JP2003192950A - Ink set for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set for multicolor inkjet recording, which is excellent in color reproducibility due to the colored fine particles contained and which scarcely loses a color balance due to fading. <P>SOLUTION: This ink set for multicolor inkjet recording is characterized in that it is made by using inks of two or more colors, at least two color inks contain colored fine particles consisting of a coloring material and a resin, and the coloring material comprises an oil-soluble dye selected from C. I. Solvent Yellow 1, 4, 29, 56, 82, 83, 88 or 162, a methine or azomethine oil-soluble magenta dye having a pyrazolotriazole structure, an oil-soluble cyan dye having a copper phthalocyanine structure, and C. I. Solvent Black 3, 21, 22 or 43. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet ink set used for ink jet recording, and particularly to 2
The present invention relates to a multicolor inkjet ink set using inks of multiple colors or more.

[0002]

2. Description of the Related Art Ink-jet recording inks can be classified into dye-based inks and pigment-based inks from the viewpoint of coloring materials. In general, dye-based inks have excellent color reproducibility However, the ink using the pigment has excellent light fastness, but tends to have poor color reproducibility. Further, in the ink in which the pigment is dispersed, it is difficult to make the dispersed particle size sufficiently small, which causes problems such as clogging of the nozzles of the printer head and poor storage stability.

Therefore, it is desired to develop an ink jet ink which improves the water resistance and light resistance of a water-based ink using a water-soluble dye and utilizes the goodness of the dye excellent in color reproducibility.

Proposals for coloring a water-dispersible resin with an oil-soluble dye or a hydrophobic dye have already been made as an ink for ink jet recording. For example, JP-A-55-1394
71, JP-A-58-45272, JP-A-3-250.
069, JP-A-8-253720, JP-A-8-92.
513, JP-A-8-183920, and JP-A-2001-
No. 11347 and the like propose an ink using emulsion-polymerized particles dyed with an oil-soluble dye or dispersed polymerized particles. Further, not only the water-dispersible resin is colored with an oil-soluble dye or a hydrophobic dye, but also coloring fine particles composed of a coloring material and a resin coating the coloring material, or coloring material particles composed of a coloring material and a resin are further formed into a film. Attempts have also been made to use colored fine particles coated with a resin.

Certainly, the colored fine particles are expected to improve the storage stability as compared with the dye alone due to the interaction between the dye and the polymer, but the color reproducibility is deteriorated due to the broadening of the absorption spectrum due to the interaction with the polymer. There was a new problem that it was easy to do.

[0006]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a multicolor ink jet ink set which is excellent in color reproducibility with colored fine particles and is less likely to lose color balance due to fading change.

[0007]

As a result of intensive studies on the above problems, the present inventors have found that a dye having a specific structure, hydrophobicity, and compatibility among a large number of dye species coexists with a polymer. It was found that the deterioration of the absorption spectrum is unlikely to occur. By adjusting the amount of impregnation of these dye structures and combining them, an ink set having excellent color reproducibility, less likely to undergo photobleaching over time, and having little color change was obtained. In particular, as a result of the molecular dispersibility in the core structure with polyvinyl butyral and the coatability in the shell structure using a styrene-acrylic copolymer, the color reproducibility and light resistance can be improved, and the present invention has been accomplished. .

That is, the above object of the present invention has been achieved by the following means. 1) In a multicolor ink jet ink set using two or more colors of ink, at least two colors of ink contain coloring fine particles composed of a coloring material and a resin, and the coloring material is C.I. I.
Solvent Yellow 1, 4, 29, 56,
82, 83, 88, 162, methine or azomethine oil-soluble magenta dye having a pyrazolotriazole structure, oil-soluble cyan dye having a copper phthalocyanine structure, C.I. I. So
An inkjet ink set that is an oil-soluble dye selected from Lvent Black 3, 21, 22, and 43.

2) In a multicolor ink jet ink set containing at least yellow, magenta and cyan inks containing colored fine particles, yellow is C.I. as a dye used as a coloring material for the colored fine particles. I. Solvent
Yellow 1,4,29,56,82,83,8
8, 162, magenta is a methine or azomethine oil-soluble magenta dye having a pyrazolotriazole structure, and cyan is C.I. I. An inkjet ink set that is an oil-soluble dye selected from Solvent Blue 70.

3) The ink set for ink jet according to 1) or 2), wherein the black ink is carbon black.

4) The use ratio of each dye is Y / M in terms of mass ratio.
= 0.8 to 1.2 and M / C = 0.5 to 1.0, the ink set for inkjet according to 1), 2) or 3).

5) The ink jet ink set according to any one of 1) to 4), wherein the colored fine particles have a core-shell structure.

