JP2000191967A - Aqueous ink for ink-jet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous black ink for ink-jet printing having high level pigmentation degree and good fixing property. SOLUTION: This aqueous black ink for ink-jet printing includes (A) an aqueous dispersion of a vinyl polymer including oil-soluble black dye or carbon black and (B) an aqueous dispersion having same ionicity as ingredient (A) at a ratio A/B=(1:2) to (8:1). The vinyl polymer is a polymer obtained by copolymerization of (a) a monomer having a salt-forming group, (b) a monomer having hydroxyl group, (c) a macromer and (d) a monomer copolymerizable therewith in the presence of a radical polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water-based black ink for ink-jet recording.

[0002]

2. Description of the Related Art An ink jet recording system is a recording system in which ink droplets are directly ejected from a very fine nozzle to a recording member and adhered to obtain characters and images. According to this method, not only the device used has the advantage of low noise and good operability, but also
It is widely used in recent years because it has an advantage that it can be easily colored and that plain paper can be used as a recording member.

[0003] Among the inks used in this ink jet printer, examples of a coloring material used for a black ink include a water-soluble black dye and an aqueous dispersion of carbon black. A water-soluble black dye is excellent in ejection stability, but poor in water resistance and light resistance. Further, the carbon black aqueous dispersion has a high degree of coloring, but has poor fixability on paper, poor scratch resistance, and poor marker resistance.

It has also been proposed to further add a polymer emulsion having film-forming properties to an aqueous dispersion of carbon black (JP-A-9-208870, JP-A-10-208870).
195355, JP-A-10-152640). However, when a large amount of the polymer emulsion is added, the fixability is improved, but the coloring does not work because it does not act as a coloring agent. On the other hand, if the amount of the polymer emulsion is small, there is almost no effect on the improvement of the fixing property. Recently, an aqueous dispersion of a vinyl polymer containing an oil-soluble black dye has been proposed (JP-A-9-241565). When this is used as an ink coloring material, it has good fixability and water resistance, and has a coloring degree close to that of a water-soluble dye, but is insufficient when a high level of coloring degree is required. When the amount of the oil-soluble black dye in the aqueous dispersion is increased to increase the colorability, the stability is reduced. When the amount of the aqueous dispersion is increased, the viscosity is increased and the ejection property is deteriorated.

An object of the present invention is to provide a water-based black ink for ink-jet recording having a high level of coloring and good fixability.

[0006]

The present invention provides (A) an aqueous dispersion of a vinyl polymer containing an oil-soluble black dye or carbon black, and (B) a carbon black having the same ionicity as (A). With the aqueous dispersion of (A) /
(B) A water-based black ink for inkjet recording, which is contained at a ratio of 1/2 to 8/1.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The component (A) used in the present invention comprises:
An oil-soluble black dye or carbon black is included in the particles of the aqueous dispersion formed by the vinyl polymer.
Methods for obtaining such an aqueous dispersion include, for example, the following methods.

[0008] The vinyl polymer is dissolved in a hydrophilic organic solvent together with an oil-soluble black dye, a neutralizing agent is added if necessary to ionize the salt-forming groups in the polymer, and then water is added. A method of distilling off and inverting the phase to an aqueous phase. The vinyl polymer is dissolved in an organic solvent, a neutralizing agent is added as necessary to ionize the salt-forming groups in the polymer, and then water and carbon black are added and kneaded. How to To a solution obtained by dissolving a vinyl polymer and an oil-soluble black dye in a water-insoluble organic solvent, water, a neutralizing agent and, if necessary, a surfactant are added to ionize a salt-forming group in the polymer, and then obtained. After emulsifying the obtained mixture, the water-insoluble organic solvent is distilled off to obtain an aqueous dispersion.

The vinyl polymer used in the present invention includes (a) a monomer having a salt-forming group, (b) a monomer having a hydroxyl group, (c) a macromer, and (d) a monomer copolymerizable therewith. Polymers obtained by copolymerization in the presence of a polymerization initiator are preferred.

