JP2006008892A - Ink for inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink capable of high-quality recording with glossiness made of a dispersible color material having sufficiently high dispersion stability and no detachment of a resin component from the color material.
A dispersible color material having a color material and a chargeable resin pseudo fine particle smaller than the color material, the dispersible color material having the color material and the charge resin pseudo fine particle fixed to each other. In the ink for ink jet recording, when an image is recorded by depositing the ink as a droplet on glossy recording medium paper, the boundary point between the location where the ink droplet is adhered and the location where the ink droplet is not adhered And a straight line formed by connecting a point where the thickness of the ink droplet closest to the boundary point is maximum is θ is 15 ° or more, where θ is an acute angle formed with respect to the paper surface. An ink for ink jet recording characterized by the above.
[Selection] Figure 1

Description

  The present invention relates to an ink used in an ink jet recording method for recording an image by ejecting ink from a nozzle.

  The ink jet method is a method for recording images, characters, etc. by causing a micro droplet of ink to fly from a nozzle to reach a recording medium (paper, etc.) based on various operating principles. It is easy to realize, has high flexibility in recording patterns, and does not require development and fixing operations, and is rapidly spreading in various applications. In particular, in recent years, full-color water-based inkjet recording technology has been remarkably developed, and it is possible to form multicolored images that are comparable to multicolored printing by conventional platemaking methods and printing by color photographic methods. In the case where the number of copies to be produced is small, printed matter can be obtained at a lower cost than ordinary multicolor printing or printing, so that it has been widely applied to the field of full-color image recording.

In response to demands for further improvement in recording characteristics such as higher recording speed, higher definition, and full color, improvements in aqueous inkjet recording apparatuses and recording methods have been made. In general, the performance required for water-based ink used in an ink jet recording apparatus is as follows: (1) A uniform image with high resolution and high density without blurring or fogging can be obtained on paper (2). Clogging due to drying of ink at the nozzle tip does not occur, ejection response and ejection stability are always good, (3) ink fixability is good on paper, and (4) weather resistance of the image. (5) long-term storage stability is good.
In particular, with the recent increase in printing speed, there has been a demand for ink that can quickly dry and fix the ink and obtain high-quality recording.

  The coloring materials used in the water-based inkjet recording method mainly include dyes and pigments. Conventionally, water-soluble dyes have been mainly used due to their ease of handling as water-based inks and high color developability. As a coloring material for water-based inkjet recording ink that can realize high weather resistance of an image, development of a coloring material that is essentially insoluble in water, particularly an ink using a pigment, has been energetically advanced. In order to use a water-insoluble colorant, particularly a pigment, as an aqueous inkjet recording ink, it is necessary to stably disperse the colorant in water. In this case, generally, a method of stabilizing the dispersion using a surfactant or a polymer dispersant (hereinafter also referred to as a dispersion resin) has been used. Further, a method for chemically modifying the surface of the water-insoluble colorant has been proposed (see, for example, Patent Document 1).

  On the other hand, a microcapsule type pigment in which a pigment is coated with a resin has been proposed (see, for example, Patent Documents 2 and 3). In Patent Document 3, “in a water-based colored fine particle dispersion containing a water-insoluble colorant, the colored fine particle dispersion is added with a vinyl monomer after the water-insoluble colorant is dispersed in an aqueous medium in the presence of the dispersant. When the dispersant is dispersed with a water-insoluble colorant, it exhibits dispersion stability, and when the vinyl monomer is polymerized in the presence of the dispersant alone, the stability of the latex produced A water-based colored fine particle dispersion characterized by poor properties "is disclosed, and when emulsion polymerization is performed on a water-insoluble colorant dispersion, the affinity of the dispersant for the vinyl monomer and the resulting polymer is not so high. For this reason, the desorption of the dispersant from the pigment surface is unlikely to occur, and the polymerization has proceeded on the pigment surface where the dispersant is adsorbed. ” By using the colored fine particle dispersion, it is excellent in dispersion stability and printability, is not dependent on the paper type, has a low metallic luster, water resistance, light resistance, and scratch resistance. It is said that a water-based ink that gives an image with excellent properties is obtained.

