 (JP, A) JP-A-7-305007 (JP, A) International publication 95/21897 (WO, A1) (58) Fields surveyed (Int. Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (12)

(57) [Claims] 1. A colorant which is hardly water-soluble or water-insoluble, and which is solid at room temperature and soluble in water, and a heated melt or aqueous solution of said colorant dissolves said colorant; An aqueous ink composition comprising at least water and a solid solvent capable of forming a solid solution with water, wherein the solid solvent is a carboxylic acid derivative or an alkylene carbonate. 2. The aqueous ink composition according to claim 1, wherein said colorant is selected from the group consisting of an oil-soluble dye, a disperse dye, and a solvent-soluble pigment. 3. The aqueous ink composition according to claim 1, wherein the melting point of the solid solvent is 30 ° C. or higher. 4. The aqueous ink composition according to claim 1, wherein the carboxylic acid derivative is a compound represented by the following formula (I). R ¹ -CO-NH-R ² (I) (wherein, R ¹ is an optionally substituted alkyl group, an optionally substituted alkoxy group, or a 5- or 6-membered nitrogen-containing one atom. R ² represents H or an optionally substituted alkyl group, or R ¹ and R ² together form a C 3-8
Represents an alkylene group, which may be substituted) 5. The aqueous ink composition according to claim 1, wherein the alkylene carbonate is a compound represented by the following formula (III). R ⁵ —O—CO—O—R ⁶ (III) (wherein, R ⁵ and R ⁶ each independently represent H or an optionally substituted alkyl group, or R ⁵ and R ⁶ Represents together with an alkylene group having 2 to 6 carbon atoms) 6. A solid solvent comprising: lactamide, acetamide,
Selected from the group consisting of N-methylacetamide, methyl carbamate, ethyl carbamate, ε-caprolactam, δ-valerolactam, α-amino-ε-caprolactam, glycolamide, dimethylol urea, ethylene urea, nicotinamide, and ethylene carbonate The aqueous ink composition according to any one of claims 1 to 5, wherein the aqueous ink composition is used. 7. The aqueous ink composition according to claim 6, wherein the solid solvent is lactamide, ε-caprolactam, methyl carbamate, δ-valerolactam, or ethylene carbonate. 8. The aqueous ink composition according to claim 1, comprising 1 to 50% by weight of a solid solvent. 9. The method for producing an aqueous ink composition according to claim 1, wherein the solid solvent is heated to a temperature equal to or higher than the melting point and melted, and a coloring agent is dissolved in the solid solvent for coloring. Obtaining a colorant solution; mixing the colorant solution in the heated and molten state with water or an aqueous solution containing a water-soluble organic solvent to obtain a dispersion in which colorant particles are dispersed; Optionally adding an optional component that forms an ink composition to the dispersion. 10. A process for producing an aqueous ink composition according to claim 1, wherein a saturated aqueous solution of a solid solvent or a concentrated aqueous solution close to the saturated aqueous solution is prepared, and a colorant is dissolved therein. Obtaining a colorant solution by mixing the colorant solution with an aqueous solution containing water or a water-soluble organic solvent to obtain a dispersion in which the colorant particles are dispersed. Optionally adding an optional component that forms the ink composition. 11. The method for producing an aqueous ink composition according to claim 1, wherein the solid solvent is heated to a temperature equal to or higher than the melting point and melted, and a coloring agent is dissolved in the solid solvent for coloring. Obtaining a colorant solution; cooling the colorant solution to obtain a colorant solid solution comprising a colorant and a solid solvent; dissolving the colorant solid solution in water or an aqueous solution containing a water-soluble organic solvent. Thereby obtaining a dispersion in which the colorant particles are dispersed, and optionally adding an optional component forming an ink composition to the dispersion. 12. The method for producing an aqueous ink composition according to claim 1, wherein a solid solvent and a volatile organic solvent are mixed, and a colorant is dissolved in the mixture. Obtaining a colorant solution, evaporating and removing the volatile organic solvent from the colorant solution to obtain a colorant solid solution, and dissolving the colorant solid solution in water or an aqueous solution containing a water-soluble organic solvent. Obtaining a dispersion in which the colorant particles are dispersed, and optionally adding an optional component that forms an ink composition to the dispersion.