JPH11131003A - Ink for recording and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition that shows excellent color tone with reduced bleeding on color boundaries and good color reproducibility, and can form clear and sharp images by using a specific coloring agent, water, a water-soluble organic solvent and a specific dispersing agent. SOLUTION: This composition comprises (A) a colorant dispersible or soluble in water that contains a macromolecular dye, having an average molecular weight of 5,000-150,000, and containing boric acid group in the recurring units (for example, a compound of formula I), (B) water, (C) a water-soluble organic solvent and (D) a dispersing agent containing (i) a macromolecular compound bearing the hydrophilic part and the hydrophobic part and/or (ii) a surfactant bearing a 5 or more carbon alkyl groups. In a preferred embodiment, the component (ii) contains a nonionic surfactant bearing polyoxyalkylene group and a polyoxyethylene alkyl ether acetate salt of formula II [R1 is a 6-14C (branched) alkyl; M is alkali metal; m is 3-12].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording ink suitable for use in ink-jet recording, water-based writing utensils, recorders, pen plotters, etc., and more particularly to a recording ink suitable for ink-jet recording, and more particularly a so-called ordinary ink. The present invention relates to an ink for ink jet recording which shows particularly excellent properties for forming a color image on paper. The present invention also relates to a recording method using the recording ink.

[0002]

2. Description of the Related Art In recent years, inkjet printers have become popular due to their advantages such as low noise and low running cost, and power printers capable of printing on plain paper have also been put on the market. In such an ink jet printer, it is necessary to satisfy color reproducibility of a color image, water and light resistance of an image, drying of an image, prevention of image bleeding, and ejection reliability. It is difficult to satisfy everything. When a color image is formed by an ink-jet printer, even if a clear image is formed in a single-color printing portion of yellow, magenta, and cyan, image bleeding and color boundaries occur in a two-color overlapping portion of red, green, and blue. There is a drawback that bleeding easily occurs and the sharpness of an image is reduced.

[0003] In particular, when a recorded image is dried by inkjet recording without using a fixing device, Japanese Patent Laid-Open No.
As described in Japanese Patent Application Laid-Open No. 5-29546, since the drying property of a recorded image is improved by increasing the permeability of a recording liquid to the recording paper, image bleeding becomes remarkable depending on the recording paper used, and the sharpness of the image is reduced. There is a disadvantage of doing so. Japanese Patent Publication No. 60-23793 discloses a method in which a dialkyl sulfosuccinate is contained as a surfactant in an ink jet recording ink to improve the drying property of an image recorded by ink jet recording and reduce the decrease in image sharpness. However, depending on the type of recording paper used, there is a problem that the pixel diameter is significantly different and the image density is significantly reduced, and the sharpness of the image is significantly reduced. It decomposes and loses the effect of the surfactant during storage of the recording ink, causing a deposit in the recording ink to cause clogging of nozzles in an ink jet printer, thereby deteriorating the discharge reliability.

Furthermore, Japanese Patent Application Laid-Open No. 56-57862 discloses that the drying property of an image recorded by ink jet recording is improved by adding a strong basic substance to the ink for ink jet recording. However, when an image is formed on a rosin-sized acidic paper, the effect of improving the drying property is obtained, but the effect of improving the drying property is not seen in the recording paper using an alkyl ketene dimer or alkenyl sulfosuccinic acid as a sizing agent, Further, even with acidic paper, there is a disadvantage that the effect of improving the drying property is not seen in the two-color superposed portion in the recorded image. Also, Japanese Patent Application Laid-Open No. 1-20
Japanese Patent No. 3483 discloses that a recording ink contains a polyhydric alcohol derivative and pectin to prevent bleeding of a recorded image by pectin as a thickener, but pectin converts hydroxyl groups to hydrophilic groups. However, since it is a nonionic compound, there is a drawback in that the ejection reliability after printing suspension is lacking.

On the other hand, dyes used in ink jet recording inks have been improved in order to achieve both color reproducibility of color images on plain paper and light fastness and water fastness. It is difficult to obtain a dye having improved water resistance and high discharge reliability. Various attempts have been made to use pigments in order to obtain water resistance and light resistance of a recorded image, but because of the problem of color tone, they are currently used except for large plotters that require particularly light resistance. Absent. Further, when a pigment is used, there is a problem that clogging occurs in an ink jet printer or the like corresponding to an increase in resolution of a recorded image, resulting in a lack of ejection reliability.

Therefore, it has been proposed to use a mixture of a pigment and a dye in order to improve color tone and color reproducibility of a color image, and to improve light fastness, water fastness and ejection reliability of the image. JP-A-60-45669 and JP-A-6-10
No. 0812, etc., the former does not have sufficient light fastness of the dye, the ink does not necessarily have sufficient penetrability and color development into plain paper, and the latter has lightfastness as compared with the former. Although it is sufficient, the color developability is insufficient, and there are problems such as the dulling of the two-colored portion, particularly the blue color.
As described above, in the related art, a recording ink capable of forming a clear image with good color tone and excellent color reproducibility with little blur of a color boundary, and an image having sufficient water resistance and light resistance, particularly It has been difficult to obtain a recording ink having high ejection reliability in ink jet recording.

