JP5488198B2 - Pigment dispersion, inkjet ink, ink cartridge, and image forming apparatus - Google Patents

Description

The present invention relates to a pigment dispersion suitable for inkjet, an inkjet ink using the pigment dispersion, an ink cartridge using the ink, and an image forming apparatus.

In general, an ink-jet pigment ink is prepared by preparing a dispersion in which a pigment and a dispersant are predispersed in an aqueous solvent such as water or alcohol, and then using a media-type disperser such as a sand mill. It is prepared by carrying out a dispersion step of dispersing to the extent and then diluting to a predetermined concentration.
In pigment-based water-based inks, it is common to use a dispersant such as a surfactant or a water-soluble resin in order to disperse a hydrophobic pigment. However, there is a problem that the reliability of an obtained image is extremely poor. Therefore, a technique for adding film-forming resin fine particles to ink for the purpose of improving image quality is known. However, it is difficult to disperse a plurality of components finely and stably over a long period of time. If a large amount of a dispersing agent such as a surfactant is used to stably disperse these fine particles, the ink tank or the head Problems such as generation of bubbles and deterioration of image quality occur. In addition, for the purpose of improving dispersibility, a method of changing the surface of the pigment to a hydrophilic group, a method using a resin containing a hydrophilic group, and the like have been studied. When different types are mixed, there is a problem that dispersion becomes unstable and storage stability deteriorates. In addition to this, various means for improving the dispersibility have been proposed. However, although a high image density can be obtained for the color pigment ink, there is still no satisfactory means for the black pigment ink. At present, improvements and developments are desired.

For example, Patent Document 1 proposes a pigment dispersion using carbon black as a black pigment and a sodium naphthalene sulfonate formalin condensate as a dispersant, and an ink using the pigment dispersion. The image density at that time is not sufficient, and the storage stability of the ink is not satisfactory.
Patent Documents 2 and 3 propose inks that use sodium naphthalene sulfonate formalin condensate as a dispersant for the carbon black dispersion and contain an anionic self-emulsifying ether polyurethane resin emulsion at the time of ink preparation. However, although the storability of the ink is improved, the image density when recorded on plain paper is insufficient.
On the other hand, Patent Document 4 describes an example using lignin sulfonate as a dispersant for a disperse dye, but does not describe use as a dispersant for a black pigment ink using carbon black. .

The present invention is a carbon black pigment dispersion suitable for inkjet which solves the above-mentioned conventional problems, and a high image density can be obtained even when recording on plain paper using the pigment dispersion. An object of the present invention is to provide an ink jet ink having excellent stability, and an ink cartridge and an image forming apparatus using the ink.

The above problems are solved by the following inventions <1> to <4>.
<1> Contains at least carbon black, a dispersant, and water, and the dispersant is partially desulfonated lignin sulfonate and / or a derivative thereof, and an anionic self-water dispersibility having a volume average particle size of 0.1 μm or less. A pigment dispersion comprising resin fine particles.
<2> An ink-jet ink comprising the pigment dispersion liquid according to <1>.
<3> An ink cartridge comprising the ink-jet ink according to <2> contained in a container.
<4> An image forming apparatus comprising discharge means for forming an image by discharging the inkjet ink according to <2>.

According to the present invention, a carbon black pigment dispersion suitable for inkjet which has solved the conventional problems, and a high image density can be obtained even when recording on plain paper using the pigment dispersion. Ink-jet ink with improved clogging and excellent discharge stability and storage stability, and an ink cartridge and an image forming apparatus using the ink can be provided.

1 is a perspective view illustrating an example of an image forming apparatus of the present invention.

Hereinafter, the present invention will be described in detail.
<Pigment dispersion>
The pigment dispersion of the present invention contains at least carbon black, a dispersant, and water, and further contains other components as necessary.
-Carbon black-
Various known carbon blacks can be used as the carbon black, and any one of channel black, gas black, and furnace black is preferable.
Carbon black preferably has an average primary particle size of 10.0 to 30.0 nm and a BET specific surface area of 100 to 400 m ² / g. More preferably, the average primary particle size is 15.0 to 20.0 nm and the BET specific surface area is 150 to 300 m ² / g.
Here, the average primary particle size can be calculated from the particle size and the number of captured images obtained by, for example, photographing particles using an electron microscope. The BET specific surface area can be measured by a BET method based on nitrogen adsorption.

