JPH08259865A - Ink jet recording ink - Google Patents

Abstract

PURPOSE: To obtain an ink jet recording ink prevented from delivery nozzle cloggings, capable of making good recording even on plain paper etc., and excellent in the water resistance and quick dryability of the recorded images on acidic paper or neutralized paper, by blending an ink jet recording ink with a compound having both heterocycle and carboxyl group. CONSTITUTION: This ink is obtained by blending an ink jet recording ink comprising (A) a colorant (pref. a phthalocyanine-based dye of the formula), (B) water (pref. deionized water) and (C) a water-soluble organic solvent (e.g. an alcohol) with (D) a compound having both heterocycle and carboxyl group (pref. histidine or tryptophan). It is preferable that the amounts of the components A, B, C and D to be blended be 1-5wt.%, 50-90wt.%, 5-20wt.% and 0.1-5wt.%, based on the whole ink composition, respectively. Besides, this ink may be formulated, as necessary, with a surfactant, pH adjuster, antiseptic, chelating agent etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ink jet ink. More specifically, when used as a recording ink by an inkjet method, the discharge nozzle is not clogged, and even if it is clogged, its recovery property is easy, and high-quality paper Good recording is possible even on recording materials such as non-coated paper such as neutral paper and bond paper, so-called plain paper and recycled paper, without deteriorating the print quality, and not only acidic paper In particular, the present invention relates to an inkjet ink which is excellent in water resistance and fast drying of a recorded image on neutral paper.

[0002]

2. Description of the Related Art Conventionally, various inks for writing instruments such as fountain pens, felt-tip pens, and water-based ballpoint pens, and ink-jet inks have been put into practical use.
Inks used in these writing instruments include pigment inks and dye inks. Pigment inks are superior in light resistance and water resistance to dye inks and can form excellent images without discoloration or fading of recorded images, and are therefore used in various fields. However, the pigment ink has a problem that the stability of the ink is not sufficient, because the pigment easily aggregates with time and precipitates during storage of the ink or the pen tip or nozzle is clogged during use. ing.

On the other hand, since dye inks have less problems such as aggregation as compared with pigment inks, various studies have been made and they are also used in a wide range of applications. For example, the non-impact recording method has an advantage that noise generation during recording is small, and high-speed recording is possible. Moreover, the ink jet recording method, which can record on so-called plain paper without requiring a special fixing process, is an extremely effective recording method, and various methods have been devised and improved to practical use. Some have been made, while others are still trying to be put into practical use.

In such an ink jet recording method, recording is performed by causing so-called ink droplets to fly and adhere to a recording material. Such ink is
A recording agent (a dye or a pigment is used) and a liquid medium for dissolving or dispersing the recording agent (water, various water-soluble organic solvents, or a mixture thereof) are used as basic constituent components, and if necessary, , Various additives are blended.

Among such recording methods, there are various inkjet recording methods, depending on the method of generating ink droplets and the method of controlling the flight direction of the droplets. For example, (1) a recording signal is applied to a recording head unit having a piezoelectric vibrator, and ink droplets are generated in accordance with this signal to perform recording,
Drop-on-demand method (pressure pulse method),
(2) Electric field control method that discharges ink by using electrostatic attraction, (3) Ink liquid droplets are continuously generated while charging, and the charged ink droplets are controlled by control electrodes Charge control method (continuous method) that uses a part of the droplet for recording, (4) Bubble jet that ejects ink by using the pressure generated by applying high heat to the ink inside the recording head chamber to form and grow bubbles A method, (5) a spark jet method in which a spark is generated in the ink under high voltage application and the explosive force ejects the ink is known.

There are various types of apparatuses for performing recording by generating droplets in this way. In order to perform good recording with this recording method, an ink (which is composed of a recording agent and a liquid medium, which is composed of a recording agent and a liquid medium, is used depending on the method of generating droplets or the method of controlling the flight direction of droplets). (Sometimes say)
However, it is necessary that the physical properties such as electric conductivity, viscosity, surface tension, and pH are within an appropriate range and that solid content is not present.

