JP2008156524A - Water-based ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an aqueous dispersion for inkjet recording, which provides printed matter having excellent printing performances such as print density, chroma, etc., and a water-based ink containing the same. <P>SOLUTION: The aqueous dispersion for inkjet recording comprises a polymer particle composed of a quinacridone solid solution pigment (A) containing two or more kinds of quinacridone-based compounds and a polar group-containing pigment derivative (B). The water-based ink comprises the aqueous dispersion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion for inkjet recording and a water-based ink, which can obtain a printed matter having excellent printing performance.

The ink jet recording system is a recording system in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle and attaching them to a recording member. This method is widely spread because it is easy to make full color and is inexpensive, and has many advantages such as the ability to use plain paper as a recording member and non-contact with the object to be printed.
In particular, from the viewpoint of weather resistance and water resistance of printed matter, those using pigment-based ink as a colorant have become mainstream (for example, see Patent Documents 1 to 4).

Patent Document 1 discloses an ink for a jet printer containing a quinacridone solid solution pigment composed of two or more quinacridone compounds.
Patent Document 2 discloses an aqueous ink containing an aqueous dispersion of water-insoluble vinyl polymer particles containing a solid solution magenta pigment, wherein the polymer is a copolymer of at least an alicyclic (meth) acrylate and a salt-forming group-containing monomer. Is disclosed.
Patent Document 3 discloses an aqueous dispersion containing water-insoluble vinyl polymer particles containing a quinacridone pigment and a pigment derivative into which an acid group is introduced.
Patent Document 4 discloses an ink jet recording pigment in which a mixture containing a quinacridone solid solution pigment, a salt-forming group-containing polymer, a neutralizing agent, an organic solvent and water is kneaded and then diluted and dispersed by adding water and / or an organic solvent. An aqueous dispersion is disclosed.
Although the above-mentioned water dispersion or water-based ink has some improvement in physical properties, it is not satisfactory in printing performance.

JP-A-10-219166 JP 2005-029597 A Japanese Patent Laying-Open No. 2005-042012 JP 2006-104367 A

  An object of the present invention is to provide an aqueous dispersion for inkjet recording, and a water-based ink including the same, which can obtain a printed matter excellent in printing performance such as ejection reliability, printing density, and saturation.

The present inventors have found that the above problem can be solved by using a quinacridone solid solution pigment in combination with a pigment derivative having a polar group.
That is, the present invention provides the following (1) and (2).
(1) An aqueous dispersion for ink jet recording comprising a quinacridone solid solution pigment (A) containing two or more kinds of quinacridone compounds and a polymer particle containing a pigment derivative (B) having a polar group.
(2) A water-based ink for ink-jet recording comprising the water dispersion of (1).

  According to the water-based ink containing the aqueous dispersion for inkjet recording of the present invention, it is possible to obtain an excellent printed matter having excellent image uniformity and fixability in addition to ejection reliability, print density and saturation, and no intercolor bleeding. it can.

  The aqueous dispersion for ink-jet recording and aqueous ink of the present invention have a quinacridone solid solution pigment containing two or more quinacridone compounds (A And polymer particles containing the pigment derivative (B) having a polar group. Hereinafter, each component used for this invention is demonstrated.

[Quinacridone solid solution pigment containing two or more quinacridone compounds (A)]
The quinacridone solid solution pigment (A) containing two or more quinacridone compounds used in the present invention (hereinafter sometimes simply referred to as “quinacridone solid solution pigment (A)”) is a mixture of two or more quinacridone compounds. It is a pigment having different physical properties such as hue, weather resistance and heat resistance.
Examples of the quinacridone compound include compounds represented by the following general formula (I).
_{X n -Q-Y m (I} )
(In the formula, Q represents a quinacridone residue or a quinacridonequinone residue, X and Y represent a hydrogen atom, a methyl group, a chloro group, or a methoxy group, and n and m represent an integer of 1 to 4.)
More specifically, unsubstituted quinacridone, 2,9-dimethylquinacridone, 2,9-dichloroquinacridone, 2,9-dimethoxyquinacridone, 3,10-dimethylquinacridone, 3,10-dichloroquinacridone, 3,10 -Dimethoxyquinacridone, 4,11-dimethylquinacridone, 4,11-dichloroquinacridone, 4,11-dimethoxyquinacridone, quinacridonequinone and the like.

Preferable examples of the quinacridone solid solution pigment (A) include solid solution pigments containing two kinds selected from the group consisting of unsubstituted quinacridone, dimethyl-substituted quinacridone and dichloro-substituted quinacridone. Specifically, (1) a solid solution pigment of dimethyl-substituted quinacridone such as unsubstituted quinacridone and 2,9-dimethylquinacridone, (2) unsubstituted quinacridone and 2,9-dichloroquinacridone, 3,10-dichloroquinacridone Solid solution pigments such as dichloro-substituted quinacridone such as dimethyl-substituted quinacridone such as 2,9-dimethylquinacridone and solid-solution pigments such as 2,9-dichloroquinacridone and dichloro-substituted quinacridone such as 3,10-dichloroquinacridone A solid solution pigment comprising a combination of these is preferred.
Among the above, the solid solution pigment of (1) unsubstituted quinacridone and dimethyl substituted quinacridone is preferable, specifically, unsubstituted quinacridone (CI Pigment Violet 19 etc.) and 2,9-dimethylquinacridone ( C. I. Pigment Red 122 etc.) is preferable from the viewpoint of hue.
As the unsubstituted quinacridone, any of α-type, β-type, and γ-type can be used, but β-type or γ-type unsubstituted quinacridone is preferable from the viewpoint of storage stability. For example, a solid solution magenta pigment disclosed in JP-A-10-219166 can also be used.

