JP2006037091A - Water-based ink, ink tank, ink jet recording apparatus, ink jet recording method, and ink jet recorded image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink which gives a high printing concentration without depending on the permeation performance of a recording medium in a pigment ink, and gives printed products having excellent scratch resistance, marker resistance and water resistance, to provide an ink tank using the ink, to provide a recording apparatus, and to provide an ink jet recorded image. <P>SOLUTION: This water-based ink comprising water, a plurality of water-soluble organic solvents and a dispersible colorant, wherein the water-soluble organic solvents comprise a good solvent and a poor solvent for the dispersible colorant, is characterized as follows. The dispersible colorant is a dispersible colorant having a colorant and chargeable resin pseudo fine particles having a smaller size than the colorant, wherein the colorant is adhered to the fine particles. A:B is in a range of 10:5 to 10:30, wherein A is the total amount of the good solvent in the ink, and B is the total amount of the poor solvent. And a water-soluble organic solvent showing the maximum Ka value among the Ka values of the water-soluble organic solvents, determined by Bristow procedure, is a poor solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aqueous ink containing a dispersible color material, an ink tank, an ink jet recording apparatus, an ink jet recording method, and an ink jet recorded image.

  Conventionally, it has been known that an image having excellent fastness such as water resistance and light resistance can be obtained by using a water-insoluble colorant as a colorant, for example, an ink containing a pigment (pigment ink). In order to use such a color material as an aqueous ink jet recording ink, it is necessary to stably disperse it 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.

  In addition, a technique for chemically modifying the surface of a water-insoluble colorant has been proposed (see, for example, Patent Document 1). Further, a microcapsule type pigment in which the pigment is coated with a resin has been proposed (for example, see Patent Documents 2 and 3). In particular, Patent Document 3 discloses a water-based colored fine particle dispersion containing a water-insoluble colorant. “The colored fine particle dispersion dispersed a water-insoluble colorant in an aqueous medium in the presence of a dispersant. When the vinyl monomer is added later and polymerized, the dispersion exhibits a dispersion stability when the water-insoluble colorant is dispersed, and the vinyl monomer is polymerized in the presence of the dispersant alone. An aqueous colored fine particle dispersion characterized by poor stability of the resulting latex is disclosed.

  On the other hand, various techniques have been proposed for the purpose of further improving the optical density of an image formed with such an ink. For example, it has been proposed that an image density can be further improved by using an ink containing self-dispersing carbon black and a specific salt (see, for example, Patent Document 4). Also, an ink for inkjet recording, which is a composition containing pigment, polymer fine particles, water-soluble organic solvent and water, and a polyvalent metal-containing aqueous solution are attached to a recording medium, and the ink composition and the polyvalent metal aqueous solution are reacted. Therefore, there is a proposal of a technique for forming a high-quality image (see, for example, Patent Document 5). In any of these techniques, the pigment existing in a dispersed state in the ink is forcibly aggregated on the surface of the recording medium, thereby suppressing the penetration of the pigment into the recording medium. An image having a higher density than that obtained with the pigment ink is obtained.

Japanese Patent Laid-Open No. 10-195360 JP-A-8-183920 JP 2003-34770 A JP 2000-198955 A JP 2000-63719 A

  However, in the presence of various recording media, an ink that can always obtain a high print density regardless of the permeation performance of the recording medium, and can sufficiently obtain the scratch resistance, marker resistance and water resistance of the printed matter. The current situation is that it has not been obtained.

  Accordingly, an object of the present invention is to provide a water-based ink that can obtain a high printing density in a pigment ink without depending on the permeation performance of the recording medium, and is excellent in scratch resistance, marker resistance and water resistance of the printed matter. The point is to provide. Another object of the present invention is to provide a water-based ink capable of always obtaining a high print density while having excellent long-term storage stability and ejection stability. Another object of the present invention is to provide a water-based ink having excellent bleed resistance in which occurrence of bleed (mixed color bleeding) with other inks is suppressed while having excellent print quality. Another object of the present invention is to provide a water-based ink having an excellent quick-drying property while always maintaining a high print density. Furthermore, another object of the present invention is to provide an ink tank, an ink jet recording apparatus, an ink jet recording method, and an ink jet recorded image using such aqueous ink.

  On the other hand, as a result of earnestly examining the means for solving the above problems, the present inventors include water, a plurality of water-soluble organic solvents, and a dispersible colorant having a novel configuration. A water-based ink containing a good solvent for the dispersible colorant and a poor solvent for the dispersible colorant at a specific ratio has excellent long-term storage stability and ejection stability, and has a penetrating performance for a recording medium. A water-based ink which can obtain a high print density without depending on the print quality and which is excellent in scratch resistance, marker resistance and water resistance of the printed matter was obtained.

That is, the present invention includes water, a plurality of water-soluble organic solvents, and a dispersible color material, and the water-soluble organic solvent includes a good solvent for the dispersible color material and a poor solvent for the dispersible color material. Water-based ink
The dispersible color material is a dispersible color material having a color material and chargeable resin pseudo fine particles smaller than the color material, and the color material and the chargeable resin pseudo fine particles are fixed,
Furthermore, when the total amount (% by mass) of the good solvent in the ink is A and the total amount (% by mass) of the poor solvent in the ink is B, A: B is in the range of 10: 5 to 10:30. In addition, the water-based ink is characterized in that the water-soluble organic solvent exhibiting the maximum Ka value among the Ka values of the plurality of water-soluble organic solvents obtained by the Bristow method is a poor solvent.

  The present invention also provides an ink tank comprising the above water-based ink.

  According to another aspect of the present invention, there is provided an ink jet recording apparatus which forms an ink jet recording image using the water-based ink.

  According to another aspect of the present invention, there is provided an ink jet recording method, wherein an image is formed by an ink jet recording apparatus using the water-based ink.

  The present invention is also an ink jet recording image formed by an ink jet recording apparatus using the water-based ink.

  According to the present invention, it has excellent long-term storage stability and ejection stability, can obtain an image with a high print density without depending on the permeation performance of the recording medium, and can also provide scratch resistance and resistance to the printed matter. An aqueous ink excellent in marker properties and water resistance is provided. Further, as another effect of the present invention, there is provided a water-based ink capable of always obtaining an image with a high print density while having excellent long-term storage stability and ejection stability. As another effect, a water-based ink excellent in bleed resistance performance while having excellent printing quality is provided. As another effect of the present invention, there is provided an aqueous ink capable of obtaining an image having excellent quick drying properties while always maintaining a high print density.

  In addition, as another effect of the present invention, an ink jet recording method that provides good printing performance even on a plain paper medium having high permeability is provided by using such water-based ink. An ink tank, an ink jet recording apparatus, and an ink jet recording image that can be suitably used are provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. The water-based ink according to the present invention can be used for a recording method using a writing instrument such as a pen, an ink-jet recording method, and various other printing methods. Used.

[Dispersible colorant]
The first feature of the dispersible color material used in the present invention is a dispersible color material comprising a color material and a chargeable resin pseudo fine particle smaller than the color material, wherein the color material is the chargeable material. The resin pseudo fine particles are fixed. FIG. 1 is a schematic diagram of a dispersible color material, which characterizes the present invention, in which chargeable resin pseudo fine particles 2 are fixed to a color material 1. A portion 2 ′ in FIG. 1B is a portion schematically showing a state in which a part of the chargeable resin pseudo fine particles 2 fixed to the surface of the color material 1 is fused.

  By fixing the chargeable resin pseudo fine particles to the color material, the charge of the chargeable resin pseudo fine particles is imparted to the surface of the color material, so that the dispersible color material can be dispersed in water or an aqueous ink medium. At the same time, the dispersible colorant has excellent adhesion to the recording medium due to the presence of the resin component adhering to the surface. At this time, since the chargeable resin pseudo fine particles, which are the characteristic of the dispersible color material used in the present invention, are not in a simple physical adsorption of the resin component, the charge resin pseudo fine particles are fixed to the color material. Since it does not detach from the color material surface, the dispersible color material used in the present invention is excellent in long-term storage stability.

  Here, the chargeable resin pseudo fine particles in the present invention are resin aggregates in which the resin component is strongly aggregated, and preferably have many physical crosslinks formed therein (resin aggregates and Is a resin component having a stable form as a fine particle form or a microaggregate close to it). Details of the chargeable resin pseudo fine particles will be described later.

  The state where the chargeable resin pseudo fine particles are fixed to the color material in the present invention is due to the strong interaction between the color material surface and the chargeable resin pseudo fine particles, and is considered to be achieved in the following state. FIG. 4 shows a schematic diagram in which the interface of the chargeable resin pseudo fine particles in contact with the color material is enlarged. First, the chargeable resin pseudo fine particles 2 are formed by intertwining polymers composed of various monomer unit compositions (indicated by 9-1 and 9-2 in the figure). Since the polymer has various structures locally at the interface with the colorant, various states are distributed in the local surface energy. The color material and the polymer are strongly bonded in that the surface energy generated from the chemical structure and the surface structure of the color material and the surface energy generated from the chemical structure and the surface structure of the polymer are well matched locally. (The part indicated by a black circle in the figure). Furthermore, as shown in FIG. 4, there are a plurality of points where the surface energies of both are locally coincident with each other at the interface where one chargeable resin pseudo fine particle is in contact with the coloring material. It is expected that the fixed state of the present application is established by the strong interaction at the plurality of locations. In the present invention, a state in which, for example, 30% or more of the surface area of the chargeable pseudo fine particles, such as 2 ′ in FIG. 1B, is in contact with the coloring material is referred to as “fusion” for convenience. Is a form of fixation, and there is no need for the chargeable pseudo fine particles and the color material to melt together at the interface.

  In particular, a strong interaction is exerted between constituent polymers inside the chargeable resin pseudo fine particles, and in some cases, the constituent polymers are entangled with each other to form a physical crosslink. For this reason, even when the chargeable resin pseudo fine particles have many hydrophilic groups, the fixed charge resin pseudo fine particles are detached from the coloring material or have hydrophilic groups from the chargeable resin pseudo fine particles. The resin component does not continue to elute. On the other hand, in the encapsulation method as described in Patent Document 2, since the highly hydrophilic resin cannot be strongly bonded to the coloring material, the resin is detached from the coloring material, and as a result, the long-term storage stability is sufficient. It may not be obtained.

  In addition, the dispersible color material used in the present invention has a merit that the chargeable resin pseudo fine particles are fixed to the color material. As a result, the specific surface area of the dispersible color material increases depending on the form, and much of the color material surface It is mentioned that the charge of the chargeable resin pseudo fine particles can be distributed on the surface. As a result, since the dispersible color material has a high specific surface area, the charge of the chargeable resin pseudo fine particles can be converted to the surface charge of the dispersible color material with extremely high efficiency. That is, the form of the dispersible color material used in the present invention is a form in which more surface charges are more efficiently arranged on the surface of the dispersible color material. High dispersion stability can be imparted even when the substantial acid value or amine value of the resin component is smaller than in the form of coating with a resin.

  In general, organic pigments are insolubilized (pigmented) by crystallization of coloring material molecules by strong interaction. In the case of a dispersible color material in which the color material used in the present invention is an organic pigment, as described above, a plurality of interaction points are distributed at the interface between the chargeable resin pseudo fine particles and the color material. The functional resin pseudo fine particles 11 are fixed across several colorant molecules 1a in the pigment particles (see FIG. 5). Therefore, the “pigment peeling” caused by locally making the colorant molecule 1a hydrophilic by the hydrophilic group 12 described in FIGS. 6A and 6B does not occur in the present invention. Preferably, when an organic pigment is used as a color material, the size of the chargeable resin pseudo fine particles is controlled to be within a range smaller than the dispersed particle diameter of the pigment and larger than the color material molecule. An organic pigment dispersible colorant imparted with high dispersibility without breaking the crystal structure can be obtained.

  In the present invention, the state in which the coloring material “fixes” the chargeable resin pseudo fine particles can be simply confirmed by a technique involving the following three stages of separation. First, in the first separation, the color material to be confirmed is separated from other water-soluble components (including water-soluble resin components) contained in the ink or water dispersion, and then the second In the separation, the coloring material and the water-insoluble resin component contained in the precipitate in the first separation are separated. Furthermore, in the third separation, the weakly adsorbed resin component is separated from the dispersible colorant fixing the charged resin pseudo fine particles, and the quantitative determination of the resin component contained in the third separation supernatant, Then, the fixation of the coloring material and the chargeable resin pseudo fine particles is confirmed by comparing the precipitate of the second separation and the precipitate of the third separation.

  Specifically, for example, it can be confirmed under the following conditions. Take 20 g of the ink or water dispersion in which the color material is dispersed, adjust the total solid content to about 10%, and use a centrifuge to perform the first test at 12,000 rpm for 60 minutes. Separation. Of the separated substances, the lower sediment containing the coloring material is redispersed in pure water approximately three times the amount of the sediment, and then the second sediment is obtained at 80,000 rpm for 90 minutes. Perform separation. The lower layer containing the color material is subjected to the third separation again under the condition of 80,000 rotations and 90 minutes by redispersing the sediment of the lower layer containing the color material in 3 times the amount of pure water. Remove the sediment. The sediment in the second separation and the sediment in the third separation were each taken to have a solid content of about 0.5 g and dried under reduced pressure at 30 ° C. for 18 hours using a scanning electron microscope. Observe at 50,000 times. Then, it was confirmed that the observed dispersible colorant had a plurality of fine particle-like substances or fine aggregates equivalent thereto attached to the surface, and the respective sediments from the second separation and the third separation. If it has the same form, it is judged that this coloring material has fixed the resin pseudo fine particles. Further, the upper layer supernatant in the third separation is gently taken from the top so as to be about half the volume, and the solid content mass is calculated from the mass change before and after drying at 60 ° C. for 8 hours. If it is less than 1%, it is considered that the resin pseudo fine particles are not detached from the dispersible color material, and it can be determined that the dispersible color material fixes the resin pseudo fine particles.