Since the discharge orifice mounted on the ink jet recording apparatus is a minute hole having a diameter of about 10 μm, compared with other inks for writing instruments, when solid content is generated during storage or use of the ink, , Susceptible to that. The presence of solids in the ink may cause the discharge orifice to be clogged, and the droplet may not be discharged at all. In addition, even if the discharge is not stopped, uniform droplet generation and droplet May adversely affect the stable flight of the recording medium, and the recording property, the ejection stability, the ejection response property, or the continuous recording property may be deteriorated.

Further, when the constituent components of the ink chemically change with time, the physical properties of the ink adjusted to desired values during the preparation change, and similarly, recording properties, ejection stability, ejection responsiveness, etc. It may decrease. Therefore, there is a demand for a chemically stable recording agent component, a liquid medium component that does not change physical properties even after storage for a long period of time, or an ink that does not cause defects by combining the above components.

Conventionally, in the ink jet recording method, as a method for preventing the clogging of the orifice, a method of adding an N, N-diethanolamine derivative to the ink (see Japanese Patent Publication No. 61-52870) and γ-butyrolactone are used. A method of adding (see Japanese Examined Patent Publication No. 61-29393), a method of adding polyethylene glycol phenyl ether (see Japanese Examined Patent Publication No. 62-14188),
Method using dicarboxylic acid ester (JP-A-5-707)
No. 26, Japanese Patent Laid-Open No. 5-70727), etc. have been proposed, but they are still insufficient when other required performances such as water resistance and sharpness of recorded images are taken into consideration.

Further, as the performance required as an ink, non-coated paper such as high-quality paper, neutral paper and bond paper used in general offices, so-called plain paper, and recorded paper such as recycled paper are recorded. Even when recorded on a material, the recorded image is clear, has a fast drying property, and the recorded image is excellent in light resistance, water resistance, scratch resistance, and the like. However, until now, an inkjet ink satisfying all of these required performances has not been obtained.

When a pigment is used as a recording agent, it is excellent in light resistance and water resistance, but it is inferior in dispersion stability and printing density. When a dye is used as a recording agent, it is excellent in storage stability and printing density, but water resistance. Was inferior to Furthermore, as the recorded image dries, dye crystals are deposited on the recording material, the recorded image reflects light, and a so-called bronze phenomenon occurs in which yellow to brown is emitted to give a metallic luster. there were.

In order to prevent this bronzing phenomenon, it is known to add alkanolamines such as monoethanolamine and diethanolamine to the ink. However, if these are added to the ink, the pH will be 11 even in a small amount.
It will rise above the above. Ink having a high pH not only has the problem of corrosion of the nozzle that comes into contact with the ink, but also lacks safety when accidentally touched by the human body during handling. Further, the ink containing the alkanolamine has a problem that the printing quality and the water resistance of the recorded image are deteriorated.

Among the various performances required for ink described above, the performances required to be improved are as follows. 1. No clogging of the discharge orifice 1. Sharpness of recorded image on plain paper, especially neutral paper (prevention of bronzing phenomenon) 3. Water resistance of recorded images on plain paper, especially neutral paper In recent years, as recording paper, neutral paper has come to be used in place of acid paper, which was often used before. Among them, the improvement of the performance of 2 and 3 is particularly required.

[0014]

The problems to be solved by the present invention are as follows. (1) To provide an ink that does not cause clogging of a discharge nozzle when used as an inkjet ink. (2) To provide an ink whose recovery is easy even if clogging should occur. (3) Good for non-coated paper such as high-quality paper, neutral paper, bond paper, and so-called plain paper and recycled paper, which are used in general offices, without causing the bronzing phenomenon. It is possible to provide an ink that can perform various recordings and that does not deteriorate print quality. (4) To provide an inkjet ink capable of obtaining a recorded image having excellent water resistance not only on acid paper but also on neutral paper.

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, previously improved the water resistance by adding a basic amino acid (lysine, arginine, etc.) to the ink. An ink that can prevent the bronzing phenomenon is proposed (Japanese Patent Application No. 6-315021). However, as a result of the subsequent examination, the previously proposed method shows that basic amino acids containing no heterocycle such as lysine and arginine are
It was found that although the effect of improving the water resistance of the recorded image on the acid paper is effective, the effect of improving the water resistance of the recorded image on the neutral paper is small. As a result of further studies, the present invention improves the water resistance of a recorded image even in neutral paper by including a compound having a heterocycle and a carboxyl group at the same time in the ink, instead of the basic amino acid. The present invention has been completed and the present invention has been completed.