The weight ratio of [unsubstituted quinacridone / dimethyl substituted quinacridone], [unsubstituted quinacridone / dichloro substituted quinacridone], and [dimethyl substituted quinacridone / dichloro substituted quinacridone]] in the quinacridone solid solution pigment (A) is: From the viewpoint of ejection reliability, print density, saturation, etc., it is preferably 10/90 to 90/10, more preferably 15/85 to 85/15.
The quinacridone solid solution pigment (A) can be produced by a known method. For example, (i) a method in which a crude unsubstituted quinacridone and a quinacridone compound are dissolved in an aprotic polar organic solvent in the presence of caustic alkali and neutralized and reprecipitated with an acid (see JP-A-60-35055), (Ii) A method of pulverizing a crude or auxiliary pigment quinacridone compound in the presence of solubilizing amounts of alcohol and base and isolating the resulting solid solution (see JP-A-2-38463), and (iii) two types Examples include a method of subjecting the above 2,5-diarylaminoterephthalic acid derivative to condensation cyclization, followed by pigmentation treatment (control of crystal form, size, crystal form) (see JP-A-10-219166). It is done.
The form of the quinacridone solid solution pigment (A) may be a powdery, granular, or massive dry pigment, or a wet cake or slurry.

  The average particle size of the quinacridone solid solution pigment (A) is preferably 0.01 to 0.3 μm, more preferably 0.03 to 0.2 μm, from the viewpoint of dispersion stability. In addition, the average particle diameter was calculated | required from the average value of the long diameter of 100 pigments by the image analysis (20,000 times) by an electron microscope (TEM).

[Pigment derivative having polar group (B)]
The pigment derivative (B) having a polar group (hereinafter, sometimes simply referred to as “pigment derivative (B)”) has a function as a surface treatment agent for the quinacridone solid solution pigment (A), and includes an aqueous dispersion and an aqueous ink. Is used to increase the dispersion stability, print density, saturation, etc.
The pigment derivative (B) is obtained by introducing a polar group into an organic pigment, and the polar group includes a sulfonic acid group, a carboxy group, a phosphoric acid group, a sulfinic acid group, an amino group, an amide group, and a phthalimide group. 1 or more types chosen from a group are mentioned. Among these, sulfonic acid groups and phthalimide groups are preferable from the viewpoint of dispersion stability and the like.

The organic pigment used for the pigment derivative (B) is not particularly limited. Examples thereof include quinacridone pigments, phthalocyanine pigments, azo pigments, quinophthalone pigments, and isoindolinone pigments. Further, the hue of the organic pigment is not limited, and any of a magenta pigment, a yellow pigment, and a cyan pigment may be used.
Examples of the magenta pigment include C.I. which is a quinacridone pigment. I. Pigment Red 122, 202, 209; C.I. I. Pigment violet 19; C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 17, 17, 22, 23, 30, 31, 31, 38, 88, 112, 114, 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 219, etc. Is mentioned.
Among these, from the viewpoint of remarkably expressing the effects of the present invention, C.I. I. Pigment red 122, 202, 209 and C.I. I. One or more selected from Pigment Violet 19 are particularly preferable.

The pigment derivative (B) preferably has the same or similar mother skeleton as the organic pigment from the viewpoint of improving the adsorptivity to the surface of the organic pigment, mixing / dispersing stability with the polymer, and saturation, More preferably, a polar group is introduced into an organic pigment having the same or similar mother skeleton as the quinacridone compound contained in the solid solution pigment (A).
The production method of the pigment derivative (B) includes (i) a method of synthesizing a compound having the same or similar mother skeleton as the organic pigment, and then introducing a polar group using the reactivity of the compound, (ii) organic Examples include a method of synthesizing a pigment derivative having a polar group introduced at the same time as the synthesis of the pigment.
Among the pigment derivatives (B), the quinacridone sulfonic acid compound (b-1) and / or the quinacridone compound (b-2) having a substituent containing a phthalimide skeleton is preferable from the viewpoint of printing density, saturation, and the like. .
In the present invention, the quinacridone sulfonic acid compound (b-1) and the quinacridone compound (b-2) are not included in the quinacridone compound in the quinacridone solid solution pigment (A).