6) The ink jet ink set according to any one of 1) to 5), wherein at least a part of the resin used for the core of the colored fine particles is polyvinyl butyral.

7) The ink jet ink set according to any one of 1) to 6), wherein at least a part of the resin used for the shell of the colored fine particles is a styrene-acrylic polymer.

8) The ink-jet ink set according to any one of 1) to 7), wherein the colored fine particles have an average particle diameter of 100 nm or less.

9) An image forming method characterized in that the ink according to any one of 1) to 8) is ejected as droplets from an ink jet head based on a digital signal, and the ink is adhered to an ink receiving medium.

The present invention will be described in more detail below. The colored fine particles having a core / shell structure in the present invention include
A method of first providing a polymer core containing a coloring material and then providing a polymer shell, and a method of simultaneously providing a core and a shell are considered.

(When providing shell after preparation of fine particle core <coloring material particle>) When a dye is used as a coloring material, the dye-containing polymer serving as the core can be prepared by various methods. For example, a method of dissolving an oil-soluble dye in a monomer, emulsifying in water, and then encapsulating the dye in the polymer by polymerization,
There are a method of dissolving a polymer and a dye in an organic solvent, emulsification in water and then removing the organic solvent, a method of adding porous polymer fine particles to a dye solution, and adsorbing and impregnating the dye with the fine particles. As a method of providing a polymer shell to it, a method of adding a water-soluble polymer dispersant to an aqueous suspension of a polymer to be a core and adsorbing it, a method of gradually dropping a monomer and depositing it on a core surface at the same time as polymerization, or an organic method There is a method in which a polymer dissolved in a solvent is gradually dropped and adsorbed on the core surface simultaneously with precipitation. For example, in the present invention, it is a method in which hydroxyethyl methacrylate and a polymerizable monomer having an unsaturated double bond are gradually dropped into an aqueous suspension of a polymer serving as a core, polymerized, and deposited on the surface of the core.

In the present invention, a method in which a monomer is gradually added dropwise to an aqueous suspension of a polymer serving as a core and deposited on the surface of the core simultaneously with polymerization is particularly preferable.

(Method of simultaneously providing core and shell at the time of forming fine particles) A method of dissolving or dispersing a core polymer and a dye in a monomer serving as a shell after polymerization, suspending in water and then polymerizing, or a solution thereof is an active agent. There is also a method in which emulsion polymerization is performed while gradually dropping into water containing micelles. The monomer may be the core and the polymer may be the shell. Alternatively, there is also a method in which a dye or a pigment is dissolved or dispersed in a mixed liquid of a monomer that can be a core and a monomer that can be a shell after polymerization, and suspension polymerization or emulsion polymerization is performed.

(Evaluation of core shell formation) It is important to evaluate whether the core shell is actually formed. In the present invention, the analysis method is limited from the viewpoint of resolution because the individual particle size is very small, 100 nm or less. TEM and TOF are used as analysis methods that meet such purposes.
-SIMS etc. can be applied. When observing the core-shelled fine particles by TEM, the dispersion can be applied and dried on the carbon support film and observed. In the TEM observation image, the contrast difference may be small only with the type of polymer that is an organic substance. Therefore, in order to evaluate whether or not it is core-shelled, the fine particles were osmium tetraoxide, ruthenium tetraoxide, chlorosulfonic acid / It is preferable to dye with uranyl acetate, silver sulfide or the like. Fine particles of only the core are dyed and observed by TEM, and compared with those having a shell. Furthermore, after mixing the fine particles provided with the shell and the fine particles not provided with the shell, they are dyed, and it is confirmed whether or not the proportion of the fine particles having different degrees of dyeing matches the presence or absence of the shell.

In a mass spectrometer such as TOF-SIMS, it is confirmed that the amount of coloring material in the vicinity of the surface is reduced by providing a shell on the particle surface as compared with the case where only the core is used. When the coloring material has an element that is not contained in the polymer of the core shell, it is possible to confirm whether or not a shell having a small coloring material content is provided by using the element as a probe.

Further, the core-shell formation can be observed more clearly by embedding the core-shell particles in an epoxy resin, preparing an ultrathin section with a microtome, and staining it. As described above, when the polymer or the coloring material has an element that can serve as a probe, the composition of the core-shell and the distribution amount of the coloring material to the core and the shell can be estimated by TOF-SIMS or TEM.

In order to obtain the required particle size, it is important to optimize the formulation and select an appropriate emulsification method. The formulation depends on the coloring material and polymer used, but since it is a suspension in water, it is generally necessary that the polymer forming the shell has a higher hydrophilicity than the polymer forming the core. Further, the colorant contained in the polymer constituting the shell is preferably less than that in the polymer constituting the core as described above, and the colorant is also required to have a lower hydrophilicity than the polymer constituting the shell. . Hydrophilic and hydrophobic
For example, the solubility parameter (SP) can be used for the estimation. Regarding the solubility parameter, its value, measurement, and calculation method are POLYMER HANDBOOK 4th edition (JOH
N WILEY & SONS, INC. ) The description from page 675 is helpful.

