JP2001072904A - Water-borne ink composition, ink jet recording method using the same, recorded matter and recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-borne ink compsn. which can realize both high printing density and good clogging resistance. SOLUTION: This compsn. comprises at least (1) a surface-modified carbon black dispersible and/or soluble in water without a dispersant, (2) glycerin in an amt. of 3-30 wt.% based on the total ink, (3) a dihydric alcohol compd. comprising hydroxyl groups on both the terminals of a molecule in an amt. of 1-20 wt.% based on the total ink and (4) water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aqueous ink composition. More specifically, the present invention relates to an aqueous pigment ink composition that achieves both high print density and good clogging resistance.

[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.

On the other hand, as an attempt to improve drying of a pigment ink using a dispersant at a fine nozzle, Japanese Patent Application Laid-Open No.
Japanese Patent No. 41396 discloses a method for defining the added amounts of glycerin and propylene glycol and the total of the added amounts. However, these inks have the problems caused by the use of the dispersant as described above, and also have the performance as clogging resistance required in actual use of ink jet recording inks and the like. Often insufficient.

[0006] 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 spontaneously treated without a surfactant or a polymer dispersant is used alone. A dispersion using a surface-modified carbon black that can be dispersed in a liquid 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.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous ink composition having a high print density and excellent clogging resistance.

[0008]

The aqueous ink composition of the present invention comprises at least (1) a surface-modified pigment which can be dispersed and / or dissolved in water without a dispersant, and (2) an amount added to the total amount of the ink. Is glycerin in the range of 3 to 30 wt%, and (3) the addition amount is 1 to 20 wt% based on the total amount of the ink.
And (4) water, which is a dialcohol compound having hydroxyl groups at both ends of the molecule.

In the aqueous ink composition of the present invention, the amount of the glycerin added is in the range of 5 to 15% by weight based on the total amount of the ink, and the amount of the dialcohol compound having hydroxyl groups at both molecular ends is added to the ink. 3 for the total amount
-10 wt%.

[0010] The aqueous ink composition of the present invention is characterized in that the surface-modified pigment is a surface-modified pigment obtained by wet oxidation of the pigment with hypohalous acid or a salt thereof.

In the aqueous ink composition of the present invention, the amount of the surface-modified pigment is 1 to 15% by weight based on the total amount of the ink.
It is characterized by being in the range.

The aqueous ink composition of the present invention is characterized in that the surface-modified pigment is a surface-modified carbon black.

The aqueous ink composition of the present invention is further characterized in that the penetration time at a coating amount of 1 mg / cm ² is less than 1 second.

The aqueous ink composition of the present invention is characterized by further comprising a glycol ether-based water-soluble organic solvent.

[0015] The aqueous ink composition of the present invention is characterized by further comprising a nonionic surfactant.

The aqueous ink composition of the present invention is characterized in that the nonionic surfactant is selected from acetylene glycol-based surfactants.

The ink jet recording method of the present invention is an ink jet recording method in which droplets of an ink composition are ejected and the droplets are adhered to a recording medium to perform recording, wherein the aqueous ink composition is used as an ink composition. It is characterized by using at least an object.

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

The ink jet recording apparatus of the present invention is an ink jet recording apparatus for discharging ink droplets of an ink composition and adhering the liquid droplets to a recording medium for recording, wherein the aqueous ink composition is used as an ink composition. It is characterized by using at least an object.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous ink composition of the present invention contains at least a surface-modified pigment, glycerin and a molecule which can be dispersed and / or dissolved in water without a dispersant such as a surfactant or a water-soluble resin. It comprises a dialcohol compound having a hydroxyl group at a terminal and water.

In the present invention, a state where the pigment is stably present in the water at a minimum particle size that can be dispersed 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 the pigment and modifying the surface, the pigment disperses spontaneously with the smallest particle size at which the pigment can be dispersed, as if the water-soluble dye were dissolved in water as a single molecule. it is conceivable that.

