JP2006008858A - Ink set for inkjet recording, inkjet recording device and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set which realizes a high optical density and gives a high-quality image well suppressed in occurrence of feathering and bleeding generating at the time of formation of neighboring images when a plurality of inks are printed on a plain paper. <P>SOLUTION: The ink set for inkjet recording comprises a black ink and a plurality of color inks, where each ink comprises a dispersible coloring material comprising a water-insoluble coloring material and a fine pseudoparticle of a chargeable resin smaller than the coloring material, the coloring material and the fine pseudoparticle of the chargeable resin being adhered to each other, and has a Ka value (absorption coefficient) of at least 0.2 but less than 1.0 (ml/m<SP>2</SP>×msec<SP>1/2</SP>) on a plain paper obtained by the Bristow method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aqueous inkjet recording ink, an ink tank, an inkjet recording apparatus, and an inkjet recording method.

  In recent years, studies on the use of pigments as coloring materials for ink jet recording inks have been energetically promoted, and it is known that the use of inks containing pigments provides images with excellent fastness such as water resistance and light resistance. It has been. In addition, when printing with a water-based ink on a recording medium called plain paper by an ink jet recording method, color blur occurs in the printed characters and images, or the ink spreads along the pulp fibers constituting the paper. In addition, it is known that a phenomenon in which wrinkle-like streaks occur (feathering) and a phenomenon in which inks cross each other and a boundary becomes unclear (bleeding) in a region where inks of two or more colors overlap. These phenomena occur remarkably when aiming at a particularly high OD (optical density).

  In Patent Documents 1 and 2, etc., there is a proposal of an ink set in which the polarity of black is different from that of black in order to reduce bleed. At the time of cleaning, there is a problem that ink is liable to be ejected or twisted due to contact and aggregation of the ink on the face surface of the printer and the ink ejection port.

  Patent Documents 3 and 4 propose a technique for forming a high-quality image by reacting an ink composition with a polyvalent metal-containing aqueous solution. However, the polyvalent metal ions used as the reactants are inherently unstable and easily precipitated, so they are complexed with coordination compounds, but this coordination state was destroyed for some reason. In such a case, the metal compound is deposited and the piping and the nozzle are blocked. In addition, separate heads are required for the reaction liquid and the ink, leading to an increase in cost.

  Patent Documents 5 to 8 and the like have proposed an ink set composed of an aqueous pigment ink for ink-jet recording for preventing color bleeding, bleeding and feathering at different color boundaries. When the amount is small, the surface tension of the ink is low (35 mN / m or less), so when printing, the ink droplets that land on the paper surface (plain paper) do not stay on the paper surface, but penetrate quickly and are high. The print density cannot be obtained.

  Further, as a method for improving the scratch resistance and bleed resistance in an aqueous pigment ink, an aqueous dispersion composed of colored resin fine particles by a method of including a pigment in a resin has been studied. For example, Patent Documents 9 to 13 propose water-based inks containing a color material in which a resin and a pigment are dispersed in an organic solvent and microencapsulated by phase inversion emulsification.

  The method of modifying the coloring material, particularly the pigment surface, with these resins may not only improve the dispersion stability of the pigment but also provide various functionalities depending on the resin to be introduced. However, these methods often do not provide sufficient dispersion stability and ejection stability due to the desorption and release of the introduced resin. In particular, when trying to satisfy the scratch resistance of the image, the effect of inclusion of the pigment is enhanced by introducing a resin having a higher molecular weight, but in order to increase the permeability of the ink, the resin dissolving power is high in the ink. It is necessary to use a large amount of an organic solvent. Therefore, non-ejection of ink is likely to occur due to a resin in which a free resin component is inherently dissolved in the ink. On the other hand, if a resin having a low molecular weight is used, the possibility of an adverse effect of the above-described dissolved resin is reduced. However, in this case, there is a disadvantage that the effect of pigment inclusion is low. In addition, since any method is complicated in operation and requires many steps and uses an organic solvent or the like, it is necessary to secure a manufacturing method by making a large-scale and huge investment. For this reason, the cost of the product is significantly increased, and environmental compatibility can be a problem.

JP 09-183224 A Japanese Patent Laid-Open No. 10-140064 JP 09-239964 A JP 2000-63719 A JP 2002-155225 A JP 2002-309132 A JP 2002-338860 A JP 2002-363462 A JP-A-8-183920 Japanese Patent Laid-Open No. 10-140065 JP-A-10-279873 JP-A-10-292143 JP 2001-234097 A

  An object of the present invention is to provide a plurality of ink sets for ink-jet recording for suppressing feathering and bleeding that occur when adjacent images are formed, particularly when printing a plurality of inks on plain paper. Another object is to provide a high-quality image having excellent ejection stability and storage stability, and excellent fastness such as marker resistance and scratch resistance.

In order to solve the above-described problems, the present inventors have pursued a correlation technical element when forming an adjacent image with a plurality of inks. As a result, a novel dispersion has been applied to the water-dispersible colorant of each ink in a plurality of ink sets. It has been found that it is effective to use a characteristic color material and to control the Ka value (absorption coefficient) for plain paper determined by the Bristow method for each ink. This technical element makes it possible to obtain a high-quality image in which the occurrence of feathering and bleeding is suppressed while exhibiting a high OD value.
In addition, as another effect, the dispersible colorant having a novel shape used in the present invention is essentially an insoluble colorant such as a pigment, and is essentially free from the need for a surfactant or a polymer dispersant. Maintains dispersion stability, and the resin component does not detach from the colorant, and has long-term storage stability. When used in ink, characteristics such as ejection stability as ink for inkjet recording And the obtained image has excellent fastness such as scratch resistance and marker resistance.

That is, the present invention is achieved by the following means.
1. In an ink set for inkjet recording composed of black ink and a plurality of color inks, each ink comprises a dispersible color material having a water-insoluble color material and chargeable resin pseudo fine particles smaller than the color material, The ink set is characterized in that the coloring material and the chargeable resin pseudo fine particles are fixed to each other, and the Ka value (absorption coefficient) for plain paper determined by the Brist method for each ink is 0.20 or more. An ink set characterized by being less than 00 (ml / m ² · msec ^1/2 ).
2. The difference between the color ink having the largest Ka value in each ink and the black ink having the smallest Ka value in each ink is 0.20 to 0.70 (ml / m ² · msec ^{1 / 2} ) The ink set described in 1 above.
3. 3. The ink set according to 1 or 2, wherein the Ka value of black ink is 0.20 or more and less than 0.60, and the Ka value of color ink is 0.40 or more and less than 1.00.
4). 4. The ink set according to any one of 1 to 3, wherein the Ka value of yellow ink is the largest among the Ka values of each color ink.
5. 5. The ink set according to any one of 1 to 4, wherein the dispersible colorant has a surface functional group density of 250 μmol / g or more and less than 1,000 μmol / g.
6). The ink set according to any one of 1 to 5, wherein the chargeable resin pseudo fine particles comprise a copolymer of monomer components including at least one type of hydrophobic monomer and at least one type of hydrophilic monomer. .

7). An ink tank comprising the water-based ink according to any one of 1 to 6 above.
8). An ink jet recording apparatus comprising the water-based ink according to any one of 1 to 6 mounted thereon.
9. 7. An ink jet recording method comprising forming an image by an ink jet recording apparatus using the water-based ink according to any one of 1 to 6 above.
10. An ink jet recording image formed by an ink jet recording apparatus using the water-based ink according to any one of 1 to 6 above.
11. The plurality of inks used in the image forming method for performing the step of forming an adjacent image with a plurality of inks each include a dispersible color material having a water-insoluble color material and chargeable resin pseudo fine particles smaller than the color material, A water-insoluble colorant and a chargeable resin pseudo fine particle are fixed to each other, and each ink has a Ka value (absorption coefficient) of 0.20 or more with respect to plain paper determined by the Brist method of each ink. A plurality of ink sets characterized by being less than 1.00 (ml / m ² · msec ^1/2 ).