-Dispersant-
Examples of the dispersant include partially desulfonated lignin sulfonate and / or a derivative thereof (hereinafter sometimes referred to as “dispersant X”) and anionic self-water dispersible resin fine particles having a volume average particle size of 0.1 μm or less ( Hereinafter, the dispersant Y may be used in combination.
Dispersant X that can be preferably used in the present invention includes sulfite pulp effluent or a lignin sulfonate and / or derivative thereof obtained by fractionation thereof at a high temperature in a known manner to obtain a degree of sulfonation. Can be partially desulfonated until the amount of propane is 0.35 mol or less per phenylpropane unit, or can be further chemically treated secondarily. These have more carboxyl groups and phenolic hydroxyl groups and less sulfonic acid groups and alcoholic hydroxyl groups after partial desulfonation than untreated ones.
As a method of partial desulfonation, the most general method includes a method of initially treating at a pH of 9 or more at 150 to 200 ° C., but is not limited to this method, and by performing a heat treatment at a lower pH. There may be a product obtained by partial desulfonation.
When the sulfite pulp effluent is subjected to partial desulfonation treatment as it is, the reactive organism may be used as it is, or only the high molecular weight section may be separated from the reactive organism and used.
The amount of the dispersant X added is preferably 0.005 to 0.3 parts by mass, and more preferably 0.01 to 0.1 parts by mass with respect to 1 part by mass of the absolutely dry mass of carbon black. If the addition amount is 0.005 parts by mass or more, the object of the present invention is easily achieved, and the storage stability of the pigment dispersion and the ink is easily secured.

The dispersant Y used in the present invention is an acid group-containing polymerizable monomer having at least one acid group selected from the group consisting of a carboxyl group, a phosphoric acid group, a sulfonic acid group, and a sulfuric acid group, and / or the acid group-containing polymerization. It consists of a copolymer (resin) obtained by reacting a functional oligomer as an essential component. The acid group is an anionic hydrophilic group for making the resin soluble in an alkaline aqueous solution, and this acid group is neutralized with an organic base or an inorganic base to become an anion in an aqueous medium and exhibit hydrophilicity.
Among the acid groups, a carboxyl group is preferable. The necessary carboxyl group amount in the dispersant Y can be represented by an acid value which is the quantity of KOH mg required to neutralize 1 g of the resin, and the acid value of the dispersant Y is preferably 10 to 300.
In the present invention, the dispersant Y is usually used as an aqueous dispersion.

The volume average particle diameter of the resin fine particles constituting the dispersant Y is 0.1 μm or less. Preferably it is 20-80 nm.
When the volume average particle diameter of the resin fine particles exceeds 0.1 μm, the dispersion stability of the pigment dispersion over time and the storage stability when converted to ink are lowered, and the ejection stability during ink jet recording is also lowered. In order to highly stabilize the pigment dispersion and the ink, it is preferable that the volume average particle diameter of the resin fine particles is smaller than the volume average particle diameter of the pigment particles.
The volume average particle diameter of the resin fine particles can be measured by particle size distribution measurement by a dynamic light scattering method. Examples of the particle size distribution measuring instrument used for the measurement include DLS-6500 (manufactured by Otsuka Electronics Co., Ltd.).

As a method for producing resin fine particles having a volume average particle size of 0.1 μm or less, a phase inversion emulsification method is preferable.
As described in JP-A-3-221137 and JP-A-5-66600, the phase inversion emulsification method is used in the production of resin fine particles composed of a water-insoluble liquid and / or a solid substance. A method of forming resin fine particles using so-called self-water-dispersible resins having a dispersibility capable of self-dispersing to a level of several μm or less in average particle size, and substantially simultaneously emulsifying and phase inversion. How to do it.
This phase inversion emulsification method does not require a special dispersion stabilizer and can obtain resin fine particles without the need for special equipment, and mainly uses a polyester resin that is difficult to produce by suspension polymerization or emulsion polymerization. The resin fine particles can be produced as a component.
By adding a base to an organic continuous phase (O phase) in which the resin having an acid group is dissolved in an organic solvent to neutralize it, and then adding an aqueous medium (W phase), W / O to O / W The resin undergoes phase transformation (so-called phase inversion emulsification) to form a discontinuous phase, and the resin is dispersed and stabilized as fine particles in an aqueous medium.

Examples of the resin include those obtained by copolymerizing acid group-containing polymerizable monomers and other polymerizable monomers in the presence of a polymerization initiator.
Specific examples of the acid group-containing polymerizable monomers include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, monobutyl itaconate, monobutyl maleate, acid phosphooxyethyl methacrylate, acid phospho Examples thereof include oxypropyl methacrylate, 3-chloro-2-acrylamido-2-methylpropane sulfonic acid, and 2-sulfoethyl methacrylate.

  Examples of the other polymerizable monomers include styrene monomers (aromatic vinyl monomers) such as styrene, vinyl toluene, 2-methyl styrene, t-butyl styrene, and chlorostyrene: methyl acrylate, ethyl acrylate, Isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate And various acrylic esters such as dodecyl acrylate: methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylic acid-n-butyl, methacrylic acid isobutyl, methacrylic acid-n-amyl, methacrylic acid Isoamyl acid, metaac Various methacrylic esters such as oxalic acid-n-hexyl, methacrylic acid-2-ethylhexyl, methacrylic acid-n-octyl, decyl methacrylate, dodecyl methacrylate: hydroxyethyl acrylate, hydroxy methacrylate Various hydroxyl group-containing monomers such as propyl: various N-substituted (meth) acrylic monomers such as N-methylol (meth) acrylamide and N-butoxy (meth) acrylamide can be exemplified.