The surface modification for "dispersing and / or dissolving" is carried out by adding 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 a salt thereof to a pigment. By directly or via an alkyl, alkyl ether, aryl group or the like. Specifically, it can be obtained by grafting a functional group or an active species containing a functional group to the pigment surface by physical treatment such as vacuum plasma or chemical treatment. Also, a method of oxidizing a pigment surface with an oxidizing agent in water to introduce a carboxyl group or a sulfone group, or p-
It is obtained by a method in which amino-benzoic acid or the like is bonded to introduce a carboxyl group via a phenyl group.

In the present invention, specific examples of the pigment as a raw material for surface modification include carbon black and pigments such as Pigment Yellow, Pigment Red, Pigment Violet, Pigment Blue, and Pigment Black described in the Color Index. But
Besides these, pigments of phthalocyanine type, azo type, anthraquinone type, azomethine type, condensed ring type and the like can also be used. Yellow No. 4, No. 5, No. 205, 401
No .: Orange No. 204; Red No. 104, No. 201, 202
Nos. 204, 220, 226-228, 405
No .: In addition to organic pigments such as Blue No. 1 and No. 404, inorganic pigments such as titanium oxide, zinc oxide, zirconium oxide, iron oxide, ultramarine, navy blue, and chromium oxide can also be used. Among these, carbon black is preferably used because a high printing density, which is an effect of the present invention, can be more remarkably obtained.

The aqueous ink composition of the present invention simultaneously contains a surface-modified pigment which can be dispersed and / or dissolved in water without the above-mentioned dispersant, glycerin and a dialcohol compound having hydroxyl groups at both molecular terminals. The addition amount of the glycerin is in the range of 3 to 30 wt% with respect to the total amount of the ink, and the addition amount of the dialcohol compound having hydroxyl groups at both molecular terminals is 1 to 20 with respect to the total amount of the ink.
It is preferably in the range of wt%. More preferably,
The addition amount of the glycerin is in the range of 5 to 15 wt%, and the addition amount of the dialcohol compound having hydroxyl groups at both molecular terminals is in the range of 3 to 10 wt%. Glycerin is added in an amount of 3 wt% or more, more preferably 5 wt% or more, and the added amount of the dialcohol compound having hydroxyl groups at both molecular ends is 1 wt%.
As described above, if the content is 3 wt% or more, good clogging resistance can be ensured. Further, if the addition amount of glycerin is 30 wt% or less, more preferably 15 wt% or less, and the addition amount of the dialcohol compound having hydroxyl groups at both molecular ends is 20 wt% or less, more preferably 10 wt% or less. The aqueous ink composition can be easily adjusted to the required viscosity, and a high print density can be secured. It is difficult to simultaneously achieve high print density and clogging resistance with a viscosity suitable for an aqueous ink composition by using glycerin or the above-mentioned dialcohol compound having hydroxyl groups at both molecular terminals alone.

In the present invention, the dialcohol compound having hydroxyl groups at both molecular ends has a main chain carbon number of 10
It is a dialcohol having hydroxyl groups at both ends of the skeleton of any of the following alkyl, alkenyl and alkynyl groups. The skeleton of the alkyl group, alkenyl group or alkynyl group may have a branched structure. Specific examples of this compound group include 1,3-propanediol,
1,4-butanediol, 1,5-pentanediol,
Examples thereof include 1,6-hexanediol, 2-methyl-1,3-propanediol, and 2-butene-1,4-diol. By using these dialcohol compounds, both higher printing density and better clogging resistance can be achieved within the range of the addition amount which is a requirement of the present invention.

In the aqueous ink composition of the present invention, the surface-modified pigment is preferably obtained by a method including wet oxidation using hypohalous acid or a salt thereof. Examples of hypohalous acid or a salt thereof include sodium hypochlorite, potassium hypochlorite, sodium hypobromite, potassium hypobromite, etc. Is particularly preferred.