As the monomer having a salt-forming group as the component (a), JP-A-9-286939, page 5, column 7, line 24 to line 8
The one described in column 29, line can be used. Examples of the cationic monomer include an unsaturated tertiary amine-containing monomer, an unsaturated ammonium salt-containing monomer, and the like, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N- (N ′, N ′). -Dimethylaminopropyl)
Acrylamide and N- (N ′, N′-dimethylaminopropyl) methacrylamide are preferred.

The anionic monomers include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers and the like, and unsaturated carboxylic acid monomers, particularly acrylic acid and methacrylic acid, are preferred.

The hydroxyl group-containing monomer of the component (b) includes:
Examples include 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, polyethylene glycol acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and polyethylene glycol methacrylate, with 2-hydroxyethyl acrylate or methacrylate being preferred.

The macromer of the component (c) is represented by the formula (1)
Is preferred, a styrene macromer composed of a homopolymer or copolymer of styrene having a polymerizable functional group at one end, or a mixture of a silicone macromer and a styrene macromer.

X (Y) _n Si (R) _3-m (Z) _m (1) (where X represents a polymerizable unsaturated group; Y represents a divalent linking group; R represents hydrogen) Represents an atom, a lower alkyl group, an aryl group or an alkoxy group, and a plurality of R may be the same or different Z: represents a monovalent siloxane polymer portion having a number average molecular weight of at least 500. n: 0 or 1 Is shown.

M: represents an integer of 1 to 3. Among the macromers, a silicone macromer is preferable in order to prevent scorching of the head, and a styrene macromer is preferable in order to sufficiently incorporate a dye or carbon black. It is particularly preferred to combine these macromers.

In the silicone macromer represented by the formula (1), X includes groups such as CH ₂ CHCH— and CH ₂ CC (CH ₃ ) —. As _{Y, -COO-, -COOC b H 2b} - ( the number of where b is 1 to 5), a phenylene group and the like, -COO
C ₃ H ₆ − is preferred. R represents a hydrogen atom, a methyl group,
Examples include an ethyl group, a phenyl group, and a methoxy group, and a methyl group is preferable. Z is preferably a number average molecular weight of 800 to 50
No. 00 is a monovalent dimethylsiloxane polymer. n is preferably 1. m is preferably 1. This silicone macromer is preferably a compound represented by the formula (1-1).

[0017]

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(Wherein, R ′ is a hydrogen atom or a methyl group, R has the above-mentioned meaning, and 2a + 3 R may be the same or different. A represents a number of 5 to 65.) Styrene macromer Preferably has a weight average molecular weight in the range of 1,000 to 10,000, and particularly preferably has an acryloyloxy group or a methacryloyloxy group as a polymerizable functional group at one end. The ratio of the styrene units constituting the styrene macromer to the copolymerizable monomer units is such that the total amount of the styrene units in the constituent monomers is at least 60% by weight, preferably at least 70% by weight. It is desirable because it can secure
Acrylonitrile and the like are mentioned as monomers copolymerizable with styrene constituting the styrene copolymer. Examples of the styrene macromer include those having a structure represented by the formula (2).

[0019]

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(Where p and q are p / q = 6/4 to 10/0)
Indicates the number at which the weight average molecular weight becomes 1,000 to 10,000. The component (d) includes methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, etc. Acrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, and dodecyl methacrylate Acid esters: styrene monomers such as styrene, vinyltoluene, 2-methylstyrene and chlorostyrene, and amide monomers such as acrylamide and methacrylamide.

The copolymerization amount of the component (a) is preferably 1 to 40% by weight based on the total amount of the components (a) to (d) in the vinyl polymer of the present invention. (b) The copolymerization amount of the component is preferably 5 to 40% by weight. The copolymerization amount of the component (c) is preferably from 1 to 30% by weight in order to improve the dye introduction rate and to prevent scorching of the heater surface.
The copolymerization amount of the component (d) is preferably from 10 to 93% by weight.