The polymer used in the core has a number average molecular weight of 500 to 100,000, particularly 1,000.
It is preferably ˜30,000 from the viewpoints of film-forming property after printing, its durability, and suspension formability.

The Tg (glass transition temperature) of the polymer is
Although various kinds of polymers can be used, it is preferable to use at least one kind of polymer having a Tg of 10 ° C. or higher among the polymers used.

In the present invention, all commonly known polymers can be used, but at least a part of the core resin is polyvinyl butyral and at least a part of the shell resin is a styrene-acrylic polymer. Is a feature. As the above-mentioned polymer, a commercially available product can be used, but it can also be synthesized by a conventional method. or,
These copolymers can also be obtained by, for example, introducing an epoxy group into one polymer molecule and then polycondensing it with another polymer, or performing graft polymerization using light or radiation.

In the colored fine particle dispersion preferred in the present invention, the polymer core mainly contains the coloring material and contributes to maintain its fastness and color tone, while the polymer shell contains fine particles containing the coloring material. It contributes to increase the stability of the ink suspension, promotes fixing of the coloring material on the medium, prevents aggregation, and contributes to improvement of image quality. It also contributes to the robustness of color materials and the retention of color tone.

In the present invention, the coloring material-containing core / shell colored fine particles used in the polymer emulsion type water-based ink have a very large surface area per unit volume when the volume average particle diameter is 5 nm or less. The effect of encapsulation in the polymer is reduced. On the other hand, 10
If the particles are larger than 0 nm, the head is likely to be clogged, sedimentation in the ink is likely to occur, and the stagnation stability is deteriorated. Therefore, the average particle diameter of the colored fine particles is 5 to 100 n.
It is preferably m, and more preferably 30 to 80 nm. When the average particle diameter exceeds 100 nm, when the aqueous ink is used, the glossiness of an image recorded on a glossy medium deteriorates, and the transparency of an image recorded on a transparent medium deteriorates significantly.

The volume average particle diameter is measured by a transmission electron microscope (T
EM) The circle-converted average particle diameter obtained from the average value of the projected area of the photograph (obtained for at least 100 particles or more)
Calculated as spherical equivalent. The coefficient of variation can be obtained by obtaining the volume average particle diameter and its standard deviation and dividing the standard deviation by the volume average particle diameter. Alternatively, the coefficient of variation can be obtained using the dynamic light scattering method. For example, it can be determined by using a laser particle size analysis system manufactured by Otsuka Electronics Co., Ltd. or a Zetasizer manufactured by Malvern Electronics Co., Ltd.

The coefficient of variation of the particle size is a value obtained by dividing the standard deviation of the particle size by the particle size. The larger this value is, the wider the distribution of the particle size is. When the variation coefficient of the volume average particle diameter is 80% or more, the particle diameter distribution becomes very wide,
The thickness of the core / shell is likely to be non-uniform, and the surface properties among the particles are likely to vary. Variations in surface properties tend to cause particle agglomeration, which tends to cause clogging of the inkjet head. In addition, the aggregation of particles easily causes light scattering of the coloring material on the medium, and thus easily deteriorates the image quality. The coefficient of variation of particle size is preferably 50% or less, more preferably 30% or less.

In the present invention, the amount of polymer used in the shell is preferably 5 to 95% by mass of the total amount of polymer. When the amount is less than 5% by mass, the thickness of the shell is insufficient and a part of the core containing a large amount of coloring material is likely to appear on the particle surface. On the other hand, if the shell polymer is too much, the ability of the core to protect the coloring material is likely to deteriorate. More preferably 10 to 90
It is% by mass.

The total amount of colorant is 20 with respect to the total amount of polymer.
It is preferably from about 1,000% by mass. If the amount of the color material is too small compared to the polymer, the image density after ejection does not increase, and if the amount of the color material is too large, the polymer protecting ability cannot be sufficiently obtained.

Next, the color material encapsulated by the polymer will be described. As the hue of the coloring material used in the present invention, yellow, magenta, cyan, black, blue, green and red are preferably used, and yellow, magenta, cyan and black dyes are particularly preferable. Oil-soluble dyes are usually water-insoluble dyes that are soluble in organic solvents that do not have water-soluble groups such as carboxylic acids and sulfonic acids, but are soluble in oil by forming a salt with a long-chain base. A dye showing is also included. For example, acid dyes, direct dyes, and salt forming dyes of reactive dyes and long-chain amines are known.

