JP2000256599A - Aqueous ink composition, ink-jet recording and record - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous ink composition having a high printing concentration and dispersion stability. SOLUTION: This ink composition comprises a surface modified carbon black which has <1 second penetration time at 1 mg/cm2 application amount, 50% accumulated diameter of >=60 nm and 90% accumulated diameter of <=300 nm and is dispersible and/or soluble in water without a dispersant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous ink using carbon black as a coloring agent. More specifically, the present invention relates to improvement of an aqueous ink composition containing a surface-modified carbon black that can be dispersed and / or dissolved in water.

[0002]

2. Description of the Related Art Conventionally, water-soluble dyes have been used as recording liquids for aqueous writing instruments and ink jet printers. In recent years, pigments such as carbon black have been used as colorants in order to improve the image quality and durability of recorded matters.

For example, JP-A-64-6074 and JP-A-64-31881 describe aqueous pigment inks in which carbon black is dispersed with a surfactant or a polymer dispersant.

However, with these inks, when the ink content of the colorant is increased in order to increase the print density of the recorded matter, there arises a problem that the viscosity of the ink sharply increases at the same time. Also, in order to stably disperse, an excess of a surfactant or a polymer dispersant is necessary, but these cause the generation of bubbles and a decrease in defoaming property. There is a problem that leads to deterioration of stability.

In order to solve these problems, Japanese Patent Laid-Open Publication No.
No. 3498 and JP-A-10-120958 disclose that a certain amount or more of surface active hydrogen or a salt thereof is introduced into carbon black, and the carbon black treated without a surfactant or a polymer dispersant is spontaneously used alone. A dispersion using a surface-modified carbon black that can be dispersed in water is described. Alternatively, Japanese Patent Application Laid-Open No. H10-110127 describes a method of introducing a sulfone group into carbon black. Further, JP-A-10-95941 proposes an inkjet ink containing the above-mentioned surface-modified carbon black and glycol ethers.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous ink composition for realizing a demand for a higher quality recorded matter. Specifically, the present invention has a higher print density and a higher dispersion stability. It is an object of the present invention to provide a suitable aqueous ink composition.

[0007]

Means for Solving the Problems The aqueous ink composition of the present invention has a surface that can be dispersed and / or dissolved in water without a dispersing agent, when the coating amount is 1 mg / cm ² and the penetration time is less than 1 second. An aqueous ink composition containing at least a modified carbon black, wherein
0% cumulative diameter is 60 nm or more and 90% cumulative diameter is 300
nm or less.

The ink jet recording method of the present invention is characterized in that the ink composition of the present invention is discharged as droplets from a fine nozzle, and the droplets are attached to a recording medium.

The recorded matter of the present invention is characterized by being printed by the aqueous ink composition ink jet recording method of the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous ink composition of the present invention contains at least a surface-modified carbon black which can be dispersed and / or dissolved in water without a dispersant such as a surfactant or a water-soluble resin. Penetration time at 1 mg / cm ² is 1
Ink that is less than a second. In addition, the above-mentioned surface-modified carbon black has a 50% cumulative diameter of 60 nm or more and 9%.
It has a 0% cumulative diameter of 300 nm or less.

When the amount of application is 1 mg / cm ² , the penetration time is 1
The ink that is shorter than a second is, for example, 360d
Pi (dot / inch) x 360 dpi area 50n
When g of ink is applied to plain paper, this refers to an ink that takes less than 1 second until the ink is not stained even when the printing surface is touched. More specifically, neutral plain paper Xerox-P (trade name, manufactured by Fuji Xerox Co., Ltd.) is used as plain paper. In these inks, a water-soluble organic solvent that reduces the surface tension of an aqueous solution or a surfactant penetration enhancer is added to improve the wettability to a recording medium, thereby increasing the permeability. Examples of the water-soluble organic solvent include lower alcohols such as ethanol and propanol; cellosolves such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; carbitols such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether;
And 1,2-alkyldiols such as 1,2-octanediol. Examples of the surfactant include anionic surfactants such as fatty acid salts and alkyl sulfate salts, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether, cationic surfactants, and zwitterionic surfactants. Surfactants and the like can be used. In particular, nonionic surfactants are suitable because they cause less ink foaming than ionic surfactants.

The surface-modified carbon black of the present invention is a colorant which can be dispersed and / or dissolved in water without using a dispersant comprising a surfactant. Activators can be used only to enhance penetration. That is, in order to normally impart dispersibility to carbon black, it is necessary to select a combination in which carbon black and each material are adsorbed, but in the present invention, it is necessary to select only the penetration promoting property without considering the combination. Can be.

