JP4914087B2 - Ink set for inkjet recording - Google Patents

Description

  The present invention relates to an ink set for ink-jet recording that reduces the bronzing phenomenon of printed matter, a recording method using the same, an ink-jet recorded matter obtained by using the method, and an aqueous dispersion used for the ink set, including the same It relates to a water-based ink.

The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them. This method is easy and inexpensive to make full color, can use plain paper as a recording member, and has many advantages such as non-contact with the printed material.
Among them, from the viewpoint of weather resistance and water resistance of printed materials, those using pigment-based inks as colorants have become mainstream, but when pigments are used as colorants, reflected light depends on the observation angle of printed materials. A bronzing phenomenon may occur in which a color different from the original color of the pigment is observed. For example, a phthalocyanine pigment contained in cyan ink may cause the reflected light to be colored red, which may significantly deteriorate the image quality. The bronze phenomenon is described in detail in “Color Science Handbook” (University of Tokyo Press), page 777.
In order to improve this bronze phenomenon, an ink composition containing a polyether-modified polysiloxane and a sulfone group-containing (co) polymer emulsion has been proposed (see Patent Document 1). In addition, an ink containing a polycyclic aromatic heteroconjugated compound is disclosed (see Patent Document 2).
However, in any of these methods, there are concerns about adverse effects on print image quality due to changes in additives and pigments.

JP 2003-306620 A JP 2004-67903 A

  The present invention includes an ink set for ink jet recording capable of reducing the bronzing phenomenon, a recording method using the ink set, an ink jet recorded matter using the method, an aqueous dispersion used for the ink set, and the same It is an object to provide a water-based ink.

The present inventors have noticed that silica particles can effectively reduce the bronze phenomenon, and have found that the above problems can be solved.
That is, the present invention provides the following (1) to (5).
(1) an ink set for ink jet recording having a water-based ink (A) containing water-insoluble polymer particles (A) containing silica particles and a water-based ink (B) containing a pigment excluding silica particles,
(2) An ink jet recording method in which the water-based ink (B) is printed on a recording medium using the ink set described in (1) above, and the water-based ink (A) is printed over the print site.
(3) A water-based ink used for the ink set according to (1) above, comprising water-insoluble polymer particles (a) containing silica particles,
(4) The method for producing a water-based ink for an ink set according to the above (3), comprising the following step 1 and step 2.
Step 1: Step of dispersing a mixture of silica particles, water-insoluble polymer (I ′), organic solvent and water Step 2: Step of removing the organic solvent from the dispersion obtained in Step 1

  The bronzing phenomenon of printed matter can be effectively reduced by the ink set for inkjet recording of the present invention, the recording method using the ink set, and the water-based ink used in the ink set.

Hereinafter, the present invention will be described in detail.
(Pigments excluding silica particles (hereinafter also simply referred to as “pigments”))
In the aqueous dispersion for inkjet recording of the present invention, a pigment excluding silica particles is used, and an organic pigment is preferably used from the viewpoint of reducing the bronzing phenomenon.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed.

  Among organic pigments, a cyan pigment is preferably used and a phthalocyanine pigment is more preferable from the viewpoint of a large effect of reducing the bronze phenomenon. Examples of phthalocyanine pigments include metal-free phthalocyanine pigments; metal phthalocyanine pigments such as copper, aluminum, nickel, cobalt, iron, titanium, and tin, and unsubstituted or halogen-substituted phthalocyanine pigments such as chlorine and bromine. . More specifically, a copper phthalocyanine pigment is preferable, and C.I. I. One or more selected from the group consisting of CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 16 and 60 are preferred. Among these, from the viewpoint of durability against light, heat and solvent, C.I. I. Pigment Blue 15: 3 and 15: 4 are particularly preferable.

  In the case of using a cyan pigment, the intensity ratio of the intensity of [630 nm / intensity of 550 nm] in the reflection spectrum of the printed material with respect to the halogen lamp C light (hereinafter sometimes simply referred to as “reflection spectrum intensity ratio”) By adjusting to 4 or less, the bronze phenomenon can be significantly improved. Such a phenomenon is due to human visual characteristics. That is, among the color matching functions indicating the spectral sensitivity of the human eye, the peak of the color matching function having a large sensitivity in the red wavelength region is around 600 to 650 nm, and the green color is around 550 nm. When the ratio of both increases, the human eye perceives red. From the viewpoint of reducing the bronze phenomenon, the reflection spectrum intensity ratio between the two is preferably adjusted to 4 or less, more preferably 1 to 4, more preferably 1 to 3.5, and most preferably 1 to 3. .

  The average primary particle size of the pigment is preferably 10 to 100 nm, more preferably 20 to 90 nm, and still more preferably 30 to 80 nm from the viewpoints of pigment dispersibility, printing density, and scratch resistance. The average primary particle diameter of the pigment can be measured by the method described later.

(Silica particles)
The water-based ink (A) constituting the ink set of the present invention contains water-insoluble polymer particles (A) containing silica particles. If silica particles are present in the vicinity of the pigment, it is considered that the silica particles have the same effect as the antireflection film, whereby the specular reflection light on the pigment surface can be reduced and the bronze phenomenon is reduced. It is considered possible.
Silica particles can be classified into precipitated silica and fumed silica depending on the production method, and any of these can be used. All of these have hydrophilic properties because silanol groups (Si—O—H) are usually present on the surface thereof. In the present invention, the silica particles may be used as they are, but from the viewpoint of the effect of reducing the bronze phenomenon due to the presence of the silica particles in the vicinity of the pigment and the affinity with the water-insoluble polymer, the surface of the silica particles It is preferable to use hydrophobic silica in which at least a part of the surface is hydrophobized. Whether or not the front surface of the silica particles is hydrophobized can be determined by visual observation whether 1 g of the silica particles can be stably dispersed (25 ° C., 1 week) in 10 g of methyl ethyl ketone.

As a method for hydrophobizing the surface of silica particles, 1. a method of modifying silanol groups on the surface of silica particles with a hydrophobic group such as an alkylsilyl group having preferably 1 to 12 carbon atoms (for example, methylsilyl group, hexylsilyl group, etc.); The method etc. which coat | cover the silica particle surface with hydrophobic resin are mentioned.
Examples of the hydrophobizing agent for hydrophobizing the silica particle surface include organochlorosilane, organoalkoxysilane, organodisilazane, cyclic organopolysilazane, and linear organopolysiloxane.
The method of modifying the silanol group on the surface of silica with a hydrophobic group such as an alkylsilyl group is, for example, a method of reacting a water-dispersed silica colloid with an alkylsilanol alkali metal salt (see Japanese Patent Publication No. 7-33250); A method in which an organic solvent, a cationic surfactant, and an alkyltrialkoxysilane are added to a silica colloid, followed by azeotropic dehydration, followed by heating to reflux (refer to JP-A-6-73389); Examples thereof include a method of reacting an alkoxysilane, an organic silicon halide compound or the like (see JP-A-6-206720, JP-A-7-187647, etc.).