  The above-described separation conditions are preferable examples, and any other separation method or separation condition can be used as long as the method achieves the purpose of the first separation and the second and third separations described above. It can be applied as a method for determining whether or not it is a dispersible colorant used in the above. That is, the first separation is for the purpose of separating the color material contained in the ink and water dispersion and the resin component adsorbed thereto, and the water-soluble component, and the second separation is the color material. The purpose is to separate the resin component adhering to the coloring material and the other resin component adsorbing to the coloring material. Furthermore, the third separation is intended to confirm that the resin component adhering to the color material is not detached. Of course, as long as the separation method achieves the respective purposes of the first, second, and third separations, any other separation method that is publicly known or newly developed may be used. Moreover, it is applicable even if it is at least.

  The second feature of the dispersible colorant used in the present invention is that it is a dispersible colorant that can be dispersed alone in an aqueous medium in a state where the water-insoluble colorant 1 has the chargeable resin pseudo fine particles 2 fixed thereto. It is in. As described above, the dispersible colorant used in the present invention is essentially a self-dispersing agent that can be stably dispersed in water and water-based inks without the aid of other surfactants or polymer dispersants. It is a sex color material. This definition and determination method will be described in detail later. Therefore, the dispersible colorant used in the present invention is added with a polymer dispersant or other resin component or a surfactant component that may be released in the long term for the purpose of stabilizing the dispersion of the colorant. There is no need to do. As a result, when the dispersible color material used in the present invention is used as a water-based ink, the degree of freedom of design regarding components other than the dispersible color material is increased. For example, the permeability of ink such as plain paper is increased. It is also possible to obtain a water-based ink that can obtain a sufficiently high printing density even on a high recording medium.

  The self-dispersibility of the dispersible color material used in the present invention can be confirmed, for example, as follows. The ink or water dispersion in which the color material is dispersed is diluted 10-fold with pure water, and concentrated to the original concentration using an ultrafiltration filter having a molecular weight cut off of 50,000. This concentrated solution is separated in a centrifuge at 12,000 rpm for 2 hours, and the sediment is taken out and redispersed in pure water. At this time, it is judged that what the sediment can redisperse well has self-dispersibility. Whether or not it is well re-dispersed depends on whether it is uniformly distributed visually, or if there is no noticeable sediment during standing for 1 to 2 hours, or if it is shaken lightly It can be comprehensively judged from the fact that the average particle size is less than twice the particle size before operation when the dispersed particle size is measured by the dynamic light scattering method.

  As described above, the dispersible colorant used in the present invention takes a form having a high specific surface area by fixing the chargeable resin pseudo fine particles, and has a large amount of charges on its vast surface. Realize excellent storage stability. Therefore, more preferable results can be obtained when the chargeable resin pseudo fine particles are scattered in large numbers and fixed to the color material. In particular, it is desirable that there is a certain distance between the adhering charged resin pseudo fine particles, and it is preferably distributed uniformly. More preferably, it is desirable that a part of the color material particle surface is exposed between the chargeable resin pseudo fine particles. Such a form can be confirmed by observing the aqueous ink according to the present invention with a transmission electron microscope or a scanning electron microscope. That is, a plurality of charged resin pseudo fine particles fixed to the color material surface are fixed at a certain distance, or the color material surface is exposed between the fixed charged resin pseudo fine particles. The state can be observed. In addition, the charged resin pseudo fine particles are sometimes close to each other and may be observed to be fused in some cases, but even in this case, there is a distance between the charged resin pseudo fine particles as a whole. If the surface of the color material is exposed and these states are distributed, it is considered that the charged resin pseudo fine particles are scattered and fixed to the color material. This will be apparent to those skilled in the art.

  Furthermore, it has been clarified that the water-based ink containing the dispersible colorant having the above-described characteristics used in the present invention exhibits excellent quick drying on the recording medium. The reason for this is not clear, but is thought to be based on the following mechanism. As described above, the dispersible color material is dispersed in the ink in a form in which charged resin pseudo fine particles are fixed to the color material surface. When this ink reaches the recording medium, the aqueous solvent in the ink (hereinafter referred to as “ink solvent”) is pores on the recording medium due to capillary action (in the case of plain paper, voids between cellulose fibers; In case of glossy paper, it is absorbed into the pores of the receiving layer) At this time, the dispersible color material used in the present invention has many fine gaps due to the morphological characteristics of the charged resin pseudo fine particles interspersed at portions where the color materials are in contact with each other. For this reason, a capillary phenomenon acts on the ink solvent existing between the color materials, and it is quickly absorbed into the recording medium. In the water-based ink according to the present invention, the dispersible colorant having a form in which charged resin pseudo fine particles are scattered on the surface exhibits a more preferable quick drying property. Expected to be achieved.

  The surface functional group density of the dispersible colorant according to the present invention is preferably 250 μmol / g or more and less than 1,000 μmol / g, and more preferably 290 μmol / g or more and less than 900 μmol / g. When the surface functional group density is smaller than this range, the long-term storage stability of the dispersible colorant may be deteriorated. In addition, when the surface functional group density is considerably larger than this range, the dispersion stability becomes too high, and it tends to penetrate on the recording medium, making it difficult to ensure a high printing density. On the other hand, when carbon black is used as a coloring material, it is necessary to increase the dispersion stability with a high specific gravity of carbon black, and in particular, a material having a high black density on a recording medium is preferred. More preferably, the surface functional group density of the coloring material is set to 350 μmol / g or more and less than 800 μmol / g.

  The surface functional group density is determined as follows, for example. First, a large excess amount of hydrochloric acid (HCl) aqueous solution is added to an aqueous dispersion or ink containing a dispersible colorant to be measured, and the mixture is precipitated by a centrifuge at 20,000 rpm for 1 hour. The sediment is collected and redispersed in pure water, and then the solid content is measured by a drying method. The redispersed sediment is weighed, and a dispersion obtained by adding a known amount of sodium hydrogen carbonate and stirring the mixture is further sedimented in a centrifuge at 80,000 rpm for 2 hours. Weigh the supernatant and subtract the known amount of sodium bicarbonate from the neutralization amount obtained by neutralization titration with 0.1 N hydrochloric acid to obtain the surface functional group density as the number of moles per gram of colorant. It is done.

  Next, each component constituting the dispersible colorant used in the present invention will be described.

[Color material]
The color material which is a constituent component of the dispersible color material used in the present invention will be described below. As the color material used in the present invention, among color materials known or newly developed, it is desirable to use a color material that is insoluble in water and can be stably dispersed in water together with a dispersant. Examples of such materials include hydrophobic dyes, inorganic pigments, organic pigments, metal colloids, and colored resin particles. Preferably, a coloring material having a dispersed particle size in the range of 0.01 to 0.5 μm (10 to 500 nm), particularly preferably in the range of 0.03 to 0.3 μm (30 to 300 nm) is used. A dispersible color material using a color material dispersed in this range is a preferable dispersible color material that gives an image having high coloring power and high weather resistance when used as an aqueous ink. In addition, let this dispersion | distribution particle size be the cumulant average value of the particle size measured by the dynamic light scattering method.

  In the present invention, examples of the inorganic pigment that can be effectively used for the coloring material include carbon black, titanium oxide, zinc white, zinc oxide, tripone, iron oxide, cadmium red, molybdenum red, chrome vermilion, and molybdate orange. , Yellow lead, chrome yellow, 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, Examples include cobalt violet and mica.

  Examples of organic pigments that can be used effectively in the present invention include azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, Various pigments such as indoline and isoindolinone are listed.

  Other organic insoluble colorants that can be used in the present invention include, for example, hydrophobic properties such as azo, anthraquinone, indigo, phthalocyanine, carbonyl, quinoneimine, methine, quinoline, and nitro. Dyes. Of these, disperse dyes are particularly preferable.

  Further, when the color material constituting the dispersible color material contained in the water-based ink of the present invention is a color material having a hydrophilic group on the surface, it has excellent print quality and is resistant to other inks. It became clear by the present inventors that the ink has a particularly excellent bleeding performance. This is because the coloring material originally has a hydrophilic group to prevent adsorption of a surfactant, a penetrating agent, a water-soluble polymer component, etc. constituting the water-based ink, and the above-described poor color on the recording medium. This is considered to be due to an increase in the image forming effect by the solvent.

As the color material having a hydrophilic group on the surface, carbon oxide is preferably used if it is carbon black, and those having many hydroxyl groups, carbonyl groups, carboxyl groups, etc. on the color material surface are preferably used. In particular, it is also preferable to use a self-dispersing pigment that enhances the dispersibility of the water-insoluble colorant itself and is dispersible without using a dispersant or the like. Examples of the self-dispersing pigment include those in which a hydrophilic group is chemically bonded to the pigment particle surface directly or through another atomic group. For example, the hydrophilic group introduced into the pigment particle surface, -COOM ^1, -SO ₃ M ¹ and _{^{-PO 3 H (M 1) 2}} (M 1 in the formula is a hydrogen atom, an alkali metal, ammonium or organic A compound selected from the group consisting of ammonium) and the like can be suitably used. Further, the other atomic group is an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group or a substituted or unsubstituted naphthylene group. More specific examples include, for example, -C ₂ H ₄ —COOM ¹ , —Ph—SO ₃ M ^1, —Ph—COOM ^{1 and the} like (where Ph represents a phenyl group) and the like can be preferably used.

  As a method for directly introducing the hydrophilic group to the surface of the coloring material, a wet oxidation method may be mentioned. This method is a method of impregnating an aqueous phase with a coloring material, adding an oxidizing agent such as peroxodiacid or peroxodiacid salt, and reacting at about 60 to 90 ° C. to perform surface oxidation. More specifically, wet oxidation of such a color material, particularly carbon black, can be performed by a method described in JP-A-2003-183539.

  As another wet oxidation method, there is a method of oxidizing using hypochlorous acid such as sodium hypochlorite and potassium hypochlorite as described in JP-A-2003-96372. At this time, more uniform oxidation is possible when relatively hydrophilic carbon such as gas black and acidic black is used as the carbon to be oxidized. In addition, a method of oxidizing carbon by ozone treatment in water, a method of wet oxidation with an oxidizing agent after ozone treatment, and modifying the carbon black surface can be suitably used.

  On the other hand, as a method for introducing a hydrophilic group into the surface of the colorant through another atomic group, for example, a method of diazotizing p-aminobenzenesulfonic acid to the colorant and reacting with the colorant can be mentioned. The present invention is not limited to these. In the introduction of the hydrophilic functional group by diazotization as described above, it is desirable that the coloring material does not have a primary amine in order to suppress side reactions.

  In the above case, the dispersible colorant of the present invention further has a hydrophilic group (surface charge) based on the chargeable resin pseudo fine particles. The hydrophilic group attributed to being directly bonded to the above-described colorant and the hydrophilic group attributed to the pseudo fine particle can be separated and distinguished as follows.

  The ink containing the dispersible colorant of the present invention is separated by a centrifuge at 12,000 rpm for 60 minutes. After the separation, the lower layer precipitate containing the coloring material is taken out, and this is put into an organic solvent having high solubility in a resin such as toluene or acetone and dissolved. For this reason, the chargeable resin pseudo fine particles that are fixed or fused are dissolved so that they are detached from the dispersible colorant, and the colorant itself is present in the organic solvent. Next, this is rotated 80,000 times in a centrifugal separator to precipitate and separate the color material. Next, the coloring material is washed and then redispersed in pure water.

  The color material taken out from the ink of the present invention is redispersed by the above method, and the surface charge can be measured. On the other hand, when it is obtained by adsorbing a dispersing agent such as a surfactant or a polymer resin, the aqueous dispersion or ink obtained by conventional microencapsulation is adsorbed when it is introduced into an organic solvent. Since the components are dissolved and desorbed from the water-insoluble colorant, they are not redispersed in pure water, and the surface charge of the water-insoluble colorant itself in the present invention cannot be measured.

  Further, the degree of hydrophilicity (oxidation) on the surface of the color material can be evaluated as a loss on heating of the color material (volatile content (%)). In the present invention, the weight loss by heating is preferably 2% by mass or more and 20% by mass or less. When the amount is less than the above range, sufficient dispersion stability alone may not be obtained due to the low hydrophilicity of the color material surface. On the other hand, when the amount is larger than the above range, there may be a case where sufficient image density, bleed or the like cannot be obtained.

  The degree of oxidation of the carbon black surface is evaluated as the volatile content (%) of carbon black. Normally, when carbon black is heated to about 1,000 ° C. under vacuum, a gas corresponding to the type of functional group present on the surface is generated, and the total amount of the gas or the gas species is analyzed. The type and amount of surface functional groups can be known. Moreover, it turns out that it is carbon which has a large amount of hydrophilic groups, so that the sum total of heating weight reduction amount is high. In general, there are almost no hydrophilic groups such as carboxyl groups and hydroxyl groups on the pigment surface, and in the case of carbon black, the volatile content of hydrophobic carbon black by the ordinary furnace method is 2% by mass or less.

[Charged resin pseudo fine particles]
The charged resin pseudo fine particles, which are another component of the dispersible color material used in the present invention, are substantially insoluble in water, and the color material to be fixed in water (or in ink). The dispersion unit (dispersion particle size) is small, and is defined as a fine body formed by aggregating resin components having a sufficiently high degree of polymerization. The form of the minute body is pseudo close to a sphere, or a plurality of minute bodies (chargeable resin pseudo fine particles) are arranged within a certain range. It is preferable that the resin components constituting the chargeable resin pseudo fine particles are physically or chemically cross-linked with each other. Whether the resin components constituting the chargeable resin pseudo fine particles are cross-linked with each other can be confirmed by using, for example, the following method. The resin component constituting the chargeable resin pseudo fine particles is estimated in advance by a known analysis method, and a linear polymer having the same chemical structure (or the same monomer unit composition) is synthesized by solution polymerization, On the other hand, when the chargeable resin pseudo fine particles and the polymer are immersed in an organic solvent, which is a good solvent, and their solubility is compared, the chargeability is determined when the solubility of the chargeable resin pseudo fine particles is lower than the solubility of the polymer. It is confirmed that the interior of the resin pseudo fine particles is crosslinked.

