JP2010070749A - Pigment dispersion liquid, ink composition, and inkjet recording method - Google Patents

Abstract

A pigment dispersion having excellent dispersibility and storage stability and high chemical safety is provided.
The color material includes carbon black having a polyaromatic hydrocarbon content of 80 ppm or less and an oxygen-containing functional group density defined by the following formula of 3 μmol / m ² or less. Pigment dispersion.
Oxygen-containing functional group density (μmol / m ² )
= [(950 ° C. × 30 minutes) CO generation amount (μmol / g) + (950 ° C. × 30 minutes) CO ₂
Generation amount (μmol / g)] / nitrogen adsorption specific surface area (m ² / g)
[Selection figure] None

Description

  The present invention relates to a pigment dispersion using specific carbon black as a coloring material. Specifically, the present invention relates to a pigment dispersion that can be suitably used for an ink composition as a recording liquid for an ink jet printer, an ink composition containing the pigment dispersion, and an ink jet recording method using the ink composition.

  Inkjet printers are rapidly becoming popular for both personal use and business use due to the ease of full color, low noise, high-resolution images at low cost, and high-speed printing. I am doing. At present, aqueous recording liquids are mainly used as recording liquids for ink jet printers, and printed materials with high resolution are being obtained.

  Conventionally, the aqueous recording liquid mainly contains a water-soluble dye and a liquid medium. However, the printed matter obtained with this aqueous recording liquid has insufficient water resistance, light resistance, ozone resistance and the like because the aqueous recording liquid contains a water-soluble dye. Therefore, in recent years, a pigment dispersion type aqueous recording liquid (hereinafter sometimes simply referred to as “ink”) in which a pigment is dispersed in an aqueous medium has been developed instead of such a dye.

  In recent years, with the improvement of the resolution of printed matter, the amount of ink discharged from the ink discharge nozzle has decreased significantly. And since the request | requirement with respect to the printing speed improvement of an inkjet printer is increasing, higher pigment dispersion stability and discharge stability are calculated | required with respect to the pigment dispersion-type aqueous recording liquid. Furthermore, due to the high versatility of inkjet printers, the high safety of recording liquids is also required at the same time.

  On the other hand, a method has been proposed in which specific carbon black is used as a color material in a pigment-dispersed aqueous recording liquid.

  In Patent Document 1, in order to improve the dispersibility at the time of preparing the recording liquid and the printing density of the printed matter, carbon black having a content of polyaromatic hydrocarbon (hereinafter referred to as “PAH”) of 500 ppm or less is used. A recording liquid characterized in that it is included has been proposed.

  In Patent Document 2, in order to improve dispersion stability, recording density, and ejection stability, carbon black from which an organic solvent soluble component is removed is used in a black aqueous ink containing at least carbon black and a water-soluble resin. A black aqueous ink composition characterized by the above has been proposed.

Japanese Patent Laid-Open No. 2001-354884 JP 2001-200194 A

  In recent years, in the pigment dispersion for inkjet printers, the demand for large-format photos and high-grade photo fields is increasing due to the high fastness of the printed matter. At the same time, in order to improve the shortcomings of business inkjet printers that have insufficient reliability and printing speed compared to laser printers, there is also a demand for pigment dispersions that can be printed on plain paper with high print density and high-speed printing. It is growing.

  Depending on the application, pigment dispersions for inkjet printers are solvent-based pigment dispersions using fast-drying organic solvents as media, and UV-based systems using polymerizable monomers as media for cross-linking by ultraviolet (UV) light after recording. A pigment dispersion, and an aqueous pigment dispersion mainly using consumer water as a medium are used.

  In any system, the chemical safety of products has been strongly demanded in recent years, and the impact on the environment and the human body has become more important. There is an increasing demand for dispersions and recording liquids that achieve high dispersibility and storage stability, which are necessary basic performances.

  Patent Document 1 describes that carbon black having a PAH content of 500 ppm or less is used for the purpose of improving the dispersibility when preparing the recording liquid and the print density of the printed matter. In addition to such hydrophobic compounds, there are acidic functional groups such as carbonyl groups (ketones, quinones, etc.), carbonyl groups and derivatives thereof (esters, lactones, etc.). Patent document 1 does not mention at all what the influence of these has on dispersibility and stability. Further, Patent Document 1 does not disclose any oxygen-containing functional group density that quantitatively indicates acidic functional groups present on the surface of carbon black.

Patent Document 2 describes that carbon black obtained by extracting and removing organic solvent-soluble components by mixing and stirring with an organic solvent is described in order to improve dispersion stability, recording density, and ejection stability. However, it is difficult to completely remove PAH by the solvent extraction described in this document, and as a result, a considerable amount of PAH is expected to remain.
Furthermore, Patent Document 2 does not mention any influence of the treatment method shown in Patent Document 2 on the density of oxygenated functional groups on the surface of carbon black. There is no indication of the degree.

  An object of the present invention is to provide a pigment dispersion having excellent dispersibility and storage stability and high chemical safety.

In order to solve such problems, the present inventors have intensively studied pigment dispersions. As a result, dispersibility and storage stability can be achieved by using carbon black having a PAH content of 80 ppm or less and an oxygen-containing functional group density defined by the following formula of 3 μmol / m ² or less as a coloring material. The present invention was completed by finding that a pigment dispersion excellent in property and chemical safety can be obtained.
Oxygen-containing functional group density (μmol / m ² )
= [(950 ° C. × 30 minutes) CO generation amount (μmol / g) + (950 ° C. × 30 minutes) CO ₂
Generation amount (μmol / g)] / nitrogen adsorption specific surface area (m ² / g)

That is, the gist of the present invention includes carbon black having a polyaromatic hydrocarbon content of 80 ppm or less and an oxygen-containing functional group density defined by the following formula of 3 μmol / m ² or less as a coloring material. A pigment dispersion characterized in that.
Oxygen-containing functional group density (μmol / m ² )
= [(950 ° C. × 30 minutes) CO generation amount (μmol / g) + (950 ° C. × 30 minutes) CO ₂
Generation amount (μmol / g)] / nitrogen adsorption specific surface area (m ² / g)

  Another gist of the present invention resides in a pigment dispersion characterized in that the content of polyaromatic hydrocarbon in the carbon black is 20 ppm or less (claim 2).

  Another gist of the present invention resides in a pigment dispersion characterized in that the carbon black is fired at a temperature of 800 to 1500 ° C. in a nitrogen atmosphere (Claim 3).

  Another gist of the present invention resides in a pigment dispersion characterized in that the pigment dispersion is aqueous.

  Another subject matter of the present invention resides in an ink composition (claim 5) containing the pigment dispersion.

  Still another subject matter of the present invention resides in an ink jet recording method (Claim 6) characterized in that a droplet of the ink composition is ejected from an ink jet head and the droplet is adhered to a recording medium.

  According to the present invention, a pigment dispersion excellent in dispersibility, storage stability, and chemical safety can be provided. In particular, the pigment dispersion liquid of the present invention can be suitably used for an ink composition as a recording liquid for an inkjet printer or the like, and the ink composition containing the pigment dispersion liquid of the present invention can be used for high quality and high durability. An ink jet recorded product can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention does not exceed the gist thereof. These contents are not specified.

In the following, “(meth) acrylate” means “acrylate and / or methacrylate”, and “(meth) acryl” means “acryl and / or methacryl”.
“Polymer” means “polymer and / or copolymer”.

  The “structural unit” is a structural unit of the basic structure of the polymer. In the case of a synthetic polymer, the basic structure of the polymer is a monomer molecule used in the production of the polymer by polymerization or copolymerization. It is a structure derived from, or a structure in which they are modified by modification. In the case of a natural polymer, it is a repeating structure or a structure modified by modification or the like.

  In the present invention, “monomer constituent unit” or “monomer as constituent unit” means a constituent unit introduced into polymer A by synthesizing a polymer using the monomer (for example, “monomer x”). The polymer is synthesized using a monomer different from the monomer x (for example, “monomer y”), and then the structural unit introduced by the monomer y is modified or modified to be introduced by the monomer x. The same structural unit as the structural unit may be formed, and even in this case, the monomer structural unit does not say "monomer y structural unit" or "monomer y is the structural unit" “Monomer x constituent unit” or “monomer x as constituent unit” shall be referred to.

In the pigment dispersion of the present invention,
There are aqueous pigment dispersions, solvent pigment dispersions, and UV pigment dispersions, all of which use a specific amount of PAH and carbon black having a high concentration of oxygen-containing functional groups as a colorant.

[Carbon black]
First, carbon black used as a colorant in the aqueous pigment dispersion, the solvent pigment dispersion, and the UV pigment dispersion of the present invention will be described.

In the present invention, as a coloring material, the content of polyaromatic hydrocarbon (PAH) (PAH amount) is 80 ppm or less, and the oxygen-containing functional group density defined by the following formula is 3 μmol / m ² or less. Carbon black is used.

Oxygen-containing functional group density (μmol / m ² )
= [(950 ° C. × 30 minutes) CO generation amount (μmol / g) + (950 ° C. × 30 minutes) CO ₂
Generation amount (μmol / g)] / nitrogen adsorption specific surface area (m ² / g)

Here, (950 ° C. × 30 minutes) CO generation amount (hereinafter simply referred to as “CO generation amount”) and (950 ° C. × 30 minutes) CO ₂ generation amount (hereinafter simply referred to as “CO ₂ generation amount”) Is the amount of CO and CO ₂ in the gas generated during the heating of carbon black at 950 ° C. for 30 minutes in vacuum, and is specifically measured as follows.

About 0.5 g of carbon black is precisely weighed, put in an alumina tube, and reduced in pressure to 0.01 Torr (1.3 Pa). Then, the reduced pressure system is closed, and is kept in an electric furnace at 950 ° C. for 30 minutes. Decomposes and volatilizes oxygen and hydrogen compounds. Volatile components are collected in a fixed-capacity gas collection tube through a quantitative suction pump. Together determine the amount of gas from the pressure and temperature, and composition analysis by gas chromatography, determined occurrence amount of carbon monoxide (CO) and carbon dioxide (CO ₂₎ to (mg), per carbon black 1 g CO emissions and CO ₂ Calculate the value converted into the amount generated (unit: mg / g). Furthermore, the generated amount of each gas obtained is converted to μmol / g.
The nitrogen adsorption specific surface area is a value measured by the method of JISK6217.

  The amount of PAH contained in the carbon black used in the present invention is 80 ppm or less, preferably 20 ppm or less, more preferably 15 ppm or less, and particularly preferably 10 ppm or less. If the PAH amount of carbon black is too large, a pigment dispersion excellent in dispersibility, storage stability and chemical safety cannot be obtained.

  PAH in carbon black is a general term for compounds having a condensed aromatic ring. Specific examples thereof include naphthalene, fluorene, acetonaphthene, acenaphthene, phenanthrene, anthracene, pyrene, benzoanthracene, benzopyrene, benzo Examples include hydrophobic compounds such as piperine. The amount of PAH in carbon black was obtained by Soxhlet extraction with toluene for 48 hours in accordance with “Method for measuring PAH content in carbon black” (issued by Cabot Corporation on July 8, 1994). The extract can be concentrated and quantified by GC-MS.

Further, the carbon black used in the present invention, the oxygen-containing functional group density, defined by the formula is less 3 [mu] mol / ^{m 2,} is preferably 2.5 .mu.mol / ^{m 2} or less, 2 [mu] mol / ^{m 2} or less It is particularly preferred. If the oxygen-containing functional group density is too high, a pigment dispersion excellent in dispersibility, storage stability, and chemical safety cannot be obtained.

The carbon black used in the present invention may be carbon black satisfying the PAH amount and the oxygen-containing functional group density, and the type of carbon black to be used, DBP oil absorption amount, nitrogen adsorption specific surface area, primary particle diameter, volatile matter, Specific examples, shapes, and average dispersed particle sizes of pH, carbon black are not particularly limited, and as a treatment for satisfying the PAH amount and oxygen-containing functional group density according to the present invention, a general production method can be used. After the production of carbon black, any treatment may be applied as long as the treatment can reduce the PAH amount to 80 ppm or less and the oxygen-containing functional group density to 3 μmol / m ² or less. Specific treatment methods include, for example, washing with water, warm water, or an organic solvent, baking treatment, and the like. These methods may be used in combination, but preferably 800 to 800 under a nitrogen atmosphere. A baking treatment at a temperature of 1500 ° C. may be mentioned.
Here, the calcination treatment in a nitrogen atmosphere is a calcination operation performed for further modifying the carbon black obtained through a general manufacturing method.
Below, carbon black obtained through such a baking treatment in a nitrogen atmosphere will be described.

  The production method of carbon black differs depending on the raw material, and general methods include, for example, a thermal method, a method using acetylene decomposition (hereinafter referred to as a thermal decomposition method), a channel method, a furnace method (hereinafter referred to as an incomplete combustion method) and the like. For example, in the furnace method, the raw material hydrocarbons are continuously pyrolyzed by the combustion heat of oil or gas to produce carbon black. Of these, the oil furnace method has a special reaction lined with brick that can withstand about 2000 ° C. Fuel and air are introduced into the furnace and completely burned to form a high temperature atmosphere of 1400 ° C. or higher, and then liquid raw material oil is continuously sprayed and thermally decomposed.

  That is, in the present invention, “carbon black obtained by firing at a temperature of 800 to 1500 ° C. in a nitrogen atmosphere” means that the carbon black obtained by the above general production process is further under a nitrogen atmosphere. It means carbon black obtained by firing at a temperature of 800 to 1500 ° C.

The following is considered as a mechanism for obtaining a carbon black suitable for the present invention by such a baking treatment.
Carbon black obtained by a general production method contains a large amount of a component called PAH, and has functional groups such as acidic groups and basic groups on the surface. In particular, PAH may be suspected to be carcinogenic, and carbon black containing these is feared to affect the living body and the environment. In addition, the presence of surface functional groups such as PAH components and acidic groups inhibits the adsorption of polymers used as pigment dispersants in aqueous pigment dispersions, making it easier for polymers to exist in the presence of organic solvents and surfactants. Desorbs and lowers the pigment dispersibility and storage stability of the pigment dispersion containing carbon black. Therefore, by baking at a temperature of 800 to 1500 ° C. under a nitrogen atmosphere, the amount of acidic functional groups on the PAH and the surface can be reduced to a high degree, thereby improving the chemical safety and improving the carbon black. It is considered that the adsorptivity of the polymer dispersant can be improved, and a pigment dispersion having high dispersibility and storage stability can be obtained.

  Further, according to the study by the present inventors, if the calcination treatment temperature is too low, sufficient effects cannot be obtained due to the low degree of removal of PAH and acidic functional groups, and if the calcination treatment temperature is too high, carbon black is not obtained. If the crystallization (graphitization) proceeds and eventually graphitizes to the inside of the particles, huge particles are formed, which makes it difficult to use in inkjet applications.

  The firing time is not particularly limited and varies depending on the firing temperature, but is usually 1 hour or longer, preferably 1 day or longer, more preferably 7 days or longer, and the upper limit is usually 60 days or shorter, preferably 40 days or shorter. . If the firing time is too short, the effect of reducing the amount of PAH and acidic functional groups is insufficient, and even if the firing time is longer than this, the effect does not change, and the processing time is wasted.

  The carbon black used in the treatment for satisfying the PAH amount and oxygen-containing functional group density according to the present invention, such as a baking treatment at 800 to 1500 ° C. in a nitrogen atmosphere, is a general production method as described above. For example, various carbon blacks such as acetylene black, channel black and furnace black can be used. Among these, channel black or furnace black is preferable, and furnace black is particularly preferable.

In addition, the DBP oil absorption of carbon black subjected to the treatment for satisfying the PAH amount and oxygen-containing functional group density according to the present invention such as firing treatment is in the range of 30 to 250 ml / 100 g from the viewpoint of dispersibility. preferable. Among these, from the viewpoint of glossiness with photographic paper, a range of 30 to 100 ml / 100 g is more preferable, and a range of 30 to 70 ml / 100 g is particularly preferable. Further, from the viewpoint of printing density on plain paper, a range of 100 to 250 ml / 100 g is preferable.
Moreover, the nitrogen adsorption specific surface area of the carbon black subjected to the treatment for satisfying the PAH amount and the oxygen-containing functional group density according to the present invention such as a firing treatment is 20 to 700 m ² / g from the viewpoint of dispersibility. A range is preferred. Among these, from the viewpoint of glossiness in the photo paper, a range of 100 to 600 m ² / g is preferable, and a range of 200 to 600 m ² / g is particularly preferable. From the viewpoint of printing density on plain paper is preferably in the range of 20 to 200 m ² / g, the range of 20~150m ² / g is particularly preferred.
The primary particle diameter of carbon black subjected to the treatment for satisfying the PAH amount and oxygen-containing functional group density according to the present invention such as a firing treatment is usually 5 nm or more, preferably 300 nm or less, more preferably It is 200 nm or less, particularly preferably 100 nm or less. Among these, 5 to 20 nm is particularly preferable from the viewpoint of glossiness on photo-dedicated paper, and 10 to 80 nm is particularly preferable from the viewpoint of printing density on plain paper.
The volatile content of the carbon black subjected to the treatment for satisfying the PAH amount and oxygen-containing functional group density according to the present invention such as a firing treatment is preferably 8% by weight or less, particularly preferably 4% by weight or less.
From the viewpoint of storage stability of the recording liquid, the pH of the carbon black to be subjected to the treatment for satisfying the PAH amount and oxygen-containing functional group density according to the present invention, such as a firing treatment, is 3 or more, particularly 6 or more. Preferably, the upper limit is 11 or less.

  Here, the DBP oil absorption amount of carbon black is a value measured by the method of JISK6221A, the nitrogen adsorption specific surface area is a value measured by the method of JISK6217, the primary particle size is an arithmetic average diameter (number average) by an electron microscope, and the volatile content is that of JISK6221. The value measured by the method, pH, is a value obtained by measuring, with a glass electrode meter, a mud cooled after boiling a suspension of carbon black and deionized water.

  Specific examples of the carbon black include, but are not limited to, the following products (1) to (4).

(1) # 2700B, # 2650, # 2650B, # 2600, # 2600B, 2450B, 2400B, # 2350, # 2300, # 2300B, # 2200B, # 1000, # 1000B, # 990, # 990B, # 980, # 980B, # 970, # 960, # 960B, # 950, # 950B, # 900, # 900B, # 850, # 850B, MCF88, MCF88B, MA600, MA600B, # 750B, # 650B, # 52, # 52B, # 50, # 47, # 47B, # 45, # 45B, # 45L, # 44, # 44B, # 40, # 40B, # 33, # 33B, # 32, # 32B, # 30, # 30B, # 25, # 25B, # 20, # 20B, # 10, # 10B, # 5, # 5B, CF9, CF9B, # 95, # 260, MA77 MA77B, MA7, MA7B, MA8, MA8B, MA11, MA11B, MA100, MA100B, MA100R, MA100RB, MA100S, MA230, MA220, MA200RB, MA14, # 3030B, # 3040B, # 3050B, # 3230B, # 3350B (and above, Mitsubishi Chemical Co., Ltd. product).

(2) Monarch 1400, Black Pearls 1400, Monarch 1300, Black Pearls 1300, Monarch 1100, Black Pearls 1100, Monarch 1000, Black Pearls 1000, Monarch 900, Black Pearl 900 800, Monarch 700, Black Pearls 700, Black Pearls 2000, Vulcan XC72R, Vulcan XC72, Vulcan PA90, Vulcan 9A32, Mogul L, Black Pearls L, Regal 660R, R gal 660, Black Pearls 570, Black Pearls 520, Regal 400R, Regal 400, Regal 330R, Regal 330, Regal 300R, Black Pearls 490, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480 Black Pearls 420, Black Pearls 410, Regal 350R, Regal 350, Regal 250R, Regal 250, Regal 99R, Regal 99I, Elftex Pellets 115, Elftex 8, Elftex 5, Elftex 12, Montex 12 h 280, Black Pearls 280, Black Pearls 170, Black Pearls 160, Black Pearls 130, Monarch 120, Black Pearls 120 (or, Cabot Company).

(3) Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Special Black 4, Special Black 4A, Special Black 4A, Special Black 4W, Color Black FW2V, Color Black FW2V. V, Printex 150T, Printex 140U, Printex 140V, Printex 95, Printex 90, Printex 85, Printex 80, Printex 75, Printex 55, Printex 45, Printex 40, Printex 40, Printex P ex
XE, Printex L6, Printex L, Printex 300, Printex 30, Printex 3, Printex 35, Printex 25, Printex 200, Printex A, Printex G, Special Black 550S Degussa product).

(4) Raven 7000, Raven 5750, Raven 5250, Raven 5000 ULTRA, Raven 3500, Raven 2000, Raven 1500, Raven 1250, Raven 1250, Raven 10170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170 Raven 1000, Raven 890H, Raven 890, Raven 850, Raven 790 ULTRA, Raven 760 ULTRA, Raven 520, Raven 500, Raven 450, Raven 430, Raven 420, Raven 420, Raven 420, Raven 420, Raven 420 ULTRA, Raven H2O, Raven C ULTRA (or more, Columbia's products).

  In the present invention, the carbon black as described above is preferably carbon black obtained by subjecting carbon black as described above to firing treatment at a temperature of 800 to 1500 ° C. in a nitrogen atmosphere. The range of 1000-1500 degreeC is more preferable from the point that the surface acidic functional group can be removed efficiently.

  However, the carbon black used as a coloring material in the present invention may be any carbon black that satisfies the above-mentioned PAH amount and oxygen-containing functional group density, and is not limited to carbon black that has undergone the above-described firing treatment in a nitrogen atmosphere. It is not something.

  In the present invention, as carbon black, one kind of such carbon black may be used alone, and various physical properties, PAH amounts according to the present invention such as firing processes under different manufacturing processes and different nitrogen atmospheres, and the like. Two or more of those subjected to treatment for satisfying the oxygen-containing functional group density may be used in combination. It can also be used in combination with other color materials.

  The shape of the carbon black may be any form such as powder, granule, or paste.