  According to the present invention, an ink set for ink jet recording (hereinafter simply referred to as an ink set) that can obtain a high OD value when printing on plain paper and can form a good image with reduced occurrence of feathering and bleeding. Is provided). Furthermore, as another effect of the present invention, an ink tank, an ink jet recording apparatus, and an ink jet recording method capable of achieving the above-described excellent image formation by using such an excellent plural ink set are provided. As another effect of the present invention, an ink set excellent in quick drying on a recording medium is provided. Furthermore, another effect of the present invention is to provide an ink set that enables formation of an image having excellent scratch resistance on a recording medium. As another effect of the present invention, an ink set having excellent ejection characteristics in an ink jet recording apparatus is provided.

  Hereinafter, the present invention will be described in detail with reference to an embodiment which is considered to be the best of the present invention. The meaning of the “dispersible colorant” used in the present invention is essentially dispersible in water or an aqueous ink medium without adding a surfactant or a polymer dispersant, that is, has a self-dispersibility. It is a color material.

The first feature of the ink set according to the present invention is that a new dispersible color material obtained by fixing the charge resin pseudo fine particles is used for each ink constituting the ink set. To do.
In the present invention, the following cases are collectively referred to as an ink set.
1) Including two or more colors of ink 2) In 1), there are two or more color inks 3) In 1), black ink single color and color ink (mainly cyan, magenta, yellow) 3) a combination of three colors) 4) 1) black ink and all color inks are all single tank independent inks 5) 1) ink other than those described above (for example, black) Ink, light ink with low color material concentration, and one or more color inks other than those described above (blue, orange, violet, green, etc.)) Disposable ink with integrated ink tank and head used First, a dispersible color material comprising a color material and chargeable resin pseudo fine particles, the color The dispersible color material in which the material adheres the chargeable resin pseudo fine particles will be described.

  FIG. 1 shows a schematic diagram of a dispersible color material obtained by adhering a chargeable resin pseudo fine particle 2 to a color material 1 that characterizes each ink constituting a plurality of inks according to the present invention. Schematic diagram of the dispersible colorant 2 ′ in FIG. 1B is a part schematically showing a state in which a part of the chargeable resin pseudo fine particles 2 fixed to the surface of the colorant 1 is fused. is there. The dispersible colorant is a colorant that is dispersible in water or an aqueous ink medium because the charge of the chargeable resin pseudo fine particles is fixed on the surface of the colorant by the colorant fixing the chargeable resin pseudo fine particles. . At the same time, the dispersible color material has excellent adhesiveness when applied to the recording medium due to the presence of the resin component fixed to the color material surface. Further, the dispersible color material used in the present invention is not a simple physical adsorption of the resin component to the color material, but is characterized in that the charged resin pseudo fine particles are fixed to the color material, and thus the chargeable resin. The pseudo fine particles are not detached from the surface of the color material and are excellent in long-term storage stability.

  The fixing state of the dispersible color material used in the present invention between the color material and the chargeable resin pseudo fine particles is due to the strong interaction between the color material surface and the chargeable resin pseudo fine particles. It is thought that it has become. FIG. 4 shows a schematic diagram in which the interface between the chargeable resin pseudo fine particles and the color material is enlarged. First, as shown in FIG. 4, at the interface with the colorant 1, the chargeable resin pseudo fine particles 2 are polymers composed of various monomer unit compositions (indicated by 9-1 and 9-2 in the figure). Are intertwined. At this time, the polymer has various structures locally, and the surface energy state is distributed. At the point where the surface energy resulting from the chemical structure and surface structure of the colorant and the surface energy resulting from the chemical structure and surface structure of the polymer are in good agreement locally (indicated by 10 in the figure), the two interfaces are It will be firmly bonded. Furthermore, at the interface where one chargeable resin pseudo fine particle is in contact with the color material, as shown in FIG. 4, there are a plurality of points where the surface energies as indicated by 10 are locally coincident. It is expected that the fixed state of the present invention is established by the interaction.

  In particular, the inside of the chargeable resin pseudo fine particles has a strong interaction between the constituent polymers, and in some cases, the constituent polymers are entangled with each other to form physical crosslinks. Even when there are many hydrophilic groups, the fixed chargeable resin pseudo fine particles are not detached from the coloring material, and the resin component having hydrophilic groups does not continue to elute from the chargeable resin pseudo fine particles. .

  In addition, the dispersible colorant used in the present invention has an advantage that the chargeable resin pseudo fine particles are fixed. As a result, the specific surface area of the dispersible colorant increases depending on the form, and the chargeable resin pseudo fine particles are in many parts. It is possible to distribute the charge on the surface. Since the dispersible color material has a high specific surface area as described above, 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 above-described form of the dispersible color material used in the present invention is a form in which more surface charges are arranged on the surface of the dispersible color material more efficiently and higher, and is represented by Patent Document 2. Thus, a high dispersion stability can be imparted to the color material as compared with a color material coated with a resin.

  Even in the case of a dispersible color material in which the color material is an organic pigment, as described above, a plurality of interaction points of the chargeable resin pseudo fine particles are randomly distributed in a state of being fixed to the color material. The charged resin pseudo fine particles adhere to several pigment molecules in the pigment crystal (see FIG. 5). Therefore, the “pigment peeling” caused by locally hydrophilizing pigment molecules as shown in FIGS. 6A and 6B does not occur in the present invention. Preferably, when an organic pigment is used as a coloring material, the size of the chargeable resin pseudo fine particles is controlled to be smaller than the pigment particles and larger than the pigment molecules. Thus, a dispersible colorant using an organic pigment imparted with high dispersibility can be obtained without breaking the crystal structure of the pigment.

  The dispersible colorant in a state in which the chargeable resin pseudo fine particles are “fixed” 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 in the second separation. Thus, the coloring material and the water-insoluble resin component contained in the precipitate in the first separation are separated. Further, in the third separation, the weakly adsorbed resin component is separated from the dispersible colorant to which the chargeable resin pseudo fine particles are fixed, and the resin component contained in the third separation supernatant is determined. Then, the adhesion between 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. Of course, any known separation method or any newly developed separation method may be used as long as the separation method achieves the purpose of the first, second and third separations, and the procedure is from three stages. It can be applied at most or at least.

  Further, the dispersible colorant according to the present invention is characterized in that the dispersible colorant composed of the colorant 1 and the chargeable resin pseudo fine particles 2 can be dispersed alone in the aqueous medium. As described above, the dispersible colorant used in the present invention is essentially a self-dispersing agent that can be stably dispersed in water or water-based ink without the aid of other surfactants or polymer dispersants. The color material of the mold. This definition and determination method will be described in detail later. Therefore, the dispersible colorant according to the present invention is added with a polymer dispersant or other resin component or surfactant component that may be released for a long time for the purpose of stabilizing the dispersion of the colorant. There is no need. As a result, when such a dispersible color material is used as a water-based ink, the degree of freedom in designing with respect to components other than the dispersible color material is increased, for example, on a recording medium having high ink permeability such as plain paper. In this case, the water-based ink can obtain a sufficiently high printing density.

  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 by forming a large number of charged resin pseudo fine particles in a scattered and fixed manner with respect to the color material. In particular, there is a certain distance between the charged charged resin pseudo fine particles, preferably uniformly distributed, and more preferably, the surface of the color material is partially exposed. Such a form is confirmed by observing the dispersible colorant with a transmission electron microscope or a scanning electron microscope. A plurality of charged resin pseudo fine particles fixed to the surface of the color material are fixed at a certain distance, or the surface of the color material is exposed between the fixed charged resin pseudo fine particles. I can observe. In the above, the chargeable resin pseudo fine particles are sometimes close to each other, and in some cases, may be observed to be fused, but there is a distance between the chargeable resin pseudo fine particles as a whole, and the surface of the colorant It is considered by those skilled in the art that the charged resin pseudo fine particles are considered to be scattered and fixed to the color material when there are exposed portions and these states are distributed. It will be obvious.