The quinacridone sulfonic acid compound (b-1) is not particularly limited, and known compounds can be used. Examples thereof include quinacridone sulfonic acids and metal salts thereof such as sodium, aluminum and calcium, and ammonium salts thereof such as ammonium, octadecyl ammonium, didodecyl ammonium, dimethyl octadecyl ammonium, dimethyl dioctadecyl ammonium and benzyl dimethyl octadecyl ammonium.
Among these, metal salts such as aluminum salts, calcium salts, and sodium salts of quinacridone sulfonic acid are preferable, and aluminum salts are more preferable from the viewpoint of suppressing the negative effects such as migration and bleed. More specifically, aluminum 3,10-dichloroquinacridone sulfonate is particularly preferable.
The quinacridone sulfonic acid compound (b-1) can be obtained by a method of introducing a sulfonic acid group into the quinacridone compound, for example, a method of reacting a sulfonating agent such as sulfuric acid, fuming sulfuric acid or chlorosulfuric acid.
The average number of sulfonic acid groups per molecule in the quinacridone sulfonic acid compound (b-1) is preferably 0.5 to 2, and more preferably 0.7 to 1.5. If the average number of substitutions is 0.5 or more, a sufficient effect is exhibited, and if it is 2 or less, ink bleeding or the like can be reduced.

The quinacridone compound (b-2) having a substituent containing a phthalimide skeleton is a quinacridone compound having a substituent, and the phthalimide skeleton is included as part of the structure of the substituent. Preferable examples thereof include phthalimidomethylated quinacridone compounds, and phthalimidated methyl-3,10-dichloroquinacridone is particularly preferable.
The average number of phthalimide skeletons per molecule in the quinacridone compound (b-2) is preferably 1 to 2, more preferably 1 to 1.5. If the average phthalimide skeleton number is 1 or more, a sufficient effect is exhibited, and if it is 2 or less, ink bleeding or the like can be reduced.
For example, when this quinacridone compound (b-2) is a phthalimidomethylated quinacridone compound, unsubstituted quinacridone, dimethylquinacridone, dichloroquinacridone, etc. are reacted with phthalimide and formaldehyde or paraformaldehyde in concentrated sulfuric acid. Can be obtained.
The average number of substitutions of phthalimidomethyl groups per molecule of reaction product obtained by this reaction may be less than 1. In this case, it can be regarded as a mixture of phthalimidomethylated quinacridone compounds and unsubstituted quinacridone pigments. . For example, when the average number of substitutions per molecule of the reaction product obtained by the above reaction is 0.7, the quinacridone compound (b-2) 0.7 having an average number of phthalimide skeletons per molecule of 0.7 And a mixture of 0.3 part of quinacridone pigment.
The pigment derivative (B) may be in the form of a powder, granule or block dry pigment, or a wet cake or slurry.

  In the water dispersion and the water-based ink of the present invention, the quinacridone solid solution pigment (A) and the pigment derivative (B) are used alone or in combination of two or more. When mixing the quinacridone solid solution pigment (A) and the pigment derivative (B), they may be synthesized and mixed in the same synthesis tank, or they may be synthesized separately, followed by a drying step, a pulverizing step, and a classification step. And may be mixed in any step such as a pigment dispersion step. It is preferable to synthesize both in the same synthesis tank from the viewpoint of uniforming the primary particle diameter and improving the dispersion stability. The mixture only needs to be mixed, and the whole does not necessarily have to be mixed uniformly.

The weight ratio of [pigment derivative (B) / quinacridone solid solution pigment (A)] is preferably 0.005 to 0.3, more preferably 0.01 to 0.2, still more preferably 0.015 to 0.15. Especially preferably, it is 0.02-0.1.
In addition, the weight ratio of [[quinacridone solid solution pigment (A) + pigment derivative (B)] / [polymer solid content]] is improved in terms of improving the printing density, saturation, etc., as well as in dispersion stability and polymer particles. From the viewpoint of easy inclusion, it is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, and particularly preferably 50/50 to 80/20.

〔polymer〕
As the polymer constituting the polymer particles used in the present invention, when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the dissolution amount is preferably 10 g or less, more preferably A water-insoluble polymer of 5 g or less, more preferably 1 g or less is preferred. The dissolution amount is the dissolution amount when the polymer salt-forming groups are neutralized 100% with acetic acid or sodium hydroxide according to the kind of the salt-forming groups.
Examples of the water-insoluble polymer include a salt-forming group-containing monomer (a) (hereinafter sometimes referred to as “(a) component”), a macromer (b) (hereinafter sometimes referred to as “(b) component”), a carbon number 12 to 22 linear or branched alkyl group or alkenyl group-containing monomer (c) (hereinafter sometimes referred to as “component (c)”) and / or aromatic ring-containing monomer (d) (hereinafter referred to as “component (d)”) A graft polymer obtained by copolymerizing a monomer mixture (hereinafter sometimes referred to as “monomer mixture”) containing a structural unit derived from “sometimes”. This graft polymer has a structural unit derived from the component (a), a structural unit derived from the component (b), a structural unit derived from the component (c) and / or a structural unit derived from the component (d). A more preferable polymer has a structural unit derived from the component (a), a structural unit derived from the component (c) and / or a structural unit derived from the component (d) in the main chain, and a structural unit derived from the component (b). In the side chain.