  As another preferred embodiment, when the dispersed particle size of the charged resin pseudo fine particles in water can be measured by, for example, the dynamic light scattering method, the average value of the dispersed particle size of the cumulant is preferably used. It is desirable to be in the range of 10 nm to 200 nm. Furthermore, from the viewpoint of long-term storage stability of the dispersible colorant, it is more preferable that the polydispersity index of the dispersed particle diameter is suppressed to less than 0.2. When the center value of the dispersed particle diameter is larger than 200 nm or when the polydispersity index is larger than 0.2, the original purpose of finely dispersing and stabilizing the coloring material may not be sufficiently achieved. Further, when the average value of the dispersed particle diameter is smaller than 10 nm, the form as the chargeable resin pseudo fine particles cannot be sufficiently maintained, and the resin is easily dissolved in water, so that the merit of the present invention cannot be obtained. There is a case. On the other hand, in the range of 10 nm or more and 200 nm or less, the particle size is smaller than the color material particles themselves, whereby the dispersion stabilization of the color material by the fixing of the chargeable resin pseudo fine particles in the present invention is effectively expressed. . The above preferred embodiment is the same when the dispersed particle size of the chargeable resin pseudo fine particles is not measurable. In that case, for example, the average diameter of the chargeable resin pseudo fine particles in the electron microscope observation is as described above. It is considered to be a preferred range or a range equivalent thereto.

  When the color material is an organic pigment, in addition to the above range, as described above, the charged resin pseudo fine particles are smaller than the pigment dispersed particle size and larger than the color material molecule. It is particularly desirable because a dispersible colorant having a structurally extremely stable and high dispersibility can be obtained.

  The chargeability in the present invention refers to a state in which a functional group that is ionized in some form in the aqueous medium itself is retained, and is desirably self-dispersible by the chargeability. Therefore, whether or not it is a chargeable resin pseudo fine particle is determined by a method of measuring the surface zeta potential of the chargeable resin pseudo fine particle by a publicly known and arbitrary method, a potentiometric titration by a method as described later, and a functional group. A method for calculating the density, a method for confirming the dependency of dispersion stability on the electrolyte concentration by adding an electrolyte to the aqueous dispersion of the charged resin pseudo fine particles, or a chemical structure analysis of the charged resin pseudo fine particles as a known method The method can be confirmed by any one of the methods of examining the presence or absence of an ionic functional group.

  The resin component constituting the chargeable resin pseudo fine particles may be any resin component such as any commonly used natural or synthetic polymer, or a newly developed polymer for the present invention, without limitation. . Examples of resin components that can be used include acrylic resins, styrene / acrylic resins, polyester resins, polyurethane resins, polyurea resins, polysaccharides, and polypeptides. In particular, from the standpoint that it can be used generally and the functional design of the chargeable resin pseudo fine particles can be easily performed, a polymer or copolymer of a monomer component having a radical polymerizable unsaturated bond, such as an acrylic resin or a styrene / acrylic resin, is used. A polymer can be preferably used.

  In the present invention, a monomer having a radical polymerizable unsaturated bond (hereinafter referred to as a radical polymerizable monomer or simply a monomer) is preferably used. For example, the following can be mentioned. Classified as hydrophobic monomers, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylate-n-propyl, acrylate-n-butyl, acrylate-t-butyl, benzyl acrylate, methyl methacrylate (Meth) acrylic acid esters such as ethyl methacrylate, isopropyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, tert-butyl methacrylate, tridecyl methacrylate and benzyl methacrylate Styrene monomers such as styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene and p-tert-butyl styrene; itaconic acid esters such as benzyl itaconate; dimethyl maleate, etc. Male like Phosphate esters; fumaric acid such as fumaric acid esters such as dimethyl acrylonitrile, methacrylonitrile and vinyl acetate. In the present invention, (meth) acrylic acid means methacrylic acid and acrylic acid.

  In addition, those classified as the following hydrophilic monomers are also preferably used. For example, monomers having an anionic group include, for example, monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid and fumaric acid, and the like. A monomer having a sulfonic acid group such as a salt, styrene sulfonic acid, sulfonic acid-2-propyl acrylamide, acrylic acid-2-ethyl sulfonate, ethyl methacrylic acid-2-ethyl sulfonate and butyl acrylamide sulfonic acid, and salts thereof, And monomers having a phosphonic acid group such as ethyl methacrylate-2-phosphonate and ethyl acrylate-2-phosphonate. Among these, it is particularly preferable to use acrylic acid and methacrylic acid.

  Monomers having a cationic group include monomers having a primary amino group such as aminoethyl acrylate, aminopropyl acrylate, methacrylamide, aminoethyl methacrylate and aminopropyl methacrylate, methylaminoethyl acrylate. Secondary amino groups such as methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, methylaminoethyl methacrylate, methylaminopropyl methacrylate, ethylaminoethyl methacrylate, and ethylaminopropyl methacrylate Monomers having dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, Monomers having tertiary amino groups such as diethylaminoethyl tacrylate, dimethylaminopropyl methacrylate and diethylaminopropyl methacrylate, dimethylaminoethyl methyl chloride acrylate, dimethylaminoethyl methyl chloride methacrylate, dimethylaminoethyl acrylate Examples thereof include monomers having a quaternary ammonium group such as benzyl chloride salt and dimethylaminoethyl benzyl chloride salt of methacrylate, and various vinylimidazoles.

  Specific examples of the nonionic hydrophilic monomer include monomers having a radical polymerizable unsaturated bond and a hydroxyl group exhibiting strong hydrophilicity in the structure at the same time. Hydroxyethyl (meth) acrylate, hydroxylpropyl (meth) acrylate, and the like are classified into this. In addition, various known or novel oligomers and macromonomers can be used without limitation.

Among the above monomers, the chargeable resin pseudo fine particles are represented by the formula (1):
^{_{CH 2 = C (R 1)}} COO (R 2 O) n R 3 (1)
(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ² represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ represents hydrogen. (The monovalent hydrocarbon group having 1 to 30 carbon atoms which may have an atom or a hetero atom, and n represents the number of 1 to 60.)
In particular, in the case of including at least a polymer polymerized by including at least a monomer represented by the following formula, it is possible to obtain a water-based ink having excellent quick-drying properties while always giving a high printing density. It became clear by examination.

  Typical examples of the monomer represented by the above formula (1) are polyethylene glycol (meth) acrylate and methoxypolyethylene glycol (1 to 30: the value of n in the formula (1) whose terminal is a hydrogen atom. Same) (meth) acrylate, methoxypolytetramethylene glycol (1-30) (meth) acrylate, ethoxypolyethylene glycol (1-30) (meth) acrylate, (iso) propoxypolyethylene glycol (1-30) (meth) acrylate , Butoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (1-30, ethylene glycol in it: 1 29) (Meta) Acrylate, and the like. These may be used alone, or two or more thereof. Among these, methoxypolyethylene glycol (1-30) (meth) acrylate having a hydrogen atom, a methyl group or an ethyl group at the terminal is preferable.

  Among the monomers represented by the formula (1), methoxy-terminated polyethylene glycol (4 mol) methacrylate ester (for example, trade name: NK ester M-40G, etc., manufactured by Shin-Nakamura Chemical Co., Ltd.), methoxy-terminated polyethylene Glycol (9 mol) methacrylate ester (for example, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M-90G, etc.), methoxy-terminated polyethylene glycol (2 mol) methacrylate ester (for example, Shin-Nakamura Chemical Co., Ltd.) Manufactured, trade name: NK ester M-230G, etc.], terminal methoxypolyethylene glycol (9 mol) acrylic acid ester [eg, Shin-Nakamura Chemical Co., Ltd., trade name: NK ester AM-90G, etc.], phenoxy-terminated polyethylene glycol (6 mol) acrylate [for example, Shin-Nakamura Chemical Co., Ltd., trade name: NK Tel AMP-60G etc.], terminal hydroxyl group polyethylene glycol (5 mol) methacrylate [for example, product name: MA-50 etc., manufactured by Nippon Emulsifier Co., Ltd.], terminal hydroxyl group polyethylene glycol (10 mol) methacrylate [for example, Japanese emulsifier ( Co., Ltd., trade name: MA-100 etc.] is preferable. Among these, from the viewpoint of obtaining superior dispersion stability and high print density, methoxy-terminated polyethylene glycol methacrylate is more preferable, and oxyethylene in the polyethylene glycol chain is 4 to 9 mol. Is more preferable.

  When the chargeable resin pseudo fine particles include at least a polymer obtained by polymerizing at least the monomer represented by the formula (1), 1% by mass or more and 70% by mass of the total chargeable resin pseudo fine particles. From the viewpoint of the morphological stability of the charged resin pseudo fine particles in the aqueous ink, it is desirable that the content be less than 3% by mass and more preferably less than 60% by mass.

  Depending on many control factors such as the type and copolymerization ratio of the monomer constituting the chargeable resin pseudo fine particles, the type and concentration of the polymerization initiator used in the preparation, various kinds of dispersible colorant and chargeable resin pseudo fine particles The characteristics can be appropriately controlled. In particular, it is desirable that the chargeable resin pseudo fine particles be composed of a copolymer of monomer components including at least one hydrophobic monomer and at least one hydrophilic monomer among the monomers listed above. . At this time, by using at least one kind of hydrophobic monomer, it is possible to achieve good form control by using at least one kind of hydrophilic monomer, and to achieve good adhesion to the colorant and thermal stability. Dispersion stability can be imparted respectively. Therefore, by using these monomers simultaneously, it is possible to obtain chargeable resin pseudo fine particles that are always well fixed to the colorant and can impart good dispersion stability. It is fixed to the dispersible colorant and / or colorant according to the present invention by appropriately selecting the monomer type and copolymerization ratio of the resin component constituting the chargeable resin pseudo fine particles while satisfying the above conditions. Further functionality can be imparted to the chargeable resin pseudo fine particles.

  For example, as the hydrophobic monomer, it is also preferable to use one having at least a monomer having a methyl group at the α-position and having a radical polymerizable unsaturated double bond. By fixing the chargeable resin pseudo fine particles using a radically polymerizable monomer having a methyl group at the α-position, particularly in a thermal ink jet method in which ink is discharged by thermal energy, the discharge property of water-based ink containing a dispersible colorant is improved. Very good. The reason for this is not clear, but resins using a radically polymerizable monomer having a methyl group at the α-position cause depolymerization at high temperatures, and therefore have a methyl group at the α-position when thermal energy is applied to the ink. Since the resin composed of the monomer component undergoes depolymerization and sticking into the discharge port is less likely to occur, it is considered that the discharge property is improved.

  Moreover, it is also a preferable form to contain at least an acrylic acid alkyl ester compound and a methacrylic acid alkyl ester compound (hereinafter referred to as a (meth) acrylic acid alkyl ester compound) as the hydrophobic monomer. The (meth) acrylic acid alkyl ester compound has good adhesion to the color material, and at the same time, is excellent in copolymerization with the hydrophilic monomer component, and is uniform in surface properties of the chargeable resin pseudo fine particles and the color material. A preferable result is given from the viewpoint of uniform adherence.

  Of the above-mentioned preferred hydrophobic monomers, it is particularly preferred to contain at least one selected from benzyl methacrylate or methyl methacrylate. In addition to the above-mentioned preferred reasons, the above two types of monomers impart preferable heat resistance and transparency to the charged resin pseudo fine particles, and therefore, the dispersible color material formed by fixing the charged resin pseudo fine particles has excellent color development. Showing gender.

  As described above, the properties of the chargeable resin pseudo fine particles fixed to the dispersible colorant and / or the colorant of the present invention can be selected by appropriately selecting the monomer type and copolymerization ratio constituting the chargeable resin pseudo fine particles. Although it can be controlled, the glass transition temperature of the copolymer component contained in the chargeable resin pseudo fine particles is −40 ° C. or higher and 60 ° C. or lower, preferably −30 ° C. or higher and 55 ° C. or lower, more preferably −25 ° C. or higher and 53 ° C. or lower. It is also a preferable form to control the temperature to be not higher than ° C. In order to obtain such chargeable resin pseudo fine particles, a monomer group that is known to have a low glass transition temperature of a homopolymer obtained from the monomer among the above-mentioned monomer groups that are preferably used is selected and used. For example, it is also a preferable embodiment to use acrylic acid-n-butyl and acrylic acid as monomers in an appropriate ratio. It is also another preferred embodiment to use ethyl methacrylate and methacrylic acid as monomers in an appropriate ratio.

  The dispersible colorant comprising a copolymer component having a glass transition temperature of −40 ° C. or more and 60 ° C. or less is adjacent to the recording paper due to the high film-forming property imparted to the chargeable resin pseudo fine particles. A strong coloring film can be formed by forming a film with a coloring material. Therefore, the printed matter obtained using the dispersible color material having such a structure not only provides high scratch resistance but also scratch resistance on a glossy recording medium that is extremely disadvantageous in scratch resistance. Excellent printed matter can be obtained.

  The glass transition temperature of the chargeable resin pseudo fine particles can be measured by the following procedure. The dispersible colorant is subjected to acid precipitation with hydrochloric acid or the like to recover the precipitate. Furthermore, the charged resin pseudo fine particles fixed to the color material can be obtained by subjecting the precipitate to Soxhlet extraction using an organic solvent such as THF (tetrahydrofuran) and distilling off the organic solvent. The glass transition temperature can be measured by performing differential scanning calorimetry of the obtained chargeable resin pseudo fine particle component. For example, a device such as DSC822e manufactured by METTTLER may be used. In the case of an aqueous dispersion in which a dispersible colorant and a water-soluble nonionic resin coexist, they can be separated using a centrifuge. For example, when separation is performed under a centrifugal separation condition of 12,000 rpm, a dispersible color material can be obtained as a sediment.

[Synthesis of chargeable resin pseudo fine particles and fixation to coloring material]
The method for synthesizing the chargeable resin pseudo fine particles and the method for fixing to the color material are carried out by a method for synthesizing the charge resin pseudo fine particles and a method for combining the charge resin pseudo fine particles and the color material. Can do. On the other hand, the present inventors, as a result of intensive studies, are dispersible colorants having the colorant and the chargeable resin pseudo fine particles smaller than the colorant, which are the characteristics of the present invention. It came to invent the manufacturing method which can obtain easily the dispersible color material of the state which this chargeable resin pseudo fine particles adhere to the material. Hereinafter, a suitable method for producing a dispersible color material, from which the dispersible color material used in the present invention can be easily obtained, will be described. Further, in the case of a self-dispersing color material, the dispersion itself is prepared.