Japanese Patent Laid-Open No. 10-195360 JP-A-8-183920 JP 2003-34770 A

  However, with the above-described technique, there are cases where the dispersion stability of the color material and the gloss of the recorded image are not sufficient. According to the study by the present inventors, it is necessary to increase the surface functional group density of the coloring material in order to improve the dispersion stability. If the acid value of the resin is increased in order to increase the dispersion stability, the hydrophilicity of the resin also increases, so that the resin tends to be detached from the color material over time. In some cases, the storage stability could not be maintained. On the other hand, in the method of chemically modifying the surface of the water-insoluble colorant by the method disclosed in Patent Document 1, there is a limit to the functional group that can be modified and its density, and the colorant is particularly an organic pigment. When chemical modification is performed directly on the surface, pigment molecules that are originally insoluble in water and crystallized are solubilized by the binding of hydrophilic groups and dissolved from the pigment particles. Such a problem arises (see FIGS. 6 (a) and 6 (b)) that the technical level is not sufficiently satisfactory.

  The object of the present invention is to solve these problems of the prior art, and to achieve high-quality recording with glossiness made of a dispersible color material that has sufficiently high dispersion stability and does not detach the resin component from the color material. It is to provide an ink that can be used.

  On the other hand, as a result of intensive investigations on means for solving the above problems, the present inventors have achieved a high dispersion stability and a resin component is removed from the color material by using a dispersible color material having a novel shape. Development of a new dispersible colorant that is storage-stable over the long term without separation, and by using such a dispersible colorant, it has sufficient ejection stability and dispersion stability for inkjet recording applications. As a result, a water-based ink giving a printed matter with high image quality was obtained. That is, the object of the present invention is achieved by the following specific means.

  As a result of intensive studies, the present inventors have determined that at least one hydrophobic monomer and at least one hydrophilic monomer are dispersed in an aqueous pigment dispersion in which the pigment is dispersed in an aqueous solution using a polymer dispersant. A resin that is not adsorbed to the pigment in the dispersible colorant dispersion obtained by adding water-based precipitation polymerization with a water-soluble radical polymerization initiator and then fixing the chargeable resin pseudo fine particles obtained in the polymerization step. The inventors have found that the above problem can be solved by reducing the amount by an ultrafiltration step, and have completed the present invention.

The object is achieved by the present invention described below.
1. Inkjet recording comprising a dispersible color material having a color material and chargeable resin pseudo fine particles smaller than the color material, wherein the color material and the charge resin pseudo fine particles are fixed to each other In the ink for recording, when an image is recorded by depositing the ink as a droplet on the glossy recording medium paper, the boundary point between the location where the ink droplet is adhered and the location where the ink droplet is not adhered, and the boundary When the straight line formed by connecting the point where the thickness of the ink droplet closest to the point of the ink is connected to the point where the thickness of the ink droplet is the maximum is θ, the θ is 15 ° or more. Ink for ink-jet recording characterized.

2. 2. The ink jet recording according to 1 above, wherein the colorant is a pigment, and a ratio of the pigment and all resin components contained in the ink (resin mass / pigment mass = B / P) is 0.5 or less. ink.

3. The hydrophobic monomer is benzyl methacrylate and / or (meth) acrylic acid alkyl ester, and the hydrophilic monomer is (meth) acrylic acid, (meth) acrylic acid methoxypolyethylene glycols and carbon chains of 4 to 40. 3. The ink for inkjet recording according to 1 or 2 above, which is at least one selected from (meth) acrylic acid long-chain alkyl esters.

4). The dispersible colorant, to which the chargeable resin pseudo fine particles are fixed, is obtained by dropping the hydrophobic monomer, the hydrophilic monomer, and the anionic or amphoteric aqueous radical polymerization initiator into an aqueous pigment dispersion and dropping the water-based precipitation polymerization. 4. The ink for inkjet recording according to any one of 1 to 3 above, which is obtained as described above.

  According to the present invention, a simple production method that uses aqueous precipitation polymerization (soap-free polymerization) in a pigment dispersion and reduces the amount of resin not adsorbed to the pigment after polymerization through an ultrafiltration step. Further, it is possible to provide an ink for ink jet recording excellent in ejection stability and color developability.

  The present invention is described in detail below. As described above, the ink for inkjet recording of the present invention is obtained by subjecting at least one hydrophobic monomer and at least one hydrophilic monomer to aqueous precipitation polymerization with a water-soluble radical polymerization initiator in a pigment dispersion. It is characterized by containing a dispersible colorant to which the obtained chargeable resin pseudo fine particles are fixed in a dispersed state.

