JP2006111845A - Aqueous ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous ink that can produce a printed matter of an image having outstanding feeling of glossiness and image clarity especially in an inkjet recording using a medium to be exclusively used for inkjet. <P>SOLUTION: The aqueous ink comprises a micro-encapsulated coloring material, wherein a grain of a coloring material having at least an anionic group on the surface is coated by a polymer having both a repeated structure unit, that is derived from a cationic hydrophilic monomer and/or a cationic polymerizable surfactant having a cationic group, a hydrophobic group and a polymerizable group, and a repeated structure unit, that is derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group and/or a hydrophilic monomer having an anionic group, and a compound represented by formula (1), wherein R<SB>1</SB>, R<SB>2</SB>are each independently a 1-10C alkyl group, m and n are each a repeated unit number, and m+n averages 0-10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-based ink capable of obtaining an image having excellent gloss on various recording media.

  Inkjet recording is a method of recording characters and figures on the surface of a recording medium by ejecting ink as small droplets from fine nozzles. As an ink jet recording method, an electrostrictive element is used to convert an electrical signal into a mechanical signal, and ink stored in the nozzle head portion is intermittently ejected to record characters and symbols on the surface of the recording medium. A method of recording characters and symbols on the surface of the recording medium, etc. by rapidly heating a part of the ink that is stored in the vicinity of the ejection part to generate bubbles and intermittently ejecting the volume due to the bubbles. It has been put into practical use.

  The ink used for such ink jet recording has no bleeding, good drying properties, can be printed uniformly on the surface of various recording media, and has multiple colors such as color printing. In the printing of the system, characteristics such as that adjacent colors do not mix are required.

  In conventional inks, many of the inks that use pigments, in particular, have been studied to ensure the print quality by suppressing ink wetting on the paper surface mainly by suppressing penetrability and keeping ink droplets near the paper surface. Has been put to practical use.

  However, ink that suppresses wetting of paper has a large difference in bleeding due to the difference in the type of paper, and in particular, recycled paper containing various paper components causes bleeding due to differences in the wetting characteristics of the ink for each component. To do. In addition, such an ink has a problem that it takes time to dry the print, and there is a problem that adjacent colors are mixed in multicolor printing such as color printing. Further, an ink using a pigment as a coloring material However, since the pigment remains on the surface of paper or the like, there is a problem that the abrasion resistance is deteriorated.

  In order to solve such problems, attempts have been made to improve the permeability of ink into paper. Addition of diethylene glycol monobutyl ether (see Patent Document 1), Surfynol 465, which is an acetylene glycol-based surfactant. The addition of Nissin Chemical (see Patent Document 2) or the addition of both diethylene glycol monobutyl ether and Surfynol 465 (see Patent Document 3) has been studied. Alternatively, use of ethers of diethylene glycol for ink has been studied (see Patent Document 4).

  In addition, in the case of an ink using a pigment, since it is generally difficult to improve the ink permeability while ensuring the dispersion stability of the pigment, the selection range of the penetrant is narrow. There are also examples using triethylene glycol monomethyl ether (see Patent Document 5) and examples using ethylene glycol, diethylene glycol or triethylene glycol ethers (see Patent Document 6).

Furthermore, as a method of coating the surface of the colorant with a polymer, a method using a microcapsule containing a dye ink as an ink for an ink jet printer (see Patent Document 7), or dissolving or dispersing a pigment in a solvent insoluble in water And a method using a microencapsulated pigment emulsified in water with a surfactant (see Patent Document 8), an inclusion in which a sublimable disperse dye is dissolved or dispersed in at least one of water, a water-soluble solvent and polyester Using a microcapsule as a recording liquid (see Patent Document 9), an ink composition composed of colored emulsion polymer particles and an aqueous material (see Patent Document 10), a method using a phase inversion emulsification method or an acid precipitation method (Patent Document) References 11 and 12) have been studied.
US Pat. No. 5,156,675 US Pat. No. 5,183,502 US Pat. No. 5,196,056 US Pat. No. 2,083,372 Japanese Patent Application Laid-Open No. 56-147861 Japanese Patent Laid-Open No. 9-111165 JP-A-62-95366 JP-A-1-170672 JP-A-5-39447 JP-A-6-313141 Japanese Patent Laid-Open No. 10-140065 JP 2004 197037 A

However, in the above patent document, nothing is mentioned about obtaining an image having excellent glossiness and image clarity.
Accordingly, an object of the present invention is to solve the above-mentioned problems, and particularly to provide an aqueous ink capable of obtaining a printed matter with excellent gloss and image clarity in ink jet recording using an ink jet dedicated medium. It is to be.

As a result of intensive studies, the present inventor has achieved the above object by adopting the following configuration, and has achieved the present invention.
That is, in the present invention, at least the colorant particles having an anionic group on the surface are derived from a cationic hydrophilic monomer and / or a cationic polymerizable surfactant having a cationic group, a hydrophobic group, and a polymerizable group. A polymer having a repeating structural unit and an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group and / or a repeating structural unit derived from a hydrophilic monomer having an anionic group A water-based ink comprising a coated microencapsulated coloring material and a compound represented by the following formula (1).

(In the formula, R ₁ and R ₂ each independently represent an alkyl group having 1 to 10 carbon atoms, m and n are respectively the number of repeating units, and m + n is 0 to 10 on average.)

In addition, the color material particles of the microencapsulated color material of the present invention are preferably pigments.
By including the specific microencapsulated color material and the specific compound represented by the above formula (1), the water-based ink of the present invention has excellent glossiness and particularly in ink jet recording using an ink jet dedicated medium. A printed image with image clarity can be obtained.

The microencapsulated color material contained in the aqueous ink of the present invention is a cationic hydrophilic monomer and / or cation in which the color material particles having an anionic group on the surface have a cationic group, a hydrophobic group and a polymerizable group. Polymer having repeating structural unit derived from anionic polymerizable surfactant, an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group and / or a hydrophilic monomer having an anionic group It is characterized by being covered with.
Such a microencapsulated color material is a method for producing a microencapsulated color material in which a color material particle having an anionic group on its surface is coated with a polymer, and is an aqueous solution of the color material particle having an anionic group on its surface. After adding and mixing the cationic hydrophilic monomer and / or cationic polymerizable surfactant to the dispersion, emulsifying by adding the anionic polymerizable surfactant and / or hydrophilic monomer having the anionic group, It can manufacture suitably by adding a polymerization initiator and carrying out emulsion polymerization.

  According to such an emulsion polymerization method, first, an anionic group on the surface of a colorant particle having an anionic group on the surface and a cationic group of a cationic hydrophilic monomer and / or a cationic polymerizable surfactant are ions. The hydrophobic group of the cationic hydrophilic monomer and / or the cationic polymerizable surfactant and the hydrophobic group of the anionic polymerizable surfactant face each other, and the anion of the anionic polymerizable surfactant A structure in which the functional group is oriented toward the aqueous phase is formed. When the polymerization reaction is performed in this state, a polymer layer maintaining the above structure is formed on the surface of the colorant particles. That is, the arrangement of the cationic hydrophilic monomer and / or the cationic polymerizable surfactant and the anionic polymerizable surfactant existing around the colorant particles before the polymerization reaction is extremely highly controlled, and the outermost In the shell, a state in which anionic groups are oriented toward the aqueous phase is formed. Then, the cationic hydrophilic monomer and / or the cationic polymerizable surfactant and the anionic polymerizable surfactant are converted into a polymer by the emulsion polymerization reaction in the highly controlled form. Therefore, the structure of the microencapsulated color material is controlled with extremely high accuracy. As a result, the microencapsulated colorant used in the aqueous ink of the present invention is

(1) Excellent dispersion stability
(2) Excellent ejection stability from the recording head.
(3) A recorded matter having excellent image fastness can be obtained.
(4) A recorded matter having a high image printing density can be obtained.
(5) A recorded matter having excellent image abrasion resistance can be obtained.
(6) Even when plain paper is used as the recording medium, it is possible to obtain a recorded matter in which an image is less likely to bleed and an image is highly colored.

Ink jet recording ink satisfying all of the above (1) to (6) can be produced. In the case of a microencapsulated color material in which a polymer prepared in advance is applied to the color material particles by using, for example, a phase inversion emulsification method or an acid precipitation method, the color is determined by the polymer being prepared in advance. It is considered that the coating state of the polymer coloring material particles satisfying all of the above (1) to (6) is not achieved because the covering state of the material particles is limited.

Here, the aspect ratio (long / short) of the microencapsulated color material is 1.0 to 1.3, and the Zingg index is 1.0 to 1.3 (more preferably 1.0 to 1.2). ) Is preferable. Thereby, the items (1), (2), (4) and (6) can be satisfied more reliably.
When the short diameter of a particle is b, the long diameter is l, and the thickness is t (l ≧ b ≧ t> 0), the aspect ratio (long / shortness) is 1 / b (≧ 1), and the flatness is b / t ( ≧ 1) and Zingg index = long / short / flatness = (l · t) / b ² . That is, the true sphere has an aspect ratio of 1 and a Zingg index of 1.
If the Zingg index is larger than 1.3, the microencapsulated color material becomes flatter and becomes less isotropic. In particular, the above (1), (2), (4) and (6) There is a tendency that sufficient results cannot be obtained for items. The method for bringing the aspect ratio and the Zingg index within the above ranges is not particularly limited, but the microencapsulated color material in which the color material particles having an anionic group on the surface are coated with the polymer by the emulsion polymerization method described above is used. Can be easily met.

In addition, in a microencapsulated color material produced by a method other than an emulsion polymerization method such as an acid precipitation method or a phase inversion emulsification method, the aspect ratio and the Zingg index are unlikely to fall within the above ranges.
When the microencapsulated color material is in the range of the above aspect ratio and Zingg index, it becomes a perfect sphere, but this makes the ink flow characteristics easy to be Newtonian and excellent ejection stability. In addition, since the particles are spherical, when encapsulated on a recording medium such as paper, the encapsulated particles are arranged at a high density on the recording medium, and printing density and color development can be expressed with high efficiency. Further, since it is spherical, it is excellent in dispersibility and dispersion stability.
Hereinafter, embodiments of the present invention will be described with reference to possible dispersion states of colorant particles in the above-described preferred production method. However, the dispersion state of the color material particles described below includes estimation.