  As a result of the study by the present inventors, it has been clarified that the dispersible colorant used in the present invention having the above-described characteristics can be produced very simply by applying the aqueous precipitation polymerization method under the following conditions. It was. In such a production method, first, a water-insoluble colorant is dispersed with a dispersant to prepare a dispersed aqueous solution of the water-insoluble colorant. Next, in this dispersed aqueous solution, the chargeable resin pseudo fine particles are fixed to the coloring material by a step of aqueous precipitation polymerization of the radical polymerizable monomer using an aqueous radical polymerization initiator. The dispersible colorant obtained through this aqueous precipitation polymerization process is a water-insoluble color in which the chargeable resin pseudo fine particles synthesized in the aqueous precipitation polymerization process are strongly and firmly adhered to the colorant. It becomes a material and has excellent dispersion stability by itself. Further, in the above aqueous precipitation polymerization process, the characteristics of the chargeable resin pseudo fine particles can be easily controlled to the preferred form as described above. And the charge resin pseudo fine particles are satisfactorily achieved. Hereinafter, preferred embodiments of the manufacturing method will be described in more detail.

(Dispersion of water-insoluble colorant)
First, the water-insoluble colorant preferably used in the present invention as described above is dispersed with a dispersant to obtain an aqueous dispersion. As the dispersant for dispersing the coloring material in the aqueous solution, any of ionic, nonionic, etc. can be used, but from the viewpoint of maintaining dispersion stability in the subsequent polymerization step, the polymer dispersant or water-soluble It is desirable to use a polymer. In particular, a radically polymerizable monomer that is sufficiently water-soluble and that serves as an adsorption site to the oil droplet interface of the radically polymerizable monomer surface and the hydrophobic monomer added in the polymerization process is preferably used. It is done. More preferably, at least one of the hydrophobic monomers used in the subsequent polymerization step is present as a unit constituting the dispersing agent, so that the color of the charged resin pseudo fine particles in the subsequent polymerization step. This is preferable from the viewpoint of easily inducing adhesion to the material.

  The production method of the polymer dispersant and the water-soluble polymer that functions as a dispersant that can be used in the present invention is not particularly limited. For example, a monomer having an ionic group and another polymerizable monomer are non-polymerized. It can manufacture by making it react in the presence or absence of a catalyst in a reactive solvent. In particular, a styrene / acrylic polymer compound obtained by polymerizing a monomer having an ionic group as described above and a styrene monomer as essential components, or a monomer having an ionic group, and the number of carbon atoms is 5. From the ionic group-containing acrylic polymer compound obtained by polymerizing the above (meth) acrylic acid ester monomer as an essential component, it has been clarified that good results can be obtained by using a dispersant selected. . At this time, when the obtained dispersible colorant is intended to have an anionic group in particular, an anionic dispersant, while the obtained dispersible colorant is intended to have a cationic group in particular. In this case, it is desirable to select a dispersant having a cationic group or a nonionic dispersant.

  From the viewpoint of coexistence of promoting the fixation of the chargeable resin pseudo fine particles to the coloring material in the subsequent aqueous precipitation polymerization process and maintaining the dispersion stability of the coloring material in the polymerization process. It is also desirable to use those having an acid value of 100 or more and 250 or less in the case of using an acid, and those having an amine value of 150 or more and 300 or less in the case of using a cationic dispersant. When the acid value and the amine value are smaller than these ranges, the affinity between the hydrophobic monomer and the dispersant becomes higher than the affinity between the colorant and the dispersant during the aqueous precipitation polymerization, and the chargeable resin pseudo In some cases, the dispersing agent may be detached from the surface of the color material before the fine particles are fixed to the color material, and the dispersed state cannot be maintained. In addition, if the acid value and amine value are larger than these ranges, the excluded volume effect of the dispersant on the surface of the color material and the electrostatic repulsion force become too strong, so that the chargeable resin pseudo fine particles adhere to the color material. May be inhibited. When using an anionic dispersant, it is preferable to select a dispersant having a carboxyl group as an anionic group from the viewpoint of not inhibiting the adhesion of the resin fine particles to the colorant.

  In the process of making a water-insoluble colorant into a dispersion aqueous solution with a dispersant, the colorant preferably has a dispersed particle diameter in the range of 0.01 μm to 0.5 μm (10 nm to 500 nm), particularly preferably 0.03 μm or more. Disperse in a range of 0.3 μm or less (30 nm or more and 300 nm or less). The dispersed particle diameter in this process largely reflects the dispersed particle diameter of the dispersible colorant to be obtained, and the above range is preferable from the viewpoint of the above-mentioned coloring power, image weather resistance, and dispersion stability.

  The dispersion particle size distribution of the water-insoluble colorant used in the present invention is preferably monodispersed as much as possible. In general, the particle size distribution of the dispersible colorant obtained by fixing the charged resin pseudo fine particles becomes narrower than the particle size distribution of the dispersed aqueous solution before the polymerization step shown in FIG. Although it tends to be, it basically depends on the particle size distribution of the dispersed aqueous solution. It is also important to narrow the particle size distribution of the color material in order to surely induce fixation due to heteroaggregation of the color material and the charged resin pseudo fine particles. According to the study by the present inventors, when the polydispersity index of the color material is in the range of 0.25 or less, the dispersion stability of the obtained dispersible color material becomes excellent.

  Here, the particle size of the colorant in a dispersed state varies depending on various measurement methods. Particularly, the organic pigment is very small when it is a spherical particle, but in the present invention, the colorant is moved by ELS-8000 manufactured by Otsuka Electronics Co., Ltd. The average particle size and the polydispersity index obtained by the measurement based on the dynamic light scattering method and cumulant analysis were used.

  The method for dispersing the water-insoluble coloring material in water may be any method that uses a dispersing agent as described above, among the methods in which the coloring material can be stably dispersed in water under the conditions described above. It is not limited to any method that is used. Alternatively, a dispersion method newly developed for the present invention may be used. In general, for example, when the water-insoluble colorant is a pigment, the addition amount of the polymer dispersant to be used is suitably 10% by mass or more and 130% by mass or less based on the pigment.

  Examples of the dispersion method of the color material used in the present invention include, for example, 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, and the like. Any dispersion method that is generally used for each color material is not limited.

[Radical polymerization initiator]
As the radical polymerization initiator used in the present invention, any general water-soluble radical polymerization initiator can be used. Specific examples of the water-soluble radical polymerization initiator include persulfates and water-soluble azo compounds. Or the redox initiator by the combination of a water-soluble radical polymerization initiator and a reducing agent may be sufficient. Specifically, in consideration of the characteristics of the colorant, dispersant, and monomer listed above, they are designed and used so as to obtain an optimal combination. Desirably, a polymerization initiator that gives a polymerization initiator residue having the same charge as the surface characteristics of the resulting dispersible colorant is selected. That is, for example, when obtaining a water-insoluble colorant having an anionic group, one having an initiator residue that is neutral or anionic is selected. Thereby, the surface charge can be obtained more efficiently. Similarly, when obtaining a dispersible colorant having a cationic group, it is preferable to select one having an initiator residue that is neutral or cationic.

  As the water-soluble azo polymerization initiator preferably used in the present invention, those generally used for conventional emulsion polymerization and the like are preferably used, and other newly developed polymerization initiators used for emulsion polymerization are: Can also be used. For example, VA-080 (2,2′-azobis (2-methyl-N- (1,1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide)), VA-086 (2,2′-azobis) (2-methyl-N- (2-hydroxyethyl) -propionamide)), VA-057 (2,2′-azobis (N- (2-carboxyethyl) amidinopropane)), VA-058 (2,2 '-Azobis (2- (3,4,5,6, -tetrahydropyrimidin-2-yl) propane) dihydrochloride), VA-060 (2,2'-azobis (2- (1- (2-hydroxyethyl ) -2-imidazolin-2-yl) propane) dihydrochloride, V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride), V-501 (4,4 ′) Azobis (4-cyanopentanoic acid)) include (all manufactured by Wako Pure Chemical Industries, Ltd.) and the like.

[Radically polymerizable monomer]
Since the radically polymerizable monomer used in the production method of the present invention becomes a component constituting the chargeable resin pseudo fine particles through the aqueous precipitation polymerization step described above, the above [substantially water-insoluble resin fine particles ], As described in the section, may be appropriately selected depending on the characteristics of the chargeable resin pseudo fine particles and the dispersible colorant to be obtained. In the production method of the present invention, any conventionally known radically polymerizable monomer or a radically polymerizable monomer newly developed for the present invention can be used.

(Aqueous precipitation polymerization)
Subsequently, a preferred embodiment of the aqueous precipitation polymerization, which is a step of synthesizing the chargeable resin pseudo fine particles, which is a feature of the present invention, and fixing it to the coloring material will be described. In addition, this invention is not restrict | limited at all by embodiment described below. FIG. 2 is a process diagram schematically showing a process flow of the manufacturing method. The process up to obtaining a dispersible colorant by this step is considered as follows. First, as shown in FIG. 2A, a dispersed aqueous solution in which the coloring material 1 is dispersed in the aqueous solution by the dispersant 3 is prepared. At this time, the coloring material is dispersed and stabilized by adsorption of the dispersing agent, and this adsorption is in a thermal equilibrium state. Next, the temperature of the dispersion aqueous solution prepared in FIG. 2A is raised while stirring, and the monomer component 4 is added thereto together with, for example, the aqueous radical polymerization initiator 5 (see FIG. 2B). The added aqueous radical polymerization initiator cleaves when heated to generate radicals, and among the monomer components added to the aqueous dispersion, a small amount of the hydrophobic monomer dissolved in the aqueous phase and the aqueous phase Contributes to the reaction with the water-soluble monomer.

  FIG. 3 is a schematic diagram illustrating a process until the monomer 4 is polymerized to produce a dispersible colorant. When the reaction of the monomer 4 as described above proceeds, the oligomer 7 generated by the polymerization reaction of the monomer component becomes insoluble in water and precipitates from the aqueous phase to become a precipitate 8. However, since the oligomer 7 deposited at this time does not have sufficient dispersion stability, the charged resin pseudo fine particles 2 are formed together. Further, the charged resin pseudo fine particles 2 cause hetero-aggregation with the hydrophobic surface of the color material in the aqueous dispersion as a nucleus, and the resin component constituting the surface of the color material 1 and the charge resin pseudo fine particles 2 has a hydrophobic interaction. Strongly adsorbed by. At this time, the polymerization reaction continues to proceed inside the chargeable resin pseudo fine particles 2, and changes to a more energetically stable form while increasing the adsorption point with the colorant 1. At the same time, since the inside of the chargeable resin pseudo fine particles 2 is highly physically crosslinked, the form that adsorbs the color material 1 most stably is fixed and is in a fixed state. On the other hand, the coloring material 1 is stabilized by fixing the plurality of chargeable resin pseudo fine particles 2, and the dispersant 3 in an equilibrium state is detached from the surface of the coloring material 1.

  FIG. 4 shows a schematic diagram of the chargeable resin pseudo fine particles 2 obtained as described above on the fixing interface side with the coloring material 1. As shown in FIG. 4, since the charged resin pseudo fine particles, which are aggregates of resin components, are present in an arbitrarily distributed hydrophilic monomer unit 9-1, hydrophobic monomer unit 9-2, etc. The surface energy has a distribution, and there are many adsorption points 10 that coincide with the surface energy of the color material.

  FIG. 5 shows an enlarged schematic view of the fixing interface portion between a part of the chargeable resin pseudo fine particles 11 and the part 1a of the color material particles. The interface 11 of the chargeable resin pseudo fine particles is shown in FIG. While adsorbing the adsorbing point 10, it takes a form corresponding to the surface shape of the part 1a of the color material and adheres stably. As described above, since the polymerization reaction is proceeding in the chargeable resin pseudo fine particles also in this process, fixation to the coloring material is achieved by fixing the adsorption in a stabilized form. Through the above-described process, the dispersible color material having the above-described configuration is easily formed (see FIG. 2D). At this time, in a system in which the chargeable resin pseudo fine particles have sufficient surface charge to achieve self-dispersibility, the charge resin pseudo fine particles are interspersed in the process of adsorption and fixation to the coloring material by heteroaggregation. When the electrostatic repulsive force acts mutually, the chargeable resin pseudo fine particles are scattered and fixed to the color material, and the preferred form described above is obtained.

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

  In the above-described steps, particularly when the chargeable resin pseudo fine particles are obtained by polymerizing a monomer component containing at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer, the monomer component is preferably an aqueous solution. It is desirable to drop it into a dispersed aqueous solution of a water-insoluble colorant that contains a radical polymerization initiator in advance. Alternatively, it is also desirable to add the water-insoluble colorant dropwise at the same time or separately from the aqueous radical polymerization initiator in the aqueous dispersion. In order to uniformly obtain desired charged resin pseudo fine particles from a mixture of monomers having different properties such as a hydrophobic monomer and a hydrophilic monomer, it is desirable to always keep the copolymerization ratio of the monomers having different properties constant. . When the mixture of monomers is added to the polymerization system in excess of the amount of monomer consumed in the polymerization reaction within a certain time, only a specific monomer species is polymerized in advance, and the remaining monomers are polymerized in advance. There is a tendency to polymerize after the consumed monomer is consumed, and in this case, a large non-uniformity occurs in the properties of the generated chargeable resin pseudo fine particles. Among the charged resin pseudo fine particles generated in this way, those having a particularly large hydrophilic monomer component content may not be able to adhere to the surface of the color material.

  Furthermore, when the resin component has a high content of the hydrophilic monomer component, it may not be precipitated due to its high hydrophilicity, and may remain in the system as a water-soluble resin component without forming charged resin pseudo fine particles. is there. On the other hand, by dropping the monomer component into a water-insoluble colorant-dispersed aqueous solution containing an aqueous radical polymerization initiator, the copolymerization ratio between the hydrophobic monomer and the hydrophilic monomer is always kept constant. Chargeable resin pseudo fine particles composed of a copolymerization ratio can be obtained uniformly.

  In addition, especially when anionic monomers such as acrylic acid and methacrylic acid are added to the polymerization system as hydrophilic monomers, they may become partially unstable depending on the characteristics of the polymer dispersant in which the colorant is dispersed. , May cause aggregation. In order to prevent this, it is also a preferred embodiment that the anionic monomer is neutralized in advance and added in the form of sodium salt or potassium salt.