[0022] The vinyl polymer of the present invention comprises the above (a) to
The component (d) is produced by polymerizing the component by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method in the presence of a radical polymerization initiator. It is preferable to manufacture by. As the solvent used in the solution polymerization method, a polar organic solvent is preferable, and a water-miscible organic solvent can be used by mixing with water. Examples of such organic solvents include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol, and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; Preference is given to ethanol, acetone, methyl ethyl ketone or a mixture of these with water.

The polymerization is usually carried out at 30 to 100 ° C., preferably at 50 to 100 ° C.
The reaction is performed at 80 ° C. for 1 to 10 hours, and is appropriately selected depending on the type of the radical polymerization initiator, the monomer, and the solvent used. The polymerization is preferably performed in an atmosphere of an inert gas such as nitrogen. After the polymerization, the copolymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation.

The weight average molecular weight of the vinyl polymer of the present invention is preferably from 3,000 to 50,000 from the viewpoints of scorching of the printer head, durability of the ink after printing, and formability of the dispersion.

As the oil-soluble black dye used in the present invention,
CI Solvent Black 3, 7, 27, 29, 34 and the like. Monarch 880, 2
80,400, Regal 400R, Mogul L (Cabot), PRI
NTEX-L, -150T, -90, -60, -80 (made by Degussa), # 950,
# 960, MA 600 (manufactured by Mitsubishi Chemical Corporation) and the like.

The particle size of the vinyl polymer aqueous dispersion containing the oil-soluble black dye or carbon black is 0.01 to 0.50 μm from the viewpoints of ink bleeding and dispersion stability.
Is preferably, and more preferably 0.02 to 0.15 μm.

The amount of the oil-soluble black dye or carbon black contained in the aqueous dispersion of the vinyl polymer is preferably 20 to the solid content of the vinyl polymer from the viewpoint of printing density and ease of inclusion.
It is preferably from 400 to 400% by weight, more preferably from 30 to 300% by weight.

Further, the compounding amount of (A) + (B) in the ink of the present invention is determined from the viewpoint of print density and ejection stability as a solid content.
It is preferably from 1 to 30% by weight, more preferably from 3 to 15% by weight.

The aqueous dispersion of carbon black as the component (B) of the present invention is obtained by dispersing carbon black using a surfactant, a polymer dispersant or the like, and imparting self-dispersibility by surface modification. Any substance may be used as long as it is stable in water, but in consideration of high-temperature storage stability, an aqueous dispersion of self-dispersible carbon black is preferable.

The component (B) must have the same ionicity as the component (A) in order to prevent aggregation of the components (A) and (B). Examples of such ionic carbon black aqueous dispersion include self-dispersible carbon in which at least one anionic or cationic hydrophilic group is bonded directly or via another atomic group to the surface of carbon black. Black aqueous dispersions are preferred.

As the anionic hydrophilic group, -COOM, -S
O ₃ M, -PO ₃ HM, -PO ₃ M ₂ , -SO ₂ NH ₂ , -SO ₂ NHCOR "
M represents a hydrogen atom; an alkali metal such as lithium, sodium or potassium; ammonium; an organic ammonium such as mono to trimethyl ammonium, mono to triethyl ammonium or mono to trimethanol ammonium, and R ″ represents an alkyl having 1 to 12 carbon atoms. A phenyl group which may have a substituent or a naphthyl group which may have a substituent.), And -COOM and -SO ₃ M are preferable.

The cationic hydrophilic group is preferably a quaternary ammonium group, and particularly preferably the following quaternary ammonium groups.

[0033]

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(R "has the above meaning.) The mixing ratio of the component (A) to the component (B) in the ink of the present invention is (A) / (B) = 1 in terms of solid content weight ratio. When the ratio (A) / (B) is less than 1/2, the fixability becomes insufficient, and when it exceeds 8/1, a satisfactory coloring degree is obtained. I can't get it.

The aqueous black ink for ink-jet recording of the present invention may contain various conventionally known additives such as wetting agents such as polyhydric alcohols, dispersants, defoamers, fungicides and / or chelating agents. Can be added.