  In the silica particle in which the silanol group on the surface of the silica particle is modified with a hydrophobic group, the silanol group on the surface of the silica particle is preferably 5 mol% or more, more preferably 10 mol% or more, further preferably 20 mol% or more. It is modified with a group. As the alkylsilyl group for modifying the silanol group, a linear or branched alkyl group having 1 to 12 carbon atoms is preferable, and specifically, a methylsilyl group, an ethylsilyl group, an n-propylsilyl group, an i-propylsilyl group. N-butylsilyl group, t-butylsilyl group, i-butylsilyl group, pentylsilyl group, hexylsilyl group, 2-ethylhexylsilyl group, octylsilyl group, dodecylsilyl group and the like are preferable.

Since the silanol groups on the silica surface can ionically adsorb amino groups and imino groups, the ratio of silanol groups modified by the hydrophobic group is the di- sity for each silica before and after the modification reaction. It can be known by measuring the amount of adsorption of -n-butylamine.
From the viewpoint of reducing the bronze phenomenon, the average particle diameter of the silica particles is preferably 3 nm or more, 100 nm or less, more preferably 50 nm or less, more preferably 30 nm or less, still more preferably 20 nm or less, From these viewpoints, 3 to 100 nm is preferable, 3 to 50 nm is more preferable, 3 to 30 nm is more preferable, and 3 to 20 nm is still more preferable. The average particle size can be measured by the method described later.

(Silica-containing polymer particles (I))
The water-insoluble polymer particles (a) constituting the water-insoluble polymer particles (a) containing silica particles (hereinafter sometimes referred to as “silica-containing polymer particles (a)”) include water-insoluble vinyl polymers and water-insoluble esters. And a water-insoluble urethane polymer. Among these, a water-insoluble vinyl polymer is preferable from the viewpoint of the stability of the aqueous dispersion. In the present invention, the water-insoluble polymer means that when it is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the dissolved amount is 10 g or less, preferably 5 g or less, more preferably 1 g or less. A polymer. When the water-insoluble polymer has a salt-forming group, the above-mentioned dissolution amount refers to the dissolution amount when the salt-forming group of the water-insoluble polymer is neutralized 100% with acetic acid or sodium hydroxide, depending on the type.

The water-insoluble polymer (A ′) preferably contains a structural unit derived from the salt-forming group-containing monomer (a), a structural unit derived from the hydrophobic monomer (b) and / or a structural unit derived from the macromer (c).
Examples of such a water-insoluble polymer (A ′) include a salt-forming group-containing monomer (a) (hereinafter sometimes referred to as “(a) component”), a hydrophobic monomer (b) (hereinafter referred to as “(b) component”). Water-insoluble vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter sometimes referred to as “monomer mixture”) containing macromer (c) (hereinafter sometimes referred to as “component (c)”) Is preferred.
In addition, the water-insoluble polymer (I ′) is preferably a water-insoluble graft polymer containing a structural unit derived from the macromer (c) from the viewpoint of stabilizing the dispersion of silica particles.

The component (a) is used from the viewpoint of enhancing the dispersion stability of the resulting dispersion, and examples thereof include a cationic monomer and an anionic monomer. Specifically, those described in JP-A-9-286939, page 5, column 7, line 24 to page 8, column 8 line 29 can be used. 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.
Representative examples of the cationic monomer include unsaturated amine-containing monomers and unsaturated ammonium salt-containing monomers, among which N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N '-Dimethylaminopropyl) (meth) acrylamide is preferred.

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 unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamide-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconate, and the like.
Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxy Examples thereof include ethyl phosphate.
Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid or methacrylic acid is more preferable from the viewpoints of dispersion stability, dischargeability, and the like.
The said (a) component can be used individually or in combination of 2 or more types, respectively.

The hydrophobic monomer (b) is used from the viewpoint of improving water resistance and scratch resistance, and examples thereof include alkyl (meth) acrylate, alkyl (meth) acrylamide, and aromatic ring-containing monomers.
Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, Cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, etc. (Meth) acrylic acid ester having an alkyl group having 1 to 22 carbon atoms.
Alkyl (meth) acrylamides include carbon atoms such as dimethyl (meth) acrylamide, diethyl (meth) acrylamide, dibutyl (meth) acrylamide, t-butyl (meth) acrylamide, octyl (meth) acrylamide, and dodecyl (meth) acrylamide. Examples include (meth) acrylamide having 1 to 22 alkyl groups.

Examples of aromatic ring-containing monomers include styrene monomers such as styrene, 2-methylstyrene and vinyltoluene, aryl esters of (meth) acrylic acid such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, ethyl vinylbenzene, 4 Preferred are vinyl monomers having an aromatic hydrocarbon group having 6 to 22 carbon atoms such as -vinylbiphenyl, 1,1-diphenylethylene, vinylnaphthalene, chlorostyrene and the like.
In the present specification, “(iso or tertiary)” and “(iso)” mean that both of these groups are present and not present, and these groups are present. If not, it indicates normal. In addition, “(meth) acrylate” indicates that both acrylate and methacrylate are included.

As the component (b), an aromatic ring-containing monomer is preferable from the viewpoint of water resistance and scratch resistance, and among them, a styrene monomer (b-1) component is preferable, and styrene and 2-methylstyrene are more preferable. The content of the component (b-1) in the component (b) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density and marker resistance.
In addition, as the component (b), an aromatic ring-containing monomer is preferable from the viewpoint of improving the glossiness, among which the (meth) acrylic acid aryl ester (b-2) component is preferable, and has 7 to 22 carbon atoms, preferably (Meth) acrylate having an arylalkyl group having 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, or 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms. A (meth) acrylate having an aryl group is preferred. Specific examples of such a monomer include benzyl (meth) acrylate and phenoxyethyl (meth) acrylate. The content of the component (b-2) in the component (b) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight from the viewpoint of improving glossiness.
The component (b) can be used alone or in combination of two or more, and it is also preferable to use the component (b-1) and the component (b-2) in combination.

Component (c) is used from the viewpoint of stably dispersing silica particles in water-insoluble polymer particles, and has a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000, and is not present at one end. Examples include macromers that are monomers having a polymerizable functional group such as a saturated group.
The number average molecular weight of the component (c) can be measured by gel permeation chromatography using polystyrene as a standard substance and tetrahydrofuran containing 50 mmol / L acetic acid as a solvent.
Specifically, as the macromer of component (c), the following (c-1) styrenic macromer, (c-2) alkyl (meth) acrylate macromer, (c-3) aromatic ring-containing (meth) acrylate Macromers, (c-4) silicon-based macromers, and the like.