The oxidation treatment with hypohalous acid or a salt thereof is carried out, for example, by adding a pigment (for example, carbon black) and a hypohalite (for example, sodium hypochlorite) having an effective halogen concentration of 10 to 30% to an appropriate amount. It can be carried out by charging in water and stirring for 5 hours or more, preferably for about 10 to 15 hours, at 50 ° C or more, preferably 95 to 105 ° C. In this case, it is preferable that the pigment is pulverized in advance, or that the pigment is reacted simultaneously with the pulverization. As a grinding method, glass, zirconia, alumina, stainless steel,
The beads of magnetism or the like are pulverized by a ball mill, an attritor, a colloid mill, a sand mill, or the like. In the case of carbon black which is easily disintegrated, the beads are pulverized by a rotary homogenizer or an ultrasonic homogenizer.

The dispersion obtained after the pulverization and oxidation is separated from beads and coarse particles and purified to remove double products of the oxidizing agent to obtain an aqueous pigment dispersion. Further, if necessary, concentration with a separation membrane or the like, filtration using a metal filter or a membrane filter, or classification by centrifugation, and neutralization with a hydroxide or an amine of an alkali metal salt can be performed.

The preferred amount of the surface-modified pigment in the aqueous ink composition of the present invention is 1 to 15% by weight. 1
If the addition amount is less than wt%, the print density is not sufficient. Also one
If it exceeds 5 wt%, it will be difficult to adjust the viscosity to the one required for the aqueous ink composition.

The aqueous ink composition of the present invention has a coating amount of 1
More preferably, the ink has a permeation time of less than 1 ^second in mg / cm ² .

The penetration time is 1 when the coating amount is 1 mg / cm ^2.
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, and carbitols such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether.

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, and cationic surfactants. An amphoteric surfactant or the like can be used. Since the surface-modified pigment of the present invention is a colorant that can be dispersed and / or dissolved in water without using a dispersant composed of a surfactant, these surfactants used in the ink of the present invention include: It can only be used to enhance penetration. That is, in order to usually impart dispersibility to the pigment, it is necessary to select a combination in which the pigment and each material adsorb, but in the present invention, it is possible to select only the permeation promoting property without considering the combination. .

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

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. Among them, glycol ether-based water-soluble organic solvents are more preferable. Specific examples of glycol ether-based water-soluble organic solvents include ethylene glycol mono-n-butyl ether, diethylene glycol-n-butyl ether, and triethylene glycol-n-
Butyl ether and the like can be exemplified. By combining these organic solvents and surface-modified pigments, it is possible to provide good printed matter with reduced bleeding during printing.

As the surfactant, a nonionic surfactant such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether is preferable. By using a nonionic surfactant, an aqueous ink composition having less foaming than an ionic surfactant can be obtained. Specific examples of the nonionic surfactant include Nissan Nonion K-211, K-220, P-213, and E-2.
15, E-220, S-215, S-220, HS-2
20, NS-212, NS-220 (all of which are trade names, manufactured by NOF Corporation) and the like. Further, among nonionic surfactants, Surfynol 61 and 8
Acetylene glycol-based surfactants such as 2, 104, 440, 465, and 485 (all of which are trade names, manufactured by Air Products and Chemicals) can produce an ink with almost no foaming, and an inkjet recording method. It is particularly suitable for use in

A water-soluble compound can be further added to the aqueous ink composition of the present invention for the purpose of further improving recording stability such as writing characteristics and ejection characteristics. By adding an appropriate water-soluble compound, a writing instrument such as a pen may have smoother writing characteristics without blurring, and an inkjet recording may have more stable ejection characteristics. As such a water-soluble compound, an organic solvent or a water-soluble solid generally used in an aqueous ink composition can be used, and specifically, ethylene glycol,
Glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol and dipropylene glycol; polyols such as 1,2,6-hexanetriol and pentaerythritol; 2-pyrrolidone;
Lacrams such as -methyl-2-pyrrolidone, ε-caprolactam, ureas such as urea, thiourea, ethylene urea, 1,3-dimethylimidazolidinone, maltitol,
Saccharides such as sorbitol, gluconolactone, and maltose can be exemplified.

The aqueous ink composition of the present invention may further contain, if necessary, a fixing agent, a pH adjuster, an antioxidant / ultraviolet absorber, a preservative / antifungal, and the like.

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 pigment of the present invention is a colorant that can be dispersed and / or dissolved in water without using a dispersant composed of a water-soluble resin. Can only be used for That is, usually, in order to impart dispersibility to the pigment, it is necessary to select a combination in which the pigment and each material adsorb, but in the present invention, it is possible to select only the fixing property without considering the combination.