The salt-forming group-containing monomer (a) is used from the viewpoint of improving the dispersion stability of the resulting aqueous dispersion. Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group, and a carboxy group is particularly preferable.
Examples of the salt-forming group-containing monomer (a) include cationic monomers and anionic monomers described in paragraph [0022] of JP-A-9-286939.
Representative examples of the cationic monomer include unsaturated amine-containing monomers and unsaturated ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.
Representative examples of anionic monomers include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and the like.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxy Examples thereof include ethyl phosphate.
Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

The macromer (b) is used from the viewpoint of improving the dispersion stability of polymer particles containing a pigment. The macromer includes a macromer which is a monomer having a polymerizable unsaturated group having a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. The number average molecular weight of the macromer (b) was standardized by gel chromatography using Tosoh Corporation G4000HXL + G2000HXL as a column and tetrahydrofuran (THF) containing 50 mM CH ₃ COOH / 1 grade as an eluent. Measured using polystyrene as material.
Among the macromers (b), from the viewpoint of dispersion stability of polymer particles, styrene macromers and aromatic group-containing (meth) acrylate macromers having a polymerizable functional group at one end are preferable.
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. Examples of the styrene monomer include styrene, 2-methylstyrene, vinyl toluene, ethyl vinyl benzene, vinyl naphthalene, chlorostyrene, and the like.

Examples of the aromatic group-containing (meth) acrylate-based macromer include a homopolymer of an aromatic group-containing (meth) acrylate or a copolymer thereof with another monomer. As an aromatic group-containing (meth) acrylate, an arylalkyl having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, which may have a substituent containing a hetero atom. (Meth) acrylate having an aryl group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a group or a substituent containing a hetero atom In addition, examples of the substituent containing a hetero atom include a halogen atom, an ester group, an ether group, and a hydroxy group. Examples include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and benzyl (meth) acrylate is particularly preferable.
The polymerizable functional group present at one end of the macromer is preferably an acryloyloxy group or a methacryloyloxy group, and the other monomer to be copolymerized is preferably acrylonitrile.
The content of the styrene monomer in the styrene macromer or the aromatic group-containing (meth) acrylate in the aromatic group-containing (meth) acrylate macromer is preferably 50% by weight from the viewpoint of increasing the affinity with the pigment. As mentioned above, More preferably, it is 70 weight% or more.

The macromer (b) may have a side chain composed of another structural unit such as an organopolysiloxane. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end represented by the following formula (1).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 1)
(In the formula, t represents a number of 8 to 40).
Examples of commercially available styrenic macromers as component (b) include Toa Gosei Co., Ltd. trade names, AS-6 (S), AN-6 (S), HS-6 (S), and the like. It is done.

The linear or branched alkyl group or alkenyl group-containing monomer (c) having 12 to 22 carbon atoms is used from the viewpoint of improving storage stability, printing density, and image uniformity. (C) As a component, the alkyl (meth) acrylate which has a C12-C22, especially C14-C20 alkyl group is preferable.
Preferable examples of the component (c) include (iso) dodecyl (meth) acrylate, (iso) tetradecyl (meth) acrylate, (iso) palmityl (meth) acrylate, (iso) stearyl (meth) acrylate and the like.

The monomer mixture may further contain a hydrophobic monomer (d) (hereinafter sometimes referred to as “component (d)”) from the viewpoint of improving the printing density and image uniformity.
The hydrophobic monomer (d) is a hydrophobic monomer other than the component (c), and examples thereof include alkyl (meth) acrylates having an alkyl group having 11 or less carbon atoms and aromatic group-containing monomers.
Examples of the alkyl (meth) acrylate having an alkyl group having 11 or less carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, and (iso or tertiary) butyl (meth). Examples include acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, and the like.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Indicates. “(Meth) acrylate” indicates acrylate, methacrylate, or both.
The aromatic group-containing monomer has an aromatic group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a substituent containing a hetero atom. Vinyl monomers are preferable, and examples thereof include the styrene monomer (d-1 component) and the aromatic group-containing (meth) acrylate (d-2 component). The above-mentioned thing is mentioned as a substituent containing a hetero atom.
Among the components (d), a styrene monomer (d-1 component) is preferable from the viewpoint of improving printing density, and styrene and 2-methylstyrene are particularly preferable as the styrene monomer (d-1 component). The content of the component (d-1) in the component (d) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density.
Moreover, as an aromatic group containing (meth) acrylate (d-2) component, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. are preferable. The content of the component (d-2) in the component (d) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density and gloss.
Moreover, it is also preferable to use (d-1) component and (d-2) component together.

The monomer mixture may further contain a hydroxyl group-containing monomer (e) (hereinafter sometimes referred to as “component (e)”). The hydroxyl group-containing monomer (e) exhibits an excellent effect of improving dispersion stability.
As the component (e), for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of added moles of oxyalkylene group. The same)) (meth) acrylate, polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, etc. Can be mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable.

The monomer mixture may further contain a monomer (f) represented by the following formula (2) (hereinafter sometimes referred to as “component (f)”).
CH ₂ = C (R ¹ ) COO (R ² O) _q R ³ (2)
Wherein R ¹ is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ is , A C1-C11 monovalent hydrocarbon group which may have a hetero atom or an aryl group which may have a C1-C8 alkyl group, q means the average number of moles added And a number of 1 to 60, preferably a number of 1 to 30.)
The component (f) exhibits an excellent effect of improving the discharge property.
In the formula (2), examples of the hetero atom include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Preferable examples of R ¹ include methyl group, ethyl group, (iso) propyl group and the like.
Preferred examples of the R ² O group include an oxyethylene group, an oxytrimethylene grave, an oxypropane-1,2-diyl group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, and two or more kinds thereof. Examples thereof include oxyalkanediyl groups having 2 to 7 carbon atoms (oxyalkylene groups).
Preferable examples of R ³ include an aliphatic alkyl group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, a phenyl group, and a benzyl group.