(C-1) Styrenic Macromer The styrenic macromer means a macromer having a styrene monomer (referred to as c-1 monomer) such as styrene, α-methylstyrene, vinyltoluene and the like. Of the styrenic monomers, styrene is preferred.
Examples of the styrenic macromer include a styrene homopolymer having a polymerizable functional group at one end, and a copolymer of styrene and another monomer having a polymerizable functional group at one end. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and by copolymerizing these, a water-insoluble graft polymer having a structural unit derived from a styrenic macromer can be obtained.

Other monomers include, for example, (1) acrylonitrile, (2) (meth) acrylic acid esters (c-2 monomer) described later, and (3) aromatic ring-containing (meth) acrylate monomers other than styrene (c -3 monomer).
In the side chain or the styrenic macromer, the content of the structural unit derived from the styrenic monomer is preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight from the viewpoint of scratch resistance. That's it.
Examples of commercially available styrenic macromers include Toa Gosei Co., Ltd. trade names, AS-6 (S), AN-6 (S), HS-6 (S), and the like.

(C-2) Alkyl (meth) acrylate-based macromer An alkyl (meth) acrylate-based macromer has an alkyl group which may have a hydroxy group, preferably 1 to 22 carbon atoms, preferably 1 to 18 carbon atoms. , A macromer having a (meth) acrylic acid ester (c-2 monomer).
Specific examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (iso or tertiary). Examples include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
The side chain containing the structural unit derived from the c-2 monomer is obtained by copolymerizing an alkyl (meth) acrylate macromer having a polymerizable functional group at one end, such as a methyl methacrylate macromer or a butyl acrylate macromer. , Isobutyl methacrylate-based macromer, lauryl methacrylate-based macromer, and the like.

Alkyl (meth) acrylate-based macromers include alkyl (meth) acrylate homopolymers having a polymerizable functional group at one end, and alkyl (meth) acrylates and other monomers having a polymerizable functional group at one end. The acryloyloxy group or the methacryloyloxy group is preferable as the polymerizable functional group. Examples of the other monomer include (1) styrene monomer (c-1 monomer) described above and (3) aromatic ring-containing (meth) acrylate monomer (c-3 monomer) other than styrene described later.
In the side chain or in the alkyl (meth) acrylate macromer, the content of the structural unit derived from the (meth) acrylic ester is the largest, and from the viewpoint of scratch resistance, it is preferably 60% by weight or more, more preferably 70%. % By weight or more, particularly preferably 90% by weight or more.

(C-3) Aromatic ring-containing (meth) acrylate-based macromer The aromatic ring-containing (meth) acrylate-based macromer means a macromer having an aromatic ring-containing (meth) acrylate (c-3 monomer). As an aromatic ring containing (meth) acrylate, the monomer represented by following formula (1) is preferable.
CH ₂ = CR ¹ COOR ² (1)
(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents an arylalkyl group having 7 to 22 carbon atoms or an aryl group having 6 to 22 carbon atoms, which may have a substituent. )
Specifically, benzyl (meth) acrylate, phenyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthyl acrylate, 2-naphthyl (meth) acrylate, phthalimidomethyl (meta ) Acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acryloyloxyethyl phthalate, and the like. Among these, benzyl (meth) acrylate is particularly preferable. These can be used alone or in combination of two or more.

A side chain containing a structural unit derived from an aromatic ring-containing (meth) acrylate can be obtained by copolymerizing an aromatic ring-containing (meth) acrylate-based macromer having a polymerizable functional group at one end.
An aromatic ring-containing (meth) acrylate-based macromer is a homopolymer of an aromatic ring-containing (meth) acrylate having a polymerizable functional group at one end, and an aromatic ring-containing (meth) acrylate having a polymerizable functional group at one end And other monomers, and the polymerizable functional group is preferably an acryloyloxy group or a methacryloyloxy group. Examples of the other monomer include (1) styrene monomer (c-1 monomer), (2) (meth) acrylic acid ester (c-2 monomer), and the like.
In the side chain or the aromatic ring-containing (meth) acrylate-based macromer, the content of the structural unit derived from the aromatic ring-containing (meth) acrylate is the largest.

(C-4) Silicon-based macromer The water-insoluble graft polymer used in the present invention may have an organopolysiloxane chain as a side chain. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end, preferably represented by the following formula (2).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} -O] _{t -Si (CH 3) 3 (} 2)
(Wherein t represents a number of 8 to 40)
Among the macromers, a styrenic macromer having a polymerizable functional group at one end is preferable from the viewpoint of high affinity with the pigment and improving storage stability.
In the present invention, the above macromers may be used alone or in combination of two or more.

  When the polymer used in the present invention is a water-insoluble graft polymer, the weight ratio of [main chain / side chain] is 1/1 to 20/1 from the viewpoint of improving scratch resistance and storage stability. It is preferably 3/2 to 15/1, more preferably 2/1 to 10/1. It is calculated that the polymerizable functional group is contained in the side chain.

In the present invention, the monomer mixture containing the components (a), (b), and (c) further contains a hydroxyl group-containing monomer (d) (hereinafter sometimes referred to as “component (d)”). Is preferred.
The component (d) increases the dispersion stability of the aqueous dispersion. Examples of the component (d) include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and polyethylene glycol (n = 2 to 30, n represents the average number of moles added of the 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 (e) represented by the following formula (3) (hereinafter sometimes referred to as “component (e)”).
^{_{CH 2 = C (R 3)}} COO (R 4 O) p R 5 (3)
(Wherein R ³ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁴ represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, R ⁵ Represents a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, but p represents the average number of added moles, and is 1 to 60, preferably 1 to 30.)
The component (e) expresses the effect of improving the discharge stability of the water-based ink.
In formula (3), examples of the hetero atom that R ⁴ or R ⁵ may have include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Typical examples of the group represented by R ⁴ or R ⁵ include an aromatic group having 6 to 30 carbon atoms, a heterocyclic group having 3 to 30 carbon atoms, an alkylene group having 1 to 30 carbon atoms, and the like. It may have a substituent. These groups may be a combination of two or more. Examples of the substituent include an aromatic group, a heterocyclic group, an alkyl group, a halogen atom, and an amino group.