[0016]

In order to solve the above-mentioned problems, the invention of claim 1 provides an inkjet ink comprising at least a colorant, water and a water-soluble organic solvent, wherein a heterocycle and a carboxyl group are contained in the same molecule. It is characterized by comprising a compound having

The present invention will be described in detail below. The inkjet ink according to the present invention is a liquid ink composition including at least a colorant (hereinafter referred to as A component), water (hereinafter referred to as B component), and a water-soluble organic solvent (hereinafter referred to as C component). It is essential that a compound having a heterocycle and a carboxyl group at the same time in the same molecule (hereinafter referred to as component D) is blended. Hereinafter, each component will be described.

The colorant (component A) used for preparing the ink-jet ink according to the present invention is an acid dye,
It can be selected from basic dyes, direct dyes, reactive dyes, disperse dyes, food dyes and the like. In particular,
The following dyes are listed. The dyes are not limited to those exemplified below.

Acid dye: C.I. I. Acid black 2,
7, 16, 17, 24, 26, 28, 31, 41, 5
2, 63, 94, 112, 118, 119; C.I. I. Acid Yellow 4,11,12,13,14,17,1
8,23,25,29,34,40,41,42,5
3,55,61,71,76,111,122; C.I.
I. Acid Red 1,4,6,8,9,15,19,
21, 30, 32, 34, 35, 37, 40, 42, 5
1, 52, 54, 80, 82, 85, 87, 92, 9
4, 106, 108, 110, 115, 119, 13
3,143,172,176,180,187,25
6,317 ,; C.I. I. Acid Blue 7, 9, 22,
23, 25, 40, 41, 43, 45, 49, 51, 5
3,55,56,59,62,78,80,81,9
0, 93, 102, 104, 111, 113, 117,
120,124,145,167,185,192,2
29, 234, 254; C.I. I. Acid Orange 7,
19; C.I. I. Acid Violet 49 etc.

Basic dye: C.I. I. Basic Black 2,8; C.I. I. Basic Yellow 2, 12, 32;
C. I. Basic Red 1, 2, 9, 12, 13, 1
4,37; C.I. I. Basic Blue 1, 3, 5, 7,
9, 24, 25, 26, 28, 29; C.I. I. Basic Violet 7, 14, 27 etc.

Direct dyes: C.I. I. Direct Black 2,9,11,14,17,19,22,27,32,
36, 38, 41, 48, 49, 51, 56, 71, 7
5,77,78,80,106,108,146,15
4; C.I. I. Direct Yellow 1,2,4,8,1
2,24,26,33,34,41,42,48,5
0,51,72,87,98; C.I. I. Direct Red 1,4,8,11,15,17,23,28,31,
46, 59, 62, 73, 75, 77, 80, 81, 8
3, 84, 85, 90, 101, 106, 108, 11
0,145,189,193,225; C.I. I. Direct Blue 1,2,6,8,22,25,34,69,
70, 71, 72, 75, 76, 78, 81, 82, 8
3,86,90,98,106,110,120,16
5,195,199,218,239,258; C.I.
I. Direct Orange 34, 39, 44, 46, 6
0; C.I. I. Direct Violet 47, 48; C.I.
I. Direct Brown 109; C.I. I. Direct green 59 etc.

Food Color: C.I. I. Hood black 1,
2; C.I. I. Food Yellow 2,4,5; C.I. I. Hood Red 2,3,7,14,52,87,94,10
5; C.I. I. Food blue 1, 2 etc.

