JP2010180419A - Microencapsulated pigment and method for manufacturing the same, aqueous dispersion, and ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet recording which is excellent in dispersion stability and discharge stability, and is excellent in image-fastness, abrasion resistance and color development, and with which a recorded matter with high print density and with an image hardly blurring is obtained, and to provide a microencapsulated pigment with which the ink is manufactured, a method for manufacturing the same, and its aqueous dispersion. <P>SOLUTION: The microencapsulated pigment comprises pigment particles having cationic groups on their surfaces, which are covered at least with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant. In the method for manufacturing the microencapsulated pigment, the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having cationic groups on their surfaces and mixed therewith, further an ionic polymerizable surfactant is added thereto and mixed therewith, and subsequently a polymerization initiator is added thereto and mixed therewith, and subsequently polymerization is achieved in water by adding a polymerization initiator. The ink for inkjet recording at least includes the microencapsulated pigment and water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a microencapsulated pigment, a method for producing the same, an aqueous dispersion, and an ink for inkjet recording.

  The ink jet recording method is a method of recording characters and figures on the surface of a recording medium such as paper by discharging ink droplets from a fine nozzle head. As an ink jet recording method, an electric signal is converted into a mechanical signal using an electrostrictive element, and ink droplets stored in the nozzle head portion are intermittently ejected to record characters and symbols on the surface of the recording medium, or A part of the ink liquid is rapidly heated at a part near the ejection part of the nozzle head to generate bubbles, and ink droplets are intermittently ejected by the volume expansion caused by the bubbles, and characters and symbols are printed on the surface of the recording medium. A method for recording the image has been put into practical use.

Recently, water-based pigment inks in which pigments are dispersed in water have been provided as inks for inkjet recording. This is because the ink using the pigment has the characteristics that it is superior in water resistance and light resistance compared to the ink using the water-soluble dye. In such a water-based pigment ink, it is generally performed to disperse a pigment in an aqueous dispersion medium using a dispersant such as a surfactant or a polymer dispersant.
For example, Patent Document 1 discloses that in a pigment ink using an acetylene glycol penetrant, a polymer dispersant is used as a dispersant for pigment particles, and water, a nonvolatile organic solvent, or a lower alcohol is used as an aqueous medium. Studies are underway to ensure stability. However, when a dispersant is used for dispersing pigment particles in this manner, the number of elements at the time of ink preparation increases, making it difficult to set desired ink physical properties such as viscosity. Further, the problem that it is difficult to secure the print density in this pigment ink is still unsolved.
Furthermore, in these water-based pigment inks, the dispersant is simply adsorbed on the surface of the pigment particles, and a strong shearing force is applied when the ink liquid is ejected through the thin nozzles of the nozzle head. There may be a tendency that the dispersant adsorbed on the particle surface is detached, the dispersibility is deteriorated, and the ejection becomes unstable. Further, when the water-based pigment ink is stored for a long period of time, there is a case where the dispersibility tends to become unstable.

As another technique for dispersing pigment particles in water, a technique for introducing sulfonic acid groups on the surface of the pigment particles has also been proposed. For example, Patent Document 2 describes a pigment ink containing a sulfonated surface-treated organic pigment obtained by treating an organic pigment dispersed in a solvent having no active protons with a sulfonating agent (conventional example). 1). According to Conventional Example 1, it is said that the pigment ink has excellent dispersion stability and good ejection stability from the nozzles of the recording head (characteristic that the recording head is stably ejected in a certain direction). ing.
Patent Document 3 describes preparing an organic pigment mass that positively charges the surface by treating the organic pigment mass introduced with a sulfonic acid group with a monovalent metal ion. A water-based ink composition containing pigment fine particles prepared from the surface positively charged organic pigment mass, a dispersant, and water and having excellent storage stability (dispersion stability) has been described (Conventional Example 2).

  However, although the ink using the surface-treated pigment particles of Conventional Example 1 and Conventional Example 2 as a colorant is superior in dispersion stability and ejection stability as compared with conventional pigment-based inkjet recording inks, The recorded material obtained by printing on a recording medium such as plain paper or an ink jet recording medium (a recording medium having an ink receiving layer for receiving ink for ink jet recording on its surface) still has insufficient abrasion resistance. It was a thing. This is presumably because the fixability of the surface-treated pigment particles on the recording medium is not good.

On the other hand, a technique using a microencapsulated pigment in which colorant particles are coated with a polymer is known for the purpose of improving the fixability of a pigment contained in a pigment-based inkjet ink to a recording medium.
Patent Documents 4 and 5 propose a method in which pigment fine particles are encapsulated, and Patent Documents 6 to 9 propose a method in which a polymer is graft-polymerized on the surface of pigment particles. Patent Document 10 proposes a method of microencapsulating a hydrophobic powder using an amphiphilic graft polymer. However, when a polymer that has been polymerized in advance is used for microencapsulation, the particle size after encapsulation becomes large. There was a problem of becoming too much.
In addition to the above proposals, Patent Documents 11 to 19 include an ink using a pigment coated with a resin having a film forming property at room temperature by a phase inversion emulsification method, and Patent Documents 20 to 29 include an anionic property by an acid precipitation method. An ink using a pigment coated with a group-containing organic polymer compound has been proposed.

  Further, Patent Documents 30 to 35 propose an ink using a polymer emulsion obtained by impregnating polymer fine particles with a colorant by a phase inversion emulsification method (Conventional Example 3). However, even in the colorant obtained by the phase inversion emulsification method or the acid precipitation method, the polymer adsorbed on the pigment particles may be detached depending on the kind of the organic solvent such as the penetrant used in the ink. In some cases, the ink may be dissolved, and ink dispersion stability, ejection stability, image quality, and the like may not be sufficient. In the ink of Conventional Example 3, since the polymer adsorbed on the pigment particles is desorbed not a little, the pigment content in the ink is limited from the viewpoint of dispersion stability. In addition, the printed image has a low printing density. In particular, when the recording medium is plain paper, there is a problem that image bleeding tends to occur and color developability is low.

JP-A-3-157464 Japanese Patent Laid-Open No. 10-110129 JP-A-11-49974 Japanese Patent Publication No. 7-94634 JP-A-8-59715 JP-A-5-339516 JP-A-8-302227 JP-A-8-302228 JP-A-8-81647 JP-A-5-320276 Japanese Patent Application Laid-Open No. 08-2158015 Japanese Patent Laid-Open No. 08-295837 Japanese Patent Application Laid-Open No. 09-3376 Japanese Patent Laid-Open No. 08-183920 Japanese Patent Laid-Open No. 10-46075 JP-A-10-292143 Japanese Patent Laid-Open No. 11-80633 JP-A-11-349870 JP 2000-7961 A JP-A-9-31360 JP-A-9-217019 JP 9-316353 A Japanese Patent Laid-Open No. 9-104834 Japanese Patent Laid-Open No. 9-151342 Japanese Patent Laid-Open No. 10-140065 JP-A-11-152424 JP-A-11-166145 Japanese Patent Application Laid-Open No. 11-199783 JP-A-11-209672 JP-A-9-286939 JP 2000-44852 A JP 2000-53897 A JP 2000-53898 A JP 2000-53899 A JP 2000-53900 A

The present invention has been made in view of the above problems, and its object is to
(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.
It is an object to provide a microencapsulated pigment capable of producing an ink for inkjet recording satisfying all of the above (1) to (6), a method for producing the same, and an aqueous dispersion.
Another object of the present invention is to provide an ink for ink jet recording that satisfies all of the above (1) to (6).

  As a result of intensive studies, the inventors of the present invention surprisingly produced the specific microencapsulated pigment and used the microencapsulated pigment as a colorant for the ink for inkjet recording. The present invention has been completed by finding that an ink for ink jet recording satisfying all of (1) can be obtained. That is, the technical configuration of the present invention is as follows.

  <1> A microcapsule in which pigment particles having a cationic group on a surface thereof are coated with a polymer having an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group, and a polymerizable group. Pigments.

  <2> By polymerizing an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group and a polymerizable group in an aqueous dispersion in which pigment particles having a cationic group on the surface are dispersed, A microencapsulated pigment obtained by coating the pigment particles with a polymer.

  <3> A repeating structural unit derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group, and a cationic group and a hydrophobic group. A microencapsulated pigment coated with a polymer having a repeating structural unit derived from a cationic polymerizable surfactant having a group and a polymerizable group.

  <4> In an aqueous dispersion in which pigment particles having a cationic group on the surface are dispersed, an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group, a cationic group and a hydrophobic group A microencapsulated pigment obtained by polymerizing a cationic polymerizable surfactant having a polymerizable group and a polymerizable group to coat the pigment particles with a polymer.

  <5> The microencapsulated pigment according to <1> to <4>, wherein the polymer further includes a repeating structural unit derived from a hydrophobic monomer.

  <6> The microencapsulated pigment according to any one of <1> to <5>, wherein the polymer further includes a repeating structural unit derived from a monomer represented by the following general formula (1): .

［ただし、Ｒ¹は水素原子又はメチル基を表す。Ｒ²はｔ−ブチル基、脂環式炭化水素基、芳香族炭化水素基、又はヘテロ環基を表す。ｍは０〜３、ｎは０又は１の整数を表す。］

[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. ]

  <7> The microencapsulated pigment according to any one of <1> to <6>, wherein the polymer further has a crosslinked structure derived from a crosslinkable monomer.

  <8> The microencapsulated pigment according to any one of <1> to <7>, wherein the pigment constituting the pigment particle is carbon black or an organic pigment.

  <9> The cationic group of the pigment particle is selected from the group consisting of a primary amine cation group, a secondary amine cation group, a tertiary amine cation group, and a quaternary ammonium cation group. The microencapsulated pigment according to <1> to <4>.

<10> The anionic group of the anionic polymerizable surfactant is a sulfonate anion group (—SO ₃ ⁻ ), a sulfinate anion group (—RSO ₂ ⁻ : R is a C1-C12 alkyl group or a phenyl group, and The microencapsulated pigment according to <1> to <4>, which is selected from the group consisting of a modified product thereof) and a carboxylate anion group (—COO ⁻ ).

  <11> The micro group according to <1> to <4>, wherein the hydrophobic group of the anionic polymerization surfactant is selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined. Encapsulated pigment.

  <12> The polymerizable group of the anionic polymerization surfactant is an unsaturated hydrocarbon group capable of radical polymerization, and includes a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. The microencapsulated pigment according to <1> to <4>, which is selected from the group consisting of:

  <13> The cationic group of the cationic polymerizable surfactant is selected from the group consisting of a primary amine cation group, a secondary amine cation group, a tertiary amine cation group, and a quaternary ammonium cation group. The microencapsulated pigment according to <3> or <4>.

  <14> The micro group according to <3> or <4>, wherein the hydrophobic group of the cationic polymerization surfactant is selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined. Encapsulated pigment.

  <15> The polymerizable group of the cationic polymerization surfactant is an unsaturated hydrocarbon group capable of radical polymerization, and includes a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. The microencapsulated pigment according to <3> or <4>, which is selected from the group consisting of:

  <16> A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having the cationic group on the surface. A method for producing a microencapsulated pigment, comprising adding an agent and mixing, further adding and emulsifying the anionic polymerizable surfactant, adding a polymerization initiator, and polymerizing in water.

  <17> A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having the cationic group on the surface. After adding and mixing the agent, the hydrophobic monomer, the anionic polymerizable surfactant and the hydrophobic monomer are added and mixed, and after emulsification, a polymerization initiator is added and polymerized in water. Method for producing encapsulated pigment.

  <18> A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface thereof are coated with a polymer, wherein the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having the cationic group on the surface. After adding and mixing the agent, the hydrophobic monomer and the crosslinkable monomer and / or the monomer represented by the general formula (1) and the anionic polymerizable surfactant are added and mixed. After emulsification, the polymerization initiator And producing a microencapsulated pigment by polymerizing in water.

  <19> A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having the cationic group on the surface. A method for producing a microencapsulated pigment, comprising adding an agent, mixing, emulsifying by adding the cationic polymerizable surfactant, adding a polymerization initiator, and polymerizing in water.

  <20> A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface thereof are coated with a polymer, wherein the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having the cationic group on the surface. A microencapsulated pigment characterized in that after adding and mixing an agent, the hydrophobic monomer and the cationic polymerizable surfactant are added and mixed, and after emulsification, a polymerization initiator is added and polymerized in water. Production method.

  <21> A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface thereof are coated with a polymer, wherein the anionic polymerizable surfactant is added to the aqueous dispersion of the pigment particles having the cationic group on the surface. After adding and mixing the agent, the hydrophobic monomer and the crosslinkable monomer and / or the monomer represented by the following general formula (1) and the cationic polymerizable surfactant are added and mixed, and after emulsification, the polymerization initiator And producing a microencapsulated pigment by polymerizing in water.

［ただし、Ｒ¹は水素原子又はメチル基を表す。Ｒ²はｔ−ブチル基、脂環式炭化水素基、芳香族炭化水素基、又はヘテロ環基を表す。ｍは０〜３、ｎは０又は１の整数を表す。］

[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. ]

  <22> The method for producing a microencapsulated pigment according to any one of <16> to <21>, wherein the pigment constituting the pigment particle is carbon black or an organic pigment.

  <23> An aqueous dispersion comprising the microencapsulated pigment according to any one of <1> to <15>.

  <24> An ink for inkjet recording comprising the aqueous dispersion according to <23>.

  <25> Further containing fine polymer particles, the fine polymer particles having an anionic group on the surface thereof, a glass transition temperature of 30 ° C. or less, a volume average particle diameter of 50 to 200 nm, and ions on the particle surface The ink for inkjet recording according to <24>, wherein the functional group is the same kind as the ionic group on the surface of the microencapsulated pigment.

  <26> The ink for inkjet recording according to any one of <24> or <25>, further comprising a water-soluble organic solvent.

According to the microencapsulated pigment and the method for producing the same according to the present invention,
(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.
It is possible to provide a microencapsulated pigment capable of producing an inkjet recording ink satisfying all of the above (1) to (6), a method for producing the same, and an aqueous dispersion.

Further, according to the ink for ink jet recording according to the present invention,
(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 provided.

It is confirmed that the anionic group of the anionic polymerizable surfactant is ionically adsorbed on the cationic group of the pigment particle having a cationic group on the surface, and that the anionic polymerizable surfactant forms a micelle state. It is a schematic diagram shown. FIG. 2 is a schematic view showing that a polymer layer is formed by polymerization of an anionic polymerizable surfactant in FIG. 1. The anionic group of the anionic polymerizable surfactant is ionically adsorbed to the cationic group of the pigment particle having a cationic group on the surface, and the anionic property is applied to the hydrophobic surface of the pigment particle having the cationic group on the surface. It is a schematic diagram showing that a hydrophobic group of a polymerizable surfactant is adsorbed and further a micelle state is formed by an anionic polymerizable surfactant. FIG. 4 is a schematic view showing that a polymer layer is formed by polymerization of an anionic polymerizable surfactant in FIG. 3.

