JP2008231178A - Inkjet recording aqueous ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording aqueous dispersion excellent in printing performance such as storage stability, discharge reliability, printing density, chroma, image uniformity and color tone stability and an aqueous ink containing the same. <P>SOLUTION: The inkjet recording aqueous dispersion is an aqueous dispersion of vinyl polymer particles containing a yellow organic pigment (A) and a pigment derivative (B) having a polar group, and the molecular weight ratio of the pigment derivative (B) to the yellow organic pigment is 1.4-3 and the vinyl polymer has a constituting unit derived from an 8-22C straight-chain or branched chain alkyl or alkenyl (meth)acrylate. The aqueous ink contains the inkjet recording aqueous dispersion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion for inkjet recording and an aqueous ink.

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 (see, for example, Patent Documents 1 to 5).

Patent Document 1 discloses a water-based ink in which a pigment is contained in a vinyl polymer, and a graft polymer using a macromer as a vinyl polymer is disclosed in order to impart a high printing density. A coloring composition for inkjet recording using a yellow azo pigment having a substituent is disclosed.
Patent Document 5 discloses an aqueous dispersion of water-insoluble vinyl polymer particles containing a yellow organic pigment and an azo compound, wherein the water-insoluble vinyl polymer is an arylalkyl group or an aryl group-containing benzyl (meth) acrylate, etc. An aqueous dispersion for inkjet recording having a structural unit derived from is disclosed.
The above-mentioned water dispersion or water-based ink has improved ink characteristics to some extent, but a higher level of excellent performance is required.

International Publication No. 00/39226 Pamphlet Japanese Patent Laid-Open No. 2003-253188 Japanese Patent Laid-Open No. 2004-182952 Japanese Patent No. 3055673 Japanese Patent Laid-Open No. 2006-124584

  An object of the present invention is to provide an aqueous dispersion for inkjet recording excellent in printing performance such as storage stability, ejection reliability, printing density, saturation, image uniformity, color tone stability, and an aqueous ink containing the same. And

The present inventors have found that the above problem can be solved by using a yellow organic pigment and a pigment derivative having a specific polar group for a specific polymer.
That is, the present invention provides the following (1) and (2).
(1) An aqueous dispersion of vinyl polymer particles containing a yellow organic pigment (A) and a pigment derivative (B) having a polar group, wherein [the pigment derivative (B) / the yellow organic pigment (A)] An aqueous dispersion for inkjet recording having a molecular weight ratio of 1.4 to 3 and the vinyl polymer having a structural unit derived from a linear or branched alkyl or alkenyl (meth) acrylate having 8 to 22 carbon atoms.
(2) A water-based ink for ink-jet recording comprising the water dispersion of (1).

  The aqueous ink containing the aqueous dispersion for inkjet recording of the present invention is excellent in storage stability, ejection reliability, print density, saturation, image uniformity, color tone stability, and the like.

  From the viewpoint of obtaining a printed matter having excellent printing performance such as storage stability, ejection reliability, printing density, saturation, image uniformity, and color stability, the aqueous dispersion for inkjet recording of the present invention and the water-based ink are yellow organic. Vinyl polymer particles containing a pigment (A) and a pigment derivative (B) having a polar group, wherein the molecular weight ratio of [the pigment derivative (B) / yellow organic pigment (A)] is 1.4 to 3. Yes, the vinyl polymer having a structural unit derived from a linear or branched alkyl or alkenyl (meth) acrylate having 8 to 22 carbon atoms is used. Hereinafter, each component used for this invention is demonstrated.

[Yellow organic pigment (A)]
Examples of the yellow organic pigment (A) used in the present invention include yellow organic pigments such as azo lake pigments, insoluble azo pigments, condensed azo pigments, polycyclic pigments, and metal complex pigments.
Examples of azo lake pigments include acetoacetyl allylide pigments, and more specifically, C.I. I. Pigment yellow 133, 168, 169 and the like.
Examples of insoluble azo pigments include acetoacetate allylide monoazo pigments, acetoacetate allylide disazo pigments, and pyrazolone pigments.
Examples of the acetoacetyl allylide monoazo pigment include Hansa pigments and benzimidazolone pigments. Examples of Hansa pigments include C.I. I. Pigment Yellow 1, 2, 3, 5, 6, 49, 63, 65, 73, 74, 75, 87, 90, 97, 98, 106, 111, 114, 116, 121, 124, 126, 127, 130 136, 152, 165, 167, 170, 174, 176, 188 and the like, and benzimidazolone pigments include C.I. I. Pigment yellow 120, 151, 154, 156, 175, 180, 181, 194, and the like.
Examples of acetoacetyl allylide disazo pigments include C.I. I. Pigment yellow 12, 13, 14, 17, 55, 81, 83, 113, 171, 172 and the like.
Examples of the pyrazolone pigment include C.I. I. Pigment yellow 10, 60, etc.