These penetration enhancers may be used alone or in combination with a water-soluble organic solvent or a surfactant so that the surface tension of the ink is less than 40 dyn / cm, preferably 35 dyn / cm.
cm.

Further, a humectant is added to the ink in order to prevent the ink from drying at the tip of the nozzle for discharging the ink when used in the ink jet recording method. The humectant is selected from water-soluble and highly hygroscopic materials, glycerin, ethylene glycol, diethylene glycol,
Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,
4-butanediol, 1,5-pentanediol 1,6
Polyols such as -hexanediol, 1,2,6-hexanetriol and pentaerythritol, lacrams such as 2-pyrrolidone, N-methyl-2-pyrrolidone and ε-caprolactam, urea, thiourea, ethylene urea,
Ureas such as 1,3-dimethylimidazolidinones and sugars such as maltitol, sorbitol, gluconolactone and maltose can be used.

These humectants can be added together with other ink additives in such an amount that the ink viscosity becomes 25 cPs or less at 25 ° C.

In the present invention, a state in which carbon black is stably present at a minimum particle size dispersible in water without using a dispersant is referred to as "dispersion and / or dissolution". The minimum dispersible particle size is a minimum particle size that does not become smaller even when the dispersion time is increased. By introducing a large amount of hydrophilic functional groups into carbon black and modifying the surface, the water-soluble dye spontaneously disperses with the smallest particle size that can be dispersed, as if the water-soluble dye were dissolved in water as a single molecule. It is thought to go.

The surface modification for "dispersing and / or dissolving" is performed by converting a hydrophilic functional group such as a carboxyl group, a carbonyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, a quaternary ammonium salt or the like, and a salt thereof into a carbon. It is carried out by bonding to the surface of the black directly or via an alkyl, alkyl ether, aryl group or the like. In particular,
It is obtained by grafting a functional group or an active species containing a functional group to the surface of carbon black by a physical treatment such as vacuum plasma or a chemical treatment. Further, it is obtained by a method of introducing a carboxyl group or a sulfone group by oxidizing a carbon black surface with an oxidizing agent in water, or a method of introducing a carboxyl group via a phenyl group by binding p-amino-benzoic acid or the like. .

According to the present invention, the particle diameter of the surface-modified carbon black at the time of dispersion is 50% cumulative diameter of 60 nm or more, and 9%.
Those having a 0% cumulative diameter of 300 nm or less are preferred. 50%
If the cumulative diameter is less than 60 nm, the transparency of the dispersed particles increases and the print density decreases. If the 90% cumulative diameter exceeds 300 nm, when the ink is allowed to stand still, a large amount of large-sized dispersed particles settle, resulting in poor dispersion stability, which tends to cause problems such as a decrease in print density.

The carbon black preferred in the present invention has a 50% cumulative diameter at dispersion of 60 nm or more and 90%
It is preferable that the cumulative diameter is 300 nm or less, and specific examples include carbon black manufactured by Mitsubishi Chemical Corporation.
A100, carbon black manufactured by Degussa Corporation, color black FW18, color black S170, special black 250, and carbon black manufactured by Cabot Corporation include Monarch 700 and Monarch 880. These are only examples of carbon black suitable for the present invention, and the present invention is not limited by these.

The surface-modified carbon black obtained by hydrophilizing the carbon black is used in an amount of 1 to 1 with respect to the total amount of the ink.
It is preferable to add in the range of 5%. Within this range, an aqueous ink having a sufficient print density can be obtained.

As the penetration enhancer used in the aqueous ink composition of the present invention, the above-mentioned water-soluble organic solvents and surfactants can be used. More preferably, a glycol ether-based water-soluble organic solvent is desirable. Glycol mono-n-butyl ether, diethylene glycol
n-butyl ether, triethylene glycol-n-butyl ether and the like. By combining these organic solvents and surface-modified carbon black, it is possible to provide good printed matter with reduced bleeding during printing.

Preferred surfactants include nonionic surfactants such as Surfynol 61, 82 and 10
Acetylene glycol-based surfactants such as 4, 440, 465, and 485 (all of which are trade names, manufactured by Air Products and Chemicals) can obtain an ink with almost no foaming and are used in an ink jet recording method. It is particularly suitable for

If necessary, a fixing agent, a pH adjuster, an antioxidant / ultraviolet absorber, a preservative / antifungal agent, etc. can be added to the aqueous ink composition of the present invention.