  The microencapsulated pigment according to the present invention is a repeating structural unit in which pigment particles having a cationic group on the surface are derived from an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group, and a polymerizable group. It is characterized by being coated with a polymer having That is, in the microencapsulated pigment according to the present invention, an anionic polymerizable surfactant and / or an anionic group in which pigment particles having a cationic group on the surface have an anionic group, a hydrophobic group, and a polymerizable group. It is characterized by being coated with a polymer having a repeating structural unit derived from a hydrophilic monomer having

  Such a microencapsulated pigment is a method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, and the anionic property is added to an aqueous dispersion of the pigment particles having a cationic group on the surface. It can be suitably produced by adding a polymerizable surfactant and mixing, then adding a polymerization initiator and polymerizing in water, specifically by emulsion polymerization.

  Further, the microencapsulated pigment according to the present invention has a repeating structure in which pigment particles having a cationic group on the surface thereof are derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group. It is characterized by being coated with a polymer having a repeating structural unit derived from the unit and a hydrophobic monomer.

  The present invention relates to a method for producing a microencapsulated pigment in which pigment particles having an anionic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface. After adding an agent and mixing, after adding a hydrophobic monomer and an anionic polymerizable surfactant and emulsifying, then adding a polymerization initiator and polymerizing in water, specifically by emulsion polymerization Can be manufactured.

  In such a microencapsulated pigment, the cationic group on the surface of the pigment particle having a cationic group is ionically bonded to the anionic group of the anionic polymerizable surfactant, and this anionic polymerizable surfactant The hydrophobic group of the agent and the hydrophobic group of another anionic polymerizable surfactant face each other, and the anionic group of the latter anionic polymerizable surfactant is oriented toward the aqueous phase side to form a micelle-like structure. Form. When the polymerization reaction is performed in this state, a polymer layer maintaining the above structure is formed on the surface of the pigment particles. In other words, the arrangement form of the anionic polymerizable surfactant existing around the pigment particles before the polymerization reaction is very highly controlled, and the state where the anionic group is oriented toward the aqueous phase is formed in the outermost shell. The Then, the anionic polymerizable surfactant is converted into a polymer by the emulsion polymerization reaction while maintaining this highly controlled form. Therefore, the structure of the microencapsulated pigment of the present invention is controlled with extremely high accuracy. That is, in the polymerization system, the hydrophilic group on the surface of the pigment particle having a cationic group on the surface and the anionic group of the anionic polymerizable surfactant are ionically bonded to each other, and then the anionic polymerizable property is outermost. Since the anionic group of the surfactant forms a micelle-like structure oriented toward the aqueous phase, and a polymer phase is formed by a polymerization reaction, the arrangement form of the monomers present around the pigment particles before emulsion polymerization Affects the polarization state of the surface of the particles after polymerization, and can therefore be controlled with extremely high accuracy.

Therefore, the microencapsulated pigment according to the embodiment 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 pigment in which a polymer prepared in advance on a pigment is coated by using a phase inversion emulsification method, an acid precipitation method, or the like, the coating on the pigment particles is performed because the polymer is prepared in advance. It is considered that the coating state of the polymer pigment particles satisfying all of the above (1) to (6) is not achieved because the state is limited.

  Here, the aspect ratio (long and short) of the microencapsulated pigment is 1.0 to 1.3, and the Zingg index is 1.0 to 1.3 (more preferably 1.0 to 1.2). It is preferable that 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 pigment becomes flatter and becomes less isotropic. In particular, the items (1), (2), (4) and (6) above. However, sufficient results are not obtained. The method of setting the aspect ratio and Zingg index within the above ranges is not particularly limited, but a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer by the above-described polymerization method can easily satisfy this condition. Can satisfy.

In addition, in a microencapsulated pigment produced by a method other than the polymerization method of the present invention 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 pigment is in the range of the above aspect ratio and Zingg index, it becomes a true sphere, but this tends to make the flow characteristics of the ink 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 pigment particles in the above-described preferred production method. However, the dispersion state of the pigment particles listed below includes estimation.

  FIG. 1 shows that pigment particles 1 having a cationic group 14 as a hydrophilic group on a surface thereof are dispersed in a solvent containing water as a main component (hereinafter also referred to as an aqueous solvent), and an anionic group 11 and a hydrophobic group 12. And an anionic polymerizable surfactant 2 having a polymerizable group 13 and an anionic polymerizable surfactant 3 having an anionic group 11 ', a hydrophobic group 12' and a polymerizable group 13 'coexist. FIG. The anionic polymerizable surfactant 2 is disposed so that the anionic group 11 faces the cationic group 14 of the pigment particle 1, and adsorbs with a strong ionic bond. And with respect to the hydrophobic group 12 and the polymerizable group 13 of the anionic polymerizable surfactant 2, the hydrophobic group 12 ′ and the polymerizable group of the anionic polymerizable surfactant 3 are caused by hydrophobic interaction. 13 ′ faces and the anionic group 11 ′ faces in the direction in which the aqueous solvent exists, that is, in the direction away from the pigment particles 1.

  By polymerizing the polymerizable groups of the anionic polymerizable surfactant 2 and the anionic polymerizable surfactant 3 by adding, for example, a polymerization initiator to such an aqueous dispersion, as shown in FIG. A microencapsulated pigment 100 ′ in which the pigment particles 1 are coated with the polymer layer 60 is produced. Here, since the surface of the polymer layer 60 has the anionic group 11 ′, the microencapsulated pigment 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 instead of the anionic polymerizable surfactant 3, a microencapsulated pigment can be prepared in the same manner. During the polymerization, if necessary, a comonomer copolymerizable with an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group may be present in the aqueous dispersion. In some cases, the polymer layer can be a copolymer layer copolymerized from an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group and a comonomer.

  In addition to the above, the possible dispersion state of the pigment particles is increased in the above-described preferred production method. FIG. 3 shows that pigment particles 1 having a cationic group 14 as a hydrophilic group on a surface thereof are dispersed in a solvent containing water as a main component (hereinafter also referred to as an aqueous solvent), and an anionic group 11 and a hydrophobic group 12. And anionic polymerizable surfactant 2 having a polymerizable group 13, and an anionic polymerizable surfactant 3 having an anionic group 11 ′, a hydrophobic group 12 ′, and a polymerizable group 13 ′. It is a figure which shows the state which coexists. The anionic polymerizable surfactant 2 is disposed so that the anionic group 11 faces the cationic group 14 of the pigment particle 1, and adsorbs with a strong ionic bond. And with respect to the hydrophobic group 12 and the polymerizable group 13 of the anionic polymerizable surfactant 2, the hydrophobic group 12 ′ and the polymerizable group of the anionic polymerizable surfactant 3 are caused by hydrophobic interaction. 13 ′ faces and the anionic group 11 ′ faces in the direction in which the aqueous solvent exists, that is, in the direction away from the pigment particles 1.

  The surface of the pigment particle 1 has a cationic group 14 chemically bonded at a specific density, and has a hydrophobic region 50 between the cationic groups 14, and the hydrophobic region 50 includes, for example, an anion. The hydrophobic group 12 ″ and the polymerizable group 13 ″ of the polymerizable polymerizable surfactant 4 are suitable. The anionic polymerizable surfactant 2 is disposed on the anionic group 11 ″ of the anionic polymerizable surfactant 4 so that the anionic group 11 faces. The hydrophobic group 12 and the polymerizable group 13 are directed to the hydrophobic group 12 ′ and the polymerizable group 13 ′ of the other anionic polymerizable surfactant 3 by hydrophobic interaction, and the anionic group 11 ′ is aqueous. The direction is the direction in which the solvent exists, that is, the direction away from the pigment particles 1.

  For example, by adding a polymerization initiator to such an aqueous dispersion to polymerize the polymerizable groups of the anionic polymerizable surfactants 2, 3 and 4, as shown in FIG. A microencapsulated pigment 100 coated with a polymer layer 60 is produced. Here, since the surface of the polymer layer 60 has the anionic group 11 ′, the microencapsulated pigment 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 instead of the anionic polymerizable surfactant 3, a microencapsulated pigment can be prepared in the same manner. During the polymerization, if necessary, a comonomer copolymerizable with an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group may be present in the aqueous dispersion. In some cases, the polymer layer can be a copolymer layer copolymerized from an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group and a comonomer.

  As described above, the dispersed state has been described with reference to the drawings. First, the pigment particles 1 have a cationic group as a hydrophilic group on the surface thereof, and thus are dispersed in an aqueous solvent. The dispersion of the pigment particles 1 in the aqueous solvent is highly dispersed as compared with the case where the pigment particles having no hydrophilic group on the surface are dispersed with a dispersant. According to the microencapsulated pigment in which pigment particles having a cationic group on the surface thereof are coated with a polymer, as shown in FIGS. 2 and 4, the anionic group on the surface of the microencapsulated pigment is an aqueous solvent. Since it is regularly and densely oriented in the existing direction, the dispersion stability of the microencapsulated pigment in an aqueous solvent is excellent. Therefore, if the microencapsulated pigment according to the present invention is used as a colorant for an ink for ink jet recording and the solvent of the ink is an aqueous solvent, the conventional microencapsulated pigment can be used even when more microencapsulated pigments are contained in the ink. Excellent dispersion stability equivalent to or better than that of encapsulated pigment ink can be obtained. If the dispersion stability is excellent, there is no possibility that the microencapsulated pigment clogs the nozzles of the recording head, and the ejection stability is also improved. That is, it is possible to produce a microencapsulated pigment ink that is excellent in dispersion stability and ejection stability and at the same time has an improved colorant weight concentration compared to conventional microencapsulated pigment inks. By performing ink jet recording using such a microencapsulated pigment ink having a high colorant concentration, it is possible to obtain a recorded material that not only has excellent image fastness but also high image print density.

  By using a cationic polymerizable surfactant having a cationic group, a hydrophobic group and a polymerizable group in place of the anionic polymerizable surfactant 3 in FIGS. A microencapsulated pigment in which the outer anionic group is replaced with a cationic group can be obtained. Such a microencapsulated pigment has excellent dispersion stability in an aqueous solvent because the cationic groups on the surface thereof are regularly and densely oriented in the direction in which the aqueous solvent exists. Therefore, if the microencapsulated pigment according to the present invention is used as a colorant for ink for inkjet recording and the solvent of the ink is an aqueous solvent, a more multiple amount of microencapsulated pigment can be contained in the ink. Excellent dispersion stability equivalent to or better than that of encapsulated pigment ink can be obtained. If the dispersion stability is excellent, there is no possibility that the microencapsulated pigment clogs the nozzles of the recording head, and the ejection stability is also improved. That is, it is possible to produce a microencapsulated pigment ink that is excellent in dispersion stability and ejection stability and at the same time has an improved colorant weight concentration compared to conventional microencapsulated pigment inks. By performing ink jet recording using such a microencapsulated pigment ink having a high weight concentration of the colorant, it is possible to obtain a recorded matter having not only excellent image fastness but also high image print density.

  More specifically, in the microencapsulated pigment of the present invention, as described above, it is considered that the anionic group or cationic group on the surface is regularly and densely oriented toward the aqueous solvent side. Therefore, it is considered that an effective electrostatic repulsive force is generated between the microencapsulated pigments. In addition to the electrostatic repulsive force, the microencapsulated pigment of the present invention is excellent in an aqueous medium because of the effect (polymer effect) caused by steric hindrance caused by the polymer coating the pigment particles. It is considered that this is one of the reasons for having high dispersion stability.

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

  On the other hand, the microencapsulated pigment of the present invention is easily adsorbed on the cellulose fiber of plain paper by the interaction between the hydrophilic group (particularly anionic group or cationic group) present on the surface and the cellulose fiber. Therefore, when the ink using the microencapsulated pigment of the present invention as a colorant is ejected from the recording head and landed on the plain paper, the colorant tends to accumulate near the landing position of the plain paper. It is thought that the occurrence of the is suppressed.

  In addition, since the ink for inkjet recording according to the present invention is such that the colorant is obtained by coating pigment particles with a polymer, compared with an ink using a conventional surface-treated pigment as a colorant, the ink has excellent fixability to a recording medium. As a result, the scratch resistance of the recorded material can be improved.

Next, the components of the macroencapsulated pigment according to the present invention will be described in detail.
Pigment particles having a cationic group on the surface can be suitably prepared by treating the surface of the pigment particles with a hydrophilic group-imparting agent. Therefore, the pigment constituting the pigment particles having a hydrophilic group on the surface is not particularly limited as long as it is a pigment that 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 pigments 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, Color Black FW2, Bck, Col Black FW2, Cck W200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, can be used Printex 140U, Special Black 6, Special Black 5, Special Black 4A, or Special Black 4 and the like. 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 (naphthol AS yarn) ) 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 organic pigments used in color inks other than magenta, cyan or yellow inks, C.I. I. Pigment green 7 (phthalocyanine green), 10 (green gold), 36, 37; C.I. 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 pigment according to the present invention, the above pigments can be used alone or in combination of two or more.

The pigment having a cationic group on the surface is obtained by substituting at least one cationic group with at least one aromatic group directly bonded to the pigment. The aromatic group can include an unsaturated cyclic hydrocarbon having one or more rings, which may be substituted or unsubstituted. Examples of the aromatic group include an aryl group and a heteroaryl group, and a phenyl group or a naphthyl group is preferable. Cationic groups include amine substituents (primary amines, secondary amines, tertiary amines), quaternary ammonium groups (—NR ₃ ⁺ ), quaternary phosphonium groups (—PR ₃ ⁺ ), and sulfoniums. A group (—SR ₂ ⁺ ) and a pyridinium group, preferably a quaternary ammonium group, a quaternary phosphonium group and a sulfonium group. A pigment having a cationic group on its surface can be obtained by adding an aromatic group to the above pigment by diazotization using a diazonium salt and substituting it with a cationic group. Specifically, it can be prepared by reacting a pigment with a diazonium salt in a liquid reaction medium to bond at least one organic ionic group to the pigment surface. The diazonium salt can have an organic ionic group that is bonded to the carbon black. A diazonium salt is an organic compound having one or more diazonium groups. Diazonium salts are typically diazotizing agents such as ammonium nitrite, butyl nitrite, dicyclohexylammonium nitrite, ethyl nitrite, isoamyl nitrite, lithium nitrite, sodium nitrite, potassium nitrite, or zinc nitrite. Any metal or organic nitrite, and can include nitrous acid, nitric oxide, nitrogen dioxide, and mixtures thereof) and is generated by reacting the treating agent / reactant at suitable conditions. The cationic treatment agent itself can contain nitrite, in which case the diazonium salt is made by subsequent addition of acid. Thus, the treating agent can include a diazotizing agent (eg, nitrite) that can be made into a diazonium salt by adding an acid.