[0036]

The aqueous black ink for ink-jet recording of the present invention has a high level of coloring and good fixability.

[0037]

EXAMPLES The parts and percentages in the examples are on a weight basis.

Production Example 1 A reactor was charged with 20 parts of methyl ethyl ketone as a polymerization solvent, and monomers and polymerization chain transfer agents described in the column of initially charged monomers in Table 1 as polymerizable unsaturated monomers. Went well. On the other hand, in a dropping funnel, 60 parts of methyl ethyl ketone, 0.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile), a monomer and a polymerization chain transfer agent described in the column of dropped monomer in Charged after replacement. Under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was raised to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 3 hours. Two hours after the completion of the dropwise addition, 2,2′-azobis (2,4-dimethylvaleronitrile) 0.1
A solution prepared by dissolving 5 parts in 5 parts of methyl ethyl ketone was added, and the mixture was further aged at 65 ° C. for 2 hours and at 70 ° C. for 2 hours to obtain a copolymer solution.

A part of the obtained copolymer solution was removed under reduced pressure.
After drying at 105 ° C. for 2 hours, the solvent was completely removed and the mixture was isolated. The molecular weight was measured by gel permeation chromatography using polystyrene as a standard substance and tetrahydrofuran as a solvent, and the weight-average molecular weight was about 10,000. Was.

The copolymer solution obtained above was dried under reduced pressure, and 5 parts of the copolymer was dissolved in 25 parts of an organic solvent shown in Table 1.
2 parts of a neutralizing agent (30% aqueous solution) shown in Table 1 was added thereto to neutralize a part of the copolymer, and further 30 parts of ion-exchanged water and 5 parts of carbon black were added and kneaded with a bead mill. . The organic solvent was completely removed from the obtained kneaded material at 60 ° C. under reduced pressure, and a solid content of 20
% Of a cationic carbon black-containing vinyl polymer aqueous dispersion (hereinafter abbreviated as BK-1).

Production Example 2 A copolymer solution was obtained in the same manner as in Production Example 1 using the monomers and the polymerization chain transfer agent shown in Table 1. When the molecular weight was measured in the same manner as in Production Example 1, the weight-average molecular weight was about 10,000.
00. 5 parts of an organic solvent shown in Table 1 and 5 parts of an oil-soluble black dye shown in Table 1 were added to 5 parts of a copolymer obtained by drying the obtained copolymer solution under reduced pressure, and completely dissolved.
2 parts of a neutralizing agent (30% aqueous solution) shown in Table 1 was added to partially neutralize the salt-forming groups of the copolymer, and 300 parts of ion-exchanged water was added.
After stirring, the mixture was emulsified for 30 minutes using a microfluidizer (manufactured by Microfluidizer). The organic solvent was completely removed from the obtained emulsion under reduced pressure at 60 ° C., and further concentrated by removing a part of water to obtain a solid content of 20%.
% Of a cationic oil-soluble black dye-encapsulated vinyl polymer aqueous dispersion (hereinafter abbreviated as BK-2).

Production Example 3 Using the monomers and the polymerization chain transfer agent shown in Table 1, a copolymer solution was obtained in the same manner as in Production Example 1. When the molecular weight was measured in the same manner as in Production Example 1, the weight-average molecular weight was about 10,000.
00. Aqueous dispersion of vinyl polymer containing anionic carbon black having a solid content of 20% in the same manner as in Production Example 1 except that the obtained copolymer solution was used and the organic solvent, neutralizing agent and carbon black shown in Table 1 were used. Body (hereinafter BK
-3).

