JP2009235320A - Water-based ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide water-based pigment ink for an inkjet printer, for which a generic pigment is used and which is excellent in dispersion stability. <P>SOLUTION: The water-based ink for inkjet recording comprises a modified pigment (D), having a polymer (P) obtained by copolymerizing a polymer (B) which is soluble in a nonaqueous solvent and which contains a polymerizable unsaturated group and at least a kind of polymerizable unsaturated monomer (C) which has at least one structure selected from a carboxylic acid group, a sulfonic acid group, and salts of them in the molecule, on the surface of a pigment (A), dispersed as a coloring agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a water-based ink for inkjet recording using a modified pigment as a coloring material.

  Conventionally, a dye ink using a dye as a coloring material has been used as a water-based ink for inkjet recording. Dye inks have many advantages such as excellent storage stability, hardly clogging the nozzles of inkjet printers, and the printed matter obtained has excellent gloss. However, it has been pointed out that there are defects derived from dyes, such as inability to store printed matter for a long time due to poor weather resistance, and poor water resistance and light resistance. In recent years, weather resistance, water resistance and light resistance have been pointed out. Development of a water-based ink for ink-jet recording (hereinafter abbreviated as water-based pigment ink) using an excellent pigment is underway.

  The aqueous pigment ink is usually a pigment dispersion in which pigment particles are uniformly dispersed in an aqueous solvent such as water. After recording, an ink film containing the pigment particles is formed on the recording medium. The image quality of the recorded matter with the aqueous pigment ink is greatly influenced by the color development and gloss of the pigment particles themselves in the ink film, and when using a recording medium with a smooth recording surface such as glossy paper, There has been a problem that the color developability and glossiness of the recording portion are impaired due to irregular reflection of light by pigment particles in the ink film. There is also a problem that the fixing property to the recording medium is insufficient and the formed image has poor abrasion resistance.

On the other hand, a technique using a microencapsulated pigment in which colorant particles are coated with a polymer is known for the purpose of improving the fixability of a pigment contained in a pigment-based inkjet ink to a recording medium.
For example, in Patent Document 1, a coloring material and a resin are dissolved in a water-insoluble organic solvent, and then emulsified and dispersed in a mixed solution of water and a water-soluble organic solvent using an emulsifier, and then the water-insoluble organic solvent is removed. It is described that a colored fine particle dispersion formed through a process is used in an inkjet ink. Patent Document 2 discloses a dispersion obtained by blending at least a pigment, a surfactant, and a resin capable of crosslinking reaction in an aqueous medium, and the resin capable of crosslinking reaction after blending the pigment and the surfactant. It is described that an aqueous pigment dispersion which has been subjected to a crosslinking reaction by addition of is used in an inkjet ink.

However, in any case, an emulsifier or a surfactant is used to make the pigment compatible with water, and this influence has a problem of affecting the water resistance of the printed matter.
JP 2004-285215 A JP 2002-294133 A

  The subject of this invention is providing the water-based pigment ink for inkjet printers which uses a general purpose pigment and is excellent in dispersion stability.

  The inventor of the present invention previously invented (Japanese Patent Application No. 2008-071349), a polymer containing a polymerizable unsaturated group soluble in a non-aqueous solvent, a carboxylic acid group, a sulfonic acid group, and their When a pigment having a polymer obtained by copolymerizing at least one polymerizable unsaturated monomer having at least one structure selected from a salt in the molecule is prepared as an aqueous pigment ink for an inkjet printer The inventors have found that the dispersion stability is excellent, and have completed the present invention.

  That is, the present invention includes, as a colorant, a polymer (B) containing a polymerizable unsaturated group soluble in a non-aqueous solvent, a carboxylic acid group, a sulfonic acid group, and salts thereof on the surface of the pigment (A). A modified pigment (D) having a polymer (P) obtained by copolymerizing with at least one polymerizable unsaturated monomer (C) having at least one selected structure in the molecule is dispersed. An aqueous ink for inkjet recording is provided.

  The present invention also provides a carboxylic acid group, a sulfonic acid group in the presence of the pigment (A), a non-aqueous solvent and a polymer (B) containing a polymerizable unsaturated group soluble in the non-aqueous solvent as a colorant. And water for inkjet recording, in which a modified pigment (D) obtained by polymerizing at least one polymerizable unsaturated monomer (C) having at least one structure selected from the salts thereof in the molecule is dispersed Provide ink.

  According to the present invention, it is possible to provide an aqueous pigment ink for an ink jet printer that uses a general-purpose pigment and is excellent in dispersion stability.

(Colorant Pigment (A))
The pigment (A) used in the present invention is at least one pigment selected from known and commonly used organic pigments or inorganic pigments. In addition, the present invention can be applied to either an untreated pigment or a treated pigment.

  Examples of the pigment (A) used for the preparation of the modified pigment (D) include inorganic pigments such as barium sulfate, lead sulfate, titanium oxide, yellow lead, bengara, chromium oxide, and carbon black, anthraquinone pigments, perylene pigments, and disazo pigments. Examples thereof include pigments, phthalocyanine pigments, isoindoline pigments, dioxazine pigments, quinacridone pigments, perinone pigments, and benzimidazolone pigments. These can be used alone or in combination.