Reactive dye: C.I. I. Reactive Black 1,4,5,8,14,21,23,26,31,3
2, 34; C.I. I. Reactive blue 2, 3, 4,
5,7,8,10,13,14,15,17,18,1
9, 21, 25, 26, 27, 28, 29, 38, 3
9, 40, 42, 43, 49, 51, 52, 65, 6
6,67,68,71,73,74,75,77,7
8, 79, 80, 89, 98, 100, 101, 10
4,105,112,113,114,115,11
9, 147, 148, 158, 160, 162, 16
9, 170, 171, 179, 182, 187; C.I.
I. Reactive Red 3,6,13,17,19,2
1, 22, 23, 24, 29, 35, 37, 40, 4
1,43,45,49,55,56,58,63,6
7,80,81,82,85,86,87,104,1
06,108,109,110,111,112,11
3,114,117,118,119,120,12
3,124,126,128,130,131,13
2,141,147,158,159,170,17
1,174,176; C.I. I. Reactive Yellow 2,3,13,14,15,17,18,23,24,
25, 26, 27, 29, 35, 37, 41, 42, 4
9,50,52,54,55,57,58,63,6
4,75,76,77,79,81,82,83,8
4,85,87,88,91,92,93,95,9
6,111,115,116,131,135; C.I.
I. Reactive orange 1,2,5,7,10,1
1, 12, 13, 15, 16, 20, 30, 34, 3
5,41,42,44,45,46,56,57,6
2, 63, 64, 67, 69, 71, 72, 73, 7
4,78,82,84,87; C.I. I. Reactive violet 1,2,3,4,5,6,7,8,9,1
6, 17, 22, 23, 24, 26, 27, 33; C.I.
I. Reactive Brown 1, 2, 5, 6, 7, 8,
9,16,17,18,19,21,24,26,30
Such

Disperse dye: C.I. I. Disperse Black 1, 3, 10, 24; C.I. I. Disperse Blue 3,
7, 9, 14, 16, 19, 20, 26, 27, 35,
43,44,54,55,56,58,60,62,6
4, 70, 72, 73, 75, 79, 81, 82, 8
3,87,91,93,94,95,96,102,1
06,108,112,113,115,118,12
0,122,125,128,130,139,14
1,142,143,146,148,149,15
3,154,158,165,167,171,17
3,174,176,191,183,185,18
6,187,189,197,198,200,20
1,205,207,211,214,224,22
5,257,259,267,268,270,28
4,285,287,288,291,293,29
5,297,301,315,330,333; C.I.
I. Disperse Red 1, 4, 5, 7, 11, 12,
13, 15, 17, 27, 43, 44, 50, 52, 5
3,54,55,56,58,59,60,65,7
2,73,74,75,76,78,81,82,8
6,88,90,91,92,93,96,103,1
05, 106, 107, 108, 110, 111, 11
3,117,118,121,122,126,12
7,128,131,132,134,135,13
7,143,145,146,151,152,15
3,154,157,159,164,167,16
9,177,179,181,183,184,18
5,188,189,190,191,192,20
0,201,202,203,205,206,20
7,210,221,224,225,227,22
9,239,240,257,258,277,27
8,279,281,288,296,303,31
0, 311, 312, 320, 324, 328; C.I.
I. Disperse Yellow 3,4,5,7,9,13,
24, 30, 33, 34, 42, 44, 49, 50, 5
1, 54, 56, 58, 60, 63, 64, 66, 6
8, 71, 74, 76, 79, 82, 83, 85, 8
6,88,90,91,93,98,99,100,1
04, 114, 116, 118, 119, 122, 12
4,126,135,140,141,149,16
0, 162, 163, 164, 165, 179, 18
0,182,183,186,192,198,19
9, 202, 204, 210, 211, 215, 21
6,218,224; C.I. I. Disperse Orange 1,3,5,7,11,13,17,20,21,2
5,29,30,31,32,33,37,38,4
2,43,44,45,47,48,49,50,5
3,54,55,56,57,58,59,61,6
6,71,73,76,78,80,89,90,9
1, 93, 96, 97, 119, 127, 130, 13
9, 142; C.I. I. Disperse Brown 1,2,
4, 9, 13, 19

Of these dyes, azo and phthalocyanine dyes are particularly preferable, and acid dyes,
Direct dyes, reactive dyes, food dyes and the like are particularly preferable.
Examples of the structures of these dyes include azo dyes represented by the following structural formulas [1], [2], [3] and [4] in the form of free acid.

[0026]

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[0027]

Embedded image

[0028]

Embedded image

[0029]

[Chemical 4]

As the dye, a phthalocyanine dye represented by the following structural formula [5] in the form of free acid is also preferably used.