  When preparing a water-based ink using the water-insoluble color material obtained by the above-described steps and having the chargeable resin pseudo fine particles fixed to the color material according to the present invention, in addition to the above steps, further purification treatment is performed. It is desirable to do. In particular, in the above, it is possible to carry out purification treatment on unreacted polymerization initiator, monomer component, dispersant, water-soluble resin component that has not been fixed, and chargeable resin pseudo fine particles, etc. Is important in maintaining high. As a purification method to be used, an optimum one may be selected from generally used purification methods. For example, purification using a centrifugal separation method or an ultrafiltration method is a preferred embodiment.

  Through the above-described steps, a dispersible color material in which charged resin pseudo fine particles made of a desired copolymer are fixed to the surface of the color material can be obtained by controlling many control factors. In particular, when an anionic monomer is used for the purpose of high dispersion stability, the dispersible colorant having undergone the process of the present invention has a large surface even if the amount of the anionic monomer used in the above process is relatively small. A functional group density can be obtained and high dispersion stability can be imparted. As a result, it becomes possible to increase the dispersion stability of the chargeable resin pseudo fine particles without impairing the long-term storage stability.

  Although this reason is not clear, the present inventors consider as follows. Polymerization is initiated by radicals generated in water, and when oligomers are precipitated to form charged resin pseudo fine particles, the portion having a large amount of anionic monomer-derived components is preferentially on the water phase side, that is, charged resin pseudo fine particles. Oriented near the surface. This state is maintained even after the chargeable resin pseudo fine particles are fixed to the color material. In the dispersible color material used in the present invention having a structurally large specific surface area, an anionic property derived from an anionic monomer component is further provided. Many groups are present, and as a result, the dispersible colorant obtained by the above-described production method is expected to be stabilized with fewer anionic monomer components.

  Next, the poor solvent and the good solvent used in the present invention will be described. Although details of the definition will be described later, a good solvent is a good dispersion stability of a dispersible colorant in the water-soluble organic solvent, and a poor solvent is a poor one. The feature of the present invention is to pay attention to the dispersible colorant having the specific shape described above and the water-soluble organic solvent contained in the water-based ink together with the dispersible colorant. On the other hand, they are classified into those showing the behavior as the poor solvent and those showing the behavior as the good solvent, and the poor solvent and the good solvent are adjusted at a specific ratio in the water-based ink. With such a configuration, it has excellent storage stability in the ink state, and on the other hand, even on plain paper that has had various problems in image formation with a conventional aqueous ink on a recording medium, A high-quality image with little bleeding is obtained, and even if the amount of ink droplets to be applied is small, it has a sufficiently large area factor and can form an image with a high OD, and also has high scratch resistance, The present inventors have found that a remarkable effect that an ink giving an image excellent in marker resistance and water resistance can be obtained is obtained, and the present invention has been achieved.

  The reason why such an effect is obtained by the present invention is not clear, but the present inventors presume as follows. In general, when an image is formed with a water-based ink on recording paper such as plain paper, it is necessary to leave the color material on the paper more efficiently in order to achieve excellent print density and print quality. is there. As a method therefor, there is a method of obtaining an excellent print density and print quality by attaching a reaction liquid to a recording medium and then attaching a pigment ink composition to a recording paper. In addition, there is a method that achieves both the storage stability of the ink and the achievement of a high print density by using a special dispersant. However, according to the study by the present inventors, it is difficult to obtain a sufficient print density even by these methods, and in particular, both high print density and excellent scratch resistance, marker resistance and water resistance are high levels. Could not be achieved.

  The water-based ink according to the present invention includes at least water, a dispersible color material, and a plurality of water-soluble organic solvents, and as the water-soluble organic solvent, a good solvent for the dispersible color material and a poor solvent for the dispersible color material. And a solvent. When the water-based ink is in an ink state, water, a water-soluble organic solvent containing a good solvent and a poor solvent for the dispersible color material, and the dispersible color material are mixed at a predetermined ratio, Storage stability is maintained by the high dispersion stability of the dispersible colorant and the ratio of the good solvent and the poor solvent.

  When such a water-based ink according to the present invention is printed on a recording medium, particularly plain paper, it is possible to provide a very excellent print density and print quality for the reasons described below. Conceivable. That is, as shown in FIG. 7A, when the ink droplet 1301 according to the present invention is printed on a recording medium 1300, for example, plain paper, the ink starts from the moment when the ink lands on the recording medium. The ratio of the water and the good solvent of the dispersible colorant and the ratio of the poor solvent to the dispersible colorant changes. That is, when the ink droplets land on the surface of the recording medium, at the same time as the evaporation of water, first, the poor solvent having a high Ka value among the water-soluble organic solvents in the ink is more on the recording medium than the good solvent having a low Ka value. It is considered that ink dots are formed by spreading radially. When attention is paid to the spread state of the ink dots in this case, it is considered that the concentration of the poor solvent is higher in the outer periphery 1302 than in the center portion 1303 of the dots. As a result, the concentration of the poor solvent with respect to the dispersible colorant increases abruptly in the process of spreading the ink dots radially on the recording medium. Along with this, the dispersible color material becomes unstable, and the dispersible color material which is the color material aggregates or breaks down. As a result, the dispersible color material 1304 stays on the surface of the recording medium 1300 on the recording medium. Thus, it is considered that ink dots are formed on the outer edge as if the dispersible color material bank was formed (FIG. 7B). Subsequently, due to evaporation and permeation of the water-soluble organic solvent in the central portion 1303 rich in good solvent, the dispersible colorant also aggregates in this portion to form dots 1305 that form an image (FIG. 7C). FIG. 7 (d)). An image formed by the process as described above has a sufficiently large area factor even with a small amount of ink droplets, has a high printing density, and sufficiently reduces the occurrence of feathering. Will be high quality.

  In this mechanism, the dispersible colorant has high dispersion stability by having a relatively small acid value at a high specific surface area in water-based ink, but once landed on the recording medium, the outer periphery of the ink dot When a concentration gradient of the poor solvent appears in the portion, it rapidly destabilizes and aggregates due to its high specific surface area and small acid value. At this time, even when an arbitrary water-insoluble color material is used in the same configuration instead of the dispersible color material, the effect of improving the print quality and the print density can be obtained by the above-described mechanism. However, when a pigment dispersed with an anionic or nonionic substantially water-soluble dispersion resin is used as a water-insoluble colorant, destabilization and aggregation of the poor solvent on the recording medium are caused. The speed is smaller than when the dispersible colorant is used. In this case, if the amount of the poor solvent in the ink is increased in order to increase the aggregation rate of the color material, it is impossible to sufficiently secure the storage stability of the ink for a long period. Similarly, even when a pigment uniformly coated with an anionic resin is used as a water-insoluble colorant, if an anionic property high enough to provide long-term storage stability of the ink is imparted, It is difficult to balance the aggregation rate of the toner and the penetration rate of the coloring material into the recording medium. On the other hand, when the dispersible color material of the present invention is used, it is possible to obtain a printed matter with superior quality in terms of feathering and print density, and the dispersible color material has scratch resistance, marker resistance, and The present inventors have found that water resistance is effectively exhibited.

  Under the assumed mechanism as described above, the good solvent and the poor solvent used in the present invention are determined depending on whether or not the dispersion state of the dispersible colorant can be maintained well. That is, it is determined in relation to the dispersible color material. Therefore, in preparing the ink according to the present invention, when selecting a good solvent and a poor solvent, the degree of dispersion stability of the dispersible colorant to be used in the solvent is observed, and the result It is preferable to obtain. And as a result of various studies on the criteria for determining good and poor solvents that bring about the effects of the present invention in relation to the effects of the present invention, the present inventors have found that the following method is preferable. That is, first, an aqueous dispersion containing about 50% by mass of the solvent to be determined and containing the dispersible colorant used in the ink in a dispersed state is dispersed in the dispersion when stored at 60 ° C. for 48 hours. The particle size (A) is measured. Next, the particle size (B) of an aqueous dispersion containing no or a small amount of the solvent to be determined and containing the dispersible colorant used in the ink in a dispersed state is measured. And when designing an ink, what the dispersion | distribution particle diameter (A) in a dispersion liquid has increased compared with the particle diameter (B) of an aqueous dispersion liquid is determined as a poor solvent, On the other hand, A water-soluble organic solvent having a dispersed particle diameter (A) that is the same as or smaller than the particle diameter (B) of the aqueous dispersion is determined as a good solvent, and is determined by the properties of these colorants It has been found that the consistency with the intended effect of the present invention is extremely good.

More specifically, the good solvent and the poor solvent are determined by the following method. First, dispersion liquids A and B of the following two dispersible color materials are prepared.
A: A solvent-containing aqueous dispersion having a composition in which the concentration of the water-soluble organic solvent in the liquid to be determined is 50% by mass, the concentration of the dispersible colorant is 5% by mass, and the concentration of water is 45% by mass;
B: An aqueous dispersion of a dispersible color material that does not contain a water-soluble organic solvent having a concentration of 5% by mass in the liquid of the dispersible color material.
The dispersion A is stored at 60 ° C. for 48 hours and then cooled to room temperature. The dispersion particle size at that time is measured using a concentrated particle size analyzer (trade name: FPAR-1000; manufactured by Otsuka Electronics Co., Ltd.). Measured. The particle size of the aqueous dispersion B was measured using the concentrated particle size analyzer. And when each particle size value of the said dispersion A and water dispersion B is made into a particle size (A) and a particle size (B), according to the following definition using these values, a good solvent and a poor solvent The ink having the configuration of the present invention was prepared using the determined good solvent and poor solvent. As a result, it was confirmed that the excellent effects as described above can be obtained. That is, in the above description, the good solvent and the poor solvent are those in which, when the particle size (A) is larger than the particle size (B), the water-soluble organic solvent as the determination target is the poor solvent, When the diameter (B) is the same as or the particle diameter (A) is smaller than the particle diameter (B), the water-soluble organic solvent as the determination target is defined as a good solvent.

  The water-based ink of the present invention includes a dispersible color material having the specific shape described above as a color material, and a water-based ink containing a conventional water-insoluble color material except that the water-soluble organic solvent has the specific configuration described above. A similar configuration may be used. That is, the first characteristic of the water-based ink according to the present invention includes at least water, a plurality of water-soluble organic solvents, and a dispersible color material, and the dispersible color material has a smaller charge than the color material and the color material. The dispersible color material having the conductive resin pseudo fine particles, and the color material and the chargeable resin pseudo fine particles are fixed to each other.

  The third feature of the present invention is that the water-soluble organic solvent is a water-soluble organic solvent that is at least one good solvent determined by the determination method as described above, and a water-soluble organic solvent that is at least one poor solvent. A: B ratio [total good solvent in ink] where A is the total amount (% by mass) of the good solvent in the ink and B is the total amount (% by mass) of the poor solvent in the ink. The amount (mass%): the total amount of poor solvent in ink (mass%)] is adjusted to be in the range of A: B = 10: 5 to 10:30.

  Furthermore, the fourth feature of the water-based ink of the present invention is that the water-soluble organic solvent having the maximum Ka value is obtained by comparing the Ka values obtained by the Bristow method for each of the plurality of water-soluble organic solvents in addition to the above. Is a poor solvent. As a result, the dispersion stability of the dispersible colorant in the ink becomes very excellent, and at the same time a sufficiently large area even with a small ink droplet amount when printed on a recording medium, particularly plain paper. It is possible to form an image that has a factor and has a very good print quality with a high print density.

Here, the Ka value obtained by the Bristow method will be described. This value is used as a measure for the penetrability of the ink into the recording medium. That is, when the ink permeability is expressed by the ink amount V per 1 m ² , the ink penetration amount V (mL / m ² = μm) after a predetermined time t has elapsed since the ink droplet was ejected. ) Is shown by the Bristow equation shown below.
V = Vr + Ka (t−tw) ^1/2

  Immediately after the ink droplets adhere to the surface of the recording medium, the ink is mostly absorbed in the uneven portion of the surface of the recording medium (the roughness portion of the surface of the recording medium) and almost penetrates into the inside of the recording medium. Not. The time between them is the contact time (tw), and the amount of ink absorbed in the uneven portion of the recording medium at the contact time is Vr. Then, when the contact time is exceeded after the ink is deposited, the amount of penetration into the recording medium increases by the time exceeding the contact time, that is, an amount proportional to (1/2) power of (t-tw). Ka is a proportional coefficient of this increase, and indicates a value corresponding to the penetration rate. The Ka value can be measured using a Bristow method dynamic liquid permeability tester (for example, trade name: Dynamic permeability tester S; manufactured by Toyo Seiki Seisakusho).

  The water-soluble organic solvent having the largest Ka value is a poor solvent when comparing the Ka values obtained by the Bristow method for each of a plurality of water-soluble organic solvents in the water-based ink according to the present invention. . Further, according to the study by the present inventors, in order to further improve the quality of the formed recorded image, it is preferable to adjust the Ka value of the ink to be less than 1.5, and further, It is preferable that the Ka value be 0.2 or more and less than 1.5. That is, if the ink is configured to have a Ka value of less than 1.5, solid-liquid separation occurs at an early stage in the process of ink penetrating into the recording medium, and a high-quality image with extremely little feathering can be obtained. It becomes possible to form.

  The Ka value according to the Bristow method in the present invention is used for plain paper [for example, a copying machine using an electrophotographic method manufactured by Canon Inc., a page printer (laser beam printer), or a printer using an ink jet recording method. PB paper or PPC paper that is a copying machine paper using an electrophotographic method] as a recording medium. As a measurement environment, a normal office environment, for example, a temperature of 20 to 25 ° C. and a humidity of 40 to 60% is assumed.

  By the way, in the case of forming an image in which black and color inks are mixed on plain paper, if the water-based ink according to the present invention is used as the black ink, as described above, the black ink is used on the paper. It is considered that the aggregation or dispersion destruction of the constituting color material proceeds relatively quickly as compared with other inks. In the ink jet recording method which is an image forming method in the present invention, the aqueous ink of the present invention is used for the black ink, and the image formation with the color ink is performed after the black ink image formation, and more preferably the black ink is applied. After scanning, at least one scan or more is left, and the scanning is performed so as to apply color ink, so that even if it comes into contact with the color ink, mixed color black and color bleeding on the paper surface occurs. Therefore, it is possible to form an image having excellent bleeding resistance. That is, a method for performing multi-pass printing that requires printing time to complete printing by scanning a plurality of times only by performing image formation with black ink and color ink with a time difference, and a recovery system with black and color ink. The above-described excellent effects can be obtained without requiring a method for increasing the size of the device such as separate devices.