  First, a dispersed color material used as an essential component in the inkjet recording ink of the present invention will be described. Any coloring material that is insoluble in water, such as hydrophobic dyes, inorganic pigments, organic pigments, metal colloids, and colored resin particles can be used as long as it can be stably dispersed in water together with the dispersant. However, it is preferably a pigment having a dispersed particle diameter in the range of 0.03 to 0.5 μm. If the colorant is larger than this range, it may be greatly inferior in terms of inkjet suitability and dispersion stability. If the color material is smaller than this range, the weather resistance, which is the merit of the dispersed color material, may not be sufficiently obtained. Furthermore, there is a concern that resin fine particles generated by soap-free polymerization cannot be stably attached.

  At this time, the particle size distribution of the coloring material is preferably monodispersed as much as possible. In general, the particle size distribution of the dispersible colorant to which the chargeable resin pseudo fine particles generated by adhering the resin fine particles are fixed tends to be narrower than the particle size distribution of the dispersion before the polymerization step. Basically, it depends on the particle size distribution of the color material. In order to obtain good dispersion stability and ejection stability as an inkjet recording ink, the ratio of the weight average particle diameter to the number average particle diameter of the color material may be in the range of 1.0 to 1.5. desirable.

  Here, the dispersed particle size differs depending on various measurement methods. In particular, organic pigments are extremely small in the case of spherical particles, but in the present invention, the dynamic light scattering method is used as a principle in ELS-8000 manufactured by Otsuka Electronics Co., Ltd. The average value of the main peak of the measured weight conversion distribution is defined as the weight average particle diameter, and the average value of the main peak of the number conversion distribution is defined as the number average particle diameter.

  In the present invention, when the color material is an organic pigment or an inorganic pigment, the method of the present invention is particularly effective. Examples of the inorganic pigment used as the coloring material include carbon black, titanium oxide, zinc white, zinc oxide, tripon, cadmium red, brown, molybdenum red, chrome vermillion, molybdate orange, yellow lead, chrome yellow, and cadmium yellow. , Yellow iron oxide, titanium yellow, chromium oxide, pyridian, cobalt green, titanium cobalt green, cobalt chrome green, ultramarine blue, ultramarine blue, bitumen, cobalt blue, cerulean blue, manganese violet, cobalt violet, mica and the like.

  Examples of the organic pigment used as the colorant include azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, isoindoline, iso And indolinone pigments.

  As the dispersant for dispersing the coloring material, any of general polymer dispersants and water-soluble polymers can be used such as ionic and nonionic. This dispersant preferably has sufficient water solubility and a hydrophobic portion that serves as an adsorption site for the surface of the colorant fine particles and the monomer droplets added in the polymerization step to the oil droplet interface.

  The polymer dispersant as the dispersant and the method for producing the water-soluble polymer are not particularly limited. For example, it can be produced by reacting a monomer having an ionic group with another polymerizable monomer in a non-reactive solvent in the presence or absence of a catalyst. In particular, in terms of achieving both the stability in the polymerization process system and the promotion of adhesion of resin fine particles to the coloring material, a monomer having an ionic group and a (meth) acrylic acid ester having 5 or more carbon atoms. An ionic group-containing acrylic polymer compound produced by polymerizing a monomer as an essential component is preferred.

  Examples of the acrylic monomer having an acidic group used herein include monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, and styrene. Monomers having a sulfonic acid group such as sulfonic acid, sulfonic acid-2-propylacrylamide, acrylic acid-2-ethyl sulfonate, methacrylic acid-2-ethyl sulfonate, butylacrylamide sulfonic acid, etc., methacrylic acid-2-phosphonic acid And monomers having a phosphonic acid group such as ethyl and ethyl acrylate-2-phosphonate. Acrylic acid and methacrylic acid are particularly preferred.

  Examples of monomers insoluble or hardly soluble in water include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-propyl, acrylic acid-n-butyl, acrylic acid-t-butyl, and benzyl acrylate. , Methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, t-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate, etc. ) Acrylic acid ester; Styrenic monomer such as styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-tert-butyl styrene, etc .; Itaconic acid ester such as benzyl itaconate; Such as dimethyl maleate Fumarate esters such as dimethyl fumarate; Acrylonitrile, methacrylonitrile, vinyl acetate; Aminoethyl acrylate, Aminopropyl acrylate, Methacrylamide, Aminoethyl methacrylate, Aminopropyl methacrylate, Acrylic acid Examples include amino group-containing monomers such as dimethylaminoethyl and dimethylaminoethyl methacrylate.