The copolymer derived from the combination of the monomers may be a copolymer of a polymerizable monomer and a polymerizable unsaturated group-containing oligomer in some cases. Furthermore, you may use what has an acid group in a polymerizable unsaturated group containing oligomer.
Examples of such polymerizable unsaturated group-containing oligomers include vinyl-modified polyesters, vinyl-modified polyurethanes, and vinyl-modified epoxy compounds.
Specific examples thereof include maleic anhydride, fumaric acid, tetrahydrophthalic anhydride, endomethylenetetrahydromaleic anhydride, α-terpinene maleic anhydride adduct, monoallyl ether of triol, pentaerythrit diallyl ether, allyl glycidyl ether, etc. In which a polymerizable unsaturated bond (vinyl group) is introduced by polycondensation or addition of these various compounds.

Furthermore, in order to introduce an acid group into the polyester, for example, if an excessive amount of a dibasic acid such as phthalic acid is used, one having a carboxyl group at the terminal can be obtained, and if trimellitic anhydride is used, the main component is obtained. What has an acid group in a chain | strand is obtained.
The vinyl-modified polyurethane can be obtained, for example, by addition polymerization of various polyols such as glycerol monoallyl ether or butadiene polyol containing 1,2-bond and diisocyanate. Alternatively, a vinyl bond is also introduced by an addition reaction between a polyurethane having an isocyanate group at the terminal and a hydroxyl group-containing polymerizable monomer. The acid component can also be introduced into the polyurethane by adding dimethylolpropionic acid or the like as a polyol component.

Examples of the vinyl-modified epoxy compound include those obtained by reacting a terminal epoxy group of an epoxy resin with a carboxyl group of acrylic acid or methacrylic acid.
Furthermore, oligomers of polymerizable monomers having a polymerizable vinyl group obtained by adding a glycidyl group-containing polymerizable monomer to a carboxyl group-containing vinyl copolymer may be mentioned. As the polymerizable monomers, other polymerizable monomers described above can be used.
In addition to the above, it is also possible to use a terminal vinyl-modified oligomer commercially available as a macromonomer, for example, manufactured by Toa Gosei Chemical Industry Co., Ltd.
Needless to say, the oligomer is not limited to the above as long as it is an oligomer having a polymerizable vinyl group.

The polymerization for obtaining these copolymers is usually performed using a polymerization initiator under anaerobic conditions.
As the polymerization initiator, known ones can be used. Typical representative examples include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroxide, 2-ethylhexanoate and the like. And various azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile.
Examples of the reaction solvent include aromatic hydrocarbon compounds such as toluene, xylene and benzene; various alcohols such as methanol, ethanol, propanol and butanol; various ether alcohols such as cellosolve and carbitol; acetone, methyl ethyl ketone and methyl Examples include organic solvents such as various ketones such as isobutyl ketone; various esters such as ethyl acetate and butyl acetate; various ether esters such as butyl cellosolve acetate.
Preferably, so-called low-boiling organic solvents such as acetone, methyl ethyl ketone, and ethyl acetate, which easily undergo phase transition in the second step described later and are easily desolvated in the third step, are preferable.
The polymerization conditions are usually carried out in a nitrogen atmosphere within a temperature range of 50 to 150 ° C., but are not limited thereto.

The amount of acid groups in the copolymer obtained is preferably about 10 to 300, preferably about 15 to 200, and more preferably about 20 to 150.
The copolymer containing an acid group preferably has a molecular weight of a certain level or more, and usually has a number average molecular weight of 3,000 to 100,000, preferably 5,000 to 50,000. When the molecular weight is less than 3,000, the effect of dispersion stabilization may not be obtained. When the molecular weight is greater than 100,000, the degree of thickening during phase inversion emulsification increases, and as a result, It is not preferable because it is difficult to control the particle size and the particle size distribution becomes wider.
In addition to the above-described resins, examples of resins that can be used in the present invention include urethane resins (for example, urethane resin dispersions disclosed in Japanese Patent Publication No. 1-287183), and epoxy resins (for example, Japanese Patent Laid-Open Publication No. 53-1228, JP-A-55-3481, and JP-A-55-9433).

As a method for preparing the dispersant Y, first, in the first step, the resin is dissolved or dispersed in an organic solvent. As the method, a normal stirring device can be used, and it is possible to accelerate dissolution or dispersion by heating and heating as necessary.
In the second step, a resin dissolved or dispersed in an organic solvent is neutralized with a base, and then phase-emulsified in an aqueous medium. When an aqueous medium is added after neutralization with a base, conversion of the resin phase from W / O to O / W is instantaneously performed, and resin fine particles are generated in the aqueous medium.
Examples of the base used in the second step include inorganic basic compounds such as alkali metal salts such as sodium hydroxide, potassium hydroxide and lithium hydroxide, or carbonates, acetates and ammonia thereof. It is done. Examples of the organic basic compound include alkylamines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine and triethylamine, and alkanolamines such as diethanolamine.
These basic compounds may be used as they are, but are usually used as an aqueous solution.