  In addition, when the water-based ink of the present invention is used, the color material in the ink remains efficiently on the recording medium for the reason described above, so that the ink amount is smaller than the conventional ink discharge amount (droplet volume). High density printing can be performed. Further, since printing can be performed with a smaller amount of ink, effects such as cost reduction in image formation and faster fixing time than conventional ink can be expected.

  The components constituting the ink of the present invention will be described below. First, the aqueous medium in which the dispersible color material is dispersed will be described.

[Aqueous medium]
The water-based ink of the present invention contains a mixed solvent of water and a water-soluble organic solvent, and the water-soluble organic solvent can be selected from those listed below. In the present invention, when selecting a water-soluble organic solvent, first, in the method described above, first, a good solvent and a poor solvent for the dispersible colorant to be used are determined, and based on the determination result, In addition, a water-soluble organic solvent is selected and blended appropriately so that at least a good solvent and a poor solvent are mixed, and the content of each water-soluble organic solvent is within the range specified in the present invention, and an ink is prepared. It is necessary to do.

  Specific examples of the water-soluble organic solvent include those having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. Alkyl alcohols; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol; Propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, etc. Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol Lower alkyl ethers of polyhydric alcohols such as monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. As the water, it is desirable to use deionized water.

  The content of the water-soluble organic solvent in the aqueous ink of the present invention is not particularly limited, but is preferably in the range of 3 to 50% by mass with respect to the total mass of the ink. The amount of water contained in the ink is preferably in the range of 50 to 95% by mass with respect to the total mass of the ink.

  As described above, the feature of the present invention is that when the total amount (% by mass) of the good solvent in the ink is A and the total amount (% by mass) of the poor solvent in the ink is B, the ratio A: The ratio A: B is more preferably 10: 6 so that B is in the range of 10: 5 to 10:30, preferably A: B is in the range of 10: 5 to 10:10. That is, the kind and content of the water-soluble organic solvent constituting the water-based ink are adjusted so as to be within a range of -10: 10. According to the detailed examination by the present inventors, when the ratio of the good solvent contained in the water-based ink is large, the storage stability is excellent, but it is difficult to obtain a high print density. When the ratio is small, a high printing density can be obtained, but the storage stability may be insufficient, but the ratio of the good solvent to the poor solvent in the water-soluble organic solvent in the ink is as described above. If controlled to this, it is possible to achieve both the storage stability of the ink and the realization of a high print density. Further, as described above, in the present invention, when determining each water-soluble organic solvent to be contained in the ink, it is a measure representing the permeability to the recording medium possessed by each water-soluble organic solvent to be contained. By controlling the value of the Ka value obtained by the Bristow method, an effect that could not be obtained in the past has a sufficiently large area factor and a high print density even with a small ink droplet amount. Can be achieved.

[Water-based ink]
The water-based ink according to the present invention includes the dispersible colorant described above and a specific water-soluble organic solvent. When the coloring material to be used is a pigment, the pigment content is generally 0.1% by mass or more and 20% by mass or less, preferably 0.3% by mass or more and 15% by mass or less with respect to the ink. Further, as the aqueous medium, water or a mixed medium containing a water-soluble organic solvent as necessary is also preferable. Further, it may contain a penetrant, an antiseptic, an antifungal agent and the like for helping the permeability to the recording medium.

  As shown in FIG. 1, the dispersible color material used in the present invention is present in the ink in a state where the chargeable resin pseudo fine particles 2 are fixed to the surface of the color material 1. Therefore, the color material adheres to the recording medium and the adjacent color material on the recording paper via the chargeable resin pseudo fine particles fixed to the surface. Accordingly, the printed matter obtained using the water-based ink of the present invention has excellent scratch resistance.

  Further, in the case of using a pigment as the coloring material, the ratio of the pigment and the chargeable resin pseudo fine particles (resin mass / pigment mass = B / P) is in the range of 0.3 or more and 4.0 or less. It can be said that this is a desirable embodiment of the present invention in order to improve the scratch resistance of the printed matter formed of the color material. By setting the B / P ratio to be 0.3 or more, it is possible to impart excellent scratch resistance to the printed matter by improving the adhesion between the color materials and between the color material and the recording medium. In particular, in the case of aqueous ink using a dispersible color material formed by fixing charged resin pseudo fine particles comprising a copolymer component having a glass transition temperature of −40 ° C. or more and 60 ° C. or less, the film formation Can be exhibited more effectively, and the result is that the scratch resistance of glossy paper is further improved. When B / P is significantly larger than 4.0, the ink becomes highly viscous as a whole. In particular, when used in an ink jet recording apparatus, ejection stability may be impaired. In addition, since the amount of resin is extremely large relative to the color material, the color density of the color material on the recording medium is hindered, and the print density may not be sufficiently obtained. By controlling the B / P value within the range of 0.3 to 4.0, the water-based ink having excellent scratch resistance and compatible with ejection stability in the ink jet recording apparatus can be obtained. it can.

  The resin mass as used herein refers to the total amount of the chargeable resin pseudo fine particles contained in the ink according to the present invention, and may include other resin components that are clearly strongly adsorbed on the pigment surface. . However, the water-soluble resin component that can be easily separated from the pigment is not included.

  The above-mentioned B / P value can be generally obtained by differential thermogravimetric analysis, but in the present invention, it is a value measured and calculated with TGA / SDTA851 manufactured by METTTLER. That is, in the present invention, the sediment obtained by centrifuging the dispersible colorant or the water-based inkjet recording ink containing the colorant according to the present invention under conditions of 80,000 revolutions and 2 hours is dried, weighed, Mass changes before and after the decomposition temperatures of the pigment and the resin component when the temperature was raised in a nitrogen atmosphere or in the air were calculated, and B / P was calculated.

[Recorded image]
The ink according to the present invention can be suitably used for recording using an ink jet recording apparatus as described later. The recording medium used at this time can be used without limitation even if it is a medium capable of ink jet recording.

(Image forming method)
The ink jet recording method according to the present invention is characterized in that an image is formed by an ink jet recording apparatus using the above-described aqueous ink of the present invention. For example, in an inkjet recording method for recording on plain paper using black ink and at least one aqueous color ink, the aqueous ink of the present invention having the configuration described above is used as the black ink, and the black ink When forming an image in which the image formed by the image and the image formed by the color are adjacent to each other, after forming the image by performing a scan to which the black ink is applied, the color is formed in the region where the image is formed. It is preferable to perform scanning for applying ink.

  Here, color inks that can be suitably used in the above will be described. In the ink jet recording method of the present invention, any conventionally known water-based color ink for ink jet recording can be used. Examples of the color material of the color ink include water-soluble dyes, and it is particularly preferable to use a water-soluble dye having an anionic group as a solubilizing group. The color of the color ink used in the present invention can be appropriately selected from, for example, cyan, magenta, yellow, red, green, blue and orange.

  The water-soluble dye having an anionic group used in the present invention is not particularly limited as long as it is a water-soluble acidic dye, a direct dye, or a reactive dye described in the color index (COLOUR INDEX). Moreover, even if it is a dye which is not described in a color index, there will be no restriction | limiting in particular if it has an anionic group, for example, a sulfone group. These dyes are used in the ink in an amount of 1 to 10% by mass, preferably 1 to 5% by mass.

Specific examples of the dye include the following.
C. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 98, 100, 110
C. I. Direct Red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 230
C. I. Direct blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226

C. I. Acid Yellow: 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99
C. I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 94, 106, 114, 115, 133, 134 145, 158, 198, 249, 265, 289
C. I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 117, 127, 138, 158, 161

In addition to the above, the color material of the color ink that can be used in the present invention includes the following 1. ~ 3. Can be mentioned. These color materials are preferable because many of them exhibit excellent water resistance when applied to a recording medium.
1. 1. A dye having a carboxyl group as a solubilizing group 2. Oil-soluble dyes Pigment

The oil-soluble dye is not particularly limited as long as it is described in the color index (COOLUR INDEX). Even if it is a new dye not described in the color index, there is no particular limitation. Specific examples include the following. These dyes are preferably used in the ink in an amount of 1 to 10% by mass, more preferably 1 to 5% by mass.
C. I. Solvent blue: 33, 38, 42, 45, 53, 65, 67, 70, 104, 114, 115, 135
C. I. Solvent Red: 25, 31, 86, 92, 97, 118, 132, 160, 186, 187, 219
C. I. Solvent yellow: 1, 49, 62, 74, 79, 82, 83, 89, 90, 120, 121, 151, 153, 154

When a pigment is used as the color material of the color ink used in the present invention, the amount of the pigment is in the range of 1 to 20% by mass, preferably 2 to 12% by mass with respect to the total mass of the ink. Used in. Examples of color organic pigments that can be used in the present invention include the following.
Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 83, C.I. I. Pigment Yellow 128 and the like.

Examples of pigments used in magenta ink include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn), C.I. I. Pigment Red 57 (Ca), C.I. I. Pigment Red ll2, C.I. I. Pigment Red 122 and the like.
Examples of pigments used for cyan ink include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16 and C.I. I. Pigment Blue 22, C.I. I. Vat Blue 4, C.I. I. Vat Blue 6 etc. are mentioned. However, it is not limited to these. In addition to the above, it is of course possible to use a pigment newly produced for the present invention.

  In addition, when a pigment is used, any dispersing agent for dispersing the pigment in the ink can be used as long as it is a water-soluble resin, but the weight average molecular weight is 1,000 to 30. In the range of 3,000, more preferably in the range of 3,000 to 15,000. Specific examples of such dispersants include styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, maleic acid, and the like. , At least two monomers selected from maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, vinyl acetate, vinylpyrrolidone, acrylamide, and derivatives thereof (of which at least one is hydrophilic) Monomer), a random copolymer, a graft copolymer, or a salt thereof. Alternatively, natural resins such as rosin, shellac and starch can be preferably used. These resins are soluble in an aqueous solution in which a base is dissolved, and are alkali-soluble resins. In addition, it is preferable to contain the water-soluble resin used as these pigment dispersants in the range of 0.1 to 5% by mass with respect to the total mass of the ink.

  A suitable aqueous liquid medium in the color ink used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent. The water is not general water containing various ions but ion-exchanged water ( Preference is given to using deionized water). Examples of the water-soluble organic solvent used by mixing with water include carbon atoms of 1 such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like. Alkyl alcohols of -4; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol Alkylene glycols having 2 to 6 carbon atoms, such as coal; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of monohydric alcohols; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred.

  The content of the water-soluble organic solvent as described above in the color ink is generally in the range of 3 to 50% by mass, preferably in the range of 3 to 40% by mass with respect to the total mass of the ink. The water content used is in the range of 10 to 90% by mass, preferably 30 to 80% by mass, based on the total mass of the ink. In addition to the above-mentioned components, the color ink used in the present invention is appropriately added with a surfactant, an antifoaming agent, a preservative, etc. in order to obtain an ink having a desired physical property value as necessary. Can be added.

  The black and color inks composed of the constituents described above used in the ink jet recording method according to the present invention preferably have characteristics that can be favorably ejected from the ink jet recording head. For this reason, from the viewpoint of ejectability from the ink jet recording head, the ink characteristics are, for example, a viscosity of 1 to 15 mPa · s, a surface tension of 25 mN / m or more, and a viscosity of 1 to 5 mPa · s. The surface tension is preferably 25 to 50 mN / m. Further, particularly when black ink and color ink are used in combination, it is more preferable that the surface tension of the color ink is lower than the surface tension of the black ink. Specifically, the black ink is 35 to 50 mN / m and the color ink is 25 to 35 mN / m.

[Image recording method and recording apparatus]
The dispersible color material used in the present invention and the water-based ink containing the color material are used for an inkjet discharge type head, and also as an ink tank in which the ink is stored or for filling the ink tank. It is also effective as an ink. In particular, the present invention provides an excellent effect in a bubble jet type recording head and recording apparatus among ink jet recording types.

  As for the typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. . This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the ink. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding the nucleate boiling to the electrothermal transducer, heat energy is generated in the electrothermal transducer, and the thermal action of the recording head This is effective because the film can be boiled on the surface and, as a result, the drive signals can be made to correspond one-to-one and bubbles in the ink can be formed. By the growth and contraction of the bubbles, ink is ejected through the ejection openings to form at least one droplet. It is more preferable that the drive signal has a pulse shape, because the bubble growth and contraction is performed immediately and appropriately, and thus ink discharge with particularly excellent responsiveness can be achieved. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by adopting the conditions described in US Pat. No. 4,313,124, which is an invention relating to the rate of temperature increase of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (linear liquid channel or right-angle liquid channel) of the discharge port, the liquid channel, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting part The present invention is also effective for configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the lens is disposed in a bending region. In addition, the present invention is also effective for a configuration (Japanese Patent Laid-Open No. 59-123670, etc.) in which a discharge hole is used as a discharge portion of the electrothermal transducer when common to a plurality of electrothermal transducers. . Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is set by combining a plurality of recording heads as disclosed in the above specification. Either a satisfying configuration or a single recording head configuration may be used, but the present invention can exhibit the above-described effects more effectively.

  In addition, it is mounted on the main body of the device so that it can be electrically connected to the main body of the device and supplied with ink from the main body of the device. The present invention is also effective when a cartridge type recording head is used. In the present invention, it is preferable to add a recovery means for the recording head, a preliminary auxiliary means, etc. provided as a configuration of the recording apparatus to be applied, because the effects of the present invention can be further stabilized. is there. Specifically, a capping unit for the recording head, a cleaning unit, a pressurizing or suction unit, an electrothermal transducer, a heating element different from this, or a preheating unit using a combination of these, recording and the like Is a preliminary discharge mode for performing another discharge.

  In particular, the image forming method preferably used in the present invention includes an inkjet image forming method in which recording is performed on plain paper using black ink and at least one aqueous color ink. When forming an image in which the water-based ink of the present invention having the structure is used and an image formed by the black ink and an image formed by the color are adjacent to each other, scanning is performed to apply the black ink. After the formation, scanning is performed in which color ink is applied to a region where the image is formed.