R ⁴ is a phenylene group which may have a substituent having 1 to 24 carbon atoms, a C 1 to 30 carbon atom, preferably an aliphatic alkylene group having 1 to 20 carbon atoms, or a carbon number having an aromatic ring. A 7-30 alkylene group and a C4-C30 alkylene group which has a heterocyclic ring are mentioned preferably. Particularly preferred specific examples of the R ⁴ O group include an oxyethylene group, an oxy (iso) propylene group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, or a carbon number of two or more of these oxyalkylenes. ˜7 oxyalkylene groups and oxyphenylene groups.
R ⁵ includes a phenyl group, an aliphatic alkyl group having 1 to 30 carbon atoms, preferably a branched chain having 1 to 20 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, or A C4-C30 alkyl group which has a heterocyclic ring is mentioned preferably. More preferred examples of R ⁵ include alkyl groups having 1 to 12 carbon atoms such as methyl group, ethyl group, (iso) propyl group, (iso) butyl group, (iso) pentyl group and (iso) hexyl group, phenyl Groups and the like.

Specific examples of the component (e) include methoxypolyethylene glycol (p is 1 to 30 in the above formula (3)) (meth) acrylate, methoxypolytetramethylene glycol (p = 1 to 30) (meth) acrylate, and ethoxypolyethylene. Glycol (p = 1-30) (meth) acrylate, (iso) propoxypolyethylene glycol (p = 1-30) (meth) acrylate, butoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxypolyethylene glycol (P = 1-30), methoxypolypropylene glycol (p = 1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, in which the ethylene glycol moiety is 1-29 ) (Meth) acrylate It is done. Among these, methoxypolyethylene glycol (p = 1-30) (meth) acrylate is preferable.
Specific examples of commercially available (d) and (e) components include: Shin-Nakamura Chemical Co., Ltd., polyfunctional acrylate monomer (NK ester) M-40G, 90G, 230G; Mer series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-1000, PP-500, PP-800, AP-150, AP-400, AP-550, AP-800, 50PEP -300,50POEP-800B etc. are mentioned.
The component (d) and the component (e) can be used alone or in combination of two or more.

The contents of the components (a) to (e) in the monomer mixture are preferably as follows.
The content of component (a) is preferably 3 to 30% by weight, more preferably 4 to 20% by weight, from the viewpoint of dispersion stability of the resulting dispersion.
The content of component (b) is preferably 10 to 70% by weight, more preferably 15 to 60% by weight, from the viewpoint of water resistance and scratch resistance.
The content of the component (c) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, from the viewpoint of stably dispersing the silica particles in the water-insoluble polymer fine particles.
The weight ratio ((a) / [(b) + (c)]) of the content of the component (a) and the total content of the components (b) and (c) is the long-term storage of the resulting water-based ink. From the viewpoints of stability, dischargeability and the like, it is preferably 0.01 to 1, more preferably 0.02 to 0.67, and still more preferably 0.03 to 0.50.

The content of the component (d) is preferably 5 to 40% by weight, more preferably 7 to 20% by weight from the viewpoints of dischargeability and print density.
The content of the component (e) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, from the viewpoints of dischargeability and dispersion stability.
From the viewpoint of stability in water, the total content of the component (a) and the component (d) is preferably 6 to 60% by weight, more preferably 10 to 50% by weight.
The total content of the component (a) and the component (e) is preferably 6 to 75% by weight, more preferably 13 to 50% by weight from the viewpoints of dispersion stability in water, dischargeability, and the like.
The total content of the component (a), the component (d), and the component (e) is preferably 6 to 60% by weight, more preferably 7 to 7% from the viewpoints of dispersion stability in water, print density, and dischargeability. 50% by weight.
The content of the components derived from the components (a) to (e) in the water-insoluble polymer is the same as the content of the components.

The water-insoluble polymer is produced by copolymerizing the 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. In the case of the solution polymerization method, effects such as high printing density and high bleed resistance can be preferably obtained.
As the solvent used in the solution polymerization method, a polar organic solvent having a high affinity for the water-insoluble polymer is preferable, and the solubility in water at 20 ° C. is preferably 50% by weight or less, and more preferably 5% by weight or more. Examples of the polar organic solvent include aliphatic alcohols such as butoxyethanol; aromatics such as toluene and xylene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate. Among these, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, butoxyethanol, or a mixed solvent of one or more of these with water is preferable.

In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), tert-butyl peroxyoctoate, dibenzoyl oxide, etc. Known polymerization initiators such as organic peroxides can be used.
The amount of the 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 can be further added.
The polymerization conditions of the monomer mixture vary depending on the type of polymerization initiator, monomer, and solvent used, but the polymerization temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C., and the polymerization time is 1 to 20 hours. is there. 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.

The weight average molecular weight of the obtained water-insoluble polymer is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, from the viewpoint of pigment dispersion stability, water resistance, dischargeability, and the like. ~ 300,000 is particularly preferred.
The weight average molecular weight of the polymer was measured using polystyrene as a standard substance by a gel permeation chromatography method using dimethylformamide in which 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide were dissolved as a solvent. Is done.

  When the water-insoluble polymer 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 kind 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, Examples include acids such as gluconic acid and glyceric acid, bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, trimethylamine, 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
On the other hand, when the salt-forming group is a cationic group, it can be obtained by the following formula.
[[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × weight of polymer (g) / (36.5 × 1000)]] × 100
The acid value and amine value can be calculated from the structural unit of the polymer, but can also be determined by a method of titrating by dissolving the polymer in an appropriate solvent (for example, methyl ethyl ketone).

As described above, when the silica particles are contained in the water-insoluble polymer particles (a), the bronzing phenomenon can be effectively reduced and excellent dispersion stability can be obtained.
The silica-containing polymer particles (A) are preferably produced by the following step 1 and step 2.
Step 1: A step of dispersing a mixture of silica particles, a water-insoluble polymer (I ′), an organic solvent and water Step 2: A step of removing the organic solvent from the dispersion obtained in Step 1 In Step 1 above First, silica particles, a water-insoluble polymer (I ') (hereinafter also simply referred to as a water-insoluble polymer), an organic solvent and water are mixed. Preferably, the water-insoluble polymer is dissolved in an organic solvent, and then Silica particles, water, and, if necessary, a neutralizing agent, a surfactant and the like are added to the organic solvent and mixed to obtain an oil-in-water dispersion.

In the above mixture, the content of silica particles is preferably 2 to 40% by weight, more preferably 2 to 20% by weight, and the content of the organic solvent is preferably 10 to 70% by weight, 50% is more preferable, the content of the water-insoluble polymer is preferably 2 to 40% by weight, more preferably 2 to 20% by weight, and the content of water is preferably 10 to 70% by weight, More preferred is ˜60% by weight.
When the water-insoluble polymer has a salt-forming group, it is preferable to use a neutralizing agent, but the water-insoluble polymer may be neutralized with a neutralizing agent in advance. The degree of neutralization is not particularly limited, but it is usually preferable to neutralize so that the liquid dispersion of the finally obtained water dispersion is neutral, for example, pH is 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the water-insoluble polymer.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents, and those having a solubility in water at 20 ° C. of 50% by weight or less and 10% by weight or more are preferable.
Specifically, examples of the alcohol solvent include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable. These solvents can be used alone or in admixture of two or more.

