JP2001115065A - Aqueous ink for ink-jet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous ink for ink-jet printing good at exhalation property and excellent in water resistance and friction resistance. SOLUTION: This aqueous ink for ink-jet printing includes a water dispersion of cationic vinyl polymer particulate and including a hydrophobic dye or pigment and is <=pH 4.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water-based 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 onto a recording member and adhered to obtain characters and images. According to this method, not only has the advantage that the device to be used has low noise and good operability, but also has the advantage that colorization is easy and plain paper can be used as a recording member. It has been widely used in recent years.

A water-soluble dye and a polyhydric alcohol are used in ink used in an ink jet printer in order to prevent clogging of the nozzle with the ink. However, this ink has poor water resistance and light resistance,
In particular, when the ink is used for a thermal jet type ink, the dye is oxidized by the heat of the heater surface, and the ink is liable to be scorched on the heater surface, resulting in a decrease in the ejection property.

In order to solve this drawback, an ink containing an aqueous dispersion of vinyl polymer particles having a specific structure and containing a hydrophobic dye has been proposed (Japanese Patent Laid-Open No. 9-2).
41565, JP-A-9-286939).
However, this ink has a disadvantage that the printed matter is blurred or distorted due to insufficient dischargeability.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-based ink for ink-jet recording which has good dischargeability, and is excellent in water resistance and scratch resistance.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a water-based ink for ink-jet recording which contains a water dispersion of cationic vinyl polymer particles containing a hydrophobic dye or pigment and has a pH of 4.5 or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a vinyl polymer, a cationic vinyl polymer is used. When this vinyl polymer is used and the pH is adjusted to 4.5 or less, excellent ejection properties are imparted to the obtained water-based ink.

It is to be noted that higher print density, higher fixability,
In order to obtain an aqueous ink having high dispersion stability, the vinyl polymer is represented by (a) a monomer having a salt-forming group (hereinafter, referred to as a component (a)) and (b) a formula (I). A monomer (hereinafter, referred to as a component (b));
Macromer [hereinafter referred to as component (c)] and (d) a monomer copolymerizable therewith [hereinafter referred to as component (d)]
Is preferably a vinyl polymer obtained by copolymerizing

Here, the salt-forming group means a group which can be neutralized with an acid to form a cationic group.

A typical example of the component (a) is a monomer containing a nitrogen atom. Specific examples thereof include unsaturated tertiary amine-containing monomers, unsaturated ammonium salt-containing monomers, and the like. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′,
N'-Dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferred.

The component (b) exhibits an excellent effect of improving the ejection stability of the water-based ink of the present invention and suppressing the occurrence of warpage even in continuous printing.

A typical example of the component (b) is represented by the following formula (I): CH ₂ ＣC (R ¹ ) COO (R ² O) _p R ³ (I)

(Wherein, R ¹ is a hydrogen atom or a lower alkyl group, and R ² is a carbon atom having 1 to 3 carbon atoms which may have a hetero atom.)
0 is a divalent hydrocarbon group, R ³ is a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and p is 1 to 6
And the like, which represents the number of 0).

In the formula (I), R ¹ is a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group include a linear or branched alkyl group having 1 to 4 carbon atoms.

R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom, a halogen atom and a sulfur atom.

Typical examples of R ² include an aromatic ring having 6 to 30 carbon atoms which may have a substituent, a heterocyclic ring having 3 to 30 carbon atoms which may have a substituent and a substituent. And an alkylene group having 1 to 30 carbon atoms which may have
Two or more of these rings or groups may be combined. Examples of the substituent include an aromatic ring having 6 to 29 carbon atoms, a heterocyclic ring having 3 to 29 carbon atoms, an alkyl group having 1 to 29 carbon atoms, a halogen atom, and an amino group.

Preferred examples of R ² include those having 1 to 24 carbon atoms.
A phenylene group which may have a substituent, having 1 to 1 carbon atoms
30, preferably an aliphatic alkylene group having 1 to 20 carbon atoms, an alkylene group having 7 to 30 carbon atoms having an aromatic ring, and an alkylene group having 4 to 30 carbon atoms having a hetero ring.