FIG. 1 shows that the colorant particle 1 having an anionic group 14 as a hydrophilic group on its surface is dispersed in a solvent containing water as a main component (hereinafter also referred to as an aqueous solvent), and a cationic group 11 and a hydrophobic group. An anionic polymerizable interface having a cationic hydrophilic monomer or a cationic polymerizable surfactant 2 having 12 and a polymerizable group 13, and an anionic group 14 ', a hydrophobic group 12' and a polymerizable group 13 '. FIG. 3 is a diagram showing a coexistence state with an activator 3. The cationic hydrophilic monomer or the cationic polymerizable surfactant 2 is disposed so that the cationic group 11 faces the anionic group 14 of the colorant particle 1 and adsorbs with a strong ionic bond. And, for the hydrophobic group 12 and the polymerizable group 13 of this cationic hydrophilic monomer or cationic polymerizable surfactant 2, the hydrophobic group of the anionic polymerizable surfactant 3 is obtained by hydrophobic interaction. 12 ′ and the polymerizable group 13 ′ face, and the anionic group 14 ′ of the other anionic polymerizable surfactant 3 faces the direction in which the aqueous solvent exists, that is, the direction away from the colorant particle 1.
For example, by adding a polymerization initiator to such an aqueous dispersion, the polymerizable group 13 of the cationic hydrophilic monomer or the cationic polymerizable surfactant 2 and the polymerizable group 13 of the anionic polymerizable surfactant 3 are used. By polymerizing ', a microencapsulated color material 100' in which the color material particles 1 are coated with the polymer layer 60 'is produced as shown in FIG. Here, since the surface of the polymer layer 60 ′ has the anionic group 14 ′, the microencapsulated color material 100 ′ can be dispersed in an aqueous solvent. In the case where a hydrophilic monomer having an anionic group as a hydrophilic group is used in place of the anionic polymerizable surfactant 3, a microencapsulated color material can be similarly produced. During polymerization, a hydrophilic monomer having a cationic hydrophilic monomer and / or a cationic polymerizable surfactant and an anionic polymerizable surfactant and / or an anionic group in an aqueous dispersion, if necessary. In which case the polymer layer comprises a cationic hydrophilic monomer and / or a cationic polymerizable surfactant and an anionic polymerizable surfactant and / or Alternatively, it can be a copolymer layer copolymerized from a hydrophilic monomer having an anionic group and a comonomer.

  Further, in addition to the above, the possible dispersion state of the colorant particles is increased in the above-described preferred production method. FIG. 3 shows that the colorant particle 1 having an anionic group 14 as a hydrophilic group on its surface is dispersed in a solvent containing water as a main component (hereinafter also referred to as an aqueous solvent), and a cationic group 11 and a hydrophobic group. Anionic polymerizable interface having a cationic hydrophilic monomer or cationic polymerizable surfactant 2 having 12 and a polymerizable group 13, an anionic group 14 ', a hydrophobic group 12' and a polymerizable group 13 ' It is a figure which shows the state coexisting with the activator 3. FIG. The cationic hydrophilic monomer or the cationic polymerizable surfactant 2 is arranged so that the cationic group 11 faces the anionic group 14 of the colorant particle 1 and adsorbs with a strong ionic bond. Then, the hydrophobic group 12 and the polymerizable group 13 of the cationic hydrophilic monomer or the cationic polymerizable surfactant 2 are bonded to the hydrophobic group of the anionic polymerizable surfactant 3 by hydrophobic interaction. 12 ′ and the polymerizable group 13 ′ are oriented, and the anionic group 14 ′ of the other anionic polymerizable surfactant 3 is oriented in the direction in which the aqueous solvent exists, that is, in the direction away from the colorant particle 1.

  Further, the surface of the colorant particle 1 has an anionic group 14 chemically bonded at a specific density, and has a hydrophobic region 50 between the anionic groups 14, and the hydrophobic region 50 includes, for example, The hydrophobic group 12 and the polymerizable group 13 of the cationic hydrophilic monomer or the cationic polymerizable surfactant 2 are suitable. Anionic polymerizable surfactant 3 is arranged on the cationic group 11 of the cationic hydrophilic monomer or cationic polymerizable surfactant 2 so that the anionic group 14 'faces, and a strong ionic bond is formed. Adsorb at. The hydrophobic group 12 ′ and the polymerizable group 13 ′ of the anionic polymerizable surfactant 3 are separated from the hydrophobic group 12 ′ and the polymerizable group of another anionic polymerizable surfactant 3 by hydrophobic interaction. 13 ′ is oriented, and the anionic group 14 ′ of the anionic polymerizable surfactant 3 is oriented in the direction in which the aqueous solvent is present, that is, in the direction away from the colorant particles 1.

  For example, by adding a polymerization initiator to the aqueous dispersion, the polymerizable group 13 of the cationic hydrophilic monomer or the cationic polymerizable surfactant 2 and the polymerizable group 13 of the anionic polymerizable surfactant 3 are used. By polymerizing ', a microencapsulated color material 100 in which the color material particles 1 are coated with the polymer layer 60 is produced as shown in FIG. Here, since the surface of the polymer layer 60 has the anionic group 14 ′, the microencapsulated color material 100 can be dispersed in an aqueous solvent. In the case where a hydrophilic monomer having an anionic group as a hydrophilic group is used in place of the anionic polymerizable surfactant 3, a microencapsulated color material can be similarly produced. During polymerization, a hydrophilic monomer having a cationic hydrophilic monomer and / or a cationic polymerizable surfactant and an anionic polymerizable surfactant and / or an anionic group in an aqueous dispersion, if necessary. In which case the polymer layer comprises a cationic hydrophilic monomer and / or a cationic polymerizable surfactant and an anionic polymerizable surfactant and / or Alternatively, it can be a copolymer layer copolymerized from a hydrophilic monomer having an anionic group and a comonomer.

  As mentioned above, although the dispersed state was mentioned using drawing, first, the color material particle 1 is in the state disperse | distributed to the aqueous solvent by having an anionic group as a hydrophilic group on the surface. The dispersion of the color material particles 1 in the aqueous solvent is highly dispersed as compared with the case where the color material particles having no hydrophilic group (anionic group) on the surface are dispersed with a dispersant. According to the microencapsulated color material in which the color material particles having the anionic group on the surface are coated with the polymer, as shown in FIGS. 2 and 4, the anionic group on the surface of the microencapsulated color material is Since it is regularly and densely oriented in the direction in which the aqueous solvent exists, the dispersion stability of the microencapsulated coloring material in the aqueous solvent can be improved. Therefore, when such a microencapsulated color material is used as a colorant for the aqueous ink of the present invention and the ink solvent is an aqueous solvent, a more multiple amount of microencapsulated color material can be contained in the ink. Dispersion stability superior to conventional microencapsulated color material ink can be imparted while maintaining a low viscosity without increasing the viscosity. If the dispersion stability is excellent, the possibility of clogging the nozzles of the ink jet recording head by the microencapsulated color material is reduced, so that the ejection stability is also improved. That is, it is possible to produce a water-based ink that is excellent in dispersion stability and ejection stability and at the same time has an improved colorant content (weight concentration) compared to conventional water-based inks.

  In addition, the microencapsulated colorant used in the present invention has a small particle size, and hydrophilic groups (particularly anionic groups) on the particle surface are regularly and densely oriented toward the aqueous phase side. It is possible to obtain a good packing property by being closely packed on the cellulose fiber of plain paper. For this reason, by performing ink jet recording using a microencapsulated color material aqueous ink having a high content (weight concentration) of the above microencapsulated color material, not only the image fastness is excellent, but also saturation A recorded matter having a high printing density can be obtained without causing any decrease.

More specifically, since the microencapsulated color material used in the aqueous ink of the present invention is considered to have an anionic group regularly and densely oriented toward the aqueous solvent side as described above. It is considered that an effective electrostatic repulsive force is generated between the microencapsulated color materials. In addition to such electrostatic repulsive force, the effect of the steric hindrance caused by the polymer covering the pigment particles (polymer effect) is also due to the fact that the microencapsulated colorant of the present invention is in an aqueous medium. This is considered to be one of the factors that have excellent dispersion stability.

  The reason why it is possible to suppress the occurrence of image bleeding when the recording medium is plain paper and the reason why the printing density of the image is high are that the microencapsulated coloring material is regularly and densely oriented toward the aqueous solvent side. It is thought that this is largely due to the action of the hydrophilic group of the pigment. When ink is ejected from the recording head and landed on plain paper, the ink solvent rapidly penetrates into the paper, but the colorant particles dispersed with the conventional dispersant (the colorant particles are covered with the dispersant) In the ink used, the colorant particles move along with the solvent in the lateral direction and deep part of the paper, and are difficult to adsorb on the cellulose fibers on the surface of plain paper (this is because the hydrophilic group amount on the surface of the colorant particles is the present invention). This is considered to be because it is less than the microencapsulated color material according to the embodiment and that the hydrophilic groups are not regularly and densely oriented.) Therefore, the print density is low and the color developability is insufficient.

  On the other hand, the microencapsulated color material used in the present invention includes various metal ions such as magnesium, calcium, and aluminum in which a hydrophilic group (particularly anionic group) present on the surface is usually contained in plain paper. It is easy to agglomerate by interaction, and the cationic starch and the cationic polymer in the plain paper used together with the sizing agent in the sizing of plain paper and the hydrophilic group (especially anion) of the microencapsulated colorant Easily adsorbs or aggregates due to the interaction with the functional groups), and adsorbs on the cellulose fibers of plain paper due to the interaction between the hydrophilic groups (especially anionic groups) of the microencapsulated colorant and the cellulose fibers. Cheap. Therefore, when ink containing the above-described microencapsulated colorant as a colorant is ejected from a recording head and landed on plain paper, the colorant tends to accumulate near the landing position of plain paper, resulting in high image density and bleeding. Is also suppressed. Further, the microencapsulated colorant used in the present invention is usually small in size, and the hydrophilic groups (particularly anionic groups) on the particle surface are regularly and densely oriented toward the aqueous phase side. Since close packing is carried out on the cellulose fiber of paper and good packing property is obtained, the color saturation which tends to occur in a general pigment ink using a pigment other than the above microencapsulated colorant as a colorant does not occur at all. Absent.

  In addition, the water-based ink according to the present invention is excellent in fixability to a recording medium compared to an ink using a conventional surface-treated pigment particle as a colorant because the color material is coated with a polymer. The recorded article can be excellent in scratch resistance.

Next, the components of the macroencapsulated color material according to the present invention will be described in detail.
Color material particles having a hydrophilic group on the surface can be suitably prepared by treating the surface of the color material particles with a hydrophilic group-imparting agent. Therefore, the color material constituting the color material particles having a hydrophilic group on the surface is not particularly limited as long as the color material does not dissolve in the hydrophilic group-imparting agent. From such a point of view, the following inorganic pigments and organic pigments can be mentioned as preferable color materials in the ink of the present invention.
Examples of inorganic pigments include carbon blacks such as furnace black, lamb black, acetylene black, and channel black (C.I. Pigment Black 7), iron oxide pigments, and the like. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxanes). Pigments, thioindigo pigments, isoindolinone pigments, or quinofuranone pigments), dye chelates (eg, basic dye-type chelates or acidic dye-type chelates), nitro pigments, nitroso pigments, or aniline black. .

More specifically, as an inorganic pigment used for black, the following carbon black, for example, No. manufactured by Mitsubishi Chemical Corporation is used. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, or No2200B, etc .; Columbia-made Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc .; 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc .; or Color Black FW1, Fla2 ck, Color Black FW2, Clk, FW2V, C, Degussa Lor Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Speck 4 or Speck.
Moreover, as the organic pigment for black, a black organic pigment such as aniline black (C.I. Pigment Black 1) can be used.