A known and conventional stirrer can be used for the phase inversion emulsification in the second step. In particular, when the particle size is controlled to be submicron or less, an emulsifier / disperser is preferable.
For example, it is generally called a high-speed shear turbine type disperser, and is a homomixer (manufactured by Koki Kogyo Kogyo Co., Ltd.), disper (manufactured by Koki Kogyo Kogyo Co., Ltd.), Ultra Turrax (Germany), Kedy Mill (USA), Sherflow (USA), Silverson mixer (UK), Harel homogenizer (Germany), etc.
Also, continuous emulsifying disperser with rotor rotating at high speed such as Thrasher (Mitsui Mining Co., Ltd.) and Cavitron (Eurotech Co., Ltd.) and stator meshing with it, Microfluidizer (Mizho Kogyo Co., Ltd.), Microhomogenizer (Mizuho Kogyo Co., Ltd.) ), Emulsifying dispersers by the interaction of specially-shaped chambers and pump supply energy, such as Menton Gaulin homogenizer (Gorin) and Nanomizer (Nanomizer), Static mixer (Noritake Company) A stationary type in-tube continuous mixer without such a drive unit can be mentioned.

In the present invention, since the dispersant X and the dispersant Y are used in combination, the respective dispersion capacities are effectively utilized, and the total amount of the dispersant used can be reduced. This ensures the initial dispersibility of the pigment dispersion, the dispersion stability over time, and the storage stability when converted to ink, and increases the image density when printed on plain paper. The reason why the image density is improved when printing on plain paper is that the pigment concentration is due to the liquid component in the ink moving to the paper layer after the ink is deposited on the plain paper because the total amount of dispersant used has been reduced. This is presumably because the dispersion stability of the ink tends to be lost when the value becomes high, and the pigment remains in the vicinity of the paper surface because the ink thickens and aggregates.
The reason why the storage stability of the pigment dispersion or ink is improved by the dispersant Y is not necessarily clear, but since the dispersant Y exists around the pigment particles in the pigment dispersion or ink, the pigment Since the particles are prevented from approaching each other and the particles are prevented from coalescing with each other, it is presumed that the pigment particles are stably held in the aqueous medium.

When only the dispersant X is used, the dispersion stability immediately after the production of the pigment dispersion (hereinafter referred to as the initial dispersibility) is excellent, but the dispersion stability over time or the ink is formed. The storage stability of is insufficient. The image density when printed on plain paper is higher than that when using sodium naphthalene sulfonate formalin condensate, but is insufficient.
On the other hand, when only the dispersant Y is used, the initial dispersibility is insufficient. In addition, the storage stability is excellent when the ink is used, but the image density when printed on plain paper is low. Further, when the dispersant Y is not blended in the pigment dispersion but is blended at the time of preparing the ink, the storage stability of the ink is excellent, but the image density when printed on plain paper is low.

In the pigment dispersion of the present invention, the total amount of the dispersant X and the dispersant Y is preferably contained at a ratio of 0.01 to 0.5 with respect to the carbon black 1 on a mass basis, and 0.02 to 0.3. More preferably, it is contained. If the content of the dispersant is 0.01 or more, the object of the present invention can be easily achieved, the storage stability of the pigment dispersion and the ink can be secured, and as a result, nozzle clogging tends not to occur. If it is 0.5 or less, the viscosity of the pigment dispersion and the ink will not be too high, and printing by the ink jet system will not be difficult.
In the pigment dispersion of the present invention, by using the above dispersant, the volume average particle size (D50) of carbon black of the pigment dispersion is 70 to 180 nm, and the particle size standard deviation in the particle size distribution of the carbon black is D50. Thus, a pigment dispersion having a high image density and good ejection stability and storage stability when used in an inkjet ink can be provided. The volume average particle size of the carbon black was measured using a particle size distribution meter (manufactured by Nikkiso Co., Ltd., UPA) in an environment of 23 ° C. and 55% RH.
The carbon black concentration in the pigment dispersion is preferably 5 to 25% by mass and more preferably 10 to 20% by mass with respect to the entire pigment dispersion. If the carbon black concentration is 5% by mass or more, the productivity is not inferior. If the carbon black concentration is 25% by mass or less, the viscosity of the pigment dispersion does not become too high and dispersion does not become difficult.

-Other ingredients-
In addition to carbon black, a dispersant, and water, the pigment dispersion of the present invention includes a water-soluble organic solvent, a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a preservative as necessary. Various additives such as can be added.
The water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose.
For example, alcohols such as methanol, ethanol, 1-propanol, 2-propanol;
Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and glycerine; pyrrolidone derivatives such as N-methylpyrrolidone and 2-pyrrolidone; ketones such as acetone and methyl ethyl ketone; monoethanolamine, diethanolamine and triethanolamine Examples include alkanolamines.
The pigment dispersion of the present invention is obtained by wet-dispersing carbon black, a dispersant, water and, if necessary, various additives with a known disperser such as a sand mill, a ball mill, a roll mill, a bead mill, a nanomizer, and a homogenizer. be able to.
Here, the wet dispersion treatment means a treatment of finely pulverizing and dispersing the mixture of the pigment dispersion materials by a so-called wet dispersion method using a disperser.
The pigment dispersion of the present invention can be suitably used particularly as a pigment-based inkjet ink.