Preferred examples of the R ² O group include an ethylene oxide group, an (iso) propylene oxide group,
C2-C7 comprising a tetramethylene oxide group, a heptamethylene oxide group, a hexamethylene oxide group, and a combination of at least one of these alkylene oxides
Alkylene oxide group and phenylene oxide group.

R ³ is a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom and a sulfur atom.

Typical examples of R ³ include an aromatic ring having 6 to 30 carbon atoms which may have a substituent, a heterocyclic ring having 3 to 30 carbon atoms which may have a substituent, Examples thereof include an alkyl group having 1 to 30 carbon atoms which may have a group. Examples of the substituent include an aromatic ring having 6 to 29 carbon atoms, a heterocyclic ring having 4 to 29 carbon atoms, a halogen atom, and an amino group.

Preferred examples of R ³ include a phenyl group, an aliphatic alkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, and a heterocyclic ring. And an alkyl group having 4 to 30 carbon atoms having the formula:

More preferred examples of R ³ include a methyl group,
Ethyl group, (iso) propyl group, (iso) butyl group,
1 carbon atom such as (iso) pentyl group and (iso) hexyl group
To 6 alkyl groups, phenyl groups and the like.

P is a number from 1 to 60,
A number of 0 is preferred.

Specific examples of the alkylene oxide group-containing monomer represented by the formula (I) include methoxypolyethylene glycol (1 to 30: the value of p in the formula (I); the same applies hereinafter) (meth) acrylate, methoxy Polytetramethylene glycol (1-30) (meth) acrylate, ethoxy polyethylene glycol (1-30)
(Meth) acrylate, (iso) propoxy polyethylene glycol (1-30) (meth) acrylate, butoxy polyethylene glycol (1-30) (meth) acrylate, methoxy polypropylene glycol (1-3)
0) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymerization) (1 to 30, ethylene glycol therein: 1 to 29) (meth) acrylate, etc., each of which may be used alone or in combination of two or more. Can be used in combination. Among these,
Methoxy polyethylene glycol (1-30) (meta)
Acrylates are preferred. In addition, "(meth) acrylate" in this specification shows acrylate or methacrylate. “(Iso) propoxy” is n
-Indicates propoxy or isopropoxy.

The component (c) has a number average molecular weight of 500
Macromers which are monomers having a polymerizable unsaturated group of １００100,000, preferably 1,000〜１０10000 are exemplified. Among them, the formula (II): X (Y) _q Si (R ⁴ ) _3-r (Z) _r (II) (where X is a polymerizable unsaturated group, Y is a divalent linking group,
R ⁴ is each independently a hydrogen atom, a lower alkyl group, an aryl group or an alkoxy group, Z is a residue of a monovalent siloxane polymer having a number average molecular weight of 500 or more, and q is 0
Or 1, r represents an integer of 1 to 3), and / or a styrene-based macromer having a polymerizable functional group at one end.

The number average molecular weight of the macromer is measured by gel chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent, using polystyrene as a standard substance.

The silicone macromer can be suitably used from the viewpoint of preventing scorching of the head of an ink jet printer.

In the silicone macromer represented by the formula (II), X is a CH ₂ ＣＨCH— group, CH ₂ ＣC
A monovalent unsaturated hydrocarbon group having 2 to 6 carbon atoms such as a (CH ₃ ) — group is exemplified. Y represents -COO- group, -CO
OC _a H _2a - group (a is an integer of 1 to 5), include a divalent linking group such as phenylene group, -COOC ₃ H ₆ -
Is preferred. R ⁴ represents a hydrogen atom; a lower alkyl group having 1 to 5 carbon atoms such as a methyl group or an ethyl group; an aryl group having 6 to 20 carbon atoms such as a phenyl group or an alkoxy group having 1 to 20 carbon atoms such as a methoxy group. And the like, and among them, a methyl group is preferable. Z is preferably a number average molecular weight of 5
It is a monovalent residue of a dimethylsiloxane polymer having a molecular weight of 00 to 5000. q is 0 or 1, but preferably 1. r is an integer of 1 to 3, and is preferably 1.