  Examples of organic pigments for yellow ink include C.I. l. Pigment Yellow 1 (Hansa Yellow), 2, 3 (Hansa Yellow 10G), 4, 5 (Hansa Yellow 5G), 6, 7, 10, 11, 12, 13, 14, 16, 17, 24 (Flavantron Yellow) , 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108 (anthrapyrimidine yellow), 109, 110, 113, 117 ( Copper complex pigment), 120, 124, 128, 129, 133 (quinophthalone), 138, 139 (isoindolinone), 147, 151, 153 (nickel complex pigment), 154, 167, 172, 180, and the like. it can.

  Further, as organic pigments for magenta ink, C.I. l. Pigment Red 1 (Paral Red), 2, 3 (Toluidine Red), 4, 5 (lTR Red), 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21 22, 23, 30, 31, 32, 37, 38 (pyrazolone red), 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88 (thioindigo), 112 (Naphthol AS series), 114 (naphthol AS series), 122 (dimethylquinacridone), 123, 144, 146, 149, 150, 166, 168 (antanthrone orange), 170 (naphthol AS series), 171, 175, 176 , 177, 178, 179 (berylene maroon), 184, 185, 187, 202, 209 (dichloroquinacridone), 219, 224 (berylene), 245 (naphtho) AS thread) or C.I. I. And CI pigment violet 19 (quinacridone), 23 (dioxazine violet), 32, 33, 36, 38, 43, and 50.

  Furthermore, as organic pigments for cyan ink, C.I. l. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16 (metal-free phthalocyanine), 18 (alkali blue toner), 22, 25, 60 ( Slen Blue), 65 (Biolantron), 66 (Indigo), C.I. l. Vat blue 4, 60 etc. can be mentioned.

Furthermore, as an organic pigment used for color inks other than magenta, cyan or yellow ink,
C. I. Pigment green 7 (phthalocyanine green), 10 (green gold), 36, 37;
C. I. Pigment brown 3, 5, 25, 26; I. Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63, etc. can be used.
In the macroencapsulated color material according to the present invention, the above color materials can be used alone or in combination of two or more.

As the hydrophilic group-imparting agent for treating the surface of the color material particles, first, a treatment agent containing sulfur can be preferably mentioned.
Examples of the treatment agent containing sulfur include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt and sulfamic acid. Among them, sulfur trioxide, sulfonated pyridine salt or sulfamine. Sulfonating agents such as acids are preferred. These can be used alone or in admixture of two or more. (Note that “sulfonating agent” means sulfonic acid (—SO ₃ H) and / or sulfinic acid (—RSO ₂ H: R is a C _{1 to} C ₁₂ alkyl group, or a phenyl group and a modified product thereof) Is a treatment agent for imparting

In addition, a solvent capable of forming a complex with the sulfur trioxide (a basic solvent such as N, N-dimethylformamide dioxane, pyridine, triethylamine, and trimethylamine, nitromethane, acetonitrile, etc.) and a solvent described later. It is also useful to form a complex with a mixed solvent with one or more kinds.
In particular, sulfur trioxide itself is too reactive to decompose or alter the colorant itself, or when it is difficult to control the reaction with a strong acid, a complex of sulfur trioxide and a tertiary amine as described above. It is preferable to perform surface treatment (in this case, sulfonation) of the colorant particles using

In addition, when using sulfuric acid, fuming sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, etc. alone, the colorant particles are easily dissolved, and it is necessary to suppress the reaction for strong acids that react per molecule. It is necessary to pay attention to the type of solvent used and the amount used.
The solvent used in the reaction is selected from those which do not react with the treatment agent containing sulfur and in which the above-mentioned coloring material becomes insoluble or hardly soluble, and sulfolane, N-methyl-2-pyrrolidone, dimethylacetamide Quinoline, hexamethylphosphoric triamide, chloroform, dichloroethane, tetrachloroethane, tetrachloroethylene, dichloromethane, nitromethane, nitrobenzene, liquid sulfur dioxide, carbon disulfide, trichlorofluoromethane, and the like.

  The treatment with the treatment agent containing sulfur is performed by dispersing the colorant particles in a solvent, adding a treatment agent containing sulfur to this dispersion, heating to 60 to 200 ° C., and stirring for 3 to 10 hours. Specifically, a method in which high-speed shear dispersion is performed in advance with a high-speed mixer or the like, or impact dispersion is performed with a bead mill or a jet mill to form a slurry (dispersion) is preferable. Then, after moving to gentle stirring, a treatment agent containing sulfur is added to introduce hydrophilic groups onto the surface of the colorant particles. At this time, the reaction conditions and the type of the treatment agent containing sulfur greatly depend on the determination of the introduction amount of the hydrophilic group. After this heat treatment, the solvent and the treating agent containing residual sulfur are removed from the slurry of the colorant particles. Removal is carried out by repeatedly washing with water, ultrafiltration, reverse osmosis, etc., centrifugation, filtration and the like.

Further, the sulfonic acid (—SO ₃ H) and / or sulfinic acid (—RSO ₂ H: R is a C _{1 to} C ₁₂ alkyl group, or a phenyl group and a modified product thereof) described above is treated with an alkali compound. As a hydrophilic group, a sulfonic acid anion group (—SO ₃ ⁻ ) and / or a sulfinate anion group (—RSO ₂ ⁻ : R is a C _{1 to} C ₁₂ alkyl group or phenyl group and a modified product thereof) are surfaced. It is possible to make the colorant particles in In the present invention, it is preferably used in this state.

As the alkali compound, the cation is an alkali metal ion or a chemical formula (R ₁ R ₂ R ₃ R ₄ N) ⁺ (R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and a hydrogen atom, an alkyl group, An alkaline compound that is a monovalent ion represented by (showing a hydroxyalkyl group or an alkyl halide group) is selected. Preferably, an alkali compound in which the cation becomes an alkanolamine cation such as lithium ion (Li ⁺ ), potassium ion (K ⁺ ), sodium ion (Na ⁺ ), ammonium ion (NH ₄ ⁺ ), and triethanolamine cation. It is.

  Hydroxyl anion is preferably used as the anion of the alkali compound. Specific examples thereof include ammonia, alkanolamine (monoethanolamine, diethanolamine, N, N-butylethanolamine, triethanolamine, propanolamine, aminomethyl). Propanol, 2-aminoisopropanol, etc.) and monovalent alkali metal hydroxides (LiOH, NaOH, KOH).

  The amount of the alkali compound added is preferably at least the neutralization equivalent of the sulfonic acid group and / or sulfinic acid group of the colorant particles. Furthermore, for volatile additives such as ammonia and alkanolamine, addition of 1.5 times or more of the neutralization equivalent is generally preferred.

  The operation can be performed by placing the colorant particles having the sulfonic acid group and / or sulfinic acid group chemically bonded to the surface in an alkali compound, and shaking with a paint shaker or the like.

Moreover, a carboxylating agent can also be suitably mentioned as a hydrophilic group provision agent for processing the surface of a color material particle. Here, the “carboxylating agent” is a treatment agent for imparting a carboxylic acid group (—COOH).
As the carboxylating agent, an oxidizing agent such as hypohalite such as sodium hypochlorite or potassium hypochlorite is used, and partial bonding (C = C, C-C) on the surface of the colorant particle is performed. By cutting and oxidizing. In addition to the chemical treatment described above, a carboxylic acid group may be imparted by physical oxidation such as plasma treatment, but in the present invention, if the treatment method can ensure dispersion stability in an aqueous medium, Various methods can be selected. Further, in the exemplified carboxylic acid introduction treatment, a quinone group or the like may be introduced although the amount is small. Even in such a case, it is not contrary to the gist of the present invention as long as the dispersion stability of the microencapsulated coloring material in the aqueous medium can be secured.

  As an example of the treatment with a carboxylating agent, the colorant particles are preliminarily sheared and dispersed in an aqueous medium with a high speed mixer or the like, or impact dispersed with a bead mill or jet mill to form a slurry (dispersion). Next, a hypohalite such as sodium hypochlorite having an effective halogen concentration of 10 to 30% is mixed in an appropriate amount of water and heated to 60 to 80 ° C. for about 5 to 10 hours, preferably 10 It is carried out by stirring for more than an hour. This operation involves a considerable amount of heat and requires safety attention. Thereafter, the solvent and the remaining carboxylating agent are removed from the slurry of the colorant particles subjected to the surface treatment by heat treatment. Further, if necessary, it is possible to obtain a desired aqueous dispersion by repeatedly performing washing, ultrafiltration, reverse osmosis and the like, centrifugation, filtration and the like.

Again, by treating the colorant particles having a carboxylic acid group (—COOH) with an alkali compound, the colorant particles having a carboxylic acid anion group (—COO ⁻ ) on the surface as a hydrophilic group can be obtained. . In the present invention, it is preferably used in this state.
The kind of alkali compound and the treatment method with the alkali compound are the same as described above.

Next, a method for examining a preferable introduction amount of the hydrophilic group to the surface of the colorant particle and an introduction state thereof will be described.
First, when hydrophilization is performed using a sulfonating agent, the amount of hydrophilic groups introduced on the surface of the colorant particles is preferably 0.01 mmol equivalent or more per gram of colorant particles. When the introduction amount of the hydrophilic group is less than 0.01 mmol / g, in the microencapsulation step of the colorant particles in the aqueous solvent, the aggregates of the colorant particles are easily generated, and the average of the microencapsulated colorant There is a tendency for the particle size to increase. As the average particle size of the microencapsulated color material increases, it becomes difficult to obtain an ink for ink jet recording that is excellent in dispersion stability and ejection stability and can increase the print density of an image.
The upper limit of the introduction amount of the hydrophilic group with respect to the color material particles is not particularly limited, but when it exceeds 0.15 mmol / g, no change is observed in the average particle size of the color material particles with the increase in the introduction amount of the hydrophilic group. Therefore, it is preferably 0.15 mmol / g or less from the viewpoint of cost.

Next, the amount of hydrophilic group introduced to the surface of the colorant particles by the carboxylating agent will be described. In the surface treatment technique used in the present invention, it is considered that a carboxylic acid group (—COOH) and / or a carboxylic acid anion group (—COO ⁻ ) is introduced into the surface of the colorant particle. In the present invention, the amount introduced is measured by the surface active hydrogen content. A detailed measurement method will be described later.
The active hydrogen content in the color material particles obtained by such a method is preferably 1.0 mmol / g or more, and more preferably 1.5 mmol / g or more. When the concentration is 1.0 mmol / g or less, water dispersibility is deteriorated, and coalescence (particles naturally gather and increase in particle size) easily occurs in the microencapsulation process.

  The color material particles having a hydrophilic group on the surface have been described in detail above. However, the average particle diameter of the color material particles having the hydrophilic group on the surface can be easily reduced to 150 nm or less by the above method. In particular, it is more preferable to set the average particle size to 20 nm to 80 nm by selecting the type of coloring material, hydrophilic group-imparting agent, introduction amount of hydrophilic groups, and the like, whereby dispersion stability and ejection stability are improved. It is possible to obtain a microencapsulated color material that is excellent and can more reliably produce an ink for ink jet recording that can increase the printing density of an image. (In this specification, the description of the average particle diameter is described by the measured value of the laser light scattering method.)