Further, the average dispersed particle size of carbon black in the pigment dispersion is usually 300 nm or less, preferably 200 nm or less. Moreover, as a minimum, it is 20 nm or more normally.
The average dispersed particle size can be measured using an electron microscope such as SEM or TEM, or can be measured using a commercially available dynamic light scattering measurement device.

  The carbon black is preferably used as it is so as not to inhibit the adsorption of the polymer to be described later to the carbon black. In order to impart self-dispersibility to carbon black that has been treated to satisfy the above requirements, it can also be used as carbon black having self-dispersibility that has been subjected to known chemical modifications. That is, the carbon black used in the pigment dispersion of the present invention is treated as it is to satisfy the PAH amount and oxygen-containing functional group density according to the present invention, such as treatment by firing under the above specific conditions. However, the surface may be chemically modified, or both may be treated, and any carbon black can be used.

[Aqueous pigment dispersion and ink composition]
Next, among the pigment dispersions of the present invention containing carbon black as described above, an aqueous pigment dispersion and an ink composition containing the same will be described.

{About polymer}
The aqueous pigment dispersion of the present invention contains a polymer as a pigment (in the present invention, the above-described carbon black is essential) as necessary. As the polymer, known polymers are used. Among them, from the viewpoint of dispersibility, a polymer having at least one hydrophobic monomer and one or more hydrophilic monomers as constituent units (hereinafter “hydrophobic / hydrophilic”). It may be referred to as “polymer”.).

<Hydrophobic monomer>
The hydrophobic monomer that is a structural unit of the hydrophobic / hydrophilic polymer is not particularly limited, and a conventionally known hydrophobic monomer can be used. In particular, at least one of the hydrophobic monomers is described below. Preferred are aromatic ring-containing monomers and / or monomers containing an aliphatic hydrocarbon group.

  The aromatic ring-containing monomer is an aromatic heterocyclic ring-containing monomer or an aromatic hydrocarbon ring-containing monomer. For example, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethylene glycol (meth) acrylate, 2-naphthyl ( (Meth) acrylate, 9-anthracenyl (meth) acrylate, 1-pyrenylmethyl (meth) acrylate styrene, vinylnaphthalene, styrene, α-methylstyrene, t-butylstyrene, p-methylstyrene, o-methoxystyrene, m-methoxystyrene , P-methoxystyrene, ot-butoxystyrene, mt-butoxystyrene, pt-butoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, vinyltoluene, ethyl Nirubenzen, 4-vinyl biphenyl, 1,1-diphenyl ethylene, vinyl phenol, vinyl benzoate, vinyl naphthalene, benzyl vinyl ether.

  Among these, from the viewpoint of affinity with the pigment, a monomer structure having an unsubstituted phenyl group such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, styrene, and α-methylstyrene is preferable. More preferred is benzyl methacrylate.

  The aliphatic hydrocarbon group contained in the aliphatic hydrocarbon group-containing monomer may be linear, cyclic, or branched.

Examples of the monomer having a linear or branched aliphatic hydrocarbon group include the following.
Olefins such as ethylene, propylene, 1-butene and isobutene;
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, i-propyl (meth) acrylate, butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, amyl ( (Meth) acrylate, i-amyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, i-octyl (meth) acrylate, decyl (meth) acrylate, i-decyl (meth) acrylate, dodecyl ( (Meth) acrylate esters such as (meth) acrylate, i-dodecyl (meth) acrylate, stearyl (meth) acrylate, i-stearyl (meth) acrylate, and behenyl (meth) acrylate;
Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether;
Nitriles such as acrylonitrile and methacrylonitrile;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride;
Allyl compounds such as allyl acetate and allyl chloride;
Dicarboxylic acid ester derivatives such as maleic acid ester and itaconic acid ester;
Vinylsilyl compounds such as vinyltrimethoxysilane;
Vinyl esters such as vinyl acetate and isopropenyl acetate:

  Examples of the monomer having a cyclic aliphatic hydrocarbon group include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) ) Acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate and other (meth) acrylate esters, cyclopentene, cycloheptene, cyclooctene, cyclododecene, 1,5-cyclooctadiene, cyclopentadiene, 1,5,9-cyclododecatriene, 1-chloro-1,5-cyclooctadiene, dicyclo Ntajien, ethylidene norbornene, 5-norbornene-2-carboxylate, and 5-norbornene 2,3-dicarboxylic acid dimethyl, etc. cyclic olefins and the like.

  Among these, (meth) acrylate esters having a linear aliphatic hydrocarbon group and (meth) acrylate esters having a cyclic aliphatic hydrocarbon group are preferable from the viewpoint of affinity with the pigment.

  These hydrophobic monomers may be used alone or in combination of two or more.

<Hydrophilic monomer>
The hydrophilic monomer that is a structural unit of the hydrophobic / hydrophilic polymer is not particularly limited, and conventionally known hydrophilic monomers can be used, and among them, anionic monomers, cationic monomers, and nonionic monomers are preferable. .

(Anionic monomer)
As the anionic monomer, those exemplified below can be used, but the anionic monomer is not limited thereto, and conventionally known monomers can be used.
Carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, or salts thereof;
Vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, styrene sulfonic acid, 2-acrylamide ethane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamide ethane sulfonic acid, 2-methacrylamide-2-methyl Propanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfone Sulfonic acid monomers such as acids or salts thereof;
Vinylphosphonic acid, methacryloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, Phosphoric monomers such as dioctyl-2- (meth) acryloyloxyethyl phosphate or salts thereof:

  As the anionic monomer, a monomer having a carboxyl group or a salt thereof is preferable from the viewpoint of printing quality such as low print density or bleeding, and methacrylic acid, acrylic acid or a salt thereof, more preferably acrylic acid or a salt thereof.

  The anionic monomer is preferably a salt, more preferably an alkali metal salt or an alkaline earth metal salt, and particularly preferably a sodium salt.

(Cationic monomer)
Although what is illustrated below can be used as a cationic monomer, It is not limited to these, A conventionally well-known thing can be used.
N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-di-t-butylaminoethyl (meth) acrylate N, N-dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminobutyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N Tertiary amino group-containing polymerizable unsaturated monomers such as N, N-dialkylaminoalkyl (meth) acrylamides such as N, N-dimethylaminopropyl (meth) acrylamide;
(Meth) acryloyloxyethyldimethyloctylammonium chloride, (meth) acryloyloxyethyldimethyloctylammonium bromide, (meth) acryloyloxyethyldimethyldodecylammonium chloride, (meth) acryloyloxyethyldimethyldodecylammonium bromide, (meth) acryloyloxyethyl Dimethyl hexadecyl ammonium chloride, (meth) acryloyloxyethyl dimethyl hexadecyl ammonium bromide, (meth) acryloyloxyethyl diethyl octyl ammonium chloride, (meth) acryloyloxyethyl diethyl octyl ammonium bromide, (meth) acryloyloxyethyl diethyl dodecyl ammonium chloride , (Meta) a Liloyloxyethyl diethyl dodecyl ammonium bromide, (meth) acryloyloxyethyl diethyl hexadecyl ammonium chloride, (meth) acryloyloxyethyl diethyl hexadecyl ammonium bromide, (meth) acryloylaminopropyldimethyloctylammonium chloride, (meth) acryloylamino Propyldimethyloctylammonium bromide, (meth) acryloylaminopropyldimethyldodecylammonium chloride, (meth) acryloylaminopropyldimethyldodecylammonium bromide, (meth) acryloylaminopropyldimethylhexadecylammonium chloride, (meth) acryloylaminopropyl Dimethyl hexadecyl ammonium bromide, (meth) ac Royloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxyethyltrimethylammonium methylsulfate, (meth) acryloyloxyethyldimethylethylammonium ethyl sulfate, (meth) acryloyloxyethyl Trimethylammonium p-toluenesulfonate, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyltrimethylammonium methyl sulfate, (meth) acryloylaminopropyldimethylethylammonium ethyl Sulfae Pass, (meta) aqua A quaternary ammonium base-containing polymerizable unsaturated monomer such as liloylaminopropyltrimethylammonium p-toluenesulfonate;
Other styrenes having a dialkylamino group such as dimethylaminostyrene and dimethylaminomethylstyrene; vinylpyridines such as 4-vinylpyridine and 2-vinylpyridine; or these alkyl halides, benzyl halides, alkyls or arylsulfones Quaternized with a known quaternizing agent such as acid or dialkyl sulfate, N-vinylformamide and N-vinylacetamide that form an amino group by hydrolysis after polymerization, allylamine hydrochloride, etc .:

  Among them, tertiary amino group-containing polymerizable unsaturated monomers such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) Preferred are quaternary ammonium base-containing polymerizable unsaturated monomers such as acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxyethyltrimethylammonium methylsulfate, (meth) acryloyloxyethyldimethylethylammonium ethylsulfate, among which More preferred are quaternary ammonium base-containing polymerizable unsaturated monomers. Of these, (meth) acryloyloxyethyltrimethylammonium chloride is most preferred.

  A polymer having a quaternary ammonium group-containing polymerizable unsaturated monomer as a constituent unit is obtained by polymerizing a tertiary amino group-containing polymerizable unsaturated monomer, followed by alkyl halide such as methyl chloride, benzyl halide such as benzyl chloride, epichloro It may be synthesized by a quaternization reaction using an alkylating agent such as hydrin, dimethyl sulfate, or diethyl sulfate, or may be synthesized by polymerizing a quaternized product in a monomer state. Among these, a polymer obtained by polymerizing a quaternized monomer is preferable.

(Nonionic monomer)
Nonionic monomers include the following, but are not limited to the following examples, and conventionally known monomers can be used.
Monomers having primary amino groups such as aminoethyl (meth) acrylate and aminopropyl (meth) acrylate;
Secondary such as methylaminoethyl (meth) acrylate, methylaminopropyl (meth) acrylate, ethylaminoethyl (meth) acrylate, ethylaminopropyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine A monomer having an amino group;
(Meth) acrylamide, N-alkyl (meth) acrylamide having 1 to 6 carbon atoms in the alkyl group, N, N-dialkyl (meth) acrylamide, C 1-3 in carbon number in the alkyl group, diacetone (meth) acrylamide, N -Methylol (meth) acrylamide, N-2-hydroxyethyl (meth) acrylamide, N, N-diethanol (meth) acrylamide, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl Amide group-containing monomers such as -N-vinylformamide, N- (2- (polyethylene glycol) ethyl) (meth) acrylamide, N, N- (2,2 '-(polyethylene glycol) diethyl) (meth) acrylamide;
2-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, N-vinylpyrrolidone, 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, N-vinyloxazolidone, 2-N-pyrrolidoneethyl A monomer having a heterocycle such as (meth) acrylate, N-vinylcaprolactam, 9-vinylcarbazole, N-vinylphthalimide, glycidyl (meth) acrylate, aziridine ring-containing monomer;
Monomers containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylic acid ester, 2-hydroxypropyl (meth) acrylic acid ester, 2,3-dihydroxypropyl (meth) acrylate, 2-hydroxyethyl vinyl ether;
Polyethylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, lauroxy polyethylene glycol (meth) acrylate, stearoxy polyethylene glycol (meth) acrylate, nonylphenoxy Polyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, poly (ethylene glycol-propylene glycol) (meth) acrylate, polyethylene glycol-polypropylene glycol (meth) acrylate, poly (ethylene glycol-) Tetramethylene glycol) (meta Acrylate, poly (propylene glycol-tetramethylene glycol) (meth) acrylate, propylene glycol polybutylene glycol (meth) acrylate, octoxy polyethylene glycol polypropylene glycol (meth) acrylate, stearoxy polyethylene glycol-polypropylene glycol (meth) acrylate, ant Oxyalkylene chain monomers such as loxypolyethylene glycol-polypropylene glycol (meth) acrylate and nonylphenoxypoly (ethylene glycol-propylene glycol) (meth) acrylate;
Glucose, mannose, galactose, glucosamine, mannosamine, galactosamine, etc., hexoses, arabinose, xylose, ribose, etc. Disaccharides such as mannobiose and sophorose, other oligosaccharides such as maltotriose, isomaltotriose, maltotetraose, maltopentaose, mannotriose and manninotriose, polysaccharides such as cellulose and modified cellulose A monomer having a structure as derived and having a glycosyl group, such as a monomer such as glucosylethyl methacrylate;
Macromonomer having a polyvinyl alcohol structure in the side chain:

  Among these nonionic monomers, from the viewpoint of dispersibility and storage stability, an amide group-containing monomer, a monomer having a heterocyclic ring, a monomer containing a hydroxyl group, an oxyalkylene chain monomer, and a polyvinyl alcohol structure as a side chain. In the case of using as a recording liquid for photographic paper, an amide group-containing monomer, a hydroxyl group-containing monomer, and an oxyalkylene chain monomer are preferred from the viewpoint of gloss of printed matter. Oxyalkylene chain monomers are particularly preferred. Of the oxyalkylene chain monomers, methoxypolyethylene glycol (meth) acrylate represented by the following general formula (5) is more preferable.

^{_{CH 2 = C (R 4)}} COO (CH 2 CH 2 O) p R 5 ... (5)
(Wherein R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a methyl group, and p represents an integer of 2 to 30, preferably 4 to 30)

  These hydrophilic monomers may be used alone or in combination of two or more.

<Monomer composition>
The hydrophobic / hydrophilic polymer is a polymer having at least one or more types of hydrophobic monomers and one or more types of hydrophilic monomers as constituent units, and the monomer composition is particularly preferably as follows.

  The content of the hydrophobic monomer constituent unit is preferably 10 mol% or more, more preferably 20 mol% or more, preferably 90 mol% or less, more preferably 80 mol% or less of the entire polymer. If the content of the hydrophobic monomer constituent unit is less than this lower limit, the polymer is difficult to adsorb on the pigment and the free polymer increases, so the viscosity of the dispersion increases, and the aqueous pigment dispersion containing this polymer is used as the recording liquid. When it is used, the dischargeability is lowered and the storage stability of the recording liquid is lowered. When the content of the hydrophobic monomer constituent unit is larger than this upper limit, the water dispersibility of the aqueous pigment dispersion is extremely lowered.

  The content of the hydrophilic monomer structural unit is preferably 10 mol% or more of the whole polymer, more preferably 20 mol% or more, preferably 90 mol% or less, more preferably 80 mol% or less. If the content of the hydrophilic monomer constituent unit is less than this lower limit, the water dispersibility of the aqueous pigment dispersion containing this polymer will be extremely lowered, and if it exceeds this upper limit, the polymer will be difficult to adsorb to the pigment and become free. Therefore, the viscosity of the aqueous pigment dispersion becomes high, and when this dispersion is used as a recording liquid, the dischargeability is lowered and the storage stability of the recording liquid is lowered.

<Polymer structure>
The polymer structure of the hydrophobic / hydrophilic polymer may be any of random copolymer, diblock copolymer, triblock or more multiblock copolymer, gradient copolymer, graft copolymer, star copolymer, etc. Random copolymers are preferred and most preferred.

<Molecular weight>
The number average molecular weight (Mn) of the hydrophobic / hydrophilic polymer is preferably 150,000 or less, more preferably 100,000 or less, and particularly preferably 1000 or more and 50,000 or less. If the molecular weight is larger than this range, the viscosity of the aqueous pigment dispersion and the recording liquid prepared using the same will increase, and the ejection performance will decrease. Dispersibility may decrease.

  The weight average molecular weight (Mw) of the hydrophobic / hydrophilic polymer is preferably 300,000 or less, more preferably 200,000 or less, particularly preferably 2000 or more and 100,000 or less. If the molecular weight is larger than this range, the viscosity of the aqueous pigment dispersion and the recording liquid prepared using the aqueous pigment dispersion will increase and the ejection performance will decrease. If the molecular weight is smaller, the polymer will peel off from the pigment when the recording liquid is prepared. Dispersibility may decrease.

  In addition, the value of a number average molecular weight (Mn) here and a weight average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography).

Among the hydrophobic / hydrophilic polymers according to the present invention, the measurement of the number average molecular weight (Mn) and the weight average molecular weight (Mw) of a polymer containing a cationic monomer in at least one of the hydrophilic monomer constituent units is specifically Is performed under the following conditions using GPC, and is determined as a value in terms of polyethylene glycol.
Column filler: Styrene-divinylbenzene copolymer Solvent: Dimethyl sulfoxide (including 50 mM LiBr (lithium bromide))
Flow rate: 0.27 mL / min
Temperature: 50 ° C

In addition, among the hydrophobic / hydrophilic polymers according to the present invention, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer whose polymer structure is a block polymer are specifically measured using GPC as follows. It is carried out under conditions and is determined as a value in terms of polyethylene glycol.
Column packing: Polyhydroxymethacrylate Solvent: Water / acetonitrile
(70/30 (v / v), 0.2 M Tris-HCl buffer, 0.1 M
(Including KCl)
Flow rate: 0.7 mL / min
Temperature: 40 ° C

Further, among the hydrophobic / hydrophilic polymers according to the present invention, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of polymers other than the above are specifically measured under the following conditions using GPC. It is calculated | required as a value of polystyrene conversion.
Column filler: Styrene-divinylbenzene copolymer Solvent: Tetrahydrofuran Flow rate: 0.7 ml / min
Temperature: 40 ° C
When insoluble in tetrahydrofuran, measurement is performed after, for example, the neutralized salt portion is dissolved by, for example, esterification with an esterifying agent such as diazomethane.

<Water solubility of hydrophobic / hydrophilic polymer>
As the aqueous pigment dispersion, as long as it is a polymer having at least one or more types of hydrophobic monomers and one or more types of hydrophilic monomers as described above, the solubility in water is not particularly limited. When used in the preparation of a recording liquid for paper, the polymer used in the aqueous pigment dispersion is 2% of the polymer in a state where 90 mol% of ionic groups present in the polymer are neutralized. “Water-dispersible” ones that do not cause precipitation in an aqueous dispersion having a concentration of weight% are preferred, and among them, “water-soluble” ones having a solubility in water at 25 ° C. of 2% by weight or more are particularly preferred. Usually, an aqueous dispersion having a concentration of 10% by weight or less at 25 ° C. that does not cause precipitation is used. Whether or not precipitation occurs is visually confirmed immediately after the polymer aqueous dispersion is prepared.

The above-mentioned “ionic group” refers to a group that can dissociate into ions in water, and examples thereof include an amino group, a carboxyl group, a sulfonic acid group, and salts thereof. The above-mentioned "in a state where 90 mol% of ionic groups present in the polymer are neutralized" means a state where 90 mol% of the ionic groups contained in the polymer is converted into a salt by the neutralizing agent. Point to. As a procedure for confirming that the polymer is contained within the above-mentioned definition range, for example, the ratio of the ionic groups in the polymer that are neutralized to form a salt (degree of neutralization of the ionic groups) is measured. The degree of neutralization of the ionic group is adjusted to 90 mol%, and this is dissolved or dispersed in water at 25 ° C. and 2 wt% concentration, and the appearance is visually observed. The degree of neutralization of the ionic group is determined by measuring the composition ratio of the ionic group with respect to the whole polymer by, for example, ¹ H-NMR, and the counter ion of the polymer forming the salt, for example, the carboxyl group forms a salt with Na. , Measure Na ⁺ charge, and divide the amount that is actually Na ⁺ salt by the amount of charge that is calculated from the composition ratio assuming that it is all Na ⁺ salt. Can be sought. As a result of the measurement, when the neutralization degree is less than 90%, the neutralization degree is adjusted by adding an alkali. As another method, it is assumed that the addition of alkali neutralizes the ionic groups of the remaining monomer without polymerizing with the ionic groups in the polymer at the same rate, and from the synthesis of the polymer to the preparation of the recording liquid By dividing the number of moles of alkali added in the series of steps up to the number of moles of all ionic groups of the charged monomer at the time of polymer synthesis, the degree of neutralization of the ionic groups in the polymer can also be estimated and confirmed. .

<Synthesis Method of Hydrophobic / Hydrophilic Polymer>
The method for synthesizing the hydrophobic / hydrophilic polymer is not particularly limited. For example, a known polymerization method such as radical polymerization, ionic polymerization, polyaddition or polycondensation can be selected, and the polymer was synthesized by these known methods. It may be a derivative or modified polymer. In addition, a pigment, a monomer, a polymerization initiator, and, if necessary, a surfactant, a reactive surfactant, and a polymer may be mixed in water or an organic solvent as a pigment dispersion aid, and polymerization may be performed. Further, the monomer may be directly reacted with the pigment surface for polymerization. Among these, since the synthesis method is simple, the random polymer is preferably a radical polymerization, and the block polymer is preferably a polymer synthesized by a living radical polymerization method, particularly an atom transfer type radical polymerization.

  A method for synthesizing a hydrophobic / hydrophilic polymer by radical polymerization, which is a preferred method for synthesizing a random copolymer suitable as a hydrophobic / hydrophilic polymer as a pigment dispersant, will be described below.

(Polymerization reaction solvent)
The radical polymerization reaction can be performed without a solvent or in the presence of a solvent, but the polymerization reaction is preferably performed in the presence of a solvent.

  As a polymerization reaction solvent, ethers such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; acetonitrile, propionitrile, benzonitrile and the like Nitriles; Carbonyl compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene carbonate, and propylene carbonate; alcohols such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol, t-butyl alcohol, and isoamyl alcohol Aromatic hydrocarbons such as benzene, toluene, xylene; chlorobenzene, methylene chloride, chloroform, chlorobenzene, carbon tetrachloride And halogenated hydrocarbons. Among these, preferred aqueous solvents as a polymerization reaction solvent.

  The aqueous solvent refers to a solvent obtained by mixing 100% water or water and a polar organic solvent at an arbitrary ratio. The polar organic solvent used here is not particularly limited as long as it can be mixed with water at an arbitrary ratio, and specific examples thereof include methanol, ethanol, isopropanol, acetonitrile, acetone, dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran. Of these, tetrahydrofuran, methanol, ethanol, and isopropanol are particularly preferable.

  The polymerization reaction solvent may be a single solvent composed of only one kind or a mixed solvent composed of two or more kinds.