[0007]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to solve such a problem and to form a clear image with less blur of color boundaries, excellent color tone and good color reproducibility. An object of the present invention is to provide a recording ink which can be formed and has excellent water resistance and light resistance of an image. A second object of the present invention is to provide a recording ink having high ejection stability in ink jet recording, particularly having excellent dispersion stability of a colorant and excellent storage stability, even after long-term storage or after printing suspension. To provide. A third object of the present invention is to form a clear image in which the recording ink has high permeability to recording paper such as plain paper, has excellent drying properties of the formed image, and prevents image bleeding. It is to provide a recording ink that can be used. Further, a fourth object of the present invention is to provide an ink jet recording method capable of forming an image having excellent water resistance and light resistance, good color reproducibility and excellent clarity at a high resolution.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a colorant which is dispersed or dissolved in water, a recording ink mainly composed of water and a water-soluble organic solvent, and having an average molecular weight of 5,000 to 15 as a colorant. Contains a polymer dye having a boric acid group in the repeating structure and contains a polymer compound having a hydrophilic portion and a hydrophobic portion and / or a surfactant having an alkyl group having 5 or more carbon atoms as a dispersant. This is achieved by a recording ink.

According to the present invention, a high molecular dye having an average molecular weight of 5,000 to 150,000 as a coloring agent and having a boric acid group in a repeating structure is used, and a high molecular compound having a hydrophilic part and a hydrophobic part as a dispersant is used. And / or carbon number 5
By using a surfactant having the above alkyl group, it is possible to form a clear image with excellent color tone and excellent color tone with less blur of the color boundary, and excellent image water resistance and light resistance. A recording ink can be obtained.

According to the present invention, the colorant has good dispersion stability, excellent storage stability, and has high ejection reliability in ink-jet recording even after long-term storage or after printing suspension. Ink can be obtained.

Furthermore, according to the present invention, the recording ink has a high permeability to recording paper such as plain paper, is excellent in drying property of the formed image, and forms a clear image by preventing image bleeding. And a recording ink that can be obtained.

The recording ink of the present invention is particularly suitable for printing a color image on plain paper, is capable of forming a clear image with excellent color tone and good color reproducibility, and is resistant to water and light. An image having excellent properties can be formed.

Further, by using the recording ink of the present invention, it is possible to perform high-speed and high-resolution stable recording on recording paper such as plain paper.

The average molecular weight used in the present invention is 5
As the polymer dye having a boric acid group in the repeating structure of 000 to 150,000, a dye having a boric acid group introduced as a hydrophilic functional group is preferably used. Examples of such a polymer dye include those in which a boric acid group is introduced into a chromophore, those in which a boric acid group is introduced into a main skeleton, and the like. Specific examples include, but are not limited to, polymer dyes represented by the structural formulas (a), (b), (c), and (d) shown in Table 1 below as free acid types. Do not mean.

[0015]

[Table 1]

These polymer dyes are disclosed in JP-A-63-3056.
No. 7, publication No. 7, etc., and purified by using a reverse osmosis membrane or an ion exchange resin to remove inorganic salt impurities such as NaCl, Na ₂ SO ₄ and CaCO _3. It is preferable to use those that have been used. By removing the inorganic salt impurities, clogging of the head in the ink jet printer and clogging of the filter in the printer can be prevented, and the discharge reliability can be improved.

The high molecular dye having an average molecular weight of 5,000 to 150,000 and having a boric acid group in the repeating structure includes sodium ion, lithium ion and quaternary ammonium represented by the following general formula (3). By using quaternary phosphonium and alkanolamine ions, the dissolution stability of the polymer dye can be further improved, and a recording ink having more excellent storage stability can be obtained. In addition, it is possible to perform inkjet recording with high ejection reliability.

Embedded image (Wherein, X represents a nitrogen atom or a phosphorus atom, and R ₃ , R ₄ ,
R ₅ and R ₆ represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a halogenated alkyl group. )

Next, the polymer compound having a hydrophilic portion and a hydrophobic portion used as a dispersant in the recording ink of the present invention and a surfactant having an alkyl group having 5 or more carbon atoms will be described. As the high molecular compound having a hydrophilic portion and a hydrophobic portion, as a hydrophilic polymer, in the natural system, a plant such as gum arabic, gum tragan, guar gum, gum karaya, low-strength bean gum, arabinogalactone, pectin, quince seed starch, etc. Functional polymers, alginic acid, carrageenan, seaweed-based polymers such as agar, gelatin, casein, albumin, animal-based polymers such as collagen, xanthene gum, microbial polymers such as dextran, semi-synthetic systems, methylcellulose, ethylcellulose, Cellulose polymers such as hydroxyethylcellulose, hydroxypropylcellulose and carboxymethylcellulose; starch polymers such as sodium starch glycolate and sodium starch phosphate; sodium alginate; propylene alginate Seaweed-based polymers such as recohol esters, pure synthetic systems include vinyl-based polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyvinyl methyl ether, non-crosslinked polyacrylamide, polyacrylic acid and alkali metal salts thereof, and water-soluble styrene acrylic resin. Acrylic resin, water-soluble styrene maleate resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleate resin, polyvinylpyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalenesulfonic acid formalin condensate,
Examples include a polymer compound having a salt of a cationic functional group such as a quaternary ammonium or an amino group in a side chain, and a natural polymer compound such as shellac.