  The colorant particle having a hydrophilic group on its surface is a repeating structural unit derived from a cationic hydrophilic monomer having a cationic group, a hydrophobic group and a polymerizable group and / or a cationic polymerizable surfactant. And a polymer having a repeating structural unit derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group and / or a hydrophilic monomer having an anionic group. Thus, the microencapsulated color material according to the embodiment of the present invention is obtained. As described above, such a microencapsulated colorant is mixed after adding a cationic hydrophilic monomer and / or a cationic polymerizable surfactant to an aqueous dispersion of colorant particles having an anionic group on the surface. It can be suitably prepared by adding an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group and then emulsifying, and then adding a polymerization initiator and emulsion polymerization.

The cationic group of the cationic hydrophilic monomer and / or cationic polymerizable surfactant is selected from the group consisting of a primary amine cation, a secondary amine cation, a tertiary amine cation, and a quaternary ammonium cation. Groups are preferred. The primary amine cation is a monoalkyl ammonium cation (RNH ₃ ⁺ ), the secondary amine cation is a dialkyl ammonium cation (R ₂ NH ₂ ⁺ ), and the tertiary amine cation is a trialkyl ammonium cation (R ₃ NH ⁺ ) and the like, and examples of the quaternary ammonium cation include (R ₄ N ⁺ ) and the like. Here, R is a hydrophobic group and a polymerizable group, and examples thereof include those shown below.
Examples of the counter anion of the above-mentioned cationic group include Cl ⁻ , Br ⁻ and I ⁻ .
The hydrophobic group is preferably selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined.
The polymerizable group is preferably an unsaturated hydrocarbon group, and more specifically selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. preferable. Among these, an acryloyl group and a methacryloyl group can be exemplified as preferable examples.

  Specific examples of the cationic polymerizable surfactant include a cationic allylic acid derivative as described in JP-B-4-65824.

The cationic polymerizable surfactants used in the present invention, for example, the general formula _{R [4- (l + m +} n)] R 1 l R 2 m R 3 n N + · X - a compound represented by (R is a polymerizable group, R ¹ , R ² and R ³ are each an alkyl group or an aryl group, X is Cl, Br or I, and l, m and n are each 1; Or 0.) Here, as the polymerizable group, a hydrocarbon group having an unsaturated hydrocarbon group capable of radical polymerization can be preferably exemplified, and more specifically, an allyl group, an acroyl group, a methacryloyl group, a vinyl group, a propylene group, Nyl group, vinylidene group, vinylene group and the like can be mentioned.

  Specific examples of the cationic polymerizable surfactant include dimethylaminoethyl dodecyl chloride methacrylate and dimethylaminoethyl desyl chloride methacrylate. Specific examples of the cationic polymerizable hydrophilic monomer include dimethylaminoethyl methyl chloride methacrylate, dimethylaminoethyl benzyl methacrylate methacrylate, methacryloyloxyethyltrimethylammonium chloride, diallyldimethylammonium chloride, 2-hydroxy-3-methacryloxypropyl. Examples thereof include trimethylammonium chloride.

  A commercial item can also be used as said cationic polymerizable hydrophilic monomer. Examples include Acryester DMC (Mitsubishi Rayon Co., Ltd.), Acryester DML60 (Mitsubishi Rayon Co., Ltd.), C-1615 (Daiichi Kogyo Seiyaku Co., Ltd.), and the like.

  The cationic hydrophilic monomers and / or cationic polymerizable surfactants exemplified above can be used alone or as a mixture of two or more.

  The addition amount of the cationic hydrophilic monomer and / or the cationic polymerizable surfactant is the total number of moles of anionic groups relative to the amount of the coloring material particles having an anionic group on the surface (= weight of the coloring material used ( g) × anionic group (mol / g) on the surface of the colorant particle is preferably in the range of 0.5 to 2 times mol, more preferably in the range of 0.8 to 1.2 times mol. . By setting the addition amount to 0.5 times mol or more, it is strongly ionically bound to the colorant particles having an anionic group as the hydrophilic group, and can be easily encapsulated. By setting the addition amount to 2 times or less, the generation of unadsorbed cationic hydrophilic monomer and / or cationic polymerizable surfactant on the color material particles can be reduced, and the color material particles are used as a core substance. Generation | occurence | production of the polymer particle (particles which consist only of a polymer) which does not have can be prevented.

  Specific examples of the anionic polymerizable surfactant include anionic properties as described in JP-B-49-46291, JP-B-1-24142, or JP-A-62-104802. Allyl derivatives, anionic propenyl derivatives as described in JP-A-62-221431, anions as described in JP-A-62-34947 or JP-A-55-11525 And anionic itaconic acid derivatives as described in JP-B-46-34898 or JP-A-51-30284.

  Examples of the anionic polymerizable surfactant used in the present invention include a general formula (31):

[Wherein, R ²¹ and R ³¹ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and Z ¹ represents a carbon-carbon single bond or a formula —CH ₂ —O—CH ₂ −
M is an integer of 2 to 20,
X is a group represented by the formula —SO ₃ M ¹ , and M ¹ is an alkali metal, an ammonium salt, or an alkanolamine]
Or a compound represented by formula (32):

[Wherein, R ²² and R ³² each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and D represents a carbon-carbon single bond or a formula —CH ₂ —O—CH ₂ —
N is an integer of 2 to 20,
Y is a group represented by the formula —SO ₃ M ² , and M ² is an alkali metal, an ammonium salt, or an alkanolamine]
The compound represented by these is preferable.

The polymerizable surfactant represented by the formula (31) is described in JP-A-5-320276 or JP-A-10-316909. By appropriately adjusting the type of R ²¹ and the value of x in the formula (31), it is possible to correspond to the degree of hydrophilicity or hydrophobicity of the surface of the colorant particles. As a preferable polymerizable surfactant represented by the formula (31), a compound represented by the following formula (310) can be exemplified. Specifically, in the following formulas (31a) to (31d) Mention may be made of the compounds represented.

[Wherein R ³¹ , m and M ¹ are the same as the compound represented by formula (31)]

A commercial item can also be used as said anionic polymerizable surfactant. For example, Aqualon HS series (Aqualon HS-05, HS-10, HS-20, HS-1025) from Daiichi Kogyo Seiyaku Co., Ltd. or Adeka Soap SE-10N, SE-20N from Asahi Denka Kogyo Co., Ltd. Can be mentioned.
Adeka Soap SE-10N manufactured by Asahi Denka Kogyo Co., Ltd. is a compound represented by formula (310) in which M ¹ is NH ₄ , R ³¹ is C ₉ H ₁₉ , and m = 10. Adeka Soap SE-20N manufactured by Asahi Denka Kogyo Co., Ltd. is a compound represented by the formula (310) in which M ¹ is NH ₄ , R ³¹ is C ₉ H ₁₉ , and m = 20.

  Examples of the anionic polymerizable surfactant used in the present invention include a general formula (33):

[Wherein p is 9 or 11, q is an integer of 2 to 20, A is a group represented by —SO ₃ M ³ , and M ³ is an alkali metal, an ammonium salt or an alkanolamine]
The compound represented by these is preferable. Preferred examples of the anionic polymerizable surfactant represented by the formula (33) include the following compounds.

[Wherein r is 9 or 11, s is 5 or 10]

  A commercial item can also be used as said anionic polymerizable surfactant. For example, Aqualon KH series (Aqualon KH-5, Aqualon KH-10) from Daiichi Kogyo Seiyaku Co., Ltd. can be mentioned. Aqualon KH-5 is a mixture of a compound represented by the above formula wherein r is 9 and s is 5 and a compound where r is 11 and s is 5. Aqualon KH-10 is a mixture of a compound represented by the above formula wherein r is 9 and s is 10, and a compound where r is 11 and s is 10.

  Moreover, as an anionic polymerizable surfactant, the compound represented by the following formula (A) is also preferable.

[In the above formula, R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, l represents a number of 2 to 20, and M ⁴ represents an alkali metal, an ammonium salt, or an alkanolamine. ]

  The anionic polymerizable surfactants exemplified above can be used alone or as a mixture of two or more.

  The addition amount of the anionic polymerizable surfactant is preferably in the range of about 1 to 10 times mol, more preferably in the range of about 1.0 to 5 times mol with respect to the cationic polymerizable surfactant. It is. By setting the addition amount to 1 mol or more, the dispersibility and dispersion stability of the encapsulated particles are excellent, and the discharge stability is also excellent. Furthermore, the adsorptivity to paper fibers is improved and the printing density and color developability are excellent. The addition amount of 10 times mol or less can suppress the generation of an anionic polymerizable surfactant that does not contribute to encapsulation, and can prevent the generation of polymer particles having no core substance other than the capsule particles.

  The anionic group of the anionic polymerizable surfactant is considered to be present on the capsule surface after being microencapsulated and oriented on the aqueous phase side. Thereby, the dispersibility and dispersion stability of the encapsulated particles in the aqueous phase are excellent. In addition, the above anionic group is likely to interact with various metal ions such as magnesium, calcium, and aluminum that are usually contained in plain paper, cationic starch, cationic polymers, and cellulose fibers. If water-based ink for inkjet recording using such a microencapsulated color material as a colorant is ejected onto plain paper, the colorant tends to accumulate near the landing position of the plain paper, so that the image density can be obtained more reliably. And the occurrence of bleeding can be suppressed.

The hydrophilic monomer having an anionic group that can be used in the present invention has at least an anionic group and a polymerizable group as a hydrophilic group in the structure, and the hydrophilic group is a sulfonic acid group or a sulfinic acid group. And those selected from the group of carboxyl groups, carbonyl groups and salts thereof.
The polymerizable group is an unsaturated hydrocarbon group capable of radical polymerization, and is preferably selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. .

Anionic groups such as sulfonic acid groups, sulfinic acid groups, carboxyl groups, carbonyl groups, and salts thereof are considered to be oriented on the water phase side on the capsule surface, and thus in the aqueous phase of the encapsulated particles. The dispersibility and the dispersion stability in this are excellent. In addition, the above anionic group easily interacts with various metal ions such as magnesium, calcium, and aluminum usually contained in plain paper, cationic starch, cationic polymer, and cellulose fiber. A microencapsulated color material is prepared using a polymerizable monomer having an anionic group as a hydrophilic group, and an aqueous ink for inkjet recording using such a microencapsulated color material as a colorant is applied to plain paper. If discharged, the colorant tends to accumulate near the landing position of the plain paper, so that the image density can be obtained more reliably and the occurrence of bleeding can be suppressed.
Preferable specific examples of the hydrophilic monomer having an anionic group include, for example, methacrylic acid, acrylic acid, phosphoric acid group-containing (meth) acrylate, sodium vinyl sulfonate, 2-sulfoethyl methacrylate, 2-acrylamido-2-methyl. And propanesulfonic acid.