As the oil-soluble dye preferably used in the ink set of the present invention, yellow (Y) includes C.I. I. So
lvent Yellow 1,4,29,56,8
2, 83, 88, 162, etc., magenta (M) is a methine or azomethine oil-soluble magenta dye having a pyrazolotriazole structure, cyan (C) is an oil-soluble cyan dye having a copper phthalocyanine structure, C.I. I. Solvent B
lue 70 etc., C.I. I. Solv
Examples include ent Black 3, 21, 22, 43, carbon black, and the like, but the following dyes can be used in combination as long as the effects of the present invention are not impaired.

For example, Vali manufactured by Orient Chemical Industry Co., Ltd.
fast Yellow 4120, 3150, 310
8, 2310N, 1101, Valifast Red
3320, 3304, 1306, Valifast
Blue 2610, 2606, 1603, Oil Y
ellow GG-S, 3G, 129, 107, 10
5, Oil Scarlet 308, Oil Red
RR, OG, 5B, Oil Pink 312, Oi
l Blue BOS, 613, 2N, OilBlac
k BY, BS, 860, 5970, 5906, 590
5; manufactured by Nippon Kayaku Co., Ltd .: Kayaset Yellow S
FG, K-CL, GN, AG, 2G, Kayase
t Red SF-4G, K-BL, A-BR, Kay
AsetMagenta 312, Kayaset Bl
ue K-FL; Arimoto Chemical Industry Co., Ltd .: FS Yellow
w 1015, FS Magenta 1404, FS
Cyan 1522, FS Blue 1504,
C. I. Solvent Yellow 88,83,8
2,79,56,29,19,16,14,04,0
3,02,01, C.I. I. Solvent Red 8
4: 1, C.I. I. Solvent Red 84,21
8, 132, 73, 72, 51, 43, 27, 24, 1
8,01, C.I. I. Solvent Blue 70,
67, 44, 40, 35, 11, 02, 01, C.I. I.
Solvent Black 43, 70, 34, 2
9, 27, 22, 7, 3, C.I. I. Solvent V
iolet 3, C.I. I. Solvent Green
3, 7 etc. Further, JP-A-9-277693 and 10-
Metal complex dyes such as those shown in Nos. 20559 and 10-30061 are also preferably used.

Disperse dyes can be used as the oil-soluble dyes, and particularly preferred specific examples include C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82,
83, 93, 99, 100, 119, 122, 124,
126, 160, 184: 1, 186, 198, 19
9, 204, 224, 237; C.I. I. Disperse Orange 13,29,31: 1,33,49,54,5
5, 66, 73, 118, 119, 163; C.I. I. Disperse Red 54, 60, 72, 73, 86, 8
8, 91, 92, 93, 111, 126, 127, 13
4,135,143,145,152,153,15
4,159,164,167: 1,177,181,2
04,206,207,221,239,240,25
8,277,278,283,311,323,34
3,348,356,362; C.I. I. Disperse Violet 33; C.I. I. Disperse Blue 56,6
0,73,87,113,128,143,148,1
54,158,165,165: 1,165: 2,17
6,183,185,197,198,201,21
4,224,225,257,266,267,28
7,354,358,365,368 and C.I. I. Examples include Disperse Green 6: 1, 9 and the like.

The colored fine particles having the core / shell morphology of the present invention are preferably incorporated in the water-based ink of the present invention in an amount of 0.5 to 50% by mass as a polymer amount.
It is more preferable that the content is ˜30% by mass. If the blending amount of the above polymer is less than 0.5% by mass, the ability to protect the coloring material is insufficient, and if it exceeds 50% by mass, the storage stability of the suspension as an ink is lowered, or the nozzle tip portion is deteriorated. Since there is a case where clogging of the printer head may occur due to thickening of the ink and aggregation of the suspension due to the evaporation of the ink, it is preferably within the above range.

On the other hand, the colorant of the above dye is preferably blended in the ink in an amount of 1 to 30% by mass,
It is more preferable that the content is ˜25% by mass. If the blending amount of the coloring material is less than 1% by mass, the printing density is insufficient, and if it exceeds 30% by mass, the stability of the suspension with time is deteriorated and the particle size tends to increase due to aggregation or the like. It is preferably within the range.

The ink of the present invention comprises a suspension of a polymer in which water is used as a medium and in which the above-mentioned coloring material is encapsulated. For the suspension, various conventionally known additives such as inorganic salts, surfactants, preservatives and antifungal agents are added. Agents, pH adjusters, viscosity adjusters, hydrotropes, wetting agents, dispersants, defoamers and the like can be added as necessary.

An inorganic salt may be added to the ink in order to keep the viscosity of the ink stable and to improve the color development. Examples of the inorganic salt include sodium chloride, sodium sulfate, magnesium chloride, magnesium sulfide and the like.