As a typical example of the silicone macromer,
Formula (II-1): CH ₂ = CR ⁵ —COOC ₃ H ₆ — [Si (R ⁶ ) ₂ —O] _b —Si (R ⁶ ) ₃ (II-1) (where R ⁵ is a hydrogen atom Or a methyl group, R ⁶ is each independently a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms,
b represents a number of 5 to 60), a silicone macromer represented by the formula (II-2): CH ₂ = CR ⁵ -COO- [Si (R ⁶ ) ₂ -O] _b -Si (R ⁶ ) ₃ (II-2) a silicone macromer represented by the formula (wherein R ⁵ , R ⁶ and b are as defined above), formula (II-3): CH ₂ = CR ⁵ -Ph- [Si (R ⁶ ) ₂ -O] _b -Si (R ⁶ ) ₃ (II-3) (wherein Ph is a phenylene group, and R ⁵ , R ⁶ and b are the same as those described above), a compound represented by the formula (II-
4): CH ₂ = CR ⁵ —COOC ₃ H ₆ —Si (OE) ₃ (II-4) (wherein, R ⁵ is the same as above. E is a formula:-[Si (R ⁵ ) ₂ O] _c -S
i (R ⁵⁾ ₃ group (R ⁵ is the same .c is a number of 5 to 65 and above) and silicone macromer etc. represented by showing a).

Among these, the silicone macromer represented by the formula (II-1) is preferable, and particularly, the silicone macromer represented by the formula (II-1a)
: CH ₂ = C (CH ₃ ) -COOC ₃ H _6- [Si (CH ₃ ) ₂ -O] _d -CH ₃ (II-1a) (where d is a number from 8 to 40) The preferred silicone macromers are: As an example, FM-071
1 (manufactured by Chisso Corporation, trade name) and the like.

The styrenic macromer can be suitably used from the viewpoint of making the vinyl polymer sufficiently contain a pigment or dye.

Examples of the styrene macromer include a styrene homopolymer having a polymerizable functional group at one terminal or a copolymer of styrene and another monomer. Among these, those having an acryloyloxy group or a methacryloyloxy group as a polymerizable functional group at one end are preferable. From the viewpoint of ensuring that the pigment is sufficiently contained in the vinyl polymer, the styrene content in the copolymer is 6%.
It is desirably 0% by weight or more, preferably 70% by weight or more. Examples of the other monomer include acrylonitrile.

As the component (d), methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary)
Butyl (meth) acrylate, (iso) amyl (meth)
Acrylate, cyclohexyl (meth) acrylate,
Benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, (Meth) acrylic esters such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate; styrene monomers such as styrene, vinyl toluene, 2-methylstyrene, and chlorostyrene; Is
Each can be used alone or in combination of two or more. In addition, "(iso or tertiary) butyl"
Indicates n-, isobutyl or tertiary butyl. “(Iso)” indicates n- or iso.

The component (d) preferably contains a styrene monomer from the viewpoint of improving the printing density and the marker resistance. As the styrene monomer, styrene and 2-methylstyrene are preferable, and these may be used alone or in combination. In this case, the content of the styrene monomer in the component (d) is preferably from 10 to 100% by weight, and more preferably from 40 to 100% by weight, from the viewpoint of improving the printing density and the marker resistance.

The component (d) preferably contains a hydroxyl group-containing monomer from the viewpoint of ejection stability in an ink jet printer. As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate are preferable, and these may be used alone or in combination.
In this case, the content of the hydroxyl group-containing monomer in the component (d) is from 10 to 80% by weight, preferably from 15 to 50%, from the viewpoint of ejection stability in an inkjet printer.
% By weight.

The content of the component (a) in the vinyl polymer is from 1 to 50 in view of the dispersion stability of the resulting dispersion.
%, Preferably 5 to 40% by weight.

The content of the component (b) in the vinyl polymer is preferably from 5 to 50% by weight, and more preferably from 10 to 40% by weight, from the viewpoint of ejection stability and dispersion stability.

The total content of the component (a) and the component (b) in the vinyl polymer is preferably from 6 to 75% by weight from the viewpoint of dispersion stability in water and ejection stability.

The content of the component (c) in the vinyl polymer is from 1 to 25% by weight, preferably from 5 to 25% by weight, from the viewpoint of increasing the content of the hydrophobic dye or pigment and suppressing the scorching of the heater surface of the ink jet printer. 20
% By weight.