  According to the study by the present inventors, it has been clarified that the water-based ink containing the dispersible color material used in the present invention as described above exhibits an excellent quick drying property on a 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 a pore on the recording medium due to capillary action (in the case of plain paper, it is a gap between cellulose fibers, coated paper and glossy In the case of paper, it is absorbed into the pores of the receiving layer). At this time, the color material used in the present invention has many fine gaps between the color materials because of the morphological characteristics of the color material. Capillary action acts on the ink solvent. For this reason, the ink solvent between the color materials is quickly absorbed into the recording medium. Among the dispersible color materials according to the present invention, those having a form in which charged resin pseudo fine particles are scattered on the surface provide a water-based ink exhibiting a more preferable quick-drying property. It is expected that

  As described above, the object of the present invention is to provide an ink set that can provide an image with a high OD when printing on plain paper and an image in which the occurrence of feathering and bleeding is well suppressed. There is to do. In order to obtain an image with a high OD, it is desirable that a large amount of color material is present on the paper surface when the image is formed. However, the more the color material is present, the more the ink printed on the paper surface dries. Time is required, and accordingly, bleeding with adjacent ink is likely to occur. In that respect, the dispersible colorant used in the present invention has the quick-drying property described above, so that it is possible to achieve both the formation of a high OD image and the formation of a good image with suppressed bleeding. Think.

  The dispersible colorant used in the present invention preferably has a surface functional group density in a weight average of 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. Is preferred. When the surface functional group density is smaller than this range, the long-term storage stability of the dispersible colorant may be inferior. Further, when the surface functional group density is considerably larger than this range, the dispersion stability is sufficiently high, but when the dispersible colorant used in the present invention is applied to the recording medium as an aqueous ink, In this case, the color material is likely to penetrate, and it may be difficult to ensure a high print density. On the other hand, when carbon black is used as the coloring material, the specific gravity of carbon black is high, so that a higher surface functional group density is required to maintain sufficient dispersion stability over a long period of time. Since a high black density is preferred, it is preferably set to 350 μmol / g or more and less than 800 μmol / g. Next, each component of the dispersible color material used in the present invention will be described.

[Color material]
First, the color material which is a constituent component of the dispersible color material used in the present invention will be described below. The color material used in the present invention is preferably a color material that is insoluble in water among known or newly developed color materials that can be stably dispersed in water together with a dispersant. Examples include hydrophobic dyes, inorganic pigments, organic pigments, metal colloids, and colored resin particles. More preferably, a colorant having a dispersed particle diameter 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. The dispersible color material having the above-described configuration using the color material dispersed in this range can give an image having high coloring power and fastness such as high scratch resistance when used in water-based ink. It becomes a preferable dispersible colorant. The dispersed particle diameter of the color material is the cumulant average value of the particle diameter measured by the dynamic light scattering method.

  Examples of the inorganic pigment that can be effectively used as a coloring material in the present invention include, for example, carbon black, titanium oxide, cadmium red, red pepper, molybdenum red, chrome vermillion, molybdate orange, yellow lead, chrome yellow, cadmium yellow, Examples include yellow iron oxide, titanium yellow, chromium oxide, pyridian, cobalt green, titanium cobalt green, cobalt chrome green, ultramarine blue, ultramarine blue, bitumen, cobalt blue, cerulean blue, manganese violet, cobalt violet, and mica.

  Examples of organic pigments that can be effectively used 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, azo, anthraquinone, indigo, phthalocyanine, carbonyl, quinoneimine, methine, quinoline, nitro, etc. Dyes. Of these, disperse dyes are particularly preferable.

[Charged resin pseudo fine particles]
Next, the chargeable resin pseudo fine particles, which are another component constituting the dispersible colorant used in the present invention, will be described. The chargeable resin pseudo fine particles are substantially insoluble in water, and are defined as microscopic bodies formed by aggregation of resin components having a sufficiently high degree of polymerization that are smaller than the color material to be fixed. Is a micro object that is pseudo close to a sphere or has a plurality of chargeable resin pseudo fine particles arranged in a certain range. Preferably, the resin components constituting the chargeable resin pseudo fine particles are desirably physically or chemically cross-linked with each other.

  Further, as another preferred embodiment, when the dispersed particle diameter of the charged resin pseudo fine particles in water can be measured by, for example, a dynamic light scattering method, preferably the cumulant average value of the dispersed particle diameter is It is desirable to be in the range of 10 nm or more and 200 nm or less. Furthermore, from the viewpoint of long-term storage stability of the dispersible colorant, it is preferable that the polydispersity index of the dispersed particle size is suppressed to less than 0.2. When the average 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 as defined above cannot be sufficiently maintained, and the resin is easily dissolved in water. May not be obtained. On the other hand, in the range of 10 nm or more and 200 nm or less, the particle diameter is smaller than the color material particles themselves, so that the dispersion stabilization of the color material by the fixation 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.

  In the present invention, the chargeability refers to a state in which a functional group that is ionized in some form in the aqueous medium itself is retained, and is preferably self-dispersible by the chargeability. Therefore, whether or not it is a chargeable resin pseudo fine particle is determined by a known and arbitrary method, for example, a method of measuring the surface zeta potential of the chargeable resin pseudo fine particle; Method of calculating as density; Method of confirming electrolyte concentration dependence of dispersion stability by adding electrolyte to aqueous dispersion of charged resin pseudo fine particles; Perform chemical structure analysis of charged resin pseudo fine particles by known methods And a method for examining the presence or absence of an ionic functional group.

  The resin component constituting the chargeable resin pseudo fine particles having the above-described form may be any resin component such as any commonly used natural or synthetic polymer, or a polymer newly developed for the present invention. It can be used without any restrictions. 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, the following monomer components having a radical polymerizable unsaturated bond, which are classified into acrylic resins and styrene / acrylic resins, can be used generally and from the viewpoint of simple functional design of chargeable resin pseudo fine particles. A polymer or a copolymer can be preferably used.

  Examples of the monomer having a radically polymerizable unsaturated bond preferably used in the present invention (hereinafter referred to as a radically polymerizable monomer or simply a monomer) include the following. Examples of those classified as hydrophobic monomers include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylate-n-propyl, acrylate-n-butyl, acrylate-t-butyl, benzyl acrylate, (Meth) such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, tert-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate Acrylic acid ester; styrene monomer such as styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-tert-butyl styrene; itaconic acid ester such as benzyl itaconate; Such as dimethyl acid It can maleate; fumaric acid dimethyl such fumaric acid esters such as acrylonitrile, methacrylonitrile, vinyl acetate, and the like.

  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, fumaric acid, and the like. A monomer having a sulfonic acid group such as a salt, styrene sulfonic acid, sulfonic acid-2-propylacrylamide, acrylic acid-2-ethyl sulfonate, methacrylic acid-2-ethyl sulfonate, butyl acrylamide sulfonic acid, and the like; 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.

  Examples of the monomer having a cationic group include a monomer having a primary amino group such as aminoethyl acrylate, aminopropyl acrylate, methacrylic acid amide, aminoethyl methacrylate, aminopropyl methacrylate, and the like. Second, such as methylaminoethyl, methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, methylaminoethyl methacrylate, methylaminopropyl methacrylate, ethylaminoethyl methacrylate, ethylaminopropyl methacrylate, etc. Monomers having secondary amino groups, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylamino methacrylate Monomer having a tertiary amino group such as diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, diethylaminopropyl methacrylate, dimethylaminoethyl methyl chloride salt, dimethylaminoethyl methyl methacrylate salt, dimethyl acrylate Examples thereof include monomers having a quaternary ammonium group such as aminoethylbenzyl chloride salt and dimethylaminoethylbenzyl chloride methacrylate, and various vinylimidazoles.