  As the black pigment, it is preferable to use carbon black such as furnace black, lamp black, acetylene black, channel black, etc., which has excellent light resistance and high hiding power. Specifically, for example, Raven 7000, Raven 5750, Raven 5250, Raven 5000 Ultra (ULTRA) II, Raven 3500, Raven 2500 Ultra, Raven 2000, Raven 1500, Raven 1255, Raven 1250, Raven 1200, Raven 1190 Ultra II, Raven 1170, Raven 1080 Ultra, Raven 1060 Ultra, Raven 790 Ultra, Raven 780 Ultra, Raven 760 Ultra (from Colombian Carbon), Regal 400R, Regal 330R, Legal 660R, Mogul (Mogul) L, Monarch 700, Monarch 800, Monarch 880, Monarch 9 0, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (manufactured by Cabot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No . 25, no. 33, no. 40, no. 45, no. 45L, no. 47, No 52, No. 900, no. 960, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation), and the like.

Furthermore, among the representative organic pigments of cyan, magenta, and yellow, which are the three primary colors, pigments that can be suitably used in the present invention are exemplified below.
Examples of cyan pigments include C.I. I. Pigment blue 1, C.I. I. Pigment blue 2, C.I. I. Pigment blue 3, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 6, C.I. I. Pigment blue 16, C.I. I. Pigment blue 22, C.I. I. Pigment blue 60, and the like.

  Examples of magenta pigments include C.I. I. Pigment red 5, C.I. I. Pigment red 7, C.I. I. Pigment red 12, C.I. I. Pigment red 48, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57, C.I. I. Pigment red 112, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 146, C.I. I. Pigment red 168, C.I. I. Pigment red 184, C.I. I. Pigment red 202, and the like.

  Examples of yellow pigments include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 2, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, and the like.

  As for the particle diameter of the pigment, the primary particle diameter is preferably in the range of 1 to 500 nm, and more preferably in the range of 20 to 200 nm. The particle diameter of the pigment after being dispersed in the medium is preferably in the range of 10 to 300 nm, and more preferably in the range of 50 to 150 nm. The primary particle diameter of the pigment can be measured by an electron microscope, a gas or solute adsorption method, an air flow method, an X-ray small angle scattering method, and the like. The pigment particle diameter after dispersion can be measured by a known and common centrifugal sedimentation method, laser diffraction method (light scattering method), ESA method, capillary method, electron microscope method and the like. Preferable is measurement by Microtrac UPA using a dynamic light scattering method.

  In the present invention, an organic pigment is particularly preferable because the effects of the present invention can be further exhibited.

(Colorant, non-aqueous solvent)
The non-aqueous solvent used in the present invention is an organic solvent in which an aliphatic and / or alicyclic hydrocarbon solvent is essential. Examples of the aliphatic and / or alicyclic hydrocarbon solvents include n-hexane, n-heptane, “Loose” or “Mineral Split EC” manufactured by Shell Chemicals, and “Isopar C” manufactured by ExxonMobil Chemical. , “Isopar E”, “Isopar G”, “Isopar H”, “Isopar L”, “Isopar M”, “Naphtha 3”, “Naphtha 5” or “Naphtha 6”, products of Idemitsu Petrochemical Co., Ltd. “Solvent 7”, “IP Solvent 1016”, “IP Solvent 1620”, “IP Solvent 2028” or “IP Solvent 2835”, “Whitesol” of Japan Energy Co., Ltd., “ “Marcazole 8”, “AF Solvent No. 4” from Shin Nippon Oil Co., Ltd., “AF SO Vent No. 5 "," AF Solvent No. 6 "and" AF Solvent No. 7 ", and the like.

Moreover, you may mix and use another organic solvent in the range which does not impair the effect of this invention. Specific examples of such organic solvents include, for example, “Swazole 100” or “Swazole 150” manufactured by Maruzen Petrochemical Co., Ltd., aromatic hydrocarbon solvents such as toluene or xylene; methyl acetate, ethyl acetate Esters such as acetone, n-butyl acetate or amyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone or cyclohexanone; or methanol, ethanol, n-propanol, i-propanol or n-butanol And alcohols such as
When mixed and used, the amount of the aliphatic and / or alicyclic hydrocarbon solvent used is preferably 50% by mass or more, and more preferably 60% by mass or more.

(Colorant: Polymer (B) containing a polymerizable unsaturated group soluble in a non-aqueous solvent)
Specifically, the polymer (B) containing a polymerizable unsaturated group soluble in a nonaqueous solvent used in the present invention is mainly an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms. Polymerization mainly comprising a polymer having a polymerizable unsaturated group introduced into a copolymer of a polymerizable unsaturated monomer as a component, or an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms This term refers to a macromonomer composed of a copolymer of unsaturated monomers.

Examples of the alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms include n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meta ) Acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like.
Examples of polymerizable unsaturated monomers other than alkyl (meth) acrylates include aromatic vinyl monomers such as styrene, α-methylstyrene, pt-butylstyrene or vinyltoluene, benzyl ( (Meth) acrylate, dimethylamino (meth) acrylate, diethylamino (meth) acrylate, (meth) acrylates such as dibromopropyl (meth) acrylate or tribromophenyl (meth) acrylate, maleic acid, fumaric acid or itaconic acid, etc. And diesters of unsaturated dicarboxylic acids and monohydric alcohols, vinyl esters such as vinyl benzoate, “Veoba” (vinyl ester manufactured by Shell of the Netherlands), and the like, and the above alkyl (meth) acrylates Can be used together with copolymerization That.
A single polymer of a polymerizable unsaturated group-containing monomer that can be used other than these alkyl (meth) acrylates has low solubility in the non-aqueous medium, so it is used as an alkyl (meth) acrylate and a random polymer. It is preferred that When the copolymerization is carried out in the form of a block or a graft, the solubility in the non-aqueous medium is remarkably lowered, which is not preferable.

  These polymerizable unsaturated monomers may be used alone or in combination of two or more. Of these, the use of linear or branched alkyl (meth) acrylates having 4 to 12 carbon atoms such as n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl methacrylate and the like is particularly preferable.