  The addition amount of the hydrophilic group monomer having an anionic group is preferably in the range of about 1 to 10 moles, more preferably, to the cationic hydrophilic monomer and / or the cationic polymerizable surfactant. The range is about 1.0 to 5 times mole. By setting the addition amount to 1 mol or more, the dispersibility and dispersion stability of the encapsulated particles are excellent, and the discharge stability is also excellent. By setting the addition amount to 10 times mol or less, it is possible to suppress the generation of hydrophilic monomers that do not contribute to encapsulation, and to prevent the generation of polymer particles having no core substance other than the capsule particles.

  In the case where an anionic polymerizable surfactant and a hydrophilic group monomer having an anionic group are used in combination, the sum of the addition amount is based on the cationic hydrophilic monomer and / or the cationic polymerizable surfactant. A range of about 1 to 10 moles is preferable, and a range of about 1.0 to 5 moles is more preferable. As described above, when the addition amount is 1 mol or more, the dispersibility and dispersion stability of the encapsulated particles are excellent. By setting the addition amount to 10 times mol or less, it is possible to suppress the generation of hydrophilic monomers that do not contribute to encapsulation, and to prevent the generation of polymer particles in which no core substance exists other than the encapsulated particles.

More specifically, the microencapsulated color material according to the embodiment of the present invention is suitably manufactured by the following procedure.
(1) A cationic hydrophilic monomer and / or a cationic polymerizable surfactant is added to a dispersion in which colorant particles having an anionic group on the surface are dispersed in water. Here, the cationic hydrophilic monomer and / or the cationic group of the cationic polymerizable surfactant are adsorbed and ionically bonded to the anionic group of the colorant particle having an anionic group on the surface for immobilization. Is done.
(2) Comonomers copolymerizable with cationic hydrophilic monomers and / or cationic polymerization surfactants, more specifically, anionic polymerizability having an anionic group, a hydrophobic group and a polymerizable group A surfactant and / or a hydrophilic monomer having an anionic group and a polymerization initiator are added to carry out emulsion polymerization.
By such a procedure, it is derived from a repeating structural unit derived from a cationic hydrophilic monomer and / or a cationic polymerizable surfactant, and a hydrophilic monomer having an anionic polymerizable surfactant and / or an anionic group. A microencapsulated color material coated with a polymer having a repeated structural unit can be suitably produced.

Furthermore, other comonomers may be added particularly for the purpose of controlling the fixability, scratch resistance and solvent resistance of the recorded matter, and controlling the storage stability of the ink.
Examples of other comonomers include hydrophilic monomers (hydrophilic monomers other than the hydrophilic monomers having an anionic group) and / or hydrophobic monomers.
In particular, the fixability and scratch resistance of the recorded material can be controlled by controlling the glass transition point (Tg) of the copolymer (copolymer) covering the colorant particles of the microencapsulated colorant according to the present invention. It is.
When printing on a recording medium such as plain paper or an inkjet-dedicated medium at room temperature with an ink using the microencapsulated color material of the present invention, an aqueous medium (water and / or water) around the microencapsulated color material particles of the present invention is printed. The microencapsulated color material particles come close to each other by penetrating into a recording medium such as plain paper or an inkjet-dedicated medium and being removed from the vicinity of the microencapsulated color material particles. At that time, when the glass transition point (Tg) of the copolymer (copolymer) covering the colorant particles of the microencapsulated colorant is not more than room temperature, the gap between the microencapsulated colorant particles In order to form a film in a state in which the copolymer (copolymer) covering the colorant particles of the microencapsulated colorant is fused and encapsulated (encapsulated) by the capillary pressure generated, The image fixing property and abrasion resistance can be particularly improved. In addition, when the ink using the microencapsulated color material of the present invention is printed on an inkjet-dedicated medium, in particular, glossy media for inkjet, the microencapsulated color material of the present invention has a small particle size and the particle surface Since the hydrophilic groups (especially anionic groups) are regularly and densely oriented toward the aqueous phase, the microencapsulated colorant is packed most closely onto the glossy media, and good packing properties are obtained. Good gloss can be obtained by this and the film forming property.

Generally, in polymer solids, especially amorphous polymer solids, when the temperature is raised from a low temperature to a high temperature, a state where a large amount of deformation occurs with a small force from a state where a very large force is required for slight deformation (glass state). A phenomenon that suddenly changes to a temperature occurs, and the temperature at which this phenomenon occurs is called the glass transition point (or glass transition temperature). Generally, in the differential heat curve obtained by temperature rise measurement with a differential scanning calorimeter, the intersection of the base line when the tangent line is drawn from the bottom of the endothermic peak toward the end point of the endotherm. Let temperature be the glass transition point.
In addition, it is known that other physical properties such as elastic modulus, specific heat, and refractive index also change abruptly at the glass transition point, and it is known that the glass transition point is also determined by measuring these physical properties. ing. In this invention, the glass transition point obtained by the temperature rising measurement with a thermal scanning calorimeter (DSC) was used.
In order to form the microencapsulated color material of the present invention more preferably at room temperature when printing on a recording medium such as plain paper or inkjet dedicated media with water-based ink using the microencapsulated color material of the present invention, The glass transition point (Tg) of the copolymer (copolymer) covering the pigment particles of the microencapsulated colorant is preferably 30 ° C. or lower, more preferably 15 ° C. or lower, and further preferably 10 ° C. or lower. Accordingly, the copolymer (copolymer) covering the colorant particles of the microencapsulated colorant is preferably designed so that the glass transition point is 30 ° C. or less, more preferably 15 ° C. or less, and further It is preferable to design at 10 ° C. or lower. However, when the glass transition point is lower than −20 ° C., the solvent resistance tends to decrease.

  The glass transition point of such a copolymer (copolymer) can be within the above range by appropriately selecting the type and composition ratio of the hydrophobic monomer to be used. If the printed material can be heated at a temperature higher than the glass transition point (Tg) of the copolymer (copolymer) covering the colorant particles of the microencapsulated colorant, the glass transition point Since the glass transition temperature may exceed 30 ° C. because the film can be formed if the temperature is lower than the heating temperature, in this case, it is necessary to attach a heating mechanism to the ink jet recording apparatus, etc. Since problems such as an increase in cost of the apparatus occur, the glass transition point is preferably set to 30 ° C. or lower.

  Examples of the hydrophilic monomer other than the hydrophilic monomer having an anionic group include those having a hydroxyl group, an ethylene oxide group, an amide group, or an amino group as the hydrophilic group. These hydrophilic groups are considered to exist along with the anionic group in the direction of the water phase on the capsule surface, and since they easily form hydrogen bonds with the OH groups of the cellulose fibers of paper, they have these hydrophilic groups. When ink jet recording ink using a microencapsulated colorant obtained in combination with a hydrophilic monomer as a colorant is ejected onto plain paper, the colorant is more easily adsorbed onto the cellulose fiber of plain paper, Since it is easy to stay in the vicinity of the landing position and in the vicinity of the paper surface, image density can be obtained and bleeding can be suppressed.

  Examples of hydrophilic monomers other than hydrophilic monomers having an anionic group include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, etc. having an OH group, ethyl diethylene glycol acrylate having an ethylene oxide group, polyethylene glycol Monomethacrylate, methoxypolyethylene glycol methacrylate, etc., acrylamide having an amide group, N, N-dimethylacrylamide, etc., N-methylaminoethyl methacrylate containing amino group, N-methylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate Acrylic acid or meta, such as diethylaminoethyl methacrylate, diethylaminoethyl methacrylate Alkylamino esters of silyl acid; unsaturated amides having alkylamino groups such as N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide, N, N-dimethylaminopropylacrylamide, etc. And vinyl ethers having an alkylamino group such as dimethylaminoethyl vinyl ether; vinyl imidazole, N-vinyl-2-pyrrolidone, and the like.

  In order to satisfy the required properties such as fixability, scratch resistance, water resistance, and solvent resistance of the recorded matter, a hydrophobic monomer can be preferably used. That is, the microencapsulated coloring material according to the present invention is a cationic hydrophilic monomer and / or cationic polymerization in which coloring material particles having an anionic group on the surface have a cationic group, a hydrophobic group, and a polymerizable group. Repeating units derived from a repeating structural unit derived from an anionic surfactant, an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group and / or a hydrophilic monomer having an anionic group In addition to the structural unit, it may further have a repeating structural unit derived from a hydrophobic monomer.

The hydrophobic monomer has at least a hydrophobic group and a polymerizable group in its structure, and the hydrophobic group is selected from the group consisting of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Can be illustrated. Examples of the aliphatic hydrocarbon group include a methyl group, an ethyl group, and a propyl group. Examples of the alicyclic hydrocarbon group include a cyclohexyl group, a dicyclopentenyl group, a dicyclopentanyl group, and an isobornyl group, and an aromatic hydrocarbon group. Examples thereof include a benzyl group, a phenyl group, and a naphthyl group.
The polymerizable group is an unsaturated hydrocarbon group capable of radical polymerization, and is preferably selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. .

  Specific examples of the hydrophobic monomer include styrene and methylstyrene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, p-chloromethylstyrene, divinylbenzene, and other styrene derivatives; methyl acrylate, ethyl acrylate, acrylic acid n-butyl, butoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, tetrahydrofurfuryl acrylate, isobol Monofunctional acrylic esters such as nyl acrylate; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate Butoxymethyl methacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, etc. Monofunctional methacrylic acid esters of allyl such as allylbenzene, allyl-3-cyclohexanepropionate, 1-allyl-3,4-dimethoxybenzene, allylphenoxyacetate, allylphenylacetate, allylcyclohexane, allyl polycarboxylate Compounds; fumaric acid, maleic acid, itaconic acid esters; N-substituted maleimide, cyclic olefin and other radically polymerizable groups Monomer, and the like that.

  As the hydrophobic monomer, those satisfying the above-mentioned required characteristics are appropriately selected, and the addition amount thereof is arbitrarily determined.

In addition, the polymer that coats the colorant particles preferably further has a repeating structural unit derived from a crosslinkable monomer.
By having a repeating structural unit derived from a crosslinkable monomer, a crosslinked structure is formed in the polymer, and solvent resistance (the property that the solvent contained in the water-based ink does not easily enter the polymer coating the colorant particles) ) Can be improved.
When the solvent penetrates the inside of the polymer that coats the colorant particles, the polymer swells or deforms, and the orientation state of the anionic group of the colorant particles facing the aqueous medium is disturbed. The dispersion stability of the material may decrease. In such a case, by forming a crosslinked structure in the polymer that coats the color material particles, the solvent resistance of the microencapsulated color material is improved, and the ink composition coexisting with the water-soluble organic solvent is more dispersed. It is excellent in stability.