As the surfactant, any of cationic, anionic, amphoteric and nonionic surfactants can be used, but nonionic surfactants are preferred.

Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts and imidazolinium salts.

As the anionic surfactant, fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-
N-methyl-β-alanine salt, N-acylglutamate, alkyl ether carboxylate, acylated peptide, alkylsulfonate, alkylbenzenesulfonate, alkylnaphthalenesulfonate, dialkylsulfosuccinate ester salt, alkylsulfo Acetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate ester salt, secondary higher alcohol sulfate ester salt, alkyl ether sulfate salt, secondary higher alcohol ethoxy sulfate, polyoxy Examples thereof include ethylene alkyl phenyl ether sulfate, monoglycol sulfate, fatty acid alkylolamide sulfate ester salt, alkyl ether phosphate ester salt, and alkyl phosphate ester salt.

Examples of the amphoteric surfactant include carboxybetaine type, sulfobetaine type, aminocarboxylic acid salts, imidazolinium betaine and the like.

As the nonionic surfactant, polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether (Emulgen 911 etc.), polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, polyoxyethylene lanolin derivative Oxyethylene polyoxypropylene alkyl ether (Newpol PE-62 etc.), polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid Ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester , Sucrose fatty acid esters, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, alkyl amine oxides, acetylene glycol, acetylene alcohol, and the like.

When these surfactants are used, they can be used alone or as a mixture of two or more kinds. By adding them in the range of 0.001 to 1.0% by mass with respect to the total amount of the ink, The surface tension of the ink can be adjusted arbitrarily.

In order to maintain the long-term storage stability of the ink, an antiseptic agent and an antifungal agent may be added to the ink. As an antiseptic agent and an antifungal agent, aromatic halogen compounds (Prevento
1CMK), methylene dithiocyanate, halogen-containing nitrogen-sulfur compound, 1,2-benzisothiazolin-3-one (PROXEL GXL, etc.) and the like.

A pH adjusting agent may be added in order to keep the inside of the ink stable. As the pH adjuster, hydrochloric acid, acetic acid, oxalic acid, sodium hydroxide, potassium hydroxide or the like can be diluted with water or used as it is.

Examples of the wetting agent include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, etc. Polyhydric alcohols and their ethers, acetates, nitrogen-containing compounds such as N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, formamide and dimethylformamide, and dimethyl sulfoxide 1 One kind or two or more kinds can be used. The amount of these wetting agents added is not particularly limited, but is preferably 0.1 to 50% by mass in the aqueous ink.
It can be blended, and more preferably 0.1 to 30% by mass.

The dispersant is not particularly limited,
It is preferable that the HLB value (hydrophilic / lipophilic balance) is 8 to 18 from the viewpoint that the effect as a dispersant is exhibited and the increase in the particle diameter of the suspension is suppressed. Polymer dispersants for pigments (Johncryl, etc.) and alkylnaphthalene sulfonates for disperse dyes can be mentioned, but low molecular weight sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, etc. Anionic surfactants are preferred.

Commercially available products can also be used as the dispersant. Examples of such commercially available products include dispersants DEMOL SNB, MS, N, SSL, ST, P (trade name) manufactured by Kao Corporation.

The amount of the dispersant blended is not particularly limited, but it is preferably 0.01 to 10% by mass in the aqueous ink of the present invention. If the compounding amount of the compound is less than 0.01% by mass, it is difficult to reduce the particle size of the suspension.
If it exceeds 0% by mass, the particle diameter of the suspension increases, the suspension stability decreases, and gelation may occur, so the content is preferably within the above range.

As the defoaming agent, commercially available products can be used without particular limitation. Such commercial products include:
For example, KF96, 66, 69, K manufactured by Shin-Etsu Silicone Co., Ltd.
S68, 604, 607A, 602, 603, KM7
3, 73A, 73E, 72, 72A, 72C, 72F,
82F, 70, 71, 75, 80, 83A, 85, 8
9, 90, 68-1F, 68-2F (trade name) and the like. The compounding amount of these compounds is not particularly limited, but 0.001 to 2 mass% is preferably compounded in the aqueous ink of the present invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are likely to be generated during ink preparation, and it is difficult to remove small bubbles in the ink, and if it exceeds 2% by mass, the generation of bubbles is suppressed. At the time of printing, repellency may occur in the ink and the print quality may be deteriorated. Therefore, the amount is preferably within the above range.