  Specific examples of the component (f) include methoxypolyethylene glycol (1 to 30: the value of q in the formula (2), the same applies hereinafter) (meth) acrylate, methoxypolytetramethylene glycol (1 to 30) ( (Meth) acrylate, ethoxy polyethylene glycol (1-30) (meth) acrylate, octoxy polyethylene glycol (1-30) (meth) acrylate, polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether, (iso) Propoxy polyethylene glycol (1-30) (meth) acrylate, butoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol) Polymerization) (1 to 30, ethylene glycol therein: 1-29) (meth) acrylate. Among these, octoxypolyethylene glycol (1-30) (meth) acrylate and polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether are preferable.

Specific examples of the commercially available (e) and (f) components include Shin-Nakamura Chemical Co., Ltd. polyfunctional acrylate monomer (NK ester) M-40G, 90G, 230G, and Nippon Oil & Fats Co., Ltd. BLEMMER series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800 , 50PEP-300, 50POEP-800B, 43PAPE600B, and the like.
The components (a) to (f) can be used alone or in admixture of two or more.

The content of the components (a) to (f) in the monomer mixture (content as an unneutralized amount; the same applies hereinafter) or the components (a) to (f) in the production of the water-insoluble polymer The content of the structural unit derived from is as follows.
The content of component (a) is preferably 2 to 40% by weight, more preferably 2 to 30% by weight, and particularly preferably 3 to 20% by weight from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (b) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, particularly from the viewpoint of enhancing the interaction with the colorant.
The content of the component (c) is preferably 10 to 70% by weight, more preferably 10 to 60% by weight from the viewpoints of storage stability, print density improvement, and image uniformity.
The content of the component (d) is preferably 2 to 70% by weight, more preferably 3 to 60% by weight, from the viewpoint of improving print density and image uniformity.
The content of component (e) is preferably 5 to 40% by weight, more preferably 7 to 20% by weight, from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (f) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, from the viewpoint of improving dischargeability.
The total content of [(c) component + (d) component] in the monomer mixture is preferably 10 to 80% by weight, more preferably 20 to 70% by weight, particularly from the viewpoint of improving printing density and image uniformity. Preferably it is 30 to 60% by weight.
Moreover, the total content of [(a) component + (e) component + (f) component] is preferably 6 to 60% by weight, more preferably from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. 7 to 50% by weight.
In addition, the weight ratio of [(a) component / {(b) component + [(c) component and / or (d) component]}]] is preferable from the viewpoint of dispersion stability and print density of the resulting dispersion. Is 0.05 to 1, more preferably 0.08 to 0.67, still more preferably 0.1 to 0.5.

(Production of water-insoluble polymer)
The water-insoluble polymer is produced by copolymerizing a monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is not particularly limited, but a polar organic solvent is preferable. When the polar organic solvent is miscible with water, it can be used by mixing with water. Examples of the polar 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; esters such as ethyl acetate and the like. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solvent of one or more of these and water is preferable.
In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), t-butyl peroxyoctate, dibenzoyl oxide, etc. Known radical polymerization initiators such as organic peroxides can be used.
The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide may be further added.

Since the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, and solvent used, it cannot be determined unconditionally. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C, and the polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained polymer can be purified by repeating reprecipitation or by removing unreacted monomers and the like by membrane separation, chromatographic method, extraction method and the like.

The weight average molecular weight of the polymer used in the present invention is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, from the viewpoint of printing density, glossiness, and dispersion stability of the colorant, and preferably from 10,000 to 30 Is more preferable, and 20,000 to 300,000 is particularly preferable. In addition, the weight average molecular weight of a polymer is measured by the method shown in an Example.
When the polymer used in the present invention has a salt-forming group derived from the salt-forming group-containing monomer (a), it is neutralized with a neutralizing agent. As the neutralizing agent, an acid or a base can be used depending on the type of the salt-forming group in the polymer. For example, hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid, gluconic acid, glyceric acid and other acids, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine , Bases such as trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine.

The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.
Here, the degree of neutralization can be determined by the following formulas (3) and (4) when the salt-forming group is an anionic group.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100 (3)
When the salt-forming group is a cationic group, it can be determined by the following formula.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100 (4)
The acid value and amine value can be calculated from the structural unit of the polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated.