  FIG. 8 is an example of a recording head used when the ink jet recording method according to the present invention is carried out. As shown in FIG. 3, the recording head has an ejection port array (Bk) for ejecting black ink and three colors of cyan (C), magenta (M), and yellow (Y) as color inks. And an ejection port array for ejecting the respective inks. In the image forming method of the present invention, when a color image is formed, a recording head in which a black ejection port array for ejecting black ink and a color ejection port array for color ink are shifted in the sub-scanning direction. Is preferably used. For this reason, for example, when forming an image using the recording head shown in FIG. 8, in the case of black-only image formation, the entire ejection port array for black is used, and color mixed with black and color. When forming an image, it is preferable to use the portion a in the drawing for black, and use the portion b in the drawing for C, M, and Y. Hereinafter, the case of forming an image in which black and color are mixed will be described in more detail with reference to FIG.

  In FIG. 8, first, the print head is scanned in the horizontal direction (main scanning direction) using the portion a of the black discharge port array, whereby black image data is printed in one pass for recording media such as plain paper. Form on top. Next, the recording medium is transported by a distance a in the vertical direction (sub-scanning direction) in the drawing, and in the forward direction of the main scanning of the next print head, the portion of the color ejection port array b is used. A color image is formed by one-pass printing in the area where the image is formed in the black a row. At this time, the black discharge port array a simultaneously forms an image in the next area. By repeating this process, black and color mixed images are formed.

  FIG. 9 shows another example of a recording head that can be used when carrying out the image forming method of the present invention. In FIG. 9, as in FIG. 8, the portion a in the discharge port array is used for black, and the portion b in the diagram corresponding to the entire region of the discharge port array is used for C, M, and Y. In the same manner as described above with reference to FIG. 3, a black and color mixed image is formed.

  FIG. 10 shows another example of a recording head that can be used when carrying out the image forming method of the present invention. Also in FIG. 10, as in the case of FIG. 8, for black, the portion a in the drawing of the ejection port array is used, and for C, M, and Y, b in the diagram corresponding to the entire region of the color ejection port array. Using this part, black and color mixed images will be formed. In the recording head illustrated in FIG. 10, as shown in the drawing, a distance corresponding to the paper feed amount “a” is provided between the “a” portion of the black discharge port array and the “b” portion of the collar. For this reason, the recording head having such a configuration causes an extra time difference for one print scan in a reciprocating period from the formation of a black image to the formation of a color image. Therefore, the recording head illustrated in FIG. 10 has a more advantageous configuration for bleeding between black and color than the configuration shown in FIG.

  FIG. 11 shows another example of a recording head that can be used when carrying out the image forming method of the present invention. Even when a recording head in which black and color discharge port arrays are arranged in a line in this order in the paper feed direction is used, a color image is formed after a black image is formed according to the paper feed. Will be.

  FIG. 12 shows another example of a recording head that can be used when carrying out the image forming method of the present invention. In the recording head shown in FIG. 12, the color ejection port arrays are cyan (C1, C2) and magenta (M1, M2) so that the order of color ink ejection is the same in the forward scanning and the backward scanning. ) And yellow (Y1, Y2), two rows each, being symmetrically provided in the main scanning direction. As a result, bidirectional printing is possible even in the formation of black and color mixed images. In this case, a black image is first formed in the black a portion, and then the recording medium is transported by a distance a, and the color ejection port in the reverse process of main scanning of the next print head. A color image is formed by one-pass printing in the region where the image is formed in the above-described black a row using the row b portion.

  Of course, in the bidirectional print head as shown in FIG. 12, as described above, the black and color nozzles are arranged so that an interval of one scan is provided between the black and color image formations. A more advantageous configuration may be used (see FIG. 13). Although the image forming method of the present invention has been described above, the form of the recording head that can be used in the method of the present invention is not limited to FIGS.

  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 as long as the gist thereof is not exceeded. In the text, “part” or “%” is based on mass unless otherwise specified.

(Preparation of pigment dispersion 1)
First, a mixed liquid composed of 10 parts of carbon black, 6 parts of glycerin, 10 parts of a styrene-acrylic acid resin dispersant, and 74 parts of water was subjected to a sand mill manufactured by Kanada Rika Kogyo Co., Ltd. at 1,500 rpm for 5 hours. Dispersion was performed to obtain Pigment Dispersion Liquid 1. In the sand mill, zirconia beads having a diameter of 0.6 mm were used, and the filling rate in the pot was 70%. The carbon black used in the present example is Black Pearls 880 (hereinafter abbreviated as BP880) marketed by Cabot Corporation in the United States. The styrene-acrylic acid resin dispersant has a copolymerization ratio of 70:30, Mw. = 8,000, acid value 170 was used. As such a styrene-acrylic acid resin dispersant, water and potassium hydroxide equivalent to the above acid value were added in advance and stirred at 80 ° C. to obtain an aqueous solution. The obtained pigment dispersion 1 was stably dispersed with an average dispersion particle size of 98 nm, and the polydispersity index was 0.16.

(Preparation of dispersible colorant 1)
Next, with the pigment dispersion 1 obtained above as 100 parts, while heating to 70 ° C. in a nitrogen atmosphere, the following three liquids were filled into the dropping device respectively while stirring with a motor, and added dropwise. Polymerization was performed for 5 hours. The three liquids were (1) 5.5 parts methyl methacrylate, (2) 0.5 parts acrylic acid, 0.12 parts potassium hydroxide and 20 parts water, (3) 0.05 parts potassium persulfate and 20 parts of water. The obtained dispersion was diluted 10-fold with water and centrifuged at 5,000 rpm for 10 minutes to remove the aggregating component. Then, it further refine | purified by centrifuging on conditions of 12,500 rpm and 2 hours, and the dispersible color material 1 which is a sediment was obtained. This fully purified dispersible colorant 1 is dispersed in water, centrifuged at 12,000 rpm for 60 minutes, and the precipitate is redispersed in water, dried, and scanned by electron microscope JSM-6700. When observed at 50,000 times (manufactured by JEOL Hitech Co., Ltd.), the dispersible colorant 1 is observed to have a state in which charged resin pseudo fine particles smaller than the colorant are fixed to the surface of carbon black. It was done. In addition, also about the color material after this described in a present Example, the form of the color material was confirmed with the method similar to the above.

(Preparation of dispersible colorant 2)
100 parts of the previously prepared pigment dispersion 1 was heated to 70 ° C. in a nitrogen atmosphere, and the following three liquids were charged into a dropping device while stirring with a motor, added dropwise, and added for 5 hours. Polymerization was performed. The three liquids were (1) methyl methacrylate 5.5 parts, (2) acrylic acid 0.3 parts, potassium hydroxide 0.12 parts and water 20 parts, (3) potassium persulfate 0.05 parts and 20 parts of water. The obtained dispersion was diluted 10-fold with water and centrifuged at 5,000 rpm for 10 minutes to remove the aggregating component. Then, it further refine | purified by centrifuging on conditions of 12,500 rpm and 2 hours, and the dispersible color material 2 which is a sediment was obtained.

(Preparation of pigment dispersion 2)
After 10 parts of BP880 and 3.41 parts of p-amino-N-benzoic acid were mixed well with 72 parts of water, 1.62 parts of nitric acid was added dropwise thereto and stirred at 70 ° C. Several minutes later, a solution of 1.07 parts of sodium nitrite dissolved in 5 parts of water was added and stirred for another hour. The obtained slurry was Toyo Filter Paper No. After filtering through 2 (manufactured by Advantis), the pigment particles were sufficiently washed with water and dried in an oven at 90 ° C., water was added to the pigment to prepare a pigment aqueous solution having a pigment concentration of 10%. By the above-described method, Pigment Dispersion Liquid 2 was obtained in which an anionically charged self-dispersing carbon black having a hydrophilic group bonded thereto via a phenyl group was dispersed on the surface.

(Preparation of dispersible colorant 3)
100 parts of the pigment dispersion 2 obtained above and 2 parts of a styrene-acrylic acid-based resin dispersant (copolymerization ratio 70:30, Mw = 8,000, acid value 170) were heated to 70 ° C. in a nitrogen atmosphere. In the heated state, the following three liquids were filled in a dropping device respectively while stirring with a motor, added dropwise, and polymerization was carried out for 5 hours. The three liquids were (1) 5.7 parts methyl methacrylate, (2) 0.9 parts sodium p-styrene sulfonate and 20 parts water, (3) 0.05 parts potassium persulfate and 20 parts water, Consists of. The obtained dispersion was diluted 10-fold with water and centrifuged at 5,000 rpm for 10 minutes to remove the aggregating component. Then, it further refine | purified by centrifuging on conditions of 12,500 rpm and 2 hours, and the dispersible color material 3 which is a sediment was obtained.

(Preparation of dispersible colorant 4)
100 parts of the previously prepared pigment dispersion 1 was heated to 70 ° C. in a nitrogen atmosphere, and while stirring with a motor, each of the following three liquids was charged into a dropping device and added dropwise to perform polymerization. It was. The three solutions were: (1) 12.84 parts of methyl methacrylate and 4.26 parts of methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: NK ester M90G), (2) 0.9 part of acrylic acid and hydroxylated It consists of 0.35 parts of potassium and 20 parts of water, (3) 0.05 part of potassium persulfate and 20 parts of water. After polymerization for 5 hours as described above, the obtained dispersion was diluted 10-fold with water, and centrifuged at 5,000 rpm for 10 minutes to remove aggregated components. Then, the dispersible color material 4 which is a sediment was obtained by further centrifuging at 12,500 rpm for 2 hours.

(Preparation of pigment dispersion 3)
Wet oxidized carbon manufactured by Tokai Carbon Co., Ltd. was used as a carbon black dispersion into which a hydrophilic group was directly introduced. The wet oxidized carbon used in this example is obtained by oxidizing the surface of carbon black in an aqueous phase using an oxidizing agent. As in the case of Example 3, when the surface oxygen content of this wet oxidized carbon was measured, the loss on heating of the carbon was 15%.

(Preparation of dispersible colorant 5)
100 parts of the previously prepared pigment dispersion 2 and 2 parts of a styrene-acrylic acid resin dispersant (copolymerization ratio 70:30, Mw = 8,000, acid value 170) were heated to 70 ° C. in a nitrogen atmosphere. While heating and stirring with a motor, the following three solutions were gradually added dropwise for polymerization. The three solutions were: (1) 12.84 parts of methyl methacrylate and 4.26 parts of methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: NK ester M90G), (2) 0.9 part of acrylic acid and hydroxylated It consists of 0.35 parts of potassium and 20 parts of water, (3) 0.05 part of potassium persulfate and 20 parts of water. After polymerization for 5 hours as described above, the obtained dispersion was diluted 10-fold with water, and centrifuged at 5,000 rpm for 10 minutes to remove aggregated components. Then, the dispersible color material 5 which is a sediment was obtained by further centrifuging at 12,500 rpm for 2 hours.

(Preparation of dispersible colorant 6)
100 parts of the pigment dispersion 3 obtained above was heated to 70 ° C. in a nitrogen atmosphere, and the following three liquids were respectively charged into a dropping device while stirring with a motor, added dropwise, and added for 5 hours. Polymerization was performed. The three liquids were (1) 5.5 parts methyl methacrylate, (2) 0.5 parts acrylic acid, 0.12 parts potassium hydroxide and 20 parts water, (3) 0.05 parts potassium persulfate and 20 parts of water. The obtained dispersion was diluted 10-fold with water and centrifuged at 5,000 rpm for 10 minutes to remove the aggregating component. Then, it further refine | purified by centrifuging on conditions of 12,500 rpm and 2 hours, and the dispersible color material 6 which is a sediment was obtained.

[Characteristics of dispersible colorants]
With respect to the dispersible colorants 1 to 5 obtained above, observation and various physical properties were measured by the methods described below. The obtained results are shown in Table 1.

<Adhesion / spotting of resin fine particles>
Each dispersible colorant is dispersed in water and dried, and observed with a scanning electron microscope JSM-6700 (manufactured by JEOL Hitec Co., Ltd.) at a magnification of 50,000 times, and the resin fine particles are fixed to the colorant. The properties of the fixed resin fine particles were evaluated as follows.

(Adhesive state of resin fine particles)
○: It was confirmed that resin fine particles were fixed.
X: It was not possible to confirm that the resin fine particles were fixed.

(Dispersion of resin fine particles)
○: At the time of observation, it was confirmed that resin fine particles were scattered.
X: At the time of observation, it was observed that the resin fine particles were localized or fixed non-uniformly.

<Average particle size>
Each dispersible colorant was measured by a dynamic light scattering method using ELS-8000 manufactured by Otsuka Electronics Co., Ltd., and the cumulant average value was defined as the average particle size.

<Surface functional group density>
The surface functional group density of each dispersible colorant was determined as follows. A large excess amount of hydrochloric acid (HCl) is added to the color material aqueous dispersion, and the precipitate settled in a centrifuge at 20,000 rpm for 1 hour is redispersed in pure water, and the solid content is determined to settle. The material was weighed, and a dispersion obtained by adding a known amount of sodium hydrogen carbonate and stirring the mixture was further sedimented in a centrifuge at 80,000 rpm for 2 hours. The supernatant was weighed, and the surface functional group density was calculated by subtracting the blank amount obtained by measuring the known amount of sodium bicarbonate and pure water from the neutralization amount obtained by neutralization titration with 0.1N HCl aqueous solution. When it was clear that a cationic group was included as a polar group, it was determined in the same manner using sodium hydroxide (NaOH) instead of HCl aqueous solution and ammonium chloride instead of sodium bicarbonate.

[Method for determining good and poor solvents of water-soluble organic solvent used]
In order to select a good solvent and a poor solvent for the pigment in the pigment dispersion or the pigment and the dispersant, the following experiment was conducted. First, a 10% solid concentration aqueous solution of the pigment dispersions 1 and 2 and the dispersible colorants 1 to 5 is prepared, and a dispersion for determining good solvents and poor solvents is used with the following blending ratios. Created.