<Inkjet ink>
The inkjet ink of the present invention contains the pigment dispersion of the present invention, and contains water, a water-soluble organic solvent, a surfactant, and other components as necessary.
The content of carbon black in the ink is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, although it depends on the prescription of the whole ink. If the carbon black content is not too low, the image density will not be too low and the print will not be sharp. If the carbon black content is not too high, the ink viscosity will be too high or the nozzle Clogging is not likely to occur.

The water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose.
For example, polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate, other water-soluble solvents, etc. Is mentioned. These may be used alone or in combination of two or more. Specifically, the same pigment dispersion can be used.
The content of the water-soluble organic solvent is preferably 0 to 50% by mass with respect to the total amount of the ink, and 5 to 40%.
The mass% is more preferable, and 10 to 35 mass% is still more preferable.
Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.
Examples of the other components include antifoaming agents, antiseptic / antifungal agents, rust preventing agents, pH adjusting agents, specific resistance adjusting agents, antioxidants, ultraviolet absorbers, oxygen absorbers, light stabilizers, and viscosity adjusting agents. Etc.

The ink-jet ink of the present invention may contain water-dispersible resin particles in order to further improve the scratch resistance of the image. Water-dispersible resin particles mean a resin emulsion in which the continuous phase is water and the dispersed phase is a resin component. Examples of the resin component in the dispersed phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, polyurethane resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, and styrene resins.
The ink-jet ink of the present invention can be produced by a known method. For example, the pigment dispersion of the present invention, water, a water-soluble organic solvent, a surfactant and the like are stirred and mixed, and a filter, a centrifugal separator, or the like is used. It is obtained by filtering coarse particles and degassing as necessary.
The ink-jet ink of the present invention can be suitably used for an ink cartridge that contains the ink, as will be described later. Further, as will be described later, an image can be formed by an ink jet recording apparatus as an image forming apparatus that ejects the ink jet ink of the present invention onto an image support such as paper.

<Ink cartridge>
The ink cartridge of the present invention is one in which the ink-jet ink of the present invention is contained in a container. There are no particular restrictions on the container, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose, for example, an ink bag formed of an aluminum laminate film, a resin film, etc. A plastic case etc. are mentioned suitably.
<Image forming apparatus>
The image forming apparatus of the present invention has an ejection unit for ejecting the inkjet ink of the present invention to form an image, and further includes other units as necessary.
As a method of printing (discharging), a continuous jet type or an on-demand type can be mentioned. Examples of the on-demand type include a piezo method, a thermal method, and an electrostatic method.

Here, the ink cartridge and the image forming apparatus (inkjet recording apparatus) of the present invention will be described with reference to FIG.
In FIG. 1, an ink cartridge 20 that accommodates the ink-jet ink of the present invention.
Is housed in the carriage 18. In FIG. 1, a plurality of ink cartridges 20 are provided, but it is not necessary to have a plurality. In such a state, the ink for inkjet is supplied from the ink cartridge 20 to the droplet discharge head 18 a mounted on the carriage 18. In FIG. 1, the discharge nozzle surface is not visible because it faces downward, but ink jet ink is discharged from the discharge nozzle.
The droplet discharge head 18 a mounted on the carriage 18 is guided and moved by the guide shafts 21 and 22 by the timing belt 23 driven by the main scanning motor 26.
On the other hand, a specific coated paper (image support) is placed at a position facing the droplet discharge head 18 a by the platen 19. In FIG. 1, 1 is an ink jet recording apparatus, 2 is a main body housing,
Reference numeral 16 denotes a gear mechanism, 17 denotes a sub-scanning motor, and 25 and 27 denote gear mechanisms.

When an image is formed on an image support using an ink jet recording apparatus containing the ink jet ink or ink cartridge of the present invention, an image forming body printed on the image support on demand is obtained. Inkjet ink can be replenished by replacing the ink cartridge unit.
There is no restriction | limiting in particular as said image support body, According to the objective, it can select suitably, For example, a plain paper, glossy paper, special paper, cloth, a film, an OHP sheet etc. are mentioned. Among these, paper is particularly preferable.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited at all by these Examples.
The average primary particle diameter of carbon black is measured by photographing particles using an electron micrograph and calculating from the diameter and number of particles in the photographed image. The BET specific surface area of carbon black is the BET by nitrogen adsorption. Measured by the method. In the examples, “%” and “part” are based on mass.

