Aqueous black ink

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to inks for printing, writing, recorders, and inkjet recordings, particularly black water-based inks capable of forming clear images having excellent color tones.

【0002】

[Conventional technology]

The inkjet recording method, which records images by ejecting liquid ink from a nozzle, is capable of printing on plain paper, is easy to handle in color, and has low driving noise and power consumption. For these reasons, it has rapidly become widespread in recent years as a printer for outputting documents and images created by computers.

【0003】

Recently, advances in inkjet recording technology have made it possible to obtain high-quality images comparable to photographs, and along with this, improvement in color tone and color reproducibility of printed images are required. Development is being actively carried out. Among such studies, there are many inventions relating to black water-based inks, which are disclosed in, for example, JP-A-05-246977, JP-A-06-041460, JP-A-06-340820 and the like. However, these black inks have problems such as insufficient color tone and image density, blurring of images, and poor light resistance when printing is performed on plain paper usually used in offices.

【0004】

Therefore, it is desired to develop a black ink capable of forming a high-quality image having an even better color tone even on plain paper as compared with such a conventional ink.

【0005】

In order to improve the color tone of black ink, there is a method of blending a dye as a complementary color with a black dye, and examples thereof include JP-A-07-102199 and JP-A-09-255906. However, in these water-based inks, by mixing two or more kinds of dyes, problems such as clogging at the time of ejection and deterioration of water resistance and light resistance may occur. At present, no black water-based ink that solves all of these problems has been obtained.

【0006】

[Problems to be Solved by the Invention]

An object of the present invention is to provide a new ink composition capable of eliminating the above-mentioned drawbacks of a conventionally used black water-based ink. That is, it is an object of the present invention to provide a black water-based ink which has excellent color tone as compared with the conventional one, has good water resistance and light resistance, can obtain a homogeneous image with less bleeding, and is less likely to cause reliability problems such as clogging. It is a thing.

【0007】

[Means for solving problems]

The dye represented by the following general formula (A) is excellent in weather resistance and solubility by itself, but has a drawback in black tone.

【0008】

[Chemical 2]

<img file="JP2001192589A_D0001.tif" />【0009】

However, R₁, R₂: Hydrogen, alkyl group, alkoxy group, hydroxyalkyl group, halogen, carboxyl group, nitrile group, sulfonic acid group, carbomoyl group, sulfamoyl group, acetyl group, acetylamino group M: Hydrogen, alkali metal, quaternary ammonium, quaternary phosphonium, organic amine cation [0010]

Therefore, as a result of various studies on complementary colorants of dyes represented by the general formula (A), the present inventors have found that a pigment dispersion having a pigment concentration of 0.005% by weight under measurement conditions of a D50 light source with a 2 ° field field and a transmitted light path length of 10 mm. CIE1976L * a * b * of all transmitted colors obtained by condensing transmitted light with an integrating sphere Pigments with hue angles H of 0 to 135 ° and 315 to 360 °, especially carbon black or CI pigment red 22 , 53: 1, 48: 1, 104, CI Pigment Orange 5, 13, 16, 38, etc. are used as complementary colors to obtain an ideal black tone when the dye represented by the general formula (A) is used. It has been found that a black water-based ink having excellent water resistance and light resistance, and which does not cause clogging can be obtained.

【0011】

CIE1976L * a * b * color system hue angle H can be calculated by using a * b *. a^* 0, b^*When 0, H = tan^-1(b^*/ a^*) a^*When 0, H = 180 + tan^-1(b^*/ a^*) a^* 0, b^*When 0, H = 360 + tan^-1(b^*/ a^*) It is expressed as. Hue angles H of 0 to 135 ° and 315 to 360 ° are ranges corresponding to red, orange, and yellow.

【0012】

In the ink of the present invention, the mixing ratio of the dye of the general formula (A) and carbon black is preferably 50: 1 to 2: 1. If the content of carbon black is higher than this range, a good black tone cannot be obtained, which may cause problems in reliability such as separation of dye and pigment, clogging due to agglomeration of coloring material, and storage stability. There is sex. If it is less than this range, a sufficient color tone correction effect may not be obtained, and water resistance, light resistance, and the like may be inferior. More preferably, the mixing ratio of the dye (A) and carbon black is ideally in the range of 30: 1 to 5: 1.