  Regarding the method for producing a pigment having a cationic group on its surface, WO96 / 18688, US Pat. No. 5,554,739, WO96 / 18696, US Pat. Nos. 5,851,280, 5,837, No. 045, No. 5,803,959, No. 5,672,198, No. 5,571,311, No. 5,630,868, No. 5,707,432, No. No. 5,803,959, No. 5,698,016, No. 5,713,988, WO 97/47697, WO 97/47699.

  The pigment having a cationic group on the surface has been described in detail above. By the above production method, the average particle diameter of the pigment having a cationic group on the surface can be easily reduced to 150 nm or less. In particular, the average particle diameter of the pigment having a cationic group on the surface is more preferably 20 nm to 80 nm, and thereby, the ink for inkjet recording capable of increasing the print density of the image while being excellent in dispersion stability and ejection stability. Can be obtained more reliably. (In this specification, the description of the average particle diameter is described by the measured value of the laser light scattering method.)

  The pigment particles having a cationic group on the surface are coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group, and a polymerizable group, The microencapsulated pigment according to the embodiment of the present invention is used. As described above, such a microencapsulated pigment is prepared by adding an anionic polymerizable surfactant to an aqueous dispersion of pigment particles having a cationic group on the surface and mixing the mixture, and then further mixing the anionic polymerizable surfactant. It can be suitably prepared by adding a hydrophilic monomer having an anionic group and emulsifying, then adding a polymerization initiator and polymerizing in water, specifically by emulsion polymerization.

  In another embodiment, the pigment particle having a cationic group on the surface thereof has a repeating structural unit and a cationic group derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group. And a microencapsulated pigment according to an embodiment of the present invention by being coated with a polymer having a repeating structural unit derived from a cationic polymerizable surfactant having a hydrophobic group and a polymerizable group . As described above, such a microencapsulated pigment is prepared by adding an anionic polymerizable surfactant to an aqueous dispersion of pigment particles having a cationic group on the surface and mixing the mixture, and then adding the cationic polymerizable surfactant. After emulsification, it can be suitably prepared by adding a polymerization initiator and polymerizing in water, specifically by emulsion polymerization.

Examples of the anionic polymerizable surfactant used in the present invention include anions 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, JP-A-62-34947 or JP-A-55-11525 Examples thereof include anionic acrylic acid derivatives and anionic itaconic acid derivatives as described in JP-B-46-34898 or JP-A-51-30284.
Specific examples of the anionic polymerizable surfactant used in the present invention include the general formula (31):

［式中、Ｒ２１及びＲ３１は、それぞれ独立して、水素原子又は炭素数１〜１２の炭化水素基であり、Ｚ１は、炭素−炭素単結合又は式−ＣＨ₂−Ｏ−ＣＨ₂−で表される基であり、ｍは２〜２０の整数であり、Ｘは式−ＳＯ₃Ｍ¹で表される基であり、Ｍ₁はアルカリ金属、アンモニウム塩、又はアルカノールアミンである］で表される化合物、又は式（３２）：

[Wherein, R21 and R31 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and Z1 represents a carbon-carbon single bond or a formula —CH ₂ —O—CH ₂ —. is a group, m is an integer of 2 to 20, X is a group represented by the formula -SO ₃ M _^1, M ¹ is represented by an alkali metal, an ammonium salt, or an alkanolamine] Or a compound of formula (32):

［式中、Ｒ２２及びＲ３２は、それぞれ独立して、水素原子又は炭素数１〜１２の炭化水素基であり、Ｄは、炭素−炭素単結合又は式−ＣＨ₂−Ｏ−ＣＨ₂−で表される基であり、ｎは２〜２０の整数であり、Ｙは式−ＳＯ₃Ｍ₂で表される基であり、Ｍ²はアルカリ金属、アンモニウム塩、又はアルカノールアミンである］で表される化合物が好ましい。

[Wherein, R22 and R32 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]. Are preferred.

  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 R21 and the value of X in the formula (31), it is possible to correspond to the degree of hydrophilicity or hydrophobicity of the pigment particle surface. 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.

［式中、Ｒ３１，ｍ，Ｍ¹は式（３１）で表される化合物と同様］

[Wherein R31, 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 the 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):

［式中、ｐは９又は１１であり、ｑは２〜２０の整数であり、Ａは−ＳＯ₃Ｍ³で表わされる基であり、Ｍ³はアルカリ金属、アンモニウム塩又はアルカノールアミンである]で表される化合物が好ましい。式（３３）で表される好ましいアニオン性重合性界面活性剤としては、以下の化合物を挙げることができる。

[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.

［式中、ｒは９又は１１、ｓは５又は１０］
前記のアニオン性重合性界面活性剤としては、市販品を用いることもできる。例えば、第一工業製薬株式会社のアクアロンＫＨシリーズ（アクアロンＫＨ−５、アクアロンＫＨ−１０）などを挙げることができる。アクアロンＫＨ−５は、上記式で示される化合物において、ｒが９、ｓが５とされた化合物と、ｒが１１、ｓが５とされた化合物との混合物である。アクアロンＫＨ−１０は、上記式で示される化合物において、ｒが９、ｓが１０とされた化合物と、ｒが１１、ｓが１０とされた化合物との混合物である。
また、アニオン性重合性界面活性剤としては、下記の式（Ａ）で表される化合物も好ましい。

[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.

［上式中、Ｒ⁴は水素原子または炭素数１から１２の炭化水素基を表し、lは２〜２０の数を表し、Ｍ4はアルカリ金属、アンモニウム塩、またはアルカノールアミンを表す。］

[In the formula, R ⁴ represents a hydrogen atom or a hydrocarbon group having a carbon number of 1 to 12, l represents the number of 2 to 20, M4 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 cationic group of the cationic polymerizable surfactant used in the present invention includes amine substituents (primary amine, secondary amine, tertiary amine), quaternary ammonium group, and quaternary phosphonium group. And a sulfonium group and a pyridinium group. The hydrophobic group of the cationic polymerizable surfactant used in the present invention 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 of the cationic polymerizable surfactant used in the present invention is preferably an unsaturated hydrocarbon group, and more specifically, a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, or vinylene. It is preferably selected from the group consisting of groups. Among these, an acryloyl group and a methacryloyl group can be exemplified as preferable examples.

  Examples of the cationic polymerizable surfactant used in the present invention include a cationic allylic acid derivative as described in JP-B-4-65824. Specific examples of the cationic polymerizable surfactant 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 surfactant. 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 polymerizable surfactants exemplified above can be used alone or as a mixture of two or more.

  In the production of the microencapsulated pigment of the present invention, the anion in the step of ionically bonding the cationic group on the surface of the pigment particle having the first cationic group on the surface and the anionic group of the anionic polymerizable surfactant The amount of the polymerizable polymerizable surfactant added is the total number of moles of the cationic group converted from the amount of the pigment having a cationic group on the surface (= weight of the pigment used [g] × anionic group on the pigment surface) A range of 0.5 to 2 moles of the amount [mol / g]) is preferable, and a range of 0.8 to 1.2 moles is more preferable. By setting the addition amount to 0.5 times mol or more, it is strongly ionically bound to pigment particles having a cationic group as a hydrophilic group, and can be easily encapsulated. By setting the addition amount to 2 times or less, it is possible to reduce the generation of an anionic polymerizable surfactant that is not adsorbed on the pigment particles, and polymer particles that do not have pigment particles as a core substance (particles made of polymer only). ) Can be prevented.

  In the production of the microencapsulated pigment of the present invention, the addition of an anionic polymerizable surfactant or a cationic polymerizable surfactant for introducing an anionic group or a cationic group into the outermost part of the encapsulated pigment, that is, The addition amount of the anionic polymerizable surfactant or the cationic polymerizable surfactant in the step of forming the micelle-like structure with the ionic group (anionic group or cationic group) directed to the aqueous phase side is the cationic group Is preferably in the range of about 1 to 10 moles, more preferably in the range of about 1.0 to 5 moles of the anionic polymerizable surfactant added first with respect to the pigment particles having on the surface. is there. 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. When an anionic polymerizable surfactant and a hydrophilic group monomer having an anionic group are used in combination, the total amount of the anionic polymerization added first to the pigment particles having a cationic group on the surface The range of about 1 to 10 times the molar amount of the surfactant is preferred, and the range of about 1.0 to 5 times the mole is more preferred. 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.

  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. If a microencapsulated pigment is prepared using a polymerizable monomer having an anionic group as a hydrophilic group, and an inkjet recording ink using such a microencapsulated pigment as a colorant is ejected onto plain paper, Since the colorant tends to accumulate near the landing position of plain paper, 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.

  More specifically, the microencapsulated pigment according to the embodiment of the present invention is preferably produced by the following procedure. (1) An anionic polymerizable surfactant is added to a dispersion in which a pigment having a cationic group on its surface is dispersed in water. Here, the anionic group of the anionic polymerizable surfactant is adsorbed and ionically bonded to the cationic group of the pigment having a cationic group on the surface and immobilized. (2) An ionic polymerizable surfactant (anionic) having an ionic group (anionic group or cationic group) copolymerizable with the anionic polymerization surfactant, a hydrophobic group, and a polymerizable group. Polymerizable surfactant or cationic polymerizable surfactant) and a polymerization initiator are added and polymerized in water, specifically emulsion polymerization. Through such a procedure, it was derived from a repeating structural unit derived from an anionic polymerizable surfactant and an ionic polymerizable surfactant (anionic polymerizable surfactant or cationic polymerizable surfactant). A microencapsulated pigment coated with a polymer having a repeating structural unit can be preferably produced.

  More specifically, (1) an anionic polymerizable surfactant is added to a dispersion in which a pigment having a cationic group on its surface is dispersed in water. Here, the anionic group of the anionic polymerizable surfactant is adsorbed and ionically bonded to the cationic group of the pigment having a cationic group on the surface and immobilized. (2) 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 polymerization initiator. And polymerizing in water, specifically emulsion polymerization. By such a procedure, a microencapsulated pigment coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant and / or a repeating structural unit derived from a hydrophilic monomer having an anionic group is obtained. It can manufacture suitably. As another embodiment, (1) an anionic polymerizable surfactant is added to a dispersion in which a pigment having a cationic group on its surface is dispersed in water. Here, the anionic group of the anionic polymerizable surfactant is adsorbed and ionically bonded to the cationic group of the pigment having a cationic group on the surface and immobilized. (2) A cationic polymerizable surfactant having a cationic group, a hydrophobic group and a polymerizable group, and a polymerization initiator are added to the anionic polymerization surfactant, and polymerization is performed in water. In the emulsion polymerization. By such a procedure, a microencapsulated pigment coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant and a repeating structural unit derived from a cationic polymerizable surfactant is suitably used. Can be manufactured.

  Furthermore, other comonomers may be added 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 matter can be achieved by controlling the glass transition point (Tg) of the copolymer (copolymer) covering the pigment particles of the microencapsulated pigment according to the present invention. . When printing on a recording medium such as plain paper or a special medium for inkjet recording at room temperature with an ink using the microencapsulated pigment of the present invention, an aqueous medium (water and / or water) around the microencapsulated pigment particles of the present invention is printed. The microencapsulated pigment particles come close to each other by penetrating into a recording medium such as plain paper or a special medium for inkjet recording, and being removed from the vicinity of the microencapsulated pigment particles. At this time, when the glass transition point (Tg) of the copolymer (copolymer) covering the pigment particles of the microencapsulated pigment is not more than room temperature, the capillary pressure generated in the gap between the microencapsulated pigment particles is reduced. As a result of the film formation, the copolymer (copolymer) covering the pigment particles of the microencapsulated pigment is fused and the pigment is encapsulated (included) inside, so that the fixing property and abrasion resistance of the image are obtained. Can be made particularly good.

  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 pigment of the present invention more preferably at room temperature when printing on a recording medium such as plain paper or a dedicated medium for inkjet recording with the ink using the microencapsulated pigment of the present invention, The glass transition point (Tg) of the copolymer (copolymer) covering the pigment particles of the encapsulated pigment is preferably 30 ° C. or lower, more preferably 15 ° C. or lower, and further preferably 10 ° C. or lower. Therefore, the copolymer (copolymer) covering the pigment particles of the microencapsulated pigment is preferably designed so that the glass transition point is 30 ° C. or less, more preferably 15 ° C. or less, and still more preferably It is preferably designed to be 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 pigment particles of the microencapsulated pigment, the glass transition point is heated. The glass transition temperature may exceed 30 ° C. because the film can be formed if the temperature is lower than the temperature, but in this case, it is necessary to attach a heating mechanism to the ink jet recording apparatus. Since problems such as cost increase occur, the glass transition point is preferably 30 ° C. or lower.

  Examples of the hydrophilic monomer other than the aqueous monomer include those having a hydroxyl group, an ethylene oxide group, an amide group, or an amino group as a hydrophilic group. These hydrophilic groups are considered to be present along the outermost ionic group (anionic group or cationic group) of the encapsulated pigment and oriented toward the aqueous phase on the capsule surface, and the OH group of the cellulose fiber of the paper. It is easy to form a hydrogen bond. Therefore, in an ink for inkjet recording using a microencapsulated pigment obtained by using a hydrophilic monomer having these hydrophilic groups in combination as a colorant, the microencapsulated pigment is more easily adsorbed on the cellulose fiber of plain paper. For this reason, it tends to stay near the landing position and near the paper surface. This further increases the image density and suppresses the occurrence of bleeding. 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, in the microencapsulated pigment according to the present invention, the pigment particles having a cationic group on the surface are repeatedly derived from an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group, and a polymerizable group. It may further have a structural unit and 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 Compound: ester cheek of fumaric acid, maleic acid, itaconic acid; has radical polymerizable group such as N-substituted maleimide, cyclic olefin 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 pigment 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 ink for ink jet recording hardly penetrates into the polymer coating the pigment) ) Can be improved. When the solvent penetrates the inside of the polymer that coats the pigment particles, the polymer swells and deforms, and the orientation of the anionic group of the pigment particles facing the aqueous medium is disturbed. Stability etc. tend to decrease. In contrast, by forming a crosslinked structure in the polymer that coats the pigment particles, the solvent resistance of the microencapsulated pigment is improved, and in the ink composition in which a water-soluble organic solvent coexists, the dispersion stability is further improved. It will be excellent. 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, Bylene 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, tetrabromopisphenol 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, trimethylolpropane triglycidyl Se roll 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 which coat | covers a pigment particle further has the repeating structural unit induced | guided | derived from the monomer represented by following General formula (1).