<Preparation of partially desulfonated lignin sulfonate and its derivative 1>
Product name: A solution obtained by adding 45% NaOH to the solid content of Sun Extract 252 (manufactured by Nippon Paper Chemicals Co., Ltd., main component sodium lignin sulfonate) at 170-180 ° C. for 60 minutes for 60 minutes with alkaline air oxidation. ₂ SO ₄ was added to pH 3, and partially desulfonated lignin sulfonate and its derivative were fractionally precipitated.
This precipitate was neutralized with NaOH to pH 8 and dried to obtain partially desulfurized sodium lignin sulfonate and derivatives thereof having a degree of sulfonation of 0.15 mol.

<Partially desulfonated lignin sulfonate and its derivative 2>
Product name: Pearl Rex DP (manufactured by Nippon Paper Chemicals Co., Ltd., sodium lignin sulfonate and its derivatives subjected to partial desulfonation reaction, methoxyl group content 9.8%)

<Preparation of anionic self-dispersible resin fine particles 1>
(Synthesis of polyurethane fine particles)
In a 1 L four-necked flask equipped with a stirrer, a reflux device, a dry nitrogen inlet tube and a thermometer, 533 g of “Bernock DN-980 (polyisocyanate manufactured by Dainippon Ink and Chemicals)”, 2,2-bis (hydroxy Methyl) 33.5 g of propionic acid, 0.05 g of dibutyltin dilaurate and 300 g of ethyl acetate are added and stirred at 80 ° C. for 3 hours. The polyurethane prepolymer has a dry solid content ratio of 50.0% and an NCO content of 6.80%. Solution was obtained.
The NCO (isocyanate group) content is determined by weighing a predetermined amount of sample solution, adding a certain amount of ethyl acetate solution of di-n-butylamine having a known concentration in excess of the isocyanate group to be measured, and reacting with excess di- It was determined by back titrating n-butylamine with an aqueous hydrochloric acid solution having a known concentration.
30 g of methyl ethyl ketone was added to 100 g of the polyurethane prepolymer solution, neutralized with 3.50 g of triethylamine, and water was added dropwise with stirring.
The prepolymer solution gradually increased in viscosity, and after about 150 g of water was dripped, the viscosity decreased remarkably and phase inversion was completed.
Further, 150 g of water was added, and then an aqueous solution in which 2.51 g of diethylenetriamine was dissolved in 50 g of water was slowly added with stirring.
Next, the obtained dispersion is heated to 30 ° C., and the organic solvent and excess water are removed under reduced pressure to obtain an aqueous dispersion of polyurethane fine particles having a dry solid content ratio of 33.5% and an average particle diameter of 78 nm. It was.
The particle diameter of the polyurethane fine particles was measured with a laser Doppler particle size distribution analyzer Microtrac UPA-150.
The acid value of the polyurethane fine particles obtained by weighing a predetermined amount of the sample solution and titrating with a methanol solution of potassium hydroxide having a known concentration was 31.2.

<Anionic self-water dispersible resin fine particles 2>
Polyurethane fine particles (trade name: U-coat UWS-145, manufactured by Sanyo Chemical Industries, Ltd., dry solid content ratio 34%, average particle size 20 nm, acid value 49)

<Preparation of anionic self-dispersible resin fine particles 3>
(Synthesis of acrylic polymer fine particles)
400 g of methyl ethyl ketone was charged into a 1 L four-necked flask equipped with a stirrer, a reflux device, a dry nitrogen inlet tube with a thermometer, and a dropping device, and the temperature was raised to 80 ° C.
Next, a solution in which 80 g of styrene, 238.9 g of methyl methacrylate, 24.5 g of methacrylic acid, 56.6 g of butyl acrylate, and 8 g of perbutyl O (a polymerization initiator manufactured by NOF Corporation) were mixed well was added dropwise over 2 hours. .
After stirring for 8 hours, 0.5 g of perbutyl O was added and further stirred for 8 hours to obtain an acrylic polymer having a dry solid content ratio of 49.5%, an acid value of 39.1, and a number average molecular weight of 20000.
The dry solid content ratio was determined by weighing about 1 part of the sample solution, weighing the sample after drying for 1 hour at 120 ° C., and mass ratio thereof.
The number average molecular weight was measured by GPC and determined as a molecular weight in terms of polystyrene.
The acid value was determined by weighing a predetermined amount of the sample solution and titrating with a methanol solution of potassium hydroxide having a known concentration.
Next, 100 g of the acrylic polymer solution was neutralized with 2.71 g of triethylamine, and water was added dropwise with stirring.
The prepolymer solution gradually increased in viscosity, and after about 150 g of water was dripped, the viscosity decreased remarkably and phase inversion was completed.
Further, 150 g of water was added, and then the resulting dispersion was heated to 30 ° C., and the organic solvent and excess water were removed under reduced pressure to obtain acrylic polymer fine particles having a dry solid content ratio of 33.7% and an average particle size of 120 nm. An aqueous dispersion was obtained.
The particle size of the acrylic polymer was measured with a laser Doppler particle size distribution analyzer Microtrac UPA-150.