[0031]

Embedded image

Further, if the preferred dye is shown in the form of the free acid, structural formulas [6], [7], [8], [9] and [1]
0] and the like.

[0033]

[Chemical 6]

(In the formula, A and B represent a phenyl group or a naphthyl group substituted with a lower alkylcarbonylamino group, a lower alkoxy group, a sulfonic acid group or a carboalkyl group.)

[0035]

[Chemical 7]

(Wherein C is a naphthyl group substituted with a sulfonic acid group or a carboxyl group, a phenylazo group optionally substituted with a sulfonic acid group or a carboxyl group,
Represents a phenyl group substituted with a lower alkyl group, a lower alkoxyl group or a lower alkylcarbonylamino group, R ₁ represents a lower alkyl group, a lower alkoxyl group, or a lower alkylcarbonylamino group, R ₂ hydrogen atom, or sulfonic acid Group, a phenyl group substituted with a carboxyl group, and n represents 0 or 1. )

[0037]

Embedded image

(In the formula, D, E and F represent a phenyl group and a naphthyl group which may be substituted with a sulfonic acid group, an amino group, an alkyl group, an alkoxyl group or a carboxyl group.)

[0039]

[Chemical 9]

(In the formula, R ³ , R ⁴ , R ⁵ and R ⁶ represent a hydrogen atom, a hydroxyl group, an alkyl group, or a phenyl group which may be substituted with an alkyl group, an alkoxyl group, a sulfonic acid group or a carboxyl group. Represents.)

[0041]

[Chemical 10]

(In the formula, R7 represents a hydrogen atom, a phenyl group which may be substituted with an alkyl group, an alkoxyl group, a sulfonic acid group or a carboxyl group, and a benzoyl group.)

These colorants may be used alone or as a mixture of two or more. The concentration of these colorants in the ink is usually 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total ink composition.

As the water (component B) used for preparing the ink-jet ink according to the present invention, it is usually preferable to use industrial water as a raw material and remove cations and anions by deionization exchange treatment. The amount of the B component in the ink is determined in a wide range depending on the kind of the water-soluble organic solvent (C component) described later, the ratio thereof, or the characteristics required for the ink, but the total ink composition is It is generally in the range of 10 to 99% by weight based on the product. If the content of water is too small, the viscosity becomes too viscous, and if it is too large, the concentration of the recording material becomes too thin, and the printing density becomes too thin, which is not preferable. Within the above range, 30 to 90% by weight is preferable, and 50 to 90 is particularly preferable.
It is in the range of% by weight.

The ink jet ink according to the present invention comprises
It is essential to include a water-soluble organic solvent (component C). C
The component acts to improve the dissolution stability and dispersion stability of the dye, and also to improve the penetrability into the recording material and the fixing stability. Examples of the C component include amides, ketones, ethers, amines, glycols, glycol ethers, heterocyclic water-soluble organic solvents, alcohols and the like.

Specific examples of the component C include the following compounds. Ketones: acetone such as dimethylformamide and dimethylacetamide, methyl ethyl ketone, etc. Ethers: tetrahydrofuran, dioxane, etc. Glycols: ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, thiodiethylene glycol,
Glycerin, 1,2,6-hexanetriol, hexylene glycol, 1,5-pentanediol, etc.

Glycol ethers: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether,
Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, etc. Amines; monoethanolamine, diethanolamine, triethanolamine, ethyldiethanolamine, etc. Heterocyclic water-soluble organic Solvent: N-hydroxyethylmorpholine, N-methyl-2-pyrrolidone, 2-pyrrolidone and other alcohols: 2-butanol, 1-butanol, 2
-Propanol, 1-propanol, ethanol, methanol, etc. Others: sulfolane, 1,3-dimethyl-2-imidazolidinone, etc.

When the above-mentioned component C is added to the ink composition, it may be used alone or as a mixture of a plurality thereof. The concentration of the C component in the ink composition is usually 1 to 40% by weight based on the total ink composition. If the content of the C component is less than 1% by weight, the ejection orifice is likely to be clogged, and the penetrability and dryness of the recorded image are generally deteriorated. If the amount exceeds 40% by weight, blurring may occur in the recorded image and the printing quality may deteriorate, which is not preferable. Particularly preferred in the above range is 3 to
It is 30% by weight, particularly preferably 5 to 20% by weight.