［ただし、Ｒ¹は水素原子又はメチル基を表す。Ｒ²はｔ−ブチル基、脂環式炭化水素基、芳香族炭化水素基、又はヘテロ環基を表す。ｍは０〜３、ｎは０又は１の整数を表す。］

[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 (1) in the polymer, reduces the flexibility of the polymer molecule, 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 pigment 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, so that the microencapsulated pigment 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 (1), 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 (1) have high Tg, mechanical strength, and heat resistance. There is an advantage that it has excellent properties and solvent resistance. However, a microencapsulated pigment coated with such a polymer is insufficient in plasticity of the polymer and tends to be in a state in which it is difficult to adhere to a recording medium. Rubability 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 (1) 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. Such a microencapsulated pigment coated with a polymer is easy to adhere to a recording medium, has excellent fixability, and has excellent solvent resistance. Therefore, the ink using the microencapsulated pigment 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 with an ink using the microencapsulated pigment 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 (1).

  Copolymerization of an anionic polymerizable surfactant with an anionic polymerizable surfactant and / or a hydrophilic monomer or a cationic polymerizable surfactant having an anionic group, in addition to these, a hydrophobic monomer, a crosslinkable monomer Alternatively, the copolymerization with the monomer represented by the general formula (1) is started by adding a polymerization initiator. As such a polymerization initiator, a water-soluble polymerization initiator is preferable, and potassium persulfate, ammonium persulfate, sodium persulfate, 2,2-azobis- (2-methylpropionamidine) dihydrochloride, or 4,4 -Azobis- (4-cyanovaleric acid) and the like.

  Then, the microencapsulated pigment according to the embodiment of the present invention is manufactured by adding the anionic polymerizable surfactant to an aqueous dispersion of pigment particles having a cationic group as a hydrophilic group on the surface, as necessary. Then, water or water and an aqueous solvent are added and mixed, and after irradiation with ultrasonic waves for a predetermined time, an ionic polymerizable surfactant (anionic polymerization surfactant or cationic polymerizable surfactant), these In addition, if necessary, the hydrophobic monomer, the crosslinkable monomer, the monomer represented by the general formula (1) are added, and if necessary, water is added again and dispersed by irradiating ultrasonic waves for a predetermined time. Suitable by raising the temperature to a predetermined temperature (temperature at which the polymerization initiator is activated) while performing ultrasonic irradiation and stirring, adding the polymerization initiator to activate the polymerization initiator, and polymerizing in water To implement Can.

  When the hydrophobic monomer is used, more specifically, an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group in an aqueous dispersion of pigment particles having the cationic group on the surface. A step of adding and mixing an agent and irradiating with ultrasonic waves, a step of adding and mixing a hydrophobic monomer, and an ionic polymerizable surfactant (anionic polymerization surfactant or cationic polymerizable surfactant) Agent) and mixing, and processing by irradiating with ultrasonic waves, and a step of adding a polymerization initiator and polymerizing in water, it can be more suitably manufactured by carrying out in the order of the steps.

  When the crosslinkable monomer and / or the monomer represented by the general formula (1) is used, more specifically, an anionic group and a hydrophobic property are added to the aqueous dispersion of pigment particles having the cationic group on the surface. A step of adding an anionic polymerizable surfactant having a group and a polymerizable group, mixing and irradiating with ultrasonic waves, and adding a crosslinkable monomer and / or a monomer represented by the general formula (1) Adding an ionic polymerizable surfactant (anionic polymerization surfactant or cationic polymerizable surfactant), mixing and irradiating with ultrasonic waves, and a polymerization initiator. In addition, it comprises a step of polymerizing in water, and it can be more suitably produced by carrying out in the order of the steps. Further, when the crosslinkable monomer and / or the monomer represented by the general formula (1) and the hydrophobic monomer are used, more specifically, an aqueous dispersion of pigment particles having a cationic group on the surface thereof. A step of adding an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group, mixing the mixture, and irradiating with ultrasonic waves; and a crosslinkable monomer and / or the general formula (1) Adding and mixing a monomer having a long-chain alkyl group with the monomer represented, and adding and mixing an ionic polymerizable surfactant (anionic polymerization surfactant or cationic polymerizable surfactant) It consists of a process of irradiating with a sound wave and a process of adding a polymerization initiator and polymerizing in water, and it can be more suitably manufactured by carrying out in the order of the processes.

  According to the emulsion polymerization method, which is a polymerization in water according to the present invention, first, an anionic polymerizable surfactant is adsorbed on a cationic group on the surface of a pigment particle having a cationic group on its surface, and then a hydrophobic monomer is added. In addition, an ionic polymerizable surfactant (anionic polymerization surfactant or cationic polymerizable surfactant) is further added and treated by irradiating with ultrasonic waves, so that a polymerizable interface existing around the pigment particles. The arrangement form of the activator and the monomer is extremely highly controlled, and in the outermost layer, a state in which ionic groups (anionic groups or cationic groups) are oriented toward the aqueous phase is formed. Then, the monomer is converted into a polymer by the emulsion polymerization while maintaining this highly controlled form, and the microencapsulated pigment 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 pigment can be reduced, and a purification process such as ultrafiltration can be further facilitated. The ink using the microencapsulated pigment has improved dispersion stability. It is excellent in ejection stability from the recording head, 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 up 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, and this initiator radical is free of the polymerizable surfactant. It starts by attacking saturated groups and 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 completion of the polymerization, it is preferable to perform filtration after adjusting the pH. Filtration is preferably ultrafiltration. In addition, when the pigment particles having a cationic group as a hydrophilic group on the surface are not in the state of an aqueous dispersion, as a pretreatment, a dispersion treatment is performed 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 microencapsulated pigment according to the embodiment of the present invention obtained as described above is a self-dispersion type and completely covers small pigment particles having a good dispersion state in water with a polymer layer (defect portion). And the outermost ionic group (anionic group or cationic group) of the capsule is considered to be regularly oriented toward the aqueous solvent (see FIGS. 2 and 4). A dispersion having high dispersion stability and low viscosity can be obtained.

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

[Aqueous dispersion]
The aqueous dispersion according to the embodiment of the present invention contains the microencapsulated pigment according to the embodiment of the present invention. As such an aqueous dispersion, the liquid after emulsion polymerization in the embodiment of the present invention is used. Can be suitably exemplified. The ink jet recording ink according to the embodiment of the present invention can be produced by further adding other blending components for preparing the ink jet recording ink to the aqueous dispersion by a conventional method.

  The aqueous dispersion according to the embodiment of the present invention is preferably purified by an ultrafiltration method, a centrifugal filtration method or the like. Thus, by refining the aqueous dispersion according to the embodiment of the present invention to reduce the concentration of unreacted substances derived from the components constituting the coating polymer of the microencapsulated pigment, the embodiment of the present invention The ink for ink jet recording according to the present invention can increase the print density (print density) while having good saturation without causing deterioration of the saturation of the image when plain paper is used. Bleeding is also suppressed. Further, when a dedicated medium for ink jet recording, particularly a glossy medium for ink jet is used, good glossiness is obtained, and in particular, the glass transition point of the coating polymer of the microencapsulated pigment is 30 ° C. or less, more preferably 15 ° C. Hereinafter, more preferably 10 ° C. or less, there is an advantage that an image having higher gloss, high saturation, and excellent sharpness can be obtained.

[Ink for inkjet recording]
As described above, the ink for inkjet recording according to the embodiment of the present invention contains an aqueous dispersion. An ink for inkjet recording according to another embodiment of the present invention includes at least the microencapsulated pigment and water according to the embodiment of the present invention. The content of the microencapsulated pigment is preferably 1% by weight to 20% by weight and more preferably 3% by weight to 15% by weight with respect to the total weight of the ink for ink jet recording. In particular, 5% by weight to 15% by weight is preferable for obtaining a high printing density and high color developability.

  In addition, the solvent of the ink for inkjet recording according to the embodiment of the present invention preferably contains water and a water-soluble organic solvent as a basic solvent, and may contain any other component as necessary. Examples of water-soluble organic solvents include alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and 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-iso-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, Triethylene glycol mono-n-butyl ether, Tylene 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 monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, propylene glycol mono-n- Glycol ethers such as butyl ether or dipropylene glycol mono-n-butyl ether; There may be mentioned formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, or sulfolane and the like.

  In addition, the ink for inkjet recording according to the embodiment of the present invention contains a wetting agent composed of a high-boiling water-soluble organic solvent as a water-soluble organic solvent for the purpose of providing water retention and wettability of the ink for inkjet recording. Is preferred. As such a high boiling water-soluble organic solvent, a high boiling water-soluble organic solvent having a boiling point of 180 ° C. or higher can be exemplified. Specific examples of the water-soluble organic solvent having a boiling point of 180 ° C. or higher include ethylene glycol, propylene glycol, diethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3- Hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol monomethyl ether, dipropylene glycol monoethyl glycol, dipropylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol, triethylene glycol monomethyl ether, Tetraethylene glycol, triethylene glycol, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl Ether, tripropylene glycol, polyethylene glycol having a molecular weight of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1, Examples include 6-hexanediol, glycerin, mesoerythritol, and pentaerythritol. An organic solvent having a boiling point of 200 ° C. or higher is preferable. These can be used alone or as a mixture of two or more. Accordingly, it is possible to provide an ink for ink jet recording that maintains fluidity and redispersibility for a long time even when left in an open state (in a state where it is exposed to air at room temperature). Furthermore, nozzle clogging is less likely to occur during printing or during restart after printing interruption, and high ejection stability can be obtained. The content of these water-soluble organic solvents is preferably about 10 to 50% by weight and more preferably 10 to 30% by weight with respect to the total weight of the ink for ink jet recording.

  In particular, in the embodiment of the present invention, by including glycerin, ink clogging reliability and storage stability can be sufficiently ensured.

  Further, as the water-soluble organic solvent, polar solvents such as 2-pyrrolidone, N-methylpyrrolidone, ε-caprolactam, dimethyl sulfoxide, sulfolane, morpholine, N-ethylmorpholine, 1,3-dimethyl-2-imidazolidinone are used. One or more of these may be selected and used. The addition of these polar solvents has an effect on dispersibility and can improve the ejection stability of ink. The content of these polar solvents is preferably 0.1% by weight to 20% by weight and more preferably 1% by weight to 10% by weight with respect to the total weight of the ink for inkjet recording.

  The ink for ink jet recording according to the embodiment of the present invention preferably contains a penetrant for the purpose of promoting the penetration of the aqueous solvent into the recording medium. By rapidly penetrating the aqueous solvent into the recording medium, it is possible to reliably obtain a recorded matter with less image bleeding. As such a penetrant, polyhydric alcohol alkyl ethers (also referred to as glycol ethers) and 1,2-alkyldiols are preferably used. By including one or more compounds selected from the group consisting of alkyl ethers of polyhydric alcohols and 1,2-alkyl diols, the permeability of the ink solvent component into the recording medium can be increased, Combined with the effect of the microencapsulated pigment according to the embodiment, image blur can be drastically reduced even when printing on plain paper, recycled paper or the like, and the print quality can be greatly improved. Examples of the alkyl ether of polyhydric alcohol include 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, ethylene glycol mono-n-propyl ether, Ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-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, -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 monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether and the like. Examples of the 1,2-alkyldiol include 1,2-pentanediol and 1,2-hexanediol. In addition to these, linear carbonization such as 1,3-propanediol, 1,4-butanediol 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, etc. It may be appropriately selected from hydrogen diols. In particular, in the embodiment of the present invention, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, 1,2-pentanediol, and 1,2-hexanediol are preferable. The content of these penetrants is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, based on the total weight of the ink for inkjet recording. In particular, by using a 1,2-alkyldiol such as 1,2-pentanediol or 1,2-hexanediol, the drying property and bleeding after printing are remarkably improved.

  The ink for inkjet recording according to the embodiment of the present invention preferably contains a surfactant, particularly an anionic surfactant and / or a nonionic surfactant. Specific examples of anionic surfactants include alkane sulfonate, α-olefin sulfonate, alkylbenzene sulfonate, alkyl naphthalene sulfonic acid, acylmethyl tauric acid, dialkyl sulfosuccinic acid and other sulfonic acid types, alkyl sulfuric acid Ester salt, sulfated oil, sulfated olefin, polyoxyethylene alkyl ether sulfate ester salt; carboxylic acid type such as fatty acid salt, alkyl sarcosine salt; alkyl phosphate ester salt, polyoxyethylene alkyl ether phosphate ester salt, And phosphoric acid ester type such as monoglycerite phosphoric acid ester salt; Specific examples of nonionic surfactants include ethylene oxide addition types such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amide; glycerin alkyl ester, sorbitan alkyl ester Polyol ester type such as sugar alkyl ester; polyether type such as polyhydric alcohol alkyl ether; alkanolamide type such as alkanolamine fatty acid amide. More specifically, examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, and specific examples of the nonionic surfactant include polyoxyethylene. Nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, etc. Ether type, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sol Tanraureto, sorbitan monostearate, may be mentioned sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, the ester and the like, such as polyoxyethylene stearate.

In particular, the ink for inkjet recording according to the embodiment of the present invention desirably contains an acetylene glycol surfactant and / or an acetylene alcohol surfactant as the surfactant. Thereby, the permeability of the aqueous solvent constituting the ink to the recording medium can be increased, and printing with less bleeding can be expected on various recording media. Preferable specific examples of the acetylene glycol compound used in the present invention include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Diol, 3,5-dimethyl-1-hexyn-3-ol and the like can be mentioned. Commercially available products available as acetylene glycol surfactants can also be used, and specific examples thereof include Surfynol (registered trademark) 104, 82, 465, 485 or TG (Air Products and Chemicals. Inc.). , Olfin (registered trademark) STG, Olfin E1010 (manufactured by Nissin Chemical Co., Ltd.). Examples of the acetylene alcohol surfactant include Surfynol 61 (produced by Air Products and Chemicals. Inc.). The content of these surfactants is preferably in the range of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total weight of the ink for inkjet recording.
Further, when the above-described glycol ethers are used, it is preferable to use an acetylene glycol compound in combination as the surfactant.