Fixing agent (Synthesis Example 1)
-Synthesis of silicone-modified acrylic resin fine particles containing no reactive silyl groups-
A flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel was sufficiently replaced with nitrogen gas, then 10 g of Aqualon RN-20 (Daiichi Kogyo Seiyaku Co., Ltd.) and 1 g of potassium persulfate. And 286 g of pure water were charged and the temperature was raised to 65 ° C.
Next, 150 g of methyl methacrylate, 100 g of 2-ethylhexyl acrylate, 20 g of acrylic acid, 20 g of vinyltriethoxysilane, 10 g of Aqualon RN-20 (Daiichi Kogyo Seiyaku Co., Ltd.), 4 g of potassium persulfate, and pure water 398. 3 g of the mixed solution was dropped into the flask over 2.5 hours.
Next, the mixture was further heated and aged at 80 ° C. for 3 hours, and then cooled and adjusted with potassium hydroxide to have a pH of 7 to 8 to obtain silicone-modified acrylic resin fine particles having a solid concentration of 30%.

[Example 1]
<Pigment dispersion (A)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 1 3.75 parts Anionic self-water dispersible resin fine particles 1 (solid content concentration 33.5%) 11. 19 parts ・ Pure water… 835.06 parts

The material mixture of the above formulation was pre-dispersed with a ball mill using zirconia beads having a diameter of 3 mm, and then a disk-type bead mill (KDL type batch type manufactured by Shinmaru Enterprises Co., Ltd.) using zirconia beads having a diameter of 0.3 mm. After dispersing for 5 minutes at a peripheral speed of 10 m / s and a liquid temperature of 10 ° C., coarse particles were centrifuged with a centrifuge (Model 3600, manufactured by Kubota Corporation), and the pigment dispersions (A ) Was produced.

<Ink liquid (a)>
A material having the following formulation containing the pigment dispersion (A) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum deaerated to prepare an ink liquid (a).

-Pigment dispersion A (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

[Example 2]
<Pigment dispersion (B)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 1 3.75 parts Anionic self-water-dispersible resin fine particles 2 (solid content concentration 34%) 11.03 parts・ Pure water: 835.22 parts

A pigment dispersion (B) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (b)>
A material having the following formulation containing the pigment dispersion (B) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore diameter of 0.8 μm, and vacuum degassed to prepare an ink liquid (b).

-Pigment dispersion B (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

Example 3
<Pigment dispersion (C)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 1 1.875 parts Anionic self-water dispersible resin fine particles 2 (solid content concentration 34%) 111.03 parts・ Pure water: 837.10 parts

A pigment dispersion (C) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (c)>
A material having the following formulation containing the pigment dispersion (C) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum deaerated to prepare an ink liquid (c).

-Pigment dispersion C (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

Example 4
<Pigment dispersion (D)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 2 3.75 parts Anionic self-water-dispersible resin fine particles 2 (solid content concentration 34%) 111.03 parts・ Pure water: 835.2 parts

A pigment dispersion (D) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (d)>
A material having the following formulation containing the pigment dispersion (D) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum deaerated to prepare an ink liquid (d).

-Pigment dispersion D (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

[Comparative Example 1]
<Pigment dispersion (E)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 1 3.75 parts Anionic self-water dispersible resin fine particles 3 (solid content concentration 33.7%) 11. 13 parts ・ Pure water… 835.12 parts

A pigment dispersion (E) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (e)>
A material having the following formulation containing the pigment dispersion (E) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum deaerated to prepare an ink liquid (e).

-Pigment dispersion E (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

[Comparative Example 2]
<Pigment dispersion (F)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) ... 150 parts ・ Naphthalene sulfonate sodium formalin condensate ... 9.375 parts (Takemoto Yushi Co., Ltd., Pionine A-45-PN)
・ Pure water: 840.625 parts

A pigment dispersion (F) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (f)>
A material having the following formulation containing the pigment dispersion (F) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore diameter of 0.8 μm, and vacuum deaerated to prepare an ink liquid (f).

-Pigment dispersion F (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

[Comparative Example 3]
<Pigment dispersion (G)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 1 9.375 parts Pure water 840.625 parts

A pigment dispersion (G) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (g)>
A material having the following formulation containing the pigment dispersion (G) was mixed, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum degassed to prepare an ink liquid (g).

-Pigment dispersion G (15% pigment concentration) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

[Comparative Example 4]
<Pigment dispersion (H)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) ... 150 parts ・ Naphthalene sulfonate sodium formalin condensate ... 9.375 parts (Takemoto Yushi Co., Ltd., Pionine A-45-PN)
・ Pure water: 840.625 parts

A pigment dispersion (H) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (h)>
After mixing the materials of the following formulation containing the pigment dispersion (H) and stirring for 30 minutes, the mixture was filtered through a membrane filter having a pore diameter of 0.8 μm and vacuum deaerated to prepare an ink liquid (h).

-Pigment dispersion H (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 6.67%
Anionic self-water dispersible resin fine particles 1 (solid content concentration 33.5%) 2.99%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.39%

[Comparative Example 5]
<Pigment dispersion (I)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Partially desulfonated lignin sulfonate and its derivative 1 9.375 parts Pure water 840.625 parts

A pigment dispersion (I) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (i)>
The materials of the following formulation containing the pigment dispersion (I) were mixed, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum degassed to prepare an ink liquid (i).