(Polymerization initiator)
A known radical polymerization initiator can be used for the radical polymerization reaction when the hydrophobic / hydrophilic polymer is synthesized.
As the polymerization initiator, either a water-soluble polymerization initiator or an oil-soluble polymerization initiator can be used.

  Examples of the water-soluble polymerization initiator include 2,2′-azobis (2-amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis [2- (2-Imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [ N- (2-carboxyethyl) -2-methylpropionamide], 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl) propane} dihydrochloride, 2, 2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2 , 2'-azobis [2 (5-methyl-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (3,4,5,6, -tetrahydropyrimidin-2-yl) propane] dihydrochloride, etc. Azo compound-based initiators; oxidizing agents such as potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide alone; or these oxidizing agents and sodium sulfite, sodium hyposulfite, ferrous sulfate, ferrous nitrate, Redox initiators combined with water-soluble reducing agents such as sodium formaldehyde sulfoxylate and thiourea can be mentioned.

  These may be used alone or in combination of two or more.

  Examples of oil-soluble polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobiscyclohexane 1-carbonitrile, , 2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, dimethyl-2,2′-azobis (2-methylpropionate), Azo compound-based initiators such as 1,1′-azobis (1-acetoxy-1-phenylethane), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile); acetylcyclohexylsulfonyl peroxide; Isobutyryl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, 2,4-dicarbonate Lobenzoyl peroxide, t-butyl peroxypivalate, 3,5,5-trimethylhexanonyl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, stearoyl peroxide, propionitrile peroxide, saxi Nick acid peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, parachlorobenzoyl peroxide, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, t-butyl peroxylaurate, cyclohexanone peroxide, t-butyl peroxyisopropyl carbonate, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, -Butyl peroxyacetate, t-butyl peroxybenzoate, diisobutyl diperoxyphthalate, methyl ethyl ketone peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butyl cumi Ruperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, paramentane hydroperoxide, pinane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and cumene Peroxide polymerization initiators such as peroxides; hydroperoxides (tret-butylhydroxyperoxide, cumenehydroxyperoxides, etc.), dialkyl peroxides (lauroyl peroxide, etc.) ) And oil-soluble peroxides such as diacyl peroxide (benzoyl peroxide, etc.), tertiary amines (triethylamine, tributylamine, etc.), naphthenates, mercaptans (mercaptoethanol, lauryl mercaptan, etc.), organometallic compounds (triethyl) And oil-soluble redox polymerization initiators used in combination with oil-soluble reducing agents such as aluminum, triethylboron, and diethylzinc.

  These may be used alone or in combination of two or more.

(Other additives)
In the radical polymerization reaction, in addition to the above polymerization initiator, known materials such as a chain transfer agent, a chain terminator, and a polymerization accelerator can be added and used in order to adjust the resulting polymer to a preferred molecular weight.

(Polymerization conditions)
When performing the polymerization reaction, the order of addition of the raw material monomer, the polymerization reaction solvent, the radical initiator, etc. is arbitrary. For example, the temperature after the raw material monomer, the polymerization reaction solvent, the radical polymerization initiator are charged all at once in the reaction vessel. And a method of conducting a polymerization reaction by raising the ratio. In this case, the monomer or radical polymerization initiator may be added as it is or in a solution. As another method, after the raw material monomer and the polymerization reaction solvent are charged into the reaction vessel and the temperature is raised, the monomer solution containing the radical polymerization initiator, the polymerization reaction solvent, or a mixture thereof is continuously added. Or the method etc. which add by dividing | segmenting and performing a polymerization reaction are mentioned.
Among these, from the viewpoint of simplicity of operation, a method in which the polymerization reaction is performed by raising the temperature after charging the raw materials all at once is preferable.

  Although the usage-amount of a polymerization reaction solvent is not specifically limited, It is 1 weight part or more normally with respect to 100 weight part of monomers, Usually 2000 weight part or less, Preferably it is 1000 weight part or less.

  The amount of the polymerization initiator used varies depending on the type of the polymerization initiator used and is not particularly limited, but is usually 0.5 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the raw material monomer.

  The polymerization temperature is not particularly limited, but is usually 0 ° C or higher, preferably 20 ° C or higher, and the upper limit is usually 200 ° C or lower, preferably 150 ° C or lower.

  Although there is no particular problem even if the polymer obtained by polymerization is used as it is unpurified, it is preferable to purify it according to a conventional method and use it for the next pigment dispersion step. Purification methods include dropping the polymer solution into a solvent in which the polymer is insoluble and the monomer and polymerization initiator are soluble, reprecipitation purification by repeating the precipitation and filtration of the polymer, and the polymer and the polymer insoluble in the polymer solution and the polymerization initiator. Add a solvent that is soluble in water, remove the unreacted monomer and reaction solvent by fractional precipitation purification, heating distillation, vacuum distillation, etc. that repeat polymer precipitation and filtration, and then replace the solvent with water and / or aqueous solvent And a method of removing low molecular impurities and low molecular weight oligomer components using an ultrafiltration membrane or a dialysis membrane.

  The hydrophobic / hydrophilic polymer contained in the aqueous pigment dispersion of the present invention may be one type or two or more types. As described above, the hydrophobic / hydrophilic polymer is preferably a polymer having at least one or more types of hydrophobic monomers and one or more types of hydrophilic monomers as constituent units, but an anionic monomer is used as the hydrophilic monomer. An anionic polymer used, a cationic polymer using a cationic monomer, and a nonionic polymer using a nonionic monomer may be used alone to prepare an aqueous pigment dispersion in which a pigment is dispersed with a polymer. You may use together. Examples of the combined use include composite polymer capsules in which a pigment is coated with a polymer using electrostatic interaction between an anionic polymer and a cationic polymer.

{About other polymers}
The aqueous pigment dispersion of the present invention preferably contains the following polymer (I) together with the above-mentioned hydrophobic / hydrophilic polymer.

  This polymer (I) is a polyvinyl alcohol containing a structural unit derived from vinyl alcohol represented by the following general formula (1) (hereinafter sometimes referred to as “vinyl alcohol structural unit”) and a hydrophobic group in the polymer. Resin. In polymer (I), only 1 type of the vinyl alcohol structural unit represented by following General formula (1) may be contained, and 2 or more types may be contained. Moreover, only 1 type of hydrophobic groups may be contained and 2 or more types may be contained.

(In formula (1), R ¹ represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms)

Specific examples of R ¹ in the general formula (1) include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, sec-butyl, pentyl, isopentyl, and neopentyl. And alkyl groups such as a group, t-pentyl group, and hexyl group. Among these, a hydrogen atom or an alkyl group having a small number of carbon atoms is preferable, specifically, an alkyl group having 1 to 3 carbon atoms is preferable, and a hydrogen atom or a methyl group is particularly preferable.

  Examples of the vinyl alcohol structural unit represented by the general formula (1) include vinyl alcohol, α-methyl vinyl alcohol, α-ethyl vinyl alcohol, α-propyl vinyl alcohol, α-butyl vinyl alcohol, and α-hexyl vinyl alcohol. The structural unit derived from etc. is mentioned.

  On the other hand, examples of the hydrophobic group include aliphatic hydrophobic groups such as alkyl groups, alkenyl groups, and alkynyl groups, alicyclic hydrophobic groups such as cyclohexyl groups and isobornyl groups, and aromatic groups such as phenyl groups and naphthyl groups. System hydrophobic groups. These groups may be unsubstituted or may further have a substituent.

  In order to introduce the vinyl alcohol constituent unit represented by the general formula (1) and the hydrophobic group into the polymer structure, a polymerizable monomer that induces a vinyl alcohol constituent unit such as a vinyl ether monomer or a vinyl ester monomer and a hydrophobic group are introduced. After polymerizing with a polymerizable monomer having a functional group and introducing them into the polymer structure, the side chain portion of the vinyl ether monomer or vinyl ester monomer is modified by the above general formula (1) by a modification reaction using acid or alkali. It may be converted into a vinyl alcohol structural unit represented by

  Examples of vinyl ether monomers that derive the vinyl alcohol structural unit represented by the general formula (1) include methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, Examples thereof include n-hexadecyl vinyl ether, 2-chloroethyl vinyl ether, phenyl vinyl ether, benzyl vinyl ether, and trimethylsilyl vinyl ether.

  Examples of the vinyl ester monomer for deriving the vinyl alcohol structural unit include, for example, vinyl acetate, vinyl propionate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl formate, vinyl caproate, vinyl caprate, myristine. Vinyl acetate, vinyl palmitate, vinyl 2-ethylhexanoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate, these α -Substituent etc. are mentioned.

  Further, the vinyl alcohol structural unit and the hydrophobic group represented by the general formula (1) contained in the polymer (I) are a main chain and / or a side chain portion in the polymer structure by a modification reaction or a modification reaction. May be introduced.

  The polymer (I) only needs to contain a vinyl alcohol structural unit represented by the general formula (1) and a hydrophobic group, and is represented by an oxyalkylene group, a hydroxyl group, an amide group, a pyrrolidone group, an oxazoline group, and the like. Hydrophilic groups, carboxylic acid groups, sulfonic acid groups, acidic groups typified by phosphoric acid groups, basic groups typified by amino groups, pyridinium groups, imidazolium groups, and acidic groups and basic groups and their It may contain an ionic dissociation group which is a salt. Especially, it is preferable that polymer (I) contains the ionic dissociation group which is an acidic group, a basic group, and its salt.

  Moreover, it is preferable that the hydrophobic group and ionic dissociation group contained in polymer (I) are contained in the polymer structure as a monomer-derived structural unit. That is, the polymer (I) is a polymer containing the vinyl alcohol structural unit represented by the general formula (1), a structural unit derived from a monomer having a hydrophobic group, and a structural unit derived from a monomer having an ionic dissociation group. It is particularly preferred.

  The structure of the polymer (I) may be any of a random copolymer, a diblock copolymer, a triblock or more multiblock copolymer, a gradient copolymer, a graft copolymer, a star copolymer and the like, and among them, a block copolymer is preferable.

The number average molecular weight (Mn) of the polymer (I) is preferably 150,000 or less, more preferably 100,000 or less, particularly preferably 1000 or more and 50,000 or less, and most preferably 3000 or more and 30,000 or less. If the number average molecular weight (Mn) is larger than this range, the viscosity of the pigment ink is high and the discharge performance is lowered. is there.
Further, from the viewpoint of obtaining a uniform and stable pigment ink, the molecular weight distribution (Mw / Mn) of the polymer (I) is preferably 4 or less, and more preferably 2 or less.

  The values of the number average molecular weight (Mn) and the weight average molecular weight (Mw) of this polymer (I) are values in terms of polyethylene glycol measured by GPC (gel permeation chromatography).

The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer (I) according to the present invention are specifically measured under the following conditions using GPC.
Column packing material: Polyhydroxymethacrylate Solvent: Water / acetonitrile
(70/30 (v / v), 0.2 M Tris-HCl buffer, 0.1 M KCl included)
Flow rate: 0.7 mL / min
Temperature: 40 ° C

  The same applies to the number average molecular weights (Mn) of blocks A and B described later constituting the polymer (I).

  Among the block copolymers, the polymer (I) is a polyvinyl alcohol block A and another block B such as a polyvinyl alcohol block copolymer represented by the following general formula (2). A block copolymer connected by (an alkylene chain which may have a substituent) is preferred.

（式（２）中、Ａは一般式（１）で表されるビニルアルコール構成単位を含むポリビニルアルコール系ブロックを示し、Ｂは疎水性基を有するモノマー構成単位及びイオン性解離基を有するモノマー構成単位を含むブロックであって、Ｂは疎水性セグメントＢ’と、ブロックＡ及びセグメントＢ’以外の親水性又は疎水性セグメントＢ”とを含むブロックを示し、Ｘ^１、Ｘ^２、Ｘ^３及びＸ^４は各々独立して水素原子、ハロゲン原子、アルキル基、アルケニル基、アラルキル基、又はアリール基を示し、ｍ１は１〜５の整数であり、ｍ２は０〜４の整数であり、ｍ１＋ｍ２は１〜５の整数である。）

(In the formula (2), A represents a polyvinyl alcohol block containing the vinyl alcohol structural unit represented by the general formula (1), and B represents a monomer structural unit having a hydrophobic group and a monomer structure having an ionic dissociation group. A block containing units, wherein B represents a block containing a hydrophobic segment B ′ and a hydrophilic or hydrophobic segment B ″ other than the block A and the segment B ′, and X ¹ , X ² , X ³ and X ⁴ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group or an aryl group, m1 is an integer of 1 to 5, m2 is an integer of 0 to 4, and m1 + m2 is 1. It is an integer of ~ 5.)

<About Block A of Polymer (I)>
The polyvinyl alcohol block A in the general formula (2) is a polyvinyl alcohol block having a vinyl alcohol structural unit represented by the general formula (1). The polyvinyl alcohol block A only needs to have a vinyl alcohol structural unit represented by the general formula (1). For example, a part of the hydroxyl group of the general formula (1) may be protected with an acyl group. .

  The acyl group is not particularly limited as long as it is a general protecting group for a hydroxyl group, but is preferably an acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, pivaloyl group, pentylcarbonyl group, neopentyl group. Carbonyl group, hexylcarbonyl group, heptylcarbonyl group, decyl group, laurolyl group, myristolyl group, palmitoyl group, stearoyl group, chloroacetyl group, dichloroacetyl group, trichloroacetyl group, trifluoroacetyl group, benzylcarbonyl group, phenethylcarbonyl group A group selected from the group consisting of halogen atoms and aryl groups such as phenylbutylcarbonyl group, diphenylmethylcarbonyl group, triphenylmethylcarbonyl group, naphthylmethylcarbonyl group, naphthylethylcarbonyl group, etc. An alkylcarbonyl group having 2 to 20 carbon atoms which may be substituted with a group; an acryloyl group, an isopropenylcarbonyl group, a 3-butenylcarbonyl group, a methacryloyl group, an allylcarbonyl group, a 1,1-dimethylallylcarbonyl group, An alkenylcarbonyl group having 2 to 20 carbon atoms such as a crotonoyl group, a 3-methylallylcarbonyl group, a 2,3-dimethylallylcarbonyl group, a 3,3-dimethylallylcarbonyl group, a cinnamoyl group, and a 3-cyclohexylallylcarbonyl group; 1 such as an arylcarbonyl group such as a benzoyl group or a naphthylcarbonyl group which may have 1 to 3 substituents selected from the group consisting of an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms Species or 2 or more types are preferable, among which acetyl group, chloroacetate are preferable. Group, an allyl group, a benzoyl group or a benzyl group. Among these, an acetyl group is preferable.

  In the polyvinyl alcohol block A, the acylation rate of the hydroxyl group of the vinyl alcohol structural unit may be appropriately selected and determined. Although the acylation has an effect of improving the water solubility of the polymer, if the acylation rate is excessively high, the polymer becomes insoluble in water. Therefore, generally, the total number of units in the polyvinyl alcohol block A is 20 % Or less, preferably 10% or less, more preferably 5% or less.

  Moreover, this polyvinyl alcohol-type block A may have 1 type, or 2 or more types of structural units other than the vinyl alcohol structural unit represented by General formula (1). For example, by introducing a monomer structural unit having an alkali metal salt of an acidic group, there is an effect of improving the dispersion stability of the pigment. However, if the amount introduced is excessively large, the effect is lost. In some cases, the content is usually 15 mol% or less, and particularly preferably 10 mol% or less, with respect to the entire polyvinyl alcohol block A.

  Examples of structural units other than the vinyl alcohol structural unit include olefins such as ethylene, propylene, 1-butene, and isobutene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, and i-acrylate. Acrylic acid esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, Methacrylic acid such as ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate Esters: acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and its salt, acrylamidopropyldimethylamine and its salt and quaternary salt, N-methylol Acrylamide derivatives such as acrylamide and derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N, N-dimethylmethacrylamide, diacetonemethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyl Methacrylamide derivatives such as dimethylamine and its salts and quaternary salts, N-methylol methacrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n Vinyl ethers such as propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, benzyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, vinylidene chloride, vinyl fluoride , Vinyl halides such as vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts and esters, itaconic acid and its salts and esters such as dicarboxylic acids and ester derivatives thereof; vinyltrimethoxysilane and the like Examples of vinyl silyl compounds: vinyl monomer structural unit units such as isopropenyl acetate, but are not limited thereto, and other known vinyl monomer structural unit units. It may be.

  The number average molecular weight (Mn) of the polyvinyl alcohol block A is generally 500 or more, particularly 800 or more, particularly 1000 or more, and the upper limit is 100,000 or less, especially 50,000 or less, more preferably 30000 or less, especially 10,000 or less. It is preferable that If the molecular weight is too small, the water dispersibility of the polymer (I) may be reduced, whereby the pigment dispersibility may be reduced and the scratch resistance of the printed matter may be reduced. On the other hand, if it is too large, the viscosity of the pigment ink becomes too high, and thus the pigment dispersibility is lowered, and the discharge property of the pigment ink may be lowered.

<Linking Group of Polyvinyl Alcohol Block A and Block B of Polymer (I)>
The linking group between the polyvinyl alcohol block A and the other block B in the general formula (2) is an alkylene group which may have a substituent.

In the general formula (2), X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aralkyl group or an aryl group. Of these, the alkyl group, alkenyl group, aralkyl group or aryl group preferably has 1 to 20 carbon atoms, and these may be linear, branched or cyclic, and the carbon atom further has a substituent. You may do it.

Specific examples of X ¹ , X ² , X ³ and X ⁴ include the following independently.
Hydrogen atom;
Halogen atoms such as F, Cl, Br and I;
Methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, sec-butyl group, pentyl group, isopentyl group, neopentyl group, t-pentyl group, hexyl group, heptyl group, decyl group Alkyl groups and substituted alkyl groups such as dodecyl group, hexadecyl group, octadecyl group, chloromethyl group, dichloromethyl group, trichloromethyl group, trifluoromethyl group;
Vinyl group, allyl group, isopropenyl group, 3-butenyl group, 1-methylallyl group, 1,1-dimethylallyl group, 2-methylallyl group, 3-methylallyl group, 2,3-dimethylallyl group, 3,3- Alkenyl groups and substituted alkenyl groups such as a dimethylallyl group, cinnamyl group, and 3-cyclohexylallyl group;
Aryl groups such as phenyl and naphthyl groups;
A substituted aryl group in which 1 to 3 hydrogen atoms in an aryl group such as a phenyl group and a naphthyl group are substituted with a functional group such as a methyl group, an ethyl group, a butyl group, a methoxy group, and an ethoxy group;
Aralkyl groups and substituted aralkyl groups such as benzyl group, phenethyl group, phenylbutyl group, diphenylmethyl group, triphenylmethyl group, naphthylmethyl group, naphthylethyl group:

  As the substituent introduced in the substituted aryl group, any substituent can be used as long as it does not impair the stability of the polymer (I). Specifically, it has 1 to 4 carbon atoms such as a methyl group, an ethyl group, and a butyl group. A linear or branched alkyl group, and a linear or branched alkoxy group having 1 to 4 carbon atoms such as a methoxy group or an ethoxy group is preferable.

X ¹ , X ² , X ³ and X ⁴ are each independently preferably a hydrogen atom, a halogen atom, an alkyl group having 4 or less carbon atoms, an alkenyl group, a benzyl group or a phenyl group, among which a hydrogen atom or a halogen atom , A methyl group, an allyl group, a benzyl group or a phenyl group, particularly preferably a hydrogen atom or a halogen atom.

  m1 is an integer of 1 to 5, m2 is an integer of 0 to 4, and m1 + m2 is an integer of 1 to 5. Among these, m1 + m2 is preferably an integer of 1 to 3, and m1 + m2 is particularly preferably 1 or 2.

  In the present invention, specific examples of the linking group between the polyvinyl alcohol block A and the block B are preferably an alkylene group or a haloalkylene group having a relatively small number of carbon atoms, and particularly preferably a haloalkylene group. Specific examples include methylene groups, ethylene groups, propylene groups, chloromethylene groups, dichloromethylene groups, dibromomethylene groups, and tetrachloroethylene groups as alkylene groups having 1 to 3 carbon atoms and haloalkylene groups. , A dichloromethylene group, a dibromomethylene group, a tetrachloroethylene group, and the like are preferable.

<About Block B of Polymer (I)>
Block B in the general formula (2) is a block having one or more types of monomer structural units having a hydrophobic group, and among them, one or more types of monomer structural units having a hydrophobic group and ions It is preferable that it is a block containing 1 type or 2 types or more of the monomer structural unit which has a sex dissociation group, and also the block B is 1 type or 2 types or more of hydrophobic segment B ', and the above-mentioned polyvinyl alcohol-type block A And a block composed of one or more of hydrophilic or hydrophobic segments B ″ other than the segment B ′. The segment here refers to a chain composed of at least two monomer constituent units. .

(Monomer constituent unit contained in block B)
Examples of the monomer structural unit having a hydrophobic group contained in the block B include structural units derived from the following monomers, but are not limited to these and include conventionally known ones.

Olefins such as ethylene, propylene, 1-butene and isobutene;
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, Amyl (meth) acrylate, i-amyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, i-octyl (meth) acrylate, decyl (meth) acrylate, i-decyl (meth) acrylate, Dodecyl (meth) acrylate, i-dodecyl (meth) acrylate, stearyl (meth) acrylate, i-stearyl (meth) acrylate, behenyl (meth) acrylate, cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate , Cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) ) (Meth) acrylate esters such as acrylate and adamantyl (meth) acrylate;
Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether;
Nitriles such as acrylonitrile and methacrylonitrile;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride;
Allyl compounds such as allyl acetate and allyl chloride;
Dicarboxylic acid ester derivatives such as maleic acid ester and itaconic acid ester;
Vinylsilyl compounds such as vinyltrimethoxysilane;
Vinyl esters such as vinyl acetate and isopropenyl acetate;
Cyclopentene, cycloheptene, cyclooctene, cyclododecene, 1,5-cyclooctadiene, cyclopentadiene, 1,5,9-cyclododecatriene, 1-chloro-1,5-cyclooctadiene, dicyclopentadiene, ethylidene norbornene, 5 -Cyclic olefins such as methyl norbornene-2-carboxylate, dimethyl 5-norbornene 2,3-dicarboxylate;
Benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethylene glycol (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, 2-naphthyl (meth) acrylate, 9-anthracenyl (meth) acrylate, 1-pyrenylmethyl (Meth) acrylate, styrene, vinylnaphthalene, α-methylstyrene, t-butylstyrene, p-methylstyrene o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, ot-butoxystyrene, mt- Butoxystyrene, pt-butoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, 1,1-diphe Ruechiren, vinylphenol, vinyl benzoate, vinyl naphthalene, aromatic compounds such as benzyl vinyl ether:

  Especially, it is preferable that the structural unit derived from aromatic compounds, such as benzyl (meth) acrylate and styrene, is contained in the block B as a monomer structural unit which has a hydrophobic group.