  The ink for inkjet recording according to the embodiment of the present invention can further contain polymer fine particles. The polymer fine particles preferably have an ionic group of the same kind as that of the microencapsulated pigment surface on the surface thereof, a glass transition temperature of 30 ° C. or lower, and a volume average particle diameter of 10 to 200 nm. .

  As described above, a microencapsulated pigment coated with a polymer having a repeating structural unit derived from a crosslinkable monomer and / or a polymer having a repeating structural unit derived from a monomer represented by formula (1) is: Although it has high mechanical strength, heat resistance, and solvent resistance, the plasticity of the polymer becomes insufficient, and the fixability to the recording medium and the abrasion resistance tend to decrease. However, the ink for ink jet recording containing the microencapsulated pigment coated with the polymer having insufficient plasticity and the polymer fine particles has a film forming property. The microencapsulated pigment can be covered on the recording medium. Therefore, particularly in the case where the polymer that coats the pigment has a crosslinked structure and / or a “bulky” group, the advantages due to the crosslinked structure and / or the “bulky” group described above as well as fixing properties and abrasion resistance are obtained. A compatible ink for ink jet recording can be obtained.

  Here, the film formability means that when polymer fine particles are dispersed in water to form an aqueous emulsion, a polymer film is formed when the water component of the aqueous emulsion is evaporated. The ink composition of the present invention containing the polymer fine particles has a property of forming a polymer film similarly when the solvent component is evaporated. By this polymer film, the microencapsulated pigment in the ink can be more firmly fixed to the surface of the recording medium. As a result, an image having better scratch resistance and water resistance can be realized. In order for the polymer fine particles to have film-forming properties, the polymer glass transition point of the polymer fine particles is preferably 30 ° C. or lower, more preferably 15 ° C. or lower, and even more preferably 10 ° C. or lower. When printing is performed on a recording medium such as plain paper or a dedicated medium for inkjet recording with an ink using the microencapsulated pigment of the present invention containing the polymer microparticles, the microencapsulated pigment particles of the present invention and the water around the polymer microparticles are printed. A medium (consisting of water and / or a water-soluble organic solvent) penetrates into a recording medium such as plain paper or a dedicated medium for ink-jet recording and is removed from the vicinity of these particles so that these particles come close to each other and are polymerized. The coating polymers of fine particles and / or microencapsulated pigment particles and / or polymer fine particles and the coating polymer of microencapsulated pigment particles are fused. As a result, since the pigment particles are encapsulated (encapsulated) by the polymer, the fixability of the image and the abrasion resistance can be particularly improved. In consideration of ease of fusion between polymers and film formability, the polymer fine particles are preferably designed so that the glass transition point of the polymer constituting the polymer is 30 ° C. or less, more preferably 15 ° C. or less, It is preferable to design at 10 ° C. or lower. The glass transition point of the polymer can be within the above range by appropriately selecting the type and composition ratio of the monomer used. In particular, in the case of using gloss media for inkjet, when the glass transition point of the coating polymer of the microencapsulated pigment is 30 ° C. or less, more preferably 15 ° C. or less, and even more preferably 10 ° C. or less, the gloss is excellent. Further, it is possible to obtain an image with high saturation and good sharpness.

  However, since the film can be formed when there is a means for heating the printed matter at a temperature higher than the glass transition point of the polymer constituting the polymer fine particles, the glass transition point may exceed 30 ° C. described above. However, in this case, since it is necessary to attach the heating mechanism to the ink jet recording apparatus, problems such as an increase in the cost of the apparatus arise. Also from this point, the glass transition temperature of the polymer constituting the polymer fine particles is preferably 30 ° C. or less.

  The glass transition point of the polymer of the polymer fine particles may be obtained from the elastic modulus, specific heat, refractive index, etc., but in the present invention, the glass transition point obtained by measuring the temperature rise with a thermal scanning calorimeter (DSC) is used. Using. That is, in the differential heat curve obtained by the temperature rise measurement using a thermal scanning calorimeter (Differential scanning calorimeter), the temperature at the intersection with the baseline when a tangent line is drawn from the bottom of the endothermic peak toward the end point of the endothermic peak. Was the glass transition temperature.

  According to a preferred embodiment of the present invention, the polymer fine particles preferably have a minimum film-forming temperature of room temperature or lower, more preferably 30 ° C. or lower, most preferably 10 ° C. or lower. It is preferable. This is because the polymer fine particles are preferably deposited at room temperature or lower. Here, the minimum film-forming temperature refers to the formation of a transparent continuous film when the polymer emulsion obtained by dispersing polymer particles in water is cast thinly on a metal plate such as aluminum and the temperature is raised. Refers to the lowest temperature to be played. A white powder is formed in the temperature range below the minimum film formation temperature. Furthermore, according to the preferable aspect of this invention, it is preferable that the glass transition point of a polymer microparticle is 30 degrees C or less.

  Moreover, it is preferable that the particle diameter of the said polymer fine particle is the range of 50-200 nm in a volume average particle diameter. When the volume particle diameter exceeds 200 nm, ink discharge tends to become unstable.

  According to a preferred embodiment of the present invention, the contact angle on the Teflon (registered trademark) plate of an aqueous emulsion in which polymer fine particles are dispersed in an aqueous medium at a concentration of 10% by weight is preferably 70 ° or more. Furthermore, the surface tension of an aqueous emulsion in which polymer fine particles are dispersed in an aqueous medium at a concentration of 35% by weight is preferably 40 × 10 −3 N / m (40 dyne / cm, 20 ° C.) ”or more. By using the polymer fine particles as described above, it is possible to prevent the flight bending and to achieve good printing. Utilization of this polymer fine particle realizes better scratch resistance and water resistance. The reason is not clear, but is considered as follows. That is, when the ink composition according to the present invention is attached to the surface of a recording medium such as paper, first, water and a water-soluble organic solvent in the ink composition penetrate into the recording medium. Then, the microencapsulated pigment and the polymer fine particles of the present invention remain in the vicinity of the surface of the recording medium. At this time, the ionic groups on the surface of the polymer fine particles act on the hydroxyl groups and carboxyl groups of cellulose constituting the paper fiber, and the polymer fine particles are strongly adsorbed on the paper fiber. The water and water-soluble organic solvent in the vicinity of the polymer fine particles adsorbed on the paper fiber penetrate into the paper and decrease. Furthermore, as described above, the image obtained using the ink composition has a film-forming property of the polymer fine particles. When disappeared, the particles are united and the microencapsulated pigment of the present invention is encapsulated and the polymer is fused, so that the pigment particles are coated with the polymer. This polymer film is more firmly fixed to the surface of the recording medium due to the presence of ionic groups. The above is only an assumption, and the present invention is not limited to the above. Furthermore, due to the high hydrophilicity of the polymer fine particle surface, the ink composition of the present invention using such polymer fine particles can obtain excellent storage stability without reducing the performance of the microencapsulated pigment of the present invention. It also has advantages.

  According to a preferred embodiment of the present invention, the polymer fine particles comprise 1 to 10% by weight of a structure derived from an unsaturated vinyl monomer having an ionic group and have two or more polymerizable double bonds. It preferably has a structure crosslinked with a crosslinkable monomer and contains 0.2 to 4% by weight of a structure derived from the crosslinkable monomer. By using a cross-linkable polymer obtained by copolymerizing three or more cross-linkable monomers having two or more polymerizable double bonds, more preferably three or more at the time of polymerization, the nozzle plate surface has an ink composition. Further, it becomes difficult to get wet by an object, flight bending can be further prevented, and discharge stability can be further improved.

  In the present invention, usable polymer fine particles include those having a single particle structure and those having a core-shell structure comprising a core portion and a shell portion surrounding the core portion. In the present invention, the “core-shell structure” means “a form in which two or more kinds of polymers having different compositions are present in phase separation in particles”. Therefore, the shell portion may not only cover the core portion completely, but may cover a portion of the core portion. Further, a part of the shell polymer may form a domain or the like in the core particle. Furthermore, it may have a multilayer structure of three or more layers including layers having different compositions in the middle between the core part and the shell part.

  The polymer fine particles used in the present invention can be obtained by known emulsion polymerization. That is, it can be obtained by emulsion polymerization of an unsaturated vinyl monomer (unsaturated vinyl monomer) in water containing a polymerization initiator and an emulsifier.

  As unsaturated vinyl monomers, acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl, which are generally used in emulsion polymerization Examples include cyanide monomers, halogenated monomers, olefin monomers, and diene monomers. Furthermore, specific examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate. Acrylates such as octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n- Hexyl methacrylate, 2-e Methacrylic esters such as ruhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, and vinyl esters such as vinyl acetate; acrylonitrile, methacrylonitrile, etc. Vinyl cyanide compounds; halogenated monomers such as vinylidene chloride and vinyl chloride; aromatic vinyl units such as styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole and vinylnaphthalene Olefins such as ethylene, propylene and isopropylene; dienes such as butadiene and chloroprene; vinyl ether and vinyl Ketones, vinyl monomers such as vinyl pyrrolidone. For monomers having no carboxyl group, it is essential to use unsaturated vinyl monomers having a carboxyl group. Preferred examples thereof include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid. And the use of methacrylic acid is preferred. Examples of emulsifiers that can be used include anionic surfactants, nonionic surfactants, and mixtures thereof.

  Further, as described above, in the present invention, it is preferable that the monomer-derived molecule has a structure in which the molecule is cross-linked by a cross-linkable monomer having two or more polymerizable double bonds. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2 ′ -Triacrylate compounds such as diacrylate compounds such as bis (4-acryloxydiethoxyphenyl) propane, trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate , Tetraacrylate compounds such as ditrimethylol tetraacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate, hexaacrylate compounds such as dipentaerythritol hexaacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol Dimethacrylate, 2 , 2′-bis (4-methacryloxydiethoxyphenyl) propane and the like, trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate, methylenebisacrylamide and divinylbenzene.

Further, by adding an acrylamide or a hydroxyl group-containing monomer in addition to the above monomer, the printing stability can be further improved. Examples of acrylamides include acrylamide and N, N′-dimethylacrylamide. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. These may be used alone or in combination of two or more. can do.
Further, the polymer fine particles having a core-shell structure are produced by a known method, generally by multi-stage emulsion polymerization. For example, it can be produced by the method disclosed in JP-A-4-76004. Examples of the unsaturated vinyl monomer used for the polymerization include those described above.
In addition, a polymerization initiator, a surfactant, a molecular weight adjusting agent, a neutralizing agent and the like used in the emulsion polymerization may be used according to a conventional method.

  In the present invention, the polymer fine particles may be mixed with the other components of the ink composition as fine particle powder. Preferably, the polymer fine particles are dispersed in an aqueous medium to form a polymer emulsion, and then the other particles of the ink composition are mixed. Preferably mixed with the ingredients. The content of the polymer fine particles in the ink composition is preferably about 0.01 to 10% by weight, more preferably about 0.01 to 5% by weight.

  Moreover, the ink for inkjet recording which concerns on embodiment of this invention can also contain a pH adjuster, Preferably, pH is the range of 7-9, More preferably, it is the range of 7.5-8.5. Is set. Specific examples of the pH adjuster include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, lithium carbonate, sodium phosphate, potassium phosphate, lithium phosphate, diphosphate. Sodium hydrogen, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium oxalate, potassium oxalate, lithium oxalate, sodium borate, sodium tetraborate, potassium hydrogen phthalate, potassium hydrogen tartrate Potassium metals such as ammonia, methylamine, ethylamine, diethylamine, trimethylamine, triethylamine, tris (hydroxymethyl) aminomethane hydrochloride, triethanolamine, diethanolamine, diethylethanolamine, triisopropeno Amine, butyl diethanolamine, morpholine, and amines such as propanol amines are preferred.

  Moreover, the ink for inkjet recording which concerns on embodiment of this invention is benzoic acid, dichlorophen, hexachlorophene, sorbic acid, p-hydroxybenzoic acid ester, ethylenediaminetetraacetic acid (for the purpose of antifungal agent, antiseptic | preservation, and rust prevention). EDTA), sodium dehydroacetate, 1,2-benchazolin-3-one [product name: Proxel XL (manufactured by Avicia)], 3,4-isothiazoline-3-one, 4,4-dimethyloxazolidine, etc. it can.

  The ink for ink jet recording according to the embodiment of the present invention may contain urea, thiourea, and / or ethylene urea for the purpose of preventing the nozzles of the recording head from drying.

Ink jet recording ink according to an embodiment of the present invention is particularly preferable.
(1) A microencapsulated pigment according to an embodiment of the present invention,
(2) one or more compounds (penetrant) selected from the group consisting of diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and / or 1,2-alkyldiol having 4 to 10 carbon atoms,
(4) glycerin,
(5) water,
At least.

  Such an ink for ink jet recording is particularly excellent in dispersion stability and ejection stability, and further, stable printing can be performed without clogging of the nozzles over a long period of time. In addition, in recording media such as plain paper, recycled paper, and coated paper, it is possible to obtain a high-quality image having good dryability after printing, no bleeding, high printing density, and excellent color development. .

Another aspect of the inkjet recording ink according to the particularly preferred embodiment of the present invention is as follows.
(1) A microencapsulated pigment according to an embodiment of the present invention,
(2) one or more compounds (penetrant) selected from the group consisting of diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and / or 1,2-alkyldiol having 4 to 10 carbon atoms,
(3) Acetylene glycol surfactant and / or acetylene alcohol surfactant,
(4) glycerin,
(5) water,
At least.

  Such an ink for ink jet recording is particularly excellent in dispersion stability and ejection stability, and further, stable printing can be performed without clogging of the nozzles over a long period of time. In addition, in recording media such as plain paper, recycled paper, and coated paper, it is possible to obtain a high-quality image with particularly good drying properties after printing, almost no bleeding, and high color density with high printing density. it can.