  Examples of the crosslinkable monomer that can be used in the present invention include compounds having two or more unsaturated hydrocarbon groups selected from a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. For example, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, allyl acrylate, bis (acryloxyethyl) hydroxyethyl isocyanurate, bis (acryloxy) Neopentyl glycol) adipate, 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, Pyrene glycol diacrylate, polypropylene glycol diacrylate, 2-hydroxy-1,3-diaacryloxypropane, 2,2-bis [4- (acryloxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) ) Phenyl] propane, 2,2-bis [4- (acryloxyethoxy diethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy polyethoxy) phenyl] propane, hydroxypentyl glycol neopentyl glycol Diacrylate, 1,4-butanediol diacrylate, dicyclopentanyl diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylolpropane tetraacrylate, penta Lithritol triacrylate, tetrabromobisphenol A diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, tris (acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol Dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate 2-hydroxy-1,3-dimetac Liloxypropane, 2,2-bis [4- (methacryloxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxydiethoxy) ) Phenyl] propane, 2,2-bis [4- (methacryloxyethoxypolyethoxy) phenyl] propane, tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate, dipentaerythritol hexamethacrylate, glycerol dimethacrylate, hydroxybiba Neopentyl glycol dimethacrylate phosphate, dipentaerythritol monohydroxypentamethacrylate, ditrimethylolpropane tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol Tetramethacrylate, triglycerol dimethacrylate, trimethylolpropane trimethacrylate, tris (methacryloxyethyl) isocyanurate, allyl methacrylate, divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diethylene glycol bis allyl carbonate.

  Moreover, it is preferable that the polymer that coats the colorant particles further has a repeating structural unit derived from a monomer represented by the following general formula (2).

[However, R ¹ represents a hydrogen atom or a methyl group. R ² represents a t-butyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group. m represents an integer of 0 to 3, and n represents an integer of 0 or 1. ]

The R ² group, which is a “bulky” group derived from the monomer represented by the general formula (2) in the polymer, reduces the flexibility of the molecule of the polymer, that is, restricts the mobility of the molecule. The mechanical strength and heat resistance of the polymer are improved, and the printed matter with ink using the microencapsulated color material of this embodiment coated with the polymer can have excellent abrasion resistance and durability. . In addition, since the R ² group, which is a “bulky” group, is present in the polymer, the penetration of the organic solvent into the polymer can be suppressed. Therefore, the microencapsulated colorant of this embodiment has excellent solvent resistance. In an ink composition in which a water-soluble organic solvent coexists, more stable ejection properties, dispersibility, and long-term storage can be obtained.

In the general formula (2), examples of the alicyclic hydrocarbon group represented by R ² include a cycloalkyl group, a cycloalkenyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, an adamantane group, a tetrahydrofuran group, and the like. Is mentioned.

As described above, a polymer having a repeating structural unit derived from a crosslinkable monomer and a polymer having a repeating structural unit derived from the monomer represented by the general formula (2) have high Tg, mechanical strength, and heat resistance. There is an advantage that it has excellent properties and solvent resistance.
However, the microencapsulated color material coated with such a polymer is inadequate in plasticity of the polymer and tends to be in a state in which it is difficult to adhere to the recording medium. As a result, the microencapsulated color material is fixed to the recording medium. Property and abrasion resistance may be reduced.

  On the other hand, since the polymer having a repeating structural unit derived from a monomer having a long-chain alkyl group among the above-mentioned hydrophobic monomers has flexibility, the repeating structural unit derived from a crosslinkable monomer and / or a general formula By adjusting the ratio of the repeating structural unit derived from the monomer represented by (2) and the repeating structural unit derived from the monomer having a long-chain alkyl group, the mechanical strength and resistance to the extent that the plasticity is not impaired. It can be set as the polymer which has solvent property. The microencapsulated color material coated with such a polymer is easy to adhere to the recording medium, has excellent fixability, and has excellent solvent resistance. Therefore, the ink using the microencapsulated color material can obtain excellent ejection stability, dispersion stability, and long-term storage stability even in an ink composition in which a water-soluble organic solvent coexists. In addition, a printed matter obtained from an ink using the microencapsulated color material has good fixability and can be excellent in abrasion resistance, durability, and solvent resistance.

  Moreover, the following are mentioned as a specific example of the monomer represented by the said General formula (2).

  Copolymerization of cationic hydrophilic monomers and / or cationic polymerizable surfactants with anionic polymerization surfactants and / or hydrophilic monomers having an anionic group, in addition to these, hydrophobic monomers and crosslinkable monomers Or the copolymerization with the monomer represented by the general formula (2) is preferably initiated by addition of a polymerization initiator, and as such a polymerization initiator, a water-soluble polymerization initiator is preferable, Examples include potassium persulfate, ammonium persulfate, sodium persulfate, 2,2-azobis- (2-methylpropionamidine) dihydrochloride, or 4,4-azobis- (4-cyanovaleric acid).

Then, the production of the microencapsulated color material according to the embodiment of the present invention is carried out by adding the cationic hydrophilic monomer and / or cationic polymerization to an aqueous dispersion of color material particles having an anionic group on the surface as a hydrophilic group. If necessary, water or water and an aqueous solvent are added and mixed, and after irradiation with ultrasonic waves for a predetermined time, an anionic polymerizable surfactant and / or hydrophilicity having an anionic group Monomers (in addition to these, the above-mentioned hydrophobic monomers, crosslinkable monomers, monomers represented by the general formula (2) can also be added) and water are added if necessary, and then ultrasonic waves are irradiated again for a predetermined time. The mixture is then dispersed and heated to a predetermined temperature (temperature at which the polymerization initiator is activated) while performing ultrasonic irradiation and stirring, and the polymerization initiator is added to activate the polymerization initiator to perform emulsion polymerization. By It can be carried out to apply.
When the hydrophobic monomer is used, more specifically, a cationic hydrophilic monomer having a cationic group, a hydrophobic group, and a polymerizable group in the aqueous dispersion of the colorant particles having the anionic group on the surface. And / or a step of adding a cationic polymerizable surfactant and mixing and irradiating with ultrasonic waves, a step of adding and mixing a hydrophobic monomer, and an anionic group, a hydrophobic group and a polymerizable group. Comprising an anionic polymerizable surfactant having and / or a hydrophilic monomer having the anionic group, mixing and irradiating with ultrasonic waves, and adding a polymerization initiator to emulsion polymerization. It can manufacture more suitably by implementing in the said process order.

When using the crosslinkable monomer and / or the monomer represented by the general formula (2), more specifically, a cationic group is added to the aqueous dispersion of the colorant particles having the anionic group on the surface. A step of adding and mixing a cationic hydrophilic monomer and / or a cationic polymerizable surfactant having a hydrophobic group and a polymerizable group and irradiating with ultrasonic waves; and a crosslinkable monomer and / or the above general formula A step of adding and mixing the monomer represented by (2), an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group and / or a hydrophilic monomer having the anionic group In addition, it comprises a process of mixing and irradiating with ultrasonic waves, and a process of adding a polymerization initiator and emulsion polymerization.
Furthermore, when using the crosslinkable monomer and / or the monomer represented by the general formula (2), more specifically, the aqueous dispersion of the colorant particles having the anionic group on the surface thereof is cationic. A step of adding and mixing a cationic hydrophilic monomer and / or a cationic polymerizable surfactant having a group, a hydrophobic group and a polymerizable group, and irradiating with ultrasonic waves; A step of adding and mixing the monomer represented by the general formula (2) and a monomer having a long chain alkyl group, an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group, and / or It consists of a step of adding and mixing a hydrophilic monomer having an anionic group and irradiating with ultrasonic waves and a step of emulsion polymerization by adding a polymerization initiator, and by carrying out in the order of the steps. Ri can be preferably produced.

  According to the emulsion polymerization method of the present invention, first, a hydrophilic group (particularly an anionic group) on the surface of a colorant particle having an anionic group on the surface thereof is replaced with a cationic hydrophilic monomer and / or a cationic polymerizable surfactant. By adsorbing the agent, then adding a hydrophobic monomer, adding an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group, and irradiating with ultrasonic waves, the colorant particles are surrounded. The arrangement form of the existing polymerizable surfactant and monomer is very highly controlled, and in the outermost layer, a state in which anionic groups are oriented toward the aqueous phase is formed. Then, by emulsion polymerization, the monomer is converted into a polymer in this highly controlled form, and the microencapsulated color material according to the embodiment of the present invention is obtained. According to said method, the production | generation of the water-soluble oligomer and polymer which are a by-product can be reduced. As a result, the viscosity of the obtained dispersion liquid of the microencapsulated color material can be reduced, and a purification process such as ultrafiltration can be further facilitated. In addition, the recording head has excellent ejection stability, and it is difficult to bleed even on plain paper, and a high-color and high-density printed image can be obtained.

The polymerization reaction preferably uses a reaction vessel equipped with an ultrasonic generator, a stirrer, a reflux condenser, a dropping funnel and a temperature controller.
The polymerization reaction is performed by raising the temperature to the cleavage temperature of the water-soluble polymerization initiator added to the reaction system to cleave the polymerization initiator to generate an initiator radical. It starts by attacking unsaturated groups or unsaturated groups of monomers.
The addition of the polymerization initiator into the reaction system can be suitably carried out by dropping an aqueous solution obtained by dissolving a water-soluble polymerization initiator in pure water into the reaction vessel. Activation of the polymerization initiator in the reaction system can be suitably carried out by raising the temperature of the aqueous dispersion to a predetermined polymerization temperature.
The polymerization temperature is preferably in the range of 60 ° C. to 90 ° C., and the polymerization time is preferably 3 hours to 10 hours. After the polymerization is completed, it is preferable to perform filtration after adjusting the pH within the range of 7.0 to 9.0. Filtration is preferably ultrafiltration.
When the colorant particles having an anionic group on the surface as a hydrophilic group are not in the state of an aqueous dispersion, the dispersion is performed as a pretreatment using a general disperser such as a ball mill, a roll mill, an Eiger mill, or a jet mill. It is preferable to carry out the treatment.

  In the microencapsulated color material according to the embodiment of the present invention obtained as described above, the color material particles having a small average particle diameter are completely covered with the polymer layer (no defect portion), and the hydrophilicity of the polymer layer Since the functional group is considered to be regularly oriented toward the aqueous solvent (see FIGS. 2 and 4), it has a high dispersion stability with respect to the aqueous solvent.

  Although the microencapsulated color material according to the embodiment of the present invention has been described above, the particle size of these microencapsulated color materials is preferably 400 nm or less, more preferably 300 nm or less, and particularly preferably 20 to 200 nm. .

  In addition, the content of the microencapsulated color material in the aqueous ink of the present invention is preferably 1% by weight to 20% by weight, more preferably 3% by weight to 15% by weight with respect to the total weight of the ink. . In particular, 5% by weight to 15% by weight is preferable in order to obtain high printing density and high color developability together with good ejection stability.

  Next, the compound represented by the following formula (1) contained in the aqueous ink of the present invention will be described.

(In the formula, R ₁ and R ₂ each independently represent an alkyl group having 1 to 10 carbon atoms, m and n are respectively the number of repeating units, and m + n is 0 to 10 on average.)