[Production of aqueous dispersion of polymer particles containing quinacridone solid solution pigment (A) and pigment derivative (B)]
The method for producing an aqueous dispersion of polymer particles containing the quinacridone solid solution pigment (A) and the pigment derivative (B) (hereinafter collectively referred to as “pigment (A + B)”) is not particularly limited. According to the method which has, it can manufacture efficiently.
Step I: Step of obtaining a dispersion of polymer particles containing pigment (A + B) by dispersing a mixture containing polymer, pigment (A + B), organic solvent, and water Step II: Dispersion obtained in Step I For removing organic solvent from water

In Step I, the polymer is first dissolved in an organic solvent, and then a premixed pigment (A + B), water, and, if necessary, a neutralizing agent and a surfactant are added to the obtained organic solvent solution. And mixing to obtain an oil-in-water dispersion. In the mixture, the pigment (A + B) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, the organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight, and the polymer is The amount is preferably 2 to 40% by weight, more preferably 3 to 20% by weight, and water is preferably 10 to 70% by weight, more preferably 20 to 70% by weight.
When the polymer has a salt-forming group, it is preferable to use a neutralizing agent, but the degree of neutralization is not particularly limited. Usually, it is preferable that the liquid dispersion of the finally obtained water dispersion is neutral, for example, pH is 4.5-10. The pH can also be determined by the desired degree of neutralization of the polymer. Examples of the neutralizing agent include those described above. Further, the polymer may be neutralized in advance.
Examples of the organic solvent include alcohol solvents such as ethanol, isopropanol and isobutanol, ketone solvents such as acetone, methyl ethyl ketone and diethyl ketone, and ether solvents such as dibutyl ether, tetrahydrofuran and dioxane. The solubility in water is preferably 50% by weight or less and 10% by weight or more at 20 ° C., and methyl ethyl ketone is particularly preferable.

There is no restriction | limiting in particular in the dispersion method of the mixture in process I. Although the average particle size of the polymer particles can be atomized only by the main dispersion until the desired particle size is reached, it is preferably pre-dispersed and then subjected to main dispersion by further applying a shear stress to obtain the average particle size of the polymer particles. It is preferable to control the diameter to a desired particle diameter. The dispersion temperature in step I is preferably 5 to 50 ° C, and more preferably 10 to 35 ° C.
When preliminarily dispersing the mixture, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring devices, Ultra Disper [Asada Steel Co., Ltd., trade name], Ebara Milder [Ebara Manufacturing Co., Ltd., trade name], TK homomixer, TK pipeline mixer, TK homo jetter, TK homomic line flow, High-speed agitating and mixing devices such as Filmix [Special Machine Industry Co., Ltd., trade name], Clear Mix [M Technique Co., Ltd., trade name], KD Mill [Kinetic Dispersion Co., Ltd., trade name] and the like are preferable.
As means for giving the shear stress of this dispersion, for example, a kneader such as a roll mill, a bead mill, a kneader, an extruder, a high-pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), a minilab 8.3H type (Rannie Co., trade name) Representative homo-valve type high-pressure homogenizer, microfluidizer (Microfluidics, trade name), nanomizer (Nanomizer, trade name), optimizer (Sugino Machine Co., trade name), Genus PY (Shiramizu Chemical Co., Ltd.) Product name], DeBEE2000 [Japan EE Co., Ltd., product name] and the like chamber type high-pressure homogenizer. Among these, when a pigment is used, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment.

In Step II, an aqueous dispersion of polymer particles containing the pigment (A + B) can be obtained from the obtained dispersion by distilling off the organic solvent by a known method to form an aqueous system. The organic solvent in the aqueous dispersion containing the obtained polymer particles is substantially removed. The amount of residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
The obtained aqueous dispersion of polymer particles containing the pigment (A + B) is one in which the solid content of the polymer containing the pigment (A + B) is dispersed in water as the main medium. Here, the form of the polymer particles is not particularly limited as long as the particles are formed of at least the pigment (A + B) and the polymer. For example, a particle form in which the pigment (A + B) is included in the polymer, a particle form in which the pigment (A + B) is uniformly dispersed in the polymer, and a particle form in which the pigment (A + B) is exposed on the surface of the polymer particle are included. .

[Aqueous dispersion for inkjet recording and water-based ink]
The aqueous ink of the present invention contains the aqueous dispersion of the present invention, and additives such as a wetting agent, a dispersant, an antifoaming agent, an antifungal agent, and a chelating agent can be added as necessary. There is no restriction | limiting in particular in the mixing method of these additives.
The content of each component in the aqueous dispersion for inkjet recording and the water-based ink is as follows from the viewpoints of print density, saturation, and the like.
The content of the polymer particles containing the quinacridone solid solution pigment (A) and the pigment derivative (B) is preferably 1 to 30% by weight, more preferably 2 to 25% by weight.
The total content of the quinacridone solid solution pigment (A) and the pigment derivative (B) is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, and particularly preferably 1 to 10% by weight.
The polymer content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, and particularly preferably 1 to 10% by weight.
The average particle diameter of the polymer particles containing the pigment (A + B) in the water dispersion and the water-based ink is preferably 40 to 400 nm, more preferably 50 to 300 nm, and particularly preferably 60 from the viewpoints of saturation, dispersion stability, and the like. ~ 200 nm. The average particle size is measured by the method described in the examples.