  On the other hand, examples of the monomer structural unit having an ionic dissociation group include those derived from monomers having acidic groups exemplified below and metal salts or ammonium salts thereof such as alkali metals and alkaline earth metals thereof. However, it is not limited to these, and conventionally known ones are included.

<Monomer having an acidic group>
Carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid;
Vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, styrene sulfonic acid, 2-acrylamide ethane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamide ethane sulfonic acid, 2-methacrylamide-2-methyl Propanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfone Sulfonic acid monomers such as acids;
Vinylphosphonic acid, methacryloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, Phosphoric monomers such as dioctyl-2- (meth) acryloyloxyethyl phosphate:

  Monomer constituent units having an ionic dissociation group further include monomers having the following basic groups, and neutralized salts thereof such as hydrogen halide, sulfuric acid, nitric acid, organic acids, alkyl halides, benzyl halides, dimethyl sulfate. Examples of monomer structural units derived from quaternized compounds such as diethyl sulfate are not limited to these and include conventionally known ones.

<Monomer with basic group>
Dimethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di-n-propylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisopropylamino (Methyl, ethyl, propyl or butyl) acrylate or methacrylate, di-n-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di-sec-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate , Diisobutylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, vinyl pyridine, 2-methyl-5-vinyl pyridi , 2-ethyl-5-vinylpyridine, N, N-dimethylamino styrene, N, N-dimethylaminomethyl styrene

  Examples of the monomer constituent unit having an ionic dissociation group include alkali metal salts (for example, sodium salts, potassium salts) and / or alkaline earth metal salts of acidic groups such as carboxylic acid groups, sulfonic acid groups, and phosphoric acid groups. It is preferable that a monomer structural unit having (for example, calcium salt, magnesium salt) as an ionic dissociation group is contained in the block B.

<Segment B ', B ">
The arrangement order of the hydrophobic segment B ′ and the hydrophilic segment B ″ in the block B is arbitrary, but is preferably arranged in the order of B ′ and B ″ from the side closer to the polyvinyl alcohol block A. B ″ is preferably a hydrophilic segment. By adopting such an arrangement, not only the dispersion stability of the pigment in the pigment ink is very good, but also the scratch resistance of the printed matter is improved at the same time. Although it is not certain, the following can be considered.

Polyvinyl alcohol block A is a water-soluble and crystalline block. Therefore, by disposing the hydrophobic segment B ′ and the hydrophilic segment B ″ in this order from the linking group in the block B bonded to the block A via the linking group, both ends of the polymer (I) are hydrophilic. The hydrophobic segment B ′ sandwiched between the hydrophilic portions is adsorbed on the hydrophobic pigment surface.
Thus, the pigments adsorbed with the polymer (I) repel each other in the aqueous medium by the hydrophilic portions on both sides of the hydrophobic segment B ′, so that aggregation in the pigment ink is suppressed and dispersion stability is suppressed. Is considered to be good.
As the hydrophilic segment B ″ in the block B, by using a hydrophilic segment composed of a monomer structural unit having an ionic dissociation group, structural repulsion due to the polyvinyl alcohol block A and the electricity of the hydrophilic segment B ″ Since both the mechanical repulsion can be utilized, the dispersion is further stabilized and preferable.

Furthermore, it is preferable that the polymer structure in the block B is a gradient copolymer structure because the pigment dispersion stability is improved.
The gradient copolymer structure refers to a structure in which the distribution of at least two or more types of monomer constituent units contained increases or decreases along the main chain of the polymer.
The reason why the pigment dispersion stability is improved by making the polymer structure in the block B a gradient copolymer structure is not clear, but the following reasons are conceivable.

  When an aqueous pigment dispersion is produced by bringing a polyvinyl alcohol block copolymer represented by the aforementioned general formula (2), which is a preferred example of the polymer (I), into contact with a pigment in an aqueous medium such as water or alcohols In addition, because the hydrophobic polymer chain is hydrophobic, it is considered that the polymer chain itself aggregates in an aqueous medium. And this agglomerate may be so firm that the agglomeration cannot be dissolved even when the pigment is dispersed, and it is difficult to cover the surface of the pigment that is hydrophobic with such a hydrophobic polymer chain. I think.

However, in the above-described hydrophobic segment B ′, by forming a gradient copolymer structure including a monomer constituent unit having a hydrophilic group in addition to the hydrophobic monomer constituent unit (for example, the hydrophobic segment B ′ mainly including a styrene monomer). Can be made flexible in the structure of the hydrophobic segment B ′ in the aqueous medium by including a monomer having a hydrophilic group such as a (meth) acrylic acid monomer, so that the pigment in the aqueous medium It is considered that it is possible to suppress the formation of a firm aggregate even at the time of dispersion. And it is thought that the polyvinyl alcohol-type block copolymer which has such a hydrophobic segment can cover the pigment surface more widely.
Thus, it is considered that the hydrophobicity of the pigment surface can be reduced by widely covering the hydrophobic pigment surface, and the dispersion stability of the pigment in the aqueous medium is improved.

  Further, it is preferable that the hydrophilic segment B ″ also has a gradient copolymer structure including a hydrophobic monomer constituent unit in addition to the hydrophilic monomer constituent unit, and more preferably a segment copolymer having a continuous segment B ′ and segment B ″. Preferably there is.

The number average molecular weight (Mn) of the block B is generally 500 or more, and the upper limit thereof is preferably 50000 or less, particularly preferably 20000 or less. If the molecular weight is too small, the adsorptive power of the polymer (I) to the pigment is lowered, and the dispersibility of the pigment may be lowered. On the other hand, if it is too large, the water-solubility is extremely lowered, which may make it difficult to disperse the pigment, increase the viscosity of the pigment ink, and greatly reduce the discharge performance of the pigment ink.
Here, since it is impossible to directly measure the number average molecular weight of the block B by GPC, the number average molecular weight of the block B is obtained by subtracting the number average molecular weight of the block A from the number average molecular weight of the polymer (II). To do.

<Synthesis Method of Polymer (I)>
An example of a method for synthesizing the polyvinyl alcohol block copolymer represented by the general formula (2), which is a preferred embodiment of the polymer (I), will be described.

  In order to produce this polyvinyl alcohol block copolymer, a polyvinyl ester polymer having a halogen atom Z at one end represented by the following general formula (3), for example, by a chain transfer polymerization method or the like (hereinafter referred to as “polyvinyl ester”). System polymer (3) ”may be obtained.

(In the formula (3), A ′ represents a polyvinyl ester polymer containing a vinyl ester structural unit represented by the following general formula (4) (in the general formula (4), R ² represents a hydrogen atom or a carbon number). 1 to 6 hydrocarbon groups, R ³ represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or an aralkyl group.), X ¹ , X ² , X ³ , and X ⁴ , and m 1 and m 2 are And is synonymous with that in the general formula (2), and Z represents a halogen atom such as F, Cl, Br, or I.)

  As Z in the general formula (3), a chlorine atom is particularly preferable.

  This polyvinyl ester polymer (3) has a structure similar to the above-mentioned polyvinyl alcohol block A except that a halogen atom is bonded to one end.

  Next, using the polyvinyl ester polymer (3) as a macroinitiator, a radical polymerizable monomer is polymerized by an atom transfer radical polymerization method or the like to obtain a block copolymer containing the polyvinyl ester polymer (3). Thereafter, the polyvinyl ester block copolymer can be obtained by saponifying the polyvinyl ester moiety in the block copolymer. However, the saponification can also be performed before the polymerization. In this case, the atom transfer type radical polymerization is performed by using the polyvinyl ester obtained by the saponification as a macroinitiator.

As specific examples of the hydrocarbon group having 1 to 6 carbon atoms for ^{R 2} in the general formula (4), a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, t- butyl group, sec -Alkyl groups such as a butyl group, a pentyl group, an isopentyl group, a neopentyl group, a t-pentyl group, and a hexyl group. Among them, R ² is preferably a hydrogen atom or an alkyl group having a small number of carbon atoms, specifically an alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom or a methyl group.

In addition, the alkyl group, alkenyl group, aryl group or aralkyl group of R ³ in the general formula (4) preferably has 1 to 20 carbon atoms, and may be linear, branched or cyclic, and the carbon atom is It may have a substituent.

Specific examples of R ³ include the following.

Methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, sec-butyl group, pentyl group, isopentyl group, neopentyl group, t-pentyl group, hexyl group, heptyl group, decyl group Alkyl groups and substituted alkyl groups such as dodecyl group, hexadecyl group, octadecyl group, chloromethyl group, dichloromethyl group, trichloromethyl group, trifluoromethyl group;
Vinyl group, allyl group, isopropenyl group, 3-butenyl group, 1-methylallyl group, 1,1-dimethylallyl group, 2-methylallyl group, 3-methylallyl group, 2,3-dimethylallyl group, 3,3- Alkenyl groups and substituted alkenyl groups such as a dimethylallyl group, cinnamyl group, and 3-cyclohexylallyl group;
Aryl groups such as phenyl and naphthyl groups;
A substituted aryl group in which 1 to 3 hydrogen atoms in an aryl group such as a phenyl group and a naphthyl group are substituted with a functional group such as a methyl group, an ethyl group, a butyl group, a methoxy group, and an ethoxy group;
Aralkyl groups and substituted aralkyl groups such as benzyl group, phenethyl group, phenylbutyl group, diphenylmethyl group, triphenylmethyl group, naphthylmethyl group, naphthylethyl group:

Among them, as R ³ , a methyl group, a chloromethyl group, an allyl group, a phenyl group, and a benzyl group are preferable, and further, an alkyl group or a substituted alkyl group having a small number of carbon atoms is preferable, specifically, having 1 to 3 carbon atoms, An alkyl group or a substituted alkyl group substituted with a halogen atom is preferable, and a methyl group or a chloromethyl group is particularly preferable.

(Preparation of polyvinyl ester polymer (3))
The polyvinyl ester polymer (3) can be prepared by the chain transfer polymerization method as follows.

The polyvinyl ester polymer (3) having a halogen atom at one end can be synthesized by a chain transfer polymerization method called telomerization (Eur. Polym. J., 18, 779 1982). That is, by conducting radical polymerization of a vinyl ester monomer in the presence of a polyhalogenated hydrocarbon having a large radical chain transfer constant called a chain transfer agent (telogen), a polyvinyl ester polymer having a halogen atom at one end ( 3) is obtained quantitatively. In the general formula (3), the linking group between A ′ and Z corresponds to the linking group of the block AB in the general formula (2) and is derived by a chain transfer agent. That is, X ¹ , X ² , X ³ , and X ⁴ in the general formula (2) are derived from a chain transfer agent.

  As this chain transfer agent, methylene chloride, ethylene chloride, dichloroethane, ethylidene chloride, ethylidene bromide, chloroform, carbon tetrachloride, carbon tetrabromide, methyl chloroform, trichloroethane, tetrachloroethane, allyl chloride, butyl chloride, butyl bromide, butyl Examples include iodide, chlorobenzene, bromobenzene, dichlorobenzene, benzyl chloride, and methallyl chloride.

  As the above-mentioned vinyl ester monomers, vinyl acetate, vinyl propionate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl formate, vinyl caproate, vinyl caprate, vinyl myristate, vinyl palmitate, 2-ethyl Examples include vinyl hexanoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl methacrylate, vinyl crotonic acid, vinyl sorbate, vinyl benzoate, vinyl cinnamate, and α-substituted products thereof. Among these, vinyl ester monomers having a large side chain such as vinyl acetate, vinyl pivalate, and vinyl formate, or vinyl ester monomers having high polarity are preferable.

  In the chain transfer polymerization method, the molecular weight can be arbitrarily adjusted by selecting the ratio between the chain transfer agent and the vinyl ester monomer, or by changing the monomer concentration when a polymerization solvent is used.

  As the radical polymerization initiator in the chain transfer polymerization method, known ones such as an azo initiator, a redox initiator, and an ultraviolet initiator can be used. Radiation and electron beams can also be used. Of these, azo initiators are preferred because they are easy to handle.

The polymerization reaction can be carried out without solvent or in the presence of a solvent.
When a solvent is used, the polymerization reaction solvent includes ethers such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, acetonitrile and propionitrile. , Nitriles such as benzonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, carbonyl compounds such as ethylene carbonate, propylene carbonate, methanol, ethanol, propanol, isopropanol, n-butyl alcohol, t-butyl alcohol, Alcohols such as isoamyl alcohol, aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, methylene chloride, chloroform, chloroben Down, four one or more halogenated hydrocarbons such as carbon tetrachloride and the like.

  Moreover, when the chain transfer agent to be used is a liquid, you may use this as a polymerization reaction solvent. The chain transfer agent used as the solvent is preferably a halogenated hydrocarbon, more preferably chloroform.

  When performing the polymerization reaction, the order of addition of vinyl ester monomer, chain transfer agent, polymerization solvent, radical polymerization initiator, etc. is arbitrary. For example, vinyl ester monomer, chain transfer agent, polymerization solvent, radical polymerization initiation A method in which the polymerization reaction is performed by raising the temperature after charging the agent in a reaction vessel at once. As another method, a monomer solution containing a radical polymerization initiator, a chain transfer agent, a polymerization solvent, or a vinyl ester monomer, a chain transfer agent, and a polymerization solvent are charged into a reaction vessel and the temperature is raised. Examples thereof include a method in which these mixtures are added continuously or dividedly to perform a polymerization reaction. Among them, the method in which a vinyl ester monomer, a chain transfer agent, and a polymerization solvent are charged into a reaction vessel and the temperature is increased, and then a polymerization solvent containing a radical polymerization initiator is added in a divided manner, which generates heat during the polymerization reaction. It is preferable because it can be controlled.

The amount of chain transfer agent used is not particularly limited, but is usually 0.01 parts by weight or more, preferably 1 part by weight or more, usually 2000 parts by weight or less, preferably 1000 parts by weight or less, relative to 100 parts by weight of the vinyl ester monomer. is there.
The amount of the radical polymerization initiator used is not particularly limited, but is usually 0.001 part by weight or more, preferably 0.01 part by weight or more, usually 15 parts by weight or less, preferably 10 parts by weight with respect to 100 parts by weight of the vinyl ester monomer. Or less.
Although the usage-amount of a solvent is not specifically limited, It is 1 to 2000 weight part normally with respect to 100 weight part of vinyl ester monomers, Preferably it is 1000 weight part or less.
The polymerization temperature is not particularly limited, but is usually 0 ° C or higher, preferably 20 ° C or higher, and the upper limit is usually 200 ° C or lower, preferably 150 ° C or lower.

  The polyvinyl ester polymer (3) thus obtained is purified according to a conventional method and is supplied to the next step. As this purification method, for example, the polymerization solution is put into a solvent in which the monomer and the polymerization solvent are soluble and the polyvinyl ester polymer (3) is insoluble, the polyvinyl ester polymer (3) is precipitated, filtered and dried. The method of letting it be mentioned. Moreover, the purification method etc. which substitute a reaction solvent after removing an unreacted monomer by distillation etc. are also mentioned. In particular, a purification method in which the reaction solvent is replaced after removing the unreacted monomer by distillation or the like is preferable. In particular, in this purification method, an alkaline component is added to the solution containing the polyvinyl ester polymer (3) during the removal operation of the unreacted monomer. Is preferable because the acid in the system produced by distillation or the like is neutralized and decomposition of the polyvinyl ester polymer (3) by the acid can be suppressed.

  When removing unreacted monomers and reaction solvent by distillation, it is preferable to carry out distillation under reduced pressure. In order to avoid polymerization of the unreacted monomer and decomposition of the polyvinyl ester polymer (3) during the vacuum distillation, it is preferably performed at 50 ° C. or lower, and it is particularly preferable to perform vacuum distillation at 40 ° C. or lower.

(Synthesis of block copolymer containing polyvinyl ester polymer (3))
The atom transfer radical polymerization method for synthesizing the block copolymer containing the polyvinyl ester polymer (3) using the polyvinyl ester polymer (3) produced as described above as a macroinitiator can be performed as follows. it can.

  The atom transfer type radical polymerization method is one method of the living radical polymerization method and is represented by the following scheme.

In the above scheme, P is a polymer or initiator, M is a transition metal, Q ¹ and Q ² are halogen atoms, L is a ligand capable of coordinating to M, s and s + 1 are valences of the transition metal, The low valence complex [1] and the high valence complex [2] constitute a redox conjugated system.

First, the low valence complex [1] radically extracts the halogen atom Q ¹ from the halogen-containing polymerization initiator PQ ¹ to form the high valence complex [2] and the carbon center radical P ·. The rate of this reaction is expressed as Kact. This radical P • reacts with the monomer as shown to form the same kind of intermediate radical species P •. The rate of this reaction is represented by Kpropagation.

The reaction between the high valence complex [2] and the radical P • produces the product PQ ¹ and at the same time regenerates the low valence complex [1]. The rate of this reaction is expressed as Kdeact. Then, low valent complex [1] to advance a new reaction further reacts with P-Q ^1. In this reaction, it is most important in controlling the polymerization to suppress the concentration of the growing radical species P · to be low.

Specific examples of the atom transfer radical polymerization method include the following reports (1) and (2).
(1) Polymerization of styrene using α-chloroethylbenzene as an initiator in the presence of a CuCl / bipyridyl complex (J. WangandK. Matyjaszewski, J. Am. Chem. Soc. 117, 5614 (1995))
(2) Polymerization of methyl methacrylate using RuCl ₂ (PPh ₃ ) ₃ , CCl ₄ in the presence of an organoaluminum compound as an initiator (M. Kato, M. Kamigaito, M. Sawamoto, T. Higashimura, Macromolecules, 28, 1821 (1995))

Therefore, the above-described polyvinyl ester polymer (3) having a halogen atom at one end is used as the macroinitiator (PQ ¹ ) of the atom transfer radical polymerization method, and the radical transfer method is performed by the atom transfer radical polymerization method. By polymerizing the polymerizable monomer, a block copolymer containing a polyvinyl ester polymer block and another block B is obtained.

  The transition metal M used in the atom transfer radical polymerization method is not particularly limited, but at least one transition metal selected from Groups 7 to 11 of the periodic table is preferable.

In the redox catalyst (redox conjugated complex), the low valence complex [1] and the high valence complex [2] reversibly change as shown in the above-described diagram. Specific examples of the low-valent metal (M) ^s include Cu ⁺ , Ni ⁰ , Ni ⁺ , Ni ²⁺ , Pd ⁰ , Pd ⁺ , Pt ⁰ , Pt ⁺ , Pt ²⁺ , Rh ⁺ , Rh ²⁺ , ^{Rh 3+, Co +, Co 2+} , Ir 0, Ir +, Ir 2+, Ir 3+, Fe 2+, Ru 2+, Ru 3+, Ru 4+, Ru 5+, Os 2+, Os 3+, Re 2+, Re 3+, Re 4+ , Re ⁶⁺ , Mn ²⁺ , Mn ³⁺ , among which Cu ⁺ , Ru ²⁺ , Fe ²⁺ , and Ni ²⁺ are preferable, and Cu ⁺ is particularly preferable.
Specific examples of the monovalent copper compound include cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide and the like.

  As the ligand L, an organic ligand is generally used. Specific examples include 2,2′-bipyridyl and derivatives thereof, 1,10-phenanthroline and derivatives thereof, tetramethylethylenediamine, pentamethyldiethylenetriamine, tris (dimethylaminoethyl) amine, triphenylphosphine, tributylphosphine, and the like. However, aliphatic polyamines such as tris (dimethylaminoethyl) amine are particularly preferred.

  As a solvent, the solvent quoted as the polymerization reaction solvent used for chain transfer polymerization can be used similarly. Of these, alcohols are preferable, and methanol, isopropyl alcohol, or a mixed solvent thereof is particularly preferable.

  Examples of the radical polymerizable monomer include acrylate monomers, methacrylate monomers, and styrene monomers. In addition, monomers such as vinyl ether, allyl ether, and allyl ester that are difficult to undergo radical polymerization alone can also be used as a copolymerization component of the radical polymerizable monomer.

  Specific examples of the above acrylate monomers include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, benzyl acrylate, cyclohexyl acrylate, lauryl acrylate, n-octyl acrylate, 2-methoxyethyl acrylate, butoxyethyl acrylate, methoxytetraethylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2- Hydroxy-3-phenoxypropyl acrylate, diethylene glycol acrylic Over DOO, polyethylene glycol acrylate, 2- (dimethylamino) ethyl acrylate, N, N- dimethyl acrylamide, N- methylol acrylamide.

  Specific examples of the above-mentioned methacrylate monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-methoxyethyl methacrylate, butoxyethyl methacrylate, methoxytetraethylene glycol methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, 2- Hydroxy-3-phenoxypropyl Methacrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate, 2- (dimethylamino) ethyl methacrylate.

  Examples of the styrenic monomer include styrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, ot-butoxystyrene, mt-butoxystyrene, pt-butoxystyrene, and o-chloromethyl. Styrene, m-chloromethyl styrene, p-chloromethyl styrene, etc. are mentioned.

The amount of the solvent used is not particularly limited, but is usually 1 part by weight or more, preferably 100 parts by weight or more with respect to 100 parts by weight of the monomer, and the upper limit is usually 2000 parts by weight or less, preferably 1000 parts by weight or less. .
The amount of the low-valent metal (M) ^s used is not particularly limited, but the concentration in the polymerization reaction system is usually 10 ⁻⁶ mol / liter or more, preferably 10 ⁻⁵ mol / liter or more, and its upper limit is Usually, it is 10 ⁻¹ mol / liter or less. And it is 0.001 mol or more normally with respect to 1 mol of initiators, Preferably it is 0.005 mol or more, The upper limit is 100 mol or less normally, Preferably it is 50 mol or less.