  Examples of the monomer having a cationic group include the amino group-containing monomers described above, and specific examples of the nonionic hydrophilic monomer include a radical polymerizable unsaturated bond and an alkyl oxide chain in the structure. Monomers that are included at the same time, such as methoxypolyethylene glycol (meth) acrylate, are classified into this. Such monomers, oligomers and macromonomers can also be used without limitation.

  As a dispersion method of the color material used in the present invention, a dispersion machine such as a paint shaker, a sand mill, an agitator mill, and a three roll mill, a high-pressure homogenizer such as a microfluidizer, a nanomizer, and an optimizer, an ultrasonic dispersion machine, etc. Any dispersion method that is generally used for color materials is not limited.

  At least one monomer used for the synthesis of the dispersible colorant to which the chargeable resin pseudo fine particles of the present invention are fixed is a monomer capable of radical polymerization that is insoluble or hardly soluble in water. Further, two or more types of monomers can be used. In that case, the dispersibility of fixing the charged resin pseudo fine particles with better dispersion stability by making the other monomer have a hydrophilic group or a hydrophilic monomer having a charged group. It can be a color material. Even if it has a functional group having other functionality, it can be used.

  Specifically, any of the monomers listed as monomers that can be used in the polymer dispersant in the previous section can be used. In addition, by including an anionic monomer having a functional group that is acidic in water in the hydrophilic monomer, a chargeable resin pseudo fine particle that provides excellent dispersion stability and dischargeability particularly in a neutral to basic region. The dispersible colorant can be fixed. Specifically, any of the monomers listed as acrylic monomers having an acidic group that can be used in the polymer dispersant can be used. Alternatively, any radically polymerizable monomer or macromonomer that has an ionic group and is anionic when soluble in water can be used without limitation. In particular, when the anionic monomer is acrylic acid or methacrylic acid, high dispersion stability and good fixability on the paper surface can be provided at the same time, which is desirable for suitability as an ink for ink jet recording.

  In addition, a nonionic hydrophilic monomer can be used at the same time. Specifically, the monomers listed as the nonionic hydrophilic monomer in the previous section can also be used without limitation.

  Furthermore, even if it is a radically polymerizable monomer or macromonomer which shows cationic property as a hydrophilic monomer, it can be used without a restriction | limiting. In this case, it is possible to obtain an ink for ink jet recording that is stable in a low pH region. Specifically, amino group-containing (meth) acrylic acid esters are desirably used from the viewpoint of the form stability of the dispersible color material to which the chargeable resin pseudo fine particles are fixed.

  In addition, as the chain transfer agent that can be used in the present invention, various chain transfer agents can be used, and particularly effective are lauryl mercaptan, octyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, Or a thiol-based compound such as 3-mercaptopropionic acid. By using the chain transfer agent, the weight average molecular weight of the resin constituting the dispersible colorant to which the chargeable resin pseudo fine particles are fixed can be reduced to 20,000 or less. If the weight average molecular weight of the resin is larger than this, the viscosity becomes high, and the ejection stability required by the present invention cannot be obtained.

  Next, in the ultrafiltration step of the present invention, the pH of the aqueous solution after aqueous precipitation polymerization, that is, the aqueous solution containing the dispersible colorant to which the chargeable resin pseudo fine particles are fixed and the resin not adsorbed to the pigment is used. It is desirable to maintain 9 to 13. If the pH is lower than this, the resin in the aqueous solution may precipitate and clog the ultrafiltration membrane. If the pH is higher than this, the resin decomposes and sufficient dispersibility to disperse the pigment is obtained. I can't.

  Various organic bases and inorganic bases can be used to adjust the pH to 9 to 13, but it is desirable to use a base that is adaptable to inkjet ink. Of these, lithium hydroxide, sodium hydroxide, potassium hydroxide and the like, which are strong inorganic bases effective in a small amount, are most preferable. Further, preferable water-soluble organic solvents to be added in the ultrafiltration step include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, Polyhydric alcohols such as thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylolpropane; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene Glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol Alkyl ethers of polyhydric alcohols such as coal monobutyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine and the like are not particularly limited, but are removed. In view of the solubility of the resin not adsorbed to the power pigment, polyhydric alcohols are desirable, and diethylene glycol is most desirable even in consideration of versatility.