The compound (D component) having a heterocycle and a carboxyl group in the same molecule at the same time, which is blended in the ink-jet ink according to the present invention, is not clear at the present time, but it is plain paper, particularly neutral paper. It improves the water resistance of a recorded image on paper, does not impair the print quality, print density, dissolution stability, and quick-drying property, and reduces the bronzing phenomenon. Specific examples of the D component that can be used include those represented by the following general formulas [11], [12] and [13].

[0050]

[Chemical 11]

(In the formula, X represents a hydrogen atom, an amino group or an optionally substituted alkyl group, and n represents 0 to 4).

[0052]

[Chemical 12]

(In the formula, X represents a hydrogen atom, an amino group or an optionally substituted alkyl group, and n represents 0 to 4).

[0054]

[Chemical 13]

(In the formula, Y represents a hydrogen atom, a hydroxyl group, or an optionally substituted alkyl group, and n represents 0 to 4.)

The compound having a heterocycle and a carboxyl group in the same molecule as the component D has a heterocycle and a carboxyl group in the same molecule in addition to the compound represented by the above general formula. Pyrolinecarboxylic acid may be used. Among these compounds having a heterocycle and a carboxyl group in the same molecule at the same time, histidine, tryptophan, proline and oxyproline are preferable, and particularly preferable are a heterocycle, a carboxyl group and an amino group in the same molecule. It has histidine and tryptophan at the same time.

The concentration of the component D in the ink-jet ink according to the present invention is usually selected in the range of 0.001 to 20% by weight based on the total ink composition. If it exceeds 20% by weight, precipitation of crystals of component D may be observed and the storage stability of the ink may be insufficient, and if it is less than 0.001% by weight, the object of the present invention may not be achieved, either of which is not preferable. . The range of 0.01 to 10% by weight is preferable, and the range of 0.1 to 5% by weight is particularly preferable.

The inkjet ink according to the present invention comprises
The above-mentioned four components of the A component, the B component, the C component and the D component are indispensable, but in addition to the above components, other components can be blended if necessary. Other components include cationic surfactants, anionic surfactants, nonionic surfactants, surfactants such as amphoteric surfactants, pH adjusting agents, preservatives, fungicides, evaporation accelerators, chelates. Examples thereof include agents, urea, thiourea, and conductivity imparting agents.

As the inorganic or organic conductivity-imparting agent,
The following compounds may be mentioned. Inorganic conductivity enhancer: lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride,
Alkali such as lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, ammonium bromide, lithium iodide, sodium iodide, potassium iodide, magnesium iodide, calcium iodide, ammonium iodide Metals, alkaline earth metals and ammonia halides, lithium nitrate, sodium nitrate,
Nitrate such as potassium nitrate, magnesium nitrate, calcium nitrate, ammonium nitrate, iron nitrate, copper nitrate, silver nitrate, zinc nitrate, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, ammonium sulfate, iron sulfate, copper sulfate, silver sulfate, Zinc sulfate, thiocyanate, etc.

Organic conductivity-imparting agents: nitrates such as morpholine and amine, and organic sulfates such as morpholine and amine, monomethylammonium chloride, dimethylammonium chloride, trimerylammonium chloride, tetramethylammonium chloride, monoethylammonium chloride. , Organic salts such as ammonium acetate, lithium acetate, sodium acetate, lithium formate, sodium formate, ammonium formate, etc.

The concentration of these other components in the ink composition is usually 10 ppm to 10% by weight with respect to the total amount of the ink composition, and particularly preferably 0.
It is in the range of 01 to 5% by weight. In the case of additives other than the surfactant, it is in the range of 0.1 to 30% by weight, particularly preferably 1 to 20% by weight.

In order to prepare the ink-jet ink according to the present invention, the above-mentioned four components are weighed in predetermined amounts, and if necessary, other components are also weighed and dissolved by stirring and mixing using a known stirrer. do it. Further, if necessary, the obtained mixture is filtered with a membrane filter or the like,
The target ink composition can be easily obtained.