Next, the emulsification method used in the production of the ink of the present invention will be described. The ink of the present invention is
For example, various emulsification methods can be used in the production of the coloring material particles to be the core. Various methods can be used as the emulsification method. Examples thereof are summarized in the description on page 86 of "Progress of Functional Emulsifier / Emulsification Technology and Application and Development (CMC)". In the present invention, it is particularly preferable to use an emulsifying / dispersing device using ultrasonic waves, high-speed rotary shearing, and high pressure.

Two types of so-called batch type and continuous type can be used for ultrasonic dispersion. The batch method is suitable for preparing a relatively small amount of sample, and the continuous method is suitable for preparing a large amount of sample. In the continuous type, for example, UH-600S
A device such as R (manufactured by SMT) can be used. In the case of such a continuous system, the irradiation time of ultrasonic waves can be obtained by the formula: volume of dispersion chamber / flow velocity × number of circulations. When there are a plurality of ultrasonic irradiation devices, the total irradiation time can be calculated. The ultrasonic wave irradiation time is actually 10,000 seconds or less. If 10,000 seconds or more is required, the load on the process is heavy, and it is necessary to shorten the emulsification / dispersion time by reselecting the emulsifier in practice. Therefore, 10,000 seconds or more is not necessary. More preferably, it is in the range of 10 to 2000 seconds.

Examples of the emulsification / dispersion apparatus using high-speed rotary shearing include a disper mixer and 251 as described on pages 255-256 of "Progress of functional emulsifier / emulsification technology and its application and development (CMC)". The homomixer described on page 256 and the ultramixer described on page 256 can be used. These types can be used properly depending on the liquid viscosity at the time of emulsion dispersion.

In these emulsifying and dispersing machines using high-speed rotary shearing, the rotation speed of the stirring blade is important. In the case of a device having a stator, the clearance between the stirring blade and the stator is usually about 0.5 mm and cannot be extremely narrowed, so the shearing force mainly depends on the peripheral speed of the stirring blade. Peripheral speed is 5-15
Within 0 m / sec, it can be used for emulsification / dispersion of the present invention. This is because when the peripheral speed is slow, it is often impossible to reduce the particle size even if the emulsification time is extended, and it is necessary to extremely improve the performance of the motor in order to achieve 150 m / sec. More preferably, it is 20 to 100 m / sec.

For emulsification and dispersion by high pressure, LAB2000
(Manufactured by SMT) or the like can be used, but the emulsification / dispersion ability thereof depends on the pressure applied to the sample. Pressure is 1
The range of 0 ⁴ kPa to ⁵ × 10 ⁵ kPa is preferable. If desired, the emulsion can be emulsified and dispersed several times to obtain a desired particle size. If the pressure is too low, the target particle size may not be achieved in many cases, no matter how many times emulsification and dispersion are performed. Also, in order to set the pressure to 5 × 10 ⁵ kPa, a large load is applied to the device, which is not practical. . More preferably 5 × 10 ⁴ kP
It is in the range of a to 2 × 10 ⁵ kPa.

These emulsifying / dispersing devices may be used alone, or may be used in combination as required. A colloid mill, a flow jet mixer, etc., alone cannot achieve the object of the present invention, but the combination with the device of the present invention can enhance the effects of the present invention such as enabling emulsification / dispersion in a short time. is there.

When an image is formed by ejecting the water-based ink of the present invention by the ink jet system, the ink jet head used may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (single cavity type, double cavity type,
Any ejection method such as a bender type, a piston type, a shear mode type, a shared wall type, etc., an electric-heat conversion method (a thermal ink jet type, a bubble jet (R) type, etc.) may be used.

In the image forming method using the water-based ink of the present invention, the ink is ejected as droplets from the ink jet head based on a digital signal by a printer or the like loaded with the water-based ink, and the ink is attached to the ink receptor. For example, an inkjet print having an image formed on the inkjet image recording medium can be obtained.

As the ink jet image recording medium, for example, any of plain paper, coated paper, cast coated paper, glossy paper, glossy film and OHP film can be used. Among them, for example, a so-called porous layer is formed. A recording medium having a void layer is preferable. The material or shape of the above-mentioned support is not particularly limited, and may have, for example, a three-dimensional structure other than a sheet-shaped support.

[0064]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

As described below, core-shell type dye-colored fine particles of each color were prepared. Production Example 1 50 g of polyvinyl butyral (manufactured by Denki Kagaku Co .: 300
0K, average degree of polymerization 800), 40 g of C.I. I. Solv
ent Yellow 162 and 10 g of C.I. I. S
olvent Yellow 29 and 400 g of ethyl acetate were put into a separable flask and stirred to completely dissolve the above polymer and dye. After 1000 g of an aqueous solution containing 5 g of sodium lauryl sulfate was dropped, the mixture was emulsified for 10 minutes using an ultrasonic disperser (manufactured by SMT: UH-150 type). Then, ethyl acetate was removed under reduced pressure to obtain dye-impregnated colored fine particles. After substituting the inside of the flask with nitrogen, 1.5 g of potassium persulfate was added to and dissolved in this dispersion, and after heating with a heater to 70 ° C., 20 more
A reaction mixture was allowed to react for 8 hours while dropping a mixed liquid of g of styrene and 10 g of 2-hydroxyethyl methacrylate to obtain core-shell type yellow colored fine particles. The average particle size of the fine particles was 78 nm (volume average particle size measured using a laser particle size analysis system manufactured by Otsuka Electronics Co., Ltd.).