Examples of condensed azo pigments include C.I. I. Pigment yellow 93, 94, 95, 128, 166 and the like.
Examples of polycyclic pigments include isoindolinone pigments, flavanthrone pigments, and quinophthalone pigments. Examples of isoindolinone pigments include C.I. I. Pigment Yellow 109, 110, 173, etc. I. Pigment Yellow 24 and the like, and quinophthalone pigments include C.I. I. And CI Pigment Yellow 138.
Examples of the metal complex pigment include C.I. I. Pigment yellow 117, 129, 150, 153, 177, 179, 257, 271 and the like.
In addition, C.I. I. Pigment Yellow 139, 185 and other isoindoline pigments, C.I. I. And anthraquinone pigments such as CI Pigment Yellow 99, 108, 123, 147, 193, and 199.
Among these, C.I. I. Pigment yellows 74 and 97, Hanza pigments, C.I. I. Insoluble azo pigments such as benzimidazolone pigments such as CI Pigment Yellow 151; I. Condensed azo pigments such as CI Pigment Yellow 93 and 128; I. Polycyclic pigments such as isoindolinone pigments such as CI Pigment Yellow 110 are preferable. I. Pigment yellow 74, C.I. I. Hansa pigments such as CI Pigment Yellow 97 are preferred.

[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 treating agent for the yellow organic pigment (A), and includes an aqueous dispersion and an aqueous ink. It is used to improve the storage stability and the like.
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 an imide group. 1 type or more chosen from a group is mentioned. Among these, a sulfonic acid group is preferable from the viewpoint of storage stability.

The pigment derivative (B) has the same or similar mother skeleton (molecular structure) as the organic pigment (A) from the viewpoints of improving the adsorptivity to the surface of the organic pigment (A), mixing and storage stability with the polymer, and hue. It is preferable to have.
Examples of the method for producing the pigment derivative (B) having the same or similar mother skeleton include, for example, (i) a method of introducing a polar group using the reactivity of the compound after synthesizing the compound of the organic pigment (A) (Ii) A method of synthesizing the pigment derivative (B) having a polar group introduced at the same time as the synthesis of the organic pigment (A). Examples of the pigment derivative (B) having such a structure include azo pigment derivatives and polycyclic pigment derivatives.
The azo pigment derivative can be obtained by (1) a method of synthesizing a ketimine pigment derivative by reacting an organic pigment molecule with an aliphatic amine, and (2) a mixed coupling method.
(2) The mixed coupling method involves coupling by mixing a diazo component or a heterogeneous coupler component into which a polar group is introduced and a diazo component or a coupler component of the pigment matrix during the synthesis of an azo pigment by an azo coupling reaction. This is a reaction method. The mixed coupling method can simultaneously synthesize an organic pigment and a pigment derivative, and can also serve as a surface treatment step for the organic pigment. From this viewpoint, a mixed coupling method is preferable as a method for producing the azo pigment derivative.
Examples of the polycyclic pigment derivative include compounds in which a polar group is introduced into a benzene nucleus in the chemical structure of an organic pigment. The polar group may be introduced by being directly substituted on the benzene nucleus, or may be introduced through a linking group such as an alkyl group.
The pigment derivatives are described in detail in “Pigment Dispersion Technology” (Technical Information Association, February 24, 1999, first printing), pages 85-88.

  The pigment derivative (B) is preferably an azo compound represented by the following formula (1) (hereinafter sometimes simply referred to as “azo compound”) from the viewpoint of storage stability and the like.