【0013】

Other pigments used in the inks of the present invention are CI Pigment Red 22, 53: 1, 48: 1, 104, CI Pigment Orange 5, 13, 16, 38 and the like. These are pigments having a hue angle H of about 30 to 60 ° in the transmission color of the pigment dispersion liquid having a pigment concentration of 0.005% by weight. These pigments may be used alone or in admixture. In addition to this, in the present invention, pigments having a CIE1976L * a * b * color hue angle H of 0 to 135 ° and 315 to 360 ° can be used.

【0014】

The average particle size of such pigments used in the present invention is preferably 0.01 to 0.lμm. If it is larger than this, reliability problems such as clogging at the time of discharge and storage stability may occur, and if it is smaller than this, various properties which are advantages of the pigment such as water resistance and light resistance may not be exhibited.

【0015】

Various dispersers such as ball mills, sand mills, roll mills, colloid mills, ultrasonic homogenizers, and high-pressure homogenizers can be used to disperse these pigments.

【0016】

Specific examples of the dye represented by the general formula (A) are listed below.

【0017】

[Chemical 3]

<img file="JP2001192589A_D0002.tif" />【0018】

The total content of the dye represented by the above general formula (A) and the pigment of carbon black or CIE1976L * a * b * color hue system hue angle H of 0 to 135 ° and 315 to 360 ° is the wetting agent and water. Although it depends on the type of iso-solvent component, the characteristics required for the recording solution, etc., it is generally in the range of 0.5 to 30% by weight, preferably 3 to 10% by weight, based on the total amount of the recording solution.

【0019】

In the present invention, various water-soluble organic solvents can be used as a wetting agent or as a dissolution stabilizer for ink components in order to prevent clogging at the nozzle portion of the inkjet printer. For example, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetra. Polyhydric alcohol alkyl ethers such as ethylene glycol monomethyl ether and propylene glycol monoethyl ether, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, N-methyl-2-virolidone, N- Nitrogen-containing heterocyclic compounds such as hydroxyethyl-2-pyrrolidone, l,3-dimethylimidazolidinone, ε-cabrolactam, γ-butyrolactone, amides such as formamide, N-methylformamide, N, N-dimethylformamide, Amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane, and thiodiethanol, propylene carbonate, ethylene carbonate, etc. are used alone or in combination of two or more. Be done. The content of these water-soluble organic solvents in the ink is preferably l to 40% by weight, more preferably 5 to 20% by weight.

【0020】

In addition, various penetrants can be used to adjust the surface tension. Specifically, alkyl and aryl ethers of polyhydric alcohols such as ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether, and polyoxy. Ethylene alkyl ether acetate, anionic surfactants such as dialkyl sulfoaquatic acid having an alkyl chain with 5 to 7 branched carbon chains, acetylene glycol type, polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ether type, etc. Non-ionic surfactants, fluorine-based surfactants, silicon-based surfactants, lower alcohols such as ethanol and 2-propanol, etc. are used alone or in combination of two or more. The content of these penetrants in the ink is preferably 0.5 to 5% by weight, more preferably 0.5 to 2% by weight.

【0021】

As a pigment dispersant, it is a hydrophilic polymer, and in the natural system, it is a vegetable polymer such as Arabic gum, tragan gum, gourd gum, karaya gum, low-strength stobean gum, arabinogalactone, pectin, quince seed starch, alginic acid, carrageenan, agar, etc. Seaweed macromolecules, animal macromolecules such as gelatin, casein, albumin, collagen, microbial macromolecules such as xantene gum, dextran, and fibers such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose in semi-synthetic systems. Elementary polymers, starch-based polymers such as sodium starch glycolate and sodium starch phosphate, seaweed-based polymers such as sodium alginate and bropylene glycol alginate, and polyvinyl alcohol, polyvinylpyrrolidone, and polyvinylmethyl ether for pure synthetic systems. Vinyl-based polymers such as non-crosslinked polyacrylamide, polyacrylic acid and its alkali metal salts, acrylic resins such as water-soluble styrene acrylic resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene. Maleic acid resin, polyvinylpyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalene sulfonic acid formarin condensate, polymer compound having a salt of a force thionic functional group such as quaternary ammonium or amino group in the side chain, cellac, etc. Examples include natural polymer compounds.