  A copolymer of a polymerizable unsaturated monomer having an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms as a main component is obtained by polymerizing the polymerizable unsaturated monomer by a conventional method. can get.

By introducing a polymerizable unsaturated group into the copolymer of a polymerizable unsaturated monomer mainly comprising an alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms, polymerizable unsaturated A polymer (B) containing groups is obtained.
As a method for introducing a polymerizable unsaturated group, for example, a carboxyl group-containing polymerizable monomer such as acrylic acid or methacrylic acid or an amino group such as dimethylaminoethyl methacrylate or dimethylaminopropylacrylamide is previously used as the copolymer component. A polymerizable monomer is blended and copolymerized to obtain the copolymer having a carboxyl group or an amino group, and then having the carboxyl group or amino group, a glycidyl group such as glycidyl methacrylate, and a polymerizable unsaturated group. A method of reacting monomers,
A hydroxyl group-containing monomer such as 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate is previously blended and copolymerized as the copolymer component to obtain the copolymer having a hydroxyl group. Next, the hydroxyl group and isocyanate ethyl methacrylate are obtained. A method of reacting a monomer having a polymerizable unsaturated group with an isocyanate group such as
During polymerization, thioglycolic acid is used as a chain transfer agent to introduce a carboxyl group at the end of the copolymer, and a monomer having a glycidyl group such as glycidyl methacrylate and a polymerizable unsaturated group is added to the carboxyl group. How to react,
As a polymerization initiator, a carboxyl group-containing azo initiator such as azobiscyanopentanoic acid is used to introduce a carboxyl group into the copolymer, and a glycidyl group such as glycidyl methacrylate and a polymerizable unsaturated group are introduced into the carboxyl group. And the like. Among them, a carboxyl group-containing monomer such as acrylic acid or methacrylic acid or an amino group-containing monomer such as dimethylaminoethyl methacrylate or dimethylaminopropylacrylamide is copolymerized, and the carboxyl group or amino group and glycidyl methacrylate are copolymerized. A method of reacting a monomer having a polymerizable unsaturated group with a glycidyl group such as the simplest is preferable.

(Colorant: at least one polymerizable unsaturated monomer (C) having at least one structure selected from a carboxylic acid group, a sulfonic acid group and a salt thereof in the molecule)
At least one polymerizable unsaturated monomer (C) having at least one structure selected from a carboxylic acid group, a sulfonic acid group and a salt thereof used in the present invention in the molecule (hereinafter simply referred to as polymerizable unsaturated group) Monomer (C)) includes (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and other unsaturated mono- or dicarboxylic acids, and these dicarboxylic acids and 1 Polymerizable unsaturated carboxylic acids such as monoesters with divalent alcohols, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid and its metal salts such as lithium, potassium and sodium, or ammonium salts, etc. And polymerizable unsaturated sulfonic acids.

In order to perform in-situ polymerization to form a modified layer more stably, in addition to the polymerizable unsaturated monomer (C), the polymerizability is soluble in a non-aqueous solvent and insoluble or hardly soluble after polymerization. It is more preferable to use an unsaturated monomer (hereinafter referred to as a polymerizable unsaturated monomer (E)).
Specifically, the polymerizable unsaturated monomer (E) is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate or i-propyl (meth) acrylate, or (meth). Vinyl monomers having no so-called reactive polar groups (functional groups) such as acrylonitrile, styrene, ethyl vinyl benzene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl fluoride or vinylidene fluoride; (meth) acrylamide Amide bond such as dimethyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N-octyl (meth) acrylamide, diacetone acrylamide, dimethylaminopropyl acrylamide or alkoxylated N-methylol (meth) acrylamides Vinyl Nomers; Dialkyl [(meth) acryloyloxyalkyl] phosphates or (meth) acryloyloxyalkyl acid phosphates, or Dialkyl [(meth) acryloyloxyalkyl] phosphites or (meth) acryloyloxyalkyl acid Phosphites; Phosphorus atom-containing vinyl monomers such as 3-chloro-2-acid phosphoxypropyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (Meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate Rate, di-2-hydroxyethyl fumarate or mono-2-hydroxyethyl monobutyl fumarate, polypropylene glycol, polyethylene glycol mono (meth) acrylate, or “Placcel FM, FA monomer” (manufactured by Daicel Chemical Industries, Ltd.) Hydroxyl group-containing polymerizable unsaturated monomers such as hydroxyalkyl esters of polymerizable unsaturated carboxylic acids such as caprolactone addition monomers) or adducts thereof with ε-caprolactone; dimethylaminoethyl (meth) acrylate , Dialkylaminoalkyl (meth) acrylates such as diethylaminoethyl (meth) acrylate; glycidyl (meth) acrylate, (β-methyl) glucidyl (meth) acrylate, (meth) allyl glycidyl acetate Isocyanate group containing α, β-ethylenically unsaturated monomers such as monomers having an isocyanate group and a vinyl group such as isocyanate ethyl (meth) acrylate; vinyl ethoxysilane, α-methacryloxypropyltrimethoxysilane , Alkoxysilyl group-containing polymerizable unsaturated monomers such as silicon monomers such as trimethylsiloxyethyl (meth) acrylate, “KR-215, X-22-5002” (Shin-Etsu Chemical Co., Ltd. product), etc. is there.
Of these, the use of C3 or lower alkyl (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate is preferred.

  In order to prevent the polymer from eluting from the pigment when the modified pigment (D) is used, it is more preferable that the polymer is crosslinked. Examples of the polyfunctional polymerizable unsaturated monomer used as the crosslinking component include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di ( (Meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol dimethacrylate, trimethylolpropane tri Ethoxytri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol Sa (meth) acrylate or allyl methacrylate, and the like.