As the surfactant having an alkyl group having 5 or more carbon atoms, a nonionic surfactant having a polyoxyalkylene group is preferable, and particularly, a polyoxyethylene alkyl represented by the following general formula (4). Phenyl ether, an acetylene glycol-based surfactant represented by the following general formula (5), a polyoxyethylene alkyl ether of the following general formula (6) or a polyoxyethylene polyoxypropylene alkyl ether of the following general formula (7) is preferable. . By using these nonionic surfactants, the surface tension of the recording ink is reduced, and the wettability between the recording ink and the surface of the recording paper is improved, whereby the recording ink for recording paper such as plain paper is used. To improve the drying property of the image and prevent the image from bleeding, thereby forming an image having excellent sharpness.

Further, the solubilization of the nonionic surfactant by the polyoxyalkylene chain improves the dispersion stability of the colorant, thereby obtaining a recording ink having excellent storage stability. Even after printing or after printing is stopped, a clear image with high resolution can be formed.

[0021]

Embedded image (In the formula, R ₇ represents a branched carbon chain having 6 to 14 carbon atoms, and k represents an integer of 5 to 20.)

[0022]

Embedded image (In the formula, m and n represent an integer of 0 to 40.)

[0023]

Embedded image (In the formula, R ₈ represents a carbon chain having 6 to 14 carbon atoms which may be branched, and n represents an integer of 5 to 20.)

[0024]

Embedded image (In the formula, R ₉ represents a carbon chain having 6 to 14 carbon atoms which may be branched, and n and m each represent an integer of 0 to 20. However, both n and m do not become 0.)

In particular, by using these surfactants and controlling the surface tension of the recording ink to 50 mN / m or less, the wettability between the recording ink and the surface of recording paper such as plain paper can be further improved. Thus, it is possible to enhance the permeability of the recording ink into the recording paper, improve the drying property of the recorded image, and prevent blurring of the image to form an image with excellent clarity.

Further, a polyoxyethylene alkyl ether acetate represented by the following general formula (1) and / or a dialkyl represented by the following general formula (2) which is an anionic surfactant together with a nonionic surfactant. It is preferred to use sulfosuccinate. By using these anionic surfactants, the permeability of the recording ink to recording paper such as plain paper is increased, the drying property of the image is improved, and the image with excellent sharpness is prevented by preventing image bleeding. Can be formed.

[0027]

Embedded image (Wherein, R ₁ represents an alkyl group which may have 6 to 14 carbon atoms and may be branched, M represents an alkali metal ion, a quaternary ammonium, a quaternary phosphonium or an alkanolamine. Represents an integer.)

[0028]

Embedded image (Wherein, R ₂ represents a branched alkyl group having 5 to 7 carbon atoms, M represents an alkali metal ion, a quaternary ammonium,
Represents quaternary phosphonium or alkanolamine. )

In particular, by using these surfactants and controlling the surface tension of the recording ink to 50 mN / m or less, the wettability between the recording ink and the surface of recording paper such as plain paper can be further improved. Thus, it is possible to enhance the permeability of the recording ink into the recording paper, improve the drying property of the recorded image, and prevent blurring of the image to form an image with excellent clarity. Prevention of image bleeding and formation of an image with excellent clarity can be achieved by using a polymer dye having an average molecular weight of 5,000 to 150,000, especially when a colorant is diffused between recording paper fibers. This is presumed to be due to suppression of the viscosity of the recording ink.

The surface tension is an index indicating the permeability of the recording ink into the recording paper.
It shows a dynamic surface tension in a short time of less than a second and is different from the static surface tension measured in the saturation time. As a measuring method, any method can be used as long as it can measure a dynamic surface tension of 1 second or less by a conventionally known method described in JP-A-63-31237.
The value is shown by a value measured using an ilhelmy type hanging plate surface tensiometer. The value of the surface tension is preferably 50 mN / m or less, and if it is particularly 40 mN / m or less, further excellent image drying properties can be obtained.

Specific examples of the polyoxyethylene alkyl ether acetate represented by the general formula (1) or the dialkyl sulfosuccinate represented by the general formula (2) are shown in Table 2 below in free acid form.

[0032]

[Table 2]

The counter ion of the polyoxyethylene alkyl ether acetate represented by the general formula (1) or the dialkyl sulfosuccinate represented by the general formula (2) includes sodium ion, lithium ion and Particularly preferred are quaternary ammonium, quaternary phosphonium and alkanolamine ions represented by the general formula (3). By setting the counter ion in this manner, the dissolution stability of these anionic surfactants can be further improved, and a recording ink having excellent storage stability can be obtained. In addition, it is possible to perform inkjet recording with high ejection reliability.