The content of the component (d) in the vinyl polymer is preferably from 5 to 93% by weight, and more preferably from 10 to 80% by weight, from the viewpoint of suppressing the scorching of the heater surface of the ink jet printer and the stability. . When the component (d) containing a styrene monomer is used, the content of the component (d) in the vinyl polymer is as follows:
10 to 60% by weight is preferred. When the component (d) containing a hydroxyl group-containing monomer is used, the content of the component (d) in the vinyl polymer is preferably from 1 to 30% by weight.

The vinyl polymer is produced by polymerizing the components (a) to (d) by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these polymerization methods, a solution polymerization method is preferable.

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 the organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol, and propanol; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate. Among them, methanol, ethanol, acetone, methyl ethyl ketone or a mixed solution of these with water is preferable.

At the time of polymerization, a radical polymerization initiator can be used. As the radical polymerization initiator,
2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisbutyrate, 2,2′-azobis (2-methyl Azo compounds such as butyronitrile) and 1,1'-azobis (1-cyclohexanecarbonitrile) are preferred. Further, organic peroxides such as t-butyl peroxyoctoate, di-t-butyl peroxide and dibenzoyl oxide can also be used.

The amount of the polymerization initiator is from 0.001 to 5 mol%, especially from 0.01 to 5 mol%, based on the total amount of the components (a) to (d).
Preferably it is 2 mol%.

In the polymerization, a polymerization chain transfer agent may be further added. Specific examples of the polymerization chain transfer agent include mercaptans such as octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, and mercaptoethanol;
Xanthogen disulfides such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide and tetrabutylthiuram disulfide; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide; hydrocarbons such as pentaphenylethane And acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate, turbinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer, and further 9,10-dihydroanthracene;
Unsaturated cyclic hydrocarbon compounds such as 1,4-dihydronaphthalene, indene, and 1,4-cyclohexadiene; 2,5
-Unsaturated heterocyclic compounds such as dihydrofuran and the like, and these can be used alone or in combination of two or more. The polymerization chain transfer agent is usually used in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of the charged monomer.

The polymerization conditions for the components (a) to (d) vary depending on the type of radical polymerization initiator, monomer and solvent used, but the polymerization temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C. And the polymerization time is 1 to 20 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as a nitrogen gas.

After completion of the polymerization reaction, reprecipitation from the reaction solution
The copolymer can be isolated by a known method such as solvent evaporation. The obtained copolymer can be purified by repeating reprecipitation or removing unreacted monomers and the like by membrane separation, chromatographic method, extraction method and the like.

The weight average molecular weight of the vinyl polymer (measured by the method described in Production Examples 1 to 3) is determined from the viewpoints of dischargeability, prevention of scorching of the printer head, durability of the aqueous ink after printing, and stability of the dispersion. From 3000 to 200,000, more preferably 5000 to 100
000.

Examples of the hydrophobic dye include oil dyes, disperse dyes, direct dyes, acid dyes, basic dyes and the like.
Among these, oil-based dyes and disperse dyes are preferred from the viewpoint of favorably including them in the vinyl polymer particles.

Examples of the oily dyes include CI Solvent Black, CI Solvent Yellow, CI Solvent Red, CI Solvent Violet, CI Solvent Blue, CI Solvent Green, CI Solvent Orange and the like.

Examples of the disperse dye include CI Disperse Yellow, CI Disperse Orange, CI Disperse Red, CI Disperse Violet, CI Disperse Blue, and CI Disperse Green Series.

As the pigment, any of an inorganic pigment and an organic pigment may be used. If necessary, extenders can be used in combination with them.

Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, metal chloride and the like. Among these, carbon black is particularly preferred for black aqueous inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.

Examples of the organic pigment include an azo pigment, a diazo pigment, a phthalocyanine pigment, a quinacridone pigment, an isoindolinone pigment, a dioxazine pigment, a perylene pigment, a perinone pigment, a thioindigo pigment, an anthoraquinone pigment, and a quinophthalone pigment.

Examples of the extender include silica, calcium carbonate, talc and the like.

The total amount of the hydrophobic dye and the pigment is from 20 to 400 parts by weight, based on 100 parts by weight of the resin solid content of the vinyl polymer, from the viewpoint of the printing density and the ease of containing the same.
Preferably, the amount is 30 to 300 parts by weight.