(Method for producing colorant)
The modified pigment (D) used in the present invention is the pigment (A), the non-aqueous solvent, and the polymer (B) containing a polymerizable unsaturated group soluble in the non-aqueous solvent, It is obtained by polymerizing the polymerizable unsaturated monomer (C).
The pigment (A) and the polymer (B) are preferably mixed before polymerization. As a mixing method, for example, a homogenizer, a disper, a bead mill, a paint shaker, a kneader, a roll mill, a ball mill, an attritor, a sand mill and the like can be used. In the present invention, the form of the pigment to be used is not limited, and any form of slurry, wet cake, and powder may be used. That is, in the production method of the present invention, even a pigment containing water such as a wet cake can be used.
After mixing the pigment (A) and the polymer (B), the polymerizable unsaturated monomer (C) and a polymerization initiator described later are further mixed and polymerized to obtain a modified pigment (D). .
At that time, the amount of the polymer (B) used is not particularly limited because it is appropriately optimized depending on the purpose, but usually 1 to 200 parts is used with respect to 100 parts of the pigment (A), more preferably. 5 to 50 parts, more preferably 5 to 30 parts.
Further, the amount of the polymerizable unsaturated monomer (C) used is not particularly limited since it is appropriately optimized depending on the purpose, but usually 0.5 to 100 parts with respect to the pigment (A). It is preferably used, more preferably 1 to 30 parts, still more preferably 2 to 20 parts. Moreover, it is preferable that the usage-amount of the said polymerizable unsaturated monomer (E) is used to such an extent that the effect of this invention is not impaired.
The amount of the polymerizable unsaturated monomer that is soluble in the non-aqueous solvent and becomes insoluble or hardly soluble after polymerization is also not particularly limited because it is appropriately optimized depending on the purpose. ) 0.5 to 100 parts are used per 100 parts, more preferably 0.5 to 25 parts, still more preferably 0.5 to 10 parts.

  Obtained by polymerization of the polymer (B) finally coated on the pigment, the polymerizable unsaturated monomer (C) and the polymerizable unsaturated monomer (E) (used as necessary) The amount of the polymer to be used is preferably 2 to 400 parts, more preferably 10 to 100 parts, and still more preferably 10 to 60 parts with respect to 100 parts of the pigment (A). At that time, the total amount of the polymerizable unsaturated monomer (C) and the polymerizable unsaturated monomer (E) is usually 10 to 400 parts relative to 100 parts of the polymer (B). Is preferably used, preferably 30 to 400 parts, more preferably 50 to 200 parts.

A method of polymerizing the polymerizable unsaturated monomer (C) and the like in the presence of the pigment (A), the non-aqueous solvent, and the polymer (B) may be performed by a known and conventional polymerization method. Usually, it is carried out in the presence of a polymerization initiator. Such polymerization initiators include azobisisobutyronitrile (AIBN), 2,2-azobis (2-methylbutyronitrile), benzoyl peroxide, t-butyl perbenzoate, t-butyl-2-ethylhexano A radical generating polymerization catalyst such as ate, t-butyl hydroperoxide, di-t-butyl peroxide, or cumene hydroperoxide may be used alone or in combination of two or more.
Since some polymerization initiators are difficult to dissolve in the non-aqueous solvent system, the polymerizable unsaturated monomer (C), or the polymerizable unsaturated monomer (C) and the polymerizable unsaturated monomer. A method of dissolving in the mixture of (E) and adding to the mixed system of the pigment (A) and the polymer (B) is preferable.
The polymerizable unsaturated monomer (C) (which may dissolve a polymerization initiator), or the polymerizable unsaturated monomer (C) and the polymerizable unsaturated monomer (E). The mixture (which may have dissolved the polymerization initiator) can be added by the dropping method in a state where the polymerization temperature has been reached, but it is added at room temperature before the temperature rise, and after the mixture is sufficiently mixed, The polymerization method is stable and preferable.
The polymerization temperature is usually in the range of 60 ° C to 130 ° C. In addition, when the pigment (A) is an organic pigment, if the polymerization temperature is too high, the pigment may undergo significant changes in form such as alteration and crystal growth. In that case, it is preferable to polymerize at 70 to 100 ° C.

  After the polymerization, the non-aqueous solvent used for the polymerization is removed by filtration, followed by drying and pulverization to obtain a powdered modified pigment (D). Nutsche, filter press, etc. can be used for the filtration method. Moreover, it can dry with well-known drying apparatuses, such as a box-type dryer, a vacuum dryer, a band dryer, and a spray dryer. For the pulverization, a known pulverizer such as a mortar, a hammer mill, a disk mill, a pin mill, or a jet mill can be used.