[0034]

Embedded image (Wherein, X represents a nitrogen atom or a phosphorus atom, and R ₃ , R ₄ ,
R ₅ and R ₆ represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a halogenated alkyl group. )

A counter ion of the above-mentioned polymer dye, or a counter ion of a polyoxyethylene alkyl ether acetate represented by the general formula (1) or a dialkyl sulfosuccinate represented by the general formula (2) is sodium ion, For example, sodium hydroxide, lithium hydroxide, or a hydroxide shown in Table 3 below can be used to convert lithium ion and quaternary ammonium, quaternary phosphonium, and alkanolamine ions represented by the general formula (3). May be added to the recording ink.

It is not necessary that all counter ions are sodium, lithium or a quaternary ammonium, quaternary phosphonium or alkanolamine ion represented by the general formula (3), and the counter ion may be mixed with another alkali ion. It can also be. Sodium, lithium or a quaternary ammonium represented by the general formula (3);
The amount of the secondary phosphonium or alkanolamine ion is determined by using a polymer dye or a compound represented by the general formula (1) or (2).
30 to the number of moles of the anionic surfactant represented by
% Or more, particularly preferably 50% or more.

[0037]

[Table 3]

The content of the polyoxyethylene alkyl ether acetate represented by the general formula (1) or the dialkyl sulfosuccinate represented by the general formula (2) in the recording ink is 0.05 to 10% by weight. % Is preferred. Within this range of content, it is possible to provide permeability to recording paper required for ink jet recording. 0.05% by weight
If it is less than this, bleeding is likely to occur at the boundary of the two-color overlapping portion, and if it exceeds 10% by weight, the anionic surfactant itself represented by the general formula (1) or (2) tends to precipitate at a low temperature. In addition, the colorant may be deposited, and the ejection reliability in the ejection recording is reduced.

Further, the content of the surfactant having an alkyl group having 5 or more carbon atoms in the recording ink is set to 0.1.
It is preferably from 0.05 to 10% by weight, particularly preferably from 0.1 to 5% by weight. Within this range of content, it is possible to provide permeability to recording paper required for ink jet recording.
If the amount is less than 0.05% by weight, bleeding is likely to occur at the boundary between the two-color overlapping portions. If the amount exceeds 10% by weight, the ejection reliability is reduced due to thickening with the passage of time.

When urea or a urea derivative such as hydroxyethyl urea or dihydroxyethyl urea is used together with the nonionic surfactant, the interaction between the polymer dye and the nonionic surfactant may be reduced. By weakening the association of the high molecular dye, the permeability of the recording ink into the recording paper can be improved, and the long-term storage stability of the recording ink and the ejection reliability in ink jet recording can be further improved. The added amount of these urea and urea derivatives is preferably 0.1 to 5% by weight of the recording ink. If the amount is less than 0.1% by weight, there is no effect. If the amount exceeds 5% by weight, the change in viscosity at the time of evaporation of water is affected, and the discharge reliability after printing pause may decrease.

The recording ink of the present invention has the above-mentioned various components dispersed or dissolved in water. However, in order to obtain the desired physical properties of the recording ink, it is necessary to dry the recording ink during storage. A water-soluble organic solvent is added to the recording ink of the invention for the purpose of preventing or improving the dissolution stability of the colorant or the surfactant.

Examples of such a water-soluble organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5 pentanediol, and 1,6.
Hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,
2,3-butanetriol, polyhydric alcohols such as petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether,
Polyhydric alcohol alkyl ethers such as propylene glycol monoethyl ether and the like, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone , 2-pyrrolidone, 1,3-dimethylimidazolidinone, nitrogen-containing heterocyclic compounds such as ε-caprolactam,
Amides such as formamide, N-methylformamide, N, N-dimethylformamide, amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, and sulfur-containing such as dimethylsulfoxide, sulfolane, thiodiethanol and the like. Compounds, propylene carbonate, ethylene carbonate, γ-butyrolactone, etc. can be exemplified,
These water-soluble organic solvents can be used alone or in combination of two or more.

Among these, particularly preferred water-soluble organic solvents are diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, and triethylene glycol.
Glycerol, 1,2,6-hexanetriol,
1,2,4-butanetriol, petriol, 1,5
-Pentanediol, N-methyl-2-pyrrolidone, N
-Hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, and the like. The use of these water-soluble organic solvents improves the dissolution stability of colorants and surfactants, and evaporates water. Can prevent drying of the recording ink, and can perform ink jet recording with excellent ejection reliability even after the recording ink is stored for a long period of time or even when printing is paused for a long period of time. it can.

In particular, when a pyrrolidone derivative such as N-hydroxyethyl-2-pyrrolidone is added to the recording ink, the dispersion stability of the colorant can be improved,
The storage stability of the recording ink can be further improved. As a result, even after the recording ink is stored for a long period of time, it is possible to perform inkjet recording with higher ejection reliability in inkjet recording.

The recording ink of the present invention has the general formulas (1), (2), and (3) for the purpose of adjusting the surface tension.
(4) In addition to the surfactant represented by (5), (6) or (7), diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether , Propylene glycol monobutyl ether, alkyl or aryl ethers of polyhydric alcohols such as tetraethylene glycol chlorophenyl ether, polyoxyethylene polyoxypropylene block copolymer, fluorine-based surfactant, or ethanol,
Lower alcohols such as 2-propanol can be added, and diethylene glycol monobutyl ether is particularly preferable.