  Moreover, as a nonionic hydrophilic monomer, for example, it has a radical polymerizable unsaturated bond and a hydroxyl group showing strong hydrophilicity in the structure such as hydroxyethyl (meth) acrylate and hydroxylpropyl (meth) acrylate at the same time. Monomers, and monomers containing an alkylene oxide group such as methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, and other known or novel Various oligomers, macromonomers, and the like can be used without limitation.

  In particular, the alkylene oxide group-containing monomer is excellent in copolymerization with the above-described hydrophobic monomer component, and in the case of the chargeable resin pseudo fine particles having a copolymer component in combination with these, the surface property is uniform. A favorable result is given from the viewpoint. In addition, the chargeable resin pseudo fine particles are formed by polymerizing an alkylene oxide group-containing monomer component, so that the monomer has high hydrophilicity, so that it exists locally on the outer surface of the fine particles and constitutes Since the glass transition temperature of the coalescing component is lowered, it takes a flat spherical shape in water, thereby increasing the surface area in contact with the color material, and the charged resin pseudo fine particles are firmly fixed or fused to the color material. It is thought that it takes the form which it wore. This dispersible color material can be formed into a film with a color material adjacent to the recording paper by a high film forming property imparted to the chargeable resin pseudo fine particles, thereby forming a strong colored film. Accordingly, high scratch resistance can be imparted to a printed matter obtained using the dispersible color material.

  Furthermore, due to the high adhesion and fusing property imparted to the chargeable resin pseudo fine particles, when forming an image by printing an aqueous ink on a recording paper with an ink jet recording apparatus or the like, it promotes aggregation of adjacent color materials. As a result, the rate of decrease in the amount of residual solvent such as moisture remaining on the recording paper can be increased, and the fixing time on the recording paper can be shortened.

  Furthermore, there is no problem even if a crosslinkable unsaturated monomer is used in combination. A crosslinkable unsaturated monomer is an unsaturated monomer having two or more polymerizable unsaturated bonds in one molecule. For example, divinylbenzene, divinylnaphthalene, divinyl ether, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, allyl methacrylate, diallyl phthalate 1,6-hexanediacrylate, methylenebisacrylamide and the like.

  The amount of the crosslinkable unsaturated monomer used in combination is preferably 0.1 to 15 parts, more preferably 0.1 to 10 parts, out of 100 parts of the resin component. When the blending amount exceeds 15 parts, gelation is caused during the polymerization, the resin viscosity becomes high, and it becomes difficult to disperse in water, so that preferable charged resin pseudo fine particles cannot be obtained.

  When preparing the chargeable resin pseudo fine particles, for example, depending on many control factors such as the type and concentration of the polymerization initiator to be used, the type of monomer constituting, and the copolymerization ratio, the dispersible colorant and the chargeable resin pseudo fine particles are used. It is possible to appropriately control various characteristics of the above, and in particular, among the charged resin pseudo fine particles described above, at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer are used. It is a desirable mode to have a constitution comprising a copolymer of monomer components to be included. At this time, by using at least one type of hydrophobic monomer, it is possible to achieve good adhesion to the colorant and heat stability, and by using at least one type of hydrophilic monomer, good form control and dispersion. Stability can be imparted to each. 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. In addition to satisfying the above conditions, the dispersible colorant used in the present invention is fixed to the colorant by appropriately selecting the monomer type and copolymerization ratio of the resin component constituting the chargeable resin pseudo fine particles. Further functionality can be imparted to the charged resin pseudo fine particles.

  The chargeable resin pseudo fine particles may be composed of a copolymer of monomer components including at least one type of hydrophobic monomer and at least one type of hydrophilic monomer, and may include at least an anionic monomer as the hydrophilic monomer. Is a preferred form. In particular, by including an anionic monomer, more anionic groups can be introduced into the chargeable resin pseudo fine particles, and the surface functional group density of the colorant is controlled to a preferable value as described above. It is also effective. In addition, by including the anionic monomer, it is possible to obtain a dispersible colorant exhibiting high dispersion stability particularly in a high pH region to a medium pH region.

  The anionic monomer is not particularly limited as long as it is a monomer having a functional group exhibiting anionic property in water. From the viewpoint of copolymerization with other monomer components, versatility, anionic strength, etc., acrylic Acid, methacrylic acid, p-styrenesulfonic acid and salts thereof are particularly preferably used.

[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 based on the method for synthesizing the charge resin pseudo fine particles and the method for combining the charge resin pseudo fine particles and the color material. Can be implemented.

  However, as a result of intensive studies, the inventors of the present invention are dispersible color materials having a color material and a chargeable resin pseudo fine particle smaller than the color material, which is a feature of the present invention. The present inventors have invented a simple method for producing a dispersible colorant characterized in that the dispersible resin pseudo fine particles are fixed. Hereinafter, a method for producing a dispersible color material used in the present invention, which is preferably implemented in the present invention, will be described.

  As a result of the study by the present inventors, it has been clarified that a dispersible colorant having the above-described characteristics can be produced very simply by applying an aqueous precipitation polymerization method under the following conditions. First, a water-insoluble colorant is dispersed with a dispersant to obtain a dispersion aqueous solution of the water-insoluble colorant, and then the radically polymerizable monomer is subjected to aqueous precipitation polymerization using the aqueous radical polymerization initiator in the dispersion aqueous solution. In this method, the chargeable resin pseudo fine particles are fixed by a process. The dispersible colorant obtained through such a process is composed of a water-insoluble colorant in which the chargeable resin pseudo fine particles synthesized in the aqueous precipitation polymerization process are firmly fixed in a uniform and scattered state. Dispersion stability is excellent. In addition, in the 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 also in this case, the fixation with the coloring material, which is a feature of the present invention. The condition is achieved well. Hereinafter, preferred embodiments of the manufacturing method will be described in detail.

(Dispersion of water-insoluble colorant)
First, an insoluble colorant that can be 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 and nonionic ones can be used. From the viewpoint of maintaining the dispersion stability in the subsequent polymerization step, a polymer dispersant or a water-soluble agent is used. It is desirable to use a functional 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 dispersant, so that the chargeable resin pseudo fine particles can be fixed in the subsequent polymerization step. From the viewpoint of easily inducing the phenomenon.

  The production method of the polymer dispersant and the water-soluble polymer functioning 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. It has been clarified that good results are obtained when a dispersant selected from ionic group-containing acrylic polymer compounds obtained by polymerizing the above (meth) acrylic acid ester monomers as essential components is used.

  At this time, it is desirable to select an anionic dispersant when the obtained dispersible colorant is intended to have an anionic group. 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 a desirable form to use those having an acid value of 100 or more and 250 or less. When the acid value is smaller than this range, the affinity between the hydrophobic monomer and the dispersant is higher than the affinity between the colorant and the dispersant during the aqueous precipitation polymerization, and the charged resin pseudo fine particles are colored. There is a case where the dispersing agent is detached from the surface of the coloring material before being fixed to the material, and the dispersed state cannot be maintained. In addition, when the acid value is larger than this range, the excluded volume effect of the dispersant on the surface of the color material and the electrostatic repulsion force become too strong, which prevents the adhesion of the chargeable resin pseudo fine particles to the color material. There is a case. When an anionic dispersant is used, it is preferable to select a dispersant having a carboxyl group as the 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 an average dispersed particle diameter in the range of 0.01 μm to 0.5 μm (10 nm to 500 nm), particularly preferably. Disperses in the range of 0.03 μm to 0.3 μm (30 nm to 300 nm). 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 there is a tendency, 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 differs depending on various measurement methods. In particular, in the present invention, ELS-8000 manufactured by Otsuka Electronics Co., Ltd. is used when the organic pigment is a spherical particle. The average particle diameter and the polydispersity index determined by measuring the dynamic light scattering method as the principle and performing cumulant analysis are used.

  As a method for dispersing the water-insoluble colorant, any of the methods that use a dispersant as described above can be used as long as the colorant can be stably dispersed in water under the above-described conditions. This method is not limited. 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.