  In the present invention, a preferable method for producing a dispersible color material having charged charge resin pseudo fine particles fixed thereto is to stir an aqueous dispersion in which the color material is dispersed in water with a dispersant, and to set the temperature of this dispersion to a predetermined value for polymerization. After the temperature is reached, each monomer is gradually added dropwise to the aqueous dispersion. During this time, a water-soluble radical polymerization initiator is added to the system at an appropriate timing to carry out the polymerization.

  As the water-dispersed color material used in the present invention, any color material that is stably dispersed in water can be used. Preferably, the average dispersed particle size is in the range of 0.03 to 0.5 μm. The narrower particle size distribution is preferable, and it is more preferable that the ratio of the weight average particle size to the number average particle size is 1.5 or less. When the particle size distribution is widened, the dispersion stability of the system is impaired, and many coloring materials may aggregate and settle.

  The method for dispersing the color material is not limited by a general dispersion method as long as the color material can be stably dispersed in water as described above. Or, of course, there is no problem with the dispersion method newly developed for the present invention. In general, for example, in the case of a pigment, the addition amount of the dispersant is suitably 1% by mass to 120% by mass with respect to the pigment.

  As the polymerization initiator, any general water-soluble radical polymerization initiator can be used. Specific examples of the water-soluble radical polymerization initiator include persulfates and azo initiators. Or the redox initiator by the combination of a water-soluble radical polymerization initiator and a reducing agent may be sufficient. Considering the colorant, dispersant, and monomer, they are used in an optimal combination. Desirably, a polymerization initiator that gives an initiator residue having the same charge as the surface charge characteristics of the dispersible colorant to which the chargeable resin pseudo fine particles to be obtained are fixed is selected.

  The polymerization reaction conditions vary depending on the properties of the polymerization initiator, the dispersant, and the monomer, but the reaction temperature is 100 ° C. or lower, preferably 40 to 80 ° C., and the reaction time is 1 hour or longer, preferably 6 to 30 hours. . The stirring speed is 50 to 500 rpm, preferably 150 to 400 rpm.

  When the obtained polymerization liquid is used as an ink for ink jet recording, a purification treatment by ultrafiltration using a membrane is performed. This technology utilizes cross-flow membrane technology. Examples of the shape of the membrane that can be used at this time include, but are not limited to, a flat sheet membrane, a cross-flow membrane, a spirally wound tube, and a hollow fiber tube. By performing the purification treatment in this way, the ratio of the resin and the total resin component contained in the ink (resin mass / pigment mass = B / P) is set to 0.5 or less, whereby the recording portion and the non-recording portion Ink for ink jet recording excellent in color development with clear boundaries can be obtained.

  Next, the present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “part” or “%” is based on mass unless otherwise specified.

  As an ink jet recording apparatus used for the evaluation, an image was formed using BJ S600 (Canon Inc.). The recording head used here has a recording density of 600 dpi and a driving frequency of 10 KHz. A head with a discharge volume per dot of 30 pl / dot was used.

[1] A boundary point between a location where an ink droplet is attached and a location where no ink droplet is attached, and a point where the thickness of the ink droplet closest to the boundary is the maximum. The acute angle θ formed by the straight line formed with respect to the paper surface is 10% when printed on glossy paper with 10% DUTY under the above recording conditions and calculated using Micromap. The case of less than 15 was evaluated as Δ, and the case of less than 10 ° was evaluated as ×.

[2] Optical density (OD) was determined by measuring the optical density (OD) of a printed material one day after printing Bk text on glossy paper. The case where the OD of the printed matter was 2.0 or more was evaluated as ◯, and the case where the OD was less than 1.9 was evaluated as ×.
The glossy paper used in this evaluation is Canon PR101, but it is not limited as long as it is a glossy recording medium.

[3] The face surface is undulated when 100 specific Bk texts are continuously printed on Canon PPC paper, and the face surface after printing is observed with an optical microscope, and no ink droplets are seen around the ejection port. The case where ink droplets exist around the ejection port is indicated by Δ, and the case where ink droplets are seen around the ejection port are indicated by ×.