The aqueous dispersion of vinyl polymer particles containing a hydrophobic dye or pigment can be prepared by, for example, dissolving a vinyl polymer in a hydrophilic organic solvent together with a hydrophobic dye, adding a neutralizing agent if necessary, A method in which the salt-forming group is cationized, and then water is added, followed by distilling off the hydrophilic organic solvent and inverting the phase to an aqueous phase, dissolving the vinyl polymer in the organic solvent, and adding a neutralizing agent as necessary to obtain the polymer A method of cationizing the salt-forming group in the mixture, then adding water and a pigment and kneading the mixture, distilling the organic solvent from the kneaded product to an aqueous system, dissolving a vinyl polymer and a hydrophobic dye in a water-insoluble organic solvent. To the resulting solution, water, a neutralizing agent and, if necessary, a surfactant are added to cationize the salt-forming group in the polymer, and then the resulting mixture is emulsified, followed by distilling off the water-insoluble organic solvent. Water dispersion It can be prepared by law or the like.

Examples of the neutralizing agent include inorganic acids such as hydrochloric acid, nitrous acid, sulfuric acid and phosphoric acid, carboxylic acids having 1 to 5 carbon atoms, and 2 carbon atoms.
And organic acids such as oxyacids such as dialkylphosphoric acid, lactic acid, glycolic acid, glyceric acid and gluconic acid. It is desirable to adjust the degree of neutralization so that the resulting aqueous dispersion has a neutral liquidity.

The particle size of the cationic vinyl polymer particles containing a hydrophobic dye or pigment is from 0.01 to 0.5 from the viewpoint of preventing bleeding of the aqueous ink and dispersion stability.
0 μm is preferable, and 0.02 to 0.15 μm is more preferable.

The amount of the aqueous dispersion of the cationic vinyl polymer particles containing the hydrophobic dye or pigment in the aqueous ink is usually the amount of the vinyl polymer particles in the aqueous ink from the viewpoint of print density and ejection stability. 1-35
It is desirable to adjust the amount to be 2% by weight, preferably 2 to 15% by weight.

The pH of the aqueous ink of the present invention is 4.5 or less, preferably 1 to 4.2, more preferably 1.5 to 1.5.
By adjusting so as to be 4.0, particularly preferably 1.5 to 3.9, it is possible to improve the ejection stability and eliminate ejection defects such as blurring and twisting. The reason why such excellent effects are exhibited is that by setting the pH to 4.5 or less, the ionicity of the water-based ink is increased, and the hydrophilicity of the water-based ink is increased. It is possible to suppress the ink droplets remaining on the face surface of the ink ejection part of the printer and around the nozzles, and as a result,
This is considered to be due to the fact that the ink droplets hardly remain around the nozzles and the direction of the ejected ink does not change even when continuous printing is performed, so that the printed matter is not blurred or distorted. It is preferable that the pH be 1.5 or more from the viewpoint of preventing disconnection of the heater wiring of the printer due to corrosion.

The pH of the water-based ink can be adjusted using an acid. Examples of the acid include an inorganic acid and an organic acid, and these can be used alone or in combination of two or more. Of these, monovalent acids are preferred from the viewpoint of dispersion stability. Incidentally, the amount of the acid depends on the desired pH.
It is preferable to adjust so that

Examples of the inorganic acid include hydrochloric acid, nitrous acid, nitric acid and the like. Further, as the organic acid, one having one carbon atom such as
To 5 carboxylic acids, lactic acid, glycolic acid, glyceric acid, gluconic acid and the like. Among these, an organic acid is preferable from the viewpoint of preventing disconnection of the heater wiring of the printer due to corrosion. In particular, oxyacids such as lactic acid, glycolic acid, gluconic acid, and glyceric acid are preferred for providing excellent ejection properties. The oxyacid and / or its salt, whether as the neutralizing agent or as a pH adjuster, is used as an acid in an aqueous ink at 0.001%.
To 20% by weight, preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, particularly preferably 0.3 to 5% by weight.
The content of 2% by weight is desirable from the viewpoint of dischargeability.

The water-based ink for ink-jet recording of the present invention may contain a wetting agent, a dispersing agent, a defoaming agent, a fungicide,
Additives such as chelating agents can be added.