(In the formula, R ¹⁰ and R ^{20 each} represents an optionally substituted aryl group having 6 to 50 carbon atoms, and at least one of them has a polar group. R ¹⁰ or R ²⁰ may be the same or different. May be.)
In formula (1), the aryl group preferably has 6 to 40 carbon atoms, and more preferably 6 to 30 carbon atoms. Moreover, as a preferable substituent, C1-C22, Preferably a C1-C12 alkoxy group, C1-C22, Preferably a C1-C12 alkyl group, an ether group, an ester group, a nitro group a hydroxyl group, a halogen group, an amide group, an amino group, a carboxyl group, a sulfonic acid group, a sulfuric acid group, phosphoric acid group, a phosphonic acid group, a sulfoxide group (-SO-), sulfone group (-SO ₂ -), a triazine group ( And those obtained by removing one or two protons from triazine). In addition, Formula (1) can also be represented by the following formula (2) as an isomer.

As said azo compound, what introduce | transduced the polar group into at least one aryl group as a hydrophilic dispersibility provision group is used. Examples of the polar group include the same groups as described above. Among these, from the viewpoint of storage stability, —SO ₃ M, —COOM, —SO ₂ M, —RSO ₂ M, —PO ₃ HM, —PO ₃ M (wherein M is a hydrogen atom, R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. 1 type or 2 or more types of functional groups chosen from the group which consists of the functional group represented by these, or its salt are mentioned suitably, A sulfonic acid group is more preferable.
Examples of the pigment derivative (B) having a sulfonic acid group include sulfonic acids and metal salts thereof such as sodium, aluminum and calcium, and ammonium, octadecylammonium, didodecylammonium, dimethyloctadecylammonium, dimethyldioctadecylammonium, and benzyldimethyloctadecyl. Examples thereof include pigment derivatives having ammonium salts such as ammonium.

Examples of the pigment derivative (B) having a polar group include C.I. which is an insoluble azo pigment. I. Pigment yellow 74, C.I. I. Pigment Yellow 97 pigment derivative is preferred.
Specific examples of the azo compound represented by the above formula (1) and a method for producing the azo compound are known methods, for example, JP-A Nos. 2003-253188, 2004-182952, and No. 3055673. Specific examples and manufacturing methods described can be given. Particularly preferred specific examples include compounds represented by the following formulas (3) and (4).
Moreover, when introducing a sulfonic acid group into an organic pigment, the organic pigment can be reacted with a sulfonating agent such as concentrated sulfuric acid, fuming sulfuric acid or chlorosulfuric acid.

Said yellow organic pigment (A) and pigment derivative (B) can use each component of (A) and (B) individually or in mixture of 2 or more types.
From the viewpoint of storage stability, color tone, saturation, color tone stability and the like, the weight ratio of [pigment derivative (B) / yellow organic pigment (A)] is preferably 1/99 to 30/70, and 1/99 to 20 / 80 is more preferable, and 1/99 to 10/90 is still more preferable. When the weight ratio is 1/99 or more, the number of adsorption points on the surface of the yellow organic pigment (A) increases, and the storage stability is improved. On the other hand, if it is 30/70 or less, the pigment derivative (B) which is not adsorbed on the surface of the yellow organic pigment (A) decreases, and the storage stability is improved.
In addition, from the viewpoint of storage stability, ejection reliability, saturation, color tone stability (no color change) and image uniformity, the molecular weight ratio of [pigment derivative (B) / yellow organic pigment (A)] is It is 1.4-3, 1.5-2.8 is more preferable, and 1.6-2.5 is still more preferable. When the molecular weight ratio is 1.4 or more, the adsorption point to the surface of the yellow organic pigment (A) increases and the affinity with the vinyl polymer is improved, and the storage stability, saturation, image uniformity, etc. are excellent. . On the other hand, when the molecular weight ratio is 3 or less, the pigment derivative (B) that is not adsorbed on the surface of the yellow organic pigment (A) is reduced, and the storage stability is improved. When two or more kinds of pigment derivatives (B) are used, the weighted average value in consideration of the molecular weight and the weight ratio is used as the molecular weight. The same applies to the yellow organic pigment (A).
When mixing the yellow organic pigment (A) and the pigment derivative (B), they may be synthesized and mixed in the same synthesis tank, or the yellow organic pigment (A) and the pigment derivative (B) are synthesized separately, You may mix in any processes, such as a subsequent drying process, a grinding | pulverization process, a classification process, and a pigment dispersion process. From the viewpoint of adjusting the primary particle diameter of the yellow organic pigment (A) and the pigment derivative (B) and improving the initial storage stability, it is preferable to synthesize both in the same synthesis tank.