Production Example 2 50 g of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd .: BL-
S, average degree of polymerization of 350), 50 g of magenta dye A and 500 g of ethyl acetate were placed in a separable flask and stirred to completely dissolve the above polymer and dye. After 900 g of an aqueous solution containing 0.5 g of sodium lauryl sulfate was dropped and stirred, an ultrasonic disperser (supra: UH-150) was used.
Emulsification for 10 minutes. Then, ethyl acetate was removed under reduced pressure to obtain colored fine particles. After replacing the inside of the flask with nitrogen, 1.5 g of potassium persulfate was added and dissolved, and after heating with a heater to 70 ° C., 20 g of styrene, 10 g of 2-ethylhexyl acrylate and 10 g of styrene.
The reaction mixture was allowed to react for 8 hours while dropping a mixed solution of 2-hydroxyethyl methacrylate (g) to obtain core-shell type magenta colored fine particles. Average particle size: 81 nm.

[0067]

[Chemical 1]

Production Example 3 50 g of polyvinyl butyral (above: BL-S, average degree of polymerization 350), 60 g of magenta dye B and 500 g
Ethyl acetate of was placed in a separable flask and stirred to completely dissolve the polymer and dye. 900 g of an aqueous solution containing 1 g of sodium lauryl sulfate was added dropwise and stirred, and then 1 using an ultrasonic disperser (previously: UH-150 type).
Emulsified for 0 minutes. Then, ethyl acetate was removed under reduced pressure to obtain colored fine particles. After replacing the inside of the flask with nitrogen, 1.5
g of potassium persulfate was added and dissolved, and after heating with a heater at 70 ° C., 20 g of styrene and 10 g of 2-
A reaction mixture was reacted for 8 hours while dropping a mixed solution of ethylhexyl acrylate and 10 g of 2-hydroxyethyl methacrylate to obtain core-shell type magenta colored fine particles.
Average particle size: 90 nm.

[0069]

[Chemical 2]

Production Example 4 50 g of polyvinyl butyral (supra: BL-S, average degree of polymerization 350), 65 g of C.I. I. Solvent B
70 g of ethyl and 500 g of ethyl acetate were placed in a separable flask and stirred to completely dissolve the polymer and dye. Aqueous solution containing 1 g of sodium lauryl sulfate 9
After dripping 00g and stirring, an ultrasonic disperser (previous: U
H-150 type) was used and emulsified for 10 minutes. Then, ethyl acetate was removed under reduced pressure to obtain colored fine particles. After replacing the inside of the flask with nitrogen, 1 g of potassium persulfate was added and dissolved, and after heating with a heater to 70 ° C., 20 g of styrene, 10 g of 2-ethylhexyl acrylate and 10 g of 2-hydroxyethyl methacrylate were added. The reaction mixture was allowed to react for 8 hours while dropping the mixed solution to obtain core-shell type cyan colored fine particles. Average particle size: 82 nm.

Production Example 5 50 g of polyvinyl butyral (supra: BL-S, average degree of polymerization 350), 50 g of C.I. I. Solvent B
rack 3 and 500 g of ethyl acetate were placed in a separable flask and stirred to completely dissolve the polymer and dye. Aqueous solution containing 1 g of sodium lauryl sulfate 9
After dripping 00g and stirring, an ultrasonic disperser (previous: U
H-150 type) was used and emulsified for 10 minutes. Then, ethyl acetate was removed under reduced pressure to obtain colored fine particles. After replacing the inside of the flask with nitrogen, 1 g of potassium persulfate was added and dissolved, and after heating with a heater to 70 ° C., 20 g of styrene, 10 g of 2-ethylhexyl acrylate and 10 g of 2-hydroxyethyl methacrylate were added. The mixture was added dropwise and reacted for 8 hours to obtain core-shell type black colored fine particles. Average particle size: 82 nm.

<Preparation and Evaluation of Aqueous Ink Containing Colored Fine Particles> Five kinds of dye-colored fine particles produced by the above method were weighed to obtain the absorbances shown in Table 1, ethylene glycol 10%, glycerin 20%, Surfynol 4
65 (manufactured by Air Products: acetylene-based activator) was prepared in an amount of 0.3% and the rest was pure water.
An inkjet ink (Example 1) was obtained by filtering with a μm membrane filter to remove dust and coarse particles.
~ 3) was obtained.