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

(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 persulfate. Further, it may be a redox initiator, an azo initiator, or a peroxide initiator based on a combination of a water-soluble radical polymerization initiator and a reducing agent. Specifically, it is designed and used so as to obtain an optimal combination in consideration of the characteristics of the colorant, dispersant, and monomer listed above. Desirably, a polymerization initiator that gives a polymerization initiator residue having the same sign 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, the surface charge can be obtained more efficiently by selecting one having an initiator residue that is neutral or anionic.

(Radically polymerizable monomer)
Since the radical polymerizable monomer used in the production method of the present invention is a component constituting the chargeable resin pseudo fine particles after passing through the aqueous precipitation polymerization, as described above, the chargeable resin pseudo fine particles to be obtained. Further, it may be appropriately selected depending on the characteristics of the dispersible color material. In the above-described production methods, any of the conventionally known radical polymerizable monomers or newly developed radical polymerizable monomers 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. 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 prepared in FIG. 2A is raised while stirring, and the monomer component 4 is added to the dispersion together with, for example, the aqueous radical polymerization initiator 5 (see FIG. 2B). The added aqueous radical polymerization initiator generates radicals by cleaving when the temperature is raised. 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 It contributes to the reaction with water-soluble monomers.

  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 proceeds as described above, the oligomer 7 generated by the polymerization reaction of the monomer component becomes insoluble in water and precipitates from the aqueous phase (8). At this time, the precipitated oligomer has sufficient dispersion stability. Since it does not have, it unites and forms the chargeable resin pseudo fine particles 2. 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 color material surface and the charge resin pseudo fine particles 2 is strongly affected by the hydrophobic interaction. Adsorb. At this time, the polymerization reaction continues to proceed inside the chargeable resin pseudo fine particles 2, and changes to a form that is more energetically stable while increasing the adsorption point with the color material. At the same time, since the physical cross-linking is highly formed inside the chargeable resin pseudo fine particles, the form that is most stably adsorbed to the coloring material is fixed and is in a fixed state. On the other hand, the coloring material 1 is stabilized by fixing a plurality of chargeable resin pseudo fine particles 2, and the dispersant in an equilibrium state is desorbed from the coloring material surface.

  Fixing of chargeable resin pseudo fine particles having a constitution comprising a monomer component copolymer containing at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer, obtained by the above method, to a color material A schematic diagram of the interface side is shown in FIG. Since the charged resin pseudo fine particles, which are aggregates of resin components, have hydrophilic monomer units 9-1, hydrophobic monomer units 9-2, etc. distributed in an arbitrary manner, the local surface energy has a distribution. There are countless adsorption points 10 that coincide with the surface energy of the color material. FIG. 5 shows an enlarged schematic diagram of the fixing interface between the chargeable resin pseudo fine particles and the coloring material. The interface 11 of the chargeable resin pseudo fine particles adsorbs the adsorption point 10 shown in FIG. It adheres stably by taking a form according to the surface shape. As described above, also in this process, since the polymerization reaction proceeds in the chargeable resin pseudo fine particles, the adsorption to the color material is achieved by fixing 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 works mutually, the chargeable resin pseudo fine particles are scattered and fixed to the color material, and the above-described preferable form is obtained.

  The polymerization reaction conditions vary depending on the properties of the polymerization initiator, dispersant, and 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 aqueous precipitation polymerization step, when the monomer component containing at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer is polymerized to obtain the chargeable resin pseudo fine particles, preferably the monomer component Is preferably added dropwise to an aqueous dispersion of a water-insoluble colorant containing an aqueous radical polymerization initiator. 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 the chargeable resin pseudo fine particles. . 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 of the hydrophobic monomer and the hydrophilic monomer is always kept constant, and the desired ratio is maintained. 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 colorant to which the chargeable resin pseudo fine particles are fixed, obtained in the above-described steps, it is desirable to further perform a purification treatment in addition to the above steps. In particular, performing a purification treatment on unreacted polymerization initiators, monomer components, dispersants, water-soluble resin components that have not been fixed, and chargeable resin pseudo fine particles maintains the storage stability of the dispersible colorant highly. It is important to do. 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 also 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 on 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 that has undergone the aqueous precipitation polymerization step has a large surface functional group even if the amount of the anionic monomer used in the step is relatively small. 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. The reason for this is not clear, but 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 colorant, and the surface of the dispersible colorant used in the present invention having a structurally large specific surface area is further anionic from the anionic monomer component. Many groups are present, and as a result, the dispersible colorant produced by the above-described production method is expected to be stabilized with fewer anionic monomer components.

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

  Examples of the water-soluble solvent used in each ink include alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, polyethylene glycol, polypropylene glycol, 1,6 hexanediol, 1,2,6 hexanetriol, ethylene glycol, diethylene glycol, and the like. Alkylene glycols, glycerol, lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether, 2-pyrrolidone and the like. The amount of such a water-soluble solvent used is 5 to 70%, preferably 5 to 50% in the whole ink, from the viewpoints of ink viscosity, dispersion stability and the like.

  Although the ink set according to the present invention will be described in detail later, when the Ka (absorption coefficient) is set to a relatively small value of 0.20 or more and less than 1.00, when printing on plain paper, A high printing density can be realized by suppressing the rate of absorption of the color material and securing the amount remaining on the paper surface. At this time, if the absorption speed is slow, the fixing speed on the paper surface is also slow, and the scratch resistance, marker resistance, and bleed property are inferior, so the ink droplets land on the paper surface and the color of water evaporates. It is desirable to include a water-soluble solvent that promotes aggregation of the material dispersion.

  Specifically, it is preferable to use alkylene glycols such as polyethylene glycol 400, 600, 1000, 2000, and polypropylene glycol 1000. The amount of the water-soluble solvent that promotes such aggregation is 10 to 70%, preferably 20 to 60%, in the water-soluble solvent in the ink. When it is less than 10%, the aggregation effect of the color material dispersion is not sufficient, and when it is more than 70%, there is a problem in the storage stability of the ink.

Each ink constituting a plurality of ink sets according to the present invention has a Ka value that is an absorption coefficient for plain paper determined by the Brist method of 0.20 or more and less than 1.00 (ml / m ² · msec ^1/2 ). It is characterized by being. Furthermore, the ink having the largest absorption coefficient is the color ink, and the smallest ink is the black ink, and the difference in Ka value between these inks is 0.20 or more and 0.70 or less. Is preferred. Further, the Ka value of the black ink is preferably 0.20 or more and less than 0.60, and the Ka value of the color ink is preferably 0.40 or more and less than 1.00. Moreover, it is preferable that the Ka value of yellow ink is the largest among the Ka values of each color ink.

  The absorption coefficient with respect to plain paper calculated | required by said Bristo method, so-called Bristo penetration speed is demonstrated. Bristol permeation rate here refers to J.I. TAPPI Paper Pulp Test Method No. Based on the liquid absorptivity test method (Brist method) of 51-87 paper and paperboard, measurement is performed with a tester described herein (for example, trade name: Dynamic permeability test apparatus S; manufactured by Toyo Seiki Seisakusho). be able to.

  Immediately after the ink droplets adhere to the surface of the recording medium, the ink is mostly absorbed by the uneven portions on the surface of the recording medium, and hardly penetrates into the recording medium. The time between them is the contact time (tw), and the amount of ink absorbed in the concavo-convex portion of the recording medium at the contact time is Vr. When the contact time is exceeded after the ink is adhered, the amount of penetration into the recording medium increases by the time exceeding the contact time, that is, an amount proportional to the 1/2 power of (t-tw). The Ka value is a proportional coefficient for this increase, and indicates a value corresponding to the penetration rate.