【0022】

Further, in addition to the above dyes and solvents, the ink of the present invention includes conventionally known additives such as antiseptic and antifungal agents, pH adjusters, chelating reagents, rust preventives, and other UV absorbers and infrared rays depending on the purpose. Absorbents, water-soluble polymer compounds, dye solubilizers and the like can be added.

【0023】

The ink of the present invention has a hue angle H of 0 to 135 ° and 315 to 360 ° of a pigment dispersion having a pigment concentration of 0.005% by weight in a dye solution in which a dye represented by the general formula (A) and other additives are dissolved. It can be produced by dispersing at least one or more pigments selected from the pigments.

【0024】

Further, the ink of the present invention is represented by the general formula (A) in a pigment dispersion solution in which at least one pigment selected from pigments having a hue angle H of 0 to 135 ° and 315 to 360 ° is dispersed in water and water. It may be produced by separately preparing a dye solution in which the above dyes and other additives are dissolved in water, mixing the colorant solutions thereof, and then dispersing the solution again.

【0025】

Generally, when dyes or pigments having different molecular structures or particle shapes are added to the ink at the same time, the dispersed state of the colorant particles becomes unstable and the colorant particles tend to aggregate. Therefore, when a plurality of colorants are added, the colorants, dispersants, and additives must be carefully selected. Further, when a dye or various additives are added to the pigment dispersion liquid at the time of ink production, the dispersed state of the pigment becomes unstable, which may cause inconveniences such as aggregation and separation. When the pigment is dispersed in a solution in which a dye or an additive is dissolved in advance as in the present invention, or when the pigment dispersion liquid and the dye solution are mixed and then redispersed, the above-mentioned pigment aggregation and separation are unlikely to occur. It is possible to prevent clogging at the time of discharge and deterioration of storage stability.

【0026】

BEST MODE FOR CARRYING OUT THE INVENTION

Examples and comparative examples of the present invention are shown below. % Are all weight%.

【0027】

Example 1 (Pigment Dispersion Liquid 1) The composition of the following formulation was roughly dispersed using a homogenizer, and then the average particle size was dispersed to 0.1 μm or less using a nanomizer to prepare a pigment dispersion liquid 1. Carbon black (surface hydrophilized with plasma) 10.0% Styrene acrylic acid copolymer 5.0% Ion-exchanged water remaining amount [0028]

(Ink Composition) Next, prepare a dye solution in which the components of the composition of the following formulation excluding the pigment dispersion are stirred and dissolved, and the pigment dispersion is mixed with this dye solution so that the pH of the solution becomes 8.5. Adjusted with lithium hydroxide. This solution was dispersed with a nanomizer and filtered with a 0.8 μm Teflon filter to prepare an ink.

【0029】

Specific example (A-1) dye 3.5% Diethylene glycol 10.0% N-Methyl-2-pyrrolidone 5.0% Sodium dehydroacetate 0.2% Pigment dispersion 1 0.5% Ion-exchanged water remaining amount [0030]

Inks of Examples 2 to 3 and Comparative Example 1 were prepared in the same manner as in Example 1 except that a material having the following composition was used.

【0031】

Example 2 (Pigment dispersion 2) Carbon black (surface hydrophilized with plasma) 10.0% Styrene Methacrylic Acid Copolymer 5.0% Ion-exchanged water remaining amount (Ink composition) Specific example (A-2) dye 3.5% Ethylene glycol 15.0% Triethylene glycol monomethyl ether 5.0% Sodium dehydroacetate 0.2% Pigment dispersion 2 0.5% water Remaining amount [0032]

Example 3 (Pigment dispersion liquid 3) CI Pigment Red 53: 1 10.0% Polyoxyethylene Polyoxyethylene Block Copolymer 4.5% Ion-exchanged water remaining amount (Ink composition) Specific example (A-3) dye 4.0% Diethylene glycol 20.0% 1,3-Dimethylimidazolidinone 5.0% 2,4-Dimethyl-6-acetoxy-m-dioxane 0.3% Pigment dispersion 0.04% Remaining water [0033]