[0065]

EXAMPLES Production Examples 1 to 3 A reaction vessel was charged with 20 parts by weight of methyl ethyl ketone, the monomers described in the column of initially charged monomers in Table 1, and a polymerization chain transfer agent, and sufficiently purged with nitrogen gas.

On the other hand, in the dropping funnel, the monomers and the polymerization chain transfer agent, 60 parts by weight of methyl ethyl ketone and 2,2′-azobis (2,4-dimethylvaleronitrile) .2 parts by weight,
It was charged after sufficient nitrogen substitution.

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, a solution prepared by dissolving 0.3 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) in 5 parts by weight of methyl ethyl ketone was added, and further added at 65 ° C. for 2 hours and at 70 ° C. 2
After aging for a time, a copolymer solution was obtained.

A part of the obtained copolymer solution was removed under reduced pressure.
Dried at 105 ° C. for 2 hours, isolated by removing the solvent, polystyrene as standard, 1 as solvent.
The weight average molecular weight was measured by gel permeation chromatography using chloroform containing mmol / L dodecyldimethylamine. Table 1 shows the results.

The copolymer solution obtained was dried under reduced pressure, and 5 parts by weight of the copolymer obtained was dissolved in 25 parts by weight of the organic solvent shown in Table 1 and the neutralizing agent (30 % Aqueous solution) to neutralize a part of the copolymer, further add 5 parts by weight of a pigment, and knead the mixture with a bead mill.

After adding 30 parts by weight of ion-exchanged water to the obtained kneaded product and stirring, the organic solvent is removed at 60 ° C. under reduced pressure, and a part of the water is further removed, whereby the solid content concentration is reduced. An aqueous dispersion of 20% pigment-containing vinyl polymer particles was obtained.

Production Example 4 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. The weight average molecular weight of the copolymer obtained in the same manner as in Production Example 1 was 43,000.

The obtained copolymer solution was dried under reduced pressure, 25 parts by weight of the organic solvent shown in Table 1 and 5 parts by weight of oil black as a hydrophobic dye were added to 5 parts by weight of the obtained copolymer, and the mixture was stirred. And a uniform composition. Next, a predetermined amount of a neutralizing agent (30% aqueous solution) shown in Table 1 was added to this solution to neutralize a part of the salt-forming groups of the copolymer, and 300 parts by weight of ion-exchanged water was added thereto. After stirring, using a microfluidizer (manufactured by Microfluidizer),
Emulsified for 30 minutes.

The emulsion obtained was completely removed at 60 ° C. under reduced pressure from the organic solvent and further concentrated by removing water to obtain an aqueous dispersion of dye-containing vinyl polymer particles having a solid content of 20% by weight. I got

The names described in Table 1 mean the following. Styrene macromer A: manufactured by Toa Gosei Co., Ltd., trade name: A
N-6 (styrene-acrylonitrile copolymer macromer, styrene content: 75% by weight, number average molecular weight: 600
0, polymerizable functional group: methacryloyloxy group) Styrene macromer B: manufactured by Toagosei Co., Ltd., trade name: A
S-6 (styrene homopolymer macromer, number average molecular weight:
6000, polymerizable functional group: methacryloyloxy group) Silicone macromer: manufactured by Chisso Corporation, trade name: FM
-0711 (number average molecular weight: 1000, compound represented by formula (II-1a)) Pigment Yellow 17: manufactured by Dainichi Seika Kogyo Co., Ltd., trade name:
ECY-215 Carbon black A: Degussa, trade name: Printex-90 Carbon black B: Cabot, trade name: Monarc
h880 oil black: manufactured by Orient Chemical Co., Ltd., trade name: oil black 860

[0075]

[Table 1]

Examples 1 to 4 40 parts by weight of an aqueous dispersion of the dye or pigment-containing vinyl polymer particles obtained in Production Examples 1 to 4, 5 parts by weight of glycerin, 10 parts by weight of urea, and an acetylene glycol / polyethylene oxide adduct ( 1 part by weight of Kawaken Fine Chemical Co., Ltd., trade name: acetylenol EH), and an acid and ion-exchanged water shown in Table 2 were mixed so that the total amount of the ink became 100 parts by weight, and the obtained liquid mixture was average pore diameter. Is a 0.5 μm filter (acetyl cellulose membrane, outer diameter: 2.5 cm,
25mL capacity with Fuji Photo Film Co., Ltd.)
Example 1 corresponding to Production Examples 1 to 4 by filtering through a needleless syringe (manufactured by Terumo Corporation) to remove coarse particles.
~ 4 aqueous inks were obtained.