The water-based ink for inkjet recording of the present invention is obtained by dispersing the modified pigment (D) in an aqueous medium by an aqueous resin by a known and conventional method, and adding a drying inhibitor, a penetrating agent, or other additives as necessary. Is obtained.
In this case, the aqueous resin to be used is not particularly limited, and a general liquid ink vehicle may be used. A water-based resin is preferable as a general-purpose ink vehicle, and preferable examples include (meth) acrylic resins such as polyvinyl alcohols, polyvinylpyrrolidones, (meth) acrylic acid- (meth) acrylic acid ester copolymers, Styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid -Styrene-acrylic resin such as acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, carboxyl group-containing urethane resin and water-based resin Salt.
Further, the compounds for forming the copolymer salt include diethylamine, ammonia, ethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, triethanolamine, diethanolamine, aminomethylpropanol, morpholine. And the like. The amount of the compound used to form these salts is preferably equal to or greater than the neutralization equivalent of the copolymer.
These aqueous resins can be used alone or in admixture of two or more. In addition, there is no restriction | limiting in particular in the form of the aqueous resin used here, such as a random copolymer and a block copolymer.
In particular, when preparing a water-based ink for inkjet recording, the weight-average molecular weight (hereinafter abbreviated as Mw) of the pigment-dispersing resin is used in order to obtain a water-based ink that suppresses kogation at the heater portion and has excellent ejection stability. Is preferably in the range of 6,000 to 20,000. If Mw is 6,000 or less, the dispersion stability of the water-based ink itself may be lowered. On the other hand, if it exceeds 20,000, the viscosity of the water-based ink tends to be high and the dispersion stability tends to be lowered. Further, kogation on the heater portion becomes severe, which may cause non-ejection of ink droplets from the nozzle tip of the thermal ink jet printer.

  It is preferable that the compounding quantity of the vehicle for inks is 1-100 mass parts with respect to 100 mass parts of pigments which have the said polymer, More preferably, it is 2-70 mass parts. The acid value of the pigment dispersing resin is preferably 50 to 300 mgKOH / g.

  In particular, when preparing a water-based ink for inkjet recording, it is preferable to use a styrene- (meth) acrylic acid copolymer or a benzyl methacrylate- (meth) acrylic acid salt from the viewpoint of more preferable dispersion stability. When a pigment is prepared by adding a carboxy group-containing polyurethane to an aqueous dispersion in which a pigment is dispersed in water with a styrene- (meth) acrylic acid copolymer or a benzyl methacrylate- (meth) acrylic acid salt, ink ejection In particular, it is possible to obtain a printed image having excellent properties and excellent abrasion resistance.

(Aqueous medium)
The aqueous medium used in the present invention may be water alone or a mixed solvent composed of a water-soluble organic solvent having compatibility between water and water. Examples of the water-soluble organic solvent include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, and 2-methoxyethanol. Alcohols such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc .; amides such as dimethylformamide, N-methylpyrrolidone, etc., and especially those having 3 to 6 carbon atoms It is preferable to use a compound selected from the group consisting of a ketone and an alcohol having 1 to 5 carbon atoms.

  The method for obtaining the water-based ink for ink jet recording of the present invention is not particularly limited and can be carried out by a known method. For example, a pigment dispersion obtained by dispersing a pigment having the polymer in the liquid vehicle in water or an aqueous solvent containing water can be diluted with a solvent as it is and used as an ink.

  As a stirring / dispersing device for dispersing the pigment, for example, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a dispermat, an SC mill, a nanomizer, and the like, various commonly known dispersions are used. You can use the machine.

Further, it is prepared by adding a drying inhibitor, a penetrating agent, or other additives as necessary.
The drying inhibitor gives an effect of inhibiting drying of the water-based ink for inkjet recording at the ink jet nozzle opening of the inkjet printer head. Usually, a water-soluble organic solvent having a boiling point equal to or higher than that of water is used.
Examples of water-soluble organic solvents that can be used as drying inhibitors include polyhydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, and glycerol, pyrrolidones such as N-methyl-2-pyrrolidone and 2-pyrrolidone, amides, and dimethyl sulfoxide. And imidazolidinone. When the solvent is water, the amount of the drying inhibitor used is preferably in the range of 1 to 150 parts with respect to 100 parts of water.

The penetrating agent is used for facilitating penetration of the water-based ink for ink jet recording, which is ejected from the ink ejecting nozzle of the ink jet printer head and adheres to the recording medium, into the recording medium. By using the penetrating agent, it is possible to obtain a recorded matter in which the aqueous solvent quickly penetrates into the recording medium and the image does not blur.
Examples of penetrants used in the present invention include polyhydric alcohols such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol, diols such as pentanediol and hexanediol, and laurin. Glycol ethers such as propylene glycol, lower alkyl ethers of polyhydric alcohols such as diethylene glycol ethyl ether and triethylene glycol monoethyl ether, lower alcohols such as ethanol and isopropyl alcohol, glycol ethers such as diethylene glycol-N-butyl ether, propylene And water-soluble organic solvents such as glycol derivatives. These can be used alone or in admixture of two or more. More preferable permeability may be obtained by using a mixture of two or more.

The water-based ink for ink-jet recording of the present invention may contain a slight amount of a surfactant for the purpose of adjusting physical properties such as the surface tension of the ink. The surfactant is not particularly limited, and anionic surfactants such as alkylbenzene sulfonates and higher fatty acid salts, nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene fatty acid esters, and other cationic surfactants. The surfactant may be appropriately selected from known and commonly used surfactants such as amphoteric surfactants. These surfactants can be used alone or in combination of two or more.
Examples of other additives include antiseptics, antifungal agents, and chelating agents for preventing nozzle clogging.

  If coarse particles are present in the water-based ink for ink jet recording, the ink jet nozzles of the ink jet printer may be clogged. Therefore, it is preferable to remove the coarse particles by centrifugal separation or filtration after the dispersion treatment.

Hereinafter, the present invention will be described with reference to examples. Unless otherwise specified, “parts” and “%” are based on mass.
<Reference Example 1 Synthesis of Polymer (B-1) Containing Polymerizable Unsaturated Group Soluble in Nonaqueous Solvent>
A four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube was charged with 500 parts of heptane and 470 parts of butyl acetate, and the temperature was raised to 90 ° C. A mixture consisting of 985 parts of butyl acid, 15 parts of methacrylic acid, and 7 parts of 2,2′-azobis (2-methylbutyronitrile) was added dropwise over 5 hours. The reaction was continued with holding. After the temperature of the reaction solution was lowered to 50 ° C., a solution in which 0.2 part of t-butylpyrocatechol was dissolved in 15 parts of butyl acetate was added, and then 15 parts of glycidyl methacrylate and 30 parts of dimethylaminoethanol were added. The solution was heated to 80 ° C. and reacted at the same temperature for 10 hours to obtain a polymer (B-1) solution containing a polymerizable unsaturated group soluble in a non-aqueous solvent.