  Generally, when dispersing a pigment, a dispersant such as a surfactant or a polymer dispersant is used. However, since these dispersants are merely adsorbed on the surface of the pigment particles, Due to environmental factors, the dispersant tends to be detached from the pigment particle surface. In contrast, in the embodiment of the present invention, as described above, the surface of the pigment particle having a cationic group on the surface is completely encapsulated by the polymer film or the crosslinked polymer film, and the surface of the pigment particle is surrounded. It is considered that the polymer film or the cross-linked polymer film that adheres to the surface of the pigment particles is very firmly fixed, so that the polymer film or the cross-linked polymer film is hardly detached from the surface of the pigment particles. More specifically, the above acetylene glycol surfactant and / or acetylene alcohol surfactant and diethylene glycol using a pigment dispersion obtained by dispersing a pigment using a dispersant such as a surfactant or a polymer dispersant. When ink is improved in permeability with penetrants such as monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, or 1,2-alkyldiol, when ejected through a thin nozzle Due to the strong shearing force applied, the dispersant easily desorbs from the pigment surface, resulting in deterioration of dispersibility, and discharge tends to be unstable. On the other hand, in the ink for inkjet recording using the microencapsulated pigment according to the embodiment of the present invention, such a phenomenon is not recognized at all and is stably ejected. In addition, since the polymer film includes the pigment particles, good solvent resistance can be obtained, so that the penetration of the penetrant from the pigment particles and the swelling of the polymer are less likely to occur. Excellent dispersion stability can be maintained. In addition, an ink composition using a pigment dispersion in which a pigment is dispersed using a dispersant such as a surfactant or a polymer dispersant and having improved permeability is generally adsorbed on the pigment surface from the beginning of dispersion. First, the viscosity of the ink composition is increased by the dispersant dissolved in the liquid, or the dispersant is desorbed from the pigment as time passes after the dispersion, and the viscosity of the ink composition is desorbed by the desorbed dispersant. Tend to be higher. For this reason, the pigment content is often limited. Therefore, particularly for plain paper and recycled paper, sufficient color density cannot be obtained, so that good color developability cannot often be obtained. On the other hand, in the ink composition using the microencapsulated pigment according to the embodiment of the present invention, since the polymer film includes the pigment particles as described above, the polymer is not easily detached from the pigment particles. No increase in viscosity of the ink composition occurs. Accordingly, it is easy to lower the viscosity of the ink composition, and there are advantages that more pigment particles can be contained, and a sufficient printing density can be obtained on plain paper or recycled paper.

  In the above-described particularly preferred embodiment of the present invention, the addition amount of diethylene glycol monobutyl ether and triethylene glycol monobutyl ether as the penetrant of (2) is preferably 10% by weight or less based on the total weight of the ink composition. More preferably, it is 0.5 to 5% by weight. Addition of diethylene glycol monobutyl ether or triethylene glycol monobutyl ether has a remarkable effect on improving the permeability and helps to improve the printing quality. Further, diethylene glycol monobutyl ether and / or triethylene glycol monobutyl ether improves the solubility of the acetylene glycol surfactant.

  In the above-described particularly preferred embodiment of the present invention, the amount of the 1,2-alkyldiol having 4 to 10 carbon atoms as the penetrant of (2) is preferably 15 wt. % Or less. A 1,2-alkyldiol having 3 or less carbon atoms is not preferable because sufficient permeability cannot be obtained. If the carbon number exceeds 15, it is difficult to dissolve in water. If the added amount exceeds 15% by weight, a tendency to increase viscosity appears, which is not suitable. Specifically, 1,2-pentanediol or 1,2-hexanediol is preferably used as the 1,2-alkyldiol, and these can be used alone or in combination. 1,2-pentanediol is preferably added in the range of 3 to 15% by weight. If it is less than 3% by weight, good permeability cannot be obtained. 1,2-hexanediol is preferably added in the range of 0.5 to 10% by weight. If it is less than 0.5% by weight, good permeability cannot be obtained.

In particular, in the ink for ink jet recording according to the embodiment of the present invention, the solid wetting agent is added in an amount of 3% by weight with respect to the total weight of the ink in order to improve the characteristic that clogging hardly occurs (clogging reliability). It is preferably contained at -20% by weight. In this specification, the solid wetting agent refers to a water-soluble substance that is solid at room temperature (25 ° C.) and has a water retention function. Preferred solid wetting agents are sugars, sugar alcohols, hyaluronate, trimethylolpropane, 1,2,6-hexanetriol. Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol. (Sorbit), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature, such as alginic acid, α-cyclodextrin, and cellulose. The derivatives of these saccharides are represented by the reducing sugars of the saccharides described above (for example, sugar alcohol (general formula HOCH ₂ (CHOH) _n CH ₂ OH (where n represents an integer of 2 to 5)). ), Oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thiosaccharides, etc.). Particularly preferred are sugar alcohols, and specific examples include maltitol, sorbitol, xylitol and the like. As the hyaluronate, a commercially available sodium hyaluronate 1% aqueous solution (molecular weight 350,000) can be used. These solid wetting agents are used alone or in admixture of two or more. Particularly preferred solid wetting agents are trimethylolpropane, 1,2,6-hexatriol, sugars and sugar alcohols. By using a solid wetting agent, water evaporation can be suppressed by its water retention function, so the ink does not increase in viscosity around the flow path and the nozzle, and a film is difficult to form, so clogging is less likely to occur. . In addition, since the above-described solid wetting agent is chemically stable, the performance can be maintained for a long time without being decomposed in the ink. Further, even when the above-described solid wetting agent is added, the ink does not wet the nozzle plate, and stable ejection can be obtained. In particular, it is excellent when trimethylolpropane, 1,2,6-hexanetriol, saccharides or sugar alcohols are used. In the present invention, when used alone, the content of the solid wetting agent is preferably 3 to 20% by weight, more preferably 3 to 10% by weight based on the total weight of the ink composition for ink jet recording. When two or more types are mixed and used, the total amount of the two or more types is preferably 3 to 20% by weight, more preferably 3 to 10%, based on the total weight of the ink for ink jet recording. % By weight. A preferable combination in the case of using a mixture of two or more kinds is a combination of a group of saccharides, sugar alcohols and hyaluronate with a group of trimethylolpropane and 1,2,6-hexanetriol. This combination is preferable because an increase in the viscosity of the ink due to the addition can be suppressed. If the content of the solid wetting agent is less than 3% by weight, a sufficient effect for improving the clogging property cannot be obtained, and if it exceeds 20% by weight, the viscosity increases and it is difficult to obtain a stable discharge. .

  In the above-described particularly preferred embodiment of the present invention, the amount of the acetylene glycol surfactant and / or acetylene alcohol surfactant (3) is preferably 0.01 to 10 with respect to the total weight of the ink. % By weight, more preferably 0.1 to 5% by weight.

  As described above, the ink for inkjet recording according to the embodiment of the present invention has been described. However, as described above, the microencapsulated pigment according to the embodiment of the present invention contained as a colorant has a spherical shape, and the ink It is thought that the fluidity of the water is likely to be Newtonian, and the anionic groups on the surface are regularly and densely oriented toward the aqueous solvent side, and an effective electrostatic repulsive force is considered to have occurred. . As a result, the ink for ink jet recording has excellent ejection stability compared to conventional microencapsulated pigments, more dispersibility (high dispersibility) and dispersion stability, and further improved colorant content. Can be produced.

  Ink jet recording is preferably performed by mounting the ink for ink jet recording according to the embodiment of the present invention on a known ink jet printer and printing on a recording medium such as plain paper or an ink jet recording medium. In addition to improving the ejection stability of the ink from the head, it is possible to obtain a recorded matter that is excellent in image fastness, abrasion resistance and color developability, has a high image printing density, and is difficult to bleed. Further, even when plain paper is used as a recording medium, a recorded matter is obtained in which the image is less likely to bleed and the color of the image is high.

<Example>
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.

“Production of carbon black particles P1 having cationic groups on the surface”
A solution prepared by dissolving 13.02 g of N- (4-aminophenyl) pyridinium nitrite in 188 ml of deionized water was charged with 100 g of carbon black having a surface area of 200 m ² / g and DBPA of 117 ml / 100 g in a reaction vessel. Mix and the resulting mixture was heated at 70 ° C. To this, 37.8 ml of 10% nitrous acid was added and reacted at 70-80 ° C. for 2-3 hours. During this time, the diazonium salt N ₂ C ₆ H ₄ NC ₅ H ₅ ²⁺ was formed and reacted with carbon black to release bubbles. The obtained dispersion was centrifuged at about 20,000 rpm with a centrifuge and filtered to reduce the carbon black particles having cationic groups on the surface to less than 0.5 μm. Carbon black particles having a cationic group on the surface had —C ₆ H ₄ NC ₅ H ₅ ⁺ group bonded thereto, and the corresponding counter anion was NO ₃ ⁻ . If necessary, anion exchange of the pigment dispersion of carbon black particles having a cationic group on the surface was performed using an ion exchange resin. When the volume average particle diameter was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop, it was in the range of 100 to 200 nm.

“Preparation of Magenta Pigment Particles M1 Having Cationic Groups on the Surface”
A solution obtained by dissolving 13.02 g of N- (4-aminophenyl) pyridinium nitrite in 188 ml of deionized water was mixed with 100 g of isoindolinone pigment (CI Pigment Red 122) in a reaction vessel, The resulting mixture was heated at 70 ° C. To this, 37.8 ml of 10% nitrous acid was added and reacted at 70-80 ° C. for 2-3 hours. During this time, the diazonium salt N ₂ C ₆ H ₄ NC ₅ H ₅ ²⁺ was formed and reacted with the magenta pigment to release bubbles. The obtained dispersion was centrifuged at about 20,000 rpm with a centrifuge and filtered to make magenta pigment particles having cationic groups on the surface less than 0.5 μm. The magenta pigment particles having a cationic group on the surface had —C ₆ H ₄ NC ₅ H ₅ ⁺ group bonded thereto, and the corresponding counter anion was NO ₃ ⁻ . If necessary, anion exchange of the pigment dispersion of carbon black particles having a cationic group on the surface was performed using an ion exchange resin. When the volume average particle diameter was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop, it was in the range of 100 to 200 nm.

Manufacture of microencapsulated pigments “MCP1” to “MCP8” “Manufacture of microencapsulated pigment“ MCP1 ””
4 g of Aqualon KH-10 represented by the following general formula as an anionic polymerizable surfactant is added to an aqueous dispersion in which 15 g of carbon black particles “P1” having a cationic group are dispersed in 75 g of ion-exchanged water. Then, the mixture was irradiated with ultrasonic waves for 15 minutes. Next, 2 g of anionic polymerizable surfactant Aqualon KH-10 and 20 g of ion-exchanged water were added and mixed, and then ultrasonic waves were irradiated again 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 0.03 g of potassium persulfate was dissolved as a polymerization initiator was added dropwise to 10 g of ion-exchanged water. Polymerized for hours. After completion of the polymerization, the pH was adjusted to 8, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a dispersion of the desired microencapsulated pigment “MCP1”. .

  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 130 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.

"Manufacture of microencapsulated pigment" MCP2 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion in which 15 g of carbon black particles “P1” having a cationic group on the surface thereof were dispersed in 75 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 6 g of benzyl methacrylate, 4 g of dodecyl methacrylate, 2 g of anionic polymerizable surfactant Aqualon KH-10, 0.5 g of 2-acrylamido-2-methylpropanesulfonic acid and 50 g of ion-exchanged water as hydrophilic monomers were added. Then, 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 0.4 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, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a dispersion of the desired microencapsulated pigment “MCP2”. .

  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 180 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.

"Manufacture of microencapsulated pigment" MCP3 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion in which 15 g of carbon black particles “P1” having a cationic group on the surface thereof were dispersed in 75 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 6 g of the cationic polymerizable surfactant dimethylaminoethylbenzyl methacrylate methacrylate and 20 g of ion-exchanged water were added and mixed, and then ultrasonic waves were irradiated again 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 raising the internal temperature of the reaction vessel to 80 ° C., an aqueous potassium persulfate solution in which 0.04 g of 2,2-azobis- (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 10 g of ion exchange water. The solution was added dropwise and polymerized at 80 ° C. for 6 hours while introducing nitrogen. After completion of the polymerization, the pH was adjusted to 6, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a dispersion of the desired microencapsulated pigment “MCP3”. .

  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 130 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.

"Manufacture of microencapsulated pigment" MCP4 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion in which 15 g of carbon black particles “P1” having a cationic group on the surface thereof were dispersed in 75 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 6 g of benzyl methacrylate, 4 g of dodecyl methacrylate, 6 g of cationic polymerizable surfactant dimethylaminoethylbenzyl chloride methacrylate and 50 g of ion-exchanged water were added and mixed, and then ultrasonic waves were irradiated again 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 raising the internal temperature of the reaction vessel to 80 ° C., an aqueous potassium persulfate solution in which 0.4 g of 2,2-azobis- (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion-exchanged water. The solution was added dropwise and polymerized at 80 ° C. for 6 hours while introducing nitrogen. After completion of the polymerization, the pH was adjusted to 6, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a dispersion of the desired microencapsulated pigment “MCP4”. .

  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 180 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.

"Manufacture of microencapsulated pigment" MCP5 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion in which 15 g of magenta pigment particles “M1” having a cationic group on the surface thereof were dispersed in 75 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 6 g of benzyl methacrylate, 4 g of dodecyl methacrylate, 2 g of anionic polymerizable surfactant Aqualon KH-10, 0.5 g of 2-acrylamido-2-methylpropanesulfonic acid and 50 g of ion-exchanged water as hydrophilic monomers were added. Then, 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 0.4 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, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a dispersion of the desired microencapsulated pigment “MCP5”. .

  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 170 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.

"Manufacture of microencapsulated pigment" MCP6 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion obtained by dispersing 20 g of carbon black particles “P1” having a cationic group on the surface thereof in 80 g of ion-exchanged water. Was irradiated for 15 minutes. Subsequently, 2.45 g of isobornyl methacrylate, 2.55 g of lauryl methacrylate, 4 g of anionic polymerizable surfactant Aqualon KH-10 and 30 g of ion-exchanged water were added and mixed, and ultrasonic waves were irradiated again 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 0.4 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, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a dispersion of the desired microencapsulated pigment “MCP6”. .

  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 180 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" MCP7 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion obtained by dispersing 20 g of carbon black particles “P1” having a cationic group on the surface thereof in 80 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 8 g of benzyl methacrylate, 3 g of dodecyl methacrylate and 0.01 g of diethylene glycol dimethacrylate were mixed and mixed with stirring, and 5 g of anionic polymerizable surfactant Aqualon KH-5 previously dissolved in 50 g of ion-exchanged water was added. Then, it was again irradiated with ultrasonic waves for 30 minutes for treatment. 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, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a desired microencapsulated pigment “MCP7” 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 150 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" MCP8 ""
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion obtained by dispersing 20 g of carbon black particles “P1” having a cationic group on the surface thereof in 80 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 8 g of benzyl methacrylate, 3 g of dodecyl methacrylate and 0.01 g of 1,6-hexanediol dimethacrylate were mixed and mixed with stirring, and the cationic polymerizable surfactant methacrylic acid previously dissolved in 50 g of ion-exchanged water. 5 g of dimethylaminoethylbenzyl chloride 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 raising the internal temperature of the reaction vessel to 80 ° C., an aqueous potassium persulfate solution in which 0.6 g of 2,2-azobis- (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion-exchanged water. The solution was added dropwise and polymerized at 80 ° C. for 6 hours while introducing nitrogen. After completion of the polymerization, the pH was adjusted to 6, and unreacted substances were removed by ultrafiltration. Then, coarse particles were removed with a membrane filter having a pore size of 1 μm to obtain a desired microencapsulated pigment “MCP8” 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 150 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 pigments“ MCP9 ”to“ MCP10 ””
MCP9 (microencapsulated black pigment) and MCP10 (microencapsulated magenta pigment) were produced according to the method described in JP-A-10-140065.