The method for dispersing the mixture in Step 1 is not particularly limited as long as it can be atomized so as to obtain water-insoluble polymer particles having a desired average particle diameter.
Examples of the disperser include a kneader such as a roll mill, a kneader, and an extruder, a disperser such as a sand mill and a bead mill, a high pressure homogenizer such as a chamber type, and the like. Among these, from the viewpoint of uniformly mixing the silica particles and the pigment, a method of wet pulverization with a disperser using a dispersion medium is preferable. Furthermore, it is also preferable to adopt a method of dispersing by a high-pressure homogenizer after wet pulverization if necessary.

The material of the dispersion medium is preferably ceramic beads such as titania (TiO ₂ ), zirconia (ZrO ₂ ), zircon (ZrSiO ₄ ) alumina (Al ₂ O ₃ ), particularly titania (TiO ₂ ), from the viewpoint of hardness and the like. Zirconia (ZrO ₂ ) is preferred. The particle size of the dispersion medium is usually 30 to 500 μm, preferably 30 to 400 μm.
In the wet pulverization dispersion, the weight ratio of the dispersion medium / dispersion liquid (including all dispersions such as silica particles, polymer, water, and organic solvent) is usually 10/1 to 4 / from the viewpoint of uniformly mixing the silica particles. 6, preferably 10/1 to 5/5.
The peripheral speed of the disperser using the dispersion medium is the speed of the outer periphery of the stirring blade when it has a stirring blade. In the present invention, it is preferably 3 to 30 m / sec, more preferably 5 to 25 m / sec. It is. When there is no stirring blade, it is the rotational speed of the container, and in the present invention, it is preferably a speed of 0.1 to 1 m / sec.
The dispersion time is preferably 1 to 15 hours, and more preferably 2 to 10 hours, from the viewpoint of uniformly mixing the silica particles. From the same point, the temperature during dispersion is preferably 0 to 60 ° C, more preferably 5 to 30 ° C.

In the step 2, the organic solvent is distilled off from the dispersion obtained in the step 1 to form an aqueous system, thereby obtaining an aqueous dispersion of water-insoluble polymer particles (i) having a desired average particle size. The organic solvent contained in the aqueous dispersion can be removed by a general method such as distillation under reduced pressure. The organic solvent in the obtained aqueous dispersion is substantially removed, and the residual amount of the organic solvent is preferably 0.1% by weight or less, more preferably 0.01% by weight or less.
Moreover, it is preferable to remove coarse particles by filtering the obtained aqueous dispersion.

The obtained aqueous dispersion is an aqueous dispersion of silica-containing water-insoluble polymer particles (A). That is, the silica-containing water-insoluble polymer particles (A) are dispersed in water as a main solvent. Here, the form of the silica-containing water-insoluble polymer particles (A) is not particularly limited, and any form may be used as long as the particles are formed by at least silica particles and the water-insoluble polymer (A ′). Particle form in which silica particles are encapsulated in '), particle form in which silica particles are uniformly dispersed in water-insoluble polymer (b), particle form in which silica particles are exposed on the surface of water-insoluble polymer particle (b), etc. Are included.
The average particle diameter of the obtained silica-containing water-insoluble polymer particles (A) is preferably 10 to 200 nm, more preferably 30 to 130 nm, and still more preferably 50 to 120 nm, from the viewpoint of preventing clogging of printer nozzles. is there. The average particle diameter can be determined by a measurement method described later.

(Water-based ink (A))
The water-based ink (A) is used for effectively reducing the bronzing phenomenon by printing a water-based ink (B) containing a pigment, which will be described later, on a recording medium and printing it on the print site.
The method for producing the water-based ink (A) is not particularly limited, and the water dispersion of the water-insoluble polymer particles (i) containing the silica particles may be used as it is as the water-based ink for ink-jet recording. It may be produced by adding a wetting agent, a penetrating agent, a dispersing agent, a viscosity modifier, an antifoaming agent, an antifungal agent, a rust preventing agent and the like which are usually used in recording water-based inks.
Furthermore, the water-based ink containing an aqueous dispersion of water-insoluble polymer particles (a) containing silica particles may contain a pigment other than silica particles as long as the present invention is not impaired. As such an embodiment, for example, the following (i) to (iii) can be used. (i) an aqueous dispersion of water-insoluble polymer particles (a) containing silica particles and a pigment other than silica particles, and (ii) water-insoluble polymer particles (a) containing silica particles and a pigment other than silica particles. An aqueous dispersion containing (iii) water-insoluble polymer particles (a) containing silica particles and water-insoluble polymer particles containing a pigment other than silica particles.

The content of each component in the water-based ink (A) is as follows. The content of silica particles is preferably 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, and still more preferably 1 to 5% by weight, from the viewpoint of reducing the bronze phenomenon.
The content of the water-insoluble polymer (I ′) is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, and further preferably 1 to 5% by weight, from the viewpoint of dispersion stability of the silica particles. is there.
The content ratio of the silica particles to the water-insoluble polymer (I ′) (water-insoluble polymer (I ′) / silica particles) is 5/95 to 90/10 in terms of weight ratio from the viewpoint of improving scratch resistance and dispersion stability. It is preferably 10/90 to 75/25, more preferably 20/80 to 50/50.

The water content in the water-based ink (A) is preferably 30 to 95% by weight, more preferably 40 to 90% by weight.
The surface tension (20 ° C.) of the aqueous ink (A) of the present invention is preferably 23 to 50 mN / m, more preferably 23 to 45 mN / m, more preferably 23 to 40 mN / m, and still more preferably 23. ˜30 mN / m. The viscosity (20 ° C.) of the water-based ink (A) is preferably 2 to 12 mPa · s, more preferably 2.5 to 10 mPa · s, and more preferably 2.5 to 6 mPa · s in order to maintain good ejection properties. Further preferred.