[0073]

[Table 1]

Set absorbance: dark yellow, magenta,
In addition to cyan and black, light color (1/4 absorbance of dark color)
Light magenta and light cyan.

An ink jet printer manufactured by Seiko Epson Corporation (Model No. PM-77
0C) Konica Photo Jet Paper Photol
It was printed on ike QP glossy paper (manufactured by Konica), and the color reproduction range and light resistance were evaluated according to the following criteria. As a comparison, printing was also performed with the genuine ink of PM-770C. The results are shown in Tables 2 and 3.

<< Color Reproduction Range >> A pure color reproduction chart was printed and measured with X-Rite 900 (manufactured by Nippon Flat Plate Equipment Co., Ltd.). Yellow, red, magenta, blue, cyan,
The part showing the maximum saturation of green was measured by C ^* .

C ^* = ((a ^* ) ² + (b ^* ) ² ) ^{1/2 The} higher the value, the higher the saturation.

Black density: The density of the portion where black is overlaid with Y, M, C and K is measured. The higher the value, the darker the color can be reproduced.

<< Light resistance test >> A sample having a stepwise changed concentration was prepared, and a low temperature Xe weather meter XL75 (manufactured by Suga Test Instruments Co., Ltd.) was used as a tester. The density change was measured by using X-Rite 900 (manufactured by Nippon Flat Plate Equipment Co., Ltd.) at the maximum print density. After exposure for 1 week, the concentration after exposure / concentration before exposure × 100 (%) was determined and used as an index of light resistance.

[0080]

[Table 2]

[0081]

[Table 3]

As is clear from Tables 2 and 3, the comparative commercially available dye inks have an imbalance in light resistance of the magenta dyes in particular, so that they are ink sets in which color change easily occurs at an early stage. The ink sets (Examples 1 to 3) using the colored fine particle water dispersion of the present invention are excellent in color reproducibility and have a color reproducibility comparable to that of a dye, and a high balance of light resistance. It turns out that it is a durable ink set. It can be seen that the ink set of Example 2 using carbon black as the black ink is an ink set having an excellent color reproduction range and an excellent balance of light resistance.

[0083]

According to the present invention, it is possible to provide a multicolor ink jet ink set which is excellent in color reproducibility with colored fine particles and is excellent in light fastness of recorded images.

Continued front page    F-term (reference) 2C056 EA13 FC02                 2H086 BA55 BA56 BA59 BA60 BA62                 4J039 AD07 BA04 BC39 BC61 BD04                       BE01 BE02 BE22 CA06 EA15                       EA16 EA17 EA19 EA29 EA44                       GA24

Claims (9)

[Claims] 1. In a multicolor inkjet ink set using two or more color inks, at least two color inks contain coloring fine particles composed of a coloring material and a resin, and the coloring material is C.I. I. Solvent Yellow 1,4,2
9,56,82,83,88,162, methine or azomethine oil-soluble magenta dye having a pyrazolotriazole structure, oil-soluble cyan dye having a copper phthalocyanine structure,
C. I. Solvent Black 3,21,2
An inkjet ink set, which is an oil-soluble dye selected from 2,43. 2. In a multicolor inkjet ink set containing at least yellow, magenta and cyan inks containing colored fine particles, yellow is C.I. as a dye used as a coloring material for the colored fine particles. I. Solvent Y
ellow1,4,29,56,82,83,88,1
62, magenta is a methine or azomethine oil-soluble magenta dye having a pyrazolotriazole structure, and cyan is C.I.
I. An inkjet ink set comprising an oil-soluble dye selected from Solvent Blue 70. 3. The ink set for ink jet according to claim 1, wherein the black ink is carbon black. 4. The use ratio of each dye is Y / M = mass ratio.
The inkjet ink set according to claim 1, 2 or 3, wherein 0.8 to 1.2 and M / C = 0.5 to 1.0. 5. The inkjet ink set according to claim 1, wherein the colored fine particles have a core-shell structure. 6. The inkjet ink set according to claim 1, wherein at least a part of the resin used for the core of the colored fine particles is polyvinyl butyral. 7. The inkjet ink set according to any one of claims 1 to 6, wherein at least a part of the resin used for the shell of the colored fine particles is a styrene-acrylic polymer. 8. The inkjet ink set according to any one of claims 1 to 7, wherein the colored fine particles have an average particle diameter of 100 nm or less. 9. An image forming method, wherein the ink according to any one of claims 1 to 8 is ejected as droplets from an ink jet head on the basis of a digital signal and adhered to an ink receiving medium.