  The polymerization temperature is not particularly limited, but is usually 0 ° C. or higher, preferably 20 ° C. or higher, and the upper limit is 200 ° C. or lower, preferably 150 ° C. This polymerization proceeds in a living manner.

The block B is preferably a polymer containing a radical polymerizable monomer as described above as a constituent component, and may be a modified product depending on the application.
Specifically, a carboxylic acid ester group is introduced into the main chain of the block B as a side chain, or the carboxylic acid ester group is hydrolyzed under an acid or alkaline condition to form a carboxylic acid structure. It can be neutralized with sodium oxide or the like to form a carboxylate structure. When the carboxylic acid ester group is hydrolyzed under acid or alkaline conditions to form a carboxylic acid structure, it may be carried out in the same step as the saponification reaction of the polyvinyl ester polymer as block A, or in a separate step. Also good. In the case of the polymer block B having a tertiary amine structure such as a dimethylaminoethyl group, a tertiary amine may be reacted with benzyl chloride or the like to form a quaternary salt structure.

Further, the block B is preferably a gradient copolymer obtained by polymerizing a plurality of radically polymerizable monomers having different reactivity as radically polymerizable monomers. As a method for producing the gradient copolymer, for example, in the above-described atom transfer radical polymerization method, the above-described polyvinyl ester polymer (3) having a halogen atom at one terminal is used as the macroinitiator (PQ ¹ ). An example is a method of synthesizing by copolymerization using two or more monomers having different reactivities.

  A method for introducing two or more monomers having different reactivity into the polymerization reaction system is arbitrary. As a specific method, for example, a method in which all kinds of monomers used for the reaction are simultaneously introduced into the reactor at the start of polymerization. As another method, there can be mentioned a method in which the monomers used for the reaction are introduced into the reactor continuously or separately as a mixture and / or a mixture at the start of the polymerization. Furthermore, a method of introducing the monomer used for the reaction into the reactor continuously or in a divided manner as a mixture having two or more different composition ratios at the start of the polymerization may be mentioned. Among them, a method in which all kinds of monomers used for the reaction at the start of polymerization are simultaneously introduced into the reactor is preferable.

  At this time, it is preferable to use a hydrophobic monomer and a hydrophilic monomer (the hydrophilic monomer includes a monomer that exhibits hydrophilicity by a modification reaction after polymerization) as the plurality of types of monomers having different reactivity. Among them, it is preferable to use a highly reactive hydrophobic monomer and a hydrophilic monomer that is less reactive than the hydrophobic monomer. By using such a hydrophobic monomer and a hydrophilic monomer, the hydrophobic monomer composition decreases at a certain rate toward the end of the block B (the end in the direction opposite to the linking group). This results in a gradient copolymer structure in which the monomer composition increases at a constant rate.

  By introducing such a gradient structure into the polymer chain, when the polyvinyl alcohol-based block copolymer is present in the aqueous medium as the polymer (I), the hydrophobic segment B ′ in the portion close to the linking group in the block B Since it contains a hydrophilic group in its structure, it is plasticized by water in an aqueous medium, so that the hydrophobic segment B ′ can have flexibility.

  Accordingly, the hydrophobic segment B ′ in the block B is flexible, and preferably has a hydrophilic segment B ″ at the end of the block B, so that the polymer (I) having this block B is a polyvinyl alcohol block copolymer. (Polymer dispersant) and the pigment are brought into contact with and dispersed in an aqueous medium such as water or alcohol to produce an aqueous pigment dispersion, the polymer chain itself of the hydrophobic segment B ′ in the aqueous medium However, the polyvinyl alcohol block copolymer covers the pigment surface more widely, thereby reducing the hydrophobicity on the pigment surface which is hydrophobic in the first place. This is considered to improve the dispersion stability of the pigment in the aqueous medium.

  Such a combination of the hydrophobic segment B ′ and the hydrophilic segment B ″ includes any hydrophobic monomer having high reactivity and any hydrophilic monomer (hydrophilic monomer having low reactivity compared to the hydrophobic monomer). May be produced using a monomer that exhibits hydrophilicity by a modification reaction after polymerization. Specifically, for example, as a monomer constituent unit constituting a hydrophobic segment in segments B ′ and B ″, Monomer constituent units having a hydrophobic group having no charge group are preferred, aryl (meth) acrylate monomers such as benzyl acrylate and benzyl methacrylate, 2-ethylhexyl acrylate, n-butyl acrylate, t-butyl acrylate, methyl acrylate, Alkyl (meth) acrylate monomers such as ethyl acrylate Constitutional unit derived from alkylene monomer is preferred. .

  Moreover, as a monomer structural unit which comprises the hydrophilic segment in segment B ", the monomer structural unit which has an ionic dissociation group is preferable, for example, acrylate monomers, such as sodium acrylate; Methacrylate monomers, such as sodium methacrylate Derived structural units are preferred.

In this way, a block copolymer including a polyvinyl ester polymer block and a block B having a gradient copolymer structure is obtained.
When the block B has a gradient copolymer structure, as described above, the polyvinyl ester polymer (3) having a halogen atom at one end as the macroinitiator (PQ ¹ ) of the atom transfer radical polymerization method as described above. And a plurality of radically polymerizable monomers, preferably a mixture of these monomers may be polymerized by an atom transfer radical polymerization method.

  In carrying out this polymerization, the order of addition of the macroinitiator, the plurality of radically polymerizable monomers, and the catalyst is arbitrary. For example, a method in which a metal catalyst is charged into a reactor, then a mixture of a macroinitiator and radical polymerizable monomers and a polymerization solvent is charged, and then an organic ligand is mixed and heated to perform polymerization, Examples thereof include a method in which a mixture of a macroinitiator, radically polymerizable monomers, and a polymerization solvent is charged into a reactor, and then a metal catalyst and an organic ligand are separately added or a solution containing the mixture is charged.

  Among them, a mixture containing a macroinitiator and a plurality of types of radically polymerizable monomers is raised to the vicinity of the reaction start temperature within a range not exceeding the reaction start temperature before the addition of the catalyst. It is preferable that the polymerization reaction is started by mixing with the catalyst after the temperature is within 15 ° C., preferably within 15 ° C., and then increasing the temperature. This method is preferable because impurities derived from the catalyst are reduced. The catalyst used in such a polymerization reaction method is arbitrary, but it is preferable to use a copper catalyst such as cuprous chloride or cuprous bromide because the effect becomes remarkable, and cuprous bromide is more preferably used. Is preferred.

  The block copolymer thus obtained is purified according to a conventional method, or is subjected to the next step without purification. Examples of the purification method include a method in which the block copolymer is precipitated in a solvent in which the polymer is insoluble and the monomer and catalyst are soluble, and filtration is repeated, and a purification method in which the reaction solvent is replaced after removing unreacted monomers by distillation or the like.

<Saponification of block copolymer containing polyvinyl ester polymer (3)>
Next, a method for saponifying a block copolymer containing the polyvinyl ester polymer (3) will be described.

  The saponification reaction of the block copolymer containing the polyvinyl ester polymer (3) is performed in the presence of a saponification catalyst. Usually, saponification is synthesized by the atom transfer radical polymerization method from polyvinyl ester polymer (3), which is a macroinitiator, to alcohols (methanol, ethanol, isopropanol, butanol, etc.), benzene, methyl acetate, etc. Dissolve the block copolymer. When the solubility of the block copolymer in the aforementioned solvent is low, ethers such as tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; acetonitrile and propio Nitriles such as nitrile and benzonitrile; carbonyl compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene carbonate, and propylene carbonate; and the like may be mixed and used as a solvent for the saponification reaction.

  As the saponification catalyst, alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium oxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate are used, but sulfuric acid, hydrochloric acid and p-toluene are used. Acid catalysts such as sulfonic acids can also be used.

The amount of the alkali catalyst used is not particularly limited, but is usually 1 mmol equivalent or more and 100 mmol equivalent or less, preferably 50 mmol equivalent or less, more preferably 30 mmol equivalent or less with respect to 1 mol of the vinyl ester monomer structural unit.
Although the usage-amount of an acid catalyst is not specifically limited, Usually, 1 millimol equivalent or more and 1000 millimol equivalent or less, Preferably it is 500 millimol equivalent or less, More preferably, it is 300 millimol equivalent or less with respect to 1 mol of vinyl ester monomer structural units.
The temperature of the saponification reaction is usually 20 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is 100 ° C. or lower, preferably 80 ° C. or lower.

  The saponification degree may be appropriately selected and determined depending on the use of the polyvinyl alcohol block copolymer as the finally obtained polymer (I), but is usually 80 mol% or more, preferably 90 mol% or more. Here, the degree of saponification is the ratio of vinyl alcohol constituent units after saponification to the units that can be converted to vinyl alcohol constituent units by saponification of vinyl ester monomer constituent units. Unit.

  Further, when a monomer having a carboxylic acid ester group is introduced into the B block, and the carboxylic acid ester group is hydrolyzed after polymerization to form a carboxylic acid structure or a carboxylate structure, a saponification reaction and a hydrolysis reaction of the block A May be performed in the same step (one pot). As a solvent for saponification and hydrolysis reaction in one pot, alcohols (methanol, ethanol, isopropanol, butanol, etc.), ethers such as benzene, methyl acetate, tetrahydrofuran, diphenyl ether, anisole, dimethoxybenzene; N, N-dimethylformamide Amides such as N, N-dimethylacetamide; Nitriles such as acetonitrile, propionitrile, benzonitrile; Carbonyl compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate; Water These may be used alone or in combination. Among them, it is preferable to use a mixture of water and a water-soluble organic solvent such as methanol or tetrahydrofuran.

  As a saponification / hydrolysis catalyst, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, alcoholate, etc. are used in the same manner as in the single saponification reaction. Alkaline catalysts are used, but acid catalysts such as sulfuric acid, hydrochloric acid, p-toluenesulfonic acid can also be used.

Although the usage-amount of an alkali catalyst is not specifically limited, 1/1000 equivalent or more and 5 equivalent or less normally with respect to the sum total of the vinyl ester-type monomer structural unit and carboxylic acid ester-type monomer structural unit in a polymer, Preferably it is 2 equivalent or less, More preferably, it is 1.5 equivalent or less.
Although the usage-amount of an acid catalyst is not specifically limited, 1/1000 equivalent or more and 5 equivalent or less normally with respect to the sum total of the vinyl ester-type monomer structural unit and carboxylic acid ester-type monomer structural unit in a polymer, Preferably it is 2 equivalent or less, More preferably, it is 1.5 equivalent or less.
The reaction temperature is usually 20 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is 100 ° C. or lower, preferably 80 ° C. or lower.

{Aqueous medium}
Examples of the aqueous medium used in the aqueous pigment dispersion of the present invention include water and / or a water-soluble organic solvent.
Although it will not specifically limit if it is generally used for this use as a water-soluble organic solvent, Specifically, it is a thing with a vapor pressure smaller than water, and the following are mentioned.

Ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, polypropylene glycol, pentamethylene glycol, trimethylene glycol, butylene Glycol, isobutylene glycol, thiodiglycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 1,2-pentanediol, 1,5-pentanediol, 2- Methyl-2,4-pentanediol, 1,3-propanediol, 1,4-butanediol, 1,7-heptanediol, 1,8-octanediol, 2 Butene-1,4-diol, polyhydric alcohols such as glycerin;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monophenyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl Ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, Lopylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol mono-t-butyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropylene ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether Polyhydric alcohol ethers such as dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether;
Ketones such as acetonylacetone;
Esters such as γ-butyrolactone, diacetin, triethyl phosphate;
Lower alkoxy alcohols such as 2-methoxyethanol and 2-ethoxyethanol;
Amines such as ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, triethylenetetramine, tetraethylenepentamine, pentamethyldiethylenetriamine;
Amides such as formamide, N, N-dimethylformamide, N-methylformamide, N, N-dimethylacetamide;
2-pyrrolidone, N-ethylpyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, morpholine, N-ethylmorpholine, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, imidazole, methylimidazole, hydroxyimidazole , Heterocycles such as dimethylaminopyridine, 1,3-propane sultone, hydroxyethylpiperazine, piperazine;
Sulfoxides such as dimethyl sulfoxide;
Sulfones such as sulfolane:

  These may be used alone or in combination of two or more.

  The aqueous medium used in the present invention is preferably water or a mixture of water and a water-soluble organic solvent as described above.

{Other color materials}
The aqueous pigment dispersion of the present invention may contain a pigment other than the above-described carbon black as a coloring material. Such pigments may be appropriately selected from those commonly used in each application, and are not particularly limited. Examples of typical pigments include calcium carbonate, kaolin clay, talc, bentonite, and mica. Extender pigments; metal oxide pigments such as titanium oxide, zinc oxide, goethite, magnetite, chromium oxide; titanium yellow, titanium buff, antimony yellow, vanadium tin yellow, cobalt green, cobalt chrome green, manganese green, cobalt Complex oxide pigments such as blue, cerulean blue, manganese blue, tungsten blue, Egyptian blue, and cobalt black; sulfide pigments such as ritbon, cadmium red yellow, and cadmium red; mineral violet Phosphate pigments typified by cobalt violet, lithium cobalt phosphate, sodium cobalt phosphate, potassium potassium phosphate, cobalt ammonium phosphate, nickel phosphate, copper phosphate; chrome lead, molybdate orange Chromate pigments; metal complex pigments such as ultramarine and Prussian blue; metal powder pigments such as aluminum paste, bronze powder, zinc powder, stainless steel flakes, nickel flakes; bismuth oxychloride, basic carbonate Inorganic pigments such as pearlescent pigments and nacreous conductive pigments such as titanium dioxide, coated mica, ITO (indium tin oxide), and ATO (antimony tin oxide); and quinacridone pigments, quinacridone quinone pigments, Dioxazine pigments, phthalocyanine pigments, anthrapies Midine pigment, Ansanthrone pigment, Indanthrone pigment, Flavanthrone pigment, Perylene pigment, Diketopyrrolopyrrole pigment, Perinone pigment, Quinophthalone pigment, Anthraquinone pigment, Thioindigo pigment, Metal complex Examples thereof include organic pigments such as pigments, azomethine pigments, and azo pigments.

  Specific examples of the pigment include pigments having the following pigment numbers and known carbon blacks generally used in the color material field. Note that terms such as “CI Pigment Red 2” mentioned below mean a color index (CI).

  Red colorant: C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 37, 38, 41, 47, 48, 48: 1, 48: 2, 48: 3, 48: 4, 49, 49: 1, 49: 2, 50: 1, 52: 1, 52: 2, 53, 53: 1, 53: 2, 53: 3, 54, 57, 57: 1, 57: 2, 58, 58: 4, 60, 63, 63: 1, 63: 2, 64, 64: 1, 68, 69, 81, 81: 1, 81: 2, 81: 3, 81: 4, 83, 88, 90: 1, 101, 101: 1, 104, 108, 108: 1, 109, 112, 113, 114, 122, 123, 144, 146, 147, 149, 151, 166, 168, 169, 170, 172, 173, 174, 175, 176, 177, 78, 179, 181, 184, 185, 187, 188, 190, 193, 194, 200, 202, 206, 207, 208, 209, 210, 214, 216, 220, 221, 224, 230, 231, 232, 233, 235, 236, 237, 238, 239, 242, 243, 245, 247, 249, 250, 251, 253, 254, 255, 256, 257, 258, 259, 260, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276;

  Blue colorant: C.I. I. Pigment Blue 1, 1: 2, 9, 14, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 19, 25, 27, 28, 29, 33, 35, 36, 56, 56: 1, 60, 61, 61: 1, 62, 63, 66, 67, 68, 71, 72, 73, 74, 75, 76, 78, 79;

  Green colorant: C.I. I. Pigment Green 1, 2, 4, 7, 8, 10, 13, 14, 15, 17, 18, 19, 26, 36, 45, 48, 50, 51, 54, 55;

  Yellow colorant: C.I. I. Pigment Yellow 1, 1: 1, 2, 3, 4, 5, 6, 9, 10, 12, 13, 14, 16, 17, 23, 24, 31, 32, 34, 35, 35: 1, 36, 36: 1, 37, 37: 1, 40, 41, 42, 43, 48, 53, 55, 61, 62, 62: 1, 63, 65, 73, 74, 75, 81, 83, 87, 93, 94, 95, 97, 100, 101, 104, 105, 108, 109, 110, 111, 116, 119, 120, 126, 127, 127: 1, 128, 129, 133, 134, 136, 138, 139, 142, 147, 148, 150, 151, 153, 154, 155, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 172, 173 174, 175, 176, 180, 181, 182, 183, 184, 185, 188, 189, 190, 191, 191: 1, 192, 193, 194, 195, 196, 197, 198, 199, 200, 202, 203, 204, 205, 206, 207, 208, 215;

  Orange colorant: C.I. I. Pigment Orange 1, 2, 5, 13, 16, 17, 19, 20, 21, 22, 23, 24, 34, 36, 38, 39, 43, 46, 48, 49, 61, 62, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79;

  Violet colorant: C.I. I. Pigment Violet 1, 1: 1, 2, 2: 2, 3, 3: 1, 3: 3, 5, 5: 1, 14, 15, 16, 19, 23, 25, 27, 29, 31, 32, 37, 39, 42, 44, 47, 49, 50

  Brown colorant: C.I. I. Pigment Brown 1, 6, 11, 22, 23, 24, 25, 27, 29, 30, 31, 33, 34, 35, 37, 39, 40, 41, 42, 43, 44, 45

  Black colorant: C.I. I. Pigment Black 1, 31, 32

  Among the above pigments, red pigments preferably include quinacridone pigments, xanthene pigments, perylene pigments, antanthrone pigments, and monoazo pigments. I. Pigment Red-5, -7, -12, -112, -81, -122, -123, 146, -147, -168, -173, -202, -206, -207, -209, C.I. I. And CI Pigment Violet-19. Among these, the solid solution which consists of a quinacridone-type pigment and two or more types of quinacridone-type pigments is more preferable from the surface of a pigment's stability and hue.

  Of the above-mentioned pigments, monoazo pigments and disazo pigments are preferable as yellow pigments because color development as printed matter is better than other pigments. Among them, C.I. I. Pigment Yellow-1, -3, -16, -17, -74, -95, -120, -128, -151, -155, -175, and -215 are particularly preferable from the viewpoint of the color, and among them, C. I. CI Pigment Yellow-74 and -155 are non-halogen compounds, and are particularly preferable from the viewpoint of little influence on the environment and hue.

  Of the above pigments, a copper phthalocyanine pigment is preferable as a blue pigment, since color development as a printed material is better than other pigments. Among them, C.I. I. Pigment Blue-15: 3 is preferable from the viewpoints of stability and hue.

As the pigment used in combination with carbon black, one of the above pigments may be used alone, or two or more may be used in combination. It can also be used in combination with other color materials.
The shape of the pigment may be any form such as paste, powder, solid solution and the like.

The primary particle size of these pigments may be arbitrarily set according to the purpose, but the primary particle size of the pigment is usually 10 nm or more, preferably 300 nm or less, more preferably 200 nm or less, particularly preferably. Is 100 nm or less.
Here, the primary particle diameter of the pigment is an arithmetic average diameter (number average) measured by an electron microscope.

The average dispersed particle size of the pigment in the recording liquid is usually 300 nm or less, preferably 200 nm or less. Moreover, as a minimum, it is 20 nm or more normally.
The average dispersed particle size can be measured using an electron microscope such as SEM or TEM, or can be measured using a commercially available dynamic light scattering measurement device.

  As with carbon black, the pigment is not chemically modified, and does not contain impurities other than the pigment, such as a crystallization inhibitor for promoting the reduction in the particle size of the pigment. It is preferable because it does not inhibit the adsorption of the polymer to the pigment. However, in order to give the pigment self-dispersibility, a pigment having self-dispersibility which has been subjected to known chemical modification in advance can also be used. That is, the pigment used in the aqueous pigment dispersion of the present invention can be any pigment, whether it is an untreated pigment or a pigment whose surface is chemically modified, as described above.

{Aqueous pigment dispersion composition}
The aqueous pigment dispersion of the present invention contains at least the above-mentioned PAH content and oxygen-containing functional group density and carbon black and an aqueous medium, and may contain a polymer and other components as necessary. Especially, it is preferable that the polymer component used as a pigment dispersant is included.

  The carbon black concentration in the aqueous pigment dispersion of the present invention is usually 30% by weight or less, preferably 20% by weight or less. Here, if the carbon black concentration is too high, the carbon black becomes poorly dispersed, the viscosity of the dispersion increases, the dispersion becomes gelled, and the dispersion may not be usable due to dispersion failure. If the carbon black concentration is too low, a sufficient printing density will not be obtained when ink is formed, and therefore it is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more.

  The weight ratio of carbon black to polymer in the aqueous pigment dispersion of the present invention may be appropriately selected and determined. Generally, however, a polymer (two or more kinds of polymers are added to 1 part by weight of carbon black). In the case of inclusion, the total) is preferably 0.01 parts by weight or more, especially 0.05 parts by weight or more, and particularly preferably 0.1 parts by weight or more, and the upper limit is 2 parts by weight or less, especially 1.5 parts by weight or less. It is preferable that If the amount of the polymer is less than this range, the dispersion stability is lowered, and if the amount is larger, the viscosity of the dispersion liquid and the recording liquid prepared using the same is increased and the dischargeability is lowered.