The Ka value according to the Bristow method in the present invention is a value using plain paper as a recording medium using the dynamic permeability test apparatus. Plain paper as used herein refers to paper that has no pigment coated on the surface of the paper. For example, PB paper used in Canon copiers, laser beam printers, inkjet recording printers, and the like. And PPC paper.
The Ka value in the present invention is specifically measured using PB paper manufactured by Canon Inc. among the above plain paper. The typical physical properties of this paper are described below.
Basis weight: 64 g / m ² (Test conditions of JIS P8111)
Steecht size: 25 seconds (Test conditions of JIS P8122)

Specific measurement conditions for the Ka value will be described in the example section. By constituting so that the Ka value of each ink constituting the ink set according to the present invention is 0.20 or more and less than 1.00 (ml / m ² · msec ^1/2 ), permeation on plain paper is prevented. Therefore, a printed matter with a high print density can be obtained. In contrast, an ink with a Ka value of less than 0.20 can provide a printed matter with a high print density, but the penetration speed is too slow, and it is sufficient to use the dispersible colorant that is a feature of the present invention. Bleedability and feathering properties cannot be obtained. On the other hand, an ink having a Ka value of 1.00 or more has a permeation speed that is too high, especially when printing at high speed or when the amount of ink shot is small, and the print density tends to be remarkably inferior. This is not preferable because the properties and the feathering properties cannot be obtained.

  In the following, preferred examples (Examples) and unfavorable examples (Comparative Examples) of the Ka value of the ink in the present invention are described. Recording inks A and C and comparative inks A and C were prepared in the same manner as in Example 1 described later, and recording inks B and D and comparative inks B and D in the same manner as in Example 2. Using this ink, recording was performed on Canon PPC paper NSK using an ink jet recording apparatus BJS-500 (manufactured by Canon Inc.), and the print density, bleeding property, and feathering property were evaluated. These are shown in Tables A to D below. Details will be described later.

  The ink having the largest absorption coefficient is color ink, the smallest ink is black ink, and the difference between these Ka values is 0.20 or more and 0.70 or less. It is done. That is, since the Ka value of the black ink is smaller than that of the color ink, the penetrability of the black ink with the lowest lightness is slow, and the black ink can be prevented from entering the color ink with high lightness. Good. Further, among the color inks, the yellow ink has the largest Ka value, so that the black ink has the smallest Ka value and the yellow ink has the largest Ka value. The yellow ink having the highest lightness has the fastest permeability, and the intrusion of the black ink and further color inks (cyan ink, magenta ink) into the yellow ink can be suppressed, so that the intercolor bleeding can be improved.

[Recorded image]
The ink set according to the present invention can be suitably used for ink jet recording, and by forming an image on a recording medium with an ink jet recording apparatus as described later, high OD, good feathering and bleeding are suppressed. A color image is obtained. The recording medium used at this time can be used without limitation even if it is a medium capable of ink jet recording.

[Image recording method and recording apparatus]
The ink set according to the present invention is used for an inkjet discharge type head, and is effective as an ink tank in which each ink constituting the set is stored or as an ink set for filling an ink tank. is there. In particular, the present invention provides an excellent effect in a bubble jet (registered trademark) type recording head and recording apparatus among ink jet recording methods.

  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, the electric circuit arranged corresponding to the sheet or liquid path holding the ink is used. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling to the heat conversion body, heat energy is generated in the electrothermal conversion body, and the heat acting surface of the recording head This is effective because the film can be boiled, 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 opening 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 immediately and appropriately performed, and in particular, ink ejection excellent in 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 using the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate 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 recovery means for the recording head, preliminary auxiliary means, etc. provided as the configuration of the recording apparatus to be applied, because the effects of the present invention can be further stabilized. . Specifically, the capping means, the cleaning means, the pressurizing or suction means for the recording head, the preheating means by the electrothermal converter or another heating element or a combination thereof, and the recording This is a preliminary discharge mode in which another discharge is performed.

  Next, an Example and a comparative example are given and this invention is demonstrated concretely. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “part” or “%” is based on mass unless otherwise specified.

[Production Example 1] (Preparation of black pigment dispersion)
A mixed solution of 10 parts of carbon black Black Pearls 880 (manufactured by Cabot), 10 parts of a styrene-acrylic acid dispersant (styrene / acrylic acid = 75/25, Mw = 10,000, acid value 190), and 80 parts of water Dispersion was performed at 1,500 rpm for 5 hours in a sand mill manufactured by Rika Kogyo Co., to obtain Pigment Dispersion Liquid 1. As beads, zirconia beads having a diameter of 0.6 mm were used, and the filling rate in the pot was 70%. The styrene-acrylic dispersant was used as a water solution by adding water and potassium hydroxide equivalent to the acid value in advance and stirring at 80 ° C. It was 109 nm when the average particle diameter of the obtained pigment resin dispersion was measured.

[Production Example 2] (Preparation of cyan pigment dispersion)
Phthalocyanine pigment PB15: 3 (manufactured by Clariant) 10 parts, styrene-n-butyl acrylate-acrylic acid dispersant (styrene / n-butyl acrylate / acrylic acid = 40/35/25, Mw = 8,000, acid value 190) 10 parts, 1 part of glycerin, 1 part of diethylene glycol and 10 parts of methyl ethyl ketone were mixed with a kneader. The obtained mixture was kneaded for 30 minutes with a two-roll mill (rotation ratio 1: 1.2 manufactured by Inoue Seisakusho Co., Ltd.) to obtain a colored resin compound (2A). At this time, the temperature was controlled so that the roll surface temperature was in the range of 60 ° C to 80 ° C. 100 parts of a colored resin compound (2A) was added to 1,000 parts by mass of a 1% aqueous sodium hydroxide solution, and the mixture was stirred for 3 hours with a dispar mill to obtain a pigment aqueous dispersion (2B).

  To 200 parts by mass of the pigment aqueous dispersion (2B), 1,600 parts of ion-exchanged water and 200 parts by mass of diethylene glycol were added to dilute 10 times (total amount = 2,000 parts by mass). At this time, the pH of the pigment aqueous dispersion was 12.8. The resin was removed from the diluted dispersion with an ultrafiltration membrane (AHP1010 manufactured by Asahi Kasei Co., Ltd., molecular weight cut off = 50,000). When the filtrate reached 1,800 parts by mass, 1,800 parts by mass of ion-exchanged water was again added to the treatment liquid, and ultrafiltration was similarly performed. Subsequently, 1,800 parts by mass of ion-exchanged water was added, and the same ultrafiltration was performed to obtain a cyan pigment aqueous dispersion (2). It was 112 nm when the average particle diameter of the obtained pigment resin dispersion was measured.

[Production Example 3] (Preparation of magenta pigment dispersion)
In Production Example 2, a magenta pigment dispersion (3) was obtained in the same manner as in Production Example 2, except that quinacridone pigment PR122 (manufactured by Clariant) was used instead of phthalocyanine pigment PB15: 3. It was 98 nm when the average particle diameter of the obtained pigment resin dispersion was measured.

[Production Example 4] (Preparation of yellow pigment dispersion)
In Production Example 2, a yellow pigment dispersion (4) was obtained in the same manner as in Production Example 2, except that yellow pigment PY180 (manufactured by Clariant) was used instead of phthalocyanine pigment PB15: 3. It was 128 nm when the average particle diameter of the obtained pigment resin dispersion was measured.

[Production Example 5]
100 parts of pigment dispersion 1 was heated to 70 ° C. in a nitrogen atmosphere, and the following three liquids were added dropwise over 6 hours while stirring with a motor. The three liquids were (1) 9.0 parts of benzyl methacrylate, (2) a mixed liquid of 1.0 part of acrylic acid and 0.7 part of potassium hydroxide, and 20 parts of water, and (3) a polymerization initiator. It is a mixed solution in which 0.15 part of potassium sulfate is dissolved in 20 parts of water. Furthermore, a colored liquid fine particle dispersion was obtained by aging for 2 hours after dropping. Next, the obtained dispersion is diluted 10-fold with water, centrifuged at 5,000 rpm for 10 minutes to remove aggregate components, and then centrifuged at 18,000 rpm for 2 hours. Thus, dispersible colorant 1 as a sediment was obtained.

[Production Example 6]
In Production Example 5, a dispersible colorant 2 was obtained in the same manner as in Production Example 5 except that Pigment Dispersion Liquid 2 was used instead of Pigment Dispersion Liquid 1.