[0063]

INDUSTRIAL APPLICABILITY The present invention has the following particularly advantageous effects, and its industrial utility value is extremely large. 1. The inkjet ink according to the present invention is a compound (D having a heterocycle and a carboxyl group at the same time in the same molecule).
Since the components are mixed, the discharge orifice is less likely to be clogged, and even if the clogged, the recovery is easy. 2. Recording with the ink-jet ink according to the present invention, even on uncoated paper such as high-quality paper and neutral paper, so-called plain paper and recycled paper, it is possible to obtain good recording without the bronzing phenomenon in the recorded image. It is possible. 3. When recorded with the ink-jet ink according to the present invention, not only plain paper such as acid paper, but also neutral paper which could not be conventionally made excellent in water resistance, similarly a recorded image excellent in water resistance. Is obtained.

[0064]

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following examples, various evaluation tests were conducted by the methods described below.

1. Recorded image density and water resistance test {OD
(Initial value), OD ratio, water resistance (visual evaluation)} OD (initial value): recording liquid (acidic paper = manufactured by Canon Inc., PP)
Dry paper for C; Neutral paper = Xerox Co., 4024)
A commercial inkjet printer (Hewlett Packard
The recording image (character printing) was solidly printed on the recording paper with Desk writer 550c) manufactured by the company, and the recording paper was dried at room temperature for 24 hours. For recorded images, Macbeth reflection densitometer (RD-91
According to 4), it was measured as OD (Optical Density), and this measured value was defined as OD (initial value). OD (initial value) is 0
It is usually in the range of 2.

OD ratio: The same recording paper was put in a container, and 2
Soak in tap water at 5 ° C for 5 minutes, pull up and dry, and measure OD similarly for the recorded image.
(Test value), and the ratio of the two is expressed by the formula {OD (test value) /
OD (initial value)} × 100 and calculated as the OD ratio. The closer the OD ratio is to 100, the better the water resistance of the recorded image.

Water resistance (visual evaluation): A recording image was printed on a recording paper with the same model as above, and the obtained recording paper was dried at room temperature for 24 hours. This recording paper was immersed in tap water of 25 ° C. placed in a container for 5 seconds, pulled up and dried, and then the quality of the recorded image was visually observed to determine the quality. The criteria are shown in Table 1 because they are common to the following evaluation items.

2. Visual judgment of print quality In the test described in the above 1, the quality of the print of the recording image printed on the recording paper was judged by visual observation. 3. Bronze visual judgment In the test described in 1 above, the recorded image printed on the recording paper
After drying at room temperature for 4 hours, the quality of the bronze was evaluated by visual observation.

4. Clogging property test A method of determining the clogging property of the discharge nozzle by printing 1000 recording images continuously on a recording paper with the same model as used in the test described in 1 above. ○ means that clogging did not occur.

[Example 1] In the above structural formula [1],
An ink composition having the following composition ratio was prepared using a sodium salt type of a water-soluble azo dye [1] in which hydrogen of a sulfonic acid group was replaced with sodium. The components below were stirred and mixed, and then filtered through a 0.2 μm membrane filter, and the ink compositions obtained were subjected to various tests according to the methods described above. The results are shown in Table 1.

[0071]

Table 1 Ink composition Water-soluble azo dye [1] Sodium type 3.0 wt% Histidine 2.0 wt% Glycerin 15.0 wt% Ethylene glycol 3.0 wt% 2-Propanol 4.0 wt% Demineralized water 73 0.0 wt% 100.0 wt%

Example 2 In the structural formula [1],
An ink composition having the following composition ratio was prepared using a sodium salt type of a water-soluble azo dye [1] in which hydrogen of a sulfonic acid group was replaced with sodium. The components below were stirred and mixed, and then filtered through a 0.2 μm membrane filter, and the ink compositions obtained were subjected to various tests according to the methods described above. The results are shown in Table 1.

[0073]

Table 2 Ink composition Water-soluble azo dye [1] Sodium type 3.0% by weight Histidine 1.0% by weight Glycerin 15.0% by weight Ethylene glycol 3.0% by weight 2-Propanol 4.0% by weight Demineralized water 74 0.0 wt% 100.0 wt%

[Example 3] In the above structural formula [1],
An ink composition having the following composition ratio was prepared using a sodium salt type of a water-soluble azo dye [1] in which hydrogen of a sulfonic acid group was replaced with sodium. The components below were stirred and mixed, and then filtered through a 0.2 μm membrane filter, and the ink compositions obtained were subjected to various tests according to the methods described above. The results are shown in Table 1.