[0043]

[Table 1]

Note) * 1 Silicone macromer FM-0711: Silicone macromer manufactured by Chisso Corporation having a structure represented by the following formula (1-1-1):

[0045]

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(In the formula, a ′ is a number such that the weight average molecular weight becomes 1000.) * 2 Styrene acrylonitrile macromer AN-6: composed of a styrene / acrylonitrile copolymer having a styrene content of 70% and a weight average molecular weight of 6,000. Styrene macromer manufactured by Toa Gosei Co., Ltd. Production Example 4 10 g of carbon black having a surface area of 230 m ² / g and a DBP oil absorption of 70 m ² / g, and 3.06 g of 3-amino-N-ethylpyridinium bromide in 72 g of water After mixing well, 1.62 g of nitric acid was added dropwise thereto, and the mixture was stirred at 70 ° C. 4 minutes later, 5g
A solution prepared by dissolving 1.07 g of sodium nitrite in water was added, and the mixture was further stirred for 1 hour. The resulting slurry is applied to Toyo filter paper.
The mixture was filtered through No. 2 (Advantis), and the carbon black particles were sufficiently washed with water. This carbon black wet cake was redispersed in 3000 mL of water and desalted with a reverse osmosis membrane until the electric conductivity was 0.2 μs. Furthermore, by concentrating this carbon black dispersion to a carbon black concentration of 10%, the formula

[0047]

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A cationic self-dispersion type carbon black aqueous dispersion (hereinafter abbreviated as BK-4) to which the group represented by the formula was bonded was obtained.

Production Example 5 Commercially available acidic carbon black (MA-77, Mitsubishi Chemical Corporation)
The mixture was mixed well with 1000 mL of water, and 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise thereto, followed by stirring at 100 to 105 ° C. for 10 hours. The obtained slurry was filtered with Toyo Filter Paper No. 2 (manufactured by Advantis), and the carbon black particles were sufficiently washed with water. This carbon black wet cake is redispersed in 3000 mL of water,
It was desalted with a reverse osmosis membrane until 0.2 μs. Further, by concentrating the carbon black dispersion (pH = 8 to 10) to a carbon black concentration of 10%, an aqueous anionic self-dispersible carbon black dispersion in which -COONa groups are bonded to the surface of carbon black. (Hereinafter abbreviated as BK-5).

Example 1 BK-1 30 parts, BK-4 20 parts, glycerin 5 parts,
5 parts of pyrrolidone, 2 parts of isopropyl alcohol, 1 part of acetylenol EH (manufactured by Kawaken Fine Chemical Co., Ltd.) and 37 parts of water were mixed to obtain a dispersion, and the dispersion was filtered through a 0.2-micron filter to remove trash and The coarse particles were removed to obtain an aqueous black ink. The solids weight ratio of the component (A) to the component (B) in this ink is 3/1.

Example 2 A water-based black was prepared in the same manner as in Example 1 except that 20 parts of BK-2 was used instead of BK-1, the amount of BK-4 was 40 parts, and the amount of water was 27 parts. Ink was obtained. The weight ratio of the solid components (A) and (B) in this ink was 1/1.

Example 3 An aqueous black ink was obtained in the same manner as in Example 1 except that the following components were used. The weight ratio of the solid components (A) and (B) in this ink was 4.3 / 1. BK-3 32.5 parts BK-5 15 parts Glycerin 5 parts N-methylglycine 5 parts Urea 5 parts Emar 20C (manufactured by Kao Corporation) 1 part Water 36.5 parts.

Example 4 Instead of BK-5, an aqueous dispersion (10% solids) of carbon black dispersed in Demol C (manufactured by Kao Corporation) was used.
In the same manner as in Example 3, except that the amount of BK-3 was 20 parts and the amount of water was 24 parts, a water-based black ink was obtained. The weight ratio of the solid components (A) and (B) in this ink was 1/1.

Comparative Example 1 BK-1 was added in an amount of 40 parts and water was added in an amount of 47 parts.
A water-based black ink was obtained in the same manner as in Example 1 except that -4 was not added.

Comparative Example 2 BK-4 was added in an amount of 80 parts and water was added in an amount of 7 parts.
An aqueous black ink was obtained in the same manner as in Example 1, except that -1 was not added.

Comparative Example 3 An aqueous dispersion of carbon black (solid content: 10%) dispersed in Demol C (manufactured by Kao Corporation) instead of BK-5
And a water-based black ink was obtained in the same manner as in Example 3, except that the amount of water added was 4 parts and BK-3 was not added.