<Reference Example 2 Synthesis of Polymer (B-2) Containing Polymerizable Unsaturated Group Soluble in Nonaqueous Solvent>
In the same reactor as in Reference Example 1, 500 parts of heptane and 500 parts of butyl acetate were charged and the temperature was raised to 90 ° C. When the same temperature was reached, 950 parts of butyl acrylate and dimethylaminoethyl methacrylate were added. A mixture comprising 50 parts and 7 parts of 2,2′-azobis (2-methylbutyronitrile) was added dropwise over 5 hours, and the reaction was continued for 10 hours at the same temperature after completion of the addition. The temperature of the reaction solution was lowered to 50 ° C., a solution in which 0.2 part of t-butyl pyrocatechol was dissolved in 20 parts of butyl acetate was added, and 20 parts of glycidyl methacrylate was further added, and the temperature was raised to 80 ° C. By performing the reaction at the same temperature for 10 hours, a polymer (B-2) solution containing a polymerizable unsaturated group soluble in a non-aqueous solvent was obtained.

<Reference Example 3 Synthesis of Modified Pigment (D-1)>
222 parts of wet cake (pigment content 45%) of Fast Gen Blue TGR (Dai Nippon Ink Chemical Co., Ltd.), 10 parts of the polymer (B-1) obtained in Reference Example 1, 1.25 mm 600 parts of zirconia beads and 300 parts of heptane were placed in a polyethylene jar and mixed for 90 minutes with a paint shaker (Toyo Seiki Co., Ltd.). After dilution with 300 parts of heptane, the zirconia beads were removed to prepare a pigment mixture.
400 parts of the obtained pigment mixed solution was charged into a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas introduction tube, and then t-butylacrylamidesulfonic acid as a polymerizable monomer (C). 4.8 parts of the above are dissolved in 20 parts of ion-exchanged water, and as a polymerizable unsaturated monomer (E), 1 part of methyl methacrylate and 1.4 parts of ethylene glycol dimethacrylate are polymerized. To the soluble monomer composition, 1.5 parts of 2,2′-azobis (2-methylbutyronitrile) and 200 parts of heptane were added. After stirring for 30 minutes at room temperature, the temperature was raised to 80 ° C., and the reaction was continued for 15 hours at the same temperature. After cooling, the modified pigment and the polymerization solvent were separated by filtration. The obtained modified pigment was dried with a hot air dryer at 100 ° C. for 5 hours and then pulverized with a pulverizer to obtain a modified pigment (D-1).

<Reference Example 4 Synthesis of Modified Pigment (D-2)>
222 parts of wet cake (pigment content 45%) of Fast Gen Blue TGR (Dai Nippon Ink Chemical Co., Ltd.), 15 parts of polymer (B-2) obtained in Reference Example 2, 1.25 mm 600 parts of zirconia beads and 300 parts of heptane were placed in a polyethylene jar and mixed for 90 minutes with a paint shaker (Toyo Seiki Co., Ltd.). After dilution with 300 parts of heptane, the zirconia beads were removed to prepare a pigment mixture.
After charging 400 parts of the obtained pigment mixed liquid in the same reaction apparatus as in Reference Example 3, 7.2 parts of acrylic acid and polymerizable unsaturated monomer (E) were used as the polymerizable monomer (C). ), 1.9 parts of 2,2′-azobis (2-methylbutyronitrile) were dissolved in 1 part of methyl methacrylate and 1.4 parts of ethylene glycol dimethacrylate. And 200 parts of heptane were added. After stirring for 30 minutes at room temperature, the temperature was raised to 80 ° C., and the reaction was continued for 15 hours at the same temperature. After cooling, the modified pigment and the polymerization solvent were separated by filtration. The obtained modified pigment was dried at 100 ° C. for 5 hours with a hot air dryer and then pulverized with a pulverizer to obtain a modified pigment (D-2).

<Reference Example 5 Synthesis of Modified Pigment (D-3)>
222 parts of wet cake (pigment content 45%) of Fastgen Blue TGR (Dai Nippon Ink Chemical Co., Ltd.), 20 parts of AB-6 (polybutyl acrylate macromonomer manufactured by Toa Gosei Co., Ltd.) 600 parts of 25 mm zirconia beads and 300 parts of heptane were placed in a polyethylene jar and mixed for 90 minutes with a paint shaker (Toyo Seiki Co., Ltd.). After dilution with 300 parts of heptane, the zirconia beads were removed to prepare a pigment mixture. After charging 400 parts of the obtained pigment mixed solution in the same reactor as in Reference Example 3, as a polymerizable monomer (C), 4.7 parts of t-butylacrylamide sulfonic acid was replaced with 20 parts of ion exchange. 1 part of styrene and divinylbenzene (containing 55% component and 45% structural isomer (ethylvinylbenzene)) are added as a polymerizable unsaturated monomer (E). To 4 parts, 1.4 parts of 2,2'-azobis (2-methylbutyronitrile) dissolved and 200 parts of heptane were added. After stirring for 30 minutes at room temperature, the temperature was raised to 80 ° C., and the reaction was continued for 15 hours at the same temperature. After cooling, the modified pigment and the polymerization solvent were separated by filtration. The obtained modified pigment was dried with a hot air dryer at 100 ° C. for 5 hours and then pulverized with a pulverizer to obtain a modified pigment (D-3).