[4] Concerning the kogation on the heater board, 100 specific Bk texts are printed continuously on Canon PPC paper, and after printing, the ink in the head is completely replaced with pure water, and then observed with an optical microscope. The test piece was evaluated as “◯” when no burnt was seen on the heater board, “△” when burnt was seen on a part of the heater board, and “X” when burnt was seen on one side.

[5] The ejection stability was judged by printing 100 specific Bk texts on Canon PPC paper continuously and comparing the initial printed matter with the last printed matter.
A: There is no streak or unevenness, and there is no difference between the initial stage and the final stage.
B: Although there are slight streaks, unevenness and twist, printing can be performed without any problem.
C: Degradation is greatly observed or printing cannot be performed.

[Example 1]
The recording ink 1 used in Example 1 was prepared as follows. A mixture of carbon black 10 parts, glycerin 6 parts, styrene-acrylic acid dispersant 10 parts and water 74 parts is dispersed in a sand mill manufactured by Kanada Rika Kogyo Co., Ltd. at 1,500 rpm for 5 hours to obtain pigment dispersion 1. It was. As beads, zirconia beads having a diameter of 0.6 mm were used, and the filling rate in the pot was 70%.
The carbon black used was Black Pearls 880 marketed by Cabot, USA, and the styrene-acrylic resin had a copolymerization ratio of 70:30, Mw = 8,000, and an acid value of 170. The styrene-acrylic resin was added in advance with water and potassium hydroxide equivalent to the acid value, stirred at 80 ° C., and used as a solution.

  100 parts of the obtained pigment dispersion 1 was heated to 70 ° C. in a nitrogen atmosphere, and while stirring with a motor, 4.28 parts of benzyl methacrylate, 1.42 parts of methoxypolyethylene glycol methacrylate, 0 of methacrylic acid .3 parts, 0.1 part of octyl mercaptan and 0.04 part of potassium persulfate in 6 parts of water were gradually added dropwise. After 5 hours of polymerization, the dispersion is diluted 3 times with water, centrifuged at 5,000 rpm for 10 minutes to remove the agglomerated components, and then 10 times with pure water to 20% diethylene glycol. After dilution, the pH was adjusted to 13 with potassium hydroxide, and purification was performed 8 times by ultrafiltration using a 300 K filter membrane with a Pill Filtron and Centramate ultrafiltration system. The dispersible colorant dispersion is further concentrated and then diluted 10 times with pure water, purified twice by ultrafiltration, and then concentrated to fix the charged resin pseudo fine particles. 1 was obtained. At this time, as the purification conditions, the pump output and the pressure in the flow path were adjusted so that the total flow rate was 1 liter / min and the membrane pressure was 0.05 MPa.

The dispersible colorant dispersion 1 to which the obtained chargeable resin pseudo fine particles are fixed is mixed with the following components to a concentration of 4%, and further filtered under pressure with a membrane filter having a pore size of 2.5 microns. Recording ink 1 was obtained.
・ Glycerol 7 parts ・ Diethylene glycol 5 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH 0.1 part ・ Ion-exchanged water remainder (amount that makes the whole 100 parts)

[Example 2]
100 parts of Pigment Dispersion Liquid 1 was heated to 70 ° C. in a nitrogen atmosphere, and 5.70 parts of benzyl methacrylate, 0.3 part of methacrylic acid, and 0.04 part of potassium persulfate were added to water 6 while stirring with a motor. After gradually adding dropwise the mixed solution dissolved in the part and stirring at 70 ° C. for 5 hours, the dispersion is diluted 3 times with water and centrifuged at 5,000 rpm for 10 minutes to remove the agglomerated components. After the removal, purification and concentration were performed by ultrafiltration under the same conditions as in Example 1 to obtain a dispersible colorant dispersion 2 in which the charged resin pseudo fine particles were not fixed. The dispersible colorant dispersion 2 to which the obtained chargeable resin pseudo fine particles were fixed was mixed and pressure-filtered in the same manner as in Example 1 to a concentration of 4% to obtain a recording ink 2.