Comparative example 1 (Ink composition) Specific example (A-1) dye 3.0% Diethylene glycol 15.0% N-Methyl-2-pyrrolidone 15.0% Sodium dehydroacetate 0.2% Pigment dispersion 1 8.5% Remaining water [0034]

Example 4 First, a dye solution was prepared by stirring and dissolving the carbon black of the following formulation and a composition other than the dispersant. Next, carbon black and a dispersant were added to this dye solution, roughly dispersed with a homogenizer, and then dispersed with an average particle size of 0.1 μm or less using a nanomizer. Further, this solution was adjusted with lithium hydroxide so that the pH became 8.5, and then filtered through a 0.8 μm Teflon filter to prepare an ink.

【0035】

Carbon black (surface hydrophilized with plasma) 0.5% Styrene acrylic acid copolymer 0.25% Specific example (A-1) dye 3.5% Diethylene glycol 20.0% Glycerin 5.0% 2,4-Dimethyl-6-acetoxy-m-dioxane 0.3% Remaining water [0036]

The inks of Examples 5 to 6 were prepared in the same manner as in Example 4 except that a material having the following composition was used.

【0037】

Example 5 CI Pigment Orange 13 0.05% Styrene Methacrylic Acid Copolymer 0.025% Specific example (A-2) dye 5.5% Diethylene glycol 15.0% Glycerin 5.0% N-Methyl-2-pyrrolidone 3.0% Sodium dehydroacetate 0.2% Remaining water [0038]

Example 6 CI Pigment Orange 104 0.02% CI Pigment Orange 13 0.05% Styrene α-styrene methacrylic acid copolymer 0.02% Specific example (A-4) dye 3.5% Diethylene glycol 20.0% Glycerin 5.0% 2,4-Dimethyl-6-acetoxy-m-dioxane 0.3% Remaining water [0039]

The composition of the following formulation was stirred and dissolved, and this solution was further adjusted with lithium hydroxide so that the pH became 8.5, and then filtered through a 0.8 μm Teflon filter to prepare inks of Comparative Examples 2 to 3.

【0040】

Comparative example 2 CI Hood Black 2 3.0% Diethylene glycol 20.0% Glycerin 5.0% 2,4-Dimethyl-6-acetoxy-m-dioxane 0.3% Remaining water [0041]

Comparative example 3 Specific example (A-2) dye 3.0% CI Direct Red 9 1.0% Polyethylene glycol 200 15.0% Triethylene glycol monomethyl ether 5.0% Sodium dehydroacetate 0.2% Remaining water [0042]

[Evaluation] The following tests were conducted on Examples 1 to 7 and Comparative Examples 1 to 3. 1) Image color tone Each ink was filled in an inkjet printer (Ricoh inkjet printer, Ipsio Jet 300), and printing was performed on commercially available plain paper.

【0043】

The reflection spectrum of the printed image sample was measured with a reflection type color spectrophotometric densitometer manufactured by X-Rite, and the color tone was examined.

【0044】

As a result, the color tone [Number 1]

<img file="JP2001192589A_D0003.tif" />Those that become are shown in the table with a circle.

[a^*, B^*Is CIE1976L^*a^*b b^*Color system (a^*, B^*) Saturation coordinates] [0045]

2) Light resistance of the image The image sample obtained in 1) was placed on a fade meter (carbon arc lamp, 63 ° C) for 3 hours, and the image density before and after light irradiation was measured with a reflective color spectrophotometric densitometer manufactured by X-Rite. The light resistance (fading rate) was determined by the formula. Fading rate (%) = [1- (Image density after light irradiation / Image density before light irradiation)] x 100 [0046]

3) Water resistance of the image Immerse the image sample obtained in 1) in water at 30 ° C for 1 minute, measure the image density before and after immersion with a reflective color spectrophotometric densitometer manufactured by X-Rite, and perform the same as the formula in item 2). The water resistance (fading rate%) was determined by the formula.