[Vinyl polymer]
As the vinyl 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 Is preferably a water-insoluble polymer of 5 g or less, more preferably 1 g or less. 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.
The vinyl polymer used in the present invention has a structural unit derived from a linear or branched alkyl or alkenyl (meth) acrylate having 8 to 22 carbon atoms. Such a vinyl polymer preferably further has a structural unit derived from a salt-forming group-containing monomer, and includes a salt-forming group-containing monomer (a) (hereinafter sometimes referred to as “component (a)”), macromer (b) ( Hereinafter referred to as “component (b)”), and linear or branched alkyl or alkenyl (meth) acrylate (c) having 8 to 22 carbon atoms (hereinafter also referred to as “component (c)”) More preferred is a graft polymer obtained by copolymerization of a monomer mixture containing (hereinafter also referred to as “monomer mixture”). This graft polymer has structural units derived from the components (a) to (c). A more preferred polymer is a graft polymer having a structural unit derived from the component (a) and a structural unit derived from the component (c) 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 dispersibility 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, from the viewpoint of dispersibility and ejection reliability, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable.

The macromer (b) is used from the viewpoint of enhancing the dispersibility of the polymer particles containing the 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), styrenic macromers and aromatic group-containing (meth) acrylate macromers having a polymerizable functional group at one end are preferable from the viewpoint of dispersibility of polymer particles.
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. Above, more preferably 70% by 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 (5).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 5)
(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 or alkenyl (meth) acrylate (c) having 8 to 22 carbon atoms is represented by the following formula (6), and is considered to improve the affinity between the yellow organic pigment and the vinyl polymer. Used from the viewpoint of improving storage stability, print density, and image uniformity.
CH ₂ = CHR ¹ COOR ² (6)
(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a linear or branched alkyl group or alkenyl group having 8 to 22 carbon atoms.)
In the formula (6), R ² is preferably a linear or branched alkyl or alkenyl group having 12 to 22 carbon atoms, more preferably 14 to 20 carbon atoms.
Preferred examples of the component (c) include 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) tetradecyl. 1 or more types chosen from the group which consists of (meth) acrylate, (iso) palmityl (meth) acrylate, and (iso) stearyl (meth) acrylate are mentioned.

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 structural unit derived from the component (d) constitutes a part of the main chain of the graft polymer.
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 7 or less carbon atoms and aromatic group-containing monomers.
Examples of the alkyl (meth) acrylate having an alkyl group having 7 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, and cyclohexyl (meth) acrylate.
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 print density, and styrene and 2-methylstyrene are particularly preferable as the (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 (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, (d-1) component and (d-2) component can also be used 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 enhancing dispersibility. The structural unit derived from the component (e) constitutes a part of the main chain of the graft polymer.
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 (7) (hereinafter sometimes referred to as “component (f)”). The structural unit derived from the component (f) constitutes a part of the main chain of the graft polymer.
CH ₂ = C (R ³ ) COO (R ⁴ O) _q R ⁵ (7)
(In the formula, R ³ is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R ⁴ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ⁵ is , A C1-C18 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 2 to 30.)
The component (f) exhibits an excellent effect of improving the discharge property.
In the formula (7), examples of the hetero atom include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Preferable examples of R ³ include a methyl group, an ethyl group, and an (iso) propyl group.
Preferred examples of the R ⁴ 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 ⁵ 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 (7); hereinafter the same) (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 the 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 dispersibility 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 1 to 70% by weight, more preferably 3 to 65% by weight, and further preferably 5 to 60% by weight from the viewpoints of ejection reliability, print density, image uniformity, and saturation. %.
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 the component (e) is preferably 5 to 40% by weight, more preferably 7 to 20% by weight, from the viewpoint of dispersibility 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.
The total content of [(a) component + (e) component + (f) component] is preferably 6 to 60% by weight, more preferably 7 from the viewpoint of dispersibility and dischargeability of the resulting dispersion. ~ 50% by weight.
Further, the weight ratio of [(a) component / {(b) component + (c) component + (d) component total amount]}] is preferably from the viewpoint of the dispersibility of the obtained dispersion and the print density. It is 0.05 to 1, more preferably 0.08 to 0.67, and 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 5,000 to 500,000, more preferably 10,000 to 400,000, and more preferably 10,000 to 300,000 from the viewpoints of printing density, glossiness, and dispersibility of the colorant. 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 formula 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
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
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 yellow organic pigment (A) and pigment derivative (B)]
The method for producing an aqueous dispersion of polymer particles containing the yellow organic pigment (A) and the pigment derivative (B) (both are referred to as “colorant”) is not particularly limited, but the method includes the following steps I and II. Therefore, it can manufacture efficiently.
Step I: Dispersing a mixture containing a polymer, a colorant, an organic solvent, and water to obtain a dispersion of polymer particles containing a colorant Step II: Removing an organic solvent from the dispersion obtained in Step I Step to remove