[Comparative Example 1]
100 parts of Pigment Dispersion Liquid 1 was heated to 70 ° C. in a nitrogen atmosphere, and 5.70 parts of benzyl methacrylate, 0.3 part of methacrylic acid, and 0.04 part of potassium persulfate were added to water 6 while stirring with a motor. After gradually adding dropwise the mixed solution dissolved in the part and stirring at 70 ° C. for 5 hours, the dispersion is diluted 3 times with water and centrifuged at 5,000 rpm for 10 minutes to remove the agglomerated components. Removal was performed to obtain a dispersible colorant dispersion 3 to which the chargeable resin pseudo fine particles were fixed. The dispersible colorant dispersion 2 to which the obtained chargeable resin pseudo fine particles were fixed was mixed and pressure-filtered in the same manner as in Example 1 so as to have a concentration of 4%, whereby Comparative ink 2 was obtained.

  Example 2 and Comparative Example 1 were also evaluated in the same manner as Example 1. The results are shown below.

  According to the present invention, a simple production method that uses aqueous precipitation polymerization (soap-free polymerization) in a pigment dispersion and reduces the amount of resin not adsorbed to the pigment after polymerization through an ultrafiltration step. Further, it is possible to provide an ink for ink jet recording excellent in ejection stability and color developability.

It is a schematic diagram which shows the basic structure of the dispersible color material which has fixed the chargeable resin pseudo fine particles by this invention. It is a schematic diagram of the typical process in the manufacturing method of this invention. It is a schematic diagram which shows the refinement | purification of the chargeable resin pseudo fine particles and the adhering process to a color material in the manufacturing method of this invention. It is the schematic diagram which expanded the chargeable resin pseudo fine particle of this invention from the interface side fixed to a coloring material. It is the schematic diagram which expanded the interface which the chargeable resin pseudo fine particles of this invention and the coloring material adhere. It is a schematic diagram of a pigment peeling phenomenon when a hydrophilic group is directly modified on an organic pigment, represented by Patent Document 1. FIG. 6 is a schematic diagram illustrating an aggregation state of a dispersible color material on a recording medium. It is a figure explaining (theta) used by this invention.

Explanation of symbols

1: Color material 1a: Part of color material 2: Charged resin pseudo fine particles 3: Dispersion resin 4: Monomer 5: Polymerization initiator aqueous solution 6: Dispersible color material 7: Oligomer 8 formed by polymerizing monomers: Precipitate in which oligomer is insolubilized in water 9-1: Hydrophilic monomer unit portion 9-2 in charged resin pseudo fine particle: Hydrophobic monomer unit portion 10 in charged resin pseudo fine particle 10: Binding site 11 with coloring material 11: Interfacial portion 12 of the chargeable resin pseudo fine particles with the color material 12: hydrophilic group 13 directly modified with the color material 13: hydrophilic colorant molecule 14: recording medium 15: repulsive force 16 acting between the charge resin pseudo fine particles: Recording portion 17 by ink droplet: boundary point where no ink droplet is attached 18: point where the thickness of the ink droplet closest to the boundary point is maximum

Claims (4)

  Inkjet recording comprising a dispersible color material having a color material and chargeable resin pseudo fine particles smaller than the color material, wherein the color material and the charge resin pseudo fine particles are fixed to each other In the ink for recording, when an image is recorded by depositing the ink as a droplet on the glossy recording medium paper, the boundary point between the location where the ink droplet is adhered and the location where the ink droplet is not adhered, and the boundary When the straight line formed by connecting the point where the thickness of the ink droplet closest to the point of the ink is connected to the point where the thickness of the ink droplet is the maximum is θ, the θ is 15 ° or more. Ink for inkjet recording characterized.   2. The ink jet recording according to claim 1, wherein the coloring material is a pigment, and a ratio of the pigment and all resin components contained in the ink (resin mass / pigment mass = B / P) is 0.5 or less. For ink.   The hydrophobic monomer is benzyl methacrylate and / or (meth) acrylic acid alkyl ester, and the hydrophilic monomer is (meth) acrylic acid, (meth) acrylic acid methoxypolyethylene glycols and carbon chains of 4 to 40. The ink for inkjet recording according to claim 1 or 2, which is at least one selected from (meth) acrylic acid long-chain alkyl esters. The dispersible colorant, to which the chargeable resin pseudo fine particles are fixed, is obtained by dropping the hydrophobic monomer, the hydrophilic monomer, and the anionic or amphoteric aqueous radical polymerization initiator into an aqueous pigment dispersion and dropping the water-based precipitation polymerization. The inkjet recording ink according to claim 1, wherein the inkjet recording ink is obtained.

Images