【0047】

4) Preservation Put the ink in a polyethylene container and store it under the conditions of -20 ° C, 4 ° C, 20 ° C, 50 ° C, 70 ° C for 3 months. The change in conductivity and the presence or absence of precipitation were examined. In the table, those that did not change in physical properties or generate precipitates under any conditions were marked with .

【0048】

5) Nozzle clogging test After printing in 1), it was left for 2 months in an environment of 20 ° C and 65% RH with the printing paused, and after leaving it, it was investigated whether normal printing was possible again. One ink sample was tested using three printers. In the table, the cases where all three printers were able to print normally are indicated by , and the cases where one or two of the three printers were unable to print normally are indicated by ×.

【0049】

[table 1]

<img file="JP2001192589A_D0004.tif" />【0050】

[Effect of the invention]

(1) In the invention of claim 1, the black water-based ink of the present invention is a dye represented by the general formula (A), and a pigment concentration of 0.005% by weight under measurement conditions of a D50 light source 2 ° field field and a transmitted light path length of 10 mm. CIE1976L * a * b * of the transmission color of the dispersion liquid Contains at least one pigment selected from pigments having a colorimetric hue angle H of 0 to 135 ° and 315 to 360 °, and is a conventional black color. Compared to water-based inks, it has an excellent black tone and is also excellent in light resistance and water resistance. In addition, the ink composition has good ejection stability and storage stability when used as an ink for an inkjet printer.

【0051】

(2) In claim 2, the black water-based ink of the present invention contains the dye represented by the general formula (A) and carbon black or surface-treated carbon black, so that the black color and light resistance are superior to those of the conventional ink. It has properties and water resistance, and does not deteriorate the ink ejection characteristics.

【0052】

(3) In claim 3, the black water-based ink of the present invention has a weight ratio of the dye represented by the general formula (A) to carbon black in the ink composition in the range of 50: 1 to 2: 1. , The black tone of the image can be improved without impairing the ink ejection characteristics.

【0053】

(4) In claim 4, the black water-based ink of the present invention is a dye represented by the general formula (A) and CI Pigment Red 22, 53: 1, 48: 1, 104, CI Pigment Orange 5, 13, 16 By containing at least one pigment selected from, 38, it has excellent black tone, light resistance, and water resistance as compared with the conventional ones, and does not deteriorate the ink ejection characteristics.

【0054】

(5) In claim 5, the black water-based ink of the present invention is a dye represented by the general formula (A) in an ink composition and CI Pigment Red 22, 53: 1, 48: 1, 104, CI Pigment Orange 5 By setting the weight ratio of at least one pigment selected from, 13, 16, and 38 to the range of 200: 1 to 20: 1, it is possible to improve the black tone of the image without impairing the ejection characteristics of the ink.

【0055】

(6) In claim 6, the black water-based ink of the present invention contains a dye represented by the general formula (A) and a pigment having an average particle size of 0.01 to 0.lμm, thereby impairing the ejection characteristics of the ink. The black tone, water resistance, and light resistance of the image can be improved without any problem.

【0056】

(7) In claim 7, the black water-based ink of the present invention is CIE1976L * a, which is a transparent color of a pigment dispersion having a pigment concentration of 0.005 wt% in a dye solution in which a dye represented by the general formula (A) is dissolved in water. * b * By dispersing at least one pigment selected from pigments having a hue-based hue angle H of 0 to 135 ° and 315 to 360 ° to produce a water-based ink, the ink ejection characteristics and storage It is possible to improve the black tone, water resistance, and light resistance of an image without impairing stability.

【0057】

(8) In claim 8, the black water-based ink of the present invention is a transparent color of a dye solution in which a dye represented by the general formula (A) is dissolved in water and a pigment dispersion having a pigment concentration of 0.005 wt% CIE1976L * a. * b * A pigment dispersion in which at least one pigment selected from pigments having a color-based hue angle H of 0 to 135 ° and 315 to 360 ° is dispersed in water is mixed, and then further redispersed. By producing the water-based ink, it is possible to improve the black tone, water resistance, and light resistance of the image without impairing the injection characteristics and storage stability of the ink.