  In particular, when the aqueous pigment dispersion of the present invention contains the hydrophobic / hydrophilic polymer and the polymer (I), the amount of the hydrophobic / hydrophilic polymer is about 1 to 100 parts by weight of carbon black. The amount is preferably in the range of 199.9 parts by weight, more preferably 5 to 100 parts by weight. If the amount of the hydrophobic / hydrophilic polymer is too small, the carbon black becomes unstable in dispersion in an aqueous medium and causes aggregation. In addition, the hydrophilic / hydrophobic balance of the hydrophobic / hydrophilic polymer, the total surface area of the carbon black particles, the affinity between the hydrophobic group and the carbon black particle surface, etc. Has a limit, and if the amount of the hydrophobic / hydrophilic polymer is excessively large, the viscosity of the dispersion is increased and the dispersion is unstable. The polymer (I) is 0.1 to 199 parts by weight, particularly 1 to 100 parts by weight with respect to 100 parts by weight of carbon black, and the total content of the hydrophobic / hydrophilic polymer and the polymer (I) is In addition, the hydrophobic / hydrophilic polymer and the polymer (I) are 1 to 200 parts by weight, particularly 5 to 100 parts by weight with respect to 100 parts by weight of carbon black, and the hydrophobic / hydrophilic polymer: polymer (I) = 99-20: It is preferable to use so that it may be contained in the range of 1-80 (weight ratio).

  The aqueous pigment dispersion of the present invention may contain components other than the aqueous medium, carbon black, and polymer, and in particular, other additions that can be contained in the ink composition of the present invention as described later. The other component illustrated as an agent may be contained.

  Further, when the aqueous pigment dispersion of the present invention contains a pigment other than carbon black, the content of all pigments including the carbon black is preferably in the preferred range of the carbon black content, It is preferable that the polymer content with respect to all the pigments including carbon black falls within the preferable range of the polymer content. In this case, in order to sufficiently obtain the effect of using the carbon black according to the present invention, the ratio of the carbon black according to the present invention in the total pigment is 50% by weight or more, particularly 70% by weight or more. preferable.

{Ink composition (recording liquid)}
The ink composition containing the aqueous pigment dispersion of the present invention exhibits an excellent effect particularly as a recording liquid, particularly an inkjet recording liquid.

  The ink composition of the present invention used as a recording liquid or the like (hereinafter referred to as “recording liquid of the present invention”) adjusts the color material concentration of the above-described aqueous pigment dispersion of the present invention as necessary, and further uses Depending on the conditions, various additives are added.

  As the coloring material, in addition to the carbon black and other pigments in the aqueous pigment dispersion liquid of the present invention described above, self-dispersing pigments, dyes, surfactants and polymers which have been surface-treated for purposes such as toning A pigment or a dye dispersed with a dispersant or the like may be additionally included.

  The concentration of all the color materials in the recording liquid of the present invention is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and the upper limit is 20% by weight, based on the total amount of the recording liquid. Hereinafter, it is preferably 15% by weight or less, particularly preferably 10% by weight or less. If the color material density is too high, the viscosity is increased and the discharge properties are deteriorated. If the color material density is too low, the print density is too low. On the other hand, the amount of the coloring material added to the aqueous pigment dispersion is usually 100 parts by weight or less, preferably 75 parts by weight or less, more preferably 100 parts by weight or less with respect to 100 parts by weight of the pigment containing carbon black in the aqueous pigment dispersion. 50 parts by weight or less, particularly preferably 25 parts by weight or less. When the additional amount of the coloring material is too large, the effect of the present invention is lowered.

  The solvent used in the recording liquid of the present invention preferably contains water and a water-soluble organic solvent, and can further contain other components as desired.

  The concentration of the water-soluble organic solvent in the recording liquid of the present invention may be appropriately selected and determined. Usually, it is preferably 1% by weight or more and 45% by weight or less, more preferably 40% by weight or less with respect to the recording liquid. In addition, the content of water in the recording liquid may be an amount that can appropriately set the concentration of the above-described coloring material, water-soluble organic solvent, and any additive component described below.

  As the water-soluble organic solvent, those exemplified as the aqueous medium of the aqueous pigment dispersion of the present invention described above can be used.

  The recording liquid of the present invention may contain various additives as necessary within the range not impairing the effects of the present invention.

  Examples of such additives include recording liquids such as penetration enhancers, surface tension modifiers, hydrotropic agents, pH adjusters, chelating agents, preservatives, viscosity modifiers, humectants, antifungal agents, and rust inhibitors. Known additives can be used.

  The content of these additives in the recording liquid of the present invention is preferably 40% by weight or less in total, based on the total amount of the recording liquid.

  Examples of penetration enhancers include lower alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol and pentanol, carbitols such as ethylene glycol monobutyl ether and triethylene glycol monobutyl ether glycol ether, and surfactants 1 A seed | species or 2 or more types is mentioned.

  As the surfactant, any one or more of nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants and the like can be used. Can be used. Of these, nonionic surfactants, anionic surfactants and polymer surfactants are preferred.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid Examples thereof include esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, acetylene glycols, and acetylene alcohols.

  Examples of the anionic surfactant include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether sulfonates, alkyl phosphates, polyoxyethylene alkyl sulfates. Examples include ester salts, polyoxyethylene alkylaryl sulfate esters, alkane sulfonates, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl phosphates, α-olefin sulfonates, and the like.

  Polymeric surfactants include polyacrylic acid, styrene / acrylic acid copolymer, styrene / acrylic acid / acrylic acid ester copolymer, styrene / maleic acid copolymer, styrene / maleic acid / acrylic acid ester copolymer, styrene / methacrylic acid. Examples include copolymers, styrene / methacrylic acid / acrylic acid ester copolymers, styrene / maleic acid half ester copolymers, styrene / styrene sulfonic acid copolymers, vinyl naphthalene / maleic acid copolymers, vinyl naphthalene / acrylic acid copolymers, and salts thereof.

  Examples of the cationic surfactant include, but are not limited to, tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like.

  In addition, silicone surfactants such as polysiloxane oxyethylene adducts, fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, oxyethylene perfluoroalkyl ethers, rhamnolipids, lysolecithins, etc. Surfactants such as biosurfactants can also be used.

  Among these surfactants, nonionic surfactants are preferable, and among them, acetylene glycols from the viewpoint of printing quality such as suppression of bleeding of printed matter, and improvement of ejection stability of recording liquid, Acetylene alcohols are more preferred, and acetylene glycols are particularly preferred. Examples of acetylene glycols include 2,5-dimethyl-3-hexyne-2,5-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 3,6-dimethyl. -4-octyne-3,6-diol and their ethylene oxide adducts and the like. Specific product names include, for example, Orphin E1010, Orphine STG, Orphin E1004, Surfinol 104, Surfinol 420, Surfy Nord 440, Surfynol 465, Surfynol 485 (all manufactured by Air Products, Inc.), acetylenol EH, acetylenol EL, acetylenol EO (all manufactured by Kawaken Fine Chemical Co., Ltd.) can be used.

  The content of these surfactants may be appropriately selected and determined. Usually, by adding in the range of 0.001 wt% or more and 5 wt% or less with respect to the recording liquid, the quick drying property and the print quality of the printed matter can be further improved.

  Examples of the surface tension adjusting agent include one or more alcohols such as diethanolamine, triethanolamine, glycerin, and diethylene glycol, nonions, cations, anions, and amphoteric surfactants.

  As the hydrotropic agent, one or more of urea, alkylurea, ethyleneurea, propyleneurea, thiourea, guanidate, tetraalkylammonium halide and the like are preferable.

  As a humectant, 1 type (s) or 2 or more types, such as glycerol and diethylene glycol, can also be added as what also serves as a water-soluble organic solvent.

  Furthermore, a solid moisturizing agent (a water-soluble substance having a water retaining function and solid at 25 ° C.) can be added. Preferred solid humectants include saccharides, sugar alcohols, hyaluronate, trimethylolpropane, 1,2,6-triol and the like. Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Specifically, glucose, fructose, ribose, xylose, arabinose, galactose, sorbit, maltose, and lactose. , Sucrose, trehalose and the like. Examples of sugar alcohols include maltitol, sorbitol, xylitol and the like, and these solid moisturizers may be used alone or in combination of two or more.

  Although it does not specifically limit as a chelating agent, 1 type (s) or 2 or more types, such as a sodium salt of ethylenediaminetetraacetic acid, a diammonium salt of ethylenediaminetetraacetic acid, are used. These are preferably used in the range of 0.005 wt% or more and 0.5 wt% or less with respect to the recording liquid.

  The antifungal agent is not particularly limited, but sodium dehydroacetate, dichlorophen, sorbic acid, sodium benzoate, p-hydroxybenzoate, 1,2-benzisothiazolin-3-one (product name: Proxel GXL (manufactured by Arch Chemicals) or the like is used. These are preferably contained in the range of 0.05% by weight or more and 1% by weight or less with respect to the recording liquid.

Further, in order to adjust the pH of the recording liquid and obtain the stability of the recording liquid, it is not particularly limited, but sodium hydroxide, potassium hydroxide, lithium hydroxide, nitric acid, ammonia, diethanolamine, triethanolamine, etc. PH adjusters and buffer solutions such as phosphoric acid can be used.
The pH of the recording liquid is usually in a neutral to alkaline range, and it is preferable to adjust to about pH 6-11.

  Further, the recording liquid of the present invention may contain a resin other than the above-mentioned hydrophobic / hydrophilic polymer and polymer (I) as long as the effects of the present invention are not impaired. Specific examples of such resins include vinyl resins such as acrylic resins, styrene-acrylic resins, polyvinyl alcohol resins, vinyl acetate resins, polyester resins, polyamide resins, polyurethane resins, epoxy resins, and butadiene. Well-known resins such as resin, petroleum resin and fluorine resin can be used. Among these, water-soluble or water-dispersible resins are preferable. Of these, polyvinyl alcohol resins and acrylic resins are more preferable.

  In the recording liquid of the present invention, the content of all polymers is usually 0.05% by weight or more, preferably 0.25% by weight or more, more preferably 0.5% by weight or more, and the upper limit is usually 20% by weight. % Or less, preferably 10% by weight or less.

  In particular, when the hydrophobic / hydrophilic polymer and the polymer (I) are used in combination, these are the same ratios as in the case where the aqueous pigment dispersion of the present invention includes the hydrophobic / hydrophilic polymer and the polymer (I). It is preferable that it is contained.

In addition, polymer fine particles may be added to the aqueous pigment dispersion of the present invention in order to further improve the fixability and abrasion resistance of the image on the recording medium. The polymer fine particles are not particularly limited, but those having an ionic group on the surface and a particle diameter of 10 to 150 nm are preferable.
The amount of the polymer fine particles used may be appropriately selected and determined within a range that does not impair the effects of the present invention. % By weight, more preferably 10 to 50% by weight.

{Aqueous pigment dispersion and method for producing ink composition}
In the method for producing an aqueous pigment dispersion of the present invention, the mixing method and the order of addition of a pigment containing carbon black, an aqueous medium, a polymer as a pigment dispersant, and the like are arbitrary. For example, a dispersion process may be performed on a mixture obtained by mixing these at once using a general disperser.

  In this dispersion treatment, it is preferable to perform the dispersion treatment using only water as an aqueous medium from the viewpoint of dispersibility and storage stability of the recording liquid.

  As the disperser used for the dispersion treatment, various dispersers that are generally used for pigment dispersion can be used.

  The disperser is not particularly limited, and a paint shaker, ball mill, sand mill, attritor, pearl mill, coball mill, homomixer, homogenizer, wet jet mill, ultrasonic homogenizer, and the like can be used. Glass beads, zirconia beads, alumina beads, magnetic beads, and styrene beads can be used for those using media as a disperser. Among these, a particularly preferable dispersion treatment method is a method in which beads are dispersed with a mill using a medium and then dispersed with an ultrasonic homogenizer.

A method for obtaining an aqueous pigment dispersion having a preferable particle size is not particularly limited, but the size of the dispersion medium of the disperser is reduced, the filling rate of the grinding media is increased, and the pigment concentration in the dispersion is increased. For example, a method such as increasing the processing time, extending the processing time, or classifying with a filter or a centrifuge after pulverization is used. Or the combination of those methods is mentioned. Although not particularly specified, when the dispersion thickens due to heat generation during dispersion, it is desirable to disperse while cooling, and when the particle size drop during dispersion due to heat is significant It is desirable to disperse at a high temperature.
The obtained dispersion is preferably subjected to pressure filtration using a filter or centrifugal separation for the purpose of removing coarse particles as necessary.

  As described above, the ink composition of the present invention is prepared by adding a coloring material and various additives as necessary to the aqueous pigment dispersion thus prepared, followed by mixing and dispersing in the same manner. .

[Solvent pigment dispersion and ink composition]
Next, the solvent type pigment dispersion of the present invention containing carbon black as described above and the ink composition containing the same will be described.

{Dispersant}
In the solvent-based pigment dispersion, an anionic, cationic or nonionic known polymer dispersant is used as a pigment dispersant as required. Examples of known polymer dispersants include commercially available products such as “Solsperse” series manufactured by Nippon Lubrizol Corporation, “Ajisper” series manufactured by Ajinomoto Fine Techno Co., Ltd., and “Disperbyk” series manufactured by Big Chemie Japan Co., Ltd. Only one type of pigment dispersant may be used, or a plurality of types may be used in combination.

{solvent}
Solvent pigment dispersions include alcohols, ketones, esters, glycol ethers, glycol acetates, saturated hydrocarbons, unsaturated hydrocarbons, and cyclic saturated carbons commonly used in inkjet inks. Organic solvents such as hydrogen, cyclic unsaturated hydrocarbons, and aromatic hydrocarbons can be widely used.

Specific examples of the organic solvent include the following.
Alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol;
Acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl isopropyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, methyl isoamyl ketone, diethyl ketone, ethyl-n-propyl ketone, ethyl isopropyl ketone, ethyl Ketones such as n-butyl ketone, ethyl isobutyl ketone, di-n-propyl ketone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, isophorone;
Esters such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, hexyl acetate, octyl acetate, methyl lactate, propyl lactate, butyl lactate;
Ethylene glycol, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene Glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl Ether, dipropylene glycol dipropyl ether, glycol and glycol ethers such as tripropylene glycol monomethyl ether;
Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol Glycol acetates such as monobutyl ether acetate and dipropylene glycol monomethyl ether acetate;
saturated hydrocarbons such as n-hexane, isohexane, n-nonane, isononane, dodecane, isododecane;
Unsaturated hydrocarbons such as 1-hexene, 1-heptene, 1-octene;
Cyclic saturated hydrocarbons such as cyclohexane, cycloheptane, cyclooctane, cyclodecane, decalin;
Cyclic unsaturated hydrocarbons such as cyclohexene, cycloheptene, cyclooctene, 1,1,3,5,7-cyclooctatetraene, cyclododecene, and aromatic hydrocarbons such as benzene, toluene, xylene, etc.

  These organic solvents may be used alone or in combination of two or more.

{Other color materials}
Similarly to the aqueous pigment dispersion, the solvent-based pigment dispersion may contain a color material other than carbon black. In this case, as the other color material, those exemplified in the section of the aqueous pigment dispersion are used. be able to.

{Solvent pigment dispersion composition}
The solvent-based pigment dispersion of the present invention contains at least the specific carbon black that satisfies the PAH amount and oxygen-containing functional group density, the dispersant and the solvent, and may contain other components as necessary. Good.

  The carbon black concentration in the solvent-based pigment dispersion is usually 50% by weight or less, preferably 30% by weight or less. Here, if the carbon black concentration is too high, the carbon black becomes poorly dispersed, the viscosity of the dispersion increases, the dispersion becomes gelled, and the dispersion may not be usable due to dispersion failure. If the carbon black concentration is too low, a sufficient printing density will not be obtained when ink is formed, and it is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more.

  The amount of the dispersant in the solvent-based pigment dispersion is usually 0.1% by weight or more, preferably 1% by weight or more, and usually 200% by weight or less, preferably 100% by weight as the content of the dispersant with respect to carbon black. It is as follows. If the amount of the dispersant is too small, sufficient dispersibility cannot be obtained, and if it is too large, the viscosity of the dispersion may be increased or the stability of the dispersion may be deteriorated.

  The solvent-based pigment dispersion of the present invention may contain components other than the solvent, carbon black, and dispersant, and in particular, as other additives that can be contained in the ink composition as described later. Other components exemplified may be included.

  In addition, when the solvent-based pigment dispersion of the present invention contains a pigment other than carbon black, it is preferable that the content of all pigments including the carbon black is within a preferable range of the carbon black content. It is preferable that the content of the dispersant with respect to all the pigments including carbon black falls within the preferable range of the dispersant content. In this case, in order to sufficiently obtain the effect of using the carbon black according to the present invention, the ratio of the carbon black according to the present invention in the total pigment is 50% by weight or more, particularly 70% by weight or more. preferable.

{Ink composition (recording liquid)}
The ink composition containing the solvent-based pigment dispersion of the present invention exhibits excellent effects particularly as a recording liquid, particularly an inkjet recording liquid.

  The ink composition of the present invention used as a recording liquid or the like is prepared by adjusting the color material concentration of the above-described solvent-based pigment dispersion of the present invention as necessary, and further adding various additives depending on the application. The

  As the coloring material, in addition to carbon black and other pigments in the solvent-based pigment dispersion of the present invention described above, self-dispersing pigments surface-treated for purposes such as toning, dyes, surfactants, A pigment or a dye dispersed with a polymer dispersant or the like may be additionally contained.

  Examples of the ink composition containing the solvent-based pigment dispersion include surfactants, binders, bactericides, fungicides, algicides, sequestering agents, buffers, corrosion inhibitors, and light stabilizers. , Anti-curling agents, thickening agents, and / or other additives, etc., may optionally include one or more other materials.

  The concentration of all the color materials in the ink composition containing the solvent-based pigment dispersion is preferably 0.1% by weight or more, and more preferably 0.5% by weight or more, based on the total amount of the ink composition. The upper limit is 20% by weight or less, preferably 15% by weight or less, and particularly preferably 10% by weight or less. If the color material density is too high, the viscosity is increased and the discharge properties are deteriorated. If the color material density is too low, the print density is too low. On the other hand, the amount of the coloring material added to the solvent-based pigment dispersion is usually 100 parts by weight or less, preferably 75 parts by weight or less, with respect to 100 parts by weight of the pigment containing carbon black in the solvent-based pigment dispersion. The amount is preferably 50 parts by weight or less, particularly preferably 25 parts by weight or less. When the additional amount of the coloring material is too large, the effect of the present invention is lowered.

  The solvent used in the ink composition containing the solvent-based pigment dispersion preferably includes the solvent contained in the solvent-based pigment dispersion described above, and may further include other components as desired.

  The solvent concentration in the ink composition containing the solvent-based pigment dispersion may be appropriately selected and determined, but is usually 1% by weight or more and 45% by weight or less, particularly 40% by weight or less based on the ink composition. It is preferable.

{Production method of solvent-based pigment dispersion and ink composition}
In the method for producing a solvent-based pigment dispersion of the present invention, the mixing method and the order of addition of a pigment containing carbon black, a solvent, a pigment dispersant and the like are arbitrary. For example, a mixture obtained by mixing these at once may be subjected to a dispersion treatment using a general disperser, and the dispersion treatment method is the same as in the aqueous pigment dispersion of the present invention.

  As described above, the ink composition containing the solvent-based pigment dispersion of the present invention is mixed in the same manner by adding colorants and various additives as necessary to the solvent-based pigment dispersion prepared as described above. It is prepared by dispersion treatment.

[UV pigment dispersion and ink composition]
Next, the UV pigment dispersion of the present invention containing carbon black as described above and the ink composition containing the same will be described.

{Dispersant}
In the UV pigment dispersion, known anionic, cationic, or nonionic polymer dispersants are used as pigment dispersants as required. Examples of known polymer dispersants include commercially available products such as “Solsperse” series manufactured by Nippon Lubrizol Corporation, “Ajisper” series manufactured by Ajinomoto Fine Techno Co., Ltd., and “Disperbyk” series manufactured by Big Chemie Japan Co., Ltd. Only one type of pigment dispersant may be used, or a plurality of types may be used in combination.

{Solvent: Polymerizable monomer}
In the UV pigment dispersion, a polymerizable monomer serves as a dispersion medium, that is, a solvent.

  As the polymerizable monomer, a radical polymerizable monomer or a cationic polymerizable monomer is used depending on the curing method after printing.

  As the radical polymerizable monomer, known ones are used, and specific examples include the following.

  Butanediol monoacrylate, N, N-dimethylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, 2-methoxyethyl acrylate, N-vinylcaprolactam, N-vinylpyrrolidone, acryloylmorpholine, N-vinylformamide, cyclohexyl acrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, glycidyl acrylate, isobornyl acrylate, isodecyl acrylate, phenoxy methacrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, 2-phenoxyethyl acrylate, 2-hydroxypropyl acrylate 4-hydroxybutyl acrylate, isobut Acrylate, t-butyl acrylate, isooctyl acrylate, isobornyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, 3-methoxybutyl acrylate, benzyl acrylate, ethoxyethoxyethyl acrylate, butoxyethyl Monofunctional monomers such as acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, methylphenoxyethyl acrylate, dipropylene glycol acrylate;

  Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, ethoxylated 1,6-hexanediol diacrylate, propoxylated 1, 6-hexanediol diacrylate, neopentyl glycol di (meth) acrylate, ethoxylated neopentyl glycol di (meth) acrylate, propoxylated neopentyl glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di Acrylate, 1,4-butanediol di (meth) acrylate, 1,9-nonanediol diacrylate, tetraethylene glycol diacrylate, 2-n-buty -2-ethyl-1,3-propanediol diacrylate, dimethylol-tricyclodecane diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, 1,3-butylene glycol di (meth) acrylate, ethoxylated bisphenol A di (meta ) Bifunctional monomers such as acrylate, propoxylated bisphenol A di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, dimethylol dicyclopentane diacrylate;

  Trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, tetramethylolpropane triacrylate, tetramethylolmethane triacrylate, caprolactone modified trimethylolpropane triacrylate, ethoxylated isocyania Trifunctional monomers such as nuric acid triacrylate, tri (2-hydroxyethyl isocyanurate) triacrylate, propoxylate glyceryl triacrylate and the like:

  These radically polymerizable monomers may be used alone or in combination of two or more as necessary.

  Known cationic polymerizable monomers are used, and specific examples include the following.