<Synthesis of Reference Example 6 Modified Pigment (D-4)>
100 parts of Fast Gen Super Magenta RTS (a quinacridone pigment manufactured by Dainippon Ink and Chemicals, Inc., CI Pigment Red 122), 10 parts of the polymer (B-2) obtained in Reference Example 2, 600 parts of 25 mm zirconia beads and 300 parts of heptane were placed in a polyethylene jar and mixed for 90 minutes with a paint shaker (Toyo Seiki Co., Ltd.). After dilution with 200 parts of heptane, the zirconia beads were removed to prepare a pigment mixture. 400 parts of the obtained pigment mixed solution was charged into the same reactor as in Reference Example 3, and then 5.3 parts of t-butylacrylamide sulfonic acid as the polymerizable monomer (C) was subjected to 20 parts of ion exchange. What was dissolved in water was added, and as a polymerizable unsaturated monomer (E), 1.1 parts of a polymerizable monomer composition of ethylene glycol dimethacrylate was added to 2,2′-azobis (2-methylbutyrate). (Lonitrile) and 1.3 parts of heptane were added. After stirring for 30 minutes at room temperature, the temperature was raised to 80 ° C., and the reaction was continued for 15 hours at the same temperature. After cooling, the modified pigment and the polymerization solvent were separated by filtration. The obtained modified pigment was dried with a hot air dryer at 100 ° C. for 5 hours and then pulverized with a pulverizer to obtain a modified pigment (D-4).

<Reference Example 7 Synthesis of Modified Pigment (D-5)>
100 parts of IRGAPHOR Yellow 8 GCF (Ciba Specialty Chemicals, Inc., CI Pigment Yellow 128), 15 parts of polymer (B-2) obtained in Reference Example 2, 600 parts of 1.25 mm zirconia beads Then, 400 parts of heptane was placed in a polyethylene jar and mixed for 90 minutes with a paint shaker (Toyo Seiki Co., Ltd.). After dilution with 300 parts of heptane, the zirconia beads were removed to prepare a pigment mixture. After charging 400 parts of the obtained pigment mixed liquid in the same reaction apparatus as in Reference Example 3, 4.9 parts of methacrylic acid was added as a polymerizable monomer (C), and the polymerizable unsaturated monomer was further added. As the body (E), 1.5 parts of t-butylperoxy-2-ethylhexanoate dissolved in a polymerizable monomer composition of 2 parts of styrene and 0.5 part of ethylene glycol dimethacrylate And 200 parts of heptane were added. After stirring for 30 minutes at room temperature, the temperature was raised to 80 ° C., and the reaction was continued for 15 hours at the same temperature. After cooling, the modified pigment and the polymerization solvent were separated by filtration. The obtained modified pigment was dried with a hot air dryer at 100 ° C. for 5 hours and then pulverized with a pulverizer to obtain a modified pigment (D-5).

<Synthesis of Reference Example 8 Modified Pigment (D-6)>
100 parts of carbon black # 960 (Mitsubishi Chemical Corporation CI Pigment Black 7), 10 parts of the polymer (B-2) obtained in Reference Example 2, 600 parts of 1.25 mm zirconia beads, heptane 400 parts were placed in a polyethylene jar and mixed for 90 minutes with a paint shaker (Toyo Seiki Co., Ltd.). After dilution with 300 parts of heptane, the zirconia beads were removed to prepare a pigment mixture. After charging 400 parts of the obtained pigment mixed liquid in the same reaction apparatus as in Reference Example 3, 4.9 parts of acrylic acid was added as a polymerizable monomer (C), and the polymerizable unsaturated monomer was further added. As body (E), 1.5 parts of t-butylperoxy-2-ethylhexanoate was dissolved in 1 part of methyl methacrylate and 1.5 parts of ethylene glycol dimethacrylate as a polymerizable monomer composition. And 200 parts of heptane were added. After stirring for 30 minutes at room temperature, the temperature was raised to 80 ° C., and the reaction was continued for 15 hours at the same temperature. After cooling, the modified pigment and the polymerization solvent were separated by filtration. The obtained modified pigment was dried with a hot air dryer at 100 ° C. for 5 hours and then pulverized with a pulverizer to obtain a modified pigment (D-6).

<Synthesis of Reference Example 9 Acrylic Copolymer (AC)>
100 parts of methyl ethyl ketone (hereinafter abbreviated as MEK) are kept at 80 ° C. in a nitrogen stream and are stirred with 87.8 parts of benzyl methacrylate, 12.2 parts of methacrylic acid, and t-butylperoxy- A mixture of 6 parts of 2-ethylhexanoate was added dropwise over 2 hours. After completion of the dropwise addition, 0.5 part of t-butylperoxy-2-ethylhexanoate was added every 4 hours, and the reaction was continued at 80 ° C. for 12 hours. Thus, an MEK solution (AC) of an acrylic copolymer having a carboxyl group having a nonvolatile content of 50% was obtained. The resin had a weight average molecular weight of 25,000 and an acid value of 80 mgKOH / g.