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

As antioxidants and ultraviolet absorbers, 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 of ICI) and the like.

The aqueous ink composition of the present invention can be used for general writing implements, printing applications, and stamps. However, droplets of the ink composition are ejected, and the droplets are attached to a recording medium for recording. It is more preferable to use it as an inkjet recording ink for performing the following. In the aqueous ink composition of the present invention as an ink for inkjet recording, the viscosity at 25 ° C is a surface-modified pigment, glycerin,
It is preferable to adjust to a range of 1.0 to 25 cPs including a dialcohol compound having hydroxyl groups at both molecular ends and water, or further including a water-soluble compound and an auxiliary agent such as a pH adjuster. If the viscosity of the ink is within the above range, it is easy to stably eject it as an ink jet recording ink.

In 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 of forcibly ejecting ink droplets by applying pressure to an ink liquid with a small pump and 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, and the ink liquid is heated and foamed by the minute electrodes in accordance with the print information signal to eject and record the ink droplets.

Any of the above methods can be used in an ink jet recording method using the aqueous ink composition of the present invention.

The recorded matter of the present invention is obtained by the above-mentioned ink jet recording method using at least the above-mentioned aqueous ink composition. This recorded matter shows a high print density by using the aqueous ink composition of the present invention. In addition, because it uses carbon black, high water resistance,
It has weather resistance, active gas resistance and the like.

The ink jet recording apparatus of the present invention is an ink jet recording apparatus which performs recording by ejecting droplets of an ink composition and attaching the droplets to a recording medium, wherein the aqueous ink having the above constitution is used as the ink composition. At least the composition is used. In the present invention, a recording apparatus employing any of the above-described ink jet recording methods can be used.

[0050]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Preparation of Pigment Dispersion> (Pigment Dispersion A) The primary particle size is 24 nm and the specific surface area is 13
100 g of 7 m ² / g acidic carbon black is added to 50 parts of water.
0 g, and pulverized by a ball mill using zirconia beads. 1500 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped into this ground stock solution, 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. This wet cake was re-dispersed in 5 kg of water, desalted and purified to a conductivity of 2 mS / cm by a reverse osmosis membrane, and further a pigment concentration of 10
The aqueous pigment dispersion A was prepared by concentrating the mixture to wt%.

(Pigment Dispersion B) Acidic carbon black having a primary particle size of 17 nm and a specific surface area of 200 m ² / g.
0 g was mixed with 1 kg of water and pulverized by a ball mill using zirconia beads. 1400 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise to the undiluted pulverized solution, reacted for 5 hours while pulverized by a ball mill, and further boiled for 4 hours with stirring 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 10 wt% to prepare an aqueous pigment dispersion B.

(Pigment Dispersion C) 100 g of carbon black used in Pigment Dispersion A, and a water-soluble resin dispersant Joncryl J-62 (trade name, manufactured by Johnson Polymer Co., Ltd.)
150 g, 6 g of sodium hydroxide and 250 g of water were 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, and the pigment concentration was 10 wt.
% Aqueous pigment dispersion C diluted to% by weight and dispersed with a water-soluble resin
Was adjusted.

<Preparation of Aqueous Ink Composition> (Ink of Example 1) 45 g of pigment dispersion A, 6 g of glycerin and 5 g of 1,4-butanediol as moisturizing components,
4 g of tert-pentanol was mixed as a penetration promoting component. Ultrapure water was added to make the total amount 100 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.

(Ink of Example 2) 45 parts of the pigment dispersion B
g, 8 g of glycerin and 4 g of 1,5-pentanediol as a humectant, and 4 g of ethanol as a penetration promoting component were mixed. Ultrapure water was added to make the total amount 100 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.

(Ink of Example 3)
g, 10 g of glycerin and 6 g of 1,3-propanediol as a humectant, and 7.5 g of diethylene glycol-mono-n-butyl ether as a penetration promoting component were mixed. Add ultrapure water to make the total amount 100 g, and further adjust the ink pH
Was added to 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.