"Manufacture of" MCP9 ""
The flask was charged with 250 g of methyl ethyl ketone, heated to 75 ° C. with stirring under a nitrogen seal, and 85 g of n-butyl methacrylate, 90 g of n-butyl acrylate, 40 g of 2-hydroxyethyl methacrylate, 25 g of methacrylic acid and a polymerization initiator perbutyl. A mixed solution composed of 20 g of O (tert-butyl peroxyoctoate manufactured by Nippon Oil & Fats Co., Ltd.) was dropped over 2 hours and reacted for 15 hours to obtain a vinyl polymer solution. 8 g of the above polymer solution is added to a stainless steel beaker together with 0.4 g of dimethylethanolamine and 8 g of black pigment (MA-100 manufactured by Mitsubishi Chemical), and ion exchange water is further added so that the total amount becomes 40 g. Was added with 250 g of 0.5 mm zirconia beads, and kneaded for 4 hours using a sand mill. After kneading, the zirconia beads were separated by filtration to obtain a dispersion of a polymer having a carboxyl group neutralized with a base and a pigment dispersed in water. While stirring at room temperature with a disperser, 1N hydrochloric acid was added until the resin was insolubilized and fixed to the pigment. The pH at this time was 3-5. The aqueous medium containing the pigment to which the polymer was fixed was filtered with suction and washed with water to obtain a water-containing cake. While stirring the water-containing cake with a disperser, 10% NaOH aqueous solution was added until the pH of the dispersion became 8.5 to 9.5, and stirring was continued for 1 hour. The carbon black microencapsulated pigment MCP9 was obtained by adjusting the concentration to 20%. The aspect ratio was 1.4 and the Zingg index was 1.4.

"Manufacture of" MCP10 ""
A flask is charged with 250 g of methyl ethyl ketone, heated to 75 ° C. with stirring under a nitrogen seal, and 170 g of n-butyl methacrylate, 58 g of n-butyl acrylate, 35 g of 2-hydroxyethyl methacrylate, 35 g of acrylic acid and a polymerization initiator perbutyl. A mixed solution composed of 20 g of O was dropped over 2 hours, and further reacted for 15 hours to obtain a vinyl polymer solution.

  Add 15 g of the above polymer solution to a stainless steel beaker together with 0.8 g of dimethylethanolamine and 15 g of magenta pigment (CI Pigment Red 122), and then add ion-exchanged water so that the total amount becomes 75 g. 250 g of zirconia beads having a diameter of 0.5 nm was added, and kneading was performed for 4 hours using a sand mill. After kneading, the zirconia beads were separated by filtration to obtain a dispersion of a polymer having a carboxyl group neutralized with a base and a pigment dispersed in water. While stirring at room temperature, 1N hydrochloric acid was added until the resin was insolubilized and fixed to the pigment. The pH at this time was 3-5. The aqueous medium containing the pigment to which the polymer was fixed was filtered with suction and washed with water to obtain a water-containing cake. While stirring the water-containing cake with a disperser, 10% NaOH aqueous solution was added until the pH of the dispersion became 8.5 to 9.5, and stirring was continued for 1 hour. The concentration is adjusted to 20% and C.I. I. Pigment Red 122 microencapsulated pigment MCP9 was obtained. The aspect ratio was 1.4 and the Zingg index was 1.4.

“Manufacture of“ polymer fine particles 1 to 4 ””
“Manufacture of“ Polymer fine particle 1 ””
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 90 g of ion-exchanged water and 1 g of anionic polymerizable surfactant Aqualon KH-5, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. Warm up. After maintaining the internal temperature at 70 ° C. and adding 2 g of potassium persulfate as a polymerization initiator and dissolving, 1 g of anionic polymerizable surfactant AQUALON KH-5 and 43.5 g of styrene are added to 45 g of ion-exchanged water in advance. -An emulsion obtained by stirring 47.5 g of butyl acrylate and 5 g of 2-acrylamido-2-methylpropanesulfonic acid was continuously dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the reaction was further continued for 3 hours. After cooling the obtained polymer emulsion to room temperature, ion exchange water and 2 mol / l potassium hydroxide aqueous solution were added to adjust the solid content to 35% by weight and pH 8. The concentration of the polymer fine particles of the obtained polymer emulsion was adjusted to 0.1% by weight, and 3 volumes thereof and 1 volume of 1 mol / l magnesium nitrate aqueous solution were contacted in the cell of the spectrophotometer U-3300 (manufactured by Hitachi, Ltd.). The time required for the transmittance at a wavelength of 700 nm to be 50% of the initial value was 90 seconds.

  Further, the volume average particle size was measured by a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co., Ltd. and found to be 100 nm. Moreover, when the obtained polymer emulsion was dried at room temperature and the glass transition point was measured using a thermal scanning calorimeter (differential scanning calorimeter: DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.), it was found to be 0 ° C. Met. The minimum film formation temperature was 10 ° C. Further, the concentration of polymer fine particles in the obtained polymer emulsion was adjusted to 10% by weight, and the contact angle between this and a Teflon (registered trademark) plate was measured, and found to be 85 °. Further, the surface tension of the obtained polymer emulsion was measured with a surface tension meter CBVP-Z (manufactured by Kyowa Interface Science) and found to be 55 × 10 −3 N / m (55 dyne / cm).

“Manufacture of“ Polymer 2 ””
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 90 g of ion-exchanged water and 1 g of anionic polymerizable surfactant Aqualon KH-5, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. Warm up. After maintaining the internal temperature at 70 ° C. and adding 2 g of potassium persulfate as a polymerization initiator and dissolving, 1 g of anionic polymerizable surfactant AQUALON KH-5 and 43.5 g of styrene are added to 45 g of ion-exchanged water in advance. -An emulsion obtained by stirring 47.5 g of butyl acrylate, 0.3 g of diethylene glycol dimethacrylate, and 5 g of 2-acrylamido-2-methylpropanesulfonic acid was continuously dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the reaction was further continued for 3 hours. After cooling the obtained polymer emulsion to room temperature, ion exchange water and 2 mol / l potassium hydroxide aqueous solution were added to adjust the solid content to 35% by weight and pH 8. The concentration of the polymer fine particles of the obtained polymer emulsion was adjusted to 0.1% by weight, and 3 volumes thereof and 1 volume of 1 mol / l magnesium nitrate aqueous solution were contacted in the cell of the spectrophotometer U-3300 (manufactured by Hitachi, Ltd.). The time when the transmittance at a wavelength of 700 nm was 50% of the initial value was 80 seconds. Further, the volume average particle size was measured by a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co., Ltd. and found to be 100 nm.
In addition, the obtained polymer emulsion was dried at room temperature, and this was measured with a thermal scanning calorimeter (differential running calorimetry).

Calorimetry: DSC) The glass transition point was measured using DSC200 (manufactured by Seiko Electronics Co., Ltd.) and found to be 3 ° C. The minimum film formation temperature was 15 ° C. Further, the concentration of polymer fine particles in the obtained polymer emulsion was adjusted to 10% by weight, and the contact angle between the polymer fine particle and the Teflon (registered trademark) plate was measured and found to be 89 °. Moreover, it was 57 * 10 < ^-3 > N / m (57 dyne / cm) when the surface tension of the obtained polymer emulsion was measured with surface tension meter CBVP-Z (made by Kyowa Interface Science).

“Manufacture of“ Polymer fine particle 3 ””
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 90 g of ion-exchanged water and 1 g of anionic polymerizable surfactant Aqualon KH-5, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. Warm up. After maintaining the internal temperature at 70 ° C. and adding 2 g of potassium persulfate as a polymerization initiator and dissolving, 1 g of anionic polymerizable surfactant AQUALON KH-5 and 43.5 g of styrene are added to 45 g of ion-exchanged water in advance. -An emulsion obtained by stirring 47.5 g of butyl acrylate, 3 g of ethylene glycol dimethacrylate, and 5 g of 2-acrylamido-2-methylpropanesulfonic acid was continuously dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the reaction was further continued for 3 hours. After cooling the obtained polymer emulsion to room temperature, ion exchange water and 2 mol / l potassium hydroxide aqueous solution were added to adjust the solid content to 35% by weight and pH 8. The concentration of the polymer fine particles of the obtained polymer emulsion was adjusted to 0.1% by weight, and 3 volumes thereof and 1 volume of 1 mol / l magnesium nitrate aqueous solution were contacted in the cell of the spectrophotometer U-3300 (manufactured by Hitachi, Ltd.). The time at which the transmittance at a wavelength of 700 nm was 50% of the initial value was 10 seconds.

Further, the volume average particle size was measured with a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co., Ltd., and it was 90 nm. Moreover, when the obtained polymer emulsion was dried at room temperature and the glass transition point was measured using a thermal scanning calorimeter (differential scanning calorimeter: DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.), it was found to be 8 ° C. Met. The minimum film formation temperature was 20 ° C. Further, the concentration of polymer fine particles in the obtained polymer emulsion was adjusted to 10% by weight, and the contact angle between the polymer fine particle and the Teflon (registered trademark) plate was measured to be 110 °. Moreover, it was 59 * 10 < ^-3 > N / m (59 dyne / cm) when the surface tension of the obtained polymer emulsion was measured with the surface tension meter CBVP-Z (made by Kyowa Interface Science).

“Manufacture of“ Polymer Fine Particles 4 ””
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. After maintaining the internal temperature at 70 ° C. and adding 2 g of potassium persulfate as a polymerization initiator and dissolving, 450 g of ion-exchanged water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 435 g of styrene, 475 g of n-butyl acrylate, and 30 g of methacrylic acid were previously added. The emulsion obtained by stirring was continuously dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the reaction was further continued for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and ammonia water were added to adjust the solid content to 40% by weight and pH 8. After cooling the obtained polymer emulsion to room temperature, ion exchange water and 2 mol / l potassium hydroxide aqueous solution were added to adjust the solid content to 35% by weight and pH 8. The concentration of the polymer fine particles of the obtained polymer emulsion was adjusted to 0.1% by weight, and 3 volumes thereof and 1 volume of 1 mol / l magnesium nitrate aqueous solution were contacted in the cell of the spectrophotometer U-3300 (manufactured by Hitachi, Ltd.). The time required for the transmittance at a wavelength of 700 nm to be 50% of the initial value was 70 seconds.

Further, the volume average particle size was measured with a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co., Ltd., and it was 90 nm. Moreover, when the obtained polymer emulsion was dried at room temperature and the glass transition point was measured using a thermal scanning calorimeter (differential scanning calorimeter: DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.), it was found to be 12 ° C. Met. The minimum film formation temperature was 22 ° C. Further, the concentration of polymer fine particles in the obtained polymer emulsion was adjusted to 10% by weight, and the contact angle between the polymer fine particle and the Teflon (registered trademark) plate was measured and found to be 89 °. Moreover, it was 57 * 10 < ^-3 > N / m (59 dyne / cm) when the surface tension of the obtained polymer emulsion was measured with the surface tension meter CBVP-Z (made by Kyowa Interface Science).

“Preparation of ink for ink jet recording; Examples 1 to 16 and Comparative Examples 1 to 13”
Based on the compositions shown in Tables 1 to 5, ink jet recording inks of Examples 1 to 16 and Comparative Examples 1 to 13 were prepared.

「評価」
実施例１〜１６，比較例１〜１３のインクジェット記録用インク、並びに、これらのインクを用いて印刷した記録物の評価を、下記に示す方法で行った。

"Evaluation"
The ink jet recording inks of Examples 1 to 16 and Comparative Examples 1 to 13 and the recorded matter printed using these inks were evaluated by the methods shown below.

Evaluation 1: Viscosity The viscosities of the inkjet recording inks of Examples 1 to 16 and Comparative Examples 1 to 13 were measured. The results are shown in Tables 6-7.
Viscosity was measured using the ink jet recording inks of Examples and Comparative Examples at 20 ° C. with a rheometer Physica MCR300 manufactured by Paar Physica, a cone plate (Paar Physica) having a cone radius of 37.50 mm, a cone angle of 1 degree, and a measurement gap of 0.05 mm. Using CP75-1), the viscosity (mPa · s) at 20 ° C. and a shear rate of 20 sec-1 was measured.

Evaluation 2-1: Dispersibility 1
The ink for ink jet recording of Examples and Comparative Examples was a cone plate having a cone radius of 37.50 mm, a cone angle of 1 degree, and a measurement gap of 0.05 mm using a Physica MCR300 manufactured by Paar Physica at 20 ° C. (CP75-1 manufactured by Paar Physica) ) Was used to measure the storage rigidity (Pa) at each angular velocity when the angular velocity was applied from 0.5 rad / sec to 5 rad / sec. The storage elastic modulus at 0.6 rad / sec was G′ω = 0.6, and the storage elastic modulus at 0.8 rad / sec was G′ω = 0.8. The dispersibility of the ink was evaluated according to the following criteria.
A: The value of (log G′ω = 0.8−log G′ω = 0.6) / (log 0.8−log 0.6) is 1.8 to 2.0.
B: The value of (log G′ω = 0.8−log G′ω = 0.6) / (log 0.8−log 0.6) is 1.6 to 1.8.
C: The value of (log G′ω = 0.8−log G′ω = 0.6) / (log 0.8−log 0.6) is 1.2 to 1.6.
D: The value of (log G′ω = 0.8−log G′ω = 0.6) / (log 0.8−log 0.6) is smaller than 1.2.

Evaluation 2-2: Dispersibility 2
The ink jet recording inks of Examples and Comparative Examples were used at 20 ° C. with a rolling ball viscometer AMVn using a capillary with an inner diameter of 0.9 mm and a steel ball with a diameter of 0.794 mm and a density of 7.850 g / cm 3 and an inclination angle of 70. The viscosities at °, 60 °, 50 °, 40 °, and 30 ° were measured, and the gradient in the sin θ-viscosity curve obtained by plotting the horizontal axis as sin θ and the vertical axis as the viscosity was determined. The dispersibility of the ink was evaluated according to the following criteria.
A: The slope in the sin θ-viscosity curve is 0 to −0.05, exhibits Newtonian properties, and particularly good dispersibility.
B: The slope in the sin θ-viscosity curve is −0.05 to −0.1, close to Newtonian property, and exhibits good dispersibility after A.
C: The gradient in the sin θ-viscosity curve is −0.1 to −0.15, indicating non-Newtonian properties, but dispersibility is slightly good.
D: The slope in the sin θ-viscosity curve is smaller than −0.15, exhibits non-Newtonian property, tends to cause sedimentation, and has poor dispersibility.