(Water-based ink (B))
Hereinafter, the water-based ink (B) containing a pigment excluding silica particles will be described.
In the water-based ink (B), the pigment needs to be dispersed and stabilized in the water-based ink. Examples of the pigment that has been dispersion-stabilized include the following (1) to (3).
(1) A pigment dispersed in water with a surfactant, a pigment derivative or a water-soluble polymer (2) A self-dispersing pigment in which a hydrophilic group is bonded to the pigment directly or through another atomic group (3 ) Water dispersion of water-insoluble polymer particles (b) containing pigment

Examples of the surfactant used in the dispersion (1) include anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants, and pigment derivatives include ionic surfactants. Examples include azo derivatives, diazo derivatives, phthalocyanine derivatives, quinacridone derivatives, isoindolinone derivatives, dioxazine derivatives, perylene derivatives, perinone derivatives, thioindigo derivatives, anthraquinone derivatives, quinophthalone derivatives having functional group or ionic functional group salts. .
The water-soluble polymer is a polymer whose dissolved amount exceeds 10 g, preferably 20 g or more, more preferably 30 g or more when dissolved in 100 g of water at 25 ° C. When the water-soluble polymer has a salt-forming group such as a carboxy group or an ammonium group, the above-mentioned dissolution amount is 100% neutralized with acetic acid or sodium hydroxide according to the type of the water-soluble polymer. The amount of dissolution.

Examples of the water-soluble polymer include (i) a water-soluble polymer obtained by subjecting a sulfonated product obtained by sulfonating a polynuclear aromatic compound or a mononuclear aromatic compound to formalin condensation, and then preferably neutralizing; (ii) carboxy A water-soluble polymer having a group is preferred. Specific examples of the polymer (i) include polynaphthalene sulfonic acid (salt) typified by sodium salt of β-naphthalenesulfonic acid formalin condensate, and include Demol NL and Demol made by Kao Corporation. Commercial products such as N and demall MS (trade name) can be used. The polymer of (ii) includes (meth) acrylic acid (salt) polymer represented by polyacrylic acid and its copolymer, sodium salt of styrene and maleic acid copolymer, diisobutylene and maleic acid copolymer. A maleic acid (salt) polymer represented by a combined sodium salt and a copolymer thereof may be mentioned, and specifically, Pois 520, Pois 521, Pois 530 and the like manufactured by Kao Corporation are preferable.
The water-soluble polymer preferably has a weight average molecular weight of 2,000 to 50,000 from the viewpoint of dispersibility. The weight average molecular weight of the water-soluble polymer was measured using polystyrene as a standard substance by a gel chromatography method using dimethylformamide in which 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide were dissolved as a solvent. can do.

In the water dispersion (3), examples of the water-insoluble polymer (b ') constituting the pigment-containing water-insoluble polymer particles (b) include water-insoluble vinyl polymers, water-insoluble ester polymers, water-insoluble urethane polymers, and the like. Can be mentioned. Among these, a water-insoluble vinyl polymer is preferable from the viewpoint of the stability of the aqueous dispersion.
The water-insoluble polymer (ro ′) preferably contains a structural unit derived from the salt-forming group-containing monomer (a), a structural unit derived from the hydrophobic monomer (b) and / or a structural unit derived from the macromer (c), As the preferred range, monomer compound and the like, the same water-insoluble polymer (A ′) constituting the above-mentioned water-insoluble polymer particles (A) can be used. However, the water-insoluble polymer (B ′) and the water-insoluble polymer (A ′) may be the same or different.

The water-insoluble polymer particles (b) containing the pigment can be preferably produced by the following steps I and II.
Step I: Dispersing a mixture of a pigment, a water-insoluble polymer (b '), an organic solvent and water Step II: A step of removing the organic solvent from the dispersion obtained in Step I In Steps I and II The preferred quantitative ratios, production conditions, and the like of each component are the same as in the case where the silica particles are replaced with pigments in the above-described Steps 1 and 2.
The aqueous dispersion obtained in Step II is an aqueous dispersion of pigment-containing water-insoluble polymer particles (b). That is, the water-insoluble polymer particles (B) containing the pigment are dispersed in water as the main solvent. Here, the form of the water-insoluble polymer particles (B) containing the pigment is not particularly limited, as long as the particles are formed by at least the pigment and the water-insoluble polymer (B '). For example, the water-insoluble polymer (B') The particle form in which the pigment is encapsulated, the particle form in which the pigment is uniformly dispersed in the water-insoluble polymer (b), the particle form in which the pigment is exposed on the surface of the water-insoluble polymer particle (b), and the like are included.

The average particle diameter of the pigment-containing water-insoluble polymer particles (b) is preferably 30 to 200 nm, more preferably 50 to 130 nm, and still more preferably 60 to 120 nm, from the viewpoint of preventing clogging of the printer nozzle and the printing density. . The particle size can be determined by a measurement method described later.
In the present invention, among the pigments (1) to (3) or dispersions thereof, it is preferable to use the aqueous dispersion of the pigment-containing water-insoluble polymer particles (b) of (3). It is preferable from the viewpoint of dispersion stability.

The content of the pigment in the water-based ink (B) is preferably 1 to 10% by weight, more preferably 2 to 10% by weight, still more preferably 3 to 10% by weight, and still more preferably 4 from the viewpoint of increasing the printing density. ~ 8 weight.
The content of the water-insoluble polymer (b ') is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, still more preferably 1 to 5% by weight, from the viewpoint of dispersion stability of the pigment. .
The content ratio of the pigment and the water-insoluble polymer (b ') (water-insoluble polymer (b') / pigment) is 5/95 to 90 / by weight from the viewpoint of improving the printing density, scratch resistance and dispersion stability. 10 is preferable, 10/90 to 75/25 is more preferable, and 20/80 to 50/50 is still more preferable.

The water-based ink (B) contains water as a main solvent, and an aqueous dispersion of water-insoluble polymer particles (b) may be used as it is as an ink-jet recording water-based ink. A wetting agent, a penetrating agent, a dispersing agent, a viscosity modifier, an antifoaming agent, an antifungal agent, an antirust agent, and the like may be added.
The water content in the water-based ink (B) is preferably 30 to 95% by weight, more preferably 40 to 90% by weight.
The surface tension (20 ° C.) of the water-based ink (B) is preferably 23 to 50 mN / m, more preferably 23 to 45 mN / m, more preferably 23 to 40 mN / m, and still more preferably 23 to 30 mN / m. m. The viscosity (20 ° C.) of the water-based ink (B) of the present invention is preferably 2 to 12 mPa · s, more preferably 2.5 to 10 mPa · s, and more preferably 2.5 to 6 mPa in order to maintain good ejection properties. -S is more preferable.

(Ink set for inkjet recording)
The ink-jet ink set of the present invention has an aqueous ink (A) containing water-insoluble polymer particles (I) containing silica particles and an aqueous ink (B) containing a pigment excluding silica particles. .
The aqueous ink (B) containing a pigment in the ink set of the present invention preferably contains one or more chromatic inks selected from the group consisting of cyan, yellow, magenta, light cyan, dark yellow and light magenta, and bronze From the viewpoint of reducing the phenomenon, it is more preferable to include cyan and / or light cyan.
The ink set of the present invention is preferably a set comprising a combination of one or more inks selected from these chromatic colors, a two-color ink set, a three-color ink set, a four-color ink set, a six-color ink set, and a seven-color ink. Any of more than a set may be sufficient.
More preferably, the ink set includes two or more different color inks selected from magenta ink, yellow ink, and cyan ink, which are the three subtractive primary colors, and the ink set including these three color inks is particularly preferable. preferable. The ink set of the present invention may further include black ink such as self-dispersing carbon black.