-Pigment dispersion I (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 6.67%
Anionic self-water dispersible resin fine particles 1 (solid content concentration 33.5%) 2.99%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.39%

[Comparative Example 6]
<Pigment dispersion (J)>
Carbon black (NIPEX160-IQ, manufactured by degussa, gas black,
BET specific surface area 150 m ² / g) 150 parts Anionic self-water-dispersible resin fine particles 1 (solid content concentration 33.5%) 55.97 parts Pure water 794.03 parts

A pigment dispersion (J) shown in Tables 1 and 2 was prepared in the same manner as the pigment dispersion (A) except that the material mixture having the above formulation was used.

<Ink liquid (j)>
After mixing the materials of the following formulation containing the pigment dispersion (J) and stirring for 30 minutes, the mixture was filtered through a membrane filter having a pore size of 0.8 μm and vacuum deaerated to prepare an ink liquid (j).

・ Pigment dispersion J (pigment concentration 15%) 53.3%
・ Glycerin 8.5%
・ 3-methyl-1,3-butanediol 17.0%
・ 2-ethyl-1,3-hexanediol 2.0%
・ 2-Pyrrolidone 2.0%
-Silicone-modified acrylic resin of Synthesis Example 1 (solid content concentration 30%) 10.0%
・ Fluorosurfactant (FS-300, DuPont, 40% active ingredient) 2.5%
-Antiseptic and fungicidal agent (Proxel LV, manufactured by Avecia) 0.05%
・ Triethanolamine 0.6%
・ Pure water 4.05%

The volume average particle diameter (D50) of the particles contained in the inks (a) to (j) was measured using a particle size distribution meter UPA manufactured by Nikkiso Co., Ltd. in an environment of 23 ° C. and 55% RH. The results are shown in Table 2.
Also, using a Ricoh inkjet printer GX5000, plain paper-fast (
The image was output in the (color matching-not) mode. In this mode, the applied voltage waveform was adjusted so that the ink adhesion amount of the black solid portion was 8.2 g / m ² .
As recording media, PPC paper 4200 manufactured by Xerox Co., Ltd. was used, and image density, ejection stability and storage stability were evaluated as follows. The results are shown in Table 2.

<Image density>
A solid image of the image sample was measured with an X-Rite densitometer (manufactured by X-Rite).

<Discharge stability>
After printing the printed matter using each ink, the printer was left in a 40 ° C. environment for one month with the printer head capped. Whether or not the discharge state of the printer after being left is restored to the initial discharge state was evaluated based on the following criteria for the number of cleaning operations.
〔Evaluation criteria〕
○: When recovered by one operation △: When recovered by two or three operations ×: When recovery is not observed even after three or more operations

<Storage stability>
Each ink was put in a polyethylene container and sealed, and the particle size, surface tension, and viscosity after storage at 70 ° C. for 3 weeks were measured, and evaluated according to the following criteria based on the rate of change from the initial physical properties.
〔Evaluation criteria〕
◎: When the change rate is less than 5% for all items of particle size, surface tension, and viscosity ○: When the change rate is less than 10% for all items of particle size, surface tension, and viscosity △: Particle size, surface When the rate of change is less than 30% for all items of tension and viscosity X: When the rate of change is 30% or more for at least one item of particle size, surface tension, and viscosity

なお、表中のα、β、γの量は、カーボンブラック１質量部に対する質量部である。

The amounts of α, β, and γ in the table are parts by mass with respect to 1 part by mass of carbon black.

  From the results shown in Table 2, the inkjet inks using the pigment dispersions of the present invention of Examples 1 to 4 have a high image density, and are superior to Comparative Examples 1 to 6 in ejection stability and storage stability. It turns out that it is a thing.

The pigment dispersion of the present invention and the ink jet ink using the pigment dispersion can be applied to various types of recording by an ink jet recording method, such as an ink jet printer,
The present invention can be suitably applied to a facsimile machine, a copying machine, and the like.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Main body housing | casing 16 Gear mechanism 17 Subscanning motor 18 Carriage 18a Droplet discharge head 19 Platen 20 Ink cartridge 21 Guide shaft 22 Guide shaft 23 Timing belt 25 Gear mechanism 26 Main scanning motor 27 Gear mechanism

JP 2008-63573 A JP 2009-0697907 JP 2009-173805 A JP 2005-263880 A

Claims (4)

  Containing at least carbon black, a dispersant, and water, the dispersant comprising partially desulfonated lignin sulfonate and / or a derivative thereof, and anionic self-water-dispersible resin fine particles having a volume average particle size of 0.1 μm or less. A pigment dispersion characterized by containing.   An ink-jet ink comprising the pigment dispersion according to claim 1. An ink cartridge comprising the ink-jet ink according to claim 2 contained in a container.   An image forming apparatus, comprising: an ejection unit that ejects the ink-jet ink according to claim 2 to form an image.

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