Evaluation 3: Dispersion stability The inks for ink jet recording of Examples and Comparative Examples were put in glass sample bottles, sealed tightly, then allowed to stand at 60 ° C. for 2 weeks, and the viscosity of the ink before and after being left was examined. The measurement was performed at 20 ° C. using a rheometer Physica MCR300 manufactured by Paar Physica using a cone plate having a cone radius of 37.50 mm, a cone angle of 1 degree, and a measurement gap of 0.05 mm (CP75-1 manufactured by Paar Physica) at a shear rate. Measured the viscosity at 150S-1. The obtained results were evaluated according to the following criteria.
A: The amount of change is less than ± 0.1 mPa · s.
B: The amount of change is ± 0.1 or more and less than 0.3 mPa · s.
C: Change amount is ± 0.3 mPa · s or more.

Evaluation 4: Sedimentability With respect to the ink jet recording inks of Examples and Comparative Examples, the sedimentation property of the colorant in the ink can be evaluated from the intensity distribution of the backscattered light and transmitted light in the height direction of the sample. It measured at 20 degreeC using TURBISCAN 2000 made from FORMUL ACTION. The measurement principle of TURBISCAN 2000 manufactured by FORMUL ACTION is shown below. In this device, when a glass tube filled with ink is set at a predetermined position of the device and measurement is started, a stage installed around the glass tube (in the radial direction) moves up and down along the glass tube. The light source installed on the stage and the detector of scattered light and transmitted light are scattered and transmitted light in the vertical direction of the glass tube in accordance with the vertical movement of the stage. Is a measuring device that can measure the intensity of light over time when there is a particle movement or particle diameter change by repeating this operation at an arbitrary time interval. is there.
Evaluation was performed according to the following criteria.
A: No sedimentation phenomenon was observed even after 2 weeks.
B: A sedimentation phenomenon was observed after 2 weeks.

Evaluation 5: Printing density Ink cartridges of Examples and Comparative Examples were filled in an ink cartridge, which was loaded into an inkjet printer PM-720C (manufactured by Seiko Epson Corporation), and plain Xerox P paper, Xerox 4024 Solid printing was performed on paper (manufactured by Xerox Co., Ltd.), and the density of the solid printing portion was measured with a spectrophotometer (GRETAG SPM-50, manufactured by Gretag Macbeth Co.), and the obtained results were evaluated according to the following criteria. .
(For black ink)
AA: OD value of black ink: 1.5 or more A: OD value of black ink: 1.4 or more and less than 1.5 B: OD value of black ink: 1.3 or more and less than 1.4 C: OD of black ink Value: Less than 1.3 (for color ink)
AA: OD value of color ink: 1.25 or more A: OD value of color ink: 1.2 or more and less than 1.25 B: OD value of color ink: 1.15 or more and less than 1.2 C: OD of color ink Value: less than 1.15

Evaluation 6: Print quality The ink for ink jet recording of Examples and Comparative Examples was filled in an ink cartridge, and loaded into an ink jet printer PM-720C (manufactured by Seiko Epson Corporation). 24 letters each of uppercase and lowercase letters of the alphabet were printed, and visually observed, and evaluated according to the following criteria.
AA: No bleeding occurs on all papers.
A: Almost no bleeding occurs on all papers.
B: Slight bleeding is only observed on 2-3 sheets.
C: Slight bleeding is observed on all papers.
D: There is much bleeding on the entire paper.
The printing paper used for the evaluation is Conqueror paper, Favorit paper, Modo paper, Rapid Copy paper, EPSON EPP paper, Xerox P paper, Xerox 4024 paper, Xerox 10 paper, Nenha Bond paper, Rcopy 6200 paper, and Yamayuri (recycled paper). Xerox R (recycled paper).

Evaluation 7: Scratch resistance The ink for ink jet recording of Examples and Comparative Examples was filled in an ink cartridge, and this was loaded into an ink jet printer PM-720C (manufactured by Seiko Epson Corporation). After printing at 100% duty on a 10 mm × 10 mm area and leaving it at a temperature of 25 ° C. for 1 hour, the above printed area was printed using a zebra yellow fluorescent highlighter ZEBRA PEN2 (trademark) at a load of 500 g. Rubbing was performed at a speed of 10 mm / second, and the presence or absence of contamination was observed. The results were evaluated according to the following criteria.
A: Dirt does not occur at all even after rubbing twice.
B: Dirt is not generated by rubbing once, but dirt is generated by rubbing the second time.
C: Dirt is generated by rubbing once.

Evaluation 8: Water resistance 1 ml of ion-exchanged water was dropped onto the printed portion of the printed matter obtained in the print density test of Evaluation 5, and the state after 20 minutes was visually observed and evaluated according to the following criteria.
A: There is no change in the whole paper.
B: Although the color material slightly flows out from the print portion, the character can be recognized.
C: It is difficult to recognize the character because the color material flows out from the printed part and the outline of the printed character is unclear.

Evaluation 9: Discharge stability About each ink of an Example and a comparative example, this is loaded in ink-jet printer PM-720C (made by Seiko Epson Corporation), and a 1 mm ruled line is used on Superfine exclusive paper made by Seiko Epson Corporation. Was printed, and the printing state such as missing dots and ink landing position deviation was visually observed and evaluated according to the following criteria.
A: Even if the number of printed sheets is 10,000 or more, there is no missing dot or ink landing position deviation.
B: When the number of printed sheets is 1000 or more and less than 10,000, dot missing or ink landing deviation occurs.
C: When the number of printed sheets is 100 or more and less than 1000, dot missing or ink landing deviation occurs.
D: When the number of printed sheets is less than 100, dot missing or ink landing deviation occurs.

Evaluation 10: Clogging reliability After the printing performed in the evaluation 6, the printer was turned off and allowed to stand, and the same printing test was performed one week later. At that time, the “ink discharge state” was visually observed. And it evaluated by the criteria shown below.
A: At the same time as sending a print signal to the printer, normal printing is started without a cleaning operation.
B: Normal printing is performed within 3 cleaning operations.
C: Normal printing is performed within 6 cleaning operations.
D: Even if the cleaning operation is repeated seven times or more, normal printing cannot be performed.

Evaluation 11: Gloss Ink recording inks of Examples and Comparative Examples were filled in an ink cartridge, and this was loaded into an ink jet printer PM-720C (manufactured by Seiko Epson Corporation). After solid printing with 100% duty on a 50 mm × 50 mm area on photographic paper (gloss) and leaving it at a temperature of 25 ° C. for 1 hour, the presence or absence of gloss was visually observed and evaluated according to the following criteria.
A: Very glossy (high gloss).
B: Glossy but inferior to A.
C: Somewhat glossy.
D: There is no gloss.

  As shown in Tables 6 and 7, the ink jet recording inks of the examples were excellent in all evaluation items. In particular, the inkjet recording inks and pigments of Comparative Examples 3 to 4 containing the conventional microencapsulated pigment as a colorant and the concentration of the microencapsulated pigment set to be the same as those of the inks of Examples were used as a dispersant. Compared to the ink jet recording inks of Comparative Examples 9 to 13 which are dispersed ink jet recording pigment inks, a low viscosity was realized.

Further, the inks for inkjet recording of Examples 1 to 16 containing the microencapsulated pigment and the solid wetting agent of the present invention showed particularly good results in clogging reliability.
The pigment inks for inkjet recording in which the pigments of Comparative Examples 9 to 13 are dispersed with a dispersant are insufficient in dispersibility, dispersion stability, printing density, print quality, abrasion resistance, and ejection stability.
In the case of using a conventional microencapsulated pigment coated with a polymer of a normal powder pigment not treated with a cationic group-imparting agent as a colorant, the concentration of the microencapsulated pigment is higher than that of the ink of the example. Although the inkjet recording inks of Comparative Examples 1 and 2 set to a low value are excellent in dispersion stability and ejection stability, sufficient results are obtained with respect to the print density, print quality, and abrasion resistance of the obtained recorded matter. I couldn't.

  On the other hand, the ink for inkjet recording of Comparative Examples 3 to 4 containing the conventional microencapsulated pigment as a colorant and the concentration of the microencapsulated pigment was set to be equivalent to the ink of the example, the dispersibility, Dispersion stability and discharge stability were particularly poor. Further, the inkjet recording inks of Comparative Examples 5 to 8 containing a pigment treated with a cationic group-imparting agent (a pigment having a cationic group on the surface) as a colorant have good dispersion stability and ejection stability. However, the water resistance and abrasion resistance were inferior.

  The present invention is not limited to the above-described embodiment, and a part of the ink liquid is rapidly heated at a part near the discharge part of the nozzle head to generate bubbles, and the ink liquid is generated by volume expansion due to the bubbles. The present invention can also be applied to applications such as inkjet recording methods, printing inks, writing instruments, and the like that intermittently eject droplets to record characters and symbols on the surface of a recording medium.

1 Pigment Particles 2, 3, 4 Anionic Polymerizable Surfactant 11, 11 ′, 11 ″ Anionic Group 12, 12 ′, 12 ″ Hydrophobic Group 13, 13 ′, 13 ″ Polymerizable Group 14 Cation on Pigment Surface Group 50 Hydrophobic surface 60, 60 'of pigment particle Polymer layer (polymer)
100,101 Microencapsulated pigment

Claims (25)

  The pigment particle having a cationic group on its surface is coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group, and a polymerizable group. A microencapsulated pigment.   The pigment particles are obtained by polymerizing an anionic polymerizable surfactant having at least an anionic group, a hydrophobic group, and a polymerizable group in an aqueous dispersion in which pigment particles having a cationic group on the surface are dispersed. A microencapsulated pigment obtained by coating with a polymer.   A pigment particle having a cationic group on its surface is a repeating structural unit derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group, and a cationic group, a hydrophobic group, and a polymer A microencapsulated pigment coated with a polymer having a repeating structural unit derived from a cationic polymerizable surfactant having a functional group.   In an aqueous dispersion in which pigment particles having a cationic group on the surface are dispersed, an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group, a cationic group and a hydrophobic group, A microencapsulated pigment in which the pigment particles are coated with a polymer by polymerizing a cationic polymerizable surfactant having a polymerizable group.   The microencapsulated pigment according to claim 1, wherein the polymer further has a repeating structural unit derived from a hydrophobic monomer. The microencapsulated pigment according to any one of claims 1 to 5, wherein the polymer further has a repeating structural unit derived from a monomer represented by the following general formula (1).

[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 microencapsulated pigment according to any one of claims 1 to 6, wherein the polymer further has a crosslinked structure derived from a crosslinkable monomer.   The microencapsulated pigment according to any one of claims 1 to 7, wherein the pigment constituting the pigment particles is carbon black or an organic pigment.   The cationic group of the pigment particle is selected from the group consisting of a primary amine cation group, a secondary amine cation group, a tertiary amine cation group, and a quaternary ammonium cation group. The microencapsulated pigment according to -4. The anionic group of the anionic polymerizable surfactant is a sulfonate anion group (—SO ₃ ⁻ ), a sulfinate anion group (—RSO ₂ ⁻ : R is a C1-C12 alkyl group or a phenyl group, and a modified product thereof. ), A microencapsulated pigment according to claim 1, which is selected from the group consisting of carboxylate anion groups (—COO ⁻ ).   The microencapsulated pigment according to claim 1, wherein the hydrophobic group of the anionic polymerization surfactant is selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined.   The polymerizable group of the anionic polymerization surfactant is an unsaturated hydrocarbon group capable of radical polymerization, and includes a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. The microencapsulated pigment according to claim 1, which is selected from:   The cationic group of the cationic polymerizable surfactant is selected from the group consisting of a primary amine cation group, a secondary amine cation group, a tertiary amine cation group, and a quaternary ammonium cation group. The microencapsulated pigment according to claim 3 or 4, wherein   The microencapsulated pigment according to claim 3 or 4, wherein the hydrophobic group of the cationic polymerization surfactant is selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined.   The polymerizable group of the cationic polymerization surfactant is an unsaturated hydrocarbon group capable of radical polymerization, and includes a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. The microencapsulated pigment according to claim 3 or 4, which is selected from the group consisting of:   A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface A method for producing a microencapsulated pigment, wherein the anionic polymerizable surfactant is further added and emulsified, followed by emulsification, followed by addition of a polymerization initiator and polymerization in water.   A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface And then mixing the hydrophobic monomer and the anionic polymerizable surfactant, mixing, emulsifying, adding a polymerization initiator, and polymerizing in water. A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface After mixing, a hydrophobic monomer and a crosslinkable monomer and / or a monomer represented by the following general formula (1) and the anionic polymerizable surfactant are added and mixed. After emulsification, a polymerization initiator is added. A method for producing a microencapsulated pigment, which is polymerized in water.

[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. ]   A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface A method for producing a microencapsulated pigment, wherein the cationic polymerizable surfactant is added and emulsified after mixing, and then a polymerization initiator is added and polymerized in water.   A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface A method for producing a microencapsulated pigment, comprising mixing a hydrophobic monomer and the cationic polymerizable surfactant, mixing the mixture, emulsifying, adding a polymerization initiator, and polymerizing in water. A method for producing a microencapsulated pigment in which pigment particles having a cationic group on the surface are coated with a polymer, wherein the anionic polymerizable surfactant is added to an aqueous dispersion of the pigment particles having a cationic group on the surface After mixing, a hydrophobic monomer and a crosslinkable monomer and / or a monomer represented by the following general formula (1) and the cationic polymerizable surfactant are added and mixed. After emulsification, a polymerization initiator is added. A method for producing a microencapsulated pigment, which is polymerized in water.

[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 method for producing a microencapsulated pigment according to any one of claims 16 to 21, wherein the pigment constituting the pigment particles is carbon black or an organic pigment.   An aqueous dispersion comprising the microencapsulated pigment according to claim 1.   An ink for inkjet recording comprising the aqueous dispersion according to claim 23.   Further containing polymer fine particles, the polymer fine particles have an anionic group on the surface thereof, a glass transition temperature of 30 ° C. or less, a volume average particle diameter of 50 to 200 nm, and an ionic group on the particle surface. The ink for inkjet recording according to claim 24, wherein the ink is the same kind as the ionic group on the surface of the microencapsulated pigment.

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