(Inkjet recording method)
In the present invention, from the viewpoint of reducing the bronze phenomenon due to silica particles, the aqueous ink (B) is printed on a recording medium using the ink set, and the aqueous ink (A) is superposed on the print site. The present invention relates to an inkjet recording method for printing.
The recording medium used in the present invention is not particularly limited as long as it can be applied to the ink jet recording method, and examples thereof include paper, plastic, and composites thereof.
The recording medium may have a void-type ink-receiving layer or an alumina-based ink-receiving layer, and may be usually referred to as glossy paper or photographic paper, and does not have an ink-receiving layer, usually plain paper or copy paper. It may be said.

In the recording method of the present invention, first, the water-based ink (B) is printed on a recording medium, and the water-based ink (A) is printed over the print site by an inkjet recording method.
Ink ejection amount for printing on a recording medium, any inks, from the viewpoint of reduction in print density and bronzing, preferably 0.1 to 40 g / m ^2, more preferably 0.5 to 30 g / m ² 1 to 20 g / m ² is particularly preferable.
Printing amount of the pigment to the recording medium, from the viewpoint of print density is preferably 0.01-5 g / m ^2, more preferably 0.05 to 2 g / m ^2, more preferably 0.1 to 1 g / m ² .
Printing of silica particles to the recording medium, from the viewpoint of reducing the bronze phenomenon, it is 0.005 g / m ² or more, 0.01 g / m ² or more preferably, 0.02 g / m ² or more is more preferable. In terms of wrinkle of the recording medium, printing the amount of the pigment to the recording medium is preferably from 5 g / m ² or less, more preferably 2 g / m ² or less, 1 g / m ² or less is more preferable. From the point of view, the amount of printing is preferably 0.005~5g / m ^2, more preferably 0.01 to 2 g / m ^2, more preferably 0.02 to 1 g / m ^2.

From the viewpoint of reducing the bronze phenomenon, the printing amount ratio between the silica particles and the pigment at the printing site (silica particles / pigment) is preferably 1/99 to 5/1, more preferably 1/99. 50 to 3/1, more preferably 1/20 to 2/1, still more preferably 1/10 to 1/1.
In the present invention, the use ratio of the water-based ink (A) and the water-based ink (B) is not particularly limited as long as the effects of the present invention can be achieved. Is preferably used in such a ratio that the value falls within the above range.

In the following production examples, examples and comparative examples, “parts” and “%” are indicated by “parts by weight” and “% by weight”, respectively, unless otherwise specified.
Production Example 1 Production of water-insoluble polymer 46 parts of benzyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd., reagent), 14 parts of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent), styrene macromer (manufactured by Toagosei Co., Ltd., product) Name: AS-6S, number average molecular weight: 6000, 50% by weight (solid content), 40 parts of polymerizable functional group: methacryloyloxy group, and polypropylene glycol monomethacrylate (addition moles of propylene oxide = average 9 moles, terminal) 100 parts of a monomer comprising 20 parts of a hydroxyl group, 20 parts of an organic solvent (methyl ethyl ketone), 1 part of a polymerization chain transfer agent (2-mercaptoethanol, manufactured by Wako Pure Chemical Industries, Ltd., reagent), a polymerization initiator (2, 2 ′ -10% of the total amount of azobis (2,4-dimethylvaleronitrile), 1 part by Wako Pure Chemical Industries, Ltd., V-65) Were mixed and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
On the other hand, the remaining 90% was used in the dropping funnel, and polymerization was carried out while dropping at 75 ° C. with stirring. After about 2 hours at 75 ° C. from the end of dropping, the mixture was aged at 80 ° C. for 1 hour to obtain a water-insoluble polymer (weight average molecular weight 18,000).

Production Example 2 Production of water-based ink (A) 50 parts of the polymer solution obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 70 parts of methyl ethyl ketone, and then 30% silica sol (average particle size 12 nm; Nissan Chemical Co., Ltd.) 167 parts of Kogyo Co., Ltd .; trade name MEK-ST) is mixed with 8.2 parts of neutralizing agent (5N aqueous sodium hydroxide) (degree of neutralization 75%) and 230 parts of ion-exchanged water. The salt-forming group was neutralized and subjected to a dispersion treatment for 2 hours at a peripheral speed of 15 m / s with Asako Tekko Picomill. The obtained mixture was subjected to 10-pass dispersion treatment at a pressure of 200 MPa with a microfluidizer (trade name, manufactured by Microfluidics).
After adding 250 parts of ion-exchanged water to the obtained dispersion and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) and filtered with a 25 mL needleless syringe (Terumo Co., Ltd.), and by removing coarse particles, silica-containing polymer particles having a solid content concentration of 20% An aqueous dispersion was obtained. The average particle diameter of the silica-containing polymer particles was 75 nm.

  Next, 20 parts of an aqueous dispersion of silica-containing polymer particles, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether, 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), Proxel XL2 (manufactured by Avicia Co., Ltd.) ) 0.3 parts and 61.7 parts of ion-exchanged water were mixed, and a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) was attached to the resulting mixture. The aqueous ink (A) having a silica concentration of 2% was obtained by filtering with a syringe without needle of 25 mL capacity to remove coarse particles.

Production Example 3 Production of water-based ink (B) 25 parts of a polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 70 parts of methyl ethyl ketone, and a neutralizer (5N aqueous sodium hydroxide solution) was dissolved therein. 4.1 parts (neutralization degree 75%) and 230 parts of ion-exchanged water were added to neutralize the salt-forming groups, and 75 parts of copper phthalocyanine pigment (CI Pigment Blue 15: 3, average primary particle size 70 nm) were further added. In addition, after pre-dispersing with a disper, 2 hours at a peripheral speed of 15 m / s at the tip of the stirring blade with Picomill (Zirconia beads (particle size: 50 μm) filling rate 80%, temperature 10 ° C.) Dispersion treatment was performed. The obtained mixture was subjected to 10-pass dispersion treatment at a pressure of 200 MPa with a microfluidizer (trade name, manufactured by Microfluidics).