(Ink of Example 4)
g, 12 g of glycerin and 5 g of 1,5-pentanediol as moisturizing components, 5 g of triethylene glycol-mono-n-butyl ether as a permeation promoting component and 0.6% of Surfynol 465 as an acetylene glycol-based surfactant.
g were mixed. Add ultrapure water to make the total amount 100g,
Further, triethanolamine was added until the ink pH reached 7.5. The mixture is stirred for 2 hours to give a pore size of about 5
A water-based ink was prepared by filtration with a μm stainless steel filter.

(Ink of Comparative Example 1)
g, 6 g of glycerin as a moisturizing component, and 7.5 g of diethylene glycol-mono-n-butyl ether as a permeation promoting component. Ultrapure water was added to make the total amount 100 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.

(Ink of Comparative Example 2)
g, 5 g of 1,4-butanediol as a moisturizing component, and 4 g of tert-pentanol as a permeation promoting component were mixed. Ultrapure water was added to make the total amount 100 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.

(Ink of Comparative Example 3)
g, 35 g of glycerin and 6 g of 1,5-pentanediol as a humectant, and 5 g of triethylene glycol-mono-n-butyl ether as a penetration promoting component 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.

(Ink of Comparative Example 4)
g, 10 g of glycerin and 30 g of 1,5-pentanediol as a humectant, and 4 g of tert-pentanol as a penetration promoting component were mixed. Add ultrapure water to make 100g
, And triethanolamine was further added until the ink pH reached 7.2. This mixture was stirred for 2 hours,
The aqueous ink was prepared by filtration with a stainless steel filter having a pore size of about 5 μm.

(Ink of Comparative Example 5)
g, 6 g of glycerin and 5 g of 1,3-propanediol as a humectant, and 4 g of ethanol as a penetration promoting component were mixed. Ultrapure water was added to make the total amount 100 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.

<Evaluation of Print Density> The print densities of the aqueous ink compositions of Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated as follows.

Each ink was filled in MJ-930C (trade name; manufactured by Seiko Epson Corporation) which is a piezoelectric element type on-demand ink jet recording apparatus. Printing was performed on neutral plain paper Xerox-P (trade name; manufactured by Fuji Xerox Co., Ltd.) as a recording medium using MJ-930C filled with each ink to obtain a recorded matter. However, Comparative Example 3 in which the addition amount of glycerin was 30 wt% or more and Comparative Example 4 in which the addition amount of glycerin was 10 wt% or more and the addition amount of the dialcohol compound having hydroxyl groups at both molecular terminals was 20 wt% or more. The aqueous ink composition of No. could not be ejected stably because of its high viscosity, and no recorded matter was obtained.

The recorded matter obtained by using the aqueous ink compositions of Examples 1 to 4 and Comparative Examples 1, 2, and 5 was dried, and the print density was measured with a Macbeth densitometer TR-927 (trade name; manufactured by Colmorgen Co., Ltd.). It was measured. The results are summarized in Table 1.

[0066]

[Table 1] As is clear from Table 1, Comparative Example 1 in which the addition amount of the dialcohol compound having hydroxyl groups at both molecular terminals is 1 wt% or less, and Comparative Example 5 in which a pigment dispersion obtained by resin dispersion is used, The aqueous ink compositions of Examples of the present invention exhibited a print density of 1.45 or more. That is, in the aqueous ink composition containing the surface-modified pigment, a high printing density can be obtained when the addition amount of the dialcohol compound having a hydroxy group at both molecular terminals is 1 wt% or more. Further, in the recorded matter using the ink composition of Example 3 to which a glycol ether was added as a penetration enhancer, the bleeding around the print was small. That is, by including a penetration enhancer selected from glycol ethers in the aqueous ink composition of the present invention, it is possible to provide a good printed matter with reduced bleeding during printing. Further, the ink composition of Example 4 further containing an acetylene glycol-based nonionic surfactant as a permeation enhancer showed very little foaming and was easy to handle.