As the colorant of the present invention, in addition to the above-mentioned polymer dye, other colorants can be mixed and used as required. Examples of such coloring agents include acid dyes, direct dyes, basic dyes, and the like in color indexes.
Water-soluble dyes classified into reactive dyes and food dyes and having excellent water resistance and light resistance are used. These are added within a range in which effects such as color reproducibility, water resistance, and light resistance are not excluded.

Specific examples of these dyes include acid dyes and food dyes such as C.I. I. Acid Yellow 1
7, 23, 42, 44, 79, 142, C.I. I. Acid Red 1,8,13,14,18,26,27,3
5,37,42,52,82,87,89,92,9
7, 106, 111, 114, 115, 134, 18
6,249,254,289, C.I. I. Acid Blue 9, 29, 45, 92, 249, C.I. I. Acid Black 1, 2, 7, 24, 26, 94, C.I. I. Food yellow 3, 4, C.I. I. Food Red 7, 9, 14,
C. I. As food black 1,2, direct dye,
C. I. Direct Yellow 1,12,24,26,3
3,44,50,86,120,132,142,14
4, C.I. I. Direct Red 1,4,9,13,1
7, 20, 28, 31, 39, 80, 81, 83, 8
9,225,227, C.I. I. Direct orange 2
6, 29, 62, 102, C.I. I. Direct Blue 1,2,6,15,22,25,71,76,79,8
6,87,90,98,163,165,199,20
2, C.I. I. Direct Black 19, 22, 32, 3
8, 51, 56, 71, 74, 75, 77, 154, 1
68,171; basic dyes such as C.I. I. Basic Yellow 1, 2, 11, 13, 14, 15, 19, 2
1,23,24,25,28,29,32,36,4
0, 41, 45, 49 • 51, 53, 63, 64, 6
5, 67, 70, 73, 77, 87, 91, C.I. I. Basic Red 2,12,13,14,15,18,2
2,23,24,27,29,35,36,38,3
9, 46, 49, 51, 52, 54, 59, 68, 6
9, 70, 73, 78, 82, 102, 104, 10
9, 112, C.I. I. Basic Blue 1,3,5
7, 9, 21, 22, 26, 35, 41, 45, 47,
54, 62, 65, 66, 67, 69, 75, 77, 7
8, 89.92, 93, 105, 117, 120, 12
2,124,129,137,141,147,15
5, C.I. I. Basic Black 2, 8 and reactive dyes include C.I. I. Reactive Black 3,4,7,1
1, 12, 17, C.I. I. Reactive Yellow 1,
5,11,13,14,20,21,22,25,4
0, 47, 51, 55, 65, 67, C.I. I. Reactive Red 1,14,17,25,26,32,37,
44, 46, 55, 60, 66, 74, 79, 96, 9
7, C.I. I. Reactive Blue 1,2,7,14,1
5,23,32,35,38,41,63,80,95
And the like, and particularly preferred are acid dyes and direct dyes.

Further, the recording ink of the present invention may contain additives known in the art, such as an antiseptic / antifungal agent, a rust inhibitor, p
An H adjuster, a water-soluble ultraviolet absorber or a water-soluble infrared absorber can be added. As preservatives and fungicides, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, and the like can be used. Sodium sulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like can be used.

As the pH adjuster, any substance can be used as long as it can adjust the pH to 6 or more without adversely affecting the prepared recording ink. pH
Specific examples of the modifier include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, and quaternary ammonium hydroxides. Examples include quaternary phosphonium hydroxides, carbonates of alkali metals such as lithium carbonate, sodium carbonate, and potassium carbonate. As the chelating reagent, for example, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like can be used.

By adjusting the pH of the recording ink of the present invention to 6 or more, especially 6 or more and 11 or less, the storage stability of the recording ink is improved, and the recording ink is left for a long time in a recording liquid cartridge in an ink jet printer or the like. Even in this case, inkjet recording can be performed without clogging of the inkjet nozzle. However, when the surfactant represented by the general formula (2) is used, pH
Is 9 or more, the surfactant is decomposed during storage of the recording ink, and the physical properties of the recording ink tend to change. Therefore, when the surfactant represented by the general formula (2) is used, the pH is 6 to 9 It is preferable to adjust to.

In order to perform ink-jet recording using the recording ink of the present invention, the recording ink is discharged from a fine discharge port having a diameter of, for example, 20 to 60 μm by thermal energy or mechanical energy, and the weight is 10 ng to 160 ng.
By forming an image on a recording material having a Steckigt sizing degree of 3 seconds or more, for example, so-called plain paper by flying at a speed of 5 to 20 m / s as liquid droplets, excellent water resistance and light resistance, and color reproducibility And a color image excellent in sharpness can be formed at high resolution.

The amount of ink adhered on the recording paper at this time is preferably 2.0 g / m ^{2 to} 100 g / m ² . According to the amount of adhesion, a good image density can be secured without causing a change in the recording paper due to water absorption such as curling or waving. In particular, 2.0 g of recording ink is applied to a recording paper having a Stighit sizing degree of 3 seconds or more.
/ M ^{2 to} 20 g / m ² , a high-resolution image with a resolution of 10 dots / mm × 10 dots / mm or more can be formed.