After adding 250 parts of ion-exchanged water to the obtained pigment dispersion and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was removed, and a 5 μm filter (acetylcellulose membrane, outer diameter). : Pigment-containing polymer particles having a solid content concentration of 20% by filtering with a 25 mL needleless syringe (made by Terumo Co., Ltd.) attached with 2.5 cm, manufactured by Fuji Photo Film Co., Ltd., and removing coarse particles. An aqueous dispersion was obtained. The average particle diameter of the pigment-containing polymer particles was 80 nm.
Aqueous dispersion of 26.7 parts by weight of this pigment-containing polymer particle, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether, 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), Proxel XL2 (Avicia Co., Ltd.) 0.3 parts) and 55 parts of ion-exchanged water were mixed, and the obtained liquid mixture was attached with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) By filtering with a 25 mL needleless syringe to remove coarse particles, an aqueous ink (B) having a pigment concentration of 4% was obtained.

Comparative Production Example 1 Production of Comparative Ink in the production of the water-based ink (A) in Production Example 2, ion exchange was performed using 4 parts of ion-exchanged water and 16 parts of glycerin instead of 20 parts of an aqueous dispersion of silica-containing polymer particles. A comparative ink was produced in the same manner as the water-based ink (A) except that 65.7 parts of water and 26 parts of glycerin were used.

Examples 1-4
Ink (A) and ink (B) obtained in Production Examples 2 and 3, respectively, are filled into a commercially available inkjet printer (manufactured by Epson Corporation, model number: PX-V630), respectively, in the cartridge slot of the printer. Installed. Of the four cartridge slots, water cyan ink (B) was installed in the cyan slot, ink (A) was installed in the magenta slot, and empty cartridges were installed in the yellow and black slots.
Using the printer, as a recording paper, a commercially available special paper [photographic paper <gloss>, manufactured by Epson Corporation]] [printing condition = paper type: EPSON photographic paper, print quality: photo, color setting: color correction The recording pattern was fixed to a discharge amount of 4 g / m ² of ink (B) in an area of 50 mm × 50 mm, and the ink (A) was set to the discharge amount shown in Table 1 and printed. . The discharge amount was confirmed by the reduced weight of the cartridge after printing a certain amount.
In this ink jet printer, first, the ink (A) is always overprinted on the print site after the cyan ink (B) is printed.

Comparative Examples 1-4
Ink cartridges of the comparative ink obtained in Comparative Production Example 1 and the cyan ink (B) obtained in Production Example 3 were respectively applied to the same ink jet printer as in Example 1 (manufactured by Epson Corporation, model number: PX-V630). And loaded into the cartridge slot of the printer. Of the four cartridge slots, water-based cyan ink (B) is installed in the cyan slot, comparative ink is installed in the magenta slot, and empty cartridges are installed in the yellow and black slots. The discharge amount of (B) was fixed at 4 g / m ² , and the comparative ink was set to the discharge amount shown in Table 1 for printing.
In this ink jet printer, first, the comparative ink is always overprinted on the print site after the cyan ink (B) is printed.

Using each of the ink sets obtained in Examples 1 to 4 and Comparative Examples 1 to 4, a bronze test was performed as shown below. The results are shown in Table 1.
Bronze test Using a commercially available inkjet printer (manufactured by Epson Corporation, model number: PX-V630), solid printing was performed on commercially available special paper [photo paper <gloss>, manufactured by Epson Corporation]] [printing condition = paper Type: EPSON photographic paper, print quality: photo, color setting: no color correction], and left for 24 hours at 25 ° C., the bronze of the obtained solid print was measured by the following method.
The printed matter prepared by the above method was mounted on a sample stage of a variable angle spectroscope Gonio-Spectrometer (manufactured by Murakami Color Material Research Laboratory, GSP-2), and a reflection spectrum at a wavelength of 390 nm to 720 nm was measured. The measurement conditions were as follows.
Incident angle 45 ° Receiving angle 45 ° Viewing angle 2 ° tilt angle 0 °
Light source: Halogen lamp C light

From the spectrum thus obtained, the intensity at a wavelength of 550 nm and the intensity at 630 nm were examined, and the reflection spectrum intensity ratio (intensity at 630 nm / intensity at 550 nm) was calculated for the value, and evaluated as follows.
(Evaluation)
Reflection intensity spectral ratio exceeds 4: Fluorescent lamps and sunlight reflected on the printed surface appear reddish.
The reflection intensity spectrum ratio is more than 3 and 4 or less: Redness is not easily recognized even when a photograph is printed.
Reflection intensity spectrum ratio of 3 or less: Red is hardly recognized even in solid printing, which is most preferable.

In addition, the measuring method of the average particle diameter of each water-insoluble polymer particle and silica particle is as follows.
Method for Measuring Average Particle Size of Pigment-Containing Polymer Particles, Silica Particle-Containing Polymer Particles, and Silica Particles The average particle size was measured with a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5 × 10 ⁻³ wt%.
The average particle diameter of the silica particles and the primary particle diameter of the pigment are 100 using a scanning electron microscope manufactured by JEOL Ltd., and the number average particle diameter calculated from image analysis is used. In addition, when there exists a long diameter and a short diameter, it calculates using a long diameter.

  The ink sets of Examples 1 to 4 were excellent in reducing the bronze phenomenon as compared with those of Comparative Examples 1 to 4.

Claims (8)

A method of using an ink set for ink-jet recording comprising a water-based ink (A) containing water-insoluble polymer particles (a) containing silica particles and a water-based ink (B) containing a pigment excluding silica particles. An ink jet recording method in which a water-based ink (B) is printed on a medium, and the water-based ink (A) is printed on the print site. The inkjet recording method according to claim 1, wherein at least part of the surface of the silica particles is hydrophobized . The inkjet recording method according to claim 1 or 2, wherein the water-insoluble polymer particles (a) containing silica particles have an average particle size of 10 to 200 nm . The inkjet recording method according to any one of claims 1 to 3, wherein a pigment excluding silica particles is contained in the water-insoluble polymer particles (b) . The water-insoluble polymer (a ′) constituting the water-insoluble polymer particles (a) is copolymerized with a monomer mixture containing (a) a salt-forming group-containing monomer, (b) a hydrophobic monomer and / or (c) a macromer. The inkjet recording method according to claim 1, which is a water-insoluble polymer . The inkjet recording method according to claim 1, wherein the pigment excluding the silica particles is a cyan pigment . The printing amount ratio (silica particles / pigments excluding silica particles) of the silica particles and the pigments excluding the silica particles at the printing site after printing the water-based ink (A) is 1/99 to 5/1 by weight ratio. The ink jet recording method according to claim 1. The inkjet according to any one of claims 1 to 7, wherein the water-based ink (A) containing water-insoluble polymer particles (a) containing silica particles is obtained by a production method having the following step 1 and step 2. Recording method.
Step 1: Step of dispersing a mixture of silica particles, water-insoluble polymer (I ′), organic solvent and water Step 2: Step of removing the organic solvent from the dispersion obtained in Step 1