Comparative Examples 1 and 2 In Examples 1 and 2, except that no acid was added,
In the same manner as in Examples 1 and 2, water-based inks of Comparative Examples 1 and 2 corresponding to Examples 1 and 2, respectively, were obtained.

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

(1) Continuous dischargeability A commercially available Hewlett Packard (HEWLETT PACKARD)
Bubble jet printer (Model: Desk Jet-720)
C), 100 sheets of text printing (1500 characters) and 10 sheets of solid printing were performed on commercially available copy paper, and the print quality after printing was visually observed, and evaluated based on the following evaluation criteria.

[Evaluation Criteria] ：: No distortion or blurring ○: Almost no distortion or blurring Δ: Slightly blurred or blurred ×: Distorted or blurred

(2) Water resistance Using the above printer, solid printing was performed on commercial copy paper, and the print density of a specific print portion of a sample dried at 25 ° C. for 1 hour was measured. The copy paper was dipped for 10 seconds and pulled up vertically.

After air-drying at 25 ° C. for 24 hours, the print density at the same location as before the immersion was measured, and the residual ratio of the print density after the immersion to the print density before the immersion was calculated by the formula: [residual rate] =
[Print density after immersion] / [Print density before immersion] × 100
And evaluated based on the following evaluation criteria.

[Evaluation Criteria] ：: Residual rate 95% or more 以上: Residual rate 90% or more and less than 95% Δ: Residual rate 70% or more and less than 90% ×: Residual rate less than 70%

(3) Scratch Resistance Using the above-mentioned printer, solid printing was carried out on a commercially available copy paper, dried at 25 ° C. for 24 hours, and the printed surface was strongly rubbed with a finger. The printing condition was evaluated based on the following evaluation criteria. [Evaluation Criteria] ：: Printing is hardly obtained and the surroundings are not stained. Δ: Printing is slightly rubbed, surroundings are slightly stained, and fingers are slightly stained. Also get quite dirty.

[0085]

[Table 2]

From the results shown in Table 2, it can be seen that the water-based inks obtained in each of the examples are excellent in continuous ejection properties, and further excellent in water resistance and scratch resistance. . Further, in Examples 2 to 4, since the oxyacid is used as the acid, it can be seen that the continuous dischargeability is further excellent.

[0087]

The water-based ink for ink-jet recording of the present invention has good ejection properties, and is excellent in water resistance and scratch resistance.

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Claims (4)

[Claims] 1. A water-based ink for ink-jet recording comprising an aqueous dispersion of cationic vinyl polymer particles containing a hydrophobic dye or pigment and having a pH of 4.5 or less. 2. A vinyl polymer comprising (a) a salt-forming group-containing monomer and (b) a compound of the formula (I): CH ₂ ＣC (R ¹ ) COO (R ² O) _p R ³ (I) , R ¹ is a hydrogen atom or a lower alkyl group, R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ is a carbon atom which may have a hetero atom. A monovalent hydrocarbon group of 1 to 30, p represents a number of 1 to 60), (c) a macromer,
2. The aqueous ink for ink-jet recording according to claim 1, which is a vinyl polymer obtained by copolymerizing (d) a monomer copolymerizable therewith. 3. The macromer is represented by the formula (II): X (Y) _q Si (R ⁴ ) _3-r (Z) _r (II) (where X is a polymerizable unsaturated group, and Y is divalent A bonding group of
R ⁴ is independently a hydrogen atom, a lower alkyl group, an aryl group or an alkoxy group, Z is a residue of a monovalent siloxane polymer having a number average molecular weight of 500 or more, and q is 0
Or 1, a or r is an integer of 1 to 3), a silicone macromer and / or a styrene macromer having a polymerizable functional group at one end. 4. The aqueous ink for inkjet recording according to claim 1, which comprises an oxyacid and / or a salt thereof.