In Step I, first, the polymer is dissolved in an organic solvent, and the resulting polymer solution is added with a colorant, water, and, if necessary, a neutralizing agent, a surfactant, and the like to obtain a mixture. A method of obtaining a dispersion of is preferable. In the mixture, the colorant 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 2 to 2% by weight. It is preferably 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, methyl isobutyl ketone and diethyl ketone, and ether solvents such as dibutyl ether, tetrahydrofuran and dioxane. The organic solvent has a solubility in 100 g of water of 20 ° C., preferably 5 g or more, more preferably 10 g or more, more specifically 5 to 80 g, and even more preferably 10 to 50 g. . In particular, methyl ethyl ketone and methyl isobutyl ketone are 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 a colorant can be obtained by distilling off the organic solvent from the obtained dispersion 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 colorant is one in which the solid content of the polymer containing the colorant 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 a colorant and a polymer. For example, a particle form in which a colorant is included in a polymer, a particle form in which a colorant is uniformly dispersed in a polymer, a particle form in which a colorant is exposed on the surface of a polymer particle, and the like 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, storage stability, and the like.
The content of the polymer particles containing the yellow organic 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 yellow organic pigment (A) and the pigment derivative (B) is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, and particularly preferably 2 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 weight ratio of [the total amount of polymer / yellow organic pigment (A) and pigment derivative (B)] is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, and particularly preferably 20. / 80 to 50/50.
The average particle diameter of the polymer particles containing the colorant in the aqueous dispersion and the water-based ink is preferably 40 to 400 nm, more preferably 50 to 300 nm, and particularly preferably 60 to 200 nm, from the viewpoints of saturation and storage stability. It is. In addition, the measurement of the average particle diameter of a colorant containing polymer particle is performed by the method as described in an Example.

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 pigment synthesis examples, polymer 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. Further, uniform microparticles (average particle size: 204 nm) manufactured by Seradyn Co. were used as a standard substance.

Synthesis example 1
In a mixed solution of 960 g of water and 327 g (3.139 mol) of 35% hydrochloric acid, 162.6 g (1.07 mol) of 3-nitro-4-toluidine and a monoazo yellow organic pigment represented by the following formula (8) 17.01 g (0.03 mol) was added and dispersed by stirring. About 700 g of ice was added to this dispersion, and after cooling, a solution in which 87 g (1.27 mol) of sodium nitrite was dissolved in 130 g of water was added and stirred for 1 hour while maintaining at 10 ° C. or lower. After the nitrous acid had disappeared, filtration was performed to obtain a diazotized liquid.

On the other hand, after 96 g (0.706 mol) of sodium acetate was dissolved in 5300 g of water, 200.9 g (1.13 mol) of acetoacetylanilide was added and dispersed in the aqueous solution, and then 90 g of 80% acetic acid (1 .199 mol) was added dropwise to adjust the pH to 6, and the temperature was adjusted to 25 ° C. to obtain a coupler solution.
To this coupler liquid, the above diazotization liquid was dropped in 120 minutes to carry out a coupling reaction. Next, the temperature was raised to 90 ° C. and heat-treated for 30 minutes, followed by filtration and washing with water to remove by-product salts and the like, followed by drying at 80 ° C. with a dryer. The dried pigment was pulverized to give a yellow azo pigment derivative B-1 (molecular weight 783; compound represented by the formula (1)) represented by the following formula (9) and C.I. I. A colorant containing CI Pigment Yellow 74 (molecular weight 386) was obtained.