As the fixing agent, water-soluble resins can be used, and water-soluble rosins, alginic acids, polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose,
Methylcellulose, styrene-acrylic acid resin, styrene-acrylic acid-acrylate resin, styrene-
Maleic acid resin, styrene-maleic acid half ester resin, acrylic acid-acrylic acid ester resin, isobutylene-maleic acid resin, rosin-modified maleic acid resin, polyvinylpyrrolidone, gum arabic starch, polyallylamine, polyvinylamine, polyethyleneimine, etc. Can be

The surface-modified carbon black of the present invention is a colorant that can be dispersed and / or dissolved in water without using a water-soluble resin dispersant. The resin can be used only for fixing. That is, in order to normally impart dispersibility to carbon black, it is necessary to select a combination in which carbon black and each material are adsorbed, but in the present invention, it is possible to select only by fixing property without considering the combination. it can.

Examples of the pH adjuster include alkali metal hydroxides and amines such as lithium hydroxide, sodium hydroxide, potassium hydroxide, triethanolamine and diethanolamine.

Examples of antioxidants and ultraviolet absorbers include allohanates such as allohanate and methyl allohanate;
L-ascorbic acid and salts thereof such as biurets such as biuret, dimethyl biuret, and tetramethyl biuret;
8, 900, 1130, 384, 292, 123, 14
4, 622, 770, 292, Irgacor 252,
153, Irganox 1010, 1076, 103
5, MD1024 or the like, or a lanthanide oxide or the like is used.

Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol,
-Pyridinethiol-1-oxide sodium, sodium sorbate, sodium dehydroacetate, 1,2-
It can be selected from dibenzisothiazolin-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN, manufactured by ICI) and the like.

As the ink jet recording method of the present invention, any method can be used as long as the ink composition is ejected as droplets from a fine nozzle and the droplets are attached to a recording medium. To explain some of them, there is the electrostatic suction method, in which a strong electric field is applied between the nozzle and the accelerating electrode placed in front of the nozzle, and ink is continuously ejected from the nozzle in the form of droplets. There is a method in which a print information signal is applied to the deflection electrode while the ink droplet flies between the deflection electrodes to perform recording, or a method in which the ink droplet is ejected in accordance with the print information signal without being deflected.

The second method is a method in which pressure is applied to the ink liquid by a small pump and the nozzle is forcibly ejected by mechanically oscillating a nozzle with a quartz oscillator or the like. The ejected ink droplet is charged at the same time as the ejection, and a print information signal is applied to the deflecting electrode and recorded while the ink droplet flies between the deflecting electrodes.

The third method is a method using a piezoelectric element, in which a pressure and a print information signal are simultaneously applied to the ink liquid by the piezoelectric element to eject and record ink droplets.

The fourth method is a method in which the volume of the ink liquid is rapidly expanded by the action of thermal energy. In this method, the ink liquid is heated and foamed by the minute electrodes in accordance with the print information signal, and the ink droplets are ejected and recorded.

By performing printing using the aqueous ink composition of the present invention using any one of the various ink jet recording methods as described above, stable ink jet recording can be performed, and an ink jet recording method. Can be provided.

[0034]

EXAMPLES <Preparation of Pigment Dispersion> (Pigment Dispersion 1) Monarch 88 as carbon black
60 g (trade name, manufactured by Cabot Corporation) was mixed with 1 kg of water, and ground with a ball mill using zirconia beads. To this ground stock solution was added 500 g of sodium hypochlorite, and the mixture was boiled for 10 hours to perform wet oxidation. The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The wet cake was redispersed in 5 kg of water, desalted and purified to a conductivity of 2 mS / cm by a reverse osmosis membrane, and further concentrated to a pigment concentration of 15 wt% to prepare a pigment dispersion.

(Pigment dispersion liquid 2) 40 g of color black S170 (trade name, manufactured by Degussa) as carbon black
Was mixed with 1 kg of water and pulverized by a ball mill using zirconia beads. To this ground stock solution, 500 g of sodium hypochlorite was added, reacted for 5 hours while grinding in a ball mill, and further boiled for 4 hours with stirring to perform wet oxidation. The obtained undiluted dispersion liquid was used as a glass fiber filter paper GA-1.
00 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. Put this wet cake in water 5
The resulting dispersion was re-dispersed into kg, desalted and purified to a conductivity of 2 mS / cm with a reverse osmosis membrane, and further concentrated to a pigment concentration of 15 wt% to prepare a pigment dispersion.