In addition, copy papers, tags, and the like generally used in offices and the like often have a pH of 5 to 6,
By performing inkjet recording using the recording ink of the present invention on these, an image having excellent water resistance and light resistance, good color reproducibility, and excellent clarity can be formed at high resolution. Furthermore, by using the recording ink of the present invention, an overhead projector (OH
An image excellent in color reproducibility and transparency can be formed on the transparent sheet for P), and a color image showing excellent color development during OHP projection can be obtained.

[0054]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 A composition having the following formulation was dissolved by stirring, adjusted with a 10% aqueous solution of lithium hydroxide so that the pH became 8.5, and filtered through a Teflon filter of 0.45 μm for recording. Ink 1 was obtained. Polymer dye of specific example (d) 3% by weight Styrene acrylic acid polymer 0.4% by weight Glycerol 5% by weight N-hydroxyethylpyrrolidone 5% by weight Surfactant of specific example (1-1) 0.5% by weight Surfactant of the general formula (4) (R ⁷ = C ₉ H ₁₉ , k = 18) 0.5% by weight Sodium dehydroacetate 0.2% by weight Deionized water

Example 2 Using the following composition, a recording ink 2 was prepared in the same manner as in Example 1 except that the pH was adjusted to 8.8 with sodium hydroxide. Polymer dye of specific example (c) 2% by weight 1,2,6-hexanetriol 4% by weight 1,5-pentanediol 8% by weight N-methyl-2-pyrrolidone 8% by weight Specific example (2-1) Surfactant 1.2% by weight Surfactant of general formula (5) (m, n = 10) 1.0% by weight 25% aqueous solution of specific example (3-1) 0.8% by weight sodium alginate 0.05 Weight% urea 5 weight% 2-pyridinethiol-1-oxide sodium 0.2 weight% ion exchange water

Example 3 A recording ink 3 was prepared in the same manner as in Example 1 except that the following composition was used and the pH was adjusted to 8.5 with lithium hydroxide. Polymer dye of specific example (b) 1.5% by weight Diethylene glycol 5% by weight Glycerol 5% by weight N-hydroxyethylpyrrolidone 10% by weight Styrene acrylic acid polymer 0.5% by weight Surfactant of general formula (4) ( R ⁷ = C ₉ H ₁₉ , k = 12) 2% by weight 0.2% by weight of a 25% aqueous solution of specific example (3-3) 0.2% by weight of sodium dehydroacetate Deionized water

Example 4 Using the following composition, a recording ink 4 was prepared in the same manner as in Example 1 except that the pH was adjusted to 9.5 with lithium hydroxide. Polymer dye of specific example (d) 1.2% by weight Ethylene glycol 5% by weight Glycerol 2% by weight 1,5-pentanediol 8% by weight 2-pyrrolidone 2% by weight Polyoxyethylene polyoxyethylene block copolymer 1% by weight % Surfactant of the general formula (7) (R ⁹ = C ₃ H ₇ , m, n = 20) 0.8% by weight 25% aqueous solution of specific example (3-4) 2% by weight Urea 5% by weight benzoic acid 0.2% by weight of sodium ion exchange water

Example 5 Using the following composition, a recording ink 5 was prepared in the same manner as in Example 1 except that the pH was adjusted to 7.8 with sodium hydroxide. Polymer dye of specific example (a) 1.5% by weight Triethylene glycol 5% by weight Petriol 10% by weight N-methyl-2-pyrrolidone 5% by weight Surfactant of the general formula (6) [R ⁸ = (C _{6 H 13) 2 CH-, n} = 12 ] 2 wt% examples (3-2 25% aqueous solution of 1.5 wt% hydroxyethyl urea 5 wt% 2-pyridine thiol-1-oxide sodium 0.2 wt.) of % Ion exchange water Remaining

Example 6 Using the following composition, a recording ink 6 was prepared in the same manner as in Example 1 except that the pH was adjusted to 8 with lithium hydroxide. Polymer dye of specific example (d) 1.5% by weight 2-Pyrrolidone 8% by weight Glycerol 7% by weight Surfactant of general formula (5) (m, n = 20) 1% by weight Interface of general formula (5) Activator (m, n = 10) 1% by weight 25% aqueous solution of specific example (3-7) 2% by weight Hydroxyethyl urea 5% by weight Sodium dehydroacetate 0.2% by weight Deionized water

Example 7 Using the following composition, a recording ink 7 was prepared in the same manner as in Example 1 except that the pH was adjusted to 8 with lithium hydroxide. 2.3% by weight of polymer dye of specific example (a) 0.8% by weight of polymer dye of specific example (c) 8% by weight of N-methyl-2-pyrrolidone 8% by weight of 1,5-pentanediol 8 Surfactant (7) (R ⁹ = lauryl group, m = 18, n = 6) 2% by weight Sodium benzoate 0.5% by weight Io-exchanged water

Comparative Example 1 In Example 1, C.I. was replaced with the polymer dye of the specific example (d). I. Example 1 except that Acid Blue 249 was used.
In the same manner as in the above, recording ink 8 was obtained.

Comparative Example 2 In Example 2, C.I. I. Example 2 except that Acid Yellow 23 was used.
In the same manner as in the above, recording ink 9 was obtained.