The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s, in order to obtain a good viscosity when used as a water-based ink. Further, the viscosity (20 ° C.) of the water-based ink is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s, in order to maintain good ejection properties. The viscosity of the water dispersion and water-based ink was measured using an E-type viscometer under the conditions of a measurement temperature of 20 ° C., a measurement time of 1 minute, a rotation speed of 100 rpm, and a standard rotor (1 ° 34 ′ × R24). taking measurement.
The preferred surface tension (20 ° C.) of the aqueous dispersion and aqueous ink of the present invention is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m as the aqueous dispersion, and preferably as the aqueous ink. Is 25-50 mN / m, more preferably 27-45 mN / m. The pH of the water-based ink is preferably 4-10.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. In addition, the measuring method of the weight average molecular weight of a polymer and the average particle diameter of a pigment containing polymer particle is as follows.
(1) Measurement of polymer weight average molecular weight Gel permeation chromatography using polystyrene as a standard substance, G4000HXL + G2000HXL manufactured by Tosoh Corporation as a column, and tetrahydrofuran (THF) containing 50 mM CH ₃ COOH / 1 grade as an eluent The weight average molecular weight was measured by chromatography.
(2) Measurement of average particle diameter of pigment-containing polymer particles Measurement was performed using ELS-8000 manufactured by Otsuka Electronics Co., Ltd. The measurement conditions were a temperature of 25 ° C., an angle between the incident light and the detector of 90 °, and an integration count of 200. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. Uniform microparticles (average particle size 204 nm) manufactured by Seradyn Co. were used as a standard substance.

Production Examples 1 and 2 (Preparation of polymer solution)
In a reaction vessel, 10 parts of methyl ethyl ketone, 0.02 part of a polymerization chain transfer agent (2-mercaptoethanol), and 20% of each monomer (shown in parts by weight) shown in Table 1 were mixed and mixed with nitrogen gas. And a mixed solution was obtained.
On the other hand, the remaining 80% of each monomer (in parts by weight) shown in Table 1 was charged into the dropping funnel, and then 0.08 part of the polymerization chain transfer agent, 10 parts of methyl ethyl ketone and the polymerization initiator (2 , 2′-azobis (2,4-dimethylvaleronitrile)) 1.0 part was mixed and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 75 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped into the reaction vessel over 3 hours. After completion of the dropping, the liquid temperature of the mixed solution is maintained at 75 ° C. for 2 hours, and then a solution obtained by dissolving 0.6 part of the polymerization initiator in 10 parts of methyl ethyl ketone is added to the mixed solution, and further at 75 ° C. for 3 hours. And aged at 85 ° C. for 2 hours to obtain a polymer solution. A portion of the resulting polymer solution was dried at 105 ° C. for 2 hours under reduced pressure, and the polymer was isolated by removing the solvent. The results are shown in Table 1.

Examples 1 to 5 and Comparative Examples 1 to 3 (Production of aqueous dispersion of pigment-containing polymer particles and water-based ink)
25 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 or 2 under reduced pressure was dissolved in 71.5 parts of methyl ethyl ketone, and 209.7 parts of ion-exchanged water and a neutralizing agent (5N-water) were dissolved therein. The salt-forming group was neutralized with a mixture in which an aqueous sodium oxide solution was added to a degree of neutralization of 65%, and the solid solution pigment (A) (CI Pigment Red 122 / CI) described in Table 2 was further neutralized. Pigment Violet 19) 75 parts of a mixture obtained by mixing 3 parts by weight of 3,10-dichloroquinacridone sulfonic acid aluminum salt (average sulfonic acid group number 1.3) as pigment derivative (B) with 97 parts by weight In addition, it was dispersed with a disper. The obtained mixture was subjected to 15-pass dispersion treatment with a microfluidizer (trade name, manufactured by Microfluidics) at a pressure of 180 MPa. Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure using an evaporator to obtain an aqueous dispersion of organic pigment-containing particles having a solid content of 20%.
50 parts of an aqueous dispersion of organic pigment-containing particles obtained above, 10 parts of glycerin, 10 parts of 2-ethyl-1,3-butanediol, 2 parts of 2-pyrrolidone, acetylene glycol EO adduct (n = 10) [ 1 part of Kawaken Fine Chemical Co., Ltd., trade name: acetylenol E100] and 27 parts of ion-exchanged water were mixed, and the resulting mixture was filtered with a 1.2 μm membrane filter (trade name: Minisart, manufactured by Sartorius). A water-based ink was obtained.
In Comparative Example 1, the same procedure as described above was performed except that a solid solution pigment not mixed with a pigment derivative was used. In Comparative Example 3, not quinacridone solid solution pigment but C.I. I. Pigment Red 122 80 parts by weight and C.I. I. Pigment violet 19 The same procedure as described above was conducted except that 97 parts by weight of a simple mixture composed of 20 parts by weight and 3 parts by weight of the pigment derivative (B) were mixed.