  Ethylene glycol monovinyl ether, triethylene glycol monovinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol Monovinyl ether compounds such as monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, monofunctional alicyclic epoxy, monofunctional oxetane Monofunctional monomer;

  Bifunctional cycloaliphatic epoxy such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol divinyl ether A bifunctional monomer such as a bifunctional oxetane;

  Trifunctional monomers such as trimethylolpropane trivinyl ether, trifunctional alicyclic epoxy, trifunctional oxetane:

  These cationically polymerizable monomers may be used alone or in combination of two or more as necessary.

{Other color materials}
Similarly to the aqueous pigment dispersion, the UV pigment dispersion may contain a color material other than carbon black. In this case, as the other color material, those exemplified in the section of the aqueous pigment dispersion are used. be able to.

{UV pigment dispersion composition}
The UV pigment dispersion of the present invention contains at least the specific carbon black satisfying the above-mentioned PAH amount and oxygen-containing functional group density, the above-mentioned dispersant and solvent (polymerizable monomer), and other components as necessary. May be included.

  The carbon black concentration of the UV pigment dispersion is usually 50% by weight or less, preferably 30% by weight or less. Here, if the carbon black concentration is too high, the carbon black becomes poorly dispersed, the viscosity of the dispersion increases, the dispersion becomes gelled, and the dispersion may not be usable due to dispersion failure. If the carbon black concentration is too low, a sufficient printing density will not be obtained when ink is formed, so that it is usually at least 0.1% by weight, preferably at least 0.5% by weight, more preferably at least 1% by weight.

  The amount of the dispersant in the UV pigment dispersion is usually 0.1% by weight or more, preferably 1% by weight or more, and usually 200% by weight or less, preferably 100% by weight as the content of the dispersant with respect to carbon black. It is as follows. If the amount of the dispersant is too small, sufficient dispersibility cannot be obtained, and if it is too large, the viscosity of the dispersion may increase and the stability of the dispersion may be deteriorated.

  The UV pigment dispersion of the present invention may contain components other than a solvent (polymerizable monomer), carbon black, and a dispersant, and in particular, may be contained in an ink composition as described later. Other components exemplified as other additives may be contained.

  Further, when the UV pigment dispersion liquid of the present invention contains a pigment other than carbon black, it is preferable that the content of all pigments including the carbon black is within the preferable range of the carbon black content. Moreover, it is preferable that the content of the dispersant with respect to all the pigments including carbon black falls within the preferable range of the dispersant content. In this case, in order to sufficiently obtain the effect of using the carbon black according to the present invention, the ratio of the carbon black according to the present invention in the total pigment is 50% by weight or more, particularly 70% by weight or more. preferable.

{Ink composition (recording liquid)}
The ink composition containing the UV pigment dispersion of the present invention exhibits excellent effects particularly as a recording liquid, particularly an inkjet recording liquid.

  The ink composition of the present invention used as a recording liquid or the like is prepared by adjusting the color material concentration of the above-described UV pigment dispersion of the present invention as necessary, and further adding various additives depending on the application. The

  As the coloring material, in addition to carbon black and other pigments in the UV-based pigment dispersion liquid of the present invention described above, self-dispersing pigments surface-treated for purposes such as toning, dyes, surfactants, A pigment or a dye dispersed with a polymer dispersant or the like may be additionally contained.

The ink composition containing the UV pigment dispersion contains a polymerization initiator such as a photo radical polymerization initiator or a photo cationic polymerization initiator, depending on the curing method after printing.
Furthermore, for example, surfactants, binders, fungicides, fungicides, algicides, sequestering agents, buffers, corrosion inhibitors, light stabilizers, anti-curling agents, thickeners, and / or other One or more other materials, such as additives, may optionally be included.

  The concentration of all the color materials in the ink composition containing the UV pigment dispersion is preferably 0.1% by weight or more, more preferably 0.5% by weight or more as the concentration of all the color materials with respect to the total amount of the ink composition. The upper limit is 20% by weight or less, preferably 15% by weight or less, and particularly preferably 10% by weight or less. If the color material density is too high, the viscosity is increased and the discharge properties are deteriorated. If the color material density is too low, the print density is too low. On the other hand, the amount of the coloring material added to the UV pigment dispersion is usually 100 parts by weight or less, preferably 75 parts by weight or less, with respect to 100 parts by weight of the pigment containing carbon black in the UV pigment dispersion. The amount is preferably 50 parts by weight or less, particularly preferably 25 parts by weight or less. When the additional amount of the coloring material is too large, the effect of the present invention is lowered.

  The solvent used in the ink composition containing the UV pigment dispersion preferably contains the solvent contained in the UV pigment dispersion described above, and may further contain other components as desired.

  The concentration of the solvent in the ink composition containing the UV pigment dispersion may be appropriately selected and determined, but is usually 1% by weight to 45% by weight, particularly 40% by weight or less based on the ink composition. It is preferable.

{Method for producing UV pigment dispersion and ink composition}
In the method for producing a UV pigment dispersion of the present invention, the mixing method and the order of addition of a pigment containing carbon black, a solvent (polymerizable monomer), a pigment dispersant and the like are arbitrary. For example, a mixture obtained by mixing these at once may be subjected to a dispersion treatment using a general disperser, and the dispersion treatment method is the same as in the aqueous pigment dispersion of the present invention.

  As described above, the ink composition containing the UV pigment dispersion of the present invention is obtained by adding a polymerization initiator and, if necessary, a coloring material and various additives to the UV pigment dispersion thus prepared. Similarly, it is prepared by mixing and dispersing.

  Hereinafter, the present invention will be described more specifically with reference to synthesis examples, examples, and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

In the following examples, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of anionic random copolymers A to E were measured under the following conditions using gel permeation chromatography (GPC).
Column filler: Styrene-divinylbenzene copolymer Solvent: Tetrahydrofuran Flow rate: 0.7 mL / min
Temperature: 40 ° C
Calibration was performed using polystyrene.
In addition, this time, it measured using the following apparatuses, detectors, and columns.
Apparatus: Waters 2690 manufactured by Nippon Waters Co., Ltd.
Detector: Waters 2410 manufactured by Nippon Waters Co., Ltd.
Column: Shodex GPC KF-604 made by Showa Denko KK
KF-603 ・ KF-602.5

The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the cation random copolymers a and b were measured under the following conditions using gel permeation chromatography (GPC).
Column filler: Styrene-divinylbenzene copolymer Solvent: Dimethyl sulfoxide (including 50 mM LiBr (lithium bromide))
Flow rate: 0.27 mL / min
Temperature: 50 ° C
Calibration was performed using polyethylene glycol.
In addition, this time, it measured using the following apparatuses, a detector, and a column, and the calibration was performed using the thing by Polymer Laboratories.
Apparatus: Waters 2695 manufactured by Nippon Waters Co., Ltd.
Detector: Waters 2414 manufactured by Nippon Waters Co., Ltd.
Column: Shodex GPC KF-G, KF-604, manufactured by Showa Denko KK
KF-603

The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the anionic random copolymer F and the block copolymer X were measured under the following conditions using gel permeation chromatography (GPC).
Column packing: Polyhydroxymethacrylate Solvent: Water / acetonitrile
(70/30 (v / v), 0.2 M Tris-HCl buffer, 0.1 M
(Including KCl)
Flow rate: 0.7 mL / min
Temperature: 40 ° C
Calibration was performed using polyethylene glycol.
In addition, this time, it measured using the following apparatuses, detectors, and columns.
Apparatus: Waters 2695 manufactured by Nippon Waters Co., Ltd.
Detector: Waters 2410 manufactured by Nippon Waters Co., Ltd.
Column: Shodex OHpak manufactured by Showa Denko KK
SB-G / SB-804HQ / SB-803HQ / SB-802.5HQ

Moreover, the structure of the obtained random polymer was confirmed by ¹ H-NMR, and the composition ratio of the monomer constitutional unit was calculated from NMR data.
In the following notation, “co” means “co” of copolymer, and “b” means “block” of blockcopolymer.

[Polymer synthesis]
Examples of the synthesis of polymers used as pigment dispersants in Examples and Comparative Examples are shown below.

<Synthesis Example 1>
Synthesis of poly (styrene-co-n-butyl acrylate-co-sodium acrylate) (anionic random copolymer A) As a polymerization initiator in a condenser equipped with nitrogen inside, a nitrogen introduction tube, a stirrer and a flask equipped with a thermometer 30 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was charged, 3500.0 g of tetrahydrofuran as a solvent, 600.0 g of acrylic acid, 600.0 g of n-butyl acrylate, and 400.0 g of styrene as monomers. . The bath temperature was raised from room temperature to 70 ° C. over 1 hour, and the polymerization reaction was carried out at 70 ° C. for 8 hours.

  After completion of the reaction, the reaction solution was cooled to room temperature, neutralized with a sodium hydroxide / methanol solution, and precipitated in isopropyl alcohol. The precipitate was filtered and vacuum dried to obtain a mixture of poly (styrene-co-n-butyl acrylate-co-sodium acrylate): anionic random copolymer A and sodium acrylate. This anionic random copolymer A had a number average molecular weight (Mn) of 11,000, a weight average molecular weight (Mw) of 18000, and a molecular weight distribution (Mw / Mn) of 1.6.

  After 30.0 g of the mixture of the anionic random copolymer A and sodium acrylate was dissolved in 970.0 g of water, sodium acrylate was removed by ultrafiltration membrane treatment. After removing sodium acrylate, the aqueous polymer solution was concentrated and dried to obtain the anionic random copolymer A.

The structure of the anionic random copolymer A was confirmed by ¹ H-NMR using heavy water as a solvent. / 21/47 (molar ratio) = 32/26/42 (weight ratio).

  The anionic random copolymer A was in a state in which almost all of the carboxylic groups, which are ionic groups, were neutralized by the above-described process. When an aqueous solution having a concentration of 13.14% by weight was prepared, it was colorless and transparent at 25 ° C.

<Synthesis Example 2>
Synthesis of polyvinyl alcohol-b-poly (sodium acrylate-co-methyl acrylate-co-sodium methacrylate-co-benzyl methacrylate-co-styrene) (block copolymer X)

  A condenser with nitrogen inside, a nitrogen inlet tube, a stirrer, and a flask equipped with a thermometer were charged with 3587 g of vinyl acetate, 1907 g of chloroform as a chain transfer agent and a solvent, and heated to 70 ° C. over 1 hour. Next, a polymerization initiator solution in which 0.3 g of azobis (2-methylbutyronitrile) as a polymerization initiator was dissolved in 534 g of chloroform was dropped over 6 hours. Thereafter, a polymerization initiator solution in which 0.5 g of azobis (2-methylbutyronitrile) as a polymerization initiator was dissolved in 444.5 g of chloroform was dropped over 5 hours. After dropwise addition of the polymerization initiator solution, the mixture was heated and polymerized for 10 hours under reflux conditions. After completion of the reaction, 0.01N sodium hydroxide / methanol solution was continuously added dropwise to the reaction solution, and unreacted vinyl acetate and chloroform were distilled off under reduced pressure at an internal temperature of 40 ° C. 74% by weight). This polyvinyl acetate had a number average molecular weight (Mn) of 3,500, a weight average molecular weight (Mw) of 8400, and a molecular weight distribution (Mw / Mn) of 2.4.

The terminal structure of the polyvinyl acetate was —CCl ₃ . This is because, in ¹ H-NMR (solvent CDCl ₃ ), a peak of a methylene group (peak of chemical shift δ = 2.8 to 3.2) was observed adjacent to the end of this polyvinyl acetate, Based on the fact that the number average molecular weight (Mn) (3500) calculated by using -CCl ₃ as the terminal structure and the number average molecular weight (Mn) obtained from GPC coincide with each other, this is a group in which one end is quantitatively halogen-substituted. It was confirmed that polyvinyl acetate having (—CCl ₃ ) could be synthesized.

  Next, in a condenser with a nitrogen-substituted condenser, a nitrogen introducing tube, a stirrer and a thermometer, 17 g of methanol as a solvent and 1048.5 g of isopropyl alcohol, 2623 g of methyl acrylate, 2142 g of benzyl methacrylate, and 63 of styrene 63 0.5 g and 1353 g of the above-mentioned polyvinyl acetate methanol solution as a macroinitiator were charged, and the temperature was raised from room temperature to 60 ° C. over 1 hour. When the internal temperature reached 60 ° C., a catalyst solution in which 0.6 g of cuprous bromide as a catalyst and 12.0 g of tris (2-dimethylamino) ethylamine as a ligand were dissolved in 30 g of methanol was added. After addition of the catalyst solution, the mixture was heated and polymerized for 30 hours under reflux conditions.

The number average molecular weight (Mn) of the obtained polymer increased with the lapse of the polymerization reaction time.
Table 1 shows the molar ratio of each monomer constituent unit of methyl acrylate (MA), benzyl methacrylate (BzMA), and styrene (St) in the polymer, calculated from gas chromatography and calculated from the monomer consumption in the polymerization solution. Shown in

  As is clear from Table 1, the composition of the block copolymer linked with polyvinyl acetate changes with an increase in its number average molecular weight (Mn), and the monomer composition in this block copolymer changes toward the end ( Gradient was confirmed to be polyvinyl acetate-b-poly (methyl acrylate-co-benzyl methacrylate-co-styrene). The polymer had a number average molecular weight (Mn) of 16,300, a weight average molecular weight (Mw) of 26600, and a molecular weight distribution (Mw / Mn) of 1.63. In this polyvinyl acetate block copolymer, the linking group connecting the polyvinyl acetate block and the other block is a dichloromethylene group.

Next, in a reactor equipped with a condenser, a stirrer and a thermometer, the above polymerization solution 502 g was dissolved in a mixed solvent of 276 g of methanol, 552 g of tetrahydrofuran and 138 g of water, and then the temperature was raised to 60 ° C. and 728 g of 5N sodium hydroxide was added. The reaction was performed at 65 ° C. for 7 hours. After completion of the reaction, 550 g of tetrahydrofuran (THF) and 140 g of water were added to the polymer mass obtained by removing the supernatant and suspended, and then 280 g of methanol was added to precipitate the polymer. The supernatant was removed again, 300 g of water was added, neutralized with acetic acid, the solution was heated to 90 ° C., and the remaining THF and methanol were distilled off to obtain an aqueous polymer solution. Thereafter, impurities were removed from the aqueous polymer solution using an ultrafiltration membrane (ACP-1050, manufactured by Asahi Kasei Corporation). Polyvinyl alcohol-b-poly (sodium acrylate-co-methyl acrylate-co-methacrylic acid) in which the copolymer linked to the polyvinyl alcohol block is a gradient copolymer by concentrating and drying the polymer aqueous solution after ultrafiltration Sodium-co-benzyl methacrylate-co-styrene) (block copolymer X) was obtained.
In this block copolymer X, the linking group linking the polyvinyl alcohol block and the other block is one in which some or all of the chlorine atoms in the linking group (dichloromethylene group) described above are replaced with hydrogen atoms.

The structure of the block copolymer X was confirmed by ¹ H-NMR using heavy water as a solvent. The composition ratio of the vinyl alcohol constitutional unit, sodium acrylate constitutional unit, methyl acrylate constitutional unit, sodium methacrylate constitutional unit, benzyl methacrylate constitutional unit, and styrene constitutional unit in the block copolymer X determined by ¹ H-NMR is as follows: 25: 26: 21: 2: 21: 5 (molar ratio). The number average molecular weight (Mn) of the block copolymer X was 14000, the weight average molecular weight (Mw) was 22300, and the molecular weight distribution (Mw / Mn) was 1.59.

  Distilled water was added to the block copolymer X to obtain an aqueous solution having a polymer concentration of 10.0% by weight. At 25 ° C., the appearance of this aqueous solution was tan transparent.

<Synthesis Example 3>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (anionic random copolymer B) As a polymerization initiator in a condenser equipped with nitrogen, nitrogen introduction tube, stirrer and thermometer flask Charged 16.8 g of 2,2′-azobis (2,4-dimethylvaleronitrile), 1817.3 g of methanol as a solvent, 455.2 g of styrene as a monomer, methoxypolyethylene glycol acrylate (light acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) In the general formula (5), p = 9) 805.2 g and 49.0 g of acrylic acid were charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution obtained by dissolving 7.0 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 70 g of methanol was added to the reaction system, and a polymerization reaction was further performed for 6 hours.

  After completion of the reaction, the reaction solution is cooled to room temperature, 95.2 g of 5N sodium hydroxide aqueous solution is added with stirring, and then deionized water is added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. It was. After removing impurities from the crude polymer aqueous solution by ultrafiltration membrane treatment, the polymer aqueous solution is concentrated and dried, and water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): anionic random copolymer B Got. This anionic random copolymer B had a number average molecular weight (Mn) of 10,000, a weight average molecular weight (Mw) of 19000, and a molecular weight distribution (Mw / Mn) of 1.9.

The structure of the anionic random copolymer B was confirmed by ¹ H-NMR using d-DMSO (dimethyl sulfoxide) as a solvent. As a result, the styrene structural unit, methoxypolyethylene glycol acrylate structural unit, and sodium acrylate structural unit in the random copolymer B were obtained. The composition ratio was 61/20/19 (molar ratio) = 36/54/10 (weight ratio).

  The anionic random copolymer B was in a state in which 70 mol% of carboxyl groups as ionic groups were neutralized by the above-described process, and when an aqueous solution having a concentration of 10.5 wt% was prepared, it was colorless and transparent at 25 ° C. .

<Synthesis Example 4>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (anionic random copolymer C) As a polymerization initiator in a condenser equipped with nitrogen inside, a nitrogen inlet tube, a stirrer and a flask equipped with a thermometer Charged 16.9 g of 2,2′-azobis (2,4-dimethylvaleronitrile), 1834.8 g of methanol as a solvent, 272.4 g of styrene as a monomer, methoxypolyethylene glycol acrylate (light acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) ) 1009.9 g and 37.7 g of acrylic acid were charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution prepared by dissolving 7.0 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 70.0 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 6 hours. .

  After completion of the reaction, the reaction solution is cooled to room temperature, 86.8 g of 5N aqueous sodium hydroxide solution is added with stirring, and then deionized water is added while removing methanol with an evaporator to obtain a crude aqueous polymer solution. It was. After removing impurities from the crude polymer aqueous solution by ultrafiltration membrane treatment, the polymer aqueous solution is concentrated and dried, and water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): anionic random copolymer C Got. This anionic random polymer C had a number average molecular weight (Mn) of 11,000, a weight average molecular weight (Mw) of 20700, and a molecular weight distribution of (Mw / Mn) of 1.9.

The structure of the anionic random copolymer C was confirmed by ¹ H-NMR using d-DMSO (dimethyl sulfoxide) as a solvent. As a result, the styrene structural unit, methoxypolyethylene glycol acrylate structural unit, and sodium acrylate structural unit in the random copolymer C were obtained. The composition ratio was 57/33/10 (molar ratio) = 26/70/4 (weight ratio).

  Anionic random copolymer C was in a state in which 83 mol% of carboxyl groups as ionic groups had been neutralized by the above-described process, and an aqueous solution having a concentration of 13.1 wt% was prepared and was colorless and transparent at 25 ° C. .

<Synthesis Example 5>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (anionic random copolymer D) As a polymerization initiator in a condenser equipped with nitrogen inside, a nitrogen introduction tube, a stirrer and a flask equipped with a thermometer 3.7 g of 2,2′-azobis (2,4-dimethylvaleronitrile) is charged, 422.4 g of methanol as a solvent, 101.5 g of styrene as a monomer, methoxypolyethylene glycol acrylate (Light acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) ) 378.7 g and 14.2 g acrylic acid. The bath temperature was raised from room temperature to 70 ° C. over 50 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution prepared by dissolving 1.7 g of 2,2′-azobis (2,4-dimethylvaleronitrile), which is a polymerization initiator, in 16.5 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 6 hours. .

  After completion of the reaction, the reaction solution was cooled to room temperature, 32.7 g of 5N sodium hydroxide aqueous solution was added with stirring, and then deionized water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. It was. After removing impurities from the crude polymer aqueous solution by ultrafiltration membrane treatment, the polymer aqueous solution is concentrated and dried, and water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): anionic random copolymer D Got. This anionic random copolymer D had a number average molecular weight (Mn) of 18,600, a weight average molecular weight (Mw) of 33,000, and a molecular weight distribution of (Mw / Mn) of 1.8.

The structure of the anionic random copolymer D was confirmed by ¹ H-NMR using d-DMSO (dimethyl sulfoxide) as a solvent. As a result, the styrene structural unit, methoxypolyethylene glycol acrylate structural unit, and sodium acrylate structural unit in the random copolymer D were obtained. The composition ratio was 60/35/5 (molar ratio) = 26/72/2 (weight ratio).

  The anionic random copolymer D was in a state in which 83 mol% of the carboxyl groups which are ionic groups were neutralized by the above-described process, and when an aqueous solution having a concentration of 18.3% by weight was prepared, it was colorless and transparent at 25 ° C. .

<Synthesis Example 6>
Synthesis of poly (styrene-co-2-hydroxyethylacrylamide-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (anionic random copolymer E) with condenser, nitrogen inlet tube, stirrer and thermometer inside Was charged with 3.85 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator, methanol 416 g as a solvent, 63.04 g of styrene as a monomer, 43.50 g of 2-hydroxyethylacrylamide, 182.55 g of methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) and 10.90 g of acrylic acid were charged into the flask. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and after performing a polymerization reaction at 70 ° C. for 5 hours, 1.60 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator. A solution prepared by dissolving 14 g of methanol in 14 g of methanol was added to the reaction system, and a polymerization reaction was further performed for 3 hours.

  After completion of the reaction, the reaction solution was cooled to room temperature, 28.70 g of 5N sodium hydroxide aqueous solution was added with stirring, and then deionized water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. It was. After removing impurities from the crude polymer aqueous solution by ultrafiltration membrane treatment, the polymer aqueous solution is concentrated and dried to poly (styrene-co-2-hydroxyethylacrylamide-co-methoxypolyethylene glycol acrylate-co-sodium acrylate). : Anionic random copolymer E was obtained. This anionic random polymer E had a number average molecular weight (Mn) of 10,300, a weight average molecular weight (Mw) of 19,500, and a molecular weight distribution of 1.9.