(Compounding ratio of dispersion for determining good and poor solvents)
-10% solid concentration aqueous solution of pigment dispersion 1, 2 or dispersible colorant 1-5: 50 parts-Water-soluble organic solvent described in Table 2: 50 parts

  Next, 10 g of the good solvent / poor solvent determination dispersion prepared as described above was placed in a transparent glass lid-equipped sample bottle, capped, and then sufficiently stirred, and placed in an oven at 60 ° C. Allowed to stand for 48 hours. Then, using the solution taken out from the oven at 60 ° C. as a measurement sample, the particle size of the water-insoluble colorant in the solution was measured using a concentrated particle size analyzer (trade name: FPAR-1000; manufactured by Otsuka Electronics Co., Ltd.). This was taken as the stock solution particle size (particle size measured without dilution) of the dispersion for determining good solvent and poor solvent after heating at 60 ° C. for 48 hours. On the other hand, as a reference, a pigment aqueous dispersion with the same solid content concentration as the good solvent and poor solvent judgment solutions, that is, for the judgment comparison of good and poor solvents with the same amount of water added instead of the water-soluble organic solvent An aqueous pigment dispersion was prepared. The water dispersion was measured for the particle size of the water-insoluble colorant in the liquid using a concentrated particle size analyzer in the same manner as described above without performing warming storage. Then, the stock solution particle size of the obtained dispersion for determination is compared with the particle size of the aqueous dispersion of the reference, and the stock solution particle size of the dispersion after warming storage at 60 ° C. for 48 hours is the water dispersion of the reference. What was larger than the liquid stock particle size of the liquid was judged as a poor solvent, and the stock solution particle size of the dispersion after heating at 60 ° C. for 48 hours was the same as or smaller than that of the reference aqueous dispersion. The thing was determined to be a good solvent.

[Ka value measurement method for each water-soluble organic solvent]
First, a dye aqueous solution having a dye concentration of 0.5% having the following composition was prepared so that the Ka value of each water-soluble organic solvent was easily measured.
Water-soluble dye C.I. I. Direct Blue 199
0.5 part pure water 99.5 parts

Then, using this 0.5% aqueous dye solution, a 20% aqueous solution of a colored water-soluble organic solvent was prepared using each water-soluble organic solvent to be measured at the following blending ratio.
80 parts of the above 0.5% dye aqueous solution 20 parts of the water-soluble organic solvent listed in Table 1 20% aqueous solution of each water-soluble organic solvent prepared above was used as a dynamic permeability test apparatus S (manufactured by Toyo Seiki Seisakusho (Trade name), and the Ka value of a 20% aqueous solution of a water-soluble organic solvent was determined by the Bristow method.

  Results of determining whether each of the water-soluble organic solvents that can be used in the ink measured as described above is a good solvent or a poor solvent for the pigment dispersions 1 to 3 and the dispersible colorants 1 to 6 Table 2 shows the measurement results of the Ka value in a 20% aqueous solution of each water-soluble organic solvent. The polyethylene glycol derivative in Table 2 is a derivative having the structure shown below and having a molecular weight of about 1,000.

<Examples 1-6>
Using each of the water-soluble organic solvents investigated above and the dispersible colorants 1 to 6 prepared above, the components listed in Table 3 were mixed, dissolved or dispersed with sufficient stirring, and then the pore size 3. The inks of Examples 1 to 6 were prepared by pressure filtration with a 0 μm microfilter (Fuji Film). At this time, when the total amount (%) of the good solvent in the ink is A and the total amount (%) of the poor solvent in the ink is B, A: B is in the range of 10: 5 to 10:30, and When the Ka value of the 20% aqueous solution of the good solvent for the water-insoluble colorant determined by the Bristow method is compared with the Ka value of each of the plurality of water-soluble organic solvents determined by the Bristow method, the water value having the maximum Ka value is obtained. The organic solvent was prepared so as to be a poor solvent.

<Comparative Examples 1-5>
(Preparation of ink)
Using each of the water-soluble organic solvents investigated above and the dispersible colorants 1, 4 to 6 prepared above, the components listed in Table 4 were mixed, dissolved or dispersed with sufficient agitation, and pore size 3 The ink of Comparative Examples 1 to 5 was prepared by pressure filtration with a 0.0 μm microfilter (Fuji Film).

<Evaluation>
For each of the inks of Examples 1 to 6 and Comparative Examples 1 to 5, an inkjet recording apparatus BJS- equipped with an on-demand type multi-recording head that ejects ink by applying thermal energy to the ink according to a recording signal. The following evaluation was performed using 700 (manufactured by Canon Inc.). The obtained evaluation results are shown in Table 5 for the examples and Table 6 for the comparative examples.

1. Average printing density Using each of the above inks and the above-described ink jet recording apparatus, character printing including a solid portion of 2 cm × 2 cm is performed on the following plain papers A to C, and a solid portion of 2 cm × 2 cm one day after printing. The print density was measured using a Macbeth RD918. The printer driver was operated in the default mode. The setting conditions for the default mode are shown below. Further, the ejection amount per dot of ink is within 30 ng ± 10%.
-Paper type: Plain paper-Print quality: Standard-Color adjustment: Automatic

Using the print density obtained as a result of the measurement as described above, the evaluation was made according to the following criteria.
A: The average print density of three papers is 1.5 or more.
X: The average of the printing density of 3 papers is less than 1.5.

As the plain paper, those shown below were used.
A: PPC paper NSK manufactured by Canon Inc.
B: Xerox Co., Ltd., PPC paper 4024
C: PPC paper prober bond manufactured by Fox River Co., Ltd.

2. Permeability plain paper printing density Among the above results, the printing density on the B paper was evaluated according to the following criteria.
A: The print density on the B paper is 1.4 or more.
X: The print density on B paper is less than 1.4.

3. Storage Stability Each of the inks of Examples 1 to 6 and Comparative Examples 1 to 5 is put into a shot bottle, sealed, put into an oven at 60 ° C., taken out after 2 months, and stored from the state of the ink at that time. Was evaluated according to the following criteria.
○: The color material in the ink is stably and uniformly dispersed.
Δ: There is little or no change in appearance, but the viscosity and average particle size are slightly increased.
X: The ink changed into a gel or the upper part of the ink was transparent. Or it is clearly thickened.

4). Character quality The 16-point character portion of the print sample was visually observed and the bleeding of the character was evaluated according to the following criteria.
A: There is almost no bleeding.
B: Some blurring characters are seen.
C: Many characters are blurred.

5. Scratch resistance When the sample was left to stand for 24 hours after printing, when the Sylbon paper was placed on the printed paper and the weight of 40 g / cm ² was placed on the recording surface, the Sylbon paper was pulled. It was visually observed whether or not stains were caused by rubbing of the printed part on the (white background part) and Sylbon paper, and evaluated according to the following criteria.
A: Dirt due to rubbing is not seen.
B: There is almost no dirt due to rubbing.
C: The dirt part by a blur is conspicuous.

6). Marker resistance The 14-point character portion of the print sample was traced once with a fluorescent yellow marker pen (Zebra Optix), and the disorder of the print portion was visually observed and evaluated according to the following criteria.
A: The printed part is not disturbed.
B: There is little disorder of printing in the traced part, and the pen tip is hardly soiled.
C: The trace of the traced part is greatly disturbed, and the pen tip is colored.

7). Water resistance The print surface of the above print sample was inclined at an angle of 45 degrees from the horizontal plane, and 1 ml of water was dropped from a height of 20 cm onto a 14-point character portion using a dropper. At this time, the printing bleeding was evaluated according to the following criteria.
A: Almost no bleeding of printing is observed.
B: Slight bleeding of printing is observed, but there is almost no trace on the blank paper portion.
C: Color flows from the printed portion, and a trace is seen on the blank paper portion.

<Examples 7 to 12>
Each of the inks of Examples 1 to 6 described above was used as the black ink, and image formation was performed in combination with the color ink. The color inks (three colors of cyan, magenta, and yellow) used at this time were prepared as follows.

(Preparation of cyan ink)
The components shown below were mixed, sufficiently stirred and dissolved, and then pressure filtered through a micro filter (manufactured by Fuji Film) having a pore size of 0.2 μm to prepare a cyan ink.
・ DBL (Direct Blue) 199 3.5 parts ・ Glycerin 7.5 parts ・ Diethylene glycol 7.5 parts ・ Acetylenol E-100 1.0 part ・ Pure water 80.5 parts

(Preparation of magenta ink)
A cyan ink was prepared in the same manner as the cyan ink with the following components.
・ AR (Acid Red) 289 2.5 parts ・ Glycerin 7.5 parts ・ Diethylene glycol 7.5 parts ・ Acetylenol E-100 1.0 part ・ Pure water 81.5 parts

(Preparation of yellow ink)
A yellow ink was prepared in the same manner with the following components.
・ DY (direct yellow) 86 2.5 parts ・ Glycerin 7.5 parts ・ Diethylene glycol 7.5 parts ・ Acetylenol E-100 1.0 part ・ Pure water 81.5 parts

<Evaluation>
Each black ink of Examples 1 to 6 is combined with the color ink prepared above, and the ink is ejected by applying thermal energy to the ink according to the recording signal as shown in FIG. The following evaluation was performed using an inkjet recording apparatus having an on-demand type multi-recording head. Table 7 shows the obtained evaluation results.

8). Ejection stability Ejection stability was evaluated according to the following criteria by visually printing 200 specific Bk texts continuously, 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.

9. Bleed-proof performance Using the evaluation paper A, solid portions of black and color (yellow, magenta, cyan) are printed adjacent to each other, and the degree of bleeding at the boundary between black and color is visually observed. The evaluation was based on the following criteria.
AA: Bleeding cannot be visually recognized.
A: Bleeding is hardly noticeable.
B: Slightly bleeding.
C: Breeding so that the color boundary line is not clear.

10. Quick-drying Using the ink jet recording apparatus used in Examples 1 to 5, printing was performed on the evaluation paper A. After 5 seconds from printing, the sample was loaded with sylbon paper on the printed paper and the recording surface was 40 g / cm ² . When pulling the Silbon paper with the weight of the load on it, visually observe whether the non-printing part (white background part) of the recording paper and the printing part are stained due to rubbing of the printing part. It was evaluated with.
A: Dirt due to rubbing is not seen.
B: There is almost no dirt due to rubbing.
C: The dirt part by a blur is conspicuous.

  According to the present invention, it has excellent long-term storability and ejection stability, can obtain a high print density without depending on the permeation performance of the recording medium, and has a scratch resistance, marker resistance and water resistance of the printed matter. An aqueous ink having excellent properties is provided. In addition, water-based inks that always have a high print density while having excellent long-term storage stability and ejection stability are provided, and further excellent print quality and excellent bleed resistance with other inks. An aqueous ink is provided. Furthermore, a water-based ink having excellent quick drying properties while always maintaining a high print density is provided. In addition, by using such an ink, an ink jet recording method that provides good printing performance even on a plain paper medium having high permeability is provided. As another effect, an ink tank and an ink jet that can be suitably used for the above recording method A recording device and an inkjet recording image are provided.

It is a schematic diagram which shows the basic structure of the dispersible coloring material which has fused the flat chargeable resin pseudo fine particles according to the present 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 flat chargeable resin pseudo fine particles and the fusion 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 fuse | melted with a coloring material. It is the schematic diagram which expanded the interface where the chargeable resin pseudo fine particles of the present invention and the color material are fused. 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 an explanatory diagram for schematically explaining a state when an ink droplet according to the present invention has landed on the surface of a recording medium. It is an example of the recording head used for this invention. It is an example of the recording head used for this invention. It is an example of the recording head used for this invention. It is an example of the recording head used for this invention. It is an example of the recording head used for this invention. It is an example of the recording head used for this invention.

Explanation of symbols

1: Color material 2: Flat chargeable resin pseudo fine particles 3: Dispersant 4: Monomer 5: Polymerization initiator aqueous solution 6: Dispersible color material 7: Oligomer formed by polymerization of monomer 8: Oligomer insolubilized in water Deposit 9-1: Hydrophilic monomer unit portion 9-2 in the flat charged resin pseudo fine particle 9-2: Hydrophobic monomer unit portion 10 in the flat charge resin pseudo fine particle 10: Bonding site 11 with the color material 11: Flat Interface portion 12 of the chargeable resin pseudo fine particles with the coloring material 12: hydrophilic group 13 directly modified with the coloring material 13: hydrophilic coloring material molecule

Claims (10)

A water-based ink comprising water, a plurality of water-soluble organic solvents, and a dispersible color material, wherein the water-soluble organic solvent includes a good solvent for the dispersible color material and a poor solvent for the dispersible color material. ,
The dispersible color material is a dispersible color material having a color material and chargeable resin pseudo fine particles smaller than the color material, and the color material and the chargeable resin pseudo fine particles are fixed,
Furthermore, when the total amount (% by mass) of the good solvent in the ink is A and the total amount (% by mass) of the poor solvent in the ink is B, A: B is in the range of 10: 5 to 10:30. The water-based ink is characterized in that the water-soluble organic solvent exhibiting the maximum Ka value among the Ka values of the plurality of water-soluble organic solvents obtained by the Bristow method is a poor solvent.   The water-based ink according to claim 1, wherein the dispersible colorant has a surface functional group density of 250 μmol / g or more and less than 1,000 μmol / g.   The water-based ink according to claim 1 or 2, wherein the color material constituting the dispersible color material has a hydrophilic group on a surface thereof.   The dispersible colorant according to claim 3, wherein the hydrophilic group is bonded to the colorant surface directly or through another atomic group.   The dispersible color material according to any one of claims 1 to 4, wherein a loss on heating of the color material is in a range of 2% by mass to 20% by mass. The chargeable resin pseudo fine particles have the formula (1):
^{_{CH 2 = C (R 1)}} COO (R 2 O) n R 3 (1)
(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ² represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ represents hydrogen. (The monovalent hydrocarbon group having 1 to 30 carbon atoms which may have an atom or a hetero atom, and n represents the number of 1 to 60.)
The water-based ink according to claim 1, comprising at least a polymer obtained by polymerizing at least a monomer represented by the formula:   An ink tank comprising the water-based ink according to any one of claims 1 to 6.   An ink jet recording apparatus comprising the water-based ink according to any one of claims 1 to 6.   An ink jet recording method comprising: forming an image by an ink jet recording apparatus using the water-based ink according to claim 1. An ink jet recording image formed by an ink jet recording apparatus using the water-based ink according to any one of claims 1 to 6.

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