The physical properties of the water-based inks obtained in each Example and each Comparative Example were evaluated based on the following methods. The results are shown in Table 2.
(1) Discharge reliability After continuously printing 100 2,000 characters / sheet on plain paper a (6200 paper, manufactured by Ricoh Co., Ltd.) using an ink jet printer manufactured by Ricoh Co., Ltd. (product number: IPSiO G717, piezo method) , Print a test document including characters, solid images and ruled lines, and evaluate three items: (i) sharp and clear characters, (ii) uniform solid images, and (iii) ruled lines with no twist. Evaluation was made according to the criteria.
〔Judgment criteria〕
○: All three items are satisfied (no problem)
Δ: All three items are almost satisfied (no problem in actual use)
×: Not satisfied with more than one item (problems in actual use)

(2) Print density A solid image is printed on the above-mentioned plain paper a (6200 paper) and plain paper b (4024 paper, manufactured by Fuji Xerox Co., Ltd.), and after standing for 1 day, optical densitometer SpectroEye (Gretag Macbeth) 10) were used to measure the average value.
(3) Image uniformity (concealment)
A solid image was printed on the plain paper a (6200 paper), and whether or not there was uneven color was visually evaluated according to the following criteria.
〔Judgment criteria〕
○: No color unevenness (no missing)
X: Color irregularity (white spots)

(4) Bleeding between colors For the plain paper a (6200 paper), a pattern in which the second liquid composition is printed on the back on which 10-point characters are printed with the first liquid composition is created. The bleed was sensory evaluated and evaluated according to the following criteria.
〔Judgment criteria〕
○: All kanji and hiragana are reproduced without problems.
Δ: Some of the kanji are not reproduced, but some are readable.
×: Kanji and hiragana cannot be read.
(5) Fixing property A solid image having a size of 20 mm × 20 mm is printed on the plain paper a (6200 paper), and the back side of another plain paper P paper is superimposed on the printed image after 10 seconds. Furthermore, the surface of the solid image was moved in a state where a load of 490 g (load area 43 mm × 30 mm) was applied from above, and the stain on the stacked paper was measured. Evaluation was performed according to the following criteria.
〔Judgment criteria〕
○: Almost no printed matter can be taken and the surroundings do not turn red.
Δ: Almost no printed matter can be taken and the surrounding area becomes slightly red, but there is no practical problem.
X: The printed matter is rubbed off, the surroundings become extremely red, and the fingers are also considerably stained.

(6) Saturation A solid image is printed on the plain paper a (6200 paper), and after standing for one day, the optical densitometer SpectroEye (manufactured by Gretag Macbeth) is set to the measurement mode L ^* a ^* b ^*. Any five locations were measured to obtain an average value, and the average value was evaluated according to the following criteria. Saturation is a scale that represents the degree of vividness of a color, and is represented by the distance from an achromatic color of equal brightness. Here, as shown in the following equation, the saturation is represented by the L ^* a ^* b ^* color system (where L ^* is lightness, a ^* is chromaticity in the red-green direction, and b ^* is in the yellow-blue direction). ) And the distance from the center (position where both a ^* b ^* are 0: achromatic color).
Saturation = {(a ^* ) ² + (b ^* ) ² } ^1/2
〔Judgment criteria〕
◎: 61.0 or more ○: 59 or more, less than 61.0 △: 57 or more, less than 59 ×: less than 57

  From Table 2, the aqueous inks of Examples 1 to 5 are superior to the aqueous inks of Comparative Examples 1 to 3 in terms of ejection reliability, print density, image uniformity, fixability, and saturation, and no intercolor bleeding. I understand that.

  According to the water-based ink containing the aqueous dispersion for inkjet recording of the present invention, a printed matter having excellent printing performance such as printing density and saturation can be obtained. The aqueous dispersion and aqueous ink of the present invention are particularly useful when a magenta pigment is used.

Claims (8)

  An aqueous dispersion for ink jet recording comprising a polymer particle containing a quinacridone solid solution pigment (A) containing two or more quinacridone compounds and a pigment derivative (B) having a polar group.   The aqueous dispersion for inkjet recording according to claim 1, wherein the weight ratio of [pigment derivative (B) / quinacridone solid solution pigment (A)] is 0.005 to 0.3.   The aqueous dispersion for inkjet recording according to claim 1 or 2, wherein the pigment derivative (B) is a quinacridone sulfonic acid compound and / or a quinacridone compound having a substituent containing a phthalimide skeleton.   The aqueous dispersion for inkjet recording according to any one of claims 1 to 3, wherein the quinacridone solid solution pigment (A) is a solid solution pigment of unsubstituted quinacridone and dimethyl-substituted quinacridone.   The aqueous dispersion for inkjet recording according to claim 4, wherein the weight ratio of [unsubstituted quinacridone / dimethyl-substituted quinacridone] is 10/90 to 90/10.   The polymer constituting the polymer particles is a structural unit derived from a salt-forming group-containing monomer (a) and a structural unit derived from a macromer (b), and a linear or branched alkyl group or alkenyl group-containing monomer having 12 to 22 carbon atoms. The aqueous dispersion for inkjet recording according to any one of claims 1 to 5, which is a graft polymer containing a structural unit derived from (c) and / or an aromatic ring-containing monomer (d).   The water dispersion for inkjet recording according to claim 6, wherein the content of the constituent unit derived from the linear or branched alkyl group or alkenyl group-containing monomer having 12 to 22 carbon atoms in the graft polymer is 10 to 70% by weight. body.   An aqueous ink for ink-jet recording, comprising the water dispersion according to claim 1.