In the compound of the above formula (1), R ₁ and R ₂ are each independently an alkyl group having 1 to 10 carbon atoms, m and n are respectively the number of repeating units, and m + n is 0 to 10 on average. However, there is little bleeding on plain paper and high color development, and it is possible to create ink that has fixability in addition to sufficient color development on dedicated paper. In order to obtain a water-based ink that can secure a sufficient line width, the carbon number of R ₁ + R ₂ is preferably 5 or more and 15 or less, and m + n is preferably in the range of 0 to 7.

  Further, the content of the compound of the above formula (1) in the aqueous ink of the present invention is preferably 0.1 to 20% by weight, more preferably 0.3 to 10% by weight, based on the total weight of the ink. . In order to obtain particularly good glossiness and image clarity, 0.5 to 10% by weight is preferable.

  Moreover, it is good to use a C4-C10 linear or branched 1, 2- alkylene glycol as a penetrant added simultaneously, and the addition amount is good to be 1.5 to 5 weight%. When the amount is 1.5% by weight or more, the bleeding is small and the printing quality is improved.

  Further, it is preferable that at least a surfactant is added to the water-based ink described above. The surfactant is preferably one or more selected from acetylene glycol surfactants, acetylene alcohol surfactants, and silicon surfactants. By using these surfactants, bleeding on plain paper is further reduced, and the line width on the ink jet dedicated medium can be adjusted to an appropriate level.

  It is preferable to include 0.1% by weight or more and 5% by weight or less of one or more selected from the above-mentioned acetylene glycol surfactants, acetylene alcohol surfactants, and silicon surfactants. More preferably, the addition amount is 0.15 to 2% by weight. Within this range, there is little bleeding, there is little increase in viscosity, good ejection stability can be obtained, and printing quality can be improved.

  Further, it is preferable to add at least glycol ether to the above-mentioned water-based ink. With these additions, the drying property of the print is improved, and even if printing is performed continuously, the previous print portion is not transferred to the back side of the next medium. Become.

  The glycol ether is preferably an alkylene glycol having 10 or less repeating units and an alkyl ether having 3 to 10 carbon atoms. Of these, di (tri) ethylene glycol monobutyl ether and / or (di) propylene glycol monobutyl ether are preferable. Moreover, it is preferable that the addition amount of the substance consisting of one or more selected from the above-mentioned (tri) ethylene glycol monobutyl ether and (di) propylene glycol monobutyl ether is 0.5 wt% or more and 30 wt% or less. . More preferably, they are 1 weight% or more and 15 weight% or less. When the content is 0.5% by weight or more, a good penetrability effect is obtained, the printing quality is improved, and when the content is within 30% by weight, the increase in the viscosity of the ink is small, so that good ejection stability is obtained.

  At least one selected from the above-mentioned acetylene glycol surfactants, acetylene alcohol surfactants and silicon surfactants, and di (tri) ethylene glycol monobutyl ether and (di) propylene glycol monobutyl ether It is preferable to add one or more selected at the same time. In ordinary paper such as PPC paper, acetylene glycol and / or acetylene alcohol surfactant and at least one selected from di (tri) ethylene glycol monobutyl ether and (di) propylene glycol monobutyl ether are used at the same time. Bleeding is reduced and print quality is improved.

  One or more selected from the above-mentioned acetylene glycol surfactants, acetylene alcohol surfactants and silicon surfactants is 0.1% by weight, and di (tri) ethylene glycol monobutyl ether and ( It is preferable that at least one selected from di) propylene glycol monobutyl ether is 1% by weight or more. One or more selected from acetylene glycol surfactants, acetylene alcohol surfactants, and silicon surfactants have the effect of improving permeability in small amounts. One or more selected from di (tri) ethylene glycol monobutyl ether and (di) propylene glycol monobutyl ether is 1% by weight or more, so that the printing quality is further improved.

  The aqueous ink of the present invention is preferably formed by further adding 2-pyrrolidone. By adding 2-pyrrolidone, ejection stability is improved. The preferable addition amount is 1 wt% or more and 15 wt% or less. When the content is 1% by weight or more, the discharge stability can be improved. When the content is 15% by weight or less, the effect on the viscosity is small. More preferably, they are 1.5 weight% or more and 5 weight% or less.

  Furthermore, the water-based ink of the present invention is preferably formed by adding a moisturizing agent in order to prevent the ink from drying and clogging in front of the nozzle, and the moisturizing agent is preferably a substance having two or more hydroxyl groups. Glycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having a number average molecular weight of 400 or less, trimethylol (having 6 or less carbon atoms) alkane, aldose, ketose and sugar alcohol. preferable. Examples of aldoses, ketoses and sugar alcohols include monosaccharides and polysaccharides, such as glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitolose, maltose, cellobiose, sucrose, trehalose, maltotriose etc. In addition, alginic acid and a salt thereof, cyclodextrins, and celluloses can be used. The addition amount is 5 to 50% by weight. When the amount is 5% by weight or more, a moisturizing effect is obtained, and when the amount is 50% by weight or less, there is little influence on the viscosity, and good ejection stability is obtained.

The water-based ink in the present invention is a dissolution aid, a penetration control agent, a viscosity modifier, a pH adjuster, a dissolution aid, an antioxidant and an antifungal agent for the purposes of standing stability and stable ejection from an ink ejection head. Various additives may be added.
Hereinafter, they will be exemplified.
It is preferable to add a water-soluble glycol to suppress drying on the nozzle surface of an ink jet or the like. Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and a molecular weight of 2000. The following polyethylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, meso There are erythritol and pentaerythritol.

  In addition, it is compatible with water and can improve the solubility of glycol ethers and ink components that are poorly soluble in water contained in the ink, and can further improve the permeability to a recording medium such as PPC paper. As examples, ethanol, methanol, butanol, propanol, isopropanol and other C1-C4 alkyl alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono- so-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1- Methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono Ethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol Glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, and other glycol ethers, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane, etc. These can be appropriately selected and used.

  In addition, other surfactants can be added to the water-based ink of the present invention in order to control the permeability to a medium such as paper or special paper. The surfactant to be added is preferably a surfactant having good compatibility with the ink system shown in this embodiment, and among the surfactants, those having high permeability and stability are preferable. Examples thereof include amphoteric surfactants and nonionic surfactants. Amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine and other imidazoline derivatives. is there. Nonionic surfactants include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene Ethers such as ethylene alkyl ether and polyoxyalkylene alkyl ether (polyoxypropylene polyoxyethylene alkyl ether), polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan mono Stearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, Ester such as polyoxyethylene stearate, and the like other fluorine alkyl esters, fluorine-containing surfactants such as perfluoroalkyl carboxylates.

  Moreover, amines such as diethanolamine, triethanolamine, propanolamine and morpholine as pH adjusters, solubilizers or antioxidants and their modified products, inorganic salts such as potassium hydroxide, sodium hydroxide and lithium hydroxide, Ammonium hydroxide, quaternary ammonium hydroxide (tetramethylammonium, etc.), potassium carbonate (hydrogen), carbonate (hydrogen) sodium, carbonates such as lithium carbonate (hydrogen), other phosphates, or N-methyl-2- Examples include ureas such as pyrrolidone, urea, thiourea, and tetramethylurea, allophanates such as allophanate and methylallohanate, biurets such as biuret, dimethylbiuret, and tetramethylbiuret, and L-ascorbic acid and salts thereof. Commercially available antioxidants, ultraviolet absorbers and the like can also be used. Examples include Ciba-Geigy Tinuvin 328, 900, 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or lanthanide oxides.

  Furthermore, examples of the viscosity modifier include rosins, alginic acids, polyvinyl alcohol, hydroxypropylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyacrylate, polyvinylpyrrolidone, gum arabic starch and the like.

  In the present invention, polymer fine particles may be added. The addition amount is 0.1 wt% or more and 10 wt% or less. More preferably, they are 1 weight% or more and 8 weight% or less, More preferably, they are 2 weight% or more and 6 weight% or less. In this range, there is little influence on the viscosity of the ink, and the rub resistance can be improved.

  The polymer fine particles are preferably used in the form of a polymer emulsion in which water is a dispersion. Further, as the polymer fine particles to be used, those produced by ordinary emulsion polymerization can be used. Moreover, the thing disperse | distributed in water using the self-emulsification property of polymer fine particle, and the thing which disperse | distributed polymer fine particle in water using an emulsifier can also be used.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples.
Here, the “introduced amount of hydrophilic group on the surface of the pigment particle” shown below was determined by the following method.
"Quantification of introduced amount of anionic group"
(When an anionic group is introduced by a sulfonating agent)
Pigment particles whose surface has been treated with a sulfonating agent are treated by an oxygen flask combustion method and absorbed in a 0.3% aqueous hydrogen peroxide solution, and then sulfate ions (divalent) are obtained by an ion chromatography method (Dionex Corporation; 2000i). ) Was quantified, and this value was converted to a sulfonic acid group and expressed as a molar amount (mmol / g) per 1 g of pigment.
(When an anionic group is introduced by a carboxylating agent)
As a method, the Twizel method is used. Diazomethane is dissolved in a suitable solvent and added dropwise to exchange all active hydrogen on the surface of the pigment particles with methyl groups. To the pigment thus treated, hydroiodic acid having a specific gravity of 1.7 is added and heated to vaporize methyl groups as methyl iodide. The methyl iodide gas is trapped with a silver nitrate solution and precipitated as methyl iodide. The amount of the original methyl group, that is, the amount of active hydrogen was measured from the weight of the silver iodide, and was shown as the molar amount (mmol / g) per 1 g of pigment. That is, the amount of active hydrogen on the pigment particle surface corresponds to the amount of carboxylic acid groups.

“Preparation of cyan pigment particle“ P1 ”having an anionic group on its surface”
20 parts of a phthalocyanine pigment (CI Pigment Blue 15: 3) is mixed with 500 parts of quinoline, and Eiger Motor Mill M250 type (manufactured by Eiger Japan Co., Ltd.) is used for 2 hours under conditions of 70% bead filling and a rotational speed of 5000 rpm. The mixture of the dispersed pigment paste and solvent was transferred to an evaporator, heated to 120 ° C. while reducing the pressure to 30 mmHg or less, and water contained in the system was distilled off as much as possible, and the temperature was controlled to 160 ° C. Next, 20 parts of a sulfonated pyridine complex is added and allowed to react for 8 hours. After completion of the reaction, it is washed several times with excess quinoline, poured into water, and filtered to give a cyan pigment having a hydrophilic group (anionic group) on the surface. Particles “P1” were obtained.
The amount of introduced anionic groups in the obtained cyan pigment particles “P1” was 0.04 mmol / g.

“Preparation of magenta pigment particle“ P2 ”having an anionic group on its surface”
In “Preparation of cyan pigment particles“ P1 ”having an anionic group on the surface”, 20 parts of a phthalocyanine pigment (CI Pigment Blue 15: 3) is added to an isoindolinone pigment (CI Pigment Red 122). ) A magenta pigment particle “P2” having an anionic group on the surface was obtained by the same treatment method except that the amount was changed to 20 parts.
The amount of anionic groups introduced into the obtained magenta pigment particles “P2” was 0.06 mmol / g.