[Production Example 7]
In Production Example 5, the pigment dispersion 3 was used in place of the pigment dispersion 1, and VA-057 [manufactured by Wako Pure Chemicals, 2,2′-azobis (as a polymerization initiator) instead of potassium persulfate ( N- (2-carboxyethyl) amidinopropane)] was used in the same manner as in Production Example 5 to obtain dispersible colorant 3.

[Production Example 8]
In Production Example 5, a dispersible colorant 4 was obtained in the same manner as in Production Example 5 except that the pigment dispersion 4 was used instead of the pigment dispersion 1.

[Production Example 9]
In Production Example 5, instead of 9.0 parts of benzyl methacrylate, 6.5 parts of benzyl methacrylate and methoxypolyethylene glycol methacrylate (made by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M90G, molecular weight = about 500) 2.5 A dispersible colorant 5 was obtained in the same manner as in Production Example 5, except that 1.0 part of methacrylic acid was used instead of 1.0 part of acrylic acid.

[Production Example 10]
In Production Example 9, a dispersible colorant 6 was obtained in the same manner as in Production Example 9 except that Pigment Dispersion Liquid 2 was used instead of Pigment Dispersion Liquid 1.

[Production Example 11]
In Production Example 9, the pigment dispersion 3 was used instead of the pigment dispersion 1, and VA-057 [Wako Pure Chemical Industries, 2,2′-azobis (N A dispersible colorant 7 was obtained in the same manner as in Production Example 9 except that-(2-carboxyethyl) amidinopropane] was used.

[Production Example 12]
In Production Example 9, a dispersible colorant 8 was obtained in the same manner as in Production Example 9 except that the pigment dispersion 4 was used instead of the pigment dispersion 1.

[Production Example 13]
In Production Example 5, in place of 9.0 parts of benzyl methacrylate, 9.0 parts of methyl methacrylate and 1.0 part of methacrylic acid instead of 1.0 part of acrylic acid were used. Preparation was performed to obtain dispersible colorant 9.

[Production Example 14]
In Production Example 5, instead of 9.0 parts of benzyl methacrylate, 6.5 parts of methyl methacrylate, 2.3 parts of methoxypolyethylene glycol methacrylate (NK ester M90G manufactured by Shin-Nakamura Chemical Co., Ltd.) and 1,6 hexanediacrylate 0 A dispersible colorant 10 was obtained in the same manner as in Production Example 5 except that 1.0 part of methacrylic acid was used instead of 1.0 part of acrylic acid.

[Characteristics of dispersible colorants]
The dispersible colorants 1 to 10 obtained in the above Production Examples 5 to 14 were observed and measured for various physical properties by the methods described below, and the obtained results are shown in Table 1.

<Stickness / spotting>
Each of the dispersible colorants 1 to 10 was dispersed in water and dried, and observed with a scanning electron microscope JSM-6700 (manufactured by JEOL Hi-Tech Co., Ltd.) at a magnification of 50,000 times. And about the state of fixation, the thing which confirmed the mode that the resin fine particle was adhering was evaluated as (circle), and the thing which was not able to be evaluated as x. In addition, when observation, it was confirmed that the resin fine particles were scattered, and the case where the particles were observed to be localized or non-uniformly adhered was indicated as X. Evaluated.

<Dispersion stability>
A 5% aqueous dispersion of each dispersible colorant is diluted 10-fold with pure water, concentrated to the original concentration using an ultrafiltration filter with a molecular weight cut off of 50,000, and the concentrated solution is centrifuged. At 80,000 rpm for 90 minutes. The separated sediment is taken out and redispersed in pure water, and is visually dispersed uniformly. The average particle diameter measured by the dynamic light scattering method described later is 2 before the operation. The dispersion stability was evaluated by confirming that the ratio was within the range of ½, and satisfying the conditions as ◯, and not satisfying the conditions as x.

<Long-term storage stability>
For long-term storage stability, each dispersible colorant was placed in a glass sample bottle in the form of a dispersed aqueous solution, and the dispersion state after standing at 60 ° C. for 1 month in a sealed state was judged visually. The evaluation criteria are as follows.
A: Solid matter flocculation / sedimentation is not observed B: Solid matter sedimentation is slightly observed, but when shaken lightly, it returns to the original uniform dispersion state C: Solid content flocculation / sedimentation is observed, shake lightly Is not even

<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 of aqueous hydrochloric acid solution is added to the color material aqueous dispersion, and the precipitate which has been precipitated at 20,000 rpm for 1 hour in a centrifuge is redispersed in pure water, and the solid content is determined to obtain the precipitate. The dispersion obtained by weighing, adding a known amount of sodium hydrogen carbonate and stirring the mixture was further precipitated with 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 value obtained by measuring the known amount of sodium hydrogen carbonate and pure water from the neutralization amount obtained by neutralization titration with 0.1 N hydrochloric acid solution.

[Preparation of recording inks 1 to 26]
Using the dispersible colorant 1 (black) obtained as described above, the following components are mixed so that the colorant concentration is 4% by mass, and further added with a membrane filter having a pore size of 1.2 microns. The recording ink 1 was prepared by pressure filtration. The total amount of ink was adjusted with water so as to be 100 parts. Further, recording inks 2 to 26 were prepared in the same manner as described above with the formulations shown in Tables 2 to 5.

・ Glycerol 7 parts ・ Ethylene glycol 8 parts ・ Polyethylene glycol 600 5 parts ・ Acetyleneol EH (manufactured by Kawaken Fine Chemicals Co., Ltd.) 0.1 part ・ Ion-exchanged water balance

For the inks 1 to 26 prepared as described above, Ka (absorption coefficient) was measured by the following method, and the obtained results are shown in Tables 2 to 5. The Ka value (absorption coefficient) of each ink was measured with a dynamic permeability test apparatus S (manufactured by Toyo Seiki Seisakusho) using Canon PPC paper NSK as a recording medium. Specific measurement conditions are as follows. Test piece (recording medium) dimensions: width 25 mm, length 297 (A4 longitudinal direction) mm
・ Rotating disc circumference: 1,000 mm
Disk peripheral speed: 0.5 mm / s, 1.25 mm / s, 2.5 mm / s, 5.0 mm / s, 10.0 mm / s
・ Head box: Slit size 0.5mm × 15mm
・ Liquid volume: 40 μl

[Example 1]
Next, the recording inks 1 to 8, 25, and 26 obtained above were combined to form an ink set composed of black (Bk), cyan (C), magenta (M), and yellow (Y) inks. Using this set, recording was performed on Canon PPC paper NSK. As the ink jet recording apparatus used, an ink jet recording apparatus BJS-500 (manufactured by Canon) equipped with an on-demand type multi recording head was used. The printer driver was used in the default mode shown below.
-Paper type: Plain paper-Print quality: Standard-Color adjustment: Automatic

  The print density, bleeding property, feathering property, scratch resistance, marker resistance, long-term storage stability and ejection stability of the printed matter obtained by printing under the above conditions were evaluated by the following methods and standards. The results are shown in Table 6.

<Print density>
As for the print density, character printing including a solid portion of 2 cm × 2 cm was performed, and the optical density (OD) of the printed matter one day after printing was measured. For an image using black ink (Bk), an OD of 1.3 or more was evaluated as A, 1.1 or more and less than 1.3 as B, and less than 1.1 as C. For an image using color ink, an OD of 1.0 or more was evaluated as A, 0.8 or more and less than 1.0 as B, and less than 0.8 as C.