The structure of the anionic random copolymer E was confirmed by ¹ H-NMR using heavy water as a solvent. As a result, the styrene structural unit, 2-hydroxyethylacrylamide structural unit, methoxypolyethylene glycol acrylate structural unit, sodium acrylate in the random copolymer E The compositional ratio of the structural units was 50/13/24/13 (molar ratio) = 27/8/59/6 (weight ratio).

  Anionic random copolymer E was in a state in which 95 mol% of carboxyl groups as ionic groups had been neutralized by the above-described process, and an aqueous solution having a concentration of 26.4% by weight was prepared and was colorless and transparent at 25 ° C. .

<Synthesis Example 7>
Synthesis of poly (styrene-co-2-methacryloyloxyethyltrimethylammonium chloride) (cationic random copolymer a)
2.76 g of 2,2′-azobisisobutyronitrile as a polymerization initiator was charged into a separable flask equipped with a nitrogen-substituted condenser, a nitrogen introducing tube, a stirrer, and a thermometer, and then a solvent as a solvent. Mix A-11 (mixed solvent of ethanol 85.5 wt% methanol 13.4 wt% IPA (isopropyl alcohol) 1.1 wt%, manufactured by Nippon Alcohol Sales Co., Ltd.) 623.6 g, and deionized water 97.0 g , 97.0 g of styrene as a monomer, 103.7 g of acrylate DMC (80% by weight aqueous solution of 2-methacryloyloxyethyltrimethylammonium chloride, manufactured by Mitsubishi Rayon Co., Ltd.), 4.76 g of 2-mercaptoethanol as a chain transfer agent, Was placed in the flask.

  The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 78 ° C. over 45 minutes, and polymerization was carried out at 78 ° C. for 10 hours. After the polymerization was completed, the polymerization solution was concentrated under reduced pressure using an evaporator, and then the polymer formed by dropping the polymerization solution 2.5 times concentrated in acetone was precipitated. The supernatant was removed by decantation, 1500 g of deionized water was added and mixed, and then the residual organic solvent was removed by atmospheric distillation to obtain an aqueous polymer solution. The obtained polymer aqueous solution was dried to obtain poly (styrene-co-2-methacryloyloxyethyltrimethylammonium chloride): cation random copolymer a.

The structure of the cationic random copolymer a was confirmed by ¹ H-NMR using DMSO (dimethyl sulfoxide) as a solvent. The composition ratio of the styrene structural unit and 2-methacryloyloxyethyltrimethylammonium chloride structural unit in the random copolymer a was 70:30 (molar ratio) = 54: 46 (weight ratio).

  The cation random copolymer a had a number average molecular weight (Mn) of 7000, a weight average molecular weight (Mw) of 9100, and a molecular weight distribution (Mw / Mn) of 1.3.

  The cationic random copolymer a was colorless and transparent at 25 ° C. when an aqueous solution having a concentration of 17.1% by weight was prepared.

<Synthesis Example 8>
Synthesis of poly (isobornyl methacrylate-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (anionic random copolymer F) In a condenser equipped with nitrogen inside, a nitrogen inlet tube, a stirrer and a flask equipped with a thermometer as a solvent 1875 g of tetrahydrofuran, 301.72 g of isobornyl methacrylate, 654.90 g of methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.), and 293.38 g of acrylic acid were charged as monomers. After raising the bath temperature to 60 ° C., 5.57 g of 2,2′-azobis (isobutyronitrile) was added as a polymerization initiator, and a polymerization reaction was carried out for 5 hours. Thereafter, the bath temperature was raised to 70 ° C., and a polymerization reaction was further performed for 2 hours.

  After completion of the reaction, the reaction mixture was cooled to room temperature, neutralized with 652 g of 5N aqueous sodium hydroxide solution, deionized water was added, and tetrahydrofuran was heated and distilled off to obtain a crude polymer aqueous solution. After removing impurities from the crude polymer aqueous solution by ultrafiltration membrane treatment, the polymer aqueous solution is concentrated and dried to obtain poly (isobornyl methacrylate-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): anionic random copolymer F. Obtained. This anionic random copolymer F had a number average molecular weight (Mn) of 12,000, a weight average molecular weight (Mw) of 22800, and a molecular weight distribution (Mw / Mn) of 1.9.

The structure of the obtained anionic random copolymer F was confirmed by ¹ H-NMR using d-DMSO as a solvent. As a result, isobornyl methacrylate structural unit, methoxypolyethylene glycol acrylate structural unit, sodium acrylate structural unit in random copolymer F were obtained. The composition ratio was 26/20/54 (molar ratio) = 28/47/25 (weight ratio).

  Anionic random copolymer F was in a state in which 80 mol% of carboxyl groups which are ionic groups were neutralized by the above-mentioned process, and when an aqueous solution having a concentration of 12.99% by weight was prepared, it was colorless and transparent at 25 ° C. .

<Synthesis Example 9>
Synthesis of poly (styrene-co-2-methacryloyloxyethyltrimethylammonium chloride) (cationic random copolymer b)
Into a separable flask equipped with a nitrogen-substituted condenser, nitrogen introducing tube, stirrer and thermometer was charged 24.3 g of 2,2′-azobisisobutyronitrile as a polymerization initiator, and then a solvent as a solvent. Mix A-11 (manufactured by Nippon Alcohol Sales Co., Ltd.) 3885 g, deionized water 578 g, styrene 727 g as a monomer, acrylate ester DMC (manufactured by Mitsubishi Rayon Co., Ltd.) 775 g, and lauryl mercaptan 61.5 g as a thiol compound Were charged into the flask.

  The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 78 ° C. over 1 hour, and polymerization was carried out at 78 ° C. for 10 hours. After the completion of the polymerization, the polymerization solution was concentrated under reduced pressure using an evaporator, and then the polymer formed by dropping twice the polymerization solution concentrated in an isopropanol / tetrahydrofuran (1/2 = v / v) mixed solvent was precipitated. The supernatant was removed by decantation, 7000 g of deionized water was added and mixed, and then the residual organic solvent was removed by atmospheric distillation to obtain an aqueous polymer solution. The obtained polymer aqueous solution was dried to obtain poly (styrene-co-2-methacryloyloxyethyltrimethylammonium chloride): cation random copolymer b.

When the structure of this cationic random copolymer b was confirmed by ¹ H-NMR using DMSO (dimethyl sulfoxide) as a solvent, the composition ratio of the styrene structural unit and 2-methacryloyloxyethyltrimethylammonium chloride structural unit in the random copolymer b was 70:30 (molar ratio) = 54: 46 (weight ratio).

The cationic random copolymer b had a number average molecular weight (Mn) of 7,500, a weight average molecular weight (Mw) of 11,000, and a molecular weight distribution (Mw / Mn) of 1.5.

  The cationic random copolymer b was colorless and transparent at 25 ° C. when an aqueous solution having a concentration of 14.9% by weight was prepared.

[Examples and Comparative Examples]
The production examples and evaluation results of aqueous pigment dispersions and recording liquids using the anionic random copolymers A to F, the cationic random copolymers a and b, and the block copolymer X obtained in Synthesis Examples 1 to 9 are shown below.

In the following, the PAH amount of the carbon black used for the preparation of the aqueous pigment dispersion is determined according to “Method for measuring PAH content in carbon black” (issued by Cabot on July 8, 1994). Black was soxhlet extracted with toluene for 48 hours, and the resulting extract was concentrated and quantified by GC-MS. Moreover, the oxygen-containing functional group density of carbon black was measured by the method described above.
Further, in the following carbon black sample α and carbon black sample β, the primary particle diameter is an arithmetic average diameter (number average) by an electron microscope, the nitrogen adsorption specific surface area is a value measured by the method of JISK6217, and the volatile content is JISK6221. Value measured by the method (volatilization (weight loss) when carbon black is heated at 950 ° C. for 7 minutes).

<Example 1>
Carbon black (carbon black sample α (furnace black; primary particle size 15 nm, nitrogen adsorption specific surface area 320 m ² / g, volatile content 2%) with a PAH amount and oxygen-containing functional group density shown in Table 2 in a nitrogen atmosphere Baked at 1200 ° C. for 30 days; powder; solid content 100 wt% 28.0 g, anionic random copolymer A aqueous solution (anionic random copolymer A concentration 13.14 wt%) 85.2 g, and deionized water 152.8 g After pre-dispersing for 10 minutes with a homomixer, the mixture was dispersed for 4 hours at 60 ° C. using a self-made bead mill with 0.5 mmφ zirconia beads as media, and then an aqueous solution of block copolymer X (block copolymer X concentration of 10. 0 wt.%) 14.0 g was added, and further 3 hours at 60 ° C. using a bead mill. After the dispersion, after removal of beads were dispersed for 1 hour at 40 ° C., to obtain a dispersion a was diluted with deionized water so that the pigment concentration of 8% by weight.

  Dispersion a was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 60 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; chip used: 36 mmφ) to obtain pigment dispersion A.

The pigment dispersion A was used to make an ink according to the following formulation.
Pigment dispersion A 3.75 g
4.00 g of deionized water
2-pyrrolidone 0.22g
Glycerin 0.57g
Triethylene glycol 0.48g
0.88 g of ethylene urea
2,4,7,9-Tetramethyl-5-decyne-4,7-diol-di (polyoxyethylene) ether (Acetylene glycol surfactant manufactured by Air Products, trade name: Olphine E1010) 0.1 g
The above components were mixed, stirred for 15 minutes, and subjected to ultrasonic treatment for 30 minutes to obtain recording liquid A.

With respect to the obtained pigment dispersion A and recording liquid A, the following properties (a) to (c) were evaluated by the following test methods, and the results are shown in Table 2.
As the printer, an inkjet recording printer (Canon PIXUS BJ-S700) was used, and as the printing paper, commercially available glossy paper (SP-101 manufactured by Canon Inc.) was used.

(A) Stability of recording liquid For the recording liquid, the dispersion particle diameter and viscosity of the pigment (carbon black) immediately after preparation and the dispersion particle diameter and viscosity of the pigment (carbon black) after being held at 70 ° C. for 15 hours are measured. did. The smaller the increase in particle size and viscosity after holding, the more stable it is.
The dispersed particle diameter of the pigment was measured by diluting the recording liquid 10,000 times with deionized water and using a dilution probe with Otsuka Electronics Co., Ltd. FPAR-1000, and the average particle diameter value was calculated by the Cumulant method. . The viscosity was measured using a rheometer (REOLOGICA AB Instruments; VAR-100; cone 1 ° / 55φ), and the value at a shear rate of 100 / sec was read.

(B) Gloss measurement of recorded image The gloss and haze of glossy paper (SP-101 manufactured by Canon Inc.) printed with a recording liquid was dried for 1 day at room temperature. Gross measurement and haze measurement were performed using a Haze-Gloss meter (Cat. No. 4601 manufactured by BYK Gardner), and a measured value of 20 ° was adopted as the gloss value. The measured Haze value and the linear Haze value have the following relationship.
Measurement Haze = 1285.1 X log (linear Haze / 20 + 1)
In general, when the gloss is high, the haze tends to be high. Therefore, it is difficult to give the superiority or inferiority of the glossiness only by comparing the respective values. Therefore, the haze / gross values were compared. It shows that glossiness is so high that this figure is small.

(C) Observation of oily impurities The prepared pigment dispersion was visually observed to check for the presence of oily substances.

<Example 2>
Firing product carbon black (carbon black sample α calcined at 1200 ° C. for 30 days in a nitrogen atmosphere; powder; solid content: 100 wt%) 28.0 g, anionic random copolymer B aqueous solution (anionic random copolymer concentration: 10.5 wt%) ) 120.1 g and 117.9 g of deionized water were mixed, and after pre-dispersing for 1 hour with CLEARMIX (MTECHNIQUE; CLM-0.8S), which is a rotary disperser, 0.3 mmφ zirconia beads were used as media. The mixture was dispersed at 60 ° C. for 4 hours using a self-made bead mill, and then 14.0 g of an aqueous solution of block copolymer X (block copolymer X concentration 10.0% by weight) was added, and further 3 at 60 ° C. using a bead mill. After time dispersion and dispersion at 40 ° C. for 1 hour to remove the beads, the pigment concentration was adjusted to 8% by weight. Dilution with deionized water was performed to obtain dispersion b.

The dispersion b was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion B.
Using this pigment dispersion B instead of pigment dispersion A, a recording liquid B was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 3>
Dispersed in the same formulation as in Example 2 except that the anionic random copolymer B aqueous solution was changed to 85.5 g of an anionic random copolymer C aqueous solution (anionic random copolymer C concentration 13.1 wt%) and the amount of water was changed to 152.5 g. The pigment dispersion E was obtained by processing.
Using this pigment dispersion C instead of pigment dispersion A, a recording liquid C was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 4>
Dispersed in the same formulation as in Example 2 except that the anionic random copolymer B aqueous solution was changed to 61.2 g of an anionic random copolymer D aqueous solution (anionic random copolymer D concentration 18.3% by weight) and the amount of water was changed to 176.8 g. Thus, a pigment dispersion D was obtained.
Using this pigment dispersion D instead of pigment dispersion A, a recording liquid D was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 5>
Dispersed in the same formulation as in Example 2 except that the anionic random copolymer B aqueous solution was changed to 42.4 g of an anionic random copolymer E aqueous solution (anionic random copolymer E concentration 26.4% by weight) and the amount of water was changed to 195.6 g. Thus, a pigment dispersion E was obtained.
Using this pigment dispersion E instead of pigment dispersion A, a recording liquid E was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 6>
Firing product carbon black (carbon black sample α calcined at 1200 ° C. for 30 days under nitrogen atmosphere; powder; solid content: 100 wt%) 28.0 g, cation random copolymer a aqueous solution (cation random copolymer a concentration 17.1 wt. %) 98.5 g and deionized water 153.5 g were mixed, pre-dispersed with a homomixer for 60 minutes, and then self-made bead mill using 0.5 mmφ zirconia beads as a medium at 60 ° C. for 7 hours, and further 40 After dispersing at 1 ° C. for 1 hour to remove the beads, the dispersion was adjusted to a pigment concentration of 8% by weight to obtain dispersion (1).

  Disperse dispersion (1) in a 500 ml tall beaker, immerse the beaker in ice water, disperse for 60 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ), and pigment dispersion (2) Got.

  After adding deionized water to the dispersion (2) and diluting it twice, the free polymer is removed with a microfiltration membrane (Spectrum Laboratories Inc: material polysulfone, pore size 0.05 μm), and then concentrated and pigmented A dispersion f having a concentration of 8% by weight was obtained.

31.47 g of an anionic random copolymer F aqueous solution (anionic random copolymer F concentration: 12.99% by weight) was dropped into 65 g of the dispersion f with stirring with a stirrer, and after stirring for 10 minutes, an ultrasonic disperser (SMT) ("Ultrasonic Homogenizer UH-600S" manufactured by ULTRASONIC) was irradiated with ultrasonic waves for 40 minutes under ice cooling. Next, free random copolymer and excess ions in the aqueous phase are removed by a microfiltration membrane (Asahi Kasei Chemicals Co., Ltd .: Microza: material polysulfone, pore size 0.1 μm), and then concentrated, and then NaOH is added. The pH was adjusted to 8 with an aqueous solution to obtain a pigment dispersion F having a pigment concentration of 8% by weight.
Using this pigment dispersion F instead of pigment dispersion A, a recording liquid F was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 7>
Carbon black was calcined carbon black (carbon black sample β (furnace black; primary particle diameter 16 nm, nitrogen adsorption specific surface area 260 m ² / g, volatile content 1.5) with PAH amount and oxygen-containing functional group density shown in Table 2. %) Was calcined at 1200 ° C. for 30 days in a nitrogen atmosphere; powder; solid content was changed to 100% by weight), and dispersed in the same formulation as in Example 1 to obtain a pigment dispersion G.
Using this pigment dispersion G instead of pigment dispersion A, a recording liquid G was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 8>
Firing product carbon black (carbon black sample β calcined at 1200 ° C. for 30 days under nitrogen atmosphere; powder; solid content 100 wt%) 28.0 g, cationic random copolymer b aqueous solution (cation random copolymer b concentration 14.9 wt. %) 112.8 g and deionized water 139.2 g were mixed, pre-dispersed with a homomixer for 60 minutes, and then self-made bead mill using 0.5 mmφ zirconia beads as a medium at 60 ° C. for 7 hours, and further 40 After dispersing at 1 ° C. for 1 hour to remove the beads, the dispersion was adjusted to a pigment concentration of 8% by weight to obtain a dispersion (3).

  Disperse the dispersion (3) in a 500 ml tall beaker, immerse the beaker in ice water, and disperse for 60 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ). Pigment dispersion (4) Got.

  After adding deionized water to the dispersion liquid (4) and diluting it twice, the free polymer is removed by a microfiltration membrane (Spectrum Laboratories Inc: material polysulfone, pore size 0.05 μm), and then concentrated to a pigment. A dispersion h having a concentration of 8% by weight was obtained.

71.6 g of an anionic random copolymer F aqueous solution (anionic random copolymer F concentration: 12.99% by weight) was dropped into 160 g of the dispersion h while stirring with a stirrer, and after stirring for 10 minutes, an ultrasonic disperser (SMT) ("Ultrasonic Homogenizer UH-600S" manufactured by ULTRASONIC) was irradiated with ultrasonic waves for 50 minutes under ice cooling. Next, free random copolymer and excess ions in the aqueous phase are removed by a microfiltration membrane (Asahi Kasei Chemicals Co., Ltd .: Microza: material polysulfone, pore size 0.1 μm). The pH was adjusted to 8 with an aqueous solution to obtain a pigment dispersion H having a pigment concentration of 8% by weight.
Using this pigment dispersion H instead of pigment dispersion A, a recording liquid H was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Example 9>
Unburned carbon black (carbon black sample β; powder; solid content: 100% by weight) 28.0 g of PAH amount and oxygen-containing functional group density shown in Table 2 and anionic random copolymer A aqueous solution (anionic random copolymer A concentration 13. 147.9%) and 124.1 g of deionized water were mixed, pre-dispersed with a homomixer for 10 minutes, and then dispersed at 60 ° C. for 7 hours using a self-made bead mill with 0.5 mmφ zirconia beads as media. Then, dispersion was carried out at 40 ° C. for 1 hour to remove the beads, and then diluted to a pigment concentration of 8% by weight to obtain a dispersion liquid i.

Dispersion i was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) for 60 minutes to obtain pigment dispersion I.
Using this pigment dispersion I instead of the pigment dispersion A, a recording liquid I was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

<Comparative Example 1>
The same formulation as in Example 1 except that the carbon black was changed to an unfired carbon black (carbon black sample α; powder; solid content: 100% by weight) having the PAH amount and oxygen-containing functional group density shown in Table 2. To obtain a pigment dispersion J.
Using this pigment dispersion J instead of pigment dispersion A, a recording liquid J was prepared in the same manner as in Example 1 and evaluated in the same manner.
The results are shown in Table 2.

From Table 2, the following is clear.
Comparative Example 1 uses carbon black that has not been fired. Compared to Example 1 using the carbon black that has been fired, the dispersion particle size is very large. The recording liquid J prepared in (1) has an increased dispersed particle diameter after storage at high temperature. On the other hand, the storage stability of the recording liquid remains good when the carbon black is used after being baked. Moreover, in Comparative Example 1, an oil film is seen on the surface of the dispersion after completion of dispersion, suggesting that a lot of impurities such as PAH components are contained, whereas the carbon black subjected to the calcination treatment is used. In Example 1 or the like, no oil film was observed in the dispersion.

  The carbon black used in Example 9 is not calcined, but the dispersed particle size is sufficiently small because the PAH amount and the oxygen-containing functional group density satisfy the scope of the present invention. However, in Example 8 where the calcination treatment was performed, a better result was obtained than in Example 9 using the carbon black which was not calcination treatment, and an example using the carbon black which was calcination treatment was used. Nos. 1 to 8 all show good storage stability.

  From the measurement results of PAH, it is clear that all the calcined carbon blacks have an extremely low PAH value of 0.0 ppm, and the chemical safety is higher than that of ordinary carbon black.

  Further, when the oxygenated functional group density of the calcined product carbon black used in Examples 1 to 6 and the unfired carbon black used in Comparative Example 1 is compared, the calcined product clearly has an oxygenated functional group. The density is reduced, which suggests that the adsorptivity of the polymer used as the dispersant is improved.

From the above results, carbon black having a PAH amount of 80 ppm or less and an oxygen-containing functional group density of 3 μmol / m ² or less, preferably carbon black subjected to a baking treatment at a temperature of 800 to 1500 ° C. in a nitrogen atmosphere is used. The recording liquid using the aqueous pigment dispersion according to the present invention had oil impurities in the dispersion as compared with the recording liquid prepared with a dispersion using carbon black having a high PAH amount and oxygen-containing functional group density. Therefore, it is clear that the chemical safety is high, and the dispersibility and storage stability are more excellent.

Claims (6)

A pigment dispersion characterized by containing, as a coloring material, carbon black having a polyaromatic hydrocarbon content of 80 ppm or less and an oxygen-containing functional group density defined by the following formula of 3 μmol / m ² or less: .
Oxygen-containing functional group density (μmol / m ² )
= [(950 ° C. × 30 minutes) CO generation amount (μmol / g) + (950 ° C. × 30 minutes) CO ₂
Generation amount (μmol / g)] / nitrogen adsorption specific surface area (m ² / g) The pigment dispersion according to claim 1, wherein the content of polyaromatic hydrocarbon in the carbon black is 20 ppm or less.
The pigment dispersion according to claim 1 or 2, wherein the carbon black is fired at a temperature of 800 to 1500 ° C in a nitrogen atmosphere.   The pigment dispersion according to any one of claims 1 to 3, wherein the pigment dispersion is aqueous.   An ink composition comprising the pigment dispersion according to any one of claims 1 to 4.   6. An ink jet recording method comprising ejecting droplets of the ink composition according to claim 5 from an ink jet head and attaching the droplets to a recording medium.