[0075]

[Table 3] Ink composition Water-soluble azo dye [1] Sodium type 3.0 wt% Tryptophan 1.0 wt% Glycerin 15.0 wt% Ethylene glycol 3.0 wt% 2-Propanol 4.0 wt% Demineralized water 74 0.0 wt% 100.0 wt%

[Embodiment 4] In the above structural formula [2],
An ink composition having the following composition ratio was prepared using a sodium salt type of a water-soluble azo dye [2] in which hydrogen of a sulfonic acid group was replaced with sodium. The components below were stirred and mixed, and then filtered through a 0.2 μm membrane filter, and the ink compositions obtained were subjected to various tests according to the methods described above. The results are shown in Table 1.

[0077]

[Table 4] Ink composition Water-soluble azo dye [2] Sodium type 3.0 wt% Histidine 1.0 wt% Diethylene glycol 13.0 wt% N-Methyl-2-pyrrolidone 5.0 wt% 2-Propanol 4.0 wt% % Demineralized water 74.0 % by weight 100.0% by weight

[Embodiment 5] In the above structural formula [2],
An ink composition having the following composition ratio was prepared using a sodium salt type of a water-soluble azo dye [2] in which hydrogen of a sulfonic acid group was replaced with sodium. The components below were stirred and mixed, and then filtered through a 0.2 μm membrane filter, and the ink compositions obtained were subjected to various tests according to the methods described above. The results are shown in Table 1.

[0079]

[Table 5] Ink composition Water-soluble azo dye [2] Sodium type 3.0 wt% Tryptophan 1.0 wt% Diethylene glycol 13.0 wt% N-Methyl-2-pyrrolidone 5.0 wt% 2-Propanol 4.0 wt% % Demineralized water 74.0 % by weight 100.0% by weight

Comparative Example 1 An ink composition was prepared by increasing the amount of demineralized water to 100.0% in the same manner as in Example 1 except that histidine was not added. . Various tests were conducted on the obtained ink composition by the above-mentioned method. The results are shown in Table 1.

Comparative Example 2 An ink composition was prepared by increasing the amount of demineralized water to 100.0% in the same manner as in Example 4 except that histidine was not added. . Various tests were conducted on the obtained ink composition by the above-mentioned method. The results are shown in Table 1.

[Comparative Example 3] An ink composition was prepared in the same manner as in Example 4, except that 1% of lysine, a basic amino acid containing no heterocycle, was added in place of histidine. Was prepared. Various tests were conducted on the obtained ink composition by the above-mentioned method. The results are shown in Table 1.

[0083]

[Table 6]

From Table-1, the following is clear. (1) With the inkjet ink according to the present invention, a recording image having excellent water resistance can be obtained not only when the recording paper is acidic paper but also when it is neutral paper. (2) A recorded image (printing) using the inkjet ink according to the present invention is of high image quality, high resolution, high quality without distortion or blurring of characters.

(3) The bronzing phenomenon does not occur in a recorded image formed by the ink-jet ink according to the present invention. (4) The inkjet ink according to the present invention does not cause clogging of the ejection nozzle.

In addition, in the example described in Example 4, the same effects as in the above example can be obtained even in the ink using the dyes represented by the structural formulas [3], [4] and [5]. Was obtained.

Claims (4)

[Claims] 1. An inkjet ink comprising at least a colorant, water and a water-soluble organic solvent, wherein a compound having a heterocycle and a carboxyl group in the same molecule is blended. 2. A compound having a heterocycle and a carboxyl group in the same molecule has an amino group at the same time.
The inkjet ink according to claim 1. 3. The compound having a heterocycle and a carboxyl group in the same molecule is selected from histidine, tryptophan, proline and oxyproline.
Alternatively, the inkjet ink according to claim 2. 4. A compound having a heterocycle and a carboxyl group in the same molecule is 0.01 to 0.01 with respect to the total composition of the ink.
The inkjet ink according to any one of claims 1 to 3, wherein the ink is blended in a range of 10% by weight.