(Pigment dispersion 3) MA of carbon black
100 g (trade name, manufactured by Mitsubishi Chemical Corporation) was mixed with 5 kg of N-methyl-pyrrolidone and pulverized by a ball mill using zirconia beads. To this ground stock solution was added 50 g of sulfamic acid and sulfonated at 150 ° C. for 10 hours. The whole amount was put into 10 kg of ice, and the undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further divided into 5 kg of water, followed by filtration and washing. This wet cake was redispersed in 2 kg of water, desalted and purified to a conductivity of 2 mS / cm by a reverse osmosis membrane, and further concentrated to a pigment concentration of 15 wt% to prepare a pigment dispersion 2.

<Preparation of Ink Composition> (Example 1) 45 g of Pigment Dispersion 1, 10 g of glycerin and 5 g of 2-pyrrolidone as moisturizing components, 4 g of tert-pentanol as a permeation promoting component and Nissan of a nonionic surfactant 1 g of Nonion NS-220 (trade name, manufactured by NOF Corporation) is mixed, and ultrapure water is added to make a total amount of 1 g.
The amount was adjusted to 00 g, and triethanolamine was further added until the ink pH reached 7.5. The mixture was stirred for 2 hours and filtered with a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink.

Example 2 An aqueous ink was prepared in the same manner as in Example 1, except that 45 g of the pigment dispersion 2 was used.

Example 3 An aqueous ink was prepared in the same manner as in Example 1 except that 45 g of the pigment dispersion 3 was used.

Example 4 45 g of Pigment Dispersion Liquid 2, 10 g of glycerin as a humectant and 5 g of diethylene glycol
g, diethylene glycol-mono-n as a penetration enhancer
7.5 g of butyl ether was mixed, ultrapure water was added to make the total amount 100 g, and triethanolamine was further added until the ink pH reached 7.3. This mixture is
After stirring for an hour, the mixture was filtered through a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink.

Example 5 45 g of Pigment Dispersion 1, 10 g of glycerin and 5 g of 1,5-pentanediol as a humectant, and 5 g of triethylene glycol-mono-n-butyl ether as a permeation enhancer were mixed. Water was added to make the total amount 100 g, and triethanolamine was further added until the ink pH reached 7.3. This mixture is
After stirring for an hour, the mixture was filtered through a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink.

Example 6 45 g of Pigment Dispersion 1, 7.5 g of glycerin and 7.5 g of 1,5-pentanediol as humectants, and 0.1 g of Surfynol 104, an acetylene glycol surfactant, as a penetration enhancer. 3 g and 1.5 g of Surfynol 485 were mixed, ultrapure water was added to make a total amount of 100 g, and triethanolamine was further added until the ink pH reached 7.3. This mixture is
After stirring for an hour, the mixture was filtered through a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink.

Example 7 45 g of Pigment Dispersion Liquid 2, 10 g of glycerin as a humectant and 5 g of diethylene glycol
g, diethylene glycol-mono-n as a penetration enhancer
-5 g of butyl ether and 1 g of Surfynol 465 as an acetylene glycol-based surfactant were mixed, ultrapure water was added to make the total amount 100 g, and triethanolamine was further added until the ink pH reached 7.2. The mixture was stirred for 2 hours and filtered with a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink.

(Comparative Example 1) Carbon black # 4
5L (trade name, manufactured by Mitsubishi Chemical Corporation) 100g with 1k of water
g. and mixed with a ball mill using zirconia beads. Add 500 sodium hypochlorite to this ground stock solution.
g was added and the mixture was boiled for 10 hours to perform wet oxidation. The obtained undiluted dispersion liquid was used as a glass fiber filter paper GA-100 (trade name,
(Advantech Toyo Co., Ltd.) and further washed with water. The wet cake was redispersed in 5 kg of water, desalted and purified to a conductivity of 2 mS / cm by a reverse osmosis membrane, and further concentrated to a pigment concentration of 15 wt% to prepare a pigment dispersion.

Using 45 g of this pigment dispersion, an aqueous ink was prepared in the same manner as in Example 4.

(Comparative Example 2) Carbon black # 2
0B (brand name, manufactured by Mitsubishi Chemical Corporation) 100g with 1k of water
g. and mixed with a ball mill using zirconia beads. Add 500 sodium hypochlorite to this ground stock solution.
g was added and the mixture was boiled for 10 hours to perform wet oxidation. The obtained undiluted dispersion liquid was used as a glass fiber filter paper GA-100 (trade name,
(Advantech Toyo Co., Ltd.) and further washed with water. The wet cake was redispersed in 5 kg of water, desalted and purified to a conductivity of 2 mS / cm by a reverse osmosis membrane, and further concentrated to a pigment concentration of 15 wt% to prepare a pigment dispersion.