Comparative Example 4 8 parts of a water-soluble black dye (CI Direct Black 195) and 76 parts of water were used instead of an aqueous dispersion (solid content: 10%) of carbon black dispersed in Demol C (manufactured by Kao Corporation). Using
Otherwise in the same manner as in Comparative Example 3, an aqueous black ink was obtained.

The physical properties of the black inks obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated by the following methods. Table 2 shows the results.

<Evaluation Method> (1) Print Density Using a commercially available bubble jet printer (Desk Jet-720C) manufactured by HEWLETT PACKARD, solid printing was performed on recycled paper for PPC (manufactured by Nippon Kaishi Paper Co., Ltd.). After air drying at room temperature for 24 hours, the optical density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth).

(2) Water resistance Solid printing was performed on recycled paper for PPC using the printer described above.
After drying for 1 hour, it was immersed vertically in still water for 10 seconds and pulled up vertically. After air drying at room temperature, the print density was measured. The residual ratio of the print density after immersion to the print density immediately after solid printing was determined, and the water resistance was evaluated according to the following criteria. ◎: Residual rate 95% or more ○: Residual rate 90% or more and less than 95% △: Residual rate 70% or more and less than 90% ×: Residual rate less than 70%.

(3) Marker resistance Using the printer described above, text printing was performed on recycled paper for PPC, and after 6 hours, the stain degree of the printed sample was traced with a commercially available water-based fluorescent pen, and the degree of staining was visually evaluated according to the following criteria. . ：: No trace such as tailing when traced with a highlighter pen. Δ: Trailing occurs when traced with a highlighter pen, but there is no practical problem. X: Trailing occurs when traced with a highlighter, resulting in severe dirt.

(4) Scratch resistance Solid printing was performed on recycled paper for PPC using the printer described above.
After drying for one day, the printed surface was strongly rubbed with a finger. The printing condition was evaluated according to the following criteria. ：: Printing is hardly taken, and the surroundings are not blackened. Δ: Printing is slightly rubbed, the surroundings are blackened, and the fingers are also slightly blacked. X: The printings are considerably rubbed out, and the surroundings are blackened.
Fingers get dirty

[0063]

[Table 2]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryoma Mizushima 1334 Minato, Wakayama-shi, Wakayama Prefecture F-term (reference) 2C056 FC01 2H086 BA53 BA55 BA59 BA62 4J039 AD02 AD09 AD10 AD12 AD20 AD22 BA04 BE01 BE02 BE06 CA06 EA19 EA36 EA42 GA24

Claims (4)

[Claims] 1. A method comprising: (A) an aqueous dispersion of a vinyl polymer containing an oil-soluble black dye or carbon black, and (B) an aqueous dispersion of carbon black having the same ionicity as in (A), A water-based black ink for inkjet recording containing (A) / (B) at a weight ratio of 1/2 to 8/1. 2. A vinyl polymer comprising: (a) a salt-forming group-containing monomer, (b) a hydroxyl group-containing monomer, (c) a macromer, and (d) a monomer copolymerizable therewith. The black ink according to claim 1, which is a polymer obtained by copolymerization in the presence. 3. The macromer is a silicone macromer represented by the formula (1), a styrene macromer comprising a homopolymer or copolymer of styrene having a polymerizable functional group at one end, or a mixture of a silicone macromer and a styrene macromer. The black ink according to claim 2, wherein X (Y) _n Si (R) _3-m (Z) _m (1) (wherein, X represents a polymerizable unsaturated group. Y: represents a divalent bonding group. R: hydrogen atom, lower. It represents an alkyl group, an aryl group or an alkoxy group, and a plurality of R may be the same or different Z: represents a monovalent siloxane polymer portion having a number average molecular weight of at least 500. n: represents 0 or 1. m: represents an integer of 1 to 3.) 4. The self-dispersible carbon black aqueous dispersion in which at least one hydrophilic group is bonded directly or via another atomic group to the surface of the carbon black. 4. The black ink according to any one of claims 1 to 3.