Comparative Example 3 In Example 3, C.I. was replaced by the polymer dye of the specific example (b). I. A recording ink 10 was obtained in the same manner as in Example 3 except that Acid Red 35 was used.

Comparative Example 4 The procedure of Example 4 was repeated, except that the polymer dye of Example (d) was replaced by C.I. I. A recording ink 11 was obtained in the same manner as in Example 4 except that Acid Blue 9 was used.

Comparative Example 5 In Example 5, C.I. I. Recording ink 12 was obtained in the same manner as in Example 5 except that Pigment Red 122 was used.

Comparative Example 6 In Example 6, C.I. was replaced with the polymer dye of the specific example (a). I. A recording ink 13 was obtained in the same manner as in Example 6, except that Direct Red 9 was used and the pH was adjusted in place of ammonium hydroxide for lithium hydroxide.

Next, the above Examples 1 to 7 and Comparative Examples 1 to 6
The following tests were performed on the recording inks obtained by the above. Table 4 shows the results.

1) Clearness of image Nozzle diameter of thermal ink jet system 45 μm, 30
Nozzle diameter 33 using inkjet printer having 0 dpi nozzle and laminated PZT for pressurizing liquid chamber flow path
μm, printing is performed on three types of recording paper, commercially available recycled paper, woodfree paper, and bond paper, using an inkjet printer having 128 nozzles, and the printed image is blurred at the boundary of a two-color overlapping portion, image blur, color tone, The density was comprehensively judged visually and the sharpness of the image was evaluated. In Table 4, a circle indicates a case where the characteristics of the printed image are good on any of the three types of recording paper, a triangle indicates a case where the characteristics of at least one type of recording paper are satisfactory, and a cross indicates that the characteristics of the three types of recording paper are good. The case where any of the papers is defective is shown. In addition, printing was performed on a PET film having a layer mainly composed of PVA on the surface using the recording inks of Examples and Comparative Examples, and the PET film having the printed image was projected by an overhead projector to evaluate the coloring properties. Was. In Table 4, the mark が indicates that the transparency is high and the color development of the two-color overlapping portion and the single-color portion is good, and the symbol Δ indicates that the coloring of the single-color portion is good but the coloring of the two-color overlapping portion is slightly dull. , And the crosses indicate that the color development in the single color portion is also poor.

2) Water resistance of image The printed image sample was immersed in water at 30 ° C. for 1 minute, and the change in image density before and after the treatment was measured with a Macbeth densitometer. The water resistance (fading rate%) was calculated by the following equation. I asked. In Table 4,
印 indicates that the water resistance (fading rate%) was less than 10% in any of the three types of recording paper, and △ indicates that the water resistance was 10% or more.
The case where it is less than 0% and the case where X is 30% or more are shown. Fading rate (%) = [1- (image density after processing / image density before processing)] × 100

3) Lightfastness of Image The printed image sample was irradiated with a xenon feed meter at a black panel temperature of 63 ° C. for 3 hours, and the change in image density before and after the treatment was measured with a Macbeth densitometer. %). In Table 4, the circles indicate light fastness (fading rate%) for all three types of recording paper.
Is less than 5%, Δ indicates a case of 5% or more and less than 30%, and X indicates a case of 30% or more. Fading rate (%) = [1- (image density after processing / image density before processing)] × 100

4) Drying of Image The filter paper was pressed against the image after printing under certain conditions, and the time until the recording ink was not transferred to the filter paper was measured. In Table 4, the case where all of the three types of recording paper were dried within 10 seconds was indicated by ○, and the case where longer time was required was indicated by ×.

5) Storage stability Each recording ink was placed in a polyethylene container and stored at -20 ° C.
It was stored for 3 months under the conditions of 5 ° C, 20 ° C, and 70 ° C, and the surface tension, viscosity, and the presence or absence of precipitates after storage were examined. In Table 4, a circle indicates that there was no change in physical properties and the like, a triangle indicates that there was no precipitation but a large change in physical properties, and a cross indicates that precipitation was observed.

6) Reliability at the time of printing suspension Using an ink jet printer equipped with a PZT-driven head having a nozzle diameter of 30 μm and 128 nozzles, how much printing suspension without capping, cleaning, etc. during operation The reliability was evaluated by examining how long the ejection direction could be shifted or the weight of the ejected droplets changing, even if the ejection could be restored. In Table 4, circles indicate that there was no problem with printing pause of 600 seconds,
The symbol “Δ” indicates that the change in the droplet weight was small and the shift in the ejection direction was small after printing for 600 seconds, and the symbol “X” indicates that significant clogging occurred after printing was stopped for 600 seconds.

[0075]

[Table 4]

As is evident from Table 4, when the recording inks obtained in the examples were used, the images were excellent in color tone, good in color reproducibility, free of bleeding and high in density, and provided clear images. An image excellent in water fastness and light fastness can be obtained using any recording paper, and the image is also excellent in drying property. Furthermore, the recording inks obtained in the examples have excellent storage stability, and can perform inkjet recording with high ejection reliability even after long-term storage or even after printing is stopped.