Using 45 g of this pigment dispersion, an aqueous ink was prepared in the same manner as in Example 4.

(Comparative Example 3) 100 g of the color black S170 (trade name, manufactured by Degussa) used in Example 4, 150 g of Joncryl J-62 (trade name, manufactured by Johnson Polymer) as a water-soluble resin dispersant, 6 g of sodium hydroxide,
250 g of water was mixed and dispersed for 10 hours by a ball mill using zirconia beads. The resulting dispersion liquid was filtered through a stainless steel filter having a pore size of about 5 μm, diluted with water to a pigment concentration of 15 wt%, and dispersed in a water-soluble resin to prepare a pigment dispersion liquid.

Using 45 g of this pigment dispersion, an aqueous ink was prepared in the same manner as in Example 4.

<Evaluation Method> (Measurement of Particle Size) The 50% and 90% cumulative diameters were measured by a Microtrac UPA particle size distribution meter (trade name, manufactured by Leeds & Northrup) using laser Doppler scattering photolysis. .

(Print Density) Neutral plain paper Xerox-P (trade name, manufactured by Fuji Xerox Co., Ltd.) using MJ-930C (trade name, manufactured by Seiko Epson Corporation) of a piezoelectric element type on-demand ink jet recording apparatus Was dried, and after drying, the OD value was measured using a Macbeth densitometer TR-927 (trade name, manufactured by Colmorgen).

(Dispersion Stability) The ink cartridge used for the MJ-930C of the ink jet recording apparatus was filled with the aqueous ink and allowed to stand for 3 months, and then continuously printed until the ink cartridge was completed, and dried. The change in the OD value was measured using a Macbeth densitometer TR-927.を when the range of change is within 2.5%, Δ when 2.5 to 5%, 5%
Is exceeded when the value exceeds.

For the aqueous inks of Examples 1 to 7 and Comparative Examples 1 to 3, 50% and 90% cumulative diameter, print density,
The sedimentation resistance was evaluated.

In Examples 1 to 7, the 50% cumulative diameter was 6
0 nm or more and 45% having a 50% cumulative diameter of less than 60 nm.
In all cases, the print density was higher than Comparative Example 1 in nm.
In addition, each of the 90% cumulative diameters is less than 300 nm,
The change in the OD value after leaving the ink cartridge standing was within 2.5%, and there was no problem due to sedimentation of the pigment particles, and the dispersion was stable. On the other hand, the 90% cumulative diameter is 300n.
m, the change in OD value was 5
%, The print density was lowered due to the sedimentation of the pigment particles, and the dispersion stability was poor.

In Comparative Example 3 in which the carbon black used in Example 4 was dispersed using a water-soluble resin as a dispersant, the print density was low even though the 50% cumulative diameter was 60 nm or more, and the print density was low. Unless the aqueous ink contains a surface-modified carbon black that can be dispersed and / or dissolved in water, a high print density cannot be obtained.

The results are summarized in Table 1.

[0057]

[Table 1]

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2C056 EA04 FA03 FA04 FA05 FA07 FC01 2H086 BA53 BA59 BA60 4J037 AA02 CA14 DD05 EE02 EE43 FF15 4J039 BA04 BA12 BC07 BC08 BC12 BC13 BC14 BC15 BC19 BC54 BE01 BE12 BE22 CA06 EA42 EA44 GA

Claims (6)

[Claims] 1. An aqueous ink composition containing at least a surface-modified carbon black which can be dispersed and / or dissolved in water without a dispersant and has a penetration time of less than 1 ^second at a coating amount of 1 mg / cm ^2. Wherein the surface-modified carbon black has a 50% cumulative diameter of 60 nm or more and a 90% cumulative diameter of 300 nm or less. 2. The aqueous ink composition according to claim 1, wherein the surface-modified carbon black is obtained by wet oxidation using hypohalous acid or a salt thereof. 3. The aqueous ink composition according to claim 1, further comprising a glycol ether-based water-soluble organic solvent. 4. The aqueous ink composition according to claim 1, further comprising an acetylene glycol-based surfactant. 5. The aqueous ink composition according to claim 1, wherein the ink composition is ejected as droplets from a fine nozzle, and the droplets adhere to a recording medium. An inkjet recording method characterized by the above-mentioned. 6. A recorded matter obtained by printing the aqueous ink composition according to claim 1 by an inkjet recording method.