Synthesis example 2
In the same manner as in Synthesis Example 1, the resultant was synthesized, heated to 90 ° C. and heat-treated for 30 minutes, filtered, washed with water to remove by-product salts and the like, and dried at 80 ° C. with a dryer. The dried pigment was pulverized to give a yellow azo pigment derivative B-2 (molecular weight 738) represented by the following formula (10) and C.I. I. A colorant containing CI Pigment Yellow 74 was obtained.

Synthesis example 3
After adding 55.0 parts of 2-methoxy-4-nitro-aniline and 3.2 parts of p-toluidine-m-sulfonic acid in a mixture of 1,300 parts of water and 290 parts of 35% hydrochloric acid, After cooling to 0 ° C., 80 parts of sodium nitrite was added for diazotization. Separately, 74.4 parts of 2-methoxyacetoacetanilide is added to 5,000 parts of water, dissolved together with 48 parts of sodium hydroxide, and then precipitated by adding a mixture of 196 parts of acetic acid and 196 parts of water. A suspension of the coupling component is obtained. The clarified diazo solution was added to the acetic acid suspension of the above coupling component by flowing down at 15 ° C. within 1 hour 30 minutes to 2 hours with good stirring. After completion of the coupling, 45 parts of rosin was added for pigment treatment, and the resulting pigment composition was filtered, washed with water, dried and pulverized to obtain 133.0 parts of C.I. I. A yellow azo pigment derivative B-3 (molecular weight 488; compound represented by the above formula (1)) represented by the following formula (11), in which a sulfone group is introduced into the aryl group of CI Pigment Yellow 74, and C . I. A colorant containing CI Pigment Yellow 74 was obtained.

Production Examples 1 to 3 (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 part of the obtained polymer solution was dried at 105 ° C. under reduced pressure for 2 hours, and was isolated by removing the solvent, and the weight average molecular weight was measured. The results are shown in Table 1.

Examples 1 to 4 and Comparative Examples 1 to 2 (Manufacture of an aqueous dispersion of colorant-containing particles and an aqueous ink)
40 parts of the polymer obtained by drying one of the polymer solutions obtained in Production Examples 1 to 3 under reduced pressure was dissolved in 72 parts of methyl ethyl ketone, and 207 parts of ion-exchanged water and a neutralizing agent (5N-hydroxylated) were contained therein. Sodium aqueous solution) The salt-forming group was neutralized with a mixture of 65% of the acid value, and the pigment (CI Pigment Yellow 74 and any one of Synthesis Examples 1 to 3) shown in Table 2 was further neutralized. 60 parts of pigment derivative B-1 to 3) were added and mixed 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 150 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%. The average particle diameter of the obtained organic pigment-containing particles was measured.
40 parts aqueous dispersion of organic pigment-containing particles obtained above, 10 parts glycerin, 10 parts 2-ethyl-1,3-butanediol, 2 parts 2-pyrrolidone, acetylene glycol EO adduct (n = 10) 1 And 37 parts of ion-exchanged water were mixed, and the resulting mixture was filtered through a 1.2 μm membrane filter (trade name: Minisart, manufactured by Sartorius) to obtain a water-based ink.

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 Using a commercially available Ricoh Co., Ltd. inkjet printer (part number: IPSiO G717, Piezo method), 100 continuous 2000 characters / sheet were printed on plain paper a (6200 paper, manufactured by Ricoh Co., Ltd.). After that, a test document including characters, solid images and ruled lines was printed, and three items were evaluated: (i) sharp and clear characters, (ii) uniform solid images, and (iii) ruled lines with no blur, The evaluation criteria were used.
〔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) Evaluation of storage stability Water-based ink was filled in a glass sealed container, and the average particle size after storage at 70 ° C. for 10 days was measured using a particle size measuring instrument (trade name: ELS-8000, manufactured by Otsuka Electronics Co., Ltd.). The particle size increase rate was obtained from the following formula (the value closer to 100% is better in storage stability) and evaluated according to the following criteria.
〔Judgment criteria〕
○: Particle size increase rate is less than 120% ×: Particle size increase rate is 120% or more Particle size increase rate = [average particle size after storage (70 ° C., particle size after 10 days storage) / average particle before storage Diameter (particle diameter before storage)] × 100