<Example 1>
20 parts of the acrylic copolymer (AC) obtained in Reference Example 9, 15.9 parts of a 5% aqueous potassium hydroxide solution, 10 parts of the modified pigment (D-1) obtained in Reference Example 3, and ion-exchanged water 20.8 parts of zirconia beads having a diameter of 0.5 mm were charged into a 250 mL plastic bottle and mixed. The mixture was dispersed with a paint conditioner for 2 hours. After the completion of dispersion, methyl ethyl ketone was removed from the liquid obtained by removing the zirconia beads using an evaporator, and after removing coarse particles by centrifugation (8200 G, 30 minutes), pure water was added to remove the non-volatile content. An aqueous pigment dispersion was obtained by adjusting 20%.
25 parts of the obtained aqueous pigment dispersion, 10 parts of diethylene glycol monobutyl ether, 15 parts of diethylene glycol, 0.8 part of Surfinol 465 (manufactured by Air Products), 49.2 parts of ion-exchanged water, Water-based ink for inkjet recording was prepared by filtering through a filter having a pore size of 6 μm.

(Determination of pigment particle size in water-based ink for inkjet recording)
After adding ion-exchanged water to the sample ink and diluting it 1000 times, using a particle size analyzer ("Microtrac UPA150" manufactured by Leeds and Northrup), pigment particles dispersed in the sample ink The diameter was measured and used as the initial particle diameter, and judged according to the following three-stage criteria.
○ Particle size less than 120 nm.
Δ: Particle size of 120 nm or more and less than 150 nm.
X Particle size of 150 nm or more.

(Storage stability of water-based ink for inkjet recording)
The aqueous ink for inkjet recording was allowed to stand at 60 ° C. for 30 days, and then the particle size of the pigment dispersed in the sample was measured using the particle size analyzer.
When the rate of change of the measured value with respect to the initial particle diameter was 10% or less, the sample was evaluated as “pass” and the sample with a change rate exceeding 10% was evaluated as “fail”. Moreover, the presence or absence of the sedimentation of the pigment particles on the bottom surface of the container was visually determined.

<Examples 2 to 6>
Except for changing the modified pigment as described in Tables 1 and 2, ink jet recording ink was prepared in the same manner as in Example 1, and the same evaluation was performed.

<Comparative Examples 1-2>
Except for changing the pigment as described in Table 2, ink jet recording inks were prepared in the same manner as in Example 1, and the same evaluation was performed.

In Tables 1 and 2,
“Surfinol 465” is “Nonionic surfactant manufactured by Air Products”.
“Carbon black # 960” is “Carbon black CI Pigment Black 7 manufactured by Mitsubishi Chemical Corporation”.
“First Gen Super Magenta RTS” is “Quinacridone pigment, CI Pigment Red 122 manufactured by Dainippon Ink and Chemicals, Inc.”.

  As a result, the inks for ink jet recording obtained in Examples 1 to 6 were excellent in storage stability because the change rate of the measured value with respect to the initial particle diameter was within 10%. On the other hand, Comparative Example 1, which was the same as Example 4 but used an unmodified pigment, had a particle size of 120 nm or more and poor storage stability. Comparative Example 2, which was the same as Example 6 but used an unmodified pigment, had a particle size of 150 nm or more and poor storage stability.

The ink jet recording ink obtained in Examples 1 to 3 (cyan), the ink jet recording ink obtained in Example 4 (magenta), and the ink jet recording ink obtained in Comparative Example 1 (magenta) Printing was performed, and the print density and gloss value were evaluated. The results are shown in Table 3.
Using a piezo type ink jet printer (EM-930C, manufactured by Seiko Epson Corporation), drawing was performed on the recording medium with sample ink, and a print density test and a gloss value test were performed. The recording medium used was “Photo Paper Gloss” manufactured by Seiko Epson Corporation.

(Print density)
Print a solid image on inkjet paper, use a print density measuring machine (GRETAG (registered trademark) D196 Gretag Macbeth Co., Ltd.), measure the color image density for 5 points of a single sample, and average the values. The printing density was used. The larger the value, the better the print density, and the determination was made according to the following four criteria for each paper.
◎ Print density 2.7 or higher.
○ Printing density is 2.5 or more and less than 2.7.
Δ: Print density is 2.0 or more and less than 2.5.
× Print density less than 2.0.

(Measure gloss value of image)
A solid image was printed on a special inkjet paper, and the gloss of the colored image was measured at a measurement angle of 20 degrees using a haze gloss meter (manufactured by BYK Gardner) as a gloss value measuring machine. Three points of a single sample were measured, and a value obtained by averaging them was defined as a gloss value. The larger the value, the better the gloss, and the determination was made according to the following four levels of criteria.
◎ Gloss value 25 or more ○ Gloss value 20 or more.
Δ: Gloss value of 10 or more and less than 20.
X Gloss value less than 10.

  As a result, the inkjet recording inks of Examples 1 to 4 had high printing density and good image gloss, but the inkjet recording ink of Comparative Example 1 produced streak in printing and a clean printed matter was obtained. The evaluation was not possible.

Claims (3)

As a colorant, at least one structure selected from a polymer (B) containing a polymerizable unsaturated group soluble in a non-aqueous solvent, a carboxylic acid group, a sulfonic acid group, and a salt thereof on the surface of the pigment (A). An ink jet comprising a modified pigment (D) having a polymer (P) obtained by copolymerizing with at least one polymerizable unsaturated monomer (C) having in the molecule thereof Water-based ink for recording. The colorant is selected from carboxylic acid groups, sulfonic acid groups, and salts thereof in the presence of the pigment (A), a non-aqueous solvent, and a polymer (B) containing a polymerizable unsaturated group soluble in the non-aqueous solvent. A water-based ink for ink jet recording, wherein a modified pigment (D) obtained by polymerizing at least one polymerizable unsaturated monomer (C) having at least one structure in the molecule is dispersed . The water-based ink for inkjet recording according to claim 1, wherein the non-aqueous solvent includes an aliphatic hydrocarbon solvent and / or an alicyclic hydrocarbon solvent.