<Bleedability>
The bleeding property was evaluated as follows by visually observing the bleeding of the printed portion. First, observe the presence or absence of bleed, ○ if the edge is sharp and there is no bleeding, there is a slight blur, △ if there is no problem in character recognition, the bleeding is severe, it is difficult to confirm small characters The thing was made into x. Then, from these observation results, the obtained printed matter was evaluated according to the following criteria, and this was regarded as bleeding property.
A: There is ○ and there is no x B: There is ○ or there is no x C: There is no ○ and there is x

<Feathering>
The feathering property was visually evaluated for the presence or absence of whiskers in the printed portion.
A: No whisker-like oozing B: Slight beard-like oozing is seen C: Beard-like oozing is clearly recognized

<Abrasion resistance>
Scratch resistance of the printed matter is rubbed 5 times with sylbon paper weighing 40 g / cm ² after 1 hour on a black printed part (1 cm x 2 cm solid part), and the printed part is visually observed. And evaluated according to the following criteria.
A: Disturbance of printing due to rubbing and no smearing on the white part are observed (the white part and the Sylbon paper are not smudged)
B: Disturbance of printing due to rubbing and dirt on the white part are scarcely noticeable (only the Sylbon paper has dirt)
C: Printing is greatly disturbed by rubbing, and stains are observed in the white part (stains in both the white part and the Sylbon paper)

<Marker resistance>
The marker resistance of the printed matter is determined by visually observing the degree of stain on the printed sample when the black printed portion (0.1 cm × 2 cm solid portion) printed portion is traced with a commercially available aqueous fluorescent marker pen after 1 hour. The evaluation was based on the following criteria.
A: Disturbance of printing due to rubbing and no smearing on the white part are observed (the white part and the Sylbon paper are not smudged)
B: Disturbance of printing due to rubbing and dirt on the white part are scarcely noticeable (only the Sylbon paper has dirt)
C: Printing is greatly disturbed by rubbing, and stains are observed in the white part (stains in both the white part and the Sylbon paper)

<Long-term storage stability>
Storage stability was determined by visual observation of the state of dispersion in the ink after each ink was placed in a glass sample bottle and allowed to stand at room temperature for one month in that state. The evaluation criteria are as follows.
A: Solid matter flocculation / sedimentation is not observed B: Solid matter sedimentation is slightly observed, but when shaken lightly, it returns to the original uniform dispersion state C: Solid content flocculation / sedimentation is observed, shake lightly Is not even

<Discharge stability>
The ejection stability was judged visually by printing 100 sheets of specific text continuously and comparing the initial printed matter with the last printed matter.
A: No streak, unevenness, etc., no difference between initial and last B: Although there are slight streaks, unevenness, and twisting, it can be printed without problems C: A large deterioration in quality is seen or printing becomes impossible

[Examples 2 to 4]
Recording was performed in the same manner as in Example 1 using an ink set composed of combinations of the inks shown in Tables 6 and 7, and the printed matter and each ink were evaluated. As a result, as shown in Tables 6 and 7, in each of Examples 1 to 4, an image having a high printing density and good bleeding property was obtained. In addition, the obtained image was excellent in scratch resistance and marker resistance, and each ink constituting the set was at a level where there was no problem in ejection stability and storage stability.

[Comparative Examples 1-5]
Next, by combining the recording inks 9 to 24 obtained above, the ink sets of Comparative Examples 1 to 5 made of black (Bk), cyan (C), magenta (M), and yellow (Y) inks did. And about the obtained ink set, evaluation similar to Example 1 was performed and the obtained result was shown to Tables 8-10. As a result, as shown in Table 8, the ink set of Comparative Example 1 has a low Ka value for all color inks, so the permeation speed is slow, and many colorant components remain on the paper surface, resulting in a high image density. It was. On the other hand, since it takes time to fix on the paper surface, the image is inferior in bleeding property, scratch resistance and marker resistance. In addition, as shown in Table 8, the ink set of Comparative Example 2 had a high Ka value for all the color inks, so that the permeation speed was too high and a high image density could not be obtained.

  Further, as shown in Table 9, the ink set of Comparative Example 3 has a Ka value of yellow ink having a value of 1 or more, so the printing density is low and the Ka value of the black ink having the smallest Ka value is the largest. The difference from the Ka value of yellow ink is 0.70 or more, and the bleedability is inferior because the penetration speed of the color ink is too high for the black ink. In the ink set of Comparative Example 4, since the Ka value of the black ink is less than 0.20 and the difference in Ka value from the magenta ink is less than 0.20, the black ink with the lowest brightness enters the color ink. The bleed between black and color is remarkably inferior. In the ink set of Comparative Example 5, since the Ka values of the black ink and the yellow ink are 1.00 or more, the print density is low, and the difference in Ka value between the black ink and the color ink is less than 0.20. Therefore, it is inferior in bleeding property.

  According to the present invention, an ink having excellent ejection stability and storage stability is obtained. When printing full-color ink on plain paper, a high density image with high OD is obtained, and occurrence of feathering and bleeding is caused. Further, an ink set that provides a high-quality image excellent in fastness such as marker resistance and scratch resistance is provided. Furthermore, as another effect of the present invention, there are provided an ink tank, an ink jet recording apparatus, and an ink jet recording method capable of achieving good image formation using such an excellent ink set.

It is a schematic diagram showing a basic structure of a dispersible color material to which charged resin pseudo fine particles contained in each ink constituting the ink set of the present invention are fixed. It is a schematic diagram of the typical process in the suitable manufacturing method of the dispersible color material used by this invention. It is a schematic diagram which shows the adhering process to the coloring material of the chargeable resin pseudo fine particles in the manufacturing method shown in FIG. It is the schematic diagram which expanded the chargeable resin pseudo fine particle in the dispersible color material used by this invention from the interface side fixed to a color material. It is the schematic diagram which expanded the interface where the chargeable resin pseudo fine particles of the dispersible color material used in the present invention and the color material are fixed. 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.

Explanation of symbols

1: Color material 2: Charged resin pseudo fine particles 3: Dispersion resin 4: Monomer 5: Polymerization initiator aqueous solution 6: Dispersible color material 7: Oligomer formed by polymerization of monomer 8: Precipitation in which oligomer is insolubilized in water Product 9-1: Hydrophilic monomer unit portion 9-2 in the charged resin pseudo fine particle 9-2: Hydrophobic monomer unit portion 10 in the charge resin pseudo fine particle 10: Bonding site with the coloring material 11: Color of the charge resin pseudo fine particle Interface part 12 with material: hydrophilic group modified directly on color material

Claims (11)

In an ink set for inkjet recording composed of black ink and a plurality of color inks, each ink comprises a dispersible color material having a water-insoluble color material and chargeable resin pseudo fine particles smaller than the color material, The ink set is characterized in that the coloring material and the chargeable resin pseudo fine particles are fixed to each other, and the Ka value (absorption coefficient) for plain paper determined by the Brist method for each ink is 0.20 or more. An ink set characterized by being less than 00 (ml / m ² · msec ^1/2 ). The difference between the color ink having the largest Ka value in each ink and the black ink having the smallest Ka value in each ink is 0.20 to 0.70 (ml / m ² · msec ^{1 /} The ink set according to claim 1, which is ² ).   The ink set according to claim 1 or 2, wherein the Ka value of the black ink is 0.20 or more and less than 0.60, and the Ka value of the color ink is 0.40 or more and less than 1.00.   The ink set according to any one of claims 1 to 3, wherein the Ka value of yellow ink is the largest among the Ka values of each color ink.   The ink set 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.   6. The chargeable resin pseudo fine particle according to claim 1, comprising a copolymer of monomer components including at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer. 7. Ink set.   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 with an ink jet recording apparatus using the water-based ink according to claim 1.   An inkjet recording image formed by an inkjet recording apparatus using the water-based ink according to any one of claims 1 to 6. The plurality of inks used in the image forming method for performing the step of forming an adjacent image with a plurality of inks each include a dispersible color material having a water-insoluble color material and chargeable resin pseudo fine particles smaller than the color material, A water-insoluble colorant and a chargeable resin pseudo fine particle are fixed to each other, and each ink has a Ka value (absorption coefficient) of 0.20 or more with respect to plain paper determined by the Brist method of each ink. A plurality of ink sets characterized by being less than 1.00 (ml / m ² · msec ^1/2 ).

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