<Evaluation of Clogging Resistance> Each of the aqueous ink compositions of Examples 1 to 4 and Comparative Examples 1, 2, and 5 was printed by the above-described ink jet recording apparatus MJ-930C, and then the ink jet recording apparatus was used. The printer was left for 4 weeks in an environment at a temperature of 50 ° C. with the print head part removed from the home position. After the standing, a printing test was performed again, and the clogging resistance was evaluated based on whether or not the ejection was stable. The judgment was classified as follows. A: The ejection after standing is extremely stable. B: The ejection after standing is unstable, and the cleaning operation of the head unit needs to be performed within two times for recovery. C: The ejection after standing is unstable, and the cleaning operation of the head unit must be performed within 5 times for recovery. NG ・ Discharge after standing is unstable and does not recover.

Table 1 shows the evaluation results.

As is clear from Table 1, the addition amount of the dialcohol compound having hydroxyl groups at both molecular ends is 1
Comparative Example 1 in which the amount of glycerin is 3 wt% or less.
The aqueous ink compositions of the examples of the present invention exhibited good clogging resistance, as compared with Comparative Example 2 in which the pigment dispersion obtained by resin dispersion was less than t% or less. That is, in the aqueous ink composition containing the surface-modified pigment,
If the amount of glycerin added is 3 wt% or more and the amount of the dialcohol compound having hydroxyl groups at both molecular terminals is 1 wt% or more, good clogging resistance can be ensured.

[0070]

The aqueous ink composition satisfying the requirements of the present invention exhibits high printing density and good clogging resistance. Further, by using an inkjet recording apparatus satisfying the requirements of the present invention,
The recorded matter obtained by performing the inkjet recording has a high print density.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 FC01 2H086 BA53 BA55 BA59 BA62 4J037 AA02 CA05 CB04 DD20 DD24 EE02 EE19 EE28 EE29 EE43 FF05 FF30 4J039 AE07 BA04 BA13 BA23 BA31 BA35 BA36 BA37 BC07 BC13 BC13 BC13 BC19 BC54 BC56 BC60 BE01 BE12 BE22 BE33 CA06 EA10 EA41 EA42 EA44 GA24

Claims (12)

[Claims] 1. At least (1) a surface-modified pigment that can be dispersed and / or dissolved in water without a dispersant; (2) glycerin whose addition amount is in the range of 3 to 30% by weight based on the total amount of the ink; 1) The amount of addition to the total amount of ink is 1 to
An aqueous ink composition comprising: a dialcohol compound having hydroxyl groups at both molecular terminals in a range of 0 wt%, and (4) water. 2. The amount of the glycerin added is in the range of 5 to 15 wt% with respect to the total amount of the ink, and the amount of the dialcohol compound having hydroxyl groups at both molecular terminals is 3 to 10 wt% with respect to the total amount of the ink. %. The aqueous ink composition according to claim 1, wherein 3. The surface-modified pigment according to claim 1, wherein the surface-modified pigment is surface-modified by wet oxidation of the pigment with hypohalous acid or a salt thereof. Aqueous ink composition. 4. The aqueous ink composition according to claim 1, wherein the amount of the surface-modified pigment is in the range of 1 to 15 wt% based on the total amount of the ink. . 5. The aqueous ink composition according to claim 1, wherein the surface-modified pigment is a surface-modified carbon black. 6. The amount of the aqueous ink composition applied is 1 mg / c.
The aqueous ink composition according to any one of claims 1 to 5, wherein the penetration time in m ² is less than 1 second. 7. The aqueous ink composition according to claim 1, further comprising a glycol ether-based water-soluble organic solvent. 8. The aqueous ink composition according to claim 1, further comprising a nonionic surfactant. 9. The aqueous ink composition according to claim 8, wherein the nonionic surfactant is selected from an acetylene glycol-based surfactant. 10. An ink jet recording method for performing recording by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the ink composition is used as the ink composition.
An inkjet recording method characterized by using at least the aqueous ink composition according to any one of the above. 11. A recorded matter obtained by printing the aqueous ink composition according to claim 1 by an inkjet recording method. 12. An ink jet recording apparatus which performs recording by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the ink composition is used as the ink composition.
A recording apparatus using at least the aqueous ink composition according to any one of the above.