(3) Color tone stability Water-based ink is filled into a glass sealed container, diluted with ion-exchanged water 2000 times after storage at 70 ° C. for 10 days, and a spectrophotometer (trade name: U, manufactured by Hitachi High-Technologies Corporation). -3010), and the difference in maximum absorbance (Δλmax) in the visible region was evaluated. Δλmax
Is less than 5,
The color sight does not change.
Δλmax = [λmax after storage (intensity after storage at 70 ° C. for 10 days) −λmax before storage (
Strength before storage)]
〔Judgment criteria〕
○: Δλmax = less than 5 ×: Δλmax = 5 or more

(4) Printing 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 one day, an optical densitometer SpectroEye (Gretag Macbeth) 10) were used to measure an average value, and an average value was obtained, and the average value was evaluated according to the following criteria.

(5) Image uniformity (concealment)
A solid image was printed on the plain paper a (6200 paper) and the plain paper b (4024 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)
(6) Intercolor bleeding The second liquid is printed on the back on which 10-point characters (kanji and hiragana) are printed with the first liquid composition on the plain paper a (6200 paper) and plain paper b (4024 paper). A pattern on which the composition was printed was prepared, and the bleeding of the character part 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.
(7) Fixability A solid image having a size of 20 mm × 20 mm is printed on the plain paper a (6200 paper), and another image is printed on the printed image after every 10 seconds, 30 seconds, and 60 seconds. The surface of the plain paper P paper was overlapped, and the surface of the solid image was moved under a load of 490 g (load area 43 mm × 30 mm) from the top, and the stain of the overlapped paper was measured. Evaluation was performed according to the following criteria.
〔Judgment criteria〕
○: Almost no printed matter can be taken and the surrounding area does not turn yellow.
Δ: Almost no printed matter can be taken and the surrounding area becomes slightly yellow, but there is no practical problem.
X: The printed matter is scraped off, the surroundings become extremely yellow, and the fingers are also considerably stained.

(8) Saturation (color reproducibility)
A solid image is printed on the plain paper a (6200 paper), and after standing for 1 day, the optical densitometer SpectroEye (manufactured by Gretag Macbeth Co.) is set to the measurement mode L ^* a ^* b ^* , and any five locations Was 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〕
○: 92 or more Δ: 90 or more, less than 92 ×: less than 90

Claims (6)

  An aqueous dispersion of vinyl polymer particles containing a yellow organic pigment (A) and a pigment derivative (B) having a polar group, wherein the molecular weight ratio of [the pigment derivative (B) / yellow organic pigment (A)] is An aqueous dispersion for ink jet recording, which is 1.4 to 3 and the vinyl polymer has a structural unit derived from a linear or branched alkyl or alkenyl (meth) acrylate having 8 to 22 carbon atoms. The aqueous dispersion for inkjet recording according to claim 1, wherein the pigment derivative (B) is an azo compound (B) represented by the following formula (1).

(In the formula, R ¹⁰ and R ^{20 each} represents an optionally substituted aryl group having 6 to 50 carbon atoms, and at least one of them has a polar group. R ¹⁰ or R ²⁰ may be the same or different. May be.)   The aqueous dispersion for inkjet recording according to claim 1 or 2, wherein the weight ratio of [pigment derivative (B) / yellow organic pigment (A)] is from 1/99 to 30/70.   The water for inkjet recording according to any one of claims 1 to 3, wherein the vinyl polymer contains 1 to 70% by weight of a structural unit derived from a linear or branched alkyl or alkenyl (meth) acrylate having 8 to 22 carbon atoms. Dispersion.   The vinyl polymer has a structural unit derived from the salt-forming group-containing monomer (a) and a structural unit derived from a linear or branched alkyl or alkenyl (meth) acrylate (c) having 8 to 22 carbon atoms in the main chain. The aqueous dispersion for inkjet recording according to claim 1, which is a graft polymer having a structural unit derived from macromer (b) in the side chain.   An aqueous ink for inkjet recording containing the aqueous dispersion for inkjet recording according to any one of claims 1 to 5.