On the other hand, the recording inks obtained in Comparative Examples did not satisfy any of these. That is, the recording ink obtained in Comparative Example 1 has poor image clarity due to bleeding, and has poor water resistance of the image, and the recording ink obtained in Comparative Example 2 has poor water resistance of the image. Met. The recording ink obtained in Comparative Example 3 is inferior in image clarity due to occurrence of bleeding and has poor image light fastness, and the recording ink obtained in Comparative Example 4 has poor image clarity and image light fastness. However, the storage stability of the recording ink was poor.

The recording ink obtained in Comparative Example 5 was inferior in image clarity due to bleeding, the storage stability of the recording ink was poor, and the ejection reliability was poor. In addition, the recording ink has poor image clarity, poor light resistance of the image, and poor storage stability of the recording ink. Furthermore, when the recording ink obtained in the example was used, the OHP suitability was good, but when the recording ink obtained in Comparative Examples 1 and 5 was used, the OHP suitability was poor. Was something.

[0079]

According to the present invention, it is possible to form a clear image having excellent color tone, good color reproducibility, little bleeding of the color boundary and little bleeding of the image, and excellent in water fastness and light fastness of the image. A recording ink can be obtained. According to the present invention, it is possible to obtain a recording ink that has excellent storage stability and high ejection reliability in ink jet recording even after long-term storage or after printing suspension.

Further, according to the present invention, the recording ink has a high permeability to recording paper such as plain paper, is excellent in drying property of the formed image, and forms a clear image by preventing bleeding of the image. And a recording ink that can be obtained. Further, by the inkjet recording method using the recording ink of the present invention, an image having excellent water resistance and light resistance, good color reproducibility, and excellent clarity can be formed at high resolution.

Further, by using the recording ink of the present invention, it is possible to form an image having excellent color reproducibility and transparency on a transparent sheet for an overhead projector (OHP), and exhibit excellent color development during OHP projection. A color image can be obtained.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Akiko Konishi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hirotaka Mochizuki 1-3-6 Nakamagome, Ota-ku, Tokyo Share Inside Ricoh Company (72) Inventor Takanori Tsukiki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Ikuko 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Masayuki Koyano Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo

Claims (8)

[Claims] 1. A recording ink comprising a colorant dispersed or dissolved in water, water and a water-soluble organic solvent as main components,
A high molecular compound having a hydrophilic part and a hydrophobic part as a dispersant and / or a polymer compound having 5 or more carbon atoms, which contains a polymer dye having an average molecular weight of 5,000 to 150,000 as a coloring agent and having a boric acid group in a repeating structure. A recording ink comprising a surfactant having an alkyl group. 2. The recording ink according to claim 1, wherein at least one of the surfactants is a nonionic surfactant having a polyoxyalkylene group. 3. A nonionic surfactant, wherein the surfactant has at least a polyoxyalkylene group, and a polyoxyethylene alkyl ether acetate represented by the following general formula (1) and / or a compound represented by the following general formula (2): The recording ink according to claim 1, which is a dialkyl sulfosuccinate represented by the following formula. Embedded image (Wherein, R ₁ represents an alkyl group which may have 6 to 14 carbon atoms and may be branched, M represents an alkali metal ion, a quaternary ammonium, a quaternary phosphonium or an alkanolamine. Represents an integer.) (Wherein, R ₂ represents a branched alkyl group having 5 to 7 carbon atoms, M represents an alkali metal ion, a quaternary ammonium,
Represents quaternary phosphonium or alkanolamine. ) 4. A polyoxyethylene alkyl ether acetate or dialkyl sulfosuccinate having a counter ion of sodium, lithium and / or a quaternary ammonium, quaternary phosphonium or alkanolamine represented by the following general formula (3): 4. A cation.
The recording ink described in the above. Embedded image (Wherein, X represents a nitrogen atom or a phosphorus atom, and R ₃ , R ₄ ,
R ₅ and R ₆ represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a halogenated alkyl group. ) 5. The nonionic surfactant having a polyoxyalkylene group is at least one selected from surfactants represented by the following general formulas (4), (5), (6) and (7). The recording ink according to claim 2, wherein the recording ink is provided. Embedded image (In the formula, R7 represents a carbon chain having 6 to 14 carbon atoms which may be branched, and k represents an integer of 5 to 20.) (In the formula, m and n represent an integer of 0 to 40.) (In the formula, R ₈ represents a carbon chain having 6 to 14 carbon atoms which may be branched, and n represents an integer of 5 to 20.) (In the formula, R ₉ represents a carbon chain having 6 to 14 carbon atoms which may be branched, and n and m each represent an integer of 0 to 20. However, both n and m do not become 0.) 6. The recording ink according to claim 2, wherein at least one urea derivative is contained together with the nonionic surfactant having a polyoxyalkylene group. 7. The recording ink according to claim 1, wherein at least one pyrrolidone derivative is contained as a water-soluble organic solvent. 8. The recording ink according to claim 1, which is jetted as fine droplets by thermal energy or mechanical energy, and the recording ink is applied to a recording material having a Steckigt sizing degree of 3 seconds or more. .0g / m ² to 20 g / m ²
A recording method characterized in that an image having a resolution of 10 dots / mm × 10 dots / mm or more is formed on a recording material by causing the recording material to adhere to the recording medium.