"Manufacture of microencapsulated pigment" MCP1 ""
Add 1.0 g of dimethylaminoethyl methyl chloride methacrylate as a cationic polymerizable hydrophilic monomer to an aqueous dispersion in which 100 g of cyan pigment particles “P1” having an anionic group are dispersed in 500 g of ion-exchanged water, and mix. After that, it was processed by irradiating with ultrasonic waves for 15 minutes. Next, 17.3 g of benzyl methacrylate, 7.7 g of dodecyl methacrylate and 0.05 g of diethylene glycol dimethacrylate were mixed and mixed with stirring, and the anionic polymerizable surfactant Aqualon KH- previously dissolved in 50 g of ion-exchanged water was mixed. As a hydrophilic monomer, 2.07 g of 2-acrylamido-2-methylpropane sulfonic acid as a hydrophilic monomer was added, and the mixture was again irradiated with ultrasonic waves for 30 minutes. This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After the internal temperature of the reaction vessel was raised to 80 ° C., an aqueous potassium persulfate solution in which 0.6 g of potassium persulfate was dissolved as a polymerization initiator was added dropwise to 20 g of ion-exchanged water. Polymerized for hours. After completion of the polymerization, the pH was adjusted to 8 with a 2 mol / l aqueous potassium hydroxide solution, and the mixture was filtered through a membrane filter having a pore size of 1 μm to remove coarse particles to obtain a desired microencapsulated pigment “MCP1” dispersion.
The volume average particle size of the obtained dispersion was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 110 nm. The obtained dispersion is diluted 100 times with ion-exchanged water, pretreated, the particles are observed with a scanning electron microscope, and the aspect ratio and Zingg index are obtained by measuring the short diameter, long diameter, and thickness of the particles. As a result, the aspect ratio was 1.0 and the Zingg index was 1.0. The obtained dispersion was dried at room temperature, and the glass transition point of the coated polymer was measured using a thermal scanning calorimeter (differential scanning calorimeter: DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). ° C.

"Manufacture of microencapsulated pigment" MCP2 ""
1.25 g of dimethylaminoethyl methyl methacrylate as a cationic polymerizable hydrophilic monomer is added to and mixed with an aqueous dispersion in which 100 g of magenta pigment particles “P2” having an anionic group are dispersed in 500 g of ion-exchanged water. After that, ultrasonic waves were irradiated for 15 minutes. Next, 12 g of benzyl methacrylate, 8 g of dodecyl methacrylate, 3.9 g of anionic polymerizable surfactant Aqualon KH-10, 2.07 g of 2-acrylamido-2-methylpropanesulfonic acid and 50 g of ion-exchanged water as hydrophilic monomers. The mixture was added and mixed, and again irradiated with ultrasonic waves for 30 minutes. This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After the internal temperature of the reaction vessel was raised to 80 ° C., an aqueous potassium persulfate solution in which 0.6 g of potassium persulfate was dissolved as a polymerization initiator was added dropwise to 20 g of ion-exchanged water. Polymerized for hours. After completion of the polymerization, the pH was adjusted to 8 with a 2 mol / l potassium hydroxide aqueous solution, and the mixture was filtered through a membrane filter having a pore size of 1 μm to remove coarse particles to obtain a dispersion of the desired microencapsulated pigment “MCP2”.
The volume average particle diameter of the obtained dispersion was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 300 nm. The obtained dispersion is diluted 100 times with ion-exchanged water, pretreated, the particles are observed with a scanning electron microscope, and the aspect ratio and Zingg index are obtained by measuring the short diameter, long diameter, and thickness of the particles. As a result, the aspect ratio was 1.0 and the Zingg index was 1.0. The obtained dispersion was dried at room temperature, and the glass transition point of the coated polymer was measured using a thermal scanning calorimeter (differential scanning calorimeter: DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). 7 ° C.

Moreover, as a comparative example, Cabjet 250C, 260M pigment (trade name, surface-treated pigment manufactured by Cabot) and a pigment prepared by the method described below were used.
"Manufacture of cyan pigments"
A reaction vessel was charged with 200 g of methyl ethyl ketone, heated to 70 ° C. with stirring under a nitrogen seal, 170 g of styrene, 5 g of α-methyl styrene, 65 g of butyl methacrylate, 10 g of lauryl methacrylate, 17 g of acrylic acid, and 20 g of polymerization initiator perbutyl O. A mixed solution consisting of 2 was added dropwise over 2 hours, reacted for another 10 hours, 1 g of t-dodecyl mercaptan dissolved in 20 g of methyl ethyl ketone was added, and further reacted for 5 hours to obtain a vinyl polymer solution.
10 g of the above polymer solution was placed in a stainless steel beaker and C.I. I. Pigment Blue 15: 3 40 g was mixed and stirred, and further dispersed with a nanomizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.). This was again transferred to a stainless steel beaker, 300 g of ion-exchanged water was added while stirring at room temperature, and a 10% NaOH aqueous solution was further added and stirred with a homogenizer until the pH reached 8.5 to 9.5. Methyl ethyl ketone was removed from this using a rotary evaporator, 10% NaOH aqueous solution was added until the pH was 8.5 to 9.5, and the mixture was stirred for 1 hour. To this, ion exchange water was added to prepare a solid content concentration of 20% to obtain a cyan pigment.
"Manufacture of magenta pigments"
In the production of the cyan pigment, C.I. I. Pigment Blue 15: 3 to C.I. I. A magenta pigment was obtained by the same treatment method except that the pigment red 122 was used.

[Examples 1-2 and Comparative Examples 1-2]
Using the pigments described above, aqueous inks of Examples 1-2 and Comparative Examples 1-2 were prepared based on the compositions shown in Table 1 below.

  In addition, DMH-20 in the said Table 1 is a compound of Formula (1), and has the following structures made by Nippon Emulsifier Co., Ltd.

(Where m + n = 2)

Table 2 below shows the evaluation of the glossiness of the recorded matter using the water-based inks of Examples 1-2 and Comparative Examples 1-2.
The glossiness is determined by printing each water-based ink on photo paper <glossy> (manufactured by Seiko Epson Corporation) at 1440 × 720 dpi using an inkjet printer EM-930C (manufactured by Seiko Epson Corporation) with an incident angle of 45 The specular gloss of the recording surface was measured with an automatic goniophotometer (GP-200, manufactured by Murakami Color Research Laboratory). The results were evaluated according to the following criteria.

A: Glossiness of 16 or more B: Glossiness in the range of 11-15 C: Glossiness in the range of 5-10 D: Glossiness in the range of 1-4

  As is clear from the results in Table 2, the water-based inks of Examples 1 and 2 have good glossiness.

Next, Table 3 below shows the evaluation of the image clarity of the recorded matter using the water-based inks of Examples 1-2 and Comparative Examples 1-2.
The image clarity of each water-based ink was solid-printed at 1440 × 720 dpi on photographic paper <glossy> (manufactured by Seiko Epson Corporation) using an ink jet printer EM-930C (manufactured by Seiko Epson Corporation), and an incident angle of 45 The image clarity of the recording surface was measured with a touch panel type image clarity measuring instrument (ICM-1T Suga Test Instruments). The results were evaluated according to the following criteria.

A: Image clarity is 26 or more B: Image clarity is in the range of 21-25 C: Image clarity is in the range of 11-20 D: Image clarity is in the range of 1-10

  As is apparent from the results in Table 3, it can be seen that the aqueous inks of Examples 1 and 2 have good image clarity.

[Examples 3 to 5 and Comparative Examples 3 to 5]
Based on the compositions shown in Table 4 below, aqueous inks of Examples 3 to 5 and Comparative Examples 3 to 5 were prepared.

  In addition, BEPD in the said Table 4 is called a butyl ethyl propanediol, is a compound of Formula (1), and has the following structure made from Kyowa Hakko Chemical Co., Ltd.

Table 5 below shows the evaluation of the glossiness of the recorded matter using the aqueous inks of Examples 3 to 5 and Comparative Examples 3 to 5.
The glossiness was measured in the same manner as in Examples 1-2 and Comparative Examples 1-2, and the results were evaluated according to the following criteria.

A: Glossiness of 16 or more B: Glossiness in the range of 11-15 C: Glossiness in the range of 5-10 D: Glossiness in the range of 1-4

  As can be seen from the results in Table 5, the water-based inks of Examples 3 to 5 have good glossiness.

Next, Table 6 below shows the evaluation of the image clarity of the recorded matter using the water-based inks of Examples 3 to 5 and Comparative Examples 3 to 5.
The image clarity was measured in the same manner as in Examples 1-2 and Comparative Examples 1-2, and the results were evaluated according to the following criteria.

A: Image clarity is 26 or more B: Image clarity is in the range of 21-25 C: Image clarity is in the range of 11-20 D: Image clarity is in the range of 1-10

  As is clear from the results in Table 6, it can be seen that the water-based inks of Examples 3 to 5 have good image clarity.

The colorant particles having an anionic group on the surface are dispersed in an aqueous solvent and coexist with the cationic hydrophilic monomer and / or the cationic polymerizable surfactant and the anionic polymerizable surfactant. It is a schematic diagram which shows the state which exists. FIG. 2 is a schematic diagram showing a state in which a cationic hydrophilic monomer and / or a cationic polymerizable surfactant and an anionic polymerizable surfactant are polymerized in the dispersed state shown in FIG. 1. The colorant particles having an anionic group on the surface are dispersed in an aqueous solvent and coexist with the cationic hydrophilic monomer and / or the cationic polymerizable surfactant and the anionic polymerizable surfactant. It is a schematic diagram which shows the state which exists. FIG. 4 is a schematic diagram showing a state in which a cationic hydrophilic monomer and / or a cationic polymerizable surfactant and an anionic polymerizable surfactant are polymerized in the dispersed state shown in FIG. 3.

Explanation of symbols

  1 colorant particle, 2 cationic hydrophilic monomer and / or cationic polymerizable surfactant, 3 anionic polymerizable surfactant, 10 hydrophilic group, 11 cationic group, 12, 12 'hydrophobic group, 13 , 13 'polymerizable group, 14, 14' anionic group, 60, 60 'polymer layer (polymer), 100, 100' microencapsulated colorant

Claims (2)

At least the colorant particle having an anionic group on the surface thereof is a repeating structural unit derived from a cationic hydrophilic monomer having a cationic group, a hydrophobic group and a polymerizable group and / or a cationic polymerizable surfactant. Microencapsulation coated with a polymer having an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group and / or a repeating structural unit derived from a hydrophilic monomer having an anionic group A water-based ink comprising a colorant and a compound represented by the following formula (1).

(In the formula, R ₁ and R ₂ each independently represent an alkyl group having 1 to 10 carbon atoms, m and n are respectively the number of repeating units, and m + n is 0 to 10 on average.)   The water-based ink according to claim 1, wherein the color material is a pigment.

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